GB2197967A - Electric motor controls and laundry machines using such motor controls - Google Patents

Abstract

A control apparatus and method for an electric motor having sensing devices which sense the frequency and polarity of EMFs in the rotor windings down to a condition where the rotor is in condition for reversing, and causing reversing of the motor when the frequency is such as to allow reversing and the polarity of a selected winding is at or near a zero crossing between positive and negative polarities. Cyclical reversal is effected by measuring the time the rotor takes to coast from a "power off" condition to the condition for reversing and with an electronically commutated motor reversing can usually be effected in one commutation period. The motor is used in a clothes washing machine or similar application where rapid reversal is required or timing of the time from one reversal to the next is required to be constant. <IMAGE>

Description

"Electric Motor Controls and Laundry Machines using such Motor Controls' This invention relates to electronic controls for electric motors, laundry machines including such controls and/or methods of operating said controls.

It is an object of the present invention to provide an electronic motor control for controlling electric motors and/or a laundry machine including such controls and/or a method of operating laundry machine using such controls which will at least provide the public with a useful choice.

Accordingly in one aspect the invention may broadly be said to consist in a method of cyclically reversing an electronically commutated motor having a plurality of windings on a stator and a rotor having magnetic poles rotatable relative to said stator and using electronic control apparatus and means to indicate the position of the rotor said method comprising the steps of (a) Initiating and then continuing a correct sequence of commutations for a desired time or desired number of commutations, (b) Removing all power from the windings and allowing the rotor to coast towards zero rotation, (c) Testing the position of the rotor relative to the stator, and (d) When the rotor is in condition to be reversed and its position relative to the stator is known, changing the sequence of commutations to cause the rotor to change direction the correct commutations following automatically to maintain rotor rotation in the changed direction, and repeating the steps to give cyclical reversal for a desired time.

In a further aspect the invention consists in control apparatus for an electronically commutated motor having a plurality of windings on a stator adapted to be selectively commutated and a rotor having magnetic poles rotatable relative to said stator said control apparatus comprising: (a) Timing means to time the period of rotation or counting means to count the number of rotations of the rotor in a desired direction, (b) Commutation switching means to disconnect power from said windings to allow the rotor to run down towards zero rotation, (c) Detecting means to indicate rotor position relative to said stator, and (d) Pattern reverse means operable in response to a signal from said detecting means when the rotor is in condition to be reversed to cause the control signals to cause commutation changes which cause said rotor to change direction without testing for rotor direction.

In a still further aspect the invention consists in a method of cyclically controlling the supply of power to an electric motor having a rotor said method including the steps of starting rotation of said rotor in one direction setting an initial "power on" time during which power is applied to said motor, switching off power at the end of said initial "power on" time, causing the rotor to slow until in a condition to be reversed, checking the ramp down time the rotor takes to slow to a condition ready for reversal, causing reversal of direction of rotation of said rotor, as soon as the rotor is in condition to be reversed, and repeating the said steps as desired.

In a still further aspect the invention consists in a method of cyclically controlling the supply of power to an electric motor having a rotor said method including the steps of setting a desired time of rotation of said rotor in one direction starting rotation of said rotor in said one direction setting an initial t'power on" time during which power is applied to said motor, switching off power at the end of said initial "power on" time, causing the rotor to slow until in a condition to be reversed, checking the ramp down time to rotor takes to slow to a condition ready for reversal, causing reversal of direction of rotation of said rotor, applying power to the applied to said rotor for a further "power on" time which is such that said further "power on" time plus said ramp down time equals said desired time, switching off power to said rotor at the end of said further "power on" time, again checking the next ramp down tie reversing direction of the rotor to said one direction when said rotor is in condition for reversal and applying power to said rotor for a still further "power on" time which is such that said still further "power on" time plus said next down ramp time equals said desired time and repeating the cycles for a desired length of time, adjusting the "power on" time at desired intervals of time so that the adjusted "power on" time for a further half cycle plus the down ramp time for a previous half cycle equals said desired time In a still further aspect the invention consists in a method of electronically cyclically controlling the supply of power to an electric motor said method including the steps of setting a desired speed of rotation of the rotor of the motor, sensing the resistance to rotation of the motor and using responses from the sensing means to actuate adjustment means to adjust the power supplied to the motor to change the motor speed towards said desired speed and then operate the motor within a range of speeds at or close to said desired speed of rotation, switching off the supply of power to the motor, stopping its rotation and then repeating the cycle of operations with the motor running in the reverse direction.

In a still further aspect the invention consists in an electrical control means for cyclically controlling the supply of electrical power to an electric motor having a rotor said control means comprising switching means to switch power to said motor on and off, coasting timing means to time the length of time said rotor takes from the time power is switched off thereto to the time when said rotor is in condition for reversal of direction of rotation, and reversing means to reverse the direction of said rotor when said rotor is in condition for reversing and to switch on said switching means when reversing is to be effected.

In a still further aspect the invention consists in an electronic control means for cyclically controlling the supply of electrical power to an electric motor said electronic control means including setting means operable to set a desired speed of rotation of the rotor of said motor, sensing means to sense resistance to rotation of the motor and adjustment means responsive to said sensing means to adjust the power supplied to the motor to accelerate said motor towards the desired speed and to then operate the motor within a range of speeds at or close to said desired speed of rotation, switching means to switch off the supply of said motor after a desired time and reversing means operable after the motor has substantially stopped to cause the cycle of operating to be repeated with the motor running in the reverse direction.

In a still further aspect the invention consists in an electrical control means for cyclically controlling the supply of electrical power to an electric motor having a rotor said control-means comprising switching means to switch power to said motor on and off, power timing means to time the length of power time when power is switched on, coasting timing means to time the length of time said rotor takes from the time power is switched off thereto to the time when said rotor is in condition for reversal of direction of rotation stroke timing means to time the stroke time during which said rotor rotates between reversals setting means to set said stroke timing means to a desired stroke time, algebraic subtracting means to algebracially subtract a previous coast time from said stroke time to arrive at a time setting for said power time and reversing means to reverse the direction of said rotor when said rotor is in condition for reversing and to switch on said switching means when reversing is to be effected.

In a still further aspect the invention consists in a method of operating a lundry machine having a container for a wash load of soiled fabrics in wash water and a reciprocable agitator in said container and an electric motor driving said agitator said method comprising the steps of starting rotation of said motor in one direction setting an initial "power on" time during which power is applied to said motor, switching off power at the end of said initial "power on" time, allowing the motor to slow down until in a condition to be reversed, checking the time between the power off condition and a condition when the rotor is in condition to be reversed causing reversal of direction of the rotor as soon as the motor is in condition for reversal and repeating the said steps as desired.

In a still further aspect the invention consists in a method of operating a laundry machine having a container for a wash load of soiled fabrics in water and a reciprocatable agitator in said container, an electric motor driving said agitator, setting means to set a desired rate and amplitude of time and/or angle of oscillating rotation of said agitator an electronic control means controlling the supply of electrical power to said electric motor in one of a plurality of sequences said method including the steps of setting a selected one of said plurality of sequences so that said agitator is driven in oscillating rotation during a wash phase in a sequence of washing operations, sensing the resistance to oscillation of said agitator due to the wash load in said container and adjusting the power supplied to said electric motor so that a selected rate of removal of soil from said soiled fabrics is substantially achieved.

In a still further aspect the invention consists in a laundry machine including a container for a wash load of soiled fabrics in water a reciprocatable agitator in said container an electric motor driving said agitator, setting means to set a desired rate and amplitude of oscillating rotation of said agitator, electronic control means controlling the supply of electrical power to said electric motor in one of a plurality of selected sequences so that said agitator is driven in oscillating rotation during a wash phase, selecting means for selecting a desired one of said sequences so that a washing action selected from such as delicate, regular, heavy duty, wool, and permanent press washing actions is to be effected by the machine said electronic control means including sensing means to sense the resistance to oscillating rotation of said agitator due to the wash load in the container and adjustment means responsive to said sensing means to adjust the power applied to said electric motor so that a washing action results such that a selected rate of removal of soil from said soiled fabrics is substantially achieved.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

Preferred forms of the invention will now be described with reference to the accompanying drawings in which, Figure 1 is a block diagram of an electronic control circuit to control an electronically commutated motor driving an agitator and spin tub of a clothes washing machine, Figures 2 and 3 illustrate EMFs in windings with the rotor rotating clockwise in relation to Figure 2 and countercloch ise in relation to Figure 3, Figure 4 is a diagram showing motor stator windings, and electronic power commutation circuitry, Figure 5 is a circuit diagram of a voltage digitising circuit used in the invention.

Figure 6 is a flow diagram of motor reversing sequences.

Figure 7 is a flow diagram of deriving values of index and indexr, Figure 8 is a flow diagram for determining the rotor position, Figure 9 is a graph showing the motor and hence the agitator velocity profile during a half cycle of agitator oscillating rotation in a wash mode.

Figure 9a is as figure 9 but illustrating action when the stroke time is variable, Figure 10 is a graph showing a series of acceleration profiles, Figure 11 is a graph showing resultant curves under operating conditions between the completion of the acceleration mode and the cutoff point of applying power to the motor, Figures 12 to 16 are flow diagrams showing various phases of operation of the control circuit of Figure 1.

Figure 16a is a diagrammatic view of a speed sensor for use with the invention, Figures 17, 18 and 19 are figures repeated from a Boyd & Muller U.S. Specification 4,540,921 to provide background to the present invention.

This invention-relates in general to a laundry machine with a cabinet a wash water container in its cabinet, a spin tub in the container reciprocating agitator in the spin tub and a motor for driving the agitator in the spin tub. Specifically it relates to sensing means for sensing the load on the agitator and adjusting means operating in response to signals from the sensing means to adjust the power by adjustment of the profile of velocity to the agitator as indicated by a velocity/time graph such that soil removal and washing activity remain substantially constant according to a desired setting for different loads.

Laundry machines are required to wash a wide variety of fabrics and garments. Different clothes and fabric types require different treatment to achieve an appropriate wash action. In general, with vertical agitator washing machines, as agitator velocity is increased, soil removal and wear and tear also increase. An appropriate balance between soil removal and wear and tear is necessary. It is a major objective of laundry machines to wash each type of fabric with an agitator action appropriate to the load type and size. For example, clothes which fall into the broad category of "delicates," often synthetic in origin, or fragile items which are susceptible to damage during the wash but which are typically only slightly soiled, require gentleness of wash action with less emphasis on soil removal, whereas "regular" items such as cottons which are strong when wet can withstand a more vigorous wash action.

Conventional vertical axis laundry machines employ various types of transmissions to convert rotary motion provided by an electric motor into oscillatory motion at the agitator for their wash mode. Such motors are generally of essentially constant speed types Therefore to provide wash actions suitable for loads ranging from delicate garments to heavily soiled hard wearing garments requires multiple gearing or switched speed motors each of which is costly. Further, as wash load is increased towards rated capacity for a constant amount of water, mean soil removal typically decreases and mean gentleness increases. Variance of soil removal and gentleness also increases, indicating less uniformity of wash action throughout the wash load. Therefore it is difficult to maintain good wash performance with laundry machines of this type under varying load conditions.

The use of agitator drive systems such as disclosed in the John Henry Boyd Australian Patent Specification AU-A-85 - 183/82 AND THE FISHER & PAYKEL United Kingdom Patent UKN2095705 wherein the agitator may be directly driven by an electronically controlled motor either with or without a simple speed reduction unit and oscillatory rotation is enabled by periodic reversal of rotation of the motor provides opportunity for varying the speed and rate of reversal of the agitator to obtain the appropriate balance between soil removal and wear and tear for each category of load. However the problem of variation of soil removal and also wear and tear with load size still remains.

In a first aspect of the invention the following describes apparatus to carry out an oscillatory rotation of the agitator during a washing phase of the cycle of operations of the washing machine and then on command to spin the spin tub in a spin phase of the washing cycle, and is principally concerned with the agitation cycle.

In a further aspect of the invention, later in this specification a detailed description is given of preferred forms of sensing means to sense the wash load in the laundry machine, correcting means to correct for velocity variations, adjusting means to adjust the power applied to the agitator by modification of the profile of velocity as indicated by a velocity/time graph, and setting means to alter the stroke angle of the agitator such that soil removal and wear and tear such that wash performance remain substantially constant for a particular setting with variation of load size.

The preferred form of the invention is based on the Boyd and Muller U.S. Specification 4,540,921 which is incorporated by reference herein.

For assistance in the full understanding of the present invention excerpts from the Boyd and Muller Specification 4,540,921 are inserted herein but no Claim is made to the subject matter described and claimed in that Specification.

Referring to figure 1 of the drawings, An electronically commutated motor (ECM) 2 is described in detail in the Boyd/Muller US Specification 14,540,921.

The ECM 2 constitutes a stationary assembly having a plurality of winding stages adapted to be selectively commutated, and rotatable means associated with that stationary assembly in selective magnetic coupling relation with the winding stages. The winding stages are commutated without brushes by sensing the rotational position of the rotor as it rotates within the stationary assembly. DC voltage is selectively applied by commutation circuit 17 to the winding stages in preselected orders of sequences leaving at least one of the winding stages unpowered at any one time while the other winding stages are powered in response to a pattern of control signal from voltage digitizing circuit 13.

The control apparatus comprises a general purpose microcomputer 10 eg an intel 8049 which receives commands for example from a console 11 having a series of push buttons or other user operable controls 9 and the microcomputer 10 stores patterns of signals which feed through a Pulse width modulation control means 18 and a comutation control signal generator 8 (which are described in more detail later) to a three phase power bridge switching circuit 17. The necessary power supplies are fed by a DC Power supply 12. In addition signals are fed from a winding of the ECM which is unpowered when other windings in the stator of the ECM are under power. This will be explained further later. Signals from the motor windings are fed to a voltage digitising circuit 13, as described in the Boyd Muller Specification and below in relation to Figure 4 of this specification, and are thence supplied to the microcomputer 10. Power switching circuits also feed through a current sensing circuit 5 to the microcomputer 10. A loop position error indicator 15 and a speed demand rate velocity timer 16 are provided and a commutation rate sensing device 14 but any other rotor speed and position varying device may be used as will be explained further later. A pulse width modulation control circuit 18 is provided.

In broad terms a clothes washing machine according to tlle present invention when operated to cause washing, functions as follows.

The operator selects a desired set of washing requirements by operating push buttons controlling its console microcomputer. As a result the console microcomputer sends a series of data values to the motor control microcomputer 10 and these are placed into registers (memory locations) of the same name, in the motor control microcomputer 10. Data transmitted from the console is broken up into 3 groups: Group 1 contains the command words: OOH - BRAKE 01H - WASH 02H - SPIN 03F - TEST 04H - MODIFY 05H - STATUS 06H - STOP 07H - PUMP Group 2 contains error codes: 08H - PARAMETER range error detected OWH - PARITY error detected OAR - COMMAND error detected Group 3 contains parameter data: OBH to 7FH The motor control microcomputer program knows which group to expect during each communication, therefore if the program has got out of step with the console in any way this will be picked up as a range error.

However due to this data structure some data in group 3 may be outside their working range so within the listing some parameters are offset after they have been received so that they fall within the correct value to be used within the program.

To maintain function overviews, at the beginning of the wash cycle the console microcomputer 19 controls the filling of the bowl. While the bowl is filling a spin command is sent to the motor control microcomputer. The spin speed is very low, approximately 70 rpm, and its main purpose is to mix the soap powder while the bowl is being filled. Once the bowl is filled the console then sends a WASH command to the motor controller 10 to start the agitate cycle. This agitate cycle starts from rest, ramps up to speed, maintains this speed for a predetermined time and then coasts to a stop all within one forward or reverse cycle of the agitator. Once the agitator has stopped the process is repeated in the opposite direction thus producing an agitating motion. The console microcomputer 19 determines all these parameters which determine what sort of wash is required eg. gentle cycle, and is loaded into the motor controller 10 before the start of the cycle.

The motor controller 10 continually modifies these wash parameters to account for the load in order to maintain the most effective dirt removal to gentleness ration. Because of the agitating motion the load is shuffled around the bowl and this affects how fast the agitator ramps to speed and how long it takes to come to a stop at the end of the stroke. Therefore to maintain constant wash effectiveness these parameters are monitored and modified each stroke cycle to maintain the ideal conditions requested by the console microcomputer.

The motor controller 10 will continue this action until it receives another command from the console microcomputer. a little more detail, the wash mode runs as follows.

On receiving a "WASH" command a jump is made to the WASH routine. Low speed windings of the motor are set and a brake is set off. The routine then waits for the Console microcomputer to send the wash cycle parameters, ie: (1) TSTROKE The time for rotation of the agitator in one direction.

(2) WRAMP The time it takes to reach speed from rest.

(3) ENDSPD The velocity which the agitator must reach after the wash ramp time is up.

When these have been placed in the appropriate registers they are then checked for errors. Checks for other errors are also made encluding a check to make sure the motor is stationary.

A routine now sets LORATE = ENDSPD = ACCSPD. LORATE is the motor speed, ACCSPD is the speed that the motor must reach to obtain the correct wash ramp rate. ACCSPD may become greater than ENDSPD to achieve the correct acceleration ramp.

As is explained in more detail later, the speed rate timer RATETMR used in the timer interrupt routine for the speed reference count is loaded with the count set in LORATE previously.

The position error counter 15 is cleared and current trip and pattern error circuits are reset. In the wash mode the program bypasses the spin cycle routine.

At this point the plateau time, TFLAT, is calculated from the original information sent by the Console microcomputer. To do this it sets the coast time at 180mS. This is a time choosen which guarantee's that the motor will have coasted to a stop with very little load. Thus the plateau time is calculated: TFLAT = TSTROKE - WRAMP - 15 (180mS time count) using a long timer a count of 15 gives: 127 x 96uS x 15 = 180mS (approx).

The routines up to this point have only been setting the wash parameters for the first stroke. The following values as referred to above, are set in the random access memory in the motor control microcomputer 10: TSTROKE total stroke time, ie. from rest to peak speed and to rest again.

WRAMP time to full speed ENDSPD full speed count LORATE (set at ENDSPD) speed rate ACCSPD (set at ENDSPD) acceleration rate ALGFLG (set FALSE) end of ramp flag ENDFLG (set FALSE) plateau time flag SLECTR position error counter RATETMR (set at LORATE) sets speed reference to speed loop error counter TFLAT calculated from above parameters; time at maximum speed At this point the wash cycle can begin.

To actually set the motor into motion we must first set bit pattern pointers INDEXR and INDEX. For the wash cycle the direction of motion has arbitrarily been set at CCW (counter clockwise) for the first stroke, thus: INDEXR = 12D INDEX = 00 and the direction register DIRECT = 01H for CCW.

The wash ramp time WRAMP is loaded into a long timer for the beginning of the wash ramp cycle. Commutation now takes place, and the motor is started up.

After passing through the required time for or number of commutation routines the program ends. At the end of the agitate cycle the console microcomputer 19 will send a command to the motor controller microcomputer 10 to stop the agitate cycle and turn on the pump to drain the wash bowl before going into the spin mode.

As will be explained in more detail later, to enable motor reversal to be effected the invention requires to determine the position of the rotor during coasting of the rotor after power to the stator has been cut off. It will be clear however that this aspect of the invention cannot be put into use until the rotor itself has been operating under an electronically commutated sequence. Accordingly when the rotor has been stopped e.g. at the very start of a washing cycle it is necessary to start the motor when the position of the rotor is not known. Accordingly tne technique described in the Bcyd Muller Specification in particular at page 55 is preferably used. In this technique the digitised voltages received from the voltage digitising circuit are tested and as soon as complementary bits or logic levels in the proper test bit order have been sensed operations proceed to advance in sequence to commutate the winding stages. If complementary bits are not sensed in the predetermined proper test bit order in a predeerminec time period operations take place to advance commJtations in tne sequence rapidly and force commutate the motor, thus causing the rotor to oscillate briefly. Thus if for example clockwise rotation is required and the sensing indicates that the rotor is starting to run in the counterclockwise direction, the rotor runs for a short distance in this direction (one or a few commutations occurring) until the force commutating is effected to cause it to run in the correct direction.

Thus referring to Figure 4 there is provided a three phase motor 20 with a common point 21 and a switching bridge in which three switching devices 22, 23 and 24 connect the lower supply positive rail 25 to the ends of the windings 26, 27 and 28 and three further switches 31, 32, and 33 connect the ends of the windings to the power supply negative rail 35. The upper switches 22, 23 and 24 may be referred to as the A+, B+ and C+ switches and the lower switches 31, 32 and 33 may be referred to as the A-, B- and C- switches.

When the motor is stationary there is no information as to the position of the rotor so it is not known as to which pair of switches to turn on to get the rotor to rotate in the correct direction so a selected upper and lower switch are turned on.

Statistically there is a 50% chance the rotor will rotate in the correct direction and a 50% chance that it will rotate in the incorrect direction. An algorithm is provided in the microprocessor 10 that once power has been applied senses whether the motor is going in the correct or the wrong direction and in the event that the rotor is rotating in the wrong direction the algorithm advances commutation signals quickly through the sequence of commutations until the correct sequence is adopted and the rotor synchronises with the commutated supply and is now running in the right direction. It may take three or four switching or more to synchronise the rotor and so with the starting algorithm 501 of the time it will start correctly and will just run into synchronism and 50 of the time it will start in the wrong direction and then stop and recover and then come back in the right direction. Thus with this arrangement every time the direction of the motor is reversed then if the present invention as will be described further later is not used then the motor is allowed sufficient time to coast to zero and then is started up using this starting algorithm. This start up algorithm is described in Boyd & Muller 4,540,921 more fully at col 8 line 23 et seq and col 23 line 57 et seq and col 24 line 43 to col 26 line 44. There must motor may require 1 to 2 commutation angles to restore correct rotation, a significant proportion of the acceleration period.

The resultant effect is a delay in reversal followed by rapid acceleration to speed often with some overshoot.

Gentleness of wash action in the washing machine is related to the acceleration of the agitator. Hence erratic reversal decreases gentleness. Further, delays in reversals also can reduce the rate of soil removal. The overall effect is reduction in desired wash performance.

Thus according to the present invention a more positive acceleration and consequently a more positive rate of soil removement and rate of wash action is achieved by monitoring the speed and position of the rotor while the rotor is coasting.

Then when the position of the rotor is monitored down to a position in which it is in condition for reversal, power is switched to the motor such that Torque is generated to cause the rotor to reverse direction preferably within a single commutation angle and allow the motor to run in the opposite direction without reverting to the start up algorithm.

Accordingly the rotor may be accelerated up to speed and maintained at speed using the power switching sequence as described in Boyd & Muller 4,540,921 referring to the tables 1 and 2 therein and in particular at col 6, lines 24 to 39 where the following passage appears: "The winding stages of motor M as explained for instance in the aforementioned Alley U.S. Patent 4,250,544 are commutated without brushes by sensing the rotational position of the rotatable assembly or rotor 15 as it rotates within the bore of stator 13 and utilising electrical signals generated as a function of the rotational position of the rotor to sequentially apply a DC voltage to each of the winding stages in different preselected orders or sequences that determine the direction of the rotation of the rotor. Position sensing may be accomplished by a position detecting circuit responsive to the back EMF of the ECM to provide a simultated signal indicative of the rotational position of the ECM rotor to control the timed sequential application of voltage to the winding stages of the motor." The present invention is concerned with the monitoring of speed and position of the rotor while coasting and using this information to reverse the motor preferably in a single commutation.

If the rotor to the motor is rotated and voltage measurements taken at the ends of the phases with respect to the star point 21 i.e. the centre of the three phase windings, EMFs will be generated and in Figures 2 and 3 such EMFs have been plotted. The Figures illustrate a single electrical revolution of the rotor in degrees and essentially show the wave forms of a three phase generator with the exception that the wave forms instead of being sinusoidal are trapezoidal. The three phases have been indicated by the letters A (pecked line), B (full line) and C (slashed line). For example in B phase it will be seen trat in Figure 2 the EMF goes from a maximum negative at zero degrees through zero voltage to a maximum positive, stays at a maximum positive for 12Co then goes from maximum through zero voltage to maximum negative stays at maximum negative for 1200 and then starts to rise again from zero degrees. It will be seen that in Figure 2 the sequence (which represents rotation in a clockwise direction) has a different sequence of EMF generations as compared with Figure 3 which represents a counterclockwise direction of rotation. Referring now to Figure 4,.applying voltages to the windings and assuming that winding 20 is A, winding 27 is C and winding 28 is B and that if we wish to have power on the motor at zero degrees such that we have a maximum EMF across the motor and thus maximum Torque in clockwise direction, switches 22 (A+) and 33 (C-) would be switched on, connecting power from the positive rail 25 through switch 22 to the A phase windings 20 through the neutral point 21 and the C phase windings 27 through switch 33 to negative rail 35. Thus referring again to Figure 2 with the notation therein indicated to obtain maximum Torque in the motor the connections would be A+ and C- to the 600 angle and then B+ and C- at the 1200 angle to B+ ar.d A- to 1800 angle then C+ and Ato the 2400 angle, C+, B- to the 3000 angle, A+ to B- to the 3600 angle, the sequence commencing at A+ and C- again. Thus there is a sequence of six different patterns and each goes to 600 of angle of rotation giving 3600 in rotation. Referring to the tables herein, Table I summarises the sequence of control signals required for each step in the sequence described above.

Referring to Table I it will be seen that the rows numbered 5 down to 0 correspond to the sequence of digital signals required to control the A+, B+ and C+ switches 22 to 24 and the A-, Band C- switches on or off. A 0 in the table indicates that the switch is turned on and a 1 in the table denotes that the switch is turned off. This is a negative notation because of the manner of operation of the microcomputer. Two further control lines are used to control whether or not the upper or lower switches are pulse width modulated to control motor current. Thus the microcomputer 10 is programmed to contain the pattern shown in Table I. The six columns from left to right for each switch control line show each step in the sequence described above with each step indexed from 0 to 5 in the row marked INDEX. Counterclockwise rotation is obtained by applying the control signals of Table 2 which is the reverse of the sequence of Table 1. The value of INDEX therefore is a reference of position in the commutation sequence for each table at any time. At each commutation INDEX is incremented by 1 until a maximum value of 5, then reset to O to continue the cycle. In each table another index is referenced "INDEXR" as mentioned in connection with flow diagrams discussed below. The INDEXR row has entries which are unique to each pattern in the sequence and different for Table I and Table 2 so that a given pattern is uniquely indentified for clockwise and counterclockwise rotation. Determination of the time for commutation is explained in detail in Boyd/Muller and excerpts are given later. Now during coasting (as described by Boyd/M.uller) trar.sitions in signals from comparators monitoring EKF signals contain position information. To repower the motor while still spinning such that the motor continues to run in sequence in the same direction requires that values of INDEX and INDEXR be computed such that correct switching sequence is intitated as explained in Boyd/Muller. In this specification is explained methods of repowering the motor such that the motor reverses direction by determining safe speeds for reversal and computing suitable values of INDEX and INDEXR such that correct switching sequence for reverse direction is initiated, preferably in a single commutation period.

It will be noted from the diagram of Figures 2 and 3 that for any 600 commutation interval in the unpowered phase the EMF is going from the maximum in one sense through a zero to a maximum in the other sense and it is that phase which is going to be turned on in the next commutation interval so that the microcomputer can determine when to turn that phase on by determining when that phase crosses through the zero point.

This is effected by the use of voltage comparators for example by circuitry as shown in Figure 5 in which VA is a measure of this voltage to zero volts appearing in winding 20, VB is a measure of the voltage to zero volts in winding 28 and VC is a meaure of the voltage to zero volts in winding 27. When for example a voltage VC is greater than the voltage VN on the neutral point N (21) Figure 4 the output of the comparator 36 will be high. When the voltage is less than the voltage VN at the neutral point, the output of the comparator 36 is low and the output of these comparators is fed directly into the microcomputer 10 which reads in the comparatives. It is to be noted that the output is comparative when the circuitry is looking at the comparator for the unused winding at any one time which will change sense when the EMF in that winding crosses zero. The microcomputer is then informed that it is almost time to commute and in accordance with the present invention with each successive zero crossing in a sequence, if there is a low to a high transition the next one is a high to a low transition then low to high high to low and continuing in that way. Thus the microcomputer knows where each winding is in the sequence and it knows which of the comparatives to look for for the next EMF sensing. The microcomputer looks for a transition and it also knows whether it should be low going high or high going low so that it can compute from the sequence where the rotor is in relation to the windings and what the next indications will be from the comparatives. Accordingly the microcomputer follows either table 1 or table 2 depending on the direction of rotation and cycles continue with the correct switches being turned on at the correct time.

In the A,B, & C circuits of figure 5, as shown with reference to the C circuit resistance 37 and capacitance 38 provide a filter effect reducing the sensitivity to transients.

Now during coasting, the EMFs are still present in the motor and thus zero crossing transitions will also still be present and result in signals being sent by the comparators to the microcomputer these signals being digitised by the digitising circuit 13, figure 5.

The Bcyd Muller Specification describes operations for repowering an ECM after coasting under control of the apparatus therein described and is repeated with reference to Figures 17, 18 and 19 as follows.

"Ir. Figure 17 the relaying routine cf step 588 is shown.

Operations commence with BENIN 651 and proceed to product the OFF pattern (all ones on lines 62) at step 653 to turn off the motor M. At step 655 microcomputer 61 issues a Low on line DB6 (figure 3) producing a High on line H from NAND gate 157, and causing relay 147 in high-low speed circuit 41 to switch from the low speed connection arrangement to a high speed connection arrangement. Microcomputer 61 waits for 10 milliseconds as by any suitable routine, such as counting from a preset number down to zero, in step 657 in order to permit the relay 147 armature 155 to come to rest in the high speed position. However, during this waiting period, the rotor 15 of motor M has, or may have, rotated through a significant angle for commutation purposes.

Accordingly, at step 659 a routine is executed for determining the value of INDEX from the sensed digitized voltages on comparator outputs A, B, and C of Figure 6 when the winding stages are temporarily unpowered, and resuming producing patterns of digital signals on lines 62 beginning with the pattern of digital signals (and thus a corresponding set of control signals from control signal generator 51) indentified by the value of INDEX so determined. The digitized back emfs for three trye-connected winding stages S1, S2 and S3 are illustrated in Figure 18 and tabulated in Tables III and IV for clockwise and counterclockwise rotation respectively.

In Figure 18 and in the first three rows of Tables III and IV, the logic levels of the digitized voltages on input lines 0, 1 and 2 of microcomputer 61 (fig 1, 4,540,921) are shown when rotor 15 (fig 2 4,540,921) is coasting. Each of the six columns shows the logic levels of the digitized back emfs present at any given time. As the rotor turns, the logic levels of a given column are replaced by the logic levels in the column next to the right. When the right-most column is reached, the logic levels begin again in the left-most column is reached, the logic levels begin again in the left-most column, cycling through the columns as before. Figure 18 shows superimposed on the logic zeros and ones a waveshape of the digitized back emfs on the input lines 0, 1 and 2. The digitized back emfs at any one time and their changes to other values at other times bear sufficient information to permit sensing the position of the turning rotor 15 and to identify the proper point in sequence for beginning commutation of such turning rotor and for resuming commutation whenever commutation is interrupted or discontinued.

Accordingly, the index-determining operations of step 659 as described in further detail in Figure 19 are used in relaying routine 588 in the preferred embodiment, and are used in other embodiments of the invention whenever it is desired to begin commutation in sequence.

In Figure 19 operations commence with BEGIN 671, and microcomputer 61, (fig 1 4,540,921) inputs all the lines 0, 1 and 2 cf port P1 at once by masking with ALLHI=07 (binary 00000111). As a result there resides in microcomputer 61 (fig 1 4,540,921) a three bit binary number having binary digits corresponding to each of the digitized voltages on the three lines. This binary number is designated DATA1 and stored in step 673. Then at step 675, micromputer 61 inputs all the lines C, 1 and 2 of port P1 again in search of digitized voltages ccrrespondng to an adJacent column of digitized voltages in Figure 18.

The digitized voltages just obtained in step 675 are sorted and designated DATA2. In step 683, DATA1 is compared with DATA2. If they are the same number, (i.e. DATA1-DATA2=)) the rotor has not turned sufficiently to move to the adjacent rightward column in Figure 18 and in the Table III or IV corresponding to the direction of rotation. When DATA1=DATA2 a branch is made back to step 675 to input another set, or instance, of digitized voltages until an instance of digitized voltages is found at step 675 which is different from DATA1. At step 685, the difference DATA2-DATA1 is computed.

When step 689 is reached, microcomputer 61 has stored values of DATAl and DATA2 which are in adjacent columns of one of the Tables III or IV. Each Table III or IV lists values of R3, which is the difference DATA2-DATA1, in the column corresponding to the digitized back emfs in DATA. Beneath a value of difference R3 in each of column of Table III cr IV are values of INDEX and INDEXR. The values of INDEX and INDEXR are precisely the values for identifying the proper Table I or Table II and the proper column therein containing the digital signal pattern which microcomputer 61 can and does then produce to resume commutation of the winding stages at the proper point in sequence. (Beneath the tabulated value of R3 in Table III is an entry designated"Offset R3" which is a number calculated in the program listing of Appendix I for microcomputer table lookup purposes).

If the direction determined is counterclockwise, a branch is made from step 689 to step 691 for table lockup in a table in microcomputer 61 (fig 1 of 4,540,921) having the information found in Table IV in rows R3 and INDEX. When INDEX is found, INDEXR is reset by adding 12 to INDEX. If the direction determined is clockwise, a branch is made from step 689 to step 693 for table lookup in a table in microcomputer 61 (fig 1 of 4,540,921) having the information found in Table III in rows R3 and INDEX. INDEXR is reset as equal to INDEX when the direction is clockwise. After step 691 or step 693 is executed, RETURN 679 is reached.

The operations of Figure 19 can be described more generally as follows. Microcomputer 61 (fig 1 of 4,540,921) identifies successive patterns of the control signals and of the digital signals of Tables I anc II by values of an index designated INDEX. A value of the index is determined from the sensed digitized voltages when the winding stages are temporarily unpowered. Microcomputer 61 (fig 1 of 4,540,921) resumes producing successive patterns of the digital signals which causes control signal generator 51 (fig 1 of 4,540,921) to generate successive patterns cf the control signals in sequence beginning with a pattern of the digital signals and control signals determined from the sensed digitized voltages. The lookup table information stored in microcomputer 61 (fig 1 of 4,540,921) is a function, i.e. a predetermined correspondence between members of two sets of numbers. The sets of numbers involved here are values of INDEX on the one hand and values cf the differences R3. Equivalently, Tables III and IV can be regarded as tabulating INDEX as a function of digitized back er.f itself. It is also to be understood that there are a multitude of equivalent ways rnace known by the disclosure made herein, of setting up a function relating the digitized back emf information to some variable such as INDEX which can be used to determine the proper point for beginning in sequence when commutation begins again. When the successive patterns of digital signals and control signals are identified by values of an index, the index is advantageously determined as a function of a number represented by the sensed digitized voltages when the winding stages are temporarily unpowered, and microcomputer 61 (fig 1 of 4,540,921) resumes producing patterns beginning with the pattern of the control signals identified by the value of the index so determined. The index is determined as a first function of a number represented by the sensed digitized voltages when the winding stages are temporarily unpowered and the preselected sequence is for clockwise rotation of the rotatable means 15 (fig 1 of 4,540,921) and determined as a second function of the number so represented when the preselected sequence is for counterclockwise rotation, and microcomputer 61 (fig 1 of 4,540,921) resumes producing patterns beginning with the pattern of the control signals identified by the value of the index so determined. The value of the index is also determined as a function of the difference of first and second numbers represented by different instances of the sensed digitized voltages, and microcomputer 61 begins with the pattern of the control signals identified by the value of the index so determined.

The value of the index is determined as a function of the difference of first and second numbers represented by different instances of the sensed digitized voltages unless one of the numbers is in a set of predetermined numbers, such as 0 and 7, and micrcomputer 61 begins with the pattern of the control signals identified by the value of the index so determined. A difference of first and second numbers represented by different instances cf the sensed digitized voltages is calculated and a value of the index is determined as a function of the difference unless the difference is in a set of predetermined numbers, such as 0, +3, and -3, and microcomputer 61 (fig 1 of 4,540,921) begins with the pattern of the control signals identified by the value of the index so determined. Microcomputer 61 (fig 1 of 4,540,921) in this way prevents sensed digitized voltages representing a number in a predetermined set, such as 1 and 7, fro being used to determine the beginning pattern of control signals. M.icrocomputer 61 (fig 1 of 4,540,921) repetitively senses the digitized voltages while the winding stages are teporarily unpcwered and determines the beginning pattern of the control signals as soon as a change occurs in any one of the sensed digitized voltages.

Tale 3 herein is equivalent to Table III in the Boyd Muller specification.

It is to be noted that in Boyd/Muller when the motor is operated in the agitate mode to reverse motor direction a definite time is allowed for the rotor to coast to a stop and then random restarting is effected with a 50 chance that the rotor will start in the wrcr.g direction necessitating adjustment of the commutation to reverse the rotor direction and accelerate to speed in tne right direction. This gives irregular accelerations to tre rotor and thus causes irregular washing action to result. Accordingly this invention is a mathematical way of finding where the rotor is and where the switching in the sequences will be. Thus with a transition the microcomputer calculates which switches should be on at any one time.

If we want to start at that time we apply power with those switches so set or indexed these tables and start applying power.

Timers are provided as follows: - SHORT TIMER, LONG TIMER, COMMUTATION TIMER.

In this implementation an INTEL 8049 1-chip microcomputer is used for motor control microcomputer 10. It contains an 8 bit timer. This timer can be driven by either an external oscillator or directly from the ALE pulse which is divided by a factor of 32 before entering the timer (ALE = CLOCK/32). The microprocessor clock runs at 10 MHZ so therefore a (10MHZ/15)/32=20.833 KHZ clock signal is applied to the timer.

This provides a count every 48 microseconds in the timer and in operation the timer is loaded with a count of 2 thus providing an interrupt pulse every 96 microseconds. This interrupt rate provides the base timing to the motor controller.

On interrupt the program is forced to jutnp to a Timer Interrupt Routine. On entry to this routine the timer is reldaded with a count of 2 to provide the 96 microsecond base time This routine has two major functions: (i) Decrementing Timer Register counts every 96 mi cro second S, and setting the appropriate timeout flag where the counts reach zero.

There are three timer registers used.

(a) Short Delay Timer (b) Commutation Delay Timer (c) Long Delay Timer.

Tne registers (a) and (b) are decrerented each interrupt, therefore using a count of 01H to OFFER timers (a) and (b) can achieve time intervals of 96 microseconds to 24 millisenconds (ie. 256 x 96 microseconds). For extended time delays using register (c), an interriediate prescaler register which is initially set to 7FH (127) is decremented every interrupt. Only when the Prescaler Register reaches zero is the register (c) decremented. Therefore the long timer can achieve time intervals of 127 x 96 = 12 milliseconds to 127 x 256 x 96 microseconds = 3 seconds.

In order for the main program to use these time delays a count must be put into the appropriate Timer Register. The timer flag must then be tested periodically to see whether the time is up.

(ii) Tne second function of this routine is to provide the Speed Demand Rate function 16 of fig 1. ie. to provide a count rate to position error counter 15 equal to the required motor commutation rate. This a achieved by setting the Speed Rate Timer Register (RATETMR) equal to the count for the period of the rec,uired commutation rate eg. AC CS PE ED, ENDSPD. Thus on every timer interrupt the RATETMR is decremented and once it is zero the Pcsiticn Error Counter 15 is decretmented. The RATETMR is automatically reloaded with the correct count and the cycle repeats for continuous operation.

Referring now the Figure 6 which is a flow chart of the reversing sequence of the present invention it will be assumed that the microcomputer has timed out the application of power to the motor and the motor is switched off i.e. all power is disconnected from the stator. A long timer 40 is set to 150-200 milliseconds preferably 180 milliseconds which is an arbitrary maximum time of coasting. As stated power is turned off as indicated in block 41 and a check is made in block 42 of the register DIRECT provided in the microcomputer 10 to indicate whether the motor is going clockwise or counterclockwise. In the event that direction of rotation is clockwise the register value is changed to counterclockwise ready for starting in the next direction and vice versa, so that the appropriate blocks 43 and 44 are used as required. There is a second timer called the short timer 45 which is set to a value of 40 milliseconds. This timer provides a safety feature in that should the rotor stop then of course the succession of EMFs will also stop and no measurable signals will be transmitted to the microcomputer to work on. Accordingly the second timer assists in avoiding tnaloperation.

There is a third timer which is the commutation timer 46 which is set to 20 milliseconds. Now that value corresponds to a rate of occurrence of zero crossings sufficiently low as to allow reversing to take place. Next there is a tag rotor (tag corresponding to R3 in the Boyd Muller Specification) position indicator, block 47, which senses the position of the rotor.

This is related to tables 4 and 5, table 4 being used when it is required to go from clockwise to counterclockwise and table 5 when it is required to go from counterclockwise to clockwise as is explained more fully in figure 8. Thus a start is made by inputting the values of A, E and C, that is the outputs cf the voltage digitising circuit. These are stored in memory as data 1 (block 60 figure 8) that is the location. Then the values corresponding to the EMF signals are inputted again and stored as data 2 block 61. These data 1 and data 2 are then compared in block 62. If they are equal and if the short timer is not equal to zero bock 63 that is to say a transition has not yet been reached the computer (as indicated by line 48) takes the measurements again of A, B and C, comparing then to the previous value. As soon as data 1 is not equal to data 2, data 1 is then subtracted from data 2 and this gives a value in hexadecimal for the transition. That is put into the storage register called "Taes" block 64. Then the flow diagram is traversed further to see if tne modulus of data 2 minus data 1 equals 0, 1, 2 or 4 each of which is one of the ailowed values. If it is not, there is something wrong and it is a matter of going back tc the beginning and restarting the whole procedure again because the values are incorrect for whatever reason. Normally hcwever such values are correct and there is a valid change and the routine above set forth is then moved out of. If there is no transition within 40 milliseconds as indicated by the short timer then the rotor is down to a speed at which reverse direction can take place. If a transition is obtained within 20 milliseconds as indicated by commutation timer then the rotor is still spinning at a rate greater than that allowable for reversal and it is necessary to run through the sequence again. If the long timer has not reached 0 as checked in block 49 then we have to check to see if the commutation timer is equal to 0 as checked in block 50, if it is not, then it is known that the rotor is still spinning. The sequence goes around monitoring the position, keeping up to date and getting a new value of the rotor position every time the sequence has gone through. If the long timer which is set for 180 milliseconds (a little longer than the expected coasting time), times out then it is necessary to apply a dynamic brake, e.g. by short circuiting all the windings one to the other. The short timer 45 is a safety device which ens position sensing) are chosen and windings energized which will cause a torque to the rotor which cause the rotor to reverse direction from its previous direction. If for example the EMF from the motor windings when the rotor is coasting are those resulting from clockwise rotation, such EMFs will follow the pattern of Figure 2, and supposing the rotor is in a position where EMF C is high, EMF B is low and EMF A is changing from low to high i.e. the transition point 55 in Figure 2 is reached and has been reached in time greater than 20 milliseconds (in normal operation) after transition point 56 has been reached. If power were applied to continue in the same direction the switchings to the windings would be A+ and iS- but since it is required to reverse direction and it will be seen that in Figure 3 transition point 57 corresponds to transition point 55 in Figure 2 se that to provide reverse torque switchings B+ and A- will energize the required windings. In some circumstances energizing of C- instead of A- may be used since EMF A is falling to the right cf transition point 57 while C is rising.

Thus in Table 4, Index 3 relating to table 2 is chosen in preference to Index 4 and when the EMF in the selected winding drops back to zero due to rotor speed dropping to zero cc::utation increments to index 4 in Table 2 and sequence continues in selected order. The position locp error counter 15 is set te a restart value ir. block 53a the speed demand rate 16 is set to a restart speed in block 53b and the microcomputer ten returns the tinting to a man commutation programme. Gf course during agitate the reverse routine shown in Figure 6 is reverted to at each reversal until the end of the wash cycle determined in this method by command module 11 which commands microcomputer 10 to cease and a further routine entered into e. g, draining then spinning.

It will be seen that by following the reverse routine in which the position of the rotor is monitored down to a point and speed in which the rotor is in condition for reversal a reversal can be effected in a single commutation period causing the motor to pass through the stop and reverse direction without loss of rhythm unless braking has had to be effected. When braking is effected it may be necessary to go back to the start routine above described in which the selected switches are turned on and indications from the windings used to indicate whether the rotor is moving in the right direction. If it is not, then the motor is force commutated to change direction of the rotor and pick up acceleration speed as above described. However this does not happen usually in practice but the smooth transition with change of direction within about one commutation period effected.

Furthermore even with dynamic braking in which the motor winding ends are connected together it is still possible to monitor the velocity of the rotor down to the point of reversal thus reducing the time in which reversal is effected. In the voltage digitizing circuit of Fig 5, unlike the Boyd Muller circuitry, the star point voltage VN is brought into the circuit 13. The voltage at the star point is the vector sum of the three E1"5F's generated in the windings and varies at the comnutation rate. The signals from the comparators are not in the same sequence as an open circuit when coasting but are in synchronism with the rotor and accordingly the velocity of the rotor can be measured and reversal commenced when the velocity falls to a desired level. Thus in testing for transitions and the agitating sequence has not been interrupted then the changes which take place are monitored and the numbers go fro all G's to all l's not all at the same time, but the pattern is sufficient to enable the time for reversal to be determined.

Thus referring figure 4, braking is effected by making switches 31, 32 and 33 conductive there is a small voltage drop in these switches and although VA VE and VC all move together and therefore it is not possible to tell the position of the rector, the comparators cf figure 5 will detect small voltage variations (about 1 or 2 volts) between the VA V5 and VC voltage and the VN voltage to enable the rate of movement to the indicated and passed on to microcomputer 10.

TABLE I P2 Rail Line Disable Sequence of Patterns D 7 Top 0 1 0 1 0 1 I G 6 Btm 1 0 1 0 1 0 I T A 5(B-) 1 1 1 1 C C L 4(Ct) 1 1 1 0 0 1 S I 3(A-) 1 1 0 0 1 1 G N 2(Bt) 1 0 0 1 1 1 A L 1(C-) 0 0 1 1 1 1 S 0(At) O 1 1 1 1 0 INDEX: O 1 2 3 4 5 INDEXR: . 0 1 2 3 4 5 CONTROL: A+ B+ B+ C+ C+ SIGNALS: C- C- A- A- B- B DIGITISED VOLTAGE 01 02 04 01 02 04 MASK: (B) (A) (C) (B) (A) (C) TABLE II DATA FOR COUNTERCLOCKWISE ROTATION P2 Rail Line Disable Sequence of Patterns D 7 Top 0 1 0 1 0 1 I G 6 Btm 1 0 1 0 1 0 I ---------------------------------------------------- T 5(B-) 0 0 1 1 1 1 A L 4(C+) 1 0 0 1 1 1 S 3(A-) 1 1 0 0 1 1 I G 2(B+) 1 1 1 0 0 1 N A 1(C-) 1 1 1 1 0 0 L S 0(At) 0 1 1 1 1 0 INDEX: O 1 2 3 4 5 INDEXR: 12 13 14 15 16 17 CONTROL: A+ C+ C+ B+ B+ SIGNALS: B- B- A- A- C- C DIGITISED VOLTAGE 04 02 01 C4 02 MASK: (C) (A) (B) (C) (A) (B) TABLE III CLOCKWISE ROTOR POSITION SENSING (LOW TO HIGHSPEED WINDINGS) B 0 0 1 1 1 0 A 1 1 1 0 0 0 C 1 0 0 0 1 1 HEX: 6 2 3 1 5 4 TAG: 2 -4 1 -2 4 -' (DATA2-DATA1) INDEX: 5 0 1 2 3 4 INDEXR: 5 0 1 2 3 4 APPENDIX TABLE IV CLOCKWISE TO COUNTERCLOCK ROTOR POSITION SENSING B O 0 1 1 1 0 A 1 1 1 0 0 0 C 1 0 0 0 1 1 HEX: 6 2 3 1 5 4 TAG: 2 -4 1 -2 4 -1 (DATA2-DATA1) INDEX: 3 2 1 0 5 4 INDEXR: 15 14 13 12 17 16 TABLE V COUNTERCLOCKWISE TO CLOCKWISE ROTOR POSITION SENSING ROTOR POSITION SENSING B 1 0 0 0 1 1 A 1 1 1 0 0 0 C O 0 1 1 1 0 HEX: 3 2 6 4 5 1 TAG: 2 -1 4 -2 1 -4 (DATA2-DATA1) INDEX: 3 2 1 0 5 4 INDEXR: 3 2 1 0 5 4 Turning now to the second aspect of the invention, as stated above the digitising circuit 13 is responsive to the Back EMF of the ECM 2 to provide a simulated signal indicative of the position of the ECM rotor.

Velocity control of the ECM 2 is provided by a microcomputer controlled digital implementation cf a position control loop referred to later. Position and velocity feedback information is contained in the outputs of the voltage digitising circuit 13. Commutation rate sensing software 14 in the motor control microprocessor 10 supplies a count of one to position error counter 15 for each commutation. Each count decrements the counter by one. The count rate is therefore proportional to motor velocity. Requested velocity information is provided by speed demand rate timer hardware/software 16 which supplies a count rate to position error counter 15 equal to the required motor commutation rate, that rate having been indirectly selected by appropriate actuation of manual selection controls in the user controls 9. Speed demand rate timer 16, amplifier stages, pulse width modulation controls 18, commutation control signal generator 8, commutation circuit 17, voltage digitising circuit 13 and commutation rate sensing circuit 14 define the feed back position control loop the summation point being the pcsitic error counter 15.

The position error counter 15 algebraically sums the positive pulse rates from the speed demand rate 16 and the negative commutation rate sensing device 12. The output from the position error counter 15 appears as an error signal being the algebraic difference between the two counts which controls the current (and hence power) in the motor by a Pulse Width Modulated Control Circuit 18 with current limit control 5. The error is the difference between the desired count as indicated from the speed demand rate indicator 16 as compared with the commutation rate device 14. A zero PWM rate is the equivaler.t of a zero count and a 100% PWM rate is the equivalent of a full scale count. This aspect is explained more fully in Patent Specification U.S. Serial No. 709043 Neil Gordon Cheyne filed 7 March 1985 which is incorporated herein by reference and which explains improved pulse width modulated control methods for controlling current (and hence power) to an inductive load with special applications to D.C. Motors. In this way the Digital Position control loop is arranged so that when the ECM is rotating at a speed less than that requested by Speed Demand Rate Timer 16 low speed power is increased until current limit is effected to give faster acceleration but during steady speed operation the error and hence PWM pulses are maintained and controlled to control the power input to the ECH to that which is sufficient to maintain speed.

User controls 9 are provided and in the preferred embodiment include a command microcomputer 19 which translates the user commands into signals to the motor control microcomputer 10.

Thus the speed demand rate is set by commands initiated by the user controls 9 and these controls have commands relating to a wash programme selection e.g. delicate, regular, heavy duty, wool, permanent press and also a selector relating to water level e.e. low, medium and high water level. Each of these imposes a different power demand, stroke angle, acceleration rate and speed from the other on the wash load imposed on the agitator 1 which is mounted within a spin tub 3 and water container 4 in the known way, In figure 1 the motor 2 is shown driving direct to the agitator 1 but of course an indirect drive could also be used.

The above describes an electronic controlling circuit which enables the speed of the motor 2 to be controlled.

Referring now to figure 9 this indicates a profile of velocity against tvme of one half cycle in the oscillatory rotation of the agitator by the motor 2. As may be seen power is applied to the motor to achieve three steps in the half cycle, an initial step 120 of acceleration from zero velocity to a desired maximum velocity a second step 121 at which the maxlmv: velocity is maintained until a cutoff point 122 is reached when power is removed from the motor and a third step during which the rotating assembly cf the motor and the agitator then coasts to a stop substantially in accordance with either for example curve 123 or as is shown in smaller pecked lines curve 124, the curve 124 starting from a different cutoff point 125 which will be explained further later. Thus there are three different times, an acceleration time 128, a plateau time referenced 129 when substantially constant speed is maintained sect to matters discussed below and a coasting time referenced 150. The sum of these times results in a total stroke time.

Of these times the acceleration time 128 and the plateau time 129 are electronically controllable but the coasting time 130 is dependent on mechanical conditions involving the inertia of the rotating assembly including the rotor of the motor and the agitator and associated drive gear against which is acting the resistance of the load of fabrics placed in the spin tub 3.

Accordingly the coast time 130 will depend on and vary according to the load placed in the washing machine plus other smaller factors such as the effect of heating up of bearings.

A desired washing action will vary from a gentle action if the delicate" control is actuated to a heavy duty vigorous action if the ?1heavy duty" control is actuated. In a particular washing machine which has been made, five types of washing actions had been provided as mentioned above namely delicate, regular, heavy duty, wool and permanent press and three different water levels so that it is possible to have 15 combinations or 15 different agitator velocity profiles that must be achieved.

To do this command microcomputer 19 feeds commands based on information from user controls 9 to the motor control microcomputer 10 which define the acceleration time, the stroke time and the maximum speed of rotation according to the selectior. made in the user control circuit 9 and which have been preprogrammed into the command microcomputer 19.

Motor control microcomputer 10 retains this information and commards the motor to agitate following the required prcfile via the digital position control loop as explained below repeatedly until instructed to stop by the command microcomputer 19.

The method for control of acceleration time 128 can be explained with reference to figure 10.

In figure 10 are shown typical curves of the velocity/time showing the effect of velocity demand on acceleration. Thus figure 10 is a plot of velocity versus time for the motor. The information provided by operating the user control in circuit 9 is based on the motor being started at zero speed and that the contents of the position error counter is at zero. Accordingly the command defines an acceleration rate i.e. requested velocity that must be achieved in the acceleration time 128 of figure 9.

That velocity can be provided either as motor RPM, agitator RPK or commutation rate ar.d suitable circuitry provided dependert on tne type of information provided. The various curves V1 to V4 in figure 10 show the different acceleration rates resulting frown velocity demand rates for one resistance to rotation of the rotor and show the time taken to reach a maximum velocity cr speed.

As can be seen in figure 9 acceleration rate increases with increasing speed demand rate. Each curve is essentially linear over its first portion. Time to reach requested speed is almost independent of speed demand rate but is a function of the loop Eain of the position control loop.

For any given velocity profile the acceleration must be such that a set speed i.e. the plateau speed 121 shown in figure 9 must be achieved in a certain time. Accordingly the ccr:canc mt be set to provide a definite acceleration rate i.e. reaching the set speed in a given time. However the load on the agitator is not at this time known and therefore initially a speed demand rate is initialised which will reach the maximum speed in the given time under arbitrary predetermined conditions. The preferred method of operation is to initially set a speed rate demand which will result in an acceleration rate which is slightly less than that ultimately desired and then to adjust the speed demand rate upwardly to the desired speed over the next dew cycles. Thus giving a wash action which is more gentle than would be obtained by moving quickly to the maximum speed with the possibility of overload occurring. This is achieved by adjusting the loop gain of the velocity control locp in any known way such that the time taken to reach the required plateau speed when speed demand rate timer 16 is loaded with that plateau speed rate is greater than the range of times required. One way is to adjust the error value contained in position error counter 15 required to achieve 100 PWM rate. If the load in the machine is light the agitator will accelerate to speed more quickly than if the load is heavy. Accordingly the present invention provides programming of the microcomputer such that the speed at the end of the required acceleration time is measured. If that speed is below the required speed the microcomputer issues an instruction to increase the speed demand rate at the beginning of the next agitatcr stroke. Similarly if the motor is above speed at that time the command is to reduce the speed demand rate and thus reduce the power applied to bring the motor up to the plateau speed. This testing of the acceleration rate is carried out on each half cycle whether that half cycle is in the forward direction as shown in figure 20 or in the reverse direction. Thus the oscillating rotation i.e. the back and forth motion of the motor 2 and the agitator 4 is such that the resistance to oscillation or rotation is measured at each half cycle and by modifying the acceleration rate to always bring that acceleration rate to a position where the plateau speed is achieved in the set acceleration time and substantial uniformity of operation is thus attained. Thus acceleration is controlled to achieve the desired plateau speed in the desired time, and this acceleration speed is maintained within practical limits.

Plateau speed is maintained by adjusting the speed demand rate 16 to the speed demand rate required for the plateau speed at titre 127 in figure 9.

However consideration must now be given to the circumstar.ce illustrated in figure 11. In this figure the demanded velocity is shown by a pecked line 13C. A series of curves are shown, the upper curve 131 showing an overshoot and curve 132 shcws a lesser overshoot while curves 133 and 134 show two undershooting curves of velocity. This is brought about by the varying position error count in the position error counter 15. If there is a heavy load it takes considerable rower to get to speed and tne power to get to speed is greater than that required to maintain that speed end that is indicated by a large counter value in the position error counter 15 and hence a high Fi\! ratio in circuit 18. Accordingly at the time of reaching the point 135 in figure 11 (which corresponds with point 127 in figure 9) there is more power applied to the motor than required to maintain the motor at the demanded velocity 137 and the motor will thus continue to accelerate for a short time and overshoot as can be seen by either of curves 131 and 132. This can be provided for by adjusting the value set in the position error counter 15. If the initial position error count is set at a low level there is an undershoot below point 135 with the power then being levelled off by the above checking of the speed and comparing that speed with a desired count rate or alternatively the acceleration power can be maintained to above point 135 so that there is an overshoot and then the automatic error counting is carried out to reduce the overshooting curve down to the demanded velocity straight line 137. The value of the position error counter or the speed demand rate can be adjusted at any time under control of the microcomputer so hat the actual count can be updated or modified as desired and since the counter is within the microcomputer, it can be loaded at any time.

Now the value cf that counter at 127 in figure 9 is an indirect measure of the wash load. Where we have a high value in the counter we have a large wash load, a small value in the counter shows a sm211 wash load. Now to further increase the power that we have applied to the load as that load increases in excess of that required to maintain the profile as explained to maintain a given level explained in background we can adjust the amount of overshoot to obtain any profile. What is done is that the value of the counter is adjusted such that with only water in the bowl there is no overshoot then as clothes are added or as the load is increased the value is adjusted in the counter to allow small amount of overshoot. Tnis small amount of overshoot increases the stroke length of the agitator slightly an Increases the turnover in the clothes. This is explained above in the background material but essentially wash action ie proviced by movement of clothes through the water and how vigorous this movement is determines the soil removal. However by increasing the stroke length slightly the required wash requirements are maintained. The acceleration rate and velocity desired in for example delicate wash are such that slight lengthening of the stroke angle does nct result in excessive washing actior..

The function of maintaining acceleration rate by adjusting the speed command rate and controlling overshoot allows slight increases so that under very heavy loads the stroke length is increased slightly. If the acceleration rate is not controlled then typically with a velocity controlled motor if just a final speed is requested, the error in position error counter increases and the acceleration rate decrease with load and results in a decreased stroke angle and lowered scil level r en' cv al It is necessary now to look at the coasting time and curves of figure 9. As stated above the deceleration rates of the agitator and motor are nct electronically controllable. The rotating assembly can only be allowed to coast to a stop or be braked to a stop and thus are not electrolc;lly controlled.

Now if the coast time were fixed so that it could be guaranteed that the motor would coast to a stop before an attempted reverse or almost to a stop before reversal could be effected it would be possible to end up with a shorter stroke time as the load increases because we have the sitation that the maximum time to coast to standstill is when there are no clothes in the water.

As the clothes load Increases the coasting time becomes shorter and thus the area under the curve in figure 9 becomes less and since that area is proportional to the stroke angle that we are applying to the clothes load or the agitator if deceleration is effected more quickly then the stroke angle applied to the load is decreased which is disadvantageous. The opposite effect is however desired namely that it is desired to increase stroke to the load as the load increases and therefore the following technique is also adopted. The stroke time is set to a precetermined figure by a command received from circuit 9. This stroke time is for practical purposes the same for all wash duties. This means that as the coast time decreases the plateau time must be increased so that the point 122 in figure 9 is not a Folr:t fixed In time but a point which is determined as follows. For each half cycle, the microprocessor measures the time to coast from plateau speed to substantially zero speed and the microprocessor subtracts that time from the stroke time and also subtacts the required acceleration time from the strcke time which leaves a plateau time required for the next stroke so that for each half cycle of the agitator the microprocessor calculates a new plateau time depending on the last ccasting time and as may be seen from figure 9 two different coasting times and two examples of different plateau times are shown. In the first the plateau time is the time to extend from point 127 to point 122 and for the second, assuming the same acceleration t;me, from the point 127 to the point 125 and the deceleratior or coasting curves are as showr. by the lines 123 and 124 respectively. Accordingly at least in the preferred form the invention comprises the combination of the three techniques for controlling acceleration and altering the acceleration time as desired controlling the overshoot cr undershoot in relation to the desired maximum speed in the second zone of figure 9, recalculating the plateau time for each half cycle depending on the coasting time in the last half cycle and then reverting the rotating assembly immediately at or near zero speed. This allows the maintenance of any required washing performance.

,erections are made continously and by monitoring the curves such as those shown in figure 9 cn a oscilloscope it can be seen that variations occur substantially all the time because the load on the agitator may well depend on the position of the clothes in the container and those clothes may be bunched or balled in some cases and almost immediately the bunching can be freed by the agitator action so that the load on a rest half cycle is considerably lighter than when the clothes are bunched. The time to accelerate to a given speed may take a number cf strokes te settle out as there is z high averaging put or which prevents big disturbances for example if a bunching is only momentary then if it were not for some delay in averaging cut there could be violent disturbances in the speed of actuation of the agitator and this could cause too vigorous an action and with a heavy load then there is an increased power input which is what is required.

In a less preferable alternative it is possible to allow the stroke time to vary. In such an alternative the maximum speed would be more closely monitored so that extra area under the curve of figure 9 and therefore the extra stroke angle for heavier loads would be gained by extending the power cut off point as required.

The sequence of operations will now be explained in relation to the flow diagrams shown in figures 12 to 16. The flow chart of the main routine shown in figure 12 can be explained with reference to figure 9. This is the routine required to agitate and the first initial block 140 is shown in more detail in figure 13 where the notations are: T-stroke is stroke time, W-ramp is ramp time, and End-speed is the maximum required speed. Once initialisation has taken place there are four things to dc, first it is necessary to start at the beginning of the stroke to accelerate till point 127 in figure 9 is reached to maintain a plateau speed along the plateau 121 shown in figure 9 and then to coast to a stop after power has been switched off at 122 and then to reverse the direction of agitation and recommence the cycle in a "upside down" disposition from that shown in figure 9. These steps are shown in figure 12 where acceleration is shown in block 141 maintain plateau speed shown in block 142 the decelerate or coast is shown in block 143 change direction is shown in block 144 and additionally in block 145 there is a decision to be made as to whether agitation is to be concluded and if so the command microcomputer 19 sends a signal to the motor control microcomputer to interrupt the sequence at a selected time that agitation is to be endec. If the answer is no then the accelerate maintain coast and change direction cycle is maintained for a further cycle and so on until the interrupt signal is given. A yes (Y) answer results in the end of agitation and the washing cycle then goes into a further routine which does not form part of the present invention.

Now measured and used as will be explained later.

As a next step it is necessary to know the speed to which the motor is to be accelerated. Again there is no information as to the speed likely to be attained in the time interval 128 on applying a known amount of power and accordingly as is shown in block 153 the speed to which the motor is to be accelerated referred to as ACC speed is shown as being the end speed I. e. the maximum speed to be obtained for the particular wash programme selected and the end speed for example as it is seen in figure 10 for any given velocity demand. Acceleraticn at the commencement is virtually linear and if commands are given to supply power to the motor so that a substantially linear acceleration is obtained up to the fixed demanded speed and for the first stroke the demanded velocity is to be equal to the plateau speed i.e. End-speed. However as explained above it is preferably to arrange the gain of the position loop such that acceleration is always less than normally required if initial acceleration speed demand rate equals End-speed when the agitator is operating in water only. The practical result of this is that End-speed or maximum speed is not actually achieved in time interval 128 for the first stroke.

Looking now at figure 14 which is a flow chart during the acceleration phase the timer is set to W-ramp which is a fixed time in block 154. This timer is a timer which is set to the time and then counts down to zero so it is set with an initial value that Is equal to the time that is required. It is set running which automatically happens when the timer is loaded and the microcomputer senses when it gets to zero so in future it knows how long it has taken to do something so the acceleration time is the acceleration portion shown in figure 9 namely slope 120. As shown in block 155 the microcomputer then loads the speed demand rate 16 and this is set at a rate equal to the acceleration speed which for the first stroke as we have discussed above is the End-speed as shown in block 153 figure 13. As shown in block 156 the rotor is started and accelerate takes place while as shown in block 157 the timer runs down to zero and at this stage the motor velocity will have reached about point 127 and at that point as shown in block 158 the actual speed is measured by use for example of the cor ;utation rate sensing shown in block 14 figure 1 where the interval between commutations is measured by the motor control tLlicorcomputer. That actual speed is compared with the speed which is required in block 19. If it is less than the End-speed then the microcomputer checks to see if the acceleration speed is less than an arbitrary maximum as seen in block 160. If it is then the acceleration speed is increnented ore step and detesting is carried out as seen ir, block 161. If the actual speed is not less than End-speed or acceleration speed is not less than the maximum then a check is made as in block 162 to check if the actual speed is greater than the End-speed. If no then again the test is ended. If it is greater than End-speed then as indicated i block 163 tests are made to see if the actual speed is greater than an arbitrary minicLc, if so then the acceleration speed is decremented by one step as indicated in block 164. In this way the acceleration rate is adjusted to provide an acceleration which will achieve the required demanded velocity within the time W-ramp. This process is effected for each half cycle.

Looking now at figure 15 which is the flow chart to maintain the plateau speed. The timer has been set to T-flat which initially was the timing calculated in block 151 of figure 13.

At point 127 figure 9 the speed demand rate is set to End-speed and the motor is intended to just maintain that speed. If the motor is not up to speed or above speed by this method the motor will automatically settle to the End-speed. The position error counter is also adjusted for whatever overshoot is required and this is illustrated in the flow chart of figure 15 where a test is made by the microcomputer in block 165 to see if the acceleration speed is greater than the End-speed if not, then no adjustment is made as indicated in block 166. If it is greater, then the position error counter is adjusted by an increment which is a constant K times the acceleration speed minus the End-speed. Of course if undershoot is desired the sign in this formula would be reversed. However in practice undershoot is not desired if the required speed is not achieved after Initialisation step. After the adjustment has been made in block 173 the motor continues at its desired speed until the timer counts down to zero as shown in block 174. At this stage, which is point 122 on the curve of figure 9, power is cut off to the motor. It is to be noted that the question of compensation is one where if there is â large load of clothes then acceleration speed will be much greater than the End-speed and an overshoot curve such as that of 131 or 132, figure 11, will be followed and the result of this is that the stroke angle will increase slightly as the load increases. The higher the load the slightly greater the stroke angle and this has an improved effect in maintaining a wash rate substantially constant as between a light and a heavy load. It is noted that the stroke time is maintained but the stroke angle increases. With a traditional agitator washing machine with an induction motor it has a fixed speed so that not only does the stroke time stay the same but the stroke angle is virtually always constant although under heavy load it may reduce slightly. With a traditional machine the actual stroke profile virtually does not change with load. The power that goes into the lcad increases but only sufficient to maintain that profile. The present invention modifies the profile in accordance with the load and that is novel. Thus in modifying the profile the present invention actually overadapts the acceleration power te give an overshoot to give a greater area under the curve of figure 9 and thus apply extra power where there is a heavier load which is a desired result of the present invention. Thus the tize to coast to zero is an indirect measure of the load on the agitator.

Having reached point 122 and the timer indicated in block 171 has timed out as shown in block 174 a coasting time of 180 milliseconds (just greater than the expected coast time) is chosen as shown in block 175 (figure 16) the motor turr.eci off as in took 176 and ther, the motor coasts and the agitator will slow down under the load imposed by the clothes and other frictional effects.

The microcomputer waits on speed to fall to zero or the timer to empty to zero as shown in block 177 whether the timer reaches zero or not is tested in block 178. If the timer equals zero then braking is effected as shown in block 179 and the coding T-flat = initial T-flat selected in the microcomputer as shown in block 180. In such a case the motor is restarted under circumstances above outlined in which it may restart in the right direction or the wrong direction at random and force commutating is necessary as described above. If the timer does not equal zero, the microcomputer is programmed te T-flat which equals the remaincer of the linear time plus the initial T-flat time. The time to coast to zero speed is an indirect measure of the load on the agitator. The position and speed of the rotor is measured and the information supplied to the microcomputer as is described above.

As described above, while the rotor is coasting, EMFs are generated in the one or more unused windings and these EFiFs can be sensed to indicate when an EMF changes sense i.e. crosses over 2 zero point. However other position or velocity and direction sensing devices can be provided e.g. Hall effect devices or light intercepting devices or with non ECM type eg. trush, indiotion or synchronous motors, it is still possible to measure the EMFs. However with such motors we do not need to know position, only speed. Thus the microcomputer senses when the rotor is approaching a position in which it is in condition for reversing and the time taken to reach this position is measured and used in calculating a new value of T-flat for the next half cycle. This is effected by taking the remainder of the timer of block 171 and if this time is not zero then the rotor has reduced to zero speed in less than 150 milliseconds.

Thus the calculation shown in block 151 (figure 13) of T-stroke minus W-ramp minus 150 milliseconds is modified by taking away the difference between 150 milliseconds and the actual time taken for the rotor to come to zero and that provides a new calculation for the plateau time which is substituted for that shown in block 151. However if the timer does get to zero in block 178 then the rotor is braked to stop in block 179 and the T-flat selected to be used is the initial T-flat as indicated in block 180. Once the rotor is at or near stopped, then unless the rotor has been braked to a stop as illustrated in block 179 then for an ECM, reversal is usually effected in a single cormutation period as is descrIbed above.

In the event that agitation is to cease as illustrated at 145 in figure 12 then other parts of the washing cycle take cver for example the drain is opened and the water allowed to drain out. As described above, the coasting time cf a previous half cycle is algebraically subtracted from the stroke time tc give the "power on" time for the next half cycle. However different adjustments are possible e. g. only every tenth or other number half cycle could be used to make the adjustment or the coasting times over a period, eg. cver one second averaged to give a "power cr." time for the next second.

An important aspect of the invention resides in the measuring of the coast time from the stroke time to give a npower on" time for the next half cycle. Thus although this invention has been described in relation to an electronically commutated motor which gives added advantages in controlling acceleration rates and maximum speeds, an important advantage of the invention is this aspect can be gained using other motor types for example an induction motor. Such a motor may only be accelerated in a manner broadly dependant on the number of poles in its rotor and the load. However by controlling the cut off point 122 at which power is applied to the motor by subtracting the coast time of one half cycle from the stroke time te give an acceleration time and plateau time for the next half cycle, considerable control is given to the rate of extracting dirt consistent with a desired degree of gentleness of washing.

Thus referring to figure 16a, a speed sensor driven by a rotor has a ring magnet 71 the multiple holes of which actuate a Fall effect transducer 72, the signals from which are in the fcrm of pulses which vary in lines according to the speed of rotation of the ring magnet 71. When the pulse time reaches a predetermined length of time, reversing is effected.

Also photo sensitive devices can be used, for example as described in U.S. Patent Specification 4,005,347 which is incorporated herein by reference. In either case the time between switching off power to the motor and the motor being in condition for reversing is measured and used in a next half cycle to determine the "power on" time which will give the required washing action.

Although the above descriptions are based on using a fixed stroke time, the invention in this aspect ca also be Fut into effect with a variable stroke time operation.

Thus where the stroke time is to be variable according to the load in the washing tub and referring to figure 9a, which is similar to figure 9, the acceleration time 81 plus the plateau time 82 are set by the operator according to a required gentleness or vigorousness of washing to a fixed "power on" time. A small load will give a coast time indicated between points 83 and 84 with a delay curve 85. A large load gives a steeper delay curve 86 with 2 coast time indicated between points 83 and 87 and accordingly the motor will be in condition for reversal much earlier than in the light load coast time curve 85. If reversing is thus effected with a shortened stroke time more consistent washing performances will be obtained, whether the load is small cr large.

Claims (1)

1. CLAIMS 1. A method of cyclically reversing an electronically commutated motor having a plurality of windings on 2 stator and a rotor having magnetic poles rotatable relative to said stator and using electronic control apparatus and means to indicate the position of the rotor said method cor!prising the steps of (a) Initiating and then continuing a correct sequence of commutations for a desired time or desired number of commutations, (b) Removing all power from the windings and allowing the rotor to coast towards zero rotation, (c) Testing the position of the rotor relative to the stator, and (d) When the rotor is in condition to be reversed and its position relative to the stator is known, changing the sequence of commutations to cause the rotor to change direction the correct commutations following automatically to maintain rotor rotation in the changed direction, and repeating steps t6 give cyclical reversal for a desired time.

   2. A method as claimed in claim 1 which includes the steps of following the direction and sequence of EMFs In said windings after power has been removed therefrom and at least as the rotor nears a position where it is in condition for reversing checking the voltage transitions points between positive and negative for each winding and changing the sequence cf commutations to cause reversal about the time when a voltage transition point occurs in a selected winding.

   :. A method as claimed in claim 1 or claim 2 whIch includes the steps of testing the EMF from at least one winding for polarits and frequency and changing the sequence of commutations when the frequency has fallen to a value such that the rotor is in condition for reversing and the polarity is at cr near a zero crossing between opposite polarities in a selected winding.

   11. A method as claimed in claim 3 which includes the step of testing all the windings to indicate the position of the rot or.

   5. A method as claimed in any one of the preceding claims wherein said change in the sequence of commutations usually occurs within a single commutation change to cause a change in direction of rotation of the rotor.

   6. A. method of cyclically reversing an electronically comm uta ted rotor when effected substantially as herein described With reference to and as illustrated by the accompanying drawings.

   7. Control apparatus for an electronically commutated motor having a plurality cf windings on a stator adapted to be selectively cormutated and a rotor having magnetic poles rotatable relative to said stator said control apparatus comprising: (a) Timing means to time the period of rotation or counting means to count the number of rotations of the rotor in a desired direction, (b) Commutation switching means to disconnect power from said windings te allow the rotor to run down towards zero rota ti on, (c) Detecting means to indicate rotor position relative to said stator, and (d) Pattern reverse means operable in response to a signal from said detecting means when the rotor is in condition to be reversed to cause the control signals to cause commutation changes which cause said rotor to change direction without testing for rotor direction.

   8. Control apparatus as claimed in claim 7 wherein said detecting means detect the direction and sequence of EMFs in each said winding after power has been removed therefron- and detect voltage transition points between positive and negative polarity and said pattern reverse means are actuated te reverse the sequence of commutations about the time when a voltage transition point occurs In a selected winding.

   9. Control apparatus as claimed in claim 7 or claim 8 wherein said control apparatus includes: (e) A commutating circuit responsive to said control signals to cause electrical power from a power source to be applied commutatively to said winding and intended to cause said rotor to rotate in a desired direction, (f) Testing means responsive to any EMF generated in at least one unpowered winding to test the polarits and frequency cf any EMF generated in that unpowered winding (g) Commutation reversing means to reverse commutation to give the correct sequence cf commutation to rotate the rotor In the desired direction.

   (h) Commutation reversing actuating means to reverse commutation when said frequency is at a value such that the motor is in condition to be reversed and the polarits in a selected winding is at or near a zero crossing between opposite polarities.

   10. Apparatus as claimed in any one of claims 24 to 28 wherein braking means to brake the motor and provided comprising switching means having some inpedance to connect one end of each winding to a similar end of other windings, the other end of the winnings being connected together and comparator means are provided to compare the voltages between opposite ends of the wlndlngs to enable the speed of the rotor during braking to be established.

   11 . Control apparatus for an electronIcally commutated rotor when onstructed arranged and operable substantially as herein described with reference to figures 1 to 8 of the accompanying $drawings.

   12. A method of cyclically Ccn of power to an electric motor having a rotor said method including the steps of starting rotation of said rotor in one direction setting an Initial power on" time Icrlrg which power is applied to said motor, switching off power at the end of said initial "power on" time, causing the rotor to slow until in a condition to be reversed, checking the ramp down time the rotor takes to slow to a condition ready for reversal, causing reversal of directior, of rotation of said rotor, as soon as the rotor is in condition to be reversed, and repeating the said steps as desired.

   13. A method of cyclically controlling, the supply of power to an electric motor having a rotor said method including the steps of setting a desired time of rotation of said rotor in one direction starting rotation of said rotor in said one direction setting an initial "power on" time during which power is applied to said motor, switching off power at the end of said initial "power on" time, causing the rotor to slow until in a condition to be reversed, checking the ramp down time the rotor takes to slow to a condition ready for reversal, causing reversal of direction of rotation of said rotor, applying power to the applied to said rotor for é further power on time which is such that said further "pcwer on" time plus said ramp down time equals said desired time, switching off power to said rotor at the end of said further "power on" time, again checking the next ramp down time reversing direction of the rotor to said one direction when said rotor is in condition for reversal and applying power to said rotor for a still further "power on" time which is such that said still further "power onn time plus said next down ramp time equals said desired time and repeating the cycles for a desired length of time, adjusting the "power on" time at desired intervals of time so that the adjusted npower on" time for a further half cycle plus the down rar.p time for a previous half cycle equals said desired time.

   14. A method of electronically cyclically controlling the supply of power to an electric motor said method including the steps of setting a desired speed of rotation of the rotor of the motor, sensing the resistance to rotation of the motor and using responses from the sensing means to actuate adJustment means to adjust the power supplied to the motor to change the motor speed towards said desired speed and then operate the motor within a range of speeds at or close to said desired speed of rotation, switching off the supply of power to the motor, stopping its rotation and the repeating the cycle of operations wlth the motor running in the reverse direction.

   15. A method as claimed in lcaim 14 which includes the step of sen soring resistance to rotation by measuring the time the rotor takes to run down from a "power off" condition to a condition in which the rotor is in condition to be reversec.

   16. A method as claimed in claim 1b cr claim 1 which includes the steps cf effecting acceleration to cause the rotor to rotate initially just below the desired speed and adjusting the supply of power so that the speed rises to said desired speed.

   17. A method as claimed in claim li: cr claim 15 which includes tne steps cf effecting acceleration to cause the rotor to accelerate to a speed just above the desired speed and adjusting the power supply so that the speed falls to the desired speed.

   18. A method as claimed in any one of claims 12 to 17 which includes the steps of adjusting the level of overshoot cr undershoot in relation to a desired plateau level of constant speed to give a desired vigorousness of motion to the rotor.

   19. A method as claimed in any one of claims 12 to 18 which includes the steps cf (a) Continuing rotor rotation for a desired time, or angle of rotation, (b) Removing all power from the windings and allowing the rotor to coast towards a condition to be reversed, (c) Testing the position of the rotor relative to the stator, and (d) When the rotor is ir. a condition to be reversed and its position relative to the stator is known, changing the sequence of commutations to cause the rotor to change direction the correct commutations following automatically to maintain rotor rotation in the changed direction, and repeating the steps to give cyclical reversal for a desired time.

   20. A method as claimed in claim 19 which includes the steps cf following the direction and sequence of EMFs in said windings after power has been removed therefrom and at least as the rotor nears a position where it is in condition for reversing checking the voltage transitions points between positive and negative for each winding and changing the sequence cf commutations to cause reversal about the time when a voltage transition point occurs in a selected winding.

   21. A method as claimed in claim 14 or claim 20 which includes the steps of testing the EMFs from at least one winding for polarits and frequency and changing the sequence of cormutation when the frequency has fallen to a value such that the rotor is in condition for reversing and the polarity is at cr near a zero crossing between opposite polarities in a selected winding.

   22. A method as claimed In claim 21 whlch includes the step of testing all the windings to indicate the positicr; of the rotcr.

   23. A method as claimed in ar.y one of claims 19 to 22 wherein salo change in the sequence of commutations usually occurs within a single e commutation change to cause a change in dIrection of rotation of the rotor.

   A A method of electronically cyclically controlling a motor when effected substantially as herein described with reference to and as illustrated by figures 9 to 16a cf the accompanying drawings.

   25. An electrical control means for cyclically controlling the supply of electrical power to an electric motor having a rotor said control means comprising switching means to switch power to said motor on and cff, coasting timing means to time the length of time said rotor takes from the time power is switched off thereto to the time when said rotor is in condition for reversal of direction of rotation, and reversing means to reverse the direction of said rotor when said rotor is in condition for reversir; & anc to ssnteh on said switching means when reversing is to be effected.

   26. An electrical control means for cyclically controlling the supply of electrical power to an electric motor having a rotor said control means comprising; switching means to switch power to said motor on and off, power timing means te time the length of power time when power is switched on, coasting timing means to time the length of time said rotor takes from the time power is switched off thereto to the time when said rotor is in condition for reversal of direction of rotation stroke timing means to time the stroke time during which said rotor rotates between reversals setting means to set said stroke timing means to a desired stroke time, algebraic subtracting means to algebracially subtract a previous coast time from said stroke time to arrive at a time setting for said power time and reversing means to reverse the direction cf said rotor when said rotor is in condition for reversing and to switch on said switching means when reversing is to be effected.

   27. An electronic control means for cyclically controlling the supply of electrical power to an electric motor said electronic control means including setting means operable to set a desired speed of rotation of the rotor of said motor, sensing means to sense resistance to rotation of the motor and adjustment means responsive to said sensing means to adjust the power supplyed to the motor to accelerate said motor towards the desired speed and to then operate the motor within a range of speeds at or close to said desired speed of rotation, switching means to switch off the supply of said motor after a desired time and reversing means operable when said motor is in condition for reversing to cause the cycle of operating to be repeated with the motor running in the reverse direction.

   28. Apparatus as claimed in claim 27 wherein said sensing means to sense resistance to rotation of the rotor comprise timing nears to measure the time the rotor takes to run down from a power off" condition to a condition in which the rotor is In ccnditicn to be reversed.

   29. Electronic control means as claimed in claim 27 or claim 28 wherein reversing means are provided comprising (a) Counting means to count the time of the period of rotation or the number of rotations of the rotor in a desired dIrection, (b) Corr.nutatlon switching means to disconnect power from said windngs, (c) Detecting means to indicate rotor position relative to said stator, and (d) Pattern reverse means operable by a signal from said detecting means to cause the control signals to cause ccrrzWtaticr. changes which cause said rotor to change direction without testing for rotor direction.

   30 Electronic control apparatus as claimed in claim 29 which includes (e) A commutating circuit responsive to said control signals to cause electrical power from a power source to be applied commutatively to said windings and intended to cause said rotor to rotate in a desired direction, (f) Testing means responsive to any EMF generated in at least one unpowered winding to test the frequency and polarity of EMFs generated in that unpowered winding, (g) Commutation reversing means to reverse commutation to give the correct sequence of commutation to rotate the rotor in the desired direction when the frequency are fallen to a value at which the rotor is in condition for reversal and this polarity of a selected winding is at or near a zero crossing between opposite polarities.

   31. Apparatus as claimed in any one of claims 25 to 30 wherein braking means to brake the rotor are provided comprisln switching means having some Inpedance to connect one end cf each winding to a similar end of other windings, the other ends of the windings being connected together and comparator means are provided to compare the voltages between opposite ends of the windings to enable the speed of the rotor during braking to be established.

   32. Electrical control means for cyclically controlling the supply of electrical power to an electric motor having a rotor said control means comprising switching means te switch power to said motor on and off, "power on" timing means to time the length of "Fower on" time when power is switched on, coasting timing means to time the length of coasting time said rotor takes from. the time power is switched off thereto to the time when said rotor is ir, condition for reversal of direction of rotation stroke ar.d reversing means to reverse the direction of said rotor when said rotor is in condition for reversing and te switch on said switching means when reversing is to be effected.

   33. Electrical control means as claimed in claim 32 wherein a stroke time during which said rotor rotates in one direction between reversals is the sum cf said "power on" time and said coasting time.

   34. Electrical control means for cyclically controlling the supply of electric power to a rotor when constructed arranged and operable substantially as herein described with reference to figures 1 to 16a of the accompanying drawings.

   35. A method of operating a laundry machine havlrg a container for a wash load of soiled fabrics in wash water arc a reciprocable agitator in said container and an electric rotor driving said agitator said method comprising the steps of starting rotation of said rotor in one direction setting an initial "power on" time during which power is applied to said motor, switching off power at the end of said initial "power on" time, allowing the motor to slow down until in a condition to be reversed, checking the time between the power off condition and a condition when the rotor is In condition to be reversed causing reversal of direction cf the rotor as soon as the motor is in condition for reversal and repeating the said steps as desired.

   36. A method of operating a laundry machine having a container for a wash load of soiled fabrics in wash water and a reciprocatable agitator in said container, an electric motor driving said agitator, setting means to set a desired rate and amplitude of oscillating rotation of said agitator an electronic control means controlling the supply of electrical power to said electric motor in one of a plurality of sequences said method including the steps of setting a selected one of said plurality of sequences se that said agitator is driven in oscillating rotation during a wash phase in a sequence of washing operations, sensing the resistance to oscillation of said agitator due to the wash load in said container and adjusting the power supplied to said electric motor so that a selected rate of removal of soil from said soiled fabrics is substantially achieved.

   37. A method as claimed in claim 36 which includes the step of sensing load on said motor by measuring the time the motor takes to run down from a power off condition to a condition in which the motor is in a condition for reversal.

   38. A laundry machine including a container for a wash load of soiled fabrics in water a reciprocatable agitator in said container an electric motor driving said agitator, setting means te set a desired rate and amplitude of oscillating rotation of said agitator, electronic control means controlling the supply cf electrical power to said electric motor in one of a plurality of selected sequences so that said agitator is driven in oscillating rotation during a wash phase selecting means for selecting a desired one of said sequences so that a washing action selected form such as delicate, regular, heavy duty, wool, and permanent press washing actions is to be effected by the machine said electronic control means including sensing means to sense the resistance to oscillating rotation of said agitator due to the wash load in the container and adjustment means responsive to said sensing means to adjust the power applleo te said electric motor so that a washing action results such that a selected rate of removal of soil from said soiled fabrics is substantially achieved.

   39. A laundry machine as claimed in claim 38 wherein said ,rotor is an electronically commutated motor aC. A laundry machine as claimed in claim 38 or 39 wherein said electronic control means include a timing means setta bl e to cause power to be applied to said motor within a predetermined acceleration time the applied power teing E:,C. as to accelerate the motor substantially to a predetermined maximum velocity within that time said timing means being also settable to fix a stroke time during which the motor is rotating in one direction for substantially that stroke time, the motor rotating from a stopped position to a substantially stopped position in that stroke time, said timer means being also settable to cause said maximum velocity to be maintained for a desired period and then to cause disconnection of power from the motor at a time such that the deceleration of the motor occurs within such time that power may be then applied to reverse motor direction approximately at the end of the stroke time, error ,easurir!g means being provided to measure any error between the actual stroke time and the desired stroke time and using the measure of that error to correct the cutoff point of power for the next stroke of the agitator being rotated by the motor.

   41. A laundry machine as claimed in claim 39 or claim 4G wherein said electronic control means supply power during acceleration such that a velocity slightly below said maximum velocity is obtained and the power is then adjusted to bring the velocity up to substantially said desired maximum velocity.

   42. A laundry machine as claimed in any one of claims 38 to 41 wherein said electronic control means supply power during acceleration such that a velocity slightly above said maximum velocity is obtained and the power is then adjusted to bring the velocity down to substantially said desired maximum velocity.

   43. A laundry machine as claimed in any one of claims 38 to 42 wherein adjustment means are provided te give a desired level of overshoot or undershoot of a desired contant speed to give a desired vigorousness of motion te said agitator.

   44. A laundry machine as claimed in any one of claims 38 to 43 wherein the time during which acceleration is carried out and the time during which said maximum velocity is substantially maintained are each constant.

   45. A laundry machine as claimed in any one of claims 38 to 44 wherein said sensing of the amplitude of the rotor velocity is effected by an ES'F sensing means.

   46. A laundry machine as claimed in claims 38 to 4; wherein monitoring means are provided to monitor the velocity of the motor with said EMF sensing means while in the decelerating mode.

   47. A laundry machine as claimed in any one of claims 38 to 46 wherein power control means are provided to control the supply of power after said acceleration period and before disconnecting power from said motor so that initial variations from a desired maximum speed are corrected to modify the motor speed to close to the desired maximum motor speed.

   48 A laundry machine as claimed in any one of claims 38 to 47 wherein reversing means are provided comprising (a) Timing means to time the period cf rotation or counting means to count the number of rctaticr.s of the rotor in a desired direction, (b) Commutation switching means to disconnect power from said windings, (c) Detecting means to indicate rotor position relative to said stator, and (a) Pattern reverse mea..s operable by a signal from said detect nag means when the rotor 15 j r. in condi or to be reversed to cause the control signals to cause commutatio changes which cause said rotor to change direction withou testir. jr for rot or dire ot. or.

   49 A laundry machine as claimed in claim 46 which includes (e) A commutating circuit responsive to said control sIrel tc cause electrical power from a power source to be applied commutatively to said windings and intended to cause said rotor to rotate in a desired direction, (f) Testing means responsive to any EMF generated in at least one unpowered winding to test the Folarits and frequency of any EFs generated in that unpowered

   The preceding claims have been superseded by the following claims:1. A method of electronically cyclically controlling the supply of power to an electric motor said method includinc the steps of settinc a desired speed of rotation of the rotor of the motor, sensing the resistance to rotation of the motor ano using responses from sensing means to actuate adjustment means to adjust the power supplied to the motor to change the motor speed towards said desired speed and then operate the motor within a range of speeds at or close to said desired speed of rotation, switching off the supply of power to the motor, stopping its rotation and then repeating operations with the motor running in the reverse direction and repeating the forward and reverse cycles as desired.

   2. A method as claimed in Claim 1 which includes the step of sensing resistance to rotation by measuring the time the rotor takes to run down from a "power off" condition to a condition in which the rotor is in condition to be reversed.

   3. A method as claimed in Claim 1 or Claim 2 which includes the steps of effecting acceleration to cause the rotor to rotate initially just below the desired speed and adjusting the supply of power so that the speed rises to said desired speed.

   4. A method as claimed in Claim 1 or Claim 2 which includes the steps of effecting acceleration to cause the rotor to accelerate to a speed just above the desired speed and adjusting the power supply so that the speed falls to the desired speed.

   5. A method as claimed in any one of Claims 1 to 4 which includes the steps of adjusting the level of overshoot or undershoot in relation to a desired plateau level of constant speed to give a desired vigorousness of motion to the rotor.

   6. A method as claimed in any one of Claims 1 to 5 which includes the steps of: (a) Continuing ro-tor rotation for a desired time, or angle of rotation, (b) Removing all power from the windings and allowing the rotor to coast towards a condition to be reversed, (c) Testing the position of the rotor relative to the stator, and (d) When the rotor is in a condition to be reversed and its position relative to the stator is known, changing the sequence of commutations to cause the rotor to change 'direction the correc-t commutations following automatically to maintain rotor rotation in the charged direction, ad repeating the steps to give cyclical reversal for a desired time.

   7. A method as claimed in Claim 6 which includes the steps of following the direction and sequence of EMFs in said windings after power has been removed therefrom and at least as the rotor nears a position where it is in condition for reversing checking the voltage transitions points between positive and negative for each winding and changing the sequence of commutations to cause reversal about the time when a voltage transition point occurs in a selected winding.

   8. A method as claimed in Claim 7 which includes the steps of testing the EY.zs fro at least one winding for polarity and frequency and changing the sequence of commutation when the frequency has fallen to a value such that the rotor is in condition for reversing and the polarity is at or near a zero crossing between opposite polarities in a selected winding.

   9. A method as claimed in Claim 8 which includes the step of testing all the windings to indicate the position of the rotor.

   10. A method as claimed in any one of Claims 7 to 9 wherein said change in the sequence of commutations usually occurs within a single commutation change to cause a change in direction of rotation of the rotor.

   11. A method as claimed in any one of the preceding Claims using an electronically commutated motor.

   12. A method of electronically cyclically controlling a motor as claimed in any one of the preceding Claims when effected substantially as herein described with reference to and as illustrated by figures 9 to 16a of the accompanying drawings.

   13. A method of operating a laundry machine having a container for a wash load of soiled fabrics in wash water a spin tub in said container and a reciprocatable agitator in said spin tub, said agitator and said spin tub being driven by an electric motor the supply of power to said electric motor being cyclically controlled by a method according to any one of the preceding claims in one of a plurality of sequences and said etoc including the steps of setting a selected one of said lurality of sequences so tat said agitator is driven in oscillating- rotation during a wash phase in a sequence of washing operations, and adjusting the power supplied to said electric motor so that a selected rate or removal of soil from said soiled fabrics is substantially achieved.

   14. A method of operating a laundry machine as claimed in Claim 13 including the step of setting said derived speed of rotation and the power applied to said motor so that washing action selected from such as delicate, regular, heavy duty, wool, and permanent press washing actions is to be effected by the machine said sensing means sensing the resistance to oscillating rotation of said agitator due to the wash load in the container and said adjustment means being responsive to said sensing means to adjust the power applied to said electric motor so that a washing action results such that a selected rate of removal of soil from said soiled fabrics is substantially achieved.

   15. A method of operating a laundry machine as claimed in Claim 13 or Claim 14 when effected substantially as herein described with reference to and as illustrated by the accompanying drawings.

   16. An electronic control means for cyclically controlling the supply of electrical power to an electric motor said electronic control means including setting means operable to set a desired speed of rotation of the rotor of said motor, sensing means to sense resistance to rotation of the motor and adjustment means responsive to said sensing means to adjust the power supplied to the motor to accelerate said motor toward the desired speed and to then operate the motor within a rance of speeds a or close to said desired speed of rotation, switching means to switch off the supply of said motor after a desired time and reversing means operable when said motor is in condition for reversing to cause the cycle of operating to be repeated with the motor running in the reverse direction.

   17. Electronic control means as claimed in Claim 15 wherein said sensing means to sense resistance to rotation of the rotor comprise timing means to measure the time the rotor takes to run down from "power off" condition to a condition in which the rotor is in condition to be reversed.

   18. Electronic control means as claimed in Claim 16 or Claim 17 wherein reversing means are provided comprising (a) Counting means to count the time of the period of rotation or the number of rotations of the rotor in a desired direction, (b) Commutation switching means to disconnect power from said windings, (c) Detecting means to indicate rotor position relative to said stator, and (d) Pattern reverse means operable by a signal from said detecting means to cause the control signals to cause commutation changes which cause said rotor to change direction without testing for rotor direction.

   19. Electronic control means as claimed in Claim 18 which includes (e) A commutating circuit responsive to said control signals to cause electrical power from a power source to be applied co-..rutatively to said windings and intended to cause said rotor to rotate in a desired direction, (f) Testing means responsive to any EMF generated in at least one unpowered winding to test the frequency and polarity of EMFs generated in that unpowered winding, (g) Commutation reversing means to reverse commutation to give the correct sequence of commutation to rotate the rotor in the desired direction when the frequency are fallen to a value at which the rotor is in condition for reversal and this polarity of a selected winding is at or near a zero crossing between opposite polarities.

   20. Electronic control means as claimed in any one of Claims 15 to 19 wherein braking means to brake the rotor are provided comprising switching means having some inpedance to connect one end of each winding to a similar end of other winnings, t other ends of the windings being connected together and comparator means are provided to compare the voltages between opposite ends of the windings to enable the speed of the rotor during braking to be established.

   21. The combination of electronic control means as claimed in any one of Claims 16 to 20 and an electric motor connected to said control means so as to be controlled thereby.

   22. The combination as claimed in Claim 20 wherein said electric motor is an electronically commutated motor.

   23. Electronic control means as claimed in any one of Claims 15 to 21 when constructed and arranged and operable substantially to and as illustrated by the accompanying drawings.

   A. A laundry machine includr.g ; container for a wash of of soiled fabrics in water a spin tub in said container a reciprocatable agitator in said spin tub, the combination of Claim 20 or Claim 21 with said electric motor selectively driving said spin tub and said agitator, and said electronic control means controlling the supply of electrical power to said electric motor in one of a plurality of selected sequences so that said agitator is driven in oscillating rotation during a wash phase and selecting means for selecting a desired one of said sequences so that a washing action selecteLfrom such as delicate, regular, heavy duty, wool, and permanent press washing actions is to be effected by the machine said adjustment means being responsive to said sensing means to adjust the power applied to said electric motor so that a washing action results such that a selected rate of removal of soil from said soiled fabrics is substantially achieved.

   25. A laundry machine as claimed in Claim 24 wherein constructed arranged and operable substantially as herein ---- described with reference to and as illustrated by the . accompanying drawings.