GB2093180A

GB2093180A - System for Determining Distance Velocity and Acceleration

Info

Publication number: GB2093180A
Application number: GB8202504A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-02-17
Filing date: 1982-01-29
Publication date: 1982-08-25

Abstract

A system for the measurement of the distance travelled, velocity and acceleration of linear, rotary or reciprocating motion, utilises a scale and an interacting sensor unit, one mounted on the moving part and the other on the fixed part and a microprocessor which calculates and displays the desired results from the interactions between scale and sensor. In the preferred embodiment, the device can measure or compare the quality of the ride of a lift or elevator car. A film strip comprising alternate exposed and unexposed portions is fixed up the length of the lift shaft and interacts with a photoelectric sensor on the lift. A velocity-time graph is produced by the microprocessor as a measure of ride quality and may be stored and compared with the ride at a later date. The sensor may alternatively be inductive, magnetic or fluidic. <IMAGE>

Description

SPECIFICATION Device for Measuring Velocity, Displacement, and Acceleration This invention relates in general to a system, model or mechanism where a measurement of linear or rotary motion is required. In particular this invention relates to the qualitative and quantitative measurement of velocity, displacement and acceleration of a lift car (or an elevator car) relative to the surrounding lift shaft structure.

The said invention is described in detail in the following paragraphs mainly as a device to measure velocity, displacement and acceleration of lift cars. However, as the device is both flexible (that is adaptable) and portable, it has other applications: some of which are mentioned in the foregoing paragraphs.

The measurement of uniform linear velocity is usually a simple problem to solve; accurate measurements of the distance travelled and the time taken is all that is usually necessary. (In case of a rotational motion revolutions per unit time are required to be measured).

However, when it comes to the measuring of velocity, acceleration and displacement of a body travelling with a nonuniform velocity or nonuniform acceleration the accurate measurement of the said velocity end the said acceleration can be a rather cumbersome task.

Measurements of the above values of velocity and acceleration in the laboratory conditions can be achieved in some cases by using different setups to suit each particular application. Equipment such as "ticker tape" is used for the measuring of acceleration but involves labourious measurements to interpret the results.

Measurements in actual "field conditions" can be even more difficult or in some cases impossible using a "ticker tape" device.

Optical shaft encoders or pulse generators are sometimes employed for the measurement of angular displacement and rotational speed. This technique involves use of an optical device and an encoder; which usually is a glass or transparent plastic disc with specially generated lines or markings which are scanned by the optical device resulting in a "pulse" which-is used to calculate the speed and the angular displacement.

Unfortunately, these devices require a special encoder disc for each particular application and although very accurate in measurement are quite expensive (because of the special discs) in use, and unsuitable for linear measurements. The said encoders are also impractical to use for "in field" conditions for applications such as lift cars of different types.

There have been attempts made and inventions claimed involving some electromagnetic or optical device to generate status signals which are then processed by a monitoring system of a lift car so as to give an early warning of any developing malfunction of the system (consisting of one or more lifts) before the actual breakdown occurs. However, such systems are elaborate, expensive and purpose built to serve a particular installation. Their main function is to monitor the faults and not the evaluation of the quality of the "ride" of the lift.

These devices are also not portable enough for the field engineers to carry with them and use on different lift cars.

The device claimed in the present invention offers a simple solution to many of the above problems. The said device is easier to setup and the results of the measurements are obtained instantly without waiting for an interpretation.

The values of the velocity, acceleration and displacement are shown on an electronic display or can be printed out in neumeric or graphic form.

The motions under study could be linear unidirectional, linear reciprocating, rotary unidirectional or rotary reciprocating. Velocity and the accelerations involved could be uniform or nonuniform.

Some examples of the applications of the said device are: 1 ) Measurement of the change in acceleration of a piston of a reciprocating engine as the said engine speeds up from zero to its peak rotating speed. The said device can handle this using a simulated laboratory set-up. See Figure 6.

2) Measurement of the quality of the ride of a lift car. This involves measuring the values of the velocity and acceleration at different points in a typical operating cycle of a lift car. The typical operating cycle is the pattern of speeding the said lift car from rest, achieving full velocity (in up or down direction), and slowing down to a halt at the chosen floor. A typical velocity diagram of the said cycle of operation would look similar to that shown in Figure 4. The said device can be used to set-up or test the "quality or ride" of the said lift as required (by adjusting the equipment that controls the lift car) and recording in graphic or neumeric form the accepted quality of the ride of the said lift car.In case of a future complaint from the user of the said lift installation, the said device can be used again to compare the values of the said velocity and the said acceleration and the said graphic diagram (if taken previously) to find out if there has been any deterioration in these values to the detriment of the "quality of the ride" of the said lift car. Up on this examination, suitable corrective action can be taken if required.

Accordingly several objects of my invention are: The invention claimed is a compact, portable unit suitable for carrying to different locations with ease.

The said device is easy to set-up and will give instantaneous readouts in neumeric or graphic form and on a hard copy if required.

The said device is relatively inexpensive to manufacture and to use especially when a specially exposed cine film (8, 1 6 or 32 millimetres size) is used as a sensing medium.

The said film can be cheaply produced and can be carried quite easily on a suitable spool. The said film is also easy to repair or extend in length when required.

Further objects and advantages of my invention will become apparent from the drawings and the ensuing description thereof.

The invention will now be described in more detail with reference to the accompanying drawings wherein:- Figure 1 is a schematic drawing illustrating the main embodiments of the invention claimed.

Figure 2 is a flow chart showing a typical method in which the signal generated by the sensing unit is processed to produce the required information with the help of a microprocessor.

Figure 3 shows a typical application where the device is used to measure the quality of the ride of a lift car.

Figure 4 shows a typical pattern of velocity diagram of a lift car cycle of operation.

Figure 5 shows a laboratory application of the said device to measure rotational speed and acceleration.

Figure 6 shows another laboratory application of the said device to measure a reciprocating motion simulation.

Figure 7 shows the preferred embodiment of the said sensor unit using a cine film as a sensing medium and a photo-electric type sensor.

Figure 8 shows the detail of a typical pattern on the said cine film used as a sensing medium.

Referring to Figure 1, it can be seen that the main embodiments of the device claimed in this invention are:- a) The sensor unit b) Microprocessor c) Registers, digital and graphic output devices and controls.

The above mentioned parts are described in detail as follows:- a) The Sensor Unit: This essentially consists of a sensing medium and a sensor. The sensor can be a photo-electric, magnetic, fluidic inductive, or electromagnetic device. The sensor is so arranged that it scans a suitable medium such as a perforated tape, magnetised tape, a film such as a cine film exposed in a particular way, slide or a disc with suitable markings or a chain. The sensor in conjunction with the sensing medium is capable of producing suitable signals or pulses which are fed into the microprocessor (b).

b) The Microprocessor: The microprocessor consists of suitable electronic components and micro-chips and other suitable ancilliary components so as to be able to process the input signal into the required digital or graphic output.

No particular micro-chips or components are mentioned by their trade name or cataloque numbers as it will be obvious to any suitably qualified person informed in microprocessors that such a microprocessor can be constructed by choosing from many of the several components available on the market. However, it will suffice to say that the said microprocessor will essentially consist of a power unit, an in-board clock of suitable frequency, a binary or suitable interface, suitable microchips to carry out the various mathematical functions within the microprocessor, a timer and counter, buses, input and output ports, printer interface and other interfaces, several memories, buffers, and suitable printed circuit board and connections all assembled within a suitable container.There are provided facilities for an input from the sensor and output from the microprocessor by the way of suitable cables or ribbons to a separate unit (item (c) in Figure 1.) consisting of registers and controls. The exact selection of the various components within the microprocessor will depend upon the general construction of tile microprocessor and the software used to programme the microprocessor.

c) Registers Digital and Graphic Output Devices and Controls: The registers and the controls are housed in a separate unit (c) which is designed as a remote control unit and is connected to the microprocessor (b) by a length of suitable cable or ribbon. The said unit (c) houses all the digital registers, and also controls necessary to switch the power on and to reset the said device and to "zero" the registers that record the measurements and to control the output devices such as a printer, plotter or a cassette recorder to record the said results.

It should be noted that the Figure 1 is not drawn to any scale and the actual sizes of each embodiment shown and its actual position relative to other embodiment bears no relation to their relative sizes shown in Figure 1.

The operation of the said device claimed in this invention will now be described in greater detail with reference to Figures 1, 2, 3, 4, 5, 6, 7, and 8.

For the ease of understanding the description is divided in the following manner: Description Part 1: the generation of the signal Description Part 2: Processing of the signal within the microprocessor.

Description Part 3: Description of the registers and controls.

Description Part 4: General comments and brief description of the laboratory uses of the said device.

Description Part 1: The generation of the signal: Throughout this part and all subsequent parts (that is description parts 1 to 4 inclusive) the sensor unit is considered to be in its preferred embodiment as shown in Figure 7, which shows a cine film f being scanned by a photo-electric sensors. The cine film may be 8 mm, 16 mm or 32 mm size film which is suitably exposed so that a continuous pattem of dark frames separated by a narrow strip of clear film Is formed on the said film as a result of the said exposure. Figure 8 shows detail of a typical cine film with the said alternating pattern of dark frames and clear strips formed on it. The said film has to be previously prepared in this manner before the said film can be used with the said sensor as a sensing medium.The said sensor in the preferred embodiment will consist of a projector and a receiver type photo-electric sensor used either singly or in multiplicity. The said projector is supplied with a suitable electric supply and when this said supply is switched on the projector will produce a beam of light which when received by the receiver results in generation of a signal as an output from the sensor unit. Thus whenever there is a relative motion between the film f and the sensor s; the sensor s will produce a signal each time the clear part of the said film f passes the beam of the projector part of the said sensor s. It is therefore quite clear from this description that the time interval between each successive said signal is the time interval required for each said dark frame to pass in front of the said beam of the said sensor.Figure 7 shows only one sensor employed to do the scanning, however as mentioned earlier additional sensors can be added to scan the same said film f simultaneously in order to increase the sensitivity of the said sensor if required. Therefore in case of the relative motion between the said film f and the said sensor s being of a uniform nature, the time intervals between the said successive signals will be exactly the same. In case of the said relative motion being of a changing nature such as involving an acceleration or deceleration, the time interval between the said signals will constantly change.

Whatever means of scanning are used, there has to be a relative motion between the said film f and the said sensors. Any one of these two elements may be stationary according to the particular application.

In the preferred embodiment of my invention as shown in Figure 3, the said device is being used to measure the "quality of the ride" of a lift car on a typical installation. Here the said sensor s is mounted in a suitable position on the said lift car and the said film f is suitably attached to lift shaft structure. The said arrangement being such that as the said lift travels up or down the said lift shaft, the said sensors scans the said film f; thus generating the said signals which are fed into the said microprocessor (not shown in Figure 3) in the form of an interrupt pulse.

Description Part 2: Processing of the signal generated within the microprocessor.

The flow chart shown in Figure 2 illustrates how the signal generated by the said sensor s is processed within a typical microprocessor. The said interrupt pulse generated by the said sensor s is fed into a binary or suitable interface via input ports of the said microprocessor. The said pulse is fed into an AND gate (item G in Figure 2), along with the clock pulse. The said AND gate is so arranged that when both the inputs (that is the said interrupt pulse and the said clock pulse) are present the gate will deliver an output signal which will be in harmony with the clock pulse; this uniform pulse will be used as a counting pulse for the time interval. This uniform pulse is fed into a counter and accumulator T which holds the total interval of time (in seconds) at any given moment as St (total elapsed time).The said interrupt pulse (which is in harmony with the output of the sensor unit s and hence in harmony with the speed of scanning) is fed to a counter IC which counts the total number of interrupts and holds the total in its accumulator as Sn (total number of interrupts at any given moment which is a pure number). The value of Sn at any given moment is fed into a multiplier D which multiplies the value of Sn by a constant X where X is the distance in millimetres the said sensing film f has to travel before interrupting the said beam of the said sensor s. The said multiplier D holds in its accumulator the total value of SnxX at any given moment which is the value of the distance scanned by the said sensor s in millimetres.The output of multiplier D is fed to a divider DM which divides the value of its input by 1000 to give the total distance travelled by the said lift (that is scanned by the said sensor) at any given moment in metres.

The output of multiplier D (which is a value in millimetres) and the output of accumulator T (elapsed time in seconds) is fed to velocity counter V~where the velocity u in m7fnmetres per second at any given moment is worked out by dividing the distance Snxx by St It will be obvious that this value of v (in millimetres per second) will be constant in case of the scanning with a uniform velocity; and will constantly change in case of a nonuniform velocity. (An alternative method of finding the value of velocity can be employed depending upon the construction of the microprocessor where: dlaO v At where dl and dO are the successive values of the distance travelled and At is the time interval between them.) The output of V is fed to the memory stack MV and the divider AV where the acceleration at any given moment is calculated using the following formula: V?-VO acceleration- At Where VX and VO are the two successive values of velocity and At is the time interval between them.

Thus it has been shown that the total elapsed time in seconds is calculated at T, the total distance travelled is calculated in metres at DM, the velocity of scanning at any given moment is calculated in millimetres per second at V and the acceleration in millimetres per second persecond is calculated at AV.

It is of course possible to generate information in units other than mentioned above by making suitable changes in the microprocessors's soft ware and programming.

Description Part 3: Description of the registers and controls.

The registers and controls are housed in a hand-held type extension which can be remote to the main microprocessor housing.

Thus it is not necessary to ride on the top of a lift car to operate the said device. Once the said sensor unit s (see Figure 3) is set up on the lift, the operator of the said device can ride inside the said lift car in complete safety with the said hand held unit c (Figure 1) containing the said registers and the said controls and also can further connect to the said unit c a printer or a plotter if required to keep the record on a hard copy. It should be noted that for the sake of clarity the unit c is not shown in Figure 3.

The said extension unit c would typically consist of four main registers with suitable electronic displays to indicate the values of the registers. These registers are: (Fig. 2).

Register I: showing the elapsed time in seconds.

Register Ill: showing the distance travelled in metres Register IV: showing the velocity in millimetres per second.

Retglsfer V: showing the acceleration in millimetres per second per second.

There can be an additional register II which can display the set value of x which is fixed for a particular set up.

The unit c has also facility for an output to a printer or a plotter where the values of the said velocity and the said acceleration can be printed out.heumerically or plotted in a graphical form.

Alternatively, the digital record can be stored on a magnetic tape by using a suitable tape and a cassette recorder.

The said extension c may also be provided with' suitable controls which are: Sw the switch to switch the power on.

R, R1 and R3 the reset buttons respectively to reset the clock, the Register I and the Register Ill respectively.

In addition, there could be additional switches to indicate to the said plotter or the said printer the direction of travel and also to control the perriferrials such as the plotter, printer, or the tape recorder etc.

It is necessary to point out that the description of the unit so far described is mainly for the preferred mode of the invention and the units in which the information is displayed by the register I to V inclusive can be changed to any other suitable system of units for applications other than the preferred mode and the microprocessor can be reprogrammed to suit.

Applications of the said device for laboratory use can be briefly described with the help of Figures 5 and 6.

Figure 5 shows the device being used to measure a rotating motion; where the film f is wound round a suitable transparent drum or cylinder CF. The shaft of the cylinder CF is connected to the rotary output being measured (not shown) in a suitable manner. The sensor s is suitably mounted so that the cylinder CF together with the film f passes between the projector and the receiver of the sensor s, thus producing a signal pulse which is further processed by the microprocessor unit (not shown in this Figure).

Figure 6 shows the said device being used to analyse a reciprocating motion simulation. It can be seen from the Figure 6 that a piston 12 is given a reciprocating motion through a connecting rod 11 and a crank 10 so that the simulated piston 12 reciprocates between the flat plate guides 13 and 14. In this Figure the piston is shown as of rectangular cross section. A sensor s is attached to one face of the piston so that the sensor s and the piston 12 move as one part. The sensor s is suitably provided with power through an extending cable. The sensing film f is fixed to the guide 14 in such a manner that the film f passes through the sensors; thus allowing the said sensor s to scan the said film f as the piston 12 reciprocates under the infiuence of the links 11 and 10. The sensor s thus will produce a signal pulse which is processed by the said microprocessor (not shown) and the results obtained and displayed by the said unit consisting of the registers and controls (not shown).

For applications where optical method of scanning is unsuitable the said sensor can be made from an inductive, magnetic or a fluidic device with suitable sensing medium in the shape of a film, a tape with perforations, a slide or a disc (with suitable markings, interruptions, holes, notches etc.) or a magnetic tape with suitable recordings.

Claims

1. A system for measuring and monitoring the quality of the ride of a lift car from a suitable position on the said lift car. The said system comprising of a sensor unit, a microprocessor and display registers and controls with suitable neumeric or graphic recording of the results as an additional facility. The said system operating in such a manner that suitable signals are generated as an interaction between the elements of the said sensor unit in the event of any apparent motion between the said elements of the said sensor unit; the signals from the said sensor unit being processed by a suitable microprocessor constructed and programmed to calculate the results required and the said results being, displayed or recorded in a suitable manner.

2. The system essentially as in claim 1 where the two elements of the said sensor unit comprise of a specially exposed cine film and a photo electric device.

3. A system essentially as per claim 1 and 2 except that the manner in which the two elements of the said sensor unit are arranged being suitably changed to suit application other than the lift cars, such as in case of rotating or reciprocating motion.

4. A system, substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 8 of the accompanying drawings.