GB2135477A - Motor control system - Google Patents
Motor control system Download PDFInfo
- Publication number
- GB2135477A GB2135477A GB08304881A GB8304881A GB2135477A GB 2135477 A GB2135477 A GB 2135477A GB 08304881 A GB08304881 A GB 08304881A GB 8304881 A GB8304881 A GB 8304881A GB 2135477 A GB2135477 A GB 2135477A
- Authority
- GB
- United Kingdom
- Prior art keywords
- motor
- rotor
- equilibrium
- signal
- point
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
- G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
- G05B19/21—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device
- G05B19/23—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for point-to-point control
- G05B19/231—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for point-to-point control the positional error is used to control continuously the servomotor according to its magnitude
- G05B19/234—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for point-to-point control the positional error is used to control continuously the servomotor according to its magnitude with current or torque feedback only
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/41—Servomotor, servo controller till figures
- G05B2219/41021—Variable gain
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/41—Servomotor, servo controller till figures
- G05B2219/41339—Using, switch reluctance or asynchronous motor in, to stepping mode motor
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/42—Servomotor, servo controller kind till VSS
- G05B2219/42122—First open loop, then closed loop
Landscapes
- Engineering & Computer Science (AREA)
- Human Computer Interaction (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Control Of Position Or Direction (AREA)
Abstract
Method of controlling the position of the rotor of a motor connected to a position transducer which serves to produce a cyclic signal in which at consecutive zero crossings the time derivative of the output signal changes. The method comprises controlling the motor current in a servo loop in dependence upon the output of the position transducer whereby to define a plurality of positions of stable equilibrium spaced from one another by points of unstable equilibrium. In order to move the rotor by one increment, a current pulse is applied to the motor to provide an initial bias to deflect the rotor in the direction of desired motion and the polarity of the feedback signal in the servo loop is reserved to change the point of stable equilibrium into one of unstable equilibrium and the adjacent point of unstable equilibrium into one of stable equilibrium. Thus, the rotor moves rapidly to the next zero crossing at which point the rotor is prevented from further movement by the servo loop.
Description
SPECIFICATION
Motor control system
The present invention relates to a control system for a motor and is particularly concerned with the system for controlling motor to move a member driven by the motor, such as a robot arm, rapidly to an accurately predetermined position.
It is already known to mount on a motor an angular position transducer or shaft encoder to provide information regarding the position of the rotor. When the rotor is in a predetermined position, the position can be maintained by means of a negative feedback loop in which the motor current is controlled by the output of the angular position transducer.
If, for example, the encoder produces a triangular waveform as the motor shaft rotates, then at every second zero crossing there is a point of stable equilibrium at which movement of the shaft away from the equilibrium point results in a motor current which applies a torque to return the rotor to the equilibrium position.
In such a system where a motor is controlled by feed back from a position transducer, every other zero crossing is a point of unstable equilibrium. In this case, movement away from the point of equilibrium results in a torque which rapidly increases to move the rotor away from the point of unstable equilibrium.
Though the servo system described above can be used to maintain the position of a motor once it has reached a predetermined position, it offers no solution to the problems of reaching that position.
The invention seeks to enable a rotor to be moved rapidly to an accurately predetermined position.
According to the one aspect of the present invention, there is provided a method of controlling the position of the rotor of a motor connected to a position transducer operative to produce a cyclic signal in which at consecutive zero crossings the time derivative of the output signal is of opposite sign, the method comprising controlling the motor current in a servo loop in dependence upon the output of the position transducer whereby to define a plurality of positions of stable equilibrium spaced from one another by points of unstable equilibrium and, in order to move the rotor by one increment, applying a current pulse to the motor to provide an initial bias to deflect the rotor in the direction of desired motion and reversing the polarity of the feedback signal in the servo loop to change the point of stable equilibrium into one of unstable equilibrium and the adjacent point of unstable equilibrium into one of stable equilibrium, whereby the rotor moves rapidly to the next zero crossing at which the rotor is prevented from further movement by the servo loop.
In accordance with a second aspect of the invention, there is provided a control circuit for an electric motor which comprises an angular position transducer for producing a cyclic signal having consecutive zero crossings of opposite slope, means for applying a current to the motor in dependence upon the output signal of the transducer to stabilise the position of the motor at a zero crossing, means for reversing the polarity of the feedback signal to provide incremental movement of the rotor to a point corresponding to an adjacent zero crossing and means for applying an initial acceleration pulse to the motor to ensure movement in the desired direction when the polarity is reversed.
The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:
Figures 1 a and 1 b show output signals in phase quadrature derived from an angular position transducer, and
Figure 2 shows a block circuit diagram of a control system in accordance with the invention.
In Figure 1, there is shown the output of a transducer. The waveform illustrated is triangular but alternatively it could be in the form of a sine wave. The zero crossings of the triangular wave form designated A and B correspond to points of equilibrium in that at these points the motor current determined by the servo loop will be zero and there will be no torque on the motor to move.
Some of these points will however be stable and others unstable.
Assuming that the points designated A are those of stable equilibrium. In these cases, movement of the rotor to one side of the point will result in a current of such polarity as to tend to return the rotor to the point of stable equilibrium.
At the other points, any movement away from the point of equilibrium will result in a current causing the motor to move still further away from that point. If the polarity of the feedback signal is reversed, then the points A will be unstable and the points B will be stable.
It is known to position the motor by other means until its position corresponds to one of the points of stable equilibrium and having reached that position to switch on the feedback loop for the purpose of maintaining that position.
In the present invention, each of the zero crossings is a possible point at which the motor can be brought to rest. If the feedback signal is reversed when the motor is at position Al then that point will be unstable but both of the adjacent points B1 and B2 will be stable. The motor shaft will move in an arbitrary direction and on reaching one of the points B1 or B2 will come to rest again.
In the system of the invention, to move the motor from the position Al to the position B1 a pulse is first applied to displace the rotor in the right direction and subsequently the polarity of the feedback loop is reversed. In other words, the rotor is given an acceleration in the right direction before the polarity is reversed. Using this method of control, a conventional motor can be used to provide accuracy of positioning comparable with that of a stepper motor with the rotor moving by increments from one zero crossing to the next.
Furthermore, on reaching the desired position the servo loop will ensure that no further movement should occur.
A circuit for implementing this method of control is shown in Figure 2 in block diagram form. The output of the shaft encoder is applied to a circuit 10 which produces position and velocity information. The output signal of the circuit 10 is applied by a way of a switch 16, a summation amplifier 14 and a gained controlled amplifier 20 to produce a control signal for the motor on the output line, thereby completing the servo loop.
The movement of the motor is effected by means of a control logic circuit 1 8 receiving three inputs.
The first being a signal as shown in Figure 1 B in quadature with the output signal of the transducer applied to the circuit 10, the second being a pulse indicating that movement is required and the third being a signal on a line to indicate direction of movement required.
When it is desired to move the rotor, the control logic circuit 1 8 applies an input to the acceleration unit 12 which superimposes a pulse on the error signal. The duration of this pulse is determined by the quadrature signal (see Figure 1 B), the acceleration pulse being removed when or before the quadrature signal crosses through zero corresponding to a peak of the error signal.
The control logic 1 8 also applies a signal to the gain controlled amplifier 20 to alter the polarity of the control signal thereby converting the stable point of equilibrium to one of unstable equilibrium and causing an incremental movement of the motor.
By switching the polarity of the feedback loop every 1 80 electrical degrees, it is possible to increment the motor fairly rapidly to the desired position and when the desired position is reached the polarity of the feed-back loop is allowed to remain fixed so that the motor remains in the desired set position.
The purpose of the switch 1 6 is to enable the feedback loop to be open circuited so as to permit open loop control of the motor. When the motor is to be moved by a considerable distance, the position control servo is open circuited and the motor is controlled by a separate control loop to achieve coarse positioning in as rapid a time as possible, once the arm is within close distance of its desired position the incremental servo described above is switched in by closing the switch 16 to take over to control and move the arm in small steps until the desired position is achieved with precision.
An advantage of the control system as described above is that while it does not use stepper motors, it enables control of a motor of a robot or a machine tool to be effected by means of a digital computer with which the logic circuit may interface directly.
Claims (5)
1. A method of controlling the position of the rotor of a motor connected to a position transducer operative to produce a cyclic signal in which at consecutive zero crossings the time derivative of the output signal is of opposite sign, the method comprising controlling the motor current in a servo loop in dependence upon the output of the position transducer whereby to define a plurality of positions of stable equilibrium spaced from one another by points of unstable equilibrium and, in order to move the rotor by one increment, applying a current pulse to the motor to provide an initial bias to deflect the rotor in the direction of desired motion and reversing the polarity of the feedback signal in the servo loop to change the point of stable equilibrium into one of the unstable equilibrium and the adjacent point of unstable equilibrium into one of stable equilibrium, whereby the rotor moves rapidly to the next zero crossing at which the rotor is prevented from further movement by the servo loop.
2. A control circuit for an electric motor which comprises an angular position transducer for producing a cyclic signal having consecutive zero crossings of opposite slope, means for applying a current to the motor in dependence upon the output signal of the transducer to stabilise the position of the motor at a zero crossing, means for reversing the polarity of the feedback signal to provide incremental movement of the rotor to a point corresponding to an adjacent zero crossing and means for applying an initial acceleration pulse to the motor to ensure movement in the desired direction when the polarity is reversed.
3. A control circuit as claimed in claim 2, in which the encoder is operative to produce a signal of triangular waveform.
4. A control circuit as claimed in claim 2 or 3, wherein the control signals for initiating movement are derived from a digital computer.
5. A control circuit substantially as herein described with reference to and as illustrated in the accompanying drawings.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08304881A GB2135477B (en) | 1983-02-22 | 1983-02-22 | Motor control system |
EP19840900867 EP0135546A1 (en) | 1983-02-22 | 1984-02-22 | Motor control system |
PCT/GB1984/000056 WO1984003368A1 (en) | 1983-02-22 | 1984-02-22 | Motor control system |
JP50096584A JPS60500590A (en) | 1983-02-22 | 1984-02-22 | motor control system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08304881A GB2135477B (en) | 1983-02-22 | 1983-02-22 | Motor control system |
Publications (3)
Publication Number | Publication Date |
---|---|
GB8304881D0 GB8304881D0 (en) | 1983-03-23 |
GB2135477A true GB2135477A (en) | 1984-08-30 |
GB2135477B GB2135477B (en) | 1986-04-23 |
Family
ID=10538403
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08304881A Expired GB2135477B (en) | 1983-02-22 | 1983-02-22 | Motor control system |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0135546A1 (en) |
JP (1) | JPS60500590A (en) |
GB (1) | GB2135477B (en) |
WO (1) | WO1984003368A1 (en) |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4130786A (en) * | 1976-11-17 | 1978-12-19 | Xerox Corporation | Apparatus for generating linear and continuous positional error and velocity signals for higher order servo systems |
CH651948A5 (en) * | 1980-08-17 | 1985-10-15 | Maag Zahnraeder & Maschinen Ag | POSITION CONTROL DEVICE WITH A DIGITAL INCREMENTAL MEASURING DEVICE. |
-
1983
- 1983-02-22 GB GB08304881A patent/GB2135477B/en not_active Expired
-
1984
- 1984-02-22 JP JP50096584A patent/JPS60500590A/en active Pending
- 1984-02-22 WO PCT/GB1984/000056 patent/WO1984003368A1/en not_active Application Discontinuation
- 1984-02-22 EP EP19840900867 patent/EP0135546A1/en active Pending
Also Published As
Publication number | Publication date |
---|---|
EP0135546A1 (en) | 1985-04-03 |
GB2135477B (en) | 1986-04-23 |
GB8304881D0 (en) | 1983-03-23 |
JPS60500590A (en) | 1985-04-25 |
WO1984003368A1 (en) | 1984-08-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JPS61185095A (en) | Controlling method for step motor | |
EP0267964A4 (en) | System for controlling the tapping operation. | |
JPS5916292B2 (en) | Spindle control method | |
US4426608A (en) | Stepping motor control system | |
US4484126A (en) | Induction motor controller | |
US3463985A (en) | Closed loop stepping motor control system | |
EP0012619A2 (en) | Machine tool drive motor control system | |
EP0089673A1 (en) | A circuit and a method for processing amplitude and phase variable multiphase signals which are required as current or voltage reference to drive synchronous motors | |
US4476420A (en) | Circuit arrangement for synthesizing a sinusoidal position signal having a desired phase and high-resolution positioning system making use of the circuit arrangement | |
GB2135477A (en) | Motor control system | |
KR910002565A (en) | Robot Control Method | |
SU1159146A1 (en) | Digital closed electric drive | |
US3803469A (en) | System for controlling speed of the tape drive in a tape recording and replaying apparatus | |
US3514680A (en) | Retrotorque braking for step servomotors | |
JPS57211605A (en) | Controlling system for track of robot | |
SU801217A1 (en) | Stepping motor control device | |
Kuo et al. | Modeling and simulation of a stepping motor | |
SU1310775A1 (en) | Servo electric drive | |
SU969109A1 (en) | Digital control servo system | |
JPS6186811A (en) | Step feed actuator device having variable stop position | |
SU1730610A1 (en) | Digital tracking system | |
SU779972A1 (en) | Two-channel follow-up drive | |
US3532958A (en) | Closed loop position control system employing a step-motor | |
Joshi et al. | Stepper Motors Controller | |
JPS63121497A (en) | Feedback controller for pulse motor |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |