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

Definitions

• 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 predeter ⁇ mined position.
• 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.
• 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.
• 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 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 curre ⁇ t 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
• 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.
• Figures la and lb show output signals in phase quadrature derived from an angular position transducer
• FIG. 2 shows a block circuit diagram of a control system in accordance with the invention.
• FIG 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.
• 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 Bl and B2 will be stable. The motor shaft will move in an arbitrary direction and on reaching one of the points Bl or B2 will come to rest again.
• a pulse is first applied to displace the rotor in the right direction and subsequently the polarity of the feedback loop is reversed.
• the rotor is given an accele ⁇ ration in the right direction before the polarity is reversed.
• 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.
• FIG. 2 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 18 receiving three inputs from suitable position setting means.
• the first is a signal as shown in Figure IB in quadature with the output signal of the transducer applied to the circuit 10, the second signal is a pulse indicating that movement is required and the third is ⁇ a signal on a line to indicate direction of movement required.
• the control logic circuit 18 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 Fig. IB), the acceleration pulse being
• the control logic 18 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.
• the purpose of the switch 16 is to enable the feedback loop to be open circuited so as to permit open loop control of the motor.
• 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 control and move the arm in small steps until the desired position is achieved with precision.
• 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.

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• 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)
• Numerical Control (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10538403

Family Applications (1)

Country Status (4)

Family Cites Families (2)

• 1983
  • 1983-02-22 GB GB08304881A patent/GB2135477B/en not_active Expired
• 1984
  • 1984-02-22 WO PCT/GB1984/000056 patent/WO1984003368A1/en not_active Ceased
  • 1984-02-22 EP EP19840900867 patent/EP0135546A1/de active Pending
  • 1984-02-22 JP JP59500965A patent/JPS60500590A/ja active Pending

Non-Patent Citations (1)

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