Position controller

• US 6,515,442 B1
• Filed: 05/24/2001
• Issued: 02/04/2003
• Est. Priority Date: 09/28/1998
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Yaskawa Denki
• Original Assignee: Kabushiki Kaisha Yaskawa Denki
• Inventors: Murata, Kenichi, Kaku, Yasuhiko, Zhang, Wennong, Okubo, Tadashi
• Primary Examiner(s): Salata, Jonathan
• Assistant Examiner(s): Duda, Rina I.
• Application Number:
  US09/806,025
• Time in Patent Office: 621 Days
• Field of Search: 318/560, 318/568.18, 318/568.22, 318/615, 318/618, 318/632
• US Class Current: 318/560
• CPC Class Codes: G05B 19/19 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
• CPC Class Codes: G05B 2219/41117 Cancel vibration during positioning of slide

Abstract

To overcome the problem of a low frequency disturbance causing minute vibrations affecting response attributable to the difficulty of adaption to the phase of the vibrations, the present invention provides a position controller, which includes a subtracter for subtracting a motor position signal from a movement position signal to produce an angle-of-twist signal; a high-pass filter for advancing the phase of the angle-of-twist signal; a low pass filter for eliminating only high-frequency components of the signal received from the high-pass filter; a circuit for multiplying the signal from a low-pass filter by a torque-corrective gain to produce a torque-corrected signal; a torque correction evaluation section for varying the torque-corrective gain according to the position deviation signal that is the difference between a position command and the movement position signal; and a subtracter for combining the torque-corrective signal and the torque command to produce a new torque command.

Claims

1. A position controller comprising:

a position control section in which a position. command and a detected movement position are inputted and from which a speed command is outputted;

a speed control section in which the speed command and a motor speed are inputted and from which a torque command is outputted;

a current control section which receives the torque command to perform amplification and outputs a current;

a motor which rotates by being supplied with the current;

a motor position detector which detects a rotational displacement of the shaft of the motor and outputs a motor position signal;

a speed processor which receives the motor position signal and outputs a motor speed signal; and

a movement position detector which detects the position of a movement section driven by the motor and outputs a movement position signal and provided with;

a motor speed-control function which makes the speed command and the motor speed signal coincident by feedback control; and

a motor position-control function which makes the position command and the movement position signal coincident by feedback control, wherein said position controller is provided with;

a subtracter which subtracts the motor position signal from the movement position signal and outputs an angle-of-twist signal;

a high-pass filter which outputs the angle-of-twist signal with its phase advanced, upon receiving the angle-of-twist signal;

a low-pass filter in which the signal from the high-pass filter is inputted and which outputs the signal with only its high-frequency components eliminated;

a coefficient multiplier which receives the signal from the low-pass filter, multiplies it by a torque corrective gain, and outputs a torque correction signal;

a section for torque correction evaluation which varies the torque corrective gain based on a position deviation signal that is the difference between the position command and the movement position signal; and

a subtracter which subtracts the torque correction signal from the torque command to produce a new torque command.

2. A position controller as set forth in claim 1, wherein

in said section for torque correction evaluation, when the absolute value of the position deviation signal is equal to or greater than a reference value, the torque corrective gain is set to zero and when the absolute value of the position deviation signal changes to be equal to the reference value or below, the torque corrective gain is changed from zero to a constant value.

3. A position controller as set forth in claim 1, wherein

in said section for torque correction evaluation, when the absolute value of the position deviation signal is greater than a reference value, the torque corrective gain is set to zero and when the absolute value of the position deviation signal changes to be equal to the reference value or below, the torque corrective gain is continuously changed from zero to a constant value.

4. A position controller comprising:

a position control section in which a position command and a movement position are inputted and from which a speed command is outputted;

a speed control section in which the speed command and a motor speed are inputted and from which a torque command is outputted;

a current control section which receives the torque command to perform amplification and outputs a current;

a motor which rotates by being supplied with the current;

a motor position detector which detects a rotational displacement of the shaft of the motor and outputs a motor position signal;

a speed processor which receives the motor position signal and outputs a motor speed signal; and

a movement position detector which detects the position of a movement section driven by the motor and outputs a movement position signal and provided with;

a motor speed-control function which makes the speed command and the motor speed signal coincident by feedback control; and

a motor position-control function which makes the position command and the movement position signal coincident by feedback control, wherein said position controller is provided with;

an observer which comprises a proportional operating means for performing proportional operation, an integration operating means for performing integration operation, an inertia model for multiplying by a gain ω

_s² and inputting a torque command outputted from the speed control section, an adder which adds the output from the inertia model, the output from the proportional operating means, and the output from the integration operating means, an integrator which integrates the output from the adder and outputs an estimated speed, and a subtracter which inputs a differential signal, obtained by subtracting the estimated speed from the motor speed outputted from the speed processor, into the proportional operating means and the integration operating means and which produces the differential signal obtained by subtracting the estimated speed from the motor speed as an output;

a high-pass filter which receives the output signal from the observer and outputs the output signal with its phase advanced;

a low-pass filter in which the signal from the high-pass filter is inputted and which outputs the signal with only its high-frequency components eliminated;

a coefficient multiplier which receives the signal from the low-pass filter and multiplies it by a torque corrective gain and outputs a torque correction signal;

a section for torque correction evaluation which varies the torque corrective gain based on a position deviation signal that is the difference between the position command and the movement position signal; and

a subtracter which subtracts the torque correction signal from the torque command to produce a new torque command.

5. A position controller as set forth in claim 4, wherein

in said section for torque correction evaluation, when the absolute value of the position deviation is greater than a reference value, the torque corrective gain is set to zero and when the absolute value of the position deviation changes to be equal to the reference value or below, the torque corrective gain is changed from zero to a constant value.

6. A position controller as set forth in claim 4, wherein

in the section for torque correction evaluation, when the absolute value of the position deviation signal is greater than a reference value, the torque corrective gain is set to zero and when the absolute value of the position deviation signal changes to be equal to the reference value or below, the torque corrective gain is continuously changed from zero to a constant value.

7. A position controller of a movement section, which performs speed control based on a speed feedback signal obtained by differentiating a rotational displacement signal of a servomotor and which performs position control based on a position feedback signal from a position detector attached to a movement section driven by the servomotor or the rotating shaft of the servomotor, comprises:

a correction evaluation section which sets a variable gain to zero when a position deviation between a position command and the position feedback signal is greater than a predetermined reference value, and which sets the variable gain to a constant positive number when the position deviation becomes equal to the reference value or below;

a differential processing section which differentiates a value obtained by multiplying the position deviation by the variable gain; and

a low-pass filter in which the output from this differential processing section is inputted and from which a speed command correction amount is outputted, wherein the speed command correction amount is added to a speed command base amount to produce the speed command of the servomotor.

8. A position controller of a movement section, which performs speed control based on a speed feedback signal obtained by differentiating a rotational displacement signal of a servomotor and which performs position control based on a position feedback signal from a position detector attached to a movement section driven by the servomotor or the rotating shaft of the servomotor, comprises:

a correction evaluation section which sets a variable gain to zero when a position deviation between a position command and the position feedback signal is greater than a predetermined reference value, and which sets the variable gain to a constant positive number when the position deviation becomes equal to the predetermined reference value or below; and

a high-pass filter in which a value obtained by multiplying the position deviation by the variable gain is inputted and from which a speed correction amount is outputted, wherein

the speed command correction amount is added to a speed command base amount to produce the speed command of the servomotor.