Displacement sensing method and motor control apparatus

Abstract

A displacement sensing method of the present invention includes the steps of superimposing a predetermined signal on a torque command to supply a drive torque to a motor, measuring an amplitude spectrum ratio between the drive torque in superimposing the predetermined signal on the torque command and a motor angle measured by a displacement sensor, generating correction data for evening out the amplitude spectrum ratio, and correcting the measured motor angle so that the motor angle measured by the displacement sensor is equal to an actual motor angle using the correction data.

What is claimed is: 
     
       1. A displacement sensing method comprising the steps of:
 superimposing a predetermined signal on a torque command to supply a drive torque to a motor; 
 measuring an amplitude spectrum ratio between the drive torque in superimposing the predetermined signal on the torque command and a motor angle measured by a displacement sensor; 
 generating correction data for evening out the amplitude spectrum ratio; and 
 correcting the measured motor angle so that the motor angle measured by the displacement sensor is equal to an actual motor angle using the correction data. 
 
     
     
       2. A motor control apparatus comprising:
 a displacement sensor that measures a displacement amount of a motor; 
 a drive unit that supplies a drive torque to the motor; 
 a signal generator that generates a predetermined signal and supplies the predetermined signal to the drive unit, wherein the drive torque is generated based on the predetermined signal; 
 a correction data generator that generates correction data using the drive torque when the predetermined signal is supplied to the drive unit and the displacement amount of the motor measured by the displacement sensor; and 
 a correction unit that corrects the measured displacement amount of the motor so that the displacement amount of the motor measured by the displacement sensor is equal to an actual displacement amount of the motor using the correction data generated by the correction data generator, 
 wherein the drive unit uses a displacement amount corrected by the correction unit to control the motor. 
 
     
     
       3. A motor control apparatus according to  claim 2 , wherein the predetermined signal is a sine wave signal. 
     
     
       4. A motor control apparatus according to  claim 2 ,
 wherein the correction data generated by the correction data generator is a correction data for evening out the amplitude spectrum ratio obtained using the drive torque and the displacement amount of the motor measured by the displacement sensor. 
 
     
     
       5. A motor control apparatus according to  claim 2 ,
 wherein the displacement sensor is an encoder. 
 
     
     
       6. A processing machine comprising the motor control apparatus according to  claim 2 . 
     
     
       7. A displacement sensing method comprising:
 superimposing a predetermined signal on a torque command to supply the superimposed torque command to a motor with the motor controlled such that the motor has each of a plurality of rotation angles; 
 measuring a ratio between a component, corresponding to the predetermined signal, of an amplitude spectrum of the superimposed torque command and a component, corresponding to the predetermined signal, of an amplitude spectrum of a rotation angle of the motor measured by a sensor, with respect to each of the plurality of rotation angles; 
 generating correction data such that the correction data evens out the ratios over the plurality of rotation angles; and 
 correcting a rotation angle of the motor measured by the sensor using the correction data. 
 
     
     
       8. A motor control apparatus comprising:
 a sensor configured to measure a rotation angle of a motor; 
 a drive unit configured to supply a torque command to the motor; 
 a signal generator configured to generate a predetermined signal to superimpose the generated predetermined signal on the torque command and supply the superimposed torque command to the motor with the motor controlled such that the motor has each of a plurality of rotation angles; 
 a correction data generator configured to generate correction data, based on a ratio between a component, corresponding to the predetermined signal, of an amplitude spectrum of the superimposed torque command and a component, corresponding to the predetermined signal, of an amplitude spectrum of a rotation angle of the motor measured by the sensor, such that the correction data evens out the ratios over the plurality of rotation angles; and 
 a correction unit configured to correct a rotation angle of the motor measured by the sensor using the generated correction data, wherein the drive unit is configured to supply the torque command to the motor based on the corrected rotation angle. 
 
     
     
       9. A motor control apparatus according to  claim 8 , wherein the predetermined signal is a sine wave signal. 
     
     
       10. A motor control apparatus according to  claim 8 , further comprising:
 a first Fourier transform unit configured to obtain the amplitude spectrum of the superimposed torque command; and 
 a second Fourier transform unit configured to obtain the amplitude spectrum of the rotation angle of the motor measured by the sensor. 
 
     
     
       11. A motor control apparatus according to  claim 8 , wherein the sensor is an encoder. 
     
     
       12. A processing machine comprising the motor control apparatus according to  claim 8 . 
     
     
       13. An actuator control apparatus comprising:
 a sensor configured to measure a displacement output of an actuator; 
 a drive unit configured to supply a command to the actuator to drive the actuator; 
 a signal generator configured to generate a predetermined signal to superimpose the generated predetermined signal on the command and supply the superimposed command to the actuator with the actuator controlled such that the actuator has each of a plurality of displacement outputs, so that a signal based on the predetermined signal is input to the actuator; 
 a correction data generator configured to generate correction data, based on a ratio between a component, corresponding to the predetermined signal, of an amplitude spectrum of the superimposed command and a component, corresponding to the predetermined signal, of an amplitude spectrum of a displacement output of the actuator measured by the sensor, such that the correction data evens out the ratios over the plurality of displacement outputs; and 
 a correction unit configured to correct an output of the sensor using the generated correction data, wherein the drive unit is configured to supply the command to the actuator based on the corrected output. 
 
     
     
       14. A processing machine comprising the actuator control apparatus according to  claim 13 . 
     
     
       15. A displacement sensing apparatus for sensing displacement by an actuator, the apparatus comprising:
 a sensor configured to sense displacement by the actuator, the actuator being controlled by a control system based on a target displacement signal and an output signal of the sensor;   a signal generator configured to generate a predetermined signal to be supplied to the control system, so that a signal based on the predetermined signal is input to the actuator; and   a correction data generator configured to generate correction data, for compensation for an error in the output signal of the sensor, based on displacement by the actuator sensed by the sensor with the predetermined signal being supplied to the control system with respect to each of a plurality of the target displacement signals.   
     
     
       16. The apparatus according to claim 15, wherein the correction data generator is configured to generate the correction data based on the sensed displacement of the actuator with the actuator being controlled in the control system based on each of the plurality of the target displacement signals and with the predetermined signal being supplied to the actuator. 
     
     
       17. The apparatus according to claim 15, wherein the correction data generator is configured to generate the correction data based on a ratio between an amplitude of the sensed displacement and an amplitude of the supplied predetermined signal with respect to each of the plurality of the target displacement signals. 
     
     
       18. The apparatus according to claim 15, wherein the correction data generator is configured to generate the correction data such that that the correction data even out the ratios over the plurality of the target displacement signal. 
     
     
       19. The apparatus according to claim 15, further comprising a correction unit configured to correct an output signal of the sensor based on the correction data. 
     
     
       20. The apparatus according to claim 15, wherein the signal generator is configured to generate, as the predetermined signal, a sine wave signal. 
     
     
       21. The apparatus according to claim 17, wherein the correction data generator is configured to obtain the amplitude of the sensed displacement and the amplitude of the supplied predetermined signal by Fourier transform of the sensed displacement and the supplied predetermined signal, respectively. 
     
     
       22. The apparatus according to claim 21, wherein the correction data generator is configured to obtain, as the amplitude of the sensed displacement, an amplitude spectrum of the sensed displacement with respect to a predetermined frequency, and to obtain, as the amplitude of the supplied predetermined signal, an amplitude spectrum of the supplied predetermined signal with respect to the predetermined frequency. 
     
     
       23. The apparatus according to claim 15, wherein the sensor is an encoder. 
     
     
       24. The apparatus according to claim 15, wherein the actuator is a motor. 
     
     
       25. A control apparatus including an actuator and controlling displacement by the actuator, the apparatus comprising: the displacement sensing apparatus, according to claim 15, for sensing the displacement. 
     
     
       26. A processing machine comprising the control apparatus according to claim 25. 
     
     
       27. The processing machine according to claim 26, further comprising a mirror to be driven by the actuator, a material being irradiate with a beam via the mirror. 
     
     
       28. A motor control apparatus comprising:
 a sensor configured to measure a rotation angle of a motor;   a drive unit configured to supply a torque command to the motor;   a signal generator configured to generate a predetermined signal to superimpose the generated predetermined signal on the torque command and supply the superimposed torque command to the motor with the motor controlled such that the motor has each of a plurality of rotation angles;   a correction data generator configured to generate correction data, based on a ratio between a component, corresponding to the predetermined signal, of an amplitude spectrum of the superimposed torque command and a component, corresponding to the predetermined signal, of an amplitude spectrum of a rotation angle of the motor measured by the sensor, such that the correction data evens out the ratios over the plurality of rotation angles;   a correction unit configured to correct a rotation angle of the motor measured by the sensor using the generated correction data;   a first Fourier transform unit configured to obtain the amplitude spectrum of the superimposed torque command; and   a second Fourier transform unit configured to obtain the amplitude spectrum of the rotation angle of the motor measured by the sensor,   wherein the drive unit is configured to supply the torque command to the motor based on the corrected rotation angle.   
     
     
       29. A displacement sensing apparatus for sensing displacement by an actuator, the apparatus comprising:
 a sensor configured to sense displacement by the actuator, the actuator being controlled in a control system based on a target displacement signal and an output signal of the sensor;   a signal generator configured to generate a predetermined signal to be supplied to the control system, so that a signal based on the predetermined signal is input to the actuator; and   a correction data generator configured to generate correction data, for compensation for an error in the output signal of the sensor, based on displacement by the actuator sensed by the sensor with the predetermined signal being supplied to the control system with respect to each of a plurality of the target displacement signals,   wherein the correction data generator is configured to generate the correction data based on a ratio between an amplitude of the sensed displacement and an amplitude of the supplied predetermined signal with respect to each of the plurality of the target displacement signals, and   wherein the correction data generator is configured to obtain the amplitude of the sensed displacement and the amplitude of the supplied predetermined signal by Fourier transform of the sensed displacement and the supplied predetermined signal, respectively.   
     
     
       30. The apparatus according to claim 29, wherein the correction data generator is configured to obtain, as the amplitude of the sensed displacement, an amplitude spectrum of the sensed displacement with respect to a predetermined frequency, and to obtain, as the amplitude of the supplied predetermined signal, an amplitude spectrum of the supplied predetermined signal with respect to the predetermined frequency. 
     
     
       31. A processing machine comprising:
 a control apparatus, wherein the control apparatus includes an actuator and controls displacement by the actuator, the control apparatus comprising:   a displacement sensing apparatus, wherein the displacement sensing apparatus for sensing displacement by an actuator, comprises:   a sensor configured to sense displacement by the actuator, the actuator being controlled in a control system based on a target displacement signal and an output signal of the sensor;   a signal generator configured to generate a predetermined signal to be supplied to the control system, so that a signal based on the predetermined signal is input to the actuator; and   a correction data generator configured to generate correction data, for compensation for an error in the output signal of the sensor, based on displacement by the actuator sensed by the sensor with the predetermined signal being supplied to the control system with respect to each of a plurality of the target displacement signal; and   a mirror to be driven by the actuator, a material being irradiated with a beam via the mirror.