Servo motor controller

1. A servo motor controller having automatic gain adjustment function for adjusting a velocity control gain, comprising:

a velocity control section that calculates a torque instruction value by multiplying a velocity deviation which is a difference between a velocity instruction value and a velocity detection value by said velocity control gain which is a product of an operation constant and an adjustment magnification factor which has been set in advance for adjusting said operation constant;

a disturbance addition section that adds a torque disturbance at a specified frequency to said torque instruction value;

an input/output characteristic estimation section that estimates an input/output gain and a phase lag with said torque disturbance as an input value to a control system and with said torque instruction value as an output value from said control system;

a frequency identification section that performs analysis based on a frequency response method and identifies a frequency of said torque disturbance exhibiting a specified phase lag;

an input/output gain identification section that identifies an input/output gain at said frequency identified by said frequency identification section; and

a magnification factor resetting section that resets said adjustment magnification factor by multiplying said adjustment magnification factor by a value obtained by multiplying a specified correction coefficient that is less than 1 to a ratio between said identified input/output gain and said specified target value of said input/output gain.

2. The servo motor controller according to claim 1 , wherein said torque disturbance represents a sine wave.

3. The servo motor controller according to claim 1 , wherein said frequency identified by said frequency identification section is a frequency at which said phase lag is about −180° or has a smaller absolute value, and wherein, with said specified target value of said input/output gain set to a specified value of 0 dB or lower, an adjustment is performed so as to bring a input/output gain at said frequency identified by said frequency identification section closer to said specified target value of the input/output gain.

4. The servo motor controller according to claim 1 , further comprising a maximum gain calculation section that obtains a maximum value of said input/output gain at a frequency lower than said frequency identified by said frequency identification section, wherein, when said maximum value is greater than a specified value of 0 dB or higher, said adjustment magnification factor of said velocity control section is decreased by a ratio of said maximum value to said specified value of 0 dB or higher.

5. The servo motor controller according to claim 1 , wherein, when an input/output gain at a resonant frequency exceeds a specified value at a frequency higher than said frequency identified by said frequency identification section, said adjustment magnification factor of said velocity control section is decreased in accordance with a ratio of said input/output gain at said resonant frequency to said specified value.

6. The servo motor controller according to claim 1 , wherein, after said adjustment magnification factor has been reset, an input/output gain is determined by using a new adjustment magnification factor, and resetting of said adjustment magnification factor is repeated to bring said input/output gain determined by using a new adjustment magnification factor closer to said specified target value of said input/output gain until resetting is terminated when said input/output gain determined by using a new adjustment magnification factor enters into a specified range including said specified target value of said input/output gain.

7. The servo motor controller according to claim 6 , wherein said specified correction coefficient used in resetting of said adjustment magnification factor for a second time is larger than said specified correction coefficient used in resetting of said adjustment magnification factor for a first time.

8. A servo motor controller having automatic gain adjustment function for adjusting a velocity control gain, comprising:

a velocity control section that calculates a torque instruction value by multiplying a velocity deviation which is a difference between a velocity instruction value and a velocity detection value by said velocity control gain which is a product of an operation constant and an adjustment magnification factor which has been set in advance for adjusting said operation constant;

a disturbance addition section that adds a velocity disturbance at a specified frequency to said velocity instruction value;

an input/output characteristic estimation section that estimates an input/output gain and a phase lag with said velocity disturbance as an input value to a control system and with said velocity instruction value as an output value from said control system;

a frequency identification section that performs analysis based on a frequency response method and identifies a frequency of said velocity disturbance exhibiting a specified phase lag;

an input/output gain identification section that identifies an input/output gain at said frequency identified by said frequency identification section; and

a magnification factor resetting section that resets said adjustment magnification factor by multiplying said adjustment magnification factor by a value obtained by multiplying a specified correction coefficient that is less than 1 to a ratio between said identified input/output gain and said specified target value of said input/output gain.

9. The servo motor controller according to claim 8 , wherein said velocity disturbance represents a sine wave.

10. The servo motor controller according to claim 8 , wherein said frequency identified by said frequency identification section is a frequency at which said phase lag is about −180° or has a smaller absolute value, and wherein, with said specified target value of said input/output gain set to a specified value of 0 dB or lower, an adjustment is performed so as to bring a input/output gain at said frequency identified by said frequency identification section closer to said specified target value of the input/output gain.

11. The servo motor controller according to claim 8 , further comprising a maximum gain calculation section that obtains a maximum value of said input/output gain at a frequency lower than said frequency identified by said frequency identification section, wherein, when said maximum value is greater than a specified value of 0 dB or higher, said adjustment magnification factor of said velocity control section is decreased by a ratio of said maximum value to said specified value of 0 dB or higher.

12. The servo motor controller according to claim 8 , wherein, when an input/output gain at a resonant frequency exceeds a specified value at a frequency higher than said frequency identified by said frequency identification section, said adjustment magnification factor of said velocity control section is decreased in accordance with a ratio of said input/output gain at said resonant frequency to said specified value.

13. The servo motor controller according to claim 8 , wherein, after said adjustment magnification factor has been reset, an input/output gain is determined by using a new adjustment magnification factor, and resetting of said adjustment magnification factor is repeated to bring said input/output gain determined by using a new adjustment magnification factor closer to said specified target value of said input/output gain until resetting is terminated when said input/output gain determined by using a new adjustment magnification factor enters into a specified range including said specified target value of said input/output gain.

14. The servo motor controller according to claim 13 , wherein said specified correction coefficient used in resetting of said adjustment magnification factor for a second time is larger than said specified correction coefficient used in resetting of said adjustment magnification factor for a first time.

15. A servo motor controller having automatic gain adjustment function for adjusting a velocity control gain, comprising:

a velocity control section that calculates a torque instruction value by multiplying a velocity deviation which is a difference between a velocity instruction value and a velocity detection value by said velocity control gain which is a product of an operation constant and an adjustment magnification factor which has been set in advance for adjusting said operation constant;

a disturbance addition section that adds a torque disturbance at a specified frequency to said torque instruction value;

an input/output characteristic estimation section that estimates an input/output gain and a phase lag with said torque disturbance as an input value to a control system and with said torque instruction value as an output value from said control system;

a frequency identification section that performs analysis based on a frequency response method and identifies a frequency of said torque disturbance exhibiting a specified phase lag;

an input/output gain identification section that identifies an input/output gain at said frequency identified by said frequency identification section; and

a magnification factor resetting section that resets said adjustment magnification factor by multiplying said adjustment magnification factor by a value obtained by subtracting 1 from a ratio between said identified input/output gain and said specified target value of said input/output gain, then multiplying a specified correction coefficient that is less than 1, and finally adding 1.

16. The servo motor controller according to claim 15 , wherein said torque disturbance represents a sine wave.

17. The servo motor controller according to claim 15 , wherein said frequency identified by said frequency identification section is a frequency at which said phase lag is about −180° or has a smaller absolute value, and wherein, with said specified target value of said input/output gain set to a specified value of 0 dB or lower, an adjustment is performed so as to bring a input/output gain at said frequency identified by said frequency identification section closer to said specified target value of the input/output gain.

18. The servo motor controller according to claim 15 , further comprising a maximum gain calculation section that obtains a maximum value of said input/output gain at a frequency lower than said frequency identified by said frequency identification section, wherein, when said maximum value is greater than a specified value of 0 dB or higher, said adjustment magnification factor of said velocity control section is decreased by a ratio of said maximum value to said specified value of 0 dB or higher.

19. The servo motor controller according to claim 15 , wherein, when an input/output gain at a resonant frequency exceeds a specified value at a frequency higher than said frequency identified by said frequency identification section, said adjustment magnification factor of said velocity control section is decreased in accordance with a ratio of said input/output gain at said resonant frequency to said specified value.

20. The servo motor controller according to claim 15 , wherein, after said adjustment magnification factor has been reset, an input/output gain is determined by using a new adjustment magnification factor, and resetting of said adjustment magnification factor is repeated to bring said input/output gain determined by using a new adjustment magnification factor closer to said specified target value of said input/output gain until resetting is terminated when said input/output gain determined by using a new adjustment magnification factor enters into a specified range including said specified target value of the input/output gain.

21. A servo motor controller having automatic gain adjustment function for adjusting a velocity control gain, comprising:

a velocity control section that calculates a torque instruction value by multiplying a velocity deviation which is a difference between a velocity instruction value and a velocity detection value by said velocity control gain which is a product of an operation constant and an adjustment magnification factor which has been set in advance for adjusting said operation constant;

a disturbance addition section that adds a velocity disturbance at a specified frequency to said velocity instruction value;

an input/output characteristic estimation section that estimates an input/output gain and a phase lag with said velocity disturbance as an input value to a control system and with said velocity instruction value as an output value from said control system;

a frequency identification section that performs analysis based on a frequency response method and identifies a frequency of said velocity disturbance exhibiting a specified phase lag;

an input/output gain identification section that identifies an input/output gain at said frequency identified by said frequency identification section; and

a magnification factor resetting section that resets said adjustment magnification factor by multiplying said adjustment magnification factor by a value obtained by subtracting 1 from a ratio between said identified input/output gain and said specified target value of said input/output gain, then multiplying a specified correction coefficient that is less than 1, and finally adding 1.

22. The servo motor controller according to claim 21 , wherein said velocity disturbance represents a sine wave.

23. The servo motor controller according to claim 21 , wherein said frequency identified by said frequency identification section is a frequency at which said phase lag is about −180° or has a smaller absolute value, and wherein, with said specified target value of said input/output gain set to a specified value of 0 dB or lower, an adjustment is performed so as to bring a input/output gain at said frequency identified by said frequency identification section closer to said specified target value of the input/output gain.

24. The servo motor controller according to claim 21 , further comprising a maximum gain calculation section that obtains a maximum value of said input/output gain at a frequency lower than said frequency identified by said frequency identification section, wherein, when said maximum value is greater than a specified value of 0 dB or higher, said adjustment magnification factor of said velocity control section is decreased by a ratio of said maximum value to said specified value of 0 dB or higher.

25. The servo motor controller according to claim 21 , wherein, when an input/output gain at a resonant frequency exceeds a specified value at a frequency higher than said frequency identified by said frequency identification section, said adjustment magnification factor of said velocity control section is decreased in accordance with a ratio of said input/output gain at said resonant frequency to said specified value.

26. The servo motor controller according to claim 21 , wherein, after said adjustment magnification factor has been reset, an input/output gain is determined by using a new adjustment magnification factor, and resetting of said adjustment magnification factor is repeated to bring said input/output gain determined by using a new adjustment magnification factor closer to said specified target value of said input/output gain until resetting is terminated when said input/output gain determined by using a new adjustment magnification factor enters into a specified range including said specified target value of the input/output gain.