Servo control apparatus, servo control method and computer-readable recording medium

A servo control method for a servo control apparatus, the method comprising:

• creating a velocity command value of a servomotor;
• detecting a velocity of the servomotor;
• inputting a signal to a velocity control gain, the signal being obtained by adding a sine-wave being swept in a predetermined frequency range to a difference between the velocity command value and the velocity detected;
• creating a torque command value for the servomotor, based on an output from the velocity control gain;
• attenuating a particular frequency band component included in the torque command value by way of at least one filter;
• and
• driving the servomotor, based on the torque command value with the particular frequency band component attenuated,
• wherein the servo control method for the servo control apparatus further comprises:
• calculating frequency characteristics of the sine-wave that is swept in the predetermined frequency range;
• detecting a resonance frequency included in the frequency characteristics calculated, while changing a value of the velocity control gain;
• adjusting the filter so as to attenuate a particular frequency band component included in the torque command value, by measuring an influence of value of the velocity control gain on a resonance frequency and resonance peak amplitude;
• evaluating a rate of increase of the resonance peak amplitude with respect to changes in the velocity control gain in multiple frequency bands based on a quantitative relationship between a value of the velocity control gain and resonance peak amplitude of frequency characteristics obtained from the calculation of frequency characteristics;
• and
• adjusting the filter while giving higher priority to the frequency band having a higher rate of increase.

A non-transitory computer-readable medium storing a servo control program causing a computer as a servo control apparatus of a servomotor to execute the processing of:

• creating a velocity command value of the servomotor;
• detecting a velocity of the servomotor;
• inputting a signal to a velocity control gain, the signal being obtained by adding a sinewave being swept in a predetermined frequency range to a difference between the velocity command value and the velocity detected;
• creating a torque command value for the servomotor, based on an output from the velocity control gain;
• attenuating a particular frequency band component included in the torque command value by way of at least one filter;
• and
• driving the servomotor, based on the torque command value with the particular frequency band component attenuated,
• wherein the program further causes the computer to:
• calculate frequency characteristics of the sine-wave that is swept in the predetermined frequency range;
• detect a resonance frequency included in the frequency characteristics calculated, while changing a value of the velocity control gain;
• adjust the filter so as to attenuate a particular frequency band component included in the torque command value, by measuring an influence of value of the velocity control gain on a resonance frequency and resonance peak amplitude;
• evaluate a rate of increase of the resonance peak amplitude with respect to changes in the velocity control gain in multiple frequency bands based on a quantitative relationship between a value of the velocity control gain and resonance peak amplitude of frequency characteristics obtained from the calculation of frequency characteristics;
• and
• adjust the filter while giving higher priority to the frequency band having a higher rate of increase.

A servo control apparatus, comprising:

• a processor;
• the processor configured to create a velocity command value of a servomotor;
• the processor configured to detect a velocity of the servomotor;
• a velocity control gain that is a control gain of a velocity control loop;
• the processor configured to create a torque command value for the servomotor;
• the processor including at least one filter configured to attenuate a particular frequency band component included in the torque command value;
• the processor configured to perform a sine-wave sweep in a predetermined frequency range;
• the processor configured to calculate frequency characteristics of a sine-wave that is swept;
• and
• the processor configured to adjust the filter so as to attenuate a particular frequency band component included in the torque command value;
• wherein
• the velocity control gain and the processor configure the velocity control loop;
• a signal is input to the velocity control gain, the signal being obtained by adding a sinewave being output from the processor to a difference between the velocity command value and the velocity detected;
• the processor is configured to detect a resonance frequency included in frequency characteristics that is calculated by way of the processor, while changing a value of the velocity control gain, and configured to adjust the filter by measuring an influence of the velocity control gain on a resonance frequency and resonance peak amplitude;
• and
• the processor is further configured to evaluate a rate of increase of the resonance peak amplitude with respect to changes in the velocity control gain in multiple frequency bands based on a quantitative relationship between a value of the velocity control gain and resonance peak amplitude of frequency characteristics obtained from the processor, and adjust the filter while giving higher priority to the frequency band having a higher rate of increase.