Control apparatus of an electric motor

A control apparatus of an electric motor, the control apparatus including:

• a first position controller for generating a speed command such that a position command transmitted from an outside of the control apparatus of the motor coincides with a load's detection position that is a detected position of a load coupled with the motor;
• a speed controller for generating a torque command such that the speed command coincides with a motor's detection speed that is a detected speed of the motor;
• a torque controller for driving the motor in accordance with the torque command;
• a torque command generator for outputting a for-adjustment torque command containing a plurality of frequency components;
• a speed feedback circuit serving as a control loop, the speed feedback circuit including the speed controller and the torque controller, the speed feedback circuit acquiring the motor's detection speed to be re-inputted to the speed controller, the motor's detection speed to-be-re-inputted being acquired from the speed command and the motor's detection speed, the speed command and the motor's detection speed having been inputted to the speed controller;
• and
• a first position feedback circuit serving as a control loop, the first position feedback circuit including the first position controller and the speed feedback circuit, the first position feedback circuit acquiring a load's detection position to be re-inputted to the first position controller, the load's detection position to-be-re-inputted being acquired from the position command and the load's detection position, the position command and the load's detection position having been inputted to the first position controller,
• wherein, the control apparatus is configured to:
• compute a present load-frequency characteristic, the present load-frequency characteristic being a load-frequency characteristic from the for-adjustment torque command to the motor's detection speed;
• compute a present speed-proportional gain range by using a speed-proportional gain and the present load-frequency characteristic such that the speed feedback circuit becomes stable, the present speed-proportional gain range being a range of a present speed-proportional gain of the speed-proportional gain serving as the control parameter used in the speed controller;
• compute a present mechanical-system characteristic constant by using the present load-frequency characteristic, the present mechanical-system characteristic constant indicating a characteristic of a mechanical system containing the motor and the load;
• compute a present proportional gain range by using the speed-proportional gain, a position-proportional gain serving as the control parameter used in the first position controller, the present load-frequency characteristic, and the present mechanical-system characteristic constant such that the position feedback circuit becomes stable, the present proportional gain range being a range of combination of the present speed-proportional gain and a present position-proportional gain of the position-proportional gain;
• compute a secular characteristic based on the present load-frequency characteristic and secular-change information transmitted from the outside of the control apparatus of the motor, the secular characteristic including a secular load-frequency characteristic being the load-frequency characteristic having undergone a secular change, and a secular mechanical-system characteristic constant being a mechanical-system characteristic constant having undergone the secular change;
• compute a secular speed-proportional gain range by using the speed-proportional gain and the secular load-frequency characteristic such that the speed feedback circuit becomes stable;
• compute a secular proportional gain range by using the speed-proportional gain, the position-proportional gain, the secular load-frequency characteristic, and the secular mechanical-system characteristic constant such that the first position feedback circuit becomes stable, the secular proportional gain range being a range of combination of a secular speed-proportional gain that is the speed-proportional gain having undergone the secular change and a secular position-proportional gain that is the position-proportional gain having undergone the secular change;
• and
• select proportional gains from computed-ranges such that each value of the selected proportional gains satisfies all of the computed-ranges, the proportional gains including a value of the speed-proportional gain and a value of the position-proportional gain, the computed-ranges including:
• the present speed-proportional gain range;
• the range of the combination of the present speed-proportional gain and the present position-proportional gain;
• the secular speed-proportional gain;
• and
• the range of the combination of the secular speed-proportional gain and the secular position-proportional gain;
• and
• control the detection position of the load coupled to the motor.