A controller of a motor that drives a driven body includes: an inertia estimating unit that estimates inertia on the basis of feedback information (torque and current) of the motor; a computing unit that computes an acceleration or deceleration time constant of the motor from the estimation inertia estimated by the inertia estimating unit; a storage unit that stores an inertia difference which is a difference between the estimation inertia and at least one known actual inertia and a time constant difference which is a difference between an actual acceleration or deceleration time constant corresponding to the actual inertia and an acceleration or deceleration time constant calculated on the basis of the estimation inertia; and a correction unit that corrects the acceleration or deceleration time constant calculated by the computing unit using the inertia difference and the time constant difference stored in the storage unit.

Provided is a feed shaft control method, wherein a speed feedback loop having a speed controller is disposed within a position feedback loop having a position controller, forming a cascade coupling, and an acceleration feedback signal which is outputted from a compensator on the basis of an output signal of an acceleration detector is subtracted from a torque instruction. Furthermore, the method implements control wherein a speed is acquired on the basis of the output signal of the acceleration detector, and a signal obtained by multiplying the acquired speed by a gain is added to a speed instruction which is outputted from the position controller.

A controller of a motor that drives a driven body includes: an inertia estimating unit that estimates inertia on the basis of feedback information (torque and current) of the motor; a computing unit that computes an acceleration or deceleration time constant of the motor from the estimation inertia estimated by the inertia estimating unit; a storage unit that stores an inertia difference which is a difference between the estimation inertia and at least one known actual inertia and a time constant difference which is a difference between an actual acceleration or deceleration time constant corresponding to the actual inertia and an acceleration or deceleration time constant calculated on the basis of the estimation inertia; and a correction unit that corrects the acceleration or deceleration time constant calculated by the computing unit using the inertia difference and the time constant difference stored in the storage unit.

Provided is a feed shaft control method, wherein a speed feedback loop having a speed controller is disposed within a position feedback loop having a position controller, forming a cascade coupling, and an acceleration feedback signal which is outputted from a compensator on the basis of an output signal of an acceleration detector is subtracted from a torque instruction. Furthermore, the method implements control wherein a speed is acquired on the basis of the output signal of the acceleration detector, and a signal obtained by multiplying the acquired speed by a gain is added to a speed instruction which is outputted from the position controller.