Position controlling apparatus capable of reducing the effect of disturbance

DETAILED DESCRIPTION Therefore, an object of the present invention is to provide a position controlling apparatus which is capable of the effect of disturbance as small as possible by estimating a disturbance torque acting upon a drive mechanism and compensating for the torque correspondingly thereto in the position controlling apparatus.
Another object of the present invention is to eliminate the measurement noises when performing position detection to thereby prevent degradation of a disturbance suppression characteristic within a high-frequency band.
Still another object of the present invention is to reduce the effects of the measurement noises and differentiation noises within a sampling frequency band especially in a digital control system.
A position controlling apparatus according to the present invention comprises a position detector for detecting the position of a driven object to be driven by a motor, to thereby output a detected value of position.
A Kalman filter estimates the position and velocity of the driven object from the detected value of position, thereafter outputting an estimated value of position and an estimated value of velocity.
A disturbance estimating unit estimates the disturbance applied to the driven object from comparison with a command value of current and the estimated value of velocity, thereafter outputting this estimated current value of disturbance.
A first subtracter computes a difference between a command value of position and the estimated value of position.
A position controller computes a command value of velocity in accordance with the difference computed by the first subtracter.
A second subtracter computes the difference between the estimated value of velocity and the command value of velocity.
A velocity controller computes a target value of current in accordance with the difference computed by the second subtracter.
A third subtracter computes a difference between the estimated current value of disturbance and the target value of current to thereby output this difference as the command value of current