Patent ID: 8508171

Claim:
A driven member position control apparatus that includes a motor position detector and a driven member position detector capable of detecting a driven member driven by a motor and is configured to perform full-closed control for controlling the position of the driven member, the position control apparatus comprising: a subtracter configured to calculate a deflection that represents a difference between a position detection value obtained by the motor position detector and a position detection value obtained by the driven member position detector; an adder configured to calculate a position feedback value by adding an output of a first-order delay circuit that receives the deflection and the position detection value obtained by the motor position detector; a speed command calculator configured to output a speed command value by proportionally amplifying a deviation between the position feedback value and a position command value input from a host apparatus; a differentiator configured to calculate a speed feedback value by differentiating the position detection value obtained by the motor position detector; a torque command calculator configured to output a torque command value by proportionally and integrally amplifying a deviation between the speed feedback value and the speed command value; a mechanism configured to drive the motor according to the torque command value; and an aging corrector configured to receive the position command value and the position detection value obtained by the driven member position detector and control a time constant of the first-order delay circuit in such a way as to increase the time constant when a vibratory state of the driven member is detected, wherein the position control apparatus suppresses low frequency vibrations occurring when a mechanical resonance frequency decreases due to aging.