Positional control of a controlled object during movement initiation

Abstract

In a positional control device for controlling a position of a controlled object using a motor, when generating a torque command value τc which serves as the command value for the servo motor of the controlled object system (), a friction compensation value for use when the controlled object initiates a movement is calculated based on a velocity command value V and a torque command value τc determined according to a positional command value Xo supplied from a superordinate device. More specifically, an initial friction compensation calculating section calculates a torque compensation amount Vsfccorresponding to a difference between torque being generated during the standstill state and torque required by the controlled object to initiate the movement, and a torque compensation amount Vsfcto an amount of change in friction that occurs during a transition from static friction to kinetic friction in a period immediately before and after initiation of the movement. Vsfcand Vsfcare then used to calculate compensated values of the torque command value τc. Positional tracking deviation generated due to friction during a movement initiation can thereby be reduced, regardless of operational conditions during the standstill state or of the movement direction and velocity effected thereafter.