Precision Positioning Control by Modeling Frictional Behaviors of Linear Ball Guideway

Abstract

Positioning devices which are composed with linear ball guideways and a linear motor are increased in recent precision positioning field. However, it is a difficult problem to achieve precision or ultra-precision positioning because rolling frictional force of the linear ball guideways is a disturbance force. Therefore, a frictional compensation is implemented by a controller. In this paper, one-axis positioning apparatus using a voice coil motor as an actuator is constructed. Moreover, several control methods are full-closed loop of measured displacement feed-back, feed-forward control of reference position and feed-forward control as like inverse transfer function using nonlinear frictional model proposed by authors. The equivalent spring constant of the nonlinear frictional model changes by the displacement. As implementing positioning tests, it is verified that the feed forward control using the nonlinear frictional model is effective for achieving the precision positioning.