Practical Highly Precise Position Control of Direct Drive Torque Motors

Abstract

The goal of this study is to control the position of Direct Drive PM DC torque motors with the accuracy being equal to the resolution limit of the accompanied digital encoder, which is 0.0042° in our case. In this study, a simple but practical algorithm to identify motor parameters is developed. Furthermore, based on experimental observation, the authors construct a stick-slip friction model using standard mechanical elements. This model can qualitively describe the behavior of stick-slip friction, which is critical to the precise position control problem. A simple state-of-art, somewhat heuristic though, control law is built to achieve our goal. Instead of using high gain control to increase system stiffness as suggested by many researchers, the main spirit of this control is to release the inner friction stress gently.