Variable Gain Feed-forward Control for Fast Positioning Servo System

The advancement of the motion control has led to increased demands for better position tracking performance to minimize maximum position error and reduce settling time form the the end of position command to controlled plant reaching the command position in servo control applications. This paper proposes a variable gain feed-forward control method, which has reduced maximum position error and settling time compared to traditional fixed gain feed-forward control. The proposed method is divided into two steps. First, determine velocity feed-forward compensation signal by dividing the motion into three phase: running phase, compensation phase, and positioning phase. Second, use acceleration command and velocity command to fit velocity feed-forward compensation signal in compensation phase. The proposed method is convenient for application and does not involve the stability of the servo system. Experimental results on rotary motor servo system and linear motor servo system show that the proposed method reduces maximum position error over than 87.5% and decreases settling time over than 84.9%.