Actuator Saturation Compensation for Fast Tool Servo Systems With Time Delays

Abstract

Fast tool servo systems with high precision and high speed pose significant challenges to servo control at the nano-scale. The saturation of the control actions, time delays and system uncertainties further complicate the control challenges. To address these problems, we propose a Smith predictor based robust anti-windup scheme in this article, such that high performance servo with nano-accuracy can be achieved in the case of saturations, time delays and model uncertainties. According to the input/output based equivalent representation, the saturation nonlinearity is transformed to the dead zone nonlinearity fulfilling a sector condition. Based on the Popov criterion, the stability conditions for the anti-windup compensator are derived, which are further formulated as an H∞ optimization problem with robustness against model uncertainties. The effectiveness of the proposed control architecture is verified through real-time experiments, where excellent servo performance, saturation compensation and robustness are demonstrated, outperforming existing results.

Keywords

• Nanopositioning
• fast tool servo
• time delay
• actuator saturation
• anti-windup compensation