System modeling and sliding mode control of fast steering mirror for space laser communication

Abstract

Fast steering mirror (FSM) is a crucial component in high-precision optical systems. However, the flexible resonance modes and complex interaxial coupling characteristics of the flexible supported FSM driven by voice coil actuators (VCAs) have seriously impacted the control performance of the space laser communication precision tracking system. To address this issue, this study proposes a novel sliding mode control approach based on system identification and model reduction. Firstly, a high-precision, high-order coupled model of the dual-axis VCA-FSM is established using the Hankel matrix system identification method based on pulse response. Subsequently, the model reduction method based on balanced truncation is employed to reduce the high-order model while preserving its accuracy. Next, the sliding mode control algorithm is designed based on the reduced-order model. The switching function is optimized using the quadratic performance index. The sliding mode control law is constructed using the Kalman filter, and the exponential power function is used to replace the signum function to suppress sliding mode control chattering. Finally, experiments on the VCA-FSM servo control system platform are conducted to evaluate the frequency domain and time domain performance. The experimental results validate the effectiveness and superiority of the modeling and control methods proposed in this research.