Adaptive Switch Gain Time-Varying Sliding Mode Controller Design for the Low Speed Servo System in a Control Moment Gyroscope

An adaptive switch gain time-varying sliding mode controller is designed for the low speed servo system in a control moment gyroscope (CMG). By introducing the integral of speed error in the sliding mode surface, the error is suppressed during the whole operation. A time-varying sliding mode controller based on error reference is proposed to solve the problem that normal time-varying sliding mode control is only related to time and can only eliminate the reaching phase at initial time. The proposed controller makes the sliding mode surface keep refreshing all the time. The global robustness is maintained. Then, an adaptive switch gain sliding mode controller is proposed to deal with the system vibration. This controller has large gain for large error and small gain for small error. Simulation and experiment were carried out for the proposed CMG low speed servo system controller. The results showed that the proposed controller have better performance in terms of smooth speed and robustness comparing with conventional PID controller.