Fuzzy active disturbance rejection control of fine tracking system for free space optical communication

In consideration of the effects of input beam jitter and satellite micro vibration on the tracking precision of a space optical communication system, a fuzzy active disturbance rejection controller is designed and a control method for the fine tracking system in optical communication is proposed. Firstly, a fine tracking system model is established, the internal and external disturbances of the system are analyzed and the satellite vibration signals are simulated. Then, focused on the uncertainties of system disturbance and input optical signals, the fuzzy active disturbance rejection controller is designed. The proposed method observes satellite vibration and unmodelled dynamics of the system by an extended state observer and uses a differential tracker to improve the dynamic response performance of the system. Then it utilizes fuzzy control theory to improve the nonlinear state error control law, by which the system can adjust adaptively proportion and differential gains. Finally, the experiments analysis are performed and compared with PID control method. It shows that the fuzzy active disturbance rejection control method improves the system tracking accuracy under the input signals with different frequencies and amplitudes, the tracking accuracy has reached to ±8 μrad, and the tracking error reduces about 50 percent. This method basically meets the requirements of tracking systems of optical communication for tracking speeds, tracking accuracy and antijamming capability.