Input Excitation Disturbance Separation-Based Energy-Saving Attitude Control for Flexible Spacecraft With Actuator Degradation

Actuator degradation (i.e., partial loss of effectiveness) of flexible spacecraft is multiplicatively coupled with the control input and mixed with the flexible vibration disturbance. How to accurately identify and compensate these disturbances is a key to improve the attitude control performances. This article studies the high-precision and energy-saving attitude control of flexible spacecraft in the presence of composite disturbances including actuator degradation, actuator bias, and flexible vibration disturbance. A refined deep-coupled attitude dynamic model is established to clearly reveal the inherent coupling relations among angular velocity, control input, and composite disturbances. In the first phase, a novel input excitation disturbance observer (IEDO) is proposed to separate the composite disturbances, and then a parameter identification method is designed to identify the parameters of actuator degradation and bias. Due to the accurate separation ability of IEDO, the parameter identification performance will not be affected by the flexible vibration disturbance. In the second phase, a sliding mode observer is designed to estimate the flexible vibration disturbance and parameter identification error, and then an energy-saving composite attitude control law is proposed by accurately compensating the composite disturbances. Finally, numerical results and experiment results are given to demonstrate the effectiveness of the proposed methods.