Research On Fault-tolerant Control Under Constrained Input For Small Satellite Attitude Control Systems During Collision Avoidance

The thesis is derived from key project of Natural science of Jiangsu Province. With the backgroundof small satellite during collision avoidance maneuver, the thesis is to study fault tolerant controltechnology for satellite attitude control systems during collision avoidance maneuver. Since theactuators may be faulty because of severe orbital environment and actuators are limited by saturationnonlinearity, tolerant control technology is studied in the paper to guarantee the safety and reliabilityof satellites. The key contributions are summarized as follows:The dynamics and kinematics model for flexible satellite during collision avoidance maneuver isestablished first. Then the effect of actuator saturation nonlinearity and disturbances for satelliteattitude is studied and the input saturation of actuators is analyzed. Key problems for fault tolerantcontrol are researched.Considering the large disturbance and actuator saturation problem during collision avoidancemaneuver, fault tolerant control methods with actuator fault are studied. If actuator fault informationis unknown, a tolerant controller based on variable structure and adaptive method is proposed torealize attitude stabilization. The controller is adjusted with an adaptive law and needs no faultdiagnosis mechanism. If the actuators are equipped with redundancy and actuator fault information isobtained and known, a tolerant controller based on on-line allocation method is designed to realizeon-orbital reconfiguration.The on-line control allocation method for fault tolerant control can becarried out without reconfiguring the baseline controller. At last, numerical simulation is carried todemonstrate the effectiveness of the methods proposed.Simulation and demonstration software for satellite attitude control system during collisionavoidance maneuver is designed. The software is designed with good interactive interface and canrealize the function of actuator and sensor configuration, fault injection, fault tolerant control strategychoosing and collision avoidance demonstration.