Adaptive Fault-tolerant Control Technology For Rigid Satellite Attitude Control System Under Actuator Faults

With the advancement of technology,satellite control technology has developed very rapidly.The satellites in flight often have the characteristics of multi-task.In addition,the speciality of the space environment also has high requirements on the function of the satellite.At this time,the control precision of the satellite and the stability of the satellite closed-loop attitude control system are extremely strict.Therefore,the research and design of satellite attitude control system is a challenging and a meaningful topic.In this paper,the nonlinear attitude control system of satellite is mainly studied.For satellite attitude systems with unknown external disturbance and actuator faults,firstly,the nonlinear satellite attitude dynamics model with actuator faults is given.Then according to the latest research methods at home and abroad,the problems that need to be solved in the current research of satellite attitude control system are grasped.Based on adaptive control theory and inversion control technology,a suitable fault-tolerant control strategy is designed to ensure that the system can meet the requirements of closed-loop stability and basic performance indicators under fault conditions.Finally,based on the simulation results,the proposed fault-tolerant control method is observed to see if the attitude control system of the satellite is effective in the event of actuator faults,which provides an important theoretical basis for solving the problem of fault-tolerant control of satellite attitude control systems.Next,the following three aspects of research will mainly be introduced:Firstly,a passive fault tolerant control for the satellite attitude systems with unknown external disturbance and actuator faults is presented.A nonlinear satellite attitude dynamics model with actuator faults is given.Then,under the framework of back-stepping control,a PI controller with adaptive tuning gain is designed,which aims to provide added robustness in the presence of large and fast but bounded uncertainties and disturbances,and its performance is better than that in traditional PI controller.Finally,simulation results are presented to demonstrate the effectiveness of the proposed fault tolerant control approach in a satellite attitude control systems subject to actuator faults.Secondly,an iterative learning observer-based fault tolerant attitude tracking control scheme is proposed to the satellite attitude systems with mixed actuator faults.Firstly,the nonlinear satellite attitude control system model and the mixed actuator faults model are given.Next,an iterative learning observer is designed for the faulty satellite attitude systems to obtain the estimatedunknown torque input produced by the mixed actuator faults.On this basis,a fault tolerant attitude tracking controller is designed by using back-stepping control technique to guarantees the stability of the satellite closed-loop attitude systems.Finally,simulation results are given to illustrate the effectiveness of the proposed fault-tolerant control approach.Thirdly,an active fault-tolerant attitude control scheme is proposed and applied to the satellite attitude system.The proposed solution solves the problem of fault tolerant controller design in the presence of severe actuator faults and external disturbances.Firstly,the nonlinear satellite attitude dynamics model with actuator faults is given.After that,an observer for fault diagnosis is designed.Next,a fault-tolerant control law based on inversion control is designed.Finally,it can be proved that the proposed design method is effective,which can ensure that all signals of the closed-loop system are uniformly ultimately bounded,and the simulation results can verify the effectiveness of the proposed fault-tolerant control method in the satellite attitude control system affected by the actuator faults.