Research On Spacecraft Attitude Fault-Tolerant Control Based On Non-smooth Control Theory

With the development of space missions,the requirement of spacecraft technology is becoming higher and higher.However,due to the harsh space environment,aging components and other factors,it is difficult to avoid the spacecraft actuator failure,even which will lead to the failure of the whole spacecraft attitude control system.Therefore,it is very important to design the attitude fault-tolerant control scheme to ensure the acceptable attitude control performance of spacecraft in case of actuator fault.In this paper,the effective fault-tolerant control schemes based on non-smooth control theory are designed to realize the fault-tolerant control of spacecraft attitude control system under actuator fault.The paper’s main work and results are as follows:The non-smooth active fault-tolerant control scheme based on terminal sliding mode observer is designed,which is avalible for the spacecraft attitude control system with actuator fault.First,a linear model of the spacecraft attitude control system under actuator fault is established.Next,a terminal sliding mode observer is designed,through this method,the estimation errors of system states converge to zero in finite time and the system actuator fault is reconstructed by the "equivalent output injection" method;then,by combining with backstepping method,an active fault-tolerant control scheme is designed.Finally,simulation results are provided to verify the validity of the design control scheme.The non-smooth fault-tolerant control schemes based on integral terminal sliding mode control are proposed for the spacecraft attitude control system in case of actuator gain fault(partial loss and complete fault).First,the mathematical model of spacecraft attitude tracking control system with actuator gain fault is presented.Next,without considering the actuator redundancy,the actuator partial loss fault,actuator saturation and external disturbance are taken as the total system uncertainty,and the fault-tolerant control scheme based on integral terminal sliding mode is proposed,so that the system achieves global asymptotic stability;then,this is then extended to handle the case with actuator redundancy,where some of the actuators fail completely,an adaptive sliding mode fault tolerant controller is designed to estimate the system uncertainty and actuator fault,respectively.Finally,simulation results are provided to verify the validity of the design scheme.The non-smooth fault-tolerant control schemes based on finite time control are proposed for the spacecraft attitude control system under combined actuator faults(gain fault and deviation fault).First,the mathematical model of spacecraft attitude tracking control system with actuator combined fault is presented.Next,without considering the redundancy of the actuator,the actuator fault,the inertia uncertainty and the external disturbance are regarded as the total system uncertainty,the fault-tolerant controller is designed based on adding a power integrator method to ensure the attitude tracking control is achieved in a finite time,so that the spacecraft tracking quaternion error and angular velocity error converge to the neighborhood of origin within a finite time;then,considering the actuator redundancy,the adaptive integral sliding mode fault-tolerant control scheme is designed to compensate the actuator fault and system uncertainty,respectively,so that the system achieves global finite time stability.Finally,simulation results are provided to verify the validity of the design scheme.