Anti-disturbance Attitude Fault Tolerant Control Method For Flexible Satellites

With the rapid development of space technology,the requirement of satellite performance is higher and higher in both military and civil fields.However,in order to meet the complex space mission and reduce the launch cost,more and more flexible accessories are carried by modern satellites.The flexible satellite in orbit has uncertainty of inertia,elastic mode,actuator failure,modeling error and control input saturation,so it is important to research the attitude control method with high reliable anti-disturbance performance.To cope with the above-mentioned problem,the main work and innovations of this thesis are listed as follows:An adaptive fault tolerant control(FTC)method based on disturbance observer control(DOBC)is proposed for attitude control system(ACS)of flexible satellite with elastic mode,modeling error,actuator failure,modeling uncertainty and space environmental disturbance.Firstly,a fault diagnosis observer(FDO)and a T-S fuzzy disturbance observer(TSFDO)are constructed to estimate the actuator fault and flexible accessories,respectively.Then,based on FDO and TSFDO,a new adaptive anti-disturbance FTC is designed to ensure the closed-loop system is asymptotically stable.Different from the traditional DOBC method,TSFDO can estimate the nonlinear disturbance.An anti-disturbance adaptive sliding mode fault-tolerant control method is addressed for ACS of satellites subject to elastic mode,space environmental disturbance,modeling error and partial loss of actuator effectiveness.Firstly,T-S fuzzy technique is used to estimate the unknown nonlinear elastic modes,where the limitation of the disturbance described by linear system in traditional DOBC method can be removed.Then,an adaptive sliding mode controller is designed to compensate the norm bounded disturbance and ensure the sliding mode surface converges to zero.Compared with the traditional terminal sliding mode control method,this method has disturbance rejection performance and higher precision.An anti-windup fault tolerant attitude control method based on DOBC is designed for ACS of flexible satellite elastic mode,actuator failure and control input saturation.Firstly,FDO and disturbance observer are constructed to estimate the actuator additive fault and flexible accessory,respectively.Furthermore,the environmental disturbance,the uncertainty of inertia and the estimation error of modeling disturbance and fault are combined into the norm bounded disturbance.Based on disturbance rejection and fault accommodation,the control accuracy and reliability of ACS for flexible are improved.The anti-windup algorithm guarantees the stability of the generalized state through the constraint function,which greatly reduces the difficulty.The simulation results show that the anti-disturbance attitude FTC methods proposed in this thesis can improve the accuracy and reliability of the ACS.The method has a certain anti-disturbance ability and good robustness,and has a certain value in engineering application.