Sliding Mode Control Based Spacecraft Attitude Control With Actuator Characteristics

In recent years,the development and breakthrough of space science and technology have attracted the significant attention of our country,which vigorously promote the manned space flight and deep space exploration program.It not only puts forward new demands for aerospace system engineering technology,but also greatly improve the requirements of the stability,reliability and fastness of spacecraft attitude control system.During the spacecraft missions,the complex space environments make unavoidable influences on the spacecraft and its components,such as actuators’ misalignments and failures.Then,these pose great challenges to the design of the high precision and stability attitude control system.Whereas,sliding mode control techniques based control system design has the advantages of strong robustness,fast convergence,and strong disturbance restraining performance,etc.,which is utilizing to solve the above challenge problems.What’s more,form the point of the optimization of time,the finite time convergence of the control system is the time optimal control method.Therefore,it has great theoretical and practical significance to study the sliding mode control based finite time control methods with fast convergence and robustness in attitude control system.On the other hand,actuator failures or uncertainties,attitude sensor failure(unknown attitude angular velocity information),and other factors affect and restrict the stability of attitude control system as well.So robust finite time fault tolerant attitude control schemes for spacecraft is an important guarantee to improve the mission completion rate and on-orbit life of spacecraft.Therefore,this paper aims at the design of finite time attitude control and fault tolerant control scheme,which are committed to solving the problems and challenges of finite time fault tolerant attitude control,output feedback control,control input constraints for spacecraft attitude control system with external disturbances,model uncertainties and actuator failures.The main contents and achievements of this dissertation are presented in the following aspects.Traditional terminal sliding mode and integral terminal sliding mode based finite time attitude control methods are investigated to deal with the spacecraft attitude control issue under uncertainties including external disturbances and the installation deviation of actuators.First of all,a simple traditional terminal sliding mode and adaptive control based continuous attitude control algorithm is proposed to ensure the finite time stability of the spacecraft attitude control system with external disturbances and the actuator misalignments.For the better control performance on convergence time and robustness,a finite time attitude controller is designed utilizing the backstepping method and integral sliding mode technique in the presence of disturbances and actuator misalignments,which can dealt with the disturbances and misalignments and also force the control system state to keep on the stable sliding mode surface.Finally,numerical simulation demonstrates the effectiveness of proposed finite time control schemes.Consider the input saturation problem,two spacecraft attitude control schemes are investigated under external disturbances,actuator misalignments or unknown attitude angular velocity and other uncertainties.Firstly,a novel nonsingular terminal sliding mode and adaptive technique based finite time attitude control law is studied;and the adaptive technique is used in this control law to deal with the complex situations under disturbances,installation deviation of actuators and control saturations.Then the attitude control system is proved to converge to the stable region in finite time utilizing the Lyapunov theory.Furthermore,an asymptotic stable filter based output feedback attitude control scheme is proposed for spacecraft without angular velocity measurement;then a class of asymptotically stable output feedback based saturated attitude controller is studied to deal with the constraints of actuators input constraints.Through numerical simulations and comparisons,one can see that all these attitude control schemes can ensure the robustness and reliability of the attitude stabilization system in the present of system uncertainties and input saturation,and the accuracy and stability of control system have improved to some degree.For the attitude control problem of spacecraft under multiple system uncertainties(such as external disturbances,installation deviation of actuators,failure or control saturations,etc.)or unknown attitude angular velocity information,several state feedback and output feedback based spacecraft attitude fault tolerant control schemes have been investigated.Firstly,consider the external disturbances and actuator failures,a novel homogeneous system theory,integral sliding mode and adaptive technique based finite time fault tolerance controller is designed.Then,a novel finite time robust fault tolerance attitude controller is proposed for spacecraft with uncertainties,actuator failures and input saturations.Furthermore,combining the homogeneous system theory,fast nonsingular terminal sliding mode,adaptive technology and robust least squares method,a novel finite time attitude fault tolerant control and fault tolerant control allocation approach incorporating with a finite time attitude angular velocity observer is proposed for spacecraft in consideration of model uncertainties,failures,input constraints of actuators,unknown attitude angular velocity measurement information and rapid convergence of attitude control systems.Finally,the effectiveness and superiority of these designed finite time attitude fault tolerant control schemes are verified using numerical simulations.