Research On Finite-Time Attitude Tracking Control And Attitude Coordination Control Methods For Spacecraft

The attitude tracking control and attitude coordination control technique of spacecraft is fundamental in many space missions and plays important roles in different fields including deep space exploration and earth monitoring.However,because many kinds of disturbances are introduced to the spacecraft system inevitably,it becomes a must that robust control algorithms are designed so that the space missions can be sucessfully accomplished with satisfactory control performance provided.Therefore,this paper aims at investigating the finite time spacescraft attitude tracking control and attitude coordination control problems based on the sliding mode control method,backstepping control method,adaptive control method,auxiliary system,dynamic surface control(DSC)method,and observer in the presence of the external disturbance,modeling uncertainty,and restrained control inputs,the main results of which are as given.Firstly,considering the attitude tracking control system parameterized with quaternion,several sliding mode surfaces including the linear sliding mode surface(LSMS),fast terminal sliding mode surface(FTSMS),fast nonsingular terminal sliding mode surface(FNTSMS),and integral terminal sliding mode surface(ITSMS)are designed using error quaternion and error angular velocity laying a foundation for the controller design of latter parts within this paper.Among the designed sliding mode surfaces,two novel integral terminal sliding mode surfaces are designed by incorporating the FTSMS,FNTSMS with a first-order filter,which is able to provide a fast finte time convergence rate for the control system without input singularity.Theory analysis about the dynamic property of the system states on the proposed sliding mode surfaces is given.Secondly,the FNTSMS is utilized to design three finite time spacecraft attitude tracking controllers in the presence of different kinds of system uncertainty.When only the external disturbance is considered and the upper bound of its time derivative is known to the designer,the first attitude tracking controller is deisgned based on the FNTSMS,FTSMS,and sign function.Because of the hierarchy structure of the proposed sliding mode surfaces,the sign function is hidden behind an integral operation which makes sure the closed-loop attitude tracking controller continuous and the actuator chattering problem is alleviated.Then,for the unknown upper bounded external disturbance,the FNTSMS is combined with the fast-TSM-type reaching law to formulate the second controller.To compensate for the external disturbance and modeling uncertainty simultaneously without requiring the respective prior knowledge,the third attitude tracking controller is designed based on the FNTSMS,fast-TSM-type reaching law,and continuous adaptive control method.Because the proposed controllers are all continuous,the actuator chattering problem is alleviated to a large extent.Rigorous analysis is given based on the Lyapunov stability theory and numerical simulation results are presented to show the feasibility of the proposed controllers.Thirdly,the finite time spacecraft attitude tracking control problem in the presence of the external disturbance,modeling uncertainty,and actuator saturation constraint is studied based on ITSMS.The first controller is designed based on the ITSMS,FNTSMS,and discontinuous adaptive control method considering all the problems mentioned above.Because of the hierarchy structure of the proposed sliding mode surfaces,the discontinuous function has to act on the spacecraft through a first-order filter,which assures the continuousness of the obtained controller and the actuator chattering problem is alleviated obviously.Then,for the attitude tracking control system with unknown upper bounded external disturbance,another finite time attitude tracking controller is proposed based on the ITSMS and fast-TSM-type reaching law.The third attitude tracking controller is designed based on the ITSMS,fast-TSM-type reaching law,and continuous adaptive control method,so that the unknown external disturbance and modeling uncertainty can be handled.Because the proposed controllers are all continuous,the actuator chattering problem is alleviated to a large extent.Rigorous analysis is given based on the Lyapunov stability theory and numerical simulation results are stated to show the feasibility of the proposed controllers.Forthly,asymptotic and finite time spacecraft attitude tracking control strategies are proposed considering the external disturbance,modeling uncertainty,and control input magnitude and rate saturations.Two asymptotic controllers are first proposed based on the LSMS,backsteping control method,adaptive control method,auxiliary system,DSC method,and observer.Then,to achieve the finite time convergence rate for the attitude tracking control system without input singularity,the third attitude tracking controller is formulated utilizing the ITSMS,backstepping control method,adaptive control method,auxiliary system,and observer considering the previous mentioned problems.Within the three proposed controllers,a dynamic model in a first-order filter form is built up to restrain the dynamic of the spacecraft onboard actuators,which is associated with an auxiliary system to meet the input magnitude and rate saturation constraints.The DSC method and observer are adopted seperately to solve the “complexity explosion problem” within the backstepping control method,so that the expected virtual control signal’s derivative is not involved by the closed-loop attitude tracking controller.Rigorous analysis is given based on the Lyapunov stability theory and numerical simulation results are stated to show the feasibility and advantages of the proposed controllers.Finally,the finite time stabilizing attitude coordination control methods are studied in the presence of different kinds of system uncertainty.For undirected communication graph,the attitude coordination controller is designed to handle unknown external disturbance and modeling uncertainty,based on the modified ITSMS and continuous adaptive control methods.Then,for directed communication graph,a robust finite time attitude coordination controller is designed to compensate for the external disturbance,modeling uncertainty,and input magnitude and rate saturations without requiring the prior knowledge based on the modified ITSMS,backstepping control method,adaptive control method,auxiliary system,and observer.The first-order filter is used to restrain the dynamic of the spacecraft onboard actuators and associated with an auxiliary system so the control input magnitude and rate are saturated.An observer is designed to handle the “complexity explosion problem”.Rigorous analysis is given based on the Lyapunov stability theory and numerical simulation results are stated to show the feasibility of the proposed controllers.