Rigid Spacecraft Attitude Tracking Control Method Research

Attitude control is the prerequisite and guarantee for spacecraft to accomplish various tasks.The attitude dynamic system is not only nonlinear,but also affected by the uncertainty part of the inertia and the disturbance of external environment.In recent years,with the increasing complexity of spacecraft structures and missions,the requirements for spacecraft control algorithms are getting higher.A single control algorithm cannot solve the multiindex optimization control problem of spacecraft attitude control system under the condition of internal uncertainty and external disturbance.In this paper,based on fixed time control and finite time control,combined with extended state observer(ESO),fixed-time extended state observer(FTESO)and back stepping method,several compound control strategies are constructed to satisfy the requirements of the system such as fast,accurate,robust and even low energy consumption of the system.The main content of this paper is as follows:Studying the rigid spacecraft attitude tracking control problem for the fast convergence rate and high-precision with uncertain part of inertia and external disturbance.By mathematical transformation,a more optimal dynamics model of spacecraft is obtained,which not only reduces the burden of the observer,but also improves the precision of the controller.The total uncertainties part of the spacecraft system accurately estimated by using the extended state observer,and the finite time control algorithm is used to achieve the highperformance attitude tracking control goal of the spacecraft.Finally,the global finite time stability of the system is demonstrated by the Lyapunov method,and the feasibility of the control method is verified by Matlab simulation.The finite time attitude tracking control problem of the spacecraft based on fixed time extended state observer is studied.The new fixed time extended state observer is designed to solve the parameter uncertainty and the influence of the external disturbance.Many previous articles have proposed that the observation errors of the observer are asymptotically stable or finite-time stable.In order to reach the higher performance requirements of the spacecraft attitude tracking control,this section designs a novel observer that does not depend on the initial value of the system.The convergence time of the observation errors is faster,the convergence accuracy is higher,and the observation errors are more robust.Based on the output of the fixed time extended state observer,a finite time controller is designed by using the Barrier Lyapunov Function(BLF).The designed control algorithm is continuous and has non-singularity,which can ensure that the attitude tracking error converges to a small neighborhood in a finite time by satisfying the attitude constraint.The Lyapunov method is used to demonstrate that the control strategy can achieve the global that the system is stable in the sense of the finite time.And the feasibility of the control method is verified by Matlab simulation.A new fixed time attitude tracking control law is proposed by using the method of backstepping and "additive power integrator".The control scheme is continuous and nonsingular.When there is no uncertainty and external disturbance,the attitude tracking error can be guaranteed to converge to the origin in a fixed time.When uncertainties and external disturbances are existed,the attitude tracking error can be guaranteed to converge to a small bounded region including zero.Finally,it is demonstrated by the Lyapunov method that the system is stable in the sense of the fixed time under the action of the controller,and the effectiveness of the proposed strategy is verified by Matlab simulation.