Research On The Theory And Method Of Spacecraft Attitude Tracking Control In Finite-time

In the aerospace field,spacecraft attitude tracking control as a research topic has attracted much attention for a long time.The study of attitude control is extremely challenging because of the nonlinear characteristics of the spacecraft model.However,the traditional spacecraft attitude control method fails to effectively solve the problems of nonlinearity,uncertainty,and saturation,which exist in process of the spacecraft attitude control,and as the spacecraft’s functional requirements increase,it fails to satisfy the performance of rapidity,stability and high accuracy.According to the problems of nonlinear characteristics and input saturation,which exist in spacecraft attitude tracking control process,this thesis has conducted an in-depth study on the control theory and method in the case of finite-time tracking.The algorithm not only takes care of the steady-state,but also considers the transient performance,which is an important tool to improve the system performance.The main results of this thesis are the following.First,the mathematical model described by quaternion of spacecraft attitude is regarded as the research object,and a kind of fast finite-time attitude tracking controller is put forward based on the optimal control theory by using fast finite-time stable theory,and one of the significant advantages of the proposed method is to improve the convergence speed of traditional finite-time control methods.Theoretical analysis shows that this tool can ensure that the angular velocity tracking error of the spacecraft converges to zero in a faster finite-time.Second,on the basis of fast finite-time control theory,the problem of input saturation is further discussed,and by introduced a new type of saturation function,a fast finite-time tracking spacecraft attitude controller with input saturation is proposed.It takes previous mathematical model of spacecraft attitude as the research target.Based on the finite-time Lyapunov stability theory,the sufficient conditions for the existence of the controller are given.Theoretical analysis and simulations show that when the system is limited by input saturation,the control strategy can reduce the energy consumption of the spacecraft system by quickly reducing the angular velocity error of the tracking spacecraft system to the equilibrium point.Finally,based on the attitude model of the spacecraft described by the modified Rodrigue parameters,a new kind of fixed-time attitude tracking controller of spacecraft with input saturation is designed by combing backstepping and fixed-time stability theory.Its main advantage is to overcome the problem of the convergence time depending on the initial states of the system in the traditional finite time algorithm.The characteristics of the proposed controller are follows:(1)Ensure that all the signals of the closed-loop system are limited;(2)Input saturation is considered,and the spacecraft attitude tracking can be achieved with a small input cost;(3)The convergence time to equilibrium point has nothing to do with the initial states of the system,it only depends on the design parameters of the controller.In the end,the feasibility and effectiveness of the design scheme are verified by numerical simulation analysis.The above results not only further enrich and develop the finite-time theory of nonlinear systems,but also provide an effective analysis method and theoretical basis for observing the condition of their spacecraft.