Research On Spacecraft Hovering Formation Control Methods

With the sustainable development of aerospace technology in the late years,people continue to carry out space missions such as space exploration and spacecraft on-orbit service,and hovering formation technology is the key to its future development.The hovering formation control of relative target spacecraft is studied in this paper.Through the improvement of control algorithms,the control performance of hovering formation can be improved.The following aspects will be studied in this thesis:To initiate the search of subject,considering the elliptic reference orbit,the linearized relative dynamics equation in the true near-point angular domain is derived.And,the model is simplified by variable substitution,and the dynamic form is independent of reference spacecraft location information,which is weak in time-varying.Furthermore,the hovering formation control is transformed into a linear quadratic optimization problem,and a widely used LQR controller is given.In order to solve the problem of matching disturbance or uncertainty during hovering flying and improve the anti-jamming performance and robustness of formation system,finite-time control and sliding mode control are studied.A non-singular terminal sliding mode control is proposed.In the process of hovering formation,the terminal sliding mode control has better control precision and convergence speed than LQR control,but the fuel consumption is higher.In order to get rid of the shortcomings of high fuel consumption and improve global convergence speed,an modified non-singular fast terminal sliding mode control algorithm is proposed.The simulation results show that the improved terminal sliding mode control can improve the control performance and reduce fuel consumption level.Then,in order to solve the problem of interference or uncertainty that does not satisfy the matching conditions during hovering formation,a backstepping design method is introduced.The approximation strategy of radial basis function(RBF)neural network is proposed.The adaptive rate is derived by Lyapunov stability theory.The problem of mismatched disturbance is solved.The influence of matched disturbance or uncertainty is eliminated by combining linear sliding mode control.In order to improve the performance of the hovering controller and reduce chattering phenomenon,a high-order sliding mode controller is designed based on the terminal sliding mode control with finite time convergence.The simulation results show that the controller eliminates the chattering phenomenon which is existing in adaptive linear sliding mode control,but the performance is deteriorated.The problem is solved by applying the improved high-order sliding mode controller with fast terminal sliding mode.The simulation results show that the improved controller improves the control accuracy,accelerates the convergence speed and reduces fuel consumption.The problem of obstacle avoidance in hovering formation of spacecraft is considered.The hovering guidance rate is obtained by artificial potential function method.The hovering formation is realized and the space obstacles are avoided.A feedback controller is obtained by combining sliding mode control,which improves the anti-jamming ability of the system.In order to improve formation efficiency and control performance,the principle of finite-time convergence of terminal sliding mode is extended.Based on the non-singular terminal sliding surface using artificial potential gradient,an improved controller is designed.The simulation results show that the improved control algorithm has advantages in accelerating convergence speed and improving control accuracy,and can reduce fuel consumption under specific conditions.