Research On Position And Attitude Coupled Control Of Spacecraft Rendezvous And Docking On An Elliptical Orbit

Based on the background of spacecraft rendezvous and docking on an elliptical or-bit,the integrated translational and rotational control problems are studied in this paper.The main contents include:First of all,the nonlinear system inverse optimal theory is introduced to deal with spacecraft orbit control problem on an elliptical orbit.While the target spacecraft runs on an elliptical orbit,the relevant orbital parameters such as the orbital angular velocity are time-varying,and it is difficult to obtain their information in real time.In order to avoid the these time-varying orbital parameters,a model transformation method based on the true anomaly ? is introduced in this research.By analyzing the transformed model and applying nonlinear system inverse optimal theory,the inverse optimal controller is designed,it can make the relative distance and relative velocity of the two spacecrafts converging to zero.At the same time,it is optimal to a given cost function.Furthermore,based on the dynamic model using the time t as an independent variable,the adaptive control theory and the inverse optimal theory are combined to design a control method by taking uncertainty of the model parameters into account.It can not only stabilize the whole closed-loop system,but also can estimate the upper bound of the uncertainty parameters in the model.Furthermore,it is optimal to a given cost function.Secondly,the input-to-state stability theory of nonlinear discrete-time system is introduced to deal with the sampled-data control problem of spacecraft rendezvous and docking on an elliptical orbit.Based on the dynamic model using the time t as an independent variable,an discretization method is utilized to obtain the discrete system of the original continuous-time system.On the basis of the discrete-time model,By analyzing the one-step consistency with the exact discrete-time model and the input-to-state stability theory of nonlinear discrete-time system,a sampled-data controller is obtained by taking the bounded external disturbances into account.It can not only make the whole closed-loop system input-to-state stable,but also can suppress the bounded external disturbances effectively.Subsequently,the finite-time input-to-state stability theory is introduced to discuss the integrated translational and rotational control problem of spacecraft rendezvous and docking on an elliptical orbit.By designing the layout of the thrusters of chaser space-craft,the integrated translational and rotational dynamic model is established.Then by applying the nonlinear system finite-time input-to-state stability theory,a robust con-troller is proposed by taking the bounded external disturbances into consideration.It can not only make all the states converging to the neighbour of the origin,but also can suppress the bounded external disturbances effectively.Finally,the vector Lyapunov function method is utilized to deal with the integrated translational and rotational control problem of spacecraft rendezvous and docking on an elliptical orbit.Since the vector Lyapunov function method has unique advantages in dealing with strongly coupled nonlinear cascade systems,the criteria of input-to-state stability for a class of general nonlinear cascaded systems are given under the framework of vector Lyapunov function method.Then based on integrated translational and rotational dynamic model,the vector Lyapunov function method is used to design the robust control scheme.The controller can make the whole closed-loop system input-to-state stable.