Research On Relative Navigation And Control In Spacecrafts Rendezvous And Docking

Rendezvous and docking (RVD) of spacecraft plays a very important role in space missions such as aerospace assembly, rotation of crew, spacecrafts maintenance and supply services. It is also one of the keys to Chinese manned spaceflight. Achieving docking of two spacecrafts is a complex and challenging space technology and the final phase is an very important phase in spacecraft rendezvous and docking. Based on studying of relative navigation and control problems in RVD, a proper theoretic project is chosen in this paper.Dynamic models, including relative orbit dynamic model, attitude dynamic and kinematic model, are established first. Hill equations are chosen as the relative orbit dynamic model for RVD final phase, and Eulerian angle is chosen for description of attitude model.Secondly, disciplines of vision-based navigation are introduced, as well as monocular vision method and binocular vision method for relative position and attitude determination. Based on analyzing of traditional monocular vision method, a new equation for relative position and attitude determination is established, which avoids quadratic nonlinearity in traditional method. The solution of the new equation, including choice of initial value and iteration method, is given on the basis of proper assumption. The problem of one camera breakdown in binocular vision is dicussed, monocular vision method is proposed to replace the binocular vision method to ensure a correct determination value.The theory of Kalman filtering algorithm is introduced and applied to estimate the relative postion and attitude of spacecraft. The computer simulation shows that the Kalman filter algorithm meets requirement of RVD in final phase.And then research is done on the problem of relative position and attitude control in RVD final phase. Based on Hill equations, a state feedback robust controller is designed for spacecraft approach, by using H∞control theory. And the problem of chaser's attitude control is studied as a problem of attitude tracking with object. Considering spacecraft engines, PWPF modulator is used to modulate constant control law to pulse sequence to adapt to practical situation. Simulation of closed-loop system is done with disturbance added. Result shows the controller is robust and feasible for spacecraft RVD.In the end, problems and direction for further research are raised.