Research On Method Of Spacecraft's Rendezvous With Maneuvering Target Based On Sight Coordinate System

Two spacecraft's Rendezvous technology in coplanar near-earth orbit with maneuvering target, based on the sight coordinate system is presented in this paper. Differential Games Guidance Law (DGGL) and Proportional Navigation (PN) are studied. DGGL is studied as the optimum control of both sides. PN is the method to obtain optimum control in condition of target without maneuvering, pursuer is controlled by feedback of opponent's information and by continually updating the gain of navigation to achieve capture of maneuvering target, thus the PN is optimum control of one-side. Theory analysis and experimental simulations of pursuit-evasion problem with maneuvering target in sight coordinate system are performed using the two methods.The first part is based on modern theory of differential games of kind, and complexity of solving Saddle Point is avoided. The constructing of the barrier and the judgment of expected result is the key of the problem. The complex nonlinear pursuit-evasion model of two spacecraft in near-earth coplanar orbit is simplified to linear model, the circular region the radius of which is equal to capture radius is defined as target set, capture is achieved when the evader come into the target set and the game is over; the Boundary of Useable Part (BUP) is determined, and the analytical form solution of the linear equations is obtained by backward integration of the state variables from the BUP, the linear barrier of the pursuit-evasion model and the optimum thrust of the both sides are thus obtained. The simplification of linearization is proved to have certain request of precision by reverting the linear state variables and experimental simulation.The second part studies optimal Pure Proportional Navigation (PPN), with time-dependent gain of navigation to maneuvering target based on proportional navigation theory. Optimal gain of navigation is constant for PPN without maneuvering; based on this, solution of time-dependent gain of navigation is given by iteration approach, and the time required for capture is given, the times of iteration is decided by comparing this time with the iteration step.