Optimal Guidance Control Strategies for Spacecraft Attaches to A Small Body

The issue of spacecraft attaching to a small body with complex weak gravitation field is challenging. In this paper, two optimal guidance control strategies are addressed with the mission background of accompany flight and attaching to a small body. First, taking the attaching mission in polar area of small body into consideration, dynamics model is constructed and simplified, as well as the constraints and time-fuel integrated optimal performance index is described. Secondly, phase plane method (PPM) is used to design optimal guidance, and optimal on-off control is given by limit circle. Next, Gauss pseudospectral method (GPM) is utilized to transform optimal guidance problem into nonlinear program (NLP) problem, and MATLAB/GPOPS optimal tool software package is utilized to obtain the numerical solution of guidance. Finally, the vector measurement based autonomous optical navigation given in the previous work is introduced to GNC simulation loop, and the two optimal guidance control strategies are verified. Simulation results show that both of them meet the requirement of mission, but the phase plane method based optimal guidance control is a little risky, while the Gauss pseudospectral method based optimal guidance control has a lower fuel consumption and higher accuracy, so the latter is feasible for engineering practice.