Research On Dynamics And Control Of Attitude And Orbit Of MMU On Orbit Servicing

Extravehicular activity(EVA) is one of the vital technologies for manned space flight. Whereas, due to the complexity of the space environment compared to the earth ground, the extravehicular astronaut has confronted lots of difficulties, even gotten into unpredictable hazards. In order to solve the problems above, the author does research on MMU(Manned maneuvering unit), it can provide the necessary safety rescue and a certain mobility abilities for astronauts during EVA. Especially, it can also provide some help on assembling the space station, maintaining and inspecting the target statellite through some manual operations.Compared to the general spacecraft, MMU's characteristics with small size and light weight lead to interference and influence to the processing of MMU attitude stability caused by limb movements of astronaut, which can not be ignored, coupling effect from human-MMU significantly. Aiming at this situation, the author simplifies astronaut as 9 rigid body model to study. According to the law of moment of momentum, the author stablishes the astronaut-MMU coupled system attitude dynamics model. Through planning astronaut's limb movements and designing the attitude controller of MMU, the author discusses the effects of different types to MMU attitude control processing, especially to responsed time and energy consumption for attitude mobility. The simulation results show that the minimum energy consumption occured when astronaut do knee exercises, and the optimal result for response time occured when astronaut do knee exercises first and stretching then. At last, we find the optimal time point of the movement in the kneebend and stretching.In part of trajectory design and optimization for MMU approaching the target, C-W equation is used to describe the relative motion between MMU and the target. Firstly, two types of engine propulsion modes are discussed in this paper, based on velocity increment modes and continuous variable thrust modes. On the basis of this, the transfer trajectory from MMU to the target is designed by PD pulse controller. Then, the author study the multi-impulse maneuver trajectory according to the idea of sliding guidance. Finally, the trajectory optimization problem is transformed into a nonlinear programming problem with constraint conditions by using the direct collocation method. Here, the energy consumption cost and the time-energy comprehensive cost are used as the performance index. The results show that MMU trajectory transfer processing has a good dynamic response under the two engine thrust modes, and it can help the astronaut complete the specified orbital maneuver mission well.The relevant data and results obtained from this paper can provide some theoretical guidance for the following training of the astronaut EVA in the future.