Research On Short Distance Motion Planning Of On-orbit Autonomous Servicing Spacecraft

On-orbit autonomous servicing is one of the important branches and directions of the on-orbit servicing technical system. It is the requirement of the industrialized and military space that autonomous spacecrafts or space robots are used to huge and multifarious on-orbit tasks that relate to space assembly, maintenance and servicing to enhance the operational life and capability of servicing targets. This dissertation focuses on the autonomous motion planning issues for servicing spacecrafts'maneuver of the short distance operations in a complex environment. The research approach of this dissertation is"planning system, modeling, individual planning and collaborative planning". The major contents of this dissertation are consisted of the following parts.Firstly, some concepts and system about on-orbit servicing are introduced. Based on these concepts, on-orbit servicing mission system is analyzed; the kinds of the servicing spacecrafts and process of the servicing are discussed. Considering this system and its missions of on-orbit servicing, the motion planning systems of the servicing spacecrafts'short distance operations are built.Secondly, mathematical descriptions, concepts for motion of the servicing spacecraft are systematically analyzed. The coordinate systems and their coordinate transformation relations are built. The pseudo body coordinate system used to describe the attitude is put forward. The differential equations and explicit equations of relative motion on orbits are derived.Thirdly, according to the flight characteristics of the agile servicing spacecraft, the motion planning of the agile spacecraft with continuous thrust is studied. The basic theories of Rapidly-Exploring Random Tree adapt properly to planning problems in higher-dimensional space and complex environment is introduced. Then the constraints and the contents of the motion planning of the agile spacecraft with continuous thrust are presented. Finally, the simulations with static, moving and unexpected obstacles prove the effective planning ability of the new motion planning algorithm based on improved RRT considering time.Fourth, the motion planning of the spacecraft with impulse thrust is studied. The theory of Probabilistic Roadmap based on randomization is introduced. Then we also present the constraints and the contents of the motion planning of the spacecraft with impulse thrust. Because of this hybrid system, it is better to carry out planning respectively with translation and rotation. In the translation planning, the mixed planning algorithm in a complex environment considering time with the explicit equations of relative motion as the local planning method is presented. In the rotation planning, two steps method based on the different coordinate axes planning is proposed to this problem. Finally, the simulations with static, moving and unexpected obstacles prove the effective planning ability of this new motion planner used to the motion planning of the spacecraft with impulse thrust.Finally, the cooperative motion planning of the multiple servicing spacecrafts system is studied. Some concepts of cooperation problem and cooperative motion planning are introduced. According to the servicing cooperation tasks and system, the cooperative motion planning method with cooperative strategies and algorithms of two kinds of servicing spacecrafts is presented. Finally, the simulations with static, moving and unexpected obstacles prove the effective planning ability of this method used to the motion planning of the spacecrafts with continuous and impulse thrust.