Path Planning Research Of The Free-Float Space Robot For Target Capturing

With the development of space exploration deeply, space robot will play more and more important role. The research on space robotic has become a worldwide hotspot. On-orbit service is one of research hotspots on space robotic. As a key technique of on-orbit service, target capturing is also a recent research hotspot. Free-floating space robot is one kind of the space robot that has the characteristics of attitude disturbance, kinematics redundancy and nonholonomic because the position and the attitude are not controlled. The paper bases on 7-DOF space robot as the research object, on the basis of completion of the space robot kinematics and dynamics modeling, the related problems of three stages of the Free-floating Space Robot for target capturing are discussed and studied, and then followed corresponding simulation. Three stages are approaching target(before touching), grabbing target(collision) and after grabbing(after touching). The main contributions of the thesis are as follows:1. Research on the kinematics modeling method and dynamic modeling method. On the basis of the multi-body dynamics theory and spacecraft attitude dynamics theory, the kinematic model is derived according to the geometric relationship and momentum conservation/ angular momentum conservation, the dynamic model is presented with the Newton-Euler method.2. Research on an obstacle avoidance path planning method for 7-DOF space manipulator to accomplish the in-orbit mission. Firstly, based on the geometric characteristics of manipulator and obstacle, this method is to simplify the model of manipulator and obstacle. On the basis of the inherent geometric characteristic of manipulator, and according to the position and orientation coordinates of obstacle, the collision conditions of manipulator's all links are analyzed. Then, the collision-free motion space of space manipulator is obtained. On this basis, the optimal collision-free path of 7-DOF space manipulator is acquired in the collision-free motion space with A* algorithm. Thereby, the obstacle avoidance path planning is achieved. Finally, the effectiveness and feasibility of the proposed method is verified by simulation and experiment.3. Research on a path planning method of space robot end effector for impact minimization. According to the kinematic model of free-floating space robot, determining the force coupling factor, establishing disturbance relationship between manipulator's movement and base posture through trajectory planning. At the same time, to optimal manipulator's configuration based on force coupling factor. Then, based on this relationship, it is concluded that the objective function of the particle swarm algorithm. Afterward, the sine function is taken to parameterize joint angle and joint speed. On this basis, using multi-objective particle swarm optimization algorithm based on crowding distance sorting to solve the optimal path, to minimize the impact force between end effector and target. Finally, the experimental simulation verifies the effectiveness of the proposed algorithm.4. Research on path planning algorithm of space robot after capturing target. In the first place, to identify dynamic parameter of the captured target object. Then using path planning in cartesian coordinates to obtain recognition parameters. Finally, the dynamic parameters of target could be obtained by using the obtained parameters.