Research On Trajectory Planning And Impact Modeling Of Space Robots For Capturing Moving Targets

The free-floating space robot (FFSR) is becoming more and more significant in space work for its low cost of energy. Target capture, as one of the basic mani-pulations in the researches of space manipulator, is of great importance. Current works are most on the capture of immobile targets, however the objects to be seized usually keep moving. This thesis is mainly on trajectory planning of free-floating space robots capturing motorial target efficiently. The problems on colli-sions between targets and the end of the space robots when capturing and the mi-nimization of the impulse during the impact with arm-mode selection are re-searched as well.Firstly, the kinematic and dynamic models of the FFSR are founded in this paper. The direct kinematic functions and the speed class inverse kinematic and dynamic functions based on Generalized Jacobi Matrix are deduced. The research subject is introduced and its peculiarity is analyzed briefly, its geometric model for virtual simulation is built. The point-to-point tracking and direct path tracking are accomplished respectively through joint space and Cartesian space program-ming based on the former founded kinematic model. The validity of modeling is verified, so as to provide the foundation of the research in this paper.Secondly, a method of track programming of the FFSR's self-tracking to moving targets is developed in this paper. With the limited capability of compu-ting, to minimize the quantum of calculation requisite in track programming, as well as the demand of speed and stability, and the concern of other index is needed by the FFSR while tracking to moving targets. Three methods are men-tioned as direct end-speed programming induction, continuous trajectory plan-ning induction and subsection standard tracking. Each advantages and disadvan-tages and applicabilities are analyzed. Predictions on parameters of trajectory movement based on Kalman filter are made, in case that the tracking precision is low of the programming method with the least quantum of calculation, improving the tracking precision of the FFSR toward moving targets.Finally, the target capturing progress of the grabbing device of the FFSR is analyzed. In the problem of impact while capturing targets, the relations among impact impulse, the relative speed between space base and the target at the im-pact-point, and the arm-mode of the manipulator, are found, using the dynamic-impact model deduced from the dynamic functions. The speed variables of the FFSR's basement and manipulator during impact are deduced, as the impact im-pulse cannot be easily measured in practice. In order that each available position for the manipulator to track and capture moving targets, and the impact impulse caused by the speed of the end of the manipulator for the arm-mode diversity of the manipulator could be analyzed, thus the optimal position for capture could be chosen.