Stability Control For Space Manipulator System In On-Orbit Self-Assembly Task

With the continuous improvement of national strength and the continuous development of science and technology,China's manned spaceflight will soon enter the space station era.In 2022,China will build the first space station of its own,and the assembly of the space station cabins will become the most basic and ultimately important step.Simply utilizing the power and control system of the cabin itself to complete the assembly task of complex structure is not conducive to the safety of long-term on-orbit operation,so it is particularly important to rely on the space manipulator to complete the self-assembly task of complex structure of the space station system.The mass,inertia and other parameters of the main cabins of the space station are large.During the self-assembly process assisted by the space manipulator,the motion coupling between the cabins and the manipulators is outstanding,and the contact and collision between the large inertia cabins will also produce large impact force.If it can not effectively control the stability of the motion of the control system and reduce the adverse impact caused by the collision of the cabin,it will directly affect the smooth progress of the space station assembly task,and may even directly damage the structure of the space station.Therefore,it is of great theoretical significance and practical application value to study the stability control method of space manipulator for self-assembly tasks with large loads.In this paper,the space manipulator is taken as the research object,and the key technologies of dynamic modeling,collision configuration optimization strategy,impedance control strategy and base stability control strategy of closed-chain structure in self-assembly mission are studied.The main research work is as follows:Firstly,the dynamic characteristics of space manipulator for large load self-assembly task are analyzed.Based on Newton Euler's method and Lagrange's dynamic equation,the dynamic equation of general space manipulator is established.Aiming at the collision problem in the process of self-assembly,the discrete and continuous collision forces are analyzed with the cone-rod docking model and the momentum theorem and Hertz damping model.On this basis,the dynamic model of closed-chain structure of self-assembly system is established and the connection is analyzed.Impact effect of impact on space manipulator system.Secondly,in order to reduce the negative impact of contact and collision between cabins on space manipulator system,the pre-collision configuration optimization method of space heavy-load manipulator for self-assembly task is studied.Based on the equivalent characteristics of the end of the space manipulator and the multi-point collision dynamics equation,the mapping function between the collision force and the configuration change of the space manipulator is analyzed,and the optimization of the collision force of the space manipulator is completed by the redundancy characteristics of the space manipulator;based on the impact effect of the contact collision the space manipulator system,the particle swarm optimization algorithm is used to realize the adjustment of the structure of the space machinery.The arm is restrained by impact moment and disturbance.Then,in order to solve the force contact problem in the process of self-assembly contact,the flexible control method of space manipulator in self-assembly task is studied.Based on the dynamic model of closed-chain structure in the self-assembly task,the impedance control strategy is designed,and the contact force tracking in the process of self-assembly is realized.Aiming at the problem of motion coupling between the manipulator and the base,a zero-space attitude-free method is introduced to decouple the motion of the space manipulator and the motion of the base,which reduces the disturbance of the Genetic-Dynamic coupling effect on the base.On this basis,an attitude-free impedance control strategy is designed to ensure the end force tracking effect of the space manipulator,reduce the disturbance of the manipulator motion to the base,and improve the stability and security of the self-assembly task.Finally,experimental study on stability control method of space manipulator for large load self-assembly task is carried out.Based on the air-floating Four-Degree-of-Freedom planar manipulator system,the modification of the ground verification platform was completed through the design of the cabin and docking installation.The experimental scheme is designed,and the experimental data are collected by sensors.The validity of the theory of stability control method of space manipulator for large load self-assembly task proposed in this paper is verified and analyzed.