Dynamics And Control Of Space Robot With Multiple Manipulators

In recent years,space robots are getting increasingly attention by its effectiveness in on-orbit services.However,most of the space robots are equipped with only one manipulator,which leads to difficulty for the relative position control when operating on a large spacecraft.Therefore,a space robot with multiple manipulators is studied in this dissertation.The considered space robot is equipped with 3 manipulators,each of which possesses 7 Degrees of Freedom.The dynamics and control of the space robot are investigated,while the strategy of the maneuver of the robot on a large spacecraft is designed and simulated.Firstly,a modified constraint force algorithm(MCFA)for dynamics of an arbitrary multibody system is developed for the dynamics modeling of the space robot with multiple manipulators.The constraint forces,which are critical parameters in designing the joint structure,can be directly obtained.The original constraint force algorithm which is only applicable to single-chained multibody systems is modified to arbitrary multibody systems by investigating the dynamics and kinematics in the nodes and discussing the constraint conditions of closed-loop structures.Secondly,the dynamics models of the space robot with multiple manipulators are established and verified through MCFA.The space robot has 4 typical topologies: the single manipulator mode,the dual-manipulators tree-topological mode,the dual-manipulators closed-loop mode,and the triple-manipulators closed-loop mode.The typical topologies of the space robot covered the configurations of the single-chained system,the tree-topological system,the single closed-loop structure and arbitrary topological system with closed-loop structure.The accuracy and the applicability of MCFA for arbitrary multibody systems are verified at the same time.Thirdly,the control strategy of the space robot with multiple manipulators is developed.The feedback linearization and the PD control are combined for trajectory tracking of the manipulators.The controller for tree-topological system and the one with closed-loop constraint are both developed.Finally,the maneuver of the robot on a large spacecraft is simulated.The maneuver is divided into 6 stages.The base body of the space robot is driven by the space manipulators.Numerical simulations show that the space robot is capable of tracking the prescribed trajectories in each stage to achieve the maneuver process under the control of feedback linearization and PD controller.