The Structure Design And Experimental Verification Of The Retractable Space Manipulator

With the gradual deepening of space exploration, there are more in-orbit tasks to complete by space manipulator. A variety of complex in-orbit tasks have different requirements on the stiffness, working space and working load of the manipulator. However, the size and weight of the space manipulator are limited by the performance of the launch vehicle. In order to solve the contradiction between the transport capacity of the launch vehicle and the huge volume of the manipulator, and to reduce the transport cost, a new space manipulator is studied in this paper.Firstly, according to the design index of the retractable space manipulator, this paper completes the mechanical structure and mechanism design of the retractable manipulator. Through the analysis of various forms of telescopic mechanism, the basic configuration of the manipulator is determined. In order to meet the demand of the high stiffness, light weight, and various working state of the manipulator, this paper adopts a mechanism of the passive stretching, both ends locking and passive wire retraction. Then we use the 3D modeling software to complete the specific structure design. The dynamic simulation of locking mechanism is conducted to determine the required locking torque, which provides the basis for the selection of the drive unit. In this paper, we check the stiffness and strength of the parts which bear greater force to ensure the safety and reliability of the manipulator.Then, this paper studies the trajectory planning of the retractable manipulator, and studies the control strategy of the joints which drive the manipulator. In order to reduce the impact caused by the abrupt change of the joint acceleration, the five segment cubic polynomial interpolation trajectory planning method is adopted, which can effectively reduce the driving torque of the joint motor. The control strategy of the driving joint and the following joint is also studied. For the driving joint, PD control is adopted for its dynamic performance and high tracking accuracy. For the following joint, impedance control is adopted. The effectiveness of the control strategy is verified by the combined simulation.Finally, the experimental prototype and platform of the scalable manipulator are developed, and the experiment verification is also carried out. In order to verify the function and performance of the manipulator, the sketching, locking, wire retraction experiments are carried out. And the stiffness of the manipulator under different working conditions is tested in the locking state of the manipulator. In order to verify the overall performance of the manipulator and control strategy of the joint, the sketching experiment of two manipulators and two joints is also carried out in this paper. The results show that the design of the scalable manipulator is feasible, and the technical indexes meet the design requirements.