Robot Astronaut Control Method Of Climbing Motion And Compliance Manipulation In Space

At present, most of the maintenance service and manipulation in space station are depended on astronauts. Every extravehicular mission is a serious challenge of the health and life safety of astronauts, and with large economic cost, time cost and human cost. The environment in space station is designed by ergonomics of astronauts, so it is significant to use robot to assist or substitute for astronauts in space manipulating missions. Based on the manipulation mode which astronauts climbing to the target area and then start to manipulate, this paper analyzes the particularity of dynamics and control needs in microgravity environment with the national defense basic scientific research and 921 manned space flight projects. Focusing on the requirement of extravehicular climbing motion and compliance manipulation of robot astronauts, the research on free floating dynamics, climbing motion control, compliance manipulation about robot astronauts are carried out. The main researches and results are as followings:Firstly, the motion status of the robot is very susceptible to the disturbing force and the changing of load in a large range, thus these brings a new challenge on rapid and steady control of robot. This paper proposed an improved space vector method to build the free floating dynamics of the robot. This method reduces the calculated amount significantly(Reduces 30% of classical space vector method), so it can meet requirements of on-time control in embedded system. The research of this method is a basis of the robots’ rapid and steady control.Secondly, to solve the problem that the motion status of the robot is very susceptible to the disturbing force and the changing of load in a large range, a feedforward method which synthesizes system dynamics, end-effector contact force and mathematic model of joint motor is proposed. Focusing on the joint control, this method can improves the response rate of joint torque control. Meanwhile, the acceleration of climbing motion is optimized based on dynamics, and a safety climbing method is proposed to avoid impact. These methods guarantee the stability and safety of robot astronauts’ climbing motion.Thirdly, focusing on the problem of multi-peg-in-hole compliance docking mission on assembling extravehicular equipments, based on the analysis of the special mechanics characteristic of docking structure, an improved impedance control method based on forgetting factor function is proposed by expanding the spring term of classical impedance control. This method can adjust the balance position of virtual spring in impedance controller to reduce vibration and contact force during docking process. Therefore the influence on stability of docking which generated by the impedance force from random localizing error can be solved. And the steady docking can be achieved.Finally, based on the robot principle prototype, the experimental platform and simulation system are built. The simulation and experimental results have validated the practicability of the research and methods proposed in this paper focusing on robot astronauts’ motion and manipulation.