Study On Compliance Control Method Of On-orbit Service Manipulator

With the completion of China’s space Station,China’s space industry has ushered in a booming spring.In the future,there will be a large number of space robotic arms into space to carry out in-orbit docking,assembly,maintenance,construction,rescue and other space missions.However,the space has a typical zero-gravity environment,and the operation has a high precision requirement,which puts forward a high requirement for the control of the manipulator.Among them,the most important one is the flexible control ability of the manipulator.It is not only necessary to ensure the trajectory accuracy of the end of the manipulator,but also to ensure the moderate operation force during the operation process,so as to ensure the completion of space tasks without damaging the operation target.Therefore,this paper studies and designs the compliant control method of the in-orbit service manipulator.The main research contents of this paper are as follows:Firstly,the system was modeled for the 3-DOF manipulator designed in this paper.D-H parameter method was used to model the forward motion of the manipulator,D-H coordinate system of the manipulator was established,and the inverse kinematics was deduced by analytical method.Considering that the Newton-Euler method can clearly analyze the force relationship of all rigid bodies in the system,the Newton-Euler method is adopted to model the dynamics of the manipulator.Later,when conducting space operations for the in-orbit service manipulator,it usually needs to meet the position servo precision and certain environmental contact force.In this paper,a hybrid force/bit control is adopted.In order to make it have a more strict nonlinear control rate,a force/bit PID control algorithm is proposed in this paper,so that the actual target trajectory can fully realize the tracking task of target rules.Aiming at the research and analysis of adjusting the position error to indirectly control the contact force at the end of the manipulator,this paper studied the impedance control algorithm in the compliant control,designed the impedance control model,and improved the impedance model,designed a position based impedance control algorithm,with the help of the target impedance relationship conversion called trajectory correction error.The position control of the end of the manipulator is realized through the converted position correction.Finally,this paper verifies through simulation that the manipulator has a good dynamic process in the movement process,and has reasonable output torque while realizing the target trajectory tracking task,and has good flexibility.