Research On Key Technologies Of Target Operation For Rigid-Flexible Dual-Arm Space Robot

With the development of aerospace technology,space robots are playing a more and more important role in satellite maintenance,space station construction,orbital garbage cleaning,etc.Traditional space robots are composed of discrete joint manipulators.Due to the limitations of volume and degrees of freedom,the difficulties of working in nonstructural,complex and narrow environments has become increasingly prominent.The new type of continuous flexible manipulator has the characteristics of slender body,good flexibility,hyper redundant degrees of freedom,and stronger environmental adaptability.Therefore,in the face of increasingly heavy and complex on orbit task requirements,a new type of rigid-flexible hybrid dual-arm space robot is proposed by combining the advantages of two different types of manipulators.And to carry out research on precise and dexterous operation technology to improve the accuracy and safety of on-orbit service tasks,which has important theoretical significance and engineering value for the development of national aerospace technology.In order to meet the requirements of national engineering tasks,this paper takes the rigid-flexible dual-arm space robot as the research object,and solves the problems of non-cooperative target satellite capture and narrow space operation as the research goal.It focuses on the key technologies such as target capture method of rigid manipulator,teleoperation interaction method of cable-driven hyper-redundants flexible manipulator,robot obstacle avoidance planning and ground verification method of space robot,and some technologies have successfully completed on-orbit applications.The main work of this paper is as follows:(1)Rigid-flexible dual-arm space robot system and operation object analysis.Aiming at the on-orbit maintenance task of faulty satellites,a new type of rigid-flexible hybrid dual-ann space robot is proposed.The design of target operation task and the analysis of key technologies are completed.Aiming at the non-cooperative satellites with typical failures of sail panels,the operability as the capture target is analyzed from many aspects,such as acquisition mode,tolerance,connection stiffness,flexibility,clamping force and time,measurement means and distance,etc.,and the satellite rocket docking ring is determined as the capture object.The kinematics solution of the redundant manipulator is the basis of planning and control.The arm angle parameterization method is introduced to establish the kinematics model of 7 DOF(degree of freedom)rigid manipulator;The kinematic model of the hyper redundant flexible Manipulator with 5 large sections,40 small sections and 80 DOF is established by using the relationship of equal angles in the joint segment.(2)Research on non cooperative target capture method of rigid manipulator.Aiming at the typical characteristic of satellite rocket docking ring,the difficulty of measurement is analyzed and an active light source is introduced to propose a target measurement scheme based double line structured light.The simulation results show that the method can achieve high-precision measurement of the docking ring.In order to simulate the space working environment,the ground gravity compensation method of six axis force sensor is studied,and the compensation effect is analyzed by experiment.Aiming at the problem of contact operation when the space manipulator captures the target,a speed based impedance control method is proposed,and the compliance control model of the robot’s speed,acceleration and end contact force is established.The performance of the compliance control method is verified by experiments,and the ability of the robot to obey external forces quickly and stably is improved.(3)Research on teleoperation interaction method of cable-driven and hyper-redundant space flexible manipulator.For the motion characteristics of cable-driven and hyper-redundant flexible manipulator and the requirements of on orbit teleoperation tasks such as rapid transfer in a large space,dexterous obstacle avoidance,narrow space operation and fine adjustment under contact state,a human-machine interaction system for teleoperation based on the combination of manual controller and virtual reality(VR)handle is designed and developed,which can adapt to a variety of working conditions.Based on the analysis on working conditions such as narrow space operation and obstacle avoidance,a teleoperation method is proposed based on the DOF dynamic combination and the synchronous planning of the end and the arm configuration.Finally,the experiment proves the effectiveness of the teleoperation interaction method for the precise,dexterous and safe control of flexible manipulators.(4)Research on obstacle avoidance planning method of space robot based on deep reinforcement learning.Aiming at the obstacle avoidance problem of space manipulator in unstructured environment,a robot active obstacle avoidance method based on virtual training is proposed.A virtual training environment is introduced to solve the problems of difficult sampling,insufficient data volume and low training efficiency;The automatic domain randomization algorithm is used to automatically adjust the environment parameters in the virtual environment to solve the problems of insufficient data diversity and weak generalization ability;The reinforcement learning method based on normalized advantage function is used to predict collision in real time and give the next step strategy,which improves the effectiveness of collision prediction.The experimental results demonstrate the effectiveness and practicability of the proposed obstacle avoidance method.(5)Ground experiment research on target operation of rigid-flexible dual-aim space robot.Based on the ground microgravity experimental verification principle of space robot,a rigid-flexible dual-arm space robot ground microgravity experiment system is designed and built,which can comprehensively verify the key technology of fault satellite capture and maintenance operation.A typical experimental scheme is designed,and experiments of non cooperative target capture and narrow space target approach are carried out to verify the correctness of the proposed relevant theoretical methods and the feasibility of engineering application.