Research On In-orbit Assembly Technology Of Space Large-Scale Structures Based On Dual-Arm Robot

Space robots replace astronauts to perform operational tasks and become a research hotspot.In the space station,robots can perform complex operational tasks such as in-orbit arrest,transportation and assemble.The dual-arm robot has the characteristics of strong load capacity,high flexibility and fine operation,so the coordinated operation of the dual-arm can replace a single arm to complete a series of meticulous work.Therefore,with the development of dual-arm robot technology,for the problem of in-orbit assembly of large-scale structures in space,the dual-arm robot technology is used to perform space manipulation tasks is of great research value,and dual-arm robots will play a more important role in the future.Based on the above analysis,the domestic researchers have not successfully demonstrated the assembly process about the use of dual-arm robots to perform in-orbit assembly tasks of large-scale structures in space,a stable controller is required in order for the dual-arm robot to complete the assembly task.Therefore,starting from the control strategy of the dual-arm robot,in this thesis the dual-arm robot is used to perform assembly tasks and conduct ground simulation experiments.Among them,the truss structure in the space telescope is selected as the assembly object of the large-scale space structure,and the truss structure model is 3D printed according to the structure.Finally,the assembly demonstration is carried out according to the truss structure model.In this thesis,a force controller based on admittance control is designed to enable the dual-arm robot to complete both the dual-arm coordinated transportation task and the dual-arm coordinated assembly task.The main research contents of this thesis are as follows.In this thesis,the kinematics of the dual-arm robot is firstly analyzed.Since the left-arm and the right-arm of the dual-arm robot belong to the same structure,so the kinematics of the single-arm is analyzed.The inverse kinematics analysis is carried out by numerical solution method according to the single-arm model,and the inverse solutions of each joint are obtained.In addition,for the cooperative transportation task of the dual-arm robot,the constraint relationships among the left-arm,the right-arm and the object are established,which includes the constraints of position,orientation and linear velocity.For the cooperative assembly task of the dual-arm robot,the constraint relationships among the left-arm,the right-arm and the assemble object are established,which includes the constraints of position,orientation,linear velocity,angular velocity and joint acceleration.Secondly,the task planning and trajectory planning of the dual-arm robot are carried out.According to the dual-arm assembly task,the assembly task is decomposed into multiple action sequences,and the capability analysis of the action sequences is performed.When the dual-arm robot performs the task,the sensitivity coefficient is proposed to detect and prevent the manipulator from colliding with obstacles.Finally,a force controller based on admittance control is designed,of which the input is the force of the robot arm,and the output is the change of the displacement of the robot arm end.The real-time changing contact force value at of the robot arm end can be converted into the change in the displacement,which realizes the compliant control of the robot end leads to good stability and robustness.Simulation and experiments show that the use of the force controller can effectively complete transportation task and assembly task.After the above analysis,the proposed control strategy is applied to the actual dual-arm robot.The ground simulation experiment is carried out on the in-orbit assembly task of large-scale space structures using the dual-arm robot,and the assembly process is demonstrated.At the same time,the use of dual-arm robot provides a theoretical basis for the orbital service of the space station.