Research Of Space Robot Tracking And Grabbing Target And Ground Experiments

With the development of human exploring space activity more and more deeply,space science and technology have been widely paid attention to.Owi ng to hardware malfunction or the depletion of fuel,every year many spacecraft can't go on on-orbit activities.Space orbital service technology has very high scientific and commercial value and will surely flourish in the field of space science in the future.Given the high development costs of such satellites,robots for space on-orbit services of performing satellite maintenance have emerged.For the space robot,space robot on-orbit to capture the target satellite is the basis for its on-orbit maintenance.While,space robot on-orbit capturing the target satellite needs to be accomplished through on-orbit attitude tracking,approaching and capturing.In this paper,we mainly study the key technologies of tracking and approaching and capturing the target satellite process of space robot and the ground verification experiments,which is the basis of space robot in-orbit service,which can provide the corresponding technical support for the subsequent space robot research.In this paper,the velocity-level kinematics equation of space robot is established.Based on this,the velocity-level kinematics based on priority idea is proposed.By establishing the mapping relationship between each sub-object and null-space,the general solution to multi-objective velocity-level kinematics of space robots is obtained.Taking into account the joint position constraints,joint speed constraints and avoidance of the singularity problems,relevant optimization methods are put forward respectively for the three constraints.Finally,the three constraints are unified into the general solution to the multi-objective priority kinematics of space robot.For the process of space robot capturing the target satellite,space robot needs to adopt visual camera or laser radar to acquire the real-time pose information of the target satellite to realize the on-line motion planning of space robot.In this paper,the realtime pose information acquired by the eye-in-hand camera to ralize the motion planning of space robot on-orbit inspection and approaching the target.At the same time,the time delay problems of the system are analyzed and compensated.In this paper,the multi-objective priority kinematics algorithm is applied to the visual servo of the tracking and approaching the target satellite of space robot,which can optimize the attitude disturbance of the base while ensuring tracking and approaching tasks.The purpose of the motion planning of attitude tracking is to track the attitude of the target satellite without disturbing the attitude of the base and optimizing the movement of the end position.The purpose of motion planning approaching the target satellite is to achieve precisely access to the capture point of the target satellite and to optimize the disturbance of the base attitude.During the capturing of the target satellite,space robot system will inevitably encounter the problem of contact or collision.In this paper,the dynamics model of space robot and the target satellite is established,and the relationship between the contact/impact force and velocity is analyzed as the theoretical basis of the velocity constraints of space robot control and motion planning.Then,the multi-object motion control method based on impedance control and base attitude disturbance optimization is proposed.This method can not only ensure the compliance of the capture contact but also reduce the disturbance to the base attitude.In order to verify the validity of the above motion planning algorithm and motion control algorithm in the real space robot system applications,the ground experiments are essential.There are many evident differences between ground environment and space environment,which can produce serious influence for the dynamics characteristic,the motion planning and control methods.In order to simulate the kinematics and dynamics property of space robot in space more truly,the ground 3-dimensional micro-gravity emulation system be developed based on hardware-in-the-loop simulation.The system can be used to simulate the sate llite base motion and the contact or collision problems during the process of space robot capturing the target.Finally,the experiments of space robot on-line motion planning based on visual servo and the contact control of capturing the target are done in this experiment system,which verify the validity of the system.