Research On Identification Of Inertial Parameters Of Non-coopeative Target

Since the first satellite was launched into orbit in1957, the aerospace field hasdrawn plenty of investments and attention from global countries due to itscommercial and military value. However, among the satellites and spacecrafts everlaunched, only a few of which were sent into the outer space for some scientificexploration missions, and the most of the rest were sent into the near-earth orbit,particularly the valuable and space-limited geosynchronous orbit. On the other hand,not every mission can obtain success to make the costly spacecrafts preciselyorbited and offer services according to the intended design. Therefore, theinevitable failures of some well-designed spacecrafts bring a tremendous waste ofresources. As a result of the above facts, the on-orbit service technologies deserveto be researched and are attracting worldwide attention, including China.With the reclaiming of dead or faulty satellites as research background, thispaper aims at the trajectory planning of the manipulator installed on the orbitservice robot and parameter identification after capturing non-cooperative targetsatellite.Firstly, the kinematic and dynamic models for the space manipulator systemare deduced respectively. The relative motion between the space robot and theground robot system leads to a dynamic coupling，on this basis，the generalJacobean matrix describing the kinematic relationship of the end effector and jointsof the manipulator is built.Secondly, in order to achieve an accurate and quick capture of a non-cooperative target, the trajectory planning of the robot arm is conducted. This paperproposes an image-based trajectory planning method, directly realizing the speedplanning of end effector in the image space. Compared with the commonlyposition-based method, this method has advantages of stronger robustness forcamera model error and easier calculation. To avoid the target’s escape from visualfield and the structure interference of manipulator, the artificial potential fieldmethod is used to restrain the position of the target in the camera visual field, andthe motion range of joint angles. Simulation results show that the constraint methodbased on artificial potential field method works well. Finally, with regard to the optimal control strategy after capturing the non-cooperative target successfully, inertial parameters identification of target is wellconducted. For there is no external force acting on the system, the non-cooperativetarget and space robot keep a constant momentum, which connect to one-bodysystem after capturing. By applying driving force, the moving state of whole systemchanges to make it possible to establish the identification equations. This papermakes use of the least square method to solve the equations, and eventually, theinertial parameters of the target are obtained.