Research On Design And Control Method Of Metamorphic Series Parallel Space Capture Mechanism

With the vigorous development of space exploration activities,the number of satellites in orbit is increasing,which also leads to more and more invalid satellites in space.In addition,abandoned satellites or detectors may also produce debris and garbage.When most spacecraft reach the expected life,their payloads can still continue to work,if they can be repaired or refueled in orbit,the service life of spacecrafts can be greatly extended.In this paper,a variable cell series parallel space capture mechanism is designed,and its structure is designed in detail.In order to achieve stable and accurate capture function,the corresponding trajectory planning method and control algorithm are designed,the movement time is optimized,and the impedance control algorithm is studied.Aiming at the capture operation of space non cooperative target,and referring to the configuration design method of series parallel mechanism,a 3（2RR1S₂-RR1S₁）mechanism is designed based on 3RRS mechanism.The metamorphic function of the mechanism can switch degrees of freedom according to different work requirements,thus reducing the number of drives.Secondly,according to the dynamic analysis method of the series parallel mechanism,the driving torque of each joint is estimated,and the driving layout scheme is designed and analyzed in detail.In order to enable the capture mechanism to perform space operations according to the specified trajectory in space,the trajectory planning of the capture mechanism is studied.Cubic B-spline interpolation is used between the trajectory points to ensure the stability and continuity of the capture mechanism movement process.At the same time,the time optimal planning based on particle swarm optimization algorithm is carried out for the movement time of the capture mechanism to ensure that the capture mechanism can complete the space operation as soon as possible on the premise that the running speed and impact meet the requirements.As a space capture mechanism,in order to complete the capture task,it is necessary to make the capture mechanism firmly lock the captured target and prevent damage to the target.Therefore,after the capture mechanism moves to the designated position according to the planned trajectory and contacts with the captured object,a certain amount of catching force should be applied on this basis.In order to track the capture force and position as soon as possible in the capture process,an impedance control algorithm suitable for series parallel capture mechanism is designed based on the impedance control algorithm of modern control theory.On this basis,an adaptive impedance control system is designed.The system can adapt to the position and stiffness changes of the captured object,quickly realize the capture force tracking,improve the control accuracy and reduce the steady-state error.Finally,the two are compared and analyzed through simulation,which verifies the tracking and adaptive ability of the adaptive impedance control algorithm.According to the designed metamorphic series parallel space capture mechanism,the prototype is manufactured,and the electrical control system is designed and built.The metamorphic motion performance,trajectory movement performance,control performance and capture performance are verified on the experimental platform.