Capture Dynamics And Stability Control Of Space Flying Net Robot System

With the increase of human space activities,the problem of space debris is becoming more and more serious.To ensure the important spacecraft on-orbit operation and maintain a good space environment,it is urgent to actively remove noncooperative targets in space.Flexible space net has a good application prospect because of its simple structure,wide capture range,and high success rate.The active removal of space debris is the research background,the capture dynamic and stability control of Space Flying Net Robot System(SFNRS)are studied in this paper.The main contents include the following parts:(1)Dynamic modeling of SFNRS.Firstly,the configuration of SFNRS is determined through comparative analysis.Then the dynamic model is established by using the lumped mass method.Finally,the influence of the space net discrete nodes number on the simulation results is studied through simulation,the space net in release and approach phase are discretized without virtual nodes,a virtual node is added between each tether when space net is discretized in collision capture phase.(2)The analysis of release characteristics of SFNRS.Firstly,based on the origami theory,the specific folding processes of the Star folding pattern and square folding pattern are given.Then,based on the traditional space net,the multi-tether space net configuration is proposed,and the comparative simulation is analyzed.Finally,two folding patterns under uncontrolled and controlled release are simulated,the star folding pattern is finally determined through the simulation results.(3)The analysis of approximation characteristics and controller design of SFNRS.Aiming at the problem of space net shape maintaining in the approximation phase,the maneuvering unit is regarded as the controlled object and the interference force between nodes is considered as disturbance.Firstly,the sliding mode controller is designed when the status of the controlled object is completely known.It’s found that the input of the system is larger than the physical limit of the actuator through simulation.Therefore,the sliding mode controller under input constraints is designed.Then,considering the stability control of the controlled object under lacking of speed,the observer is used to observe the speed,and the controller under input constraints is design by using the observed speed.Finally,the stability control under the uncertainty of parameters and disturbance’s upper bound is studied.Based on RBF neural network,RBF neural network controller with limited input is designed.The effectiveness of controllers design in this chapter are verified by simulation.(4)Collision dynamics modeling and control for SFNRS.Aiming at the collision between the SFNRS and the capture target in the capture phase.Firstly,the dynamic model is established by nonlinear Hertz collision theory.Then,the collision detection method and detection process are given.Finally,the capture effect of different size ratios of the space net and the capture target is studied.This paper mainly studies the dynamic modeling and the stability control of SFNRS in the deployment,approximation,and capture period,which is significant to the development of active debris removal technology.