The Study Of Space Manipulator Trajectort Tracking Control Considering The Effects Of Gravity

With the rapid development of space technology, especially the birth and successfulapplication of the space station, space shuttle, and the space robot, the space manipulatoras a key technology of on-orbit support and service have been into space, and got moreand more attention of people. Therefore, the development of space manipulatortechnology will become the main trend of future space operation. In this paper, the spacemanipulator trajectory tracking control was carried out considering the influences ofgravity that from ground adjustable to space application. The specific content are asfollows:Firstly, this paper describes the current status of microgravity motion behavior andthe development of space manipulator at home and aboard. At the same time, thekinematics and dynamic models for a specific simulation model are described respectively.This provides a theoretical basis for the controller design of subsequent chapters.Secondly, considering gravity change from ground alignment to space applications,this paper considers a two-link planar space manipulator system as the control object andby combining the fuzzy approach with the PID control method, a fuzzyproportional-integral-differential (PID) control strategy is proposed to make the spacemanipulator track the desired trajectories in different gravity environments. Simulationresults verified the effectiveness of this method.Since the fuzzy rules is difficult to select, the design of the controller has strongdependence, a sliding mode controller (SMC) is proposed to control the space manipulator.By introducing a nonlinear structure of special configuration fal function, a new SMCbased on the reaching-law is proposed. The asymptotic stability of system is guaranteedbased on the Lyapunov theory. Simulation results show that by using this strategy, thesystem can complete the trajectory tracking task under different gravity environment andhas strong robust.The system chattering is greatly reduced by using the improved controller, but thechattering still exists and cannot be completely eliminated. In order to make the systemachieve better control performance, an active disturbance rejection control (ADRC) method is used to cope with the model change in the space manipulator caused by thevariations of gravity, when it is aligned on the ground and applied in the space. In thismethod, we treated the model change and the unknown disturbances as the total systemdisturbance which is observed and compensated by means of an extended state observer(ESO). Simulation results show that good trajectory tracking results can be achieved withADRC even when the model is changing. This control algorithm not only adapts to themodel change and rejects the system disturbance as shown in the simulation, but alsoimproves the system robustness in comparison to the PD control and adaptive robustcontrol.