The Study Of Modeling And Trajectory Tracking Control Of Areospace Manipulator With Clearance Considering Gravity

More and more countries focus on space development today,research that related to space agencies also will increasingly become the focus of academia,the space manipulator is a very important mechanism in space,undertake the most of space task,so people will call the accuracy requirements getting higher and higher.The installation and debugging of space manipulator need to be carried out on the ground,but the applications are in the space microgravity environment.The space manipulator joint clearance in microgravity coupling,will make the dynamics of the space manipulator changes,so the accuracy of the end trajectory of the space manipulator will be damaged,or even cause vibration or out of control.In this paper,a two degrees of freedom space manipulator with joint clearance is presented as the object of study.The model is established and the validity of the model is proved by experiments,and designed three kinds of parameters that can make the manipulator reach the desired end trajectory tracking accuracy without changing the parameters.The specific content are as follows:Firstly,the dynamic characteristics of the gap hinge are analyzed,and the math model of the articulated arm with articulated joints is established.And a test method based on flexible cantilever beam strain gauge and laser displacement sensor is designed based different gravity orientation platform.The validity of the proposed model is proved by the comparison between the experimental data and the simulation data.Finally,the Math model of the two degree of freedom space manipulator with joint clearance is established.Secondly,on the basis of the model of the space manipulator with the joint clearance,the fractional sliding mode controller which can adapt to different gravity environment is studied,and its stability have been proved.And then a simulation using MATLAB have been running and the results show that the controller can track the trajectory of the manipulator in different gravity environment,and has good immunity to external disturbance.Finally,considering the situation of the controlled object model is unknown in the controller design,this paper presents two kinds of controller does not depend on the object model,which are fractional orders PID controller with ESO and fractional orders PD sliding mode controller,and also prove theirs stability.And then,by using the IWOPSO optimization algorithm,the parameters of controller are been optimized,so that the tracking accuracy of the end trajectory is further improved.