Differential Driving Force Analysis And Trajectory Tracking Control Of Space Manipulators Under Different Gravity Environments

As mankind's exploration of space continues to deepen,space robotic arms that can be used flexibly in space are receiving more and more attention.In the application of space manipulator,the positioning accuracy of the manipulator is very important,and high positioning accuracy means high reliability in the completion of the task.However,the space manipulator is installed in the ground environment and applied in space,due to the change of gravity environment,the friction and clearance between the joints of the space manipulator will change,resulting in changes in the driving force of the joints,which will affect the positioning accuracy of the robot to some extent.Therefore,this paper studies the joint friction and clearance of the space manipulator under different gravity environments,analyzes the difference of the driving force of the space manipulator under the ground gravity environment and the space microgravity environment,and at the same time proposes an adaptive control algorithm for the tracking control of the end trajectory of the robot arm,considering the changes in the dynamic model of the robot arm due to gravity release,in order to improve the positioning accuracy of the space manipulator under different gravity environments.The main contents are as follows:Firstly,in order to analyze the differences in motor driving forces of space mechanism under different gravity environments,a single-joint manipulator is used as the object of study,a single-joint manipulator dynamics model is established using Lagrange equation,moment equilibrium principle,and simulation conditions such as different loads,friction and speed are set.After the completion of the theoretical simulation,a set of single-joint drive robotic arm test device is designed to conduct ground gravity,ground simulated microgravity and drop tower microgravity environment test,and carefully analyze the difference of motor driving force under different gravity environment based on the test data,and identify the friction parameters in the kinetic model based on the test data,so as to obtain the modified kinetic simulation model and provide theoretical and test support for the kinetic design and application of space agencies..Secondly,Secondly,in order to analyze the influence of friction and clearance on the end trajectory and joint driving force of the space manipulator under different gravity environments,the two-link joint robot is used as the object of study,and the mass-free light rod model is used to establish the equivalent model of the space manipulator in ground gravity environment and space microgravity environment,and on this basis,the kinematic and dynamic equations of the space manipulator taking friction and clearance into account are established,and the control algorithm is proposed in the next chapter to track the end trajectory of the space manipulator.Finally,a control strategy based on a model-free algorithm is proposed for tracking the trajectory of a space manipulator with model uncertainty considering friction and clearance in different gravity environments,and the superiority of the model-free control algorithm compared with the PD control algorithm is verified when the dynamics of the manipulator model changes due to different gravity.