Dynamics Modeling And Control Of 3-RRRU Parallel Robots

Parallel robots are playing an increasingly important role in industry,agriculture,service and other industries.In order to reduce the driving load of the manipulator and save the control cost,the robot gradually develops towards the direction of high speed,lightweight and high precision.The manipulator structure uses lightweight flexible materials instead.However,due to the structure characteristics of large size and low quality of flexible link,the elastic deformation of flexible link will reduce the positioning accuracy of end-effector and even make the mechanism fit failure under the condition of high speed and heavy load.Therefore,it is very important to establish the rigid-flexible coupling dynamics model which can reflect the dynamic characteristics of the flexible parallel robot.In this paper,the spatial flexible parallel robot is taken as the research object,and its dynamics model and control algorithm are studied.The main research contents are as follows:In order to better analyze the relationship between the position,velocity and acceleration of each mechanism of 3-RRRU parallel robot at any time or other variables in the process of motion,the inverse kinematics solutions of 3-RRRU parallel robot,velocity inverse solutions and acceleration inverse solutions are derived in detail.On the basis of the inverse kinematics analysis,the visual analysis of the workspace is carried out.Explore the limit position of 3-RRRU parallel robot in workspace.Aiming at the complex problem of establishing rigid-flexible coupling dynamics model for space flexible parallel robots,a simplified rigid-flexible coupling dynamics model is obtained by integrating branch structure method,Lagrange method,assumed mode method and independent coordinate method,which is convenient for designing controllers.In order to actively suppress the continuous oscillation of the moving platform caused by the elastic deformation of the flexible link,based on the singular perturbation method,the RBF neural network control and the PD control of the flexible vibration of the space flexible parallel robot system are proposed under the condition that the system parameters are uncertain.The simulation results show that the control strategy can not only realize the progressive tracking of the trajectory,but also effectively suppress the vibration of the flexible link.In order to reduce the complexity of the control strategy,the RBF neural network compensation control scheme based on mixed trajectory is designed when the model is uncertain.The simulation results show that the proposed control scheme can not only ensure the robustness of the model under uncertain conditions,but also suppress the vibration of the flexible link,which verifies the feasibility and effectiveness of the proposed control scheme.