Study On The Dynamics Control Method Of Three Degree Of Freedom Parallel Manipulator

This paper take the Delta manipulator with three degrees of freedom as the research object,focusing on the goal of improving the mechanical performance of highspeed parallel manipulator.Firstly,the simplification of the establishment of the dynamic model of the parallel manipulator is discussed,the reason of the error of the traditional simplification method is analyzed,and a more accurate and effective method for the establishment of the dynamic model of the simplified is put forward.Secondly,the servo control system is modeled,and the time-varying parameters in the servo system are identified by the parameter identification method,and a higher precision servo system is obtained.Finally,the application of PID control,dynamic feed-forward control and other control methods in the control of high-speed parallel manipulator is discussed,and the effectiveness of the proposed control method is verified by simulation and experiment.The main contents of this paper are as follows:In the research of the rigid body dynamics model of the parallel manipulator,the vector method is used to establish the kinematic model of the three degree of freedom parallel manipulator,and then the virtual work principle is used to establish its complete rigid body dynamics model.The meanings of each item in the complete rigid body dynamics model and the significance of its simplification are analyzed.Next,the rigid body dynamics model proposed by the predecessors is simplified.The main reason of reducing the accuracy of the simplified model is found by tracing the error of the simplified method.Based on this,a simplified method of rigid body dynamics with double independent coefficients is proposed.A general method of simplified coefficient is proposed with the minimum RMSE of the simplified rigid body dynamics model and the complete rigid body dynamics model as the index.The simulation results show that the simplified method is feasible and effectiveness.In the research of servo system parameter identification method,firstly,the servo system of high-speed parallel manipulator is modeled to obtain the parameter identification model of servo system;secondly,the winding inductance and resistance of servo motor are determined as the parameters to be identified,and the application of iterative learning control in parameter identification is studied.An experimental platform for parameter identification and control of servo system is built.The input and output signals of the single axis of the parallel manipulator are identified by iterative learning identification method to obtain more accurate time-varying values of the parameters to be identified.In the aspect of the research of the manual mechanical control method of the parallel machine,firstly,the feed-forward control model of the high-speed parallel machine is established,the principle of reducing the error of the feed-forward control is deduced,and the dynamic feed-forward coefficient is adjusted by Simulink simulation.Next,the feed-forward + H_∞ control method and the ADRC(Auto Disturbance Rejection Control)strategy are studied.The H_∞ controller and the ADRC controller are designed for the research object.Based on the simulation results,it is found that H_∞ controller can greatly improve the robustness of the manipulator,but it will have a great impact on the dynamic follow characteristics of the manipulator.Therefore,the controller parameters should be modified to some extent.The modified controller gets better control effect in the simulation experiment.Finally,the feedforward control experiment of the parallel manipulator is carried out with the help of the servo system parameter identification control experimental platform built before.By comparing with the experimental results of the traditional PID control,it is verified that the maximum tracking error of the manipulator end position in the dynamic feedforward control method is reduced.