Research On Control System Of Three DOF Spraying Robot Based On OPC Communication

This paper presents the design and development of a three-degree-of-freedom(3-DOF)spraying robot to meet the demand for automation in small and medium-sized automotive parts spraying companies.To address the problem of decreased control precision and stability in the electro-mechanical servo system of the 3-DOF spraying robot caused by nonlinear friction,a feedforward compensation control theory is studied.A feedforward compensation controller is designed to improve the control precision and stability,which is validated through simulation and experiments.The main research contents are as follows:(1)Design of the 3-DOF spraying robot.Based on the design requirements of the automotive wing panel spraying robot,the design goals and standards are established,and the structure composition of the 3-DOF spraying robot is analyzed.The main body structure transmission scheme is determined,and a 3D model of the 3-DOF spraying robot is designed using Catia software.The main hardware performance parameters of the 3-DOF spraying robot are determined based on the 3D model and design requirements.(2)Dynamics analysis of the 3-DOF spraying robot and establishment of friction model.The composition and working principle of the electro-mechanical servo system are analyzed,and a mathematical model of the X-axis electro-mechanical servo system of the 3-DOF spraying robot is established.To address the problem of decreased control precision and stability caused by nonlinear friction force during the operation of the 3-DOF spraying robot,the Lu Gre model is used to describe the friction characteristics of the electro-mechanical servo system of the 3-DOF spraying robot.Different identification methods are used to identify the dynamic and static parameters of the Lu Gre model,and the effectiveness of the proposed identification methods is validated through simulation.(3)Study of feedforward fuzzy PID control theory and controller design.To improve the control precision and stability of the electro-mechanical servo system of the 3-DOF spraying robot,a feedforward fuzzy PID compensation control scheme is proposed by using the Lu Gre friction model for feedforward compensation and fuzzy algorithm for self-tuning of PID parameters.A feedforward compensation controller is designed based on the feedforward fuzzy PID compensation control scheme.The feedforward fuzzy PID compensation control scheme is simulated and validated in Simulink,and the simulation results show that compared with traditional PID control,the feedforward fuzzy PID compensation control scheme can effectively improve the control precision and stability of the electro-mechanical servo system,which is beneficial for the high-precision control of the 3-DOF spraying robot.(4)Construction of experimental platform and analysis of experimental results.A mechanical prototype is built according to the structure scheme of the 3-DOF spraying robot,and a motion control system based on Mitsubishi FX5 U 64-MT/ES programmable logic controller(PLC)is studied.A spraying motion control program is designed,and an experimental platform for the 3-DOF spraying robot is constructed.The feedforward fuzzy PID compensation scheme designed in MATLAB is applied to the PLC control through OPC communication technology.The feedforward fuzzy PID compensation experiment is conducted under the same motion conditions as the simulation,and the experimental results show that the feedforward compensation control scheme can improve the control precision and stability of the 3-DOF spraying robot.