Research On The Mechanism And Control Method Of Cartessian Arc Welding Robot

With the increasing requirement of automation in industrial production,the research on the structure and control method of mobile welding robot has become a hot spot in the field of welding.In this paper,aiming at the common linear weld and large curvature weld in industrial production,a mobile welding robot is designed under the guidance of laser vision,which can independently complete the seam tracking task,combined with the characteristics of uneven ground in the welding environment.It includes the research of robot structure design and control system.The main contents of this paper are as follows:Firstly,based on the actual working environment of the robot and the characteristics of the workpiece to be welded,the motion actuators of the mobile welding robot are designed,including the mobile platform,the magnetic adsorption mechanism and the precise fine-tuning mechanism of the welding torch.As the workpiece to be welded is a weld with little lateral variation,and the ground is not smooth in the actual welding environment,this paper adopts a four-wheel parallel direct moving platform.In order to enhance the stability of the robot's center of gravity,the adjustable magnetic adsorption mechanism is designed based on the principle of sinusoidal mechanism.The welding torch precise fine-tuning mechanism utilizes the cross slide mechanism mounted on the mobile platform.Then,based on the structure design of mobile welding robot,Adams kinematics simulation is carried out to verify the rationality of the structure design.Secondly,kinematics modeling of mobile welding robot is carried out.According to the structure characteristics of mobile welding robot,kinematics models of mobile platform and welding torch precise fine-tuning mechanism are carried out.Combining the structure and principle of laser vision sensor,the filtering method of scanning information of weld groove image is studied,and based on the idea of feature extraction from complexity to simplification,All welds can be regarded as geometric superposition of I-type and V-shaped welds,and feature points are extracted by slope extreme value method and oblique intercept method,respectively,and verified by MATLAB algorithm.Then,on the basis of feature point extraction,the weld seam is reconstructed based on the least square straight line fitting,and the real-time control algorithm of welding seam position correction is given in combination with the inverse kinematics of mobile welding robot.In the weld seam tracking control method,variable universe fuzzy PID control is adopted.The welding seam tracking process is a nonlinear time-varying system,and the traditional PID control effect is not ideal.Therefore,a self-tuning fuzzy PID control is designed by combining fuzzy control with PID control in this paper.In order to further improve the control accuracy,the variable universe fuzzy PID control is designed by adding a functional based expansion factor domain self-adjusting mechanism to the fuzzy PID controller.Then,through MATLAB/Simulink module,the traditional PID controller and the variable universe fuzzy PID controller are compared to verify the superiority of variable theory domain fuzzy PID control.The mobile welding robot platform was built and the hand-eye calibration of the robot was carried out by the five-point calibration method based on Gramm matrix.Finally,the welding seam tracking is implemented on the robot platform,the average tracking accuracy is achieved,and the feasibility of the robot structure and algorithm is verified.