Arc Additive Manufacturing High Precision Control Experimental Study

The arc additive manufacturing technology uses arc as heat source and welding wire as additive material.It is layered and manufactured according to the three-dimensional model of the parts and stacked layer by layer until the parts are formed.Three servo motors are used to complete the three-dimensional space movement.Since the multi-axis motor drive system is a non-linear,strongly coupled time-varying system,and the molding process is liable to deviate from the planned value due to positional deviation and cannot continue to follow the planned path.Therefore,it is an urgent problem to be solved to improve the position accuracy of the multi-axis motor.In this paper,the servo system of MOTOMAN-UP6 was deeply studied,theoretical analysis and experimental research on model parameter identification and controller parameter setting of the servo system controlled object,and verified on the laboratory arc welding robot equipment.1.Taking the MOTOMAN-UP6 six-axis robot as the research object,the position accuracy of the servo motor control system is the control target.The mathematical model of the servo motor was introduced,and the characteristics of the servo motor control system were analyzed in detail and an equivalent model was established to provide the basis for model parameter identification of the controlled object in the paper.2.The recursive least square method was used to identify the approximate model of the speed loop.According to the identification results,the PID parameters were adjusted according to the principle of the best system.The optimal parameter values of the controller were obtained.The simulation results show that the identification results can reflect the dynamic performance of the actual system.3.For the position accuracy in the arc additive manufacturing process,with speed closed loop and integral link as controlled objects,P+ feedforward and fuzzy PID controllers were designed to track the position error.The simulation results show that the position closed loop control system based on fuzzy PID algorithm is more error tracking than P+ feedforward control algorithm.4.The SigmaWin+ PC software was used on the six-axis robotic platform to compare the feedback tracking error after the parameters of the two control algorithms were adjusted.The maximum error of the system with fuzzy PID algorithm was ±0.04 mm,and the robot arm was used for online verification.Experimental results show that the positioning after fuzzy PID parameter adjustment is more accurate.