Fuzzy PID Control System Research For Laser-plasma Hybrid Welding

Laser-plasma hybrid welding is an advanced efficient and energy-saving welding connecting technique which has size the attention of many researchers home and abroad with its wide application prospect.Laser-plasma hybrid welding connecting technique is a new patter of connecting technique combining the two welding techniques of laser and plasma.It not only overcomes the shortcomings to a large extent than the two applied separately but also maintain the each others' strength.As a result,the hybrid welding technique boosted the overall energy utilization rate.Besides,effective energy and high-speed in the welding provide a strong guarantee for the high-quality automatic welding process.Laser-plasma hybrid welding is also a complex industrial process.Without a nonlinear control system,it is not easy to build a precise mathematical model.Consequently,the traditional control algorithm cannot reach a satisfying welding performance.However the intellectual-fuzzy control algorithm opens a new way which needs only the rich experience but a precise mathematical model.With empirical approach,a fuzzy controller will be built and eventually a control system established.This experiment has built a primary mathematical model of the laser-plasma hybrid welding system simulate the experiment by using simulink of the software MATLAB.The mathematical model is mainly built through three methods:image processing,finite element analysis and actual measurement.The model,along with the mass data got from the simulation debugging,a fuzzy controller with an effective rules and fuzzy reasoning statement will be built and eventually a complete reasonable fuzzy control system be built.The hardware platforms of the hybrid welding mainly include KUKA robot,welding power supply and laser welding machine,etc.By connecting the Siemens control system with PLC S300 and making molten pool as controlled object,temperature of molten pool as manipulated variable and welding speed as control variable,the welding process of the 7075 aluminum alloy board will be finished on the platform.The 7075 aluminum alloy has excellent welding property and mechanical property which make it widely used in many fields,especially in the aviation field.The advancing society put forward higher quality on the aluminum alloy welding and an efficient and high-quality control system.For the welding joints of 7075 aluminum alloy,the quality tests are both exterior and interior.Exterior detection is mainly the observation of whether there is obvious apparent defect,while the interior detection often involves the use of scanning electron microscope,micro-hardness tester,stretch test machine and bending test machine.The respective welding performance under the control of traditional PID-control system and fuzzy PID control system are compared after the detection.At last,the conclusion is draw.The result shows that,laser-plasma hybrid welding fuzzy PID control system's simulation result keeps good consistency with the practical welding performance,which proves the relative accuracy of the mathematical model.At the same time,the quality detection of the welding joints shows that the fuzzy PID control system is superior to the traditional PID control system for it can reach the high-quality welding requirement.