Design And Realization Of Control System Of Laser Welding Machine

With the development of manufacturing industry towards high precision,laser welding has been widely used in automotive,aerospace,electronics,semiconductor,nuclear power and other industries because of its large welding penetration and small heat affected zone.However,most of the existing control systems of laser welding equipment in the market use programmable logic controller(PLC)or personal computer(PC).These systems have the disadvantages of high cost,large volume,poor flexibility and low real-time performance.Also,these systems do not have the function of adaptive control of laser power,so the weld quality in the arc starting and arc falling sections is not high and pits are easy to appear.Moreover,due to the small laser spot,the laser welding equipment has good applicability in narrow gap scenarios,but poor applicability in wide gap scenarios and scenarios with special weld texture requirements.To solve the above problems,this thesis designs a laser welding machine control system based on Advanced RISC Machine(ARM)+field programmable gate array(FPGA).The control system provides the functions of laser power adaptive control and galvanometer scanning,which can effectively improve the quality of welding joints and broaden the application scenarios of laser welding machines.The main contents of this thesis are as follows:(1)It designs the framework of laser welding machine including manipulator and its control cabinet,laser,galvanometer motors,etc.,constructs the model of laser power adaptive control,analyzes the causes of galvanometer scanning distortion,and studies the polynomial fitting function model based on least square method for correcting galvanometer distortion.(2)The control system in this thesis adopts ARM+FPGA structure,and designs laser control circuit,galvanometer scanning control circuit,ethernet interface circuit,liquid crystal display(LCD)and touch screen interface circuit,storage circuit of static random access memory(SRAM),STM32 minimum system circuit,key circuit and power supply circuit.The printed circuit board(PCB)is designed and manufactured.(3)In this thesis,the software of the control system is designed on ARM microprocessor and FPGA respectively.The software on the ARM microprocessor is developed based on the μC/OS-Ⅲ real-time operating system.Combined with STemwin and light weight internet protocol(LWIP),four functional modules including welding parameter setting,graphical user interface(GUI),ethernet communication and laser power adaptive welding are realized.The software design on FPGA realizes the functions of serial peripheral interface(SPI)communication,motor circular interpolation,galvanometer scanning and correction.(4)The system test in this thesis includes a series of actual tests on the galvanometer scanning function,laser power adaptive welding function of the laser welding machine control system and welding strength.The results show that the galvanometer can scan point,line,square,circle and other figures,and the size of the figure can also be adjusted.Within the square range of 160.00mm*160.00mm,the coordinate deviation of the laser point is only 0.03mm;it can weld a variety of weld texture;for 2mm cold-rolled carbon steel plate,welding can be carried out in the scenario where the welding gap is 0.2mm or less;for welding 2mm thick cold-rolled carbon steel plate,the pit depth of the welding joint in the arc starting and arc falling sections is only 0.077mm;when cold rolled carbon steel plates with thickness of 1.5mm and 2mm are welded,the welding strength is more than 300MPa.The main technical indicators of the laser welding machine control system developed in this thesis are higher than or the same as the similar products in the market,while it has the advantages of low cost,small volume,high flexibility and so on.In particular,with the laser power adaptive control technology adopted,the system can effectively improve the welding joint quality in the arc starting and arc falling sections.In addition,the system can not only realize the set weld texture,but also weld the workpiece with wide gap,which increases the applicable scenarios of the laser welding machine.