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The automatic submerged-arc welding(SAW) has much merit, such as high efficiency of production, excellent quality of welding product, SAW is the earlist mechanized welding method and now is wildly used in industry. Along with the developing science, the auto matization and intelligence of welding process is the development tendency of welding technology. So applying the digital control technique into the control system of SAW machine has important academic meaning and practical purpose of appliance. In particular, the technology of MCU control of the arc welding rectification, with an effective algorithm and the right software, can be very effective control of the welding process, improve the welding quality.According to the characteristic of SAW, this paper designed the digital control system for SAW on the base of The main circuit of MZ-1000A SCR automatic SAW machine, and the control core is MSP430F149 MCU.The paper has designed the system circuit and software program for the digital control system for submerged-arc welding machine. The system circuit contains welding voltage and welding current sampling circuit, synchronization and trigger circuit, welding machine operator control driving circuit, protection circuit, etc. Prepared simultaneously and trigger pulse control procedures module, in design process of igniting arc used separate control of thinking, used the method of phase shift and asynchronous trigging thyristor to resolve the 30°phase software compensation of synchronization signal, make the control angleαphase-shifting range of 0°~148°.Designing system software modularizly,carving up module according to various function, include welding rectifier synchronization and trigger control, man-machine interfance, system parameter seting, parameter preseting, etc. Power source control and welding process control algorithms are used PI control algorithms, uses Simulink in MATLAB to emulate the system, the result of the emulation can help to adjust the PI control parameters.Used asynchronous and delay trigging thyristor approach to the preparation of arc extinguishing control procedures, to load waveform changes in the basic linear attenuation, by adjusting the time delay trigger to control the time of current decay in the arc extinguishing, met the different welding current and welding technology, such as speed under the conditions of forming the request of the welding technology.Debug the design of the controller and a welding machine offline and online, no-load and load, after static load testing and technological experiments show that, the system have static output characterist of current descending,when the no-load voltage of 65V, current feedback control parameters for the Kp= -0.055, KI= 0.95, welding speed of 2.0 cm/s case, mske the process of igniting arc is smooth, welding process more stable. Finally,current linear attenuation arc extinguishing control can achieve good crater molding effect.
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