| The digital pulsed MIG welding power source is a kind of intelligent new welding machine which is designed by combining digital signal process(DSP)with traditional MIG arc welding process.With the aplication of DSP,the digital pulsed MIG welding power source,compared to traditional welding machine,has higher accuracy of control and stability of controlling parameters,and better perfomance of welding process. In recent years,the welding products are called for better quality,resulting in that the new welding power source has been a substitute for the traditional welding machine to aply to industrial production.The paper puts forward a control system of digital unified pulsed MIG welding power source,based on summarizing the digital pulsed MIG welding power source at home and abroad.The system makes DSP as the controlling core and is a DSP+MCU binuclear system,which includes hardware circuit system and software programming system.Thus,the output characteristics of the power source can be sophisticatedly controlled.In the designed system,on the one hand,DSP,the main controlling chip,is responsible for the whole welding process,including data sampling,control algorithm realizing,PWM outputting and output characteristics controlling;on the other hand,MCU,the controlling chip of human-computer interaction system,is responsible for events managing,including parameters presetting and displaying,data communicating and power state monitoring.Firstly,the hardware circuit of the system is made of DSP+MCU binuclear system that includes DSP control system and MCU human-computer interaction system,IGBT drive system and wire feeding air supply system.The DSP control system,using TMS320F2812 as the controlling core and presiding over the whole welding process,is made up of DSP minimum system,sampling circuit,protecting circuit,communicating circuit and so on;The human-computer interaction system,using MCU STC89C58RD+ as main controlling chip and presiding over pisplaying of welding parameters;is made up of parameters presetting circuit,MAX7219 displaying circuit,communicating circuit and so on.The driving circuit is digital,based on optical coupler HCPL-316 J and presiding over amplifying PWM from DSP,controlling conducting pulse width of IGBT full-bridge and isolating the power circuit from controlling circuit to make output under control.Second,this article describes the control system software programming.Software program mainly includes DSP and MCU procedures,adopt modular,C programming language and present the flowchart of main progra m and interruption subroutine. Programs in DSP are responsible for external characteristics control,control software programs including the DSP main program,the PWM signal output,PI control subroutine,A/D conversion program,arc length control subroutine,the design of the pulse output control program and interrupt service routines.MC U is responsible for the preset parameters,control software programs including the main program MCU,encoder phase program,and electricity saving,unified welding parameter database stored procedures and communication protocol is a set of two.Last,we have made hardware circuit of control system and compile and debug software program according to the requirements.After then,test each module,including the human-computer interaction system debugging,digital PWM testing,protective circuit testing and the test waveform.Separate modules have been measured signal correctly,assemble and test the prototype,including no-load voltage testing and sampling circuit debugging,PI parameter setting,external characteristic test and welding pulse output test,to test output parameters of the welding machine.The experiments proved that the digital control system of unified pulsed MIG welding power source could realise multi-function full digital control and achieves stability,reliability and high accuracy of control. |
