The Development Of The Digital Pulse Mig Welding Inverter Power Source

The Pulsed Metal Inert Gas Welding (PMIG) can give all droplet transfer formats from short-circuit transfer to spraying transfer through wide input current range. The digital control pulsed MIG welding machine occupies an important position in the national manufacturing industry, because it has many advantages such as rapid dynamic response, low-loss of power device switching, small light transformer, flexible control strategy, strong adaptability. Developing the digital control pulsed MIG welding machine is of great significance.This thesis introduced the overall structure of the pulsed MIG welding machine, the components and the functions. Meanwhile, it analyzed the main circuit in detail. Base on that, we proposed a control framework and designed a "DSC+MCU" structural main control system and made a printed circuit board (PCB). It described in detail the design of the DSC system circuit and MCU system circuit; the design of sample channel circuit about the voltage and the current using the analog to digital convertor (ADC); the design of output channel circuit using the digital to analog convertor (DAC); the design of digital signal isolation circuit about the gun switch, thermal relay, fan driver and so on; the design of bus interfaces including RS-485, CAN and UART interconnections.This thesis described the system control block diagram of the welding machine and the relationship of blocks in detail. It introduced the varibable parameter PI control arithmetic and described the realization of it in emphasis. It also introduced the Expert System (ES) and described the solution in the pulsed welding machine.Programes in MC56F8323 (DSC) compiled and debugged were shown in this thesis. It realized start-arc control, welding process control, end-arc control and welding control under four modes that is two-step, four-step, special four-step and spot welding. The real-time kernel of the μC/OS-II was reduced and ported in MCU MC9S12DG128. Five task-based task subroutines were designed. The first and the second tasks realized the input setting and the display of the parameters separately from Human-Machine Interface (HMI) on welding machine body and Remote HMI. The third actualized the control functions about the wire feeder. The fourth implemented communication between MCU and DSC, parameters transfer and status synchronizition. The fifth designed the welding expert system's framework to carry out the parameters' unifying adjustment.Some specific problems during the welding machine's realization progress were described in detail in this thesis. An isolated TOPSwitch DC-DC power supply circuit which was designed can meet all the system's power demands. A wire feeder control circuit which can cooperate with main control board and a Human-Machine Interface (HMI) circuit were designed. After that the three circuits' printed circuit board (PCB) also was designed and worked well. Further more a welding machine was assembled and tested. The results of fieldwork welding achieved our aims.Finally, sum up the design scheme of the digital control pulsed MIG welding machine. Future research and development of the digital control pulsed MIG welding machine was proposed.