DSP-based Control System Design Of The SAW Power Source

Submerge Arc Welding (SAW) is widely used in many industry fields such as shipbuilding, energy source and mechanism because of its high productivity, excellent welding quality, and comfort working condition.. At present, submerged arc welding power source is still the way to control the use of analog circuit, control circuit complexity, poor control of flexible, functional extension of the inconvenienceIn this paper, according to the current problems about submerged arc welding power source, decided to use digital control system to replace the original analog control system. It used TI's TMS320F2812 DSP chip as the core of welding power control, and acquired the feedback welding current signal using Hall-current sensor by on-chip 12-bit A/D. The acquisition signal has been filtered by the FIR filter to avoid the impact of digital controller from high frequency interference. It designed and produced the circuit boards, working with the DSP on-chip PWM module to achieve D/A conversion function, and tested the board by the IQmath library The analog control volume outputting by D/A conversion compared with the sawtooth sync signal to generate main circuit thyristors trigger signals.Control strategy was the algorithm of integral separation PID to avoid the integral saturation to make the controller instability. It was easy to ignite the arc by the certain procedures to ensure the high no-load voltage, and the LED lights flicker on the board showed the welding state. Both hardware and software have joined the anti-interference measures. During the design process, it used the Multisim8 to aid the circuit design, got the FIR filter coefficients and simulated the PID parameter tuning by Matlab.Debugging results showed that the design of digital control system for submerged arc welding power source achieved the requirements, and the power source had the drop characteristic for the submerged arc welding.