Inteligent Control System Of Spot Welding Inverter Power Based On DSP

The successful application of power inverter technology in resistance spot welding leads to a more promising future for developing of spot welders in precision and intelligent. At present, the main circuit by using IGBT switch technique has developed perfectly. Being a new generation of microprocessor in control system, DSP (digital signal processor) is being selected to replace existing SCM (Single Chip Micyoco) technique. The subject was proposed from this background, in which the design and development of intelligent control systems for soft switch inverter of spot welding were implemented.The hardware system was constructed based on DSP system with peripheral circuit including command input circuit, sampling circuit, PWM (pulse-width modulation) output circuit , display circuit, and protection circuit. The software design implemented PWM output and sequence control module, keyboard input module, LED display module, current and voltage sampling module and fuzzy neural algorithm self study module. Based on obverse- and reverse-models of spot welding inverting process, which were derived theoretically, and combination of fuzzy set and artificial neural network, the control system of constant current output were constructed. By integrating sine-function input and then constant input in segmentation into BP algorithm, the fuzzy neural network was trained to realize parameter regulation online of the subjection function, which makes the control system perceivable and capable of suppressing the external interference.The entire system control was simulated by using MATLAB coding environment. The result shows that the fuzzy neural network realizes the constant current control with accuracy and quick responding. While the input voltage fluctuates ±20% and the occupation ratio equals 0.5, the deviation correcting time is less than 5 inverting cycles showing quick responding of the system, and the control error less than 2% showing accuracy in steady state.The system can also implement steady rising and descending control of the current according to the settings of time-depend variables. It is necessary to coordinate the aspects of responding speed and stability in steady state while selecting multipliers KE, KEC and KDU, in which over-regulating and surging of the system should be avoided while high responding speed is in pursuit.