| Keyhole Plasma Arc Welding (PAW) is a high-octane and high-efficiency technology, it has a wide foreground. However, the welding technologic parameters matching zone of PAW is so narrow that it makes the keyhole unstable, which leads to the instability of the welding process and the joint quality. Therefore, how to improve welding stability is a promising problem in the research field of PAW. The key of penetration control in Keyhole PAW is to control the state of the keyhole, and in order to control the state of the keyhole, it is important to control the heat input of welding process. Pulse welding method is effective to control heat input. Because of the non-linear characteristic of PAW penetration control system, it is hard to establish the exact mathematics model of penetration control. Thereby, the adoption of traditional control means can't be satisfying. The intelligent control theory creates a new world for penetration control of PAW. The simulation mathematics model of Pulse Plasma Arc Welding (PPAW) fuzzy control system is established, which later is simulated with the software of MATLAB in the paper. PPAW fuzzy control system based on the single-chip of AVR ATmega128, which achieves fuzzy control in PPAW penetration process, is also designed in the paper. The system can not only establish the welding technologic parameters, but also regulate pulse current parameters in real time on the basis of the state of keyhole which is detected in welding process, and in this way, it is able to be used to control penetration of welded joint in real time. The system realizes both intelligent control which is called "one pulse one keyhole" in PPAW process and uniformity of welded joint. The results of experiments indicate that there is favorable consistency between the simulation and the practical welding. So the mathematics model of PPAW fuzzy control system based on the single-chip is correct, and the software and hardware empoldered are credible.
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