| Welding is a set function manufacturing technology and makes the materials for permanent connection. With the rapid development of economy, the global competitiveness of manufacturing is growing up, especially in automotive, container and etc., more and more sheet thin plate are used, so low-energy requirement is put up for the welding of thin plates. In order to adapt to this rising demand, the short-circuit arc welding as low-cost and low-energy got attention, and can be tried to make more reasonable. However, this method is still in early stage of development, it has few information can be found at home and abroad. Therefore, it is hard and important to study the principle of control AC short-circuit transfer and energy distribution, to bring up an ideal control scheme and build up a welding system.In order to meet the process requirement of AC short-circuit arc welding, the system for welding thin plates based on DSP and CPLD was designed and investigated. The entire welding system included main circuit, control circuit and wire feed system. The main circuit was used of two inverters and high-voltage full-bridge arc stability circuit to re-igniting the arc. The control circuit was to achieve by DSP (TMS320F2812) and CPLD (EPM7192S), all sequential control and many core computing in the system were controlled by DSP, while CPLD was to transmit and distribute the signals from the DSP to external parts, as well as implement level compatibility. At the same time, CPLD had another important function, which is to transform the processed data from the DSP to digital PWM output signals.Energy input is a very sensitive factor, and the stability of wire feed system is a great impact on the accuracy and stability of the entire system, therefore, it can not be avoided to how to improve the accuracy and dynamic performance of wire feeding system. In this thesis, the closed-loop control of the wire feeding system was achieved through DSP (TMS320F2812) and electro-optical encoder to acquire the electrical wire feed speed directly. In order to improve the overall performance of system, the fuzzy PI algorithm was applied. The results showed that it had a perfect wire feeding stability, furthermore, the static and dynamic performance of the system were better than ordinary one.It is too hard to bring up a best project about the energy distribution on the short-circuit arc welding, because the welding method is new. In this thesis, a variety of factors impacting heat input were analyzed during different stages of the welding process. According to the theoretical study and combining to the analysis of actual welding waveform, a new and flexible AC short-circuit arc welding was brought up. It can complete the energy regulation in one short-circuit arcing cycle, make sure the stability of the welding process and increase the flexibility of energy regulation at the meantime.A new waveform control project was proposed to better transfer different welding process in the AC short-circuits arc welding. At the short circuit stage, multi-curvature waveform control was to control the ascending curvature of welding current to reduce spatter; at EN stage, constant current control was to make sure the current stability; at EP stage, multi-step voltage control was to implement welding arc length control through self-regulation of arc.Based on dual closed-loop control and varying parameters PI algorithm, a new AC short-circuit arc welding method was brought up to achieve stable and rapid control successfully during different status of welding process. Furthermore, rational procedures were designed to make sure the requirement of time sequence at polarity transferring, and complete the control of generating the arc, arc interruption, high-voltage arc stability and other related functions.There exits two current zero during one cycle in AC short-circuit arc welding, so it is a key to make sure arc re-ignition and stability at welding process. In the thesis, high-voltage pulse was to re-ignite arc successfully. In addition, in order to better understand the impact on arc re-ignition, the voltage amplitude, pulse width, the imposition of time and the current before zero-point were investigated to determine the best program.Many experiments were carried out for study the relation between the welding parameters and energy distribution in the AC short-circuit arc welding. The results of theoretical analysis were confirmed through measurement of welding current and voltage, the welding shape, high-speed camera pictures and etc.
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