Optimal Control And Expert System Of Intelligent Arc Welding Power

With the development of the power electronics and microprocessor technology, high power switching components and MCU, DSP are applied to the field of arc welding power. To make the arc welding power digital and intelligent becomes the hot spot of the research. An intelligent arc welding power has several characteristics, such as unified parameters regulation, automatically parameters generation, multi-function integration, flexible control, high-precision control and humanized operation interface. In this research, by optimizing the control of the digital welding power and establishing a welding expert system, Power Pulse?â… and Power Pulse?â…¡, two deferent models based on deferent core are developed.The situation of recent research is introduced in this paper firstly. Key technologies like P-GMAW, DP-GMAW, droplet transfer control, waveform control, multi-function integration, unified parameters regulation, expert system and so on are analyzed. And the tasks of the research are declared.The overall design of the intelligent arc welding power is discussed in Chapter 2. By employing the circuit topology of full-bridge inverter, the IGBT and the amorphous transformer, the power circuit could be built. Two deferent design of the control core,"MCU + hardware driver"and"DSP integrated control", are discussed for different applications. In order to improve the stability of the power, modular design method is introduced, and the peripheral circuits are modularized, including signal feedback and regulating, PWM signal generating, IGBT driver, wire feeding, abnormal signal detecting, and human machine interface.According to the characteristics of intelligent arc welding power, the system control software is developed. Three key methods are emphasized in this part. The first one is the variable frequency arc length control in P-GMAW and DP-GMAW, as well as the introduction of the data structure of queue, in order to calculate the average voltage. The second is the design of the communication protocol between the H-M interface and the main control board, which is based on the software handshaking. At last, the original idea of automatic parameter regulating based on long-step calibration and part Newton interpolation is discussed, as well as the principle of the multi-attribution storage of the welding parameters.A complete platform for the test of the intelligent arc welding power is built in this research. The constant current characteristic and constant voltage characteristic, both static characteristic and dynamic characteristic are tested. The wire feeding system is also tested and the correspondence between the control value and the velocity of the wire feeding is achieved.The controls of allover welding processes are optimized. After analyzing the characteristics of the continuous PID control, the optimal PID parameters are achieved by experimental setting. The principle of adaptive fuzzy PID control is also introduced, and the effectiveness is proved by the simulation of the MATLAB. The control of arc starting is optimized by using special waveform, and the success rate of the arc starting is improved. By adding the filter to the output terminals, the output voltage is controlled in an ideal interval. The optimal control of the droplet transfer is emphasized in this part, especially the calibration of the curve of the One-Pulse-One-Droplet critical current of various welding wires.The welding parameters of CO₂ welding iron, P-GMAW of iron and DP-GMAW of aluminum are long-step calibrated through a lot of tests. And the effectiveness of the parameter self-adjusting algorithm based on long-step calibration and part Newton interpolation is proved through lots of tests.