| Aluminum alloy is more and more widely applied in many fields, such as automobiles, vessels, aerospace, and so on, because of to its excellent comprehensive performance of light weight, wear-resistance, corrosion resistance, good anti-impact properties, recycleability, and so on. And in the manufacturing of aluminum alloy production, welding plays a very important role. One key point in the welding of aluminum alloy is the precise control of the welding current. If the input current is not appropriate, the welding process would be unstable, and there would be defects in welding points. The waveform modulation method and technological mechanism for the DPMIG welding of aluminum alloy is studied in this paper. This will be academically and practically valuable for the intelligent arc welding power supply technology and welding control strategy. The research work is supported by Guangdong Natural Science Foundation(2016A030313117), and Speacial Project on the Integration of Industry, Education and Research of Guangdong Province(2013B090600098、2013B090600030).The DPMIG welding power is the basis to realize aluminum alloy welding technology, so the hardware system of welding power is firstly studied in this paper, including the main circuit of phase-shifted soft switching, power circuit, DSP control core, modular circuit unit, IGBT driving circuit, wire-feed circuit, man-machine interactive system, and so on. This sets a basis for the subsequent waveform modulation and technological mechanism.Then the system simulation model with Simulink is built on the basis of the hardware design of aluminum alloy welding power, including the main circuit model, control current model, current waveform model and PID control model, as well as the simulation analysis is carried out. In the Simulink simulation, the correctness of the topologies of the hardwre is verified, the key element parameters of welding power is optimizied. In order to control the current more precisely, the conventional PID control and genetic optimized PID control based on the fuzzy function are compared. The results tells that the genetic optimized PID control based on the fuzzy function has good robustness and adaptability.Since that the DPMIG welding parameters of aluminum alloy are diverse and they are inconvenient to adjust. Moreover, the welding specification is complex, the expert database of DPMIG welding is studied based on the analysis for the static and dynamic properties of welding power source. Firstly, the Lagrange interpolation, Newton interpolation and the cubic spline interpolation are compared. Then arc-length control of frequency conversion for the pulse current is studied. Finally the unified adjustive and gradually changing database of parameters based on the large-step calibration and cubic spline interpolation is established.On the base of hardware circuit design, simulation of Simulink software and expert databse, the DPMIG of aluminium alloy and its software system are developed. Then the technological property tests of DPMIG welding are performed on the DPMIG welding power of aluminum alloy on the welding test platform constructed by ourselves. The influences of the ratio of the number of strong pulse to the number of weak pulse, the number of strong and weak pulse groups, high frequency fH, and low frequency fL on the welds, weld forming, and welding quality are verified. Moreover, the neural network algorithm is used for the predictive modeling of wire-feed speed. With all the parameters of DPMIG welding given, the wire-feed speed is predicted by the predictive model, and then the wire-feed speed is verified by the test. The results show that the wire-feed speed prediction model of neural network have better prediction performance and could effectively guide the selection of welding parameters in the process of practical production.In addition, the modified DPMIG welding technology is proposed for the energy mutation in the process of square-wave DPMIG welding of aluminum alloy. The work principles of trapezoid wave and sinusoid wave are analyzed, then the trapezoid wave and sinusoid wave DPMIG welding tests as well as the sinusoid wave and square wave DPMIG welding tests are contrasted, respectively. It is found that the process of trapezoid wave and sinusoid wave aluminum alloy welding are more stable than those of square wave aluminum alloy welding, the welds of trapezoid-wave aluminum alloy welding are more normative. This suggested that the modified DPMIG welding technology has an important reference significance for the study on aluminum alloy welding.Finally, electrical signal feature information of the welding process including the probability density ratio, the periodic repetition rate based on the working points of U-I graph and sample entropy, and their impact on the quality assessment of welding are discussed in this paper. In order to avoid the uncertainty of single evaluation index, as well as in the process of evaluation peoples’ s subjective randomness and delay of offline testing, A online welding quality inspection of fuzzy comprehensive evaluation method is proposed. By observing the feature information P, L and CSaEn to obtain expert experience, then get the membership functions and summarize the fuzzy logic reasoning rules. By the weld verification of TPMIG, the fuzzy logic reasoning evaluation system achieved an accuracy of 83.3%, demonstrating the effectiveness of the quantitative assessment system. |
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