| Besides the advantages of the traditional longitudinal induction heating and the transverse flux induction heating, the traveling wave induction heating (TWIH) has further advantages, for example, the reduction of the alternate component of the electromagnetic forces affecting the system elements and producing vibration and noise. Especially, it can bring more uniform temperature field distribution. The coupled multi-fields computation in traveling wave induction heating is a difficult and important problem of electromagnetics, so that its research has very significant theoretical value. For its application, traveling wave induction heating refers to very important engineering technology, so its research results could greatly promote the metal processing equipments' development.This dissertation simplified the theoretical model and then established the reasonable coupled analysis model, so as to study the magnetic field and eddy current field distribution in the metal strip. Because of the complex structure of the traveling wave induction heating equipment, the whole research area has been divided into several sub parts based on its material characteristics. Each subfield adopts its own potential function and then the integration can be taken in the common subfield and the public interface. Every field vector coupled indirectly. This computation method has borrowed ideas from the research of transverse flux induction heating, and the finite element method was adopted here.Main achievements of this dissertation include:(1) The slotless model can overcome slots effects in a certain degree. The 2D magnetic field and eddy current field have been analyzed. In the traditional traveling wave induction heating system, the efficient airgap between the coil and load is longer than the airgap between the tooth and load. The magnetic permeability of the metal yoke is much bigger than that of the air, so the induced magnetic flux density below the tooth position will be bigger than the air position in the strip. The 2D magnetic field analysis shows that some of the magnetic lines do not pass through the load, and this will put a dent in the efficiency of the power transferred between coils and load.(2) The 3D magnetic field computation of the traditional and the crossed traveling wave induction heating systems has been carried out. The simulation results reveal that the energy transmission efficiency of the crossed TWIH system is higher than that in the traditional TWIH system. Due to the offset of the two inductors, the induced magnetic field could distribute in a larger efficient area on the workpiece. Flux densities in the upper and lower inductors make up for the weak areas of each other more efficiently, so as to obtain a more uniform magnetic field distribution on the metal strip surface.(3) A new particle swarm optimization (PSO) with allied strategy formed in the evolutionary process of human society has been introduced to avoid the premature problem in traditional PSO. The modified PSO algorithm decreases the gene similarity by the allied strategy and protects the individual fitness through the intragenic crossing-over. The superiority of new PSO has been verified by applied to optimize the Rastrigin function.(4) Based on the analysis of reason for the premature convergence causing in PSO, and enlightened by the phenomenon of mutation and disaster in the biology evolution procession, a population disappearance particle swarm optimization was presented. The particles are divided into several swarms in the same size, the same numbers of individuals disappear after several iterations, and same numbers of new individuals are added to these swarms to maintain the suitable swarm size. Simulation results of Schaffer's f6 function show that the algorithm can easily find the global optimum solution.Finally, the work of this dissertation is summarized and the prospective of future research is discussed. |
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