Aspects Regarding the Optimization of the Induction Heating Process using Fmincon, Minimax functions and Simple Genetic Algorithm Mihaela Novac * , Ecaterina Vladu ** , Ovidiu Novac ** and Mircea Gordan* * Department of Electrotechnics, Measurements and using of Electrical Energy, University of Oradea, Faculty of Electrical Engineering and Information Technology, 410087,1 , Universităţii Str., Oradea, Romania, E-Mail: mnovac@uoradea.ro ** Department of Computers, University of Oradea, Faculty of Electrical Engineering and Information Technology, 410087,1 , Universităţii Str., Oradea, Romania, E-Mail: evladu@rdslink.ro Abstract : The aim of this paper is to study the induction heating processes by using optimal design with Genetic Algoritms (GAs) respectively fmincon and minimax optimisation methods. The optimisation is performed in order to obtain a high value of electrical efficiency of the inductor, as well a minimum non-uniformity of the temperature distribution in the workpiece. The optimisation is performed in two different ways: by using a simple genetic algorithm and with fmincon and minimax functions. Keywords: induction heaters, numerical modelling, optimisation, simple genetic algorithm. I. INTRODUCTION The aim of this paper is to investigate the ways the evolutionary optimisation technics can be applied in the design of electromagnetic devices, in particular of the induction heaters in order to automate some parts of the designing process and to compare the obtained results with other optimisation methods, namely fmincon and minimax. For the electromagnetic problems, the optimal design is usually a multiobjective task where different specifications, often in conflict among them, have to be pursued with several design degrees of freedom, which are the design parameters. Also, the device parameters have to satisfy some technological and physical constraints. Therefore it is necessary to use a multiobjective optimisation strategy. Due to the presence of multiple quasi-optimal solutions and to the typical complexity of electromagnetic computations, the automatic optimal design of electromagnetic devices is a very complex task. The design process of the induction heating devices, takes into account the inductor’s electrical efficiency,[1]. By this point of view, induction coils with a small coupling gap are more efficient than loosely coupled ones, so that the magnetic flux would flow through the workpiece surface, generating eddy currents. Higher frequency is also beneficial, [2],[4],[5]. Carrying out the design must consider the heating of the entire internal length of a workpiece, such as the temperature distribution would be as uniform as possible. In this work considerations regarding simple genetic algorithm and fmincon and minimax functions optimization are presented, having the aim to increase the electrical efficiency, as well as to assure a uniform temperature distribution along the workpiece. These are important steps in the optimal design of the induction heating processes. For optimisation, three methods where applied: simple genetic algorithm, in which the two objectives are combined in a single fitness function by using weghting coefficients, optimisation with fmincon function and optimisation with minimax function. II. MODELLING THE INDUCTION HEATING DEVICE The induction heater for cylindrical pieces was selected for this experiment (Figure 1). Figure 1. Inductor heater and a cylindrical piece, where: 1- piece; 2- magnetic coil; 3 – water; 4- turn 3 2 4 r H 0 a 1 d 2 d 1 h z 1 64