Multimaterial Topology Optimization Method Based on Global Search by Combinatorial Optimization and Local Search by Variable Design Region Method

This paper presents a novel multi-material topology optimization method for electric motors. In the proposed method, the search process is divided into two steps. First, combinatorial optimization is conducted, wherein two different types of motors are used. Owing to this, for example, motor shapes that have both the high torque density of permanent magnet motors and the variable flux capability of wound field motors can be obtained. Second, the optimal solution obtained through the combinatorial optimization is used as the initial solution, and multi-material topology optimization with variable design region method is performed. By using the proposed method, we can obtain design solutions that have high performance on complex motors with various materials, such as hybrid field motors and permanent magnet assisted synchronous reluctance motors. To validate the effectiveness, rotors of a hybrid field motor and a permanent magnet assisted synchronous reluctance motor are optimized using the proposed method. From the numerical results, it can be confirmed that the solution obtained by the proposed method has a better performance than that of the conventional multi-material topology optimization.