Because the performance of permanent magnet synchronous motor (PMSM) is strongly dependent on the quality of magnetization in the permanent magnet, the operation for magnetization has to be exactly performed. Therefore, to identify the distribution of magnetization beforehand is significant from the viewpoint of high-quality-manufacturing of PMSM. Then, the nondestructive estimation method to identify the magnetization distribution is strongly required. In this paper, the estimation method, in which the steepest descent method is applied to the optimization method and sigmoid function is applied to the intensity of magnetization formulated in spherical coordinate system to restrict the generation of infeasible distribution, is proposed. To verify the validity of the proposed method, its performance is compared with some conventional methods
