1. Department of Electronics and Information Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan
2. Department of Mechanical and Energy Systems Engineering, Oita University, 700 Dannoharu, Oita 870-1192, Japan
3. Department of Electric and Electronic Engineering, Tokyo University of Technology, 1404-1 Katakuramachi, Hachioji City, Tokyo 192-0982, Japan