1. Department of Mechanical Engineering & Intelligent Systems, University of Electro-Communications, Tokyo, Chofu, Tokyo 182-8585, Japan
2. Graduate School of University of Electro-Communications, Tokyo, Chofu, Tokyo 182-8585, Japan
3. Aluminum Development Division, Aisin Takaoka Corp., Toyoda, Aichi 473-0934, Japan
4. Power and Industrial Systems Research and Development Center, Toshiba Corp., Yokohama, Kanagawa 235-8523, Japan