1. Graduate School and Faculty of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
2. Research Institute of Advanced Electric Propulsion Aircrafts, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
3. Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan