1. Research Centre for Electrical Power & Mechatronics, Indonesian Institute of Sciences, Komp LIPI Jl Cisitu 21/54D, Gd 20, Bandung 40135, Indonesia
2. Graduate School of Information, Production and Systems, Waseda University, 2-7 Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka 808-0135, Japan