Affiliation: | aElectrical and Electronics Engineering, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan;bMechanical Systems Engineering, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan;cMeidensha Corporation, Riverside Bldg 36-2, Nihonba-shi Hokozaki-cho, Chuo-ku, Tokyo 103-8515, Japan |