1. Department of Engineering, Kyoto University of Advanced Science, Yamanouchi-Gotandacho, Ukyo-ku, Kyoto 615-8577, Japan
2. Nagamori Institute of Actuators, Kyoto University of Advanced Science, Yamanouchi-Gotandacho, Ukyo-ku, Kyoto 615-8577, Japan
3. Department of Applied Science and Engineering, Fukui University of Technology, 3-6-1 Gakuen, Fukui 910-8505, Japan