1. Department of Systems and Control Engineering, Tokyo Institute of Technology, Tokyo 152-8552, Japan
2. Department of Mechanical Engineering, University of California, Santa Barbara, California 93106, USA
3. Department of Mechanical and Environmental Informatics, Tokyo Institute of Technology, Tokyo 152-8552, Japan
4. Ricoh Company Ltd., Tokyo 143-8555,
Japan
5. Department of Statistics and Mathematics, Boston University, Boston, Massachusetts 02215, USA
6. Department of Mathematical Science and Advanced Technology, Japan Agency for Marine-Earth Science and Technology, Yokohama 236-0001,
Japan