1. AIST/ ISRI-CNRS / STIC Joint French-Japanese Robotics Laboratory (JRL), National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, Japan
2. LISV Laboratoire d'lngénierie des Systèmes de Versailles, 10/12 avenue de l'Europe, 78140 Vélizy, France
3. Humanoid Research Group, Intelligent Systems Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, Japan