1. School of Mechanical and Electrical Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
2. Chair of Mechanics and Robotics, University of Duisburg-Essen, 47057 Duisburg, Germany
3. G-SCOP Laboratory, Grenoble-INP/UJF-Grenoble 1/CNRS, 46 Avenue Félix Viallet, 38031 Grenoble Cedex 1, France