1. e-mail:
2. Postdoctoral Research Associate e-mail: Centre for Robotic Research, Kings's College London, London WC2R 2LS, UK
3. Chair of Mechanisms and Robotics, MoE Key Laboratory for Mechanism Theory and Equipment Design, Tianjin University, Tianjin, China
4. Centre for Robotic Research, Kings's College London, London WC2R 2LS, UK e-mail: