1. Centre for Robotic Research, King’s College London, London WC2R 2LS, UK e-mail:
2. Mem. ASME Centre for Robotic Research, Kings’s College London, London WC2R 2LS, UK e-mail:
3. ASME Fellow Chair of Mechanisms and Robotics MoE Key Laboratory for Mechanism Theory and Equipment Design, Tianjin University, Tianjin, 300072, China; Centre for Robotic Research, King’s College London, London WC2R 2LS, UK e-mail: