1. School of Mechanical & Aerospace Engineering, Queen's University Belfast, Belfast BT9 5AH, UK e-mail:
2. Department of Engineering, Indiana University Purdue University, Fort Wayne, IN 46805 e-mail:
3. School of Mechanical Engineering, Tianjin University, Tianjin 300072, China e-mail:
4. Northern Ireland Technology Centre, Queen's University Belfast, Belfast BT9 5AH, UK e-mail:
5. School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China e-mail: