1. School of Mechatronic Engineering, Jiangsu Normal University, Xuzhou 221116, P. R. China
2. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P. R. China
3. College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, P. R. China