1. School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, P. R. China
2. Key Laboratory of Welding Robot and Application Technology of Hunan Province, Xiangtan University, Xiangtan 411105, P. R. China
3. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P. R. China