1. School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi Province, P.R. China
2. Shaanxi Key Laboratory of Intelligent Robots, Xi’an Jiaotong University, Xi’an, Shaanxi Province, P.R. China
3. School of Mechanical Engineering, Xinjiang University, Urumqi, Xinjiang Uygur Autonomous Region, P.R. China