1. Shaanxi Key Laboratory of Intelligent Robots, School of Mechanical Engineering, Xi'an Jiaotong University 1 , Xi'an, Shaanxi 710049, People's Republic of China
2. State Key Laboratory for Strength and Vibration of Mechanical Structures, Soft Machines Lab, Department of Engineering Mechanics, Xi'an Jiaotong University 2 , Xi'an, People's Republic of China