1. The State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing University, P. R. China
2. College of Mechanical and Vehicle Engineering, Taiyuan University of Technology, P. R. China
3. Zhejiang Yiduan Precision Machinery Co., Ltd, Ningbo, P. R. China
4. School of Electrical Automation and Information Engineering, Tianjin University, P. R. China