1. School of Mechanical Engineering, Tianjin University, Tianjin, P.R. China
2. Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, P.R. China
3. Tianjin Key Laboratory of Nonlinear Dynamics and Control, Tianjin, P.R. China
4. College of Aeronautical Engineering, Civil Aviation University of China, Tianjin, P.R. China