1. College of Mechanical and Electrical EngineeringNanjing University of Aeronautics and Astronautics Nanjing 210016 P. R. China
2. College of AstronauticsNanjing University of Aeronautics and Astronautics Nanjing 210016 P. R. China
3. Faculty of Mechanical and Precision Instrument EngineeringXi`an University of Technology Xi'an 710048 P. R. China
4. Department of Mechanical EngineeringChiba University Chiba 263‐0022 Japan