1. College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016 Jiangsu, China
2. College of Energy and Powder Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016 Jiangsu, China
3. National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016 Jiangsu, China