1. Jiangxi province key laboratory of maglev technology, Jiangxi University of Science and Technology, Ganzhou 341000, People's Republic of China
2. School of Electrical Engineering and Automation, Jiangxi University of Science and Technology, Ganzhou 341000, People's Republic of China
3. School of mechanical and electrical engineering, Jiangxi University of Science and Technology, Ganzhou 341000, People's Republic of China
4. College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China