1. College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, the Key Laboratory of Nuclear Technology Application and Radiation Protection in Astronautics (Nanjing University of Aeronautics and Astronautics), Ministry of Industry and Information Technology, and Nondestructive Detection and the Monitoring Technology for High Speed Transportation Facilities, Key Laboratory of Ministry of Industry and Information Technology, Nanjing, 211106 China. (e-mail: autonavinuaa@163.com)
2. College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, the Key Laboratory of Nuclear Technology Application and Radiation Protection in Astronautics (Nanjing University of Aeronautics and Astronautics), Ministry of Industry and Information Technology, and Nondestructive Detection and the Monitoring Technology for High Speed Transportation Facilities, Key Laboratory of Ministry of Industry and Information Technology, Nanjing, 211106 China.