1. Lecturer, Mechanical and Electrical Engineering Institute, Hebei Univ. of Engineering, Handan, Hebei 056038, China (corresponding author).
2. Professor, School of Automation Science and Electrical Engineering, Beihang Univ., Division 303, Beijing 100191, China.
3. Professor, School of Aeronautic Science and Engineering, Beihang Univ., Division 505, Beijing 100191, China.