1. Professor, School of Electromechanical Engineering, Xidian Univ., Xi’an 710071, China.
2. Student, School of Electromechanical Engineering, Xidian Univ., Xi’an 710071, China.
3. Professor, School of Electromechanical Engineering, Xidian Univ., Xi’an 710071, China (corresponding author).
4. Engineer, Aerospace System Engineering Shanghai, Zhongchun Rd., Minhang District, Shanghai 201109, China.