1. Professor, College of Automation Engineering, Nanjing Univ. of Aeronautics and Astronautics, Nanjing 210016, P.R. China (corresponding author).
2. Masters Student, College of Automation Engineering, Nanjing Univ. of Aeronautics and Astronautics, Nanjing 210016, P.R. China.
3. Professor, Dept. of Electrical and Computer Engineering, Univ. of Virginia, Charlottesville, VA 22903.
4. Professor, College of Automation Engineering, Nanjing Univ. of Aeronautics and Astronautics, Nanjing 210016, P.R. China.