1. Graduate Student, Dept. of Electrical Engineering and Automation, Jiangsu Normal Univ., Xuzhou 221116, China.
2. Professor, Dept. of Electrical Engineering and Automation, Jiangsu Normal Univ., Xuzhou 221116, China (corresponding author).
3. Associate Professor, Dept. of Electrical Engineering and Automation, Jiangsu Normal Univ., Xuzhou 221116, China.