1. School of Mechanical Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
2. Shandong Institute of Mechanical Design and Research, Jinan 250031, China
3. Electrical Engineering College, Jinan University, Jinan 250022, China
4. School of Control Science and Engineering, Shandong University, Jinan 250061, China