1. School of Mechanical and Automation, Weifang University, Weifang 261061, China
2. School of Mechanical and Automation, Weifang University, Weifang 261061, China;
3. Shandong Tianrui Heavy Industry Co., Ltd, Weifang 261061, China;
4. Shandong Magnetic Suspension Technology Industry Research Institute, Weifang 261061, China