1. College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao, China
2. College of Mechanical Engineering and Automation, Huaqiao University, Xiamen, Fujian, China
3. Robotics Institute, Ningbo University of Technology, Zhejiang, China
4. Department of Electronic and Information Systems, Shibaura Institute of Technology, Saitama, Japan