1. School of Mechanical Engineering, Shandong University, Jinan 250061, China, also with the Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, Shandong University, Jinan 250061, China, and also with the National Demonstration Center for Experimental Mechanical Engineering Education, Shandong University, Jinan 250061, China (e-mail: kaiguo@sdu.edu.cn)
2. School of Automation, Beijing Institute of Technology, Beijing 100081, China (e-mail: ddongzheng@outlook.com)
3. School of Mechanical Engineering, Shandong University, Jinan 250061, China, also with the Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, Shandong University, Jinan 250061, China, and also with the National Demonstration Center for Experimental Mechanical Engineering Education, Shandong University, Jinan 250061, China.