1. School of Automation; Nanjing University of Science and Technology; Nanjing 210014 China
2. School of Energy and Mechanical Engineering; Nanjing Normal University; Nanjing 210042 China
3. Jiangsu Key Laboratory of 3D Printing Equipment and Manufacturing; Nanjing 210042 China
4. Department of Electrical and Computer Engineering; The University of Texas at San Antonio; San Antonio 78249 Texas USA