1. School of Printing, Packaging Engineering and Digital Media Technology, Xi’an University of Technology, Xi’an 710054, P. R. China
2. School of Mechanical and Precision, Instrument Engineering, Xi’an University of Technology, Xi’an 710054, P. R. China
3. Shaanxi Key Laboratory of Advanced Manufacturing and Evaluation of Robot Key Components, Baoji University of Arts and Sciences, 721016, Baoji, P. R. China