1. College of Mechanical and Electronic Engineering, Fujian Agriculture and Forestry University, Fuzhou, Fujian, P. R. China
2. Key Lab of Contemporary Design and Integrated Manufacturing Technology of Ministry of Education, Northwestern Polytechnical University, Xi'an, Shaanxi, P. R. China
3. Lab of Aeronautical & Astronautical Assembly, School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an, P. R. China