1. School of Construction Machinery, Chang'an University, Xi'an, P. R. China;
2. State Key Laboratory for Manufacturing System Engineering, Xi'an Jiaotong University, Xi'an, P. R. China;
3. Shaanxi Key Laboratory of Intelligent Robots, Xi'an Jiaotong University, Xi'an, P. R. China;
4. State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha, P. R. China