1. School of Automation, China University of Geosciences, Wuhan 430074, P. R. China
2. Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan 430074, P. R. China
3. College of Automation, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
4. Department of Mechanical Engineering, Boston University, Boston, MA 02215, USA