Bian Yushu received Ph.D. from Beihang University in 1998 and now is an associate professor in Beihang University. His main research interests are flexible manipulator and vibration control. Corresponding author at: School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China. Tel.: + 86 10 82317745. E-mail address: bian_bys@buaa.edu.cn (Y. Bian).