DAN TIAN1,2, YINGKUI DU1,2 AND DALI CHEN2
1Department of Information Engineering
Shenyang University
Shenyang, 110044 P.R. China
2State key Laboratory of Robotics
Shenyang Institute of Automation
Chinese Academy of Sciences
Shenyang, 110016 P.R. China
E-mail: www.sltd2008@163.com