SHANG Fang Ph. D. candidate at the School of Control Science and Engineering, Shandong University. Her research interest covers nonlinear output feedback control and adaptive control theory. E-maih shangfang929@ 163.com LIU Yun-Gang Professor at the School of Control Science and Engineering, Shandong University. His research interest covers stochastic control, nonlinear system analysis, and adaptive control. Corresponding author of this paper. E-mall: lygfr@sdu.edu.cn