1. National Key Laboratory of Science and Technology on Holistic Control, School of Automation Science and Electrical Engineering, Beihang University, No. 37, Xueyuan Road, Haidian District, Beijing, 100191, P. R. China
2. State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, No. 37, Xueyuan Road, Haidian District, Beijing, 100191, P. R. China