1. State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, Beijing 100083, P. R. China
2. Automation Science and Electrical Engineering, Beihang University, Beijing 100083, P. R. China
3. Biomedical Engineering College, Beihang University, Beijing 100083, P. R. China
4. Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing 100083, P. R. China