1. Laboratory of the Intelligent Microsystem Beijing Information Science and Technology University Beijing 100192 P. R. China
2. School of Instrument Science and Opto‐Electronics Engineering Beijing Information Science and Technology University Beijing 100192 P. R. China
3. Department of Mechanical Engineering City University of Hong Kong Hong Kong 999077 P. R. China
4. School of Mechanical Engineering, Beijing Institute of Technology Beijing 100081 P. R. China
5. Institute of Medical Equipment Science and Engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China
6. State Key Laboratory of Precision Testing Technology and Instruments Tsinghua University Beijing 100084 P. R. China