1. Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen 518055, China.
2. Berkeley Sensor and Actuator Center, Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720, USA.
3. Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
4. School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China.
5. Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15289, USA.
6. Department of Electromechanical Engineering, Centre for Artificial Intelligence and Robotics, University of Macau, Macao 999078, China.