1. School of Computer Science and Engineering, Center for Robotics, University of Electronic Science and Technology of ChinaChengdu611731People's Republic of China
2. Department of Electrical and Computer EngineeringNational University of SingaporeSingapore119077Singapore
3. Centre for Robotics, University of Electronic Science and Technology of ChinaChengdu611731People's Republic of China
4. School of Automation and Electrical Engineering, University of Science and Technology BeijingBeijing100083People's Republic of China