1. a Department of Electrical Engineering, National Chiao-Tung University, Hsinchu, Taiwan, ROC
2. b Department of Electrical Engineering, National Chiao-Tung University, Hsinchu, Taiwan, ROC
3. c Department of Electrical Engineering, National Chiao-Tung University, Hsinchu, Taiwan, ROC
4. d Department of Electrical Engineering, National Chiao-Tung University, Hsinchu, Taiwan, ROC
5. e Robotics System Integration Technology Department, Intelligent Robotics Technology Division, Mechanical and Systems Research Laboratories, ITRI, Taiwan, ROC