1 School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China. rykhit@hit.edu.cn.
2 School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China. rykhit@hit.edu.cn and State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China. jhy_hit@hit.edu.cn.