1. a State Key Laboratory on Robotics, Shenyang Institute of Automation, Shenyang 110016, P. R. China; Shenyang Institute of Aeronautical Engineering, Shenyang 110034, P. R. China
2. b State Key Laboratory on Robotics, Shenyang Institute of Automation, Shenyang 110016, P. R. China; Department of Robotics, Ritsumeikan University, Kusatsu 525-8577, Japan
3. c State Key Laboratory on Robotics, Shenyang Institute of Automation, Shenyang 110016, P. R. China
4. d State Key Laboratory on Robotics, Shenyang Institute of Automation, Shenyang 110016, P. R. China