1. Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
2. Sydney Institute for Robotics and Intelligent Systems, The University of Sydney, Camperdown, NSW, Australia
3. CNRS-AIST JRL (Joint Robotics Laboratory), IRL3218, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
4. Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan