1. a Fanuc Robotics North America, Inc., 3900 West Hamlin Road, Rochester Hills, M148309-3253, USA
2. b Department of Systems Science and Mathematics, Washington University, St Louis, MO 63130, USA
3. c Department of Electrical Engineering, Michigan State University, MI 48824, USA
4. d Department of Systems Science and Mathematics, Washington University, St Louis, MO 63130, USA