Gregg Robert D, Righetti Ludovic
Department of Mechanical Engineering, Northwestern University and the Center for Bionic Medicine, Rehabilitation Institute of Chicago, Chicago, IL 60611
Max-Planck Institute for Intelligent Systems, Tübingen, Germany
IEEE Trans Automat Contr. 2013 Oct;58(10):2679-2685. doi: 10.1109/TAC.2013.2256011.
This paper shows that viscous damping can shape momentum conservation laws in a manner that stabilizes yaw rotation and enables steering for underactuated 3D walking. We first show that unactuated cyclic variables can be controlled by passively shaped conservation laws given a stabilizing controller in the actuated coordinates. We then exploit this result to realize controlled geometric reduction with multiple unactuated cyclic variables. We apply this underactuated control strategy to a five-link 3D biped to produce exponentially stable straight-ahead walking and steering in the presence of passive yawing.