Energetic Effects of Adding Springs at the Passive Ankles of a Walking Biped Robot. - K. D. Farrell; Christine Chevallereau; E. R. Westervelt (ICRA, 2007)

Analysis results and tools for the control of planar bipedal gaits using hybrid zero dynamics. - E. R. Westervelt; B. Morris; K. D. Farrell (Auton. Robots, 2007)