TY - JOUR
T1 - Design and experimental implementation of a hybrid zero dynamics-based controller for planar bipeds with curved feet
AU - Martin, Anne E.
AU - Post, David C.
AU - Schmiedeler, James P.
N1 - Funding Information:
The support of this research by the National Science Foundation (CHE8504737) is gratefully acknowledged. We thank the University of Massachusetts Computing Center for generous allocation of computer time. The authors also express appreciation to Professor John Ragle for many helpful discussions.
PY - 2014/6
Y1 - 2014/6
N2 - This paper extends the use of virtual constraints and hybrid zero dynamics (HZD), a successful control strategy for point-foot bipeds, to the design of controllers for planar curved foot bipeds. Although the rolling contact constraint at the foot-ground interface increases complexity somewhat, the measure of local stability remains a function of configuration only, and a closed-form solution still determines the existence of a periodic orbit. The formulation is validated in experiment using the planar five-link biped ERNIE. While gaits designed for point feet yielded stable walking when ERNIE was equipped with curved feet, errors in both desired speed and joint tracking were significantly larger than for gaits designed for the correct radius curved feet. Thus, HZD-based control of this biped is shown to be robust to some modeling error in the foot radius, but at the same time, to require consideration of foot radius to achieve predictably reliable walking gaits. Additionally, under HZD-based control, this biped walked with lower specific energetic cost of transport and joint tracking errors for matched curved foot gait design and hardware compared to matched point-foot gait design and hardware.
AB - This paper extends the use of virtual constraints and hybrid zero dynamics (HZD), a successful control strategy for point-foot bipeds, to the design of controllers for planar curved foot bipeds. Although the rolling contact constraint at the foot-ground interface increases complexity somewhat, the measure of local stability remains a function of configuration only, and a closed-form solution still determines the existence of a periodic orbit. The formulation is validated in experiment using the planar five-link biped ERNIE. While gaits designed for point feet yielded stable walking when ERNIE was equipped with curved feet, errors in both desired speed and joint tracking were significantly larger than for gaits designed for the correct radius curved feet. Thus, HZD-based control of this biped is shown to be robust to some modeling error in the foot radius, but at the same time, to require consideration of foot radius to achieve predictably reliable walking gaits. Additionally, under HZD-based control, this biped walked with lower specific energetic cost of transport and joint tracking errors for matched curved foot gait design and hardware compared to matched point-foot gait design and hardware.
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U2 - 10.1177/0278364914522141
DO - 10.1177/0278364914522141
M3 - Article
AN - SCOPUS:84896489522
SN - 0278-3649
VL - 33
SP - 988
EP - 1005
JO - International Journal of Robotics Research
JF - International Journal of Robotics Research
IS - 7
ER -