This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (16) Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Popovic, M. B. Articles by Herr, H. Search for Related Content Social Bookmarking                         What's this?

Ground Reference Points in Legged Locomotion: Definitions, Biological Trajectories and Control Implications

The Media Laboratory, Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA, marko{at}media.mit.edu

Ambarish Goswami

Honda Research Institute, Mountain View, CA 94041, USA, AGoswami{at}hra.com

Hugh Herr

MIT Media Laboratory, MIT-Harvard Division of Health Sciences and Technology, Spaulding Rehabilitation Hospital, Harvard Medical School, Cambridge, MA 02139-4307, USA, hherr{at}media.mit.edu

The zero moment point (ZMP), foot rotation indicator (FRI) and centroidal moment pivot (CMP) are important ground reference points used for motion identification and control in biomechanics and legged robotics. In this paper, we study these reference points for normal human walking, and discuss their applicability in legged machine control. Since the FRI was proposed as an indicator of foot rotation, we hypothesize that the FRI will closely track the ZMP in early single support when the foot remains flat on the ground, but will then significantly diverge from the ZMP in late single support as the foot rolls during heel-off. Additionally, since spin angular momentum has been shown to remain small throughout the walking cycle, we hypothesize that the CMP will never leave the ground support base throughout the entire gait cycle, closely tracking the ZMP. We test these hypotheses using a morphologically realistic human model and kinetic and kinematic gait data measured from ten human subjects walking at self-selected speeds. We find that the mean separation distance between the FRI and ZMP during heel-off is within the accuracy of their measurement (0.1% of foot length). Thus, the FRI point is determined not to be an adequate measure of foot rotational acceleration and a modified FRI point is proposed. Finally, we find that the CMP never leaves the ground support base, and the mean separation distance between the CMP and ZMP is small (14% of foot length), highlighting how closely the human body regulates spin angular momentum in level ground walking.

Key Words: legged locomotion • control • biomechanics • human • zero moment point • center of pressure • foot rotation indicator • centroidal moment pivot

The International Journal of Robotics Research, Vol. 24, No. 12, 1013-1032 (2005)
DOI: 10.1177/0278364905058363


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				O. Hohn and W. Gerth Probabilistic Balance Monitoring for Bipedal Robots The International Journal of Robotics Research, February 1, 2009; 28(2): 245 - 256. [Abstract] [PDF]

				K. Hauser, T. Bretl, J.-C. Latombe, K. Harada, and B. Wilcox Motion Planning for Legged Robots on Varied Terrain The International Journal of Robotics Research, November 1, 2008; 27(11-12): 1325 - 1349. [Abstract] [PDF]

				V. M. F. Santos and F. M. T. Silva Design and Low-Level Control of a Humanoid Robot Using a Distributed Architecture Approach Journal of Vibration and Control, December 1, 2006; 12(12): 1431 - 1456. [Abstract] [PDF]