Stride-to-stride energy regulation for robust self-stability of a torque-actuated dissipative spring-mass hopper


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Ankarali M. M. , Saranli U.

CHAOS, vol.20, 2010 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 20
  • Publication Date: 2010
  • Doi Number: 10.1063/1.3486803
  • Journal Name: CHAOS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: gait analysis, legged locomotion, springs (mechanical), stability, LEGGED LOCOMOTION, MODEL, DYNAMICS, WALKING, PLANAR, ROBOTS, ENERGETICS, BODY, GAIT
  • Middle East Technical University Affiliated: Yes

Abstract

In this paper, we analyze the self-stability properties of planar running with a dissipative spring-mass model driven by torque actuation at the hip. We first show that a two-dimensional, approximate analytic return map for uncontrolled locomotion with this system under a fixed touchdown leg angle policy and an open-loop ramp torque profile exhibits only marginal self-stability that does not always persist for the exact system. We then propose a per-stride feedback strategy for the hip torque that explicitly compensates for damping losses, reducing the return map to a single dimension and substantially improving the robust stability of fixed points. Subsequent presentation of simulation evidence establishes that the predictions of this approximate model are consistent with the behavior of the exact plant model. We illustrate the relevance and utility of our model both through the qualitative correspondence of its predictions to biological data as well as its use in the design of a task-level running controller. (c) 2010 American Institute of Physics. [doi: 10.1063/1.3486803]