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Stepping for Balance Maintenance Including Push-Recovery

  • Jerry E. Pratt
  • Sylvain Bertrand
  • Twan Koolen
Reference work entry

Abstract

Taking steps is fundamental to walking since it is necessary for moving ground supports in the direction of travel. Without stepping, a legged system would not get very far. Beyond simply moving from A to B, stepping is critical for balance and disturbance recovery since it allows a legged system to quickly modify its base of support in order to shift the direction of forces on the center of mass. When humans are pushed, trip, or otherwise disturbed during walking, they will typically take a very fast step or two to recover balance. To be robust to disturbances, humanoid robots must likewise be able to fairly quickly and accurately step to an appropriate place.

This chapter will focus on where to step, how quickly, and how accurately, in order to maintain or regain balance. While focused on stepping, this analysis will also briefly include the center of pressure and angular momentum–based balance strategies, which can be combined with stepping. Analysis will show the relative merits of each strategy using a common metric. Simple models will be used to analyze stepping strategies and motivate control algorithms for balance recovery via stepping. The linear inverted pendulum model will provide a set of linear differential equations governing walking. This model leads to the instantaneous capture point. n-Step capturability will be used to analyze situations where multiple steps may be required to regain balance. More complex models will provide additional resolution, particularly when the center of mass height and vertical velocity fluctuates significantly.

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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  • Jerry E. Pratt
    • 1
  • Sylvain Bertrand
    • 1
  • Twan Koolen
    • 2
  1. 1.Institute for Human and Machine CognitionPensacolaUSA
  2. 2.Massachusetts Institute of TechnologyCambridgeUSA

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