Stability and control of planar compass gait walking with series-elastic ankle actuation

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2017-03-01

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KERIMOGLU, Deniz
MORGUL, Omer
Saranlı, Uluç

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Passive dynamic walking models are capable of capturing basic properties of walking behaviours and can generate stable human-like walking without any actuation on inclined surfaces. The passive compass gait model is among the simplest of such models, consisting of a planar point mass and two stick legs. A number of different actuation methods have been proposed both for this model and its more complex extensions to eliminate the need for a sloped ground, balancing collision losses using gravitational potential energy. In this study, we introduce and investigate an extended model with series-elastic actuation at the ankle towards a similar goal, realizing stable walking on level ground. Our model seeks to capture the basic structure of how humans utilize toe push-off prior to leg liftoff, and is intended to eventually be used for controlling the ankle joint in a lower-body robotic orthosis. We derive hybrid equations of motion for this model, and show numerically through Poincare analysis that it can achieve asymptotically stable walking on level ground for certain choices of system parameters. We then study the bifurcation regimes of period doubling with this model, leading up to chaotic walking patterns. Finally, we show that feedback control on the initial extension of the series ankle spring can be used to improve and extend system stability.

Subject Keywords

Dynamic walking, Passive compass gait, Series-elastic actuation, Ankle actuation, Bifurcation analysis, Feedback control

URI

https://hdl.handle.net/11511/38603

Journal

TRANSACTIONS OF THE INSTITUTE OF MEASUREMENT AND CONTROL

DOI

https://doi.org/10.1177/0142331216663823

Collections

Department of Computer Engineering, Article

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Citation Formats

D. KERIMOGLU, O. MORGUL, and U. Saranlı, “Stability and control of planar compass gait walking with series-elastic ankle actuation,” TRANSACTIONS OF THE INSTITUTE OF MEASUREMENT AND CONTROL, pp. 312–323, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/38603.