February 15, 2015 / by George Council / In news

Rigorous Enclosures of a Slow Manifold

Slow-fast dynamical systems have two time scales and an explicit parameter representing the ratio of these time scales. Locally invariant slow manifolds along which motion occurs on the slow time scale are a prominent feature of slow-fast systems. This paper introduces a rigorous numerical method to compute enclosures of the slow manifold of a slow-fast system with one fast and two slow variables.

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February 15, 2015 / by George Council / In news

Bifurcation and chaos in the simple passive dynamic walking model with upper body

We present some rich new complex gaits in the simple walking model with upper body by Wisse et al. We first show that the stable gait found by Wisse et al. may become chaotic via period-doubling bifurcations.

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February 05, 2015 / by George Council / In news

The roller coaster flight strategy of bar-headed geese conserves energy during Himalayan migrations

A paper that explores the flight pattersn of migrating geese over the Himalayan Mountains. Beyond presenting a measured result that disputes prior hypothesis, it also illustrates that geese are demonstrating a behavior that is very 'non-engineer-like' - humans would never build a passanger aircraft that varies altitude so dramatically

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February 05, 2015 / by George Council / In news

Stabilization of Nonlinear Systems Nonlinearly Depending on Fast Time-Varying Parameters- An Immersion and Invariance Approach

A paper that might be interesting to compare to the lab's own investigation in how to detail with parameter uncertainty in hybrid systems. Mitigating the influence of unknown parameter changes in a system is a major concern in locomotion, and being able to extend this papers result to a hybrid system could provide a new tool

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February 05, 2015 / by George Council / In news

Preparing the leg for ground contact in running - the contribution of feed-forward and visual feedback

A paper, among many, that explores the usage of feedforward control in perserving periodic gaits in SLIP-like models. As the lab has contributed to this discussion in a very general way, it is useful to examine other groups' special-case result to see if our result encompasses it, or it is an novel technique. Interestingly, this paper consists of experiemental measurements of acutal muscle activity in moving humans - suggesting that feedforward muscle activity is sufficient to explain previously observed feed-forward leg adjustments.

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