Elastic Coupling Of Limb Joints Enables Faster Bipedal Walking

October 22, 2008

The passive dynamics of bipedal limbs alone are sufficient to produce

a walking motion, without need for control. Humans augment these

dynamics with muscles, actively coordinated to produce stable and

economical walking.

Present robots utilizing passive dynamics walk much slower, perhaps

because they lack elastic muscles that couple the joints. Elastic

properties are well-known to enhance running gaits, but their effect

on walking has yet to be explored.

Here we use a computational model of dynamic walking to show that

elastic joint coupling can help coordinate faster walking. In walking

powered by trailing leg push-off, the model's speed is normally

limited by a swing leg that moves too slowly to avoid stumbling. A

uni-articular spring about the knee allows for faster but

uneconomical walking.

A combination of uni-articular hip and knee springs can speed the

legs for improved speed and economy, but not without the swing foot

scuffing the ground. Bi-articular springs coupling the hips and knees

can yield high economy and good ground clearance similar to humans.

An important parameter is the knee-to-hip moment arm, which greatly

affects the existence and stability of gaits, and when selected

appropriately can allow for a wide range of speeds. Elastic joint

coupling may contribute to the economy and stability of human gait.

Journal of the Royal Society Interface

Journal of the Royal Society Interface is the Society's cross-

disciplinary publication promoting research at the interface between

the physical and life sciences. It offers rapidity, visibility and

high-quality peer review and is ranked fifth in JCR's

multidisciplinary category. The journal also incorporates Interface

Focus, a peer-reviewed, themed supplement, each issue of which

concentrates on a specific cross-disciplinary subject.

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