Running and walking with compliant legs

Abstract

It has long been the dream to build robots which could walk and run with
ease. To date, the stance phase of walking robots has been characterized by
the use of either straight, rigid legs, as is the case of passive walkers, or by the
use of articulated, kinematically-driven legs. In contrast, the design of most
hopping or running robots is based on compliant legs which exhibit quite
natural behavior during locomotion.

Here we ask to what extent spring-like leg behavior could be useful in
unifying locomotion models for walking and running. In so doing, we combine
biomechanical experimental and computer simulation approaches with
theoretical considerations and simple legged robots.

We have found that (1) walking and running result from mechanical stability
which corresponds to the experimentally observed gait dynamics, (2)
running is a subset of stable movement patterns for high system energies,
and (3) walking with knee flexion during stance can result from passive leg
mechanics with elastic structures spanning the joints.