Reactive balance control in walking based on a bipedal linear inverted pendulum model

Abstract

Dynamic balance depends on proper foot placement in legged locomotion and corresponding placement strategies have mainly been developed using the linear inverted
pendulum model as theoretical framework. While this model
can identify single leg strategies for balance control, it does
not consider the double support that is common to bipedal
locomotion, indicating that current strategies do not fully
exploit the theoretical potential of balance control in bipedal
systems. Here we extend the linear inverted pendulum model to
a bipedal system which includes double support dynamics, and
derive a reactive balance controller based on foot placement
and double stance length. We show that this controller enables
the model to stand and walk at user-defined target speeds,
to transition between these behaviors by acceleration and
deceleration, and to react to intermittent disturbances and
compensate for permanent ones, as long as they are compatible
with the swing leg dynamics placing the feet. Finally, we
discuss how the versatility of this balance controller depends on
including double support and suggest further steps to improve
dynamic balance control in bipedal systems.