Centre for Robotics Research (CoRE)

This paper proposes a novel approach to improve
walking in prosthetics, orthotics and robotics without closed
loop controllers. The approach requires impedance profiles to
be formed in a walker and uses state feedback to update
the profiles in real-time via a simple policy. This approach
is open loop and inherently copes with the challenge of
uncertain environment. In application it could be used either
online for a walker to adjust its impedance profiles in realtime
to compensate for environmental changes, or offline to
learn suitable profiles for specific environments. So far we
have conducted simulations and experiments to investigate the
transient and steady state gaits obtained using two simple
update policies to form damping profiles in a passive dynamic
walker known as the rimless wheel (RW). The damping profiles
are formed in the motor that moves the RW vertically along a
rail, analogous to a knee joint, and the two update equations
were designed to a) control the angular velocity profile and
b) minimise peak collision forces. Simulation results show that
the velocity update equation works within limits and can cope
with varying ground conditions. Experiment results show the
angular velocity average reaching the target as well as the peak
force update equation reducing peak collision forces in realtime.