About these movies:
These movies, taken in March 2003, are of the biped prototype called
RABBIT
located at the LAG in
Grenoble, France. This robot is part of the French project Commande
de Robots à Pattes of the CNRS - GdR Automatique. These
movies demonstrate the utility of the theoretical framework developed
in the thesis. In these videos, the "training wheels" attached to the
boom in no way support RABBIT's weight. The prismatic post of the
training wheels simply prevents the RABBIT's hips from dropping too
low (RABBIT falling to the ground) in the event of an experimental
mishap.
Walking at 0.7 m/s:
Description: In this first experiment, RABBIT was controlled
with a feedback designed to induce walking at 0.7 m/s. The experiment
lasted approximately 93 seconds during which RABBIT took 170 steps
making six laps about the center stand.
Demonstration of robustness to perturbations:
Description: This second experiment demonstrates the robustness
of controllers designed via the theoretical framework. Two types of
perturbations were applied to RABBIT controlled by a feedback designed
to induce walking at 0.9 m/s. The first was a 10 kg mass added to the
torso (the black plate shown in the videos), which resulted in a shift
of the average walking rate from 0.9 m/s to 1.0 m/s. In addition to
the sizable perturbation to the robot's model (RABBIT weighs 32 kg),
the second perturbation was short duration forces applied to the
RABBIT's torso by an experimenter in both the forward and reverse
directions. Despite both these significant perturbations, RABBIT did
not fall during the experiment which lasted approximately 74 seconds
where RABBIT took 164 steps.
Transitioning between controllers:
Description: This third experiment demonstrates the use of
transition controllers for the composition of controllers that induce
walking at a fixed rate. For the experiment, the controller applied
to RABBIT was transitioned between controllers at 0.1 m/s intervals
from 0.5 m/s to 0.8 m/s and then back from 0.8 m/s to 0.5 m/s twice.
The experiment lasted approximately 86 seconds during which RABBIT
took 139 steps.
Using event-based integral control to modify the fixed
point:
Description: In this fourth experiment, the same feedback used
in the first experiment to induce walking at 0.7 m/s was applied with
the addition of an event-based PI control used to modify the steady
state average walking rate from 0.7 m/s to 0.6 m/s. The event-based
control acts through step-to-step modifications of the Bézier
polynomial coefficients synchronized with double support. The
experiment lasted approximately 110 seconds during which RABBIT took
181 steps.
Using event-based integral control to reject a
perturbation:
Description: In this fifth experiment, the same feedback used
in the first experiment to induce walking at 0.7 m/s was applied but
with a 10 kg mass attached to the torso. This perturbation resulted
in a shift of the average walking rate from 0.7 m/s to approximately
0.85 m/s (the change in average walking rate was determined in a
separate experiment not reported in the dissertation). The average
walking rate of 0.7 m/s was recovered using the same event-based
integral control used for the previous experiment applied on the 14th
step (at approximately 11 seconds). The experiment lasted
approximately 95 seconds during which RABBIT took 164 steps.
Using event-based integral control to stop the robot:
Description: In this sixth experiment, event-based integral
control was used to stop RABBIT from steady state average walking rate
of 0.5 m/s. This was achieved by slowing the average walking rate of
RABBIT to where it did not have enough energy to successfully complete
a step. The integral control used in the previous two experiments
with a desired average walking rate of 0 was applied on the 34th step
(at approximately 29 seconds) and RABBIT was stopped by the 39th step
(at approximately 34 seconds). After stopping, RABBIT rocked back and
forth until all kinetic energy from walking was dissipated.
RABBIT's joint friction:
Description: This video demonstrates RABBIT's large amount of
joint friction and inertia due to its motors and gear reducers. These
additional dynamics kill all internal passive motions of RABBIT.
Walking without the "training wheels":
Description: This experiment is to show that the "training
wheels" that are normally attached to RABBIT's boom to provide a
measure of safety (see the next experiment) do not support in any way
RABBIT's weight.
RABBIT falling:
Description: In this experiment RABBIT's controller
accidentally stopped causing RABBIT to fall. The experiment
illustrates that 1) without feedback control RABBIT's joint friction
quickly dampens out any motions and that 2) the "training wheels"
attached to RABBIT's boom prevent RABBIT from falling to the
ground.
Pushing RABBIT backward:
Description: This experiment demonstrates that under the
feedback control developed in this work RABBIT may be pushed backward
making interactions with the robot safer and more intuitive than other
proposed control schemes.
Unwinding RABBIT's cables:
Description: This video demonstrates how RABBIT's cabling was
unwound from the center stand after each experiment. The cabling
supplies power and communications (in the form of an Ethernet cable)
to the dSPACE system and power electronics located atop the center
stand.
TV interview:
Description: Carlos Canudas-de-Wit and Eric Westervelt were
interviewed by French Channel 3 at the conclusion of the research
experiment where the above videos were taken, French Channel
3, 6:55 p.m., March 14, 2003 (MPEG-4, 13Mb).
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