(3MB)
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An elastic strip for a mobile manipulator with nine
degrees of freedom. It can be seen how the trajectory
is modified in real time as two obstacles (mobile
robots) render the original path infeasible. The
white lines indicate the lines swept by points on the
robot along the trajectory. The red line indicates
the desired task: in this case for the end-effector to
follow a straight-line trajectory. Notice how pure
obstacle avoidance interferes with task execution.
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(3MB)
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Path modification in the elastic strip framework can
be performed in a task-consistent manner,
such that obstacle avoidance and task execution can be
performed simultaneously.
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(3MB)
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It is possible that task execution and obstacle
avoidance conflict and cannot be performed
simultaneously. This occurs, for example, if the
manipulator reaches the boundary of its work space.
This situation can be recognized during path
modification. To address this problem task execution
can be automatically suspended and resumed. This can
be seen as the robot circumnavigates the second mobile
robot.
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(10MB)
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This video contains experiments on the real robot
demonstrating task-consistent, real-time path
modification.
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(1MB)
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Redundant degrees of freedom can be used to combine
task behavior and obstacle avoidance. Redundancy can
also be exploited to impose additional behavior during
the execution of a motion. One example of such
behavior is the maintenance of balance for a humanoid
robot. This video demonstrates how the robot would
avoid obstacles, if balance constraints were not taken
into account.
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(1MB)
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Using the elastic strip framework it is very easy to
integrate various behaviors into a global, real-time
motion generation scheme. Here, in addition to
obstacle avoidance, the posture of the humanoid figure
is controlled to maintain balance. The motion of the
robot is computed in real-time to avoid the beam,
while at the same time maintaining a physically
feasible posture.
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(3MB)
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The elastic strip framework allows to generate motion
in dynamic environments by performing incremental path
modification. Changes in the environment might cause
the result of that modification to be suboptimal. An
improvement of the modified path might require a
global search. There are a number of situations,
however, in which an improved, but topologically
distinct path can be found using only local
methods. Intuitively, this is accomplished by
obstacles "popping through" the elastic strip.
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(5MB)
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An application of the elastic strip framework to
character animation. Note how all degrees of freedom
are moving in reaction to the environment: the overall
trajectory is modified to avoid the evil snowman and
the poles are tucked in to pass through the gate; at
the same time a feasible posture is being maintained.
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(6MB)
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An earlier version of the posture experiment for
humanoid robots.
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(6MB)
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An earlier version of the posture experiment for
humanoid figures.
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(23MB)
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This is the video presented at ICRA 2002. It consists
of several of the clips above and contains narration.
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