| Volume 27 Issue 11-12 - Publication Date: 1 November 2008 |
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| Motion Planning for Legged Robots on Varied Terrain |
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| Kris Hauser
Department of Computer Science
Stanford University
Stanford, CA 94305-5447, USA,
Timothy Bretl
University of Illinois at Urbana-Champaign,
Urbana, IL 61801-2935, USA,
Jean-Claude Latombe
Department of Computer Science
Stanford University
Stanford, CA 94305-5447, USA,
Kensuke Harada
Humanoid Research Group
Intelligent Systems Research Institute
National Institute of Advanced Industrial Science and Technology
(AIST)
Tsukuba, Ibaraki 305-8568, Japan,
and Brian Wilcox
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109 |
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| In the classical image-based visual servoing framework, error signals
are directly computed from image feature parameters, allowing, in
principle, control schemes to be obtained that need neither a complete
three-dimensional (3D) model of the scene nor a perfect camera calibration.
However, when the computation of control signals involves
the interaction matrix, the current value of some 3D parameters is required
for each considered feature, and typically a rough approximation
of this value is used. With reference to the case of a point feature,
for which the relevant 3D parameter is the depth Z, we propose a visual
servoing approach where Z is observed and made available for
servoing. This is achieved by interpreting depth as an unmeasurable
state with known dynamics, and by building a non-linear observer
that asymptotically recovers the actual value of Z for the selected
feature. A byproduct of our analysis is the rigorous characterization
of camera motions that actually allow such observation. Moreover, in
the case of a partially uncalibrated camera, it is possible to exploit
complementary camera motions in order to preliminarily estimate the
focal length without knowing Z. Simulations and experimental results
are presented for a mobile robot with an on-board camera in order
to illustrate the benefits of integrating the depth observation within
classical visual servoing schemes. |
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| Multimedia Key |
= Video |
 = Data |
= Code |
= Image |
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Extension |
Type |
Description |
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1 |
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Example
1: HRP-2 taking a single step to place a foot |
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2 |
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Example
2: HRP-2 taking a single step to remove a foot |
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3 |
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Example
3: ATHLETE walking with an alternating tripod gait on smooth terrain (feasible). |
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4 |
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Example
4: ATHLETE walking with an alternating tripod gait on uneven terrain (infeasible). When the chassis is green, the configuration is feasible. When the chassis changes color, one or more constraints have been violated. |
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5 |
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Example
5: ATHLETE walking with no fixed
gait on smooth terrain. |
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6 |
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Example
6: ATHLETE walking with no fixed
gait on uneven terrain. |
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7 |
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Example
7: ATHLETE rappelling down an irregular
60° slope with no fixed gait on
smooth terrain. |
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8 |
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Example
8: HRP-2 on slightly uneven terrain
(planar walking primitive). |
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9 |
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Example
9: HRP-2 climbing a ladder with uneven
rungs (ladder-climbing primitive). |
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10 |
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Example
10: HRP-2 traversing large boulders
(side-step primitive). |
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11 |
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Example
11: HRP-2 on steep and uneven terrain
(multiple primitives). |
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