| Volume 25 Issue 9 - Publication Date: 1 September 2006 |
| Special Issue on CLAWAR 2004 |
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| Decentralized Control of Elastic
Limbs in Closed Kinematic Chains |
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| A. Schneider, H. Cruse,
and J. Schmitz Dept. of Biological Cybernetics, Faculty of Biology,
University of Bielefeld, PO Box 10 01 31, 33501, Bielefeld, Germany |
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| The generation of movements
in closed kinematic chains as opposed to open kinematic chains is a challenging
task because all participating joints have to be moved in a highly coordinated
manner in order to avoid destructive tensions in the limb. In this paper
we present a new decentral joint controller which uses low level interactions
between a moving joint and its environment consisting of neighboring joints,
the body and the surroundings the agent is placed in. This local joint controller
is based on a Local Positive Velocity Feedback (LPVF) mechanism which exploits
the elastic properties of the joint. The control strategy is inspired by
biological findings in the walking system of stick insects. We will show
that a closed kinematic chain consisting of several LPVF controlled joints,
though lacking a central controller, can solve tasks which need a high level
of inter-joint coordination. As an example, a planar manipulator turning
a crank is presented. In a further step, the LPVF algorithm is extended
to switched LPVF in order to improve the mechanical power conversion. The
extended capabilities are proven in a second experiment in which a 3DoF
test leg generates powerful stance movements. |
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| Multimedia Key |
= Video |
 = Data |
= Code |
= Image |
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Extension |
Type |
Description |
| 1 |
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Example
1: A real planar manipulator equipped with LPVF controllers turns
a crank. (4.1 MB) |
| 2 |
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Example
2: A single leg with LPVF controllers walks on a treadmill (front
view). (4.8 MB) |
| 3 |
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Example
3: A single leg with LPVF controllers walks on a treadmill (side
view). (6.0 MB) |
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