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Bug in SpatialInertia shift() method, and composite body inertias #334

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sherm1 opened this issue Feb 6, 2015 · 1 comment
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Bug in SpatialInertia shift() method, and composite body inertias #334

sherm1 opened this issue Feb 6, 2015 · 1 comment
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Simbody 4.0

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sherm1 commented Feb 6, 2015

The SpatialInertia::shift() method does not work correctly for a SpatialInertia with a non-zero COM offset. This method is used in calcCompositeBodyInertias() and related methods so those are also wrong. Neither of these is commonly used.

The problem was reported for Simbody 3.5.1 by Gordon Deane in this forum post.

There was a regression test for this but it had a zero COM offset so didn't detect the bug; that should be changed.
@sherm1 sherm1 added the bug label Feb 6, 2015
@sherm1 sherm1 self-assigned this Feb 6, 2015
@sherm1 sherm1 added this to the Simbody 4.0 milestone Feb 6, 2015
sherm1 added a commit that referenced this issue Feb 6, 2015
@sherm1
Fixed bug in SpatialInertia::shift() method (see issue #334). This al…
934cbc7 
…so broke composite body inertias.

Added a regression test for SpatialInertia.
Improved composite body inertia regression to use non-zero COM offset.
Added comments clarifying that the ArticulatedInertia::shift() method actually shifts by the *negative* of the given vector.
@sherm1 sherm1 mentioned this issue Feb 6, 2015
Merged
sherm1 added a commit that referenced this issue Feb 6, 2015
@sherm1
Fixed bug in SpatialInertia::shift() method (see issue #334). This al…
88d37b8 
…so broke composite body inertias.

Added a regression test for SpatialInertia.
Improved composite body inertia regression to use non-zero COM offset.
Added comments clarifying that the ArticulatedInertia::shift() method actually shifts by the *negative* of the given vector.

(cherry picked from commit 934cbc7)
@sherm1 sherm1 mentioned this issue Feb 6, 2015
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sherm1 commented Feb 6, 2015

Fixed in Simbody 3.6 and 4.0.

@sherm1 sherm1 closed this as completed Feb 6, 2015
sherm1 added a commit that referenced this issue Jun 14, 2015
@sherm1
Fixed bug in SpatialInertia::shift() method (see issue #334). This al…
c1fcca8 
…so broke composite body inertias.

Added a regression test for SpatialInertia.
Improved composite body inertia regression to use non-zero COM offset.
Added comments clarifying that the ArticulatedInertia::shift() method actually shifts by the *negative* of the given vector.

(cherry picked from commit 934cbc7)
@sherm1 sherm1 mentioned this issue Jun 14, 2015
Merged
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