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Better explain the TMT calculation for inertia forces#228

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moorepants merged 4 commits into
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tmt-other-inertia-forces
Apr 19, 2026
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Better explain the TMT calculation for inertia forces#228
moorepants merged 4 commits into
masterfrom
tmt-other-inertia-forces

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@moorepants moorepants commented Apr 17, 2026

Fixes #217

Shows more carefully how to calculate the inerital forces that are linear in the velocities (Coriolis, gyroscopic, centripital). It is worth noting that Euler's equation is:

dH/dt = Iw' + w x (Iw)

and is equivalent to:

dH/dt = I'w + Iw'

but when grouping linear and rotational equation in one single big matrix equation you can't write the cross product form because it only applies to a 3D vector. You can probably write this succintly with the Clifford Algebra based dynamics approaches.

It still seems that papers leave out the I'w term (but that might because they are only about 2D systems). This confused me several times.

Fixes #217

Shows more carefully how to calculate the inerital forces that are
linear in the velocities (Coriolis, gyroscopic, centripital). It is
worth noting that Euler's equation is:

dH/dt = Iw'' + w x (Iw)

and is equivalent to:

dH/dt = I'w + Iw'

but when grouping linear and rotational equation in one single big
matrix equation you can't write the cross product form because it only
applies to a 3D vector. You can probably write this succintly with the
Clifford Algebra based dynamics approaches.

It still seems that papers leave out the I'w term (but that might
because they are only about 2D systems). This confused me several times.
@moorepants
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@Peter230655 @phdejong you both may be interested in this. If either of you are willing to review my explanation and math on this one, that is appreciated.

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Comment thread tmt.rst Outdated
@moorepants moorepants merged commit 653fd85 into master Apr 19, 2026
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@moorepants moorepants deleted the tmt-other-inertia-forces branch April 20, 2026 08:32
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Update the TMT chapter to calculate the C in Mq'' + C(q') = F using the Jacobian of the constraints

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