Rotational spring / damping

[n doherty]

Hi,

I'm trying to set up a pydy solution for ship roll damping.  This problem is essentially a mass spring damper problem but rotating rather than translating.

What I've tried to do is set it up as a rigid body with an inertia dyadic (learned from the human standing tutorial).

I'm coming unstuck trying to apply a righting moment (spring) and a damping moment.  Is there an equivalent in rotational terms to calculate the righting moment as a function of angle as the 'Point.pos_from()' function that can be used to calculate a linear spring force?

Thanks,

Nick

[Jason Moore]

 Nick,

You can determine the orientation between two reference frames with the .dcm() method. If you constructed it as a simple rotation, you can use the specific angle dynamic symbol that you used in the construction.

Jason

moorepants.info
+01 530-601-9791

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[n doherty]

Thanks a lot Jason much appreciated

On Wednesday, 13 September 2017 16:30:26 UTC+1, moorepants wrote:

 Nick,

You can determine the orientation between two reference frames with the .dcm() method. If you constructed it as a simple rotation, you can use the specific angle dynamic symbol that you used in the construction.

Jason

moorepants.info
+01 530-601-9791

On Wed, Sep 13, 2017 at 4:06 AM, n doherty <chis...@gmail.com> wrote:

Hi,

I'm trying to set up a pydy solution for ship roll damping.  This problem is essentially a mass spring damper problem but rotating rather than translating.

What I've tried to do is set it up as a rigid body with an inertia dyadic (learned from the human standing tutorial).

I'm coming unstuck trying to apply a righting moment (spring) and a damping moment.  Is there an equivalent in rotational terms to calculate the righting moment as a function of angle as the 'Point.pos_from()' function that can be used to calculate a linear spring force?

Thanks,

Nick

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