Kangaroo2 goals - Modelling Active-bending Structures with minimal surface

Hello Daniel,

I am trying to model an active bending structure constituted of a flexible edge beam bearing a tension membrane. The concept is similar to the structure in the following picture, but I am aiming at modelling a much simpler edge beam shape.

I tried to use Kangaroo2 goals to minimize the edges of the mesh representing the membrane, while keeping the length of the edge beam constant, and a zero angle between to successive parts of the edge beam.

Unfortunately, the algorithm fails to converge... Even though it oscillates around the correct shape.

I was hoping you could help me find to solve this problem?

Please find my Rhino and Grasshopper files attached.

Attachments:

Form_active_structure.3dm, 28 KB
Form_active_structure.gh, 19 KB

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Permalink Reply by Anders Holden Deleuran on February 9, 2017 at 1:00am

Here's a minimal working example of the pringle from way back when we went from K1 to Joey/K2, seems to still work, so might help you troubleshoot..

Edit: I recently uploaded two slideshows (Design Modelling Symposium and TensiNet) from some presentations we did using Kangaroo2 to model form-active hybrids. Might be useful as well. There's a lot of modelling videos in both, hence the file sizes.

Permalink Reply by Anders Holden Deleuran on February 9, 2017 at 1:04am

...and the GH file, doh! You'll probably want to update all the components to the latest versions BTW, noticed it's using the old solver.

Attachments:

150503_BATM_Kangaroo2_03.gh, 26 KB

Permalink Reply by Lucas Grisoni on February 9, 2017 at 1:19am

Thank you very much!

I will dig into that right away.

PS : Actually I recently watch this lecture of yours (https://vimeo.com/149290722), which fascinated me, and gave me the motivation for studying those structures during my current research project. So one more time : thank you very much!

Permalink Reply by Anders Holden Deleuran on February 9, 2017 at 1:43am

No worries, glad to hear it. Hope it helps (despite the awkward video!)

Permalink Reply by Daniel Piker on February 9, 2017 at 3:39am

Hi Lucas,

I think Anders has done more than anyone on using Kangaroo for this sort of thing, and I'd recommend trying his tools, which really ease the process of creating the topology.

In your definition above, the instability is being caused by the high bending strength. For an elastic rod, the strength of the length goals acting on the segments of the rod should always be much higher (eg. a ratio of at least 10:1) than that of the angle goals between consecutive segments (since the theoretical model it is based on is only valid for slender rods, where this will always be the case).

To then make the rod straighten out more, try reducing the strength of the interior mesh tension instead of upping the angle strength.

Also - since Kangaroo 2.0 there is no need to use the timer component - the solver does that automatically when it is on.

Permalink Reply by Lucas Grisoni on February 9, 2017 at 6:22pm

I have made the corrections and it works perfectly, thank you very much!

Waiting your next videos!

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