Kinectic arch design issues or kangaroo?

Goodday,

After trying out a single actuated tensegrity module,I tried working on a simple arch and designing a simple 2D arch with actuators in the middle, based on a design of the ORAMBRA.

Except i can't get it to work, and i wonder if i'm doing something wrong with kangaroo again or is the 2D design just to stable to move?

The desired effect is to see how and how much the arch will move under movement of the actuators. The arch is just a example which I can base further models on, but with the same end goal.

In de design of ORAMBRA the outer and inner lines are cables, do I adjust the stiffness ?
The actuators don't seem to move in the simulation, too stiff or tolerance to high in kangaroo ?
Do I add a extra downward force (gravity)?
...

Thanks in advance

If you have any question or if you need more info, just shoot.

Attachments:

KineticArchTest1.ghx, 454 KB

Replies to This Discussion

Permalink Reply by Carlor on March 20, 2011 at 4:53pm

And another question :

the stiffness of the springs, in what unit is it declared in kangaroo ?

And i presume kangaroo calculates the strain so the structure can move, so the stiffness has to be accurate, which i haven't done.

Permalink Reply by Amir Gazit on March 21, 2011 at 3:10am

Hi
I am not 100% sure about what you are trying to simulate but to be able to see the arch moving
I would suggest:
1. Flatten Force objects on Kangaroo engine input
2. Lower the springs rest length
3. Optional: Plug a Geometry component (Params-Geometry) to Kangaroo engine output “Geometry out” and disable preview of Kangaroo engine
Regards,
Amir

Permalink Reply by Carlor on March 21, 2011 at 5:35am

Adding a geometry object at the end of the geometry out end, does not seem to work.

I do get a runtime error:

1.Solution exception, the index is out of range. The index cannot be negative or bigger than collection.

Permalink Reply by Nick Cole on March 21, 2011 at 7:02pm

Fixed. I also added a force so that you can put some compression in the arch and see when it becomes unstable. Now you have an arch that can move the interesting question is what shape do you make it and how do you automate the actuatoors to get the arch into the right shape?

Attachments:

KineticArchTest2.ghx, 465 KB

Permalink Reply by Carlor on March 22, 2011 at 7:48am

Aha, thank you very much Nick,

however i can't seem to find my mistake, what have you adjusted, if i may ask?

Added Geom out
Added Geom in, but didn't flatten it ?
Added force on the upper points of the arch
?

And indeed the important question is the actuation, which is part of my dissertation at the university.

However the title of the dissertation is the simulation of these structure, so i would like to see my mistakes, so i can generalize to more structures.

Thanks in advance !

Permalink Reply by Nick Cole on March 28, 2011 at 3:49pm

Sorry for the slow reply. It was an insanely busy week last week.

- The main thing i did was flatten the Force Objects input.

- There was also a Crv box that was messing up the input for the diagonals. Don't know why, but it wasn't needed anyway.

- Then you generally have to play with the settings for stiffness, drag and timestep to tune it to your particular model. The user manual that Daniel has been writing has an explanation about how Kangaroo works and the effect of the various settings and forces.

Daniel it would be useful to have a link to your draft Kangaroo user manual on the front page of this group. Or could it go as a fixed discussion topic like Davids Galapagos explanation? Several questions have come up recently (and i'm sure many more that haven't been asked) about units and modelling real world behaviour. It would be useful to have something about this in the manual. Or did i just miss it in the first one?

Permalink Reply by Nick Cole on March 29, 2011 at 3:27pm

It would also be really interesting to understand the difference between the different solvers and the best ways to use each of them.

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