12 May 2020 at 16:42 #16170
Hi there, I am trying to model a series of springs with dampers, where each spring is connected by a spherical joint in a daisy-chain configuration. These spherical joints also require angular springs and and dampers. I have experimented with both the JointSpringforcefield, and have tried articulations with angular springs also, however I am uncertain if there is a more effective way of modelling this.
Any advice would be greatly appreciated!
Thank you.15 May 2020 at 10:15 #16255
Hi @eddhoare !
This part of SOFA is a bit rusty indeed. JointSpringForcefield are a bit cumbersome to describe. You also have the AngularSpringForcefield.
But you are using the right components.
What are you modeling exactly?
Hugo15 May 2020 at 12:37 #16260
Thanks for the response!
I am looking at making two models, first a series of rigid links connected by rotational joints, (figure 4 of this link https://www.spiedigitallibrary.org/journals/journal-of-medical-imaging/volume-5/issue-01/010902/Navigation-of-guidewires-and-catheters-in-the-body-during-intervention/10.1117/1.JMI.5.1.010902.full)
For this I have used articulated system mapping along with angular stiffness and feel that I have made progress.
My confusion is with the second model, it is very similar to the first model, however each joint has a linear spring between it also as shown here. https://www.researchgate.net/figure/Mass-spring-model-of-the-catheter_fig3_261735316
My problem with the articulated system mapping is that the articulation points for each rigid body appear to be fixed relative to one another.
Any advice on this would be greatly appreciated, as I have spent a fair while trying to make it work!
Thank you.15 May 2020 at 21:28 #16295
Hi @eddhoare !
To model catheter or endoscope, why not choosing a approach based on the beam theory?
You can directly get inspired from the example scene : examples/Components/forcefield/BeamFEMForcefield.scn
Hugo16 May 2020 at 14:54 #16300
I understand, as this was something I originally looked into. My issue is that one of the requirements of my models is that it must execute in real-time. I will be modelling from the femoral artery all the way up to the aortic arch,and have been told in a different thread that FEM would unlikely handle real-time execution with the additional load.
For this reason I am initially developing two analytical models (mass-spring & rigid multibody); then perhaps if I’m successful with that I may consider a hybrid model between FEM and analytical.
Thank you!23 May 2020 at 22:43 #16345
For your information, the following work was performed with FEM:
Hugo24 May 2020 at 00:24 #16347
Thank you I really appreciate it!
Did you have any luck regarding modelling the daisy chained springs previously mentioned?
Thank you for your help!
Kind regards, Edward31 May 2020 at 18:59 #16466
Sorry for my delayed reply, weeks are busy.
You are right, the articulated system mapping is made up of articulation points for each rigid body appear, defined relatively one to another. No spring is defined (thus no deformation is possible). It is useful to describe robotic/cinematic structures, not deformable bodies.
In case you want a deformable chain, you must go for stiff springs and angular springs (and dampers): JointSpringForcefield, AngularSpringForcefield. I think you should go for this second option regarding your definition, even if for catheter modeling I still recomand to use a Beam approach, compatible with real-time constraints.
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