[SOLVED] A question on applying surface pressure on body

Dear all,

I’d like to simulate a pneumatic actuator with applying surface pressure on cavity surface. My plan is to do the simulation in SOFA, and use the same material and boundary conditions in Abaqus for validation to convience others SOFA is a reliable tool for this kind of simulation. Here is the demonstration model I built.

https://www.dropbox.com/s/7nr8kj5p80cba48/grasp_pressure_validation.tar.gz?dl=0

The unit system I use is:
tonne, m, s -> MPa, N

Question 1

Please allow me to explain the problem in detail. I understand this function is included in the SoftRobot plugin, and actually this model borrowed many ideas from the SoftRobot plugin tutorial. However, as this plugin is no longer included in the release version, I would like to try some other ways to implement it. Here is how the implementation goes:
1) Use a separate node “cavity” to represent the surface where pressure is applied
2) Apply pressure using “SurfacePressureForceField” on the cavity surface
3) Use BarycentricMapping to map the force between “cavity” and “finger”.

My question is: Is this a valid (correct) method to apply this kind of pressure? Will the mismatch of meshes cause significant errors in the simulation results? I understand the best way is to identity the boundary triangles by indices. However, for a very complex internal cavity, this is almost impossible. Is there a better way to do this?

After running the simulation for this model, we can see clearly that the 2nd and 4th gap of this actuator did not open enough, maybe because not enough pressure applied?

Alternatively, is there a more practical way to extract the indices of desired cavity surface number? So I don’t need to do the mapping, which could introduce huge error.

I’ve careflly read through related topic as: https://www.sofa-framework.org/community/forum/topic/pneumatic-actuator-using-surfacepressureconstraint/, but it seems the problem is a bit different as what I met here.

Question 2
If you look into the controller python script, you may find I commented line 23. This line is intended to apply moving on the finger by change the rest position with a prescribed velocity. However, this method ONLY works with release version:
1) “SOFA_v19.06.99_custom_Linux_v5.1” (I remember this is the version from SoftRobot plugin developer group, if I’m not wrong. This version contains the SoftRobot plugin)

While for other versions I’ve tested as:
1) v19.06.01
2) v19.12.00
3) Compiled latest master branch

All these versions can not correctly apply pressure on the surface when the finger is moving. If I did not move the finger, then everthing is fine. If this is an implementation problem, is there any way for me to apply pressure while moving the finger?

Sorry for this long question. I’ve carefully read through related topic as: https://www.sofa-framework.org/community/forum/topic/pneumatic-actuator-using-surfacepressureconstraint/, but it seems the problem is a bit different as what I met here.

Thank a lot.