[SOLVED] Forces on bending pneunet

[twxu]

I have a SOFA scene with a single pneunet actuator. It is oriented horizontally, with the base fixed in place (gravity is off), and it bends downward as its cavity is pressurized. (Near identical to the pneunet example from the SoftRobots plugin.)

I’ve added a Monitor object to export the force data on certain nodes on the underside of the pneunet. What I’ve observed is: as the pressure increases in the pneunet and it bends, these forces increase. When the maximum pressure is reached and pressure stops increasing (maintains the max pressure), the forces decrease to a steady, non-zero value (pneunet stops bending further and holds its shape).

(Unsure how to post images here, but the shape is the same as a static/dynamic friction graph: force increases over time, reaches a maximum, then drops to a steady value)

My question is:
After maximum pressure is reached and held, and the pneunet maintains its shape without bending further, why don’t the forces drop to zero? I would expect that after the pneunet stops moving and inertial effects are gone, the forces would gradually decrease back to zero instead of maintaining steady values.

(Also, any resources on how exactly the Monitor object calculates forces would be greatly appreciated)

Thanks!

[antonio.8196]

Hi, I’m really new with SOFA and i need to install the SoftRobots plugin and i’m kind of lost, how did you do it? Did you just downloaded the binaries files? I’m sorry for not being able to help you but maybe if you helped me i could be more into the software and help you later.

[Hugo]

Dear @twxu I think I replied to you in the other thread where you had the similar question.

Dear @antonio-8196 you can either:
– download the binaries of SOFA+SoftRobot– or download+compile SOFA and then download+compile SoftRobot.

Hugo

[antonio.8196]

Hi @Hugo, so i just downloaded the binares of SOFA+SoftRobot but this error appears

[ERROR]   [PluginManager] Plugin loading failed (/home/einklugerjaeger/SOFA/lib/libSofaPython.so): libpython2.7.so.1.0: cannot open shared object file: No such file or directory
[ERROR]   [PluginManager] Plugin loading failed (/home/einklugerjaeger/SOFA/plugins/STLIB/lib/libSTLIB.so): libpython2.7.so.1.0: cannot open shared object file: No such file or directory
[ERROR]   [PluginManager] Plugin loading failed (/home/einklugerjaeger/SOFA/plugins/SoftRobots/lib/libSoftRobots.so): libpython2.7.so.1.0: cannot open shared object file: No such file or directory
[ERROR]   [PluginManager] Plugin loading failed (/home/einklugerjaeger/SOFA/plugins/SoftRobots.Inverse/lib/libSoftRobots.Inverse.so): libSoftRobots.so: cannot open shared object file: No such file or directory
[ERROR]   [PluginManager] Plugin loading failed (/home/einklugerjaeger/SOFA/plugins
/ModelOrderReduction/lib/libModelOrderReduction.so): libpython2.7.so.1.0: cannot open shared object file: No such file or directory

I have already installed python2.7 and numpy in my Xubuntu 20.04, what would be the problem?

[Hugo]

Dear @twxu,

Strange, are you sure of having python2.7 ?
Could you try to load manually the SofaPython plugin from the PluginManager (Edit->PluginManager) ?

best,

Hugo

[antonio.8196]

Hey @Hugo, i’m sorry, this is not my thread so i will start responding you from here .

[Hugo]

I close this topic since two other topics where open:
here
and here.

Hugo

[Author]

Posts