CODEWITHSUNDEEP
simulationmodelicaopenmodelicafluid-dynamics
Matthias Mayr
Matthias Mayr

Reputation: 11

How to model mechanical stops to hydraulic cylinders in Modelica?

I was wondering how a mechanical stop can be modeled most efficiently.

I do a hydraulic simulation with a controlled hydraulic cylinder in OpenModelica. For the hydraulic cylinder I use the sweptVolume model from the Modelica Standard Library.
What bugs me about this model is that there is no mechanical stop if the piston reaches the bottom of the cylinder.

I tried several ideas with no good result. I tried to reset the displacement of the piston to zero, if it hits the bottom, via an if-expression. But this is not really a good option due to the fact that the volume is calculated using the piston's displacement.

I then tried to introduce a force that equals the force applied to the piston, if the piston hits the stop. This option didn't work either, because in this case the pressure inside the cylinder can not be calculated.

The third try was to use the MSL model of MassWithStopAndFriction linked to the translational flange of the sweptVolume model, but this model seems to be broken for me.

Now I count on you as a competent community to bring in some more ideas for me to test.

Upvotes: 1

Views: 762

Answers (1)

edren
edren

Reputation: 11

Depending on your application, you may deploy the Hydraulics library? The library aims to model (compressible) fluid power systems and contains cylinders with end-stops. Its scope is different than the Fluid package you are using. Using when and/or if statements for this task, I'd strongly discourage from experience. You may get one cylinder to work, but using that in a larger system will definitely get you into numerical problems. Have a look at the Mechanics package and analyse if the ElastoGap can be of any use to you.

Upvotes: 1

Related Questions