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Modelica

modelica.org

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Re: Modelica

#71

Post by michaeltiller »

bobim wrote: post #59
michaeltiller wrote: post #45

Earlier quoted context omitted.

Over 20 years ago I modeled an internal combustion engine, an automatic transmission and a multibody chassis model all in a single model. IIRC, the model had something like 250,000 equations in it and it modeled combustion, hydraulics, friction, and 3D rigid body motion. It is capable of far more than simple models. https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&d...

Ah! You're the author of Modelica by example?

Yes. And "Introduction to Physical Modeling with Modelica". I also built the Modelica Playground (which I deliberately didn't link to because a thundering herd of HN readers would have crashed it).

Re: Modelica

#72

Post by michaeltiller »

jrowen wrote: post #60
Cthulhu_ wrote: post #4

Earlier quoted context omitted.

It apparently sells merchandising for their own brand though.

Downvoted but relevant...nothing says corporate bullshit like a niche programming language with logos and merch featured far more prominently than examples or explanation...

Just to be clear, there is absolutely nothing "corporate" about that web site. It is a non-profit organization.

Re: Modelica

#73

Post by michaeltiller »

anothertroll123 wrote: post #55
michaeltiller wrote: post #48

Earlier quoted context omitted.

OK, those are three quite different things. Modelica allows you to create models in a similar way to spice by describing components and how they are connected. But instead of a netlist of nodes, Modelica has a concept of connectors. But otherwise it is fairly similar. However, Modelica's scope is well beyond that of Spice or Verilog-A. Those languages claim that by analogy they can do other domains but you are mainly…

This is a fair description. I want to use Modelica but I can't get out of the Simulink ecosystem just yet. Do you know if there's a decent C autocoding solution like that of Simulink?

Well most Modelica tools generate C code. I think all of them also generate FMUs (lookup Functional Mockup Interface, if you don't know what an FMU is). Some FMUs are source code FMUs (suitable for running on HiL hardware, for example).

But it sounds like you might be talking about autocoding of an embedded controller. In that case, I'm not aware of any tools with that target. Part of this is because Modelica can be used to model the controls, the plant or both. But for autocoding you'd need a clear partitioning and some way of connecting the controls to a scheduler. But I don't know of a Modelica tool that supports this. My hope is that the next generation of tools will address this (that's part of my day job ;-)).

Re: Modelica

#74

Post by aetherspawn »

OpenModelica is teetering on the edge of something finally being good enough to replace Simulink without paying $20k+ per user per year.

It is, perhaps, only a few toolboxes away (Simulink Test, Simulink Coverage, Simulink Coder).

Re: Modelica

#75

Post by standeven »

michaeltiller wrote: post #45
bglazer wrote: post #7

Earlier quoted context omitted.

Here are some examples. Looks like a simplified framework for writing physical and electrical system simulations. https://mbe.modelica.university/

Over 20 years ago I modeled an internal combustion engine, an automatic transmission and a multibody chassis model all in a single model. IIRC, the model had something like 250,000 equations in it and it modeled combustion, hydraulics, friction, and 3D rigid body motion. It is capable of far more than simple models. https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&d...

That’s incredible, I had no idea this was even possible. Are most auto manufacturers modelling their vehicles this way? Seems like an amazing way to search for optimizations, predictive failures, etc.

Re: Modelica

#77

Post by RossBencina »

baggepinnen wrote: post #29
alhirzel wrote: post #17

Earlier quoted context omitted.

If you intend to explore OpenModelica you may also like ModelingToolkit.jl: https://docs.sciml.ai/ModelingToolkit/dev/ There is also a project by Hilding Elmqvist, who worked for Dassault on Dymola (the leading commercial implementation of Modelica). His project is Modia.jl: https://github.com/ModiaSim/Modia.jl I can personally feel the Julia community settling on MTK, but Modia was ahead in the early stages of dynam…

Hilding Elmqvist not only worked on Dymola, he is the original creator of modelica

In fact Dymola was published (including source code) in Hilding Elmqvist's doctoral thesis:

Elmqvist, H. (1978). A Structured Model Language for Large Continuous Systems. [Doctoral Thesis (monograph), Department of Automatic Control]. Department of Automatic Control, Lund Institute of Technology (LTH).

portal: https://portal.research.lu.se/en/publications/a-structured-m...

direct pdf link: https://lucris.lub.lu.se/ws/portalfiles/portal/4602422/85704...

Re: Modelica

#78

Post by chthonicdaemon »

runningmike wrote: post #76

Switch to https://insightmaker.com/ if you can. It is FOSS , maintained and used as powerfull but simpeler alternative.

I don't think that System Dynamics modelling tools offer the depth of control over the governing equations that Modelica has. In addition, Modelica has a nice standard library with many physical components that you can link together to form a system.

In short, Modelica is better for simulation well-specified physical systems. System Dynamics is good for simulating the approximate behaviour of larger, often poorly understood systems.

Re: Modelica

#79

Post by wolvesechoes »

alhirzel wrote: post #19
hazrmard wrote: post #11

From the website: > Modelica is a high-level declarative language for describing mathematical behavior. It is typically applied to engineering systems... We use Modelica quite a bit in HVAC industry. In my case (controls engineer), I can request FMUs of various components from systems engineers for optimization work. (Functional Mockup Unit (FMU)[1]: stand-alone binary representing a dynamical system that can be driv…

Another up-and-coming solution is Julia's simulation ecosystem [1]. It is powered by the commercial organization behind the Julia programming language, which has received DARPA funding [2] to build out these tools. This ecosystem unifies researchers in numerical methods [3], scalable compute, and domain experts in modeling engineering systems (electrical, mechanical, etc.) I believe this is where simulation is headed…

"Another up-and-coming solution is Julia's simulation ecosystem"

Still not comparable with Modelica that has proper specification, including graphical representation of models.

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