ModOnda: Modelica simulation in a browser tab

Simulating a physical system in Modelica usually starts with installing a large desktop tool. ModOnda starts with a link. It is a Modelica workbench that runs in a browser tab, and it is now a free public beta.

Modelica is a language for describing engines, circuits, vehicles, hydraulics and control loops as parts and the connections between them. ModOnda compiles that description, solves it, and shows the results next to the diagram.

Try it in a minute

Open the torque converter launch example. It loads straight into the model.

1. Look at the Diagram tab. A throttle drives two copies of the same drivetrain.
2. Press Simulate (or Ctrl+Enter). You stay on the model, and the plot strip under the diagram fills with the result.
3. Open Simulation in the header. The Animation tab shows the 3-D view. Press play. Two cars launch side by side. One uses a static K-factor torque converter, and the other adds a 50 ms lag to the fluid torque build-up.
4. Switch to Plot and tick a variable to draw it. Engine speed and vehicle speed show the engine flaring toward stall speed before the lock-up clutch closes.

Signing in is optional. The workbench works without an account.

What runs where

The compiler and the solvers are written in Rust and compiled to WebAssembly. They run in a Web Worker inside your tab, so a simulation does not send your model to a server. A few optional features do reach out, and only when you choose them: the AI assistant sends your messages and the model files it reads to OpenRouter and the provider of the model you pick, and Run on server (in the ▾ menu next to Simulate) sends a model to a hosted engine.

What is in the page

• The Modelica Standard Library 4.1.0, loaded in the browser, with MultiBody, electrical, thermal, hydraulic and media models.
• A package browser, and icon, diagram and text views of every class, with a variable browser and a plot window that converts display units.
• 3-D animation of MultiBody models and of every example in the library.
• Solvers you can choose: BDF, Radau IIA, ESDIRK, and Dopri5 with automatic switching to BDF when a model turns stiff.
• An equation and initialization debugger, linear analysis (Bode, step response, poles and zeros), and sensitivity and calibration tools.

The documentation covers each of them, and Getting started is the shortest way in.

How do we know the numbers are right?

Every example in the Modelica Standard Library comes with reference results published by the Modelica Association. ModOnda runs all 534 examples and compares them with those references, signal by signal. 533 run to the end and 517 match. Validated against the Modelica reference results explains how the comparison works, and where the references themselves look wrong.

What it is not

This is a beta, and not every Modelica model runs yet. Some of the larger Modelica Fluid systems still differ from their references. There is nothing to download: the workbench is the product for now.

If a model of yours breaks, or something is confusing, write to hello@modonda.com. We read every message.