Build Your First Model

In this tutorial, you will learn the core workflow of Simit by building a simple Mass-Spring-Damper system. We will focus on how to use the editor rather than the physics theory.

Goal: Create a model that simulates a mass oscillating on a spring.

1. Create a Project

1. Click File > New Model in the top menu.
2. Name it “FirstSim”.
3. Set the solver settings in the right panel:
   • Step Size: 0.001 (1ms)
   • Duration: 10.0 seconds

2. Add Blocks

You can add blocks by searching the palette.

1. Press / (forward slash) to open the Quick Search.
2. Type Integrator and press Enter to place it.
3. Repeat this to add:
   • Another Integrator
   • Three Gain blocks
   • A Sum block
   • A Step source
   • A Scope sink

3. Connect and Wire

1. Drag from the output port of the Step block to the input of the Sum block.
2. Connect the blocks in a feedback loop (Integrator -> Integrator -> Scope).
   • Tip: You can select a block and press R to rotate or Flip to mirror it for cleaner wiring.

4. Configure Parameters

Double-click a block to edit its parameters.

1. Step Block: Set Final Value to 1.0.
2. Gain Blocks: Set values to represent Mass ($1/m$), Spring ($k$), and Damper ($c$).
   • Gain 1: 1.0 (1/m)
   • Gain 2: 50.0 (Spring Stiffness)
   • Gain 3: 0.5 (Damping Coefficient)
3. Sum Block: Change signs to + - - to subtract the spring and damping forces.

5. Run and Visualize

1. Press the Run button (▶) in the top toolbar.
2. Double-click the Scope block to see the results.
3. You should see an oscillating line that eventually settles.

Challenge: Try changing the Damping Coefficient to 2.0 and run it again. How does the curve change?

What’s Next? Now that you can build a simple flat model, learn how to organize complex logic using Subsystems.