Simulating Simulink Models with the sim Command

Simulating Simulink Models with the sim Command

Use this skill when you need to configure a simulation non-destructively — parameter overrides, custom inputs, batch execution, or structured output access. For persistent, reusable pass/fail behavioral testing (especially of individual subsystems), use testing-simulink-models instead. For trivial one-shot simulations without configuration, a direct sim() call suffices without this skill.

When to Use

• Overriding model or block parameters non-destructively (setVariable, setBlockParameter, setModelParameter) — without modifying the .slx file
• Passing custom input signals to root-level Inport blocks via setExternalInput with a Dataset
• Running parameter sweeps or batch simulations (SimulationInput arrays, parsim, Fast Restart)
• Accessing logged signal data (logsout) for analysis after simulation

When NOT to Use

• Trivial one-shot simulations without parameter overrides or custom inputs — a direct sim('ModelName') call works without this skill
• Writing declarative Gherkin-based tests → use testing-simulink-models
• Testing an individual subsystem or component → use testing-simulink-models (requires Simulink Test; auto-creates a harness, compiles only the subsystem — much faster than sim() which always compiles the entire model)
• Adding, connecting, or deleting blocks → use building-simulink-models
• Checking model structure for unconnected ports → use model_check tool directly
• Generating requirements from model behavior → use generate-requirement-drafts

Minimal working pattern

Always simulate using Simulink.SimulationInput and Simulink.SimulationOutput:

in = Simulink.SimulationInput('MyModel');
in = in.setModelParameter('StopTime', '10');
out = sim(in);

Setting parameters

Use SimulationInput methods to configure the simulation:

% Model-level parameters (StopTime, SolverType, SimulationMode, etc.)
in = in.setModelParameter('StopTime', '10', 'SolverType', 'Fixed-step');

% Block parameters — resolve path from blk_X ID (never type block names manually)
blkPath = Simulink.ID.getFullName('MyModel:5');