SimulinkHow-ToBeginner · 4 min read

How to Use Stateflow with Simulink Blocks: Simple Guide

To use Stateflow with Simulink blocks, add a Stateflow chart block to your Simulink model and connect it with other blocks using input and output ports. Inside the Stateflow chart, define states and transitions to control logic, which interacts with Simulink signals for simulation.

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Syntax

The basic syntax involves adding a Stateflow Chart block inside your Simulink model. Connect inputs and outputs to this block to exchange signals with other Simulink blocks.

Inside the chart, use states to represent modes or conditions, and transitions to define rules for moving between states. Use entry, during, and exit actions to specify behavior.

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Stateflow Chart Block:
- Inputs: signals from Simulink blocks
- Outputs: signals to Simulink blocks

Inside Stateflow Chart:
state StateName {
  entry: action;
  during: action;
  exit: action;
}

Transition:
StateA -> StateB [condition];

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Example

This example shows a simple Stateflow chart controlling a Simulink model input signal. The chart switches between two states based on the input value and outputs a control signal.

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1. Open Simulink and create a new model.
2. Add a <code>Constant</code> block (input signal).
3. Add a <code>Stateflow Chart</code> block.
4. Connect the Constant block output to the Stateflow Chart input.
5. Inside the Stateflow Chart, create two states: <code>Low</code> and <code>High</code>.

Stateflow Chart code:

state Low {
  during: output = 0;
}

state High {
  during: output = 1;
}

Low -> High [input > 5];
High -> Low [input <= 5];

6. Connect the Stateflow Chart output to a <code>Display</code> block to see the output.
7. Run the simulation to observe the output switching based on the input value.

Output

When input <= 5, output = 0 (Low state). When input > 5, output = 1 (High state).

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Common Pitfalls

Not connecting inputs/outputs properly: The Stateflow chart must have input and output ports connected to Simulink signals to interact correctly.
Missing conditions on transitions: Transitions without conditions cause unexpected behavior or errors.
Incorrect data types: Ensure input and output signal data types match between Simulink blocks and Stateflow.
Forgetting to initialize outputs: Always define output values in all states to avoid undefined signals.

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Wrong transition without condition:
Low -> High;

Right transition with condition:
Low -> High [input > 5];

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Quick Reference

Concept	Description
Stateflow Chart Block	Block added to Simulink model to define state logic
States	Represent modes or conditions inside the chart
Transitions	Rules to move between states, must have conditions
Entry/During/Exit Actions	Actions executed when entering, during, or exiting a state
Input/Output Ports	Connect chart to Simulink signals for data exchange

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Key Takeaways

Add a Stateflow Chart block to your Simulink model and connect inputs and outputs properly.

Define states and transitions inside the chart to control logic based on input signals.

Always specify conditions on transitions to avoid unexpected behavior.

Match data types between Simulink signals and Stateflow inputs/outputs.

Initialize outputs in all states to ensure defined simulation results.