How to Use Simulink with MATLAB

Edited 3 months ago by ExtremeHow Editorial Team

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Simulink is a block diagram environment for multi-domain simulation and model-based design. It supports system-level design, simulation, automated code generation, and continuous testing and verification of embedded systems. Simulink is used in conjunction with MATLAB to provide a complete engineering workflow. In this guide, you will learn how to use Simulink with MATLAB. We will cover the basics of setting up your environment, creating models, simulating them, and incorporating MATLAB code into your Simulink models.

Getting started with Simulink

To start using Simulink, you must first install MATLAB on your computer, as Simulink is a part of MATLAB's environment. Open the MATLAB desktop, and you will find the Simulink icon in the toolbar. Clicking this icon opens the Simulink start page where you can create a new model or open an existing model.

On the Simulink start page, you will find various templates and examples to help you get started. You can choose a blank model, or start with one of the tutorial models. For starters, we will start with a blank model to learn about the basic functionalities.

Creating your first model

After opening the blank model, you will see an untitled block diagram window. This is where you will create your model using Simulink blocks. Simulink provides a wide range of blocks that you can use to create your models. These blocks are organized into Signal Routing, Signal Operation, Sinks, Sources, and many more libraries that you can browse through the Library Browser or search directly.

Let's create a simple model: sine wave input to scope. First, open the Library Browser and locate the sine wave block under Source. Drag and drop it onto your model. Next, find the scope block under Sinks and drag it onto the model. Connect the outputs of the sine wave block to the inputs of the scope block by clicking and dragging a line between them.

Now, you have created a simple model of the sine wave going into the scope. You can configure the properties of the sine wave block by double-clicking on it. You can change parameters such as amplitude, frequency, and phase to suit your model needs.

Running the simulation

After setting up your model, the next step is to simulate it. In Simulink, running a simulation means solving the underlying mathematical equations in your model with respect to time. To simulate your model, go to the toolbar and click the green Play button. Your model will begin simulating, and the Scope block will display the sine wave output in real time.

You can adjust the simulation time by modifying the 'Stop Time' from the Simulation tab in the toolbar. Depending on the complexity of your model, you may get different simulation outputs that can be configured to better understand the model behavior.

Incorporating MATLAB functions

One of the major advantages of using Simulink is that it is seamlessly integrated with MATLAB. You can use MATLAB functions in your Simulink model using the MATLAB function block. This block allows you to write MATLAB code within it and use it as part of the model.

For example, if you want to customize the processing of a signal, you can create a MATLAB script or function and call it using a MATLAB function block. Here is a simple example code that adds constants to a signal:

function y = fcn(u) %#codegen y = u + 5; end
function y = fcn(u) %#codegen y = u + 5; end

In this code, `u` is an input to the function, and the function adds 5 to the input signal and outputs the result `y`. You place this custom code inside a MATLAB function block.

Parameterizing models

Parameterizing models makes them more flexible and reusable. You can use MATLAB variables and parameters in Simulink models to define dynamic behavior. For example, you may have several blocks that require the same parameter, such as a gain value that needs to be tuned.

Suppose you have a gain block in your model, and you want to use MATLAB's workspace variable for its value. First, define the variable in the MATLAB workspace:

GainValue = 10;
GainValue = 10;

Then, in the Parameter field of the Gain block, enter `GainValue`. Simulink will fetch the current workspace variable when it runs the model, allowing you to change the value dynamically without modifying the block diagram.

Using callbacks

Callbacks are an advanced feature in Simulink and MATLAB that allows you to execute commands at specific times during a model simulation cycle or editing session. You can define custom code to run when the model loads, when the simulation starts, or even at the end of the simulation.

Callbacks can be found in the Model Properties under the File menu, where you can define actions such as setting up the environment, checking parameters, or starting data logging each time the model is loaded or simulated.

Working with subsystems

Subsystems help you organize a complex model into a more manageable hierarchy by grouping related blocks. To create a subsystem, select several blocks, right-click and choose 'Create Subsystem from Selection'. This action collapses the selected elements into a single block, simplifying the top-level view of your model.

Saving and managing models

To save your Simulink model, click File > Save As and choose a directory and name for your file. The default file format is .slx, which is compressed and more efficient than the older .mdl format.

When working with Simulink models, especially in a team environment, it is recommended to use a version control system such as Git. Export the model to a text-based file format to help track changes over time and collaborate with others.

Simulink model debugging

Debugging is important to ensure that your models work correctly. Simulink provides various debugging tools to help you identify and fix problems. Some of these tools include:

• Diagnostic Viewer: Displays errors and warnings during simulation, and provides detailed messages to help diagnose problems.
• Scope block: Use to look at signals and check if they follow the expected pattern.
• Assertions: Add assertions to ensure that signals stay within expected limits.

Advanced features

As you become more familiar with Simulink, you will be able to explore more advanced features, such as:

• Stateflow: Use for modeling complex logic for systems with finite state machines, flow charts, and transition diagrams.
• Code Generation: Automatically generate C/C++ code from your Simulink models to integrate with embedded systems.
• Simulink Real-Time: Connect and use Simulink models with real-time hardware to prototype systems.

Conclusion

Simulink integrates seamlessly with MATLAB, providing a powerful environment for modeling, simulating, and analyzing dynamic systems. Using block diagrams, Simulink allows engineers and scientists to easily navigate and model complex behaviors. As you explore its capabilities and incorporate MATLAB functions, you will discover its versatility and effectiveness in solving complex engineering problems.

Continuous learning and experimenting with different blocks and tools will increase your proficiency in Simulink. Consider joining a community or forum where you can share insights, ask questions, and learn from others. Enjoy modeling!

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