Create Your First Model with Software-In-The-Loop Simulation

Software-in-the-Loop (SITL) simulation is a technique that allows you to test and validate flight control algorithms in a virtual environment before deploying them to physical hardware. Using the UAV Toolbox Support Package for ArduPilot® Autopilots, you can build flight control models in Simulink® and run them together with the ArduPilot SITL environment. This helps you see how your algorithms work on different types of vehicles, like multirotors and fixed-wing aircraft, and fix any problems early. In this topic, you will learn how to create a basic Simulink model and check how it works using SITL simulation. Perform these steps.

This topic helps you to:

  • Build a basic Simulink model using blocks from the UAV Toolbox Support Package for ArduPilot Autopilots.

  • Configure the model to run with the ArduPilot SITL (Software-in-the-Loop) simulation environment.

  • Run and monitor your simulation in External mode, verifying live data and interacting with the SITL tools.

Create a Simulink Model

Create a Simulink model by launching Simulink in MATLAB and building a basic model using required blocks from the UAV Toolbox Support Package for ArduPilot Autopilots.

  1. Start MATLAB®. From the MATLAB toolstrip, click the Simulink button.

  2. Click the Blank Model template.

    The Simulink Editor opens.

  3. Add a required block using the quick insert menu. For example, Timestamp block.

    Double-click anywhere in the model canvas. In the quick insert menu that appears, enter Timestamp. A list of blocks appears. Verify that the Timestamp block from the UAV Toolbox Support Package for ArduPilot Autopilots library is selected. Check the library name listed under the block name and the block description in the pane to the right of the search results.

    Add block

    Add the Timestamp block to the model by pressing Enter.

    Add block

  4. Add a Dipslay block and connect the blocks by creating lines between output ports and input ports. Then, save your model.

Configure Model Parameters for SITL

Set up your model’s configuration parameters to target the ArduPilot SITL environment, specifying your vehicle type and ensuring all settings match the recommended configuration.

  1. In the Simulink model, go to the Modeling > Model Settings to open Configuration Parameters dialog box.

    Model settings

  2. In the Configuration Parameters dialog box, set the required parameters.

    Ardupilot host target configuration

    1. Click Hardware Implementation and select ArduPilot Host Target from the Hardware board list.

    2. In the Build options, ensure that Build, load and run is selected for the Build action and sitl is selected for the Board.

    3. Set the options for Vehicle.

      Vehicle

      1. Select the required ArduPilot vehicle type.

      2. For Simulator, ensure you select SITL in Host Target.

      3. Select the desired Airframe from the drop-down list.

      4. Select the options for Launch MAVProxy Console and Launch MAVProxy Map. This will automatically launch the corresponding SITL windows when you start the simulation.

        • MAVProxy Console: This window allows you to interact with and monitor the SITL simulation using command-line commands.

        • MAVProxy Map: This window displays a real-time map view of the simulated vehicle.

    4. Verify the options for External mode.

      You can use Monitor and Tune (External Mode) action to tune parameters and monitor a Simulink model running on the host target. For more information, see Monitor and Tune the Model Running on ArduPilot Autopilots.

      External mode

      • Verify the settings match exactly as shown in the image. Do not modify any of the options.

      Do not change any other options.

  3. Click Apply and OK.

Perform Monitor & Tune Simulation

The Monitor and Tune workflow in Simulink allows you to observe signal values and adjust parameters on your deployed algorithms in real time. Perform these steps.

  1. Set a value for the Simulation stop time parameter. The default value is 10.0 seconds. To run the model for an indefinite period, enter inf.

    Stop time

  2. On the Hardware tab, in the Mode section, click Run on board and then select Run on board (External mode). If you see Connected IO selected instead of Run on board, click on it and choose Run on board (External mode).

    Monitor and tune

  3. Click Monitor & Tune .

    Simulink automatically generates code from your control model. This code is then integrated with the ArduPilot autopilot firmware, built, and deployed to the autopilot hardware, where it is executed to control your vehicle.

  4. Wait for the Host Target to launch.

    • The SITL simulation environment (Host Target) will start automatically.

    • Wait for the ArduPilot SITL, MAVProxy Console, and MAVProxy Map windows to launch completely before proceeding.

      ArduPilot SITL, MAVProxy Console, and MAVProxy Map windows

Observe and Analyze Simulation Data

  • The Display block in your Simulink model will show the live output from the Timestamp block during the simulation.

    Timestamp output

  • You can also visualize and analyze the recorded signal data using the Simulink Data Inspector.

    Data inspector

  • The MAVProxy Console window allows you to interact with and monitor the SITL simulation using command-line commands.

  • The MAVProxy MAP windows gives a real-time map view of the simulated vehicle’s position and status.

See Also

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