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Generate a Standalone ROS 2 Node from Simulink

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This example shows you how to generate and build a standalone ROS 2 node from a Simulink® model. You configure a model to generate C++ code for a standalone ROS 2 node. Then, build and run the ROS 2 node on your host computer.

Prerequisites

Configure a Model for Code Generation

Configure a model to generate C++ code for a standalone ROS 2 node. The model is the proportional controller introduced in the Feedback Control of a ROS-Enabled Robot Over ROS 2 example.

  • Open the robot feedback control model configured for ROS 2. Alternatively, call open_system("robotControllerROS2").

  • Under ROS tab, in Prepare, click Hardware settings. In the Hardware implementation pane, Hardware board settings section contains settings specific to the generated ROS 2 package, such as information to be included in the package.xml file. Change Maintainer name to ROS 2 Example User.

  • The model requires variable-sized arrays. To enable this option, check variable-size signals under Code Generation > Interface > Software environment.

  • In the Solver pane, ensure that Solver Type is set to Fixed-step, and set Fixed-step size to 0.05. In generated code, the Fixed-step size defines the actual time step, in seconds, that is used for the model update loop (see Execution of Code Generated from a Model (Simulink Coder)). It can be made smaller (e.g., 0.001 or 0.0001) but for current purposes 0.05 is sufficient.

  • Specify external ROS packages as dependencies: To specify external ROS 2 packages as dependencies to the generated ROS 2 node, specify appropriate toolchain options. In the Configuration parameters, under Code Generation > Toolchain Settings, specify the Build configuration as Specify from the drop-down. Then, you can specify the Required Packages, Include Directories, Link Libraries, Library Paths and Defines based on the external ROS 2 packages that you wish to integrate with the generated ROS 2 node.

  • Specify custom source and include files: You can specify custom source and include files in the configuration parameters, under Simulation Target > Custom Code. In the Code Information section, specify Include headers, Include directories and Source files. In the configuration parameters, under Code Generation > Custom Code, select Use the same custom code settings as Simulation Target.

  • Click OK.

Configure the Connection to the ROS 2 Device

A ROS 2 device is any Linux system that has ROS 2 installed and is capable of building and running a ROS 2 node. If you have Simulink Coder, you can generate code for a standalone ROS 2 node. If your system is connected to a ROS 2 device, Simulink can also transfer the generated code to the ROS 2 device, build an executable, and run the resulting ROS 2 node (this is referred to as "deploying" the ROS node).

In this task, you decide if you want to generate code for the ROS 2 node or if you want to build and run it on a ROS 2 device. If you are connected to a ROS 2 device, you can configure Simulink to use it as a deployment target for your ROS 2 node.

  • Under the Modeling tab, click Model Settings.

  • In the Hardware Implementation pane of Configuration Parameters dialog, select an Build action under Hardware board settings > Target hardware resources > Groups > Build Options. The selected build action affects the behavior of Simulink when building the model. None (the default setting) only generates the code for the ROS 2 node, without building it on an external ROS 2 device. Build and load generates the code, transfers it to an external device and builds a ROS 2 node executable. If you select Build and run, the resulting node executable is started automatically at the end of the build.

  • Set the Build action to Build and run.

  • Configure the connection to your external ROS 2 device. Under the ROS tab, from the Deploy to drop-down, click Manage Remote Device. This opens the Connect to a ROS device dialog. In this dialog, you can enter all the information that Simulink needs to deploy the ROS 2 node. This includes the IP address or host name of your ROS 2 device, your login credentials, and the Catkin workspace. Change Catkin workspace to ~/ros2_ws_test.

ROS 2 Folder is the location of the ROS 2 installation on the ROS 2 device. If you do not specify this folder, the settings test (see next step) tries to determine the correct folder for you.

  • If the ROS 2 device is turned on and accessible from your computer, you can verify the connection settings by clicking Test. The test verifies every device setting and display warnings and errors in the Simulink Diagnostic Viewer if problems are found. If possible, the test also suggests how the problems can be fixed. Click Test now.

  • Most likely, the Catkin workspace ~/ros2_ws_test does not exist on the target device. The test detects this problem and suggests to create the folder and initialize the workspace. Click Fix to apply this action automatically. After a few seconds, you should see a green notice that the folder has been created successfully. In the following figure you can see an example of creating the folder successfully. To verify that the Catkin workspace is now available, click Test in the connection settings dialog again. The warning has disappeared and the Catkin workspace is ready to build your ROS 2 node.

  • Change the device connection settings and test them until no other warnings or errors are shown. If an automatic fix to your settings is possible, Simulink suggests it by displaying the Fix button. Once you have a good set of settings, click OK in the connection settings dialog to save the settings.

The connection settings are not specific to a single model, but apply to all ROS 2 models in Simulink.

Generate the C++ ROS 2 Node

In this task, you generate code for a standalone ROS 2 node, and automatically build, and run it on the host computer.

  • In MATLAB®, change the current folder to a location where you have write permission.

  • Under the Simulation tab, in Prepare, select ROS Toolbox > ROS Network.

  • Set the Domain ID (ROS 2) of ROS 2 network. This example uses Domain ID as 25.

  • If you are deploying to a local device, set the environment variable ROS_DOMAIN_ID to the value 25, using setenv in MATLAB.

  • Set the ROS Middleware (ROS 2) of ROS 2 network. This example uses ROS Middleware as rmw_cyclonedds_cpp.

  • If you are deploying to a local device, set the environment variable RMW_IMPLEMENTATION to rmw_cyclonedds_cpp, using setenv in MATLAB.

  • In ROS tab, from the Deploy section dropdown, click Build & Run. If you get any errors about bus type mismatch, close the model, clear all variables from the base MATLAB workspace, and re-open the model. Click on the View Diagnostics link at the bottom of the model toolbar to see the output of the build process.

Once the code generation completes, the ROS 2 node builds in the present working folder starts to run automatically in a synchronous fashion based on the sample time of the model. When running in Windows®, a Command window opens. Do not close the window, but use Ctrl+C to shutdown the ROS 2 node.

Use ros2 node to list all running nodes is the ROS 2 network. robotControllerROS2 should be in the displayed list of nodes.

ros2('node','list')
/robotControllerROS2
/ros_bridge

Verify that the deployed node publishes data on the ROS 2 topic, /cmd_vel, to control the motion of simulated robot.

ros2('topic','list')
/clock
/cmd_vel
/gazebo/link_states
/gazebo/model_states
/imu
/joint_states
/odom
/parameter_events
/rosout
/rosout_agg
/scan
/tf

Specify Code Generation and Build Options

You can choose different code generation and build behaviors by specifying one of these Deployment options from the toolstrip under ROS tab.

  • Generate code — Generates the ROS package source code on localhost or remote device.

  • Build Model — Generates the ROS package source code and builds the standalone executable on localhost or remote device.

  • Build & Run — Generates the ROS package source code, builds the standalone executable and starts running it on localhost or remote device.