Monitor and Tune ROS 2 Models Using External Mode

Overview of External Mode

External mode allows real-time interaction between Simulink^® and deployed ROS 2 nodes on target hardware, making it ideal for rapid prototyping. When you use external mode simulations, a communication channel is established between Simulink on your development computer (host) and the target hardware running the executable file generated by the code build process. This feature facilitates:

• Parameter Tuning — Modify parameters and observe immediate effects without restarting the simulation.

• Signal Monitoring — Visualize real-time signals in the Sink (Simulink) block or Simulation Data Inspector (SDI) (Simulink) for effective debugging and optimization. XCP-based external mode enables SDI, which provides advanced capabilities for parameter tuning by allowing you to:

  • Log and compare signals from multiple runs.

  • Validate and refine models with data visualizations in real time.

Communication Interfaces in External Mode

This table lists the two communication protocols supported by ROS Toolbox.

Communication Protocols	Purpose	Usage
XCP on TCP/IP	It is an advanced communication protocol, leveraging the Universal Measurement and Calibration Protocol (XCP) for efficient data exchange and monitoring.	It offers logging capabilities with the Dashboard (Simulink) blocks in addition to Sources (Simulink) and Sink (Simulink) blocks, and real-time signal visualization in SDI. It is ideal for applications requiring larger data buffers and custom polling times.
TCP/IP	It is a standard communication protocol for parameter tuning and signal monitoring.	It offers logging capabilities with the Dashboard (Simulink) blocks in addition to Sources (Simulink) and Sink (Simulink) blocks, but does not enable SDI for real-time signal visualization.

This table below provides a comprehensive comparison of the two communication protocols.

Feature	XCP on TCP/IP	TCP/IP
Parameter Tuning	Usage of Dashboard blocks Parameter tuning of tunable block parameters	Same as XCP on TCP/IP
Buffer Customization	User-defined buffer size	Not available
Polling Time	Customizable	Fixed
SDI	Yes	No
Blocks that receive and display signals from target application	Dashboard library Floating Scope, Scope Display To Workspace User-written S-Function. For details, see External Mode Simulations for Parameter Tuning, Signal Monitoring, and Code Execution Profiling (Simulink Coder) Record	Same as XCP on TCP/IP except Dashboard library

Configure External Mode in ROS 2 Models

External mode enables Simulink on your host computer to communicate with a deployed model on your robotics hardware during runtime. For ROS Toolbox, deployed models are ROS 2 nodes running on the target hardware that communicates with Simulink over XCP on TCP/IP or TCP/IP.

To use external mode with ROS Toolbox models:

1. On the Apps tab, under Control Systems, click Robot Operating System (ROS).

2. In the Robot Operating System (ROS) dialog box that opens up, select Robot Operating System 2 (ROS 2) from the ROS Network drop-down list. This opens up the ROS tab in the toolstrip and that shows the specified ROS Network in the Connect section.

3. In the Connect section, set Deploy To to Remote Device, from the drop-down list. To configure the remote device details such as IP address and user details, select Manage Remote Device from the drop-down list.

4. In the Prepare section, click Hardware Settings to open the model configuration parameters dialog box. In Target Hardware Resources under Hardware board settings, set the External mode parameters. Click OK.

   1. Select the Communication interface from one of these options:

      • XCP on TCP/IP for advanced data logging and signal monitoring. This is on by default.

      • TCP for basic parameter tuning.

   2. Configure Parameters for XCP on TCP/IP — When you set the Communication interface to XCP-based external mode, the Logging buffer size (bytes) and Polling time (in seconds) parameters become available.

      • Logging buffer size (bytes): Specify this parameter to set the size of the buffer for logging data during simulation in bytes. The default value is 1,000,000 bytes. Adjust this value based on your signal logging needs.

        Polling time (in seconds): Specify this parameter to set the interval to check the status of the external mode simulation, the signal triggering logic, and the current simulation time when signal streaming is disabled or data flow stops in XCP. The default value is 2 seconds. Lower polling times increase responsiveness but can burden the hardware.

        Increase polling time if the step function execution time exceeds the current polling time or if real-time task scheduling is slow.

Your model connects to the Device Address specified in the Connect to ROS Device dialog box, which opens when you select Manage Remote Device from the Deploy To drop-down list. The model uses this address to connect to your ROS device when you deploy it.

Run External Mode Simulations on ROS 2 Feedback Control Robot Model

• Feedback Control of ROS 2 Robot with TCP/IP External Mode

• Feedback Control of ROS 2 Robot with XCP-Based External Mode

Feedback Control of ROS 2 Robot with TCP/IP External Mode

This example contains the Simulink® model of feedback control robot in ROS 2 that uses TCP/IP communication interface to monitor and tune parameters during simulation.

Prepare Feedback Control Robot Model

1. To run this example, install and set up Docker using the instruction provided in Install and Set Up Docker for ROS, ROS 2, and Gazebo.

2. Refer to the Get Started with Gazebo and Simulated TurtleBot example to configure and run the Gazebo world.

3. Once the Gazebo world starts running, open and run the ROS 2 feedback control robot model for simulation over TCP/IP in external mode.

open_system("robotTCPIPExternalModeExample.slx")

4. Enable data logging for signals you want to monitor by right-clicking the signal and select Enable Data Logging. Simulink® displays a logged signal indicator for each logged signal, however, you will be unable to view these signals due to inaccessibility to to Simulation Data Inspector.

Use one or more Dashboard (Simulink) blocks such as the Knob block in the model to dynamically tune parameters through dialing during simulation and place Sink blocks like Scope (Simulink) or Display (Simulink) to monitor simulation outputs.

Run Model and Perform Simulation

On the Run On Hardware tab, select Monitor & Tune.

Tune Parameters and Observe Outputs

1. While the simulation is running, modify parameters such as the proportional gain or desired position.

2. Observe the effects in real time through the Sink block such as the Scope.

Stop Simulation

After fine tuning the parameters, click Stop in the Hardware tab.

Feedback Control of ROS 2 Robot with XCP-Based External Mode

This example contains the Simulink® model of feedback control robot in ROS 2 that uses XCP-Based communication interface to monitor and tune parameters during simulation.

Prepare Feedback Control Robot Model

1. To run this example, install and set up Docker using the instruction provided in Install and Set Up Docker for ROS, ROS 2, and Gazebo.

2. Refer to the Get Started with Gazebo and Simulated TurtleBot example to configure and run the Gazebo world.

3. Once the Gazebo world starts running, open and run the ROS 2 feedback control robot model for simulation over XCP on TCP/IP in external mode.

open_system("robotXCPExternalModeExample.slx")

4. Enable data logging for signals you want to monitor by right-clicking the signal and select Enable Data Logging. Simulink® displays a logged signal indicator for each logged signal and you can view them in the Simulation Data Inspector(SDI).

5.Use one or more Dashboard (Simulink) blocks such as the Knob block in the model to dynamically tune parameters through dialing during simulation. Connect Display (Simulink) block and mark the signals connected to them for logging.

Run Model and Perform Simulation

On the Run On Hardware tab, select Monitor & Tune.

Tune Parameters and Observe Outputs

Open the SDI for detailed analysis. Click the Simulation Data Inspector button to open the Inspect pane. The Inspect pane lists all logged signals in rows, organized by simulation run. You can expand or collapse any of the runs to view the signals in a run. For more information on signal grouping, see Signal Grouping section in Configure the Simulation Data Inspector (Simulink).

We recommend you to use simulation Data Inspector (SDI) rather than using Sink blocks for the following reasons:

• Streaming data to SDI does not store data in memory, making more efficient use of the memory available on the hardware. Sink blocks such as Scope (Simulink) stores data in buffers before sending the data to the host.

• Using SDI, you can stream signals from top models and reference models simultaneously. Scope blocks can only log signals from a top-level model.

Adjust Parameters

Modify parameters like buffer size or polling interval in the Hardware board settings under Hardware Implementation for subsequent runs.

Stop Simulation

After fine tuning the parameters, click Stop in the Hardware tab.