C++/ROS 2 Ultra-Short Baseline (USBL) Simulator

Author:

• Maximilian Nitsch m.nitsch@irt.rwth-aachen.de

Affiliation: Institute of Automatic Control - RWTH Aachen University

Maintainer:

• Maximilian Nitsch m.nitsch@irt.rwth-aachen.de

Description and Features

This project provides a high-fidelity USBL simulator written in C++ and a ROS 2 node that acts as a wrapper for the simulator.

The simulator implements the following features:

• USBL measurement simulation in USBL-centroid and NED frame
• USBL array simulation with transducer and hydrophone positions
• Standard and inverse USBL configuration (USBL on air-water interface, transponder on AUV)
• Round-trip-time (RTT) noise and quantization simulation
• Time-Difference-of-Arrival (TDOA) noise and quantization simulation
• Internal Attitude and Heading Reference System (AHRS) simulation (Xsens MTi-100 Inertial Measurement Unit)
• Acoustic path delay simulation
• Acoustic position fix loss simulation (exponential loss model)
• All parameters for the USBL can be configured in a YAML file
• All models and effects can be enabled/disabled separately

An example config file for an OEM 120/180 OEM USBL is provided. Parameters for an S2C R 7/17 USBL are found in the references below. For other parameters, we refer to EvoLogics.

Scope and Limitations of this Simulator:

• This simulator does not model the exact acoustic signal propagation and interactions with the environment. This would require a full acoustic simulation of the environment i.e. using ray tracing techniques.
• Instead, the simulator propagates white noise measurements through the geometry of the USBL to provide realistic measurements under ideal (datasheet) conditions.
• This simulator is intended for testing and validation of navigation algorithms (sensor fusion) and their real-time performance.
• This simulator only simulates the localization feature of the USBL. The acoustic communication capability of EvoLogics modems is not simulated.

Future Features

The following features are planned for future releases:

• Acoustic position fix outlier simulation (i.e. due to multipath)
• Parameter files for other EvoLogics USBL products
• Reverse USBL (USBL array on AUV, transponder on air-water interface)
• Double-sided USBL (USBL array on AUV and air-water interface)
• Gazebo plugin

Working Principle of USBL

A USBL can measure the position of the AUV body frame within its sensor frame (USBL-centroid frame). It measures the RTT of an acoustic signal between the so-called transceiver (TC) and transponder (TP) modem transducers. Transducers convert electrical signals into acoustic signals and vice versa. Furthermore, measuring the TDOAs between multiple hydrophones (H) transducers, also known as USBL antenna, delivers the Angle-of-Arrival (AOA). Hence, a USBL uses the triangulation technique.

The USBL is usually installed at the air-water interface (often under a ship). Depending on the use case, the USBL sends the position solution from the air-water interface to the AUV via an acoustic link. This results in an initial latency of three sound paths, which reduces to two after the acoustic link is established for communication.

A transponder modem is located on the AUV. It responds to the interrogation of the transceiver modem, typically installed at the air-water interface. The transponder modem is usually installed at the AUV. Consequently, the position fix is calculated on the air-water interface and then sent to the AUV via the acoustic link.

Take a look into the References for more information.

Table of Contents

• Dependencies
• ROS 2 Node
  • Publishers
  • Subscribers
• Installation
• Usage
• Coding Guidelines
• References
• Reports
• Contributing
• License

Dependencies

This project depends on the following literature and libraries:

• Eigen3: Eigen is a C++ template library for linear algebra: Eigen website.
• ROS 2 Humble: ROS 2 is a set of software libraries and tools for building robot applications: ROS 2 Installation page.
• nanoauv_sensor_driver_interfaces: TRIPLE-project specific ROS 2 package with nanoAUV interfaces. You don't need to build that package.

ROS 2 Node Description

The USBL simulator node implements several publishers, depending on the CMake build macro, and subscribes to one topic. ROS 2 services or actions are not provided.

Publishers

This node publishes the following topics:

Topic Name	Message Type	Description	Link
*/usbllong	nanoauv_sensor_driver_interfaces/UsblLong.msg	Custom USBL Cartesian position message holding USBLLONG.	UsblLong.msg
*/usblangles	nanoauv_sensor_driver_interfaces/UsblAngles.msg	Custom USBL spherical position message holding USBLANGLES.	UsblAngles.msg
*/pos_fix_cartesian_ned_frame	geometry_msgs/PointStamped.msg	Position vector in Cartesian coordinates w.r.t. NED frame.	PointStamped.msg

If the nanoAUV interface package is not used, the following publishers are available:

Topic Name	Message Type	Description	Link
*/round_trip_time	std_msgs/Float64.msg	Round-trip-time measurement of USBL.	Float64.msg
*/time_differences_of_arrival	std_msgs/Float64MultiArray.msg	Time-differences-of-arrival measurements of USBL.	Float64MultiArray.msg
*/ahrs	std_msgs/Float64.msg	Euler angles from internal Attitude Heading Reference System (AHRS).	PointStamped.msg
*/direction_vector	diagnostic_msgs/DiagnosticArray.msg	Direction vector pointing from USBL transceiver to transponder.	PointStamped.msg
*/pos_fix_cartesian_ned_frame	geometry_msgs/PointStamped.msg	Position vector in Cartesian coordinates w.r.t. NED frame.	PointStamped.msg
*/pos_fix_cartesian_usbl_frame	geometry_msgs/PointStamped.msg	Position vector in Cartesian coordinates w.r.t. USBL frame.	PointStamped.msg
*/pos_fix_spherical_ned_frame	geometry_msgs/PointStamped.msg	Position vector in spherical coordinates w.r.t. NED frame.	PointStamped.msg
*/pos_fix_spherical_usbl_frame	geometry_msgs/PointStamped.msg	Position vector in spherical coordinates w.r.t. USBL frame.	PointStamped.msg
*/accuracy	std_msgs/Float64.msg	Accuracy (standard deviation) of position fix.	Float64.msg
*/diagnostic	diagnostic_msgs/DiagnosticArray.msg	Array with diagnostic information about the state of ROS 2 node.	DiagnosticArray.msg

Subscribers

This node subscribes to the following topics:

Topic Name	Message Type	Description	Link
*/odometry	nav_msgs/Odometry.msg	Ground truth odometry of the robot.	Odometry.msg

Installation

To install the usbl_simulator_package, you need to follow these steps:

1. Install Eigen3: Eigen3 is a dependency for your package. You can install it using your package manager. For example, on Ubuntu, you can install it using the following command:

   sudo apt-get install libeigen3-dev

2. Install ROS 2 Humble: Ensure you have ROS 2 (Humble) installed. You can follow the official installation instructions provided by ROS 2. Visit ROS 2 Humble Installation page for detailed installation instructions tailored to your platform.

3. Clone the Package: Clone the package repository to your ROS 2 workspace. If you don't have a ROS 2 workspace yet, you can create one using the following commands:

   mkdir -p /path/to/ros2_workspace/src
   cd /path/to/ros2_workspace/src

   Now, clone the package repository:

   git clone <repository_url>

   Replace <repository_url> with the URL of your package repository.

4. Build the Package: Once the package is cloned, you must build it using colcon, the default build system for ROS 2. Navigate to your ROS 2 workspace and run the following command:

   cd /path/to/ros2_workspace
   colcon build

   This command will build all the packages in your workspace, including the newly added package.

5. Source the Workspace: After building the package, you need to source your ROS 2 workspace to make the package available in your ROS 2 environment. Run the following command:

   source /path/to/ros2_workspace/install/setup.bash

   Replace /path/to/ros2_workspace with the actual path to your ROS 2 workspace.

That's it! Your usbl_simulator_package should now be installed along with its dependencies and ready to use in your ROS 2 environment.

Usage

1. Configure your YAML file for your USBL or use the default file.

2. Start the USBL simulator with the launch file:

   ros2 launch usbl_simulator_package usbl_simulator.launch.py

The USBL simulator prints your settings and waits for a ground truth odometry message.

3. Provide an odometry publisher from you vehicle simulation.

4. Check ROS 2 topics the USBL values should now be published.

Important Usage Information:

• The odometry message must be published with at least the USBL data rate/sample time.
• The message */diagnostic will show WARN if the odometry rate is lower.
• If no odometry message is published, the message */diagnostic will show STALE.
• If everything is correct */diagnostic will show OK.

Coding Guidelines

This project follows these coding guidelines:

• https://google.github.io/styleguide/cppguide.html
• http://docs.ros.org/en/humble/The-ROS2-Project/Contributing/Code-Style-Language-Versions.html

References

The USBL simulator implementation follows the following publications and datasheets:

• M. Nitsch, "Navigation of a miniaturized autonomous underwater vehicle exploring waters under ice," Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, Aachen, RWTH Aachen University, 2024. DOI: 10.18154/RWTH-2024-05964.
• Bannasch, R.; Kebkal, K.; Yakovlev, S.; Kebkal, A. "Fast and Reliable Underwater Communication: Successful Applications of Biologically Inspired Techniques." In: Volume 1: Offshore Technology; Offshore Wind Energy; Ocean Research Technology; LNG Specialty Symposium, 25th International Conference on Offshore Mechanics and Arctic Engineering, Hamburg, Germany: ASMEDC, Jan. 1, 2006, pp. 741–747. doi: 10.1115/OMAE2006-92550.
• Caiti, A.; Di Corato, F.; Fenucci, D.; Allotta, B.; Costanzi, R.; Monni, N.; Pugi, L.; Ridolfi, A. "Experimental Results with a Mixed USBL/LBL System for AUV Navigation." In: 2014 Underwater Communications and Networking (UComms), Sept. 2014, pp. 1–4. doi: 10.1109/UComms.2014.7017129.
• Ehlers, F. "Autonomous Underwater Vehicles: Design and Practice." The Institution of Engineering and Technology, 2020.
• Evologics GmbH, ed. "S2C Reference Manual, Edition Standard, Firmware Version 2.0." Evologics GmbH, Nov. 2019.
• Evologics GmbH, ed. "S2CR 48/78 USBL Product Information Datasheet." Evologics GmbH, June 2012.
• Evologics GmbH, ed. "USBL Positioning and Communication Systems Product Information Guide." Evologics GmbH, Oct. 2021.
• Evologics GmbH, ed. "S2C T 30/60 Underwater Acoustic Modem Datasheet." Evologics GmbH, Aug. 2022.
• Evologics GmbH, ed. "USBL Positioning and Communication System S2CR 30/60 USBL Product Information Datasheet." Evologics GmbH, July 2022.
• Hildebrandt, M.; Creutz, T.; Wehbe, B.; Wirtz, M.; Zipper, M. "Under-Ice Field Tests with an AUV in Abisko/Torneträsk." In: OCEANS 2022, Hampton Roads, Oct. 2022, pp. 1–7. doi: 10.1109/OCEANS47191.2022.9977094.
• Jakuba, M. V.; Roman, C. N.; Singh, H.; Murphy, C.; Kunz, C.; Willis, C.; Sato, T.; Sohn, R. A. "Long-Baseline Acoustic Navigation for Under-Ice Autonomous Underwater Vehicle Operations." In: Journal of Field Robotics, vol. 25, no. 11-12 (2008), pp. 861–879. doi: 10.1002/rob.20250.
• Kebkal, K. G.; Kebkal, O. G.; Bannasch, R.; Yakovlev, S. G. "Performance of a Combined USBL Positioning and Communication System Using S2C Technology." In: 2012 Oceans - Yeosu, May 2012, pp. 1–7. doi: 10.1109/OCEANS-Yeosu.2012.6263376.
• Kebkal, K. G.; Mashoshin, A. I. "AUV Acoustic Positioning Methods." In: Gyroscopy and Navigation, vol. 8, no. 1 (Jan. 1, 2017), pp. 80–89. doi: 10.1134/S2075108717010059.
• Knapp, C.; Carter, G. "The Generalized Correlation Method for Estimation of Time Delay." In: IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 24, no. 4 (Aug. 1976), pp. 320–327. doi: 10.1109/TASSP.1976.1162830.
• Morgado, M.; Oliveira, P.; Silvestre, C. "Tightly Coupled Ultrashort Baseline and Inertial Navigation System for Underwater Vehicles: An Experimental Validation." In: Journal of Field Robotics, vol. 30, no. 1 (2013), pp. 142–170. doi: 10.1002/rob.21442.
• Morgado, M.; Oliveira, P.; Silvestre, C.; Vasconcelos, J. F. "Embedded Vehicle Dynamics Aiding for USBL/INS Underwater Navigation System." In: IEEE Transactions on Control Systems Technology, vol. 22, no. 1 (Jan. 2014), pp. 322–330. doi: 10.1109/TCST.2013.2245133.
• Morgado, M.; Oliveira, P.; Silvestre, C.; Vasconcelos, J. "USBL/INS Tightly-Coupled Integration Technique for Underwater Vehicles." In: 2006 9th International Conference on Information Fusion, July 2006, pp. 1–8. doi: 10.1109/ICIF.2006.301607.
• Richmond, K.; Gulati, S.; Flesher, C.; Hogan, B. P.; Stone, W. C. "Navigation, Control, and Recovery of the ENDURANCE Under-Ice Hovering AUV." In: International Symposium on Unmanned Untethered Submersible Technology (UUST), Aug. 25, 2009, p. 13.
• Tan, H.-P.; Diamant, R.; Seah, W. K.; Waldmeyer, M. "A Survey of Techniques and Challenges in Underwater Localization." In: Ocean Engineering, vol. 38, no. 14-15 (Oct. 2011), pp. 1663–1676. doi: 10.1016/j.oceaneng.2011.07.017.
• Xsens. "MTi Series: A Complete Line of MEMS Motion Trackers - IMU, VRU, AHRS and GNSS/INS." Xsens Technologies B.V.

Contributing

If you want to contribute to the project, see the CONTRIBUTING file for details.

License

This project is licensed under the BSD-3-Clause License. Please take a look at the LICENSE file for details.