sbg_driver

ROS2 driver package for SBG Systems IMU, AHRS and INS.
This driver package uses the sbgECom binary protocol to read data and configure SBG Systems devices.

Initial work has been done by ENSTA Bretagne.

Author: SBG Systems
Maintainer: SBG Systems
Contact: support@sbg-systems.com

Features

The driver supports the following features:

• Configure ELLIPSE products using yaml files (see note below)
• Parse IMU/AHRS/INS/GNSS using the sbgECom protocol
• Publish standard ROS messages and more detailed specific SBG Systems topics
• Subscribe and forward RTCM data to support DGPS/RTK mode with centimeters-level accuracy
• Calibrate 2D/3D magnetic field using the on-board ELLIPSE algorithms

[!NOTE] Only ELLIPSE devices can be configured from the ROS driver. For High Performance INS such as EKINOX, APOGEE and QUANTA, please use the sbgInsRestApi

Installation

Installation from Packages

User can install the sbg_ros2_driver through the standard ROS installation system.

• Galactic sudo apt-get install ros-galactic-sbg-driver
• Foxy sudo apt-get install ros-foxy-sbg-driver

Building from sources

Dependencies

• Robot Operating System (ROS)
• sbgECom C Library (embeds v4.0.1987-stable - compatible with ELLIPSE firmware 2.5 and above)

Building

1. Clone the repository (use a Release version)
2. Build using the ROS colcon build system

cd colcon_ws/src
git clone https://github.com/SBG-Systems/sbg_ros2_driver.git
cd sbg_ros2_driver
rosdep update
rosdep install --from-path .
cd ../..
colcon build
source install/setup.bash

Usage

To run the default Ros2 node with the default configuration

ros2 launch sbg_driver sbg_device_launch.py

To run the magnetic calibration node

ros2 launch sbg_driver sbg_device_mag_calibration_launch.py

Config files

Default config files

Every configuration file is defined according to the same structure.

• sbg_device_uart_default.yaml This config file is the default one for UART connection with the device.
  It does not configure the device through the ROS node, so it has to be previously configured (manually or with the ROS node).
  It defines a few outputs for the device:
  • /sbg/imu_data, /sbg/ekf_quat at 25Hz
  • ROS standard outputs /imu/data, /imu/velocity, /imu/temp at 25Hz
  • /sbg/status, /sbg/utc_time and /imu/utc_ref at 1Hz.
• sbg_device_udp_default.yaml This config file is the default one for an Udp connection with the device.
  It does not configure the device through the ROS node, so it has to be previously configured (manually or with the ROS node).
  It defines a few outputs for the device:
  • /sbg/imu_data, /sbg/ekf_quat at 25Hz
  • ROS standard outputs /imu/data, /imu/velocity, /imu/temp at 25Hz
  • /sbg/status, /sbg/utc_time and /imu/utc_ref at 1Hz.

Example config files

• ellipse_A_default.yaml Default config file for an Ellipse-A.

• ellipse_E_default.yaml Default config file for an Ellipse-E with an external NMEA GNSS.

• ellipse_N_default.yaml Default config file for an Ellipse-N using internal GNSS.

• ellipse_D_default.yaml Default config file for an Ellipse-D using internal GNSS.

Launch files

Default launch files

• sbg_device_launch.py Launch the sbg_device node to handle the received data, and load the sbg_device_uart_default.yaml configuration.

• sbg_device_mag_calibration_launch.py Launch the sbg_device_mag node to calibrate the magnetometers, and load the ellipse_E_default.yaml configuration.

Nodes

sbg_device node

The sbg_device node handles the communication with the connected device, publishes the SBG output to the Ros environment and subscribes to useful topics such as RTCM data streams.

Published Topics

SBG Systems specific topics

SBG Systems has defined proprietary ROS messages to report more detailed information from the AHRS/INS.
These messages try to match as much as possible the sbgECom logs as they are output by the device.

• /sbg/status sbg_driver/SbgStatus

  Provides information about the general status (Communication, Aiding, etc..).

• /sbg/utc_time sbg_driver/SbgUtcTime

  Provides UTC time reference.

• /sbg/imu_data sbg_driver/SbgImuData

  IMU status, and sensors values.

• /sbg/ekf_euler sbg_driver/SbgEkfEuler

  Computed orientation using Euler angles.

• /sbg/ekf_quat sbg_driver/SbgEkfQuat

  Computed orientation using Quaternion.

• /sbg/ekf_nav sbg_driver/SbgEkfNav

  Computed navigation data.

• /sbg/ekf_vel_body sbg_driver/SbgEkfVelBody

  Computed velocity expressed in the INS body/vehicle frame.

• /sbg/ekf_rot_accel_body sbg_driver/SbgEkfRotAccel

  Computed rotations rate and accelerations in the INS body/vehicle frame.

• /sbg/ekf_rot_accel_ned sbg_driver/SbgEkfRotAccel

  Computed rotations rate and accelerations in North, East, Down (NED) navigation frame.

• /sbg/mag sbg_driver/SbgMag

  Calibrated magnetic field measurement.

• /sbg/mag_calib sbg_driver/SbgMagCalib

  Magnetometer calibration data.

• /sbg/ship_motion sbg_driver/SbgShipMotion

  Heave, surge and sway data.

• /sbg/gps_vel sbg_driver/SbgGpsVel

  GPS velocities from GPS receiver.

• /sbg/gps_pos sbg_driver/SbgGpsPos

  GPS positions from GPS receiver.

• /sbg/gps_hdt sbg_driver/SbgGpsHdt

  GPS true heading from dual antenna system.

• /sbg/gps_raw sbg_driver/SbgGpsRaw

  GPS raw data for post processing.

• /sbg/odo_vel sbg_driver/SbgOdoVel

  Odometer velocity.

• /sbg/event[ABCDE] sbg_driver/SbgEvent

  Event on sync in the corresponding pin.

• /sbg/pressure sbg_driver/SbgPressure

  Pressure data.

ROS standard topics

In order to define ROS standard topics, it requires sometimes several SBG messages, to be merged. For each ROS standard, you have to activate the needed SBG outputs.

• /imu/data sensor_msgs/Imu

  IMU data. Requires /sbg/imu_data and /sbg/ekf_quat.

• /imu/temp sensor_msgs/Temperature

  IMU temperature data. Requires /sbg/imu_data.

• /imu/velocity geometry_msgs/TwistStamped

  IMU velocity data. Requires /sbg/imu_data.

• /imu/mag sensor_msgs/MagneticField

  IMU magnetic field. Requires /sbg/mag.

• /imu/pres sensor_msgs/FluidPressure

  IMU pressure data. Requires /sbg/pressure.

• /imu/pos_ecef geometry_msgs/PointStamped

  Earth-Centered Earth-Fixed position. Requires /sbg/ekf_nav.

• /imu/utc_ref sensor_msgs/TimeReference

  UTC time reference. Requires /sbg/utc_time.

• /imu/nav_sat_fix sensor_msgs/NavSatFix

  Navigation satellite fix for any Global Navigation Satellite System. Requires /sbg/gps_pos.

• /imu/odometry nav_msgs/Odometry

  UTM projected position relative to the first valid INS position. Requires /sbg/imu_data and /sbg/ekv_nav and either /sbg/ekf_euler or /sbg/ekf_quat. Disabled by default, set odometry.enable in configuration file.

[!NOTE] Please update the driver configuration to enable standard ROS messages publication. Also, the driver only publish standard ROS messages if the driver is setup to use ENU frame convention.

NMEA topics

The driver can publish NMEA GGA messages from the internal GNSS receiver. It can be used with third party NTRIP client modules to support VRS networks providers.

Disabled by default, set nmea.publish to true in .yaml config file to use this feature.

• /ntrip_client/nmea nmea_msgs/Sentence

  Data from /sbg/gps_pos serialized into NMEA GGA format. Requires /sbg/gps_pos.
  Namespace ntrip_client and topic_name nmea can be customized in .yaml config files.

Subscribed Topics

RTCM topics

The sbg_device node can subscribe to RTCM topics published by third party ROS2 modules.
Incoming RTCM data are forwarded to the INS internal GNSS receiver to enable DGPS/RTK solutions.

Disabled by default, set rtcm.subscribe to true in .yaml config file to use this feature.

• /ntrip_client/rtcm rtcm_msgs/Message

  RTCM data from /ntrip_client/rtcm will be forwarded to the internal INS GNSS receiver.
  Namespace ntrip_client and topic_name rtcm can be customized in .yaml config files.

sbg_device_mag node

The sbg_device_mag node is used to execute on board in-situ 2D or 3D magnetic field calibration.
If you are planning to use magnetic based heading, it is mandatory to perform a magnetic field calibration in a clean magnetic environnement.

Only ELLIPSE products support magnetic based heading and feature the on-board magnetic field calibration process.

Services

• /sbg/mag_calibration std_srvs/Trigger

  Service to start/stop the magnetic calibration.

• /sbg/mag_calibration_save std_srvs/Trigger

  Service to save in FLASH memory the latest computed magnetic field calibration.

HowTo

Configure the SBG device

The SBG Ros driver allows the user to configure the device before starting data parsing.
To do so, set the corresponding parameter in the used config file.

# Configuration of the device with ROS.
confWithRos: true

Then, modify the desired parameters in the config file, using the Firmware Reference Manual, to see which features are configurable, and which parameter values are available.

Configure for RTK/DGPS

The sbg_device node can subscribe to rtcm_msgs/Message topics to forward differential corrections to the INS internal GNSS receiver.

The RTCM data stream is sent through the serial/ethernet interface used by ROS to communicate with the INS.
This enables simple and efficient RTK operations without requiring additional hardware or wiring.

When combined with a third party NTRIP client, it offers a turnkey solution to access local VRS providers and get centimeter-level accuracy solutions.

The driver and the device should be properly setup:

• Configure the INS to accept RTCM corrections on the interface used by the ROS driver:
  • For ELLIPSE, simply use the sbgCenter and in Assignment panel, RTCM should be set to Port A.
  • For High Performance INS, either use the configuration web interface or the sbgInsRestApi.
• Install and configure a third party node that broadcast RTCM corrections such as a NTRIP client
• Update the node config yaml file to set rtcm.subscribe and nmea.publish to true
• If you use a different node to broadcast RTCM topics, you might have to update the config yaml file to update topics and namespaces.

Calibrate the magnetometers

ELLIPSE products can use magnetometers to determine the heading. A calibration is then required to compensate for soft and hard iron distortions due to the vehicle the product is installed on. The magnetic calibration procedure should be held in a clean magnetic environnement (outside of buildings).

You can read more information about magnetic field calibration procedure from the SBG Systems Support Center.

The ROS driver provides a dedicated node to easily use ELLIPSE on board magnetic field calibration algorithms.
The ELLIPSE offers both a 2D and 3D magnetic field calibration mode.

1) Make sure you have selected the desired 2D or 3D magnetic field calibration mode (calibration.mode in the configuration yaml file). 2) Start a new magnetic calibration session once you are ready to map the magnetic field:

ros2 launch sbg_driver sbg_device_mag_calibration_launch.py
ros2 service call /sbg/mag_calibration std_srvs/srv/Trigger

response: std_srvs.srv.Trigger_Response(success=True, message=’Magnetometer calibration process started.’)

3) Rotate as much as possible the unit to map the surrounding magnetic field (ideally, perform a 360° with X then Y then Z axis pointing downward). 4) Once you believe you have covered enough orientations, compute a magnetic field calibration:

ros2 service call /sbg/mag_calibration std_srvs/srv/Trigger

response: std_srvs.srv.Trigger_Response(success=True, message=’Magnetometer calibration is finished. See the output console to get calibration information.’)

5) If you are happy with the results (Quality, Confidence), apply and save the new magnetic calibration parameters.
If not, you can continue to rotate the product and try to perform a new computation (and repeat step 4)

ros2 service call /sbg/mag_calibration_save std_srvs/srv/Trigger

response: std_srvs.srv.Trigger_Response(success=True, message=’Magnetometer calibration has been uploaded to the device.’)

6) Reset/Power Cycle the device and you should now get an accurate magnetic based heading.

Enable communication with the SBG device

To be able to communicate with the device, be sure that your user is part of the dialout group.
Once added, restart your machine to save and apply the changes.

sudo adduser $USER dialout

Create udev rules

Udev rules can be defined for communication port, in order to avoid modifying the port in configuration if it has changed. Udev documentation

A symlink can be configured and defined to uniquely identify the connected device.
Once it is done, configuration file could be updated portName: "/dev/sbg".

See the docs folder, to see an example of rules with the corresponding screenshot using the udev functions.

Time source & reference

ROS uses an internal system time to time stamp messages. This time stamp is generally gathered when the message is processed and published. As a result, the message is not time stamped accurately due to transmission and processing delays.

SBG Systems INS however provides a very accurate timing based on GNSS time if available. The following conditions have to be met to get absolute accurate timing information:

• The ELLIPSE-N or D should have a connected GNSS antenna with internal GNSS enabled
• The ELLIPSE-E should be connected to an external GNSS receiver with a PPS signal
• A valid GNSS position has to be available to get UTC data
• The ELLIPSE internal clock should be aligned to PPS signal (clock status)
• The ELLIPSE should be setup to send SBG_ECOM_LOG_UTC message

You can select which time source to use with the parameter time_reference to time stamp messages published by this driver:

• ros: The header.stamp member contains the current ROS system time when the message has been processed.
• ins_unix: The header.stamp member contains an absolute and accurate time referenced to UNIX epoch (00:00:00 UTC on 1 January 1970)

Configuration example to use an absolute and accurate time reference to UNIX epoch:

# Time reference:
time_reference: "ins_unix"

Frame parameters & conventions

Frame ID

The frame_id of the header can be set with this parameter:

# Frame name
frame_id: "imu_link_ned"

Frame convention

The frame convention can be set to NED or ENU:

• The NED convention is SBG Systems native convention so no transformation is applied
• The ENU convention follows ROS standard REP-103

Please read the SBG Systems Support Center article for more details.

You can select the frame convention to use with the following parameter:

# Frame convention
use_enu: true

[!NOTE] The driver only publish standard ROS messages if the driver is setup to use ENU frame convention.

Body/Vehicle Frame:

The X axis should point the vehicle forward direction for both NED and ENU frame conventions. The table below summarizes the body/vehicle axis frame definitions for each convention:

Navigation Frame:

The navigation frame also referred by ROS as the cartesian representation is defined as follow:

Heading Example:

Based on the definitions above, when using a NED frame, if the vehicle X axis is pointing North, the INS should return a zero heading. When using a ENU frame, the INS should return a zero heading when the vehicle X axis is pointing East.

Troubleshooting

If you experience higher latency than expected and have connected the IMU via an USB interface, you can enable the serial driver low latency mode:

/bin/setserial /dev/<device> low_latency

Contributing

Bugs and issues

Please report bugs and/or issues using the Issue Tracker

Features requests or additions

In order to contribute to the code, please use Pull requests to the devel branch.
If you have some feature requests, use the Issue Tracker as well.

Changelog for package sbg_driver

3.2.0 (2024-10-17)

• Update README with ROS2 commands to launch magnetic calibration
• Fix segfault when running magnetic calibration
• Removed unused flags from SbgEkfStatus message
• Added new flags to SbgShipMotionStatus message
• Improved SbgStatusAiding message with new flags
• Improved SbgPosStatus message with new flags
• Improved SbgEkfStatus message with new flags
• Improved SbgStatusGeneral message with datalogger and cpu flags
• Updated documentation for sbgGpsPos message
• Updated documentation for sbgGpsHdt message
• Improved SbgUtcTime message with internal clock quality indicators
• Improved SbgStatusCom message with ethernet tx and rx status
• Improved SbgGpsHdt message with number of SV tracked and used
• Improved SbgGpsPos message with numSvTracked
• Improved SbgGpsPosStatus message with spoofing, jamming and OSNMA status
• Updated config files with new messages
• Removed obsolete documentation
• Updated published topic list
• Added missing topic names
• Updated dependencies requirement
• Added settings log_ekf_rot_accel_body / log_ekf_rot_accel_ned / log_ekf_vel_body
• Fixed functions description
• Added SbgEkfRotAccel body and NED messages
• Added SbgEkfVelBody message
• Fixing compiling issues
• Updated sbgECom lib with version 4.0-1987-stable
• Fixed typos about lever arm
• Fixed config applier for IMU Alignment / Aiding / Odometer lever arms
• Remove boost dependency (cherry picked from commit ab54c33f1e442c3737dd8e1c09a8b6f36c2c1afa)
• Cleanup
• Moved LLAtoECEF into a helper
• Variable naming
• WIP code cleanup
• Class documentation
• Code indentation
• Utm as class
• Indentation fix
• Updated sbg_utm documentation and function prototype
• Added documentation on Utm structure
• Added documentation on Position class
• Added Position class
• Factory for UTM data
• Fixed space / tabluations issues
• Code indentation
• SbgUtm documentation
• Using fma for computation
• Added constexpr to some variables
• Using pow instead of multiply
• Reworked createRosPointStampedMessage computations
• Removed sendTransform in fillTransform method
• Moved functions into helper namespace
• Moved UTM initialization into its own class
• Removed catkin reference in CMakeLists.txt
• Updated naming convention
• Improved ENU/NED documentation
• Disabling ROS standard message when in NED frame convention
• Reverted NED to ENU quaternion conversion
• Quaternion: cleaner version for NED to ENU conversion
• Reworked odometry message
• Quaternion: NED to ENU conversion rework
• Updated readme about ENU frame convention
• Reworked angle wrapping functions
• Added range for Euler angle measurement.
• More explicit naming for quaternions
• Reverted NED to ENU array conversion
• Documentation update
• odom->base_link is now correct in NED mode
• Renamed function.
• Fixed variable inversion.
• odom->base_link is now correct in NED mode
• Refactored NED to ENU array conversion
• Updated ROS messages documentation
• Fixed Euler / Quaternion orientation in ENU mode
• Fixed nmea output condition
• Compilation fixes
• NTRIP: GGA generation Work In Progress with the following fixex:
  • GPS to UTC time correctly apply leap second offset
  • GGA only sent if a valid position is available
  • GGA is sent at 1 Hz only

  - Minor improvements Code is not yet tested nor build

• Compilation fix
• Improved GGA generation and code cleanup
• Improved RTCM and NMEA parameters naming
• Code cleanup - removed (void) as it is not recommended in C++
• Reworked and improved main project README and small fixed in yaml examples
• Added documentation about RTCM messages and device configuration.
• Removed MessageSubscriber class
• Switched dependency from mavros_msgs to rtcm_msgs
• Updated documentation
• Removed SbgInterface as class member
• Removed threaded subscription.
• Namespace related coding style fix
• Fixes in GGA serialization
• Realigned members.
• Code documentation
• Improved NMEA GGA message
• Added rtcm / nmea parameters in config files
• Fixed deprecated header warning
• Added publisher for nmea msg
• Added subscription to RTCM msg
• remove build status
• fix build on Windows
• time_reference parameter fix
• Fix deprecated use of rosidl_target_interfaces The use of rosidl_target_interfaces is deprecated (see [Humble release notes](http://docs.ros.org.ros.informatik.uni-freiburg.de/en/humble/Releases/Release-Humble-Hawksbill.html#deprecation-of-rosidl-target-interfaces). Here that actually causes an issue with CMake not setting the right include directory paths, breaking [colcon build]{.title-ref} on humble. This applies the documented update, making the driver build under Humble
• Contributors: Michael Zemb, Raphael Siryani, Samuel Toledano, SanderVanDijk-StreetDrone, Timon Mentink, VladimirL, cledant, rsiryani

3.1.0 (2021-10-18)

• Add imu/odometry publisher
  • Fix dependencies
  • Fix wrong SbgGpsHdt description
  • Update doc
  • Add missing MIT licences
  • Based on release 3.1 of ros1 driver
• Add ENU/NED option, rework frame IDs, time stamps and driver frequency.
  • Add parameters to set frame ID and ENU convention
  • Add a parameter to select header stamp source and read ROS time when publishing the message
  • Remove node ros::Rate period auto computation and only read it from a node parameter
  • Update documentation and messages definitions
  • Fix timeStamp value initializing in SbgEkfNavMessage
  • Based on release 3.0.0 of ros1 driver
• update maintainer
• print interface details at startup
• fix configuration files
• Contributors: Michael Zemb, Raphael Siryani

1.0.1 (2020-07-09)

• Update Licenses
• First version