Inertial Sense ROS

A ROS wrapper for the InertialSense uINS3 RTK-GPS-INS and Dual GPS (GPS Compassing) sensor.

NOTICE:

To use this node, the uINS should be updated with the latest firmware found on the Inertial Sense release page. Download the appropriate .hex file and use the firmware_update ROS service to update the firmware

rosservice call /firmware_update ~/Download/IS_uINS-3_<...>.hex

Installation

This ROS package, uses the inertial-sense-sdk as a submodule. Clone this package into the catkin workspace src folder, then pull the submodule.

mkdir -p catkin_ws/src
cd catkin_ws/src
catkin_init_workspace
git clone https://github.com/inertialsense/inertial_sense_ros
cd inertial_sense_ros
git submodule update --init --recursive
cd ../..
catkin_make

Running the Node

rosrun inertial_sense inertial_sense_node

The user must be a member of the dailout group, or the user won’t have access to the serial port.

For instructions on changing parameter values and topic remapping from the command line while using rosrun refer to the Remapping Arguments page. To set vector parameters, use the following syntax:

rosparam set /inertial_sense_node/GPS_ref_lla "[40.25, -111.67, 1556.59]"
rosrun inertial_sense inertial_sense_node

To set parameters and topic remappings from a launch file, refer to the Roslaunch for Larger Projects page, or the sample launch/test.launch file in this repository.

Time Stamps

If GPS is available, all header timestamps are calculated with respect to the GPS clock but are translated into UNIX time to be consistent with the other topics in a ROS network. If GPS is unvailable, then a constant offset between uINS time and system time is estimated during operation and is applied to IMU and INS message timestamps as they arrive. There is often a small drift in these timestamps (on the order of a microsecond per second), due to variance in measurement streams and difference between uINS and system clocks, however this is more accurate than stamping the measurements with ROS time as they arrive.

In an ideal setting, there should be no jump in timestamps when GPS is first acquired, because the timestamps should be identical, however, due to inaccuracies in system time, there will likely be a small jump in message timestamps after the first GPS fix.

Topics

Topics are enabled and disabled using parameters. By default, only the ins topic is published to save processor time in serializing unecessary messages.

• ins(nav_msgs/Odometry)
  • full 12-DOF measurements from onboard estimator (pose portion is from inertial to body, twist portion is in body frame)
• imu(sensor_msgs/Imu)
  • Raw Imu measurements from IMU1 (NED frame)
• gps(inertial_sense_ros/GPS)
  • unfiltered GPS measurements from onboard GPS unit
• gps/info(inertial_sense_ros/GPSInfo)
  • sattelite information and carrier noise ratio array for each sattelite
• mag (sensor_msgs/MagneticField)
  • Raw magnetic field measurement from magnetometer 1
• baro (sensor_msgs/FluidPressure)
  • Raw barometer measurements in kPa
• preint_imu (inertial_sense_ros/DThetaVel)
  • preintegrated coning and sculling integrals of IMU measurements
• RTK/info (inertial_sense_ros/RTKInfo)
  • information about RTK status
• RTK/rel (inertial_sense_ros/RTKRel)
  • Relative measurement between RTK base and rover

!!! important RTK positioning or RTK compassing mode must be enabled to stream any raw GPS data.

• gps/obs (inertial_sense_ros/GNSSObservation)
  • Raw satellite observation (psuedorange and carrier phase)
• gps/eph (inertial_sense_ros/GNSSEphemeris)
  • Satellite Ephemeris for GPS and Galileo GNSS constellations
• gps/geph
  • Satellite Ephemeris for Glonass GNSS constellation

Parameters

• ~port (string, default: “/dev/ttyUSB0”)
  • Serial port to connect to
• ~baudrate (int, default: 921600)
  • baudrate of serial communication
• ~frame_id (string, default “body”)
  • frame id of all measurements
• ~LTCF (int, default: 0)
  • Local Tangent Coordinate Frame: 0 - NED, 1 - ENU

Topic Configuration

• ~navigation_dt_ms (int, default: Value retrieved from device flash configuration)
  • milliseconds between internal navigation filter updates (min=2ms/500Hz). This is also determines the rate at which the topics are published.
• ~stream_INS (bool, default: true)
  • Flag to stream navigation solution or not
• ~stream_IMU (bool, default: false)
  • Flag to stream IMU measurements or not
• ~stream_baro (bool, default: false)

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