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12 - VB3i IMU Integration - Roof Mount

When using the IMU roof mount, the user has the option to translate the data from the roof to another point on the vehicle. By default, when the roof mount is enabled, a 1 m Z offset is added, translating the filtered speed down in to the vehicle, towards the centre of gravity.


If the Kalman Filter data is required relative to an alternate or more precise location on the vehicle, then measurements should be made from the centre of the IMU to the desired location. As the IMU is housed within the enclosure, precise measurements are not easy to make. So a Z measurement can be taken from the centre of the GPS antenna, provided 3 cm is subtracted from the physical measurement. Translation measurements need to be made in all 3 axis, X, Y and Z.

Required equipment

VB3i (IMU04 ready)
VBOX Tools
RLCAB119 VBOX – IMU connecting cable
RLCAB001 / RLCAB066-2 – VB3i PC connection cable
VBOX Manager (optional)

Hardware Setup

Important note: IMU04 must be connected to VB3i before power is applied to ensure data is correctly synchronised.

  1. Fit the VBOX 3i into the test vehicle, and mount the IMU roof mount on the vehicle roof.
  2. Connect antenna from IMU roof mount to the primary antenna of the VB3i (antenna A).
  3. Connect RLCAB119 cable from left hand port on roof mount IMU (CAN/KF) to VBOX 3i-V3/V4 25W D analogue input port.
  4. Take data translation measurements in X, Y and Z axis from centre of IMU, if required.  Default 1m under IMU.
  5. After IMU is connected, apply power to VBOX 3i.
  6. Enable IMU integration using either VBOX Manager or VBOX Tools - VBOX Setup.
VBOX 3i-V3/V4 and IMU04


Setup using VBOX Tools

  1. Ensure IMU04 is connected via RLCAB119, and the VBOX 3i is powered on.
  2. Connect VBOX 3i to PC using RLCAB001 or RLCAB066-2 cable (RS232 or USB).
  3. Open VBOX Tools and connect to VBOX 3i by selecting COM Port (Options from Toolbar).
  4. Run VBOX Setup.
  5. Ensure 'High Dynamics' GPS Optimisation is selected, and log rate is set to 100 Hz (Logging tab).
  6. Tick 'Use IMU' box. Once VBOX Tools has completed the initial enabling, tick the Roof mount box.

  7. Enter the distances measured from IMU to required translation point.
  8. If using IMU04, IMU Attitude channels (Head_imu, Pitch_imu and Roll_imu) will automatically be set to log.  If IMU Attitude data is required to be displayed as a Live Serial data display then the user must tick the channels for Send over serial.

  9. Perform initialisation and full calibration procedure before commencing testing.

Setup using VBOX Manager

1. Ensure IMU04 is connected via RLCAB119, and the VBOX 3i is powered on.

2. Enter SETUP, select 'IMU-INS'then click on 'ENABLE ROOF MNT'.  

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3. Once OK confirmation screen has cleared, ENABLE IMU and ENABLE ROOF MNT should be ticked.
4. Apply IMU TRANSLATION using IMU to translation point measurement distances.

5. IMU Attitude and 3 Axis Modules channels will be automatically set to log. If IMU Attitude or 3 Axis data is required to be displayed as a Live Serial data display (with VBOX Tools) then the user must enter VBOX Setup and tick the channels for 'Send over serial'.

6. Perform initialisation and full calibration procedure before commencing testing.

7. If the IMU is not mounted on a flat surface, perform ANGLE OFFSETS calibration. This will zero the Pitch_imu and Roll_imu channels. Calibration must be performed after the calibration has been completed, and the vehicle is static on a level surface.

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When using IMU integration, an initialisation phase is required when the IMU is first connected to the VBOX after being set up. This will be run through automatically after the VBOX has successfully gained satellite lock. When the IMU LED on VB3i front panel has turned a flashing green, the initialisation is complete.

Note: If you are using a VB3i-V1, which has no IMU LED, read the LED indicators section below for LED behaviour. 

LED Indicators VBOX 3i (V2/V3/V4) and IMU04

VBOX 3i LED Solid Orange Flashing Orange Flashing Green Solid Green
IMU IMU enabled, no IMU connected. SAT lock OK. 30 second stationary initialisation in progress. If vehicle moves, LED will continue to flash until 30 seconds stationary completed. Initialisation complete – movement not yet detected. Movement detected – IMU integration working OK.
IMU04 LED Red Orange Green
Power Initial boot up phase Temperature checks. If temperature outside optimum operation range, LED will remain orange. Fully operational.
Coms No coms Using IMU integration, inertial data being sent to host VBOX via RS232. Inertial data being sent to host system via CAN.
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Last modified
14:59, 13 Feb 2017


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