Using VB3i with Wheel Speeds
Introduction
GPS measurement of speed, position and acceleration has become an essential part of the process in assessing the performance of many aspects of a vehicle. Test tracks are rarely perfect places for satellite reception, with trees, bridges and tunnels all having an effect on the quality of the measured data. When the tests are carried out on the road, this problem becomes even greater, with more objects obscuring the direct view to the satellites.
VB3i can limit these obstacles by utilising the latest multi-frequency, multi-constellation GPS receiver and integrating inertial and vehicle speed data.
Accuracy within a built-up urban area
An added advantage of using multi-frequency techniques is the time taken to recover accuracy after a bridge or tunnel is often less than 2 seconds. In areas where there is no view of the sky at all, such as tunnels, inertial sensors and wheel-speeds can fill in the gaps for periods of up to 5 minutes.
Accuracy through tunnel
In the data above, you can clearly see the difference that the inertial and wheel-speed data is making to the accuracy of the estimated trajectory, with the IMU doing a good job of estimating the position during the tunnel, ending up with a 15 m error at the end (purple trace). Adding the wheel-speeds into the system (blue trace) significantly reduces the errors, tracking the vehicle through the tunnel with great accuracy.
Configuration
It is necessary to ensure VB3i is configured for wheel speed use, please follow the instructions below.
IMU Integration
Ensure that VB3i is correctly connected to the IMU04, instructions for in-vehicle mounting can be found here, and roof mounting here.
IMU Integration needs to be 'Enabled', this can be done via the VBOX Setup Software or using the VBOX Manager.
Once IMU Integration has been Enabled, it is important to perform the full calibration procedure before meaningful testing commences. The calibration procedure is a series of specific manoeuvres that should be performed to help the Kalman Filter characterise the outputs from the IMU. More information on this is available here.
VBOX Setup Software
- Ensure IMU04 is connected via RLCAB119 and the VBOX 3i is powered on.
- Connect VB3i to a computer either via Bluetooth, an RLCAB001 cable to the 'SER' input and the computer's serial port (usb-serial adapter may be required), or via an RLCAB066-2 cable to one of the computer's USB ports.
- Open VBOX Setup and connect to VB3i by selecting the correct COM Port.
- Select the 'IMU' menu and then the 'Settings' tab.
- Select 'Enabled' within the 'IMU integration' section.
- If you are using a roof mounted IMU solution, ensure Roof mount is 'Enabled'.
- Enter the Antenna to IMU/ reference offsets, more information on this is available here.
- Select 'Write to unit' to save the settings.
VBOX Manager
- Ensure IMU04 is connected via RLCAB119 and the VBOX 3i is powered on.
- Connect VBOX Manager to the VBOX.
- Enter the 'SETUP' menu of VBOX Manager.
- Select 'IMU-INS' and then click on the 'IMU Integration' menu.
- Enter the 'SETUP' menu of VBOX Manager.
- Select 'IMU-INS' and then click on the 'IMU Integration' menu.
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- Scroll to 'Enable' and select. Once the 'OK' confirmation screen has cleared, 'Enabled' will be displayed.
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- If you are using a roof mounted IMU solution, ensure Roof mount is 'Enabled'.
- Enter the Antenna to IMU/ reference offsets, more information on this is available here.
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Wheel Speed Inputs
In order to obtain the wheel speed information, the best solution is to use the sensors already fitted to the vehicle by connecting to the vehicle’s CAN bus by using an RLCAB069L, RLCAB015L or RLACS182L cable. Before testing commences, ensure that the VB3i unit is correctly connected to either the speed sensors or to the vehicle CAN bus.
Wheel speed input needs to be 'Enabled' and configured, this can be done via the VBOX Setup Software or using the VBOX Manager. However, wheel speed CAN inputs can only be configured using VBOX Setup Software.
VBOX Setup Software
- Ensure IMU04 is connected via RLCAB119, and the VBOX 3i is powered on.
- Connect VBOX 3i to a computer either via Bluetooth, an RLCAB001 cable to the 'SER' input and the computer's serial port (usb-serial adapter may be required), or via an RLCAB066-2 cable to one of the computer's USB ports.
- Open VBOX Setup and connect to VBOX 3i by selecting COM Port.
- Select the 'IMU' menu and then the 'Wheel speed input' tab.
- Select 'Enabled' within the 'Wheel speed input' section.
- Enter the Antenna to wheel reference point offsets, these are the x,y,z distances (m) between wheel speed reference point and the antenna. The reference point is the centre point between the rear wheels, as shown in the image below.
- Use the Wheel speed 1 and 2 'Configure' buttons to open up the CAN setup area where you can load in a .dbc file or manually set up the CAN parameters by selecting the 'User' option. Alternatively, selecting 'Vehicle database' enables you to browse the Racelogic Vehicle CAN database within the software and select your vehicle. Once selected, CAN channels specific to your vehicle will appear on the left. If available, CAN connection information for the vehicle will also appear on the right of the window. Click on a wheel speed channel and select 'OK' to save the configuration. Repeat for the other wheel speed channel.
- Select 'Write to unit' to save the settings.
VBOX Manager
- Ensure IMU04 is connected via RLCAB119, and the VBOX 3i is powered on.
- Connect VBOX Manager to the VBOX.
- Enter the 'SETUP' menu of VBOX Manager.
- Select 'IMU-INS' and then click on the 'IMU Integration' menu.
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- Scroll to the 'Wheel Speed' menu and select.
- Choose 'Enable' and select. Once the 'OK' confirmation screen has cleared, 'Enabled' will be displayed.
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- Scroll to the 'Ant to Wheel' menu and enter the distances measured between the wheel speed reference point and the antenna. The reference point is the centre point between the rear wheels, as shown in the image above.
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- Before testing commences, ensure that the wheel speed CAN inputs have been configured through VBOX Setup Software.
Dynamic Mode
The dynamic mode should be set as 'High', this can be done via the VBOX Setup Software or using the VBOX Manager. More information on Dynamic Modes is available here.
VBOX Setup Software
- Ensure VB3i is powered.
- Connect VB3i to a computer either via Bluetooth, an RLCAB001 cable to the 'SER' input and the computer's serial port (usb-serial adapter may be required), or via an RLCAB066-2 cable to one of the computer's USB ports.
- Open VBOX Setup and connect to VB3i by selecting the correct COM Port.
- Select the 'GPS' menu and then the 'Settings' tab.
- Select 'High dynamics' from the 'GNSS optimisation' options.
- Select 'Write to unit' to save the settings.
VBOX Manager
- Ensure IMU04 is connected via RLCAB119 and the VBOX 3i is powered on.
- Connect VBOX Manager to the VBOX.
- Enter the 'SETUP' menu of VBOX Manager.
- Scroll to 'Dynamic Mode', select and then choose 'High', press to confirm.
Elevation mask
It may also be necessary to adjust the Satellite Elevation Mask dependent on the environment, more information on this is available here.