Using VBOX 3iS with Wheel Speeds for Urban Use
Introduction
GNSS 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.
VB3iS can limit these obstacles by utilising the latest multi-frequency, multi-constellation GNSS 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 VB3iS is optimally configured for urban use, please follow the instructions below.
IMU Integration
IMU Integration needs to be 'Enabled', this can be done via the VBOX Setup Software, the Front Panel of the unit 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 VB3iS is powered.
- Connect VB3iS to a computer using the supplied loom, connect an RLCAB001 cable to the 'CONFIG' lead and connect the serial plug to the computers serial port – this can be done via a serial > USB convertor if required.
- Open VBOX Setup and connect to VB3iS 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 an External IMU, select 'External' within the 'Location' 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.
- If the Internal IMU is being used, select the 'Orientation' tab and ensure that the sides of the unit facing down and forward are indicated correctly.
- Select 'Write to unit' to save the settings.
Front Panel
- Press the 'OK' button to enter the menu, navigate to 'IMU' using the 'Down' arrow and then press the 'OK' button.
- Press the 'OK' button again to Enable IMU Integration.
- 'Enabled' will then be displayed.
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- If you are using an External IMU, navigate to 'IMU Location' using the 'Down' arrow and press the 'OK' button. Use the 'Down' arrow to select 'External' and press the 'OK' button to confirm. If you are using a roof mounted IMU solution, ensure Roof Mount is 'Enabled'.
- Navigate to 'Ant to IMU/Ref. Offset' using the 'Down' arrow, press the 'OK' button to enter the menu. Use a combination of the 'Up' and 'Down' arrows and the 'OK' button to enter the measured ahead/behind, right/left and above/below offset values, more information on this is available here.
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- If the Internal IMU is being used, navigate to 'Side facing down' using the 'Down' arrow and press the 'OK' button to enter the menu. Use the 'Up' and 'Down' arrows to ensure the correct side is indicated and press the 'OK' button to confirm. Repeat for 'Side facing forwd'.
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. Before testing commences, ensure that the VB3iS unit is correctly connected to either the speed sensors or to the vehicle CAN bus using the 'CAN' D type connector lead on the supplied loom.
- Ensure VB3iS is powered.
- Connect VB3iS to a computer using the supplied loom, connect an RLCAB001 cable to the 'CONFIG' lead and connect the serial plug to the computers serial port – this can be done via a serial > USB convertor if required.
- Open VBOX Setup and connect to VB3iS by selecting the correct 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 offsets, these are the x,y,z distances (m) between the antenna and the wheel speed reference point. 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.
Dynamic Mode
The dynamic mode should be set as 'High', this can be done via the VBOX Setup Software, the Front Panel of the unit or using the VBOX Manager. More information on Dynamic Modes is available here.
VBOX Setup Software
- Ensure VB3iS is powered.
- Connect VB3iS to a computer using the supplied loom, connect an RLCAB001 cable to the 'CONFIG' lead and connect the serial plug to the computers serial port – this can be done via a serial > USB convertor if required.
- Open VBOX Setup and connect to VB3iS by selecting the correct COM Port.
- Select the 'GNSS' menu and then the 'Settings' tab.
- Select 'High dynamics' from the 'GNSS optimisation' options.
- Select 'Write to unit' to save the settings.
Front Panel
- Press the 'OK' button to enter the menu, navigate to 'GNSS' and press the 'OK' button.
- Navigate to 'Dynamic Mode' using the 'Up' and 'Down' arrows. It will display whichever mode has been previously set.
- To change the setting, press the 'OK' button then select 'High' using the 'Up' arrow.
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- Press the 'OK' button again 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.