Installing the SPEEDBOX +RTK+IMU
The installation instructions in this section apply to the SPEEDBOX +RTK+IMU.
The following checklist is designed to be a quick reference for connecting the system in day-to-day usage. It is recommended that the more detailed explanations of each step are read in their entirety before initially installing the unit.
- Ensure the power is disconnected.
- Secure the unit safely in the vehicle, taking careful note of the mounting orientation.
- Mount the antennas on the vehicle roof as detailed in the diagrams below – do not crush the cable in the doors or windows.
- Connect the rear antenna to “RF 1” and the front antenna to “RF 2”
- Connect the power to a fused 9 – 30V DC supply, e.g. a “cigarette-lighter” type plug, or other fused power supply.
Mounting the SPEEDBOX Base Unit
An engineering drawing of the SPEEDBOX is included here.
In order to give accurate speed and acceleration readings, the SPEEDBOX base unit should be mounted so that it is flat, level, in the correct orientation, protected from vibration, as close as possible horizontally to the antenna, and restrained from moving relative to the vehicle. The SPEEDBOX (+RTK)+IMU option uses a high accuracy Inertial Measurement Unit located within the main SPEEDBOX unit, so to achieve the higher accuracy results the mounting of the unit is of paramount importance.
Correct orientation of the unit is essential. The unit must be mounted with the direction of travel as shown by the arrows on the top of the unit. When mounted correctly the longitudinal acceleration will read positive whilst accelerating and negative whilst braking.
The unit should be mounted as flat and level as possible. The combined speed calculation will compensate for a mounting angle of up to 20° from level, but accuracy is slightly reduced, so for best accuracy mount as level as possible. Neither the raw 20Hz GPS position and speed outputs nor the angular measurements from the RTK option are sensitive to the mounting orientation or level.
Mounting the GPS Antennas – RTK Option
The RTK option requires 2 separate antennas to be mounted at set distance apart. The default distance between the antennas is 800mm, (though this can be changed if required and the new baseline distance set up in the software). The antennas must be installed on the vehicle with the correct baseline distance, otherwise the RTK solution will fail.
It is vitally important that both of the antennas used are of the same type. Using two different types of antenna may cause the RTK solution to fail.
A magnetic template is supplied to assist with installation, setting the antenna baseline to 800mm, with the antennas oriented correctly and the antennas labelled correctly for the direction of travel:
Figure 1. Magnetic mounting template for 2 separate antennas (RTK option only)
Figure 2. Mounting arrangement for 2 separate antennas (RTK option only)
The general arrangement for mounting two antennas for the RTK unit is shown in Figure 2 above. Both antennas should be mounted on the roof of the vehicle, on the vehicle centreline. The distance between them must be measured, and must be the same as the configured baseline length (this can be changed using the configuration software to match the measured distance if required). The rear antenna is the “base” antenna, and must be connected to “RF 1” on the unit. The forward antenna is the “moving” antenna, and must be connected to “RF 2” on the unit. If the antennas are connected the wrong way around, the unit will not reliably obtain an RTK solution when the vehicle is moving. Both antennas should be mounted in the same orientation; i.e. the cable should emerge from the same side of both antennas to minimise the effect of antenna “phase centre”. It is also absolutely essential that the antennas are of the same type, model and manufacturer.
Setting up the SPEEDBOX Antenna Offset
For firmware newer than v3.7.3 a lever arm can be set up between the antenna location and the SPEEDBOX unit containing the accelerometers (SPEEDBOX-INS systems do not need to set this lever arm) the unit uses this information to model the dynamics of vehicle pitch to produce increased accuracy through braking tests that feature pitching movement either during or immediately prior to the test. This offset is optional, but is highly recommended for braking tests.
SPEEDBOX Antenna Offset option in v4.2.8 or later SPEEDBOX Configuration Utility Software
Note: Measurements shown are only an example, actual values must be measured from your installation. Measurements must be made to the rear "Base" antenna connected to Rf 1.
Setting up the SPEEDBOX Measurement Offset
For firmware newer than v3.7.3 a measurement offset can be set up, allowing the SPEEDBOX unit to model the dynamics of the vehicle, referencing the measurement to a specific point on the vehicle, a separate component such as a laser barrier used for triggering a test, or a reference system for direct comparison. Configuring this function correctly results in increased accuracy.
SPEEDBOX measurement output offset in v4.2.8 or later SPEEDBOX Configuration Utility Software
Note: Measurements shown are only an example, actual values must be measured from your installation.
For both the SPEEDBOX lever arm and measurement offset, the locations are referenced to the SPEEDBOX unit. Measure the distances below, ahead (and right for INS units), using negative values for opposite directions, and input these into the configuration software (v4.2.8 or later).
The SPEEDBOX requires a stable DC power supply, which must be in the range 9 – 30V. This should be connected to the cable loom assembly that is supplied with the SPEEDBOX via a fused connection to the vehicle. A 1A fast blow type fuse is recommended. Once connected to the power supply, the SPEEDBOX will automatically power up and commence its initialisation routine. The current consumption of the SPEEDBOX ranges from approximately 230mA @ 12V for the standard SPEEDBOX to 400mA @ 12V for the SPEEDBOX-INS. More current may be drawn during startup.
Unreliable power supplies are a common source of problems. In the event of any problems, please check the reliability of the power source or try an alternative supply in the first instance. The SPEEDBOX may also be powered from an external battery pack. If you require a battery pack, Race Technology keeps a wide selection in stock - please contact us with your requirements. Because of the current supply requirements, only rechargeable batteries should be used. Disposable cells are not suitable.