Using the Complete Automotive Testing System for Brake Testing

Installation in a vehicle:

The system can be quickly set-up in a vehicle. The roof mounted antenna assembly also contains the inertial sensor, so correct installation of this assembly is critical to achieving maximum accuracy from the system.

Antenna (Sensor) Assembly

The roof mounted sensor assembly should be mounted to meet the following criteria:

  • It must be mounted on an area of the roof with high stiffness, this is typically on the leading or trailing edge of the roof. Do not mount in the centre of the roof.
  • The cable should exit from the roof assembly towards the rear of the car
  • Typically the unit should be on the centre line of the car
  • The unit should be within 10 degrees of level in the pitch direction
  • The unit should be as level as possible with regards the roll direction

Main Units

The main electronics unit can be mounted almost anywhere in the vehicle, subject to keeping it away from sources of high radio interference, high vibration, and high temperature. It doesn’t need to be mounted in any particular orientation.

Display

The DASH4PRO is typically mounted on the windscreen. Note that there are 2 types or DASH4PRO, using either OLED or LCD display technology. The OLED is clearer, but will “wash out” is there is sunlight directly on the screen. The LCD type is slightly less clear, but remains usable in all lighting conditions.

System initialisation:

Once the system is installed in the vehicle the system needs to be initialised before you can start any brake testing. The procedure is very simple and typically takes a few minutes.

  • Power up the system. At this stage the DASH4PRO will report the firmware versions, and report any system errors.
  • Allow the system to get a GPS fix, with a clear view of the sky this takes about 30 seconds to 1 minute. The number of satellites are displayed on the DASH4PRO.
  • The vehicle now needs to be driven to allow the INS system to “converge”. For initial INS convergence no particular driving manoeuvres are needed, and typically 2 minutes of normal driving is sufficient.

Display – Standard Layout Brake Testing

The DASH4PRO screen is highly configurable, it’s possible to display any parameter anywhere on the screen in a range of font sizes. Further, it’s also possible to add on almost any text messages, bar charts, alarms, user defined equations and functions for the LEDs. The display is supplied with a default configuration that has been developed in conjunction with existing users which suits many brake test application requirements. If you want to change any aspect of the DASH4PRO behaviour, then please refer to the DASH4PRO configuration software.

  1. The “LOG” text is displayed when the DL2 is currently logging
  2. Number of satellites; note that this only counts the number of satellites that have a high enough quality to be fully used in the solution. Satellites that are very low in the sky, WAAS satellites, or satellites with a poor signal to noise ratio are not counted.
  3. Convergence, this goes from 0 to 100%, 0% means the INS system has not started to converge, 100% means the system is fully converged and all data is available, although not necessary at full accuracy.
  4. System accuracy, this goes from 0% to 100%. 0% means minimum accuracy, or not converged. 100% means the system has recently seen some high dynamics and the GPS system has a good view of the sky and as such the system is operating near its maximum accuracy. In practice, for a very typical 100kph brake test error will be in the range of 10cm for a reported accuracy of 50%, down to a few cm at a reported accuracy of 100%.
  5. Speed, this is the current measured speed, note that this will display “0.0” until the INS system is converged.
  6. Screen number.
  7. T is displayed when the trigger input is active, this is used for testing the input is connected properly.
  8. Test status, this is either: Prepare to test, this means that the initial test conditions have not been met, for example the vehicle is not going quickly enough to start the brake test. Test armed, this means that the initial test conditions are met and the test can be started. Test in progress, this means that a test is underway.
  9. This is the path distance of the last test completed.
  10. This is the estimated accuracy of the last test completed.
  11. These LEDs indicate the system accuracy, with all LEDs illuminated the system is at full accuracy.
  12. These LEDs indicate the test status. All red LEDs means the system is ready and the brake test can start, all green LEDs means that the braking test is currently in progress.

System Reported Accuracy

What good is a measurement if you have no idea how accurate it is?

The Complete Automotive Testing System and all SPEEDBOX-INS products continuously monitor their own performance and report the maximum error for each test. The maximum error is calculated based on many factors, including GPS quality, using an advanced statistical model. After each brake test the system reports both the braking distance and maximum error, for example 42.33m braking distance and +/-3cm maximum error. Engineers and QA Managers can now for the first time be certain that results are valid and measured to an acceptable standard.

System Accuracy (From independent testing)

Independent brake testing results from 60 tests (10 each of 6 different tests)*

Our Complete Automotive Testing System (CATS) has been extensively tested by Race Technology and also completely independently for both speed accuracy, and accuracy for braking tests. The results shown above are taken from the independent testing so give a good indication of typical distance error for the different test conditions and start speeds.