A common test for evaluating the performance of braking systems is the trigger activated test to standstill. A trigger switch is added either to the face of the brake pedal, or into the electrical system system, to detect when the brake pedal has been pressed. This signals the start of the test and it ends when the vehicle comes to a complete stop. The distance between these two points is then calculated to measure braking performance. The VBOXTools software then applies the necessary maths and the average (or MFDD) deceleration is calculated.
As this test starts when the pedal is pressed, it measures both the response of the braking system, as well as the performance of the tyre, brake pads, discs and other components.
In a trigger activated test, it is critical to accurately capture the point at which the brake pedal is pressed because the vehicle is usually traveling quite fast at this point. The VBOX 3i uses a very sophisticated method which measures this to within 25 billionth of a second!
Another popular assessment of performance is the brake test between two different speeds. ADR 35 - heavy Vehicle braking - specifies a formula for determining the start and finish speeds. A choice can then be made to either stop froma slower speed to zero, or a higher speed to a lower speed.
Again, the Software can be utilised to provide the necessary test Start and End parameters and provide the output results.
This involves both sides of the vehicle running on different surfaces to determine how the braking system copes with different levels of traction. This test also allows engineers to analyse the stability of the vehicle. It is also a certification requirement for ABS systems as part of ADR 31 (ECE R13H) and ECE R78.
In this example of a split mu brake stop, one side of the vehixle is braking on a low mu wet tile and the opposite side a wet bitumen surface. The design rule specifies the minimum performance requirements of the ABS system under these conditions.
However, the integration of an IMU04 with a suitably upgraded VBOX 3i can be used to counteract this 'lever-arm' effect by placing the IMU at the COG, which measures the vehicle pitch as it brakes. This data, when combined with that from GPS, provides a compensation for the overshoot and allows for consistent brake stop testing.
VBOX test equipment enables you to capture pedal force and travel sensor outputs via analogue inputs at 500Hz.