When conducting VBOX Touch deceleration tests using a VBOX Brake Pedal Trigger, an 'MFDD' channel is created and displayed within the results. The MFDD (Mean Fully Developed Deceleration) figure shows the maximum deceleration figure a vehicle can achieve. It is usually the deceleration between 80% and 10% of the trigger activation speed, the time at which the vehicle is loaded up and braking at its highest achievable level.
The MFDD settings can be defined with the Deceleration Test Settings area. They allow you to set up the start and end period of the MFDD analysis period.
MFDD is calculated by the following formula (using default 80% – 10% value):
MFDD = ((v_08)² – (v_01)²) / (25.92 * (s_01 – s_08))
- v_08 is the speed at 80% of the brake trigger activation speed.
- v_01 is the speed at 10% of the brake trigger activation speed.
- s_01 is the distance at which the speed is v_01.
- s_08 is the distance at which the speed is v_08.
MFDD can be also calculated using Speed by tapping the Percentage label until it reads Speed and entering the required values.
To change any values, press the current value and use the keypad presented.
MFDD From Speed Keypad Example
To save the value inputted, press the Confirm Button on the bottom right of the screen, or press the Cancel Button on the bottom left of the screen to return the Settings screen without saving.
Minimum/ Maximum Values
- The maximum From speed selectable is the value inputted as Minimum Trigger Speed.
- The minimum From speed selectable is the greater value of 5 km/h or the To value +1.
Note: The maximum input value for speed is 999.9 and can be entered up to 1 decimal place.
- The maximum From percentage selectable is 100%.
- The minimum From percentage selectable is the To value +1.
- The maximum To speed selectable is the From value -1.
- The minimum To speed selectable is 0.
- The maximum To percentage selectable is the From value -1.
- The minimum To percentage selectable is 0.