FAQ #106
Brake system plausibility device

Last Updated On 11/01/2019 03:55 PM by

mikez

Question
This rule states that: "A standalone non-programmable circuit must be used on the car such that when braking hard (without locking the wheels) and when a positive current is delivered from the motor controller (a current to propel the vehicle forward), the AIRs will be opened." Does this imply that the current measurement must be performed between the motor controller and the motor, or is it just as valid to measure current between the accumulator and the motor controller? Also, is it allowed to use an output from the main controller (microcontroller) to determine if the driver is "braking hard", or is the non-programmable circuit also responsible for interpreting the braking input? And a related question... Is there a definition for what "braking hard" is?
Answer
It is valid to measure the current between the accumulator and the motor controller. The non-programmable circuit has also to determine whether the driver is braking hard, thus using a microcontroller for this task is prohibited. The rules say "braking hard (without locking the wheels)", which is interpreted as a brake pressure/brake pedal position which is close to the point of locking the wheels. We are aware that this specification is rather blurry and will take that into account at Scrutineering.
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Rule Numbers
2013:EV5.6