I’m really afraid of what some Formula Student Event Organizers think what we are doing but on 3rd of May there was a new rule in the reglement for FS Hungary was published. In order to get all systems working as soon as possible its really hard to understand how a new rule is developed so late this season…

But here is the rule in more detail:

B7.5 Brake Panic Switch
B7.5.1 All electric vehicles must be equipped with a brake panic switch such
that in the event of a panic braking incident, the brake panic switch will
be activated and will turn off the traction system or any drive by wire
actuators.
B7.5.2 The switch must be connected to the brake circuit such that it is
triggered at a pressure which is high enough to lock the wheels in dry
conditions.
B7.5.3 The switch must be implemented with analogue components and not
through recourse to programmable logic controllers, engine control units,
or similar functioning digital controllers.
B7.5.4 This system must latch until manually reset. This may be reset by the
driver in the driver’s cell.
B7.5.5 The performance of the switch will be tested during the brake test.

There are several points i have to criticise.

1. The main point is, that such a panic switch has to be implemented only with non programmable logic. I do not understand that requirement, because if the pedal box is not functioning properly there will be other problems but surely not only by evaluating the brake preassure, aside from the short circuit and broken wire detection for each brake pressure sensor and additional plausibility checks.
2. If the performance of the switch will be tested at the brake test, the X-by-Wire Box has to function properly, otherwise the car won’t accelerate anyway.

So the next days will be busy to design the schematic and the board for the required feature. Fortunately there is some free space in the X-by-Wire box, where the new, i’ll call it “Feature Addon Board”, can be placed.