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In an ABS system there are sensors on each of the wheels which determine the angular velocity in order to pulse the brake of an individual wheel which registers a diverging reading indicating brake lock-up.

My understanding is that when one of the angular velocities is significantly lower than the others, indicating that the wheel is sliding or about to slide, the system kicks in on that wheel.

My question is, what would the best way of determining quantitatively:

1) which of the wheels is in danger (some multiple of std dev from the mean of all wheels?)

2) how much deviation would be permissible, because there is always going to be a variation when the car is turning and we would not want to activate the ABS for such a situation.

ose
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  • What parameters are set in the software? – Solar Mike Mar 06 '20 at 17:41
  • I am trying to determine what parameters to set in the software – ose Mar 06 '20 at 17:54
  • First thought what is the speed differential between 4 wheels based in a given wheelbase and track when it negotiates a curve... once you have an expression for that you may be able to get somewhere... – Solar Mike Mar 06 '20 at 17:57
  • I think you might be underthinking this one a bit. The 2015 Ford GT had 20 million lines of code, 15 sensor systems, 28 processors, and generated 300MB of data per second. Sensors were clocked at 8 milliseconds. There were over 3000 separate data signals. The idea is to establish the speed the tire should be going (contact patch circumferential speed) and compare that to the actual speed. You need a model (pretty good one) of the actual dynamics of the actuator system to determine how the system responds on patchy ice in a swerve, for example. – Phil Sweet Mar 07 '20 at 12:55
  • You also need a model of tire dynamic loads for sliding + spinning under all angles and surface conditions. Tranny sensors, pedal sensors, steering wheel sensors, temp sensors, yaw rate sensors, load sensors, AWD systems and inflation sensors can all contribute. You are trying to maximize the forces that deliver what the driver is trying to do. And this is a hard problem. – Phil Sweet Mar 07 '20 at 13:06

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