This assumption is good except during wheelspin or lock-up.

Hallo Mahmood,

what Andy told is right. And more: What about driving curves? When sensor is mounted at only one wheel, signal is different, when driving right curve or left curve.

May be, that sensors of exisiting ABS system can be used? These ones are mounted at each wheel. Then, some averaging of the four wheels could be done. Also a plausibility check for detecting Andy's 'wheelspin or lock-up' condition. And finally, use of more than one sensor increases redundance, which might be important, when certain failure modes like cable break or else are not tolerated.

Like Charles already stated, there's a also the possibility of using some analog signal conditioning. Most of them perform an averaging by design.

Bye,
Kai