sensorless electric motor position detection

[Bob R. McElroy]

It was a wheel that you could rotate and a readout that showed position
using the signature that the magnet poles made as they spun. I proceeded =

to rotate the wheel 180 degrees and behold! a reading that was 180=20
degrees in error! i really didnt expect to fool it, i also could trick=20
its position calculation by quickly passing a mark, then returning it to =

that mark.  Novel idea, needed more time to complete but looks possible=20
if you can overcome the detection of which magnet winding you were=20
looking at. aparrently its cheating if you manufacture a flaw into a=20
motor winding on purpose.=20
I thought you thinkers would be interested in this.
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Sounds cool.  Who developed it, and when do they expect to have it on =
the market?
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anyway, can someone tell me how ABS detects wheel position/movement?
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ABS doesn't care what the actual position of the wheel is.  ABS only =
cares how fast the wheel is turning, as far as I know.  The Hall effect =
sensor cannot directly measure the acceleration of the wheel, but =
compares the currently measured RPM with the previously measured wheel =
RPM and calculates the instantaneous wheel acceleration (deceleration.)  =
A preprogrammed maximum deceleration is then compared to the =
instantaneous wheel acceleration.  If the computer calculates a larger =
deceleration value for a particular wheel, the computer then knows that =
the wheel in question is skidding.  I don't know if the deceleration =
threshold value must be exceeded by a certain amount or for a certain =
time length before the ABS computer takes control.  Also, there must =
exist some hysterisis allowances, since you would want the ABS to take =
control of the braking at a different point than you want it to return =
control to the driver.  The flaw, IMHO, is that an average deceleration =
value is programmed at the factory, and doesn't compensate for actual =
vehicle weight or the minor variations from vehicle to vehicle.  I have =
never done a thorough investigation of ABS, and what I know was learned =
through reading articles in Motor Trend and my conclusions and =
assumptions from that information, so I am by no means any type of =
authority on ABS.  Any know if my assumptions are even somewhat valid?