Anti-lock braking systems...

[Nelson David E]

I am currently developing an ABS system for my masters thesis and I'd 
like to know if any of you all know of any discussion groups/UP-TO-DATE 
books for anti-lock braking systems? Also, if any of you have any 
thoughts/suggestions on the following topic, I'd appreciate it.

PWM 
How does one determine the optimum freq. for pwm.  Common sense (as 
opposed to theory) tells me that I would want the period of the pwm less 
than the time constant (T.C.) of the mechanical devive.  In the non-famous 
words of one of my profs., how much is how much? Is an order of magnitude 
sufficient/too much/too little.  Or should I go with 5 * T.C.  Or am way 
off on this kind of thinking?  I am planning on using an hc11 and using 
the output compares, but if my period is so low, I fear that I'll run out 
of CPU time.  Motorola makes an hc11k4 that has PWM built in that pretty 
much takes care of itself, however, as many (maybe all of you know) 
getting these special uP's from motorola isn't always a walk in the 
park.  Asking other individuals the same question has produced some 
varied answers from they agree to thinking to "I just picked a freq. and 
went with that" to "I chose 20 kHz since that way I can't hear the 
high pitched noise".  Any suggestions/recommendations on the above?

			Thanks,

-- 

David /\/elson
D-Nelson at taiu.edu

	******  Two wrongs don't make a right, but three do!  ******