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From: gt0869a@prism.gatech.EDU (WATERS,CLYDE GORDON)
Newsgroups: sci.electronics
Subject: Re: measuring vehicle speed
Message-ID: <31696@hydra.gatech.EDU>
Date: 23 Jun 91 23:14:23 GMT
References: <1991Jun20.024446.18473@en.ecn.purdue.edu> <4746@guppie4.UUCP> <10922@plains.NoDak.edu>
Organization: Georgia Institute of Technology
Lines: 40

In article <10922@plains.NoDak.edu> csmith@plains.NoDak.edu (Carl Smith) writes:
>In article <4746@guppie4.UUCP> svoboda@motcid.UUCP (David Svoboda) writes:
>>From article <1991Jun20.024446.18473@en.ecn.purdue.edu>, by jbs@en.ecn.purdue.edu (Spaggie):
>>>  [description of laser speckle patter speed measurement system deleted]
>>Outstanding.  But I could envision a problem with an inconsistant ground
>>surface, as well as a problem illuminating the ground sufficiently from
>>under the car to be picked up reliably by the receiver.
>Anything that has a direct "view" of the road surface will soon be
>covered with a layer of dirt, even if the road isn't wet and muddy.
>Laser beams don't go far through mud.
>I don't know how this could be solved...  Maybe mount the laser and
>detector behind a glass window with a little window wiper...  :)


I made a suggestion to the original poster that I will share here due 
to the apparent interest:
I read a while back about how F1 racing teams wanted to have info on
car-ground speed, ride height, etc. Their method seemed a little more
practical- 
They used an ultrasound source (I think) and bounced sound off the ground.
The transmitter was surrounded by little directional recievers (mics?)
The time the beam took to come back compared to the shift laterally or
longitudinally of the beam reflected referenced to the original transmission
position can easily be used to calculate vehicle speed (a simple ratio)
This should be usable, if the transmission pulses are fast enough, to 
not only give ground speed, but ride height in relation to time also.
I have no idea how the reception worked, but I think the transmitter was
placed in a small waveguide tube.(to concentrate the beam into a small
area) Anyone with more knowledge on ultrasound mapping could be of 
much more help.


Regards,
Gordon.

-- 
WATERS,CLYDE GORDON-Georgia Institute of Technology Atlanta Ga 30332 
******<LANGUAGE IS A VIRUS! - Laurie Anderson-Home of the Brave>******* 
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