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To: Nate Williams <nate@mt.sri.com>
cc: Mike Smith <mike@smith.net.au>,
        cliff ainsworth III <cliff@cliffsworld.com>,
        freebsd-hardware@freebsd.org
Subject: Re: project truck.....ideas wanted 
In-reply-to: Your message of "Mon, 06 Oct 1997 12:33:07 CST."
             <199710061833.MAA01027@rocky.mt.sri.com> 
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Date: Wed, 08 Oct 1997 14:31:34 +0930
From: Mike Smith <mike@smith.net.au>
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> > Just off the top of my head, you'll probably be interested in:
> > 
> >  - inlet air temperature and pressure
> >  - exhaust temperature, pressure and oxygen concentration
> >  - knocking
> >  - timing advance & dwell
> >  - throttle position
> >  - engine RPM
> >  - fuel pressure & flow rate
> >  - oil pressure, temperature (engine, transmission, maybe diff)
> >  - tailshaft RPM (wheel speed)
> >  - ground speed (fifth wheel, ground doppler, other techniques?)
> >  - coolant temperature, pressure
> >  - outside air temperature
> >  - inertials (2D or 3D accelerometer)
> 
> Barometric pressure, moisture (as long as we're dreaming ;)

You can get barometric pressure from the inlet manifold if the engine 
isn't running.  Inlet air moisture content is pretty easy too.

As for "dreaming", none of the sensors above are particularly difficult 
to implement or manage, except for the ground speed measurement and you 
killed that one with the DGPS suggestion.  Even a cheap accelerometer 
is easy to look after.

> > GPS might be useful depending on the length of the run; I suspect that 
> > its basic accuracy won't be good enough to give you useful figures.
> 
> Actually, GPS is *very* accurate.  If you really want to do GPS, setup a
> stationary unit, and use the data collected from it.  You can get better
> than 1-meter accuracy that way (differential GPS.)

Damn, I forgot DGPS.  You will want a decent wireless radio link 
between the truck and your base station to run the DGPS data (from 
memory the Rockwell modules want 9600 bps) over.  A relatively cheap 
shorthaul wireless modem set should give you enough to run PPP over.  
You could use this for realtime telemetry.  8)

With DGPS you get real groundspeed, from which you can calculate your 
acceleration.  This lets you forget about inertials, as well as 
calculating drive slip (fairly important if you're worried about 
running from a standing start).

> > Watch out for fifth-wheel speed recorders; they have a tendancy to 
> > disintegrate under severe conditions.
> 
> Not only that, they tend to slow you down. :)

This is when they're working, or after they've become small rototillers 
dragging clumps of the roadway behind you? 

mike