Thermal Sensor and Load Sensor

[Andrew Ghali]

>There is a rotary load sensor on the market.  The company is called 'Land And
>Sea" , they make dyno stands and a real time on car dyno.
>
>The real time on car dyno uses a rotary strain guage that replaces the drive
>shaft yoke.  From what I remember of their info sheet, there is also a front
>wheel drive system avalible.

The problem with strain gauges is that you'll need a) some sort of slip ring
contacts for the rotating part or b) magnetic power and signal coupling to
transfer as a variable frequency, right?  The problems with (a) are obvious;
(b) is a bit complex and probably fairly expensive, and subject to calibration
problems.  The concept of a phase-based sensor is old, and can utilize the
same technology used in synchro/resolver equipment.  Yes, filtering would be
required on any method - your data will be delayed a few turns of the shaft -
not too bad?  The one problem that none of these methods addresses came up
in a discussion with a Motorola automotive-group field application engineer:
work hardening of the shaft.  You are depending on a known modulus of the
shaft in order to determine the torque from its deflection.  That's what the
Moto guy told me was the reason the method was not used in passenger cars.
I suppose race cars with new shafts every race would have no problem, but in
the long haul...

As an aside; somebody mentioned MAP, RPM, & a cal table instead.  I'm no
expert here but this seems pretty rough to me.  You'd have to add about a
dozen other values in before you could get close - like advance/retard,
AFR, engine temp, air temp, etc. then add in other constants like engine
friction, efficiency, etc.  Once you had all that cal'ed from a series of
dyno runs, the next time you changed your air filter, or over time as your
rings and valve seats wear...

I hope I haven't muddied this up too much.  I am intrigued about the
commercial systems though.  I'd like to know how they've solve some of
these problems and what approaches they used.  It's the engineer in me.

Andrew