On Tue, 08 Mar 2005 00:33:00 GMT, Ernest Christley
wrote:

Frank van der Hulst wrote:
Ron Webb wrote:

"Predictor" wrote in message
oups.com...

Ernest Christley wrote:
"Dan, did you ever get a chance to work with fuzzy logic?"



Why overcomplicate things. This is just too easy an application with a
BasicX board and an accerleometer.


Actually, its not that simple. Trust me, I worked on a similar problem
for 2 years. How can you tell whether you are straight and level? If
you're in a balanced turn, your accelerometer (which actually measures
net force) will believe you are straight and level.

And a GPS won't help much at all, mostly because its response rate is
too slow.

Frank

And the cruise control on your motorhome doesn't allow you to go to the
back and get a cup of coffee while tooling down the highway.

Why does it have to be all or nothing, people? Why can't it be an
electonic 'assistant' that can take the edge off of a bumpy ride and
keep the course drift to a minimum, without being asked to save the
pilot from an IFR death spiral? How can it tell your straight and
level? It WON'T, and no one need ask it to. Just pretty much maintain
the status quo, thereby making flight more enjoyable.

It's that "bumpy ride" that takes a quick response.

You need response (and sensing) times in milliseconds.
By far the simplest I can think of would be to tie into a gyro for
both pitch and roll. Then if you have the time and inclination, add
the output from the blind altitude encoder for altitude hold.

For an experiment, feed the gyro signals into a lap-top and process
them. You could even use an old AI for a test. Just let the
calculated outputs drive bar graphs, or position indicators and record
the functions. It'd be nice to be able to record the actual control
inputs as well for comparison. When the outputs look good then move
on to driving servos for trim tabs.

All failure modes should be neutral. Failure of any signal should
drop the system off line and that would put the servos at neutral.

A while back a friend had the elevator trim tab break. This
immediately put them into a 6-G pull up. Only a good pilot (who's
hand was on the stick) saved their bacon. BTW that was in IMC.

There is no need for an amateur built AP to be a dangerous exercise,
but the risk depends solely on how much foresight is put into the
system. Never leave a control system with a single point failure
mode.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com