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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: control system problem [RFI? <grin> ]
Organization: The Armory
Date: Fri, 29 Jul 1994 09:10:43 GMT
Message-ID: <Ctp2tx.322@armory.com>
References: <CtMnH3.IH6@freenet.buffalo.edu>
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In article <CtMnH3.IH6@freenet.buffalo.edu>,
Elizabeth M. Phillips <ad302@freenet.buffalo.edu> wrote:
>
>Hello I have a stability problem I would like to fix on a model flying
>wing.  A flying wing has a seveer YAW problem (in 3 space say X and Y
>are the viewing plane and Z is depth) this is rotation about the
>Y axis.  Sort of like a boomerang (hehehe OUCH).  Well it's anoying.
>I was considering using a control system to REACT to user inputs:
>1:	to translate "standard" stabalizer/rudder input to elevon movement
>2:	to reduce insesant pitch control problems (IE the plane has a 
>	tendancy to flip end over end :) 
>3:	solve the "boomerang" effect (equally anoying! :)
>4:	prevent "sudden" movements that could send the plan out of control
>
>I plan to use on each side a split elevon (IE an independant elevon for
>each surface [top and bottom]).  This will allow for air braking as well
>as other capabilities.  I'm sure many of you have played with model airplane
>servos.
>
>So here is how "I" believe it can be achieved (then you can rip apart my
>silly notions and stomp on them! [not that I really need that but ...])
>use 12bit D/A convertors as digital trim pots to modulate signals from 
>the CPU (likely to be a PIC for size and speed reasons) for each servo,
>convert the posistional information into "useful" data for the CPU by
>using A/D convertors (12bit) frequency to voltage convertors OR simply 
>sampling the data present on the outputs of the reciever at regular 
>intervals for the proper resolution.  use strain guages to measure
>aceleration (for limiting speed of control surface changes) 
>
>Is thier anything I should consider?  Would using a gyroscope help?
>
>Yes I'm clueless as too exactly how to proceed.  I just want a plane
>that doesn't flip or spin in circles :)
----------------------------------------
I think your problem may be mostly aerodynamic. Do you have large enough
rudders on the trailing edge, and are they far enough apart??? If you have
no rudders, you would have to do a lot of quick shit with remote control,
the fly-by-wire kind of stuff. Good Fuxking Luck! If you have rudders which
extend above and below the trailing edge, then you are doing just what Jack
Northrup ran into and that's the fix! Without rudders you DO have a damned
boomerang!!! You can't translate elevon motion (elevator trailing ailerons)
to stabilize yaw! The B-2 uses a combo of airbrakes and engine separation
for that!!! And it still slips like crazy. The best fix for a model is
large quadruple transparent rudders with no control, just for stability!
Make them of piano wire and apply the clear dip film to them. At least they
won't show up much in the air. An arrow needs feathers in two planes,
preferably with their intersection parallel with direction of flight!
I suppose you want to bank your turns for a wing. Rudder/elevator control
would make it look hoaky, like a flying saucer turning. You could put
ruddervators on it, but I suppose that would spoil it for you. And they'd
have to be big! Good luck!
-Steve Walz   rstevew@armory.com

