42 replies to this topic

[elossam]

I was told that time ago was developed a system for stability augmentation based on the electrocstatic diferential between two sensors fitted on both wings extremes.
Has anyone more info about it?

[Temporary Insanity]

I can only offer that Maynard Hill did research on this many years ago. I no longer remember the outcome. You do know about the FMA Copilot that works of far infrared?

[elossam]

Yes , i know and use the FMA co-pilot but it has some well known limitations. Google search gives lots of results and shows this system is used in many UAVs. Will keep serarching the net. Thanks T.I.

[Delcam]

In 1973, in the february issue of "Flying models" and in august of that same year in American Aircraft Modeler, two articles concerning the electrostatic autopilot were published. I do have rather old and whethered photocopies of these! If you want a PDF from them send me a mail through a PM on this forum and I will mail you back through your private e-mail address. The PDF file is huge but I cannot make it any smaller because quality will suffer so that it won't be readable...21 meg......

Hans Delemarre, the Netherlands

Edited by Delcam, 06 May 2005 - 11:29 AM.

[kd7ost]

Hans

I can't get the PM to work for me. Is there a chance you can make that file available to me as well? I would greatly appreciate it. Thanks

Dan

Edited by kd7ost, 13 May 2005 - 09:49 PM.

[Terry]

Hans was very kind in sending the PDF on disc, I have borrowed my sisters web space and uploaded the file he sent me. I hope this is ok with you Hans ?
The file is big (21Mb) and will only be on the site for a limited time, so be quick !
http://myweb.tiscali...nford/index.htm

Terry

Edited by Terry, 14 May 2005 - 03:06 AM.

[kd7ost]

Thank you Hans and Terry,

Download is complete and articles are great.

I wonder if anyone has continued doing any research? The one problem I see right off with doing this today is getting ones hands on 250 to 500 micro curie Palonium radioisotopes. Or would one even want to? The article from then says they are safe. Would they be by todays standards? (Hmmm, where does one purchase hobby grade radioactive material and a lead vest?)

It would seem however, that gain in op amps have improved dramaticaly over the years since the research was first done. There may be other sensor type devices that could do the same type of electrical amplification. But that is pretty well beyond me to figure out. Perhaps high impedance CMOS amps with a high input impedance may not need the added amplification of the Palonium sensors.

Any idea's anyone?

Dan

[Terry]

I had all the same ideas when I read the articles as you Dan ! The problem is I have the same questions too
Why are the Palonium radioisotopes needed ? Could you make use of a smoke detedtor that uses this method ?
How exactly are the sensors made ?
Hmmm

Terry

[Mr.RC-Cam]

I googled around for a source of polonium. All I found was that it is used to reduce static during photographic material manufacturing. I also found this warning that came out at about the same time Maynard's article was published:
"Thirty-two years ago, scientists discovered that tobacco contains high concentrations of radioactive material. The radioactive nuclide that tobacco contains is polonium-210. Polonium-210 is an alpha emitter, the most highly ionizing radiation known to mankind, and particularly dangerous when in contact with living tissue."

[kd7ost]

Well, I don't think the articles describe the process well. It sounds like the palonium radioisotopes emit alpha rays. But it doesn't explain how that process detects the variations in voltage as altitude increases or decreases. It is interesting to note that by partially covering the emiters, you can reduce sensitivity and response characteristics. (I think thats what I read) Also, that the voltage varies by 100 to 150 volts per meter near the earths surface. It would seem like that would be easy to detect as it's such a huge potential. But I guess the real trick is measuring the voltage difference between 400' and 400' 1/4" while sensors are just a few feet apart in some cases.

I'm assuming that just putting wires out won't do it. There needs to be some form of detector out there. Something that actually develops a potential from the atmosphere and converts it to a measurable DC level for the op amp.

I don't quite see how the pulses would feed into the circuit or come back out being varied. I don't know the vintage of servo they are using. Are they using the error voltage to the feed back pot of the servos used for positioning that servo?

Dan

Edited by kd7ost, 14 May 2005 - 04:00 PM.

[kd7ost]

I did some digging on the KPS 9 servo that was referenced in the Flying Models article. It used a variable cap for feedback instead of the variable pot. (Fun facts to know and tell I guess) I don't know if it used a standard pulse to operate though. It was from an early Kraft digital RC system.

The caption for the schematic in the American Aircraft Modeler states, "A circuit suited for model planes and sport flyers will be seen in a later issue".

Anybody got access to that?

Dan

[Mr.RC-Cam]

It used a variable cap for feedback instead of the variable pot. (Fun facts to know and tell I guess) I don't know if it used a standard pulse to operate though. It was from an early Kraft digital RC system.

Kraft's old Series 72 servo was essentially the same as what is used today. That is, it had an IC servo amp IC that did all the work. The analog signal from Maynard's device was connected to the servo IC at pin-3, which is part of its one-shot reference generator. Full details to the servo can be found here:
ftp://ftp.rogueview.com/Radio_Control/Kra...Servo%20Amp.pdf

But, because of the warning in the article about protecting the servo from stalling (plastic gear breaker!), the real solution is to use a microcontroller to do all the work. That would eliminate modifying the servo too. That part sounds pretty easy to me - Just add a PIC and some firmware.

The article states that the radioactive source came from a store bought record cleaning brush. I used these all the time back when turntables were king. With luck, cheap home-use versions are still available (hard to say, with all the environmental related consumer laws in place). From what I can tell, all you need to do is attach a wire to it.

Here is a professional photographer's brush that uses the radioactive source: http://www.halfhill.com/dust1.html. It looks just like what I used to clean LP's. The Holy Grail is found here: http://www.amstat.co...aticmaster.html. The 500 microcuries ionizer component, which is pretty much what Maynard used, is expensive though -- $35 each. Measurement labs install these near their weight balances. They are replaced annually, so maybe someone can dig up some used ones for free.

Edited by Mr.RC-Cam, 14 May 2005 - 07:18 PM.

[kd7ost]

Excellent work. I agree on the PIC chip instead of hacking the servo. That’s up your alley. Very nice find on the brush components too. I was searching for turntable parts and couldn't find anything definitive. It is a bit higher cost than I would have thought but it seems like it would resolve the common problems found in rate gyro’s, co-pilot or such devices. Shall we persue the design? I am interested in a one axis device. I wish to employ roll control only.

Dan

[Mr.RC-Cam]

The second article by Don suggested {to me} that the design is not a slam dunk. The question is, are the limitations of Maynard's project something that is "better" than, say, a FMA Co-Pilot? My gut feeling is that it will be a coin toss. For sure, it would be nice to see someone build it.

[Dave Jones]

Guys
Wile Maynard's electrostatic wing lever worked great under ideal conditions you need to follow up on what would happen if a thunder storm rolled in wile the aircraft was flying, I vaguely remember reading about how the electrostatic field of the earth would reverse causing the aircraft to roll inverted.
If I remember correctly this is one of the reasons that it was never put into production for the common RC flyer.
Dave Jones.
AUAV.net

[Terry]

The artical dose state that it worked ok even with a thunderstorm within a 2 mile radius and also in light drizzle !
It would be nice to re-evaluate the system to see if this was true, although I dont fly in thunderstorms anyway

Terry

[kd7ost]

I agree, I have no reason or interest in Thunderstorm dodging. My bigger interest is because in the winter months, I have been out at times where the co-pilot couldn't tell the temperature difference between the earth and sky. The BTA AS-06 works in that case but it's power hungry and rather large. The co-pilot is a fair weather device that works most of the time we would be interested in flying. But not in real cold weather which by me is still OK to fly.

I also want to fly a GPS guided glider to a landing spot after having lofted it under a weather balloon to in excess of 75,000 feet MSL. I don't think the co-pilot will work after having been cal'd on the ground, then lofted to where the temperature is -60 f. An Electrostatic stabilization system just might be the ticket. Of course the article also alludes to the voltage potential diminishing as altitude increases away from the earths surface. So who knows, it might not work up there either.

Dan

[Delcam]

Terry,

better late than never..... I only saw your posting today! Perfect idea to "publish" the articles in this way. Thanks.

Hans Delemarre

[elossam]

Searching the net I found an article of a guy that made a master thesis about it. It is in chinese but at least there are some graphics that could be interesting to be checked.
Here the web
http://etdncku.lib.n...-0710102-190435
And here the PDF file
http://etdncku.lib.n...0102-190435.pdf

Edited by elossam, 20 May 2005 - 12:38 PM.

[Terry]

Hmm, I cant seem to veiw these but I see he is using transistors at the sensor end, is that right ?
Was he sucessfull ?

Terry