That one goes back even further than that. There was a fellow at Langly that developed an autopilot using that technology. I attended his seminar at the EAA at the annual Oshkosh Fly-In in the early '80's. The auto pilot was working quit well using a boost tab on one aileron. He had a couple of ways to generate the airstream. One was a motor & fan, the other used a tiny speaker that functioned as a pump. The critical part was the tiny thermisters that he used in the bridge. They needed to be low mass to allow a reasonable time constant. The bridge was novel in that the thermistors were heated by the bridge. His organization was whatever preceded NASA so the information should be public domain, if you can find it. Needless to say, the General Aviation autopilot manufacturers were not happy that they even held the seminar! John Ferrell 6241 Phillippi Rd Julian NC 27283 Phone: (336)685-9606 johnferrell@earthlink.net Dixie Competition Products NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" ----- Original Message ----- From: "John Sanderson" To: Sent: Saturday, July 26, 2003 3:35 PM Subject: [OT]: Dynamic tilt angle sensor > Hello Robert, Nate & PIC.ers, > > > > >Date: Fri, 25 Jul 2003 10:31:34 -0600 > >From: Robert Ussery > >Subject: Re: [OT]: Dynamic tilt angle sensor > > > >Thanks, Nate! > > As I said, I'm aware of the uselessness of a static tilt sensor in an > >aircraft, since it will only function as a turn coordination indicator. I > >was just wondering if there was some other solution, i.e., el-cheapo > >gyroscopes, etc. > >Fortunately, gyro or accelerometer drift shouldn't be an issue, since I'll > >be able to periodically re-center it by flying straight on a heading for a > > > > > A long time ago (20+ yrs) I was also involved in the research side of a UAV > project. It was my mission to dig up whatever material I could on guidance > techniques, magnetometry, etc, etc. > > I've just had a quick grovel & can't find the report, but a description will > do for now. > Some privateers at NASA had built themselves a *turn rate* sensor using, > of all things, an air stream generated by a very low flow (laminar region) > jerry rigged fan. It was a *low* flow, as in your-breath-is-too-much. > The stream was directed at a PTC thermistor (or pair, I think?) and these > were kept at a `constant-ish' temperature by way of their resistance > characteristic (cheap control-loop that). If the stream deviated from > straight, then one PTC would be force-cooled more than the other & it > would automatically start drawing more current to maintain it's temperature. > The currents in the PTC were then monitored to find the rate-of-rotation > of the device around the axis, I think they used a Wheatstone bridge with > the two PTCs in diagonally opposite corners to give a directly readable > voltage o/p. > It was meant to be used as a yaw-rate sensor, much as the traditional panel > gyro turn-rate indicator, but which had a transmittable output & could be > used for a simple wing-leveller controller. > > Could a 3-axis version give you what you're looking for? > > > bestos, John > > eMail from the desk of John Sanderson. > JS Controls, PO Box 1887, Boksburg 1460, Rep. of S. Africa. > Tel / Voice / Fax : 27 11 893 4154 > Cell : 082 741 6275 > email : john@jscontrols.co.za > Web http://www.jscontrols.co.za > Manufacturer & Purveyor of laboratory force testing apparatus and related > products & services. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads