Newbie question (I think)

[ob1]

I am posting this question in the UAV forum because I think ipeople who are interested in and build UAVs will be more likely to know the answer than the folks in the AP forum....so here goes :)

Even though it is not a UAV, I have a wireless video camera mounted on my AP/AV airplane. I built in a hardpoint at various places such as under the nose, on the side of the fuse, and under one of the wing leading edges. This gives me a variety of places (and viewpoints) to mount my camera. I created a (rather nifty) camera mount which can attach to any of the hard-points, and allows servo-driven tilt of the camera from the Tx of up to 90-degrees in flight, from full-forward facing all the way to full-down facing or anywhere between. I like this capability but have been considering another "approach"....and this is where you guys come in. I would like to point the camera and have it remain stable (pointed at roughly the same place) even as the pitch of my plane changes up or down (within reason of course). So as an example, imagine a plane flying at 0-degrees incidence and the camera pointed straight ahead at 0-degrees as well. Now as I feed in up elevator and climb at say 20-degrees, I would like to still have my camera pointed at 0-degrees (which means it is technically pointed more down that it was previously), and as I level the plane back to 0-degrees the camera reduces its down pitch back to 0-degrees. This effectively allows what I would call "damping" of the up-and-down pitch motion you see in a lot of videos. I tried using a piezo gyro thinking that as the pitch angle of the plane increased, the gyro would cause the camera tilt servo to move in the opposite direction, and as the pitch angle decreased the tilt servo would return to the original position, but this was not the case at all (bad idea). So what "method" can I use to accomplish my goal? Any and all suggestions are welcome...especially if you have already done something like this in one of your UAV camera setups. Clearly it wouldn't take too much imagination to realize that if this can be accomplished for pitch, I could use the same approach to dampen roll as well (reduce or eliminate the tilted horizon in a banked turn)....thx
ob1

[mwraight]

Well, I'm not quite the electrical engineer on this sort of stuff - but I do work with UAVs and a group of talented guys and have picked up a bit from them. I understand mechanical systems much better than all this electronics stuff!

I'm not sure why the gyros wouldn't work for you...it stands to reason that if they were set up correctly they would easily be able to do this task. On the autopilot we were using - if you pitched the plane up, the gyro would sense this and give the appropriate control action to nose down. You could do the same with a piezo gyro but you have to have some sort of programming to process all that information and do what you want.

Another method you might want to look into is the Paparazzi autopilot system. While you don't need the full capabilities of that - you can probably modify it to do what you need. Paparazzi uses thermopiles to detect pitch and roll. Most of the information on Paparazzi can be found in these forums. Its quite an interesting project and something that is easily available and relatively inexpensive.

A low tech, not always reliable, easy way to stabilize your camera would be to simply make your own mechanical gyro. All you need is a weighted disk spinning at a good clip on one axis. It wouldn't have to be huge or heavy, but enough to keep the camera pointed horizontal. Of course it would be subject to gyroscopic precession and other inacurracies. If you want to get an idea of how this would work (assuming you don't already know) look up how an attitude indicator or directional gyro works in a full scale plane.

Sorry I can't give you any definitive answers and say "here's exactly how you do it". I'm better with ideas and concepts - and like to throw things out to see if they stick!

Good luck.

[flyingvranch]

You should look into the FMA Copilot system. It's designed for use as an airplane or helicopter autopilot, but I believe with a little work on your camera mount it would work just as you describe. For example, I have one on my heli. It runs the servos that control the swashplate ring on the mainshaft. When I manually tilt the heli left or right or forward or aft the swash ring stays level to the horizon. I see no resaon why this would not work for what you need. Just a thought....

[ob1]

I may be able to answer my own question :D ......check this out.....there may be others who are interested as well.
http://www.spartanrc.com/products/visionlock/visionlock.htm