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Radio - Servo - Gyro - Gov - Batt > Three gyros? What happens?

rsilvers
Senior Heliman
Location: Marshfield, MA

So what happens if you use 3 HH gyros, one for yaw, pitch, and roll, on a heli? Will it allow nearly hands-off flying? I mean, if you get it into a stable position, will it just sit there?

I am asking because the optical or thermal autopilots can still be fooled. The Co-Pilot does not work on a non-level ground, and will be fooled near a building. So I would think some combination of gyros and accelerometers would be best. Accelerometers could detect lateral drifting and stop it.

The goal would be to make something that can be flown out of sight, through a video and telemetry link.

04-03-2002 Over year old.

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rsilvers
Senior Heliman
Location: Marshfield, MA

What happens if the wind blows it over?

04-03-2002 Over year old.

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andymcallister
Veteran
Location: Palm Beach, Florida

If you want to fly everything hands off join American Airlines, helicopters need to be flown to stay airbourne.

04-03-2002 Over year old.

Doug
Elite Veteran
Location: Naples Florida....

There is no "wind" if you are "flying"

04-03-2002 Over year old.

rsilvers
Senior Heliman
Location: Marshfield, MA

Ok, I am asking an advanced question now about something that is groundbreaking. You are answering with what you have seen in the past. Take a look at this http://web.mit.edu/whall/www/heli/, expand your mind, then let me know if there is a cheaper way to do this.

04-03-2002 Over year old.

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MikeDD
Senior Heliman
Location: Elkhart, IN

This guy is working on one;
Carvec

BTA made a heli version($1500) of their auto pilot system. 3 Gyros and mercury tilt switches to sense constant tilt.

Michiana R/C Choppers

04-03-2002 Over year old.

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ed vega
Key Veteran
Location: nyc, queens

with 3 gyro's it looks and flys like this..

04-03-2002 Over year old.

rsilvers
Senior Heliman
Location: Marshfield, MA

http://controls.ae.gatech.edu/labs/..._fraser2001.pdf

This is interesting.

And this. http://www.u-nav.com/

04-03-2002 Over year old.

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rsilvers
Senior Heliman
Location: Marshfield, MA

Some people have done some neat things:

http://www.yamaha-motor.co.jp/sky-e/r50.html
http://pdv.cs.tu-berlin.de/MARVIN/
http://www.micropilot.com/
http://www.auav.net/boomerang11.html
http://bordelon.net/freespace/

04-03-2002 Over year old.

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Doug
Elite Veteran
Location: Naples Florida....

A very effective gyro sits on the rotor head in the form of your flybar. The advantage of the flybar is that is is self adjusting to airspeed. A gyro that had no way to know which way was up would naturally crash in a very stable manner

04-03-2002 Over year old.

rsilvers
Senior Heliman
Location: Marshfield, MA

So you need more than gyros. One company used mercury switches to know when things are level. But boy would I love a UAV that you could pilot from a van within a few miles and take photos. It coule be an airplane as that would be much easier, but those require landing strips.

04-03-2002 Over year old.

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Heli-Driver
Elite Veteran
Location: Arlington, TX

3 gyros over FMA

If you used 3 gyros, you still have to situate the heli level.

Remember the gyro keeps the heading of an axis.... it does not keep it "level".

The gyro doesn't care if the heli is level or not. if you flew it at a 30 degree roll angle the roll axis gyro would try to keep it at that axis.

I don't see where that would be a big benefit. I don't see why the FMA wouldn't be a better choice.

Raymond

Predator Gasser SE/231 X 2
Century Helicopters

04-03-2002 Over year old.

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rsilvers
Senior Heliman
Location: Marshfield, MA

The FMA should be better unless it gets fooled by a heat source.

Why would several rings of mercury switches not be the best way to keep a heli level? One ring of 4 would say it is not level. A second ring of 4 would say it is pitched a lot and need much correction. Maybe you could make a rheostat with a drop of mercury on it that would give proportional data.

04-03-2002 Over year old.

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MoSupaFly
Heliman
Location: Planet Earth

You should check out what they do at my alma mater:

Autonomous Helis

Cool stuff. Makes me wish I continued onto graduate school. Ah well...

04-04-2002 Over year old.

JohnC
Veteran
Location: East Yorkshire, England

I'm the guy who's doing the CARVEC system, which I hope will achieve many of the things you are talking about. Whilst developing it, I have come across a lot of problems regarding the things you mention and, like everything else, it's never as straightforward as you think:

The mercury switches are really just gravity-sensors and you would use a solid-state accelerometer to obtain a variable signal proportional to the amount of tilt. However, even when you've done this it would not work!. The problem is that when the heli tilts away from upright, it starts to accelerate sideways. This sideways acceleration cancels out the extra acceleration sensed from the gravity component you are now detecting!. So, as far as your on-board system is concerned, you are at the same angle.

Secondly, two heading hold gyros on the pitch/roll axis would not work either!. The problem here is that they are not sensing pitch and roll, they are sensing helicopter X and Y axis movement. Taken to the extreme to illustrate the point, imagine a heli straight and level: now pitch it up 90 degrees so it is looking upwards. Now rotate it 90 degrees about the Z axis (tail rotor movement). The heli is now at a pitch angle of zero degrees and a roll angle of 90 degrees - whereas the two X and Y heading hold gyros have not turned at all.

A further problem with standard gyros is that the heli vibrates a lot more in the X and Y axis than the Z axis, because they are directly affected by vibrations in the main rotor. The Z axis is at 90 degrees to the plane of vibration and so give a relatively clean signal. I think a normal gyro would cause a lot of servo-movement and possibly shake itself to death if you tried - but I may be wrong as I haven't. I would be interested to hear the results of anyone who has successfully done it ??.

The optical sensor systems like the FMA co-pilot are ingeniously simple - and appear to do an excellent job considering the compromises they have to make. However, they can't realistically form the sensing elements of a proper autopilot - they have too many constraints.

I hope you find this interesting. This is just the tip of the iceberg ...

John C.

04-05-2002 Over year old.

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spincycl
Veteran
Location: Marietta, GA

Good Thread

I am a long time member of Southern Polytechnic State University's Aerial Robotics Team (My personal Xcell "used" to be a robot).

I have read some reports of limited success using gyros on X and Y.
Rate gyros "can" work on a normal heli, but HH gyros tend to interact badly with the flybar. Vario makes a 2 axis gyro stabalizer for the purpose of making flybarless helis easier to fly.

As far as my Universitiy's robot we have on-board:

Pentium 166 MMX computer (embedded card)
Novatel Differencial GPS for positioning
3 axis gyro sensor, plus 2.5 axis magetometers (magnetic compasses), otherwise known as a AHRS
3 axis accelerometer sensor
RS-232 to PWM converters to drive the servos
On-Board cameras and transmitters for the search program

And it is all carried by a Bergen Industrial Twin heli

We can just give it a coordinate (or list of coordinates), and the heli will fly to it, and hover, or go to the next one.

For our competition that we enter every year, the robot does a completely autonimous search and recon. mission.

Check out the site: http://a-robotics.spsu.edu

04-05-2002 Over year old.

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tetsuo1
Senior Heliman
Location: Hendersonville, TN

Where's the Fun?

Lets just say that ten years from now these devices exist. All you have to do is install these devices and start the engine and the heli hovers itself. Why stop there?? These might evolve into programmable mini computers that will do an entire flight routine.

Where is the fun in that? If it flies itself there is no challenge, no gratification (like when you perfect a new maneuver), and to me no enjoyment. The whole love I have of flying is that you actually FLY it. If you are just watching as it goes by itself (either hovering or otherwise)you might as well not bother.

Also, what about safety concerns? If you have the thing set up to hover by itself I am sure that will breed complacency and carelessness in new pilots (or observers since they are not piloting anything).

I do not mean to knock the developers of this technology for other uses, whatever they may be. I just think that using devices like this for helis is a bad idea.

Jason

04-05-2002 Over year old.

rsilvers
Senior Heliman
Location: Marshfield, MA

Jason,

The fun in it now is to develop such a system. These guys are using their minds, and they find it fun. I am sure the developers of the V2 rocket found it fun to develop a rocket that flew to a target on its own. As for 10 years from now when you can buy this from TowerHobbies for $79, it will be for people who have a task to do, like taking an aerial photo of their property or cropdusting. People who fly for fun will not be forced to use this system any more than the owner of a Porsche 911 is forced to drive all the time with cruise control on. I hate automatic transmissions in cars which is why I would never want a Lexus. I would like to say I just ignore them, but I suppose I am like you, I am a bit irate that there are automobiles in which I cannot choose -- like most Mercedes (except for the SLK) and all Lexuses. I can look at a nice car and then look in the window, and say "Oh.. It is an automatic" then instant soft-on.

But then again, when Sikorsky was working on the helicopter he did not say "Let's make this unstable so it is more fun."

04-05-2002 Over year old.

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tetsuo1
Senior Heliman
Location: Hendersonville, TN

I HATE Automatic Trannys

I agree 100% about the car analogy. Every time I walk by a shiny new Vette and it has an automatic transmission I want to puke.

Well, to each his (of her) own I guess...

As I said before about the autopilot in helis, I do think that there could be some very specific uses for a technology like that. If used in a controlled environment and by experienced pilots, the safety concerns could be minimized. Those who develop such devices are to be respected for breaking new ground and solving complex problems. It is not them who worries me.
I think using something like this as a learning tool for new heli pilots is the bad idea. The standard method or putting on training gear and hopping around the field works very well and is generally safe with the proper setup. As soon as you put a completely new pilot on the field and he thinks this device will save him is when bad things are going to start happening.

Geezus... Do I sound like a grumpy old man?

Jason

04-05-2002 Over year old.

MobileRaptor
Veteran
Location: Orange, Texas

Like Rsilvers said, Fun Is what is fun to you, I enjoy flying my helicopters and airplanes very much, But I probably spend 50 time as much time building, setting up modifying and REPAIRING as I do flying. I build 35 and 40% aircraft (planes) for other people as a part time business, I don't make a lot of money doing it but it does supports My hobby desires. I like to modify and test different ideas with the best of them. I've been into helo's for a little over a year and currently have five of them, 2 raptor, 1 hawk which in my opinion is junk, one Ergo 46 and a TSK Mystar under construction. My next project is to attempt to install a OS 30 rotary engine (wankle) into the hawk. Why ? one to see if I can do it, two it,s an engine with almost no vibration with the same hp as the OS-32. lets play.

04-05-2002 Over year old.

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Radio - Servo - Gyro - Gov - Batt > Three gyros? What happens?

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