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Old Aug 02, 2011, 05:07 AM
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I think you are missing the point. A balloon rights up because it is buoyant against gravity. Here there is no buoyancy, there's only an airstream, and it's dependent on the prop's orientation.
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Old Aug 02, 2011, 06:08 AM
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I think the CG in relation to control surfaces is pretty important, ie the moment available.

That's why I think his double set of surfaces helps.

I am no aerodynamic expert though.
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Old Aug 02, 2011, 07:11 AM
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Quote:
Originally Posted by Gary Mortimer View Post
I think the CG in relation to control surfaces is pretty important, ie the moment available.

That's why I think his double set of surfaces helps.

I am no aerodynamic expert though.
Hi !
Gary are You using any gyros in version 2 ?
I have Tri-Copter with 4 HK401B gyros (@$12) and this thing is hovering very nice.
Also MultiWii controler can be use (3 axis gyro @$20 + 3 axis accelerometer @$20)
Tom
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Old Aug 02, 2011, 07:14 AM
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Ultimately, it's the thrust vector in relation to the CG that will control the craft. How the thrust vector is modified is not overly important. so, the furthest the control surface are from the CG, the more authority they will have. However, they will not work to stabilize the craft in any way. If you want this to have passive stability you will need a teetering rotor above the CG and a flybar, only then the gravity pulling on the craft body will work to stabilize things.
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Old Aug 02, 2011, 08:32 AM
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@Brando thats what I should have said, at Tifani I am using a CopterControl board from the OpenPilot project.
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Old Aug 08, 2011, 11:40 AM
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Hello Gary and Brandano.

I completely agree with Brandano’s comments above. Perhaps is could be also mentioned that control of the craft and passive stability could be considered two separate objectives. Control can be a achieved by the use of control surfaces placed in many configurations, passive stability is a much more problematic as Brandano mentions the need of flybar / helicopter style of gyroscopic stabilization system.

Arthur Young invented the flybar system from the time period of 1927 to 1941 with a series of fantastic model experiments that he recorded with various movie cameras. Here is a link that will show home movies of the development of the flybar and teetering rotor head and other various means he tried to achieve stability. It is well worth watching and seeing a complete semi – remote control helicopter with gyro stabilization of the rotor head via the flybar / teetering rotor head and even a gyro for the tail rotor all working very well circa 1941 or sooner.

http://www.youtube.com/user/arthurmy...C95D4821B4CFCE

With respect to the Japanese flying ball, the upper control surfaces are in line with the CG so they produce no pitching/roll moment, only yaw control. The lower set of surfaces as you can see from the one movie posted on this tread, works in unison for pitch, roll, and yaw control. At least that is my best estimate as to what is going on for control deflection.

I suspect that the upper set of control (yaw ) surfaces may be working with the Yaw rate gyro, the lower set of control surfaces work with the pitch and roll control rate gyros, but not the yaw rate gyro. Thus the lower set of surfaces are available for an increase of yaw control rate if so required by the pilot, but otherwise the upper set of surfaces actively control the yaw axis.

The lower set of control surface actively control pitch and roll via gyro control, but maybe employed for an increase in yaw control. Yaw function on the lower set of surfaces are not controlled via gyro(s). This is my best guess at this point, since I can’t read Japanese patents.

Why break out the yaw control onto separate surfaces that are in- line with the CG (ie the upper set of control surfaces)? By doing this the yaw control moments don’t affect the pitch and roll moments for more precise hover control. Yaw control is best situated on the CG, and the pitch and roll control need to me at a maximum distance from the CG to increase their moments of control (power).

Question: #1 I’m wondering if this device employs a form of GPS or other complex active control system other that rate gyros. It seems exceeding stable. I noticed the CopterControl works well, but does have the holding power seen in the Japanese device.

Question #2 for Gary, can you please give us some details about the CopterControl as you have it configured, the website for this device mentions that it can be used to stabilize helicopter and has an auto leveling control system. Is this the feature set that you are using, details please?

Kelly
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Old Aug 08, 2011, 12:14 PM
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Kelly, love the videos thanks for sharing, I shall add one in this post

The Birth of the Bell Helicopter (Part 1) (14 min 21 sec)


I also think yaw is separated from pitch and roll. The stability of the machine is due to a much better job I think.

If I have time I will try and make a better 8 vaned version. I shall take into account your thoughts they seem eminently sensible to me.

Yes I am using the attitude sensing part of the CC board, that's why I can so easily let it fly hands free. GPS in itself would'nt make the ball more stable especially indoors.
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Old Aug 08, 2011, 12:45 PM
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UAV Test Flight - Flying Can Design 2009 (3 min 15 sec)


Gary,

Take a look at this video. I contacted the poster Rai41478 for details and he furnished this information posted below. I ask for further details on what model of gyros he is using on two occasions, but he has not replied as yet and this was several months ago. He did a fine job and I applaud his workmanship. I noticed that this device is as stable as the Japanese ball device. Very impressive considering how simple a craft it appears to be. If you go to the posters channel site you find a total of 3 videos for this device. Very Impressive stability!

To :corocopter

Hi thanks for the interest.
The Servos are digital.
The gyros are all set to rate, I had a lot of issues with heading hold on the yaw axis.
The entire frame and shell of the craft is constructed of carbon fiber.
The spars and frame are made from carbon square tube with epoxy glue.
The shell is mirror finished carbon fiber sheet, The use of this material is very important to reduce weight and maintain rigidity of the craft.
Brush-less motor, Li-Po battery pack, use the lightest prop you can find to reduce gyroscopic effect. I'm using cheap light plastic 3 bladed props. also balance the craft in the middle of the prop to save yourself headaches.
Have a new version of both craft posting new videos as soon as the weather gets nice.
Thanks
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Old Aug 08, 2011, 01:36 PM
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Gary,

I imagine that the construction material has the greatest impact on stability control. Foam is quite flexible as apposed to carbon fiber. I think the bending and flexing of the foam structure of your balls sets up a hysteresis loop that the attitude controller canít follow. The use of a stiffer material and very fast servos may make a great deal of difference.

Are you using digital servos?

Can you adjust the rates of the gyros on the CopterControl board, if this is true, can you describe how this is accomplished? Are you happy with this device? Do you thing it would work with glow engines? They have considerable vibration and the accelerometers may not like this problem, your thoughts please.

One other thought, you could use just one rate gyro for yaw and a FMA copilot for pitch and roll if you plan to fly only outside. That way you have a known reference point to establish a negative feedback loop or reference point for pitch and roll. These devices are very simple and cheap and work exceeding well for under $60.00 USD. Do a search on google videos for FMA copilot and you see many helicopters that fly completely hands off with this device. I own one myself and it will be used on my VTOL aircraft setup as mentioned above.

FMA copilots donít like digital servos, at least that was the last I heard from FMA via their website but it still does a great job. This device is very simple, small and does the job by referencing the temperature difference between the edge of the earths horizon compared to the temperature of deep space.

Kelly
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Last edited by corocopter; Aug 08, 2011 at 01:44 PM.
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Old Aug 13, 2011, 06:36 AM
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Why not Build a BORG Cube around ??



and electronik FC from KKmulticopter

Single and Two Motor VTOL ............

Video:
Single Prop VTOL - kkMultiCopter (3 min 21 sec)

DualCopter - kkMultiCopter (2 min 26 sec)


Mike
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Old Aug 13, 2011, 07:10 AM
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Humm I have a stick hanging around I might have to build a more stable version of that second one ;-)

It certainly does not have the stability of the sphere though, very clever design all the same.
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Old Aug 13, 2011, 12:49 PM
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Heli Halle / Gary,

Thanks for posting those two videos; they demonstrate the affect of the stability created by the spinning prop. The upper single motor craft is much more stable, the lower twin motor craft cancels out the gyroscope stability making the attitude guidance system work much harder to reduce the oscillations in the pitch and roll axis.

I came up with the idea of stabilizing an aircraft by spinning a set of weights attach to a bearing plate that is driven by propeller blast. You have to machine a propeller extension shaft with a bearing and at least two impeller blades to drive the weights.

Here you can see it working very well on my friends modified Turboplan or Turboplane depending upon whether your searching in German or English. I came up with this idea while I was working on a full size free turbine engine for a Hughes 500D. It works much the same as a free power turbine in a turboshaft jet engine.

RC UFO Vtol Turboplan V6 (0 min 16 sec)


RC UFO Turboplan V7 (0 min 20 sec)


I was building a copy of the 1980’s TurboPlan which was an Austrian invention that had some success before the arrival of the mass produce model helicopter. Below is Hank Renz’s copy of the Turboplan. The upper set of vanes cancel out the torque of the engine the lower set of vanes are for pitch and roll. The spinning ring is a huge gyroscope for stablility.

Hank later removed the ring, and added the device I developed that attaches to the prop shaft. This free turbine idea is much easier to implement than making the center section bearing system. This craft has only one electronic gyro for yaw stability. The large ring handles pitch and roll stability.

RC UFO Turboplan V4 (1 min 12 sec)
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Old Aug 13, 2011, 04:24 PM
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The Borg Cube is a very good idea.
Something to try for the next indoor season.


Dirk.
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Old Aug 15, 2011, 04:25 PM
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Austria
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Single Ducted Prop

Here is another one: http://www.rcgroups.com/forums/showthread.php?t=990117

My latest version is stabilized by a KK-flightcontroller:
SDP-VTOL V1.2 - Testflight (0 min 53 sec)


Quote:
Ultimately, it's the thrust vector in relation to the CG that will control the craft. How the thrust vector is modified is not overly important. so, the furthest the control surface are from the CG, the more authority they will have. However, they will not work to stabilize the craft in any way. If you want this to have passive stability you will need a teetering rotor above the CG and a flybar, only then the gravity pulling on the craft body will work to stabilize things.
...agree with brandano.

Have fun! Michael
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Old Aug 15, 2011, 04:44 PM
Gaftopher
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Very nice, now I really must make one!
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