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My gut feeling is that it would be a substantial effort to design a Altitude Hold system that can easily accommodate every aircraft. Those that are in the process of designing their own no doubt understand the needs of their airframe, so that will direct what they need to design.

If I were to go about creating one, I would just aim for a design that would work well on a small/slow stable parkflyer aircraft. It is what I fly, so that sort of leads me toward that direction. So, I'm sort of looking for something that would work on a Slow Stick or MagpieAP sort of airframe. Rather than for UAV, I'm more interested in a model that can just loiter at constant altitude, while photos are taken. I think there would be some interest in that sort of thing.

I've got a laundry list going. The design must be able to support Alt-Throttle or Alt-Elevator schemes. The PID loops are different for the two, but a simple user configuration scheme would take care of that. I've got a schematic nearly completed. All I need is about 100 hours of free time to write and debug the code. Sounds like a good winter project. :)

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I like that idea. We've also been talking about the "Way Point Sequencer" on the other site. What I would like to see is the ability to have an altitude lock as you describe. Couple that with a GPS enable type device. In this case you aren't loading in waypoints, but the electronics is looking at Lat and Lon from a GPS. You can fly via RC and Video link to a specific location to photograph or observe. Once you manually fly to a location where you want to loiter, enabling the device will lock in the altitude as well as cause the plane to start to loiter around that location. It would stay that way till you take it back by disabling the unit. The pilot at that point can focus on filming or shooting pictures. It would be a workable solution for first responder type folks at accident scenes with chemical spill's, etc. We aren't talking to far away in this case. Not outside the range of the stock RC system.

I should bring it up to MX over there.

Dan

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I should bring it up to MX over there.

My first thought was to just use his ZLog for the barometric data and I may just do that. But, it would be more elegant to include my own sensor to allow for a nicely integrated design. My proposed hardware is setup to accommodate either, so I have plenty of time to decide which way to go.

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I understand what you are saying Mr.RC, Its the code thats taking the time for me,especialy the PID,although I'm not fully convinced a full PID is needed? time will tell!

Terry I am very interested you are using a Gyro for stabilisation.I have one of the original Rotomotion 6 DOF kits I assembled a while ago though I see they don't supply them in kit anymore. I would be interested to know you'r gyro setup?

All the best Lyn.

Edited by Johnstorm

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Hi Lyn, my basic setup is a mechanical gyro with weak springs fitted sensing yaw but controlling the ailerons.

Terry

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From my experience co-pilot type stability device will hold plane horizontal and altitude pretty well if RPM is selected to be in the right range for level flight. I've had PDC-20 (barometric altitude hold from U-Nav.com) for over couple of years on my plane and it saw little use. The accuracy of PDC-20 was not any better than altitude hold based on GPS supplied altitude. Unless you are ready to spend time fine-tuning PID loops for simultaneous elevator and throttle control I can't see that the device will justify the expense of extra sensor and everything that goes with it. Just my 2c.

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I agree that with the co-pilot giving you attitude hold an altitude hold becomes far less important.

Terry

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Unless you are ready to spend time fine-tuning PID loops for simultaneous elevator and throttle control I can't see that the device will justify the expense of extra sensor and everything that goes with it.

I'm thinking the same thing. But, being the curious type, I'm somewhat interested in how effective this sort of device could be made work to maintain altitude on a loitering model. That is to say, does it substantially help at all (even on a "stable" model), and if it does, how simple can it be?

That is why I have been looking for evidence of DiY Alt-hold projects. Lots of project starts, but none to the finish line that I can see. For the sake of R/C science, someone has to go the full Monty. :)

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I am very interested in an altitude hold, and I agree with Mr. RcCam about making it happen for the sake of RC science. I wonder how well it would work on a RC heli? Actually, I suppose that would require a whole new bag of tricks...

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As someone that dose not use the co-pilot I am keen for you to 'go for it' as your programing skills are way ahead of mine.

The other idea's I had while on the altitude hold planning were to include an auto climb and an auto decent. I wanted this so I could just flick a switch after take off and let the 'return to field' gps hold the aircraft in a climb at a steady rate over my head. The same thing for decending. Not a feature I realy need but it could be fun if its not too hard to include.

Terry

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What about using an accelerometer for altitude hold?

Analog Devices makes some. The trouble I read about is having the right software to filter out unwanted vibrations (Kahlman filtering?).

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How well does the Copilot hold altitude? I've been planning on installing mine on my slow stick, but haven't got around to it yet. I mainly just fly FPV so should I install it? Will it help me maintain a nice, stable, efficent flight?

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It can not directly hold altitude but you can set it to balance the angle/pitch of the aircraft and the throttle setting to good effect.

It will help you fly smoother especialy in gusty conditions.

Terry

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Just as a thought here, could you not use a doppler rangefinder (Like the "Distance Measurer/Estimator" tools at DIY stores) to get the altitude? This would have the added bonus of being able to point the plane at a target and have it auto-fly, avoiding obstacles, landmarks, and hills (Like the F14's that fly in @ 100ft).

In fact, combine that with GPS (With, say, a Gumstix and GPStix machine) and you could have the aeroplane take off, fly a course of waypoints, circle the target (For video surveillance or photographic tasks) and come back in when ordered to (Or when fuel gets low, or signal dissappears, or whatever other situation you would require).

As to the whole "Accelleration vs. elevation" debate, you could set the system to favor one or the other, to maximise flight time, and to match the characteristics of your particular craft.

Just a thought.

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Any news on the Altitude Hold project? I still dream of a working altitude hold for my Slow Stick...I think it would be really nice to have so when I fly FPV I could focus on using an extra couple of channels on a pan and tilt system so I could "look around" without having to worry about the altitude.

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Any news on the Altitude Hold project? Curiosity is killing me...heh heh.

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In my case, I'm taking a wait-and-see position on this. From what I can tell, there are currently about a half dozen folks actively working on one.

The lastest such projects are mentioned here:

http://www.rcgroups.com/forums/showthread....old#post5852106

http://www.rcgroups.com/forums/showthread....d.php?p=6156068

http://www.rcgroups.com/forums/showthread.php?t=564570

There are others working on their alt-hold device as well. It makes no sense for me to go at it too.

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Thanks for posting links! Makes it easy for me to track who is doing what so I'll eventually be able to get an altitude hold. I just really like the idea of not having to worry about maintaining altitude while I'm flying and using a pan and tilt to look around.

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I wish I had an altitude hold also. I think the market would be there if someone were able to make one for a reasonable price :D

I was waiting for this:

http://scalerobotics.com/store/catalog/pro...?products_id=36

But it has been listed as comming soon for almost a year, so I guess they have lost interest in it. Has anyone come up with an altitude hold yet ?

JettPilot

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Hummm, I was thinking about the Zlog, but I don't have enough skills about the technology available to put any idea together. <_<

My electronics knowledge needs some updates !!! B)

Edited by wilson

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