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Thread: Altitude Hold

  1. #1
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    Altitude Hold

    Hi everyone,

    Ok...I have the Mega 2560 with the 2.1 sheild and v3 software uploaded on. Flies great in rate mode and need some small adjustment for more percise flight in attitude mode. I would like to try and set my Altitude Hold if at all possible. I understand that the "altitude hold" is still in the experimental stage, but I was wondering if someone could help me on setting the altitude on the config. I am just starting to understand the PID settings and what it means for each adjustment and the "altitude hold" on the config looks very simular, but I just don't want to start making guesses when it comes to this and have it take off on me.
    Needless to say, I am ready to help test the software for Altitude Hold for those of you put under the task of developing it . Either way, any help would be greatly appreciated.

    Jayson

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    Senior Pilot xtrmtrk's Avatar
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    My advice is to put the altitude hold on & off switch in a VERY convenient spot so you can quickly turn it off!

    I've seen it work great on other people's quads, but I've never been able to make it work well on mine.
    2013 Carnage (so far!): 26 propellers, 1 frame, 5 arms, 1 motor mount, 2 motors, 2 ESCs, 1 GPS

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    Hi there xtrmtrk (hope I spelled the right...lol),

    Yes, I have assigned it to a convenient switch on the transmitter. I am just affraid to test it. When I look at the settings on the "configuration" for Altitude Hold on the configurator, I have no idea what im looking at. I don't know what does what if I adjust the numbers. I don't know where the setting is for adjusting altitude hight is...anything.

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    Senior Pilot xtrmtrk's Avatar
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    The idea is that it will capture the height you're at when you turn on altitude hold and keep your craft at that height.

    Are you using the sonar sensor? That should add better resolution to the held altitude.

    I've seen it work perfectly for some people with the default PID settings, but that's not the case for me. My experience has been that after I flip the switch there are oscillations in altitude that grow larger and larger the longer I have altitude hold on. After a while it's about to hit the ground and I turn altitude hold off to regain control.

    A few weeks ago I started to debug this, but got distracted building, crashing, and now rebuilding a new smaller quad. I'll get back to the altitude problem eventually.
    2013 Carnage (so far!): 26 propellers, 1 frame, 5 arms, 1 motor mount, 2 motors, 2 ESCs, 1 GPS

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    I wouldn't be too afraid of turning altitude hold on and just trying it. Remember that the maximum throttle adjust values aren't set very large, so even if the algorithm goes nuts it won't cause your quad to instantly shoot into orbit or dig a new well. Just get the quad up reasonably high (even 3 meters will be enough), flick it on, and be ready to flick it off again if it does something strange.
    Log: http://coding.zencoffee.org Tx: Spektrum DX8 Power: 5000mAh 3S1P 20C Zippy Flightmax
    Quad 1: 19" Homebrew Frame, AQ 3.0.1 on custom 2.0.7a shield, Turnigy Plush 25A ESC (SimonK Firmware) + Turnigy 2217-16 Motors, 10x4.5 HK SF Props, OrangeRx R610 Rx
    Quad 2: HoverThings HT-FPV, ArduCopter 2.6, ArduPilotMega v2, HK F-30 ESC (SimonK Firmware) + Turnigy 2217-16 Motors, 10x4.5 HK SF Props, AR8000/TM1000 Rx, 3DR Telemetry

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    Now that is the answer I have been looking for. Now looking back at the wiki on "Altitude Hold" it states the same thing. It just didn't click in my brain I guess. Well thank you xtrmtrk and Darkwolf for your help. The easiest answer and quickest fix. That and when women say "No" which means "Yes" right? Cuz that's how I role. Can I get a high five!!? Hahaha...just kidding.

    Thank again,
    Jayson
    Last edited by jysnchl; 06-04-2012 at 04:31 AM.

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    A follow up question on the altitude hold.
    When hold is activated, how is the throttle stick input handled? Is it completely decoupled from the throttle control or can it be used to increase or decrease the held altitude in some way? Or should I just leave the throttle stick alone for it to be at the correct position when I switch off altitude hold?

    Is it possible to land when in altitude hold? let's say I panic and can't remember the hold switch but need to land quickly.

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    All of the above

    The bump value is the amount of throttle shift that needs to be given to cause the altitude hold to start varying the altitude. So if you push up a little, it will start moving up. Put it back to the hold position and it'll continue to hold in the new height. The panic value is the amount of throttle shift that will force altitude hold off. So if you slam the throttle up or down a lot, it will cut out the altitude hold until you toggle it again.

    You should try and get the throttle position such that the quad is already hovering before trying to activate altitude hold, otherwise the controller will be fighting against the wrong setting all the time.
    Log: http://coding.zencoffee.org Tx: Spektrum DX8 Power: 5000mAh 3S1P 20C Zippy Flightmax
    Quad 1: 19" Homebrew Frame, AQ 3.0.1 on custom 2.0.7a shield, Turnigy Plush 25A ESC (SimonK Firmware) + Turnigy 2217-16 Motors, 10x4.5 HK SF Props, OrangeRx R610 Rx
    Quad 2: HoverThings HT-FPV, ArduCopter 2.6, ArduPilotMega v2, HK F-30 ESC (SimonK Firmware) + Turnigy 2217-16 Motors, 10x4.5 HK SF Props, AR8000/TM1000 Rx, 3DR Telemetry

  9. #9
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    Thanks for the info, couldn't find this in the wiki. It's scary to just try it out without knowing how it's supposed to behave

    How good does it work with the ultrasonic sensor? can I activate hold at a meter of the ground and then fly over a hill without adding throttle? i.e., will it follow the landscape contour?
    Last edited by SwiftingSpeed; 06-04-2012 at 08:57 AM.

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    Senior Pilot wooden's Avatar
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    It will if you're not moving too fast or have your ultrasonic sensor on a gimbal (always pointing straight down). Otherwise, a severe lean of the craft causes the sonar to read the wrong values.

    I've found my Altitude Hold (using baro only) needs a lot more I term than the defaults - this minimizes the oscillations. I haven't messed with it enough to really get it tuned well but I'll report my findings if the weather clears up around here...
    push the envelope, watch it bend


 
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