Adding a stabilising gyro to the AXN Floater

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I thought I'd try adding a gyro to my AXN Floater to provide some el-cheapo stabilisation (when I didn't want the ArduPilot onboard).

I found a heading hold gyro from DealExtreme and hoped it would work (the standard HobbyKing 401B one wasn't in stock). It really does come in a "Lithium Polymer Battery" package and had no instructions, but looking around at similar products on the web gives you the general idea of how to use it.

It's attached with double sided foam tape and hooked up inline on the elevator channel and a control channel so I can switch it on and off mid-flight.

The control channel determines how the gyro behaves:

  • "Left" or "negative"
    The gyro is in rate mode. It will dampen wobbles and slowly adjust to the new roll angle (i think the delay pot controls how fast this happens)
  • "Center" or "zero"
    The gyro is off and has no effect.
  • "Right" or "positive"
    Heading hold mode, generally used by helicopters and not what is normally recommended for use in planes. This doesn't really seem to be a problem, when you let go of the elevator stick it will hold the current roll angle, rather than levelling itself back out. This is quite easy to get used to when flying as it's basically what the plane will do without the gyro but it does mean it handles differently to how the ArduPilot stabilisation mode works, which is to "magically" right the plane and keep it flying straight and level when you let go of the sticks.

To set this up on the Turnigy 9X transmitter, I did the following:

  1. Go to [AUX-CH] and set CH5 to THRO HOLD (this is the switch on the back left of the transmitter and will be used to switch the gyro on/off)
  2. Go to [PROG.MIX] and set up MIX1 as follows:
    State: ACT
    Master: GYR
    Slave: FLP
    Offset: 000
    Uprate: 000
    Dnrate: 075 (This is the gain, you can tweak this to make it more or less sensitive)
    Sw: NOR
  3. The above is for "heading hold" mode, for "rate" mode, change use the values below instead:
    Uprate: -075
    Dnrate: 000
  4. Plug the gyro control plug into CH6 on the receiver.

The above is a bit random, FLP probably should be the master and GYR the slave, but that didn't work for some reason, and ideally you'd use one of the pots to adjust the gain. Using the PIT TRIM directly to control the gain works, but doesn't allow you to quickly find the zero position and switch the gyro off if you need to, so I went with the switch option instead. Someday I may try and program this into the 3 position switch so it had off/rate/heading hold modes.

I haven't flown with it in the wind yet, but expect it should work and it's certainly a cheap and easy experiment.

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