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Need help understanding failsafe

Posted by Jonathan Challinger on July 15, 2011 at 9:16am

My setup:

DX5e 6-channel radio

AR600 6-channel receiver.

AR600 channel 6 connected to APM channel 8. AR600 channel 5 connected to APM channel 7. APM channel 7 set to mode select. This way I can engage the hardware failsafe to go to manual mode by holding the bind switch, and I can switch between 2 modes with channel 5.

So, I want to know how to set up the failsafe. Ideally I would be able to select between FBW and auto on my ch5 switch, while still having an RTL on signal loss.

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Replies

  • Developer
    Doug Weibel July 16, 2011 at 3:25pm

    If you are using ch8 for mode selection then the hardware mux will put you in manual regardless of what flight mode you assign to position 5.  You may think that is annoying but not nearly as annoying as the dev team finds explaining again and again to people why when they assign some mode other than manual to position 5 it goes to manual anyway (by hardware).  Consequently it cannot be changed.

     

    Yes, the two parameters (long and short) just determine whether Loiter and Auto modes are disturbed by a failsafe or not.  The manual explains that on this page - http://code.google.com/p/ardupilot-mega/wiki/Failsafe

     

    If you find the documentation lacking there is plenty of room on the dev team for anyone wanting to work on it ;)

     

     

  • Developer
    Doug Weibel July 15, 2011 at 10:24am

    Failsafe is a confusing subject, because there are several features called "failsafe".  It sounds like you already understand the "hardware failsafe".

     

    To set up the loss of signal failsafe for RTL to this:

    • Run the throttle trim as low as possible on the TX, set your mode switches in some position other than hardware manual, and then bind the RX.  This is the throttle value you want the RX to output if it looses signal.
    • Run the pwm test and see what this pwm value is on the throttle.
    • Set the throttle failsafe value for a slightly higher value.
    • Move the throttle trim on your TX up to some normal value above the failsafe value you just set and leave it there.
    • Recalibrate your ESC so that it recognizes low stick and the new trim value as zero throttle
    • Redo the radio calibration for APM
    • Set the long and short failsafe enable values as desired depending on if you want to go RTL if you are in Loiter or Auto modes.  You will always go RTL on a throttle failsafe from the other modes.
  • Jonathan Challinger July 15, 2011 at 10:14am

    Excerpt from AR600 manual:

    AR600 Failsafe
    • Prevents unintentional electric motor response on start-up.
    • Establishes low-throttle failsafe if the RF signal is lost.
    • The AR600 removes servo output pulses to all channels except the throttle channel during failsafe.
    • The AR600 throttle failsafe position is stored via the throttle stick position on the transmitter during binding

    So, how do I set up APM to work with this failsafe? How do I ground test failsafe?

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