Replies to This Discussion

Permalink Reply by Jonathan Challinger on 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?

• ▶ Reply

DeveloperPermalink Reply by Doug Weibel on 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.

• ▶ Reply

Permalink Reply by Jonathan Challinger on July 15, 2011 at 11:30am

I understand now. I would never ever have figured that out. The wiki should to be amended to be more clear and descriptive.

Thank you.

• ▶ Reply

Permalink Reply by Jonathan Challinger on July 15, 2011 at 2:41pm

FS_LONG_ACTN and FS_SHORT ACTN are completely undocumented as far as I can tell. What do they even do? What should I set them to?

• ▶ Reply

Permalink Reply by Jonathan Challinger on July 15, 2011 at 3:06pm

It won't let me set "Position 5" on my mode select switch to anything but "manual."

I already have manual by engaging the hardware failsafe. How do I disable this annoying handholding feature?

• ▶ Reply

Permalink Reply by Jonathan Challinger on July 16, 2011 at 7:24am

I ended up editing the code to allow this. I also looked up FS_LONG_ACTN AND FS_SHORT ACTN. If FS_SHORT_ACTN is set to 1, the aircraft will almost immediately go into RTL mode from auto mode.

If FS_LONG_ACTN is set to 1 and FS_SHORT_ACTN is 0, the aircraft will wait 20 seconds to go to RTL mode from auto mode.

It didn't seem to be switching to circle mode from FBW when I had FS_SHORT_ACTN set to 1, but I haven't flight-tested the failsafe.

• ▶ Reply

DeveloperPermalink Reply by Doug Weibel on 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 ;)

 

 

• ▶ Reply

Permalink Reply by Jonathan Challinger on July 16, 2011 at 6:07pm

Actually it forces manual on position 5 no matter what channel you select for mode selection.

Those two parameters affect FBW modes as well.

The failsafe thing in the wiki is terribly hard to understand. I would be quite willing to clean it up. For now, I'll just add a comment to it when I get to a real computer.

• ▶ Reply