I've been struggling to understand how to get the APM failsafe working properly and have yet to find some clear instructions that a noob like I can follow. It suddenly dawned on me how to get it all setup.
Here is my normal zero throttle output:
Here it is when the radio is off:
The AR8000 can be taught what to do if it looses contact with the mothership. The default is to leave or move the throttle to zero. As you can see, zero is normal and not enough to invoke the APM failsafe. (see here for more info on the APM Failsafe: http://code.google.com/p/arducopter/wiki/AC2_Failsafe)
What you need to do is tell the AR8000 to go below zero when the radio is lost and here's how you do it:
- Turn on the radio and go into servo setup.
- Find the throttle travel setup (on the DX8 it's the first screen)
- Scroll down to negative travel (Left hand 100%). Change that to as high as it'll go. 140% in my case.
- Confirm in Mission Planner that throttle input is now around 920uS
- Turn off radio and receiver.
- Insert Bind plug into RX and turn on.
- Remove bind plug from rx. Light should continue blinking.
- Ensure throttle stick is down.
- Turn on radio while holding down bind button. Radio should rebind.
- Turn everything off.
- Turn radio back on and change the throttle throw back to 100%
- Turn on quad and connection with MP
- Confirm that minimum throttle is back to around 1100.
- Turn off radio and throttle should now drop to around 920uS (or whatever it was beforehand)
- If not, start again.
- Now go to parameters in MP
- Find THR_FAILSAFE and set it to 1.
- Find THR_FS_ACTION and set it to 2 (1 = continue on Auto mission, 2 is RTL)
- Click on the write params.
- Click on Refresh to ensure it wrote it.
What you have done is told the receiver that when you loose contact, this is the new throttle position. It is of course, way lower than normal range. The low value is enough to trigger the APM failsafe which will RTL and land.
This all works in theory for me and MP seems to agree, I'll be out testing it tomorrow but just wanted to get it all down on paper so to speak.
Comments
Have you found a solution?
I have the same problem!
Good idea I ll try that also!
Ah, that should be fine then. The roads look a bit like the roll-out areas on a runway but not quite which is why I was a bit confused.
What you can do, I think I wrote about it somewhere, is to set the mixer in your radio to "fake" fail-safe.
You can then trigger failsafe by causing the throttle to go way down. The advantage here is that you are not turning the radio off and back on again which goes against everything when your expensive toy is in the air. :)
Thank you Grispin for you answers! It's not an airport but an industrial area 60km from the nearest airport. So I guess it's the criteria on your first answer that I don;t meet and that was a great relief for me!
Thank you again!
Also Alex, that location of yours looks like it might be an airport of sorts. Is that so?
Not sure of the detail and how much it has been followed but I thought that had implemented the "don't fly near airport" feature so your plane might not work there.
The motors will not start if they're not already running.
If I remember correctly, the following needs to happen:
Armed, motors running (as if it was flying)
It has to be more than 20m from take-off point for FS to trigger RTL
And 5m above where it was.
I may be wrong - cannot remember all the criteria.
basically, if it's not flying or near home, it won't RTL by itself
Just followed the procedure at home,Failsafe is activated, first short and then long, but the motor does not start. Any comments on that before I go for field test?
Good news that it works when turning the tx off. :) Nervous times.
One thing that I was convinced was a problem though - talking from memory here so may be wrong or things have changed since:
To cancel FS you have to have a mode change. I had a a few crashes when flying auto and on the edge of the Tx range. My thoughts are such:
Rx loses signal, drops throttle to FS value.
Rx regains signal and comes out of FS
Rx loses signal and goes back to FS.
At some point, the APM thinks it's throttle-down and your quad crashes.
I had it twice and a friend once - auto flight, about 3/4 of a mile from where I was standing. First two times, while flying auto, radio was dangling by my side, antenna pointing down, against my leg; loads of attenuation. Heli crashed, logs showed nothing interest other than FS triggering.
Tried again with radio held up above my head and it flew fine.
I'm scared to test the scenarios....
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