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Old Feb 14, 2012, 07:08 PM
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Austin, TX
Joined Jan 2009
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Failsafe...again

Sorry, but I only get to read this thread once a day....I will try to make this a simple step by step sequence to understand "failsafe"....for this discussion I am talking about V1.2 release only.

First, lets start with the NAZA controller itself....on its "U" input the NAZA controller determines which of three modes it is in: MAN, ATTI, or FAILSAFE...
IF its receiving pulses from the receiver, then its in whatever mode, the pulse width directs...look at the Assistant screen...in a narrow range around one end of the channel throw it will be in MAN, and ATTI in the other...everywhere else it in the NAZA failsafe mode (not to be confused with the TX/TRX failsafe if they have one)
IF its not receiving pulses (4 channel or signal loss on some RX types) then it will be in ATTI mode. (I don't know if it looks at throttle channel to detemine if it should go into FAILSAFE mode or stay in ATTI mode...I would have designed it to detect the missing pulse on throttle and force FAILSAFE...but I cant test this...)

Second, the behaviour of the NAZA controller when in its FAILSAFE mode is to autoland...period...it IGNORES all other control inputs in this mode...

Third, depending on what your RX system outputs to the NAZA when it loses signal, will determine the NAZA mode:

Case 1: RX holds last valid output on all its channels....then the NAZA will fly away...bye bye...why? last valid input was MAN or ATTI mode..throttle at whatever position to fly it...if it was below 50%, descending, then it will continue....hovering, it will continue....climbing, it will continue..
Case 2 : RX goes to a failsafe setting that you set up...Then it can go into NAZA FAILSAFE, or stay in ATTI or MAN mode at a predetemined throttle position...you decide...I have mine set to force the U channel such that FAILSAFE occurs and it autolands ..all other control inputs are ignored in FAILSAFE..set em anywhere you like...it doesn't matter(note: low voltage autoland is a little different...see below)
(I also have a switch set up to force this U channel value so I can force autoland anytime I wish without turning off my TX)
...if you want you can have it stay/go to ATTI mode and have a throttle setting below 50% to try to do your own autoland...but why? NAZA does it automatically and better...it judges altitude to "home" and changes descent rate as it nears the ground (Assuming its the same elevation as when you powered it up)...but you can if you wish..
Case 3:: RX holds last valid output on all channels but zeros throttle.....U channel hasn't changed so mode doesn't switch...same effect as pulling the throttle below 10% in whichever mode you are in MAN or ATTI...behaviour determined by motor cutoff mode...fast descent or fall out of the air..
Case 4: RX stops outputting signals....beats me, can't test it...it will EITHER go into FAILSAFE or ATTI mode with a tbd throttle setting...again, when they updated to 1.2 software to include 4 channel operation in ATTI mode only, I would have made sure that missing pulses on throttle channel forced FAILSAFE...but I can't test that..

finally a note about low voltage autoland...UNLIKE FAILSAFE autoland, you DO have a tiny bit of control....you can slow the descent with increasing throttle...but the control range is small and continuosly decreases as it nears its "home" altitude..not of much use in my opinion...I have tested this by the way...
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Last edited by Atx_Heli; Feb 14, 2012 at 07:15 PM.
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Old Feb 14, 2012, 08:41 PM
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Is there a Futaba 8FG specific programming guide for the f450 with Naza? I can't seem to find where this is. Any help is appreciated!
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Old Feb 14, 2012, 08:52 PM
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United States, FL, Orlando
Joined Mar 2011
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Atx, thank you very much for the breakdown. It has helped me understand much better the correlation between the Rx Failsafe and the Naza failsafe.

It does raise one question for me though. In my case, my mode switch drifted into failsafe territory. When that happens, is it actually able to engage the rx failsafe the same as if the tx was turned off? If so that makes sense and explains why nothing I could do would restore control. I was thinking that the mode switch going into failsafe territory would still not override the built in Rx failsafe for when the Tx was off.
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Old Feb 14, 2012, 08:56 PM
'FPV'er...not a "LOS'er
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Las Vegas, NV
Joined Sep 2003
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Thanks Atx-Heli. That really does help explain a lot. It looks like the best option for an Rx with failsafe capability is to engage Failsafe mode and low/no throttle so the Naza can bring it down safely. With your explanation I'm sure several folks will be able to try and verify failsafe response.

With this info I went back into my Tx and reconfigured my 3-way mode switch. I originally had my low position for Manual mode, mid position for Failsafe mode, and upper position for ATTI mode. This meant to pass from Manual to ATTI and back I had to transition through failsafe....for no reason. I reconfigured my 3-way switch so now low position is Manual, Mid position is ATTI, and upper position is Failsafe. Now I can transition from Manual and ATTI without passing through failsafe...yet can get to failsafe easily if wanted/needed.
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Old Feb 14, 2012, 09:02 PM
'FPV'er...not a "LOS'er
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Quote:
Originally Posted by Blucross View Post
Atx, thank you very much for the breakdown. It has helped me understand much better the correlation between the Rx Failsafe and the Naza failsafe.

It does raise one question for me though. In my case, my mode switch drifted into failsafe territory. When that happens, is it actually able to engage the rx failsafe the same as if the tx was turned off? If so that makes sense and explains why nothing I could do would restore control. I was thinking that the mode switch going into failsafe territory would still not override the built in Rx failsafe for when the Tx was off.
It sounds like whenever the Naza enters failsafe mode it ignores all Tx commands and should enter 'autoland' mode. That certainly doesn't explain why, if you truly were in Naza failsafe mode, your 'copter ascended and drifted away. It should have started coming down. So...we have your report of a fly away for some reason and another with video showing the Naza holding altitude when the Tx was shut off. Both kind of contrary to the above failsafe description. Curious...
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Old Feb 14, 2012, 09:08 PM
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I have set my Naza up with Tx failsafe, LOS = throttle at 50%, gear switch to failsafe and all other channels to center, and without Tx failsafe. When I turn off the transmitter or switch the failsafe switch, the Naza lands the same way, slow decent to land and the motors turn off. If the Naza is moving, i.e., not hovering, the Naza will land with the same momentum it had when it went into failsafe. If your Tx/Rx offers a receiver based failsafe option, I would use it. If not, it will still work. I like redundancy when available. You guys are way over thinking this.
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Old Feb 14, 2012, 09:16 PM
Gravity is a cruel mistress...
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United States, FL, Orlando
Joined Mar 2011
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Ed,

I completely agree this shouldn't be rocket science. Seems like the Naza malfunctioned in some way then since it should autoland regardless of the condition.

Between you, Van, Atx and others I have gotten a great understanding of this behavior. Thanks again

Time to cut my losses and move on. I just keep replaying it my head and saying "WHY!?!?"
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Old Feb 14, 2012, 09:17 PM
'FPV'er...not a "LOS'er
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Las Vegas, NV
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Quote:
Originally Posted by Tahoe Ed View Post
I have set my Naza up with Tx failsafe, LOS = throttle at 50%, gear switch to failsafe and all other channels to center, and without Tx failsafe. When I turn off the transmitter or switch the failsafe switch, the Naza lands the same way, slow decent to land and the motors turn off. If the Naza is moving, i.e., not hovering, the Naza will land with the same momentum it had when it went into failsafe. If your Tx/Rx offers a receiver based failsafe option, I would use it. If not, it will still work. I like redundancy when available. You guys are way over thinking this.
What cutoff mode are you using? I'm thinking it doesn't matter, but just curious.

Have you and Freddie gotten together yet? Perhaps this weekend we can get together somewhere and fly...
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Old Feb 14, 2012, 09:26 PM
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Quote:
Originally Posted by Vantasstic View Post
What cutoff mode are you using? I'm thinking it doesn't matter, but just curious.

Have you and Freddie gotten together yet? Perhaps this weekend we can get together somewhere and fly...
I use intelligent and I don't think it makes any difference.

I talked to Freddie today and he is still getting settled and the wife and I had plans for this afternoon/evening. The plan is for tomorrow. If he doesn't have to leave this weekend you guys may be able to get together. We are going to spend a week at our Tahoe condo. I think I will take my WKM with me this time.
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Old Feb 14, 2012, 09:37 PM
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Mankato, MN
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Blucross,
I maybe missed it but how do you know your transmitter drifted into failsafe?
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Old Feb 14, 2012, 09:43 PM
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United States, FL, Orlando
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Quote:
Originally Posted by leif-mindy View Post
Blucross,
I maybe missed it but how do you know your transmitter drifted into failsafe?
Well, I don't know for sure but it is plausible. WHen it was on the bench and connected to the Assistant software I noticed the U channel flickering slightly in and out of mode until I put it right in the middle of the end points.

When I came back to it an hour later, it was in failsafe right off the bat and I had to further adjust the endpoints again to bring the channel back into function. It worked fine for the next few hours, but later that night I attempted to fly it in my front yard and again, fast flashing yellow light, had to bring it inside and re adjust the end points a few clicks to knock it back to normal operation. This should have been a red flag to me, but I figured worst case it would land itself if it happened during flight.

On the day I lost it, I noticed the yellow light again fast flashing which I believe means it has gone into failsafe mode. I can't think of any other explanation as to why it did what it did given the track record.

So, technically, I am not 100% sure, but all of the signs tell me that's what happened.

This video is a good example of what I mean, except in my case it was the U channel that was doing it pretty badly.

Turnigy 9x TX Tansmitter Drift (5 min 2 sec)


After doing some research it seems to be an issue with the stock 9x transmitter module and not the actual transmitter itself. People who switched to another module did not experience this issue. I am going to put my FrySky module in it and test to see if it happens again. I NEED to be able to trust my gear.

Maybe I should be tethering my quads with fishing line until I get that confidence back.
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Old Feb 14, 2012, 09:46 PM
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Mankato, MN
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Sorry, I forgot to say naza failsafe. Maybe it was just Rx failsafe and it let it fly away. The naza may not have ever gone into failsafe?
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Old Feb 14, 2012, 09:54 PM
'FPV'er...not a "LOS'er
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Las Vegas, NV
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Quote:
Originally Posted by leif-mindy View Post
Sorry, I forgot to say naza failsafe. Maybe it was just Rx failsafe and it let it fly away. The naza may not have ever gone into failsafe?
If the Naza's VU is fast flashing yellow then its in failsafe mode...doesn't matter if if it was via Rx failsafe commanded or Naza failsafe commanded. I believe Blucross mentioned it was fast flashing yellow in his last post...thus thinks it had entered into failsafe mode. Flicking back to Manual mode should have exited the failsafe unless it too had drifted outside of the 'window'.
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Old Feb 14, 2012, 09:56 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
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Quote:
Originally Posted by Blucross View Post
Well, I don't know for sure but it is plausible. WHen it was on the bench and connected to the Assistant software I noticed the U channel flickering slightly in and out of mode until I put it right in the middle of the end points.

When I came back to it an hour later, it was in failsafe right off the bat and I had to further adjust the endpoints again to bring the channel back into function. It worked fine for the next few hours, but later that night I attempted to fly it in my front yard and again, fast flashing yellow light, had to bring it inside and re adjust the end points a few clicks to knock it back to normal operation. This should have been a red flag to me, but I figured worst case it would land itself if it happened during flight.

On the day I lost it, I noticed the yellow light again fast flashing which I believe means it has gone into failsafe mode. I can't think of any other explanation as to why it did what it did given the track record.

So, technically, I am not 100% sure, but all of the signs tell me that's what happened.

This video is a good example of what I mean, except in my case it was the U channel that was doing it pretty badly.

http://www.youtube.com/watch?v=kkjBJ9SEJi8

After doing some research it seems to be an issue with the stock 9x transmitter module and not the actual transmitter itself. People who switched to another module did not experience this issue. I am going to put my FrySky module in it and test to see if it happens again. I NEED to be able to trust my gear.

Maybe I should be tethering my quads with fishing line until I get that confidence back.
I've been using a FlySky 9X for a bit now and never noticed any drift problem. Also I've not been using the stock Rx either though. I'm using a Dragon Link UHF transmitter deck in my 9X. If the drift is Rx related then that would explain why I've never noticed this. I'm also not using the stock 9X firmware. The er9x firmware makes this into a much more powerful system than stock.
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Old Feb 14, 2012, 10:01 PM
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Mankato, MN
Joined Jun 2006
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Quote:
Originally Posted by Vantasstic View Post
If the Naza's VU is fast flashing yellow then its in failsafe mode...doesn't matter if if it was via Rx failsafe commanded or Naza failsafe commanded. I believe Blucross mentioned it was fast flashing yellow in his last post...thus thinks it had entered into failsafe mode. Flicking back to Manual mode should have exited the failsafe unless it too had drifted outside of the 'window'.
I see that now, thanks. Tapatalk didn't update fast enough for me to see his last post.
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