Naza Lite RTH fail-safe crash (maybe related to altitude hold)

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paland3

New Member
Hey everyone,

Yesterday we tried our hexacopter (naza m lite, multistar 40A ESC-s, 600mm frame, NTM 800kv motors 300W) on a really big field to test the various safety functions. This includes the home orientation settings which worked well, battery voltage check (we have some problems here, it starts to flash red way before it should, so we are playing with the limits) and the failsafe RTH function. The biggest problem occurred at this one. I was flying the multi about 40 m away, 8m above the ground, nothing exceptional. (please note the field is bigger than a football pitch and nobody use it, so it was perfect for crashes) as it was the last flight that day, and the multi was hard to see, we chose the failsafe instead of the home lock (which worked pretty well before). Afer turning on failsafe, the yellow flash came on, and the multi started to ascend. After reaching some height, it navigated back above the starting point very well, and started the hovering. But after the hover (~15 sec I guess) the motors simply turned off. We have a video about it:
https://www.dropbox.com/s/67j3uzcirkz5fao/fall.avi?dl=0

sorry for the quality. Also, my friend put the camera away in shock, so the crash is not recorded. However, you can see and hear that the motors stop, while the led (and the naza I guess) is still on.

We had a lucky crash from 20 meters afterall, all we need is a new frame.
Do you have any ideas what happened?
our ideas:
  • barometer is off, and it thought it has already landed
    • strange, because we had stong gps signal on the ground and did not take off before the led light.
    • but also the altitude holding was a little bit strange during the flight, had to play with throttle to keep it, ~+-3m change was often (we had a fairly tricky wind, though)
  • ESC -s cut off way before they should have
  • Naza motor cut off (intelligent/immediate) problem?
  • Naza firmware bug?

Please let me now what you think. Best wishes, paland3
 

Gary Seven

Gary Seven

Rocketman
Paland3, the best way to help us diagnose your issue would be to tell us exactly how you had things set-up in the Naza Assistant software. What was your motor cut-off setting?

What was the discharge state of the battery at the time of failure? I don't know anything about your ESC's as I use the DJI E300 system, but we're they calibrated?

What you described is an in-flight ECO (engine cut off). To me, the usual suspects would be battery voltage, ESC's, Naza Intelligent vs. Immediate motor control, or operator error.
 

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paland3

New Member
Thank you for your answer, Gary. I checked the things you asked.
Motor cut-off setting is intelligent (I plugged in the naza, and read the values, nobody changed them since the crash).
The battery is 3000mAh, and the charger said we could charge 1600 mAh in to it, so it should have been near to half of its capacity.
The ESC-s are left at default settings (no calibration was done). But I think with intelligent motor cut-off and with half the battery left, the escs should not be the weak link. Are they?
We have a programming board for them, and planning to set them to slow cut down, and low voltage (to make sure that not ECO happens caused by them). But I am really not sure they were the problem and do not know how to check it.

Thanks again, paland3
 

RobBurn

RobBurn

Member
So was this the first time you flew this hex? A lot of information missing... Like was this the first flight for this lipo? What was the cut off voltage setting? I don't know if you have experience with lipos? I ask these questions because if you were unfamiliar with the lipo and is it trustworthy ie. I fly my new batt low so like 10 feet or so and see that it behaves as expected before I trust it. So do you remember if the lipo was hot? I'm wondering how long was this last flight? You mention early that "it started to flash red way before it should" this makes me think you had the voltage cutoff set to high. So based on what you thought flashed red before it should was how long were you into this flight compared to your last flight. It was in RTM mode so it gains altitude and further drops the battery and your esc's cutoff and down she came. Another possibility is you lowered the throttle below 10% and it shut the motors off.

a lot of unknowns, so this is a spit ball response.

Rob
 

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paland3

New Member
RobBurn said:
So was this the first time you flew this hex? A lot of information missing... Like was this the first flight for this lipo? What was the cut off voltage setting? I don't know if you have experience with lipos? I ask these questions because if you were unfamiliar with the lipo and is it trustworthy ie. I fly my new batt low so like 10 feet or so and see that it behaves as expected before I trust it. So do you remember if the lipo was hot? I'm wondering how long was this last flight? You mention early that "it started to flash red way before it should" this makes me think you had the voltage cutoff set to high. So based on what you thought flashed red before it should was how long were you into this flight compared to your last flight. It was in RTM mode so it gains altitude and further drops the battery and your esc's cutoff and down she came. Another possibility is you lowered the throttle below 10% and it shut the motors off.

a lot of unknowns, so this is a spit ball response.

Rob
Click to expand...

No, it was not the first time, was around the fifth. The lipo flew before, and was not hot. The flight was no longer than any previous ones, around 7 minutes top. The flash red is from the naza, it is a problem we still have to handle, but the cut off voltage (of the ESC-s you ask right?) is not known, we will recalibrate them. The throttle was not touched but left in middle position, and also failsafe was on, so it should not matter I think. Your other theory abot the altitude gain can be right! However, the cut off was long after the ascending, during the hovering state. So you think it is a really unfortunate coincidence that the voltage dropped below the ESC cutoff limit (All of them stopped) just before it should descend? Do you have idea how to check this? We are afraid to run the RTH function again. Should we?
Thank you, paland3
 

Gary Seven

Gary Seven

Rocketman
paland3 said:
No, it was not the first time, was around the fifth. The lipo flew before, and was not hot. The flight was no longer than any previous ones, around 7 minutes top. The flash red is from the naza, it is a problem we still have to handle, but the cut off voltage (of the ESC-s you ask right?) is not known, we will recalibrate them. The throttle was not touched but left in middle position, and also failsafe was on, so it should not matter I think. Your other theory abot the altitude gain can be right! However, the cut off was long after the ascending, during the hovering state. So you think it is a really unfortunate coincidence that the voltage dropped below the ESC cutoff limit (All of them stopped) just before it should descend? Do you have idea how to check this? We are afraid to run the RTH function again. Should we?
Thank you, paland3
Click to expand...
[MENTION=17303]paland3[/MENTION]; I agree with [MENTION=14729]RobBurn[/MENTION]; that you are not giving us enough information so we are forced with "spit ball" responses. Is your battery 3S or 4S? You do realize that the flashing red LED from the Naza is indicating a low voltage condition and to land immediately. However, it's only reacting to what you have set under "Voltage" in the Naza Assistant software.

This is what I have currently set up for my Zippy Flightmax 3S, 4000mAh battery. I usually start seeing the flashing red LED at around 15-16 min flight time, depending. Of course if I hit the throttle at this point I'll see the flashing red light due to sag, but when I let off the flashing stops. I know to land my F450 once the red LED starts complaining under hover conditions:

attachment.php


Key points here if you insist on using Voltage alerts: You MUST first calibrate using a known, charged battery. Take a reading with your multimeter, fire up your MR and the Naza software, and calibrate the voltage. Next, be sensible (and conservative) when playing with this feature. Clearly, if your Naza was complaining during flight with the red LED warning but later you only put back 1600 mA on a 3000 mAh battery, there is an issue.

You must also consider the battery itself. It's possible you have one of your cells bad, and even though you are fine on capacity during a flight you may be reaching a critical low voltage condition. Like I said before I don't know anything about your ESC's, but clearly they shut down for a reason. The Naza software won't tell you if one of your cells is bad...only the overall voltage condition. Do you have one of these (or similar)?

http://www.hobbyking.com/hobbyking/...larm_UK_Warehouse_.html?strSearch=low voltage

If not, get one so you can individually measure the voltage of each cell. You can use this during flight as a low voltage alarm and dispense with the Naza Low Voltage Alert altogether. Does your charger do balancing? Are you able to measure IR of the battery and it's individual cells?

HTH some.
 

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paland3

New Member
Thanks guys for the answers!
I will try to provide more information.

Here is the video about the fall:
https://www.dropbox.com/s/67j3uzcirkz5fao/fall.avi?dl=0
(Sorry for the quality)

Here is a video about the hexa during a normal flight (so you can check the usual performance, size, etc)
https://www.dropbox.com/s/fjaflsg0btew3hp/_DSC6446.MOV?dl=0

Here is our ESCs:
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=44304

These are our batteries:
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=44304

Thank you for the card, Cbergen. We already got one, and successfully burnt it (reversed polarity...).
A voltage meter is already on the way. Currently, we are using the charger for that.

We calibrated the vlotage alert today, worked fine, even the landing.
Also did a recalibration, naza dance, and re-positioned the important parts. (had to replace half of the frame)
However, we did not dare to try the failsafe, not even the simple landing, because I am afraid the barometer is off (and that is why it fell). Do you have some tips how to check that?

thanks again for the answers, paland3
 

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