I was maidening a mini H-quad with a Pixhawk running AC3.1. On my first hover in stabilize mode, it worked beautifully. It was hovering perfectly still without any trimming needed. About 4 minutes into the hover, with the quad at about 2 meters high, all the motors suddenly cut off, and the quad just fell to the ground. I have attached the Pixhawk log file and hope some knowledgeable kind soul can help me decipher what went wrong.
Thanks for any help rendered!
Staq
PS: The quad suffered no damage, only 2 broken props. Really wish to know what really happened up there. Dare not fly it at the moment.
Replies
no, if all ESC's was out of power/underperforming for any reason, you'd see logs indicate a huge increase in motor PWM and ThrOut.
If motor 4 was actually delivering 100% when commanded, and the other close to nothing, you'd see it tumble vey fast.
What you see is attitude get out of control, and the three other motors dropping throttle in order not to flip the quad, as motor 4 lost it's power.
Once you rear-right arm was lower than the rest, it had to proportonally reduce the throttle to the other motors, if it did not, but increased/maintained throttle, it would get lateral speed, and then tumble uncontrollably in the air
Andre, please see my attached graph in reply to Tim's post. Why does all current and voltage readings cut out just before the spike in signal to ESC 4?
Sorry, I as about to recheck the log, and I must have been looking at wrong log, or failed to see the cause:
Plot ATT.Roll vs ATT.DesRoll - , you'll see a huge error near line 16000
same for ATT.Pitch vs APP.DesPitch ,
now you can plot RCOUT.Chan1...4 , you'll see that all are reducing thrust, except for motor 4 - that is asked for 100% at line 16212. - that did not help the attitude.
Conclusion is simple; you had an ESC or mechanical failure on rear-right motor.
Basically Tim was right, I was commenting on one of the other 40 logs I had in download folder :)
ESC or power delivery problem suspected, could you explain the rest of the setup as I would be happy to try and diagnose
Quad is a 250 size H-frame mini quad.
Motor: Tiger Motor MN2204 2300kV (brand new)
Props: Gemfan 5030
ESC: Afro 12A pre-flashed with the latest SimonK firmware
Batt: 2x Turnigy nano-tech 1300 mAh connected in parallel
Just a thought, what if the 3DR power module is faulty? Will it give the kind of problem I am experiencing?
Looks like a hardware problem, like sync loss. What combination of ESC/motor/prop are you using?
I'm not an expert on logs, but it looks like you had a motor or ESC failure, or burp. The following throttle in/out picture shows that Pixhawk suddenly increased throttle out in response to trying to keep the copter stable (while throttle in was steady). The roll/pitch graph shows the tumbling of the copter. The final picture shows RCOut for the 4 motors and it's clear that all of a sudden one motor (channel 4) gets maxed out, presumably because it or its ESC has failed and APM is trying to compensate by boosting its power. Your battery volts and current look okay and there was no brownout of the PIxhawk.
Please have a look at the attached graph. I have plotted RCOut together with Voltage, Current and Vcc. Notice that all voltages and current and Vcc already stopped recording just *before* the moment RCOut Channel 4 spiked. So, that could mean no power is going into ESC 4 even though Pixhawk send in a 100% signal to it. In other words, I cannot conclude an ESC problem when there is no power going to all the ESC. But why is Pixhawk still able to log its final dying moments? Could be the backup power from its servo rail as I have a single ESC +5V connected to the servo rail. Is this a symptom of a faulty power supply module (original 3DR component)?
Any thoughts?
crash1.jpg
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