Story: Performed QSTABILIZE, Performed QHOVER. No Vibrations whatsoever.
In Q Loiter I wanted to perform some basic axes moves. Ascent, roll, yaw, pitch forward, pitch back. Altitude of performance was about 2m. When was about to perform the final maneuver (pitch back) I heard motors rpm to drop all of a sudden and the plane crashed.
The whole aircraft is performing as it should after the crash in the bench. The 4+1 ESC works, the 4 motors spin.
Power to the VTOL engines has suddenly been cut off.
The current (yellow line) drops abruptly from over 40 amps to almost 0 amps. The motor controllers do their best to regulate upwards in order to compensate, but without a power supply, this is not possible.
That is exactly what i heard with my ears. A sudden reduction in RPM. A motors cutoff in other words. All maneuvers prior to that performed nicely. I should have enabled ESC telemetry but i thought it would not be needed. I wonder what may be the cause of the cutoff. What are the most possible reasons?
The outputs are indeed running at ~1700μs which is high. In the next hover test i will connect the esc telemetry to be able to view the rpm and the temp. Is it a good idea to give thrust while holding the vehicle in the ground to record the ESC response instead of hovering? After looking at the log files i spotted the RATE→Aout plot.
What this plot actually inform us? Given the description in the right bottom it is the percentage of vertical thrust output current being used. The readings are fairly low.
Btw the ESC is 4X55A and given that the total vehicle current consumption at hover was ~50A each individual ESC managed ~12.5A during the hover. This is way lower than the 55A capacity. It should not overheat when working below 1/4 of its full Amperage capacity. Is it a crucial factor that the ESC is enclosed inside the fuselage?
Is the ESC still working after the crash? Do you have any idea whether the interface connector on the ESC might have come loose? Could a high-current cable connected to the ESC have come loose due to a cold solder joint? If the ESC is working, you could test it carefully on the ground with the propellers facing down in QSTABILIZE mode.
I’ve had a 10kg VTOL drop due to it’s 4-in-1 ESC thermal throttling due to the lack of airflow within the fuselage. Personally I moved to 4 individual ESCs mounted in the airflow of the props and that fixed everything. But in my case my 4-in-1 ESC did have ESC telemetry so that was an easy spot.
I will check the servo-style connectors from the flight controller to the ESC.
Cold solder joints are a nightmare. I have learned my lesson from the past where in a simple RC plane i held some bullet connectors with a small metallic vice when soldering them. The metallic vice absorbed some heat during the soldering resulting in some cold joints. From there on, i do all my connector soldering holding the connectors in wooden slots. I will first try to move ESC’s cabling extensively with my hand to check for discontinuities while motors working without propellers. If i find something suspicious i will redo all the power joints to the ESC.
Do you mean interchanging the propellers in the motors in order for the thrust to generate upwards? It is a good idea. I was planning to perform static tests on the ground by holding the UAV towards the ground to observe ESC temperature, but your method seems more reasonable! I will try to connect ESC telemetry to observe what temperature reading the ESC gives, but in addition i will monitor the ESC with an infrared thermometer manually.
If i encounter a temperature problem in the static tests what is the next move? Will a fan blowing air away from the ESC is a solution? The fuselage has air inlets in the nose and air outlets in the tail but those are for the horizontal flight. When on hover these holes has no usefulness. If i put a fan in the 4in1 ESC the hot air will be trapped inside the fuselage again
thank you for your input on this. Only real temperature measurements will tell the truth in my situation. I originally bet that there will not be any temperature problem because the ESC will work in 1/4 of its rated current (12.5A per ESC when the manufacturer rates each ESC for 55A). I will see when testing. It is a really shame damaging such aircrafts.. Thank you for your input.
These 4in1 ESCs are meant for quadcopters and to be mounted in open frames.
These quads typically have very very short high load times, so the max. amps rating is accordingly. They can handle these currents until they got thermally limited.
Just do some maths:
The 4in1 ESC has about 95% efficiency at best. During hover the VTOL total electric power is approx 1000W (20V x 50A) This results in 50W heating power in small space, likely more. Compare this to an old lighting bulb (60W input, cannot be touched after a short time)
For VTOL flying you need a forced airflow. Put at least one fan to the side of the ESC. It needs airflow on both sides. Better 2 and have inlets in the front and outlets in the back. Outlets need to be bigger than the inlets to avoid compression inside the fuselage which affects the baro readings.
I had single ESCs mounted in a foam fuselage without much airflow heating to >100°C at 10A - max rating 55A.
This might be a battery connector issue. Check the quality of your connectors (XT90 or XT150?) and make sure they can handle the current. Some cheap (Chinese) connectors claim to be able to handle the current, but they aren’t.
I use XT90 genuine AMASS connectors, bought from a large and reputable eshop. They have green anti-spark lanes also. I will check the soldering again. Thank you!
