Motor almost off in the air and high cliping

[alberto.munizaga (AMV)]

Hi!

I was trying the first flight of one of my new builded drone.

I have set some PID for the model, some manual twiching from another similar drone I have build with the same specs before.

So I was seeing the drone, 15 meter high, and I saw the motor 1 was very very slow… not stoped, just very slow. The drone doesnt lose control, but I felt on the remote the drone was less responsive.

So I tought, if the motor 1 was almost dead, the ESC or some elctronics could have some problems, and on the telemetry Log I will see a very high signal on motor 1 from the FC, and a low signal for the motor number 2.

But this is what I get, I got the opposite

So i understand from the graph the FC sent the signal to Motor1 to be that slow to that point. Em I right? So no electronics or hardware problem I think.

meanwhile I was flying, I put the tune graph from MP to check the vibrations, the Vibe window, and the EKF barrs to check the flight. The numbers were ok over all the flight.

This is the Vibe numbers.

I think its a normal chart.

BUT, the cliping of the number 2 was awful:

I understand the cliping is related with the vibrations on the first chart, or im wrong? And i think my vibrations are no to high to have that kind of cliping.

So, that cliping can be related with the motor problem? Bad PID can result in high cliping?

Here is the Log

http://robomotic.dyndns.org:16211/archivos/logs/motorIssue.bin

I did 5 flight, and 3 of them were OK, no motor problem. Here is a log from a normal flight

http://robomotic.dyndns.org:16211/archivos/logs/goodFlight.bin

I will appreciate all your comments and help!

Im using Pixhawk 2.1 BlackCube, 3.6.11FW, Here GPS

Thanks!

[mboland (Mike Boland)]

Looking at the RCout I see a failure of motor 2 and the reduction of motor 1 to compensate.

The IMU vibrations look quite acceptable

So it is curious why clip 0 and 1 should be flat and clip 2 increasing like that.
If anyone knows what could effect clip2 without being seen on clip 0 and 1 please chime in.
That may be a clue and warrants further investigation.

You can see here where your desired and actual deviate at the time of the motor shutdown.
Do your ESC’s have thermal protection?
Current limiting?
Any other settings that would hinder its operation?

[alberto.munizaga (AMV)]

Thanks Mike!

But! I was looking the drone at the moment of the fail, and I saw the motor 1 slow down, the motor 2 was OK. So I think the FC send the signal to the motor 1 to slow down, maybe because the cliping…

I was cheking my olds logs with the same setup, and I never get that kind of cliping. Then I realize the Cube im using had a crush, so im changing the cube for a “uncrush one” and do the test againg.

May be thats why the motor fails too…

[dkemxr (Dave)]

Motor 1 would slow down if there was a thrust problem with motor 2.

[alberto.munizaga (AMV)]

Thanks Dave!, but im very sure Motor2 was OK, I was looking at, and was spining just fine, the necesary to keep it straight…

[alberto.munizaga (AMV)]

hi!

Ok, some news. I have change the FC and the FC carrier, so no more motor problem.

But the cliping still there.

Here is the link to the log
http://robomotic.dyndns.org:16211/archivos/logs/lastFLight.bin

I have realize the cliping happend at the moment of hard braking. For example, rolling the drone left to right very hard, when I do a hard braking especially to de left, 100 or more cliping appear.

If the drone is hovering, no cliping. if the drone is moving slow, no cliping. But running faster and turn right or left faster, cliping appear.

Its normal?

I have tried with another kind of props, and the result is the same.

[proficnc]

Quite normal in situations like that. Clipping by itself is not a concern, continuously clipping is bad

[whatgoesup (Robert Jones)]

How many imu units are there? The 0,1,2 referred to under vibe selection could be for separate imus. The flight controller spec should be able confirm the number.

[proficnc]

You are correct Robert, it’s actually the third IMU, so it’s not at all of concern as that’s not isolated