Wrong behavior - Quad / Tarot 650 / T-motor 2012-13

ArduCopter Copter 3.4
1

Hi guys!

I’m have quad with Pixhawk (3.4.5 - Latest Stable), a Tarot 650 frame with T-motor 2012-13 (kv340).

So the thing is when i used only the vibration mount plate with the pixhawk on top the everything was working good, just had the Vibe Z too high (above 30 /40 when doing auto missions but everything else was working very well). I was using a 12k 6s lipo.

So my idea was to try to remove that vibe and i put a foam* between the vibration mount plate and the pixhawk and the vibes went down, at least in my initial flights and using a 5000mah lipo 6s.

The problems started when i start to test my 12000mah 6s, very unresponsive in althold.

Using the foam with 12k lipo log:
https://drive.google.com/file/d/0Bxn0zmjADHHVeHdTVGdrVEc5ZmM/view?usp=sharing

Using the foam with 5k lipo log:
https://drive.google.com/file/d/0Bxn0zmjADHHVajl2WmN0SEoxdGs/view?usp=sharing

When i land with the 5k lipo the pixhawk do what is supposed to do and i can disarmed with my RC.

But when i use the 12k the pixhawk keeps the motor running in high rpm and wont let me disarmed with RC, i have to disarmed with the GSC.

Any thoughts what could it be? Vibes?

The last problem is that i cant connect** the pixhawk using the USB cable to the pc, the IO board led wont start. But if i connect the lipo everything boot up and if i connect the usb cable i can connect to my pc.

The pixhawk is a chinese clone, i think.

Any thoughts what could this be when looking at the logs, too much foam? anything more serious than that?

Thank you guys.

And sorry for all this questions, i’m a new pixhawk fan (i used to use a quad with a dji wkm).

** image with the red light: https://drive.google.com/file/d/0Bxn0zmjADHHVUTVicUFHNEtoalU/view?usp=sharing

edit. fixed the link to the 12k log (sorry, i put the wrong one but now is the correct one)

2

I have found the ‘ball’ type vibration mounts to be OK but not great, as you have found.
One solution is to add some mass to the Pixhawk.
On my setups I use a layer of foam/1mm sheet lead/layer of foam/Pixhawk
The added mass really has an effect on the transmitted vibrations.

Your USB connection from a computer is generally limited to 500mA and with added components it’s not unusual to exceed this.
It can sometimes be a less than optimal USB cable or weak port on the PC.
I have one setup that does exactly the same thing, previously with the 3DR Pixhawk1 and now with a Pixhawk2.1.
If I unplug all the peripherals it works fine but there is only so much you can run only 500mA.

From a quick look at the logs it appears the Y axis vibrations might be the issue.
I looked at the VIBE initially which is supposed to be some combined summary which did not show anything but a slight increase in Y axis vibes from 7to8 for the 5K to 27to30 for the 12K, but I checked out the IMU accel data and noted that the Y axis looked ok with the 5K battery but increased greatly to what I would call actionable levels with the 12K battery.

Screen Shot 2017-03-03 at 7.08.04 am.png2126×1229 907 KB

Something in your frame or prop setup is not liking the extra load.

3

Thank you mboland.

my guess would be the extra foam (very very soft, maybe too much) and with the 12k lipo the pixhawk keeps balancing from one way to another (its very visible the movement) due to the vibe.

Gonna try with another type of foam (more rigid).

Thanks again.

edit. But mboland how about the ‘‘But when i use the 12k the pixhawk keeps the motor running in high rpm and wont let me disarmed with RC, i have to disarmed with the GSC.’’

Any ideas? Could it be related to the Y excessive vibes?

4

Yes, the acceleration is probably high enough that it won’t set the ‘landed’ flag and disarm.

5

Thank you, jfield.

Well i made a new batch of tests, without the soft foam, and the results are way better:

Lipo 12k: https://drive.google.com/file/d/0Bxn0zmjADHHVR3otYk9fZ3B4MW8/view?usp=sharing

Lipo 5k: https://drive.google.com/file/d/0Bxn0zmjADHHVbzNsZW5CWHp1MUk/view?usp=sharing

The Vibe Z still have picks of 21. But i bet that when i start to do again my auto missions (with speed above 7m/s) the Z gonna go above 30.
How can i reduce the Z? Its so hard to reduce this one.

How important is to reduce the Z, when comparing to the X and Y?

Any good tips?

6

The Z vibration will impact the vertical positioning the most.
So it is quite important to eliminate as much as possible.

In the IMU graph I like to get it down to +/-1 or 2
Not sure about the VIBE values, the dev’s talk about +/-30 but I don’t see the correlation between VIBE and IMU ACC readings.
The VIBE doesn’t seem to give as clear an indication as to the amount or source of vibration.

7

Mboland thx once again for the advices.

Well the IMU graph isnt bad at all:

IMU.AccX (Min: -2, Max:2)
IMU.AccY (Min: -2, Max:3)
IMU.AccZ (Min: -14, Max:-8)

Vibe:

Vibe.VibeX (Min: 0, Max:5)
Vibe.VibeY (Min: 0, Max:7)
Vibe.VibeZ (Min: 0, Max:21)

So any advices to try to remove as much as possible the Z vibe?

edit. the ‘‘IMU.AccZ (Min: -14, Max:-8)’’ was on landing.