M4: Motor trouble when it comes to GPS Fix

[fseider]

Hi,

i have trouble with my quad 250 size.
I have the problem that it makes little short twitches in PH mode again and again. This means that the motors turn up briefly and then everything is back to normal.
I have found out that it only happens when it get an GPS fix. This can be seen on the log

0-14000: GPS covered with carbon, Manual Mode -> No interference
14000-23000: GPS coveredwith carbon, PH Mode -> No interference, high peak at 22000 is the landing
22000-45000: Waiting for GPS fix, at 45000 blue lamp is on
45000-52000: GPS Fix, Manual Mode -> slight disturbances
52000-60000: GPS fix, PH Mode -> clearly noticeable disturbances
60000- 70000: GPS Fix, Manual Mode -> clearly noticeable disturbances

Here the Thread in the German FPV-Forum with the original File. (005-AQL.LOG.zip)

M4v2; aqv7.0.r442.b1848-hwv8.6-ext_esc; N4 Exp. Board (without BT); KISS 12A; Motor: X1608 2300KV;

Any Ideas?

Regard Frank

[fseider]

it would really important when someone could help me, because I do not have trust in this system...

[bluuu]

post hAcc and vAcc graph

[fseider]

Here it is:

In the first Picture I've cut the peak.
The second is the original.

[JussiH]

The nature of the UKF means that if you take off without a good heading estimation and no GPS lock, the system will make this behavior as the GPS corrects the heading estimate and the gyro bias. Its perfectly normal, and usually it will go away after a short while (once the UKF has converged on the correct heading), or you can land for a second and take off again.

The solution is to properly calibrate the Magnetometer and wait for a GPS fix before take off.

[fseider]

I do not think this is the solution. Generel I start with a GPS fix and the engines twitch from the beginning. The compass is calibrated!

[aBUGSworstnightmare]

Hi Frank,

is this reproducible with another expansion board (M4-BLDC i.e.)?
Can you post a picture from the setup, showing what's next to the GPS antenna uFL connector?

Joerg

[JussiH]

Post the log files and params here, pls. I am not a member at FPV-Community.

A video with corresponding logfile showing the phenomenon would be very helpful.

Take a look at your heading estimation before takeoff - is it correct?

I read on the other site that you are powersupplying via 5V. You should not do that, the N4 expander supplies 4V directly onto Vcom+ via the expansion headers. If you have the 5V hooked to Vbus+, then you would have charge circuit coming on to try and charge the battery.

[fseider]

Hi, the job is done, and now the hobby
@Jörg: This problem is reproducible with any other Expansion Board. I've build the copter for the first time with your Exp. Board and an external BEC (I use 4s). Than I change the boards, because with the N4 no external BEC is necessary.

@Jussi: I power the M4 only with the N4 Board. The 5V only connected to the S-Bus Inverter. From the S-Bus Inveter are only the PWM and the mass cable connected to the M4.

To take a Video from the disturbances is al little bit difficult, because most of the motor paeks are small. You better can here it. Sometimes there are big peaks, but it takes time...

So here the Parameter file. But how can I attech the log files? Everytime I want to upload the file, nothing happens. Is it because the file size? The Log with GPS (zip) is 7,1 MB and the log without GPS 6,1 MB.

[fseider]

The maximum File Size is 256K. How should I attached the files?