Emlid

Community Forum

About Magnetic Interference


(Kedar Thaker) #1

We are facing magnetic interference in compass and error was about 12-20 degrees.we are using P80 T-motor bldc motor with 30*15 propeller and battery pack of 12 cells lithium ion having thickness of 5 mm so the elevation between battery and compass module is about 18 cm and distance between motors and compass module is about 12 cm. Can anyone help me, how to reduce or eliminate magnetic interference encountered by me in gcs ?


#2

From what I read most people rise the compass up and away from the vessel.
But if you have continuously stable offset you could calibrate with it


(Kedar Thaker) #3

After completing the test manual flying of my agriculture drone with empty payload, I did the log analysis, and found compass fail error:

Test: Compass = FAIL- Large change in mag_field (82.34%)

For Drone I am using:

  • P 80 100KV T motor
  • Flame 80A ESC
  • 30 x 10.5 Propeller
  • 12s12p 44.4V 34.8Ah Li-ion battery (Dimension - 25x25x7 cm , 7cm thickness)
  • Flight controller - EDGE
  • GPS - UAVCAN GNSS

Battery is placed on the top cover of fuselage. and from battery Gps position is 15 cm above).

Note: Before my test flying, I completed the Compass calibration process.

My queries are -

  1. Why Compass is showing that much of error ( Compass = FAIL- Large change in mag_field (82.34%))?
  2. Is UAVCAN GNSS contain only External compass?

Magnetic Compass - Fail Error (Agriculture Quadcopter 15 L FERTILIZER-SPREADER)
#4

That is one massiv battery. Have you checked for el.mag. field from it when disconnected and connected with a load?

Both gnss and Magnetometers


(Christian Grüner) #5

You will likely have a big EM field on that platform, following the amount of amps.

Have you tried calibrating the compass in a different location?


(Kedar Thaker) #6

Yes i do had tried the compass at different locations, and its fine showing 3D Fix, so now i just to check the system without props and downloaded the log file and got to know there is not much interference, but when i use to fix the props and run the system magnetic error comes with large deviation. So what should be the cause of this ?

Then, i also changed the gnss module location far from the battery and esc wires so that less magnetic interference will come now with props i have to check.


(Christian Grüner) #7

Did you run the motors with and without props? I can’t tell from your reply.


(Kedar Thaker) #8

yes, i did do now with and without props, there is no much difference in magnetic interference value, but on field its coming too high ?


(Christian Grüner) #9

The amps from running with props on will much increase the magnetic field strength wise, so that is expected.


(Kedar Thaker) #10

So , now sir what’s the solution for this problem ? Any methods or remedies for it ?


(Kedar Thaker) #11

We have a test flight and it got crashed due to some RC transmission after downloading the log file from the Emlid flight controller we got error like
Test: Compass = Warn- Moderate change in mag_field (34.39%),Max mag field length (581.81)> recommended (550)
flight observation
As the bird took off from the ground it yaws towards right and keep pitching over the forward side and pilot noticed that the controls are ineffective and initially before flying he centered the trim switches.
What should be the cause ?


(Christian Grüner) #12

On a multi rotor, there should never be a need to manually trim the controls on the RC. That is a sign of a bad/suboptimal accelerometer/gyro calibration.
On top of your compass issue, I would simply ground the craft, until you have completed a calibration for leveling.


(Christian Grüner) #13

The solution is clearly stated in the video, as far as I am concerned:

  • All power-wires must run in parallel with its own +/- counterpart.
  • Twist/braid your wires where possible.
  • use shielded wires for signal-transmission.
  • place compass away for power-wires.
  • if a buzzer is installed, place that away from the compass.

Magnetic Compass - Fail Error (Agriculture Quadcopter 15 L FERTILIZER-SPREADER)