LibrePilot Forum

General Category => General Discussion => Topic started by: zukenj on March 19, 2016, 03:28:23 am

Title: GPS HoldPosition goes in circle
Post by: zukenj on March 19, 2016, 03:28:23 am

When I switch to GPS HoldPosition in flight mode the quad goes in circle and rocking

Title: Re: GPS HoldPosition goes in circle
Post by: f5soh on March 19, 2016, 09:38:15 am

This is the normal behavior while the mag is disturbed (Mag alarm) or AuxMag is not oriented correctly.

This behavior is also called "Toilet Bowl effect", because the heading is wrong the vehicle try to compensate position error in a wrong direction.

Title: Re: GPS HoldPosition goes in circle
Post by: zukenj on March 20, 2016, 04:30:55 am

Ok I will calibrate the mag again and try

Title: Re: GPS HoldPosition goes in circle
Post by: Mateusz on March 20, 2016, 08:42:46 am

@zukeni

If you have problems with magnetic interference, calibration is not going to fix that.

• A wire carrying electric current will produce a magnetic field with closed field lines surrounding the wire.
• The closer to wire the stronger the field
• Right hand rule - thumb points current flow, fingers grabbing wire are field lines
• Field strength depends on current

From that you know that magnetometer should be far from high current lines, and that you can redirect magnetic field by twisting wires.
Imagine wire horizontally, placed below magnetometer, right hand rule you can see magnetic field lines hitting magnetometer. Now you twist the same wire, so your magnetic field becomes like ellipsoid stretching in the direction of wire. That way there is weaker field hitting magnetometer.