An interesting article about the toilet bowl effect

[darwin-t]

http://www.rcgroups.com/forums/showpost.php?p=27053987&postcount=1068

 

[ianwood]

That would be one of many possible sources of compass issues. Compass issues being the main cause of TBE. Because the magnetometer is on the leg of the Phantom, it doesn't have a big issue with this.

A much easier method of looking for localized electro-mechanical magnetic interference caused by the P2 itself would be to clamp it down, use a magnetometer app on your phone to measure magnetic levels as close to the compass location as possible. An analog compass will work even better. Do this while off, while powered up, while idling and while under power. There should be as little variation as possible in the readings.

Here's an example:

[youtube]https://www.youtube.com/watch?v=OHEzD7uP6hI[/youtube]

 

[SteveMann]

All this video shows is that things carrying electrical power generate magnetic fields. The only measurement that is important is what is the influence on the compass module. That's why the compass module on the Phantom should be far away from any other electrical component. If you have any other wires on the same leg as the compass, then you can expect problems.

 

[Hughie]

All this video shows is that things carrying electrical power generate magnetic fields. The only measurement that is important is what is the influence on the compass module. That's why the compass module on the Phantom should be far away from any other electrical component. If you have any other wires on the same leg as the compass, then you can expect problems.

It also shows the importance of coupling signal or power pairs together so that noise affecting one is minimised if it exists in the other as well. Basic electronics though.

 

[darwin-t]

The post and video convinced me to put the battery on the bottom of my F550 build. And twist all of the wires. I'm going to heat shrink the high current wires, too.

 

[Narrator]

I gather from reading through, the TBE is yawing on take-off?

As a private pilot, we have to recalibrate the gyro compass to the magnetic compass regularly and only while flying straight and not accelerating or decelerating. I imagine the Phantom compass might suffer a similar 'drift' effect.

 

[ianwood]

I gather from reading through, the TBE is yawing on take-off?

As a private pilot, we have to recalibrate the gyro compass to the magnetic compass regularly and only while flying straight and not accelerating or decelerating. I imagine the Phantom compass might suffer a similar 'drift' effect.

The gyro on a plane drifts and needs recalibration to be accurate for navigation purposes. The Phantom gyro (which is a tiny circuit by comparison to its enormous mechanical cousin) is used primarily to maintain attitudinal stability and does not serve a navigational purpose. As result, a gradual drift is less critical and effectively resets after each flight.

The Phantom also uses a magnetometer which does not have the same inertial issues as an analog magnetic compass which will wander as result of external forces.

It is possible to use gyro and compass data together to obtain more accurate data for both.

 

[ravivraz]

lots of theory on the ardupilot wiki pages.