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擦，才不是我发明的，APM/Pixhawk 官方wiki有明确的说明的！
Compass interference
Interference from the power distribution board, motors, battery, esc and other electrical devices near the APM or PX4 can throw off the compass heading which can lead to circling (aka “toilet bowling”) or even the copter flying off in completely the wrong direction. Graphing the tlog’s mag_field (found under “CUSTOM”) and throttle (found under VFR_HUD) values are the easiest way to quickly see the amount of interference.
In the graph’s below shows an acceptable amount of magnetic interference. You can see the mag_field fluctuates when the throttle is raised but only moves around by about 10% ~ 20%. Below 30% inteference is acceptable. Between 30% ~ 60% is in the grey zone where it might be ok (some users are ok, some are not) and really bad magnetic interference will show up as jumps of over 60% when the throttle is raised.
Accurately setting up the compass is critical because it is the primary source of heading information. Without an accurate heading the vehicle will not move in the correct direction in autopilot modes (i.e. AUTO, LOITER, PosHold, RTL, etc). This can lead to circling (aka “toiletbowling”) or fly-aways.
ArduPilot currently allows up to three compasses to be connected. Only one compass (specified using the COMPASS_PRIMARY parameter) is used for navigation. While many autopilots have an internal compass, most will instead use an external compass. This provides more reliable data than an internal compass because of the separation from other electronics.
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发表于 2015-6-22 06:07
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