I have an APM2.5 with internal compass, my compass motor interference is a little high 30-40% I calibrate compass, etc. but always the copter turns 20-30 degrees rigth when I take off and stays there, can I resolve changing COMPASS- DEC? my value is -0.05788675 any suggestion?
Another suggestion for compass motor interference? (not possibility to change gps in short time)
SUMMARY DISCUSSION: (for newbies)
I'm trying to summarize the most important things from this post for newbies here, if someone notice any mistake or something usefull to write here too, please let me known (Orthographic mistakes are welcome too ;) if someone wants to re-write better, I change it, english isn't my native language)
WARNING!!! : BE CAREFULL WITH YOUR COMPASS INTERFERENCES!!!, you can crash your copter if you don't paid attention to them.
REMEMBER: If your compass read is inconsistent with your GPS your copter LAND by default, you can switch to stab or Alt Hold if you like to abort LAND http://copter.ardupilot.com/wiki/configuration/ekf-inav-failsafe/
BE CAREFULL: Not use magnetized screwdrivers or bolt in your ship. (better plastic or aluminium)
Prefer to calibrate compass outside far from metal things
Avoid fly compass dependent modes near buildings or other metal things.
Check your compass before calibrating that have correct orientation on MPlanner map
Do the compass mot
READ INSTRUCTIONS: http://copter.ardupilot.com/wiki/ac_compasssetupupadvanced/
SOLVE YOUR INTERFERENCES: you can buy an external compass and set on a mast far from interferences (like this http://store.3drobotics.com/products/hmc5883l-triple-axis-magnetometer )
OR FOLLOW THIS SUGGESTIONS:
Forrest:
Until you can get an external compass, try different orientation/location of the:
- battery
- creating more distance between the APM and wires between the battery-ESC
- creating more distance between the APM and power distribution board or power module
- creating more distance between the APM and ESC (2 cm can make a big difference)
You can test the distance theory by putting the APM up high away from the electronics. In your experiments, the ship does not have to take off so the changes can be temporary and not fly worthy. You just need to know if changing the orientation or location of something with an electrical field stops the initial rotation as you power up. Take the props off and just watch MP (does the heading change as you power up).
ColinC suggestions:
buy a cheap hand-held compass. I got mine at the local Scout shop for under $5. You can learn a lot just by passing it around your rig. You can also learn a lot about your room just by walking around.
The compass and the level are the two basic tools. Oldies but goodies. Cheap and very low current draw.
And look's ColinC interesting test here: http://diydrones.com/forum/topics/compass-interferences?groupUrl=arducopterusergroup&groupId=705844%3AGroup%3A394475&id=705844%3ATopic%3A1907171&page=5#comments
Enjoy your fligth :)
Replies
Would like an education here.
What is MagX, MagY, and MagZ? I know they are the compass's raw axis values, but what is that in layman terms?
For example, if a ship yaws 360 degrees in a non-interference zone (or does a forward flip) with a stable magnetic north, will MagX, MagY, or MagZ change 360 degrees during the yaw or flip? If not, then does only magnetic interference change this? And is so, how? Like in Cala's case a metal roof or frig along the side of her house or a ferrite rock in the open field? And the how being something like, the gyros aren't changing but the magnetic north is?
Please give a layman explanation. Thanks
I'm not sure of what I'm saying but the three mag_x, mag_y, mag_z are the three axis components of a measured magnetic field. So indeed if, in this 3 axis referential system, a magnetic source modifies the magnetic field, it will result in a change of these three magnetic vectors.
A test to be sure of what it means: approach a magnet from different directions and observe the changes in the log of these three values.
PS : Gold is not magnetic, so please do not dig next to your house :)
so are they a measure of magnetic field strength in the x, y, and z direction, thus determining via the square root of the numbers, the vector length pointing at the magnetic source?
is so, then in the case of Cala:
front of house - sqrt(-83^2+ -87^2 + 64^2) = 136 in the NW direction
open field - sqrt(-83^2 + 87^2 + -70^2) = 139 in the SW direction?
or am i way off?
About vector length, sqrt of the sum is correct. Not sure about the sense of the arrow.
Heading is atan(Y/X). If programmming, use H = atan2(Y/X).
Cheers,
Colin
help. an expert out there?
if the above is correct, the direction would be where the x, y, and z planes that go perpendicular through each axis (at the indicated value) intersect at a single point. not sure if i have the axis defined right above (best guess). the above makes the following guess:
z is up/down
x is side to side
y is fore/aft
thus more +z would point more upward, more +y would point more north, and more +x would point more east. no idea if this is a relative (to ship orientation) or fixed geometry (only relative to ship magnetics).
with an expert would interject and give us an education. it would be nice to know.
If the mag is installed normally, X is forward/aft, Y is left/right, Z is up/down.
You can't make assumptions about how it's installed though. On my GPS, it's installed upside-down on the bottom of the board, and rotated 90 deg. On my DiscoveryF3 board it's just back-to-front, 180 deg.
Cheers,
Colin
Thank's Collin, in this case is an internal compass APM2.5 as default
My god, you have found an alien underground base I guess :)
GOLD!!! lol
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