MPU6000 scaling issue
Thanks to help from Sami Finnila and Wesley Chuen we've found an issue with the default MPU6000 accelerometer scaling in some of the recent APM2 boards shipped in the last month or so. You can find the original discussion from Sami here.
Internally we use "DCM" to merge the gyro and accelerometer values together to calculate attitude. With the recent boards we are finding the accelerometer values are 2x as big as they should be which leads to an inaccurate attitude estimate. It's apparently possible to fly with this misconfiguration but it at least makes "the leans" more common (you can recognise "the leans" by your copter requiring more and more manual roll or pitch to keep it level as you fly).
UPDATE (11-May-2012):
Craig and Tridge have completed a patch to automatically detect the scaling of the accelerometer so we can compensate.
This patched version is being called 2.5.5-Beta and is in the downloads area. After a short testing period (maybe 24h ~ 48h), if all goes well it will be available in the mission planner.
We're still working on the next official release 2.6 so we haven't included any improvements to flight dynamics in this patch except Adam's "Retro" loiter. This uses the ground speed directly from the GPS instead of calculating it using lat/lon position. You can enable this by setting the "RETRO_LOITER" parameter to "1". BTW, it's "retro" because this is the method used in the popular 2.0.49 version of Arducopter.
Feel free to post comments / issues regarding this patch release in the discussion below.
If you have recieved an APM2 in the last month, please try the test shown above:
- hold your APM2 flat and check the "az" value in the mission planner's Flight Data, Status screen is approximately 1000 (it should be for everyone, regardless of whether you have a new or old board)
- hold your APM2 up-side-down (but still level) and check the "az" value again. If it's not close to 1000 then we want your tlog! :-)
Next just roll and pitch your board a bit and attach your tlogs below. These logs can be found in your AP Mission Planner's log directory. On a windows machine you will likely find a recently updated file here: C:\Program Files (x86)\APM Planner\logs\YYYY-MM-DD HH-MM-SS.tlog
Thanks for your help.
Tags: ArduCopter, ArduPlane, MPU6000, Scaling
Replies to This Discussion
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ModeratorPermalink Reply by Dean Wynton on -
Are you using apm1 or apm2?
Cual tienes? apm1 o apm2
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Permalink Reply by PACEFE on -
When will be DMP available!!!!
I still remember
- When using the internal sensor fusion processor of the MPU-6000, more than half of the Atmega2560 processing capacity is free for new advanced features.
Or I bougth something that promised what can not be delivered??
I think with DMP all scaling and no sense problems should be gone.
For a board that flight absolutelly not better than a 50USD MWC I would like to have some extra features...
Pablo
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Permalink Reply by Andke on -
Well, last time I checked, this was an open source/community project, so if you programmed as fast as you type those exclamation marks ... :)
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Permalink Reply by PACEFE on
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DMP released has nothing to do with open source or programming skills.
I can also collaborate with APM open source testing and reporting bugs I can documents as good as possible. An example of it was AHRS hanging on GPS first lock and some code bugs like issue 356.
DMP software is ready realease but some restrictions from AD prevent from that.
!!!! :-)
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Permalink Reply by PACEFE on
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Who: Sorry, Invensense..
What: read previous posts
Why: as above
!!! :-)
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DeveloperPermalink Reply by R_Lefebvre on -
Yes, apparently there's an issue where we need to use some code in the main APM code to make the MPU6000 do it's thing. I think that code would come from Invensense. But they won't allow us to release that code in an open environment.
So it's a bit of a pickle.
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Permalink Reply by Andke on
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ouch - why do we do business with that company then ? - are they really that good ?
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DeveloperPermalink Reply by R_Lefebvre on -
I don't have any opinion or answer on that. It's disappointing, yes, but I do not have enough info to know what's really going on.
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Permalink Reply by PACEFE on
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But as far I can see in the web, there is a lot of people that has this feature working without using propetary software from Invensense.
What would be then the problem of using this code? I paid the money for the chip, if I can develop my own software for using all features in the chip why shouldnt I be able to do it?
If not invensense should have prevent us for doing so using some kind unbrakeable encriptation to access this feature, or?
@Andke !!! :-D
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ModeratorPermalink Reply by Dean Wynton on -
With DPM the difference would be great..
I believe some of the developers have access to the code? but cant release it as open source.. :(
There has to be some way around this? such as signing a form or something? as you do when you download software??
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