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DIMU upgrade: when do I calibrate?

PostPosted: Mon May 12, 2014 11:29 am
by HeliHenkie
Hi all,

How do I determine when is it relevant to calibrate my AQ board with DIMU upgrade?

I installed my board with DIMU upgrade on my quadcopter. After executing TARE and storing the values I'm able to fly around. Position hold works fine, even in strong winds. Altitude hold works reasonable, but I experience slow upward drift. I was not able to correct this drift with PID adjustment.

So I put my quadcopter on the dining table and connected to mission planner. When I look at my acc-x, acc-y and acc-z values I see them drift (with the rising temperature of the IMU).
For example my acc-z drifts from 9.2 to 9.6, with rising temperature of the IMU.
- What effect does this have on altitude hold? My acc-z values are way off from the ideal 9,806 m/s2.
- What values can be expected? Can anyone with the DIMU upgrade post their values?

Best regards,

Jan Willem
The Netherlands

Re: DIMU upgrade: when do I calibrate?

PostPosted: Mon May 12, 2014 1:35 pm
by bn999
If you performed a tare and successfully stored the values, you're ACC magnitude should not be that far off. I suspect the save did not complete.

You are on the right track. Spend a bit of time experimenting with a connection to the ground. On a level table, perform the tare and watch what happens to the ACC's mag. Write it to EEPROM with the stick combination and restart to see that the magnitude is the same.

Once you have a handle on this, then you can investigate the effects of temperature. There is a reason why temperature compensation can be important, but a drift from 9.2 to 9.6 is on the large side.

The closer the ACC is to being properly calibrated, the better your altitude hold will be. However, even a poorly calibrated ACC will eventually be biased by the UKF during flight given a good GPS signal. It just takes more time.

If you are still having problems, you will need to take a closer look at flight logs.

Re: DIMU upgrade: when do I calibrate?

PostPosted: Mon May 12, 2014 6:24 pm
by HeliHenkie
Hi Bill (or others),

Is it possible to do just part of the calibration procedure, just for the temperature compensation?
For example steps 1 to 3 in combination with the TARE function?
In which parameters is the temparature compensation stored?

Best regards,

Jan Willem

Re: DIMU upgrade: when do I calibrate?

PostPosted: Mon May 12, 2014 6:48 pm
by bn999
No. Temperature compensation is only possible with a full calibration.

Re: DIMU upgrade: when do I calibrate?

PostPosted: Mon Oct 13, 2014 8:19 am
by michal_e
hi , I have a questions about calibration AQ witw DIMU 1.1: ( QGC 1.5 and aqv7.0.r403.b1762-hwv6.1-dimu1.1.hex)
1. what should I do before data gathering ( static (temp) and calibso) with DIMU EEPROM ? -
- can I gathering data after TARE function or should I do click DEFAULT, TRANSMIT and CALIB save ?
same for GYO and MAG ?
2. I have gatered DATA after DEFAULT and in calculation (4a,4b) with checked using digital IMU, sim crasching after 1-2 min with still 0 loops
Loops: 0

#define DEFAULT_IMU_GYO_SCAL_X +1.000000000000 // 0.000000100000 +1.000000000000
#define DEFAULT_IMU_GYO_SCAL_Y +1.000000000000 // 0.000000100000 +1.000000000000
#define DEFAULT_IMU_GYO_SCAL_Z +1.000000000000 // 0.000000100000 +1.000000000000
#define DEFAULT_IMU_GYO_ALGN_XY +0.000000000000 // 0.000010000000 +0.000000000000
#define DEFAULT_IMU_GYO_ALGN_XZ +0.000000000000 // 0.000010000000 +0.000000000000
#define DEFAULT_IMU_GYO_ALGN_YX +0.000000000000 // 0.000010000000 +0.000000000000
#define DEFAULT_IMU_GYO_ALGN_YZ +0.000000000000 // 0.000010000000 +0.000000000000
#define DEFAULT_IMU_GYO_ALGN_ZX +0.000000000000 // 0.000010000000 +0.000000000000
#define DEFAULT_IMU_GYO_ALGN_ZY +0.000000000000 // 0.000010000000 +0.000000000000

Pentium I7 load 88 to 75% and "Process terminated (aborted or crashed)."

what is wrong, please any help

OK. solved : "Process terminated (aborted or crashed)." because following WIKI I didn't do step 3 . If I do step 3, step 4a/b works OK. :-)