imu data not consistent with earth gravity at rest (needs zgo calibration?) #319

diablodale · 2021-12-31T01:01:07Z

Data returned from an IMU node is not consistent with Earth gravity of 9.81 m/s^2 on the Y-axis.
My OAK-D instead returns a vector magnitude value 10.20799. And the gravity component changes between X and Y axes.
Please reference the IMU Datasheet provided by Luxonis https://www.ceva-dsp.com/wp-content/uploads/2019/10/BNO080_085-Datasheet.pdf

Setup

OAK-D via BW1098OBC
depthai-core v2.13.3 + xlink move/thread fixes
Microsoft Windows [Version 10.0.19044.1415]

Repro

Place your OAK-D on a flat stable non-moving surface with the RGB camera facing you and the USB port towards Earth center.
Run the example imu_gyroscope_accelerometer.exe

Result

Accelerometer timestamp: 3867 ms
Accelerometer [m/s^2]: x: -0.306 y: 10.190 z: -0.498
Gyroscope timestamp: 3868 ms
Gyroscope [rad/s]: x: 0.009 y: -0.007 z: 0.007
Accelerometer timestamp: 3885 ms
Accelerometer [m/s^2]: x: -0.345 y: 10.190 z: -0.421
Gyroscope timestamp: 3886 ms
Gyroscope [rad/s]: x: 0.007 y: -0.006 z: 0.001
Accelerometer timestamp: 3901 ms
Accelerometer [m/s^2]: x: -0.345 y: 10.190 z: -0.498
...

The magnitude of the accelerometer data above is 10.20799 which is 4% larger than expected.
The IMU datasheets claims an accuracy of 0.3 m/s^2.
10.20799 - 9.81 = 0.39799 making it outside the datasheet's accuracy claim and 5% larger than expected 9.81.

This unexpected accelerometer data is seen in all enums ACCELEROMETER, ACCELEROMETER_RAW, and GRAVITY
In a separate app I wrote, I see the same errors across different outputs...

ACCELEROMETER       -10.109375    -0.34375    -0.460938
ACCELEROMETER_RAW    -0.344765    10.151415   -0.459687
GRAVITY             -10.1875      -0.34375    -0.492188

In addition, the gravity component (very likely the 10.1 value) changes between the X and Y axes depending on what output is chosen with enum class dai::IMUSensor. This is unexpected and not in alignment with the IMU datasheet section 2 which specifies a fixed coordinate system. This would then make it impossible for the gravity component to change axes.

Expected

At rest, the normal of the x,y,z vector from the accelerometer should be ~9.81.

I would expect the coordinate system for acceleration and gravity to be shared as documented in IMU datasheet section 2. Since gravity is derived from the raw accelerometer. Meaning I would e:xpect: accelerometer_linear + gravity = accelerometer. But that is not possible given the actual data being output via depthai APIs.

It is also unusual the gravity component changes +/-, but maybe the documentation is lax in that.
Yes, I can negate and flip order...but it is suspicious that the "10" component is changing its coordinate system. It makes me suspect math error, or pointer offset error, struct member name/misuse, etc.

Notes

Is the 5% error due to section 3.2.1 ZGO errors?
If so, then we need a mechanism to "dynamic calibrate" datasheet section 3 the accelerometer -as distinct- from extrinsic calibration of #155

Or has there been a "Static calibration" datasheet section 3 burned into the IMU already?

The text was updated successfully, but these errors were encountered:

SzabolcsGergely · 2021-12-31T04:38:36Z

I would expect the coordinate system for acceleration and gravity to be shared as documented in IMU datasheet section 2. Since gravity is derived from the raw accelerometer. Meaning I would e:xpect: accelerometer_linear + gravity = accelerometer. But that is not possible given the actual data being output via depthai APIs.

This indeed should be the case, as a matter of fact, I tested on several boards, and the coordinate system is the same for gravity/accelerometer. Here is the test script.
Can you set DEPTHAI_LEVEL=info and confirm that the IMU FW version is the following:

[IMU(0)] [info] IMU product ID:
[IMU(0)] [info] Part 10004148 : Version 3.9.7 Build 224
[IMU(0)] [info] Part 10003606 : Version 1.7.3 Build 337
[IMU(0)] [info] Part 10004135 : Version 5.5.1 Build 159
[IMU(0)] [info] Part 10004149 : Version 5.1.11 Build 182

Currently we don't calibrate IMU, so no extrinsic calibration or static/dynamic calibration is performed therefore there are differences between boards/accuracy. We expect to add IMU calibration next year in Q1.

diablodale · 2021-12-31T17:27:15Z

Hi. I see unexpected results.

installed current v3.0.7 using https://docs.luxonis.com/en/latest/#demo-script
verified demo py app works
saved your linked test script to file
ran that script

// dai.IMUSensor.GRAVITY
Accelerometer timestamp: 1388.323 ms
Accelerometer [m/s^2]: x: -10.171875 y: -0.625000 z: 0.570312
Total: 10.20700359377233

// dai.IMUSensor.ACCELEROMETER
Accelerometer timestamp: 688.716 ms
Accelerometer [m/s^2]: x: -10.109375 y: -0.613281 z: 0.613281
Total: 10.146511256280561

// dai.IMUSensor.ACCELEROMETER_RAW
Accelerometer timestamp: 685.052 ms
Accelerometer [m/s^2]: x: -0.651223 y: 10.113108 z: 0.574608
Total: 10.15033068502249

The "10" component is changing axes between X and Y.
This is the same unexpected results I got with my C++ in OP.

Info debug output shows significantly different versions that yours...

[14442C10C1A1C6D200] [107.872] [system] [info] Memory Usage - DDR: 0.12 / 358.55 MiB, CMX: 2.05 / 2.50 MiB, LeonOS Heap: 6.72 / 78.59 MiB, LeonRT Heap: 2.88 / 23.84 MiB
[14442C10C1A1C6D200] [107.872] [system] [info] Temperatures - Average: 30.01 ┬░C, CSS: 31.77 ┬░C, MSS 29.83 ┬░C, UPA: 28.62 ┬░C, DSS: 29.83 ┬░C
[14442C10C1A1C6D200] [107.872] [system] [info] Cpu Usage - LeonOS 11.92%, LeonRT: 2.45%
[14442C10C1A1C6D200] [107.882] [system] [info] SIPP (Signal Image Processing Pipeline) internal buffer size '16384'B
[14442C10C1A1C6D200] [108.133] [IMU(0)] [Accelerometer timestamp: 0.000 ms
Accelerometer [m/s^2]: x: -0.612916 y: 10.113108 z: 0.536301
Total: 10.145847994191397
info] IMU product ID:
[14442C10C1A1C6D200] [108.133] [IMU(0)] [info] Part 10004148 : Version 3.2.13 Build 6

[14442C10C1A1C6D200] [108.133] [IMU(0)] [info] Part 10003606 : Version 1.2.4 Build 230

[14442C10C1A1C6D200] [108.133] [IMU(0)] [info] Part 10003254 : Version 4.4.3 Build 485

[14442C10C1A1C6D200] [108.133] [IMU(0)] [info] Part 10003171 : Version 4.2.10 Build 548

SzabolcsGergely · 2021-12-31T20:25:14Z

@diablodale you have a device that was shipped before factory calibration, which has older IMU FW. We don't have access to the IMU FW, this issue looks like got fixed with a FW update.
Please checkout the following branch: https://github.com/luxonis/depthai/tree/UI-test-tools-Production
Run install_requirements.py then oak-d.sh (python3 depthai_demo.py -s left right previewout meta_d2h jpegout -monor 400 -monof 10 -rgbf 10 -tm OAK_D_test).
It will update IMU firmware to the latest.

diablodale · 2021-12-31T20:46:02Z

Yes. This was discovered and led to me using the cali tool for depth<->color several weeks ago.

It is possible now or in the future for customers to have IMUs that don't meet the requirements of depthai-core. My OAK-D is an example.
Could depthai-core do the check itself on IMU startup?
Or can it expose the firmware versions so my app can do the check?

dai::EepromData doesn't show any obvious way to check IMU firmware.

SzabolcsGergely · 2021-12-31T22:14:42Z

Could depthai-core do the check itself on IMU startup

Yes, will add it.

diablodale · 2021-12-31T22:39:40Z

Got it. I also understand you have a queue of dev work.
I will delay updating my IMU firmware as long as I can. Hopefully that will be enough time for you to add code and then I can verify that my app correctly handles the error/exception on IMU startup.
Happy new year! 🎉🎆

diablodale · 2022-02-01T21:09:41Z

No improvement with updated IMU firmware. My OAK-D IMU accelerometer outputs are still unexpected/inconsistent

I followed your IMU firmware update procedure. I got the green dot after it updated.

I then ran your imu_test script. It now reports exact the same firmware as you list above.

[14442C10C1A1C6D200] [96.995] [IMU(0)] [Accelerometer timestamp: 0.000 ms
Accelerometer [m/s^2]: x: -10.171875 y: -0.257812 z: -0.523438
infoTotal: 10.188596327129046
] IMU product ID:
[14442C10C1A1C6D200] [96.995] [IMU(0)] [info] Part 10004148 : Version 3.9.7 Build 224
[14442C10C1A1C6D200] [96.995] [IMU(0)] [info] Part 10003606 : Version 1.7.3 Build 337
[14442C10C1A1C6D200] [96.996] [IMU(0)] [info] Part 10004135 : Version 5.5.1 Build 159
[14442C10C1A1C6D200] [96.996] [IMU(0)] [info] Part 10004149 : Version 5.1.11 Build 182

I then ran the imu_test script with the three different IMU outputs: accelerometer, accelerometer_raw, and gravity

Result

No change. The outputs continue to be unexpected. I get the same signs and values as in the OP.
Here are outputs from your test script and changing line 18-20 to get the different outputs
My early production OAK-D is somewhat level sitting on a table.

// ACCELEROMETER
Accelerometer timestamp: 515.076 ms
Accelerometer [m/s^2]: x: -10.156250 y: -0.296875 z: -0.468750
Total: 10.171394957950703
Accelerometer timestamp: 530.792 ms
Accelerometer [m/s^2]: x: -10.269531 y: -0.269531 z: -0.488281
Total: 10.284665175325577

// ACCELEROMETER_RAW
Accelerometer timestamp: 506.852 ms
Accelerometer [m/s^2]: x: -0.287304 y: 10.199299 z: -0.497994
Total: 10.215490143768207
Accelerometer timestamp: 522.568 ms
Accelerometer [m/s^2]: x: -0.287304 y: 10.160992 z: -0.507571
Total: 10.177717005808487

// GRAVITY
Accelerometer timestamp: 184.832 ms
Accelerometer [m/s^2]: x: -10.210938 y: -0.273438 z: -0.523438
Total: 10.228000758296742
Accelerometer timestamp: 204.582 ms
Accelerometer [m/s^2]: x: -10.210938 y: -0.273438 z: -0.523438
Total: 10.228000758296742

SzabolcsGergely · 2022-02-12T02:16:25Z

@diablodale check #375

Calibration will be adressed later.

chengguizi · 2022-06-01T02:11:54Z

@diablodale I would agree with you here that I observe the same thing on quite a few Series 2 units I have, installed with BNO085. The gravity vector is often too large at rest.

diablodale · 2022-06-01T15:19:29Z

@szabi-luxonis I tested again with depthai-core v2.15.4 (it includes pr #375)
The axis are now aligned similar/expected.

// ACCELEROMETER_RAW
Accelerometer [m/s^2]: x: -10.142 y: -0.536 z: 0.871
Accelerometer [m/s^2]: x: -10.104 y: -0.546 z: 0.910

// ACCELEROMETER
Accelerometer [m/s^2]: x: -10.000 y: -0.555 z: 0.918
Accelerometer [m/s^2]: x: -10.090 y: -0.480 z: 0.883

// GRAVITY
Accelerometer [m/s^2]: x: -10.000 y: -0.555 z: 0.922
Accelerometer [m/s^2]: x: -10.000 y: -0.547 z: 0.922

I consider the axis portion of this issue as resolved. 👍
I understand the calibration is to be addressed later.

diablodale · 2023-03-02T10:22:44Z

hi @szabi-luxonis, how can an app using depthai-core v2.20.2 know that the IMU needs a firmware update?
#744

diablodale · 2024-03-19T17:32:40Z

The accelerometer data on my OAK-D-PRO-POE continues to be wrong. #375 did not fix this. Below data is with both sensors level using depthai-core v2.25.0 example imygyroaccel.exe adapted to show accel and accel_raw.

OAK-D-PRO-POE

[18443010318EF50800] [192.168.2.23] [5.323] [IMU(0)] [info] IMU product ID:
[18443010318EF50800] [192.168.2.23] [5.323] [IMU(0)] [info] Part 10004563 : Version 3.9.9 Build 2
[18443010318EF50800] [192.168.2.23] [5.323] [IMU(0)] [info] Part 10003606 : Version 1.8.0 Build 338
[18443010318EF50800] [192.168.2.23] [5.323] [IMU(0)] [info] Part 10004135 : Version 5.5.3 Build 162
[18443010318EF50800] [192.168.2.23] [5.323] [IMU(0)] [info] Part 10004149 : Version 5.1.12 Build 183
Accelerometer     [m/s^2]: x: 11.574 y: 0.191 z: -0.238 
Accelerometer     [m/s^2]: x: 11.539 y: 0.152 z: -0.258 
Accelerometer     [m/s^2]: x: 11.586 y: 0.172 z: -0.305 
Accelerometer     [m/s^2]: x: 11.539 y: 0.191 z: -0.289 
Accelerometer     [m/s^2]: x: 11.551 y: 0.172 z: -0.219 
Accelerometer     [m/s^2]: x: 11.551 y: 0.172 z: -0.305 
...
Accelerometer Raw [m/s^2]: x: 11.530 y: 0.172 z: -0.278 
Accelerometer Raw [m/s^2]: x: 11.550 y: 0.182 z: -0.249 
Accelerometer Raw [m/s^2]: x: 11.588 y: 0.211 z: -0.259 
Accelerometer Raw [m/s^2]: x: 11.559 y: 0.201 z: -0.239 
Accelerometer Raw [m/s^2]: x: 11.588 y: 0.172 z: -0.249 
Accelerometer Raw [m/s^2]: x: 11.588 y: 0.230 z: -0.230 
Accelerometer Raw [m/s^2]: x: 11.569 y: 0.163 z: -0.230

OAK-D

[14442C10C1A1C6D200] [2.12] [0.911] [IMU(0)] [info] IMU product ID:
[14442C10C1A1C6D200] [2.12] [0.911] [IMU(0)] [info] Part 10004563 : Version 3.9.9 Build 2
[14442C10C1A1C6D200] [2.12] [0.911] [IMU(0)] [info] Part 10003606 : Version 1.8.0 Build 338
[14442C10C1A1C6D200] [2.12] [0.911] [IMU(0)] [info] Part 10004135 : Version 5.5.3 Build 162
[14442C10C1A1C6D200] [2.12] [0.911] [IMU(0)] [info] Part 10004149 : Version 5.1.12 Build 183
Accelerometer     [m/s^2]: x: -10.008 y: 0.066 z: 0.785 
Accelerometer     [m/s^2]: x: -9.973 y: 0.133 z: 0.758 
Accelerometer     [m/s^2]: x: -10.000 y: 0.133 z: 0.777 
Accelerometer     [m/s^2]: x: -9.965 y: 0.145 z: 0.777 
Accelerometer     [m/s^2]: x: -10.000 y: 0.133 z: 0.832 
Accelerometer     [m/s^2]: x: -10.008 y: 0.152 z: 0.785
...
Accelerometer Raw [m/s^2]: x: -10.046 y: 0.182 z: 0.795 
Accelerometer Raw [m/s^2]: x: -10.027 y: 0.153 z: 0.795 
Accelerometer Raw [m/s^2]: x: -9.998 y: 0.153 z: 0.776 
Accelerometer Raw [m/s^2]: x: -9.969 y: 0.172 z: 0.757 
Accelerometer Raw [m/s^2]: x: -9.989 y: 0.144 z: 0.766 
Accelerometer Raw [m/s^2]: x: -9.979 y: 0.105 z: 0.785 
Accelerometer Raw [m/s^2]: x: -9.979 y: 0.153 z: 0.757 
Accelerometer Raw [m/s^2]: x: -9.989 y: 0.144 z: 0.757

SzabolcsGergely mentioned this issue Feb 12, 2022

Swap ACCELEROMETER_RAW x and y axis to match ACCELEROMETER #375

Merged

diablodale mentioned this issue Mar 24, 2022

OAK-D-Pro-PoE sends no IMU data to host #431

Closed

diablodale mentioned this issue Mar 3, 2023

[BUG] IMU firmware updater re-writes duplicate versions of firmware, no API to check versions, log spelling issue #744

Closed

diablodale mentioned this issue Mar 19, 2024

accelerometer data on OAK-D-PRO-POE is wrong #987

Open

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imu data not consistent with earth gravity at rest (needs zgo calibration?) #319

imu data not consistent with earth gravity at rest (needs zgo calibration?) #319

diablodale commented Dec 31, 2021 •

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diablodale commented Dec 31, 2021

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diablodale commented Dec 31, 2021

diablodale commented Feb 1, 2022

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chengguizi commented Jun 1, 2022

diablodale commented Jun 1, 2022 •

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diablodale commented Mar 19, 2024

imu data not consistent with earth gravity at rest (needs zgo calibration?) #319

imu data not consistent with earth gravity at rest (needs zgo calibration?) #319

Comments

diablodale commented Dec 31, 2021 • edited

Setup

Repro

Result

Expected

Notes

SzabolcsGergely commented Dec 31, 2021

diablodale commented Dec 31, 2021

SzabolcsGergely commented Dec 31, 2021 • edited

diablodale commented Dec 31, 2021

SzabolcsGergely commented Dec 31, 2021

diablodale commented Dec 31, 2021

diablodale commented Feb 1, 2022

Result

SzabolcsGergely commented Feb 12, 2022

chengguizi commented Jun 1, 2022

diablodale commented Jun 1, 2022 • edited

diablodale commented Mar 2, 2023 • edited

diablodale commented Mar 19, 2024

OAK-D-PRO-POE

OAK-D

diablodale commented Dec 31, 2021 •

edited

SzabolcsGergely commented Dec 31, 2021 •

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diablodale commented Jun 1, 2022 •

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