Comments (5)
thomas-haslwanter
commented on July 2, 2024
I have changed line 357, and will update this in the next upload. It does not make any difference in practice, because most IMUs are not that accurate anyway.
Line 358 is correct, though. I always use a space-fixed coordinate system where the z-axis is defined by gravity. If the IMU is oriented differently, it has to be indicated (approximately) by adjusting "R_initialOrientation".
The thing about coordinate systems is really confusing, and in fact, I am just about finishing a book on "3D Kinematics" for Springer, which is intended to provide the theoretical background when working in this area. What is your background, and how did you get into this area? I am still working on the 3D viewer (i.e.with OpenGL or PyGame), but have no satisfactory solution yet.
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ivan866
commented on July 2, 2024
I am now an affiliate researcher for some institute and we have a project which uses Tobii Glasses 2 eyetracker, which has MEMS gyro / accel built-in.
My question is how do I define an initial rotation matrix for a case when a person's gaze is headed towards Z axis, and vertical is Y positive, while left shoulder is X positive?
I tried http://andre-gaschler.com/rotationconverter/ and it seems that numpy.eye(3) is right. Still I get very high position values (about -100 meters on vertical axis).
And why is it that I must change the initial orientation if I have different axis configuration, I thought I just change columns ordering before setting in_data.
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thomas-haslwanter
commented on July 2, 2024
import numpy as np
x = [0,1,0]
y = [0,0,1]
z = [1,0,0]
rot_mat = np.column_stack( (x,y,z) )
# assuming the data are in column form
rotated = (rot_mat @ data.T).T
should do the trick
…---
Prof. (FH) PD Dr. Thomas Haslwanter
School of Applied Health and Social Sciences University of Applied Sciences Upper Austria FH OÖ Studienbetriebs GmbH
Garnisonstraße 21
4020 Linz/Austria
Tel.: +43 (0)5 0804 -52170
Fax: +43 (0)5 0804 -52171
E-Mail: [email protected]
Web: bim.fh-linz.at
or work.thaslwanter.at
________________________________
From: Ivan <[email protected]>
Sent: Sunday, December 24, 2017 4:13 PM
To: thomas-haslwanter/scikit-kinematics
Cc: Haslwanter Thomas; State change
Subject: Re: [thomas-haslwanter/scikit-kinematics] Compensation for gravity hard-coded on 3rd axis (#15)
I am now an affiliate researcher for some institute and we have a project which uses Tobii Glasses 2 eyetracker, which has MEMS gyro / accel built-in.
My question is how do I define an initial rotation matrix for a case when a person's gaze is headed towards Z axis, and vertical is Y positive, while left shoulder is X positive?
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ivan866
commented on July 2, 2024
That code simply reorders axes like that: X->Y, Y->Z, Z->X.
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thomas-haslwanter
commented on July 2, 2024
... which is all that should be required if your coordinate system points in the wrong direction ....
…---
Prof. (FH) PD Dr. Thomas Haslwanter
School of Applied Health and Social Sciences University of Applied Sciences Upper Austria FH OÖ Studienbetriebs GmbH
Garnisonstraße 21
4020 Linz/Austria
Tel.: +43 (0)5 0804 -52170
Fax: +43 (0)5 0804 -52171
E-Mail: [email protected]
Web: bim.fh-linz.at
or work.thaslwanter.at
________________________________
From: Ivan <[email protected]>
Sent: Wednesday, January 3, 2018 12:36 AM
To: thomas-haslwanter/scikit-kinematics
Cc: Haslwanter Thomas; State change
Subject: Re: [thomas-haslwanter/scikit-kinematics] Compensation for gravity hard-coded on 3rd axis (#15)
That code simply reorders axes like that: X->Y, Y->Z, Z->X.
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Related Issues (20)
- Denavit-Hartenberg convention HOT 2
- Real motion for test data HOT 1
- Sample rate vs. Sample period HOT 2
- Madgwick and Mahony 6Dof HOT 2
- initialization of orientation calculation for Kalman, Madgwick & Mahony HOT 3
- remove pos calculation from analytical(), make rotating q[0] to reference optional for all 4 orientation functions
- expose Kalman tunable parameters HOT 1
- the Kalman implementation questions HOT 2
- Madgwick and Mahony Update() does not support arrays with shape (N,3) HOT 1
- ImportError: cannot import name 'dist' from 'matplotlib.mlab' HOT 7
- Raspbian Buster installation anomaly
- Enable scikit-kinematics to run without OpenGL HOT 3
- ImuBase.calc_position wrongly uses normalized acc HOT 1
- Real time application HOT 3
- [question] IMU position estimate, bias issue?
- How to compute distance from positions? HOT 1
- R_init doesn't work as intended with manual sensors. HOT 2
- assertion failure in tests/test_imus.py HOT 1
- Xens data file doesn't work HOT 9
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