Comments (8)
Regarding the quaternion to rotation, two formulas are used in the code:
dcm = eye(3) + 2*qt_b_mod_s*skew(qt_b_mod_r) + 2 * skew(qt_b_mod_r)^2;
in the quite used frame2pos
function and
dcm = eye(3) - 2*qt_b_mod_s*skew(qt_b_mod_r) + 2 * skew(qt_b_mod_r)^2;
in the rest of the code. As far as I remember the one with the minus is the correct one, but I think it is good if we all agree on which fix is the one most correct.
from mex-wholebodymodel.
Guys, I'm really frustrated, since I remember that I personally worked on that, and I tried to fix this stuff with @gabrielenava. I don't know why these obscure formulae keep going around. I remember that the first one should be right, instead [1, p. 101, Eq. 3.8]. Anyways, please try to write these functions once for all in appropriate separate files, so we can debug them only once.
[1] https://www-sop.inria.fr/act_recherche/formulaire/uploads/phd-425.pdf
from mex-wholebodymodel.
I checked and apparently the formula with a plus
is the one consistent with Rodriguez Formula.
from mex-wholebodymodel.
I also checked and apparently mex-wholebodymodel_balancing
code is not using the minus
version anywhere.
from mex-wholebodymodel.
Ack.
from mex-wholebodymodel.
I have no idea why the incorrect version crept in. I remember fixing this a while ago also with @gabrielenava. I guess with automated tests this will stop being a problem.
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Given that it was the source of the error in #30 and an important piece of computation in general, I will now investigate how to consolidated all the different functions implementing the "Constrained Dynamics with Torque as a input".
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@gabrielenava Can you fix the last point in #42 (comment) ?
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Related Issues (20)
- Provide a example on how to load a simple URDF model HOT 1
- Warning: quaternions numerical integration errors HOT 7
- error while use wbm_jacobian HOT 2
- Cmake: check dependencies HOT 3
- windows compilation failed HOT 1
- Matlab crash when running the ctest HOT 8
- Semi Positive Definite Mass Matrix from URDF using mexWholeBodyModel HOT 3
- Unused wbm_setWorldLink.m function HOT 3
- Provide a shim of mex-wholebodymodel against iDynTree classes HOT 1
- torqueBalancing not working HOT 6
- Bug: DBL_MAX in yarpWholeBodyModelV2::getJointLimitFromModel HOT 5
- wbm_jacobian retrieves always the CoM jacobian when called with non-existent frames HOT 8
- Create CI files HOT 2
- latest mex-subroutine causes numerical problems HOT 3
- Clarification on the function `dquat2tform.m` HOT 3
- wbm_getState return nan in the vector-quaternion transformation HOT 33
- ChangeLog is broken HOT 1
- Deprecation of codyco-superbuild HOT 6
- Move this repo to Robotology Legacy? HOT 6
- bug in rotm2quat.m HOT 3
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from mex-wholebodymodel.