I have opened the issue yesterday.
(https://github.com/orocos/orocos_kinematics_dynamics/issues/130)
Since the kdl is used in several projects, please participate in the
issue discussion.
I took a look in our kdl_parser library that creates kdl::Tree from URDF
file:
https://github.com/rock-control/control-kdl_parser/blob/master/src/kdl_parser.cpp
At the row 202-207 the inertial information is added into the root
segment. Even there is a comment "//warn if root link has inertia. KDL
does not support this". But sadly no warning. o.O
So we should decide:
- we forbidden to use inertial information in root segment, therefore it
is required to use empty root link in urdf
- or we discuss this issue with kdl developers to add the support for
inertial information of the root link
Best regards,
Anna
On 16.02.2018 12:13, Sylvain Joyeux wrote:
Seems legit to me ... I would suggest reporting this to the KDL
developers (preferably with a correcting pull request ;-))
https://github.com/orocos/orocos_kinematics_dynamics.git
Sylvain
On Thu, Feb 15, 2018 at 9:06 AM, Anna Born <anna.b...@dfki.de> wrote:
Hi,
by copying or assigning the KDL::Tree the inertia information of the root
segment is not copied and is restored to zero.
The inertia information:
segment.getInertia().getMass() segment.getInertia().getCOG()
segment.getInertia().getRotationalInertia()
Hier is the code:
bool is_success = kdl_parser::treeFromFile(file, this->kdlTree);
printOutTree(this->kdlTree);
KDL::Tree treeTest(kdlTree);
printOutTree(treeTest);
For test the urdf model of asguard was used:
https://git.hb.dfki.de/models-robots/asguard_v4/blob/master/urdf/asguard_v4.urdf
The original, kdlTree:
---body
Mass: 2
COG: 0.035 0 0.07825
RotationalInertia: 0.0281261 0 -0.0054775 0 0.0641161 0 -0.0054775 0 0.05125
.......
---wheel_front_right_motor
Mass: 0.1
COG: -0.00031 -0.00016 0.00047
RotationalInertia: 0.00176002 -4.96e-09 1.457e-08 -4.96e-09 0.00346003
7.52e-09 1.457e-08 7.52e-09 0.00176001
Its copy, treeTest:
---body
Mass: 0
COG: 0 0 0
RotationalInertia: 0 0 0 0 0 0 0 0 0
........
---wheel_front_right_motor
Mass: 0.1
COG: -0.00031 -0.00016 0.00047
RotationalInertia: 0.00176002 -4.96e-09 1.457e-08 -4.96e-09 0.00346003
7.52e-09 1.457e-08 7.52e-09 0.00176001
Has someone know more about this issue?
I tried with our kdl version (commit:
264ef3f7c4ad553e7a391e0f104fda1ec5051925) and with the newest kdl version
(commit: d798f594552cb6f6223981b9c304d3db2b6a7d18). Both versions give the
same result.
With best regards,
Anna
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