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<p>I have opened the issue yesterday.
(<a class="moz-txt-link-freetext" href="https://github.com/orocos/orocos_kinematics_dynamics/issues/130">https://github.com/orocos/orocos_kinematics_dynamics/issues/130</a>)<br>
</p>
<p>Since the kdl is used in several projects, please participate in
the issue discussion. <br>
</p>
<p>I took a look in our kdl_parser library that creates kdl::Tree
from URDF file:
<a class="moz-txt-link-freetext" href="https://github.com/rock-control/control-kdl_parser/blob/master/src/kdl_parser.cpp">https://github.com/rock-control/control-kdl_parser/blob/master/src/kdl_parser.cpp</a></p>
<p>At the row 202-207 the inertial information is added into the
root segment. Even there is a comment "<span class="pl-c" style="box-sizing: border-box; color: rgb(106, 115, 125); font-family: SFMono-Regular, Consolas, "Liberation Mono", Menlo, Courier, monospace; font-size: 12px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: pre; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial;">//</span><span style="color: rgb(106, 115, 125); font-family: SFMono-Regular, Consolas, "Liberation Mono", Menlo, Courier, monospace; font-size: 12px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: pre; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"> warn if root link has inertia. KDL does not support this</span>".
But sadly no warning. o.O</p>
<p>So we should decide:</p>
<p>- we forbidden to use inertial information in root segment,
therefore it is required to use empty root link in urdf<br>
</p>
<p>- or we discuss this issue with kdl developers to add the support
for inertial information of the root link<br>
</p>
<p>Best regards,</p>
<p>Anna<br>
</p>
<br>
<div class="moz-cite-prefix">On 16.02.2018 12:13, Sylvain Joyeux
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAKDpF4So=TtG6MmijbvU8cmrCEBhL46ZALHR=0Om5r0kqu_wyQ@mail.gmail.com">
<pre wrap="">Seems legit to me ... I would suggest reporting this to the KDL
developers (preferably with a correcting pull request ;-))
<a class="moz-txt-link-freetext" href="https://github.com/orocos/orocos_kinematics_dynamics.git">https://github.com/orocos/orocos_kinematics_dynamics.git</a>
Sylvain
On Thu, Feb 15, 2018 at 9:06 AM, Anna Born <a class="moz-txt-link-rfc2396E" href="mailto:anna.born@dfki.de"><anna.born@dfki.de></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">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:
<a class="moz-txt-link-freetext" href="https://git.hb.dfki.de/models-robots/asguard_v4/blob/master/urdf/asguard_v4.urdf">https://git.hb.dfki.de/models-robots/asguard_v4/blob/master/urdf/asguard_v4.urdf</a>
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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</pre>
</blockquote>
</blockquote>
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