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# URDF joint axis

I am working on a project but I am stuck with determining the joint rotation axis with my own built model.

How do I determine the joint axis to let the robot rotate about a point? Just like the human knee joint.

Below shows part of my urdf file,

Please help me, thanks a lot!

Blockquote

name="thigh_r">
<inertial>
<origin
xyz="0.43096 -0.040854 0.12418"
rpy="0 0 0" />
<mass
value="0.20" />
<inertia
ixx="0.0052338"
ixy="3.2827E-07"
ixz="-0.00046547"
iyy="0.0061653"
iyz="3.0465E-06"
izz="0.00096993" />
</inertial>
<visual>
<origin
xyz="0 0 0"
rpy="0 0 0" />
<geometry>
<mesh
filename="package://exo1/meshes/thigh_r.STL" />
</geometry>
<material
name="">
<color
rgba="0.79216 0.81961 0.93333 1" />
</material>
</visual>
<collision>
<origin
xyz="0 0 0"
rpy="0 0 0" />
<geometry>
<mesh
filename="package://exo1/meshes/thigh_r.STL" />
</geometry>
</collision>
name="hip_r"
type="revolute">
<origin
xyz="0 0 0"
rpy="0 0 -1.5708" />
<parent
link="base_link" />
<child
link="thigh_r" />
<axis
xyz="0 0.01 0" />
<limit
lower="-0.1"
upper="0.4"
effort="150"
velocity="0.5" />


</joint>

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## 1 Answer

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link text

xyz = roll - pitch - yaw; a knee I would asume is pitch

<axis xyz="0 1 0"/>


My urdf looks different, maybe its just a copy paste issue, but things seem missing.

<link name="Link_A">
...
</link>

<joint name=Joint_A" type="revolute">
...
<axis xyz="0 1 0"/>
...
</joint>

more

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Asked: 2021-01-03 10:04:39 -0500

Seen: 469 times

Last updated: Jan 04 '21