On Tue, Jun 1, 2010 at 3:58 PM, Kirila Adamova <kirila.adamova@dfki.de>wrote:

> Thank you,
>
> That placed the cylinder correctly. However, I still have the rotation
> problem.
>     <link name="hips">
>        <inertial>
>            <origin xyz="0 0 0.570" rpy="0 2.2 0"/>
>            <mass value="50"/>
>            <inertia ixx="1" ixy="0" ixz="0" iyy="0" iyz="0" izz="0"/>
>        </inertial>
>        <visual>
>             <origin xyz="-0.169 0 0" rpy="0 2.2 0"/>

            <geometry>
>                <cylinder radius="0.060" length="0.420"/>
>            </geometry>
>        </visual>
>        <collision>
>                   <origin xyz="-0.169 0 0" rpy="0 2.2 0"/>
>                   <geometry>
>                    <cylinder radius="0.060" length="0.400"/>
>                  </geometry>
>            </collision>
>    </link>
>
>    <joint name="knees" type="revolute">
>        <parent link="feet"/>
>        <child link="hips"/>
>        <origin xyz="0 0 0.275"/>
>        <axis xyz="0 1 0"/>
>        <limit lower="1.31" upper="3.22" effort="30" velocity="1.0"/>
>    </joint>
>

The <axis> element is specific to a joint, not a link, and specifies the
direction of motion (rotation, in your case).
If you are interested in orienting a link with respect to to a joint, then
you should use the rpy attribute of the <origin> element. For example, in
the above code, you state:

<origin xyz="-0.169 0 0" rpy="0 2.2 0"/>

Here you are specifying a pitch angle of 2.2 radians. You can choose a
suitable roll, pitch, yaw triplet that will reorient your cylinder as you
would expect.
I'm not sure if I understood your question correctly... Does this solve your
issue?

Adolfo


> If in the joint, <axis xyz="0 0 1">, the cylinder rotates around the z
> axis. When I set it to <axiz xyz="0 1 0">, it rotates around the y axis
> as I want it to, but the whole robot also jumps and rotates and falls to
> its side...
>
> Kirila
>
> Adolfo Rodríguez Tsouroukdissian wrote:
> > On Tue, Jun 1, 2010 at 3:32 PM, Kirila Adamova <kirila.adamova@dfki.de
> > <mailto:kirila.adamova@dfki.de>> wrote:
> >
> >     Hi all,
> >
> >     I am currently writing a 3D model in urdf. I have two cylinders,
> which
> >     are connected with a joint. The second cylinder, however, is
> >     rotated and
> >     can be rotated further in the same direction. When I visualize them
> in
> >     gazebo, the joint is in the center of the second cylinder. Is there a
> >     way to make it at the end of the cylinder because that is the point
> >     around which I need to rotate it. To make it more clear (or even more
> >     confusing), here is sample code:
> >
> >     <link name="feet">
> >            <inertial>
> >                <origin xyz="0 0 0.275" rpy="0 0 0"/>
> >                <mass value="100"/>
> >                <inertia ixx="1" ixy="0" ixz="0" iyy="0" iyz="0" izz="0"/>
> >            </inertial>
> >            <visual>
> >                <origin xyz="0 0 0" rpy="0 0 0"/>
> >                <geometry>
> >                    <cylinder radius="0.100" length="0.250"/>
> >                </geometry>
> >            </visual>
> >            <collision>
> >                      <origin xyz="0 0 0" rpy="0 0 0"/>
> >                      <geometry>
> >                        <cylinder radius="0.100" length="0.230"/>
> >                      </geometry>
> >                </collision>
> >        </link>
> >
> >        <link name="hips">
> >            <inertial>
> >                <origin xyz="0 0 0.570" rpy="0 2.2 0"/>
> >                <mass value="50"/>
> >                <inertia ixx="1" ixy="0" ixz="0" iyy="0" iyz="0" izz="0"/>
> >            </inertial>
> >            <visual>
> >                <origin xyz="0 0 0" rpy="0 2.2 0"/>
> >                <geometry>
> >                    <cylinder radius="0.060" length="0.420"/>
> >                </geometry>
> >            </visual>
> >            <collision>
> >                      <origin xyz="0 0 0" rpy="0 2.2 0"/>
> >                      <geometry>
> >                        <cylinder radius="0.060" length="0.400"/>
> >                      </geometry>
> >                </collision>
> >        </link>
> >
> >        <joint name="knees" type="revolute">
> >            <parent link="feet"/>
> >            <child link="hips"/>
> >            <origin xyz="0 0 0.275"/>
> >            <axis xyz="0 0 1"/>
> >            <limit lower="1.31" upper="3.22" effort="30" velocity="1.0"/>
> >        </joint>
> >
> >
> >     Currently, the axis xyz is set to z, although it needs to be y,
> >     because
> >     when it's set somewhere else, the whole model goes crazy (jumps and
> >     turns around) in gazebo.
> >
> >
> >
> > Kirila,
> >
> > The cylinder primitive makes its center coincide with the
> > corresponding origin (visualization, collision) and is aligned with
> > the z axis. For your robot, it should suffice to specify an
> > appropriate origin for your visualization and collision geometries
> > (with respect to the joint origin). For more details refer to the
> > available documentation:
> >
> > http://www.ros.org/wiki/urdf/XML/Link
> > http://www.ros.org/wiki/urdf/XML/Joint
> >
> > HTH,
> >
> > Adolfo
> >
> >
> >     Help will be greatly appreciated,
> >
> >     Kirila
> >
> >     p.s. End result must rotate the second cylinder around the point
> >     between
> >     the two cylinders around the y axis.
> >     _______________________________________________
> >     ros-users mailing list
> >     ros-users@code.ros.org <mailto:ros-users@code.ros.org>
> >     https://code.ros.org/mailman/listinfo/ros-users
> >
> >
> >
> >
> > --
> > Adolfo Rodríguez Tsouroukdissian, Ph. D.
> >
> > Robotics engineer
> > PAL ROBOTICS S.L
> > http://www.pal-robotics.com
> > Tel. +34.93.414.53.47
> > Fax.+34.93.209.11.09
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