How to use floating joint and planar joint in URDF file (Syntax)?

[Joseph1001]

Hi, i was trying to create a Floating joint between 2 links so that it can move freely in all 6 directions.
When i run the URDF file, i get the error, Warning me that joint is will be converted into a fixed joint instead of a Floating joint. The same error occurs when i try to use a planar joint as well.

process[joint_state_publisher_gui-1]: started with pid [26552]
process[robot_state_publisher-2]: started with pid [26555]
process[rviz-3]: started with pid [26556]
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-user'
[ WARN] [1646757463.223350587, 176.555000000]: Converting unknown joint type of joint 'roll_joint' into a fixed joint
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-user'
^C[rviz-3] killing on exit

URDF used:

<?xml version="1.0"?>
<robot name="mira">
    <link name="base_link">
        <visual>
        <origin rpy="0 0 0" xyz="0 0 0"/>
        <geometry>
            <cylinder radius="0.06" length="0.09"/>
        </geometry>
        </visual>
    </link>
  
    <link name="roll_M1_link">
        <visual>
            <origin rpy="0 0 0" xyz="0 0 0"/>
            <geometry>
                <cylinder radius="0.06" length="0.09"/>
            </geometry>
        </visual>
    </link>
    

        <joint name="roll_joint" type="floating">
        <parent link="base_link"/>
        <child link="roll_M1_link"/>
        <origin xyz="0.0023 0 -0.0005" rpy="0 0 0"/>
        <limit effort="0.1" velocity="0.005"/>
        <!-- <axis xyz="0 0 1"/> -->
    </joint>
  
</robot>

I have gone through a similar post as linked below but could not find the required solution.

URDF's floating joint not working in Gazebo

Hi, There are many ways of doing this. I reccomend you to have a look at this simulation of Haro. Itrs a floating robot that can move in any direction and orientation, which seems what you want to accomplish here: HARO GIT

@staff Can you edit the above-mentioned joint definition so that it works as a floating joint ? could you also do this for planar joint as well?

[duckfrost2]

Hi,

The floating joint in my experience doesn’t work.

As said in the post you comment on, you have to create this floating effect by using a combination of prismatic joints or as in the Haro example, create a robot that gravity doesn’t affect him an therefore floats around.