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nan value after changing inertia matrix [closed]

asked 2016-01-18 11:08:12 -0500

F.Brosseau gravatar image

Hello everybody,

I am the following problem with my robot (rear wheels don't touch the ground): image description

So I have changed the inertia of my links but I got an error when I change the matrix of some wheels (it's strange because the link in the error message is not linked to the wheels involved in the problem):

[ERROR] [1453136122.044577471, 24.646000000]: Ignoring transform for child_frame_id "fourche" from authority "unknown_publisher" because of a nan value in the transform (-nan -nan -nan) (0.000000 0.000000 0.000000 1.000000)

Urdf description of my wheels (diameter: 125mm, height: 50mm) :

<link name="${prefix}_motor_wheel">
        <gazebo>
            <self_collide>false</self_collide>
        </gazebo>
        <visual>
            <material name="Yellow">
                <color rgba="0.8 0.8 0.0 1.0"/>
            </material>
            <geometry>
                <mesh filename="package://agv/urdf/model/motor_wheel_left.dae"/>
            </geometry>
        </visual>
        <collision>
            <geometry>
                <mesh filename="package://agv/urdf/model/motor_wheel_left.dae"/>
            </geometry>
        </collision>
        <inertial>
            <mass value="1.8"/>
            <inertia
            ixx="0.0021" ixy="0.0" ixz="0.0"
            iyy="0.0035" iyz="0.0"
            izz="0.0021"/>
        </inertial>
        <!--<inertial>
            <mass value="1"/>
            <inertia
            ixx="1.0" ixy="0.0" ixz="0.0"
            iyy="1.0" iyz="0.0"
            izz="1.0"/>
        </inertial>-->
    </link>

Thanks in advance

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Closed for the following reason the question is answered, right answer was accepted by F.Brosseau
close date 2016-01-19 03:26:33.366898

1 Answer

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answered 2016-01-19 02:45:06 -0500

Sounds like you're experiencing physics engine instability. Have a look at the Q/A here and the link posted there.

It looks like the collision geometry of your robot is wrong if the wheels don't touch the ground (You can visualize it inside Gazebo by selecting it in the menu). Changing the inertias probably will not help there.

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Thanks a lot. It's working now. The problem was not coming from the collision geometry. But like you said in your link, the d parameter of my wheel's controllers had a to high value.

F.Brosseau gravatar imageF.Brosseau ( 2016-01-19 03:09:25 -0500 )edit

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Asked: 2016-01-18 11:08:12 -0500

Seen: 69 times

Last updated: Jan 19 '16