Cute Mira body issue

Course Support URDF for Robot Modeling
1

Hello guys, When I tried to import the dae file to the urdf. The position of the Mira’s body inclined for no reason.

What happend?

image

Here is the code:

<?xml version="1.0"?>
<robot name="mira">

    <material name="blue">
        <color rgba="0 0 0.8 1"/>
    </material>
    <material name="red">
        <color rgba="0.8 0 0 1"/>
    </material>
    <material name="green">
        <color rgba="0 0.8 0 1"/>
    </material>
    <material name="grey">
        <color rgba="0.75 0.75 0.75 1"/>
    </material>
    <material name="white">
        <color rgba="1.0 1.0 1.0 1"/>
    </material>
    <material name="black">
        <color rgba="0 0 0 1"/>
    </material>

	<!-- * * * Link Definitions * * * -->
    <link name="base_link">

        <visual>
            <origin rpy="0.0 0 0" xyz="0 0 0"/>
            <geometry>
                <mesh filename="package://my_mira_description/models/mira/meshes/mira_body_v3.dae"/>
            </geometry>
        </visual>
	</link>



    <link name="roll_M1_link">

        <visual>
            <origin rpy="0 0 0" xyz="0 0 0"/>
            <geometry>
                <cylinder length="0.005" radius="0.01"/>
            </geometry>
            <material name="red"/>
        </visual>
    </link>

    <joint name="roll_joint" type="revolute">
    	<parent link="base_link"/>
    	<child link="roll_M1_link"/>
        <origin xyz="0.0023 0 -0.0005" rpy="0 0 0"/>
        <limit lower="-0.2" upper="0.2" effort="0.1" velocity="0.005"/>
        <axis xyz="1 0 0"/>
	</joint>



    <link name="pitch_M2_link">

        <visual>
            <origin rpy="0 0 0" xyz="0 0 0"/>
            <geometry>
                <cylinder length="0.005" radius="0.01"/>
            </geometry>
            <material name="green"/>
        </visual>
    </link>


    <joint name="pitch_joint" type="revolute">
    	<parent link="roll_M1_link"/>
    	<child link="pitch_M2_link"/>
    	<origin xyz="0 0 0" rpy="0 -1.5708 0"/>
        <limit lower="0" upper="0.44" effort="0.1" velocity="0.005"/>
        <axis xyz="0 1 0"/>
	</joint>


    <link name="yaw_M3_link">

        <visual>
            <origin rpy="0 0 0" xyz="0 0 0"/>
            <geometry>
                <cylinder length="0.005" radius="0.01"/>
            </geometry>
            <material name="blue"/>
        </visual>
    </link>

    <joint name="yaw_joint" type="continuous">
    	<parent link="pitch_M2_link"/>
    	<child link="yaw_M3_link"/>
        <origin xyz="0.01 0 0" rpy="0 1.5708 0"/>
        <limit effort="0.1" velocity="0.01"/>
        <axis xyz="0 0 1"/>
	</joint>


    <link name="head_link">

		<visual>
            <origin rpy="0.0 0 0" xyz="0 0 0"/>
            <geometry>
                <mesh filename="package://my_mira_description/models/mira/meshes/mira_head_v5.dae"/>
            </geometry>
            <material name="white"/>
        </visual>
	</link>


    <joint name="base_head_joint" type="fixed">
    	<parent link="yaw_M3_link"/>
    	<child link="head_link"/>
    	<origin xyz="0 0 0.06" rpy="0 0 0"/>
	</joint>

    <link name="left_eye_link">

		<visual>
            <origin rpy="0.0 0 0" xyz="0 0 0"/>
            <geometry>
                <mesh filename="package://my_mira_description/models/mira/meshes/mira_eye_v4.dae"/>
            </geometry>
            <material name="black"/>
        </visual>
	</link>

    <link name="right_eye_link">

		<visual>
            <origin rpy="0.0 0 0" xyz="0 0 0"/>
            <geometry>
                <mesh filename="package://my_mira_description/models/mira/meshes/mira_eye_v4.dae"/>
            </geometry>
            <material name="black"/>
        </visual>
	</link>

    <joint name="head_lefteye_joint" type="fixed">
        <parent link="head_link"/>
        <child link="left_eye_link"/>
        <origin xyz="0.0095 0.057 0.0085" rpy="-1.5708 0 0"/>
    </joint>

    <joint name="head_righteye_joint" type="fixed">
        <parent link="head_link"/>
        <child link="right_eye_link"/>
        <origin xyz="-0.0095 0.057 0.0085" rpy="-1.5708 0 0"/>
    </joint>

    <link name="camera_link">
		<visual>
            <origin rpy="0.0 0 0" xyz="0 0 0"/>
            <geometry>
                <box size="0.0005 0.0005 0.0005"/>
            </geometry>
            <material name="green"/>
        </visual>
	</link>


    <joint name="head_camera_joint" type="fixed">
        <parent link="head_link"/>
        <child link="camera_link"/>
        <origin xyz="0 0.057 0.0255" rpy="0 0 0"/>
    </joint>


</robot>
2

What happens is that the new 3D model and the previous one share the same origin point, which is at a distance of 0.06 from the parent link. Now though the old shape,sphere, fits snugly, the shape of the new dae model is complety different resulting in it looking offset.

Feel free to ask if this didn’t clear your question

2 Likes
3

Thank you so much! @Joseph1001

1 Like
4

@Joseph1001 Hello, Joseph. I have a doubt. Why were we making spawn, control, launch file separately, and we had to create another launch file for launching those two. Why not just write them into a same launch file? Is it because we want to split each function so that we can “import” them quickly and easily?

5

Yes, this is so that we can import the same core launch files for multiple projects, and only have to change the values of required variables.

1 Like
6

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