随便写

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

<material name="blue">
<color rgba="0 0 0.8 1"/>
</material>

<material name="white">
<color rgba="1 1 1 1"/>
</material>

<link name="base_link">
<visual>
<geometry>
<cylinder length="0.6" radius="0.2"/>
</geometry>
</visual>
</link>

<link name="right_leg">
<visual>
<geometry>
<box size="0.6 0.1 0.2"/>
</geometry>
<origin rpy="0 1.57075 0" xyz="0 0 -0.3"/>
<material name="white"/>
</visual>
</link>

<link name="left_leg">
<visual>
<geometry>
<box size="0.6 0.1 0.2"/>
</geometry>
<origin rpy="0 1.57075 0" xyz="0 0 -0.3"/>
<material name="white"/>
</visual>
</link>

<joint name="base_to_left_leg" type="fixed">
<parent link="base_link"/>
<child link="left_leg"/>
<origin xyz="0 0.22 0.25"/>
</joint>

<link name="right_base">
<visual>
<geometry>
<box size="0.4 0.1 0.1"/>
</geometry>
<material name="white"/>
</visual>
</link>

<joint name="right_base_joint" type="fixed">
<parent link="right_leg"/>
<child link="right_base">
<origin xyz="0 0 -0.6"/>
</joint>

<link name="left_base">
<visual>
<geometry>
<box size="0.4 0.1 0.1"/>
</geometry>
<material name="white"/>
</visual>
</link>

<joint name="left_base_joint" type="fixed">
<parent link="left_leg"/>
<child link="right_base">
<origin xyz="0 0 -0.6"/>
</joint>

<link name="right_front_wheel">
<visual>
<origin rpy="1.57075 0 0" xyz="0 0 0"/>
<geometry>
<cylinder length="0.1" radius="0.035"/>
</geometry>
<material name="black"/>
<origin rpy="0 0 0" xyz="0 0 0"/>
</visual>
</link>

<joint name="right_front_wheel_joint" type="fixed">
<parent link="right base"/>
<child link="right_front_wheel">
<origin rpy="0 0 0" xyz="0.133333333333 0 -0.085"/>
</joint>

<link name="right_back_wheel">
<visual>
<origin rpy="1.57075 0 0" xyz="0 0 0"/>
<geometry>
<cylinder length="0.1" radius="0.035"/>
</geometry>
<material name="black"/>
<origin rpy="0 0 0" xyz="0 0 0"/>
</visual>
</link>

<joint name="right_front_wheel_joint" type="fixed">
<parent link="right base"/>
<child link="right_front_wheel">
<origin rpy="0 0 0" xyz="-0.133333333333 0 -0.085"/>
</joint>