ROS Robotics By Example No transform from [left_wheel] to [base_link]

1、问题描述

在第二章中搭建双轮机器人

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

    <!-- base link-->
    <link name="base_link">
        <visual>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0"/>
            <geometry>
                <box size="0.5 0.5 0.25"/>
            </geometry>
        </visual>
    </link>

    <!-- Right Wheel-->
    <link name="right_wheel">
        <visual>
            <origin xyz="0.0 0.0 0.0" rpy="1.570795 0.0 0.0"/>
            <geometry>
                <cylinder radius="0.2" length="0.1"/>
            </geometry>
        </visual>
    </link>
    <joint name="joint_right_wheel" type="continuous">
        <parent link="base_link"/>
        <child link="right_wheel"/>
        <origin xyz="0 -0.30 0.0" rpy="0.0 0.0 0.0"/>
        <axis xyz="0.0 1 0.0"/>
    </joint>

    <!-- Left Wheel-->
    <link name="left_wheel">
        <visual>
            <origin xyz="0 0 0" rpy="1.570795 0.0 0.0"/>
            <geometry>
                <cylinder radius="0.2" length="0.1"/>
            </geometry>
        </visual>
    </link>
    <joint name="joint_left_wheel" type="continuous">
        <parent link="base_link"/>
        <child link="left_wheel"/>
        <origin xyz="0 0.30 0.0" rpy="0 0 0"/>
        <axis xyz="0 1 0"/>
    </joint>
</robot>

使用URDF自搭建双轮小车时出现如下问题

No transform from [left_wheel] to [base_link]
No transform from [right_wheel] to [base_link]

如图所示

2、原因与解答

launch一有处错误

<node name="robot_state_publisher" pkg="robot_state_publisher" type="state_publisher" />

改为

<node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher" />