遇到一个问题。本节开始尝试在gazebo中仿真上一节构建的模型。
先贴一下现象，启动launch之后，gazebo显示正常移动。但是在rviz中查看就是有问题的：
fixedframe:选择odom.显示添加机器人，按topic 选择。提示：
no transform from left wheel to odom
No transform from [right_wheel_link] to [odom]
可以通过键盘控制小车移动，对比视频：不能显示小车两个轮子TF转动。
如果 fixedframe切回base_link ，在rviz显示是正常的，轮子部件都在。
在gazebo显示正常
TF tree对比视频不太一样，视频里面左右轮子right_wheel_link都是在 base_footprint下。
关键代码：
启动脚本
python
import launch
import launch.launch_description_sources
import launch_ros
from ament_index_python.packages import get_package_share_directory
def generate_launch_description():
# 获取功能包默认路径
urdf_tutorial_path = get_package_share_directory('fishbot_description')
default_model_path = urdf_tutorial_path + '/urdf/fishbot/fish_robot.urdf.xacro'
default_world_path = urdf_tutorial_path + '/world/custom_room.world'
# 为 Launch 声明参数
action_declare_arg_mode_path = launch.actions.DeclareLaunchArgument(
name='model', default_value=str(default_model_path),
description='加载模型文件的绝对路径')
# 获取文件内容生成新的参数
robot_description = launch_ros.parameter_descriptions.ParameterValue(
launch.substitutions.Command(
['xacro ', launch.substitutions.LaunchConfiguration('model')]),
value_type=str)
# 状态发布节点
robot_state_publisher_node = launch_ros.actions.Node(
package='robot_state_publisher',
executable='robot_state_publisher',
parameters=[{'robot_description': robot_description}]
)
# 通过 IncludeLaunchDescription 包含另外一个 launch 文件
launch_gazebo = launch.actions.IncludeLaunchDescription(
launch.launch_description_sources.PythonLaunchDescriptionSource([get_package_share_directory(
'gazebo_ros'), '/launch', '/gazebo.launch.py']),
# 传递参数
launch_arguments=[('world', default_world_path),('verbose','true')]
)
#请求gazebo 加载机器人
action_spawn_entity = launch_ros.actions.Node(
package= 'gazebo_ros',
executable='spawn_entity.py',
arguments=['-topic', '/robot_description','-entity', 'fishbot']
)
return launch.LaunchDescription([
action_declare_arg_mode_path,
robot_state_publisher_node,
launch_gazebo,
action_spawn_entity,
])定义模型
XML
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="fishbot">
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/base.urdf.xacro" />
<!-- 传感器组件 -->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/sensor/imu.urdf.xacro" />
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/sensor/laser.urdf.xacro" />
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/sensor/camera.urdf.xacro" />
<!-- 执行器组件 -->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/actuator/wheel.urdf.xacro" />
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/actuator/caster.urdf.xacro" />
<!--gazebo插件-->
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/plugins/gazebo_control_plugin.xacro" />
<xacro:base_xacro length="0.12" radius="0.1" />
<!-- 传感器 -->
<xacro:imu_xacro xyz="0 0 0.02" />
<xacro:laser_xacro xyz="0 0 0.10" />
<xacro:camera_xacro xyz="0.10 0 0.075" />
<!-- 执行器主动轮+从动轮 -->
<xacro:wheel_xacro wheel_name="left_wheel" xyz="0 0.10 -0.06" />
<xacro:wheel_xacro wheel_name="right_wheel" xyz="0 -0.10 -0.06" />
<xacro:caster_xacro caster_name="front_caster" xyz="0.08 0.0 -0.076" />
<xacro:caster_xacro caster_name="back_caster" xyz="-0.08 0.0 -0.076" />
<xacro:gazebo_control_plugin />
</robot>轮子定义：
XML
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
<xacro:include filename="$(find fishbot_description)/urdf/fishbot/common_inertia.xacro" />
<xacro:macro name="wheel_xacro" params="wheel_name xyz">
<link name="${wheel_name}_link">
<visual>
<origin xyz="0 0 0" rpy="1.57079 0 0" />
<geometry>
<cylinder length="0.04" radius="0.032" />
</geometry>
<material name="yellow">
<color rgba="1.0 1.0 0.0 0.8"/>
</material>
</visual>
<collision>
<origin xyz="0 0 0" rpy="1.57079 0 0" />
<geometry>
<cylinder length="0.04" radius="0.032" />
</geometry>
<material name="yellow">
<color rgba="1.0 1.0 0.0 0.8"/>
</material>
</collision>
<xacro:cylinder_inertia m="0.1" h="0.04" r="0.032"/>
</link>
<gazebo reference="${wheel_name}_link">
<mu1 value="20.0" />
<mu2 value="20.0" />
<kp value="1000000000.0" />
<kd value="1.0" />
</gazebo>
<joint name="${wheel_name}_joint" type="continuous">
<parent link="base_link" />
<child link="${wheel_name}_link" />
<origin xyz="${xyz}" />
<!--轮子绕那个轴旋转-->
<axis xyz="0 1 0" />
</joint>
</xacro:macro>
</robot>差速控制：
XML
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
<xacro:macro name="gazebo_control_plugin">
<gazebo>
<plugin name='diff_drive' filename='libgazebo_ros_diff_drive.so'>
<ros>
<namespace>/</namespace>
<remapping>cmd_vel:=cmd_vel</remapping>
<remapping>odom:=odom</remapping>
</ros>
<update_rate>30</update_rate>
<!-- wheels -->
<left_joint>left_wheel_joint</left_joint>
<right_joint>right_wheel_joint</right_joint>
<!-- kinematics -->
<wheel_separation>0.2</wheel_separation>
<wheel_diameter>0.064</wheel_diameter>
<!-- limits -->
<max_wheel_torque>20</max_wheel_torque>
<max_wheel_acceleration>1.0</max_wheel_acceleration>
<!-- output -->
<publish_odom>true</publish_odom>
<publish_odom_tf>true</publish_odom_tf>
<publish_wheel_tf>true</publish_wheel_tf>
<odometry_frame>odom</odometry_frame>
<robot_base_frame>base_footprint</robot_base_frame>
</plugin>
</gazebo>
</xacro:macro>
</robot>