init: ROS2 learning suite

2026-08-03 18:09:35 +08:00
commit 5ef38ab508
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+"""
+robot_tf2_launch.py —— 启动 3 关节机械臂的 TF2 演示。
+
+启动顺序:
+    joint_state_publisher (本包) → /joint_states
+                                ↓
+    robot_state_publisher  (系统包 ros-humble-robot-state-publisher)
+       读取 URDF + JointState → 算 base_link -> link1 -> link2 -> gripper 的 TF → /tf
+                                ↓
+    tf2_listener (本包) 查 base_link -> gripper,周期打印末端位姿。
+
+URDF 通过 CommandLineAction 用 xacro/直接读 XML,
+这里用 'command' 直接 cat 文件,launch 时读出来给 robot_state_publisher。
+"""
+
+import os
+
+from launch import LaunchDescription
+from launch.actions import DeclareLaunchArgument
+from launch.substitutions import LaunchConfiguration
+from launch_ros.actions import Node
+
+from ament_index_python.packages import get_package_share_directory
+
+
+def generate_launch_description():
+    pkg_share = get_package_share_directory('cpp_robot_tf2')
+    urdf_path = os.path.join(pkg_share, 'urdf', 'simple_arm.urdf')
+
+    # robot_description 参数:把 URDF 文件内容作为字符串直接传入。
+    # 注意:不在 launch 时执行 shell 命令(launch 的 Command 列表拼接有时会
+    #       丢空格,产生 'cat/root/...' 之类错误);改为 launch 启动前直接读文件。
+    with open(urdf_path, 'r', encoding='utf-8') as f:
+        robot_description = f.read()
+
+    use_sim_time = LaunchConfiguration('use_sim_time')
+
+    return LaunchDescription([
+        DeclareLaunchArgument(
+            'use_sim_time', default_value='false',
+            description='Use simulation (Gazebo) clock if true'),
+
+        # 1) JointState 发布者:本包 C++ 节点,模拟关节运动。
+        Node(
+            package='cpp_robot_tf2',
+            executable='joint_state_publisher',
+            name='joint_state_publisher_cpp',
+            output='screen',
+            parameters=[{'use_sim_time': use_sim_time}],
+        ),
+
+        # 2) robot_state_publisher:ROS2 系统包,URDF + JointState -> /tf。
+        Node(
+            package='robot_state_publisher',
+            executable='robot_state_publisher',
+            name='robot_state_publisher',
+            output='screen',
+            parameters=[{
+                'robot_description': robot_description,
+                'use_sim_time': use_sim_time,
+            }],
+        ),
+
+        # 3) tf2_listener:本包 C++ 节点,周期打印 gripper 位姿。
+        Node(
+            package='cpp_robot_tf2',
+            executable='tf2_listener',
+            name='tf2_listener_cpp',
+            output='screen',
+            parameters=[{'use_sim_time': use_sim_time}],
+        ),
+    ])