初识Qos并创建一个订阅Mavros话题的ROS2节点

环境

树莓派4B
ArduCopter 4.0.7
Ubuntu mate 22.04
ROS2 Humble
(本人搭建所使用的软件硬件版本，仅供参考)

上篇文章我们实现了在终端中打印mavros中的imu数据。但是光打印是不够的，本节的任务是创建一个订阅Mavros话题的ROS2节点。

然而事情并不简单。刚开始尝试写了一个基础的订阅者程序imu_node，订阅“/mavros/imu/data”话题并打印加速度数据

结果出现以下警告，没有任何输出。警告提示QoS策略不兼容

[WARN] [1723023136.939607569] [imu_node]: New publisher discovered on topic '/mavros/imu/data', offering incompatible QoS. No messages will be sent to it. Last incompatible policy: RELIABILITY_QOS_POLICY

 运行下面指令查看详细信息

ros2 topic info /mavros/imu/data --verbose

输出结果 

Type: sensor_msgs/msg/Imu

Publisher count: 1

Node name: imu
Node namespace: /mavros
Topic type: sensor_msgs/msg/Imu
Endpoint type: PUBLISHER
GID: 01.0f.80.84.b1.11.a3.7d.00.00.00.00.00.01.b0.03.00.00.00.00.00.00.00.00
QoS profile:
  Reliability: BEST_EFFORT
  History (Depth): UNKNOWN
  Durability: VOLATILE
  Lifespan: Infinite
  Deadline: Infinite
  Liveliness: AUTOMATIC
  Liveliness lease duration: Infinite

Subscription count: 1

Node name: imu_node
Node namespace: /
Topic type: sensor_msgs/msg/Imu
Endpoint type: SUBSCRIPTION
GID: 01.0f.80.84.5b.13.91.16.00.00.00.00.00.00.12.04.00.00.00.00.00.00.00.00
QoS profile:
  Reliability: RELIABLE
  History (Depth): UNKNOWN
  Durability: VOLATILE
  Lifespan: Infinite
  Deadline: Infinite
  Liveliness: AUTOMATIC
  Liveliness lease duration: Infinite

结果显示发布者发布的话题/mavros/imu/data的QoS策略是Best effort，imu_node（订阅者）的策略是Reli