xs
229 lines
5.7 KiB
Markdown
229 lines
5.7 KiB
Markdown
# 21 · DDS 配置 + colcon overlay 完全指南
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> **目标**: 理解 ROS2 DDS 中间件配置、colcon overlay 混合工作空间,能为多机 / 跨网段部署做正确配置。
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---
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## 目录
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- [1. DDS 是什么](#1-dds-是什么)
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- [2. RMW 实现](#2-rmw-实现)
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- [3. 关键环境变量](#3-关键环境变量)
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- [4. domain ID 隔离](#4-domain-id-隔离)
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- [5. 跨网段发现](#5-跨网段发现)
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- [6. Cyclone DDS 配置](#6-cyclone-dds-配置)
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- [7. colcon overlay](#7-colcon-overlay)
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- [8. 三机部署实操](#8-三机部署实操)
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- [9. 推荐阅读](#9-推荐阅读)
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---
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## 1. DDS 是什么
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**DDS (Data Distribution Service)** = OMG 制定的实时通信中间件标准。
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ROS2 默认用 DDS 做底层通信,不同 RMW 实现:
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- `rmw_fastrtps_cpp`(默认,Fast DDS)
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- `rmw_cyclonedds_cpp`(Cyclone DDS)
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DDS 提供:
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- 自动节点发现(基于 UDP multicast)
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- 多种 QoS
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- 实时性(零拷贝、共享内存)
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## 2. RMW 实现
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| RMW | 包 | 适用 |
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|---|---|---|
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| `rmw_fastrtps_cpp` | `ros-humble-rmw-fastrtts-cpp` | 通用,默认 |
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| `rmw_cyclonedds_cpp` | `ros-humble-rmw-cyclonedds-cpp` | 跨网段 / Xenomai 实时 |
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切换:
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```bash
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export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp
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# 然后 colcon build + 启动节点
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```
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**注意**: 切换 RMW 后必须 `rm -rf build/ install/ log/` 再 build,否则 CMake 配置缓存导致 link 错误。
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## 3. 关键环境变量
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| 变量 | 用途 | 默认 |
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|---|---|---|
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| `ROS_DOMAIN_ID` | DDS 域 ID(0-232) | 0 |
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| `RMW_IMPLEMENTATION` | RMW 实现 | `rmw_fastrtts_cpp` |
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| `ROS_STATIC_PEERS` | 跨网段单播发现 | `<unset>` |
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| `ROS_DISCOVERY_SERVER` | 集中式发现服务 | `<unset>` |
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| `ROS_LOCALHOST_ONLY` | 仅本机 | 0 |
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| `CYCLONE_DDS_URI` | Cyclone DDS XML 配置 URI | `<unset>` |
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| `FASTRTPS_DEFAULT_PROFILES_FILE` | FastDDS XML 配置路径 | `<unset>` |
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## 4. domain ID 隔离
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同 `ROS_DOMAIN_ID` 才能互通,改 ID 就隔离:
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```bash
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# PC 端
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ROS_DOMAIN_ID=42 ros2 launch my_pkg demo.py
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# RK3506 端
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ROS_DOMAIN_ID=42 ros2 launch my_pkg demo.py
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# 两端可见
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# 改 ID 后不可见
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ROS_DOMAIN_ID=43 ros2 launch my_pkg demo.py
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```
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**注意**: 域 ID 范围 0-232(ROS2 DDS 协议)。
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## 5. 跨网段发现
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### 问题
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UDP multicast **不跨路由器**,跨网段(如 192.168.1.x ↔ 192.168.2.x)默认看不见。
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### 方案 1: 单播发现 (`ROS_STATIC_PEERS`)
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```bash
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# PC 端(知道 RK3506 IP)
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ROS_STATIC_PEERS="192.168.2.10;192.168.2.11" \
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ros2 launch my_pkg demo.py
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```
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### 方案 2: Discovery Server
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```bash
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# PC 端启 discovery server
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ros2 run discovery_server discovery_server --address 0.0.0.0 --port 11811
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# 客户端
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export ROS_DISCOVERY_SERVER=192.168.2.10:11811
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ros2 launch my_pkg demo.py
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```
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### 方案 3: Cyclone DDS LAN 配置
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`cyclonedds.xml`:
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```xml
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<CycloneDDS>
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<NetworkInterface name="eth0" priority="default" multicast="default"/>
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</CycloneDDS>
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```
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## 6. Cyclone DDS 配置
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### 安装
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```bash
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sudo apt install ros-humble-rmw-cyclonedds-cpp
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```
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### 配置 XML
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```bash
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export CYCLONE_DDS_URI=file:///etc/cyclonedds.xml
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```
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`/etc/cyclonedds.xml`:
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```xml
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<?xml version="1.0" version="1.0"?>
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<CycloneDDS xmlns="https://cdds.io/config">
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<Domain id="any">
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<General>
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<Interfaces>
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<NetworkInterface autodetermine="true" priority="default" multicast="default"/>
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</Interfaces>
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</General>
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</Domain>
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</CycloneDDS>
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```
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## 7. colcon overlay
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**colcon overlay** = 多个 colcon 工作空间叠加,后者覆盖前者(同名包优先用 overlay)。
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### 工作流
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```bash
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# 主工作空间 base(完整)
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mkdir -p ~/ros2_main_ws/src
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cd ~/ros2_main_ws/src
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git clone <完整仓库> # 或 git pull
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cd ..
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colcon build --symlink-install # build 全部
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# overlay 工作空间(只 build 修改的包)
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mkdir -p ~/ros2_overlay_ws/src
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cd ~/ros2_overlay_ws/src
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# 符号链接主工作空间的 src(只覆盖你想改的包)
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ln -s ~/ros2_main_ws/src/my_pkg .
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# 修改 my_pkg
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cd ..
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colcon build --symlink-install --packages-select my_pkg
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# 激活:先 base 后 overlay
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source ~/ros2_main_ws/install/setup.bash
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source ~/ros2_overlay_ws/install/setup.bash # 覆盖
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```
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### 典型场景
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- **稳定版 + 开发版**:base 用稳定版,overlay 跑新代码
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- **共享代码 + 私有修改**:base 装共享库,overlay 装你的定制
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- **CI**:base 装大型依赖,overlay 只 build 改的
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## 8. 三机部署实操
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**典型拓扑**:
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```
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PC (192.168.1.10, ROS_DOMAIN_ID=0)
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│
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├─ RDK X5 (192.168.1.20, ROS_DOMAIN_ID=0)
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│
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└─ RK3506 × 2 (192.168.1.30, 192.168.1.31, ROS_DOMAIN_ID=0)
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```
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**配置**: 三机同 ROS_DOMAIN_ID + 同 LAN,FastDDS multicast 自动发现。
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**RK3506 精简**: 用 `ros-humble-ros-base`,关 daemon:
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```bash
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# 装精简包
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sudo apt install ros-humble-ros-base
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# 关 daemon(省内存)
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sudo systemctl disable --now ros2-daemon
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# 设置环境变量(~/.bashrc)
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export ROS_DOMAIN_ID=0
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source /opt/ros/humble/setup.bash
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```
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详见 [`doc/100-embedded-deployment.md`](100-embedded-deployment.md)。
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## 9. 推荐阅读
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- [ROS2 DDS 概念](https://docs.ros.org/en/humble/Concepts/About-DDS-Implementations.html)
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- [FastDDS 文档](https://fast-dds.docs.eprosima.com/)
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- [Cyclone DDS 文档](https://cyclonedds.io/docs/)
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- [colcon 文档](https://colcon.readthedocs.io/)
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- [REP-2002 ROS 2 Design](https://www.ros.org/reps/rep-2002.html)
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- [`py_overlay_dds` 包](../src/py_overlay_dds/README.md)
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- [三机部署实操](100-embedded-deployment.md)
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---
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---
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## 📖 阅读路径导航
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