ROS2 参数服务器设置

1. 参数服务器节点（Parameter Server Node）
   负责在启动时一次性声明若干参数，并对外提供查询/修改服务。

2. 客户端节点（Parameter Client Node）
   演示如何在运行时通过 C++/Python API 读取/设置/列出参数。

示例参数：robot_name（string）、max_speed（double）、enable_debug（bool）。

---

1. 目录结构（C++ 版）

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ws
└─src
   └─param_server_demo
      ├─CMakeLists.txt
      ├─package.xml
      ├─src
      │  ├─param_server.cpp
      │  └─param_client.cpp
      └─launch
         └─demo.launch.py

---

一、创建功能包

bash

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ros2 pkg create --build-type ament_cmake param_server_demo \
  --dependencies rclcpp rclpy

---

二、参数服务器节点（C++） 文件：src/param_server.cpp

cpp

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#include <chrono>
#include <memory>
#include "rclcpp/rclcpp.hpp"

class ParameterServer : public rclcpp::Node
{
public:
  ParameterServer()
  : Node("parameter_server",
         rclcpp::NodeOptions()
             .allow_undeclared_parameters(true)   // 允许动态声明
             .automatically_declare_parameters_from_overrides(true))
  {
    // 1) 声明并设置默认值
    this->declare_parameter("robot_name", "turtlebot3");
    this->declare_parameter("max_speed", 1.0);
    this->declare_parameter("enable_debug", false);

    RCLCPP_INFO(this->get_logger(),
                "[ParameterServer] ready, parameters declared.");
  }
};

int main(int argc, char ** argv)
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<ParameterServer>());
  rclcpp::shutdown();
  return 0;
}

---

三、参数客户端节点（C++） 文件：src/param_client.cpp

cpp

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#include <chrono>
#include <memory>
#include "rclcpp/rclcpp.hpp"

class ParameterClient : public rclcpp::Node
{
public:
  ParameterClient()
  : Node("parameter_client")
  {
    client_ = std::make_shared<rclcpp::AsyncParametersClient>(this, "parameter_server");

    // 等待服务器上线
    while (!client_->wait_for_service(std::chrono::seconds(1))) {
      if (!rclcpp::ok()) return;
      RCLCPP_INFO(this->get_logger(), "waiting for parameter server ...");
    }

    demo();
  }

private:
  void demo()
  {
    // 1) 读取
    auto params = client_->get_parameters(
      {"robot_name", "max_speed", "enable_debug"});
    if (rclcpp::spin_until_future_complete(shared_from_this(), params) ==
        rclcpp::FutureReturnCode::SUCCESS)
    {
      RCLCPP_INFO(this->get_logger(),
                  "robot_name = %s, max_speed = %.2f, enable_debug = %s",
                  params.get()[0].as_string().c_str(),
                  params.get()[1].as_double(),
                  params.get()[2].as_bool() ? "true" : "false");
    }

    // 2) 修改
    client_->set_parameters({
      rclcpp::Parameter("max_speed", 3.14),
      rclcpp::Parameter("enable_debug", true)
    });

    // 3) 列出全部
    auto list_future = client_->list_parameters({}, 10);
    if (rclcpp::spin_until_future_complete(shared_from_this(), list_future) ==
        rclcpp::FutureReturnCode::SUCCESS)
    {
      for (auto & name : list_future.get().names) {
        RCLCPP_INFO(this->get_logger(), "param name: %s", name.c_str());
      }
    }
  }

  std::shared_ptr<rclcpp::AsyncParametersClient> client_;
};

int main(int argc, char ** argv)
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<ParameterClient>());
  rclcpp::shutdown();
  return 0;
}

---

四、Python 版（可选） 文件：param_server_demo/param_server_py.py

Python

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import rclpy
from rclpy.node import Node

class ParameterServerPy(Node):
    def __init__(self):
        super().__init__('parameter_server_py',
                         allow_undeclared_parameters=True,
                         automatically_declare_parameters_from_overrides=True)
        self.declare_parameter('robot_name', 'turtlebot3_py')
        self.declare_parameter('max_speed', 0.5)
        self.declare_parameter('enable_debug', False)
        self.get_logger().info('[ParameterServerPy] ready.')

def main():
    rclpy.init()
    rclpy.spin(ParameterServerPy())
    rclpy.shutdown()

if __name__ == '__main__':
    main()

文件：param_server_demo/param_client_py.py

Python

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import rclpy
from rclpy.node import Node
from rcl_interfaces.srv import ListParameters

class ParameterClientPy(Node):
    def __init__(self):
        super().__init__('parameter_client_py')
        self.cli = self.create_client(ListParameters, '/parameter_server_py/list_parameters')
        self.declare_parameter('dummy', 0)  # 让节点提前初始化

        # 用同步接口
        from rclpy.parameter_client import SyncParametersClient
        self.client = SyncParametersClient(self, 'parameter_server_py')

        # 读取
        robot_name = self.client.get_parameter('robot_name')
        max_speed  = self.client.get_parameter('max_speed')
        debug      = self.client.get_parameter('enable_debug')
        self.get_logger().info(f'robot_name={robot_name}, max_speed={max_speed}, debug={debug}')

        # 设置
        self.client.set_parameters([
            rclpy.parameter.Parameter('max_speed', rclpy.Parameter.Type.DOUBLE, 2.71),
            rclpy.parameter.Parameter('enable_debug', rclpy.Parameter.Type.BOOL, True)
        ])

        # 列出
        names = self.client.list_parameters()
        self.get_logger().info(f'All params: {names}')

def main():
    rclpy.init()
    node = ParameterClientPy()
    rclpy.spin_once(node)
    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

---

五、统一启动 launch 文件 文件：launch/demo.launch.py

Python

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from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
        # 参数服务器（C++）
        Node(
            package='param_server_demo',
            executable='param_server',
            name='parameter_server',
            parameters=[{
                'robot_name': 'my_robot',
                'max_speed': 2.0,
                'enable_debug': False
            }]
        ),
        # 客户端（C++）
        Node(
            package='param_server_demo',
            executable='param_client',
            name='parameter_client',
            output='screen'
        ),
        # Python 版
        Node(
            package='param_server_demo',
            executable='param_server_py.py',
            name='parameter_server_py',
            parameters=[{'robot_name': 'py_robot'}]
        ),
        Node(
            package='param_server_demo',
            executable='param_client_py.py',
            name='parameter_client_py',
            output='screen'
        ),
    ])

---

六、编译 & 运行

bash

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cd ~/ws
colcon build --packages-select param_server_demo
source install/setup.bash

# 方式1：launch 一键启动
ros2 launch param_server_demo demo.launch.py

# 方式2：单独启动
# 终端1
ros2 run param_server_demo param_server
# 终端2
ros2 run param_server_demo param_client

---

七、命令行验证

bash

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# 查看参数
ros2 param list /parameter_server
# 读取
ros2 param get /parameter_server max_speed
# 设置
ros2 param set /parameter_server max_speed 9.9