使用机器人操作系统ROS 2和仿真软件Gazebo 9服务进阶实战（八）- mobot行驶至目标位置---zhangrelay

ROS2在基本概念上与ROS1相似，但是实现上差别较大，比如编程规范等。

主题，节点，消息（主题消息）～

那么服务呢，服务器<->客户端，如何实现一个机器人

获取目标点坐标？行驶到目标点？显示行驶进度？

这样，三步功能呢，课程复习同样放置在文末。先看效果吧（无解说）：

https://www.bilibili.com/video/bv1iK411W7gg

核心要点：

srv：

float32 x float32 y --- bool success

x，y为目标坐标，success反馈是否成功接受到坐标。

1. 只接受坐标，机器人mobot不行动！

这里放个水，直接给出参考源码，注意代码并不规范优雅，仅为功能实现。

服务器端：

#include "rclcpp/rclcpp.hpp" #include "mobot/srv/drivegoalsrv.hpp" #include <memory> void get(const std::shared_ptr<mobot::srv::Drivegoalsrv::Request> request, std::shared_ptr<mobot::srv::Drivegoalsrv::Response> response) { if(request->x>0.0) { response->success=1; RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Get Goalnx: %lf" " y: %lf", request->x, request->y); RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Flag: [%d]", response->success); } else { response->success=0; RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Error, x>0!!!nx: %lf" " y: %lf", request->x, request->y); RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Flag: [%d]", response->success); } } int main(int argc, char **argv) { rclcpp::init(argc, argv); std::shared_ptr<rclcpp::Node> node = rclcpp::Node::make_shared("get_goal_server"); rclcpp::Service<mobot::srv::Drivegoalsrv>::SharedPtr service = node->create_service<mobot::srv::Drivegoalsrv>("get_goal", &get); RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Ready to get goal."); rclcpp::spin(node); rclcpp::shutdown(); }

客户端：思考实现！三个功能客户端都是一样的，就是送个坐标给服务器而已。

需要修改CMakeLists.txt和package.xml。

2. 行驶到目标点

此为实践作业，需独立完成。

3. 显示进度

详细内容参考前文视频链接。

补充思考题：

如何用行动（action）实现第三个功能呢，显示进度的功能。

复习：服务

官方示例： sum=a+b

客户端发送a b，

服务器计算求和并返回给客户端。

案例非常简单，稍微复杂一下，如上述机器人案例，发送目标坐标，机器人行驶到目标坐标。

客户端：add_two_ints_client.cpp

#include "rclcpp/rclcpp.hpp" #include "example_interfaces/srv/add_two_ints.hpp" #include <chrono> #include <cstdlib> #include <memory> using namespace std::chrono_literals; int main(int argc, char **argv) { rclcpp::init(argc, argv); if (argc != 3) { RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "usage: add_two_ints_client X Y"); return 1; } std::shared_ptr<rclcpp::Node> node = rclcpp::Node::make_shared("add_two_ints_client"); rclcpp::Client<example_interfaces::srv::AddTwoInts>::SharedPtr client = node->create_client<example_interfaces::srv::AddTwoInts>("add_two_ints"); auto request = std::make_shared<example_interfaces::srv::AddTwoInts::Request>(); request->a = atoll(argv[1]); request->b = atoll(argv[2]); while (!client->wait_for_service(1s)) { if (!rclcpp::ok()) { RCLCPP_ERROR(rclcpp::get_logger("rclcpp"), "Interrupted while waiting for the service. Exiting."); return 0; } RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "service not available, waiting again..."); } auto result = client->async_send_request(request); // Wait for the result. if (rclcpp::spin_until_future_complete(node, result) == rclcpp::executor::FutureReturnCode::SUCCESS) { RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Sum: %ld", result.get()->sum); } else { RCLCPP_ERROR(rclcpp::get_logger("rclcpp"), "Failed to call service add_two_ints"); } rclcpp::shutdown(); return 0; }

服务器端：add_two_ints_server.cpp

#include "rclcpp/rclcpp.hpp" #include "example_interfaces/srv/add_two_ints.hpp" #include <memory> void add(const std::shared_ptr<example_interfaces::srv::AddTwoInts::Request> request, std::shared_ptr<example_interfaces::srv::AddTwoInts::Response> response) { response->sum = request->a + request->b; RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Incoming requestna: %ld" " b: %ld", request->a, request->b); RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "sending back response: [%ld]", (long int)response->sum); } int main(int argc, char **argv) { rclcpp::init(argc, argv); std::shared_ptr<rclcpp::Node> node = rclcpp::Node::make_shared("add_two_ints_server"); rclcpp::Service<example_interfaces::srv::AddTwoInts>::SharedPtr service = node->create_service<example_interfaces::srv::AddTwoInts>("add_two_ints", &add); RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Ready to add two ints."); rclcpp::spin(node); rclcpp::shutdown(); }

CMakeLists.txt：

cmake_minimum_required(VERSION 3.5) project(cpp_srvcli) find_package(ament_cmake REQUIRED) find_package(rclcpp REQUIRED) find_package(example_interfaces REQUIRED) add_executable(server src/add_two_ints_server.cpp) ament_target_dependencies(server rclcpp example_interfaces) add_executable(client src/add_two_ints_client.cpp) ament_target_dependencies(client rclcpp example_interfaces) install(TARGETS server client DESTINATION lib/${PROJECT_NAME}) ament_package()

其中要点，解析参考官方文档。

---来自腾讯云社区的---zhangrelay