ROS2在基本概念上與ROS1相似,但是實現上差別較大,比如編程規範等。
上一節是主題實戰,有興趣可以編寫代碼實現機器人速度發佈和座標訂閱。
主題,節點,消息(主題消息)~
那麼服務呢,服務器<->客戶端,如何實現一個機器人
- 獲取目標點座標?
- 行駛到目標點?
- 顯示行駛進度?
這樣,三步功能呢,課程複習同樣放置在文末。先看效果吧(無解說):
核心要點:
srv:
float32 x
float32 y
---
bool success
x,y爲目標座標,success反饋是否成功接受到座標。
1. 只接受座標,機器人mobot不行動!
這裏放個水,直接給出參考源碼,注意代碼並不規範優雅,僅爲功能實現。
服務器端:
#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 Goal\nx: %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();
}
客戶端:思考實現!三個功能客戶端都是一樣的,就是送個座標給服務器而已。
需要修改CMakeLists.txt和package.xml。
2. 行駛到目標點
此爲實踐作業,需獨立完成。
3. 顯示進度
詳細內容參考前文視頻鏈接。
補充思考題:
如何用行動(action)實現第三個功能呢,顯示進度的功能。
複習:服務
官方示例: sum=a+b
客戶端發送a b,
服務器計算求和並返回給客戶端。
案例非常簡單,稍微複雜一下,如上述機器人案例,發送目標座標,機器人行駛到目標座標。
客戶端: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;
}
服務器端: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 request\na: %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()
其中要點,解析參考官方文檔。