ROS2编程基础课程--Actions

Actions 行动

About 关于

Actions are a form of asynchronous communication in ROS. Action clients send goal requests to action servers. Action servers send goal feedback and results to action clients. For more detailed information about ROS actions, please refer to the design article.

行动是ROS中异步通信的一种形式。 Action客户端将目标请求发送到操作服务器。 操作服务器将目标反馈和结果发送给操作客户端。有关ROS操作的更多详细信息，请参考设计文章。

This document contains a list of tutorials related to actions. For reference, after completing all of the tutorials you should expect to have a ROS package that looks like the package action_tutorials.

本文档包含与操作相关的教程列表。作为参考，在完成所有教程之后，需要有一个类似于action_tutorials的ROS包。

Prequisites 预备基础

Install ROS (Dashing or later) 安装ROS（Dashing或更高版本）

Install colcon 安装colcon

Setup a workspace and create a package named action_tutorials:

设置工作区并创建名为action_tutorials的包：

Remember to source your ROS 2 installation. 记得要安装ROS 2。

Linux / OSX:

mkdir -p action_ws/src

cd action_ws/src

ros2 pkg create action_tutorials

Windows:

mkdir -p action_ws\srccd action_ws\src

ros2 pkg create action_tutorials

Tutorials

Creating an Action

Writing an Action Server (C++)

Writing an Action Client (C++)

Writing an Action Server (Python)

Writing an Action Client (Python)

在完成文档阅读之后，学习源码：

Fibonacci.action

int32 order

---

int32[] sequence

---

int32[] partial_sequence

Server/member_functions.cpp

#include

#include

#include "example_interfaces/action/fibonacci.hpp"

#include "rclcpp/rclcpp.hpp"

// TODO(jacobperron): Remove this once it is included as part of 'rclcpp.hpp'

#include "rclcpp_action/rclcpp_action.hpp"

class MinimalActionServer : public rclcpp::Node

{

public:

using Fibonacci = example_interfaces::action::Fibonacci;

using GoalHandleFibonacci = rclcpp_action::ServerGoalHandle;

explicit MinimalActionServer(const rclcpp::NodeOptions & options = rclcpp::NodeOptions())

: Node("minimal_action_server", options)

{

using namespace std::placeholders;

this->action_server_ = rclcpp_action::create_server(

this->get_node_base_interface(),

this->get_node_clock_interface(),

this->get_node_logging_interface(),

this->get_node_waitables_interface(),

"fibonacci",

std::bind(&MinimalActionServer::handle_goal, this, _1, _2),

std::bind(&MinimalActionServer::handle_cancel, this, _1),

std::bind(&MinimalActionServer::handle_accepted, this, _1));

}

private:

rclcpp_action::Server::SharedPtr action_server_;

rclcpp_action::GoalResponse handle_goal(

const rclcpp_action::GoalUUID & uuid,

std::shared_ptr goal)

{

RCLCPP_INFO(this->get_logger(), "Received goal request with order %d", goal->order);

(void)uuid;

// Let's reject sequences that are over 9000

if (goal->order > 9000) {

return rclcpp_action::GoalResponse::REJECT;

}

return rclcpp_action::GoalResponse::ACCEPT_AND_EXECUTE;

}

rclcpp_action::CancelResponse handle_cancel(

const std::shared_ptr goal_handle)

{

RCLCPP_INFO(this->get_logger(), "Received request to cancel goal");

(void)goal_handle;

return rclcpp_action::CancelResponse::ACCEPT;

}

void execute(const std::shared_ptr goal_handle)

{

RCLCPP_INFO(this->get_logger(), "Executing goal");

rclcpp::Rate loop_rate(1);

const auto goal = goal_handle->get_goal();

auto feedback = std::make_shared();

auto & sequence = feedback->sequence;

sequence.push_back(0);

sequence.push_back(1);

auto result = std::make_shared();

for (int i = 1; (i < goal->order) && rclcpp::ok(); ++i) {

// Check if there is a cancel request

if (goal_handle->is_canceling()) {

result->sequence = sequence;

goal_handle->canceled(result);

RCLCPP_INFO(this->get_logger(), "Goal Canceled");

return;

}

// Update sequence

sequence.push_back(sequence[i] + sequence[i - 1]);

// Publish feedback

goal_handle->publish_feedback(feedback);

RCLCPP_INFO(this->get_logger(), "Publish Feedback");

loop_rate.sleep();

}

// Check if goal is done

if (rclcpp::ok()) {

result->sequence = sequence;

goal_handle->succeed(result);

RCLCPP_INFO(this->get_logger(), "Goal Suceeded");

}

}

void handle_accepted(const std::shared_ptr goal_handle)

{

using namespace std::placeholders;

// this needs to return quickly to avoid blocking the executor, so spin up a new thread

std::thread{std::bind(&MinimalActionServer::execute, this, _1), goal_handle}.detach();

}

};  // class MinimalActionServer

int main(int argc, char ** argv)

{

rclcpp::init(argc, argv);

auto action_server = std::make_shared();

rclcpp::spin(action_server);

rclcpp::shutdown();

return 0;

}

Client/member_functions.cpp

#include

#include

#include

#include

#include "example_interfaces/action/fibonacci.hpp"

#include "rclcpp/rclcpp.hpp"

// TODO(jacobperron): Remove this once it is included as part of 'rclcpp.hpp'

#include "rclcpp_action/rclcpp_action.hpp"

class MinimalActionClient : public rclcpp::Node

{

public:

using Fibonacci = example_interfaces::action::Fibonacci;

using GoalHandleFibonacci = rclcpp_action::ClientGoalHandle;

explicit MinimalActionClient(const rclcpp::NodeOptions & node_options = rclcpp::NodeOptions())

: Node("minimal_action_client", node_options), goal_done_(false)

{

this->client_ptr_ = rclcpp_action::create_client(

this->get_node_base_interface(),

this->get_node_graph_interface(),

this->get_node_logging_interface(),

this->get_node_waitables_interface(),

"fibonacci");

this->timer_ = this->create_wall_timer(

std::chrono::milliseconds(500),

std::bind(&MinimalActionClient::send_goal, this));

}

bool is_goal_done() const

{

return this->goal_done_;

}

void send_goal()

{

using namespace std::placeholders;

this->timer_->cancel();

this->goal_done_ = false;

if (!this->client_ptr_) {

RCLCPP_ERROR(this->get_logger(), "Action client not initialized");

}

if (!this->client_ptr_->wait_for_action_server(std::chrono::seconds(10))) {

RCLCPP_ERROR(this->get_logger(), "Action server not available after waiting");

this->goal_done_ = true;

return;

}

auto goal_msg = Fibonacci::Goal();

goal_msg.order = 10;

RCLCPP_INFO(this->get_logger(), "Sending goal");

auto send_goal_options = rclcpp_action::Client::SendGoalOptions();

send_goal_options.goal_response_callback =

std::bind(&MinimalActionClient::goal_response_callback, this, _1);

send_goal_options.feedback_callback =

std::bind(&MinimalActionClient::feedback_callback, this, _1, _2);

send_goal_options.result_callback =

std::bind(&MinimalActionClient::result_callback, this, _1);

auto goal_handle_future = this->client_ptr_->async_send_goal(goal_msg, send_goal_options);

}

private:

rclcpp_action::Client::SharedPtr client_ptr_;

rclcpp::TimerBase::SharedPtr timer_;

bool goal_done_;

void goal_response_callback(std::shared_future future)

{

auto goal_handle = future.get();

if (!goal_handle) {

RCLCPP_ERROR(this->get_logger(), "Goal was rejected by server");

} else {

RCLCPP_INFO(this->get_logger(), "Goal accepted by server, waiting for result");

}

}

void feedback_callback(

GoalHandleFibonacci::SharedPtr,

const std::shared_ptr feedback)

{

RCLCPP_INFO(

this->get_logger(),

"Next number in sequence received: %" PRId64,

feedback->sequence.back());

}

void result_callback(const GoalHandleFibonacci::WrappedResult & result)

{

this->goal_done_ = true;

switch (result.code) {

case rclcpp_action::ResultCode::SUCCEEDED:

break;

case rclcpp_action::ResultCode::ABORTED:

RCLCPP_ERROR(this->get_logger(), "Goal was aborted");

return;

case rclcpp_action::ResultCode::CANCELED:

RCLCPP_ERROR(this->get_logger(), "Goal was canceled");

return;

default:

RCLCPP_ERROR(this->get_logger(), "Unknown result code");

return;

}

RCLCPP_INFO(this->get_logger(), "Result received");

for (auto number : result.result->sequence) {

RCLCPP_INFO(this->get_logger(), "%" PRId64, number);

}

}

};  // class MinimalActionClient

int main(int argc, char ** argv)

{

rclcpp::init(argc, argv);

auto action_client = std::make_shared();

while (!action_client->is_goal_done()) {

rclcpp::spin_some(action_client);

}

rclcpp::shutdown();

return 0;

}

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