FollowWaypoints Action

Package: nav2_msgs
Category: Navigation

Navigate robot through a series of waypoints with optional task execution at each point

Message Definitions

Goal Message

Field Type Description
number_of_loops uint32 How many times to repeat the complete waypoint sequence (0=no looping)
goal_index uint32 Starting waypoint index in the poses array (default 0 for beginning)
poses geometry_msgs/PoseStamped[] Array of poses defining waypoints or path

Result Message

Field Type Description
NONE uint16 Success status code indicating the action completed without errors
UNKNOWN uint16 Generic error code for unexpected or unclassified failures
TASK_EXECUTOR_FAILED uint16 Error code indicating a task executor plugin failed to execute at a waypoint
NO_VALID_WAYPOINTS uint16 Error code indicating the provided waypoints are invalid or unreachable
STOP_ON_MISSED_WAYPOINT uint16 Error code indicating the action stopped because a waypoint could not be reached
missed_waypoints WaypointStatus[] Array of waypoints that could not be reached due to obstacles or navigation failures
error_code uint16 Numeric error code indicating specific failure reason (0=success, various codes for different failure types)
error_msg string Human-readable error message describing what went wrong during action execution

Feedback Message

Field Type Description
current_waypoint uint32 Index of the current waypoint being pursued in a sequence

Usage Examples

Python

import rclpy
from rclpy.node import Node
from rclpy.action import ActionClient
from nav2_msgs.action import FollowWaypoints

class Nav2ActionClient(Node):
    def __init__(self):
        super().__init__('nav2_action_client')
        self.action_client = ActionClient(self, FollowWaypoints, 'follow_waypoints')
        
    def send_goal(self):
        goal_msg = FollowWaypoints.Goal()
        waypoint = geometry_msgs.msg.PoseStamped()
        waypoint.header.frame_id = 'map'
        waypoint.pose.position.x = 2.0
        waypoint.pose.position.y = 1.5
        waypoint.pose.orientation.w = 1.0
        goal_msg.poses = [waypoint]
        
        self.action_client.wait_for_server()
        future = self.action_client.send_goal_async(
            goal_msg, feedback_callback=self.feedback_callback)
        return future
        
    def feedback_callback(self, feedback_msg):
        self.get_logger().info(f'Received feedback: {feedback_msg.feedback}')

C++

#include "rclcpp/rclcpp.hpp"
#include "rclcpp_action/rclcpp_action.hpp"
#include "nav2_msgs/action/follow_waypoints.hpp"

class Nav2ActionClient : public rclcpp::Node
{
public:
    using FollowWaypointsAction = nav2_msgs::action::FollowWaypoints;
    using GoalHandle = rclcpp_action::ClientGoalHandle<FollowWaypointsAction>;

    Nav2ActionClient() : Node("nav2_action_client")
    {
        action_client_ = rclcpp_action::create_client<FollowWaypointsAction>(
            this, "follow_waypoints");
    }

    void send_goal()
    {
        auto goal_msg = FollowWaypointsAction::Goal();
        geometry_msgs::msg::PoseStamped waypoint;
        waypoint.header.frame_id = "map";
        waypoint.pose.position.x = 2.0;
        waypoint.pose.position.y = 1.5;
        waypoint.pose.orientation.w = 1.0;
        goal_msg.poses.push_back(waypoint);
        
        action_client_->wait_for_action_server();
        
        auto send_goal_options = rclcpp_action::Client<FollowWaypointsAction>::SendGoalOptions();
        send_goal_options.feedback_callback = 
            std::bind(&Nav2ActionClient::feedback_callback, this, 
                     std::placeholders::_1, std::placeholders::_2);
        
        action_client_->async_send_goal(goal_msg, send_goal_options);
    }

private:
    rclcpp_action::Client<FollowWaypointsAction>::SharedPtr action_client_;
    
    void feedback_callback(GoalHandle::SharedPtr, 
                          const std::shared_ptr<const FollowWaypointsAction::Feedback> feedback)
    {
        RCLCPP_INFO(this->get_logger(), "Received feedback");
    }
};