docking_server.cpp

// Copyright (c) 2024 Open Navigation LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#include "angles/angles.h"
#include "nav2_ros_common/rate.hpp"
#include "opennav_docking/docking_server.hpp"
#include "tf2_geometry_msgs/tf2_geometry_msgs.hpp"
#include "tf2/utils.hpp"
 
using namespace std::chrono_literals;
using rcl_interfaces::msg::ParameterType;
using std::placeholders::_1;
 
namespace opennav_docking
{
 
DockingServer::DockingServer(const rclcpp::NodeOptions & options)
: nav2::LifecycleNode("docking_server", "", options)
{
  RCLCPP_INFO(get_logger(), "Creating %s", get_name());
}
 
nav2::CallbackReturn
DockingServer::on_configure(const rclcpp_lifecycle::State & state)
{
  RCLCPP_INFO(get_logger(), "Configuring %s", get_name());
  auto node = shared_from_this();
  param_handler_ = std::make_unique<ParameterHandler>(
    node, get_logger());
  params_ = param_handler_->getParams();
 
  vel_publisher_ = std::make_unique<nav2_util::TwistPublisher>(node, "cmd_vel");
  tf2_buffer_ = nav2::create_transform_buffer(node);
 
  // Create odom subscriber for backward blind docking
  odom_sub_ = std::make_unique<nav2_util::OdomSmoother>(node, params_->odom_duration,
    params_->odom_topic);
 
  // Create the action servers for dock / undock
  docking_action_server_ = node->create_action_server<DockRobot>(
    "dock_robot",
    std::bind(&DockingServer::dockRobot, this),
    nullptr, nullptr, std::chrono::milliseconds(500),
    true);
 
  undocking_action_server_ = node->create_action_server<UndockRobot>(
    "undock_robot",
    std::bind(&DockingServer::undockRobot, this),
    nullptr, nullptr, std::chrono::milliseconds(500),
    true);
 
  // Create composed utilities
  controller_ = std::make_unique<Controller>(node, tf2_buffer_, params_->fixed_frame,
      params_->base_frame);
  navigator_ = std::make_unique<Navigator>(node);
  dock_db_ = std::make_unique<DockDatabase>(param_handler_->getMutex());
  if (!dock_db_->initialize(node, tf2_buffer_)) {
    on_cleanup(state);
    return nav2::CallbackReturn::FAILURE;
  }
 
  return nav2::CallbackReturn::SUCCESS;
}
 
nav2::CallbackReturn
DockingServer::on_activate(const rclcpp_lifecycle::State & /*state*/)
{
  RCLCPP_INFO(get_logger(), "Activating %s", get_name());
 
  auto node = shared_from_this();
 
  tf2_listener_ = nav2::create_transform_listener(*tf2_buffer_, this, true);
  dock_db_->activate();
  navigator_->activate();
  vel_publisher_->on_activate();
  docking_action_server_->activate();
  undocking_action_server_->activate();
  param_handler_->activate();
  curr_dock_type_.clear();
 
  // Create bond connection
  createBond();
 
  return nav2::CallbackReturn::SUCCESS;
}
 
nav2::CallbackReturn
DockingServer::on_deactivate(const rclcpp_lifecycle::State & /*state*/)
{
  RCLCPP_INFO(get_logger(), "Deactivating %s", get_name());
 
  docking_action_server_->deactivate();
  undocking_action_server_->deactivate();
  dock_db_->deactivate();
  navigator_->deactivate();
  vel_publisher_->on_deactivate();
  param_handler_->deactivate();
  tf2_listener_.reset();
 
  // Destroy bond connection
  destroyBond();
 
  return nav2::CallbackReturn::SUCCESS;
}
 
nav2::CallbackReturn
DockingServer::on_cleanup(const rclcpp_lifecycle::State & /*state*/)
{
  RCLCPP_INFO(get_logger(), "Cleaning up %s", get_name());
  tf2_buffer_.reset();
  docking_action_server_.reset();
  undocking_action_server_.reset();
  dock_db_.reset();
  navigator_.reset();
  curr_dock_type_.clear();
  controller_.reset();
  vel_publisher_.reset();
  params_->dock_backwards.reset();
  odom_sub_.reset();
  return nav2::CallbackReturn::SUCCESS;
}
 
nav2::CallbackReturn
DockingServer::on_shutdown(const rclcpp_lifecycle::State &)
{
  RCLCPP_INFO(get_logger(), "Shutting down %s", get_name());
  return nav2::CallbackReturn::SUCCESS;
}
 
template<typename ActionT>
void DockingServer::getPreemptedGoalIfRequested(
  typename std::shared_ptr<const typename ActionT::Goal> goal,
  const typename nav2::SimpleActionServer<ActionT>::SharedPtr & action_server)
{
  if (action_server->is_preempt_requested()) {
    goal = action_server->accept_pending_goal();
  }
}
 
template<typename ActionT>
bool DockingServer::checkAndWarnIfCancelled(
  typename nav2::SimpleActionServer<ActionT>::SharedPtr & action_server,
  const std::string & name)
{
  if (action_server->is_cancel_requested()) {
    RCLCPP_WARN(get_logger(), "Goal was cancelled. Cancelling %s action", name.c_str());
    return true;
  }
  return false;
}
 
template<typename ActionT>
bool DockingServer::checkAndWarnIfPreempted(
  typename nav2::SimpleActionServer<ActionT>::SharedPtr & action_server,
  const std::string & name)
{
  if (action_server->is_preempt_requested()) {
    RCLCPP_WARN(get_logger(), "Goal was preempted. Cancelling %s action", name.c_str());
    return true;
  }
  return false;
}
 
void DockingServer::dockRobot()
{
  std::lock_guard<std::mutex> lock_reinit(param_handler_->getMutex());
  action_start_time_ = this->now();
  nav2::Rate loop_rate(this, params_->controller_frequency);
 
  auto goal = docking_action_server_->get_current_goal();
  auto result = std::make_shared<DockRobot::Result>();
  result->success = false;
 
  if (!docking_action_server_ || !docking_action_server_->is_server_active()) {
    RCLCPP_DEBUG(get_logger(), "Action server unavailable or inactive. Stopping.");
    return;
  }
 
  if (checkAndWarnIfCancelled<DockRobot>(docking_action_server_, "dock_robot")) {
    docking_action_server_->terminate_all();
    return;
  }
 
  getPreemptedGoalIfRequested<DockRobot>(goal, docking_action_server_);
  Dock * dock{nullptr};
  num_retries_ = 0;
 
  try {
    // Get dock (instance and plugin information) from request
    if (goal->use_dock_id) {
      RCLCPP_INFO(
        get_logger(),
        "Attempting to dock robot at %s.", goal->dock_id.c_str());
      dock = dock_db_->findDock(goal->dock_id);
    } else {
      RCLCPP_INFO(
        get_logger(),
        "Attempting to dock robot at position (%0.2f, %0.2f).",
        goal->dock_pose.pose.position.x, goal->dock_pose.pose.position.y);
      dock = generateGoalDock(goal);
    }
 
    // Check if robot is docked or charging before proceeding, only applicable to charging docks
    if (dock->plugin->isCharger() && (dock->plugin->isDocked() || dock->plugin->isCharging())) {
      RCLCPP_INFO(
        get_logger(), "Robot is already docked and/or charging (if applicable), no need to dock");
      result->success = true;
      docking_action_server_->succeeded_current(result);
      return;
    }
 
    // Send robot to its staging pose
    publishDockingFeedback(DockRobot::Feedback::NAV_TO_STAGING_POSE);
    const auto initial_staging_pose = dock->getStagingPose();
    const auto robot_pose = getRobotPoseInFrame(initial_staging_pose.header.frame_id);
    if (!goal->navigate_to_staging_pose ||
      utils::l2Norm(robot_pose.pose,
        initial_staging_pose.pose) < params_->dock_prestaging_tolerance)
    {
      RCLCPP_INFO(get_logger(), "Robot already within pre-staging pose tolerance for dock");
    } else {
      std::function<bool()> isPreempted = [this]() {
          return checkAndWarnIfCancelled<DockRobot>(docking_action_server_, "dock_robot") ||
                 checkAndWarnIfPreempted<DockRobot>(docking_action_server_, "dock_robot");
        };
 
      navigator_->goToPose(
        initial_staging_pose,
        rclcpp::Duration::from_seconds(goal->max_staging_time),
        isPreempted);
      RCLCPP_INFO(get_logger(), "Successful navigation to staging pose");
    }
 
    // Construct initial estimate of where the dock is located in fixed_frame
    auto dock_pose = utils::getDockPoseStamped(dock, rclcpp::Time(0));
    tf2_buffer_->transform(dock_pose, dock_pose, params_->fixed_frame);
 
    // Get initial detection of dock before proceeding to move
    doInitialPerception(dock, dock_pose);
    RCLCPP_INFO(get_logger(), "Successful initial dock detection");
 
    // Get the direction of the movement
    bool dock_backward = params_->dock_backwards.has_value() ?
      params_->dock_backwards.value() :
      (dock->plugin->getDockDirection() == opennav_docking_core::DockDirection::BACKWARD);
 
    // If we performed a rotation before docking backward, we must rotate the staging pose
    // to match the robot orientation
    auto staging_pose = dock->getStagingPose();
    if (dock->plugin->shouldRotateToDock()) {
      staging_pose.pose.orientation = nav2_util::geometry_utils::orientationAroundZAxis(
        tf2::getYaw(staging_pose.pose.orientation) + M_PI);
    }
 
    // Docking control loop: while not docked, run controller
    while (rclcpp::ok()) {
      try {
        // Perform a 180º to face away from the dock if needed
        if (dock->plugin->shouldRotateToDock()) {
          rotateToDock(dock_pose);
        }
        // Approach the dock using control law
        if (approachDock(dock, dock_pose, dock_backward)) {
          // We are docked, wait for charging to begin
          RCLCPP_INFO(
            get_logger(), "Made contact with dock, waiting for charge to start (if applicable).");
          publishZeroVelocity();
          if (waitForCharge(dock)) {
            if (dock->plugin->isCharger()) {
              RCLCPP_INFO(get_logger(), "Robot is charging!");
            } else {
              RCLCPP_INFO(get_logger(), "Docking was successful!");
            }
            result->success = true;
            result->num_retries = num_retries_;
            publishZeroVelocity();
            dock->plugin->stopDetectionProcess();
            stashDockData(goal->use_dock_id, dock, true);
            docking_action_server_->succeeded_current(result);
            return;
          }
        }
 
        // Cancelled, preempted, or shutting down (recoverable errors throw DockingException)
        publishZeroVelocity();
        dock->plugin->stopDetectionProcess();
        stashDockData(goal->use_dock_id, dock, false);
        docking_action_server_->terminate_all(result);
        return;
      } catch (opennav_docking_core::DockingException & e) {
        if (++num_retries_ > params_->max_retries) {
          RCLCPP_ERROR(get_logger(), "Failed to dock, all retries have been used");
          if (params_->max_retries > 0) {
            try {  // swallow new exceptions, so as to report original failure
              resetApproach(staging_pose, dock_backward);
            } catch (const std::exception & ex) {
              RCLCPP_ERROR(
                get_logger(), "Failed to return to staging pose: %s", ex.what());
            }
          }
          throw;
        }
        RCLCPP_WARN(get_logger(), "Docking failed, will retry: %s", e.what());
      }
 
      // Reset to staging pose to try again
      if (!resetApproach(staging_pose, dock_backward)) {
        // Cancelled, preempted, or shutting down
        publishZeroVelocity();
        dock->plugin->stopDetectionProcess();
        stashDockData(goal->use_dock_id, dock, false);
        docking_action_server_->terminate_all(result);
        return;
      }
      RCLCPP_INFO(get_logger(), "Returned to staging pose, attempting docking again");
    }
  } catch (const tf2::TransformException & e) {
    result->error_msg = std::string("Transform error: ") + e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::UNKNOWN;
  } catch (opennav_docking_core::DockNotInDB & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::DOCK_NOT_IN_DB;
  } catch (opennav_docking_core::DockNotValid & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::DOCK_NOT_VALID;
  } catch (opennav_docking_core::FailedToStage & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::FAILED_TO_STAGE;
  } catch (opennav_docking_core::FailedToDetectDock & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::FAILED_TO_DETECT_DOCK;
  } catch (opennav_docking_core::FailedToControl & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::FAILED_TO_CONTROL;
  } catch (opennav_docking_core::FailedToCharge & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::FAILED_TO_CHARGE;
  } catch (opennav_docking_core::DockingException & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::UNKNOWN;
  } catch (std::exception & e) {
    result->error_code = DockRobot::Result::UNKNOWN;
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
  }
 
  result->num_retries = num_retries_;
  publishZeroVelocity();
  if (dock) {
    dock->plugin->stopDetectionProcess();
  }
  // Store dock state for later undocking and delete temp dock, if applicable
  stashDockData(goal->use_dock_id, dock, false);
  docking_action_server_->terminate_current(result);
}
 
void DockingServer::stashDockData(bool use_dock_id, Dock * dock, bool successful)
{
  if (dock && successful) {
    curr_dock_type_ = dock->type;
  }
 
  if (!use_dock_id && dock) {
    delete dock;
    dock = nullptr;
  }
}
 
Dock * DockingServer::generateGoalDock(std::shared_ptr<const DockRobot::Goal> goal)
{
  auto plugin = dock_db_->findDockPlugin(goal->dock_type);
  if (!plugin) {
    throw opennav_docking_core::DockNotValid(
      "Dock type '" + goal->dock_type + "' has no valid plugin!");
  }
 
  auto dock = new Dock();
  dock->frame = goal->dock_pose.header.frame_id;
  dock->pose = goal->dock_pose.pose;
  dock->type = goal->dock_type;
  dock->plugin = plugin;
  return dock;
}
 
void DockingServer::doInitialPerception(Dock * dock, geometry_msgs::msg::PoseStamped & dock_pose)
{
  publishDockingFeedback(DockRobot::Feedback::INITIAL_PERCEPTION);
 
  if (!dock->plugin->startDetectionProcess()) {
    throw opennav_docking_core::FailedToDetectDock("Failed to start the detection process.");
  }
 
  nav2::Rate loop_rate(this, params_->controller_frequency);
  auto start = this->now();
  auto timeout = rclcpp::Duration::from_seconds(params_->initial_perception_timeout);
  while (!dock->plugin->getRefinedPose(dock_pose, dock->id)) {
    if (this->now() - start > timeout) {
      throw opennav_docking_core::FailedToDetectDock(
              "Failed initial dock detection: Timeout exceeded");
    }
 
    if (checkAndWarnIfCancelled<DockRobot>(docking_action_server_, "dock_robot") ||
      checkAndWarnIfPreempted<DockRobot>(docking_action_server_, "dock_robot"))
    {
      return;
    }
 
    loop_rate.sleep();
  }
}
 
void DockingServer::rotateToDock(const geometry_msgs::msg::PoseStamped & dock_pose)
{
  const double dt = 1.0 / params_->controller_frequency;
  auto target_pose = dock_pose;
  target_pose.pose.orientation = nav2_util::geometry_utils::orientationAroundZAxis(
    tf2::getYaw(target_pose.pose.orientation) + M_PI);
 
  nav2::Rate loop_rate(this, params_->controller_frequency);
  auto start = this->now();
  auto timeout = rclcpp::Duration::from_seconds(params_->rotate_to_dock_timeout);
 
  while (rclcpp::ok()) {
    auto robot_pose = getRobotPoseInFrame(dock_pose.header.frame_id);
    auto angular_distance_to_heading = angles::shortest_angular_distance(
      tf2::getYaw(robot_pose.pose.orientation), tf2::getYaw(target_pose.pose.orientation));
    if (fabs(angular_distance_to_heading) < params_->rotation_angular_tolerance) {
      break;
    }
 
    auto current_vel = std::make_unique<geometry_msgs::msg::TwistStamped>();
    current_vel->twist.angular.z = odom_sub_->getRawTwist().angular.z;
 
    auto command = std::make_unique<geometry_msgs::msg::TwistStamped>();
    command->header = robot_pose.header;
    command->twist = controller_->computeRotateToHeadingCommand(
      angular_distance_to_heading, current_vel->twist, dt);
 
    vel_publisher_->publish(std::move(command));
 
    if (this->now() - start > timeout) {
      throw opennav_docking_core::FailedToControl("Timed out rotating to dock");
    }
 
    loop_rate.sleep();
  }
}
 
bool DockingServer::approachDock(
  Dock * dock, geometry_msgs::msg::PoseStamped & dock_pose, bool backward)
{
  nav2::Rate loop_rate(this, params_->controller_frequency);
  auto start = this->now();
  auto timeout = rclcpp::Duration::from_seconds(params_->dock_approach_timeout);
 
  while (rclcpp::ok()) {
    publishDockingFeedback(DockRobot::Feedback::CONTROLLING);
 
    // Stop and report success if connected to dock
    if (dock->plugin->isDocked() || (dock->plugin->isCharger() && dock->plugin->isCharging())) {
      return true;
    }
 
    // Stop if cancelled/preempted
    if (checkAndWarnIfCancelled<DockRobot>(docking_action_server_, "dock_robot") ||
      checkAndWarnIfPreempted<DockRobot>(docking_action_server_, "dock_robot"))
    {
      return false;
    }
 
    // Update perception
    if (!dock->plugin->getRefinedPose(dock_pose, dock->id) && !dock->plugin->shouldRotateToDock()) {
      throw opennav_docking_core::FailedToDetectDock("Failed dock detection");
    }
 
    // Transform target_pose into base_link frame
    geometry_msgs::msg::PoseStamped target_pose = dock_pose;
    target_pose.header.stamp = rclcpp::Time(0);
 
    // The control law can get jittery when close to the end when atan2's can explode.
    // Thus, we backward project the controller's target pose a little bit after the
    // dock so that the robot never gets to the end of the spiral before its in contact
    // with the dock to stop the docking procedure.
    const double backward_projection = 0.25;
    const double yaw = tf2::getYaw(target_pose.pose.orientation);
    target_pose.pose.position.x += cos(yaw) * backward_projection;
    target_pose.pose.position.y += sin(yaw) * backward_projection;
    tf2_buffer_->transform(target_pose, target_pose, params_->base_frame);
 
    // Make sure that the target pose is pointing at the robot when moving backwards
    // This is to ensure that the robot doesn't try to dock from the wrong side
    if (backward) {
      target_pose.pose.orientation = nav2_util::geometry_utils::orientationAroundZAxis(
        tf2::getYaw(target_pose.pose.orientation) + M_PI);
    }
 
    // Compute and publish controls
    auto command = std::make_unique<geometry_msgs::msg::TwistStamped>();
    command->header.stamp = now();
    if (!controller_->computeVelocityCommand(target_pose.pose, command->twist, true, backward)) {
      throw opennav_docking_core::FailedToControl("Failed to get control");
    }
    vel_publisher_->publish(std::move(command));
 
    if (this->now() - start > timeout) {
      throw opennav_docking_core::FailedToControl(
              "Timed out approaching dock; dock nor charging (if applicable) detected");
    }
 
    loop_rate.sleep();
  }
  return false;
}
 
bool DockingServer::waitForCharge(Dock * dock)
{
  // This is a non-charger docking request
  if (!dock->plugin->isCharger()) {
    return true;
  }
 
  nav2::Rate loop_rate(this, params_->controller_frequency);
  auto start = this->now();
  auto timeout = rclcpp::Duration::from_seconds(params_->wait_charge_timeout);
  while (rclcpp::ok()) {
    publishDockingFeedback(DockRobot::Feedback::WAIT_FOR_CHARGE);
 
    if (dock->plugin->isCharging()) {
      return true;
    }
 
    if (checkAndWarnIfCancelled<DockRobot>(docking_action_server_, "dock_robot") ||
      checkAndWarnIfPreempted<DockRobot>(docking_action_server_, "dock_robot"))
    {
      return false;
    }
 
    if (this->now() - start > timeout) {
      throw opennav_docking_core::FailedToCharge("Timed out waiting for charge to start");
    }
 
    loop_rate.sleep();
  }
  return false;
}
 
bool DockingServer::resetApproach(
  const geometry_msgs::msg::PoseStamped & staging_pose, bool backward)
{
  nav2::Rate loop_rate(this, params_->controller_frequency);
  auto start = this->now();
  auto timeout = rclcpp::Duration::from_seconds(params_->dock_approach_timeout);
  while (rclcpp::ok()) {
    publishDockingFeedback(DockRobot::Feedback::INITIAL_PERCEPTION);
 
    // Stop if cancelled/preempted
    if (checkAndWarnIfCancelled<DockRobot>(docking_action_server_, "dock_robot") ||
      checkAndWarnIfPreempted<DockRobot>(docking_action_server_, "dock_robot"))
    {
      return false;
    }
 
    // Compute and publish command
    auto command = std::make_unique<geometry_msgs::msg::TwistStamped>();
    command->header.stamp = now();
    if (getCommandToPose(
        command->twist, staging_pose, params_->undock_linear_tolerance,
        params_->undock_angular_tolerance, false,
        !backward))
    {
      return true;
    }
    vel_publisher_->publish(std::move(command));
 
    if (this->now() - start > timeout) {
      throw opennav_docking_core::FailedToControl("Timed out resetting dock approach");
    }
 
    loop_rate.sleep();
  }
  return false;
}
 
bool DockingServer::getCommandToPose(
  geometry_msgs::msg::Twist & cmd, const geometry_msgs::msg::PoseStamped & pose,
  double linear_tolerance, double angular_tolerance, bool is_docking, bool backward)
{
  // Reset command to zero velocity
  cmd.linear.x = 0;
  cmd.angular.z = 0;
 
  // Determine if we have reached pose yet & stop
  geometry_msgs::msg::PoseStamped robot_pose = getRobotPoseInFrame(pose.header.frame_id);
  const double dist = std::hypot(
    robot_pose.pose.position.x - pose.pose.position.x,
    robot_pose.pose.position.y - pose.pose.position.y);
  const double yaw = angles::shortest_angular_distance(
    tf2::getYaw(robot_pose.pose.orientation), tf2::getYaw(pose.pose.orientation));
  if (dist < linear_tolerance && abs(yaw) < angular_tolerance) {
    return true;
  }
 
  // Transform target_pose into base_link frame
  geometry_msgs::msg::PoseStamped target_pose = pose;
  target_pose.header.stamp = rclcpp::Time(0);
  tf2_buffer_->transform(target_pose, target_pose, params_->base_frame);
 
  // Compute velocity command
  if (!controller_->computeVelocityCommand(target_pose.pose, cmd, is_docking, backward)) {
    throw opennav_docking_core::FailedToControl("Failed to get control");
  }
 
  // Command is valid, but target is not reached
  return false;
}
 
void DockingServer::undockRobot()
{
  std::lock_guard<std::mutex> lock_reinit(param_handler_->getMutex());
  action_start_time_ = this->now();
  nav2::Rate loop_rate(this, params_->controller_frequency);
 
  auto goal = undocking_action_server_->get_current_goal();
  auto result = std::make_shared<UndockRobot::Result>();
  result->success = false;
 
  if (!undocking_action_server_ || !undocking_action_server_->is_server_active()) {
    RCLCPP_DEBUG(get_logger(), "Action server unavailable or inactive. Stopping.");
    return;
  }
 
  if (checkAndWarnIfCancelled<UndockRobot>(undocking_action_server_, "undock_robot")) {
    undocking_action_server_->terminate_all(result);
    return;
  }
 
  getPreemptedGoalIfRequested<UndockRobot>(goal, undocking_action_server_);
  auto max_duration = rclcpp::Duration::from_seconds(goal->max_undocking_time);
 
  try {
    // Get dock plugin information from request or docked state, reset state.
    std::string dock_type = curr_dock_type_;
    if (!goal->dock_type.empty()) {
      dock_type = goal->dock_type;
    }
 
    ChargingDock::Ptr dock = dock_db_->findDockPlugin(dock_type);
    if (!dock) {
      throw opennav_docking_core::DockNotValid("No dock information to undock from!");
    }
    RCLCPP_INFO(
      get_logger(),
      "Attempting to undock robot of dock type %s.", dock->getName().c_str());
 
    // Check if the robot is docked before proceeding
    if (dock->isCharger() && (!dock->isDocked() && !dock->isCharging())) {
      RCLCPP_INFO(get_logger(), "Robot is not in the dock, no need to undock");
      return;
    }
 
    bool dock_backward = params_->dock_backwards.has_value() ?
      params_->dock_backwards.value() :
      (dock->getDockDirection() == opennav_docking_core::DockDirection::BACKWARD);
 
    // Get "dock pose" by finding the robot pose
    geometry_msgs::msg::PoseStamped dock_pose = getRobotPoseInFrame(params_->fixed_frame);
 
    // Make sure that the staging pose is pointing in the same direction when moving backwards
    if (dock_backward) {
      dock_pose.pose.orientation = nav2_util::geometry_utils::orientationAroundZAxis(
        tf2::getYaw(dock_pose.pose.orientation) + M_PI);
    }
 
    // Get staging pose (in fixed frame)
    geometry_msgs::msg::PoseStamped staging_pose =
      dock->getStagingPose(dock_pose.pose, dock_pose.header.frame_id);
 
    // If we performed a rotation before docking backward, we must rotate the staging pose
    // to match the robot orientation
    if (dock->shouldRotateToDock()) {
      staging_pose.pose.orientation = nav2_util::geometry_utils::orientationAroundZAxis(
        tf2::getYaw(staging_pose.pose.orientation) + M_PI);
    }
 
    // Control robot to staging pose
    rclcpp::Time loop_start = this->now();
    while (rclcpp::ok()) {
      // Stop if we exceed max duration
      auto timeout = rclcpp::Duration::from_seconds(goal->max_undocking_time);
      if (this->now() - loop_start > timeout) {
        throw opennav_docking_core::FailedToControl("Undocking timed out");
      }
 
      // Stop if cancelled/preempted
      if (checkAndWarnIfCancelled<UndockRobot>(undocking_action_server_, "undock_robot") ||
        checkAndWarnIfPreempted<UndockRobot>(undocking_action_server_, "undock_robot"))
      {
        publishZeroVelocity();
        undocking_action_server_->terminate_all(result);
        return;
      }
 
      // Don't control the robot until charging is disabled
      if (dock->isCharger() && !dock->disableCharging()) {
        loop_rate.sleep();
        continue;
      }
 
      // Get command to approach staging pose
      auto command = std::make_unique<geometry_msgs::msg::TwistStamped>();
      command->header.stamp = now();
 
      if (getCommandToPose(
          command->twist, staging_pose, params_->undock_linear_tolerance,
          params_->undock_angular_tolerance, false,
          !dock_backward))
      {
        // Perform a 180º to the original staging pose
        if (dock->shouldRotateToDock()) {
          rotateToDock(staging_pose);
        }
 
        // Have reached staging_pose
        RCLCPP_INFO(get_logger(), "Robot has reached staging pose");
        vel_publisher_->publish(std::move(command));
        if (!dock->isCharger() || dock->hasStoppedCharging()) {
          RCLCPP_INFO(get_logger(), "Robot has undocked!");
          result->success = true;
          curr_dock_type_.clear();
          publishZeroVelocity();
          undocking_action_server_->succeeded_current(result);
          return;
        }
        // Haven't stopped charging?
        throw opennav_docking_core::FailedToControl("Failed to control off dock");
      }
 
      // Publish command and sleep
      vel_publisher_->publish(std::move(command));
      loop_rate.sleep();
    }
  } catch (const tf2::TransformException & e) {
    result->error_msg = std::string("Transform error: ") + e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::UNKNOWN;
  } catch (opennav_docking_core::DockNotValid & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::DOCK_NOT_VALID;
  } catch (opennav_docking_core::FailedToControl & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::FAILED_TO_CONTROL;
  } catch (opennav_docking_core::DockingException & e) {
    result->error_msg = e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::UNKNOWN;
  } catch (std::exception & e) {
    result->error_msg = std::string("Internal error: ") + e.what();
    RCLCPP_ERROR(get_logger(), "%s", result->error_msg.c_str());
    result->error_code = DockRobot::Result::UNKNOWN;
  }
 
  publishZeroVelocity();
  undocking_action_server_->terminate_current(result);
}
 
geometry_msgs::msg::PoseStamped DockingServer::getRobotPoseInFrame(const std::string & frame)
{
  geometry_msgs::msg::PoseStamped robot_pose;
  robot_pose.header.frame_id = params_->base_frame;
  robot_pose.header.stamp = rclcpp::Time(0);
  tf2_buffer_->transform(robot_pose, robot_pose, frame);
  return robot_pose;
}
 
void DockingServer::publishZeroVelocity()
{
  auto cmd_vel = std::make_unique<geometry_msgs::msg::TwistStamped>();
  cmd_vel->header.stamp = now();
  vel_publisher_->publish(std::move(cmd_vel));
}
 
void DockingServer::publishDockingFeedback(uint16_t state)
{
  auto feedback = std::make_shared<DockRobot::Feedback>();
  feedback->state = state;
  feedback->docking_time = this->now() - action_start_time_;
  feedback->num_retries = num_retries_;
  docking_action_server_->publish_feedback(feedback);
}
}  // namespace opennav_docking
 
#include "rclcpp_components/register_node_macro.hpp"
 
// Register the component with class_loader.
// This acts as a sort of entry point, allowing the component to be discoverable when its library
// is being loaded into a running process.
RCLCPP_COMPONENTS_REGISTER_NODE(opennav_docking::DockingServer)