demo_recoveries.py

#! /usr/bin/env python3
# Copyright 2021 Samsung Research America
#
# 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.
 
from geometry_msgs.msg import PoseStamped
from nav2_simple_commander.robot_navigator import BasicNavigator, TaskResult
import rclpy
from rclpy.duration import Duration
 
"""
Basic recoveries demo. In this demonstration, the robot navigates
to a dead-end where recoveries such as backup and spin are used
to get out of it.
"""
 
 
def main() -> None:
    rclpy.init()
 
    navigator = BasicNavigator()
 
    # Set our demo's initial pose
    initial_pose = PoseStamped()
    initial_pose.header.frame_id = 'map'
    initial_pose.header.stamp = navigator.get_clock().now().to_msg()
    initial_pose.pose.position.x = 0.0
    initial_pose.pose.position.y = 0.0
    initial_pose.pose.orientation.z = 0.0
    initial_pose.pose.orientation.w = 1.0
    navigator.setInitialPose(initial_pose)
 
    # Wait for navigation to fully activate
    navigator.waitUntilNav2Active()
 
    goal_pose = PoseStamped()
    goal_pose.header.frame_id = 'map'
    goal_pose.header.stamp = navigator.get_clock().now().to_msg()
    goal_pose.pose.position.x = 8.21
    goal_pose.pose.position.y = 1.3
    goal_pose.pose.orientation.w = 1.0
 
    go_to_pose_task = navigator.goToPose(goal_pose)
 
    i = 0
    while not navigator.isTaskComplete(task=go_to_pose_task):
        i += 1
        feedback = navigator.getFeedback(task=go_to_pose_task)
        if feedback and i % 5 == 0:
            print(
                f'Estimated time of arrival to destination is: \
                {Duration.from_msg(feedback.estimated_time_remaining).nanoseconds / 1e9}'
            )
 
    # Robot hit a dead end, back it up
    print("Robot hit a dead end (let's pretend), backing up...")
    backup_task = navigator.backup(backup_dist=0.5, backup_speed=0.1)
 
    i = 0
    while not navigator.isTaskComplete(task=backup_task):
        i += 1
        feedback = navigator.getFeedback(task=backup_task)
        if feedback and i % 5 == 0:
            print(f'Distance traveled: {feedback.distance_traveled}')
 
    # Turn it around
    print('Spinning robot around...')
    spin_task = navigator.spin(spin_dist=3.14)
 
    i = 0
    while not navigator.isTaskComplete(task=spin_task):
        i += 1
        feedback = navigator.getFeedback(task=spin_task)
        if feedback and i % 5 == 0:
            print(f'Spin angle traveled: {feedback.angular_distance_traveled}')
 
    result = navigator.getResult()
    if result == TaskResult.SUCCEEDED:
        print('Dead end confirmed! Returning to start...')
    elif result == TaskResult.CANCELED:
        print('Recovery was canceled. Returning to start...')
    elif result == TaskResult.FAILED:
        (error_code, error_msg) = navigator.getTaskError()
        print(f'Recovering from dead end failed!:{error_code}:{error_msg}')
        print('Returning to start...')
 
    initial_pose.header.stamp = navigator.get_clock().now().to_msg()
    go_to_pose_task = navigator.goToPose(initial_pose)
    while not navigator.isTaskComplete(task=go_to_pose_task):
        pass
 
    exit(0)
 
 
if __name__ == '__main__':
    main()