🧭 第15课：导航框架(Nav2)

📋 课程目标

• 理解Nav2导航框架的整体架构
• 掌握Nav2的核心组件与数据流
• 学会Nav2的安装与配置
• 理解生命周期节点在Nav2中的应用
• 掌握Nav2的启动与基本使用

🧠 Nav2是什么？

Navigation2（Nav2）是ROS2的官方导航框架，提供从A点到B点的自主移动能力。它是一个模块化、可扩展的框架，集成了路径规划、路径跟踪、避障、恢复行为等功能。

📦 安装Nav2

# 安装Nav2完整包
sudo apt install ros-humble-navigation2
sudo apt install ros-humble-nav2-bringup

# 安装SLAM工具
sudo apt install ros-humble-slam-toolbox

# 验证安装
ros2 pkg list | grep nav2

📊 Nav2核心组件

📄 Nav2配置文件

# nav2_params.yaml - Nav2核心参数配置
amcl:
  ros__parameters:
    use_sim_time: True
    alpha1: 0.2
    alpha2: 0.2
    alpha3: 0.2
    alpha4: 0.2
    alpha5: 0.2
    base_frame_id: "base_footprint"
    beam_skip_distance: 0.5
    beam_skip_error_threshold: 0.9
    beam_skip_threshold: 0.3
    global_frame_id: "map"
    max_particles: 2000
    min_particles: 500
    odom_frame_id: "odom"
    laser_model_type: "likelihood_field"
    max_beams: 60
    z_hit: 0.5
    z_rand: 0.5
    sigma_hit: 0.2

bt_navigator:
  ros__parameters:
    use_sim_time: True
    global_frame: map
    robot_base_frame: base_link
    bt_loop_duration: 10
    default_server_timeout: 20
    behavior_tree_files:
      - navigate_to_pose_w_replanning_and_recovery.xml

controller_server:
  ros__parameters:
    use_sim_time: True
    controller_frequency: 10.0
    min_x_velocity_threshold: 0.001
    min_y_velocity_threshold: 0.5
    min_theta_velocity_threshold: 0.001
    progress_checker_plugins: ["progress_checker"]
    goal_checker_plugins: ["goal_checker"]
    controller_plugins: ["FollowPath"]

    progress_checker:
      plugin: "nav2_controller::SimpleProgressChecker"
      required_movement_radius: 0.5
      movement_time_allowance: 10.0

    goal_checker:
      plugin: "nav2_controller::SimpleGoalChecker"
      stateful: True
      xy_goal_tolerance: 0.25
      yaw_goal_tolerance: 0.25

    FollowPath:
      plugin: "dwb_core::DWBLocalPlanner"
      debug_trajectory_details: True
      min_vel_x: 0.0
      min_vel_y: 0.0
      max_vel_x: 0.26
      max_vel_y: 0.0
      max_vel_theta: 1.0
      min_speed_xy: 0.0
      max_speed_xy: 0.26
      min_speed_theta: 0.0
      acc_lim_x: 2.5
      acc_lim_y: 0.0
      acc_lim_theta: 3.2
      decel_lim_x: -2.5
      decel_lim_y: 0.0
      decel_lim_theta: -3.2
      vx_samples: 20
      vy_samples: 5
      vtheta_samples: 40
      sim_time: 1.5
      critics: ["RotateToGoal", "Oscillation", "BaseObstacle", "GoalAlign", "PathAlign", "PathDist", "GoalDist"]

planner_server:
  ros__parameters:
    use_sim_time: True
    expected_planner_frequency: 5.0
    planner_plugins: ["GridBased"]
    GridBased:
      plugin: "nav2_navfn_planner::NavfnPlanner"
      tolerance: 0.5
      use_astar: True
      allow_unknown: True

local_costmap:
  local_costmap:
    ros__parameters:
      use_sim_time: True
      update_frequency: 5.0
      publish_frequency: 2.0
      global_frame: odom
      robot_base_frame: base_link
      rolling_window: True
      width: 3
      height: 3
      resolution: 0.05
      robot_radius: 0.22
      plugins: ["obstacle_layer", "inflation_layer"]
      obstacle_layer:
        plugin: "nav2_costmap_2d::ObstacleLayer"
        enabled: True
        observation_sources: scan
        scan:
          topic: /scan
          max_obstacle_height: 2.0
          clearing: True
          marking: True
          raytrace_max_range: 3.0
          raytrace_min_range: 0.0
          obstacle_max_range: 2.5
          obstacle_min_range: 0.0
      inflation_layer:
        plugin: "nav2_costmap_2d::InflationLayer"
        cost_scaling_factor: 3.0
        inflation_radius: 0.55

global_costmap:
  global_costmap:
    ros__parameters:
      use_sim_time: True
      update_frequency: 1.0
      publish_frequency: 1.0
      global_frame: map
      robot_base_frame: base_link
      robot_radius: 0.22
      resolution: 0.05
      track_unknown_space: True
      plugins: ["static_layer", "obstacle_layer", "inflation_layer"]
      static_layer:
        plugin: "nav2_costmap_2d::StaticLayer"
        map_subscribe_transient_local: True
      obstacle_layer:
        plugin: "nav2_costmap_2d::ObstacleLayer"
        enabled: True
        observation_sources: scan
        scan:
          topic: /scan
          max_obstacle_height: 2.0
          clearing: True
          marking: True
      inflation_layer:
        plugin: "nav2_costmap_2d::InflationLayer"
        cost_scaling_factor: 3.0
        inflation_radius: 0.55

🚀 启动Nav2

# 方法1：使用Nav2 Bringup Launch
ros2 launch nav2_bringup navigation_launch.py \
  use_sim_time:=True \
  params_file:=/path/to/nav2_params.yaml

# 方法2：使用Bringup完整Launch（含SLAM）
ros2 launch nav2_bringup bringup_launch.py \
  use_sim_time:=True \
  slam:=True \
  params_file:=/path/to/nav2_params.yaml

# 方法3：使用已有地图
ros2 launch nav2_bringup bringup_launch.py \
  use_sim_time:=True \
  slam:=False \
  map:=/path/to/map.yaml \
  params_file:=/path/to/nav2_params.yaml

🎮 发送导航目标

# 命令行发送导航目标
ros2 action send_goal /navigate_to_pose nav2_msgs/action/NavigateToPose \
  "{pose: {header: {frame_id: 'map'}, pose: {position: {x: 2.0, y: 1.0, z: 0.0}, \
  orientation: {w: 1.0}}}}"

# RViz2中点击 "2D Goal Pose" 工具

# Python发送目标
ros2 run nav2_simple_commander navigator_demo

🐍 Python导航示例

#!/usr/bin/env python3
"""使用Nav2 Python API发送导航目标"""

from geometry_msgs.msg import PoseStamped
from nav2_simple_commander.robot_navigator import BasicNavigator
import rclpy


def main():
    rclpy.init()
    navigator = BasicNavigator()

    # 等待Nav2就绪
    navigator.waitUntilNav2Active()

    # 设置导航目标
    goal = PoseStamped()
    goal.header.frame_id = 'map'
    goal.header.stamp = navigator.get_clock().now().to_msg()
    goal.pose.position.x = 2.0
    goal.pose.position.y = 1.0
    goal.pose.orientation.w = 1.0

    navigator.goToPose(goal)

    # 等待完成
    while not navigator.isTaskComplete():
        feedback = navigator.getFeedback()
        print(f'剩余距离: {feedback.distance_remaining:.2f}m')

    result = navigator.getResult()
    print(f'导航结果: {result}')

    rclpy.shutdown()


if __name__ == '__main__':
    main()

🎯 练习题

🏆 成就解锁