EasyNav Simple Stack Tutorials

The easynav_simple_stack provides a minimal working setup for EasyNav based on a 2D binary occupancy grid. This stack is ideal for introductory testing and basic indoor navigation scenarios.

It includes the following packages:

• easynav_simple_common: Defines the SimpleMap structure used across the stack.

• easynav_simple_controller: A simple controller that follows a path using a PID approach.

• easynav_simple_localizer: A basic AMCL-like localizer using 2D occupancy grid maps.

• easynav_simple_maps_manager: A manager that fuses a static map with incoming perceptions.

• easynav_simple_planner: A basic A* planner that generates paths over the map.

The SimpleMap Representation

At the heart of this stack is the SimpleMap data structure. It represents the environment as a 2D occupancy grid where each cell can be either 0 (free), 1 (occupied), or -1 (unknown). SimpleMap supports:

• Resolution and size configuration

• Conversion to and from ROS 2 nav_msgs/msg/OccupancyGrid

• Metric/cell coordinate transformation

• Basic drawing and manipulation utilities

SimpleMap is used for both static maps (loaded from file) and dynamic maps (updated from perceptions).

HowTo

• Mapping with SLAM Toolbox and EasyNav

Stack Reference

easynav_simple_maps_manager

This component manages and fuses the static map and incoming perceptions into a dynamic map.

ROS Parameters:

Parameter	Description
freq	Execution frequency (Hz)
plugin	Plugin name
package	Package where map lives
map_path_file	Path to .map file

Topics:

Publishes:

• /dynamic_map: nav_msgs/msg/OccupancyGrid

NavState Access:

Key	Type	Direction
points	PointPerceptions	Read
map.static	SimpleMap	Write
map.dynamic	SimpleMap	Write

easynav_simple_localizer

A basic AMCL-style localizer using particles and static maps.

ROS Parameters:

Parameter	Description
plugin	Plugin name
rt_freq	Real-time update freq (Hz)
freq	Slow cycle update freq
reseed_freq	Reseed frequency (Hz)
num_particles	Number of particles
noise_translation	Noise (m)
noise_rotation	Noise (rad)
initial_pose.{x,y,yaw…}	Initial pose + stddev

NavState Access:

Key	Type	Direction
map.static	SimpleMap	Read
points	PointPerceptions	Read
robot_pose	nav_msgs/msg/Odometry	Write

easynav_simple_planner

An A* planner over SimpleMap representations.

ROS Parameters:

Parameter	Description
plugin	Plugin name
freq	Execution frequency (Hz)
robot_radius	Robot radius in meters

NavState Access:

Key	Type	Direction
map.dynamic	SimpleMap	Read
robot_pose	nav_msgs/msg/Odometry	Read
goals	nav_msgs/msg/Goals	Read
path	nav_msgs/msg/Path	Write

easynav_simple_controller

A PID-based controller that tracks a path in real time.

ROS Parameters:

Parameter	Description
plugin	Plugin name
rt_freq	Real-time frequency (Hz)
max_linear_speed	Max forward velocity (m/s)
max_angular_speed	Max rotation speed (rad/s)
look_ahead_dist	Look-ahead distance (m)
k_rot	Angular correction factor

NavState Access:

Key	Type	Direction
robot_pose	nav_msgs/msg/Odometry	Read
path	nav_msgs/msg/Path	Read
cmd_vel	geometry_msgs/msg/TwistStamped	Write

Example Configuration

controller_node:
  ros__parameters:
    use_sim_time: true
    controller_types: [simple]
    simple:
      rt_freq: 30.0
      plugin: easynav_simple_controller/SimpleController
      max_linear_speed: 0.6
      max_angular_speed: 1.0
      look_ahead_dist: 0.2
      k_rot: 0.5

localizer_node:
  ros__parameters:
    use_sim_time: true
    localizer_types: [simple]
    simple:
      rt_freq: 50.0
      freq: 5.0
      reseed_freq: 1.0
      plugin: easynav_simple_localizer/AMCLLocalizer
      num_particles: 100
      noise_translation: 0.05
      noise_rotation: 0.1
      noise_translation_to_rotation: 0.1
      initial_pose:
        x: 0.0
        y: 0.0
        yaw: 0.0
        std_dev_xy: 0.1
        std_dev_yaw: 0.01

maps_manager_node:
  ros__parameters:
    use_sim_time: true
    map_types: [simple]
    simple:
      freq: 10.0
      plugin: easynav_simple_maps_manager/SimpleMapsManager
      package: easynav_playground_kobuki
      map_path_file: maps/home.map

planner_node:
  ros__parameters:
    use_sim_time: true
    planner_types: [simple]
    simple:
      freq: 0.5
      plugin: easynav_simple_planner/SimplePlanner
      robot_radius: 0.3

sensors_node:
  ros__parameters:
    use_sim_time: true
    forget_time: 0.5
    sensors: [laser1]
    perception_default_frame: odom
    laser1:
      topic: /scan_raw
      type: sensor_msgs/msg/LaserScan
      group: points
    camera1:
      topic: /rgbd_camera/points
      type: sensor_msgs/msg/PointCloud2
      group: points

system_node:
  ros__parameters:
    use_sim_time: true
    position_tolerance: 0.1
    angle_tolerance: 0.05