Navigating with SimpleStack and EasyNav

This HowTo explains how to perform navigation using the Simple Stack in EasyNavigation (EasyNav). The Simple Stack operates on a binary occupancy map.

Warning

The Simple stack is a minimal example, with very basic algorithms, made to show how EasyNav works and how plugins are written. Do not expect good navigation from it. For real use, see Navigating with the Costmap Stack.

Overview

This tutorial uses the Kobuki PlayGround, which ships a map of its world (maps/home.map). To navigate in your own map, create it first following Mapping with SLAM Toolbox and EasyNav.

Setup

Build EasyNav and the Kobuki PlayGround as described in Getting Started.

The Parameter File

In this example we will use:

• The Simple Maps Manager to load the binary map.

• The AMCL localizer of the Simple stack (easynav_simple_localizer).

• The Simple Planner, an A* over the binary map.

• The SeReST controller for path tracking (see SeReST Controller Fine-Tuning).

• The Simple recovery system, which brakes before an obstacle ahead, rotates to relocalize and backs up when stuck (see Recovery System).

This is params/simple.serest.params.yaml of the Kobuki PlayGround:

controller_node:
  ros__parameters:
    use_sim_time: true
    robot_limits:
      max_linear_vel: 0.6
      min_linear_vel: -0.6
      max_angular_vel: 1.5
      max_linear_acc: 0.8
      max_linear_decel: 1.0
      max_angular_acc: 2.0
      max_angular_decel: 2.0
    controller_types: [serest]
    serest:
      rt_freq: 30.0
      plugin: easynav_serest_controller/SerestController
      allow_reverse: true
      v_progress_min: 0.08
      k_s_share_max: 0.5
      k_theta: 2.5
      k_y: 1.5
      goal_pos_tol: 0.1
      goal_yaw_tol_deg: 6.0
      slow_radius: 0.80
      slow_min_speed: 0.02
      final_align_k: 2.5
      final_align_wmax: 0.8
      corner_guard_enable: true
      corner_gain_ey: 1.8
      corner_gain_eth: 0.7
      corner_gain_kappa: 0.4
      corner_min_alpha: 0.35
      corner_boost_omega: 1.0
      a_lat_soft: 0.9
      apex_ey_des: 0.05

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

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

system_node:
  ros__parameters:
    use_sim_time: true
    robot_geometry:
      radius: 0.25
      height: 0.5
    position_tolerance: 0.3
    angle_tolerance: 0.15

recovery_node:
  ros__parameters:
    use_sim_time: true
    recovery_manager:
      plugin: easynav_simple_recovery/SimpleRecoveryManager
      stop_distance: 0.3
      sensors_timeout: 5.0
      max_position_variance: 1.0

To use your own map, change package and map_path_file (both are needed: the map is looked up in the share directory of package).

Running the Simulation

1. Launch the simulator, EasyNav and RViz2:

   ros2 launch easynav_playground_kobuki easynav_simple_serest.launch.yaml
   

   You can disable the Gazebo GUI with gui:=false, and use your own parameter file with params_file:=/path/to/my.params.yaml.

2. Send navigation goals: in RViz2, use the “2D Goal Pose” tool. The robot will plan and navigate toward them.

Notes

• The Simple Stack uses a binary map: cells are free or occupied (no graded cost), so paths are not kept away from obstacles. For cost-aware planning, use the Costmap Stack (Navigating with the Costmap Stack).

• easynav_simple.launch.yaml runs the same stack with the Simple controller, the one of Getting Started.