erl_active_mapping_ros

This package provides ROS nodes that wrap the erl_active_mapping library for autonomous exploration and active mapping in robotics applications. It includes support for frontier-based exploration strategies with 2D grid mapping.

Features

• Frontier-Based Exploration: Autonomous exploration using frontier detection
• Online Mapping: Real-time occupancy map building from laser scan data
• External Map Support: Option to use pre-built maps for exploration planning
• ROS2 Integration: Full integration with ROS2 interfaces
• Flexible Precision: Supports both single and double precision computation
• Configurable QoS: Flexible QoS settings for all topics
• Auto-Replanning: Automatic path replanning based on exploration progress
• Exploration Metrics: Real-time tracking of distance traveled, observed area, and exploration ratio

Nodes

Common Parameters for Active Mapping Nodes

All active mapping nodes inherit from a common base class (ActiveMappingNode) that provides the following shared parameters:

Core Settings

• double_precision (bool, default: false): Use double precision instead of float
• global_frame (string, default: "map"): Global reference frame
• robot_frame (string, default: "base_link"): Robot reference frame

Exploration Control

• auto_replan (bool, default: false): Enable automatic path replanning
• stop_exploration_ratio (double, default: 0.95): Stop exploration when this ratio of area is observed (0.0-1.0)
• max_observed_area (double, default: 10.0): Maximum expected observable area for computing exploration ratio

Default QoS Settings

• default_qos_reliability (string, default: "reliable"): Default QoS reliability for topics
• default_qos_durability (string, default: "volatile"): Default QoS durability for topics

Output Topics

• path_topic (string, default: "path"): Planned path output topic
• path_topic_reliability (string, default: uses default_qos_reliability)
• path_topic_durability (string, default: uses default_qos_durability)
• dist_topic (string, default: "distance"): Total distance traveled output topic
• dist_topic_reliability (string, default: uses default_qos_reliability)
• dist_topic_durability (string, default: uses default_qos_durability)
• observed_area_topic (string, default: "observed_area"): Observed area output topic
• observed_area_topic_reliability (string, default: uses default_qos_reliability)
• observed_area_topic_durability (string, default: uses default_qos_durability)
• observed_ratio_topic (string, default: "observed_ratio"): Exploration ratio output topic
• observed_ratio_topic_reliability (string, default: uses default_qos_reliability)
• observed_ratio_topic_durability (string, default: uses default_qos_durability)
• replan_topic (string, default: "replan"): Replan signal output topic
• replan_topic_reliability (string, default: uses default_qos_reliability)
• replan_topic_durability (string, default: uses default_qos_durability)

Services

• plan_srv_name (string, default: "plan_path"): Planning service name

---

1. frontier_based_grid_2d_node

Frontier-based autonomous exploration planner for 2D grid-based environments.

Subscriptions

• map (nav_msgs/OccupancyGrid): External occupancy grid map (when use_external_map is true, default topic: "map")
• scan (sensor_msgs/LaserScan): Laser scan data for online mapping (when use_external_map is false, default topic: "scan")

Publications

• path (nav_msgs/Path): Planned exploration path
• distance (std_msgs/Float64): Total distance traveled by the robot
• observed_area (std_msgs/Float64): Total observed area in square meters
• observed_ratio (std_msgs/Float64): Ratio of observed area to maximum expected area (0.0-1.0)
• replan (std_msgs/Bool): Signal indicating whether replanning is needed
• internal_map (nav_msgs/OccupancyGrid): Internal occupancy map (default topic: "internal_map")

Services

• plan_path (std_srvs/srv/Trigger): Trigger exploration path planning

Parameters

See Common Parameters for Active Mapping Nodes above.

Additional Node-Specific Parameters:

Agent Configuration:

• agent_config_file (string, required): Path to agent configuration YAML file

Map Configuration (for online mapping):

• map_min (double[], default: [-10.1, -10.1]): Minimum corner of the map [x_min, y_min]
• map_max (double[], default: [10.1, 10.1]): Maximum corner of the map [x_max, y_max]
• map_resolution (double, default: 0.05): Map resolution in meters per cell

Map Source:

• use_external_map (bool, default: false): Use external map (true) or build map from laser scans (false)

Input Topics (when use_external_map is true):

• map_topic (string, default: "map"): External occupancy grid topic
• map_topic_reliability (string, default: "reliable"): QoS reliability setting
• map_topic_durability (string, default: "transient_local"): QoS durability setting

Input Topics (when use_external_map is false):

• scan_topic (string, default: "scan"): Laser scan topic
• scan_topic_reliability (string, default: "reliable"): QoS reliability setting
• scan_topic_durability (string, default: "volatile"): QoS durability setting

Output Topics:

• internal_map_topic (string, default: "internal_map"): Internal map topic
• internal_map_topic_reliability (string, default: "reliable"): QoS reliability setting
• internal_map_topic_durability (string, default: "transient_local"): QoS durability setting

Usage Examples

Basic Frontier-Based Exploration with Online Mapping

# Launch with default parameters (online mapping from laser scans)
ros2 run erl_active_mapping_ros frontier_based_grid_2d_node --ros-args \
  -p agent_config_file:=/path/to/frontier_based_grid_2d.yaml \
  -p auto_replan:=true \
  -p stop_exploration_ratio:=0.95 \
  -p map_min:="[-10.0, -10.0]" \
  -p map_max:="[10.0, 10.0]" \
  -p map_resolution:=0.05 \
  -p max_observed_area:=100.0

# Trigger initial planning if auto_replan is false
ros2 service call /plan_path std_srvs/srv/Trigger

Exploration with External Map

# Launch with external map
ros2 run erl_active_mapping_ros frontier_based_grid_2d_node --ros-args \
  -p agent_config_file:=/path/to/frontier_based_grid_2d.yaml \
  -p use_external_map:=true \
  -p auto_replan:=true \
  -p stop_exploration_ratio:=0.95 \
  -p max_observed_area:=400.0

# The node will subscribe to /map and use it for planning

Custom Parameters

# Launch with custom parameters
ros2 run erl_active_mapping_ros frontier_based_grid_2d_node --ros-args \
  -p double_precision:=true \
  -p global_frame:=map \
  -p robot_frame:=base_link \
  -p auto_replan:=true \
  -p stop_exploration_ratio:=0.90 \
  -p agent_config_file:=/path/to/config.yaml \
  -p map_resolution:=0.1 \
  -p scan_topic:=scan \
  -p path_topic:=exploration_path \
  -p default_qos_reliability:=reliable \
  -p default_qos_durability:=transient_local

Using Launch File

# Launch test example
ros2 launch erl_active_mapping_ros test_frontier_based_grid_2d_node_launch.py

# Launch with rqt_plot for monitoring
ros2 launch erl_active_mapping_ros test_frontier_based_grid_2d_node_launch.py open_rqt_plot:=true

Monitoring Exploration Progress

# Monitor distance traveled
ros2 topic echo /distance

# Monitor observed area
ros2 topic echo /observed_area

# Monitor exploration ratio
ros2 topic echo /observed_ratio

# Check if replanning is needed
ros2 topic echo /replan

Agent Configuration

The agent_config_file parameter should point to a YAML file that configures the frontier-based exploration agent. Example configuration can be found in the erl_active_mapping package under config/frontier_based_grid_2d.yaml.

Key configuration parameters typically include:

• Frontier detection thresholds
• Path planning parameters
• Sensor model parameters
• Exploration strategy settings

Dependencies

• erl_active_mapping: Core active mapping algorithms
• erl_env: Environment representations
• erl_common: Common utilities
• nav_msgs: Navigation messages for paths and maps
• sensor_msgs: Sensor messages for laser scans
• geometry_msgs: Geometry messages for poses
• std_msgs: Standard messages
• std_srvs: Standard services
• tf2_ros: Transform library for ROS2
• ROS2 Humble or later

Building

ROS2

# In your ROS2 workspace
colcon build --packages-select erl_active_mapping_ros --cmake-args -DCMAKE_BUILD_TYPE=Release

# Source the workspace
source install/setup.bash

Topics Summary

Published Topics

Topic	Type	Description
/path	nav_msgs/Path	Planned exploration path
/distance	std_msgs/Float64	Total distance traveled
/observed_area	std_msgs/Float64	Total observed area (m²)
/observed_ratio	std_msgs/Float64	Exploration completion ratio
/replan	std_msgs/Bool	Replanning needed signal
/internal_map	nav_msgs/OccupancyGrid	Internal occupancy map

Subscribed Topics

Topic	Type	Description	Condition
/map	nav_msgs/OccupancyGrid	External occupancy grid	use_external_map=true
/scan	sensor_msgs/LaserScan	Laser scan data	use_external_map=false

Services

Service	Type	Description
/plan_path	std_srvs/srv/Trigger	Trigger path planning

License

This package is released under the MIT License. See the LICENSE file for details.