lianshangni0922 / mcl

mcl

mcl is an alternative Monte Carlo localization (MCL) package to amcl (http://wiki.ros.org/amcl). Differently from amcl, KLD-samping and adaptive MCL are not implemented.

This package is suitable for learning MCL due to its simplicity.

Nodes

mcl_node

This node transforms laser scans and odometry transform messages to pose estimations by using an occupancy grid map.

Subscrbed Topics

• scan (sensor_msgs/LaserScan)
  • laser scans
• tf (tf/tfMessage)
  • transforms
• initialpose (geometry_msgs/PoseWithCovarianceStamped)
  • pose of particles for replacement

Published Topics

• mcl_pose (geometry_msgs/PoseWithCovarianceStamped)
  • the mean pose of the particles with covariance
• particlecloud (geometry_msgs/PoseArray)
  • poses of the particles
• tf (tf/tfMessage)
  • the transform from odom (which can be remapped via the ~odom_frame_id parameter) to map

Services Called

• static_map (nav_msgs/GetMap)
  • mcl initializes the map for localization

Parameters

• ~odom_freq (int, default: 20 [Hz])
  • frequency of odometry update
• ~num_particles (int, default: 1000)
  • number of particles
• ~odom_frame_id (string, default: "odom")
  • the frame for odometry
• ~base_frame_id (string, default: "base_footprint")
  • the frame of the localized robot's base
• ~global_frame_id (string, default: "map")
  • the frame for localization
• ~initial_pose_x (double, default: 0.0 [m])
  • initial x coordinate of particles
• ~initial_pose_y (double, default: 0.0 [m])
  • initial y coordinate of particles
• ~initial_pose_a (double, default: 0.0 [rad])
  • initial yaw coordinate of particles
• ~odom_fw_dev_per_fw (double, default: 0.19 [m/m])
  • standard deviation of forward motion noise by forward motion
• ~odom_fw_dev_per_rot (double, default: 0.0001 [m/rad])
  • standard deviation of forward motion noise by rotational motion
• ~odom_rot_dev_per_fw (double, default: 0.13 [m/m])
  • standard deviation of rotational motion noise by forward motion
• ~laser_likelihood_max_dist (double, default: 0.2 meters)
  • maximum distance to inflate occupied cells on the likelihood field map

Notes

likelihood field

This implemenation uses an ad-hoc likelihood field model. Occupied cells on the map are inflated so that each collision detection between a laser beam and an occupied cell is relaxed. The likelihood for each cell is given with a pyramidal kernel function. The parameter ~laser_likelihood_max_dist gives the length from the center cell to the edge of the pyramid.