Robot localization is the process of determining where a mobile robot is located with respect to its environment. Localization is one of the most fundamental competencies required by an autonomous robot as the knowledge of the robot’s own location is an essential precursor to making decisions about future actions.
ROS provides robot_localization package, which is a collection of state estimation nodes, each of which is an implementation of a nonlinear state estimator for robots moving in 3D space. It contains two state estimation nodes, ekf_localization_node and ukf_localization_node. In addition, robot_localization provides navsat_transform_node, which aids in the integration of GPS data.
[TODO: VIDEO: RVIZ visualization /odometry/filtered]
Below is the configuration for robot_localization package for a planar robot with encoders and imu. The data from encoders and imu are fused to generate a more robust, corrected odometry at /odometry/filtered topic.
ekf_filter_node:
ros__parameters:
frequency: 10.0
sensor_timeout: 0.1
two_d_mode: true
transform_time_offset: 0.0
transform_timeout: 0.0
print_diagnostics: true
debug: false
debug_out_file: /tmp/ekf_debug.txt
permit_corrected_publication: true
publish_acceleration: false
publish_tf: true
map_frame: map
odom_frame: odom
base_link_frame: base_footprint
world_frame: odom
odom0: odom
# The order of the values is x, y, z, roll, pitch, yaw, vx, vy, vz, vroll, vpitch, vyaw, ax, ay, az.
# [vx, vy, vyaw]
odom0_config: [false, false, false,
false, false, false,
true, true, false,
false, false, true,
false, false, false]
odom0_queue_size: 3
odom0_nodelay: false
odom0_differential: false
odom0_relative: false
odom0_pose_rejection_threshold: 6.283185 # 2 PI
odom0_twist_rejection_threshold: 4.712388 # 3/2 PI
imu0: imu/data
# The order of the values is x, y, z, roll, pitch, yaw, vx, vy, vz, vroll, vpitch, vyaw, ax, ay, az.
# [roll, pitch, yaw, vyaw, ax]
imu0_config: [false, false, false,
true, true, true,
false, false, false,
false, false, true,
true, false, false]
imu0_nodelay: false
imu0_differential: false
imu0_relative: true
imu0_queue_size: 6
imu0_pose_rejection_threshold: 6.283185 # 2 PI
imu0_twist_rejection_threshold: 6.283185 # 2 PI
imu0_linear_acceleration_rejection_threshold: 9.81 # 1G
imu0_remove_gravitational_acceleration: true
use_control: true
stamped_control: false
control_timeout: 0.1
control_config: [ true, false, false, false, false, true ]
acceleration_limits: [1.3, 0.0, 0.0, 0.0, 0.0, 3.4]
deceleration_limits: [1.3, 0.0, 0.0, 0.0, 0.0, 4.5]
acceleration_gains: [0.8, 0.0, 0.0, 0.0, 0.0, 0.9]
deceleration_gains: [1.0, 0.0, 0.0, 0.0, 0.0, 1.0]
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