AMCL

Source code on Github.

AMCL implements the server for taking a static map and localizing the robot within it using an Adaptive Monte-Carlo Localizer.

Parameters

alpha1

Type

Default

double

0.2

Description

Expected process noise in odometry’s rotation estimate from rotation.

alpha2

Type

Default

double

0.2

Description

Expected process noise in odometry’s rotation estimate from translation.

alpha3

Type

Default

double

0.2

Description

Expected process noise in odometry’s translation estimate from translation.

alpha4

Type

Default

double

0.2

Description

Expected process noise in odometry’s translation estimate from rotation.

alpha5

Type

Default

double

0.2

Description

For Omni models only: translation noise.

base_frame_id

Type

Default

string

“base_footprint”

Description

Robot base frame.

beam_skip_distance

Type

Default

double

0.5

Description

Ignore beams that most particles disagree with in Likelihood field model. Maximum distance to consider skipping for (m).

beam_skip_error_threshold

Type

Default

double

0.9

Description

Percentage of beams after not matching map to force full update due to bad convergance.

beam_skip_threshold

Type

Default

double

0.3

Description

Percentage of beams required to skip.

do_beamskip

Type

Default

bool

False

Description

Whether to do beam skipping in Likelihood field model.

global_frame_id

Type

Default

string

“map”

Description

The name of the coordinate frame published by the localization system.

lambda_short

Type

Default

double

0.1

Description

Exponential decay parameter for z_short part of model.

laser_likelihood_max_dist

Type

Default

double

2.0

Description

Maximum distance to do obstacle inflation on map, for use in likelihood_field model.

laser_max_range

Type

Default

double

100.0

Description

Maximum scan range to be considered, -1.0 will cause the laser’s reported maximum range to be used.

laser_min_range

Type

Default

double

-1.0

Description

Minimum scan range to be considered, -1.0 will cause the laser’s reported minimum range to be used.

laser_model_type

Type

Default

string

“likelihood_field”

Description

Which model to use, either beam, likelihood_field, or likelihood_field_prob. Same as likelihood_field but incorporates the beamskip feature, if enabled.

set_initial_pose

Type

Default

bool

False

Description

Causes AMCL to set initial pose from the initial_pose* parameters instead of waiting for the initial_pose message.

initial_pose

Type

Default

Pose2D

{x: 0.0, y: 0.0, z: 0.0, yaw: 0.0}

Description

X, Y, Z, and yaw coordinates of initial pose (meters and radians) of robot base frame in global frame.

max_beams

Type

Default

int

60

Description

How many evenly-spaced beams in each scan to be used when updating the filter.

max_particles

Type

Default

int

2000

Description

Maximum allowed number of particles.

min_particles

Type

Default

int

500

Description

Minimum allowed number of particles.

odom_frame_id

Type

Default

string

“odom”

Description

Which frame to use for odometry.

pf_err

Type

Default

double

0.05

Description

Particle Filter population error.

pf_z

Type

Default

double

0.99

Description

Particle filter population density.

recovery_alpha_fast

Type

Default

double

0.0

Description

Exponential decay rate for the fast average weight filter, used in deciding when to recover by adding random poses. A good value might be 0.001.

recovery_alpha_slow

Type

Default

double

0.0

Description

Exponential decay rate for the slow average weight filter, used in deciding when to recover by adding random poses. A good value might be 0.001.

resample_interval

Type

Default

int

1

Description

Number of filter updates required before resampling.

robot_model_type

Type

Default

string

“nav2_amcl::DifferentialMotionModel”

Description

The fully-qualified type of the plugin class. Options are “nav2_amcl::DifferentialMotionModel” and “nav2_amcl::OmniMotionModel”. Users can also provide their own custom motion model plugin type.

Note for users of galactic and earlier

The models are selectable by string key (valid options: “differential”, “omnidirectional”) rather than plugins.

save_pose_rate

Type

Default

double

0.5

Description

Maximum rate (Hz) at which to store the last estimated pose and covariance to the parameter server, in the variables ~initial_pose_* and ~initial_cov_*. This saved pose will be used on subsequent runs to initialize the filter (-1.0 to disable).

sigma_hit

Type

Default

double

0.2

Description

Standard deviation for Gaussian model used in z_hit part of the model.

tf_broadcast

Type

Default

bool

True

Description

Set this to false to prevent amcl from publishing the transform between the global frame and the odometry frame.

transform_tolerance

Type

Default

double

1.0

Description

Time with which to post-date the transform that is published, to indicate that this transform is valid into the future.

update_min_a

Type

Default

double

0.2

Description

Rotational movement required before performing a filter update.

update_min_d

Type

Default

double

0.25

Description

Translational movement required before performing a filter update.

z_hit

Type

Default

double

0.5

Description

Mixture weight for z_hit part of model, sum of all used z weight must be 1. Beam uses all 4, likelihood model uses z_hit and z_rand..

z_max

Type

Default

double

0.05

Description

Mixture weight for z_max part of model, sum of all used z weight must be 1. Beam uses all 4, likelihood model uses z_hit and z_rand.

z_rand

Type

Default

double

0.5

Description

Mixture weight for z_rand part of model, sum of all used z weight must be 1. Beam uses all 4, likelihood model uses z_hit and z_rand..

z_short

Type

Default

double

0.005

Description

Mixture weight for z_short part of model, sum of all used z weight must be 1. Beam uses all 4, likelihood model uses z_hit and z_rand.

always_reset_initial_pose

Type

Default

bool

False

Description

Requires that AMCL is provided an initial pose either via topic or initial_pose* parameter (with parameter set_initial_pose: true) when reset. Otherwise, by default AMCL will use the last known pose to initialize.

scan_topic

Type

Default

string

scan

Description

Laser scan topic to subscribe to.

map_topic

Type

Default

string

map

Description

Map topic to subscribe to.

first_map_only

Type

Default

bool

False

Description

Allows AMCL to accept maps more than once on the map_topic. This is especially useful when you’re using the LoadMap service in map_server. Prior to Humble, this is first_map_only_.

Example

amcl:
  ros__parameters:
    alpha1: 0.2
    alpha2: 0.2
    alpha3: 0.2
    alpha4: 0.2
    alpha5: 0.2
    base_frame_id: "base_footprint"
    beam_skip_distance: 0.5
    beam_skip_error_threshold: 0.9
    beam_skip_threshold: 0.3
    do_beamskip: false
    global_frame_id: "map"
    lambda_short: 0.1
    laser_likelihood_max_dist: 2.0
    laser_max_range: 100.0
    laser_min_range: -1.0
    laser_model_type: "likelihood_field"
    max_beams: 60
    max_particles: 2000
    min_particles: 500
    odom_frame_id: "odom"
    pf_err: 0.05
    pf_z: 0.99
    recovery_alpha_fast: 0.0
    recovery_alpha_slow: 0.0
    resample_interval: 1
    robot_model_type: "nav2_amcl::DifferentialMotionModel"
    save_pose_rate: 0.5
    sigma_hit: 0.2
    tf_broadcast: true
    transform_tolerance: 1.0
    update_min_a: 0.2
    update_min_d: 0.25
    z_hit: 0.5
    z_max: 0.05
    z_rand: 0.5
    z_short: 0.05
    scan_topic: scan
    map_topic: map
    set_initial_pose: false
    always_reset_initial_pose: false
    first_map_only: false
    initial_pose:
      x: 0.0
      y: 0.0
      z: 0.0
      yaw: 0.0