Controller Server

Source code on Github.

The Controller Server implements the server for handling the controller requests for the stack and host a map of plugin implementations. It will take in path and plugin names for controller, progress checker and goal checker to use and call the appropriate plugins. It also hosts the local costmap.

Parameters

`controller_frequency`

Type: double Default: 20.0: Frequency to run controller (Hz).

`costmap_update_timeout`

Type: double Default: 0.3: The timeout value (seconds) for the costmap to be fully updated before a control effort can be computed.

`use_realtime_priority`

Type: bool Default: false: Adds soft real-time prioritization to the controller server to better ensure resources to time sensitive portions of the codebase. This will set the controller's execution thread to a higher priority than the rest of the system (90) to meet scheduling deadlines to have less missed loop rates. To use this feature, you use set the following inside of /etc/security/limits.conf to give userspace access to elevated prioritization permissions: <username> soft rtprio 99 <username> hard rtprio 99

`publish_zero_velocity`

Type: bool Default: true: Whether to publish a zero velocity command on goal exit. This is useful for stopping the robot when a goal terminates.

`controller_plugins`

Type: vector<string> Default: ["FollowPath"]

List of mapped names for controller plugins for processing requests and parameters.

Note

Each plugin namespace defined in this list needs to have a plugin parameter defining the type of plugin to be loaded in the namespace.

Example:

controller_server:
  ros__parameters:
    controller_plugins: ["FollowPath"]
    FollowPath:
      plugin: "dwb_core::DWBLocalPlanner"

`progress_checker_plugins`

Type: vector<string> Default: ["progress_checker"]

Mapped name for progress checker plugin for checking progress made by robot.

Note

The plugin namespace defined needs to have a plugin parameter defining the type of plugin to be loaded in the namespace.

Example:

controller_server:
  ros__parameters:
    progress_checker_plugins: ["progress_checker"]
    progress_checker:
      plugin: "nav2_controller::SimpleProgressChecker"

`goal_checker_plugins`

Type: vector<string> Default: ["goal_checker"]

Mapped name for goal checker plugin for checking goal is reached. When the number of the plugins is more than 2, each FollowPath action needs to specify the goal checker plugin name with its goal_checker_id field.

Note

The plugin namespace defined needs to have a plugin parameter defining the type of plugin to be loaded in the namespace.

Example:

controller_server:
  ros__parameters:
    goal_checker_plugins: ["goal_checker"]
    goal_checker:
      plugin: "nav2_controller::SimpleGoalChecker"

`path_handler_plugins`

Type: vector<string> Default: ["PathHandler"]

Mapped name for path handler plugin for processing path from the planner. When the number of the plugins is more than 2, each FollowPath action needs to specify the path handler plugin name with its path_handler_id field.

Note

The plugin namespace defined needs to have a plugin parameter defining the type of plugin to be loaded in the namespace.

Example:

controller_server:
  ros__parameters:
    path_handler_plugins: ["PathHandler"]
    path_handler:
      plugin: "nav2_controller::FeasiblePathHandler"

`min_x_velocity_threshold`

Type: double Default: 0.0001: The controller server filters the velocity portion of the odometry messages received before sending them to the controller plugin. Odometry values below this threshold (in m/s) will be set to 0.0.

`min_y_velocity_threshold`

Type: double Default: 0.0001: The controller server filters the velocity portion of the odometry messages received before sending them to the controller plugin. Odometry values below this threshold (in m/s) will be set to 0.0. For non-holonomic robots

`min_theta_velocity_threshold`

Type: double Default: 0.0001: The controller server filters the velocity portion of the odometry messages received before sending them to the controller plugin. Odometry values below this threshold (in rad/s) will be set to 0.0.

`failure_tolerance`

Type: double Default: 0.0: The maximum duration in seconds the called controller plugin can fail (i.e. the computeVelocityCommands function of the plugin throwing an exception) before the nav2_msgs::action::FollowPath action fails. Setting it to the special value of -1.0 makes it infinite, 0 to disable, and any positive value for the appropriate timeout.

`speed_limit_topic`

Type: string Default: "speed_limit": Speed limiting topic name to subscribe. This could be published by Speed Filter (please refer to Speed Filter Parameters configuration page). You can also use this without the Speed Filter as well if you provide an external server to publish these messages.

`odom_topic`

Type: string Default: "odom": Topic to get instantaneous measurement of speed from.

`odom_duration`

Type: double Default: 0.3: Time (s) to buffer odometry commands to estimate the robot speed.

`enable_stamped_cmd_vel`

Type: bool Default: true: Whether to use geometry_msgs::msg::Twist or geometry_msgs::msg::TwistStamped velocity data. true uses TwistStamped, false uses Twist.

`bond_heartbeat_period`

Type: double Default: 0.25: The lifecycle node bond mechanism publishing period (on the /bond topic). Disabled if inferior or equal to 0.0.

`introspection_mode`

Type: string Default: "disabled": The introspection mode for services and actions. Options are "disabled", "metadata", "contents".

`allow_parameter_qos_overrides`

Type: bool Default: true: Whether to allow QoS profiles to be overwritten with parameterized values.

`search_window`

Type: double Default: 2.0: How far (in meters) along the path the searching algorithm will look for the closest point.

Provided Plugins

The plugins listed below are inside the nav2_controller namespace.

SimpleProgressChecker

Monitors forward progress by distance traveled.

Go
PoseProgressChecker

Monitors progress by pose change over time.

Go
AxisGoalChecker

Checks goal with independent along-path and cross-track tolerances.

Go
AdaptiveToleranceGoalChecker

Uses fine and coarse tolerances with velocity and progress monitoring.

Go
SimpleGoalChecker

Basic distance and angle goal tolerance check.

Go
StoppedGoalChecker

Verifies the robot has fully stopped at the goal.

Go
PositionGoalChecker

Position-only goal check (ignores orientation).

Go
FeasiblePathHandler

Handles infeasible path segments from the planner.

Go

Default Plugins

When the progress_checker_plugins, goal_checker_plugin, path_handler_plugin or controller_plugins parameters are not overridden, the following default plugins are loaded:

Namespace	Plugin
"progress_checker"	"nav2_controller::SimpleProgressChecker"
"goal_checker"	"nav2_controller::SimpleGoalChecker"
"path_handler"	"nav2_controller::FeasiblePathHandler"
"FollowPath"	"dwb_core::DWBLocalPlanner"

Example

controller_server:
  ros__parameters:
    controller_frequency: 20.0
    costmap_update_timeout: 0.3
    min_x_velocity_threshold: 0.001
    min_y_velocity_threshold: 0.5
    min_theta_velocity_threshold: 0.001
    failure_tolerance: 0.3
    odom_topic: "odom"
    odom_duration: 0.3
    progress_checker_plugins: ["progress_checker"]
    goal_checker_plugins: ["goal_checker"]
    path_handler_plguins: ["PathHandler"]
    controller_plugins: ["FollowPath"]
    progress_checker:
      plugin: "nav2_controller::SimpleProgressChecker"
      required_movement_radius: 0.5
      movement_time_allowance: 10.0
    goal_checker:
      plugin: "nav2_controller::SimpleGoalChecker"
      xy_goal_tolerance: 0.25
      yaw_goal_tolerance: 0.25
      path_length_tolerance: 1.0
      stateful: True
    PathHandler:
      plugin: "nav2_controller::FeasiblePathHandler"
      prune_distance: 2.0
      enforce_path_inversion: True
      enforce_path_rotation: False
      inversion_xy_tolerance: 0.2
      inversion_yaw_tolerance: 0.4
      minimum_rotation_angle: 0.785
      reject_unit_path: False
    FollowPath:
      plugin: "dwb_core::DWBLocalPlanner"