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.

Parameters¶

controller_frequency:

Type	Default
double	20.0

Description: Frequency to run controller (Hz).

controller_plugins:

Type	Default
vector<string>	[‘FollowPath’]

Description

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_plugin:

Type	Default
string	‘progress_checker’

Description

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_plugin: "progress_checker"
    progress_checker:
      plugin: "nav2_controller::SimpleProgressChecker"

goal_checker_plugin:

Type	Default
string	‘goal_checker’

Description

Mapped name for goal checker plugin for checking goal is reached.

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_plugin: "goal_checker"
    goal_checker:
      plugin: "nav2_controller::SimpleGoalChecker"

min_x_velocity_threshold:

Type	Default
double	0.0001

Description: 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	Default
double	0.0001

Description: 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	Default
double	0.0001

Description: 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	Default
double	0.0

Description: 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	Default
string	“speed_limit”

Description: 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	Default
string	“odom”

Description: Topic to get instantaneous measurement of speed from.

Provided Plugins¶

The plugins listed below are inside the nav2_controller namespace.

Default Plugins¶

When the progress_checker_plugin, goal_checker_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”

“FollowPath” “dwb_core::DWBLocalPlanner”

Example¶

controller_server:
  ros__parameters:
    use_sim_time: True
    controller_frequency: 20.0
    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"
    progress_checker_plugin: "progress_checker"
    goal_checker_plugin: "goal_checker"
    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
      stateful: True
    FollowPath:
      plugin: "dwb_core::DWBLocalPlanner"