Behavior Server¶

Source code on Github.

The Behavior Server implements the server for handling recovery behavior requests and hosting a vector of plugins implementing various C++ behaviors. It is also possible to implement independent behavior servers for each custom behavior, but this server will allow multiple behaviors to share resources such as costmaps and TF buffers to lower incremental costs for new behaviors.

Note: the wait recovery behavior has no parameters, the duration to wait is given in the action request. Note: pre-Rolling/Humble this was the Recovery server, not behavior server. Launch files, behaviors and tests were all renamed.

Behavior Server Parameters¶

local_costmap_topic

Type	Default
string	“local_costmap/costmap_raw”

Description: Raw costmap topic for collision checking on the local costmap.

global_costmap_topic

Type	Default
string	“global_costmap/costmap_raw”

Description: Raw costmap topic for collision checking on the global costmap.

local_footprint_topic

Type	Default
string	“local_costmap/published_footprint”

Description: Topic for footprint in the local costmap frame.

global_footprint_topic

Type	Default
string	“global_costmap/published_footprint”

Description: Topic for footprint in the global costmap frame.

cycle_frequency

Type	Default
double	10.0

Description: Frequency to run behavior plugins.

action_server_result_timeout

Type	Default	Unit
double	10.0	seconds

Description: The timeout value (in seconds) for action servers to discard a goal handle if a result has not been produced. This used to default to 15 minutes in rcl but was changed to 10 seconds in this PR #1012, which may be less than some actions in Nav2 take to run. For most applications, this should not need to be adjusted as long as the actions within the server do not exceed this deadline. This issue has been raised with OSRF to find another solution to avoid active goal timeouts for bookkeeping, so this is a semi-temporary workaround

transform_tolerance

Type	Default
double	0.1

Description: TF transform tolerance.

local_frame

Type	Default
string	“odom”

Description: Local reference frame.

global_frame

Type	Default
string	“map”

Description: Global reference frame.

robot_base_frame

Type	Default
string	“base_link”

Description: Robot base frame.

behavior_plugins

Type	Default
vector<string>	{“spin”, “back_up”, “drive_on_heading”, “wait”}

Description

List of plugin names to use, also matches action server names.

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:

behavior_server:
  ros__parameters:
    behavior_plugins: ["spin", "backup", "drive_on_heading", "wait"]
    spin:
      plugin: "nav2_behaviors/Spin"
    backup:
      plugin: "nav2_behaviors/BackUp"
    drive_on_heading:
      plugin: "nav2_behaviors/DriveOnHeading"
    wait:
      plugin: "nav2_behaviors/Wait"

Default Plugins¶

When the behavior_plugins parameter is not overridden, the following default plugins are loaded:

Namespace

Plugin

“spin”

“nav2_behaviors/Spin”

“backup”

“nav2_behaviors/BackUp”

“drive_on_heading”

“nav2_behaviors/DriveOnHeading”

“wait”

“nav2_behaviors/Wait”

Spin Behavior Parameters¶

Spin distance is given from the action request

simulate_ahead_time

Type	Default
double	2.0

Description: Time to look ahead for collisions (s).

max_rotational_vel

Type	Default
double	1.0

Description: Maximum rotational velocity (rad/s).

min_rotational_vel

Type	Default
double	0.4

Description: Minimum rotational velocity (rad/s).

rotational_acc_lim

Type	Default
double	3.2

Description: maximum rotational acceleration (rad/s^2).

BackUp Behavior Parameters¶

Backup distance, speed and time_allowance is given from the action request.

simulate_ahead_time

Type	Default
double	2.0

Description: Time to look ahead for collisions (s).

DriveOnHeading Behavior Parameters¶

DriveOnHeading distance, speed and time_allowance is given from the action request.

simulate_ahead_time

Type	Default
double	2.0

Description: Time to look ahead for collisions (s).

AssistedTeleop Behavior Parameters¶

AssistedTeleop time_allowance is given in the action request

projection_time

Type	Default
double	1.0

Description: Time to look ahead for collisions (s).

simulation_time_step

Type	Default
double	0.1

Description: Time step for projections (s).

cmd_vel_teleop

Type	Default
string	cmd_vel_teleop

Description: Topic to listen for teleop messages.

Example¶

behavior_server:
  ros__parameters:
    local_costmap_topic: local_costmap/costmap_raw
    local_footprint_topic: local_costmap/published_footprint
    global_costmap_topic: global_costmap/costmap_raw
    global_footprint_topic: global_costmap/published_footprint
    cycle_frequency: 10.0
    behavior_plugins: ["spin", "backup", "drive_on_heading", "wait", "assisted_teleop"]
    spin:
      plugin: "nav2_behaviors/Spin"
    backup:
      plugin: "nav2_behaviors/BackUp"
    drive_on_heading:
      plugin: "nav2_behaviors/DriveOnHeading"
    wait:
      plugin: "nav2_behaviors/Wait"
    assisted_teleop:
      plugin: "nav2_behaviors/AssistedTeleop"
    local_frame: odom
    global_frame: map
    robot_base_frame: base_link
    transform_timeout: 0.1
    simulate_ahead_time: 2.0
    max_rotational_vel: 1.0
    min_rotational_vel: 0.4
    rotational_acc_lim: 3.2