Only released in EOL distros:   electric fuerte

Overview

Provides a move_base global-planner plugin, that uses anytime ARA* search as implemented by the sbpl motion planner. In addition to finding a global plan for the base as required by move base, it also publishes a corresponding plan for the cart. The planner is currently configured to plan in (x,y,theta,cartangle) space where (x,y,theta) is the position and orientation of the robot base. The cart angle is the articulation angle of the cart about an (imaginary) pivot point that can be configured using ROS parameters (below). Currently, the planner plans only from and to states where the cart angle is zero.

ROS interface

Advertised topics

sbpl_robot_cart_plan (cart_pushing_msgs/RobotCartPath)

• Whenever planning is done, a corresponding plan for the base and cart is published on this topic.

sbpl_plan_array (visualization_msgs/MarkerArray)

• This is used to visualize the plan as a series of arrows with green arrows representing the path of the robot and red arrows representing the path of the cart.

sbpl_plan_footprint (visualization_msgs/MarkerArray)

• This is used to visualize the plan as a series of robot and cart polygons. The visualizer_skip_poses parameter below affects the density of waypoints displayed.

Main ROS parameters

Cart parameters

These are in the cart_pushing namespace.

{length, width}

• cart dimensions

footprint_{x,y}_offset

• offset of cart reference point from corner

cart_init_pose/position

• Initial position of cart reference point.

Planner parameters

These are in the private namespace of the plugin.

allocated_time default: 10.0

• Max time (seconds) the planner is allowed to take

initial_epsilon default: 3.0

• Initial epsilon parameter to ARA* algorithm (higher epsilon means start off with a very fast, suboptimal search)

environment_type default: XYThetaLattice

• This is currently the only option and should not be changed

planner_type default: ARAPlanner

• This is currently the only option and should not be changed

forward_search default: false

• If false, backwards search will be performed to the goal. This is the preferable mode.

cart_pivot_offset\x default: 0.6

• The x offset of the imaginary pivot point for the cart in the base_footprint frame of the robot. This is the point around which the planner will articulate the cart.

cart_pivot_offset\y default: 0.0

• The y offset of the imaginary pivot point for the cart in the base_footprint frame of the robot. This is the point around which the planner will articulate the cart.

visualizer_skip_poses default: 10

• This parameter controls the number of waypoints that are displayed on the sbpl_plan_footprint topic. A parameter value of 1 will display every single waypoint while a parameter value of 10 will display every 10th waypoint.

primitive_filename default="$(find sbpl_cart_planner)/launch/pr2_cart_articulate.mprim" />

• This is the motion primitive filename. This parameter must point to a valid motion primitive file.

Configuration file location

By default, these parameters are launched from the sbpl_cart_planner/launch/move_base/sbpl_global_planner.yaml file.

Configuring the motion primitives

There are currently two sets of motion primitive files available for cart pushing.

• sbpl_cart_planner/launch/pr2_cart_articulate.mprim

  • - This set of primitives includes articulation primitives that allow the robot to articulate the cart about the articulation point defined by the parameters above.

• sbpl_cart_planner/launch/pr2_cart.mprim
  • - This set of primitives encodes basic motions of the PR2+cart system. It allows for forward, backwards, rotation in place and sideways strafing. It essentially models the robot+cart as a long robot with no articulation capabilities.

Sample path