## repository: https://code.ros.org/svn/wg-ros-pkg
<<PackageHeader(single_joint_position_action)>>
<<TOC(4)>>

See also [[robot_mechanism_controllers/JointSplineTrajectoryController]], which is used by this action.

{{attachment:sjposition_action_topics.png}}

== Usage ==

You can find an example of using the single joint position action on the PR2 in the [[pr2_controllers/Tutorials/Moving the torso|Moving the Torso tutorial]].

== ROS API ==

The ROS API consists of three parts: private parameters, an action server that achieves position goals, and an interface to a trajectory controller.

=== Parameters ===
{{{
#!clearsilver CS/NodeAPI
param {
  0.name=~joint
  0.type=string
  0.default=Required
  0.desc=The joint to command
  1.name=~goal_threshold
  1.type=double
  1.default=0.1
  1.desc=The maximum distance from the goal at which to report success.
}
}}}

=== Action interface ===

The joint trajectory action provides an action server (see [[actionlib]]) that takes in goals of the type <<MsgLink(pr2_controllers_msgs/SingleJointPositionGoal)>>.

{{{
#!clearsilver CS/NodeAPI
sub {
  0.name=~position_joint_action/goal
  0.type=pr2_controllers_msgs/SingleJointPositionActionGoal
  0.desc=The goal describes the position for the robot to achieve
  1.name=~position_joint_action/cancel
  1.type=actionlib_msgs/GoalID
  1.desc=A request to cancel a specific goal.
}
pub {
  0.name=~position_joint_action/feedback
  0.type=pr2_controllers_msgs/SingleJointPositionActionFeedback
  0.desc=Feedback describing the progress the mechanism is making on reaching the goal position
  1.name=~position_joint_action/status
  1.type=actionlib_msgs/GoalStatusArray
  1.desc=Provides status information on the goals that are sent to the action.
  2.name=~position_joint_action/result
  2.type=pr2_controllers_msgs/SingleJointPositionActionResult
  2.desc=empty
}
}}}


=== Controller interface ===

{{{
#!clearsilver CS/NodeAPI
sub {
  0.name=~state
  0.type=pr2_controllers_msgs/JointTrajectoryControllerState
  0.desc=Listens to the state of the controller.
}
pub {
  0.name=~command
  0.type=trajectory_msgs/JointTrajectory
  0.desc=Sends joint trajectories to the controller.
}
}}}


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