joint_trajectory_interface

ROS joint trajectory action helpers.

This module provides helpers for ROS FollowJointTrajectory action clients used by RobotBlockSet robot interfaces. It manages trajectory points, goal sending, status monitoring, and result handling for joint-space motion commands.

based on: http://sdk.rethinkrobotics.com/wiki/Simple_Joint_trajectory_example

class robotblockset.ros.joint_trajectory_interface.JointTrajectory(controller_ns: str, do_motion_check: bool = False, motion_check_callback: Callable[[Any], bool] | None = None)[source]

Bases: object

Helper for ROS FollowJointTrajectory action clients.

Attributes:

  • robot (Any) – Robot object passed to the motion-check callback.

  • generic_state (GoalStatus) – Reusable goal-status message used for status comparisons.

  • state (int) – Cached action state.

  • READY (int) – Readiness flag indicating whether a new trajectory can be sent.

Initialize a ROS joint-trajectory action client.

Parameters:

  • controller_ns (str) – Controller namespace used to resolve action and status topics.

  • do_motion_check (bool, optional) – If True, use the feedback callback to monitor motion execution.

  • motion_check_callback (callable, optional) – Callback used to decide whether motion should be interrupted.

Notes

The constructor subscribes to the controller status topic, creates the action client, queries the joint names from ROS parameters, and resets the internal goal state.

__init__(controller_ns: str, do_motion_check: bool = False, motion_check_callback: Callable[[Any], bool] | None = None) → None[source]

Initialize a ROS joint-trajectory action client.

Parameters:

  • controller_ns (str) – Controller namespace used to resolve action and status topics.

  • do_motion_check (bool, optional) – If True, use the feedback callback to monitor motion execution.

  • motion_check_callback (callable, optional) – Callback used to decide whether motion should be interrupted.

Notes

The constructor subscribes to the controller status topic, creates the action client, queries the joint names from ROS parameters, and resets the internal goal state.

handle_status_callback(data: actionlib_msgs.msg.GoalStatusArray) → None[source]

Update controller readiness from the latest action-status message.

Parameters:

data (GoalStatusArray) – Action-status message received from the controller.

Notes

The helper marks the controller as ready only when all reported goal statuses are in the SUCCEEDED state.

add_point(positions: ndarray, velocities: ndarray, accelerations: ndarray | None = None, delta_time: float = 0.01) → None[source]

Append a trajectory point to the active goal.

Parameters:

  • positions (JointConfigurationType) – Joint positions of the trajectory point.

  • velocities (JointVelocityType) – Joint velocities of the trajectory point.

  • accelerations (JointAccelerationType, optional) – Joint accelerations of the trajectory point.

  • delta_time (float, optional) – Time offset from the previous point in seconds.

start(max_wait_until_controller_ready: float = 10) → None[source]

Send the currently prepared trajectory goal.

Parameters:

max_wait_until_controller_ready (float, optional) – Maximum time to wait for the controller to become ready before the goal is sent.

Notes

The trajectory header timestamp is forced to zero as a workaround for controllers that may drop the first points when they are stamped in the near future.

callback_wrapper(gh: Any) → None[source]

Wrap the user motion-check callback for action feedback handling.

Parameters:

gh (Any) – Action feedback payload forwarded by the ROS action client.

Notes

The feedback object is not used directly. The wrapper forwards the stored robot instance to _motion_check_callback.

stop() → None[source]

Cancel the currently active trajectory goal.

wait(timeout: float = 10.0) → None[source]

Wait until the active trajectory goal finishes or times out.

Parameters:

timeout (float, optional) – Maximum time to wait in seconds.

result() → Any[source]

Return the action result for the current trajectory goal.

Returns:

Result object returned by the ROS action client.

Return type:

Any

clear() → None[source]

Reset the current trajectory goal and point accumulator.

Notes

The method creates a fresh goal, restores the joint-name list, resets the time tolerance, and clears the accumulated trajectory duration.

Classes

JointTrajectory(controller_ns[, ...])

Helper for ROS FollowJointTrajectory action clients.