pose_behavior.md

Pose Behavior

The "Pose" transition makes use a StateMachine container with three states, including the InputState discussed in "Rotate" and TeleportAbsoluteState first discused in "Home".

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User Input

This demonstration presumes you have started the input_action_server on the OCS computer:

ros2 run flexbe_input input_action_server

This input_action_server interacts with the InputState. This simple input_action_server demonstration is intended to provide basic functionality for limited primitive inputs such as numbers or list/tuples of numbers.

See Complex Data Input for more information about the InputState usage.

Note: The InputState makes use of the pickle module, and is subject to this warning from the Pickle manual:

Warning The pickle module is not secure against erroneous or maliciously constructed data. Never unpickle data received from an untrusted or unauthenticated source.

If using the InputState it is up to the user to protect their network from untrusted data.

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The InputState remaps its userdata data key to provide the pose key used by the TeleportAbsoluteState.

In the InputState configuration, we

• specify result type 3 (BehaviorInput.Goal.REQUEST_3D) to request a list (or tuple) of three numbers from the user,
• specify the prompt message for the user interface
• specify a timeout value for the input_action_server to become available
• specify the output userdata key mapping (e.g. pose in this case)

Note: For 2D, 3D, 4D request types, we accept list (e.g. '[1., 2, 3]'), tuple (e.g. '(1., 2, 3)'), or just a comma separated string of numbers (e.g. '1., 2, 3') of the appropriate length as input on the UI.

Note: The InputState timeout refers to waiting for the action server to become available. The system will wait indefinitely for the operator to respond.

The TeleportAbsoluteState extracts the pose data from the userdata and makes the non-blocking service call as described in "Home".

        if 'pose' in userdata and isinstance(userdata.pose, (list, tuple)):
            try:
                self._srv_request.x = float(userdata.pose[0])
                self._srv_request.y = float(userdata.pose[1])
                self._srv_request.theta = 0.0
                if len(userdata.pose) == 3:
                    # setting angle is optional
                    self._srv_request.theta = float(userdata.pose[2])

                Logger.localinfo(f"Using position = ({self._srv_request.x:.3f}, {self._srv_request.y:.3f}), "
                                 f"angle={self._srv_request.theta:.3f} radians from userdata")

            except Exception as exc:  # pylint: disable=W0703
                Logger.logwarn(f"{self._name}: Invalid pose userdata {userdata.pose} - "
                               f"needs list of 2 or 3 numbers!\n  {type(exc)} - {exc}")
                self._return = 'failed'
                return
        else:
            Logger.localinfo(f"Using position = ({self._srv_request.x:.3f}, {self._srv_request.y:.3f}), "
                             f"angle={self._srv_request.theta:.3f} radians")

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This example discussed the use of InputState to provide more complex operator data to the onboard behavior in collaborative autonomy. See "Rotate" and "Home" discussions for more details about the individual states, and "Eight" for more discussion of the StateMachine container.

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