Executor

The Executor module is responsible for requesting a plan to the Planner, and carry it out, calling to the nodes in the client application that implements the actions. While executing each action, it checks the requisites (At Start, At End and Over all, in case of durative Actions). If the requirements are not meet, it cancels the plan execution. It also is responsible for applying the effects of the actions, requesting updates to the Problem Expert.

The main class of Executor is plansys2::ExecutorNode, which is instantiated from executor_node.cpp.

The executions of plans are carried out using ROS2 actions, in particular, plansys2_msgs::action::ExecutePlan. Take note that the goal must be already in the Domain Expert.

ExecutorNode ask for the domain and problem, and ask for a plan to the Planner. For each action in the plan, ExecuterNode creates a plansys2::ActionExecutor. The lifetime of this object is only one action. This object calls the actions implemented in the client appliciation using the ROS2 actions plansys2_msgs::action::ExecuteAction. Each client action implementation can use the class plansys2::ActionExecutorClient to avoid the complexity of managing ROS2 actions.

Using the feedback information from plansys2_msgs::action::ExecuteAction, feedback for plansys2::ExecutorNode is composed and returned to plansys2::ExecutorClient. It contains the current action in the plan and the progress in the currently executing action.

Next graph shows an example of the execution flow:

Actions:

• /execute_plan [plansys2_msgs::action::ExecutePlan]

(in ActionExecutorClient)

• /${ACTION_NAME}[plansys2_msgs::action::ExecuteAction]

Services:

• /executor/get_ordered_sub_goals [plansys2_msgs::srv::GetOrderedSubGoals]

Subscribed topics:

(in ActionExecutor)

• /problem_expert/update_notify [std_msgs::msg::Empty]

Parameters:

(in ExecutorNode)

• ~/action_timeouts/actions [list of strings]

  • List of actions which have duration overrun percentages specified.

• ~/action_timeouts/[ACTION_NAME]/duration_overrun_percentage [double]

  • Defines the allowable time overrun of an action based on a percentage of the predicted plan duration. For example, if the plan predicts that an action should take 1000 secs and a duration overrun percentage of 20% is specified, then the action should be halted if the actual duration exceeds 1200 secs.

executor:
  ros__parameters:
    action_timeouts:
      actions: ["move"]
      move:
        duration_overrun_percentage: 20.0

Changelog for package plansys2_executor

1.0.10 (2021-07-03)

• Minor update
• Fix tests
• Fix rate conversions
• Add rate parameter
• Remove node parameter in client constructors
• ros2-plan-msg: Passing plan to executor to add further separation between plan creation and plan execution.
• Suggestion for #118
• pddl-tree-messages: Performing some minor cleanup.
• pddl-tree-messages: Using explicit specifier for single parameter constructors in plansys2_core/Types.hpp.
• pddl-tree-messages: Replacing user access function calls with shorter versions where possible.
• pddl-tree-messages: Adding predicate user access functions to problem expert client.
• pddl-tree-messages: Adding predicate user access functions to problem expert client.
• pddl-tree-messages: Applying ament uncrustify.
• pddl-tree-messages: Updating addInstance and removeInstance calls to use helper classes.
• pddl-tree-messages: Reverting change to log statement severity.
• pddl-tree-messages: Removing a couple unnecessary includes.
• pddl-tree-messages: Merging master and resolving conflicts.
• action-timeout-clean: Renaming test behavior tree.
• Using custom behavior tree to enable action timeouts.
• pddl-tree-messages: Merging upstream master and resolving conflicts.
• pddl-tree-messages: Using ROS messages to define the PDDL construct trees.
• Adding action execution status (as color changes) to the plan dotgraph. Adding legend to plan dotgraph, adding node params for dotgraph legend and printing plan graph to terminal.
• Fix tests and linting
• linting
• Configurable action BT
• Configurable BT Action
• Reducing log message severity because lack of a plan isn\'t necessarily an error.
• Reduce debug output
• Plansys2_tests package
• Adding unit test for getOrderedSubGoals.
• Add GetOrderedSubGoals service to Executor, allowing executor clients to get the order in which sub-goals will be completed by the current plan.
• Update version
• Contributors: Alexander Xydes, Francisco Mart