Terminal Usage

Overview

The terminal is an application that allows the interaction with PlanSys2 to test or monitor its operation. It is not essential to use PlanSys2 since your application is expected to manage the plans’ knowledge and execution automatically. Still, it is useful and convenient to get to know the terminal in these first tutorials.

This tutorial shows how to use the terminal and the main commands and is also a good starting point for working with PlanSys2.

Tutorial Steps

0- Requisites

Follow the same process as in Getting Started for installing PlanSys2.

We will use a test PDDL domain. If you do not know what PDDL is, it is recommended to take a look at one of these links first:

Download a simple PDDL domain for this tutorial. Later, you could reproduce the steps of this tutorial with your own domain:

wget -P /tmp https://raw.githubusercontent.com/IntelligentRoboticsLabs/ros2_planning_system_examples/master/plansys2_simple_example/pddl/simple_example.pddl

1- Launch PlanSys2

PlanSys2 can be launched with two different launchers that implement two different execution forms: distributed or monolithic. In distributed form, each component of PlanSys2 runs in a different process, and to launch it, each component’s launchers are called in cascade. In monolithic form, all components are released in the same process.

In the first steps with PlanSys2, it is irrelevant how we execute it to choose any of them. Both launchers have a parameter where the PDDL domain file to use is specified.

ros2 launch plansys2_bringup plansys2_bringup_launch_distributed.py model_file:=/tmp/simple_example.pddl

If all went well, all components of PlanSys2 will have been launched and awaits requests.

2- Execute PlanSys2 terminal

The PlanSys2 terminal is executed by entering the following command in another terminal:

ros2 run plansys2_terminal plansys2_terminal

At that moment, an interactive shell will open in which we can enter commands. We can use the up and down arrows to navigate between the commands already entered or use Ctrl-R as in the shell to search for commands. It also has autocompletion with the Tab key. You can quit anytime typing “quit” or pressing Ctrl-D.

It should be noted that the state of the system is at PlanSys2 components, not in the terminal. You can close and reopen (or even use several terminals), and the system’s state persists. If you want to reset the system, press Ctrl-C in the terminal where you launched PlanSys2, and relaunch it.

ROS2 Planning System console. Type "quit" to finish
>

2- Interactive session

  1. The first thing is to check the domain that is being used. In the PlanSys2 terminal window type:

get domain

( define ( domain simple )
( :requirements :strips :adl :typing :durative-actions :fluents )
( :types
  robot - object
  room - object
)
( :predicates
  ( robot_at ?robot0 - robot ?room1 - room )
  ( connected ?room0 - room ?room1 - room )
  ( battery_full ?robot0 - robot )

  ...

  1. To see what types of instances the model contains, type:

get model types
Types: 2
          robot
          room

  1. Use other variations of get model to get more information of the domain:

get model actions
Actions: 0
  move (durative action)
  askcharge (durative action)
  charge (durative action)

get model predicates
Predicates: 5
  robot_at
  connected
  battery_full
  battery_low
  charging_point_at

  1. It is also possible to get the details of a predicate or an action:

get model predicate robot_at
Parameters: 2
 robot - ?robot0
 room - ?room1

get model action move
Type: durative-action
Parameters: 3
 ?0 - robot
 ?1 - room
 ?2 - room
AtStart requirements: (and (connected ?1 ?2)(robot_at ?0 ?1))
OverAll requirements: (and (battery_full ?0))
AtEnd requirements:
AtStart effect: (and (not (robot_at ?0 ?1)))
AtEnd effect: (and (robot_at ?0 ?2))

5. So far, we have seen how to inspect the model, which remains unchanged during the execution of PlanSys2. We could say that it is the static part of the planning ingredients. The other ingredient is the problem, which contains the instances, grounded (not generic as in the domain, but already with instances) predicates, and goals. We will check that it is empty for now.

get problem instances
Instances: 0

get problem predicates
Predicates: 0

get problem goal
Goal:

6. First, let’s add instances. If you analyze the domain, we want a robot to be able to move between rooms. For this, the robot must have a battery, and the rooms must be connected. Therefore, we need rooms and a robot:

set instance leia robot
set instance entrance room
set instance kitchen room
set instance bedroom room
set instance dinning room
set instance bathroom room
set instance chargingroom room

If no errros, these instances can be checked by typing:

get problem instances
Instances: 7
 leia    robot
 entrance        room
 kitchen room
 bedroom room
 dinning room
 bathroom        room
 chargingroom    room

  1. To add predicates, we type:

set predicate (connected entrance dinning)
set predicate (connected dinning entrance)

set predicate (connected dinning kitchen)
set predicate (connected kitchen dinning)

set predicate (connected dinning bedroom)
set predicate (connected bedroom dinning)

set predicate (connected bathroom bedroom)
set predicate (connected bedroom bathroom)

set predicate (connected chargingroom kitchen)
set predicate (connected kitchen chargingroom)

set predicate (charging_point_at chargingroom)
set predicate (battery_low leia)
set predicate (robot_at leia entrance)

Let’s check it:

get problem predicates
Predicates: 13
(connected entrance dinning)
(connected dinning entrance)
(connected dinning kitchen)
(connected kitchen dinning)
(connected dinning bedroom)
(connected bedroom dinning)
(connected bathroom bedroom)
(connected bedroom bathroom)
(connected chargingroom kitchen)
(connected kitchen chargingroom)
(charging_point_at chargingroom)
(battery_low leia)
(robot_at leia entrance)

8. The predicates and instances previously added to the problem are the knowledge used to generate the plan. Also, we need to have an objective of our planning, which is a logic expression to end up being true. It is usually a predicate that we want to add to the knowledge:

set goal (and(robot_at leia bathroom))

  1. At this time we can ask that the plan be calculated to obtain this goal:

get plan
plan:
0        (askcharge leia entrance chargingroom)  5
0.001    (charge leia chargingroom)      5
5.002    (move leia chargingroom kitchen)        5
10.003   (move leia kitchen dinning)     5
15.004   (move leia dinning bedroom)     5
20.005   (move leia bedroom bathroom)    5

To create the plan, the first thing to do is generate two files: `/tmp/domain.pddl` and `/tmp/problem.pddl`. You can check that they are there from the last planning. In fact, we can run the planner directly by typing in a shell in another terminal:

ros2 run popf popf /tmp/domain.pddl /tmp/problem.pddl

  1. We can also delete instances, predicates or the goal:

remove instance leia
remove predicate (connected entrance dinning)
remove goal

11. What we will not be able to do is execute the plan (we would do it with the run command) because there is no node running right now that implements the domain actions. We will see that in the next tutorial.