Prolog planner for UR5 pick and place

Project for my bachelor degree at the University of Trento A.Y.2022/2023

Developed by:
De Martini Davide

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• Project Description
• Project Structure
• Requirements
  • PROLOG ONLY
  • PROLOG + ROS SIMULATION
• Installation
  • PROLOG ONLY
  • PROLOG + ROS SIMULATION
• Running
  • PROLOG ONLY
  • PROLOG + ROS SIMULATION
• Thanks to

Project Description

The goal of this project was to develop a Prolog Task planner for performing pick and place tasks. The main task is to build a tower with a "user defined" height. At first a prolog program block_world.pl was created. Then it was wrapped inside a ROS node for communicating to the robot.

Project Structure

The main folder is:

• prolog_project it contains the ROS node (motion node and planner node)
  • scripts: Contains the two node plus the utilities
  • msg: Contains the .msg file for ROS communication

block_world.pl is the prolog file, the core of this project.

python_node_poc.py is a simple proof of concept for the pyswip wrapper for prolog

Requirements

For install the requirements I suggest to follow the Installation section.

PROLOG ONLY

For the prolog only version you will only need the SWI Prolog interpeter.

PROLOG + ROS SIMULATION

For the ROS simulation you will need:

• SWI Prolog interpeter
• ROS noetic
• Python verion >= 3.8
• Locosim framework for simulating the UR5.
• Pyswip

Installation

I reccomend to use Ubuntu 20.04 (I used it for developing the project)

PROLOG ONLY

1. For testing the prolog only version at first install the prolog interpreter SWI Prolog. Installation is the following:

   sudo apt-add-repository ppa:swi-prolog/stable
   sudo apt update
   sudo apt install swi-prolog

2. Clone the project wherever you want

   git clone https://github.com/davidedema/prolog_planner.git

3. Load the file with the swipl interpeter

   cd ~/prolog_planner
   swipl block_world.pl

PROLOG + ROS SIMULATION

1. Follow the prolog installation (only step 1 and 2)
2. Install Pyswip

   pip3 install git+https://github.com/yuce/pyswip@master#egg=pyswip

3. Follow the locosim repository for installing ROS and the UR5 simulation
4. Clone this repository inside ~/ros_ws/src

   git clone https://github.com/davidedema/prolog_planner
   

5. Build the project

   cd ~/ros_ws
   catkin_make install
   source install/setup.bash
   

Running

PROLOG ONLY

In order to create a pillar use the pillar/7 rule. This needs 7 parameters in input:

• x: x coord for the pillar generation
• y: y coord for the pillar generation
• z: z coord for the pillar generation
• High: Pillar High
• Width: Pillar width
• Depth: Pillar depth
• Actions: Our "output" variable

It will return in the output variable the plan that the robot has to execute in order to perform the pillar creation

For example, let's create the pillar with height = 0.1 at (1, 0, 0)

pillar(1,0,0,0.1,0.05,0.05,A).

PN: In prolog every instruction finish with the dot '.'.

After the instruction we will see an output like this:

?- pillar(1,0,0,0.1,0.05,0.05,A).
A = [rotate(b1, 0.27, -0.26, 0.685, 1), move(b1, 0.27, -0.26, 0.685, 1, 0, 0), move(b2, 0.41, -0.26, 0.685, 1, 0, -0.05), link(b2, b1)] .

We can see the freshly created pillar with the instruction listing(block/13).

PROLOG + ROS SIMULATION

Before running the simulation we need to setup some parameters for the robot:

• ENABLE GRIPPER
  • Edit the file /locosim/robot_control/lab_exercises/lab_palopoli/params.py at line 44 and 45: set the two flags at True. Now the 2 finger gripper and grasping plugin is enabled.
• SETUP THE WORLD
  • Copy the X1-Y1-Z2 folder (is the folder model) inside /locosim/ros_impedance_controller/worlds/models/
  • Overwrite the world file: /locosim/ros_impedance_controller/worlds/tavolo.world with the tavolo.world inside this repository
• After these two changes run:

  cd ~/ros_ws
  catkin_make install
  source install/setup.bash
  

Now you are able to run the simulation with the command:

python3 -i ~/ros_ws/src/locosim/robot_control/lab_exercises/lab_palopoli/ur5_generic.py

To enable the two nodes (motion and prolog planner) run these two commands in two separated terminal

python3 -i ~/ros_ws/src/prolog_project/prolog_project/scripts/motion_node.py
python3 -i ~/ros_ws/src/prolog_project/prolog_project/scripts/prolog_node.py

Thanks to

• Luigi Palopoli (Thesis Supervisor): luigi.palopoli@unitn.it
• Marco Roveri (Supervisor): marco.roveri@unitn.it
• Edoardo Lamon (Supervisor): edoardo.lamon@unitn.it
• Enrico Saccon (Supervisor): enrico.saccon@unitn.it