Supplementary material for the paper

The TAM: abstracting complex tasks
in swarm robotics research

Arne Brutschy, Lorenzo Garattoni, Manuele Brambilla, Gianpiero Francesca, Giovanni Pini, Marco Dorigo, and Mauro Birattari

Last change: November 11th, 2014

Submitted to the Journal of Swarm Intelligence
Related IRIDIA Technical Report: TR/IRIDIA/2010-015

Table of Contents
  1. Introduction
    1. Note on versions
    2. Abstract of the paper
    3. Demo videos
  2. The TAM
    1. License
    2. Photos
    3. Electronics - schematics
    4. Electronics - PCBs
    5. Plastic body - plans
    6. Bill of materials
    7. Extension and reproduction
  3. Reliability experiments
    1. TAM visibility
    2. 2 TAM task experiment
    3. 50 TAM task experiment
  4. Proof-of-concept demonstration
    1. Full Petri net
    2. Videos
    3. Detailed data

1. Introduction

This page provides multimedia and technical information for the TAM, a device used for task abstraction in experiments involving the e-puck robot. For further technical information, please see the GitHub page of the TAM.

The paper has been submitted to the Journal of Swarm Intelligence.

1.1 Note on versions

Please note that this page gives the details for the prototype version of the TAM as used for the experiments in the paper (version 5, revision D). The information on this page will remain constant, even if there is a new version of the TAM.

For the latest version of the TAM including all CAD files, soft- and firmware, central controlling framework etc., please see the GitHub page of the TAM.

Current version: version 5, revision D

1.2 Abstract of the paper

Research in swarm robotics focuses mostly on how robots interact and cooperate to perform tasks, rather than on the details of task execution. As a consequence, researchers often consider abstract tasks in their experimental work. For example, foraging is often studied without physically handling objects: the retrieval of an object from a source to a destination is abstracted into a trip between the two locations—no object is physically transported. Despite being commonly used, so far task abstraction has only been implemented in an ad-hoc fashion.

In this paper, we propose a new approach to abstracting complex tasks in swarm robotics research. This approach is based on a physical device called the task abstraction module (\TAM) that abstracts single-robot tasks to be performed by an e-puck robot. A complex multi-robot task can be abstracted using a group of TAMs by first modeling the task as the set of its constituent single- robot subtasks and then abstracting each subtask with a TAM. We present a collection of tools for modeling complex tasks, and a framework for controlling a group of TAMs such that the behavior of the group implements the model of the task. The TAM enables research on cooperative behaviors and complex tasks with simple, cost-effective robots such as the e-puck—research that would be difficult and costly to conduct using specialized robots or ad-hoc task abstraction.

We demonstrate how to abstract a complex task with multiple TAMs in an example scenario involving a swarm of e-puck robots.

Keywords: Swarm robotics, task allocation, task partitioning, swarm intelligence, robotics, e-puck

1.3 Demo videos


2. The TAM

This section gives the technical details of the TAM.

2.1 License

The work presented in this section is licensed under a

Creative Commons License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.


2.2 Photos

Figure 2.2a: TAM with simple e-puck Figure 2.2a: The TAM with an e-puck that has no extensions. The sensors relevant to the TAM are the forward facing camera for the detection of the TAM and the IR transceiver for communication with the TAM.

Figure 2.2b: TAM with complex e-puck Figure 2.2b: The TAM with an e-puck that has several extensions: the range and bearing sensor, the embedded computer running Linux, and the omni-directional camera. The TAM is compatible with all these extensions; the omni-directional camera is used to detect the TAM instead of the forward facing camera, if present.

Figure 2.2c: TAM back view Figure 2.2c: The TAM seen from the back. The TAM features a 2.4 GHz IEEE 802.15.4 mesh networking module that allows it to exchange data with other TAMs and the researcher's workstation. The battery is the same one used for the e-puck robot, which eases charging and handling of the batteries during the course of an experiment.


2.3 Electronics - schematics

The TAM consists of three boards: the mainboard in the middle, which holds the main electronics (micro-controller, radio transceiver, battery etc.). The left board and right board, on the two sides of the TAM (seen from the front). Below, you can see the schematics of the three boards.

Figure 2.3a: Main board schematics - sheet 1 Figure 2.3a: Main board schematics - sheet 2 Figure 2.3a: Main board schematics - sheet 3 Figure 2.3a: Main board schematics - sheet 4 Figure 2.3a: Main board schematics - sheet 5 Figure 2.3a: The schematics of the main board, including the main electronics (micro-controller, radio transceiver, battery etc.).

Figure 2.3b: Left board schematics Figure 2.3b: The schematics of the left board, with one RGB LED, the proximity sensor and the IR LED for the light barrier.

Figure 2.3c: Right board schematics Figure 2.3c: The schematics of the right board, with one RGB LED and an IR transistor for the light barrier.

Download as PDF


2.4 Electronics - PCBs

Below, you can see the three PCBs.

Figure 2.4a: Main board Figure 2.4a: The main board, including the main electronics (micro-controller, radio transceiver, battery etc.).

Figure 2.4b: Left board Figure 2.4b: The left board, with one RGB LED, the proximity sensor and the IR LED for the light barrier.

Figure 2.4c: Right board Figure 2.4c: The right board, with one RGB LED and an IR transistor for the light barrier.

Download as PDF

Download as Gerbers


2.5 Plastic body - plans

Figure 2.5: TAM exploded view Figure 2.5: TAM, exploded view.

The TAM consists of four parts, machined from POM plastic: the two sides, the top bracket, and the diffuser. Below, we show only the isometric view on these four parts. Detailed plans can be downloaded compressed as a zip.

Figure 2.5a: Shell, left part Figure 2.5a: TAM shell, left part.

Figure 2.5b: Shell, right part Figure 2.5b: TAM shell, right part.

Figure 2.5c: Shell, top part Figure 2.5c: TAM shell, top part.

Figure 2.5d: Diffuser Figure 2.5d: TAM shell, diffuser.

Figure 2.5d: Left side bumper Figure 2.5d: TAM shell, bumper (left side).

Figure 2.5d: Right side bumper Figure 2.5d: TAM shell, bumper (right side).

Download as PDF

The ZIP contains all plans necessary to produce the TAM shell by a professional service.


2.6 Bill of materials

Download as PDF

Download as XLS


2.7 Extension and reproduction

Figure 2.7: extension connector Figure 2.7: Extension connector of the TAM.

The philosophy of the TAM follows the extensibility of Arduino and of the e-puck. To this end, the TAM features an extension connector that allows researchers to extend its capabilities. Additionally to supplying power, the extension connector provides 10 input/output channels: 2 channels for PWM LED control, 4 digital channels and 4 analog channels. The variety of channels enables a wide range of possible extensions. An example of a possible extension is a light sensor that allows to model the day/night cycle of a colony by changing the behavior of a group of TAMs depending on the ambient light.

The license mentioned above allows others to modify and reuse the design as long as it remains open source. Additionally, the license grants the rights to produce the TAM commercially. All electronic components are common and easily sourceable from distributors all over the world. Apart from the electronic components, all parts can be produced in-house given hobbyist-level equipment. Nevertheless, we advise that the PCBs and the plastic parts of the body are produced by a professional service. The cost of the TAM is relatively low provided that final assembly is done in-house: the total cost of a single TAM is 140 EUR/TAM for a quantity of 50 TAMs (with the electronic components at ~60 EUR, the plastic parts for the body at ~60 EUR, and PCB including assembly at ~20 EUR).

Download as PDF



3. Reliability experiments

This section gives supplementary data for the TAM reliability experiments.

3.1 TAM visibility

Figure 3.1: TAM visibility Figure 3.1: Visibility of the TAM when using an e-puck equipped with the omni-directional camera extension. The e-puck has been placed with random orientations. The asymmetric field of view results most likely from imperfections in the mirror of the omni-directional camera extension.

To obtain this image, an e-puck has been placed on a 10cm x 10cm grid that extends over a square meter. If the e-puck was able to perceive the TAM (located at the bottom of the image), it lit up its LEDs in red. Each placement has been recorded using an overhead camera, the resulting 100 images have been overlaid to produce this image. In the image, the ground has been edited in order to increase readability.


3.2 Experiment 1 (2 interrelated TAMs)



In this experiment, a single e-puck robot has to perform an complex task. The complex task consists of two interrelated single-robot subtasks: the green task has to be executed before the blue task. The experiment is terminated once the battery of the robot is depleted. In the experiment shown in this video, the resulting runtime is 40 minutes, during which the robot executes a total of 48 complex tasks (hence, 96 single-robot tasks). No task failures occur during the runtime of the experiment.

Download data


3.3 Experiment 2 (50 non-interrelated TAMs)



In this experiment, two e-puck robots have to perform atomic tasks of two types: green and blue. At the beginning of the experiment, a total of 50 tasks are available (randomly chosen from the two task types). Tasks successfully performed do not become available anew. The experiment terminates after all tasks have been executed. In the experiment shown in this video, the resulting runtime is approximately 17 minutes.

Download data




4. Proof-of-concept demonstration

This section gives supplementary data for the proof-of-concept demonstration.

4.1 Full Petri net of the low-level model

Figure 4.1: Full Petri net Figure 4.1: Full Petri net of the low-level model of the example task t_disaster. The image is a screen capture of the low-level model reproduced in PIPE (Platform Independent Petri net Editor). PIPE allows one to simulate a Petri net. The PIPE project file used to simulate the low-level model of the example task can be found below. Note that the layout shown is the one produced by PIPE and cannot be freely modified due to limitations of PIPE.

Download as PDF


4.2 Videos

Proof-of-concept demonstration 1



Proof-of-concept demonstration 1: single instance of a complex task consisting of 3 TAMs, 6 e-puck robots.

Proof-of-concept demonstration 2



Proof-of-concept demonstration 2: six instances of a complex task consisting of 3 TAMs (18 TAMs total), 20 e-puck robots.

4.3 Detailed data

This section contains detailed data for the proof-of-concept demonstrations.

Figure 4.3a: Tracking system data Figure 4.1: Tracking system data of demonstration 2. Dots present locations of robots over the course of the demonstration. Darker regions represent higher robot density. The locations of the 6 task instances (TAMs) are clearly visible.

Download data

These ZIP files contain all logs and data taken during demonstration 1 and 2.