IRIDIA - Supplementary Information (ISSN: 2684-2041)

Supplementary material for the paper:

Phormica: Photochromic Pheromone Release and Detection System for Stigmergic Coordination in Robot Swarms

Muhammad Salman, David Garzón Ramos, Ken Hasselmann, and Mauro Birattari (July 2020)

Table of Contents
  1. Abstract
  2. Demonstrative Videos
  3. Code, Experimental Data, and Datasheets


Stigmergy is a form of indirect communication and coordination in which agents modify the environment to pass information to their peers. In nature, animals use stigmergy by, for example, releasing pheromone that conveys information to other members of their species. A few systems in swarm robotics research have replicated this process by introducing the concept of artificial pheromone. In this paper, we present Phormica, a system to conduct experiments in swarm robotics that enables a swarm of e-puck robots to release and detect artificial pheromone. Phormica emulates pheromone-based stigmergy thanks to the ability of robots to project UV light on the ground, which has been previously covered with a photochromic material. As a proof of concept, we test Phormica on three collective missions in which robots act collectively guided by the artificial pheromone they release and detect. Experimental results indicate that a robot swarm can effectively self-organize and act collectively by using stigmergic coordination based on the artificial pheromone provided by Phormica.

Demonstrative Videos

Below we show demonstrative videos of experiments on three different collective missions: (1) COVERAGE, (2) FORAGING, and (3) TASKING. For each collective mission, we perform two experiments: (i) the robot swarm performs the collective mission without using artificial pheromone ; and (ii) the robot swarm takes advantage of Phormica and uses artificial pheromone.


The arena is divided into small cells to make a mesh. This mesh has 128 quadrilateral cells and eight triangular cells—see Figure 4. A robot swarm must visit each quadrilateral cell at least once in one minute of the experiment duration.



All videos of 20 runs of Basic-COVERAGE and Phormica-COVERAGE.


The arena contains two source areas (black circles) and a nest (gray area). A green light is placed behind the nest to help the robots to navigate. In this idealized version of foraging, a robot is deemed to retrieve an object when it enters a source and then the nest. The goal of the swarm is to retrieve as many objects as possible.



All videos of 20 runs of Basic-FORAGING and Phormica-FORAGING.


Tasking is a mission in which a robot swarm must perform a number of abstract tasks in a manufacturing facility. Robots perform a task in workstations that are indicated by gray patches on the floor and LED blocks displaying the color green.



All videos of 20 runs of Basic-TASKING and Phormica-TASKING.

Code, Experimental Data, and Datasheets

The instances of control software, hardware configuration, and the prominent behaviors of all experiments are available for download here:

The information regarding the material used in Artificial Pheromone Environment is available here: