# Automatic Design of Collective Behaviors for Robots that Can Display and Perceive Colors
###### Abstract  
Research in swarm robotics has shown that automatic design is an effective approach to realize robot swarms. In automatic design methods, the collective behavior of a swarm is obtained by automatically configuring and fine-tuning the control software of individual robots. In this paper, we present TuttiFruti: an automatic design method for robot swarms that belongs to AutoMoDe--a family of methods that produce control software by assembling preexisting software modules via optimization. The peculiarity of TuttiFruti is that it designs control software for e-puck robots that can display and perceive colors using their RGB LEDs and omnidirectional camera. Studies with AutoMoDe have been so far restricted by the limited capabilities of the e-pucks. By enabling the use of colors, we significantly enlarge the variety of collective behaviors they can produce. We assess TuttiFruti with swarms of e-pucks that perform missions in which they should react to colored light. Results show that TuttiFruti designs collective behaviors in which the robots identify the colored light displayed in the environment and act accordingly. The control software designed by TuttiFruti endowed the swarms of e-pucks with the ability to use color-based information for handling events, communicating, and navigating. s 2020 10 4654 [topsep=0 pt]  
communication-based behaviors [14] and are more robust to the so-called reality gap [8; 15], that is, the possibly subtle but unavoidable differences between reality and the simulation models used in the design process. In this paper, we present TuttiFrutti: a method for the automatic design of swarms of e-pucks (extended with an omnidirectional vision turret [16]) that can display and perceive colors. TuttiFrutti designs control software for the individual robots in the swarm by selecting, tuning, and assembling preexisting software modules into probabilistic finite state machines. TuttiFrutti is an instance of AutoMoDe [8]--a family of modular methods for the realization of robot swarms. TuttiFrutti differentiates from previous instances of AutoMoDe by enabling the production of control software that operates with information expressed in the form of colors. More precisely, TuttiFrutti is intended to solve classes of missions in which robots shall act according to colors displayed by objects in their environment and/or their peers. With TuttiFrutti, we significantly enlarge the variety of collective behaviors that can be obtained by AutoMoDe. The study we present in this paper is framed within the tenets of the automatic off-line design of robot swarms, as recently defined by [PERSON] et al. [17]: (i) TuttiFrutti is not intended to solve a specific design problem but rather a class thereof, without the need to undergo any problem-specific modification or adjustment; (ii) once a design problem is specified, human intervention is not provided for in any phase of the design process. In our research, we address the following questions: Is TuttiFrutti capable of deciding whether a color displayed in the environment provides information useful to accomplish a mission? Can TuttiFrutti produce collective behaviors that exhibit color-based communication between robots? Do the extended capabilities of the e-puck increase the difficulty of automatically designing control software for the robot swarm? How could these new resources be used to create more complex missions? We consider a model of the e-puck that can use its RGB LEDs for emitting color signals, and its omnidirectional vision turret [16] for detecting robots or other objects that display colors in the environment. We conduct our study to demonstrate that e-pucks that display and perceive colors enable the automatic design of collective behaviors with event-handling, communication and navigation properties. As a proof of concept, we assess TuttiFrutti in three missions in which colors displayed in the environment play a different role: stop, aggregation, and foraging.