Swarm-Enabling Technology for Multi-Robot Systems The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Chamanbaz, Mohammadreza, David Mateo, Brandon M. Zoss, Grgur Tokić, Erik Wilhelm, Roland Bouffanais, and Dick K. P. Yue. “Swarm- Enabling Technology for Multi-Robot Systems.” Frontiers in Robotics and AI 4 (April 19, 2017). As Published http://dx.doi.org/10.3389/FROBT.2017.00012 Publisher Frontiers Media SA Version Final published version Citable link http://hdl.handle.net/1721.1/118127 Terms of Use Creative Commons Attribution 4.0 International License Detailed Terms http://creativecommons.org/licenses/by/4.0/ TECHNOLOGY REPOrt published: 19 April 2017 doi: 10.3389/frobt.2017.00012 Swarm-Enabling Technology for Multi-Robot Systems Mohammadreza Chamanbaz 1, David Mateo 1, Brandon M. Zoss 2, Grgur Toki´c 2, Erik Wilhelm1, Roland Bouffanais1,2* and Dick K. P. Yue 2 1 Applied Complexity Group, Singapore University of Technology and Design, Singapore, Singapore, 2 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA Swarm robotics has experienced a rapid expansion in recent years, primarily fueled by specialized multi-robot systems developed to achieve dedicated collective actions. These specialized platforms are, in general, designed with swarming considerations at the front and center. Key hardware and software elements required for swarming are often deeply embedded and integrated with the particular system. However, given the noticeable increase in the number of low-cost mobile robots readily available, practitioners and hobbyists may start considering to assemble full-fledged swarms by minimally retrofitting such mobile platforms with a swarm-enabling technology. Here, we report one possible embodiment of such a technology—an integrated combination of hardware and soft- ware—designed to enable the assembly and the study of swarming in a range of gener- al-purpose robotic systems. This is achieved by combining a modular and transferable software toolbox with a hardware suite composed of a collection of low-cost and off-the- Edited by: shelf components. The developed technology can be ported to a relatively vast range of Tansel Yucelen, robotic platforms—such as land and surface vehicles—with minimal changes and high University of South Florida, USA levels of scalability. This swarm-enabling technology has successfully been implemented Reviewed by: Heiko Hamann, on two distinct distributed multi-robot systems, a swarm of mobile marine buoys and a University of Paderborn, Germany team of commercial terrestrial robots. We have tested the effectiveness of both of these Jonathan M. Aitken, distributed robotic systems in performing collective exploration and search scenarios, University of Sheffield, UK as well as other classical cooperative behaviors. Experimental results on different swarm *Correspondence: Roland Bouffanais behaviors are reported for the two platforms in uncontrolled environments and without [email protected] any supporting infrastructure. The design of the associated software library allows for a seamless switch to other cooperative behaviors—e.g., leader–follower heading consen- Specialty section: This article was submitted sus and collision avoidance, and also offers the possibility to simulate newly designed to Multi-Robot Systems, collective behaviors prior to their implementation onto the platforms. This feature greatly a section of the journal facilitates behavior-based design, i.e., the design of new swarming behaviors, with the Frontiers in Robotics and AI possibility to simulate them prior to physically test them. Received: 13 January 2017 Accepted: 28 March 2017 Keywords: swarm robotics, distributed multi-robot systems, cooperative control, flocking, distributed communication Published: 19 April 2017 Citation: Chamanbaz M, Mateo D, Zoss BM, 1. INTRODUCTION Toki ´c G, Wilhelm E, Bouffanais R and Yue DKP (2017) Swarm-Enabling A swarm robotics system consists of autonomous robots with local sensing and communication Technology for Multi-Robot Systems. capabilities, lacking centralized control or access to global information, situated in a possibly unknown Front. Robot. AI 4:12. environment performing a collective action (Brambilla et al., 2013). Based on this definition, one can doi: 10.3389/frobt.2017.00012 easily distinguish swarm robotics systems from other multi-robot approaches (Iocchi et al., 2001). Frontiers in Robotics and AI | www.frontiersin.org 1 April 2017 | Volume 4 | Article 12 Chamanbaz et al. Swarm-Enabling Technology for Multi-Robot Systems It is not uncommon for multi-robot systems to lack some form original experiments. Our proposed technological solution aims of decentralization at the computation, communication, and/or at filling this gap by offering a platform-agnostic framework—an operation levels (Vásárhelyi et al., 2014). Swarm robotics systems integrated combination of a hardware suite with a software layer— are often inspired by natural systems in which large numbers easily portable to a host of hardware platforms and facilitating the of simple agents perform complex collective behaviors— implementation of various swarm algorithms, while reducing the e.g., schooling fish, flocking birds—through repeated local inter- burden associated with platform-dependent interfacing. actions between themselves and their environment (Bouffanais, Here, we report a unified platform-agnostic hardware/soft- 2016). The swarm robotics design paradigm allows a multi-robot ware tool capable of: (i) assembling and transforming a collection system to overcome the aforementioned limitations (local sens- of basic mobile robots into full-fledged swarms and (ii) achieving ing, lack of centralized control, etc.) and operate autonomously versatile swarming behaviors using an easily programmable soft- in a coordinated fashion. ware library. The modular nature of both the hardware suite and One main challenge in artificial swarming is the design of software layer allows for possible evolution, upgrade, and exten- systems that, while maintaining decentralized control, have sion of the technology independently from the specifications of agents capable of (i) acquiring local information through sens- the mobile platform. We present some preliminary results vali- ing, (ii) communicating with at least some subset of agents, and dating the technology on two vastly different swarming systems. (iii) making decisions based on the dynamically gathered sensed This swarm-enabling technology is a combination of hardware/ data. While decentralization denies the agents the benefits of a software that allows a wide range of multi-robot platforms to large central computation and/or communication hub, it affords perform versatile and responsive swarming. This is achieved the system robustness. The system is thus capable of perform- by providing each agent with an additional interface hardware ing global collective actions under a wide range of group sizes built from low-cost and off-the-shelf components, which are (scalability), despite the possible sudden loss of multiple agents integrated with a specifically developed general purpose software (robustness), and under unknown and dynamic circumstances library. We believe that this technology that decouples swarming (flexibility) (Brambilla et al., 2013). considerations from robotics ones could be of interest to both There have been a number of notable efforts to design robotic researchers and educators primarily interested in the study of swarms. The kilobit (Rubenstein et al., 2012), e-puck (Mondada artificial swarming. et al., 2009), Swarm-bots (Dorigo et al., 2004), marXbot (Bonani The software—written in Python, but also tested in++ C —is et al., 2010), Alice (Caprari and Siegwart, 2005), iAnt (Hecker et al., designed in a modular way so as to make the technology portable 2012), Scarab (Michael et al., 2008), I-Swarm (Woern et al., between platforms as seamlessly as possible, i.e., with minimal 2006), r-one (McLurkin et al., 2013), and Pi Swarm (Hilder hardware/software changes. To assess the effectiveness of the et al., 2014) are only a few examples of different swarm/distributed proposed technology, we used it on two different platforms oper- multi-robot platforms that have been developed. Each platform ating in uncontrolled environments: a differential drive robot and explores the potential and feasibility of a few aspects of swarming a water surface platform (sensing mobile buoy). Furthermore, and not all of them fulfill all requirements of a robotic swarm a number of collective behaviors such as heading consensus, system—according to the definition above—or are capable of perimeter defense, and collective marching are tested on these operating in real and uncontrolled environments without any platforms, thereby confirming the versatility of our swarm- supporting infrastructure. The technological advances imple- enabling technology. mented on each platform make it challenging to port to others due to the specificities of each robot. Indeed, these platforms have 2. MATERIALS AND METHODS been conceived with swarming considerations at the core of their design. As a consequence, the central components necessary to To enable swarming, it is essential to achieve distributed com- enable swarming are fully integrated inside the robots. Moreover, munication and decentralized decision-making (Hamann et al., the software layer is often highly dependent