%0 Journal Article %J Nature Communications %D 2022 %T Hysteresis stabilizes dynamic control of self-assembled army ant constructions %A Helen McCreery %A Georgina Gemayal %A Ana Pais %A Simon Garnier %A Radhika Nagpal %X Biological systems must adjust to changing external conditions, and their resilience depends on their control mechanisms. How is dynamic control implemented in noisy, decentralized systems? Army ants’ self-assembled bridges are built on unstable features, like leaves, which frequently move. Using field experiments and simulations, we characterize the bridges’ response as the gaps they span change in size, identify the control mechanism, and explore how this emerges from individuals’ decisions. For a given gap size, bridges were larger after the gap increased rather than decreased. This hysteresis was best explained by an accumulator model, in which individual decisions to join or leave a bridge depend on the difference between its current and equilibrium state.This produces robust collective structures that adjust to lasting perturbations while ignoring small, momentary shifts. Our field data support separate joining and leaving cues; joining is prompted by high bridge performance and leaving by an excess of ants. This leads to stabilizing hysteresis, an important feature of many biological and engineered systems. %B Nature Communications %V 13 %G eng %U https://www.nature.com/articles/s41467-022-28773-z %N 1660 %0 Conference Paper %B Intl. Conf. on Swarm Intelligence (ANTS) %D 2022 %T An Approach Based on Particle Swarm Optimization for Inspection of Spacecraft Hulls by a Swarm of Miniaturized Robots %A Bahar Haghighat %A Johannes Boghaert %A Zev Minsky-Primus %A Julia Ebert %A Fanghzheng Liu %A Martin Nisser13th International Conference on Swarm Intelligence (Swarm robotics and swarm %A Ariel Ekblaw %A Radhika Nagpal %B Intl. Conf. on Swarm Intelligence (ANTS) %G eng %0 Thesis %B PhD Thesis, School of Engineering and Applied Sciences (CS), Harvard University. %D 2022 %T Distributed Decision-making Algorithms for Inspection by Autonomous Robot Collectives %A Julia Ebert %B PhD Thesis, School of Engineering and Applied Sciences (CS), Harvard University. %G eng %9 PhD Thesis %0 Journal Article %J Science Robotics %D 2021 %T Implicit coordination for 3D underwater collective behaviors in a fish-inspired robot swarm %A Florian Berlinger %A Melvin Gauci %A Radhika Nagpal %X Many fish species gather by the thousands and swim in harmony with seemingly no effort. Large schools display a range of impressive collective behaviors, from simple shoaling to collective migration and from basic predator evasion to dynamic maneuvers such as bait balls and flash expansion. A wealth of experimental and theoretical work has shown that these complex three-dimensional (3D) behaviors can arise from visual observations of nearby neighbors, without explicit communication. By contrast, most underwater robot collectives rely on centralized, above-water, explicit communication and, as a result, exhibit limited coordination complexity. Here, we demonstrate 3D collective behaviors with a swarm of fish-inspired miniature underwater robots that use only implicit communication mediated through the production and sensing of blue light. We show that complex and dynamic 3D collective behaviors—synchrony, dispersion/aggregation, dynamic circle formation, and search-capture—can be achieved by sensing minimal, noisy impressions of neighbors, without any centralized intervention. Our results provide insights into the power of implicit coordination and are of interest for future underwater robots that display collective capabilities on par with fish schools for applications such as environmental monitoring and search in coral reefs and coastal environments. %B Science Robotics %V 6 %G eng %N 50 %0 Conference Paper %B Intl. Conference on Automation and Robotics (ICRA) %D 2021 %T Self-Organized Evasive Fountain Maneuvers with a Bio-inspired Underwater Robot Collective %A Florian Berlinger %A Paula Wulkop %A Radhika Nagpal %X

Several animal species self-organize into large groups to leverage vital behaviors such as foraging, construc- tion, or predator evasion. With the advancement of robotics and automation, engineered multi-agent systems have been inspired to achieve similarly high degrees of scalable, robust, and adaptable autonomy through decentralized and dynamic coordination. So far however, they have been most successfully demonstrated above ground or with partial assistance from central controllers and external tracking. Here we demonstrate an underwater robot collective that realizes full spatiotempo- ral coordination. Using the example of fish-inspired evasive maneuvers, our robots display alignment, formation control, and coordinated escape, enabled by real-time on-board multi- robot tracking and local decision making. Accompanied by a custom simulator, this robotic platform advances the physically- validated development of algorithms for collective behaviors and future applications including collective exploration, track- ing and capture, or environmental sampling.

%B Intl. Conference on Automation and Robotics (ICRA) %G eng %0 Thesis %B PhD Thesis, School of Engineering and Applied Sciences (CS), Harvard University. %D 2021 %T Blueswarm: 3D Self-organization in a Fish-inspired Robot Swarm %A Florian Berlinger %B PhD Thesis, School of Engineering and Applied Sciences (CS), Harvard University. %G eng %9 PhD thesis %0 Journal Article %J Bioinspiration & Biomimetics %D 2021 %T Fish-like three-dimensional swimming with an autonomous, multi-fin, and biomimetic robot %A Florian Berlinger %A Mehdi Saadat %A Hossein Haj-Hariri %A George V Lauder %A Radhika Nagpal %X Fish migrate across considerable distances and exhibit remarkable agility to avoid predators and feed. Fish swimming performance and maneuverability remain unparalleled when compared to robotic systems, partly because previous work has focused on robots and flapping foil systems that are either big and complex, or tethered to external actuators and power sources. By contrast, we present a robot – the Finbot – that combines high degrees of autonomy, maneuverability, and biomimicry with miniature size (160 cm3). Thus, it is well-suited for controlled three-dimensional experiments on fish swimming in confined laboratory test beds. Finbot uses four independently controllable fins and sensory feedback for precise closed-loop underwater locomotion. Different caudal fins can be attached magnetically to reconfigure Finbot for swimming at top speed (122 mm/s ≡ 1 BL/s) or minimal cost of transport (CoT = 8.2) at Strouhal numbers as low as 0.53. We conducted more than 150 experiments with 12 different caudal fins to measure three key characteristics of swimming fish: (i) linear speed-frequency relationships, (ii) U-shaped costs of transport, and (iii) reverse Kármán wakes (visualized with particle image velocimetry). More fish-like wakes appeared where the cost of transport was low. By replicating autonomous multi-fin fish-like swimming, Finbot narrows the gap between fish and fish-like robots and can address open questions in aquatic locomotion, such as optimized propulsion for new fish robots, or the hydrodynamic principles governing the energy savings in fish schools. %B Bioinspiration & Biomimetics %V 16 %G eng %U https://dx.doi.org/10.1088/1748-3190/abd013 %N 2 %0 Journal Article %J Bioinspiration & Biomimetics %D 2021 %T Hydrodynamic advantages of in-line schooling %A Mehdi Saadat %A Florian Berlinger %A Artan Sheshmani %A Radhika Nagpal %A George V Lauder %A Hossein Haj-Hariri %X

Fish benefit energetically when swimming in groups, which is reflected in lower tail-beat frequencies for maintaining a given speed. Recent studies further show that fish save the most energy when swimming behind their neighbor such that both the leader and the follower benefit. However, the mechanisms underlying such hydrodynamic advantages have thus far not been established conclusively. The long-standing drafting hypothesis—reduction of drag forces by judicious positioning in regions of reduced oncoming flow–fails to explain advantages of in-line schooling described in this work. We present an alternate hypothesis for the hydrodynamic benefits of in-line swimming based on enhancement of propulsive thrust. Specifically, we show that an idealized school consisting of in-line pitching foils gains hydrodynamic benefits via two mechanisms that are rooted in the undulatory jet leaving the leading foil and impinging on the trailing foil: (i) leading-edge suction on the trailer foil, and (ii) added-mass push on the leader foil. Our results demonstrate that the savings in power can reach as high as 70% for a school swimming in a compact arrangement. Informed by these findings, we designed a modification of the tail propulsor that yielded power savings of up to 56% in a self-propelled autonomous swimming robot. Our findings provide insights into hydrodynamic advantages of fish schooling, and also enable bioinspired designs for significantly more efficient propulsion systems that can harvest some of their energy left in the flow.

%B Bioinspiration & Biomimetics %V 16 %G eng %U https://iopscience.iop.org/article/10.1088/1748-3190/abe137 %N 4 %0 Journal Article %J Frontiers in Robotics and AI %D 2021 %T Validating a termite-inspired construction coordination mechanism using an autonomous robot %A Nicole Carey %A Paul Bardunias %A Radhika Nagpal %A Werfel, Justin %B Frontiers in Robotics and AI %G eng %0 Conference Proceedings %B Intl. Conference on Robotics and Automation (ICRA) %D 2020 %T Bayes Bots: Collective Bayesian Decision-Making in Decentralized Robot Swarms %A Julia Ebert %A Melvin Gauci %A Frederick Mallmann-Trenn %A Radhika Nagpal %B Intl. Conference on Robotics and Automation (ICRA) %G eng %0 Conference Proceedings %B Intl. Conferenc on Robotics and Automation (ICRA) %D 2020 %T Eciton robotica: Design and Algorithms for an Adaptive Self-Assembling Soft Robot Collective %A Melinda Malley %A Bahar Haghighat %A Lucie Houel %A Radhika Nagpal %B Intl. Conferenc on Robotics and Automation (ICRA) %G eng %0 Journal Article %J Proceedings of the Royal Society B: Biological Science %D 2020 %T The extension of internal humidity levels beyond the soil surface facilitates mound expansion in Macrotermes %A Paul Bardunias %A Daniel Calovi %A Nicole Carey %A Rupert Soar %A J. Scott Turner %A Radhika Nagpal %A Werfel, Justin %X Termites in the genus Macrotermes construct large-scale soil mounds above their nests. The classic explanation for how termites coordinate their labour to build the mound, based on a putative cement pheromone, has recently been called into question. Here, we present evidence for an alternate interpretation based on sensing humidity. The high humidity characteristic of the mound's internal environment extends a short distance into the low-humidity external world, in a ‘bubble’ that can be disrupted by external factors like wind. Termites transport more soil mass into on-mound reservoirs when shielded from water loss through evaporation, and into experimental arenas when relative humidity is held at a high value. These results suggest that the interface between internal and external conditions may serve as a template for mound expansion, with workers moving freely within a zone of high humidity and depositing soil at its edge. Such deposition of additional moist soil will increase local humidity, in a feedback loop allowing the ‘interior’ zone to progress further outward and lead to mound expansion. %B Proceedings of the Royal Society B: Biological Science %V 287 %G eng %N 1930 %0 Journal Article %J IEEE Robotics and Automation Letters (RAL) %D 2020 %T Tunable Multi-Modal Locomotion in Soft Dielectric Elastomer Robots %A Mihai Duduta %A Florian Berlinger %A Radhika Nagpal %A David Clarke %A Rob Wood %A Zeynep Temel %B IEEE Robotics and Automation Letters (RAL) %G eng %0 Thesis %B PhD Thesis, School of Engineering and Apllied Sciences (Mech. Eng), Harvard University %D 2020 %T Army Ant Inspired Adaptive Self-Assembly with Soft Climbing Robots %A Melinda Malley %B PhD Thesis, School of Engineering and Apllied Sciences (Mech. Eng), Harvard University %G eng %9 PhD Thesis %0 Journal Article %J Philosophical Transactions of the Royal Society %D 2019 %T Surface curvature guides early construction activity in mound-building termites %A Daniel Calovi %A Paul Bardunias %A Nicole Carey %A J. Scott Turner %A Radhika Nagpal %A Werfel, Justin %X

Termite colonies construct towering, complex mounds, in a classic example of distributed agents coordinating their activity via interaction with a shared environment. The traditional explanation for how this coordination occurs focuses on the idea of a ‘cement pheromone’, a chemical signal left with deposited soil that triggers further deposition. Recent research has called this idea into question, pointing to a more complicated behavioural response to cues perceived with multiple senses. In this work, we explored the role of topological cues in affecting early construction activity in Macrotermes. We created artificial surfaces with a known range of curvatures, coated them with nest soil, placed groups of major workers on them and evaluated soil displacement as a function of location at the end of 1 h. Each point on the surface has a given curvature, inclination and absolute height; to disambiguate these factors, we conducted experiments with the surface in different orientations. Soil displacement activity is consistently correlated with surface curvature, and not with inclination nor height. Early exploration activity is also correlated with curvature, to a lesser degree. Topographical cues provide a long-term physical memory of building activity in a manner that ephemeral pheromone labelling cannot. Elucidating the roles of these and other cues for group coordination may help provide organizing principles for swarm robotics and other artificial systems.

This article is part of the theme issue ‘Liquid brains, solid brains: How distributed cognitive architectures process information’.

%B Philosophical Transactions of the Royal Society %V 374 %G eng %U https://royalsocietypublishing.org/doi/10.1098/rstb.2018.0374 %N 1774 %0 Journal Article %J Journal of Experimental Biology %D 2019 %T Effects of load mass and size on cooperative transport in ants over multiple transport challenges %A Helen McCreery %A Jenna Bilek %A Radhika Nagpal %A Michael Breed %X Some ant species cooperatively transport a wide range of extremely large, heavy food objects of various shapes and materials. While previous studies have examined how object mass and size affect the recruitment of additional workers, less is understood about how these attributes affect the rest of the transport process. Using artificial baits with independently varying mass and size, we reveal their effects on cooperative transport in Paratrechina longicornis across two transport challenges: movement initiation and obstacle navigation. As expected, object mass was tightly correlated with number of porters as workers adjust group size to the task. Mass affected performance similarly across the two challenges, with groups carrying heavy objects having lower performance. Yet, object size had differing effects depending on the challenge. While larger objects led to reduced performance during movement initiation – groups took longer to start moving these objects and had lower velocities – there was no evidence for this during obstacle navigation, and the opposite pattern was weakly supported. If a group struggles to start moving an object, it does not necessarily predict difficulty navigating around obstacles; groups should persist in trying to move ‘difficult’ objects, which may be easier to transport later in the process. Additionally, groups hitting obstacles were not substantially disrupted, and started moving again sooner than at the start, despite the nest direction being blocked. Paratrechina longicornis transport groups never failed, performing well at both challenges while carrying widely varying objects, and even transported a bait weighing 1900 times the mass of an individual. %B Journal of Experimental Biology %V doi: 10.1242/jeb.206821 %G eng %U https://jeb.biologists.org/content/222/17/jeb206821 %0 Journal Article %J Smart Materials and Structures %D 2019 %T Electrically-latched compliant jumping mechanism based on a dielectric elastomer actuator %A Mihai Duduta %A Florian Berlinger %A Radhika Nagpal %A David Clarke %A Wood, Robert %A Zeynep Temel %B Smart Materials and Structures %V 28 %8 2019 %G eng %N 09LT01 %0 Thesis %B EPFL Master's Thesis %D 2019 %T Self-assembly of soft-robots in simulation inspired by army ant bridge behavior %A Lucie Houel %B EPFL Master's Thesis %G eng %9 Master's Thesis %0 Thesis %B Senior Thesis, Harvard University. %D 2019 %T Teach a Fish to Swim: Evaluating the Ability of Turing Learning to Infer Schooling Behavior %A Katherine Binney %X

Turing Learning is a promising evolutionary design method for swarm robotics that uses ob- servation of natural or artificial systems to infer controllers for agents in a swarm. However, Tur- ing Learning has thus far only been used to infer very simple swarm behaviors. In this work, we expand Turing Learning to infer dispersion, a much more complex swarm behavior, by a simulated school of robotic fish. Turing Learning depends on the co-evolution of replicas and classifiers. Replicas mimic ideal behavior and classifiers distinguish between data samples from replica and ideal agents. We model replicas and classifiers with neural networks and investigate the architecture of each component independently in order to determine needed modifications to Turing Learning for it to infer fish schooling. We find that previously formulated data samples led to the inference of behaviors that locally mimicked the agent trajectories in dispersion, yet poorly mimicked dispersion of an entire swarm. We present three alternative data samples that consider the spatial arrangement of agents in a swarm. We also introduce three new classifier fitness func- tions that accelerate evolution of high-accuracy classifiers. We find in a preliminary trial that using one of our data samples (metrics) and classifier fitness functions (foutputs) enables the successful inference of dispersion via Turing Learning.

%B Senior Thesis, Harvard University. %G eng %9 Bachelor's Thesis %0 Conference Paper %B IEEE OCEANS conference %D 2018 %T A Biomimetic Actuation Method for a Miniature, Low-Cost Multi-jointed Robotic Fish %A Katherina Soltan %A Jamie O'Brien %A Florian Berlinger %A Radhika Nagpal %A Jeff Dusek %B IEEE OCEANS conference %G eng %0 Conference Paper %B Intl. Conf. on Robotics and Automation (ICRA) %D 2018 %T A Modular Dielectric Elastomer Actuator to Drive Miniature Autonomous Underwater Vehicles %A Florian Berlinger %A Mihai Duduta %A Hudson Gloria %A David Clarke %A Radhika Nagpal %A Wood, Robert %X

Abstract—In this paper we present the design of a fin-like dielectric elastomer actuator (DEA) that drives a miniature autonomous underwater vehicle (AUV). The fin-like actuator is modular and independent of the body of the AUV. All electronics required to run the actuator are inside the 100 mm long 3D-printed body, allowing for autonomous mobility of the AUV. The DEA is easy to manufacture, requires no pre-stretch of the elastomers, and is completely sealed for underwater operation. The output thrust force can be tuned by stacking multiple actuation layers and modifying the Young’s modulus of the elastomers. The AUV is reconfigurable by a shift of its center of mass, such that both planar and vertical swimming can be demonstrated on a single vehicle. For the DEA we measured thrust force and swimming speed for various actuator designs ran at frequencies from 1Hz to 5Hz. For the AUV we demonstrated autonomous planar swimming and closed- loop vertical diving. The actuators capable of outputting the highest thrust forces can power the AUV to swim at speeds of up to 0.55body lengths per second. The speed falls in the upper range of untethered swimming robots powered by soft actuators. Our tunable DEAs also demonstrate the potential to mimic the undulatory motions of fish fins. 

%B Intl. Conf. on Robotics and Automation (ICRA) %G eng %0 Conference Paper %B Intl. Conf. on Autonomous Agents and Multiagent Systems (AAMAS) %D 2018 %T Multi-Feature Collective Decision Making in Robot Swarms %A Julia Ebert %A Melvin Gauci %A Radhika Nagpal %X

Collective decision making has been studied extensively in the fields of multi-agent systems and swarm robotics, inspired by its pervasiveness in biological systems such as honeybee and ant colonies. However, most previous research has focused on collective decision making on a single feature. In this work, we introduce and investigate the multi-feature collective decision making problem, where a collective must decide on multiple binary features simultaneously, given no a priori information about their relative difficulties. Each agent may only estimate one feature at any given time, but the agents can locally communicate their noisy estimates to arrive at a decision. We demonstrate a decentralized algorithm for single-feature decision making and a dynamic task allocation strategy that allows the agents to lock in decisions on multiple features in finite time. We validate our approach using simulated and physical Kilobot robots. Our results show that a collective can correctly classify a multi-feature environment, even if presented with pathological initial agent-to-feature allocations. 

%B Intl. Conf. on Autonomous Agents and Multiagent Systems (AAMAS) %G eng %0 Conference Paper %B IEEE/RSJ Intl Conference on Intelligent Robots and Systems (IROS) %D 2017 %T Flippy: A Soft, Autonomous Climber with Simple Sensing and Control %A Melinda Malley %A Michael Rubenstein %A Radhika Nagpal %X

Climbing robots have many potential applications including maintenance, monitoring, search and rescue, and self-assembly. While numerous climbing designs have been investigated, most are limited to stiff components. Flippy (Fig. 1) is a small, flipping biped robot with a soft, flexible body and on-board power and control. Due to its built-in compliance, flipping gait, and corkscrew gripper, it can autonomously climb up and down surfaces held at any angle relative to gravity and transition from one surface to another, without complex sensing or control. In this paper, we demonstrate the robot’s ability to flip consistently over a flat Velcro surface and 2D Velcro track, where it reliably climbs vertically, upside down and back to a flat surface, completing all the interior transitions in-between. 

%B IEEE/RSJ Intl Conference on Intelligent Robots and Systems (IROS) %G eng %0 Journal Article %J IEEE Robotics and Automation Letters (RA-L) %D 2017 %T Robust Maneuverability of a Miniature Low-Cost Underwater Robot using Multiple Fin Actuation %A Florian Berlinger %A Jeff Dusek %A Melvin Gauci %A Radhika Nagpal %X

In this paper we present the design of a miniature (100 mm) autonomous underwater robot that is low-cost ($ 100), easy to manufacture, and highly maneuverable. A key aspect of the robot design that makes this possible is the use of low-cost magnet-in-coil actuators, which have a small profile and minimal sealing requirements. This allows us to create a robot with multiple flapping fin propulsors that independently control robot motions in surge, heave, and yaw. We present several results on the robot, including: (i) quantified open-loop swimming characteristics; (ii) autonomous behaviors using a pressure sensor and an IMU to achieve controlled swimming of prescribed trajectories; (iii) feedback from an optic sensor to enable homing to a light source. The robot is designed to form the basis for underwater swarm robotics testbeds, where low cost and ease of manufacture are critical, and 3D maneuverability allows testing complex coordination inspired by natural fish schools. Individually, miniature and low-cost underwater robots can also provide a platform for the study of 3D autonomy and marine vehicle dynamics in educational and resource-constrained settings. 

%B IEEE Robotics and Automation Letters (RA-L) %V PP %G eng %N 99 %0 Journal Article %J Architectural Design, Special Issue: Autonomous Assembly: Designing for a New Era of Collective Construction %D 2017 %T Complex Design by Simple Robots: A Collective Embodied Intelligence Approach to Construction %A Kirstin Petersen %A Radhika Nagpal %X Nature's builders – from termites to beavers – offer a model of collective intelligence that can inspire robotic construction. Kirstin Petersen, Assistant Professor in Electrical and Computer Engineering at Cornell University, Ithaca, New York, and Radhika Nagpal, Professor in Computer Science at the Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts, describe several recent projects in this field that they have been involved in, both separately and collaboratively. %B Architectural Design, Special Issue: Autonomous Assembly: Designing for a New Era of Collective Construction %V 87 %P 44-49 %G eng %N 4 %0 Journal Article %J PLoS computational biology %D 2017 %T Costs of task allocation with local feedback: Effects of colony size and extra workers in social insects and other multi-agent systems %A Tsvetomira (Mira) Radeva %A Anna Dornhaus %A Lynch, Nancy %A Radhika Nagpal %A Hsin-Hao Su %X (Author summary) 

Many complex systems have to allocate their units to different functions: cells in an embryo develop into different tissues, servers in a computer cluster perform different cal- culations, and insect workers choose particular tasks, such as brood care or foraging. Here we demonstrate that this process does not automatically become easier or harder with sys- tem size. If more workers are present than needed to complete the work available, some workers will always be idle; despite this, having surplus workers makes redistributing them across the tasks that need work much faster. Thus, unexpectedly, such surplus, idle workers may potentially significantly improve system performance. Our work suggests that interdisciplinary studies between biology and distributed computing can yield novel insights for both fields. 

%B PLoS computational biology %V 13 %G eng %U http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1005904 %N 12 %0 Conference Paper %B 16th International Conference on Autonomous Agents and Multiagent Systems (AAMAS) %D 2017 %T Error Cascades in Collective Behavior: A Case Study of the Gradient Algorithm on 1000 Physical Agents %A Melvin Gauci %A Monica Ortiz %A Michael Rubenstein %A Radhika Nagpal %X

The gradient, or hop count, algorithm is inspired by nat- ural phenomena such as the morphogen gradients present in multi-cellular development. It has several applications in multi-agent systems and sensor networks, serving as a basis for self-organized coordinate system formation, and finding shortest paths for message passing. It is a simple and well- understood algorithm in theory. However, we show here that in practice, it is highly sensitive to specific rare errors that emerge at larger scales. We implement it on a system of 1000 physical agents (Kilobot robots) that communicate asynchronously via a noisy wireless channel. We observe that spontaneous, short-lasting rare errors made by a sin- gle agent (e.g. due to message corruption) propagate spa- tially and temporally, causing cascades that severely hinder the algorithm’s functionality. We develop a mathematical model for temporal error propagation and validate it with experiments on 100 agents. This work shows how multi- agent algorithms that are believed to be simple and robust from theoretical insight may be highly challenging to im- plement on physical systems. Systematically understanding and quantifying their current limitations is a first step in the direction of improving their robustness for implementation.

%B 16th International Conference on Autonomous Agents and Multiagent Systems (AAMAS) %G eng %0 Journal Article %J Proceedings of the Royal Society B %D 2017 %T Excavation and aggregation as organizing factors in de novo construction by mound-building termites %A Ben Green %A Paul Bardunias %A J. Scott Turner %A Radhika Nagpal %A Werfel, Justin %X Termites construct complex mounds that are orders of magnitude larger than any individual and fulfil a variety of functional roles. Yet the processes through which these mounds are built, and by which the insects organize their efforts, remain poorly understood. The traditional understanding focuses on stigmergy, a form of indirect communication in which actions that change the environment provide cues that influence future work. Termite construction has long been thought to be organized via a putative ‘cement pheromone’: a chemical added to deposited soil that stimulates further deposition in the same area, thus creating a positive feedback loop whereby coherent structures are built up. To investigate the detailed mechanisms and behaviours through which termites self-organize the early stages of mound construction, we tracked the motion and behaviour of major workers from two Macrotermes species in experimental arenas. Rather than a construction process focused on accumulation of depositions, as modelsbased on cement pheromone would suggest, our results indicated that the primary organizing mechanisms were based on excavation. Digging activity was focused on a small number of excavation sites, which in turn provided templates for soil deposition. This behaviour was mediated by a mechanism of aggregation, with termites being more likely to join in the work at an excavation site as the number of termites presently working at that site increased. Statistical analyses showed that this aggregation mechanism was a response to active digging, distinct from and unrelated to putative chemical cues that stimulate deposition. Agent-based simulations quantitatively supported the interpretation that the early stage of de novo construction is primarily organized by excavation and aggregation activity rather than by stigmergic deposition. %B Proceedings of the Royal Society B %V 284 %G eng %U http://rspb.royalsocietypublishing.org/cgi/content/abstract/rspb.2016.2730 %N 1856 %0 Conference Paper %B IEEE Winter Conference on Applications of Computer Vision (WACV) %D 2017 %T Fast, accurate, small-scale 3D scene capture using a low-cost depth sensor %A Nicole Carey %A Radhika Nagpal %A Werfel, Justin %X

Commercially available depth sensing devices are pri- marily designed for domains that are either macroscopic, or static. We develop a solution for fast microscale 3D re- construction, using off-the-shelf components. By the addi- tion of lenses, precise calibration of camera internals and positioning, and development of bespoke software, we turn an infrared depth sensor designed for human-scale motion and object detection into a device with mm-level accuracy capable of recording at up to 30Hz. 

%B IEEE Winter Conference on Applications of Computer Vision (WACV) %G eng %0 Conference Paper %B IEEE Artificial Life Conference (ALIFE) %D 2017 %T Models of Adaptive Navigation, Inspired by Ant Cooperative Transport in the Presence of Obstacles %A Elizabeth E. Esterley %A Helen McCreery %A Radhika Nagpal %X

Cooperative transport is an impressive example of collective behavior in ants, where groups of ants work together to move heavy food objects back to their nest over heterogeneous terrain. This behavior also serves as a model for bio-inspired robotics. While many studies have considered the mechanisms by which ants transport objects in simple settings, few have looked at how they deal with obstacles and heterogeneous terrain. A recent study on Paratrechina longicornis (crazy ants) demonstrated that groups of these ants implement a stochastic, adaptive, and robust cooperative transport strategy that allows them to succeed at navigating challenging obstacles that require moving away from their goal. In this paper, we use group-level computational models to investigate the significance and implications of this biological strategy. We develop an algorithm that reproduces important elements of the strategy, and compare it to several benchmark algorithms for a range of obstacle sizes and shapes. Our results show that, for smaller obstacles, the ant-inspired adaptive stochastic strategy is adept at efficient navigation, due to its ability to match the level of randomness it uses to unknown object size and shape. We also find some unexpected differences between our results and the original ant transport behavior, suggesting new biological experiments. 

%B IEEE Artificial Life Conference (ALIFE) %G eng %0 Conference Paper %B ACM/IEEE International Conference on Human-Robot Interaction (HRI) %D 2017 %T Piggybacking Robots: Human-Robot Overtrust in University Dormitory Security %A Serena Booth %A James Tompkins %A Hanspeter Pfister %A Jim Waldo %A Krzysztof Gajos %A Radhika Nagpal %X

Can overtrust in robots compromise physical security? We posi- tioned a robot outside a secure-access student dormitory and made it ask passersby for access. Individual participants were as likely to assist the robot in exiting the dormitory (40% assistance rate, 4/10 individuals) as in entering (19%, 3/16 individuals). Groups of people were more likely than individuals to assist the robot in entering (71%, 10/14 groups). When the robot was disguised as a food delivery agent for the ￿ctional start-up Robot Grub, individ- uals were more likely to assist the robot in entering (76%, 16/21 individuals). Lastly, participants who identi￿ed the robot as a bomb threat demonstrated a trend toward assisting the robot (87%, 7/8 individuals, 6/7 groups). ￿us, overtrust—the unfounded belief that the robot does not intend to deceive or carry risk—can represent a signi￿cant threat to physical security at a university dormitory. 

%B ACM/IEEE International Conference on Human-Robot Interaction (HRI) %G eng %U files/ssr/files/hri2017-booth.pdf %0 Journal Article %J Journal of Experimental Biology %D 2016 %T Collective strategy for obstacle navigation during cooperative transport by ants %A Helen F. McCreery %A Zachary A. Dix %A Michael D. Breed %A Radhika Nagpal %X

Group cohesion and consensus have primarily been studied in the context of discrete decisions, but some group tasks require making serial decisions that build on one another. We examine such collective problem solving by studying obstacle navigation during cooperative transport in ants. In cooperative transport, ants work together to move a large object back to their nest. We blocked cooperative transport groups of Paratrechina longicornis with obstacles of varying complexity, analyzing groups' trajectories to infer what kind of strategy the ants employed. Simple strategies require little information, but more challenging, robust strategies succeed with a wider range of obstacles. We found that transport groups use a stochastic strategy that leads to efficient navigation around simple obstacles, and still succeeds at difficult obstacles. While groups navigating obstacles preferentially move directly toward the nest, they change their behavior over time; the longer the ants are obstructed, the more likely they are to move away from the nest. This increases the chance of finding a path around the obstacle. Groups rapidly changed directions and rarely stalled during navigation, indicating that these ants maintain consensus even when the nest direction is blocked. Although some decisions were aided by the arrival of new ants, at many key points, direction changes were initiated within the group, with no apparent external cause. This ant species is highly effective at navigating complex environments, and implements a flexible strategy that works for both simple and more complex obstacles.

%B Journal of Experimental Biology %V 219 %P 3366-3375 %G eng %U http://jeb.biologists.org/content/jexbio/219/21/3366.full.pdf %N 21 %0 Conference Paper %B 13th International Symposium on Distributed Autonomous Robotic Systems (DARS) %D 2016 %T Programmable Self-Disassembly for Shape Formation in Large-Scale Robot Collectives %A Melvin Gauci %A Radhika Nagpal %A Michael Rubenstein %X

We present a method for a large-scale robot collective to autonomously form a wide range of user-specified shapes. In contrast to most existing work, our method uses a subtractive approach rather than an additive one, and is the first such method to be demonstrated on robots that operate in continuous space. An initial dense, stationary configuration of robots distributively forms a coordinate system, and each robot decides if it is part of the desired shape. Non-shape robots then re- move themselves from the configuration using a single external light source as a motion guide. The subtractive approach allows for a higher degree of motion paral- lelism than additive approaches; it is also tolerant of much lower-precision motion. Experiments with 725 Kilobot robots allow us to compare our method against an additive one that was previously evaluated on the same platform. The subtractive method leads to higher reliability and an order-of-magnitude improvement in shape formation speed. 

 

%B 13th International Symposium on Distributed Autonomous Robotic Systems (DARS) %G eng %0 Conference Paper %B Intl. Conference on Robotics and Automation (ICRA) %D 2015 %T Towards Self-assembled Structures with Mobile Climbing Robots %A Lucian Cucu %A Michael Rubenstein %A Radhika Nagpal %B Intl. Conference on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra15-cucu.pdf %0 Conference Paper %B Intl. Conference on Robotics and Automation (ICRA) %D 2015 %T AERobot: An Affordable One-Robot-Per-Student System for Early Robotics Education %A Michael Rubenstein %A Bo Cimino %A Radhika Nagpal %A Werfel, Justin %B Intl. Conference on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra15-aerobot.pdf %0 Journal Article %J Behavioural Processes %D 2015 %T Arrestant property of recently manipulated soil on Macrotermes michaelseni as determined through visual tracking and automatic labeling of individual termite behaviors %A Kirstin Petersen %A Paul Bardunias %A Nils Napp %A Werfel, Justin %A Radhika Nagpal %A J. Scott Turner %B Behavioural Processes %V 116 %P 8-11 %G eng %U http://www.sciencedirect.com/science/article/pii/S0376635715001023 %0 Thesis %B ES100 Senior Capstone Project %D 2015 %T Seaturtle: A low-cost underwater Robot %A Johnathan Budd %B ES100 Senior Capstone Project %G eng %U files/ssr/files/es100-2015-budd.pdf %0 Journal Article %J Science %D 2014 %T Designing Collective Behavior in a Termite-Inspired Robot Construction Team %A Werfel, Justin %A Kirstin Petersen %A Radhika Nagpal %X Complex systems are characterized by many independent components whose low-level actions produce collective high-level results. Predicting high-level results given low-level rules is a key open challenge; the inverse problem, finding low-level rules that give specific outcomes, is in general still less understood. We present a multi-agent construction system inspired by mound-building termites, solving such an inverse problem. A user specifies a desired structure, and the system automatically generates low-level rules for independent climbing robots that guarantee production of that structure. Robots use only local sensing and coordinate their activity via the shared environment. We demonstrate the approach via a physical realization with three autonomous climbing robots limited to onboard sensing. This work advances the aim of engineering complex systems that achieve specific human-designed goals. %B Science %V 343 %G eng %N 6172 %0 Journal Article %J Science %D 2014 %T Programmable self-assembly in a thousand-robot swarm %A Michael Rubenstein %A Alejandro Cornejo %A Radhika Nagpal %X Self-assembly enables nature to build complex forms, from multicellular organisms to complex animal structures such as flocks of birds, through the interaction of vast numbers of limited and unreliable individuals. Creating this ability in engineered systems poses challenges in the design of both algorithms and physical systems that can operate at such scales. We report a system that demonstrates programmable self-assembly of complex two-dimensional shapes with a thousand-robot swarm. This was enabled by creating autonomous robots designed to operate in large groups and to cooperate through local interactions and by developing a collective algorithm for shape formation that is highly robust to the variability and error characteristic of large-scale decentralized systems. This work advances the aim of creating artificial swarms with the capabilities of natural ones. %B Science %V 345 %G eng %N 6198 %0 Journal Article %J Bioinspiration & Biomimetics %D 2014 %T Design and control of a bio-inspired soft wearable robotic device for ankle-foot rehabilitation %A Yong-Lae Park %A Bor-Rong Chen %A Nestor Presez-Arancibia %A Diana Young %A Leia Stirling %A Wood, Robert %A Eugene Goldfield %A Radhika Nagpal %B Bioinspiration & Biomimetics %V 9 %G eng %U http://iopscience.iop.org/1748-3190/9/1/016007 %N 1 %0 Conference Paper %B IEEE Intl. Conf on Robotics and Automation (ICRA) %D 2014 %T Autonomous MAV guidance with a lightweight omnidirectional vision sensor %A Richard Moore %A Karthik Dantu %A Geoffery Barrows %A Radhika Nagpal %B IEEE Intl. Conf on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra14-moore.pdf %0 Thesis %B Doctoral Thesis, Harvard University %D 2014 %T Collective Construction by Termite-Inspired Robots %A Kirstin Petersen %B Doctoral Thesis, Harvard University %G eng %U files/ssr/files/phd14-petersen.pdf %9 phd %0 Conference Paper %B Intl. Workshop on the Algorithmic Foundations of Robotics (WAFR) %D 2014 %T Distributed Range-Based Relative Localization of Robot Swarms %A Alex Cornejo %A Radhika Nagpal %B Intl. Workshop on the Algorithmic Foundations of Robotics (WAFR) %G eng %U files/ssr/files/wafr14-cornejo.pdf %0 Conference Paper %B IEEE Intl. Conf on Robotics and Automation (ICRA) %D 2014 %T Robotic Construction of Arbitrary Shapes with Amorphous Materials %A Nils Napp %A Radhika Nagpal %B IEEE Intl. Conf on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra14-napp-shape.pdf %0 Conference Paper %B IEEE Intl. Conf on Robotics and Automation (ICRA) %D 2014 %T Simple Passive Valves for Addressable Pneumatic Actuation %A Nils Napp %A Brandon Araki %A Michael T. Tolley %A Radhika Nagpal %A Wood, Robert J. %B IEEE Intl. Conf on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra14-napp-valve.pdf %0 Conference Paper %B Intl. Symposium on Distributed Computing (DISC) %D 2014 %T Task Allocation in Ant Colonies %A Alex Cornejo %A Anna Dornhaus %A Lynch, Nancy %A Radhika Nagpal %X In this paper we propose a mathematical model for studying the phenomenon of division of labor in ant colonies. Inside this model we investigate how simple task allocation mechanisms can be used to achieve an optimal division of labor. We believe the proposed model captures the essential biological features of division of labor in ant colonies and is general enough to study a variety of different task allocation mechanisms. Within this model we propose a distributed randomized algorithm for task allocation that imposes only minimal requirements on the ants; it uses a constant amount of memory and relies solely on a primitive binary feedback function to sense the current labor allocation. We show that with high probability the proposed algorithm converges to a near-optimal division of labor in time which is proportional to the logarithm of the colony size. %B Intl. Symposium on Distributed Computing (DISC) %G eng %U files/ssr/files/disc14-cornejo.pdf %0 Thesis %B Master's Thesis, EPFL %D 2014 %T Towards Self-Assembled Structures with Mobile Climbing Robots %A Lucian Cucu %B Master's Thesis, EPFL %G eng %U files/ssr/files/epflmasters14-cucu.pdf %9 masters %0 Conference Paper %B Intl. Conf. on Autonomous Agents and Multiagent Systems (AAMAS) %D 2013 %T Collective Transport of Complex Objects by Simple Robots: Theory and Experiments %A Mike Rubenstein %A Adrian Cabrera %A Werfel, Justin %A Golnaz Habibi %A James McLurkin %A Radhika Nagpal %B Intl. Conf. on Autonomous Agents and Multiagent Systems (AAMAS) %G eng %U files/ssr/files/aamas13-rubenstein.pdf %0 Journal Article %J Nano Today %D 2013 %T A computational framework for identifying design guidelines to increase the penetration of targeted nanoparticles into tumors %A Sabine Hauert %A Spring Berman %A Radhika Nagpal %A Sangeeta N. Bhatia %B Nano Today %G eng %U files/ssr/files/nanotoday14-hauert.pdf %0 Journal Article %J Scientific American %D 2013 %T Flight of the Robobees %A Wood, Robert %A Radhika Nagpal %A Gu-Yeon Wei %B Scientific American %G eng %0 Conference Paper %B IEEE/RSJ Intl. Conf. on Intelligent Robots and Systems (IROS) %D 2013 %T Massive Uniform Manipulation: Controlling Large Populations of Simple Robots With a Common Input Signal %A Aaron Becker %A Golnaz Habibi %A Werfel, Justin %A Michael Rubenstein %A James McLurkin %B IEEE/RSJ Intl. Conf. on Intelligent Robots and Systems (IROS) %G eng %U files/ssr/files/iros13-becker.pdf %0 Conference Paper %B Advances in Neural Information Processing Systems (NIPS) %D 2013 %T Message Passing Inference with Chemical Reaction Networks %A Nils Napp %A Ryan Adams %B Advances in Neural Information Processing Systems (NIPS) %G eng %U files/ssr/files/nips13-napp.pdf %0 Conference Paper %B IEEE Intl. Conference on Robots and Systems (IROS) %D 2012 %T Active Modular Elastomer Sleeve for Soft Wearable Assistance Robots %A Yong-Lae Park %A Bor-Rong Chen %A Carmel Majidi %A Rob Wood %A Radhika Nagpal %A Eugene Goldfield %B IEEE Intl. Conference on Robots and Systems (IROS) %G eng %U files/ssr/files/iros12-park.pdf %0 Thesis %B Master's Thesis, EPFL %D 2012 %T Collective Transport in Large Swarms of Simple Robots %A Adrian Cabrera %B Master's Thesis, EPFL %G eng %U files/ssr/files/epflmasters12-cabrera.pdf %9 masters %0 Conference Paper %B IEEE Intl. Conference on Robots and Systems (IROS) %D 2012 %T A Comparison of Deterministic and Stochastic Approaches for Allocating Spatially Dependent Tasks in Micro-Aerial Vehicle Collectives %A Karthik Dantu %A Spring Berman %A Bryan Kate %A Radhika Nagpal %B IEEE Intl. Conference on Robots and Systems (IROS) %G eng %U files/ssr/files/iros12-dantu.pdf %0 Conference Paper %B Symposium on Distributed Autonomous Robotic Systems (DARS) %D 2012 %T Distributed Amorphous Ramp Construction in Unstructured Environments %A Nils Napp %A Radhika Nagpal %B Symposium on Distributed Autonomous Robotic Systems (DARS) %G eng %U files/ssr/files/dars12-napp.pdf %0 Conference Paper %B IEEE Intl. Conf on Robotics and Automation (ICRA) %D 2012 %T Kilobot: A Low Cost Scalable Robot System for Collective Behaviors %A Michael Rubenstein %A Christian Ahler %A Radhika Nagpal %B IEEE Intl. Conf on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra12-rubenstein.pdf %0 Conference Paper %B IEEE Intl. Conference on Robots and Systems (IROS) %D 2012 %T Materials and Mechanisms for Amorphous Robotic Construction %A Nils Napp %A Olive Rappoli %A Jessica Wu %A Radhika Nagpal %B IEEE Intl. Conference on Robots and Systems (IROS) %G eng %U files/ssr/files/iros12-napp.pdf %0 Conference Paper %B Intl. Conf. on Information Processing in Sensor Networks (IPSN) %D 2012 %T Simbeeotic: A Simulator and Testbed for Micro-Aerial Vehicle Swarm Experiments %A Bryan Kate %A Jason Waterman %A Karthik Dantu %A Welsh, Matt %B Intl. Conf. on Information Processing in Sensor Networks (IPSN) %G eng %U files/ssr/files/ipsn12-kate.pdf %0 Journal Article %J Cell %D 2011 %T Control of the Mitotic Cleavage Plane by Local Epithelial Topology %A William Tyler Gibson %A J. Veldhuis %A B. Rubinstein %A H. Cartwright %A N. Perrimon %A W. Brodland %A Radhika Nagpal %A Matthew C. Gibson %B Cell %V 144 %P 414-426 %G eng %N 3 %R 10.1016/j.cell.2011.12.035 %0 Conference Paper %B Modular Robotics Workshop, Intl. Conference on Robots and Systems (IROS) %D 2011 %T Distributed Multi-Robot Algorithms for the TERMES 3D Collective Construction System %A Werfel, Justin %A Kirstin Petersen %A Radhika Nagpal %B Modular Robotics Workshop, Intl. Conference on Robots and Systems (IROS) %G eng %U files/ssr/files/iros11wksp-werfel.pdf %0 Conference Paper %B Intl. Conference on Robots and Systems (IROS) %D 2011 %T Effect of Sensor and Actuator Quality on Robot Swarm Algorithm Performance %A Nicholas Hoff %A Wood, Robert %A Radhika Nagpal %B Intl. Conference on Robots and Systems (IROS) %G eng %U files/ssr/files/iros11-hoff.pdf %0 Thesis %B Doctoral Thesis, Harvard University %D 2011 %T Multi-Robot Foraging for Swarms of Simple Robots %A Nicholas Hoff %B Doctoral Thesis, Harvard University %G eng %U files/ssr/files/phd11-hoff.pdf %9 phd %0 Conference Paper %B Intl. Conference on Robots and Systems (IROS) %D 2011 %T Optimization of Stochastic Strategies for Spatially Inhomogeneous Robot Swarms: A Case Study in Commercial Pollination %A Spring Berman %A Radhika Nagpal %A Adam Halasz %B Intl. Conference on Robots and Systems (IROS) %G eng %U files/ssr/files/iros11-berman.pdf %0 Conference Paper %B Intl. Conf. on Embedded Networked Sensor Systems (Sensys) %D 2011 %T Programming Micro-Aerial Swarms with Karma %A Karthik Dantu %A Bryan Kate %A Jason Waterman %A Bailis, Peter %A Welsh, Matt %B Intl. Conf. on Embedded Networked Sensor Systems (Sensys) %G eng %U files/ssr/files/sensys11-dantu.pdf %0 Conference Paper %B Robotics: Science and Systems Conference (RSS) %D 2011 %T TERMES: An Autonomous Robotic System for Three-Dimensional Collective Construction %A Kirstin Petersen %A Radhika Nagpal %A Werfel, Justin %B Robotics: Science and Systems Conference (RSS) %G eng %0 Thesis %B Doctoral Thesis, Harvard University %D 2011 %T Topological biases and feedbacks in proliferating tissues %A William Tyler Gibson %B Doctoral Thesis, Harvard University %G eng %U files/ssr/files/phd11-gibson.pdf %9 phd %0 Journal Article %J Journal of Materials Engineering and Performance %D 2011 %T Applicability of Shape Memory Alloy Wire for an Active Soft Orthotic %A Leia Stirling %A Chih-han Yu %A Jason Miller %A Eliot Hawkes %A Rob Wood %A Eugene Goldfield %A Radhika Nagpal %B Journal of Materials Engineering and Performance %G eng %U files/ssr/files/jmep11-stirling.pdf %0 Conference Paper %B Intl. Conference on Robots and Systems (IROS) %D 2011 %T Bio-inspired Active Soft Orthotic Device for Ankle Foot Pathologies %A Yong-Lae Park %A Bor-Rong Chen %A Diana Young %A Leia Stirling %A Rob Wood %A Eugene Goldfield %A Radhika Nagpal %B Intl. Conference on Robots and Systems (IROS) %G eng %U files/ssr/files/iros11-park.pdf %0 Conference Paper %B IEEE International Conference on Robotics and Automation %D 2011 %T Design of Control Policies for Spatially Inhomogeneous Robot Swarms with Application to Commercial Pollination %A Spring Berman %A Vijay Kumar %A and Radhika Nagpal %B IEEE International Conference on Robotics and Automation %G eng %U files/ssr/files/icra11-berman.pdf %0 Journal Article %J Technical Report TR-06-11 %D 2011 %T Kilobot: A Low Cost Scalable Robot System for Collective Behaviors %A Michael Rubenstein %A Nicholas Hoff %A Radhika Nagpal %B Technical Report TR-06-11 %G eng %U ftp://ftp.deas.harvard.edu/techreports/tr-06-11.pdf %0 Conference Paper %B Twenty-Fourth AAAI Conference on Artificial Intelligence (AAAI) %D 2010 %T Biologically-Inspired Control for Multi-Agent Self-Adaptive Tasks %A Chih-han Yu %A Radhika Nagpal %B Twenty-Fourth AAAI Conference on Artificial Intelligence (AAAI) %G eng %U files/ssr/files/aaai10-yu.pdf %0 Thesis %B Doctoral Thesis, Harvard University %D 2010 %T Biologically-Inspired Control for Self-Adaptive Multiagent Systems %A Chih-han Yu %B Doctoral Thesis, Harvard University %G eng %U files/ssr/files/phd10-yu.pdf %9 phd %0 Conference Paper %B Intl Symposium on Distributed Autonomous Robotic Systems (DARS) %D 2010 %T Distributed Colony-Level Algorithm Switching for Robot Swarm Foraging %A Nicholas Hoff %A Wood, Robert %A Radhika Nagpal %B Intl Symposium on Distributed Autonomous Robotic Systems (DARS) %G eng %U files/ssr/files/dars10-nhoff.pdf %0 Conference Paper %B Modular Robotics Workshop, IEEE Intl. Conf. on Robotics and Automation (ICRA) %D 2010 %T KiloBot: A Robotic Modules for Demonstrating Collective Behaviors %A Mike Rubenstein %A Radhika Nagpal %B Modular Robotics Workshop, IEEE Intl. Conf. on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra2010-rubenstein-workshoppaper.pdf %0 Conference Paper %B Modular Robotics Workshop, IEEE Intl. Conf. on Robotics and Automation (ICRA) %D 2010 %T Mechanical Design and Locomotion of Modular-Expanding Robots %A Rebecca Belisle %A Chih-han Yu %A Radhika Nagpal %B Modular Robotics Workshop, IEEE Intl. Conf. on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra2010-belisle-workshoppaper.pdf %0 Conference Paper %B Intl. Conference on Swarms Intelligence (ANTs) %D 2010 %T Positional Communication and Private Information in Honeybee Foraging Models %A Bailis, Peter %A Radhika Nagpal %A Werfel, Justin %B Intl. Conference on Swarms Intelligence (ANTs) %G eng %0 Conference Paper %B IEEE International Conference on Robotics and Biomimetics (ROBIO) %D 2010 %T Two Foraging Algorithms for Robot Swarms Using Only Local Communication %A Nicholas Hoff %A Amelia Sagoff %A Wood, Robert J. %A Radhika Nagpal %B IEEE International Conference on Robotics and Biomimetics (ROBIO) %G eng %U files/ssr/files/robio10-nhoff.pdf %0 Conference Paper %B Intl. Conf on Autonomous Agents and Multi-Agent Systems (AAMAS) %D 2010 %T Collective Decision-Making in Multi-Agent Systems by Implicit Leadership %A Chih-han Yu %A Werfel, Justin %A Radhika Nagpal %B Intl. Conf on Autonomous Agents and Multi-Agent Systems (AAMAS) %G eng %U files/ssr/files/aamas10-chihhan.pdf %0 Conference Paper %B IEEE International Conference on Robotics and Automation (ICRA) %D 2010 %T Coordinating Collective Locomotion in an Amorphous Modular Robot %A Chih-han Yu %A Werfel, Justin %A Radhika Nagpal %B IEEE International Conference on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra10-chihhan.pdf %0 Journal Article %J Intl Journal of Robotics Research %D 2010 %T A Self-Adaptive Framework for Modular Robots in Dynamic Environment: Theory and Applications %A Chih-han Yu %A Radhika Nagpal %B Intl Journal of Robotics Research %G eng %U files/ssr/files/ijrr10-yu.pdf %0 Journal Article %J PLoS Comput Biol 5(6):e1000412 %D 2009 %T Modeling and Inferring Cleavage Patterns in Proliferating Epithelia %A Ankit Patel %A William Tyler Gibson %A Matt Gibson %A Radhika Nagpal %B PLoS Comput Biol 5(6):e1000412 %V 5 %P 1000412 %G eng %U http://www.ploscompbiol.org/doi/pcbi.1000412 %N 6 %0 Conference Paper %B IEEE International Conference on Robotics and Automation (ICRA) %D 2009 %T Self-Adapting Modular Robotics: A Generalized Distributed Consensus Framework %A Chih-han Yu %A Radhika Nagpal %B IEEE International Conference on Robotics and Automation (ICRA) %G eng %U files/ssr/files/iros09-yu.pdf %0 Journal Article %J BioEssays %D 2008 %T Epithelial topology. Problems and Paradigms %A Radhika Nagpal %A Ankit Patel %A Matt Gibson %B BioEssays %V 30 %P 260-266 %G eng %U files/ssr/files/bioessays08-nagpal.pdf %N 3 %0 Thesis %B Doctoral Thesis, Harvard University %D 2008 %T Modeling and Inferring Cleavage Patterns in Proliferating Epithelia %A Ankit Patel %B Doctoral Thesis, Harvard University %G eng %U files/ssr/files/phd08-patel.pdf %9 phd %0 Conference Paper %B IEEE Intl. Conference on Intelligent Robots and Systems (IROS) %D 2008 %T Morpho: A Self-Deformable Modular Robot Inspired By Cellular Structure %A Chih-han Yu %A Kristina Haller %A Donald Ingber %A Radhika Nagpal %B IEEE Intl. Conference on Intelligent Robots and Systems (IROS) %G eng %U files/ssr/files/iros08-yu.pdf %0 Conference Paper %B Intl. Conf on Autonomous Agents and Multi-Agent Systems (AAMAS) %D 2008 %T Sensing-based Shape Formation Tasks on Modular Multi-Robot Systems: A Theoretical Study %A Chih-han Yu %A Radhika Nagpal %B Intl. Conf on Autonomous Agents and Multi-Agent Systems (AAMAS) %G eng %U files/ssr/files/aamas08-chihhan.pdf %0 Thesis %B Doctoral thesis, Harvard University %D 2008 %T A Theory of Local-to-Global Algorithms for One-Dimensional Spatial Multi-Agent Systems %A Yamins, Daniel %B Doctoral thesis, Harvard University %G eng %U files/ssr/files/phd08-yamins.pdf %9 phd %0 Journal Article %J International Journal of Robotics Research %D 2008 %T Three-dimensional construction with mobile robots and modular blocks %A Werfel, Justin %A Radhika Nagpal %B International Journal of Robotics Research %V 27 %P 463-479 %G eng %U files/ssr/files/ijrr08-werfel.pdf %N 3-4 %0 Conference Paper %B IEEE Intl. Conf. on Self-Organising Systems (SASO) %D 2008 %T Towards Desynchronization of Multi-hop Topologies %A Julius Degesys %A Radhika Nagpal %B IEEE Intl. Conf. on Self-Organising Systems (SASO) %G eng %U files/ssr/files/saso08-degesys.pdf %0 Conference Paper %B Intl. Conf on Autonomous Agents and Multi-Agent Systems (AAMAS) %D 2008 %T Automated Global-to-Local Programming in 1-D Spatial Multi-Agent Systems %A Yamins, Daniel %A Radhika Nagpal %B Intl. Conf on Autonomous Agents and Multi-Agent Systems (AAMAS) %G eng %U files/ssr/files/aamas08-yamins.pdf %0 Conference Paper %B IEEE Conference on Intelligent Robots and Systems (IROS) %D 2007 %T Collective Construction of Environmentally-adaptive Structures %A Werfel, Justin %A Donald Ingber %A Radhika Nagpal %B IEEE Conference on Intelligent Robots and Systems (IROS) %G eng %U files/ssr/files/iros07-jkwerfel.pdf %0 Conference Paper %B International Conference on Information Processing in Sensor Networks (IPSN) %D 2007 %T DESYNC: Self-Organizing Desynchronization and TDMA on Wireless Sensor Networks %A Julius Degesys %A Ian Rose %A Ankit Patel %A Radhika Nagpal %B International Conference on Information Processing in Sensor Networks (IPSN) %G eng %U files/ssr/files/ipsn07-degesys.pdf %0 Conference Paper %B IEEE Conference on Self-Adaptive and Self-Organizing Systems (SASO) %D 2007 %T Desynchronization: The Theory of Self-Organizing Algorithms for Round-Robin Scheduling %A Ankit Patel %A Julius Degesys %A Radhika Nagpal %B IEEE Conference on Self-Adaptive and Self-Organizing Systems (SASO) %G eng %U files/ssr/files/saso07-patel.pdf %0 Conference Paper %B IEEE Conference on Self-Adaptive and Self-Organizing Systems (SASO) %D 2007 %T Global-to-Local Programming: Design and Analysis for Amorphous Computers %A Radhika Nagpal %A Yamins, Daniel %B IEEE Conference on Self-Adaptive and Self-Organizing Systems (SASO) %G eng %U files/ssr/files/saso-tutorial-overview.pdf %0 Conference Paper %B IEEE International Conference on Pervasive Computing and Communication (Percom) %D 2007 %T Macro Programming through Bayesian Networks: Distributed Inference and Anomaly Detection %A Marco Mamei %A Radhika Nagpal %B IEEE International Conference on Pervasive Computing and Communication (Percom) %G eng %U files/ssr/files/percom07-mamei.pdf %0 Journal Article %J and Systems (IROS) %D 2007 %T Self-organizing Environmentally-adaptive Shapes on a Modular Robot %A Chih-han Yu %A FX Williems %A Donald Ingber %A Radhika Nagpal %B and Systems (IROS) %G eng %U files/ssr/files/iros07-chihhan.pdf %0 Conference Paper %B Workshop on Self-reconfigurable Robot Systems and Applications, IEEE Conference on Intelligent Robots and Systems (IROS) %D 2007 %T Towards a Common Comparison Framework for Global-to-Local Programming of Self-assembling Robotic Systems %A Werfel, Justin %A Radhika Nagpal %B Workshop on Self-reconfigurable Robot Systems and Applications, IEEE Conference on Intelligent Robots and Systems (IROS) %G eng %U ftp://ftp.deas.harvard.edu/techreports/tr-14-07.pdf %0 Thesis %B Doctoral thesis, Massachusetts Institute of Technology %D 2006 %T Anthills Built to Order: Automating Construction with Artificial Swarms %A Werfel, Justin %B Doctoral thesis, Massachusetts Institute of Technology %G eng %U files/ssr/files/phd06-werfel.pdf %9 phd %0 Conference Paper %B Robot Exhibition, National Conference on Artificial Intelligence %D 2006 %T Collective Construction Using Lego Robots %A Crystal Schuil %A Matthew Valente %A Werfel, Justin %A Radhika Nagpal %B Robot Exhibition, National Conference on Artificial Intelligence %G eng %U files/ssr/files/aaai06-schuil.pdf %0 Conference Paper %B IEEE International Conference on Robotics and Automation (ICRA) %D 2006 %T Distributed Construction by Mobile Robots with Enhanced Building Blocks %A Werfel, Justin %A Bar-Yam, Yaneer %A Daniela Rus %A and Radhika Nagpal %B IEEE International Conference on Robotics and Automation (ICRA) %G eng %U files/ssr/files/icra06-werfel.pdf %0 Journal Article %J IEEE Intelligent Systems %D 2006 %T Extended Stigmergy in Collective Construction %A Werfel, Justin %A Radhika Nagpal %B IEEE Intelligent Systems %V 21 %P 20-28 %G eng %U files/ssr/files/ieeeis06-werfel.pdf %N 2 %0 Journal Article %J IEEE Intelligent Systems %D 2006 %T Self-Organizing Shape and Pattern: From Cells to Robots %A Radhika Nagpal %B IEEE Intelligent Systems %V 21 %G eng %U files/ssr/files/ieeeis06-nagpal.pdf %N 2 %0 Conference Paper %B Workshop on Self-Reconfigurable Modular Robots, Robotics: Science and Systems (RSS) %D 2006 %T Three-dimensional Directed Construction by Mobile Robots %A Werfel, Justin %A Radhika Nagpal %B Workshop on Self-Reconfigurable Modular Robots, Robotics: Science and Systems (RSS) %G eng %U files/ssr/files/rsswk06-werfel.pdf %0 Journal Article %J Nature %D 2006 %T The Emergence of Geometric Order in Proliferating Metazoan Epithelia %A Gibson, Matthew %A Ankit Patel %A Radhika Nagpal %A Perrimon, Norbert %X

The predominantly hexagonal cell pattern of simple epithelia was noted in the earliest microscopic analyses of animal tissues1, a topology commonly thought to reflect cell sorting into optimally packed honeycomb arrays2. Here we use a discrete Markov model validated by time-lapse microscopy and clonal analysis to demonstrate that the distribution of polygonal cell types in epithelia is not a result of cell packing, but rather a direct mathematical consequence of cell proliferation. On the basis of in vivo analysis of mitotic cell junction dynamics in Drosophila imaginal discs, we mathematically predict the convergence of epithelial topology to a fixed equilibrium distribution of cellular polygons. This distribution is empirically confirmed in tissue samples from vertebrate, arthropod and cnidarian organisms, suggesting that a similar proliferation-dependent cell pattern underlies pattern formation and morphogenesis throughout the metazoa.

%B Nature %V 442 %G eng %N 7106 %0 Conference Paper %B Intl. Joint Conference on Artificial Intelligence (IJCAI '05) %D 2005 %T Building Patterned Structures with Robot Swarms %A Werfel, Justin %A Bar-Yam, Yaneer %A Radhika Nagpal %B Intl. Joint Conference on Artificial Intelligence (IJCAI '05) %G eng %U files/ssr/files/ijcai05-werfel.pdf %0 Conference Paper %B ACM Conference on Embedded Networked Sensor Systems (SenSys '05) %D 2005 %T Firefly-Inspired Sensor Network Synchronicity with Realistic Radio Effects %A Geoff Werner-Allen %A Geetika Tewari %A Ankit Patel %A Welsh, Matt %A Radhika Nagpal %B ACM Conference on Embedded Networked Sensor Systems (SenSys '05) %G eng %U files/ssr/files/sensys05-werner.pdf %0 Conference Paper %B National Conference on Artificial Intelligence (AAAI '05) %D 2005 %T Robust and Self-repairing Formation Control for Swarms of Mobile Agents %A Jimming Cheng %A Winston Cheng %A Radhika Nagpal %B National Conference on Artificial Intelligence (AAAI '05) %G eng %U files/ssr/files/aaai05-cheng.pdf %0 Conference Paper %B Autonomous Agents and Multi Agent Systems Conferences (AAMAS) %D 2005 %T Towards a Theory of "Local to Global" in Distributed Multi-Agent Systems (II) %A Yamins, Daniel %B Autonomous Agents and Multi Agent Systems Conferences (AAMAS) %G eng %U files/ssr/files/aamas05-yamins2.pdf %0 Conference Paper %B Autonomous Agents and Multi Agent Systems Conferences (AAMAS) %D 2005 %T Towards a Theory of "Local to Global" in Distributed Multi-Agent Systems (I) %A Yamins, Daniel %B Autonomous Agents and Multi Agent Systems Conferences (AAMAS) %G eng %U files/ssr/files/aamas05-yamins1.pdf %0 Journal Article %J International Symposium on Distributed Autonomous Robotic Systems (DARs) %D 2004 %T Self-reconfiguration using Directed Growth (for a modular robot) %A Kasper Stoy %A Radhika Nagpal and %B International Symposium on Distributed Autonomous Robotic Systems (DARs) %G eng %U files/ssr/files/dars04-stoy.pdf %0 Conference Paper %B IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) %D 2004 %T Self-repair and Scale-independent Self-reconfiguration (for a modular robot) %A Kasper Stoy %A Radhika Nagpal %B IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) %G eng %U files/ssr/files/iros04-stoy.pdf %0 Journal Article %J Methodologies and Software Engineering for Agent Systems %D 2003 %T Engineering Amorphous Computing Systems %A Radhika Nagpal %A Marco Mamei %B Methodologies and Software Engineering for Agent Systems %G eng %U files/ssr/files/nagpal-mamei-chapter.pdf %0 Journal Article %J Telecommunications Systems Journal %D 2003 %T Experimental Results and Theoretical Analysis of a Self-Organizing Global Coordinate System for Ad Hoc Sensor Networks %A Jonathan Bachrach %A Radhika Nagpal %A Micheal Salib %A Howard Shrobe %B Telecommunications Systems Journal %G eng %U files/ssr/files/tsjournal03-bachrach.pdf %0 Conference Paper %B Processing in Sensor Networks (IPSN '03) %D 2003 %T Organizing a Global Coordinate System from Local Information on an Ad Hoc Sensor Network %A Radhika Nagpal %A Howard Shrobe %A Jonathan Bachrach %B Processing in Sensor Networks (IPSN '03) %G eng %U files/ssr/files/ipsn03-nagpal.pdf %0 Conference Paper %B AAAI Spring Symposium on Computational Synthesis: From Basic Building Blocks to High Level Functionality %D 2003 %T Programming Methodology for Biologically-Inspired Self-Assembling Systems %A Radhika Nagpal %A Attila Kondacs %A Catherine Chang %B AAAI Spring Symposium on Computational Synthesis: From Basic Building Blocks to High Level Functionality %G eng %U files/ssr/files/aaaiSS03-nagpal.pdf %0 Conference Paper %B Workshop on Adaptability in Multi-Agent Systems, RoboCup Australian Open %D 2003 %T Self-Assembly and Self-Repairing Topologies %A Lauren Clement %A Radhika Nagpal %B Workshop on Adaptability in Multi-Agent Systems, RoboCup Australian Open %G eng %U files/ssr/files/arobocup03-clement.pdf %0 Conference Paper %B Workshop on Engineering Self-organising Applications, Autonomous Agents and Multiagents Systems Conference (AAMAS) %D 2003 %T Towards a Catalog of Biologically-inspired Primitives %A Radhika Nagpal %B Workshop on Engineering Self-organising Applications, Autonomous Agents and Multiagents Systems Conference (AAMAS) %G eng %U files/ssr/files/esoa03-nagpal.pdf %0 Conference Paper %B Proceedings of the 4th International Conference on Complex Systems (ICCS) %D 2002 %T Programmable Pattern-Formation and Scale-Independence %A Radhika Nagpal %B Proceedings of the 4th International Conference on Complex Systems (ICCS) %G eng %U files/ssr/files/ICCS02-nagpal.pdf %0 Conference Paper %B Proceedings of the 1st International Joint Conference on Autonomous Agents and Multi-Agent Systems (AAMAS) %D 2002 %T Programmable Self-Assembly Using Biologically-Inspired Multiagent Control %A Radhika Nagpal %B Proceedings of the 1st International Joint Conference on Autonomous Agents and Multi-Agent Systems (AAMAS) %G eng %U files/ssr/files/aamas02-nagpal.pdf %0 Thesis %B PhD Thesis, MIT Artificial Intelligence Laboratory %D 2001 %T Programmable Self-Assembly: Constructing Global Shape Using Biologically-Inspired Local Interactions and Origami Mathematics %A Radhika Nagpal %B PhD Thesis, MIT Artificial Intelligence Laboratory %G eng %U http://www.swiss.ai.mit.edu/projects/amorphous/Progmat/nagpal-thesis.ps %9 phd %0 Journal Article %J Communications of the ACM %D 2000 %T Amorphous Computing %A Harold Abelson %A Don Allen %A Daniel Coore %A Chris Hanson %A George Homsy %A Thomas Knight %A Radhika Nagpal %A Erik Rauch %A Gerald Sussman %A Weiss, Ron %B Communications of the ACM %V 43 %G eng %U files/ssr/files/cacm2000-abelson.pdf %N 5 %0 Conference Paper %B International Conference on Architectural Support for Programming Languages and Operating Systems, Wild & Crazy Ideas Session %D 1998 %T Programming Biological Cells %A Weiss, Ron %A George Homsy %A and Radhika Nagpal %B International Conference on Architectural Support for Programming Languages and Operating Systems, Wild & Crazy Ideas Session %G eng %U files/ssr/files/asplos98-weiss.pdf