Author name cluster

Seth Copen Goldstein

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16 papers

2 author rows

IROS Conference 2018 Conference Paper

Electing an Approximate Center in a Huge Modular Robot with the k-BFS SumSweep Algorithm

Andre Naz
Benoît Piranda
Julien Bourgeois
Seth Copen Goldstein

Among the diversity of the existing modular robotic systems, we consider in this paper the subset of distributed modular robotic ensembles composed of resource-constrained identical modules that are organized in a lattice structure and which can only communicate with neighboring modules. These modular robotic ensembles form asynchronous distributed embedded systems. In many algorithms dedicated to distributed system coordination, a specific role has to be played by a leader, i. e. , a single node in the system. This leader can be elected using various criteria. A possible strategy is to elect a center node, i. e. , a node that has the minimum distance to all the other nodes. Indeed, this node is ideally located to communicate with all the others and this leads to better performance in many algorithms. The contribution of this paper is to propose the k-BFS SumSweep algorithm designed to elect an approximate-center node. We evaluated our algorithm both on hardware modular robots and in a simulator for large ensembles of robots. Experimental results show that k-BFS SumSweep is often the most accurate approximation algorithm (with an average relative accuracy between 90% to 100%) while using the fewest messages in large-scale systems, requiring only a modest amount of memory per node, and converging in a reasonable length of time.

IROS Conference 2015 Conference Paper

ABC-Center: Approximate-center election in modular robots

Andre Naz
Benoît Piranda
Seth Copen Goldstein
Julien Bourgeois

Modular robots are composed of many independent connected modules which are able to achieve common goals through communications. Many distributed algorithms have better performance if the modules that have to communicate with all the others, are placed at the center of the system. In this paper, we propose ABC-Center, an iterative algorithm for electing an approximate-center module in modular robots. ABC-Center uses O(1) space per module and O(kd) time, where k is the number of iterations required to terminate and d the diameter of the system. We evaluated our algorithm both on hardware modular robots and in a simulator for large ensemble of robots. The average expected eccentricity of the module elected by ABC-Center is less than 1. 25 blocks off for random systems composed of up to 1000 modules. Furthermore, experiments show that our algorithm terminates after a few iterations. Hence, ABC-Center is scalable and adapted to modular robots with low memory resources.

TAAS Journal 2011 Journal Article

Detecting Locally Distributed Predicates

Michael De Rosa
Seth Copen Goldstein
Peter Lee
Jason Campbell
Padmanabhan S. Pillai

In this article, we formalize locally distributed predicates, a concept previously introduced to address specific challenges associated with modular robotics and distributed debugging. A locally distributed predicate (LDP) is a novel construction for representing and detecting distributed properties in sparse-topology systems. Our previous work on LDPs presented empirical validation; here we show a formal model for two variants of the LDP algorithm, LDP-Basic and LDP-Snapshot, and establish performance bounds for these variants. We prove that LDP-Basic can detect strong stable predicates, that LDP-Snapshot can detect all stable predicates, and discuss their applicability to various distributed programming domains and to spatial computing in general. LDP detection in bounded-degree networks is shown to be scale-free, making the approach particularly attractive for specific topologies, even though LDPs are less efficient than snapshot algorithms in general distributed systems.

IROS Conference 2009 Conference Paper

A tale of two planners: Modular robotic planning with LDP

Michael DeRosa
Seth Copen Goldstein
Peter Lee 0001
Padmanabhan Pillai
Jason Campbell

LDP (Locally Distributed Predicates) is a distributed, high-level language for programming modular reconfigurable robot systems (MRRs). In this paper we present the implementation of two motion-planning algorithms in LDP, and analyze both their performance and ease of implementation. We present multiple variations of one planner, including a novel resource allocation algorithm. We then draw conclusions about both the utility of the motion-planning algorithms and the suitability of LDP to the problem space. Our experiments suggest that metamodule-based planning approaches have a cost in time and/or energy terms, but that the cost can be worth paying in exchange for the additional generality and separation-of-concerns offered by these techniques. The particular tradeoff for a given system will depend upon its goals and the details of the underlying modules.

IROS Conference 2009 Conference Paper

Design of prismatic cube modules for convex corner traversal in 3D

Michael Philetus Weller
Brian T. Kirby
H. Benjamin Brown
Mark D. Gross
Seth Copen Goldstein

The prismatic cube style of modular robot is a promising design for realizing self-reconfigurable 3D lattices. Cubic lattices with prismatic transitions simplify many aspects of the hardware and planning control needed for reconfiguration. Despite much research on how cubic modules can coordinate to reconfigure, until now these transitions have not been fully demonstrated in hardware. We describe our movement primitives for both orthogonal and convex corner transitions with prismatic cube modules. We discuss the design of a hardware module capable of performing these transitions, as well as assess the performance of this hardware in an initial demonstration of these transitions.

IROS Conference 2009 Conference Paper

Stress-driven MEMS assembly + electrostatic forces = 1mm diameter robot

Mustafa Emre Karagozler
Seth Copen Goldstein
James Robert Reid

As the size of the modules in a self-reconfiguring modular robotic system shrinks and the number of modules increases, the flexibility of the system as a whole increases. In this paper, we describe the manufacturing methods and mechanisms for a 1 millimeter diameter module which can be manufactured en masse. The module is the first step towards realizing the basic unit of claytronics, a modular robotic system designed to scale to millions of units.

IROS Conference 2008 Conference Paper

Generalizing metamodules to simplify planning in modular robotic systems

Daniel J. Dewey
Michael P. Ashley-Rollman
Michael DeRosa
Seth Copen Goldstein
Todd C. Mowry
Siddhartha S. Srinivasa
Padmanabhan Pillai
Jason Campbell

In this paper we develop a theory of metamodules and an associated distributed asynchronous planner which generalizes previous work on metamodules for lattice-based modular robotic systems. All extant modular robotic systems have some form of non-holonomic motion constraints. This has prompted many researchers to look to metamodules, i. e. , groups of modules that act as a unit, as a way to reduce motion constraints and the complexity of planning. However, previous metamodule designs have been specific to a particular modular robot. By analyzing the constraints found in modular robotic systems we develop a holonomic metamodule which has two important properties: (1) it can be used as the basic unit of an efficient planner and (2) it can be instantiated by a wide variety of different underlying modular robots, e. g. , modular robot arms, expanding cubes, hex-packed spheres, etc. Using a series of transformations we show that our practical metamodule system has a provably complete planner. Finally, our approach allows the task of shape transformation to be separated into a planning task and a resource allocation task. We implement our planner for two different metamodule systems and show that the time to completion scales linearly with the diameter of the ensemble.

ICRA Conference 2008 Conference Paper

Programming modular robots with locally distributed predicates

Michael DeRosa
Seth Copen Goldstein
Peter Lee 0001
Padmanabhan Pillai
Jason Campbell

We present a high-level language for programming modular robotic systems, based on locally distributed predicates (LDP), which are distributed conditions that hold for a connected subensemble of the robotic system. An LDP program is a collection of LDPs with associated actions which are triggered on any subensemble that matches the predicate. The result is a reactive programming language which efficiently and concisely supports ensemble-level programming. We demonstrate the utility of LDP by implementing three common, but diverse, modular robotic tasks.

IROS Conference 2007 Conference Paper

A modular robotic system using magnetic force effectors

Brian T. Kirby
Burak Aksak
Jason Campbell
James F. Hoburg
Todd C. Mowry
Padmanabhan Pillai
Seth Copen Goldstein

One of the primary impediments to building ensembles of modular robots is the complexity and number of mechanical mechanisms used to construct the individual modules. As part of the Claytronics project - which aims to build very large ensembles of modular robots - we investigate how to simplify each module by eliminating moving parts and reducing the number of mechanical mechanisms on each robot by using force-at-a-distance actuators. Additionally, we are also investigating the feasibility of using these unary actuators to improve docking performance, implement intermodule adhesion, power transfer, communication, and sensing. In this paper we describe our most recent results in the magnetic domain, including our first design sufficiently robust to operate reliably in groups greater than two modules. Our work should be seen as an extension of systems such as Fracta [9], and a contrasting line of inquiry to several other researchers' prior efforts that have used magnetic latching to attach modules to one another but relied upon a powered hinge [10] or telescoping mechanism [12] within each module to facilitate self-reconfiguration.

IROS Conference 2007 Conference Paper

A scalable distributed algorithm for shape transformation in multi-robot systems

Ramprasad Ravichandran
Geoffrey J. Gordon
Seth Copen Goldstein

Distributed reconfiguration is an important problem in multi-robot systems such as mobile sensor nets and metamorphic robot systems. In this work, we present a scalable distributed reconfiguration algorithm, hierarchical median decomposition, to achieve arbitrary target configurations. Our algorithm is built on top of a novel distributed median consensus estimator. The algorithms presented are fully distributed and do not require global communication. We show results from simulations in an open source multi-robot simulator.

ICRA Conference 2007 Conference Paper

Distributed Watchpoints: Debugging Large Multi-Robot Systems

Michael DeRosa
Jason Campbell
Padmanabhan Pillai
Seth Copen Goldstein
Peter Lee 0001
Todd C. Mowry

Tightly-coupled multi-agent systems such as modular robots frequently exhibit properties of interest that span multiple modules. These properties cannot easily be detected from any single module, though they might readily be detected by combining the knowledge of multiple modules. Testing for distributed conditions is especially important in debugging or verifying the correctness of software for modular robots. We have developed a technique we call distributed watchpoint triggers which can efficiently recognize such distributed conditions. Our watchpoint description language can handle a variety of temporal, spatial, and logical properties spanning multiple robots. This paper presents that language, describes our fully-distributed, online mechanism for detecting distributed conditions in a running system, and evaluates the performance of our implementation. We found that the performance of the system is highly dependent on the program being debugged, scales linearly with ensemble size, and is small enough to make the system practical in all but the worst case scenarios

IROS Conference 2007 Conference Paper

Electrostatic latching for inter-module adhesion, power transfer, and communication in modular robots

Mustafa Emre Karagozler
Jason Campbell
Gary K. Fedder
Seth Copen Goldstein
Michael Philetus Weller
Byung Woo Yoon

A simple and robust inter-module latch is possibly the most important component of a modular robotic system. This paper describes a latch based on electric fields and capacitive coupling. Our design provides not only significant adhesion forces, but can also be used for inter-module power transmission and communication. The key insight presented in this paper, and the factor that enables electrostatic adhesion to be effective at the macroscale, is the use of electric field attraction to generate frictional shear forces rather than electric field attraction alone. A second important insight is that a specific degree of flexibility in the electrodes is essential to maximize their mutual coupling and the resulting forces - electrodes which are too flexible or too rigid will perform less well. To evaluate the effectiveness of our latch we incorporate it into a cubic module 28 cm on a side. The result is a latch which requires almost zero static power and yet can hold 0. 6 N/cm 2 of latch area.

IROS Conference 2007 Conference Paper

Meld: A declarative approach to programming ensembles

Michael P. Ashley-Rollman
Seth Copen Goldstein
Peter Lee 0001
Todd C. Mowry
Padmanabhan Pillai

This paper presents Meld, a programming language for modular robots, i. e. , for independently executing robots where inter-robot communication is limited to immediate neighbors. Meld is a declarative language, based on P2, a logicprogramming language originally designed for programming overlay networks. By using logic programming, the code for an ensemble of robots can be written from a global perspective, as opposed to a large collection of independent robot views. This greatly simplifies the thought process needed for programming large ensembles. Initial experience shows that this also leads to a considerable reduction in code size and complexity. An initial implementation of Meld has been completed and has been used to demonstrate its effectiveness in the Claytronics simulator. Early results indicate that Meld programs are considerably more concise (more than 20× shorter) than programs written in C++, while running nearly as efficiently.

IROS Conference 2006 Conference Paper

Hierarchical Motion Planning for Self-reconfigurable Modular Robots

Preethi Srinivas Bhat
James J. Kuffner
Seth Copen Goldstein
Siddhartha S. Srinivasa

Motion planning for a self-reconfigurable robot involves coordinating the movement and connectivity of each of its homogeneous modules. Reconfiguration occurs when the shape of the robot changes from some initial configuration to a target configuration. Finding an optimal solution to reconfiguration problems involves searching the space of possible robot configurations. As this space grows exponentially with the number of modules, optimal planning becomes intractable. We propose a hierarchical planning approach that computes heuristic global reconfiguration strategies efficiently. Our approach consists of a base planner that computes an optimal solution for a few modules and a hierarchical planner that calls this base planner or reuses pre-computed plans at each level of the hierarchy to ultimately compute a global suboptimal solution. We present results from a prototype implementation of the method that efficiently plans for self-reconfigurable robots with several thousand modules. We also discuss tradeoffs and performance issues including scalability, heuristics and plan optimality

ICRA Conference 2006 Conference Paper

Scalable Shape Sculpting via Hole Motion: Motion Planning in Lattice-constrained Modular Robots

Michael DeRosa
Seth Copen Goldstein
Peter Lee 0001
Jason Campbell
Padmanabhan Pillai

We describe a novel shape formation algorithm for ensembles of 2-dimensional lattice-arrayed modular robots, based on the manipulation of regularly shaped voids within the lattice ("holes"). The algorithm is massively parallel and fully distributed. Constructing a goal shape requires time proportional only to the complexity of the desired target geometry. Construction of the shape by the modules requires no global communication nor broadcast floods after distribution of the target shape. Results in simulation show 97. 3% shape compliance in ensembles of approximately 60, 000 modules, and we believe that the algorithm will generalize to 3D and scale to handle millions of modules

IROS Conference 2005 Conference Paper

The robot is the tether: active, adaptive power routing modular robots with unary inter-robot connectors

Jason Campbell
Padmanabhan Pillai
Seth Copen Goldstein

This paper describes a novel approach to powering a radical type of microrobot. Our long-term aim is to enable the construction of ensembles of millions of coordinated near-spherical, submillimeter microrobots. Both the large number of potential simultaneous neighbors of each robot (12) and the difficulty of fine actuation at such small scales preclude the use of complex connectors previously developed in many modular robotics efforts. Instead, we propose to leverage multirobot cooperation to simplify the mechanics of modular robot docking. In our approach, the robots actively cooperate to route virtual power busses (both supply and ground) to all the robots in the ensemble using only unary (single conductor) electrical connectors between robots. A unary connector allows for larger tolerances in engagement angle, simplifies robot manufacture, speeds reconfiguration, and maximizes the proportion of the connector surface area useful for carrying current. The algorithms we present permit a robot ensemble to efficiently harvest and distribute power from sources discovered in the environment and/or carried by the ensemble. We evaluate these algorithms in a variety of simulated deployment conditions and report on the impact of hardware defects, limited on-board power storage, and the ensemble-environment interface.