We describe the design, implementation, and experimentation with a collection of robots that, starting from an amorphous arrangement, can be assembled into arbitrary shapes and then commanded to self-disassemble in an organized manner. Each of the 28 modules in the system is implemented as a 1.8-inch autonomous cube-shaped robot able to connect to and communicate with its immediate neighbors. Two cooperating microprocessors control each module's magnetic connection mechanisms and infrared communication interfaces. When assembled into a structure, the modules form a system that can be virtually sculpted using a computer interface. We report on the hardware design and experiments from hundreds of trials.

This paper explores the space of active modular trusses, ranging from a passive truss with one independent active climbing module to fully self-reconfiguring dynamically controllable trusses comprised of active modules and passive struts. We describe a hardware design for truss climbing and present hierarchical algorithms for controlling hyper-redundant modular trusses

In this paper we describe a modular self-reconfiguring robot composed of Molecule robot modules. We present the architecture of this robot and discuss how self-reconfiguration can be used as a locomotion gait for this system. We present two types of locomotion algorithms for this robot: a statically stable tumbling algorithm and a dynamically stable algorithm that achieves locomotion by modifying the center of mass of the robot. For each algorithm we analyze the efficiency of the self-reconfiguration gait for locomotion. Finally we present experimental data for the tumbling algorithm implemented on a four-module Molecule robot.

We propose a novel modular underwater robot which can self-reconfigure by stacking and unstacking its component modules. Applications for this robot include underwater monitoring, exploration, and surveillance. Our current prototype is a single module which contains several subsystems that later will be segregated into different modules. This robot functions as a testbed for the subsystems which are needed in the modular implementation. We describe the module design and discuss the propulsion, docking, and optical ranging subsystems in detail. Experimental results demonstrate depth control, linear motion, target module detection, and docking capabilities.

In this paper we present a novel platform for underwater sensor networks to be used for long-term monitoring of coral reefs and fisheries. The sensor network consists of static and mobile underwater sensor nodes. The nodes communicate point-to-point using a novel high-speed optical communication system integrated into the TinyOS stack, and they broadcast using an acoustic protocol integrated in the TinyOS stack. The nodes have a variety of sensing capabilities, including cameras, water temperature, and pressure. The mobile nodes can locate and hover above the static nodes for data muling, and they can perform network maintenance functions such as deployment, relocation, and recovery. In this paper we describe the hardware and software architecture of this underwater sensor network. We then describe the optical and acoustic networking protocols and present experimental networking and data collected in a pool, in rivers, and in the ocean. Finally, we describe our experiments with mobility for data muling in this network.

In this paper we present generic distributed algorithms for assembling and repairing shapes using modular self-reconfiguring robots. The algorithms work in the sliding cube model. Each module independently evaluates a set of local rules using different evaluation models. Two methods are used to determine the correctness of the algorithms - a graph analysis technique which can prove the rule set is correct for specific instances of the algorithm, and a statistical technique which can produce arbitrary bounds on the likelihood that the rule set functions correctly. An extension of the assembly algorithm can be used to produce arbitrary non-cantilevered convex shapes without holes. The algorithms have been implemented and evaluated in simulation.

Previous work on self-reconfiguring modular robots has concentrated primarily on hardware and reconfiguration algorithms for particular systems. We introduce a type of generic locomotion algorithm for self-reconfigurable robots. The algorithms presented are inspired by cellular automata, using geometric rules to control module actions. The actuation model used is a general one, presuming that modules can generally move over the surface of a group of modules. These algorithms can then be instantiated on to a variety of particular systems. Correctness proofs of the rule sets are also given for the generic geometry, with the intent that this analysis can carry over to the instantiated algorithms to provide different systems with correct locomotion algorithms.

In this paper we present algorithms for planning the motion of robotic "molecules" (modules) on a substrate of other molecules. Our approach is to divide self-reconfiguration planning into three levels: trajectory planning, configuration planning, and task-level planning. This paper focuses on algorithms for trajectory planning, moving a single molecule from a start location to a goal location, and configuration planning, moving a set of molecules from a starting configuration to a goal configuration. We also present our scaffold planning approach in which the interior of a structure contains three-dimensional tunnels. This allows molecules to move within a structure as well as on the surface, simplifying molecule motion planning as well as increasing parallelism. In addition, we present a new gripper-type connection mechanism for the molecule which does not require power to maintain connections.

We discuss a robotic module called a molecule. Molecules can be the basis for building self-reconfiguring robots. They support multiple modalities of locomotion and manipulation. We describe the design, functionality, and control of the molecule. We show how a set of molecules can aggregate as active three-dimensional structures that can move and change shape. Finally, we discuss our molecule experiments.

In this paper we present a geometric approach to specifying and planning the motion of robotic molecules on a substrate of molecules in O(n) time, where n is the number of molecules in the substrate. We describe a language for specifying the molecule motion. We give algorithms for performing global translations, rotations, and stacking of molecular structures. We show that these motions are sufficient to guarantee certain classes of motion for molecular structures. We also examine a geometric approach to synthesizing language expressions for moving a molecule on a substrate of other molecules.

Task-reconfigurable robots consist of a set of one or more identical autonomous modules that can adapt their shape and function to tasks. We describe a module, the Inchworm robot, that can function as a climbing robot, a manipulator, or a leg in a multi-legged walker. This module can make autonomous transitions between these states. We present the control algorithms that enable our robot to be a versatile navigator and manipulator and report on our experimental results.

We wish to navigate across complicated three-dimensional structures. We describe a robot that can propel itself on a web of surfaces oriented around arbitrary directions in three-space. This robot is an inchworm-like robot with a simple, modular, and flexible design. We present control algorithms for the task-level skills that allow the robot to walk vertically, horizontally, and inverted, and the algorithms that allow the robot to make transitions between surfaces. Finally, we discuss our experiments.