Mark H. Yim

PolyBot: a modular reconfigurable robot

Modular, self-reconfigurable robots show the promise of great versatility, robustness and low cost. The paper presents examples and issues in realizing those promises. PolyBot is a modular, self-reconfigurable system that is being used to explore the hardware reality of a robot with a large number of interchangeable modules. PolyBot has demonstrated the versatility promise, by implementing locomotion over a variety of terrain and manipulation versatility with a variety of objects. PolyBot is the first robot to demonstrate sequentially two topologically distinct locomotion modes by self-reconfiguration. PolyBot has raised issues regarding software scalability and hardware dependency and as the design evolves the issues of low cost and robustness will be resolved while exploring the potential of modular, self-reconfigurable robots.

Modular Reconfigurable Robots in Space Applications

Robots used for tasks in space have strict requirements. Modular reconfigurable robots have a variety of attributes that are well suited to these conditions, including: serving as many different tools at once (saving weight), packing into compressed forms (saving space) and having high levels of redundancy (increasing robustness). In addition, self-reconfigurable systems can self-repair and adapt to changing or unanticipated conditions. This paper will describe such a self-reconfigurable modular robot: PolyBot. PolyBot has significant potential in the space manipulation and surface mobility class of applications for space.

Connecting and disconnecting for chain self-reconfiguration with PolyBot

Chain modular robots form systems with many degrees of freedom which are capable of being reconfigured to form arbitrary chain-based topologies. This reconfiguration requires the detaching of modules from one point in the system and reattaching at another. The internal errors in the system (especially with large numbers of modules) are such that accurate movement of chain ends, required for the attaching of modules, can be extremely difficult. A three-phase docking process is described that utilizes both open- and closed-loop techniques. This process has been shown to work with an early version. Issues raised during this testing have been addressed in a later version. Discussion of these issues, their solutions, and preliminary results of the testing the latest version are given.

Indoor automation with many mobile robots

The goal of the GOFER project is to control the operations of many mobile robots (several dozens) in an indoor environment. This project raises many research issues: implementation of nonconflicting sensor systems, man-robot and robot-robot communication systems and protocols, contingency-tolerant motion control, multi-robot motion planning, multi-robot task planning and scheduling. The aim of this paper is to provide an overview of the project and present the current solutions to these problems.<<ETX>>

Distributed Control for 3D Metamorphosis

In this paper, we define Proteo as a class of three-dimensional (3D) metamorphic robotic system capable of approximating arbitrary 3D shapes by utilizing repeated modules. Each Proteo module contains embedded sensors, actuators and a controller, and each resides in a 3D grid space. A module can move itself to one of its open neighbor sites under certain motion constraints. Distributed control for the self-reconfiguration of such robots is an interesting and challenging problem. We present a class of distributed control algorithms for the reconfiguration of Proteo robots based on the “goal-ordering” mechanism. Performance results are shown for experiments of these algorithms in a simulation environment, and the properties of these algorithms are analyzed.

A complete, local and parallel reconfiguration algorithm for cube style modular robots

We present a complete, local, and parallel reconfiguration algorithm for metamorphic robots made up of Telecubes, six degree of freedom cube shaped modules currently being developed at PARC. We show that by using 2 /spl times/ 2 /spl times/ 2 meta-modules we can achieve completeness of reconfiguration space using only local rules. Furthermore, this reconfiguration can be done in place and massively in parallel with many simultaneous module movements. Finally we present a loose quadratic upper bound on the total number of module movements required by the algorithm.

Phase automata: a programming model of locomotion gaits for scalable chain-type modular robots

Modular reconfigurable robots have the potential for great versatility and robustness; however, programming locomotion gaits for hundreds of modules remains a challenge. In this paper we present a formal model for programming locomotion gaits in chain-type modular robots: phase automata. A phase automation is an event-driven state automation with an initial phase delay. The phase delay is normally a real value between 0 and 1. Phase automata are compact representation of locomotion gaits and capable of being embedded and distributed across modules. The concepts of phase automata have been implemented on both PCs and embedded micro-processors. An XML script language and programming interface for phase automata are being built. Locomotion gaits programmed using phase automata have been tested both in simulation with 100+ modules and in hardware with 50+ modules.

Six Degree of Freedom Sensing for Docking Using IR LED Emitters and Receivers

Six DOF offset sensing between two plates is important for automatic docking mechanisms. This paper presents an easy and inexpensive implementation of such a system using four commercial-off-the-shelf (COTS) infrared (IR) light emitting diode (LED) emitters and two COTS IR receivers on each of two docking plates. The angular intensity distribution of an emitter and the sensitivity distribution of a receiver allow for estimation of the angle and distance between them. Simple experiments have been conducted indicating that such a setup is able to give positional offset in any of 6 degrees of error (x, y, z, pitch, roll, and yaw) within a range. A theoretical framework is also established using least squares minimization. The theoretical framework is general and applies to other configurations of emitter and receiver parts and positioning.

Walk on the wild side [modular robot motion]

Designers of the PolyBot robot system solve the challenges of locomotion by mimicking locomotion in the animal world. PolyBot is a robot system made of many repeated simple modules. These modules can be connected together to form a variety of shapes to form a new system enabling a variety of functionalities.

MEMS-Based Control of Structural Dynamic Instability

This paper describes the design, analysis and characterization of a prototype active column that applies distributed MEMS technology to the active stabilization of a buckling compressive member. The axial load bearing capacity of structural members can be increased by actively controlling the dynamic instability of buckling. Effective active stabilization is dependent on three primary factors: sensor precision, actuator authority, and control system bandwidth. A networked array of MEMS sensors, filamentary PZT actuators, and recently developed optimal control strategies are combined to demonstrate active control of an inherently unstable column. The active system, designed and simulated using finite element and optimization methods, stabilizes an experimental column for compressive axial loads up to 2.9 times the critical buckling load. Additionally, the system is stable for all loads in the range from tension to this maximum compressive axial load.