Design News, April 2013

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transforming robots are SuperBot, created by researchers at the Information Sciences Institute of USC's Viterbi School of Engineering, and CKbot (Connector Kinetic robot), developed by engineers at the University of Pennsylvania's Modular Robotics Laboratory. Modular, self-reconfigurable robot hardware implementations are often classified into three basic types: chain, lattice-based, and hybrid, according to Daniel Pickem, graduate student in robotics at Georgia Tech's GRITS (Georgia Robotics and Intelligent Systems) Lab. Chain-type robots such as CKbot look like snakes or trees, and are made of a series of connected modules. "In lattice-based robots, modules are arranged in a regular pattern; common architectures include square or hexagonal 2D shapes and cubes or dodecahedrons," Pickem said. A robot either rearranges or adds modules to form a shape, the selfassembly approach, or removes modules it doesn't need, the self-disassembly approach. Hybrids such as SuperBot, created to aid NASA in planetary exploration, combine chain-type with lattice-based implementations. These assemble modules to form linear shapes or fold up to form solid shapes. Pickem says he's only seen prototypes so far, not finished products, of these three types. On the software side of modular robot development, several algorithms have been proven to produce a specific reconfiguration sequence. The focus has shifted recently from simulation to building hard- The Distributed Robotics Laboratory of MIT's Computer Science and Artificial Intelligence Lab is pursuing a decentralized, self-disassembly method. At 12 mm per side, each Smart Pebble robotic cube contains only a microprocessor, 32 kilobytes of program code, and two kilobytes of working memory, requiring very efficient algorithms to guide the cubes, which attach and detach via electropermanent magnets. ware prototypes. The three main hardware challenges are actuation, connectors, and structural stability. "Actuation challenges include the fact that robots must be small, yet strong enough to lift themselves and other modules," said Pickem. "Connectors must form reliable and strong connections for structural stability, yet also break when necessary. Because modular robots don't have the same structural stability as monolithic robots designed for the manufacturing floor, the challenge there is how to make them both light and small, as well as strong." Self-reconfigurable robots can be built using different design principles: deterministic or stochastic, self-assembling or self-disassembling, centralized or decentralized, and homogeneous or heterogeneous. Deterministic schemes can locate modules at any given time, but require more planning and control because they tell every module what to do. In stochastic architectures, modules' connections and disconnections happen randomly, and are more likely to occur as module count increases. Self-assembly schemes are more common than selfdisassembly schemes, said Pickem. One self-disassembly method has been built by a team led by Daniela Rus, a principal investigator at MIT's Computer Science and Artificial Intelligence Lab (CSAIL). Developed under the aegis of CSAIL's Distributed Robotics Laboratory (DRL), small robotic cubes self-disassemble to duplicate an object placed in a heap of them. Measuring 12 mm per side, the Smart Design News | april 2013 | www.d esign n –39– Source: GRITS Lab/Georgia Tech Source: Wyss Institute for Biologically Inspired Engineering The 3D brick approach to self-assembly at the nanoscale is based on short synthetic strands of DNA that form building blocks, which self-assemble into 100 different, precise 3D shapes such as letters and numbers. Like the models of 80 of these shapes shown here, each unique shape measures about 25 nm per side.

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