|
The modular building blocks usually consist of some primary structural actuated unit, and potentially additional specialized units such as grippers, feet, wheels, cameras, payload and energy storage and generation.
====A taxonomy of architectures====
Modular self-reconfiguring robotic systems can be generally classified into several architectural groups by the geometric arrangement of their unit (lattice vs. chain). Several systems exhibit hybrid properties.
* ‘’Lattice’’Lattice architectures’’ have units that are arranged and connected in some regular, space-filling three-dimensional pattern, such as a cubical or hexagonal grid. Control and motion are executed in parallel. Lattice architectures usually offer simpler computational representation that can be more easily scaled to complex systems.
* ‘’Chain’’Chain/tree architectures’’ have units that are connected together in a string or tree topology. This chain or tree can fold up to become space filling, but underlying architecture is serial. Chain architectures can reach any point in space, and are therefore more versatile but more computationally difficult to represent and analyze.
Modular robotic systems can also be classified according to the way by which units are reconfigured (moved) into place.
* ‘’Deterministic’’Deterministic reconfiguration’’ rely on units moving or being directly manipulated into their target ___location during reconfiguration. The exact ___location of each unit is known at all times. Reconfiguration times can be guaranteed, but sophisticated feedback control is necessary to assure precise manipulation. Macro-scale systems are usually deterministic.
* ‘’Stochastic reconfiguration’’ rely on units moving around using statistical processes (like Brownian motion). The exact ___location of each unit only known when it is connected to the main structure, but it may take unknown paths to move between locations. Reconfiguration times can be guaranteed only statistically. Stochastic architectures are more favorable at micro scales.
There are two key motivations for designing modular self reconfiguring robotic systems.
* ‘’Functional’’Functional advantageadvantage’’: Self reconfiguring robotic systems are potentially more robust and adaptive than conventional systems. The reconfiguration ability allows a robot or a group of robots to disassemble and reassemble machines to form new morphologies that are better suitable for new tasks, such as changing from a legged robot to a snake robot and then to a rolling robot. Since robot parts are interchangeable (within a robot and between different robots), machines can also replace faulty parts autonomously, leading to self-repair.
* ‘’Economic’’Economic advantageadvantage’’: Self reconfiguring robotic systems can potentially lower overall robot cost by making a range of complex machines out of a single (or relatively few) types of mass-produced modules.
Both these advantages have not yet been fully realized. A modular robot is likely to be inferior in performance to any single custom robot tailored for a specific task. However, the advantage of modular robotics is only apparent when considering multiple tasks that would normally require a set of different robot.
==Challenges and opportunities==
Since the early demonstrations of early modular self-reconfiguring systems, the size, robustness and performance has been continuously improving. In parallel, planning and control algorithms have been progressing to handle thousands on units. There are, however, several key steps that are necessary for these systems to realize their promise of ‘’’adaptability’’’adaptability, robustness and low cost’’’. These steps can be broken down into challenges in the hardware design, in planning and control algorithms and in application. These challenges are often intertwined.
====Hardware design challenges ===
Several robotic fields have identified ‘’Grand Challenges’’ that act as a catalyst for development and a short-term goal in absence of immediate ‘’killer apps’’. The Grand Challenge is not in itself a research agenda or milestone, but a means to stimulate and evaluate coordinated progress across multiple technical frontiers. Several Grand Challenges have been proposed for the modular self-reconfiguring robotics field:
* ‘’Demonstration’’Demonstration of a system with >1000 units’’. Physical demonstration of such a system will inevitably require rethinking key hardware and algorithmic issues, as well as handling noise and error.
* ‘’Robosphere’’’’Robosphere’’. A self-sustaining robotic ecology, isolated for a long period of time (1 year) that needs to sustain operation and accomplished unforeseen tasks.
* ‘’Self’’Self replication’’ A system with many units capable of self replication by collecting scattered building blocks will require solving many of the hardware and algorithmic challenges.
[[Category:Robotics]]
| 