Hardware Design Pioneering Research

To build reconfiguring robots in hardware involves designing and constructing the basic modular units that combine to form the robot itself. Such modules differ from the wheels, arms, and grippers of fixed architecture robots in that they are functional only as a group as opposed to individually. Because we are interested in developing general algorithms for classes of robots instead of particular systems, familiarity with the entire spectrum of existing systems is valuable. Current systems can be divided into classes based on a number of module properties. Systems composed of a single module type are known as homogeneous systems, and those with multiple module types are called heterogeneous systems.

Modules can connect to each other in various ways, and the combination of connection and actuation mechanisms determine the possible positions a module can occupy in physical space, relative to neighbor modules. This gives rise to the major division within SR systems, lattice-based versus chain-based systems. In lattice-based systems, modules move among discrete positions, as if embedded in a lattice. Chain-based systems, however, attach together using hinge-like joints and permit snake-type configurations that connect to form shapes such as legged walkers and tank treads. Another class of modular systems cannot self-reconfigure, but can reconfigure with outside intervention. This class is called manually reconfiguring systems.

Cell Structured Robot (CEBOT) was the first proposed self-reconfiguring robot as an implementation of a Dynamically Reconfigurable Robotic System (DRRS). The DRRS definition parallels our current conception of self-reconfiguring robots - the system is made up of robotic modules (cells) which can attach and detach from each other autonomously to optimize their structure for a given task. The idea is directly inspired by biological concepts and this is reacted in the chosen terminology. It is interesting that this proposed SR robot is heterogeneous: cells have a specialized mechanical function and fall into one of three “levels”. Level one cells are joints (bending, rotation, sliding) or mobile cells (wheels or legs). Linkage cells are part of Level two, and Level three contains end-effectors such as special tools. Communication and computation are assumed for all cells.

CEBOT is the physical instantiation of DRRS. Various versions range from reconfigurable modules to “Mark-V,” which more closely resembles a mobile robot team.