Robots out on the factory floor pretty much know what's coming. Constrained as they are by programming and geometry, their world is just an assembly line. But for robots operating out doors, away from civilization, both mission and geography are unpredictable. Here, robots with the ability to change their shape could adapt to constantly varying terrain.

Metamorphic robots are designed so that they can change their external shape without human intervention. One general way to achieve such functionality is to build a robot composed of multiple, identical unit modules. If the modules are designed so that they can be assembled into rigid structures, and so that individual units within such structures can be relocated within and about the structure, then self-reconfiguration is possible.

These systems claim to have many desirable properties including versatility, robustness and low cost. Each module has its own computer, a rich set of sensors, actuators and communication networks. However, the practical application outside of research has yet to be seen .One outstanding issue for such systems is the increasing complexity for effectively programming a large distributed system, with hundreds or even thousands of nodes in changing configurations. PolyBot has been developed through as third generation at the Xerox Palo alto Research Center. Conro robot built at the information sciences institute at the University of Southern California are examples for metamorphic robots.

SELF-RECONFIGURATION THROUGH MODULARITY

Modularity means composed of multiple identical units called modules. The robot is made up of thousands of modules. The systems addressed here are automatically reconfiguring, and for this the hardware systems that tend to be more homogenous than heterogenous. That is the system may have different types of modules but the ratio of the number of module types to the number of modules is very low. Systems with all of these characteristics are called n-modular where n refers to the number of module types and n is small typically one or two. (e.g. a system with two types of modules is called 2-modular ).

The general philosophy is to simplify the design and construction of components while enhancing functionality and versatility through larger numbers of modules. Thus, the low heterogeneity of the system is a design leverage point getting more functionality for a given amount of design .The analog in architecture is the building of a cathedral from many simple bricks in which bricks are of few types .In nature. The analogy is complex organisms like mammals, which have billions of cells, but only hundreds of cell types.

THREE PROMISES OF N-MODULAR SYSTEMS

1. Versatility

Versatility stems from the many ways in which modules can be connected, much like a child's Lego bricks. It can shape itself to a dog , chair or to a house by reconfiguration. The same set of modules could connect to form a robot with a few long thin arms and a long reach or one with many shorter arms that could lift heavy objects. For a typical system with hundred of modules, there are usually millions of possible configurations, which can be applied to many diverse tasks.

Modular reconfiguration robots with many modules have the ability to form a large variety of shapes to suit different tasks. Figure 2 shows robot in the form of a loop rolling over a flat terrain. Figure 3 shows an earthworm type to slither through obstacles.. Finally Figure 4 shows a spider form to stride over bumpy or hilly terrain.