The Novice Writer: Self-Reconfigurable Modular Systems

Self-Reconfigurable Modular Systems

Introduction:

Modular self-re-configuring robotic systems or self-reconfigurable modular robots are autonomous kinematic machines with variable morphology.
Beyond conventional actuation, sensing and control typically found in fixed-morphology robots, self-reconfiguring robots are also able to deliberately change their own shape by rearranging the connectivity of their parts, in order to adapt to new circumstances, perform new tasks, or recover from damage.
Modularity benefits include the capability of self-assembly and self-reconfiguration.
Modular self-reconfigurable robots involve various modules that can combine themselves autonomously into meta-module or a structure that is capable of performing a specific task under certain circumstances.
Self-reconfigurable nature of these robots allows them for metamorphosis which in turn makes them capable of performing different sorts of kinematics.
For example, a robot made of such components could assume a worm-like shape to move through a narrow pipe, reassemble into something with spider-like legs to cross uneven terrain, then form a third arbitrary object (like a ball or wheel that can spin itself) to move quickly over a fairly flat terrain; it can also be used for making "fixed" objects, such as walls, shelters, or buildings.
Self-reconfiguration is different from the concept of self-replication, which is not a quality, that a self-reconfigurable module or collection of modules needs to possess.

6 different types of classes:

Lattice Architecture:

In this architecture, modules are arranged in a 2D or 3D pattern or virtual grid that can be used as a guide for modules to determine their possible positions and form the new shape.
All the modules in this architecture remain attached to the main body.
Units move only to the neighboring positions within the lattice.
Planning and control become less complex compared to when units move to any arbitrary position.
Capable of offering simpler re-configurations compared to other architectures.

Chain Architecture:

Also known as tree architecture.
Modules are connected together in a string or tree topology.
Modules reconfigure by attaching and detaching to and from themselves.
Generally, chain architecture is used to form limbs.
Termed to be the most versatile though, difficult to implement because it can reach to any point in space via articulation.
Difficult to control and computationally expensive.

Hybrid Architecture:

Takes advantages of both previous architectures. Control and mechanism are designed for lattice reconfiguration but also allows reaching any point in the space.

Mobile Architecture:

Modules detach from the main body and maneuver independently using the environment to link up at new locations in order to form new shapes.
This makes mobile architecture less explored as compared to the previous structures because of the reconfiguration difficulty; which out-weighs the functionality game.

Deterministic Architecture:

Modules move directly to their target locations during the self-configuration process.
Each unit’s locations can be known at all times or calculated at run time, such that the reconfiguration time is predetermined.
This makes it easier to be implemented compared to other architectures.

Stochastic Architecture:

Modules move in 2D or 3D environment using statistical process. For example, the Brownian motion, those are used to guarantee reconfiguration’s time.
So, the exact location of each unit is only known when it is connected to the main structure but the path is taken by those units to move between locations are unknown.

Applications:

Poly-bot:

It is the first modular robotics system, to demonstrate self-reconfiguration.
It changed its geometry and locomotion mode depending on the terrain type.
Programming the motion of a modular system that composes of “n” number of modules can be difficult especially if “n” is large.
So, reconfigurations can be pre-planned offline between the processes especially when a fixed number of configurations is sufficient.
Class of poly-bot is Hybrid architecture.

Space exploration:

One application that highlights the advantages of self-reconfigurable systems is long-term space missions.
These require long-term self-sustaining robotic ecology that can handle unforeseen situations and may require self-repair.
Self-reconfigurable systems have the ability to handle tasks that are not known a prior, especially compared to fixed configuration systems.
In addition, space missions are high volume and mass constrained.
Sending a robot system that can reconfigure to achieve many tasks may be more effective than sending many robots that each can do one task.