by Ali Minai
One of the most interesting and memorable characters in sci-fi films is the T-1000, the shape-shifting, nearly indestructible robot from the classic film Terminator 2: Judgment Day, starring Arnold Schwarzenegger. There are other, less prominent examples of shape-shifting intelligent beings in sci-fi – for example Odo, the chief of security on Star Trek’s Deep Space Nine, or the electromagnetic, gaseous, and otherwise inchoate life-forms encountered in various Star Trek episodes. These fictional examples raise the interesting question of whether intelligent beings without a fixed structure are feasible in practice – naturally or through technology (In fact – speaking of Star Trek – the question could potentially be extended to teleportation as well since that would presumably involve the re-assembly of a disassembled body, but that is too remote a possibility to consider for now.)
Recently, several research groups have worked on building robots that can reconfigure themselves autonomously into different shapes and perform different types of actions suitable to their current form. For example, a robot consisting of a large group of small, identical modules could turn itself into a compact sphere to roll down smooth surfaces, flatten itself to slide under doors, grow limbs to climb stairs, or take a snake-like form to crawl away. Such robots, with various degrees of reconfigurability, have now been implemented extensively, both in simulation and in actuality. Some of these robots are, in fact, controlled by external computers to which they are connected or by a centralized brain built into the robot, but the more interesting ones are based on distributed autonomous control: Each module in the robot communicates with other modules near it and, based on the information obtained, triggers one of several simple programs it is pre-loaded with. These programs might cause the module to send out a particular signal to its neighbor or make a simple move such as a rotation, alignment, detachment, or attachment. As all these mechanically connected modules signal and move in response to their triggered programs, the robot assumes different shapes and global behaviors such as locomotion or climbing emerge through self-organized coordination.
The primary feature in these robots is what might be termed radical reconfigurability, i.e., no elementary component has a fixed location in the body or is specialized to a task; like Lego pieces, it can serve any role anywhere. However, this property depends on another, more general attribute: radical distributedness. A radically distributed system consists of identical and exchangeable modules with no permanent functional specialization: Any module can take on any role as needed. Read more »