Hinged-Tetro: A self-reconfigurable module for nested reconfiguration

Nested reconfiguration is an emerging research area in modular robotics. Such a novel design concept utilizes individual robots with distinctive reconfiguration characteristics (intra-reconfigurability) capable of combining with other homogeneous/heterogeneous robots (inter-reconfigurability). The objective of this approach is to generate more complex morphologies for performing specific tasks that are far from the capabilities of a single module or to respond to programmable assembly requirements. The two-level reconfiguration process in nested reconfigurable robotic system implies several technical challenges in hardware design, planning algorithms, and control strategies. In this paper, we discuss the theory, concept, and initial mechanical design of Hinged-Tetro, a self-reconfigurable module conceived for the study of nested reconfiguration. Hinged-Tetro is a mobile robot that uses the principle of hinged dissection of polyominoes to transform itself into any of the seven one-sided tetrominoes, the Tetris pieces, in a straightforward way. The robot can also combine with other modules for shaping complex structures or giving rise to a robot with new capabilities. Some preliminary experiments of intra-reconfigurability with an implemented prototype are presented.