Configuration independent kinematics for modular robots

A modular robotic system consists of standardized joint and link units that can be assembled into a number of different kinematic configurations. This paper describes the design and kinematic issues of a newly developed modular robot aimed for assembly tasks. All modules are designed as cubic units. There are connecting interfaces, termed connecting ports, on all faces of the cubes so that different kinematic configurations can be achieved by just re-connecting the modules into different ports. A graph based representation scheme, termed assembly incidence matrices (AIM), is employed to indicate the ever changing configurations. The dyad kinematics based on product-of-exponentials formula is introduced. Using dyad kinematics along with a graph traversing algorithm, the authors are able to derive forward kinematics for a modular robot with specific configuration automatically. This formulation can be applied to modular robots with hybrid geometries and is demonstrated by a 3-DOF serial modular robot example