Dynamic rolling of modular robots

Highly redundant modular robots may undergo large shape changes which significantly affect the geometry and dynamics of the robot. In these motions, the shape change may induce a tipping or rolling behavior of the robot itself. The paper describes the dynamic modeling, control, and simulation of such rolling motions for the Tetrobot modular robots. The motion is described by the path profiles of controlled nodes, the tipping criteria and dynamic tipping motion, and an impact-reaction model of contact with the ground. These phases of motion are described using Newton-Euler dynamic equations and the principle of conservation of angular momentum. Simulation results illustrate the tipping behavior of a tetrahedron, the dynamic contact and rolling of an icosahedral Tetrobot, and dynamic control of the rolling Tetrobot. The resulting models are useful to analyze and control both intentional rolling as a new mode of mobility as well as the avoidance of unintentional tipping and rolling during task execution.