Abstract: This paper presents a review of recent rolling robots including Rollo from Helsinki University of Technology, Spherical Mobile Robot from the Politecnico of Bari, Sphericle from the University of Pisa, Spherobot from Michigan State University, August from Azad University of Qazvin and the University of Tehran, Deformable Robot from Ritsumeijan University, Kickbot from the Massachusetts Institute of Technology, Gravitational Wheeled Robot from Kinki University, Gyrover from Carnegie Mellon University, Roball from the Université de Sherbrooke, and Rotundus from the Ångström Space Technology Center.
Seven rolling robot design principles are presented and discussed (Sprung central member, Car driven, Mobile masses, Hemispherical wheels, Gyroscopic stabilisation, Ballast mass – fixed axis, and Ballast mass – moving axis). Robots based on each of the design principles are shown and the performances of the robots are tabulated. An attempt is made to grade the design principles based on their suitability for movement over an unknown and varied but relatively smooth terrain. The result of this comparison suggests that a rolling robot based on a mobile masses principle would be best suited to this specific application.
Some wonderful rolling organisms are introduced and defined as “active” or “passive” depending on whether they generate their own rolling motion or external forces cause their rolling.

Key words: Rolling robot, tumbleweed, wheel, ballast, Gryoscope