Adhesion techniques for climbing robots: State of the art and experimental considerations

Climbing robots are now widely accepted as valid options in situations where it is important to move on sloped or vertical structures in order to inspect, paint, clean or perform the required operations. Even if the first applications of climbing robots appeared more than 40 years ago, many new ideas are continuously being proposed in the scientific literature and in the market. In this work a classification of the different adhesion techniques proposed for climbing robots is proposed and discussed. Adhesion methodologies can be classified as active when they require an external energy supply to support the robot, or passive if no energy is needed (e.g. permanent magnets or suction cups). Another classification can be done on the basis of the nature of the forces required to support the robot: pneumatic, if the adhesion force is generated by a pressure difference; magnetic if the force is magnetic; mechanical if it depends only on mechanical supports, chemical if it is due to some particular glue, or electrostatic. Moreover within each of these categories, different kind of robots have been proposed in the last years, also on the basis of the locomotion architectures: walking with legs, frame walking, with wheels, sliding, jumping, etc. Recently biologically-inspired gripping methods, trying in many cases to imitate gecko skin, appeared in several research works. However some doubts remain concerning the applicability of such systems in real applications. Some critical considerations on the different techniques and on their practical advantages and drawbacks will be exposed and an overview of the different climbing robots developed in the last 12 years at University of Catania is also presented.