Lightweight Magnetic Foot With Variable Force, for Docking/Landing With Micro-Helicopters on Rust-Covered Walls in Boiler Furnaces

Abstract

This paper describes the design, implementation and application of a lightweight magnetic foot with variable force, which was developed for docking/landing on vertical walls with a micro-helicopter in order to perform inspection tasks there; and afterwards undock to fly away without problems. Even if not being a complete climbing robot, the magnetic foot on the helicopter uses technologies which were originally developed for climbing robots, operates in an environment which is difficult to access (furnaces in coalfired boilers) and could be useful for future climbing robots with inchworm-locomotion. By using a lightweight actuation concept based on miniature pulley-wire-transmissions, a simple and robust control strategy and a mechanical design that is well shielded against ferromagnetic dust or other types of aggressive dirt; the here presented magnetic foot with variable adhesion force achieves several advantages over previous designs -such as an excellent compromise concerning lightweight design at strong adhesion force (Fadh,max/(m*g)>100), robustness against most environmental hazards, low residual force (Fadh,max/Fred<30) and low manufacturing cost. After explaining the environment constraints, the basic concept of docking with an unmanned micro-helicopter and the requirements for the magnetic foot; a brief overview on most principles for force variation in magnetic feet is provided. This comparison is followed by the presentation of the basic design concept and its implementation in a prototype. The paper concludes with the measured values of this prototype and provides an outlook on future work and how this technology can be used in other applications.