Controllability of Magnetic Force in Magnetic Wheels

Magnetic adhesion on mobile robots has advantages such as fast locomotion and no additional energy for adhesion process, and one definite disadvantage like difficulty to control magnetic force. This paper focuses on this issue, i.e., controllable magnetic force, and describes the design of a magnetic wheel using two permanent magnets (PMs) for controlling magnetic force between the wheel and interior surfaces of ferromagnetic pipes. It is composed of a central PM, one aluminum ring, two wheel rims, and one housing. The housing also has a rotatable PM which is connected to a servo motor via two pulleys and a timing belt. A commercial program, MAXWELL-3D, is used to model and analyze the magnetic wheel. Then, the wheel is made and is subjected to the experiments. From the simulation results, the flux lines are thicker as the PM2 rotates from free-state to adhered-state, which means that more magnetic flux flow through the steel pipe. A digital push-pull force gauge is used to measure the magnetic force by pulling the magnetic wheel vertically. It can be concluded that the proposed method is effective to control magnetic force between the wheel and interior surfaces of ferromagnetic pipes.