Exploration of Magnetic Field Actuated Strings of Spherical Magnets for Swimming Robot Locomotion

Robots capable of operating in fluid have a variety of applications from biomedical devices to use in piping systems for monitoring and inspection. If these robots can be driven remotely by methods other than traditional motors, they can be less technologically complex, safer and more durable. The following paper describes a method for generating locomotion using magnetism by exciting chains of magnetic spheres with a rotating magnetic field. A mathematical model was used to characterize the dynamic behavior of spherical magnets based on their magnetic properties. From the dipole-dipole interaction of several magnets in series the ‘stiffness' of a chain of magnets can be characterized and therefore the natural frequencies and mode shapes of this chain can be obtained. Chains of 3/16" magnetic spheres were held neutrally buoyant in water then driven by a magnetic field at their predicted natural frequency. The amplitude of the magnetic field was gradually increased resulting in the downward locomotion of the chains. For a chain 3 beads in length an average velocity of -2.99x10-3 m/s was measured.