Apparatus and method for controlling movement of an object through a medium using a magnetic field by combining the magnetic field of a primary electromagnetic coil having a central axis with the magnetic fields of a plurality of secondary electromagnetic coils having axes generally parallel to the central...http://www.google.com.au/patents/US6842324?utm_source=gb-gplus-sharePatent US6842324 - Apparatus and method for controlling movement of an object through a medium using a magnetic field
