| This dissertation explores the design and use of an electromagnetic manipulation system that has been optimized for the dipole-field model. This system can be used for noncontact manipulation of adjacent magnetic tools and combines the field strength control of current electromagnetic systems with the analytical modeling of permanent-magnet systems. To design such a system, it is first necessary to characterize how the shape of the field source affects the shape of the magnetic field.;The magnetic field generated by permanent magnets and electromagnets can be modeled, far from the source, using a multipole expansion. The error associated with the multipole expansion is quantified, and it is shown that, as long as the point of interest is 1.5 radii of the smallest sphere that can fully contain the magnetic source, the full expansion will have less than 1% error. If only the dipole term, the first term in the expansion, is used, then the error is minimized for cylindrical shapes with a diameter-to-length ratio of √4/3 and for rectangular-bars with a cube.;Applying the multipole expansion to electromagnets, an omnidirectional electromagnet, comprising three orthogonal solenoids and a spherical core, is designed that has minimal dipole-field error and equal strength in all directions. Although this magnet can be constructed with any size core, the optimal design contains a spherical core with a diameter that is 60% of the outer dimension of the magnet. The resulting magnet's ability to dextrously control the field at a point is demonstrated by rotating an endoscopic-pill mockup to drive it though a lumen and roll a permanent-magnet ball though several trajectories. Dipole fields also apply forces on adjacent magnetized objects. The ability to control these forces is demonstrated by performing position control on an orientation-constrained magnetic float and finally by steering a permanent magnet, which is aligned with the applied dipole field, around a rose curve. |
