Date of Award
Doctor of Philosophy
Electrical and Computer Engineering
This dissertation addresses different aspects of employing permanent magnets in the structure of noncontact magnetic manipulators. These systems employ controllable arrays of magnets to generate proper magnetic fields within their operation region and steer magnetic objects remotely without mechanical contact. This noncontact feature makes magnetic manipulators of particular interest in medical applications. They allow physicians to drive magnetic objects in closed and hard-to-reach environments including the human body for non- or minimally invasive diagnostic and therapeutic applications. As a case study, a magnetic manipulator composed of six diametrically magnetized permanent magnet cylinders is proposed. Each magnet in this scheme is equipped with an independent servomotor that can rotate as required. Number and size of the magnets for this proposed magnetic manipulator are then studied and optimized. An analytical model is introduced and employed to describe behavior of diametrically magnetized permanent magnet cylinders that are used in the proposed magnetic manipulator. Accuracy of this model is experimentally verified via employing real data extracted from a 3-axis magnetic field mapper. Dynamics of a magnetic object motion under the influence of magnetic force and resisting force in the proposed system are presented through a nonlinear set of state-space equations. Unstable nature of magnetic manipulators indicated by the describing equations, dictates utilizing feedback control as an essential part in magnetic manipulators. Thus, linear feedback control and nonlinear technique of feedback linearization are explored in this dissertation to address the control problem of steering a magnetic object by means of the proposed permanent magnetic manipulator. Performance of the linear feedback controller is improved through optimizing the equilibrium point for linearization purpose. To implement feedback linearization, two different methods are used resulting in approximate feedback linearization and exact feedback linearization. For the latter, nonlinear algebraic equations of the system are numerically solved via homotopy continuation technique. To enhance efficiency of this technique, scalar homotopy is also developed and its results are compared to vector homotopy, which is the basic approach to implement homotopy. Furthermore, direction control is developed in an open-loop manner to provide 3-D planar control of a magnetic object by means of the proposed magnetic manipulator.
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