الفهرس 
Title : Variable-flux permanent magnet for structure resonance frequency adjustment
SummaryOnly 14 pages are availabe for public view
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Abstract
Magnetic forces are typically obtained through a magnetic field produced by a permanent magnet or using an electric current passing through a coil wrapped about an iron core, known as an electromagnet. Magnetic forces are controlled by adjusting the magnetic field passing through a magnetic core medium. They could be controlled either mechanically by changing the configuration of a permanent magnet or by changing the current passing through electric coils.
In this thesis, a magnetic flux modulating device is proposed, which includes a permanent magnet, enclosed by magnetic cores. The variable-flux permanent magnet (VFPM) device works by mechanically adjusting the configuration of the permanent magnet and consequently altering the magnetic field passing through the device’s cores.
Analytical and finite element models were developed based on Maxwell’s equations for the derivation of the magnetic force as a function of both the configuration of the permanent magnet and the gap between the fixed and moving cores of the device. Based on these models, an experimental setup was built including a rotational neodymium permanent magnet, a fixed iron core made of silicon steel sheet, a movable iron core, in addition to a motor, coupled to the magnet. The experimental results were used to calibrate the analytical and finite element models. Experiments showed the viability of the proposed methods and the ability of the VFPM to produce a variable magnetic flux using mechanical methods.
This VFPM device was also integrated with an experimental setup consisting of a cantilever beam with tip mass. The VFPM device’s magnetic force was axially applied to the cantilever beam to vary the natural frequency of the structure by varying the beam’s stiffness. Experimental results show the variation of the beam’s natural frequency with the applied magnetic force, which validates the VFPM device’s potential in energy harvesting and active suspension applications.