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Bird, Jonathan Z.

Publications and source records attributed to Bird, Jonathan Z..

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Using an Analytic-Based Magnetic Charge Fourier Series Model to Study a Magnetic Lead Screw when Operating as a Magnetic Spring

A magnetic charge field analysis approach is presented that models an array of magnets by using a magnetic vector Fourier series representation. Using a Fourier series function enables the magnets' relative permeability to be accounted for and also reduces the computational burden. The accuracy of the presented modelling approach is validated by studying the fields and forces created by a magnetic lead screw when acting as a magnetic spring

Kouhshahi, Mojtaba Bahrami↗
DOE OSTI2023

Studying the Peak Force of Magnetic Linear Motion Devices Using Dimensional Neutrality

The merits of different sizing equations for linear motion magnetic force devices are assessed. A peak force scaling analysis for a linear magnetic coupling with respect to the volumetric force density, mass force density, magnetic shear stress and energy density is compared. By utilizing a 3-D analytic based model of a Halbach cylinder magnetic coupling it is shown that the maximizing of volumetric and mass force density is not an appropriate sizing metric for a linear magnetic actuator. Only energy density and magnetic shear stress are dimensionally neutral sizing metrics for linear actuators.

16 TIDAL AND WAVE POWER↗
DOE OSTI2022

A Multi-Stack Variable Stiffness Magnetic Torsion Spring for a Wave Energy Converter

This paper presents the design of a multi-stack high torque adjustable stiffness torsional magnetic spring for use in a wave energy converter. The torsional magnetic spring has a ±45 degrees linear stroke length with peak torque of 823 N⋅m. A 3-D magnetostatic finite element analysis parameter sizing sweeping analysis was performed and the peak energy density for the selected torsion spring was computed to be 12.6 J/kg. The required torque was increased by using a unique seven-stage multi-stacking design. The stiffness of magnetic torsion spring is adjusted through the axial translation of the inner rotor. The presented design is shown to be capable of providing both positive and negative stiffness with equal characteristics and has a very high degree of linearity. The experimental prototype assembly and test-setup used to verify the torsional spring performance is presented.

16 TIDAL AND WAVE POWER↗
DOE OSTI2021

Analysis and Experimental Testing of a New Type of Variable Stiffness Magnetic Spring with a Linear Stroke Length

In this paper a new type of variable stiffness magnetic spring is proposed. The magnetic spring is composed of radially magnetized outer rotor magnets coupled with axially magnetized inner cylindrical magnets. It is shown that this magnet arrangement creates a highly linear stroke length. By rotating the inner magnetic rotor, the stiffness of the spring can be adjusted. The force as a function of stroke length and torque required to adjust the stiffness were computed using finite element analysis and then verified using an experimental test setup.

16 TIDAL AND WAVE POWER↗
DOE OSTI2021

An Adjustable Stiffness Torsional Magnetic Spring with a Linear Stroke Length

This paper presents the analysis, mechanical design, and proof-of-principle experimental testing of a new type of adjustable stiffness torsional magnetic spring for an ocean generator application. Unlike prior published designs the rotary magnetic spring is shown to have a highly linear adjustable stroke length. The presented torsional spring is experimentally shown to be able to create a ± 45° angular stroke range with a peak torque of ± 39.1 N·m. The stiffness is adjusted by using a stepper motor to axially adjust the axial magnet offset. The stepper motor contains a brake so that power is not expended when maintaining a desired spring stiffness. It is shown that by using a series spring arrangement the stroke length can be extended to ± 90°.

16 TIDAL AND WAVE POWER↗