Pivot Bearings for Efficient Torsional Magneto-Mechanical Resonators

TL;DR

This paper introduces flexure-based pivot bearings for magneto-mechanical resonators, significantly reducing damping and enabling efficient low-frequency magnetic signal generation for communication and energy applications.

Contribution

It presents a novel flexure pivot bearing design that offers large angular motion, high transverse stiffness, and low damping for magneto-mechanical resonators, with detailed modeling and experimental validation.

Findings

Damping coefficient up to 80 times lower than ball bearings

Large angular rotation with high transverse stiffness achieved

Broad applicability to coupled torsional oscillator systems

Abstract

Rotating magnets have recently emerged as an efficient method for producing ultra-low frequency signals for through-earth and through-seawater communications. Magneto-mechanical resonator (MMR) arrays, which are magnetized torsional rotors with a restoring torque, are a promising implementation of this idea that use resonance to enhance the magnetic signal generation. The fundamental challenge for MMR design is to have a suspension system for the rotors capable of resisting large transverse magnetic forces while allowing for a large angle of motion at low dissipation and hence high efficiency. Here, we study flexure-based pivot bearings as compliant support elements for MMR rotors which address this challenge and demonstrate their efficient low damping operation. A crossed-flexure configuration enables large angular rotation around a central axis, large transverse stiffness, and compact assembly of closely spaced rotor arrays via geometric flexure interlocking. We characterize the eigen frequency performance and structural damping of MMR supported by these proposed pivot bearings. We develop analytical and numerical models to study their static and dynamic behaviors, including their coupled dynamic modes. We demonstrate that their damping coefficient is up to 80 times lower than corresponding ball bearing MMR. This study is broadly applicable to various systems that leverage arrays of coupled torsional oscillators such as magneto-mechanical transmitters, metamaterials, and energy harvesters.