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 degrees 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 degrees.

Automated summary

This paper introduces a new type of adjustable stiffness torsional magnetic spring designed for ocean generator application, showing its linear adjustable stroke length through experimental testing. The torsional spring is capable of achieving a +/- 45 degrees angular stroke range, with the possibility of extending the stroke length to +/- 90 degrees through a series spring arrangement.