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An investigation of the Matteucci effect on amorphous wires and its application to bend sensing

Alimohammadi, Sahar 2019. An investigation of the Matteucci effect on amorphous wires and its application to bend sensing. PhD Thesis, Cardiff University.
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The study of wearable sensors for human biometrics has recently developed into an important research area due to its potential for personalised health monitoring. To measure bending parameters in humans such as joint movement or posture, several techniques have been proposed however, the majority of these suffer from poor accuracy, sensitivity and linearity. To overcome these limitations, this research aims to develop a novel flexible sensor for the measurement of bending by utilising the Matteucci effect on amorphous wires. The Matteucci effect occurs in all ferromagnetic wires but the advantages of amorphous wires are their superior soft magnetic and magnetoelastic properties and a Matteucci effect that is very sensitive to applied stresses like tensile and torsion. For these reasons a sensor based on Matteucci effect was investigated for use as a wearable bending sensor. Previous studies of the Matteucci effect have been interpreted in terms of simple phenomenological models using conveniently sized lengths of amorphous wire. In this work, the Matteucci effect has been characterised in short, sensor-compatible, wires. In addition, a thorough examination of the stress dependency of the Matteucci effect was also investigated as this is an area that has been neglected in the past. The main aim of this work was to study the effect of tensile and torsion stresses on the Matteucci effect in both highly positive magnetostrictive and nearly zero magnetostrictive amorphous wires. A measurement rig was specifically built to characterise the Matteucci effect for a range of magnetic field amplitudes, frequencies, torsions and axial stresses. The second major aim was to use this characterisation data to ascertain the optimum working parameters to design and construct a novel flexible bending sensor. In this work, the Matteucci effect in amorphous wires was found to be very sensitive to both axial and torsional applied stresses and dependent upon the sign of the magnetostriction. Insights gained here were used to develop the bend sensor in three steps. The initial prototype was a non-flexible strain sensor for measuring tensile stress and exhibited a very high gauge factor equal to 601± 30. The second step resulted in a strain sensor prototype utilising a flexible planar coil to magnetise the amorphous wire. The final step produced a bend sensor this time consisting of a flexible solenoid with greater magnetising capability. It resulted in a bend sensor IV with a high output voltage sensitivity of 5.62 ± 0.02 mV/cm which is the slope of the voltage due to curvature and excellent linearity (R2 = 0.98). In this case the sensor’s operating range was 1.11 rad to 2.49 rad with ± 0.003 rad uncertainty. This range is scalable and dependent on the sensor configuration. This work has demonstrated the feasibility of utilising the Matteucci effect as a bend sensor with a performance exceeding that found in many commercial sensors.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Matteucci effect; Amorphous wires; Wearable sensors; Flexible bending sensor; Magnetics; Soft magnetic materials.
Date of First Compliant Deposit: 20 May 2020
Last Modified: 05 Apr 2022 02:49

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