Development of a Bio-Inspired Tactile Magnetostrictive Whisker Sensor Using Alfenol

Abstract

Alfenol (FexAl100−x) is an alloy similar to Galfenol (Fe-Ga alloys) in crystal lattice structure and magnetostriction trend (peaking at ∼20% composition). Although single-crystal Fe80Al20 exhibits lower magnetostriction (∼184 ppm, about half of Fe80Ga20), its magneto-elastic coupling coefficient is on par with that of Fe-Ga. In addition, characteristics such as machinability and rollability are superior to that of Galfenol, making it possible to achieve textured sheets (thickness∼200 μm) which, while having a high elastic modulus, are very flexible. Furthermore, Aluminum is non toxic, cheap (∼1% the cost of Ga) and is available in abundance. These attributes make Alfenol an ideal candidate for a bio-inspired whisker-like tactile sensor (mimicking mystacial vibrissae of cats, sea lions, etc.). This work deals with the design and development of an accurate, cost efficient, real-time, and non-invasive sensor prototype that tracks displacements, vibrations and scour on bridge piers with minimal signal conditioning. Making such a sensor is possible thanks to Alfenol’s linear response to strain in the presence of appropriate bias magnets. The change in its magnetic state due to inverse magnetostriction from applied bending stresses will be observed using Hall Effect sensors to derive deflection information. A protocol to manufacture rolled and textured Alfenol whisker samples will be presented in this research. The effect of bias conditions on sensor performance will be studied empirically and by using multi-physics simulations. Optimization of the sensor by varying the dimensions of the whisker, and its correlation to flux leakage will also be examined followed by an effort to understand the micro-magnetic response of Alfenol to mechanical stimulation. Finally, results from using this biomimetic sensor to measure displacements and vibrations, and its viability to be used as a flow sensor will be discussed. The robustness of this sensor has been exploited to develop a novel real-life application to provide an early warning system for bridge pier scour due to soil transportation during a weather event. The effectiveness of these sensors for scour detection in riverbeds will subsequently be simulated in a water flume and analyzed.

Design of Galfenol and Alfenol microstructures for bending mode energy harvesters

“…It demonstrates a considerable magnetoelastic coupling [3] and high Curie temperature [4]. The applications of Alfenol include transducers [5] and sensors [6][7][8].…”

Influence of Frequency on the Resolution of Magnetostrictive Bio-Inspired Whisker Sensors

“…This characteristic makes them potentially applicable in the sensing field. To this end, Raghunath and coworkers developed a magnetostrictive whisker [14]. On the basis of magnetoelastic effect mechanism, a magnetostrictive whisker can measure both stress and vibration.…”

Magnetostrictive Bioinspired Whisker Sensor Based on Galfenol Composite Cantilever Beam Realizing Bidirectional Tactile Perception

“…Until now, the reported bioinspired whiskers include capacitive whisker, piezoelectric whisker, elastic whisker, and magnetostrictive whisker [ 6 – 11 ]. Wherein, magnetostrictive whisker shows the advantages of working under static or low-frequency conditions [ 12 , 13 ], comparing to piezoelectric and capacitive whiskers.…”