Galfenol-based Sensor/Actuator Devices for Smart by-Wire Steering System for Automobile Technology.

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Galfenol-based Sensor/Actuator Devices for Smart by-Wire Steering System for Automobile Technology. Yasubumi Furuya1, Chihiro Saito2, Teiko Okazaki1, Kazumi Okada1, Yusuke Sado1, Takeo Chinen1, Naoki Ogasawara1, Muneaki Shimada3 1. Intelligent Machines and System Engineering, Hirosaki University, Hirosaki, Japan. 2. NJC Research Center, Namiki Precision Jewel Co.,Ltd , Tokyo, Japan. 3. Technical Research Institute, NISSAN Motor Co.Ltd, Yokosuka, Japan. ABSTRACT Polycrystalline Galfenol (Fe-Ga-X, X=Al, C, Zr etc.) alloys were fabricated as a bulk sample from ark-melted and annealing process method for enhancing various engineering applicability. (Fe-Ga0.15-Al0.05)99.0-Zr0.5-C0.5 [at.%] sample showed a maximum magnetostriction of 134 ppm as well as a tensile stress over σ=800MPa. This large magnetostriction is caused by A2 phases without the excessive precipitation of ordered phases such as fcc ordered L12 and bcc ordered D03 phases. Secondarily, we will introduce an application as a smart torque sensor by utilizing Galfenol-ring around the steering shaft for steering-by-wire system of automobile. In this system, a torque sensing system by using the magnetostrictive ring of FeGa (Galfenol) alloy was developed and magnetic flux leaked from the Galfenol ring attached on the rotating shaft was experimentally measured by using two differential Hall probe sensor. As a result, the sensitivity in (Fe0.80Ga0.15Al0.05)99Zr0.5C0.5 ring increased by 2.9 times in comparison with the (Fe0.80Ga0.15Al0.05)98.5C1.5 alloy at rotations speed 500 rpm. INTRODUCTION Ferromagnetic materials that can exhibit large Joule magnetostriction in low magnetic fields are of interest for use as sensors and actuators [1.2]. The


earliest crystalline magnetostrictive alloys used in transducers were nickel-based alloys, and large magnetostriction values have been obtained in RFe2( R = rare earth elements ) intermetallic compounds with C15 structure such as Terfenol-D ( Dy0.7Tb0.3)Fe2 alloy [3]. These alloys show magnetostrictions of over 1000 ppm. However, these alloys are expensive, very brittle and require high fields for magnetic saturation. Galfenol alloy (Fe-Ga) which has A2 phase [4,5], exhibit large magnetostriction of over 100 ppm, soft magnetic material and low prices. However, Galfenol alloy is not strong enough for use as a robust actuator / sensor material in the severe environments experienced by engineering machinery. [6]. [7]. [9]. [10 ]. [11]. [13]. We have been investigated material design to enhance the strength of Galfenol with the addition of carbon and boron as well as via novel material processing techniques of rapid solidification or spark plasma sintering (SPS) [6]. The (Fe0.80Ga0.15Al0.05)98.5C1.5 alloy which we have developed exhibits strength of over 600 MPa [6], but its magnetostriction decreases to 40-50 ppm due to the A2 to LI2 (Fe3GaC0.5) phase change caused by carbon addition. In this study, we investigate magnetostriction and strength of Galfenol alloys which were added in small amounts( 99.9%). These allo