<title>Micromotors using magnetostrictive thin films</title>

Abstract

This study deals with a micromotor based on the use ofmagnetostrictive thin films. This motor belongs to the category of the Standing Wave Ultrasonic Motors (SWLJMs). The active part ofthe motor is the rotor, which is a 100 im thick ring vibrating in a flexural mode. Teeth (300 jim high) are placed on special positions of the rotor and produce an oblique motion which can induce the relative motion ofany object in contact with them.The magnetic excitation field is radial and uses the transverse coupling of the 4 im thick magnetostrictive film. The film, deposited by sputtering on the ring, consists of layers of different rare-earth/iron alloys and was developed during a European Brite-Euram project.The fmite element technique was used in order to design a prototype of the motor and to optimize the active rotor and the energizer coil.The prototype we built delivered a speed of 30 turns per minute with a torque of 2 rN.m (without prestress applied on the rotor). Our experimental results show that the performance ofthis motor could easily be increased by a factor of 5.The main advantage of this motor is the fact that it is remotely powered and controlled. The excitation coil, which provides both power and control, can be placed away from the active rotor. Moreover, the rotor is completely wireless and is not connected to its support or to any other part.It is interesting to note that it would not be possible to build this type ofmotor using piezoelectric technology.Medical applications of magnetostrictive micromotors could be found for internal microdistributors of medication (the coil staying outside the body). Other applications include remote control micropositioning, micropositionrng of optical components, and for the actuation of systems such as valves, electrical switches, and relays.

A Finite Element Analysis for Magnetostrictive Thin Film Structures and Its Experimental Verification

“…Since the theoretical equations proposed by many researchers [20][21][22] made the cantilever with a single deposited magnetostrictive layer an object of their study, those cannot be applied to new application areas such as the sandwiched cantilever, the partially coated cantilever and a traveling machine [23]. Finite element models can neither directly handle the anisotropic magnetostriction [24] nor describe the flexural stiffness calculation procedures in detail. We thus propose a beam element shown in Fig.…”

Nonlinear and hysteretic magnetomechanical model for magnetostrictive transducers

“…This case is illustrated in Figure 2.16 [60]. Recent research work [66] suggests that it is feasible to produce remotely powered and con trolled standing wave ultrasonic motors (SWUMs) using thin film rare earth-iron alloys. The motor is completely wireless, and the excitation coil can be placed away from the active rotor.…”