A Single-Element Tuning Fork Piezoelectric Linear Actuator

Missouri University of Science and Technology Scholars' Mine

Mechanical and Aerospace Engineering Faculty Research & Creative Works Mechanical and Aerospace Engineering

01 Jan 2003

J. Satonobu

K. Nakamura

S. Ueha

Daniel S. Stutts Missouri University of Science and Technology, [email protected] et. al. For a complete list of authors, see https://scholarsmine.mst.edu/mec_aereng_facwork/3398

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Recommended Citation J. Satonobu et al., "A Single-Element Tuning Fork Piezoelectric Linear Actuator," IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Institute of Electrical and Electronics Engineers (IEEE), Jan 2003. The definitive version is available at https://doi.org/10.1109/TUFFC.2003.1182121

This Article - Journal is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in Mechanical and Aerospace Engineering Faculty Research & Creative Works by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. IEEE TRAXSACTIONS ON ULTRASONICS, FERROELECTRICS. AND FREQUENCY COPTROL; VOL. 50, NO. 2. FERRUARY 2003 1i!J

A Single-Element Tuning Fork Piezoelectric Linear Actuator James R. Friend, Member, IEEE, Juii Satonobu, Kentaro Nakamura, Sadaynki Ucha, arid Daniel S. Stutts

Abstract-This paper describes the design of a piezo- Uchino and Ohnishi [8] and their associates at ALPS electric tuning-fork, dual-mode motor. The motor uses a Corporation, Niigata, Japan, developed small lincar mo- single multilayer piezoelectric element in combination with tors using either one or two multilayer piezoelectric sctu- tuning fork and shearing motion to form an actuator using a single drive signal. Finite-element analysis was used ators (MLPA). In one version [SI, an MLPA was pla,ced in the design of the motor, and the process is described horizontally in between the top arm of an H-structure. along with the selection of the device's materials and its The bottom armof t,he H-structure acted against a slider, performance. Swaging was used to mount the multilayer and each arm possessed a different resomnce frequency. piezoelectric element within the stator. Prototypes of the The direction of the slider was controlled by changing the 25-mm long bidirectional actuator achieved a maximum linear no-load speed of 16.5 cm/s, a maximum linear force of frequency of excitation from the resonance frequency of 1.86 N, and maximum efficiency of 18.9%. the left leg to the resonance frequency of the right leg. In a similar vein, an inverted U-shaped structure was used with the ivlLPA placed between tlic legs. But the h4LPA I. INTllODUCTlON remained parallel with t,he sliding surface, and the different resonance freqnencies of the legs were exploited to oh- IEZOELE~TRICmotor systems exploit the transduction tain sliding motion. With these designs, one of the two P phenomenon from electrical energy input to mecheni- legs was pulled, essentially statically, hehiiid tbe structure cal energy ontput within piezoelectric matcrials. Tlic solid- as it niovcd against the slider; and the placement of the state construction possihlc with such devices, coupled with MLPA parallel t,o the sliding surface prevented generation their peculiar advant,agcs over standai-d elcctroma,gnetic of significant motion perpendicular to the sliding surface. motors, is constrained hy their sensit,ivity to heat, rela- In another version [9], [lo], either one or two MLPAs tively low efficiency, and short operating life 111. However, were used to excite elliptical motion along the output end inroads arc heing made 011 these problems, and conimcr- of a simple I-shaped beam, wit,h the MLPAs placed at an cially iiseful actnators are becoming more common. This angle at the top of the beam. The output, at the hottom paper, a sinall step in this process: details the design, coli- of the heam, was used by placing the beam perpendicular stroction, and testing of a small sjrigIe-piezoclec.trjc elc- to the slider. For the single-MLPA version, the direction of illelit linear actuator for lowvoltage applications. motion was changed hy changing the excitation frequency Some piezoelectric motor systems have hcen cornmcr- over several tens of kilohertz. For the double-MLPA ver- cially siiccessful due to their extrsordiIiarily high torque; sion, the direction of motion was reversed by reversing Toshiikii Sashida's Shinsei (Shinsei Corporation, Tokyo, the X/4 krnporal phase difference of excitation between Japan) motor [Z], [3] is an excellent example. Others have tlie two MLPAs. Another double-MLPA version iised a, so- been successfid because they arc extremely t,iny; Seiko's called II-shaped struct,ure, with two MLPAs placed at an (Seiko Epson Corporation, Tokyo, Japan) 8 inm motor [4], angle at the top corners of the structure. Tlie slider was 151 is used in watches to turn an eccentric disk to act as placed against the hottoin legs of the structure. In each of a silent alarm. More recent linear motor designs are ex- these designs, one end of t,he MLPA remains unattached; tremely powerful and demonstrate t,he extraordinary slid- the deformation of the MLPA at that end during vibration ing forces possible using large piezoelectric actuators [6]~ is not used in the operstion of t,hc actuators and, therefore, [7]. Still others are successful because t,lie niotion they de- does not make full use of the MLPAs deformation. velop is linear, extrcrnely precise, or botli. The device described herein is a small tuning-fork- shaped linear actuator designed to address some of the Manuscript received June 12, 2002; accepted September 10; 2002. shortcomings of the Alps motors, using, to the knowledge Thc authors appreciate support of this work by grants 0-5-2G010867, of the authors, previously unpublished construction tech- 0-5-20113786 from Honcyweli, NSF grant CMS-9409937, and a grant-in-aid from the .Jtipanese Ministry of Education, Culture, niques. Inherent in its dcsign is the use of a single MLPA Sports, Science and Technology ellclosed in the structure, placctf at an angle with respect R. Friend, K. Nakamura, and S. Ueha are with the Precision and to the sliding surface. As a result, both eiids of the MLPA Intelligence Laboratory, Tokyo Institute of Technology, Yokohama, Japan Oamesfriend~ieee.org). are used to excite mot.ion not only along the sliding surface, J. Satonobo is with the Department of Akchariicd Engineering, hilt also perpendicular to it, cnhancing the contact forces University of Hiroshima, Miroshinra, Jap~n. bctwecn tlic actuator and slider. Furtherniore, the design D. S. Stutts is with Lhe Department of Mechanical and Aerospace Engiircering and Engineering Mechanics at tlrc University of of the actuator is tailored to match the resonance frequcn- hlissouri-Rolla, Rolla, MO. cies of tlic forks, enabling both forks to participat,e in the

0885-30lO/$lO.O0 @ 20113 IEEE i an IF-EE TRANSACTIONS OX IJLTRASONJCS, FERROELECTRICS: AND FHEQUENCY CONI'IIOL; VOL. 5U, XO. 2. FEBRllARY 2003

3 27 1

Slider

Mount- Ring 0 5 10 15 20 25 30 PZT Angle, Theta (deg)

Fig. 3. The res~iiancefrequencics of the two fundarricntal tuning- fork/lifting modes versus MLF'A angle, 8; deririt.ed 1st and 2nd.

2nd

Fig. 1. The tuning fork actuator concept

Tuning Fork Lifting Diagonal Sliding Motion Motion Motion Motion

Fig. 2. Generating diagonal motion along the stat,or forks. Fig. 4. Compensating for the asymmetry in the st,ator. Finite element operation of tlie actuator in both directions. By inonnt- analysis results of the first two tuning/lifting fork modes (a) with no compensation, (b) with grinding of thc top fork (1.5 rnm) and ing t,he MLPA in the actuatorl it may be compressively bottom of the ring section (2 mnr). Note the addition of the w& in prestressed, enhancing the MLPA's longevity [I 11. the structure and the asymmetric motion of the forks in the originid When operated at its design freqnencies, the actuator configuration. The shading indicates displacement in the U-dircction. uses a relatively low voltage, roughly 5 VRA,~.This fea- tire serves as an advantage in higli-altitude, spacecraft,, or M;irtian atniosplieres in which ionization of the gas sur- that can be driven by tlic PZT are all tuning fork motions. ronnding the actuator could permit arcing even at modest However, once t,lic PZT is turned, each of these modes ser)- voltages [12], and that advantage is one of the reasons for arate into two different niodes bccause of the introduction pursuing this study. of asymmetry in the sbator. Because tlic PZT is turned, t,he top fork is longer, causing its rcsoiiance to occur at a lower frequency than the bottoiri fork. For exarnple, the 11. DESIGN fundamental tuning-fork niodc in this case separates into a motion dominated by the top fork, followed by motion ap The tuning fork device retains the traditional arrange- pearing mostly in tlie lower fork, at a higher frequency-. The ment of a piezoelectric actuator: piezoelectric material ex- separation in frequency of t,he two niodes that arise from cit,ing ultrasonic vibration in a nietal st,ator to move a sur- the fnndanierital t,iniing-fork niodc is shown in Fig. 3. For face in contact,, the slider, (Fig. 1). By placing tlie piczo- 0 = 25", the nsyninictric iriotiori is illustrated in Fig. 4(a). clectric material at an angle, 0, siniplc tuning-fork mo- Coincidentally, a 1-inm thick web was placed across the tions inarried with fork-lifting niotions, as shown in Fig. 2, forks to increase the resonance frequencics of all the modes cm gencrate diagonal niotiori along the contact interface. above tlic audible range; the data rcported was calcnlatcd This mot,ioii tlicii can be used to move the slider. When from a stat,or with the web. In these figures, the two modes the st,ack angle, 0, is zero, the mode shapes of the stator arc seferrecl to as tlie first, and second fiindanieiital tuniiig FRIEND ct al.: DESiGS 01' PIEZOELECTRIC TUKING-FOKKI DUAL-MODE hl fork/liftiiig modes. Note the first mode has motion mostly ill the top leg, and the second mode's Iiiotioii is within thc bottom leg, with a frequency separation betwccri thcni of about 5 kHL. The frequency separation needs to be reduced to cause a more balanced response among the two Icgs. Early in the design process, thc values of the parani- 678 12 II L6 10 12 Id eters uscd to define the stah's geometry were changed in an attempt to bring these two mode shapes' resonance frequeiicics closer together, as shown in Fig. 5. But tliis was not possible bccause the as,yrrimetry of the stator remained. However, by grinding away part of the bottom n of tlie ring and the top side of the top fork, the asymmetry was compensated. The grinding along the bottom 032 OB09 1.0 1.8 I2 22 U 26 IS ring lowered its stiffness and, thcreforc, its resonance fre- Ribmishcri (mm) RotorDir. I-) Ring Outer Dis. (mml quency; grinding t,he top fork near its end lowered its inass Fig. 5. Rcsoiianrc frequencies of the two frindanrcntal tuning-fork and, therefore, raised its rcsonaiicc frequcmcy. modes versus six geometry parameters; 1st arid 2nd indicate the By making thesc changes, the forks' displacement mag- loner and higher frequency fundamental tuningforkllifting modes, nitude moved much closer together. The ratio of maxi- respectively. niiim displacement of the tip of Ihe top fork to the tip of the hott,oin fork in the y-direction was originally 2.02 at TABLE I 22.7 kHz and 5.8 at 27.1 kHz in Fig. 4(a), but bccame 1.58 FIYALDMENSIONS OF TiiE TUNINGFORK ACTUATOR at 24.1 kHz and 1 at 25.9 kHa, respectively. Also important, howcver, is generating bidirectional Paranleter Value ~mm~* Geometrv motion. Though tlierc are scveral ways to achieve this, 12 the siniplcst method is first to align the rnodes as mnch 25 as possihle, then use a second or higher harmonic of the 25 paired fiindanierital tuning-forkllifting modes. This way, 6 the phase between the tuning -fork motion and the lifting 5 niotion explicitly depends on the inode shape througliout 12 5 tlie resoriaiice pcak. In Fig. 4 the pha,sing of the legs at 10 24.12 kHz is not useful for rriotioii-the Icgs move together 0 and apart at t.he same timc. At, 25.95 kHz, the motion is 5 bettcr, with t,lie forks nioving in the same direction and 5 with a strong lifting motion, gcnerating diagonal motion 10 with a ratio of riiaxiimiim x-to-y displacement of 0.72 for 'Refer tu Fig. 1 for paranretar definitions the top fork and 0.55 for the bottom fork, as calciilatcd in ANSYS. Several modes betweeii 20 and 75 kHz are il- Iustratctl in Fig. 6. Sortie of these modes have synchro- changing the frequency of excitation. thus the difference nized tuning-fork motion mrl large fork-lifting motions, between the motions in Fig. 2(a) and (b). The dimensions and thus may be iiseful for generating sliding. The niodc of the final design for the stator is given in Table I. shape at, 25.95 kHz, discussed before, is such a model as are the inodes as 52.01 and 58.58 kHz. Others, including the inode at 44.07 kHz, have out-of-plane motion or have 111. ACTUATOR AND TESTFIXTURE CONSTRUCTION motion sonicplace other than the fork tips. The mode at 74.72 kHz has significant fork motion, but it a,lso has large The stator was machined using computer numericdly displacements within t,he ring past of the stator. controllcd milling of Cl020 low-corrosion steel plate. The The directiori of motion is controlled by the oricrita- fort tips and MLPA moiints were polished to a 5-prm tion of the dkagonal iriotion generated at the fork tips, as finish in preparation for mountiiig friction material and shown in Fig. 2. If the diagonal motion is orientcd upward the RILPA. The MLPA was placcd within the stator and as the forks approach thc slider, they will move the slidcr checkcd for a sling fit, taken out and replaced wit,h epoxy upward. The difkrence ill tlie norriial force, and therefore along the interfaces bctween the MLPA and stator, and the slidirig force, as tlic forks move toward and away from rnechanically sccured im placc by swaging the stator at two the slidcr make this motion possible. To change tbe dircc- or more places near the mounting interfaces, as shown in tion of sliding motion, the orienta,tionof the diagorial fork Fig. 7. motion must he changed. One way to achieve this is to The swaging was pcrformed before the epoxy cured. In use &her modes that have the other fork inotiori orient&- early trials, the epoxy was allowed to cure before swaging, tion. In other words, thc direction of slidiiig is reversed by but, the coupling of the stator to the piezoelectric uiatcrial 52.01 lcHz 58.58 lcHz 44.07 kHz 74.72 kHz

(4 @)

Fig. 6. Predictcd mode shapcs according to finite elemcnt analysis. The contours indicate the relative magnitude of deHectiori in the direction ofthe arrow slrown on thc left (except for the plot at 44.07 kHz, which indicates deHection in and out of the page) for (a) riiodes that might be useful for actuation, and (b) ir\odes that BTC to be avoided.

piece of aliiniina plate, polislied to have parallel faces, was mounted onto a light sliding platform with a snlall linear ticaring to farm the slider. An encoder grating, made by printing a regular pattern of lines on an overhcad t,rans- parency on a laser printer, wt~sattached to the slidcr's end. By mounting an inexpensive optoelect,ronic switch: with the encoder serving as the gat,e in conjunct,ion with (a) rb) (C) a digital oscilloscope and sorne software, it was relatively easy tu nieasiire tlic velocity of the slider with respect to Fig. 7. Mounting the MLPA within the stiltor using swaging time. A drawback of this approach is tllc low resolntion (a) CRIISBS (b) cxpansion of the stator niaterial near thc MLPA, se- curing it, c~ shown in il prototype (c). of the velocity signal, particularly during the start of the sliding motion when the actuator is capable of acceler- ating the slider over a very short distance. Howcver, fm- was poor. The depth of the swage and numher of swage this study, the incasurement of the acceleration wit,h large operations also affects the coupling of the MLPA and sta- masses placed on the rnonofilament line was still possible. t,or; having too many or pressing too deeply causes nn- The preload force was placed ilpori the actuator hy using wanted flexibility near t,he MLPA. Swaging accomplishes a preload spring to press against t,hc actuator's niounting, thrcc goals: firndy coupling tlie piezoelectric niaterial to which was free to slidc vertically; the-preload was deter- the stator on both ends; placing the MLPA under coni- rniiicd by measuring the deflection distarice in this spring. prcssive prestress, thus enhancing its dnrahility [ll];and thinning the epoxy bond. Though it is probably possible IV. RESULTS to eliniinate t,lic use of epoxy to bond t,he MLPA to the stator, it was not tried for these prototypes. The actuator's electrical, vibration: and linear actuation Two mat,erials were used for contact om the stator, alii- charact,eristicswere measured; the results are indicated in mina, and asbestos brake liner rnat.eria,l. For the slider, the following sections. alumina was used throughout. In particular, the alumina/alumina interface has been shown to he a durable A. Electrical Ch,nractenstics and convenient choice [13], (141. In each case, the materials were polished to 0.5 N 1 iiim thickness and bonded The impedance characteristics of tlie actuator were to tlie stator using the same Loctite epoxy. The thickness measured usirig a standard HP 4104A (Hcwlctt-Packard, of the epoxy was rniriiiniacd by fast,eiiing the parts in a Palo Alto, CA) analyzer at 0.5 V~hrs.From Fig. 9(a), precision milling vise during curing. the t~worriodes at, 24-25 kHz appear, with the cross ("x") Tlie contact counterfaces were polished to 3 prn rongh- and t,he douhle circle ('Q'')indicating not useful and very ness, using either increasingly fine sandpaper or several useful modes, rcspectively. The modes appearing at 47 arid grades of diamond grit lapping powder in oil on a t,ool 57 kHz correspond to the 52 and 58 kHz modes in the AN- steel polishing plate. In either case, firm1 hand polishing SYS analysis, and are both marked as being useful; the w-as performed using standard writing paper and alcohol shift is due to the assumption of an ideally fixed base (see on a flat glass plat,e. Fig. 1).The actual base can vibrate along with tlic actua- A small, v-sh;yxxl notch uns machined into the ring sec- tor, and these inorlcs have motion at the basel dike the tion of the stator (see Fig. l),along with a 3-nim threaded mode at 26 kHz; t.he consequence is the modes' frequen- hole to receive a bolt, to provide a secure mount,. This cies are reduced. Not siirprisiiigly: the Imdcsirable mode moiirit prcvented turning of t,he stator to ensure tlie feet, that appears in ANSYS at 44 kHz does not appear in the of the stator were in parallel contact wit,h the slider. impedance test,; it cannot he driven by the MLPA. Though A test fixture was constructed to hold the stator and not very prominent, there is a slight peak at, 59 kHz that slider, and to permit rneasnremerit of the actuator's perfor- indicates another out-of-plane mode. At, 74 kHz, the mode mance. The test fixture's arrangerrielit is shown in Fig. 8. A corresponds to the ANSYS analysis. Although not very FRlEPin et al.: DESIGN OF PlEZOELECTRlC 'TUNING-FORK, DUAL-hlODE MOTOR 183

Fig. 8. Thc test fixture.

-10

-30

-50 2 ~70 -90 1.5 8 -E '3I 'B 0.5 z

0 15 25 35 45 55 65 75 85 95 I'requenry (kll') Frequency @HZ]

(=) (I.)

Fig. 9. Impedance arriplitudc and phase characteristics of thc stator with respect to excitation frequency (a) without slider and (b) with a slider at 1.98 N prrload; "x" indicates a useless model "0;' a potentially useful model and "@ B useful nrude. useful; it is marked with a singlc circle (Q), irriplying it Fig. 10 illust,rates t,hc effect of swaging the &tor on the potentially could he useful because it does possess fork mo- impedance. Beforc the swaging was performed, an MLPA tion. Above this rnoile, Iiowever, tlie motions are primarily was monntcd in a stator using epoxy with a press fit tol- witliin the MLP.4. a,nd so arc of little use for actuation. erance. After the epoxy." cured. tlic impedance svectrnrn for tlic unswaged stator was nieasiiretl. Subsequently. the Placing tlie stator into contact with a slider caused stator was swaged, and the impedance spcctrum for the significant, change in the iinpedaiice spcctrinn, as shown swaged version was measured. Notice that the general ef- in Fig. 9(b). The contact interface was aliiiiiiria/aluinina, fcct is the larger mi~iirriuniphase for most resonances, indi- though other contact interfaces produced siniilar results. eating an iniproved coupling between the stator and MLPA In particular, thc modc at 47 kH4 amplified enough t,o and, pcrhaps, indicating improvement froin t.1~static com- become nsefiil, as will be shown latcr. Unfortunately, the pression of the MLPA within the stator. Furthermore, reverse is also true; the useful mode at 25.25 kHz, iridi- thc resonances are generally narroiver, cspecia,lly the large cated with an asterisk in Fig. 9: alrnost disappcared when peak at around 55 kHz, representing an iiicreasc in the the slider vas introduced. Certainly the introduction of the quality factor froin 35 to 110 for this particular peak. An- slidcr also alters the mode shapes, just as it has altered the other effect of t,lic swaging is the lowcring of the rcsonance impedance spectrum, hut the effect was not included in t~hc frequcncies of many of the modes, froin 1 to as much as finite element analysis due to the extraordinary expense of 5 kHz. The reason for this shift is the increased iicxibil- contact analysis. 184

I - swaged 1 unswaged - 1.0 I 0- 9 0.8 I 0.00 0.05 0.10 0.15 0.20 9 06 Sliding Velocity (m/s) 0.4 .Uz 0.2 .... Fig. 12. Eificiency versus sliding vclocity with brake liner/;tlumina * 0.0 contact cannterfaccs BI, 47.1 kHz. 20 30 40 50 60 70 80 90 100

Frequent? (I.H.1

Fig. 10. Admittance and phase with respcct to excitation frequcncy, wi1.h MLPA, swaged and unswaged. The arrows indicate the relcvant axis for each curve.

/1 t4.63N -+--8.51 N

0.0 I I , I 0.w 0.05 0.10 0.15 0.20 Sliding Velocity (m/s)

Fig. 13. Sliding force versus sliding wlocity with brake liner/alumina contact counterfaces at 55.3 kflz. The lines represent leust-square fits of the data. 0.k 0.05 a.io 0.15 0.20 Sliding Velocity (m/s)

Fig. 11. Sliding force versus sliding velocity with brakc liner/alorrrina sliding vclocity, divided by true averagc power in, or the contact counterfaces at 47.1 kHz. The lines represent least-square fits time-avcrage of tlie product of the instantaneous volt,aSe of the data. times tlie instantaiieoiis current (taking tlie phase into ac- count). Thc 47.1 and 55.3 kHz resonaiiccs correspond to ity in the stator around the swaged arm, which obviously the 52 kHz and 58 kHz mode sliapes in Fig. 5: respectively, affects the mode shape. However, the bcnefit of increased wit,h the shift being due to the Rcxibility of the base and the swaging of tlie stator. The applied voltage in all caecs response was helievcd to outweigh this problem, and so all stators used in testing reported here were swaged. was 3.5 VRnrs, witli a positive direct current (DC) bias of 2.5 V to maintain the poling witliin the MLPA. B. Linear Motion Results Maximum sliding forces of 1.86and 2.31 N were reached using a. prcload of 11.27 N in the 47.1 and 55.3 kHz direc- Using the test fixture in Fig. 8; measureriients of the tions? while inaxiinum velocities of 16.5 and 18.8 cmjs, slider's velocity with respect to sliding force, preload, volt- were reached at a prcload of 16.2 N in the 47.1 and age applied to tlie MLPA, stator version, arid mass on tlie 55.3 kHa directions, respcctively. A maximum efficiency monofilament line were made. From thesc measiirement,s, of 19.7% was rcached in the 47.1 kHz direction at a slid- the axial force the stator could deliver to the slider based ing velocity of 11.2 cmjs using a preload of 16.2 N. In the on these variables was determined. 55.3 kHz direction, tlie efficiency peaked at 18.9% at the Figs. 11 and 12 plot the sliding force amd efficiency saiiie preload and a sliding velocity of 11.5 cm/s. vcrsus sliding velocity at a frequency of 47.1 kHz, using From 4.63 N to 11.2 N of prcload, tllc trend of brake liner/aliimina contact counterfaces. Figs. 13 and 14 the actuator's response is generally toward larger sliding provide the same data but at 55.3 kHz: at which tlic ac- force/velocity, but the liiglicr 16.2 D! preload gives a dif- tliator moved in the opposite direction. Thc efficiency is fcrent response, with a dramatically lliglicr sliding veloc- defined here as the power out, os slidirrg forcc times the ity aid reduccd sliding force. This possihly could bc to a FRIEND et al.: DESIGN OF PIEZOF.I.ECI'KIC TUNING-FORK: DUAI,-MODE M<)TOR 185 15 -15.9 N,47.3 !&Iz - B- 30.5 N, 47.3 !+Lz --A-15.9N,55.3& -*--30.5 N,55.3 kHz

:'ti : ;," :'ti I T4.6: N ~~',,> - -8 --8.51 N 1 -.+--ll.ZN - B.B. ... ~A.... 16.2 N s 0 A.--- 6- 0 0.00 0.05 0.10 0.15 0.20 0 Sliding Velocity (m/s) 0.00 0.02 0.04 0.06 Sliding velocity (m/s) Fig. 14. Efficierrcy versus sliding velocity wibh brake liner/alumina contact counterfaces at 55.3 kHz. Fig. 16. EOiciency versus velocity for alumina/aliirnina contact coun- terfaccs at 47.3 kHz arid 53.3 kIlz.

1.5 -15.9N, 47.3% 10.3% at 1.32 cm/s, 15.9 N preload, and in the 47.3 kHz - m- 34.5 N. 47.3 kHz --A- 15.9N, 55.3 kHz direction. Generally, the efficiency is less than 5%. --4--30.5N, 55.3% E 1.0 .. V. CONCLUSIONS . A novel piezoelcctric linear act,uator was presented, using a single piezoclectric element mounted in the stator \. .. .- 55.3 kH2 structure with swaging. The basic concept, along with its 00 0.00 0.02 0.04 0.06 improvement via finite clement aiialysis, was shown. For a Sliding Velmity (m/s) few select choices of two different stator designs and three different coiltact niaterials, the irmpedance characteristics Fig. 15. Sliding force \,crsiis vclncit,y for alnnrina/alumina contact, of the stat.or along with the performance of the actuator counterfaces at 47.4 kHa and 53.3 kHz. Thc lines represent least- square fits of the dirta. were measiircd. Thc experinient,al results demonstrate the feasibility of the dcsigii concept. Bidirectioiial motion, with a maximum sliding force of change in the mo1.ion along the contact interface from re- 1.86 N and a maxiniuni velocity of 16.5 cm/s in either di- distribution of the contact force along the interface. The rection, was obtained using alumina/brakc liner contact. brake liner material's coniplia.nce, ;~tlow preload servcs to The efficiency of the alumina/brake liner actuator was transmit the vibration of the stator to the slider usithout about lo%, hut it achieved a maximum cfficiency of 18.9%. much effect on the stator's vibration. At a higher preload, Using an alurnina/aluinina interface, bidirectional mo- beyond 10 N or so, the friction liner material may be fiilly tion was obtained; but tlic efficiency was mucli lower; gen- compressed. crally less than 5%. From the aluminalalnmina actua- For an alumina/almnina contact interface, Figs. 15 and tor, a maximum (bidirectional) sliding force of 0.927 N 16 indicat,e the force versus velocity and efficiency versiis and velocity of 3.38 cm/s were obtained. Thoiigh alu- velocity in both sliding directions, respectively. Becausc mina/aluniina interfaces have been successfill in some the counterfaces are far stiffer, a higher preload is neces- piezoelectric actuator dcsigns, in this case the more com- sa1-y: which reqnires a higher applied voltage of 4.20 V~nis pliant alurnina/brake liner contact interface performs far to excite siifficient vibration in the structure. A positive hct,ter, particularly with regard to thc maximnnm sliding DC bias of 2 V also was applied. The direction of sliding vclocity. is indicat,ed in Fig. 15. For future work, the authors would like to pursuc the i\t a preload of 15.9 N; the maximuin ineasiired sliding revision of this actuator to improve upon the design of forces were 1.27 and 0.524 N; the niaxiinuin velocities were the stator, using hard PZT multilayer piezoelect.ric actu- 3.38 cm/s and 3.57 cm/s in the 47.3 and 55.3 kHz dircc- ators in order to iniprnve the efficiency. of the system at tions, respect,ivcly. At 30.5 N preload, the slidirig forcm iilt,rasonic freqiicncies. Furtlmrniore, the authors cnvisiori arid velocities peaked at 0.927 and 1.12 N; and 5.56 and a dctailed study of the fork arms' motion and their shape 2.08 cmjs in the 47.3 and 55.3 kHz directions. Thc ef- to obtain improved performance. Using this actuator for ficiency of this configuration is consistently lower than sliding perpendicular to t,he forks, or rotation of a shaft the aluminalbrake liner configuration, with a inaximnrn of placed bctween the forks, will be considered. 186 IEEE TRANSACTIOIS ON ULTR.4SONICS. FERROELECTRICS, AND FREQUENCY CON'I'IIOL, "01.. 50, SO. 2. FEBRUARY 200,'j

ACKNOWLEDGMENT He is a member of IEEE, ASME, and the Acoustical Society of Japan, arid an associstte member of Sigma Xi. The authors would like to acknowledge the assistance of Dr. Takaaki Ishii, without whoin this work would have been impossible. Jun Satonobu was born in Hirosirima prefecture, .lapan, on Augwt 1064. He received the B.Eng., the M.Eng.l and the D.Eng. degrees from the Tokyo Institute of Technology, Tokyo, dapnii in 1987, 19811, arid 1998, respcctively. He has been irr the Faculty of Engineering, Hi- REFERENCES roshima Univcrsity since April, 1998, and has rescarched as a Visiting Fellow in the Department of Mechanical and Aerospace Engincering at the Univcrsity of Colorado at Colorado Springs from Jam, 2090 S. Ueha arid Y.Toniikawn, Ultrasonic Motors-Theory and Ap- (11 to March, 2001. plications. SCT. Monographs in Electrical and Electronic Er@ neering, vol. 29, Oxford: Clareridon Press: 1093. Dr. Satorlobti is a merrher of the Acoustical Svciety of Japan aud the Japan Socicty of Rlechenical Engineers. [Z] T. Sashida, "Supersonic vibration driven motor device," U.S. Patent 4,548,090, Oct. 22> 1985. [3] T. Sashidn; "Motur device utilizing ultrasonic oscillation," US. Patent Number 4,562374, Dec. 311 1985. (41 h.I. Kasuga, T. Mori; and N. Tsukada, "Traveiling-wave m- Kentaro Nakamura was born in Tokyol tor? USPatent Number 5>008,746,Apr. 9, 1991. .Japan, on July 3. 1963. He received the [5] Al. Kim-sta, F. Oanwa, h.1. Kasuga, hl. Suauki, and T. B.Eng.> the MEng., and the D.Eng. de- Shibayanra, "Ultrasonic motor," U.S. Patent Number 5,091.6701 grees from the Tokyo Institute of Technology, Feb. 25, 1992. Tokvo. Juoan in 1987. 1989. arid 1992. re- [GI C:H. Ynn, T. Ishiil K. Nakamura, S. Ueha, and K. Akadri, has becir an associate professor "A high power ultrasonic linear motor using a longitudinal and \- of the Prccision arid Intelligence Laboratory. bcriding hybrid bolt-clamped langeviri t,ype transducer: Jpn. J. Tokyo Institute of Technology, Tokyo, Japan, Appl. Phys., vol. 402 no. 5B, pp. 3773-3776, 2001. since 1996. His field of research is the appli- 17) RI. K. Kurosawe, 0.Kcldaira. Y. Tsuchitoi, and T. Higuchi, cation of ultrasonics and the measurcnient of "Transducer for high speed and large thrust ultrasonic linear vibration and sound iisinr ootid methods. motor using two sandwich-type vibrators," IEEE Tmns. Ultra- He has received thc AwqZa Kiyoshi Award son., Ferroelect.. Freq. Contr., vol. 45, no. 5, pp. 118R-1195, fur encouragcrnent of research from the Acoustical Society of Japan in 1998. 1996. Dr. Nalwmora is a member of the Acoustical Society of Japan, [8] K. Uchino and K. Ohnishi, "Linear motor," U.S. Patcnt Numbcr the .lapan Society of Applied Physics. the Institute of Elcctiical En- 4,857,791, Aug. 1980. gineers of Japan, and the Institute of Electronics, Information and 19) K. Ohnishi arid K. Yarnakoshi, "Ultrasonic linear actuator using Cornrrrunicatiori Engineers. coupled vibration," J. Acout. Soc. Amer., vol. 11; no. 4; pp. 235-241, 1990. [lo] K. Ohnishi, K. Naito, and T. Nakacawa, "Ultrasonic wave linear motor: USPatent Numbcr 5j21G,3131June 1, 1903. Sadayuki Ueha was born in Kyoto Prefcc. [Ill "Multilayer picioelectric acnators (chouunpe denki ture, Japan, on February 28, 1943. He 1% aknchuayta)," Report EC-O11. Voi. 3: Tokin Co., Ltd., ' ceived the B.Eng. degree in electronic engi- 1987. (in .Japanese) neering from the Nagoya Institute of Tcrh- [I21 T. Swindle, A. Chutjian, .J. Hoffman, J. .Jordanl J. Kargel, ' nology in 1965. the M.Eng. degree in 1967, R. hlcEntirc. and L. Nyquist, "Isotopic analysis md evolved and thc D.Eng. degree in 1970; both in elt:c- gases," in Planetanj Surface Instmments Workshop.T. Kostiuk, ~ tric cngineering, from the Tokyo Institute uf C. hleyer, and A. Treinian, Eds. 1996>pp. 21-40. Technology. Tokyo: Japan. He currently COR [13] T. Ishii and K. Uchino, "Ultrasonic motor using alumina ccrm- _-_- i ducts research in high power oitrasonics. He ics? in 89th A~LU.Meeting. American Ceramic Society, 1987, has beer, a professor uf the Precision and Intel-

pp. 124-128. AB~ ligence Laboriltory, Tokyo Institute of Ted>- (141 P. Rehbeiri and J. Wdiaschek, "Riction and wear behaviour of nology, since 1992. polymer/steel and uhinrinalaluniina under high-frequency fret- He is a steering committee nicrnber of thc World Congress on ting conditions," Wear: vol. 21G1 pp. 97-105, 1998. Ultrasonics arid serves tu the secretariat of WCU97. He received the Best Paper Award from The Japan Society of Applied Physics in 1975 and from the Acoustical Society of Japan in 1980: respectively. Dr. Ueha is a member of the Japan Society of Applied Physics. the Acoustical Society of .Japanl the Institute of Electronics, Information James R. Friend (S'98-A:98-A4'03) was born in Lubbock, Texas, on Septcnrher 13, 1970. He received the B.S. degree in aerospace cngineering, magna cum laude, ilnd the h.I.S. and P1i.D. degrecs in mechanical engineering from the University of Missouri-Rolla in 1992, 1994. and 1998, rcspectively. He re- Daniel S. Stutts was born in Canton. GA: ceived the Aincrican Socicty of Mechanical OLI January 9: 1959. He reccived bachelors Engineers (ASME) Best Paper award and and masters degrees in mechanical engineer- Americaii Institute of Aeronautics and Astr- ing from thc Luuisiana StiLtr University in Ih nautics (AIAA) Jefferson Goblet Student Pa- ton Rouge, LA in 1983 and 1987, respectivdy per Award for il paper delivered at thc 97th He earned Iris Ph.D. in mechanical engineer- Annual AIAAIASAlEIAmerican Helicopter Society/American Soci- ing in 1990 from Purduc University in \Vest ety of Civil Engineering Structural Dynamics and Mechanics Confer- Lafayatte, IN. In 1991, he joined the faculty of ence in 1990. In 1999, he joined the faculty at the newly formed De mechanicai engineering and engineering me- partment of Mechanical Engineering at thc University of Colorad- chanics at the University of Missouri-Rolla, Colorado Springs, He is now at the Precision and Intelligcnce Lab Rolia, MO, and was promoted to associate oratory, Toky-o Institute of Technology, Tokyo: Japan, as a research profcssor in 1997. He has worked in the area Lssociate. with research interests in milliinctcr- and micrometer-scale of piezoelectric actuator desigil and modeling since 1993. His hobbies piezoelectric actuators and their applications. iriciude cycling and music.