CA1294659C - Shear motor for dynamic mount for laser-beam steering mirror - Google Patents

Abstract

Abstract of the Invention A dynamic mount and actuator for a laser mirror 20 comprising three piezoelectric motors 40 mounted 120° apart on a motor-mount member 32.
Each motor 40 comprises a rectangular block 44 composed of horizontal layers of electroded piezoelectric wafers 46 adjacent layers being bonded together. The one-axis movements of each shear motor 40 are amplified by and transmitted to an axially extending flex-joint assembly 36 which is formed with two universal-type flex joints 102, 104 therein. The back of the laser mirror 20 has three backing plates 22 affixed thereto at locations corresponding with the locations of the flex-joint assemblies 36 and the motor-mount member 32 has three suspension ring assemblies 27 affixed thereto, one at each backing plate location. Each suspension ring assembly 27 comprises a suspension ring holder 29 affixed to the motor-mount member 32 and a suspension ring 26 within the holder 29, movably attached to the holder 29. A space exists between the back of the suspension ring 26 and the front of its holder 29 and contains a flexure assembly 28 comprising three slotted, flexible, ring-shaped washers 124 separated by two spaced, concentric annular spacers 126. The flexure assembly 28 permits axial, tip and tilt movements of its associated mirror-backing plate 22. A support member 34 coupled to the flex-joint assembly 36 extends from the front end thereof through the suspension ring holder 29, flexure assembly 28, suspension ring 26 and mirror-backing plate 24 and is fastened to the mirror 20 by an interface pin 30 which does not distort the mirror 20.

Description

5~

8~R38-1 SHEAR MOTOR FOR DYNAMIC MOUNT
FOR LASER-BEAM STEERING MIRROR

: Theodore A. He1n~
,, ~S~
: 5 l. F1eld o~ the Invent10n Thls 1nventlon relates to a h19h-performance, reactlonless, dynaMlc mount for a laser-beam steerlng mlrror and espec1ally to a motor for actuat1ng a m~rror supported by such a mount.

2. Oescr1pt10n of the Pr1or Art Hlgh-energy laser ~HEL) systems generally employ an : ad~ustable, tooled m1rror to steer the laser beam. The m1rrors are large and heavy, and beam control requ1res prec1se po1nt1ng, focuslng and : stab111zat~on of the beam 1n a severely vlbrat~onal env1ronment. To date, a m1rror: mount1ng-and-movlng dev1ce capable of sat~sfactorlly perform1ng ~ these control funct10ns has not been demonstrated even though extens~ve eFfort bas ~een expended ther~on.

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-2- 83R38-l Perturbat10ns ar1slng from acoust k , thermal and maneuverlng loads 1n the m1rrori 1ts mount and 1ts dynam1c actuator requ1re the actuator ~or motor) to be capable of provld1ng several m1111rad1ans of stroke and to have an operat~ng bandwtd~h from ~.C. to several k110hertz (KHz). Stroke preclslon 1s on the nrd~r of a few mlcroradlans. The h~gh 1ntens~ty of the beam on the m1rror surfa~e and the low allowable d1stortlon of the m1rror surfaee comblne w1th h19h dynam1c loads to 1ncrease m1rror s1ze and we1ght (tn excess of 30 lbs.).
- Mountlng a HEL 1n an a1rcraft or a space satelllte places a prem1um!
on dr~ve power component we1ght. Large values of actuator heat' d1ss1pat~on ln the m1rror dynam1c mount contrlbute to thermal d1stort10n~
and compl1cate thermal m~na~ement. Add1t10nally, 1t 1s des~rable to m1n1mlze d1sturbances 1n the support1ng opt1cs structure, ar1s1ng from the large react10n forces 1n the dynam1c devlces.
Actuators formed from stacks of p1ezoceram1c wafers have been used for some ttme to control the surface or1entatlon of laser mlrrrors or as dynam1c dr1vers for small m1rrors and elements of m1rror arrays. These actuators uttl1ze stra1ns tmpQsed by an electr1c f1eld 1n the d~rect10n of th9ckness ~d33 d1rect10n) or length (d3l dlrectton). Actuators of th~s type are 11m1ted to 200-300 m1cro1nches of movement per lnch of the1r l~ngth e~en lf operated at a h1gh voltage ~e.g., 30-50 voltsJ.ODl 1nch o~
- wafer th~ckness~.
In an operat1n~ system, the dynam1c mlrror mount actuators are dr1ven by a Uclosed loop", electrun1c servo system. ~rror s19nals may be obta1ned from a var~ety of opt1cal sensor arrangements depend1ng u~on spec~f1c system cons1derattQns. In all cases, however, stab11~ty of a pract1cal servo drlve requ1res that structural resonances of the actuator dr1ve tratn be h1gher than opera~1ng frequencles. Control of heavy heat exchanger-type mlrrors (cooled mlrrors) at several kllohert2 requ1res actuator spr1n~ rates of tens of m11110ns of pounds per lnch of deflect10n -3- 83R38-l P1ezoceram9c actuators appear bas1cally as pure capaclt1ve loads to the dr1vlng ampl1f1er. As a consequence almost all oF the dr1vlng power ls d1ss1pated ~n the output stage of the ampl~f~er. Th1s 1s an advantage 1n thermal management of the actuators but places heavy burdens on S ampl~1er deslgn. The quantlty of dr1ver-dlsslpated or react1ve power~
1s a functlon of the square cf the drlver output voltage for a g1ven operat1ng frequency. Reactl~e power also lncreases ~n proport~on to frequency. For example ~f an actuator requ~res lOG volts to achleve a re~ulred d~splacement at a frequency of 300 ~Iz and th~s correspondonds to a react1ve power of 200 watts the reactlve power would 1ncrease to 20 000 ~atts ~f the requlred voltage were lOOO volts. Thus lo~er operatlng voltages are deslrable for p~e~oceram1c actuat1ng motors.
~s descr1bed the convent~onal p1ezoceramtc actuator requ1res exsess1ve length to ach~eve requ~red deflectlons the resultant structural proport10ns result1ng ln excesslYely low resonance character~stlcs.
Practkal power consld~rat10ns preclude h1gh-frequency operat~on at hlgh volta~e. The un~ue p~ezoceram1c shear motor used ~n the present ; lnvent10n proY1des a dlsplacement per volt wh~ch ~s slx tlmes as much as that prov~ded by a conventl4nal P~T actuator. The block-11ke proportlons are ldeally su1ted to h1gh structural resonance des~gn. Also the conflgurat~on used 1s lnherently react10nless.
Ob~ects of the Invent10n An ob~ect of the 1nventlon 1s to prov1de an ~nherently react~onless dynam~c mount for a HEL laser beam-steerlng m~rror Another ob~ect ls to prov~de a hlgh-performance mount for a ~L
bea~~steer~ng m1rror.
A Further ob~ect 1s to ~ncrease the deflectlon per volt prov~ded by p~e~oceram1c actuators.

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_4- a3R38-l Yet another ob~ect 1s to prov1de a p1ezoelectr~c actuator havlng a h19h structural resonance frequency.
Other obJects, advantages and novel features of the present lnventlon w111 become apparent from the followlng deta11ed descrlptlon of S the 1nventlon when cons~dered 1n con~unct10n w~th the ac~ompany1ng drawtngs.
Summary of the Inventlon The ob~ects and advantages oF the present ~nvent10n are attalned by a .dynamlc mount-and-actuator assembly for ob~ects such as laser mlrrors.
The actuator 1s a novel plezoelectrl. shear motor three of whlch are . mounted 1n a hold1ng means 120 apart wlth respect to a central ax1s.
In frant of each motor and afflxed to the hold1ng means 1s a suspens~on assembly comprls1ng an annular r1ng holder surround1ng but spaced ax1ally from a suspens~on r1ng. The suspens10n assembly 1s attached to a suspenslon plate, wh~ch supports the m1rror, throug~ a support member.
~: The support member 1s formed ln two sect10ns, the front part be1ng attached to the suspenslon plate by an 1nterface pln and the rear part :~ belng aff1xed to the susp~nslon r1ng holder and to the front part by a p1n, an axlal space be1ng present betw~en the front and rear parts.
The axlal movements of each shear motor are transferred to an ax1ally extend1ng, novel, stlff l~nkage, or flex-~o1nt assembly,by a lever ~:~ ar~, or vert1cal s~rut. The 11nkage transfers the movements to the m~rror through the support memb~r for the suspens10n plate.
The novel 11nkage 1ncludes a palr of flex ~o1nts wh~ch allow for ;~ 25 small flextngs of the 11nkage 1n a non-axial d1rectton. Further flexlng ln a non-axlal d1rectlon between the suspens10n plate or, more preclsely, the suspens~on r1ng and the r1ng hol~er Is orov~ded by a ~1exure assembly ~' .
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-5- 83R~8-l wh kh ls placed ~n the space between the rlng holder and the suspenslon rln~ and 0xtends lnto the space between the front and rear sectlons oF the support member.
The mount permlts ax1al, tlp and tllt movements of the m1rror under h19h-speed actuatlon by the shear motors.
~r~ef DescrlPt~on of the F1~ures F1g. l ls a front v~ew of a dynam1c m~rror actuat10n assembly ln accordance w~th the lnvent~on.
Flg. 2 ls a slde vlew of the assembly shown ln Flg. l.
Flg. 3 ls a cross-sectlonal vlew of a shear motor taken along llne A-A ln F1g. l.
F1gs 4A, 4B and 4C are lsometrlc v1ews of three adJacent plezoelectrlc elements of shear motor. Flgs. 4A and 4B show ad~acent vertlcal 21ements and F1gs. 4A and 4C show adJacent hor~zontal elements.
Flgs. 5A and 5B are a slde and top v~ew of the actuator load~ng plate.
F1g. 5C ls an lsometr1c exploded vlew of the Yertlcal strut, trunn10n member and actuator loadlng plate.
F1g. 6 15 a slde vlew of several shear elements show~ng the electrode arrangement and the arrangement of the electrlcal contact wlth the electrod~s on the shear elements.
F1g. 7 1s a schematlc 111ustratlon of the manner 1n whlch three layers of sh~ar elements would move 1n response to an appl~ed voltage.
F19. 8 1s a part~ally broken-away slde vlew of the l~nkage, or flex-~olnt assembly.
Flg. 9 ls an lsometrlc exploded vlew of the front flex-~oln~.
Flg. lO ls a s1de vlew of the flexure assembly.
F~g. ll ~s a front vlew of a flex1ble washPr.
F19. 12 ls a front vlew of a spacer.
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The same elements or parts through the figures of the drawings are designatecl by the same reference characters, while equivalent elements bear a prime designation.

Det~iled Description of tha Invention A front view of a dynamic mirror actuation assembly in accordance with this invention is shown in Fig. 1 and a side view in Fig. 2. A laser mirror 20 is mounted on a mirror backing plate 22, or support plate, by means three interface pins 30 which are embedded near the outer edge o~ the mirror 20 at 120 int~rvals. The pins 30 project from horizontal support members 34 and are designed so that they do not distort the mirror 20. Three shear motors 40 are mounted at 120 intervals around a motor-mount member 32 to the front of which is attached a suspension plate 24. The suspension plate 24 carries three suspension assemblies 27 at 120 intervals, each of which encircles a support member 34 which holds one end of an interface pin 30 and one end of a horizontal force~
transmission linkage, or flex-joint asse~bly, 36. The other end of the flex-joint assembly 36 is coupled to the lower end of a strut 38 which is part of a vertical strut assembly 42. ~xially directed (referring to the longitudinal axis of the flex-joint assembly 36) forces from a shear motor 40 are transmitted through the lever-like action of the vertical strut assembly 42 to an associated ~lex-joint assembly 36, and thence through the : support member 34 and mirror backing plate 22 to the mirror 20.

A mirror backing plate 22 is affixed to the rear of the mirror 30 and a susp~nsion plate 24 is affixed to the motor mount 32. Three suspension assemblies 27 are integrally formed as part of the suspension ,~ ~

~L2~659 -7- 8~R38-1 plate 24 at 120 1ntervals around the outer port~on of the plate 24.
Each suspenslon assembly 27 comprlses an outer suspens10n r1ng holder 23, preferably annular, and a flexure assembly 2a, preferably annular, wh1ch f1ts lns~de a recess 1n the suspens10n rlng holder 29. A roughly S cyl1ndr1cal support member 34 extends between the center of the suspens10n assembly 27 and the m1rror backlng plate 22, to whlch 1t ls attached by an 1nterface p1n 30. The support member 3~ 1s formed 1n two parts wh~ch are p1nned to each other but are separated by a flexure assembly 2~ wh1ch also 1s placed between the suspenslon r1ng 26 and the suspenslon r1ng holder 29 so that relat1ve movement w1th s1x degrees of freedum ls posslble between th~ m1rror 20 and the suspens~on plate 24. The mlrror mount thus permlts ax1al deflectlons and tlp and t11t movements at each suspens10n assembly A shear motor 40 comprlses a shear block 44 cons1st1ng, for example, of 379 p1ezoelectr1c rectangular wafers, or str1ps, 46, each of whlch 1s 3" deep, .050" th1ck and ~J8" w1de. These are put together to ,, .
form 60 layers ln a 3x4x3U block, the top and bottom layers be1ng : lnsulated. Each str1p 46 1s polarlzed (dlrect10n of arrow 78) durlngmanu~acture so that appllcatlon of a voltage across the str1p 46 produces a shear straln 7B across 1ts w1dth when the voltage 1s applled perpend1cular to the shear planes. The top of the str1p 46 ls plated wlth , : an ~lectrode 48 whlch folds around one end (the rear ln Flg. 4A) and does not extend completely to the front end. The bottom of the str1p 46 1s plated w1th another electrode 50 wh1ch folds around the front end of the str1p ~6 and does not extend completely to the rear end.
Vert kally adJacent str1ps 46 are arranged as shown 1n F1gs. 4A, 4B
- ~nd 4C so that the shear mot10n of adJacent str1ps occurs ln the same d1rectlon. Ad3acent hor1zontal str1ps 46 are arranged as shown ln F1gs.

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-8- 83R38-l 4A and 4C so that the shear mot10n of these strlps also occurs ln the same dlrectlon. The dlrect10n of the applled voltage ~l.e., the dlrect10n of an arrow 7n 1ndScatlng the dlrectlon of appl1ed voltage~ of strips 46 ln the same hor1zontal layer ls the same; but the dlrectlon of the applled voltage arrows ln s$r1ps 46 1n ad~acent hor1zontal layers 1s opposlte.
Only one shear element 47 extends from front to rear of the motor 40 ~front to rear as shown ln Flg. 2, or depth D as shown ~n F1g.6) but a plurallty of elements are arranged hor1zontally to form hor~ontal layers, as shown. The elements are lnsulated from each other vertlcally by 1nsulat1ve adhes1ve bondlng materlal 53,53'.
F~g. 7 lnd1cates'the shear1ng movements of several ad~acent layers 80, 81 and ~2. The ldyers are bonded together; theref4re, the total extent of movement 1s cumulat~ve.
A flnæ-woven wlre ~esh 49, 49' ~see fSg.6) ~s afflxed to the electrode plat1ngs, one on each s1de, by a sultable ronduct1ve adheslYe, such as a conduct1ve res1n (not shown). Each mesh may be fabr1ca$ed 25 a double layer, 1f des1red, for rel1ab~11ty. A conduct1ve termlnal 51, 51' ls afflxed to each wlre mesh for conneçtlon to a source of control voltage, su~h as a closed-loop electron1c servo system. Test data has shown that the deflect10n per volt for th1s conf19urat10n ls approxlmately ; 6 tlmes that of a convent~onal PZT stack oF the same leng~h and str1p element th1ckness.
The shear block ~4 ls supported ln a frame 52 and rests upon a bottom plate 54 wh1ch 1s formed w~th an lndentatlon ln whSch a Yespel trunnlon bear1ng 56 1s placed. Actuat~on Forces are transmStted lnto the vertlcal strut asse~bly 42 through a trunnlon member 5~ wh~ch has rounded ends wh1ch f1t lnto the upper Vespel trunnlon bearlng 56 and a ~2~i5~ , -9- 83R38-l ~ower ~espel trunn1On bear1ng ~0 ln an actuator loadtng plate 62. The trunn1On member 5~ p1vots about an 1mag1nary p1vot polnt ~4 ~as seen ln F1g.2). The center of curYdture 63 of the upper Vespel trunnlon beartng 56 prov1des another lmagtnary potnt on the trunn1On member, s seen tn F1g.
2. The dlstance between the center of curvature 63 and the p~vot po1nt 64 1s 1~3 the d1stance between the pivot polnt 64 and ~he center line of the hor1zontal strut 36, thus prov1dlng a 3:1 mec~anlcal ampl1flcat1On at the horlzontal strut 36. That 1s~ a deflect1On generated by the shear motor 40 1s m~n1~1ed three t1mes at the hor1zontal strut 36 wh1ch appl1es the ampl1f1ed d1splacement to the m1rror 20 A top v1ew of the actuator load1ng plate 62 ls shown ln Flg. 5B.
It can be s~en that the plate 62 has two Yespel bear1ngs ~0 and 60', one on e1ther s1de of the vert1cal strut 38 for movably supportlng the ends of the trunnlon member 5~. F19. 5A shows a s1de vlew of the actuator bearlng plate 62~ as also shown 1n F1g. 7. Flg. 5C shows tn an 1sometrlc exploded v1ew vert~cal strut 3a, the oval-cross-sect1On bar constltut1ng the trunn1On member 58 and the actuator load~ng plate 62 wlth lts Vespel bearlngs 60,60' wh1ch contact the ends of the trunnlon memb~rs 58. The trunn1On memb~r 58 1s aff1xed, e.g., by brazlng, to the vert1cal strut 38 at the1r area of contact.
The actuator loadlng plate 62 wh1ch contalns the lower p1vot bear~ngs 60,60'(see Flgs. 5A, 5B and 5C) also prov1des a 400 lb.
eompresslve forc~ Por the shear block q4 and trunn~on bear1ngs. Tests ~ave shown th1s preload to be an lmportant factor ~n reduclng shear block creep and hysteresis. The preload 1s obta~ned by proper stz1ng of the actuator-load1ng-plate spr1ng rate and assembly clearances.

65~3 -lO~ B3R38 1 If a hor1zontal plane ls passed through the p1vot po1nt 64 (as vlewed 1n Flg.2), then durlng operat10n of the shear motor, the mot10n of all components above the plane ls opposlte 1n dlrect~on to that of all compon~nts below the plane. If the component we1ghts are not properly balanced, react10n moments may ex1st and ~t may be necessary to add tr1mmlng we19hts. One such 1s shown as a we1ght 68 threaded on the rear of the flex-~o~nt assembly 36. Others may be attached to the bottom of the load~ng plate 54, 1f necessary, at po1nts 66, 66', for example.
A threaded attachment r191dly Jo1ns the lower end of the vert~cal strut 38 w1th the hor1zontal strut, or flex-~olnt assembly, 36. The lower : end 39 of the vert~cal strut 38 1s posltloned and kept 1n place by be1ng clamped between a reta~n1ng r1ng 70 and a nut 71. Hor1~ontal movements to the left (or rlght) of the bottom plate 54 of the shear block move the flex-~o1nt assembly 36 to the r~ght (or left) through transfer by the vert~oal strut assembly 42.
The hor1zontal strut assembly 36 compr1ses a central shaft 86, F1g.
8, and two outer shafts, the forward shaft and the rear shaft 88 and 90.
The shafts are couplPd at one end wlth trunn~on blocks 92,. 94 wh1ch f~t ~nto assoc1ated trunnlon bear~ngs, the front ~o1nt bear1ngs B9 and 93, and 29 th~ rear Jo1nt bear1ngs 89 and lOO, respect1vely. E~ch block 92,94 ~s ~n the form of a double ~edge which to~ether wlth 1ts bear1ng forms what may be call~d a flex ~o1nt, there belng a forward flex ~o1nt lO~ and a rear flex ~o~nt lO~. Each flex Jo1nt 1s capabl¢ of movement 1n two degrees of freedGm along orthogonal axes. Both ~o1nts move along the same s~t oF
axes.
F~g. 9 shows an 1sometrlc exploded v~ew of the front flex ~o~nt, prov1d1ng a better understand1ng o~ the shape and act10n of the ~olnt. A

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~ 83R38-l front or horlzontal seml-cyllndrlcal Vespel bear1ng 89 f1ts lnto the seml-cyllndrlcal apex of a front or horlzontal trunn~on block recelver 91 whlch has trlangular flar1ng sldes and forms lnto the rear end of the fr~nt shaft B8. The ~ront or hor~zontal edge of the trunn~on block g2 f1ts lnto the recelver 91 and Vespel bearlng 89. Behlnd the block 92 there ~s a rear or vert~cal Vespe) bear~ng 93 wh~ch f~ts lnto a rear or vert~cal trunnlon block recelver ~5 whlch ls or~ente~ 1n a 90 rotat~on from the or1entatlon of the horlzontal recelver 91 and ~orms ~nto the front end of the central shaFt 86. If a set of orthogonal axes ~abelled X and Y ls orthogonal ~o the axls Z through the w1re 96 runn~ng centrally through the flex-Solnt asembly then the front edge 106 of the trunn10n block 92 rotates around the X ax1s and the rear edge 108 rotates around the Y axls and the block 92 can move wlth two degrees of freedom ln the X-Y plane.
The assembly 36 ls held together by two sets of spaced retainlng ; rlngs and a stressed lnternal w~re 96~ e.g. a plece of l/16 1nch plano wlre. The f~rst set of retalnlng r~ngs has one ~6 wh kh ~s pressed around the front shaft ~B o~er the area where the front 106 of the block 92 meets the ~espel bearlng 89. The second r~ng 7~ 15 pressed over the central shaft B6 where the front trunn10n block 92 contacts the Vespel bear~ng 93. The rear retalnlng rlngs 72 and 70 have the same spa~al r~latlonsh1ps w~th the rear flex Jo~nt 104 and the shafts 86 and 90. The reta~nlng r~ngs malntaln la~eral al~gnment of the flex-Jolnt ass~mbly components.
The flex ~o~nts are preloaded to several hun~red pounds e.g. ~00 ~bs. by a hlgh-strength res111ent wlre 96 e.g. a plano w1re passlng t -12- a3R3B-l through a hole dr111ed along the center llne of the shafts for the entlre length of the flex-~olnt assembly 36. The w1re 86 ls afflxed e.g. by solderlng to threaded end components such as ferrules 114 116. Tenslon can be placed on the w~re a6 by tlgbtenlng a tens10n1ng nut 11~ whlch ls threaded over the rear ferrule 116 and abuts agalnst the tear outer shaft 99. The nut 118 and ferrule 116 are set lnto a recess 120 w1th the forward edge of the nut 11~ abutt1ng agalnst a shoulder 122 of the shaft 90 wlthln the recess 120. The wlre 86 ~s fttted snugly lnto the passage ~n the center shaft B6 and the ad~acent bore ~n each outer shaft B8 and 90 ls relleved over a length requ1red to establlsh the des1red b~ndlng straln.
Frlct~on ls mlnlm1zed by uslng lo~-fr~tlon Vespel bearlng 1nserts at the flex ~olnts 102 104.
The dynam1c flex Jolnts provlde the horl~ontal strut assembly 36 wlth low-fr~ctlon small-angle allgnment capab~l1ty wh11e ma~ntalnlng an unusually st~ff load path of the order of se~eral m~lllon lbs~1n. whlch ls unusual for thls type of devlce. Thls very hlgh sprlng rate ls necessary because th1s system requlres a hlgh resonance frequency. It should be noted that 1n h~gh spr~ng rate devlces the output amplltude corresponds ~losely to th lnput amplltude.
~ The flexure assembly 28 ~s placed 1n the space betwecn the suspens10n r1ng 26 and the support1ng rlng holder 29. It also Flts between the front sect10n of the support member 34 and a spacer 35 between the support-member sectlons. The flexure assembly 28 perm~ts movement 1n slx degrees of freedom between the suspenslon rlng 26 and the suspens10n plate 24 whlch 1s f~xed the spr1ng rate of each degree of freedom belng det~rmlned as requlred by deslgn. The mlrror 20 of course moves ~lth the suspenslon rlng 26 and thus may be tlpped tllted or moved axlally.

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-13- 83R3a-l The flexure assembly 2~ as shown 1n F19. 10 compr1ses a set of three flex~ble washers 124 each adJacent pa1r separated by a spacer 126.
Each washer or suspens10n element 124 (see Flg.ll) 1s a slot~ed clrele of .015-1nch-thlck beryll~um-copper spr1ng metal. Each ~asher 12~
comprlses a perlpheral or outer rlng 128 and an ~nner r~ng 130 the lnner r1ng 130 be1n~ deflned by a central aperture 132 and a set of ~hree 1nner arcuate slots 134 13~ 138 whlch are .030~ lnches wlde ~n the rad1al dlrect~Qn. The outer rlng 128 ls def~ned by the per1phery of the washer 124 and three outer arc~ate slots 140 142 144. The nearest ends of the arcuate slot pa1rs 134 and 144 136 and 140 138 and 142 are onnected by the short radtal slots 146 14~ and 150 respectlvely. The slots form beams 152 154 156 wh1ch are sol1d port10ns whose areas are outl~ned by the 510ts. For example beam 152 1s wtth~n the slots 140 ; 1~8 134 and 146. All slots have the same w1dth.
There are two spacers 126 between each washer 124 each spacer be~ng formed ln two annular sect10ns an o~ter sectlon 1~6 and an lnner : s~ctlon 126U. ~he outer sectlon 126 1s f4rmed w1th equally spaced per1pheral holes 127 to match those ~n the outer r1ng 128 of each washer 124. The 1nner spacer rlng 126 ~s formed wt~h a central aperture 132 match1ng the central aperture 132 4~ each washer 128 whlch apertures f1t around a central shoulder sec~ton of the support member 34. ~he spacers haYe the same thlckness and are formed from the same sprtng mater1al as the washers.
In assembly the f~rst and th1rd washers are orlented SQ thdt s~ml~ar slots are al1~ned; the m1ddle washer ~s rotated 60 wtth respect to the ot~er two. A set of three washers and two spacers are employed to increase the stiffness of the flexure assemhly 28 and therefore of the dynamic mirror mount. Less or more may be used as necessary. The rotation of the middle washer with respect to the other two washers also increases the uniformity of the flexure assembly 280 The assembly 28 can be kept together in the proper orientation by passing one or more pins (not shown) through the alignment, or pin, holes 127, 127 in the washers and spacers.

Obviously, many modifications and variations of the present invention are possible in light o~ the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims (12)

1. A piezoelectric shear motor providing actuating shear movements along an axis comprising:
a plurality of polarized piezoelectric strips arranged in a vertical stack of horizontal layers to provide movement along a horizontal axis in response to applied electrical signals, adjacent horizontal layers bonded together so that the bottom surface of the upper layer moves to the same extent as the top surface of the lower layer, the movement of each horizontal layer being a shear movement along a shear plane, the strips being arranged so that all individual shear movements in response to a given signal produce a shear strain across the width of each strip when the electrical signal is applied perpendicular to the shear plane and the shear strain across the width of each strip occurs in the same direction along an axis; and mechanical means affixed to the piezoelectric motor for accepting the movements and for applying them to an object.

2. A shear motor as in Claim 1 wherein the mechanical means comprises a support frame and a base plate for the plurality of piezoelectric strips.

3. A shear motor as in Claim 2 wherein the base plate is formed with a concavity, and the mechanical means further includes:
lever arms means one of which fits into the concavity for movement thereby, the lever arm means being pivoted at a point such that a mechanical amplification exists at the end thereof which is opposite the end in contact with the base plate.

4. A shear motor as in Claim 3 wherein the mechanical amplification is approximately 3 to 1.

5. A piezoelectric shear motor providing actuating movements along one axis comprising:
a plurality of rectangular piezoelectric shear elements arranged side by side in horizontal layers, the layers being arranged vertically adjacent to each other to form a rectangular shear block, adjacent layers being bonded to each other so that the bottom surface of an upper layer moves to the same extent as the top surface of the lower layer to which it is bonded, the full movement of the block being the sum of the extents of movement of all individual layers, each shear element comprising a polarized piezoelectric strip having a first electrode in contact with the top and one end face of the strip and a second electrode in contact with the bottom and other end face of the strip, all first and second electrodes being respectively similarly located on said strips relative to the polarization of the strip, the shear elements being insulated from each other and placed together in such arrangement that all first electrodes are placed at one end of the shear block and all second electrodes are located at the other end, the movement of each strip being a shear movement;
first electrical contact means arranged to make contact with all first electrodes at one end of the block;
second electrical contact means arranged to make contact with all second electrodes at the other end of the block; and actuated means coupled to said block for movement thereby along one axis.

6. A shear motor as in Claim 5, wherein:
said horizontal layers are one shear element deep.

7. A shear motor as in Claim 5, wherein:
said actuated means is a bottom plate which supports said block of shear elements.

8. A shear motor as in Claim 5, wherein:
said piezoelectric strips are formed from a piezoceramic material.

9. A shear motor as in Claim 5, wherein:
each of said first and second electrical contact means comprise a wire mesh.

10. A shear motor as in Claim 5, wherein:
said actuated means comprises a base plate affixed to said block.

11. A shear motor as in Claim 6, further including:
lever arm means one end of which fits movably into said base plate for movement thereby, said lever arm means being pivoted at a point such that a mechanical advantage exists at its end which is opposite the end in contact with the base plate.

12. A shear motor as in Claim 11, wherein:
said mechanical advantage is approximately 3:1.