Base excitation of the glass mount X

Transcription

1 Actie Vibration Isolation of Rear-View Mirrors ased on Piezoceraic Double Spiral Actuators.T. Kletz,2, J. Melcher 2, M. Sinapius,2 TU raunschweig, Institute of Adaptronics and unction Integration - IA Langer Kap 8, 3806 raunschweig, Gerany eail: [email protected] 2 Deutsches entru für Luft- und Raufahrt (DLR), Geran Aerospace Center, Institute of Coposite Structures and Adaptronics, Lilienthalplatz 7, 3808 raunschweig, Gerany Abstract or safety and cofort reasons, rear-iew irror ibrations hae to be reduced. The sources of those ibrations are ehicle body ibrations and aerodynaic forces. This paper shows that an enhanced infinite stiff irror syste would not sole the ibrating irror proble because the ibrations that are induced by the ehicle body would still excite the irror. To sole this proble conentionally, a re-design of both the irror syste dynaics as well as the ehicle dynaics would be needed. To preent such a cost intensie process this paper inestigates noel actie, ulti axial ibration isolation interfaces that hae an elastic behaior towards base plate ibrations and proide in parallel high stiffness with respect to external loads. ased on low stiffness double spiral interfaces with attached piezoelectric patch actuators it is shown how these opposed properties can be reached. The use of such interfaces enhances not only the dynaical properties of the irror, but - in the anner of a truly ultifunctional eleent - it replaces the otor to adjust the irror position as well. This paper describes the analysis of the coplete actie isolation syste, its actuator design and discusses dierse interface ersions. Introduction In the autootie industry ibration of ehicle exterior rear-iew irrors reduce safety and are a source of custoer coplaints. Especially irrors of big cars, trucks and coaches suffer fro those ibrations but een relatiely sall irrors of otorcycles show large ibration aplitudes. Great efforts are ade to reduce those ibrations. A classical and a coonly used approach enhance the dynaic behaior of the irror by increasing the irror stiffness. This approach includes each coponent of the irror syste. Those coponents are basically the ount, the irror housing, the irror glass adjusting deice and the glass itself. Other approaches try to increase the daping between irror coponents. Conentionally, ibration isolation is used either for source insulation (reduction of the transission of forces to the enironent) or recipient insulation (shielding an object fro exposure to ibrations origination in the enironent) []. In both cases a coproise between ibration isolation at higher frequencies and the aplification at the resonance has to be ade in purely passie systes [2]. Reducing the ibration aplification at the resonance of the isolation syste can be actiely achieed with inertial or skyhook daping [3]. Different fro the described approaches this paper deals with isolation systes under concurrent excitations by different ibration sources. Three different interface concepts are proposed and the requireents for a fully isolated irror glass are described. An iportant aspect of the interfaces is the ability to enhance the passie isolation characteristics with the use of piezoelectric transducers, actiely. 305

2 306 PROCEEDINGS O ISMA202-USD202 This paper closes with the experientally exained ibration isolation capabilities of one of the proposed isolation interfaces. 2 Mirror Syste Extensie tests of different irror systes were perfored in laboratories and in different road tests. The identification of the dynaic behaior of the irror syste and the assignent of the contributions of the different excitation sources to the obsered ibrations are possible because of these tests. A irror syste of a large an was tested and the obtained results of a specific irror syste are presented exeplarily. Those results ephasize the need to apply the proposed double spiral actuator. Measureents of accelerations were perfored at different positions on the irror syste and on the car body. In igure the used coordinate syste can be found. To distinguish between the ibration directions the colors used in the following figures are the sae as for the axes in the coordinate syste of ig.. 2. Laboratory Tests y using a shaker, the irror fairing is excited directly on its back while the whole irror syste is ounted to a stiff plate. This is an essential characterization because dynaic air loads significantly excite the back of the irror fairing during driing (cf. solid arrows in ig. 2). Point ipedances were easured at the shaker exciting point; accelerations were easured at the irror carrier and the irror glass. The irror syste was tested fro 0 to 00 Hz. Doinating natural frequencies at 43 and 60 Hz were found at the ain irror carrier cf. ig 3. Those ibrations were transitted to the irror glass without additional odes in the exained frequency range. To siulate the excitation through the dynaics of the ehicle, the irror syste was also excited through its ount. Here, the noticed natural frequencies of the preious test were confired. So far, the irror syste was excited by different ethods but the irror glass itself was excited in both cases through its ount in the irror housing (cf. table ). igure : Axes orientation of the irror syste, origin of the coordinate syste is the center of the irror glass. igure 2: Mirror excitations by air loads (adubrated by arrows).

3 ACTIVE NOISE AND VIRATION CONTROL 307 Wind loads on the back of the irror housing Vehicle ibrations transitted to the irror ounting Wind loads caused by dynaic stall ase excitation of the glass ount X X Direct excitation of the glass (force) X Table : Excitations of irror parts and excitations noticed by the irror glass. The liited stiffness of the irror folding joint and the irror carrier leads to the described natural frequencies. As a consequence irror ount ibrations are strongly aplified. Direct excitations by air pressures on the irror fairing also perit significant ibration aplitudes at those natural frequencies. On the other hand, the glass is excited directly by arying air pressures. Those air pressures are the result of dynaic stall (cf. dashed arrows in ig. 2). To siulate those loads, the irror glass was excited directly by a shaker. Again, ipedances and accelerations were easured. With this type of excitation the natural frequencies of the irror syste were also detected at 43 and 60 Hz. The ibrations were easured on the irror glass and on the irror carrier. Vibrations were transitted fro the irror glass to the irror carrier. Elastic odes of the irror glass are not present below 00 Hz. The irror glass ount is placed in between the irror carrier and the irror glass. ecause of the obtained results for the transission of ibrations fro the irror carrier to the irror glass and ice ersa it is shown that the actual irror glass ount is not a source for the ibration proble of the irror syste. Safety reasons [4] liit the stiffness of the folding joint, prohibiting the needed ibrational altering by stiffening the folding joint. Other techniques for reducing ibrations hae to be considered. 2.2 Road Tests With road tests the acceleration aplitudes and natural frequencies of the irror syste and of the adjoining car body parts were easured. Vibration aplitudes were easured under realistic conditions for different driing elocities. Generally, laboratory and road easureents show good agreeent to each other (cf. ig 3). In the low frequency range fro 5 to 30 Hz and at 50 Hz ain differences are obious. The natural frequencies of the car body enable significant additional ibrations. Those additional ibrations of the car body are transitted through the irror ounting and the irror carrier to the irror glass. Abs [ / s a 2 ] 0,04 0,03 a Abs [g] 0,04 0,03 0,02 0,02 0,0 0,0 0,00 0, f [Hz] f [Hz] igure 3: Vibrations on the irror glass (laboratory (left) and road tests).

4 308 PROCEEDINGS O ISMA202-USD202 Generally an increase in driing elocity results in higher ibration aplitudes. Low frequency ibrations (5-30 Hz) are ore aplified than higher frequency ibrations (30 80 Hz). 2.3 Optial Mirror Syste It is shown that ibrations at the irror glass are not only dependent on the dynaic properties of the irror syste. Additionally, the dynaics of the car body cause ibrations at the irror glass. An as stiff as possible construction could only reduce ibrations caused by direct (force) excitations. A disadantage of such an infinite stiff construction is that the transfer of ibrations fro the car body to the irror glass is still possible. esides stiffness liitation for the irror syste through laws [4], such a strategy could only lead to significant ibration reduction if the car body would be re-constructed to draatically stiffen the car body. Such a car body should hae its natural frequencies well aboe the considered frequency range. Constraints as axiu ehicle weight and costs, liit the feasible axiu stiffness of the car body. or ehicles that are already in the arket, such an intensie reconstruction would be practically unfeasible because of the expensie reconstruction process. Consequently, constructions that enable the transfer of ibrations fro the car body and the irror carrier to the irror glass (daping, high stiffness) are not adequate ways to reduce irror glass ibrations. Without stiffening of both the irror syste and the ehicle body, ibration isolation techniques are proposed for reducing irror glass ibrations. Ideally the ibration isolation interface is to be placed between the irror carrier (inside the irror housing) and the irror glass. With such a setup, ibrations of the car body and the irror carrier are isolated for the irror glass. Isolation should start at frequencies of about 5 to 8 Hz. It s iportant that quasi static oeents are not isolated, because the irror has to oe like the ehicle body in fast cures and on rough road conditions. An iportant additional requireent is that ibration aplification ust not occur in the considered frequency range. Preiously, laboratory easureents showed a relatiely stiff assebly of the irror glass and the irror carrier. The use of isolation interfaces requires the critical consideration of the arying air pressures that excite the irror glass directly because of dynaic stall. Ideally, the isolation interface has to be infinite stiff with respect to directly acting air pressures and at the sae tie infinite soft with respect to ibrations that are ascertainable on the irror carrier. This paper proposes the use of a soft ount interface that is enhanced with piezoelectric patch actuators to reach these opposed requireents. 3 Theoretical and Siulatie Inestigations The preious section showed the need to design an isolation interface. The reason for a piezoelectric enhanceent of the proposed soft ount isolation interface is deonstrated throughout the theoretical findings in this chapter. Ipedance based forulations are used for the following calculations. 3. Model Description To deonstrate the perfored analysis, a one degree of freedo syste is used (cf. ig. 4). As described in section two, the irror glass is excited through base ibrations (accelerations of the irror carrier) and direct forces (pressures acting directly on the glass). The syste is described with, d, and k; the applying loads are and D.

5 ACTIVE NOISE AND VIRATION CONTROL 309 direct excitation force sensor D force sensor ass interface Hauptasse (z.. Hochhaus) d k s reactie force (actuator) force sensor base base excitation igure 4: Mechanical connection schee of a ibration isolation syste. A reactie force S is present only in actie ersions of the ibration isolation interface. In such cases an actuator acts between the base and the syste ass. This can be achieed with a piezoelectric actuator. Otherwise the syste is described as passie. One sensor is placed to directly easure the applied force on the irror glass; a second sensor easures the base excitation through an acceleration sensor. The ai of all calculations is the reduction of ibrations at the irror glass, here described as ass. Those ibrations are characterized by its elocity (). The soft ount interface is characterized by the ideal coponents d, k and in the actie cases additionally by an actuator generating the force S. In the following calculations the base is assued to hae an infinite ipedance. 3.2 Passie Syste A syste that is excited only by a direct force without a reactie force and without base exciteents can be transferred to an ipedance connection schee as shown in ig. 6. The schee for a syste that is only excited by base ibrations can be found in ig 5. ig. 7 cobines these two excitation sources to a four pole schee. Excitations through base ibrations ( ) are described as case, while excitations through direct forces ( D ) are described as case 2 in this docuent. In all calculation it counts s j. () I I base excitation R i /k d /k d D direct force excitation R i 0 D D igure 5: Case, base excitation. D igure 6: Case 2, direct force excitation.

6 30 PROCEEDINGS O ISMA202-USD202 I base excitation R i /k d D direct force excitation R i 0 D D igure 7: Cobined base excitation and direct force excitation. D The ipedances of the coponents of the syste are described as follows: k k s (2) d d (3) or copact writing the su of k and s. (4) d is substituted by Eq. (5):. (5) The ipedance and the resulting elocity of the ass are described by Eq. (6-8). These equations are alid for case (exclusie base excitation): ( k d (6) ) (7). (8) In case 2 (exclusie direct force excitation) the ipedance and the elocity at the ass are found in Eq. (9-): D D (9) (0) D D D. () Vibrations at the ass are not present in the case equals zero. Relatie ibration elocities are independent fro the actual excitation agnitude and describe the conersion of the excitation to the

7 ACTIVE NOISE AND VIRATION CONTROL 3 ibration of the ass. Those relatie ibrations are shown in Eq. 8 and. To eliinate ibrations of the ass in case and 2, Eq. 8 and lead to totally different requireents for the ipedance. In case this ipedance should be ideally zero, while in case 2 the ipedance should be infinite. In conclusion such passie isolation systes are not able to fully eliinate ibration at the ass or irror glass if direct force excitation and base ibrations are present, concurrently. ig. 8 shows the typical characteristics of a passie soft ount isolation syste for base excitation (solid line) and force excitation (dashed line). Paraeters of the syste are assued to be =20 g, k=20 N/ and d=0,3 kg/s. Using force excitation and syste paraeters increased by factor 5, the dotted-dashed graph in igure 8 represents the relatie ibration in case 2. Obiously, the induced ibrations by the force D are reduced as the interface and ass ipedance are increased. Deiant for those changes the ibrations induced by base excitation are not changed when syste paraeter are altered in the described way. Consequently a high ass isolation syste should be aspired to reduce the ibrations induced by the direct force D. It shall be noted that in any applications the ipedances and can not be considerably increased because the axial ass of a syste is often liited. The ibration and the resulting force of a passie syste under cobined excitations are shown in Eq. (2) and (3)., D D ( (2), D ) D (3) Abs, Abs D Abs Abs D Abs D Original syste paraeters Syste paraeters increased by factor f [Hz] igure 8: Relatie ibrations caused by different excitation sources and syste paraeters.

8 32 PROCEEDINGS O ISMA202-USD Actie Syste In the actie case a reactie force S can be applied. In addition to ig. 3 and ig.4 a further schee is to be drawn for the exclusie presence of the reactie force S. This case is to be described as case 3 and shown in ig. 9. or the analysis of a ibration isolation syste with concurrently present excitations as in case, 2 and 3 a cobined six pole schee is created and shown in ig. 0. The resulting ipedance and ibration elocities at the ass for exclusie presence of the secondary, reactie force are shown in Eq. (4-6). s s (4) I (5) s s s (6) /k d I actuator s s R i 0 s igure 9: Case 3, secondary force excitation. base excitation R i /k d actuator I D direct force excitation R i 0 D s D s R i 0 s igure 0: Cobined base, direct force and secondary force excitation. D

9 ACTIVE NOISE AND VIRATION CONTROL 33 The cobination of all three ibration sources leads to the ibration elocity of the ass and the resulting force of the actie syste as described in Eq. (7) and (8)., D, s D s (7),, D s D s (8) 3.3. Ideal actie syste Referring to Eq. 7 an ideal, ibration free ass requires the presence of a reactie force S. This force is adjusted depended on the excitations D and.the ideal reactie force is shown in Eq. (9): s. (9) D With this reactie force, the force in between the interface and the ass results in D. This relationship describes a force equilibriu in static and dynaic state for the direct force excitation, actio = reactio. In this state no ibrations at the ass are caused by the orce D. or ideal ibration isolation, all current has to flow through the interface, too. The requireent I - has to be et. Therefore Eq. (20) describes the ideal ipedance of an actuator placed in the position of : s D s. (20) s This section shows that ibration isolation of a ass is possible een though excitations of the base and of direct forces are present, siultaneously. Different as in the passie case, actie ibration isolation enables the optial adjustent of the ipedance of a ibration isolation interface. Requireents for this to be achieed are a reactie force actuator and sensors that easure both excitations. urther possibilities for the eliination of the ibrations of the ass are the use of the total elocity or the force. The force can be easured in between the isolation interface and the ass. In the case of using as control signal, the secondary, reactie force in Eq. (7) is to be replaced by Eq. (2): s : HV. (2) H V is the used gain when elocity for ibration eliination is used as input to geerate the control force. It turns out that a gain H is optial for the eliination of ibrations of the ass.,opt The use of the force as control signal requires the replaceent of S by the following Eq. (22): s : H. (22) H is the used gain when is used as input for the control. Optially the following alue of needed to eliinate ibrations at the ass: H S H is,opt. (23) D In case of using as control signal, it turns out that the single use of is not sufficient for eliinating all ibrations. Additionally, inforation of both excitations as well as the ipedances of the ass and the daper are essentially needed to enable the correct adjustent of H.

10 34 PROCEEDINGS O ISMA202-USD202 The obtained results are alid for a one DO syste and need to be expanded in case the considered ibration proble needs isolation in ulti degree of freedo. Isolation in ulti degree of freedo needs a passie interface that is able to isolate in these DOs Siulatie Results A passie one DO isolation syste with the paraeters =0.8, k=2000 N/, d=0.5 Ns/ and the concurrent excitations and D is siulated. The excitations are odeled with swept sine signals. In ig. the corresponding agnitudes can be found. The resulting ibration elocities at the ass are presented in ig. 2. In the siulation of a syste with a present reactie force actuator and an applied controller the ibrations at the ass are reduced significantly. The controller design is done according to Eq. 20. Theoretically, the ibrations at the ass can be copletely eliinated with such a controller (cf. ig. 2). Abs Abs [] [N] D f [Hz] f [Hz] igure : Excitations ( (left) and D ) of the isolation syste. Abs [ / s] Abs [ / s] x Spectru [Ch-] (lin) f [Hz] f [Hz] igure 2: Vibrations of the ass (passie syste (left) and actie syste with optial controller). 4 Multifunctional Actie Interface Concepts As described preiously, ibration isolation is based on a passie, soft isolation interface in this paper. This design ust be able to be enhanced with reactie force actuators. Here piezoelectric actuators are considered. Soft interfaces are only feasible if the actuators do not stiffen the passie interface significantly. In such a case the soft ount would be transferred to a hard ount syste. or this reason piezoelectric foil actuators are chosen to be optial. The design of the interface is strongly dependent on the DO in which isolation is needed, for axis orientation cf. ig..

11 ACTIVE NOISE AND VIRATION CONTROL 35 a) b) igure 3: Double ending isolation concept, right igure is shown without stringers and without adjusting otor [6]. Moeents of the irror around the X axis, around the Y axis and along the X axis result in a different part of the enironent that is reflected on the surface of the irror. In result, irror glass isolation is needed in at least two but optially in three directions. Additionally, the interface has to carry the static loads of the irror. This requires direction depended stiffness of the interface. In the isolation directions low stiffness is needed while in the respectiely direction high stiffness is required. Additional odes than the isolation odes of the isolation syste ust not occur in the exained frequency range to preent a reduction in ibration isolation capabilities [5]. or that reason the interfaces hae to be optiized so that all higher odes are present well aboe 00 Hz. The following concepts are patent pending, ct. [6]. igure 3 shows the double bending interface inside the irror housing. At the left side the adjusting otor of the irror glass is adubrated. Two bending springs are directed opposing to each other. ecause of the thin eleents bending is easily possible. This configuration is shown in ig. 3b. Additionally the bending springs are enhanced with stringers (ct. ig. 3a) to preent the irror fro bending around the Y axis because of the static irror glass oent. A high stiffness is archied in this direction. This configuration enables isolation along the X axis and around the axis. Rotations are enabled around the center of the irror glass because of the opposing directed bending springs. Isolation around Y is not possible when stringers are used. Piezoelectric patch actuators can be easily applied to the bending eleents of this concept to enable the application of reactie forces. igure 4 shows the ebrane isolation concept. Here the irror glass is ounted by an elastoeric ebrane which is fixed inside an inner irror housing. The adjustent of the irror glass is possible through adjustents of the inner housing. The static load of the irror can be carried because the ebrane is pre-stressed and ounted directly in the center of graity for the Y- plane. Reactie forces could be applied if ery soft respectiely ery thin piezoelectric foil actuators would be added in parallel to the elastoeric ebrane. Different fro that, ig. 5 shows the use of a etallically interface. The concept is based on a flat double spiral. ro the center of the irror glass two spiral ars with opposed chirality are opening towards the outer radius. At the outer points the double spiral is connected to the irror carrier fro inside the irror housing. This concept enables isolation in the three needed directions while a high stiffness in Y direction is proided. The additional ass is added to abrogate the static rotational oent around the y axis so that

12 36 PROCEEDINGS O ISMA202-USD202 the double spiral is located in the displaced center of graity. ig. 5a and 5b adubrate six piezoelectric patch actuators (three on each spiral ar). Through those actuators reactie forces can be applied in each isolation direction. Additionally, foil sensors e.g. piezoelectric sensors, PVD sensors or strain gauges can be applied to the back of the spiral to receie inforation about the deforation of the spiral. Those signals can be used for control purposes. The additional ass is not necessarily without additional function. Eleents inside the irror housing like radio aplifiers could be placed in that position. ecause of the two rotatory degrees of freedo that are inherent to this isolation interface, the piezoelectric actuators can also be used as an adjusting deice for the irror glass. In such a case the conentional irror adjusting otor is dispensable. This arises the ibration isolation interface to a truly ultifunctional eleent. ecause of this cobined features future broad arket use of such eleents is highly probable. igure 4: Mebrane isolation concept with inner housing [6]. a) b) igure 5: Double spiral isolation concept, shown with 6 piezoelectric actuators [6].

13 ACTIVE NOISE AND VIRATION CONTROL 37 5 Experiental Results The results that are discussed at this point are only alid for the double spiral isolation interface and its ariants which are always integrated between the irror carrier and the irror glass. With shaker excitation on the irror fairing, the first results were recorded for the passie ariant. The isolation interface shows significant ibration reduction in all three DO in which isolation has to be achieed. ecause all three DO in which isolation is needed contain oeent coponents in X direction the use of two single axis acceleroeters is sufficient to record the ibration reduction. Sensor S on the irror fairing (cf. ig. 6) detects not only the oeent in X direction but as well the X coponents of the two rotational oeents around the Y and axes. The piot points of these latter oeents are found at the irror folding joint and at the ounting point of the irror syste on the car body. y calculating the transissibility of the ibration fro Sensor S to Sensor S2 (cf. Eq. 24), the perforance of the ibration isolation syste can be shown: a S 2 T. (24) as The agnitude of the transfer function in the frequency range fro 0 to 25 Hz is shown in ig. 7a. The resonances of the isolation interface for each direction are clearly seen at 7.9, at 9.8 and at 2.5 Hz. In the cases that the absolute alue of the transissibility function is greater than one T, the ibrations of the irror carrier are aplified transitted to the irror glass. When the agnitude of the transfer function is below one T, isolation in all three DO is achieed. or the tested interface, ibration reduction is achieed between 8 and the axiu exained frequency of 00 Hz (cf. ig. 7b). The absolute peak alues need to be reduced to about one to preent ibration aplification. This can be achieed by the use of the reactie piezoelectric actuators. As noticed before, isolation should start at frequencies of about 5 to 8 Hz. or that reason the double spiral need to be reduced in stiffness in each direction. igure 6: Position of sensors used for calculation the transissibility of ibration fro S to S2. 24 a) b) 22 T f(hz) 2,0,8,6,4,2,0 0,8 0,6 0,4 0,2 0, igure 7: Transissibility of a double spiral isolation interface integrated in the irror housing, shown in different frequency ranges and scaling of T. T f(hz) Aplification Isolation

14 38 PROCEEDINGS O ISMA202-USD202 0,45 Piezo Piezo 4 Piezo 2 Piezo , ,35 8 0, U [V] 0,25 2 T 0,20 0 0, ,0 4 0,05 2 0, igure 8: Transissibility of a double spiral ariant (right axis) in coparison to oltages easurable at attached piezoelectric eleents (left axis). A different setup of the double spiral actuator with four piezoelectric patch actuators shows an isolation behaior as presented in igure 8. Lower stiffness is generated here in eery isolation direction. This results in effectie passie isolation stating at 9 Hz. The black line indicates the transissibility while the colored lines indicate the oltage signals that can be easured at the piezoelectric eleents if those are used as sensors. With this diagra it can easily be seen which actuators are suited best for sensing respectiely controlling a certain isolation ode. It is seen that the piezoelectric eleents -4 can be used to control ode one. This ode indicates a oeent along the X axis which results in isolation in that direction for higher frequencies. Actuators two and four can control ode one but additionally the second ode can be controlled. The third ode can be controlled with actuators one and three. The odes two and three can be noticed as oeents around the Y and axes. At certain frequencies peak reduction was already achieed by anually adjusting the gain and the phase relations of the control oltages of the piezoelectric eleents. The phase relation was set by taking reference fro the signal that was used for exciting the irror fairing by a shaker. y actuating the piezoelectric eleents, the irror can also be rotated statically around the Y and axes. The aplitudes of the oeents were easured at the edges of the irror glass. The strokes easurable at these positions were about 3. This enables the adjusting of the irror as required by the drier. urther tests are planed to be perfored under the usage of the theoretical findings of chapter three. A controller that distinguishes the inputs of and D for each isolation direction has to be set up to reduce the agnitude of the transfer function at the natural frequencies of the isolation interface. This controller is about to reduce the axia in the transfer function under base excitations, under direct excitations and under cobined excitation by both ibration sources. f [Hz] 6 Conclusion To effectiely reduce ibrations of exterior ehicle irrors, the need to apply ibration isolation techniques is ascertained in this paper. The ibration sources are identified to be the ibrations of the car body, the wind loads on the irror fairing as well as those on the irror glass. Een if those concurrent excitations are acting on the irror syste, ibration reduction is feasible if the proposed actiely enhanced, soft ount ibrations isolation interfaces are used and the theoretical findings presented in this paper are applied. The theoretical basis to design such systes is gien as an exaple for a one DO syste. Isolation interfaces hae to be integrated between the irror carrier and the irror glass. Different concepts of those ulti DO ibration isolation systes are described. A double spiral actuator is designed to be capable of isolating the irror glass in the three DO in which isolation is needed. Experiental tests are presented and proe that such interfaces are well suited to isolate the irror glass

15 ACTIVE NOISE AND VIRATION CONTROL 39 fro ibrations. Actiely enhanced ariants of those systes are exained. The controllability of the three isolation odes with piezoelectric patch actuators is shown by experiental results. Not only significant ibration reduction of the irror glass can be achieed, but also the adjusting otor of the irror syste can be dispensed with the proposed syste. This is possible because the actie, double spiral ibration isolation interface is able to statically rotate the irror glass, achieing displaceents at the edges of the irror of about three. References [] VDI Richtlinien, Vibration Insulation ters and ethods, VDI e.v., Düsseldorf (20). [2] E.E. Ungar, Vibration Isolation, in L.L. eranek, I.L. Vér, editors, Noise and Vibration Control Engineering, New York (992), pp [3] A. Preuont, Vibration Control of Actie Structures, erlin Heidelberg (20), pp [4] DIRECTIVE 2003/97/EC, Official Journal of the European Union (2004). [5] M.J. rennan, N.S. erguson, Vibration Control, in. ahy, J. Walker, editors, Adanced Applications in Acoustics, Noise an Vibration, London and New York (2004), pp [6].T. Kletz, J. Melcher, J. Redlich, Geran Patent Application, DE and PCT/EP202/ , Schwingungsfreie Lagerung eines Objekts an einer Struktur, Deutsches entru für Luft- und Raufahrt e.v., Köln (20).

16 320 PROCEEDINGS O ISMA202-USD202