Magnetorheological Fluid Engine Mounts: A Review on Structure Design of Semi Active Engine Mounting

Transcription

1 Magnetorheologcal Flud Engne Mounts: A Revew on Structure Desgn of Sem Actve Engne Mountng M.Z.Sarman, M.Hafz Harun, A.K.Mat Yamn, F.Ahmad, and M.R Yunos Abstract The demand for low cost, quet operaton, and ncreased operator comfort n automobles and other applcatons requres new technques to be developed for nose and vbraton solaton. One approach to reduce nose vbraton and harshness (NVH) s to develop a small low cost vbraton solator that can be used to mount components that generate vbraton. Passve, sem-actve and actve control methods as well as dfferent types of smart materals were studed to develop ths solator. Based on ths study, the most promsng approach seems to be a sem-actve magnetorheologcal solator. In ths paper, an overvew of recent advances n sem actve engne mounts are presented, n term of workng operaton of Magnetorheologcal (MR) Flud namely flow mode, shear mode, squeeze mode and mx mode. The ssues are dscussed wth regard to the desgn and performance as vbraton solator devce. The fndng of ths paper proposed the new sem actve engne mounts desgn. Keywords Flow mode, Magnetorheoloccal Flud (MR),, squeeze mode, shear mode. I. INTRODUCTION agnetorheologcal (MR) materals are a class of smart Mmaterals that are currently used n many applcatons. Smart materals are the materals wth controllable propertes that changes by external stmul such as stress, temperature, ph, mosture, electrc or magnetc felds. Magnetorheologcal materal can be a form of fluds, gel or even a sold materal such as elastomers. A magnetorheologcal flud manly conssts of mcron-szed ron partcle that s suspended n carrer ol []. MR flud has an ablty of changng from freeflowng lqud state nto a sem-sold condton wth restrcted flud movement n fast response wthn several mllseconds when exposed to the external magnetc feld. The advantages of MR fluds lead to the development of MR based devce n a wde range applcaton such as n cvl sectors [2],[3], medcal sectors and as well as automotve sectors. Ths work was supported n part by the Fakulty of Mechancal Engneerng and Faculty of Engneerng Technology under Grant PJP/203/FTK/S056. M.Z. Sarman s wth the Unverst Teknkal Malaysa Melaka, Hang Tuah Jaya, 7600 Duran Tunggal, Melaka, Malaysa. (correspondng author to provde phone: ; e-mal: zaharudn58@gmal.com M.H. Harun, s wth Faculty of Engneerng Technology, Unverst Teknkal Malaysa Melaka (UTeM), Hang Tuah Jaya, 7600 Duran Tunggal, Melaka, Malaysa. (e-mal: mohamadhafz@utem.edu.my). There s also another smart materal that has the same operatng concept as MR flud whch s named electrorheologcal (ER) flud. The comparson of the performance of ER flud and MR flud had been dscussed by many publcatons [],[4],[5]. However ths paper focused on applcaton the MR fluds for sem actve engne mounts because of ts ablty to stand KPa of yeld stress and hgher densty of 0. J/cm 3 [6]. Snce the ERF and MRF has characterstc to change ther propertes to from soft to hard and hard to soft therefore t was well-known as the vbraton solator devces [5],[7],[8]. For the automotve sectors, most famous applcaton of MRF on the suspenson system was known as MR damper [6],[9]-[3]. Besdes that, MR applcaton for rotary damper such as MR brake had been used wdely snce a long tme ago [4]-[8]. There are also others applcaton of MR mount solator whch had been used on DVD or CD player on vehcles that had been dscovered by Ahn et al. [9]. Mountng systems are one of the most popular MR flud applcaton devces especally for automotve mountng system. Generally, engne mountng system can be classfed nto three categores whch are passve engne mount system, sem actve mount system and actve mount system [20]. Passve engne mount system was dscovered by Marc Bucuchon [2] earler, s the common suspenson system nstalled n most vehcles nowadays whch typcally conssts of damper and sprng n parallel confguraton. Sem actve engne mount s smlar wth the passve system but the stffness of the component whether sprng or/and damper can be controlled to solate the vbraton on the engne. Whle, actve engne mount s a system wth nvolvement of actve actuators such as electromagnetc [22], servo-hydraulc [23], hydro [24], pneumatcs [25] and pezoelectrc [26]. The actve actuators functon s to provde external force to counter the exstng force upon the engne mountng. Thus, actve engne mount s the best vbraton solator [27],[28]. The enhancement of engne mount performance s due to the drawback of passve engne mount performance whch s unable to solate at the certan frequency. Therefore, actve engne mount and sem actve engne mount systems becomng alternatves to replace the conventonal system. In ths case, A. K. Mat Yamn s wth the Faculty of Mechancal Engneerng Unverst Teknkal Malaysa Melaka (UTeM), Hang Tuah Jaya, 7600 Duran Tunggal, Melaka, Malaysa (e-mal: ahmadkamal@utem.edu.my). ISSN:

2 rubber engne mount s the conventonal engne mount that has smple desgn and less producton cost.however the rubber engne mounts work only at certan range of frequences. Meanwhle, the rotatng engne has dfferent Revoluton per Mnutes (RPM) that also lead to the varable range of frequences of the vehcle accordng to speed nput from drver. The problem caused by the conventonal engne mounts lead to the new fndngs whch are sem-actve engne mount and actve engne mount as the methods to solve ths problem. Even though the actve engne mounts system capable of achevng very good soluton n solatng the varable vbraton frequency, they has some constrans whch are hgh cost, hgh energy consumpton, complex confguraton, nstablty ssues and dffculty durng mantenance. Cost and complexty of the actve engne mount beng the most crtcal ssues as far as automotve ndustres are concerned. The countermeasure to ths problem s to nstalled sem actve engne mounts where t stll mantans the smplcty of passve mount and at the same tme t can be controlled. Thus, sem actve engne mount s sad as the medocre solutons to the vbraton solaton problems. The man advantages of these system compared to the actve mount system are the sem actve mount does not use actuatng force resultng n lower power consumpton and nstablty rsk. Moreover, sem actve mount effectvely dsspate vbraton energy by controllng the mount s parameter such as dampng. There are many types and classes of sem-actve engne mounts that have been developed accordng to ther functon and performance. The ntal desgns of the sem-actve engne mountng used the conventonal hydraulc desgn [29] and the dfference was the used of MR fluds replacng the hydraulc ol. Besdes that, the desgn of the hydraulc engne mount had been dscovered a long prevous tme by Flower [30]. The electrc current flow through the ron core col wll generate magnetc feld. Snce sem actve engne mounts performance dependng on the concentraton magnetc feld regon, thus the amount of electrc current supply can be controlled. Many publcatons had dscussed the effect of the magnetc feld to the performance of engne mounts to solate the vbraton. The focus of ths paper s to provde the study on the current advances n sem actve engne mounts, n term of varety nnovatons of structural and magnetc crcut desgns as well as modelng technques nvolved n each nnovaton. The revew s started wth bref explanatons of the operatonal modes, followed by the classfcaton of sem actve mounts. Next, the mathematcal equatons and dfferent controllers used by the prevous researchers were also studed. The proposed new desgn of sem actve engne mounts s dscussed n the last secton. been proposed by Goncalves [3], called magnetc gradent pnch mode. Furthermore, MR devces can be operated n a combnaton of these modes. Flow mode, also known as the valve mode, occurs when MR fluds s exposed to a magnetc feld whlst the flud flows between two fxed parallel magnetc surfaces. Fgure llustrates the concept of flow. Smlar to shear mode, flow mode has an effectve area, whch s defned as the area where the flowng MR fluds s exposed to magnetc feld. Flow mode s commonly appled n dampers and n other applcatons n whch the devces requre a valve to control flud flow. Fg. MR Flud operaton Flow mode, Shear mode, (c) Squeeze mode [32] Shear modes, also known as the clutch mode, occurs when MR flud s exposed to the magnetc feld between two parallel magnetc surfaces, n whch one s movng whlst the other s fxed, as shown n Fgure. The flud shear area where MR flud s exposed to magnetc feld s called effectve area of shear mode. Squeeze mode occurs when MR flud s exposed to the magnetc feld whle at the same tme beng compressed or decompressed as depcted n Fgure (c). Squeeze mood s commonly used to solate small exctaton snce t nvolves very small dsplacement. However, the resstve forces are very hgh. As the other modes, the magntude of these resstve forces can be controlled by the magnetc feld between the poles. Thus, t has been explored for use n small ampltude vbraton and mpact damper. Mountng devce s one of the applcatons of squeeze modes operaton [33]. The latest workng mode s called magnetc gradent pnch mode. The basc dea of ths mode s smlar to flow mode but wth a dfferent desgn confguraton of magnetc crcut. In the magnetc gradent pnch mode, as shown n Fgure 2, the magnetc poles are arranged axally along the flow path and separated by a non-magnetc materal. Ths knd of poles arrangement wll create ellptcal magnetc fbrls, whch wll block the flow of MR flud n the valve gap. II. OPERATIONAL MODES OF MAGNETORHEOLOGICAL FLUID There are three basc operatonal modes n any utlzaton of MR flud n a devce, namely shear mode, flow mode and squeeze mode. However, another workng mode was recently ISSN:

3 Fg. 2 MR Flud operaton named gradent pnch mode [5]. One of the unque characterstcs of ths mode s the slope between pressure and velocty relatonshp n magnetc gradent pnch mode wll be sgnfcantly ncreased when the magnetc feld s ncreased. Ths s unque, snce n the conventonal flow mode the slope tends to reman constant under any magnetc feld strength modfcatons. Another advantage s the possblty to use MR flud wth coarser partcles up to 00 µm, snce a larger orfce s feasble to be used wthn the magnetc gradent pnch mode. III. TYPES OF SEMI-ACTIVE MR MOUNTS The MR mounts are categorzed accordng to the types of MR operatonal fluds whch are flow mode, shear mode, squeeze mode and gradent pnch mode. However, applcaton of gradent pnch mode as applcaton n mounts devce s not common as the other 3 basc modes. The lterature revew about the applcaton of MR flud has been dscovered n many publcatons such as Elahna [34] and Imaduddn [5] A. Flow mode Bascally, MR mounts s clamed to operate n flow mode also known as valve mode. Most of the desgns of ER flud and MR fluds based are mantanng the prncple that conventonal passve mounts. The replacement of smart fluds n the mounts enables the stffness and dampng characterstcs to be controlled n real tme. The MR and ER flud wll flow through the small holes (orfce) or otherwse the flud flows at specal path whch called nerta tracks. The dameter sze of the holes and the dstance of nerta tracks have been dscussed by the Barszcz [35]. ) Fluds Engne Mounts Hydraulc engne mounts also called flud mounts are elastomerc mounts n whch flud movng n between the top complant and the bottom complant rubber chamber. There are 2 types of flud mounts whch are sngle pumper flud mounts [36] and double pumper flud mounts [37]. The llustraton of sngle and double pumper engne mounts s shown n Fgure 3. The name of sngle pumper came because only one of the cavtes does pumpng whle the double pumpers use both cavtes. Snce the upper and lower of plate are connected, t creates fals-safe condton. In case of one of the rubber fals, the other rubber stll can functon as they are lnked. In addton, the top and bottom rubber secton are stff therefore the double pumper flud mount are easer to be pressurzed than sngle pumper flud mount. Fg. 3 Typcal sngle pumper hydraulc engne mount [38]. Double pumper hydraulc engne mount [37] Fg. 4 Smplstc model of a sngle and double pumper flud mount [37] The sngle pumper flud mount had dscovered n [36],[37] successfully cabn nose and reducton vbraton at only one frequency whch s at the notch frequency. The notch frequency s produced by the oscllatng flud between the two fluds chambers due to the moton act on the flud mount [39]. As the technology grows, the desgn of flud mount mproves n term of applcaton and performance. Thus, new desgn namely double notch passve flud mount was dscovered to be the same concept desgn [36],[38] but add one more chamber as llustrate n Fgure 6. Ths desgn able to gve vbraton and nose solaton at two frequences compare to the sngle pumper that only solate at only one frequency [36]. ISSN:

4 Fg. 5 varable sprng rate flud mount desgn t smplstc model [36] The model of double notch flud mount model s mproved by usng two dfferent workng fluds so that t s able to behave for double notch frequency and also one notch frequency [38]. Besdes that, Vahdat [39] had proposed a varable bottom chamber volumetrc stffness flud mount desgn as shown n Fgure 6. The sem actves type engne mount comes wth mult-layer pezoelectrc (PZT) beam. Ths desgn s able to reduce the notch frequency tunng cycle tme, and elmnates flud mount redesgns and re-manufacturng processes thus t save cost and tme relatvely. Besdes that, due to the dynamc stffness for a varous notch frequency, t suts to a wder range of dsturbance frequences. However, there are some drawbacks had been dscussed, PZT multlayer beams can only wthstand small dynamc moton and hgh stress on the three layer PZT beam would cause t breaks or shattered. Fg. 6 Double notch passve hydraulc propose by Tkan [38] Varable bottom chamber volumetrc stffness flud mounts desgn by Vahdat [39]. 2) Controllable Inerta Track of Hydraulc Mounts Changng n the nerta track area affects the dynamc propertes of the mount [40]. The controllable nerta track of hydraulc mount desgn was proposed by Truong [4]. The notch and resonant frequences of the mount change accordng to the dvergence of the area of the nerta track. However, changng the geometry of the nerta track has a crucal effect on the flow resstance but t was gnored. Besdes that, the hydraulc engne mounts prototype usng multple tracks and orfces had been studed by Barszcz [35]. The prototypes used varous desgn of nerta track and orfce and the number of nerta tracks n a controlled manner as shown n Fgure 8. The effect of dameter szed of the nerta tracks and orfce also had been studed. Also, the performance of the hydraulc prototypes wth external capllary tube-type tracks and three nternal orfce-type tracks has been dscovered. In addton, Zhang [42] has proposed the desgn of hydraulc engne mounts (HEM) wth multple nerta tracks (MIT). There are 2 types of nerta track were used whch has sngle and double for entrance and exts. However, the sgnfcant reduces of transmssblty of the mount requre at certan optmal tunng of nerta track area. Fg. 7 Hydraulc mount wth controllable nerta track: cross secton of a hydraulc mount and assembly components [4]. ISSN:

5 (c) Fg. 9 MR Flud elastromers [46]. (d) Fg. 8 Confguraton of prototype mounts experment [35]. Schematc dagram wth nerta track and orfce. (b, c, d and e) desgn that use n the experment (top vew). Many publcatons have proven the effectveness of the engne mount wth movng plate decoupler, multple numbers and varous dstances of nerta tracks. General nerta tracks acts at lower frequences, whle the decoupler s domnant at hgher frequency. Thus, proper fne tune controller s needed. B. Squeeze Mode For an MR devce operatng n the squeeze mode, MR flud s compressed between two end plates that also work as magnetc poles for a magnetc feld to pass through as shown Fgure (c). As the flud s compressed, the avalable volume between these end plates contnuously become smaller, requrng a mean for the MR fluds n the gap to escape to avod hydraulc lock-up. In facts, the MR flud flow operaton has been less appled n automotve ndustry however t has been dscovered very useful to solate vbraton as engne mountng due to the vbraton from engne and power trans systems nvolvng small ampltude or dsplacement [43]. One of the sem actve engne mount that had dscovered earler s MR elastomers. ) MR Elastomers Gong et al. [44] had proposed the good gudelne to prepare the new MR elastomer. MR elastomers had shown great potental as a tuneable vbraton solator accordng to [45] MR flud Elastomer undergong an oscllatory nput can acheve approxmately 75% ncrease n output force wth the addton of a magnetc feld. The MR flud elastomer was used by Wang descrbe as n Fgure 9, where the elastomers act as casng and MR flud n the centre cavty. The system setup places one magnetc pole drectly below the flud chamber separated by the elastomer, and a magnetc sheld above the mount. (e) The magnetc crcut, however, has been altered to place the poles of the electromagnet drectly above and below the flud chamber for mproved magnetc effcency. Ths desgn uses a large magnetc feld generator whch may be dffcult to package. The magnetc feld ntensty, however, s able to acheve a suffcent amount of flux densty n the flud. Davd York et al. [47] had proposed a MR flud elastomer (MRF-E) mounts developed usng RTV65A/B (RTV) slcon and a polybutadene polyol based polyurethane (poly BDpolyurethane) to be selected as the base elastomer materals for the MRF-E mount. Anna Boczkowska et al. [48] proposed urethane magnetorheologcal elastomers (MREs) whch s manufactured usng Polyurethane gel. From the compresson test conducted under magnetc feld, hgher compressve strength dstngushed. The stffness of elastomer ncreases sgnfcantly as the number of ferromagnetc partcle ncreases n the materal. S. R. Kumbhar.et al. [49] had fabrcated four Sylgard s84 MR elastomer (60mm x 20mm) whch two of them were prepared by usng 20% ron powder wth thckness 0 mm and 5 mm and another two of them was usng 30% of ron power. A test was conducted to study the fractonal change n shear modulus and n resonant frequency versus load (0 N, 2 N, and 4 N). As the results concluded, the fractonal change n shear modulus and fractonal change n resonant frequency ncreases by ncreasng appled magnetc feld and also by ncreasng appled load [49]. The advantage of ths MRE s t can operate wth and wthout magnetc feld. However, there are some drawbacks wthn ths desgn ncludng MRE nablty to be appled for the hgh load. C. Shear Mode The applcaton of shear mode operaton MR flud n automotve ndustry had been developed extensvely on MR Brake and MR rotary damper. However, there are also mountngs that used the prncple workng flud but not n sngle mode operaton. The operaton of shear mode usually mxed wth other modes as explaned n mx modes secton. D. Mx mode The mxed mode conssts of flow-squeeze mode, flow-shear mode and shear-squeeze mode. Ths mode has become man focus n any mplement of MR flud n a devce. Ths s due to the effectveness of mx modes to gve hgh workng performance on the devce. ISSN:

6 ) Flow-squeeze Mode The mxed mode MR flud mount model shown n Fgure 0 proposed by Wang [50] has two workng modes: flow mode and squeeze mode. They are nduced by separate electromagnetc cols so that the effects of each workng mode and combned workng mode can be nvestgated. When the MR flud travel from one chamber to the other through the nerta track, the outer col s actvated and produces the magnetc feld and the flow mode s on. The actvaton of the nner col can hnder the moton of the rod whch makes the squeeze mode. The stffness and dampng are therefore adjusted by the actvaton of the two workng modes. El Wahed and McEwan [5] proposed a MR flud cell wth mxed squeeze and flow mode MR flud operaton. Ths paper dstngushes the performance between sngle modes and mxed mode. The sngle mode operatons tested were squeeze mode and flow mode. The contour lne of flux lne densty and magnetc feld dstrbuton for each mode clearly shows usng Ansyss software. Expermental assessment was done as to compare the effectveness of the proposed mxed mode desgn. The performance of MR flud under the mxed mode was sgnfcant enhanced over those n the squeeze and also flow modes. Although these desgns prove the effectveness of MR flud n mxed mode MR operaton, but the frequency that used s very small, whch s 5 Hz. Snce the engne vbraton may produce larger than the used frequency, thus the capablty of the MR flud cell desgned stll cannot proved to be work for larger frequency. 2) Flow-shear Mode Another example of mx mode operaton of vbraton s as proposed and had been fabrcated by Cho et al [52] whch used flow and shear mode operaton. The mounts was successfully fabrcated and tested for the purpose to solate structural vbratons. The desgn s smple as shows n Fgure. Furthermore, the mount has compact structure and operates wthout frctonal components. However, there are some drawbacks of ths desgn that can be dscussed. Frstly, the natural rubber used has reacton wth the MR flud [53]. After perod of tme, the rubber wll corrode and the elastcty of the rubber wll decrease thus affect the stffness of the rubber to support the object. 3) Shear-squeeze Mode Even though the flow mode can produce large dampng force due to MR effect but performance control can be worse f the exctaton magntude s small. Meanwhle, the squeeze mode s capable to acheve hgh dampng force generated from MR effect. However ths mode can work effectvely n a very small vbraton area only. Lastly, shear mode s capable to avod soldfcaton state n hgh feld ntensty, n contrast to the dampng force generated from the MR effect whch s relatvely small compare the other modes. Thus, due to the drawbacks of sngle modes MR flud operaton, the mxed modes operaton was the man focus as desgned n the vbraton solator devce. Instead of usng flow mode combne wth shear mode or squeeze mode, Yazd [54] proposed the squeeze and shear mxed modes va MR damper. Fg. 0 Mxed mode sem actve engne Mound Squeeze and flow mode (A) Schematc dagram (B) Physcal Model [50] Fg. 2 Mxed mode desgn proposed by Cho [52]. IV. MODELING THE RESPONSE OF THE MR MOUNTS The dynamc characterstc models of hydraulc engne mount had been shown n many publcatons [27], [29], [55]. There are also some publcatons that used hydraulc mounts model wth an addton of smart materals to mprove the work performance of sem-actve operatonal whch was proposed by Cu [56]. There are also varous mathematcal model proposed for actve engne mounts model for examples, Fakhar [57] was usng Langrange s and Newton-Euler equaton to model the engne on the mounts. A Hossen et al. [58] modelled engne mounts wth solenod actuator. Fg. MR flud cell [5]. ISSN:

7 P P = I Q + R Q P 2 MR () P = pressure n the upper chamber. P = pressure n lower chamber of the mount. 2 I = flud nerta. R = flud drag at zero magnetc feld. Q = flud flow rate through the flow passage. P MR = pressure drop due to the yeld stress of the MR flud. The flud pressure n upper and lower chambers can be calculated from the flow contnuty equatons: Ap Q P = x C C (2) 2 Q P 2 = (3) C C = complances of the upper chambers. C = complances of the lower chambers. 2 A = pston area of the top rubber part. p x = velocty of the top of the mounts. Assumng that: Q = A x (4) A = cross sectonal area of the flow passage. x = flud average velocty through the flow passage. By substtutng the ntegratons of (2) and (3) nto () yelds the followng equatons of moton for the flud passng through the flow passage: Ap I A x + R A x + A + x = x + PMR C C (5) 2 C x = dsplacement at the mount top. The pressure dfference nduced by the MR effect can be expressed as: L PMR = C τ y ( H ) sgn( x ) (6) h C = s equal to 2, whch corresponds to low-flow condton. L = length nsde the flow channel over whch the magnetc feld s appled. h = Dstance between the magnetc poles ( equal to the gap of the annular duc. τ Y (H ) = MR flud yeld stress at whch magnetc feld s dependent. The hydraulc-related parameters are defned by Adguna et al. [59]. Snce the flow path s straght, the nerta of the flud nsde the flow passage s smplfed by: L = ρ L (7) A ρ = Densty of the MR flud. L = Length of the flow passage. The flud resstance wthn the flow passage s approxmated based on the orfce geometry whch s rectangular, 4 R = 28η L πdh (8) η = MR flud vscosty, whch s shear rate dependent but assumed to be constant for ths study. D h = Hydraulc dameter for an annular duct ( Dh = Douter Dnner = 2h). The equaton of moton pertanng to the squeeze mode s done by Hong et al. [7] as shown below: M x + ce x + ke x + Csq x + Fsq + ApP = Fn (9) F n = Exctaton force. c e = Rubber dampng coeffcents. k e = Rubber stffness coeffcents. The dampng constant assocated wth the vscous flow s 3 3πR C sq = (0) 2( h ) x The dampng force due to the flud squeeze s 3 3πR F sq = τ ( H ) sgn( x ) () 4( h0 + x) The varables from the prevous equatons are as follows: s the gap between the parallel plates at the statc deflecton and s the radus of the two plates. After substtutng P by (2) nto (9), the fnal equaton of moton can be wrtten: M A A A + 2 p p x + cex + ke + x + Csq x + Fsq = x F (2) n C C V. CONTROL OF THE MR MOUNTS Varous control algorthms for MR flud-based devces have been researched and proposed so that these sem-actve devces can acheve adequate performance for vbraton solaton. The control algorthms studed are descrbed below and nclude lnear quadratc Gaussan (LOG) control, ground hook control, skyhook control, fuzzy logc control, neural networks control, nverson-based control, ntegrator back steppng-based control, and herarchcal control. These ISSN:

8 controllers are used n dfferent systems to acheve effectve vbraton solaton. A. LOG Control Hong and Cho [52], [60] desgned a lnear quadratc Gaussan controller for a mxed mode, flow, and shear, MR flud-based mount used to solate the vbraton of a structural system. Non-dmensonal formulaton of the Bngham plastc flow model for the MR flud was appled n the control strategy. The structural system composes of a vbratng mass, sem-actve MR flud mount, and passve rubber mounts. The MR mount s nstalled as a sem-actve solator between the vbratng mass and the beam structure whch s hold up by two passve rubber mounts. The rubber element on the top of the MR mounts supports the mass on the one sde and solates the vbraton transmsson at the non-resonant frequency on the other sde. The governng equaton s presented and rewrtten n a state space model. The LOG controller s desgned and expermentally verfed as shown n x ( = Ax( + Bu( (3) x ( = Control state vector A = The control system matrx, B = The control nput matrx, u ( = The control system nput, The performance ndex chosen to be mnmzed s shown as follows: J = 0 T T { x( Qx( + u( Ru( } dt (4) Q = state weghtng sem postve matrx. R = nput weghtng postve matrx. LQR s obtaned as follows: T u( = P B x( = Kx( (5) K = state feedback gan matrx. P = soluton of an algebrac Rccat equaton to obtan feedback sgnals. Two accelerometers are fxed on the vbratng mass and the flexble beam. The control voltage s calculated by LQG and appled to the MR mount va a dgtal-to-analog converter and a current generator. The acceleraton levels of the structural system are dmnshed effectvely by controllng the dampng of the MR mount. The force transmsson through the two rubber mounts s also conceals by actvatng the MR mount. However, the results show that acceleraton and force transmsson wth the LQG control are hgher than the one wthout control at hgher frequences. B. Skyhook Control Skyhook control s one of the most popular control methods for the R fluds devce. Wang [50], [6] proposed a skyhook control desgned for 2 DOF quarter car model usng a mxed mode MR flud mount. The force and dsplacement transmssblty are controlled to acheve smulaton results. The governng equatons can be represented as: x ( x z ) > 0 x ( x z ) < 0 Feld Feld On Off (6) x = s absolute velocty of engne. ( x z ) = s the relatve velocty between the engne and the chasss. The condton of magnetc turn on s when the absolute velocty of the engne and the relatve velocty between the engne and the chasss have the same drecton. Meanwhle the off condton occurred when they have the opposte drecton. Thus, the skyhook desgned was to nvestgate the effect of skyhook control between flow mode, squeeze mode and combned modes. The skyhook controller has smple desgn and good to control the transmssblty. However, the dsplacement and force transmssblty need to be control under dfferent condton. C. Fuzzy Skyhook/Groundhook Control Cheng [62] used fuzzy controller to regulate the dampng of the MR damper and control the sem- actve suspenson system of vehcle. Matlab fuzzy logc controller had been used because of t convenent operaton, easer and ntutve. As compared to the tradtonal passve suspenson system, the fuzzy control enhances smoothness of the vehcle runnng wth sem-actve suspenson. Thus, t reduces the body vbraton. Mna M.S. Kaldas [63] proposed adaptve fuzzy logc controller for sem actve suspenson. The rule base and nterface engne are based on Mamdan-Type of fuzzy nterface, whle the defuzzfcaton process s based on center of area method. The optmzaton routne was used to mnmze the body acceleraton and dynamc tre load, but at the same tme mantan the suspenson workng space n the allowable lmts. D. Neural Networks Control Wang and Lao [64] presented the modelng and control of MR flud dampers usng neural networks. Based on the modfed Bouc-Wen consttutve model for MR fluds, the nherent nonlnear behavor of the MR flud was modeled n feed forward neural networks (FNN) and recurrent neural networks (RNN). The results prove that the drect dentfcaton dynamc model usng RNN can expect the dampng force accurately, and the nverse dynamc mode usng RNN can act as a damper controller to provde the command voltage for the MR flud damper n sem-actve mode. The ISSN:

9 smulaton results are mpressve and provde a new method for the MR flud damper controller. However, ths controller requres tranng. The tranng data needs to cover most stuatons occurrng n practcal applcatons and needs to be smple, n order to speed up the tranng process. Furthermore, the neural networks control works lke a black box as the process of generatng the outcome s not explctly stated. Mao Yu et al.[65] proposed a control structure for the purpose to stablze the passenger vehcle system wth magnetorheologcal (MR) flud suspensons by usng Fuzzy Neural Network (FNN) controller. The general algorthm (GA) and fuzzy assocatve memory neural network (FAMNN) were adopted n a desgned FNN controller n order to mprove roll stablty. The effectveness of the proposed controller method was demonstrated and later compared by computer smulaton and also road test experment. The results from both tests were supported and valdated by comparng to the conventonal skyhook controller. The sgnfcant result shows the effectveness of FNN controller reduced the vertcal acceleraton, ptch, and roll angular acceleraton n frequency doman compared to the skyhook controller. In other word, the proposed FNN controller va MR suspenson can mprove both rde comfort and stablty of vehcle. E. Herarchcal Control R L et al [66] desgned a control system for the squeeze mode MR flud mount. Based on a model of three degree of freedom MR mount, a herarchcal fuzzy controller has been desgned to decrease the vertcal vbraton force and roll moment transmtted from an engne. Where, a fuzzy controller was desgned to solate the engne vertcal vbraton on the control level. Whle, on the coordnaton level, fuzzy reasonng s adopted to realze a coordnaton strategy for tunng the dampng of each engne mount n order to mnmze the transmtted torque. MATLAB smulnk software was used for the smulaton and the valdaton of the smulaton by usng the expermental solaton system whch usng real engne. Smulaton shows sgnfcant results between herarchcal fuzzy controller strategy and passve/hydraulc mount. Ths results was supported from the expermental results confrmed that engne herarchcal fuzzy controller system va MRF mounts performance s greater compared to the passve mounts system. The results of ths research provde nsght nto the development of the control system for other effectve solaton devces. VI. IMPROVEMENT OF THE SEMI ACTIVE ENGINE MOUNTS From the present and current MR mounts desgns there are a few pro and contra that had been dscovered. Besdes that, the mportant characters to be had n engne mounts also had been determned. The past researchers manly focus on the physcal desgn of MR mounts compare to the current researcher that focus on optmzaton of Magnethorheologcal flud characterstc on damper, brake and other automotve applcaton[67]. The factor that affectng the MR fluds whch are current supply and magnetc ntensty produced can be nvestgate wdely through Fnte Element Method Magnetc(FEMM)[68]. Snce MR flud has 4 types of modes, thus MR mounts can be classfed nto 2 whch were sngle and double modes. Sngle modes most problems are on the less effectve upon the varable frequency dsturbance. Squeeze mode s sutable for provdng large dampng however the workng area s small, shear modes performance dependng on surface contact area whle flow mode has ablty to absorb force exctaton due to large dampng force but to control the small exctaton could be worse. The combnatons of these modes encounter the drawback from the sngle modes [5]. However, combnatons of these modes requre a hgh current supply to actvate the mounts magnetcally. Besdes that, n term of the performance t shows slghtly ncrement and moreover the complex controller needed to ensure the operaton each mode. Therefore, usng sngle mode s more preferred and the drawback could mprove by optmzaton and modfcaton. Flow modes and squeeze operaton s most sutable to be apply n MR mounts however ths paper focus on the flow modes operaton because the successful applcaton on shock absorber could be mply on the MR mounts. Therefore ths paper would proposed the desgn of MR mounts should consder three parameter whch are sze of orfce, number of orfce, poston of solenod col and workng tracks area. VII. NEW DESIGN OF MR MOUNTS Ths paper proposed new desgn of sem-actve engne mount usng the MR flud as shown n Fgure 3. Generally the concept of ths desgn based on the MR flow mode operaton. Snce the vbraton of engne came from any drecton ths desgn assume that there were three moton that act on ths desgn whch are ptch, roll and engne vertcal acceleraton. By assumng these moton acts on the engne mount, the ball jont () s used to receve any of those moton excte by the engne. The exctaton force act on the ball jont wll transfer to the pston rod (4) that connects to the pston (5) sldng upward and downward. In other word, the varable force drecton change nto sngle movement by the pston. The sldng movement of the pston channel by a chamber (9), besdes that ths chamber s a place where the operaton of vbraton reducton takes place. There are several parts that nvolve n the vbraton reducton process whch are sprng (6), bearng seal (7), bearng cover (8), ol seal (0), MR flud volume (4) and ron col (2). The functon of the sprng s to accommodate the load of engne n statc poston. As the engne excte force to the engne mount, the sldng of pston up and down compress the MR flud to flow up and down through small holes called orfce. Snce the pston s surrounded by the ron core that s used to generate magnetc feld n the present on electrc current, the vscosty of MR flud becomng hgher. As the result, the force generated from the engne s scaled down before reach the vehcle body. The ol seal s placed n the bearng seal and lock up by the bearng cover. These combnatons are to prevent leakage of MR flud ISSN:

10 n the system. In addton, the O rng () s use at the pston due to the same purpose. ACKNOWLEDGMENT The Author thanks to Techncan, colleague and ACTIVE laboratory, of Unverst Teknkal Malaysa Melaka (UTeM), Malaysa for the facltes n completng ths work. Fg. 3 Proposed a new sem actve engne mount desgn. VIII. CONCLUSION An overvew of varous desgns of engne mounts has been presented and categorzed based on the MR flud operatonal fluds, namely flow modes, shear modes and mx modes. The overvew of the flow mode MR mounts was dscovered and categorzed nto two types namely flud engne mounts also called elastomerc mount and controllable nerta track s mount. Although a lot of MR mount desgn n flow mode operaton had been developed, ther potental to generate large dampng force however performance could be deterorated n controllng small exctaton magntude. In contrast, squeeze mode MR mount s also able to produce hgh dampng force but the effectve workng area s very small. The squeeze mode MR mount can be classfed nto two types; MR elastromer (MRE) and MR squeeze mount. As compared to shear modes mounts, t produces lower dampng force but t can avod soldfcaton state at hgh ntensty regon. The shear mode MR mount was not wdely used as sngle operaton n applcaton of MR mounts. It s well known and appled to the rotatonal MR damper n applcaton of MR brake devces. The mxed modes MR mount can be observed as the superposton of two ndvdual modes. The dynamc stffness envelope s very large, whch can provde desred stffness at any frequency. Besdes that, the ablty to set dynamc stffness for any exctaton ampltude optmzed the vbraton process. Ths feature also provdes the flexblty to desgn the optmal control desgn for the mount wth the least energy consumpton. The future works nclude desgnng a sutable control strategy requred n order to develop optmal operaton of sem actve MR mount and the nstallaton of ths mounts nto a real vehcle body for actual experment. 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