Keywords: Active Suspension System, Hybrid Electric Vehicle, Simultaneous Simulation

Transcription

1 IUST International Jornal of Engineering Science, Vol. 9, No.5-, 28, Page 97-4 ACTIVE SUSPENSION SYSTEM IN PARALLEL HYBRID ELECTRIC VEHICLES Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 Morteza Montazeri-Gh & Mahdi Soleymani Abtract: In previo tdie, active penion ytem in conventional powertrain ytem wa invetigated. Thi paper preent the application of active penion ytem in parallel hybrid electric vehicle a a novel idea. The main motivation for thi tdy i invetigation of the potential advantage of thi application over the conventional one. For thi prpoe, a imltaneo imlation i developed that integrate the powertrain and active penion ytem in a nified media where the power and inpt data between two ytem are exchanged. Uing thi concrrent imlation tool, the impact of the active penion load on the internal combtion engine repone i tdied for both conventional and hybrid electric configration. The imlation relt preented in thi tdy how that there are qite remarkable advantage for application of the active penion in parallel hybrid electric vehicle in comparion with the conventional one. Keyword: Spenion Sytem, Hybrid Electric Vehicle, Simltaneo Simlation. Introdction The prpoe of an atomobile penion i to adeqately pport the chai, to maintain tire contact with the grond, and to manage the compromie between vehicle road handling and paenger comfort []. Spenion ytem can be claified a paive, emi-active, and active penion (AS) ytem. In order to poitively inflence thee propertie, active component are introdced. component enable the penion ytem to adapt to vario driving condition. By adding a feedback controlled actator, the vehicle driving comfort and afety can be coniderably improved compared to a penion etp with fixed propertie [2]. Application of AS in conventional vehicle ha been invetigated extenively in previo tdie. Previo tdie have reported that the application of AS ytem in conventional vehicle enconter ome obtacle [3]. One of the drawback in conventional vehicle i that the power reqired for the AS ytem i directly pplied by the vehicle internal combtion engine (ICE). In thi cae, the ICE reqire time to adjt itelf to the time-varying AS load de to it dynamic. If the AS load vary fater than the engine can adjt, then, the penion will not fnction properly temporarily. Coneqently, the vehicle may heitate. If, on the other Paper firt received March. 5, 28. and in revied form Sep Morteza Montazeri-Gh i Aociate Profeor with the Department of Mechanical Engineering and director of Sytem Simlation and Control Laboratory at Iran Univerity of Science and Technology, Tehran. montazeri@it.ac.ir Mahdi Soleymani i a PhD tdent at the ame Department. m_oleimani@it.ac.ir hand, the load get redced too fat, the vehicle rge may occr [3]. A a relt, the ICE dynamic i a major concern for the AS ytem in conventional vehicle. Moreover, AS load may hift the ICE operating point to the inefficient region where the intant emiion and fel conmption may be increaed. Hybrid electric vehicle (HEV) i one of the mot viable oltion to the world need for cleaner and more felefficient vehicle. In order to overcome the drawback of conventional vehicle, HEV encompa two energy converter to generate the power reqired to drive the vehicle. Mot typically, the architectre of HEV inclde an ICE with an aociated fel tank and an electric machine with it aociated energy torage ytem (ESS) i.e. battery. The powertrain ytem for a parallel hybrid electric vehicle incorporate two power drive inclding an ICE and an electric motor (EM). In HEV, nlike the conventional vehicle, the vehicle bytem may be powered by either mechanical ICE or the electrical power orce. Thi can be epecially helpfl when one of the power orce can not provide the reqired power de to it performance contraint. Moreover, HEV can provide the capability of regeneration of the AS energy while it i working in a power recovery mode [4 and 5]. In thi paper, the idea of the application of AS ytem in HEV i preented. The main motivation for thi tdy i invetigation of the potential advantage for thi application over the conventional one. For thi prpoe, and a a preliminary goal, a imlation tool i developed in which the penion and powertrain ytem are imlated imltaneoly. In thi approach, the powertrain and AS ytem imlation are

2 98 Spenion Sytem in Parallel Hybrid Electric Vehicle Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 integrated in order to tdy the exchange of power and data between AS and powertrain ytem. Uing thi concrrent imlation approach, the idea of AS application in HEV i tdied from energy and performance point of view. The trctre of the paper i a follow. The imlation and control of AS ytem i firtly decribed. The powertrain ytem imlation for both conventional and hybrid electric vehicle are then preented. In addition, the fzzy-baed control approach employed for HEV power management i decribed. Finally, the imltaneo imlation approach i introdced and the imlation relt and analyi are diced. 2. Spenion Simlation and Control AS imlation and control i preented in thi ection. The vehicle penion dynamic eqation of motion are firtly preented. The inflence of the peed pattern on the time-domain ditrbance of the penion ytem i then diced. Finally, the control method ed for active penion i decribed. 2- Spenion Sytem Dynamic Eqation of Motion In thi tdy, a fll-vehicle model (Fig. ) i ed for the penion ytem imlation. Thi model i a itable choice for the ride qality evalation a it captre the effective motion for the ride comfort aement i.e. body bonce, pitch and roll acceleration. eqilibrim poition. Tire-road holding force i alo modeled a a nonlinear fnction a follow:. F F holding holding K ( x x ) t if if ( x x ) ( x x ) tat tat (2) where, K t,x, x, and tatic are tire tiffne coefficient, nprng ma diplacement, road diplacement ditrbance, and penion pring tatic deflection, repectively Environmental Inpt Road time-domain ditrbance depend not only on the road profile geometry, bt alo the vehicle peed. Therefore it i eential to conider the effect of the driving pattern on the time-domain ditrbance of the penion ytem. The concept of the inflence of the peed pattern on the penion ytem ditrbance can be decribed when a vehicle i moving on a ine wave road with a variable peed driving pattern. Since the freqency content of the tranmitted vibration to the vehicle depend on the vehicle peed, the paenger perception of the tranmitted vibration varie with the peed variation. In the real traffic condition, the vehicle peed varie freqently and thee peed flctation hold be conidered in the timedomain ride evalation of the penion ytem [6] AS Sytem Control Deign For control prpoe of the AS ytem, the flly active kyhook control approach [7] i employed. In thi method, the well-known kyhook control trategy patented by Karnop [8] i employed for the control force calclation. A the name implie, the kyhook configration ha a damper connected to ome inertial reference in the ky, a hown in Fig. 2. Fig.. Spenion ytem in a 7 DOF vehicle model. The governing dynamic eqation of motion for thi model in a matrix form are a follow: M X C X K X F U X x ; ; ; x ; ; ; xfr ; xfl ; xrr ; xrl () Where, M, K, C, and F are ma, tiffne, damping, and forcing matrice repectively. X denote the tate vector whoe element are body bonce, pitch, and roll motion and their derivative a well a nprng mae vertical diplacement and their derivative repectively. It i amed that body and wheel diplacement are meared from their tatic Fig. 2. Skyhook model. In order to implement the kyhook control law to the fll-vehicle model, it i amed that the body i pended at it corner by the kyhook damper. Conidering thi cenario, the fll-vehicle model ha been divided to for eparate qarter model. The logic behind thi control deign i that, redcing tranmitted force from penion ytem to the body at it corner, the total tranmitted force to the body are redced. Thi redction, coneqently, will relt in

3 Morteza Montazeri-Gh & Mahdi Soleymani 99 Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 redction of the body bonce, pitch and roll acceleration. In other word, the vehicle body motion i controlled by the AS actator force at for corner of the body. Thee force are calclated at each corner ing the kyhook control trategy. Flly active control tate that the reqired control force i eqal to the prodct of the prng ma velocity and the kyhook damping coefficient a eqation 4 implie, and therefore i capable of ptting energy into the ytem a well a take energy ot. Thi make flly active control a powerfl tool in affecting the motion of the prng ma [7]. The AS ytem eqation of motion are a eqation 3. x k (x x ) c( x x ) F m x k (x x ) c ( x x ) k t (x x ) F m F act C. x kyhook Where C kyhook i the kyhook coefficient. In the AS model, the tiffne coefficient of the penion pring are lowered p to three forth of their original vale. AS intant power conmption demanded continoly from the powertrain ytem i calclated ing eqation 5. P act F act. V act C kyhook. x.( x x ) (5) 3. Powertrain Simlation In thi ection, the powertrain imlation i decribed. The main objective of the powertrain imlation i obtaining an acceptable etimation of the fel conmption (FC) and exhat emiion of conventional vehicle and HEV in the preence of AS load. Thi objective i reflected in the imlation approach. The powertrain imlation method ed in thi tdy incorporate a backward-facing approach [9]. Backward-facing approach i hown in Fig. 3 a a chematic diagram. Thi approach doe not reqire any model for driver behavior. Intead, a driving cycle i tracked by the vehicle. The driving cycle i a velocity ver time peed profile which repreent the driving pattern in a pecific geographical region. Vehicle reqired traction force and velocity are then tranlated into the reqired torqe and velocity that mt be provided by the vehicle wheel and other component ptream. Thi calclation approach carrie backward throgh the driveline againt the tractive power flow direction ntil the fel e and/or the electrical energy e that wold be neceary to meet the trace i compted. Backward approach (3) (4) depend on the ICE characteritic map to a great extent. Fig. 3. Backward facing imlation approach chematic diagram The ADvanced VehIcle SimlatOR (ADVISOR) [9] and MATLAB-SIMULINK are ed for imlation tdy. ADVISOR employ a combined forward/backward facing approach for the vehicle performance imlation. Simlation are performed for both conventional and HEV. In the former cae, AS reqired power i demanded directly from the combtion engine while in the later one it i demanded from HEV power b. The imlation parameter a well a the vehicle component model have been et for a parallel HEV and a conventional vehicle deigned in the previo tdie []. 4. Hybrid Electric Powertrain Control Fzzy control approach i employed to devie HEV control deign in thi tdy. The main objective of the fzzy controller i to cae the ICE to work in the vicinity of it optimal operating point []. The optimal operating point of the engine are determined baed on ICE parameter at the crrent vehicle peed to minimize intantaneo FC and emiion. At any particlar point in time, the peed of rotation for the ICE i determined baed on the powertrain configration and the crrent gear ratio. Thi i the peed at which the intantaneo optimiation i performed. For the crrent peed, all poible torqe that the ICE can provide are conidered. Then the FC and emiion (HC, CO and NOx) for all torqe at the crrent peed are taken from the engine map and the following cot fnction i calclated for all of thee point: j w FC HC NO x CO w w w2 3 (6) w2 w3 FC HC NO x CO in which all variable are normalized to their correponding target vale limit. The target vale of the FC i defined by the deigner while for the emiion, the tandard of tailpipe emiion are ed. Moreover, wi are relative weight which are aigned to each parameter baed on their importance. Thi i one large degree of freedom, and the weight mt be elected baed on the deign objective. For intance, when the main objective i the minimization of the vehicle FC, the weight of FC i et to and the weight

4 Spenion Sytem in Parallel Hybrid Electric Vehicle Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 of emiion will be et to zero. In thi tdy, PNGV paenger car contraint [2] are ed to enre that the vehicle performance i not acrificed dring the trade off oltion. The actal torqe delivered by the ICE mt be determined ch that the driver torqe reqet (from brake and accelerating pedal) are atified conitently and the battery i fficiently charged at all time. Therefore, the actal otpt torqe of the ICE i compted by fzzy control trategy baed on the optimal operating point of the ICE, driver torqe reqet and the battery tate of charge (SOC). The remaining torqe at that peed, reqired to meet driver command i provided by the EM. The EM may prodce either poitive or negative torqe. A chematic of thi control trategy i hown in Fig. 4. The FLC deign detail have been decribed in a previo work []. Fig. 4. Hybrid Powertrain Control Strategy. 5. Simltaneo Simlation of Powertrain and AS Sytem In order to tdy the AS and powertrain ytem imlation in a nified media, a imltaneo imlation tool i developed in thi tdy. The imltaneo imlation concept i introdced in thi ection. The problem of imltaneo imlation i tdied from three apect inclding environmental inpt, vehicle dynamic, and energy interaction. The environmental inpt of the penion and powertrain ytem are qite different. Spenion ytem main ditrbance inclde the road irreglaritie modelled by either random or bmpy ignal, while the powertrain ytem inpt relate to the vehicle peed pattern repreented by a predefined driving pattern. In addition, penion ytem inpt depend trongly on vehicle peed which i determined by the driving pattern. Therefore, the penion ytem ditrbance mt be tned continoly according to vehicle peed. Different dynamic of the ytem i the other concern. Powertrain imlation i mainly baed on the qaiteady imlation approach in which teady-tate characteritic map of the component are employed for calclation. However, penion ytem dynamic i introdced by mch fater differential eqation. In thi cae, de to the qai-teady amption, the reqired nmerical dicrete time-tep for the powertrain i far greater than the AS ytem one. The acceptable nmerical time-tep i therefore crcial in the imltaneo imlation of thee two ytem. Finally, AS and powertrain ytem have an interaction in term of energy. The AS reqired power i demanded from the powertrain ytem continoly. The energy interaction of AS and powertrain ytem in conventional vehicle and HEV are alo different. In the conventional vehicle, thi power load i impoed on the combtion engine while, in the HEV it may be demanded form the ESS. In thi tdy, energy interaction of conventional and HEV ha been conidered eparately. In the conventional vehicle, the AS load i modelled a an extra torqe added p to the engine reqired torqe a hown in Fig. 5. In the HEV, however, thi load i conidered a an additional electrical acceory load reqeted from the electrical power b a hown in Fig. 6. The total reqired electrical power b i then provided by the generator or ESS, according to the control trategy. Fig. 5. Data flow for imltaneo imlation of AS and conventional powertrain ytem Fig. 6. Data flow for imltaneo imlation of AS and HEV powertrain ytem 6. Simlation Stdy and Relt Analyi Compter imlation relt are preented in thi ection. The imlation are performed for the mentioned powertrain-penion combination. The penion parameter are et a table. Moreover, the hybrid electric powertrain parameter are et for a parallel HEV with the following pecification: _ Gearbox: five peed manal gearbox with following gear ratio; 2.84, 3.77, 5., 5.57 and It hold be noted that final drive ratio ha been inclded in gearbox ratio. Efficiency of gearbox i amed 95%.

5 Morteza Montazeri-Gh & Mahdi Soleymani Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 _ IC engine: 4kW SI engine, obtained by caling of Geo Metro. l SI engine. _ Electric motor: 3.5kW AC motor, obtained by caling of Wetinghoe AC indction motor with a maximm power otpt of 75 kw. _ Energy torage ytem: 4 2V Hawker Genei valve-reglated lead-acid battery, model 2V26AhEP. _ Catalyt converter: cloe-copled conventional converter for an SI engine. Tab.. 7 dof model parameter vale. Decription Symbol Vale Sprng ma m kg Sprng ma moment of inertia abot x-/y- axi Unprng ma (front/rear) Vehicle tiffne of tire (front/rear) Spenion tiffne (front/rear) Spenion damping coefficient (front/rear) I x /I y / kg.m 2 m f /m r 4 / 4 kg k tf / k kr 8287 / 8287 N/m k f / k r / 92.7 N/m c f / c r 24 /25 N./m Track t.44 m Wheel bae L 2.63 m Ditance between y-axi and (front/rear) tire l f /l r.2 /.5 m The ize of the engine and electric motor and the nmber of battery modle are obtained baed on a previo tdy throgh a caling techniqe ing a GA approach []. Beide, for the conventional powertrain imlation, the caled verion of the HEV combtion engine i ed. Frthermore, the powertrain ytem time-tep ha been fined p to an acceptable AS time-tep level. Thi will not violate the imlation relt of the powertrain ytem in the backward-facing approach. Intead the rn time will increae coniderably. Combining the road ditrbance and the driving pattern, two combined ditrbance are developed for the penion ytem a lited in table 2. Tab. 2. Combined road-driving pattern ditrbance etp. Combined Speed Spenion Road Ditrbance Pattern Ditrbance I Bmpy ECE Bmpy-ECE Contant Random- II Random Speed Contant In the firt etp, the vehicle trace the ECE peed pattern (Fig. 7) while it pae over a bmpy road. In the econd etp, it i amed the vehicle i rnning over the random road with contant 8 km/hr velocity. Fig. 8 depict the combined Bmpy-ECE ditrbance. Fig. 9 alo how the time-domain random road ditrbance at the contant velocity. In the imlation with the combined Bmpy-ECE ditrbance, the engine i tarted at the cold condition while in the imlation with the Random-Contant ditrbance; it i tarted at hot condition. Elevation (m) Velocity (m/) Time() Fig. 7. ECE driving pattern Fig. 8. Combined ECE-Bmpy ditrbance Elevation (m) 8 x Fig. 9. Random road ditrbance Figre and, repectively, illtrate the vehicle body bonce and pitch acceleration with active and paive penion ytem in the preence of the combined Bmpy-ECE ditrbance. A it i een in thee figre, AS ytem ha caed coniderable decreae in the tranmitted acceleration to the body. Moreover, the peed variation apparently affect the tranmitted vibration to the body implying the inflence of the peed pattern on the ride comfort. In thi cae, the amplitde and freqencie of the tranmitted acceleration increae with peed increae.

6 2 Spenion Sytem in Parallel Hybrid Electric Vehicle Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 Bonce Acceleration (m/ 2 ) Fig.. Body bonce acceleration for Bmpy-ECE combined ditrbance Pitch Acceleration (/ 2 ) Fig.. Pitch acceleration for for Bmpy-ECE combined ditrbance Figre 2, 3 illtrate the power conmption for the combined Random-Contant and Bmpy-ECE ditrbance repectively. A it i een in Fig. 3, the AS intant power demand increae dramatically with vehicle velocity increae for the Bmpy-ECE combined ditrbance. It can be tated at thi point that the vehicle peed pattern affect both vehicle ride qality and AS ytem energy conmption. Thi i an important conclion that implie the e of an adaptive control ytem when a vehicle i experiencing different road profile and driving condition. Table 3 how the vehicle emiion and FC relt. A it can be een in thi table, AS ytem load ha caed an increae in the FC and emiion of both conventional vehicle and HEV. However thi increae i more coniderable for the Bmpy-ECE road-cycle ditrbance, where AS ytem intant power demand i mch more than the one for Random-Contant roadcycle ditrbance (Figre 2 and 3). Moreover, ince combtion chamber temperatre ha a prononced effect on the emiion [3], the emiion are apparently redced for the Random- Contant cae that the ICE i tarted at the hot condition. Figre 4 and 5 how the combtion engine operating point for conventional and hybrid electric powertrain ytem, repectively, ing the combined Bmpy-ECE ditrbance. A it i een in thee figre, the AS load cae an pward hift in the combtion engine reqired torqe. Fig. 2. Intant power conmption of AS for Random-Contant road-cycle ditrbance. Fig. 3. Intant power conmption of AS for Bmpy-ECE road-cycle ditrbance. Engine Torqe (N.m) Engine Speed (rpm) Efficiency Fig. 4. ICE operating point for conventional vehicle with combined Bmpy-ECE ditrbance. Engine Torqe (N.m) 6 Efficiency Engine Speed (rpm).34 Fig. 5. ICE operating point for HEV with combined Bmpy-ECE ditrbance

7 Morteza Montazeri-Gh & Mahdi Soleymani 3 Tab. 3. Emiion and fel conmption relt Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 Objective Vale FC (Lit/Km) HC+NOx (gr/km) CO (gr/km ) : conventional, Random-Contant 2: conventional, Bmpy-ECE 3: HEV, Random-Contant 4: HEV, Bmpy- ECE In order to frther tdy the effect of AS load on the powertrain ytem, the engine reqired torqe i examined more preciely. Figre 6 and 7 depict the combtion engine reqired torqe for the conventional vehicle and HEV powertrain ytem repectively. Engine Reqired Torqe (N. m) Fig. 6. ICE reqired torqe for HEV with the combined Bmpy-ECE ditrbance Engine Reqired Torqe (N. m) Fig. 7. ICE reqired torqe for the conventional vehicle with combined Bmpy-ECE ditrbance In the conventional powertrain ytem, the ICE i affected apparently by the AS load dynamic a hown in Fig. 7. A it i een in thi figre, the AS load i tranlated a a high freqency torqe load applied to the ICE. However, a the combtion engine reqire time to adjt to the time-varying load impoed on it, it i not capable of providing the AS ytem with the reqired power, and therefore, a power hortage i occrred. On contrary, the AS load in hybrid electric powertrain ytem cae a relatively niform hift in the engine reqired torqe ignal a hown in Fig. 6. In HEV, a hare of the AS power demand i provided by the electrical ESS. Figre 8 and 9 depict the SOC hitory withot and with AS load, repectively. The SOC hitory withot the AS load i a mooth diagram a hown in Fig. 8. However, a it i een in Fig. 9, ome ripple are een in the SOC hitory of the ESS while it i experiencing the AS load. 7. Conclion The idea of application of AS ytem in HEV i tdied in thi paper. A imltaneo imlation approach in which AS and powertrain ytem are imlated concrrently i propoed for thi prpoe. In the imlation approach, data and energy interaction are modeled. Simlation relt reveal that the AS load cae an

8 4 Spenion Sytem in Parallel Hybrid Electric Vehicle Downloaded from ijiepr.it.ac.ir at 2:7 IRST on Friday September 28th 28 increae in FC and emiion of both conventional vehicle and HEV. However, in the conventional vehicle, the AS load i tranlated a an additional highfreqency torqe load on the combtion engine while in the HEV, it cae a mooth pward hift in the combtion engine torqe. Therefore, in conventional vehicle, de to low repone dynamic of combtion engine, the AS power hortage a well engine heitation and rge are more likely to occr. In addition, the imlation relt prove the effectivene of the idea of AS ytem application in the HEV a an alternative platform for AS ytem power pply. SOC Fig. 8. SOC for HEV with Bmpy-ECE ditrbance and paive penion ytem SOC [5] Ping. H, "Power Recovery Property of Electrical Spenion Sytem" IEEE, 9624, 996. [6] Montazeri-Gh, M., Jazayeri-M, S.Y., Soleymani, M., Vehicle Ride Evalation Baed on a Time-Domain Variable Speed Driving Pattern, International Jornal of Vehicle Deign, Vol. 47, No. /2/3/4, pp.8, 28. [7] Goncalve, F.D., "Dynamic Analyi of Semi- Control Techniqe for Vehicle Application", M.S.C Diertation, Virginia Polytechnic Intitte and State Univerity, 2. [8] Karnopp, D., Croby, M.J., "Sytem for Controlling the Tranmiion of Energy Between Spaced Member". United State Patent #3,87,678, 974. [9] Wipke, K.B., Cddy, M.R., Brch, S.D., "ADVISOR 2.: a Uer-Friendly Advanced Powertrain Simlation Uing a Combined Backward/Forward Approach", IEEE Tran. Vehiclar Technology, 48 (6), 999, pp [] Montazeri, M., Poramad, A., B. Ghalichi, "Application of Genetic Algorithm for Optimization of Control Strategy in Parallel Hybrid Electric Vehicle", Jornal of the Franklin Intitte, 343, 26, pp [] Johnon, V.H., Wipke, K.B., Raen, D.J., "HEV Control Strategy for Real-Time Optimization of Fel Economy and Emiion". Proceeding of the Ftre Car Congre, SAE Paper No , 2. [2] Moore, T.C., Lovin, A.B., "Vehicle Deign Strategie to Meet and Exceed PNGV Goal", Electric and Hybrid Vehicle Implementation of Technology SAE Special Pblication SP-5, 995, pp [3] Schafer, F., Bahyen, R.V., Redced Emiion and Fel Conmption in Atomotive Engine, Fig. 9. SOC for HEV with Bmpy-ECE ditrbance and active penion ytem Reference [] Hac, A., "Optimal Linear Preview Control of Spenion", Vehicle Sytem Dynamic, Vol. 2, 992, pp [2] Ficher, D., Iermann, R., "Mechatronic Semi- and Vehicle Spenion", Control Engineering Practice, 2, 24, pp [3] Mrad, R.B., Faoi, S.D., Levitt, L.A., "A Polyniminal- Algebric Method for Non-Stationary TARMA Signal Analyi- Part II: Application to Modeling and Predicting Power Conmption in Atomobile Spenion Sytem", Signal Proceing, 65, 998, pp [4] Montazeri-Gh, Kahani, M., "Energy Regeneration of Spenion Sytem in Hybrid Electric Vehicle", Advanced Vehicle Control Conference, Japan, 22.