A Comparative Study and Analysis of an Optimized Control Strategy for the Toyota Hybrid System

Transcription

1 Pag 563 Wol Elctic Vhicl Jounal Vol. 3 - ISSN AVERE EVS4 Stavang, Noway, May 13-16, 9 A Compaativ Stuy an Analysis of an Optimiz Contol Statgy fo th Toyota Hybi Systm Tho Hofman 1, Thijs Punot 1 Autho 1 (cosponing autho) Tchnisch Univsitit Einhovn, P.O. Box 513, 56 MB EINDHOVEN, Th Nthlans, Phon: , Fax: , t.hofman@tu.n Abstact Th Toyota Pius quipp with th Toyota Hybi Systm (THS) II vhicl uss a combination of a combustion ngin an two lctic machins in o to incas th fficincy an th ful conomy. Th Engy Managmnt Statgy (EMS) of th THS II is analyz using masumnt ata collct with a Toyota Pius un iffnt iving conitions on th oa an compa with an optimiz EMS bas on simulations. Th main goal of this pap is to vify th contol statgy as implmnt in th Pius by compaing th masu statgy with an optimiz statgy bas on Engy Consumption Minimization Statgy (ECMS). Th iffncs btwn th simulation sults an th actual masu statgy a analys an iscuss. Kywos: Hybi Elctic Vhicls, Molling an Simulation, Hybi Statgy, Engy Efficincy, Engy Consumption, Pow Tain, Tansmission, Optimal Contol 1 Intouction Th Toyota Pius (s, Figu 1) quipp with th Toyota Hybi Systm (THS) II vhicl uss a combination of a combustion ngin an two lctic machins in o to incas th fficincy an th ful conomy [1,,3,4,6,7]. Th Engy Managmnt Statgy (EMS) of th THS II is analyz using masumnt ata collct with a Toyota Pius un iffnt iving conitions on th oa an compa with an optimiz EMS bas on simulations. Th main goal of this pap is to vify th contol statgy as implmnt in th Pius by compaing th masu statgy with an optimiz statgy bas on Engy Consumption Minimization Statgy (ECMS) [3]. Th outlin of th pap is as follows. In Sction, th vhicl mol is iscuss incluing th contol mol. In Sction 3, th simulation appoach is iscuss. Figu 1: Toyota Pius quipp with th THS II Accoingly, in Sction 4 th simulation sults by compaing th ful conomy sults with th catalogus valus on two iv cycls a scib. Aitionally, in Sction 4, th contol statgy of th mol is futh optimiz using actual masumnt ata of th Toyota Pius un iffnt iving cicumstancs. This is pfom using a fin optimization cition, which minimizs th optimal ngin opation points EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 1

2 Pag 564 comput with th simulation mol an known contol statgy an th masu opation points with unknown contol optimization algoithm implmnt in th Toyota Pius. Finally, th conclusions a scib in Sction 5. Vhicl Simulation Mol Th vhicl simulation mol is a backwas contol mol [3]. Th qust vhicl iv pow P an qust vhicl sps a th inputs of th mol. Ths inputs a us to calculat th optimal ngin output toqu T an sp o st points. Figu shows a schmatic ovviw of this mol. Th batty pow P bat is tmin using th gnato an lctic moto pow. o I m N Ns Ns I m N NIz f NIz g f N Ns N N N s s T m T NI NI g I N N F R I N I z N I z N N s s s ti T g g f g f f, (1) wh I v is th lump intia of th ing ga I an th lctic moto I m, I g th lump intia of th sun ga I s an th gnato I g an I th lump intia of th combustion ngin I an th cai ga I c : Iv Im I, () I I I, (3) g g s c I I I. (4) Tabl 1: Squnc of calculation fo th ngin toqu an sp bas on a givn moto an gnato, vhicl iv toqu, an vhicl sp Figu : Pow-bas contol mol fo th THS [3].1 Dynamic iv tain mol In Tabl 1 an ovviw is givn of th squnc of calculation fo th ngin toqu T an sp bas on a givn moto T m an gnatot g, vhicl iv toqu T, an angula vhicl sp. Th optimal valu fo th lctic machin toqus follow fom th optimal contol statgy, which is iscuss in Sction.. Th lation btwn th acclation of th ing ga (which is ictly lat to th angula vhicl acclation ) an th toqus in th tansmission: 1. Givn th scib vhicl sp, th ing ga acclation is tmin an th ing sp chang hols t.. Fo th chosn valus of T g ant m an th pscib valu oft, th ngin toqu T is tmin using (1). 3. Givn th chosn valus of T g an T m an th pscib valu oft, th ngin acclation an ngin sp a tmin using (6). 4. Using th ing ga sp an th ngin sp, th gnato sp is calculat z z 1 with using g pgs pgs plantay ga atio not as z pgs. 5. Finally, th gnato an lctic moto pow a tmin using th calculat toqus an sps of th lctic machins. Th plantay ga atio z is fin by th aii of th ing ga an sun ga o by th numb of tth of th ing ga ( N ) an th sun ga ( N ): pgs s EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium

3 Pag 565 z R N pgs R s N. (5) s Moov, th final iv fficincy, whl ty aius, th iv foc a not as, R ti an F spctivly. Th lation btwn th ngin acclation an th toqus in th iv tain is givn by: N zfi Ns I N Ns N Ns Im N Ns Ig N zf Ns T N Ns Im N Ns Ig z N N N F R f s ti T m T g Im Ig Im f f (6) In this pap, th ngin an ing ga sp, which a lat to th vhicl sp via th plantay ga, a us as th two stats.. Contol Mol Th Engy Managmnt Statgy EMS us fo th ynamic contol mol is bas on th Engy Consumption Minimization Statgy (ECMS) [3]. Th ECMS is us to fin an optimal st point fo th lctic machins pows in ach tansmission opating point. Knowing th toqus an sps in th tansmission, th ECMS [3] is appli to fin th optimal st point of th gnato pow P g an lctic moto pow P m. R, Pm if P MO MO PS, Pm if f < f o o Pm, Pg max MO P Pm Pm Pbatmax PS PS Pm, Pg lswh (7) with th lctic moto pow uing th Moto- Only (MO) iving mo: MO P Pm PL, (8) m an th Rgnativ (R) baking mo: R P max P m m sat fbf P, (9) wh f bf [-] psnts th bak pow istibution facto. PS PS PS Pm, Pg ag min f Pm, Pg T, Pm, Pg Q (1) wh Q covs th st of constaints fo th iv tain componnts: Q Tg, Tm min t t max t g min t g t g max t m min t m t m max t T,min t T t T,max t. Tg min t Tg t Tg max t Tm min t Tm t Tm max t Pg min t Pg t Pg max t Pm min t Pm t Pm max t Pbat min t Pg t Pm t PL Pbat max t Th quivalnt ful cost fo iving lctically is: MO 1 MO f Pm, (11) bat an th quivalnt ful costs fo chaging o moto-assisting uing iving is givn by PS PS f f P, P T, P, (1) m g s wh psnts th quivalnt ful cost facto in [g/j]. Fo th pow-split mo (PS) a ns gi of lctic machin pows is us to fin th PS PS optimal st point Pm, P g. Th avantag of using a gi in th optimization pocu is that no quimnts a pos fo convxity of th objctiv function. Howv, in cas th os not xist a uniqu global minimum, th solution with th lowst batty activity is slct. Th optimization outin is pat using vaiabl valus of th quivalnt ful cost facto, until th optimal valu o o is foun. Fo, th systm is chag sustaining ov th chosn iv cycl.. 3 Simulation Appoach Using th ynamic quations fo th iv tain an th contol mol fom Sction an th spcifications of th THS II [1,,6,7], a simulation mol is buil in a Matlab/Simulink nvionmnt. Th vhicl block in th mol (s, Figu 3) contains th vhicl paamts. Th block is us to calculat th qust vhicl iv toqu an sp using th pscib vhicl sp that follows fom th iv cycl block. EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 3

4 Pag 566 Mol JP1-15 Tabl : Simulation sults Ful Consumption [l/1km] Compa NEDC to baslin [%] Compa to baslin [%] Baslin ECMS THS II Figu 3: Simulation mol fo th THS Th hybi contoll block contains th ECMS optimization statgy, as iscuss in Sction. Thfo, th ynamic quations an th paamts fo th gnato, lctic moto, final iv an plantay ga st a inclu in th hybi contoll block. Futhmo, th hybi contoll is ivi into th pats that scib th iffnt iv mos, which can occu: (i) pow-split, (ii) lctic-iv an (iii) bak ngy covy mo. Th combustion ngin block an tank block a us fo tmining th ful consumption cosponing to th ngin sp an toqu that follow fom th hybi contoll. Th batty stat of chag, voltag an cunt a also comput. 4 Simulation Rsults Th ful consumption ov two fnc iv cycl (JP1-15, NEDC) has bn comput an compa with th catalogu valus (s, Tabl ). Th tansmission sp atio with th baslin mol is contoll maximizing th systm fficincy whby th batty pow flow is zo ov th whol cycl. It can b sn that th is a iffnc of 9.1% an 11.9% btwn th catalogu an th simulat valus on th JP115 an th NEDC cycl spctivly. A iv tain paamt vaiation (+/- 5%) stuy has bn pfom in o to invstigat if th mol assumptions (final iv fficincy, vhicl mass, bak foc istibution) w sufficintly coct. It was foun that lag vaiation of iv tain paamts w qui to uc th iscpancy an th ful conomy snsitiv to paamt vaiation was lativ low. Thfo, it is mo likly that iffncs in ful conomy btwn th ECMS mol an th THS II vhicl a caus by iffncs in ngy managmnt statgy. This assumption will b invstigat nxt. 4.1 Compaison btwn masu contol statgy an ECMS fo th THS II using a constant In o to mak a compaison btwn th masu contol statgy an th optimiz, vhicl ata fom masumnt tsts pfom on a THS II vhicl a us. Th ata was obtain using a CAN-bus a that was connct to th CAN-bus conncto of th THS II vhicl. Using th CAN-bus a, vhicl ata can b ictly snt to a comput wh it is pocss. Th CAN-bus ata is obtain fom th intnal vhicl snsos. Th signals fom ths snsos a also us by th vhicl ngy managmnt systm. In total nin signals a a using th CAN-bus a. Ths nin signals a masu fo tn tst iv cycls, ach containing iffnt iving situations. Th following figu shows th lvant vhicl ata that is us to analyz th ngy managmnt statgy of th THS II vhicl. Th masu signals a inicat in black. Th signals that a calculat using th masu signals a illustat in gay. Figu 4: Simulation mol fo th THS Figu 4 shows that also th gnato an lctic moto toqu a a fom th CAN-bus. Th toqu signals fom th CAN-bus a tmin using th cunt an/o voltag signals fom th lctic machins. Th signals a masu fo tn iffnt iving situations: six shot tim pio an fou long tim pio masumnts, which can ach b consi as iv cycls. Th th most suitabl masu iving situations that will EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 4

5 Pag 567 b analyz a illustat in Figu 5, wh th vhicl sp fo ach situation is plott. V [km/h] V [km/h] V [km/h] 1 5 City cycl Highway cycl Combin cycl Figu 5: Masu sps fo th th masu iv cycls that will b analyz in this pap. Th constant quivalnt ful cost (in th nxt sction a vaiabl will b invstigat) is chosn such that th n valu of th batty ngy fo th simulation mol quals th n valu of th masumnt ata. Th influnc of th quivalnt ful cost facto on th iffnc in batty ngy n valus btwn th simulation mol an th masu ata is illustat in Figu 6 fo th th iffnt iv cycls shown in Figu 3. Th valus of that sult in a iffnc in batty ngy n valus btwn th simulation mol an th masu ata qual to zo (City: =3.7, Highway: =3.7, Combin: =3.5) w us in th simulation mol fo gnating th sults as shown in Tabl 3. In th sam tabl th ful consumption sults a shown using th masu ngin sp an comput ngin sp bas on masumnt ata. Fo computing th ful consumption bas on th masu vhicl stats as shown in Figu, th sam componnt fficincy ata is us as fo th simulation mol. In Figu 7, 8 an 9 som simulat an masu sults on th city iv cycl a shown. P ng [kw] ECMS simulation mol Masu ata Figu 7: Engin pow P as function of tim fo th simulation mol an masu vhicl ata (city iv cycl (s, Figu 3, top iagam)). Significant iffncs in ngin pow btwn th masu vhicl ata an th simulation mol ata a noticabl fo all th masu iv cycls. Th stat-of-ngy SOE signals fo th simulation mol an th masu vhicl ata a illustat in Figu ECMS simulation mol Masu ata E(n) S - E(n) M [MJ] City cycl Highway cycl Combin cycl [g/j] Figu 6: Diffnc in n valus of batty ngy btwn th masu ata (M) an th simulation mol (S) as a function of th quivalnt ful cost facto. SOE [%] Figu 8: Batty stat-of-ngy as a function of tim fo th simulation mol an th masu ata (city iv cycl). Figu 8 shows that th masu THS II stat-ofngy lss fluctuat than th stat-of-ngy comput with th simulation mol. Tabl 3 shows that th ful consumption fo th simulation mol shows a small bnfit fo th highway cycl (.4%) an th combin cycl (6.8%) compa EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 5

6 Pag 568 to th masu ful consumption valus. Fo th city cycl, th bnfits in ful consumption a much high (36%). Tabl 3: Ful consumption using simulation mol, th masu vhicl ata Ful consumption [l/1 km] City Highway Comb. Simulation Masumnt Th low ful consumption is patially caus by th fin ECMS, which assums that th vhicl can switch fom lctic iv mo to pow split mo instantly. Th ngin opats at th si sp an toqu lvl immiatly an thfo always in th most fficint aa. In ality, th combustion ngin has to b cank an vl up bfo switching to pow-split mo can occu. Th ngin can not opat in its most fficint aa immiatly. In Figu 9, th ngin opating points a plott fo th simulation mol an th masu ata. ngin toqu [Nm] combustion ngin map masu ata simulation mol simulation mol an th masu ngin opation points. 4. Compaison btwn masu contol statgy an ECMS fo th THS II using a vaiabl In o to impov th accuacy of th ECMS simulation mol an cas th iffncs compa to th masu vhicl ata, th influnc of a tim pn vaiabl quivalnt ful cost facto t is invstigat. Th vaiabl t lamba is obtain using an optimization cost function bas on th combustion ngin opating point. Th sults of th ECMS mol using th vaiabl lamba will b analys an iscuss Optimization mtho Th optimization outin is bas on minimizing th iffnc in combustion ngin opating points, T btwn th simulation mol an th masu ata. Th sp an toqu of th combustion ngin togth with th qust vhicl sp an iv pow tmin all th pows, sps an toqus in th tansmission. Consquntly, also th batty stat-of-ngy is tmin by th ngin opating point. Minimization of th iffnc in ngin toqu an sp btwn th ECMS mol an th masu vhicl ata will sult in an accuat fit fo all th pows, toqus an sps in th tansmission. Th outlin of th minimization mtho is pict in Figu ngin sp [pm] Figu 9: Engin opating points fo simulation mol an masu vhicl ata fo th city iv cycl. T ng T P Masu Although, th iffnc in ful consumption btwn th simulation mol an th masu vhicl a lativ small fo th highway an combin cycl, th iffnc fo th city cycl is lag. Futhmo, iffnc in ngin opation an batty pow flow is foun to b lag. Th ECMS in this sction was bas on a constant quivalnt ful cost facto in th nxt sction a vaiabl quivalnt ful cost facto is optimiz using a cost cition minimizing th comput ngin opation points with th Simulation,T = f() ng Figu 1: Illustation of outlin of th us minimization mtho. Th ngin opating point of th ECMS simulation mol can b contoll by vaiation of th quivalnt ful cost facto. Thfo, is us fo minimizing th iffnc in ngin toqu T an ngin sp. This is on by EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 6

7 Pag 569 minimizing th iffnc in ngin pow P, which can b wittn as (s, also Figu 1): T. (13) P Th simulation mol is analys using a vcto of valus fo th quivalnt ful cost facto. At ach tim instant t on th iv cycl, P is tmin as a function of using a cost function not with J. Th cost function J as a function of tim an is fin as: S M S M J t, T t, T t t, t (14) wh S nots Simulation mol an M th masu ata. Th optimal quivalnt ful cost facto at ach tim point in th iv cycl t is tmin by minimizing th iffnc in ngin pow P an thus by minimizing cost function J fo ach tim stp in th iv cycl: t ag min J( t, ), (15) L wh L is th vcto of valus of that was analys. Using t an th cosponing ngin sp S S t an ngin toqu T t, all th oth sps, toqus an pows in th tansmission an th batty ngy a tmin. 4.. Simulation sults using a vaiabl Th optimization outin bas on minimizing th iffnc in ngin toqu an sp btwn th ECMS simulation mol an th masu vhicl by vaiation of th quivalnt ful cost facto is pfom fo th th iffnt iv cycls (s, Figu 5). Th vaiabl quivalnt ful cost facto t obtain with th optimization outin is illustat fo th iffnt iv cycls in Figu 11. Figu 11 shows that th t that follows fom th optimization outin vais stongly fom th optimal constant quivalnt ful cost facto that was obtain in Sction 4.1. Th optimal vaiabl facto t cospons to an optimiz combustion ngin opating point fo th simulation mol. Th ngin toqu an sp that follow fom th optimization outin a shown in Figu 1. Th ngin toqu an sp fom th masu vhicl ata an th simulation mol using a constant quivalnt ful cost facto a also inicat in th sam figu. Th sults in Figu 1 show that th us of a vaiabl quivalnt ful cost facto impovs th accuacy of th ECMS mol. Th fit of th ngin toqu an sp of th simulation mol with th masu valus is significantly impov with spct to th us of a constant quivalnt ful cost facto. [g/j] [g/j] [g/j] City cycl 1 vaiabl 5 constant Highway cycl Combin cycl Figu 11: Vaiabl an constant quivalnt ful cost facto fo iffnt iv cycls. T ng [Nm] ng [a/s] masu constant vaiabl Figu 1: Engin toqu an sp fo constant an vaiabl quivalnt ful cost facto, an fo th masu vhicl. Th impov fit of th simulation mol ngin toqu an sp also affcts th accuacy of th oth tansmission signals. This is shown in Figu 13, wh th ngin pow an batty ngy a plott fo th simulation mol using vaiabl, constant quivalnt ful cost facto, an fo th masu vhicl ata. Th accuacy of th simulation using a vaiabl is significantly impov with spct to th constant simulation mol. EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 7

8 Pag 57 P ng [kw] E s [J] x masu constant vaiabl Figu 13: Engin pow an batty ngy fo th simulation mol using a constant an vaiabl quivalnt ful cost facto, an fo th masu vhicl. In Tabl 4 th ful consumptions sults a list fo th simulation mol using a vaiabl an constant, an fo th masu vhicl. In contay to usag of a constant, it can b obsv that th ful consumption fo th city cycl using a vaiabl quivalnt ful consumption facto iffs significantly lss fom th masu ful consumption (+3.4%). Fo th combin cycl, th sults a th sam fo both constant an vaiabl (-4.4%). On th highway cycl, th vaiabl sults in significantly low ful consumption compa to th masu vhicl (-14.6%). This is caus by limitations in th optimization outin an by iffncs in ngy managmnt statgy. Tabl 4: Ful consumption fo th simulation mol using constant an vaiabl an fo th masu vhicl Simulation mol, constant Simulation mol, vaiabl Masu THS II vhicl Ful consumption [l/1km] City Highway Combin Discussion Howv, iffncs in ngin opating points btwn th vaiabl simulation mol an th masu vhicl ata still occu. Ths iffncs oiginat fom th pincipl of th ECMS an th us of th quivalnt ful cost facto as a contol vaiabl. Th ngin opating point of th ECMS simulation mol is contoll by vaiation of. Fo xampl, in Figu 14, th ngin opating points at a tim instant (t = s) on th combin cycl fo vaious valus of a shown. Th optimal ngin opating point is also inicat (cicl), as wll as th masu ngin opating point (squa). T [Nm] Combin cycl, t = s , T fo vaious 6 optimal, T 55 masu [a/s] Figu 14: Influnc of th quivalnt ful cost facto on ngin opating point. It can b obsv that th us of a vaiabl quivalnt ful cost facto os not guaant an accuat fit with th masu ata. Th vaiabl os not povi nough contol fom to position th ngin opating point in th si masu opating point. Th vaiabl is us fo contolling two systm stats, th ngin toqu an ngin sp. A compomis is ma btwn ths two stats fo fining th optimal lamba. Futhmo, ECMS always povis an optimal solution fo th contol of th ngin opating point, inpnntly of th valu of. Thfo, it is not possibl fo th ECMS simulation mol to opat in a non-optimal point, whas th THS II coul pf this non-optimal ngin point fo vaious oth yt unknown asons (.g., low batty stat-of-ngy, tmpatu, an lif tim issus) which a not incopoat in th simulation mol EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 8

9 Pag 571 Wol Elctic Vhicl Jounal Vol. 3 - ISSN AVERE 5 Conclusions Th Engy Managmnt Statgy (EMS) of th THS II is analyz using masumnt ata collct with a Toyota Pius un iffnt iving conitions on th oa an compa with an optimiz EMS bas on simulations. Th ECMS mtho uss an quivalnt ful consumption facto fo computing th optimal ngin opation points whil satisfying th ngy balanc an oth fin iv tain constaints. Thfo, th optimal vaiabl quivalnt ful cost facto is tmin using an optimization outin that is bas on minimizing th iffnc in ngin toqu an ngin sp btwn th simulation mol an th masu vhicl. Th analysis of th us of a vaiabl quivalnt ful cost facto las to th following conclusions: (i) th us of a vaiabl quivalnt ful cost facto in th ECMS simulation mol las to sults significantly clos to th masu vhicl ata, compa to th us of a constant quivalnt ful cost facto. (ii) Howv, th us of a vaiabl quivalnt ful cost facto in th ECMS simulation mol os not significantly impov th ful consumption, compa to th us of a constant quivalnt ful cost facto. Fo ach analys iv cycl, th batty statof-ngy bhavs significantly mo constant than fo th ECMS simulation mol. It is foun that th EMS of th Toyota Pius tns to focus mo on minimization of th batty pow in pow-split mo. Th ECMS focuss on minimizing th ful consumption. Th us of ECMS with a constant in a Toyota Pius las to an impovmnt in ful consumption of 36% in city taffic,.5% in highway taffic an 7% in combin taffic compa to th masu vhicl ata. CVT Typ, IEEE Tansactions on pow Elctonics, Vol. 1(3), May, 6 [5] J.T.B.A. Kssls, M.W.T. Koot, R.M.L. Ellnbok, M.F.M. Psgns, F.E. Vlpaus, P.P.J. van n Bosch, M. Eift, D.B. Kok, Vhicl Moling fo Engy Managmnt Statgis, in Poc. of th 7 th Intnational Symposium on Avanc Vhicl Contol, Anhm, 4 [6] J. S. Hsu, C. W. Ays, C. L. Coom, Rpot on Toyota/Pius Moto Dsign an Manufactuing Assssmnt, ORNL/TM- 4/137 [7] K. Muta, M. Yamazaki an J. Tokia, Dvlopmnt of Nw-Gnation Hybi Systm THS II Dastic Impovmnt of Pow Pfomanc an Ful Economy, SAE pap, 4 Authos T. (Tho) Hofman civ his M.Sc.- (with honos) an Ph.D.-g in Mchanical Engining fom Einhovn Univsity of Tchnology, Einhovn. Sinc Sptmb 7, h is a post-octoal fllow with th Contol Systms Tchnology goup. His sach intsts a moling, sign, an contol of hybi an lctic tchnologis fo populsion systms. T. (Thijs) Punot civ his B.Sc.- g in Mchanical Engining fom Einhovn Univsity of Tchnology, Einhovn, Th Nthlans, in 6. Rfncs [1] J. Liu, H. Png an Z. Filipi, Moling an Analysis of th Toyota Hybi Systm, in Intnational Confnc on Avanc Intllignt Mchatonics 5 [] R. H. Staunton, C. W. Ays, L. D. Malino, J. N. Chiasson, T. A. Buss, Evaluation of 4 Toyota Pius Hybi Elctic Div Systm, May 6 [3] J.T.B.A. Kssls, Engy Managmnt fo Automotiv Pow Nts, PhD Thsis, Einhovn Univsity of Tchnology, Fbuay 7 [4] J.M. Mill, Hybi Elctic Vhicl Populsion Systm Achitctus of th - EVS4 Intnational Batty Hybi an Ful Cll Elctic Vhicl Symposium 9