Modeling and Development of the Real-time Control Strategy For Parallel Hybrid Electric Urban Buses

Transcription

1 Modling and Dvlopnt of th Ral-ti Control Stratgy For Paralll Hybrid Elctric Urban Buss YUANJUN HUANG, CHENGLIANG YIN, JIANWU ZHANG School of Mchanical Enginring Shanghai Jiao Tong Univrsity 800 Dongchuan Rd., Shanghai, , CHINA Abstract: - This papr proposs a fd-forward control odl for SWB6105 paralll hybrid lctric urban bus (PHEUB) by using Matlab/Siulink. In ordr to optiiz th ful conoy, balanc th battry stat of charg (SOC), and satisfy th rquirnts of th vhicl prforanc and drivability as wll, a logic thrshold torqu distribution control stratgy (LTTDCS) incorporating with an instantanous optiization algorith was dvlopd for th PHEUB. Bnch tsts rsults for th ky coponnts of th hybrid powrtrain ar slctd as rliabl rfrncs in th odling. Th control stratgy is validatd by th siulation rsults of th ngin, th otor and th battry in trs of ful conoy and dviations of battry SOC. Ky-Words: - Paralll hybrid lctric urban bus (PHEUB), Hybrid powrtrain, Hybrid syst odling, Logic thrshold torqu distribution control stratgy (LTTDCS), Instantanous optiization algorith, Ral-ti control 1 Introduction Powrtrain of a paralll hybrid lctric vhicl (HEV) is a hybrid syst of ngin and lctric driv syst. Th driv forc rqustd by th drivr is optially distributd btwn th ngin and th otor undr th control of th advancd vhicl control unit (VCU), which is th krnl of th ral-ti control stratgy of th paralll HEV and also on of th ky tchnologis in which any rsarchrs ar ngagd. Th goal of th ral-ti control stratgy is to achiv high fficincy, nrgy saving and low issions vhicl by controlling hybrid powrtrain syst coordinatly. Th prforancs of a paralll HEV strongly dpnd on th control stratgy of th hybrid powrtrain syst, which consists of th ngin, lctric otor, lctrical nrgy syst, autoatic clutch, transissions, tc. Many rsarch works on th control stratgy of paralll HEV hav bn conductd in rcnt yars. In gnral, ths works can b roughly classifid into two catgoris. Th first is to ploy huristic control tchniqus such as logic thrshold, fuzzy logic, nural ntworks and gntic algorith for stiation and control algorith dvlopnt [1-5]. Its basic ida is that it is rul basd. Advantags of this thod includ th as in handling ral-ti control typical hybrid syst oprating ods, dynaic switching aong ths ods as wll as th xpandability for intgrating vhicl dynaic control in th futur. Th scond catgory is to us optiization control thoris, such as instantanous optiization thod and global optiization tchniqus. Instantanous optiization control stratgy is basd on ral-ti coputation of th quivalnt ful consuption and ission at possibl oprating points [6-8]. Global optiization tchniqus, such as dynaic prograing [9], athatic prograing [10], and optiization algoriths basd on classical variational approach [11], ar not applicabl in ral-ti control bcaus thy rquir a prior known driving cycl. Currntly, thy ar ainly usd for valuating th quality of othr control stratgis. Control stratgis that ar basd on th iniization of th ful consuption s to b on stp ahad of huristic control stratgis that ar basd upon sipl ruls and aps. Th forr, also known as optial controllrs can provid or gnrality and rduc th nd for havy tuning of th control paratrs. Bcaus of th advantags discussd abov, a logic thrshold torqu distribution control stratgy incorporating with an instantanous optiization algorith for ral-ti control of a paralll hybrid lctric urban bus (PHEUB) is put forward. Th logic thrshold torqu distribution stratgy is dvlopd on th basis of nginring pirical xprinc and th analysis of coponnts fficincy tabls and charts. It ralizs ral-ti control th oprating ods of th hybrid syst and th dynaical transition btwn ths ods. Basd on this control stratgy, an instantanous ISSN: Issu 7, Volu 5, July 2008

2 optiization algorith is introducd to prfor ral-ti optiization for thos oprating ods that both th ngin and th otor ar working in. Th purpos of th proposd control stratgy is to achiv accptabl vhicl prforanc and drivability rquirnts whil siultanously axiizing th ngin ful conoy and aintaining th battry stat of charg (SOC) in its oprational rang at all tis. Th rst of this papr is organizd as follows: In Sction 2, th configuration of th powrtrain syst and th paratrs of th PHEUB ar brifly dscribd. Thn, th odling of th PHEUB syst is prsntd in Sction 3. Nxt, th dvlopd control stratgy applid in this rsarch is discussd in Sction 4. Aftr that, th siulation rsults for iniu ful consuption ar givn in Sction 5. And Sction 6 is th conclusions. 2 Syst Configuration Th schatic diagra of th spcific PHEUB powrtrain syst is shown in Fig.1. It s dsignd with a disl ngin as th ain powr sourc and an AC lctric otor as a scondary powr sourc. Th otor is installd ahad of th transission. Th output torqu of th ngin and th otor ar coupld into th torqu couplr. Th output torqu is thn transittd into AMT through which th vhicl is proplld in th nd. Gar shifting procss is controlld by th AMT controllr indpndntly. Thr is a on-way clutch locating btwn th ngin and th torqu couplr. Th paratrs for th ain coponnts of th PHEUB powrtrain syst ar listd in Tabl 1. 24V BATTERY CONVERTER BATTERY CONTROLE UNIT DC/DC CLUTCH MOTOR NiMH BATTERY AMT TORQUE on-way clutch ENGINE COUPLER COMPRESSOR ALTERNATOR STEER PUMP AIR PUMP Tabl1. Basic paratrs of th PHEUB powrtrain ICE Typ Disl ngin Strok volu 3900 c 3 Pak powr 119 kw Maxiu torqu 550 N EM Typ A.c. induction achin Pak powr 125 kw Continuous powr 45 kw Ratd spd 2500 r/in Maxiu spd 4000 r/in Battry Typ Nickl tal hybrid (NiMH) Capacity 55 Ah Noinal voltag 312 V Transission Typ Fiv-spd autoatd anual transission Gar ratio 6.11/3.39/2.05/1.32/1/5.22 Final rduction gar ratio Vhicl Vhicl Curb Wight 11140kg Drag cofficint 0.79 Whl Rolling radius Syst Modling Bcaus of th coplxity of ngin, otor, battry, AMT and othr subsysts, it is hard to dscrib th oprating procss of ach coponnt statd abov accuratly and thoroughly only by using th analytical thod. A coplx analytic odl will rquir considrably larg coputation. Morovr, any siplification and hypothsis usd to stablish th analytic odl will rduc th coputation accuracy and ak it hav no supriority ovr th purly pirical odls. Thrfor, a odling thod cobining thortic analysis and xprintal data is adoptd for currnt PHEUB rsarch [12-16]. In this thod, th prforancs of th ky coponnts of th powrtrain, such as th ngin, th otor, th battry, tc., ar ainly dpictd by th xprintal data, whil th dynaic quation of th vhicl syst is still stablishd by using analytic thod. In othr words, it is ssntially a quasi-linar odl basd on thrdinsional prforanc ap. Hybrid powrtrain bnch tst is carrid out on th tst bd to obtain ky coponnt tsting data. By using Matlab/Siulink, a fd-forward siulation odl is dvlopd basd on th powrtrain syst (showd in Fig.1) and th control stratgy (dscribd in sction 4). Th block diagra is shown in Fig.2. Fig.1 Schatic diagra of th PHEUB powrtrain ISSN: Issu 7, Volu 5, July 2008

3 Fig.2 Diagra of PHEUB siulation odl Th objctiv of th ngin control for th hybrid powrtrain is to kp th ngin oprating at its high fficincy rgion as uch as possibl, which is ralizd by coanding th xognous control variabls such as th control of ful fding syst for th disl ngin. Th ndognous control variabls, such as th xhaust gas rcirculation, th air-to-ful ratio (A/F), tc., ar rgardd as prcalibratd control variabls and not considrd in odling. Thrfor, th ain task for ngin odling is to stablish th rlationship btwn th ful control coand, th torqu output of th ngin and th ful consuption of th ngin. Th ngin output torqu is dscribd as: t i Q = Q dt = Q ( T, n) dt (2) 0 0 t Whr Q () is a two-dinsional look-up tabl function. It is constructd by stablishing th rlationship of th ngin ful consuption Q vrsus ngin torqu T and ngin spd n, which is shown in Fig.3 (b). T = f ( θ, n ) (1) Whr f () is a two-dinsional look-up tabl function. It is constructd by stablishing th rlationship of th ngin output torqu vrsus ngin ful control coand θ and ngin spd n, which is shown in Fig.3 (a). Th ful consuption is dscribd as: (a) Engin ful coand charactristics ISSN: Issu 7, Volu 5, July 2008

4 (b) Th ful consuption charactristics of ngin Fig.3 Nurical odls of th ngin Th lctric driv syst copriss an AC lctric otor, an invrtr and a otor controllr. Th otor controllr is rsponsibl for rgulating th otor torqu to t th torqu rqust coandd by th VCU. Th voltag control signals producd by th otor controllr ar snt to th invrtr to gnrat thr-phas PWM voltag, which is usd to anipulat th AC otor. In so prvious rsarch [17,18], an lctroagntic dynaic odl of quivalnt circuit was proposd for th invstigation of otor s transint bhavior thoroughly. Howvr, ti-consuing rquirnt of th dtaild odl aks it not suitabl for driving-cycl-basd vhicl siulation. Thrfor, an pirical ap-basd odl is usd in this study. Th AC Elctric otor, invrtr and otor controllr ar rgardd as a singl syst for odling. Th input paratrs ar otor torqu coand β ([0,1]), otor oprating od coand λ (driv od, charging od, racing od, and spd rgulating od), th bus voltag of th lctric sourc U and th otor spd n, which is calculatd fro th rotational dynaic quation in th vhicl odl. Th output paratrs ar otor actual output torqu T, inrtia of th rotor shaft J and th invrtr currnt I. Undr th control of th driv od, th otor output torqu T is dscribd as : T = β T (3) Whr _ax T _ax is th axiu torqu th otor can gnrat and it is a function of rotational spd and tpratur. Th otor can oprat at pak powr for a short priod of ti. With incrasing tpratur of th otor, thr is a rquirnt of rducing powr output to aintain thral balanc of th otor. T_ax = f( n, t ) (4) Excpt for th prforanc liitation iposd by itslf, is also liitd by both th voltag U T _ax I _ax and th axiu lctric currnt. Thrfor, undr th driving od th T _ax is dtrind by th following quation: _ax T_ax in f( n, t), 9.55 UI = (5) n If th otor works undr th charging od thn T _ax can b xprssd as: _ax T_ax ax f( n, t), 9.55 UI = n (6) Th otor lctric currnt I can b calculatd fro th following quations: P I = U (7) Tn / η T 0 P = Tn η T < 0 (8) whr is th otor input(driving od) or output P (charging od) powr, η is th otor fficincy rgarding spd and torqu and it is obtaind by conducting otor prforanc tst. It can b xprssd as: η = f ( T, n ) (9) whr f () is two-dintional look-up tabl function dpnding on th otor output torqu and th otor rotational spd which ar shown in Fig.4. Fig.4 Nurical odls of th traction otor including controllr ISSN: Issu 7, Volu 5, July 2008

5 Fig.5 shows th nurical odl of th high powr battry pack. Th battry odl consists of a prfct opn circuit voltag sourc ( U o ) and a rsistor (intrnal rsistanc, R ). Both and int U R o ar th function of th battry SOC ( S c ), battry tpratur ( t ) and th dirction of currnt of flow B ( I B ). Battry intrnal rsistanc R int can b calculatd fro th following quation: Rint = f ( IB, SC, tb) (10) Th opn circuit voltag can b calculatd fro th following quation: U o = f ( SC, tb ) (11) Exprintal data of th battry illustratd in Fig.5 (b), Fig.5 (c) and Fig.5 (d) ar all usd to calculat U and R. Fig.5 (b) shows th battry o pack opn circuit voltag. Fig.5 (c) and Fig.5 (d) illustrat th charging and discharging rsistanc of th battry pack rspctivly. (c) Battry pack discharg rsistanc (d) Battry pack charg rsistanc Fig.5 Nurical odls for th NiMH battry pack (a) Elctric schatic of th NiMH battry Th VCU is th vhicl control unit odl that consists of th input odul, th control algorith odul, which is th cor of th VCU odl, and th output odul. Th functions of th VCU ar to accpt th drivr coand and onitor th whol vhicl oprating status siultanously. Its output coands calculatd by th control algorith ar usd to anipulat th hybrid syst xcuting th corrsponding action. Th control algorith is prograd using standard C and wrappd by Siulink S-Function. Thrfor, th progra can work aftr bing copild and transfrrd to th ral controllr without any odification. (b) Battry pack opn-circuit voltag ud + - Δu PI ΔT Pdal opration β acc_ pdal β brak_ pdal ua Fig. 6 Input and outputs of th drivr odl ISSN: Issu 7, Volu 5, July 2008

6 4 Analysis and Dsign of th Ral- Ti Control Algorith Basd upon th schatic diagra of th powrtrain syst shown in Fig.1, all th possibl oprating ods for th PHEUB ar listd in Tabl 2. Thy includ not only th stady oprating ods but also th transint ons. Th oprating od transition diagra of th PHEUB, which suarizd fro th opration ods, is illustratd in Fig.7. In this figur, th llips blocks rprsnt th PHEUB stady oprating ods; th circular blocks rprsnt th transint ons; th arrow lins btwn ths blocks illustrat th transfr dirction of th oprating ods. Th transition btwn th two oprating ods connctd by a singl arrow lin can only b ad by following th dirction of th arrow. As for th doubl arrow lin, th od transition can b ad back and forth btwn ths two oprating ods connctd. Following th principl of od transition shown in Fig.7, th control of th PHEUB switchs btwn all th oprating ods utually. Which od th syst should b working in is coandd by th VCU. Th drivr s acclrator pdal coand, shift position, brak pdal ffort, currnt vhicl spd, battry SOC and othr vhicl stat inforation ar all usd to dtrin th syst oprating od. Fig.7 oprating od transition control rul Tabl 2. Opration od classification of th PHEUB Status nubr A B C D E F G H I J K L M Status dscription Vhicl stop Pur lctric driving od Start ngin Hybrid driving with both ngin and otor Vhicl drivn by ngin alon Driving whil charging th battry Coating with ngin on Shift gar with ngin on Shutdown ngin Rgnrativ braking Friction braking Shift gar with ngin off Coasting with ngin off In this study, a logic thrshold torqu distribution control stratgy (LTTDCS) is introducd to control th switchs btwn th oprating ods ntiond abov whnvr th vhicl is oprating. It is basd on th nginring pirical xprincs and th analysis of coponnts fficincy tabls and charts, which is a popular and ffctiv dsign approach. Th objctiv of th LTTDCS is to raliz ful conoy optiization by distributing th torqu rqustd by th drivr btwn th ngin, th otor and th friction brak syst, which can b xprssd as: T = T + ρ T + T (12) rq b n ρ = (13) n Whr T rq is th torqu rqustd by th drivr; T ( 0) b is th rquird torqu for th friction brak syst to dlivr; T is th rquird torqu for th otor to supply, and th otor torqu is constraind ISSN: Issu 7, Volu 5, July 2008

7 by th battry scurity as wll as th otor capability; T is th torqu rquird for th ngin to dlivr; ρ is th spd ratio btwn th otor shaft and th ngin shaft; n th otor and th ngin rspctivly., n ar th spd of In ordr to guarant th fficincy as wll as th scurity of th battry s charging and discharging prforancs whnvr th paralll HEV is oprating, th control stratgy should kp th balanc of th battry SOC. Thr ar ainly two thods daling with th battry SOC control for th paralll HEV [16, 17]: Th first thod is iplntd by controlling th SOC btwn th lowr SOC liit ( S ) and th L uppr SOC liits ( S ), which ar prdfind by th H control stratgy for th us of th battry. If th actual SOC is lss than S L, th battry is activly chargd by th hybrid syst; If th actual SOC is gratr than S H, th hybrid syst stops both activ charging and passiv charging which is rgnratd during barking and dclrating. Th scond thod is iplntd by dfining a targt valu of SOC ( S ). Whnvr th SOC T dviats fro th S, a charg or discharg T coand is gnratd by th control stratgy to control th SOC closr to th S T. Th or th SOC dviats fro its targt, th highr powr th battry is rquird. For both thods, in ordr to dcras th nrgy losss during charging and discharging procss, th SOC is always controlld in th rgion whr both intrnal charg and discharg rsistanc is rlativ sall. In our work, th first thod is slctd for battry control. According to th torqu rqustd by th drivr, th torqu distribution stratgy should b analyzd for two diffrnt situations: (1) Th torqu rqustd by th drivr is ngativ which ans that th vhicl is undr th braking procss. Th otor rcovrs th axiu possibl rgnrativ braking nrgy within th constrains iposd by th otor, th battry, th braks and th vhicl stability considrations. Th dficincy of th brak torqu, if xists, is ad up by th friction braks syst. (2) Th torqu rqustd by th drivr is positiv which ans that th vhicl is undr th driving procss; th rqustd torqu is distributd btwn th ngin and th otor. In ordr to iplnt th LTTDCS, a coupl of ngin working curvs should b prdfind for th ngin control [18,19]: th ngin axiu torqu curv T ax ; th ngin optial fficincy torqu curv opt T ; th ngin iniu stady rotary spd working curv n in ; off th ngin iniu oprating torqu curv. Th prdfind working curvs ar shown in Fig. 8. Fig.8 Torqu distribution stratgy for PHEUB Basd on th dfind ngin working curvs and th battry SOC, th torqu distribution stratgy of th paralll HEV can b dvlopd according to th following ruls: in If n < n, th clutch is disngagd and th otor drivs th vhicl alon, whr n is th actual rotation spd of th ngin. rq in Undr th condition that T < T : if th bat try SOC is rlativly high, th otor drivs th vhicl individually, andt rq = 0 ; if battry SOC is rlativly low, th ngin drivs th vhicl and provids xcss charg torqu, which passs through th otor to charg th battry for kping th balanc of th battry SOC and th nhanc load rat of th ngin for iprovnt of th ful conoy, and T < 0. in rq ax Undr th conditi on that T : if < T < T battry SOC is rlativly low a nd thr is torqu lft for th ngin bsids satisfying th torqu rqustd by th drivr, th battry is chargd by fding ths rsidual torqu to otor; if battry SOC is rlativly high, th vhicl is just drivn by ngin alon, thnt = 0. rq ax Whnvr T > T, which ans th ngin torqu availabl can not satisfy th rquirnt of th torqu rqust fro drivr, th ngin drivs th vhicl at axiu torqu T ax and th otor is T ISSN: Issu 7, Volu 5, July 2008

8 rq ax activatd to ak up th diffrnc ( T T ) for assistant driving. Th control stratgy ntiond abov is basically a rul-basd control stratgy. Whn a crtain condition is satisfid, th hybrid syst oprats in th corrsponding od. For xapl, undr th condition that th acclration pdal is prssd slightly, whil th vhicl vlocity is low nough and th battry SOC is high nough, th hybrid syst oprats in lctrical driving od. Though this control stratgy has any advantags, such as that it is sipl and asy to b iplntd into th C progra languag cods which aks it accptabl to ral-ti control application, dos not rquir any lins of cod, and coputationally fficincy and robust, LTTDCS appars to hav so drawbacks, such as th ability to optiiz vhicl prforanc is liitd, th ngin oftn oprats at non-optial fficincis and th charging of th battry is prford at tis without considration th loss paths for th particular oprating point. Sinc th control stratgy would not ncssarily rsult in a balanc of battry SOC, th battry would probably b chargd or dischargd ovr ti, and th controllr would vntually hav to switch to a charging or discharging od forcibly to rstor th battry charg. Th ovrall fficincy of th hybrid syst will b coproisd, vn though th ovrall fficincy bfor is rlativly high. In ordr to ovrco ths drawbacks and ak th hybrid syst work in th axiu ovrall fficincy, an instantanous optiization algorith is introducd to rctify th LTTDCS. Th purpos is to kp th balanc of th battry SOC and utiliz th vhicular nrgy or ffctivly than bfor. Th advantag of th introducd optiization algorith is that it not only considrs th fficincy losss and th fr rgnrativ nrgy, but also ts th rquirnt of ral ti control [18]. Sinc th objctiv of optiization is th ngin oprating point, onc th syst ntrs into th oprating ods whr th ngin is wording in, control coand is gnratd to shift th ngin oprating point closr to th points, which ak th ovrall fficincy of th hybrid syst or optial. Th optiization algorith of th ngin oprating points is dscribd as th following stps: (1) Stup th ful consuption look-up tabl Q ) indxd by th ngin torqu and th ngin (,t spd. (2) Stup th battry SOC variation look-up tabl of th ( ) indxd by th input or output powr of Q s,t th battry and th battry SOC. (3) Dtrin th fasibl working rang by using th following quation. T = T,nax : Ts : T,pax Whr T is th otor output torqu of ach valid candidat oprating point; T,nax and T,pax ar th axiu ngativ and positiv torqu of th T otor rspctivly; s is th calculation stp of th T otor torqu, th sallr th s is, th bttr th calculation rsults would b. (4) Calculat th ful consuption Q i for ach candidat oprating point by looking up th ap of th ful consuption tabl Q. For th point whr, t T = 0, th ful consuption is dnotd as Q. 0 (5) Calculat th Δ S gnratd by c, i T for ach candidat oprating point by looking up th battry SOC variation tabl Q. It is notworthy s,t that positiv otor torqu gnrats ngativ ΔS c whil ngativ on gnrats positiv Δ S. c (6) Calculat th rgnrativ nrgy Δ S c, r basd on th statistics of typical driving cycls and th past driving data. Δ S is usd to corrct th c, r Δ S c, i in stp (5): Δ S = c, i Δ S + c, i Δ S. c, r Although th lctricity nrgy obtaind fro th vhicl kintic nrgy rcapturd by th rgnrativ braking can not b prdictd bforhand, it can b stiatd by tracking th rgnrativ nrgy during th driving cycl and avraging it ovr a crtain ti priod. (7) Stup th look-up tabl Q c, Δ by stablishing th rlationship btwn Q i and ΔS fro stp c, i (4)~(6). (8) Calculat th actual SOC chang ΔS c, a during a ti stp for ach candidat oprating points. In ordr to kp th battry chargconsud at currnt ti stp ust b copnsatd sustain, th aount of th lctricity nrgy in th futur. Thrfor, th aount of SOC copnsation should b: Δ S c, c = Δ S c, a. Its corrsponding ngin ful consuption Q, c can b obtaind by looking up tabl Q fro stp (7). c, Δ Th quivalnt ful consuption usd to copnsat ΔS is dnotd as c, c Q, which can c, i b calculatd by th quation Qc, i = Q, c Q. 0 (9) Th quivalnt ful consuption ndd to copnsat th qual Δ S at diffrnt SOC lvl c should b diffrnt. In ordr to rgulat th pric of lctricity with diffrnt SOC, a pnalty function ISSN: Issu 7, Volu 5, July 2008

9 which is shown in Fig. 9 is introducd to corrct th quivalnt ful consuption: Q, r = Qc, i f ( soc), whr Q, r is th corrctd quivalnt ful consuption [20]. Fig. 9 Pnalty function for SOC corrction (10) Calculat th total ful consuption Q = Q + Q. t, i i, (11) Rpat stp (8)~(10), Calculat Q t, i for ach candidat oprating point. According to th oprating od transition control rul as wll as vhicl currnt oprating od, th iniu ful consuption oprating point is slctd as th ost optial oprating point Th flowchart of th optiization control algorith is shown in Fig. 10. Th iplntation of th proposd controllr within th vhicl is dpictd in th control sch shown in Fig.11. Th proposd control stratgy is coposd of two oduls: on is th LTTDCS odul; th othr is th instantanous optiization algorith odul. Th whol control procss is dscribd as follows: first, th LTTDCS is usd to dtrin th dsird dstination oprating od basd on th fdback vhicl inforation such as vhicl actual spd, ngin actual ngin, otor actual spd, battry SOC, gar location and clutch status as wll as th sapld A/D inforation fro r th acclration pdal, braking pdal and th gar shift handl which rprsnts th drivr s intntion; and thn, th optiization algorith is utilizd to sarch for th optial working points insid th dsird opration od, and ov th working point closr to th optial oprating point. Start Dfin working ara: T,i =T,nax : Ts : T,pax For i=1:n T,i=Trq-T,i Coput th ful consuption for ach candidat oprating point: Qi= Q,t(T,i,n) T,i==0 Qi=Q0 Coput SOC variation ΔS c, i gnratd by T for ach candidat oprating point: ΔS c, i = Qs,t(T,i,,n, SOC) Corrct SOC variation ΔS c, by i rgnrativ ngrgy ΔS c, for ach r candidat oprating point: ΔS c, i = ΔSc, i + ΔSc, r Establishing rlationship tabl btwn ful consuption Qi and SOC variation ΔS c, i : Q, Δ( ΔSc, i) 1 1 For i=1:n Dtrin th corrsponding SOC copnsation basd on SOC variation: ΔS c, c = ΔSc, i Coput th corrsponding ngin ful consuption basd on SOC variation ΔS c, : c Q, c = Q, Δ ( ΔSc, i ) Coput th corrsponding quivalnt ful consuption corrsponding to SOC variation ΔS c, : c Qc,i=Q,c-Q0 Corrct th quivalnt ful consuption for ach candidat oprating point: Q, r = Qc, i f(soc) Coput ovrall ful consuption for ach candidat oprating point: Qt, i =Qi + Q, r Gt th iniu valu of th ful consuption and rcord th corrsponding indx: Qopt = in(qt, i); p= i; Gt th optial oprating point: T=T, p, T=T, p Fig.10 Flowchart of th optiization control algorith End ISSN: Issu 7, Volu 5, July 2008

10 Drivr intntion Oprating Rul Fig.11 Iplntation of th proposd control stratgy controllr in applid PHEUB 5 Validation of th Control Stratgy In ordr to us th siulation odl dvlopd in Sction 3, any siulations ar prford to validat th proposd control algorith (Optial Control Stratgy, OCS). Th siulation rsults ovr th China Typical Bus Driving Schdul at Urban District (CTBDS_UD) with th initial SOC of 0.5 and 0.7 ar shown in Fig.12(a) and Fig.12(b) rspctivly, which illustrat th ngin torqu ( T ), th otor torqu ( T ) as wll as th drivr s rqust rq torqu ( T ) by intrprting acclration and brak pdal. Th battry SOC and th vhicl vlocity variations ( ) ar also rcord and prsntd in th u a figurs. Fig. 12 also rvals that th SOC rains within th oprational rang in spit of th initial SOC. Fro Fig.12(c), which prsnts th changs of th SOC ovr a long ti horizon siulation (3 CTBDS_UDs), it can b obsrvd obviously that th proposd control stratgy works vry wll in aintaining th SOC. At th bginning, th SOC is rlativly low (0.3) and th control stratgy uss th ngin ostly to rcharg th battry in addition to satisfying th vhicl rquirnt. With th incras of th SOC, th lctricity usag incrass. Th siulation rsults donstrat that th proposd control stratgy is ffctiv in aintaining th SOC. (a) With th initial SOC of 0.7 ISSN: Issu 7, Volu 5, July 2008

11 (b) With th initial SOC of 0.5 (b) With th initial SOC of 0.5 (c) Chang of th SOC ovr a long ti horizon siulation. Fig. 12 Siulation rsults using OCS Fig.13 prsnts th siulation rsults using th logic torqu distribution stratgy without optiization algorith (LTTDCS). It is obsrvd fro th coparisons btwn Fig.13 and Fig.12 that, th ngin load is rlativly high ovr th cycl in Fig.13, whil rlativly sall in Fig.13. Th ngin probably frquntly oprats in non-highfficincy rang using th LTTDCS. Fig. 13 Siulation rsults using LTTDCS In ordr to invstigat th bhaviors of th ngin, th ngin oprating points (sapl ti is 1s) ar calculatd and scattrd into th torquspd plan with th initial SOC valu of 0.7 for two diffrnt control stratgis, as shown in Fig.14. Th background of th figur is ad up of ful fficincy contours and th axiu torqu curv of th ngin. For th OCS, th oprating points of th ngin ar ostly concntratd in th high fficincy rang; whil for th LTTDCS, th oprating points of th ngin ar sprad out ovr th ap and any of th ar in th low load and low fficincy rang. This indicats that th OCS is or ffctiv in controlling th ngin oprating in high fficincy rang. In addition, it is ncssary to xplain that so of th points nar th coordinat axis ar not th ral ngin working points. Thy ar th transition points of th ngin during start or stop procss, which ar sapld by th siulation odl. (a) With th initial SOC of 0.7 (a) LTTDCS ISSN: Issu 7, Volu 5, July 2008

12 Tabl 3. Ful conoy siulation rsults coparison btwn LTTDCS and OCS Avrag fficincy OCS LTTDCS (b) OCS Engin (%) Motoring (%) Gnrating (%) Battry discharging (%) Battry charging (%) Drivtrain (%) Initial SOC (%) End SOC (%) Ful conoy (L/100k) Ful conoy with SOC corrction Q s /(L/100k) Fig.14 Oprating points of th ngin with th initial SOC of 0.7 using (a) th LTTDCS (b) OTCS on CTBDS_UD. Th coparisons of th ful conoy rsults as wll as th fficincis of th ain coponnts btwn OCS and LTTDCS ovr CTBDS_UD with th initial SOC of 0.7 ar suarizd in Tabl 3. Th data in Tabl 3 donstrat again that th OCS is or ffctiv than th LTTDCS in kping th ngin oprating at high fficincis. Th avrag fficincy of th ngin for th OCS is 35.45%, whil that for th LTTDCS is only 29.42%. No significant diffrnc xists btwn th avrag fficincis of th two stratgis for th otor and th battry, bcaus th fficincis of th otor and th battry ar rlativly high inhrntly, and th high fficincy rangs ar uch widr and insnsitiv to load. Although th ful conoy for th LTTDCS (23.25 L/100 k) is lss than that for th OCS (25.12 L/100 k), th SOC drops only by 2% for th OCS whil by 15% for th LTTDCS. Nin sts of ful conoy and SOC chang rsults ar obtaind by siulation ovr th sa driving cycl svn tis with diffrnt initial SOC fro 0.3 to 0.7 for ach run. A linar rgrssion is usd to calculat th corrctd ful conoy corrsponding to th zro SOC chang ovr th cycl. Th corrctd ful conoy for th OCS is L/100 k and for th LTTDCS is L/100 k. It is thus obvious that th OCS is suprior to th LTTDCS in trs of ful conoy. 6 Conclusion Th ral-ti optial control stratgy is th ky tchnology for PHEUB. In this papr, a novl control stratgy using torqu distribution stratgy is proposd with th corporation of instantanous optiization algorith. This control stratgy is dvlopd in two stps: First, logic torqu distribution control ruls ar suarizd by utilizing nginring intuition and analysis of coponnt fficincy tabls or charts; Nxt, an instantanous optiization algorith is applid to conqur th inhrit dficincis of th currnt torqu distribution stratgy and thrfor achiv rlativly highr ovrall nrgy fficincy. Exprintal data of th ngin, th otor and th battry ar usd for th fd-forward syst odling of PHEUB by using Matlab/Siulink. Siulation rsults anifst that not only th ful conoy of PHEUB is iprovd significantly but also th battry SOC aintains within its oprating rang whil satisfying th rquirnt of th drivr. In suary, th proposd thod that intgrating thortical algorith with nginring practical xprincs is fasibl, and th ral-ti control stratgy prsntd in this papr is ffctiv and practical. As for th futur rsarch rgarding odling and th dvlopnt of th control stratgy for paralll hybrid lctric urban buss, two aspct contnts should b addd. On is for syst odling, th othr is for syst control. As for odling of th hybrid powrtrain syst, thr is a rquirnt to incras th prcision of th xisting odl. Morovr, in ordr to invstigat th dynaic control of th gar-shifting procss and oprating od transfr, a transint dynaic siulation odl of th HEV should b proposd to facillat th rsarch and dvlopnt of th vhicl control ISSN: Issu 7, Volu 5, July 2008

13 stratgy. Anothr aspct of th contnts is that th function of th fault protction and procssing during th vhicl driving should b add to th control stratgy. Acknowldgnts This projct is supportd by Scinc and Tchnology Coission of Shanghai Municipality China (Ky Tchnology Rsarch Projct for Hybrid Elctric Urban Bus, No ). Rfrncs: [1] Lin, C. C., t al., Intgratd, fd-forward hybrid lctric vhicl siulation in Siulink and its us for powr anagnt studis. SAE Papr No , [2] Koo, E. S., t al, Torqu control stratgy for a paralll-hybrid vhicl using fuzzy logic, Procdings of th 1998 IEEE Industry Application Confrnc, St.Louis, Missouri, USA, 1998, pp [3] L, H. D., t al, Fuzzy-logic-basd torqu control stratgy for paralll-typ hybrid lctric vhicl, IEEE Transaction on Industrial Elctronics, Vol.45, No.4, 1998, pp [4] Schoutn, N. J., t al., Fuzzy logic control for paralll hybrid vhicls, IEEE Transaction on Control Systs Tchnology, Vol.10, No.3, 2002, pp [5] Schoutn, N. J., t al., Enrgy anagnt stratgis for paralll hybrid vhicls using fuzzy logic. Control Enginring Practic, Vol.11, No.2, 2003, pp [6] Johnson, V. H., t al., HEV control stratgy for ral-ti optiization of ful conoy and issions. SAE Tchnical Papr, , [7] Paganlli, G., t al., Gnral suprvisory control policy for th nrgy optiization of charg-sustaining hybrid lctric vhicls. JSAE Rviw, Vol.22, No.4, 2001, pp [8] Paganlli, G., t al., Siulation and assssnt of powr control stratgis for a paralll hybrid car. Procding of Institut of th Mchanical Engirs Part D: Journal of th Autoobil Enginring, Vol.214, No.7, 2000, pp [9] Lin, C. C., t al., Powr anagnt stratgy for a paralll hybrid lctric truck, IEEE Transaction on Control Systs Tchnology, Vol.11, No.6, 2003, pp [10] Galdi, V., t al., Multiobjctiv optiization for ful conoy and ission of HEV using th goal-attainnt thod, Procdings of th 18 th Intrnational Elctric Vhicl Syposiu, Brlin, Grany, [11] Dlprat, S., t al., Optial control of a paralll powrtrain: fro global optiization to ral ti control stratgy, Procdings of th 18th Intrnational Elctric Vhicl Syposiu, Brlin, Grany, [12] Powll, B., t al., Dynaic odling and control of hybrid lctric vhicl powrtrain syst, IEEE Control Syst Managnt, Vol.18, No.5, 1998, pp [13] Karn, L., t al., Matlab-Basd Modling and Siulation Packag for Elctric and Hybrid Elctric Vhicl Dsing, IEEE Transaction of Vhicular Tchnology, Vol.48, No.6, 1999, pp [14] Pu, J., t al., Modling and dvlopnt of th control stratgy for a hybrid car, Journal of Shanghai Jiaotong Univrsity, Vol.38, No.11, 2004, pp [15] Johnson, V. H. Battry prforanc odls in ADVISOR, Journal of Powr Sourcs, Vol.110, No.2, 2002, pp [16] Dong,Y. H., t al., A nw typ copositiv hybrid powr syst-e.t.drivr and its application in HEV. WSEAS Transactions on Systs, Vol.7, No.3, 2008, pp [17] L, Y. B., t al., Dsign and prforanc analysis of air blowr syst opratd with BLDC otor for PEM FC vhicl, WSEAS Transaction on Systs, Vol.4, No9, 2005, pp [18] EI-Sousy, F.M., t al., Fuzzy adaptiv nuralntwork odl-following spd control for PMSM drivs. WSEAS Transactions on Systs, Vol4, No4, 2005, pp [19] Fukuo K, t al., Dvlopnt of th ultra-lowful-consuption hybrid car-insight. JSAE Rviw, Vol.22, No.4, 2001, pp [20] Sasaki, S., t al., Toyota s nwly dvlopd lctric gasolin ngin hybrid powrtrain syst, Procdings of th 14th Intrnational Elctric Vhicl Sysposiu, Orlando, Florida, USA, [21] Nils, J. S., t al., Fuzzy logic control for paralll hybrid vhicls. IEEE Transaction on Control Systs Tchnology, Vol.10, No.3, 2002, pp [22] PU, J., t al., Fuzzy torqu control stratgy for paralll hybrid lctric vhicls. Intrnational Journal of Autootiv Tchnology, Vol.6, No.5, 2005, pp [23] Paganlli, G., t al., Control dvlopnt for a hybrid-lctric sport-utility vhicl: stratgy, iplntation and fild tst rsults. ISSN: Issu 7, Volu 5, July 2008

14 Procdings of th Arican Control Confrnc, Arlington, Virginia, USA, 2001, pp ISSN: Issu 7, Volu 5, July 2008