`l. Forster. Bso, PhD
`
`3
`
`oerosmos
`EXHIBIT
`
`Indexing remit: Optimal control. Oprirnisartort, rilgarithms, Mathentattcnl technique:
`
`Abstract: The paper examines the potential of
`hybrid electric vehicles and, in particular, a hybrid
`electric passenger-car. Two operating objectives
`are identified. one for energy saving and the other
`for
`substituting petroleum fuel by electrical
`energy. The way in which the power train control
`and component rating can be optimised to meet
`these particular operating objectives isdiscussed.
`in the final part of the paper the performance of
`the optimised hybrid vehicles are compared with
`both IC engine and electric vehicles and the pet-
`roleum substitution design is shown to warrant
`further development.
`
`‘I
`
`Introduction
`
`A hybrid vehicle can be defined as a vehicle which utilises
`two or more energy storage mediums within its drive
`train, any of which is capable of driving the vehicle when
`connected to the road wheels through a suitable prime
`mover. In this paper, the hybrid electric vehicle is con-
`sidered with cncrgy being stored in petroleum fuel and an
`electric traction battery. The associated prime movers are
`
`engine power and speed to be controlled independently
`of the power and speed demand at the road wheels. In
`contrast.
`the second basic arrangement connects both
`prime movers in parallel, as shown in Fig. 2. In such a
`parallel arrangement, both prime movers are capable of
`driving the road wheels directly with the ‘mix’ of power
`at any instant beingcontrollod.
`The first hybrid vehicles appeared in the early part of
`this century when the electric traction motor was used to
`augment the power output of the then limited IC engine
`[1]. However, the rapid development of the IC engine
`soon made the electric traction motor unnecessary and
`hybrid vehicles were not again considered seriously until
`the 19605. At this time. concern was being expressed at
`the level of exhaust emissions from conventional [C
`engine vehicles, and the hybrid emerged as one possible
`way in which exhaust emissions could be dramatically
`reduced [2]. However, with the oil crises of 1974 and
`1979 there became immediate concern about the depen-
`dence of the Western World on oil-based fuels. The
`hybrid vehicie now became one possible way of reducing
`the dependency of the transport sector on petroleum-
`based fuels, either by reducing the amount of energy used
`[3] or by substituting petroleum fuel by broader based
`electrical energy [4]. These latter objectives are equally
`wheels
`
`oecelerotor
`
`bro he
`
`controller
`
`Fig. 1
`
`Series hybrid electric vehicle drive train
`
`an internal combustion (IC} engine and electric traction
`motor.
`respectively. To utilise the prime movers. a
`number of difierent power train configurations are pos-
`sible. but, in general, fall into one or two basic categories.
`In the series arrangement of Fig.
`l, the IC engine does
`not drive the road wheels directly, but is connected indi-
`rectly through an electric generator and electric traction
`motor. Introducing a traction battery between the gener-
`ator and motor buffers the engine output, allowing the
`
`Paper 552lD [C12, S1) received mt February was
`The authors are with the Departrttent of Engineering. University or
`Durham. Sdenee Laboratories, South Road, Durham DHI 3LE.
`United Kingdom
`
`LEE rnocesorucs, Vol. :34. Pr. 0. No. 5, NOVEMBER :93:
`
`occelr.-rotor
`
`Fig. 2
`
`Parallel hybrid electric uehicfe driue train
`
`3‘-'3
`
`Page 1 of 15
`
`FORD EXHIBIT 1104
`
`1
`
`PAICE 2112
`Ford v. Paice & Abell
`IPR2014-00579
`
`
`
`valid today, and it is this particular aspect of reducing
`the dependency of road vehicles on petroleum-based fuels
`that this paper addresses.
`To achieve the objectives outlined so far, both series
`and parallel hybrid anangeznents have been evaluated in
`the past. Although the series arrangement allows great
`flexibility in component positioning, it is not a generally
`favoured arrangement. The main reason for this is that
`the acceleration and maximum continuous speed require-
`ments of most vehicles necessitates the use cl’ :1 large,
`heavy and expensive traction motor rated to meet both
`the maximum torque and maximum continuous power
`demand of the vehicle. Consequently. when the vehicle is
`used over mild urban driving cycles. the traction motor
`operates at part
`load with a relatively low efficiency.
`When this is combined with the cfliciency of the gener-
`ator. controller and IC engine,
`the result
`is reduced
`energy performance when compared with the parallel
`arrangement [5]. However, if a vehicle is to be designed
`for a specific duty cycle, for example a city bus, then the
`potential of the series arrangement increases. Indeed, it is
`for this particular use that the series hybrid has seen most
`development [6, 7].
`As a result of these considerations, it is the parallel
`hybrid arrangement that offers most potential. However,
`even within this framework, the component arrangement,
`rating and control offers innumerable possible alterna-
`tives. To develop a suitable control strategy, and decide
`on the appropriate component sizing and arrangement. a
`number of
`studies have
`been
`commissioned and
`published, for example see References 3 and 9. The most
`recent of the hybrid vehicle studies have been conducted
`during the feasibility stage ol the Near Term Electric and
`Hybrid Vehicle Programme commissioned by the US
`Department of Energy [10]. The tendency in all of the
`most recent studies is to use some form of computer
`simulation to assess the performance of the vehicle over a
`predefined driving cycle. Parametric studies are then con-
`ducted to show how modifications in control strategy,
`component sizing and arrangement effect the vehicle per-
`formance. Typical of these studies are those conducted by
`the General Electric Company (USA) [11, 12], where
`computer simulation methods were used to evaluate and
`design a hybrid vehicle suitable for the American car
`market. The aim of this vehicle being to substitute pet-
`roleum fuel by ‘wall plug electricity‘.
`in this paper, rather than postulating a number of
`control options and exploring their relative benefits, an
`optimisation process is used which seeks to minimise an
`energy—based objective function, the aim of which is to
`reduce the dependence of the vehicle on petroleum-haw
`fuels. This process then leads to the definition of a
`control algorithm that can be used in a vehicle suitable
`for the European car market. Parametric studies are then
`conducted to optimise component ratings and further
`improve the vehicle performance. The final part of the
`paper compares the optimised hybrid dcsign[s) with an
`IC engine vehicle and electric vehicle, and their relative
`features are discussed.
`
`2
`
`Base vehicle parameters
`
`A previous analysis of the UK national energy statistics
`has shown that,
`in the road transport
`sector, cars
`between lollflcc and 2000cc (cc-—_:cm’) are the major
`users of petroleum fuel. consuming approximately 40%
`of all the energy used [13]. They also represent a large
`market in potential sales, with approximately one million
`374
`
`vehicles being sold per annum. Consequently, it’ either a
`reduction in the amount of petroleum used, or a transfer
`from petroleum to electrical energy could be achieved
`within this market,
`there is significant potential for a
`‘reduction in the UK dependence on petroleum-based
`uel.
`Analysis of the usage pattern of the type of vehicle
`described here shows that 95% of all car journeys are less
`than 30 km and could, therefore, be satisfied by an elec-
`tric vehicle. However, the usage pattern also shows that
`this type of vehicle is used regularly for journeys in excess
`of 80 km, for example at weekends and holidays. Conse-
`quently, although 95% of all journeys are under 80 km,
`any vehicle restricted to 30 km or less may only be useful
`80% of the time [14] and would be unlikely to find
`general acceptance. For any hybrid vehicle to be
`accepted, it must achieve a reduction in the petroleum
`fuel used, while not suffering the range limitation of the
`electric vehicle.
`An initial set of parameters representative of a parallel
`hybrid car able to meet these needs are outlined in Table
`I. The size of the [C engine has been selected to give a
`maximum level cruise speed in exoem of 120 km/h. while
`the electric traction motor augments this to provide the
`necessary acceleration performance and low-speed elec-
`tric opcration. The torque/speed envelope for the com-
`bined systcm is shown in Fig. 3. A set of parameters for
`250
`
`.. ano
`
`turque_Nm
`
`5000
`
`FOOD
`
`4000
`3030
`ZDCO
`engine speed, revlmin
`Rare hybrid‘ electric pev;fJrrn.orrcecrti'r:e.s
`Fly. 3
`a Combined maximum torque line
`it Traction motor torque
`4: Engine mu throttle torque
`A ccralant spa.-d rond load
`
`an equivalent IC engine car are also included in Table I.
`In both cases, performance is comparable and, through-
`out
`the paper, vehicles will be compared assuming a
`similar performance criterion with component weight
`changes being automatically included. A weight propaga-
`tion lactor of 1.35 is used throughout
`the study. To
`achieve uniformity in terms of body perforrnance, both
`the hybrid and the IC engine vehicle are assumed to have
`the same drag and rolling resistance characteristics. This
`ensures that any benefits accruing from the hybrid are
`identified as coming from the power train. The values
`used are typical of good present day vehicles.
`In assessing the performance of the hybrid Vehicle,
`the standard European urban driving cycle, ECE-15, is
`used along with 90 km/ii and 120 ltrnfh cruise results.
`IEE PROCEEDJNCFS. Vol. :34, n. o, No. 5. NO vsmaes :93?
`
`Page 2 of 15
`
`FORD EXHIBIT 1104
`
`2
`
`
`
`Table 1: Base vehicle data
`
`Parallel hybrid
`
`Conventional
`
`before any control can be attempted, it is necessary to
`define precisely the purpose of the control. For example,
`
`Vehicle weights:
`kerb weight
`test weight
`battery
`Vehicle parameters:
`C,
`C’,
`A
`Component sizes:
`It‘: engine
`traction motor
`batlerv
`
`final drive
`transmissions
`
`Pertorrnance
`0-60 milejh
`(driver only)
`Max. speed:
`It: engine only
`hybrid
`' at 5000 rev]:-nin
`
`1340 kg
`1330 kg
`300 kg
`
`0.35
`0.01
`1.95 m'-’
`
`945 Itg
`1‘|B5|tg
`
`0.35
`0.01
`1.95 m’
`
`Izlcet-Ierotion
`
`55 law. 5000 r.o.m.
`—
`—
`
`velocity
`
`35 kw. 5000 tevfmin
`35 kw. shunt
`laadfaeid EV2-‘I3
`E, u too k..I;Iq;
`(42 Wltfkg)
`3.5 : ‘I
`danced automatic
`gear ratios
`1st
`3.5 :1
`2nd 2.4: 1
`3rd
`1.3 .' 1
`-Iltlt
`1.0 : 1
`
`14 a
`
`130 kmfh
`145 ltm,-‘h
`
`3.5 : 1
`abspeed manual
`I
`3.5:
`:1
`.4
`2
`:1
`.3
`I
`:1
`.0
`1
`
`2
`
`145 Itn1,!h'
`
`Fig. 43
`
`J22?‘ schedule ‘a ' series afdriuing cycles
`
`Parameter
`
`Maiccpeed
`v:.m'tIn'h
`llu:el.li.Tl'Ie
`r,.s
`Cruisetime
`t,.s
`Coaslliroe
`r,_.s
`Brnlrerir-no
`r,.s
`ldluirne
`r_.s
`Totallirne.
`:
`
`A
`
`Driving cycle
`I:
`
`E
`
`D
`
`ltltl
`
`-Itl
`0
`
`11:1
`3;t:t
`
`2011
`1?-_t:1
`I.9:l:l
`
`30:1
`Hit!
`
`205:].
`
`8;|:l
`411
`st: 91!
`
`-151:1
`2312
`
`50:2
`llilgl
`
`9:1
`15-_l-2
`
`Silil 25:2 2512
`39:2 72:2 8012 I121!
`
`the main objective of the control may be to maximise the
`accelerative perforrnancc of the vehicle, minimise exhaust
`emissions or to minimise energy use. An alternative
`objective, and the subject of this paper,
`is to examine
`ways
`in which the dependence of
`the vehicle on
`petroleurn—based fuels can be reduced. This objective can
`be achieved either by improving the overall energy con-
`sumption of the vehicle, or by transferring some of the
`energy demand to the electrical system. To examine the
`type of control policy that would achieve this, an energy-
`based objective function:
`
`F:-2,5, +2,e,
`
`in
`
`is defined, where E, and E, are the onboard petroleum
`and electrical energy requirements, respectively, and R,
`and A; are weighting factors.
`The two energies E, and E, depend on the way in
`which the load is divided between two prime movers.
`Examination of Fig. 2 suggests that the demand torque
`could be supplied either by the IC engine or the electric
`motor alone, or from some appropriate combination oi
`the two. Indeed, the IC ennc could supply torque in
`excess of the value demanded at the road wheels, such
`that the excess energy is used to charge the traction bat-
`teries. These various possibilities can be rationalised by
`defining a torque split fraction. or ratio. which defines
`the percentage of the road torque supplied by the IC
`engine as shown in Fig. 5. AI torque split values in excess
`of one, the IC engine supplies the full torque demand,
`and additional energy is used to charge the traction hat-
`teries.
`Although E, and E, depend directly on the ratio in
`which the demand torque is divided between the two
`prime movers, they are also dependent on the efficiency
`of the prime movers and associated equipment. As the
`375
`
`The ECE.-15 cycle is shown in Fig. 4A and, besides defin-
`ing precisely the velocity time profile, gear change points
`are also defined. As will be seen in Section 6, the use of a
`different gear change schedule, optimised to the actual
`vehicle, can significantly reduce the urban fuel consump-
`tion. ,¢.s the hybrid vehicle necessitates total control of
`the drive train, the ECE-l5 gear change schedule will not
`be adhered to- This is similar to current testing practice
`for vehicles with automatic transmissions.
`£0
`
`velocity,rmlerh atB8
`
`
`
`velocitylrrnlh
`
`M
`
`6
`
`0
`
`20 M)
`
`60
`
`120 MO 160 180 200
`
`100
`BO
`time ,5
`Fig. 4% ECE-I5 when driving cycie
`
`The ECE-15 cycle is a relatively mild cycle and,
`because of this, some aspects of hybrid vehicle per-
`formance can be difficult to interpret clearly, while when
`a slightly more severe cycle is used these performance
`aspects are clarified. In such situations, ECE-15 results
`are augmented by simulations over the 32273-D urban
`cycle shown in Fig. 4B.
`
`3
`
`Hybrid vehicle control
`
`3.1 Control optimisation
`When two or more power sources are used in a vehicle
`power train. the way in which they are controlled is fun-
`damental
`to the performance of the vehicle. However,
`IEE PROCEEDINGS, Vol. I3-I, Pt. D, No. 0. N0 VEMBER I983
`
`Page 3 of 15
`
`FORD EXHIBIT 1104
`
`3
`
`
`
`elliciency of either the engine or the traction motor
`depends strongly on its operating torque and speed, then
`
`0.5
`torque split rolio
`
`Efect cflarqtae split ratio on the torque distribution
`Fig. 5
`a [C engine torque
`b Electric motor torque
`er + b Demand torque
`
`torque split ratio and transmission gear ratio are the two
`control variables within the drive train that vary the
`value of the objective function at any given demand
`load. The aim of the control optimisation is therefore to
`minimise the objective function defined in eqn. 1, with
`torque split and gear ratio as the control variables.
`During a driving cycle, the torque demand and oper-
`ating speed of the prime movers is continually changing,
`and therefore it is necessary to minimise the objective
`function on a continuous basis. To implement the opti-
`misation process, the hybrid vehicle is simulated over a
`defined driving cycle using the Janus road vehicle simula-
`tion program [IS]. This program calculates the torque
`and speed requirement at the road wheels, at each second
`of the driving cycle, and then reflecls this demand back
`through the power
`train to the energy sourcefs)
`to
`compute the net
`input energy required over that one
`second interval. Throughout this process, full account is
`taken of the losses associated with each of the drive train
`components. These losses vary both with load and speed
`and, within the prime movers, can be particularly
`complex. For these components. efficiency maps of actual
`components are used. By calculating the energy supplied
`from both the IC engine and the battery at each time
`instant, over a range of torque splits and for all gear
`ratios, a three-dimensional map can be generated with
`torque split ratio and gear ratio as the two independent
`variables and the objective function as the dependent
`variable. A direct search technique is then employed to
`find the minimum of the objective function. Repealing
`this process at each second throughout the cycle allows a
`minimum energy path through the driving cycle to be
`obtained.
`
`1 shows that E, and E,
`Further examination of eqn.
`are dependent on the ctficiency and operating character-
`istics of all the power train components, while at, and 1,
`allow a weighting to be placed on the relevant impor-
`tance of the two energy sources. By varying the ratio of
`weighting factors,
`llqplz,
`the effect on the control of
`placing greater emphasis on one energy source relative to
`the other can be assessed. By selecting the correct ratio of
`weighting factors. the effect of the conversion efficiency to
`the raw energy source (e.g. power station), the elTecl of
`376
`
`.
`
`Page 4 of 15
`
`FORD EXHIBIT 1 1 04
`
`I-‘IE PROCEEDINGS. Vol. :31. er. 9. Na. 6. NOVEMBER ms:
`
`different pricing policies, the influence of lite] supply or
`the influence of government policy towards electrical
`energy use on the hybrid control can be qualitatively
`assessed.
`When the torque split is greater than unity, battery
`charging is initiated and the flow of electrical energy
`becomes negative with all the energy being supplied from
`the petroleum fuel, 1:‘, now represents that proportion of
`the petroleum derived energy,
`less any conversion loss,
`that is converted to chemical energy and stored in the
`battery. To utilise this energy at a later time, account
`should be taken of the power train efficiency when this
`chemical energy is reconverted and appears at the torque
`split point. This reconversion elliciency includes
`the
`battery discharge efliciency, motor and controller ell"-
`ciency and the gear efficiency of the torque split. As this
`net efliciency varies with load and speed, an optimistic
`value cl‘ 90% is assumed implying a :1, value during this
`operating mode of 1.1 regardless of the value set on 1,.
`Throughout
`the optimisation process, although E,
`is
`directly related to the petroleum fuel used, E; is depen-
`dent on the rate at which the battery is discharged. E, is
`therefore calculated as the product of the incremental
`change in the battery state of charge and the battery five-
`hour energy capacity.
`The optimisation process must also lake into account
`any physical constraints imposed by the drive train. Fig.
`2 shows a clutch between the engine and transmission
`and, although an operating condition where this clutch is
`continually slipped or modulated can be conceived, it is
`not particularly attractive. The optimisation process is
`therefore constrained not to allow this mode of oper-
`ation.
`
`3.2 Optimal control of the base hybrid vehi'ci'e
`Implementing the above optimisation with the base
`hybrid vehicle parameters of Table 1 allows vehicle range
`(i.e. distance travelled until the battery is discharged] and
`petroleum use to be plotted against the ratio 4,121 for the
`ECE-15 driving cycle as shown in Fig. 6. The full curve
`in this Figure refers to the base vehicle with a standard
`
`....P:1
`
`
`
`
`
`luelconsumption_llll'Cl'lDlJItl'l'I
`
`0—-Nto:.~ulon4onno
`
`tuel consurnp Ion
`T“ '-~..
`
`0.25
`
`as
`
`to"
`
`1.25
`
`15
`
`0.75
`Mill:
`lryhcznee of weighting factor ratio on the pe|1'o.rmartce :5!‘ the
`Fig. 8
`bane hybrid vehicle
`j -tvspeed transmission
`- — - ~ Continuously variable lfl nsrnissinn
`at Fueteonsurnption at base [C engine vehicle
`It 80 ltm range. 9555 of all journeys
`0? 50 km range. 90% oiniljourneys
`d 30 lrm range. M-°Ai ofall journeys
`
`4
`
`
`
`centage of the cycle time that the engine spent in dilierent
`portions of the map is shown. The optimal control policy
`maximises engine eliiciency by moving each operating
`I00
`90
`59
`'30
`SD
`
`
`
`percentagecldemandtorquemetbyprimary
`
`sourcefl.
`
`
`
`speed,kmlh
`
`0
`
`20
`
`loll
`
`50
`
`it!)
`8)
`I‘In1e_s
`
`120
`
`ltd}
`
`150
`
`1B0
`
`10?}
`
`four—speed transmission, while the dashed lines show the
`effect of introducing a continuously variable transmission
`{CV'i'). At low ratios of 14/41, vehicle range is infinite, as
`the energy drained from the battery during motoring is
`replaced
`by
`energy recovered
`during regenerative
`braking. As J.,}A;, increases. the petroleum consumption
`reduces with range remaining infinite. When Alli, 20.3
`to 0.35, all the energy recuperated during regenerative
`braking is used during the motoring phase, and the state
`of charge of the battery is the same at the end of the cycle
`as at the beginning. At the other extreme when 41,141,
`is
`greater than one, the vehicle essentially operates as an
`electric vehicle with no petroleum fuel being used. In
`between thwe two extremes, as al,/A, is increased. greater
`emphasis is placed on the electrical system with increas-
`ing substitution of petroleum fuel by electricity.
`These observations lead to the specification of two
`types of hybrid vehicle. In the lirst vehicle, the battery
`state of charge is the same at the end of the cycle as at
`the beginning. with all the energy being supplied directly
`from the petroleum fuel. The electrical system now seeks
`to accept regenerative braking energy and provide pro-
`pulsion power when the IC engine efficiency is low. This
`has the effect of increasing the average engine load factor
`and efficiency. Battery weight should be minimised to
`improve the hybrid performance, and, as a result, no sig-
`nificant all—electric range should be anticipated. Such a
`vehicle can be termed an ‘energy saving hybrid’. In con-
`trast, the second type of vehicle sacrifices urban range for
`reduced petroleum fuel consumption, thereby achieving
`significant petroleum displacement. This would ideally
`require a battery weight above that of the base vehicle, to
`achieve a range as an electric vehicle of typically 60 km.
`Such a vehicle may be described as a ‘petroleum substi-
`tution hybrid’.
`
`3.3 Energy saving hybrid
`From an overall energy point of view /1, and .12 can be
`selected to represent minimisation of raw energy. If an
`eiliciency of 25% is assumed, for power generation, trans-
`mission and battery charging and an efficiency of 90%
`for the petroleum production process. 1,11, 2 0.28. This
`implies energy minimisation will be achieved with the
`energy-saving hybrid. However, should petroleum be
`produced from coal,.with a conversion efliciency of 60%,
`then energy minimisation would be obtained with
`Amt; 2 0.42. This now points to mild hybrid operation.
`Although the above argument indicates the type of
`hybrid design that would minimise energy use, an overall
`energy saving would only be achieved if a comparable 1C
`engine vehicle had a higher fuel consumption. The urban
`fuel consumption for the base IC engine vehicle described
`in Table l is shown in Fig 6, and is substantially higher
`than the fuel consumption of the energy-saving hybrid
`with optimal control.
`The variation of the two control variables, torque split
`and gear ratio throughout the cycle are shown in Fig. 7
`for the energy-saving hybrid with ll,/J1, :2 0.3 to 0.35.
`These results suggest that charging of the batteries from.
`the IC engine is not a favoured option owing to the low
`conversion and reeonversion eiliciency associated with
`this route, while operation on one or other of the two
`energy sources is generally favoured. When operating on
`the [C engine, the lowest gear ratio (highest gear) is sci-
`ected to increase the engine output torque, reduce engine
`speed and hence increase engine efficiency. Greater detail
`of how the [C engine is used during the cycle is shown on
`the engine usage map of Fig. 8. In this Figure. the per-
`IEE PROCEEDINGS. Vol. 134, Pt. D, No. 6, NOVEMBER I937
`
`Variation of torque split ratio [%l during the ECE-15 when
`Fig. TA
`driving cyclefor the optimally controlled’ energy saving hybrid’
`
`ED
`
`30
`
`ill] MD
`
`‘IEO
`
`130 200
`
`100
`1‘n-no.5
`Variation cfpear during the ECE-J5 when rlriufug cyclefor
`Fig. 73
`[lI£ optirrtnlly controlled energy saulng hybrid
`I00
`90
`BO
`-4 D
`O" G
`
`
`
`engineloadioctorflu
`
`.i'."- 0
`
`GalI.)I)‘o0ca
`
`an O
`
`D
`
`201:0
`
`SD
`
`ilDll!'.|l2D 150
`time}
`Variation of engine load factor during the ECE-I5 urban
`Fig. TC
`driving cyclefor the optimally controlled energy saving hybrid
`torque
`engine loud teeter -
`x 100%
`maximum torque available
`
`I50
`
`180 100
`
`‘I0
`
`50
`56
`ex6
`u0
`
`
`
`.oO(30_,
`
`
`
`
`
`motorloudtoelcrfr.
`
`Variation of motor load factor during the ECE-l5 when
`Fig. 70
`drlning eyrtefor the oprrmully controllld £8-9'91’ Sflltiflti -"J-'5'“ "‘”'~"‘
`
`171
`
`Page 5 of 15
`
`FORD EXHIBIT 1104
`
`5
`
`
`
`region as shown in Fig. 9, with increased emphasis being
`placard on the electric traction system.
`The distribution of torque between the two prime
`movers is shown in Fig. 10, for the base vehicle of Table 1
`with .1,/.1, 2 0.6 and subject to the constrained optimised
`:-.1:
`
`5338133383
`
`0
`
`20
`
`1.0
`
`60
`
`80
`I00
`time, 9
`
`l20
`
`IA‘-U
`
`I60
`
`I80 200
`
`:3Ii-
`‘.5
`3-\.
`
`dEI
`
`.B
`
`krnlh
`SDEEG
`Variation of torque split ratio [Sta] during the £C£-.l.l urban
`'5. 10A
`$1!"
`filing eyclefov the optimally controlled petroleum substitution hybrid
`
`:'1U..
`i:
`et-1}E.I!
`H
`
`0 i
`
`no mo
`
`too
`
`130
`
`200
`
`0
`
`40
`
`so
`
`too
`so
`time _ s
`Variation ofgear during the ECE-I5 when driving cyttlejor
`Fig. 103
`the optimally controlled petroleum sl-tbstitutlon hybrid
`I00
`90
`G(D
`
`______—
`.05" ‘-...._________a
`\
`"I-_
`__p"' F. - —
`.__—_—-u—_—_n———_- -"‘—g
`ts_9____
`‘GTE
`
`EIn
`3-3..-
`13C
`EflD.-
`
`engineloadloctnr,'I. 3LI.50|
`
`_ I3
`
`3.4 Petroleum-substitution hybrid
`from the
`The petroleum-substitution design differs
`energy-saving aim primarily in the emphasis placed on
`the electric traction system- When the ratio of weighting
`factors is increased such that 1,/at, -_~ 0.6, the use of the
`[C engine is further restricted towards the high-eflieicncy
`to-no
`sec
`
`r
`
`800
`mo
`sou
`500
`400
`300
`200
`100
`
`5- -'
`1.5 as...-"--;.
`.3.-9-.‘_’-5“"
`--n5 1
`0,5 as
`\ t
`~
`
`-—r‘
`
`~_____.u-——..___“___.-"~ *~
`kl
`
`I20
`
`lfcll
`
`ISD
`
`I30 200
`
`20M)
`
`50
`
`80
`
`ID!)
`tirne,s
`Variation qt‘ engine local factor during the ECE-J5 urban
`Fig. 106
`driving epelefor tlre optimally controlled petroleltnt substitution hybrid
`70
`60
`
`
`
`
`
`motorloudfoctot;'l.
`
`1::E
`
`
`
`
`
`
`
`brakemeanettectivepressureitPo
`
`engine speed , rev {min
`{C engine usage doto for the oprlntalfy controlled petroletmt
`Fig. 9
`substitution hybrid over the ECE-l5 urban cycle
`373
`
`Variation of motor load flzctor during the ECE-4'5 urban
`Fig. ‘I00
`tlriuirrg cycle for the optimally controlled petroleum substitution hybrrd
`vehicle
`
`IEEPROCEEDINGS. Val. H4. Pt. D; No.6. N0 VENEER 1987
`
`Page 6 of 15
`
`FORD EXHIBIT 1104
`
`3 U
`
`55
`
`
`
`
`
`point as close to the maximum ellicienoy region as _the
`available transmission ratios will allow. Thus there is a
`
`3 Icon9
`H
`‘Al
`G
`U!
`
`
`
`
`
`brakemeanetteetivepressure,k
`
`2000
`
`3000
`
`-5000
`
`5000
`
`engine speed , re-vlrnin
`JC engine usage dntafor the optimally controlled energy rotting
`Fig. 8
`hybrid over the ECE-I5 urban cycle
`Percentage time engine oil’ = 53.6%
`
`tendency to use low gear ratios {high gears) as much as
`possible when the IC engine is selected as the power
`source. The use of the electric drive is also shown in Fig.
`7 and, during this cycle,
`is used only for regenerating
`braking and initial movement of the vehicle. Torque
`transfers to the IC engine when the engine speed and
`load is sulliciently high to give acceptable eiliciency.
`During a more severe cycle, the electric traction system
`may augment the IC engine torque to give the required
`performance.
`These results suggest that the IC engine can be regard-
`ed as the principle power source, when the aim of the
`optimal control is to maintain the elliciency of this com-
`ponent as high as possible. This is achieved by allowing
`operation only in the most eliicient part ofthe engine fuel
`map and by switching off and decoupling the engine
`when not in operation. In addition, a proportion of the
`acoelerative energy is recovered by regenerating into the
`battery. For the energy-saving hybrid, as the battery state
`of charge is the same at the end of the cycle as at the
`beginning, this policy can be regarded as essentially being
`an improved power train energy management system.
`
`6
`
`
`
`control. The increased use of the electric traction system
`is evident and is used for initial vehicle movement, as in
`the energy-saving hybrid, but now also during the cruise
`periods, when the torque and speed loading imposed on
`the engine would give a low efficiency. One exception to
`this is the firs: low-speed cruise, when the efllciency of
`both systems is low and, for this particular drive train,
`the IC engine operation is preferred. To further maximise
`engine efficiency, engine torque loadings above about
`90% are avoided and. if the engine cannot provide the
`necessary power at high cfliciency, it is augmented by the
`electric traction motor. An example of this is during the
`acceleration phase between 128 and 142 s. It
`is inter-
`esting to note that. for the energy-saving hybrid.
`this
`acceleration was driven solely on the [C engine, but in a
`lower gear (higher gear ratio). This operating condition is
`not selected in this case, as with the different ratio of
`weighting factors it would now lead to an increase in the
`value of the objective function being minimised.
`One particular requirement of the petroleum substitu-
`tion vehicle is to extend the use of the electric traction
`system. to enable the complete urban cycle to be driven
`in an all-electric mode. thereby eliminating the high fuel
`penalty associated with a cold engine. It is
`therefore
`necessary that this vehicle has adequate electric range. As
`discussed in Section 2, 95% of all car journeys are under
`80 km and. although the base hybrid design cannot
`satisfy this in an electric mode, it can achieve a range of
`40 ltrrr. This would satisfy approximately 90% of all jour-
`neys, with the vehicle having to resort to hybrid oper-
`ation for urban journeys in excess of this. Such range
`demands on the vehicle are shown in Fig. 6 and indicate
`the degree of hybrid operation, and the emphasis that
`must be placed on the IC engine to meet a particular
`range requirement. Consequently, the petroleum substi-
`tution hybrid exhibits all
`the benefits of an electric
`vehicle, but has no range limitation clue to the presence
`of the [C engine, and is also capable of high-speed, long-
`distanoe cruise perfon-nance.
`
`35 General’ consr'dsrarr’on.s
`Discussion so far has centred on urban use of the hybrid,
`with no comment being made on cruise perfonnance. At
`90 Itmlh and 120 kmfh, the efficiency of the IC engine in
`the conventional vehicle is high, typically 20-25%, and
`here the aim of the hybrid is not to compromise this
`good fuel economy due to the increased vehicle weight.
`The ways in which this can be achieved are discussed in
`Section 4.
`
`Further consideration of the optimal policy described
`earlier points to a number of factors which limit its prac-
`tical application. First, the implementation of the optimal
`algorithm requires substantial computation time because
`of the direct search technique used. As a result, it cannot
`be implemented in real
`time. Other optimisation tech-
`niques have been explored, but
`the highly non-linear
`nature of the loss variations make these dillieult to use
`reliably. Secondly. some of the operating conditions
`imposed on the system are unacceptable, for example the
`number of gear changes being made. However, a sub-
`optimal policy that overcomes these problems can be
`developed. the effect of which is described in Section 5.
`
`4
`
`Optimisation of power train component sizing
`
`Although the component ratings described in Table l
`form a good initial estimate of those appropriate to a
`hybrid car, further performance improvements can be
`IEE PROCEEDINGS. Vol. J34, Pt. D. No. 6. NOVEMBER I987
`
`obtained by considering rating variations about this base.
`Inevitably, factors such as battery size and the relative
`rating of the power sources will differ if a vehicle is to
`meet either the energy saving or petroleum substitution
`aims. This is particularly true during urban operation,
`when the specific requirements for each type of hybrid
`must be exatrtined separtely.'l'he effect on the two hybrid
`strategies of varying the component sizing is examined in
`the following Sections, assuming the vehicle to be opti-
`mally controlled.
`
`4.? Energy~savr'ng hybrid: battery size and 16‘ engine
`power fraction
`In the energy-saving objective, the role of the electric
`traction system is to maximise petroleum fuel economy,
`with the battery state of charge being approximately the
`same at the end of the cycle as at the beginning. When
`operating in such a mode, the fuel economy returned by
`the optimally controlled base vehicle defined in Table l,
`when simulated over the ECE-I5 and 1227a-D urban
`cycles,
`is shown in Fig 11. The results show the fuel
`W
`
`
`
`
`
`luelconsurnplion_litrellllflkm
`
`Ill0'!Id5U!0'!'-I
`
`0.2
`
`0.3
`
`0.1.
`
`0.5
`
`0.6
`
`0.7
`
`0.3
`
`tc engine power fraction
`Urbcrrr perybrrnurrcr ofrlre energy saving hybrid with optin-um
`
`Fly. 11
`control
`C-0 203 kg, lead acid battery
`it — rt
`Zlffl kg, lead acid battery
`A—A 4-Ill kg. lead acid battery
`
`economy returned for these urban cycles as the 1C engine
`power fraction is varied for three different weights