Ulllted States Patent [19]
`Boberg et al.
`
`USOOS 95 9420A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,959,420
`Sep. 28, 1999
`
`[54] HEAT ENGINE AND ELECTRIC MOTOR
`TORQUE DISTRIBUTION STRATEGY FOR A
`HYBRID ELECTRIC VEHICLE
`
`[75] Inventors; Evan S_ Boberg; Brian P_ Gebby, both
`of Hazel Park, Mich.
`
`.... .. 123/140
`4/1979 Little, Jr. et al. ..
`4,149,507
`5,376,869 12/1994 Konrad .................................. .. 318/587
`5,578,911 11/1996 Carter et al. .
`5,680,917 10/1997 Bray .................................. .. 477/18OX
`5,695,430 12/1997 Moyer ................................... .. 477/189
`
`[73] Assignee: Chrysler Corporation, Auburn Hills,
`Mich
`
`P '' imary Examiner—Karen Masih
`Attorney, Agent, or Firm—Jennifer M. Stec
`
`[21] Appl. N0.: 08/982,047
`.
`_
`Dec‘ 1’ 1997
`[22] Flled'
`[51] Int. Cl.6 ...................................................... .. H02P 7/00
`[52] US. Cl. ........................ .. 318/432; 318/587; 318/139;
`318/254; 318/138; 318/439; 318/434; 180/282
`[58] Field Of Search ................................... ..318/587,139,
`318/254, 138, 439, 434; 180/282; 123/40;
`477/189, 180
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`[57]
`
`ABSTRACT
`
`A method is provided for controlling a poWer train system
`for a hybrid electric vehicle. The method includes a torque
`distribution strategy for controlling the engine and the
`electric motor- The engine and motor Commands are deter
`mined based upon the accelerator position, the battery state
`of Charge and the amount of engine and motor tOrqu9
`available. The amount of torque requested for the engine is
`restricted by a limited rate of rise in order to reduce the
`emissions from the engine. The limited engine torque is
`supplemented by motor torque in order to meet a torque
`request determined based upon the accelerator position.
`
`3,916,862 11/1975 Clouse et al. ..................... .. 123/140 X
`
`8 Claims, 7 Drawing Sheets
`
`10K
`
`26
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`16
`
`26
`
`DIFFERENTIAL
`
`18
`/\/
`
`TRANSMISSION
`
`N ENGINE
`14
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`
`Q40
`
`36k BATTERY _ ACC
`
`Page 1 of 13
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`U.S. Patent
`
`Sep.28, 1999
`
`Sheet 1 of7
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`US. Patent
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`U.S. Patent
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`Sep.28, 1999
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`

`1
`HEAT ENGINE AND ELECTRIC MOTOR
`TORQUE DISTRIBUTION STRATEGY FOR A
`HYBRID ELECTRIC VEHICLE
`
`STATEMENT OF GOVERNMENT INTEREST
`
`The government of the United States of America has
`rights in this invention pursuant to Subcontract No. ZAN
`6-16334-01 aWarded by the US. Department of Energy.
`
`BACKGROUND OF THE INVENTION
`Field of the Invention
`The present invention relates generally to a hybrid electric
`vehicle and, more particularly, to a heat engine and electric
`motor torque distribution control strategy for a hybrid elec
`tric vehicle.
`
`10
`
`15
`
`BACKGROUND AND SUMMARY OF THE
`INVENTION
`
`Since the invention of poWer vehicles, many different
`poWertrain systems have been attempted, including a steam
`engine With a boiler or an electric motor With a storage
`battery. It Was, hoWever, the discovery of petroleum in 1856
`and the four-stroke internal combustion engine invented by
`Otto in 1876, that provided the impetus for the modern
`motor vehicle industry.
`Although fossil fuel emerged as the fuel of choice for
`motor vehicles, recent concerns regarding fuel availability
`and increasingly stringent federal and state emission regu
`lations have reneWed interest in alternative fuel poWered
`vehicles. For example, alternative fuel vehicles may be
`poWered by methanol, ethanol, natural gas, electricity, or a
`combination of these fuels.
`Adedicated electric poWered vehicle offers several advan
`tages: electricity is readily available, an electric poWer
`distribution system is already in place, and an electric
`poWered vehicle produces virtually no emissions. There are,
`hoWever, several technological disadvantages that must be
`overcome before electric poWered vehicles gain acceptance
`in the marketplace. For instance, the range of an electric
`poWered vehicle is limited to approximately 100 miles ,
`compared to approximately 300 miles for a similar fossil
`fuel poWered vehicle. Further, the costs of batteries are
`signi?cantly more than that of a comparable fossil fuel
`poWered vehicle.
`Hybrid poWered vehicles, poWered by both an internal
`combustion engine and an electric motor, have been Widely
`proposed for overcoming the technical disadvantages of a
`dedicated electric vehicle While still offering an increased
`ef?ciency. The performance and range characteristics of a
`hybrid poWered vehicle is comparable to a conventional
`fossil fuel poWered vehicle. HoWever, a great deal of devel
`opment is still necessary in order to provide a hybrid electric
`vehicle Which Would be Widely accepted by the consuming
`public. The present invention deals With the issue of deter
`mining a desirable amount of torque distribution by the
`engine and electric motor of a hybrid electric vehicle in
`order to provide the bene?ts of rapid acceleration, increased
`fuel economy, and reduced emissions. Thus, there is a need
`in the art for a hybrid poWertrain system for a motor vehicle
`that is energy efficient, has loW emissions, and offers the
`performance of a conventional fossil fuel poWered vehicle.
`Accordingly, it is an object of the present invention to
`provide an improved poWer distribution system for a hybrid
`poWertrain system.
`To achieve the foregoing objects, the present invention
`provides a hybrid poWertrain system for a motor vehicle
`
`25
`
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`
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`
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`5,959,420
`
`2
`including a transmission operably connected to an engine of
`the motor vehicle, and an electric motor/generator operably
`connected to the transmission, Wherein the electric motor/
`generator produces either one of positive and regenerative
`torque. The engine and motor torque are distributed accord
`ing to a distribution strategy in order to provide reduced
`emissions While maintaining the desired amount of respon
`siveness to the accelerator position.
`Further areas of applicability of the present invention Will
`become apparent from the detailed description provided
`hereinafter. It should be understood hoWever that the
`detailed description and speci?c examples, While indicating
`preferred embodiments of the invention, are intended for
`purposes of illustration only, since various changes and
`modi?cations Within the spirit and scope of the invention
`Will become apparent to those skilled in the art from this
`detailed description.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The present invention Will become more fully understood
`from the detailed description and the accompanying
`draWings, Wherein:
`FIG. 1 is a schematic diagram of a hybrid poWertrain
`system for a motor vehicle according to the present inven
`tion;
`FIG. 2 is a data How diagram shoWing the torque distri
`bution control strategy for the hybrid poWertrain system
`according to the principles of the present invention;
`FIG. 3 is a data How diagram illustrating the calculation
`of the estimated motor torque available according to the
`principles of the present invention;
`FIG. 4 is a data floW diagram illustrating the calculation
`of the engine torque available according to the principles of
`the present invention;
`FIG. 5 is a data How diagram illustrating the calculation
`of the motor torque available and the torque request for
`charging and discharging according to the principles of the
`present invention;
`FIG. 6 is a data How diagram illustrating the calculation
`of an altered torque request according to the principles of the
`present invention;
`FIG. 6a is a graphical representation of a sample look-up
`table used in the data How diagram of FIG. 6;
`FIG. 7 is a data How diagram illustrating the calculation
`of an engine control command according to the principles of
`the present invention; and
`FIG. 8 is a data How diagram illustrating the calculation
`of a motor control command according to the principles of
`the present invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`Referring to FIG. 1, a hybrid poWertrain system 10,
`according to the present invention, is illustrated for a motor
`vehicle, generally shoWn at 8. The hybrid poWertrain system
`10 includes a heat engine 14 operating on a hydrocarbon
`based or fossil fuel. In this example, the engine 14 is a
`compression-ignited engine fueled by a diesel fuel.
`Preferably, the engine 14 is siZed comparable to an engine
`for a nonhybrid motor vehicle.
`The hybrid poWertrain system 10 also includes a clutch
`mechanism 16, as is knoWn in the art, for operably inter
`connecting engine 14 and transmission 18. The Clutch
`mechanism 16 compensates for the difference in rotational
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`3
`speed of engine 14 and transmission 18, to smooth engage
`ment between engine 14 and transmission 18.
`Transmission 18 connects to engine 14 through clutch 16
`and transmits engine rotation and poWer at various ratios to
`a pair of drive Wheels 26 of the motor vehicle. Thus,
`transmission 18 enables the motor vehicle 8 to accelerate
`through predetermined gear ratios, While engine 14 func
`tions Within a predetermined operating range. Examples of
`knoWn transmission types include an automatic
`transmission, a manual transmission and a continuously
`variable transmission. It should be appreciated that in a
`preferred embodiment transmission 18 is a ?ve-speed
`manual transmission as is Well knoWn in the art.
`Transmission 18 drives a differential unit 28. Differential
`unit 28 engages a pair of aXle shafts 30 Which are operably
`connected to the pair of Wheels 26.
`The hybrid poWertrain system 10 also includes an electric
`motor 32 operably connected to transmission 18 at the
`opposite end of an input shaft from clutch 16. Electric motor
`32 is connected to the input shaft opposite from clutch 16 by
`a gear train 33. The electric motor 30 is able to provide both
`positive and regenerative torque, by functioning as a motor
`and a generator, respectively. An eXample of an electric
`motor 32 is an induction motor or a permanent magnet
`motor, such as manufactured by Delphi Electronics Corpo
`ration.
`As a generator, electric motor 32 produces a regenerative
`torque, preferably as an alternating current (A/C), Which is
`transferred to a control mechanism, such as a motor con
`troller 34. Motor controller 34 changes the alternating cur
`rent into a direct current (D/C), as is Well knoWn in the art.
`The direct current may then be transmitted to an energy
`storage apparatus 38, such as a battery. Alternatively, as a
`motor, the electric motor 32 produces a positive torque that
`is applied to the input shaft of the transmission 18 and is
`ultimately used to drive Wheels 26.
`Motor vehicle 8 is provided With a regenerative braking
`system, capable of capturing kinetic energy from the
`momentum of the motor vehicle as it is sloWing doWn and
`storing this energy as potential energy in the energy storage
`apparatus 38 to be described. Electric motor 32 sloWs the
`motor vehicle doWn by applying a braking force that sloWs
`doWn the rotation of the input shaft. Electric motor 32
`functions as a generator and captures the reverse energy
`?oW.
`Hybrid poWertrain system 10 also includes a transmission
`controller 50, such as an electronic control unit. Transmis
`sion controller 50 enables electronic control of transmission
`18 to enable the transmission 18 to be con?gured as a
`manual-style transmission, but to be operated from a drivers
`standpoint as an automatic transmission. To effect such
`operation, transmission 18 has a pair of actuators 52 and 54
`Which simulate positioning of the stick shift actuators as in
`a conventional manual transmission. Further, actuator 56
`enables operation of clutch 16 in replacement of a clutch
`pedal as on a conventional manual transmission. In order to
`generate such control signals, transmission controller 50
`receives input signals from engine 14 or an engine controller
`58. EXamples of such information received from engine 14
`or engine controller 58 include vehicle speed, RPM, or the
`like. Similarly, transmission controller 50 generates output
`signals to control actuators 52, 54, and 56 and also outputs
`diagnostic and other communication signals to engine 14
`and/or engine controller 58. Transmission controller 50 may
`also receive other vehicle condition signals, depending on a
`particular con?guration of the transmission 18.
`
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`In operation, as Will be described in greater detail herein,
`transmission controller 50 receives input signals from
`engine 14, engine controller 58, clutch 16, clutch actuator
`56, transmission 18, and from additional sensors. Actuator
`56 is preferably a rotary actuator Which causes linear move
`ment to effect engagement and disengagement of clutch 16.
`With respect to actuators 52 and 54, these actuators combine
`to mimic movement of the shift lever in a conventional
`manual transmission. That is, in visioning the standard “H”
`shaped shift con?guration, actuator 52 may operate as the
`cross over actuator, i.e., determining What leg of the “H” the
`shifter is in. Similarly, actuator 54 operates as a select
`actuator Which mimics an upWard or doWnWard movement
`of the shifter Within the leg of the H. The actuators 52, 54,
`and 56 receive control signals from transmission controller
`50 to operate the shifting portion of transmission 18 as in a
`conventional manual transmission. Further, transmission
`controller 50 sends control signals to electric motor 32
`through motor controller 34, to effect activation and deac
`tivation of electric motor 32 as determined by the control
`strategy described herein.
`Hybrid poWertrain system 10 includes an energy storage
`apparatus 38, such as battery, to store potential energy for
`later use by the motor vehicle. For eXample, the potential
`energy stored in the battery may be transferred, as DC
`current, to operate an accessory component 40. In a typical
`motor vehicle, engine 14 operably supplies a battery With
`potential energy. In this example, electric motor 32 operat
`ing as a generator supplies battery 38 With potential energy
`for storage.
`Hybrid poWertrain system 10 includes at least one acces
`sory component 40. An eXample of an accessory component
`may be a poWer steering pump, a Water pump, a lighting
`system, and a heating and cooling system, Which are all
`conventional and Well knoWn in the art. Accessory compo
`nents 40 are usually mechanically driven by the engine 14 or
`electrically poWered With energy from battery 38. For
`eXample, accessory component 40, such as the poWer steer
`ing pump, is operably connected to engine 14 and mechani
`cally driven by engine 14. The lighting system relies on
`energy supplied by the battery 38, as a source of poWer.
`Upon command from the motor controller 34, battery 38
`supplies potential energy, such as a D/C current, to motor
`controller 34, Which converts it into an A/C current. The A/C
`current is directed to the electric motor 32, causing it to act
`as a motor and produce a positive torque. The positive torque
`is applied to the transmission 18, Which in turn induces the
`rotation of the aXle shaft 30 and the rotation of the drive
`Wheels 26 of the motor vehicle.
`With reference to FIGS. 2—8, a heat engine and electric
`motor torque distribution strategy for a hybrid electric
`vehicle Will be described. FIG. 1 illustrates the data How
`diagram for the torque distribution strategy of the present
`invention. The torque distribution strategy includes ?rst
`detecting a state of charge of a vehicle battery (SOC) at 100,
`detecting an accelerator position (APOS) at 102, detecting a
`gear number (GN) at 104, detecting an engine speed (SE) at
`108, and a motor speed (SM) at 110.
`An estimated amount of motor torque available TM is
`detected at 112. With reference to FIG. 3, the motor speed
`S M as converted by the gear ratio of the gear train 34 (at 114)
`is input into a motor torque look-up table 116 and based
`upon the motor speed, an estimated motor torque available
`value TM is obtained.
`An amount of engine torque available TEA is determined
`at 120. With reference to FIG. 4, the engine torque available
`
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`TEA is determined based upon an engine speed SE Which is
`input into a non-extrapolating torque table 122 to provide an
`engine torque TE. The derivative of the engine speed S E over
`time (du/dt) is calculated at 124. The engine speed SE is
`input into ?rst gear, second gear, and third gear engine speed
`rise limiters 126, 128, 130, respectively, Which each provide
`a look-up table to provide a multiplier Which varies With the
`engine speed SE. The multiplier obtained from ?rst gear,
`second gear, and third gear rise limiters 126—130 are then
`multiplied by the maximum engine torque available TE to
`provide a modi?ed maximum engine torque available TELl,
`TEL2, TEL3 at “Product” 132, “Product 1” 134, and “Product
`2” 136, respectively. Based upon the calculated derivative of
`engine speed over time (du/dt), the “use 1st limit” 138, “use
`2nd limit” 140, and “use 3rd limit” 142 boxes each deter
`mine Whether to use the maximum engine torque available
`values TELl, TEL2, TEL3, or the maximum engine torque
`available TE values, respectively. Based upon the gear
`number (GN) that has been detected, boxes labeled “?rst”
`144, “second” 146, and “third” 148, determine Whether to
`use the calculated engine torque value based upon Whether
`the transmission is in ?rst gear, second gear, or third gear. If
`the transmission is in a gear higher than the third gear, the
`calculated maximum engine torque available TE is selected
`in box 148. In other Words, blocks “?rst” 144, “second” 146,
`and “third” 148 determine Which engine torque value to use
`based upon Which gear number has been detected.
`A torque request for charging and discharging TRCD as
`Well as an available motor torque TMA is determined at the
`box labeled “SOC and motor torque assist” 150. With
`reference to FIG. 5, the battery state of charge SOC detected
`at 100 is input into box 152 labeled “Thermostat Charge.”
`Box 152 provides a boolean output of “0” or “1.” When the
`detected state of charge is beloW a predetermined level, then
`the output of box 152 is equal to 1 Which indicates that the
`battery is loW. This provides a charge rate command K (at
`152) Which Will be described herein. At box 156, the
`accelerator position APOS is multiplied by the estimated
`motor torque available TMAE Which provides an amount of
`torque available for charging the battery. This value is then
`multiplied by the charge rate constant K at box 158.
`At box 160 labeled “motor assist”, a boolean output of “0”
`or “1” is provided. The boolean output of “1” is provided
`When the detected state of charge is greater than a prede
`termined state of charge, generally indicating that the battery
`has a state of charge greater than a desired level. If the
`boolean operator is “1”, then an assist command K is
`provided at box 162. If the boolean operator is “0”, no assist
`command is provided. At box 164, the assist command K is
`multiplied by the detected accelerator position APOS. At
`box 166, it is determined Whether the detected state of
`charge SOC is greater than a minimum state of charge
`(minimum SOC). Box 166 also provides a boolean operator.
`In the case that the state of charge SOC is greater than
`minimum SOC, a boolean operator equal to “1” is provided.
`When SOC is not greater than minimum SOC, a boolean
`operator equal to “0” is provided. The boolean operator from
`box 166 is multiplied by the estimated motor torque avail
`able at box 168. Accordingly, the calculated value TMA in
`box 168 is either equal to the estimated motor torque
`available TMAE or equal to Zero in the case that the detected
`state of charge SOC is not greater than the minimum state of
`charge (minimum SOC). Effectively, if the state of charge
`SOC is not greater than the minimum state of charge, the
`motor torque available TMA is equal to Zero. The motor
`torque available TMA is multiplied by the product of the
`accelerator position APOS multiplied by the assist command
`
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`K (obtained in box 164), in box 170. This value Which
`represents a torque discharge request TRD is subtracted from
`the determined limited torque amount available for charging
`TRC at box 172 to provide a torque request for charging and
`discharging TRCD.
`At box 176, labeled “Sum1”, the calculated engine torque
`available TEA and motor torque available TMA are added to
`provide a total torque available TTA. At box 178 labeled
`“requested torque” the calculated total torque available TTA
`is multiplied by the accelerator position APOS to provide a
`requested torque TR. At box 180 labeled “Sum3”, the
`requested torque TR is added to the calculated amount of
`requested torque for charging and discharging TRCD, to
`provide a total torque request TTR.
`At box 182, labeled “Torque assist”, as shoWn in FIG. 6,
`the calculated total torque request TTR is limited at box 184
`by a “limit rate of torque rise” characteristic curve, to
`provide a limited total torque request TLTR. Typically, at the
`rate of torque rise of the engine increases, the engine
`emissions also increase. Therefore, the system of the present
`invention limits the rate of torque rise for the engine in order
`to minimiZe the engine emissions. HoWever, When the
`vehicle is operated in an aggressive manner, as represented
`by the accelerator position APOS exceeding a predetermined
`value, the limits imposed on the rate of torque rise are
`reduced in order to provide the necessary torque response as
`required by the accelerator position APOS. In other Words,
`the goal of reducing emissions is at least partially reduced in
`value in order to meet the requirements of aggressive
`acceleration commands. The factor of aggressive driving
`commands are taken into consideration at box 186 of FIG.
`6, the accelerator position APOS is provided to a look-up
`table Which provides a variable output based upon the
`accelerator position. For example, as shoWn in FIG. 6a,
`When the accelerator position is less than a predetermined
`value, for example 0.8 (representative of 80 percent open
`throttle) the value provided by look-up table 186 is equal to
`Zero. HoWever, betWeen the predetermined accelerator posi
`tion (0.8 for example) and Wide open throttle (1.0), a linear
`relationship is provided for providing a limiting multiplier 1
`Which is multiplied by the difference betWeen the total
`torque requested TTR minus the limited total torque
`requested TLTR calculated in box 184. The product of this
`value is then added to the limited total torque requested TLTR
`in box 190 to provide an altered torque request TAR. In
`essence, When the value of the accelerator position is less
`than the predetermined value, the multiplier l is equal to
`Zero. Therefore, the altered torque TAR is equal to the limited
`total torque request TLTR. HoWever, When the accelerator
`position exceeds the predetermined position (for example
`0.8), the altered torque request TAR is equal to the limited
`total torque request TLTR plus the product of the total torque
`request TTR minus the limited total torque request TLTR times
`the multiplier I. As the multiplier l approaches 1, the altered
`torque request ATR approaches the total torque request TTR.
`Therefore, the effect of limiting the engine torque rise is at
`least partially negated after the accelerator position exceeds
`the predetermined value. It should be understood that the
`example Look-Up Table as illustrated in ?gure 62 could be
`altered in many Ways. For example, a non-linear or step
`increase in the value I may be utiliZed. In addition, as an
`alternative to the multiplier l, the system of the present
`invention could, upon the accelerator position reaching a
`predetermined value, ignore the limited total torque request
`TLTR and simply use the total torque request TTR as the
`altered torque TAR value. In effect, this Would be the
`equivalent of using a step increase for l to go from “0” to “1”
`When accelerator position exceeded a predetermined value.
`
`Page 11 of 13
`
`FMC 1012
`
`

`

`5,959,420
`
`7
`In boX 192, a normal engine command is determined. The
`engine command EC is equal to the ratio of the altered
`torque request TAR divided by the maXimum engine torque
`available TEA as calculated in boX 194 of FIG. 7. The engine
`command EC is then multiplied by the engine torque avail
`able TEA in boX 196 to provide an engine torque request TER.
`The engine torque request TER is then subtracted from the
`requested torque TR in boX 198 to provide a motor torque
`request TMR in boX 200, a motor command MC is deter
`mined as shoWn in FIG. 8. The motor command MC is equal
`to the ratio of the motor torque request TMR divided by the
`estimated motor torque available TMAE as calculated in boX
`202.
`Accordingly, the engine and motor commands EC and
`MC are determined based upon a strategy to reduce emis
`sions and provide the desired amount of driving torque.
`The invention being thus described, it Will be obvious that
`the same may be varied in many Ways. Such variations are
`not to be regarded as a departure from the spirit and scope
`of the invention, and all such modi?cations as Would be
`obvious to one skilled in the art are intended to be included
`Within the scope of the folloWing claims.
`What is claimed is:
`1. A hybrid electric poWertrain system, comprising:
`a transmission for driving a pair of Wheels of a passenger
`vehicle;
`a heat engine coupled to said transmission;
`an electric motor/generator coupled to said transmission;
`an accelerator pedal including a position sensor for detect
`ing a position of said accelerator pedal; and
`a controller unit for generating electrical control signals to
`said heat engine and said electric motor/generator,
`Wherein an electrical engine control signal is deter
`mined based upon a limited rate of torque rise and a
`detected accelerator position.
`2. A hybrid electric poWertrain system, comprising:
`a transmission for driving a pair of Wheels of a passenger
`vehicle;
`a heat engine coupled to said transmission;
`an electric motor/generator coupled to said transmission;
`an accelerator pedal including a position sensor for detect
`ing a position of said accelerator pedal;
`a controller unit for generating control signals to said heat
`engine and said electric motor/generator, Wherein an
`engine control signal is determined based upon a lim
`ited rate of torque rise and a detected accelerator
`position; and
`Wherein a motor control signal is determined based upon
`a difference betWeen a determined torque request and a
`determined engine torque request.
`3. The hybrid electric vehicle according to claim 2,
`Wherein said determined torque request is determined based
`upon a determined amount of total torque available and a
`detected accelerator position.
`4. The hybrid electric vehicle according to claim 3,
`Wherein said determined amount of total torque available is
`determined based upon a determine amount of engine torque
`available and a determined amount of motor torque available
`for driving.
`5. The hybrid electric vehicle according to claim 4,
`Wherein said controller determines a torque request for
`charging a vehicle battery based upon a detected state of
`charge of the battery.
`6. A method of controlling a hybrid electric poWertrain
`system including a heat engine and an electric motor/
`
`10
`
`15
`
`25
`
`35
`
`45
`
`55
`
`8
`generator each coupled to a transmission for driving a pair
`of Wheels of a passenger vehicle, comprising the steps of:
`a. determining an amount of motor torque available;
`b. determining an amount of engine torque available;
`c. determining an amount of motor torque that can be used
`to assist the engine in driving the vehicle;
`d. determining an amount of engine torque required for
`battery charging;
`e. determining a total amount of driving torque available
`by adding said determined amount of motor torque
`available for driving and said determined amount of
`engine torque available;
`f. determining an amount of requested torque based upon
`a detected accelerator position and said determined
`total amount of driving torque available;
`g. calculating a total torque request by adding said deter
`mined amount of torque required for battery charging
`and said determined amount of requested torque;
`h. determining a limited total torque request based upon
`a limited rate of increase for the calculated total engine
`torque request and said detected accelerator position;
`and
`i. determining an altered torque request based upon said
`calculated total torque request, said determined limited
`total torque request and said detected accelerator posi
`tion.
`7. The method according to claim 6, further comprising
`the steps of:
`determining an engine command based upon said deter
`mined amount of engine torque available and said
`determined altered torque request.
`calculating a motor torque request by subtracting an
`engine torque request from said determined amount of
`requested torque; and
`determining a motor command based upon said calculated
`motor torque request and said determined amount of
`motor torque available.
`8. A method of controlling a hybrid electric poWertrain
`system including a heat engine and an electric motor/
`generator each coupled to a transmission for driving a pair
`of Wheels of a passenger vehicle, comprising the steps of:
`detecting a state of charge of a vehicle battery, an accel
`erator position, a value representative of a current
`transmission gear ratio, engine speed and motor speed;
`determining an amount of motor torque available, based
`upon a detected motor speed;
`determining an amount of engine torque available based
`upon a detected engine speed and a detected value
`representative of a current transmission gear ratio;
`determining an amount of motor torque that can be used
`to assist the engine in driving the vehicle based upon a
`detected battery state of charge, a detected accelerator
`position and a determined amount of motor torque
`available;
`determining an amount of engine torque required for
`battery charging and alternatively an amount of motor
`torque required for discharging stored energy from said
`battery based upon a detected battery state of charge, a
`determined amount of motor torque available and a
`detected accelerator position;
`determining a total amount of driving torque available by
`adding said determined amount of motor torque ava