The present disclosure relates generally to a method and a system for controlling hybrid electric vehicle. The method and system is implemented on hybrid electric vehicles to optimize fuel efficiency.
BACKGROUND
[0002] For many years research has been conducted to solve the problem of reduction in fuel consumption of automobiles operating on internal combustion engine. Electric vehicles are an attractive alternative to replace existing automobiles operating on internal combustion engine. However, electric vehicles are a relatively new concept and further research and infrastructure development is still needed in this field. Thus, replacing internal combustion engine based automobile with electric vehicles is still not feasible in most parts of the world due to lack of infrastructure.
[0003] To overcome the drawbacks of internal combustion engine based
automobiles and electric vehicles, hybrid electric vehicles are a good alternative. Hybrid electric vehicles are the type of vehicles which combines the best features of internal combustion engines and electric motors. Hybrid electric vehicles use a combination of consumable fuel (gasoline, natural gas etc) and battery stored electricity. Such combination increases overall fuel efficiency.
[0004] To further improve the fuel efficiency, hybrid electric vehicles use generation to recharge the battery while in driving mode. Rather than braking by friction and turning that kinetic energy into wasted heat via brakes, hybrid electric vehicles use it to run the electric motor as generator to recharge the on-board battery. Hybrid electric vehicles are also capable of using some of the energy supplied by the engine to recharge the battery directly.

[0005] In hybrid electric vehicles, the internal combustion engine and the electric motor can be operated individually or in combination to fulfill real time torque demand of the driver. A hybrid control unit is provided in the hybrid vehicles to take decision on mode of operation of hybrid vehicles in various modes such as motor assist mode, only engine mode, only motor mode or engine load shift mode etc., depending on various vehicle parameters and the magnitude of real time torque demand of the driver. Thus, hybrid control unit is responsible for distribution of real time driver demand torque between engine & electric motor.
[0006] The hybrid control unit operates the hybrid electric vehicle without information regarding engine's optimal brake specific fuel consumption (bsfc) torque. The optimal engine bsfc torque is the torque produced by engine at the highest efficiency. Running engine at optimal engine bsfc zone provides best efficiency which will ultimately reduce fuel consumption while driving. Thus, the hybrid control unit does not work with the objective of increasing fuel efficiency of the hybrid electric vehicles.
[0007] Accordingly, there is a need for a method and a system for controlling hybrid electric vehicle which takes into account optimal engine bsfc torque to operate the hybrid vehicle with optimised fuel efficiency.
SUMMARY
[0008] This summary is provided to introduce concepts related to a method and system for controlling hybrid electric vehicle. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0009] The present disclosure relates to a method for controlling hybrid electric vehicle. The method comprises receiving, by a hybrid control unit, a plurality of operating parameters; determining, by the hybrid control unit, real time driver torque demand and optimal engine bsfc torque based on at least one of the received

operating parameters, and pre-set driver target torque map and engine bsfc optimal torque map stored in memory operatively coupled to the hybrid control unit; determining, by the hybrid control unit, engine target torque and motor target torque based on the determined real time driver torque demand and optimal engine bsfc torque; sending, by the hybrid control unit, the determined engine target torque and the motor target torque to the engine control unit along with engine running status , clutch engagement and the motor control unit to operate the hybrid vehicle with optimised fuel efficiency.
[0010] In an aspect, the plurality of operating parameters comprises battery current state of charge, upper limit of battery charge capacity and lower limit of battery charge capacity received from Battery Management System; brake pressure signal and accelerator pedal signal received from engine control unit; maximum motor generation torque and maximum motor torque received from motor control unit; driver calculated brake pressure received from ABS control unit; and driver clutch engagement received from transmission control unit.
[0011] In an aspect, when the determined real time driver torque demand is greater than the optimal engine bsfc torque and the summation of the optimal engine bsfc torque and maximum motor torque is greater than the determined real time driver torque demand, the engine control unit operate the engine at optimal engine bsfc torque and the motor control unit supplement the engine torque by operating the motor to provide adequate torque to meet the determined real time driver torque demand.
[0012] In an aspect, when the determined real time driver torque demand is greater than the optimal engine bsfc torque and the summation of the optimal engine bsfc torque and maximum motor torque is not greater than the determined real time driver torque demand, the motor control unit operate the motor to provide maximum motor torque and the engine control unit supplement the motor torque by operating the engine to provide adequate torque to meet the determined real time driver torque demand.

[0013] In an aspect, when the determined real time driver torque demand is not greater than the optimal engine bsfc torque and the summation of the optimal engine bsfc torque and maximum motor generation torque is not greater than the determined real time driver torque demand, the engine control unit operate the engine at optimal engine bsfc torque and the motor control unit operate the motor in generator mode to charge battery by using the remaining torque.
[0014] In an aspect, when the determined real time driver torque demand is not greater than the optimal engine bsfc torque and the summation of the optimal engine bsfc torque and maximum motor generation torque is greater than the determined real time driver torque demand, the motor control unit operate the motor in generator mode to charge battery by using maximum motor generation torque and the engine control unit operate the engine at a higher torque.
[0015] In an aspect, the hybrid control unit determine the real time driver torque demand and the optimal engine bsfc torque when there is no brake pressure signal and a positive accelerator pedal signal from the engine control unit and battery current state of charge between the upper limit of battery charge capacity and lower limit of battery charge capacity as received from the Battery Management System.
[0016] In an aspect, the method further comprises determining and transmitting, by the hybrid control unit, mechanical break pressure to the ABS control unit, based on the received plurality of operating parameters; determining and transmitting, by the hybrid control unit, electric brake pressure to the motor control unit, based on the received plurality of operating parameters; determining and transmitting, by the hybrid control unit, engine running state to the engine control unit, based on the received plurality of operating parameters; and determining and transmitting, by the hybrid control unit, clutch engagement state to the transmission control unit, based on the received plurality of operating parameters.
[0017] The present disclosure further relates to a system for controlling a hybrid electric vehicle. The system comprises a hybrid control unit configured to receive a plurality of operating parameters; determine real time driver torque demand and

parameters, and pre-set driver target torque map and engine bsfc optimal torque map stored in memory operatively coupled to the hybrid control unit; determine engine target torque and motor target torque based on the determined real time driver torque demand and optimal engine bsfc torque; and send the determined engine target torque and the motor target torque to the engine control unit and the motor control unit to operate the hybrid vehicle with optimized fuel efficiency.
[0018] In an aspect, the plurality of operating parameters comprises battery current state of charge, upper limit of battery charge capacity and lower limit of battery charge capacity received from Battery Management System; brake pressure signal and accelerator pedal signal received from engine control unit; maximum motor generation torque and maximum motor torque received from motor control unit; driver calculated brake pressure received from ABS control unit; and driver clutch engagement received from transmission control unit.
[0019] In an aspect, when the determined real time driver torque demand is greater than the optimal engine bsfc torque and the summation of the optimal engine bsfc torque and maximum motor torque is greater than the determined real time driver torque demand, the engine control unit operate the engine at optimal engine bsfc torque and the motor control unit supplement the engine torque by operating the motor to provide adequate torque to meet the determined real time driver torque demand.
[0020] In an aspect, when the determined real time driver torque demand is greater than the optimal engine bsfc torque and the summation of the optimal engine bsfc torque and maximum motor torque is not greater than the determined real time driver torque demand, the motor control unit operate the motor to provide maximum motor torque and the engine control unit supplement the motor torque by operating the engine to provide adequate torque to meet the determined real time driver torque demand.
[0021] In an aspect, when the determined real time driver torque demand is not greater than the optimal engine bsfc torque and the summation of the optimal engine

determined real time driver torque demand, the engine control unit operate the engine at optimal engine bsfc torque and the motor control unit operate the motor in generator mode to charge battery by using the remaining torque.
[0022] In an aspect, when the determined real time driver torque demand is not greater than the optimal engine bsfc torque and the summation of the optimal engine bsfc torque and maximum motor generation torque is greater than the determined real time driver torque demand, the motor control unit operate the motor in generator mode to charge battery by using maximum motor generation torque and the engine control unit operate the engine at a higher torque.
[0023] In an aspect, the hybrid control unit determine the real time driver torque demand and the optimal engine bsfc torque when there is no brake pressure signal and a positive accelerator pedal signal from the engine control unit and battery current state of charge between the upper limit of battery charge capacity and lower limit of battery charge capacity as received from the Battery Management System.
[0024] In an aspect, the system further comprises the hybrid control unit further configured to determine and transmit mechanical break pressure to the ABS control unit, based on the received plurality of operating parameters; determine and transmit electric brake pressure to the motor control unit, based on the received plurality of operating parameters; determine and transmit engine running state to the engine control unit, based on the received plurality of operating parameters; and determine and transmit clutch engagement state to the transmission control unit, based on the received plurality of operating parameters.
[0025] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the scope of the present subject matter.
[0026] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description

of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF FIGURES
[0027] The illustrated embodiments of the present disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:
[0028] FIG. 1 illustrates an exemplary system for controlling a hybrid vehicle that can be utilized to implement one or more exemplary embodiments of the present disclosure;
[0029] FIG. 2 illustrates a flow chart of the working of the system that can be utilized to implement one or more exemplary embodiments of the present disclosure; and
[0030] FIG. 3 illustrates a flow chart of the method 300 for controlling hybrid vehicle that can be utilized to implement one or more exemplary embodiments of the present disclosure.
[0031] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0032] A few aspects of the present disclosure are explained in detail below with reference to the various figures. Example implementations are described to illustrate the disclosed subject matter, not to limit its scope, which is defined by the

claims. Those of ordinary skill in the art will recognize a number of equivalent variations of the various features provided in the description that follows.
EXEMPLARY IMPLEMENT A TIONS
[0033] While the present disclosure may be embodied in various forms, there are shown in the drawings, and will hereinafter be described, some exemplary and non-limiting embodiments, with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated. Not all of the depicted components described in this disclosure may be required, however, and some implementations may include additional, different, or fewer components from those expressly described in this disclosure. Variations in the arrangement and type of the components may be made without departing from the scope of the claims as set forth herein.
[0034] Some embodiments of this invention, illustrating all its features, will be discussed in detail.
[0035] The techniques described below may be implemented using one or more computer programs executed on (or executable by) a programmable computer including any combination of any number of the following: a processor, a sensor, a storage medium readable and/or writable by the processor (including for example volatile and non-volatile memory and/or storage elements), plurality of inputs units, plurality of output devices and networking devices.
[0036] Method steps as disclosed by present disclosure may be performed by one or more computer processors executing a program tangibly embodied on a computer-readable medium to perform functions of the invention by operating on input and generating output. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, the processor receives (reads) instructions and content from a memory (such as a read only memory and/or random access memory) and writes (stores) instructions and content to the memory.

Storage devices suitable for tangibly embodying computer program instructions and content include, for example, all forms of non-volatile memory, such as semiconductor memory devices, including EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disk and removable disks, magneto-optical disks, and CD-ROMs. Any of the foregoing may be supplemented by, or incorporated in, specially-designed ASICs (application specific integrated circuits) or FPGAs (Field-Programmable Gate Arrays).
[0037] Any content disclosed herein may be implemented, for example, in one or more content structures tangibly stored on a non-transitory computer-readable medium. Embodiments of the invention may store such content in such content structure(s) and read such content from such content structure(s).
[0038] The present disclosure provides a method and a system for controlling a hybrid electric vehicle.
[0039] FIG. 1 illustrates an exemplary system 100 for controlling a hybrid electric vehicle that can be utilized to implement one or more exemplary embodiments of the present disclosure. The system 100 comprises a hybrid control unit 101, an ABS control unit 102, a battery management system 103, an engine control unit 104, a transmission control unit 105 and a motor control unit 106. In an embodiment the hybrid control unit 101, the ABS control unit 102, the battery management system 103, the engine control unit 104, the transmission control unit 105 and the motor control unit 106 comprises at least one processor and at least one memory. Further, the hybrid control unit 101, the ABS control unit 102, the battery management system 103, the engine control unit 104, the transmission control unit 105 and the motor control unit 106 are configured to send and receive signals to each other over CAN BUS 107 (communication channel).
[0040] The hybrid control unit 101 is configured to distribute real time driver torque demand Xio between engine and electric motor. The hybrid control unit 101 take into account plurality of operating parameters and distribute the real time driver torque demand Xio between engine and electric motor accordingly. The memory

101a which is operatively coupled to the hybrid control unit 101 has a pre-set driver target torque map 101b and an engine bsfc optimal torque map 101c stored.
[0041] The ABS control unit 102 is operative to determine and transmit driver calculated brake pressure X5 to the hybrid control unit 101.
[0042] The battery management system 103 is operative to monitor and transmit battery current state of charge X3, upper limit of battery charge capacity X4 and lower limit of battery charge capacity X7 to the hybrid control unit 101.
[0043] The engine control unit 104 is operative to determine and transmit brake pressure signal Xi and accelerator pedal signal X2 to the hybrid control unit 101.
[0044] The transmission control unit 105 is operative to determine and transmit driver clutch engagement Xn to the hybrid control unit 101.
[0045] The motor control unit 106 is operative to determine and transmit maximum motor generation torque Xs and maximum motor torque X9 to the hybrid control unit 101.
[0046] The hybrid control unit 101 receives the plurality of operating parameters which includes brake pressure signal Xi, accelerator pedal signal X2, driver calculated brake pressure X5, battery current state of charge X3, upper limit of battery charge capacity X4, lower limit of battery charge capacity X7, maximum motor generation torque Xs, maximum motor torque X9 and driver clutch engagement Xn. In addition to this, the hybrid control unit 100 has pre-set driver target torque map 101b and engine bsfc optimal torque map 101c stored in the memory 101a. The hybrid control unit 101 determines real time driver torque demand X10 and optimal engine bsfc torque X12 by taking into account at least one of the received plurality of operating parameters and the pre-set driver target torque map 101b and engine bsfc optimal torque map 101c stored in the memory 101a.
[0047] In an embodiment, the hybrid control unit is operative to determine and transmit mechanical break pressure Yi to the ABS control unit 102. Further, the hybrid control unit is operative to determine and transmit electric brake pressure Y2

control unit is operative to determine and transmit engine running state Y3 and engine target torque Y5 to the engine control unit 104. Also, the hybrid control unit 101 is operative to determine and transmit clutch engagement state Y4 to the transmission control unit 105.
[0048] In an embodiment, the hybrid control unit 101 only determine the real time driver torque demand X10 and the optimal engine bsfc torque X12 when some prerequisite conditions are fulfilled. In an aspect, these condition includes that there should be no brake pressure signal Xi and there should be a positive accelerator pedal signal X2. These signals are transmitted to the hybrid control unit 101 by the engine control unit 104. Further, the battery current state of charge X3 should be between the upper limit of battery charge capacity X4 and the lower limit of the battery charge capacity X7. These signals are transmitted to the hybrid control unit 101 by the battery management system 103.
[0049] Subsequent to determining the real time driver torque demand X10 and optimal engine bsfc torque X12, the hybrid control unit 101 determines engine target torque Y5 and motor target torque Y6.
[0050] The hybrid control unit 101 further send the determined engine target torque Y5 to the engine control unit 104 and the determined motor target torque Y6 to the motor control unit 106. The engine control unit 104 then operate the engine according to the received engine target torque Y5 and the motor control unit 106 operate the motor according to the received motor target torque Y6.
[0051] FIG. 2 illustrates a flow chart of the working of the system 100 that can be utilized to implement one or more exemplary embodiments of the present disclosure.
[0052] First, the hybrid control unit 101 checks for the prerequisite conditions to fulfill which includes absence of brake pressure signal Xi, a positive accelerator pedal signal X2 and battery current state of the charge X3 between the upper limit of battery charge capacity X4 and the lower limit of the battery charge capacity X7. Only after fulfilling these prerequisite conditions the hybrid control unit 101

determines the real time driver torque demand Xio and the optimal engine bsfc torque X12.
CASE-I
[0053] The determined real time driver torque demand Xio is greater than the determined optimal engine bsfc torque X12 and the summation of the determined optimal engine bsfc torque X12 and received maximum motor torque X9 is greater than the determined driver torque demand Xio. The hybrid control unit 101 send the determined engine target torque Y5 to the engine control unit 104 such that the engine control unit 104 operate the engine at optimal engine bsfc torque X12. Further, the hybrid control unit 101 send the motor target torque Y6 to the motor control unit 106 such that the motor control unit 106 operate the motor to provide adequate torque to meet the determined real time driver torque demand Xio. Thus, in this case, the motor target torque Y6 supplement the engine target torque Y5 to meet the real time driver torque demand Xio. In this case, the engine is running at optimized bsfc zone with better efficiency and motor is supplementing the engine torque to meet real time driver torque demand Xio. Thus, the hybrid vehicle is working with optimized fuel efficiency.
CASE-II
[0054] The determined real time driver torque demand Xio is greater than the determined optimal engine bsfc torque X12 and the summation of the determined optimal engine bsfc torque X12 and received maximum motor torque X9 is not greater than the determined real time driver torque demand Xio. The hybrid control unit 101 send the motor target torque Y6 to the motor control unit 106 such that the motor control unit 106 operate the motor to provide maximum motor torque X9. The hybrid control unit 101 send the engine target torque Y5 to the engine control unit 104 such that the engine control unit 104 operate the engine to provide adequate torque to meet the determined real time driver torque demand Xio. Thus, in this case, the engine target torque Y5 supplement the motor target torque Y6 to meet the real time driver torque demand Xio. In this case, the engine is running near to the

optimized bsfc zone with better efficiency. Thus, the hybrid vehicle is working with optimized fuel efficiency.
CASE-III
[0055] The determined real time driver torque demand Xio is not greater than the optimal engine bsfc torque X12 and the summation of the optimal engine bsfc torque X12 and maximum motor generation torque Xs is not greater than the determined real time driver torque demand Xio. The hybrid control unit 101 send the engine target torque Y5 to the engine control unit 104 such that the engine control unit 104 operate the engine at optimal engine bsfc torque X12. Further, the hybrid control unit 101 send the motor target torque Y6 to the motor control unit 106 such that the motor control unit 106 operate the motor in generator mode to charge the battery by using the remaining torque. Thus, in this case, the motor target torque Y6 recharges the battery. In this case, the engine is running at optimized bsfc zone with better efficiency and motor is working in generator mode to recharge the battery. In this case, net fuel consumption maybe higher at any particular instant. However, running engine in better efficiency zone and utilizing battery energy at lower engine efficiency later improves the overall fuel consumption.
CASE-IV
[0056] The determined real time driver torque demand Xio is not greater than the optimal engine bsfc torque X12 and the summation of the optimal engine bsfc torque X12 and maximum motor generation torque Xs is greater than the determined real time driver torque demand Xio. The hybrid control unit 101 send the motor target torque Y6 to the motor control unit 106 such that the motor control unit 106 operate the motor generator mode to charge the battery by using maximum motor generation torque Xs. The hybrid control unit send the engine target torque Y5 to the engine control unit 104 such that the engine control unit 104 operate the engine with the remaining torque. Thus, in this case, the motor target torque Y6 recharges the battery. In this case, the engine is running near the optimized bsfc zone with better efficiency and motor is working in generator mode to recharge the battery.

running engine in better efficiency zone and utilizing battery energy at lower engine efficiency later improves the overall fuel consumption.
[0057] Table 1 below illustrates some exemplary parameters with respect to each case discussed above for better understanding.

Variable XI X2 X3 X4 X7 X10 X12 X9 X8 Y5 Y6
^arametpr brake pressure ace pedal Battery SOC real time Battery upperSOC limit Battery lower SOC limit III Optimal bsfc torque Max motor torque Max
generatio ntorque Engine Target torque Motor Target torque
Unit kPa % % % X Nm VTI Nm Nm Nm Nm
Case 1 0 >0 45% 90% 20% 100 80 25 -25 80 20
Case 2 0 >0 45% 90% 20% 100 80 15 -15 85 15
Case 3 0 >0 45% 90% 20% 100 120 25 -25 120 -20
Case 4 0 >0 45% 90% 20% 100 120 15 -15 115 -15
[0058] FIG. 3 illustrates a flow chart of the method 300 for controlling hybrid vehicle that can be utilized to implement one or more exemplary embodiments of the present disclosure.
[0059] At block 302, the method 300 includes receiving plurality of operating parameters by the hybrid control unit 101. The plurality of operating parameters includes brake pressure signal Xi, accelerator pedal signal X2, driver calculated brake pressure X5, battery current state of charge X3, upper limit of battery charge capacity X4, lower limit of battery charge capacity X7, maximum motor generation torque Xs, maximum motor torque X9 and driver clutch engagement Xn. In addition to this, the hybrid control unit 101 has pre-set driver target torque map 101b and engine bsfc optimal torque map 101c stored in the memory 101a.
[0060] At block 304, the method 300 includes determining real time driver torque demand X10 and optimal engine bsfc torque X12. The hybrid control unit 101 determines real time driver torque demand X10 and optimal engine bsfc torque X12

by taking into account at least one of the received plurality of operating parameters and the pre-set driver target torque map 101b and engine bsfc optimal torque map 101c stored in the memory 101a. In addition, the hybrid control unit 101 determines mechanical brake pressure Yi, electrical brake pressure Y2, engine running state Y3, clutch engagement state Y4 and send the corresponding signals to their respective control units.
[0061] At block 306, the method 300 includes determining engine target torque Y5 and motor target torque Y6. The engine target torque Y5 and the motor target torque Y6 is determined based on the already determined real time driver torque demand X10 and the optimal engine bsfc torque X12.
[0062] At block 308, the method 300 includes, sending the determined engine target torque Y5 and the motor target torque Y6 to the engine control unit 104 and motor control unit 106, respectively. The engine control unit 105 then operate the engine according to the received engine target torque Y5 and the motor control unit 106 operate the motor according to the received motor target torque Y6.
[0063] Figure 2 already discussed the case-I, case-II, case-Ill and case-IV on the basis of which the hybrid control unit 101 send the engine target torque Y5 and the motor target torque Y6 to the engine control unit 104 and motor control unit 106, respectively. The method 300 works in the same way as already disclosed for the system 100. Therefore, for the sake of brevity, the method 300 has not being explained again.
WORKING EMBODIMENT 1 [ENGINE ASSIST]
[0064] Let us consider that a driver is pressing 30% accelerator pedal and battery current state of charge is 45% at any instance. The corresponding engine rpm is 2000 resulting in vehicle speed of 40 Km/Hr. Further, no brake pressure signal in detected.
[0065] The engine control unit 104 determines the accelerator pedal signal X2 and transmit the same to the hybrid control unit 101 over CAN BUS 107. The battery management system 102 monitor and transmit battery current state of charge

X3, upper limit of battery charge capacity X4 and lower limit of battery charge capacity X7 to the hybrid control unit 101. The hybrid control unit 101 receive the accelerator pedal signal X2 and the signals send by the battery management system 102. Further, the hybrid control unit 101 compares the battery current state of charge X3 with the upper X4 and lower X7 limit. Once, the prerequisite conditions are met, the hybrid control unit 101 determine the real time driver torque demand Xio (based on the pre-set driver target torque map 101b) and the optimized bsfc torque X12 (based on the pre-set engine bsfc optimal torque map 101c).
[0066] Let us consider real time driver torque demand Xio value as 100 Nm at 2000 rpm, and optimized bsfc torque value X12 at same rpm to be as 80 Nm at this instance. Hybrid control unit 101 compares these two values and will proceed accordingly.
[0067] As demand in this exemplary embodiment is greater than optimized engine torque, the hybrid control unit 101 proceeds to run engine nearby optimized engine torque value (for better fuel efficiency) and supplement remaining torque from motor (driving from battery is required this is why battery limit was checked in step one). However, to ensure that engine along with motor is always meeting real time driver torque demand Xio a second level of comparison is done in next step. Here, sum of optimized engine bsfc torque X12 (80 Nm) & maximum capacity of motor torque X9 at 2000 rpm (let us assume as 25 Nm) will be compared with the real time driver torque demand Xio. As engine optimized bsfc torque X12 (80Nm) & maximum motor torque X9 (25 Nm) sum is greater than requested driver torque demand Xio (100 Nm), this will result in a situation where engine will run at efficient zone producing 80 Nm of torque and supplemented by motor for remaining 20 Nm torque. Alternatively, if this second level of comparison was not met, torque as per Fig. 2 would be produced. This will result in lower net fuel consumption as a lower value of torque is produced at same rpm.
WORKING EMBODIMENT 2 [ENGINE LOAD SHIFT]
[0068] Let us now consider a different example to understand generation

[0069] Let us assume a condition where driver has pressed 50% of accelerator pedal at 2500 rpm. Battery current state of charge (let us assume as 55%) is within working limits.
[0070] At this instance, the hybrid control unit 101 determines the real time driver torque demand Xio as 70 Nm & optimized engine bsfc torque X12 as 90 Nm. Here, running engine at optimized bsfc torque X12 will provide system energy which will be more than requirement. However, running engine at 90 Nm @2500 rpm instead of 70 Nm @2500 will result in better efficiency. Demand is of only 70 Nm and torque from engine is more, so remaining energy will be utilized by motor in generation mode to charge the battery. This battery energy will be used at later stage to supplement engine torque when engine runs in poor efficiency zone. A second level equation comparison is done in similar lines (as in assist mode) to ensure that there is always sufficient consumption through motor and demand is always met irrespective of maximum motor torque X9.
[0071] Let us assume at 2500 rpm the maximum charging torque available with motor is -23 Nm. As per second level of comparison (90 Nm + (-23) Nm < 70 Nm), in this scenario as per Fig. 2, the hybrid control unit 101 send engine target torque Y5 to the engine to produce 90 Nm of torque at optimized bsfc zone and the remaining torque (equivalent to -20 Nm of torque) will be fed into motor to charge the battery for usage at later stage. In this way the proposed method and system ensures that most of the times engine is running at or nearby optimized bsfc zone (higher efficiency) and will result in overall less fuel consumption.
[0072] The present disclosure provides a method and a system for controlling hybrid vehicles which takes into account optimal engine bsfc torque to operate the hybrid vehicle with optimised fuel efficiency.
[0073] The above description does not provide specific details of the manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be

employed. Those in the art are capable of choosing suitable manufacturing and design details.
[0074] It should be understood, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, as apparent from the discussion herein, it is appreciated that throughout the description, discussions utilizing terms such as "receiving," or "retrieving," or "comparing," or "generating," or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
[0075] The exemplary embodiment also relates to a system for performing the operations discussed herein. This system may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer-readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, solid state drives, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus.
[0076] Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by

those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0077] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0078] It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

We Claim:

1. A method (300) for controlling a hybrid vehicle, the method (300)
comprising:
receiving (302), by a hybrid control unit (101), a plurality of operating parameters,
determining (304), by the hybrid control unit (101), real time driver torque demand (Xio) and optimal engine bsfc torque (X12) based on at least one of the received operating parameters, and pre-set driver target torque map (101b) and engine bsfc optimal torque map (101c) stored in memory (101a) operatively coupled to the hybrid control unit (101),
determining (306), by the hybrid control unit (101), engine target torque (Y5) and motor target torque (Ye) based on the determined real time driver torque demand (Xio) and optimal engine bsfc torque (X12);
sending (308), by the hybrid control unit (101), the determined engine target torque (Y5) and the motor target torque (Ye) to the engine control unit (104) and the motor control unit (106) to operate the hybrid vehicle with optimised fuel efficiency.
2. The method (300) as claimed in claim 1, wherein the plurality of operating parameters comprises:
battery current state of charge (X3), upper limit of battery charge capacity (X4) and lower limit of battery charge capacity X7 received from Battery Management System (103);
brake pressure signal (Xi) and accelerator pedal signal (X2) received from engine control unit (104);
maximum motor generation torque (Xs) and maximum motor torque (X9) received from motor control unit (106);
driver calculated brake pressure (X5) received from ABS control unit
(102); and

driver clutch engagement (Xn) received from transmission control unit (105).
The method (300) as claimed in claim 1, wherein when the determined real time driver torque demand (Xio) is greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor torque (X9) is greater than the determined real time driver torque demand (Xio), the engine control unit (104) operate the engine at optimal engine bsfc torque (X12) and the motor control unit (106) supplement the engine torque by operating the motor to provide adequate torque to meet the determined real time driver torque demand (Xio).
The method (300) as claimed in claim 1, wherein when the determined real time driver torque demand (Xio) is greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor torque (X9) is not greater than the determined real time driver torque demand (Xio), the motor control unit (106) operate the motor to provide maximum motor torque (X9) and the engine control unit (104) supplement the motor torque by operating the engine to provide adequate torque to meet the determined real time driver torque demand (Xio).
The method (300) as claimed in claim 1, wherein when the determined real time driver torque demand (Xio) is not greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor generation torque (Xs) is not greater than the determined real time driver torque demand (Xio), the engine control unit (104) operate the engine at optimal engine bsfc torque (X12) and the motor control unit (106) operate the motor in generator mode to charge battery by using the remaining torque.

The method (300) as claimed in claim 1, wherein when the determined real time driver torque demand (Xio) is not greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor generation torque (Xs) is greater than the determined real time driver torque demand (Xio), the motor control unit (106) operate the motor in generator mode to charge battery by using maximum motor generation torque (Xs) and the engine control unit (104) operate the engine at a higher torque.
The method as claimed in claim 1, wherein the hybrid control unit (101) determine the real time driver torque demand (Xio) and the optimal engine bsfc torque (X12) when there is no brake pressure signal (Xi) and a positive accelerator pedal signal (X2) from the engine control unit (104) and battery current state of charge (X3) between the upper limit of battery charge capacity (X4) and lower limit of battery charge capacity (X7) as received from the Battery Management System (103).
The method as claimed in claim 1, wherein the method (300) further comprises:
determining and transmitting, by the hybrid control unit (101), mechanical break pressure (Yi) to the ABS control unit (102), based on the received plurality of operating parameters;
determining and transmitting, by the hybrid control unit (101), electric brake pressure (Y2) to the motor control unit (106), based on the received plurality of operating parameters;
determining and transmitting, by the hybrid control unit (101), engine running state (Y3) to the engine control unit (104), based on the received plurality of operating parameters; and

determining and transmitting, by the hybrid control unit (101), clutch engagement state (Y4)to the transmission control unit (105), based on the received plurality of operating parameters.
9. A system (100) for controlling a hybrid vehicle, the system (100) comprises:
a hybrid control unit (101) configured to:
receive a plurality of operating parameters,
determine real time driver torque demand (Xio) and optimal engine bsfc torque (X12) based on at least one of the received operating parameters, and pre-set driver target torque map (101b) and engine bsfc optimal torque map (101c) stored in memory (101a) operatively coupled to the hybrid control unit (101),
determine engine target torque (Y5) and motor target torque (Ye) based on the determined real time driver torque demand (Xio) and optimal engine bsfc torque (X12);
send the determined engine target torque (Y5) and the motor target torque (Ye) to the engine control unit (104) and the motor control unit (106) to operate the hybrid vehicle with optimised fuel efficiency
10. The system (100) as claimed in claim 9, wherein the plurality of operating
parameter comprises:
battery current state of charge (X3), upper limit of battery charge capacity (X4) and lower limit of battery charge capacity (X7) received from Battery Management System (103);
brake pressure signal (Xi) and accelerator pedal signal (X2) received from engine control unit (104);
maximum motor generation torque (Xs) and maximum motor torque (X9) received from motor control unit (106);
driver calculated brake pressure (X5) received from ABS control unit
(102); and

driver clutch engagement (Xn) received from transmission control unit (105).
11. The system (100) as claimed in claim 9, wherein when the determined real time driver torque demand (Xio) is greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor torque (X9) is greater than the determined real time driver torque demand (Xio), the engine control unit (104) operate the engine at optimal engine bsfc torque (X12) and the motor control unit (106) supplement the engine torque by operating the motor to provide adequate torque to meet the determined real time driver torque demand (Xio).
12. The system (100) as claimed in claim 9, wherein when the determined real time driver torque demand (Xio) is greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor torque (X9) is not greater than the determined real time driver torque demand (Xio), the motor control unit (106) operate the motor to provide maximum motor torque (X9) and the engine control unit (104) supplement the motor torque by operating the engine to provide adequate torque to meet the determined real time driver torque demand (Xio).
13. The system (100) as claimed in claim 9, wherein when the determined real time driver torque demand (Xio) is not greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor generation torque (Xs) is not greater than the determined real time driver torque demand (Xio), the engine control unit (104) operate the engine at optimal engine bsfc torque (X12) and the motor control unit (106) operate the motor in generator mode to charge battery by using the remaining torque.

14. The system (100) as claimed in claim 9, wherein when the determined real time driver torque demand (Xio) is not greater than the optimal engine bsfc torque (X12) and the summation of the optimal engine bsfc torque (X12) and maximum motor generation torque (Xs) is greater than the determined real time driver torque demand (Xio), the motor control unit (106) operate the motor in generator mode to charge battery by using maximum motor generation torque (Xs) and the engine control unit (104) operate the engine at a higher torque.
15. The system (100) as claimed in claim 9, wherein the hybrid control unit (101) determine the real time driver torque demand (Xio) and the optimal engine bsfc torque (X12) when there is no brake pressure signal (Xi) and a positive accelerator pedal signal (X2) from the engine control unit (104) and battery current state of charge (X3) between the upper limit of battery charge capacity (X4) and lower limit of battery charge capacity (X7) as received from the Battery Management System (103).
16. The system (100) as claimed in claim 9, wherein the system further comprises:
the hybrid control unit (101) further configured to:
determine and transmit mechanical break pressure (Yi) to the ABS control unit (102), based on the received plurality of operating parameters;
determine and transmit electric brake pressure (Y2) to the motor control unit (106), based on the received plurality of operating parameters;
determine and transmit engine running state (Y3) to the engine control unit (104), based on the received plurality of operating parameters; and
determine and transmit clutch engagement state (Y4) to the transmission control unit (105), based on the received plurality of operating parameters.