Description:TECHNICAL FIELD
[0001] The present disclosure relates to the field of electric power trains. Specifically, the present disclosure relates to the field of regenerative braking in electric power trains. More particularly, the present disclosure provides a system and a method for improving regeneration energy efficiency in an electric power train.

BACKGROUND
[0002] As known in the art, vehicles like an electric vehicle (EV), a fuel cell vehicle or a hybrid EV, all comprise an electric drive motor for generating torque by electrical energy and supplying power to the vehicle. The EVs utilize the power of the electric drive motor operated by a battery pack whereas the hybrid EV uses a combination of power from an internal combustion (IC) engine and the electric drive motor. In EVs, there is a regenerative braking mechanism applied as an energy recovery mechanism which slows down the EV by converting its kinetic energy into an electrical energy for charging/recharging of the battery pack.
[0003] The EVs generally do not comprise a damping element between the electric drive motor and a driving shaft, which causes vibration due to the torque of the electric drive motor. In the EVs, as the damping element is absent, vibrations such as shock, jerk and/or vibration of the driving shaft occur during shifting and tip-in/out (e.g., operation of pressing or separating accelerator pedal, disengaging and engaging the pedal) occur which results in deterioration of ride comfort, drivability and regeneration energy efficiency during regenerative braking.
[0004] Further, the electric vehicle including the driving motor may use vibration reduction mechanism that recognizes a deviation between ideal speed and actual speed of the electric drive motor and multiples the deviation between the two speeds by a predetermined value to obtain a result, and feeds back the result to suppress the vibration. In other words, vibration reduction is obtained by applying a positive torque or a negative torque based on a currently generated torque according to vibration of the electric drive motor.
[0005] As conventionally known, a vibration control torque is a control strategy used in EVs power train to reduce or eliminate vibrations that occur due to various factors such as uneven road surfaces, vehicle dynamics and driver behaviour. Conventional vibration control torque strategy is, however, incompetent to utilize the maximum regeneration energy.
[0006] Referring FIG. 1A, vibration distribution can be observed in an EV. As seen from the FIG. 1A, as the speed of the EV increases, the frequency of the vibration/vibration torque also increases, and thus, the torque is not static as it gets influenced by external factors such as the road conditions, vehicle dynamics and driver behaviour. Vibration torque in electric vehicle has several adverse effects including reduced ride comfort, increased noise, mechanical wear/tear, reduced energy efficiency and in extreme cases, it can also lead to instability of the EVs.
[0007] Generally, the motor vibration torque control is relied on the motor variables only (e.g., voltage, current, speed) for suppressing wheel torque vibrations. The key aspect of damping the vibrations is to provide the torque correction signal required to adapt the commanded torque according to the vehicle wheel-road operating condition. Since, wheel-road contact act as a disturbance to the motor, a disturbance-observer may be used to estimate the motor load torque which contains the vibration transferred from the wheel shaft.
[0008] Various ways to reduce vibration torque include electric drive motor structure optimization, controller improvements, and application of extra suspension components. Electric drive motor structure optimization is very challenging as it has multiple constraints as well as multiple objectives, and reduces vibrations in the motor and not eliminates it completely.
[0009] Another approach to control the vibration torque is to improve voltage and current control methods, using active vibration cancellation, control of current chopping, direct control and direct phase current control. Active vibration control is used to suppress wheel torque vibrations.
[0010] Referring FIG. 1B, vehicle drive data analysis representing a variation in target torque and actual torque points for a drive cycle for an EV is illustrated. The graph of FIG. 4C can be validated using the Table 1.1 as below:
Tserr 0-1
(Nm) 1-2
(Nm) 2-3
(Nm) 3-4
(Nm) 4-5
(Nm) 5-6
(Nm) 6-7
(Nm) 7-8
(Nm) 8-9
(Nm) 9-10
(Nm) 10-11
(Nm) 11-12
(Nm) 12-13
(Nm) 13-14
(Nm) 14-15
(Nm) 15-16
(Nm)
No. Counts 36155 38218 23389 11068 4770 1910 840 420 240 130 140 80 50 20 30 30
% 30.8 32.5 19.9 9.4 4.1 1.6 0.7 0.4 0.2 0.1 0.1 0.1 0.0 0.0 0.0 0.0

TABLE 1.1
[0011] As seen from FIG. 4C, a research is performed and vehicle drive data is collected from 117,490 data points over a total drive distance of 1906.46 km. The focus of this analysis is on the 𝑇𝑠𝑒𝑟𝑟, an error between the target torque and the actual torque of the motor. Referring FIG. 4C and TABLE 1.1, the analysis shows that only 0.1% or less of the drive data points collected are associated with a 𝑇𝑠𝑒𝑟𝑟 greater than 10 Nm, which indicates that the available torque band is sufficient to control vibration. It also indicates that the vibration control torque band greater than 12 Nm is insignificant.
[0012] However, on further observation, a lower vibration control torque limit band leads to poor drivability and stability, while a tighter or narrower vibration control torque band results in higher regeneration energy from the electric drive/traction motor. Therefore, there is a need for a balance between vibration control torque limit and regeneration efficiency. The optimization of vibration control torque limit is critical for an e-Powertrain (electric power/drive train) system to achieve higher regeneration. The research emphasizes that any vibration torque limits greater than 10 Nm for a heavy EV, like a passenger EV, will result in over-design with poor utilization of regeneration energy or regeneration efficiency.
[0013] Another important aspect is driving comfort and drivability, which are essential when the vehicle is accelerating, and the motor torque is positive. During this time, no regeneration occurs. Conversely, when torque is negative, a powertrain system with a narrow torque control is beneficial. Fixed vibration control torque values are not an optimal solution. Instead, an adaptive or controlled vibration control torque limit approach, as proposed in the present disclosure, is highly useful for improving regeneration efficiency and increasing the vehicle's range.
[0014] Therefore, this analysis of vehicle drive data demonstrates that an optimized vibration control torque limit is crucial for maximizing regeneration efficiency in an e-Powertrain, wherein a lower vibration control torque band can improve regeneration efficiency but may result in compromised drivability and ride comfort. Therefore, a balance must be struck between these factors, and an adaptive or controlled vibration control torque limit approach, as described as the present disclosure, is preferable to a constant or fixed value.
[0015] While the various conventional systems and methods, as discussed above, facilitate an increase in the regeneration efficiency, there is still a scope for providing an improved solution for improving regeneration energy efficiency in an electric power train of an electric vehicle.

OBJECTS OF THE PRESENT DISCLOSURE
[0016] A general object of the present disclosure is to provide a system and method that obviates the above-mentioned limitations of existing systems and method, and facilitates an improvement in regeneration energy efficiency during regenerative braking.
[0017] An object of the present disclosure is to provide a system and method for improving regeneration energy efficiency in an electric power train of an electric vehicle (EV).
[0018] Another object of the present disclosure is to provide a system and method that ensures improvement in regeneration energy efficiency in the vehicle based on an adaptive or variable vibration control torque.
[0019] Yet another object of the present disclosure is to provide a system and method for improvement in the energy efficiency of a battery pack of the EV.
[0020] Yet another object of the present disclosure is to provide a system and method for improvement in the state of charge of the battery pack of the EV.
[0021] Yet another object of the present disclosure is to provide a system and a method for improvement of range of the vehicle in which an electric power train is used.
[0022] Still another object of the present disclosure is to provide a smart, reliable, and efficient system and method for improving regeneration energy efficiency in the electric power train of the EV.

SUMMARY
[0023] Aspects of the present disclosure relates to the field of electric power trains. Specifically, the present disclosure relates to the field of regenerative braking in electric power trains. More particularly, the present disclosure provides a system and a method for improving regeneration energy efficiency in an electric power train.
[0024] An aspect of the present disclosure pertains to a system for improving regeneration energy efficiency in an electric power train of a vehicle. The system comprises a battery pack, an inverter-rectifier unit, a motor-generator unit and a control unit. The battery pack may be configured for supplying power to the electric power train via the inverter-rectifier unit. The motor-generator unit may be configured for supplying torque to one or more wheels of the vehicle and for performing electric power regeneration in the electric power train of the vehicle. The control unit may be in communication with the battery pack, the inverter-rectifier unit and the motor-generator unit.
[0025] In an aspect, the control unit may comprise a processor coupled with a memory for storing one or more instructions executable by the processor to: determine, an operating mode of the vehicle; vary, a vibration control torque limit for the electric power train; determine, a battery chemical limit based on a real-time state of charge and a real-time temperature of the battery pack; calculate, an available charging power limit and a charging energy of the battery pack based on the vibration control torque limit, the battery chemical limit, a real-time speed of the vehicle and a real-time motor power input of the motor-generator unit; compute, an estimated state of charge of the battery pack; update, the battery chemical limit of the battery pack based upon the estimated state of charge and the real-time temperature of the battery pack; and regulate, the real-time motor power input of the motor-generator unit.
[0026] In an aspect, the system comprises one or more sensors for sensing one or more real-time data of the battery pack and one or more real-time data of the vehicle, wherein the one or more real-time data of the battery pack includes the real-time temperature, the real-time current output, a thermal resistance and an ambient temperature of the battery pack and the one or more real-time data of the vehicle includes the real-time speed, of the vehicle.
[0027] In an embodiment, for the one or more real-time data of the battery pack being a state of charge (SOC) of the battery pack, the system may comprise one or more sensors and one or more estimation methods for estimating the SOC of the battery pack using a real-time battery pack temperature, battery current, and the calculated charging energy of the battery pack.
[0028] In another aspect, the available charging power limit of the battery pack may be calculated as a function of the vibration control torque limit, the battery chemical limit and the real-time speed of the vehicle.
[0029] In yet another aspect, the charging energy of the battery pack may be calculated as an integration function of the available charging power limit and the real-time motor power input.
[0030] In yet another aspect, the real-time temperature of the battery pack may be determined as a function of the real-time current output, the thermal resistance and the ambient temperature of the battery pack.
[0031] Another aspect of the present disclosure pertains to a method for improving regeneration energy efficiency in an electric power train of a vehicle. The method may comprise the steps of: determining, an operating mode of the vehicle; varying, a vibration control torque limit for the electric power train corresponding to the operating mode of the vehicle; determining, a battery chemical limit based on a real-time state of charge and a real-time temperature of the battery pack; calculating, an available charging power limit and a charging energy of the battery pack based on the vibration control torque limit, the battery chemical limit, a real-time speed of the vehicle and a real-time motor power input of the motor-generator unit; computing, an estimated state of charge of the battery pack based on the real-time temperature, the charging energy and a real-time current output of the battery pack; updating, the battery chemical limit of the battery pack based upon the estimated state of charge and the real-time temperature of the battery pack; and regulating, the real-time motor power input of the motor-generator unit.
[0032] In an aspect, the method may further comprise the steps of: determining, the operating mode of the vehicle as a drive mode or a regenerative mode based on the real-time motor power input of the motor-generator unit; selecting, the operating mode of the vehicle as the regenerative mode for a negative value of the real-time motor power input and as the drive mode for a positive value of the real-time motor power input; and setting, the vibration control torque limit as -9 Nm for the regenerative mode and +20 Nm for the drive mode of the vehicle.
[0033] In another aspect, the method may also comprise the steps of: computing, an estimated output torque of the motor-generator unit; comparing, the estimated output torque with an actual output torque of the motor-generator unit to obtain a correction torque; and regulating, the real-time motor power input of the motor-generator unit based on the correction torque.
[0034] 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 THE DRAWINGS
[0035] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0036] FIG. 1A illustrates an exemplary bar chart representing vibration distribution in electric vehicles (EVs), in accordance with an embodiment of the present disclosure.
[0037] FIG. 1B illustrates an exemplary graphical data analysis of a variation in target torque and actual torque points for a drive cycle with a tolerance band of ± 9 Nm for a drive cycle for an EV.
[0038] FIG. 1C illustrates an exemplary graphical representation for a fixed vibration control torque (± 20 Nm), in accordance with an embodiment of the present disclosure.
[0039] FIG. 1D illustrates an exemplary graphical representation for relationship between regeneration energy efficiency and conventional vibration torque control, in accordance with an embodiment of the present disclosure.
[0040] FIG. 1E illustrates an exemplary graphical representation showing an impact of vibration control torque on regeneration energy efficiency, in accordance with an embodiment of the present disclosure.
[0041] FIG. 2 illustrates an exemplary regenerative braking architecture of the proposed system for improving regeneration energy efficiency in an electric power train, to illustrate its overall working, in accordance with an embodiment of the present disclosure.
[0042] FIG. 3 illustrates exemplary functional units of a control unit associated with the proposed system, in accordance with an exemplary embodiment of the present disclosure.
[0043] FIG. 4A illustrates an exemplary graphical representation for an adaptive or variable vibration control torque, in accordance with an embodiment of the present disclosure.
[0044] FIG. 4B illustrates an exemplary graphical representation for variable vibration control torque limit, in accordance with an embodiment of the present disclosure.
[0045] FIG. 4C illustrates an exemplary graphical representation for vibration control torque data analysis, in accordance with an embodiment of the present disclosure.
[0046] FIG. 5 illustrates an exemplary block diagram depicting the proposed system for improving regeneration energy efficiency in relation with a power input and vibration torque control in drive and regeneration mode, in accordance with an embodiment of the present disclosure.
[0047] FIG. 6 illustrates an exemplary block diagram depicting an exemplary simulation model for the proposed system, in accordance with an embodiment of the present disclosure.
[0048] FIG. 7 illustrates an exemplary graphical representation for percentage improvement in charging energy and SOC for a battery, in accordance with embodiments of the present disclosure.
[0049] FIG. 8 illustrates a flow diagram depicting an exemplary proposed method for improving regeneration energy efficiency in an electric power train, in accordance with an embodiment of the present disclosure.
[0050] FIG. 9A and 9B illustrate an exemplary graphical representation for NEDC drive cycle with constant vibration control torque and adaptive vibration control torque, respectively, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0051] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such details as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosures as defined by the appended claims.
[0052] Embodiments explained herein relate to the field of electric power trains. Specifically, the present disclosure relates to the field of regenerative braking in electric power trains. More particularly, the present disclosure provides a system and a method for improving regeneration energy efficiency in an electric power train.
[0053] Referring FIG. 1C, an exemplary graphical representation for a fixed vibration control torque (± 20 Nm) is illustrated. Further, as discussed with reference to FIG. 1A, 4C and TABLE 1.1, and referring FIG. 1C, a fixed vibration control parameter is not recommended, as a higher magnitude of vibration torque can substantially restrict the regeneration power limit imposed by the battery manufacturer.
[0054] For enhancing the regeneration efficiency, a smaller torque band of ± 9 Nm is being identified for analysis and study, as a torque value of ± 9 Nm is significantly better for regeneration without a significant impact on drivability and ride comfort. By narrowing the torque band, the regeneration efficiency of an e-Powertrain system can be improved which can increase the vehicle's range. Therefore, a carefully calibrated vibration control parameter is chosen, which can adapt to changing driving conditions and optimize regeneration efficiency while maintaining a high level of drivability and ride comfort.
[0055] By implementing an adaptive/variable or controlled vibration control torque limit approach, higher regeneration efficiency and a more extended vehicle range can be achieved.
[0056] Further, a correction torque is a dynamical quantity derived from a control algorithm/logic that modifies the torque command input to enhance the drivability of the vehicle.
[0057] The fixed vibration torque limit control methodology utilizes the target motor torque (𝑇𝑒∗) and feedback motor torque (𝑇𝑓), from a control unit of the EV, as inputs to implement the control logic. It employs a constant vibration control torque limit value throughout the system operation, which helps in reducing mechanical vibrations and noise in the motor. However, it has certain limitations and constraints, such as not being able to adapt to changing conditions during operation.
[0058] To address this limitation of the fixed vibration torque limit control methodology, a proposed adaptive/variable vibration torque control method is developed. This employs a dynamically varying correction torque quantity which is derived from the control algorithm/logic. The correction torque modifies the torque command input to enhance the drivability of the vehicle while reducing mechanical vibrations and noise. Unlike the fixed control methodology, the adaptive vibration torque control method can adapt to changing conditions and adjust the torque output accordingly.
[0059] The vehicle traction controller unit can command the electromagnetic torque input, which can determine the charging power during regeneration. Hence, the command torque value becomes an essential input parameter in the adaptive control method.
[0060] Referring FIG. 1D-1E, the relationship between regeneration energy efficiency and conventional vibration torque control, and an impact of vibration control torque on regeneration energy efficiency, are illustrated, respectively, in accordance with an embodiment of the present disclosure. Further, the graph of FIG. 1E can be validated using the Table 1.2, depicting the simulation results for a time instant (e.g., t = 86 sec) of a drive cycle, as below:
Sr. No. Parameter Value
1 Vibration control torque in Nm – 20
2 Power requirement (Pin) in KW – 7.402
3 Battery chemical limit in KW (Plim_chem) – 1.423
4 Power limited by vibration torque in KW (Plim_Vib) – 1.06
TABLE 1.2
[0061] Referring TABLE 1.2 with FIG. 1E, following observations can be made:
Extra Charging power limitation due to vibration control torque = (Plim_chem) - (Plim_Vib)
At t= 86 sec,
 Extra Charging power limitation due to vibration control torque = 1.423 - 1.06 = 0.363 KW
 363 W regenerative power is wasted due to vibration control torque limitation.
 Available charging power during regeneration = 7.402 KW
 Available charging power after chemical limit and vibration torque limits = 1.06 KW
[0062] Thus, even if huge amount of power is available during regenerative braking, it cannot be utilize completely due to battery chemical limit and vibration torque limit.
[0063] Referring FIG. 1D, a conventional vibration control torque method with constant vibration control torque limits the energy efficiency by throttling the regeneration power much below the available charging capacity of battery. Hence, the conventional vibration control torque method is not energy efficient during regeneration mode of the EV.
[0064] Referring FIG. 1E, a relation between battery charging power and vibration control torque limit can be deduced as:
Available charging power limit = [Battery chemical limit – (Vibration control torque × vehicle speed)]
[0065] The battery chemical limit refers to the maximum amount of energy that can be stored or released by a battery cell based on its chemical composition and design. It can be determined by the chemical reactions that occur within the battery cell, which generate and store electrical energy.
[0066] Based on battery state of charge (SOC) and temperature, only some part of energy can be stored by the battery safely which limits the utilization of regeneration energy. Further, during regenerative braking, the electric drive motor can be used as a generator to convert the kinetic energy of the vehicle into electrical energy, which is then stored in the battery for later use.
[0067] However, regenerative braking can generate high levels of vibrations in the electric drive motor and other components of the EV. Thus, to reduce these vibrations, the motor controller uses vibration control methodology to adjust the torque output of the electric drive motor. This limits the maximum torque output of the electric drive motor during regenerative braking, which reduce the amount of energy recovered.
[0068] Further, available charging power limit refers to maximum power that can be delivered to the EV battery pack during regenerative braking. It depends on several factors including SOC, temperature of battery, speed of the vehicle and vibration control torque algorithm used in the vehicle. The recovery of power during regenerative braking can become limited by battery chemical limit and further by vibration control torque.
[0069] In constant vibration control torque approach, this available charging power limit is drastically reduced as the vibration control torque band is constant and wide (± 20 Nm). Therefore, the energy recovery during regeneration is reduced.
[0070] In adaptive/variable vibration control torque approach, this band is reduced for regenerative mode. During drive mode, considering drivability, the band is kept wide. However, to improve the energy efficiency, the band is shrunk during regeneration. Referring FIG. 4A, the vibration control torque limit can be changed from +20 Nm to -9 Nm when motor power changes from positive to negative. This implies that vibration control torque limit is shrunk from +20 Nm to -9 Nm, as the vehicle enters regeneration mode.
[0071] Now, referring to FIG. 2, exemplary network architecture of the proposed system 100 (interchangeably referred to as system 100, herein) is depicted. The system 100 for improving regeneration energy efficiency in an electric power train of a vehicle 110 comprises a battery pack 120, an inverter-rectifier unit 130, a motor-generator unit 140, and a control unit 150. The battery pack 120 can supply power to the electric power train via the inverter-rectifier unit 130. The motor-generator unit 140 can supply torque to one or more wheels of the vehicle 110 and can perform electric power regeneration in the electric power train.
[0072] In an embodiment, for the one or more real-time data of the battery pack 120 being a state of charge (SOC) of the battery pack 120, the system 100 may comprise one or more sensors and one or more estimation methods for estimating the SOC of the battery pack 120 using a real-time battery pack temperature, battery current, and the calculated charging energy of the battery pack 120.
[0073] In an aspect, the control unit 150 can be in communication with the battery pack 120, the inverter-rectifier unit 130 and the motor-generator unit 140. The control unit 150 can include a processor 202 coupled with a memory 204, wherein the memory 204 can store one or more instructions executable by the processor 202 to: determine, by the processor 202, an operating mode of the vehicle 110; vary, by the processor 202, a vibration control torque limit for the electric power train corresponding to the operating mode of the vehicle 110; determine, by the processor 202, a battery chemical limit based on a real-time state of charge and a real-time temperature of the battery pack 120; calculate, by the processor 202, an available charging power limit and a charging energy of the battery pack 120 based on the vibration control torque limit, the battery chemical limit, a real-time speed (Ꞷm) of the vehicle 110 and a real-time motor power input (Pin) of the motor-generator unit 140; compute, by the processor 202, an estimated state of charge of the battery pack 120 based on the real-time temperature, the charging energy and a real-time current output of the battery pack 120; update, by the processor 202, the battery chemical limit of the battery pack 120 based upon the estimated state of charge and the real-time temperature of the battery pack 120; and regulate, by the processor 202, the real-time motor power input (Pin) of the motor-generator unit 140.
[0074] In an embodiment, the system 100 can include one or more sensors for sensing one or more real-time data of the battery pack 120 and one or more real-time data of the vehicle 110. In an aspect, the one or more real-time data of the battery pack 120 can include the real-time temperature, the real-time current output, a thermal resistance and an ambient temperature of the battery pack 120, and the one or more real-time data of the vehicle 110 can include the real-time speed (Ꞷm) of the vehicle 110.
[0075] In an embodiment, the operating mode of the vehicle 110 can be selected as a drive mode or a regenerative mode based on the real-time motor power input (Pin) of the motor-generator unit 140. In an aspect, the vehicle 110 can be considered to be operating in the regenerative mode for a negative value of the real-time motor power input (Pin) and in the drive mode for a positive value of the real-time motor power input (Pin).
[0076] In an aspect, the vibration control torque limit can be set as -9 Nm for the regenerative mode and +20 Nm for the drive mode.
[0077] In another embodiment, the available charging power limit of the battery pack 120 can be calculated as a function of the vibration control torque limit, the battery chemical limit and the real-time speed of the vehicle 110 and the charging energy of the battery pack 120 can be calculated as an integration function of the available charging power limit and the real-time motor power input (Pin).
[0078] In an aspect, the real-time temperature of the battery pack 120 can be determined as a function of the real-time current output, the thermal resistance and the ambient temperature of the battery pack 120.
[0079] Referring to FIG. 3, block diagram 200 represents exemplary functional units of the control unit 150. The control unit 150 can include one or more processor(s) 202. The one or more processor(s) 202 can be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, logic circuitries, and/or any devices that manipulate data based on operational instructions. Among other capabilities, the one or more processor(s) 202 are configured to fetch and execute computer-readable instructions stored in a memory 204 of the control unit 150. The memory 204 can store one or more computer-readable instructions or routines, which may be fetched and executed to create or share the data units over a network service. The memory 204 can include any non-transitory storage device including, for example, volatile memory such as RAM, or non-volatile memory such as EPROM, flash memory, and the like.
[0080] In an embodiment, the control unit 150 can also include an interface(s) 206. The interface(s) 206 may include a variety of interfaces, for example, interfaces for data input and output devices, referred to as I/O devices, storage devices, and the like. The interface(s) 206 may facilitate communication of the system 100 with various devices coupled to the control unit 150. The interface(s) 206 may also provide a communication pathway for one or more components of the control unit 150. Examples of such components include, but are not limited to, processing engine(s) 208 and database 210.
[0081] In an embodiment, the processing engine(s) 208 can be implemented as a combination of hardware and programming (for example, programmable instructions) to implement one or more functionalities of the processing engine(s) 208. In examples described herein, such combinations of hardware and programming may be implemented in several different ways. For example, the programming for the processing engine(s) 208 may be processor executable instructions stored on a non-transitory machine-readable storage medium and the hardware for the processing engine(s) 208 may include a processing resource (for example, one or more processors), to execute such instructions.
[0082] In the present examples, the machine-readable storage medium may store instructions that, when executed by the processing resource, implement the processing engine(s) 208. In such examples, the control unit 150 can include the machine-readable storage medium storing the instructions and the processing resource to execute the instructions, or the machine-readable storage medium may be separate but accessible to the system 100 and the processing resource. In other examples, the processing engine(s) 208 may be implemented by electronic circuitry. The database 210 can include data that is either stored or generated as a result of functionalities implemented by any of the components of the processing engine(s) 208. In an embodiment, the processing engine(s) 208 can include a signal triggering unit 212, an actuating unit 214, a transmitting unit 216, and other units(s) 218. The other unit(s) 218 can implement functionalities that supplement applications/ functions performed by the control unit 150.
[0083] According to an embodiment, the signal triggering unit 212 can trigger a first signal for performing one or more executable instructions stored in the memory 204 such as: determining the operating mode of the vehicle 110, varying the vibration control torque limit, determining the battery chemical limit, calculating the available charging power limit and the charging energy of the battery pack 120, computing the estimated state of charge of the battery pack 120, updating the battery chemical limit, and regulating the real-time motor power input (Pin) of the motor-generator unit 140.
[0084] According to another embodiment, the actuating unit 214 can enable selective actuation of the above discussed one or more executable instructions stored in the memory 204 and executable by the processor 202.
[0085] In another embodiment, the actuating unit 214 can also enable de-actuation of the said one or more executable instructions stored in the memory 204 and executable by the processor 202.
[0086] According to an embodiment, the transmitting unit 216 can facilitate transmission of parameters comprising the operating mode of the vehicle 110, the vibration control torque limit, the battery chemical limit, the available charging power limit, the charging energy of the battery pack 120, the estimated state of charge of the battery pack 120, the battery chemical limit, and the real-time motor power input (Pin) of the motor-generator unit 140.
[0087] Now, referring FIG. 4A-4C, the graph, as shown in FIG. 4C, depicts the location of the 9 Nm torque point within the overall measured drive cycle data of approximately 1000 km. This value represents less than 0.2 % of the total drive sample data points. For the purposes of simulation and analysis, the 9 Nm value has been utilized, and the resultant findings are presented in FIG. 4B.
[0088] Now, referring FIG. 4C, a graph for torque variations and percentage of data points covered against vibration control torque (Target torque - Actual torque) is depicted, in accordance with an exemplary embodiment of the present disclosure.
[0089] The control unit 150 (electric drive motor controller or vehicle 110 control unit (VCU)) can specify a commanded torque value, which is also termed as 𝑻𝒆∗. The 𝑻𝒆∗ value can be used to achieve a particular vehicle 110 speed by adjusting the output torque of the electric drive motor. On the other hand, the actual torque at the electric drive motor output, referred to as 𝑻𝒔, is the amount of torque acting to overcome the resistance or load on the electric drive motor while it is operating. 𝑻𝒔 can primarily be determined by external forces acting on the electric drive motor, such as the resistance of the road, aerodynamic drag, and the weight of the EV. The difference between 𝑻𝒔 and 𝑻𝒆∗ is known as vibration torque. Analysis of various drive cycle data indicates that more than 99 % of vibration torque values are less than 9 Nm, and hence, a vibration control torque limit of ±9 Nm is optimal. The system 100 can allow the use of a wider vibration control torque limit (+20 Nm) when the vehicle 110 is in drive mode, improving drivability and ride comfort. However, when the vehicle 110 is in regeneration mode, the vibration control torque limit will be reduced to -9 Nm from -20 Nm. By using the system 100, the battery pack 120 can utilize more regeneration power, thereby reducing charging time and improving the overall efficiency of the vehicle 110.
[0090] Referring FIG. 5, an exemplary block diagram 500 depicting the proposed system 100 for improving regeneration energy efficiency in relation with a power input and vibration torque control in drive and regeneration mode is illustrates.
[0091] Here, at block 510, the real-time motor power input (Pin) is used to determine the operating mode of the vehicle 110 being a drive mode or a regenerative mode.
[0092] At block 520, if Pin is negative, the vehicle 110 is considered to be in regenerative mode, and otherwise, the vehicle 110 is considered to be in drive mode. Based on operating mode of the vehicle 110, a vibration control torque limit is set. For regenerative mode, the vibration control torque limit is set to -9 Nm, and for drive mode, it is set to +20 Nm.
[0093] At block 530, the available charging power limit is determined using the vibration control torque limit, the real-time speed of the vehicle 110 and the battery chemical limit, wherein the battery chemical limit is determined based on the SOC and temperature of the battery pack 120 at block 570.
[0094] At block 540, using motor power input and available charging power limit, the charging energy of the battery pack 120 is calculated by integrating the available charging power limit.
[0095] At block 550, using the battery current, the real-time temperature and the charging energy, SOC of the battery pack 120 is estimated.
[0096] At block 560, the real-time battery temperature is calculated using the real-time battery current, battery thermal resistance, and an ambient temperature of the battery pack 120 of the vehicle 110.
[0097] At last, both the real-time battery temperature and the estimated SOC of the battery pack 120 are fed back to determine the estimated battery chemical limit, such that the real-time motor power input (Pin) of the motor-generator unit 140 can be efficiently regulated for improving the regeneration energy efficiency of the system 100.
[0098] Now, referring FIG. 6, an exemplary block diagram depicting an exemplary simulation model 600 for the proposed system 100 is illustrated. The verification of the system 100 can also be carried out on a simulation model 600 (for e.g., developed in MATLAB Simulink). The model 600 can be divided into four modules or subsystems: input power data module 610, Pin processing module 620, battery module 630, and results module 640. The model 600 is based on New European Driving Cycle (NEDC).
[0099] In an aspect, the input power data module 610 takes all the input data from the experiment and outputs the real-time motor power input (Pin) and the real-time speed (Ꞷm) of the vehicle 110.
[00100] The Pin processing module 620 then takes the real-time motor power input (Pin), the real-time speed (Ꞷm), SOC and real-time battery temperature as inputs and calculates the charging power limit by vibration control torque. This module also uses Pin as input to derive the mode of vehicle, whether the vehicle is in drive mode or regeneration mode. As per vehicle mode of operation, it changes the vibration control torque and calculates charging power limit using vehicle speed and battery chemical limit. It also determines Pin for constant vibration control torque limit ± 20 Nm and for adaptive/variable vibration control toque + 20 Nm (drive mode) and -9 Nm (regenerative mode) (refer FIGs. 9A and 9B, depicting exemplary graphical representation for NEDC drive cycle with constant vibration control torque and adaptive vibration control torque, respectively).
[00101] The battery module 630 takes the real-time motor power input (Pin) and the charging power limit by vibration control torque as inputs and mainly performs calculation of the charging energy, the estimated SOC and the real-time battery temperature of the battery pack 120. Finally, the results module 640 collects and compiles all the outputs from the input power data module 610, the Pin processing module 620 and the battery module 630, for feedback and utilization by the system 100.
[00102] Now, referring FIGs. 7 and 9A-9B, it can be observed that the application of the varying/adaptive vibration control torque method improves the battery charging energy by a significant amount. This has been confirmed by conducting simulations on a NEDC drive cycle using an EV powertrain model. Further, a significant percentage improvement in charging energy and in SOC has been observed because of narrower vibration control torque limit. The said observations can be seen as confirmed by the experimental values of TABLE 1.3.
Drive cycle used: NEDC
Charging Energy in KWh Initial SOC Final SOC
NEDC drive cycle with constant vibration control torque (FIG. 9A) 2.697 95 36.05
NEDC drive cycle with adaptive vibration control torque (FIG. 9B) 2.867 95 36.74
Difference in charging energy in KWh 0.170
Percentage improvement in charging energy 6.30 %
Percentage improvement in SOC 1.91 %
TABLE 1.3
[00103] Thus, referring FIGs. 7, 9A-9B and above TABLE 1.3, it can be observed that the application of the varying/adaptive vibration control torque method has improved the battery charging energy from 2.6KWh to 2.8KWh. Further, the percentage improvement in charging energy is 6.30 % and that of SOC is 1.91 % because of narrower vibration control torque limit.
[00104] FIG. 8 illustrates a flow diagram depicting an exemplary proposed method 800 for improving regeneration energy efficiency in an electric power train, in accordance with an embodiment of the present disclosure.
[00105] In an aspect, the method 800 for improving regeneration energy efficiency in an electric power train of a vehicle 110 can comprise the step 810 of determining, by a processor 202 of a control unit 150 of the vehicle 110, an operating mode of the vehicle 110.
[00106] In another aspect, the method 800 can comprise the step 820 of varying, by the processor 202, a vibration control torque limit for the electric power train corresponding to the operating mode of the vehicle 110.
[00107] In an aspect, the method 800 can comprise the step 830 of determining, by the processor 202, a battery chemical limit based on a real-time state of charge and a real-time temperature of the battery pack 120.
[00108] In another aspect, the method 800 can comprise the step 840 of calculating, by the processor 202, an available charging power limit and a charging energy of the battery pack 120 based on the vibration control torque limit, the battery chemical limit, a real-time speed (Ꞷm) of the vehicle 110 and a real-time motor power input (Pin) of the motor-generator unit 140.
[00109] In yet another aspect, the method 800 can comprise the step 850 of computing, by the processor 202, an estimated state of charge of the battery pack 120 based on the real-time temperature, the charging energy and a real-time current output of the battery pack 120.
[00110] In yet another aspect, the method 800 can comprise the step 860 of updating, by the processor 202, the battery chemical limit of the battery pack 120 based upon the estimated state of charge and the real-time temperature of the battery pack 120.
[00111] In yet another aspect, the method 800 can comprise the step 870 of regulating, by the processor 202, the real-time motor power input (Pin) of the motor-generator unit 140.
[00112] In an embodiment of the present disclosure, the step 820 of varying the vibration control torque limit for the electric power train can comprises: determining, by the processor 202, the operating mode of the vehicle 110 as a drive mode or a regenerative mode based on the real-time motor power input (Pin) of the motor-generator unit 140; selecting, by the processor 202, the operating mode of the vehicle 110 as the regenerative mode for a negative value of the real-time motor power input (Pin) and as the drive mode for a positive value of the real-time motor power input (Pin); and setting, by the processor 202, the vibration control torque limit as -9 Nm for the regenerative mode and +20 Nm for the drive mode of the vehicle 110.
[00113] In another embodiment of the present disclosure, the method 800 can further comprise: computing, by the processor 202, an estimated output torque of the motor-generator unit 140; comparing, by the processor 202, the estimated output torque with an actual output torque of the motor-generator unit 140 to obtain a correction torque; and regulating, by the processor 202, the real-time motor power input (Pin) of the motor-generator unit 140 based on the correction torque.
[00114] In another embodiment, the step 820 of varying the vibration control torque limit can further facilitate an increase in the charging energy of the battery pack 120 by at least 6.3% and an increase in the state of charge of the battery pack 120 by at least 1.9%, in the regenerative mode of the vehicle 110.
[00115] In an embodiment, the increase in the charging energy and the state of charge of the battery pack 120 depends upon the battery pack capacity, drive cycle, and the vehicle dynamics. In an aspect, the electric power train with a battery pack 120 having a capacity of 25 kWh, when tested using the New European Driving Cycle (NEDC) for 18 rounds of testing, the charging energy is observed to be improved by 6.3%, which is dependent on the electric power train configuration and the drive cycle (NEDC). Further, the state of charge of the battery pack 120 is observed to be increased by 1.9%, specifically during the regenerative mode of the vehicle 110.
[00116] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[00117] The present disclosure provides a system and method that obviates the above-mentioned limitations of existing systems and method, and facilitates an improvement in regeneration energy efficiency during regenerative braking.
[00118] The present disclosure provides a system and method for improving regeneration energy efficiency in an electric power train of an electric vehicle (EV).
[00119] The present disclosure provides a system and method that ensures improvement in regeneration energy efficiency in the vehicle based on an adaptive or variable vibration control torque.
[00120] The present disclosure provides a system and method for improvement in the energy efficiency of a battery pack of the EV.
[00121] The present disclosure provides a system and method for improvement in the state of charge of the battery pack of the EV.
[00122] The present disclosure provides a system and method for improvement in the range of the vehicle in which an electric power train is used.
[00123] The present disclosure provides a smart, reliable, and efficient system and method for improving regeneration energy efficiency in the electric power train of the EV.
, Claims:1. A system (100) for improving regeneration energy efficiency in an electric power train of a vehicle (110), the system (100) comprising:
a battery pack (120) for supplying power to the electric power train via an inverter-rectifier unit (130);
a motor-generator unit (140) for supplying torque to one or more wheels of the vehicle (110) and performing an electric power regeneration in the electric power train of the vehicle (110); and
a control unit (150) in communication with the battery pack (120), the inverter-rectifier unit (130) and the motor-generator unit (140), the control unit (150) comprising a processor (202) coupled with a memory (204), wherein the memory (204) stores one or more instructions executable by the processor (202) to:
determine, by the processor (202), an operating mode of the vehicle (110);
vary, by the processor (202), a vibration control torque limit for the electric power train corresponding to the operating mode of the vehicle (110);
determine, by the processor (202), a battery chemical limit based on a real-time state of charge and a real-time temperature of the battery pack (120);
calculate, by the processor (202), an available charging power limit and a charging energy of the battery pack (120) based on the vibration control torque limit, the battery chemical limit, a real-time speed (Ꞷm) of the vehicle (110) and a real-time motor power input (Pin) of the motor-generator unit (140);
compute, by the processor (202), an estimated state of charge of the battery pack (120) based on the real-time temperature, the charging energy and a real-time current output of the battery pack (120);
update, by the processor (202), the battery chemical limit of the battery pack (120) based upon the estimated state of charge and the real-time temperature of the battery pack (120); and
regulate, by the processor (202), the real-time motor power input (Pin) of the motor-generator unit (140).
2. The system (100) as claimed in claim 1, wherein the system (100) comprises one or more sensors configured to sense one or more real-time data of the battery pack (120) and one or more real-time data of the vehicle (110), wherein the one or more real-time data of the battery pack (120) includes the real-time temperature, the real-time current output, a thermal resistance and an ambient temperature of the battery pack (120) and the one or more real-time data of the vehicle (110) includes the real-time speed (Ꞷm), of the vehicle (110).
3. The system (100) as claimed in claim 1, wherein the operating mode of the vehicle (110) is selected as a drive mode or a regenerative mode based on the real-time motor power input (Pin) of the motor-generator unit (140), wherein the vehicle (110) is considered to be operating in the regenerative mode for a negative value of the real-time motor power input (Pin) and in the drive mode for a positive value of the real-time motor power input (Pin).
4. The system (100) as claimed in claim 3, wherein the vibration control torque limit is set as -9 Nm for the regenerative mode and +20 Nm for the drive mode.
5. The system (100) as claimed in claim 1, wherein:
the available charging power limit of the battery pack (120) is calculated as a function of the vibration control torque limit, the battery chemical limit and the real-time speed of the vehicle (110); and
the charging energy of the battery pack (120) is calculated as an integration function of the available charging power limit and the real-time motor power input (Pin).

6. The system (100) as claimed in claim 2, wherein the real-time temperature of the battery pack (120) is determined as a function of the real-time current output, the thermal resistance and the ambient temperature of the battery pack (120).
7. A method (800) for improving regeneration energy efficiency in an electric power train of a vehicle (110), the method (800) comprising:
determining (810), by a processor (202) of a control unit (150), an operating mode of the vehicle (110);
varying (820), by the processor (202), a vibration control torque limit for the electric power train corresponding to the operating mode of the vehicle (110);
determining (830), by the processor (202), a battery chemical limit based on a real-time state of charge and a real-time temperature of the battery pack (120);
calculating (840), by the processor (202), an available charging power limit and a charging energy of the battery pack (120) based on the vibration control torque limit, the battery chemical limit, a real-time speed (Ꞷm) of the vehicle (110) and a real-time motor power input (Pin) of the motor-generator unit (140);
computing (850), by the processor (202), an estimated state of charge of the battery pack (120) based on the real-time temperature, the charging energy and a real-time current output of the battery pack (120);
updating (860), by the processor (202), the battery chemical limit of the battery pack (120) based upon the estimated state of charge and the real-time temperature of the battery pack (120); and
regulating (870), by the processor (202), the real-time motor power input (Pin) of the motor-generator unit (140).
8. The method (800) as claimed in claim 7, wherein the step of varying (820) the vibration control torque limit for the electric power train comprises:
determining, by the processor (202), the operating mode of the vehicle (110) as a drive mode or a regenerative mode based on the real-time motor power input (Pin) of the motor-generator unit (140);
selecting, by the processor (202), the operating mode of the vehicle (110) as the regenerative mode for a negative value of the real-time motor power input (Pin) and as the drive mode for a positive value of the real-time motor power input (Pin); and
setting, by the processor (202), the vibration control torque limit as -9 Nm for the regenerative mode and +20 Nm for the drive mode of the vehicle (110).
9. The method (800) as claimed in claim 7, comprising:
computing, by the processor (202), an estimated output torque of the motor-generator unit (140);
comparing, by the processor (202), the estimated output torque with an actual output torque of the motor-generator unit (140) to obtain a correction torque; and
regulating, by the processor (202), the real-time motor power input (Pin) of the motor-generator unit (140) based on the correction torque.
10. The method (800) as claimed in claim 7, wherein the step of varying (820) the vibration control torque limit facilitates an increase in the charging energy of the battery pack (120) by at least 6.3% and an increase in the state of charge of the battery pack (120) by at least 1.9%, in the regenerative mode of the vehicle (110), for a New European Driving Cycle (NEDC), wherein the battery pack (120) is configured to be of 25 kWh capacity.