CN111572529B

CN111572529B - Architecture and control strategy for mild hybrid vehicles

Info

Publication number: CN111572529B
Application number: CN201910116898.1A
Authority: CN
Inventors: 刘斌; 杨舟; 黄承修
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2019-02-15
Filing date: 2019-02-15
Publication date: 2023-06-20
Anticipated expiration: 2039-02-15
Also published as: CN111572529A

Abstract

Disclosed is a method for controlling a motor generator ("MG") in a mild hybrid vehicle, the method comprising: determining a status of a fan powered by the engine; determining a speed of the engine; estimating power drawn by the fan in response to the fan status and the engine speed; obtaining a belt drive power limit that represents an amount of power that can be supplied under load by a belt coupled to the fan, the MG, and the engine; determining a power limit for the MG using the estimated power drawn by the fan and the belt drive power limit; determining a power command for the MG in response to a power limit value for the MG and a power demand for the MG; and providing the power command to the MG to control an amount of power that the MG may draw when in the energy recovery mode.

Description

Architecture and control strategy for mild hybrid vehicles

Technical Field

The present disclosure relates generally to hybrid vehicles, and more particularly to an architecture and control strategy for limiting power drawn by a motor-generator in a belt drive configuration to prevent belt slip in a commercial mild hybrid electric vehicle (mild hybrid electric vehicle).

Background

Various types of hybrid electric vehicles are known to provide fuel savings and emissions reductions compared to vehicles powered solely by internal combustion engines. In general, larger hybrid vehicles require higher power motor generators. Such mild hybrid electric vehicles ("MHEVs") typically use a 48 volt battery system in combination with one or more high power motor generators. While mild hybrid systems may be more suitable for large passenger vehicles, no standard architecture is established for commercial vehicles. To provide acceptable hybridization of such commercial vehicles, it is desirable to minimize impact on vehicle layout and design while still achieving the improved power, higher energy efficiency, and reduced emissions provided by the 48 volt mild hybrid system. Thus, improvements, implementation, and control of a mild hybrid vehicle architecture are needed.

Disclosure of Invention

According to one embodiment, the present disclosure provides a method for controlling a motor generator ("MG") in a mild hybrid vehicle, the method comprising: determining a status of a fan powered by an engine of the vehicle; determining the working speed of an engine; estimating power drawn by the fan in response to a state of the fan and an operating speed of the engine; obtaining (access) a belt drive power limit representative of an amount of power that can be supplied under a load by a belt coupled to the fan, the MG, and the engine; determining a power limit value for the MG using the estimated power drawn by the fan and the belt drive power limit; acquiring the power demand of the MG; determining a power command for the MG in response to the power limit value for the MG and the power demand of the MG; and providing a power command to the MG to control an amount of power that the MG may draw when in the energy recovery mode. One aspect of this embodiment further comprises: determining whether the vehicle is in a belt slip mode by: determining the actual working speed of the MG; determining an actual belt ratio by dividing an actual operating speed of the MG by an operating speed of the engine; determining a difference value indicative of a difference between the actual belt ratio and the MG belt ratio; and determining that the vehicle is in a belt slip mode when the difference is greater than a threshold. In a variation of this aspect, the MG belt ratio is the diameter of a pulley (pulley) coupled to the crankshaft of the engine divided by the diameter of a pulley coupled to the MG. In another modification, the step of determining the actual operating speed of the MG includes the steps of: signals are received from a speed sensor coupled to the MG. In another aspect of this embodiment, the step of determining the status of the fan comprises the steps of: the fan is determined to be in an on mode in response to receiving a signal indicating engagement of a clutch coupled to the fan, and the fan is determined to be in an off mode in response to receiving a signal indicating disengagement of the clutch. In another aspect, the step of determining the operating speed of the engine comprises the steps of: a signal is received from a speed sensor coupled to the engine. In yet another aspect, the step of determining the power limit value for the MG includes the steps of: the estimated power drawn by the fan is subtracted from the belt drive power limit. In yet another aspect of the embodiment, the step of determining the power command for the MG includes the steps of: when the power demand of the MG is greater than a power limit value, a power command is established in accordance with the power limit value. In another aspect, the step of providing the power command to the MG includes the steps of: the power command is transmitted from the hybrid control unit to the motor control unit.

In another embodiment, the present disclosure provides a mild hybrid vehicle comprising: an engine; a motor generator ("MG") coupled to the engine through an engine belt, the MG operable in a torque assist mode in which the MG provides power to the engine through the engine belt and an energy recovery mode in which the MG draws power from the engine through the engine belt to thereby apply an MG load to the engine; a fan coupled to the engine belt by a clutch, the fan operable in a closed mode when the clutch is disengaged and in an open mode when the clutch is engaged to apply a fan load to the engine; a controller including a processor and a memory device including instructions that, when executed by the processor, cause the controller to determine whether the vehicle is operating in a belt slip mode and, in response to determining that the vehicle is operating in the belt slip mode, determine whether the fan is operating in the off mode or in the on mode, determine an operating speed of the engine, estimate power drawn by the fan using the operating speed of the engine when the fan is operating in the on mode, determine a power limit for the MG when the MG is operating in the energy recovery mode, the power limit being a difference between a belt drive power limit and the estimated power drawn by the fan, the belt drive power limit representing power that can be supplied by the engine belt, determine a power command for the MG by comparing the power limit with a power demand of the MG, and provide the power command to the MG, wherein the power command is in a power recovery mode when the power demand of the MG is greater than the power limit is reduced. One aspect of this embodiment further comprises: an engine speed sensor coupled to the engine; and an MG speed sensor coupled to the MG; wherein the controller determines whether the vehicle is operating in the belt slip mode by: the method includes receiving an actual engine speed from the engine speed sensor, receiving an actual MG speed from the MG speed sensor, determining an actual engine belt ratio by dividing the actual engine speed by the actual MG speed, determining a difference value indicative of a difference between the actual engine belt ratio and an MG belt ratio, and determining that the vehicle is in the belt slip mode when the difference value is greater than a threshold value. In a variation of this aspect, the MG belt ratio is a ratio of a diameter of a first pulley coupled to the MG to a diameter of a second pulley coupled to a crankshaft of the engine over which the engine belt extends. In another aspect, the power command is the power limit value when the power demand of the MG is greater than the power limit value. In yet another aspect, the controller provides the power command to the MG by transmitting the power command from a hybrid control unit to a motor control unit in communication with the MG. In yet another aspect of this embodiment, the MG is coupled to the engine in a belt integrated starter generator architecture. Another aspect also includes a battery system coupled to the controller, the battery system including a plurality of 48 volt battery packs.

In yet another embodiment, the present disclosure provides a hybrid control unit for a mild hybrid vehicle including an engine and a motor generator ("MG") coupled to the engine by an engine belt, the hybrid control unit comprising: a processor; and a memory device comprising instructions that, when executed by the processor, cause the processor to: determining whether a fan coupled to the engine belt is operating in an on mode, determining an operating speed of the engine, estimating power drawn by the fan using the operating speed of the engine when the fan is operating in the on mode, determining a power limit value for the MG when the MG is operating in an energy recovery mode, the power limit value being a difference between a belt drive power limit representing power that can be supplied by the engine belt and the estimated power drawn by the fan, determining a power command for the MG by comparing the power limit value with a power demand of the MG, and providing the power command to the MG, wherein the power command causes the MG to reduce an amount of power that can be drawn from the engine when the MG is in the energy recovery mode when the power demand of the MG is greater than the power limit value. In one aspect of this embodiment, the instructions, when executed by the processor, further cause the processor to determine whether the vehicle is operating in a belt slip mode by: the method includes receiving an actual engine speed from an engine speed sensor, receiving an actual MG speed from an MG speed sensor, determining an actual engine belt ratio by dividing the actual engine speed by the actual MG speed, determining a difference value indicative of a difference between the actual engine belt ratio and the MG belt ratio, and determining that the vehicle is in the belt slip mode when the difference value is greater than a threshold value. In a variation of this aspect, the MG belt ratio is a ratio of a diameter of a first pulley coupled to the MG to a diameter of a second pulley coupled to a crankshaft of the engine over which the engine belt extends. In another aspect, the power command is the power limit value when the power demand of the MG is greater than the power limit value.

Drawings

The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a simplified conceptual diagram of various architectures for an MHEV;

FIG. 2 is a more detailed conceptual diagram of an MHEV having an architecture and control system according to one embodiment of the present disclosure;

FIG. 3 is a simplified functional diagram of a control method according to one embodiment of the present disclosure;

FIG. 4 is a diagram depicting the relationship between a motor generator pulley and an engine crankshaft pulley of an MHEV;

FIG. 5 is a chart of motor generator power commands according to one embodiment of the present disclosure;

FIG. 6 is a flowchart of a method for determining whether an MHEV is operating in a belt slip mode according to one embodiment of the present disclosure; and

FIG. 7 is a flowchart of a method for determining a power command for an MHEV according to one embodiment of the present disclosure.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the disclosure, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner.

Detailed Description

For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings described below. The exemplary embodiments disclosed herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed in the following detailed description. Rather, the exemplary embodiments are chosen and described so that others skilled in the art may utilize their teachings.

The term "coupled" and variants thereof are used to include both arrangements in which two or more components are in direct physical contact and arrangements in which two or more components are not in direct contact with each other (e.g., the components are "coupled" via at least a third component) but still cooperate or interact with each other. Moreover, the terms "coupled," "coupled," and variations thereof refer to any connection of machine parts known in the art, including, but not limited to, connections with bolts, screws, threads, magnets, electromagnets, adhesives, friction clamps, welding, snaps, clips, and the like.

Throughout this disclosure and in the claims, numerical terms such as first and second are used to reference various components or features. Such use is not intended to indicate ordering of such components or features. Rather, numerical terms are used to aid the reader in identifying the referenced components or features and should not be construed narrowly to provide a particular order of components or features.

Those of ordinary skill in the art will recognize that the embodiments provided may be implemented in hardware, software, firmware, and/or combinations thereof. The programming code according to an embodiment may be implemented in any viable programming language, such as C, C ++, HTML, XTML, JAVA, or any other viable high-level programming language, or a combination of high-level and low-level programming languages.

To meet future government emissions restrictions (e.g., CO ₂ Limit), vehicle manufacturers must turn to more energy efficient automobiles. While reducing weight and losses and increasing driveline efficiency helps achieve greater energy efficiency and thus reduce emissions, in many cases, electrical mixing of the driveline is necessary to meet upcoming emission limits. As an additional benefit, hybrid powertrains generally improve dynamic performance due to the nearly instantaneous torque response of the motor. Mild hybrid electric vehicles ("MHEVs") (as described in more detail below) are becoming increasingly popular as vehicle manufacturers address ever-changing demands concerning the automotive and truck transportation industries.

MHEVs typically utilize a 48 volt battery system and one or more motors, which typically provide 10kW to 20kW of power. According to the size of the vehicle As small as about 10% to 20% CO savings can be achieved by MEHV as compared to a vehicle powered by an internal combustion engine alone ₂ Discharge amount. MHEVs have been largely successful in entering the compact to large (and advanced) passenger car market segment, as compared to the mini car market segment where mini-hybrid (12 volt) vehicles are more popular because of their lower cost. MHEVs, however, are not prevalent in the commercial vehicle market.

As discussed further below, MHEVs may use a variety of architectures including: a belt integration architecture in which a motor generator ("MG") is integrated on the engine side, a transmission integration architecture in which the MG is integrated on the transmission side, and a crankshaft integration architecture in which the MG is integrated between the engine and the transmission. MHEVs gain increasing acceptance in part because they have minimal impact on conventional vehicle and transmission architecture.

Referring now to FIG. 1, a simplified conceptual diagram of various types of MHEV architecture is depicted. Generally, the MHEV 10 includes an internal combustion engine 12, a crankshaft 14, a clutch 16, a transmission 18, a drive shaft 20, at least one differential 22, at least one axle 24, a plurality of wheels 26, and at least one MG (generally designated 28). It should be appreciated that fig. 1 depicts five architectures for MG 28 in the same figure. Only one of these five architectures is typically implemented in a particular MHEV application.

In a first architecture, where MG 28A is engine integrated, MG 28A is directly coupled to crankshaft 14, which is rotationally driven by operation of engine 12, as is known in the art. MG 28A, when in torque-assist mode, applies additional rotational force to crankshaft 14, which powers operation of transmission 18 and the remainder of the driveline, including driveshaft 20, differential 22, shaft 24, and wheels 26, through clutch 16. The mechanical connection from MG 28A to crankshaft 14 is through a gearbox or gear set (not shown), and thus different gear connections may be required to couple to different engines 12.

In a second architecture, where MG 28B is non-engine integrated, MG 28B is laterally attached to crankshaft 14 by belt 30, MG 28B' is laterally attached to transmission 18 by belt 32, or MG 28B "is integrated between engine 12 and transmission 18 on the transmission side of clutch 16. In these different configurations, MG 28B is separate from engine 12 and typically operates at the same speed or a multiple thereof as engine 12.

In a third architecture where MG 28C is non-engine integrated, MG 28C is coupled to transmission 18 or MG 28C' is directly coupled to drive shaft 20 via gear mesh 34. In these configurations, MG 28C is decoupled from engine 12 and typically operates at a speed that is a multiple of the speed of wheels 26.

In a fourth architecture, where MG 28D is non-engine integrated, multiple MGs 28D are coupled to

axles

24A, 24B of MHEV 10, or MG 28D' is coupled to one or both

differentials

22A, 22B. In either case, MG 28D is separated from engine 12.

In a fifth architecture, sometimes referred to as a belt integrated starter generator ("BiSG") architecture, MG 28E is engine integrated via a connection with engine 12 through a belt 36 on a front end accessory drive ("FEAD"). Such an architecture is cost effective because of its very limited impact on existing vehicle architecture. No gearbox is required and integration with different engines can be achieved as the tension of the belt 36 is changed. However, under high power conditions, the belt 36 may slip, resulting in reduced performance. Although not shown in the figures, one or more variable belt tensioners are used with belt 36 to provide increased tension during torque assist operation of MG 28E (i.e., when torque is transferred from MG 28E to engine 12 during cranking and/or lifting (boost)), during energy recovery operation of MG 28E (i.e., when torque is transferred from engine 12 to MG 28E), and to reduce tension during normal running operation to reduce friction losses.

The present disclosure focuses on the fifth architecture described above and provides a method and system for inhibiting belt 36 slip while controlling operation of MG 28E. Accordingly, embodiments of the present disclosure may overcome the disadvantages of the BiSG architecture (limited power due to belt slip) while maintaining minimal impact on vehicle layout, design flexibility, and low cost.

Referring now to FIG. 2, a more detailed conceptual diagram of the MHEV 10 of FIG. 1 having a BiSG architecture is shown. In addition to the components depicted in fig. 1, MHEV 10 also includes: a fan clutch 38, a fan 42, an aftertreatment system 44, a battery system 46, an engine control unit ("ECU") 48, a motor control unit ("MCU") 50, a hybrid control unit ("HCU") 52, and a DC/DC converter 54. In some applications, the engine 12 is an internal combustion engine that uses a fuel such as diesel, gasoline, natural gas, or some combination thereof to generate power that is, among other things, converted into motion of the MHEV 10. In other applications, other types of engines may be used. MG 28E may be any of a number of different devices configured to convert electrical energy to mechanical energy and vice versa. Although MG 28E is shown as a single device, it will be appreciated by those skilled in the art that separate devices (e.g., motor separate from generator) may be used. MG 28E is coupled to engine 12 by an engine belt 36. In some applications, the operation of MG 28E is controlled by MCU 50, which in this example includes a DC-AC converter that provides three-phase AC power to MG 28E. MCU 50 also receives measurements of the operating speed of MG 28E from a speed sensor 37 coupled to MG 28E. The MCU 50 is coupled to the battery system 46, which battery system 46 includes in some embodiments: a battery management unit (not shown), a plurality of battery packs (not shown), and a battery cooling system (not shown). In certain embodiments, DC power is provided to the MCU 50 from the battery pack of the battery system 46 under the control of the battery management unit. In certain applications, the battery pack includes a plurality of lithium ion battery packs, although in other applications, a variety of other suitable energy storage techniques may be used.

The exhaust aftertreatment system 44 is shown in simplified form as including a diesel oxidation catalyst 56, a diesel particulate filter 58, and a selective catalytic reduction catalyst 60. Exhaust aftertreatment system 44 removes harmful particulate matter and chemicals from the exhaust gas produced by engine 12 in a manner known to those skilled in the art.

Combustion occurring within the engine 12 causes rotation of the crankshaft in a conventional manner to provide torque or power to the driveline 20 (i.e., the transmission 18, the driveshaft 20, and the

differentials

22A, 22B). In one application, the crankshaft 14 is coupled to a clutch 16 of a transmission 18, which in turn is coupled to

differentials

22A, 22B through a drive shaft 20 to transfer torque to drive

wheels

26A, 26B of the MHEV 10. The operation of the powertrain and its variants is known to those skilled in the art.

In addition to controlling the flow of DC power to the MCU 50, the battery management unit of the battery system 46 also controls the flow of DC power from the battery pack to the DC/DC converter 54. In this example, the battery pack of MHEV 10 generates 48 volts of DC power for use by MG 28E (after conversion to AC power) in the manner described above. The DC/DC converter 54 converts 48VDC power to 24VDC, which is suitable for use with the various components of the MHEV 10, as shown by the 24V load 62 of fig. 2. In other applications, different voltages may be used.

Control of the operation of the various components of the MHEV 10 is provided by various controllers including the MCU50, ECU48, and HCU 52. In this example, advanced control is provided by an HCM 52, which HCU 52 is coupled to MCU50, ECU48, and DC/DC converter 54. As illustrated herein, for example, HCU 52 controls operation of MG 28E in response to signals from ECU48 indicative of the state of fan 42 and the speed of engine 12, as measured by an engine speed sensor 68 in communication with ECU 48. In this example, the HCU 52 is coupled to these various devices and systems through a CAN bus 64. However, it should be appreciated that any of a variety of suitable connections and networks (wired or wireless) may be used. The ECM 48 provides functional control of the engine 12, the aftertreatment system 44, and other engine related components in a conventional manner. Although ECU48, HCU 52, and MCU50 are shown as separate devices, in some embodiments, the various functions of each device may be implemented by a combination of devices and/or distributed across multiple devices. Accordingly, these various devices may be collectively referred to hereinafter as "controller 66" for purposes of simplifying this description.

In certain embodiments, controller 66 may include a non-transitory memory having instructions that, in response to execution by a processor, cause the processor to determine a speed or torque value of engine 12 or MG 2E and/or various other parameter values of other components as described herein based on input measurements from appropriate sensors. The processor, non-transitory memory, and controller 66 are not particularly limited and may be physically separate, for example.

In some implementations, the controller 66 may form part of a processing subsystem including one or more computing devices with memory, processing, and communication hardware. The controller 66 may be a single device or a distributed device, and the functions of the controller 66 may be performed by hardware and/or as computer instructions on a non-transitory computer readable storage medium (such as non-transitory memory).

In certain embodiments, the controller 66 includes one or more interpreters, determinants, evaluators, regulators, and/or processors that functionally execute the operations of the controller 66. The description herein including an interpreter, a determiner, an evaluator, a regulator, and/or a processor is a structural independence that emphasizes certain aspects of the controller 66, and illustrates a set of operations and responsibilities of the controller 66. Other groupings that perform similar overall operations are understood to be within the scope of the present disclosure. The interpreter, determiner, evaluator, regulator, and processor can be implemented in hardware and/or as computer instructions on a non-transitory computer-readable storage medium, and can be distributed across various hardware or computer-based components.

Examples and non-limiting implementation components that functionally perform the operations of controller 66 include sensors that provide any of the values identified herein, sensors that provide any of the values that are precursors to the values identified herein, data links and/or network hardware, including communication chips, oscillating crystals, communication links, cables, twisted pair wires, coaxial wires, shielded wires, transmitters, receivers and/or transceivers, logic circuits, hardwired logic circuits, reconfigurable logic circuits in a particular non-transient state configured according to a module specification, any actuators (including at least electric, hydraulic, or pneumatic actuators), solenoids, operational amplifiers, analog control components (springs, filters, integrators, adders, subtractors, gain components), and/or digital control components.

Certain operations described herein include operations for interpreting, estimating, and/or determining one or more parameters or data structures. Interpreting, estimating, or determining as utilized herein includes receiving a value by any method known in the art, including at least receiving a value from a data link or network communication, receiving an electronic signal (e.g., a voltage, frequency, current, PWM signal, or pressure signal) indicative of the value, receiving a computer-generated parameter indicative of the value, reading the value from a memory location on a non-transitory computer-readable storage medium, receiving the value as an operational parameter by any means known in the art, and/or receiving a value from which an interpretation parameter can be calculated, and/or by reference to a default value that is interpreted as a parameter value.

The main function of the HCU 52 is to determine a power command to the MG28E in response to a load condition on the FEAD. The two main loads on the engine 12 are MG28E and fan 42. As shown, MG28E may operate in a torque assist mode, wherein no load is placed on engine 12, and in effect power boost is provided to engine 12 via belt 36. MG28E may also operate in an energy recovery mode (e.g., during regenerative braking) in which power is transferred to a generator portion of MG28E via belt 36 to permit MG28E to convert mechanical energy to electrical energy in a manner known in the art. This mode places a relatively high load on the engine 12. As shown herein, using a higher power MG (such as MG28E of MHEV 10) may save more fuel, but when MG28E is operated in the energy recovery mode, it also places a greater load on engine 12 and is more prone to belt 36 slipping than a low power MG (such as in a small passenger vehicle wheel). Finally, MG28E may operate in an idle mode in which it neither provides power to engine 12 nor draws power from engine 12.

The fan 42 operates in one of two modes: the clutch 38 is engaged to transfer power from the belt 36 to operate the fan 42 in an open mode, or in a closed mode in which the clutch 38 is disengaged and the fan 42 is off. When the fan 42 is in the on mode, it places another relatively high load on the engine 12. It has been determined that belt 36 is prone to slip when MG28E is in the energy recovery mode and fan 42 is simultaneously in the on mode, especially in large commercial vehicles that use large fans 42. In all other operating mode combinations of MG28E and fan 42, the risk of belt 36 slipping may be acceptably low.

Referring now to FIG. 3, a high level representation of a control method according to the present disclosure is shown. As shown, ECU 48 determines the status of clutch 38 of fan 42 and provides this information to HCU 52 in the manner described herein. The HCU 52 then uses other information as described herein to determine adjustments to the power command issued to the MG 28E by the MCU 50 to enable the MG 28E to be used to the extent possible in the energy recovery mode while avoiding slipping of the belt 36. More specifically, when the fan 42 is in the on mode and the MG 28E is in the energy recovery mode (hereinafter referred to as "high load mode"), the HCU 52 may reduce the level of recovery power (e.g., from 20kW to 10 kW) that the MG 28E may generate by loading the belt 36 to prevent the belt 36 from slipping, depending on the power drawn by the fan 42 and the calibrated power limit of the belt 36 (as described below).

The degree to which belt 36 is slipping is related in part to the ratio of the size of the pulley coupled to MG 28E to the size of the pulley coupled to engine crankshaft 14. Referring to fig. 4, pulley 70 represents a pulley coupled to MG 28E, while pulley 72 represents a pulley coupled to crankshaft 14. When MG 28E is in the energy recovery mode, belt 36 is driven by pulley 72 to transfer energy to pulley 70 (and MG 28E). When MG 28E is in the power assist mode described above, belt 36 is driven by both pulley 72 and pulley 70. The ratio of the diameter of the pulley 70 to the diameter of the pulley 72 is hereinafter referred to as "MG belt ratio". For example, if the diameter of pulley 70 is 3 inches and the diameter of pulley 72 is 4.75 inches, then the MG belt ratio is 4.75 inches divided by 3 inches, or 1.583.

Referring now to fig. 5, when MG 28E is in the energy recovery mode, the power command issued by HCU 52 to MG 28E through MCU50 may be adjusted to inhibit belt 36 slip depending on the state of fan 42 (i.e., in the open mode or in the closed mode) and the speed value of engine 12. In graph 76 of fig. 5, the y-axis represents the amount of power that MG 28E may generate when in the energy recovery mode, as controlled by the power command from HCU 52. The x-axis represents the operating speed (e.g., in RPM) of the engine 12. For relatively low engine speeds (i.e., speeds below threshold 78), the power command permits MG 28E to resume a linearly increasing amount of power with increasing engine speed, indicated by line segment 80. Under certain operating conditions as described herein, the power command, when in the energy recovery mode, permits MG 28E to continue to resume increasing amounts of power until a maximum power resume value (represented by point 82). For all engine speeds greater than the engine speed corresponding to point 82, HCU 52 commands MG 28E to operate at this maximum power restoration level, as indicated by dashed line 84. However, if the fan 42 is operating (or is beginning to operate) in an on mode, the HCU 52 may issue a power command to the MG 28E to operate at a lower power restoration value, as indicated by the dashed

lines

86 and 88, depending on other operating conditions of the MHEV 10 as described below.

The HCU 52 determines when to control the power command to the MG 28E by identifying when the MHEV 10 is in the belt slip mode, depending on the operating speed of the MG 28E, the operating speed of the engine 12, and the MG belt ratio described above. When the HCU 52 determines that the MHEV 10 is operating in the belt slip mode, the HCU 52 may limit the power command to the MG 28E if the HCU 52 further determines that the MHEV 10 is operating in the high load mode (i.e., the MG 28E is in the energy recovery mode and the fan 42 is in the on mode). Referring now to FIG. 6, a method 90 of the HCU 52 identifying the operation of the MHEV 10 in a belt slip mode is depicted in flowchart form. At block 92, HCU 52 determines the operating speed of MG 28E as identified by MCU 50 based on measurements of speed sensor 37 coupled to MG 28E. At block 94, HCU 52 determines an operating speed of engine 12 as identified by ECU 48 based on measurements of speed sensor 68 coupled to engine 12. At block 96, the HCU 52 divides the operating speed of the MG 28E by the operating speed of the engine 12 to determine the actual ratio of the belt 36, as indicated at block 98.

At block 100, the HCU 52 calculates the MG belt ratio in real time (as described above) for comparison with the actual belt ratio. In other embodiments, the MG belt ratio may be a value stored in a memory device accessible by the HCU 52. At block 102, the HCU 52 subtracts the actual belt ratio from the MG belt ratio. For example, if the actual motor speed is 1000RPM and the actual engine speed is 1500RPM, then the actual ratio of belt 36 is 1500/1000 or 1.5. With the example provided above, if the diameter of the pulley 70 coupled to the MG 28E is 3 inches and the diameter of the pulley 72 coupled to the crankshaft 14 is 4.75 inches, then the MG belt ratio is 1.583. At block 102, in this example, the HCU 52 determines the difference between the MG belt ratio (1.583) and the actual belt ratio (1.5), resulting in a value of 0.083. At block 104, the HCU 52 compares the difference between the MG belt ratio and the actual belt ratio to a threshold value that may be stored in a memory device accessible to the HCU 52. In one embodiment and by way of example, the threshold may be 0.03. In the example provided above, the difference between the MG belt ratio and the actual belt ratio (i.e., 0.083) is greater than 0.03. Accordingly, the HCU 52 determines that the MHEV 10 is operating in a belt slip mode, as indicated by block 106. As indicated above, if the HCU 52 determines that the MHEV 10 is operating in the belt slip mode, the HCU 52 controls the power command provided to the MG 28E to inhibit the belt 36 from slipping in the manner described herein. If the difference between the MG-belt ratio and the actual belt ratio is less than the threshold, the HCU 52 determines that the MHEV 10 is not in a belt slip mode, but is instead operated in a normal operating mode, as depicted at block 108.

It should be appreciated that because the operating conditions of the MHEV 10 are dynamic (i.e., the speed of the engine 12 and the speed of the MG 28E are highly variable), the HCU 52 may filter or otherwise interpret the instantaneous indication of the MHEV 10 operating in the belt slip mode when executing the method 90 of fig. 6. For example, the HCU 52 may periodically perform the method 90, identify during each iteration whether the MHEV 10 is operating in the belt slip mode, and determine that the MHEV 10 is operating in the belt slip mode for a time that may require adjustment of the power command to the MG 28E in the manner described herein only after a certain number of iterations indicate that the MHEV 10 is operating in the belt slip mode.

After the HCU 52 determines that the MHEV 10 is operating in the belt slip mode in the manner described above with reference to fig. 6, the HCU 52 may execute the control method 110 to determine the appropriate power command to the MG 28E, as shown in flow chart form in fig. 7. At block 112, HCU 52 determines the state of clutch 38 (i.e., whether fan 42 is in an on mode or an off mode), as identified by ECU 48. At block 114, HCU 52 determines the operating speed of engine 12 (as identified by ECU 48) based on the measurements from speed sensor 68. At block 116, the HCU 52 estimates the power drawn by the fan 42 based on the state of the fan 42 and the speed of the engine 12. When in the on mode, the fan 42 draws more power through the belt 36, and the amount of power drawn by the fan 42 when in the on mode depends on the speed of the engine 12.

At block 118, the HCU 52 determines a power limit value for the MG 28E based on the estimate of fan power determined at block 116 and the belt drive power limit represented by block 120. The belt drive power limit of block 120 is a value provided by the belt manufacturer and stored in a memory device accessible by the HCU 52. This value represents the amount of torque (and power) that the belt 36 can provide for a given load condition. At block 118, the HCU 52 subtracts the estimated fan power determined at block 116 from the belt drive power limit indicated at block 120 to determine a power limit value for the MG 28E. In other words, the power limit for MG 28E is equal to the power limit that can be provided by belt 36 (i.e., the belt drive power limit) minus the amount of power drawn by fan 42 as estimated at the current speed condition of engine 12. This represents the maximum amount of power that MG 28E may draw without exceeding the belt drive power limit (e.g., when in energy recovery mode).

The HCU 52 determines the power command to the MG 28E by comparing the motor power demand from block 124 to the power limit for the MG 28E. In certain embodiments, motor power demand is provided to the HCU 52 by a power split control module that determines the amount of power provided by the engine 12 and the amount of power provided by the MG 28E in a manner known to those skilled in the art. When the motor power demand from block 124 is less than the power limit for MG 28E as determined at block 118, HCU 52 provides a power command to MG 28E through MCU 50 corresponding to the power demanded by MG 28E. On the other hand, when the motor power demand from block 124 is greater than the power limit for MG 28E (i.e., the motor power demand is likely to cause belt 36 to slip), HCU 52 limits the power command to MG 28E to the power limit for MG 28E, as determined at block 118 and represented by dashed

lines

84, 86, 88 in fig. 5. In other words, the amount of power commanded to be drawn by MG 28E when, for example, in the energy recovery mode while fan 42 is in the on mode is limited or truncated (e.g., from 20kW to 10 kW) to avoid slipping of belt 36. By controlling the MG 28E in this manner, a higher power MG can be used for larger commercial vehicles, such as MHEV10 employing the BiSG architecture, resulting in high energy efficiency, reduced impact on vehicle layout compared to other architectures, design flexibility, and low cost.

While this invention has been described as having an exemplary design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Moreover, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Moreover, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element. Accordingly, the scope is not to be limited by nothing other than the appended claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more".

Furthermore, where a phrase similar to "A, B, or at least one of C" is used in the claims, the phrase is intended to be construed to mean that there may be a single a in an embodiment, a single B in an embodiment, a single C in an embodiment, or any combination of elements A, B or C in a single embodiment; for example, a and B, A and C, B and C, or a and B and C.

Systems, methods, and devices are provided herein. In the detailed description herein, references to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading this description, one of ordinary skill in the relevant art will understand how to implement the present disclosure in alternative embodiments.

Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim herein should be construed in accordance with the provision of 35u.s.c. ≡112 (f) unless the phrase "means for..once again" is used to explicitly recite the element. As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Claims

1. A method for controlling a motor generator MG in a mild hybrid vehicle, the method comprising the steps of:

determining a status of a fan powered by an engine of the vehicle;

determining an operating speed of the engine;

estimating power drawn by the fan in response to a state of the fan and the operating speed of the engine;

obtaining a belt drive power limit representative of an amount of power that a belt coupled to the fan, the MG, and the engine can supply under load;

Determining a power limit value for the MG using the estimated power drawn by the fan and the belt drive power limit;

acquiring the power demand of the MG;

determining a power command for the MG in response to the power limit value of the MG and the power demand of the MG; and

the power command is provided to the MG to control an amount of power that the MG is able to draw when in an energy recovery mode.

2. The method of claim 1, further comprising determining whether the vehicle is in a belt slip mode by:

determining an actual operating speed of the MG;

determining an actual belt ratio by dividing the actual operating speed of the MG by the operating speed of the engine;

determining a difference value indicative of a difference between the actual belt ratio and the MG belt ratio; and

and when the difference is greater than a threshold, determining that the vehicle is in the belt slip mode.

3. The method of claim 2, wherein the MG belt ratio is a diameter of a pulley coupled to a crankshaft of the engine divided by a diameter of a pulley coupled to the MG.

4. The method of claim 2, wherein determining an actual operating speed of the MG comprises receiving a signal from a speed sensor coupled to the MG.

5. The method of any of claims 1-4, wherein determining the status of the fan comprises determining that the fan is in an on mode in response to receiving a signal indicating engagement of a clutch coupled to the fan, and determining that the fan is in an off mode in response to receiving a signal indicating disengagement of the clutch.

6. The method of any of claims 1-4, wherein determining an operating speed of the engine comprises receiving a signal from a speed sensor coupled to the engine.

7. The method of any one of claims 1 to 4, wherein the step of determining a power limit value for the MG includes subtracting the estimated power drawn by the fan from the belt drive power limit.

8. The method according to any one of claims 1 to 4, wherein the step of determining a power command for the MG includes establishing the power command at the power limit value when the power demand of the MG is greater than the power limit value.

9. The method of any one of claims 1 to 4, wherein the step of providing the power command to the MG includes transmitting the power command from a hybrid control unit to a motor control unit.

10. A mild hybrid vehicle, the mild hybrid vehicle comprising:

an engine;

a motor generator MG coupled to the engine through an engine belt, the MG being operable in a torque assist mode in which the MG provides power to the engine through the engine belt and an energy recovery mode in which the MG draws power from the engine through the engine belt, thereby applying an MG load on the engine;

a fan coupled to the engine belt by a clutch, the fan being operable in a closed mode in which the fan is in when the clutch is disengaged and an open mode in which the fan is in when the clutch is engaged, thereby applying a fan load on the engine;

a controller comprising a processor and a memory device comprising instructions that, when executed by the processor, cause the controller to determine whether the vehicle is operating in a belt slip mode, and in response to determining that the vehicle is operating in the belt slip mode

Determining whether the fan is operating in the off mode or in the on mode,

the operating speed of the engine is determined,

when the fan is operating in the on mode, the operating speed of the engine is used to estimate the power drawn by the fan,

determining a power limit value of the MG, which is a difference between a belt drive power limit representing power that can be supplied by the engine belt and the estimated power drawn by the fan, when the MG is operating in the energy recovery mode,

determining a power command for the MG by comparing the power limit value with a power demand of the MG, and

the power command is provided to the MG, wherein the power command causes the MG to reduce an amount of power that can be drawn from the engine when in the energy recovery mode when the power demand of the MG is greater than the power limit value.

11. The mild hybrid vehicle according to claim 10, further comprising:

an engine speed sensor coupled to the engine; and

An MG speed sensor coupled to the MG;

wherein the controller determines whether the vehicle is operating in the belt slip mode by:

an actual engine speed is received from the engine speed sensor,

an actual MG speed is received from the MG speed sensor,

an actual engine belt ratio is determined by dividing the actual engine speed by the actual MG speed,

determining a difference value representing a difference between the actual engine belt ratio and the MG belt ratio, an

12. The mild hybrid vehicle according to claim 11, wherein the MG belt ratio is a ratio of a diameter of a first pulley coupled to the MG to a diameter of a second pulley coupled to a crankshaft of the engine over which the engine belt extends.

13. The mild hybrid vehicle according to any one of claims 10 to 12, wherein the power command is the power limit value when the power demand of the MG is greater than the power limit value.

14. The mild hybrid vehicle according to any one of claims 10 to 12, wherein the controller provides the power command to the MG by transmitting the power command from a hybrid control unit to a motor control unit that communicates with the MG.

15. The mild hybrid vehicle according to any one of claims 10 to 12, wherein the MG is coupled to the engine in a belt-integrated starter-generator architecture.

16. The mild hybrid vehicle of any one of claims 10 to 12, further comprising a battery system coupled to the controller, the battery system comprising a plurality of 48 volt battery packs.

17. A hybrid control unit for a mild hybrid vehicle including an engine and a motor generator MG coupled to the engine by an engine belt, the hybrid control unit comprising:

a processor; and

memory device including instructions that, when executed by the processor, cause the processor to

Determining whether a fan coupled to the engine belt is operating in an open mode,

the operating speed of the engine is determined,

determining a power limit value of the MG, which is a difference between a belt drive power limit representing power that can be supplied by the engine belt and the estimated power drawn by the fan, when the MG is operating in an energy recovery mode,

the power command is provided to the MG, wherein the power command causes the MG to reduce an amount of power that can be drawn from the engine when the MG is in the energy recovery mode when the power demand of the MG is greater than the power limit value.

18. The hybrid control unit of claim 17, wherein the instructions, when executed by the processor, further cause the processor to determine whether the vehicle is operating in a belt slip mode by:

the actual engine speed is received from an engine speed sensor,

the actual MG speed is received from the MG speed sensor,

19. The hybrid control unit of claim 18, wherein the MG belt ratio is a ratio of a diameter of a first pulley coupled to the MG to a diameter of a second pulley coupled to a crankshaft of the engine over which the engine belt extends.

20. The hybrid control unit according to any one of claims 17 to 19, wherein the power command is the power limit value when the power demand of the MG is greater than the power limit value.