CN111572529A

CN111572529A - Architecture and control strategy for mild hybrid vehicle

Info

Publication number: CN111572529A
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: 2020-08-25
Anticipated expiration: 2039-02-15
Also published as: CN111572529B

Abstract

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

Description

Architecture and control strategy for mild hybrid vehicle

Technical Field

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

Background

Hybrid electric vehicles of various types are known to provide fuel savings and emissions reductions compared to vehicles powered solely by internal combustion engines. Generally, larger hybrid vehicles require higher power motor generators. Such mild hybrid electric vehicles ("MHEVs") typically use a 48 volt battery system in conjunction with one or more high power motor generators. While mild hybrid systems may be more suitable for large passenger vehicles, no standard architecture has been established for commercial vehicles. To provide acceptable hybridization of such commercial vehicles, it is desirable to minimally impact vehicle layout and design while still achieving the improved power, higher energy efficiency, and reduced emissions provided by 48 volt mild hybrid systems. Accordingly, improvements, implementation, and control of mild hybrid vehicle architectures 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 state of a fan powered by an engine of the vehicle; determining the working speed of the engine; estimating the power drawn by the fan in response to the state of the fan and the operating speed of the engine; obtaining (accessing) a belt drive power limit representing 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 MG; determining a power command for the MG in response to a power limit value for the MG and a 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. An 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 representing 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 modification of this aspect, the MG belt ratio is a diameter of a pulley (pully) coupled to a crankshaft of the engine divided by a 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: a signal is 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 method includes 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. 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 still 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 this embodiment, the step of determining a power command for the MG includes the steps of: when the power demand of the MG is larger than a power limit value, a power command is established at the power limit value. In another aspect, the step of providing the power command to the MG includes the steps of: a 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 by an engine belt, the MG being operable in a torque-assist mode in which the MG powers the engine by the engine belt and an energy recovery mode in which the MG draws power from the engine by the engine belt to apply an MG load on the engine; a fan coupled to the engine belt by a clutch, the fan operable in an off mode when the clutch is disengaged and in an on mode when the clutch is engaged to place 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, determine whether the fan is operating in the off mode or 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 value for the MG when the MG is operating in the energy recovery mode, the power limit value 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 may be supplied by the engine belt, 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 reduces an amount of power that the MG can draw from the engine when in the energy recovery mode when the power demand of the MG is greater than the power limit value. An 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: 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 representing a difference between the actual engine belt ratio and 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, the engine belt extending over the first and second pulleys. 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 communicating 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 further 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 open 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 open 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 and the estimated power drawn by the fan, the belt drive power limit representing power that can be supplied by the engine belt, 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 when the power demand of the MG is greater than the power limit value, the power command causes the MG to draw power from the engine when the MG is in the energy recovery mode The amount of power of (3) is reduced. 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 a MG speed sensor, determining an actual engine belt ratio 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, and determining that the vehicle is in the belt slip mode when the difference value is greater than a threshold value. In a modification 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, the engine belt extending over the first and second pulleys. 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 a MHEV;

FIG. 2 is a more detailed conceptual diagram of a MHEV having an architecture and a 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 the motor-generator pulley and the engine crankshaft pulley of a MHEV;

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

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

FIG. 7 is a flow chart of a method for determining a power command for a 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 and 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 terms "coupled," "coupled," and variations 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., "coupled" via at least a third component), but yet still cooperate or interact with each other. Moreover, the terms "couple," "coupled," and variations thereof refer to any connection of machine components known in the art, including, but not limited to, connections with bolts, screws, threads, magnets, electromagnets, adhesives, friction clamps, welds, 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. This use is not intended to indicate a ranking of such components or features. Rather, numerical terms are used to help the reader identify referenced components or features, and should not be construed narrowly as providing a particular order of components or features.

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

To meet future government emissions limits (e.g., CO) for vehicles₂Limit), vehicle manufacturers must turn to more energy efficient automobiles. While reducing weight and losses and improving powertrain efficiency help achieve greater energy efficiency and thus reduced emissions, in many cases, electrical hybridization of the powertrain is necessary to meet upcoming emission limits. As an additional benefit, hybrid powertrains typically 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 more and more prevalent as vehicle manufacturers address the ever-changing needs associated with 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. Depending on the size of the vehicle, a MEHV may save about 10% to 20% of CO compared to a vehicle powered by an internal combustion engine only₂And (4) discharging the amount. Compared to the minicar segment market, where miniature hybrid (12 volt) vehicles are more prevalent due to their lower cost, MHEVs are primarily successful in entering the compact to large (and premium) passenger car segment market. However, MHEVs are not prevalent in the commercial vehicle market.

As discussed further below, MHEVs may use various architectures including: a motor generator ("MG") is integrated in an engine-side belt integrated architecture, a transmission integrated architecture with a MG integrated in a transmission side, and a crankshaft integrated architecture with a MG integrated between the engine and the transmission. Part of the reason MHEVs gain increasing acceptance is that they have minimal impact on conventional vehicle and transmission architectures.

Referring now to FIG. 1, a simplified conceptual diagram of various types of MHEV architectures is depicted. Generally speaking, the MHEV10 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 understood that fig. 1 depicts five architectures for MG28 in the same figure. Only one of these five architectures is typically implemented in a particular MHEV application.

In a first architecture in which the MG 28A is engine integrated, the MG 28A is directly coupled to the crankshaft 14, which is rotationally driven by operation of the engine 12 as is known in the art. MG 28A, when in the torque-assist mode, applies additional rotational force to crankshaft 14, which powers the operation of transmission 18 and the remainder of the powertrain, including drive shaft 20, differential 22, shafts 24, and wheels 26, through clutch 16. The mechanical connection from the MG 28A to the 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 a belt 30, MG 28B' is laterally attached to transmission 18 by a belt 32, or MG 28B "is integrated between engine 12 and transmission 18 on the transmission side of clutch 16. In these different configurations, the MG 28B is separate from the engine 12 and typically operates at the same speed as the engine 12 or a multiple thereof.

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

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

shafts

24A, 24B of the MHEV10, or MG 28D' is coupled to one or both

differentials

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

In a fifth architecture, sometimes referred to as a belt integrated starter generator ("BiSG") architecture, the MG28E is engine-integrated via a connection to the engine 12 through a belt 36 on a front end accessory drive ("FEAD"). Such an architecture is cost effective because its impact on existing vehicle architectures is very limited. No gearbox is required and integration with different engines can be achieved with varying tension of belt 36. 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 the belt 36 to provide increased tension during torque assist operation of the MG28E (i.e., when torque is transferred from the MG28E to the engine 12 during cranking and/or lift (boost)), increased tension during energy recovery operation of the MG28E (i.e., when torque is transferred from the engine 12 to the MG 28E), and reduced tension to reduce frictional losses during normal driving operation.

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 MHEV10 of FIG. 1 with a BiSG architecture is shown. In addition to the components depicted in FIG. 1, the MHEV10 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 converted into the motion of the MHEV10, among other things. In other applications, other types of engines may be used. MG28E may be any of a number of different devices configured to convert electrical energy to mechanical energy and mechanical energy to electrical energy. While MG28E is shown as a single device, those skilled in the art will appreciate that separate devices (e.g., a motor separate from a generator) may be used. MG28E is coupled to engine 12 by an engine belt 36. In some applications, the operation of MG28E is controlled by MCU50, which in this example comprises a DC-AC converter that provides three-phase AC power to MG 28E. MCU50 also receives measurements of the operating speed of MG28E from a speed sensor 37 coupled to MG 28E. The MCU50 is coupled to the battery system 46, which battery system 46 in some embodiments includes: a battery management unit (not shown), a plurality of battery packs (not shown), and a battery cooling system (not shown). In some embodiments, DC power is provided to the MCU50 from a battery pack of the battery system 46 under the control of a battery management unit. In some applications, the battery pack includes a plurality of lithium ion battery packs, although in other applications, various other suitable energy storage technologies 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 crankshaft rotation 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 transmit torque to drive

wheels

26A, 26B of the MHEV 10. 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 MCU50, 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 MHEV10 generates 48 volts of DC power for use by MG28E (after conversion to AC power) in the manner described above. The DC/DC converter 54 converts 48VDC power to 24VDC, which is suitable for various components of the MHEV10, 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 MHEV10 is provided by various controllers including the MCU50, the ECU48, and the HCU 52. In this example, advanced control is provided by the HCM 52, which HCU 52 is coupled to the MCU50, the ECU48, and the DC/DC converter 54. As explained herein, the HCU 52 controls operation of the MG28E in response to signals from the ECU48 indicative of the state of the fan 42 and the speed of the engine 12, as measured by the engine speed sensor 68 in communication with the ECU48, for example. In this example, the HCU 52 is coupled to these various devices and systems by 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 the ECU48, HCU 52, and MCU50 are shown as separate devices, in certain embodiments, the various functions of each device may be implemented by a combination of devices and/or distributed across multiple devices. Accordingly, for purposes of simplifying this description, these various devices may be collectively referred to hereinafter as "controller 66".

In certain embodiments, the controller 66 may include non-transitory memory having instructions that, in response to execution by a processor, cause the processor to determine a speed or torque value of the 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 certain embodiments, the controller 66 may form part of a processing subsystem, including one or more computing devices having memory, processing, and communication hardware. The controller 66 can be a single device or a distributed device, and the functions of the controller 66 can be performed by hardware and/or as computer instructions on a non-transitory computer readable storage medium (e.g., non-transitory memory).

In certain embodiments, controller 66 includes one or more interpreters, determiners, evaluators, regulators, and/or processors that functionally execute the operations of controller 66. The description herein including interpreters, determiners, evaluators, regulators, and/or processors is intended to emphasize the structural independence of certain aspects of controller 66 and to illustrate a set of operations and responsibilities of 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 may be implemented in hardware and/or as computer instructions on a non-transitory computer-readable storage medium, and may be distributed across various hardware or computer-based components.

Example and non-limiting implementation components that functionally perform the operations of controller 66 include sensors that provide any values determined herein, sensors that provide any values that are precursors to values determined herein, data link and/or networking 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 certain non-transient states configured according to module specifications, any actuator (including at least an electric, hydraulic, or pneumatic actuator), 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 on-time parameter by any means known in the art, and/or by receiving a value from which an interpretation parameter can be calculated, and/or by referencing a default value that is interpreted as a parameter value.

The main function of the HCU 52 is to determine a power command for the MG28E in response to a load condition on the FEAD. The two primary loads on the engine 12 are the MG28E and the fan 42. As shown, the MG28E may operate in a torque-assist mode, wherein there is no load on the engine 12 and the engine 12 is actually powered up via the belt 36. MG28E may also operate in an energy recovery mode (e.g., during regenerative braking), wherein 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 operating in the energy recovery mode, it also places a greater load on engine 12 and makes it easier for belt 36 to slip than a lower power MG (such as in a small passenger wheel). Finally, MG28E may operate in an idle mode, wherein it neither provides power to engine 12 nor draws power from engine 12.

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

Referring now to FIG. 3, a high level representation of a control method according to the present disclosure is shown. As shown, the ECU48 determines the state of the clutch 38 of the fan 42 in the manner described herein and provides this information to the HCU 52. The HCU 52 then uses the other information as described herein to determine adjustments to the power commands issued by the MCU50 to the MG28E to enable the MG28E to be used in the energy recovery mode to the extent possible while avoiding belt 36 slippage. More specifically, when the fan 42 is in the on mode and the MG28E is in the energy recovery mode (hereinafter "high load mode"), the HCU 52 may reduce the level of recovered power that the MG28E may generate by loading the belt 36 (e.g., from 20kW to 10kW) to prevent the belt 36 from slipping, depending on the power drawn by the fan 42 and calibrated power limits of the belt 36 (described below).

The degree to which the belt 36 is susceptible to slipping is related in part to the ratio of the size of the pulley coupled to the MG28E to the size of the pulley coupled to the engine crankshaft 14. Referring to fig. 4, the pulley 70 represents a pulley coupled to the MG28E, and the pulley 72 represents a pulley coupled to the crankshaft 14. When MG28E is in the energy recovery mode, belt 36 is driven by pulley 72 to transfer energy to pulley 70 (and MG 28E). When the MG28E is in the power assist mode described above, the belt 36 is driven by both the pulley 72 and the pulley 70. The ratio of the diameter of the pulley 70 to the diameter of the pulley 72 is hereinafter referred to as the "MG belt ratio". For example, if the diameter of the pulley 70 is 3 inches and the diameter of the 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 the MG28E is in the energy recovery mode, the power command issued by the HCU 52 to the MG28E through the MCU50 may be adjusted to inhibit belt 36 from slipping depending on the state of the fan 42 (i.e., whether in the on or off mode) and the speed value of the engine 12. In graph 76 of FIG. 5, the y-axis represents the amount of power that MG28E may generate when in energy recovery mode, as controlled by power commands from the HCU 52. The x-axis represents the operating speed of the engine 12 (e.g., in RPM). For relatively low engine speeds (i.e., speeds below threshold 78), the power command permits MG28E to resume a linearly increasing amount of power as engine speed increases, as represented by line segment 80. Under certain operating conditions as described herein, the power command, when in the energy recovery mode, permits MG28E to continue to resume increasing amounts of power up to a maximum power recovery value (represented by point 82). The HCU 52 commands the MG28E to operate at this maximum power recovery level for all engine speeds greater than the engine speed corresponding to point 82, as indicated by dashed line 84. However, if the fan 42 is operating (or beginning to operate) in the on mode, the HCU 52 may issue a power command to the MG28E to operate at a lower power recovery value, as indicated by dashed

lines

86 and 88, depending on other operating conditions of the MHEV10 as described below.

The HCU 52 determines when to control the power command to the MG28E by identifying when the MHEV10 is in the belt slip mode, depending on the operating speed of the MG28E, the operating speed of the engine 12, and the MG belt ratio described above. When the HCU 52 determines that the MHEV10 is operating in the belt slip mode, the HCU 52 may limit the power command to the MG28E if the HCU 52 further determines that the MHEV10 is operating in the high load mode (i.e., the MG28E 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 operation of the MHEV10 in a belt slip mode is depicted in flow chart form. At block 92, the HCU 52 determines the operating speed of the MG28E as identified by the MCU50 based on measurements of the speed sensor 37 coupled to the MG 28E. At block 94, the HCU 52 determines the operating speed of the engine 12 as identified by the ECU48 based on measurements of the speed sensor 68 coupled to the engine 12. At box 96, the HCU 52 divides the operating speed of the MG28E by the operating speed of the engine 12 to determine the actual ratio of the belt 36, as indicated by box 98.

At block 100, the HCU 52 calculates the MG belt ratio (as described above) in real time 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 the belt 36 is 1500/1000 or 1.5. Using the example provided above, if the diameter of the pulley 70 coupled to the MG28E 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, 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 in this example. 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 by 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 MHEV10 is operating in a belt slip mode, as shown in block 106. As indicated above, if the HCU 52 determines that the MHEV10 is operating in a belt slip mode, the HCU 52 controls the power commands provided to the MG28E to inhibit belt 36 slip as 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 MHEV10 is not in a belt slip mode, but is operating in a normal operating mode, as shown in block 108.

It should be appreciated that because the operating conditions of the MHEV10 are dynamic (i.e., the speed of the engine 12 and the speed of the MG28E are highly variable), the HCU 52 may filter or otherwise interpret the instantaneous indication that the MHEV10 is operating in the belt slip mode when executing the method 90 of fig. 6. For example, the HCU 52 may periodically execute the method 90, identifying whether the MHEV10 is operating in the belt slip mode during each iteration, and determining that the MHEV10 is operating in the belt slip mode for a time that may require adjustment of the power command to the MG28E in the manner described herein only after a certain number of iterations indicate that the MHEV10 is operating in the belt slip mode.

After the HCU 52 determines that the MHEV10 is operating in the belt slip mode in the manner described above with reference to FIG. 6, the HCU 52 may execute a control method 110 to determine an appropriate power command for the MG28E, as shown in flow chart form in FIG. 7. At block 112, the HCU 52 determines the state of the clutch 38 (i.e., whether the fan 42 is in an on mode or an off mode), as identified by the ECU 48. At block 114, the HCU 52 determines the operating speed of the engine 12 (as identified by the ECU 48) based on the measurements from the 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 is dependent on the speed of the engine 12.

At block 118, the HCU 52 determines a power limit value for the MG28E 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 represented by block 120 to determine a power limit value for the MG 28E. In other words, the power limit for the MG28E is equal to the power limit that can be provided by the belt 36 (i.e., the belt drive power limit) minus the amount of power drawn by the fan 42 as estimated at the current speed conditions of the engine 12. This represents the maximum amount of power that MG28E can draw without exceeding the belt drive power limit (e.g., when in energy recovery mode).

The HCU 52 determines the power command for the MG28E by comparing the motor power demand from block 124 to the power limit value for the MG 28E. In certain embodiments, the motor power demand is provided to the HCU 52 by a power distribution control module that determines the amount of power provided by the engine 12 and the amount of power provided by the MG28E 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 MG28E as determined at block 118, HCU 52 provides a power command to MG28E through MCU50 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 the MG28E (i.e., the motor power demand is likely to cause the belt 36 to slip), the HCU 52 limits the power command for the MG28E to the power limit for the MG28E, 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 MG28E is limited or truncated (e.g., from 20kW to 10kW) when, for example, in the energy recovery mode while fan 42 is in the on mode to avoid belt 36 slipping. By controlling the MG28E in this manner, higher power MGs may be used for larger commercial vehicles, such as MHEVs 10 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 may 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. Further, 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.

Furthermore, 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 of any or all the claims. Accordingly, the scope is not to be limited by anything else than the appended claims, in which 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, it is intended that the phrase be interpreted to mean that there may be a alone in an embodiment, a alone B in an embodiment, a alone 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 apparatuses 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. Further, 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, it will become apparent to a person skilled in the relevant art how to implement the 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. Any claims herein should not be construed in accordance with the provisions of 35u.s.c. § 112(f), unless the element is explicitly recited using the phrase "means for. 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 state of a fan powered by an engine of the vehicle;

determining an operating speed of the engine;

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

obtaining a belt drive power limit representing an amount of power a belt coupled to the fan, the MG, and the engine is capable of supplying under load;

determining a power limit value of 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 for the MG and the power demand for the MG; and

providing the power command to the MG to control an amount of power the MG is capable of drawing 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 representing a difference between the actual belt ratio and the MG belt ratio; and

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

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 the actual operating speed of the MG comprises receiving a signal from a speed sensor coupled to the MG.

5. The method of claim 1, wherein determining the status of the fan comprises determining that the fan is in an on mode in response to receiving a signal indicating that a clutch coupled to the fan is engaged, and determining that the fan is in an off mode in response to receiving a signal indicating that the clutch is disengaged.

6. The method of claim 1, wherein the step of determining the operating speed of the engine comprises receiving a signal from a speed sensor coupled to the engine.

7. The method of claim 1, wherein determining the power limit for the MG includes subtracting the estimated power drawn by the fan from the belt drive power limit.

8. The method of claim 1, wherein determining a power command for the MG includes establishing the power command at the power limit when the power demand of the MG is greater than the power limit.

9. The method of claim 1, wherein 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, comprising:

an engine;

a Motor Generator (MG) coupled to the engine by an engine belt, the MG being operable in a torque assist mode in which the MG powers the engine by the engine belt and an energy recovery mode in which the MG draws power from the engine by the engine belt to apply an MG load on the engine;

a fan coupled to the engine belt by a clutch, the fan operable in an off mode when the clutch is disengaged and an on mode when the clutch is engaged, the fan being in the on mode to place 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 the on mode,

determining an operating speed of the engine and,

estimating the 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 the energy recovery mode, the power limit value 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,

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 the MG can draw 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:

receiving an actual engine speed from the engine speed sensor,

receives 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 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, the engine belt extending over the first and second pulleys.

13. The mild hybrid vehicle according to claim 10, 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 claim 10, 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 in communication with the MG.

15. The mild hybrid vehicle according to claim 10, wherein the MG is coupled to the engine in a belt integrated starter generator architecture.

16. The mild hybrid vehicle according to claim 10, 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

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 open mode,

determining an operating speed of the engine and,

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

providing the power command to the MG, wherein the power command causes the MG to reduce an amount of power that the MG can draw 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:

receives the actual engine speed from the engine speed sensor,

receives the actual MG speed 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, the engine belt extending over the first and second pulleys.

20. The hybrid control unit of claim 17, wherein the power command is the power limit value when the power demand of the MG is greater than the power limit value.