Adaptive energy management control for hybrid powertrain

Abstract

The invention provides an adaptive energy management control for a hybrid powertrain. A hybrid vehicle includes a powertrain having an engine, an electric machine, and a disconnect clutch configured to selectively couple the engine and the electric machine. The vehicle also includes a controller programmed to command a torque distribution between the engine and the electric machine for a given operating point defined by a driveline speed and a driver demand torque, the torque distribution depending on a duration during which the driveline has been at the given operating point in a previous drive cycle, the torque commanded to the engine decreases and the torque commanded to the electric machine increases as the duration decreases for successive driving cycles.

Description

TECHNICAL FIELD

[0001] The present application relates generally to energy management for hybrid vehicles. BACKGROUND

[0002] Hybrid electric vehicles include a traction battery comprised of multiple battery cells in series and / or parallel. The traction battery provides electrical power for vehicle propulsion and accessory features. During operation, the traction battery can be charged or discharged based on operating conditions including battery state of charge (BSOC), driver demand, and regenerative braking. SUMMARY

[0003] According to one embodiment, a hybrid vehicle includes a powertrain having an engine, an electric machine, and a disconnect clutch configured to selectively couple the engine and the electric machine. The vehicle further includes a controller programmed to command a torque split between the engine and the electric machine for a given operating point defined by powertrain speed and driver demand torque as a function of a duration that the powertrain has been at the given operating point in a previous drive cycle, such that for successive drive cycles, as the duration decreases, the torque commanded to the engine decreases and the torque commanded to the electric machine increases.

[0004] According to another embodiment, a hybrid vehicle powertrain includes a controller programmed to command a torque split between an engine and an electric machine for a given operating point defined by powertrain speed and driver demand torque as a function of a duration that the powertrain has been at the given operating point in a previous drive cycle, such that for successive drive cycles, as the duration increases, the torque commanded to the engine increases and the torque commanded to the electric machine decreases.

[0005] According to yet another embodiment, a method of controlling a hybrid powertrain includes commanding a torque split between an engine and an electric machine for a given operating point defined by powertrain speed and driver demand torque as a function of a duration that the powertrain has been at the given operating point in a previous drive cycle. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 is a schematic representation of a hybrid electric vehicle according to one embodiment.

[0007] Figure 2 is a schematic representation of a lookup table for controlling engine and electric machine torque.

[0008] Figure 3is a control map for determining whether a vehicle powertrain is in a transient condition or a steady state condition and for determining a torque split between an engine and an electric machine.

[0009] Figure 4 is a plot of powertrain parameters for a given operating condition of a powertrain.

[0010] Figure 5 is a flowchart of an algorithm for commanding torque to an engine and an electric machine based on adaptive energy management control. DETAILED DESCRIPTION

[0011] Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features can be exaggerated or minimized for the purpose of clarity and illustration. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present application. As those skilled in the art will appreciate, the various features shown and described herein can be combined to produce embodiments that are not explicitly shown or described. The combination of features from different embodiments is within the scope of the disclosure.

[0012] Reference Figure 1 , a schematic diagram of a hybrid electric vehicle (HEV) 10 is shown in accordance with embodiments of the present disclosure. Figure 1 Representative relationships among components are shown. The physical layout and orientation of components within a vehicle can vary. The HEV 10 includes a powertrain 12. The powertrain 12 includes an engine 14 driving a transmission 16, which can be referred to as a modular hybrid transmission (MHT). As will be described in further detail below, the transmission 16 includes an electric machine, such as a motor / generator (M / G) 18, an associated traction battery 20, a torque converter 22, and a multi-step-ratio automatic transmission or gear box 24. The engine 14, M / G 18, torque converter 22, and automatic transmission 16 are connected in series, as shown in Figure 1 For simplicity, the M / G 18 can be referred to as a motor.

[0013] Both engine 14 and M / G 18 are drive sources for HEV 10 and can be referred to as actuators. Engine 14 generally represents a power source, which can include an internal combustion engine, such as a gasoline, diesel, or natural gas powered engine. When decoupling clutch 26 is at least partially engaged between engine 14 and M / G 18, engine 14 generates engine power and corresponding engine torque, which is supplied to M / G 18. M / G 18 can be implemented by any of a variety of types of electric machines. For example, M / G 18 can be a permanent magnet synchronous motor. Power electronics condition direct current (DC) power provided by battery 20 as required by M / G 18, as described below. For example, the power electronics can provide three-phase alternating current (AC) power to M / G 18.

[0014] When decoupling clutch 26 is at least partially engaged, power flow from engine 14 to M / G 18 or from M / G 18 to engine 14 is possible. For example, decoupling clutch 26 can be engaged, and M / G 18 can act as a generator to convert rotational energy provided by crankshaft 28 and M / G shaft 30 into electrical energy for storage in battery 20. Decoupling clutch 26 can also be disengaged to isolate engine 14 from the rest of powertrain 12, so that M / G 18 can be used as the sole drive source for HEV 10. Shaft 30 extends through M / G 18. M / G 18 is continuously drivingly connected to shaft 30, while engine 14 is drivingly connected to shaft 30 only when decoupling clutch 26 is at least partially engaged. When decoupling clutch 26 is locked (fully engaged), crankshaft 28 is fixed to shaft 30.

[0015] A separate starter motor 31 can be selectively engaged with engine 14 to rotate the engine to allow combustion to begin. Once engine 14 is started, starter motor 31 can be disengaged from engine 14 via, for example, a clutch (not shown) between starter motor 31 and engine 14. In one embodiment, starter motor 31 is a belt integrated starter generator (BISG). In one embodiment, engine 14 is started by starter motor 31 while decoupling clutch 26 is disengaged, thereby keeping engine 14 disconnected from M / G 18. Once engine 14 has been started and brought up to the same rotational speed as M / G 18, decoupling clutch 26 can couple engine 14 to M / G 18 to allow engine 14 to provide drive torque.

[0016] In another embodiment, starter motor 31 is not provided and engine 14 is started by M / G 18. To do so, disconnect clutch 26 is partially engaged to transfer torque from M / G 18 to engine 14. M / G 18 can be required to ramp torque to meet driver demand while also starting engine 14. Once engine speed reaches that of the M / G, disconnect clutch 26 can be fully engaged.

[0017] M / G 18 is connected to torque converter 22 via shaft 30. Thus, when disconnect clutch 26 is at least partially engaged, torque converter 22 is connected to engine 14. Torque converter 22 includes a pump wheel 23 fixed to M / G shaft 30 and a turbine wheel 25 fixed to transmission input shaft 32. Torque converter 22 provides a hydraulic coupling between shaft 30 and transmission input shaft 32. When pump wheel 23 is rotating faster than turbine wheel 25, torque converter 22 transfers power from pump wheel 23 to turbine wheel 25. The magnitude of turbine torque and pump torque generally depends on the relative rotational speeds. When the ratio of pump wheel speed to turbine wheel speed is high enough, turbine torque is several times the pump torque. A torque converter bypass clutch 34 can also be provided that, when engaged, frictionally or mechanically couples pump wheel 23 and turbine wheel 25 of torque converter 22, allowing for more efficient power transfer. Torque converter bypass clutch 34 can operate as a launch clutch to provide a smooth vehicle launch. Alternatively or in combination, for applications that do not include torque converter 22 or torque converter bypass clutch 34, a launch clutch similar to disconnect clutch 26 can be provided between M / G 18 and gear box 24. In some applications, disconnect clutch 26 is generally referred to as an upstream clutch, while launch clutch 34, which can be a torque converter bypass clutch, is generally referred to as a downstream clutch.

[0018] Gear box 24 can include a gear set, such as a planetary gear set, that is selectively placed in different gear ratios by selective engagement of frictional elements, such as clutches and brakes, to establish a desired number of discrete or stepped transmission ratios. For simplicity, gear ratios can be referred to as gears, i.e., first gear, second gear, etc. The frictional elements can be controlled by a shift schedule that connects and disconnects certain elements of the gear set to control the speed and torque ratio between transmission output shaft 36 and transmission input shaft 32. Gear box 24 can have six speeds, including first through sixth gears. In this example, sixth gear can be referred to as the highest gear. First gear has the lowest transmission ratio and highest torque ratio between input shaft 32 and output shaft 36, and the highest gear has the highest transmission ratio and lowest torque ratio. Gear box 24 is automatically shifted from one ratio to another by an associated controller, such as a powertrain control unit (PCU), based on various vehicle and environmental operating conditions. Gear box 24 then provides a powertrain output torque to output shaft 36.

[0019] It should be understood that the hydraulically controlled gearbox 24 used with the torque converter 22 is merely one example of a gearbox or transmission arrangement; any multi-ratio gearbox that accepts one or more input torques from an engine and / or motor and then supplies torque to the output shaft at different ratios is acceptable for use with embodiments of this disclosure. For example, gearbox 24 can be implemented by an automated mechanical (or manual) transmission (AMT) that includes one or more servo motors to cause shift forks to translate / rotate along shift rails to select the desired gear ratio. As is generally understood by those skilled in the art, AMTs can be used, for example, in applications with high torque requirements.

[0020] like Figure 1 As shown in a representative embodiment, output shaft 36 is connected to differential 40. Differential 40 drives a pair of wheels 42 via a corresponding axle 44 connected to differential 40. Differential 40 transmits approximately equal torque to each wheel 42, while allowing slight speed differences, such as when the vehicle 10 is turning. Different types of differentials or similar devices can be used to distribute torque from the powertrain to one or more wheels. In some applications, torque distribution may vary according to, for example, a specific operating mode or condition.

[0021] The powertrain system 12 also includes one or more controllers 50, such as a powertrain control unit (PCU), an engine control module (ECM), and a motor control unit (MCU). Although shown as a single controller, controller 50 may be part of a larger control system and may be controlled by various other controllers throughout the vehicle 10, such as a vehicle system controller (VSC). Therefore, it should be understood that controller 50 and one or more other controllers may be collectively referred to as the “controller,” which, in response to signals from various sensors, controls various actuators to control functions such as starting / stopping, operating the M / G 18 to provide wheel torque or charge the battery 20, selecting or scheduling transmission shifts, etc. Controller 50 may include a microprocessor or central processing unit (CPU) that communicates with various types of computer-readable storage devices or media. Computer-readable storage devices or media may include volatile and non-volatile storage devices, such as read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operational variables when the CPU is powered off. The computer-readable storage device or medium may be implemented using any of a number of known memory devices, such as PROM (programmable read-only memory), EPROM (electric PROM), EEPROM (electrically erasable PROM), flash memory, or any other electrical, magnetic, optical, or combined memory device capable of storing data, some of which represents executable instructions used by controller 50 to control vehicle 10.

[0022] The controller 50 communicates with various vehicle sensors and actuators via an input / output (I / O) interface, which can be implemented as a single integrated interface providing conditioning, processing, and / or conversion, short-circuit protection, etc., for various raw data or signals. Alternatively, one or more dedicated hardware or firmware chips can be used to condition and process specific signals before they are supplied to the CPU. Figure 1 As generally shown in the representative embodiments, controller 50 can transmit signals to and / or from engine 14, disengagement clutch 26, M / G 18, start-up clutch 34, transmission gearbox 24, and power electronics 56. Although not explicitly shown, those skilled in the art will recognize various functions or components that can be controlled by controller 50 within each of the subsystems identified above. Representative examples of parameters, systems, and / or components that can be directly or indirectly actuated using control logic executed by controller 50 include: fuel injection timing, rate, and duration; throttle position; spark plug ignition timing (for spark-ignition engines); intake / exhaust valve timing and duration; front-end accessory drive (FEAD) components (such as alternators, air conditioning compressors), battery charging, regenerative braking, M / G operation, clutch pressure for disengagement clutch 26, start-up clutch 34, and transmission gearbox 24, etc. Sensors that transmit input via the I / O interface can be used to indicate, for example, turbocharger boost pressure, crankshaft position (PIP), engine speed (RPM), wheel speed (WS1, WS2), vehicle speed (VSS), coolant temperature (ECT), intake manifold pressure (MAP), accelerator pedal position (PPS), ignition switch position (IGN), throttle position (TP), air temperature (TMP), exhaust oxygen (EGO) or other exhaust component concentration or presence, intake airflow (MAF), transmission gear, ratio or mode, transmission oil temperature (TOT), transmission-turbo speed (TS), torque converter bypass clutch 34 status (TCC), and deceleration or shift mode (MDE).

[0023] The control logic or functions performed by controller 50 may be represented by flowcharts or similar diagrams in one or more accompanying figures. These figures provide representative control strategies and / or logic that can be implemented using one or more processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, etc. Therefore, the various steps or functions shown may be performed in the order shown, may be performed in parallel, or may be omitted in some cases. Although not always explicitly shown, those skilled in the art will recognize that one or more of the shown steps or functions may be repeatedly performed depending on the specific processing strategy used. Similarly, the processing order is not necessarily necessary to achieve the features and advantages described herein, but is provided for ease of illustration and description. The control logic may be implemented primarily in software executed by a microprocessor-based vehicle, engine, and / or powertrain controller (such as controller 50). Of course, depending on the specific application, the control logic may be implemented in one or more controllers in software, hardware, or a combination of software and hardware. When implemented in software, the control logic may be provided in one or more computer-readable storage devices or media storing data representing code or instructions executed by a computer to control a vehicle or vehicle subsystem. Computer-readable storage devices or media may include one or more of a number of known physical devices that utilize electrical storage, magnetic storage and / or optical storage to store executable instructions and associated calibration information, operating variables, etc.

[0024] The driver of vehicle 10 uses accelerator pedal 52 to provide the required torque, power, or drive command to propel vehicle 10. Generally, pressing and releasing pedal 52 generates an accelerator pedal position signal, which can be interpreted by controller 50 as requiring increased or decreased power, respectively. This may be referred to as driver-demanded torque. Based at least on the input from pedal 52, controller 50 commands torque from engine 14 and / or M / G 18. Controller 50 also controls the timing of gear shifts within gearbox 24, as well as the engagement or disengagement of disengagement clutch 26 and torque converter bypass clutch 34. Like disengagement clutch 26, torque converter bypass clutch 34 can be modulated between an engaged and disengaged position. This also produces variable slip in torque converter 22, in addition to the variable slip generated by the hydraulic connection between pump impeller 23 and turbine 25. Alternatively, depending on the specific application, torque converter bypass clutch 34 can operate as locked or disengaged without using a modulated operating mode.

[0025] In order to drive the vehicle 10 with the engine 14, the disengagement clutch 26 is at least partially engaged to transmit at least a portion of the engine torque to the M / G 18, and then from the M / G 18 through the torque converter 22 and the gearbox 24. This operating mode, when the engine 14 alone provides the torque required to propel the vehicle, may be referred to as "engine mode," "engine-only mode," or "mechanical mode."

[0026] M / G 18 can assist engine 14 by providing additional power to rotate shaft 30. This operating mode can be referred to as "hybrid mode", "engine-motor mode" or "electric assist mode".

[0027] To use the M / G 18 as the sole power source to drive the vehicle 10, the power flow remains constant except that the disengagement clutch 26 isolates the engine 14 from the rest of the powertrain 12. During this period, combustion in the engine 14 can be deactivated or otherwise shut off to conserve fuel. The traction battery 20 transmits stored electrical energy via wiring 54 to power electronics 56, which may include, for example, an inverter. Power electronics 56 converts the DC voltage from the battery 20 into AC voltage to be used by the M / G 18. The controller 50 commands the power electronics 56 to convert the voltage from the battery 20 into AC voltage supplied to the M / G 18 to provide positive torque (drive torque) or negative torque (regenerative braking) to the shaft 30. This operating mode may be referred to as "pure electric mode," "EV (electric vehicle) mode," or "motor mode."

[0028] In any operating mode, M / G 18 can act as a motor and provide driving force to the powertrain 12. Alternatively, M / G 18 can act as a generator and convert kinetic energy from the powertrain 12 into electrical energy for storage in the battery 20. For example, M / G 18 can act as a generator when the engine 14 provides propulsion to the vehicle 10. M / G 18 can also act as a generator during regenerative braking, in which rotational energy from the rotating wheels 42 is transferred back through the gearbox 24 and converted into electrical energy for storage in the battery 20. When acting as a generator, M / G 18 can be referred to as providing negative torque.

[0029] It should be understood that Figure 1 The schematic diagrams shown are merely exemplary and not intended to be limiting. Other configurations utilizing the selective engagement of both the engine and motor for transmission via a gearbox are contemplated. For example, the M / G 18 may be offset from the crankshaft 28, and / or the M / G 18 may be positioned between the torque converter 22 and the gearbox 24. Other configurations are contemplated without departing from the scope of this disclosure.

[0030] The traction battery 20 can be constructed from various chemical formulations. Typical battery pack chemistry can be lead-acid, nickel metal hydride (NIMH), or lithium-ion. The battery management system can have one or more controllers, such as a battery energy control module (BECM) that monitors and controls the performance of the traction battery. The BECM may include sensors and circuitry that monitor several battery pack level characteristics, such as battery pack current, battery pack voltage, and battery pack temperature. The BECM may have non-volatile memory, allowing data to be retained when the BECM is in an off state. The retained data is available in the next key cycle.

[0031] In addition to the battery pack level characteristics, there may also be measured and monitored battery cell level characteristics. For example, the terminal voltage, current, and temperature of each cell can be measured. The battery management system can use sensor modules to measure battery cell characteristics. Depending on the capacity, the sensor module may include sensors and circuitry for measuring the characteristics of one or more of the battery cells. The battery management system may utilize sensor modules or a battery monitoring integrated circuit (BMIC) to measure the characteristics of all battery cells. Each sensor module can transmit the measured values ​​to the BECM for further processing and coordination. The sensor module can transmit signals to the BECM in analog or digital form. In some embodiments, the functionality of the sensor module can be incorporated into the BECM. That is, the sensor module hardware can be integrated as part of the circuitry within the BECM, and the BECM can process the raw signals. The BECM may include circuitry for interfacing with one or more contactors. The positive and negative terminals of the traction battery 20 may be protected by contactors.

[0032] The state of charge (SOC) of a battery provides an indication of how much charge remains in the battery cell or battery pack 20. The battery pack SOC can be output to inform the driver how much charge remains in the battery pack 20, similar to a fuel gauge. The battery pack SOC can also be used to control the operation of the electric vehicle or hybrid electric vehicle 10. The battery pack SOC can be calculated using various methods. One possible method for calculating the battery SOC is to perform the integration of the battery pack current over time. This is well known in the art as ampere-hour integration.

[0033] Battery SOC can also be derived from model-based estimation. Model-based estimation can provide SOC estimates using cell voltage measurements, battery pack current measurements, and cell and battery pack temperature measurements; these can also be referred to as calculated SOC or actual SOC.

[0034] The BECM can always have available power. The BECM may include a wake-up timer, allowing it to be scheduled for wake-up at any time. The wake-up timer can wake the BECM to perform a predetermined function. The BECM may include non-volatile memory, allowing data to be stored when the BECM is powered off or loses power. Non-volatile memory may include electrically erasable programmable read-only memory (EEPROM) or non-volatile random access memory (NVRAM). Non-volatile memory may also include the microcontroller's flash memory.

[0035] refer to Figure 1 and Figure 2 The control logic and representative lookup table for controlling engine 14 and M / G 18 are shown. As indicated at 200, the driver's torque request τ is received. d 230. Driver's required torque τ d 230 is equal to the driver power request divided by the current vehicle speed. The driver power request 230 may correspond to the position of the accelerator pedal 160, or it may be automatically generated by controller 50 or another controller, such as when operating with cruise control, or when applied to an autonomous vehicle. As indicated at 210, the current engine speed ωe (e.g., RPM) is also received. In some embodiments, the engine speed may be used as the powertrain speed. At operation 212, the corresponding engine torque τ for the current engine speed ωe and the driver-demanded torque 230 is obtained. opt This is to achieve desired system operation objectives, such as minimizing engine fuel consumption, minimizing instantaneous or long-term battery consumption, and maximizing instantaneous or long-term system efficiency. Operation 212 may include retrieving a value from a lookup table stored in memory, the value representing an engine torque τ calibrated to provide desired characteristics at a given engine speed ωe. opt The desired characteristic curve 214 is given, where the engine speed is determined based on the current vehicle speed and the transmission gear ratio. The desired characteristic can be, for example, peak system efficiency, minimum fuel consumption, or minimum system losses. The desired characteristic may also include emission reduction, or various other characteristics, or combinations thereof.

[0036] For illustrative purposes, operation 212 is represented as a graph of the operating area of ​​engine 14, which includes multiple system efficiency contour lines 216 defined by the maximum engine torque curve 218. The desired characteristic curves and contour lines can be calibrated by vehicle testing, computer simulation, or other suitable methods. If the desired characteristic is system efficiency, the efficiency curves and contour lines will depend on engine braking ratio fuel consumption, motor efficiency diagram, battery state of charge (SOC), powertrain efficiency, and other factors. The operation can be embodied in one or more lookup tables, equations, algorithms, or other methods. Then, a selected engine torque τ that approximates or achieves the desired characteristic is... opt Provided to operation 220. At operation 220, the engine torque τ associated with the selected engine operating point is determined. opt With the driver's torque request τ d The difference between 230 and 230. The resulting difference is determined by τ. m des The desired motor torque is indicated. The engine 14 will be commanded to provide torque equal to τ. opt Expected engine torque τ e des And will provide command M / G 18 equal to τ m des The torque.

[0037] Depending on the specific type of engine, commanding the engine to provide the desired engine torque can include controlling various vehicle systems or actuators. For example, for a spark-ignition gasoline engine, the controller can control the throttle to control vacuum or intake manifold airflow, spark ignition timing, fuel injection metering and timing, etc. For a compression-ignition diesel engine, the controller can control fuel injection metering and timing, etc. Commanding the electric motor to provide the desired energy management torque can include controlling the current supplied from the battery to the electric motor operating as a motor to increase output torque, or controlling the current supplied from the electric motor operating as a generator to the battery to decrease output torque.

[0038] However, because the size of the traction battery is finite, the magnitude and duration of the motor or energy management torque are limited by the battery's charge capacity and the current state of charge (SOC). Therefore, given the powertrain speed and the driver's requested or demanded torque, the system's most efficient operating point is affected by the duration for which the battery can sustain the requested EM torque. For example, if the most efficient operating point is the point of aggressive battery charging but the battery SOC is near its maximum limit, the efficiency of subsequent powertrain operating points after reaching the maximum SOC may be significantly lower than the chosen initial point. This can result in a series of alternating operating points, leading to overall inefficient use of the HV battery and fuel during the duration of driving maneuvers. Therefore, adjustments or modifications can be made based on the battery's state of charge (SOC) and whether the driver's demanded torque and powertrain speed are in transient or steady-state operation, as referenced. Figure 2 The selected engine operating point is described.

[0039] In one or more embodiments, a similar approach is provided. Figure 2 The lookup table, as shown in the diagram, specifies the motor torque using a first lookup table for transient operation and a second lookup table for steady-state operation. Instead of using engine speed as an index or input parameter, the motor torque lookup table selects or determines the desired motor torque based on the torque converter pump impeller speed and the driver's required torque, with a specific lookup table selected based on either steady-state or transient operation. The steady-state lookup table is calibrated to minimize long-term system energy losses by taking into account the battery's limited charge storage capacity, while the transient operation lookup table is calibrated to minimize instantaneous system losses.

[0040] Figure 3 This is a block diagram illustrating the operation of a system or method for detecting steady-state operation and controlling the transition from transient to steady-state EM torque control. Control strategy or logic 300 includes a transient operation lookup table 310 that outputs a target or desired operating point for the motor torque based on the current powertrain speed 312 and the driver's required torque 314. The transient operation lookup table 310 may include values ​​that minimize instantaneous system losses. A steady-state operation lookup table 316 is accessed to retrieve or select the corresponding target or desired operating point for the motor torque based on the current powertrain speed 312 and the driver's required torque 314. The steady-state operation lookup table 316 may include values ​​determined to minimize long-term system energy losses by taking into account the finite charge storage capacity of the traction battery and the current state of charge (SOC). The motor torque retrieved from lookup tables 310, 316 is provided to a disturbance-free transfer arbitration strategy or function 320, which determines the optimal output torque 392 for the motor and engine based on inputs from blocks 310, 316, 372, 380, and 390, which are described in more detail below.

[0041] Logic or algorithm 330 detects steady-state operation based on a driver-demanded torque 314 and a powertrain speed 312 change less than an associated threshold for a continuously calibrable predetermined time period. At 332, a rolling average of the powertrain speed 312 is calculated, and at 334, the rolling average is compared to the current instantaneous value of the powertrain speed 312. The rolling average may have a calibrable time constant that determines the number of samples or the amount of time associated with the value forming the rolling average. The rolling average 332 may be a weighted average, where, depending on the specific application, newer values ​​have greater weight than older values. Other statistical operations or functions may be applied to the powertrain speed values ​​to provide an indication of the rate or amount of change over the predetermined time period. At 336, the absolute value of the difference 334 between the rolling average 332 and the current powertrain speed 312 is determined, and at 338, the absolute value is compared to an associated calibrable threshold or limit 340. When the difference between the current value of the powertrain speed 312 and the rolling average 332 is less than the threshold 340, the steady-state powertrain speed is indicated, wherein the output trigger or flag from block 338 is provided to block 360.

[0042] A rolling average 342 of the driver's demand torque 314 is calculated and compared at 344 with the current instantaneous value of the driver's demand torque. The rolling average may have a calibrable time constant that determines the number of samples or the amount of time associated with the value forming the rolling average. The rolling average 342 may be a weighted average, where, depending on the specific application, newer values ​​have a greater weight than older values. Other statistical operations or functions may be applied to the driver's demand torque value to provide an indication of the rate or amount of change over a predetermined time period. At 346, the absolute value of the difference 344 between the rolling average 342 and the current driver's demand torque 314 is determined, and at 348, the absolute value is compared with an associated calibrable threshold or limit 350. When the difference 344 between the current value of the driver's demand torque 314 and the rolling average 342 is less than the associated limit or threshold 350, a steady-state driver's demand torque is indicated, wherein an output trigger or flag from block 348 is provided to block 360.

[0043] When both the powertrain speed 312 and the driver-demanded torque 314 are in a steady state, as detected at box 360, timer 362 (or counter) increments. When the powertrain speed or driver-demanded torque is not in a steady state (i.e., transient), timer 362 is reset or reinitialized via a NOT input 364. At 372, timer 362 is compared with an associated timeout threshold or limit 370. When the steady-state timer 362 exceeds the associated calibrable steady-state time limit 370, a corresponding output or flag indicating that steady-state operation has been detected is provided to arbitration logic or strategy 320 by box 372.

[0044] The uninterrupted transmission arbitration strategy 320 uses a calibrable steady-state transition rate 380 and a calibrable transient transition rate 390 to control the transition between motor torque targets selected or retrieved from the transient operation lookup table 310 and the steady-state operation lookup table 316 in response to changes in steady-state operation detected by the algorithm 330. The uninterrupted transmission arbitration strategy 320 determines the optimal motor torque 392 based on the lookup table 310 during transient operation, the lookup table 316 during steady-state operation, and the target values ​​between the transient target value and the steady-state target value constrained by the transition rates 380 and 390 when transitioning between steady-state and transient operation.

[0045] refer to Figure 4 In one or more embodiments, vehicle 10 is configured to optimize efficiency during steady-state operation by using historical data from previous driving cycles to adjust engine and motor torque toward the most efficient engine torque 400 (for a given operating point of the powertrain defined by the speed of the powertrain and the torque demanded by the driver). Figure 4 Multiple graphs are shown for various parameters for a given powertrain speed 312 and driver-demanded torque 314. Trace 402 represents total powertrain losses, trace 404 represents engine fuel energy losses due to inefficient operation, trace 406 represents battery losses, trace 408 represents motor losses, and trace 410 represents electrical losses.

[0046] As discussed above, motor 18 has a limited torque, and battery 20 has a limited amount of energy. Therefore, it may not be possible to maintain powertrain 12 at the optimal operating point 400 for an extended period, as battery 20 may deplete. Point 412 is an operating point that balances long-term use with efficiency. That is, vehicle 10 can operate at point 412 for extended periods, such as during steady-state conditions. The ability to operate the vehicle at point 412 comes with a trade-off between the efficiency at point 412 and the efficiency at the most efficient operating point 400. Point 412 can be determined during vehicle development and represents a conservative value known to provide reasonable efficiency for long-term operation. When the vehicle is at the powertrain operating point shown, the vehicle can be pre-programmed so that the engine torque at point 412 is the commanded engine torque. However, when the vehicle is reasonably expected to perform at that level for an appropriate amount of time, vehicle efficiency can be improved by shifting the curve downwards toward point 400.

[0047] Vehicle 10 is configured to receive a wide variety of data from onboard sensors and external sources. This data may include GPS data, map data, traffic data, weather data, historical usage data, and many other types of data. Vehicle 10 may include both hardware and software modules to enable the use of this data. For example, vehicle 10 may include a route selection engine, a GPS module, and a map and navigation module. These modules are configured to send and receive signals to each other to enable selected functionalities of vehicle 10. Vehicle 10 may also include a vision system having multiple sensors that inspect the area surrounding vehicle 10. The vision system may employ radar, lidar, cameras, ultrasonic or sonar, and any combination thereof.

[0048] Map data can include information such as road gradients and speed limits for road segments. Road gradient refers to the slope or change in elevation, that is, the angle between the road and the horizontal plane of the earth. Road gradients can be expressed as a percentage or a decimal. Road gradients can be sloping, such as uphill, or sloping downward, such as downhill. Uphill gradients can be expressed as a positive percentage or a decimal, while downhill gradients can be expressed as a negative percentage or a decimal.

[0049] Using this data, the controller's machine learning algorithm uses historical data to adjust point 412 toward point 400. That is, data from previous driving cycles indicates the amount of time the driver spends at a given powertrain operating point (powertrain speed, driver-demanded torque). For example, the learning algorithm can determine how long a user typically spends at a given operating point and use closed-loop feedback control to shift the commanded engine torque from the default pre-programmed steady-state point 412 toward the optimal point 400. In other words, vehicle 10 can include a hybrid adaptive energy management torque feature for steady-state efficiency optimization, which adaptively determines, as part of an energy management strategy, what the steady-state condition should be for a given driver-demand condition (i.e., engine / transmission input speed and driver-demanded torque) to maximize powertrain efficiency when a steady-state condition exists. The following example method can be used to achieve this functionality.

[0050] During vehicle use and vehicle development, vehicle 10 will determine the historical usage of the powertrain operating system for various different uses at various vehicle speeds, transmission input speeds, and driver-demanded torques.

[0051] Different uses can be based on vehicle weight, the presence of trailers, the combined vehicle + trailer weight, route characteristics (speed, gradient, etc.), driver behavior, etc. Use can also be estimated based on vehicle modeling data and route characteristics (gradient, stop light locations, highway entrance ramps, etc.) determined using electronic horizon data, vehicle-to-vehicle data, and / or vehicle-to-infrastructure communication.

[0052] Based on the powertrain usage data and vehicle (e.g., dynamometer) mapping data, the real-world instantaneous optimal powertrain operation calibration (e.g., 400) and steady-state system operating point (e.g., 412) will be determined for various transmission input speeds and driver-demanded torques.

[0053] (It can also be based on vehicle speed.)

[0054] As discussed above, the instantaneous optimal operating point can be used for rapid transients to operate the system most efficiently, while the steady-state operating point is used for efficient operating conditions that can be maintained for a longer period. During customer use, vehicle 10 can sample the use of the powertrain and determine the average and standard deviation of the time spent achieving steady-state operation under each condition. This usage sampling can be specific to the driver, vehicle weight, road conditions, and other usage-specific inputs as described above.

[0055] Vehicle 10 can use this information to perform adaptive closed-loop calibration and reposition the "steady-state" operating point closer to or further from the optimal point, such as 400, by balancing the torque request of electric motor 18 and biasing it by an appropriate amount. A newly selected point can be chosen to ensure that the powertrain can maintain the operating point for at least an average amount of time, such as +X (1, ​​2, 3, etc.) standard deviation, which has been determined based on historical usage.

[0056] The calculation of how long a certain powertrain operating condition can be maintained can be predetermined by assuming an allowable energy buffer, or it can be based on real-time calculations of the remaining energy buffer in the HV battery, the discharge / charge limits of the electric motor 18 and battery 20, and the expected discharge / charge rate of the powertrain 12 when the requested driver-demanded torque 230 is met. That is, for example, if the electric motor 18 is discharging at X kW and there is a remaining energy buffer of Y kWh before the calibrated low battery SOC limit, then this powertrain operating condition can be maintained for Z seconds. By performing this optimization, the powertrain 12 can operate close to an ideal point (e.g., 400) and prevent frequent cycling between various powertrain operating conditions and torque distributions, which can improve the fuel economy of the vehicle 10.

[0057] Figure 5 This is a flowchart 500 of the algorithm used to control the powertrain system of vehicle 10. At operation 502, controller 50 determines whether the powertrain system is in a steady-state condition. If not, control proceeds to operation 504, where controller 50 commands transient torque to motor 18 and engine 14, as discussed above. If yes at operation 502, controller 50 receives the battery state of charge at operation 506. Controller 50 also receives the driver's required torque 230 and powertrain speed at operations 508 and 510. As discussed above, the powertrain speed can be a measured speed of one of the components of the powertrain system. For example, the powertrain speed can be a measured speed of motor 18 or a measured speed of the pump impeller 23 of torque converter 22.

[0058] At operation 512, controller 50 uses the received driver-demanded torque and powertrain speed to select the appropriate steady-state lookup table 316 corresponding to those torques at that speed. As discussed above, the lookup table specifies the engine torque to be commanded for the vehicle's current operating point. As discussed above, the lookup table is derived from historical data.

[0059] In other words, the engine / motor torque distribution values ​​stored in a lookup table are changed based on the duration the powertrain has been at a given operating point in a previous driving cycle. For example, the controller is programmed to increase the motor torque value in the lookup table and proportionally decrease the engine torque value in the lookup table for a given operating point defined by powertrain speed and driver-demanded torque, when the driver has reduced the duration at the given operating point in a previous driving cycle. (This will cause the engine torque to move along curve 402 toward point 400.) The controller can also be programmed to change the torque distribution in another way when the driver has increased the duration at the given operating point.

[0060] The lookup table can also consider the battery state of charge (SOC), or the SOC can consider individual battery stacks. For example, the controller can select engine torque from the lookup table and then determine whether the current battery SOC is sufficient to provide that torque for a meaningful amount of time. If so, the controller can use the engine torque from the lookup table; otherwise, it can increase the engine torque based on the battery SOC. In this way, the lookup table provides a predetermined engine torque to allow the battery SOC to remain above a threshold SOC (lower limit) for a threshold time period.

[0061] At operation 514, controller 50 determines the torque to be commanded to motor 18 based on the received driver-demanded torque and the engine torque selected at operation 512. For example, the motor torque could be equal to the driver-demanded torque minus the engine torque. Of course, gain, offset, or scalers can also be used in the calculation to account for losses or inaccuracies in the powertrain 12. At operation 516, controller 50 commands torque to engine 14 and motor 18.

[0062] As discussed above, vehicle 10 modulates and adjusts its steady-state torque value relative to the instantaneous system optimum based on historical data indicating how long vehicle 10 operates at the steady-state operating point. This allows the steady-state torque value to become closer to the instantaneous system optimum. The following is a non-limiting example to help understand how the vehicle adjusts its steady-state torque. In this example, assume the engine operates at 1500 RPM with a driver-demanded torque of 300 Nm. At this operating point, the instantaneous system optimum is 200 Nm of engine torque and 100 Nm of electric motor torque, and the steady-state default calibration (before adjustment) is 270 Nm of engine torque and 30 Nm of electric motor torque. In this example, the vehicle could operate at the instantaneous system optimum for 60 seconds based on the HV battery's energy capacity at this time, or the calibration could "assume" that the maximum time at that point can be supported, regardless of battery energy. However, historically, the driver has only operated for 20 seconds at this point (1500 RPM, 300 Nm of driver-demanded torque). This results in a 40-second error. (Error = Default Calibration (60) - Historical Average (20).) Therefore, the vehicle will adjust the "steady-state" electric motor torque request based on a 40-second "error". For this operating point, the new calibrated value of the electric motor torque is equal to the previous value of the electric motor torque request plus a calibration gain, for example, 0.1. This gain can be a function of torque, powertrain speed, or vehicle speed. The new motor torque request can be calculated using the default value - gain * error. Or, in this example, it equals 270 - 0.1 * 40 = 266 Nm. This value can be stored in the lookup table described above in operation 512. This value can be updated periodically based on driving history data. That is, the vehicle can continuously adjust the lookup table as new data is collected. As can be seen from the above example, the engine torque is reduced rather than the motor torque is increased, thus improving fuel economy.

[0063] While exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms covered by the claims. The terms used in this specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of this disclosure. As previously stated, features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or shown. Although various embodiments may have been described as providing advantages or superiority over other embodiments or prior art implementations with respect to one or more desired characteristics, those skilled in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, strength, durability, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described with respect to one or more characteristics as less desirable than those desired by other embodiments or prior art implementations are within the scope of this disclosure and may be desirable for a particular application.

[0064] According to the present invention, a hybrid vehicle is provided, the hybrid vehicle having: a powertrain including an engine, an electric motor, and a disengagement clutch configured to selectively engage the engine and the electric motor; and a controller programmed to: for a given operating point defined by a powertrain speed and a driver-demanded torque, command a torque distribution between the engine and the electric motor, the torque distribution depending on the duration for which the powertrain has been at the given operating point in a previous driving cycle, such that for consecutive driving cycles, as the duration decreases, the torque commanded to the engine decreases and the torque commanded to the electric motor increases.

[0065] According to an embodiment, the controller is also programmed to increase the torque commanded to the engine and decrease the torque commanded to the electric motor as the duration increases.

[0066] According to an embodiment, the controller is also programmed to command the torque distribution between the engine and the electric motor based on predefined values ​​when data from previous driving cycles is unavailable.

[0067] According to an embodiment, the controller is also programmed to suppress an increase in torque commanded to the motor and a decrease in torque commanded to the engine in response to a battery state of charge being less than a threshold.

[0068] According to an embodiment, the controller is also programmed to increase the torque commanded to the engine and decrease the torque commanded to the motor in response to a battery state of charge being less than a threshold, wherein the threshold is based on the duration for which the powertrain was at a given operating point in a previous driving cycle.

[0069] According to an embodiment, in further response to changes in the powertrain speed remaining below a speed threshold and changes in the driver's required torque remaining below a torque threshold, the torque commanded to the engine decreases and the torque commanded to the electric motor increases.

[0070] According to an embodiment, the controller is also programmed to: in response to a change in the speed of the powertrain exceeding a speed threshold and a change in the torque demanded by the driver exceeding a torque threshold, reduce the torque commanded to the engine and increase the torque commanded to the motor.

[0071] According to an embodiment, the rate of change of the decrease in torque commanded to the engine and the increase in torque commanded to the electric motor is limited based on a caliable rate limit.

[0072] According to an embodiment, the controller is also programmed to calculate the average time spent at the operating point based on previous driving cycles, and to update the torque distribution to the operating point based on the average time.

[0073] According to an embodiment, the update of torque distribution for the operating point is further based on the standard deviation of the time spent at the operating point.

[0074] According to an embodiment, the invention is further characterized by a sensor configured to measure the rotational speed of a powertrain system.

[0075] According to an embodiment, the invention is further characterized by a torque converter operably coupled to a motor and including a pump impeller, wherein the power transmission system speed is a measured speed of the pump impeller.

[0076] According to the embodiment, the speed of the power transmission system is the measured speed of the motor.

[0077] According to an embodiment, the decrease in torque commanded to the engine is proportional to the increase in torque commanded to the electric motor.

[0078] According to the present invention, a hybrid vehicle powertrain system is provided, the hybrid vehicle powertrain system having: a controller programmed to: for a given operating point defined by the powertrain speed and the torque demanded by the driver, command a torque distribution between the engine and the motor, the torque distribution depending on the duration for which the powertrain has been at the given operating point in a previous driving cycle, such that for consecutive driving cycles, as the duration increases, the torque commanded to the engine increases and the torque commanded to the motor decreases.

[0079] According to an embodiment, the controller is also programmed to decrease the torque commanded to the engine and increase the torque commanded to the electric motor as the duration decreases.

[0080] According to an embodiment, the controller is also programmed to suppress an increase in torque commanded to the engine and a decrease in torque commanded to the motor in response to a battery state of charge being less than a threshold.

[0081] According to an embodiment, the controller is also programmed to command the torque distribution between the engine and the electric motor based on predefined values ​​when data from previous driving cycles is unavailable.

[0082] According to an embodiment, the invention is further characterized by: an engine; an electric motor; and a disengagement clutch configured to selectively engage the engine and the electric motor.

[0083] According to the present invention, a method for controlling a hybrid powertrain includes: for a given operating point defined by the powertrain speed and the torque demanded by the driver, commanding a torque distribution between the engine and the electric motor, the torque distribution depending on the duration for which the powertrain has been at the given operating point in a previous driving cycle.

Claims

1. A hybrid vehicle comprising: a powertrain including an engine, an electric machine, and a disconnect clutch configured to selectively couple the engine and the electric machine; and a controller programmed to command a torque split between the engine and the electric machine for a given operating point defined by a powertrain speed and a driver demand torque, the torque split dependent on a duration of time the powertrain has been at the given operating point in a previous drive cycle, such that for successive drive cycles, as the duration of time decreases, torque to the engine decreases and torque commanded to the electric machine increases.

2. The hybrid vehicle of claim 1, wherein the controller is further programmed to increase the torque commanded to the engine and decrease the torque commanded to the electric machine as the duration of time increases.

3. The hybrid vehicle of claim 1, wherein the controller is further programmed to command the torque split between the engine and the electric machine based on a predefined value when data from a previous drive cycle is not available.

4. The hybrid vehicle of claim 1, wherein the controller is further programmed to inhibit the increase in the torque commanded to the electric machine and the decrease in the torque commanded to the engine in response to a battery state of charge being less than a threshold value.

5. The hybrid vehicle of claim 1, wherein the controller is further programmed to increase the torque commanded to the engine and decrease the torque commanded to the electric machine in response to a battery state of charge being less than a threshold value, wherein the threshold value is based on the duration of time the powertrain is at the given operating point in the previous drive cycle.

6. The hybrid vehicle of claim 1, wherein the torque commanded to the engine decreases and the torque commanded to the electric machine increases further in response to a change in the powertrain speed remaining less than a speed threshold value while a change in the driver demand torque remains less than a torque threshold value.

7. The hybrid vehicle of claim 6, wherein the controller is further programmed to decrease the torque commanded to the engine and increase the torque commanded to the electric machine in response to the change in the powertrain speed exceeding the speed threshold value while the change in the driver demand torque exceeds the torque threshold value.

8. The hybrid vehicle of claim 7, wherein the rate of change of the decrease in the torque commanded to the engine and the increase in the torque commanded to the electric machine is limited based on a calibratable rate limit.

9. The hybrid vehicle of claim 1, wherein the controller is further programmed to calculate an average time spent at the operating point based on the previous drive cycle and update the torque split for the operating point based on the average time. ​ 10. The hybrid vehicle of claim 9, wherein the update to the torque split for the operating point is further based on a standard deviation of the time spent at the operating point.

11. The hybrid vehicle of claim 1, further comprising a sensor configured to measure the powertrain speed.

12. The hybrid vehicle of claim 1, further comprising a torque converter operably coupled to the electric machine and comprising a pump wheel, wherein the powertrain speed is a measured speed of the pump wheel.

13. The hybrid vehicle of claim 1, wherein the powertrain speed is a measured speed of the electric machine.

14. The hybrid vehicle of claim 1, wherein the decrease in the torque commanded to the engine is proportional to the increase in the torque commanded to the electric machine.

15. A hybrid vehicle powertrain, comprising: a controller programmed to, for a given operating point defined by a powertrain speed and a driver demand torque, command a torque split between an engine and an electric machine, the torque split dependent on a duration of time that the powertrain has been at the given operating point in a preceding drive cycle, such that for successive drive cycles, as the duration of time increases, a torque commanded to the engine increases and a torque commanded to the electric machine decreases.

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