Suppression of engine shutdown based on previous driving history

Abstract

Vehicle (10), comprising: a steering wheel with an associated steering wheel angle sensor; a motor (14); a gearbox (24); a motor-generator capable of providing drive torque, which is optionally coupled to the motor (14) via a clutch (26) and optionally coupled to the transmission (24); and a control unit (50) which is programmed to prevent the clutch (26) from disengaging and the engine (14) from stopping on the basis of a moving average of previous steering wheel angle positions that exceeds a threshold value.

Description

TECHNICAL AREA

[0001] This revelation refers to a control strategy for suppressing engine shutdown in a hybrid vehicle based on the previous driving history of various factors. BACKGROUND

[0002] In an electric hybrid vehicle (HEV), either one or both of the (internal combustion) engine and the electric motor are capable of supplying power to the vehicle's wheels. Different HEV designs exist. In a "series" hybrid powertrain, for example, there is no mechanical coupling between the engine and the wheels. Instead, the engine acts as a power generation unit, and its energy output is converted into electrical energy, which is stored in a battery for use by a main drive electric motor. In a "parallel" hybrid powertrain, the engine, like the drive electric motor, can be selectively coupled to the wheels. One or both of the engine and the electric motor can supply drive power to the wheels. Other hybrid architectures, such as "series-parallel" hybrid vehicles, are also known.

[0003] German patent application DE 10 2014 011 751 A1 discloses a control device for a hybrid vehicle which is configured to start and stop an internal combustion engine when preset start and stop conditions of the internal combustion engine are met.

[0004] German patent application DE 10 2015 210 295 A1 discloses a vehicle control device installed in hybrid vehicles. A control unit switches between HEV and EV operating modes based on a comparison between the drive force requested by the driver and a predetermined threshold. To prevent the combustion engine from oscillating during the switch between HEV and EV modes, the control unit modifies the predetermined threshold.

[0005] Hybrid vehicles are advantageous due to their increased fuel efficiency. To improve fuel economy, processors in the vehicle are specifically programmed to stop or "shut down" the engine when it is not needed to propel the vehicle. For example, the engine can be shut down and stopped when the driver's power demands are relatively low, allowing the electric motor to handle all propulsion needs. If the driver's power demand increases to such an extent that the electric motor cannot provide sufficient power to meet the demand, then the engine can be activated or "spinned up" to fulfill the power requirement.

[0006] Excessive engine starting and stopping can lead to reduced comfort and handling of the vehicle, which is perceived by the occupants, as well as reduced fuel efficiency. If performance demands change frequently and abruptly while driving, the engine may start and stop unnecessarily often. Known control strategies employ filters or other algorithms to "learn" a driver's driving habits and reduce the frequency of engine starts and stops accordingly. SUMMARY

[0007] Based on this prior art, a vehicle with the features of independent claim 1 is created. Advantageous embodiments can be found in the dependent claims.

[0008] According to one embodiment of this disclosure, a vehicle comprises a steering wheel with an associated steering wheel angle sensor, a motor, a transmission, and an electric motor-generator capable of providing drive torque. The electric motor-generator is also optionally coupled to the motor via a clutch and optionally coupled to the transmission. The vehicle includes at least one control unit programmed to prevent the clutch from disengaging and the motor from stalling based on a moving average of previous steering wheel angle positions that exceeds a threshold value.

[0009] According to another embodiment, a vehicle comprises an accelerator pedal with an associated pedal position sensor. The vehicle also comprises an engine, a transmission, and an electric motor-generator capable of providing drive torque. The electric motor-generator is optionally coupled to the engine via a clutch and optionally coupled to the transmission. The vehicle includes at least one control unit programmed to prevent the clutch from disengaging and the engine from stopping based on a moving average of previous pedal position values ​​that exceeds a pedal position threshold.

[0010] In a further embodiment not covered by the invention, a method for suppressing engine shutdown in a vehicle is provided. The method comprises (1) receiving a signal indicating driving condition data relating to road gradient, accelerator pedal position, or steering wheel position, (2) initializing a timer in response to an engine stop request, and (3) following initialization, preventing the engine from stopping based on a moving average of the driving condition data and the remaining time of the timer. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a hybrid vehicle according to one embodiment. Fig. Figure 2 is a flowchart of an exemplary algorithm for suppressing an internal combustion engine shutdown based on a weighted average of previous driving condition data. Fig. 3A is a graphical illustration of the comparison of the accelerator pedal position with two different thresholds for stopping and starting the vehicle, while Fig. 3B is a graphical illustration of a moving average of the accelerator pedal position over a longer period of time, compared to a single threshold value. Fig. 4A is a graphical illustration of a moving average of the steering angle over a longer period and an associated engine shutdown suppression threshold, while Fig. 4B is a graphical illustration of comparing the accelerator pedal position with two different threshold values; and Fig. 5A is a further graphical illustration of a moving average of the steering angle over a longer period and an associated engine shutdown suppression threshold, while Fig. Figure 5B is a graphical illustration of comparing the accelerator pedal position with two different threshold values. DETAILED DESCRIPTION

[0011] Embodiments of the present disclosure are described herein. However, it should be noted that the disclosed embodiments are merely examples, and other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may have been enlarged or reduced to show details of certain components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a descriptive basis to help the person skilled in the art understand the different applications of the embodiments.As will be obvious to those skilled in the art, the features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to create embodiments that are not expressly illustrated or described. The combinations of illustrated features represent exemplary embodiments for typical applications. However, various combinations and modifications of the features in accordance with the teachings of this disclosure may be advantageous for certain applications or implementations.

[0012] Referring to Fig. Figure 1 illustrates a schematic representation of an electric hybrid vehicle (HEV) 10 in accordance with an embodiment of the present disclosure. Fig. Figure 1 illustrates the relationships between the components. The physical placement and orientation of the components within the vehicle may vary. The HEV 10 comprises a powertrain 12. The powertrain 12 includes a motor 14 that drives a transmission 16, which can be described as a modular hybrid transmission (MHT). As will be described in more detail below, the transmission 16 includes an electric machine, for example, an electric motor-generator (MG) 18, an associated traction battery 20, a torque converter 22, and a multi-speed automatic or manual transmission 24.

[0013] Motor 14 and MG 18 are both drive sources for the HEV 10. Motor 14 generally represents a drive source that can include an internal combustion engine, for example, a gasoline, diesel, or natural gas-powered engine, or a fuel cell. Motor 14 generates motor power and a corresponding motor torque, which is supplied to MG 18 when a disconnect clutch 26 between Motor 14 and MG 18 is at least partially engaged. MG 18 can be implemented by any of a variety of electrical machine types. For example, MG 18 can be a permanent magnet synchronous motor. Power electronics determine the direct current (DC) power supplied by battery 20 to meet the requirements of MG 18, as will be described below. For example, power electronics can supply three-phase alternating current (AC) to MG 18.

[0014] If the disconnect clutch 26 is at least partially engaged, power can flow from the motor 14 to the motor 18 or from the motor 18 to the motor 14. For example, the disconnect clutch 26 can be engaged, and the motor 18 can operate as a generator to convert the rotational energy provided by a crankshaft 28 and a motor shaft 30 into electrical energy to be stored in the battery 20. The disconnect clutch 26 can also be disengaged to isolate the motor 14 from the rest of the drive train 12, allowing the motor 18 to act as the sole power source for the HEV 10. Shaft 30 extends through the motor 18. The motor 18 is continuously driven by shaft 30, whereas the motor 14 is only driven by the motor 30 when the disconnect clutch 26 is at least partially engaged.

[0015] The MG 18 is connected to the torque converter 22 via shaft 30. The torque converter 22 is therefore connected to the motor 14 when the disconnect clutch 26 is at least partially engaged. The torque converter 22 comprises a drive wheel attached to the MG shaft 30 and a turbine attached to a transmission input shaft 32. The torque converter 22 thus provides a hydraulic coupling between shaft 30 and the transmission input shaft 32. The torque converter 22 transmits power from the drive wheel to the turbine when the drive wheel rotates faster than the turbine. The magnitude of the turbine torque and the drive wheel torque generally depends on the relative speeds. If the ratio of the drive wheel speed to the turbine speed is sufficiently high, then the turbine torque is a multiple of the drive wheel torque.A torque converter bypass clutch 34 may also be provided such that, when engaged, it frictionally or mechanically couples the drive gear and the turbine of the torque converter 22, enabling more efficient power transmission. The torque converter bypass clutch 34 can be operated as a launch clutch to provide a smooth vehicle start. Alternatively, or in combination with this, a launch clutch similar to the disconnect clutch 26 may be provided between the MG 18 and the transmission 24 for applications that do not include a torque converter 22 or a torque converter bypass clutch 34. In some applications, disconnect clutch 26 is commonly referred to as an upstream clutch, and launch clutch 34 (which may be a torque converter bypass clutch) is commonly referred to as a downstream clutch.

[0016] The transmission 24 can include (not shown) gear sets that are selectively positioned in different gear ratios by selectively engaging friction elements, such as clutches and (not shown) brakes, to produce the desired multiple separate or staged drive ratios. The friction elements are controllable by a switching scheme that connects and disconnects specific elements of the gear sets to control the ratio between a transmission output shaft 36 and the transmission input shaft 32. The transmission 24 is automatically shifted from one ratio to another based on various vehicle and environmental operating conditions by an associated control unit, such as a powertrain control unit (PCU). The transmission 24 then provides powertrain output torque to the output shaft 36.

[0017] It should be noted that the hydraulically controlled transmission 24 used with a torque converter 22 is merely one example of a transmission or gearbox arrangement; any multi-stage transmission that accepts input torque(s) from a motor and / or an electric motor and then provides torque to an output shaft at different ratios is acceptable for an application with embodiments of the present disclosure. For example, transmission 24 can be implemented by an automated mechanical (or manual) transmission (AMT) comprising one or more servo motors to drive / rotate shift forks along a shift rail to select a desired gear ratio. As is generally understood by those skilled in the art, an AMT can, for example, be used in applications with higher torque requirements.

[0018] As in the representative embodiment of Fig. As shown in Figure 1, the output shaft 36 is connected to a differential 40. The differential 40 drives a pair of wheels 42 via corresponding axles 44 connected to the differential 40. The differential transmits approximately the same torque to each wheel 42 while allowing for slight differences in rotational speed, such as when the vehicle turns a corner. Different types of differentials or similar devices can be used to distribute the torque from the drivetrain to one or more wheels. In some applications, the torque distribution can vary, for example, depending on the specific operating mode or condition.

[0019] The powertrain 12 further comprises an associated control unit 50, for example, a powertrain control unit (PCU). While the control unit 50 is illustrated as a single control unit, it may be part of a larger control system and may be controlled by various other control units throughout the vehicle 10, for example, a vehicle system control unit (VSC). It is therefore noted that the powertrain control unit 50 and one or more control units collectively may be referred to as a “control unit” that controls various actuators in response to signals from various sensors to control functions such as starting / stopping engine 14, actuating MG 18 to provide wheel torque or to charge battery 20, selecting or scheduling gear shifts, etc.Control unit 50 can include a microprocessor or central processing unit (CPU) communicating with various types of computer-readable storage devices or media. Computer-readable storage devices or media can include, for example, volatile and non-volatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM). KAM is persistent or non-volatile memory that can be used to store various operating variables while the CPU is shutting down.Computer-readable storage devices or media may be implemented using any of a number of known storage devices, for example PROMs (programmable read-only memory), EPROMs (electrically programmable read-only memory), EEPROMs (electrically erasable PROMs), flash memory, or any other electrical, magnetic, optical, or combination storage devices capable of storing data, some of which may be executable instructions used by the control unit to control the engine or vehicle.

[0020] The control unit communicates with various motor / vehicle sensors and actuators via an input / output (I / O) interface, which can be implemented as a single integrated interface providing various raw data or signal conditioning, processing and / or conversion, short-circuit protection, and the like. Alternatively, one or more associated hardware or firmware chips can be used to condition and process certain signals before they are fed to the CPU. As is generally the case in the illustrative embodiment of Fig. As illustrated in Figure 1, control unit 50 can transmit signals to and / or from motor 14, disconnect clutch 26, gearbox 18, starting clutch 34, transmission 24, and power electronics 56. A person skilled in the art will recognize various functions or components controlled by control unit 50 within each of the subsystems identified above, even though these are not explicitly illustrated.Representative examples of parameters, systems and / or components that can be actuated directly or indirectly by applying control logic executed by the control unit include fuel injection timing, speed and duration, throttle position, spark plug ignition timing (for spark-ignition engines), intake / exhaust valve timing and duration, front-end auxiliary drive (FEAD) components, for example an AC generator, air conditioning compressor, battery charging, regenerative braking, MG operation, clutch pressures for disconnect clutch 26, starting clutch 34, and manual transmission 24 and the like.Sensors that communicate an input through the I / O interface can be used to indicate, for example, turbocharger boost pressure, crankshaft position (PIP), engine speed (RPM), wheel speeds (WS1, WS2), vehicle speed (VSS), coolant temperature (ECT), manifold absolute pressure (MAP), accelerator pedal position (PPS), ignition switch position (IGN), throttle valve position (TP), ambient air temperature (TMP), exhaust oxygen (EGO) or other exhaust component concentration or presence, intake airflow (MAF), transmission gear, gear ratio or mode, transmission oil temperature (TOT), transmission turbine speed (TS), torque converter bypass clutch status (TCC), deceleration or shift mode (MDE).

[0021] The control logic or functions executed by the control unit 50 can be represented by flowcharts or similar diagrams in one or more figures. These figures provide representative control strategies and / or logic that may be implemented using one or more processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Therefore, various illustrated steps or functions can be executed in the illustrated sequence, in parallel, or, in some cases, omitted. It will be obvious to a person skilled in the art, although not always explicitly illustrated, that one or more of the illustrated steps or functions can be executed repeatedly, depending on the specific processing strategy applied.Similarly, the processing sequence is not strictly necessary to achieve the features and benefits described herein, but is provided for better understanding, illustration, and description. The control logic may be primarily implemented in a microprocessor-based vehicle, engine, and / or powertrain control unit, for example, Control Unit 50. Of course, the control logic may be implemented in software, hardware, or a combination of software and hardware in one or more control units, depending on the specific application. If implemented in software, the control logic may be provided in one or more computer-readable storage devices or media containing stored data representing code or instructions that are executed by a computer to control the vehicle or its subsystems.The computer-readable storage devices or media may comprise one or more from a number of known physical devices that employ electrical, magnetic and / or optical storage to retain executable instructions and associated calibration information, operating variables and the like.

[0022] An accelerator pedal 52 is used by the vehicle's driver to provide a requested torque, power, or control command to propel the vehicle. Generally, pressing and releasing the pedal 52 generates an accelerator pedal position signal, which can be interpreted by the control unit 50 as a request for increased or decreased power, respectively. Based on at least the input from the pedal, the control unit 50 requests torque from the motor 14 and / or the gearbox 18. The control unit 50 also controls the timing of gear changes within the transmission 24, as well as the engagement or disengagement of the disconnect clutch 26 and the torque converter bypass clutch 34. Like the disconnect clutch 26, the torque converter bypass clutch 34 can be modulated over a range between the engaged and disengaged positions.This generates variable slip in the torque converter 22 in addition to the variable slip generated by the hydrodynamic coupling between the drive wheel and the turbine. Alternatively, the torque converter bypass clutch 34 can be operated as locked or open without applying a modulated operating mode that depends on the specific application.

[0023] To power the vehicle with the engine 14, the disconnect clutch 26 is at least partially engaged to transmit at least some of the engine torque through the disconnect clutch 26 to the motor 18, and then from the motor 18 through the torque converter 22 and the transmission 24. If the engine 14 alone provides the torque required to power the vehicle, this process can be referred to as the "engine mode", "engine-only mode", or "mechanical mode".

[0024] The MG 18 can assist the motor 14 by providing additional power to rotate the shaft 30. This operating mode can be described as a “hybrid mode”, a “motor-electric motor mode”, or an “electrically assisted mode”.

[0025] To power the vehicle with the MG 18 as the sole power source, the power flow remains the same, except that the disconnect clutch 26 isolates the motor 14 from the rest of the drivetrain 12. Combustion in the motor 14 can be deactivated or otherwise switched off during this period to save fuel. The traction battery 20 transfers stored electrical energy through wiring 54 to the power electronics 56, which may include, for example, an inverter. The power electronics 56 converts the DC voltage from the battery 20 into the AC voltage to be applied by the MG 18. The control unit 50 instructs the power electronics 56 to convert the voltage from the battery 20 into the AC voltage supplied to the MG 18 to provide positive or negative torque to the shaft 30.This operating mode can be referred to as an "electric-only mode", "EV (electric vehicle) mode" or "electric motor mode".

[0026] In each operating mode, the MG 18 can act as a motor and provide drive power for the drivetrain 12. Alternatively, the MG 18 can act as a generator and convert kinetic energy from the drivetrain 12 into electrical energy, which is stored in the battery 20. The MG 18 can act as a generator while, for example, the motor 14 provides drive power for the vehicle 10. The MG 18 can also act as a generator during regenerative braking, in which rotational energy from the rotating wheels 42 is transferred back through the transmission 24 and converted into electrical energy for storage in the battery 20.

[0027] It is pointed out that the in Fig. The schematic representation shown in Figure 1 is merely exemplary and should not be interpreted as limiting. Other configurations are considered that employ the optional use of either a motor or an electric motor for transmission through the gearbox. For example, the MG 18 may be offset from the crankshaft 28, an additional electric motor may be provided for starting the engine 14, and / or the MG 18 may be positioned between the torque converter 22 and the gearbox 24. Other configurations are considered without deviating from the scope of protection of this disclosure.

[0028] As described above, the control unit 50 is programmed to produce specific effects in the powertrain during driving. The control unit 50 may include software with a Powertrain Mode Manager (PMM) feature that issues commands to the various drive modes described above. When transitioning from one operating mode to another, the engine can be instructed to start or stop. For example, if conditions dictate to the PMM to switch from hybrid mode to all-electric mode, then the engine 14 is instructed to turn off or "shut down." Conversely, if conditions dictate to the PMM to switch from all-electric mode to hybrid mode, then the engine is instructed to turn on or "start up."

[0029] Engine start-up or shutdown requests and drive mode selections, performed by the control unit 50, depend on various factors, such as the accelerator pedal position and the overall drive power or torque requirements. Excessive fluctuation of these factors could cause corresponding fluctuations in engine start or stop commands without some active control to prevent the engine from stopping or starting too frequently.

[0030] For certain vehicle maneuvers, the control unit might order an unnecessary number of engine start and stop cycles. Such maneuvers include entering and exiting a curve, temporary changes in road gradient, or irregular accelerator pedal positions that result in inconsistent driver input. For example, consider a scenario where the engine is running and the vehicle is entering a curve. The driver may lift their foot off the accelerator pedal while entering the curve. This may cause the PMM logic in the control unit to order the engine to shut off based on the reduced driver input. However, once the vehicle exits the curve, the driver may press the accelerator pedal again, causing the control unit to order the engine to restart.This short engine shutdown time can reduce driver comfort and potentially lead to reduced fuel savings due to the energy consumed during engine restart. The present disclosure provides a control strategy to account for driving scenarios such as these and to modify the PMM logic in the control unit accordingly by suppressing engine shutdown in certain situations.

[0031] Engine shutdown can occur, in particular, due to changes in road gradient, accelerator pedal position (i.e., driver input), or steering angle. Various accelerometers and sensors are located throughout the vehicle and transmit information to the control unit regarding changes in road gradient, accelerator pedal position, and steering angle to determine the appropriate operating mode. For example, an accelerator pedal position sensor helps determine driver input; a steering wheel angle or position sensor helps determine steering effort when entering and exiting a curve; force sensors, GPS technology, accelerometers, or visual (e.g., radar) sensors can be useful in determining road gradient.Data relating to road gradient, accelerator pedal position, and steering angle are sent to the control unit 50, and the PMM uses this information to determine the appropriate driving mode for the vehicle. This data sent to the control unit can be referred to as driving condition data.

[0032] According to various aspects of this disclosure, a moving average of different driving condition data is used to determine whether an engine shutdown should be prevented, even when current driving conditions would normally warrant an engine shutdown. A moving average of previous driving condition data allows the control unit to use past driving behavior information to infer current or future driving behavior information and prevent an engine shutdown. While common filters are applied to attenuate fluctuations and noise in data, they cannot precisely prevent an engine shutdown or restart in certain driving scenarios. The moving average used in this disclosure better accounts for variations in road gradient, accelerator pedal position, and steering wheel angle.

[0033] A moving average is a data analysis tool that generates a series of averages for different subsets of the full dataset. A weighted moving average is a type of moving average and can be particularly useful for the driving condition data in this disclosure. In a weighted moving average, the driving condition data are recorded and weighted less heavily over time. That is, weighting is applied to the driving condition data to a degree that decreases progressively; the most recent data are weighted most heavily. An exponential moving average can also be applied, in which the weighting decreases exponentially for each older reference point.

[0034] Fig. Figure 2 is a flowchart of an example algorithm 100 for suppressing engine shutdown based on a weighted average of previous driving condition data. If the control unit implements this algorithm, the weighted average of the previous driving condition data can reduce the frequency of engine stop and start cycles while driving, resulting in improved drivability and fuel savings.

[0035] The algorithm begins at 102. At 104, the control unit determines whether the engine is switched on or off. If the engine is off, the algorithm can end at 106. If the engine is switched on (for example, the vehicle is in hybrid or engine-only mode), the control unit continuously monitors various data at 108 to determine if an engine shutdown request exists. As explained above, an engine shutdown request can typically be made due to reduced driver demand, increased battery charge, or other factors that lead the control unit to conclude that the engine can be switched off to save fuel. If no engine shutdown request is made or received, the control strategy ends and returns to 106.

[0036] Upon receiving an engine shutdown request, a timer is initialized at 110. The timer can be any programmable time value and, in certain embodiments, is in the range of 0.5 to 2.0 seconds. At 112, the road condition data (for example, data indicating road gradient, accelerator pedal position, and steering angle) is subjected to a weighted average, as explained above. The road condition data can, for example, be recorded on a storage medium while the vehicle is in motion and can be retrieved for the purpose of applying the weighted average, where the most recent driving condition is weighted more heavily than older driving condition data.

[0037] At step 114, the weighted average of the preceding road condition data is compared to a threshold. This threshold is programmable and can be modified for different drive types or in different vehicles. This threshold determines whether the engine should actually be shut down or remain running. For example, a weighted average of the road condition data above the threshold indicates a genuine desire to stop the engine, while a weighted average of the road condition data below the threshold indicates a genuine desire to keep the engine running. In this example algorithm, if the weighted average of the road condition data rises above the threshold before the timer expires, the algorithm continues at step 116.If the weighted average of the road condition data does not exceed the threshold, or if the timer has expired, the engine will be stopped at 118.

[0038] At 116, in response to the weighted average exceeding the threshold before the timer expires, the engine shutdown request is ignored, and the engine is prevented from stopping. The engine thus remains running, even though typical driving conditions might otherwise require the control unit to stop the engine to save fuel. The control unit then performs continuous monitoring to ensure that the engine shutdown request is still present at 120. While the engine shutdown request remains, the algorithm continues to compare the weighted average with the threshold. If the timer, with the weighted average still above the threshold, as indicated at 114, has expired, then the engine can finally stop at 118. The engine is no longer prevented from stopping and can comply with the engine shutdown request.

[0039] Fig. 3A illustrates a raw or filtered accelerator pedal position over an extended period. How Fig. As illustrated in Figure 3A, a conventional hybrid system can apply a first threshold which, when exceeded by the accelerator pedal position, causes the engine to start (i.e., the "start-up threshold"). This start-up threshold indicates driver demand; thus, if the accelerator pedal position exceeds the start-up threshold, the driver demand is high, and the control unit commands the engine to start. The system can also apply a second threshold. If the accelerator pedal position falls below the second threshold, the control unit stops the engine (i.e., the "stop-down threshold"). The application of two distinct and separate thresholds allows for a time delay between engine start and stop operations and can provide hysteresis in determining when to activate and deactivate the engine.

[0040] With reference to Fig. 3A, specifically before time t0, the vehicle is operating in all-electric mode or another mode in which the engine is off and provides no drive torque. At time t1, the accelerator pedal position exceeds the start-up threshold, and the engine is started. The vehicle is thus operating in hybrid mode, all-engine mode, or another mode in which the engine is on and provides drive torque. Because the accelerator pedal position fluctuates and even falls below the start-up threshold, the engine remains on until time t2, when the accelerator pedal falls below the shut-down threshold. This returns the engine to all-electric mode or another mode in which the engine is off. Shortly thereafter, the driver quickly presses the accelerator pedal, as indicated at time t3, at which point the accelerator pedal position again exceeds the start-up threshold. This starts the engine.The engine remains running until time t4, at which point the accelerator pedal falls below the shutdown threshold. At this point, the engine stops again. The engine remains off because the driver begins to drive in neutral, with the accelerator pedal position remaining relatively low and below both thresholds.

[0041] As illustrated by this embodiment, rapid variations in the accelerator pedal can lead to corresponding rapid changes in engine operation. For example, the engine switches off at time t2 but restarts quickly at time t3 if the accelerator pedal exceeds the start-up threshold. These harsh driving conditions and frequent changes in engine operation can impair the vehicle's handling if the driver perceives the engine switching on and off at an undesirable speed.

[0042] As explained above, a moving average of various driving condition data can be used to prevent engine shutdown. Vehicle controls can be implemented with a moving average mapped to accelerator pedal position data to improve drivability. An example of a moving average is shown below: Y=∑(Wi∗Xi)∑Wi where Y is the weighted average of the accelerator pedal position, W is the weights as a function of the number (N) of a previous time interval, and X is the number (N) of previous accelerator pedal values ​​with weights that are more heavily weighted towards the nearest previous values. The weights that are heavier towards the nearest previous values ​​provide a weighted moving average, as discussed above as an example of a moving average. The weighted moving average acts like a low-pass filter and attenuates the accelerator pedal position history, as compared to Fig. 3B with Fig. 3A is shown.

[0043] With reference to Fig. 3B, it has one threshold instead of two: a "suppression shutdown threshold". The graph of Fig. 3B is intended to illustrate the results of a supplementary control strategy and complements the one in Fig. 3A graphically represented results. In Fig. 3A The control unit reacts to two threshold values ​​(the ramp-up threshold and the ramp-down threshold) to control the motor. Fig. However, in section 3B, shutdown requirements are now also compared against a single weighted average threshold. The control strategy, which is defined in Fig. The results shown in 3A can be achieved through the control strategy of Fig. 2 and the corresponding results achieved by Fig. 3B may be supplemented or replaced.

[0044] With the initial accelerator pedal movement before time t0, the moving average of the accelerator pedal position has already increased after exceeding the shutdown threshold. As long as the moving average of the accelerator pedal position remains above this threshold, the control system prevents or suppresses the engine from shutting down or stopping. This control can be applied regardless of the engine state. For example, the control system can prevent the engine from stopping even if it has not yet started; once the engine has started, it will prevent it from stopping as long as the moving average of the accelerator pedal position remains above the threshold.

[0045] As in Fig. As can be seen in 3B, the moving average of the accelerator pedal position remains above the suppression-shutdown threshold, past t1 and continuing to t5. This means that the engine remains running, even during the irregular accelerator pedal movement described above and in Fig. As shown in Figure 3A. Only at time t5 does the moving average of the accelerator pedal position fall below a suppression / shutdown threshold. At this point, the control system can allow the engine to shut down or stop if the driver demands are such that stopping the engine would increase efficiency. Thus, the Fig. 2 and Fig. Figure 3B illustrated the control logic of additionally switching off the motor at time t2 and immediately starting it at time t3. Fig. 3A.

[0046] With reference to Fig. 4A and Fig. 4B is subject to similar restrictions to the engine shutdown activity, except that these now relate to the steering angle. Steering angle or steering wheel angle position can be determined based on one or more sensors on or near the vehicle's steering wheel. Similar to the accelerator pedal position example above, a moving average of steering angle positions can be calculated as follows: Y=∑(Wi∗Xi)∑Wi where Y is the weighted mean steering angle, W is the weights as a function of previous numbers (N) of time intervals, and X is the previous number (N) of steering angle position values ​​with weights placed more heavily on recent past data.

[0047] Fig. 4A and Fig. Figure 4B illustrates a scenario in which the vehicle enters a curve with the engine running, for example, when the vehicle is in hybrid mode or engine-only mode. A typical driver will ease off the accelerator pedal pressure when entering a curve, which would normally cause the control unit to issue an engine shutdown command, as at time t2 in Figure 4B. Fig. Figure 4B illustrates how the accelerator pedal position falls below the deceleration threshold. As the vehicle exits the curve, the driver can press the accelerator pedal again, triggering a corresponding engine start command at time t3, at which point the accelerator pedal position exceeds the acceleration threshold.

[0048] However, if the moving average algorithm described above is applied by the control system, then this momentary engine shutdown, immediately followed by an engine start-up, can be avoided. With reference to Fig. 4A, when the vehicle is driven straight ahead, the moving average of the steering angle is 0. This is shown before time t0. The vehicle enters the curve at time t0. Shortly thereafter, at time t1, the moving average of the steering angle rises above a "suppression-down threshold," which (like the suppression-down threshold in Fig. 3B) may be calibrated. As long as the moving average of the steering angle remains above this threshold, the controls will prevent or suppress the engine from shutting down, regardless of accelerator pedal position or other factors. The reason for this is that the control system is programmed to recognize that while driving, a turn is typically followed by accelerator pedal movement, and therefore it can be inferred that driver demands may increase shortly after the steering angle returns to 0.

[0049] This will be in Fig. 4A and Fig. Figure 4B illustrates this. As the vehicle exits the curve, the pressure on the accelerator pedal can increase above the ramp-up threshold at time t3. Normally, this would cause the control unit to activate the engine. However, because the moving average of the steering angle still exceeds the ramp-up threshold, the engine remains running. The moving average of the steering angle eventually falls below the ramp-up threshold at time t4, but by this time the driver (as predicted) has increased the pressure on the accelerator pedal to continue driving. Thus, the engine remains running throughout the entire curve and is not simply stopped and started based on the accelerator pedal position.The control strategy thus prevents the engine from stopping and starting (at time t2 and time t3 respectively), which would otherwise occur without the moving average of steering angles.

[0050] Comparing the actual steering angle position with the moving average of the steering angle positions also delays the time at which the engine can be switched off. This can also reduce unwanted engine start-stop cycles and improve the vehicle's handling.

[0051] Fig. 5A and Fig. 5B are with Fig. 4A and Fig. 4B is identical, except for the illustration of the effect of varying steering angle positions over multiple curves. Fig. 5A, for example, could be a sharp turn followed by an even sharper turn. As can be seen, the actual steering angle can rise rapidly and fall back to zero during the first turn. During the subsequent turn, the steering angle position reaches a higher point during a sharper turn. The moving average of the steering angle rises above the suppression-shutdown threshold at time t1 and remains above the threshold even when the actual steering angle falls back to zero a second time at time t2. The engine remains prevented from stopping until time t3 if the moving average of the steering angle falls below the suppression-shutdown threshold.

[0052] The advantages of a moving average (for example, a weighted moving average) are illustrated in the example of Fig.5A highlighted. A first-order filter is standard and typically implemented in various vehicle technologies. If a simple first-order filter were implemented in the control system, rather than the moving average of a steering angle position, sharp movements and transitions in the actual steering angle would usually be tracked until the filter reaches its limit. This would result in multiple crossings of the suppression-shutdown threshold (or multiple thresholds), consequently enabling undesirable engine start-up and stop-start events. A typical ramp filter is also illustrated. The steering angle transitions load the ramp filter, and the ramp filter slowly "unloads" after the peak value in the actual steering angle position, filtering down from that level.This in turn allows multiple engine start and stop cycles during the curves, and delays the time in which the engine can be allowed to stop (as shown by the long delay until the ramp filter falls below the suppression shutdown threshold).

[0053] By applying a moving average of the steering angle, the engine is prevented from stopping during both turns. Specifically, the accelerator pedal position falls below the shutdown threshold after a time t1. However, at time t1, the moving average has risen to exceed the suppression shutdown threshold. Thus, the engine remains running and is prevented from shutting down.

[0054] Similar moving averages can be applied to road gradient data while driving to prevent the engine from shutting off due to poor visibility. For example, the same calculation can be applied: Y=∑(Wi∗Xi)∑Wi where Y is the estimated road gradient at the next time example, W is the weights assigned to the road gradient as a function of the number (N) of previous time intervals, and X is the previous number (N) of road gradient values. If the vehicle is traveling uphill, Y can represent a weighted average road gradient over the previous examples. A negative change in the actual road gradient can result in less torque required to propel the vehicle, which in turn causes the control unit to issue a motor shutdown command. By applying this control strategy, the motor shutdown command is prevented from being executed for the next time examples until Y falls below a threshold or a calibratable timer expires.This control system improves fuel efficiency and drivability when the change in road gradient is temporary, triggering a prevention of unnecessary engine stop / start operations due to the delay in switching off the engine.

[0055] The methods, procedures, or algorithms disclosed herein may be available for implementation by a processing device, control unit, or computer, which may include any existing programmable electronic control unit or associated electronic control unit. Similarly, the methods, procedures, or algorithms may be stored as data and instructions executable by a control unit or computer in many forms, including, but not limited to, information stored on non-writable storage media, such as ROM devices, and information stored modifiably on writable storage media, such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media.The process methods, procedures, or algorithms can also be implemented in a software executable object. Alternatively, the process methods, procedures, or algorithms can be implemented in whole or in part using suitable hardware components, such as application-specific integrated circuits (ASICs), general-purpose circuits (FPGAs), state machines, control units, or other hardware components or devices, or a combination of hardware, software, and firmware components.

[0056] Although exemplary embodiments are described above, these embodiments are not to be understood as describing all possible forms encompassed by the claims. The terms used in the description are descriptive and not limiting, and it is pointed out that different modifications can be made without altering the essence and scope of the disclosure. As previously described, the features of different embodiments can be combined to form further embodiments of the invention, which may not be expressly described or illustrated.Although various embodiments may have been described as offering advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, the person skilled in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system properties that depend on the specific application and implementation. These properties may include, but are not limited to, cost, strength, service life, life cycle costs, marketability, appearance, packaging, size, functionality, weight, manufacturability, ease of assembly, etc.Therefore, insofar as the embodiments are described as less desirable than other embodiments or prior art implementations with regard to one or more characteristics, these embodiments are not outside the scope of protection of the disclosure and may be desirable for certain applications.

Claims

[1] Vehicle (10), comprising: a steering wheel with an associated steering wheel angle sensor; a motor (14); a gearbox (24); a motor-generator capable of providing drive torque, which is optionally coupled to the motor (14) via a clutch (26) and optionally coupled to the transmission (24); and a control unit (50) which is programmed to prevent the clutch (26) from disengaging and the engine (14) from stopping on the basis of a moving average of previous steering wheel angle positions that exceeds a threshold value. [2] Vehicle (10) according to claim 1, wherein the control unit (50) is further programmed to engage the clutch (26) and start the engine (14) in response to the moving average value falling below the threshold value. [3] Vehicle (10) according to claim 1, wherein the control unit (50) is further programmed to initialize a timer in response to an engine-OFF request, and wherein the control unit (50) is further programmed, following receipt of an engine-OFF request and while the moving average exceeds the threshold, to disengage the clutch (26) and stop the engine (14) in response to the expiry of the timer. [4] Vehicle (10) according to claim 1, wherein the control unit (50) is further programmed to prevent the clutch (26) from disengaging and the engine (14) from stopping on the basis of the moving average value that exceeds the threshold value regardless of an accelerator pedal position or a brake pedal position. [5] Vehicle (10) according to claim 1, further comprising an accelerator pedal (52) with an associated pedal position sensor, wherein the control unit (50) is further programmed to prevent the clutch (26) from disengaging and the engine (14) from stopping on the basis of a moving average of previous pedal position values ​​that exceeds a pedal position threshold. [6] Vehicle (10) according to claim 1, wherein the moving average is a weighted moving average.

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