System and method for controlling driving of hybrid vehicle

A system and method for controlling driving of a hybrid vehicle are provided. The method includes determining whether acceleration of the hybrid vehicle is predicted and increasing a conversion reference value converting a driving mode of the hybrid vehicle from an electric vehicle (EV) mode to a hybrid electric vehicle (HEV) mode when acceleration of the hybrid vehicle is predicted.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0010646 filed in the Korean Intellectual Property Office on Jan. 23, 2017, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Field of the Invention

The present invention relates to a control method and system for a vehicle, and more particularly, to a system and method for controlling driving of a hybrid vehicle to reduce unnecessary energy consumption.

(b) Description of the Related Art

An environmentally-friendly vehicle includes a fuel cell vehicle, an electric vehicle, a plug-in electric vehicle, and a hybrid vehicle, and typically includes a motor that generates driving force. A hybrid vehicle, which is an example of an environmentally-friendly vehicle, uses an internal combustion engine and power of a battery together to drive the vehicle. In other words, the hybrid vehicle efficiently combines and uses power of the internal combustion engine and power of a motor. The hybrid vehicle includes an engine, a motor, an engine clutch to adjust power between the engine and the motor, a transmission, a differential gear apparatus, a battery, a starter-generator that starts the engine or generates electricity by output of the engine, and wheels.

Further, the hybrid vehicle includes a hybrid control unit (HCU) configured to operate the hybrid vehicle, an engine control unit (ECU) configured to operate the engine, a motor control unit (MCU) configured to operate the motor, a transmission control unit (TCU) configured to operate the transmission, and a battery control unit (BCU) configured to operate and manage the battery. The battery control unit may be referred to as a battery management system (BMS). The starter-generator may be referred to as an integrated starter and generator (ISG) or a hybrid starter and generator (HSG).

Further, the hybrid vehicle may be driven in various driving modes, such as an electric vehicle (EV) mode, which is an electric vehicle mode using power of the motor, a hybrid electric vehicle (HEV) mode, which uses rotational force of the engine as main power and uses rotational force of the motor as auxiliary power, and a regenerative braking (RB) mode for collecting braking and inertial energy during driving by braking or inertia of the vehicle through electricity generation of the motor to charge the battery. A technology of the related art classifies driving environments according to driving information of a vehicle to vary driving control of the vehicle. The related art may collect the vehicle data having driver characteristics to predict current driving environment and to adjust the vehicle performance based on the predicted or detected driving environment.

SUMMARY

The present invention provides a method for controlling driving of a hybrid vehicle which is capable of reducing unnecessary energy consumption on a real road using a control logic for predicting an acceleration state of the vehicle to prevent an unnecessary switching (e.g., an on state of an engine) from an electric vehicle (EV) mode to a hybrid electric vehicle (HEV) mode.

An exemplary embodiment of the present invention provides a method for controlling driving of the hybrid vehicle that may include: determining, by a controller, whether acceleration of the hybrid vehicle is predicted; and increasing, by the controller, a conversion reference value that converts a driving mode of the hybrid vehicle from an electric vehicle (EV) mode to a hybrid electric vehicle (HEV) mode when acceleration of the hybrid vehicle is predicted.

The controller may be configured to determine whether acceleration of the hybrid vehicle is predicted based on a change rate of speed of the vehicle and a change rate of an acceleration pedal position sensor (APS) value generated during a predetermined driving time after the hybrid vehicle stops or decelerates to a predetermined speed. The method may further include: determining, by the controller, whether a slope of a road on which the vehicle is traveling is less than or equal to a threshold value. The controller may be configured to predict acceleration of the vehicle when the slope is less than or equal to the threshold value.

Additionally, the method may include: determining, by the controller, a type of a road on which the vehicle is traveling based on an average speed of the vehicle. The controller may be configured to predict acceleration of the vehicle when the type of the road is determined as a street in a downtown. The method may further include: determining, by the controller, a type of a road on which the vehicle is traveling based on an average speed of the vehicle. The controller may be configured to predict acceleration of the vehicle when the type of the road is determined as an expressway.

Further, the controller may be configured to determine whether acceleration of the hybrid vehicle is predicted based on traffic signal information or precision map information received by the vehicle. The method may further include: determining, by the controller, a type of a road on which the vehicle is traveling based on precision map information. The controller may be configured to predict acceleration of the vehicle when the type of the road is determined as a street in a downtown.

The method for controlling driving of the hybrid vehicle may further include: determining, by the controller, a type of a road on which the vehicle is traveling based on precision map information. The controller may be configured to predict acceleration of the vehicle when the type of the road is determined as an expressway. The vehicle may be operated by the controller to travel in the EV mode after the conversion reference value is increased. The method for controlling driving of the hybrid vehicle according to the exemplary embodiment of the present invention may increase fuel efficiency of the vehicle using driving information (or a driving pattern) of the vehicle.

The exemplary embodiment of the present invention may increase fuel efficiency by reducing an unnecessary on state of an engine in various acceleration situations occurring while the vehicle is being driven. Further, the exemplary embodiment of the present invention may reduce fuel consumption due to an acceleration pattern of the vehicle that has a substantial effect on fuel consumption. Thus, fuel consumption caused by a driver who aggressively starts the vehicle may be reduced and fuel efficiency deviation according to the driver may be reduced.

DETAILED DESCRIPTION

In order to sufficiently understand the present invention and the object achieved by embodying the present invention, the accompanying drawings illustrating exemplary embodiments of the present invention and contents described in the accompanying drawings are to be referenced.

Hereinafter, the present invention will be described in detail by describing exemplary embodiments of the present invention with reference to the accompanying drawings. In describing the present invention, well-known configurations or functions will not be described in detail since they may unnecessarily obscure the gist of the present invention. Throughout the accompanying drawings, the same reference numerals will be used to denote the same components.

Terms used in the present specification are only used in order to describe specific exemplary embodiments rather than limiting the present invention. Throughout this specification and the claims that follow, when it is described that an element is “coupled” to another element, the element may be “directly coupled” to the other element or “electrically or mechanically coupled” to the other element through a third element.

Unless defined otherwise, it is to be understood that the terms used in the present specification including technical and scientific terms have the same meanings as those that are generally understood by those skilled in the art. It must be understood that the terms defined by the dictionary are identical with the meanings within the context of the related art, and they should not be ideally or excessively formally defined unless the context clearly dictates otherwise.

In order for a vehicle to perform a high-efficiency energy-saving driving on a road (or a real road), energy consumption according to a repeated acceleration driving pattern of the vehicle needs to be managed. Since a method for classifying an ordinary driving pattern based on an average value of a vehicle speed or an average value of an acceleration pedal position sensor (APS) value according to related art uses all driving information, it may be difficult to classify (or extract) some distinguishing driving characteristics. In other words, since all the driving information is considered together in the related art, it may be difficult to extract driving characteristics therefrom. A response to a momentary driving event may be difficult due to a control based on a constant cycle according to the method. Therefore, there is a need to minimize energy consumption by appropriately classifying an acceleration driving pattern of the vehicle which causes a substantial amount of instantaneous fuel consumption and an unnecessary engine operation to adjust a conversion reference value switching from an electric vehicle (EV) mode to a hybrid electric vehicle (HEV) mode when acceleration of the vehicle is predicted or detected (e.g., detected by an acceleration sensor).

For a control based on determination of the driving pattern according to the related art, distinguishing driving information may disappear since ordinary driving tendency is extracted using driving information such as the vehicle speed. For example, a sudden deceleration of the vehicle after a sudden acceleration is the distinguishing driving information, but the distinguishing driving information may be removed in the process of calculating the average value for extracting the ordinary driving tendency. Therefore, there is a need for a method to improve driving efficiency of the vehicle using the distinguishing driving information.

The acceleration of the vehicle may be classified into two types as follows. One classification may be when the vehicle starts from a stop of the vehicle to accelerate and one when the vehicle accelerates after the vehicle decelerates for entering an interchange or passing a toll gate while the vehicle is being driven. The above classification may be again classified into an acceleration pattern (or an acceleration-travel pattern) on a street in a downtown and an acceleration pattern on an expressway.

FIG. 1is a graph illustrating a normal acceleration situation of a vehicle.FIG. 2is a graph illustrating a reference value switching from the EV mode shown inFIG. 1to the HEV mode. Referring toFIGS. 1 and 2, in the normal acceleration situation of the vehicle, the hybrid vehicle may travel in the EV mode which is an operation mode that is less than the reference value10when a state of charge (SOC) of a battery is greater than the reference value. The reference value10may be determined in advance by a test and is not limited thereto.

FIG. 3is a graph illustrating a sudden acceleration situation where a fuel is ineffectively used in the vehicle.FIG. 4is a graph illustrating a conversion reference value for switching from the EV mode shown inFIG. 3to the HEV mode according to an exemplary embodiment of the present invention.FIG. 5is a flowchart illustrating a method for controlling driving of a hybrid vehicle according to an exemplary embodiment of the present invention.FIG. 7is a block diagram illustrating the hybrid vehicle to which the method for controlling driving of the hybrid vehicle according to the exemplary embodiment of the present invention is applied. The method to be described herein below may be executed by a controller having a processor and a memory.

Referring toFIGS. 3, 4, 5, and 7, in a determination step100, a controller305may be configured to determine a type of a road on which the hybrid vehicle300is being driven (e.g., is traveling) based on an average speed of the hybrid vehicle. In particular, the controller305may be configured to determine the type of the road on which the hybrid vehicle300is being driven based on a map table that includes the type of the road according to the average speed of the hybrid vehicle. For example, the road type may be a street, an arterial, or an expressway. The map table may include the road type that corresponds to the average speed (or an average value of the vehicle speed), an average value of an acceleration pedal position sensor (APS) value, or an average value of a brake pedal position sensor (BPS) value (or a combination of the average value of the vehicle speed, the average value of the APS value, and the average value of the BPS value). The map table may be generated by a test.

For example, the controller305may be one or more microprocessors operated by a program or hardware including the microprocessor. The program may include a series of commands for executing the method for controlling driving of the hybrid vehicle according to the exemplary embodiment of the present invention. The hybrid vehicle300may include the controller305, an engine310, a hybrid starter-generator (HSG)320, an engine clutch325, a motor (or a driving motor)330which may be an electric motor, a battery340, a transmission350, and wheels (or driving wheels)390. The controller305may be configured to operate the other components of the vehicle300.

The hybrid vehicle300, which is a hybrid electric vehicle, may use the engine310and the motor330as power sources, and may include the engine clutch325disposed between the engine310and the motor330and thus, the hybrid vehicle300may be operated in an electric vehicle (EV) mode in which the hybrid vehicle300travels by the motor330when the engine clutch325is opened, and in a hybrid electric vehicle (HEV) mode in which the hybrid vehicle300is capable of travelling by both the motor330and the engine310when the engine clutch325is closed.

The hybrid vehicle300may include a power train of a transmission mounted electric device (TMED) type in which the motor330is connected to the transmission350. The hybrid vehicle300may be driven in various driving modes, such as the EV mode, which is the electric vehicle mode using power of the motor, and the HEV mode, which uses rotational force of the engine as main power and uses rotational force of the motor as auxiliary power based on whether the engine clutch325disposed between the engine310and the motor330is engaged (or connected). In particular, in the hybrid vehicle300including a structure in which the motor330may be directly connected to the transmission350, revolutions per minute (RPM) of the engine may be increased by operation of the HSG320, power delivery and power cutoff between the engine and the motor may be performed via engagement and release of the clutch325, a driving force may be transmitted (or transferred) to the wheels390through a power transmission system which may include the transmission350, and torque of the engine may be transmitted to the motor via engagement of the clutch325when transmission of the engine torque is requested.

The controller305may include a hybrid control unit (HCU), a motor control unit (MCU), an engine control unit (ECU), and a transmission control unit (TCU). The HCU may be configured to start the engine310by operating the HSG320when the engine stops. The HCU may be a highest controller or an upper controller, and may be configured to operate the controllers (e.g., the MCU) connected via a network such as a controller area network (CAN) which is a vehicle network, and may be configured to execute overall operation of the hybrid vehicle300.

The MCU may be configured to operate the HSG320and the motor330. The MCU may be configured to adjust an output torque of the driving motor330via the network based on the control signal output from the HCU, and thus may be configured to operate the motor at maximum efficiency. The MCU may include an inverter configured as a plurality of power switching elements. A power switching element included in the inverter may include an insulated gate bipolar transistor (IGBT), a field effect transistor (FET), a metal oxide semiconductor FET (MOSFET), a transistor, or a relay. The inverter may be configured to convert a direct current (DC) voltage supplied from the battery340into a three-phase alternating current (AC) voltage to drive the driving motor330. The MCU may be disposed between the battery340and the motor330.

The ECU may be configured to adjust a torque of the engine310. In particular, the ECU may be configured to adjust an operating point (or a driving point) of the engine310via the network based on a control signal output from the HCU, and may be configured to operate the engine to output an optimal torque. The TCU may be configured to operate the transmission350. The engine310may include a diesel engine, a gasoline engine, a liquefied natural gas (LNG) engine, or a liquefied petroleum gas (LPG) engine, and may output a torque at the operating point based on a control signal output from the ECU. The torque may be combined with driving force of the driving motor330in the HEV mode. The engine310may be connected to the motor330via the engine clutch325to generate a power transmitted to the transmission350.

The HSG320may operate as a motor based on a control signal output from the MCU to start the engine310, and may operate as a generator when start of the engine310is maintained to provide generated electric power to the battery340via the inverter. The HSG320may be connected to the engine310via a belt. The HSG320, which is a motor that cranks the engine, may be directly connected to the engine. The engine clutch325may be disposed (or mounted) between the engine310and the driving motor330, and may be operated to switch power delivery between the engine310and the motor330. The engine clutch325may connect or intercept power between the engine and the motor based on switching of the HEV mode and the EV mode. Operation of the engine clutch325may be adjusted by the controller305.

The motor330may be operated by a three-phase AC voltage output from the MCU to generate a torque. The motor330may be operated as a generator during coasting drive or regenerative braking to supply a voltage (or regenerative energy) to the battery340. The battery340may include a plurality of unit cells. A high voltage for providing a driving voltage (e.g., about 350-450 V DC) to the motor330that provides driving power to the wheels390or the HSG320may be stored in the battery340.

The transmission350may include a multiple speed transmission, such as an automatic transmission or a dual clutch transmission (DCT), or a continuously variable transmission (CVT), and may shift to a desired gear using hydraulic pressure based on control of the TCU to operate engagement elements and disengagement elements. The transmission350may be configured to transmit driving force of the engine310and/or the motor330to the wheels390, and may intercept power delivery between the motor330(or the engine310) and the wheels390.

According to a determination step105, the controller305may be configured to determine whether the determined type of the road is the street in a downtown (e.g., a more congested area). In particular, the street type may be detected based on the map table (e.g., a memory) that includes driving environment based on the average speed of the vehicle. For example, when the average vehicle speed is less than a predetermined speed, the controller may be configured to determine that the vehicle is being driven in a highly congested area, that is, a downtown street. The method for controlling driving of the hybrid vehicle may continue to a determination step110when the determined type of the road is the street. The process may then proceed to a determination step135when the determined type of the road is not the street (e.g., the average speed is determined to be greater than the predetermined speed).

According to the determination step110, the controller305may be configured to detect whether the hybrid vehicle300is stopped or decelerated to a specific speed using a signal output from a speed sensor of the hybrid vehicle. For example, determining whether the hybrid vehicle300is stopped or decelerated to the specific speed may be performed by calculating a moving average in real time by continuously collecting vehicle speed data during a predetermined time interval. According to a determination step115, when the hybrid vehicle300is stopped or decelerated to the specific speed, the controller305may be configured to determine whether a slope of the road on which the hybrid vehicle is being driven is less than or equal to a threshold value. In particular, to prevent degradation of driving responsiveness, the exemplary embodiment of the present invention may determine the slope of the road. Thus, when an uphill road having a slope greater than the threshold value is detected, the method for controlling driving of the hybrid vehicle according to the exemplary embodiment may not be performed in the street.

According to a calculation step120, when the slope of the road on which the hybrid vehicle300is being driven is less than or equal to the threshold value, the controller305may be configured to calculate a change rate of the vehicle speed and a change rate of the acceleration pedal position sensor (APS) value during a specific driving time of the hybrid vehicle. According to a determination step125, the controller305may be configured to determine whether acceleration of the hybrid vehicle shown inFIG. 3is predicted based on the change rate of the vehicle speed and the change rate of the APS value. For example, the controller305may be configured to determine that the acceleration of the hybrid vehicle is predicted when the change rate of the vehicle speed is greater than a reference value and the change rate of the APS value is greater than a reference value.

According to an adjustment step130, when the acceleration of the hybrid vehicle300is predicted and a state of charge (SOC) of the battery340is equal to or greater than a threshold value for performing the predicted acceleration, the controller305may be configured to increase the conversion reference value for converting the driving mode of the hybrid vehicle from the EV mode to the HEV mode, as shown inFIG. 4. Reference numeral15inFIG. 4may indicate the conversion reference value. The hybrid vehicle300may enter the HEV mode when the hybrid vehicle operates in a region that is equal to or greater than the conversion reference value, and the hybrid vehicle300may enter the EV mode when the hybrid vehicle300operates in a region that is less than the conversion reference value.

Further, the controller305may be configured to operate the hybrid vehicle300in the EV mode after the conversion reference value is increased (or adjusted). For example, the conversion reference value may be the speed of the vehicle, a torque required by a driver of the vehicle, or a power required by the driver. According to a determination step135, the controller305may be configured to determine whether the determined road type is an expressway, highway, interstate, or the like. In particular, the expressway may be detected or confirmed based on the map table that includes the driving environment according to the average speed of the vehicle.

The process may proceed to a determination step140when the determined road type is detected as the expressway. The process may proceed to the determination step105when the determined road type is not detected to be the expressway. According to the determination step140, the controller305may be configured to determine whether the hybrid vehicle300stops or decelerates to a specific speed using the signal output from the speed sensor. For example, determining whether the hybrid vehicle300stops or decelerates to the specific speed may be performed by calculating a moving average calculated in real time by continuously collecting vehicle speed data during a predetermined time interval.

According to a determination step145, when the hybrid vehicle300stops or decelerates to the specific speed, the controller305may be configured to determine whether a slope of the road on which the hybrid vehicle is being driven is less than or equal to a threshold value. In particular, to prevent degradation of driving responsiveness, the exemplary embodiment of the present invention may determine the slope of the road. Thus, when an uphill road having a slope greater than the threshold value is detected, the method for controlling driving of the hybrid vehicle according to the exemplary embodiment may not be performed in the expressway.

According to a calculation step150, when the slope of the road on which the hybrid vehicle300is being driven is less than or equal to the threshold value, the controller305may be configured to calculate a change rate of the vehicle speed and a change rate of the acceleration pedal position sensor (APS) value during a specific driving time of the hybrid vehicle. According to a determination step155, the controller305may be configured to determine whether acceleration of the hybrid vehicle shown inFIG. 3is predicted based on the change rate of the vehicle speed and the change rate of the APS value. For example, the controller305may be configured to determine that the acceleration of the hybrid vehicle is predicted when the change rate of the vehicle speed is greater than a reference value and the change rate of the APS value is greater than a reference value.

According to an adjustment step160, when the acceleration of the hybrid vehicle300is predicted and the SOC of the battery340is equal to or greater than the threshold value for performing the predicted acceleration, the controller305may be configured to increase the conversion reference value for converting the driving mode of the hybrid vehicle from the EV mode to the HEV mode, as shown inFIG. 4. After the conversion reference value is increased, the controller305may be configured to operate the hybrid vehicle300in the EV mode.

As described above, the exemplary embodiment of the present invention may classify the acceleration pattern of the vehicle into driving on the street and driving of the expressway to thus control driving of the hybrid vehicle that is suddenly started or accelerated. After the acceleration pattern is classified, the conversion reference value that changes based on the SOC of the battery340may be increased for a predetermined time interval, as shown inFIG. 4.

FIG. 6is a flowchart illustrating the method for controlling driving of the hybrid vehicle according to another exemplary embodiment of the present invention. Referring toFIGS. 3, 4, 6, and 7, in a determination step200, the controller305may be configured to determine a type of a road on which the hybrid vehicle300is being driven based on precision map information (or precise road map information). The precision map may represent a three-dimensional (3D) map which has high accuracy information on the road and geographical features around the road.

According to a determination step205, the controller305may be configured to determine whether the determined type of the road is the street in a downtown area. In particular, the street may be confirmed or detected based on the precision map information. The method for controlling driving of the hybrid vehicle may proceed to a determination step210when the determined type of the road is the street. The process may then proceed to a determination step220when the determined type of the road is not the street (e.g., based on a detected vehicle speed).

According to the determination step210, the controller305may be configured to determine whether acceleration of the hybrid vehicle shown inFIG. 3is predicted based on traffic signal information or the precision map information received at the hybrid vehicle300. The traffic signal information or the precision map information may be transmitted from a server extraneous to the vehicle. For example, the traffic signal information may include traffic signal change information such as information indicating a switch from a red traffic light to a green traffic light, and the precision map information may include speed hump position information. An acceleration state of the hybrid vehicle may include an acceleration state of the vehicle occurring after the vehicle stops in front of a crossroad or an acceleration state of the vehicle occurring after the vehicle passes through a speed hump.

According to an adjustment step215, when the acceleration of the hybrid vehicle300is predicted and the SOC of the battery340is equal to or greater than a threshold value for performing the predicted acceleration, the controller305may be configured to increase the conversion reference value for converting the driving mode of the hybrid vehicle from the EV mode to the HEV mode, as shown inFIG. 4. The controller305may be configured to operate the hybrid vehicle300in the EV mode after the conversion reference value is increased (or adjusted). According to a determination step220, the controller305may be configured to determine whether the determined road type is the expressway. In particular, the expressway may be detected based on the precision map information. The process may then proceed to a determination step225when the determined road type is the expressway. The process may proceed to the determination step205when the determined road type is not the expressway.

According to the determination step225, the controller305may be configured to determine whether acceleration of the hybrid vehicle shown inFIG. 3is predicted based on the precision map information received at the hybrid vehicle300. For example, the precision map information may include toll gate location information or interchange (IC) location information. An acceleration state of the hybrid vehicle may include an acceleration state of the vehicle occurring after the vehicle passes through an interchange or an acceleration state of the vehicle occurring after the vehicle passes through a speed hump.

According to an adjustment step230, when the acceleration of the hybrid vehicle300is predicted and the SOC of the battery340is equal to or greater than the threshold value for performing the predicted acceleration, the controller305may be configured to increase the conversion reference value for converting the driving mode of the hybrid vehicle from the EV mode to the HEV mode, as shown inFIG. 4. After the conversion reference value is increased, the controller305may be configured to operate the hybrid vehicle300in the EV mode.

As set forth above, exemplary embodiments have been disclosed in the accompanying drawings and the specification. Herein, specific terms have been used, but are just used for the purpose of describing the present invention and are not used for qualifying the meaning or limiting the scope of the present invention, which is disclosed in the appended claims. Therefore, it will be understood by those skilled in the art that various modifications and equivalent exemplary embodiments are possible from the present invention. Accordingly, the actual technical protection scope of the present invention must be determined by the spirit of the appended claims.

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