Control system for electric vehicle drift driving

Abstract

A control system for drift driving of an electric vehicle includes a driving information detector provided to detect vehicle driving information in an electric vehicle having a virtual shift function, an interface provided to be used by a driver to activate a drift mode and to select a virtual gear, and a control unit provided to control at least one of a wheel slip control zone configured to zone a performance of a torque intervention control for rear wheel slip suppression, an upshift limit zone configured to zone a performance of upshift, and a downshift limit zone configured to zone a performance of downshift, based on the vehicle driving information detected by the driving information detector and based on whether the driver selects to activate the drift mode through the interface.

Description

Background Technology

[0001] (a) Technical Field

[0002] This disclosure relates to a control system for drift driving of an electric vehicle, which allows the driver to control the amount of rear wheel slippage to a desired level during the execution of a drift mode.

[0003] (b) Background Art

[0004] The electric vehicle market is gradually expanding. In the electric vehicle sector, most of the technical bottlenecks of internal combustion engine vehicles, such as response speed, fuel efficiency, and emissions regulations, have been resolved, opening up possibilities for the development of various new technologies. Recently, moving away from the development model of internal combustion engine vehicles and ensuring a unique selling point (USP) through expanded functionality has become a crucial factor in the competitiveness of electric vehicles in the market.

[0005] In particular, as a representative USP element that leverages the high degree of freedom in driving force control of electric vehicles, drift mode, which includes functions specifically developed for the pursuit of driving pleasure, is also under development.

[0006] Drift mode is a drive force control strategy that ensures vehicle stability under normal use, but only stops rear wheel slip control intervention when requested by the driver to allow the driver to drift freely in a rear-wheel-guided drive force state. In this state, the rear wheel limited-slip differential (LSD) engages, and drive force is applied only to the rear wheels to help the driver drift freely.

[0007] Drifting in electric vehicles is a known technology. This technology involves a strategy that generates driving force only through the rear wheel motor (rear wheel steering drive force) while simultaneously providing the driver with an environment conducive to inducing rear wheel slip by engaging an electronic limited-slip differential (e-LSD).

[0008] According to existing technology, it is easy to cause rear wheel slippage when drifting mode is executed alone, but it is not easy to control the occurrence of rear wheel slippage to the extent desired by the driver.

[0009] The reason for this is that, due to the characteristics of electric vehicles, their torque response is very fast, and the torque range generated when performing drift mode is set to the entire available torque range of the motor.

[0010] This problem does not occur in existing internal combustion engine vehicles because most internal combustion engine vehicles are equipped with multi-speed transmissions, and drivers can select the desired torque range and engine speed (RPM) range by shifting gears appropriately during drift driving.

[0011] Given this background, there is a need for a drive force control technology and a drift driving control technology that can compensate for the shortcomings of existing electric vehicles without actual transmissions in drift mode.

[0012] The above information is provided only to enhance understanding of the background of this disclosure and therefore may contain information that does not constitute prior art known to those skilled in the art in this country. Summary of the Invention

[0013] This disclosure aims to solve the aforementioned problems related to the prior art, and the purpose of this disclosure is to provide a control system for drift driving of electric vehicles that allows the driver to control the amount of rear wheel slippage to a desired level during drift mode execution.

[0014] Another object of this disclosure is to provide a control system for drift driving of an electric vehicle, which, when drift mode is activated, allows the driver to track the desired amount of slip using the torque and virtual engine speed (virtual RPM) applied to each virtual gear of the virtual shift function.

[0015] On one hand, this disclosure provides a control system for drift driving of an electric vehicle, comprising: a driving information detector for detecting vehicle driving information in an electric vehicle with virtual gear shifting function; an interface for use by a driver to activate a drift mode and select a virtual gear; and a control unit for: based on the vehicle driving information detected by the driving information detector, controlling at least one of wheel slip control differentiation, upshift limitation differentiation, and downshift limitation differentiation according to whether the driver selects to activate the drift mode through the interface, wherein the wheel slip control differentiation is configured to differentiate the performance of torque intervention control for suppressing rear wheel slippage, the upshift limitation differentiation is configured to differentiate the performance of upshifting, and the wheel slip control differentiation is configured to differentiate the performance of downshifting.

[0016] In one embodiment, wheel slip control differentiation is performed such that if a drift mode is selected to be activated during the execution of the virtual shift function, then, compared to a non-drift mode that performs torque intervention control for wheel slip suppression, torque intervention control for wheel slip suppression is not performed under the same vehicle driving conditions, or the conditions for starting torque intervention control for wheel slip suppression are set differently, wherein the non-drift mode is a mode in which the drift mode is not activated.

[0017] In another embodiment, the control unit may determine the driver's accelerator pedal input for drift driving of the electric vehicle based on a signal from the accelerator pedal sensor of the driving information detector while the drift mode is active, and then perform torque intervention control for wheel slip suppression when the rear wheel speed detected by the rear wheel speed sensor of the driving information detector is greater than or equal to the torque intervention activation threshold based on wheel speed corresponding to the virtual gear selected by the driver, and when the drift mode is activated, the torque intervention activation threshold based on wheel speed may be set in the control unit to a value greater than the torque intervention activation threshold based on wheel speed in non-drift mode.

[0018] In another embodiment, in the control unit, for each virtual gear of the virtual shift function, the torque intervention start threshold based on wheel speed can be set to a different value; and the higher the virtual gear, the larger the torque intervention start threshold based on wheel speed can be set to.

[0019] In yet another embodiment, in the control unit, the torque intervention activation threshold based on wheel speed can be set to be inversely proportional to the virtual gear ratio value of each virtual gear of the virtual shift function.

[0020] In yet another embodiment, during torque intervention control for rear wheel slip suppression, the control unit may perform target speed tracking control, which is configured to control the rear wheel speed to track a target speed based on wheel speed corresponding to a virtual gear selected by the driver.

[0021] In another embodiment, in the control unit, for each virtual gear of the virtual shift function, the target speed based on wheel speed can be set to a different value, and the higher the virtual gear, the larger the target speed based on wheel speed is set to.

[0022] In another embodiment, if torque intervention control for rear wheel slip suppression is not performed, the control unit may cease applying torque to the rear wheels or apply regenerative braking torque to the rear wheels to prevent the divergence of rear wheel slip when the rear wheel speed detected by the rear wheel speed sensor of the driving information detector approaches, reaches, or exceeds the wheel speed-based speed limit corresponding to the virtual gear selected by the driver within the set range.

[0023] In yet another embodiment, in the control unit, for each virtual gear of the virtual shift function, the speed limit based on wheel speed can be set to a different value, and the higher the virtual gear, the larger the speed limit based on wheel speed can be set to.

[0024] In yet another embodiment, when the drift mode is active, the control unit can determine the driver accelerator pedal input for drift driving of the electric vehicle from the signal from the accelerator pedal sensor of the driving information detector, and execute torque intervention control for wheel slip suppression when the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector is greater than or equal to a set torque intervention activation threshold based on the virtual engine speed, and when the drift mode is activated, the torque intervention activation threshold based on the virtual engine speed can be set in the control unit to a value greater than the torque intervention activation threshold based on the virtual engine speed in the non-drift mode.

[0025] In yet another embodiment, if torque intervention control for rear wheel slip suppression is not performed, then when the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector approaches, reaches, or exceeds the speed limit based on the virtual engine speed within the set range, the control unit may stop applying torque to the rear wheels or apply regenerative braking torque to the rear wheels to prevent the divergence of rear wheel slip.

[0026] In yet another embodiment, the control for distinguishing upshift limits can be configured such that if drift mode activation is selected, the forced upshift function is disabled, thereby preventing upshifts from being performed. This forced upshift function is configured to automatically perform upshifts using the virtual shift function based on the vehicle's driving state.

[0027] In yet another embodiment, when the forced upshift function is disabled, the control unit can determine the driver's accelerator pedal input for drift driving of the electric vehicle from the signal from the accelerator pedal sensor of the driving information detector, and when it is determined that the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector reaches a predetermined virtual fuel cut-off start threshold, the torque of the rear wheel motor that tracks the torque demanded by the driver is reduced according to the torque curve configured to realize the virtual fuel cut-off function.

[0028] In yet another embodiment, the control unit may control the torque of the rear wheel motor to track the target torque after upshifting, after reducing the torque of the rear wheel motor according to a torque curve configured to achieve virtual fuel cut-off.

[0029] In yet another embodiment, the torque of the rear wheel motor, which is reduced according to the torque curve, can be obtained by multiplying the scaling factor value of the real-time virtual engine speed, which corresponds to the virtual fuel cut-off threshold and the speed limit based on the virtual engine speed, by the driver's required torque. The scaling factor value, which is set according to the real-time virtual engine speed and is between the virtual fuel cut-off threshold and the speed limit based on the virtual engine speed, is set to a smaller value as the virtual engine speed increases.

[0030] In yet another embodiment, with the forced upshift function disabled, the control unit can determine the driver's accelerator pedal input for drift driving of the electric vehicle from the signal from the accelerator pedal sensor of the driving information detector, and then determine the torque value calculated by the speed tracking controller as the torque of the rear wheel motor, the speed tracking controller being configured to cause the virtual engine speed to track a predetermined speed limit based on the virtual engine speed, wherein the virtual engine speed is obtained from the drive system speed detected by the speed sensor of the driving information detector.

[0031] In another embodiment, the control for distinguishing downshift limits can be configured such that, when the drift mode is selected and active, if there is a driver's manual downshift request via driver virtual gear selection, the downshift limit configured not to perform virtual gear shifting is released so that downshifting can be performed.

[0032] In yet another embodiment, if there is a driver's manual downshift request when the downshift restriction is released, the control unit can reduce the motor torque, increase the motor torque to the driver's required torque after downshifting, and then control the motor torque to track the driver's required torque after downshifting.

[0033] In yet another embodiment, when the downshift restriction is released, if there is a driver's manual downshift request, the control unit can reduce the motor torque until the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector reaches the virtual engine speed to be increased when performing a manual downshift, and then maintain the motor torque constant, and when the virtual engine speed decreases and reaches a predetermined required torque tracking recovery threshold while maintaining the motor torque constant, the motor torque is increased to the driver's required torque after downshifting.

[0034] In yet another embodiment, during the reduction of motor torque, the control unit can reduce the motor torque to a regenerative braking torque, which is set to a distinguishing value for each virtual gear of the virtual shift function, and then maintain the motor torque at the regenerative braking torque.

[0035] Other aspects and embodiments of this disclosure are discussed below. Attached Figure Description

[0036] The above and other features of this disclosure will now be described in detail with reference to certain exemplary embodiments shown in the accompanying drawings, which are given illustratively only and therefore do not limit this disclosure, and wherein:

[0037] Figure 1 A block diagram illustrating the configuration of a system for performing a drift driving control process according to the present disclosure;

[0038] Figure 2A , 2B Views 2C and 2C are views illustrating a wheel slip control differentiation method in one embodiment of this disclosure;

[0039] Figure 3A and 3B A view showing the control state in a conventional non-drift mode for comparison with this disclosure;

[0040] Figure 3C and 3D A view illustrating a shift limit differentiation method in one embodiment of this disclosure;

[0041] Figure 4A A view showing the control state in a conventional non-drift mode for comparison with this disclosure; and

[0042] Figure 4B A view illustrating a downshift limitation differentiation method in one embodiment of this disclosure.

[0043] It should be understood that the accompanying drawings are not drawn to scale and are presented in a slightly simplified manner to illustrate various preferred features used to illustrate the basic principles of this disclosure. Specific design features of this disclosure, such as specific dimensions, orientations, positions, and shapes, will depend in part on the specific intended application and environment of use. Many figures in the accompanying drawings refer to the same or equivalent portions of this disclosure. Detailed Implementation

[0044] Various embodiments of this disclosure will be described in detail below, examples of which are illustrated in the accompanying drawings and described hereinafter. The specific structural or functional descriptions of the embodiments of this disclosure given in the specification will exemplarily describe embodiments of this disclosure, and this disclosure may be embodied in various alternative forms. Furthermore, it should be understood that this disclosure should not be construed as limited to the embodiments described herein; the embodiments of this disclosure are only used to fully disclose this disclosure and cover modifications, equivalents, or alternatives within the scope and technical range of this disclosure.

[0045] In the following description of the embodiments, terms such as “first” and “second” are used only to describe various elements, and these elements should not be construed as being limited by these terms. These terms are used only to distinguish one element from other elements. For example, without departing from the scope of this disclosure, a first element described below may be referred to as a second element, and similarly, a second element described below may be referred to as a first element.

[0046] When a component or layer is described as being "connected to" or "coupled to" another component or layer, it may be directly connected or coupled to the other component or layer, or there may be intermediate components or layers. Conversely, when a component or layer is described as being "directly connected to" or "directly coupled to" another component or layer, there may be no intermediate components or layers. Other terms used to describe relationships between components should be interpreted similarly, such as "between" versus "directly between," "adjacent to," etc.

[0047] Where possible, the same reference numerals will be used throughout the accompanying drawings to refer to the same or similar parts. The terminology used herein is for describing particular embodiments only and is not intended to be limiting. As used herein, the singular form may also be intended to include the plural form unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, components, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0048] This disclosure addresses the shortcomings of existing electric vehicle drift modes and relates to a control system for drift driving in electric vehicles. This system allows the driver to control rear wheel slip to a desired level during drift mode execution in electric vehicles without a multi-speed transmission using a Virtual Shift (VGS) function. This disclosure relates to a control system for drift driving suitable for electric vehicles equipped with a virtual shift system and capable of performing the virtual shift function. Automakers are developing virtual shift functionality, providing a virtual shift effect, as a new unique selling point (USP) to enhance the driving pleasure of transmissionless electric vehicles.

[0049] Virtual gear shifting (VGS) for electric vehicles is a known technology. VGS in electric vehicles can be described as a technology that, instead of setting the motor's torque range to its maximum value, determines the virtual gear based on the vehicle's real-time driving status and adjusts the motor torque range accordingly. Simultaneously, it applies a corresponding gear ratio to each virtual gear to calculate, realize, and express the virtual engine speed (VRPM) and its range.

[0050] In short, the virtual engine speed (virtual RPM) used in this disclosure can be described as a virtual engine speed determined based on the current operating state of the vehicle, assuming the presence of an engine (internal combustion engine) in an electric vehicle without an engine. Specifically, the virtual engine speed is one of the virtual variable information used to generate and realize the virtual shifting experience, and can be obtained from the actual vehicle drive system speed detected by the speed sensor of the driving information detector, which will be described below. The virtual engine speed can also be a virtual speed determined by the controller based on the real-time drive system speed (i.e., actual drive variable information). In electric vehicles, in order to obtain the virtual engine speed from the drive system speed, which is an actual driving variable, another piece of virtual variable information—virtual gear information—can be used. In this document, the virtual gear information can be the virtual gear ratio value corresponding to the current virtual gear.

[0051] Just as engine speed is the transmission input speed in an internal combustion engine vehicle equipped with an engine and transmission, when assuming the existence of a virtual engine and virtual transmission in an electric vehicle, the virtual engine speed becomes the virtual transmission input speed.

[0052] In this paper, the virtual engine speed and the virtual transmission input speed can be determined as values ​​related to the actual motor speed (the rotational speed of the motor). That is, the virtual engine speed can be calculated as a variable multiple of the drive system speed detected by the speed sensor of the driving information detector, and in this paper, the drive system speed can be the motor speed.

[0053] In this way, the virtual engine speed can be calculated as a variable multiple of the motor speed, obtained by multiplying the motor speed by a variable coefficient. In this paper, the value of multiplying the variable coefficient by the motor speed to calculate the virtual engine speed can be a value determined based on the current virtual gear.

[0054] Specifically, the variable coefficient can be a virtual gear ratio value determined for each virtual gear. Therefore, the virtual engine speed can be determined from the real-time drive system speed detected by the speed sensor of the driving information detector and the virtual gear ratio value corresponding to the current virtual gear.

[0055] More specifically, the virtual engine speed can be determined as a value obtained by multiplying the real-time motor speed detected by the speed sensor of the driving information detector by the gear ratio value corresponding to the current virtual gear.

[0056] In this disclosure, virtual engine speed is a variable that has been used as information to indicate the driving state of an electric vehicle, and therefore a detailed description of virtual engine speed will be omitted herein.

[0057] In this disclosure, when the drift mode is activated, the characteristics of the torque and virtual engine speed (virtual RPM) of each virtual gear applied to the virtual shift function are used to control the driving force of the vehicle in order to use the applied, thereby tracking the amount of rear wheel slippage desired by the driver.

[0058] The principle of this disclosure is based on the fact that variations in the available motor torque range and the virtual engine speed range associated with the virtual gear in the virtual shift function can improve the ease of torque control for the driver during drifting.

[0059] Without enabling the virtual shift function, if the driver depresses the accelerator pedal to 100% during drift driving, then 100% of the available motor torque corresponding to the range of available motor torque that can be generated at the current motor speed is produced. Due to the characteristics of drift mode, rear wheel slippage is allowed, so wheel slippage may still occur at the maximum motor speed.

[0060] Because this characteristic leads to very rapid tire wear and increases the likelihood of rapid changes in yaw rate and oversteer, drivers need very precise accelerator pedal control to maintain proper drifting. Therefore, the excessive sensitivity associated with drift mode can reduce driving enjoyment.

[0061] If the virtual shift function is used properly, the range of available motor torque will be limited according to each virtual gear, and the virtual engine speed (virtual RPM) will also be limited according to each virtual gear, thereby mitigating excessive sensitivity and helping to produce the appropriate rear wheel slippage, oversteer, and yaw rate required by the driver.

[0062] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Figure 1 To illustrate the configuration of a system for performing a drift driving control process according to this disclosure, a detailed description of the system will be provided below. This disclosure is applicable to electric vehicles in which the drive unit configured to drive the vehicle is an electric motor 31, and specifically, to vehicles in which the front and rear wheels are driven by independent drive units, i.e., vehicles equipped with a front-wheel drive unit that applies torque to the front wheels and a rear-wheel drive unit that applies torque to the rear wheels.

[0063] In this article, the front-wheel drive device and the rear-wheel drive device can be a front-wheel motor and a rear-wheel motor. Figure 1 The motor 31 can be a front wheel motor or a rear wheel motor, and Figure 1 The drive wheel 33 can be the front wheel or the rear wheel connected to each motor, so that power from the motor can be transmitted to the corresponding wheel.

[0064] As shown in the figure, the motor 31, which serves as the drive device, is connected to the drive wheel 33 via a reducer and a differential 32 to transmit power to the drive wheel 33. For example, the front wheel motor is connected to the front wheel via a front wheel reducer and a differential to transmit power to the front wheel, and the rear wheel motor is connected to the rear wheel via a rear wheel reducer and a differential to transmit power to the rear wheel.

[0065] In this disclosure, the vehicle's drive system includes a front-wheel drive system and a rear-wheel drive system, and both the front-wheel drive system and the rear-wheel drive system include drive elements such as an electric motor for driving the vehicle, drive wheels, a drive shaft between the electric motor and the drive wheels, a reducer and a differential, and axles.

[0066] In other words, a front-wheel drive system includes a front wheel motor, front wheels, a drive shaft (not shown) between the front wheel motor and the front wheels, a reducer and a differential, and an axle (not shown), while a rear-wheel drive system includes a rear wheel motor, rear wheels, a drive shaft (not shown) between the rear wheel motor and the rear wheels, a reducer and a differential, and an axle (not shown).

[0067] In front-wheel drive and rear-wheel drive systems, the torque output from each of the front and rear wheel motors can be transmitted to the corresponding drive wheels (i.e., the front or rear wheels) through drive system components such as drive shafts, reducers and differentials, and axles.

[0068] Furthermore, despite Figure 1 Not shown, but the battery is connected to the motor via an inverter to enable charging and discharging. The inverter may include a front-wheel inverter configured to drive and control the front-wheel motor, and a rear-wheel inverter configured to drive and control the rear-wheel motor.

[0069] In electric vehicles, the operation of motor 31 (driving and regenerative braking) is controlled according to torque commands generated by control unit 20. Control unit 20 determines the driver's required torque based on information indicating the vehicle's driving state (i.e., vehicle driving information) acquired by driving information detector 10, and determines the front wheel torque and rear wheel torque, which are the torques allocated from the driver's required torque.

[0070] Subsequently, the control unit 20 uses the determined front wheel torque and rear wheel torque as command values ​​to generate and output front wheel torque commands and rear wheel torque commands as torque commands for each motor, i.e., motor torque commands used to generate front wheel torque and rear wheel torque respectively. Furthermore, based on the front wheel torque commands and rear wheel torque commands, the control unit 20 controls the operation of each motor via the inverter.

[0071] Unless the motor is divided into front and rear wheels, the torque and torque command can be the total torque and total torque command of the motor (the motor is the drive unit used to drive the vehicle). The total torque command can be the command allocated before the front axle torque and rear axle torque, specifically, it can be the motor torque command allocated before the front wheel torque command and rear wheel torque command. The front wheel torque command is the torque command for the front wheel motor, and the rear wheel torque command is the torque command for the rear wheel motor. The control unit 20 may include a first controller 21, which determines the required torque for driving the vehicle based on vehicle driving information detected by the driving information detector 10, or receives the required torque from another control unit (such as an advanced driver assistance system (ADAS) control unit), and generates and outputs a torque command based on the required torque; and a second controller 22, which controls the operation of the motor according to the torque command output from the first controller 21.

[0072] The first controller 21 may be a vehicle control unit (VCU) for determining and generating torque commands required for driving a vehicle in a normal driving mode. The methods and processes for determining the torque commands required for driving the vehicle based on vehicle driving information, and for determining torque commands for controlling the torque of the drive system including the electric motor in normal driving mode, are well-known in the art, and therefore their detailed description is omitted here.

[0073] When the first controller 21 outputs a torque command, the second controller 22 receives the torque command and controls the operation of the motor 31 via the inverter. Thus, the torque output by the motor 31 is applied to the drive wheels 33 via the reducer and differential 32.

[0074] The second controller 22 may be a general-purpose motor control unit (MCU) that controls the operation of a motor via an inverter based on torque commands output from the vehicle control unit in the electric vehicle. This motor is the drive unit that drives the electric vehicle. Vehicle driving information, such as driver input values ​​input to the control unit 20, information indicating the vehicle's driving status, and may include sensor detection information detected by the driving information detector 10 and input to the control unit 20 via the vehicle network.

[0075] In this disclosure, the driving information detector 10 may include an accelerator position sensor (APS; not shown) for detecting the driver's accelerator pedal input value (APS value, %), a speed sensor (not shown) for detecting the rotational speed of the drive system, and a sensor (not shown) for detecting the vehicle speed.

[0076] The rotational speed of the drive system can be either the rotational speed of the motor 31 or the rotational speed of the drive wheel 33. The speed sensor for detecting the drive system rotational speed can be a sensor that detects the rotational speed of the motor 31, and can also be a general-purpose rotary transformer that detects the rotor position of the motor 31. Alternatively, the speed sensor for detecting the drive system rotational speed can be a general-purpose wheel speed sensor that detects the rotational speed (wheel speed) of the drive wheel 33.

[0077] In addition, the sensor for detecting vehicle speed can also be a wheel speed sensor. Obtaining vehicle speed information from signals from wheel speed sensors is a well-known technical problem in the art, and therefore its detailed description will be omitted.

[0078] As the vehicle driving information required by the control unit 20 to determine and generate the torque demanded by the driver, the driver accelerator pedal input value (APS value, %), the rotational speed of the motor 31, the rotational speed of the drive wheel 33 and the vehicle speed detected by the driving information detector 10 may be selectively used.

[0079] In addition, vehicle driving information may include information determined by the generalized control unit 20 itself, and may also include information (e.g., torque demand information) input to control unit 20 from another control unit in the vehicle (e.g., ADAS control unit) via the vehicle network.

[0080] The control system for drift driving according to one embodiment of the present disclosure may further include an interface 11. The interface 11 may include a mode selection device, which is an input device for the driver to select one of the drift mode being on or off, and any unit through which the driver performs operations and inputs within the vehicle may be used as a mode selection device without limitation.

[0081] For example, the mode selection device of interface 11 may include operating devices, such as buttons or switches provided in the vehicle, or input devices or touch screens of audio, video and navigation (AVN) systems.

[0082] In addition, interface 11 may also include a shift control device, which the driver operates to select a virtual gear as another input device. The driver can manually select and input the desired virtual gear by operating the shift control device.

[0083] Interface 11 can be connected to control unit 20, and may include a display device in addition to the input devices described above. In this document, interface 11 may be a device with integrated functions and forms of input and display devices, such as a touchscreen.

[0084] Although the control entity is divided into a first controller 21 and a second controller 22 in the above description, the torque control process according to this disclosure can be performed by a single integrated control element rather than multiple controllers.

[0085] The aforementioned multiple controllers and one integrated control element can be collectively referred to as the control unit, and the torque control process described below can be executed by the control unit.

[0086] In the following description, the first controller 21 and the second controller 22 will be collectively referred to as control unit 20. Furthermore, the control entity that performs the control process according to this disclosure, as described below, is control unit 20.

[0087] The configuration of a system for performing a drift drive control process according to this disclosure has been described above, and the drift drive control process performed by the above system will be described below. In the following description, the state in which the drift mode is not operated and not executed, i.e., the normal driving state in which the drift mode is not activated to prevent the vehicle from entering the drift mode, is defined as the non-drift state.

[0088] The drift mode is not activated during normal driving to prevent the vehicle from entering drift mode. The existing driving mode, not the drift mode, is defined as the non-drift mode. When the driver turns on the drift mode through the mode selection device on interface 11, the drift mode is activated, and when the driver turns off the drift mode through interface 11, the drift mode is deactivated, and the vehicle can be driven in a non-drift state.

[0089] In order to properly utilize the virtual shift function when drift mode is activated, a special torque control strategy must be implemented for drift mode when the current virtual engine speed (virtual RPM) is close to the limit range of the speed (RPM) range accompanying the virtual shift function.

[0090] Therefore, the control unit 20 in this disclosure can be configured to perform control over at least one predetermined distinction among wheel slip control distinction, upshift limit distinction, and downshift limit distinction, as will be described below.

[0091] 1) Wheel slip control differentiation: Depending on whether the driver selects to activate drift mode, torque intervention control for wheel slip suppression is differentiated based on vehicle driving information (i.e., information indicating the vehicle's driving state detected by the driving information detector 10). Before drift mode is activated, torque intervention control for wheel slip suppression is performed in the virtual shift function. However, in drift mode, in order to induce slippage, torque intervention control for wheel slip suppression may not be performed even under the same vehicle driving conditions as in non-drift mode, or the activation conditions for torque intervention control for wheel slip suppression (based on wheel speed or virtual engine speed conditions described below) may be set differently from those in non-drift mode.

[0092] 2) Upshift Limit Differentiation: Upshifting is determined based on whether the driver selects to activate drift mode. If drift mode is activated, the forced upshift function (automatically upshifting based on vehicle driving status via virtual gear shifting) is disabled. Because the driver must select a gear that allows for easy adjustment of slippage, upshifting may not be performed even if the virtual engine speed is close to the limit unless a separate driver upshift request is entered.

[0093] 3) Downshift Limit Differentiation: Whether to downshift depends on whether the driver selects to activate drift mode, based on information collected from the vehicle (including vehicle driving information). Because the driver must select a gear that allows for easy adjustment of slippage through his / her own decision, a downshift can be performed even if the virtual engine speed is close to the limit range if a downshift request is entered by the driver.

[0094] In the control of the above downshift restriction distinction, in addition to the vehicle driving information detected by the driving information detector 10, the information collected from the vehicle may also include information about the virtual gear selected by the driver through the shift control device of the interface 11.

[0095] Each of the above control methods will be described in detail in the following description. First, Figure 2A , 2B Views 2C and 2D are views illustrating wheel slip control differentiation in one embodiment of this disclosure. The torque diagrams in each view represent motor torque values ​​(which may be command values). Referring to these figures, a control method for wheel slip control differentiation in this disclosure will be described, and the control entity in the control process described below is control unit 20.

[0096] When the drift mode is activated, if the drive system speed detected by the speed sensor of the driving information detector 10 (specifically, the wheel speed detected by the wheel speed sensor) is greater than or equal to the torque intervention activation threshold (which is the speed value) based on the wheel speed corresponding to the virtual gear (the gear after shifting) selected by the driver, then the control unit 20 performs torque intervention control to control wheel slippage.

[0097] On the other hand, if the wheel speed detected by the wheel speed sensor is less than the torque intervention activation threshold based on wheel speed corresponding to the virtual gear selected by the driver, then the control unit 20 does not execute torque intervention control for wheel slippage control. At this time, the control unit 20 executes vehicle drive force control and motor torque control that track the torque demanded by the driver (see...). Figure 2A (APS value and torque graphs).

[0098] If the drift mode is activated, then during the execution of the virtual shift function, in order to prevent torque intervention control for wheel slip suppression from being executed under the same vehicle driving conditions as the non-drift mode when the drift mode is not activated, or to reduce the degree or frequency of torque intervention under the same vehicle driving conditions, the torque intervention activation threshold based on wheel speed (which is the speed value) when the drift mode is activated can be set to a value greater than the torque intervention activation threshold based on wheel speed in the non-drift mode.

[0099] This also applies to the torque intervention activation threshold based on virtual engine speed, which will be described below. That is, the torque intervention activation threshold based on virtual engine speed (which is a speed value) when drift mode is activated can be set to a value greater than the torque intervention activation threshold based on virtual engine speed in non-drift mode.

[0100] In the following description of this disclosure, if the front wheel and the rear wheel are not specifically distinguished, then wheel slippage refers to rear wheel slippage, wheel speed refers to rear wheel speed, and wheel speed sensor refers to rear wheel speed sensor that detects rear wheel speed.

[0101] Furthermore, in this disclosure, the driver's accelerator pedal input for drift driving of the vehicle can be determined based on accelerator pedal input value (APS value) information obtained from the signal from the accelerator pedal sensor of the driving information detector 10.

[0102] In the existing non-drift mode without drift mode, wheel slip control is set to sensitively generate torque intervention for wheel slip control once a small amount of slip is detected, in order to track the optimized amount of tire slip for maximum acceleration.

[0103] However, considerable rear wheel slippage must be allowed in drift mode. This can be achieved by taking measures to prevent the operation and intervention of rear wheel slippage control, thereby limiting the occurrence of rear wheel slippage in drift mode.

[0104] In this disclosure, wheel slip control for limiting slippage is torque intervention control for rear wheel slip suppression and limitation, which can be control of the torque applied to the rear wheels of the vehicle, and this can mean control of the rear wheel motor.

[0105] In this disclosure, if wheel slip control is not intervened as described above, the speed limit (i.e., as the allowable RPM limit value) can be calculated by pre-determining a virtual gear ratio for each virtual gear, and the divergence of rear wheel slip can be prevented by ceasing to apply torque or applying regenerative braking torque to the rear wheels if the corresponding speed is close to, reaches, or exceeds the speed limit within the set range.

[0106] In this article, the speed limit can be a wheel speed-based speed limit corresponding to the current virtual gear (gear after shifting) selected by the driver, as described below. If the rear wheel speed detected by the rear wheel speed sensor of the driving information detector 10 is close to, reaches, or exceeds the wheel speed-based speed limit within the set range, the control unit 20 may no longer generate rear wheel torque or may generate regenerative braking torque to prevent the divergence of rear wheel slip.

[0107] Alternatively, the speed limit may be a speed limit based on the virtual engine speed, as will be described below, and if the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector 10 approaches, reaches, or exceeds the speed limit based on the wheel speed within the set range, then the control unit 20 may no longer generate rear wheel torque or may generate regenerative braking torque to prevent the divergence of rear wheel slip.

[0108] Ultimately, using only the above method, the driver can set and achieve the desired maximum motor speed limit when performing drift mode by selecting the desired virtual gear to perform a virtual gear shift. In this article, the action of selecting the desired virtual gear can be performed by the driver manually selecting and inputting the desired virtual gear through the shift control device.

[0109] In this disclosure, as a method to prevent the execution of wheel slip control and intervention in drift mode, wheel slip control differentiation can be achieved by setting the control intervention time for limiting wheel slip occurrence in drift mode (i.e., torque control for limiting rear wheel slip) later than in non-drift mode.

[0110] Specifically, regarding wheel speed, the torque intervention initiation threshold based on wheel speed (which is the starting condition for torque intervention control of rear wheel slippage) can be set to a larger value. That is, the torque intervention initiation threshold based on wheel speed (i.e., the wheel speed reference value at which torque intervention to initiate wheel slippage control) is set to a value greater than the torque intervention initiation threshold based on wheel speed used in normal wheel slippage control that can be performed in non-drift mode.

[0111] At this point, the torque intervention start threshold based on wheel speed can be set as a differentiated value for each virtual gear, thereby ensuring that the allowable slippage can be easily adjusted according to the driver's own virtual gear selection.

[0112] More specifically, the higher the virtual gear, the larger the torque intervention start threshold based on wheel speed (which is the starting condition for wheel slip control) can be set to. Alternatively, a method can be applied to set the torque intervention start threshold based on wheel speed to a value that is inversely proportional to the virtual gear ratio value of each virtual gear.

[0113] In the same manner as the torque intervention start threshold based on wheel speed, the tracking target speed based on wheel speed and the speed limit based on wheel speed, as described below, can be set as distinct values ​​for each virtual gear.

[0114] In other words, the torque intervention start threshold based on wheel speed, the target tracking speed based on wheel speed, and the speed limit based on wheel speed can all be values ​​that depend on the virtual gear (see...). Figure 2B and 2C ).

[0115] At this point, when the virtual gear is high, the torque intervention start threshold based on wheel speed can be set to a larger value (i.e., the value in a higher gear is greater than the value in a lower gear), and in the same way, the higher the virtual gear, the larger the tracking target speed based on wheel speed and the speed limit based on wheel speed can be set to (i.e., the value in a higher gear is greater than the value in a lower gear) (see...). Figure 2B and 2C ).

[0116] In this disclosure, the torque intervention start threshold and the wheel speed limit are the same speed values ​​as the wheel speed tracking target speed, and in all virtual gears, the wheel speed limit is set to a value greater than the wheel speed tracking target speed, and the wheel speed tracking target speed is set to a value greater than the wheel speed torque intervention start threshold (see [link to disclosure]). Figure 2A , 2B (and 2C).

[0117] Therefore, the torque intervention start threshold based on wheel speed can be differentiated for each virtual gear, but the torque intervention start threshold based on virtual engine speed (i.e., the start condition for torque intervention control based on wheel slippage in relation to virtual engine speed) can be set to the same value for all virtual gears.

[0118] Specifically, in addition to the torque intervention start threshold based on virtual engine speed, the tracking target speed based on virtual engine speed and the speed limit based on virtual engine speed can be set to the same value for all virtual gears.

[0119] In other words, regardless of whether the virtual gear is high or low, the torque intervention start threshold based on virtual engine speed can be set to the same value (i.e., it is set to the same value regardless of whether the virtual gear is high or low), and in the same way, regardless of whether the virtual gear is high or low, the tracking target speed based on virtual engine speed can be set to the same value. Furthermore, regardless of whether the virtual gear is high or low, the speed limit based on virtual engine speed can be set to the same value (see [link to relevant documentation]). Figure 2B and 2C ).

[0120] In this disclosure, the torque intervention start threshold based on virtual engine speed and the speed limit based on virtual engine speed are speed values ​​in the same manner as the tracking target speed based on virtual engine speed. The speed limit based on virtual engine speed is set to a value greater than the tracking target speed based on virtual engine speed, and the tracking target speed based on virtual engine speed is set to a value greater than the torque intervention start threshold based on virtual engine speed (see [link]). Figure 2A , 2B (and 2C).

[0121] Furthermore, the torque intervention start threshold based on virtual engine speed can be set to a value obtained by multiplying the speed limit based on virtual engine speed by a ratio value set to be greater than 0% but less than or equal to 100%.

[0122] Furthermore, there is a key difference in the objectives of slip control intervention compared to non-drift mode. In non-drift mode, the objective is to suppress slippage, but in drift mode, the objective of torque intervention is to maintain slippage.

[0123] However, when the engine speed is less than (below) the slip allowance threshold, torque must be generated based on the driver input, and torque to maintain the target speed at or above the slip allowance threshold will only be generated when torque intervention begins.

[0124] In this disclosure, the tracking target speed above the slippage tolerance threshold can be set to a value obtained by multiplying a speed limit based on the virtual engine speed by a ratio value set to be greater than 0% but less than or equal to 100%.

[0125] In other words, the slip tolerance threshold (or the target speed for tracking that is higher than the slip tolerance threshold) serves as both the tracking target for speed control and the target value for maintaining the amount of slip. Therefore, torque feedback control that tracks the slip tolerance threshold in advance can be executed starting from the time point when the speed approaches the slip tolerance threshold within the set range.

[0126] However, the target speed can be set to a value greater than the torque intervention start threshold based on the virtual engine speed, or the target speed can be set to the value obtained by adding a predetermined additional speed (RPM) to the calculated torque intervention start threshold based on the virtual engine speed.

[0127] Figure 2A This illustrates a state where the rear wheel speed is below the torque intervention activation threshold based on wheel speed. If the rear wheel speed is below the torque intervention activation threshold based on wheel speed, torque intervention control for wheel slippage control is not executed; instead, control that tracks the driver's required torque based on the driver's accelerator pedal input value (APS value) is executed.

[0128] refer to Figure 2B and 2C As can be seen, when the drift mode is active, during the execution of the virtual shift function, after the driver depresses the accelerator pedal (APS value input) to drive the vehicle, torque intervention control for wheel slip control will be executed. If the rear wheel speed is greater than or equal to the torque intervention activation threshold based on the wheel speed, then the control unit 20 executes target speed tracking control to control the rear wheel speed, thereby tracking the target speed of the virtual gear selected by the driver after the shift.

[0129] Therefore, wheel speed and virtual engine speed track their respective target speeds, with reference to... Figure 2B and 2C It can be seen that the wheel speed is controlled to converge to the tracking target speed based on the wheel speed, and the virtual engine speed is controlled to converge to the tracking target speed based on the virtual engine speed.

[0130] Figure 2B This shows the virtual gear position as low, and Figure 2C Showing with Figure 2B Compared to the case where the virtual gear is at a higher gear, and referring to these diagrams, it can be seen that, according to the virtual gear function, the torque range in lower gears is wider than the torque range in higher gears (see...). Figure 2BAccording to the virtual gear function, the torque range in higher gears is smaller than the torque range in lower gears (see...). Figure 2C ).

[0131] Next, Figure 3A and 3B To illustrate a view of the control state in a conventional non-drift mode for comparison with this disclosure, and Figure 3C and 3D This is a view illustrating the upshift limit differentiation in one embodiment of the present disclosure. The torque graph in each view represents the motor torque value (which may be a command value).

[0132] Because in drift mode, the driving force is applied to the rear wheels using only the rear wheel motor, therefore in this disclosure, as Figure 3C and 3D As shown, the torque in drift mode is the torque applied to the rear wheels through the rear wheel motor, i.e., the rear wheel motor torque.

[0133] In other words, Figure 3C and 3D The torque graph in the diagram is for drift mode and is therefore a graph indicating the torque applied to the rear wheels, i.e., a graph indicating the torque value of the rear wheel motor. On the other hand, in this disclosure, the torque in non-drift mode is the sum of the front wheel torque (front wheel motor torque) and the rear wheel torque (rear wheel motor torque).

[0134] Referring to this, the control method for distinguishing upshift limits in this disclosure will be described, and the control subject of the control process described below is the control unit 20.

[0135] Figure 3A This demonstrates an example of unrestricted forced upshifts performed in non-drift mode, and Figure 3B An example is shown where forced upshifting is restricted in non-drift mode, specifically, forced upshifting is not performed and the gear is fixed (i.e., the gear ratio is fixed).

[0136] Figure 3C and Figure 3D An example is shown where forced upshifts are restricted in drift mode according to this disclosure, and more specifically, Figure 3C An example using gradually decreasing torque control is shown, and Figure 3D An example is shown where a speed tracking controller is used to make the virtual engine speed track the speed limit.

[0137] To explain in detail, in non-drift mode, to prevent the virtual engine speed from exceeding the speed limit based on the virtual engine speed after (APS value), such as... Figure 3AAs shown, when the driver presses the accelerator pedal, the virtual engine speed increases and reaches the upshift threshold (i.e., the speed value), and then the virtual upshift is automatically executed to reduce the virtual engine speed.

[0138] Furthermore, even if forced upshifting is not activated, the motor torque will decrease to prevent the virtual engine speed from exceeding the speed limit based on the virtual engine speed, until the virtual engine speed drops to a certain value or lower. Then, when the virtual engine speed drops to a certain value or lower, torque control is performed to track the target torque again after upshifting.

[0139] In torque control, the control unit 20 generates and outputs a torque command for controlling the motor torque, and this torque command can be... Figure 3A The torque value indicated by the torque graph is used as the command value.

[0140] exist Figure 3B , 3C In the 3D example, a virtual fuel cut-off function is performed to prevent the virtual engine speed from exceeding a speed limit based on the virtual engine speed (or exceeding a certain level or more), and therefore, the torque value after the virtual fuel cut-off function intervention becomes the command value for torque control.

[0141] Figure 3B This describes the situation where the gear is fixed and no gear shifting occurs in non-drift mode. As shown in the figure, with the required torque tracking recovery threshold (which is the engine speed value) set, after the driver depresses the accelerator pedal, torque control is executed to track the driver's required torque determined based on the accelerator pedal input value (APS value) (execute driver required torque tracking control).

[0142] When performing driver-demand torque tracking control, if the virtual engine speed reaches a speed limit based on the virtual engine speed, a virtual fuel cut-off function is executed, and the torque is reduced to the value simulating the fuel cut-off state (see [link]). Figure 3B ("Torque after virtual fuel cut-off intervention" in the text).

[0143] Subsequently, when the virtual engine speed decreases to the demand torque tracking recovery threshold and then becomes below the demand torque tracking recovery threshold, control for tracking the demand torque is restored to increase the torque to the driver's demand torque determined based on the accelerator pedal input value (APS value).

[0144] Even if forced upshifts are disabled in non-drift mode in this way, driver demand torque tracking control and virtual fuel cut-off control will still repeat as the virtual engine speed increases and decreases between the speed limit based on the virtual engine speed and the demand torque tracking recovery threshold.

[0145] This process is accompanied by torque fluctuations, which are suitable for expressing and simulating the emotions of an internal combustion engine. However, because the torque fluctuations that occur during drifting are not based on the driver's intention, they can have a significant and adverse impact on rear wheel slippage control, making the above control method unsuitable.

[0146] Therefore, in the virtual shift function when the drift mode is activated according to this disclosure, the forced upshift function is disabled, which restricts upshifting, and the torque control method that prevents the virtual engine speed from exceeding the speed limit based on the virtual engine speed differs from the torque control in the existing non-drift mode.

[0147] To enable the driver to naturally cope with the speed limit in drift mode, a threshold that expands the speed limit range and gradually reduces torque can be implemented until the virtual engine speed exceeds the virtual fuel cut-off start threshold and reaches the speed limit based on the virtual engine speed.

[0148] In this disclosure, the meaning of the threshold for expanding the speed limit range can be, for example, using... Figure 3B The speed limit is set in the existing non-drift mode, and an additional speed limit is set and used when the motor torque begins to decrease.

[0149] In this article, the separate speed limit at which the motor torque begins to decrease can be considered another RPM limit (i.e., the virtual fuel cut-off activation threshold), which is set separately from the speed limit based on the virtual engine speed to activate the virtual fuel cut-off function.

[0150] Therefore, in Figure 3B In non-drift mode, when the virtual engine speed reaches the upshift threshold (which is a limit), a virtual fuel cut-off function is executed to reduce the torque required to track the driver's torque needs. Figure 3C In drift mode, when the virtual engine speed reaches the virtual fuel cut-off activation threshold (which is an additionally set separate limit), a virtual fuel cut-off function is executed to reduce the torque required by the driver.

[0151] To explain in more detail, such as Figure 3C As shown, in drift mode, when the driver depresses the accelerator pedal (APS value input), torque control based on the driver's required torque is executed. When the virtual engine speed increases and reaches the set virtual fuel cut-off activation threshold, virtual fuel cut-off control is activated to gradually reduce the torque of the rear wheel motors until the virtual engine speed reaches the speed limit based on the virtual engine speed (see...). Figure 3C (The torque after virtual fuel cut-off function intervention). In this disclosure, the torque can be gradually reduced according to the torque curve to achieve the virtual fuel cut-off function.

[0152] In this article, torque control refers to the vehicle's drive force control, specifically the torque control of the rear wheel motor. Furthermore, torque control is the control by which the control unit 20 generates and outputs torque commands, which are torque commands for the rear wheel motor, and utilize the torque generated by… Figure 3C The torque value indicated by the torque graph is used as the command value. Figure 3D (The example is the same).

[0153] Alternatively, the speed limit based on the virtual engine speed is set to be the same as... Figure 3C The values ​​in the example are the same, but the virtual fuel cut-off threshold for starting control, which gradually reduces torque, can be set to greater than [value missing]. Figure 3B The values ​​in the example. That is, the speed limit range for implementing gradual torque reduction control is set to be greater than... Figure 3B The area is a smaller area.

[0154] In this case, a proportional factor value of 1 to 0 or a setting value less than 1 can be set in the control unit 20 based on the virtual engine speed, which ranges from the virtual fuel cut-off start threshold to the speed limit based on the virtual engine speed. (A negative value can be set in the case of regenerative braking.)

[0155] In addition, the control unit 20 can determine the torque value of the torque curve for realizing the virtual fuel cut-off function by multiplying the proportional factor value corresponding to the real-time virtual engine speed by the value obtained by the driver's required torque based on the accelerator pedal input value (APS value). That is, the torque command value of the rear wheel motor.

[0156] Regarding the proportional factor in this disclosure, the control unit 20 may set the proportional factor value of the virtual fuel cut-off start threshold to 1, and set the proportional factor value of the speed limit based on the virtual engine speed to 0 or a value less than 1, or set it to a negative value in the case of regenerative braking.

[0157] In addition, the scaling factor between the virtual fuel cut-off start threshold and the speed limit based on virtual engine speed is set to vary between 1 and 0 or a set value.

[0158] At this point, the scaling factor value of the virtual engine speed corresponding to the virtual fuel cut-off start threshold and the speed limit based on the virtual engine speed can be set to be variable, so that the scaling factor gradually decreases as the virtual engine speed increases.

[0159] In another method, such as Figure 3D As shown, the control unit 20 can be configured to determine a torque value calculated by the speed tracking controller as a torque command (torque command for the rear wheel motor), which enables the virtual engine speed to track an adjustment limit based on the virtual engine speed.

[0160] Next, Figure 4A To illustrate a view of the control state in a conventional non-drift mode for comparison with this disclosure, and Figure 4B A view illustrating the downshift limitation distinction in one embodiment of this disclosure.

[0161] The torque graph in each view represents the motor torque value (which can be a command value). Figure 4B The torque diagram is the torque diagram in drift mode, and therefore it is a torque diagram representing the torque of the rear wheels, that is, a torque diagram representing the torque value of the rear wheel motor.

[0162] Referring to this, the control method for downshift limit differentiation in this disclosure will be described, and the control subject of the control process described below is the control unit 20.

[0163] Figure 4A This illustrates an example of applying downshift limitation in non-drift mode, specifically, an example of not performing downshifts and limiting downshifts in non-drift mode. Figure 4B This shows an example of releasing downshift limit in drift mode.

[0164] In the existing non-drift mode, manual downshifting via driver input is performed by determining whether the virtual engine speed that will increase when downshifting is within the speed limit range, and using this as one of the conditions for performing the downshift.

[0165] In other words, if the virtual engine speed required to increase during a manual downshift exceeds a speed limit based on the virtual engine speed, the manual downshift will not be performed. The virtual engine speed required to increase during a manual downshift can be determined using the current virtual engine speed and the virtual gear ratio of the virtual gear after the downshift.

[0166] refer to Figure 4A If a downshift request exists after the driver releases the accelerator pedal input in non-drift mode (i.e., if there is a manual shift operation for downshifting as the driver's downshift input), then downshifting is restricted, and therefore the torque range does not change due to the shift.

[0167] Figure 4A The bottom diagram illustrates that if the virtual engine speed exceeds the speed limit based on the virtual engine speed after downshifting, and if the virtual engine speed is expected to exceed the speed limit based on the virtual engine speed when downshifting is performed, the downshift limit is executed in a manner that does not reflect the driver's downshift request.

[0168] However, in drift mode, if the driver feels that the currently available motor torque range is insufficient to meet the needs or determines that the current allowable slippage is too large, and therefore wants to downshift, then the driver's intention needs to be reflected.

[0169] In internal combustion engine vehicles equipped with a transmission, such downshifting by the driver is prohibited. This is because downshifting causes the engine speed (RPM) to exceed the speed limit, which can cause permanent and fatal damage to the engine.

[0170] However, in this disclosure, virtual shifting is implemented virtually in an electric vehicle that does not have an actual multi-speed transmission, rather than in reality. Therefore, without worrying about the aforementioned problems, the characteristics of the virtual shifting function can be used to perform downshifts that reflect the driver's intentions, thereby increasing the ease of drift driving.

[0171] In other words, such as Figure 4B As shown, even if the virtual engine speed is expected to exceed the speed limit based on the virtual engine speed when downshifting is performed, downshifting will be performed first by reflecting the driver's downshift request, and virtual overrun occurrence will be allowed.

[0172] However, if the virtual engine speed becomes greater than the speed limit based on the virtual engine speed due to downshifting, such as Figure 4B As shown, the vehicle can decelerate sufficiently to reduce the virtual engine speed to a speed limit based on the virtual engine speed or lower, and then generate torque that tracks the driver's torque demand. In other words, torque reduction measures are implemented until the virtual engine speed drops to the speed limit range or lower, thereby achieving normalization.

[0173] In this disclosure, the virtual engine speed decreasing to or below the speed limit range means, in order to... Figure 3B In the same way as the example, when the demand torque tracking recovery threshold (which is a speed value) is set, the virtual engine speed is reduced to the set demand torque tracking recovery threshold or lower.

[0174] Furthermore, the torque reduction measure involves the control unit 20 reducing the torque value of the torque command (command value), and if there is a driver downshift request, the control unit 20 reduces the torque until the virtual engine speed reaches the virtual engine speed that would be increased when performing a manual downshift. At this point, the torque is reduced to the regenerative braking torque.

[0175] Subsequently, the control unit 20 maintains the regenerative braking torque (which is a reduced torque) constant, thereby reducing the virtual engine speed, and then, when the virtual engine speed reaches the required torque tracking recovery threshold, controls the torque to track the driver's required torque after downshifting.

[0176] Therefore, if the virtual engine speed decreases to the required torque tracking recovery threshold and then becomes lower than the required torque tracking recovery threshold, then the control used to track the required torque is restored to increase the torque to the driver's required torque based on the accelerator pedal input value (APS value) after downshifting.

[0177] Furthermore, if the virtual engine speed becomes greater than the speed limit based on the virtual engine speed due to downshifting, a predetermined torque can be generated to cause sufficient vehicle deceleration.

[0178] At this point, a regenerative braking torque command, set to a distinguishing value for each virtual gear, can be generated and output to perform the motor's regenerative operation. It is well known that regenerative braking torque can be defined as torque in the negative (-) direction or torque with a negative (-) value, and is the torque in both the vehicle deceleration direction and the motor regenerative braking direction.

[0179] In this disclosure, the regenerative braking torque command for each virtual gear can be determined to be the same torque value as the regenerative braking torque command for each virtual gear calculated when performing the virtual shift function in the existing non-drift mode, or it can be determined to be a torque value that is larger than a predetermined value or a predetermined ratio.

[0180] The braking torque command is applied only when the virtual engine speed becomes greater than the speed limit based on the virtual engine speed due to downshifting, and when the vehicle decelerates sufficiently and the virtual engine speed becomes lower than or equal to the required torque tracking recovery threshold, the motor torque command is generated and output again to track the driver's required torque, and the operation of the motor is controlled according to the generator-motor torque command.

[0181] The vehicle drift driving control system according to an embodiment of the present invention has been described in detail above. According to the present disclosure described above, the ease of controlling oversteer in each virtual gear reflecting the driver's intention in drift mode can be improved, and the sensitivity to excessive torque range (a disadvantage in drift mode) inherent in electric vehicles can be mitigated.

[0182] Furthermore, according to the above disclosure, the marketability of electric vehicles capable of performing drift modes can be improved and the USP can be enhanced by reflecting the driver's intention to shift gears autonomously.

[0183] As is evident from the above description, the control system for drift driving of electric vehicles according to this disclosure can, during the execution of drift mode in electric vehicles without a multi-speed transmission, use a virtual shift function to control the amount of rear wheel slippage to the level desired by the driver.

[0184] Although the present disclosure has been described in detail with reference to its exemplary embodiments, the scope of the present disclosure is not limited to the above embodiments, and it should be understood that various modifications and improvements made by those skilled in the art using the basic concepts of the present disclosure as defined in the claims are also included within the scope of the present disclosure.

Claims

1. A control system for drift driving of an electric vehicle, comprising: The driving information detector is configured to detect vehicle driving information in electric vehicles with virtual gear shifting capabilities; The interface is configured for use by the driver to activate drift mode and select virtual gears; as well as The control unit is configured to: based on the vehicle driving information detected by the driving information detector and based on whether the driver activates the drift mode through the interface, control at least one of wheel slip control differentiation, upshift limitation differentiation, and downshift limitation differentiation, wherein the wheel slip control differentiation is configured to differentiate the performance of torque intervention control for rear wheel slip suppression, the upshift limitation differentiation is configured to differentiate the performance of upshifting, and the wheel slip control differentiation is configured to differentiate the performance of downshifting.

2. The system of claim 1, wherein the wheel slip control differentiation is performed such that when a drift mode is selected to be activated during the execution of the virtual shift function, compared with a non-drift mode in which torque intervention control for wheel slip suppression is performed, the torque intervention control for wheel slip suppression is not performed under the same vehicle driving conditions in the mode where the drift mode is not activated, or the conditions for starting torque intervention control for wheel slip suppression are set differently, wherein the non-drift mode is a mode in which the drift mode is not activated.

3. The system according to claim 2, wherein: In the active state of the drift mode, the control unit is configured to: determine the driver accelerator pedal input for drift driving of the electric vehicle based on the signal from the accelerator pedal sensor of the driving information detector, and execute torque intervention control for wheel slip suppression when the rear wheel speed detected by the rear wheel speed sensor of the driving information detector is greater than or equal to the torque intervention activation threshold based on wheel speed corresponding to the virtual gear selected by the driver. as well as When the drift mode is activated, the torque intervention activation threshold based on wheel speed is set in the control unit to a value greater than the torque intervention activation threshold based on wheel speed in the non-drift mode.

4. The system according to claim 3, wherein: In the control unit, for each virtual gear in the virtual shift function, the torque intervention activation threshold based on wheel speed is set to a different value; and The higher the virtual gear, the larger the torque intervention start threshold based on wheel speed is set to.

5. The system of claim 4, wherein in the control unit, the torque intervention activation threshold based on wheel speed is set to be inversely proportional to the virtual transmission ratio of each virtual gear of the virtual shift function.

6. The system of claim 3, wherein the control unit is configured to perform target speed tracking control during torque intervention control for rear wheel slip suppression, the target speed tracking control being configured to control the rear wheel speed to track a target speed based on wheel speed corresponding to the virtual gear selected by the driver.

7. The system according to claim 6, wherein: In the control unit, for each virtual gear of the virtual shift function, the target speed for tracking based on the wheel speed is set to a different value; as well as The higher the virtual gear, the higher the target speed for tracking, which is based on wheel speed.

8. The system according to claim 2, wherein, When the torque intervention control for suppressing rear wheel slip is not executed, when the rear wheel speed detected by the rear wheel speed sensor of the driving information detector approaches, reaches, or exceeds the speed limit based on wheel speed corresponding to the virtual gear selected by the driver within the set range, the control unit no longer applies torque to the rear wheels or applies regenerative braking torque to the rear wheels to prevent the divergence of rear wheel slip.

9. The system according to claim 8, wherein: In the control unit, for each virtual gear in the virtual shift function, the speed limit based on wheel speed is set to a different value; and The higher the virtual gear, the larger the speed limit based on wheel speed is set to.

10. The system according to claim 2, wherein: The control unit is configured to: determine the driver accelerator pedal input for drift driving of the electric vehicle based on the signal from the accelerator pedal sensor of the driving information detector when the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector is greater than or equal to a set torque intervention start threshold based on the virtual engine speed; and execute the torque intervention control for wheel slip suppression when the virtual engine speed is greater than or equal to a set torque intervention start threshold based on the virtual engine speed. as well as When the drift mode is activated, the torque intervention start threshold based on virtual engine speed is set in the control unit to a value greater than the torque intervention start threshold based on virtual engine speed in the non-drift mode.

11. The system according to claim 2, wherein, If the torque intervention control for suppressing rear wheel slip is not performed, then when the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector approaches, reaches, or exceeds the speed limit based on the virtual engine speed within the set range, the control unit will no longer apply torque to the rear wheels or apply regenerative braking torque to the rear wheels to prevent the divergence of rear wheel slip.

12. The system of claim 1, wherein the control for distinguishing upshift limits is configured to: when the drift mode is selected for activation, disable the forced upshift function so as not to perform the upshift, the forced upshift function being configured to automatically perform the upshift of the virtual shift function according to the vehicle driving state.

13. The system according to claim 12, wherein, In the state where the forced upshift function is disabled, the control unit is configured to: determine the driver's accelerator pedal input for drift driving of the electric vehicle based on the signal from the accelerator pedal sensor of the driving information detector, and when it is determined that the virtual engine speed obtained from the drive system speed detected by the speed sensor of the driving information detector reaches a predetermined virtual fuel cut-off start threshold, reduce the torque of the rear wheel motor that tracks the torque demanded by the driver based on the torque curve configured to implement the virtual fuel cut-off function.

14. The system of claim 13, wherein the control unit is configured to: after reducing the torque of the rear wheel motor according to a torque curve configured to achieve the virtual fuel cut-off function, control the torque of the rear wheel motor to track the target torque after upshifting.

15. The system according to claim 13, wherein: The torque of the rear wheel motor, reduced according to the torque curve, is obtained by multiplying the scaling factor value corresponding to the real-time virtual engine speed between the virtual fuel cut-off start threshold and the speed limit based on the virtual engine speed by the driver's required torque. as well as The scaling factor, set according to the real-time virtual engine speed, between the virtual fuel cut-off start threshold and the speed limit based on the virtual engine speed, is set to a smaller value as the virtual engine speed increases.

16. The system of claim 12, wherein, in the state where the forced upshift function is disabled, the control unit is configured to: determine the driver accelerator pedal input for drift driving of the electric vehicle based on a signal from the accelerator pedal sensor of the driving information detector, and determine the torque value calculated by the speed tracking controller as the torque of the rear wheel motor, the speed tracking controller being configured to: cause the virtual engine speed to track a predetermined speed limit based on the virtual engine speed, wherein, The virtual engine speed is obtained from the drive system speed detected by the speed sensor of the driving information detector.

17. The system according to claim 1, wherein, The control used for downshift restriction differentiation is configured such that, when the drift mode is selected as active, if there is a driver's manual downshift request via driver virtual gear selection, the downshift restriction that is configured not to perform virtual gear shifting is released so that downshifting can be performed.

18. The system of claim 17, wherein in the downshift limit released state, the control unit is configured to: When the driver requests a manual downshift, reduce the motor torque; After downshifting, the motor torque is increased to the driver's required torque; and Control the motor torque so that it can track the driver's torque demand after downshifting.

19. The system of claim 18, wherein in the downshift limit released state, the control unit is configured to: When a driver requests a manual downshift, the motor torque is reduced until the virtual engine speed, obtained from the drive system speed detected by the speed sensor of the driving information detector, reaches the virtual engine speed to be increased when the manual downshift is performed, and then the motor torque is maintained constant; and When the virtual engine speed decreases and reaches the predetermined torque tracking recovery threshold, and the motor torque remains unchanged, the motor torque is increased to the driver's required torque after downshifting.

20. The system of claim 19, wherein the control unit is configured to: During the reduction of motor torque, the motor torque is reduced to the regenerative braking torque, which is set to a distinguishing value for each virtual gear of the virtual shifting function; and Maintain the motor torque at the regenerative braking torque.

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