Methods for controlling the implementation of a vehicle's drift driving state

Abstract

Method for controlling the implementation of a drift driving state of a vehicle, wherein the method comprises: Reduce, by means of a control, the front wheel distribution torque of an all-wheel drive (AWD) system when the vehicle enters a curve in a state where a drift mode is selected and the system is engaged; and Enabling, through control, the vehicle to enter a drift driving state by adding slip control torque corresponding to the lateral acceleration of the vehicle to the front wheel distribution torque when rear wheel slip is generated; characterized by Maintaining, by controlling, the vehicle's drift driving state by releasing the entire front wheel distribution torque when a counter-steering state is confirmed by a driver.

Description

BACKGROUND OF THE INVENTION Technical field

[0001] The present invention relates in general to a method for controlling the implementation of a driving state of a vehicle and in particular to a method for controlling a vehicle with all-wheel drive (AWD) and limited slip differential (LSD) functions, which enables the vehicle to perform drift driving. Description of the related prior art

[0002] Drifting refers to a continuous driving condition in which a vehicle is put into an oversteering direction by slipping or sliding of the drive wheels using the vehicle's driving force, and a steering angle direction of the front wheels is operated in a direction opposite to the direction of rotation of the vehicle.

[0003] In sporty and high-performance vehicles such as sedans, coupes and sports cars, the possibility of drifting can be a very important marketing point to increase driving interest.

[0004] However, drifting is impossible if the vehicle has an all-wheel drive system (AWD system), even if the vehicle is a high-performance vehicle, due to a slip suppression function of the all-wheel drive system.

[0005] When consumers buy vehicles, they must therefore choose between a two-wheel drive (2WD) vehicle based on a front engine and rear drive (FR), which offers the pleasure of drifting but is unstable while driving, and an all-wheel drive (AWD) vehicle based on FR, which does not allow drifting but has excellent driving stability and traction performance.

[0006] The all-wheel drive (AWD) system now implements a torque distribution function between the front and rear wheels of a vehicle, but it cannot distribute torque between the left and right sides. On the other hand, the limited-slip differential (LSD) performs the distribution between the left and right drive wheels, allowing the vehicle to be easily maneuvered on rough roads. Furthermore, when the vehicle turns or corners, slippage of the inside wheels is suppressed, and understeer is mitigated by directing torque to the outside wheels, thus improving the vehicle's handling and preserving its ability to drift.

[0007] From US patent 9,296,424 B2, a method for controlling the implementation of a drift driving state of a vehicle with the features in the preamble of claim 1 is known. PRESENTATION OF THE INVENTION

[0008] The object of the present invention is to provide a method for controlling the implementation of a driving state of a vehicle that is essentially rear-wheel driven using a limited-slip differential (LSD) and equipped with an all-wheel drive (AWD) system that controls the contribution torque distributed to the front wheels according to the vehicle's driving situation. Accordingly, the vehicle offers excellent driving stability and traction performance in normal driving situations and also provides driving pleasure by enabling drifting according to the driver's preference, thus ultimately improving the vehicle's marketability. A method according to the invention is defined in claim 1. Further developments of the invention are described in the dependent claims.

[0009] Various aspects of the present invention provide a method for controlling the implementation of a drift driving state of a vehicle, wherein the method comprises: a slip induction step in which, in a state in which a drift mode is selected, when a vehicle enters or begins to enter a curve or cornering or circular driving state and is in an on state orWhen the system is engaged, a control unit reduces the front-wheel drive (AWD) system's distribution torque compared to cases other than drift mode; a slip torque control step, in which, if rear wheel slip is generated, the control unit allows the vehicle to enter a drift driving condition by adding slip control torque, corresponding to the vehicle's lateral acceleration, to the front-wheel drive distribution torque; and a drift maintenance step, in which, if a counter-steering condition is acknowledged by a driver, the control unit maintains a drift driving condition of the vehicle by releasing all of the front-wheel drive distribution torque.

[0010] The slip control torque can be determined such that it has a relatively smaller value as the lateral acceleration of the vehicle increases.

[0011] The slip control torque can be determined such that it has a relatively smaller value as the lateral acceleration of the vehicle increases, and when the lateral acceleration of the vehicle exceeds a predetermined reference lateral acceleration, the slip control torque can be released.

[0012] The slip control torque can be determined by multiplying a base slip control torque, which is determined by a slip of the rear wheels and a slip change rate, and a gain according to the lateral acceleration of the vehicle, and the gain can be set so that it has a smaller value as lateral acceleration increases.

[0013] The control procedure may further include a stabilization step in which, if the yaw angular acceleration of the vehicle exceeds a predetermined reference angular acceleration, a damping torque is applied to the front wheels to reduce the yaw angular acceleration of the vehicle.

[0014] According to an exemplary embodiment of the present invention, the vehicle is equipped with both a limited-slip differential (LSD) system and an all-wheel drive (AWD) system, and is therefore excellent in terms of driving stability and traction performance. Furthermore, the vehicle can enter a drift driving state according to the driver's preference, and a stable drift driving state can be maintained after entering the drift driving state, thus offering the driver a pleasant driving experience.

[0015] The methods and devices of the present invention have further features and advantages which will become apparent from the accompanying drawings and the following detailed description or which are set out in more detail therein, which serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a conceptual view of a vehicle equipped with both a limited-slip differential (LSD) system and an all-wheel drive (AWD) system, which can be applied to the present invention. Fig. Figure 2 is a flowchart that represents an exemplary embodiment of a method for controlling the implementation of a drift driving state of a vehicle according to an exemplary embodiment of the present invention. Fig. Figure 3 is a view that represents the implementation of a drift driving state of a vehicle according to an exemplary embodiment of the present invention.

[0016] It is understood that the accompanying drawings are not necessarily to scale and represent a somewhat simplified depiction of various features illustrating the basic principles of the invention. The specific design features of the present invention, as contained herein, including, for example, specific dimensions, orientations, positions, and shapes, are partly determined by the specific intended application and operating environment.

[0017] In the figures, the reference numbers in the multiple figures of the drawing refer to identical or equivalent parts of the present invention. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. Although the invention(s) are described in connection with exemplary embodiments of the present invention, it is understood that the present description is not intended to limit the invention(s) to these exemplary embodiments.

[0019] With reference to Fig. 1. The rear wheels of a vehicle are connected by a limited-slip differential (LSD). Accordingly, the LSD provides a differential function between the left and right wheels, and the drive torque between the left and right wheels is distributed according to the driving situation. Furthermore, an all-wheel drive (AWD) system comprises: a transfer case (TF) designed to direct a portion of the power supplied by the engine (E) to the rear wheels towards a transmission (TM) and to supply that portion to the front wheels; and a controller (CLR) for controlling the transfer case (TF).

[0020] When slippage occurs between a road surface and the rear wheels, which act as the main drive wheels, the control system (CLR), by receiving information such as the wheel speed of the front and rear wheels and the output torque of the transmission, suppresses the slippage by increasing the front wheel distribution torque supplied to the front wheels, thus improving the vehicle's driving stability and traction.

[0021] A method for controlling the implementation of a drift driving state of a vehicle according to an exemplary embodiment of the present invention is applied to the vehicle as described above, so that drifting of the vehicle is possible according to the driver's preference.

[0022] With reference to Fig. 2 and Fig. 3 The procedure includes: a slip induction step (S10) in which, in a state where a drift mode is selected, when a vehicle enters a turn and is in an engaged state, a control reduces the front wheel distribution torque of the all-wheel drive (AWD) system compared to cases other than drift mode; a slip torque control step (S20) in which, when rear wheel slip of the vehicle is generated, the control allows the vehicle to enter a drift driving state by adding slip control torque to the front wheel distribution torque in accordance with the vehicle's lateral acceleration; and a drift maintenance step (S30) in which, when a counter-steering state is acknowledged by a driver, the control maintains a drift driving state of the vehicle by releasing all of the front wheel distribution torque.

[0023] In other words, the control system (CLR) determines that a driver intends to actively drift when the vehicle enters a corner in a state where the driver has selected drift mode, thus reducing the front-wheel drive torque distributed to the front wheels by the all-wheel drive (AWD) system. Consequently, unlike a conventional vehicle with an AWD system, the vehicle enters a drifting state by inducing rear-wheel slip.

[0024] In this context, the control unit (CLR) can detect whether the driver selects drift mode via any separate switch in the vehicle, and can determine whether the vehicle is rotating, cornering, or driving in a circle and is in the switched-on state via a signal from a steering angle sensor and a signal from an accelerator pedal sensor.

[0025] Furthermore, in the slip induction step (S10), reducing the front wheel distribution torque compared to cases other than drift mode means reducing it compared to the front wheel distribution torque that is determined to be supplied to the front wheels to prevent wheel slip by the all-wheel drive (AWD) system when all other driving conditions, such as road surface, turning radius, and vehicle speed, are the same, and the situation is a normal cornering or driving situation in which drift mode is not selected. Consequently, this means that the front wheel distribution torque is reduced to a level that allows rear wheel slip.

[0026] In a state of reducing the front wheel distribution torque as described above, rear wheel slip is easily induced if the driver increases the amount of pressure applied to an accelerator pedal.

[0027] When the rear wheel slip is generated as described above, the control unit (CLR) performs the slip torque control step (S20), thus practically enabling entry into a drift state.

[0028] In other words, the slip control torque is determined such that it has a relatively smaller value as the vehicle's lateral acceleration increases, and is added to the reduced front distribution torque to be supplied to the front wheels. In an exemplary embodiment of the present invention, the slip control torque is set such that it is reduced as the vehicle's lateral acceleration increases.

[0029] In this context, on a road with high friction and relatively high lateral acceleration, the traction control torque is rarely applied, thus enabling drifting. On a snowy or icy road with low lateral acceleration, however, even when drift mode is selected, the traction control torque is additionally applied to the front wheels to ensure vehicle stability, effectively preventing the onset of a drift.

[0030] Finally, the slip torque control step, as described above, only allows drifting under road conditions where the vehicle can practically enter a drift state while remaining stable. If it is determined that vehicle stability is more important in light of road conditions, even if the drift mode is selected by driver error, the vehicle will be prevented from entering a drift state and its stability will be ensured.

[0031] Therefore, the slip control torque is determined such that it has a relatively smaller value as the vehicle's lateral acceleration increases and can be released when the vehicle's lateral acceleration exceeds a predetermined reference lateral acceleration. Accordingly, in the case of cornering or driving in a circle on a road with typically high friction, since the lateral acceleration of a vehicle is 0.6G or more, the reference lateral acceleration can, for example, be set to 0.6G.

[0032] As a reference, in Fig. 2. When rear wheel slip is initiated by the slip induction step (S10), the slip torque control step (S20) is executed. If the vehicle's lateral acceleration is less than the reference lateral acceleration, the slip control torque caused by the lateral acceleration is added to the front wheel distribution torque, which is determined by the slip induction step (S10), to control the transfer case (TF). Conversely, if the lateral acceleration exceeds the reference lateral acceleration, the vehicle enters drift mode by releasing the slip control torque.

[0033] Furthermore, the slip control torque determines the basic slip control torque according to the slip of the rear wheels and a slip change rate and can be determined by multiplying the gain according to the lateral acceleration of the vehicle.

[0034] In an exemplary embodiment of the present invention, the slip control torque is determined by multiplying the basic slip control torque, which is determined by a slip of the rear wheels and a slip change rate and gain corresponding to the lateral acceleration of the vehicle.

[0035] In this context, the gain can be adjusted to a smaller value as the lateral acceleration increases. In an exemplary embodiment of the present invention, the gain can be set such that it decreases as the lateral acceleration increases.

[0036] As described above, the vehicle initiates drifting through the slip torque control step (S20), and a counter-steering condition is checked in which the driver operates a steering wheel in the opposite direction of rotation. The control system (CLR) determines that a drift driving condition has begun, so that all of the front wheel distribution torque intended for the front wheels is released to continuously maintain the drift condition.

[0037] In the drift driving condition maintained as above, if a driver error occurs, such as excessive use of the accelerator pedal, the vehicle may skid without maintaining the drift condition.

[0038] According to an exemplary embodiment of the present invention, to safeguard against this case, if the yaw angle acceleration of the vehicle exceeds a predetermined reference angle acceleration, a stabilization step (S40) can be carried out in which a damping torque is applied to the front wheels to reduce the yaw angle acceleration of the vehicle.

[0039] In other words, while maintaining the drift state, the system detects any potential skidding of the vehicle due to driver error by a change in yaw rate acceleration, and then distributes the torque accordingly. This ultimately prevents the vehicle from skidding and maintains a stable drift state.

[0040] This allows the driver to maintain the vehicle's drift driving state more easily and safely.

[0041] With reference to Fig. Figure 3 illustrates how drifting is performed according to an exemplary embodiment of the present invention. State A represents a situation in which a vehicle begins to circle or turn, and state B represents a situation in which oversteer is generated due to slip at the rear wheel by acceleration during cornering. Thus, the current state is one in which rear wheel slip is generated by the slip induction step (S10), so that the slip torque control step (S20) is initiated and the vehicle enters a drift driving state.

[0042] State C is a state in which the driver begins to operate the steering wheel in a counter-steering state, and in state C the front wheels are fully in a counter-steering state. Thus, these states are situations in which a practical drift driving condition is implemented.

[0043] In states C and D, the drift maintenance step (S30) fully releases the front wheel torque distribution, causing the rear wheels to slip or slide continuously, thus maintaining the drift driving condition. Furthermore, the stabilization step (S40) prevents the vehicle from skidding due to driver error, thereby maintaining a stable drift driving condition.

[0044] State E represents a situation in which the drift control of the present invention is enabled because the driver steers in a normal direction in accordance with the direction of rotation of the vehicle.

[0045] For the sake of clarity and precise definition in the attached claims, the terms “top”, “bottom”, “inside”, “outside”, “upwards”, “downwards”, “upper”, “lower”, “upwards”, “downwards”, “front”, “backwards”, “inside”, “outside”, “inwards”, “outwards”, “internal”, “external”, “inner”, “outer”, “forwards” and “backwards” are used to describe features of the exemplary embodiments in relation to the positions of the features shown in the figures.

[0046] The foregoing descriptions of specific exemplary embodiments of the present invention have been provided for illustrative and descriptive purposes. They are not intended to be exhaustive or to limit the invention to the disclosed forms, and obviously, in light of the teachings above, many modifications and variations are possible. The exemplary embodiments have been selected and described to explain certain principles of the invention and their practical application, so that the person skilled in the art can produce and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof.

Claims

[1] Method for controlling the implementation of a drift driving state of a vehicle, wherein the method comprises: Reduce, by means of a control, the front wheel distribution torque of an all-wheel drive (AWD) system when the vehicle enters a curve in a state where a drift mode is selected and the system is engaged; and To enable the vehicle to enter a drift driving state by adding slip control torque to the front wheel distribution torque in accordance with the lateral acceleration of the vehicle when rear wheel slip is generated; characterized by Maintaining, by controlling, the vehicle's drift driving state by releasing the entire front wheel distribution torque when a counter-steering state is confirmed by a driver. [2] Method according to claim 1, wherein the slip control torque is determined such that it is reduced with increasing lateral acceleration of the vehicle. [3] Method according to any of the preceding claims, wherein the slip control torque is determined such that it is reduced as the lateral acceleration of the vehicle increases, and where, if the lateral acceleration of the vehicle exceeds a predetermined reference lateral acceleration, the slip control torque is released. [4] Method according to one of the preceding claims, wherein, if the lateral acceleration of the vehicle is less than a predetermined reference lateral acceleration, the slip control torque is added to the front wheel distribution torque. [5] Method according to any of the preceding claims, wherein the slip control torque is determined by multiplying a base slip control torque and a gain. [6] Method according to one of the preceding claims, wherein the basic slip control torque is determined by a slip of the rear wheels of the vehicle and a slip change rate. [7] Method according to one of the preceding claims, wherein the amplification is determined according to the lateral acceleration of the vehicle. [8] Method according to any of the preceding claims, wherein the reinforcement is set such that it is reduced with increasing lateral acceleration. [9] Method according to any of the preceding claims, further comprising: Applying a damping torque to the front wheels of the vehicle to reduce the vehicle's yaw rate acceleration when the vehicle's yaw rate acceleration exceeds a predetermined reference yaw rate acceleration.

Images