DRIFT ASSISTANCE SYSTEM FOR A VEHICLE

Abstract

A drift assist system, which helps a driver maintain a drift maneuver, contains one or more controllers, each containing one or more processors that execute instructions to compare the steering wheel's rotation angle to a minimum steering wheel angle input value during a minimum input duration, and to compare each of several drift criterion parameters to its corresponding input value. In response to the determination that the steering wheel's rotation angle is greater than the minimum steering wheel angle input value during the minimum input duration, and that each of the several drift criterion parameters matches its corresponding input value, the one or more controllers shift the executed steering wheel position closer to an ideal drift range associated with the steering wheel, thus successfully executing the drift maneuver.

Description

The present invention relates to a drift assist system for a vehicle that assists a driver in maintaining a drift maneuver according to the preamble of claim 1.A generic drift assistance system is known in the art essentially from DE 10 2013 218 828 A1.Further prior art is also evident from the publications DE 10 2018 105 598 A1, DE 10 2013 200 027 A1 and DE 10 2022 133 301 A1.Some automotive and engine sportists may want to perform a driving maneuver commonly referred to as drifting. A vehicle drifts around a curve on the road when a driver intentionally oversteers the vehicle with loss of traction, so that the slip angle corresponding to the rear wheels of the vehicle exceeds the slip angle corresponding to the front wheels of the vehicle and the front wheels are oriented in a direction away from the curve. However, it should be noted that a driver requires a relatively high level of skill to drive a vehicle into and maintain a drift maneuver therein. Specifically, the driver must sharply change the angle at which the steering wheel is oriented, adjust the torque of the powertrain to cause and maintain wheel slip, and maintain the control of the vehicle, all simultaneously to maintain drifting. Accordingly, a driver may need considerable exercise and skill to successfully execute a drift maneuver.Thus, while current vehicles fulfil their intended purpose, there is a need in the art for an approach to assist a driver in maintaining a drift maneuver.It would therefore be desirable to be able to utilize a drift assistance system which enables even an inexperienced driver to execute a drift maneuver reliably.This object is achieved with a drift assistance system which is distinguished by the features of claim 1.The vehicle includes a steering wheel, wherein the drift assist system includes one or more controllers, each including one or more processors executing instructions to receive a signal indicative of a rotational angle of the steering wheel and signals indicative of values corresponding to a plurality of drift criteria parameters. The one or more controllers compare the angle of rotation of the steering wheel to a minimum steering wheel angle input value during a minimum input period, the minimum steering wheel angle input value representing a minimum threshold angle of rotation of the steering wheel demonstrating that the driver of the vehicle intends to control lateral movement of the vehicle. The one or more controllers compare each of the plurality of drift criteria parameters to a corresponding input value and, in response to determining that the angle of rotation of the steering wheel is greater than the minimum steering wheel angle input value during the minimum input period and each of the plurality of drift criteria parameters corresponds to its corresponding input value, determine that the angle of rotation of the steering wheel is within a drift assist range associated with the steering wheel. In response to determining that the angle of rotation of the steering wheel is within the drift assist range associated with the steering wheel, the one or more controllers move an executed position of the steering wheel closer to an ideal drift range associated with the steering wheel, such that the drift maneuver is successfully executed.In another aspect, the executed position of the steering wheel determined by the drift assist system represents a commanded position of the steering wheel transmitted to a wired steering system that is part of the vehicle.In yet another aspect, the one or more controllers execute instructions to further monitor the signal indicative of the angle of rotation of the steering wheel after shifting the executed position of the steering wheel to be closer to the ideal drift range, and in response to determining that the angle of rotation of the steering wheel falls within the ideal drift range associated with the steering wheel, direct the wired steering system to increase a steering ratio of the vehicle from a nominal steering ratio.In one aspect, the one or more controllers execute instructions to further direct the wired steering system to increase the steering ratio of the vehicle from the nominal steering ratio until at least one of the following is satisfied: the angle of rotation of the steering wheel is outside of a steering wheel angle output range for a minimum output period and at least one of the plurality of drift criteria parameters corresponds to its corresponding output value.In another aspect, the plurality of drift criteria parameters includes an amount of braking force applied by the driver of the vehicle to a brake pedal of the vehicle, a vehicle slip angle, and a vehicle speed.In yet another aspect, the one or more controllers command a steering wheel actuator to apply tactile feedback to the steering wheel in response to determining that the angle of rotation of the steering wheel is within the drift assist range and the plurality of drift criteria parameters is matched.In one aspect, the ideal drift range associated with the steering wheel represents a range of the steering wheel rotational angles that allow the vehicle to maintain the drift maneuver.According to a further aspect, the drift assistance region assigned to the steering wheel represents a range of the rotational angles of the steering wheel in which the executed position of the steering wheel determined by the drift assistance system is shifted in the direction of the ideal drift region, such that the drift maneuver is carried out successfully.In yet another aspect, a steering response spline is stored in memory of the one or more controllers, the steering response spline representing a relationship between an actual position of the steering wheel and the executed position of the steering wheel.In one aspect, the steering reaction spline includes a linear region disposed along an x-axis and a nonlinear region in which the steering reaction spline includes a nonlinear profile.According to another aspect, the non-linear region of the steering reaction spline includes a drift assist width corresponding to the drift assist region associated with the steering wheel and an ideal drift width corresponding to the ideal drift region associated with the steering wheel.According to yet another aspect, the ideal drift region of the steering reaction spline contains a height measured along the y-axis, wherein the height of the ideal drift width indicates a measure of the assistance provided by the drift assistance system to the driver of the vehicle when executing the drift maneuver.In one aspect, the amount of assistance provided by the drift assist system to the driver of the vehicle during the maintenance of the drift maneuver increases as the height of the ideal drift width of the steering reaction spline increases.In another aspect, the amount of assistance that the drift assist system provides to the driver refers to a difference between the actual position of the steering wheel and the executed position of the steering wheel.In yet another aspect, the one or more controllers execute instructions to, in response to receiving a user input indicating that the amount of assistance provided by the drift assist system to the driver of the vehicle is to be decreased, increase the amount of ideal drift width of the steering response spline, and in response to receiving a user input indicating that the amount of assistance provided by the drift assist system to the driver of the vehicle is to be increased, decrease the amount of ideal drift width of the steering response spline.According to one aspect, a drift assist system is disclosed that assists a driver of a vehicle in maintaining a drift maneuver. The vehicle includes a steering wheel, and the drift assist system includes one or more controllers, each including one or more processors that execute instructions to receive a signal indicative of a rotational angle of the steering wheel and signals indicative of values corresponding to a plurality of drift criteria parameters. The one or more controllers compare the angle of rotation of the steering wheel to a minimum steering wheel angle input value during a minimum input period, the minimum steering wheel angle input value representing a minimum threshold angle of rotation of the steering wheel demonstrating that the driver of the vehicle intends to control lateral movement of the vehicle. The one or more controllers compare each of the plurality of drift criteria parameters to a corresponding input value. In response to determining that the angle of rotation of the steering wheel is greater than the minimum steering wheel angle input value during the minimum input period and that each of the plurality of drift criteria parameters corresponds to its corresponding input value, the one or more controllers determine that the angle of rotation of the steering wheel is within a drift assist range associated with the steering wheel. In response to determining that the angle of rotation of the steering wheel is within the drift assist range associated with the steering wheel, the one or more controllers move an executed position of the steering wheel closer to an ideal drift range associated with the steering wheel such that the drift maneuver is successfully performed, wherein the executed position of the steering wheel determined by the drift assist system represents a commanded position of the steering wheel transmitted to a wired steering system that is part of the vehicle. The one or more controllers further monitor the signal indicative of the angle of rotation of the steering wheel after shifting the executed position of the steering wheel to be closer to the ideal drift region. In response to determining that the angle of rotation of the steering wheel falls within the ideal drift range associated with the steering wheel, the one or more controllers instruct the wired steering system to increase a steering ratio of the vehicle from a nominal steering ratio.In another aspect, the controller or controllers execute instructions to further direct the wired steering system to increase the steering ratio of the vehicle from the nominal steering ratio until at least one of the following is satisfied: the angle of rotation of the steering wheel is outside of a steering wheel angle output range for a minimum output period and at least one of the plurality of drift criteria parameters corresponds to its corresponding output value.In yet another aspect, the plurality of drift criteria parameters includes an amount of braking force applied by the driver of the vehicle to a brake pedal of the vehicle, a vehicle slip angle, and a vehicle speed.In one aspect, the one or more controllers actuate a steering wheel actuator to apply tactile feedback to the steering wheel in response to determining that the angle of rotation of the steering wheel is within the drift assist range and is matched to the plurality of drift criteria parameters.According to one aspect, a drift assist system is disclosed that assists a driver of a vehicle in maintaining a drift maneuver. The vehicle includes a steering wheel, and the drift assist system includes one or more controllers, each including one or more processors executing instructions to receive a signal indicative of a rotational angle of the steering wheel and signals indicative of values corresponding to a plurality of drift criteria parameters, the plurality of drift criteria parameters including an amount of braking force applied by the driver of the vehicle to a brake pedal of the vehicle, a vehicle slip angle, and a vehicle speed. The one or more controllers compare the angle of rotation of the steering wheel to a minimum steering wheel angle input value during a minimum input period, the minimum steering wheel angle input value representing a minimum threshold angle of rotation of the steering wheel demonstrating that the driver of the vehicle intends to control lateral movement of the vehicle. The one or more controllers compare each of the plurality of drift criteria parameters to a corresponding input value. In response to determining that the angle of rotation of the steering wheel is greater than the minimum steering wheel angle input value during the minimum input period and that each of the plurality of drift criteria parameters corresponds to its corresponding input value, the one or more controllers determine that the angle of rotation of the steering wheel is within a drift assist range associated with the steering wheel. In response to determining that the angle of rotation of the steering wheel is within the drift assist range associated with the steering wheel, the one or more controllers move an executed position of the steering wheel closer to an ideal drift range associated with the steering wheel such that the drift maneuver is successfully performed, wherein the executed position of the steering wheel determined by the drift assist system represents a commanded position of the steering wheel transmitted to a wired steering system that is part of the vehicle. The one or more controllers continue to monitor the signal indicative of the angle of rotation of the steering wheel after shifting the executed position of the steering wheel to be closer to the ideal drift region. In response to determining that the angle of rotation of the steering wheel falls within the ideal drift range associated with the steering wheel, the one or more controllers direct the wired steering system to increase a steering ratio of the vehicle from a nominal steering ratio, and further direct the wired steering system to increase the steering ratio of the vehicle from the nominal steering ratio until at least one of the following is satisfied: the angle of rotation of the steering wheel is outside of a steering wheel angle output range for a minimum output time period, and at least one of the plurality of drift criteria parameters corresponds to its corresponding output value.Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are provided for purposes of illustration only.The drawings described herein are for illustrative purposes only; it shows: FIG. 1 is a schematic diagram of a vehicle including the disclosed drift assist system having one or more controllers in electronic communication with a steering wheel angle sensor for a steering wheel and a wired steering system, according to an example embodiment; FIG. 2 is a graph illustrating an ideal drift region and a drift assist region associated with the steering wheel shown in FIG. 1, according to an exemplary embodiment; FIG. 3 is an illustration of an exemplary steering reaction spline representing a relationship between an actual position of the steering wheel and the executed position of the steering wheel according to an exemplary embodiment; and FIG. 4 is an illustration of an example graph generated by the one or more controllers in FIG. 1 shown on a display of the drift assist system, according to an example embodiment.The following description is merely exemplary in nature and is not intended to limit the present invention, application, or uses.Referring now to FIG. 1, a vehicle 10 including the disclosed drift assist system 12 is illustrated. As will be explained below, the drift assist system 12 assists a driver of the vehicle 10 in maintaining a drift maneuver. It should be noted that the vehicle 10 may be any type of vehicle, such as, but not limited to, a sedan, truck, sport utility vehicle, custom motor vehicle that has been specifically modified to execute a drift maneuver, a cope, a roadster, three-wheeled vehicles, or an off-road vehicle. The drift assist system 12 includes one or more controllers 20 electronically connected to a steering wheel angle sensor 22, one or more vehicle dynamics controllers 24, a wired steering system 26, a brake system 28, a user input device 30, and a display 32.As seen in FIG. 1, the wired steering system 26 includes the steering wheel angle sensor 22, a steering wheel 40, a steering wheel actuator 42, a road wheel actuator 44, and one or more controllers 46 that are electronically in communication with the one or more controllers 20, the steering wheel angle sensor 22, the steering wheel actuator 42, and the road wheel actuator 44. The steering wheel 40 receives a driver input indicating an intended direction of the vehicle 10. The steering wheel angle sensor 22 generates an output indicating a rotation angle of the steering wheel 40 with respect to a reference or straight-ahead position of the steering wheel 40 of the vehicle 10. The steering wheel actuator 42 provides tactile feedback to the steering wheel 40 of the vehicle 10, and the road wheel actuator 44 converts the driver input into road wheel actuation by affecting the wheels 18 of the vehicle 10. The road wheel actuator 44 also transmits feedback from the wheels 18 of the vehicle 10 to the steering wheel actuator 42.A steering ratio of the vehicle 10 is stored in memory of the one or more controllers 46 of the wired steering system 26. The steering ratio refers to the ratio between the rotation of the steering wheel 40, which is measured in degrees, and the rotation of the wheels 18 of the vehicle 10, which is also measured in degrees. As will be explained below, the one or more controllers 20 may instruct the one or more controllers 46 of the wired steering system 26 to adjust the steering ratio of the vehicle 10 to assist a driver in maintaining a drift maneuver. Specifically, the one or more controllers 20 command the wired steering system 26 to increase the steering ratio of the vehicle 10 from a nominal steering ratio in response to determining that the angle of rotation of the steering wheel 40 falls within an ideal drift range 50 (shown in FIG. 2 ) and that multiple drift criteria parameters are met. The plurality of drift criteria parameters are described below and are summarized in Table 1. It should be noted that increasing the steering ratio of the vehicle 10 allows a driver of the vehicle 10 to have greater control over the slip angle of the vehicle 10, thereby assisting the driver in maintaining the drift maneuver.The one or more controllers 20 receive one or more vehicle dynamics variables from the one or more vehicle dynamics controllers 24. The brake system 28 includes a set of brakes corresponding to each wheel 18 of the vehicle 10. The brake system 28 generates a brake actuation signal that is transmitted to the one or more controllers 20, the brake actuation signal indicating an amount of braking force that the driver of the vehicle 10 applies to a brake pedal 48 of the vehicle 10. The amount of braking force is expressed as a percentage.The user input device 30 is any type of device for receiving user input generated by the driver of the vehicle 10, such as a touchscreen, keypad, or microphone. The display 32 displays graphics and images visible to the driver of the vehicle 10 and may be, for example, a liquid crystal display (LCD).FIG. 2 is a graph illustrating the ideal drift region 50 and a drift assist region 52 associated with the steering wheel 40 shown in FIG. 1. In FIGS. 1 and 2, the ideal drift region 50 represents a range of the rotational angles of the steering wheel 40 that allow the vehicle 10 to maintain the drift maneuver. When the angle of rotation of the steering wheel 40 falls within the ideal drift range 50 and is matched to the plurality of drift criteria parameters, the one or more controllers 20 command the wired steering system 26 to increase the steering ratio of the vehicle 10 from the nominal steering ratio. The range of the rotational angles of the steering wheel 40 that enable the vehicle 10 to maintain the drift maneuver is a calibrateable value based on the variables required to activate an electronic stability control (ESC) system. Specifically, the variables required to activate an ESC system include, but are not limited to, a road wheel angle, a vehicle speed, a wheel speed, a yaw rate, and an axle torque.It should be noted that for any given vehicle speed v, there is a range of total slip angles β 1- β 2 of the vehicle 10 that maintain the drift maneuver depending on the axle torque τ. It should be noted that the range of the total slip angles β 1- β 2 of the vehicle 10 may be estimated based on the linear range of vehicle operation. It should also be appreciated that the vehicle speed v, the axle torque τ, and the range of total slip angles β 1- β 2 of the vehicle 10 are dynamic values that change when the vehicle 10 maintains the drift maneuver, and therefore the range of the rotational angles of the steering wheel 40 included as part of the ideal drift range 50 also changes when the vehicle 10 maintains the drift maneuver. Furthermore, assuming a stable drift maneuver, the vehicle speed v is inversely proportional to the total slip angle of the vehicle 10, wherein lower vehicle speeds require higher total slip angles and higher vehicle speeds require lower total slip angles. Accordingly, the range of the rotational angles of the steering wheel 40 for the ideal slip range 50 is inversely proportional to the vehicle speed v.In FIGS. 1 and 2, the drift assist region 52 represents a range of the rotation angles of the steering wheel 40 in which an executed position of the steering wheel 40 determined by the drift assist system 12 is shifted toward the ideal drift region 50. As will be explained below and shown in FIG. 4, according to an embodiment, the range of the rotational angles of the steering wheel 40 of the drift assist region 52 is adjustable by a user of the vehicle 10. In FIGS. 1 and 2, when the angle of rotation of the steering wheel 40 is within the drift assist region 52 and is matched to the plurality of drift criteria parameters, the one or more controllers 20 shift the executed position of the steering wheel 40 determined by the drift assist system 12 to be closer to the ideal drift region 50 so that the drift maneuver is successfully performed. The executed position of the steering wheel 40 determined by the drift assist system 12 represents a commanded position of the steering wheel 40 transmitted to the wired steering system 26. A successful drift maneuver is a maintained oversteering of the vehicle after the drift input conditions have been fulfilled.In addition to shifting the executed position of the steering wheel 40, according to one embodiment, the one or more controllers 20 may also command the steering wheel actuator 42 to apply tactile feedback to the steering wheel 40 in response to determining that the angle of rotation of the steering wheel 40 is within the drift assist region 52 and is matched to the plurality of drift criteria parameters. Tactile feedback is applied to the steering wheel 40 to encourage or urge the driver to manipulate the steering wheel 40 from the drift assist region 52 toward the ideal drift region 50. For example only, according to one embodiment, the tactile feedback includes oscillations urging the driver of the vehicle 10 to turn the steering wheel 40 toward the ideal drift region 50.As seen in FIG. 2, the drift assist region 52 of the steering wheel 40 surrounds the ideal drift region 50 of the steering wheel 40. that is, the range of the rotational angles of the steering wheel 40 represented by the drift assist region 52 is larger than the range of the rotational angles of the steering wheel 40 represented by the ideal drift region 50. According to the example shown, the steering wheel actuator 42 applies tactile feedback to the steering wheel 40 to urge the driver, depending on the current angle of rotation of the steering wheel 40, to influence the steering wheel 40 either clockwise C or counter-clockwise CC toward the ideal drift region 50.In FIGS. 1 and 2, the one or more controllers 20 of the drift assist system 12 receive a signal from the steering wheel angle sensor 22 indicative of the angle of rotation of the steering wheel 40 and signals indicative of the values corresponding to the plurality of drift criteria parameters from the one or more vehicle dynamics controllers 24 and the brake system 28. Specifically, the plurality of drift parameters includes the amount of braking force the driver of the vehicle 10 applies to a brake pedal 48 of the vehicle 10 from the brake system 28, the vehicle slip angle of the vehicle 10 received from the one or more vehicle dynamics controllers 24, and the vehicle speed received from the one or more vehicle dynamics controllers 24. The one or more controllers 20 compare the angle of rotation of the steering wheel 40 (the steering wheel angle in Table 1) with a minimum steering wheel angle input value (SteeringWheelAngleEntryMin in Table 1) during a minimum input time period (EntryTimeMin in Table 1), where the minimum steering wheel angle input value represents a minimum threshold of the angle of rotation of the steering wheel 40 demonstrating that the driver of the vehicle intends to control the lateral movement of the vehicle 10. The minimum input time period is expressed in seconds and represents a minimum threshold time period in which the vehicle 10 is executing the drift maneuver before the steering ratio of the vehicle 10 is increased.The one or more controllers 20 also compare each of the plurality of drift criteria parameters to a corresponding input value as well. Specifically, the one or more controllers 20 compare the amount of braking force (BrakeAppl in Table 1) with a brake operation input value (BrakeApplEntMin in Table 1). When the amount of braking force exceeds the brake operation input value, the vehicle 10 cannot maintain the drift maneuver. The one or more controllers 20 compare the absolute value of the vehicle slip angle to a vehicle slip angle input value (VehicleSlipAngleEntryMin in Table 1), where the vehicle slip angle input value is part of a one-dimensional look-up table with corresponding values for the vehicle speed stored in memory of the one or more controllers 20. The vehicle slip angle input value is chosen to indicate that the driver of the vehicle 10 initiates the drift maneuver in either a right direction or a left direction. The one or more controllers 20 compare the vehicle speed to a minimum speed input value (VehicleSpeedEntryMin in Table 1), where the minimum speed input value is selected to be slow enough to support drift maneuvers with a relatively narrow radius (i.e., doughnuts) but greater than a minimum speed output value, which is explained below to avoid hysteresis.In response to determining that the angle of rotation of the steering wheel 40 is greater than the minimum steering wheel angle input value during the minimum input period and each of the plurality of drift criteria parameters corresponds to its corresponding input value, the one or more controllers 20 determine that the angle of rotation of the steering wheel 40 is within the drift assist region 52, shifting the executed position of the steering wheel 40 to be closer to the ideal drift region 50, such that the drift maneuver is successfully performed. Specifically, the plurality of drift criteria parameters correspond to their corresponding input values when the amount of braking force is less than the brake operation input value and an absolute value of the vehicle slip angle is greater than the vehicle slip angle input value and the vehicle speed is greater than the minimum speed input value. As mentioned above, according to an embodiment, in addition to shifting the executed position of the steering wheel 40, the one or more controllers 20 may also command the steering wheel actuator 42 to apply the tactile feedback to the steering wheel 40 in response to determining that the angle of rotation of the steering wheel 40 is within the drift assist region 52 and each of the plurality of drift criteria parameters corresponds to its corresponding input value.The one or more controllers 20 further monitor the signal from the steering wheel angle sensor 22 indicative of the angle of rotation of the steering wheel 40 after shifting the executed position of the steering wheel 40 to be closer to the ideal drift region 50. In response to determining that the angle of rotation of the steering wheel 40 falls within the ideal drift range 50 of the steering wheel 40, the one or more controllers 20 then command the wired steering system 26 to increase the steering ratio of the vehicle 10 from the nominal steering ratio.It should be noted that the drift assist system 12 further instructs the wired steering system 26 to increase the steering ratio of the vehicle 10 from the nominal steering ratio until the angle of rotation of the steering wheel 40 is outside the steering wheel angle output range during a minimum output period (SWAExitTimerMinin Table 1), or when at least one of the plurality of drift criteria parameters corresponds to its corresponding output value. Once the angle of rotation of the steering wheel 40 is outside of the steering wheel angle output range during the minimum output period, or when at least one of the plurality of drift criteria parameters corresponds to its corresponding output value, the one or more controllers 20 direct the wired steering system 26 to reset the steering ratio back to its nominal value. Specifically, during the minimum output period, the one or more controllers 20 compare the rotation angle of the steering wheel 40 with the steering wheel angle output range. The steering wheel angle output range indicates that the rotation angle of the steering wheel 40 is outside the drift assist range 52, and includes a minimum steering wheel output value and a maximum steering wheel output value.The minimum steering wheel output value is a difference between an absolute value of the lower limit of the drift assist range 52 (Abs (lower limit of the drift assist range in Table 1) and a minimum steering wheel output value (SWALowExit in Table 1). The minimum steering wheel output value is part of a one-dimensional look-up table having corresponding values for vehicle speed stored in memory of the one or more controllers 20. The minimum steering wheel output value is an indication that the driver of the vehicle 10 is no longer performing the drift maneuver. The steering wheel maximum output value is a difference between an absolute value of the lower limit of the drift assist region 52 and a steering wheel maximum output value (SWA-HighEx in Table 1). The maximum steering wheel output value is also part of a one-dimensional look-up table having corresponding values for vehicle speed stored in the memory of the one or more controllers 20. The maximum steering wheel output value is an indication that the driver of the vehicle 10 is no longer performing the drift maneuver. The minimum output time duration represents a time duration threshold in which the angle of rotation of the steering wheel 40 is outside the drift assist regions 52, and is calibrated such that the drift assist system 12 does not switch on and off increasing the steering angle ratio.The corresponding output values for the plurality of drift criteria parameters will now be described. A minimum speed output (VehicleSpeedExitMin in Table 1) corresponds to the vehicle speed and indicates the minimum speed at which the vehicle 10 maintains the drift maneuver. As mentioned above, the minimum output speed value is smaller than the minimum input speed value to avoid hysteresis. In response to determining that the vehicle speed is less than the minimum speed output value, the one or more controllers 20 determine that the vehicle speed corresponds to its corresponding output value. A vehicle slip angle output value (VehicleSlipAngleExitMin in Table 1) corresponds to the vehicle slip angle and is part of a one-dimensional look-up table that includes corresponding values for vehicle speed stored in the memory of the one or more controllers 20. The vehicle slip angle output value represents a minimum slip angle required for the vehicle 10 to maintain the drift maneuver. In response to determining that an absolute value of the vehicle slip angle is less than the starting slip angle value during a minimum slip angle output period (VehicleSlipAngleExitTimeMin in Table 1), the one or more controllers 20 determine that the vehicle slip angle corresponds to its corresponding starting value. A brake operation output value (BrakeApplExitMin in Table 1) corresponds to the amount of the braking force and indicates a value at which the vehicle 10 can no longer maintain the drift maneuver. In response to determining that the amount of braking force is greater than the brake actuation output value, the one or more controllers 20 determine that the amount of braking force corresponds to its corresponding output value. As mentioned above, the respective input values and the respective output values for the plurality of drift criteria parameters are summarized in Table 1 below. Table 1 Table 1Corresponding entry valuesBrake apply < BrApplMin &&[Abs(Fahrzeugschräglaufwinkel ) > VehicleSlipAngleEntryMin & & & Steering wheel angle > SteeringWheelAngleEntryMin] for timer > EntMin & & & Vehicle speed > VehicleSpeedEntryMinCorresponding output valuesVehicle speed < VehicleSpeedExitMin ||Abs(Fahrzeugschräglaufwinkel ) < VehicleSlipAngleExitMin for timer > VehicleSlipAngleExitTimerMin|| Steering wheel angle < (Abs (lower limit of the drift assist range) - SWALowExit) | | Steering wheel angle > (Abs (lower limit of the drift assist range) + SWAHighExit) for timer > SWAExitTimerMin | | Brake apply > BrakeApplExitMinFIG. 3 is an exemplary illustration of a steering response spline 60 stored in memory of the one or more controllers 20 (FIG. 1 ), wherein the steering response spline 60 represents a relationship between an actual position of the steering wheel 40 measured in degrees and the executed position of the steering wheel 40 also measured in degrees. Specifically, as seen in FIG. 3, the actual position of the steering wheel 40 is depicted along an x-axis 62, while the executed position of the steering wheel 40 is depicted along a y-axis 64. The steering reaction spline 60 includes a linear region 66 and a nonlinear region 68. the linear region 66 represents where the steering reaction spline 60 includes a linear profile, while the nonlinear region 68 represents where the steering reaction spline 60 includes a curved or nonlinear profile. The non-linear region 68 of the steering reaction spline 60 includes a drift assist width W corresponding to the drift assist region 52 (FIG. 2 ) associated with the steering wheel 40 and an ideal drift width w corresponding to the ideal drift region 50 (FIG. 2 ) associated with the steering wheel 40. As can be seen in FIG. 3, the drift width W corresponding to the drift assistance region 52 is greater than the ideal drift width w corresponding to the ideal drift region 50, wherein the ideal drift width w completely falls within the drift assistance width W.The ideal drift region of the steering reaction spline 60 also includes a height h measured along the y-axis 64, where the height h of the ideal drift width w of the steering reaction spline 60 is the product of the ideal drift width w and a compression ratio p or h=pwm. The height h of the ideal drift width w is an indicator of the extent of assistance provided by the drift assistance system 12 to the driver of the vehicle 10 when executing the drift maneuver. Specifically, the amount of assistance provided by the drift assist system 12 to the driver of the vehicle 10 during the maintenance of the drift maneuver decreases as the height h of the ideal drift width w of the steering reaction spline 60 increases, while the amount of assistance provided by the drift assist system 12 to the driver of the vehicle 10 during the maintenance of the drift maneuver increases as the height h of the ideal drift width w of the steering reaction spline 60 decreases or becomes flatter. The amount of assistance refers to the difference between the actual position of the steering wheel 40 and the executed position of the steering wheel 40. As an example, if the actual position of the steering wheel 40 is approximately equal to the executed position of the steering wheel 40 sent to the wired steering system 26, then almost no additional assistance is provided to the driver while attempting to execute the drift maneuver.Equations 1-8 summarize the relationship between the actual position of the steering wheel 40 and the executed position of the steering wheel 40 of the steering reaction spline 60, which are as follows, where y represents the executed position of the steering wheel 40 along the steering reaction spline 60, x represents the actual position of the steering wheel 40 along the steering reaction spline, and g represents a midpoint of the ideal drift width w.According to one embodiment, the amount of assistance that the drift assistance system 12 provides to the driver of the vehicle 10 during the maintenance of the drift maneuver is an adjustable value that is modified in response to receiving user input from the user input device 30 (FIG. 1 ) of the vehicle 10. FIG. 4 is an illustration of an example graphic 70 generated by the one or more controllers 20 and shown on the display 32 of the drift assist system 12. The graphic 70 includes a menu 72 including an off key 74, an auto key 76, and a manual key 78, wherein the auto key 76 has been selected. In FIGS. 1 and 4, the one or more controllers 20 turn off the drift assist system 12 in response to receiving user-generated user input from the user input device 30 indicating that the off key 74 is selected. In response to receiving a user input from the user input device 30 indicating that the automatic button 76 is selected, the one or more controllers 20 operate the drift assist system 12 in an automatic mode that does not require additional input from the user to initiate increasing the steering ratio provided to the wired steering system 26.In contrast to the automatic mode, the drift assist system 12 operates in the manual mode in response to receiving a user input from the user input device 30 indicating that the manual button 78 is selected, requiring additional user input before instructing the wired steering system 26 to increase the steering ratio of the vehicle 10 from the nominal steering ratio. The additional user input may be any type of user-initiated selection, such as a shift paddle train performed on the shift paddle mounted on the steering wheel 40.The graph 70 also includes a user-selectable controller 80 that allows the user to adjust the range of the rotational angles of the steering wheel 40 of the drift assist region 52 (FIG. 2 ). According to the example shown in FIG. 4, the user-selectable controller 80 is a slide 82, wherein moving the slide 82 rightward increases the range of the rotational angles, and moving the slide 82 leftward decreases the range of the rotational angles of the steering wheel 40.The graph 70 also includes a user-selectable controller 84 that allows the user to adjust the amount of assistance that the drift assistance system 12 provides to the driver of the vehicle 10 during the maintenance of the drift maneuver that increases, which may be referred to as the amount of assistance aggression. Specifically, in FIGS. 1-4, in response to the one or more controllers 20 receiving a user input from the user input device 30 indicating that the amount of assistance provided by the drift assistance system 12 to the driver of the vehicle 10 is to be decreased, the height h of the ideal drift width w increases. Similarly, in response to the one or more controllers 20 receiving a user input from the user input device 30 indicating that the amount of assistance provided by the drift assist system 12 to the driver of the vehicle 10 is to be increased, the height h of the ideal drift width w of the steering response spline 60 shown in FIG. 3 decreases. According to the example shown in FIG. 4, the user-selectable controller 84 is a slider 86, wherein moving the slider 86 to the right increases the amount of assistance provided by the drift assistance system 12 to the driver of the vehicle 10 and moving the slider 86 to the left decreases the amount of assistance provided by the drift assistance system 12 to the driver of the vehicle 10.With general reference to the figures, the disclosed drift assist system provides various technical effects and advantages. Specifically, the disclosed drift assist system provides an approach to assist a driver in maintaining a drift maneuver by increasing the steering ratio of the vehicle. It should be noted that the drift assist system is implemented without additional hardware and only requires changes to the software of the vehicle. According to one embodiment, the disclosed drift assist system also includes a manual mode of operation that requires additional user input before the steering ratio of the vehicle is increased from the nominal steering ratio. The drift assist system may also include selectable controls that enable the driver to set and modify the amount of assist that the drift assist system provides to the driver of the vehicle in maintaining the drift maneuver. The selectable controls may be used by the driver as a training tool to gradually reduce the amount of assistance provided by the drift assist system to the driver as the driver gets more skilled to maintain a drift maneuver over time.The controllers may refer to or be part of an electronic circuit, a combinational logic circuit, a field programmable gate array (FPGA), a processor (shared, dedicated, or group) that executes code, or a combination of some or all of the above, such as in a system on a chip. Additionally, the controllers may be microprocessor-based, such as a computer having at least one processor, a memory (RAM and / or ROM), and associated input and output buses. The processor may operate under the control of an operating system residing in memory. The operating system may manage the computer resources such that the computer program code embodied as one or more computer software applications, such as an application residing in memory, may include instructions executed by the processor. According to an alternative embodiment, the processor may execute the application directly; in this case, the operating system may be omitted.

Claims

A drift assist system (12) that assists a driver of a vehicle (10) in maintaining a drift maneuver, the vehicle (10) including a steering wheel (40), the drift assist system (12) comprising: one or more controllers (20) each including one or more processors executing instructions to: receive a signal indicative of a rotational angle of the steering wheel (40) and signals indicative of values corresponding to a plurality of drift criteria parameters; characterized in that the one or more controllers (20) further each include one or more processors executing instructions to: compare the angle of rotation of the steering wheel (40) with a minimum steering wheel angle input value during a minimum input time period, the minimum steering wheel angle input value representing a minimum threshold angle of rotation of the steering wheel (40) demonstrating that the driver of the vehicle (10) intends to control lateral movement of the vehicle (10); compare each of the plurality of drift criteria parameters with a corresponding input value; in response to determining that the angle of rotation of the steering wheel (40) is greater than the minimum steering wheel angle input value during the minimum input time period and each of the plurality of drift criteria parameters corresponds to its corresponding input value, determining that the angle of rotation of the steering wheel (40) is within a drift assist range associated with the steering wheel (40); and in response to determining that the angle of rotation of the steering wheel (40) is within the drift assist range associated with the steering wheel (40), shifting an executed position of the steering wheel (40) closer to an ideal drift range associated with the steering wheel (40) such that the drift maneuver is successfully performed.The drift assist system (12) of claim 1, characterized in that the executed position of the steering wheel (40) determined by the drift assist system (12) represents a commanded position of the steering wheel (40) that is transmitted to a wired steering system (26) that is part of the vehicle (10).The drift assist system (12) of claim 2, characterized in that the one or more controllers (20) execute instructions to: further monitor the signal indicative of the angle of rotation of the steering wheel (40) after shifting the executed position of the steering wheel (40) to be closer to the ideal drift range; and in response to determining that the angle of rotation of the steering wheel falls within the ideal drift range associated with the steering wheel (40), direct the wired steering system (26) to increase a steering ratio of the vehicle (10) from a nominal steering ratio.The drift assist system (12) of claim 3, characterized in that the one or more controllers (20) execute instructions to: further direct the wired steering system (26) to increase the steering ratio of the vehicle (10) from the nominal steering ratio until at least one of the following is satisfied: the angle of rotation of the steering wheel (40) is outside a steering wheel angle output range for a minimum output time period, and at least one of the plurality of drift criteria parameters corresponds to its corresponding output value.The drift assist system (12) of claim 1, characterized in that the plurality of drift criteria parameters includes an amount of braking force that the driver of the vehicle (10) applies to a brake pedal of the vehicle (10), a vehicle slip angle, and a vehicle speed.The drift assist system (12) of claim 1, characterized in that the one or more controllers (20) direct a steering wheel actuator to apply tactile feedback to the steering wheel (40) in response to determining that the angle of rotation of the steering wheel (40) is within the drift assist range and is matched to the plurality of drift criteria parameters.The drift assistance system (12) according to claim 1, characterized in that the ideal drift range associated with the steering wheel (40) represents a range of the angles of rotation of the steering wheel (40) that allow the vehicle (10) to maintain the drift maneuver.The drift assist system (12) of claim 1, characterized in that a steering response spline is stored in memory of the one or more controllers (20), and wherein the steering response spline represents a relationship between an actual position of the steering wheel (40) and the executed position of the steering wheel (40).The drift assist system (12) of claim 8, characterized in that the steering response spline includes a linear region disposed along an x-axis and a nonlinear region where the steering response spline includes a nonlinear profile.

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