Vehicle wheel slip control method

Abstract

The present application provides a wheel slip control method for a vehicle, the method comprising: estimating equivalent inertia information of a drive system based on operation information of the drive system when the vehicle is traveling; determining whether slip of a drive wheel occurs from the estimated equivalent inertia information of the drive system; if it is determined that the drive wheel slips, determining whether the wheel is in an uneven wheel slip state in which slip occurs only in one of the left and right wheels of the drive wheel from left and right wheel speeds detected by a sensor; and if it is determined that the wheel is in an uneven wheel slip state, controlling the operation of a braking device so that a braking force is applied to the wheel where slip occurs.

Description

Technical Field

[0001] The present disclosure relates to a wheel slip control method of a vehicle, and more particularly, to a wheel slip control method of a vehicle that can suppress wheel slip without unnecessarily reducing driving force in a vehicle equipped with an open differential. Background Art

[0002] Generally, there are electronic control systems for improving the safety of a vehicle while it is traveling, such as an anti-lock braking system (ABS) configured to prevent brake lock due to wheel slippage on a slippery road surface when the vehicle brakes, a traction control system (TCS) configured to control driving force or braking force during sudden unexpected acceleration and sudden acceleration of the vehicle to prevent wheel slippage, an electronic stability program (ESP) configured to stably control the posture of the vehicle, and the like.

[0003] Among them, TCS is an active safety device that is configured to prevent reverse slip of the drive wheels when the vehicle starts or accelerates, or when the vehicle turns on a low-friction or asymmetric road surface, thereby preventing the vehicle from rotating and improving the vehicle's starting and acceleration performance, operating stability and driving stability.

[0004] If excessive driving force is generated when the vehicle starts or accelerates on a slippery road and thus wheel slip of the drive wheels occurs, the TCS reduces the driving force (driving torque) of the vehicle to control the speed of the drive wheels, thereby suppressing wheel slip.

[0005] Here, the driving force of the vehicle is the force that drives the vehicle; that is, the force generated by the torque output by the driving device of the vehicle, and the force transmitted from the driving device to the wheels (driving wheels) through the driving shaft.

[0006] Depending on the vehicle type, the drive device of the vehicle configured to reduce driving force to suppress wheel slip when TCS operates can be an electric motor (pure electric vehicle, fuel cell vehicle), an engine (internal combustion engine vehicle), or both an electric motor and an engine (hybrid vehicle).

[0007] For example, an electric motor-driven vehicle such as a pure electric vehicle (battery electric vehicle), a fuel cell vehicle or a hybrid vehicle determines a target drive wheel speed that can obtain the optimal driving force in the drive wheel based on the amount of slip generated between the drive wheel and the road surface, the road friction coefficient, etc., and controls the motor torque to follow the target drive wheel speed.

[0008] Furthermore, when the vehicle turns on a corner road, the motor torque is reduced to prevent vehicle instability so that the vehicle can turn safely.

[0009] When TCS operates, the torque is adjusted in the direction of suppressing slip by calculating the slip of the wheels based on the actual vehicle speed during driving, and control of reducing and correcting the torque command of the drive device to reduce the driving force (driving torque) is performed to suppress slip.

[0010] At the same time, despite the introduction of various electronic control systems in vehicles, the behavior of the vehicle is ultimately limited by the friction of the road surface.

[0011] This is because the behavior of a vehicle is obtained through the friction between the tires and the road, making how to effectively use friction an important factor in determining the behavior of a vehicle.

[0012] The maximum road friction is affected by the combined effects of road surface characteristics, longitudinal / lateral tire slip, tire vertical load, etc., and as the slip size increases, the available friction decreases.

[0013] Therefore, it is important to suppress the tire slip (wheel slip) of the wheels to maintain effective longitudinal / lateral friction, and an electronic control system such as ABS or TCS in the vehicle is responsible for the above-mentioned role.

[0014] However, the conventional wheel slip suppression control method has the following problems.

[0015] As we all know, the slip between the tire and the road surface reduces the available traction of the corresponding wheel, and when the available traction of the wheel is reduced, the vehicle's starting ability is reduced. This is particularly fatal for low-friction roads.

[0016] To solve this problem, the related art performs a driving force reduction control (torque reduction control) that reduces the driving force transmitted from a driving device of the vehicle to the wheel to suppress slip, taking into account the reduction in available traction in the wheel where slip occurs.

[0017] The driving force generated by the driving device may be construed as having the same meaning as the torque generated by the driving device (ie, driving torque), unless particularly classified and otherwise described in the following description.

[0018] The following is described in more detail Figure 1 is a diagram illustrating a problem of the related art, wherein reference numeral 1 denotes a drive device and reference numeral 2 denotes a speed reducer.

[0019] Figure 1 An example is shown in which the drive force reduction control is executed when slip occurs in a vehicle equipped with the inexpensive open differential 3 instead of the expensive electronic limited slip differential (LSD).

[0020] The vehicle on which the general open differential 3 is mounted has a distribution ratio of driving force for the left and right wheels 4 and 5 that is fixed to a ratio of 50:50, which means that driving force having the same magnitude is applied to the left and right wheels.

[0021] Figure 1 An uneven wheel slip state is shown, in which slip occurs in only one of the left wheel 4 and the right wheel 5 .

[0022] exist Figure 1 In the upper and lower figures in FIG. 1 , the size (radius) of the circle indicated on each of the left and right wheels represents the available traction size of the corresponding wheel.

[0023] also, Figure 1 The arrow pointing upward for each wheel in the upper and lower figures in the drawings (arrow in the forward direction of the vehicle) shows that driving force is applied to the corresponding wheel, wherein the length of the arrow indicates the magnitude of the driving force.

[0024] refer to Figure 1 In a state where the available traction of the left wheel is less than the available traction of the right wheel, the driving force having the same magnitude is distributed to the left wheel 4 and the right wheel 5 through the open differential 3 .

[0025] exist Figure 1 In the example, since the left wheel 4 has a driving force greater than the available traction, wheel slip occurs, and since the right wheel 5 has an available traction greater than the driving force, wheel slip does not occur.

[0026] As described above, the uneven wheel slip state in which slip occurs only in the left wheel 4 may be a state in which slip occurs only in the left wheel 4 due to the lateral road surface friction on an asymmetric road surface in which the road surface on which the left wheel is grounded is a low-friction road surface compared to the road surface on which the right wheel 5 is grounded, or a state in which slip occurs only in the left wheel due to the lateral load when the vehicle turns left.

[0027] If the vehicle turns left, an uneven wheel slip state may occur in which wheel slip does not occur in the right wheel 5 as the outer wheel, and wheel slip occurs only in the left wheel 4 as the inner wheel due to the vehicle tilt and the lateral load.

[0028] The increase in the rotational speed of a wheel experiencing slip compared to the vehicle speed without slip is a technical phenomenon known in the art.

[0029] like Figure 1 As shown, in an uneven wheel slip state in which slip occurs only in the left wheel 4, according to a conventional wheel slip control method, when the driving force (driving torque) is reduced to suppress wheel slip, in a vehicle equipped with an open differential 3, the driving force in the left wheel 4 and the right wheel 5 is reduced by the same amount.

[0030] As a result, Figure 1 In the example of FIG. 1 , even if the right wheel 5 in which slip does not occur has available traction greater than the driving force and therefore has space for available traction (see FIG. 1 ), Figure 1 ), even in the right wheel where no slip occurs, the driving force is unnecessarily reduced by the same amount as that of the left wheel 4 where slip occurs, in order to suppress wheel slip (see Figure 1 in the figure below).

[0031] This is because the open differential 3 may distribute the torque to the left wheel 4 and the right wheel 5 only at a ratio of 50:50, and may not reduce the driving force for only one of the left and right wheels.

[0032] Therefore, there is a need for a method that can resolve the unnecessarily reduced driving force even for a wheel that does not slip, which can ensure additional traction as with a wheel that slips, to suppress slip in an uneven wheel slip state.

[0033] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art. Summary of the invention

[0034] The present disclosure is intended to solve the above-mentioned problems, and an object of the present disclosure is to provide a wheel slip control method of a vehicle, which can solve the problem that the driving force is unnecessarily reduced even for wheels that do not slip, and which can ensure additional traction in the driving force reduction control.

[0035] Specifically, an object of the present disclosure is to provide a wheel slip control method for a vehicle, which can suppress wheel slip without having to reduce driving force in a vehicle equipped with a general open differential without an expensive LSD.

[0036] In addition, another object of the present disclosure is to provide a wheel slip control method for a vehicle, which can control a driving device so that in a state of uneven wheel slip, a driving force within the available traction range can be applied to the slipping wheel without reducing the driving force output by the driving device, thereby quickly suppressing the slip of the wheel.

[0037] Yet another object of the present disclosure is to provide a method capable of controlling wheel slip of a wheel without using a known reference speed in the vehicle.

[0038] In order to achieve the above-mentioned purpose, an exemplary embodiment of the present disclosure provides a wheel slip control method for a vehicle, comprising: estimating, by a control unit, equivalent inertia information of a drive system based on operation information of the drive system when the vehicle is traveling; determining, by the control unit, whether slip of a drive wheel occurs from the estimated equivalent inertia information of the drive system; if it is determined that slip of the drive wheel occurs, determining, by the control unit, from left wheel speed and right wheel speed detected by a sensor, whether the wheel is in an uneven wheel slip state in which slip occurs only in one of the left and right wheels of the drive wheel; and if it is determined that the wheel is in an uneven wheel slip state, controlling, by the control unit, the operation of a braking device so that a braking force is applied to the wheel where slip occurs.

[0039] Here, the vehicle may be a vehicle equipped with an open differential that distributes a driving force of a driving device configured to drive the vehicle to left and right wheels at a ratio of 50:50.

[0040] Furthermore, the value of the equivalent inertia information may be an equivalent inertia change amount as a difference between an equivalent inertia obtained in real time of the driving system and a basic equivalent inertia having a predetermined value.

[0041] In addition, the wheel slip control method of a vehicle according to an exemplary embodiment of the present disclosure may also include: calculating, by a control unit, a lateral load movement amount of the vehicle from current vehicle driving information collected by the vehicle; comparing, by the control unit, the calculated lateral load movement amount of the vehicle with a first movement amount threshold; and if the calculated lateral load movement amount of the vehicle is greater than the first movement amount threshold, controlling, by the control unit, the operation of the braking device by determining that an uneven load of a predetermined level or greater occurs in the vehicle when the vehicle turns, so that a braking force is applied to the wheel corresponding to the inner wheel when turning.

[0042] In addition, the wheel slip control method of a vehicle according to an exemplary embodiment of the present disclosure may further include: while applying braking force to the wheel where slip occurs by controlling the operation of a braking device, a control unit determines whether a current vehicle state reaches a slip suppression mitigation condition based on a lateral load movement amount of the vehicle obtained by estimated equivalent inertia information of a drive system and current vehicle driving information; and if the current vehicle state reaches the slip suppression mitigation condition, controlling the operation of the braking device so that the braking force applied to the wheel where slip occurs is reduced by a predetermined amount.

[0043] In addition, the wheel slip control method of a vehicle according to an exemplary embodiment of the present disclosure may further include: if it is determined from the left wheel speed and the right wheel speed detected by the sensor that the wheel is in a state where slip occurs in both the left wheel and the right wheel of the driving wheel, the control unit performs a driving force reduction control to reduce the driving force of the driving device transmitted to the driving wheel.

[0044] As a result, the wheel slip control method of the vehicle according to the present disclosure can individually maximize the road traction of each of the left and right wheels connected to one drive shaft through the differential by selectively applying braking force only to the wheel where slip occurs in a state where uneven wheel slip occurs.

[0045] Therefore, the wheel slip control method of a vehicle according to the present disclosure can solve the problem of the conventional driving force reduction control that the driving force is unnecessarily reduced even for a wheel in which no slip occurs, which can ensure additional traction.

[0046] Furthermore, the present disclosure can maximize the road traction of each wheel simply by improving the control logic without increasing the cost or incurring additional cost in a vehicle equipped with an open differential without an expensive LSD.

[0047] Furthermore, the present disclosure determines the occurrence of wheel slip based on equivalent inertia information, and determines the braking force application amount, driving force reduction amount, etc. based on the equivalent inertia information. Unlike conventional TCS control, the speed does not necessarily use a reference speed.

[0048] In addition, due to reasons such as wheel speed signal processing for preventing control cycle delays or failures, conventional TCS control methods have difficulty maintaining ideal control performance and thus cannot maintain a slipping state that applies maximum road friction and causes greater slip, but the present disclosure can limit wheel slip in advance even in a transition portion before conventional TCS control or when operating wheel slip control using equivalent inertia information, thereby improving the vehicle's driving stability compared to conventional TCS control methods.

[0049] It should be understood that the term "automobile" or "vehicle" or other similar terms as used herein include general motor vehicles, such as passenger cars (including sports utility vehicles (SUVs), buses, trucks), various commercial vehicles, watercraft (including various ships and boats), aircraft, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more power sources, such as a gasoline-powered vehicle and an electric vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The above and other features of the present disclosure will now be described in detail with reference to certain exemplary examples of the present disclosure shown in the accompanying drawings, which are given hereinafter by way of illustration only and thus do not limit the present disclosure, and in which:

[0051] Figure 1is a diagram illustrating a problem of a wheel slip control method of a vehicle according to the related art.

[0052] Figure 2 is a diagram showing a wheel slip control state according to the present disclosure.

[0053] Figure 3 is a diagram illustrating a control method in a case where slip occurs in both the left and right wheels according to the present disclosure.

[0054] Figure 4 is a diagram showing a control method of a comparative example of applying braking force to both wheels in a case where slip occurs simultaneously in the left and right wheels.

[0055] Figure 5 is a block diagram showing a configuration of a vehicle that executes a wheel slip control process of the vehicle according to the present disclosure.

[0056] Figure 6 and Figure 7 is a flowchart illustrating a wheel slip control method according to an exemplary embodiment of the present disclosure.

[0057] Figure 8 is a diagram showing the vehicle Ackermann geometry motion of a turning vehicle.

[0058] It should be understood that the accompanying drawings are not necessarily to scale, and that they present a somewhat simplified representation of various preferred features that illustrate the basic principles of the present disclosure. The specific design features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the specific intended application and use environment.

[0059] In the drawings, reference numbers refer to the same or equivalent parts of the present disclosure throughout the several figures of the drawing. DETAILED DESCRIPTION

[0060] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present disclosure pertains can easily implement the present disclosure. However, the present disclosure is not limited to the exemplary embodiments described herein and may also be specified in other forms.

[0061] Throughout the specification, when a component is referred to as “comprising” a component, it means that other components may be further included rather than excluding the other components, unless specifically stated otherwise.

[0062] Using a braking device installed on each wheel and capable of being individually controlled in the vehicle, individual slip control is performed on each wheel to apply braking force only to the wheel where slip occurs among the left and right wheels connected to the drive device via a single drive shaft, and wheel slip control technology based on equivalent inertia is applied, etc.

[0063] Here, the braking device may be a known hydraulic braking device as a friction braking device, and a known wheel brake which is mounted on each of the left and right wheels and is capable of generating and applying a braking force which is individually controlled for each wheel.

[0064] The background of introducing wheel slip control technology based on equivalent inertia is described in the present disclosure. The problem is that the known ABS or TCS control methods have difficulty maintaining ideal control performance due to reasons such as wheel speed signal processing for preventing control cycle delays or failures, thereby failing to maintain slip conditions that apply maximum road friction and causing large slip.

[0065] Therefore, in addition to the conventional TCS control that reduces the driving force based on the slip speed, the wheel slip suppression control technology based on the equivalent inertia can be used, and the wheel slip suppression control technology based on the equivalent inertia is effective for suppressing the slip amount itself of the wheels connected to a single drive shaft.

[0066] However, there is a limitation that the wheel slip suppression control technology based on equivalent inertia may not be able to control the slip of each wheel individually; that is, the individual slips of the left and right wheels among the drive wheels relative to the multiple wheels connected to a single drive shaft.

[0067] In addition, the wheel slip suppression control technology based on equivalent inertia can have the effect of maximizing road traction by suppressing the slip of the wheels (front wheels or rear wheels) connected to a separate drive shaft such as a front-wheel drive shaft or a rear-wheel drive shaft, but for each of the two wheels (the left and right wheels of the drive wheels) connected to a single drive shaft through a differential, there is a limitation in maximizing the road traction of the wheel individually.

[0068] In addition, the wheel slip suppression control technology based on equivalent inertia can achieve the effect of maximizing the road traction of each of the front and rear wheels individually by individually controlling the slip suppression of the front and rear drive shafts connected to the corresponding independent drive devices, but there are limitations on maximizing the road traction of each of the front and rear wheels connected to a single drive shaft.

[0069] Therefore, the present disclosure proposes an improved wheel slip suppression control method that can maximize road traction individually even for wheels connected to a single drive shaft by applying a braking control technique to each wheel and wheel slip control based on equivalent inertia.

[0070] The wheel slip control method according to the present disclosure may not change the distribution ratio of driving force for left and right wheels, and is useful for a vehicle equipped with a general open differential that distributes the same driving force to left and right wheels at a ratio of 50:50.

[0071] Figure 2 is a diagram showing a wheel slip control state according to the present disclosure, wherein reference numeral 1 denotes a drive device, and reference numeral 2 denotes a speed reducer.

[0072] Figure 2 An example is shown in which the occurrence of slip is suppressed by applying a braking force to the left wheel 4 which may slip in a situation where side wheel slip may occur.

[0073] For example, a state in which wheel slip occurs only in the left wheel 4 may be a state in which slip occurs only in the left wheel due to lateral road surface friction on an asymmetric road surface in which the road surface on which the left wheel contacts the ground is a low-friction road surface compared to the road surface on which the right wheel 5 contacts the ground, or a state in which slip occurs only in the left wheel due to a lateral load when the vehicle turns left.

[0074] When the vehicle turns left, no slip occurs in the right wheel 5 as the outer wheel, and slip may occur only in the left wheel 4 as the inner wheel. Conversely, when the vehicle turns right, no slip occurs in the left wheel 4 as the outer wheel, and slip may occur only in the right wheel 5 as the inner wheel.

[0075] Furthermore, in a vehicle equipped with the open differential 3, when the driving force is distributed to the left and right wheels 4 and 5 of the driving wheels at a ratio of 50:50, slip may occur only in one wheel when the available traction of one of the left and right wheels is less than the driving force.

[0076] As described above, according to the present disclosure, the control unit senses an uneven wheel slip state in which slip occurs only in one wheel of the left wheel 4 and the right wheel 5 of the driving wheels where available traction is reduced, so as to apply a braking force to the wheel where slip occurs, so that the wheel where slip occurs can be driven by a force having a magnitude obtained by subtracting the braking force from the driving force transmitted from the drive device 1.

[0077] As a result, braking force is applied only to the wheel where slip occurs so that the magnitude of force obtained by subtracting the braking force from the driving force transmitted from the drive device can be smaller than the available traction force, thereby suppressing slip of each wheel.

[0078] Figure 2The upper figure in shows a state where uneven wheel slip occurs, in which it can be seen that the driving force is distributed to the left wheel 4 and the right wheel 5 in a ratio of 50:50, and the driving force of the same magnitude is applied to the left wheel 4 and the right wheel 5 via the reducer 2 in the drive device 1 through the open differential 3.

[0079] Figure 2 The example shows a state in which the available traction of the left wheel 4 is reduced compared to the available traction of the right wheel 5, wherein the driving force is greater than the available traction in the left wheel 4, causing slippage, and the driving force is less than the available traction in the right wheel 5, causing no slippage.

[0080] According to the present disclosure, if uneven wheel slip occurs, for example, if slip occurs only in the left wheel 4, the braking force for suppressing slip is additionally applied to the wheel where slip occurs, that is, the left wheel 4 having an available traction force less than the driving force for suppressing slip in the left wheel 4, instead of reducing the driving force transmitted to all wheels.

[0081] That is, the driving force and the braking force are simultaneously applied to the left wheel 4 as the wheel where slip occurs, so that the occurrence of slip in the left wheel 4 is suppressed.

[0082] At this time, when the braking force is applied to the left wheel 4, slip in the left wheel can be suppressed only when the value obtained by subtracting the braking force from the driving force is smaller than the available traction in the left wheel.

[0083] To this end, the driving force distributed from the drive device 1 to the left wheel 4 and the right wheel 5 is not reduced and remains unchanged, and the braking force that makes the value obtained by subtracting the braking force from the driving force become a level that may be smaller than the available traction in the left wheel 4 can be applied only to the left wheel.

[0084] Or, the driving force of the right wheel before the braking force is applied to the left wheel 4 (see Figure 2 Compared with the lower figure in FIG. 1 , it is possible to increase the driving force of the left wheel 4 and the right wheel 5 within the margin of the available traction force (which may be a value obtained by subtracting the driving force from the available traction force) (see FIG. 1 ). Figure 2 in the figure above).

[0085] At this time, preferably, the braking force application amount of the left wheel is determined so that a value obtained by subtracting the additionally applied braking force from the increased driving force in the left wheel 4 is not larger than the available traction force in the left wheel.

[0086] As described above, it is possible to suppress the slip of all wheels including the wheel where slip occurs, simply by additionally applying a braking force having an appropriate magnitude to the wheel where slip occurs without reducing the driving force and keeping it as it is.

[0087] Furthermore, even if the driving force instead increases, when the braking force application amount can be controlled so that the difference between the driving force and the braking force applied from the wheel where slip occurs is not greater than the available traction, it is possible to suppress slip in the wheel.

[0088] Although referenced Figure 2 A method for suppressing slip in an uneven wheel slip state in which slip occurs in the left wheel 4 is described, but the present disclosure is not limited to the case in which slip occurs in the left wheel, and even in the case of an uneven wheel slip state in which slip occurs only in the right wheel 5, similarly, when braking force is applied to the right wheel in the same way, the occurrence of slip in all wheels including the right wheel can be suppressed.

[0089] at the same time, Figure 3 is a diagram illustrating a control method in a case where slips occur simultaneously in the left and right wheels according to the present disclosure.

[0090] also, Figure 4 is a diagram showing a control method of a comparative example in which braking force is applied to both wheels if slip occurs simultaneously in the left and right wheels.

[0091] Figure 3 The upper figure in FIG. 1 shows that when the driving force generated and provided by the driving device 1 is applied to the left wheel 4 and the right wheel 5 through the open differential 3 via the speed reducer 2 in the vehicle equipped with the open differential 3, all available traction in the left wheel 4 and the right wheel 5 is less than the driving force, so that slip occurs in both the left wheel 4 and the right wheel 5.

[0092] As described above, if slip occurs in both the left wheel 4 and the right wheel 5, for example, when the slip amounts generated by the left and right wheels are the same as each other or similar to each other but have a difference of a predetermined level or less, the present disclosure performs a driving force reduction control that reduces the driving force applied by the drive device 1 to each wheel 4, 5 to ensure traction in all wheels, such as Figure 3 As shown in the figure below, instead of applying braking force to any one wheel, the sliding of both wheels is suppressed.

[0093] According to the present disclosure, a reduction in driving force (driving torque) means a reduction in driving torque, which is a torque output by a driving device 1 such as an engine, a motor, or an engine and a motor, and control to reduce the driving force (driving torque) means control to reduce the torque command of the driving device generated and output by a control unit.

[0094] As described above, if slip occurs in both the left wheel 4 and the right wheel 5, the present disclosure performs the driving force reduction control (ie, the torque reduction control) to suppress the slip.

[0095] According to the present disclosure, if slip occurs simultaneously in the left and right wheels, control to reduce driving force (ie, torque reduction control to reduce driving torque) is similar to conventional TCS control in that driving force is reduced to suppress slip.

[0096] However, as will be described later, the present disclosure differs from conventional TCS control in that equivalent inertia-based torque (driving force) reduction control is performed, wherein equivalent inertia-based torque reduction control means control for reducing driving torque based on an equivalent inertia change amount.

[0097] According to the present disclosure, the control unit determines the torque (driving force) reduction amount as a value corresponding to the equivalent inertia change amount, and performs correction to reduce the torque command of the drive device 1 according to the determined torque reduction amount during the torque reduction control based on the equivalent inertia.

[0098] Figure 4 An example is shown in which, when slip occurs in both the left wheel 4 and the right wheel 5 , braking force is applied to both wheels where slip occurs, thereby ensuring sufficient traction.

[0099] As shown in the figure, it can be considered to apply a braking force to each of the left wheel 4 and the right wheel 5 where slipping occurs, so as to suppress the wheel slip of the vehicle.

[0100] Here, if Figure 2 As shown in the example of , the braking force applied to the left wheel 4 and the right wheel 5 can be determined so that the value obtained by subtracting the braking force from the driving force is not greater than the available traction of each wheel.

[0101] However, when the available traction is smaller than the driving force in the left wheel 4 and the right wheel 5 so that slip occurs in both wheels, it is not preferable to apply braking force to both the left and right wheels to ensure sufficient traction of the wheels because the energy consumption is greater than the reduction in driving force, which is neither economical nor effective, and there are also problems such as reduced durability due to excessive use of brake pads.

[0102] Therefore, if slip occurs in both the left wheel 4 and the right wheel 5, the present disclosure performs control of reducing the driving force applied to both wheels, rather than performing a method for applying a braking force to both wheels.

[0103] That is, the present disclosure does not apply braking force to both wheels but reduces the torque command of the drive device 1 to reduce the torque (driving force) applied to both wheels, but reduces the torque of the drive device by an amount corresponding to the equivalent inertia change.

[0104] Figure 5 is a block diagram showing a configuration of a vehicle that executes a wheel slip control process of the vehicle according to the present disclosure.

[0105] As shown in the figure, the vehicle includes a control unit 20 configured to perform wheel slip control according to the present disclosure, a drive device 1 configured to drive the vehicle, an open differential 3 configured to transmit the driving force of the drive device 1 to wheels 4, 5, braking devices 31, 32 configured to apply braking force to each wheel 4, 5, and speed detection units 15, 16 configured to detect the rotation speed of each wheel 4, 5.

[0106] Here, the drive device 1 may be an engine (in the case of an internal combustion engine vehicle), a motor (battery electric vehicle, fuel cell vehicle), or an engine and a motor (in the case of a hybrid vehicle) depending on the vehicle.

[0107] The control unit 20 includes a driving force control unit 21 configured to control the driving force of the vehicle, and a braking force control unit 22 configured to control the braking force of the vehicle, wherein the driving force control unit 21 controls the operation of the driving device 1 by generating and outputting a torque command.

[0108] Furthermore, the braking force control unit 22 controls the operation of the braking devices 31 , 32 mounted on the respective wheels 4 , 5 , wherein the braking devices 31 , 32 may be friction braking devices, and specifically, known wheel brakes as hydraulic braking devices.

[0109] According to the present disclosure, the driving force control unit 21 as the top-level control unit of the vehicle can be a control unit within the vehicle, which is configured to control the operation of the driving device 1 by generating and outputting torque instructions of the engine, motor, or engine and motor as the driving device 1.

[0110] For example, the driving force control unit 21 may be a vehicle control unit (VCU) or a hybrid control unit (HCU), which is a top-level control unit in an electric vehicle or a hybrid vehicle.

[0111] The braking force control unit 22 may be a known brake control unit configured to individually control the operation of the brake devices 31 , 32 mounted on the respective wheels 4 , 5 .

[0112] The wheel slip control according to the present disclosure is performed in the coordinated control of the driving force control unit 21 and the braking force control unit 22, and the driving force control unit 21 performs driving force control and correction for the wheel slip control and senses the slip of each wheel 4, 5, and performs a braking force control request to the braking force control unit 22 when uneven wheel slip is sensed.

[0113] Here, as will be described later, the driving force correction refers to correction of the torque command of the driving device 1 in order to reduce the driving force.

[0114] According to the present disclosure, when the wheels are in an uneven wheel slip state in which slip occurs only in one of the left wheel 4 and the right wheel 5 while the vehicle is traveling, the braking force control unit 22 controls the operation of the braking devices 31, 32 so that the braking force can be applied only to the wheel where slip occurs according to the request of the driving force control unit 21 as the top control unit.

[0115] At this time, the braking force control unit 22 controls the operation of the braking devices 31 , 32 mounted on the wheels where slipping occurs so that the braking force can be applied only to the corresponding wheels.

[0116] In addition, according to the present disclosure, in the process of coordinated control with the braking force control unit 22, the driving force control unit 21 can generate a torque command (braking torque command) for the braking devices 31 and 32 and transmit it to the braking force control unit 22, or the braking force control unit 22 can receive necessary information from the driving force control unit 21 to generate and output the torque command of the braking devices 31 and 32 for braking force control.

[0117] exist Figure 5 In the structure of the device shown, the drive device 1 generates and outputs a driving force (driving torque) according to a torque command output by a driving force control unit 21, at which time the driving force (driving torque) is transmitted to the left wheel 4 and the right wheel 5 via a reducer (not shown) through an open differential 3.

[0118] At this time, the driving force is distributed to the left wheel 4 and the right wheel 5 at a ratio of 50:50 through the open differential 3, and the vehicle equipped with the open differential 3 can equally reduce the driving force applied to the left wheel 4 and the right wheel 5 by reducing the driving force output by the drive device 1.

[0119] If slip occurs in both the left wheel 4 and the right wheel 5, particularly if slip of the same or similar amount occurs in both the left wheel and the right wheel, the present disclosure reduces the driving force of the driving device 1, thereby suppressing slip of both wheels simultaneously.

[0120] The speed detection unit includes a left wheel speed detection unit 15 configured to detect the rotation speed (wheel speed) of the left wheel 4, and a right wheel speed detection unit 16 configured to detect the rotation speed of the right wheel 5, and each speed detection unit 15, 16 can be a well-known wheel speed sensor installed on each of the left wheel 4 and the right wheel 5.

[0121] According to the present disclosure, the driving force control unit 21 of the control unit 20 determines whether the wheel slips from the signals of the left wheel speed detection unit 15 and the right wheel speed detection unit 16, and in particular, determines whether the slip occurs only in one of the left wheel 4 and the right wheel 5, or whether the slip occurs on both sides (both the left wheel 4 and the right wheel 5).

[0122] In addition, reference Figure 5 The vehicle may also be installed with a steering angle sensor 12 configured to detect a steering angle according to a driver's steering wheel operation, a lateral acceleration sensor 13 configured to detect a lateral acceleration of the vehicle, and a yaw rate sensor 14 configured to detect a yaw rate of the vehicle, and all sensors are used to detect vehicle state information necessary for the wheel slip control processing according to the present disclosure.

[0123] Furthermore, as described later, the vehicle may additionally include an interface unit 11 for the driver to select and input on or off of the wheel slip control function according to the present disclosure.

[0124] The interface unit 11 is suitable as long as it is a device that the driver can operate to turn on and off the control function.

[0125] The interface unit 11 can be connected to the driving force control unit 21 of the control unit 20 , so when the driver performs opening and closing operations, the opening and closing operation signals issued by the driver can be input from the interface unit 11 to the driving force control unit 21 of the control unit 20 .

[0126] Figure 6 and Figure 7 is a flowchart showing a wheel slip control method according to an exemplary embodiment of the present disclosure, wherein: Figure 6 is a flowchart showing a wheel slip substantially canceling mode as an exemplary embodiment of the present disclosure, Figure 7 is a flowchart illustrating a wheel slip post-cancellation mode as another exemplary embodiment of the present disclosure.

[0127] An embodiment of a method including a wheel slip primary cancelling mode and an embodiment of a method including a wheel slip post cancelling mode may be adopted as a wheel slip control method in the present disclosure.

[0128] The wheel slip basic offset mode of the two offset modes is a control process including applying a braking force if a lateral load movement having a reference value or more occurs when the wheel slip of the equivalent inertia change amount is not detected (corresponding to Figure 6 mode of steps S12 and S13).

[0129] In contrast, the wheel slip post-cancellation mode is a mode in which, when uneven wheel slip of the equivalent inertia change amount is detected, control is performed to additionally apply braking force and driving force to the wheel where slipping occurs.

[0130] The wheel slip post-cancellation mode is advantageous over the wheel slip basic cancelation mode in terms of brake pad durability, but the wheel slip basic cancelation mode is advantageous over the wheel slip post-cancellation mode in terms of responsiveness and stability of vehicle behavior.

[0131] First, the basic wheel slip compensation mode is described, such as Figure 6 As shown, the wheel slip control process according to the present disclosure determines whether the control unit 20 is in a state where the control function becomes on (S11), and executes the process if the control unit 20 is in a control on state.

[0132] That is, if the driver turns on the control function through the interface unit 11 in the vehicle, the subsequent wheel slip control process is executed, and Figure 6 In step S11 shown, it is determined that the control unit 20 is in the control-on state, and then the subsequent wheel slip control process is executed.

[0133] If the control unit 20 is not in the control-on state in step S11 , that is, if the control unit 20 is in the control-off state, the control logic is terminated.

[0134] Furthermore, in the case of the control-on state as described above, the driving force control unit 21 of the control unit 20 calculates the vehicle lateral load movement amount from the current vehicle travel information collected by the vehicle.

[0135] Here, the vehicle travel information may include steering angle information according to a driver's steering wheel operation, lateral angular velocity information and yaw rate information of the vehicle, and wheel speed (vehicle wheel speed) information.

[0136] Such information can be detected by sensors, and the steering angle can be detected by a steering angle sensor 12, the lateral acceleration of the vehicle can be detected by a lateral acceleration sensor 13, and the yaw rate and wheel speed of the vehicle can be detected by a yaw rate sensor 14 and a speed detection unit (wheel speed sensor) 15, 16 respectively.

[0137] As described above, the driving force control unit 21 of the control unit 20 can receive information about the steering angle, lateral acceleration and yaw rate of the vehicle, as well as the wheel speed detected by the sensor to calculate the lateral load movement of the vehicle, and the lateral load movement is a control variable widely used in vehicle control in the prior art, so a detailed description of its calculation method will be omitted.

[0138] For example, the following reference discloses a method capable of estimating the amount of lateral load movement: Cho, Wanki, et al., “Estimation of tire forces for application to vehicle stability control,” IEEE Transactions on Vehicle Technology 59.2 (2009): 638-649.

[0139] Subsequently, the driving force control unit 21 compares the lateral load movement amount calculated as described above with a predetermined first movement amount threshold value (δ0) (S12), and then, if the lateral load movement amount is greater than the first movement amount threshold value (δ0), it is determined that an uneven load of a predetermined level or greater occurs in the vehicle when the vehicle turns, to request application of braking force from the braking force control unit 22.

[0140] Subsequently, when the vehicle turns according to the request of the driving force control unit 21, the braking force control unit 22 applies the braking force only to the wheel corresponding to the inner wheel (S13).

[0141] That is, when the lateral load movement of the vehicle exceeds a predetermined level during driving, the braking force control unit 22 performs feedforward (FF) uneven braking control through the coordinated control of the driving force control unit 21 and the braking force control unit 22 of the control unit 20, and the feedforward uneven braking control only applies a predetermined braking force to the inner wheel.

[0142] According to an exemplary embodiment of the present disclosure, Figure 5 The subsequent steps after step S14 shown are control processing performed to suppress wheel slip after wheel slip in the vehicle is sensed by equivalent inertia information, and steps S12 and S13 are uneven braking control processing that applies a feed-forward (FF) braking force to the inner wheel to suppress the occurrence of wheel slip when an uneven load occurs even if wheel slip is not sensed by equivalent inertia information.

[0143] As described above, the present disclosure applies uneven braking force when an uneven load having a baseline value or greater occurs even if wheel slip is not sensed by the equivalent inertia information described later, and a mode further including steps S12 and S13 is a wheel slip basic offset mode, and a mode excluding steps S12 and S13 is a wheel slip post offset mode.

[0144] According to an exemplary embodiment of the present disclosure, the magnitude of the feedforward (FF) braking force applied to the inner wheel during feedforward uneven braking control can be determined as a value corresponding to the calculated lateral load movement amount in the driving force control unit 21 or the braking force control unit 22 of the control unit 20.

[0145] At this time, as the lateral load movement amount increases, the magnitude of the feedforward braking force applied to the inner wheel in the control unit 20 is set to a larger value.

[0146] Then, in the case of a state where uneven braking control is performed, as Figure 5As shown, the control unit 20 executes step S14, however if the lateral load movement amount is the first movement amount threshold (δ0) or less, the control unit 20 directly executes step S14 without executing the uneven braking control.

[0147] In step S14, the driving force control unit 21 estimates the real-time equivalent inertia information of the driving system based on the real-time operation information of the driving system, and determines whether the current wheel slips based on the estimated equivalent inertia information of the driving system.

[0148] Here, the equivalent inertia information of the driving system may include the real-time equivalent inertia value of the driving system and the equivalent inertia change obtained from the equivalent inertia. At this time, the equivalent inertia change may be defined by the difference between the equivalent inertia value of the driving system obtained in real time and the predetermined basic equivalent inertia value.

[0149] The operation information of the driving system necessary for estimating the equivalent inertia information may include a torque (driving force) command of a previous control cycle of the driving device 1 configured to drive the vehicle, and speed information of the driving system.

[0150] For example, in a motor-driven vehicle equipped with the drive device 1 as the drive device 1 , the torque command may be a drive torque (drive force) command, that is, a motor torque command for the motor.

[0151] The speed of the drive system may be the rotational speed of a drive element existing in a path through which a driving force is transmitted from a drive device 1 configured to drive a vehicle to a drive wheel, and may be real-time rotational speed information of the drive system as a measured value detected by a speed detection unit.

[0152] Specifically, the speed of the drive system can be a predetermined single speed among the engine speed, the motor speed, the transmission input shaft rotation speed, the transmission output shaft rotation speed, the drive wheel rotation speed, and the rotation speed of an integrated starter generator (ISG) which serves as a starter generator connected to the engine.

[0153] According to the exemplary embodiment of the present disclosure, when the speed of the driving system is the rotation speed of the driving wheels, the speed detection unit is the speed detection unit (wheel speed sensor) 15 , 16 mounted on the driving wheels.

[0154] At this time, the speed of the driving system may be a higher speed value of the left wheel speed detected by the left wheel speed detection unit 15 and the right wheel speed detected by the right wheel speed detection unit 16, or an average value of the left wheel speed and the right wheel speed.

[0155] Furthermore, according to the present disclosure, when the speed of the driving system is the rotation speed of the driving device 1 , the speed detection unit may be a known engine speed sensor configured to detect engine speed, or a known resolver configured to detect motor speed.

[0156] As described above, according to the present disclosure, the rotation speed of the driving element related to the speed of the driving wheel may be used as the speed of the driving system configured to estimate the equivalent inertia information.

[0157] Furthermore, according to the exemplary embodiment of the present disclosure, the driving force control unit 21 of the control unit 20 may calculate the equivalent inertia of the driving system by a value obtained by dividing the torque command of the previous control cycle by the angular acceleration of the driving system.

[0158] The driving force control unit 21 can basically calculate the equivalent inertia value using the relationship of the following equation 1, where “T q " denotes torque, "I" denotes equivalent inertia, and "α" denotes angular acceleration which is a velocity (angular velocity) differential value.

[0159] Equation 1

[0160] T q =I×α

[0161] According to an exemplary embodiment of the present disclosure, as a simple example, the driving force control unit 21 can obtain the angular acceleration (α) obtained from the speed of the driving system and the driving torque (T q )Calculate the necessary equivalent inertia (I).

[0162] Here, the speed of the driving system may be a rotation speed of the driving system detected by a speed detection unit (ie, a sensor such as a resolver or a wheel speed sensor), and the driving torque may be a torque command of the driving device.

[0163] More specifically, the torque (T q ) may be a torque command of a previous control cycle as the final torque command of the drive device 1, and if a driving force reduction control to be described later is performed and a torque correction is thereby performed based on the previous equivalent inertia information in the previous control cycle, the torque command of the previous control cycle may be a corrected torque command.

[0164] Of course, the uncorrected torque command is a general torque command generated by the driving force control unit 21 for the running of the vehicle according to the operation input of the driver, the cruise mode input, etc.

[0165] According to the present disclosure, the equivalent inertia is precisely the vehicle equivalent rotational inertia, which refers to the inertia value used to maintain the current rotation state as a value related to the weight of the vehicle, and the actual vehicle is not a rotating object but an object that performs linear motion, so that the general discussion of inertia is mass.

[0166] However, from the perspective of the driving force providing source, the mass of the vehicle itself serves as a load in the acceleration and deceleration of the angular velocity, and the value obtained by converting the mass value corresponding to the load in consideration of the rotating system is the vehicle equivalent moment of inertia.

[0167] The derivation of the equivalent inertia (equivalent rotational inertia) in the relationship between driving force (driving torque) and angular acceleration is described exemplarily. First, if "F=m×a" is substituted into the acceleration state of the vehicle, F corresponds to the driving force, m corresponds to the mass or inertia of the vehicle, and a corresponds to the longitudinal acceleration of the vehicle.

[0168] When "F = m × a" is converted from the perspective of the rotation system, it becomes "T q =I×α”, and T q refers to the driving torque, I refers to the equivalent inertia, and α refers to the angular acceleration of the rotating system of the vehicle.

[0169] The equivalent inertia can be expressed using "I = T q / α”, and for example, the equivalent inertia can be obtained by “driving torque / angular acceleration”, where wheel angular acceleration, motor angular acceleration, engine angular acceleration, etc. can be used as angular acceleration.

[0170] When wheel slip occurs, the calculated equivalent inertia value changes rapidly; when the formula "I = T q / α” When calculating the equivalent inertia, the equivalent inertia can be obtained by the same formula even when wheel slip does not occur; and if wheel slip occurs, the wheel angular acceleration will increase significantly even if the wheel slip speed does not increase significantly.

[0171] Therefore, when the same torque (T q ) value is divided by the greatly increased wheel angular acceleration (α), the equivalent inertia (I) that decreases instantly is calculated, and at this time, the change of the equivalent inertia (I) is faster than the change of the wheel slip speed.

[0172] As a result, according to the present disclosure, when the equivalent inertia information is calculated using the operating information of the drive system (i.e., the torque command of the previous control cycle as the final torque command) and the drive system speed information according to Equation 1, the drive force control unit 21 can use the calculated equivalent inertia information to determine whether wheel slip occurs.

[0173] As expressed in Equation 1, the entire equivalent inertia of the vehicle when wheel slip does not occur can be obtained by the final torque command and the wheel angular acceleration, and thus the obtained equivalent inertia value of the vehicle is relatively greater than the equivalent inertia value when wheel slip occurs.

[0174] The reason is that when wheel slip occurs, the driving torque only accelerates the drive wheel instead of accelerating the vehicle, and as a result, when this relationship is taken into consideration, when the calculated equivalent inertia of the vehicle decreases to a predetermined value or less, it can be determined that the wheel is in a wheel slip state.

[0175] Therefore, according to the present disclosure, the driving force control unit 21 calculates the equivalent inertia change, which is the difference between the equivalent inertia value of the driving system obtained in real time and the predetermined basic equivalent inertia value, and compares the equivalent inertia change with a predetermined first change threshold (δ1) (S14).

[0176] Here, the first change threshold (δ1) is a pre-set reference value to determine whether wheel slip occurs by comparing with the real-time equivalent inertia change, and when the calculated equivalent inertia change is greater than the first change threshold (δ1), the driving force control unit 21 determines that wheel (drive wheel) slip occurs.

[0177] Subsequently, the driving force control unit 21 compares the difference between the rotation speed of the left wheel detected by the left wheel speed detection unit 15 (hereinafter referred to as the "left wheel speed") and the rotation speed of the right wheel detected by the right wheel speed detection unit 16 (hereinafter referred to as the "right wheel speed") with a predetermined threshold speed difference (δ2) (S15).

[0178] If the difference between the left wheel speed and the right wheel speed is greater than the threshold speed difference (δ2), the driving force control unit 21 determines that it is in an uneven wheel slip state in which slip occurs in one of the left wheel or the right wheel.

[0179] At this time, the driving force control unit 21 can recognize that slip has occurred in the fast wheels of the left and right wheels.

[0180] For example, the uneven wheel slip state may be a state in which slip occurs only in one wheel due to uneven road friction on an asymmetric road surface having different friction coefficients between the road surface where the right wheel is grounded and the road surface where the left wheel is grounded, or a state in which slip occurs only in the left wheel due to uneven load when the vehicle turns left.

[0181] Subsequently, if it is determined that the wheel is in an uneven wheel slip state, while applying driving force to the left wheel 4 and the right wheel 5, the driving force control unit 21, through coordinated control with the braking force control unit 22, performs feedback uneven braking control only on the wheel where slipping occurs, that is, additional feedback (FB) braking force is applied to suppress slip.

[0182] At this time, the wheel where slipping occurs can be determined from the detected left and right wheel speeds, and the wheel rotating at a higher speed among the left and right wheels (i.e., the wheel rotating at a larger speed among the left and right wheels) is the wheel where slipping occurs.

[0183] When slip occurs in one of the left wheel 4 and the right wheel 5, the speed of the wheel where slip occurs increases instantaneously, and at this time, the equivalent inertia change amount also increases instantaneously.

[0184] When a feedback (FB) braking force is applied to a wheel in which slip occurs in a non-uniform wheel slip state, it is possible to reduce slip occurring in the corresponding wheel.

[0185] According to an exemplary embodiment of the present disclosure, when a feed-forward (FF) braking force is applied from step S13, the control unit applies a feedback (FB) braking force in addition to the feed-forward braking force in step S16, and in a state where the feed-forward (FF) braking force is not applied, only the feedback (FB) braking force is applied in step S16.

[0186] According to an exemplary embodiment of the present disclosure, the magnitude of the feedback (FB) braking force applied to the wheel where slip occurs (hereinafter referred to as the "slip occurring wheel") can be determined as a value corresponding to the current equivalent inertia change in the driving force control unit 21 or the braking force control unit 22 of the control unit 20.

[0187] Alternatively, by setting the speed of a wheel where slip does not occur (hereinafter referred to as a "non-slip wheel") as a target speed, the feedback (FB) braking force can be determined as a value corresponding to the speed difference (speed error) between the slip-occurring wheel and the non-slipping wheel.

[0188] That is, the feedback braking force may be determined as a control input value in which the speed of the slip occurring wheel follows the speed of the slip non-occurring wheel, and when the feedback braking force is applied to the slip occurring wheel, the speed difference between the two wheels gradually decreases.

[0189] As described above, when the uneven wheel slip state is determined, the control unit 20 may perform feedback uneven braking control that reduces the speed difference between the slip occurring wheel and the slip non-occurring wheel by applying feedback braking force to the slip occurring wheel.

[0190] In addition, as described above, the control unit 20 can perform feedback uneven braking control in which a braking force is applied to the slip occurring wheel, allowing the speed of the slip occurring wheel to follow the speed of the slip non-occurring wheel reflecting the kinematic characteristics of the vehicle, by setting the speed of the slip non-occurring wheel reflecting the kinematic characteristics of the vehicle as a target speed, rather than performing feedback uneven braking control in which a braking force is applied to the slip occurring wheel, allowing the speed of the slip occurring wheel to follow the speed of the slip non-occurring wheel, by setting the speed of the slip non-occurring wheel as a target speed.

[0191] Figure 8 is a diagram showing the vehicle Ackermann geometry kinematics of a turning vehicle, and Figure 8 R 1 , R 2 , R 3 and R 4 It refers to the turning radius of each wheel and is related to the steering angle, where the steering angle can be the Ackermann steering angle.

[0192] When the radius of the tire is r and the linear speed of each wheel is V i , the rotation speed of each wheel is ω i And when the vehicle yaw rate is ψ, the yaw rate is expressed by the following equation 2.

[0193] Equation 2

[0194]

[0195] The relationship between the individual wheel speeds and the vehicle yaw rate is given by the following equation 3 through V i =ω i ×r.

[0196] Equation 3

[0197]

[0198] Referring to Equation 3, it is possible to know the rotation speed relationship between the inner wheel and the outer wheel when the vehicle turns, and if uneven wheel slip occurs when the vehicle turns, then Figure 8 , the speed of the wheel where slip occurs refers to ω1, which is the inner wheel speed, and the speed of the wheel where slip does not occur refers to ω2, which is the outer wheel speed; and it is possible to know the relationship between the outer wheel speed which is the target speed during feedback uneven braking control and the inner wheel speed which follows the outer wheel speed.

[0199] Meanwhile, the driving force control unit 21 determines whether the current vehicle state reaches the slip suppression mitigation condition based on the equivalent inertia change amount as the current equivalent inertia information of the driving system and the vehicle lateral load movement amount obtained by the vehicle travel information.

[0200] During this process, the driving force control unit 21 compares the current equivalent inertia change with a predetermined second change threshold (δ3) which serves as a reference for determining the slip suppression reduction (S17), and at this time, subsequently, when the equivalent inertia change decreases to a value smaller than the second change threshold (δ3), the driving force control unit 21 compares the vehicle lateral load movement with a predetermined second movement threshold (δ4) (S18).

[0201] At this time, when the equivalent inertia change is less than the second change threshold (δ3), the vehicle lateral load movement is less than the second movement threshold (δ4), and the driving force control unit 21 determines that the current vehicle state meets the slip suppression reduction conditions to start the braking force application reduction control (S19).

[0202] According to an exemplary embodiment of the present disclosure, the second movement amount threshold value (δ4) for determining the slip suppression mitigation condition may be predetermined to be a smaller value than the first movement amount threshold value (δ0) for determining the feedforward uneven braking force application condition in step S11.

[0203] According to an exemplary embodiment of the present disclosure, when it is determined that the current vehicle state satisfies the slip suppression mitigation conditions, the driving force control unit 21 can reduce the braking force (feedback uneven braking force) applied to the wheel where slip occurs by a predetermined amount through coordinated control with the braking force control unit 22, and then return to step S11 to repeat the process of steps S11 to S19 again.

[0204] According to an exemplary embodiment of the present disclosure, when steps S11 to S19 are repeated again, in steps S11 to S19 , the driving force control unit 21 and the braking force control unit 22 again reduce the braking force applied to the slip-occurring wheel by a predetermined set amount in each control cycle.

[0205] Meanwhile, when the equivalent inertia change amount is the second change amount threshold value (δ3) or more in step S17, or when the lateral load movement amount is the second movement amount threshold value (δ4) or more in step S18, the process proceeds to step S15.

[0206] At this time, when the difference between the left wheel speed and the right wheel speed is greater than the threshold speed difference (δ2) in step S15, the uneven braking control of additionally applying the feedback braking force only to the slip-occurring wheel is continuously executed in step S16.

[0207] In addition, when the equivalent inertia change exceeds the first change threshold (δ1) in step S14, but the difference between the left wheel speed and the right wheel speed in step S15 is the threshold speed difference (δ2) or less, the driving force control unit 21 of the control unit 20 determines that both the left wheel 4 and the right wheel 5 have slipped, and in this case, reduces the torque command of the drive device 1 to reduce the driving force.

[0208] That is, when it is determined that wheel slip occurs based on equivalent inertia in step S14, but the speed difference between the left and right wheels is the threshold speed difference or less in step S15, slip occurs in both wheels instead of an uneven wheel slip state.

[0209] As described above, if slip occurs in both left and right wheels instead of uneven wheel slip, the control unit 20 performs driving force reduction control (S20) of reducing the driving force of the driving device 1 in step S20 without applying braking force to the wheels.

[0210] In addition, steps S17 and S18 are in a state where the FB braking force in step S16 as the previous step is applied to the slip-occurring wheel. Then, as described above, if the answers to steps S17 and S18 are "No", the process proceeds to step S15, and when the speed difference between the left and right wheels in step S15 is the threshold speed difference or less, the driving force reduction control in step S20 may be performed.

[0211] That is, while the FB braking force is being applied in step S16, the driving force reduction control in step S20 may also be performed additionally. Conversely, while the driving force reduction control is being performed in step S20, the process returns after executing steps S21 and S22, and then the FB uneven braking force may also be applied in step S16 through steps S11 to S15.

[0212] The reduction in the driving force of the drive device in step S20 means a reduction in the torque output by the drive device, and further, the reduction in the torque output by the drive device means a correction to reduce the torque command of the drive device.

[0213] That is, according to the present disclosure, the driving force control unit 21 of the control unit 20 performs correction to reduce the torque command of the driving device 1 in order to reduce the driving force, and at this time, the torque command correction amount indicating the driving force reduction amount can be set according to the equivalent inertia change amount.

[0214] As a result, the driving force control unit 21 of the control unit 20 determines the torque command correction amount as a value corresponding to the equivalent inertia change amount, and then performs a correction to reduce the torque command based on the determined torque command correction amount, and then outputs the corrected torque command, so that the drive of the drive device 1 is controlled by the corrected torque command.

[0215] As a result, when slip occurs in both wheels, the torque command is corrected based on the equivalent inertia information so that the torque and the driving force output by the drive device 1 decrease.

[0216] As a related patent application, there can be Korean patent application number 10-2019-0092527 (July 30, 2019) (hereinafter, referred to as "patent application 1"), in which a wheel slip control method of a vehicle includes a process in which a control unit (corresponding to a driving force control unit according to the present disclosure) estimates equivalent inertia information of a drive system based on operating information of the drive system.

[0217] Here, the control unit calculates a correction amount for correcting a torque command of a drive device configured to drive the vehicle from the estimated equivalent inertia information of the drive system, and then uses the calculated correction amount to correct the torque command of the drive device so that control of the torque applied to the drive wheel is performed according to the corrected torque command.

[0218] Subsequently, when the drive force reduction control is executed in step S20 , the drive force control unit 21 determines whether the current vehicle state reaches the slip suppression mitigation condition based on the current equivalent inertia change amount of the drive system.

[0219] During this process, the driving force control unit 21 compares the current equivalent inertia change with the second change threshold (δ3) which serves as a reference for determining the slip suppression reduction, and when the equivalent inertia change decreases to a value less than the second change threshold (δ3), it is determined that the current vehicle state satisfies the slip suppression reduction condition to start the driving force reduction reduction control (S21).

[0220] According to an exemplary embodiment of the present disclosure, the driving force control unit reduces the torque command correction amount in step S21 to be smaller than the torque command correction amount in step S20 so as to perform the driving force reduction reduction control in step S21, corrects the torque command according to the reduced torque command correction amount, and then controls the drive of the drive device 1 by the corrected torque command.

[0221] At this time, the result of the control of reducing the driving force reduction amount in step S21 is no different from the result of increasing the driving force by a predetermined amount compared to the reduced driving force in step S20, and the reduction of the torque command correction amount in step S21 means that the corrected torque command is increased by the reduction amount again in step S20.

[0222] As described above, if it is determined during the drive force reduction control that the current vehicle state satisfies the slip suppression mitigation condition, the drive force reduction amount (torque command correction amount) is reduced by a predetermined amount, and then the process of steps S11 to S21 may be repeated again.

[0223] According to the exemplary embodiment of the present disclosure, when the process of steps S11 to S21 is repeated again, in steps S11 to S21 , the driving force control unit 21 of the control unit 20 reduces the driving force reduction amount by the set reduction amount in each control cycle.

[0224] at the same time, Figure 7 is a diagram showing the wheel slip post-compensation mode, such as Figure 7 As shown, the wheel slip post-compensation mode does not determine the process of vehicle lateral load movement having a reference value or greater by comparison with the wheel slip basic compensation mode (S12), and the process of performing feedforward uneven braking control (S13), however, only in the state where wheel slip is detected by the equivalent inertia change, one of the feedback uneven braking control and the driving force reduction control is performed, or both controls are performed simultaneously.

[0225] Compared to the wheel slip basic compensation mode, if a vehicle lateral load movement having a baseline value or greater occurs in the wheel slip post-compensation mode, all remaining processes except the process of performing feedforward uneven braking control are the same as those of the wheel slip basic compensation mode, and therefore, there is no difference between the description of all processes of the wheel slip post-compensation mode and the above description of the wheel slip basic compensation mode, so that repeated descriptions will be omitted.

[0226] As described above, although the exemplary embodiments of the present disclosure have been described in detail, the scope of the present disclosure is not limited thereto, and various changes and modifications made by those skilled in the art using the basic concept of the present disclosure defined by the appended claims are also included in the scope of the present disclosure.

Claims

1. A method for controlling wheel slip of a vehicle, the method comprising: calculating, by a control unit, an amount of lateral load movement of the vehicle from current vehicle travel information collected by the vehicle; comparing, by the control unit, the calculated lateral load movement amount of the vehicle with a first movement amount threshold; When it is determined that the calculated lateral load movement amount of the vehicle is greater than the first movement amount threshold, the control unit controls the operation of the braking device by determining that an uneven load of a predetermined level or more occurs in the vehicle when the vehicle turns so that a braking force is applied to the wheel corresponding to the inner wheel when turning; as well as When it is determined that the calculated lateral load movement amount of the vehicle is equal to or less than the first movement amount threshold, the control unit performs estimation of equivalent inertia information of a drive system, and steps subsequent to the estimation of the equivalent inertia information, estimating, by the control unit, the equivalent inertia information of the drive system based on operation information of the drive system when the vehicle is traveling, wherein the operation information of the drive system includes a torque command of a previous control cycle for a drive device configured to drive the vehicle, and a rotation speed of the drive system detected by a speed detection unit, and wherein the equivalent inertia information of the drive system includes an equivalent inertia value of the drive system, the equivalent inertia value of the drive system being calculated by a value obtained by dividing the torque command of the previous control cycle by an angular acceleration of the drive system obtained by the rotation speed of the drive system, wherein the equivalent inertia value is an equivalent inertia change amount, which is a difference between an equivalent inertia of the drive system obtained in real time and a basic equivalent inertia having a predetermined value; determining, by the control unit, from the estimated equivalent inertia information of the driving system whether slip of the driving wheel occurs; In response to determining that the drive wheel slips, determining by the control unit from left and right wheel speeds detected by sensors whether the drive wheel is in an uneven wheel slip state in which slip occurs in only one of the left and right wheels of the drive wheel; and In response to determining that the wheel is in the uneven wheel slip state, the operation of the braking device is controlled by the control unit so that a braking force is applied to the wheel where slipping occurs.

2. The vehicle wheel slip control method according to claim 1, in, The vehicle is a vehicle equipped with an open differential that distributes a driving force of a driving device configured to drive the vehicle to the left wheel and the right wheel at a ratio of 50:

50.

3. The vehicle wheel slip control method according to claim 1, in, The control unit compares the equivalent inertia change amount with a predetermined first change amount threshold value to determine that the drive wheel slips if the equivalent inertia change amount is greater than the first change amount threshold value.

4. The vehicle wheel slip control method according to claim 1, in, If the calculated lateral load movement of the vehicle is greater than the first movement threshold, the control unit controls the operation of the braking device so that the braking force is applied to the wheel corresponding to the inner wheel when turning, and then performs estimation of the equivalent inertia information of the drive system, as well as steps subsequent to the estimation of the equivalent inertia information.

5. The vehicle wheel slip control method according to claim 1, in, When the operation of the brake device is controlled so that the braking force is applied to the wheel corresponding to the inner wheel when turning, the braking force is determined by the control unit to be a value corresponding to the calculated lateral load movement amount of the vehicle.

6. The vehicle wheel slip control method according to claim 1, in, The braking force is determined by the control unit to be a value corresponding to the equivalent inertia change amount when controlling the operation of the braking device.

7. The vehicle wheel slip control method according to claim 1, in, When controlling the operation of the braking device, the control unit determines the braking force as a value corresponding to the speed difference between the wheel of the driving wheel that slips and the wheel that does not slip, and by setting the speed of the wheel of the driving wheel that does not slip as a target speed, the speed of the wheel that slips becomes a control input value, and the control input value follows the speed of the wheel that does not slip.

8. The vehicle wheel slip control method according to claim 7, in, The speed of the wheel without slipping that reflects the kinematic characteristics of the vehicle is used as the speed of the wheel without slipping of the drive wheels.

9. The vehicle wheel slip control method according to claim 1, further comprising: while applying the braking force to the wheel where slip occurs by controlling the operation of the braking device, determining by the control unit whether a current vehicle state reaches a slip suppression mitigation condition based on a lateral load shift amount of the vehicle obtained by estimated equivalent inertia information of the drive system and current vehicle travel information; as well as If the current vehicle state reaches the slip suppression mitigation condition, the operation of the braking device is controlled so that the braking force applied to the wheel where slip occurs is reduced by a predetermined amount.

10. The vehicle wheel slip control method according to claim 9, in, In determining whether the current vehicle state reaches the slip suppression mitigation condition, the value of the equivalent inertia information is an equivalent inertia change amount which is a difference between an equivalent inertia obtained in real time of the drive system and a basic equivalent inertia having a predetermined value, and If the equivalent inertia change amount is smaller than a predetermined second change amount threshold and the lateral load movement amount of the vehicle is smaller than a predetermined second movement amount threshold, the control unit determines that the current vehicle state meets the slip suppression mitigation condition.

11. The vehicle wheel slip control method according to claim 1, further comprising: If a state in which slip occurs in both the left and right wheels of the drive wheels is determined from the left and right wheel speeds detected by the sensor, the control unit performs a drive force reduction control that reduces the drive force of the drive device transmitted to the drive wheels.

12. The vehicle wheel slip control method according to claim 11, in, When the driving force reduction control is executed, the reduction amount of the driving force is determined to be a value corresponding to the equivalent inertia information, and The equivalent inertia information is an equivalent inertia change amount, and the equivalent inertia change amount is a difference between the equivalent inertia obtained in real time of the drive system and a basic equivalent inertia having a predetermined value.

13. The vehicle wheel slip control method according to claim 11, further comprising: determining, by the control unit, whether a current vehicle state reaches a slip suppression mitigation condition based on the estimated equivalent inertia information of the drive system while the control unit executes the drive force reduction control; and If the current vehicle state reaches the slip suppression mitigation condition at the time of the drive force reduction control, the drive force reduction amount mitigation control is executed by the control unit by applying the drive force reduction amount reduced by a predetermined amount.

14. The vehicle wheel slip control method according to claim 13, in, In determining whether the current vehicle state reaches the slip suppression mitigation condition, the value of the equivalent inertia information is an equivalent inertia change amount which is a difference between an equivalent inertia obtained in real time of the drive system and a basic equivalent inertia having a predetermined value, and If the equivalent inertia change is less than a predetermined second change threshold, the control unit determines that the current vehicle state reaches the slip suppression mitigation condition.

15. The vehicle wheel slip control method according to claim 11, in, The control unit compares the difference between the left wheel speed and the right wheel speed with a predetermined threshold speed difference to determine that the drive wheel is in an uneven wheel slip state in which slip occurs in only one of the left and right wheels if the difference between the left and right wheel speeds is greater than the threshold speed difference, and If the difference between the left wheel speed and the right wheel speed is equal to or smaller than the threshold speed difference, it is determined that the drive wheel is in a state where slip occurs in both the left wheel and the right wheel.

Images