Method and device for controlling a four-wheel steering system

Abstract

An independent four-wheel steering control device characterized in that it has the following: a command front wheel angle sensor (100) configured to detect a command front wheel angle (FWA); a four-wheel target angle calculator (300) configured to to calculate a turning radius (R) using a bicycle model in a state where a front wheel angle of the bicycle model is simulated as the command front wheel angle (FWA), a rotation angle (δ' cg ) in the center of gravity (cg) of the bicycle model based on a ratio (K ss ) to calculate the rotation angles of the front and rear wheels of a vehicle, calculated from a state parameter of the vehicle, and a target angle (WA FL , WA FR , WA RL , WA RR ) each of the vehicle's four wheels based on the turning radius (R) and the angle of rotation (δ'cg to calculate; and a control unit (400) that is configured to steer the four wheels using the calculated respective target angle (WA) FL , WA FR , WA RL , WA RR ) to control independently, where the turning radius (R) is a distance from a center of rotation (cr) when the vehicle turns, to a center of gravity (cg) in the bicycle model defined for the vehicle.

Description

CROSS-REFERENCE TO RELATED REGISTRATION BACKGROUND OF THE INVENTION AREA

[0001] The following description relates to a device and a method for controlling a four-wheel steering system, and in particular to a device and a method for controlling a four-wheel steering system that independently control the steering of four wheels. DISCUSSION OF RELATED STATE OF THE ART

[0002] An active front steering (AFS) system used in a vehicle is equipped with a variable steering ratio device between the steering wheel and a steering actuator. It receives the steering angle from the steering wheel, outputs a modified steering angle to the AFS actuator, and changes the steering ratio, thereby providing responsive front-wheel steering and vehicle stability. Additionally, a rear-wheel steering (RWS) system receives the steering angle, vehicle speed, and similar data, determines the rear wheel angle, and drives an RWS actuator to control the rear wheel angle, thus providing responsive rear-wheel steering and vehicle stability.

[0003] Recently, research has focused on a technology for independently controlling the steering of four wheels mounted on a vehicle, in order to ensure the vehicle's degree of freedom in driving maneuvers such as parallel driving (e.g., parallel parking), diagonal driving (e.g., diagonal parking), or turning on the spot. In two-wheel steering (or front-wheel steering), two front wheels are mechanically coupled via an Ackerman geometry model to achieve front-wheel steering, whereas in independent four-wheel steering, the angles of each wheel must be controlled independently, as they are not mechanically coupled.

[0004] While the aforementioned prior art is based on internal knowledge, NPL literature: Steering Systems for Commercial Vehicles, Piotr Dudzinski, Berlin-Heidelberg / Springer Verlag, 2005. - ISBN 3-540-22788-1 discloses a generic device and a generic method. Further prior art can be found in DE 10 2017 105 772 A1, DE 602 24 618 T2 and DE 690 05 148 T2. SUMMARY OF THE INVENTION

[0005] The object of the invention is to improve the independent steering control of four wheels mounted on a vehicle. This object is achieved by a device with the features of claim 1 and by a method with the features of claim 11. Advantageous embodiments are described in the dependent claims.

[0006] According to the invention, a four-wheel steering control device is provided for independently controlling the steering of four wheels mounted on a vehicle, wherein the device comprises a command front wheel angle sensor configured to detect a command front wheel angle, a four-wheel target angle calculator configured to calculate a turning radius using a bicycle model in a state where a front wheel angle of the bicycle model is simulated as the command front wheel angle, to calculate a rotation angle at the center of gravity of the bicycle model based on a ratio of rotation angles of the front and rear wheels of the vehicle, calculated from a state parameter of the vehicle, and to calculate a target angle of each of the four wheels based on the turning radius and the rotation angle, and a controller configured toto independently control the steering of the four wheels using the calculated respective target angle, where the turning radius is a distance from a center of rotation, when the vehicle turns, to a center of gravity in the bicycle model defined for the vehicle.

[0007] The four-wheel target angle calculator can be configured to calculate the turning radius based on a distance from a front axle to a rear axle in the bicycle model, a reference rotation angle at the center of gravity of the bicycle model when the rear wheels are in a neutral state, and the front wheel angle command.

[0008] The four-wheel target angle calculator can be configured to calculate the rotation angle at the center of gravity of the bicycle model using the ratio of the rotation angles and a reference front wheel angle and a reference rear wheel angle, respectively, which are defined by first and second parameters in the bicycle model. The first parameters can include a distance from the front axle to the center of gravity of the bicycle model and a distance from the center of gravity to the reference point in the bicycle model. The second parameters can include a distance from the rear axle to the center of gravity of the bicycle model and the distance from the center of gravity to the reference point in the bicycle model, in response to one foot of a perpendicular drawn from the center of rotation to a straight line connecting the front and rear axles in the bicycle model, which is defined as the reference point.

[0009] The rotation angle at the center of gravity of the bicycle model can be calculated as different values, depending on whether the front and rear wheels of the bicycle model are in phase or out of phase, determined by the ratio of the rotation angles.

[0010] The four-wheel target angle calculator can be configured to calculate a target angle of a left front wheel and a target angle of a right front wheel using the first and third parameters, and to calculate a target angle of a left rear wheel and a target angle of a right rear wheel using the second and third parameters, where the third parameters can include a reference distance calculated from the turning radius and the rotation angle, and a profile of the vehicle.

[0011] The four-wheel target angle calculator can be configured to calculate the target angle for each of the four wheels based on... WAFL=tan−1(a+cRr−W2)×sign(FWA) WAFR=tan−1(a+cRr+W2)×sign(FWA) WARL=tan−1(c−bRr−W2)×sign(FWA) WARR=tan−1(c−bRr+W2)×sign(FWA) where WA FL the target angle of the left front wheel, WA FR the target angle of the right front wheel, WA RL the target angle of the left rear wheel, WA RR the target angle of the right rear wheel, a the distance from the front axle to the center of gravity of the bicycle model, b the distance from the rear axle to the center of gravity of the bicycle model, c the distance from the center of gravity to the reference point in the bicycle model, R r the reference distance, W the profile, and sign(FWA) can be a sign for the command front wheel angle.

[0012] The device may include a steering mode determiner configured to select any one of a general mode, an on-the-spot turning mode, a parallel mode, and a diagonal mode as a steering mode for controlling the steering of the four wheels, wherein the four-wheel target angle calculator may be configured to calculate the turning radius, calculate the angle of rotation at the center of gravity of the bicycle model, and calculate the target angle of each of the four wheels in response to the general mode being determined by the steering mode determiner.

[0013] The four-wheel target angle calculator can be configured to calculate the target angle of each of the four wheels based on a distance from a front axle to a rear axle of the vehicle and the profile, when the on-the-spot turning mode is determined by the steering mode determiner.

[0014] The four-wheel target angle calculator can be configured to calculate an absolute target angle value of 90° for each of the four wheels, in response to the parallel mode being determined by the steering mode determiner.

[0015] The four-wheel target angle calculator can be configured to calculate the target angle of each of the four wheels as the command front wheel angle, in response to the diagonal mode being determined by the steering mode determiner.

[0016] Furthermore, according to the invention, a processor-implemented method for four-wheel steering control is provided for independently controlling the steering of four wheels mounted on a vehicle, the method comprising: acquiring a command front wheel angle at a command front wheel angle acquiring device, calculating a turning radius at a four-wheel target angle calculator using a bicycle model in a state in which a front wheel angle of the bicycle model is simulated as the command front wheel angle, calculating a rotation angle at the center of gravity of the bicycle model at the four-wheel target angle calculator based on a ratio of rotation angles of the front and rear wheels of the vehicle, which is calculated from a state parameter of the vehicle, and calculating a target angle of each of the four wheels based on the turning radius and the rotation angle in a four-wheel target angle calculator.and a control unit independently steers the four wheels using the calculated respective target angle, where the turning radius is a distance from a center of rotation, when the vehicle turns, to a center of gravity in a bicycle model defined for the vehicle.

[0017] Calculating the turning radius may involve calculating the turning radius based on the distance from a front axle to a rear axle in the bicycle model, a reference rotation angle at the center of gravity of the bicycle model when the rear wheels are in a neutral state in the bicycle model, and the command front wheel angle.

[0018] Calculating the rotation angle may involve calculating the rotation angle at the center of gravity of the bicycle model on the four-wheel target angle calculator using the ratio of the rotation angles, and a reference front wheel angle and a reference rear wheel angle, each defined by first and second parameters in the bicycle model, where the first parameters may include a distance from the front axle to the center of gravity of the bicycle model and a distance from the center of gravity to the reference point in the bicycle model, and the second parameters may include a distance from the rear axle to the center of gravity of the bicycle model and the distance from the center of gravity to the reference point in the bicycle model, in response to one foot of a perpendicular drawn from the pivot point to a straight line connecting the front and rear axles in the bicycle model, defined as a reference point.

[0019] The rotation angle at the center of gravity of the bicycle model can be calculated as different values, depending on whether the front and rear wheels of the bicycle model are in phase or out of phase, determined by the ratio of the rotation angles.

[0020] Calculating the target angle can include calculating a target angle of a left front wheel and a target angle of a right front wheel in the four-wheel target angle calculator using the first and third parameters, and calculating a target angle of a left rear wheel and a target angle of a right rear wheel using the second and third parameters, where the third parameters can include a reference distance calculated from the turning radius and the rotation angle, and a profile of the vehicle.

[0021] Calculating the target angle can involve calculating the target angle of each of the four wheels using the four-wheel target angle calculator, based on WAFL=tan−1(a+cRr−W2)×sign(FWA) WAFR=tan−1(a+cRr+W2)×sign(FWA) WARL=tan−1(c−bRr−W2)×sign(FWA) WARR=tan−1(c−bRr+W2)×sign(FWA) where WA FL the target angle of the left front wheel, WA FR the target angle of the right front wheel, WA RL the target angle of the left rear wheel, WA RR the target angle of the right rear wheel, a the distance from the front axle to the center of gravity of the bicycle model, b the distance from the rear axle to the center of gravity of the bicycle model, c the distance from the center of gravity to the reference point in the bicycle model, R r The reference distance, W the profile, and sign(FWA) can be a sign of the command front wheel angle.

[0022] The method may include determining, on a steering mode determiner, any one of a general mode, a turn-on-the-spot mode, a parallel mode and a diagonal mode as a steering mode for controlling the steering of the four wheels, wherein the calculation of the turning radius, the calculation of the rotation angle and the calculation of the target angle may include a calculation of the turning radius, a calculation of the rotation angle and a calculation of the target angle in response to the determination of the general mode by the steering mode determiner.

[0023] The procedure may include a calculation, at the four-wheel target angle calculator, of the target angle of each of the four wheels based on a distance from a front axle to a rear axle of the vehicle and the profile, in response to the fact that the on-the-spot steering mode is determined by the steering mode determiner.

[0024] The procedure can include a calculation, at the four-wheel target angle calculator, of an absolute value of the target angle of each of the four wheels as 90°, in response to the fact that the parallel mode is determined by the steering mode determiner.

[0025] The procedure can include a calculation, at the four-wheel target angle calculator, of the target angle of each of the four wheels as the command front wheel angle, in response to the diagonal mode being determined by the steering mode determiner.

[0026] Further features and aspects will become apparent from the following detailed description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram showing a four-wheel steering control device according to the present embodiment. Fig.Figure 2 is a diagram illustrating a process in which the four-wheel steering control device according to the present embodiment calculates a turning radius using a bicycle model. Fig. 3 and Fig. Figure 4 shows a process in which the four-wheel steering control device calculates a rotation angle according to the present embodiment. Fig. 5 and Fig. Figure 6 shows diagrams illustrating a process in which the four-wheel steering control device calculates target angles according to the present embodiment. Fig. Figure 7 is a diagram illustrating a process in which the four-wheel steering control device according to the present embodiment calculates target angles in an in-place rotation mode. Fig.Figure 8 is a diagram illustrating a process in which the four-wheel steering control device, according to the present embodiment, calculates target angles in a parallel mode. Fig. Figure 9 is a diagram illustrating a process in which the four-wheel steering control device, according to the present embodiment, calculates target angles in a diagonal mode. Fig. Figure 10 is a flowchart showing a method for four-wheel steering control in accordance with the present embodiment.

[0027] In the drawings and the detailed description, unless otherwise described or indicated, the same drawing numbers refer to the same elements, features, and structures. The drawings may not be to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION OF THE ILLUSTRATED EXECUTION FORMS

[0028] The following detailed description is intended to help the reader gain a comprehensive understanding of the methods, devices, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, devices, and / or systems described herein will be apparent upon understanding the disclosure of this application. For example, the sequences of operations described herein are merely examples and are not limited to those set forth herein, but may be modified as is evident from understanding the disclosure of this application, with the exception of operations that necessarily occur in a specific order.

[0029] The features described herein can be embodied in various forms and are not to be understood as being limited to the examples described herein. Rather, the examples described herein are provided merely to illustrate some of the many possible ways of implementing the methods, devices, and / or systems described herein, which will be apparent from an understanding of the disclosure of this application.

[0030] Terms such as first, second, A, B, (a), (b), or similar can be used here to describe components. Each of these designations is not used to define the nature, order, or sequence of a given component, but merely to distinguish that component from other components. For example, a first component can be called a second component, and likewise, a second component can also be called a first component.

[0031] When a component is described as "connected" or "coupled" to another component, it can be directly "connected" or "coupled" to that other component, or one or more other components can be interposed. In contrast, an element described as "directly connected to another element" or "directly coupled to another element" cannot have any other elements in between.

[0032] The singular forms "ein", "ein", and "die" also include the plural forms unless the context clearly indicates otherwise. Furthermore, it is understood that the terms "umfasst / umfasst" and / or "aufweisen / aufweist", when used here, specify the presence of certain features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or populations thereof.

[0033] Fig. Figure 1 is a block diagram illustrating a four-wheel steering control device according to the present embodiment. Fig. Figure 2 is a diagram illustrating a process in which the four-wheel steering control device according to the present embodiment calculates a turning radius using a bicycle model. Fig.3 and Fig. Figure 4 shows a process in which the four-wheel steering control device, according to the present embodiment, calculates a rotation angle. Fig. 5 and Fig. Figure 6 shows a process in which the four-wheel steering control device, according to the present embodiment, calculates the target angle. Fig. Figure 7 is a diagram illustrating a process in which the four-wheel steering control device according to the present embodiment calculates target angles in an in-place rotation mode, Fig. Figure 8 is a diagram illustrating a process in which the four-wheel steering control device according to the present embodiment calculates target angles in a parallel mode, and Fig. Figure 9 is a diagram illustrating a process in which the four-wheel steering control device according to the present embodiment calculates target angles in a diagonal mode.

[0034] Referring to Fig. 1 The four-wheel steering control device according to the present embodiment can comprise a command front wheel angle detection unit 100 (may also be referred to as “angle detector 100”), a steering mode determination unit 200 (may also be referred to as “steering mode determiner 200”), a four-wheel target angle calculation unit 300 (may also be referred to as “four-wheel target angle calculator 300”) and a control unit 400 (may also be referred to as “control 400”).

[0035] The Command Front Wheel Angle Detection Unit 100 can detect a command front wheel angle (FWA) by applying the overall gear ratio (TGR) of a variable steering ratio device to a steering angle formed by a driver steering with respect to a steering wheel or a steering angle command input from an ADAS system. The detected command front wheel angle (FWA) serves as a base parameter for calculating target angles (WA). FL , WA FR , WA RL and WA RR , which are described below.

[0036] The steering mode selector unit 200 can select any of the following steering modes—general mode, in-place rotation mode, parallel mode, and diagonal mode—for independent control of the steering of four wheels mounted on a vehicle. The steering mode can be selected by the driver actuating a predetermined switch located in the vehicle or by a CAN signal input from an external system.

[0037] The four-wheel target angle calculation unit 300 can operate, the target angles WA FL , WA FR , WA RL and WA RR the four wheels are to be determined in a differential procedure according to the steering mode determined by the steering mode determination unit 200, and the control unit 400 can control the steering of the four wheels using the respective target angles WA calculated by the four-wheel setpoint calculation unit 300. FL , WA FR , WA RL and WARR Control independently. In the present embodiment, the target angles WA correspond to FL , WA FR , WA RL and WA RR Angles formed between the longitudinal direction of the vehicle (e.g., a straight line connecting the front and rear wheels) and the wheels.

[0038] The following describes a process in which the four-wheel target angle calculation unit 300 determines the target angle WA. FL , WA FR , WA RL and WA RR calculated in each steering mode, and when the definition of terms is particularly necessary, the term "reference" is used. 1. General Mode 1-1. Turning Radius Calculation

[0039] As in Fig.As shown in Figure 2, the four-wheel target angle calculation unit 300 can calculate a turning radius R, which is a distance from the center of rotation cr when the vehicle is turning to the center of gravity cg of the bicycle model defined for the vehicle, by using the bicycle model in a state where a front wheel angle of the bicycle model is simulated as the command front wheel angle FWA. That is, in the present embodiment, a basic model for calculating the target angles WA described below is used. FL , WA FR , WA RL and WA RR the bicycle model is used in which two front wheels and two rear wheels are each modeled as one wheel.

[0040] As in Fig.As shown in Figure 2, the turning radius R can be calculated assuming that the rear wheels in the bicycle model are in a neutral state, and if a leg of a perpendicular drawn from the center of rotation cr to a straight line connects the front and rear axles in the bicycle model, as a target point P t The distance Rt between the center of rotation cr and the target point P can be defined. t expressed by the following equation 1. Rt=Ltan(abs(FWA))

[0041] In equation 1 above, L denotes the distance from the front axle to the rear axle in the bicycle model (essentially corresponding to the distance from a front axle to a rear axle of the vehicle) and FWA denotes the command front wheel angle.

[0042] Furthermore, if the rear wheels are in a neutral position in the bicycle model, a reference rotation angle δ can be determined. cgin the center of gravity cg of the bicycle model (which is referred to as a reference rotation angle to distinguish it from a rotation angle δ' cg to distinguish (which is described below) by the equation 2 below. δcg=tan−1(bRt)

[0043] In equation 2 above, b denotes the distance from the rear axle to the center of gravity cg of the bicycle model.

[0044] Based on the bicycle model in Fig. From equations 1 and 2 above, the turning radius R, which is a distance from the pivot point cr when turning the vehicle to the center of gravity cg of the bicycle model, can be expressed by equation 3 below. R=Rtcos δcg=Lcos δcg⋅tan(abs(FWA))

[0045] According to equation 3, the turning radius R can be determined based on the distance L between the front axle and the rear axle of the bicycle model, the reference turning angle δ cgThe center of gravity cg of the bicycle model, when the rear wheels are in a neutral state of the bicycle model, and the command front wheel angle FWA are calculated. 1-2. Calculation of rotation angle

[0046] The four-wheel target angle calculation unit 300 can calculate the rotation angle δ' cg in the center of gravity cg of the bicycle model (i.e., the angle between a straight line representing the center of rotation cr and a reference point P to be described below) r (connects, and a straight line that indicates the turning radius R) based on the ratio K ss Calculate the rotation angles of the front and rear wheels of the vehicle (hereinafter referred to as the rotation angle ratio), which is calculated from vehicle condition parameters.

[0047] First, the angle of rotation ratio K ss a ratio between a front wheel angle δ f and a rear wheel angle δ rin the bicycle model and can be expressed by equation 4 below. Kss=δrδf

[0048] The angle ratio K ss It can be calculated that a slip angle is 0 at a given vehicle speed, and can be expressed by Equation 5 below using the vehicle condition parameters shown in Table 1. In Table 1, a vehicle speed can be detected by a vehicle speed sensor, and a vehicle mass, yaw moment of inertia, front axle-to-center distance cg, rear axle-to-center distance cg, front cornering coefficient, and rear cornering coefficient can be predefined in the four-wheel target angle calculation unit 300. Table 1 V Vehicle speed M Vehicle mass I Yaw moment of inertia Lf Distance from front axle to center of gravity Lr Distance from rear axle to center of gravity Cf. Front cornering coefficient Cr Rear cornering coefficient KssBG−FCFD−BH where B=CrLr−CfLfmV2−1 C=CfmV D=CrmV F=−(CfLf2+CrLr2IV) G=CfLfI H=−CrLrI

[0049] If the rotation angle ratio K ss The four-wheel target angle calculation unit 300 is determined based on the rotation angle ratio K. ss , whether the front and rear wheels of the bicycle model are in phase or out of phase. That is, if the rotation angle ratio K ss If the angle of rotation is greater than 0, the four-wheel target angle calculation unit 300 determines that the front wheels and the rear wheels are in phase (steering directions of the front wheels and the rear wheels are essentially the same), and if the rotation angle ratio K ss If the value is less than 0, the four-wheel target angle calculation unit 300 determines that the front wheels and the rear wheels are out of phase (steering directions of the front wheels and the rear wheels are opposite).

[0050] The four-wheel target angle calculation unit 300 can calculate a reference front wheel angle δ. fand a reference rear wheel angle δ r The first and second parameters are defined in the bicycle model. If the base of the perpendicular line drawn from the center of rotation cr to the straight line connecting the front and rear axles in the bicycle model is used as a reference point P... r The first parameters can be defined as a distance a from the front axle to the center of gravity cg of the bicycle model and a distance c from the center of gravity to the reference point P. r in the bicycle model, and the second parameters can be a distance b from the rear axle to the center of gravity of the bicycle model and the distance c from the center of gravity cg to the reference point P. r in the bicycle model.

[0051] Fig. Figure 3 shows an example of a process for calculating the angle of rotation δ' cg , when the front and rear wheels of the bicycle model are in phase. With reference to Fig.3. The aforementioned reference front wheel angle δ can be used. f and the reference rear wheel angle 8, which is determined by the first parameters a and c and the second parameters b and c according to equation 6 below. δf=tan−1(a+cRr), δr=tan−1(c−bRr)

[0052] In equation 6 above, R denotes r a reference distance to be described below and is not considered a direct factor for calculating the rotation angle δ' cg considered, since it is used in the calculation of the rotation angle δ' cg is removed according to equation 8 below.

[0053] With reference to Fig. 3. c of the above equation 6 can be expressed by the following equation 7. c=R⋅sin δcg'

[0054] In equation 7 above, R represents a turning radius and δ' cg stands for a rotation angle to be calculated.

[0055] If the above equation 6 is substituted into the above equation 4, a relational expression such as the following equation 8 can be derived. Kss=δrδf=tan−1(c−bRr)tan−1(a+cRr)≈c−bRra+cRr=c−ba+c

[0056] If the above equation 7 is substituted into the above equation 8, the rotation angle δ' can be determined. cg expressed by the following equation 9. δcg'=sin−1(b+aKssR(1−Kss))

[0057] Fig. Figure 4 shows an example of a process for calculating the angle of rotation δ' cg , when the front and rear wheels of the bicycle model are in opposite phase. Equations 6 to 9 above are applied analogously to the case of opposite phase in Fig. 4 applied. However, in the case of the opposite phase, the distance c from the center of mass cg to the reference point P rIn the bicycle model, if the distance b from the rear axle to the center of gravity cg of the bicycle model (cb<0) is smaller, the reference rear wheel angle δ r of the above equation 6 and K ss The equation above has 8 negative values, and therefore the rotation angle δ' cg According to the equation above, 9 are calculated as different values ​​in the case of same phase and opposite phase. 1-3. Target angle calculation

[0058] As described above, the first parameters are defined: the distance a from the front axle to the center of gravity of the bicycle model and the distance c from the center of gravity cg to the reference point P. r to include in the bicycle model, and the second parameters are defined: the distance b from the rear axle to the center of gravity cg of the bicycle model and the distance c from the center of gravity cg to the reference point P. rto be included in the bicycle model. Third parameters can be used as additional parameters for calculating the target angle WA. FL , WA FR , WA RL and WA RR A reference distance R can be defined and is defined. r , which is derived from the calculated turning radius R and the rotation angle δ' cg is calculated, and includes a running surface W of the vehicle.

[0059] Fig. Figure 5 shows an example where the case of the front and rear wheels of the bicycle model being in phase is extended to a four-wheeled model of a vehicle. Referring to Fig. 5 can be the reference distance R r expressed by the following equation 10. Rr=R⋅cos δcg'

[0060] In equation 10 above, R represents a turning radius and δ' cg represents a rotation angle.

[0061] If the reference distance R rAs calculated according to equation 10 above, the four-wheel target angle calculation unit 300 can determine the target angle WA. FL of the left front wheel and the target angle WA FR of the right front wheel using the first parameters a and c and the third parameter R r and calculate W, and the target angle WA RL of the left rear wheel and the target angle WA RR of the right rear wheel using the second parameters b and c and the third parameter R r and calculate W according to equation 5 above. This can be expressed by equation 11 below. WAFL=tan−1(a+cRr−W2)×sign(FWA)WAFR=tan−1(a+cRr+W2)×sign(FWA)WARL=tan−1(c−bRr−W2)×sign(FWA)WARR=tan−1(c−bRr+W2)×sign(FWA)

[0062] In equation 11 above, WA denotes FL the target angle of the left front wheel, WA FR designates the target angle WA FR of the right front wheel, WA RLdenotes the target angle of the left rear wheel, WA RR denotes the target angle of the right rear wheel, a denotes the distance from the front axle to the center of gravity cg of the bicycle model, b denotes the distance from the rear axle to the center of gravity cg of the bicycle model, c denotes the distance (equation 7 above) from the center of gravity cg to the reference point P r in the bicycle model, R r denotes the reference distance and W denotes the running surface.

[0063] Fig. Figure 6 shows an example in which the case where the front and rear wheels of the bicycle model are in opposite phase is extended to a four-wheeled model of a vehicle. Equations 10 and 11 above are also extended to the opposite phase case in the bicycle model. Fig. 6 applied. In the case of the opposite phase, however, since the distance c from the center of mass cg to the reference point P rIn the bicycle model, if the distance b from the rear axle to the center of gravity cg of the bicycle model is smaller than (cb<0), the target angles WA are FL , WA FR , WA RL and WA RR according to the above equation 11, each is calculated as different values ​​in the case of in-phase and out-of-phase. 2. In-place Turning Mode

[0064] In the present embodiment, the in-place turning mode is defined as a mode in which the front-back direction of the vehicle is changed to the longitudinal direction of the vehicle while maintaining the vehicle's center of rotation (i.e., while the vehicle remains in place).

[0065] If the in-place turning mode is determined by the steering mode determination unit 200, the four-wheel target angle calculation unit 300 can determine the respective target angles WA. FL , WA FR , WARL and WA RR Calculate the four wheels based on the distance L from the front axle to the rear axle of the vehicle and the tread area W.

[0066] Fig. Figure 7 illustrates the relationship between the respective target angles WA. FL , WA FR , WA RL and WA RR the four wheels, the distance L from the front axle to the rear axle of the vehicle, and the tread surface W in the in-place turning mode. With reference to Fig. 7 can be the respective target angles WA FL , WA FR , WA RL and WA RR The four wheels of the in-place turning mode can be expressed by the equation 12 below. WAFL=WARR=tan−1(LW)WAFR=WARL=tan−1(LW)

[0067] In equation 12, WA denotes FL the target angle of the left front wheel, WA FR designates the target angle WA FR of the right front wheel, WA RLdenotes the target angle of the left rear wheel, WA RR L denotes the target angle of the right rear wheel, L denotes the distance from the front axle to the rear axle of the vehicle, and W denotes the tread surface. 3. Parallel mode

[0068] In the present embodiment, the parallel mode is defined as a mode in which the vehicle moves in a transverse direction perpendicular to the longitudinal direction of the vehicle. Fig. Figure 8 illustrates the arrangement of the four wheels in parallel mode. Referring to Fig. 8. The four-wheel target angle calculation unit 300 can provide the absolute values ​​of the respective target angles WA. FL , WA FR , WA RL and WA RR Calculate the four wheels as 90° (i.e., |WA). FL |=|WA FR |=|WA RL |=|WA RR |=90°). 4. Diagonal mode

[0069] In the present embodiment, the diagonal mode is defined as a mode in which the vehicle moves in a diagonal direction. Fig. Figure 9 shows the arrangement of the four wheels in diagonal mode. Referring to Fig. 9. The four-wheel target angle calculation unit 300 can determine the respective target angles WA. FL , WA FR , WA RL and WA RR calculate the four wheels as the command front wheel angle FWA, which is detected by the command front wheel angle detection unit 100.

[0070] Fig. Figure 10 is a flowchart illustrating a method for four-wheel steering control according to the present embodiment. The four-wheel steering control method of the present embodiment is described with reference to Fig.As described in section 10, a detailed description for parts that overlap with the above content is omitted, and mainly a time-series configuration is described.

[0071] First, the steering mode determination unit 200 selects one of the general mode, the in-place turning mode, the parallel mode and the diagonal mode as a steering mode for controlling the steering of the four wheels mounted on the vehicle according to a driver actuation of a predetermined switch present in the vehicle or a CAN signal input from an external system (S100).

[0072] In step S100, when the general mode is determined to be the steering mode, step S200 is started, and the command front wheel angle sensing unit 100 senses the command front wheel angle FWA (S210).

[0073] The four-wheel target angle calculation unit 300 then calculates the turning radius R, which is a distance from the center of rotation cr when turning the vehicle to the center of gravity cg of the bicycle model defined for the vehicle, using the bicycle model in a state where the front wheel angle of the bicycle model is simulated as the command front wheel angle FWA (S220). In step S220, the four-wheel target angle calculation unit 300 calculates the turning radius R based on the distance L from the front axle to the rear axle in the bicycle model and the reference rotation angle δ. cg in the center of gravity cg of the bicycle model when the rear wheels are in a neutral state in the bicycle model, and the command front wheel angle FWA.

[0074] The four-wheel target angle calculation unit 300 then calculates the rotation angle δ' cg in the center of gravity cg of the bicycle model based on the ratio K ssthe rotation angle of the front and rear wheels of the vehicle calculated from the vehicle condition parameters (S230).

[0075] In step S230, the four-wheel target angle calculation unit 300 calculates the rotation angle δ' cg in the center of gravity cg of the bicycle model using the reference front wheel angle δ f and the reference rear wheel angle δ r , which are each determined by the first and second parameters in the bicycle model, and the rotation angle ratio K ss In such a case, if the foot of the vertical, drawn from the center of rotation cr to the straight line connecting the front and rear axles in the bicycle model, is used as the reference point P r The first parameters are defined: the distance a from the front axle to the center of gravity cg of the bicycle model and the distance c from the center of gravity cg to the reference point P. rto include in the bicycle model, and the second parameters are defined: the distance b from the rear axle to the center of gravity cg of the bicycle model and the distance c from the center of gravity cg to the reference point P. r to include in the bicycle model. Accordingly, the rotation angle δ' cg calculated using equations 4 to 9 above and calculated as different values ​​depending on whether the front and rear wheels of the bicycle model are in phase or out of phase, determined by the rotation angle ratio K ss .

[0076] After step S230, the four-wheel target angle calculation unit 300 calculates the target angles WA. FL , WA FR , WA RL and WA RR of the four wheels based on the turning radius R calculated in step S220 and the rotation angle δ' calculated in step S230 (S240). cg .

[0077] In step S240, the four-wheel target angle calculation unit 300 calculates the target angle WA. FL of the left front wheel and the target angle WA FR of the right front wheel using the first and third parameters, and calculates the target angle WA RL of the left rear wheel and the target angle WA RR of the right rear wheel using the second and third parameters. The third parameters are defined from the turning radius R and the rotation angle δ' cg calculated reference distance R r and to include the vehicle's running surface W. Accordingly, the four-wheel target angle calculation unit 300 calculates the respective target angles WA in step S240. FL , WA FR , WA RL and WA RR of the four wheels according to the above equation 11.

[0078] Meanwhile, in step S100, when the on-site turning mode is determined as the steering mode, the four-wheel target angle calculation unit 300 calculates the respective target angles WA. FL , WA FR , WA RL , and WA RR the four wheels based on the distance L from the front axle to the rear axle of the vehicle and the tread surface W (S300).

[0079] Furthermore, in step S100, when parallel mode is selected as the steering mode, the four-wheel target angle calculation unit 300 calculates the absolute values ​​of the respective target angles WA. FL , WA FR , WA RL , and WA RR the four wheels as 90° (S400).

[0080] Furthermore, in step S100, if the diagonal mode is determined to be the steering mode, step S500 is started and the command front wheel angle detection unit 100 detects the command front wheel angle FWA (S510), and the four-wheel target angle calculation unit 300 calculates the respective target angles WA. FL , WA FR , WA RL , and WA RR of the four wheels as the command front wheel angle FWA (S520) recorded in step S510.

[0081] If the respective target angles WA FL , WA FR , WA RL , and WA RR The steering angles of the four wheels are calculated by step S200, step S300, step S400 or step S500, and the control unit 400 independently controls the steering of the four wheels using the calculated respective target angles WA. FL , WA FR , WA RL , and WA RR (S600).

[0082] According to one aspect of the present disclosure, a steering mechanism is proposed that is capable of independently controlling the steering of four wheels. Therefore, it is possible to provide a vehicle drive control mechanism capable of minimizing vehicle slip while maintaining essentially the same turning radius as two-wheel steering. Since not only front-wheel steering but also rear-wheel steering is taken into account, it is also possible to reduce the lateral slip angle compared to prior art front-wheel steering, thereby improving driving stability. Furthermore, independent four-wheel steering enables special driving maneuvers such as parallel driving, diagonal driving, and turning on the spot, which are not possible with two-wheel steering.

[0083] As described above, there is a device and method for four-wheel steering control which uses a control mechanism capable of minimizing the slippage of a vehicle while having essentially the same turning radius as a two-wheel steering system and independently controlling the steering of four wheels.

[0084] As described above, a steering mechanism is proposed that is capable of independently controlling the steering of four wheels. Therefore, it is possible to provide a vehicle drive control mechanism that can minimize vehicle slip while maintaining essentially the same turning radius as two-wheel steering. Since not only front-wheel steering but also rear-wheel steering is taken into account, it is also possible to reduce the lateral slip angle compared to prior art front-wheel steering, thereby improving driving stability. Furthermore, independent four-wheel steering enables special driving maneuvers such as parallel driving, diagonal driving, and turning on the spot, which are impossible with two-wheel steering.

[0085] The Angle Detection Unit 100, the Angle Sensor 100, the Steering Mode Determination Unit 200, the Steering Mode Determiner 200, the Four-Wheel Target Angle Calculation Unit 300, the Four-Wheel Target Angle Calculator 300, the Control Unit 400, the Controller 400, and other devices, equipment, units, modules, and components described herein are implemented by hardware components. Examples of hardware components that may be used to perform the operations described in this application include controllers, sensors, generators, drivers, memory, comparators, arithmetic logic units, adders, subtractors, multipliers, dividers, integrators, and any other electronic components configured to perform the operations described in this application.In other examples, one or more of the hardware components that perform the operations described in this application are implemented by computer hardware, such as one or more processors or computers. A processor or computer can be implemented by one or more processing elements, such as an array of logic gates, a controller and an arithmetic logic unit, a digital signal processor, a microcomputer, a programmable logic controller, a field-programmable gate array, a programmable logic array, a microprocessor, or any other device or combination of devices configured to respond to instructions and execute them in a specific manner to achieve a desired result.In one example, a processor or computer includes or is connected to one or more memories in which instructions or software are stored for execution by the processor or computer. Hardware components implemented by a processor or computer can execute instructions or software, such as an operating system (OS) and one or more software applications that run on the OS to perform the operations described in that application. In response to the execution of the instructions or software, the hardware components can also access, manipulate, process, create, and store data.For the sake of simplicity, the singular term "processor" or "computer" may be used in the description of the examples described in this application, but in other examples, multiple processors or computers may be used, or a processor or computer may contain multiple processing elements or multiple types of processing elements, or both. For example, a single hardware component or two or more hardware components may be implemented by a single processor or two or more processors, or by a processor and a controller. One or more hardware components may be implemented by one or more processors or by a processor and a controller, and one or more other hardware components may be implemented by one or more other processors or by another processor and another controller.One or more processors, or a processor and a controller, can implement a single hardware component or two or more hardware components. A hardware component can have one or more different processing configurations, e.g.,a single processor, independent processors, parallel processors, single-instruction single-data (SISD) multiprocessing, single-instruction multiple-data (SIMD) multiprocessing, multiple-instruction single-data (MISD) multiprocessing, multiple-instruction multiple-data (MIMD) multiprocessing, a controller and an arithmetic logic unit (ALU), a DSP, a microcomputer, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic unit (PLU), a central processing unit (CPU), a graphics processing unit (GPU), a neural processing unit (NPU), or any other device capable of responding to instructions and executing them in a specific manner.

[0086] In one example, the processor includes a communication device such as a computer, a mobile phone, a portable / personal digital assistant (PDA), and other devices that facilitate the communication of information between end users.

[0087] The procedures that perform the operations described in this application are executed by computer hardware, such as one or more processors or computers implemented as described above, which execute instructions or software to perform the operations described in this application. For example, a single operation or two or more operations may be performed by a single processor, two or more processors, or a processor and a controller. One or more operations may be performed by one or more processors or a processor and a controller, and one or more other operations may be performed by one or more other processors or another processor and another controller.One or more processors, or a processor and a control unit, can perform a single operation or two or more operations.

[0088] The software may contain a computer program, code, instruction, or a combination thereof, to instruct or configure the processing device, independently or uniformly, to operate as desired. Software and data may be permanently or temporarily embodied in any type of machine, component, physical or pseudo-device, computer storage medium or device, or in a propagating signal wave capable of delivering instructions or data to, or being interpreted by, the processing device. The software may also be distributed across networked computer systems, such that the software is stored and executed in a distributed manner. The software and data may be stored on one or more non-transient, computer-readable recording media.

[0089] The instructions or software for controlling a processor or computer to implement the hardware components and perform the procedures described above are written as computer programs, code segments, instructions, or any combination thereof, to instruct or configure the processor or computer, individually or collectively, to operate as a machine or specialized computer to perform the operations carried out by the hardware components and the procedures described above. For example, the instructions or software include machine code that is executed directly by the processor or computer, such as machine code generated by a compiler.In one example, the instructions or software comprise at least one of the following: an applet, a dynamic link library (DLL), middleware, firmware, a device driver, or an application program containing the method for controlling four-wheel steering to independently control the steering of four wheels mounted on a vehicle. In another example, the instructions or software comprise higher-level code that is executed by the processor or computer using an interpreter. Ordinary programmers can readily write the instructions or software based on the block diagrams and flowcharts shown in the drawings and the corresponding descriptions in the specification, which disclose algorithms for performing the operations carried out by the hardware components and procedures, as described above.

[0090] The instructions or software for controlling a processor or computer to implement the hardware components and to carry out the procedures described above, as well as all associated data, data files, and data structures, are recorded, stored, or fixed in or on one or more non-transient, computer-readable storage media. Examples of non-transient, computer-readable storage media include read-only memory (ROM), programmable random-access memory (PROM), electrically erasable programmable random-access memory (EEPROM), random-access memory (RAM), magnetic RAM (MRAM), spin-transfer-torque (STT) MRAM, static random-access memory (SRAM), thyristor RAM (TRAM), zero-capacitor RAM (ZRAM), twin-transistor RAM (TTRAM), conductive bridging RAM (CBRAM), ferroelectric RAM (FeRAM), phase-change RAM (PRAM), resistive RAM (RRAM), nanotube RRAM, and polymer RAM (PoRAM).Nano-floating-gate memory (NFGM), holographic memory, molecular electronic storage device, insulator-resistive variable memory, dynamic random-access memory (DRAM), static random-access memory (SRAM), flash memory, non-volatile memory, CD-ROMs, CD-Rs, CD+Rs, CD-RWs, CD+RWs, DVD-ROMs, DVD-Rs, DVD+Rs, DVD-RWs, DVD+RWs, DVD-RAMs, BD-ROMs, BD-Rs, BD-R LTHs, BD-REs, Blu-ray or optical disk storage, hard disk drive (HDD), solid-state drive (SSD), flash memory, a card-like storage device such as a multimedia microcard or card (e.g., Secure Digital (SD) or Extreme Digital (XD)), magnetic tapes, floppy disks, magneto-optical data storage devices, magnetic tapes, floppy disks, magneto-optical data storage devices, hard disks, Solid-state drives and any other device configured to execute instructions or software and all associated data,Stores data files and data structures in a non-transitory manner and makes the instructions or software and all associated data, data files, and data structures available to a processor or computer so that the processor or computer can execute the instructions. In one example, the instructions or software and all associated data, data files, and data structures are distributed across networked computer systems so that the instructions and software and all associated data, data files, and data structures are stored, retrieved, and executed by one or more processors or computers.

[0091] While this disclosure contains specific examples, it will be evident from an understanding of the disclosure of this application that various changes in form and detail can be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be understood in a descriptive sense only and not for the purpose of limitation. Descriptions of features or aspects in each example are to be considered applicable to similar features or aspects in other examples. Suitable results may be obtained if the described techniques are carried out in a different sequence and / or if components in a described system, architecture, device, or circuit are combined in a different manner and / or replaced or supplemented by other components or their equivalents.Therefore, the scope of the disclosure is not defined by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be interpreted as being contained in the disclosure.

Claims

[1] An independent four-wheel steering control device that characterized by is that it has the following: a command front wheel angle detector (100) configured to detect a command front wheel angle (FWA); a four-wheel target angle calculator (300) configured to to calculate a turning radius (R) using a bicycle model in a state where a front wheel angle of the bicycle model is simulated as the command front wheel angle (FWA), an angle of rotation (δ' cg ) in the center of gravity (cg) of the bicycle model based on a ratio (K ss ) of rotation angles of front and rear wheels of a vehicle, calculated from a state parameter of the vehicle, and a target angle (WA FL , WA FR , WA RL , WA RR ) of each of the vehicle's four wheels based on the turning radius (R) and the angle of rotation (δ' cg) to be calculated; and a controller (400) configured to steer the four wheels using the calculated respective target angle (WA FL , WA FR , WA RL , WA RR ) independently, where the turning radius (R) is a distance from a center of rotation (cr) when the vehicle turns to a center of gravity (cg) in the bicycle model defined for the vehicle. [2] The apparatus according to claim 1, wherein the four-wheel target angle calculator (300) is further configured to calculate the turning radius (R) based on a distance (L) from a front axle to a rear axle in the bicycle model, a reference turning angle (δ cg ) in the center of gravity (cg) of the bicycle model when the rear wheels are in a neutral state in the bicycle model and the command front wheel angle (FWA). [3] The apparatus according to claim 1 or 2, wherein the four-wheel target angle calculator (300) is further configured to calculate the rotation angle (δ' cg ) in the center of gravity (cg) of the bicycle model using the ratio (K ss ) the angle of rotation and a reference front wheel angle (δ f ) and a reference rear wheel angle (δ r ) which are respectively determined by first and second parameters in the bicycle model, and the first parameters are a distance (a) from the front axle to the center of gravity (cg) of the bicycle model and a distance (c) from the center of gravity (cg) to the reference point (P r ) in the bicycle model, and the second parameters are a distance (b) from the rear axle to the center of gravity of the bicycle model and the distance (c) from the center of gravity (cg) to the reference point (P r) in the bicycle model, in response to a foot of a perpendicular drawn from the center of rotation (cr) to a straight line connecting the front and rear axles in the bicycle model being used as a reference point (P r ) is defined. [4] Device according to claim 3, wherein the angle of rotation (δ' cg ) in the center of gravity (cg) of the bicycle model is calculated as different values ​​depending on whether the front wheels and the rear wheels of the bicycle model are in phase or antiphase, determined by the ratio (K ss ) the angle of rotation. [5] The apparatus according to claim 3 or 4, wherein the four-wheel target angle calculator (300) is further configured to calculate a target angle (WA FL ) of a left front wheel and a target angle (WA FR ) of a right front wheel using the first parameters (a, c) and third parameter (R r , W) and a target angle (WA RL) of a left rear wheel and a target angle (WA RR ) of a right rear wheel using the second parameters (b, c) and the third parameters (R r , W), and where the third parameters (R r , W) one of the turning radius (R) and the angle of rotation (δ' cg ) calculated reference distance (R r ) and a tread (W) of the vehicle. [6] The apparatus of claim 5, wherein the four-wheel target angle calculator (300) is further configured to calculate the target angle (WA FL , WA FR , WA RL , WA RR ) each of the four wheels based on WAFL=tan−1(a+cRr−W2)×sign(FWA)WAFR=tan−1(a+cRr+W2)×sign(FWA)WAR=tan−1(c−bRr−W2)×sign(FWA)WARR=tan−1(c−bRr+W2)×sign(FWA) where WA FL the target angle of the left front wheel is WA FR the target angle of the right front wheel is WA RL the target angle of the left rear wheel is WA RRis the target angle of the right rear wheel, a is the distance from the front axle to the center of gravity (cg) of the bicycle model, b is the distance from the rear axle to the center of gravity (cg) of the bicycle model, c is the distance from the center of gravity (cg) to the reference point in the bicycle model, R r is the reference distance, W is the tread, and sign(FWA) is a sign of the command front wheel angle (FWA). [7] Device according to one of claims 1 to 6, further comprising: a steering mode determiner (200) configured to determine any one of a general mode, a turn-on-the-spot mode, a parallel mode, and a diagonal mode as a steering mode for controlling the steering of the four wheels, wherein the four-wheel target angle calculator (300) is further configured to calculate the turning radius (R), the angle of rotation (δ' cg ) in the center of gravity (cg) of the bicycle model and to calculate the target angle (WA FL , WAFR , WA RL , WA RR ) of each of the four wheels in response to the general mode being determined by the steering mode determiner (200). [8] The apparatus of claim 7, wherein the four-wheel target angle calculator (300) is further configured to calculate the target angle (WA FL , WA FR , WA RL , WA RR ) of each of the four wheels based on a distance (L) from a front axle to a rear axle of the vehicle and the tread (W) in response to the on-the-spot turning mode being determined by the steering mode determiner (200). [9] The apparatus according to claim 7 or 8, wherein the four-wheel target angle calculator (300) is further configured to calculate an absolute value of the target angle (WA FL , WA FR , WA RL , WA RR ) each of the four wheels as 90° in response to the parallel mode being determined by the steering mode determiner (200). [10] The apparatus according to any one of claims 7 to 9, wherein the four-wheel target angle calculator (300) is further configured to calculate the target angle (WA FL , WA FR , WA RL , WA RR ) of each of the four wheels as the command front wheel angle (FWA) in response to the diagonal mode being determined by the steering mode determiner (200). [11] Processor-controlled method for independent four-wheel steering control, the method characterized by is that it includes: detecting (S210) a command front wheel angle (FWA) at a command front wheel angle detector (100); Calculating (S220) a turning radius (R) on a four-wheel target angle calculator (300) using a bicycle model in a state where a front wheel angle of the bicycle model is simulated as the command front wheel angle (FWA); Calculating (S230) on the four-wheel target angle calculator (300) a rotation angle (δ' cg) at the center of gravity (cg) of the bicycle model based on a ratio (K ss ) of angle of rotation of front and rear wheels of a vehicle, calculated from a state parameter of the vehicle; Calculating (S240) a target angle (WA) on the four-wheel target angle calculator (300) FL , WA FR , WA RL , WA RR ) of each of the vehicle's four wheels based on the turning radius (R) and the angle of rotation (δ' cg ); and a controller (400) controls (S600) a steering of the four wheels independently of one another using the calculated respective target angle (WA FL , WA FR , WA RL , WA RR ), where the turning radius (R) is a distance from a center of rotation (cr) when the vehicle turns to a center of gravity (cg) in a bicycle model defined for the vehicle. [12] The method according to claim 11, wherein calculating (S220) the turning radius (R) comprises calculating the turning radius (R) based on the distance (L) from a front axle to a rear axle in the bicycle model, a reference turning angle (δ cg ) in the center of gravity (cg) of the bicycle model when the rear wheels are in a neutral state in the bicycle model, and the command front wheel angle (FWA). [13] Method according to claim 11 or 12, wherein the calculation (S230) of the angle of rotation (δ' cg ) calculating, on the four-wheel target angle calculator (300), the angle of rotation (δ' cg ) at the center of gravity (cg) of the bicycle model using the ratio of the rotation angles and a reference front wheel angle (δ f ) and a reference rear wheel angle (δ r ), which are respectively determined by first and second parameters in the bicycle model, and the first parameters are a distance (a) from the front axle to the center of gravity (cg) of the bicycle model and a distance (c) from the center of gravity (cg) to the reference point (P r ) in the bicycle model, and the second parameters are a distance (b) from the rear axle to the center of gravity of the bicycle model and the distance (c) from the center of gravity (cg) to the reference point (P r ) in the bicycle model, in response to a foot of a perpendicular drawn from the center of rotation (cr) to a straight line connecting the front and rear axles in the bicycle model being used as a reference point (P r ) is defined. [14] Method according to claim 13, wherein the angle of rotation (δ' cg ) in the center of gravity (cg) of the bicycle model is calculated as different values ​​depending on whether the front wheels and the rear wheels of the bicycle model are in phase or antiphase, determined by the ratio (Kss ) the angle of rotation. [15] The method according to claim 13 or 14, wherein the calculation (S240) of the target angle comprises calculating, at the four-wheel target angle calculator (300), a target angle (WA FL ) of a left front wheel and a target angle (WA FR ) of a right front wheel using the first parameters (a, c) and third parameter (R r , W) and calculating a target angle (WA RL ) of a left rear wheel and a target angle (WA RR ) of a right rear wheel using the second parameters (b, c) and the third parameters (R r , W), and wherein the third parameters (R r , W) one of the turning radius (R) and the angle of rotation (δ' cg ) calculated reference distance (R r ) and a tread (W) of the vehicle. [16] The method according to claim 15, wherein calculating (S240) the target angle comprises calculating, at the four-wheel target angle calculator (300), the target angle (WA FL , WA FR , WA RL , WA RR ) each of the four wheels includes on the basis of WAFL=tan−1(a+cRr−W2)×sign(FWA)WAFR=tan−1(a+cRr+W2)×sign(FWA)WAR=tan−1(c−bRr−W2)×sign(FWA)WARR=tan−1(c−bRr+W2)×sign(FWA) where WA FL the target angle of the left front wheel is WA FR the target angle of the right front wheel is WA RL the target angle of the left rear wheel is WA RR is the target angle of the right rear wheel, a is the distance from the front axle to the center of gravity (cg) of the bicycle model, b is the distance from the rear axle to the center of gravity (cg) of the bicycle model, c is the distance from the center of gravity (cg) to the reference point in the bicycle model, R ris the reference distance, W is the tread, and sign(FWA) is a sign of the command front wheel angle (FWA). [17] A method according to any one of claims 11 to 16, further comprising: Determining (S100), at a steering mode determiner (200), any one of a general mode, a turn-on-the-spot mode, a parallel mode, and a diagonal mode as a steering mode for controlling the steering of the four wheels, wherein the calculation (S220) of the turning radius (R), the calculation (S230) of the angle of rotation (δ' cg ) and calculating (S240) the target angle (WA FL , WA FR , WA RL , WA RR ) calculating (S220) the turning radius (R), calculating (S230) the angle of rotation (δ' cg ) and calculating (S240) the target angle (WA FL , WA FR , WA RL , WA RR ) in response to the general mode being determined by the steering mode determiner (200). [18] The method of claim 17, further comprising: Calculate (S240) the target angle (WA) on the four-wheel target angle calculator (300) FL , WA FR , WA RL , WA RR ) each of the four wheels based on a distance (L) from a front axle to a rear axle of the vehicle and the tread (W) in response to the on-the-spot turn mode being determined by the steering mode determiner (200). [19] The method of claim 17 or 18, further comprising: Calculating (S400) on the four-wheel target angle calculator (300) an absolute value of the target angle (WA FL , WA FR , WA RL , WA RR ) each of the four wheels as 90° in response to the parallel mode being determined by the steering mode determiner (200). [20] A method according to any one of claims 17 to 19, further comprising: Calculate (S520) the target angle (WA) on the four-wheel target angle calculator (300) FL, WA FR , WA RL , WA RR ) of each of the four wheels as the command front wheel angle (FWA) in response to the diagonal mode being determined by the steering mode determiner (200).

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