Lateral control method, device, electronic equipment and storage medium for four-wheel steering vehicle

Abstract

The present disclosure provides a lateral control method, device, electronic equipment and storage medium of a four-wheel steering vehicle. The lateral control method of the four-wheel steering vehicle of the present disclosure comprises: acquiring the wheelbase, current speed, current front wheel steering angle, current position information and current path information of the four-wheel steering vehicle, the current path information comprising information of a reference position corresponding to the current position on the current path and road curvature; determining a steering angle coefficient of the four-wheel steering vehicle; determining a current heading angle deviation and a road lateral deviation of the four-wheel steering vehicle according to the current position information and the reference position information of the four-wheel steering vehicle; and determining the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle at a future time according to the wheelbase, the steering angle coefficient, and the current front wheel steering angle, the current heading angle deviation, the road lateral deviation, the speed, and the road curvature corresponding to the current position of the four-wheel steering vehicle. The present disclosure can realize independent control of the lateral motion of the four-wheel steering vehicle, and has the advantages of high precision and strong robustness in a low-speed scenario.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a lateral control method and device of a four-wheel steering vehicle, an electronic device and a storage medium. BACKGROUND

[0002] Lateral control is a key control technology of an automatic driving four-wheel steering vehicle. The advantages and disadvantages of the lateral control technology affect the tracking accuracy, comfort, etc. of the four-wheel steering vehicle. The four-wheel steering vehicle has obvious improvement in comfort, stability, flexibility, etc. compared with the traditional front-wheel steering four-wheel steering vehicle. In a low-speed scene, the front and rear wheel angles of the four-wheel steering vehicle are opposite, the turning radius is reduced, and the maneuverability of the four-wheel steering vehicle is improved. In a high-speed scene, the front and rear wheel angles of the four-wheel steering vehicle are the same, and the stability of the four-wheel steering vehicle is improved.

[0003] With the development of automatic driving technology, the scenarios faced by the automatic driving four-wheel steering vehicle are also more and more complex. The maneuverability of the automatic driving four-wheel steering vehicle becomes the key to pass through narrow and complex scenes. The four-wheel steering vehicle has strong maneuverability, and therefore, the lateral control technology of the four-wheel steering vehicle is of great significance and high application value in the automatic driving field.

[0004] In the related art, the dynamics model of the four-wheel steering vehicle mainly has the following two problems: 1) the dynamics model mainly studies the motion state of the center of mass position of the four-wheel steering vehicle, and the center of mass position of the four-wheel steering vehicle changes with the change of the load, such as the number and position of passengers, which causes the change of the center of mass position; 2) the dynamics model depends on the lateral velocity of the four-wheel steering vehicle perceived by the sensor, and in a low-speed scene, the lateral velocity is easily affected by external interference, such as the four-wheel steering vehicle passing through a deceleration zone, a low signal-to-noise ratio, etc. The above two aspects will affect the lateral control accuracy of the four-wheel steering vehicle. SUMMARY

[0005] In order to solve at least one of the above technical problems, the present disclosure provides a lateral control method and device of a four-wheel steering vehicle, an electronic device and a storage medium.

[0006] According to a first aspect of the present disclosure, a lateral control method of a four-wheel steering vehicle is provided, comprising:

[0007] obtaining the wheelbase, the current speed, the current front wheel angle, the current position information and the current path information of the four-wheel steering vehicle, the current path information comprising information of a reference position corresponding to the current position on the current path and road curvature;

[0008] determining a turning angle coefficient of the four-wheel steering vehicle, the turning angle coefficient representing a proportional relationship between the front wheel angle and the rear wheel angle of the four-wheel steering vehicle;

[0009] determining a current heading angle deviation and a road lateral deviation of the four-wheel steering vehicle according to the current position information and the reference position information of the four-wheel steering vehicle;

[0010] determining a front wheel steering angle and a rear wheel steering angle of the four-wheel steering vehicle at a future time according to a wheelbase of the four-wheel steering vehicle, a steering angle coefficient, the current front wheel steering angle, the heading angle deviation, the road lateral deviation, a speed, and a road curvature corresponding to the current position of the four-wheel steering vehicle.

[0011] In some embodiments of the present disclosure, the steering angle coefficient comprises a local proportional coefficient and a global proportional coefficient, the global proportional coefficient indicating a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle in a first angle interval, and the local proportional coefficient indicating a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle in a second angle interval.

[0012] In some embodiments of the present disclosure, the first angle interval contains the second angle interval, and the second angle interval contains the current front wheel steering angle of the four-wheel steering vehicle.

[0013] In some embodiments of the present disclosure, the steering angle coefficient of the four-wheel steering vehicle is determined by linear fitting using historical motion data of the four-wheel steering vehicle, the historical motion data comprising a front wheel steering angle and a corresponding rear wheel steering angle of the four-wheel steering vehicle in a past predetermined period.

[0014] In some embodiments of the present disclosure, the front wheel steering angle of the four-wheel steering vehicle at the future time is determined by:

[0015] calculating a feedback front wheel steering angle of the four-wheel steering vehicle based on a predetermined state space equation according to the wheelbase of the four-wheel steering vehicle, the local proportional coefficient, the current front wheel steering angle, the heading angle deviation, the road lateral deviation, the speed, and the road curvature corresponding to the current position of the four-wheel steering vehicle.

[0016] determining a feedforward front wheel steering angle of the four-wheel steering vehicle according to the wheelbase of the four-wheel steering vehicle, the global proportional coefficient, and the road curvature corresponding to the current position of the four-wheel steering vehicle.

[0017] determining the front wheel steering angle of the four-wheel steering vehicle at the future time using the feedback front wheel steering angle and the feedforward front wheel steering angle of the four-wheel steering vehicle.

[0018] In some embodiments of the present disclosure, the predetermined state space equation is:

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025] wherein v represents the current speed of the four-wheel steering vehicle, L represents the wheelbase of the four-wheel steering vehicle, u represents the feedback front wheel steering angle of the four-wheel steering vehicle, δ c represents the current front wheel steering angle of the four-wheel steering vehicle, e1 represents the current lateral deviation of the four-wheel steering vehicle, e2 represents the current heading angle deviation of the four-wheel steering vehicle, represents the first order derivative of e1 with respect to time, represents the first order derivative of e2 with respect to time, k r represents the road curvature corresponding to the current position on the current path, r l represents the local proportional coefficient of the four-wheel steering vehicle.

[0026] In some embodiments of the present disclosure, the feedforward front wheel steering angle of the four-wheel steering vehicle at a future time is calculated by the following formula:

[0027]

[0028] wherein δ f represents the feedforward front wheel steering angle of the four-wheel steering vehicle, r g represents the global proportional coefficient of the four-wheel steering vehicle, L represents the wheelbase of the four-wheel steering vehicle, k r represents the road curvature corresponding to the current position on the current path.

[0029] In some embodiments of the present disclosure, the feedback front wheel steering angle of the four-wheel steering vehicle at the current time is calculated based on a predetermined state space equation by using a linear quadratic regulator or model predictive control.

[0030] In some embodiments of the present disclosure, the current position information of the four-wheel steering vehicle includes the current heading angle of the four-wheel steering vehicle; and the current heading angle deviation of the four-wheel steering vehicle is the included angle between the direction of the current heading angle of the four-wheel steering vehicle and the tangential direction of the reference position.

[0031] In some embodiments of the present disclosure, the current position information of the four-wheel steering vehicle includes the current rear axle center position of the four-wheel steering vehicle; and the current lateral deviation of the four-wheel steering vehicle is the projection length of the distance between the current rear axle center position of the four-wheel steering vehicle and the reference position in the normal direction of the reference position.

[0032] In some embodiments of this disclosure, the rear wheel steering angle of the four-wheel steering vehicle at a future time is determined based on the front wheel steering angle of the four-wheel steering vehicle at a future time and the local proportional coefficient of the four-wheel steering vehicle.

[0033] According to a second aspect of this disclosure, a lateral control device for a four-wheel steering vehicle is provided, comprising:

[0034] The acquisition unit is used to acquire the wheelbase, current speed, current front wheel angle, current position information and current path information of the four-wheel steering vehicle. The current path information includes the reference position information corresponding to the current position on the current path and the road curvature.

[0035] A coefficient determination unit is used to determine the steering angle coefficient of a four-wheel steering vehicle, wherein the steering angle coefficient represents the proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle;

[0036] The deviation determination unit is used to determine the current heading angle deviation and road lateral deviation of the four-wheel steering vehicle based on the current position information and reference position information of the four-wheel steering vehicle.

[0037] The steering angle determination unit is used to determine the front wheel angle and rear wheel angle of the four-wheel steering vehicle at a future time based on the wheelbase, steering coefficient, current front wheel steering angle, heading angle deviation, road lateral deviation, speed, and road curvature corresponding to the current position of the four-wheel steering vehicle.

[0038] According to a third aspect of this disclosure, an electronic device is provided, comprising:

[0039] The memory stores execution instructions; and,

[0040] The processor executes the execution instructions stored in the memory, causing the processor to perform the lateral control method for the four-wheel steering vehicle described above.

[0041] According to a fourth aspect of this disclosure, a readable storage medium is provided that stores execution instructions, which, when executed by a processor, are used to implement the lateral control method for the four-wheel steering vehicle described above.

[0042] The embodiments disclosed herein can predict the front wheel angle and rear wheel angle of a four-wheel steering vehicle in real time based on its current position and current path, enabling independent control of the lateral movement of the four-wheel steering vehicle. It has advantages such as high accuracy and strong robustness in low-speed scenarios. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure.

[0044] Figure 1 is a flowchart of a lateral control method of a four-wheel steering vehicle according to some embodiments of the present disclosure.

[0045] Figure 2 is an example diagram of global proportional curve and front-rear wheel angle relationship curve of a four-wheel steering vehicle in a low-speed scenario according to some embodiments of the present disclosure.

[0046] Figure 3 is an example diagram of local proportional curve and front-rear wheel angle relationship curve of a four-wheel steering vehicle in a low-speed scenario according to some embodiments of the present disclosure.

[0047] Figure 4 is a diagram of relative relationship between current position and current path of a four-wheel steering vehicle according to some embodiments of the present disclosure.

[0048] Figure 5 is a diagram of four-wheel steering model of a four-wheel steering vehicle according to some embodiments of the present disclosure.

[0049] Figure 6 is a structural schematic block diagram of a lateral control device of a four-wheel steering vehicle with a hardware implementation of a processing system according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0050] The present disclosure will be described in further detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related content, and not to limit the present disclosure. In addition, it should be noted that, for the sake of description, only parts related to the present disclosure are shown in the drawings.

[0051] It should be noted that the embodiments and features in the present disclosure can be combined with each other without conflict. The technical solutions of the present disclosure will be described in detail below with reference to the drawings and in combination with the embodiments.

[0052] Unless otherwise specified, the exemplary embodiments / examples shown will be understood to provide exemplary features of various details that can implement the technical concepts of the present disclosure in practice. Therefore, unless otherwise specified, the features of various embodiments / examples can be additionally combined, separated, interchanged and / or rearranged without departing from the technical concepts of the present disclosure.

[0053] The use of cross-hatching and / or shading in the drawings is generally used to make the boundaries and regions of adjacent components more clearly understood. As such, unless specifically stated otherwise, the presence of cross-hatching or shading in one part of a figure does not necessarily constitute a preference or requirement for a specific material, material property, dimension, ratio, commonality of components between illustrated parts, or any other characteristic, attribute, property, or the like of the components in that figure. Moreover, the size and relative sizes of parts shown in the drawings can be exaggerated or shown significantly larger or significantly smaller than actually intended for the sake of clarity and / or description. When exemplary embodiments can be practiced differently, a specific sequence of processes can be performed in an order other than described. For example, two consecutively described processes can be performed at substantially the same time or in the reverse order of the described sequence. Moreover, like reference numerals are used to denote like parts throughout the specification.

[0054] When a component is referred to as being "on" or "over" another component, "connected to" or "coupled to" another component, it can be directly on, connected, or coupled to the other component, or intervening components can be present. However, when a component is referred to as being "directly on", "directly connected to", or "directly coupled to" another component, there are no intervening components present. By the term "connected" is meant physical or electrical connection, with or without intervening components.

[0055] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms "including", "includes", "having", "has", "a", "an", "one" or "said" and variants thereof are used in either the detailed description and / or the claims, such terms are intended to be inclusive in a manner similar to the term "comprising" as an open transition term without precluding any additional or other elements. It is also noted that, as used herein, the terms "substantially", "approximately" and other similar terms are used as synonyms for "about", unless expressly specified otherwise.

[0056] Figure 1 A flowchart illustrating a lateral control method of a four-wheel steering vehicle is shown. As shown in the figure, the lateral control method of the four-wheel steering vehicle of the embodiment of the present disclosure can include the following steps: Figure 1

[0057] In step S102, the wheelbase of the four-wheel steering vehicle, the current speed, the current front wheel steering angle, the current position information, and the current path information including the information of the reference position corresponding to the current position on the current path and the road curvature are obtained. ​

[0058] Step S104, determining a turning angle coefficient of the four-wheel steering vehicle, the turning angle coefficient representing a proportional relationship between a front wheel turning angle and a rear wheel turning angle of the four-wheel steering vehicle;

[0059] Step S106, determining a current heading angle deviation and a road lateral deviation of the four-wheel steering vehicle according to current position information and reference position information of the four-wheel steering vehicle;

[0060] Step S108, determining a front wheel turning angle and a rear wheel turning angle of the four-wheel steering vehicle at a future time according to a wheelbase of the four-wheel steering vehicle, the turning angle coefficient, and the current front wheel turning angle, the heading angle deviation, the road lateral deviation, a speed, and a road curvature corresponding to the current position of the four-wheel steering vehicle.

[0061] In the embodiments of the present disclosure, the current time refers to the current time, and the future time is a time after the current time. The future time can be the next time of the current time, or the future time can be separated from the current time by a fixed time length or a specific time length.

[0062] In the embodiments of the present disclosure, the current position information of the four-wheel steering vehicle can include a current position and a current heading angle of the four-wheel steering vehicle, and both the current position and the current heading angle are based on the center of the rear axle of the four-wheel steering vehicle. For example, the current position can be the coordinates of the center of the rear axle of the four-wheel steering vehicle in a Cartesian coordinate system, which can be a two-dimensional rectangular coordinate system parallel to the ground, or a three-dimensional rectangular coordinate system with the Z-axis perpendicular to the ground and facing the sky.

[0063] In step S102, the current position information of the four-wheel steering vehicle can be obtained from a positioning module of the four-wheel steering vehicle through a control bus (for example, a CAN bus) of the four-wheel steering vehicle, the path information of the four-wheel steering vehicle can be obtained from a path planning module of the four-wheel steering vehicle through the control bus of the four-wheel steering vehicle, and the wheelbase and other parameters of the four-wheel steering vehicle can be read from the pre-stored parameters of the four-wheel steering vehicle itself.

[0064] The reference position on the current path can be flexibly selected according to actual needs. For example, the reference position can be, but is not limited to, the position of the point with the closest lateral distance between the current position of the four-wheel steering vehicle on the current path, and the point is referred to as a reference point.

[0065] In step S104, the turning angle coefficient of the four-wheel steering vehicle can be determined by offline calibration or the like. In some embodiments, the turning angle coefficient of the four-wheel steering vehicle can be determined by linear fitting using historical motion data of the four-wheel steering vehicle, and the historical motion data includes the front wheel turning angle and the corresponding rear wheel turning angle of the four-wheel steering vehicle in a predetermined period in the past.

[0066] In step S104, the steering angle coefficient can include a local proportional coefficient and a global proportional coefficient. The global proportional coefficient can indicate a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle in a first angle interval, and the local proportional coefficient can indicate a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle in a second angle interval. The first angle interval can be determined according to the upper limit of the front wheel steering angle of the four-wheel steering vehicle, the first angle interval contains the second angle interval, and the second angle interval contains the current front wheel steering angle of the four-wheel steering vehicle.

[0067] Generally, the front wheel steering of the four-wheel steering vehicle is opposite to the rear wheel steering, and the front wheel steering angle is greater than the rear wheel steering angle. For example, the upper limit of the front wheel steering angle of the four-wheel steering vehicle is generally about 30°, while the upper limit of the rear wheel steering angle of the four-wheel steering vehicle is generally 10° or less. The steering angle coefficient can represent this feature of the four-wheel steering vehicle by "numerical size" and "numerical positive and negative". For example, the steering angle coefficient can be a negative number with an absolute value less than 1, "negative number" indicating that the front wheel steering of the four-wheel steering vehicle is opposite to the rear wheel steering, and "absolute value less than 1" exactly meeting the feature that the front wheel steering angle of the four-wheel steering vehicle is greater than the rear wheel steering angle.

[0068] When the steering angle coefficient includes the local proportional coefficient and the global proportional coefficient, the local proportional coefficient and the global proportional coefficient can both be negative numbers with an absolute value less than 1.

[0069] In step S104, the real front wheel steering angle and the real rear wheel steering angle of the four-wheel steering vehicle in a certain period of time in the past can be collected to form historical motion data of the four-wheel steering vehicle, and the global proportional coefficient and the local proportional coefficient of the four-wheel steering vehicle can be determined by fitting the historical motion data using, for example, the least square method or other similar linear fitting algorithm.

[0070] The first angle interval corresponding to the global proportional coefficient can be selected as the entire angle range of the front wheel steering angle, or as a part of the angle range. For example, assuming that the upper limit of the front wheel steering angle of the four-wheel steering vehicle is 30 degrees, the first angle interval can be selected as [-30, 30], or the first angle interval can be selected as [-25, 25], [-20, 20], etc.

[0071] Figure 2 An example diagram of the global proportional curve and the front-rear wheel steering angle relationship curve in a low-speed scenario is shown. Generally, the left and right steering angles of the vehicle have symmetry, Figure 2 In the example, the global proportional curve and the front-rear wheel steering angle relationship curve are shown when the front wheel steering angle is between 0 and 30, and the rear wheel steering angle is between -4.5 and 0, by Figure 2 It can be seen that the front wheel steering angle and the rear wheel steering angle have a linear relationship in a large range, and the linear proportional coefficient (i.e., the global proportional coefficient) in the global range is basically fixed.

[0072] The local proportional coefficient can be selected in the first angle interval centered on the current front wheel steering angle of the four-wheel steering vehicle. For example, assuming that the current front wheel steering angle of the four-wheel steering vehicle is equal to δ c The interval [δ c -5, δ c +5], [δ c -10, δ c +10] can be selected as the second angle interval.

[0073] Figure 3 An example diagram of the local proportional curve and the front-rear wheel steering angle relationship curve in the low-speed scenario is shown. Given the symmetry of the left and right steering angles of the four-wheel steering vehicle, Figure 3 In the example, only the local proportional curve and the front-rear wheel steering angle relationship curve in which the front wheel steering angle is between [8, 22] and the rear wheel steering angle is between [-3, -0.5] are shown. It can be seen that Figure 3 The front wheel steering angle and the rear wheel steering angle also present a linear relationship in a local range, and the proportional coefficient (i.e., the local proportional coefficient) of the local range is basically fixed.

[0074] The global proportional coefficient can reflect the global linear relationship of the front wheel steering angle and the rear wheel steering angle in a certain range, and the local proportional coefficient can reflect the local linear relationship of the front wheel steering angle and the rear wheel steering angle near the current front wheel steering angle. Through the combination of the global proportional coefficient and the local proportional coefficient, the linear relationship of the front wheel steering angle and the rear wheel steering angle can be more accurately described, thereby improving the accuracy of the vehicle lateral control.

[0075] It should be noted that the steering angle coefficient in step S104 can only include one of the global proportional coefficient and the local proportional coefficient, which can be adjusted in real time according to different scenarios and accuracy requirements in specific applications.

[0076] In step S106, the current heading angle deviation of the four-wheel steering vehicle can be the included angle between the current heading angle direction of the four-wheel steering vehicle and the tangent direction of the reference position. The current road lateral deviation of the four-wheel steering vehicle can be the projection length of the distance between the current rear axle center position of the four-wheel steering vehicle and the reference position in the normal direction of the reference position.

[0077] Specifically, in step S106, the projection length of the distance between the current position of the four-wheel steering vehicle and the corresponding reference position in the normal direction of the reference position can be calculated, which is the current road lateral deviation of the four-wheel steering vehicle; the included angle between the current heading angle direction of the four-wheel steering vehicle and the tangent direction of the reference position can be calculated, that is, the difference between the current heading angle of the four-wheel steering vehicle and the included angle between the tangent direction of the reference position and the horizontal axis of the Cartesian coordinate system, and the included angle or the difference is the current heading angle deviation of the four-wheel steering vehicle.

[0078] Figure 4 A schematic diagram showing the relative relationship between the current position of the four-wheel steering vehicle and the current path of the four-wheel steering vehicle is shown. Figure 4 In the figure, xoy is a Cartesian coordinate system parallel to the ground, p is the current rear axle center position of the four-wheel steering vehicle, i.e. the current position of the four-wheel steering vehicle; r represents the point on the current path closest to the current position of the four-wheel steering vehicle, and the position of the point r is the reference position on the path corresponding to the current position of the four-wheel steering vehicle; τ represents the tangent direction of the point r, and the positive direction is along the forward direction of the current path; n represents the normal direction of the point r, and the positive direction points to the left side of the forward direction; e1 represents the projection of the distance between the current position of the four-wheel steering vehicle and the reference position in the normal direction of the reference point, i.e. the lateral deviation of the road in the embodiment of the present disclosure; e2 represents the included angle between the heading angle direction of the four-wheel steering vehicle and the tangent direction of the reference position, i.e. the heading angle deviation in the embodiment of the present disclosure. e1 and e2 are positive values in the case shown. Figure 2 If the current position p of the four-wheel steering vehicle is located on the right side of the tangent direction of the reference point r, e1 is negative. If the heading angle of the four-wheel steering vehicle is smaller than the angle of the tangent direction of the reference point, e2 is negative.

[0079] The feedforward front wheel angle refers to the expected front wheel steering angle, and the feedback front wheel angle represents the change amount of the front wheel steering angle determined based on the real-time state of the four-wheel steering vehicle. Both the front wheel steering angle and the rear wheel steering angle determined in step S108 can be used to control the lateral motion of the four-wheel steering vehicle. After the front wheel steering angle and the rear wheel steering angle are determined, the front wheel steering angle and the rear wheel steering angle can be provided to the actuator through a vehicle control bus (such as a CAN bus, etc.), and the actuator controls the front wheel steering of the four-wheel steering vehicle based on the front wheel steering angle and controls the rear wheel steering of the four-wheel steering vehicle based on the rear wheel steering angle, thereby achieving automatic control of the lateral motion of the four-wheel steering vehicle.

[0080] In some embodiments, in step S108, the front wheel steering angle can be determined through steps a1-a3 as follows:

[0081] Step a1: calculating the feedback front wheel steering angle of the four-wheel steering vehicle based on a predetermined state space equation according to the wheelbase of the four-wheel steering vehicle, the local proportional coefficient, and the current front wheel steering angle, the heading angle deviation, the lateral deviation of the road, the speed, and the road curvature corresponding to the current position of the four-wheel steering vehicle;

[0082] Step a2: determining the feedforward front wheel steering angle of the four-wheel steering vehicle according to the wheelbase of the four-wheel steering vehicle, the global proportional coefficient, and the road curvature corresponding to the current position of the four-wheel steering vehicle;

[0083] Step a3: determining the front wheel steering angle of the four-wheel steering vehicle at a future time by using the feedback front wheel steering angle and the feedforward front wheel steering angle of the four-wheel steering vehicle.

[0084] In some embodiments, the state space equation can be expressed as the following equations (1)-(6):

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091] In equation (1), A is a system matrix describing the real-time motion state of the four-wheel steering vehicle, B is a control matrix describing the real-time motion state of the four-wheel steering vehicle, W represents the disturbance noise of the real-time motion state of the four-wheel steering vehicle, and x is a state variable of the real-time motion state of the four-wheel steering vehicle. The state space equation can accurately describe the lateral motion state of the four-wheel steering vehicle and reflect the actual motion state of the four-wheel steering vehicle. Through equation (1), the decoupling of the lateral and longitudinal motions of the four-wheel steering vehicle is realized, and the equation can be applied to the scenario of low-speed driving of the four-wheel steering vehicle.

[0092] In equations (1)-(6), v represents the current speed of the four-wheel steering vehicle, L represents the wheelbase of the four-wheel steering vehicle, u represents the feedback front wheel steering angle of the four-wheel steering vehicle, δ c represents the current front wheel steering angle of the four-wheel steering vehicle, e1 represents the current road lateral deviation of the four-wheel steering vehicle, e2 represents the current heading angle deviation of the four-wheel steering vehicle, represents the first-order derivative of e1 with respect to time, represents the first-order derivative of e2 with respect to time, k r represents the road curvature corresponding to the current position on the current path, r l represents the local proportional coefficient of the four-wheel steering vehicle.

[0093] In step a1, the feedback front wheel steering angle of the four-wheel steering vehicle can be calculated based on the aforementioned state space equation by using, but not limited to, a linear quadratic regulator (LQR), a model predictive control (MPC), or other similar methods. It should be noted that the specific algorithm for determining the feedback front wheel steering angle based on the aforementioned state space equation is not limited in the embodiments of the present disclosure.

[0094] In some embodiments, in step a2, the feedforward front wheel steering angle of the four-wheel steering vehicle at a future time is calculated by the following equation (7):

[0095]

[0096] Where, δ f The feedforward front wheel steering angle, r, represents the angle of forward steering of a four-wheel steering vehicle. g The value represents the global proportionality coefficient for a four-wheel steering vehicle, L represents the wheelbase of the four-wheel steering vehicle, and k represents the global proportionality coefficient. r This represents the road curvature corresponding to the current position on the current path.

[0097] In step a3, the front wheel steering angle of the four-wheel steering vehicle at a future time can be equal to the sum of the current feedforward front wheel steering angle and the current feedback front wheel steering angle. That is, the front wheel steering angle at the future time is: δ f +u,δ f Let u be the feedforward front wheel angle determined in step a2, and let u be the feedback front wheel angle determined in step a1.

[0098] In step S108, the future rear wheel angle of a four-wheel steering vehicle can be determined based on the future front wheel angle. For example, if the front and rear wheels of the four-wheel steering vehicle are controlled in tandem, the future front wheel angle can be provided to the actuator, which can then calculate the future rear wheel angle. If the front and rear wheels of the four-wheel steering vehicle are controlled independently, the future rear wheel angle can be determined based on the future front wheel angle and the local proportionality coefficient of the four-wheel steering vehicle. For example, the future rear wheel angle can be the product of the future front wheel angle and the local proportionality coefficient; that is, the rear wheel angle can be equal to "(δ f +u)r l "r l This is a local scaling factor.

[0099] The principle of equation (7) and its derivation process will be explained in detail below.

[0100] See Figure 5 As shown, according to the sine theorem, the four-wheel steering model of a four-wheel steering vehicle satisfies the following equation (1):

[0101]

[0102] Equation (8) can be transformed to obtain the following equation (9):

[0103]

[0104] Where L represents the wheelbase of the four-wheel steering vehicle, P represents the instantaneous center of rotation of the four-wheel steering vehicle, v represents the velocity direction of the front wheels of the four-wheel steering vehicle, and δ f δ represents the front wheel steering angle of a four-wheel steering vehicle. rR represents the turning radius of the four-wheel steering vehicle, and K represents the curvature of the four-wheel steering vehicle, i.e. the reciprocal of the turning radius.

[0105] According to the Taylor first approximation f(x0+Δx)=f(x0)+f ′ (x0)·Δx, f ′ (x0) represents the first derivative of the function f(x) at x0. The sin(δ f +δ r ) can be expressed approximately at δ f , i.e. the following formula (10) is established:

[0106] sin(δ f +δ r )≈sin(δ f )+cos(δ f )·δ r (10)

[0107] Bringing formula (10) into formula (8), the following formula (11) can be obtained

[0108]

[0109] Because the Taylor expansion of the tangent function tan(x) at 0 can be expressed as (taking the first two terms) the following formula (12):

[0110]

[0111] Therefore, tan(δ f ) can be expressed as the following formula (13)

[0112]

[0113] Also known is δ r =r g ·δ f , and by substituting formula (11) and (13) into formula (8), the following formula (14) can be obtained:

[0114]

[0115] Formula (14) is a monomial cubic equation, and can be solved by using the solving method of cubic equations. Here, the Cardan formula is used to solve and prove that formula (14) has only one real root.

[0116] According to the Cardan formula method, the discriminant of formula (14) is the following formula (15):

[0117]

[0118] Since the change range of the front wheel steering angle is greater than that of the rear wheel steering angle, |r g <1, then Δ > 0. According to the discriminant Δ > 0 of the Cardan formula, it is known that formula (14) has only one real root. According to the Cardan formula, the real root δ of formula (14) can be solved f Satisfy formula (7).

[0119] The four-wheel steering vehicle lateral control method of the embodiment of the present disclosure can predict the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle at a future time based on the current position and the current path of the four-wheel steering vehicle in real time, and can realize independent control of the lateral motion of the four-wheel steering vehicle, and has the advantages of high precision and strong robustness in a low-speed scene. In addition, the four-wheel steering vehicle lateral control method of the embodiment of the present disclosure takes the center position of the rear axle of the vehicle as the control target instead of the center of mass position of the vehicle, and solves the problems of insufficient vehicle lateral control precision caused by factors such as inaccurate estimation of the center of mass position and low signal-to-noise ratio of the yaw rate signal.

[0120] Figure 6 is a structural schematic block diagram of a four-wheel steering vehicle lateral control device of an embodiment of the present disclosure in a hardware implementation manner using a processing system.

[0121] The device can include corresponding modules that perform each or several steps in the above flowcharts. Therefore, each or several steps in the above flowcharts can be performed by corresponding modules, and the device can include one or more of these modules. The modules can be one or more hardware modules specially configured to perform the corresponding steps, or implemented by a processor configured to perform the corresponding steps, or stored in a computer readable medium for implementation by a processor, or implemented by some combination.

[0122] The hardware structure can be implemented by a bus architecture. The bus architecture can include any number of interconnected buses and bridges, depending on the particular application of the hardware and overall design constraints. The bus 700 connects various circuits including one or more processors 800, memories 900, and / or hardware modules together. The bus 700 can also connect various other circuits 1000 such as peripheral devices, voltage regulators, power management circuits, external antennas, etc.

[0123] Bus 700 can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Component (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, this diagram uses only one connection line, but this does not imply that there is only one bus or one type of bus.

[0124] Any process or method description in the flowcharts or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this disclosure includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of this disclosure pertain. The processor performs the various methods and processes described above. For example, the method embodiments of this disclosure may be implemented as software programs tangibly contained in a machine-readable medium, such as memory. In some embodiments, part or all of the software program may be loaded and / or installed via memory and / or a communication interface. When the software program is loaded into memory and executed by the processor, one or more steps of the methods described above may be performed. Alternatively, in other embodiments, the processor may be configured to perform one of the methods described above by any other suitable means (e.g., by means of firmware).

[0125] The logic and / or steps represented in the flowchart or otherwise described herein may be specifically implemented in any readable storage medium for use by, or in conjunction with, an instruction execution system, apparatus or device (such as a computer-based system, a processor-included system or other system that can fetch and execute instructions from, an instruction execution system, apparatus or device).

[0126] For the purposes of this specification, a "read only memory" can be any apparatus that can contain, store, communicate, propagate or transport programs for use by or in connection with an instruction execution system, apparatus or device. More specific examples (a non-exhaustive list) of the read only memory include the following: an electrical connection having one or more wires (electrical apparatus), a portable computer diskette (magnetic apparatus), a random access memory (RAM), a read only memory (ROM), an erasable programmable read only memory (EPROM or Flash memory), an optical fiber device, and a portable compact disc read only memory (CDROM). In addition, a read only memory can even be paper or another suitable medium upon which the program can be printed, as the program can be electronically captured, for example by the optically scanning the paper or other medium, then electronically converted into a form which can be further processed by a computer into an electronically usable form which can be stored in the memory.

[0127] It should be understood that portions of the present disclosure can be implemented in hardware, software, or a combination thereof. In the above embodiments, a plurality of steps or methods can be implemented by software stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, and as in another embodiment, any of the following technologies known in the art or their combinations can be used: discrete logic circuitry having logic gates for implementing logic functions on data signals, application specific integrated circuits having appropriate combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), etc.

[0128] Those skilled in the art of the present technology can understand that all or part of the steps of the above-mentioned embodiments can be completed by programs instructing related hardware, and the programs can be stored in a readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiments.

[0129] In addition, each functional unit in each embodiment of the present disclosure can be integrated into one processing module, or each unit can be physically present separately, or two or more units can be integrated into one module. The above integrated module can be realized in the form of hardware or in the form of a software functional module. The integrated module, if realized in the form of a software functional module and sold or used as an independent product, can also be stored in a readable storage medium. The storage medium can be a read only memory, a magnetic disk or an optical disk, etc.

[0130] Figure 6 is a schematic diagram of a structure of a four-wheel steering vehicle lateral control device 600 according to an embodiment of the present disclosure. As shown in Figure 6 The four-wheel steering vehicle lateral control device 600 according to the present disclosure can include, as shown in

[0131] The acquisition unit 602 is configured to acquire the wheelbase of the four-wheel steering vehicle, the current speed, the current front wheel steering angle, the current position information, and the current path information, the current path information including information of a reference position corresponding to the current position on the current path and a road curvature;

[0132] The coefficient determination unit 604 is configured to determine a steering angle coefficient of the four-wheel steering vehicle, the steering angle coefficient representing a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle.

[0133] The deviation determination unit 606 is configured to determine a current heading angle deviation and a road lateral deviation of the four-wheel steering vehicle according to the current position information and the reference position information of the four-wheel steering vehicle.

[0134] The steering angle determination unit 608 is configured to determine the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle at a future time according to the wheelbase of the four-wheel steering vehicle, the steering angle coefficient, and the current front wheel steering angle, the heading angle deviation, the road lateral deviation, the speed, and the road curvature corresponding to the current position of the four-wheel steering vehicle.

[0135] Other technical details of the four-wheel steering vehicle lateral control device 600 according to the embodiments of the present disclosure can be referred to the method part described above, and will not be described herein.

[0136] The present disclosure further provides an electronic device, including a memory storing execution instructions, and a processor or other hardware module executing the execution instructions stored in the memory, so that the processor or other hardware module executes the lateral control method of the four-wheel steering vehicle.

[0137] The present disclosure further provides a readable storage medium, in which execution instructions are stored, and the execution instructions are executed by a processor to implement the lateral control method of the four-wheel steering vehicle.

[0138] In the description of the present disclosure, the description of the terms "one embodiment / way", "some embodiments / ways", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment / way or example are included in at least one embodiment / way or example of the present disclosure. In the present disclosure, the illustrative description of the above terms is not necessarily the same embodiment / way or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments / ways or examples. In addition, the person skilled in the art can combine and combine the different embodiments / ways or examples described in the present disclosure and the features of the different embodiments / ways or examples without contradiction.

[0139] Furthermore, the terms "first", "second", etc. are used herein for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly pointing to the number of technical features indicated. Thus, features defined with "first", "second" etc. can explicitly or implicitly include at least one of such features. In the description of the application, the meaning of "plurality" is at least two, for example two, three, etc., unless explicitly and specifically defined otherwise.

[0140] Those skilled in the art will understand that the above-described embodiments are merely intended to clarify the present disclosure, and are not intended to limit the scope of the present disclosure. Other changes or modifications can be made by those skilled in the art based on the above disclosure, and such changes or modifications are still within the scope of the present disclosure.

Claims

1. A lateral control method for a four-wheel steering vehicle, characterized by, The method comprises: obtaining the wheelbase, current speed, current front wheel steering angle, current position information and current path information of the four-wheel steering vehicle, wherein the current path information comprises information of a reference position corresponding to the current position on the current path and road curvature; determining a steering angle coefficient of the four-wheel steering vehicle, wherein the steering angle coefficient represents a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle; determining a current heading angle deviation and a road lateral deviation of the four-wheel steering vehicle according to the current position information and the reference position information of the four-wheel steering vehicle; determining the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle at a future time according to the wheelbase, the steering angle coefficient, the current front wheel steering angle, the heading angle deviation, the road lateral deviation, the speed, and the road curvature corresponding to the current position of the four-wheel steering vehicle; the current position information of the four-wheel steering vehicle comprises a current heading angle of the four-wheel steering vehicle; and the current heading angle deviation of the four-wheel steering vehicle is an included angle between the direction of the current heading angle of the four-wheel steering vehicle and the tangent direction of the reference position; the current position information of the four-wheel steering vehicle comprises a current rear axle center position of the four-wheel steering vehicle; and the current road lateral deviation of the four-wheel steering vehicle is a projection length of the distance between the current rear axle center position of the four-wheel steering vehicle and the reference position in the normal direction of the reference position.

2. The lateral control method for a four-wheel steering vehicle according to claim 1, characterized by, The steering angle coefficient comprises a local proportional coefficient and a global proportional coefficient, wherein the global proportional coefficient indicates a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle in a first angle interval, and the local proportional coefficient indicates a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle in a second angle interval.

3. The lateral control method for a four-wheel steering vehicle according to claim 2, characterized by The first angle interval contains the second angle interval, and the second angle interval contains the current front wheel steering angle of the four-wheel steering vehicle.

4. The lateral control method for a four-wheel steering vehicle according to claim 2, characterized by The front wheel steering angle of the four-wheel steering vehicle at the future time is determined by: calculating a feedback front wheel steering angle of the four-wheel steering vehicle based on a predetermined state space equation according to the wheelbase, the local proportional coefficient, the current front wheel steering angle, the heading angle deviation, the road lateral deviation, the speed, and the road curvature corresponding to the current position of the four-wheel steering vehicle; determining a feedforward front wheel steering angle of the four-wheel steering vehicle according to the wheelbase, the global proportional coefficient, and the road curvature corresponding to the current position of the four-wheel steering vehicle; and determining the front wheel steering angle of the four-wheel steering vehicle at the future time by using the feedback front wheel steering angle and the feedforward front wheel steering angle of the four-wheel steering vehicle.

5. The lateral control method for a four-wheel steering vehicle according to claim 4, characterized by The predetermined state space equation is: wherein, denotes the current speed of the four-wheel-steering vehicle, denotes the wheelbase of the four-wheel-steering vehicle, denotes the feedback front wheel steering angle of the four-wheel-steering vehicle, denotes the current front wheel steering angle of the four-wheel-steering vehicle, denotes the current lateral road deviation of the four-wheel-steering vehicle, denotes the current heading angle deviation of the four-wheel-steering vehicle, denotes the first order derivative with respect to time, denotes the first order derivative with respect to time, denotes the road curvature at the current position on the current path, denotes the local proportional coefficient of the four-wheel-steering vehicle.

6. The lateral control method for a four-wheel steering vehicle according to claim 4, characterized by The feedforward front wheel steering angle of the four-wheel steering vehicle at the future time is calculated by: wherein, represents a feedforward front wheel angle of a four-wheel steering vehicle, represents a global proportional coefficient of a four-wheel steering vehicle, represents a wheelbase of a four-wheel steering vehicle, represents a road curvature on a current path corresponding to a current position.

7. The lateral control method for a four-wheel steering vehicle according to claim 4, characterized by the feedback front wheel steering angle of the four-wheel steering vehicle at the current time is calculated based on the predetermined state space equation by using a linear quadratic regulator or model predictive control.

8. The lateral control method for a four-wheel steering vehicle according to claim 2, characterized by The rear wheel steering angle of the four-wheel steering vehicle at the future time is determined according to the front wheel steering angle of the four-wheel steering vehicle at the future time and the local proportional coefficient of the four-wheel steering vehicle.

9. A four-wheel steering vehicle lateral control device characterized by comprising: The method comprises: The acquisition unit is configured to acquire a wheelbase of the four-wheel steering vehicle, a current speed, a current front wheel steering angle, current position information, and current path information, wherein the current path information comprises information of a reference position corresponding to the current position on a current path and a road curvature; The coefficient determination unit is configured to determine a steering angle coefficient of the four-wheel steering vehicle, wherein the steering angle coefficient represents a proportional relationship between the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle; The deviation determination unit is configured to determine a current heading angle deviation and a road lateral deviation of the four-wheel steering vehicle according to the current position information and the reference position information of the four-wheel steering vehicle; The steering angle determination unit is configured to determine the front wheel steering angle and the rear wheel steering angle of the four-wheel steering vehicle at a future time according to the wheelbase of the four-wheel steering vehicle, the steering angle coefficient, and the current front wheel steering angle, the current heading angle deviation, the current road lateral deviation, the current speed, and the road curvature corresponding to the current position of the four-wheel steering vehicle; The current position information of the four-wheel steering vehicle comprises a current heading angle of the four-wheel steering vehicle; and the current heading angle deviation of the four-wheel steering vehicle is an included angle between a direction of the current heading angle of the four-wheel steering vehicle and a tangent direction of the reference position. The current position information of the four-wheel steering vehicle comprises a current rear axle center position of the four-wheel steering vehicle; and the current road lateral deviation of the four-wheel steering vehicle is a projection length of a distance between the current rear axle center position of the four-wheel steering vehicle and the reference position in a normal direction of the reference position.

10. An electronic device, comprising: The memory stores execution instructions; The processor executes the execution instructions stored in the memory, so that the processor executes the four-wheel steering vehicle lateral control method in any one of claims 1 to 8. The readable storage medium stores execution instructions, and the execution instructions are executed by the processor to implement the four-wheel steering vehicle lateral control method in any one of claims 1 to 8. ​ 11. A readable storage medium, characterized by, ​

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