Road surface recognition method, electric power steering system control method

Abstract

The present invention discloses a road surface recognition method and a control method for an electric power steering system, the method comprising: obtaining the current vehicle speed and wheel angular velocity of a vehicle; obtaining the vehicle's slip rate according to the current vehicle speed and wheel angular velocity; obtaining a road surface characteristic value according to the slip rate and a pre-constructed road surface characteristic function curve; and obtaining the road surface state of the vehicle according to the road surface characteristic value. Thus, the method can accurately identify different road surface states.

Description

Technical Field

[0001] The present invention relates to the field of vehicle technology, and in particular to a road surface recognition method, a control method for an electric power steering system, a computer-readable storage medium, a vehicle controller and a vehicle. Background Art

[0002] With the rapid development of unmanned and intelligent vehicles, EPS (Electric Power Steering) is an inevitable trend in the development of vehicle steering systems, with unprecedentedly huge market prospects. Domestic research on EPS control strategies is mainly limited to considering vehicle speed, steering wheel torque and steering wheel angle, ignoring the impact of road adhesion coefficient on EPS power characteristics.

[0003] For example, the related art proposes a method of calculating the boost gain according to the vehicle speed and the steering wheel torque to adjust the auxiliary torque of the electric power steering, calculating the value of the phase shift according to the steering wheel torque and the steering angular velocity, determining the road surface state based on the comparison of the friction coefficient threshold of the boost gain and the phase shift, and outputting a road surface determination signal. However, the boost gain calculation in this method requires an external lateral acceleration sensor, which is only a simple compensation for roads with different friction coefficients, and cannot reflect the impact of real-time road characteristics on the performance of the steering system.

[0004] Another related technology proposes to calculate the tire side slip angle and steering force through a road friction coefficient estimation unit, and estimate the road friction coefficient based on the ratio of the calculated steering force to the calculated tire side slip angle. However, the estimated road friction coefficient in this technology changes in real time, and the road surface is not identified and the correction of the power assistance is not introduced. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the first object of the present invention is to provide a road surface recognition method that can accurately recognize different road surface conditions.

[0006] A second objective of the present invention is to provide a control method for an electric power steering system.

[0007] A third object of the present invention is to provide a computer-readable storage medium.

[0008] A fourth object of the present invention is to provide a vehicle controller.

[0009] A fifth object of the present invention is to provide a vehicle.

[0010] To achieve the above-mentioned purpose, the first aspect of the present invention proposes a road surface identification method, which includes: obtaining the current vehicle speed and wheel angular velocity of the vehicle; obtaining the slip rate of the vehicle according to the current vehicle speed and the wheel angular velocity; obtaining a road surface characteristic value according to the slip rate and a pre-constructed road surface characteristic function curve; and obtaining the road surface state of the vehicle according to the road surface characteristic value.

[0011] The road surface recognition method according to the embodiment of the present invention can accurately recognize different road surface conditions.

[0012] To achieve the above-mentioned purpose, the second aspect of the embodiment of the present invention proposes a control method for an electric power steering system, the method comprising: using the road surface recognition method to obtain the road surface state of the vehicle, and using a fuzzy control algorithm to obtain a road surface adjustment gain based on the road surface state and the current speed of the vehicle; obtaining the steering wheel angle of the vehicle and the hand torque applied to the steering wheel, and obtaining a target power control parameter based on the current vehicle speed, the steering wheel angle and the hand torque; and controlling the electric power steering system based on the road surface adjustment gain and the target power control parameter.

[0013] The control method of the electric power steering system according to the embodiment of the present invention can effectively eliminate oscillations during road switching control, allowing the vehicle to adapt to different road conditions, and can also improve the safety and stability of the electric power steering system while taking into account good braking performance.

[0014] To achieve the above-mentioned purpose, the third aspect of the present invention proposes a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the road surface recognition method or the electric power steering system control method is implemented.

[0015] To achieve the above-mentioned objectives, the fourth aspect of the present invention proposes a vehicle controller, including a memory, a processor and a computer program stored in the memory. When the computer program is executed by the processor, the road surface recognition method or the electric power steering system control method is implemented.

[0016] To achieve the above-mentioned purpose, a fifth aspect of the present invention provides a vehicle, including the vehicle controller.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1is a flow chart of a road surface recognition method according to an embodiment of the present invention;

[0019] Figure 2 is a schematic diagram of a road surface characteristic-slip rate relationship curve of a specific embodiment of the present invention;

[0020] Figure 3 is a road surface adhesion coefficient-slip rate relationship curve diagram of a specific embodiment of the present invention;

[0021] Figure 4 is a flow chart of a control method of an electric power steering system according to an embodiment of the present invention;

[0022] Figure 5 is a schematic structural diagram of a vehicle controller according to an embodiment of the present invention;

[0023] Figure 6 1 is a schematic structural diagram of a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0025] The following describes the invention of the embodiments of the present invention with reference to the accompanying drawings.

[0026] Figure 1 FIG. 1 is a flow chart of a road surface recognition method according to an embodiment of the present invention. Figure 1 As shown, the road surface recognition method includes the following steps:

[0027] S101. Obtain the current vehicle speed and wheel angular velocity of the vehicle.

[0028] Specifically, the current vehicle speed V of the vehicle can be obtained through the CAN (Controller Area Network) bus. x and wheel angular velocity ω without any additional cost.

[0029] S102: Obtain the vehicle slip rate according to the current vehicle speed and wheel angular velocity.

[0030] Specifically, step S102 may include: obtaining the state of the vehicle; if the vehicle is in a braking state, obtaining the slip rate as the ratio of the difference between the current vehicle speed and the vehicle speed without ground braking to the current vehicle speed; if the vehicle is in a driving state, obtaining the slip rate as the ratio of the difference between the vehicle speed without ground braking and the current vehicle speed to the vehicle speed without ground braking; wherein the vehicle speed without ground braking is equal to the product of the wheel radius without ground braking and the wheel angular velocity.

[0031] Specifically, the vehicle can be in a braking state or a driving state. Since the tire is a nonlinear elastic body, it will slip when it is subjected to a tangential force from the road. The slip rate is usually used to quantitatively describe the degree of tire slip when the vehicle is in a braking state or a driving state. When the vehicle is in a braking state, the slip rate s is the current vehicle speed V x The difference between the vehicle speed V0 when there is no ground braking and the current vehicle speed V x When the vehicle is in driving state, the slip rate s is the difference between the vehicle speed V0 when there is no ground braking and the current vehicle speed V x The ratio of the vehicle speed V0 to the vehicle speed without ground braking. The vehicle speed V0 without ground braking is equal to the product of the wheel radius R without ground braking and the wheel angular velocity ω. Thus, the vehicle slip rate is obtained according to the vehicle state, current vehicle speed and wheel angular velocity.

[0032] S103: Obtain a road surface characteristic value according to the slip rate and a pre-constructed road surface characteristic function curve.

[0033] Specifically, step S103 may include: obtaining N road surface characteristic values ​​according to the slip rate and N pre-constructed road surface characteristic function curves, wherein the N road surface characteristic function curves correspond to N test road surfaces, and N is an integer greater than 1, wherein an integration operation is performed on the pre-constructed i-th road surface characteristic function curve according to the slip rate to obtain the corresponding i-th road surface characteristic value.

[0034] Specifically, see Figure 2 , assuming that N is 7, 7 pavement characteristic function curves are pre-constructed, and the 7 pavement characteristic function curves correspond to 7 test pavements, for example: the first test pavement (ice pavement), the second test pavement (snow pavement), the third test pavement (wet cobblestone pavement), the fourth test pavement (wet asphalt pavement), the fifth test pavement (dry cement pavement), the sixth test pavement (dry asphalt), and the seventh test pavement (dry cobblestone). The i-th pavement characteristic value is the pre-constructed i-th pavement characteristic function curve T i The integral of (s) on the interval [0, s] is Wherein, i=1, 2, ..., 6, 7 refer to 7 test road surfaces, s≥0, s is the slip rate. When the slip rate s is input for integration operation, the corresponding i-th road surface characteristic value is output, namely, the characteristic value L1(s) of the first road surface (ice road surface), the characteristic value L2(s) of the second road surface (snow road surface), the characteristic value L3(s) of the third road surface (wet cobblestone road surface), the characteristic value L4(s) of the fourth road surface (wet asphalt road surface), the characteristic value L5(s) of the fifth road surface (dry cement road surface), the characteristic value L6(s) of the sixth road surface (dry asphalt), and the characteristic value L7(s) of the seventh road surface (dry cobblestone). Thus, according to the slip rate and the pre-constructed N road surface characteristic function curves, N road surface characteristic values ​​are obtained.

[0035] S104: Obtain the road condition where the vehicle is located according to the road characteristic value.

[0036] As an example, step S104 includes steps S201-S204:

[0037] S201. Compare the minimum value among N-i+1 road surface characteristic values ​​with the i-th preset threshold, where i is an integer greater than or equal to 1 and less than or equal to N, the i-th preset threshold is obtained according to the road surface characteristic function curve of the i-th test road surface, and the i-th preset threshold is less than the i+1-th preset threshold.

[0038] In this example, for the i-th test road surface, the step of constructing the corresponding road surface characteristic function curve may include: obtaining M slip rates of the vehicle on the i-th test road surface and their corresponding lateral adhesion coefficients and longitudinal adhesion coefficients, wherein M is an integer greater than or equal to 2; performing curve fitting on the M slip rates and their corresponding lateral adhesion coefficients to obtain a lateral adhesion coefficient-slip rate curve, and performing curve fitting on the M slip rates and their corresponding longitudinal adhesion coefficients to obtain a longitudinal adhesion coefficient-slip rate curve; and obtaining the road surface characteristic function curve of the i-th test road surface according to the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve. The lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve of the i-th test road surface are weightedly superimposed to obtain the road surface characteristic function curve of the i-th test road surface.

[0039] Specifically, see Figure 3 , the lateral adhesion coefficient corresponding to M slip rates s is a nonlinear function of the M slip rates s. The M slip rates s and their corresponding lateral adhesion coefficients are curve fitted to obtain the lateral adhesion coefficient-slip rate curve, where the numerator of the function expression of the lateral adhesion coefficient-slip rate curve is the product of the curve slope k and the slip rate s, and the denominator is the P1s and P2s corresponding to each road surface. 2The sum of P1 and P2 is the lateral adhesion coefficient of each road surface. The longitudinal adhesion coefficient corresponding to the M slip rates s is also a nonlinear function of the M slip rates s, which is divided into two parts: nonlinear and linear. The nonlinear part is The linear part is the sum of -c3s and c1, where c1, c2, and c3 are the longitudinal adhesion coefficients of each road surface. The M slip rates s and their corresponding longitudinal adhesion coefficients are curve fitted to obtain the longitudinal adhesion coefficient-slip rate curve, where the function expression of the longitudinal adhesion coefficient-slip rate curve is the linear sum of the nonlinear and linear parts. Thus, the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve are obtained through the M slip rates of the vehicle on the i-th test road surface and their corresponding lateral adhesion coefficients and longitudinal adhesion coefficients.

[0040] And reference Figure 2 Since the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve are used separately, the curves of different road surfaces are similar and inconvenient to identify. The present invention proposes to perform weighted superposition on the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve of the i-th test road surface to obtain the road surface characteristic function curve T of the i-th test road surface. i (s), that is, T i (s) = w1*C1(s)+w2*C2(s), where w1 and w2 are weights, the sum of w1 and w2 is 1, and C1(s) and C2(s) are the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve of the i-th test road surface, respectively. Thus, by weighted superposition of the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve of the i-th test road surface, the significant difference in adhesion coefficients between different road surfaces can be improved, so that there are significant differences between different road surfaces, making it easier to identify road surfaces and simplifying the processing method.

[0041] It should be noted that during the steering process, the change of the road adhesion coefficient of different road surfaces has a direct impact on the steering resistance torque, which in turn affects the formulation of the EPS control strategy, and the change of the road adhesion coefficient will also directly affect the driver's road feel. Ignoring the road adhesion coefficient will cause a lack of road feel, which will seriously endanger driving safety. For the braking system, the road adhesion coefficient directly affects the adhesion of the road surface and thus determines the braking effect. For the electric power steering system, most of them use vehicle speed and steering wheel torque as important factors of EPS power-assisting characteristics, while ignoring the impact of different road adhesion coefficients on the steering system. The present invention reduces the impact of different road adhesion coefficients on the steering system by weighted superposition of the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve of the i-th test road surface.

[0042] In addition, according to the theory of automobiles, near the optimal slip ratio, the lateral force adhesion coefficient also remains at a relatively high level. Therefore, in order to study the safety and stability of steering control on the basis of ensuring good braking performance, the present invention performs an integral operation on the i-th road surface characteristic function curve according to the optimal slip ratio to obtain the corresponding characteristic threshold, and then obtains the i-th preset threshold according to the characteristic threshold.

[0043] Specifically, the steps for obtaining the i-th preset threshold include: obtaining the corresponding optimal slip ratio according to the road surface characteristic function curve of the i-th test road surface; performing an integral operation on the i-th road surface characteristic function curve according to the optimal slip ratio to obtain the corresponding characteristic threshold; and obtaining the i-th preset threshold according to the characteristic threshold.

[0044] Specifically, for the road surface characteristic function curve T i (s) of the i-th test road surface, the extreme point obtained by taking the derivative is the optimal slip ratio spi of the corresponding test road surface. Then, let the upper limit s of the integral of the i-th road surface characteristic function curve T i (s) be the optimal slip ratio spi, and perform an integral operation on the i-th road surface characteristic function curve T i (s) according to the optimal slip ratio spi to obtain the corresponding characteristic threshold L mi , that is m, where i is an integer greater than or equal to 1 and less than or equal to N. That is to say, the characteristic threshold L mi is the area enclosed by the i-th road surface characteristic function curve T i (s) before the optimal slip ratio. Finally, obtain the i-th preset threshold according to the characteristic threshold L mi .

[0045] Furthermore, compare the minimum value among the N - i + 1 road surface characteristic values with the i-th preset threshold.

[0046] Specifically, referring to Figure 2 , assuming N is 7, 7 road surface characteristic values corresponding to 7 test road surfaces are obtained, the characteristic value L1(s) of the first road surface (ice road surface), the characteristic value L2(s) of the second road surface (snow road surface), the characteristic value L3(s) of the third road surface (wet cobblestone road surface), the characteristic value L4(s) of the fourth road surface (wet asphalt road surface), the characteristic value L5(s) of the fifth road surface (dry cement road surface), the characteristic value L6(s) of the sixth road surface (dry asphalt), and the characteristic value L7(s) of the seventh road surface (dry cobblestone), and L1(s) < L2(s) < L3(s) < L4(s) < L5(s) < L6(s) < L7(s). And since the road surface characteristic value L i (s) changes with the slip ratio s, even on a road surface with a high adhesion coefficient, the road surface characteristic value L i(s) is very small, so the first road surface (icy road surface) must be identified at the beginning. As the slip rate s increases, the road surface characteristic value L i (s) also gradually increases, and it is necessary to judge in real time whether the minimum value among the seven road feature values ​​L1(s), L2(s), ..., L6(s), L7(s) is less than or equal to the i-th preset threshold, where i is 1.

[0047] S202. If the minimum value among the N-i+1 road surface characteristic values ​​is less than or equal to the i-th preset threshold, the road surface on which the vehicle is located is the i-th test road surface.

[0048] S203. If the minimum value among the N-i+1 road surface characteristic values ​​is greater than the i-th preset threshold, and i is less than N-1, the minimum value among the N-i+1 road surface characteristic values ​​is discarded, N-i+1 is updated, and the step of comparing the minimum value among the N-i+1 road surface characteristic values ​​with the i-th preset threshold is returned, that is, return to step S201.

[0049] S204. If the minimum value among the N-i+1 road surface characteristic values ​​is greater than the i-th preset threshold value, and i is equal to N-1, then the road surface on which the vehicle is located is the N-th test road surface.

[0050] Specifically, if the minimum value among L1(s), L2(s), ..., L6(s), and L7(s) is less than or equal to the first preset threshold, then the road surface on which the vehicle is located is the first test road surface (icy road surface); if the minimum value among L1(s), L2(s), ..., L6(s), and L7(s) is greater than the first preset threshold, and since N=7, i=1, and i is less than N-1 at this time, the first road surface (icy road surface) characteristic value L1(s) is discarded, and it is determined whether the minimum value among L2(s), ..., L6(s), and L7(s) is less than or equal to the second preset threshold; if the minimum value among L2(s), ..., L6(s), and L7(s) is greater than the first preset threshold, then the first road surface (icy road surface) characteristic value L1(s) is discarded, and it is determined whether the minimum value among L2(s), ..., L6(s), and L7(s) is less than or equal to the second preset threshold; If the value is less than or equal to the second preset threshold, the road surface on which the vehicle is located is the second road surface (snow road surface); if the minimum value among L2(s), ..., L6(s), and L7(s) is greater than the second preset threshold, and since N=7, i=2, and i is less than N-1 at this time, the second road surface (snow road surface) characteristic value L2(s) is discarded, and it is determined whether the minimum value among L3(s), ..., L6(s), and L7(s) is less than or equal to the third preset threshold; if the minimum value among L3(s), ..., L6(s), and L7(s) is less than or equal to the third preset threshold, the road surface on which the vehicle is located is the third road surface (wet cobblestone road surface); if L3(s), ..., L6(s), L7(s) is greater than the third preset threshold, and since at this time N=7, i=3, i is less than N-1, the third road surface (wet cobblestone road surface) characteristic value L3(s) is discarded, and it is determined whether the minimum value of L4(s), L5(s), L6(s), L7(s) is less than or equal to the fourth preset threshold; if the minimum value of L4(s), L5(s), L6(s), L7(s) is less than or equal to the fourth preset threshold, the road surface on which the vehicle is located is the fourth road surface (wet asphalt road surface), if the minimum value of L4(s), L5(s), L6(s), L7(s) is greater than the fourth preset threshold, and since at this time N=7, i=4, i is less than N-1, the fourth road surface (wet asphalt road surface) characteristic value L4(s) is discarded, and it is determined whether the minimum value of L5(s), L6(s), L7(s) is less than or equal to the fourth preset threshold. is equal to the 5th preset threshold; if the minimum value among L5(s), L6(s), and L7(s) is less than or equal to the 5th preset threshold, the road surface on which the vehicle is located is the 5th road surface (dry cement road surface); if the minimum value among L5(s), L6(s), and L7(s) is greater than the 5th preset threshold, and since N=7, i=5, and i is less than N-1 at this time, the 5th road surface (dry cement road surface) characteristic value L5(s) is discarded, and it is determined whether the minimum value among L6(s) and L7(s) is less than or equal to the 6th preset threshold; if the minimum value among L6(s) and L7(s) is less than or equal to the 6th preset threshold, the road surface on which the vehicle is located is the 6th road surface (dry asphalt); if the minimum value among L6(s) and L7(s) is greater than the 6th preset threshold, and since N=7, i=6, and i is equal to N-1 at this time, it is obtained that the road surface on which the vehicle is located is the 7th road surface (dry cobblestone). .

[0051] To summarize, the road surface recognition method obtains the vehicle's slip rate through the current vehicle speed and wheel angular velocity, and then obtains the road surface characteristic value based on the slip rate and the pre-constructed road surface characteristic function curve. Finally, based on the road surface characteristic value, the road surface state of the vehicle is obtained, and different road surface states can be accurately identified.

[0052] It should be noted that, based on the study of the ideal hand torque of the driver under different working conditions, the ideal hand torque preferred by Chinese drivers at different vehicle speeds is obtained. The steering resistance torque on different road surfaces is different, and the required power assistance is also different. To solve the above problems, the present invention considers the impact of road surface conditions on traditional EPS to ensure the ideal hand torque of the driver on different road surfaces, and proposes the following control method for the electric power steering system. The embodiments of the present invention are described in detail below.

[0053] Figure 4 FIG. 1 is a flow chart of a control method of an electric power steering system according to an embodiment of the present invention. Figure 4 As shown, the control method of the electric power steering system includes the following steps:

[0054] S301. Obtain the road surface state of the vehicle using the road surface recognition method, and obtain the road surface adjustment gain according to the road surface state and the current speed of the vehicle using a fuzzy control algorithm.

[0055] Specifically, considering that the vehicle speed changes within a range, EPS power-assisted control mostly relies on relevant parameters obtained by looking up the vehicle speed table. In addition, the vehicle speed also affects the road adhesion coefficient, and there is a certain degree of coupling between the two. The driver's sensitivity to vehicle speed and road surface is limited, and there is no need to establish an accurate mathematical model. The fuzzy control algorithm has a simple structure, is resistant to interference, and has strong robustness. Therefore, after using the above-mentioned road recognition method to obtain the road surface state of the vehicle, a fuzzy control algorithm (i.e., a dual-input-single-output fuzzy control algorithm) is used to obtain the road surface adjustment gain according to the road surface state and the current speed of the vehicle. Specifically: first, the operator or expert experience is compiled into fuzzy rules, and the fuzzy control algorithm (i.e., a dual-input-single-output fuzzy control algorithm) is used to adjust the road surface state and the current speed V of the vehicle. x Fuzzy the road surface and the vehicle's current speed V x As the input of fuzzy rules, the fuzzy rule reasoning is completed, and the output obtained after reasoning is defuzzified to obtain the road surface adjustment gain.

[0056] S302: Obtain the steering wheel angle of the vehicle and the hand torque applied to the steering wheel, and obtain target power-assist control parameters according to the current vehicle speed, steering wheel angle and hand torque.

[0057] Specifically, the TAS sensor can be used to obtain the vehicle's steering wheel angle A and the hand torque T applied to the steering wheel, and then according to the current vehicle speed V x , steering wheel angle A and hand torque T, and obtain the target power-assist control parameters.

[0058] S303: Control the electric power steering system according to the road surface adjustment gain and the target power control parameter.

[0059] Specifically, the road surface adjustment gain is multiplied by the target power-assistance control parameter to obtain the optimized target power-assistance control parameter, and then the electric power steering system is controlled according to the optimized target power-assistance control parameter.

[0060] In summary, the control method of the electric power steering system obtains the road state of the vehicle by utilizing the above-mentioned road recognition method, and obtains the road adjustment gain according to the road state and the current speed of the vehicle by utilizing the fuzzy control algorithm, and then obtains the target power control parameters according to the current speed, steering wheel angle and hand torque, and then controls the electric power steering system according to the road adjustment gain and the target power control parameters, which can effectively eliminate the oscillation in the road switching control process, so that the vehicle can adapt to different road conditions, and can also improve the safety and stability of the electric power steering system while taking into account good braking performance.

[0061] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned road surface recognition method or the above-mentioned electric power steering system control method is implemented.

[0062] The computer-readable storage medium of an embodiment of the present invention, when the computer program corresponding to the above-mentioned road surface recognition method or the above-mentioned electric power steering system control method stored thereon is executed by a processor, can effectively eliminate oscillations in the road surface switching control process, so that the vehicle can adapt to different road conditions, and can also improve the safety and stability of the electric power steering system while taking into account good braking performance.

[0063] Figure 5 FIG. 1 is a schematic diagram of the structure of a vehicle controller according to an embodiment of the present invention. Figure 5 As shown, the vehicle controller 100 includes a memory 110, a processor 120 and a computer program 130 stored in the memory 110. When the computer program 130 is executed by the processor 120, the above-mentioned road surface recognition method or the above-mentioned electric power steering system control method is implemented.

[0064] The vehicle controller of an embodiment of the present invention, when the computer program corresponding to the above-mentioned road surface recognition method or the above-mentioned electric power steering system control method stored thereon is executed by the processor, can effectively eliminate oscillations in the road surface switching control process, so that the vehicle can adapt to different road conditions, and can also improve the safety and stability of the electric power steering system while taking into account good braking performance.

[0065] Figure 6 FIG. 1 is a schematic diagram of the structure of a vehicle according to an embodiment of the present invention. Figure 6 As shown, a vehicle 200 includes the vehicle controller 100 described above.

[0066] The vehicle of the embodiment of the present invention can effectively eliminate oscillations during road surface switching control through a vehicle controller, so that the vehicle can adapt to different road conditions. It can also improve the safety and stability of the electric power steering system while taking into account good braking performance.

[0067] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0068] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0069] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0070] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0071] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0072] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0074] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A road surface recognition method, characterized in that: The method comprises: Get the vehicle's current speed and wheel angular velocity; Obtaining a slip rate of the vehicle according to the current vehicle speed and the wheel angular velocity; Obtaining a road surface characteristic value according to the slip rate and a pre-constructed road surface characteristic function curve; Obtaining the road surface state of the vehicle according to the road surface characteristic value; The obtaining, according to the road surface characteristic value, the road surface state where the vehicle is located, comprises: The minimum value among N-i+1 road surface characteristic values ​​is compared with the i-th preset threshold, where N is an integer greater than 1, i is an integer greater than or equal to 1 and less than or equal to N, the i-th preset threshold is obtained according to the road surface characteristic function curve of the i-th test road surface, and the i-th preset threshold is less than the i+1-th preset threshold.

2. The road surface recognition method according to claim 1, characterized in that: The obtaining of the road surface characteristic value according to the slip rate and the pre-constructed road surface characteristic function curve includes: According to the slip rate and N pre-constructed road surface characteristic function curves, N road surface characteristic values ​​are obtained, wherein the N road surface characteristic function curves correspond to N test road surfaces, and N is an integer greater than 1.

3. The road surface recognition method according to claim 2, characterized in that: An integration operation is performed on the pre-constructed ith road surface characteristic function curve according to the slip rate to obtain a corresponding ith road surface characteristic value.

4. The road surface recognition method according to claim 2 or 3, characterized in that: If the minimum value among the N-i+1 road surface characteristic values ​​is less than or equal to the i-th preset threshold value, then the road surface on which the vehicle is located is the i-th test road surface; If the minimum value among the N-i+1 road surface characteristic values ​​is greater than the i-th preset threshold value, and i is less than N-1, the minimum value among the N-i+1 road surface characteristic values ​​is discarded, N-i+1 is updated, and the step of comparing the minimum value among the N-i+1 road surface characteristic values ​​with the i-th preset threshold value is returned; If the minimum value among the N-i+1 road surface characteristic values ​​is greater than the i-th preset threshold value, and i is equal to N-1, then the road surface on which the vehicle is located is the N-th test road surface.

5. The road surface recognition method according to claim 4, characterized in that: For the i-th test road surface, the steps for constructing the corresponding road surface characteristic function curve include: Obtaining M slip rates of the vehicle on the i-th test road surface and their corresponding lateral adhesion coefficients and longitudinal adhesion coefficients, where M is an integer greater than or equal to 2; Performing curve fitting on the M slip rates and their corresponding lateral adhesion coefficients to obtain a lateral adhesion coefficient-slip rate curve, and performing curve fitting on the M slip rates and their corresponding longitudinal adhesion coefficients to obtain a longitudinal adhesion coefficient-slip rate curve; A road surface characteristic function curve of the i-th test road surface is obtained according to the lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve.

6. The road surface recognition method according to claim 5, characterized in that: The lateral adhesion coefficient-slip rate curve and the longitudinal adhesion coefficient-slip rate curve of the i-th test road surface are weightedly superimposed to obtain a road surface characteristic function curve of the i-th test road surface.

7. The road surface recognition method according to claim 5, characterized in that: The step of obtaining the i-th preset threshold value includes: Obtain the corresponding optimal slip rate according to the pavement characteristic function curve of the i-th test pavement; Performing an integration operation on the i-th road surface characteristic function curve according to the optimal slip rate to obtain a corresponding characteristic threshold; The i-th preset threshold is obtained according to the characteristic threshold.

8. The road surface recognition method according to claim 1, characterized in that: The step of obtaining the slip rate of the vehicle according to the current vehicle speed and the wheel angular velocity comprises: Acquiring the state of the vehicle; If the vehicle is in a braking state, the slip rate is obtained as a ratio of the difference between the current vehicle speed and the vehicle speed without ground braking to the current vehicle speed; If the vehicle is in a driving state, the slip rate is obtained as a ratio of the difference between the vehicle speed when there is no ground braking and the current vehicle speed to the vehicle speed when there is no ground braking; The vehicle speed when there is no ground braking is equal to the product of the wheel radius when there is no ground braking and the wheel angular velocity.

9. A control method for an electric power steering system, characterized in that: The method comprises: Using the road surface recognition method according to any one of claims 1 to 8 to obtain the road surface state of the vehicle, and using a fuzzy control algorithm to obtain a road surface adjustment gain according to the road surface state and the current speed of the vehicle; Acquiring a steering wheel angle of the vehicle and a hand torque applied to the steering wheel, and obtaining a target power assist control parameter according to the current vehicle speed, the steering wheel angle and the hand torque; The electric power steering system is controlled according to the road surface adjustment gain and the target power steering control parameter.

10. The control method of the electric power steering system according to claim 9, characterized in that: The controlling the electric power steering system according to the road surface adjustment gain and the target power control parameter includes: multiplying the road surface adjustment gain by the target power-assistance control parameter to obtain an optimized target power-assistance control parameter; The electric power steering system is controlled according to the optimized target power steering control parameter.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the road surface recognition method according to any one of claims 1 to 8, or the control method of the electric power steering system according to claim 9 or 10 is implemented.

12. A vehicle controller comprising a memory, a processor and a computer program stored in the memory, characterized in that: When the computer program is executed by the processor, the road surface recognition method according to any one of claims 1 to 8, or the control method of the electric power steering system according to claim 9 or 10 is implemented.

13. A vehicle, characterized in that: Comprising a vehicle controller as claimed in claim 12.

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