Braking force distribution method and device based on double-layer self-adaption, vehicle and storage medium

Abstract

The invention relates to the technical field of vehicle energy recovery, and particularly discloses a braking force distribution method and device based on double-layer self-adaption, a vehicle and a storage medium, and the method comprises the steps that in response to a braking signal, the battery pack remaining capacity, a vehicle speed signal, the wheel longitudinal adhesive force, the wheel vertical force and the braking demand strength of the vehicle are obtained; the remaining electric quantity of the battery pack and the vehicle speed signal are used for entering the precondition of braking force distribution, and a real-time adhesion coefficient is determined based on a preset tire-road adhesion coefficient recognition model; based on the real-time adhesion coefficient, the wheel longitudinal adhesion force and the wheel vertical force, the optimal slip rate and the optimal adhesion coefficient of the vehicle are determined; and according to the optimal slip rate, the optimal adhesion coefficient and the braking demand strength and based on the braking force distribution model, the braking force distribution of the front and rear wheels of the vehicle is determined, the direction stability of the vehicle is effectively improved, and meanwhile, the braking energy recovery efficiency is improved to the maximum extent on the premise that the braking direction stability is met.

Description

Technical Field

[0001] The present application relates to the field of vehicle energy recovery technology, and in particular to a method, device, vehicle and storage medium based on double-layer adaptive braking force distribution. Background Art

[0002] The braking energy recovery system can greatly improve the energy efficiency of electric commercial vehicles and has a significant effect on improving the energy management and energy utilization efficiency of the entire vehicle. However, maximizing the recovery of braking energy while maintaining optimal braking performance remains a challenging problem.

[0003] In related technologies, more attention is paid to maximizing braking efficiency or regenerative energy, but the impact of the target vehicle control system on braking force distribution has not been fully considered, which means that there is still a lot of room for optimization of energy recovery. At the same time, there is still a lot of room for improvement in braking smoothness and safety on the basis of maximizing energy recovery efficiency. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a method, device, vehicle and storage medium based on a double-layer adaptive braking force distribution, which is based on an adaptive braking force distribution strategy to ensure optimal braking performance to the maximum extent, while maximizing the efficiency of braking energy recovery and reducing energy consumption.

[0005] In a first aspect, an embodiment of the present application provides a method for distributing braking force based on a double-layer adaptive braking force, comprising: In response to a brake pedal brake signal of the target vehicle, obtaining a current battery pack SOC, a vehicle speed signal, a wheel longitudinal adhesion, a wheel vertical force, and a braking demand intensity of the target vehicle; Determine whether the battery pack SOC is less than a preset power threshold, and if so, determine whether the vehicle speed signal is greater than or equal to a preset speed threshold; If yes, obtain the road information and the real-time slip rate in the current planned driving trajectory segment of the target vehicle, and determine the current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model; Determining an optimal slip ratio and an optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force; The front and rear wheel braking force distribution of the target vehicle is determined according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model.

[0006] In some examples that may be implemented, if yes, obtaining road information and a real-time slip rate in a current planned driving trajectory segment of the target vehicle, and determining the current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model, includes: Determining corresponding model parameters in the tire-road adhesion coefficient identification model according to the road information; The model parameters and the real-time slip ratio are input into the tire-road adhesion coefficient identification model, and the real-time tire-road adhesion coefficient is output, wherein the expression of the tire-road adhesion coefficient identification model is: Wherein, μ(s) represents the real-time tire-road adhesion coefficient of the tire-road, C1, C2 and C3 represent model parameters, and s represents the real-time slip rate.

[0007] In some possible examples, determining the optimal slip rate and the optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force includes: The ground adhesion coefficient is determined according to the wheel longitudinal adhesion force and the wheel vertical force, wherein the calculation expression of the ground adhesion coefficient is: In the formula, represents the ground adhesion coefficient at time t, Indicates the longitudinal adhesion of the wheel, , T represents the target vehicle wheel output torque, r represents the effective radius of the target vehicle wheel, represents the vertical force of the wheel; Determining a distribution ratio parameter of the optimal slip rate and the optimal adhesion coefficient according to the ground adhesion coefficient and the real-time tire-road adhesion coefficient; The optimal slip ratio and the optimal adhesion coefficient are determined according to the upper and lower limits of the optimal slip ratio and the optimal adhesion coefficient and the distribution ratio parameter.

[0008] In some possible examples, the determining, according to the ground adhesion coefficient and the real-time tire-road adhesion coefficient, a distribution ratio parameter of the optimal slip rate and the optimal adhesion coefficient includes: The calculation expression of the allocation ratio parameter is: In the formula, represents the upper limit of the range of the optimal adhesion coefficient at time t, Indicates the upper limit of the range of the optimal adhesion coefficient at time t.

[0009] In some possible examples, determining the optimal slip rate and the optimal adhesion coefficient according to the upper and lower limits of the optimal slip rate and the optimal adhesion coefficient and the allocation ratio parameter includes: The calculation expression of the optimal slip ratio is: s osr (t) = s up_max (t)+K s up_max (t)-K s down_max (t); The calculation expression of the optimal adhesion coefficient is: µ osr (t) = µ up_max (t)+K µ up_max (t)-K µ down_max (t); In the formula, represents the allocation ratio parameter, s up_max (t) represents the upper limit of the optimal slip ratio range at time t, s down_max (t) represents the upper limit of the optimal slip ratio at time t, µ up_max (t) represents the upper limit of the optimal adhesion coefficient at time t, µ down_max (t) represents the upper limit of the range of the optimal adhesion coefficient at time t.

[0010] In some possible examples, the front and rear wheel braking force distribution of the target vehicle is determined based on the optimal slip ratio, the optimal adhesion coefficient, and the braking demand intensity and based on a preset braking force distribution model, and the creation of the braking force distribution model includes: Determining a braking force distribution curve of the braking force distribution model based on the ideal braking force distribution curve and the ideal braking force adjustment curve; Based on the optimal adhesion coefficient, determining at least one braking intensity threshold of the braking force distribution curve, wherein the at least one braking intensity threshold comprises a first braking intensity threshold and a second braking intensity threshold, wherein the first braking intensity threshold and the second braking intensity threshold are segmentation points of the braking force distribution curve; The calculation expression of the first braking intensity threshold is: in, In the formula, represents the maximum torque of the vehicle's motor; m represents the total mass of the vehicle; R represents the vehicle's wheelbase; n represents the vehicle's transmission ratio; W represents the correction coefficient of the tire-road adhesion condition. is the positive threshold of the tire-road adhesion coefficient; is the negative threshold of the tire-road adhesion coefficient; is the optimal adhesion coefficient; The calculation expression of the second braking intensity threshold is: In the formula, is the front axle mass distribution coefficient of the vehicle; is the height of the vehicle's center of mass, R The front and rear wheelbase of the vehicle.

[0011] In some possible examples, the determining the front and rear wheel braking force distribution of the target vehicle according to the optimal slip ratio, the optimal adhesion coefficient, and the braking demand intensity and based on a preset braking force distribution model further includes: Determining a braking force distribution area on the braking force distribution curve based on the braking demand intensity and the braking intensity threshold; Based on the optimum slip ratio and the optimum adhesion coefficient, a front and rear wheel braking force distribution data value of the target vehicle in the braking force distribution area is determined.

[0012] In a second aspect, an embodiment of the present application provides a dual-layer adaptive braking force distribution device, comprising: An acquisition module is configured to obtain a current battery pack SOC, a vehicle speed signal, a wheel longitudinal adhesion, a wheel vertical force, and a braking demand intensity of the target vehicle in response to a brake signal of a brake pedal of the target vehicle; a determination module configured to determine whether the battery pack SOC is less than a preset power threshold, and if so, to determine whether the vehicle speed signal is greater than or equal to a preset speed threshold; A first determination module is configured to obtain road information and a real-time slip rate in a current planned driving trajectory segment of the target vehicle, and determine a current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model; a second determination module, configured to determine an optimal slip rate and an optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force; The third determination module is configured to determine the front and rear wheel braking force distribution of the target vehicle according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model.

[0013] In a third aspect, an embodiment of the present application provides a vehicle, including: processor; a memory for storing instructions executable by the processor; Wherein, the processor is configured to: Implement the steps of a double-layer adaptive braking force distribution method as described in any one of the embodiments of the first aspect above.

[0014] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium having computer program instructions stored thereon, characterized in that when the program instructions are executed by a processor, the steps of a method based on a double-layer adaptive braking force distribution as described in any one of the embodiments of the first aspect above are implemented.

[0015] Compared with the prior art, the technical solution provided by the above embodiments of the present application includes at least the following beneficial effects: The method of the present application firstly takes the battery pack SOC and the vehicle speed signal as the prerequisite for entering the double-layer adaptive braking force distribution strategy, so as to avoid the target vehicle from performing inefficient braking force distribution and energy recovery under the premise of high battery pack SOC or slow vehicle speed. After entering the double-layer adaptive braking force distribution strategy, the road type information, braking demand intensity and real-time slip rate in the current planned driving trajectory segment are firstly collected, and the current real-time tire-road adhesion coefficient of the target vehicle is determined through the tire-road adhesion coefficient identification model. The real-time slip rate and the real-time tire-road adhesion coefficient are dynamically adjusted to obtain the optimal slip rate and the optimal adhesion coefficient. In order to improve the safety and braking efficiency of subsequent target vehicles, a braking force distribution model is set. The braking force distribution model is created based on an ideal braking force distribution curve and an ideal braking force adjustment curve. It redefines the braking force distribution of the front and rear wheels of the vehicle corresponding to various braking intensities and tire-road adhesion coefficients, and then determines the actual value of the optimal braking force distribution of the front and rear wheels of the vehicle through the optimal slip rate, the optimal adhesion coefficient and the braking demand intensity. The method optimizes the braking force distribution ratio under various braking intensities, effectively improving the directional stability of the vehicle. At the same time, taking into account the influencing factors of regenerative braking, the efficiency of energy recovery is maximized while meeting the braking directional stability.

[0016] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 is a flow chart of a dual-layer adaptive braking force distribution method provided according to an embodiment of the present application; Figure 2 It is a schematic diagram of a vehicle model based on a double-layer adaptive braking force distribution method provided in an embodiment of the present application; Figure 3 is a first braking force distribution curve diagram corresponding to the braking force distribution model provided in an embodiment of the present application; Figure 4 is a second braking force distribution curve diagram corresponding to the braking force distribution model provided in an embodiment of the present application; Figure 5 is a vehicle speed-time variation curve diagram based on a braking force distribution method simulation provided in an embodiment of the present application; Figure 6 is a motor output torque-time variation curve diagram based on the braking force distribution method simulation provided in an embodiment of the present application; Figure 7 It is a SOC power-time variation curve diagram based on the braking force distribution method simulation provided in an embodiment of the present application; Figure 8 is a block diagram of a double-layer adaptive braking force distribution device provided according to an embodiment of the present application; Fig. 9 It is a block diagram of a vehicle provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] The embodiments of the present application are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific implementations and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0021] Example 1 See also Figure 1and Figure 4 This embodiment provides a dual-layer adaptive braking force distribution method, including: Step S100: In response to a brake pedal brake signal of a target vehicle, obtaining a current battery pack SOC, a vehicle speed signal, a wheel longitudinal adhesion, a wheel vertical force, and a braking demand intensity of the target vehicle; It should be noted that the method of this embodiment is applied to the driving process of the target vehicle after the vehicle is powered on. The brake signal generated by the user stepping on the brake pedal of the target vehicle is collected. If a brake signal is collected, the subsequent steps are performed. If no brake signal is collected, the subsequent steps based on the double-layer adaptive braking force distribution method in this embodiment are not executed.

[0022] In some embodiments, after responding to a brake signal, the battery status is monitored in real time through a battery management system (BMS) to obtain the remaining battery capacity (SOC). The vehicle speed signal can be calculated through a wheel speed sensor or through the wheel speed of the vehicle. The longitudinal adhesion of the wheel can be calculated through the wheel speed sensor and the vehicle dynamics model. The longitudinal adhesion of the wheel is one of the important factors that determine the braking efficiency of the vehicle, which involves the vehicle's braking ability and ability to prevent skidding. The vertical force of the wheel can be measured by the suspension system and wheel sensors, or estimated through parameters such as vehicle speed and vehicle weight. The braking demand intensity can be obtained through a brake pedal sensor. The force applied by the driver when pressing the brake pedal is converted by the sensor into an electrical signal that is transmitted to the vehicle's braking control system (such as an electronic brake control system EBC) to obtain the braking demand intensity.

[0023] It is understandable that the battery pack SOC, vehicle speed signal, wheel longitudinal adhesion, wheel vertical force and braking demand intensity can also be obtained through other methods, which can be selected according to actual needs and are not limited here.

[0024] It should also be noted that if Figure 2 As shown, the target vehicle can be a pure electric commercial vehicle, and it is also a front-engine, front-wheel drive vehicle. The power is driven by the front axle. The regenerative braking system consists of two systems: a hydraulic braking system and an electric braking system. The electric braking system can realize braking energy recovery, and the braking energy recovery can only be realized when the electric braking system is started. The four wheels are equipped with hub motors, inverters and motor controllers. The vehicle controller controls by sending and receiving analog signals. The power battery and energy management system are used for power supply and storage. The hydraulic braking system controls the hydraulic braking of the four wheels through hydraulic pipelines. The regenerative braking system can independently control each wheel through braking control.

[0025] Step S200: determining whether the battery pack SOC is less than a preset power threshold, and if so, determining whether the vehicle speed signal is greater than or equal to a preset speed threshold; In this step, it is found in actual experiments that when the battery pack SOC, i.e., the remaining power, is relatively full, if braking energy recovery is performed at this time, the benefit of the recovered power is less than mobilizing various components for braking energy recovery and the loss of vehicle-related parts, especially the loss of the battery pack. Therefore, the collected battery pack SOC is compared with a preset power threshold. The power threshold can be 80%, 85% or 90% of the remaining power of the battery pack. The specific selection is based on actual needs and is not limited here. When the battery pack SOC is less than the power threshold, braking energy recovery is performed in subsequent steps, and when the battery pack SOC is greater than or equal to the power threshold, the hydraulic braking system is directly used for braking.

[0026] Optionally, when the battery pack SOC is less than the power threshold, it is determined whether the collected vehicle speed signal is greater than or equal to a preset speed threshold, wherein the speed threshold may be 15 km\h, 20km\h or 25km\h, and the specific selection is made based on actual needs and is not limited here. When the vehicle speed signal is less than the preset speed threshold, it means that the speed of the target vehicle is too low at this time, and if the braking energy is recovered, its efficiency is very low. Therefore, at this time, the hydraulic braking system is directly used for braking or the subsequent control strategy of the method is not performed. When the vehicle speed signal is greater than or equal to the speed threshold, the subsequent control strategy based on the double-layer adaptive braking force distribution method is performed.

[0027] Step S300: If yes, obtain the road information and the real-time slip rate in the current planned driving trajectory segment of the target vehicle, and determine the current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model; In this step, if the vehicle speed signal is greater than or equal to the speed threshold, the road information and real-time slip rate in the current planned driving trajectory segment of the target vehicle are obtained. The road information includes the type of road surface. The road information can be obtained through the navigation system or through the on-board camera module for image recognition. The type of road surface may include but is not limited to asphalt road surface, dirt road surface, cement road surface and ice surface.

[0028] Optionally, the corresponding model parameters in the tire-road adhesion coefficient identification model are determined according to the road information; through the collected road information, based on the preset data table of road information and model parameters, the data table can be stored in the target vehicle memory in the form of an array and read by calling. Exemplarily, the data table of road information and model parameters can be as shown in Table 1: Table 1 is a data table of road surface information and model parameters Optionally, the model parameters and the real-time slip ratio are input into the tire-road adhesion coefficient identification model, and the real-time tire-road adhesion coefficient is output, wherein the expression of the tire-road adhesion coefficient identification model is: Wherein, μ(s) represents the real-time tire-road adhesion coefficient of the tire-road, C1, C2 and C3 represent model parameters, and s represents the real-time slip rate.

[0029] Optionally, the slip ratio s can be calculated from the wheel speed difference using the following formula: Where, v is the current speed of the target vehicle, v w is the current wheel speed of the target vehicle.

[0030] Step S400: determining the optimal slip rate and the optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force; In this step, the ground adhesion coefficient is determined according to the longitudinal adhesion force of the wheel and the vertical force of the wheel, wherein the calculation expression of the ground adhesion coefficient is: In the formula, represents the ground adhesion coefficient at time t, Indicates the longitudinal adhesion of the wheel, , T represents the target vehicle wheel output torque, r represents the effective radius of the target vehicle wheel, Indicates the vertical force of the wheel; determines the distribution ratio parameters of the optimal slip rate and the optimal adhesion coefficient according to the ground adhesion coefficient and the real-time tire-road adhesion coefficient; determines the optimal slip rate and the optimal adhesion coefficient according to the upper and lower limits of the optimal slip rate and the optimal adhesion coefficient and the distribution ratio parameters.

[0031] Optionally, when µ (s(t))>f(t), the upper limit of the tire-ground adhesion coefficient is calculated as follows: µ up (s)=min[µ max (s(t))] When µ(s(t))≤f(t), the lower limit of the tire-ground adhesion coefficient is calculated as follows: µ down (s)=max[µ max (s(t))] Of course, the upper and lower limits of the range of values ​​with the greatest slip rate on the road and the upper and lower limits of the real-time tire-road adhesion coefficient can also be obtained through the preset curve relationship; The calculation expression of the allocation ratio parameter is: In the formula, represents the upper limit of the range of the optimal adhesion coefficient at time t, Indicates the upper limit of the range of the optimal adhesion coefficient at time t.

[0032] Optionally, the optimal slip rate and the optimal adhesion coefficient are determined according to the upper and lower limits of the optimal slip rate and the optimal adhesion coefficient and the distribution ratio parameter. The calculation expression of the optimal slip rate is: s osr (t) = s up_max (t)+K s up_max (t)-K s down_max (t); The calculation expression of the optimal adhesion coefficient is: µ osr (t) = µ up_max (t)+K µ up_max (t)-K µ down_max (t); In the formula, represents the allocation ratio parameter, s up_max (t) represents the upper limit of the optimal slip ratio range at time t, s down_max (t) represents the upper limit of the optimal slip ratio at time t, µ up_max (t) represents the upper limit of the optimal adhesion coefficient at time t, µ down_max (t) represents the upper limit of the range of the optimal adhesion coefficient at time t.

[0033] It can be understood that by obtaining the optimal slip rate and the optimal adhesion coefficient through data processing, the subsequent braking force distribution process can be controlled more accurately, thereby ensuring braking safety, generating the optimal braking distribution force, and maximizing the efficiency and effect of energy recovery.

[0034] Step S500: Determine the front and rear wheel braking force distribution of the target vehicle according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model.

[0035] In this step, the preset braking force distribution model can be the front and rear wheel braking force and corresponding slip ratio working distribution curves. It should be noted that these curves can be converted into arrays and stored in the memory of the target vehicle, and obtained by calling data. After that, data can be searched based on the obtained optimal slip ratio, optimal adhesion coefficient and braking demand intensity. The search method can be binary search, hash search or linear search. Finally, the front and rear wheel braking force distribution of the target vehicle is determined.

[0036] In some embodiments, the creation of a braking force distribution model may include: determining a braking force distribution curve of the braking force distribution model based on an ideal braking force distribution curve and an ideal braking force adjustment curve, wherein it should be noted that the ideal braking force distribution curve (i.e., Type I braking force distribution curve) and the ideal braking force adjustment curve are existing braking force distribution and adjustment curves, and control based on the curve ensures that the vehicle maintains balance and stability during braking, whereas in the prior art, the ideal braking force distribution curve is basically used alone for braking force distribution, and a single ideal braking force distribution curve or an ideal braking force adjustment curve has multiple control areas where hydraulic braking is used or the braking effect is poor, and thus, optimization of braking energy recovery is not considered.

[0037] like Figure 3 and Figure 4 As shown, based on the optimal adhesion coefficient, at least one braking intensity threshold of the braking force distribution curve is determined, and the at least one braking intensity threshold includes a first braking intensity threshold and a second braking intensity threshold, wherein the first braking intensity threshold and the second braking intensity threshold are segmentation points of the braking force distribution curve, and the first braking intensity threshold It can be the position of the working point A, that is, the first intersection point of the ideal braking force distribution curve and the ideal braking force adjustment curve, the second braking intensity threshold It can be the position of the working point B, that is, the second intersection point of the ideal braking force distribution curve and the ideal braking force adjustment curve, The first braking intensity threshold The calculation expression is: in, In the formula, represents the maximum torque of the vehicle's motor; m represents the total mass of the vehicle; R represents the vehicle's wheelbase; n represents the vehicle's transmission ratio; W represents the correction coefficient of the tire-road adhesion condition. is the positive threshold of the tire-road adhesion coefficient; is the negative threshold of the tire-road adhesion coefficient; is the optimal adhesion coefficient; Optionally, point M is the intersection with the front wheel braking force (x axis), and the second braking intensity threshold The calculation expression is: In the formula, is the front axle mass distribution coefficient of the vehicle; is the height of the vehicle's center of mass, R The front and rear wheelbase of the vehicle.

[0038] It is understandable that when the required braking intensity is less than In order to ensure braking safety and recover braking energy at the same time, the front and rear wheel braking forces are distributed linearly. As the front wheel braking force continues to increase, if the braking torque provided by the regenerative braking torque is insufficient, the motor maintains the maximum torque and reaches the peak When the vehicle moves along the curve, the insufficient braking force is compensated by the hydraulic braking system until it reaches the working point B of the type I braking force distribution curve.

[0039] Optionally, based on the braking demand intensity and the braking intensity threshold, a braking force distribution area in the braking force distribution curve is determined; based on the optimal slip rate and the optimal adhesion coefficient, front and rear wheel braking force distribution data values ​​of the target vehicle in the braking force distribution area are determined.

[0040] Combination Figure 4 As shown, in order to reduce the complexity of data processing and to more efficiently perform feedback execution of the data processing results, the braking force distribution curve can be divided into sections, that is, from the origin to the working point A, the working point A to the point M, the point M to the working point B, and the working point B to the working point C. For example, the braking distribution of the front and rear wheels can also be: light braking (braking demand intensity < first braking intensity threshold): when the ground adhesion coefficient is small ( < ) when the wheels are at risk of locking and slipping during braking, such as on ice. Therefore, the front and rear wheel braking distribution should follow the I-type braking force distribution curve section on the working point W1 to ensure braking efficiency; if the adhesion coefficient is better ( > ), the braking working point should follow the curve on the working point W2, the front wheel braking torque is provided by the motor, and the rear wheel hydraulic pressure is 0. When the adhesion coefficient is not high enough ( < ), there is also a risk of locking and slipping due to the high braking intensity. Therefore, the braking operating point should follow the I curve on the working point W3 to ensure braking efficiency. If the adhesion coefficient is high ( > ), the braking operating point should follow the "MB" curve on the working point W4 to achieve good braking efficiency while maximizing the recovery of braking energy; under emergency braking conditions (the braking demand intensity is greater than the second braking intensity threshold), there is a risk of locking and skidding due to the large braking intensity. Therefore, the braking operating point should follow the I-type braking force distribution curve section on the working point W5 to ensure braking efficiency; the rear wheel braking torque is provided by the hydraulic braking system. The motor provides the maximum regenerative torque applied to the front wheels.

[0041] In the method steps of the above-mentioned embodiment, the battery pack SOC and the vehicle speed signal are used as the prerequisites for entering the double-layer adaptive braking force distribution strategy. In this way, it is avoided that the target vehicle performs inefficient braking force distribution energy recovery under the premise of a high battery pack SOC or a slow vehicle speed. After entering the double-layer adaptive braking force distribution strategy, the road type information, braking demand intensity and real-time slip rate in the current planned driving trajectory segment are first collected, and the current real-time tire-road adhesion coefficient of the target vehicle is determined through the tire-road adhesion coefficient identification model. The real-time slip rate and the real-time tire-road adhesion coefficient are dynamically adjusted to obtain the optimal slip rate and the optimal adhesion coefficient. , thereby improving the safety and braking efficiency of subsequent target vehicles. The braking force distribution model is set. The braking force distribution model is created based on the ideal braking force distribution curve and the ideal braking force adjustment curve. It redefines the braking force distribution of the front and rear wheels of the vehicle corresponding to various braking intensities and tire-road adhesion coefficients. Then, the optimal braking force distribution actual value of the front and rear wheels of the vehicle is determined through the optimal slip rate, the optimal adhesion coefficient and the braking demand intensity. The method optimizes the braking force distribution ratio under various braking intensities and effectively improves the directional stability of the vehicle. At the same time, considering the influencing factors of regenerative braking, the efficiency of energy recovery is maximized under the premise of meeting the braking directional stability.

[0042] See also Figures 5 to 7 This application provides a simulation experiment of a target vehicle equipped with a double-layer adaptive braking force distribution method, establishes a regenerative braking model based on an optimization distribution algorithm of a variable braking force ratio, and then uses the model in a new ADVISOR 2002 pure electric vehicle model. Figure 5 The comparison results of the simulated vehicle speed and the required speed under a typical road cycle condition are shown. The trends of the two curves of the simulation structure after strategy optimization and the original data in different time periods are consistent. Therefore, the vehicle with the optimized control strategy can complete the entire simulation process according to the real-time vehicle speed requirements of the simulated working conditions.

[0043] Figure 6The change of motor torque using the original design of the braking energy recovery control strategy and the optimized control strategy under the corresponding typical driving conditions is shown. It can be seen that during the driving process, for the same driving force, the positive motor torque output determined by the same driving strategy is consistent. During the vehicle braking process, two different strategies were used. The first is the regenerative braking strategy method provided by the above embodiment, and the second is the original strategy. In both cases, the negative motor torque output generated by the first strategy is greater than the torque output generated by the second strategy, which may be due to the maximum regenerative braking force of the motor under the new strategy. Therefore, with the new strategy, the proportion of the motor braking torque increases, and the braking energy recovery also increases accordingly.

[0044] Figure 7 The simulation curves of the battery SOC under the two strategies corresponding to typical driving conditions are shown. At the beginning of the simulation, the battery SOC is 60%. From the simulation results, it can be seen that the battery SOC of the target vehicle based on the double-layer adaptive braking force distribution method of the above embodiment decreases slowly. Under the same test environment, the final battery SOC value is higher (that is, more remaining power), and more braking energy is recovered. The specific data values ​​are shown in Table 2. Table 2 Energy recovery comparison table See also Figure 8 This embodiment provides a dual-layer adaptive braking force distribution device, and the dual-layer adaptive braking force distribution device 200 includes: The acquisition module 210 is configured to obtain the current battery pack SOC, vehicle speed signal, wheel longitudinal adhesion, wheel vertical force and braking demand intensity of the target vehicle in response to the brake signal of the brake pedal of the target vehicle; The judging module 220 is configured to judge whether the SOC of the battery pack is less than a preset power threshold, and if so, to judge whether the vehicle speed signal is greater than or equal to a preset speed threshold; The first determination module 230 is configured to obtain road information and a real-time slip rate in a current planned driving trajectory segment of the target vehicle, and determine the current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model; A second determination module 240 is configured to determine an optimal slip rate and an optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force; The third determination module 250 is configured to determine the front and rear wheel braking force distribution of the target vehicle according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model.

[0045] In some embodiments, the first determination module 230 is further used to determine corresponding model parameters in the tire-road adhesion coefficient identification model according to the road information, and input the model parameters and the real-time slip rate into the tire-road adhesion coefficient identification model, and output the real-time tire-road adhesion coefficient, wherein the expression of the tire-road adhesion coefficient identification model is: Wherein, μ(s) represents the real-time tire-road adhesion coefficient of the tire-road, C1, C2 and C3 represent model parameters, and s represents the real-time slip rate.

[0046] In some embodiments, the second determination module 240 is further configured to determine the ground adhesion coefficient according to the longitudinal adhesion force of the wheel and the vertical force of the wheel, wherein: The calculation expression of the ground adhesion coefficient is: In the formula, represents the ground adhesion coefficient at time t, Indicates the longitudinal adhesion of the wheel, , T represents the target vehicle wheel output torque, r represents the effective radius of the target vehicle wheel, represents the vertical force of the wheel; Determine the distribution ratio parameters of the optimal slip rate and the optimal adhesion coefficient according to the ground adhesion coefficient and the real-time tire-road adhesion coefficient; The optimal slip rate and the optimal adhesion coefficient are determined according to the upper and lower limits of the optimal slip rate and the optimal adhesion coefficient and the distribution ratio parameters.

[0047] The calculation expression of the allocation ratio parameter is: In the formula, represents the upper limit of the range of the optimal adhesion coefficient at time t, Indicates the upper limit of the range of the optimal adhesion coefficient at time t.

[0048] In some embodiments, the creation of the braking force distribution model in the third determination module 250 includes: Determining a braking force distribution curve of a braking force distribution model based on an ideal braking force distribution curve and an ideal braking force adjustment curve; Based on the optimal adhesion coefficient, at least one braking intensity threshold of the braking force distribution curve is determined, and the at least one braking intensity threshold includes a first braking intensity threshold and a second braking intensity threshold, wherein the first braking intensity threshold and the second braking intensity threshold are segmentation points of the braking force distribution curve, The calculation expression of the first braking intensity threshold is: in, In the formula, represents the maximum torque of the vehicle's motor; m represents the total mass of the vehicle; R represents the vehicle's wheelbase; n represents the vehicle's transmission ratio; W represents the correction coefficient of the tire-road adhesion condition. is the positive threshold of the tire-road adhesion coefficient; is the negative threshold of the tire-road adhesion coefficient; is the optimal adhesion coefficient; The calculation expression of the second braking intensity threshold is: In the formula, is the front axle mass distribution coefficient of the vehicle; is the height of the vehicle's center of mass, R The front and rear wheelbase of the vehicle.

[0049] Optionally, the third determination module 250 is further configured to determine a braking force distribution area in the braking force distribution curve based on the braking demand intensity and the braking intensity threshold; Based on the optimum slip ratio and the optimum adhesion coefficient, the front and rear wheel braking force distribution data values ​​of the target vehicle in the braking force distribution area are determined.

[0050] It should be understood that Figure 8 In the structural block diagram of the double-layer adaptive braking force distribution device 200 shown in FIG. Figure 1-Figure 4 The steps in the corresponding embodiments, and for Figure 1-Figure 4 Each step in the corresponding embodiment has been explained in detail in the above embodiment. Figure 1-Figure 4 as well as Figure 1-Figure 4 The relevant descriptions in the corresponding embodiments are not repeated here.

[0051] Compared with the related art, the above embodiment has the following beneficial effects: by taking the battery pack SOC and the vehicle speed signal as the prerequisite for entering the double-layer adaptive braking force distribution strategy, it is possible to avoid the target vehicle from performing inefficient braking force distribution and energy recovery under the premise of a high battery pack SOC or a slow vehicle speed. After entering the double-layer adaptive braking force distribution strategy, firstly, the road type information, braking demand intensity and real-time slip rate in the current planned driving trajectory segment are collected, and the current real-time tire-road adhesion coefficient of the target vehicle is determined through the tire-road adhesion coefficient identification model, and the optimal slip rate and the optimal tire-road adhesion coefficient are obtained by dynamically adjusting the real-time slip rate and the real-time tire-road adhesion coefficient. The optimal adhesion coefficient is obtained, thereby improving the safety and braking efficiency of subsequent target vehicles. The braking force distribution model is set, and the braking force distribution model is created based on the ideal braking force distribution curve and the ideal braking force adjustment curve. It redefines the braking force distribution of the front and rear wheels of the vehicle corresponding to various braking intensities and tire-road adhesion coefficients. Then, the optimal braking force distribution actual value of the front and rear wheels of the vehicle is determined through the optimal slip rate, the optimal adhesion coefficient and the braking demand intensity. The method optimizes the braking force distribution ratio under various braking intensities, effectively improving the directional stability of the vehicle. At the same time, considering the influencing factors of regenerative braking, the efficiency of energy recovery is maximized under the premise of meeting the braking directional stability.

[0052] See also Fig. 9 , Fig. 9 is a block diagram of a vehicle 800 according to an exemplary embodiment. For example, the vehicle 800 may be a pure electric commercial vehicle, and the vehicle 800 may be provided with a braking energy recovery "regenerative braking" system.

[0053] like Fig. 9 As shown, the vehicle 800 may include various subsystems, for example, an infotainment system 810, a perception system 820, a decision control system 830, a drive system 840, and a computing platform 850. The vehicle 800 may also include more or fewer subsystems, and each subsystem may include multiple components. In addition, each subsystem and each component of the vehicle 800 may be interconnected by wire or wireless means.

[0054] In some embodiments, the infotainment system 810 may include a communication system, an entertainment system, and a navigation system, etc.

[0055] The perception system 820 may include several sensors for sensing information about the environment around the vehicle 800. For example, the perception system 820 may include a global positioning system (the global positioning system may be a GPS system, or a Beidou system or other positioning systems), an inertial measurement unit (IMU), a laser radar, a millimeter wave radar, an ultrasonic radar, and a camera.

[0056] The decision control system 830 may include a computing system, a vehicle controller, a steering system, a throttle, and a braking system.

[0057] The drive system 840 may include components that provide powered motion for the vehicle 800. In one embodiment, the drive system 840 may include an engine, an energy source, a transmission system, and wheels. The engine may be one or a combination of an internal combustion engine, an electric motor, and an air compression engine. The engine is capable of converting energy provided by the energy source into mechanical energy.

[0058] Some or all functions of the vehicle 800 are controlled by a computing platform 850. The computing platform 850 may include at least one processor 851 and a memory 852, and the processor 851 may execute instructions 853 stored in the memory 852.

[0059] The processor 851 may be any conventional processor, such as a commercially available CPU. The processor may also include a graphics processor (Graphic Process Unit, GPU), a field programmable gate array (Field Programmable Gate Array, FPGA), a system on chip (System on Chip, SOC), an application specific integrated circuit (Application Specific Integrated Circuit, ASIC) or a combination thereof.

[0060] The memory 852 may be implemented by any type of volatile or nonvolatile memory device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk, or optical disk.

[0061] In addition to instructions 853 , memory 852 may also store data, such as road maps, route information, vehicle location, direction, speed, etc. The data stored in memory 852 may be used by computing platform 850 .

[0062] In some embodiments, the processor 851 may execute instruction 853 to complete all or part of the steps of the above-mentioned dual-layer adaptive braking force distribution method.

[0063] In some embodiments, a vehicle is also provided, comprising a processor; a memory for storing processor-executable instructions; Wherein, the processor is configured to: implement the steps of the double-layer adaptive braking force distribution method provided in the aforementioned method embodiment.

[0064] In some embodiments, a computer-readable storage medium is also provided, on which computer program instructions are stored. When the program instructions are executed by a processor, the steps of the dual-layer adaptive braking force distribution method provided by the present disclosure are implemented.

[0065] In some embodiments, a computer program product is also provided, on which computer program instructions are stored. When the program instructions are executed by a processor, the steps of the dual-layer adaptive braking force distribution method provided by the present disclosure are implemented.

[0066] The terms "first", "second", "third", etc. in the specification and claims of the present application and the drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a series of steps or units are included, or optionally, steps or units not listed are included, or optionally, other steps or units inherent to these processes, methods, products or devices are included.

[0067] Only the part relevant to the present application is shown in the accompanying drawings, but not all of the content. Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processing or methods depicted as flow charts. Although the flow chart describes each operation (or step) as a sequential process, many of the operations therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of each operation can be rearranged. When its operation is completed, the process can be terminated, but it can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0068] The terms "component", "module", "system", "unit", etc. used in this specification are used to represent computer-related entities, hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or distributed between two or more computers. In addition, these units can be executed from various computer-readable media having various data structures stored thereon. Units can communicate through local and / or remote processes, for example, based on signals having one or more data packets (e.g., data from a second unit interacting with another unit in a local system, a distributed system, and / or a network. For example, the Internet interacts with other systems via signals).

[0069] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative 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 application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0070] Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present embodiment application. The appearance of this phrase in various positions in the specification is not necessarily the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It can be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0071] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

[0072] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the disclosure disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

Claims

1. A method for distributing braking force based on double-layer adaptive braking, characterized in that: include: In response to a brake pedal brake signal of the target vehicle, obtaining a current battery pack SOC, a vehicle speed signal, a wheel longitudinal adhesion, a wheel vertical force, and a braking demand intensity of the target vehicle; Determine whether the battery pack SOC is less than a preset power threshold, and if so, determine whether the vehicle speed signal is greater than or equal to a preset speed threshold; If yes, obtain the road information and the real-time slip rate in the current planned driving trajectory segment of the target vehicle, and determine the current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model; Determining an optimal slip ratio and an optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force; The front and rear wheel braking force distribution of the target vehicle is determined according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model.

2. The method for distributing braking force based on double-layer adaptive braking according to claim 1, characterized in that: If so, obtaining road information and a real-time slip rate in a current planned driving trajectory segment of the target vehicle, and determining the current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model, including: Determining corresponding model parameters in the tire-road adhesion coefficient identification model according to the road information; The model parameters and the real-time slip ratio are input into the tire-road adhesion coefficient identification model, and the real-time tire-road adhesion coefficient is output, wherein the expression of the tire-road adhesion coefficient identification model is: Wherein, μ(s) represents the real-time tire-road adhesion coefficient of the tire-road, C1, C2 and C3 represent model parameters, and s represents the real-time slip rate.

3. The method for distributing braking force based on double-layer adaptive braking according to claim 1, characterized in that: The determining the optimal slip rate and the optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force includes: The ground adhesion coefficient is determined according to the wheel longitudinal adhesion force and the wheel vertical force, wherein the calculation expression of the ground adhesion coefficient is: In the formula, represents the ground adhesion coefficient at time t, Indicates the longitudinal adhesion of the wheel, , T represents the target vehicle wheel output torque, r represents the effective radius of the target vehicle wheel, represents the vertical force of the wheel; Determining a distribution ratio parameter of the optimal slip rate and the optimal adhesion coefficient according to the ground adhesion coefficient and the real-time tire-road adhesion coefficient; The optimal slip ratio and the optimal adhesion coefficient are determined according to the upper and lower limits of the optimal slip ratio and the optimal adhesion coefficient and the distribution ratio parameter.

4. The method for distributing braking force based on double-layer adaptive braking according to claim 3, characterized in that: The step of determining the distribution ratio parameter of the optimal slip rate and the optimal adhesion coefficient according to the ground adhesion coefficient and the real-time tire-road adhesion coefficient comprises: The calculation expression of the allocation ratio parameter is: In the formula, represents the upper limit of the range of the optimal adhesion coefficient at time t, Indicates the upper limit of the range of the optimal adhesion coefficient at time t.

5. The method for distributing braking force based on double-layer adaptive braking according to claim 3, characterized in that: The determining the optimal slip rate and the optimal adhesion coefficient according to the upper and lower limits of the optimal slip rate and the optimal adhesion coefficient and the allocation ratio parameter comprises: The calculation expression of the optimal slip ratio is: s osr (t)=s up_max (t)+K s up_max (t)-K s down_max (t); The calculation expression of the optimal adhesion coefficient is: µ osr (t)=µ up_max (t)+K µ up_max (t)-K µ down_max (t); In the formula, represents the allocation ratio parameter, s up_max (t) represents the upper limit of the optimal slip ratio range at time t, s down_max (t) represents the upper limit of the optimal slip ratio at time t, µ up_max (t) represents the upper limit of the optimal adhesion coefficient at time t, µ down_max (t) represents the upper limit of the range of the optimal adhesion coefficient at time t.

6. The method for distributing braking force based on double-layer adaptive braking according to claim 1, characterized in that: The method of determining the front and rear wheel braking force distribution of the target vehicle according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model, wherein the creation of the braking force distribution model includes: Determining a braking force distribution curve of the braking force distribution model based on the ideal braking force distribution curve and the ideal braking force adjustment curve; Based on the optimal adhesion coefficient, determining at least one braking intensity threshold of the braking force distribution curve, wherein the at least one braking intensity threshold comprises a first braking intensity threshold and a second braking intensity threshold, wherein the first braking intensity threshold and the second braking intensity threshold are segmentation points of the braking force distribution curve; The calculation expression of the first braking intensity threshold is: in, In the formula, represents the maximum torque of the vehicle's motor; m represents the total mass of the vehicle; R represents the vehicle's wheelbase; n represents the vehicle's transmission ratio; W represents the correction coefficient of the tire-road adhesion condition. is the positive threshold of the tire-road adhesion coefficient; is the negative threshold of the tire-road adhesion coefficient; is the optimal adhesion coefficient; The calculation expression of the second braking intensity threshold is: In the formula, is the front axle mass distribution coefficient of the vehicle; is the height of the vehicle's center of mass, R The front and rear wheelbase of the vehicle.

7. The method for distributing braking force based on double-layer adaptive braking according to claim 6, characterized in that: The method of determining the front and rear wheel braking force distribution of the target vehicle according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model further includes: Determining a braking force distribution area on the braking force distribution curve based on the braking demand intensity and the braking intensity threshold; Based on the optimum slip ratio and the optimum adhesion coefficient, a front and rear wheel braking force distribution data value of the target vehicle in the braking force distribution area is determined.

8. A dual-layer adaptive braking force distribution device, characterized in that: include: An acquisition module is configured to acquire a current battery pack SOC, a vehicle speed signal, a wheel longitudinal adhesion, a wheel vertical force, and a braking demand intensity of the target vehicle in response to a brake signal of a brake pedal of the target vehicle; a determination module configured to determine whether the battery pack SOC is less than a preset power threshold, and if so, to determine whether the vehicle speed signal is greater than or equal to a preset speed threshold; A first determination module is configured to obtain road information and a real-time slip rate in a current planned driving trajectory segment of the target vehicle, and determine a current real-time tire-road adhesion coefficient of the target vehicle according to the road information and the real-time slip rate and based on a preset tire-road adhesion coefficient identification model; a second determination module, configured to determine an optimal slip rate and an optimal adhesion coefficient of the target vehicle based on the real-time tire-road adhesion coefficient, the wheel longitudinal adhesion force, and the wheel vertical force; The third determination module is configured to determine the front and rear wheel braking force distribution of the target vehicle according to the optimal slip ratio, the optimal adhesion coefficient and the braking demand intensity and based on a preset braking force distribution model.

9. A vehicle, characterized in that: include: processor; a memory for storing instructions executable by the processor; Wherein, the processor is configured to: Implement the steps of a double-layer adaptive braking force distribution method as described in any one of claims 1 to 7.

10. A computer-readable storage medium having computer program instructions stored thereon, characterized in that: When the program instructions are executed by a processor, the steps of a method based on double-layer adaptive braking force distribution according to any one of claims 1 to 7 are implemented.

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