Vehicle driving assistance control method and device, storage medium and vehicle

Abstract

The embodiment of the invention provides a vehicle driving assistance control method and device, a storage medium and a vehicle. The method comprises the steps that the road adhesion coefficient of the vehicle is obtained in real time; updating a slip rate condition and a PI control parameter based on the currently obtained road adhesion coefficient; and when it is determined that the slipping to-be-processed driving shaft exists, the torque output by a power system to the to-be-processed driving shaft is controlled based on the updated PI control parameters, and the slip rate of the vehicle driving shaft meets the updated slip rate condition. By acquiring the road adhesion coefficient in real time and by referring to the adhesion coefficient, the PI control parameters can be adjusted and selected in advance according to the ground adhesion coefficient before the vehicle slips, so that the anti-slip control is quick in response, and a better anti-slip effect of the four-wheel-drive vehicle is acquired.

Description

Technical Field

[0001] The present application relates to the field of vehicle driving control technology, and in particular to a vehicle driving assistance control method and device, a storage medium and a vehicle. Background Art

[0002] Electric inter-axle four-wheel drive is a type of vehicle driving power configuration, which means that the front and rear axles of the vehicle are equipped with driving force, which is directly transmitted through the front and rear drive shafts. The inter-axle four-wheel drive system usually includes an electronic control unit that can automatically adjust the torque distribution of the front and rear axles according to road conditions and vehicle motion status. In the field of four-wheel drive torque control, four-wheel drive vehicle control is generally divided into feedforward control and feedback control. When a four-wheel drive vehicle slips, the industry uses the PI algorithm to perform feedback control of the slip. However, performing slip control after the vehicle starts to slip will still affect the vehicle's driving stability and reduce the driving experience. Summary of the invention

[0003] The embodiments of the present application provide a vehicle driving assistance control method and device, a storage medium and a vehicle. The method can obtain the road adhesion coefficient in real time, and by referring to the adhesion coefficient, the PI control parameters can be adjusted and selected in advance according to the ground adhesion coefficient before the vehicle slips, so that the anti-skid control responds quickly and obtains a better anti-skid effect for four-wheel drive vehicles.

[0004] In a first aspect, an embodiment of the present application provides a vehicle driving assistance control method, including: acquiring the vehicle's road adhesion coefficient in real time; updating the slip rate condition and PI control parameters based on the currently acquired road adhesion coefficient; when it is determined that there is a slipping drive shaft to be processed, based on the updated PI control parameters, controlling the torque output by the power system to the drive shaft to be processed so that the slip rate of the vehicle drive shaft meets the updated slip rate condition.

[0005] In one possible implementation, the determination of the drive shaft to be processed that is slipping includes: based on the vehicle's center of mass speed, wheelbase, track width and distance from the rear axle to the center of mass, applying the Ackerman angle, and calculating in real time the target speeds corresponding to the center of mass speed when projected onto the four wheels respectively, wherein the target speeds corresponding to the four wheels include the target speed corresponding to the left front wheel, the target speed corresponding to the right front wheel, the target speed corresponding to the left rear wheel and the target speed corresponding to the right rear wheel; calculating the slip rates of the four wheels based on the wheel speeds, tire radius, steering angle and the target speeds of the four wheels, wherein the slip rates of the four wheels include the slip rates of the left front wheel, the slip rates of the right front wheel, the slip rates of the left rear wheel and the slip rates of the right rear wheel; and determining the slip states of the front and rear drive shafts of the vehicle based on the slip rates of the four wheels.

[0006] In a possible implementation, the target vehicle speed corresponding to the vehicle center speed projected to the four wheels in real time is calculated based on the vehicle center speed, wheelbase, track width, and distance from the rear axle to the center of mass of the vehicle by applying the Ackerman angle, and includes:

[0007] The target vehicle speed corresponding to the left front wheel is calculated in real time by the following formula:

[0008]

[0009] Among them, V1” represents the target vehicle speed corresponding to the left front wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle;

[0010] The target vehicle speed corresponding to the right front wheel is calculated in real time by the following formula:

[0011]

[0012] Among them, V2” represents the target vehicle speed corresponding to the right front wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle;

[0013] The target vehicle speed corresponding to the left rear wheel is calculated in real time by the following formula:

[0014]

[0015] Among them, V3” represents the target vehicle speed corresponding to the left rear wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle;

[0016] The target vehicle speed corresponding to the right rear wheel is calculated in real time by the following formula:

[0017]

[0018] Among them, V4" represents the target vehicle speed corresponding to the right rear wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle.

[0019] In one possible implementation, determining the slip state of the front and rear drive shafts of the vehicle based on the slip rates of the four wheels includes: calculating an average value based on the slip rates of the left front wheel and the right front wheel to obtain the slip rate of the front drive shaft, and if the slip rate of the front drive shaft exceeds a first slip rate threshold, determining that the front drive shaft is a drive shaft with slip to be processed; calculating an average value based on the slip rate of the left rear wheel and the slip rate of the right rear wheel to obtain the slip rate of the rear drive shaft, and if the slip rate of the rear drive shaft exceeds the first slip rate threshold, determining that the rear drive shaft is a drive shaft with slip to be processed.

[0020] In one possible implementation, the torque output by the power system to the drive shaft to be processed is controlled so that the slip rate of the vehicle drive shaft meets the updated slip rate condition, including: when the absolute value of the vehicle speed is not less than a first preset vehicle speed, the torque output by the power system to the drive shaft to be processed is adjusted so that the slip rate of the adjusted drive shaft is not greater than a second slip rate threshold.

[0021] In one possible implementation, when the absolute value of the vehicle speed is less than a first preset vehicle speed, the torque output by the power system to the drive shaft to be processed is adjusted so that the rotational speed of the adjusted drive shaft is less than the first rotational speed.

[0022] In one possible implementation, the real-time acquisition of the vehicle's road adhesion coefficient includes: real-time acquisition of the longitudinal driving force of the four wheels and the entire wheel load; based on the longitudinal driving force of the four wheels and the entire wheel load, using the linear recursive least squares method to estimate the road adhesion coefficient in real time.

[0023] In a second aspect, an embodiment of the present application further provides a vehicle driving assistance control device, the device comprising: a processor and a memory, the memory being used to store at least one instruction, and the instruction, when loaded and executed by the processor, implements the vehicle driving assistance control method provided in the first aspect.

[0024] In a third aspect, an embodiment of the present application further provides a vehicle, which includes the vehicle driving assistance control device provided by the second aspect.

[0025] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the vehicle driving assistance control method provided in the first aspect is implemented.

[0026] Through the above technical solution, during the driving process of the vehicle, the road adhesion coefficient between the vehicle tire and the road surface can be obtained in real time, and the slip rate condition and PI control parameters can be updated based on the currently obtained road adhesion coefficient. When it is determined that there is a slipping drive shaft to be processed, based on the updated PI control parameters, the torque output by the power system to the drive shaft to be processed is controlled so that the slip rate of the vehicle drive shaft meets the updated slip rate condition. Before the vehicle slips, the PI control parameters can be adjusted and selected in advance according to the ground adhesion coefficient, so that the anti-skid control responds quickly and obtains a better anti-skid effect for four-wheel drive vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 A schematic diagram of a process framework of driving assistance control is provided for one embodiment of the present application;

[0029] Figure 2 A schematic diagram of a vehicle driving assistance control method flow chart provided in one embodiment of the present application;

[0030] Figure 3 A schematic diagram of a functional architecture of drive shaft slip detection provided by an embodiment of the present application;

[0031] Figure 4 Ackerman angle set diagram provided for one embodiment of the present application;

[0032] Figure 5 A schematic diagram of wheel load estimation provided for one embodiment of the present application;

[0033] Figure 6 A tire force diagram provided for one embodiment of the present application;

[0034] Figure 7 A schematic diagram of the corresponding relationship between tire force and slip rate provided by an embodiment of the present application;

[0035] Figure 8 A schematic diagram of the structure of a vehicle driving assistance control device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] Figure 1 A schematic diagram of a process framework of driving assistance control is provided for one embodiment of the present application.

[0038] Reference Figure 1 As shown, the process framework may include:

[0039] S1: Drive shaft slip detection.

[0040] S2: Drive shaft slip control.

[0041] During vehicle driving, when the vehicle's road assist mode is activated, it is possible to determine whether the vehicle is slipping based on the slip of the vehicle's drive shaft. Furthermore, when the vehicle is slipping, the driving assistance control strategy provided in this application can be executed to suppress the vehicle's slipping, thereby achieving the purpose of smooth vehicle driving.

[0042] S1 and S2 are described in detail below with reference to the accompanying drawings.

[0043] In general scenarios, the method for determining whether the drive shaft is slipping is to calculate the slip rate based on the vehicle speed and wheel speed. Specifically, the calculation method is:

[0044] Axle speed = (axle front wheel speed + axle front wheel speed) / 2

[0045] After the shaft speed is calculated, the shaft speed is converted into the shaft end vehicle speed. Further, the collected vehicle speed is obtained by receiving the vehicle speed provided by the sensor, and the slip ratio is calculated by a calculation formula based on the shaft end vehicle speed and the collected vehicle speed. However, the above calculation method cannot calculate the correct slip ratio when all four wheels of the front and rear drive shafts are slipping.

[0046] In order to overcome the above-mentioned technical problems, the vehicle driving assistance control method provided in the present application takes into account the relationship between the steering angle and the vehicle's center of mass, and thus, when the drive shaft slip is detected, the vehicle speed at the center of mass position (center of mass speed) can be mapped to the four wheels to calculate the slip rate of each wheel individually, so that when all four wheels are slipping, the accurate slip rates of the four wheels can be calculated separately.

[0047] Figure 2 A schematic flow chart of a vehicle driving assistance control method provided for one embodiment of the present application.

[0048] Reference Figure 2 As shown, the vehicle driving assistance control method may include the following steps:

[0049] S201: Obtaining the road adhesion coefficient of the vehicle in real time.

[0050] S202: Update the slip rate condition and PI control parameters based on the currently acquired road adhesion coefficient.

[0051] S203: When it is determined that there is a drive shaft to be processed that is slipping, based on the updated PI control parameters, control the torque output by the power system to the drive shaft to be processed so that the slip rate of the vehicle drive shaft meets the updated slip rate condition.

[0052] In some embodiments, during the driving process of the vehicle, the drive shaft slip control of the vehicle can be performed before the vehicle slips. Specifically, the ground adhesion coefficient between the vehicle tires and the ground can be estimated in real time, and in the drive slip control, the slip rate condition and PI control parameters can be updated and set according to μ. When the drive shaft to be processed is detected, the torque output by the power system to the drive shaft to be processed is controlled based on the updated PI control parameters so that the slip rate of the vehicle drive shaft meets the updated slip rate condition.

[0053] In some embodiments, determining that a drive shaft to be processed is slipping includes: based on the vehicle's center of mass speed, wheelbase, track width and distance from the rear axle to the center of mass, applying the Ackerman angle, and calculating in real time the target speeds corresponding to the projected center of mass speeds onto the four wheels, wherein the target speeds corresponding to the four wheels include a target speed corresponding to the left front wheel, a target speed corresponding to the right front wheel, a target speed corresponding to the left rear wheel and a target speed corresponding to the right rear wheel; calculating the slip rates of the four wheels based on the wheel speeds, tire radius, steering angle and the target speeds of the four wheels, wherein the slip rates of the four wheels include a slip rate of the left front wheel, a slip rate of the right front wheel, a slip rate of the left rear wheel and a slip rate of the right rear wheel; and determining the slip state of the front and rear drive shafts of the vehicle based on the slip rates of the four wheels.

[0054] Figure 3 A schematic diagram of the functional architecture of drive shaft slip detection provided in one embodiment of the present application.

[0055] Reference Figure 3 As shown, based on the vehicle's center of mass speed, wheelbase, track width and distance from the rear axle to the center of mass, the Ackerman angle can be applied to calculate in real time the target speed corresponding to the center of mass speed when it is projected onto the four wheels.

[0056] In some embodiments, after the Ackerman angle principle is applied, the target shaft speed of the drive shaft can be calculated based on the following formula:

[0057] N F =(V1”+V2”) / 2

[0058] Among them, N F Indicates the target speed of the front axle, V1” indicates the speed of the left front wheel projected from the reference speed of the center of mass, and V2” indicates the speed of the right front wheel projected from the reference speed of the center of mass

[0059] N B =(V3”+V4”) / 2

[0060] Among them, N B Indicates the target speed of the rear axle, V3” indicates the speed of the left rear wheel projected from the reference speed of the center of mass, and V4” indicates the speed of the right rear wheel projected from the reference speed of the center of mass.

[0061] Figure 4 An Ackerman angle set diagram provided for one embodiment of the present application.

[0062] Combination Figure 3 and Figure 4 As shown, applying the Ackerman angle, considering the projection of the center of mass reference speed to the wheel speed of the four wheels is calculated as follows:

[0063] The vehicle speed V1" projected from the center of mass reference speed to the left front wheel can be calculated based on the following formula:

[0064]

[0065] The speed V2" projected from the center of mass reference speed to the right front wheel can be calculated based on the following formula:

[0066]

[0067] The speed V3" of the center of mass reference speed projected to the right front wheel can be calculated based on the following formula:

[0068]

[0069] The vehicle speed V4" projected from the center of mass reference speed to the right front wheel can be calculated based on the following formula:

[0070]

[0071] Among them, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear axle to the center of mass, and α0 represents the vehicle steering angle.

[0072] After the vehicle speed (target vehicle speed) (V1", V2", V3", V4") of the center of mass reference vehicle speed projection wheel of each wheel (left front wheel, right front wheel, left rear wheel and right rear wheel) is calculated by the above formula, the slip rate of each wheel can be further calculated, which can be specifically calculated by the following formula:

[0073]

[0074] Among them, ω w represents wheel speed, r eff Indicates the tire radius, V x Represents the target vehicle speed, that is, V1”, V2”, V3”, and V4” can be substituted into the above formula to calculate the slip rate k of each wheel.

[0075] After calculation, the slip rate k1 of the left front wheel, the slip rate k2 of the right front wheel, the slip rate k3 of the left rear wheel and the slip rate k4 of the right rear wheel can be obtained.

[0076] In some embodiments, whether the front and rear axles of the vehicle are slipping can be determined based on the slip rates of the four wheels. Specifically, determining the slip state of the front and rear drive shafts of the vehicle based on the slip rates of the four wheels includes: calculating an average value based on the slip rate of the left front wheel and the slip rate of the right front wheel to obtain the slip rate of the front drive shaft. If the slip rate of the front drive shaft exceeds a first slip rate threshold, the front drive shaft is determined to be a drive shaft to be processed with slip; calculating an average value based on the slip rate of the left rear wheel and the slip rate of the right rear wheel to obtain the slip rate of the rear drive shaft. If the slip rate of the rear drive shaft exceeds the first slip rate threshold, the rear drive shaft is determined to be a drive shaft to be processed with slip. Exemplarily, the first slip rate threshold can be set to 20%, that is, when the slip rate of the drive shaft exceeds 20%, it can be determined that the drive shaft is a drive shaft to be processed with slip.

[0077] In some application scenarios, after obtaining the slip rates of the four wheels and determining that the front and rear drive shafts of the vehicle are slipping, drive slip control can be performed to improve the driving stability of the vehicle.

[0078] In some embodiments, the road slip rate control thresholds and PI control parameters corresponding to different adhesion coefficients can be set, and the whole vehicle can be controlled within a normal slip rate range through torque control and PI feedback control, thereby achieving vehicle skidding suppression.

[0079] In some embodiments, controlling the torque outputted by the power system to the drive shaft to be processed so that the slip rate of the vehicle drive shaft meets the updated slip rate condition includes: when the absolute value of the vehicle speed is not less than the first preset vehicle speed, adjusting the torque outputted by the power system to the drive shaft to be processed so that the adjusted slip rate of the drive shaft is not greater than the second slip rate threshold. Exemplarily, the first preset vehicle speed can be set to 7 kph, i.e., 7 kilometers per hour. The second slip rate threshold can be set to 8%.

[0080] In some embodiments, when the absolute value of the vehicle speed is less than a first preset vehicle speed, the torque output by the power system to the drive shaft to be processed is adjusted so that the adjusted rotational speed of the drive shaft is less than the first rotational speed.

[0081] In some embodiments, the slipping scenario of the drive shaft may include a driving slipping scenario and a deceleration slipping scenario. The specific implementation methods of the drive shaft slipping control in each scenario are described below.

[0082] In a drive slip scenario, if the front axle of the vehicle experiences drive slip, the target axle speed of the front axle can be controlled within a preset range by adjusting the torque output to the front axle by the power system.

[0083] In some embodiments, the driving slip control for the front axle can be divided into states based on the absolute value of the vehicle's speed. Specifically, when the absolute value of the vehicle's speed is greater than or equal to the preset speed, for example, the absolute value of the speed is ≥7Kph, the target shaft speed of the front axle is controlled within a first preset range by adjusting the torque output to the front axle by the power system. Specifically, the slip rate corresponding to the adjusted target shaft speed is less than or equal to the preset slip rate, for example, the preset slip rate is 0.08 (i.e., 8%). When the absolute value of the vehicle's speed is less than the preset speed, for example, the absolute value of the speed is <7Kph, the target shaft speed of the front axle is controlled within a second preset range by adjusting the torque output to the front axle by the power system. For example, the actual rotation speed of the front axle is controlled to be less than 10Kph.

[0084] In some embodiments, the driving slip control for the rear axle can also be divided into states based on the absolute value of the vehicle's speed. Specifically, when the absolute value of the vehicle's speed is greater than or equal to the preset speed, for example, the absolute value of the speed is ≥7Kph, the target shaft speed of the front axle is controlled within a first preset range by adjusting the torque output to the front axle by the power system. Specifically, the slip rate corresponding to the adjusted target shaft speed must be less than or equal to the preset slip rate, for example, the preset slip rate is 0.08. When the absolute value of the vehicle's speed is less than the preset speed, for example, the absolute value of the speed is <7Kph, the target shaft speed of the front axle is controlled within a second preset range by adjusting the torque output to the front axle by the power system. For example, the actual speed of the front axle is controlled to be less than 10Kph.

[0085] In a deceleration and slipping scenario, if the front axle of the vehicle experiences drive slip, the target axle speed of the front axle can be controlled within a preset range by adjusting the torque output to the front axle by the power system.

[0086] In some embodiments, the driving slip control for the front axle can be divided into states based on the absolute value of the vehicle's speed. Specifically, when the absolute value of the vehicle's speed is greater than or equal to the preset speed, for example, the absolute value of the speed is ≥7Kph, the target shaft speed of the front axle is controlled within a first preset range by adjusting the torque output to the front axle by the power system. Specifically, the slip rate corresponding to the adjusted target shaft speed must be less than or equal to the preset slip rate, for example, the preset slip rate is 0.08. When the absolute value of the vehicle's speed is less than the preset speed, for example, the absolute value of the speed is less than 7Kph, the target shaft speed of the front axle is controlled within a second preset range by adjusting the torque output to the front axle by the power system. For example, the actual speed of the front axle is controlled to be less than 2Kph.

[0087] In some embodiments, the driving slip control for the rear axle can also be divided into states based on the absolute value of the vehicle's speed. Specifically, when the absolute value of the vehicle's speed is greater than or equal to the preset speed, for example, the absolute value of the speed is ≥7Kph, the target shaft speed of the front axle is controlled within a first preset range by adjusting the torque output to the front axle by the power system. Specifically, the slip rate corresponding to the adjusted target shaft speed must be less than or equal to the preset slip rate, for example, the preset slip rate is 0.08. When the absolute value of the vehicle's speed is less than the preset speed, for example, the absolute value of the speed is less than 7Kph, the target shaft speed of the front axle is controlled within a second preset range by adjusting the torque output to the front axle by the power system. For example, the actual speed of the front axle is controlled to be less than 2Kph.

[0088] In some embodiments, the preset slip rate may be calibrated based on a road adhesion coefficient. In other embodiments, the preset slip rate may be calibrated based on a road adhesion coefficient and a driving mode of the vehicle, wherein the driving mode may include a snow mode.

[0089] In some embodiments, real-time acquisition of the vehicle's road adhesion coefficient includes: real-time acquisition of the longitudinal driving force of the four wheels and the entire wheel load; based on the longitudinal driving force of the four wheels and the entire wheel load, using the linear recursive least squares method to estimate the road adhesion coefficient in real time.

[0090] Tire-Road Friction Coefficient Estimation

[0091] The tire-road adhesion coefficient estimation function should have the following two steps:

[0092] Step 1: Calculate the tire force Fx based on the tire dynamic model (general), that is, the longitudinal force Fx of each tire (tire force estimation function)

[0093] Step 2: Estimate μ based on Fx and tire load Fz using linear recursive least squares method.

[0094] Since Fz, i.e., wheel load force, has been obtained from the above module wheel load estimation model, the following describes the process and method of estimating tire force and tire parameters to output tire longitudinal rigidity and road friction coefficient:

[0095] The tire-road adhesion coefficient is estimated using the longitudinal tire brush model + linear recursive least squares method using slip rate (the slip rate formula is explained above), tire longitudinal force and tire vertical force. It has the following characteristics:

[0096] - This method can detect different μ on both sides of the separated μ surface

[0097] -This method can achieve good accuracy and robustness before the tire reaches the friction limit

[0098] - Since the relevant parameters of the tire are not predetermined (such as tire hardness), the actual μ is estimated more accurately.

[0099] In some embodiments, the whole wheel load Fz value is estimated and the force analysis principle is as follows:

[0100] The model first calculates the wheel loads of the front and rear axles, distributes and calculates the wheel loads of each tire according to the change in lateral acceleration, innovatively considers the lift generated above a certain speed threshold, and further calculates and outputs the tires of each wheel, so that more accurate wheel loads can be obtained in each speed range, which is convenient for the introduction, utilization and calculation of subsequent functional modules.

[0101] Figure 5 A schematic diagram of wheel load estimation provided for one embodiment of the present application.

[0102] Reference Figure 5 As shown, the wheel load estimation function requires external input: lateral acceleration y and longitudinal acceleration x signals from ESC, with an accuracy of less than 10ms (generally, the bus may be set to 20ms); vehicle control internal transmission quantity: vehicle weight m, slope β, and the distances a and b from the center of mass to the front and rear axles respectively according to the known center of mass position of the vehicle;

[0103] The detailed calculation process is as follows:

[0104]

[0105] -Fzf and Fzr: represent the front axle load and rear axle load, unit: Nm

[0106] -β: road slope, unit: ° (degrees).

[0107] -m: vehicle weight, unit: kg.

[0108] -Vx: longitudinal acceleration, unit: m / s 2

[0109] -a, b: represent the distance from the front axle to the center of mass and the distance from the rear axle to the center of mass respectively, unit: m.

[0110] Since steering affects the forces on the tires, the lateral acceleration should be considered to distribute the loads on the left and right tires, as follows:

[0111] Front axle:

[0112]

[0113] Rear axle:

[0114]

[0115] -Fz,fl, Fz,fr: represent the left front and right front tire loads respectively, unit: Nm

[0116] -Fz,rl, Fz,rr: Represents the left rear and right rear tire loads, unit: Nm

[0117] -d: wheelbase, unit: m

[0118] -h: center of mass height, unit: m

[0119] - Longitudinal acceleration, unit: m / s 2

[0120] - Lateral acceleration, unit: m / s 2

[0121] The wheel load estimation function takes into account the influence of lift. When the vehicle speed exceeds a certain threshold, lift plays a certain role. Therefore, the tire load equation is modified as follows:

[0122]

[0123] ——Flift refers to the lift of the car, here is the general formula

[0124] ρ: air density;

[0125] Cd,lift: air resistance coefficient;

[0126] Alift: vehicle lift area

[0127] In some embodiments, the tire longitudinal force Fx is estimated and the force analysis principle is as follows:

[0128] Figure 6 A tire force diagram provided for one embodiment of the present application.

[0129] Reference Figure 6 As shown, the tire force estimation function should estimate the longitudinal force Fx based on the dynamic model of the individual tires.

[0130] The equation of motion for the tire (moment of inertia * angular acceleration = torque) is as follows:

[0131]

[0132] -Fx,i represents the longitudinal force of each tire, unit: Nm.

[0133] -Frr,i=fr*Fz,i represents the rolling resistance of the wheel Frr,i=rolling resistance coefficient of the wheel fr*tire load Fz,i acting on this wheel, unit: Nm.

[0134] -Iw represents the moment of inertia of the wheel, unit: kg / m2.

[0135] Indicates wheel speed, unit: rad / s.

[0136] T shaft Indicates the driving torque acting on the wheel, unit: Nm.

[0137] Tb,i represents the braking torque acting on the wheel, unit: Nm.

[0138] -Rw: represents the tire radius, unit: m.

[0139] The general slip ratio k for a tire is defined as follows:

[0140]

[0141] -ω w : wheel speed; Vx: vehicle speed; r eff Indicates the tire radius.

[0142] Figure 7 A schematic diagram of the corresponding relationship between tire force and slip rate provided by an embodiment of the present application.

[0143] The application principle of the brush model is based on Figure 7 The relationship between tire force and slip ratio shown reflects the nonlinear characteristics of the tire, that is, before reaching a certain slip ratio, the longitudinal tire force Fx increases with the increase of the tire slip ratio k; after reaching a certain slip ratio, Fx reaches its maximum value F x，max =μF z .

[0144] In some embodiments, based on the longitudinal tire brush model (general model), the tire stiffness and the road adhesion coefficient μ estimated using the LRLS method should be as follows:

[0145]

[0146] F i =μF z if f i > 3μF z

[0147]

[0148] Among them, the preconditions for calculating Fi are divided according to the fact that the slip rate and Fx are generally divided into regions of <3μFz and >3μFz, and Taylor expansion linearization is performed on the nonlinear system.

[0149] -Cx: tire longitudinal stiffness;

[0150] -f i : The maximum friction that the ground and tires can provide;

[0151] -Fi: Theoretical value of the maximum longitudinal tire force of the vehicle.

[0152] Since the longitudinal tire brush model is nonlinear, the tire brush model should be linearized using Taylor expansion so that μ and Cx for each wheel can be estimated using the linear recursive least squares method LRLS.

[0153] For nonlinear systems:

[0154] y(k)=f(k,θ)

[0155] y(k) can be approximated as follows:

[0156]

[0157] in:

[0158]

[0159] The following linearized form can be obtained (linear least squares method):

[0160]

[0161] The Jacobian matrix is ​​a matrix in which the first-order partial derivatives are arranged in a certain way. Its determinant is called the Jacobian determinant, and its application is as follows:

[0162]

[0163] if f i ≤3μF z ,

[0164]

[0165] if f i >3μF z ,

[0166]

[0167] Expressed as a state estimation matrix:

[0168] Z(k) is Fx, the longitudinal force of the tire.

[0169] The RLS equation after linearization is as follows:

[0170]

[0171] Finally, when the tire brush model is saturated, becomes 0, from which it can be concluded that μ is a function of Fx and Fz.

[0172] The LRLS algorithm should use the regression vector The past input and output data contained in iteratively update the unknown parameter vector

[0173] Minimize the sum of squared modeling errors:

[0174] By choosing appropriate parameters, such as the forgetting factor λ, the sum of squares of the modeling error minimize.

[0175] The process of the LRLS algorithm is as follows:

[0176] Step 1: Measure the system output y(t) and calculate the regression vector

[0177] Step 2: Calculate the recognition error e(t), which is the difference between the actual output value of the system at that moment and the estimated output value. The estimated output value is the result of the previous

[0178] The model parameters obtained at a time θ(t-1) are estimated as:

[0179]

[0180] Step 3: Calculate the updated gain vector K(t):

[0181] In the linear recursive least squares method of the road adhesion coefficient estimation function, the parameter R is specially introduced. R is the noise covariance matrix. The purpose is to introduce the uncertainty of the measurement noise to increase the robustness of the system. Therefore, the gain vector K(t) is rewritten as:

[0182]

[0183] Calculate the error covariance matrix P(t):

[0184]

[0185] Among them, the diagonal matrix Λ=diag[λ 1 ,λ 2 , ..., λ n ]

[0186] The "vector forgetting factor" is used here because There are two system states Cx and μ in , and their changing rates are different. The changing rate of Cx is slower than that of μ, so different forgetting factors should be used.

[0187] The fourth step is to update the estimated parameter vector θ(t):

[0188] θ(t)=θ(t-1)+K(t)e(t)The parameter λ in the LRLS algorithm is the forgetting factor, which can effectively reduce the impact of old and invalid data on the model, so that parameter estimation can quickly track changes in the process.

[0189] The forgetting factor λ should be a function of the slip rate taking into account the following factors:

[0190] λ should be given higher priority for larger slip ratios, since higher excitation can lead to better estimation of μ.

[0191] Considering the recognition error e(t), a larger recognition error means that the road surface is changing, so λ should be smaller to allow the change of μ to be quickly recognized when the road surface changes.

[0192] The μ estimator should be disabled if any of the following conditions hold:

[0193] The brake pedal is pressed. The braking force is not available, so Fx cannot be estimated, and μ cannot be estimated.

[0194] The front wheel steering angle is greater than the threshold, that is, μ is not estimated during steering.

[0195] The vehicle speed is too low, i.e. μ is not estimated when the vehicle is stationary.

[0196] The wheel slip rate is too high or too low. When the slip rate is too high, it is in the nonlinear region between the tire longitudinal force and the slip rate. When the slip rate is too low, the slip rate noise is large and it is not suitable for estimating μ.

[0197] The wheel slip rate change rate is lower than the threshold and the slip rate sampling points are too concentrated, which will lead to inaccurate μ estimation.

[0198] When the wheel output torque is lower than the threshold, that is, the tire excitation is too small, μ is not estimated.

[0199] If any of the deactivation conditions hold, the estimator should be deactivated and the current estimate should be stored.

[0200] If the deactivation condition is not met for a certain period of time, the estimator should be activated, and the estimated value at the activation time is the last stored value.

[0201] Figure 8 A schematic diagram of the structure of a vehicle driving assistance control device provided in one embodiment of the present application.

[0202] Reference Figure 8 As shown, the vehicle driving assistance control device may include a processor 801 and a memory 802, and the memory 802 is used to store at least one instruction, and when the instruction is loaded and executed by the processor 801, the vehicle driving assistance control method provided in any embodiment of the present application is implemented.

[0203] The embodiment of the present application also provides a vehicle, which may include Figure 8 The illustrated embodiment provides a vehicle driving assistance control device.

[0204] An embodiment of the present application also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the vehicle driving assistance control method provided by any embodiment of the present application is implemented.

[0205] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0206] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0207] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0208] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0209] The above-mentioned integrated unit implemented in the form of a software functional unit can be stored in a computer-readable storage medium. The above-mentioned software functional unit is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor (Processor) to perform some steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), disk or optical disk and other media that can store program codes.

[0210] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

[0211] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A vehicle driving assistance control method, characterized in that: The method comprises: Obtain the vehicle's road adhesion coefficient in real time; Update the slip rate condition and PI control parameters based on the currently acquired road adhesion coefficient; When it is determined that there is a drive shaft to be processed that is slipping, the torque output by the power system to the drive shaft to be processed is controlled based on the updated PI control parameters so that the slip ratio of the vehicle drive shaft meets the updated slip ratio condition.

2. The method according to claim 1, characterized in that The step of determining the drive shaft to be processed that is slipping comprises: Based on the vehicle's center of mass speed, wheelbase, track width, and distance from the rear axle to the center of mass, the Ackerman angle is applied to calculate in real time the target speeds corresponding to the center of mass speed when projected onto the four wheels, wherein the target speeds corresponding to the four wheels include a target speed corresponding to the left front wheel, a target speed corresponding to the right front wheel, a target speed corresponding to the left rear wheel, and a target speed corresponding to the right rear wheel; Calculating the slip rates of the four wheels based on the wheel speed, tire radius, steering angle and target vehicle speed of the four wheels, wherein the slip rates of the four wheels include the slip rate of the left front wheel, the slip rate of the right front wheel, the slip rate of the left rear wheel and the slip rate of the right rear wheel; The slip states of the front and rear drive shafts of the vehicle are determined based on the slip rates of the four wheels.

3. The method according to claim 2, characterized in that The target vehicle speed corresponding to the vehicle center speed projected to the four wheels in real time based on the vehicle center speed, wheelbase, track width and the distance from the rear axle to the center of mass of the vehicle and the Ackerman angle is calculated in real time, including: The target vehicle speed corresponding to the left front wheel is calculated in real time by the following formula: Among them, V1” represents the target vehicle speed corresponding to the left front wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle; The target vehicle speed corresponding to the right front wheel is calculated in real time by the following formula: Among them, V2” represents the target vehicle speed corresponding to the right front wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle; The target vehicle speed corresponding to the left rear wheel is calculated in real time by the following formula: Among them, V3” represents the target vehicle speed corresponding to the left rear wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle; The target vehicle speed corresponding to the right rear wheel is calculated in real time by the following formula: Among them, V4" represents the target vehicle speed corresponding to the right rear wheel, V represents the vehicle speed at the center of mass, L represents the wheelbase, C represents the track width, B represents the distance from the rear drive shaft to the center of mass, and α0 represents the vehicle steering angle.

4. The method according to claim 2, characterized in that: The determining the slip state of the front drive shaft and the rear drive shaft of the vehicle based on the slip ratios of the four wheels comprises: Calculating an average value based on the slip rate of the left front wheel and the slip rate of the right front wheel to obtain the slip rate of the front drive shaft, and if the slip rate of the front drive shaft exceeds a first slip rate threshold, determining that the front drive shaft is a drive shaft to be processed with slippage; An average value is calculated based on the slip rate of the left rear wheel and the slip rate of the right rear wheel to obtain the slip rate of the rear drive shaft. If the slip rate of the rear drive shaft exceeds a first slip rate threshold, the rear drive shaft is determined to be a drive shaft to be processed with slippage.

5. The method according to claim 1, characterized in that The step of controlling the torque outputted by the power system to the drive shaft to be processed so that the slip ratio of the vehicle drive shaft satisfies the updated slip ratio condition comprises: When the absolute value of the vehicle speed is not less than the first preset vehicle speed, the torque output by the power system to the drive shaft to be processed is adjusted so that the slip rate of the adjusted drive shaft is not greater than a second slip rate threshold.

6. The method according to claim 5, characterized in that When the absolute value of the vehicle speed is less than the first preset vehicle speed, the torque output by the power system to the drive shaft to be processed is adjusted so that the adjusted rotational speed of the drive shaft is less than the first rotational speed.

7. The method according to claim 1, characterized in that The real-time acquisition of the road adhesion coefficient of the vehicle includes: Obtain the longitudinal driving force of the four wheels and the entire wheel load in real time; Based on the longitudinal driving force of the four wheels and the entire wheel load, the road adhesion coefficient is estimated in real time using a linear recursive least squares method.

8. A vehicle driving assistance control device, characterized in that: The device includes: a processor and a memory, wherein the memory is used to store at least one instruction, and when the instruction is loaded and executed by the processor, the vehicle driving assistance control method as described in any one of claims 1 to 7 is implemented.

9. A vehicle, characterized in that: The vehicle includes the vehicle driving assistance control device according to claim 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the vehicle driving assistance control method as described in any one of claims 1 to 7 is implemented.

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