A coordinated control method for energy recovery system and anti-lock braking system of new energy car

Abstract

The present invention provides a method for coordinated control of an energy recovery system of a new energy car and an anti-lock braking system of an automobile, the method comprising: obtaining real-time data of the automobile; inputting the real-time data into a prediction model to predict the wheel braking torque demand; comparing the wheel braking torque demand with the maximum braking torque that can be provided by the motor, and completing the coordinated control of the whole vehicle braking energy recovery system and the anti-lock braking system of the automobile. Under the premise of satisfying the functions of the two systems, the present invention recovers the energy generated during braking as much as possible, improves the utilization efficiency of energy, and has a positive effect on improving the mileage of new energy vehicles.

Description

Technical Field

[0001] The invention belongs to the field of automobile braking, and in particular relates to a coordinated control method of an energy recovery system of a new energy car and an automobile anti-lock braking system. Background Art

[0002] The coordinated control of the automobile anti-lock braking system\brake energy recovery system (ABS\RBS) mainly includes the coordinated control of the four aspects of braking awareness recognition, braking force distribution, anti-lock coordinated control, and pressure control. At present, there are two types of braking force distribution algorithms: superposition type and coordination type. The superposition type distribution algorithm is also called the parallel distribution algorithm, which is mostly used in parallel braking systems. When new energy vehicles use the superposition type distribution algorithm, their regenerative braking system and hydraulic braking system can only work independently, and cannot coordinate the control of the motor and hydraulic braking force. Summary of the invention

[0003] The purpose of the present invention is to provide a coordinated control method for an automobile anti-lock braking system\brake energy recovery system (ABS\RBS). Under the premise of ensuring vehicle safety, the coordinated control of the automobile anti-lock braking system (ABS) and the brake energy recovery system (RBS) is considered by applying driving conditions and driver braking awareness prediction, so as to recover as much energy as possible under the premise of ensuring braking safety, thereby improving the vehicle's mileage.

[0004] The technical solution of the present invention is as follows:

[0005] A method for coordinated control of an energy recovery system of a new energy car and an anti-lock braking system of a car, the method comprising:

[0006] Get real-time data of the car;

[0007] Inputting the real-time data into a prediction model to predict the wheel braking torque requirement;

[0008] The wheel braking force requirement is compared with the maximum braking torque that the motor can provide, and the coordinated control of the vehicle's braking energy recovery system and the vehicle's anti-lock braking system is completed.

[0009] Furthermore, the real-time data of the vehicle includes an accelerator pedal signal, a pressure signal and a wheel speed signal of the vehicle.

[0010] Furthermore, the prediction model is a three-degree-of-freedom vehicle dynamics model, which includes the longitudinal motion of the vehicle and the rotational motion of the front and rear wheels, specifically:

[0011]

[0012] Where M is the mass of the car, Front tire acceleration, Rear tire acceleration, is the longitudinal acceleration of the vehicle, F x1 (k), F x2 (k) represents the longitudinal force on the front / rear wheels, T b1 (k), T b2 (k) is the braking torque on the front / rear wheels, where k is the moment and R is the radius of the vehicle tire.

[0013] Furthermore, the formula of the front / rear wheel hydraulic braking force torque is:

[0014]

[0015] in, They are the front / rear wheel hydraulic braking force torque respectively; is the dynamic torque of the motor; k is the moment k at that time.

[0016] Furthermore, the formula for the longitudinal force on the front / rear wheels is:

[0017] F x1 (k) = μF z1 (k)Dsin(C tan -1 {Bs1(k)-E[Bs1(k)-tan -1 (Bs1(k))]})

[0018] F x2 (k) = μF z2 (k)Dsin(Ctan -1 {Bs2(k)-E[Bs2(k)-tan -1 (Bs2(k))]})

[0019] Among them, B is the stiffness coefficient, C is the forming factor, D is the crest factor; μ is the road adhesion coefficient, E is the curvature factor; F z1 (k), F z2 (k) is the vertical reaction force of the ground on the front / rear wheels, s1(k) and s2(k) are the slip rates of the front / rear wheels, respectively, where k is the time k;

[0020]

[0021] Where a is the horizontal distance from the center of gravity of the vehicle to the front axle, b is the horizontal distance from the center of gravity of the vehicle to the rear axle, L is the distance between the front and rear axles of the vehicle, and h is the distance between the front and rear axles of the vehicle. g is the height from the center of gravity of the vehicle to the ground, g is the ground gravity acceleration, is the longitudinal acceleration at time (k-1).

[0022] Furthermore, when predicting the real-time data of the car, it is necessary to add constraints on the braking torque received by the wheel, the braking torque change rate, and the wheel slip rate, specifically:

[0023]

[0024] Among them, T b1min 、T b2min are the minimum braking torques on the front and rear wheels respectively; T b1max 、T b2max are the maximum braking torques on the front and rear wheels respectively; ΔT b1min , ΔT b2min are the minimum adjustment values ​​of the braking torque on the front and rear wheels respectively; ΔT b1max , ΔT b2max are the maximum braking torque adjustments of the front and rear wheels respectively; s min is the minimum tire slip rate, s max is the maximum tire slip rate.

[0025] Furthermore, the formula for the wheel braking torque requirement is:

[0026]

[0027]

[0028] Among them, (k+i|k) represents the prediction of parameter (k+i) when time is k; s r To predict the slip rate, Q1 and Q2 represent weight coefficients used to adjust the safety performance of the front and rear wheels during braking; R1 and R2 represent weight coefficients for adjusting the change in braking torque applied to the front and rear wheels.

[0029] Furthermore, the wheel braking force requirement is compared with the maximum braking torque that the motor can provide, and the coordinated control of the vehicle braking energy recovery system and the vehicle anti-lock braking system is completed as follows:

[0030] If the braking torque required by the wheel is greater than the maximum braking torque that the motor can provide, the motor outputs the maximum braking torque, and the remaining required braking torque is provided by the hydraulic braking system; if the motor braking torque is less than the maximum braking torque that the motor can provide, the motor provides the required braking torque.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention proposes a coordinated control method based on a brake energy recovery system (RBS) and an anti-lock braking system (ABS) of a front-wheel drive car. On the premise of satisfying the functions of the two systems, the energy generated during braking is recovered as much as possible to improve the energy utilization efficiency, which has a positive effect on improving the mileage of new energy vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings generally illustrate various embodiments by way of example and not limitation, and together with the description and claims, serve to illustrate the embodiments of the invention. Where appropriate, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

[0034] Figure 1 A schematic diagram of the method flow of the present invention is shown;

[0035] Figure 2 A schematic diagram of the controller arrangement structure of the present invention is shown. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] The embodiment of the present invention provides a coordinated control of the anti-lock braking system and the energy recovery system of a new energy car. The specific steps are as follows Figure 1 .flow chart.

[0038] Prediction Module:

[0039] The prediction model used in the present invention is a three-degree-of-freedom vehicle dynamics model, which includes the longitudinal motion of the vehicle and the rotational motion of the front and rear wheels, and can be written as:

[0040]

[0041] Where M is the mass of the car, Front tire acceleration, Rear tire acceleration, is the longitudinal acceleration of the vehicle, F x1 (k), F x2 (k) represents the longitudinal force on the front / rear wheels, T b1 (k), T b2 (k) is the braking torque on the front / rear wheels, where k is the moment and R is the radius of the vehicle tire.

[0042] in:

[0043]

[0044] in They are the front / rear wheel hydraulic braking force torque respectively; is the dynamic torque of the motor; k is the moment k at that time.

[0045] The ground braking force required by the front and rear wheels can be calculated using the magic tire formula:

[0046] F x1 (k) = μF z1 (k)Dsin(Ctan -1 {Bs1(k)-E[Bs1(k)-tan -1 (Bs1(k))]})

[0047] F x2 (k) = μF z2 (k)Dsin(Ctan -1 {Bs2(k)-E[Bs2(k)-tan -1 (Bs2(k))]})

[0048] B is the stiffness coefficient, C is the forming factor, D is the crest factor; μ is the road adhesion coefficient, E is the curvature factor, F is the z1 (k), F z2 (k) is the vertical reaction force of the ground on the front / rear wheels, s1(k) and s2(k) are the slip rates of the front / rear wheels respectively, and k is the moment k.

[0049]

[0050] a is the horizontal distance from the center of gravity of the vehicle to the front axle, b is the horizontal distance from the center of gravity of the vehicle to the rear axle, L is the distance between the front and rear axles of the vehicle, h is g is the height from the center of gravity of the vehicle to the ground, g is the ground gravity acceleration, is the longitudinal acceleration at time (k-1).

[0051] Through this prediction model, the relationship between the current and future states of the wheel slip ratio is expressed as follows:

[0052] The longitudinal velocity of the vehicle and the angular acceleration of the front / rear wheels at time k can be used to obtain the longitudinal velocity of the vehicle and the angular acceleration of the front / rear wheels at time (k+1):

[0053]

[0054] Where T s is the sampling period of the vehicle. Then the vehicle slip rate at the future (k+1) time can be obtained:

[0055]

[0056]

[0057] Where Δv is the change in vehicle speed, Δω1 and Δω2 are the changes in front and rear vehicle wheel speeds respectively.

[0058] This process is the model prediction of the vehicle, where ν(k), ω1(k), ω2(k), s1(k), s2(k), T b1 (k), T b2 (k), F x1 (k), F x2 (k) is the actual data obtained by the vehicle at the previous moment, which is transmitted to the model prediction by the vehicle module, and then the predicted values ​​are obtained: s1(k+1), s2(k+1), v(k+1), ω1(k+1), ω2(k+1).

[0059] Working conditions requirements:

[0060] In the present invention, the cost function of the next link is mainly constrained by the braking torque received by the wheel, the braking torque change rate and the wheel slip rate.

[0061]

[0062] T b1min 、T b2min are the minimum braking torques on the front and rear wheels respectively; T b1max 、T b2max are the maximum braking torques on the front and rear wheels respectively; ΔT b1min , ΔT b2min are the minimum adjustment values ​​of the braking torque on the front and rear wheels respectively; ΔT b1max , ΔT b2max are the maximum braking torque adjustments of the front and rear wheels respectively; s min is the minimum tire slip rate, s max is the maximum tire slip rate.

[0063] Cost function:

[0064] According to the current state of the vehicle, the future N can be inferred from the model prediction pThe wheel slip state in a sampling period. If the wheel slip rate is to be controlled at the expected value to fully utilize the road conditions for braking, it is necessary to find the braking torque required by the corresponding tire. Since the optimal slip rate of most roads is around 0.2, the expected slip rate is set to 0.2 to ensure that the anti-lock braking system (ABS) of the vehicle has excellent braking performance on various road surfaces. The optimal braking torque adjustment ΔT required for the front / rear wheels in the next sampling period is obtained by the minimum value of the cost function. b1 , ΔT b2 , and apply corresponding braking torque changes to the wheels, so that the slip rate of the front and rear wheels quickly reaches the expected value during the braking process of the anti-lock braking system (ABS). In addition, the effect of the braking torque on the wheels is considered in the cost function to reduce the effect of the braking torque on the wheels. Therefore, its cost function can be listed as:

[0065]

[0066]

[0067] Among them, (k+i|k) represents the prediction of parameter (k+i) when time is k; s r To predict the slip rate, Q1 and Q2 represent weight coefficients used to adjust the safety performance of the front and rear wheels during braking; R1 and R2 represent weight coefficients for adjusting the change in braking torque applied to the front and rear wheels.

[0068] Feedback equation:

[0069] Through the J1(k) and J2(k) minimum cost equations, the optimal sequence of control variables for the braking torque adjustment can be obtained. Then the first element of the optimal sequence of control variables is used as the braking torque adjustment required by the wheel in the feedback equation, so it can be listed as:

[0070]

[0071] Considering the braking performance and braking stability of the vehicle, the present invention performs braking control according to the principle of independent control of the two front wheels and low-selective control of the two rear wheels. The current state of each front wheel is used to calculate the wheel braking torque adjustment corresponding to the next moment to control the slip rate of the two front wheels to be maintained near the expected value, thereby improving the braking performance, and the wheel braking torque adjustment is calculated according to the state of the wheel with the smaller wheel speed among the two rear wheels, and the same braking torque is applied to the two rear wheels to avoid vehicle braking instability caused by unequal ground braking forces on the left and right wheels of the rear axle. In order to coordinate the braking energy recovery system (RBS) and the automobile anti-lock braking system (ABS) to control the wheel slip rate, the braking torque required by the wheel is compared with the maximum braking torque that the motor can provide. If the braking torque required by the wheel is greater than the maximum braking torque that the motor can provide, the motor outputs the maximum braking torque, and the remaining required braking torque is provided by the hydraulic braking system. If the motor braking torque is less than the maximum braking torque that the motor can provide, the motor provides the required braking torque.

[0072] Furthermore, it can be seen from the flow chart that the braking torque predicted by the front and rear wheels is obtained through the feedback equation. If the braking torque required by the wheel is greater than the maximum braking torque that the motor can provide, the motor outputs the maximum braking torque, and the remaining required braking torque is provided by the hydraulic braking system. If the motor braking torque is less than the maximum braking torque that the motor can provide, the motor provides the required braking torque.

[0073] Depend on Figure 2 .It can be obtained that it is a controller layout structure diagram between the vehicle braking energy recovery control system (RBS) and the automobile anti-lock braking system (ABS). As shown in the figure, the vehicle obtains the vehicle's accelerator pedal signal, pressure signal, wheel speed signal, etc. through sensors, and transmits the signal to the brake controller. The brake controller has control prediction function modules such as braking awareness recognition, hydraulic control, energy recovery control (RBS), vehicle state estimation, hydraulic state detection, and anti-lock braking control (ABS). By predicting the braking force at the next moment, the motor torque demand is transmitted to the vehicle controller through CAN communication. The vehicle controller transmits the target torque and limit signal to the motor controller and the battery controller respectively to control the motor and the battery. Then the motor controller and the battery controller transmit speed, torque, SOC temperature and other signals to the vehicle controller. The vehicle controller then feeds back the actual motor regeneration torque signal to the brake controller. If the motor braking fails to meet the braking requirements and triggers hydraulic braking, the coordinated control of the vehicle braking energy recovery system (RBS) and the automobile anti-lock braking system (RBS) is completed.

[0074] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for coordinated control of energy recovery system and anti-lock braking system of new energy cars, characterized in that: The method comprises: Get real-time data of the car; Inputting the real-time data into a prediction model to predict the wheel braking torque requirement; Compare the wheel braking torque requirement with the maximum braking torque that the motor can provide, and complete the coordinated control of the vehicle's braking energy recovery system and the vehicle's anti-lock braking system; When predicting the real-time data of the car, it is necessary to add constraints on the braking torque received by the wheel, the braking torque change rate, and the wheel slip rate, specifically: Among them, T b1min , T b2min are the minimum braking torques on the front and rear wheels respectively; T b1max , T b2max are the maximum braking torques on the front and rear wheels respectively; ΔT b1min , ΔT b2min are the minimum adjustment values ​​of the braking torque on the front and rear wheels respectively; ΔT b1max , ΔT b2max are the maximum braking torque adjustments of the front and rear wheels respectively; s min is the minimum tire slip rate, s max is the maximum tire slip rate; T b1 (k+i|k) is the predicted value of the front wheel braking torque at time k for time (k+i); T b2 (k+i|k) is the predicted value of the rear wheel braking torque at time k for time (k+i); ΔT b1 (k+i|k) is the predicted value of the front wheel braking torque adjustment at time k to time (k+i); ΔT b2 (k+i|k) is the predicted value of the rear wheel braking torque adjustment at time k versus time (k+i); s1(k+i|k) is the predicted value of the front wheel slip rate at time k versus time (k+i); s2(k+i|k) is the predicted value of the rear wheel slip rate at time k versus time (k+i); The formula for the wheel braking torque requirement is: Among them, (k+i|k) represents the prediction of parameter (k+i) when time is k; s r To predict the slip rate, Q1 and Q2 represent the weight coefficients used to adjust the safety performance of the front and rear wheels during braking; R1 and R2 represent the weight coefficients for adjusting the change in braking torque on the front and rear wheels; J1(k) is the cost function of the front wheel, J2(k) is the cost function of the rear wheel, and N p is the Nth time after k p At time t, u(k|k) is a summary function including slip ratio and adjustment braking torque.

2. The coordinated control method of the energy recovery system and the anti-lock braking system of a new energy car according to claim 1 is characterized in that: The real-time data of the vehicle includes an accelerator pedal signal, a pressure signal and a wheel speed signal of the vehicle.

3. The coordinated control method of the energy recovery system and the anti-lock braking system of a new energy car according to claim 1 is characterized in that: The prediction model is a three-degree-of-freedom vehicle dynamics model, which includes the longitudinal motion of the vehicle and the rotational motion of the front and rear wheels. Specifically, Where M is the mass of the car, Front tire acceleration, Rear tire acceleration, is the longitudinal acceleration of the vehicle, F x1 (k), F x2 (k) represents the longitudinal force on the front / rear wheels, T b1 (k), T b2 (k) is the braking torque on the front / rear wheels, where k is the moment k, R is the radius of the vehicle tire, and J is the moment of inertia of the wheel.

4. The coordinated control method of the energy recovery system and the anti-lock braking system of a new energy car according to claim 3 is characterized in that: The formula of the front / rear wheel hydraulic braking force torque is: Among them, T b1 (k) They are the front / rear wheel hydraulic braking force torque respectively; is the dynamic torque of the motor; k is the moment k at that time.

5. The coordinated control method of the energy recovery system and the anti-lock braking system of a new energy car according to claim 4 is characterized in that: The formula for the longitudinal force on the front / rear wheels is: F x1 (k)=μF z1 (k)Dsin(Ctan -1 {Bs1(k)-E[Bs1(k)-tan -1 (Bs1(k))]}) F x2 (k)=μFz2(k)Dsin(Ctan -1 {Bs2(k)-E[Bs2(k)-tan -1 (Bs2(k))]}) Among them, B is the stiffness coefficient, C is the forming factor, D is the crest factor; μ is the road adhesion coefficient, F z1 (k), F z2 (k) is the vertical reaction force of the ground on the front / rear wheels, s1(k) and s2(k) are the slip rates of the front / rear wheels, respectively, where k is the time k; Where a is the horizontal distance from the center of gravity of the vehicle to the front axle, b is the horizontal distance from the center of gravity of the vehicle to the rear axle, L is the distance between the front and rear axles of the vehicle, and h is the distance between the front and rear axles of the vehicle. g is the height from the center of gravity of the vehicle to the ground, g is the ground gravity acceleration, is the longitudinal acceleration at time (k-1).

6. The coordinated control method of the energy recovery system and the anti-lock braking system of a new energy car according to claim 1 is characterized in that: Compare the wheel braking torque requirement with the maximum braking torque that the motor can provide, and complete the coordinated control of the vehicle braking energy recovery system and the vehicle anti-lock braking system as follows: If the braking torque required by the wheel is greater than the maximum braking torque that the motor can provide, the motor outputs the maximum braking torque, and the remaining required braking torque is provided by the hydraulic braking system; if the motor braking torque is less than the maximum braking torque that the motor can provide, the motor provides the required braking torque.

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