CN112298141B - A control method of a vehicle braking system - Google Patents

Abstract

The invention provides a control method for a vehicle braking system, which first obtains the pressure-increasing and decompressing characteristics, then obtains the target braking torque according to the state information of the vehicle through the established slip controller, and then obtains the target pressure of the brake air chamber , and then control the intake valve and exhaust valve of the brake air chamber to work according to the supercharging characteristic curve or the decompression characteristic curve, thereby realizing pressure braking. The pressure-increasing and decompression characteristics obtained by the calibration method of the present invention can bring convenience to the regulation and control of the braking pressure of the whole vehicle, thereby improving the regulation efficiency of the method for regulating and controlling the braking pressure of the whole vehicle.

Description

A control method of a vehicle braking system

Divisional application

This application is a divisional application of a patent application with an application number of 202010121004.0, an application date of February 26, 2020, and an invention title of "a method for regulating vehicle brake pressure based on a pneumatic brake-by-wire system".

technical field

The invention relates to the field of automobile braking, in particular to a control method of a vehicle braking system.

Background technique

Vehicle anti-lock braking system (ABS) is one of the active safety devices of the vehicle. It adjusts the degree of wheel locking by controlling the braking torque according to the wheel speed feedback, which can make full use of the road adhesion and ensure the vehicle during emergency braking. Stability is crucial to improving vehicle stability and safety. When the brake pressure of the existing vehicle is regulated, the time required to open the intake valve and the exhaust valve of the brake air chamber can only be determined after a complex calculation according to the adjusted pressure change, which will inevitably affect the braking system. Respond promptly.

SUMMARY OF THE INVENTION

Based on the above status quo, the main purpose of the present invention is to provide a control method for a vehicle braking system, so as to solve the problem of slow braking response caused by complex calculation of the time when the intake valve and the exhaust valve of the brake chamber need to be opened. question.

For achieving the above object, the technical scheme adopted in the present invention is as follows:

The invention provides a control method for a vehicle braking system, comprising the steps of:

和增压时间t1，制动减压特性曲线图中包括减压压力调整量

和减压时间t3，其中，m、n分别为min，2，3，…，max；S10: Acquire the pressure-increasing and decompression characteristics and braking signals of the entire vehicle, where the pressure-increasing and decompressing characteristics are represented as a brake pressure-increasing characteristic curve and a brake pressure-reducing characteristic curve, and the brake pressure-increasing characteristic curve includes the pressure-boosting pressure Adjustment amount

and the boost time t1, the brake decompression characteristic curve includes the decompression pressure adjustment

and decompression time t3, where m and n are min, 2, 3, ..., max respectively;

S20: Obtain vehicle status information;

S30: establish a slip rate controller, and confirm the actual slip rate and the target slip rate according to the vehicle state information;

S40: According to the actual slip rate and the target slip rate, combined with the slip rate controller, assign a target braking torque to each driving wheel

的函数，然后结合各所述驱动轮的所述目标制动扭矩

通过对所述制动成本函数求极值得到所述预期总再生制动扭矩T_d、各所述驱动轮的预期气压制动扭矩

S50: Establish a braking cost function of the vehicle, where the braking cost function is the expected total regenerative braking torque T _d of the vehicle and the expected pneumatic braking torque of each of the driving wheels

, then combined with the target braking torque of each of the drive wheels

The expected total regenerative braking torque T _d and the expected pneumatic braking torque of each of the driving wheels are obtained by finding the extreme value of the braking cost function

确定所述目标压力P_i，并获取所述制动气室的实际压力P_i0，计算其与所述目标压力的压力差ΔP_i＝P_i-P_i0，根据所述压力差ΔP_i和所述增减压特性曲线图确定所述制动气室的进气阀或者排气阀的打开方式，并按照所述打开方式对制动压力进行调控；S60: According to the expected air brake torque

Determine the target pressure P _i , obtain the actual pressure P _i0 of the brake air chamber, calculate the pressure difference ΔP _i =P _i -P _i0 between it and the target pressure, according to the pressure difference ΔP _i and the The pressure-increasing and decompression characteristic curve diagram determines the opening mode of the intake valve or the exhaust valve of the brake air chamber, and regulates the braking pressure according to the opening mode;

和最小扭矩

确定所述电机的实际输出制动扭矩T_e，并控制所述电机输出实际输出制动扭矩T_e。S70: According to the expected total regenerative braking torque T _d combined with the maximum torque that the motor can provide

and minimum torque

Determine the actual output braking torque _Te of the electric motor, and control the electric motor to output the actual output braking torque _Te .

Preferably, in the step S30, the establishing a slip rate controller includes:

S31: Set the proportional integral model: S _i =e _i +α _i ∫e _i dt, wherein, e _i =λ _i -λ _di ;

S32: Establish the slip rate controller as:

The step S40 includes:

S41: Derive the proportional-integral model to obtain a reciprocal model

得到各所述驱动轮的目标制动扭矩

S42: make

Obtain the target braking torque of each of the drive wheels

为预设系数。Among them, λ _i is the actual slip rate of the vehicle, λ _di is the target slip rate of the vehicle, sat is the saturation function, α _i , ε ₁ , ε ₀ ,

is the default coefficient.

Preferably, the actual slip rate λ _i is calculated according to the following formula:

The target slip rate _λdi is calculated according to the following formula:

按如下公式计算：In the step S42, the target braking torque

Calculated according to the following formula:

为利用摩擦系数；M_thre为用于偏航控制的偏航力矩阈值；l为所述车辆的驱动轮轮距；J_i为所述车辆的驱动轮的转动惯量、F_xi为所述车辆的驱动轮的纵向力；F_zi为所述驱动轮在其转动轴方向的垂直力；f^-1为预设的摩擦系数表。Wherein, u _x is the longitudinal speed of the vehicle, ω _i is the driving wheel angular velocity of the vehicle, P _i is the driving wheel radius of the vehicle; K _λ is a preset coefficient; μ is the road surface on which the vehicle travels friction coefficient;

is the use of friction coefficient; M _thre is the yaw moment threshold for yaw control; l is the wheel track of the driving wheel of the vehicle; J _i is the moment of inertia of the driving wheel of the vehicle, F _xi is the longitudinal force of the driving wheel; F _zi is the vertical force of the driving wheel in the direction of its rotation axis; f ^-1 is a preset friction coefficient table.

Preferably, the step S50 includes:

S51: Establish a braking cost function of the vehicle

为所述驱动轮的预期气压制动扭矩；

为所述驱动轮的目标制动扭矩；T_d为所述预期总再生制动扭矩；K_r为预设系数；ΔP_ai为驱动轮的压力变化量，

为最佳再生制动扭矩；

为所述再生制动扭矩的最大值；

为储备间隙；in,

is the expected air brake torque of the drive wheel;

is the target braking torque of the driving wheel; T _d is the expected total regenerative braking torque; K _r is a preset coefficient; ΔP _ai is the pressure change of the driving wheel,

for the best regenerative braking torque;

is the maximum value of the regenerative braking torque;

for reserve clearance;

通过对所述制动成本函数求极值得到所述预期总再生制动扭矩T_d、各所述驱动轮的预期气压制动扭矩

S52: Combined with the target braking torque of each of the driving wheels

The expected total regenerative braking torque T _d and the expected pneumatic braking torque of each of the driving wheels are obtained by finding the extreme value of the braking cost function

和最小扭矩

确定电机的实际输出制动扭矩T_e，然后控制电机输出实际制动扭矩T_e，包括步骤：Preferably, in the step S70, according to the expected total regenerative braking torque T _d combined with the maximum torque that the motor can provide

and minimum torque

Determine the actual output braking torque T _e of the motor, and then control the motor to output the actual braking torque T _e , including steps:

S71: Determine the expected braking torque output by the motor according to the expected total regenerative braking torque T _d

和最小扭矩

S72: Obtain the maximum torque that the motor can provide

and minimum torque

与最大扭矩

最小扭矩

的大小：S73: Determine the expected braking torque output by the motor

with maximum torque

Minimum torque

the size of:

则

like

but

则

like

but

则

like

but

S74: Control the motor to output the actual braking torque _Te .

确定所述目标压力P_i，具体为：Preferably, in the step S60, according to the expected air pressure braking torque

Determine the target pressure P _i , specifically:

Among them, K _i is the conversion coefficient.

Preferably, the step S60 includes:

确定所述目标压力P_i:；S61: According to the expected air pressure braking torque

Determine the target pressure P _i :;

S62: Acquire the actual pressure P _i0 of the brake air chamber, and calculate the pressure difference ΔP _i =P _i -P _i0 between it and the target pressure;

S63: Determine whether the pressure difference ΔP _i exceeds the minimum decompression pressure adjustment amount in the brake decompression characteristic graph or exceeds the minimum boost pressure adjustment amount in the brake boost pressure characteristic graph, if yes , then execute S64; otherwise, execute S65;

S64: pressure keeping;

S65: Determine whether the pressure difference ΔP _i is greater than 0, if so, execute S66; if not, execute S67;

若是，则一直打开所述制动气室的进气阀，并持续第一预设时间，然后返回S62；若否，则根据所述制动增压特性曲线图，确定所述压力差ΔP_i对应的最小的增压时间t1，并按照所述最小的增压时间t1、所述增压保压周期t2的设置方式周期性打开所述制动气室的进气阀，并持续第二预设时间，然后返回S62；其中，所述第二预设时间大于或者等于所述增压保压周期；S66: Determine whether the pressure difference ΔP _i is greater than the maximum boost pressure adjustment amount in the brake boost pressure characteristic curve

If yes, open the intake valve of the brake air chamber all the time for a first preset time, and then return to S62; if not, determine the pressure difference ΔP _i according to the brake boosting characteristic curve The corresponding minimum supercharging time t1, and periodically open the intake valve of the brake chamber according to the setting of the minimum supercharging time t1 and the supercharging and pressure maintaining period t2, and continue for the second preset time. Set the time, and then return to S62; wherein, the second preset time is greater than or equal to the pressurization and pressure holding period;

若是，则一直打开所述制动气室的排气阀，并持续第三预设时间，然后返回S62；若否，则根据所述制动减压特性曲线图，确定所述压力差ΔP_i对应的最小的减压时间t3，并按照所述最小的减压时间t3、所述减压保压周期t4的设置周期性打开制动气室的排气阀持续第四预设时间，然后返回S62；其中，所述第四预设时间大于或者等于所述减压保压周期。S67: Determine whether the pressure difference ΔP _i is less than the maximum decompression pressure adjustment amount in the brake decompression characteristic curve

If yes, open the exhaust valve of the brake air chamber all the time for a third preset time, and then return to S62; if not, determine the pressure difference ΔP _i according to the brake decompression characteristic curve The corresponding minimum decompression time t3, and periodically open the exhaust valve of the brake air chamber for the fourth preset time according to the settings of the minimum decompression time t3 and the decompression and pressure holding period t4, and then return to S62; wherein, the fourth preset time is greater than or equal to the decompression and pressure maintaining period.

Preferably, in the step S10, the pressure-increasing and decompression characteristics are represented by a brake pressure-increasing characteristic curve and a braking pressure-reducing characteristic curve,

The steps of acquiring the brake boosting characteristic curve diagram include:

S11: Set the boosting time t1 and the boosting and maintaining period t2, t1≤t2;

S12: Periodically control the opening and closing of the intake valve of the brake air chamber according to the supercharging pressure maintaining period t2 until the pressure in the braking air chamber no longer rises, and record each of the supercharging and maintaining pressure The pressure change of the brake air chamber in the period of period t2; wherein, in each supercharging pressure maintaining period t2, the intake valve is in an open state in the supercharging time t1, and the The intake valve is closed;

S13: Execute S11 and S12 multiple times in a loop, wherein each time the pressurization time t1 is longer than the previous pressurization time t1;

建立所述制动增压特性曲线图，其中，所述制动增压特性曲线图中以各所述增压压力调整量

为纵坐标，各次的实际时间为横坐标；S14: Select each set of pressure data and subtract it from the previous set of pressure data at the same time to obtain the boost pressure adjustment amount

establishing the brake boosting characteristic curve, wherein each of the boosting pressure adjustment amounts is used in the braking boosting characteristic curve

is the ordinate, and the actual time of each time is the abscissa;

The step of obtaining the brake decompression characteristic curve diagram includes:

S15: Set the decompression time t3 and the decompression and pressure maintenance period t4, t3≤t4;

S16: Periodically control the opening and closing of the exhaust valve of the brake air chamber according to the decompression and pressure maintaining period t4 until the pressure in the brake air chamber no longer drops, and record each decompression The pressure change of the brake air chamber in the time period of the pressure maintaining period t4; wherein, in each decompression and pressure maintaining period t4, the exhaust valve is in an open state during the decompression time t3, and within the time period t4-t3 the exhaust valve is in a closed state;

S17: cyclically execute S15 and S16 multiple times, wherein the decompression time t3 of each time is longer than the decompression time t3 of the last time;

以建立制动减压特征曲线图，其中，所述制动减压特性曲线图中以各所述减压压力调整量

为纵坐标，各次的实际时间为横坐标。S18: Select each set of pressure data and subtract it from the previous set of pressure data at the same time to obtain the decompression pressure adjustment amount

To establish a brake decompression characteristic curve, wherein the brake decompression characteristic curve is based on the adjustment amount of each decompression pressure

is the ordinate, and the actual time of each time is the abscissa.

The method for calibrating the pressure-increasing and decompressing characteristics of the present invention, through multiple tests of the pressure-increasing and decompressing processes, demarcates the different time required for each increase or decrease of a certain pressure adjustment amount of the brake air chamber. When it is applied to the vehicle brake pressure regulation method, after obtaining the target pressure that needs to be adjusted in the brake air chamber, it does not need to go through a lot of complicated calculations. The difference between the target pressure and the actual pressure can be calculated first, and then the increase The opening method of the intake valve or the exhaust valve can be obtained from the brake boosting characteristic curve and the braking decompression characteristic curve of the decompression characteristic. Therefore, the calibration method of the boosting and decompression characteristics is the regulation of the braking pressure of the whole vehicle. It brings convenience, thereby improving the regulation efficiency of the vehicle brake pressure regulation method.

Other beneficial effects of the present invention will be illustrated in the specific embodiments through the introduction of specific technical features and technical solutions. Those skilled in the art should be able to understand the technical features and technical solutions through the introduction of these technical features and technical solutions. beneficial technical effects.

Description of drawings

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the picture:

Fig. 1 is the flow chart of a preferred embodiment of the calibration method of pressure-increasing and pressure-reducing characteristics provided by the present invention;

FIG. 2 is a brake boosting characteristic curve diagram and a braking decompression characteristic curve diagram obtained by using the method for calibrating the boosting characteristics provided by the present invention;

FIG. 3 is a system diagram of a preferred embodiment of the device for acquiring pressure-increasing and pressure-reducing characteristics provided by the present invention;

FIG. 4 is a flowchart of a preferred embodiment of the vehicle brake pressure regulation method provided by the present invention;

FIG. 5 is a flowchart of another preferred embodiment of the vehicle brake pressure regulation method provided by the present invention;

FIG. 6 is a flowchart of a preferred embodiment of the control method of the vehicle braking system provided by the present invention.

Detailed ways

The present invention is described below based on examples, but the present invention is not limited to these examples only. In the following detailed description of the present invention, some specific details are described in detail. In order to avoid obscuring the essence of the present invention, well-known methods, procedures, procedures and elements are not described in detail.

Furthermore, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Unless clearly required by the context, words such as "including", "comprising" and the like throughout the specification and claims should be construed in an inclusive rather than an exclusive or exhaustive sense; that is, "including but not limited to" meaning.

In the description of the present invention, it should be understood that the terms "first", "second" and the like are used for descriptive purposes only, and should not be construed as indicating or implying relative importance. Also, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

λ_i、λ_di、e_i、S_i、

α_i、ω_i、R_i、F_zi中，i代表左前FL、右前FR、左后RL、右后RR。Among them, the text

λ _i , λ _di , e _i , S _i ,

In α _i , ω _i , R _i , and F _zi , i represents left front FL, right front FR, left rear RL, and right rear RR.

The invention provides a method for calibrating the pressure-increasing and decompressing characteristics of a pneumatic brake-by-wire system. The pressure characteristic curve and the braking pressure reduction characteristic curve are obtained, and the calibration method includes the steps of acquiring the braking pressure increasing characteristic curve and the acquiring step of the braking pressure reducing characteristic curve.

As shown in Figure 1, the steps for obtaining the brake boosting characteristic curve diagram include:

S11: Set the boosting time t1 and the boosting and maintaining period t2, t1≤t2;

S12: Periodically control the opening and closing of the intake valve of the brake chamber according to the boost pressure maintaining period t2 until the pressure in the brake chamber no longer rises, and record the system pressure during each boost pressure maintaining period t2. The pressure change of the dynamic air chamber; wherein, in each supercharging pressure holding period t2, the intake valve is in an open state in the supercharging time t1, and the intake valve is in a closed state in the time t2-t1;

S13: Execute S11 and S12 multiple times in a loop, wherein the boosting time t1 of each time is longer than the previous boosting time t1, and the boosting pressure maintaining period t2 remains unchanged, that is, during the boosting pressure maintaining period t2, the intake air The opening time of the valve is gradually extended, and the closing time is gradually shortened;

即在相邻的两次数据中，增压压力调整量

等于同一时间对应的第二次的压力值减去第一次的压力值；然后建立制动增压特性曲线图，其中，制动增压特性曲线图中以各增压压力调整量

为纵坐标，各次的实际时间为横坐标，如图2所示；S14: Select each set of pressure data and subtract it from the previous set of pressure data at the same time to obtain the boost pressure adjustment amount

That is, in the two adjacent data, the boost pressure adjustment amount

It is equal to the second pressure value corresponding to the same time minus the first pressure value; then establish a brake boosting characteristic curve, wherein the braking boosting characteristic curve is based on the adjustment amount of each boosting pressure

is the ordinate, and the actual time of each time is the abscissa, as shown in Figure 2;

Continuing to refer to FIG. 1 , the steps of acquiring the brake decompression characteristic curve diagram include:

S15: Set the decompression time t3 and the decompression and pressure maintenance period t4, t3≤t4;

S16: Periodically control the opening and closing of the exhaust valve of the brake air chamber according to the decompression and pressure maintenance period t4 until the pressure in the brake air chamber does not drop any more, and record the time period of each decompression and pressure maintenance period t4. The pressure change of the dynamic air chamber; wherein, in each decompression and pressure holding period t4, the exhaust valve is in an open state during the decompression time t3, and the exhaust valve is in a closed state during the time t4-t3;

S17: Execute S15 and S16 multiple times in a loop, wherein the decompression time t3 of each time is longer than the decompression time t3 of the previous time, that is, in the decompression and pressure maintenance period t4, the opening time of the exhaust valve is gradually extended, and the closing time is gradually shorten;

即在相邻的两次数据中，减压压力调整量

等于同一时间对应的第二次的压力值减去第一次的压力值；然后建立制动减压特征曲线图，其中，制动减压特性曲线图中以各减压压力调整量

为纵坐标，各次的实际时间为横坐标，如图2所示；S18: Select each set of pressure data and subtract it from the previous set of pressure data at the same time to obtain the decompression pressure adjustment amount

That is, in the two adjacent data, the decompression pressure adjustment amount

It is equal to the second pressure value corresponding to the same time minus the first pressure value; then establish a brake decompression characteristic curve, wherein the brake decompression characteristic curve is based on the adjustment amount of each decompression pressure

is the ordinate, and the actual time of each time is the abscissa, as shown in Figure 2;

和

中m、n分别为min，2，3，…，max。Among them, the above

and

where m and n are min, 2, 3, ..., max, respectively.

可以穷举，增压时间t1也可以穷举，同理，制动减压特性曲线图中的减压压力调整量

和减压时间t3也可以穷举，因此，增压时间t1和减压时间t3可以统称为持续时间，即打开进气阀或者排气阀的持续时间

压力调整量The boost pressure adjustment amount in the brake boost pressure characteristic curve obtained by the calibration method of the pressure boost and pressure reduction characteristics above

It can be exhaustive, and the boosting time t1 can also be exhausted. Similarly, the decompression pressure adjustment amount in the brake decompression characteristic curve

and the decompression time t3 can also be exhaustive, therefore, the boost time t1 and the decompression time t3 can be collectively referred to as duration, that is, the duration of opening the intake valve or exhaust valve

pressure adjustment

Therefore, the above-mentioned pressure increase and pressure characteristics can be expressed as: ΔP _a =f(P _j , _{u j} , ta ), where P _j is the pressure in the brake air chamber, u _j is the pressure regulation state, which can be represented by +1 Pressurization, 0 means maintaining pressure, -1 means decompression.

It should be noted that, no matter it is the step of obtaining the supercharging characteristic curve or the step of obtaining the braking decompression characteristic curve, in each test, the intake valve and exhaust valve are closed first, and then at the initial time of recording, the Open the intake or exhaust valve.

大于零；在制动减压特性曲线图的获取步骤中，制动气室内的压力是逐渐减小，因此，各减压压力调整量

小于零。It can be understood that in the step of acquiring the brake boosting characteristic curve, the pressure in the brake air chamber is gradually increased, therefore, each boosting pressure adjustment amount is

greater than zero; in the step of obtaining the brake decompression characteristic curve, the pressure in the brake air chamber is gradually reduced, therefore, the adjustment amount of each decompression pressure

less than zero.

The present invention also provides an acquisition device based on the pressure-increasing and decompression characteristics of the air pressure brake-by-wire system. As shown in FIG. 3, the acquisition device includes a compressor 1, an air storage tank 2, and a brake air chamber 3 that are connected in sequence. The brake air chamber 3 has an intake valve 31 and an exhaust valve 32 , both of which are electronic valves. The brake air chamber 3 communicates with the air storage tank 2 through the intake valve 31 and communicates with the outside world through the exhaust valve 32 . The acquisition device also includes a pressure sensor 4 and a controller 5. The pressure sensor 4 is arranged in the brake air chamber 3 to measure the pressure of the brake air chamber 3; the controller 5 is connected to the intake valve 31, the exhaust valve 32 and the pressure sensor. 4 are connected for operation according to the above calibration method. It should be noted that the brake air chamber 3 in the obtaining device may not be the brake air chamber in the vehicle, it is only used to simulate the brake air chamber in the vehicle, of course, the closer it is to the brake air chamber in the vehicle the better.

The present invention also provides a vehicle brake pressure control method based on a pneumatic brake-by-wire system. As shown in FIG. 4 , the vehicle brake pressure control method includes the steps:

S1: Acquire the pressure-increasing and decompressing characteristics of the brake air chamber of the vehicle obtained by using the above-mentioned calibration method, that is, obtain the above-obtained braking pressure-increasing characteristic curve and braking decompression characteristic curve;

S2: Obtain the target pressure _Pi of the brake air chamber of the vehicle, which can be determined according to the braking demand of the vehicle, which can be the demand for active braking (for example, in automatic driving, the vehicle control center detects that there is an obstacle in the traveling brakes), or it can be the driver's demand for braking by pressing the brake pedal;

S3: Obtain the actual pressure P ₀ of the brake air chamber, which can be obtained according to the pressure sensor provided in the vehicle brake air chamber, and calculate the pressure difference ΔP _i =P _i −P _i0 between the pressure sensor and the target pressure;

S4: Determine the opening mode of the intake valve or the exhaust valve of the brake air chamber according to the pressure difference ΔP _i and the pressure increase and decrease characteristics obtained in step S1, and adjust the brake pressure according to the opening mode.

The above-mentioned method for calibrating the pressure-increasing and decompressing characteristics, through multiple tests of the pressure-increasing and decompressing processes, calibrates the different time required for each increase or decrease of a certain pressure adjustment amount ΔP _a in the brake air chamber. When it is applied to the vehicle brake pressure regulation method, after obtaining the pressure difference ΔP that needs to be adjusted in the brake air chamber, it is not necessary to go through a lot of complicated calculations, and the brake pressure increase characteristic curve of the pressure increase and pressure characteristics can be directly searched. The opening method of the intake valve or the exhaust valve can be obtained from the curve of the brake decompression characteristic. Therefore, the calibration method of the pressure increase and decompression characteristics brings convenience to the regulation of the braking pressure of the whole vehicle, thereby improving the overall performance of the vehicle. The regulation efficiency of the brake pressure regulation method enables the vehicle braking to respond in time.

Specifically, in the above calibration method, the first values of the boost time t1 and the decompression time t3 can be selected as 1ms, 3ms, 5ms, 8ms, etc., respectively. Preferably, in the step of acquiring the brake booster characteristic curve , the first boosting time t1 is 1ms; in the step of obtaining the brake decompression characteristic curve, the first decompression time t3 is 1ms; the boosting and maintaining period t2 and the decompression and maintaining period t4 are both It is 30ms, and the above settings can make the obtained brake boost characteristic curve and brake decompression characteristic curve closer to the actual boost and decompression characteristics of the vehicle, thereby improving the accuracy of vehicle brake pressure regulation. sex.

In step S13, the difference Δt1 between two adjacent pressurization times t1 may be unequal. In a preferred embodiment, each pressurization time t1 is increased by Δt1 compared to the previous pressurization time t1, and Δt1>0 , that is to say, each pressurization time t1 increases gradually in an arithmetic progression. Using this method is beneficial to the control of the entire calibration process and the processing of subsequent data.

Similarly, in step S17, the difference Δt2 between two adjacent decompression times t3 may not be equal. In a preferred embodiment, each decompression time t3 is increased by Δt2 and Δt2 compared to the previous decompression time t3. >0, that is to say, the boosting time t1 of each time increases gradually in an arithmetic progression.

In order to obtain more accurate pressure-increasing and pressure-reducing characteristics, preferably, step S13 specifically includes: cyclically executing S11 and S12 until the pressure-increasing time t1 is equal to the pressure-increasing and pressure-retaining period t2, where Δt1=1ms; step S17 specifically includes: S15 and S16 are executed cyclically until the decompression time t3 is equal to the decompression and pressure retention period t4, wherein Δt2=1ms. That is to say, each time the intake valve or exhaust valve is opened is increased at intervals of 1ms, so that it is not only beneficial to the realization of the control of the intake valve and the exhaust valve, but also can obtain more times of boosting and decompression times, so as to improve the accuracy of comparison when the increase and decrease characteristics are applied to the brake pressure regulation method.

Specifically, the specific operation of S12 in the step of obtaining the brake boosting characteristic curve diagram is as follows: in the first test, the opening and closing of the intake valve is periodically controlled according to the method that the intake valve is first opened for 1ms, and then closed for 29ms, Until the pressure in the brake chamber no longer increases by this periodic control, and record the change of the pressure in the brake chamber with time throughout the test; then in the second test, with the intake valve first Periodically control the opening and closing of the intake valve by opening for 2ms, then closing for 28ms, until the pressure in the brake chamber no longer increases through this periodic control method, and record the pressure in the brake chamber throughout the test Changes with time; such a cycle is carried out for many times, in the penultimate time, the opening and closing of the intake valve is periodically controlled in the manner that the intake valve is first opened for 29ms, and then closed for 1ms, until through this periodic The control method makes the pressure in the brake chamber no longer increase, and records the change of the pressure in the brake chamber with time during the whole test; the last time, the intake valve is first opened for 30ms, and then closed for 0ms. Periodically control The opening and closing of the intake valve (that is, the intake valve is always open) until the pressure in the brake chamber no longer increases through this periodic control method, and the pressure in the brake chamber is recorded throughout the test. change with time.

Similarly, in the step of obtaining the brake decompression characteristic curve, the specific operation of S16 is: in the first test, the opening and closing of the exhaust valve is periodically controlled according to the method that the exhaust valve is first opened for 1ms, and then closed for 29ms. Until the pressure in the brake chamber is no longer reduced by this periodic control, and record the change of the pressure in the brake chamber with time throughout the test; then in the second test, according to the exhaust valve First open for 2ms, then close for 28ms to periodically control the opening and closing of the exhaust valve until the pressure in the brake air chamber no longer decreases through this periodic control method, and record the brake air throughout the test Indoor pressure changes with time; such a cycle is carried out for many times, in the penultimate time, the opening and closing of the exhaust valve is periodically controlled in such a way that the exhaust valve is first opened for 29ms, and then closed for 1ms, until through this Periodic control mode makes the pressure in the brake chamber no longer decrease, and records the change of the pressure in the brake chamber with time during the whole test; the last time, the intake and exhaust valves are first opened for 30ms, and then closed for 0ms. The method periodically controls the opening and closing of the exhaust valve (that is, the exhaust valve is always open), until the pressure in the brake chamber is no longer reduced by this periodic control method, and records are recorded throughout the test. The pressure in the pneumatic chamber varies with time.

It is worth noting that the opening and closing periods of the exhaust valve and the intake valve defined by the present invention are not limited to the above-mentioned embodiments, that is, the supercharging time t1, the supercharging pressure maintaining period t2, the decompression time t3 and the decompression maintaining pressure Other specific values can be selected for the period t4.

Referring to FIG. 5, in the vehicle brake pressure regulation method, step S4 specifically includes the steps:

时，判断

是否成立，如果是，则执行S42；否则执行S43；S41: Determine whether the pressure difference ΔP _i exceeds the minimum pressure adjustment amount in the brake decompression characteristic curve or exceeds the minimum pressure adjustment amount in the brake pressure increase characteristic curve, that is, in the

when, judge

Whether it is established, if yes, execute S42; otherwise, execute S43;

S42: maintaining pressure;

S43: Judging whether the pressure difference ΔP _i is greater than 0, that is, judging whether ΔP _i > 0 is established, if so, it means that the brake air chamber needs to be pressurized, therefore, it is necessary to open the intake valve and close the exhaust valve, which is executed according to S44. ; If no, it means that the brake air chamber needs to be decompressed, therefore, it is necessary to open the exhaust valve and close the intake valve, which is performed according to S45;

时，判断

是否成立，若是，则说明现在制动气室内的压力太小了，超过了制动增压特性曲线图中标定的最大压力调整范围，此时需要在整个增压保压周期内调节制动气室内的压力，使制动气室内快速进入更多的气体，因此，采用粗调制动气室的压力，即一直打开制动气室的进气阀持续第一预设时间，以获得快速的压力响应，然后返回S3；若否，则说明现在制动气室内的压力需要进行较小的调整，可以根据制动增压特性曲线图，确定压力差ΔP_i对应的最小的增压时间t1，即从制动增压特性曲线图中，选出与ΔP_i对应的ΔP_a，进而选出ΔP_a对应的最小t_a，作为最小的增压时间t1，并按照最小的增压时间t1、增压保压周期t2的设置方式周期性打开制动气室的进气阀，并持续第二预设时间，以在最短的时间内使制动气室达到目标压力P_i，然后返回S3；其中，第二预设时间大于或者等于增压保压周期；S44: Determine whether the pressure difference ΔP _i exceeds the maximum boost pressure adjustment amount in the brake boost pressure characteristic curve, that is, at

when, judge

Whether it is true or not, if it is, it means that the pressure in the brake air chamber is too small, which exceeds the maximum pressure adjustment range calibrated in the brake boosting characteristic curve. The pressure in the brake chamber can quickly enter more gas into the brake chamber. Therefore, the pressure of the brake chamber is roughly adjusted, that is, the intake valve of the brake chamber is always opened for the first preset time to obtain a fast pressure response. , and then return to S3; if not, it means that the pressure in the brake air chamber needs to be adjusted slightly, and the minimum pressure increase time t1 corresponding to the pressure difference ΔP _i can be determined according to the brake pressure increase characteristic curve, that is, from In the brake boosting characteristic curve, ΔP _a corresponding to ΔP _i is selected, and then the minimum _ta corresponding to ΔP _a is selected as the minimum boosting time t1, and the minimum boosting time t1, boosting protection The setting method of the pressure period t2 periodically opens the intake valve of the brake air chamber for a second preset time, so as to make the brake air chamber reach the target pressure P _i in the shortest time, and then returns to S3; 2. The preset time is greater than or equal to the pressurization and pressure holding period;

时，判断

是否成立，若是，则说明现在制动气室内的压力太大，超过了制动减压特性曲线图中标定的最大压力调整范围，此时需要在整个减压保压周期内调节制动气室内的压力，使制动气室快速排出更多的气体，因此，一直打开制动气室的排气阀持续第三预设时间，以获得快速的压力响应，然后返回S3；若否，则说明现在制动气室内的压力需要进行较小的调整即可，可以根据制动减压特性曲线图，确定压力差ΔP_i对应的最小的减压时间t3，即从制动减压特性曲线图中，选出与ΔP_i对应的ΔP_a，进而选出ΔP_a对应的最小t_a，作为最小的减压时间t3，也是持续打开排气阀的最优时间，并按照最小的减压时间t3、减压保压周期t4的设置方式周期性打开制动气室的排气阀，并持续第四预设时间，然后返回S3；其中，第四预设时间大于或者等于减压保压周期。S45: Determine whether the pressure difference ΔP _i exceeds the maximum decompression pressure adjustment amount in the brake decompression characteristic curve, that is, in

when, judge

Whether it is true or not, if it is, it means that the pressure in the brake air chamber is too large now, which exceeds the maximum pressure adjustment range calibrated in the brake decompression characteristic curve. The pressure of the brake chamber makes the brake chamber quickly discharge more gas. Therefore, the exhaust valve of the brake chamber is always opened for the third preset time to obtain a fast pressure response, and then return to S3; if not, explain Now the pressure in the brake air chamber needs to be adjusted slightly. According to the brake decompression characteristic curve, the minimum decompression time t3 corresponding to the pressure difference ΔP _i can be determined, that is, from the brake decompression characteristic curve , select ΔP _a corresponding to ΔP _i , and then select the minimum _ta corresponding to ΔP _a as the minimum decompression time t3, which is also the optimal time for continuously opening the exhaust valve, and according to the minimum decompression time t3, The setting method of the decompression and pressure maintaining period t4 periodically opens the exhaust valve of the brake air chamber for a fourth preset time, and then returns to S3; wherein, the fourth preset time is greater than or equal to the decompression and pressure maintaining period.

The pressure of the brake air chamber is adjusted in different ways according to the above-mentioned situations, which can make the pressure response in the brake air chamber more timely, thereby making the entire brake pressure regulation method more accurate.

Optionally, the first preset time may also be greater than or equal to the pressurization and pressure maintaining period, and the third preset time may be greater than or equal to the decompression and pressure maintaining period. When selecting, the first preset time, the second preset time, the third preset time and the fourth preset time can be determined according to needs, and the four can be equal, or only two or three of them can be are equal, or none of the four are equal.

It should be noted that, in the above steps, unless otherwise specified, for the same brake chamber, when the intake valve is opened, the exhaust valve is in a closed state; when the exhaust valve is opened, the intake The valve is closed; and during the boosting process, the exhaust valve is always closed; during the decompression process, the intake valve is always closed.

The order of the above steps S1 and steps S2 and S3 is not necessarily executed in sequence, as long as S1 is executed before S4, S1 can be executed first and then S2 and S3 can be executed, or S2 and S3 can be executed first and then S1 is executed. Actually, it can be executed at the same time. S1 and S2, S3, or S1 and S3 are executed together. It can be understood that, in fact, before the vehicle leaves the factory, the pressure-increasing and reducing characteristics have been obtained through S11 to S18, and it is only necessary to read the pressure-increasing and reducing characteristics in S1.

In actual use, in the brake pressure regulation methods of the above embodiments, steps S1 to S4 are respectively performed on each wheel (including its brake air chamber). Generally, the pressure-increasing and decompressing characteristics of the brake air chambers of each driving wheel are designed to be as consistent as possible to facilitate control. Therefore, as long as the pressure-increasing and decompressing characteristics are obtained, the control of each driving wheel can be used. Of course, the pressure-increasing and pressure-reducing characteristics of each driving wheel can also be obtained through the above-mentioned calibration method.

The vehicle braking pressure regulation method provided by the above embodiments can be applied to a vehicle with a pneumatic braking system, and can also be applied to a vehicle that is jointly controlled by pneumatic braking and regenerative braking.

At the same time, the present invention also provides a control method for a distributed brake-by-wire system of a commercial vehicle. The control method can be used for electric and hybrid vehicles. Specifically, the vehicle may only have rear wheels as driving wheels, or may have four wheels. Both are drive wheels. As shown in Figure 6, the control method includes the steps:

S100: get the braking signal;

S200: Obtain vehicle status information;

S300: Establish a slip rate controller, and confirm the actual slip rate and the target slip rate according to the vehicle state information;

其中，i代表左前FL、右前FR、左后RL、右后RR，如

为右后轮的目标制动扭矩；S400: According to the actual slip rate and the target slip rate, combined with the slip rate controller, assign the target braking torque to each driving wheel

Among them, i represents left front FL, right front FR, left rear RL, right rear RR, such as

is the target braking torque of the right rear wheel;

的函数，结合驱动轮的目标制动扭矩

通过对制动成本函数求极值得到所述预期总再生制动扭矩T_d、各驱动轮的预期气压制动扭矩

可以理解地，预期总再生制动扭矩T_d等于各驱动轮的预期再生制动扭矩之和，如在只有两个后轮为驱动轮的实施例中，预期总再生制动扭矩T_d等于右后轮的预期再生制动扭矩与左后轮的预期再生制动扭矩之和，通过对制动成本函数J求极值，能够得到右后轮的预期再生制动扭矩与左后轮的预期再生制动扭矩之和T_d，以及右后轮的预期气压制动扭矩

和左后轮的预期气压制动扭矩

S500: Establish a braking cost function J of the vehicle, where the braking cost function J is the expected total regenerative braking torque T _d of the vehicle and the expected air pressure braking torque of each driving wheel

A function of , combined with the target braking torque of the drive wheels

The expected total regenerative braking torque T _d and the expected pneumatic braking torque of each driving wheel are obtained by finding the extreme value of the braking cost function

It can be understood that the expected total regenerative braking torque T _d is equal to the sum of the expected regenerative braking torques of the respective driving wheels, as in an embodiment where only two rear wheels are driving wheels, the expected total regenerative braking torque T _d is equal to The sum of the expected regenerative braking torque of the rear wheel and the expected regenerative braking torque of the left rear wheel, by finding the extreme value of the braking cost function J, the expected regenerative braking torque of the right rear wheel and the expected regeneration of the left rear wheel can be obtained. The sum of the braking torques T _d and the expected air brake torque of the right rear wheel

and the expected air brake torque of the left rear wheel

按照上述任一项所述的制动压力调控方法控制气压制动系统工作；其中，在制动压力调控方法中步骤S2具体包括：根据预期气压制动扭矩

确定目标压力P_i；S600: According to each expected air brake torque

Control the operation of the pneumatic brake system according to any one of the brake pressure regulation methods described above; wherein, step S2 in the brake pressure regulation method specifically includes: according to the expected pneumatic brake torque

Determine the target pressure P _i ;

和最小扭矩

确定电机的实际输出制动扭矩T_e，并控制电机输出实际输出制动扭矩T_e。S700: Based on the expected total regenerative braking torque T _d combined with the maximum torque the motor can provide

and minimum torque

Determine the actual output braking torque _Te of the motor, and control the motor to output the actual output braking torque _Te .

The above control method establishes a slip rate controller and a braking cost function, and combines the control strategy of layered control. The braking cost function is set to distribute the pneumatic braking torque and the regenerative braking torque, so as to realize the utilization of regenerative energy, and the braking torque is distributed through the braking cost function, which can achieve the maximum energy regeneration; and considering the pneumatic braking The delay of the regenerative braking and the pneumatic braking can work at the same time, and the regenerative braking can be used to compensate the delay of the pneumatic braking, further improve the response speed of the vehicle braking, and better ensure the stability and safety of the vehicle braking. sex.

Wherein, S600 and S700 may be executed simultaneously or separately, and in a preferred embodiment, both are executed at the same time, so as to quickly respond to braking.

Specifically, step S2 is specifically:

Among them, K _i is the conversion coefficient.

The vehicle state information in step S200 includes: friction coefficient μ of the road surface on which the vehicle travels, mass m of the vehicle, longitudinal speed u _x , driving wheel angular velocity ω _i , driving wheel radius R _i , driving wheel rotational inertia, and driving wheel longitudinal force F _xi , the vertical force F _zi of the driving wheel in the direction of its rotation axis, some of these state parameters can be provided when the vehicle leaves the factory or obtained by subsequent measurement, and some can be measured by sensors and other instruments in actual use. There are no restrictions.

In order to make the actual slip rate as close as possible to the target slip rate, in an embodiment of the present invention, a slip rate controller is established in step S300, including:

S310: Set the proportional integral model, such as formula (1):

S _i =e _i +α _i ∫e _i dt, (1)

Among them, e _i =λ _i -λ _di ; (2)

S320: The slip rate controller is established as, as in formula (3):

为预设系数，可以根据需要进行设置，以调节滑移率控制器使制动系统的制动效果更好。Among them, λ _i is the actual slip rate of the vehicle, λ _di is the target slip rate of the vehicle, sat is the saturation function, α _i , ε ₁ , ε ₀ ,

It is a preset coefficient, which can be set as required to adjust the slip rate controller to make the braking effect of the braking system better.

In this embodiment, step S400 includes:

S410: Derive the proportional integral model to obtain the reciprocal model

得到各驱动轮的目标制动扭矩

S420: make

Obtain the target braking torque of each drive wheel

Using the above steps, by setting the proportional-integral model, the static error of the slip rate can be eliminated as much as possible, and at the same time, by setting the slip rate controller with the saturation function sat, the possible chattering of the wheel speed can be reduced. The reciprocal is equal to the set slip rate controller, which can make the actual slip rate closer to the target slip rate in the goal of the entire control method, thereby improving the utilization rate of regenerative energy.

Specifically, the actual slip rate λ _i can be calculated according to the following formula (4):

The target slip rate _λdi is calculated according to the following formula (5):

为利用摩擦系数；M_thre为用于偏航控制的偏航力矩阈值；l为车辆的驱动轮轮距，如在只有两个后轮为驱动轮时，该值为左后轮和右后轮的轮距；F_zi为驱动轮在其转动轴方向的垂直力；f^-1为预设的摩擦系数表，具体可以根据实验测得；其中上述预设粘度可以选为0.5。Among them, u _x is the longitudinal speed of the vehicle, ω _i is the angular velocity of the driving wheel of the vehicle, R _i is the radius of the driving wheel of the vehicle; K _λ is a preset coefficient, which can be obtained according to experiments; μ is the friction coefficient of the road surface on which the vehicle runs;

is the use of friction coefficient; M _thre is the yaw torque threshold for yaw control; l is the driving wheel track of the vehicle. For example, when only two rear wheels are driving wheels, the value is the left rear wheel and the right rear wheel. F _zi is the vertical force of the driving wheel in the direction of its rotation axis; f ^-1 is a preset friction coefficient table, which can be measured according to experiments; the preset viscosity can be selected as 0.5.

It should be noted that, in the braking system and control method of the present invention, the vehicle is regarded as a rigid body, and only its longitudinal motion is considered. Therefore, the dynamic equation of the vehicle is formula (7):

Among them, F _xi is the longitudinal force on the driving wheel, and the right side of the formula is the sum of the longitudinal force of each wheel (including the driving wheel and the non-driving wheel).

The rotational motion of the driving wheel under the action of longitudinal force and braking torque can be expressed as formula (8):

的表达式(9)：According to formulas (1) to (8), the target braking torque can be obtained

Expression (9) of :

如在仅两个后轮为驱动轮的实施例中，可以分别求出左后轮的目标制动扭矩

和右后轮的目标制动扭矩

That is, in step S400, the target braking torque can be obtained according to the formula (9)

For example, in the embodiment in which only two rear wheels are driving wheels, the target braking torque of the left rear wheel can be obtained separately

and the target braking torque of the right rear wheel

In the above embodiments, the braking cost function in step S500 can be specifically expressed as formula (10):

为驱动轮的目标制动扭矩；T_d为预期总再生制动扭矩；

为最佳再生制动扭矩，其由制动能量再生关注点和ABS(即气压制动)控制关注点共同决定，为了最大程度地提高制动能量的再生效率并确保将再生制动扭矩补偿气压制动扭矩的不足，将其设置为接近但小于再生制动扭矩的最大值

考虑到具有ABS的制动系统中，若再生制动扭矩太大，会造成气压制动系统不提供任何扭矩，导致车轮必定会锁定，因此，再生制动扭矩不能太大而超过目标制动扭矩

具体可以按照公式(11)选取；

为再生制动扭矩的最大值，该值由车辆的电机决定，一般选为电机的额定输出转矩；

为储备间隙，可以通过实验获得，为定值。Among them, T _pi is the expected pneumatic braking torque of the driving wheel;

is the target braking torque of the driving wheel; T _d is the expected total regenerative braking torque;

For the optimal regenerative braking torque, it is jointly determined by the braking energy regeneration concern and the ABS (i.e. air brake) control concern, in order to maximize the regeneration efficiency of braking energy and ensure that the regenerative braking torque is compensated for the air pressure. Insufficient braking torque, set it close to but less than the maximum value of regenerative braking torque

Considering that in the braking system with ABS, if the regenerative braking torque is too large, the air brake system will not provide any torque, resulting in the wheel locking. Therefore, the regenerative braking torque cannot be too large and exceed the target braking torque.

Specifically, it can be selected according to formula (11);

is the maximum value of the regenerative braking torque, which is determined by the motor of the vehicle, and is generally selected as the rated output torque of the motor;

It is the reserve gap, which can be obtained through experiments and is a fixed value.

In the embodiment where only two rear wheels are driving wheels, equation (11) simplifies to equation (12):

Correspondingly, the braking cost function is expressed as Equation (12):

Further, considering that in the pressure adjustment cycle of each air brake, a delayed response will occur due to the pressure change, therefore, the above braking cost function is expressed as formula (13),

The air brake torque can be predicted in the form of formula (14):

Among them, (k+1) represents the predicted value of the next control cycle, k represents the value of the current control cycle, K _r is a preset coefficient; ΔP _di is the pressure change of the driving wheel.

预期总再生制动扭矩T_d、最佳再生制动扭矩

均不变，从而得到优化的制动能量函数，步骤S500中的制动成本函数表达式如公式(15)：In a preferred embodiment of the present invention, in order to reduce the computational burden, the expected air brake torque is set in one control cycle

Expected total regenerative braking torque T _d , optimum regenerative braking torque

Therefore, the optimized braking energy function is obtained. The braking cost function expression in step S500 is as formula (15):

Among them, K _r is a preset coefficient; ΔP _ai is the pressure change of the driving wheel, which is equivalent to ΔP _a in the above-mentioned pressure-increasing and decompressing characteristics, which can be exhausted, that is,

预期总再生制动扭矩T_d，对于各驱动轮的气压制动系统分别采用上述制动压力调控方法进行控制。In this way, the expected pneumatic braking torque of each driving wheel can be obtained by taking the minimum value of the braking cost function

The expected total regenerative braking torque T _d is controlled by the above-mentioned braking pressure regulation method for the pneumatic braking system of each driving wheel.

等于预期总再生制动扭矩T_d与损耗扭矩的和。For the expected total regenerative braking torque T _d , since the regenerative braking output by the motor will cause torque loss in the process of transmission to the driving wheel, generally, the torque output by the motor needs to pass through the gearbox and differential before being distributed to the On each drive wheel, therefore, the actual expected braking torque output by the motor

is equal to the sum of the expected total regenerative braking torque T _d and the loss torque.

Specifically, in a vehicle with a differential, the regenerative braking torque on the axle can be expressed as equation (16):

Among them, J _e is the moment of inertia of the motor rotor; i _g is the gear ratio of the gear box on the drive shaft; i ₀ is the gear ratio of the differential; J _g is the moment of inertia of the gear box _; Moment of inertia; ω _d is the angular velocity of the differential case; η is the transmission efficiency;

可以表达为公式(17)：Therefore, the desired braking torque output by the motor

It can be expressed as formula (17):

和最小扭矩

确定电机的实际输出制动扭矩T_e，并控制电机输出实际输出制动扭矩T_e，包括步骤：Based on the above analysis, in step S700, according to the expected total regenerative braking torque T _d combined with the maximum torque that the motor can provide

and minimum torque

Determine the actual output braking torque T _e of the motor, and control the motor to output the actual output braking torque T _e , including steps:

具体可以根据公式(17)计算得到；S71: Determine the expected braking torque output by the motor according to the expected total regenerative braking torque T _d

Specifically, it can be calculated according to formula (17);

和最小扭矩

S72: Calculate the maximum torque that the motor can provide

and minimum torque

与最大扭矩

最小扭矩

的大小：S73: Determine the expected output braking torque of the motor

with maximum torque

Minimum torque

the size of:

则

like

but

则

like

but

则

like

but

最小扭矩

与电机的角速度ω_e有关，即可以表达为公式(18)，而电机的角速度ω_e可以表达为公式(19)：Among them, the maximum torque

Minimum torque

It is related to the angular velocity ω _e of the motor, which can be expressed as formula (18), and the angular velocity ω _e of the motor can be expressed as formula (19):

S74: Control the motor to output the actual braking torque _Te .

After the motor outputs the actual braking torque T _e torque, after removing the torque loss of the transmission shaft, it is distributed to the wheel ends of each driving wheel through the differential, and finally transmitted to the vehicle drive axle for braking.

Those skilled in the art can understand that, under the premise of no conflict, the above preferred solutions can be freely combined and superimposed.

It should be understood that the above-mentioned embodiments are only exemplary rather than restrictive, and those skilled in the art can make various obvious or equivalent to the above-mentioned details without departing from the basic principles of the present invention. Modifications or substitutions will be included within the scope of the claims of the present invention.

Claims (8)

1. A control method of a whole vehicle brake system is characterized by comprising the following steps:

s10: acquiring the pressure increasing and reducing characteristic and the braking signal of the whole vehicle, wherein the pressure increasing and reducing characteristic is represented by a braking pressure increasing characteristic curve graph and a braking pressure reducing characteristic curve graph, and the braking pressure increasing characteristic curve graph comprises a pressure increasing and reducing adjustment quantity

And a boost time t1, the brake pressure reduction characteristic curve chart including a pressure reduction pressure adjustment amount

And decompression time t3, wherein m and n are min, 2, 3, … and max respectively;

s20: acquiring vehicle state information;

s30: establishing a slip rate controller, and confirming an actual slip rate and a target slip rate according to the vehicle state information;

s40: distributing target braking torque for each driving wheel according to the actual slip rate and the target slip rate and combining the slip rate controller

S50: establishing a braking cost function for the vehicle, the braking cost function being an expected total regenerative braking torque T for the vehicle_dExpected air brake torque of each of the drive wheels

Then combining said target braking torque of each of said drive wheels

Obtaining the expected total regenerative braking torque T by extremizing the braking cost function_dExpected air brake torque of each of the drive wheels

S60: according to the expected air braking torque

Determining a target pressure P_iAnd obtaining the actual pressure P of the brake chamber_i0Calculating the pressure difference delta P between the target pressure and the pressure_i＝P_i-P_i0According to said pressure difference Δ P_iDetermining the opening mode of an air inlet valve or an air outlet valve of the brake air chamber according to the pressure increasing and decreasing characteristic curve graph, and regulating and controlling the brake pressure according to the opening mode;

s70: based on the expected total regenerative braking torque T_dAnd combined with what the motor can provideHigh torque

And minimum torque

Determining an actual output brake torque T of the electric machine_eAnd controlling the motor to output actual output brake torque T_e。

2. The control method according to claim 1, wherein in the step S30, the establishing slip ratio controller includes:

s31: setting a proportional integral model: s_i＝e_i+α_i∫e_idt of, wherein e_i＝λ_i-λ_di；

S32: the slip rate controller is established as follows:

the step S40 includes:

s41: the proportional integral model is subjected to derivation to obtain a reciprocal model

S42: make it

Obtaining a target braking torque of each of the drive wheels

Wherein λ is_iIs the actual slip ratio, λ, of the vehicle_diSat is a saturation function, alpha, for a target slip ratio of the vehicle_i、ε₁、ε₀、

Is a preset coefficient.

3. Control method according to claim 2, characterized in that the actual slip ratio λ_iCalculated according to the following formula:

the target slip ratio lambda_diCalculated according to the following formula:

in step S42, the target braking torque

Calculated according to the following formula:

wherein u is_xIs the longitudinal speed, ω, of the vehicle_iIs the driving wheel angular velocity, R, of the vehicle_iIs a drive wheel radius of the vehicle; k_λIs a preset coefficient; μ is a friction coefficient of a road surface on which the vehicle travels;

to utilize the coefficient of friction; m_threIs a yaw moment threshold for yaw control; l is the driving wheel track of the vehicle; j. the design is a square_iIs the moment of inertia of the driving wheel of the vehicle,F_xiIs a longitudinal force of a drive wheel of the vehicle; f_ziThe vertical force of the driving wheel in the direction of the rotating shaft of the driving wheel; f. of^-1Is a preset friction coefficient table.

4. The control method according to claim 3, wherein the step S50 includes:

s51: establishing a braking cost function for the vehicle

Wherein,

an expected air brake torque for the drive wheel;

a target braking torque for the drive wheel; t is_dIs the expected total regenerative braking torque; k_rIs a preset coefficient; delta P_aiIn order to change the amount of pressure change of the driving wheel,

for optimal regenerative braking torque;

is the maximum value of the regenerative braking torque;

to reserve forA gap;

s52: combining the target braking torques of the respective drive wheels

Obtaining the expected total regenerative braking torque T by extremizing the braking cost function_dExpected air brake torque of each of the drive wheels

5. The control method according to claim 1, characterized in that in said step S70, the total regenerative braking torque T is expected according to the total regenerative braking torque T_dIn combination with the maximum torque that the motor can provide

And minimum torque

Determining the actual output brake torque T of the electric machine_eThen controlling the motor to output the actual braking torque T_eThe method comprises the following steps:

s71: based on the expected total regenerative braking torque T_dDetermining a desired braking torque output by an electric machine

S72: obtaining the maximum torque that the motor can provide

And minimum torque

S73: determining a desired braking torque output by the motor

With maximum torque

Minimum torque

The size of (2):

if it is

Then

If it is

Then

If it is

Then

S74: controlling the motor to output an actual braking torque T_e。

6. The control method according to claim 1, wherein in the step S60, the air brake torque is predicted according to the expected air brake torque

Determining the target pressure P_iThe method specifically comprises the following steps:

wherein, K_iAre conversion coefficients.

7. The control method according to claim 1, wherein the step S60 includes:

s61: according to the expected air braking torque

Determining the target pressure P_i；

S62: acquiring the actual pressure P of the brake air chamber_i0Calculating the pressure difference delta P between the target pressure and the pressure_i＝P_i-P_i0；

S63: determining the pressure difference Δ P_iWhether the minimum decompression pressure adjustment amount in the brake decompression characteristic diagram is exceeded or the minimum boost pressure adjustment amount in the brake boost characteristic diagram is exceeded, and if so, S64 is executed; otherwise, executing S65;

s64: maintaining the pressure;

s65: determining the pressure difference Δ P_iIf greater than 0, if yes, go to S66; if not, go to S67;

s66: determining the pressure difference Δ P_iWhether or not it is larger than the maximum boost pressure adjustment amount in the brake boost characteristic map

If yes, opening an air inlet valve of the brake chamber all the time for a first preset time, and then returning to S62; if not, determining the pressure difference delta P according to the brake pressure increasing characteristic curve graph_iThe corresponding minimum supercharging time t1 is provided, the air inlet valve of the brake chamber is opened periodically according to the setting mode of the minimum supercharging time t1 and the supercharging pressure maintaining period t2, the air inlet valve lasts for a second preset time, and then the operation returns to S62; the second preset time is greater than or equal to the pressurization and pressure-holding period;

s67: determining the pressure difference Δ P_iWhether or not it is less than the maximum decompression pressure adjustment amount in the brake decompression characteristic map

If yes, opening an exhaust valve of the brake chamber all the time for a third preset time, and then returning to S62; if not, determining the pressure difference delta P according to the brake pressure reduction characteristic curve graph_iThe corresponding minimum decompression time t3 is set according to the minimum decompression time t3 and the decompression and pressure maintaining period t4, the exhaust valve of the brake air chamber is opened periodically for a fourth preset time, and then the process returns to S62; wherein the fourth preset time is greater than or equal to the pressure reduction and pressure maintaining period.

8. The control method according to any one of claims 1 to 7, wherein in step S10, the pressure increasing and decreasing characteristics are expressed as a brake pressure increasing characteristic map and a brake pressure decreasing characteristic map,

the obtaining step of the brake boosting characteristic map includes:

s11: setting a pressurization time t1 and a pressurization and pressure maintaining period t2, wherein t2 is not less than t 1;

s12: periodically controlling an air inlet valve of a brake air chamber to open and close according to the pressure increasing and maintaining period t2 until the pressure in the brake air chamber does not rise any more, and recording the pressure change of the brake air chamber in each pressure increasing and maintaining period t 2; wherein, in each pressure increasing and pressure maintaining period t2, the air inlet valve is in an open state in a pressure increasing time t1, and the air inlet valve is in a closed state in a time t2-t 1;

s13: circularly executing S11 and S12 for a plurality of times, wherein the pressurization time t1 at each time is longer than the pressurization time t1 at the last time;

s14: selecting a group of pressure data at each time and subtracting the group of pressure data at the same time at the last time to obtain the boost pressure adjustment quantity

Establishing the brake boost characteristic curve chart, wherein each boost pressure adjustment amount is used in the brake boost characteristic curve chart

Is a vertical coordinate, and the actual time of each time is a horizontal coordinate;

the brake decompression characteristic curve graph obtaining step includes:

s15: setting a decompression time t3 and a decompression and pressure maintaining period t4, wherein t4 is more than or equal to t 3;

s16: opening and closing an exhaust valve of the brake air chamber are periodically controlled according to the pressure reducing and maintaining period t4 until the pressure in the brake air chamber does not decrease any more, and the pressure change of the brake air chamber in each pressure reducing and maintaining period t4 is recorded; wherein, in each pressure reducing and maintaining period t4, the exhaust valve is in an open state within the pressure reducing time t3, and the exhaust valve is in a closed state within the time t4-t 3;

s17: performing S15, S16 for a plurality of times in a circulating manner, wherein the decompression time t3 of each time is longer than the last decompression time t 3;

s18: selecting a group of pressure data each time and subtracting the group of pressure data with the same time at the last time to obtain the decompression pressure adjustment quantity

To establish a brake pressure reduction characteristic curve chart, wherein each pressure reduction pressure adjustment amount is used in the brake pressure reduction characteristic curve chart

The ordinate is the actual time of each time, and the abscissa is the actual time of each time.

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