CN111231917B - Vehicle braking pressure regulation and control method based on air pressure line control braking system - Google Patents

Vehicle braking pressure regulation and control method based on air pressure line control braking system Download PDF

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Publication number
CN111231917B
CN111231917B CN202010121004.0A CN202010121004A CN111231917B CN 111231917 B CN111231917 B CN 111231917B CN 202010121004 A CN202010121004 A CN 202010121004A CN 111231917 B CN111231917 B CN 111231917B
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pressure
brake
time
air
characteristic curve
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CN111231917A (en
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杨义勇
魏凌涛
陶兴军
鲁之轩
李亮
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China University of Geosciences Beijing
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China University of Geosciences Beijing
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/24—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being gaseous
    • B60T13/26—Compressed-air systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L7/00—Electrodynamic brake systems for vehicles in general
    • B60L7/10—Dynamic electric regenerative braking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/66—Electrical control in fluid-pressure brake systems
    • B60T13/68—Electrical control in fluid-pressure brake systems by electrically-controlled valves
    • B60T13/683—Electrical control in fluid-pressure brake systems by electrically-controlled valves in pneumatic systems or parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
    • B60T17/18—Safety devices; Monitoring
    • B60T17/22—Devices for monitoring or checking brake systems; Signal devices
    • B60T17/221—Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/17—Using electrical or electronic regulation means to control braking
    • B60T8/176—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS
    • B60T8/1761—Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS responsive to wheel or brake dynamics, e.g. wheel slip, wheel acceleration or rate of change of brake fluid pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2270/00—Further aspects of brake control systems not otherwise provided for
    • B60T2270/60—Regenerative braking

Abstract

The invention provides a calibration method and an acquisition device for a pressure increasing and decreasing characteristic based on an air pressure line control brake system, a whole vehicle brake pressure regulating method and a control method of a whole vehicle brake system, wherein the pressure increasing and decreasing characteristic is used for the air pressure line control brake system, the pressure increasing and decreasing characteristic is represented by a brake pressurization characteristic curve graph and a brake decompression characteristic curve graph, and the acquisition steps of the pressure increasing and decreasing characteristic curve and the brake decompression characteristic curve comprise: the method comprises the steps of periodically controlling the opening and closing of an air inlet valve or an exhaust valve of a brake air chamber according to a pressure maintaining period by changing the duration of each opening of the air inlet valve and the exhaust valve until the pressure in the brake air chamber does not change any more, recording the change of the pressure of the brake air chamber along with the time each time, and then obtaining a brake pressurization characteristic curve graph and a brake decompression characteristic curve graph through data processing. The pressure increasing and decreasing characteristic obtained by the calibration method can bring convenience for regulating and controlling the brake pressure of the whole vehicle, so that the regulation and control efficiency of the whole vehicle brake pressure regulation and control method is improved.

Description

Vehicle braking pressure regulation and control method based on air pressure line control braking system
Technical Field
The invention relates to the field of automobile braking, in particular to a calibration method and an acquisition device for the pressure increasing and decreasing characteristic based on an air pressure line control braking system, a whole automobile braking pressure regulation and control method and a whole automobile braking system control method.
Background
An anti-lock braking system (ABS) for a vehicle is one of active safety devices of the vehicle, which adjusts a locking degree of a wheel by controlling a braking torque according to a velocity feedback of the wheel, can sufficiently utilize a road adhesion and ensure a stability of the vehicle in an emergency braking, and is important for improving the stability and the safety of the vehicle. When the existing vehicle brake pressure is regulated and controlled, the time for opening an air inlet valve and an air outlet valve of a brake chamber can be determined according to the regulated pressure variation after complex operation, so that the timely response of a brake system is necessarily influenced.
Disclosure of Invention
Based on the above situation, the main objective of the present invention is to provide a calibration method and an obtaining device for increasing/decreasing pressure characteristics based on a pneumatic brake-by-wire system, a vehicle brake pressure regulation method, and a vehicle brake system control method, so as to solve the problem of slow brake response caused by complex calculation of the time when the air intake valve and the exhaust valve of the brake chamber need to be opened.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention provides a calibration method of the pressure increasing and decreasing characteristic based on the pneumatic wire-controlled brake system, the pressure increasing and decreasing characteristic is represented by a brake pressure increasing characteristic curve graph and a brake pressure reducing characteristic curve graph,
the obtaining step of the brake boosting characteristic curve comprises the following steps:
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
Figure GDA0002751615590000021
Establishing the brake boost characteristic curve chart, wherein each boost pressure adjustment amount is used in the brake boost characteristic curve chart
Figure GDA0002751615590000022
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
Figure GDA0002751615590000023
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
Figure GDA0002751615590000024
Is a vertical coordinate, and the actual time of each time is a horizontal coordinate;
wherein m and n are min, 2, 3, … and max respectively.
Preferably, in the step of obtaining the brake pressure increasing characteristic map, the first pressure increasing time t1 and the first pressure decreasing time t3 are 1 ms.
Preferably, the pressure increasing and pressure maintaining period t2 and the pressure reducing and pressure maintaining period t4 are both 30 ms.
Preferably, in the step S13, the pressure-increasing time t1 at each time is increased by Δ t1 from the last time of the pressure-increasing time t 1;
in step S17, the depressurization time t3 at each time is increased by Δ t2 from the last depressurization time t 3.
Preferably, the step S13 specifically includes: circularly executing S11 and S12 until the pressurization time t1 is equal to the pressurization and pressure maintaining period t2, wherein delta t1 is 1 ms;
the step S17 specifically includes: and circularly executing S15 and S16 until the decompression time t3 is equal to the decompression and pressure maintaining period t4, wherein the delta t2 is 1 ms.
The second aspect of the invention provides a whole vehicle brake pressure regulating and controlling method based on an air pressure line control brake system, which comprises the following steps:
s1: acquiring the pressure increase and decrease characteristics of a brake chamber of the vehicle acquired by using any one of the calibration methods;
s2: obtaining a target pressure P of a brake chamber of the vehiclei；
S3: acquiring the actual pressure P of the brake air chamberi0And calculating the pressure difference delta P between the target pressure and the pressurei＝Pi-Pi0；
S4: according to said pressure difference Δ PiAnd determining 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 characteristics, and regulating and controlling the brake pressure according to the opening mode.
Preferably, the step S4 includes the steps of:
s41: determining the pressure difference Δ PiWhether 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, S42 is executed; otherwise, executing S43;
s42: maintaining the pressure;
s43: determining the pressure difference Δ PiIf greater than 0, if yes, go to S44; if not, go to S45;
s44: determining the pressure difference Δ PiWhether or not it is larger than the maximum boost pressure adjustment amount in the brake boost characteristic map
Figure GDA0002751615590000031
If yes, opening an air inlet valve of the brake chamber all the time for a first preset time, and then returning to S3; if not, determining the pressure difference delta P according to the brake pressure increasing characteristic curve graphiThe 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 and pressure maintaining period t2, the air inlet valve lasts for a second preset time, and then the operation returns to S3; the second preset time is greater than or equal to the pressurization and pressure-holding period;
s45: determining the pressure difference Δ PiWhether or not it is less than the maximum decompression pressure adjustment amount in the brake decompression characteristic map
Figure GDA0002751615590000032
If yes, opening an exhaust valve of the brake chamber all the time for a third preset time, and then returning to S3; if not, determining the pressure difference delta P according to the brake pressure reduction characteristic curve graphiThe corresponding minimum decompression time t3 is set, the exhaust valve of the brake chamber is opened periodically for a fourth preset time according to the minimum decompression time t3 and the decompression and pressure maintaining period t4, and then the process returns to S3; wherein the fourth preset time is greater than or equal to the pressure reduction and pressure maintaining period.
The third aspect of the invention provides a control method of a whole vehicle brake system, which comprises the following steps:
s100: acquiring a brake signal;
s200: acquiring vehicle state information;
s300: establishing a slip rate controller, and confirming an actual slip rate and a target slip rate according to the vehicle state information;
s400: 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
Figure GDA0002751615590000041
S500: establishing a braking cost for the vehicleA function of the braking cost as an expected total regenerative braking torque T of the vehicledExpected air brake torque of each of the drive wheels
Figure GDA0002751615590000042
Then combining said target braking torque of each of said drive wheels
Figure GDA0002751615590000043
Obtaining the expected total regenerative braking torque T by extremizing the braking cost functiondExpected air brake torque of each of the drive wheels
Figure GDA0002751615590000044
S600: according to each expected air pressure braking torque
Figure GDA0002751615590000045
Controlling the work of the air pressure braking system according to the braking pressure regulation and control method; wherein, the step S2 specifically includes: according to the expected air braking torque
Figure GDA0002751615590000046
Determining the target pressure Pi；
S700: based on the expected total regenerative braking torque TdIn combination with the maximum torque that the motor can provide
Figure GDA0002751615590000047
And minimum torque
Figure GDA0002751615590000048
Determining an actual output brake torque T of the electric machineeAnd controlling the motor to output actual output brake torque Te。
Preferably, the step S2 is specifically:
Figure GDA0002751615590000049
wherein, KiAre conversion coefficients.
Preferably, the braking cost function in step S500 is:
Figure GDA00027516155900000410
wherein, KrIs a preset coefficient; delta PaiIn order to change the amount of pressure change of the driving wheel,
Figure GDA00027516155900000411
a fourth aspect of the present invention provides an apparatus for acquiring an increase/decrease characteristic based on a pneumatic brake-by-wire system, including:
the air compressor, the air storage tank and the brake chamber are connected in sequence, the brake chamber is provided with an air inlet valve and an air outlet valve, and the brake chamber is communicated with the air storage tank through the air inlet valve and is communicated with the outside through the air outlet valve;
the pressure sensor is arranged in the brake chamber and used for measuring the pressure of the brake chamber;
and the controller is connected with the air inlet valve, the exhaust valve and the pressure sensor and is used for working according to the calibration method of any one of the air inlet valve, the exhaust valve and the pressure sensor.
The method for calibrating the pressure increasing and decreasing characteristic calibrates different time required by increasing or decreasing a certain pressure adjustment quantity of a brake chamber through multiple tests of the pressure increasing and decreasing processes. When the method is applied to a vehicle brake pressure regulation and control method, after the target pressure of a brake chamber to be regulated is obtained, a large amount of complex operation is not needed, the difference value between the target pressure and the actual pressure can be calculated firstly, and then the brake pressure increasing characteristic curve and the brake pressure reducing characteristic curve of the pressure increasing and decreasing characteristic are directly searched to obtain the opening mode of the air inlet valve or the air outlet valve.
Other advantages of the present invention will be described in the detailed description, and those skilled in the art will understand the technical features and technical solutions presented in the description.
Drawings
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the figure:
FIG. 1 is a flow chart of a preferred embodiment of a method for calibrating a pressure increase/decrease characteristic provided by the present invention;
FIG. 2 is a brake boost characteristic curve and a brake decompression characteristic curve obtained by using the method for calibrating boost characteristics provided by the present invention;
FIG. 3 is a system diagram of a preferred embodiment of the apparatus for obtaining an increasing or decreasing pressure characteristic provided by the present invention;
FIG. 4 is a flowchart of an exemplary embodiment of a method for regulating vehicle brake pressure according to the present invention;
FIG. 5 is a flowchart of another preferred embodiment of a method for regulating and controlling a vehicle brake pressure according to the present invention;
fig. 6 is a flowchart of a preferred embodiment of a control method of a vehicle brake system according to the present invention.
Detailed Description
The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in order to avoid obscuring the nature of the present invention, well-known methods, procedures, and components have not been described in detail.
Further, 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 the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".
In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
Therein, the text
Figure GDA0002751615590000061
λi、λdi、ei、Si、
Figure GDA0002751615590000062
αi、ωi、Ri、FziIn the above, i represents front left FL, front right FR, rear left RL, and rear right RR.
The invention provides a calibration method of a pressure increasing and decreasing characteristic based on a pneumatic brake-by-wire system, wherein the pressure increasing and decreasing characteristic is used for a whole vehicle brake system based on the pneumatic brake-by-wire system and is represented by a brake pressure increasing characteristic curve graph and a brake pressure reducing characteristic curve graph.
As shown in fig. 1, the step of obtaining 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 the opening and closing of an air inlet valve of the brake air chamber according to a 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 within the pressure increasing time t1, and the air inlet valve is in a closed state within the time t2-t 1;
s13: performing the steps S11 and S12 in a loop for a plurality of times, wherein each time the supercharging time t1 is longer than the last supercharging time t1, the supercharging and pressure maintaining period t2 is unchanged, that is, in the supercharging and pressure maintaining period t2, the opening time of the intake valve is gradually prolonged, and the closing time is gradually shortened;
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
Figure GDA0002751615590000063
I.e. the boost pressure adjustment amount in two adjacent data
Figure GDA0002751615590000064
The pressure value of the second time corresponding to the same time is subtracted by the pressure value of the first time; a brake boost characteristic map is then created, wherein the brake boost characteristic map is adjusted by the boost pressure in each case
Figure GDA0002751615590000071
As ordinate, the actual time of each time is abscissa, as shown in fig. 2;
with continued reference to fig. 1, the brake pressure reduction signature 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: the method comprises the steps of periodically controlling an exhaust valve of a brake air chamber to be opened and closed according to a pressure reducing and maintaining period t4 until the pressure in the brake air chamber does not decrease any more, and recording the pressure change of the brake air chamber in each pressure reducing and maintaining period t 4; 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 and S16 in a circulating mode for multiple times, wherein the decompression time t3 of each time is longer than the last decompression time t3, namely the opening time of the exhaust valve is gradually prolonged and the closing time is gradually shortened in the decompression and pressure maintaining period t 4;
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
Figure GDA0002751615590000072
I.e. the amount of adjustment of the pressure reduction pressure in two adjacent data
Figure GDA0002751615590000073
The pressure value of the second time corresponding to the same time is subtracted by the pressure value of the first time; then, a brake decompression characteristic curve chart is established, wherein the amount of decompression pressure adjustment is carried out on the brake decompression characteristic curve chart according to each decompression pressure adjustment amount
Figure GDA0002751615590000074
As ordinate, the actual time of each time is abscissa, as shown in fig. 2;
wherein, the above
Figure GDA0002751615590000075
And
Figure GDA0002751615590000076
wherein m and n are min, 2, 3, … and max respectively.
The boost pressure adjustment quantity in the brake boost characteristic curve chart obtained by the calibration method of the boost and decompression characteristic
Figure GDA0002751615590000077
May be exhaustive, and the pressurization time t1 may also be exhaustive, and similarly, the amount of pressure reduction pressure adjustment in the brake pressure reduction characteristic curve
Figure GDA0002751615590000078
And decompression time t3 may also be exhaustive, and thus, the boost time t1 and the decompression time t3 may be collectively referred to as durations, i.e., durations of opening of intake or exhaust valves
Figure GDA0002751615590000079
Amount of pressure adjustment
Figure GDA00027516155900000710
Therefore, the pressure increasing and reducing characteristics can be expressed as:ΔPa＝f(Pj，uj，ta) Wherein P isjFor braking the pressure in the air chamber ujFor the pressure regulation state, it is possible to use +1 for pressurization, 0 for pressure holding and-1 for depressurization.
In both the step of acquiring the supercharging characteristic map and the step of acquiring the brake decompression characteristic map, the intake valve and the exhaust valve are closed first and then the intake valve or the exhaust valve is opened first at the recording initial timing for each test.
It is to be understood that, in the step of obtaining the brake boost characteristic map, the pressure in the brake chamber is gradually increased, and therefore, the respective boost pressure adjustment amounts
Figure GDA0002751615590000081
Is greater than zero; in the step of acquiring the brake decompression characteristic map, the pressure in the brake chamber is gradually reduced, and therefore, the respective decompression pressure adjustment amounts
Figure GDA0002751615590000082
Is less than zero.
The invention also provides an acquiring device based on the pressure increasing and decreasing characteristic of the air pressure brake-by-wire system, as shown in fig. 3, the acquiring device comprises a compressor 1, an air storage tank 2 and a brake air chamber 3 which are connected in sequence, the brake air chamber 3 is provided with an air inlet valve 31 and an air outlet valve 32, both of which are electronic valves, and the brake air chamber 3 is communicated with the air storage tank 2 through the air inlet valve 31 and is communicated with the outside through the air outlet valve 32. The acquiring device further comprises a pressure sensor 4 and a controller 5, wherein the pressure sensor 4 is arranged on the brake chamber 3 and used for measuring the pressure of the brake chamber 3; the controller 5 is connected to all of the inlet valve 31, the outlet valve 32 and the pressure sensor 4 for operation according to the calibration method described above. It should be noted that the brake chamber 3 in the acquisition device may not be a brake chamber in the vehicle, but is merely used for simulating a brake chamber in the vehicle, and of course, the closer to the brake chamber in the vehicle, the better.
The invention also provides a whole vehicle brake pressure regulating and controlling method based on the air pressure line control brake system, and as shown in fig. 4, the whole vehicle brake pressure regulating and controlling method comprises the following steps:
s1: acquiring the pressure increasing and decreasing characteristics of the brake chamber of the vehicle obtained by the calibration method, namely acquiring the obtained brake pressure increasing characteristic curve and brake pressure reducing characteristic curve;
s2: obtaining a target pressure P of a brake chamber of a vehicleiThis value may be determined according to the braking demand of the vehicle, may be a demand for active braking (such as braking by the vehicle control center detecting the presence of an obstacle in travel in autonomous driving), or may be a demand for a driver to press the brake pedal to request braking;
s3: obtaining the actual pressure P of the brake chamber0Specifically, the pressure difference Δ P between the pressure sensor and the target pressure may be calculated by obtaining the pressure from a pressure sensor provided in a brake chamber of the vehiclei＝Pi-Pi0；
S4: according to pressure difference Δ PiAnd step S1, determining the opening mode of the air inlet valve or the air outlet valve of the brake air chamber according to the pressure increasing and decreasing characteristics, and regulating and controlling the brake pressure according to the opening mode.
According to the method for calibrating the pressure increasing and reducing characteristics, through multiple tests of the pressure increasing and reducing processes, the pressure adjustment quantity delta P is calibrated when the brake chamber increases or decreases a certain pressureaThe different times required. When the method is applied to a vehicle brake pressure regulation and control method, after the pressure difference delta P of a brake chamber to be regulated is obtained, the opening mode of an air inlet valve or an air outlet valve can be obtained by directly searching a brake pressure increasing characteristic curve graph and a brake pressure reducing characteristic curve graph of pressure increasing and decreasing characteristics without a large amount of complex operation, so that the calibration method of the pressure increasing and decreasing characteristics brings convenience for regulation and control of the brake pressure of the whole vehicle, the regulation and control efficiency of the whole vehicle brake pressure regulation and control method is improved, and vehicle brake can respond in time.
Specifically, in the above calibration method, the first values of the pressurization time t1 and the depressurization time t3 may be selected to be 1ms, 3ms, 5ms, 8ms, and the like, respectively, and preferably, in the step of obtaining the brake pressurization characteristic graph, the first pressurization time t1 is 1 ms; in the step of obtaining the brake decompression characteristic curve, the first decompression time t3 is 1 ms; the pressure increasing and maintaining period t2 and the pressure reducing and maintaining period t4 are both 30ms, and by adopting the arrangement, the obtained brake pressure increasing characteristic curve and brake pressure reducing characteristic curve can be closer to the actual pressure increasing and pressure reducing characteristics of the vehicle, so that the accuracy of regulating and controlling the brake pressure of the whole vehicle is improved.
In step S13, the difference Δ t1 between the two adjacent supercharging times t1 may not be equal, and in a preferred embodiment, each supercharging time t1 is increased by Δ t1 compared with the last supercharging time t1, and Δ t1 is greater than 0, that is, each supercharging time t1 is gradually increased in an arithmetic progression, in this way, the control of the whole calibration process and the processing of subsequent data are facilitated.
Similarly, in step S17, the difference Δ t2 between the pressure-reducing times t3 of two adjacent times may not be equal, and in a preferred embodiment, the pressure-reducing time t3 of each time is increased by Δ t2 compared with the last pressure-reducing time t3, and Δ t2 is greater than 0, that is, the pressure-increasing time t1 of each time is gradually increased in an arithmetic progression.
In order to obtain more accurate pressure increasing and decreasing characteristics, step S13 preferably specifically includes: circularly executing S11 and S12 until the pressurization time t1 is equal to the pressurization and pressure maintaining period t2, wherein the time delta t1 is 1 ms; step S17 specifically includes: and circularly executing S15 and S16 until the pressure reducing time t3 is equal to the pressure reducing and maintaining period t4, wherein the delta t2 is 1 ms. That is, the time for opening the intake valve or the exhaust valve at each time is increased at intervals of 1ms, so that the number of times of pressure increase and the number of times of pressure decrease can be obtained more times while the control of the intake valve and the exhaust valve is facilitated, and the accuracy of comparison is improved when the pressure increase and decrease characteristic is applied to the brake pressure control method.
Specifically, S12 specifically operates in the acquisition step of the brake pressure increase characteristic map as follows: in the first test, the opening and closing of the inlet valve are periodically controlled in such a way that the inlet valve is first opened for 1ms and then closed for 29ms until the pressure in the brake chamber is no longer increased by this periodic control, and the change of the pressure in the brake chamber with time is recorded throughout the test; then in a second test, the opening and closing of the inlet valve is periodically controlled in such a way that the inlet valve is first opened for 2ms and then closed for 28ms until the pressure in the brake chamber is no longer increased by this periodic control, and the change in pressure in the brake chamber over time is recorded throughout the test; the test is carried out in a circulating mode, at the last time, the opening and the closing of the air inlet valve are periodically controlled in a mode that the air inlet valve is firstly opened for 29ms and then closed for 1ms until the pressure in the brake air chamber is not increased any more through the periodic control mode, and the change of the pressure in the brake air chamber along with the time in the whole test is recorded; finally, the opening and closing of the inlet valve is periodically controlled (i.e. the inlet valve is always open) in such a way that the inlet valve is first opened for 30ms and then closed for 0ms until the pressure in the brake chamber is no longer increased by this periodic control, and the change in the brake chamber pressure over time is recorded throughout the test.
Similarly, in the step of acquiring the brake pressure reduction characteristic diagram, the step S16 specifically includes: in the first test, the opening and closing of the exhaust valve are periodically controlled in a mode that the exhaust valve is firstly opened for 1ms and then closed for 29ms until the pressure in the brake air chamber is not reduced any more by the periodic control mode, and the change of the pressure in the brake air chamber along with the time in the whole test is recorded; then in a second test, the opening and closing of the exhaust valve are periodically controlled in a mode that the exhaust valve is firstly opened for 2ms and then closed for 28ms until the pressure in the brake air chamber is not reduced any more through the periodic control mode, and the change of the pressure in the brake air chamber along with the time in the whole test is recorded; the test is carried out in a circulating mode for a plurality of times, when the test is carried out for the second last time, the opening and the closing of the exhaust valve are periodically controlled in a mode that the exhaust valve is firstly opened for 29ms and then closed for 1ms until the pressure in the brake air chamber is not reduced any more through the periodic control mode, and the change of the pressure in the brake air chamber along with the time in the whole test is recorded; finally, the opening and closing of the exhaust valve was periodically controlled (i.e., the exhaust valve was always open) in a manner such that the inlet and exhaust valves were first opened for 30ms and then closed for 0ms until the pressure in the brake chamber was no longer decreasing by this periodic control, and the change in the brake chamber pressure over time was recorded throughout the test.
It should be noted that the opening and closing periods of the exhaust valve and the intake valve defined in the present invention are not limited to the above-described embodiment, i.e., the pressure increasing time t1 and the pressure increasing and maintaining period t2, the pressure reducing time t3 and the pressure reducing and maintaining period t4 may be selected to have other specific values.
Referring to fig. 5, in the method for regulating and controlling the braking pressure of the entire vehicle, step S4 specifically includes the steps of:
s41: determining the pressure difference Δ PiWhether the minimum pressure adjustment in the brake pressure reduction characteristic diagram or the minimum pressure adjustment in the brake pressure buildup characteristic diagram is exceeded, i.e. is present
Figure GDA0002751615590000101
Time, judge
Figure GDA0002751615590000102
If not, if yes, executing S42; otherwise, executing S43;
s42: maintaining the pressure;
s43: determining the pressure difference Δ PiIf it is greater than 0, determine Δ PiIf yes, the brake chamber needs to be pressurized, so that the air inlet valve needs to be opened and the air outlet valve needs to be closed, and the operation is specifically executed according to S44; if not, the pressure of the brake chamber needs to be reduced, so that the exhaust valve needs to be opened and the intake valve needs to be closed, and the operation is specifically executed according to S45;
s44: determining the pressure difference Δ PiWhether the maximum boost pressure adjustment in the brake boost characteristic curve has been exceeded, i.e. in
Figure GDA0002751615590000111
Time, judge
Figure GDA0002751615590000112
If yes, the pressure in the brake air chamber is too small to exceed the brake boosting characteristicAdjusting the pressure in the brake air chamber within the whole pressure increasing and maintaining period to enable the brake air chamber to quickly enter more air, so that the pressure of the brake air chamber is roughly adjusted, namely an air inlet valve of the brake air chamber is opened for a first preset time all the time to obtain quick pressure response, and then the pressure returns to S3; if not, the pressure in the brake air chamber needs to be adjusted slightly, and the pressure difference delta P can be determined according to the brake pressure increasing characteristic curve chartiThe corresponding minimum boost time t1, i.e. the value Δ P selected from the brake boost characteristic curveiCorresponding Δ PaFurther select Δ PaCorresponding minimum taThe minimum supercharging time t1 is set as the 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 and is continued for the second preset time, so that the brake chamber reaches the target pressure P in the shortest timeiThen returns to S3; wherein the second preset time is greater than or equal to the pressurization and pressure-maintaining period;
s45: determining the pressure difference Δ PiWhether the maximum decompression pressure adjustment in the brake decompression characteristic diagram is exceeded, i.e. in
Figure GDA0002751615590000113
Time, judge
Figure GDA0002751615590000114
If so, it is indicated that the pressure in the brake air chamber is too large and exceeds the maximum pressure adjustment range calibrated in the brake pressure reduction characteristic curve chart, at this time, the pressure in the brake air chamber needs to be adjusted in the whole pressure reduction and pressure maintaining period, so that the brake air chamber rapidly discharges more air, therefore, the exhaust valve of the brake air chamber is opened for a third preset time all the time to obtain rapid pressure response, and then the process returns to S3; if not, the pressure in the brake air chamber needs to be adjusted slightly, and the pressure difference delta P can be determined according to the brake decompression characteristic curve chartiThe corresponding minimum decompression time t3 is selected from the brake decompression characteristic diagramAnd Δ PiCorresponding Δ PaFurther select Δ PaCorresponding minimum taAs the minimum decompression time t3, the optimal time for continuously opening the exhaust valve is also used, the exhaust valve of the brake chamber is periodically opened according to the setting mode of the minimum decompression time t3 and the decompression and pressure maintaining period t4, the exhaust valve is continuously opened for the fourth preset time, and then the operation returns to S3; and the fourth preset time is greater than or equal to the pressure reduction and pressure maintaining period.
The pressure of the brake air chamber is adjusted in different modes according to the different conditions, so that the pressure response in the brake air chamber is more timely, and the whole brake pressure regulation and control method is more accurate.
Alternatively, the first preset time may be greater than or equal to the pressure increasing and maintaining period, and the third preset time may be greater than or equal to the pressure reducing and maintaining period. When selecting, the first preset time, the second preset time, the third preset time and the fourth preset time may be determined as needed, and the four times may be equal, only two or three of the four times may be equal, or all four times are different.
In the above steps, unless otherwise specified, the exhaust valve is in a closed state when the intake valve is opened for the same brake chamber; when the exhaust valve is opened, the intake valve is in a closed state; in the process of pressurization, the exhaust valve is always in a closed state; during decompression, the inlet valve is always closed.
The above-mentioned sequence of step S1 and steps S2, S3 is not necessarily performed in sequence, and S1 may be performed before S4, and S1 may be performed first and then S2, S3, or S2, S3 may be performed first and then S1 may be performed, or S1 and S2, S3 may be performed at the same time, or S1 and S3 may be performed together. It is understood that, in practice, the pressure increase/decrease characteristic is obtained in S11 to S18 before the vehicle is shipped from the factory, and the pressure increase/decrease characteristic may be read in S1.
In actual use, in the brake pressure control method according to each of the above embodiments, the steps S1 to S4 are performed for each wheel (including the brake chamber). In general, the pressure increase/decrease characteristics of the brake chambers of the respective drive wheels are desired to be as uniform as possible in design for control, and therefore, the control of the respective drive wheels can be used as long as the pressure increase/decrease characteristics are obtained. Of course, the pressure increase and decrease characteristics of each driving wheel can also be obtained by the calibration method.
The whole vehicle brake pressure regulation and control method provided by each embodiment can be applied to vehicles with an air pressure brake system, and can also be applied to vehicles with cooperative brake control of air pressure brake and regenerative brake.
Meanwhile, the invention also provides a control method of the distributed wire control brake system of the commercial vehicle, which can be used for electric and hybrid vehicles, specifically, the vehicle can only use the rear wheels as driving wheels, and also can use four wheels as driving wheels. As shown in fig. 6, the control method includes the steps of:
s100: acquiring a brake signal;
s200: acquiring vehicle state information;
s300: establishing a slip rate controller, and confirming an actual slip rate and a target slip rate according to vehicle state information;
s400: according to the actual slip rate and the target slip rate and in combination with a slip rate controller, distributing target brake torque for each driving wheel
Figure GDA0002751615590000121
Wherein i represents front left FL, front right FR, rear left RL, rear right RR, e.g
Figure GDA0002751615590000122
A target braking torque for the right rear wheel;
s500: establishing a braking cost function J for the vehicle, the braking cost function J being an expected total regenerative braking torque T for the vehicledExpected air brake torque of each driving wheel
Figure GDA0002751615590000131
In combination with a target braking torque of the driving wheel
Figure GDA0002751615590000132
Obtaining the expected total regenerative braking torque T by extremizing a braking cost functiondExpected air brake torque of each driving wheel
Figure GDA0002751615590000133
Understandably, the total regenerative braking torque T is expecteddEqual to the sum of the expected regenerative braking torques of the drive wheels, e.g. total regenerative braking torque T in the embodiment where only two rear wheels are the drive wheelsdEqual to the sum of the expected regenerative braking torque of the right rear wheel and the expected regenerative braking torque of the left rear wheel, and the sum T of the expected regenerative braking torque of the right rear wheel and the expected regenerative braking torque of the left rear wheel can be obtained by extremizing the braking cost function JdAnd expected air brake torque of the right rear wheel
Figure GDA0002751615590000134
And expected air brake torque of the left rear wheel
Figure GDA0002751615590000135
S600: according to each expected air braking torque
Figure GDA0002751615590000136
Controlling a pneumatic braking system to work according to any one of the brake pressure regulation and control methods; wherein, step S2 in the braking pressure regulating method specifically includes: braking torque according to expected air pressure
Figure GDA0002751615590000137
Determining a target pressure Pi；
S700: based on expected total regenerative braking torque TdIn combination with the maximum torque that the motor can provide
Figure GDA0002751615590000138
And minimum torque
Figure GDA0002751615590000139
Determining the actual output brake torque T of the electric machineeAnd controlling the motor to output the actual output braking torque Te。
According to the control method, the slip rate controller and the brake cost function are established, the control strategy of layered control is combined, the actual slip rate of the vehicle is made to approach the target slip rate as much as possible through the slip rate controller, then the air pressure brake torque and the regenerative brake torque are distributed through the brake cost function, so that the utilization of regenerative energy is realized, and the brake torque is distributed in a brake cost function mode, so that the maximum energy regeneration can be realized; and the regenerative braking and the pneumatic braking work simultaneously in consideration of the delay of the pneumatic braking, the delay of the pneumatic braking can be compensated by the regenerative braking, the response speed of the vehicle braking is further improved, and the stability and the safety of the vehicle braking are better ensured.
S600 and S700 may be executed simultaneously or separately, and in a preferred embodiment, they are executed simultaneously to perform quick response to braking.
Specifically, step S2 specifically includes:
Figure GDA00027516155900001310
wherein, KiAre conversion coefficients.
The vehicle state information in step S200 includes: coefficient of friction mu of road surface on which vehicle is running, mass m of vehicle, longitudinal velocity uxAngular velocity omega of driving wheeliRadius of driving wheel RiRotational inertia of the drive wheel, longitudinal force F of the drive wheelxiVertical force F of the driving wheel in the direction of its axis of rotationziSome of the state parameters may be provided or obtained by subsequent measurement when the vehicle leaves a factory, and some of the state parameters may be obtained by measurement of instruments such as a sensor in actual use, and the specific obtaining mode is not limited.
In order to make the actual slip ratio as close as possible to the target slip ratio, in one embodiment of the present invention, the step S300 of establishing a slip ratio controller includes:
s310: setting a proportional integral model as formula (1):
Si＝ei+αi∫eidt， (1)
wherein e isi＝λi-λdi； (2)
S320: the slip rate controller is established as in equation (3):
Figure GDA0002751615590000141
wherein λ isiIs the actual slip ratio, λ, of the vehiclediSat is a saturation function, alpha, for a target slip ratio of the vehiclei、1、0、
Figure GDA0002751615590000142
The coefficient can be preset according to the requirement so as to adjust the slip ratio controller to ensure that the braking effect of the braking system is better.
In this embodiment, step S400 includes:
s410: the integral model of the proportion is derived to obtain a reciprocal model
Figure GDA0002751615590000143
S420: make it
Figure GDA0002751615590000144
Obtaining target braking torque of each driving wheel
Figure GDA0002751615590000145
By adopting the steps, the static error of the slip rate can be eliminated as far as possible by arranging the proportional-integral model, meanwhile, the chattering possibly generated by the wheel speed can be reduced by arranging the slip rate controller containing the saturation function sat, and the actual slip rate can be closer to the target slip rate in the target of the whole control method by enabling the reciprocal of the proportional-integral model to be equal to the arranged slip rate controller, so that the utilization rate of the regenerative energy is improved.
Specifically, the actual slip ratio λiIt can be calculated as the following equation (4):
Figure GDA0002751615590000146
target slip ratio lambdadiCalculated according to the following equation (5):
Figure GDA0002751615590000147
Figure GDA0002751615590000148
wherein u isxIs the longitudinal speed, omega, of the vehicleiIs the driving wheel angular velocity, R, of the vehicleiIs the radius of the driving wheel of the vehicle; kλThe coefficient is preset and can be obtained according to experiments; μ is the coefficient of friction of the road surface on which the vehicle is traveling;
Figure GDA0002751615590000151
to utilize the coefficient of friction; mthreIs a yaw moment threshold for yaw control; l is the wheel track of the driving wheels of the vehicle, and if only two rear wheels are the driving wheels, the value is the wheel track of the left rear wheel and the right rear wheel; fziThe vertical force of the driving wheel in the direction of the rotating shaft of the driving wheel; f. of-1The friction coefficient table is a preset friction coefficient table, and can be measured according to experiments; wherein the above-mentioned preset viscosity may be selected to be 0.5.
It is to be noted that, in the brake system and the control method of the invention, the vehicle is regarded as a rigid body, and only the longitudinal motion thereof is considered, and therefore, the kinetic equation of the vehicle is formula (7):
Figure GDA0002751615590000152
wherein, FxiThe longitudinal force borne by the driving wheel is shown on the right of the formula, and the sum of the longitudinal forces of all wheels (including the driving wheel and the non-driving wheel) is obtained.
The rotational movement of the driving wheel under the longitudinal force and the braking torque can be expressed as formula (8):
Figure GDA0002751615590000153
the target braking torque can be obtained according to the formulas (1) to (8)
Figure GDA0002751615590000154
Expression (9):
Figure GDA0002751615590000155
that is, the target braking torque can be obtained according to the formula (9) in step S400
Figure GDA0002751615590000156
As in the embodiment where only two rear wheels are the drive wheels, the target braking torque of the left rear wheel can be found separately
Figure GDA0002751615590000157
And target braking torque of the right rear wheel
Figure GDA0002751615590000158
In the above embodiments, the braking cost function in step S500 can be specifically expressed as formula (10):
Figure GDA0002751615590000159
wherein, TpiAn expected air brake torque for the drive wheel;
Figure GDA00027516155900001510
a target braking torque for the drive wheel; t isdIs the expected total regenerative braking torque;
Figure GDA00027516155900001511
to maximize the regenerative efficiency of the braking energy and to ensure that the regenerative braking torque compensates for the lack of the pneumatic braking torque, it is set to be close to but less than the maximum value of the regenerative braking torque
Figure GDA00027516155900001512
Considering that in a braking system having an ABS, if the regenerative braking torque is too large, the pneumatic braking system will not provide any torque, resulting in that the wheels will necessarily lock, therefore, the regenerative braking torque cannot be too large to exceed the target braking torque
Figure GDA00027516155900001513
Specifically, the method can be selected according to formula (11);
Figure GDA00027516155900001514
a maximum value of the regenerative braking torque, which is determined by the electric machine of the vehicle, generally selected as the rated output torque of the electric machine;
Figure GDA00027516155900001515
for the reserve gap, it can be obtained experimentally, as a constant value.
Figure GDA0002751615590000161
In embodiments where only two rear wheels are the drive wheels, equation (11) is simplified to equation (12):
Figure GDA0002751615590000162
accordingly, the braking cost function is expressed as equation (12):
Figure GDA0002751615590000163
further, considering that a time-delayed response occurs due to a pressure variation amount in a pressure regulation period of each air brake, the above-mentioned brake cost function is expressed as formula (13),
Figure GDA0002751615590000164
and the pneumatic brake torque can be given in the predicted form according to equation (14):
Figure GDA0002751615590000165
wherein (K +1) represents the predicted value of the next control period, K represents the value of the current control period, and KrIs a preset coefficient; delta PaiIs the pressure variation of the driving wheel.
In a preferred embodiment of the present invention, in order to reduce the calculation load, the expected air brake torque is set within one control cycle
Figure GDA0002751615590000166
Expected total regenerative braking torque TdOptimal regenerative braking torque
Figure GDA0002751615590000167
All are unchanged, so as to obtain an optimized braking energy function, and the braking cost function expression in the step S500 is as formula (15):
Figure GDA0002751615590000168
wherein, KrIs a preset coefficient; delta PaiFor pressure change of driving wheelThe amount of change is equivalent to Δ P in the pressure increasing and decreasing characteristicsaMay be exhaustive, i.e.
Figure GDA0002751615590000169
Thus, the expected air pressure braking torque of each driving wheel can be obtained by minimizing the braking cost function
Figure GDA00027516155900001610
Expected total regenerative braking torque TdAnd the pneumatic braking systems of the driving wheels are respectively controlled by adopting the braking pressure regulating and controlling method.
For expected total regenerative braking torque TdSince regenerative braking of the motor output causes a loss of torque during transmission to the drive wheels, the torque output from the motor is generally distributed to the drive wheels after passing through a gear box and a differential, and therefore, a desired braking torque output from the motor is actually desired
Figure GDA00027516155900001611
Equal to the expected total regenerative braking torque TdAnd the sum of the loss torque.
Specifically, in a vehicle with a differential, the regenerative braking torque on the axles may be expressed as equation (16):
Figure GDA0002751615590000171
wherein ieIs the moment of inertia of the motor rotor; i.e. igThe gear ratio of the gear box on the driving shaft; i.e. i0Is the gear ratio of the differential; j. the design is a squaregIs the moment of inertia of the gearbox; j. the design is a square0Is the moment of inertia of the differential case; omegadIs the angular velocity of the differential case; eta is transmission efficiency;
thus, the desired braking torque output by the motor
Figure GDA0002751615590000172
Can be expressed as a formula(17)：
Figure GDA0002751615590000173
Based on the above analysis, in step S700, the total regenerative braking torque T is expecteddIn combination with the maximum torque that the motor can provide
Figure GDA0002751615590000174
And minimum torque
Figure GDA0002751615590000175
Determining the actual output brake torque T of the electric machineeAnd controlling the motor to output the actual output braking torque TeThe method comprises the following steps:
s71: based on the expected total regenerative braking torque TdDetermining a desired braking torque output by an electric machine
Figure GDA0002751615590000176
Specifically, the calculation can be carried out according to the formula (17);
s72: calculating the maximum torque that the motor can provide
Figure GDA0002751615590000177
And minimum torque
Figure GDA0002751615590000178
S73: judging expected output braking torque of motor
Figure GDA0002751615590000179
With maximum torque
Figure GDA00027516155900001710
Minimum torque
Figure GDA00027516155900001711
The size of (2):
if it is
Figure GDA00027516155900001712
Then
Figure GDA00027516155900001713
If it is
Figure GDA00027516155900001714
Then
Figure GDA00027516155900001715
If it is
Figure GDA00027516155900001716
Then
Figure GDA00027516155900001717
Wherein the maximum torque
Figure GDA00027516155900001718
Minimum torque
Figure GDA00027516155900001719
Angular velocity omega with the motoreRelated, i.e. can be expressed as formula (18), and the angular velocity ω of the motoreCan be expressed as formula (19):
Figure GDA00027516155900001720
Figure GDA00027516155900001721
s74: controlling the motor to output the actual braking torque Te。
Outputting actual braking torque T at motoreAfter the torque is applied, the torque loss of the transmission shaft is removed, and the torque is distributed to the wheel end of each driving wheel through a differential mechanism and finally transmitted to a vehicle driving axle for braking.
It will be appreciated by those skilled in the art that the above-described preferred embodiments may be freely combined, superimposed, without conflict.
It will be understood that the embodiments described above are illustrative only and not restrictive, and that various obvious and equivalent modifications and substitutions for details described herein may be made by those skilled in the art without departing from the basic principles of the invention.

Claims (8)

1. A calibration method for increasing and decreasing pressure characteristics based on a pneumatic brake-by-wire system is characterized in that the increasing and decreasing pressure characteristics are expressed by a brake pressure increasing characteristic curve graph and a brake pressure decreasing characteristic curve graph,
the obtaining step of the brake boosting characteristic curve comprises the following steps:
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 quantityEstablishing the brake boost characteristic curve chart, wherein each boost pressure adjustment amount is used in the brake boost characteristic curve chart
Figure FDA0002779306400000012
As ordinate, the actual time of each time is abscissaCoordinates;
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
Figure FDA0002779306400000013
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
Figure FDA0002779306400000014
Is a vertical coordinate, and the actual time of each time is a horizontal coordinate;
wherein m and n are min, 2, 3, … and max respectively.
2. The calibration method according to claim 1, wherein in the brake pressure increasing characteristic curve obtaining step and the brake pressure reducing characteristic curve obtaining step, the first pressure increasing time t1 and the first pressure reducing time t3 are 1 ms.
3. The calibration method according to claim 1, wherein in the brake boost characteristic curve obtaining step and the brake decompression characteristic curve obtaining step, the boost pressure-holding period t2 and the decompression pressure-holding period t4 are both 30 ms.
4. A calibration method according to any one of claims 1-3, wherein in the step S13, each time the pressurization time t1 is increased by Δ t1 compared with the last time the pressurization time t 1;
in step S17, the depressurization time t3 at each time is increased by Δ t2 from the last depressurization time t 3.
5. The calibration method according to claim 4, wherein the step S13 specifically includes: circularly executing S11 and S12 until the pressurization time t1 is equal to the pressurization and pressure maintaining period t2, wherein delta t1 is 1 ms;
the step S17 specifically includes: and circularly executing S15 and S16 until the decompression time t3 is equal to the decompression and pressure maintaining period t4, wherein the delta t2 is 1 ms.
6. A whole vehicle brake pressure regulating and controlling method based on a pneumatic line control brake system is characterized by comprising the following steps:
s1: acquiring the pressure increase and decrease characteristics of a brake chamber of a vehicle, which are obtained by using the calibration method of any one of claims 1 to 5;
s2: obtaining a target pressure P of a brake chamber of the vehiclei；
S3: acquiring the actual pressure P of the brake air chamberi0And calculating the pressure difference delta P between the target pressure and the pressurei＝Pi-Pi0；
S4: according to said pressure difference Δ PiAnd determining 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 characteristics, and regulating and controlling the brake pressure according to the opening mode.
7. A control method of a whole vehicle brake system is characterized by comprising the following steps:
s100: acquiring a brake signal;
s200: acquiring vehicle state information;
s300: establishing a slip rate controller, and confirming an actual slip rate and a target slip rate according to the vehicle state information;
s400: 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
Figure FDA0002779306400000031
S500: establishing a braking cost function for the vehicle, the braking cost function being an expected total regenerative braking torque T for the vehicledExpected air brake torque of each of the drive wheels
Figure FDA0002779306400000032
Then combining said target braking torque of each of said drive wheels
Figure FDA0002779306400000034
Obtaining the expected total regenerative braking torque T by extremizing the braking cost functiondExpected air brake torque of each of the drive wheels
Figure FDA0002779306400000033
S600: according to each expected air pressure braking torque
Figure FDA0002779306400000035
Controlling the operation of the pneumatic brake system according to the brake pressure regulating method of claim 6; wherein, the step S2 specifically includes: according to the expected air braking torque
Figure FDA0002779306400000036
Determining the target pressure Pi；
S700: based on the expected total regenerative braking torque TdIn combination with the maximum torque that the motor can provide
Figure FDA0002779306400000037
And minimum torque
Figure FDA0002779306400000038
Determining an actual output brake torque T of the electric machineeAnd controlling the motor to output actual output brake torque Te。
8. An acquisition device for increasing and decreasing pressure characteristics based on a pneumatic brake-by-wire system is characterized by comprising:
the air compressor, the air storage tank and the brake chamber are connected in sequence, the brake chamber is provided with an air inlet valve and an air outlet valve, and the brake chamber is communicated with the air storage tank through the air inlet valve and is communicated with the outside through the air outlet valve;
the pressure sensor is arranged in the brake chamber and used for measuring the pressure of the brake chamber;
a controller connected to said intake valve, said exhaust valve and said pressure sensor for operating in accordance with the calibration method of any one of claims 1 to 5.
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