CN111976677B - Combined braking anti-lock control system and control method for pure electric vehicle - Google Patents

Combined braking anti-lock control system and control method for pure electric vehicle Download PDF

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CN111976677B
CN111976677B CN202010909530.3A CN202010909530A CN111976677B CN 111976677 B CN111976677 B CN 111976677B CN 202010909530 A CN202010909530 A CN 202010909530A CN 111976677 B CN111976677 B CN 111976677B
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braking
braking force
torque
automobile
regenerative braking
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CN111976677A (en
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于德亮
王文嵩
路钢
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Harbin University of Science and Technology
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Harbin University of Science and Technology
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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
    • 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
    • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
    • 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
    • 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
    • B60L7/18—Controlling the braking effect
    • 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
    • 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
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • 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
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/42—Drive Train control parameters related to electric machines
    • B60L2240/423—Torque
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)
  • Regulating Braking Force (AREA)

Abstract

The invention discloses a composite braking anti-lock control system and a control method for a pure electric vehicle, and relates to the technical field of electric vehicle braking control. The invention aims to solve the problem that the traditional anti-lock braking control system distributes braking force according to a fixed proportion and cannot realize optimal control on complex road conditions. The invention judges the conversion rate of the braking force according to the braking force, and determines the optimal slip rate according to the conversion rate of the braking force; calculating a required torque according to the actual slip rate and the optimal slip rate; determining the maximum regenerative braking torque at the current moment; when the braking torque is distributed, the required braking force preferentially selects the regenerative braking torque as the main braking torque, and the insufficient part is complemented by the mechanical braking force of the automobile; according to the invention, under the condition of various complex pavements of automobile running, the optimal slip rate of wheels is identified and controlled, and the braking energy is recovered to the greatest extent on the premise of realizing the optimal braking effect and safety of the automobile.

Description

Combined braking anti-lock control system and control method for pure electric vehicle
Technical Field
The invention relates to the technical field of electric automobile brake control, in particular to a combined brake anti-lock control system and a control method for a pure electric automobile.
Background
While the traditional fuel power automobile utilizes mechanical friction to carry out mechanical braking, the hybrid power and pure electric automobile can enable the motor to work in a power generation state in an inertial driving mode during braking, and the braking torque provided by the motor in the power generation state can reduce part of mechanical braking. Although the braking torque provided by the motor is not mechanical braking, the friction force between the wheel tires and the ground can be formed, the effect of decelerating braking force is provided for the electric automobile, the loss of a traditional mechanical braking structure can be reduced by utilizing the regenerative braking principle of the electric automobile, the running endurance of the electric automobile is improved through the electric energy recovered by regenerative braking, and the waste of the electric energy is saved. At present, a braking force control and energy recovery strategy of an electric automobile mainly adopts a fixed proportion distribution mode, takes the charge state SOC of a battery, the braking force required by a driver and the braking strength as inputs, and distributes the magnitude of mechanical braking force and regenerative braking force through a pre-defined braking force distribution curve. The control strategy can not utilize the maximum adhesion coefficient of the tire and the road surface to the maximum extent, so as to achieve the optimal braking control effect.
If the purpose of simply recovering the regenerative braking energy of the electric automobile is to use the regenerative braking force as much as possible as the main braking mode of the automobile during braking, but because the regenerative braking is limited by a plurality of factors, under certain braking working conditions, the simple regenerative braking cannot meet the braking requirement of a driver, the safety and the stability of the electric automobile during braking are affected, and a compound braking mode is adopted at the moment. The traditional automobile ABS system mainly considers the braking efficiency of the automobile and the locking condition of wheels, when complex working conditions occur, the excessive braking force can cause the locking phenomenon of the wheels of the automobile before the ABS system acts, and particularly when the electric automobile drives on a low-adhesion road surface, because the automobile is braked on an ice-snow road surface, most braking force distribution schemes use regenerative braking as main braking force, and the traditional anti-lock braking system of the electric automobile can reduce mechanical braking force. At this time, a locking phenomenon is likely to occur, thereby reducing the driving stability of the automobile.
In the existing anti-lock brake control based on an automobile ABS system, the slip rate of wheels often shows larger fluctuation near the optimal slip rate, and because the road surface condition is very complex and the optimal slip rates corresponding to the peak attachment coefficients corresponding to different road surfaces are different when the automobile actually runs, the traditional anti-lock brake control system cannot recognize and control the optimal slip rate of the automobile, so that the optimal brake effect cannot be achieved. Therefore, it is necessary to study an automobile brake control method based on optimal slip ratio control for a complex road surface.
Disclosure of Invention
In order to solve the problems, the invention provides a pure electric vehicle composite braking anti-lock control system and a control method, which can identify and control the optimal slip rate of wheels under various complex roads on which the vehicle runs, and can recover braking energy to the greatest extent on the premise of realizing the optimal braking effect and safety of the vehicle.
In one aspect, the present invention provides a hybrid brake anti-lock control system for a pure electric vehicle, including:
the sensing unit is used for acquiring the wheel speed and the vehicle speed of the vehicle at the current moment;
the braking force observer is used for calculating the braking force observation value received by the current wheel according to the wheel speed and the vehicle speed of the automobile;
the optimal slip rate judging module is used for judging a braking force conversion rate according to the braking force and determining an optimal slip rate according to the braking force conversion rate;
the self-adaptive sliding mode controller is used for calculating the required torque according to the actual sliding rate and the optimal sliding rate;
the whole vehicle controller determines the maximum regenerative braking torque at the current moment;
and the braking torque distribution module is used for comparing the maximum regenerative braking torque with the required torque, when the maximum regenerative braking torque is larger than or equal to the required torque, the braking force of the current automobile is completely provided by the regenerative braking force, and when the maximum regenerative braking torque is smaller than the required torque, the maximum regenerative braking torque is provided firstly, and the rest part is provided by the mechanical braking force.
The invention further provides a combined braking anti-lock control method for the pure electric vehicle, which comprises the following steps of:
acquiring the wheel speed and the vehicle speed of an automobile at the current moment;
calculating the observed value of the braking force received by the current wheel according to the wheel speed and the vehicle speed of the automobile;
judging a braking force conversion rate according to the braking force, and determining an optimal slip rate according to the braking force conversion rate;
calculating a required torque according to the actual slip rate and the optimal slip rate;
determining the maximum regenerative braking torque at the current moment;
and the braking torque distribution module is used for comparing the maximum regenerative braking torque with the required torque, when the maximum regenerative braking torque is larger than or equal to the required torque, the braking force of the current automobile is completely provided by the regenerative braking force, and when the maximum regenerative braking torque is smaller than the required torque, the maximum regenerative braking torque is provided firstly, and the rest part is provided by the mechanical braking force.
Further, the actual slip rate of the automobile is calculated by the following formula:
Figure BDA0002662728940000021
wherein lambda is the actual slip ratio, V is the speed of the automobile, omega is the wheel speed of the automobile wheel, and R is the wheel radius.
Further, the method for determining the optimal slip ratio includes:
recording, by the controller, the estimated braking force F for each step X And calculate F X (k) And F is equal to X (k+1) determining the braking force change rate DeltaF x Is of a size of (a) and (b).
When DeltaF X (k) When the slip ratio is more than 0, the current slip ratio is in a stable region, and the regenerative braking torque at the moment is the maximum regenerative braking torque output;
when DeltaF X (k) When the slip ratio is less than 0, the current slip ratio is in an unstable area, and the regenerative braking torque which is not provided to the wheels is set at the moment;
when DeltaF X (k) When=0, it indicates that the current slip ratio is at the optimal slip ratio.
Further, the method for obtaining the required torque includes:
the optimum slip ratio is input as a target, and the actual slip ratio is a negative feedback signal, so there are:
e＝λ m -λ；
wherein lambda is m The optimal slip rate is shown, and lambda is the actual slip rate;
the following slip plane is defined:
s＝e+a∫edt；
the following relationship is established:
Figure BDA0002662728940000031
establishing an approach law meeting the Lyapunov stability:
Figure BDA0002662728940000032
Figure BDA0002662728940000033
wherein k is 1 、k 2 A constant greater than 0, G(s) being a continuous function, and obtaining the required torque T according to the above relation m The method comprises the following steps:
Figure BDA0002662728940000034
further, the maximum regenerative braking torque is smaller than the rated torque of the motor, and when the SOC is more than or equal to 90%, regenerative braking is not used any more to provide braking force.
Further, the method for acquiring the observed braking force value comprises the following steps:
the following single-round rotation model is established:
Figure BDA0002662728940000041
wherein J is the rotational inertia of the wheel, R is the radius of the wheel, T b Mu is the road adhesion coefficient, F z The method is applied to the tyre;
observe the braking force F x As an unknown state to be observed, the following state equation is established:
Figure BDA0002662728940000042
the following high gain observer is established:
Figure BDA0002662728940000043
where z1, z2, d are constants greater than zero.
As described above, the present invention has the following effects:
1. according to the invention, slip rate control is introduced in the braking process of the electric automobile, the running condition of the automobile is identified through the high-gain braking force observer, and the braking force observation value is determined; judging the optimal slip rate under the current road condition by using a slope method, and outputting the required braking torque by combining the slip rate with the self-adaptive slip mode controller; the motor is high in working accuracy and high in reaction speed, and the wheel slip rate is controlled to be in an optimal state, so that the utilization of the maximum attachment coefficient of the road surface is realized, and the self-adaptive sliding mode controller ensures the rapid and strong robustness of slip rate identification.
2. The invention aims at the problem that the traditional anti-lock braking control system can not realize optimal control on complex road conditions by distributing braking force according to fixed proportion, when braking torque is distributed, the required braking force preferentially selects the regenerative braking torque as main braking torque, and the insufficient part is supplemented by the mechanical braking force of the automobile, thereby realizing the utilization of the regenerative braking force to the greatest extent, achieving the good effect of recovering braking energy and ensuring the safety and stability of the automobile during braking.
Drawings
FIG. 1 is a schematic block diagram of a hybrid brake anti-lock control system for a pure electric vehicle according to an embodiment of the present invention;
FIG. 2 is a graph of μ - λ relationship under a typical road surface from a Burckhardt tire model of an embodiment of the present invention;
FIG. 3 is a control flow chart of an optimal slip ratio determination controller according to an embodiment of the present invention;
FIG. 4 is a graph of the optimal slip ratio obtained by the observer and slope determination method according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of an adaptive slip-form controller controlling braking torque output in accordance with an embodiment of the present invention;
FIG. 6 is a graph showing the control of brake speed using slip ratio during braking conditions according to an embodiment of the present invention.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.
It should be noted that the illustrations provided in the following embodiments merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the illustrations, not according to the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
For a composite braking control system of an electric automobile, the first problem to be considered is to ensure the safety and stability of the braking effect, and on the basis, the regenerative braking is considered to be used as the main braking force preferentially, so that the maximum recovery of braking energy is realized. In compound braking, slip ratio control is introduced to achieve optimal braking effect, while facing two problems: firstly, how to obtain the optimal slip rate of the current running under the condition of unknown road surface condition, and secondly, how to effectively control the optimal slip rate.
In the braking process of the automobile, the wheel speed of the automobile is gradually reduced along with the braking torque applied to the wheel end by the motor and the mechanical braking structure, and the speed of the automobile is gradually reduced along with the braking torque applied to the wheel end by the motor and the mechanical braking structure. The wheel speed and the vehicle speed are not synchronously reduced, if the applied braking force is too large, the wheel speed tends to zero before the vehicle speed, and the wheels are in a locking state at the moment and the vehicle is still running. Wheel locking, especially front wheel locking before rear wheel locking, can have a great influence on the safety and stability of running of the automobile, and the process from rolling to locking of the wheels can be represented by the slip rate lambda.
As shown in fig. 1, a hybrid braking anti-lock control system for a pure electric vehicle according to this embodiment includes:
the sensing unit is used for acquiring the actual wheel speed and the vehicle speed of the automobile at the current moment, and the actual wheel speed and the vehicle speed are respectively input into the high-gain braking force observer and the actual slip rate calculation module;
the high-gain braking force observer is used for calculating the braking force observed value received by the current wheel according to the wheel speed and the vehicle speed of the automobile;
the optimal slip rate judging module is used for judging a braking force conversion rate according to the braking force and determining an optimal slip rate according to the braking force conversion rate;
the actual slip rate calculation module calculates the actual slip rate of the current automobile by utilizing the wheel speed and the speed signal of the automobile;
the self-adaptive sliding mode controller is used for calculating the required torque according to the actual slip rate and the optimal slip rate, and a required braking torque signal output by the self-adaptive sliding mode controller is transmitted to a VCU whole vehicle controller of the vehicle;
the whole vehicle controller determines the maximum regenerative braking torque at the current moment;
and the braking torque distribution module is used for comparing the maximum regenerative braking torque with the required torque, when the maximum regenerative braking torque is larger than or equal to the required torque, the braking force of the current automobile is completely provided by the regenerative braking force, and when the maximum regenerative braking torque is smaller than the required torque, the maximum regenerative braking torque is provided firstly, and the rest part is provided by the mechanical braking force.
The method for controlling the anti-lock braking of the composite brake of the pure electric vehicle comprises the following steps:
s1, acquiring the actual wheel speed omega, the vehicle speed V and the wheel end braking moment T of the automobile at the current moment b ；
S2, calculating the actual slip rate lambda of the current automobile by using the actual wheel speed omega and the vehicle speed V signals, wherein the actual slip rate lambda under the braking working condition is as follows:
Figure BDA0002662728940000061
wherein lambda is the actual slip ratio, V is the speed of the automobile, omega is the wheel speed of the automobile wheel, and R is the wheel radius.
When the slip rate is zero, the wheels roll completely, and when the slip rate is 100%, the wheels are locked completely. The relation between the slip rate and the road adhesion coefficient mu is that the slip rate is increased and then reduced, and in general, when the slip rate of the wheel is between 0.015 and 0.2, the maximum road adhesion coefficient mu max can be achieved between the tire and the ground. As shown in fig. 2, the relationship diagram of mu-lambda under a typical road surface is obtained according to the Burckhardt tire model, and as can be seen, if the wheels are ensured to be always at the optimal slip ratio, the road surface adhesion coefficient can be utilized to the greatest extent, so that the automobile achieves the optimal braking effect.
S3, calculating the observed value F of the braking force received by the current wheel according to the actual wheel speed omega and the vehicle speed V of the automobile x ；
The method specifically comprises the following steps:
s31, in order to estimate the optimal slip rate under the complex road conditions, neglecting the rolling resistance of the automobile tire and the air resistance during running, and establishing the following single-wheel rotation model:
Figure BDA0002662728940000062
wherein omega is the wheel speed of an automobile wheel, J is the rotational inertia of the wheel, R is the radius of the wheel, and T b Mu is the road adhesion coefficient, F z The method is characterized in that the method is applied to the tire, V is the speed of the automobile, and lambda is the actual slip rate;
s32, when the automobile actually runs, mu is in an unknown state, and during the braking process, the normal acting force F borne by the front wheels and the rear wheels of the automobile z Also receives acceleration and changes in braking intensity, the present embodiment observes the braking force observed value F x As an unknown state to be observed, build up asThe following equation of state:
Figure BDA0002662728940000071
wherein A is the ratio of the radius of the wheel to the moment of inertia
Figure BDA0002662728940000072
B is->
Figure BDA0002662728940000073
U represents the output torque T b 。
In order to achieve the observation of X2 in the above state equation, the following high gain observer is established:
Figure BDA0002662728940000074
where z1, z2, d are constants greater than zero.
S4, judging a braking force conversion rate according to the braking force, and determining an optimal slip rate according to the braking force conversion rate, wherein the method specifically comprises the following steps of:
recording, by the controller, the estimated braking force F for each step X And calculate F X (k) And F is equal to X (k+1) determining the braking force change rate DeltaF x Is of a size of (2);
when DeltaF X (k) When > 0, the current slip ratio is in the stable region, and the regenerative braking torque at this time is the maximum regenerative braking torque T bmax ；
When DeltaF X (k) When the slip ratio is less than 0, the current slip ratio is in an unstable area, and the regenerative braking torque which is not provided to the wheels is set at the moment;
when DeltaF X (k) When=0, the current slip ratio is at the optimal slip ratio, and the optimal slip ratio adaptive slip mode controller is started at this time, so that the control slip ratio is kept at the current value.
As shown in fig. 4 and 5, when running under a road surface with an adhesion coefficient of 0.5, the slip ratio and torque output control conditions were determined at this point to be about 0.15 as the optimum slip ratio.
S5, according to the actual slip rate lambda and the optimal slip rate lambda m Calculating a required torque;
s51, setting the optimal slip rate lambda m As a target input, the actual slip ratio λ is a negative feedback signal, and therefore there is:
e＝λ m -λ；
wherein lambda is m The optimal slip rate is shown, and lambda is the actual slip rate;
s52, defining the following sliding mode surface:
s＝e+a∫edt；
s53, establishing the following relation:
Figure BDA0002662728940000081
s54, establishing an approach law meeting the Lyapunov stability:
Figure BDA0002662728940000082
Figure BDA0002662728940000083
wherein k is 1 、k 2 A constant greater than 0, G(s) being a continuous function, and obtaining the required torque T according to the above relation m The method comprises the following steps:
Figure BDA0002662728940000084
and S6, determining the maximum regenerative braking torque at the current moment, wherein the maximum regenerative braking torque is smaller than the rated torque of the motor, and when the SOC is more than or equal to 90%, the regenerative braking is not used for providing braking force.
And S7, a braking torque distribution module compares the maximum regenerative braking torque with the required torque, when the maximum regenerative braking torque is larger than or equal to the required torque, the braking force of the current automobile is completely provided by the regenerative braking force, when the maximum regenerative braking torque is smaller than the required torque, the maximum regenerative braking torque is provided first, and the rest part is provided by the mechanical braking force.
As shown in fig. 6, the vehicle speed and wheel speed change map of the anti-lock braking of the vehicle is performed under the simulated braking condition. The initial speed is 80km/h, the automobile cruises at constant speed in the first 1s, the driver presses the brake pedal in one second, the wheel slip rate is rapidly increased, the slip mode controller is started, the slip rate is finally controlled to be stabilized at the optimal point, the composite braking is carried out, the braking duration is 4.5 seconds, and the final speed of the automobile is reduced to zero.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (5)

1. The utility model provides a pure electric vehicles composite braking anti-lock control system which characterized in that includes:
the sensing unit is used for acquiring the wheel speed and the vehicle speed of the vehicle at the current moment;
a braking force observer for calculating the current braking force observed value F received by the wheels according to the wheel speed and the vehicle speed of the automobile x The method comprises the steps of carrying out a first treatment on the surface of the The method for acquiring the braking force observation value comprises the following steps:
the following single-round rotation model is established:
Figure FDA0004209507960000011
wherein J is the rotational inertia of the wheel, R is the radius of the wheel, T b Mu is the road adhesion coefficient, F z To which the tyre is subjectedA law phase acting force;
observe the braking force F x As an unknown state to be observed, the following state equation is established:
Figure FDA0004209507960000012
the following high gain observer is established:
Figure FDA0004209507960000013
wherein z1, z2 and d are constants greater than zero;
the optimal slip rate judging module is used for judging a braking force conversion rate according to the braking force and determining an optimal slip rate according to the braking force conversion rate;
an adaptive slip-form controller for calculating a required torque T according to an actual slip rate and the optimal slip rate m The method comprises the following steps:
Figure FDA0004209507960000014
wherein e=λ m -λ，λ m For optimum slip ratio, lambda is the actual slip ratio, is
Figure FDA0004209507960000015
V is the speed of the automobile, R is the radius of the wheel;
the whole vehicle controller determines the maximum regenerative braking torque at the current moment;
and the braking torque distribution module is used for comparing the maximum regenerative braking torque with the required torque, when the maximum regenerative braking torque is larger than or equal to the required torque, the braking force of the current automobile is completely provided by the regenerative braking force, and when the maximum regenerative braking torque is smaller than the required torque, the maximum regenerative braking torque is provided firstly, and the rest part is provided by the mechanical braking force.
2. The anti-lock control method for the composite braking of the pure electric vehicle is characterized by comprising the following steps of:
acquiring the wheel speed and the vehicle speed of an automobile at the current moment;
according to the wheel speed and the vehicle speed of the automobile, calculating a braking force observed value received by the current wheel, wherein the method for acquiring the braking force observed value comprises the following steps:
the following single-round rotation model is established:
Figure FDA0004209507960000021
wherein J is the rotational inertia of the wheel, R is the radius of the wheel, T b Mu is the road adhesion coefficient, F z The method is applied to the tyre;
observe the braking force F x As an unknown state to be observed, the following state equation is established:
Figure FDA0004209507960000022
the following high gain observer is established:
Figure FDA0004209507960000023
wherein z1, z2 and d are constants greater than zero;
judging a braking force conversion rate according to the braking force, and determining an optimal slip rate according to the braking force conversion rate;
calculating a required torque according to an actual slip rate and the optimal slip rate, wherein the required torque obtaining method comprises the following steps:
the optimum slip ratio is input as a target, and the actual slip ratio is a negative feedback signal, so there are:
e＝λ m -λ；
wherein lambda is m The optimal slip rate is shown, and lambda is the actual slip rate;
the following slip plane is defined:
s＝e+a∫edt；
the following relationship is established:
Figure FDA0004209507960000031
establishing an approach law meeting the Lyapunov stability:
Figure FDA0004209507960000032
Figure FDA0004209507960000033
wherein k is 1 、k 2 A constant greater than 0, G(s) being a continuous function, and obtaining the required torque T according to the above relation m The method comprises the following steps:
Figure FDA0004209507960000034
determining the maximum regenerative braking torque at the current moment;
and the braking torque distribution module is used for comparing the maximum regenerative braking torque with the required torque, when the maximum regenerative braking torque is larger than or equal to the required torque, the braking force of the current automobile is completely provided by the regenerative braking force, and when the maximum regenerative braking torque is smaller than the required torque, the maximum regenerative braking torque is provided firstly, and the rest part is provided by the mechanical braking force.
3. The method for controlling the anti-lock braking of the hybrid electric vehicle according to claim 2, wherein the actual slip rate of the vehicle is calculated by the following formula:
Figure FDA0004209507960000035
wherein lambda is the actual slip ratio, V is the speed of the automobile, omega is the wheel speed of the automobile wheel, and R is the wheel radius.
4. The method for controlling the anti-lock braking of the hybrid electric vehicle according to claim 2, wherein the method for determining the optimal slip ratio comprises the following steps:
recording, by the controller, the estimated braking force F for each step X And calculate F X (k) And F is equal to X (k+1) determining the braking force change rate DeltaF x Is of a size of (2);
when DeltaF X (k) When the slip ratio is more than 0, the current slip ratio is in a stable region, and the regenerative braking torque at the moment is the maximum regenerative braking torque output;
when DeltaF X (k) When the slip ratio is less than 0, the current slip ratio is in an unstable area, and the regenerative braking torque which is not provided to the wheels is set at the moment;
when DeltaF X (k) When=0, it indicates that the current slip ratio is at the optimal slip ratio.
5. The method for controlling the hybrid braking anti-lock of the pure electric vehicle according to claim 2, wherein the maximum regenerative braking torque is smaller than the rated torque of the motor, and when the SOC is more than or equal to 90%, the regenerative braking is not used any more to provide the braking force.
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