CN114987441A

CN114987441A - Active safety control system and method based on four-wheel independent driving/braking vehicle

Info

Publication number: CN114987441A
Application number: CN202210549424.8A
Authority: CN
Inventors: 李静; 冉印; 冯佰东; 王阳
Original assignee: Yanshan University
Current assignee: Yanshan University
Priority date: 2022-05-20
Filing date: 2022-05-20
Publication date: 2022-09-02

Abstract

The invention relates to an active safety control system and method based on four-wheel independent driving/braking vehicles. An active safety control system based on four-wheel independent driving/braking vehicles comprises a vehicle real-time data module, a central computing module, an active control coordination module and an actuating mechanism module. The control method comprises the following steps: judging the yaw stability, judging the rollover stability, judging the wheel locking, calculating the optimal slip rate, calculating an ESC additional yaw moment, calculating an RSC additional yaw moment, carrying out ESC and RSC coordinated control and carrying out anti-lock ABS coordinated control. The invention fully considers the possible situations of yaw instability, side inclination, wheel locking and the simultaneous occurrence of a plurality of situations of the yaw instability, the side inclination and the wheel locking in the running process of the four-wheel independent driving/braking vehicle, and can effectively reduce the wheel locking on the basis of ensuring the running stability of the vehicle and improve the running safety of the vehicle by carrying out the combined control of ABS, ESC and RSC.

Description

Active safety control system and method based on four-wheel independent drive/brake vehicle

Technical Field

The invention belongs to the technical field of vehicle stability control and active safety driving, and particularly relates to an active safety control system and method based on four-wheel independent driving/braking vehicles.

Background

With the continuous development of automobile technology and society, the active safety technologies of the automobile, such as ABS, ESC and RSC, have gradually become vehicle standards, which can greatly improve the stability and handling performance of the vehicle when the vehicle meets emergency, thereby ensuring the driving safety performance of the vehicle. However, ESC controls the yaw stability of the vehicle by applying brakes to the corresponding wheels to generate an additional yaw moment, and RSC also controls the roll stability of the vehicle by applying brakes to the corresponding wheels to reduce the yaw acceleration of the vehicle and the vehicle speed. However, the wheels and control targets of ESC and RSC control are not exactly the same, and there is a possibility of conflict during actual implementation. Meanwhile, when the vehicle meets an emergency, the control of the ESC and the RSC may cause the locking of wheels, so that the vehicle is unstable or loses controllability, the negative control on the vehicle is caused, and the driving safety of the vehicle cannot be ensured.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention provides an active safety control system and method based on a four-wheel independent driving/braking vehicle, which comprehensively consider the influence on the vehicle caused by the combined action of ESC and RSC, and reduce the locking of the wheels by performing the combined control of ABS, ESC and RSC on the basis of ensuring the driving stability of the vehicle.

The technical scheme for solving the problems is as follows: an active safety control system based on four-wheel independent driving/braking vehicle is characterized in that:

the system comprises a vehicle real-time data module, a central computing module, an active control coordination module and an actuating mechanism module;

the vehicle real-time data module is used for acquiring four-wheel driving torque, four-wheel angular speed, yaw angular speed, mass center slip angle, vehicle longitudinal speed, vehicle lateral speed and vehicle fixed parameters;

the central computing module comprises a vehicle state judging module, an ESC control module and an RSC control module;

the vehicle state judging module comprises a yaw stability judging unit, a side turning stability judging unit, a road adhesion coefficient estimating unit and a wheel locking judging unit, and the vehicle state judging module is used for judging the yaw stability, the side turning stability and the wheel locking state of the vehicle and estimating the road adhesion coefficient by receiving the parameter signals output by the vehicle real-time data module;

the ESC control module is used for calculating an additional yaw braking moment required for recovering stability after the vehicle is subjected to yaw instability, and obtaining braking force of the additional yaw braking moment according to a corresponding rule and distributing the braking force to corresponding wheels;

the RSC control module is used for calculating an additional yaw braking moment required by vehicle rollover instability after recovery, and obtaining braking force of the additional yaw braking moment according to a corresponding rule and distributing the braking force to corresponding wheels;

the active control coordination module comprises an ESC (electronic stability control), an RSC (signal code modulation) coordination control module and an anti-lock ABS (anti-lock braking system) coordination control module;

the ESC and RSC coordinated control module receives the corresponding four-wheel additional braking force output by the ESC control module and the RSC control module, and carries out coordinated control on the four-wheel additional braking force output by the ESC control module and the RSC control module to obtain an expected four-wheel braking force;

the anti-lock ABS coordinated control module receives the expected four-wheel braking force output by the ESC and RSC coordinated control module, carries out anti-lock regulation and outputs the final four-wheel additional braking force and the final four-wheel additional driving force;

the actuating mechanism module comprises a brake-by-wire actuating module and a drive-by-wire actuating module; the brake-by-wire execution module brakes the wheels according to the final four-wheel additional braking force, and the drive-by-wire execution module drives the wheels according to the four-wheel additional driving force.

Further, the vehicle structure fixed parameter information is stored in the vehicle fixed parameter, and includes: the mass of the whole vehicle, the distance between the front axle and the centroid, the distance between the rear axle and the centroid, the equivalent lateral deviation rigidity of the front axle, the equivalent lateral deviation rigidity of the rear axle, the wheel track of the front axle, the wheel track of the rear axle, the rotational inertia of the wheel and the radius of the wheel.

In addition, the invention also provides a control method of the active safety control system based on the four-wheel independent driving/braking vehicle, which is characterized by comprising the following steps:

the method comprises the following steps: estimating the road adhesion coefficient according to the parameters provided by the vehicle real-time data module;

step two: performing yaw instability judgment on the vehicle, wherein the ESC does not work if the vehicle is in a stable state, and when the vehicle is in an unstable state, the ESC starts to work;

step three: judging rollover instability of the vehicle, and if the vehicle is about to rollover, RSC intervenes to work;

step four: wheel locking judgment is carried out, and if the wheel is judged to be locked, ABS intervenes in the work;

step five: when the yaw instability condition occurs, performing ESC control calculation, including yaw instability additional yaw moment calculation and additional yaw moment to perform braking force distribution;

step six: when rollover instability occurs, RSC instability calculation is carried out, and the RSC instability calculation comprises rollover instability additional yaw moment calculation and additional yaw moment to carry out braking force distribution;

step seven: ESC and RSC coordinately control ESC and RSC to output additional four-wheel braking force;

step eight: when the additional four-wheel braking force output by the ESC and RSC is distributed to each wheel through the ESC and RSC coordinated control module outputting the expected four-wheel additional braking force, the maximum braking force of the wheel cannot exceed the braking force corresponding to the optimal slip rate at the moment, if the maximum braking force exceeds the optimal slip rate, the wheel is locked, and anti-lock ABS coordinated control is required;

step nine: and finally outputting the four-wheel additional braking force and the four-wheel additional driving force to the brake-by-wire execution module and the drive-by-wire execution module corresponding to the execution mechanism module.

Further, in the first step, the road adhesion coefficient is estimated according to the parameters provided by the vehicle real-time data module, and the calculation formula is as follows:

wherein m is the vehicle mass, g is the gravity acceleration value, a is the distance between the front axle and the mass center, b is the distance between the rear axle and the mass center, and h _c Is the height of the center of mass of the vehicle, B is the distance between the front and rear axles of the vehicle, v _x Is the longitudinal speed of the vehicle, v _y Is the lateral speed of the vehicle, T _i For the four-wheel drive torque of the vehicle, I _i Is the four-wheel moment of inertia of the vehicle, omega _i The four-wheel angular velocity R of the vehicle _i The rolling radius N of the four wheels of the vehicle _i The vertical load of four wheels of the vehicle and mu are estimated road adhesion coefficients, wherein i ═ fl, fr, rl and rr represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle.

Further, the yaw instability determination in the second step is specifically:

the yaw rate and the mass center slip angle are two main parameters for controlling the stability of the vehicle, so that the threshold value of the parameters is set to judge whether the vehicle has instability during running, and the judgment formula is as follows:

|Δe _γ |＝|γ-γ ₀ |≤|c ₁ γ|

|β+c ₂ β′|≤c ₃

in the formula, c ₁ 、c ₂ 、c ₃ Is constant, gamma is the actual yaw rate of the vehicle, gamma ₀ Desired yaw rate, Δ e, for the vehicle _γ The deviation of the actual yaw rate of the vehicle from the expected yaw rate is beta, the actual centroid slip angle of the vehicle is beta, and beta' is the derivative of the actual centroid slip angle of the vehicle;

when the vehicle state meets the two equations, the vehicle is considered to be in a stable state, the ESC does not work, when the vehicle state does not meet any one of the equations, the vehicle is considered to be in an unstable state, and the ESC is involved to start working.

Further, in the third step, the rollover instability is specifically determined as follows:

judging whether the vehicle has the rollover condition by adopting the transverse load transfer rate, wherein the transverse load transfer rate is calculated according to the following formula:

wherein, K ₁ For the transverse load transfer rate of the vehicle, N _fl For vertical loading of the left front wheel of the wheel, N _fr Vertical load of the right front wheel of the wheel, N _rl For vertical loading of the left and rear wheels of a vehicle, N _rr Vertical load of the right rear wheel of the wheel;

it can be known that | K is not more than 0 ₁ I is less than or equal to 1, when I K ₁ The larger the numerical value of |, the more easily the vehicle is subjected to rollover instability, K ₁ When 1, the vehicle rolls over to the left, K ₁ When the vehicle turns right, the vehicle is represented as-1; from the situation of preventing rollover instability as early as possible and ensuring complete running of the vehicle, taking the value of K ₁ |＝c ₄ To trigger RSC threshold, when | K ₁ |<c ₄ Indicating that the vehicle is not rolling over, when | K ₁ |≥c ₄ Indicating an impending vehicle rollover condition, at which time RSC intervenes into service.

Further, the wheel locking judgment in the fourth step is specifically as follows:

calculating the tire slip ratio:

wherein λ is _i The slip ratios of four wheels (i ═ fl, fr, rl, rr represent the left front wheel, right front wheel, left rear wheel, right rear wheel of the vehicle), u represents the vehicle speed, and ω represents the vehicle speed _i The four vehicle rotating speeds (i ═ fl, fr, rl and rr represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle), and R _i Is the wheel rolling radius.

When wheel slip ratio lambda _i Since the adhesion coefficient reaches a maximum value at 15% to 20%, the slip ratio is controlled to be in the range of 15% to 20% in order to obtain the optimum braking effect. Taking the optimum slip ratio as lambda _ref Therefore, the braking force of the vehicle wheel corresponding to the slip ratio is the maximum braking force when the vehicle is not locked, and when the wheel braking force is greater than the maximum braking force corresponding to the optimal slip ratio, the vehicle is considered to be locked, and the ABS intervenes in the work.

Further, the ESC control calculation in the fifth step specifically includes:

if the front inner wheel or the rear outer wheel is braked, the braking force is too large, so that the generated yaw moment has an opposite effect, and the stability control of the vehicle is not facilitated. When the braking force is around 1800N, the yaw moment generated by the four-wheel braking force is very efficient, so a threshold value is set here;

F _{s_max} ＝1800

in the formula, F _{s_max} For the single wheel braking force threshold value, when the single wheel braking force exceeds 1800N, the single-side braking is adopted, and each vehicle can be maximally utilizedA yaw moment generated by the wheels;

(1) computing additional yaw moment of yaw instability

When the ESC controls the yaw stability of the vehicle, the yaw speed and the mass center side slip angle are controlled, so that an additional yaw moment required for maintaining the yaw stability of the vehicle is calculated.

Wherein, the Deltam is the additional yaw moment of the ESC calculation to the unstable vehicle, c ₅ 、c ₆ 、c ₇ Is a constant value, beta is the actual centroid slip angle of the vehicle,

the desired centroid slip angle for the vehicle, γ the actual yaw rate of the vehicle,

a desired yaw rate for the vehicle;

when the system sets the steering wheel to turn left, delta is more than or equal to 0, and when the yaw angular velocity changes anticlockwise, gamma,

The number of the positive ions is positive,

(2) additional yaw moment for braking force distribution

Additional yaw moment output by the ESC calculation module is distributed to the braked wheels

In the formula, F _fl 、F _fr 、F _rl 、F _rr Respectively adding a left front wheel additional braking force, a right front wheel additional braking force, a left rear wheel additional braking force and a right rear wheel additional braking force, wherein delta m is an additional yaw moment output by an ESC (electronic stability control) calculation module, B is the wheelbase of the vehicle, and c ₈ 、c ₉ 、c ₁₀ 、c ₁₁ To distribute the coefficients, wherein c ₈ +c ₉ +c ₁₀ +c ₁₁ ＝1；

When the front wheel corner delta is greater than or equal to 0

a 1: if Δ ω<0, it is known that the vehicle is unstable in left turn and understeer occurs, and if the yaw moment is completely transferred to brake the left rear wheel, F _rl +F _rl0 <F _{s_max} And, preferably, single-wheel braking is adopted, and c is adopted at the moment ₈ ＝c ₉ ＝c ₁₁ ＝0、c ₁₀ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _rl +F _rl0 ≥F _{s_max} Preferably, the left rear wheel and the left front wheel are adopted to brake together, and at the moment c ₉ ＝c ₁₁ ＝0、c ₈ ＝c ₁₀ 0.5, output F _fl 、F _fr 、F _rl 、F _rr Wherein F is _rl0 Original braking force for the left rear wheel;

a 2: if Δ ω>0, it is known that the vehicle is unstable in left turn and oversteers, and if the yaw moment is fully turned to brake the right front wheel, F _fr +F _fr0 <F _{s_max} Then, preferably, single wheel braking is employed, at which time c ₈ ＝c ₁₀ ＝c ₁₁ ＝0、c ₉ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _fr +F _fr0 ≥F _{s_max} The front right wheel and the rear right wheel are preferably adopted to brake together, and c is the moment ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr ；

When the front wheel turning angle delta is less than 0

a 1: if Δ ω<0, the vehicle is known to be unstable in right turning and oversteer, and if the yaw moment is completely transferred to brake the left front wheel, F _fl +F _fl0 <F _{s_max} Then, preferably, single wheel braking is employed, at which time c ₉ ＝c ₁₀ ＝c ₁₁ ＝0、c ₈ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _fl +F _fl0 ≥F _{s_max} Then the left front wheel and the left rear wheel are preferentially adopted to brake together at the moment c ₉ ＝c ₁₁ ＝0、c ₈ ＝c ₁₀ 0.5, output F _fl 、F _fr 、F _rl 、F _rr ；

a 2: if Δ ω>0, it is known that the vehicle is unstable in right turning and understeer occurs, and if the yaw moment is completely transferred to the rear wheel on the right side of the brake, F _rr +F _rr0 <F _{s_max} Then, preferably, single wheel braking is employed, at which time c ₈ ＝c ₉ ＝c ₁₀ ＝0、c ₁₁ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _rr +F _rr0 ≥F _{s_max} Preferably, the right rear wheel and the right front wheel are adopted to brake together, and c is carried out ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr 。

Further, in the sixth step, when rollover instability occurs, the RSC instability calculation specifically includes:

the single-wheel braking mainly limits the lateral acceleration of the vehicle by reducing the yaw velocity of the vehicle, thereby realizing the anti-rollover control; the unilateral braking is the optimization of the single wheel braking, and can provide larger braking torque; the double-side braking aims at reducing the yaw angular speed and the vehicle speed of the vehicle, so that the anti-rollover control is realized.

Setting a critical vehicle speed v _s ＝c ₁₂ When the actual vehicle speed u is less than or equal to v _s When the vehicle is in use, the side turning instability is controlled by reducing the yaw angular velocity; when the actual vehicle speed u>v _s When the vehicle is in use, the side turning instability is controlled by reducing the yaw angular velocity and the vehicle speed;

(1) side-turning instability additional yaw moment calculation

Wherein, Δ m is an additional yaw moment required by the rollover instability, c ₁₃ 、c ₁₄ 、c ₁₅ Is a constant value coefficient, and the coefficient is,

in order to be a side-tilt angle deviation,

in order to achieve an actual vehicle roll angle,

a desired vehicle roll angle;

(2) additional yaw moment for braking force distribution

When the front wheel corner delta is more than or equal to 0;

if the vehicle speed u is less than or equal to v _s And when the vehicle is in a rollover state, the vehicle rollover instability condition is limited by reducing the yaw velocity of the vehicle, the single-wheel braking efficiency is highest, and the single-wheel braking is preferentially adopted. Braking force F required for adding yaw moment when performing single-wheel braking _fr <F _{s_max} At this time, the right front wheel is braked, at this time c ₈ ＝c ₁₀ ＝c ₁₁ ＝0、c ₉ 1, output F _fl 、F _fr 、F _rl 、F _rr ；

If F _fr ≥F _{s_max} When the front wheel and the rear wheel are braked on one side, the front wheel and the rear wheel are braked on the right side, and at the moment c ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr 。

If the speed u of the vehicle>v _s During the process, the vehicle rollover instability condition is limited by reducing the vehicle speed and the yaw velocity of the vehicle, the rollover stability is controlled by braking the right front wheel, the right rear wheel and the left rear wheel, and at the moment, c ₈ ＝0、

Output F _fl 、F _fr 、F _rl 、F _rr ；

When the front wheel turning angle delta is less than 0;

if the vehicle speed u is less than or equal to v _s And when the vehicle is in a rollover state, the vehicle rollover instability condition is limited by reducing the yaw velocity of the vehicle, the single-wheel braking efficiency is highest, and the single-wheel braking is preferentially adopted. Braking force F required for adding yaw moment when performing single-wheel braking _fl <F _{s_max} At this time, the left front wheel is braked, at this time c ₉ ＝c ₁₀ ＝c ₁₁ ＝0、c ₈ 1, output F _fl 、F _fr 、F _rl 、F _rr ；

If F _fl ≥F _{s_max} When the front wheel and the rear wheel are braked, the front wheel and the rear wheel are braked on one side, and at the moment c ₉ ＝c ₁₁ ＝0、c ₈ ＝c ₁₀ 0.5, output F _fl 、F _fr 、F _rl 、F _rr ；

If the speed u of the vehicle>v _s During the process, the vehicle rollover instability condition is limited by reducing the vehicle speed and the yaw velocity of the vehicle, the rollover stability is controlled by braking the left front wheel, the left rear wheel and the right rear wheel, and at the moment, c ₉ ＝0、

Output F _fl 、F _fr 、F _rl 、F _rr 。

Further, the coordination control of ESC and RSC in the seventh step is specifically:

the ESC and RSC coordinated control module is used for coordinating the problem that the ESC conflicts with the RSC to output additional four-wheel braking force and performing correct and rapid instability control on the vehicle after the vehicle is unstable;

the vehicle state judgment module transmits signals to the ESC and RSC coordination control module;

(1) when the vehicle is not subjected to rollover instability and yaw instability, the output value of the ESC and RSC coordination control module is 0;

(2) when the vehicle only generates the yaw instability, the ESC and RSC coordination control module outputs the additional yaw four-wheel braking force F output by the ESC control module _fl 、F _fr 、F _rl 、F _rr ；

(3) When the vehicle is in the rollover instability condition, setting a constant c ₁₂ To trigger an emergency threshold value of RSC, where | c ₄ |<|c ₁₂ |<1；

a. When | K ₁ |≥|c ₁₂ If yes, the vehicle is in a limit state of rollover instability, rollover prevention control is preferentially carried out, and the ESC and RSC coordinated control module outputs additional yaw four-wheel braking force F output by the RSC control module _fl 、F _fr 、F _rl 、F _rr ；

b. When | K ₁ |<|c ₁₂ When l:

b1, if no yaw instability occurs, the ESC and RSC coordination control module outputs the additional yaw four-wheel braking force F output by the RSC control module _fl 、F _fr 、F _rl 、F _rr ；

b2, if the vehicle has yaw instability and is in an oversteer state, the ESC is consistent with the control target of RSC, so the ESC and RSC coordination control module outputs the additional yaw four-wheel braking force F output by the RSC control module _fl 、F _fr 、F _rl 、F _rr ；

b3, if the vehicle has yaw instability and is in understeer state, the ESC and RSC coordination control module adds the additional braking force output by the ESC control module to the additional yaw four-wheel braking force output by the RSC control module and acts on the inner front wheels, and the total four-wheel additional braking force F is output _fl 、F _fr 、F _rl 、F _rr 。

Further, the ABS coordination control in the step eight is specifically:

four wheels are analyzed, a single wheel model is established firstly for dynamic analysis:

mu′＝-F _x

Iω′＝F _x gr ₀ -T _μ

where m is the mass of a single wheel, u is the vehicle speed, Fx is the ground braking force, I is the moment of inertia of the wheel, ω _i Is four vehicle rotating speeds (i ═ fl, fr, rl, rr represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle), r ₀ Is the rolling radius of the wheel, T _μ A wheel braking torque;

assuming that when the wheel is at the optimum slip ratio λ _ref While the ground braking force can provide the maximum braking force F _xmax ，F _xmax ＝F _z gμ

Wherein, F _xmax To maximum braking force, F _z The normal force of the ground against the wheel, mu adhesion coefficient.

The maximum braking force which can be generated by the current road surface on which the vehicle runs is estimated by estimating the adhesion coefficient in real time, so that the threshold value of the maximum braking force of the ABS on the current road surface is changed in real time to obtain the optimal braking effect.

When the additional four-wheel braking force output by the ESC and RSC is distributed to each wheel through the ESC and RSC coordinated control module outputting the expected four-wheel additional braking force, the maximum braking force of the wheel cannot exceed the braking force corresponding to the optimal slip rate at the moment, if the maximum braking force exceeds the optimal slip rate, the wheel is locked, and anti-lock ABS coordinated control needs to be carried out.

(1) If the braking signal output by the ESC and RSC coordinated control module is a single wheel i ₁ Braking, so that the total braking force on the wheel is F _{i1_all} ＝F _i1 +F _i10 ；

Wherein, F _{i1_all} Is a single wheel i ₁ Total braking force of _i1 Pair single wheel i for ESC and RSC coordinated control module output ₁ Additional braking force of F _i10 Is a single wheel i ₁ The initial braking force of (a);

a. if F _{i1_all} <F _xmax If yes, the anti-lock ABS coordinated control module outputs expected four-wheel additional braking force output by the ESC and RSC coordinated control module;

b. if F _{i1_all} ≥F _xmax The wheel additional braking force output is F _{i1_e} ＝F _xmax -F ₀ Corresponding side wheel i thereof ₂ Increasing the driving force F _{Te_i2} ＝F _{i1_all} +(F _i1 -(F _xmax -F ₀ ) Thus balancing the additional yaw moment formed by the expected four-wheel additional braking force output by the ESC and RSC coordinated control module originally, and at the moment, the anti-lock ABS coordinated control module outputs the changed four-wheel additional braking force and four-wheel additional driving force;

wherein, F _{i1_e} For a single wheel i after being controlled by an anti-lock ABS coordinated control module ₁ Additional braking force of F _{Te_i2} For vehicle wheel i ₂ Additional driving force added by the anti-lock ABS coordination control module;

(2) if the braking signal output by the ESC and RSC coordinated control module is unilateral braking, the braking force on each wheel on the side is F _{i1_all} ＝F _i1 +F _i10 ；

b. if F _{i1_all} ≥F _xmax Then each wheel on the side is attachedThe applied braking force output is F _{i1_e} ＝F _xmax -F ₀ Which increases the driving force F corresponding to the side wheel _{Te_i2} ＝F _{i1_all} +(F _i1 -(F _xmax -F ₀ ) So as to balance the additional yaw moment formed by the expected four-wheel additional braking force output by the ESC and RSC coordinated control module originally, and at the moment, the anti-lock ABS coordinated control module outputs the changed four-wheel additional braking force and four-wheel additional driving force;

(3) if the braking signal output by the ESC and RSC coordinated control module is double-side braking, the braking force of each wheel on the additional braking wheel is F _{i1_all} ＝F _i1 +F _i10 ；

a. If F _{i1_all} <F _xmax If the braking force is larger than the preset braking force, the anti-lock ABS coordinated control module outputs the expected four-wheel additional braking force output by the ESC and RSC coordinated control module;

b. if F _{i1_all} ≥F _xmax The wheel additional braking force output is F _{i1_e} ＝F _xmax -F ₀ Inner front wheel driving force F _{Te_L} ＝F _{i1_all} +(F _i1 -(F _xmax -F ₀ ) So as to balance the additional yaw moment formed by the expected four-wheel additional braking force output by the ESC and RSC coordinated control module originally, and at the moment, the anti-lock ABS coordinated control module outputs the changed four-wheel additional braking force and four-wheel additional driving force;

wherein, F _{Te_L} And the additional driving force is output for the inner front wheel through an anti-lock ABS coordinated control module.

The invention has the advantages that:

the invention discloses an active safety control system and method based on four-wheel independent driving/braking vehicle, the control system includes: the system comprises a vehicle real-time data module, a central computing module, an active control coordination module and an actuating mechanism module. The control method comprises the following steps: judging yaw stability, judging rollover stability, judging wheel locking, calculating optimal slip rate, calculating an ESC additional yaw moment, calculating an RSC additional yaw moment, carrying out ESC and RSC coordinated control and carrying out anti-lock ABS coordinated control; the invention fully considers the possible situations of yaw instability, side inclination, wheel locking and the simultaneous occurrence of a plurality of situations of the yaw instability, the side inclination and the wheel locking in the running process of the four-wheel independent driving/braking vehicle, and can effectively reduce the wheel locking on the basis of ensuring the running stability of the vehicle and improve the running safety of the vehicle by carrying out the combined control of ABS, ESC and RSC.

Drawings

FIG. 1 is a block diagram of an active safety control system for a four-wheel independent drive/brake based vehicle according to the present invention;

FIG. 2 is a flow chart of an ESC control module in the active safety control system of the four-wheel independent drive/brake vehicle according to the present invention;

FIG. 3 is a block flow diagram of the RSC control module of the active safety control system of the four-wheel independent drive/brake based vehicle of the present invention;

FIG. 4 is a block flow diagram of the ESC, RSC coordinated control module of the active safety control system of the four-wheel independent drive/brake based vehicle of the present invention;

FIG. 5 is a block diagram of the flow of the anti-lock ABS coordination control module in the active safety control system of the four-wheel independent drive/brake vehicle according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments of the present invention, belong to the protection scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention.

Referring to fig. 1, an active safety control system based on a four-wheel independent drive/brake vehicle includes a vehicle real-time data module, a central computing module, an active control coordination module, and an actuator module.

The vehicle real-time data module is used for acquiring four-wheel driving torque, four-wheel angular speed, yaw angular speed, mass center slip angle, vehicle longitudinal speed, vehicle lateral speed and vehicle fixed parameters. Specifically, the vehicle fixed parameter stores the vehicle structure fixed parameter information, including: the mass of the whole vehicle, the distance between the front axle and the centroid, the distance between the rear axle and the centroid, the equivalent lateral deflection rigidity of the front axle, the equivalent lateral deflection rigidity of the rear axle, the wheel track of the front axle, the wheel track of the rear axle, the rotational inertia of the wheel and the radius of the wheel.

The central computing module comprises a vehicle state judging module, an ESC control module and an RSC control module. The vehicle state judgment module comprises a yaw stability judgment unit, a rollover stability judgment unit, a road adhesion coefficient estimation unit and a wheel locking judgment unit, and judges the yaw stability, rollover stability and wheel locking state of the vehicle and estimates the road adhesion coefficient by receiving the parameter signal output by the vehicle real-time data module.

And the ESC control module is used for calculating an additional yaw braking moment required by the vehicle for recovering stability after the vehicle is subjected to yaw instability, and obtaining braking force of the additional yaw braking moment according to a corresponding rule and distributing the braking force to corresponding wheels.

The RSC control module is used for calculating an additional yaw braking moment required by vehicle rollover instability and then recovering stability, and obtaining braking force distribution to corresponding wheels according to corresponding rules by the additional yaw braking moment.

The active control coordination module comprises an ESC, an RSC coordination control module and an anti-lock ABS coordination control module; the ESC and RSC coordinated control module receives the four-wheel additional braking force output by the ESC control module and the RSC control module, and coordinates and controls the four-wheel additional braking force output by the ESC control module and the RSC control module to obtain the expected four-wheel braking force.

And the anti-lock ABS coordinated control module receives the expected four-wheel braking force output by the ESC and RSC coordinated control module, performs anti-lock regulation, and outputs the final four-wheel additional braking force and the final four-wheel additional driving force.

In addition, the invention also provides a control method of the active safety control system based on the four-wheel independent driving/braking vehicle, which comprises the following steps:

specifically, the road adhesion coefficient estimation calculation formula is as follows:

wherein m is the vehicle mass, g is the gravity acceleration value, a is the distance between the front axle and the mass center, b is the distance between the rear axle and the mass center, and h _c Is the height of the center of mass of the vehicle, B is the distance between the front and rear axles of the vehicle, v _x Is the longitudinal speed of the vehicle, v _y For the lateral speed of the vehicle, T _i For the four-wheel drive torque of the vehicle, I _i Is the four-wheel moment of inertia of the vehicle, omega _i The four-wheel angular velocity R of the vehicle _i The rolling radius N of the four wheels of the vehicle _i The vertical load of four wheels of the vehicle and the estimated road adhesion coefficient are mu, wherein i ═ fl, fr, rl and rr represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle.

specifically, the method comprises the following steps: the yaw rate and the mass center slip angle are two main parameters for controlling the stability of the vehicle, so that the threshold value of the parameters is set to judge whether the vehicle has instability during running, and the judgment formula is as follows:

|Δe _γ |＝|γ-γ ₀ |≤|c ₁ γ|

|β+c ₂ β′|≤c ₃

in the formula, c ₁ 、c ₂ 、c ₃ Is constant, gamma is the actual yaw rate of the vehicle, gamma ₀ Desired yaw rate, Δ e, for the vehicle _γ The deviation of the actual yaw angular velocity of the vehicle and the expected yaw angular velocity is obtained, beta is the actual barycenter slip angle of the vehicle, and beta' is the derivative of the actual barycenter slip angle of the vehicle;

Step three: and (4) judging rollover instability of the vehicle, and if the vehicle is about to rollover, the RS C intervenes to work.

The side-turning instability judgment specifically comprises the following steps:

judging whether the vehicle has the rollover condition by adopting the lateral load transfer rate, wherein the lateral load transfer rate is calculated according to the following formula:

wherein, K ₁ For the transverse load transfer rate of the vehicle, N _fl Being a wheelVertical load of left front wheel, N _fr For the right front wheel vertical load of the wheel, N _rl For vertical loading of the left and rear wheels of a vehicle, N _rr The vertical load is the right rear wheel of the wheel;

it can be known that | K is not more than 0 ₁ I is less than or equal to 1, when I K ₁ The larger the numerical value of |, the more easily the vehicle is subjected to rollover instability, K ₁ When 1, the vehicle rolls over to the left, K ₁ When the vehicle turns right, the vehicle is represented as-1; from the situation of preventing rollover instability as soon as possible and ensuring complete vehicle running, taking K ₁ |＝c ₄ To trigger RSC threshold, when | K ₁ |<c ₄ Indicating that the vehicle is not rolling over, when | K ₁ |≥c ₄ Indicating an impending vehicle rollover condition, at which time RSC intervenes into service.

wheel locking judgment specifically comprises the following steps:

calculating the tire slip ratio:

wherein λ is _i The slip ratios of four wheels (i ═ fl, fr, rl, rr represent the left front wheel, right front wheel, left rear wheel, right rear wheel of the vehicle), u represents the vehicle speed, and ω represents the vehicle speed _i The four vehicle rotating speeds (i ═ fl, fr, rl and rr represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle), and R represents the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle _i Is the wheel rolling radius.

When wheel slip ratio lambda _i Since the adhesion coefficient reaches a maximum value at 15% to 20%, the slip ratio is controlled to be in the range of 15% to 20% in order to obtain the optimum braking effect. Taking the optimum slip ratio as lambda _ref Therefore, the braking force of the vehicle wheel corresponding to the slip ratio is the maximum braking force when the vehicle is not locked, and when the braking force of the wheel is greater than the maximum braking force corresponding to the optimal slip ratio, the vehicle is considered to be locked, and the ABS intervenes in the work.

Step five: when the yaw instability occurs, performing ESC control calculation, including yaw instability additional yaw moment calculation and additional yaw moment for braking force distribution;

the ESC control calculation specifically includes:

referring to fig. 2, if the front inner wheel or the rear outer wheel is braked, when the braking force is too large, the opposite result occurs to the yaw moment generated by the front inner wheel or the rear outer wheel, which is disadvantageous to the stability control of the vehicle. When the braking force is around 1800N, the yaw moment generated by the four-wheel braking force is very efficient, so a threshold value is set here;

F _{s_max} ＝1800

in the formula, F _{s_max} The single-wheel braking force threshold value is adopted, when the braking torque of the single-wheel braking exceeds 1800N, the single-side braking is adopted, and the yaw moment generated by each wheel can be utilized to the maximum extent;

(1) computing additional yaw moment of yaw instability

a desired yaw rate for the vehicle;

The number of the positive ions is positive,

(2) additional yaw moment for braking force distribution

In the formula, F _fl 、F _fr 、F _rl 、F _rr Respectively adding braking force to the left front wheel, the right front wheel, the left rear wheel and the right rear wheel, wherein delta m is the additional yaw moment output by the ESC calculation module, B is the wheelbase of the vehicle, c ₈ 、c ₉ 、c ₁₀ 、c ₁₁ To distribute the coefficients, wherein c ₈ +c ₉ +c ₁₀ +c ₁₁ ＝1；

When the front wheel corner delta is greater than or equal to 0

a 1: if Δ ω<0, it is known that the vehicle is unstable in left turn and understeer occurs, and if the yaw moment is completely transferred to brake the left rear wheel, F _rl +F _rl0 <F _{s_max} Then, then you areFirst of all, single-wheel braking is used, at this time c ₈ ＝c ₉ ＝c ₁₁ ＝0、c ₁₀ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _rl +F _rl0 ≥F _{s_max} Preferably, the left rear wheel and the left front wheel are adopted to brake together, and at the moment c ₉ ＝c ₁₁ ＝0、c ₈ ＝c ₁₀ 0.5, output F _fl 、F _fr 、F _rl 、F _rr Wherein F is _rl0 Original braking force for the left rear wheel;

a 2: if Δ ω>0, it is known that the vehicle is unstable in left turn and oversteers, and if the yaw moment is fully turned to brake the right front wheel, F _fr +F _fr0 <F _{s_max} Then the single wheel brake is preferably adopted, at this moment c ₈ ＝c ₁₀ ＝c ₁₁ ＝0、c ₉ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _fr +F _fr0 ≥F _{s_max} The front right wheel and the rear right wheel are preferably adopted to brake together, and c is the moment ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr ；

When the front wheel turning angle delta is less than 0

a 2: if Δ ω>0, it is known that the vehicle is unstable in right turning and understeer occurs, and if the yaw moment is completely transferred to the rear wheel on the right side of the brake, F _rr +F _rr0 <F _{s_max} Then, preferably, single wheel braking is employed, at which time c ₈ ＝c ₉ ＝c ₁₀ ＝0、c ₁₁ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _rr +F _rr0 ≥F _{s_max} Preferably, the right rear wheel and the right front wheel are used for braking together, and c is ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr 。

Step six: when rollover instability occurs, RSC instability calculation is carried out, and the RSC instability calculation comprises rollover instability additional yaw moment calculation and additional yaw moment distribution;

when rollover instability occurs, the RSC instability calculation specifically comprises the following steps:

referring to fig. 3, the single wheel braking mainly limits the lateral acceleration of the vehicle by reducing the yaw rate of the vehicle, thereby implementing the anti-rollover control; the unilateral braking is the optimization of the single wheel braking, and can provide larger braking torque; the double-side braking aims at reducing the yaw angular speed and the vehicle speed of the vehicle, so that the anti-rollover control is realized.

(1) side-turning instability additional yaw moment calculation

Where Δ m is the additional yaw moment required for the roll-over instability, c ₁₃ 、c ₁₄ 、c ₁₅ Is a constant value coefficient, and the coefficient is,

in order to correct the roll angle deviation,

in order to achieve an actual vehicle roll angle,

a desired vehicle roll angle;

(2) additional yaw moment for braking force distribution

When the front wheel corner delta is more than or equal to 0;

If F _fr ≥F _{s_max} When the front wheel and the rear wheel are braked on one side, the front wheel and the rear wheel are braked on the right side, and c ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr 。

Output F _fl 、F _fr 、F _rl 、F _rr ；

When the front wheel turning angle delta is less than 0;

if the vehicle speed u is less than or equal to v _s When the vehicle is turned over, the rolling angle speed of the vehicle is reduced to limit the side turning instability of the vehicle, and the single wheel braking efficiency is the highestHigh, single wheel braking is preferred. Braking force F required for adding yaw moment when performing single-wheel braking _fl <F _{s_max} At this time, the left front wheel is braked, at this time c ₉ ＝c ₁₀ ＝c ₁₁ ＝0、c ₈ 1, output F _fl 、F _fr 、F _rl 、F _rr ；

Output F _fl 、F _fr 、F _rl 、F _rr 。

ESC and RSC coordination control specifically comprises the following steps:

referring to fig. 4, the ESC and RSC coordination control module is used for coordinating the problem that the ESC and RSC output additional four-wheel braking force conflict with each other, and is used for performing correct and rapid instability control on the vehicle after the vehicle has been unstable;

(3) When the vehicle is in the condition of side turning instability, the vehicle is provided withConstant c ₁₂ To trigger an emergency threshold for RSC, where | c ₄ |<|c ₁₂ |<1；

b. When | K ₁ |<|c ₁₂ When l:

b3, if the vehicle has yaw instability and is in understeer condition, the ESC and RSC coordination control module adds the additional braking force output by the ESC control module to the additional yaw four-wheel braking force output by the inner front wheel and the RSC control module to output the total four-wheel additional braking force F _fl 、F _fr 、F _rl 、F _rr 。

the anti-lock ABS coordination control specifically comprises the following steps:

mu′＝-F _x

Iω′＝F _x gr ₀ -T _μ

assuming that when the wheel is at the optimum slip ratio λ _ref At the time, the ground braking force can provide the maximum braking force F _xmax ，F _xmax ＝F _z gμ

(1) If the braking signal output by the ESC and RSC coordinated control module is a single wheel i ₁ Braking, the total braking force on the wheel is F _{i1_all} ＝F _i1 +F _i10 ；

a. if F _{i1_all} <F _xmax The anti-lock ABS coordinated control module outputs ESC and RThe SC coordinates the expected four-wheel additional braking force output by the control module;

b. if F _{i1_all} ≥F _xmax Then the wheel additional braking force output is F _{i1_e} ＝F _xmax -F ₀ Corresponding side wheel i ₂ Increasing the driving force F _{Te_i2} ＝F _{i1_all} +(F _i1 -(F _xmax -F ₀ ) So as to balance the additional yaw moment formed by the expected four-wheel additional braking force output by the ESC and RSC coordinated control module originally, and at the moment, the anti-lock ABS coordinated control module outputs the changed four-wheel additional braking force and four-wheel additional driving force;

wherein, F _{i1_e} For single wheel i after being controlled by anti-lock ABS coordinated control module ₁ Additional braking force of F _{Te_i2} For vehicle wheel i ₂ Additional driving force added by the anti-lock ABS coordination control module;

b. if F _{i1_all} ≥F _xmax The additional braking force output per wheel on the side is F _{i1_e} ＝F _xmax -F ₀ Which increases the driving force F corresponding to the side wheel _{Te_i2} ＝F _{i1_all} +(F _i1 -(F _xmax -F ₀ ) So as to balance the additional yaw moment formed by the expected four-wheel additional braking force output by the ESC and RSC coordinated control module originally, and at the moment, the anti-lock ABS coordinated control module outputs the changed four-wheel additional braking force and four-wheel additional driving force;

a. If F _{i1_all} <F _xmax Then ABS coordination is lockedThe control module outputs the expected four-wheel additional braking force output by the ESC and RSC coordination control module;

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures or equivalent flow transformations made by using the contents of the specification and the drawings, or applied directly or indirectly to other related systems, are included in the scope of the present invention.

Claims

1. An active safety control system based on four-wheel independent driving/braking vehicle is characterized in that:

the vehicle state judgment module comprises a yaw stability judgment unit, a rollover stability judgment unit, a road adhesion coefficient estimation unit and a wheel locking judgment unit, and judges the yaw stability, rollover stability and wheel locking state of the vehicle and estimates the road adhesion coefficient by receiving the parameter signal output by the vehicle real-time data module;

2. The active safety control system of a four-wheel independent drive/brake vehicle according to claim 1, wherein:

the vehicle fixed parameter is stored with the vehicle structure fixed parameter information, and comprises: the mass of the whole vehicle, the distance between the front axle and the centroid, the distance between the rear axle and the centroid, the equivalent lateral deflection rigidity of the front axle, the equivalent lateral deflection rigidity of the rear axle, the wheel track of the front axle, the wheel track of the rear axle, the rotational inertia of the wheel and the radius of the wheel.

3. The method of the active safety control system based on the four-wheel independent drive/brake vehicle as claimed in claim 1 or claim 2, characterized by comprising the following steps:

step four: wheel locking judgment is carried out, and if the wheel is judged to be locked, ABS intervenes in work;

4. The method of claim 3, wherein:

in the first step, the road adhesion coefficient is estimated according to the parameters provided by the vehicle real-time data module, and the calculation formula is as follows:

wherein m is the vehicle mass, g is the gravity acceleration value, a is the distance between the front axle and the mass center, b is the distance between the rear axle and the mass center, and h _c Is the height of the center of mass of the vehicle, B is the distance between the front and rear axles of the vehicle, v _x Is the longitudinal speed of the vehicle, v _y For the lateral speed of the vehicle, T _i Is the four-wheel drive torque of the vehicle, I _i Is the four-wheel moment of inertia of the vehicle, omega _i The four-wheel angular velocity R of the vehicle _i The rolling radius N of the four wheels of the vehicle _i The vertical load of four wheels of the vehicle and the estimated road adhesion coefficient are mu, wherein i ═ fl, fr, rl and rr represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle.

5. The method of claim 4, wherein:

the yaw instability judgment in the second step is specifically as follows:

|Δe _γ |＝|γ-γ ₀ |≤|c ₁ γ|

|β+c ₂ β′|≤c ₃

6. The method of claim 5, wherein:

in the third step, the judgment of the rollover instability is specifically as follows:

wherein, K ₁ For the transverse load transfer rate of the vehicle, N _fl For vertical loading of the left front wheel of the wheel, N _fr For the right front wheel vertical load of the wheel, N _rl For vertical loading of the left and rear wheels of a vehicle, N _rr The vertical load is the right rear wheel of the wheel;

then, 0 is less than or equal to | K ₁ | is less than or equal to 1, when | K ₁ The larger the numerical value is, the more easily the vehicle is subjected to rollover instability, and K ₁ When 1, the vehicle rolls over to the left, K ₁ When the vehicle turns to the right side, the vehicle is represented as-1(ii) a From the situation of preventing rollover instability as soon as possible and ensuring complete vehicle running, taking K ₁ |＝c ₄ To trigger RSC threshold, when | K ₁ |<c ₄ Indicating that the vehicle is not rolling over, when | K ₁ |≥c ₄ Indicating an impending vehicle rollover condition, at which time RSC intervenes into service.

7. The method of claim 6, wherein:

and the wheel locking judgment in the fourth step specifically comprises the following steps:

calculating the tire slip ratio:

wherein λ is _i The slip ratios of four wheels (i ═ fl, fr, rl, rr represent the left front wheel, right front wheel, left rear wheel, right rear wheel of the vehicle), u represents the vehicle speed, and ω represents the vehicle speed _i The four vehicle rotating speeds (i ═ fl, fr, rl and rr represent the left front wheel, the right front wheel, the left rear wheel and the right rear wheel of the vehicle), and R _i Is the wheel rolling radius;

when wheel slip ratio lambda _i The adhesion coefficient reaches the maximum value when the adhesion coefficient is 15% -20%, so that the slip ratio is controlled to be in the range of 15% -20% in order to obtain the optimal braking effect; and when the braking force of the wheel is greater than the maximum braking force corresponding to the optimal slip rate, the locking is considered to occur, and the ABS intervenes to work.

8. The method of claim 7, wherein:

the ESC control calculation in the fifth step specifically includes:

if the front inner wheel or the rear outer wheel is braked, the opposite result of the yaw moment generated by the front inner wheel or the rear outer wheel can be caused when the braking force is too large, and the stability control of the vehicle is not facilitated; when the braking force is around 1800N, the yaw moment generated by the four-wheel braking force is very efficient, so a threshold value is set here;

F _{s_max} ＝1800

(1) yaw instability additional yaw moment calculation

When the ESC controls the yaw stability of the vehicle, the yaw velocity and the centroid side slip angle are controlled, so that an additional yaw moment required for maintaining the yaw stability of the vehicle is calculated;

a desired yaw rate for the vehicle;

The number of the positive ions is positive,

(2) braking force distribution by adding yaw moment

The additional yaw moment output by the ESC calculation module is distributed to the braking wheels

In the formula, F _fl 、F _fr 、F _rl 、F _rr Respectively adding a left front wheel additional braking force, a right front wheel additional braking force, a left rear wheel additional braking force and a right rear wheel additional braking force, wherein delta m is an additional yaw moment output by an ESC (electronic stability control) calculation module, B is the wheelbase of the vehicle, and c ₈ 、c ₉ 、c ₁₀ 、c ₁₁ To assign a coefficient, wherein c ₈ +c ₉ +c ₁₀ +c ₁₁ ＝1；

When the front wheel corner delta is greater than or equal to 0

a 1: if Δ ω<0, it is known that the vehicle is unstable in left turn and understeer occurs, and if the yaw moment is completely transferred to brake the left rear wheel, F _rl +F _rl0 <F _{s_max} And, preferably, single-wheel braking is adopted, and c is adopted at the moment ₈ ＝c ₉ ＝c ₁₁ ＝0、c ₁₀ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _rl +F _rl0 ≥F _{s_max} Preferably, the left rear wheel and the left front wheel are adopted to brake together, and at the moment c ₉ ＝c ₁₁ ＝0、c ₈ ＝c ₁₀ 0.5, output F _fl 、F _fr 、F _rl 、F _rr Wherein，F _rl0 Original braking force for the left rear wheel;

a 2: if Δ ω>0, it is known that the vehicle is unstable in left turning and oversteers, and if the yaw moment is completely transferred to the braking of the right front wheel, F _fr +F _fr0 <F _{s_max} Then, preferably, single wheel braking is employed, at which time c ₈ ＝c ₁₀ ＝c ₁₁ ＝0、c ₉ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _fr +F _fr0 ≥F _{s_max} Preferably, the right front wheel and the right rear wheel are used for braking together, and c is ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr ；

When the front wheel turning angle delta is less than 0

a 2: if Δ ω>0, it is known that the vehicle is unstable in the right turn and understeer occurs, and if the yaw moment is completely transferred to the rear wheel of the right brake, F _rr +F _rr0 <F _{s_max} Then, preferably, single wheel braking is employed, at which time c ₈ ＝c ₉ ＝c ₁₀ ＝0、c ₁₁ 1, output F _fl 、F _fr 、F _rl 、F _rr (ii) a If F _rr +F _rr0 ≥F _{s_max} Preferably, the right rear wheel and the right front wheel are used for braking together, and c is ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr 。

9. The method of claim 8, wherein:

in the sixth step, when rollover instability occurs, the RSC instability calculation specifically includes:

setting a critical vehicle speed v _s ＝c ₁₂ When the actual speed u is less than or equal to v _s When the vehicle is in use, the side turning instability is controlled by reducing the yaw angular velocity; when the actual vehicle speed u>v _s When the vehicle is in use, the side turning instability is controlled by reducing the yaw angular velocity and the vehicle speed;

(1) additional yaw moment calculation for rollover instability

in order to be a side-tilt angle deviation,

in order to achieve an actual vehicle roll angle,

a desired vehicle roll angle;

(2) braking force distribution by adding yaw moment

When the front wheel corner delta is more than or equal to 0;

if the vehicle speed u is less than or equal to v _s When the vehicle is in a rollover state, the yaw velocity of the vehicle is reduced to limit the rollover instability condition of the vehicle, the single-wheel braking efficiency is highest, and single-wheel braking is preferentially adopted; if it is advancedBraking force F required for adding yaw moment during single-wheel braking _fr <F _{s_max} At this time, the right front wheel is braked, at this time c ₈ ＝c ₁₀ ＝c ₁₁ ＝0、c ₉ 1, output F _fl 、F _fr 、F _rl 、F _rr ；

If F _fr ≥F _{s_max} When the front wheel and the rear wheel are braked on one side, the front wheel and the rear wheel are braked on the right side, and at the moment c ₈ ＝c ₁₀ ＝0、c ₉ ＝c ₁₁ 0.5, output F _fl 、F _fr 、F _rl 、F _rr ；

Output F _fl 、F _fr 、F _rl 、F _rr ；

When the front wheel turning angle delta is less than 0;

if the vehicle speed u is less than or equal to v _s When the vehicle is in a rollover state, the yaw velocity of the vehicle is reduced to limit the rollover instability condition of the vehicle, the single-wheel braking efficiency is highest, and single-wheel braking is preferentially adopted; braking force F required for adding yaw moment when performing single-wheel braking _fl <F _{s_max} At this time, the left front wheel is braked, at this time c ₉ ＝c ₁₀ ＝c ₁₁ ＝0、c ₈ 1, output F _fl 、F _fr 、F _rl 、F _rr ；

If the speed u of the vehicle>v _s When the vehicle is turned over, the vehicle speed and the yaw rate are reduced to limit the side turning instability of the vehicle togetherControlling the rollover stability by braking the left front wheel, the left rear wheel and the right rear wheel, at the moment, c ₉ ＝0、

Output F _fl 、F _fr 、F _rl 、F _rr 。

10. The method of claim 9, wherein:

the ESC and RSC coordination control in the seventh step specifically comprises the following steps:

b. When | K ₁ |<|c ₁₂ When |:

b2, if the vehicle has yaw instability and the vehicle is in an oversteer state, the ESC and RSC control targets are consistent, so the ESC and RSC coordination control module outputs the additional yaw four wheels output by the RSC control moduleBraking force F _fl 、F _fr 、F _rl 、F _rr ；

b3, if the vehicle has yaw instability and is in understeer state, the ESC and RSC coordination control module adds the additional braking force output by the ESC control module to the additional yaw four-wheel braking force output by the RSC control module and acts on the inner front wheels, and the total four-wheel additional braking force F is output _fl 、F _fr 、F _rl 、F _rr ；

The anti-lock ABS coordination control in the step eight specifically comprises the following steps:

four wheels are analyzed, a single-wheel model is established firstly for dynamic analysis:

mu′＝-F _x

Iω′＝F _x gr ₀ -T _μ

assuming that when the wheel is at the optimum slip ratio λ _ref At the time, the ground braking force can provide the maximum braking force F _xmax ，

F _xmax ＝F _z gμ

Wherein, F _xmax To maximum braking force, F _z The normal acting force of the ground to the wheel, mu adhesion coefficient;

estimating the maximum braking force which can be generated by the current road surface on which the vehicle runs by estimating the adhesion coefficient in real time, so as to change the threshold value of the maximum braking force of the ABS on the current road surface in real time;

when the additional four-wheel braking force output by the ESC and RSC is distributed to each wheel through the ESC and RSC coordinated control module outputting the expected four-wheel additional braking force, the maximum braking force of the wheel cannot exceed the braking force corresponding to the optimal slip rate at the moment, if the maximum braking force exceeds the optimal slip rate, the wheel is locked, and anti-lock ABS coordinated control is required;

(1) if the braking signal output by the ESC and RSC coordinated control module is to a single wheel i ₁ Braking, the total braking force on the wheel is F _{i1_all} ＝F _i1 +F _i10 ；

Wherein, F _{i1_all} Is a single wheel i ₁ Total braking force of F _i1 Pair single wheel i for ESC and RSC coordinated control module output ₁ Additional braking force of F _i10 Is a single wheel i ₁ The initial braking force of (a);

b. if F _{i1_all} ≥F _xmax The wheel additional braking force output is F _{i1_e} ＝F _xmax -F ₀ Corresponding side wheel i ₂ Increasing the driving force F _{Te_i2} ＝F _{i1_all} +(F _i1 -(F _xmax -F ₀ ) So as to balance the additional yaw moment formed by the expected four-wheel additional braking force output by the ESC and RSC coordinated control module originally, and at the moment, the anti-lock ABS coordinated control module outputs the changed four-wheel additional braking force and four-wheel additional driving force;

b. if F _{i1_all} ≥F _xmax Then the side additional braking force output per wheel is F _{i1_e} ＝F _xmax -F ₀ Which increases the driving force F corresponding to the side wheel _{Te_i2} ＝F _{i1_all} +(F _i1 -(F _xmax -F ₀ ) Thus balancing the additional yaw moment formed by the expected four-wheel additional braking force output by the ESC and RSC coordinated control module originally, and at the moment, the anti-lock ABS coordinated control module outputs the changed four-wheel additional braking force and four-wheel additional driving force;

(3) if the braking signal output by the ESC and RSC coordinated control module is bilateral braking, the braking force of each wheel on the additional braking wheel is F _{i1_all} ＝F _i1 +F _i10 ；

wherein, F _{Te_L} And the additional driving force is output by the inner front wheel through the anti-lock ABS coordination control module.