CN101786452B - Driving anti-slip control system of shaft-driven electric vehicle and control method thereof - Google Patents

Abstract

The invention relates to a driving anti-slip control system of a shaft-driven electric vehicle, belonging to the technical field of a vehicle control system. The invention is characterized in that the speed interval of a vehicle is judged according to the instant vehicle speed. At the high-speed stage, a motor moment is adopted to carry out independent control, so as to ensure the driving stability of the vehicle; at the medium/low-speed stage, the road surface condition of the vehicle is judged according to the slippage rate of two driving wheels, so as to adopt different control methods to the vehicle. Aiming at the bisectional road surface, the motor moment and a braking moment are adopted to carry out coordination control, namely the motor moment is adopted to carry out high-selection control and the braking moment is applied on the driving wheel at the low-adhered side for intervention, thereby ensuring the accelerating capacity of the vehicle; aiming at the single road surface, the motor moment is adopted to carry out independent control, namely the motor moment is adopted to carry out low-selection control, thereby ensuring the accelerating smoothness of the vehicle.

Description

Driving anti-skid control system of shaft-driven electric vehicle

Technical Field

The invention relates to a vehicle control system, in particular to a drive anti-skid control system of an axle-driven electric vehicle.

Background

An anti-Slip Control System (ASR) for an automobile is a vehicle Control System for preventing the Slip or idle rotation of a driving wheel of the automobile during starting or accelerating, particularly preventing the Slip of the driving wheel of the automobile on an asymmetric road surface, thereby improving the stability and controllability of the automobile and improving the Traction capability of the automobile by adjusting the Slip rate of the driving wheel.

The slip ratio of the wheel is related to the ground adhesion coefficient as shown in fig. 1. Along with the increase of the wheel slip rate, the longitudinal ground adhesion coefficient is increased sharply and gradually reduced after reaching a peak value, and the lateral ground adhesion coefficient is reduced along with the increase of the slip rate. Therefore, when the slip ratio of the wheel is excessively large, the lateral adhesion capability of the wheel is drastically reduced, the running stability of the vehicle is degraded, and the traction performance of the vehicle is degraded due to the degradation of the longitudinal adhesion capability of the wheel. The drive anti-skid control system can control the slip rate of the wheel in a shaded area shown in figure 1, and ensures that the wheel has high longitudinal and lateral adhesion coefficients.

The conventional anti-skid control method for the automobile mainly comprises the following steps. The output torque of the engine is adjusted by adjusting the ignition parameters, fuel supply and the opening degree of a throttle valve of the engine, braking torque is applied to driving wheels, and a controllable antiskid differential is adopted. For electrically driven vehicles, the method of engine output torque regulation is no longer applicable and requires coordinated control of motor torque and wheel braking torque.

The invention patent 'anti-skid control system and method of electric vehicle' applied by bianddy limited (application No. 200610021215.7, publication No. CN101088818A, published as 2007.12.19) discloses an anti-skid control system of electric vehicle, which adjusts the output torque of the motor in real time according to the magnitude of the wheel slip rate when an ABS/ASR integrated control unit receives an acceleration signal, but the invention patent does not relate to how to coordinate and control the output torque of the motor and the wheel braking torque. The invention discloses a driving anti-skid control method of a four-wheel drive electric vehicle, which is applied by Shanghai fuel cell vehicle power system Limited company and is named as a driving anti-skid system and a driving anti-skid method of the four-wheel drive electric vehicle (application number is 200610147758.3, publication number is CN101024377A, publication number is 2007.08.29), wherein the adhesion state of a running road surface of the vehicle is estimated according to the driving torque of a motor, the rotating speed of the wheel and the estimated vertical load of the wheel, and the driving anti-skid control is realized by adjusting the driving torque of the motor on the four wheels, but the invention does not relate to the braking torque control of the wheel. The united states patent US6321154B1 proposes a device and a method for controlling the slipping of a driving wheel of an automobile, which mainly aim at controlling the driving torque of an engine according to an engine speed reference value in the vehicle starting stage, only perform braking torque intervention on the wheel which starts slipping first, and also lack the content of coordinated control of the driving torque and the braking torque of a motor.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a driving antiskid control system for an axle-driven electric vehicle with a good antiskid control effect.

The present invention is characterized in that the axle-driven electric vehicle drive antiskid control system includes: a vehicle control unit, four wheel speed sensors: a left front wheel speed sensor, a right front wheel speed sensor, a left rear wheel speed sensor and a right rear wheel speed sensor, a drive anti-skid controller, a motor controller and a vehicle dynamics control VDC/vehicle stability control VSC/electronic stabilizer ESP brake pressure regulator, wherein:

drive anti-slip controller is equipped with five inputs: the motor torque target value input end is followed the vehicle control unit inputs motor torque target value, four fast signal input ends of wheel, follow respectively four fast sensor inputs the fast signal of wheel that corresponds, are equipped with two outputs again: a driving wheel cylinder brake pressure regulating signal output end for outputting control signals to the vehicle dynamics control VDC/vehicle stability control VSC/electronic stability device ESP brake pressure regulator, and a motor torque control signal output end for outputting motor torque command values to the motor controller, wherein the driving anti-skid controller of the shaft-driven electric vehicle comprises the following control steps:

step (1), driving the antiskid controller to initialize, and setting:

a slip ratio threshold value S1 with a value range of [0.15, 0.2], a vehicle speed threshold value V1 with a value range of [30km/h, 40km/h ], a continuous decompression time t0 for increasing the brake pressure and then reducing the brake pressure for the left driving wheel or the right driving wheel with a value range of [1.5S, 2S ], a brake torque intervention continuous working time upper limit value t1 with a value range of [10S, 11S ],

step (2), calculating the instantaneous vehicle speed v, the instantaneous slip rate s _ l of the left driving wheel and the instantaneous slip rate s _ r of the right driving wheel according to the following formulas respectively:

$v=\frac{1}{2}({\mathrm{\ω}}_{\mathrm{el}}\·r+{\mathrm{\ω}}_{\mathrm{er}}\·r)$

$s\_l=\frac{{\mathrm{\ω}}_{\mathrm{dl}}\·r-v}{{\mathrm{\ω}}_{\mathrm{dl}}\·r},$ $s\_r=\frac{{\mathrm{\ω}}_{\mathrm{dr}}\·r-v}{{\mathrm{\ω}}_{\mathrm{dr}}\·r},$ wherein, ω is

e_llAnd ω_erRespectively a left driven wheel speed and a right driven wheel speed,

ω_dland ω_drRespectively a left side driving wheel speed and a right side driving wheel speed,

r is the radius of the wheel,

and (3) judging the slip conditions of the two driving wheels according to the instantaneous vehicle speed v, the slip rate s _ l of the left driving wheel and the slip rate s _ r of the right driving wheel, and determining which control method is adopted:

if: max (S _ l, S _ r) ≧ S1, and V < V1, but one of the two drive wheel slip rates is greater than the slip rate threshold value S1 and the other is less than the slip rate threshold value S1,

entering a motor torque and braking torque coordination control stage, and executing the step (4), wherein:

max (s l, s r) is the maximum of the two drive wheel slip rates,

if: max (S _ l, S _ r) ≥ S1, and V ≥ V1,

or V is less than V1, S _ l is more than or equal to S1 and S _ r is more than or equal to S1,

then entering a motor torque single control stage, executing the step (5),

and (4) entering the following four parallel programs:

(4.1) selection of controlled quantity s in Torque control of Motor^*：

Let s^*Min (s _ l, s _ r), judge:

if the left driving wheel braking torque intervention Flag _ l is equal to 1, it is considered that the left driving wheel has braking torque intervention,

then order s^*＝s_r，

If the right driving wheel braking torque intervention Flag _ r is equal to 1, it is considered that there is braking torque intervention at the right driving wheel,

then order s^*＝s_l，

If the left and right side driving wheel braking torque intervention flags Flag _ l and Flag _ r are not equal to 1,

then order s^*＝min(s_l,s_r)，

(4.2) controlling the torque of the motor,

and enabling the motor torque command value Tm _ cmd to be equal to the command value at the previous moment, and judging:

if: s^*And is equal to or more than S1, the command value Tm _ cmd of the motor torque is reduced,

if: s^*< S1, the command value Tm _ cmd for the motor torque is increased,

the motor torque is repeatedly adjusted until the controlled quantity s of the motor torque control^*When the slip rate is smaller than the threshold value S1 and the motor torque command value Tm _ cmd is larger than 90% of the motor torque target value Tm _ tgt, the motor torque control is considered to be finished, and the motor torque command value is enabled to beTm _ cmd is equal to the motor torque command value Tm _ cmd at the previous time,

(4.3) the braking torque of the left driving wheel intervenes,

let the left driving wheel braking torque intervention Flag _ l be 0,

if: s _ l is more than or equal to S1, S _ r is less than S1, the intervention Flag _ r of the right driving wheel braking torque is equal to 0,

the brake pressure is increased to the left driving wheel and the left driving wheel brake torque intervention Flag _ l is set to 1 until S _ l < S1, the brake pressure of the left driving wheel is decreased,

if: it is again detected that S _ l ≧ S1,

the brake pressure is increased to the left driving wheel, and the left driving wheel cylinder pressure is repeatedly adjusted so far until S _ l < S1 and the pressure is continuously reduced for more than time t0, and the left driving wheel brake torque intervention Flag _ l is made 0, assuming that the brake torque intervention is finished.

(4.4) the braking torque of the right driving wheel intervenes,

let the right-side drive wheel braking torque intervention Flag _ r be 0,

if: s _ r is more than or equal to S1, S _ l is less than S1, the left driving wheel braking torque intervention Flag is equal to 0,

the brake pressure is increased to the right driving wheel and the right driving wheel brake torque intervention Flag _ r is set to 1 until S _ r < S1, the brake pressure of the right driving wheel is decreased,

if: it is again detected that S _ r ≧ S1,

the brake pressure is increased to the right drive wheel, and the right drive wheel cylinder pressure is repeatedly adjusted in this manner until S _ r < S1 and pressure reduction continues for the time t0, the brake torque intervention is considered to be ended, the right drive wheel brake torque intervention Flag _ r is made 0,

when the slip rates S _ l and S _ r of the two driving wheels are both smaller than a slip rate threshold value S1, the torque control is in a non-torque-reduction stage, the motor torque command value Tm _ cmd is larger than 90% of a motor torque target value Tm _ tgt, the left driving wheel braking torque intervention Flag _ l is equal to 0 and the right driving wheel braking torque intervention Flag _ r is equal to 0, the motor torque and braking torque coordination control stage is considered to be finished, and the motor torque command value Tm _ cmd is equal to the motor torque target value Tm _ tgt,

in the process of executing step (4), when the instantaneous vehicle speed V is greater than the vehicle speed threshold value V1, or both of the drive wheel slip rates S _ l and S _ r are greater than the slip rate threshold value S1, or the braking torque intervenes in continuous operation for more than time t1, the routine shifts from step (4) to step (5),

step (5), controlling the controlled quantity s of the motor torque control^*Max (s _ l, s _ r), while performing motor torque control:

keeping the motor torque command value Tm _ cmd as a command value of the previous moment, and judging:

if: s^*≥S1，

The command value Tm _ cmd for the motor torque is decreased,

if: s^*＜S1，

The motor torque command value Tm _ cmd is increased,

the motor torque is repeatedly adjusted until the controlled quantity s of the motor torque control^*When the slip rate threshold value S1 is smaller and the motor torque command value Tm _ cmd is larger than 90% of the motor torque target value TM _ tgt, the motor torque single control phase is considered to be finished, the motor torque command value Tm _ cmd is equal to the motor torque target value Tm _ tgt,

in the process of executing step (5), when the instantaneous vehicle speed V does not exceed the vehicle speed threshold value V1, and one of the slip rates S _ l and S _ r of the two drive wheels is greater than the threshold value S1 and the other is less than the threshold value S1, the routine proceeds from step (5) to step (4).

Due to the adoption of the technical scheme, the invention has the following advantages: 1. the invention judges the speed interval of the vehicle according to the instantaneous vehicle speed. And the motor torque is independently controlled at a high-speed stage, so that the driving stability of the vehicle is ensured. 2. And in the medium and low speed stage, judging the condition of the road surface where the vehicle is positioned according to the slip rates of the two driving wheels, and adopting different control methods for the vehicle. Aiming at the split road surface, the motor torque and the braking torque are coordinated for control, namely the motor torque high selection control is adopted, and meanwhile, the braking torque intervention is applied to the driving wheel on the low-adhesion side, so that the acceleration capability of the vehicle is ensured; the motor torque is independently controlled aiming at a single road surface, namely, the motor torque low-selection control is adopted, so that the acceleration smoothness of the vehicle is ensured.

Drawings

FIG. 1 is a schematic diagram of the relationship between the adhesion coefficient and the slip ratio of a car tire.

Fig. 2 is a schematic structural diagram of the drive antiskid control system of the present invention.

Fig. 3 is a flow chart of a control method of the antiskid controller.

Detailed Description

The invention is described in detail below with reference to the figures and examples.

As shown in fig. 2, the drive antiskid control system of the present invention includes a vehicle control unit 1, a left front wheel speed sensor 2, a right front wheel speed sensor 3, a left rear wheel speed sensor 4, and a right rear wheel speed sensor 5, a drive antiskid controller 6, a motor controller 7, and a vehicle dynamics control VDC/vehicle stability control VSC/electronic stabilizer ESP brake pressure regulator 8.

Drive antiskid controller 6 is equipped with five inputs: motor torque target value input is from vehicle control unit 1 input motor torque target value Tm _ tgt, and four fast signal input of wheel are respectively from the fast sensor 2 of four wheels, 3, 4, 5 input corresponding fast signal of wheel, are equipped with two outputs again: and a driving wheel cylinder brake pressure adjusting signal output end outputs a control signal to a vehicle dynamics control VDC/vehicle stability control VSC/electronic stability control ESP brake pressure adjuster 8 to adjust the driving wheel cylinder brake pressure, and a motor torque control signal output end outputs a motor torque command value Tm _ cmd to the motor controller 7 to control the motor torque.

Fig. 3(a), (b) and (c) are schematic control flows of the antiskid controller. In the figure, s _ l and s _ r are the left and right drive wheel slip rates, respectively. s^*For controlled quantities for motor torque control, s is ensured by controlling the motor torque^*Near the optimal slip ratio, s _ l and s _ r are calculated as follows:

$v=\frac{1}{2}({\mathrm{\&omega;}}_{\mathrm{el}}\&CenterDot;r+{\mathrm{\&omega;}}_{\mathrm{er}}\&CenterDot;r)--\left(1\right)$

$s\_l=\frac{{\mathrm{\&omega;}}_{\mathrm{dl}}\&CenterDot;r-v}{{\mathrm{\&omega;}}_{\mathrm{dl}}\&CenterDot;r}---\left(2\right)$

$s\_r=\frac{{\mathrm{\&omega;}}_{\mathrm{dr}}\&CenterDot;r-v}{{\mathrm{\&omega;}}_{\mathrm{dr}}\&CenterDot;r}---\left(3\right)$

wherein, ω e_{l and}ω_erthe left driven wheel speed and the right driven wheel speed, omega respectively_dlAnd ω_drThe left side driving wheel speed and the right side driving wheel speed are respectively, r is the wheel radius, and v is the instantaneous speed of the vehicle.

In fig. 3(a), after the process is started, the motor torque command value Tm _ cmd is made equal to the motor torque target value Tm _ tgt. When it is detected that the maximum value max (S _ l, S _ r) of the slip rates of the two drive wheels exceeds the slip rate threshold value S1, it is determined whether the instantaneous vehicle speed V at that time is less than the vehicle speed threshold value V1. If the instantaneous vehicle speed V at that time is smaller than a vehicle speed threshold value V1, then whether the slip rates S _ l and S _ r of the two driving wheels are both larger than a threshold value S1 is judged, if one of the slip rates S _ l and S _ r of the two driving wheels is larger than a threshold value S1 and the other is smaller than a threshold value S1, the vehicle is considered to enter a split road surface, and the program enters a motor torque and braking torque coordination control stage, namely, the following four parallel programs are entered, as shown in FIG. 3 (b).

1) Selecting controlled quantity s in motor torque control^*. The specific method is that firstly the controlled quantity s is ordered^*Equals to the minimum value min (s _ l, s _ r) of the slip rates of the two driving wheels, then detects the left driving wheel braking torque intervention Flag _ l, and if the left driving wheel power intervention Flag _ l equals to 1, the left driving wheel is considered to have braking torque intervention, the controlled quantity s is controlled^*Equal to the slip ratio s _ r of the right driving wheel, if the braking torque intervention mark Flag _ l of the left driving wheel is not equal to 1, the braking torque intervention mark Flag _ r of the left driving wheel is considered not to intervene, the braking torque intervention mark Flag _ r of the right driving wheel is detected, if the braking torque intervention mark Flag _ r of the right driving wheel is equal to 1, the braking torque intervention mark of the right driving wheel is considered to intervene, the controlled quantity s is controlled^*Equal to the slip ratio s _ l of the left driving wheel, if the intervention marks Flag _ l and Flag _ r of the braking torque of the left and right driving wheels are not equal to 1, the controlled quantity s is controlled^*Equal to the minimum of the two drive wheel slip rates min (s _ l, s _ r).

2) The motor torque is controlled. Firstly, a motor torque command value Tm _ cmd is kept at a command value of the previous moment, and the selected controlled quantity s of motor torque control is judged^*Whether the torque is greater than the slip rate threshold value S1, if the torque of the motor is controlled by the controlled quantity S^*If the slip ratio is larger than the threshold value S1, the command value of the motor torque is reduced, and if the controlled quantity S of the motor torque control is larger than the threshold value S1, the command value of the motor torque is reduced^*If the slip ratio threshold value S1 is not exceeded, the motor torque command value Tm _ cmd is increased, and the motor torque is repeatedly adjusted until the controlled quantity S of the motor torque control^*When the slip rate threshold value S1 is smaller and the motor torque command value Tm _ cmd is larger than 90% of the motor torque target value Tm _ tgt, the motor torque control is considered to be finished, and the motor torque command value Tm _ cmd is equal to the motor torque command value Tm _ cmd at the previous moment.

3) And the braking torque of the left driving wheel intervenes. First, the left driving wheel braking torque intervention Flag _ l is set to 0, when the left driving wheel slip rate S _ l exceeds the slip rate threshold value S1, the right driving wheel slip rate S _ r does not exceed the slip rate threshold value S1 and the right driving wheel braking torque intervention Flag _ r is equal to 0, the braking pressure is increased to the left driving wheel, and the left driving wheel braking torque intervention Flag _ l is set to 1, until the left driving wheel slip rate S _ l is less than the slip rate threshold value S1, the braking pressure of the left driving wheel is reduced, when the left driving wheel slip rate S _ l is detected to be greater than the slip rate threshold value S1 again, the braking pressure is increased to the left driving wheel, the left wheel cylinder pressure is repeatedly adjusted until the left driving wheel slip rate S _ l is less than the slip rate threshold value S1 and the pressure is continuously reduced for a time t0, and the braking torque intervention is considered to be over, let the left driving wheel braking torque intervention Flag _ l be 0.

4) And the braking torque of the right driving wheel intervenes. First, the right driving wheel braking torque intervention Flag _ r is set to 0, when the right driving wheel slip rate S _ r exceeds the slip rate threshold value S1, the left driving wheel slip rate S _ l does not exceed the slip rate threshold value S1 and the left driving wheel braking torque intervention Flag _ l is equal to 0, the braking pressure is increased to the right driving wheel, and the right driving wheel braking torque intervention Flag _ r is set to 1, until the right driving wheel slip rate S _ r is smaller than the slip rate threshold value S1, the braking pressure of the right driving wheel is reduced, when the right driving wheel slip rate S _ r is detected to be larger than the slip rate threshold value S1 again, the braking pressure is increased to the right driving wheel, so that the right wheel cylinder pressure is repeatedly adjusted until the right driving wheel slip rate S _ r is smaller than the slip rate threshold value S1 and the pressure is continuously reduced for a time t0, and the braking torque intervention is considered to be finished, the right drive wheel braking torque intervention Flag _ r is made 0.

And when the slip rates S _ l and S _ r of the two driving wheels are both smaller than a slip rate threshold value S1, the torque is controlled in a non-torque-reduction stage, the motor torque command value Tm _ cmd is larger than 90% of the motor torque target value Tm _ tgt, the left driving wheel braking torque intervention Flag _ l is equal to 0, and the right driving wheel braking torque intervention Flag _ r is equal to 0, the motor torque and braking torque coordination control stage is considered to be finished. If the program is in the motor torque and braking torque coordinated control stage, when the instantaneous vehicle speed V is greater than a vehicle speed threshold value V1, or the slip rates S _ l and S _ r of two driving wheels are both greater than a slip rate threshold value S1, or the braking torque intervenes to continuously work for more than time t1, the program is transferred from the motor torque and braking torque coordinated control stage to the motor torque single control stage.

In fig. 3(a), if it is detected that the maximum value max (S _ l, S _ r) of the slip ratios of the two driving wheels exceeds the slip ratio threshold value S1 and the instantaneous vehicle speed V at that time is greater than the vehicle speed threshold value V1, or when the instantaneous vehicle speed V is less than the vehicle speed threshold value V1 but both the slip ratios S _ l and S _ r of the two driving wheels are greater than the slip ratio threshold value S1, the motor torque individual control phase is entered, as shown in fig. 3 (c). Controlled quantity s for controlling motor torque^*Equal to the maximum value max (s _ l, s _ r) of the slip ratios of the two driving wheels, while the motor torque control is performed. Firstly, a motor torque command value Tm _ cmd is kept at a command value of the previous moment, and the selected controlled quantity s of motor torque control is judged^*Whether the torque is greater than the slip rate threshold value S1, if the torque of the motor is controlled by the controlled quantity S^*If the slip ratio is larger than the threshold value S1, the command value of the motor torque is reduced, and if the controlled quantity S of the motor torque control is larger than the threshold value S1, the command value of the motor torque is reduced^*If the slip ratio threshold value S1 is not exceeded, the motor torque command value Tm _ cmd is increased, and the motor torque is repeatedly adjusted until the controlled quantity S of the motor torque control^*And when the slip rate threshold value S1 is smaller and the motor torque command value Tm _ cmd is larger than 90% of the motor torque target value Tm _ tgt, the motor torque single control phase is considered to be finished, and the motor torque command value Tm _ cmd is equal to the motor torque target value Tm _ tgt.

If the program is in the motor torque individual control phase, when the instantaneous vehicle speed V does not exceed the vehicle speed threshold value V1 and one of the slip rates S _ l and S _ r of the two drive wheels is greater than the threshold value S1 and the other is less than the threshold value S1, the program is transferred from the motor torque individual control phase to the motor torque and brake torque cooperative control phase.

Wherein the value range of the vehicle speed threshold value V1 is [30km/h, 40km/h]The value range of the slip ratio threshold value S1 is [0.15, 0.2]]，t₀The value range is [1.5s, 2s ]]，t₁The value range is [10s, 11s]。

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (1)

1. Axle drives electric vehicle drive antiskid control system, its characterized in that includes: a vehicle control unit, four wheel speed sensors: a left front wheel speed sensor, a right front wheel speed sensor, a left rear wheel speed sensor and a right rear wheel speed sensor, a drive anti-skid controller, a motor controller and a vehicle dynamics control VDC/vehicle stability control VSC/electronic stabilizer ESP brake pressure regulator, wherein:

drive anti-slip controller is equipped with five inputs: the motor torque target value input end is followed vehicle control unit inputs motor torque target value, and four fast signal input ends of wheel are followed respectively four fast sensor inputs of wheel correspond fast signal, are equipped with two outputs again: a driving wheel cylinder brake pressure regulating signal output end for outputting control signals to the vehicle dynamics control VDC/vehicle stability control VSC/electronic stability device ESP brake pressure regulator, and a motor torque control signal output end for outputting motor torque command values to the motor controller, wherein the driving antiskid controller comprises the following control steps:

step (1), driving the antiskid controller to initialize, and setting:

a slip ratio threshold value S1 with a value range of [0.15, 0.2], a vehicle speed threshold value V1 with a value range of [30km/h, 40km/h ], a continuous decompression time t0 for increasing the brake pressure and then reducing the brake pressure for the left driving wheel or the right driving wheel with a value range of [1.5S, 2S ], a brake torque intervention continuous working time upper limit value t1 with a value range of [10S, 11S ],

step (2), calculating the instantaneous vehicle speed v, the instantaneous slip rate s _ l of the left driving wheel and the instantaneous slip rate s _ r of the right driving wheel according to the following formulas respectively:

wherein,

ω_eland ω_erRespectively a left driven wheel speed and a right driven wheel speed,

ω_dland ω_drRespectively a left side driving wheel speed and a right side driving wheel speed,

r is the radius of the wheel,

and (3) judging the slip conditions of the two driving wheels according to the instantaneous vehicle speed v, the slip rate s _ l of the left driving wheel and the slip rate s _ r of the right driving wheel, and determining which control method is adopted:

if: max (S _ l, S _ r) ≧ S1, and V < V1, but one of the two drive wheel slip rates is greater than the slip rate threshold value S1 and the other is less than the slip rate threshold value S1,

entering a motor torque and braking torque coordination control stage, and executing the step (4), wherein:

max (s l, s r) is the maximum of the two drive wheel slip rates,

if: max (S _ l, S _ r) ≥ S1, and V ≥ V1,

or V is less than V1, S _ l is more than or equal to S1 and S _ r is more than or equal to S1,

then entering a motor torque single control stage, executing the step (5),

and (4) entering the following four parallel programs:

(4.1) selecting a controlled quantity s in the motor torque control:

let s^*Min (s _ l, s _ r), judge:

if the left driving wheel braking torque intervention Flag _ l is equal to 1, it is considered that the left driving wheel has braking torque intervention,

then order s^*＝s_r，

If the right driving wheel braking torque intervention Flag _ r is equal to 1, it is considered that there is braking torque intervention at the right driving wheel,

then order s^*＝s_l，

If the left and right side driving wheel braking torque intervention flags Flag _ l and Flag _ r are not equal to 1,

then order s^*＝min(s_l,s_r)，

(4.2) controlling the torque of the motor,

and enabling the motor torque command value Tm _ cmd to be equal to the command value at the previous moment, and judging:

if: s^*And is equal to or more than S1, the command value Tm _ cmd of the motor torque is reduced,

if: s^*< S1, the command value Tm _ cmd for the motor torque is increased,

the torque of the motor is repeatedly adjusted until the motor is powered onControlled quantity s of mechanical moment control^*When the slip rate threshold value S1 is smaller and the motor torque command value Tm _ cmd is larger than 90% of the motor torque target value Tm _ tgt, the motor torque control is considered to be finished, the motor torque command value Tm _ cmd is equal to the motor torque command value Tm _ cmd at the previous moment,

(4.3) the braking torque of the left driving wheel intervenes,

let the left driving wheel braking torque intervention Flag _ l be 0,

if: s _ l is more than or equal to S1, S _ r is less than S1, the intervention Flag _ r of the right driving wheel braking torque is equal to 0,

the brake pressure is increased to the left driving wheel and the left driving wheel brake torque intervention Flag _ l is set to 1 until S _ l < S1, the brake pressure of the left driving wheel is decreased,

if: it is again detected that S _ l ≧ S1,

the brake pressure is increased to the left driving wheel, and the left driving wheel cylinder pressure is repeatedly adjusted so far until S _ l < S1 and the pressure is continuously reduced for more than time t0, and the left driving wheel brake torque intervention Flag _ l is made 0, assuming that the brake torque intervention is finished.

(4.4) the braking torque of the right driving wheel intervenes,

let the right-side drive wheel braking torque intervention Flag _ r be 0,

if: s _ r is more than or equal to S1, S _ l is less than S1, the left driving wheel braking torque intervention Flag is equal to 0,

the brake pressure is increased to the right driving wheel and the right driving wheel brake torque intervention Flag _ r is set to 1 until S _ r < S1, the brake pressure to the right driving wheel is decreased,

if: it is again detected that S _ r ≧ S1,

the brake pressure is increased to the right drive wheel, and the right drive wheel cylinder pressure is repeatedly adjusted in this manner until S _ r < S1 and pressure reduction continues for the time t0, the brake torque intervention is considered to be ended, the right drive wheel brake torque intervention Flag _ r is made 0,

when the slip rates S _ l and S _ r of the two driving wheels are both smaller than a slip rate threshold value S1, the torque control is in a non-torque-reduction stage, the motor torque command value Tm _ cmd is larger than 90% of a motor torque target value Tm _ tgt, the left driving wheel braking torque intervention Flag _ l is equal to 0 and the right driving wheel braking torque intervention Flag _ r is equal to 0, the motor torque and braking torque coordination control stage is considered to be finished, and the motor torque command value Tm _ cmd is equal to the motor torque target value Tm _ tgt,

in the process of executing step (4), when the instantaneous vehicle speed V is greater than the vehicle speed threshold value V1, or both of the drive wheel slip rates S _ l and S _ r are greater than the slip rate threshold value S1, or the braking torque intervenes in continuous operation for more than time t1, the routine shifts from step (4) to step (5),

step (5), controlling the controlled quantity s of the motor torque control^*Max (s _ l, s _ r), while performing motor torque control:

keeping the motor torque command value Tm _ cmd as a command value of the previous moment, and judging:

if: s^*≥S1，

The command value Tm _ cmd for the motor torque is decreased,

if: s^*＜S1，

The motor torque command value Tm _ cmd is increased,

the motor torque is repeatedly adjusted until the controlled quantity s of the motor torque control^*When the slip rate threshold value S1 is smaller and the motor torque command value Tm _ cmd is larger than 90% of the motor torque target value Tm _ tgt, the motor torque single control phase is considered to be finished, the motor torque command value Tm _ cmd is equal to the motor torque target value Tm _ tgt,

in the process of executing step (5), when the instantaneous vehicle speed V does not exceed the vehicle speed threshold value V1, and one of the slip rates S _ l and S _ r of the two drive wheels is greater than the threshold value S1 and the other is less than the threshold value S1, the routine proceeds from step (5) to step (4).

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