CN117125052A - Road adhesion coefficient estimation method and torque control method and device - Google Patents

Abstract

The embodiment of the invention provides a road adhesion coefficient estimation method and a torque control device, wherein the road adhesion coefficient estimation method comprises the following steps: acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel; judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value; and determining a first target attachment rate according to the vehicle parameters in the first attachment state, and determining a road surface attachment coefficient according to the first target attachment rate. According to the embodiment of the invention, the trend of the slip of the vehicle is prejudged in advance according to the change rate of the acceleration of the angular speed of the wheel, so that the road surface adhesion coefficient is calculated according to the vehicle parameters at an earlier moment, the hysteresis of the calculation of the road surface adhesion coefficient is reduced, and the accuracy of the road surface adhesion coefficient is ensured.

Description

Road adhesion coefficient estimation method and torque control method and device

Technical Field

The invention relates to the technical field of automobiles, in particular to a method and a device for estimating road adhesion coefficient and a method and a device for controlling torque.

Background

Under the safety control scene of the automobile, the road adhesion coefficient has a particularly important effect, and the automobile can sense the road adhesion condition under different road conditions through the road adhesion coefficient, so that different control strategies can be made, and the safe and stable running of the automobile can be ensured.

In the prior art, the calculation of the road adhesion coefficient has a certain hysteresis, such as for a slip event of a vehicle, the road adhesion coefficient is usually calculated according to the fed back vehicle parameters after the vehicle has already performed the slip event relative to the road surface, that is, the road adhesion coefficient is calculated according to the vehicle parameters at a later time, so as to perform corresponding control, and the hysteresis can affect the safe and stable running of the vehicle.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: how to reduce the hysteresis of road attachment coefficient calculation.

In order to solve the above technical problems, an embodiment of the present invention provides a method for estimating a road adhesion coefficient, including:

acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;

judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value;

And determining a first target attachment rate according to the vehicle parameters in the first attachment state, and determining a road surface attachment coefficient according to the first target attachment rate.

Optionally, the determining the first target attachment rate according to the vehicle parameter in the first attachment state includes:

determining a plurality of first attachment rates according to the vehicle parameters in the plurality of first attachment states;

and determining a first target attachment rate according to the first attachment rates.

Optionally, the determining the first target attachment rate according to the plurality of first attachment rates includes:

acquiring a first moment and a second moment in two adjacent first attachment states, and determining a time interval according to the first moment and the second moment, wherein the first moment is earlier than the second moment;

when the time interval is larger than a preset time interval, taking a first attachment rate in the first attachment state corresponding to the first moment as a first target attachment rate;

and when the time interval is smaller than or equal to the preset time interval, taking the first attachment rate in the first attachment state corresponding to the second moment as a first target attachment rate.

Optionally, the determining the road surface adhesion coefficient according to the first target adhesion rate includes: and determining the first target attachment rate as a road attachment coefficient.

Optionally, the determining the road surface adhesion coefficient according to the first target adhesion rate includes:

determining a second attachment rate based on the vehicle parameters in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value;

determining a second target attachment rate from at least one of the second attachment rates;

and determining a road surface adhesion coefficient according to the first target adhesion rate and the second target adhesion rate.

Optionally, the determining the road surface adhesion coefficient according to the first target adhesion rate and the second target adhesion rate includes:

determining an adhesion difference value of the first target adhesion rate and the second target adhesion rate;

determining that the first target adhesion rate is a road surface adhesion coefficient under the condition that the absolute value of the adhesion difference value is larger than a preset adhesion difference value;

and determining that the second target adhesion rate is a road adhesion coefficient in the case that the absolute value of the adhesion rate difference is less than or equal to a preset adhesion rate difference value.

Optionally, the determining the second target attachment rate according to at least one of the second attachment rates includes:

And determining a plurality of corresponding second attachment rates according to the vehicle parameters in the second attachment states, and selecting the maximum value of the second attachment rates as a second target attachment rate.

The embodiment of the invention also provides a torque control method, which comprises the following steps:

acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;

judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value;

when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road surface adhesion state is a second adhesion state;

controlling the motor torque corresponding to the wheels to be reduced in the first attaching state until the road surface attaching state enters the second attaching state;

and in the second attaching state, controlling the motor torque corresponding to the wheels to rise until the road surface attaching state enters the first attaching state.

Optionally, the method further comprises:

obtaining a road adhesion coefficient;

And determining the equivalent torque of the adhesion capacity of the road surface according to the road surface adhesion coefficient.

Optionally, in the second attachment state, controlling the motor torque corresponding to the wheel to rise until the road surface attachment state enters the first attachment state includes:

in the second attaching state, if the current torque is smaller than the attaching capability equivalent torque and the absolute value of the torque difference value of the attaching capability equivalent torque is larger than a first preset torque difference value, adding the first preset torque difference value to the attaching capability equivalent torque by taking the first preset torque difference value as a first step length until the absolute value of the torque difference value of the attaching capability equivalent torque is smaller than or equal to the first preset torque difference value;

if the current torque is smaller than the attaching capability equivalent torque and the torque difference between the current torque and the attaching capability equivalent torque is smaller than or equal to a first preset torque difference, taking the attaching capability equivalent torque as the motor output torque;

after the equivalent torque of the attaching capability is used as the motor output torque, if the road surface attaching state is still the second attaching state, gradually increasing the motor output torque by a second step length until the road surface attaching state enters the first attaching state;

The second step size is smaller than the first step size.

Optionally, the determining the equivalent torque of the adhesion capability of the road surface according to the road surface adhesion coefficient includes:

acquiring axle load and wheel rolling radius;

and determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.

Alternatively, obtaining the road surface adhesion coefficient includes referring to the estimation method of the road surface adhesion coefficient as described above.

The embodiment of the invention also provides a device for estimating the road adhesion coefficient, which comprises the following steps:

the first change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;

the first road surface adhesion state judging module is used for judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and the threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value;

and the road surface adhesion coefficient determining module is used for determining a first target adhesion rate according to the vehicle parameters in the first adhesion state and determining the road surface adhesion coefficient according to the first target adhesion rate.

The embodiment of the invention also provides a torque control device, which comprises:

the second change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;

the second road surface adhesion state judging module is used for judging the road surface adhesion state of the wheels according to the change rate of the acceleration of the angular speed of the wheels and the threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value; when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road surface adhesion state is a second adhesion state;

the first attaching state torque control module is used for controlling the motor torque corresponding to the wheels to be reduced in the first attaching state until the pavement attaching state enters the second attaching state;

and the second adhesion state torque control module is used for controlling the motor torque corresponding to the wheels to rise under the second adhesion state until the road surface adhesion state enters the first adhesion state.

In the embodiment of the invention, the change rate of the acceleration of the wheel angular velocity is obtained according to the obtained wheel angular velocity, the road surface attachment state of the wheel is judged according to the change rate of the acceleration of the wheel angular velocity and the threshold value, when the change rate of the acceleration of the wheel angular velocity is larger than the threshold value, the road surface attachment state is the first attachment state, then the first target attachment rate is determined according to the vehicle parameter in the first attachment state, and the road surface attachment coefficient is determined according to the first target attachment rate, so that the trend of the vehicle slip is prejudged according to the change rate of the acceleration of the wheel angular velocity, the road surface attachment coefficient is calculated according to the vehicle parameter at an earlier moment, the calculated hysteresis of the road surface attachment coefficient is reduced, the accuracy of the road surface attachment coefficient is ensured, and a relatively accurate basis is further provided for corresponding control, and the safe and stable running of the vehicle is ensured.

According to the torque control method, torque control is carried out according to the attached state of the wheels on the road surface, so that the attached state of the wheels on the road surface is switched between the second attached state close to the first attached state and the first attached state close to the second attached state, the torque is fluctuated in a small range, and the driving stability of the vehicle is improved.

Drawings

In order to more clearly illustrate the technical solutions of the present invention, the drawings that are needed in the description of the present invention will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art.

FIG. 1 is a diagram of an overall architecture according to one embodiment of the present invention;

FIG. 2 is a flowchart illustrating a method for estimating road adhesion coefficient according to an embodiment of the present invention;

FIG. 3a is a graph showing torque versus slip ratio according to one embodiment of the present invention;

FIG. 3b is a schematic diagram showing an example of estimating road adhesion coefficient according to an embodiment of the present invention;

FIG. 4 is a flow chart of steps of a method of torque control according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an example of torque control provided by an embodiment of the present invention;

FIG. 6a is a schematic diagram of a torque control effect provided by an embodiment of the present invention;

FIG. 6b is a schematic illustration of another torque control effect provided by an embodiment of the present invention;

FIG. 7 is a block diagram showing a road adhesion coefficient estimating apparatus according to an embodiment of the present invention;

fig. 8 is a block diagram of a torque control apparatus according to an embodiment of the present invention.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

In the embodiment of the invention, as shown in fig. 1, on one hand, the attachment state of the road surface is judged by the rotation speed of the wheels, namely, whether the torque exceeds the attachment capacity of the road surface, and on the other hand, the attachment rate of the front and rear axles is calculated by vehicle parameters such as the longitudinal acceleration, the gradient, the front and rear motor torque, the wheelbase, the front and rear wheelbase, the centroid height and the like of the whole vehicle.

After the attachment rate and the attachment state are obtained, the maximum attachment rate of the front and rear axles, namely the attachment capacity coefficient of the road surface, can be calculated according to the attachment rate and the attachment state, then the attachment capacity equivalent torque of the road surface is calculated by combining the front and rear axle loads and the rolling radius of the wheels, and further the torque control can be performed according to the attachment capacity equivalent torque.

In torque control, the torque requirement of the road surface adhesion capability can be met by adjusting the obtained total torque requirement by adopting the adhesion capability equivalent torque.

The following describes embodiments of the present invention in detail:

referring to fig. 2, a flowchart illustrating a method for estimating a road adhesion coefficient according to an embodiment of the present invention may specifically include the following steps:

in step 201, the angular velocity of the wheel is obtained, and the rate of change of the acceleration of the angular velocity of the wheel is obtained from the angular velocity of the wheel.

In a specific implementation, the wheel angular velocity may be read by a wheel speed sensor of the vehicle, the wheel angular velocity may include a wheel angular velocity of a wheel of a front axle of the vehicle and a wheel angular velocity of a wheel of a rear axle of the vehicle, and further, the acceleration of the wheel angular velocity may be calculated according to the read wheel angular velocity, the acceleration of the wheel angular velocity is a derivative of the wheel angular velocity, and then the change rate of the acceleration of the wheel angular velocity may be calculated according to the acceleration of the wheel angular velocity, the change rate of the acceleration of the wheel angular velocity is a derivative of the acceleration of the wheel angular velocity, that is, the change rate of the acceleration of the wheel angular velocity is a second derivative of the wheel angular velocity.

Step 202, judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value.

As for the road surface adhesion state of the wheels, which can reflect whether the longitudinal driving force provided by the current torque in the vehicle to the wheels exceeds the adhesion capability of the road surface, the following is specifically analyzed:

the dynamics equations of the contact points of the front axle wheels and the rear axle wheels with the road surface are as follows:

wherein J is _w Equivalent total moment of inertia, ω, of the front or rear axle wheels _f 、ω _r The angular velocities of the front axle wheel and the rear axle wheel are respectively, specifically the average value of the angular velocities of the two wheels on each axle,the derivatives of the angular velocities of the front and rear axle wheels, respectively, i.e. the acceleration of the angular velocity, T _f 、T _r Front axle wheels or rear axles, respectivelyMotor output torque of axle wheel, i _f 、i _r Main speed reducer speed ratios of a front shaft and a rear shaft respectively, F _X1 、F _X2 Road surface longitudinal driving forces respectively received by the front axle wheels and the rear axle wheels, specifically the sum of the road surface longitudinal driving forces received by the two wheels on each axle, r _t The wheel rolling radius is the front axle wheel or the rear axle wheel.

Respectively representing the longitudinal driving force actually used for accelerating by the front axle wheel and the rear axle wheel, T _f i _f 、T _r i _r Characterizing the longitudinal driving force provided by the current torque of the motor to the front axle wheels and the rear axle wheels respectively, F _X1 r _t 、F _X2 r _t Longitudinal driving forces are respectively provided for the front axle wheels and the rear axle wheels for the road surface.

As can be seen in conjunction with fig. 3a, as the current torque of the motor increases, the current torque of the motor provides the longitudinal driving force to the wheels (as T in fig. 3a _f i _f Corresponding curve) is gradually increased, the road surface provides the longitudinal driving force to the wheels (as shown by F in fig. 3a _X1 r _t Corresponding curve) increases as well.

When the current torque of the motor provides a longitudinal driving force to the wheels greater than the maximum value of the longitudinal driving force provided to the wheels by the road surface (F in fig. 3a _X1 r _t The highest point of the corresponding curve), i.e., the longitudinal driving force provided by the current torque to the wheels exceeds the adhesion capability of the road surface, the following situations may occur thereafter:

1. the acceleration of the wheel angular velocity accelerates.

2. Along with the acceleration of the angular velocity of the wheels, the acceleration of the angular velocity of the wheels is larger than the acceleration of the speed of the whole vehicle, so that the slip rate is increased, and the phenomenon of slipping is aggravated.

The slip rate may be indicative of the severity of slip as the vehicle progresses, which may be expressed as follows:

Where s is slip ratio, v is vehicle speed, and ω is wheel angular velocity.

3. The road surface may provide a longitudinal driving force to the wheels (e.g. F in fig. 3a _X1 r _t The corresponding curve) is further reduced, thereby exacerbating cases 1 and 2.

Based on this, the road surface adhesion state of the wheel can be judged by combining the change rate of the acceleration of the wheel angular velocity with a threshold value, and the value range of the threshold value can be 10rad/s ³ To 100rad/s ³ When the rate of change of the acceleration of the angular velocity of the wheel is greater than a preset threshold value, it may be determined that the road surface adhesion state is a first adhesion state, that is, the longitudinal driving force provided by the current torque of the motor to the wheel exceeds the road surface adhesion capability.

Step 203, determining a first target attachment rate according to the vehicle parameters in the first attachment state, and determining a road attachment coefficient according to the first target attachment rate.

Under the condition that the wheels are in the first attachment state, vehicle parameters can be obtained, then the first target attachment rate can be determined according to the vehicle parameters, then the road surface attachment coefficient can be determined according to the first target attachment rate, and the road surface attachment coefficient can be used for representing the attachment capacity of the road surface.

For the front axle attachment rate and the rear axle attachment rate, the equivalent gradient of the whole vehicle can be determined according to the acceleration of the whole vehicle and the gradient of the road surface in the vehicle parameters, and then the attachment rate can be determined according to the torque distribution ratio and the equivalent gradient in the vehicle parameters.

Specifically, for the equivalent gradient, the acceleration of the whole vehicle can be measured from the obtained acceleration sensor of the whole vehicle, the gradient of the road surface is read from the output signal of the gradient estimation related module, and then the equivalent gradient of the whole vehicle is calculated according to the acceleration of the whole vehicle and the gradient of the road surface, and the following formula is shown:

wherein q is a longitudinal acceleration sensor signal, A _x And the acceleration of the whole vehicle is that theta is the gradient of the road surface, and g is that of gravity.

For the torque distribution ratio, the torque distribution ratio may be a torque distribution ratio of any one of the front axle or the rear axle, the torque distribution ratio of the other axle may be calculated by subtracting the total ratio, specifically, the current torque may be read from the motor controller output signal, the torque of the front axle and the torque of the rear axle may be included, and then the torque distribution ratio may be calculated according to the torque of the front axle and the torque of the rear axle, as shown in the following formula:

wherein ψ is the torque distribution ratio of the rear axle, T _r T is the torque of the rear axle _f Is the torque of the front axle.

After the equivalent gradient and the torque distribution ratio are obtained, the attachment rates of the front axle tire and the rear axle tire can be calculated respectively by combining the whole vehicle wheelbase, the front axle base, the rear axle base and the whole vehicle centroid height, and the following formulas are shown:

Wherein,the attachment rates of the front axle tire and the rear axle tire are respectively, L is the wheel base of the whole vehicle, a is the front wheel base, b is the rear wheel base, h _g The mass center height of the whole vehicle.

In an embodiment of the present invention, the determining the first target attachment rate according to the vehicle parameter in the first attachment state may include:

and a substep 11 of determining a plurality of first attachment rates according to the plurality of vehicle parameters in the first attachment state.

The first attachment rate may be calculated according to the acquired vehicle parameters each time the first attachment state is entered, i.e. a plurality of first attachment rates may be obtained.

A substep 12 of determining a first target attachment rate from a plurality of said first attachment rates.

After obtaining the first attachment rates in the plurality of first attachment states, the first target attachment rate may be determined based on the first attachment rates in the plurality of first attachment states.

In one embodiment of the present invention, sub-step 12 may include:

step 121, obtaining a first time and a second time in two adjacent first attachment states, and determining a time interval according to the first time and the second time, where the first time is earlier than the second time.

In a specific implementation, the corresponding first attachment rate may be calculated at each time in the first attachment state, and for two adjacent times in the first attachment state, it may be the nearest two times, and the time interval between the two times may be calculated.

And a sub-step 122, when the time interval is greater than a preset time interval, taking the first attachment rate in the first attachment state corresponding to the first time as a first target attachment rate.

When the time interval is greater than the preset time interval, for example, the value range of the preset time interval may be 10ms to 100ms, and the first attachment rate in the first attachment state corresponding to the first time may be taken as the first target attachment rate, i.e., the first attachment rate at the previous time is taken as the first target attachment rate.

And a substep 123, when the time interval is less than or equal to the preset time interval, taking the first attachment rate in the first attachment state corresponding to the second moment as a first target attachment rate.

When the time interval is larger than the preset time interval, the first attachment rate in the first attachment state corresponding to the second time may be taken as the first target attachment rate, i.e., the first attachment rate at the later time may be taken as the first target attachment rate.

In an embodiment of the present invention, the first attachment rate in a first attachment state may be used as the first target attachment rate.

In an embodiment of the present invention, the determining the road surface adhesion coefficient according to the first target adhesion rate may include: and determining the first target attachment rate as a road attachment coefficient.

In a specific implementation, the first target attachment rate may be directly taken as the road attachment coefficient.

In an embodiment of the present invention, the determining the road surface adhesion coefficient according to the first target adhesion rate may include:

a substep 21 of determining a second attachment rate based on the vehicle parameters in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value.

When the rate of change of the acceleration of the angular velocity of the wheel is less than or equal to the threshold value, it may be determined that the road surface adhesion state is a second adhesion state, that is, the longitudinal driving force provided by the current torque of the motor to the wheel does not exceed the road surface adhesion capability, and in entering the second adhesion state, the second adhesion rate may be calculated according to the acquired vehicle parameters.

A substep 22 of determining a second target attachment rate based on at least one of said second attachment rates.

After the second attachment rate is obtained, a second target attachment rate may be determined from the at least one second attachment rate.

In one embodiment of the present invention, sub-step 22 may include: and determining a plurality of corresponding second attachment rates according to the vehicle parameters in the second attachment states, and selecting the maximum value of the second attachment rates as a second target attachment rate.

For a plurality of moments in the second attachment state, a plurality of second attachment rates can be obtained, and further, the largest second attachment rate can be selected therefrom as the second target attachment rate.

Specifically, the second attachment rate at the later time may be compared with the second attachment rate at the previous time, with the larger second attachment rate being taken as the second target attachment rate.

In an embodiment, the second target attachment rate may be the second attachment rate at a single time.

A substep 23 of determining a road surface adhesion coefficient according to the first target adhesion rate and the second target adhesion rate.

After the first target adhesion rate and the second target adhesion rate are obtained, the road surface adhesion coefficient may be determined based on the first target adhesion rate and the second target adhesion rate.

In an embodiment of the present invention, the substep 23 may include:

in a substep 231, an adhesion difference value between the first target adhesion rate and the second target adhesion rate is determined.

After the specific implementation, the difference between the first target adhesion rate and the second target adhesion rate may be calculated, resulting in an adhesion difference.

And a substep 232 of determining that the first target adhesion rate is a road adhesion coefficient when the absolute value of the adhesion difference is greater than a preset adhesion difference.

In the case where the absolute value of the adhesion difference is larger than the preset adhesion difference, for example, the preset adhesion difference may have a value ranging from 0.1 to 0.5, and the first target adhesion rate may be determined to be the road surface adhesion coefficient.

In the substep 233, in the case that the absolute value of the adhesion rate difference is less than or equal to the preset adhesion rate difference, the second target adhesion rate is determined to be the road adhesion coefficient.

In the case where the absolute value of the adhesion difference is less than or equal to the preset adhesion difference, the second target adhesion rate may be determined as the road surface adhesion coefficient.

The invention is illustrated below in connection with fig. 3 b:

1. the attachment state of the front axle tire or the rear axle tire, the attachment rate C, and the corresponding time point t are input.

2. The first target attachment rate a is calculated as follows:

and 2.1, judging whether the axle torque exceeds the road surface adhesion capacity, wherein the axle torque exceeds the road surface adhesion capacity in a first adhesion state, and the axle torque does not exceed the road surface adhesion capacity in a second adhesion state.

2.2 recording a first time t when the axle torque exceeds the road adhesion capability _k And determine the t _k First adhesion rate n=c (k) at time.

2.3, recording a second time t when the axle torque exceeds the road surface adhesion capacity again, namely, enters the first adhesion state again _k+1 。

2.4 calculating the time interval t of two moments _k+1 -t _k And determine the time interval t _k+1 -t _k Whether or not it is greater than a preset time interval T ₁ At time interval t _k+1 -t _k Is greater than a preset time interval T ₁ In the case of (2), t _k A is given as a first target attachment rate at a first attachment rate n at a time interval t _k+1 -t _k Less than or equal to a preset time interval T ₁ In the case of (2), t _k+1 The first attachment rate C (k+1) at the time is regarded as the first target attachment rate a.

3. The second target attachment rate e is calculated as follows:

3.1, judging whether the second attachment rate C (i) at the later moment i is larger than the second attachment rate C (i-1) at the later moment i-1 under the condition that the axle torque does not exceed the road attachment capability, and taking the larger second attachment rate as a second target attachment rate e.

4. And calculating an adhesion difference e-a between the first target adhesion rate a and the second target adhesion rate e, and judging whether the absolute value of the adhesion difference e-a is larger than a preset adhesion difference K.

5. In the case where the absolute value of the adhesion difference e-a is larger than the preset adhesion difference K, the first target adhesion rate a is taken as the road surface adhesion coefficientIn the case where the absolute value of the adhesion difference e-a is less than or equal to the preset adhesion difference K, the second target adhesion e is taken as the road adhesion coefficient +. >

In the embodiment of the invention, the change rate of the acceleration of the wheel angular velocity is obtained according to the obtained wheel angular velocity, the road surface attachment state of the wheel is judged according to the change rate of the acceleration of the wheel angular velocity and the threshold value, when the change rate of the acceleration of the wheel angular velocity is larger than the threshold value, the road surface attachment state is the first attachment state, then the first target attachment rate is determined according to the vehicle parameter in the first attachment state, and the road surface attachment coefficient is determined according to the first target attachment rate, so that the trend of the vehicle slip is prejudged according to the change rate of the acceleration of the wheel angular velocity, the road surface attachment coefficient is calculated according to the vehicle parameter at an earlier moment, the calculated hysteresis of the road surface attachment coefficient is reduced, the accuracy of the road surface attachment coefficient is ensured, and a relatively accurate basis is further provided for corresponding control, and the safe and stable running of the vehicle is ensured.

Referring to fig. 4, a flowchart illustrating steps of a method for torque control according to an embodiment of the present invention may specifically include the following steps:

in step 401, the angular velocity of the wheel is obtained, and the rate of change of the acceleration of the angular velocity of the wheel is obtained from the angular velocity of the wheel.

Reference is made to the above description of step 201 for a description of step 401.

Step 402, judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value; when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road surface adhesion state is a second adhesion state.

Reference is made to the above description of step 202, sub-step 21 for a description of step 402.

In an embodiment of the present invention, the method may further include: obtaining a road adhesion coefficient; and determining the equivalent torque of the adhesion capacity of the road surface according to the road surface adhesion coefficient.

In a specific implementation, the road surface adhesion coefficient may be obtained as described above with reference to step 103, and then the adhesion capability equivalent torque of the fixed road surface may be determined based on the road surface adhesion coefficient.

In an embodiment of the present invention, the determining the equivalent torque of the adhesion capability of the road surface according to the road adhesion coefficient may include: acquiring axle load and wheel rolling radius; and determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.

In specific implementation, the rolling radius of the wheel can be obtained first, the axle loads of the front axle and the rear axle can be obtained through calculation, then the axle loads and the rolling radius of the wheel can be used for converting the road surface adhesion coefficient into the adhesion capacity equivalent torque of the road surface, and the following formula can be adopted:

wherein T is _fmax 、T _rmax Equivalent torque of the adhesion capability of the front axle and the rear axle respectively,road adhesion coefficients of front axle and rear axle, F _z1 、F _z2 The axle loads of the front axle and the rear axle respectively, r _t Is the rolling radius of the wheel.

The axle load can be calculated according to the whole vehicle mass, the gravity acceleration, the road gradient, the front axle base, the rear axle base, the whole vehicle mass center height and the whole vehicle acceleration, and the following formula is shown:

wherein F is _z1 、F _z2 The axle loads of a front axle and a rear axle respectively, M is the mass of the whole automobile, g is the gravity acceleration, a is the front axle base, b is the rear axle base, L is the axle base of the whole automobile, and h _g The mass center height of the whole vehicle.

Step 403, in the first adhesion state, controlling the motor torque corresponding to the wheels to decrease until the road surface adhesion state enters the second adhesion state.

In the first adhesion state, that is, when the longitudinal driving force provided by the current torque of the motor to the wheels exceeds the road adhesion capability, the motor torque corresponding to the wheels can be controlled to be reduced until the road adhesion state enters the second adhesion state, for example, the motor torque can be reduced according to the step length with the value ranging from-200 Nm to-10 Nm.

And step 404, in the second attachment state, controlling the motor torque corresponding to the wheels to rise until the road surface attachment state enters the first attachment state.

In the second attachment state, that is, when the current torque of the motor provides the longitudinal driving force to the wheels that does not exceed the road attachment capability, the torque of the motor corresponding to the wheels can be controlled to rise until the road attachment state enters the first attachment state.

In an embodiment of the present invention, step 404 may include:

and a substep 31, in the second attachment state, if the current torque is smaller than the attachment capacity equivalent torque and the absolute value of the torque difference between the current torque and the attachment capacity equivalent torque is larger than a first preset torque difference, adding the first preset torque difference to the attachment capacity equivalent torque by taking the first preset torque difference as a first step length until the absolute value of the torque difference of the attachment capacity equivalent torque is smaller than or equal to the first preset torque difference.

Under the condition that the current torque is smaller than the attaching capability equivalent torque, the absolute value of the torque difference between the current torque and the attaching capability equivalent torque can be calculated, and when the absolute value of the torque difference is larger than a first preset torque difference, if the value range of the first preset torque difference can be 10Nm to 100Nm, that is, the difference between the current torque and the attaching capability equivalent torque is larger, the first preset torque difference can be the first step size, the attaching capability equivalent torque is increased, and the attaching capability equivalent torque is gradually approached.

And step 32, if the current torque is smaller than the attachment capacity equivalent torque and the torque difference between the current torque and the attachment capacity equivalent torque is smaller than or equal to a first preset torque difference, taking the attachment capacity equivalent torque as the motor output torque.

When the absolute value of the torque difference is smaller than or equal to the first preset torque difference, that is, the difference between the current torque and the adhesion equivalent torque is smaller, the adhesion equivalent torque can be directly used as the motor output torque to control the torque rise.

And step 33, after taking the equivalent torque of the attaching capability as the motor output torque, if the road surface attaching state is still the second attaching state, gradually increasing the motor output torque by a second step length until the road surface attaching state enters the first attaching state.

Wherein the second step size may be smaller than the first step size.

After the equivalent torque of the adhesion capability is taken as the output torque of the motor, whether the road surface adhesion state enters the first adhesion state from the second adhesion state or not can be detected again, if so, the torque is controlled in a mode of the first adhesion state, and if not, the torque increase can be controlled continuously with a smaller second step length.

The invention is illustrated below in connection with fig. 5:

1. the current torque demand T_req is increased by taking Step0 as a Step length, the value range of Step0 can be 10Nm to 100Nm, the actual torque (namely the current torque) of the motor at the moment K is T_actl, and the equivalent torque of the attachment capability is T_max.

2. Judging whether the axle torque exceeds the road surface adhesion capacity, wherein the axle torque exceeds the road surface adhesion capacity, namely in a first adhesion state, the axle torque does not exceed the road surface adhesion capacity, namely in a second adhesion state.

3. When the torque exceeds the road adhesion capability, i.e., in the first adhesion state, torque is reduced in Step size by Step2, step2 may take a value in the range of-200 Nm to-10 Nm, i.e., t_req (k+1) =t_req (k) +step2.

4. When the axle torque does not exceed the road adhesion capability, namely in a second adhesion state, calculating an absolute value T_actl-T_max of a torque difference value between the current torque T_actl and the adhesion capability equivalent torque T_max, and judging whether the absolute value T_actl-T_max of the torque difference value is smaller than a first preset torque difference value Step0.

5. And under the condition that the absolute value T_actl-T_max of the torque difference is larger than the first preset torque difference Step0, continuously increasing the torque by taking Step0 as a Step length.

6. In case the absolute value of the torque difference t_act-t_max is smaller than or equal to the first preset torque difference Step0, then the attachment capability equivalent torque may be directly taken as the motor output torque, i.e. t_req (k+1) =t_max.

7. After the equivalent torque of the attaching capability is taken as the output torque of the motor, whether the shaft torque exceeds the attaching capability of the road surface can be judged again, torque control can be performed according to the first attaching state when the shaft torque exceeds the attaching capability of the road surface, namely, the first attaching state is entered, and torque increase can be continuously controlled by a smaller second Step1 when the shaft torque does not exceed the attaching capability of the road surface, namely, the first attaching state is not entered, and the value range of Step1 can be 10Nm to 100Nm.

In the embodiment of the invention, the change rate of the acceleration of the wheel angular velocity is obtained according to the wheel angular velocity, the road surface attached state of the wheel is judged according to the change rate of the acceleration of the wheel angular velocity and the threshold value, when the change rate of the acceleration of the wheel angular velocity is larger than the threshold value, the road surface attached state is in the first attached state, when the change rate of the acceleration of the wheel angular velocity is smaller than or equal to the threshold value, the road surface attached state is in the second attached state, then the motor torque corresponding to the wheel is controlled to be reduced under the first attached state until the road surface attached state enters the second attached state, and the motor torque corresponding to the wheel is controlled to be increased under the second attached state until the road surface attached state enters the first attached state, so that torque control is performed according to the attached state of the wheel on the road surface, the torque is close to the attached force of the road surface, the accuracy of torque control is improved, and the safety and the stability of the vehicle are ensured.

The beneficial effects of the present invention are described below with reference to fig. 6a and 6 b:

as shown in fig. 6a, in which the torque demand T is controlled by using the equivalent torque of the road surface as the torque reference value, and as shown in fig. 6b, in which the torque demand T is not controlled by using the equivalent torque of the road surface as the torque reference value, the following advantages are obtained when the torque demand T is controlled by using the equivalent torque of the road surface as the torque reference value:

1. in the torque increasing stage, the equivalent torque of the adhesion capability of the road surface is used as the torque increasing reference value of the front axle torque and the rear axle torque, the torque increasing rate can be adjusted after the maximum torque increasing rate reaches the reference value, and compared with a general torque increasing step size limiting mode, the response time can be effectively reduced.

2. After the torque reduction control is carried out to a vehicle stable state, a torque recovery stage is carried out to calculate the adhesion capability equivalent torque of the road surface to be used as a torque increase reference value of the front axle motor and the rear axle motor, so that the phenomenon that wheels slip again due to unlimited torque increase is avoided, and the torque reduction control is triggered.

In the prior art, whether slipping occurs or not is judged according to the difference value of the actual slipping rate and the preset slipping rate, and the slip judgment result can be obtained only after the wheel speed rises to the slipping phenomenon. In addition, the torque is controlled according to the slip ratio, and the torque range to be adjusted from the slip state to the normal state is larger and the time required is longer due to the hysteresis of judgment (see fig. 6 b).

According to the torque control method, the torque is controlled according to the slip trend, namely the first attachment state and the second attachment state, the torque is timely reduced under the first attachment state, namely the slip trend is generated, the slip risk is avoided, the torque is increased again after the torque is reduced to enter the second attachment state from the first attachment state, namely the torque is controlled until the first attachment state is reentered, namely the torque is timely increased to enable the wheels to enter the first attachment state again after the first attachment state enters the second attachment state from the first attachment state, and the torque is timely reduced to enable the wheels to enter the second attachment state again after the second attachment state enters the first attachment state, so that the stay time of the road surface attachment state of the wheels in the first attachment state and the second attachment state is short, the control range of the torque is also in a small range, particularly in a small range of the attachment capacity equivalent axis of the road surface, fluctuation (see fig. 6 a), and the driving stability of the vehicle is improved. In addition, since the wheels have a tendency to slip in the first attachment state, but no slip occurs, the running safety of the vehicle is also ensured.

It should be noted that, for simplicity of description, the method embodiments are shown as a series of acts, but it should be understood by those skilled in the art that the embodiments are not limited by the order of acts, as some steps may occur in other orders or concurrently in accordance with the embodiments. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred embodiments, and that the acts are not necessarily required by the embodiments of the invention.

Referring to fig. 7, a block diagram of a road adhesion coefficient estimating apparatus according to an embodiment of the present invention may specifically include the following modules:

the first change rate determining module 701 is configured to obtain a wheel angular velocity, and obtain a change rate of acceleration of the wheel angular velocity according to the wheel angular velocity.

A first road surface adhesion state judging module 702, configured to judge a road surface adhesion state of a wheel according to a change rate of acceleration of the angular velocity of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value.

The road surface adhesion coefficient determination module 703 is configured to determine a first target adhesion rate according to the vehicle parameter in the first adhesion state, and determine a road surface adhesion coefficient according to the first target adhesion rate.

In an embodiment of the present invention, the road adhesion coefficient determination module 703 may include:

a plurality of first attachment rate determination submodules for determining a plurality of first attachment rates according to the vehicle parameters in the plurality of first attachment states;

a plurality of first attachment rate determination target attachment rate sub-modules for determining a first target attachment rate from the plurality of first attachment rates.

In an embodiment of the present invention, the plurality of first attachment rate determining target attachment rate submodules may include:

the time interval determining unit is used for obtaining a first time and a second time in two adjacent first attaching states and determining a time interval according to the first time and the second time, wherein the first time is earlier than the second time;

the device comprises a target unit, a first time and a second time, wherein the target unit is used for taking the attachment rate at the first moment as a target unit, and the target unit is used for taking the first attachment rate in the first attachment state corresponding to the first moment as a first target attachment rate when the time interval is larger than a preset time interval;

And taking the attachment rate at the second moment as a target unit, and taking the first attachment rate in the first attachment state corresponding to the second moment as a first target attachment rate when the time interval is smaller than or equal to the preset time interval.

In one embodiment of the present invention, the road adhesion coefficient determination module 703 includes:

and a unit for determining the first target attachment rate as the road surface attachment coefficient and determining the first target attachment rate as the road surface attachment coefficient.

In one embodiment of the present invention, the road adhesion coefficient determination module 703 includes:

a second attachment rate determination unit configured to determine a second attachment rate based on the vehicle parameter in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value;

a second target attachment rate determination unit configured to determine a second target attachment rate according to at least one of the second attachment rates;

and the second target attachment rate determining unit is combined and used for determining the road surface attachment coefficient according to the first target attachment rate and the second target attachment rate.

In an embodiment of the present invention, in combination with the second target attachment rate determining unit, it may include:

An adhesion-difference-value determination subunit configured to determine an adhesion-difference value of the first target adhesion rate and the second target adhesion rate;

a first target adhesion rate is determined to be a road adhesion coefficient subunit, and the first target adhesion rate is determined to be a road adhesion coefficient when the absolute value of the adhesion difference is greater than a preset adhesion difference value;

and determining the second target adhesion rate as a road adhesion coefficient subunit, configured to determine that the second target adhesion rate is a road adhesion coefficient if the absolute value of the adhesion difference is less than or equal to a preset adhesion difference value.

In an embodiment of the present invention, the second target attachment rate determining unit is specifically configured to:

and determining a plurality of corresponding second attachment rates according to the vehicle parameters in the second attachment states, and selecting the maximum value of the second attachment rates as a second target attachment rate.

Referring to fig. 8, a block diagram of a torque control apparatus according to an embodiment of the present invention is shown, which may specifically include the following modules:

the second change rate determining module 801 is configured to obtain a wheel angular velocity, and obtain a change rate of acceleration of the wheel angular velocity according to the wheel angular velocity.

A second road surface adhesion state judging module 802, configured to judge a road surface adhesion state of the wheel according to a change rate of acceleration of the angular velocity of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value; when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road surface adhesion state is a second adhesion state.

And the first adhesion state torque control module 803 is configured to control, in the first adhesion state, a motor torque corresponding to a wheel to decrease until the road adhesion state enters the second adhesion state.

And the second adhesion state torque control module 804 is configured to control the motor torque corresponding to the wheel to rise in the second adhesion state until the road adhesion state enters the first adhesion state.

In an embodiment of the present invention, the apparatus may further include:

the road surface adhesion coefficient acquisition module is used for acquiring the road surface adhesion coefficient;

and the adhesion capacity equivalent torque determining module is used for determining the adhesion capacity equivalent torque of the road surface according to the road surface adhesion coefficient.

In one embodiment of the present invention, the second attachment state torque control module 804 may include:

A sub-module is added in a first step length, and is used for adding the first preset torque difference value to the attaching capability equivalent torque until the absolute value of the torque difference value of the attaching capability equivalent torque is smaller than or equal to the first preset torque difference value if the current torque is smaller than the attaching capability equivalent torque and the absolute value of the torque difference value of the attaching capability equivalent torque is larger than the first preset torque difference value in the second attaching state;

the method comprises the steps of taking the equivalent torque of the attachment capability as an output sub-module, and taking the equivalent torque of the attachment capability as the output torque of the motor if the current torque is smaller than the equivalent torque of the attachment capability and the torque difference between the current torque and the equivalent torque of the attachment capability is smaller than or equal to a first preset torque difference;

the second step increasing sub-module is used for gradually increasing the motor output torque by the second step when the road surface adhesion state is still the second adhesion state after the adhesion capacity equivalent torque is used as the motor output torque, until the road surface adhesion state enters the first adhesion state;

wherein the second step size is smaller than the first step size.

In an embodiment of the present invention, the attachment capability equivalent torque determination module may include:

The axle load and radius acquisition sub-module is used for acquiring the axle load and the rolling radius of the wheel;

and the combined axle load and radius determining submodule is used for determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.

In one embodiment of the present invention, obtaining the road surface adhesion coefficient includes referring to the road surface adhesion coefficient estimating means as described above.

An embodiment of the present invention further provides an electronic device, which may include a processor, a memory, and a computer program stored on the memory and capable of running on the processor, where the computer program when executed by the processor implements the above road adhesion coefficient estimation method or torque control method.

An embodiment of the present invention also provides a computer-readable storage medium having a computer program stored thereon, which when executed by a processor implements the above road adhesion coefficient estimation method or torque control method.

For the device embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for relevant points.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (14)

1. A method for estimating road adhesion coefficient, the method comprising:

acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;

judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value;

and determining a first target attachment rate according to the vehicle parameters in the first attachment state, and determining a road surface attachment coefficient according to the first target attachment rate.

2. The method of claim 1, wherein the determining a first target attachment rate based on the vehicle parameters in the first attachment state comprises:

determining a plurality of first attachment rates according to the vehicle parameters in the plurality of first attachment states;

and determining a first target attachment rate according to the first attachment rates.

3. The method of claim 2, wherein said determining a first target attachment rate from a plurality of said first attachment rates comprises:

acquiring a first moment and a second moment in two adjacent first attachment states, and determining a time interval according to the first moment and the second moment, wherein the first moment is earlier than the second moment;

When the time interval is larger than a preset time interval, taking a first attachment rate in the first attachment state corresponding to the first moment as a first target attachment rate;

and when the time interval is smaller than or equal to the preset time interval, taking the first attachment rate in the first attachment state corresponding to the second moment as a first target attachment rate.

4. A method according to any one of claims 1-3, wherein said determining the road adhesion coefficient from said first target adhesion rate comprises: and determining the first target attachment rate as a road attachment coefficient.

5. A method according to any one of claims 1-3, wherein said determining the road adhesion coefficient from said first target adhesion rate comprises:

determining a second attachment rate based on the vehicle parameters in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value;

determining a second target attachment rate from at least one of the second attachment rates;

and determining a road surface adhesion coefficient according to the first target adhesion rate and the second target adhesion rate.

6. The method of claim 5, wherein determining the road attachment coefficient from the first target attachment rate and the second target attachment rate comprises:

determining an adhesion difference value of the first target adhesion rate and the second target adhesion rate;

determining that the first target adhesion rate is a road surface adhesion coefficient under the condition that the absolute value of the adhesion difference value is larger than a preset adhesion difference value;

and determining that the second target adhesion rate is a road adhesion coefficient in the case that the absolute value of the adhesion rate difference is less than or equal to a preset adhesion rate difference value.

7. The method of claim 6, wherein said determining a second target attachment rate from at least one of said second attachment rates comprises:

and determining a plurality of corresponding second attachment rates according to the vehicle parameters in the second attachment states, and selecting the maximum value of the second attachment rates as a second target attachment rate.

8. A method of torque control, the method comprising:

acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;

judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value;

When the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road surface adhesion state is a second adhesion state;

controlling the motor torque corresponding to the wheels to be reduced in the first attaching state until the road surface attaching state enters the second attaching state;

and in the second attaching state, controlling the motor torque corresponding to the wheels to rise until the road surface attaching state enters the first attaching state.

9. The method of claim 8, wherein the method further comprises:

obtaining a road adhesion coefficient;

and determining the equivalent torque of the adhesion capacity of the road surface according to the road surface adhesion coefficient.

10. The method of claim 9, wherein in the second attachment state, controlling the increase in motor torque corresponding to the wheel until the road attachment state enters the first attachment state comprises:

in the second attaching state, if the current torque is smaller than the attaching capability equivalent torque and the absolute value of the torque difference value of the attaching capability equivalent torque is larger than a first preset torque difference value, adding the first preset torque difference value to the attaching capability equivalent torque by taking the first preset torque difference value as a first step length until the absolute value of the torque difference value of the attaching capability equivalent torque is smaller than or equal to the first preset torque difference value;

If the current torque is smaller than the attaching capability equivalent torque and the torque difference between the current torque and the attaching capability equivalent torque is smaller than or equal to a first preset torque difference, taking the attaching capability equivalent torque as the motor output torque;

after the equivalent torque of the attaching capability is used as the motor output torque, if the road surface attaching state is still the second attaching state, gradually increasing the motor output torque by a second step length until the road surface attaching state enters the first attaching state;

the second step size is smaller than the first step size.

11. The method according to claim 9 or 10, wherein said determining the adhesion-ability equivalent torque of the road surface from the road surface adhesion coefficient comprises:

acquiring axle load and wheel rolling radius;

and determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.

12. The method of claim 9, wherein obtaining the road adhesion coefficient comprises referring to the method of any one of claims 1-7.

13. An apparatus for estimating road adhesion coefficient, the apparatus comprising:

The first change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;

the first road surface adhesion state judging module is used for judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and the threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value;

and the road surface adhesion coefficient determining module is used for determining a first target adhesion rate according to the vehicle parameters in the first adhesion state and determining the road surface adhesion coefficient according to the first target adhesion rate.

14. A torque-controlled apparatus, the apparatus comprising:

the second change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;

the second road surface adhesion state judging module is used for judging the road surface adhesion state of the wheels according to the change rate of the acceleration of the angular speed of the wheels and the threshold value; wherein the road surface adhesion state is a first adhesion state when a rate of change of acceleration of the wheel angular velocity is greater than a threshold value; when the rate of change of the acceleration of the wheel angular velocity is less than or equal to a threshold value, the road surface adhesion state is a second adhesion state;

The first attaching state torque control module is used for controlling the motor torque corresponding to the wheels to be reduced in the first attaching state until the pavement attaching state enters the second attaching state;

and the second adhesion state torque control module is used for controlling the motor torque corresponding to the wheels to rise under the second adhesion state until the road surface adhesion state enters the first adhesion state.