RU2779538C1 - Identification system for the maximum values of the sliding friction coefficients of vehicle wheels - Google Patents

Abstract

FIELD: wheel speed sensors.

SUBSTANCE: system contains wheel speed sensors, a microcontroller, and an interface device. The microcontroller contains a block for analyzing signals from wheel speed sensors, a block for estimating vehicle motion parameters, a block for calculating the normal components of dynamic loads acting on each wheel, a block for calculating the distribution of traction-braking forces acting on each wheel, a block for solving the inverse problems of piecewise linear approximation of the coefficient of sliding friction, a block for filtering estimates of the maximum values ​​of the coefficients of friction for wheels sliding, a block for outputting data to external display devices for the driver and inputting tuning data.

EFFECT: obtaining indirect measurements of the maximum values of the sliding friction coefficients of the wheels of the vehicle is achieved.

1 cl, 4 dwg

Description

The invention relates to the automotive industry, in particular, to methods and devices for the active safety of vehicles (TC).

A device is known for estimating the coefficient of sliding friction of the wheels with the road and a method for estimating the coefficient of friction of the wheels with the road, in which the coefficient of sliding friction of the wheels with the road is determined based on the ratio of the calculated turning force to the estimated tire side slip angle. The vehicle travels on multiple road surfaces that differ in friction coefficient, and tire side slip angles and turning forces on the road surfaces are predetermined. The friction coefficient estimator stores in memory the correlation between the detected tire side slip angles, the detected cornering forces and the road friction coefficients as numerical values or a mathematical expression, and estimates the road friction coefficient using the correlation stored in the memory (see EP 2572947 A1, applicant JTEKT Corp, published 10/26/2016).

The main disadvantage of the method is the approximation of the determined value of the sliding friction coefficient of the vehicle wheels, the complex procedure for processing data from vehicle sensors and the applicability of the method only in conditions of uneven road surface.

There is a known method for determining the coefficient of sliding friction of wheels based on a database, in which information about the current coefficient of sliding friction of the wheels, geometric features of the site, coordinates and time is received from other vehicles in the form of a database (see US patent application US 20170357669 A1, Applicant Robert Bosch GmbH, published 12/14/2017).

The main disadvantage of this method is the need for transceivers in cars, a significant amount of information received and transmitted, and the question of the relevance of this information.

The closest in technical essence is a method for determining the coefficient of friction of the road surface. In the method under consideration, the wheel friction coefficients are determined by converting the wheel speeds from the ABS sensors into the wheel slip speeds and other values necessary to calculate the sliding friction coefficients for each of the wheels. The average coefficient of friction is determined by using a weighting function for the coefficients of friction of all wheels (see Japanese patent JP 4159811 B2, applicants Koji Takao and BRIDGESTONE CORP, publ. 01.10.2008).

The disadvantage of this method is the uncertainty in the choice of the weighting factor for each of the averaged values of the final coefficient of sliding friction.

The technical problem to be solved by the present invention consists in indirect measurements of the maximum values of the sliding friction coefficients of the wheels of the vehicle.

The technical problem is solved by the fact that the system for identifying the maximum values of the coefficients of sliding friction of the wheels of the vehicle, containing sensors 1, 2, 3, 4 wheel speeds, electrically connected to the microcontroller device 5 information processing, through communication lines with the device 6 interface with the microcontroller device 5, the microcontroller information processing device 5 includes: a block 7 for analyzing signals from sensors 1, 2, 3, 4 of wheel speeds, a block 8 for estimating vehicle motion parameters, a block 9 for calculating the normal components of dynamic loads acting on each wheel, a block 10 for calculating the distribution traction-braking forces acting on each wheel, block 11 for solving the inverse problem of a piecewise linear approximation of the coefficient of sliding friction, block 12 for filtering estimates of the maximum values of coefficients of friction for sliding wheels, block 13 input-output is used to enter setup data and output cutting ltats of calculations to external devices and for indication to the driver, and in the system block 9 for calculating the normal components of dynamic loads, block 10 for calculating the distribution of traction-braking forces, block 11 for solving the inverse problem, block 12 for filtering, block 13 for input-output of data are made on the basis of a microcontroller device 5 with the possibility of software execution of block 9 for calculating the normal components of dynamic loads, block 10 for distributing traction-braking forces, block 11 for solving the inverse problem, block 12 for filtering, block 13 for input-output of data, block 9 for calculating the normal components of dynamic loads acting on each wheel, is configured to take into account the influence of longitudinal and transverse accelerations on the distribution of normal components of dynamic loads, the block 10 for distributing traction-braking forces is configured to take into account the distribution of traction forces from the engine and transmission and from the brake system along the wheels, block 11 for solving the inverse problem designed with the possibility of generating estimates of the maximum values of the coefficients of sliding friction of the wheels in the slip range of a stable section of the typical dependence of the friction force on sliding, the evaluation filtering unit 12 is configured to reduce the influence of measurement noise on the identification results by eliminating data outliers as a result of checking by ranges and data smoothness , satisfying the conditions of restrictions on the first and second derivatives, the data input-output unit 13 is configured to promptly input the tuning data of the used mathematical model for tires of different models and output the output data to the driver and to the functional blocks of the active safety system.

The technical results are achieved by creating a system for identifying the maximum values of the sliding friction coefficients of the wheels of the vehicle, in which the blocks are connected in a certain way as indicated above.

The system for identifying the maximum values of the sliding friction coefficients of the vehicle wheels contains sensors 1, 2, 3, 4 of the wheel speeds, electrically connected to the microcontroller device 5 for information processing, via communication lines with the device 6 for interfacing with the microcontroller device 5, the microcontroller device 5 for information processing includes : block 7 for analyzing signals from sensors 1, 2, 3, 4 of wheel speeds, block 8 for estimating vehicle motion parameters, block 9 for calculating the normal components of dynamic loads acting on each wheel, block 10 for calculating the distribution of traction-braking forces acting on each wheel, block 11 for solving the inverse problem of a piecewise linear approximation of the coefficient of sliding friction, block 12 for filtering estimates of the maximum values of coefficients of friction for sliding wheels, block 13 for input-output of data to external display devices for the driver and input of tuning data, characterized in that in si system block 9 for calculating the normal components of dynamic loads, block 10 for calculating the distribution of traction-braking forces, block 11 for solving the inverse problem, block 12 for filtering, block 13 for input-output of data are made on the basis of a microcontroller device 5 with the possibility of software execution of block 9 for calculating the normal components of dynamic loads, block 10 for distributing traction-braking forces, block 11 for solving the inverse problem, block 12 for filtering, block 13 for input-output of data, block 9 for calculating the normal components of dynamic loads acting on each wheel, is configured to take into account the influence of longitudinal and lateral accelerations on distribution of the normal components of dynamic loads, block 10 for distributing traction-braking forces is configured to take into account the distribution of traction forces from the engine and transmission and from the brake system along the wheels, block 11 for solving the inverse problem is configured to generate estimates of the maximum values of the coefficients m of the sliding of the wheels in the slip range of the stable section of the typical dependence of the friction force on the slip, the evaluation filtering unit 12 is configured to reduce the influence of measurement noise on the identification results by eliminating data outliers as a result of checking over the ranges and smoothness of the data that satisfies the conditions of the restrictions on the first and second derivative, the data input-output unit 13 is configured to promptly input the tuning data of the used mathematical model for tires of different models and output the output data to the driver and to the functional blocks of the active safety system.

The proposal is illustrated by drawings.

On FIG. 1 shows a block diagram of a system for identifying the maximum values of sliding friction coefficients of vehicle wheels.

In FIG. 2 shows a family of dependences of the coefficients of sliding friction k _s on the magnitude of the longitudinal slip 5.

от скорости V_m на различных покрытиях.In FIG. 3 shows the dependence

on the speed V _m on different surfaces.

Fig. 4 contains a computational block of the algorithm for the maximum values of the sliding friction coefficients of the wheels of the vehicle.

The proposed system works as follows.

When the vehicle is moving, the sensors 1, 2, 3, 4 generate pulse signals corresponding to the rotational speeds of the vehicle wheels, and since they are electrically connected by communication lines through the interface device 6 with the microcontroller device 5, these signals are through the communication lines with the interface device 6 enter the microcontroller device 5 for information processing, which includes a software block 7 for analyzing signals from sensors 1, 2, 3, 4 of wheel speeds, which compares their values with the operating range of sensor signals and identifies sensors that have malfunctions in the form of signal loss for a limited time interval, while the readings of such a sensor are automatically excluded from further analysis.

Further, in the microprocessor device 5 for processing information, the software unit for estimating 8 vehicle motion parameters compares the signals from the vehicle wheel speed sensors 1, 2, 3, 4 and receives, according to the computer program algorithm, data characterizing the vehicle motion parameters, in particular, longitudinal velocity of the center of mass, longitudinal and transverse acceleration, angle of rotation of the steered wheels, longitudinal slip speeds of the wheels, air pressure in tires, etc. (See certificate of state registration of the computer program No. .E., Elkin D.S.// Rospatent 2009).

In block 9 for calculating the normal components of dynamic loads, the distribution of the normal components of the forces acting on each wheel is calculated, taking into account the total mass and weight distribution along the axes, wheel radii, track width, wheelbase and height of the center of mass specified in the setting data of block 13 of the input- output, as well as longitudinal and transverse accelerations, determined in block 8.

In block 10 for calculating the distribution of traction and braking forces on the wheels, the calculation of traction and braking forces acting on the wheels is performed, taking into account the type of drive (front, rear, full) and the parameters of the braking system specified in the setting data of the block 13 input-output.

In block 11 for solving the inverse problem of piecewise linear approximation of the dependence of the sliding friction coefficient on the amount of wheel slip, the maximum value of the sliding friction coefficient is calculated for one of the three sections of the initial curve approximation depending on the measured wheel slip.

In block 12 filtering estimates of the maximum values of the coefficients of friction of sliding wheels, the conditions for the reliability of the obtained estimates are checked by comparing them with the allowable range of changes, the allowable values of the first and second derivatives specified in the setting data of the block 13 input-output.

The input-output block 13 performs the functions of input and storage of tuning data, as well as indication to the driver of the estimates of the maximum values of the wheel sliding friction coefficients and their transmission to external active safety devices.

.The proposal is illustrated by drawings explaining the calculation formulas and the process of calculating intermediate parameters using them, where in Fig. 2 shows a family of dependences of sliding friction coefficients k _s on the value of longitudinal slip S, presented as odd functions k _s (S)=-k _s (-S) for various surfaces with maximum values

.

(1≤i≤4 для 4-х колесной схемы) шин и передаваемые силы при разгонах, торможениях и поворотах, существенно зависят от целого ряда определенных факторов и могут изменяться в достаточно широких пределах.The experience gained as a result of studies of the properties of tires shows that in real operation, the values of the coefficients of sliding friction

(1≤i≤4 for a 4-wheel scheme) tires and the transmitted forces during acceleration, braking and cornering significantly depend on a number of specific factors and can vary within a fairly wide range.

, относятся:Among the main factors that significantly affect

, relate:

- the speed of the longitudinal sliding of the tire;

- the composition of the rubber compound of the tire tread material;

- depth and shape of the tire tread pattern;

- tire and road surface temperature;

- tire profile width;

- air pressure in the tire;

- condition of the road surface;

- depth of the water layer on the surface of the road surface;

- the speed of the longitudinal movement of the center of mass of the car.

современных шоссейных шин ограничен сверху величиной порядка 1, 2 для сухого асфальтобетона, а для сликов может доходить до значений 1, 8 и более, снизу эти значения ограничены величиной порядка 0,05 в случае движения по таящему льду. В режиме аквапланирования величина

может снижаться практически до нулевых значений.The range of changes in the maximum values of the coefficients of sliding friction

of modern road tires is limited from above by a value of the order of 1.2 for dry asphalt concrete, and for slicks it can reach values of 1, 8 or more, from below these values are limited by a value of the order of 0.05 in the case of movement on melting ice. In hydroplaning mode, the value

can drop to almost zero.

от скорости V_m на различных покрытиях.In FIG. 3 shows the dependence

on the speed V _m on different surfaces.

сопровождаются соответствующими изменениями граничной скорости пробуксовок ведущих колес, граничных скоростей заноса и сноса колес задней и передней осей, граничных значений безопасных дистанций между попутными ТС и тормозного пути.Changes

are accompanied by corresponding changes in the limiting speed of slippage of the driving wheels, the limiting speeds of skidding and drifting of the wheels of the rear and front axles, the limiting values of safe distances between passing vehicles and the stopping distance.

максимальных значений коэффициентов трения скольжения в соответствии с третьим законом Ньютона и основана на уравнении равенства тягово-тормозных сил и сил трения скольжения.The identification of sliding friction coefficients consists in the formation of adequate estimates

maximum values of sliding friction coefficients in accordance with Newton's third law and is based on the equation of equality of traction-braking forces and sliding friction forces.

F _i - traction-braking force acting on the ie wheel;

F _Ni - normal component of the dynamic load on the wheel ie;

k _Si - sliding friction coefficient of the i-ro wheel.

Sliding friction coefficients in longitudinal k _Sdi and transverse k _Sqi directions interconnected by the restriction of the "Kamm circle":

- топовое (максимальное) значение коэффициента трения скольжения i-го колеса.

- top (maximum) value of the sliding friction coefficient of the i-th wheel.

Fig. 4 contains a computational block of the algorithm for the maximum values of the sliding friction coefficients of the wheels of the vehicle, which implements the following steps of the method:

14 - data entry of the tuning parameters of the mathematical model of the vehicle;

15 - input of data on wheel speeds;

16 - calculation of vehicle movement parameters;

17 - calculation of the normal components of the dynamic load on each wheel;

18 - calculation of traction and braking forces acting on each wheel; 19 - solution of the inverse problem of piecewise linear approximation of the coefficient of sliding friction;

20 - filtering estimates of the maximum values of the coefficients of sliding friction of the wheels;

21 - data output to external devices.

The input of the tuning data of the parameters of the mathematical model of the vehicle and the tires used is performed once in the input-output block 13 of the input of the tuning data when setting up the system in cases of making changes, for example, when replacing tires from summer to winter or vice versa.

Changes to the seasonal settings of the parameters of the tires used are performed automatically when the commands "Summer" or "Winter" are entered from the data input device.

The signals generated by the pulse sensors 1, 2, 3, 4 wheel speeds of the vehicle, register and transmit them through the interface 6 to the microcontroller device 5 information processing.

In the microcontroller information processing device 5, the calculation of the motion parameters of the wheeled vehicle is carried out according to the known method of indirect measurements (See _RF Patent No. transverse accelerations (a _m , a _q ), angle of rotation of the steered wheels (ϕ _c ) and longitudinal slips of the wheels (S _i , 1≤i≤4).

In block 9 for calculating the normal components of dynamic loads, the values of wheel loads are calculated. The normal components of the wheel load ie F _Ni are defined as:

m ₁ , m ₂ , m ₃ , m ₄ - masses attributable respectively to the front left (i=1), front right (i=2), rear left (i=3) and rear right (i=4) wheel;

g - free fall acceleration;

m _O - the total mass of the car;

a _dT \u003d (a _d -a _T ) - longitudinal traction-braking acceleration of the center of mass;

- тяговое ускорение центра масс;

- traction acceleration of the center of mass;

F _di , 1≤i≤4, - traction force applied to the i-th wheel;

- тормозное замедление центра масс;

- braking deceleration of the center of mass;

F _Ti , 1≤i≤4, - braking force applied to the i-th wheel;

- поперечное ускорение центра масс;

- transverse acceleration of the center of mass;

R _m - turning radius;

b - wheelbase;

a - track width;

h _m - height of the center of mass;

R _d - dynamic radius of the wheels;

a _T - pitch angle;

β _k - angle of roll of the pavement;

k _z1 , k _z2 , k _z3 , k _z4 - coefficients of aerodynamic drag along the vertical axis;

V _m - longitudinal velocity of the center of mass.

Under conditions of movement close to rectilinear (a _q ≈ 0) on a horizontal smooth surface, without longitudinal (a _T ≈ 0) and transverse slopes (β _k ≈ 0) of the road surface and anti-wings, the system of equations (3) is used to calculate in the block 9 normal load components per wheel.

The value of traction-braking acceleration a _dT is determined in block 10 based on the calculation of the distribution of traction-braking forces from the equation of Newton's second law in the form:

where: k _x - drag coefficient;

k _tr - tire rolling friction coefficient.

The values of a _m and V _m included in the vector of motion parameters are measured according to the signals of the sensors 1, 2, 3, 4 wheel speeds, the values of k _x , k _tr and m _o are entered as settings. Under conditions of movement on surfaces close to horizontal (а _Т ≈ 0), the value a _dT is uniquely determined.

The distribution of traction F _di and braking forces F _Ti over the wheels (1≤i≤4) is given by the equations:

K _3i - gains of the i-th brake;

- управляющее воздействие на тормозную систему;

- control action on the brake system;

P _T - pressure in the brake system;

P _Tmax - maximum pressure in the brake system.

The value of U ₃ is determined according to the measurement data a _dT in the form:

a _min - the minimum value of deceleration during braking with the transmission not disabled, set in the tuning data;

a _max - maximum deceleration value.

колеса аппроксимируют в блоке 11 кусочно-линейной функцией вида:The dependence of the coefficient of sliding friction in the longitudinal direction on the magnitude of the longitudinal sliding

the wheels are approximated in block 11 by a piecewise linear function of the form:

Е, S _Gr1 , S _Gr2 - settings for used tire models in summer and winter conditions (for example, Е=0.005, S _Gr1 =0.15, S _Gr2 =0.3);

a ₀ , b ₀ , are real numbers specified when setting the piecewise linear approximation (for example, a ₀ =0.25, b ₀ =5.0).

The current values of the coefficients of sliding friction k _Si are determined from the equation (1) of Newton's 3rd law, corresponding to the equality of the external forces acting on the wheels and the forces of sliding friction.

в дискретном времени определяют как решение в блоке 11 обратной задачи кусочно-линейной аппроксимации k_Si (Si):Estimates of the maximum values of sliding friction coefficients

in discrete time is defined as a solution in block 11 of the inverse problem of piecewise linear approximation k _Si (Si):

и

.Estimates of the maximum (top) values of the sliding friction coefficients of the driven wheels are not determined in the modes of acceleration and movement at a constant speed (a _dT > 0) and are set equal to the estimates of the driving wheels of one side

and

.

The filtering of the estimates of the maximum values of the coefficients of sliding friction of the wheels in order to limit the influence of measurement noise on the results is performed in block 12 for filtering the estimates according to the known algorithms of restrictions on the allowable range and smoothness on the restrictions on the first and second derivatives.

The final estimate of the maximum value of the sliding friction coefficients of the wheels is determined as:

Data output to an external device is performed, for example, to a visual display device and/or motion control units for use as input for providing safe control, traction, brakes and steering.

The considered algorithm for identifying the maximum values of the sliding friction coefficients of the wheels was implemented programmatically in block 12 for filtering the estimates of the maximum values of the sliding friction coefficients of the wheels for driving problems and registered with Rospatent (Certificate of official registration of computer programs No. ", 2007).

Among the advantages, that is, the technical results achieved by the proposed system, are the following:

- identification of the maximum values of the sliding friction coefficients of tires is performed during acceleration, movement at a constant speed and braking;

- low cost of technical means, due to the absence of the need to introduce additional physical sensors of primary information necessary to solve the set technical problem;

- the possibility of functioning in an incomplete configuration of wheel speed sensors, including failures of one or two sensors from different sides of the vehicle;

- reduced power consumption due to the absence of additional information sensors;

- higher operational reliability due to the minimum configuration of the technical means used, including primary information sensors;

- no influence of the state of the environment, including illumination, precipitation, fog, etc., on the efficiency of the system.

Based on the foregoing, the following can be stated.

The stated technical problem is solved by technical means and can be used in the proposed form both in new and in vehicles in operation in the national economy, therefore, the proposal meets the criterion of the invention "industrial applicability".

The proposal differs from the known system, therefore, meets the criterion of invention "novelty".

The use of all known and new actions of the method of operation of the system of the proposed technical solution in the creation and modernization of active safety systems of vehicles makes it possible to achieve new, previously unknown technical results, therefore, it meets the criterion of the invention "inventive step".

List of positions

1. wheel speed sensor 1,

2. 2 wheel speed sensor,

3. 3 wheel speed sensor,

4. 4 wheel speed sensor.

5. microcontroller device 5 information processing

6. communication lines with the device 6 for interfacing with the microcontroller device 5 for information processing

7. block 7 for analyzing the signals of sensors 1, 2, 3, 4 of the wheel speed,

8. block 8 for estimating vehicle motion parameters,

9. block 9 for calculating the normal components of dynamic loads acting on each wheel,

10. block 10 for calculating the distribution of traction and braking forces acting on each wheel,

11. block 11 for solving the inverse problem of piecewise linear approximation of the coefficient of sliding friction,

12. block 12 filtering estimates of the maximum values of the coefficients of sliding friction of the wheels,

13. block 13 for input-output of data to external display devices for the driver and input of tuning data, a computing unit for the algorithm for the maximum values of the coefficients of sliding friction of the wheels of the vehicle, which implements the following steps of the method

14. data entry of the tuning parameters of the mathematical model of the vehicle;

15. data input about wheel speeds;

16. calculation of vehicle movement parameters;

17. calculation of the normal components of the dynamic load on each wheel;

18. calculation of traction and braking forces acting on each wheel;

19. solution of the inverse problem of piecewise linear approximation of the coefficient of sliding friction;

20. filtering estimates of the maximum values of the coefficients of sliding friction of the wheels;

21. data output to external devices.

Claims (1)

The system for identifying the maximum values of the sliding friction coefficients of the vehicle wheels contains sensors (1, 2, 3, 4) of wheel speeds electrically connected to the microcontroller device (5) for processing information through communication lines with the device (6) for interfacing with the microcontroller device (5 ), a microcontroller device (5) for processing information includes: a block (7) for analyzing signals from sensors (1, 2, 3, 4) of wheel speeds, a block (8) for estimating vehicle motion parameters, a block (9) for calculating normal components of dynamic loads acting on each wheel, block (10) for calculating the distribution of traction-braking forces acting on each wheel, block (11) for solving the inverse problem of piecewise linear approximation of the coefficient of sliding friction, block (12) for filtering estimates of the maximum values of coefficients of sliding friction of the wheels, block (13) for outputting data to external display devices for the driver and inputting setup data, different which in the system block (9) for calculating the normal components of dynamic loads, block (10) for calculating the distribution of traction-braking forces, block (11) for solving the inverse problem, block (12) for filtering, block (13) for data input-output are executed based on a microcontroller device (5) with the possibility of software execution of a block (9) for calculating the normal components of dynamic loads, a block (10) for distributing traction-braking forces, a block (11) for solving an inverse problem, a filtering block (12), an input block (13) - data output, the block (9) for calculating the normal components of dynamic loads acting on each wheel is configured to take into account the influence of longitudinal and transverse accelerations on the distribution of normal components of dynamic loads, the block (10) for distributing traction-braking forces is configured to take into account the distribution of traction forces from the engine and transmission and from the brake system along the wheels, block (11) for solving the inverse problem is made with the possibility of forming estimating the maximum values of the sliding friction coefficients of the wheels in the slip range of the stable section of the typical dependence of the friction force on the slip, the block (12) for filtering the estimates is designed to reduce the influence of measurement noise on the identification results by eliminating data outliers as a result of checking by ranges and data smoothness, satisfying the conditions of restrictions on the first and second derivatives, the data input-output block (13) is configured to promptly input the tuning data of the used mathematical model for tires of different models and output the output data to the driver and functional blocks of the active safety system.

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