RU2465564C1 - Device for determination of wheel adhesion with road surface properties in laboratory conditions - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: pneumatic wheel is installed in bearing assembly on projecting shaft having hinged bearing permitting to engage pneumatic wheel due to forces of friction with backing plate on which road surface sample is placed. The backing plate is spinned up using electric motor on the shaft of which it rigidly fixed. Slip angle of pneumatic wheel is simulated by angular displacement of backing plate centre relative to longitudinal axis of projecting shaft, and wheel movement speed is simulated by angular velocity of electric motor shaft. Force impact of wheel engagement with backing plate forces perceived by projecting shaft is measured by force sensor. Engagement forces determine pneumatic wheel and backing plate acceleration and runout processes therefore for determination of kinematic characteristics of pneumatic wheel and backing plate rotation in the device there are sensors for measuring these characteristics. According to kinematic characteristics of backing plate and pneumatic wheel, to amount of force impact on projecting shaft the value of pneumatic wheel longitudinal adhesion and lateral adhesion factor is estimated.

EFFECT: enhancement of device functionality and scope of its application, approximation of test conditions to actual operation conditions.

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Description

The invention relates to testing equipment and can be used to study the mechanism of adhesion of a car wheel to the road surface.

The adhesion of the wheel to the roadway depends on a large number of different factors, and first of all on the road surface and its condition, on the nature of the interaction of the wheel with the road [1]. The adhesion of the wheel to the road surface depends on the condition of the car tire, its construction, material or air pressure in it, the loads on the wheel, the speed and slipping of the wheel [2, 3] and is characterized by the coefficient of adhesion. In this case, the friction coefficient is subdivided into the longitudinal friction coefficient φ _x when the wheel moves with longitudinal sliding and slipping and the lateral friction coefficient φ _y when the wheel moves at an angle to its rolling plane, i.e. when the wheel rotates at the same time and slides in the lateral (transverse) direction.

There are a large number of various methods and instruments for experimental determination of the coefficient of adhesion; some of them are described in [4].

Devices for determining longitudinal grip (coefficient φ _x ), as a rule, are a trolley, the wheels of which can determine the force of adhesion of the wheel to the road, examples can be examples of AS USSR No. 630982, No. 976778, No. 1033935, No. 1567917, No. 1604881, No. 1281960. As analogues of devices for the experimental determination of the longitudinal coefficient of adhesion, you can specify the device according to the patents of the Russian Federation for invention No. 2112829, No. 2134415, No. 215633, No. 2211891 and others.

For devices used to measure the coefficient of lateral adhesion, there are specific features. These trolleys recreate the rolling conditions of the wheel under the action of lateral force, that is, they imitate the phenomenon of a car skidding without braking. Moreover, with the lateral sliding of the wheels take the coefficient of lateral adhesion

Thus, currently there are no stands (devices) that would allow us to determine the values of the coefficients of the longitudinal and transverse coefficient of adhesion of the wheel with the roadbed. Thus, the disadvantage of the known stands and devices designed to determine the characteristics of the adhesion of the wheel to the road, is the limited functionality: they do not allow testing at different speeds of rotation of the wheel and various conditions of the roadway.

The prototype adopted a stand for determining the coefficient of adhesion of a wheel with a road surface according to as USSR No. 1151640 [5], comprising a bed, a pneumatic wheel placed on the shaft, connected by means of a transmission system with an electric motor, a trolley with dynamometric and measuring devices mounted on the bed, while the wheel shaft is placed on a movable frame. This device, like analogues, does not allow determining the coefficients of longitudinal and transverse adhesion during the tests, since the device has only one measurable quantity that determines the value of the longitudinal adhesion coefficient and which is characterized by the movement of a spring-loaded trolley under the influence of a wheel. The device does not allow to determine the law of change in the coefficient of adhesion of the wheel to the roadbed from changes in the speed of rotation of the wheel during its braking.

The purpose of the invention is the expansion of the functionality of the device and its scope, as well as the approximation of the test conditions to the actual operating conditions.

This goal is achieved by the fact that the device for determining the coefficients of adhesion of road surfaces with a car wheel (longitudinal grip coefficient and lateral grip coefficient) in a laboratory environment contains a bed, a pneumatic wheel placed on a power shaft, which is connected through a hinge to a dynamic platform of the device located in roller guides. At the same time, the roller guides are mounted on a stand that is mounted on the bed, and the dynamic platform itself is unintentional from movements in the roller guides with a force sensor, which makes it possible to determine the force exerted along the axis of the power shaft. The device has a trolley with an electric motor mounted on it, on the axis of which a disk with a pavement sample placed on it is mounted, and the trolley itself is mounted on skids with a system for fixing the position of the trolley relative to the skids. The skids themselves, which are made in the form of a rigid power frame, have the ability to rotate in a horizontal plane on an axis mounted on the bed. The frame with runners has mechanisms for fixing its position relative to the plane of the bed, and the angular position of the runners relative to the longitudinal axis of the bed allows you to simulate the angle of the wheel. The electric motor has a system for controlling the rotation speed of its output shaft, the plane of the supporting disk parallel to the longitudinal axis of the power shaft of the wheel, and the device itself has measuring sensors for determining such kinematic characteristics of the pneumatic wheel and disk as their angular rotational speeds, the number of revolutions made by the output shaft electric motor and pneumatic wheel.

Figure 1 shows the proposed device.

The device comprises a frame 1, a trolley 2 with an electric motor 3 installed in it, and the trolley 2 is made in the form of a slide mounted on a skid frame 4 made in the form of a power flat frame that can rotate about axis 5 along the plane of the bed 1. At the output the shaft 6 of the electric motor 3 has a support disk 7 on which a pavement specimen 8 is fixed. The device comprises a pneumatic wheel 9 mounted by means of a bearing assembly on a power shaft 10 having a hinge joint 11, by means of which the power shaft 10 is mounted on a dynamic platform 12. The dynamic platform 12, by means of guide rollers 13, is mounted on a slider 14, by which it can be moved along the strut 15 moreover, the device has a mechanism for fixing the position of the slider 14 on the rack 15, which is not shown in figure 1. The rack 15 is installed and rigidly fixed perpendicular to the plane of the bed 1. The movement of the dynamic platform 12 along the guides 13 is limited by a force sensor 16, for preloading which the device has a spring 17. The device has a control system for the operation of the electric motor 3, which is also not shown in Fig. 1. The device is equipped with stroboscopes 18 and 19 for determining the angular velocity of rotation of the pneumatic wheel 9 and the supporting disk 7, respectively. To simulate the force of the pneumatic wheel on the roadway, the load 20 is fixed on the power shaft 10.

The stand works as follows. A sample of the pavement 8 is fixed to the disk 7. A load 20 is installed on the power shaft 10. Turning the skid frame 4 on the axis 5 to an angle α set the angle of the wheel 9 γ. As follows from figure 1, α = γ. Moving the slide 2 on the runners 4, set the distance of the contact point of the wheel 9 with the pavement pattern. After these operations, stoppers, not shown in figure 1, fixes the position of the electric motor 3 relative to the runners 4, and the position of the frame-runners relative to the bed 1. After performing these operations, the device is ready for operation. Next, the wheel 9, turning in a vertical plane in the hinge 11, the power shaft 10, is brought out of contact with the sample 8. By turning on the electric motor 3, the disk 7 is brought into rotation, accelerating it to the required, for example, maximum rotation speed, which is measured by the angular velocity sensor and the number of revolutions of rotation 18. The engine is turned off, and the wheel 9 is lowered by means of the power shaft 10 until the pneumatic wheel 9 contacts the specimen 8 mounted on the disk 7. Due to the friction forces, the pneumatic wheel 8 is untwisted and the brake the rotation of the disk 7. The value of the friction forces is determined by the coefficient of longitudinal φ _x and lateral φ _{y of the} adhesion of the pneumatic wheel with the road surface sample, which depend on the speed of the wheel (angular speed of rotation) and the angle of movement. The lateral adhesion force, depending on the lateral adhesion coefficient φ _y , causes the forces acting on the dynamic platform 12 and which are measured by the force sensor 16. The acceleration characteristics of the wheel 9 and the rotor run-out of the electric motor 3 also depend on the values of the longitudinal and lateral adhesion coefficients. The forces measured by the sensor 16, the parameters of the acceleration of the wheel 9 and the parameters of its further braking, the parameters of the acceleration of the rotor of the electric motor 3 and the characteristics of its run-out are judged on the coefficients of longitudinal and transverse adhesion.

The design scheme for determining the coefficients of longitudinal and lateral adhesion is shown in figure 2.

In figure 2, the positions indicated: 1 - supporting disk; 2 - pneumatic wheel; 3 - power shaft; 4, 5 - guides of a dynamic platform; 6 - force sensor; 7 - bed; 8 - cargo.

At the contact point of the wheel 2 with the disk 1, the longitudinal and transverse friction forces arise, respectively, Φ ^τ and Φ ⁿ . The main calculated dimensions are shown in figure 2, there are indicated the reaction of the bonds. In accordance with the Coulomb-Amonton law [6] we will have

From geometric considerations, in accordance with the sine theorem, we have

From the bottom figure in figure 2 we will have

For the upper figure, we have the following equilibrium equations

In the system (5), T ₁ and T ₂ are the friction forces in the roller guides of the dynamic platform. N ₁ and N ₂ are normal reactions in roller bearings. Denoting the coefficient of sliding friction in the roller bearings by k, we obtain

From the second equation of system (5) we obtain

then from the third equation of system (5) we obtain

and for N ₁ we get

From the first equation of system (5) we have

where do we get

Having determined from (4) the value of N, for (11) we obtain

In equation (12), R is the force sensor reading. Equation (12) includes both of the desired friction coefficients, φ _x and φ _y . We obtain additional equations for determining the friction coefficients from the equations of motion of the support disk (1) and the pneumatic wheel (2).

We write the equation of motion of the support disk (1) in the form

where ε ₁ is the angle of rotation of the support disk (1);

I ₁ - moment of inertia of the reference disk;

M _mp1 - moment of resistance (friction in the bearing units);

M ₁ = Δsinβ · N · φ _y ;

M ₂ = rcosα · N · φ _x ;

Δ, α, β, r - geometric characteristics of the device.

The equation of motion of the pneumatic wheel will be

where I ₂ is the moment of inertia of the pneumatic wheel;

M _mp2 is the moment of resistance (friction in the bearing units);

ε ₂ - the angle of rotation of the pneumatic wheel;

The change in the angular velocity of rotation of the support disk will be obtained from equation (13)

where C ₁ - const integration.

Assuming that when the electric motor 3 (Fig. 1) is turned off, at the moment of contact of the pneumatic wheel 2 (Fig. 2) with the support disk 1 (Fig. 2), the angular velocity of rotation of the support disk is ω ₀ , we obtain C ₁ = ω ₀ I ₁ .

The supporting disk 1 (figure 2) after contact with it of the pneumatic wheel 2 (figure 2) is braked, and the pneumatic wheel itself is untwisted in accordance with equation (14), from which we get

where C ₂ is the integration constant.

Since at the initial moment of time the pneumatic wheel was stationary, then C ₂ = 0.

After some time, the linear speeds at the contact point of the support disk 1 and the pneumatic wheel 2 (figure 2) are equalized. The equality of speeds at the point of contact will be equal

To determine the velocity equalization time t *, we have

опорного диска 1 и угловую скорость пневматического колеса 2 (фиг.2)

в момент выравнивания скоростей в точке контакта определим из уравнений (15) и (16)Angular velocity

the supporting disk 1 and the angular velocity of the pneumatic wheel 2 (figure 2)

at the moment of velocity equalization at the contact point, we determine from equations (15) and (16)

where t * is determined from equation (18).

The kinetic energy at time t * in the system will be equal to

Kinetic energy W is spent on overcoming the resistance forces

- угол проворота опорного диска;Where

- angle of rotation of the support disk;

- угол проворота пневматического колеса.

- angle of rotation of the pneumatic wheel.

и

- углы проворота опорного диска и пневматического колеса с момента выравнивания скоростей до полной остановки опорного диска 1 и пневматического колеса 2 (фиг.2).

and

- the rotation angles of the support disk and the pneumatic wheel from the moment of speed equalization to the complete stop of the support disk 1 and the pneumatic wheel 2 (figure 2).

и

.From (17) we obtain the coupling equation for the rotation angles

and

.

From equation (19) we obtain

and from (20) we will have

Then from equation (22) we obtain the expression for calculating the angle of rotation of the support disk

до момента выравнивания скоростей опорного диска и пневматического колеса в точке контактаFrom equation (15) you can get the angle of rotation of the support disk 1 (figure 2)

until the speeds of the support disk and the pneumatic wheel are aligned at the point of contact

Then the total number of revolutions that the support wheel made before it stopped completely would be equal to

In accordance with figure 1, the parameter n ₁ can be determined by the readings of the sensor (18). Equation (28) and equation (12) allow us to determine the values of the friction coefficients φ _x and φ _y .

As noted in [1], the coefficient of lateral and longitudinal adhesion depends on the rolling speed of the wheel along the roadbed. The device, the circuit of which is shown in figure 1, allows you to study changes in the coefficients of longitudinal and lateral adhesion depending on the rolling speed of the wheel and the angle of its removal. The force sensor allows in accordance with equation (12) to determine the law of change in the set of coefficients of friction of the system from time to time. By measuring the rotation angles and rotation angles of the support disk 7 and the pneumatic wheel 9 in FIG. 1 using rotation sensors 18 and 19, the force R can be applied at the corresponding time points to the measured kinematic characteristics of the support disk and the pneumatic wheel, which allows one to obtain an additional equation for determine the desired parameters. At the same time, the basic characteristics of the rotation of the supporting disk should be taken as the main indicators, and the characteristics of the rotation of the pneumatic wheel are calibration characteristics that allow us to evaluate the correctness of the measurements.

Thus, in contrast to the prototype, the proposed device allows in one experiment to determine the law of variation of the coefficient of longitudinal and lateral adhesion depending on the rolling speed of the pneumatic wheel along the support disk and depending on the angle of the wheel.

Literature

1. Ilarionov V.A., Pchelin I.K., Kalinin E.I. Tire grip and road safety. - Moscow, MADI, 1989 .-- 77 p.

2. Petrov M.P. The work of the car wheel in braking mode // Zap. Sib. book Publishing House, Omsk Branch, 1973. - 123 p.

3. Porozhnyakov B.C. Estimation of tire adhesion to automotive coatings. - M.: Higher School, 1967. - 71 p.

4. Berezuev M.N., Kuznetsov N.P., Soloviev S.M., Yurtikov R.A. Modeling in the reconstruction of the collision mechanism of a car with an obstacle. - Moscow - Izhevsk: Research Center "Regular and chaotic dynamics", 2005. - 208 p.

5. A bench for determining the coefficient of adhesion of pavements in laboratory conditions. / Copyright certificate No. 11516440, KPI Е01С 23/07 // Malyshev A.A., Khristolyubov N.N., Publ. 04/23/85 Issue No. 15.

6. Dobronravov VV, Nikitin NN The course of theoretical mechanics: a Textbook for mechanical engineering. specialist. universities. - 4th ed., Revised. and add. - M .: Higher. School, 1983, 575 pp.

Claims (1)

A device for determining the adhesion properties of a road-covered wheel in laboratory conditions, comprising a bed, a pneumatic wheel placed by means of a bearing assembly on a power shaft, a trolley with an electric motor, a load cell, angular velocity sensors of rotation of a pneumatic wheel and an output shaft of an electric motor, characterized in that to determine the coefficient of longitudinal adhesion of the wheel to the road and the coefficient of transverse adhesion of the power shaft with pneumatic with a wheel through a hinge in the vertical plane it is mounted on the dynamic platform of the device, which is a tubular frame located in roller guides located in the vertical plane on the slider, which can be moved around the device rack, which is fixed in the device perpendicular to the plane of the bed, and the slider itself has elements of fixing its position on the device rack, while the dynamic platform is involuntarily displaced from movements in the guides by a force sensor, allowing to divide the force exerted on the dynamic platform by the adhesion forces of the pneumatic wheel with the support disk mounted on the axis of the electric motor, the pavement mounted on the disk and the carriage on which the engine is mounted mounted on skids with a system for fixing the position of the carriage relative to the skids, which are made in the form of a rigid power frame that can rotate in a horizontal plane on an axis mounted on the frame, and the frame with runners has mechanisms for fixing it along относительно relative to the plane of the bed, and the angular position of the runners relative to the longitudinal axis of the bed allows you to simulate the angle of the wheel, while the electric motor has a speed control system for its output shaft, and the plane of the supporting disk is parallel to the longitudinal axis of the power shaft, and the device itself has measuring sensors to determine kinematic characteristics of a pneumatic wheel and a support disk.

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