Method of determining grip of wheel with airdrome pavement

FIELD: measuring technique.

SUBSTANCE: method comprises determining the force of dynamic braking down of the measuring wheel when its rotation energy is converted into the electric energy as a heat energy at the active load.

EFFECT: enhanced precision.

3 dwg

 

The invention relates to devices and systems for assessing the surface condition runway (runway) airfields, but can also be used to determine the coefficient of adhesion road surface.

Known commercially produced by the Swedish company Saab-Scania device for measuring grip Saab 900/9000 (Method of determining the coefficient of coupling this device shows the log Hoverfoil News 8 No. 9-10 .1-definition of runway friction).

In the known device the maximum value of the coefficient of adhesion (fmax) is determined by measuring the maximum force of adhesion (PSCP. max) measuring wheel with the surface of airfield pavement at wetting of the surface coating and the constant thrashing of the measuring wheel by 15-17%. When this coefficient of friction is calculated by the formula

fmax=PSCP. max/Pg,

where fmax- maximum friction measuring wheel with the surface of the coating;

PSCP. max- adhesive force measuring wheel with his constant stalling;

Pg- normal force load on the measuring wheel.

The disadvantage of this method is that at some latitudes winter prevents wetting of the surface, and the constant thrashing underestimates the maximum value of the adhesion factor (f max).

Another known device is the commercially available "airfield brake cart" ATT-2 ("Device for determining the coefficient of coupling of wheels with airfield floor" - Copyright certificate №630982, CL G01N 19/02. The method of determining the coefficient of coupling is given in the Manual of civil airfields of the Russian Federation ", ed. M., "Air transport", 1955, str-157).

The method of determining the coefficient of coupling of the known device is that when the movement of the measuring trolley due to the difference in the diameters of the leading and measuring wheels connected by a gearbox via a locking clutch, is the movement of the measuring wheel slip relative to the surface of the airfield pavement. The ratio of the diameters of the leading and measuring wheels to enable movement of the measuring wheel with slip 17%.

Due to the measuring wheel slippage occurs maximum longitudinal force of adhesion (PSCP. max). The maximum value of the coefficient of adhesion is calculated by the formula

fmax=PSCP. max/Pg,

where fmax- the maximum value of the coefficient of adhesion;

PSCP. max- longitudinal maximum adhesive force measuring wheel when the slip;

P - normal force load on the measuring wheel.

The disadvantage of this method is the presence of significant errors in determination of the maximum value of the coefficient of coupling, since the movement due to the difference in the diameters of the slave and the measuring wheel is skidding measuring truck - you receive the transverse braking force, and the constant slippage reduces the maximum longitudinal force clutch.

Closest to the claimed invention to the technical essence is "a Device for determining the coefficient of coupling wheel with airfield floor". (Application of the Russian Federation No. 2004101376/11(001331) from 08.01.2004, patent No. 2259669, G01P 15/08), in which the method of determining the coefficient of coupling is closest to the claimed invention. The structural scheme of the device for implementing the known method (prototype) is shown in figure 1.

The said device comprises a measuring trolley 1 and the recording unit 2. Measuring trolley 1 is equipped with a measuring wheel 3 - aviation chassis and driven wheels 17 - car chassis.

In the measuring cart 1 includes:

independent vertical load 6, which provide the normal (vertical) force Rgon the measuring wheel 3;

- locking clutch 4, which is before the carrying out of Areni connect the measuring wheel 3 with gear 5;

the gear 5, which provide the required range of speed of rotation of the rotor of the DC generator 8;

the freewheel 7, which provide the transmission of torque in one direction (from gear 5 to the rotor of the generator 8);

- the DC generator 8, which operates in two modes - starter and generator; in starter mode provides the acceleration of the rotor of the generator 8 to the nominal speed of rotation, which prevents overloading of the measuring wheel 3 at the time of acceleration of the towing vehicle; generator generator mode 8 provide grip force measuring wheel with the surface of the airfield pavement;

- the power key 9, which change the load of the generator 8 in accordance with signals from the control unit 22;

active load 10;

the first 11 and second 12 the angular velocity sensors designed for measuring angular velocities, respectively, measuring 3 and the follower 17 wheels;

- starting resistance 13;

- rechargeable battery 14, which provide the starter generator mode 8;

the voltage regulator 15 supports voltage generator 8 permanent;

the contactor 16 in starter mode connects through the starting resistance 13 and the battery 14 to the generator 8;

- frame measurement is eliki 18;

- measuring element 19, which determine the strength of dynamic braking measuring wheel 3 Rtand measuring trolley 1.

Block register 2 contains:

the calculator 20;

- remote control 21;

the control unit 22;

- memory block 23;

controller 24;

display 25.

The transmitter 20 receives information from the sensors 11 and 12, the angular velocity of rotation, respectively, measuring 3 and the follower 17 wheels and takes away from the measuring element 19 information traction force measuring trolley 1 and the information of the dynamometer power stand when performing calibration of the device. The transmitter 20 in accordance with the software through the control unit 22 controls the power key 9, and the recording and reading information from the memory unit 23 determines the maximum value of the coefficient of adhesion (fmaxwith the airfield surface, determines the speed of the movement, gives the necessary information on the display 25, and reads from the memory unit 23 through the controller 24 information on measurements.

In the known method the maximum value of the coefficient of adhesion (fmax) is calculated by measuring the maximum force longitudinal dynamic braking measuring wheel along the surface of the aerodrome coatings obtained by the transformation as well a constant current generator in the generator mode, when the maximum mechanical strength of adhesion (PSCP. max) measuring wheel is transformed into electrical power and is in the form of thermal energy in the active load, and the friction is calculated by the formula

fmax=PSCP. max/Pg,

where

fmax- the maximum value of the friction wheel with airfield floor;

PSCP. max- maximum longitudinal adhesive force measuring wheel with the surface of the airfield pavement;

Pg- normal force load on the measuring wheel.

Determining in a known manner the longitudinal maximum adhesion factor (fmax) wheels with airfield floor.

The method of determining the coefficient of coupling is divided into two stages - search and tracking.

In the search mode searches for the maximum adhesion forces (PSCP. max) measuring wheel 3 with the surface of the airfield pavement.

In the tracking mode the tracking of the maximum grip force measuring wheel 3 with the coating surface, while the desired adjustment.

The search mode begins with a minimum and uniform increase of the current on the active load unit 10. When this power dynamic braking (Rt) measuring wheel 3 is also proportional the increase.

However, the greatest strength of dynamic braking Ptmeasuring wheel 3 reaches during its slippage. The degree of slippage of the measuring wheel 3 with respect to the surface of airfield pavement is characterized by relative slippage S

S=(ωinISM)/ωin,

where ωin- the angular velocity of the driven wheel 17;

ωISM- angular velocity measuring wheel 3,

(the radii of the measurement and the driven wheels is equal to).

The maximum value of the coefficient of adhesion (fmax) is determined based on the surface condition of the coating relative slip S from 0.1 to 0.2 (10-20%).

In the presence of relative slip S maximum longitudinal force of adhesion (PSCP. max) measuring wheel 3 with the surface of airfield pavement is controlled by the measuring element 19.

When increasing the current on the active load unit 10 readings of the measuring element 19 reaches the maximum value, the search mode ends. Enables the tracking mode, in which in accordance with the software tracked the maximum adhesion (PSCP. max) measuring wheel 3 with the surface of airfield pavement, the maximum value of the coefficient of adhesion (fmax) wycis aetsa by the above formula

fmax=PSCP. max/Pg.

The disadvantage of this method of determining the maximum value of the coefficient of adhesion (fmax) is that in this way, as in known analog methods, there is a constant slippage of the measuring wheel 3 from 10 to 20% of the measured distance.

Due to the constant thrashing the surface of the measuring wheel is heated, the rubber softens and the maximum adhesive force measuring wheel with the surface of the coating decreases (decreases PSCP. maxand, respectively, fmax). More undesirable fixed (specified) slipping of the measuring wheel without taking into account the condition of the surface coating, as is the case in analog ways of measuring the coefficient of adhesion.

To reduce heating of the measuring wheel is sometimes applied wetting of the surface of the coating. But on a dry surface dust and moisture form the lubricant between the wheel and the surface, thereby reducing the measured maximum value of the coefficient of adhesion. Wetting of the surface does not exclude heat measuring wheel and may not always apply. In winter, the wetting of the surface coating is eliminated. The accuracy of determining the maximum adhesion coefficient decreases as well due to the fact that Maxi is the social adhesive force does not have a pronounced character. (RSCP. maxhas a flat top - 2).

The aim of the proposed method is to improve the accuracy of measuring the maximum value of the coefficient of adhesion (fmax).

The goal in "the Way of determining the friction wheel with the airfield coverage is achieved by the fact that in it, as in the prototype, the friction wheel with the airfield coating is determined by the method of dynamic braking when the motor operates in the generator mode, in which the mechanical energy of the brake element (measuring wheel) is transformed into electrical power and is allocated in the form of thermal energy to the active load, and the determined normal (vertical) force load on the measuring wheel (Pg).

Additionally determine the longitudinal traction force measuring wheel with the surface of the aerodrome coating (RSCP) and the coefficient of dynamic braking (k), the maximum value of the coefficient of adhesion (fmax) is calculated by the formula

fmax=(RSCP/Pg)k,

where

fmax- the maximum value of the friction measuring wheel with airfield floor;

PSCP- longitudinal adhesive force measuring wheel with the surface of the coating;

Pg- normal force load to measure concentration of the nutrient wheel;

k - coefficient of dynamic braking, which is calculated when performing calibration of the device, as the ratio RSCP. maxto RSCP

k=PSCP. max/Rscp,

where

PSCP. max- maximum adhesive force measuring wheel.

In the known technical solutions signs, similar to the distinctive features of the claimed method was not found, therefore we can assume that the proposed method corresponds to inventive step.

The use of this method and its implementation will help to improve safety during the landing of aircraft by improving the accuracy of determination of the coefficient of adhesion of aviakassi with the surface of the runway of the airfield.

The essence of the proposed "method of determining the coefficient of coupling wheel with airfield floor" is illustrated by drawings, where:

figure 1 - structural diagram of the device that implements the proposed method of determining the maximum value of the coefficient of adhesion;

figure 2 - chart explaining the method of calculation of the coefficient of dynamic braking - k;

figure 3 - algorithm of the proposed method of measuring the coefficient of adhesion (fmax) wheels with airfield floor.

In the proposed "Method of determining the coefficient of coupling of wheels with Aero is a great floor", as in the prototype, the friction wheel with the airfield coating is determined by the method of dynamic braking when the motor operates in the generator mode, in which the mechanical energy of the brake element (measuring wheel) is transformed into electrical power and is allocated in the form of thermal energy in the active load, and the determine the normal force load on the measuring wheel (Pg).

Additionally determine the longitudinal traction force measuring wheel with the surface of the aerodrome coating (RSCP) and the coefficient of dynamic braking (k), the maximum value of the coefficient of adhesion (fmax) is calculated by the formula

fmax=(RSCP/Pg)k,

where

fmax- the maximum value of the friction measuring wheel with airfield floor;

PSCP- longitudinal adhesive force measuring wheel with the surface of the airfield pavement;

Pg- normal (vertical) force load on the measuring wheel;

k - coefficient of dynamic braking, which is calculated when performing calibration of the device, as the ratio RSCP. maxto RSCP

k=PSCP. max/PSCP),

where

PSCP. max- maximum adhesive force measuring wheel.

For realizatiobuilding method, you use the Device for determination of the friction wheel with the airfield coating", which implements the method of the prototype. Structural diagram of the device shown in figure 1. For the implementation of the proposed method determines the bond strength (PSCP) measuring wheel 3 and the coefficient of dynamic braking (k). PSCPdefine the measurement process, k determines the strength stand during the calibration device. But k and determine in the field. To determine k in field conditions, choose the relatively flat, dry and clean asphalt floor length up to 1 km

Car towing accelerate to the set speed (V), which determines the maximum value of the friction measuring wheel 3 with the surface of the airfield pavement. Speed determined by the angular rate sensor 12 of the driven wheel 17 in accordance with the formula

Vainr,

where Va- the vehicle speed of the towing vehicle, m/s;

ωin- the angular velocity of the driven wheel, rad/s;

r is the radius of the driven wheel, m

In case of equality of the velocities V and Vathe transmitter 20 includes program, which determine the change in the power dynamic braking Ptmeasuring wheel 3 with increasing current JHthe active load unit 10 from the minimum to the maximum value.

In the memory unit 23 writes is:

- the angular velocity sensor 12 of the driven wheel 17;

- the angular velocity sensor 11 of the measuring wheel 3;

- current active load JHblock 10;

- readings of the measuring element 19.

Readings of the measuring element 19 is

Pand-Rt+Pto,

where Rand- power towing measuring trolley 1;

Pt- power dynamic braking measuring wheel 3;

Pto- the force of rolling resistance of driven wheels 17.

When this force of rolling resistance of driven wheels 17 determine on the power stand or calculated by the formula

Pk=GY,

where G is the normal load on the axle of the driven wheels 17;

Y is the coefficient of rolling resistance, which at speeds up to 80 km/h is equal 0,012.

After measurements and processing of the received information are charting changes the power dynamic braking Ptmeasuring wheel from changes in the load current JHin block 10 (Figure 2). In the diagram (Figure 2) there are several specific areas.

When changing the JHfrom 0 to J1accordingly increases the power dynamic braking Ptfrom 0 to a - 2. This slipping of the measuring wheel 3 is missing, because the power dynamic braking Ptless power clutch (PSCPmeasuring wheel 3 with the surface

Pt<PSCP.

At point "a" appears slipping of the measuring wheel 3, while the power dynamic braking Ptbecomes equal to the force of the clutch PSCP

Pt=PSCP=Pg,

where f is the friction measuring wheel with the surface.

With increasing JHthe active load 10 from the J1to J2increases the power dynamic braking Ptfrom "a" to "b" (Figure 2), while increasing and slipping of the measuring wheel 3. At point "b" power dynamic braking reaches the maximum value (Pso max), which is equal to the maximum traction wheels 3 (PSCP. maxsurface coating

Pso max=PSCP. max=fmaxPg,

where fmax- the maximum value of the friction measuring wheel with the surface.

With further increase of JHon the active load of the J2to J3the power of the Pso max(RSCP. max) decreases from "b" to "C" (Figure 2). This is because at the same time with the increase of JHincreased slipping of the measuring wheel 3, the wheel is heated, the rubber softens the power of the Pso max(RSCP. max) decreases, and fmax.

On the obtained values of RSCPand RSCP. maxcalculate to efficient dynamic braking k

k=PSCP. max/PSCP.

If you change the state of the surface coating are changed respectively PSCPand RSCP. maxbut their attitude (factor k) is stored. The ratio recorded in the memory of computer 20, which is then used to calculate the fmax.

The method of determining the maximum grip.

Before determination of the coefficient of coupling is carried out preparatory work (Figure 3):

- toggle "calibration/measurement" on the control panel 21 is installed in the "measure"position;

- include a locking clutch 4;

- buttons of the remote control 21 set the date, number of lanes, direction - set information recorded in the memory unit 23;

- press the start button, control panel 21, while the closed circuit of the switching of the contactor 16 and the power bus of the battery 14 through the starting resistance 13 is connected to the motor 8. The rotor of the electric motor 8 is unwound up to rated speed.

After preparatory work vehicle towing gaining speed V.

The process of determining the maximum adhesion coefficient is divided into two stages - search and tracking.

In the search mode search power dynamic braking Ptthat is the power of the clutch P SCPmeasuring wheel 3 with the coating surface. In case of equality of Ptand RSCPmeasuring wheel 3 starts problemsabout.

In the tracking mode to track the beginning of the measuring wheel slippage. This ensures the equality of forces Ptand RSCP.

The search mode starts with the minimum and uniform increase of the current, JHthe active load unit 10. When this power dynamic braking measuring wheel 3 is also proportional to grow (Figure 2). When the power of the Ptbecomes equal to the power PSCPappears slippage of the measuring wheel. Slippage is fixed according to the angular velocity sensors 11 and 12. This search mode is finished.

In the tracking mode provide tracking start thrashing measuring wheel 3. Information sensors 11 and 12 (measuring 3 and the follower 17 wheels) is fed to the computer 20, where their readings are compared.

Slipping of the measuring wheel is missing - readings of the angular velocity sensors 11 and 12 are equal to each other. In this case, the transmitter 20 to the control unit 22 receives the signal increase in the load on the generator 8. The signal increase of the load control unit 22 enters the power key 9, which increases the load current of the unit 10. Increases the load on the generator 8, uvelichivaet the power dynamic braking measuring wheel 3, with the advent of slippage which increase the current on the active load unit 10 is terminated.

If slipping of the measuring wheel 3 is greater than the specified value, then decrease the current of the active load unit 10, respectively, reduces the load on the generator 8, reduced power dynamic braking measuring wheel 3, reduces slippage. When the desired value of slip further reduction of the load current of the unit 10 is terminated.

In accordance with the software of the computer 20 to provide the specified minimum range of slip - nbwithin which determine the strength of dynamic braking Pt(RSCP), with Pt=PSCP.

The maximum friction measuring wheel with the surface of airfield pavement is defined as

fmax=(RSCP/Pg)k.

The proposed method of determining the maximum value of the friction wheel with the surface of the aerodrome coating prevents slipping of the measuring wheel in the process of measurement except for fixing the beginning of the slippage in the specified minimum range - nbthat increases the accuracy of determining the maximum value of the coefficient of adhesion. In the search modes and tracking more precisely defined the Ute and track longitudinal grip force R SCPmeasuring wheel, since the beginning of his thrashing is pronounced and is determined by the minimum range thrashing nbwith greater accuracy. The proposed method does not require wetting the surface. The measurements are performed on the traces of the main pillars of the aircraft at any time of the day regardless of the surface condition of the airfield pavement. Increases the accuracy of measurements, increases safety for flight operations.

The method for determining the friction wheel with airfield coating by the method of dynamic braking when the motor operates in the generator mode, in which the mechanical energy of the brake element (measuring wheel) is transformed into electrical power and is allocated in the form of thermal energy in the active load, and the determine the normal force load on the measuring wheel (Pg), characterized in that it further determine the longitudinal traction force measuring wheel with the surface of the aerodrome coating (RSCP.) and the coefficient of dynamic braking (K), the maximum value of the coefficient of adhesion (fmax.) is calculated by the formula:

fmax.=(RSCP./Pg)k,

where fmax.- the maximum value of the friction measuring the CSOs wheels with airfield coating;

PSCP.- longitudinal adhesive force measuring wheel with the surface of airfield pavement, measured at the beginning of his thrashing;

Pg- normal force load on the measuring wheel;

k - coefficient of dynamic braking, which is calculated when performing calibration of the device, as the ratio Rscpma.to RSCP.

k=Pscpma./PSCP.,

where Rscpma.- longitudinal maximum adhesive force measuring wheel.



 

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FIELD: engineering of equipment for friction tests.

SUBSTANCE: as sample holder a shaft is used, which is connected by means of connecting rod mechanism to swinging movement drive, made with possible setting of shaft rotation angle and its rotation speed during rotation for given angle. On top of sample a counter-sample is mounted with its own holder. Sample loading unit abuts by rollers on counter-sample holder. Measuring system includes forces indicator, connected to counter-sample holder, sample movement indicator, connected to its holder, indicator of load output, connected to samples loading unit, optical-mechanical indicators, each one of which is made in form of disk with slits pinned onto axis of arrow of appropriate indicator between emitter and photo-detector, and is connected to computer through mouse port.

EFFECT: increased trustworthiness and precision of tribological characteristics of round and spherical bodies during rotation thereof.

6 cl, 3 dwg

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