RU2259569C1 - Device for determining engagement coefficient of wheel with airstrip covering - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: device has measuring cart and registration block. Measuring cart has measuring wheel, blocking sleeve, reducer, measuring element and measuring cart frame. Measuring wheel by blocking sleeve is mechanically connected to reducer, registration block has computer and control panel, which is connected to first input of computer, and output of measuring element via flexible cable is connected to second input of computer. Measuring cart additionally has independent load, free drive sleeve, direct current generator, force keys block, active load block, first and second angular speeds sensors, launch resistance, accumulator battery, voltage adjuster, contactor, following wheels.

EFFECT: higher precision.

5 dwg

Description

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

Known pendulum type decelerometer used to determine runway adhesion coefficient. It consists of an air-damped pendulum connected to an arrow showing negative acceleration.

To measure the coefficient of adhesion, the car accelerates to a set speed, then the driver presses the foot brake pedal. The decelerometer pendulum, together with the locking arrow, deviates in the direction of travel. The value of the negative acceleration is read. By simple calculations, the coefficient of adhesion is determined. This device has significant errors in determining the coefficient of adhesion (the design and operation of the decelerometer are given in the "Operation Manual for Civil Aerodromes in the Russian Federation" Ed. M. "Air Transport", 1955, p. 152).

Another well-known device is the Saab 900/9000 adhesion coefficient measurement system, commercially available by the Swedish company Saab-Scania (for a description of the system’s operation, see Hoverfoil News, 1977, No. 8-10-10.1, definition of runway adhesion coefficient.

The known device is located on a car and incorporates a measuring wheel connected through a gearbox to the driving wheels of the car, a longitudinal force sensor, a vertical load, a vertical load sensor, a control panel, a display, a speed sensor, a computer for measurement and calculation, a water tank for wetting runway surfaces during measurements.

However, this device has a number of significant disadvantages:

- in the known device, the slipping of the measuring wheel is constant - without taking into account the status of the runway, which introduces an error in the measurement of the coefficient;

- slip of driving wheels is not taken into account, which also increases measurement errors;

- high cost of operation.

Closest to the claimed invention in technical essence is the commercially available "Airfield brake trolley" ATT-2.

(The design and operation of the "Airfield Brake Cart" is given in the "Operation Manual for Civil Aerodromes of the Russian Federation, ed. M" Air Transport ", 1955, pp. 154-157).

The known prototype device (Figure 1) contains a measuring trolley 1 and a registration unit 2, which contain a measuring wheel 3, a locking clutch 4, a gearbox 5, a measuring element 6, a calculator 7, a control panel 8, a measuring device 9, the frame of the measuring trolley 10 , the center link of the drawbar 11, the side link 12, the guide link 13 and the drive wheel 14.

The work of a known device.

The principle of the known device is that when the measuring trolley 1 moves due to the difference in the diameters of the driving 4 and measuring 3 wheels connected by a reducer 5 through the blocking clutch 4, the measuring wheel 3 moves with slipping relative to the surface of the runway of the airfield.

The ratio of the diameters of the driving 4 and the measuring 3 wheels provides the movement of the measuring wheel 3 with slippage in the range of 11-17%.

Due to the slipping of the measuring wheel 3, a longitudinal traction force occurs. The amount of adhesion depends on the state of the coating.

The specified longitudinal adhesion force applied to the frame 10 of the measuring cart 1 in the plane of rotation of the measuring wheel 3 causes the frame 10 of the measuring cart 1 to rotate relative to its center of gravity by a certain angle, depending on the longitudinal adhesion force.

The rotation of the frame 10 of the measuring trolley 1 prevents the guide rod 13 of the measuring device 6, pivotally connected to the lateral link of the drawbar 12.

The force transmitted by the lateral draft of the drawbar 12 from the frame 10, the guide rod 13 causes the deformation of the measuring element 6.

The sensor signal of the measuring element 6 is supplied to the calculator 7 of the registration unit 2.

The calculated value of the coefficient of adhesion (φ) is recorded by the device 9.

The control panel 8 determines the mode of operation of the calculator 7.

A disadvantage of the known device is the presence of a significant error in determining the coefficient of adhesion φ.

The adhesion coefficient φ is determined during the movement of the measuring trolley 1.

The operator monitors the readings of the arrow of indicator 9 and writes the numerical value of the coefficient of adhesion φ to the log, which does not exclude subjective error.

Measuring 3 and driving 14 wheels have both longitudinal and lateral sliding, which also increases the measurement error.

The aim of the proposed device is to increase the accuracy of measurements of the adhesion coefficient φ of the wheel with an airfield coating and the introduction of automation of measurements.

The goal in the “Device for determining the coefficient of adhesion with the airfield coating” is achieved by the fact that it, as in the prototype, contains a measuring trolley and a registration unit.

The measuring trolley comprises a measuring wheel, a locking sleeve, a gearbox, a measuring element and a measuring trolley frame.

In this case, the measuring wheel is mechanically connected to the gearbox by a blocking clutch.

The registration unit contains a computer and a control panel, which is connected to the first input of the computer.

The output of the measuring element via a flexible cable is connected to the second input of the calculator.

In addition, the measuring trolley includes an independent load, a freewheel, a DC generator, a power switch unit, an active load unit, first and second angular velocity sensors, a starting resistance, a battery, a voltage regulator, a contactor, and driven wheels.

In this case, an independent load is normally connected to the measuring wheel. A freewheel coupling connects the gearbox to the rotor of the DC generator. The power bus of the battery through the contactor and the starting resistance is connected to the power input / output of the DC generator, the power input / output of which is connected to the active load unit through the power switch block, and also connected to the input of the DC generator, which is the input of its winding, through the voltage regulator excitement.

The second output of the battery is connected to the second input of the contactor.

The measuring and driven wheels are connected respectively to the first and second angular velocity sensors, the driven wheels are connected to the frame of the measuring trolley, which is connected to the vehicle through the measuring element.

The registration unit further comprises a control unit, a memory unit, a display and a controller.

The input / output port of the calculator is connected to the memory unit, and the first, second, and third outputs of the calculator are connected respectively to the display, control unit, and controller through which communication with external devices is performed.

The measuring trolley is connected by a flexible cable to the registration unit, while the outputs of the first and second angular velocity sensors are connected to the third and fourth analog inputs of the computer, the output of the control unit is connected to the second input of the power switch unit, and the second contactor output and the power bus outputs of the DC generator and the battery are connected respectively to the first and second inputs of the control panel, the fifth free analog input of the calculator is provided for connecting a dynamo Etra power stand (during device calibration).

The maximum value of the coefficient of adhesion (φ _max ) is calculated by measuring the maximum longitudinal dynamic braking force of the measuring wheel on the surface of the airfield coating obtained when the DC generator is in the generator mode, when the maximum mechanical adhesion force (P _scc.max ) of the measuring wheel is converted into electric and is released as thermal energy in the active load unit.

Cohesion coefficient (φ _max ) is calculated by the formula

φ _max = P _spp.max / P _g ,

where φ _max - the maximum value of the coefficient of adhesion of the wheel with an airfield coating;

P _scp.max - maximum traction force of the measuring wheel with the surface of the airfield coating;

R _g - normal load force on the measuring wheel.

Through the controller, communication with external devices is carried out continuously through radio communications or after measurements, the information about the surface condition of the runway is copied to a portable memory unit for detailed analysis and documentation at the control center of the aerodrome.

In the known technical solutions, features similar to the distinguishing features of the claimed device are not found, as a result of which it can be considered that the proposed device corresponds to the inventive step.

The use of this device in its implementation will improve safety during aircraft landing by increasing the accuracy of determining the coefficient of adhesion of the aircraft chassis to the surface of the runway of the airfield.

The essence of the proposed "Device for determining the coefficient of adhesion of the wheel with an airfield coating" is illustrated by drawings, which show:

figure 1 is a structural diagram of a prototype;

figure 2 is a structural diagram of the proposed device;

figure 3 is a typical diagram of a power stand for determining the dynamic braking force (P _t ) of the measuring wheel;

figure 4 is a diagram explaining the operation of the proposed device;

figure 5 - algorithm for measuring the coefficient of adhesion (φ _max. ) wheels with an airfield coating.

The proposed "Device for determining the coefficient of adhesion of the wheel with an airfield coating", as well as the prototype, contains a measuring trolley 1 and a registration unit 2. The measuring trolley 1 contains a measuring wheel 3, a locking sleeve 4, a gearbox 5, a measuring element 6 and the frame of the measuring trolley 10.

In this case, the measuring wheel 3 by a locking clutch 4 is mechanically connected to the gearbox 5.

The registration unit 2 contains a calculator 7 and a control panel 8, which is connected to the first input of the calculator 7.

The output of the measuring element 6 via a flexible cable is connected to the second input of the calculator 7 of the registration unit 2.

Additionally, the measuring trolley 1 includes an independent load 15, a freewheel 16, a DC generator 17, a power key block 18, an active load block 18, the first 20 and second 21 angular velocity sensors, a starting resistance 22, a battery 23, a voltage regulator 24, the contactor 25 and the driven wheels 26-1 and 26.

In this case, the independent load 15 is normally connected to the measuring wheel 3.

The freewheel 16 connects the gearbox 5 to the rotor of the DC generator 17.

The power bus of the battery 23 through the contactor 25 and the starting resistance 22 is connected to the power input / output of the DC generator 17, the power input / output of which through the power key block 18 is connected to the active load unit 19, and also connected to the generator input through the voltage regulator 24 DC 17, which is the input of its field winding.

The second output of the battery 23 is connected to the second input of the contactor 25.

Measuring 3 and driven 26-1 wheels are connected respectively to the first 20 and second 21 angular velocity sensors.

The driven wheels 26-1 and 26 are connected to the frame 10 of the measuring trolley, which through the measuring element 6 is connected to the vehicle.

The registration unit 1 further comprises a control unit 27, a memory unit 28, displays 29, and a controller 30.

The input / output port of the calculator 7 is connected to the memory unit 28.

The first, second and third outputs of the calculator 7 are connected respectively to the display 29, the control unit 27 and the controller 30, through which communication with external devices is carried out.

The measuring carriage 1 is connected by a flexible cable to the recording unit 2, while the outputs of the first 20 and second 21 angular velocity sensors are connected respectively to the third and fourth analog inputs of the calculator 7.

The output of the control unit 27 is connected to the second input of the power key unit 18.

The second output of the contactor 25 and the outputs of the power bus of the DC generator 17 and the battery 23 are connected respectively to the first and second inputs of the control panel 8.

The fifth free analog input of the calculator 7 is provided for connecting the dynamometer of the power stand (during calibration of the device).

The maximum value of the adhesion coefficient (φ _max ) is calculated by measuring the maximum longitudinal dynamic braking force of the measuring wheel 3 on the surface of the airfield coating, obtained when the DC generator 17 is in the generator mode, when the maximum mechanical adhesion force (P _SCP.max ) of the measuring wheel 3 turns into electrical energy and is released as thermal energy in the active load unit 18.

The maximum value of the coefficient of adhesion (φ _max ) is calculated by the formula

φ _max = P _spp.max / P _g ,

where φ _max - the maximum value of the coefficient of adhesion of the wheel with an airfield coating;

P _scp.max - maximum traction force of the measuring wheel with the surface of the airfield coating;

R _g - normal load force on the measuring wheel 3.

The design of the proposed device

The proposed device consists of a measuring trolley 1 and a registration unit 2, which are interconnected by a flexible cable.

During measurements, the registration unit 2 is located in the driver's cab of the towing vehicle.

The measuring trolley 1 is equipped with a measuring wheel 3 of the aircraft chassis and two driven wheels 26 and 26-1 of the automobile chassis.

The driven wheels 26 and 26-1 and the measuring wheel 3 are located symmetrically with respect to the thrust of the measuring carriage 1 of the axial line of movement, which ensures track stability during all stages of movement.

The measuring trolley includes an independent vertical load 15, which provides normal (vertical) force (P _g ) on the measuring wheel;

Before taking measurements, the locking wheel 4 connects the measuring wheel 3 to the gearbox 5.

The gearbox 5 provides the necessary range of rotational speed of the rotor of the DC generator 17.

The freewheel clutch 16 provides the transmission of torque in one direction (from the gearbox 5 to the rotor of the generator 17).

The DC generator 17 operates in two modes: starter and generator.

In starter mode, the generator 17 receives power from the battery 23.

In the starter mode, the rotor of the generator 17 is accelerated, which eliminates the overload of the measuring wheel 3 at the time of acceleration of the vehicle.

The generator mode of the generator 17 is provided by the adhesion force of the measuring wheel 3 with the surface of the airfield coating. The DC generator 17 generates a voltage of 20-30 volts, which guarantees its safe operation, and the power generated by it provides the necessary dynamic braking of the measuring wheel 3.

The power key block 18 changes the load of the generator 17 in accordance with the signals coming from the control unit 27. Each of the power keys of the block 18 has its own active load in the block 19.

The voltage regulator 24, when the load is changed by the power switch unit 18, keeps the voltage of the generator 17 constant.

The angular velocity sensors 20 and 21 measure the angular velocity of the measuring wheel 20 and the driven wheel 26-1, respectively.

The measuring element 6 determines the traction force (P _g ) and measuring cart 1.

On the front panel of the control panel 8 there is a “Start” button, a voltage indicator, a “Measurement / Calibration” toggle switch, three buttons for setting the date and time of measurements, as well as a button for registering the lane and direction of movement. In this case, the first and second inputs of the control panel 8 are connected respectively to the "Start" button and the voltage indicator. The control panel 8 determines the mode of operation of the calculator 7.

The calculator 7 is a microcontroller of the PIC 18 family, which is manufactured with FLASH programmable program memory, random access memory, 10-bit analog-to-digital converters, 16-bit timers, a real-time timer and corresponding input, output and information ports and input port / output. The calculator 7 receives information from the sensors 20 and 21 of the angular velocity of rotation of the measuring 3 and driven 26-1 wheels, respectively. It receives from the measuring element 6 the information of the traction force (P _g ) of the measuring cart 1 and the dynamometer information of the power stand during calibration of this device.

The calculator 7 in accordance with the software through the control unit 27 controls the power key block 17, as well as writes and reads information from the memory block 28, determines the maximum value of the coefficient of adhesion (φ _max ) with an airfield coating, determines the speed of movement, provides the necessary information on display 29 and reads from the memory unit 28 through the controller 30 information about the measurements.

Calibration of the proposed device

The calibration of the proposed device is carried out on a typical power stand (figure 3).

The device and the work of the power stand.

The power stand consists of an electric motor 32, a worm 33 and a balanced 34 gearboxes, two rollers 35 of a chain drive 36 and a dynamometer 37.

To realize the full traction force P _{t of the} measuring wheel 3 during dynamic braking, the surface of the rollers 35 is corrugated or coated with friction material. The rollers 35 are connected by a chain gear 36 and are driven into rotation from an electric motor 23 through a worm 33 and balanced 34 gearboxes. The frame of the balanced gearbox 34 under the action of a reactive moment proportional to Р _{т of the} traction force of dynamic braking of the measuring wheel 3 is rotated and acts on the dynamometer 37. According to the dynamometer 37, a conclusion is drawn about the traction force Р _{t of the} dynamic braking of the measuring wheel 3.

Device calibration methodology.

The measuring wheel 3 is mounted on the rollers 35 of the power stand. Dynamometer 37 is connected to the fifth input of the calculator 7 (registration unit 2). The locking clutch 4 (measuring trolley 1) is engaged. The “Start” button on the control panel is pressed 8. The rotor of the DC generator 17 spins up to the rated speed. The electric motor 32 of the power stand is turned on. The measuring wheel 3 spins up to a speed equal to the speed of the measuring carriage 1, when measuring the friction coefficient φ, while the freewheel 16 connects the gearbox 5 with the rotor of the DC generator 17.

It is understood that the circumferential force P _{t of the} measuring wheel 3 is equal to the dynamic braking force loading the dynamometer 37.

The rotation speed of the measuring wheel 3 is determined by the speed of the measuring trolley 1 and is calculated by the formula:

V = n _k r m / s (V = πn _k r / 30 · 36 km / h),

where n _k is the angular velocity of the measuring wheel 3, rad / sec (rpm);

r is the radius of the measuring wheel 3, m;

π-3.14 ...

V is the speed of the measuring carriage 1 (towing vehicle).

The value of V is displayed on the display 29 for monitoring and is entered in the permanent memory of the calculator 7.

At a given rotational speed of the measuring wheel 3, in accordance with the software of the calculator 7, a control code is issued from its output to block 27. In block 27, signals are generated that are fed to the control electrodes of the power keys of block 18. The power spikes of block 18 smoothly change the current of the active load of the block 18 from a minimum (I _{n min} ) to its maximum value (I _{n max} ) with a discrete equal to the least significant bit (Fig. 4.41).

Therefore, the dynamic braking force P _{t of the} measuring wheel 3 will vary from minimum to maximum value (from P _t ^' _min to P _t ^' _max ) (Figure 4 from 38 to 39).

The value of the traction force P _t dynamic braking of the measuring wheel 3 is removed from the dynamometer 37 of the power stand.

According to the measurement results, a table of changes in traction force P _t dynamic braking of the measuring wheel 3 from a change in the code at the input of the control unit 27 is compiled.

The table is entered in the memory unit 28, in the permanent memory of the calculator 7, and is also attached to the documentation for this device.

In this case, the adhesion coefficient measurement range φ is determined from φ ' _min to φ' _max.

D = φ ' _max- φ _min (Fig. 4.40).

where φ is the range of measurement of the coefficient of adhesion;

φ ' _min and φ'max, respectively, the minimum and maximum values of the coefficient of adhesion (obtained by taring).

φ'min = P _t ' _min / P _g (Fig. 4.38); φ ' _max = P _t ' _max / P _g (Fig.4.39).

R _t ' _min and R _t ' _max - respectively, the minimum and maximum value of the traction force RT dynamic braking of the measuring wheel 3, (removed from the danamometer 37.

R _g - independent normal load on the measuring wheel 3.

On the power stand can be determined by the rolling resistance force P _{to the} driven wheels 26 and 26-1 of the measuring cart 1, for which the driven wheels 26 and 26-1 are installed on the rollers 35 of the power stand. The driven wheels 26 and 26-1 are untwisted up to speed V. The dynamometer reading 37 shows the rolling resistance force P _{to the} driven wheels 26 and 26-1. The rolling resistance force P _{to the} driven wheels is entered into the memory unit 28, into the read-only memory of the calculator 7, and is attached to the documentation for this device.

The rolling resistance force P _{to the} driven wheels 26 and 26-1 can be determined by the formula:

P _k = Gf,

where P _to - rolling resistance force;

G is the normal axle load of the driven wheels 26 and 26-1, N (kg);

f is the coefficient of rolling resistance.

The rolling resistance coefficient f at a speed of up to 80 km / h is 0.012.

Determination of the maximum longitudinal grip coefficient (φ _max ) of an aerodrome-coated wheel.

Before determining the coefficient of adhesion, preparatory work is carried out:

- the toggle switch "measurement / taring is set to the" measurement "position;

- the locking clutch 4 is turned on;

- the buttons of the control panel 8 set the date, time of work, lane number, direction of movement along the lane; all of the above is recorded in the memory unit 28 and is accordingly displayed on the display 29;

- the “Start” button is pressed for a few seconds - the contactor 25 circuit is closed. The power bus of the battery is connected to the generator 17. The rotor of the DC generator 17 is untwisted to the rated rotation speed, while the free input clutch 16 disconnects the gearbox 5 from the generator rotor 17.

When the "Start" button is pressed on the voltage indicator of the control panel 8, the voltage of the battery 25 is controlled, and when the generator 17 is in the generator mode, its output voltage. After the preparatory work, the towing vehicle gains a speed V equal to the speed of the measuring wheel 3 when calibrating the device on the power stand.

The speed of movement is determined by the speed of rotation of the driven wheel 26-1

V _a = V; V _a = ω * r ₁ ;

where V is the speed of the measuring wheel 3 on the power stand; m / s;

V _a - towing vehicle speed, m / s;

ω is the angular velocity of the driven wheel 26-1, rad / sec;

r ₁ - the radius of the driven wheel 26-1, m

If the speeds V and V _{a are} equal, the equality signal is displayed on display 29 and the program for determining the maximum coefficient of longitudinal maximum adhesion (φ _max ) of the tire of the measuring wheel 3 with the surface of the airfield coating is turned on.

It should be noted that the driven wheels 26 and 26-1 do not slip, since the strength of their rolling resistance P _{to is} much less than the adhesion force of the driven wheels to the surface of the airfield coating.

P _to (Gf) ≪P _ssp (Gφ),

where P _to - the rolling resistance of the driven wheels 26 and 26-1;

G is the normal axle load of the driven wheels 26 and 26-1;

f is the coefficient of rolling resistance;

φ is the coefficient of adhesion of the driven wheels to the surface of the airfield coating.

If the rotation speeds of the output shaft of the gearbox 5 and the rotor of the generator 17 are equal, the freewheel 16 connects the gearbox 5 to the rotor of the generator 17.

Figure 4 shows the effect of the state of the airfield coating on the adhesion coefficient.

In Fig.4,41 shows changes in traction force P ' _t braking of the measuring wheel 3 on the power stand when the load current in the block 19 from J _min to J _max .

And in FIGS. 4-44, 45, 46 and 47, a change in the traction force P _{t of} braking of the measuring wheel 3, respectively, on a dry, wet, snow-covered and icy surface of the airfield coating.

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

In the search mode, a search is made for the maximum traction force (P _scp.max ) of the measuring wheel 3 with the surface of the airfield coating.

In the tracking mode, tracking the maximum adhesion force of the measuring wheel 3 with the surface of the airfield coating, while making the necessary adjustments.

The search mode begins with a minimum (J _min ) and a uniform increase in current at the active load of unit 19. In this case, the traction force P _{t of} dynamic braking of the measuring wheel 3 will also be proportionally increased.

Suppose that by determining the adhesion coefficient on a wet airfield coating, the load current of the block 19 was increased to J _n1 (Fig. 4), respectively, the traction force P _{t of} braking of the measuring wheel 3 reached the value indicated in point 4 by 48. There is no slipping of the measuring wheel 3 since P _t less than the adhesion force P _SCP wheels with the surface of the airfield coating

R _t ≪Р _ssp

Therefore, the angular speeds of the measuring 3 and driven 26-1 wheels are equal to each other, respectively, n _k = ω.

The readings of the measuring element 6 in this case is equal to

P _g = P _t + P _k

where P _g - towing force of the measuring trolley 1, N (Kg);

P _t - traction force of dynamic braking of the measuring wheel 3, which at current J _{n1 is} numerically equal to P _t when calibrating the device, N (Kg);

Pk is the rolling resistance force of the driven wheels 26 and 26-1; H (Kg).

Under the condition P _t ≪ P _ssp (n _k = ω), programmed self-monitoring of the operability of the proposed device is organized.

When the load of the generator 17 increases, the traction force P _{t of} dynamic braking of the measuring wheel 3 increases accordingly.

And at a current J _n2 at the load of the block 19, the traction force P _{t of} braking of the measuring wheel 3 becomes equal to the adhesion force P _{ssp of the} wheel 3 with the surface of the airfield coating (Fig.4,49).

P _t = P _ssp = φP _g ,

where φ is the coefficient of adhesion;

R _g - normal (vertical) force of the independent load 15 on the measuring wheel 3.

This violates the equality of the angular velocities of the measuring 3 and driven 26-1 wheels.

Therefore, a sign of equality of the traction force P _t braking of the measuring wheel 3 to its adhesion force (P _ssp ) to the runway surface is the presence of slipping of the measuring wheel 3, that is, n _k <ω.

.However, the greatest adhesion force (R _{SCP. Max} ) measuring wheel 3 reaches in the presence of significant slippage. The degree of slipping of the measuring wheel 3 with respect to the surface of the airfield coating is characterized by relative slippage

.

where ω is the angular velocity of the driven wheel 26-1;

n _to - the angular velocity of the measuring wheel 3.

=0,1-0,2 (фиг.4).The coefficient of adhesion (φ _max ) reaches its maximum value with relative slip

= 0.1-0.2 (figure 4).

(пробуксовка измерительного колеса 3) тяговая сила Р_т торможения измерительного колеса 3 контролируется по показаниям измерительного элемента 6.In the presence of relative slippage

(slipping of the measuring wheel 3) the traction force P _t braking of the measuring wheel 3 is controlled by the readings of the measuring element 6.

With increasing load current J _n in block 19, the growth of readings Р _{g of the} measuring element 6 slows down (Fig. 4 for a conditionally taken case — the wet surface of the airfield coating — this is curve 45).

And at current J _{n3 the} growth of readings Р _{g of the} measuring element 6 stops (Fig. 4, point 50), which corresponds to the maximum value of the traction force (Р _{t max} ) of braking of the measuring wheel 3, the maximum force of its adhesion (Р _{scp. Max} ) to the surface airfield cover and, therefore, the maximum value of the coefficient of adhesion (φ _max ).

P _{t max} = P _{ssp. max} = φ _max P _g

R _{t max} (R _{sdp max} ) can be calculated

P _{t max} (P _{spp. Max} ) = P _g -P _k

where P _to - the rolling resistance of the driven wheels 26 and 26-1 for the set speed is constant.

Therefore, we can calculate φ _max

This ends the search mode.

The tracking mode provides tracking of the maximum adhesion coefficient φ _max when the state of the airfield coating changes.

увеличится в соответствии со степенью загрязнений.Suppose that during the measurement process the next surface area of the airfield coating became more dirty. In this case, the readings P _{g of the} measuring element 6 will become smaller, and the relative slip

will increase in accordance with the degree of pollution.

станет меньше.Or, conversely, the next section of the coating surface has become cleaner, then the readings P _{g of the} measuring element 6 will increase, and the relative slip

will become less.

Then, in accordance with the software of the calculator 7, the active load current J _n on the elements of the block 19 will decrease in the first case and increase in the second, correspondingly decreasing or increasing the reading of the measuring element 6, achieving its maximum values of P _{g max} .

Then, according to the previously given formulas, the maximum value of the traction force (R _{t max} ) of braking of the measuring wheel 3 and the maximum coefficient of adhesion (φ _max ) of the wheel to the surface of the airfield coating are calculated.

P _{t max} (P _{spp. Max} ) = P _g -P _k

The positive effect of the proposed device is to increase safety when landing aircraft on the runway, which consists in reliably determining the maximum coefficient of adhesion of the aircraft chassis to the surface of the airfield coating. In this case, the maximum coefficient of longitudinal adhesion φ _max is determined taking into account the state of the runway, in accordance with the requirements of ICAO (international civil aviation organization).

от 0,1 до 0,2 в зависимости от состояния поверхности взлетно-посадочной полосы.Known devices, like the prototype, use a constant, fixed degree of slipping of the measuring wheel without taking into account the surface condition of the airfield coating. But when determining the maximum coefficient of adhesion (φ _max ), a change in relative slippage is required

from 0.1 to 0.2, depending on the state of the surface of the runway.

- the service life of the chassis of the measuring wheel 3 is increased, since its slipping is carried out only during measurements and is excluded during acceleration and other movements of the measuring trolley 1.

- When accelerating the measuring trolley 1 (before measurement) slippage of the measuring wheel 3 is excluded, the heating of the tire surface of the wheel 3 is reduced, which increases the reliability of the measurements of the adhesion coefficient.

When taking measurements, the proposed device does not require special water wetting of the surface of the runway.

The proposed device can be performed as follows.

The most important element in the proposed device is a direct current generator 17, therefore, the GS-12TO used in auxiliary power systems TA-6A for starting turbojet aircraft engines is used as a direct current generator.

измерительного колеса 3 от 0,1 до 0,25.The generator is safe in operation, operating conditions provide the required climatic operating conditions (relative humidity ~ 98%, temperature from +690 to -60 ° С) and significant shock and vibration loads. The operating range of rotation of the generator 17 provides relative slippage

measuring wheel 3 from 0.1 to 0.25.

Pavlovsky N.I. "Auxiliary power plants of aircraft", M. "Transport", 1977.

- voltage regulator 24 type RN-18Ohm - included in the kit of the DC-generator GS-12TO;

- calculator 7 - microcontroller family PIC18. Authors B.Ya. Prokhorenko et al. M. DODEKA, 1999;

- memory block 25 - non-volatile memory chip company ATMEL, author V.VTrebnev ed. St. Petersburg, EFO, 1977;

- display 29 - digital microcrystalline display company PLANAR;

- controller 30 - controller type FLASC-CAPD, designed to connect external devices;

- measuring wheel 3 - aircraft chassis;

- driven wheels 26 and 26-1 - automobile chassis;

- measuring element 6 - dynamometer;

- angular velocity sensors 20 and 21 - tachogenerators;

- control unit 27 - block optocouplers;

- power key block 18 - built on the basis of power transistors or thyristors;

- rechargeable battery 23 - two batteries of type 12SM-28 or 20KNBN;

- contactor 25 - contactor TKS601KOD;

- starting resistance 22 - resistance, type PS-200-012D.

Claims (1)

A device for determining the adhesion coefficient of a wheel with an airfield coating, comprising a measuring trolley and a registration unit, a measuring trolley contains a measuring wheel, a locking clutch, a gearbox, a measuring element and a measuring trolley frame, while the measuring wheel is mechanically connected to the gearbox by a locking clutch, the registration unit contains a calculator and a control panel that connects to the first input of the calculator, and the output of the measuring element via a flexible cable is connected to the second the input of the calculator, characterized in that the measuring trolley further comprises an independent load, a freewheel, a direct current generator, a power key block, an active load unit, first and second angular velocity sensors, a starting resistance, a battery, a voltage regulator, a contactor, slaves wheels, while an independent load is normally connected to the measuring wheel, a freewheel coupling connects the gearbox to the rotor of the DC generator, the battery bus through the tactor and starting resistance are connected to the power input / output of the DC generator, the power input / output of which is connected to the active load unit through the power switch block, and also the second generator output is connected to the input of the DC winding, which is the input of its field winding, through the voltage regulator the batteries are connected to the second input of the contactor, and the measuring and driven wheels are connected respectively to the first and second angular velocity sensors, the driven wheels are connected to the meter frame the trolley, which is connected through the measuring element to the vehicle, while the registration unit further comprises a control unit, a memory unit, a display and a controller, the input / output port of the computer connected to the memory unit, and the first, second and third outputs of the computer connected respectively to the display, the control unit and the controller through which communication with external devices is carried out, and the measuring trolley is connected by a flexible cable to the registration unit, while the outputs of the first and second sensor at angular speeds are connected respectively to the third and fourth analog inputs of the calculator, the output of the control unit is connected to the second input of the power switch unit, and the second output of the contactor and the outputs of the power bus of the DC generator and the battery are connected respectively to the first and second inputs of the control panel, the fifth - a free analog input of the calculator is provided for connecting the dynamometer of the power stand (during calibration of the device), while the maximum value of the coefficient s Warming (φ _max ) is calculated by measuring the maximum longitudinal dynamic braking force of the measuring wheel over the surface of the airfield coating obtained when the DC generator is in the generator mode, when the maximum mechanical adhesion force (P _{SCP max} ) of the measuring wheel is converted into electric and released in the form of thermal energy in the block of active load, while the coefficient of adhesion (φ _max ) is calculated by the formula φ _max = P _{ssp max} / P _g , where φ _max - the maximum value of the coefficient of adhesion of the wheel with an airfield coating; P _{SCP max} - the maximum longitudinal force of adhesion of the measuring wheel with the surface of the airfield coating; R _g - normal load force on the measuring wheel.

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