RU2298166C1 - Method of determining grip of wheel with airdrome pavement - Google Patents

Abstract

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.

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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.

A Saab 900/9000 friction coefficient measurement device is known which is commercially available by the Swedish company Saab-Scania (The method for determining the friction coefficient of this device is given in the magazine Hoverfoil News, 8 No. 9-10.1 — determination of the friction coefficient of a runway).

In the known device, the maximum value of the coefficient of adhesion (f _max ) is determined by measuring the maximum adhesion force (P _{scp. Max} ) of the measuring wheel with the surface of the airfield coating while wetting the surface of the coating and constant slipping of the measuring wheel by 15-17%. In this case, the coefficient of adhesion is calculated by the formula

f _max = P _{SCP. max} / P _g

where f _max - the maximum coefficient of adhesion of the measuring wheel with the coating surface;

R _{ssp. max} - traction force of the measuring wheel with its constant slipping;

R _g - normal load force on the measuring wheel.

The disadvantage of this method is that at some latitudes, winter time eliminates surface wetting, and constant slipping underestimates the maximum value of the coefficient of adhesion (f _max ).

Another well-known device is the ATT-2 commercially available “Airfield Brake Trolley” (“A device for determining the coefficient of adhesion of wheels with an airdrome coating” - Copyright Certificate No. 630982, class G01N 19/02. A method for determining the coefficient of adhesion is also given in the “Operation manual” civil aerodromes of the Russian Federation ", ed. M.," Air transport ", 1955, pp. 154-157).

The method for determining the adhesion coefficient of the known device is that when the measuring trolley moves due to the difference in the diameters of the drive and measuring wheels connected by the gearbox through the blocking clutch, the measuring wheel moves with a slip relative to the surface of the airfield coating. The ratio of the diameters of the driving and measuring wheels provides the movement of the measuring wheel with a slip of 17%.

Due to the slipping of the measuring wheel, a longitudinal maximum traction force (P _{scp. Max} ) _occurs . The maximum value of the coefficient of adhesion is calculated by the formula

f _max = P _{SCP. max} / R _g

where f _max - the maximum value of the coefficient of adhesion;

R _{ssp. max} - longitudinal maximum traction force of the measuring wheel during its slipping;

R _g - normal load force on the measuring wheel.

The disadvantage of this method is the presence of significant errors in determining the maximum value of the coefficient of adhesion, since when driving due to the difference in the diameters of the driven and measuring wheels, the measuring trolley skids - transverse braking force appears, and the presence of constant slipping reduces the maximum longitudinal adhesion force.

Closest to the claimed invention in technical essence is the "Device for determining the coefficient of adhesion of the wheel with an airfield coating." (Application of the Russian Federation No. 2004137376/11 (001331) dated 01/08/2004 - patent No. 2259669, G01P 15/08), in which the method of determining the coefficient of adhesion is closest to the claimed invention. The structural diagram of a device for implementing the known method (prototype) is shown in Fig.1.

Said device comprises a measuring trolley 1 and a registration unit 2. The measuring trolley 1 is equipped with a measuring wheel 3 — an aircraft chassis and driven wheels 17 — an automobile chassis.

The composition of the measuring trolley 1 includes:

- independent vertical load 6, which provide normal (vertical) force P _g on the measuring wheel 3;

- a locking clutch 4, which before measuring connect the measuring wheel 3 with the gear 5;

- gear 5, which provide the necessary range of rotational speed of the rotor of the DC generator 8;

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

- DC generator 8, which operates in two modes - starter and generator; in starter mode, the rotor of the generator 8 is accelerated to the nominal rotation speed, which eliminates the overload of the measuring wheel 3 at the time of acceleration of the towing vehicle; the generator mode of the generator 8 provides a force of adhesion of the measuring wheel with the surface of the airfield coating;

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

- active load 10;

- the first 11 and second 12 angular velocity sensors, designed to measure angular velocities respectively measuring 3 and driven 17 wheels;

- starting resistance 13;

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

- voltage regulator 15 maintains the voltage of the generator 8 constant;

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

- frame measuring trolley 18;

- measuring element 19, which determines the dynamic braking force of the measuring wheel 3 P _t and measuring cart 1.

Registration block 2 contains:

- calculator 20;

- control panel 21;

- control unit 22;

- memory block 23;

- controller 24;

- display 25.

The calculator 20 receives information from the sensors 11 and 12 of the angular velocity of the measuring 3 and the driven 17 wheels, respectively, and receives from the measuring element 19 the traction information of the measuring trolley 1 and the dynamometer information of the power stand when calibrating the device. The calculator 20 in accordance with the software through the control unit 22 controls the power key unit 9, as well as writes and reads information from the memory unit 23, determines the maximum value of the coefficient of adhesion (f _max ) with the airfield coating, determines the speed of movement, provides the necessary information on display 25 and reads from the memory unit 23 through the controller 24 information about the measurements.

Moreover, in the known method, the maximum value of the adhesion coefficient (f _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 _{SCP. Max} ) is _measured the wheel turns into electric and is released in the form of thermal energy in the active load unit, while the adhesion coefficient is calculated by the formula

f _max = P _{SCP. max} / P _g

Where

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

R _{ssp. max} — maximum longitudinal adhesion force of the measuring wheel to the surface of the airfield coating;

R _g - normal load force on the measuring wheel.

The definition of a known method of longitudinal maximum adhesion coefficient (f _max ) wheels with an airfield coating.

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

In search mode, a search is made for the maximum adhesion force (P _{scp. Max} ) of the measuring wheel 3 with the surface of the airfield coating.

In tracking mode - tracking the maximum adhesion force of the measuring wheel 3 with the surface of the coating, while making the required adjustment.

The search mode begins with a minimum and uniform increase in current at the active load of unit 10. In this case, the dynamic braking force (P _t ) of the measuring wheel 3 will also be proportionally increased.

However _{, the} measuring wheel 3 reaches the greatest dynamic braking force P _t when it is slipping. The degree of slipping of the measuring wheel 3 with respect to the surface of the airfield coating is characterized by a relative slip S

S = (ω _in -ω _ism ) / ω _in ,

where ω _in - the angular velocity of the driven wheel 17;

ω _ISM - the angular velocity of the measuring wheel 3,

(the radii of the measuring and driven wheels are equal).

The maximum value of the coefficient of adhesion (f _max ) is determined taking into account the state of the surface of the coating with a relative slip S from 0.1 to 0.2 (10-20%).

In the presence of relative slippage S, the maximum longitudinal adhesion force (P _{scp. Max} ) of the measuring wheel 3 with the surface of the airfield coating is controlled by the readings of the measuring element 19.

When, with increasing current at the active load of block 10, the readings of the measuring element 19 reach their maximum value, the search mode ends. The tracking mode is activated, in which, in accordance with the software, the maximum adhesion (P _{scp. Max} ) of the measuring wheel 3 with the surface of the airfield coating is monitored, while the maximum value of the coefficient of adhesion (f _max ) is calculated by the formula given above

f _max = P _{SCP. max} / P _g

A disadvantage of the known method for determining the maximum value of the coefficient of adhesion (f _max ) is that in this method, as in the known analogue methods, there is a constant slipping of the measuring wheel 3 from 10 to 20% of the measured distance.

As a result of constant slipping, the surface of the measuring wheel warms up, the rubber softens and the maximum adhesion force of the measuring wheel to the coating surface decreases (P _{cfp max} and, accordingly, f _max decreases). Moreover, a fixed (predetermined) slipping of the measuring wheel without taking into account the state of the coating surface is this is the case in analog adhesion coefficient measurement methods.

To reduce the heating of the measuring wheel, wetting of the coating surface is sometimes used. But on a dry coating, dust and moisture form a lubricant between the wheel and the surface, thereby reducing the measured maximum adhesion coefficient. Surface wetting does not exclude heating of the measuring wheel and may not always be applicable. In winter, wetting of the coating surface is excluded. The accuracy of determining the maximum coefficient of adhesion is also reduced due to the fact that the maximum adhesive force is not pronounced. (P _{SCP. Max} has a flat top - Figure 2).

The aim of the proposed method is to increase the accuracy of measuring the maximum value of the coefficient of adhesion (f _max ).

The goal in the "Method for determining the coefficient of adhesion of the wheel with the airfield coating" is achieved by the fact that in it, as in the prototype, the coefficient of adhesion of the wheel with the airfield coating is determined by the dynamic braking method, when the electric motor is in generator mode, in which the mechanical energy of the brake element (measuring wheels) turns into electric and is released in the form of thermal energy at the active load, while the normal (vertical) force of the load on the measuring e wheel (P _g).

Additionally, the longitudinal adhesion force of the measuring wheel to the surface of the airfield cover (P _scp ) and the dynamic braking coefficient (k) are determined, while the maximum value of the _friction coefficient (f _max ) is calculated by the formula

f _max = (P _ssp / P _g ) k,

Where

f _max - the maximum value of the coefficient of adhesion of the measuring wheel with an airfield coating;

P _SCP - the longitudinal adhesion force of the measuring wheel with the coating surface;

R _g - normal load force on the measuring wheel;

k is the dynamic braking coefficient, which is calculated during the calibration of the device, as the ratio P _{SCP. max} to P _ssp

k = P _{ssp. max} / _RSCP ,

Where

R _{ssp. max} - maximum traction force of the measuring wheel.

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

Using this method during its implementation will improve safety during landing of aircraft 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 "Method 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 device that implements the proposed method for determining the maximum value of the coefficient of adhesion;

figure 2 is a diagram explaining the method of calculating the coefficient of dynamic braking - k;

figure 3 - algorithm of the proposed method for measuring the coefficient of adhesion (f _max ) wheels with an airfield coating.

In the proposed "Method for determining the coefficient of adhesion of the wheel with the airfield coating", as in the prototype, the coefficient of adhesion of the wheel with the airfield coating is determined by the dynamic braking method, when the electric motor operates in the generator mode, in which the mechanical energy of the brake element (measuring wheel) is converted into electrical and is released in the form of thermal energy in the active load, while determining the normal load force on the measuring wheel (P _g ).

Additionally, the longitudinal adhesion force of the measuring wheel to the surface of the airfield cover (P _scp ) and the dynamic braking coefficient (k) are determined, while the maximum value of the _friction coefficient (f _max ) is calculated by the formula

f _max = (P _ssp / P _g ) k,

Where

f _max - the maximum value of the coefficient of adhesion of the measuring wheel with an airfield coating;

P _SCP - the longitudinal adhesion force of the measuring wheel with the surface of the airfield coating;

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

k is the dynamic braking coefficient, which is calculated during the calibration of the device, as the ratio P _{SCP. max} to P _ssp

k = P _{ssp. max} / P _SCP ),

Where

R _{ssp. max} - maximum traction force of the measuring wheel.

To implement the proposed method, a “Device for determining the coefficient of adhesion of a wheel with an airfield coating” is used, in which the prototype method is implemented. The block diagram of the device shown in Fig.1. To implement the proposed method, the adhesion force (P _SCP ) of the measuring wheel 3 and the dynamic braking coefficient (k) are determined. P _{SCP is} determined during the measurement process, k is determined on the power stand during calibration of the device. But k is also determined in the field. To determine k in the field, a relatively even, dry and clean asphalt pavement up to 1 km long is chosen.

The towing vehicle is accelerated to a set speed (V) at which the maximum value of the coefficient of adhesion of the measuring wheel 3 to the surface of the airfield coating is determined. The speed of movement is determined by the angular velocity sensor 12 of the driven wheel 17 in accordance with the formula

V _a = ω _in r,

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

ω _in - the angular speed of the driven wheel, rad / s;

r is the radius of the driven wheel, m

If the speeds V and V _{a are} equal, the calculator 20 starts a program that determines the change in the dynamic braking force P _{t of the} measuring wheel 3 with increasing current J _H at the active load of block 10 from minimum to maximum value.

In this case, in the memory block 23 write:

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

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

- current strength of the active load J _H block 10;

- readings of the measuring element 19.

The readings of the measuring element 19 are

P _and -P _t + P _to

where P _and is the towing force of the measuring trolley 1;

P _t - dynamic braking force of the measuring wheel 3;

P _to - the rolling resistance of the driven wheels 17.

In this case, the rolling resistance force of the driven wheels 17 is determined on a power stand or calculated by the formula

P _k = GY,

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

Y is the coefficient of rolling resistance, which at a speed of up to 80 km / h is equal to 0.012.

After taking measurements and processing the information received, a diagram is plotted for changes in the dynamic braking force P _{t of the} measuring wheel from changes in the load current J _H in block 10 (Figure 2). On the diagram (Figure 2) several characteristic sections are highlighted.

When changing J _H from 0 to J ₁ , the dynamic braking force P _t increases from 0 to "a", respectively - Fig.2. In this case, the slipping of the measuring wheel 3 is absent, since the dynamic braking force P _{t is} less than the adhesion force (P _SCP ) of the measuring wheel 3 with the coating surface

P _t <P _ssp .

At point "a" there is a slipping of the measuring wheel 3, while the dynamic braking force P _t becomes equal to the adhesion force P _SCP

P _t = P _ssp = P _g

where f is the coefficient of adhesion of the measuring wheel with the surface of the coating.

With an increase in J _H at the active load 10 from J ₁ to J ₂ , the dynamic braking force P _t increases from "a" to "c" (Figure 2), at the same time, the slip of the measuring wheel 3 increases. At the point "c", the dynamic braking force reaches a maximum value (P _{t max} ), which is equal to the maximum adhesion of the wheel 3 (P _{SCP. max} ) with the coating surface

R _{t. Max} = R _{ssp. max} = f _max P _g

where f _max - the maximum value of the coefficient of adhesion of the measuring wheel with the surface of the coating.

With further increase in J _H in the active load of ₂ J to J _3, the force F _{t. Max} (P _{SCP. Max)} decreases from "a" to "c" (Figure 2). This is because at the same time as J _H increases, the slippage of the measuring wheel 3 increases, the wheel heats up, the rubber softens, the force P _{t max} (P _{spp. Max} ) decreases, and f _max .

According to the obtained values of R _SCP and P _{SCP. max} calculate the coefficient of dynamic braking k

k = P _{ssp. max} / P _SCP .

With a change in the state of the surface of the coating, P _scp and P _scp respectively change _{. max} , but their ratio (coefficient k) is preserved. The coefficient is recorded in the RAM of the calculator 20, which is then used to calculate f _max .

The method of determining the maximum coefficient of adhesion.

Before determining the coefficient of adhesion, preparatory work is carried out (Figure 3):

- the toggle switch "calibration / measurement" on the control panel 21 is set to the "measurement" position;

- include a locking clutch 4;

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

- press the "Start" button of the control panel 21, while closing the contactor 16 switching circuit and the power bus of the battery 14 is connected to the electric motor via the starting resistance 13. The rotor of the electric motor 8 is untwisted to the rated rotation speed.

After carrying out the preparatory work, the vehicle towing picks up a predetermined speed V.

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

In the search mode, they search for dynamic braking force P _t equal to the adhesion force P _{SCP of the} measuring wheel 3 with the coating surface. With the equality of P _t and P _SCP measuring wheel 3 begins to slip.

In tracking mode, the start of slipping of the measuring wheel is monitored. At the same time ensure the equality of forces P _t and P _SCP .

The search mode begins with a minimum and uniform increase in current J _H at the active load of unit 10. In this case, the dynamic braking force of the measuring wheel 3 will also increase proportionally (Figure 2). When the force P _t becomes equal to the force P _SCP , a slipping of the measuring wheel appears. Slipping is recorded according to the information of the angular velocity sensors 11 and 12. This completes the search mode.

In the tracking mode, they provide tracking of the start of slipping of the measuring wheel 3. The information of the sensors 11 and 12 (measuring 3 and driven 17 wheels) enters the calculator 20, where their readings are compared.

There is no slipping of the measuring wheel - the readings of the angular velocity sensors 11 and 12 are equal to each other. In this case, the signal from the calculator 20 receives a signal to increase the load on the generator 8. The signal to increase the load from the control unit 22 is supplied to the power switch unit 9, which increases the load current of the block 10. The load on the generator 8 increases, the dynamic braking force of the measuring wheel 3, with the appearance of slipping of which the increase in current at the active load of block 10 stops.

If the slip of the measuring wheel 3 is greater than a predetermined value, then the current of the active load of the block 10 is reduced, the load on the generator 8 accordingly decreases, the dynamic braking force of the measuring wheel 3 decreases, its slip decreases. When the specified slippage is reached, a further decrease in the load current of the block 10 is stopped.

In accordance with the software, the calculator 20 provides a predetermined minimum slipping range of n _b , within which the dynamic braking force P _t (P _scc ) is _determined , with P _t = P _scc .

The maximum coefficient of adhesion of the measuring wheel with the surface of the airfield coating is determined as

f _max = (P _ssp / P _g ) k.

The proposed method for determining the maximum value of the coefficient of adhesion of the wheel to the surface of the airfield coating eliminates slippage of the measuring wheel during the measurement process, except for fixing the beginning of slipping in the specified minimum range of n _b , which increases the accuracy of determining the maximum value of the coefficient of adhesion. Moreover, in search and tracking modes, the longitudinal adhesion force P _{ssp of the} measuring wheel is more accurately determined and tracked, since the beginning of its slipping has a pronounced character and is determined by the minimum slipping range n _b with greater accuracy. The proposed method does not require wetting of the surface. Measurements are taken in the wake of the main supports of the aircraft at any time of the day, regardless of the state of the surface of the airfield coating. The accuracy of measurements is increased, safety is enhanced while ensuring flights.

Claims (1)

The method of determining the coefficient of adhesion of a wheel with an airfield coating by dynamic braking, when the electric motor is in the generator mode, in which the mechanical energy of the brake element (measuring wheel) is converted into electrical energy and released in the form of thermal energy in the active load, and the normal force of the load on the measuring wheel (P _g ), characterized in that it further determines the longitudinal adhesion force of the measuring wheel to the surface of the airfield coating (R _SCP. ) And dynamic braking coefficient (k), while the maximum value of the coefficient of adhesion (f _max. ) Is calculated by the formula: f _max. = (P _spp. / P _g ) k, where f _max. - the maximum value of the coefficient of adhesion of the measuring wheel with an airfield coating; R _ssp. - the longitudinal adhesion force of the measuring wheel to the surface of the airfield coating, measured at the beginning of its slipping; P _g - normal load force on the measuring wheel; k is the coefficient of dynamic braking, which is calculated during the calibration of the device, as the ratio P _{SCP max.} to R _ssp . k = P _{spp. max.} / R _ssp. , where P _spp.max. - longitudinal maximum traction force of the measuring wheel.

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