A method for determining the rolling friction coefficient of an aircraft on a rough runway

Abstract

This application belongs to the field of flight test technology, and particularly relates to a method for determining the rolling friction coefficient of an aircraft on a simple runway. The method includes: Step 1, set up test equipment, the test equipment includes a test vehicle and a tractor. A test wheel, an aircraft brake and a brake control rate module are installed on the test vehicle, and a dynamometer is arranged between the test vehicle and the tractor; Step 2, calculate the equivalent single-wheel load of the aircraft, and determine the load of the test wheel according to the equivalent single-wheel load of the aircraft; Step 3, determine the test vehicle counterweight according to the load of the test wheel; Step 4, determine multiple different brake efficiencies; Step 5, load the test vehicle counterweight and brake efficiency onto the test equipment and conduct a taxiing test to obtain the pulling force data under different brake efficiencies; Step 6, process the pulling force data to obtain the rolling friction coefficient. This application can determine the rolling friction coefficient of the aircraft when braking and not braking on a simple runway.

Description

Technical Field

[0001] This application belongs to the technical field of flight test, and particularly relates to a method for determining the rolling friction coefficient of an aircraft on a simple runway. Background Art

[0002] A simple runway generally refers to a runway whose pavement has not been paved or only needs simple treatment to take off and land an aircraft. There are many pavement materials, mainly including land, snow, ice, grass, sand, gobi, etc. As the main form of a simple runway, the soil simple runway is the simplest and easiest type of simple runway to build. When an aircraft taxis on a simple runway, the rolling of the wheels causes large deformation of the pavement, forming deep wheel ruts on the pavement. When the aircraft taxis, it is subjected to a large rolling friction force, which seriously affects the takeoff and landing performance of the aircraft.

[0003] The rolling friction force that an aircraft experiences when taxiing on a simple runway is related to pavement material, pavement strength, tire pressure, aircraft weight, tire type, braking efficiency, etc. Especially when the pavement strength is different, the depth of the wheel ruts is different, and it is difficult to establish a mathematical model for accurate calculation. The rolling friction coefficient directly affects the takeoff and landing roll distance of the aircraft and has a great impact on the runway length requirement of the aircraft. Therefore, determining the rolling friction coefficient of an aircraft on a simple pavement has become one of the key factors for evaluating the takeoff and landing performance of an aircraft on a simple runway.

[0004] At present, there are mainly two methods for measuring the rolling friction coefficient of an aircraft on a simple runway: one is that the aircraft directly taxis on the simple runway, and the rolling friction coefficient it experiences is obtained through the dynamic equation of the aircraft taxiing; the other is to use a tractor to tow the aircraft to taxi uniformly on the simple runway, and the pulling force value is measured with a dynamometer, thereby calculating the rolling friction coefficient. However, both of these two methods require the aircraft to taxi on the test site, and the test cost and risk are relatively high, especially for large aircraft, the test cost is even more huge.

[0005] Therefore, it is desired to have a technical solution to overcome or at least mitigate at least one of the above-mentioned defects of the prior art. Summary of the Invention

[0006] The purpose of this application is to provide a method for determining the rolling friction coefficient of an aircraft on a simple runway to solve at least one problem existing in the prior art.

[0007] The technical solution of this application is as follows:

[0008] A method for determining the rolling friction coefficient of an aircraft on a simple runway includes:

[0009] Step 1: Set up the test equipment. The test equipment includes a test vehicle and a towing vehicle. A test wheel, an aircraft brake, and a brake control rate module are installed on the test vehicle. A dynamometer is arranged between the test vehicle and the towing vehicle.

[0010] Step 2: Calculate the equivalent single-wheel load of the aircraft and determine the load of the test wheel according to the equivalent single-wheel load of the aircraft.

[0011] Step 3: Determine the counterweight of the test vehicle according to the load of the test wheel.

[0012] Step 4: Determine multiple different brake efficiencies.

[0013] Step 5: Load the counterweight of the test vehicle and the brake efficiency onto the test equipment, conduct a taxiing test, and obtain the pulling force data under different brake efficiencies.

[0014] Step 6: Process the pulling force data to obtain the rolling friction coefficient.

[0015] In at least one embodiment of the present application, in Step 1, the single wheel of the main landing gear is used as the test wheel, and 2 such test wheels are installed on the test vehicle.

[0016] In at least one embodiment of the present application, in Step 1, the tire pressure of the test wheel is equal to the tire pressure when the aircraft reaches its maximum takeoff weight.

[0017] In at least one embodiment of the present application, the dynamometer has a data recording function, and the data recording frequency is not less than 4 times per second.

[0018] In at least one embodiment of the present application, in Step 2, calculating the equivalent single-wheel load of the aircraft and determining the load of the test wheel according to the equivalent single-wheel load of the aircraft includes:

[0019] Calculate the equivalent single-wheel load borne by the single wheel of the main landing gear. The equivalent single-wheel load of the aircraft is:

[0020] ;

[0021] where ESWL is the equivalent single-wheel load of the aircraft, W is the weight of the aircraft, D n is the distance between the nose landing gear and the center of gravity, D0 is the distance between the nose landing gear and the center of the main landing gear, n is the number of wheels, and K is the equivalent single-wheel load amplification factor;

[0022] Take the equivalent single-wheel load of the aircraft as the load of the test wheel.

[0023] In at least one embodiment of the present application, in Step 3, determining the counterweight of the test vehicle according to the load of the test wheel includes:

[0024] After loading the test vehicle with counterweights, the load on each of the test wheels is equal to the equivalent single-wheel load of the aircraft.

[0025] In at least one embodiment of the present application, in step four, determining multiple different braking efficiencies includes:

[0026] Selecting multiple different braking efficiencies from [0%, 100%].

[0027] In at least one embodiment of the present application, in step five, when conducting the taxiing test, ensure that the rut of the test wheel does not coincide with the rut of the tractor during the taxiing process.

[0028] In at least one embodiment of the present application, in step six, processing the tensile force data to obtain the rolling friction coefficient includes:

[0029] S601: Plot the tensile force values in the tensile force data as a curve in chronological order;

[0030] S602: Sort the tensile force values in the tensile force data by magnitude:

[0031] T1 ≤ T2 ≤ …… ≤ T n ;

[0032] where T1, T2, ……, T n are different tensile force values, and n is the number of tensile force values;

[0033] Determine the lower limit value a and the upper limit value b such that all the tensile force values are included in the interval [a, b];

[0034] S603: Divide the interval [a, b] into equal parts to obtain m + 1 different dividing points:

[0035] a = c1 ≤ c2 ≤ …… ≤ c m+1 = b;

[0036] m = integer(n / 3);

[0037] where c1, c2, ……, c m+1 are different dividing points;

[0038] S604: Determine the number f i , c i+1 of tensile force values falling in each sub-interval [c i , and sort them by magnitude:

[0039] f1 ≥ f2 ≥ …… ≥ f m ;

[0040] And for the first x f iSum to satisfy:

[0041] ;

[0042] The value of x when the above conditions are satisfied is k;

[0043] S605. Calculate the average value of the pulling force values corresponding to the first k f i :

[0044] ;

[0045] Wherein, is the average value of the pulling force values corresponding to the first k f i ;

[0046] S606. Calculate the rolling friction coefficient:

[0047] ;

[0048] Wherein, μ is the rolling friction coefficient.

[0049] In at least one embodiment of the present application, in S601, the pulling force values in the starting stage and the stopping stage of the curve are deleted, and the pulling force values in the sliding stage are retained.

[0050] The invention has at least the following beneficial technical effects:

[0051] The method for determining the rolling friction coefficient of an aircraft on a simple runway in the present application can determine the rolling friction coefficients of the aircraft when braking and not braking on a simple runway, reduce the test cost, provide accurate test data support for evaluating the takeoff and landing performance of the aircraft on a simple runway, ensure the test flight safety of the aircraft on a simple runway, and effectively resolve the potential safety hazards brought by the test flight of the aircraft. Description of the Drawings

[0052] Figure 1 is a flowchart of the method for determining the rolling friction coefficient of an aircraft on a simple runway according to an embodiment of the present application;

[0053] Figure 2 is a schematic diagram of the test equipment according to an embodiment of the present application;

[0054] Figure 3 is a layout diagram of the test wheels of the test equipment according to an embodiment of the present application;

[0055] Figure 4 is a schematic diagram of the landing gear layout of an aircraft according to an embodiment of the present application. Detailed Embodiments

[0056] To make the objectives, technical solutions, and advantages of the present application clearer, the following will describe in more detail the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals throughout indicate the same or similar elements or elements with the same or similar functions. The described embodiments are some but not all of the embodiments of the present application. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application. The following will explain in detail the embodiments of the present application with reference to the accompanying drawings.

[0057] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the scope of protection of the present application.

[0058] The following will further describe the present application in detail with reference to the appended Figures 1 to 4 drawings.

[0059] The present application provides a method for determining the rolling friction coefficient of an aircraft on a simple runway, as Figure 1 shown, which includes the following steps:

[0060] Step 1: Set up the test equipment. The test equipment includes a test vehicle and a tractor. A test wheel, an aircraft brake, and a brake control rate module are installed on the test vehicle. A tensiometer is arranged between the test vehicle and the tractor;

[0061] Step 2: Calculate the equivalent single-wheel load of the aircraft, and determine the load of the test wheel according to the equivalent single-wheel load of the aircraft;

[0062] Step 3: Determine the counterweight of the test vehicle according to the load of the test wheel;

[0063] Step 4: Determine multiple different brake efficiencies;

[0064] Step 5: Load the counterweight of the test vehicle and the brake efficiency onto the test equipment, conduct a taxiing test, and obtain the tensile force data under different brake efficiencies;

[0065] Step 6: Process the tensile force data to obtain the rolling friction coefficient.

[0066] The method for determining the rolling friction coefficient of an aircraft on a simple runway according to the present application, asFigure 2 , 3 As shown, in Step 1, the test equipment is set up. The test vehicle can slide uniformly through the simple runway under the traction of the towing vehicle. In the preferred embodiment of the present application, the single wheel of the main landing gear is used as the test wheel, and 2 test wheels are installed on the test vehicle. The test wheels should be the same as the wheels of the aircraft to be tested, and the tire pressure of the test wheels should be kept consistent with the tire pressure when the aircraft takes off at its maximum takeoff weight. The tensiometer is used to measure the pulling force value of the towing vehicle on the test vehicle. The tensiometer has a data recording function and can read data. The data recording frequency is not less than 4 times per second.

[0067] In the method for determining the rolling friction coefficient of an aircraft on a simple runway of the present application, in Step 2, taking the determination of the rolling friction coefficient of a certain type of aircraft on a soil simple runway as an example, the strength of the soil simple runway can meet the takeoff and landing of the aircraft. The maximum takeoff weight of the aircraft on the soil simple runway is known. The aircraft adopts a rear center of gravity and a nose-gear three-point landing gear. The nose gear has 2 wheels and the main gear has 8 wheels (4 wheels on each side), as Figure 4 shown. The aircraft weight W is the maximum takeoff weight of the aircraft.

[0068] In this embodiment, the equivalent single-wheel load of the aircraft borne by the single wheel of the main landing gear is calculated. The equivalent single-wheel load of the aircraft is:

[0069] ;

[0070] where ESWL is the equivalent single-wheel load of the aircraft, W is the aircraft weight, D n is the distance between the nose landing gear and the center of gravity, D0 is the distance between the nose landing gear and the center of the main landing gear, n is the number of wheels, and K is the equivalent single-wheel load amplification factor;

[0071] The equivalent single-wheel load of the aircraft is used as the load of the test wheel.

[0072] The equivalent single-wheel load amplification factor K is related to the landing gear structure. The load distributed to each landing gear wheel may be different and is determined by referring to relevant manuals.

[0073] In the preferred embodiment of the present application, in Step 3, after loading the test vehicle with counterweights, the load on each test wheel is equal to the equivalent single-wheel load of the aircraft. In Step 4, multiple different braking efficiencies are selected from [0%, 100%]. Before conducting the taxiing test, the braking efficiency of the test is clarified and the braking efficiency is input into the aircraft brake and brake control rate module of the test vehicle. The input value of the braking efficiency is a number between 0 and 1. For example, when the input value is 0, there is no brake; when the input value is 0.70, the braking efficiency is 70%; when the input value is 1, the braking efficiency is 100%.

[0074] The method for determining the rolling friction coefficient of an aircraft on a simple runway in this application. In step five, when conducting the taxiing test, ensure that the wheel tracks of the test wheels do not coincide with those of the tractor during the taxiing process. In an embodiment of this application, under the traction of the tractor, the weighted test vehicle passes through the simple runway at a constant speed of 20 km / h, and the taxiing time is 5 minutes. Record the pulling force value in real time. During the taxiing process, ensure that the wheel tracks of the test wheels do not coincide with those of the tractor, and there is a certain distance between them.

[0075] The method for determining the rolling friction coefficient of an aircraft on a simple runway in this application. Finally, in step six, after the taxiing test is completed, download the recorded real-time pulling force value from the data recorder of the pulling force meter and perform data processing on it to obtain the rolling friction coefficient. In this embodiment, the specific process of data processing includes:

[0076] S601. Plot the pulling force values in the pulling force data as a curve in chronological order;

[0077] In this embodiment, the pulling force meter records 4 data per second for the pulling force value. There are approximately 1200 data during the 5-minute taxiing. Plot these data as a curve in chronological order, and delete the pulling force values with a large degree of dispersion in the starting stage and the stopping stage of the curve, and retain the pulling force values in the relatively stable middle taxiing stage.

[0078] S602. Sort the pulling force values in the pulling force data according to their magnitudes:

[0079] T1 ≤ T2 ≤ …… ≤ T n ;

[0080] where, T1, T2, ……, T n are different pulling force values, and n is the number of pulling force values;

[0081] Determine the lower limit value a and the upper limit value b such that all the pulling force values are included in the interval [a, b];

[0082] In this embodiment, a is slightly less than T1, and b is slightly greater than T n .

[0083] S603. Divide the interval [a, b] into equal parts to obtain m + 1 different dividing points:

[0084] a = c1 ≤ c2 ≤ …… ≤ c m+1 = b;

[0085] m = (n / 3) rounded down;

[0086] where, c1, c2, ……, c m+1 are different dividing points;

[0087] S604. Determine the number of pulling force values falling into each sub-interval [ci , c i+1 The number f in i , and sort them by size:

[0088] f1 ≥ f2 ≥ …… ≥ f m ;

[0089] And sum the first x f i to satisfy:

[0090] ;

[0091] The value of x that satisfies the above conditions is k;

[0092] S605. Calculate the average value of the tensile force values corresponding to the first k f i :

[0093] ;

[0094] Among them, is the average value of the tensile force values corresponding to the first k f i ;

[0095] S606. Calculate the rolling friction coefficient:

[0096] ;

[0097] Among them, μ is the rolling friction coefficient.

[0098] The method for determining the rolling friction coefficient of an aircraft on a simple runway in this application obtains the rolling friction coefficient by setting up test equipment, conducting taxiing tests, and processing test data. This application can accurately measure the rolling friction coefficient of the aircraft without braking and the equivalent rolling friction coefficient under different braking efficiencies, can accurately evaluate the takeoff and landing performance of the aircraft on a simple runway, ensure the safety of the aircraft taking off and landing on a simple runway, thereby effectively reducing the test flight cost, shortening the test flight cycle, and accelerating the aircraft development process. This application is applicable to measuring the rolling friction coefficient of an aircraft on a simple runway, and has the characteristics of strong generality, simple implementation, low cost, and accurate results.

[0099] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claimed rights.

Claims

1. A method for determining the rolling friction coefficient of an aircraft on a simple runway, characterized in that, Including: Step 1: Set up the test equipment. The test equipment includes a test vehicle and a towing vehicle. A test wheel, an aircraft brake, and a brake control rate module are installed on the test vehicle. A dynamometer is arranged between the test vehicle and the towing vehicle. Step 2: Calculate the equivalent single-wheel load of the aircraft and determine the load of the test wheel according to the equivalent single-wheel load of the aircraft. Step 3: Determine the test vehicle counterweight according to the load of the test wheel. Step 4: Determine multiple different brake efficiencies. Step 5: Load the test vehicle counterweight and the brake efficiency onto the test equipment, conduct a taxiing test, and obtain the pulling force data under different brake efficiencies. Step 6: Process the pulling force data to obtain the rolling friction coefficient. In Step 2, calculating the equivalent single-wheel load of the aircraft and determining the load of the test wheel according to the equivalent single-wheel load of the aircraft includes: Calculating the equivalent single-wheel load borne by a single main landing gear wheel. The equivalent single-wheel load of the aircraft is: Among them, ESWL is the equivalent single-wheel load of the aircraft, W is the weight of the aircraft, D n is the distance between the nose landing gear and the center of gravity, D0 is the distance between the center of the nose landing gear and the main landing gear, n is the number of wheels, and K is the equivalent single-wheel load amplification factor; Taking the equivalent single-wheel load of the aircraft as the load of the test wheel. In Step 6, processing the pulling force data to obtain the rolling friction coefficient includes: S601: Plot the pulling force values in the pulling force data as a curve in chronological order. S602: Sort the pulling force values in the pulling force data by magnitude: T1 ≤ T2 ≤ …… ≤ T n Among them, T1, T2, ……, T n are different tensile force values, and n is the number of tensile force values; Determine the lower limit value a and the upper limit value b such that all the pulling force values are included in the interval [a, b]. S603: Divide the interval [a, b] equally to obtain m + 1 different dividing points: a = c1 ≤ c2 ≤ …… ≤ c m+1 = b m = integer part of (n / 3) Among them, c1, c2, ……, c m+1 are different separation points; S604. Determine the number f of the tensile force values falling within each sub-interval [c i , c i+1 , and sort them in ascending order: i ​ f1≥f2≥……≥f m And sum the first x f i such that it satisfies: When the above conditions are met, the x value obtained is k. S605. Calculate the first k f's i The average value of the corresponding tensile force values: Among them, is the average value of the tensile force values corresponding to the first k f i ; S606: Calculate the rolling friction coefficient: where μ is the rolling friction coefficient.

2. The method for determining the rolling friction coefficient of an aircraft on a dirt runway according to claim 1, characterized in that, In Step 1, take a single main landing gear wheel as the test wheel, and install 2 such test wheels on the test vehicle.

3. The method for determining the rolling friction coefficient of an aircraft on a dirt runway according to claim 2, characterized in that In Step 1, the tire pressure of the test wheel is equal to the tire pressure when the aircraft is at its maximum takeoff weight.

4. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 3, characterized in that, The dynamometer has a data recording function, and the data recording frequency is not less than 4 times per second.

5. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 4, characterized in that, In Step 3, determining the test vehicle counterweight according to the load of the test wheel includes: After loading the test vehicle counterweight onto the test vehicle, the load on each test wheel is equal to the equivalent single-wheel load of the aircraft.

6. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 5, characterized in that In Step 4, determining multiple different brake efficiencies includes: Selecting multiple different brake efficiencies from [0%, 100%].

7. The method for determining the rolling friction coefficient of an aircraft on a rough runway according to claim 6, characterized in that, In Step 5, when conducting the taxiing test, ensure that the wheel tracks of the test wheels do not coincide with the wheel tracks of the towing vehicle during the taxiing process.

8. The method for determining the rolling friction coefficient of an aircraft on a dirt runway according to claim 7, characterized in that, In S601, delete the pulling force values in the starting stage and the stopping stage of the curve, and retain the pulling force values in the taxiing stage.

Images