A method for calculating brake efficiency of aircraft discrete pressure

Abstract

The application discloses a kind of brake efficiency calculation methods of aircraft discrete pressure, in prior art, only propose pressure efficiency method calculation, without considering the problem that wheel deep skidding state exists, fully consider engineering practice, remove inappropriate peak point, remove deep skidding point, obtain discrete pressure P envelope line curve, the discrete data processing method proposed can be directly applied to aircraft parameters.The application gives specific operation process, has engineering implementation value, can be used in existing engineering technology, and the processing time of a group of data is shortened from original 2 person·h to 2min, greatly improve data processing efficiency and batch processing capacity.

Description

Technical Field

[0001] This invention relates to the field of aircraft wheels, specifically a method for calculating the braking efficiency of discrete pressure. Background Technology

[0002] Braking efficiency is a crucial performance indicator of anti-skid braking systems, and it needs to be assessed in braking system qualification tests and aircraft flight tests. A commonly used method for calculating braking efficiency is the area method, which is the ratio of the area enclosed by the actual braking record curve (pressure or torque) to the area enclosed by the envelope line (the line connecting the peaks of the actual braking record curve). Figure 1 As shown. Expressed as a formula:

[0003]

[0004] In the formula:

[0005] η b --Braking efficiency;

[0006] A -- The area enclosed by the brake pressure curve and the horizontal axis of time t;

[0007] A0 -- The area enclosed by the envelope of the brake pressure curve and the horizontal axis of time t.

[0008] An investigation revealed that the research paper, "Research on Calculation Methods of Civil Aircraft Braking Efficiency," proposes a pressure efficiency method. However, it only suggests finding the peak points on the curve to form a pressure envelope, without disclosing the method for extracting these peak points. This method lacks feasibility and fails to consider deep wheel slippage, thus contradicting engineering realities. The original factory test involved printing discrete pressure curves onto graph paper, manually connecting the peaks to obtain the envelope curve, and then counting the area A between the discrete pressure curve and the time axis (t), as well as the area A between the envelope curve and the time axis (t). This method is inefficient and inaccurate. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies in calculating braking efficiency, such as poor operability, low calculation efficiency, and poor accuracy, this invention proposes a method for calculating braking efficiency based on discrete pressure of an aircraft.

[0010] The specific process of this invention is as follows:

[0011] Step 1, calculate the difference value of the discrete data pressure P:

[0012] The difference value of the discrete data pressure P is obtained by formula (2):

[0013] Difference matrix X = [P(2)-P(1),P(3)-P(2),P(4)-P(3),……,P(n)-P(n-1)] (2)

[0014] In equation (2), X is the difference matrix and P(n) is the nth pressure data.

[0015] The difference matrix X = [x(1), x(2), x(3), ..., x(i)] of the discrete data pressure P is obtained. x(i) is the i-th data in the difference matrix X. i = n-1.

[0016] Step 2, determine the sign of the difference matrix X after differencing:

[0017] When x(i) > 0, assign y(i) the value 1; when x(i) = 0, assign y(i) the value 0; when x(i) < 0, assign y(i) the value -1.

[0018] The symbol matrix Y = [y(1), y(2), y(3), ..., y(i)] is obtained.

[0019] Step 3, obtain the difference matrix M of the symbol Y:

[0020] The difference matrix M of Y obtained by formula (3):

[0021] Difference matrix M=[y(2)-y(1),y(3)-y(2),y(4)-y(3),...,y(n-1)-y(n-2)] (3)

[0022] The difference matrix M = [m(1),m(2),m(3),……,m(n-2)] is used to obtain the symbol Y.

[0023] Step 4, determine the extreme point matrix F:

[0024] The points in matrix M that are -2 are the extreme points. The extreme point matrix F is obtained as [f(1),f(2),f(3),……,f(j)].

[0025] In the extreme point matrix F, the number of extreme points j is determined according to the sampling points of the original pressure data. Connecting f(1) to f(j) yields the extreme point curve of discrete pressure P.

[0026] The number of extreme points j is the number of points with a value of -2 in the difference matrix M.

[0027] Step 5, remove slippage points from extreme points:

[0028] Because sensor sampling fluctuates, maximum points are extracted when the wheels slip, and the curves formed by these points are not envelopes.

[0029] Delete the points in f(j) where the pressure is <6MPa to obtain a new extreme point matrix D = [d(1),d(2),d(3),……,d(k)].

[0030] Connecting d(1) to d(k) yields the discrete pressure P envelope curve 5.

[0031] Step 6, calculate the braking efficiency η b :

[0032] The braking efficiency η is obtained by comparing the area A of the pressure curve with the area A0 of the envelope curve. b .

[0033] The method for calculating braking efficiency η b The specific process is as follows:

[0034] The pressure curve area A is the area enclosed by the discrete data pressure P curve and the horizontal axis time t, and the envelope curve area A0 is the area enclosed by the discrete pressure P envelope curve and the horizontal axis time t.

[0035] The braking efficiency η of the aircraft is calculated using formula (1). b

[0036]

[0037] In the formula

[0038] η b --Braking efficiency;

[0039] A -- The area enclosed by the brake pressure curve and the horizontal axis of time t;

[0040] A0 -- The area enclosed by the envelope of the brake pressure curve and the horizontal axis of time t.

[0041] This completes the method for calculating the braking efficiency of discrete pressure aircraft.

[0042] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0043] 1. The paper "Research on Calculation Method of Braking Efficiency of Civil Aircraft" proposes the pressure efficiency method, but only proposes to find the peak point on the curve to form the pressure envelope. However, it does not disclose the peak point extraction method and is not feasible. This invention provides a specific operation process, which has engineering implementation value and can be used in existing engineering technology.

[0044] 2. The "Research on the Calculation Method of Braking Efficiency of Civil Aircraft" proposed the pressure efficiency method for calculation, but did not consider the deep slippage state of the wheels, and only obtained curve 4 in this invention. This invention fully considers the actual engineering situation, removes unsuitable peak points and deep slippage points, and obtains curve 5 in this invention.

[0045] 3. The method of calculating the envelope of the parameter interval for fault isolation proposed in "A Method for Calculating the Envelope of the Parameter Interval" uses the upper and lower functions. However, this method is only suitable for continuous variables. For discrete variables, a high-order fitting can be performed and then the envelope can be obtained using this method. However, high-order fitting will seriously distort the accuracy of the data. The discrete data processing method proposed in this invention can be directly applied to aircraft parameters.

[0046] 4. In the original factory test, the discrete pressure curves were printed onto graph paper, and the peak values ​​of the discrete pressure curves were manually connected to obtain the envelope curve. The area A of the curve enclosed by the discrete pressure curve and the time t x-axis, as well as the area of ​​the curve enclosed by the envelope and the time t x-axis, were counted. While this method requires two people to process a set of data, the algorithm proposed in this invention only requires 2 minutes, greatly improving data processing efficiency and batch processing capabilities. Attached Figure Description

[0047] Figure 1 This is a schematic diagram for calculating braking efficiency.

[0048] Figure 2 It is a discrete data pressure P curve.

[0049] Figure 3 It is the curve of the extreme points of discrete pressure P.

[0050] Figure 4 It is the envelope curve of discrete pressure P.

[0051] Figure 5 This is a flowchart of the present invention.

[0052] In the figure: 1. Envelope; 2. Braking pressure; 3. Discrete data pressure P curve; 4. Discrete pressure P extreme point curve; 5. Discrete pressure P envelope curve. Detailed Implementation

[0053] This embodiment describes a method for calculating the braking efficiency of an aircraft based on field pressure data. The specific process is as follows:

[0054] Discrete data pressure P = [P(1),P(2),P(3),……,P(n)] is shown in curve 3 of discrete data pressure P, which is the raw pressure data collected by the aircraft. In this example, the data consists of 884 discrete collection points, i.e., n is 884.

[0055] Step 1, calculate the difference value of the discrete data pressure P:

[0056] The difference value of the discrete data pressure P is obtained by formula (2):

[0057] Difference matrix X = [P(2)-P(1), P(3)-P(2), P(4)-P(3),……, P(n)-P(n-1)](2)

[0058] In equation (2), X is the difference matrix and P(n) is the nth pressure data.

[0059] The difference matrix X = [x(1), x(2), x(3), ..., x(i)] of the discrete data pressure P is obtained. x(i) is the i-th data in the difference matrix X. i = n-1.

[0060] Step 2, determine the sign of the difference matrix X after differencing:

[0061] When x(i) > 0, assign y(i) the value 1; when x(i) = 0, assign y(i) the value 0; when x(i) < 0, assign y(i) the value -1.

[0062] The symbol matrix Y = [y(1), y(2), y(3), ..., y(i)] is obtained.

[0063] Step 3, obtain the difference matrix M of the symbol Y:

[0064] The difference matrix M of Y obtained by formula (3):

[0065] Difference matrix M=[y(2)-y(1),y(3)-y(2),y(4)-y(3),...,y(n-1)-y(n-2)]=[m(1),m(2),m(3),...,m(n-2)].

[0066] Step 4, determine the extreme points:

[0067] The points in matrix M that are -2 are the extreme points. The extreme point matrix F is obtained as [f(1),f(2),f(3),……,f(j)].

[0068] The number of extreme points j is determined based on the sampling points of the original pressure data; in this example, j is 188. Connecting f(1) to f(j) yields the discrete pressure P extreme point curve 4.

[0069] The number of extreme points j is the number of points with a value of -2 in the difference matrix M.

[0070] Step 5, remove slippage points from extreme points:

[0071] Because sensor sampling fluctuates, maximum points are extracted when the wheels slip, and the curves formed by these points are not envelopes.

[0072] Delete the points in f(j) with pressure < 6MPa to obtain a new extreme point matrix D = [d(1), d(2), d(3), ..., d(k)], where k is 170 in this embodiment.

[0073] Connecting d(1) to d(k) yields the discrete pressure P envelope curve 5.

[0074] Step 6, calculate the braking efficiency:

[0075] Find the area A of the pressure curve formed by the discrete pressure P curve 3 and the horizontal axis time t, A = 136.48, and the area A0 of the envelope curve formed by the discrete pressure P envelope curve 5 and the horizontal axis time t, A0 = 149.43.

[0076] The braking efficiency η of the aircraft is calculated using formula (1). b

[0077]

[0078] In the formula:

[0079] η b --Braking efficiency;

[0080] A -- The area enclosed by the brake pressure curve and the horizontal axis of time t;

[0081] A0 -- The area enclosed by the envelope of the brake pressure curve and the horizontal axis of time t.

[0082] In this embodiment, η b =91.33%.

[0083] This completes the method for calculating the braking efficiency of discrete pressure aircraft.

[0084] Discrete data pressure P = [P(1),P(2),P(3),……,P(n)] is shown in Figure 3. It is the original pressure data collected by the aircraft. This data has 884 discrete collection points, that is, n is 884.

Claims

1. A method for calculating the braking efficiency of an aircraft under discrete pressure, characterized in that, The specific process is as follows: Step 1: Calculate the difference value of the discrete pressure P; The difference value of the discrete pressure P is obtained by formula (2): The difference matrix X = [P(2)- P(1), P(3)- P(2), P(4)- P(3),……, P(n)- P(n-1)] (2) In equation (2), X is the difference matrix, and P(n) is the nth pressure data. The difference matrix X = [x(1), x(2), x(3), ..., x(n-1)] is obtained for the discrete pressure P; Step 2, determine the sign of the difference matrix X after differencing: x(i) is the i-th data in the difference matrix X; i = 1 to n-1; when x(i) > 0, y(i) is assigned the value 1; when x(i) = 0, y(i) is assigned the value 0; when x(i) < 0, y(i) is assigned the value -1. The symbol matrix Y = [y(1), y(2), y(3), ..., y((n-1)] is obtained; Step 3, obtain the difference matrix M of the sign matrix Y: The difference matrix M of Y obtained by formula (3): Difference matrix M=[y(2)- y(1), y(3)- y(2), y(4)- y(3),…, y(n-1)- y(n-2)] (3) Step 4, determine the extreme point matrix F: The points in matrix M that are -2 are the extreme points; thus, the extreme point matrix F = [f(1), f(2), f(3), ..., f(j)] is obtained. In the extreme point matrix F, the number of extreme points j is determined according to the sampling points of the original pressure data. Connecting f(1) to f(j) yields the discrete pressure P extreme point curve. The number of extreme points j is the number of points with a value of -2 in the difference matrix M; Step 5, remove slippage points from extreme points: Because sensor sampling fluctuates, maximum points are extracted when the wheels slip, and the curves formed by these points are not envelope lines. Delete the points in f(j) where the pressure is < 6 MPa to obtain a new extreme point matrix D = [d(1), d(2), d(3), ..., d(k)]; Connecting d(1) to d(k) yields the discrete pressure P envelope curve; Step 6, Calculate the braking efficiency : Braking efficiency is obtained by comparing the area A of the pressure curve and the area A0 of the envelope curve. ; The calculation of braking efficiency The specific process is as follows: The pressure curve area A is the area enclosed between the discrete pressure P curve and the horizontal axis time t, and the envelope curve area A0 is the area enclosed between the discrete pressure P envelope curve and the horizontal axis time t. The braking efficiency of the aircraft is calculated using formula (1). ; （1） This completes the calculation of the braking efficiency of the aircraft's discrete pressure.

2. The method for calculating braking efficiency based on discrete aircraft pressure as described in claim 1, characterized in that, The difference matrix M = [m(1), m(2), m(3), ..., m(n-2)] is used to obtain the symbol matrix Y.

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