Rocket engine pressure signal extraction method based on empirical mode decomposition

Abstract

The invention relates to the technical field of rocket engine pressure signal processing, and particularly discloses a rocket engine pressure signal extraction method based on empirical mode decomposition, which comprises the following steps of: firstly, performing empirical mode decomposition on an obtained rocket engine pressure signal to obtain a plurality of intrinsic mode function (IMF) components; then obtaining a correlation coefficient between each component and the last component, namely a residual term, if an absolute value of the correlation coefficient is not less than a set threshold value, considering that the eigenmode function component belongs to the rocket engine pressure signal to be extracted, otherwise, considering that the eigenmode function component does not belong to the rocket engine pressure signal to be extracted; and finally summing the eigenmode function component belonging to the rocket engine pressure signal and the residual term to obtain a final rocket engine pressure signal to be extracted. The noise interference in the rocket engine pressure signal can be reduced, the pressure signal is accurately extracted, and the identifiability of the signal is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rocket engine pressure signal processing, and in particular relates to a rocket engine pressure signal extraction method based on empirical mode decomposition. Background Art

[0002] The pressure signal characteristics at key parts of rocket engine tanks, pipelines, turbo pumps, etc. can effectively characterize the working conditions of the engine and are important indicators reflecting the working characteristics of rocket engines. However, during the flight of a rocket, due to the influence of factors such as overload, vibration, impact and noise, the measured pressure signal will have a lot of interference, which seriously affects the recognition of the pressure signal characteristics and makes it difficult to accurately evaluate the working status of the rocket engine. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a rocket engine pressure signal extraction method based on empirical mode decomposition, which reduces noise interference in the rocket engine pressure signal, accurately extracts the pressure signal, and improves the identifiability of the signal.

[0004] The present invention is achieved through the following technical solutions.

[0005] The present invention provides a method for extracting a rocket engine pressure signal based on empirical mode decomposition, comprising the following steps: Step 1: Perform empirical mode decomposition on the collected rocket engine pressure raw signal data to obtain several eigenmode function components. The specific decomposition process is as follows: S1: Find the original signal All local maximum and minimum points of are processed by cubic spline interpolation, and the upper envelope of the original signal is fitted. , lower envelope , calculate the mean of the upper and lower envelopes : S2: Get the original signal and Difference : judge Does it meet the eigenmode function component standard? If it does, then The original signal The first-order eigenmode function component of Consider it as the original signal and repeat steps S1-S2 until Satisfies the eigenmode function component criterion, where is the number of repetitions; S3: Subtract the obtained intrinsic mode function component from the original signal, that is, separate it from the original signal , and the residual signal is obtained ,Right now: Will Consider it as the original signal, repeat steps S1-S3 to obtain the 2nd, 3rd, 4th, ..., until the nth order intrinsic mode function component. When the residual signal When is a constant or a monotonic function, the decomposition process ends; At this point, the original signal can be expressed as: Step 2: Obtain the correlation coefficient between each eigenmode function component and the last component, i.e., the residual term; Step 3: Set the correlation coefficient threshold λ, compare the absolute value of the correlation coefficient obtained in step 2 with the threshold λ, if the absolute value of the correlation coefficient is not less than the set threshold, it is considered that the intrinsic mode function component corresponding to the correlation coefficient belongs to the rocket engine pressure signal to be extracted, otherwise it is considered that the intrinsic mode function component does not belong to the rocket engine pressure signal to be extracted; Step 4: Sum the intrinsic mode function component belonging to the rocket engine pressure signal and the residual term to obtain the final rocket engine pressure signal to be extracted.

[0006] Furthermore, the eigenmode function component standard in step 1 is: the means of the upper envelope formed by all maximum points and the lower envelope formed by all minimum points are both zero; the number of extreme value points and the number of zero-crossing points in the entire data differ by at most 1.

[0007] Furthermore, the components of each eigenmode function in step 2 and the residual term The correlation coefficient can be:

[0008] In the formula, For the eigenmode function components, =1,2,3,...,n, n is the number of eigenmode function components, For the The first component of the eigenmode function Collection points, = 1,2,3... , is the length of the eigenmode function component.

[0009] Furthermore, in step three, the correlation coefficient threshold λ=0.5.

[0010] The beneficial effects achieved by the present invention are: Compared with the prior art, the present invention provides a rocket engine pressure signal extraction method based on empirical mode decomposition. First, the acquired rocket engine pressure signal is subjected to empirical mode decomposition to obtain a plurality of intrinsic mode function components; then the correlation coefficient between each component and the last component, i.e., the residual term, is obtained, and the intrinsic mode function component belonging to the rocket engine pressure signal is identified by analyzing the correlation coefficient; finally, the intrinsic mode function component belonging to the rocket engine pressure signal is summed with the residual term to accurately extract the pressure signal, thereby reducing noise interference in the pressure signal and improving the signal recognizability. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a flow chart of a method for extracting pressure signals of a rocket engine based on empirical mode decomposition in the present invention; Figure 2 This is the original rocket engine pressure signal diagram collected in the present invention; Figure 3 The first order intrinsic mode function component IMF1 signal diagram of the original pressure signal is obtained; Figure 4 The second order intrinsic mode function component IMF2 signal diagram of the original pressure signal is obtained; Figure 5 The third-order intrinsic mode function component IMF3 signal diagram of the original pressure signal is obtained; Figure 6 The fourth-order intrinsic mode function component IMF4 signal diagram of the original pressure signal is obtained; Figure 7 The fifth-order intrinsic mode function component IMF5 signal diagram of the original pressure signal is obtained; Figure 8 The sixth-order intrinsic mode function component IMF6 signal diagram of the original pressure signal is obtained; Fig. 9 The seventh-order intrinsic mode function component IMF7 signal diagram of the original pressure signal is obtained; Fig.10 The residual signal diagram of the original pressure signal is obtained; Fig.11 The rocket engine pressure signal diagram extracted in the present invention; Fig.12 This is a comparison diagram of the original rocket engine pressure signal and the extracted pressure signal in the present invention. DETAILED DESCRIPTION

[0012] The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments so that those skilled in the art can more fully understand the present invention, but the present invention is not limited in any way.

[0013] like Figure 1 FIG. 1 is a flow chart of a method for extracting a pressure signal of a rocket engine based on empirical mode decomposition according to the present invention. Figure 1 The embodiments of the present invention are described with reference to the accompanying drawings and examples.

[0014] Example The present invention proposes a method for extracting a rocket engine pressure signal based on empirical mode decomposition, which specifically comprises the following steps: Step 1: Perform empirical mode decomposition on the collected original signal data of rocket engine pressure to obtain several intrinsic mode function components. The original rocket engine pressure signal contains 1500 sampling points, such as Figure 2 The specific decomposition process is as follows: S1: Find the original signal All local maximum and minimum points of are processed by cubic spline interpolation, and the upper and lower envelopes of the original signal are fitted, which are , , calculate the mean of the upper and lower envelopes : S2: Get the original signal and Difference : Original signal Subtract the envelope mean , which is equivalent to removing a low-frequency component and judging Does it meet the eigenmode function component standard? If it does, then The original signal The first-order eigenmode function component of Consider it as the original signal and repeat steps S1-S2 until Satisfy the eigenmode function component standard, is the number of repetitions.

[0015] The eigenmode function component standard is: the mean of the upper envelope formed by all maximum points and the mean of the lower envelope formed by all minimum points are both zero; the number of extreme points and the number of zero-crossing points in the entire data differ by at most 1.

[0016] S3: Subtract the obtained intrinsic mode function component from the original signal, that is, separate it from the original signal , and the residual signal is obtained ,Right now: Will Consider it as the original signal, repeat steps S1-S3 to obtain the second, third, fourth, ..., until the nth order intrinsic mode function component. When the residual signal When is a constant or a monotonic function, the decomposition process ends; At this point, the original signal can be expressed as: The empirical mode decomposition results of the original rocket engine pressure signal are as follows: Figure 3-Figure 10 As shown, the signal is decomposed into IMF1, IMF2, IMF3, IMF4, IMF5, IMF6, IMF7 and the residual term.

[0017] Step 2: According to formula (5), the correlation coefficient between each eigenmode function component and the last component, i.e., the residual term, is obtained. The correlation coefficient expression is:

[0018] In the formula, For the eigenmode function components, =1,2,3,...,n, n is the number of eigenmode function components, For the The first component of the eigenmode function Collection points, = 1,2,3... , is the length of the eigenmode function component.

[0019] After solving, in this embodiment, the correlation coefficients between the intrinsic mode function components IMF1, IMF2, IMF3, IMF4, IMF5, IMF6, and IMF7 and the residual term are: -0.0004, -0.0279, 0.0221, -0.0936, 0.0403, 0.2485, and -0.5725, respectively.

[0020] Step 3. Compare the absolute value of the correlation coefficient obtained in step 2 with the threshold λ, and take the threshold λ=0.5. After comparison, the absolute value of the correlation coefficient between the IMF7 component and the residual term is greater than the threshold 0.5. It is considered that the intrinsic mode function component belongs to the rocket engine pressure signal to be extracted. The absolute values ​​of the correlation coefficients between IMF1, IMF2, IMF3, IMF4, IMF5, and IMF6 and the residual term are all less than the threshold 0.5. It is considered that these 6 intrinsic mode function components do not belong to the rocket engine pressure signal to be extracted.

[0021] Step 4: Sum the intrinsic mode function component of the rocket engine pressure signal and the residual term to obtain the final rocket engine pressure signal to be extracted. ,Right now:

[0022] The final extracted rocket engine pressure signal is as follows: Fig.11 shown.

[0023] Comparison of the original rocket engine pressure signal and the extracted pressure signal Fig.12 shown.

[0024] The above describes in detail the implementation modes of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes. The implementation modes can still be changed within the knowledge scope of ordinary technicians in the field. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting rocket engine pressure signals based on empirical mode decomposition, characterized in that: The steps include: Step 1: Perform empirical mode decomposition on the collected original signal data of rocket engine pressure to obtain several eigenmode function components. The specific decomposition process is as follows: S1: Find the original signal All local maximum and minimum points of are processed by cubic spline interpolation, and the upper envelope of the original signal is fitted. , lower envelope , calculate the mean of the upper and lower envelopes : S2: Get the original signal and Difference : judge Does it meet the eigenmode function component standard? If it does, then The original signal The first-order eigenmode function component of Consider it as the original signal and repeat steps S1-S2 until Satisfies the eigenmode function component criterion, where is the number of repetitions; S3: Subtract the obtained intrinsic mode function component from the original signal, that is, separate it from the original signal , and the residual signal is obtained ,Right now: Will Treat it as the original signal and repeat steps S1-S3 to obtain the 2nd, 3rd, 4th, ..., until the nth order eigenmode function component. When the residual signal When is a constant or a monotonic function, the decomposition process ends; At this point, the original signal can be expressed as: Step 2: Obtain the correlation coefficient between each eigenmode function component and the last component, i.e., the residual term; Step 3: Set the correlation coefficient threshold λ, compare the absolute value of the correlation coefficient obtained in step 2 with the threshold λ, if the absolute value of the correlation coefficient is not less than the set threshold, it is considered that the intrinsic mode function component corresponding to the correlation coefficient belongs to the rocket engine pressure signal to be extracted, otherwise it is considered that the intrinsic mode function component does not belong to the rocket engine pressure signal to be extracted; Step 4: Sum the intrinsic mode function component belonging to the rocket engine pressure signal and the residual term to obtain the final rocket engine pressure signal to be extracted.

2. The method for extracting rocket engine pressure signals based on empirical mode decomposition according to claim 1, characterized in that: The eigenmode function component standard in step 1 is: the means of the upper envelope formed by all maximum points and the lower envelope formed by all minimum points are both zero; the number of extreme points and the number of zero-crossing points in the entire data differ by at most 1.

3. The method for extracting rocket engine pressure signals based on empirical mode decomposition according to claim 1, characterized in that: The components of each eigenmode function and the residual term in step 2 The correlation coefficient can be: In the formula, For the eigenmode function components, =1,2,3,...,n, n is the number of eigenmode function components, For the The first component of the eigenmode function Collection points, = 1,2,3... , is the length of the eigenmode function component.

4. The method for extracting rocket engine pressure signals based on empirical mode decomposition according to claim 1, characterized in that: In step 3, the correlation coefficient threshold λ=0.5.

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