Reciprocating compressor full-period angular domain signal extraction method based on differential characteristic analysis

Abstract

The invention provides a reciprocating compressor full-period angular domain signal extraction method based on differential characteristic analysis. The reciprocating compressor full-period angular domain signal extraction method based on differential characteristic analysis comprises the steps that 1, signals of all measuring points of a compressor are synchronously collected; 2, discrete differential characteristic analysis is carried out on the dynamic pressure signal array, and a whole-period signal of each measuring point is extracted; step 3, reconstructing a periodic signal; and step 4, converting the reconstructed periodic signal into an angular domain signal. According to the reciprocating compressor full-period angular domain signal extraction method based on differential characteristic analysis, the defects that in the prior art, deviation is large and many influence factors exist when the reciprocating compressor full-period angular domain signal is collected are overcome, and the reciprocating compressor full-period angular domain signal extraction method which is simple in algorithm and accurate in result is provided.

Description

Technical Field

[0001] The invention relates to the technical field of reciprocating compressor fault diagnosis, and in particular to a method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis. Background Art

[0002] Reciprocating compressors are widely used in the petroleum and chemical industries and are key equipment in the process industry. However, due to the complex structure, many moving parts and many excitation sources of reciprocating compressors, there are many fault problems in reciprocating compressors. Therefore, in order to ensure safe production, the online monitoring and diagnosis system of reciprocating compressors is indispensable. Pressure signals, displacement signals and vibration signals are the data sources for the online monitoring and diagnosis system to evaluate the operating status of the compressor. However, the direct data acquisition of the above signals obtains time-varying time-domain signals, which cannot intuitively analyze and diagnose the faults of the reciprocating compressor. Reciprocating compressors have significant periodic characteristics. Each signal quantity changes periodically with the crank angle of the reciprocating compressor. The change curve of the angle value of the crank angle when the piston is at the top dead center is the horizontal coordinate, with the size of each signal quantity as the vertical coordinate, the crank angle when the piston is at the top dead center as the starting point, and the angle value of the crank angle when the crank rotates one circle as the horizontal coordinate is called the full cycle angle domain signal of the reciprocating compressor. This signal can be used to draw fault analysis maps such as the reciprocating compressor indicator diagram, pressure angle domain diagram, displacement angle domain diagram, and vibration angle domain diagram. It can also be associated with the operation process of the reciprocating compressor. It is an important basis for state monitoring and fault diagnosis of reciprocating compressors.

[0003] At present, the method for extracting the full-cycle angular domain signal of a reciprocating compressor commonly used in industry is to install a key phase block and a key phase sensor at the position of the flywheel or coupling, and make the overlapping position of the key phase block and the key phase sensor correspond to the top dead center of the piston, and use the key phase signal of the key phase sensor as a reference signal to trigger the start of the acquisition of other signals, so as to determine the starting point of the full-cycle angular domain signal. Then, based on the rated speed of the reciprocating compressor, the time for the crankshaft to rotate one circle is determined, and the sampling rate of the time and the signal is used to calculate the number of sampling points, so as to realize the acquisition of the full-cycle angular domain signal. However, this method is greatly affected by the key phase signal and the rated speed. When the key phase block falls off, there is a corresponding deviation between the key phase block and the top dead center of the piston, or the key phase sensor fails, the correct reference signal cannot be obtained, resulting in inaccurate starting point of the full-cycle angular domain signal acquisition. In addition, due to the deviation between the rated speed and the actual speed of the compressor, the number of sampling points calculated based on the rated speed is not equal to the number of sampling points of the actual full cycle, resulting in inaccurate end point of the full cycle angular domain signal acquisition.

[0004] In the Chinese patent application with application number: 202011419522.7, a method for periodic segmentation of a reciprocating compressor signal in the keyless phase angle domain is involved, which belongs to the technical field of fault diagnosis of reciprocating compressors. This invention aims to solve the problem that fault diagnosis and analysis cannot be carried out due to abnormal or even lost key phase signals in online monitoring of reciprocating compressors in practice, and completes the interception of the entire cycle of the signal by mining the effective information inside the signal itself. It includes the following steps: 1) obtaining the vibration signal and converting it into an image; 2) determining the size of the interception window; 3) identifying the impact of valve opening; 4) calculating the phase of valve opening and intercepting the entire cycle signal. This method realizes the whole cycle re-segmentation of the collected compressor original signal without installing a key phase sensor or when the key phase sensor fails. While eliminating the high cost of key phase equipment, it also avoids the problems of the inability of the online monitoring system to perform effective diagnosis and the failure of the gas volume control system due to the failure of the monitoring equipment, effectively improving the reliability of the compressor monitoring and control system. However, when using this method, it is necessary to calculate the valve opening phase, which is related to the expansion coefficient, suction pressure, and exhaust pressure. The expansion coefficient, suction pressure, and exhaust pressure during the actual operation of the compressor are difficult to obtain accurately. Therefore, the full cycle signal obtained by this method has a certain deviation.

[0005] In the Chinese patent application with application number: 201510428935.4, the problem of abnormal key phase signal in the actual online monitoring of reciprocating compressors causing the inability to perform fault analysis and diagnosis is involved. The signal phase calibration method is studied, and a reciprocating compressor signal full cycle phase calibration method based on similarity analysis is proposed. Taking advantage of the fact that the waveforms with phase deviation due to abnormal key phase signal at each measuring point of the reciprocating compressor are similar to the waveforms with normal phase, the waveforms after the phase deviation are phase shifted, and then compared with the normal waveform, and the similarity coefficient is calculated. Through continuous offset iterative calculation, the offset phase value corresponding to the maximum value of the similarity coefficient is obtained; when the offset phase values ​​corresponding to the maximum similarity coefficients of most signal waveforms are equal, the waveform after the key phase signal is abnormal can be phase-calibrated by the offset phase value. This method effectively solves the problem of fault diagnosis being unable to be performed due to abnormal key phase signal, and also lays the foundation for the next step of research on reciprocating compressor fault feature extraction methods. However, this method relies on normally collected compressor signals, and for a compressor operating under variable operating conditions, it is necessary to normally collect compressor signals of multiple groups of operating conditions. When the compressor operates under conditions where there is no normally collected signal as basic data, this method fails.

[0006] In the article "Determination Method and Experimental Device of Dynamic Gas Force on Valve Plate of Reciprocating Compressor" in Volume 13, Issue 2, 1987 of "Journal of Gansu University of Technology", a method for measuring and calculating the dynamic gas force on valve plate of reciprocating compressor was proposed. The dynamic gas force on valve plate was measured for the first time on a running reciprocating compressor. The design of experimental valve, experimental device and related experimental test technology were also introduced. In this article, the signal output of the displacement sensor installed at the flywheel position is used as the angle recognition signal of the cylinder gas pressure signal and the valve plate displacement signal.

[0007] In the development of a comprehensive performance test system for reciprocating compressors in the 6th issue of Volume 36 of Chemical Machinery in 2009, the development method of a comprehensive performance test system for reciprocating compressors was introduced, and the system hardware composition, test method, configuration software design and implementation functions were explained. In this paper, the output pulse of the rotary encoder is used as the external trigger signal for cylinder pressure sampling to obtain the angular domain pressure signal, and then the indicator diagram is obtained.

[0008] The above existing technologies are significantly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new method for extracting the full-cycle angular domain signal of a reciprocating compressor based on differential characteristic analysis. Summary of the invention

[0009] The object of the present invention is to provide a method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis, which has the advantages of reducing hardware cost and improving the reliability of an online monitoring and diagnosis system for a reciprocating compressor.

[0010] The object of the present invention can be achieved by the following technical measures: a method for extracting the full-cycle angular domain signal of a reciprocating compressor based on differential characteristic analysis, the method for extracting the full-cycle angular domain signal of a reciprocating compressor based on differential characteristic analysis comprises:

[0011] Step 1, synchronously collecting signals from various measuring points of the compressor;

[0012] Step 2, performing discrete differential characteristic analysis on the dynamic pressure signal array to extract the whole cycle signal of each measuring point;

[0013] Step 3, reconstruct the periodic signal:

[0014] Step 4: Convert the reconstructed periodic signal into an angular domain signal.

[0015] The purpose of the present invention can also be achieved by the following technical measures:

[0016] Step 1 includes:

[0017] 1.1, calculate the rated operating cycle T of the compressor;

[0018] 1.2, calculate the number of sampling points M during the two cycles of compressor operation (2T);

[0019] 1.3, with sampling rate f and number of sampling points per channel M as sampling parameters, synchronous signal acquisition is performed on the dynamic pressure measurement point, vibration measurement point and displacement measurement point of the compressor.

[0020] In step 1.1, the rated operating cycle T of the compressor is calculated according to the rated operating speed N of the compressor.

[0021] In step 1.2, according to the set signal sampling rate f, the number of sampling points M within the time 2T of two cycles of the compressor operation is calculated, where M=2Tf.

[0022] In step 1.3, the sampling rate f and the number of sampling points per channel M are used as sampling parameters to synchronously collect signals from the dynamic pressure measurement point, vibration measurement point, and displacement measurement point of the compressor. The above measurement points are denoted as P, V, and D respectively. The collected dynamic pressure measurement point signal array is {P1, P2, ···, P M}, the array of vibration measurement point signals collected is {V1, V2, ···, V M}, the array of displacement measurement point signals collected is {D1, D2, ···, D M}, where the subscripts 1, 2,...,M represent the position numbers of the data points in the entire array.

[0023] Step 2 includes:

[0024] 2.1, for the dynamic pressure measurement point signal array {P1, P2, ···, P M}Perform discrete differentiation to obtain discrete differential array Y;

[0025] 2.2, find the position numbers of the two adjacent maximum values ​​of array Y:

[0026] 2.3, intercept the whole period signal array.

[0027] In step 2.1, the dynamic pressure measurement point signal array {P1, P2, ···, P M} Perform discrete differentiation and use the second-order central differentiation method to obtain the discrete differential array Y of the dynamic pressure measurement point signal array. Where i = 1, 2, ···M; dt represents the difference in the position numbers of two adjacent data in the array; P0 takes P1, P M+1 Take P M .

[0028] Step 2.2 includes:

[0029] Ⅰ) Find the solution that satisfies Y j Array element Y ≥ Y(j=1,2···M)j ;

[0030] II) Remove Y j from the array Y to obtain the Y' array;

[0031] III) Find the array elements Y k ' that satisfy Y i ' (i = 1, 2 ··· M - 1); k

[0032] IV) When j > k, set j = k and k = j; when j < k, set k = k + 1;

[0033] V) Obtain the position numbers of two adjacent maximum values of the array Y: j and k.

[0034] In step 2.3, for the dynamic pressure measurement point signal array P, the vibration measurement point signal array V, and the displacement measurement point signal array D, intercept the full - cycle signal arrays starting from the position number j and ending at k - 1: the full - cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1}, the full - cycle vibration measurement point signal array {V j , V j+1 , ···, V k-1}, and the full - cycle displacement measurement point signal array {D j , D j+1 , ···, D k-1}.

[0035] Step 3 includes:

[0036] 3.1, Search for the array element P q+1 that satisfies P j ≤P q-1 ; q

[0037] 3.2, Reconstruct the full - cycle dynamic pressure measurement point signal array, the full - cycle vibration measurement point signal array, and the full - cycle displacement measurement point signal array into full - cycle signals starting from the top dead center of the piston.

[0038] In step 3.1, traverse to search for the array element P q+1 that satisfies P j ≤P q-1 (q = k - 2, k - 3, ···, j + 1), and stop searching once found. q

[0039] In step 3.2, for the full - cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1}、Full cycle vibration measurement point signal array {V j , V j+1 ,···,V k-1}、Full cycle displacement measurement point signal array {D j , D j+1 ,···,D k-1} is reconstructed and converted into a full-cycle signal starting from the piston top dead center, that is, the dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1}.

[0040] In step 4, the dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1} are the ordinate values, with is the horizontal coordinate, where m=1, 2, ···, (kj), and a curve graph is drawn in the two-dimensional coordinate system, that is, the angular domain signal of the entire cycle of the reciprocating compressor with the top dead center of the piston as the starting point is obtained.

[0041] The present invention overcomes the shortcomings of the prior art in collecting the full-cycle angular domain signals of reciprocating compressors, such as large deviations, many influencing factors, and high dependence on hardware. The present invention can extract the full-cycle pressure, vibration, displacement and other angular domain signals of the reciprocating compressor only through in-depth analysis of the compressor dynamic pressure signals. While ensuring accuracy, it also saves hardware overhead. At the same time, the present invention can adapt to the extraction of full-cycle angular domain signals of reciprocating compressors driven by fixed-frequency motors and variable-frequency motors, laying a foundation for reciprocating compressor fault diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart of a specific embodiment of the method for extracting the full-cycle angular domain signal of a reciprocating compressor based on differential characteristic analysis of the present invention;

[0043] Figure 2 It is a data spectrum of dynamic pressure measurement point signal, vibration measurement point signal and displacement measurement point signal of a reciprocating compressor in a specific embodiment of the present invention;

[0044] Figure 3 A dynamic pressure signal array and its discrete differential array spectrum in a specific embodiment of the present invention;

[0045] Figure 4 It is a full-cycle data spectrum of dynamic pressure measurement point signal, vibration measurement point signal and displacement measurement point signal of a reciprocating compressor in a specific embodiment of the present invention;

[0046] Figure 5 It is a full-cycle signal spectrum of a dynamic pressure measurement point, a vibration measurement point, and a displacement measurement point with the piston top dead center as the starting point in a specific embodiment of the present invention;

[0047] Figure 6 It is a full-cycle angular domain signal spectrum of a dynamic pressure measuring point, a vibration measuring point, and a displacement measuring point with the piston top dead center as the starting point in a specific embodiment of the present invention;

[0048] Figure 7 A spectrum diagram of a compressor dynamic pressure signal in a specific embodiment of the present invention;

[0049] Figure 8 It is a work diagram of a reciprocating compressor in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0050] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0051] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0052] The method for extracting the full-cycle angular domain signal of a reciprocating compressor based on differential characteristic analysis of the present invention comprises:

[0053] The first step is to synchronously collect the signals of each measuring point of the compressor:

[0054] 1.1 According to the rated operating speed N of the compressor, calculate the rated operating cycle T of the compressor.

[0055] 1.2 According to the set signal sampling rate f, calculate the number of sampling points M in the two cycles of compressor operation within 2T time, M = 2Tf;

[0056] 1.3 With sampling rate f and number of sampling points per channel M as sampling parameters, synchronous signal acquisition is performed on the dynamic pressure measurement point, vibration measurement point and displacement measurement point of the compressor. The above measurement points are denoted as P, V, and D respectively. The array of dynamic pressure measurement point signals acquired is {P1, P2, ···, P M}, the array of vibration measurement point signals collected is {V1, V2, ···, V M}, the array of displacement measurement point signals collected is {D1, D2, ···, D M}, where the subscripts 1, 2, ···M represent the position number of the data point in the entire array;

[0057] The second step is to perform discrete differential characteristic analysis on the dynamic pressure signal array and extract the full-cycle signal of each measuring point:

[0058] 2.1 Dynamic pressure measurement point signal array {P1, P2, ···, P M} Perform discrete differentiation and use the second-order central differentiation method to obtain the discrete differential array Y of the dynamic pressure measurement point signal array. Where i = 1, 2, ···M; dt represents the difference in the position numbers of two adjacent data in the array; P0 takes P1, P M+1 Take P M ;

[0059] 2.2 Find the position numbers of the two adjacent maximum values ​​of array Y:

[0060] Ⅰ) Find the solution that satisfies Y j Array element Y ≥ Y(j=1,2···M) j ;

[0061] II) Remove Y j from the array Y to obtain the Y' array;

[0062] III) Find the array elements Y k ' that satisfy Y i '≥Y k ' (i = 1, 2 ··· M - 1);

[0063] IV) When j > k, set j = k and k = j; when j < k, set k = k + 1.

[0064] V) Obtain the position numbers of two adjacent maximum values of the array Y: j and k;

[0065] 2.3 Intercept the full - cycle signal arrays from the dynamic pressure measurement point signal array P, the vibration measurement point signal array V, and the displacement measurement point signal array D starting from the position number j and ending at k - 1: the full - cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1}, the full - cycle vibration measurement point signal array {V j , V j+1 , ···, V k-1}, and the full - cycle displacement measurement point signal array {D j , D j+1 , ···, D k-1};

[0066] The third step, reconstruct the periodic signal:

[0067] 3.1 Traverse to find the array element P q+1 that satisfies P j ≤P q-1 (q = k - 2, k - 3, ···, j + 1), and stop searching once found; q

[0068] 3.2 Reconstruct the full - cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1}, the full - cycle vibration measurement point signal array {V j , V j+1 , ···, V k-1}, and the full - cycle displacement measurement point signal array {D j , D j+1 , ···, D k-1} into a full - cycle signal starting from the top dead center of the piston, that is, the dynamic pressure measurement point signal array {P q , P q+1 , ···, P k-1 ​, P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1};

[0069] The fourth step is to convert it into an angular domain signal:

[0070] The dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1} are the ordinate values, with is the horizontal coordinate, where m=1, 2, ···, (kj), and a curve graph is drawn in the two-dimensional coordinate system, that is, the angular domain signal of the entire cycle of the reciprocating compressor with the top dead center of the piston as the starting point is obtained.

[0071] The following are several specific embodiments of the present invention.

[0072] Example 1

[0073] In a specific embodiment 1 of the present invention, Figure 1 As shown, Figure 1 The flowchart of the method for extracting the full-cycle angular domain signal of a reciprocating compressor based on differential characteristic analysis of the present invention is as follows:

[0074] (1) Synchronously collect the signals of each measuring point of the compressor

[0075] First, based on the rated operating speed of the compressor N = 375 rpm, the rated operating cycle of the compressor T = 0.16 s is calculated;

[0076] Secondly, the signal sampling rate f = 3000 Hz is set, and the number of sampling points M = 960 in the two cycles 2T of the compressor operation is calculated;

[0077] Finally, the dynamic pressure measurement point, vibration measurement point, and displacement measurement point of the compressor are synchronously collected with sampling rate f = 3000 Hz and sampling points per channel M = 960 as sampling parameters. The above measurement points are denoted as P, V, and D respectively. The collected dynamic pressure measurement point signal array is {P1, P2, ···, P 960}, the array of vibration measurement point signals collected is {V1, V2, ···, V 960}, the array of displacement measurement point signals collected is {D1, D2, ···, D 960}, where the subscripts 1, 2...960 represent the position number of the data point in the entire array. The above measurement point signal data spectrum refers to the attached Figure 2 ;

[0078] (2) Perform discrete differential calculation on the dynamic pressure signal array to extract the full-cycle signal of each measuring point:

[0079] First, the dynamic pressure measurement point signal array {P1, P2, ···, P 960}Use the second-order central differential method for discrete differentiation to obtain the discrete differential array Y of the dynamic pressure measurement point signal array, Where i=1,2,···960,;dt=1;P0=P1,P 961 =P 960 ; Draw array P and array Y in the same coordinate system, refer to the attached Figure 3 ; Since the meaning of the discrete differential array Y of the dynamic pressure measurement point signal array is the slope of each point of the dynamic pressure signal curve, the slope will continue to increase when the compressor runs to the compression stage. After reaching the maximum, the exhaust valve opens and the slope decreases. Therefore, for a single-cycle dynamic pressure measurement point signal, the position of the maximum value of the discrete differential array is the opening moment of the compressor exhaust valve. For multiple-cycle dynamic pressure measurement point signals, the dynamic pressure signal data between two adjacent maximum values ​​is the full-cycle pressure signal data;

[0080] Secondly, find the position numbers of the two adjacent maximum values ​​of array Y:

[0081] Ⅰ) Find the solution that satisfies Y j Array element Y ≥ Y (j = 1, 2 · · · 960)j ;

[0082] Ⅱ) Remove Y j from the array Y to obtain the Y' array;

[0083] Ⅲ) Find the array elements Y k ' that satisfy Y i ' (i = 1, 2 ··· 959); k '

[0084] Ⅳ) When j > k, swap the values of j and k so that k > j; when j < k, set k = k + 1.

[0085] Ⅴ) Obtain the position numbers of two adjacent maximum values of the array Y: j and k;

[0086] Finally, intercept the full-cycle signal arrays for the dynamic pressure measurement point signal array P, the vibration measurement point signal array V, and the displacement measurement point signal array D starting from the position number j and ending at k - 1: the full-cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1}, the full-cycle vibration measurement point signal array {V j , V j+1 , ···, V k-1}, and the full-cycle displacement measurement point signal array {D j , D j+1 , ···, D k-1}, and refer to the data spectrograms of the above full-cycle measurement point signal arrays in the appendix Figure 4 ;

[0087] (3) Reconstruct the full-cycle measurement point signals

[0088] Since the starting point of the full-cycle signal intercepted in the second step is the valve opening moment, in order to change the starting point to the moment when the piston is at the top dead center, cycle signal reconstruction is required;

[0089] First, traverse to find the array element P q+1 that satisfies P j ≤ P q-1 (q = k - 2, k - 3, ···, j + 1), and stop searching once found; q ;

[0090] Second, for the full-cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1}, the full-cycle vibration measurement point signal array {V j , V j+1 , ···, V k-1}、Full cycle displacement measurement point signal array {D j , D j+1 ,···,D k-1} is intercepted and spliced ​​to reconstruct a full-cycle signal starting from the piston top dead center;

[0091] Finally, the dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1}, refer to the attached Figure 5 ;

[0092] (4) Convert the integer period signal into an integer period angular domain signal:

[0093] The dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1} are the ordinate values, with As the horizontal coordinate, where m = 1, 2, ···, (kj), a curve diagram is drawn in the two-dimensional coordinate system, that is, the angular domain signal of the entire cycle of the reciprocating compressor with the piston top dead center as the starting point is obtained. Figure 6 .

[0094] Since the meaning of the discrete differential array of the dynamic pressure measurement point signal array is the slope of each point on the dynamic pressure signal curve, the slope will continue to increase when the compressor runs to the compression stage. After reaching the maximum, the exhaust valve opens and the slope decreases. Therefore, for a single-cycle dynamic pressure measurement point signal, the position of the maximum value of the discrete differential array is the opening moment of the compressor exhaust valve. For multiple-cycle dynamic pressure measurement point signals, the dynamic pressure signal data between two adjacent maximum values ​​is the full-cycle pressure signal data. The full-cycle signal is then segmented and reconstructed, converted into a signal with the piston at the top dead center as the starting point, and the horizontal axis is converted into an angle, so as to obtain the full-cycle angular domain signal of the reciprocating compressor with the piston at the top dead center as the starting point.

[0095] Example 2

[0096] Embodiment 1 demonstrates a method for extracting the full-cycle angular domain signal of a reciprocating compressor driven by a fixed-frequency motor with a constant speed. Embodiment 2 realizes the extraction of the full-cycle angular domain signal of a reciprocating compressor driven by a variable-frequency motor by modifying step 1 in the invention content.

[0097] The first step is to synchronously collect the signals of each measuring point of the compressor:

[0098] 1.1 The sampling rate f and the number of sampling points per channel S are used as sampling parameters to collect signals from the compressor dynamic pressure measurement point, and the collected signals are analyzed by spectrum to obtain the pressure signal spectrum diagram, as shown in Figure 7 As shown, each frequency and its corresponding amplitude are expressed as {(0, p1), (1, p2), ···, (f n , p n ), ···}, where f n represents frequency, p n Indicates the amplitude. Calculate the first peak of the spectrum graph corresponding to (f n , p n ), the compressor operation cycle

[0099] 1.2 According to the set signal sampling rate f, calculate the number of sampling points M in the two cycles of compressor operation within 2T time, M = 2Tf;

[0100] 1.3 With sampling rate f and number of sampling points per channel M as sampling parameters, synchronous signal acquisition is performed on the dynamic pressure measurement point, vibration measurement point and displacement measurement point of the compressor. The above measurement points are denoted as P, V, and D respectively. The array of dynamic pressure measurement point signals acquired is {P1, P2, ···, P M}, the array of vibration measurement point signals collected is {V1, V2, ···, V M}, the array of displacement measurement point signals collected is {D1, D2, ···, D M}, where the subscripts 1, 2 ··· M represent the position sequence numbers of the data points in the entire array;

[0101] Step 2: Conduct discrete differential characteristic analysis on the dynamic pressure signal array and extract the full-cycle signals of each measuring point:

[0102] 2.1 Perform discrete differentiation on the dynamic pressure measuring point signal array {P1, P2, ···, P M}, and use the second-order central differential method to obtain the discrete differential array Y of the dynamic pressure measuring point signal array, where i = 1, 2, ··· M; dt represents the difference in position sequence numbers between two adjacent data in the array; P0 takes P1, P M+1 takes P M ;

[0103] 2.2 Obtain the position sequence numbers of two adjacent maximum values in the array Y:

[0104] Ⅰ) Find the array elements Y j ≥ Y(j = 1, 2 ··· M) in the array Y j ;

[0105] Ⅱ) Remove Y j from the array Y to obtain the Y' array;

[0106] Ⅲ) Find the array elements Y' k ≥ Y' i (i = 1, 2 ··· M - 1) in the array Y' k ;

[0107] Ⅳ) When j > k, take j = k, k = j; when j < k, take k = k + 1.

[0108] Ⅴ) Obtain the position sequence numbers of two adjacent maximum values in the array Y: j and k;

[0109] 2.3 Starting from the position sequence number j and ending at k - 1, intercept the full-cycle signal arrays for the dynamic pressure measuring point signal array P, the vibration measuring point signal array V, and the displacement measuring point signal array D: the full-cycle dynamic pressure measuring point signal array {P j , P j+1 , ···, P k-1}, the full-cycle vibration measuring point signal array {V j , V j+1 , ···, V k-1}, the full-cycle displacement measuring point signal array {D j , D j+1 , ···, D k-1};

[0110] Step 3: Reconstruct the periodic signal:

[0111] 3.1 Traverse to find the solution that satisfies P q+1 ≤P j ≤P q-1 The array element P of (q=k-2, k-3, . . . , j+1) q , stop searching when you find it;

[0112] 3.2 Full cycle dynamic pressure measurement point signal array {P j , P j+1 ,···,P k-1}、Full cycle vibration measurement point signal array {V j , V j+1 ,···,V k-1}、Full cycle displacement measurement point signal array {D j , D j+1 ,···,D k-1} is reconstructed and converted into a full-cycle signal starting from the piston top dead center, that is, the dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1};

[0113] The fourth step is to convert it into an angular domain signal:

[0114] The dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1}、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1}、Displacement measurement point signal array {D q , D q+1,···,D k-1 , D j , D j+1 ,···,D q-1} are the ordinate values, with is the horizontal coordinate, where m=1, 2, ···, (kj), and a curve graph is drawn in the two-dimensional coordinate system, that is, the angular domain signal of the entire cycle of the reciprocating compressor with the top dead center of the piston as the starting point is obtained.

[0115] Example 3

[0116] In the specific embodiment 3 of the present invention, an important fault diagnosis diagram of the reciprocating compressor, namely, the dynamometer diagram, can be drawn by acquiring the angular domain pressure signal of the entire cycle of the reciprocating compressor.

[0117] The first step is to collect the compressor dynamic pressure signal:

[0118] 1.1 According to the rated operating speed N of the compressor, calculate the rated operating cycle T of the compressor.

[0119] 1.2 According to the set signal sampling rate f, calculate the number of sampling points M in the two cycles of compressor operation within 2T time, M = 2Tf;

[0120] 1.3 The sampling rate f and the number of sampling points per channel M are used as sampling parameters to collect signals from the dynamic pressure measuring points of the compressor. The measuring point is recorded as P. The array of collected dynamic pressure measuring point signals is {P1, P2, ···, P M}, where the subscripts 1, 2, ···M represent the position number of the data point in the entire array;

[0121] The second step is to perform discrete differential characteristic analysis on the dynamic pressure signal array and extract the full-cycle signal of each measuring point:

[0122] 2.1 Dynamic pressure measurement point signal array {P1, P2, ···, P M} Perform discrete differentiation and use the second-order central differentiation method to obtain the discrete differential array Y of the dynamic pressure measurement point signal array. Where i = 1, 2, ···M; dt represents the difference in the position numbers of two adjacent data in the array; P0 takes P1, P M+1 Take P M ;

[0123] 2.2 Find the position numbers of the two adjacent maximum values ​​of array Y:

[0124] Ⅰ) Find the solution that satisfies Y j Array element Y ≥ Y(j=1,2···M) j ;

[0125] II) Remove Y j from the array Y to obtain the Y' array;

[0126] III) Find the array elements Y' that satisfy Y' k ≥Y' i (i = 1, 2 ··· M - 1); k ;

[0127] IV) When j > k, set j = k and k = j; when j < k, set k = k + 1.

[0128] V) Obtain the position numbers of two adjacent maximum values of the array Y: j and k;

[0129] 2.3 Intercept the full - cycle signal array from the dynamic pressure measurement point signal array P starting from the position number j and ending at k - 1: the full - cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1};

[0130] The third step, reconstruct the periodic signal:

[0131] 3.1 Traverse to find the array elements P that satisfy P q+1 ≤P j ≤P q-1 (q = k - 2, k - 3, ···, j + 1), and stop searching once found; q ;

[0132] 3.2 Reconstruct the full - cycle dynamic pressure measurement point signal array {P j , P j+1 , ···, P k-1} and convert it into a full - cycle signal starting from the top dead center of the piston, that is, the dynamic pressure measurement point signal array {P q , P q+1 , ···, P k-1 , P j , P j+1 , ···, P q-1};

[0133] The fourth step, convert to angular domain signal:

[0134] Using the elements of the dynamic pressure measurement point signal array {P q , P q+1 , ···, P k-1 , P j , P j+1 , ···, P q-1} as the ordinate values, and using is the horizontal coordinate, where m=1, 2, ···, (kj), and a curve graph is drawn in the two-dimensional coordinate system, that is, the angular domain pressure signal of the entire cycle of the reciprocating compressor with the top dead center of the piston as the starting point is obtained.

[0135] Step 5: Draw the indicator diagram:

[0136] Calculate the instantaneous cylinder volume according to the following formula:

[0137] V i =x i ·π·D 2 / 4

[0138] Among them, V i represents the instantaneous cylinder volume, x i represents the instantaneous piston displacement; D represents the piston diameter. i The calculation is done using the following formula:

[0139]

[0140] Where r is the crank radius; L is the connecting rod length; α i represents the instantaneous crank angle,

[0141] Finally, the dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1} is the ordinate value, the instantaneous cylinder volume V i As the horizontal axis, the reciprocating compressor indicator diagram is obtained, such as Figure 8 shown.

[0142] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0143] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis, characterized in that: The method for extracting the whole-cycle angular domain signal of a reciprocating compressor based on differential characteristic analysis includes: Step 1: Synchronously collect the signals of each measuring point of the compressor. Step 2: Conduct discrete differential characteristic analysis on the dynamic pressure signal array to extract the whole-cycle signals of each measuring point. Step 3: Reconstruct the periodic signal: Step 4: Convert the reconstructed periodic signal into an angular domain signal.

2. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 1 is characterized in that: Step 1 includes: 1.1 Calculate the rated operating cycle T of the compressor. 1.2 Calculate the number of sampling points M within the time of two operating cycles 2T of the compressor. 1.3 Synchronously collect signals from the dynamic pressure measuring points, vibration measuring points, and displacement measuring points of the compressor with the sampling rate f and the number of sampling points M per channel as sampling parameters.

3. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 2 is characterized in that: In step 1.1, the rated operating cycle T of the compressor is calculated according to the rated operating speed N of the compressor.

4. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 2 is characterized in that: In Step 1.2, according to the set signal sampling rate f, calculate the number of sampling points M within the time of two operating cycles 2T of the compressor, M = 2Tf.

5. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 2, characterized in that: In step 1.3, the sampling rate f and the number of sampling points per channel M are used as sampling parameters to synchronously collect signals from the dynamic pressure measurement point, vibration measurement point, and displacement measurement point of the compressor. The above measurement points are denoted as P, V, and D respectively. The collected dynamic pressure measurement point signal array is {P1, P2, ···, P M }, the array of vibration measurement point signals collected is {V1, V2, ···, V M }, the array of displacement measurement point signals collected is {D1, D2, ···, D M }, where the subscripts 1, 2,...,M represent the position numbers of the data points in the entire array.

6. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 1, characterized in that: Step 2 includes: 2.1, for the dynamic pressure measurement point signal array {P1, P2, ···, P M }Perform discrete differentiation to obtain discrete differential array Y; 2.2 Obtain the position serial numbers of two adjacent maximum values of the array Y. 2.3 Intercept the whole-cycle signal array.

7. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 6, characterized in that: In step 2.1, the dynamic pressure measurement point signal array {P1, P2, ···, P M } Perform discrete differentiation and use the second-order central differentiation method to obtain the discrete differential array Y of the dynamic pressure measurement point signal array. Where i = 1, 2, ···M; dt represents the difference in the position numbers of two adjacent data in the array; P0 takes P1, P M+1 Take P M .

8. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 6, characterized in that: Step 2.2 includes: Ⅰ) Find the solution that satisfies Y j Array element Y ≥ Y(j=1,2···M) j ; Ⅱ) Y j Remove from array Y to get array Y'; III) Find the solution that satisfies Y k '≥Y i '(i=1,2···M-1) array element Y k '; Ⅳ) When j > k, take j = k and k = j; when j < k, take k = k + 1. Ⅴ) Obtain the position serial numbers of two adjacent maximum values of the array Y: j and k.

9. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 6, characterized in that: In step 2.3, the dynamic pressure measurement point signal array P, the vibration measurement point signal array V, and the displacement measurement point signal array D are intercepted with position number j as the starting point and k-1 as the end point to obtain the whole cycle signal array: the whole cycle dynamic pressure measurement point signal array {P j , P j+1 ,···,P k-1 }、Full cycle vibration measurement point signal array {V j , V j+1 ,···,V k-1 }、Full cycle displacement measurement point signal array {D j , D j+1 ,···,D k-1 }.

10. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 1, characterized in that: Step 3 includes: 3.1, Finding the solution that satisfies P q+1 ≤P j ≤P q-1 The array element P q ; 3.2 Reconstruct the whole-cycle dynamic pressure measuring point signal array, the whole-cycle vibration measuring point signal array, and the whole-cycle displacement measuring point signal array, and convert them into whole-cycle signals starting from the top dead center of the piston.

11. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 10, characterized in that: In step 3.1, traverse to find the q+1 ≤P j ≤P q-1 The array element P of (q=k-2, k-3, . . . , j+1) q , stop searching when you find it.

12. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 10, characterized in that: In step 3.2, the full cycle dynamic pressure measurement point signal array {P j , P j+1 ,···,P k-1 }、Full cycle vibration measurement point signal array {V j , V j+1 ,···,V k-1 }、Full cycle displacement measurement point signal array {D j , D j+1 ,···,D k-1 } is reconstructed and converted into a full-cycle signal starting from the piston top dead center, that is, the dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1 }、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1 }、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1 }.

13. The method for extracting full-cycle angular domain signals of a reciprocating compressor based on differential characteristic analysis according to claim 12, characterized in that: In step 4, the dynamic pressure measurement point signal array {P q , P q+1 ,···,P k-1 , P j , P j+1 ,···,P q-1 }、Vibration measurement point signal array {V q , V q+1 ,···,V k-1 , V j , V j+1 ,···,V q-1 }、Displacement measurement point signal array {D q , D q+1 ,···,D k-1 , D j , D j+1 ,···,D q-1 } are the ordinate values, with is the horizontal coordinate, where m=1, 2, ···, (kj), and a curve graph is drawn in the two-dimensional coordinate system, that is, the angular domain signal of the entire cycle of the reciprocating compressor with the top dead center of the piston as the starting point is obtained.

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