A Pneumatic System Fault Diagnosis Method and System

Abstract

The present invention provides a pneumatic system fault diagnosis method and system, the method comprising: obtaining an air circuit diagram of a pneumatic system to be diagnosed, disassembling a balancing valve into an air circuit subsystem composed of simple component ports, establishing an equal number of two-dimensional static matrices describing the state of each process step according to the number of process steps, and establishing a three-dimensional dynamic state matrix of the entire cycle in combination with the sequence of the process steps; partitioning the periodic response audio of the pneumatic system under normal conditions in time according to the process steps, and performing short-time Fourier transform on each section to obtain a corresponding spectrum; performing short-time Fourier transform on the periodic response audio of the pneumatic system to be diagnosed as a whole, and dividing the response spectrum according to the time sequence of the process steps according to the dynamic state matrix; combining the spectra obtained by short-time Fourier transform of each section of the periodic response audio of the pneumatic system under normal conditions, and obtaining abnormal spectrum segments through comparison; and then determining the faulty component and the fault type through the dynamic state matrix.

Description

Technical Field

[0001] The present invention belongs to the technical field of pneumatic equipment maintenance of mechanical equipment maintenance, and specifically relates to a pneumatic system fault diagnosis method and system. Background Art

[0002] Pneumatic systems use compressed gas as their working medium. They utilize various components to form basic circuits with different functions, which are then organically integrated into a whole to transmit and control power or signals. Pneumatic transmission, with its outstanding advantages such as cleanliness, compactness, lightness, integration, and rapid response, is widely used in factories, offering significant advantages in production efficiency and speed. Complex pneumatic machinery typically includes components such as pneumatic travel, pneumatic clamps, load balancing control, pneumatic logic control, and pneumatic brakes. However, troubleshooting complex pneumatic systems presents a significant challenge. Several major issues exist: 1. When a pneumatic load balancing system fails, the complex structure of the balancing valve components and the numerous connected logic control elements make it difficult to quickly identify the root cause. 2. The complex control logic and long control chains of pneumatic clamps make pneumatic system fault diagnosis difficult. 3. Measuring dynamic parameters within pneumatic systems is difficult, making fault diagnosis overly reliant on experience and time-consuming. Traditional diagnostic methods rely on experience and fail to utilize information such as the pneumatic system's response audio and process step timing. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and to provide a pneumatic system fault diagnosis method and system.

[0004] In order to achieve the above object, the present invention proposes a pneumatic system fault diagnosis method, comprising:

[0005] Step 1) Obtain an air circuit diagram of the pneumatic system to be diagnosed, disassemble the balancing valve into an air circuit subsystem consisting of simple component ports, establish an equal number of two-dimensional static matrices describing the state of each process step according to the number of process steps of the pneumatic system, and establish a three-dimensional dynamic state matrix for the entire cycle of the pneumatic system based on the sequence of the pneumatic system steps within the cycle;

[0006] Step 2) The normal response audio of the pneumatic system is partitioned in time according to the process steps, and each section is short-time Fourier transformed to obtain a corresponding spectrum; the periodic response audio of the pneumatic system to be tested is short-time Fourier transformed as a whole, and the response spectrum is segmented according to the time sequence of the process steps based on the periodic dynamic state matrix of the pneumatic system; the spectrum obtained by short-time Fourier transform of each section under normal conditions of the pneumatic system is combined and compared to obtain an abnormal spectrum segment;

[0007] Step 3) According to the segments corresponding to the abnormal spectrum segments, the faulty component is determined by comparing the pneumatic system periodic dynamic state matrix, and the fault type is determined by comparing the spectrum segments.

[0008] Preferably, the step 1) disassembling the balancing valve into a gas path subsystem consisting of simple component ports includes:

[0009] The balancing valve is represented by 9 ports, including 4 control ports and 5 output ports. The 4 control ports are the main air source input port, the quick exhaust control port, the nut control port, the load adjustment input port and the top ball control port. The 5 output ports are the cylinder load output port, the exhaust port, the breathing port, the nut control port and the remote control port.

[0010] Preferably, the step 1) establishes a two-dimensional static matrix of equal number to the number of process steps of the pneumatic system, respectively describing the state of each step, including:

[0011] Starting from the air source of the pneumatic system to be diagnosed, each primary branch is numbered incrementally, and the primary branch number is used as the matrix row label; on each branch, the pneumatic components are numbered incrementally from near to far. If a secondary branch is encountered, all the component ports in the first secondary branch are numbered, and then the component ports in the second secondary branch are numbered, and so on, until all the component ports in the secondary branches are numbered, and the component ports on each branch are used as the matrix column label;

[0012] For the first-level branch number i, the state S of the jth port in the first-level branch pipeline ij , according to the state assignment of each port, when there is air pressure, the value is 1, otherwise it is 0, and a two-dimensional static matrix describing the state of the pneumatic system is established.

[0013] Preferably, the step 1) establishes a pneumatic system periodic dynamic state matrix in combination with the intra-periodic state; comprising:

[0014] The two-dimensional static matrix is taken as the third coordinate of the corresponding process step, and the two-dimensional static matrices of each process step are combined into a three-dimensional matrix according to the step number k to represent the change of the state matrix within a cycle, thereby obtaining the periodic dynamic state matrix of the pneumatic system. For n process steps, the periodic dynamic state matrix includes n two-dimensional static matrices.

[0015] Preferably, the step 2) comprises:

[0016] According to the process steps, the response audio of the pneumatic system to be diagnosed is segmented according to the step time and then short-time Fourier transform is performed on each segment to obtain the spectrum of each segment, and then the standard deviation of the spectrum of each segment is obtained;

[0017] Then, the standard deviation of the spectrum corresponding to each segment obtained by short-time Fourier transform under normal circumstances is compared segment by segment. When the difference in the standard deviation of a segment exceeds the threshold, it is judged as an abnormal spectrum segment, and the corresponding segment t is the fault segment.

[0018] Preferably, the step 3) comprises:

[0019] The three-dimensional dynamic state response matrix S of the fault segment t is ijk Segment t of ijt Call out, and S of t-1 segment ij(t-1) In contrast, in S ijt -S ij(t-1) In the obtained matrix, find the element that is not 0. The coordinates of the branch number and the port number in the branch are i. x j y , corresponding to the static matrix S ij , the fault point is located at the i x The jth of the first-level branches y For the component corresponding to the component port, when the standard deviation within the fault spectrum is lower than the normal value, it is a gas pressure shortage or leakage fault.

[0020] In another aspect, the present invention provides a pneumatic system fault diagnosis system, comprising:

[0021] The matrix establishment module is used to obtain the air circuit diagram of the pneumatic system to be diagnosed, disassemble the balancing valve into an air circuit subsystem composed of simple component ports, and establish an equal number of two-dimensional static matrices describing the status of each process step according to the number of process steps of the pneumatic system. Combined with the sequence of pneumatic system steps within the cycle, a three-dimensional dynamic state matrix of the entire pneumatic system cycle is established;

[0022] The fault location module is used to divide the periodic response audio of the pneumatic system under normal conditions into time zones according to the process steps, and perform short-time Fourier transform on each zone to obtain the corresponding spectrum. The periodic response audio of the pneumatic system to be diagnosed is short-time Fourier transformed as a whole, and the response spectrum is segmented according to the time sequence of the process steps based on the three-dimensional dynamic state matrix. The spectrum obtained by short-time Fourier transforming each zone of the periodic response audio under normal conditions of the pneumatic system is combined and compared to obtain the abnormal spectrum segment.

[0023] The fault diagnosis module is used to determine the fault component by comparing the pneumatic system periodic dynamic state matrix according to the segment corresponding to the abnormal spectrum segment, and to determine the fault type by comparing the spectrum segments.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] In this invention, a dynamic matrix of the pneumatic system is established and combined with the audio short-time Fourier transform spectrum of the system response. By comparing the standard deviation of the system response spectrum in each time period, the step time period where the fault occurs can be identified. The fault point can then be determined based on the changes in the dynamic matrix within that time period. By comparing the standard deviation of the spectrum of the faulty section with various abnormal spectra, the fault can be classified. This provides the advantages of rapid identification of the root cause of the fault and prompt diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the pneumatic system fault diagnosis method of the present invention. DETAILED DESCRIPTION

[0027] The diagnostic method starts with the gas circuit diagram and establishes a dynamic state matrix for the system. Complex pneumatic components are treated as equivalent gas circuit subsystems based on their principles and response characteristics, replacing the complex components in the gas circuit diagram. Spectrum analysis is introduced, combining dynamic spectrum analysis results with the state matrix to identify fault points and help diagnose faults.

[0028] Preferably, the balancing valve in the pneumatic balancing system of the complex component realizes the balancing function. The main pipeline of the balancing valve is connected to the air source and the balancing cylinder respectively, and the top input port is connected to the logic air circuit. The air pressure output by the logic air circuit controls the required load balancing air pressure. There is a quick exhaust hole at the bottom of the valve. When the load balancing cylinder needs to drop quickly, the excess gas in the cylinder can be discharged at a set speed through here. There are also breathing holes and micro-leakage valves in the middle of the balancing valve. The air source is connected to the upper part of the main balancing chamber through a detachable micro-leakage valve, and then connected to the breathing hole through a top ball. The breathing hole is always exhausting in most cases. The most precise channel of the balancing valve is between the main air source and the breathing hole. On this air path, there are two precision components, the micro-leakage valve and the top ball at the front end of the breathing hole. The air source is constantly replenishing compressed air to the upper cavity of the main balancing chamber through the small hole inside the micro-leakage valve, and the function of the top ball is to respond to changes in the input end and the load end. When the total input pressure exceeds the load pressure, the ball is compressed, and the amount of gas added to the upper chamber of the main air chamber from the micro-leak valve exceeds the amount released from the breather hole. This increases the pressure in the upper chamber, depressing the main valve core, and the output pressure rises until it matches the total input pressure. When the load pressure exceeds the total input pressure, the ball is released, and the amount of gas added to the upper chamber from the micro-leak valve is less than the amount released from the breather hole. This decreases the pressure in the upper chamber, causing the main valve core to rise, and the output pressure drops until it matches the total input pressure. The response of the balancing valve is closely related to the micro-leak valve and the ball. When these two components fail, the exhaust sound from the breather hole will change. The simplified sub-circuit system of the balancing valve can be represented by nine ports: four control ports (main air source input, quick exhaust control port, nut control port, load adjustment input, and ball control port) and five output ports (cylinder load output port, exhaust port, breather port, nut control port, and remote control port). These 9 ports can be equivalent to a sub-gas path system, which can replace the complex components in the original gas path diagram to form an equivalent overall gas path diagram.

[0029] Preferably, the establishment of the system dynamic state matrix is as follows: redundant modeling is performed according to a fixed rule based on the equivalent overall gas path diagram of the pneumatic system. Modeling method: 1. Starting from the gas source, number each primary branch, and use the primary branch number as the matrix row label. 2. On each branch, number each pneumatic component from near to far. If a secondary branch is encountered, all the component ports in the first secondary branch are marked, and then the component ports in the second secondary branch are marked. Finally, a two-dimensional static matrix S is obtained. ij , i is the matrix row number, i.e. the first-level branch number, j is the column number, i.e. the jth component port in the i-th first-level branch. After obtaining the static matrix, the dynamic three-dimensional matrix S can be constructed by adding the step time variable ijk , k is the step time variable. This three-dimensional matrix represents the state of each component port in the entire pneumatic system within one cycle and can be used to describe the process state of the entire pneumatic system.

[0030] Preferably, the pneumatic system response spectrum is obtained by segmenting normal audio into time-step segments and then performing a short-time Fourier transform on each segment to obtain a normal spectrum for each step. The system response audio to be tested is subjected to a short-time Fourier transform, and the spectrum is then segmented according to the time of the process steps. If the standard deviation of the spectrum in the corresponding segment exceeds 10%, it is determined to be a faulty segment.

[0031] Preferably, the fault finding is as follows: the process step time period corresponding to the fault segment is k1, then the fault segment S ijk1 -S ij(k1-1) The elements in the matrix that are not 0 are the changing elements of this step, and the corresponding coordinates i1j1 are the fault locations, which are entered into the static matrix S ij , we can find that the first-level branch number where the faulty port is located is i1, and the port in the branch is j1.

[0032] Preferably, the fault judgment is: calling the standard deviation of the short-time Fourier transform spectrum of various types of faults of the i1j1 element, and the fault type with the closest standard deviation of the fault spectrum can be judged as the fault.

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] In this invention, a dynamic matrix of the pneumatic system is established and combined with the audio short-time Fourier transform spectrum of the system response. By comparing the standard deviation of the system response spectrum in each time period, the step time period where the fault occurs can be identified. The fault point can then be determined based on the changes in the dynamic matrix within that time period. The fault can be classified by comparing the standard deviation of the spectrum of the faulty section with various abnormal spectra.

[0035] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] This embodiment provides a pneumatic fault diagnosis method, such as Figure 1 As shown, it includes constructing the pneumatic system state matrix, comparing the pneumatic system response spectrum, locating faults, and classifying faults.

[0038] Establish the system's dynamic state matrix: Based on the pneumatic circuit diagram, first consider the complex pneumatic component, the balancing valve, as an equivalent pneumatic circuit subsystem composed of simple components based on its principles and response characteristics, and draw it into the pneumatic circuit diagram. Redundancy modeling is then performed according to fixed rules based on the pneumatic circuit diagram of the pneumatic system containing only simple components.

[0039] Pneumatic response spectrum comparison: Compare the normal spectrum of normal audio after segmenting it by step time with the spectrum of the system response partition to be tested. When the spectrum standard deviation of the corresponding interval exceeds 10%, it is judged as a faulty segment.

[0040] Fault location: The port corresponding to the changed element in the dynamic matrix of the pneumatic system corresponding to the fault section is the fault port, and the component to which the fault port belongs is the fault component.

[0041] Classification fault: Compare the fault spectrum segment with the spectrum of various fault types of the faulty component, and the closest one is the fault type.

[0042] Assume that after the system is equivalent, there are N1 primary branches starting from the gas source in the system dynamic matrix, and each branch contains a maximum of N2 equivalent ports. The entire cycle can be divided into N3 time steps. The overall system modeling method is to perform redundant modeling according to a fixed rule: starting from the gas source, number each primary branch, and use the primary branch number as the matrix row label; on each primary branch, label each pneumatic component from near to far. If a secondary branch is encountered again, all ports in the first secondary branch are labeled, and then the ports in the second secondary branch are labeled. Finally, a two-dimensional static matrix S is obtained. ij , i is the matrix row number, i.e. the pneumatic system branch number, j is the column number, i.e. the jth component port in the i-th primary branch. After obtaining the static matrix, assign a value to each port state, with compressed air value 1 and no compressed air value 0. Blank elements are marked with 0. By adding the step time variable, a dynamic three-dimensional matrix S is constructed. ijk , k is the process step variable. System dynamic matrix S ijk Containing N1×N2×N3 elements, this three-dimensional matrix represents the state between each component and each port of the entire pneumatic system within one cycle, and can be used to describe the process state of the entire pneumatic logic system.

[0043] For spectrum comparison, the normal audio is divided into N3 segments in the time domain based on the time step. Each segment is subjected to a short-time Fourier transform (SFT) to obtain N3 normal spectra. The standard deviation of each spectrum segment is calculated, resulting in N3 standard deviations. The spectrum obtained by the SFT of the audio to be tested can be divided into N3 segments based on the time of the process steps. The standard deviation of each spectrum segment is calculated, resulting in N3 standard deviations. The two sets of standard deviations are compared one-to-one. Any segment with a difference exceeding 10% is identified as a faulty segment. Assume that the faulty segment is labeled t (t ≤ N3).

[0044] Find the fault location. ijt Call out, and the t-1 segment S ij(t-1) In contrast, in S ijt -S ijt-1 In the obtained matrix, find the element that is not 0. The coordinates of the branch number and the port number in the branch are i. x j y , corresponding to the static matrix S ij , the fault point is located at the i xThe jth of the first-level branches y The component corresponding to the component port.

[0045] After locating the faulty component and port, retrieve the standard deviation of the short-time Fourier transform spectrum of various abnormal audio responses at that component and port. Compare the standard deviation of the audio spectrum of the fault to be detected with the retrieved standard deviations. If the standard deviation difference is within 10%, it can be identified as that type of fault. Generally, a standard deviation lower than the normal value within the fault spectrum indicates insufficient pneumatic system response, insufficient air pressure, or a leak.

[0046] Example 2

[0047] Embodiment 2 of the present invention discloses a pneumatic system fault diagnosis system, which is implemented based on the method of embodiment 1 and includes:

[0048] The matrix establishment module is used to obtain the air circuit diagram of the pneumatic system to be diagnosed, disassemble the balancing valve into an air circuit subsystem composed of simple component ports, and establish an equal number of two-dimensional static matrices describing the status of each process step according to the number of process steps of the pneumatic system. Combined with the sequence of pneumatic system steps within the cycle, a three-dimensional dynamic state matrix of the entire pneumatic system cycle is established;

[0049] The fault location module is used to divide the periodic response audio of the pneumatic system under normal conditions into time zones according to the process steps, and perform short-time Fourier transform on each zone to obtain the corresponding spectrum. The periodic response audio of the pneumatic system to be diagnosed is short-time Fourier transformed as a whole, and the response spectrum is segmented according to the time sequence of the process steps based on the three-dimensional dynamic state matrix. The spectrum obtained by short-time Fourier transforming each zone of the periodic response audio under normal conditions of the pneumatic system is combined and compared to obtain the abnormal spectrum segment.

[0050] The fault diagnosis module is used to determine the fault component by comparing the pneumatic system periodic dynamic state matrix according to the segment corresponding to the abnormal spectrum segment, and to determine the fault type by comparing the spectrum segments.

[0051] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A pneumatic system fault diagnosis method comprising: Step 1) Obtain an air circuit diagram of the pneumatic system to be diagnosed, disassemble the balancing valve into an air circuit subsystem consisting of simple component ports, establish an equal number of two-dimensional static matrices describing the state of each process step according to the number of process steps of the pneumatic system, and establish a three-dimensional dynamic state matrix for the entire cycle of the pneumatic system based on the sequence of the pneumatic system steps within the cycle; Step 2) The periodic response audio of the pneumatic system under normal conditions is partitioned in time according to the process steps, and each section is short-time Fourier transformed to obtain a corresponding spectrum; the periodic response audio of the pneumatic system to be diagnosed is short-time Fourier transformed as a whole, and the response spectrum is segmented according to the time sequence of the process steps according to the three-dimensional dynamic state matrix; the spectrum obtained by short-time Fourier transforming each section of the periodic response audio of the pneumatic system under normal conditions is combined and compared to obtain an abnormal spectrum segment; Step 3) determining the faulty component by comparing the pneumatic system periodic dynamic state matrix based on the segments corresponding to the abnormal spectrum segments, and determining the fault type by comparing the spectrum segments; The step 1) establishes an equal number of two-dimensional static matrices describing the state of each process step according to the number of process steps of the pneumatic system, including: Starting from the air source of the pneumatic system to be diagnosed, each primary branch is numbered incrementally, and the primary branch number is used as the matrix row label; on each branch, the pneumatic components are numbered incrementally from near to far. If a secondary branch is encountered, all the component ports in the first secondary branch are numbered, and then the component ports in the second secondary branch are numbered, and so on, until all the component ports in the secondary branches are numbered, and the component ports on each branch are used as the matrix column label; For the first-level branch number i, the state S of the jth port in the first-level branch pipeline ij , according to the state assignment of each port, when there is air pressure, the value is 1, otherwise it is 0, and a two-dimensional static matrix describing the state of the pneumatic system is established; The step 1) establishes a three-dimensional dynamic state matrix of the entire cycle of the pneumatic system in combination with the sequence of steps of the pneumatic system within the cycle; including: The two-dimensional static matrix is taken as the third coordinate of the corresponding process step, and the two-dimensional static matrices of each process step are combined into a three-dimensional matrix according to the step number k to represent the change of the state matrix within a cycle, thereby obtaining the periodic dynamic state matrix of the pneumatic system. For n process steps, the periodic dynamic state matrix includes n two-dimensional static matrices.

2. The pneumatic system fault diagnosis method according to claim 1, characterized in that: The step 1) disassembling the balancing valve into a gas path subsystem composed of simple component ports includes: The balancing valve is represented by 9 ports, including 4 control ports and 5 output ports. The 4 control ports are the main air source input port, the quick exhaust control port, the nut control port, the load adjustment input port and the top ball control port. The 5 output ports are the cylinder load output port, the exhaust port, the breathing port, the nut control port and the remote control port.

3. The pneumatic system fault diagnosis method according to claim 1, characterized in that: The step 2) comprises: According to the process steps, the response audio of the pneumatic system to be diagnosed is segmented according to the step time and then short-time Fourier transform is performed on each segment to obtain the spectrum of each segment, and then the standard deviation of the spectrum of each segment is obtained; Then, the standard deviation of the spectrum corresponding to the response audio of each segment under normal circumstances obtained by short-time Fourier transform is compared segment by segment. When the difference in the standard deviation of a segment exceeds the threshold, it is judged as an abnormal spectrum segment, and the corresponding segment t is the fault segment.

4. The pneumatic system fault diagnosis method according to claim 3, characterized in that: The step 3) comprises: The three-dimensional dynamic state response matrix S of the fault segment t is ijk Segment t of ijt Call out, and S of t-1 segment ij(t-1) In contrast, in S ijt -S ij(t-1) In the obtained matrix, find the element that is not 0. The coordinates of the branch number and the port number in the branch are i. x j y , corresponding to the static matrix S ij , the fault point is located at the i x The jth of the first-level branches y For the component corresponding to the component port, when the standard deviation within the fault spectrum is lower than the normal value, it is a gas pressure shortage or leakage fault.

5. A system based on the pneumatic system fault diagnosis method according to claim 1, characterized in that: include: The matrix establishment module is used to obtain the air circuit diagram of the pneumatic system to be diagnosed, disassemble the balancing valve into an air circuit subsystem composed of simple component ports, and establish an equal number of two-dimensional static matrices describing the status of each process step according to the number of process steps of the pneumatic system. Combined with the sequence of pneumatic system steps within the cycle, a three-dimensional dynamic state matrix of the entire pneumatic system cycle is established; The fault location module is used to divide the periodic response audio of the pneumatic system under normal conditions into time zones according to the process steps, and perform short-time Fourier transform on each zone to obtain the corresponding spectrum. The periodic response audio of the pneumatic system to be diagnosed is short-time Fourier transformed as a whole, and the response spectrum is segmented according to the time sequence of the process steps based on the three-dimensional dynamic state matrix. The spectrum obtained by short-time Fourier transforming each zone of the periodic response audio under normal conditions of the pneumatic system is combined and compared to obtain the abnormal spectrum segment. and The fault diagnosis module is used to determine the fault component by comparing the pneumatic system periodic dynamic state matrix according to the segment corresponding to the abnormal spectrum segment, and to determine the fault type by comparing the spectrum segments.

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