Pneumatic system fault diagnosis method and system

Abstract

The invention provides a pneumatic system fault diagnosis method and system, and the method comprises the steps: obtaining a gas path diagram of a to-be-diagnosed pneumatic system, disassembling a gas path subsystem composed of simple element ports of a balance valve, building two-dimensional static matrixes which are equal to the number of process steps and respectively describe the state of each process step according to the number of the process steps, and carrying out the fault diagnosis of the to-be-diagnosed pneumatic system. Establishing a three-dimensional dynamic state matrix of the whole period by combining a process step sequence; the method comprises the following steps of: partitioning periodic response audio of a pneumatic system under a normal condition in time according to process steps, and respectively performing short-time Fourier transform on each section to obtain a corresponding frequency spectrum; performing short-time Fourier transform on the whole to-be-diagnosed periodic response audio of the pneumatic system, and segmenting a response frequency spectrum according to the dynamic state matrix and a process step time sequence; in combination with a frequency spectrum obtained by short-time Fourier transform of each section of periodic response audio under the normal condition of the pneumatic system, an abnormal frequency spectrum section is obtained through comparison; and determining a fault element and a 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] The pneumatic system uses compressed gas as the working medium. It uses various components to form basic circuits with different functions, and then several basic circuits are organically combined into a whole to transmit and control power or signals. Pneumatic transmission is widely used in factories with its outstanding advantages such as cleanliness, small and light weight, integration, and rapid response. It has obvious advantages in production efficiency and production speed. For complex pneumatic mechanical equipment, it usually includes pneumatic drive walking, pneumatic clamps, load balancing control, pneumatic logic control, pneumatic brakes and other parts. However, the fault diagnosis of complex pneumatic systems is a major challenge. It has several major problems: 1. When the pneumatic load balance fails, it is difficult to quickly determine the root cause of the fault due to the complex structure of the balancing valve element and the large number of connected logic control elements; 2. The control logic of the pneumatic clamp is complex and the control chain is long, which makes it difficult to judge the fault of the pneumatic system; 3. It is difficult to measure the dynamic parameters inside the pneumatic system, and the fault judgment is too dependent on experience and takes a long time. Traditional diagnostic methods rely on experience and it is difficult to use the information of the pneumatic system response audio and process step time. 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) obtaining the pneumatic circuit diagram of the pneumatic system to be diagnosed, disassembling the pneumatic circuit subsystem composed of the balancing valve as a simple component port, establishing a two-dimensional static matrix of the same number to describe the state of each process step according to the number of process steps of the pneumatic system, and establishing 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;

[0006] Step 2) The normal response audio of the pneumatic system is divided into time zones according to the process steps, and each zone is short-time Fourier transformed to obtain the corresponding spectrum; the periodic response audio of the pneumatic system to be detected is short-time Fourier transformed as a whole, and the response spectrum is divided according to the time sequence of the process steps according to the periodic dynamic state matrix of the pneumatic system; the spectrum obtained by short-time Fourier transform of each zone under normal conditions of the pneumatic system is combined, and the abnormal spectrum segment is obtained by comparison;

[0007] Step 3) According to the segment corresponding to the abnormal spectrum segment, the faulty component is determined by comparing the periodic dynamic state matrix of the pneumatic system, 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 composed of simple component ports comprises:

[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, and the load adjustment input and 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 primary branch number i, the state S of the jth port in the primary 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 ​​used with the corresponding process step as the third coordinate. 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, and the periodic dynamic state matrix of the pneumatic system is obtained. 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 respectively 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 corresponding to the spectrum obtained by short-time Fourier transform of each segment under normal circumstances is compared segment by segment. When the difference of 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 corresponding branch number and the port number coordinate in the branch are i. x j y , corresponding to the static matrix S ij , the fault point is located at the i-th x The jth of the first-level branches y For the component corresponding to the component port, when the standard deviation in the fault spectrum is lower than the normal value, it is a fault of insufficient air pressure or leakage.

[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 gas circuit diagram of the pneumatic system to be diagnosed, disassemble the gas circuit subsystem composed of the balancing valve into simple component ports, and 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. Combined with the sequence of steps of the pneumatic system within the cycle, a three-dimensional dynamic state matrix of the entire cycle of the pneumatic system 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 divided according to the time sequence of the process steps according to the three-dimensional dynamic state matrix; the spectrum obtained by short-time Fourier transform of each zone of the periodic response audio of the pneumatic system under normal conditions is combined, and the abnormal spectrum segment is obtained by comparison;

[0023] The fault diagnosis module is used to determine the faulty component by comparing the periodic dynamic state matrix of the pneumatic system according to the section 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 the present invention, a dynamic matrix of the pneumatic system is established and combined with the system response audio short-time Fourier transform spectrum. By comparing the standard deviation of the spectrum of the system response in each time period, the step time period where the fault is located is found, and then according to the change of the dynamic matrix in the time period, the fault point can be determined. By comparing the standard deviation of the fault section spectrum with various abnormal spectra, the fault can be classified. It has the advantages of quickly determining the root cause of the fault and rapid 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 from the gas circuit diagram and establishes the dynamic state matrix of the system. The pneumatic components with complex structures are equivalent to a gas circuit subsystem to replace the complex components in the gas circuit diagram according to their principles and response characteristics. The spectrum analysis method is introduced to combine the dynamic spectrum analysis results and the state matrix to find the fault point and help judge the fault;

[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 bead. 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 bead at the front end of the breathing hole. The air source has been replenishing compressed air to the upper cavity of the main balancing cavity through the small hole inside the micro-leakage valve, and the function of the top bead is to respond to changes in the input end and the load end. When the total air pressure at the input end is greater than the load, the top ball is compressed, the gas added to the upper chamber of the main air chamber from the micro-leak valve is more than the gas released from the breathing hole, the air pressure in the upper chamber of the main air chamber increases, the main valve core is pressed down, and the pressure at the output end rises until it is consistent with the total pressure at the input end. When the pressure at the load end is greater than the total pressure at the input end, the top ball is released, the amount of gas added to the upper chamber of the main air chamber from the micro-leak valve is less than the amount of gas released from the breathing hole, the air pressure in the upper chamber of the main air chamber decreases, the main valve core rises, and the pressure at the output end drops until it is consistent with the total pressure at the input end. The response of the balancing valve is closely related to the micro-leak valve and the top ball. When there are problems with these two parts, the exhaust sound of the breathing hole will change. The simplified sub-gas system of the balancing valve can be represented by 9 ports, including 4 control ports (main air source input port, quick exhaust control port, nut control port, load adjustment input and top ball control port), and 5 output ports (cylinder load output port, exhaust port, breathing port, nut control port, remote control port). These 9 ports can be equivalent to a sub-gas circuit system, which can replace the complex components in the original gas circuit diagram to form an equivalent overall gas circuit 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, each primary branch is numbered, and the primary branch number is used as the matrix row label. 2. On each branch, the pneumatic components are numbered from near to far in sequence. 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 will be obtained. ij , i is the matrix row number, i.e. the primary branch number, j is the column number, i.e. the jth component port in the i-th primary 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 one cycle of the entire pneumatic system and can be used to describe the process state of the entire pneumatic system.

[0030] Preferably, the pneumatic system response spectrum is obtained by dividing the normal audio into segments according to the step time and then performing short-time Fourier transform respectively to obtain the normal spectrum of each step. The system response audio to be tested is short-time Fourier transformed, and then the spectrum is divided into zones according to the process step time. When the standard deviation of the spectrum of the corresponding interval exceeds 10%, it is judged as a faulty section.

[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, entering 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: retrieving 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 the present invention, a dynamic matrix of the pneumatic system is established and combined with the system response audio short-time Fourier transform spectrum. By comparing the standard deviation of the spectrum of the system response in each time period, the step time period where the fault is located is found, and then according to the change of the dynamic matrix in the time period, the fault point can be determined. By comparing the standard deviation of the fault section spectrum with various abnormal spectra, the fault can be classified.

[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 a pneumatic system state matrix, comparing pneumatic system response spectra, locating faults, and classifying faults.

[0038] Establish the dynamic state matrix of the system: Based on the gas circuit diagram, the complex pneumatic component balance valve is firstly equivalent to a gas circuit subsystem composed of simple components according to its principle and response characteristics, and then drawn into the gas circuit diagram. Redundancy modeling is performed according to the fixed rules based on the gas circuit diagram of the pneumatic system containing only simple components.

[0039] Pneumatic response spectrum comparison: Compare the normal spectrum of the 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 section.

[0040] Fault location: The port corresponding to the changed element in the dynamic matrix of the pneumatic system corresponding to the faulty section is the faulty port, and the component to which the faulty port belongs is the faulty 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 there are N1 primary branches starting from the gas source in the system dynamic matrix after the system is equivalent, and each branch contains at most 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, number each pneumatic component from near to far. If a secondary branch is encountered again, all ports in the first secondary branch are marked, and then the ports in the second secondary branch are marked. Finally, a two-dimensional static matrix S will be obtained. ij , i is the row number of the matrix, i.e. the branch number of the pneumatic system, 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 a value of 1 for compressed air and 0 for none. Blank elements are marked with 0. By adding step time variables, 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 of 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] Spectrum comparison: normal audio is divided into N3 segments in the time domain according to the time step. Each segment is short-time Fourier transformed to obtain N3 normal spectra. The standard deviation of each spectrum segment is calculated to obtain N3 standard deviations. The spectrum obtained by the short-time Fourier transform of the audio to be tested can be divided into N3 segments according to the process step time. The standard deviation of each spectrum segment is calculated to obtain N3 standard deviations. The two sets of standard deviations are compared one by one. The difference exceeding 10% can be judged as a fault segment. Assume that the fault 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 corresponding branch number and the port number coordinate in the branch are i. x j y , corresponding to the static matrix S ij , the fault point is located at the i-th 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 change spectrum of various abnormal audio responses of the component 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 judged as this type of fault. Usually, the standard deviation in the fault spectrum is lower than the normal value, which means that the pneumatic system is not responding enough, and there is insufficient air pressure or air leakage.

[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 gas circuit diagram of the pneumatic system to be diagnosed, disassemble the gas circuit subsystem composed of the balancing valve into simple component ports, and 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. Combined with the sequence of steps of the pneumatic system within the cycle, a three-dimensional dynamic state matrix of the entire cycle of the pneumatic system 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 divided according to the time sequence of the process steps according to the three-dimensional dynamic state matrix; the spectrum obtained by short-time Fourier transform of each zone of the periodic response audio of the pneumatic system under normal conditions is combined, and the abnormal spectrum segment is obtained by comparison;

[0050] The fault diagnosis module is used to determine the faulty component by comparing the periodic dynamic state matrix of the pneumatic system according to the section 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 only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A pneumatic system fault diagnosis method, comprising: Step 1) obtaining the pneumatic circuit diagram of the pneumatic system to be diagnosed, disassembling the pneumatic circuit subsystem composed of the balancing valve as a simple component port, establishing a two-dimensional static matrix of the same number to describe the state of each process step according to the number of process steps of the pneumatic system, and establishing 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; Step 2) The periodic response audio of the pneumatic system under normal conditions is divided in time according to the process steps, and each section is short-time Fourier transformed 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 divided 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 the abnormal spectrum segment is obtained by comparison; Step 3) According to the segment corresponding to the abnormal spectrum segment, the faulty component is determined by comparing the periodic dynamic state matrix of the pneumatic system, and the fault type is determined by comparing the spectrum segments.

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, and the load adjustment input and 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 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: 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 primary branch number i, the state S of the jth port in the primary 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.

4. The pneumatic system fault diagnosis method according to claim 3, characterized in that: The step 1) establishes a pneumatic system periodic dynamic state matrix in combination with the periodic state; comprising: The two-dimensional static matrix is ​​used with the corresponding process step as the third coordinate. 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, and the periodic dynamic state matrix of the pneumatic system is obtained. For n process steps, the periodic dynamic state matrix includes n two-dimensional static matrices.

5. 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 respectively to obtain the spectrum of each segment, and then the standard deviation of the spectrum of each segment is obtained; Then, the standard deviation corresponding to the spectrum obtained by short-time Fourier transform of the response audio of each segment under normal circumstances is compared segment by segment. When the difference of 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.

6. The pneumatic system fault diagnosis method according to claim 5, 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 corresponding branch number and the port number coordinate in the branch are i. x j y , corresponding to the static matrix S ij , the fault point is located at the i-th x The jth of the first-level branches y For the component corresponding to the component port, when the standard deviation in the fault spectrum is lower than the normal value, it is a fault of insufficient air pressure or leakage.

7. A pneumatic system fault diagnosis system, characterized in that: include: The matrix establishment module is used to obtain the gas circuit diagram of the pneumatic system to be diagnosed, disassemble the gas circuit subsystem composed of the balancing valve into simple component ports, and 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. Combined with the sequence of steps of the pneumatic system within the cycle, a three-dimensional dynamic state matrix of the entire cycle of the pneumatic system 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 divided according to the time sequence of the process steps according to the three-dimensional dynamic state matrix; the spectrum obtained by short-time Fourier transform of each zone of the periodic response audio of the pneumatic system under normal conditions is combined, and the abnormal spectrum segment is obtained by comparison; and The fault diagnosis module is used to determine the faulty component by comparing the periodic dynamic state matrix of the pneumatic system according to the section corresponding to the abnormal spectrum segment, and to determine the fault type by comparing the spectrum segments.

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