A fault diagnosis method for explosion-proof electromagnetic valve based on current detection

Abstract

The application discloses a kind of explosion-proof electromagnetic valve fault diagnosis methods based on current detection, belongs to electromagnetic valve fault diagnosis technical field.The application includes the following steps: step 1, the transient current waveform when standard electromagnetic valve acts is obtained, and the eigen triangle area S1 of the transient current waveform is calculated;Step 2, the transient current waveform when the electromagnetic valve to be measured acts is obtained, and the eigen triangle area S2 of the transient current waveform is calculated;Step 3, the area change rate of S2 relative to S1 is calculated, if the area change rate exceeds the set threshold value, then determine that the electromagnetic valve to be measured fails;Eigen triangle refers to the maximum value level reference line of the transient current waveform when electromagnetic valve acts and the triangle-like area surrounded by transient current waveform curve.This application has lower requirement for data operation, lower cost, and has higher popularization and application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic valve fault diagnosis, and particularly relates to a fault diagnosis method for an explosion-proof electromagnetic valve based on current detection. BACKGROUND

[0002] An electromagnetic valve is an automatic basic element for controlling fluid direction and belongs to an actuator. The electromagnetic valve is usually used in mechanical control and process industry valve control. The electromagnetic valve controls the position of a valve core through an electromagnetic coil. Power is cut off or turned on to achieve the purpose of changing the direction of fluid flow, so as to control the direction of medium and achieve the control of the opening and closing of the valve. The electromagnetic valve has the advantages of small size, low cost, fast response, simple structure and the like, and is widely applied in petrochemical and chemical process industries. However, due to the harsh application environment of the electromagnetic valve and frequent operation, long-term wear and corrosion cause frequent failures of the electromagnetic valve, which eventually leads to the decline of the overall efficiency and reliability of the control system. Therefore, the fault diagnosis of the electromagnetic valve is particularly important for stable operation of the system. The failure of the electromagnetic valve is the result of long-term accumulation, and the failure of the electromagnetic valve is usually discovered until the electromagnetic valve completely fails.

[0003] In the prior art, the following schemes are generally used for electromagnetic valve fault detection:

[0004] 1. The electromagnetic valve is judged to be faulty by detecting the action current of the electromagnetic valve. This scheme usually samples the current when the electromagnetic valve is opened or turned off, calculates the change of the current in the action time, and then judges whether the electromagnetic valve is faulty;

[0005] 2. The electromagnetic valve is judged to be faulty by detecting the action voltage of the electromagnetic valve. This method is usually used to detect the physical failure of the electromagnetic valve coil, but it cannot effectively detect the failure of the electromagnetic valve core;

[0006] 3. The electromagnetic valve is diagnosed to be faulty by detecting the action sound of the electromagnetic valve. This method compares the audio signal of the electromagnetic valve with a preset sound threshold to determine whether the electromagnetic valve is faulty and the type of the fault. In a noisy environment, this method is not suitable;

[0007] 4. The electromagnetic valve is diagnosed to be faulty by detecting the vibration signal generated when the electromagnetic valve is in action. This method compares the vibration signal of the electromagnetic valve with a preset vibration spectrum to determine whether the electromagnetic valve is faulty. This method is costly and not suitable in a noisy environment.

[0008] Among the above four schemes, the first one is the most mature and the most widely applicable. A current detection-based electromagnetic valve fault diagnosis method is disclosed in Chinese Patent No. ZL201310209422.5. According to the characteristics of the current step signal, an electric quantity isolation sensor is connected in series at the driving end of the electromagnetic valve, the current rate of change is decomposed by three layers of wavelet, and the corresponding energy value is extracted as a feature vector. Then, the BP neural network is used to classify the normal valve signal, the valve core stuck valve, the spring broken valve and the valve core unable to reset valve, and the corresponding state of the electromagnetic valve is accurately determined, including the valve core stuck valve, the spring broken valve and the valve core unable to reset valve.

[0009] However, the above method needs a large amount of historical data support, and the calculation process is relatively complex, and the cost is relatively high. Moreover, for most users of electromagnetic valves, they are not interested in fault types, but only need to find faults in time and then replace the electromagnetic valve to ensure the safety and efficiency of equipment operation, so the promotion and application value of the above method is not high. SUMMARY

[0010] The purpose of the present application is to solve the problems existing in the prior art, and to provide a current detection-based explosion-proof electromagnetic valve fault diagnosis method, which has lower data operation requirements, lower cost and higher promotion and application value.

[0011] The purpose of the present application is achieved by the following technical solutions:

[0012] A current detection-based explosion-proof electromagnetic valve fault diagnosis method, comprising the following steps:

[0013] Step 1, obtaining the transient current waveform when the standard electromagnetic valve is actuated, and calculating the intrinsic triangular area S1 of the transient current waveform;

[0014] Step 2, obtaining the transient current waveform when the to-be-tested electromagnetic valve is actuated, and calculating the intrinsic triangular area S2 of the transient current waveform;

[0015] Step 3, calculating the area change rate of S2 relative to S1, if the area change rate exceeds a set threshold, determining that the to-be-tested electromagnetic valve has a fault;

[0016] The intrinsic triangle refers to a triangle-like region surrounded by the maximum value horizontal reference line of the transient current waveform when the electromagnetic valve is actuated and the transient current waveform curve.

[0017] The application creatively introduces the eigen triangle concept capable of reflecting the transient current waveform form when the electromagnetic valve operates, and takes the area of the eigen triangle as the judgment basis, and obtains the eigen triangle area change rate of the electromagnetic valve to be tested relative to the standard electromagnetic valve through a simple algorithm, and after comparison with the set threshold, the conclusion whether the electromagnetic valve is faulty is obtained. The whole diagnosis process and algorithm are simple and efficient, accurate in judgment, and low in cost, and are especially suitable for the electromagnetic valve users.

[0018] As the preferred embodiment of the application, the calculation method of the eigen triangle area is:

[0019]

[0020] Wherein, S ∆ is the eigen triangle area, A is the collection time of the peak point, B is the collection time of the peak isopotential point, D n is the current value when the collection time is n.

[0021] As the preferred embodiment of the application, the calculation method of the area change rate is:

[0022] .

[0023] As the preferred embodiment of the application, the collection method of the electromagnetic valve operating current is: collecting the electromagnetic valve operating current at a constant time interval, and the collection interval is not more than 1 / 100 of the electromagnetic valve operating time.

[0024] As the preferred embodiment of the application, the electromagnetic valve operating current is collected by a Hall current sensor or a fluxgate current sensor.

[0025] As the preferred embodiment of the application, the acquisition method of the set threshold in step 3 is: under the same fluid condition, the eigen triangle areas of the standard electromagnetic valve and the faulty electromagnetic valve under different fluid pressures are calculated respectively, and the set threshold is obtained according to the maximum eigen triangle area change rate between different pressure conditions and the minimum eigen triangle area change rate between the fault and non-fault conditions.

[0026] As the preferred embodiment of the application, the set threshold in step 3 has multiple thresholds corresponding to different fluid ranges respectively, and is obtained through the acquisition method of the set threshold according to the conditions of the electromagnetic valve under different fluids.

[0027] As the preferred embodiment of the application, the eigen triangle area of the operating current waveform of the standard electromagnetic valve is obtained through multiple collection and calculation.

[0028] The application has the advantages that the whole diagnosis process and algorithm are simple and efficient, accurate in judgment, and low in cost, and has high practicability and popularization, and is suitable for electromagnetic valve fault diagnosis in industrial control systems. Attached Figure Description

[0029] Figure 1 This is a flowchart of a fault diagnosis method for explosion-proof solenoid valves based on current detection according to the present invention.

[0030] Figure 2 This is a current waveform diagram from the present invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] This invention primarily utilizes the characteristics of the current step signal during the startup of a solenoid valve, specifically the following general properties of a solenoid valve during operation: After the solenoid valve coil is energized, the current increases rapidly, and simultaneously, the coil generates a magnetic force that attracts the valve core to move; during the valve core's movement, the magnetic flux of the solenoid valve coil changes, and the current decreases rapidly; when the valve core reaches its position, the magnetic flux recovers, the coil current increases rapidly again, and after approaching coil saturation, the current no longer changes and remains constant. Figure 2 As shown, the inventors discovered during their research that there is a significant difference in the transient current waveforms of a standard solenoid valve (i.e., a normally functioning solenoid valve) and a faulty solenoid valve (especially one with an abnormal valve core) during operation. This difference in current waveform can be used to determine whether a solenoid valve is faulty. Furthermore, after multiple tests, it was found that the main difference lies in the process of the current waveform decreasing from a maximum value to a minimum value, and then gradually increasing from the minimum value. To make the judgment more convenient and efficient, further research and calculation analysis of the test data revealed that the significant difference in this process also causes a significant change in the area of ​​a certain region in the current waveform diagram. Specifically, the triangular-like region enclosed by the current waveform curve showing the process of the current decreasing from a maximum value to a minimum value and then increasing from the minimum value to equal the maximum value, and the maximum value horizontal reference line, is the intrinsic triangle concept introduced in this method.

[0033] Based on the above research, this invention provides a fault diagnosis method for explosion-proof solenoid valves based on current detection, such as... Figure 1 As shown, it includes the following steps:

[0034] Step 1: Obtain the transient current waveform when the standard solenoid valve operates, and calculate the area S1 of the intrinsic triangle of the transient current waveform;

[0035] Step 2: Obtain the transient current waveform when the solenoid valve under test is activated, and calculate the area S2 of the intrinsic triangle of the transient current waveform;

[0036] Step 3: Calculate the area change rate of S2 relative to S1. If the area change rate exceeds the set threshold, the solenoid valve under test is determined to be faulty.

[0037] Wherein, based on the purpose of simplifying the diagnostic process of the application, the sampling of the solenoid operating current is preferably a non-contact means, such as using a Hall current sensor or a fluxgate current sensor, etc. The solenoid operating time is generally 0.1 seconds, so in order to ensure that the solenoid operating current waveform curve is not distorted, the current should be sampled at least once every 1 millisecond, that is, the sampling frequency is not less than 1 kHz. Of course, in order to further reduce the error, we can collect and calculate multiple times, and eliminate the data with larger error.

[0038] Because the current waveform is a curve, that is, an intrinsic triangle and not a regular triangle, it cannot be calculated by the conventional triangle area formula, and the area of the intrinsic triangle needs to be considered as the sum of the areas of several rectangular strips, with the sampling interval as the base and the difference between the maximum value of the current waveform and each sampling value as the height. At the same time, since the sampling interval is small enough, the error caused by this calculation is negligible and will not affect the final judgment result. Moreover, we need to calculate a rate of change, which is a ratio, and the sampling interval is consistent, that is, whether the sampling interval is considered or not, the final calculation result is the same. Therefore, we can further simplify the calculation method and ignore the sampling interval, and only use the difference between the maximum value and the sampling value as the area reference value of the rectangular strip for accumulation. Thus, the calculation method of the area of the intrinsic triangle is obtained:

[0039]

[0040] Wherein, S ∆ is the area of the intrinsic triangle, A is the collection time of the peak point, B is the collection time of the peak point, D n is the current value at the collection time n.

[0041] The calculation method of the area change rate is more conventional:

[0042] .

[0043] In this way, we complete the calculation of the area change rate, and finally through comparison with the set threshold, we can judge whether the solenoid valve is faulty. Therefore, the selection of the set threshold will also affect the accuracy of the final judgment result. In addition to the failure of the solenoid valve, the solenoid operating current waveform will also be affected by the type and pressure of the fluid, but generally the influence of the fluid factors is relatively small, and the value of the area change rate is generally below 5%, while the area change rate caused by the failure is generally above 10%. Therefore, we can set the threshold to 10%, which can realize reliable judgment.

[0044] To obtain more accurate and reasonable threshold, we can test the threshold of an electromagnetic valve under different fluid conditions. The specific method is as follows: under the same fluid condition, the eigen triangle areas of the standard electromagnetic valve and the fault electromagnetic valve under different fluid pressures are calculated respectively. Assuming that the eigen triangle areas of the standard electromagnetic valve are 90, 95 and 100 respectively when the pressures are A, B and C, and the eigen triangle areas of the fault electromagnetic valve are 70, 75 and 80 respectively, since pressure is a disturbance factor, we need to consider the maximum disturbance, that is, we need to calculate the maximum area change rate between 90, 95 and 100, that is, (100-90) / 90*100%=11.1%. Since the purpose of the judgment is whether the fault exists or not, we need to consider the most easily disturbed condition, that is, the condition closest to the above 11.1%, and calculate three sets of area change rates: (90-70) / 90*100%=22.2%, (95-75) / 95*100%=21.1%, (100-80) / 100*100%=20%, take the minimum area change rate, that is, 20%, according to 11.1% and 20%, we can select the intermediate value as the final set threshold, that is, 15.6%. The above data is not real data, but is intended to clearly illustrate the method.

[0045] Through the above method, we can accurately test the set threshold under each fluid condition. Generally, there is a certain gap between the maximum area change rate under the pressure factor and the minimum area change rate under the fault factor, such as 20%-11.1%=8.9% in the above hypothetical data. The difference between different types of fluids is large or small, so in order to further simplify the setting of the threshold, we can classify the results tested according to the fluid type factor, assuming that in addition to the above 20% and 11.1%, we test another kind of fluid and get the data of 19% and 10%. In this way, we can take the overlapping part of the two, that is, 19% and 11.1%, and take the intermediate value 15.1% as the common threshold of the two fluids. Thus, we do not need to set a threshold for each fluid, but only use several thresholds to cover the range of fluids suitable for electromagnetic valves, simplifying the process.

[0046] In summary, the application creatively introduces the concept of eigen triangle which can reflect the shape of the transient current waveform when the electromagnetic valve is in action, and takes the area of the eigen triangle as the basis for judgment. Through simple algorithm, the eigen triangle area change rate of the electromagnetic valve to be tested relative to the standard electromagnetic valve is calculated, and after comparing with the set threshold, the conclusion of whether the electromagnetic valve is faulty is obtained. The whole diagnosis process and algorithm are simple and efficient, accurate in judgment, and low in cost, especially suitable for the vast number of electromagnetic valve users.

[0047] The above merely describes a preferred embodiment of the present application, which is one implementation under the overall concept of the present application, and the protection scope of the present application is not limited thereto, any changes or replacements within the technical scope disclosed by the present application, which can be easily conceived by those skilled in the art, should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A fault diagnosis method for explosion-proof solenoid valves based on current detection, characterized in that, Includes the following steps: Step 1: Obtain the transient current waveform when the standard solenoid valve operates, and calculate the area S1 of the intrinsic triangle of the transient current waveform; Step 2: Obtain the transient current waveform when the solenoid valve under test is activated, and calculate the area S2 of the intrinsic triangle of the transient current waveform; Step 3: Calculate the area change rate of S2 relative to S1. If the area change rate exceeds a set threshold, the solenoid valve under test is determined to be faulty. The intrinsic triangle refers to the triangular region enclosed by the horizontal reference line of the maximum value of the transient current waveform when the solenoid valve is activated and the transient current waveform curve.

2. The method for fault diagnosis of explosion-proof solenoid valve based on current detection according to claim 1, characterized in that, The method for calculating the area of ​​the intrinsic triangle is as follows: Among them, S ∆ Let A be the area of ​​the intrinsic triangle, B be the acquisition time of the crest point, and D be the acquisition time of the point at the same height as the crest. n This represents the current value when the sampling time is n.

3. The method for fault diagnosis of explosion-proof solenoid valves based on current detection according to claim 1, characterized in that, The method for calculating the area change rate is as follows: 。 4. The method for fault diagnosis of explosion-proof solenoid valve based on current detection according to claim 1, characterized in that, The method for collecting the solenoid valve operating current is as follows: the solenoid valve operating current is collected at constant time intervals, and the collection interval does not exceed 1 / 100 of the solenoid valve operating time.

5. The method for fault diagnosis of explosion-proof solenoid valve based on current detection according to claim 1, characterized in that, The operating current of the solenoid valve is acquired by a Hall current sensor or a fluxgate current sensor.

6. The method for fault diagnosis of explosion-proof solenoid valve based on current detection according to claim 1, characterized in that, The set threshold is 10%.

7. The method for fault diagnosis of explosion-proof solenoid valve based on current detection according to claim 1, characterized in that, The method for obtaining the threshold in step 3 is as follows: Under the same fluid conditions, calculate the intrinsic triangle area of ​​the standard solenoid valve and the faulty solenoid valve at different fluid pressures. Based on the maximum area change rate of the intrinsic triangle between different pressure conditions and the minimum area change rate of the intrinsic triangle between faulty and non-faulty conditions, the threshold is obtained.

8. The method for fault diagnosis of explosion-proof solenoid valve based on current detection according to claim 7, characterized in that, The set threshold in step 3 has multiple thresholds corresponding to different fluid ranges. These thresholds are calculated and classified according to the solenoid valve under different fluid conditions using the set threshold acquisition method.

9. The method for fault diagnosis of explosion-proof solenoid valve based on current detection according to claim 1, characterized in that, The area of ​​the intrinsic triangle of the operating current waveform of the standard solenoid valve was obtained through multiple data acquisitions and calculations.

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