A method and system for acquiring characteristic parameters of a solenoid valve

Abstract

The application discloses a kind of electromagnetic valve characteristic parameter acquisition method and system.The disclosed scheme is based on second-order difference algorithm to decouple wave peak and wave trough search and screening process, ensure that only single factor influences the search of wave peak and wave trough characteristic point at the same time, and adopt the method of data mapping, fill the gap between original data and filtered data, so that the electromagnetic valve characteristic parameter is extracted from original data in accurate way, solve the time misjudgment problem caused by phase shift and signal characteristic reduction.

Description

Technical Field

[0001] This invention relates to the field of solenoid valve performance testing, specifically to a method for detecting characteristic parameters of solenoid valves based on second-order difference, wherein the characteristic parameters include opening time T. on Closing time T off And the steady-state current Cur, further includes turning on the peak-to-peak difference ΔH ON and the peak difference ΔH OFF . Background Technology

[0002] Currently, solenoid valve testing employs dedicated ground-based testing equipment to collect data on the solenoid valve's circuit integrity, steady-state current, and current changes during the opening and closing processes. The testing also considers the steady-state current and the inflection point time (opening time T) of the opening and closing currents. on Closing time T off To determine the performance and installation status of the solenoid valve.

[0003] Different solenoid valves have different steady-state currents, and the inflection point time of their current curves when opening and closing will also differ. These parameters are determined during the design of the solenoid valve. After testing, the results are compared with the theoretical design values ​​to determine whether the solenoid valve is working properly.

[0004] Existing methods for detecting characteristic parameters of solenoid valves involve filtering the solenoid valve current data. First, the starting points of the solenoid valve's opening and closing segments are identified. Then, a search-and-screen method is used to find peak-valley pairs in both the opening and closing segments. For the opening segment current data, peaks are searched first, followed by matching troughs to form a peak-valley pair, and this process continues. For the closing segment current data, troughs are searched first, followed by matching peaks to form a peak-valley pair, and this process continues. The difference between each peak-valley pair in both the opening and closing segments is then calculated. Finally, the maximum peak-valley difference in the opening segment is taken as the opening peak-peak difference, and the time corresponding to the trough value minus the opening segment start point is taken as the opening time of the solenoid valve. Similarly, the maximum peak-valley difference in the closing segment is taken as the closing peak-peak difference, and the time corresponding to the peak value minus the closing segment start point is taken as the closing time of the solenoid valve.

[0005] During the final assembly inspection or overall acceptance inspection, the above-mentioned method for detecting the characteristic parameters of solenoid valves revealed that the current curve of the solenoid valve was distorted after being processed by the filtering algorithm. Features such as inflection points and peak-to-peak differences were smoothed out, weakening the characteristic characteristics. Furthermore, the phase of the curve shifted backward, resulting in a time lag and causing the interpretation time to be inconsistent with the actual time. Summary of the Invention

[0006] To address the shortcomings or deficiencies of existing technologies, this invention provides a method for obtaining characteristic parameters of a solenoid valve, wherein the characteristic parameters include the opening time T. on Closing time T off And the steady-state current Cur, characterized in that.

[0007] Therefore, the method for obtaining the characteristic parameters of a solenoid valve provided by the present invention includes:

[0008] Step 1: Collect the solenoid valve current signal to obtain the raw solenoid valve current data R, with the number of sampling points LEN, LEN≥2000;

[0009] Step 2: Filter the original data R to obtain the filtered data F;

[0010] Step 3: Traverse the data F. If the current value of the M1 points after a certain point increases continuously, then consider that point as the starting point of the open segment F. a The time corresponding to this point is Zero_on; take the start point F of the open segment. a The M2th point F to the right b Execute step 4 or / and step 5. If the start point of the open segment F is not found... a Then return to step 1 to resample; M1 takes natural numbers, M2 takes natural numbers;

[0011] Step 4, obtain the opening time T on

[0012] Step 41, traverse point F sequentially. a Point F a With point F b Points between and point F b Execute steps 1 and 2 to obtain the peaks and troughs of the traversed points:

[0013] Step 1: Perform first-order difference calculation on the current data: If (F[n+1]-F[n])>0, then E[n]=1; if (F[n+1]-F[n])<0, then E[n]=-1; if (F[n+1]-F[n])=0, then E[n]=0; F[n+1] and F[n] are points F a Point F a With point F b Points between and point F b The current values ​​of any two adjacent points in the array are given by F[n+1], where F[n+1] is the current value of the point following F[n]; E[n] is the first-order difference data between the current values ​​of F[n+1] and F[n].

[0014] Step 2, calculate the second difference of the current data: if (E[n]-E[n-1])<0, then F[n] is a peak; if (E[n]-E[n-1])>0, then F[n] is a trough.

[0015] Step 42: Execute operation A at least once until the time interval between adjacent peaks in the remaining peaks is greater than or equal to a first threshold. Operation A is: find the peak with the largest current value among all peaks, and remove peaks whose time interval with the peak with the largest current value is less than the first time threshold. The removed peaks do not participate in the next execution of operation A. All peaks are initially the peaks obtained in step 41. Execute operation B at least once until the time interval between adjacent valleys in the remaining valleys is greater than or equal to a second time threshold. Operation B is: find the valley with the smallest current value among all valleys, and remove valleys whose time interval with the valley with the smallest current value is less than the second threshold. The removed valleys do not participate in the next execution of operation B. All valleys are initially the valleys obtained in step 41.

[0016] Step 43: Traverse the remaining peaks processed in step 42 sequentially from front to back, and find the peak F that simultaneously satisfies conditions ① and ②. d Then proceed to step 44, where condition ① is that the current value of the peak is at least M greater than that to its left. 51 A peak current value, wherein condition ② is that the current value of the peak is greater than at least M on its right. 52 The current value at each sampling point; if no peak satisfying both conditions ① and ② is found, proceed to step 1 to re-acquire the current signal; M 51 Take a natural number, M 52 Take natural numbers;

[0017] Step 44: Traverse the remaining troughs processed in step 42 sequentially from front to back, and find the trough F that simultaneously satisfies conditions ③ and ④. e Then proceed to step 45, where condition ③ is that the trough is located at the peak F. d Subsequently, condition ④ states that the current value at the trough is less than the current value at the peak F. d The current value; if no trough that simultaneously satisfies conditions ③ and ④ is found, execute step 1 to re-acquire the current signal;

[0018] Step 45, trough F e The location is mapped to the original data R to obtain the reference trough R. e Reference trough R e The minimum current value among the M7 consecutive points ahead is the value that opens the trough, and the corresponding time is denoted as Tmr_on; M7 is a natural number.

[0019] Step 46: Calculate the solenoid valve Open time T on : Open time T on The difference between the opening trough time Tmr_on and the opening segment start time Zero_on is T on =Tmr_on-Zero_on;

[0020] Step 5, obtain the shutdown time T off and steady-state current Cur

[0021] Step 51, open segment start point F a The M2th point F to the right b The current value and F b The average current value of the M3 points after point M is Steady-state current Cur; M3 takes a natural number;

[0022] Step 52, from F b If, looking backwards from a given point, the current values ​​at the M4 points following that point continuously decrease and the current value at the M4th point is less than half of the steady-state current, then that point is considered the starting point F of the closed segment. c The time corresponding to this point is Zero_off; if the start point F of the closed segment is not found. c Then return to step 1 to reacquire the current signal; M4 is a natural number;

[0023] Step 53, traverse the starting point F of the closed segment c Closing segment start point F c For all points between the last point in data F and the last point in data F, the peaks and troughs of the traversed points are obtained using the methods described in steps 1 and 2. In step 1, F[n+1] and F[n] are the starting points of the closed segment F. c Closing segment start point F c The current values ​​of all points between the last point in data F and the last point in data F, and the current values ​​of any two adjacent points between the last point in data F.

[0024] Step 54: Execute at least one operation C until the time interval between adjacent peaks in the remaining peaks is greater than or equal to the first threshold. Operation C is: find the peak with the largest current value among all peaks, and remove peaks whose time interval with the peak with the largest current value is less than the third time threshold. The removed peaks do not participate in the next execution of operation C. All peaks are initially the peaks obtained in step 53. Execute at least one operation D until the time interval between adjacent valleys in the remaining valleys is greater than or equal to the fourth time threshold. Operation D is: find the valley with the smallest current value among all valleys, and remove valleys whose time interval with the valley with the smallest current value is less than the second threshold. The removed valleys do not participate in the next execution of operation D. All valleys are initially the valleys obtained in step 53.

[0025] Step 55: Traverse the remaining peaks processed in step 54 sequentially from back to front, and find the peak F that simultaneously satisfies conditions ⑤ and ⑥.g Then proceed to step 56, where condition ⑤ is that the current value of the peak is at least M greater than that to its left. 53 A peak current value, wherein condition ⑥ is that the current value of the peak is greater than at least M values ​​to its right. 54 The current value at each sampling point; if no peak satisfying conditions ⑤ and ⑥ is found, proceed to step 1 to re-acquire the current signal; M 53 Take a natural number, M 54 Take natural numbers;

[0026] Step 56: Traverse the remaining troughs processed in step 54 sequentially from back to front, and find the trough F that simultaneously satisfies conditions ⑦ and ⑧. h Then proceed to step 57, where condition ⑦ is that the trough is located at the peak F. g Ahead, condition ⑧ is that the current value of the trough is less than the current value of the peak F. g The current value; if no trough that simultaneously satisfies conditions ⑦ and ⑧ is found, execute step 1 to re-acquire the current signal;

[0027] Step 57, peak F g The position is mapped to the original data R to obtain the reference peak R. g Reference peak R g The maximum current value among the preceding M8 consecutive points is the peak value of the shutdown waveform, and the corresponding time is denoted as Tmr_off; M8 is a natural number.

[0028] Step 58, calculate the solenoid valve Closure time T off : Closure time T off The difference T between the peak closing time Tmr_off and the closing start time Zero_off is... off =Tmr_off-Zero_off.

[0029] Furthermore, the characteristic parameter also includes the peak-to-peak difference ΔH. ON and the peak difference ΔH OFF ;

[0030] Step 45 is replaced by: replacing the peak F d and wave trough F e The position is mapped to the original data R to obtain the reference peak R. d and reference trough R e Reference peak R d The maximum current value among the preceding M6 consecutive points is the peak value On_peak; the reference trough R e The minimum current value among the M7 consecutive points ahead is the valley opening value On_valley, and the corresponding time is denoted as Tmr_on; M6 is a natural number;

[0031] The peak difference △H ON To open the difference between the peak value and the trough value, ΔH ON =On_peak - On_valley;

[0032] Step 57 is replaced by: replacing peak F g and wave trough F h The position is mapped to the original data R to obtain the reference peak R. g and reference trough R h Reference peak R g The maximum current value among the preceding M8 consecutive points is the off-peak value Off_peak, and the corresponding time is denoted as Tmr_off; refer to the trough R. h The minimum current value among the preceding M9 consecutive points is the off-valley value; M9 is a natural number.

[0033] The peak difference ΔH of the closed peak OFF To close the peak value and close the trough value, ΔH Off =Off_peak-Off_valley.

[0034] Optionally, the sampling rate in step 1 is greater than or equal to 5kHz, and the values ​​of the first time threshold, the second time threshold, the third time threshold, and the fourth time threshold range from 2 to 6ms. Further optionally, the sampling rate in step 1 is 10kHz, and the values ​​of the first time threshold, the second time threshold, the third time threshold, and the fourth time threshold are all 3ms.

[0035] Furthermore, the filtering in step 2 employs a sliding filter.

[0036] Furthermore, regarding point F a Point F a With point F b Points between and point F b After normalizing the current value, proceed to steps 42-44.

[0037] Furthermore, regarding the starting point F of the closed segment... c Closing segment start point F c After normalizing the current value of all points between the last point in data F and the last point in data F, proceed to steps 54-56.

[0038] Optional, M1=20, M2=600, M3=99, M4=15, M 51 =30, M 52 =30, M 53 =30, M 54 =30, M6=10, M7=5, M8=8, M9=5.

[0039] This invention also provides a system for acquiring characteristic parameters of a solenoid valve. The system includes a data acquisition module, a filtering module, and a characteristic parameter acquisition module; the data acquisition module is used to acquire the solenoid valve current signal, obtain the raw solenoid valve current data R, and the number of sampling points LEN, where LEN ≥ 2000;

[0040] The filtering module is used to filter the original data R to obtain the filtered data F; the feature parameter acquisition module is used to execute the above method to obtain the feature parameters of the solenoid valve under test.

[0041] Compared with the prior art, the beneficial effects of the method in this application are:

[0042] (1) The present invention decouples the peak and valley search and screening process. First, all feature points are searched, and then fine screening is performed. This ensures that only a single factor affects the search of peak and valley feature points at the same time. That is, the present invention separates the search and screening, and can find the error links in the process.

[0043] (2) The present invention uses a data mapping method to bridge the difference between the original data and the filtered data, so that the characteristic parameters of the solenoid valve can be extracted from the original data in an accurate manner, thus solving the problem of time misjudgment caused by phase shift and signal feature reduction.

[0044] (3) Liquid rocket engines are equipped with various types of solenoid valves to control the propellant supply in various pipelines of the engine system. The correctness of valve operation and time response characteristics play a decisive role in the normal operation of the engine system. Therefore, in the inspection of engine electrical performance, it is necessary to accurately determine the reliability of the solenoid valve itself. The determination of operational reliability depends on the characteristic parameters of the solenoid valve's operating current curve. Therefore, the selection of a method for extracting characteristic parameters is particularly critical. The method of this invention is especially suitable for obtaining the characteristic parameters of solenoid valves during the electrical performance testing of liquid rocket engines. Attached Figure Description

[0045] Figure 1 (a) shows the original data R and the filtered data F collected in the embodiment of the present invention; where the black line is the original data and the red line is the filtered data; Figure 1 (b) is Figure 1 (a) Enlarged view of the open segment on the curve; Figure 1 (c) is Figure 1 (a) Enlarged view of the closed segment on the curve; Figure 1 (d) is obtained by the method of the present invention. Figure 1 (a) is a diagram showing the location of the feature parameters of the original data.

[0046] Figure 2 To obtain using existing methods Figure 1(a) shows the feature parameters of the original data;

[0047] Figure 3 To obtain by the method of the present invention Figure 1 (a) shows the feature parameters of the original data. Detailed Implementation

[0048] Unless otherwise specified, the terminology used in this document is based on the understanding of those skilled in the art.

[0049] This invention decouples the peak and valley search and screening process based on the second-order difference algorithm, ensuring that only a single factor affects the search of peak and valley feature points at any given time. It also uses a data mapping method to bridge the difference between the original data and the filtered data, enabling the solenoid valve feature parameters to be extracted from the original data in a precise manner.

[0050] It should be explained that, in the method of this invention, "before and after" refers to the timing of sampling. For a specific sampling point, the point before its sampling time is the point in front of it, and correspondingly, the point after its sampling time is the point behind it.

[0051] The value of parameter M2 involved in the method of this invention is ensured to be: from the opening starting point F a The M2th point after this point is in the steady-state phase of the solenoid valve opening. Other parameters M1, M3, M4, and M... 51 M 52 M 53 M 54 The specific values ​​of M1, M6, M7, M8, and M9 are determined based on the dynamic characteristics of the solenoid valve being measured. Taking the 5D55-0 model solenoid valve for a liquid oxygen / kerosene engine as an example, M1 = 20, M2 = 600, M3 = 99, M4 = 15, M... 51 =30, M 52 =30, M 53 =30, M 54 =30, M6=10, M7=5, M8=8, M9=5.

[0052] The first time threshold, the second time threshold, the third time threshold, and the fourth time threshold are determined based on the dynamic characteristics of the solenoid valve being measured and the sampling frequency of the current value. The common range of the first, second, third, and fourth threshold values ​​is 2-6 ms, and the four threshold values ​​may be the same or different.

[0053] Based on the present invention, to improve the search effect, some solutions first normalize the sampling point data of the corresponding segment when searching for the peaks and troughs of the collected data, and then use the corresponding method of the present invention to search for and filter the peaks and troughs. For example, when searching for point F... a Point Fa With point F b Points between and point F b When identifying peaks and troughs in the waveform, the current values ​​at all points are first normalized, i.e., point F is located. a Point F a With point F b Points between and point F b The maximum current value is calculated, and the current values ​​at all other points are divided by this maximum value to normalize the data, resulting in normalized current data. Then, steps 42-44 are executed, during which peaks and troughs are found and filtered by comparing the normalized values. Finally, the peaks F found through the normalized values ​​are... d and wave trough F e The location is mapped to the original data R to find the reference peak and reference trough; for the start point F of the closed segment c Closing segment start point F c The method for finding and filtering all points between the last point in data F and the last point in data F is the same as described above.

[0054] It should also be explained that steps 4 and 5 of the present invention can be performed sequentially or simultaneously without affecting the results obtained.

[0055] Example:

[0056] This embodiment uses the method of the present invention to obtain the characteristic parameters of the 5D55-0 model solenoid valve on a liquid rocket engine, specifically obtaining the opening time T of the solenoid valve. on Closing time T off Steady-state current Cur, peak-to-peak difference ΔH ON and the peak difference ΔH OFF .

[0057] In this embodiment, M1=20, M2=600, M3=99, M4=15, M5=30, M6=10, M7=5, M8=8, M9=5; the values ​​of the first threshold, the second threshold, the third threshold, and the fourth threshold are all 3ms; LEN=3200; the sampling rate is 10kHz;

[0058] Figure 1 (a) is a comparison chart of the solenoid valve current curve data before and after filtering in this embodiment. The black line represents the original data, and the red line represents the filtered data. The data for the opening and closing segments are magnified, as shown in the figure. Figure 1 (b) Figure 1 As shown in (c), the filtered signal characteristics are weakened and there is a phase shift, which is more obvious in the open segment. Figure 1 (d) is a schematic diagram showing the characteristic parameters of the solenoid valve measured in this embodiment using the method of the present invention;

[0059] against Figure 1 (a) The solenoid valve current curve data was analyzed using OriginPro software. The theoretical characteristic parameters were calculated manually from the raw data and the filtered data. The results are shown in Table 1. It can be seen that after filtering, the current data: firstly, the peak-to-peak difference ΔH of the characteristic parameter is turned on. ON The impact is quite significant, amounting to half of the theoretically calculated value of the original data, with the peak-to-peak difference ΔH turned off. Off The results are largely consistent with theoretical values. Furthermore, the opening start point Zero_on, closing start point Zero_off, and steady-state current Cur of the solenoid valve are consistent with the theoretically calculated values ​​from the original data. However, due to signal phase shift after data filtering, the opening trough time Tmr_on and the closing peak time Tmr_off deviate from the theoretical values ​​by 0.1ms to 0.5ms. This is further confirmed by formula T... on =Tmr_on-Zero_on and T off =Tmr_off - Zero_off Calculated opening time T on and closing time T off It takes longer than the theoretical time.

[0060] Table 1 Theoretical Calculation Results of Solenoid Valve Characteristic Parameters

[0061] Characteristic parameters and process variables Solenoid valve raw data Data after solenoid valve filtering Open the starting point Zero_on(ms) 56.6 56.6 Enable the trough time Tmr_on(ms) 66.9 67.1 <![CDATA[Opening time T on (ms)]]> 10.3 10.5 <![CDATA[Open peak-to-peak difference △H ON (A)]]> 0.13 0.06 Turn off the starting point Zero_off(ms) 160.9 160.9 Turn off peak time Tmr_off(ms) 211.2 211.6 <![CDATA[Closing time T off (ms)]]> 50.3 50.7 <![CDATA[Closed peak-to-peak difference △H Off (A)]]> 0.05 0.05 Steady-state current Cur(A) 1.21 1.21

[0062] Obtain using existing methods (the method disclosed in CN202010916220.4) Figure 1 (a) shows the feature parameter values ​​of the original data and the opening time T. on The shutdown time is 10.5ms, and the shutdown time is T. off The steady-state current Cur( ) is 50.7 ms. Figure 2 The value of I) in the figure is 1.21A, and the peak-to-peak difference ΔH is enabled. ON ( Figure 2 The peak difference ΔH1 is 0.06A, and the peak-to-peak difference ΔH is turned off. OFF ( Figure 2 The value of ΔH2 is 0.05A, and the results are shown in [the original text]. Figure 2 The results are consistent with the theoretical characteristic parameters after filtering in Table 1.

[0063] Figure 3 To obtain by using the method of the present invention Figure 1 (a) shows the characteristic parameter values ​​of the original data and the opening time T. on The shutdown time is 10.3ms, and the shutdown time is T. off The steady-state current Cur(50.3ms) is 50.3ms. Figure 3 The value of I) in the figure is 1.21A, and the peak-to-peak difference ΔH is enabled. ON ( Figure 2 The peak difference ΔH1 is 0.13A, and the peak-to-peak difference ΔH is turned off. OF ( Figure 2 The value of ΔH2 in the table is 0.05A, which matches the solenoid valve characteristic parameters based on the original data in Table 1, accurately reflecting the operating characteristics of the solenoid valve.

Claims

1. A method for obtaining characteristic parameters of a solenoid valve, wherein the characteristic parameters include opening time T. on Closing time T off And steady-state current Cur, characterized in that, The method includes: Step 1: Collect the solenoid valve current signal to obtain the raw solenoid valve current data R, with the number of sampling points LEN, LEN≥2000; Step 2: Filter the original data R to obtain the filtered data F; Step 3: Traverse the data F. If the current value of the M1 points after a certain point increases continuously, then consider that point as the starting point of the open segment F. a The time corresponding to this point is Zero_on; take the starting point F of the open segment. a The M2th point F to the right b Perform steps 4 and 5. If the starting point of the open segment F is not found... a Then return to step 1 to resample; M1 takes natural numbers, M2 takes natural numbers; Step 4, obtain the opening time T on Step 41, traverse point F sequentially. a Point F a With point F b Points between and point F b Execute steps 1 and 2 to obtain the peaks and troughs of the traversed points: Step 1: Perform first-order difference operations on the current data: If (F[n+1] - F[n]) > 0, then E[n] = 1; if (F[n+1] - F[n]) < 0, then E[n] = -1; if (F[n+1] - F[n]) = 0, then E[n] = 0; F[n+1] and F[n] are points F a Point F a With point F b Points between and point F b The current values ​​of any two adjacent points in the array are given by F[n+1], where F[n+1] is the current value of the point following F[n]; E[n] is the first-order difference data between the current values ​​of F[n+1] and F[n]. Step 2, calculate the second difference of the current data: if (E[n] - E[n-1]) < 0, then F[n] is a peak; if (E[n] - E[n-1]) > 0, then F[n] is a trough. Step 42: Execute operation A at least once until the time interval between adjacent peaks in the remaining peaks is greater than or equal to a first threshold. Operation A is: find the peak with the largest current value among all peaks, and remove peaks whose time interval with the peak with the largest current value is less than the first time threshold. The removed peaks do not participate in the next execution of operation A. All peaks are initially the peaks obtained in step 41. Execute operation B at least once until the time interval between adjacent valleys in the remaining valleys is greater than or equal to a second time threshold. Operation B is: find the valley with the smallest current value among all valleys, and remove valleys whose time interval with the valley with the smallest current value is less than the second threshold. The removed valleys do not participate in the next execution of operation B. All valleys are initially the valleys obtained in step 41. Step 43: Traverse the remaining peaks processed in step 42 sequentially from front to back, and find the peak F that simultaneously satisfies conditions ① and ②. d Then proceed to step 44, where condition ① is that the current value of the peak is at least M greater than that to its left. 51 A peak current value, wherein condition ② is that the current value of the peak is greater than at least M on its right. 52 The current value at each sampling point; if no peak satisfying both conditions ① and ② is found, proceed to step 1 to re-acquire the current signal; M 51 Take a natural number, M 52 Take natural numbers; Step 44: Traverse the remaining troughs processed in step 42 sequentially from front to back, and find the trough F that simultaneously satisfies conditions ③ and ④. e Then proceed to step 45, where condition ③ is that the trough is located at the peak F. d Subsequently, condition ④ states that the current value at the trough is less than the current value at the peak F. d The current value; if no trough that simultaneously satisfies conditions ③ and ④ is found, execute step 1 to re-acquire the current signal; Step 45, trough F e The location is mapped to the original data R to obtain the reference trough R. e Reference trough R e The minimum current value among the M7 consecutive points ahead is the value that opens the trough, and the corresponding time is denoted as Tmr_on; M7 is a natural number. Step 46: Calculate the solenoid valve opening time T on Opening time T on The difference between the opening trough time Tmr_on and the opening segment start time Zero_on is T on = Tmr_on - Zero_on; Step 5, obtain the shutdown time T off and steady-state current Cur Step 51, open segment start point F a The M2th point F to the right b The current value and F b The average current value of the M3 points following point M3 is the steady-state current Cur; M3 is a natural number. Step 52, from F b If, looking backwards from a given point, the current values ​​at the M4 points following that point continuously decrease and the current value at the M4th point is less than half of the steady-state current, then that point is considered the starting point F of the closed segment. c The time corresponding to this point is Zero_off; if the start point F of the closed segment is not found. c Then return to step 1 to reacquire the current signal; M4 is a natural number; Step 53, traverse the starting point F of the closed segment c Closing segment start point F c For all points between the last point in data F and the last point in data F, use the methods described in steps 1 and 2 to obtain the peaks and troughs of the traversed points. In step 1, F[n+1] and F[n] are the starting points of the closed segment F. c Closing segment start point F c The current values ​​of all points between the last point in data F and the last point in data F, and the current values ​​of any two adjacent points between the last point in data F. Step 54: Execute at least one operation C until the time interval between adjacent peaks in the remaining peaks is greater than or equal to the first threshold. Operation C is: find the peak with the largest current value among all peaks, and remove peaks whose time interval with the peak with the largest current value is less than the third time threshold. The removed peaks do not participate in the next execution of operation C. All peaks are initially the peaks obtained in step 53. Execute at least one operation D until the time interval between adjacent valleys in the remaining valleys is greater than or equal to the fourth time threshold. Operation D is: find the valley with the smallest current value among all valleys, and remove valleys whose time interval with the valley with the smallest current value is less than the second threshold. The removed valleys do not participate in the next execution of operation D. All valleys are initially the valleys obtained in step 53. Step 55: Traverse the remaining peaks processed in step 54 sequentially from back to front, and find the peak F that simultaneously satisfies conditions ⑤ and ⑥. g Then proceed to step 56, where condition ⑤ is that the current value of the peak is at least M greater than that to its left. 53 A peak current value, wherein condition ⑥ is that the current value of the peak is greater than at least M values ​​to its right. 54 The current value at each sampling point; if no peak satisfying conditions ⑤ and ⑥ is found, proceed to step 1 to re-acquire the current signal; M 53 Take a natural number, M 54 Take natural numbers; Step 56: Traverse the remaining troughs processed in step 54 sequentially from back to front, and find the trough F that simultaneously satisfies conditions ⑦ and ⑧. h Then proceed to step 57, where condition ⑦ is that the trough is located at the peak F. g Ahead, condition ⑧ is that the current value of the trough is less than the current value of the peak F. g The current value; if no trough that simultaneously satisfies conditions ⑦ and ⑧ is found, execute step 1 to re-acquire the current signal; Step 57, peak F g The position is mapped to the original data R to obtain the reference peak R. g Reference peak R g The maximum current value among the preceding M8 consecutive points is the peak value of the shutdown waveform, and the corresponding time is denoted as Tmr_off; M8 is a natural number. Step 58, calculate the solenoid valve closing time T. off Closing time T off The difference T between the peak closing time Tmr_off and the closing start time Zero_off is... off = Tmr_off - Zero_off.

2. The method for obtaining characteristic parameters of a solenoid valve as described in claim 1, characterized in that, The characteristic parameters also include peak difference ΔH. ON and the peak difference ΔH OFF ; Step 45 is replaced by: replacing the peak F d and wave trough F e The position is mapped to the original data R to obtain the reference peak R. d and reference trough R e Reference peak R d The maximum current value among the preceding M6 consecutive points is the peak value On_peak; the reference trough R e The minimum current value among the M7 consecutive points ahead is the valley opening value On_valley, and the corresponding time is denoted as Tmr_on; M6 is a natural number; The peak difference △H ON To open the difference between the peak value and the trough value, ΔH ON = On_peak - On_valley; Step 57 is replaced by: replacing peak F g and wave trough F h The position is mapped to the original data R to obtain the reference peak R. g and reference trough R h Reference peak R g The maximum current value among the preceding M8 consecutive points is the off-peak value Off_peak, and the corresponding time is denoted as Tmr_off; refer to the trough R. h The minimum current value among the preceding M9 consecutive points is the off-valley value; M9 is a natural number. The peak difference ΔH of the closed peak OFF To close the peak value and close the trough value, ΔH Off = Off_peak - Off_valley.

3. The method for obtaining characteristic parameters of a solenoid valve as described in claim 1, characterized in that, The sampling rate in step 1 is greater than or equal to 5kHz, and the values ​​of the first time threshold, the second time threshold, the third time threshold and the fourth time threshold are in the range of 2-6ms.

4. The method for obtaining characteristic parameters of a solenoid valve as described in claim 1, characterized in that, The sampling rate in step 1 is 10kHz, and the values ​​of the first time threshold, the second time threshold, the third time threshold and the fourth time threshold are all 3ms.

5. The method for obtaining characteristic parameters of a solenoid valve as described in claim 1, characterized in that, The filtering in step 2 uses sliding filtering.

6. The method for obtaining characteristic parameters of a solenoid valve as described in claim 1, characterized in that, For point F a Point F a With point F b Points between and point F b After normalizing the current value, proceed to steps 42-44.

7. The method for obtaining characteristic parameters of a solenoid valve as described in claim 1, characterized in that, For the starting point F of the closed segment c Closing segment start point F c After normalizing the current value of all points between the last point in data F and the last point in data F, proceed to steps 54-56.

8. The method for obtaining characteristic parameters of a solenoid valve as described in claim 1, characterized in that, M1=20,M2=600,M3=99,M4=15,M 51 =30,M 52 =30,M 53 =30,M 54 =30,M6=10, M7=5,M8=8, M9=5。 9. A system for acquiring characteristic parameters of a solenoid valve, wherein the characteristic parameters include opening time T. on Closing time T off And steady-state current Cur, characterized in that, It includes a data acquisition module, a filtering module, and a feature parameter acquisition module; the data acquisition module is used to acquire the solenoid valve current signal, obtain the raw solenoid valve current data R, and the number of sampling points LEN, LEN≥2000; The filtering module is used to filter the original data R to obtain the filtered data F; the feature parameter acquisition module is used to execute steps 3, 4 and 5 of any one of claims 1, 3-8 to obtain the feature parameters of the solenoid valve under test.

10. The solenoid valve characteristic parameter acquisition system as described in claim 9, characterized in that, The characteristic parameters also include peak difference ΔH. ON and the peak difference ΔH OFF The feature parameter acquisition module is used to execute steps 3, 4 and 5 of claim 2 to obtain the feature parameters of the solenoid valve under test.

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