Method and system for measuring liquid level height of cascade liquid level sensor during flight

Abstract

The present invention provides a method and system for measuring the liquid level height of a cascaded liquid level sensor during flight, comprising: filtering the triangular wave and linear wave of the liquid level signal collected in real time; making an initial node determination of the number of sensor nodes according to the values ​​of the triangular wave and the linear wave; correcting the current number of sensor nodes according to the current linear wave height curve and the voltage value of the linear wave; updating the maximum and minimum values ​​of the triangular wave in the liquid level height calculation formula; finding the platform section of the sensor cascade and correcting the slope of the linear wave height curve; calculating the liquid level height of the liquid level sensor by means of the triangular wave; and making a real-time fault determination of the liquid level height by means of the liquid level height calculated by the linear wave and the liquid level height calculated by the triangular wave.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor signal processing, and in particular to a method and system for measuring liquid level height of a cascade liquid level sensor during flight. Background Art

[0002] At present, cascaded segmented capacitive sensors are generally used to measure the liquid level height of the tank on the rocket of the thrust system. The measurement range of a single sensor is limited. In order to meet the full-scale liquid level height measurement of the tank, cascaded segmented capacitive sensors are used for rockets that require thrust adjustment.

[0003] In the existing liquid level measurement technology, the liquid level height is calculated by using a linear wave, which will cause the error of the linear wave to accumulate in the entire measurement range, resulting in a large error in the liquid level height measurement.

[0004] In the existing liquid level measurement technology, triangular waves are used to calculate the liquid level height, which can avoid the error accumulation caused by linear wave calculation of the liquid level height. However, during the rocket flight, when the tank liquid level is consumed, the existing method uses the change in the slope of the triangular wave to determine the inflection point. When the liquid level data will have serious jitter, it is easy to misjudge the inflection point of the triangular wave, which will lead to errors in the number of nodes, and ultimately lead to errors in the calculation of the liquid level height.

[0005] Patent document CN112798077B (application number: 202011594750.8) discloses a liquid level height analysis method, device, equipment, storage medium and system. The method includes: continuously acquiring the output voltage and constructing a triangular curve and a monotonic curve, performing least squares filtering and Gaussian filtering operations on the triangular curve and the monotonic curve, and solving the height of the current section of the continuous liquid level sensor where the liquid surface is located and the number of continuous liquid level sensor sections where the liquid surface is located according to preset rules, and determining the real-time height of the liquid level in combination with the height of the current section of the continuous liquid level sensor where the liquid surface is located and the number of continuous liquid level sensor sections where the liquid surface is located. Summary of the invention

[0006] In view of the defects in the prior art, an object of the present invention is to provide a method and system for measuring the liquid level height of a cascade liquid level sensor during flight.

[0007] According to the present invention, a method for measuring the liquid level height of a cascade liquid level sensor during flight includes:

[0008] Step S1: performing filtering and fitting processing on the triangular wave and linear wave of the liquid level signal collected in real time to obtain the triangular wave and linear wave of the liquid level signal after filtering;

[0009] Step S2: determining the initial node of the sensor according to the triangular wave and linear wave voltage values ​​of the liquid level signal after filtering;

[0010] Step S3: The triangular wave voltage value of the liquid level signal after filtering is used to find the maximum and minimum inflection points of the triangular wave by using an inflection point finding algorithm, and the maximum and minimum values ​​and the number of sensor nodes in the liquid level height calculation formula are updated based on the found maximum and minimum inflection points of the triangular wave;

[0011] Step S4: Find the sensor cascade platform period according to the triangular wave voltage value, linear wave voltage value and sensor node number of the filtered liquid level signal, and correct the slope of the linear wave height curve according to the linear wave voltage value of the platform period and the pre-installed platform period height;

[0012] Step S5: Calculate the absolute height of the liquid level using the updated liquid level calculation formula according to the triangular wave voltage value after filtering and the node number where the sensor is currently located;

[0013] Step S6: Perform liquid level height fault judgment based on the liquid level height calculated by the triangular wave and the liquid level height calculated by the linear wave, so as to provide a reliable basis for the propulsion system to utilize the liquid level height.

[0014] Preferably, step S1 includes: using a weighted sliding average filtering method for the triangular wave and linear wave of the liquid level signal collected in real time, dividing the data in the sliding window into equal parts, and weighting each part with different coefficients to obtain the initial filtered value; performing linear regression fitting on the initial filtered value within the sliding window range to obtain the triangular wave and linear wave voltage values ​​of the liquid level signal after filtering and fitting.

[0015] Preferably, the step S2 comprises:

[0016] Step S2.1: After startup, the number of sensor nodes to be confirmed is calculated based on the current linear wave voltage. The calculation formula is:

[0017]

[0018]

[0019] in, It is the sensor range height calculated based on the linear wave. This height does not include the reference height, follower dead zone and node dead zone. k is the slope of the pre-installed tank linear wave height curve. b is the pre-installed linear wave height curve offset. is the linear wave voltage value; is the calculated current section of the sensor, NUM represents the total number of sections of the tank sensor, and unitheight is the length of a single section of the tank sensor. The symbol indicates rounding down;

[0020] Step S2.2: Determine whether to perform a secondary confirmation of the initial node based on whether the current triangular wave voltage is in the triangular wave maximum or minimum value search area; if a secondary confirmation of the initial node is required, when the triangular wave finds the maximum value and is out of the triangular wave maximum value search area, and the number of sensor nodes to be confirmed is an odd number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed; when the triangular wave finds the minimum value and is out of the triangular wave minimum value search area, and the number of sensor nodes to be confirmed is an even number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed.

[0021] Preferably, the step S4 comprises:

[0022] Step S4.1: judging whether the cascade platform period has been reached according to whether the current number of nodes of the sensor is between the cascade platforms and whether the current triangular wave voltage is constant and in the minimum value search area;

[0023] Step S4.2: After reaching the cascade plateau, the slope of the linear wave height curve is corrected according to the linear wave voltage at that time and the pre-installed plateau liquid level. The correction formula is:

[0024]

[0025] in, is the slope of the linear wave height curve after correction, ALTx is the preset platform height, is the linear wave voltage value recorded during the plateau period, and b is the offset of the preset linear wave height curve.

[0026] Preferably, the step S5 comprises: selecting a corresponding liquid level height calculation formula according to the parity of the number of sensor nodes and the current voltage value of the triangle wave to calculate the liquid level height;

[0027] Step S5.1: When the sensor has an odd number of nodes, the height calculation formula is:

[0028]

[0029] Step S5.2: When the sensor has an even number of nodes, the height calculation formula is:

[0030]

[0031] in, is the liquid level height calculated by the triangular wave, represents the maximum value of the triangle wave found, Indicates the minimum value of the triangular wave found, unitheight indicates the single-section height of the sensor, NUM indicates the total number of sections after the sensor is cascaded, curN indicates the current section number of the sensor, BaseHeight indicates the installation height of the sensor, and Deadlength indicates the dead zone length of the sensor. Indicates the current triangle wave voltage value.

[0032] Preferably, step S6 comprises:

[0033] Step S6.1: Calculate the liquid level according to the current voltage value of the linear wave. The height calculation formula is:

[0034]

[0035] in, is the range height of the linear wave, BaseHeight is determined according to the installation height of the cascade sensor, and Deadlength indicates the dead zone length of the sensor;

[0036] Step S6.2: Compare the liquid level height calculated by the triangular wave with the liquid level height calculated by the linear wave. If the difference between the two liquid level heights is not greater than the length of the single-section liquid level sensor, the current liquid level height data is considered to be credible. Otherwise, the current liquid level height data is considered to be unreliable. At this time, the push-pull system does not use the calculated liquid level height as the control basis.

[0037] According to the present invention, a system for measuring liquid level height of a cascade liquid level sensor during flight includes:

[0038] Module M1: Perform filtering and fitting processing on the triangular wave and linear wave of the liquid level signal collected in real time to obtain the triangular wave and linear wave of the liquid level signal after filtering;

[0039] Module M2: Determine the initial node of the sensor based on the triangular wave and linear wave voltage values ​​of the liquid level signal after filtering;

[0040] Module M3: The triangular wave voltage value of the liquid level signal after filtering is used to find the maximum and minimum inflection points of the triangular wave by using the inflection point finding algorithm. Based on the maximum and minimum inflection points of the triangular wave found, the maximum and minimum values ​​in the liquid level height calculation formula and the number of sensor nodes are updated;

[0041] Module M4: Find the sensor cascade platform period according to the triangular wave voltage value, linear wave voltage value and sensor node number of the filtered liquid level signal, and correct the slope of the linear wave height curve according to the linear wave voltage value of the platform period and the pre-installed platform period height;

[0042] Module M5: Calculate the absolute height of the liquid level using the updated liquid level calculation formula according to the triangular wave voltage value after filtering and the current node number of the sensor;

[0043] Module M6: Perform liquid level height fault judgment based on the liquid level height calculated by the triangle wave and the liquid level height calculated by the linear wave, providing a reliable basis for the propulsion system to use the liquid level height.

[0044] Preferably, the module M1 comprises: using a weighted sliding average filtering method to equally divide the data in the sliding window for the triangular wave and linear wave of the liquid level signal collected in real time, and taking different coefficients to weight each equal part to obtain the initial filtered value; performing linear regression fitting on the initial filtered value within the sliding window range to obtain the filtered and fitted triangular wave and linear wave voltage values ​​of the liquid level signal;

[0045] The module M2 comprises:

[0046] Module M2.1: After startup, the number of sensor nodes to be confirmed is calculated based on the current linear wave voltage. The calculation formula is:

[0047]

[0048]

[0049] in, It is the sensor range height calculated based on the linear wave. This height does not include the reference height, follower dead zone and node dead zone. k is the slope of the pre-installed tank linear wave height curve. b is the pre-installed linear wave height curve offset. is the linear wave voltage value; is the calculated current section of the sensor, NUM represents the total number of sections of the tank sensor, and unitheight is the length of a single section of the tank sensor. The symbol indicates rounding down;

[0050] Module M2.2: Determine whether to perform a secondary confirmation of the initial node based on whether the current triangular wave voltage is in the triangular wave maximum or minimum value search area; if a secondary confirmation of the initial node is required, when the triangular wave finds the maximum value and is out of the triangular wave maximum value search area, and the number of sensor nodes to be confirmed is an odd number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed; when the triangular wave finds the minimum value and is out of the triangular wave minimum value search area, and the number of sensor nodes to be confirmed is an even number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed.

[0051] Preferably, the module M4 comprises:

[0052] Module M4.1: Determine whether the cascade platform period has been reached based on whether the number of nodes of the current sensor is between the cascade platforms and whether the current triangle wave voltage is unchanged and in the minimum value search area;

[0053] Module M4.2: After reaching the cascade plateau, the slope of the linear wave height curve is corrected according to the linear wave voltage at that time and the pre-installed plateau liquid level. The correction formula is:

[0054]

[0055] in, is the slope of the linear wave height curve after correction, ALTx is the preset platform height, is the linear wave voltage value recorded during the plateau period, and b is the offset of the preset linear wave height curve.

[0056] Preferably, the module M5 comprises: selecting a corresponding liquid level height calculation formula to calculate the liquid level height according to the parity of the number of sensor nodes and the current voltage value of the triangle wave;

[0057] Module M5.1: When the sensor has an odd number of nodes, the height calculation formula is:

[0058]

[0059] Module M5.2: When the sensor has an even number of nodes, the height calculation formula is:

[0060]

[0061] in, is the liquid level height calculated by the triangular wave, represents the maximum value of the triangle wave found, Indicates the minimum value of the triangular wave found, unitheight indicates the single-section height of the sensor, NUM indicates the total number of sections after the sensor is cascaded, curN indicates the current section number of the sensor, BaseHeight indicates the installation height of the sensor, and Deadlength indicates the dead zone length of the sensor. Indicates the current triangle wave voltage value;

[0062] The module M6 comprises:

[0063] Module M6.1: Calculate the liquid level according to the current voltage value of the linear wave. The height calculation formula is:

[0064]

[0065] in, is the range height of the linear wave, BaseHeight is determined according to the installation height of the cascade sensor, and Deadlength indicates the dead zone length of the sensor;

[0066] Module M6.2: By comparing the liquid level height calculated by the triangular wave and the liquid level height calculated by the linear wave, if the difference between the two liquid level heights is not greater than the length of the single-section liquid level sensor, the current liquid level height data is considered to be credible, otherwise the current liquid level height data is considered to be unreliable. At this time, the push-pull system does not use the calculated liquid level height as the control basis.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] 1. The present invention uses the height difference threshold Q and the number of consecutive times N of the triangular wave to find the extreme point, which improves the accuracy and correctness compared with the traditional extreme value finding method relying on the slope transformation of the triangular wave;

[0069] 2. The present invention dynamically searches for the maximum and minimum points of the triangular wave, and according to the maximum and minimum values ​​of the triangular wave liquid level calculation formula, improves the accuracy of liquid level measurement and avoids the liquid level measurement error caused by the change of dielectric constant;

[0070] 3. The present invention uses linear waves to determine the number of nodes and uses triangular waves to calculate the height, thereby avoiding errors in determining the number of sensor nodes due to incorrect determination of the inflection point of the triangular wave, which in turn leads to errors in calculating the liquid level height.

[0071] 4. The present invention uses the liquid level height calculated by triangular wave and the liquid level height calculated by linear wave to make liquid level height fault judgment, providing an important and reliable basis for the propellant liquid level height for the thrust system to utilize the liquid level height, laying a foundation for solving the thrust adjustment of the thrust system. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0073] Figure 1 The present invention is a flow chart of a method for measuring liquid level height of a cascade liquid level sensor during flight.

[0074] Figure 2 It is a schematic diagram of a curve showing the change of the cascade liquid level sensor signal over time according to the present invention. DETAILED DESCRIPTION

[0075] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0076] Example 1

[0077] According to a method and system for measuring the liquid level height of a cascaded liquid level sensor during flight provided by the present invention, the advantages of linear waves and triangular waves are combined to jointly calculate the liquid level height, and a reliable method for finding the inflection point voltage of the triangular wave is provided. At the same time, a method for determining liquid level signal faults is provided, thereby providing a reliable reference for the liquid level height for the use of the thrust system.

[0078] like Figure 1 As shown, the method for measuring the liquid level height of the cascade liquid level sensor during flight includes the following steps:

[0079] Real-time filtering and fitting of triangular waves and linear waves: real-time acquisition of triangular waves and linear waves, filtering and fitting of the acquired triangular waves and linear waves, eliminating the burrs and jitters of the triangular wave voltage signals and linear wave voltage signals, and obtaining a smooth triangular wave and linear wave voltage signal, which is convenient for subsequent operations to find the maximum and minimum values ​​of the triangular wave.

[0080] Furthermore, the filtering method is: using a weighted sliding average method for filtering, dividing the data in the sliding window into equal parts, weighting each part with different coefficients, and obtaining the initial filtered value; further, performing linear regression fitting on the initialized filtered value within the sliding window range to obtain the final filtered fitted liquid level signal triangular wave and linear wave voltage values.

[0081] Whether to perform sensor initial node determination:

[0082] Sensor initial node determination: The sensor initial node determination is performed through the triangular wave and linear wave voltage values ​​after filtering and fitting;

[0083] Furthermore, the linear wave is used to determine the number of sensor nodes: the nodes of the current sensor are calculated based on the linear wave.

[0084] Further, find the maximum value of the triangular wave, correct the number of sensor nodes and the maximum value of the triangular wave: the trigger condition for finding the maximum value of the triangular wave is: when the triangular wave voltage value is within the threshold range for finding the maximum value, the maximum value search operation is performed; it is limited to only finding the maximum value once in the maximum value search area. When the triangular wave voltage leaves the maximum value search area and drops to near the median voltage, the next maximum value search operation can be activated.

[0085] Further, the method for finding the maximum value of the triangular wave is as follows: in the triangular wave maximum value finding area, the algorithm needs to record a current maximum value, and when it is detected that the current maximum value minus the current value of the triangular wave voltage is greater than the height difference threshold Q for N consecutive times, it is determined that the maximum value of the triangular wave voltage value is found, that is, the inflection point of the maximum value of the triangular wave voltage is found;

[0086] Further, find the minimum value of the triangular wave, correct the number of sensor nodes and the maximum value of the triangular wave: the trigger condition for finding the minimum value of the triangular wave is: when the triangular wave voltage value is in the minimum value search area, the minimum value is searched; it is limited to only search for the minimum value of the triangular wave once in the minimum value search area, when the triangular wave voltage is out of the minimum value search area and rises to near the median voltage, the next operation of finding the minimum value of the triangular wave can be continued.

[0087] Further, the method for finding the minimum value of the triangular wave is as follows: in the triangular wave minimum value finding area, the algorithm needs to record a current triangular wave minimum value, and when it is detected that the current value of the triangular wave voltage minus the current minimum value is greater than the height difference threshold Q for N consecutive times, it is determined that the minimum value of the triangular wave voltage value is found, that is, the inflection point of the minimum value of the triangular wave voltage is found;

[0088] This method can accurately find the maximum and minimum values ​​of the triangle wave, avoiding calculation errors caused by data fluctuations due to liquid surface shaking;

[0089] When the maximum value of the triangle wave is found, the maximum value of the triangle wave in the liquid level height calculation formula is updated with the found maximum value of the triangle wave; when the minimum value of the triangle wave is found, the minimum value of the triangle wave in the liquid level height calculation formula is updated with the found minimum value of the triangle wave;

[0090] The current linear wave liquid level height is calculated using the pre-installed linear wave slope and height curve offset parameters. The calculation method is shown in formula (1);

[0091] (1)

[0092] in, It is the sensor range height calculated based on the linear wave. This height does not include the reference height, follower dead zone and node dead zone. k is the slope of the pre-installed tank linear wave height curve. b is the pre-installed linear wave height curve offset. is the linear wave voltage value;

[0093] Furthermore, the current number of sensor nodes is calculated according to the current linear wave liquid level height. The corresponding formula is shown in formula (2);

[0094] (2)

[0095] in, is the calculated current node of the sensor, It is the height calculated based on the linear wave. This height does not include the installation height and the dead zone length. NUM represents the total number of sections of the tank sensor. Unitheight is the length of a single section of the tank sensor. The symbol indicates rounding down;

[0096] Find the cascade platform segment and correct the slope in the linear wave height curve formula: determine whether the cascade platform period has been reached based on whether the current number of sensor nodes is between the cascade platforms and whether the current triangular wave voltage is in a constant state and in the minimum value search area; after finding the cascade platform, record the linear wave voltage value at this time and correct the slope of the linear wave height curve based on the preset platform height. The correction formula is shown in formula (3).

[0097] (3)

[0098] in, is the slope of the linear wave height curve after correction, ALTx is the preset platform height, is the linear wave voltage value recorded during the plateau period, and b is the offset of the preset linear wave height curve;

[0099] According to the number of sensor nodes, use the triangular wave to calculate the liquid level height: According to the triangular wave to calculate the absolute height of the liquid level, the number of sensor nodes determines the calculation method of the liquid level height. Different numbers of sensor nodes correspond to different dead zone lengths. After the cascade installation method is adopted, the linear wave output by the sensor will appear piecewise linear. Different segments will affect the dead zone length and lead to different calculation methods. At the same time, when using the triangular wave to calculate the liquid level height, the odd and even nodes of the triangular wave are different, and the calculation formula is different.

[0100] When the sensor has an odd number of nodes, the height calculation formula is shown in formula (4).

[0101] (4)

[0102] When the number of sensor nodes is an even number, the height calculation formula is shown in formula (5).

[0103] (5)

[0104] in, is the liquid level height calculated by the triangular wave, represents the maximum value of the triangle wave, Indicates the minimum value of the triangle wave, unitheight indicates the single-section height of the sensor, NUM indicates the total number of sections after the sensor is cascaded, curN indicates the current section number of the sensor, BaseHeight indicates the installation height of the sensor, and Deadlength indicates the dead zone length of the sensor. Indicates the current triangle wave voltage value.

[0105] The method uses the liquid level calculated by triangle wave as the basis for the output liquid level, avoiding the full-scale cumulative error caused by the liquid level calculated by linear wave, and improving the accuracy of liquid level calculation.

[0106] Calculate the liquid level height according to the linear wave and judge the liquid level height fault: This method provides a method for judging the current liquid level height fault of the sensor. By comparing the consistency between the liquid level height calculated by the triangular wave and the liquid level height calculated by the linear wave, it is determined whether the liquid level height output by the current propellant is reliable, ensuring that accurate liquid level height input is provided to the thrust regulating system;

[0107] Use the linear wave to calculate the current absolute height of the liquid level. The calculation formula is shown in Formula 6.

[0108] (6)

[0109] in, is the range height of the linear wave, BaseHeight is determined according to the installation height of the cascade sensor, and Deadlength indicates the dead zone length of the sensor;

[0110] Furthermore, the difference between the absolute liquid level height calculated by the triangular wave and the absolute liquid level height calculated by the linear wave is compared. If the height difference is less than the single section length of the sensor, the output liquid level height is normal, otherwise the output liquid level height is faulty.

[0111] The present invention also provides a system for measuring the liquid level height of a cascade liquid level sensor during flight. The system for measuring the liquid level height of a cascade liquid level sensor during flight can be realized by executing the process steps of the method for measuring the liquid level height of a cascade liquid level sensor during flight, that is, those skilled in the art can understand the method for measuring the liquid level height of a cascade liquid level sensor during flight as a preferred implementation of the system for measuring the liquid level height of a cascade liquid level sensor during flight.

[0112] Example 2

[0113] Embodiment 2 is a preferred embodiment of Embodiment 1

[0114] See Figure 1 , Figure 2 The present invention provides a method for measuring the liquid level height of a cascade liquid level sensor during flight, comprising:

[0115] Filter the triangle wave and linear wave of the liquid level signal;

[0116] The initial node determination of the sensor is performed through the triangular wave and linear wave voltage values ​​after filtering and fitting;

[0117] According to the triangular wave voltage value after filtering, the inflection point finding algorithm is used to find the maximum and minimum inflection points of the triangular wave, and the maximum and minimum values ​​and the number of sensor nodes in the liquid level calculation formula are updated;

[0118] In a specific embodiment, a schematic diagram of the change of the liquid level signal of the cascade liquid level sensor over time is shown as follows: Figure 2 As shown, the numbers 1-10 in the figure represent the section number of the current sensor, 1 represents the first section, 2 represents the second section, 3 represents the third section, 4 represents the fourth section, 5 represents the fifth section, 6 represents the sixth section, 7 represents the seventh section, 8 represents the eighth section, 9 represents the ninth section, and 10 represents the tenth section;

[0119] According to the triangular wave voltage value, linear wave voltage value and sensor node number after filtering and fitting, the sensor cascade platform period is found, and according to the linear wave voltage value of the platform period and the pre-installed platform period height, the slope of the linear wave height curve is corrected;

[0120] Calculate the absolute height of the liquid level based on the triangular wave voltage value after filtering and fitting and the node number where the sensor is currently located;

[0121] Liquid level height fault judgment is performed based on the liquid level height calculated by the triangle wave and the liquid level height calculated by the linear wave.

[0122] In a specific implementation, a weighted sliding filtering method is used for preliminary filtering, and the least square method is used to fit the linear regression equation of the sliding window interval to the triangular wave and the linear wave after preliminary filtering, and the slope K_tri and the offset b_tri of the linear regression equation of the triangular wave voltage, and the slope K_linear and the offset b_linear of the linear regression equation of the linear wave are calculated;

[0123] In a specific implementation, after the filtering process is completed, the initial node determination work is first performed, the current sensor node number is calculated according to the current linear wave voltage, and the area is searched according to whether the current triangle wave voltage is at the maximum or minimum value to determine whether the initial node secondary confirmation determination is required; after startup, the initial node determination work is only performed once throughout the process; in a specific implementation, Figure 2Taking the cascade sensor shown as an example, the single section length of the sensor unitheight is 300, the liquid level height ALTx of the cascade platform stage 1 is 1206, the installation height baseHeight of the first section sensor is the height from the bottom of the sensor to the bottom of the tank, the installation height baseHeight of the second section sensor is the height from the bottom of the sensor to the bottom of the tank, the total number of sections NUM of the cascade sensor is 10, the dead zone length of a single sensor is 2, the number of sections of the first-stage sensor is 6, the number of sections of the second-stage sensor is 4, the dead zone length deadlength of the first stage is (NUM-curN-1)*2, and the dead zone length deadlength of the second stage is (NUM-curN)*2;

[0124] In a specific implementation, the slope k and offset b of the linear wave height curve need to be pre-installed, and curve fitting is performed according to the characteristics of the matching sensor and the converter or the relationship between the linear wave of the measured liquid level signal and the liquid level height to obtain the slope k of the linear wave height curve and the offset b of the linear wave height curve;

[0125] In a specific implementation, the current number of sensor nodes is calculated according to the sensor linear wave height curve. The specific formula is shown in formula (2);

[0126] In a specific implementation, the maximum value of the extreme point of the triangular wave is found. The method described in this article uses the height difference of the triangular wave to find the maximum value. The method sets an area for finding the maximum value. When the triangular wave exceeds 3.8, the maximum value search operation is performed. The filtered triangular wave is used to find the extreme value, and a historical triangular wave maximum value is recorded. When it is detected that the recorded maximum value minus the current triangular wave voltage value is greater than the height difference threshold of 0.2 for three consecutive times, it is determined that the maximum value of the triangular wave voltage value is found, that is, the maximum value of the triangular wave voltage is found, and the maximum value of the triangular wave in the height calculation is replaced; after the maximum value is found and the triangular wave is out of the maximum value search area, if a secondary confirmation judgment of the initial node is required at this time, when the number of sensor nodes to be confirmed is an odd number of nodes, the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed;

[0127] In a specific implementation, the minimum value of the extreme point of the triangular wave is found. The method described in this article uses the height difference of the triangular wave to find the minimum value. The method sets an area for finding the minimum value. When the triangular wave is less than 0.4, the minimum value search operation is performed. The filtered triangular wave is used to find the minimum value, and a historical triangular wave minimum value is recorded. When it is detected that the current value of the triangular wave voltage minus the current minimum value is greater than the height difference threshold of 0.2 for three consecutive times, it is determined that the minimum value of the triangular wave voltage value is found, that is, the minimum value of the triangular wave voltage is found, and the minimum value of the triangular wave in the height calculation is replaced; after the minimum value is found and the triangular wave is out of the minimum value search area, if a secondary confirmation judgment of the initial node is required at this time, when the number of sensor nodes to be confirmed is an even number of nodes, the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed;

[0128] In a specific embodiment, Figure 2 For example, if the number of nodes of the current sensor is between 6 and 7 and the minimum value of the triangular wave is less than 0.4, a plateau search procedure is performed. If the difference of the triangular wave within a period of time is less than 0.1, it is considered to be in the plateau period. The linear wave value at this time is recorded, and the slope k of the linear wave height curve is corrected by formula (3).

[0129] In a specific embodiment, Figure 2 Take for example, according to the current number of sensor nodes, the liquid level height is calculated. When the sensor has an odd number of nodes, the height calculation formula is shown in formula (4).

[0130] (4)

[0131] Furthermore, when the number of sensor nodes is an even number, the height calculation formula is shown in formula (5).

[0132] (5)

[0133] in, is the liquid level height calculated by the triangular wave, represents the maximum value of the triangle wave found, Indicates the minimum value of the triangular wave found, unitheight indicates the single-section height of the sensor, NUM indicates the total number of sections after the sensor is cascaded, curN indicates the current section number of the sensor, BaseHeight indicates the installation height of the sensor, and Deadlength indicates the dead zone length of the sensor. Indicates the current triangle wave voltage value;

[0134] Furthermore, the current absolute height of the liquid level is calculated using the linear wave. The calculation formula is shown in formula (6);

[0135] (6)

[0136] in, is the range height of the linear wave, BaseHeight is determined according to the installation height of the cascade sensor, and Deadlength indicates the dead zone length of the sensor;

[0137] In a specific embodiment, Figure 2 Take the example of the sensor, and compare the difference between the absolute height of the liquid level calculated by the triangular wave and the absolute height of the liquid level calculated by the linear wave. If the height difference is less than the single section length of the sensor, the output liquid level height is normal, otherwise the output liquid level height is faulty.

[0138] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0139] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for measuring the liquid level height of a cascade liquid level sensor during flight, characterized in that: include: Step S1: performing filtering and fitting processing on the triangular wave and linear wave of the liquid level signal collected in real time to obtain the triangular wave and linear wave of the liquid level signal after filtering; Step S2: determining the initial node of the sensor according to the triangular wave and linear wave voltage values ​​of the liquid level signal after filtering; Step S3: The triangular wave voltage value of the liquid level signal after filtering is used to find the maximum and minimum inflection points of the triangular wave using an inflection point finding algorithm, and the maximum and minimum values ​​and the number of sensor nodes in the liquid level height calculation formula are updated based on the found maximum and minimum inflection points of the triangular wave; Step S4: Find the sensor cascade platform period according to the triangular wave voltage value, linear wave voltage value and sensor node number of the filtered liquid level signal, and correct the slope of the linear wave height curve according to the linear wave voltage value of the platform period and the pre-installed platform period height; Step S5: Calculate the absolute height of the liquid level using the updated liquid level calculation formula according to the triangular wave voltage value after filtering and the node number where the sensor is currently located; Step S6: Perform liquid level height fault judgment based on the liquid level height calculated by the triangular wave and the liquid level height calculated by the linear wave, so as to provide a reliable basis for the propulsion system to utilize the liquid level height; The step S4 comprises: Step S4.1: judging whether the cascade platform period has been reached according to whether the current number of nodes of the sensor is between the cascade platforms and whether the current triangular wave voltage is constant and in the minimum value search area; Step S4.2: After reaching the cascade plateau, the slope of the linear wave height curve is corrected according to the linear wave voltage at that time and the pre-installed plateau liquid level. The correction formula is: in, is the slope of the linear wave height curve after correction, ALTx is the preset platform height, is the linear wave voltage value recorded during the plateau period, and b is the offset of the preset linear wave height curve.

2. The method for measuring liquid level height of a cascade liquid level sensor during flight according to claim 1, characterized in that: The step S1 includes: using a weighted sliding average filtering method to equally divide the data in the sliding window for the triangular wave and linear wave of the liquid level signal collected in real time, and weighting each equal part with different coefficients to obtain the initial filtered value; performing linear regression fitting on the initial filtered value within the sliding window range to obtain the triangular wave and linear wave voltage values ​​of the liquid level signal after filtering and fitting.

3. The method for measuring liquid level height of a cascade liquid level sensor during flight according to claim 1, characterized in that: The step S2 comprises: Step S2.1: After startup, the number of sensor nodes to be confirmed is calculated based on the current linear wave voltage. The calculation formula is: in, It is the sensor range height calculated based on the linear wave. This height does not include the reference height, follower dead zone and node dead zone. k is the slope of the pre-installed tank linear wave height curve. b is the offset of the preset linear wave height curve. is the linear wave voltage value; is the calculated current section of the sensor, NUM represents the total number of sections of the tank sensor, and unitheight is the length of a single section of the tank sensor. The symbol indicates rounding down; Step S2.2: Determine whether to perform a secondary confirmation of the initial node based on whether the current triangular wave voltage is in the triangular wave maximum or minimum value search area; if a secondary confirmation of the initial node is required, when the triangular wave finds the maximum value and is out of the triangular wave maximum value search area, and the number of sensor nodes to be confirmed is an odd number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed; when the triangular wave finds the minimum value and is out of the triangular wave minimum value search area, and the number of sensor nodes to be confirmed is an even number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed.

4. The method for measuring liquid level height of a cascade liquid level sensor during flight according to claim 1, characterized in that: The step S5 comprises: selecting a corresponding liquid level height calculation formula according to the parity of the number of sensor nodes and the current voltage value of the triangle wave to calculate the liquid level height; Step S5.1: When the sensor has an odd number of nodes, the height calculation formula is: Step S5.2: When the sensor has an even number of nodes, the height calculation formula is: in, is the liquid level height calculated by the triangular wave, represents the maximum value of the triangle wave found, Indicates the minimum value of the triangular wave found, unitheight indicates the single-section height of the sensor, NUM indicates the total number of sections after the sensor is cascaded, curN indicates the current section number of the sensor, BaseHeight indicates the installation height of the sensor, and Deadlength indicates the dead zone length of the sensor. Indicates the current triangle wave voltage value.

5. The method for measuring liquid level height of a cascade liquid level sensor during flight according to claim 1, characterized in that: The step S6 comprises: Step S6.1: Calculate the liquid level according to the current voltage value of the linear wave. The height calculation formula is: in, is the range height of the linear wave, BaseHeight is determined according to the installation height of the cascade sensor, and Deadlength indicates the dead zone length of the sensor; Step S6.2: Compare the liquid level height calculated by the triangular wave with the liquid level height calculated by the linear wave. If the difference between the two liquid level heights is not greater than the length of the single-section liquid level sensor, the current liquid level height data is considered to be credible. Otherwise, the current liquid level height data is considered to be unreliable. At this time, the push-pull system does not use the calculated liquid level height as the control basis.

6. A cascade liquid level sensor liquid level height measurement system during flight, characterized in that: include: Module M1: Perform filtering and fitting processing on the triangular wave and linear wave of the liquid level signal collected in real time to obtain the triangular wave and linear wave of the liquid level signal after filtering; Module M2: Determine the initial node of the sensor based on the triangular wave and linear wave voltage values ​​of the liquid level signal after filtering; Module M3: The triangular wave voltage value of the liquid level signal after filtering is used to find the maximum and minimum inflection points of the triangular wave by using the inflection point finding algorithm. Based on the maximum and minimum inflection points of the triangular wave found, the maximum and minimum values ​​in the liquid level height calculation formula and the number of sensor nodes are updated; Module M4: Find the sensor cascade platform period according to the triangular wave voltage value, linear wave voltage value and sensor node number of the filtered liquid level signal, and correct the slope of the linear wave height curve according to the linear wave voltage value of the platform period and the pre-installed platform period height; Module M5: Calculate the absolute height of the liquid level using the updated liquid level calculation formula according to the triangular wave voltage value after filtering and the current node number of the sensor; Module M6: According to the liquid level height calculated by the triangle wave and the liquid level height calculated by the linear wave, the liquid level height fault is judged, providing a reliable basis for the propulsion system to use the liquid level height; The module M4 comprises: Module M4.1: Determine whether the cascade platform period has been reached based on whether the current number of sensor nodes is between cascade platforms and whether the current triangle wave voltage is constant and in the minimum value search area; Module M4.2: After reaching the cascade plateau, the slope of the linear wave height curve is corrected according to the linear wave voltage at that time and the pre-installed plateau liquid level. The correction formula is: in, is the slope of the linear wave height curve after correction, ALTx is the preset platform height, is the linear wave voltage value recorded during the plateau period, and b is the offset of the preset linear wave height curve.

7. The system for measuring liquid level height of cascade liquid level sensors during flight according to claim 6, characterized in that: The module M1 comprises: for the triangular wave and linear wave of the liquid level signal collected in real time, a weighted sliding average filtering method is used to divide the data in the sliding window into equal parts, and each equal part is weighted by different coefficients to obtain the initial filtered value; the initial filtered value is subjected to linear regression fitting within the sliding window range to obtain the triangular wave and linear wave voltage values ​​of the liquid level signal after filtering and fitting; The module M2 comprises: Module M2.1: After startup, the number of sensor nodes to be confirmed is calculated based on the current linear wave voltage. The calculation formula is: in, It is the sensor range height calculated based on the linear wave. This height does not include the reference height, follower dead zone and node dead zone. k is the slope of the pre-installed tank linear wave height curve. b is the offset of the preset linear wave height curve. is the linear wave voltage value; is the calculated current section of the sensor, NUM represents the total number of sections of the tank sensor, and unitheight is the length of a single section of the tank sensor. The symbol indicates rounding down; Module M2.2: Determine whether to perform a secondary confirmation of the initial node based on whether the current triangular wave voltage is in the triangular wave maximum or minimum value search area; if a secondary confirmation of the initial node is required, when the triangular wave finds the maximum value and is out of the triangular wave maximum value search area, and the number of sensor nodes to be confirmed is an odd number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed; when the triangular wave finds the minimum value and is out of the triangular wave minimum value search area, and the number of sensor nodes to be confirmed is an even number, then the current number of sensor nodes is the number of sensor nodes to be confirmed plus 1, otherwise the current number of sensor nodes is the number of sensor nodes to be confirmed.

8. The system for measuring liquid level height of cascaded liquid level sensors during flight according to claim 6, characterized in that: The module M5 includes: selecting a corresponding liquid level height calculation formula according to the parity of the number of sensor nodes and the current voltage value of the triangle wave to calculate the liquid level height; Module M5.1: When the sensor has an odd number of nodes, the height calculation formula is: Module M5.2: When the sensor has an even number of nodes, the height calculation formula is: in, is the liquid level height calculated by the triangular wave, represents the maximum value of the triangle wave found, Indicates the minimum value of the triangular wave found, unitheight indicates the single-section height of the sensor, NUM indicates the total number of sections after the sensor is cascaded, curN indicates the current section number of the sensor, BaseHeight indicates the installation height of the sensor, and Deadlength indicates the dead zone length of the sensor. Indicates the current triangle wave voltage value; The module M6 comprises: Module M6.1: Calculate the liquid level according to the current voltage value of the linear wave. The height calculation formula is: in, is the range height of the linear wave, BaseHeight is determined according to the installation height of the cascade sensor, and Deadlength indicates the dead zone length of the sensor; Module M6.2: By comparing the liquid level height calculated by the triangular wave and the liquid level height calculated by the linear wave, if the difference between the two liquid level heights is not greater than the length of the single-section liquid level sensor, the current liquid level height data is considered to be credible, otherwise the current liquid level height data is considered to be unreliable. At this time, the push-pull system does not use the calculated liquid level height as the control basis.

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