Liquid rocket engine center of mass dynamic measurement system based on ultrasonic waves

Abstract

The application belongs to the technical field of engine detection, and specifically relates to a liquid rocket engine centroid dynamic measurement system based on ultrasonic waves. The system comprises a first ultrasonic transducer array, a second ultrasonic transducer array, a signal processing module and a calculation unit. The first ultrasonic transducer array is arranged at a position corresponding to the position of a liquid fuel storage tank, and the second ultrasonic transducer array is arranged at a position corresponding to the position of a liquid oxidizer storage tank. The first ultrasonic transducer array and the second ultrasonic transducer array each comprise a plurality of ultrasonic transducers arranged in the same vertical plane. The calculation unit is used to calculate the coordinates of each liquid surface echo point according to each reflection echo received by each ultrasonic transducer array. The calculation unit is also used to calculate the centroid coordinates of the liquid rocket engine according to the coordinates of each liquid surface echo point corresponding to the first ultrasonic transducer array and the second ultrasonic transducer array. The application can realize real-time monitoring of the centroid position of the liquid rocket engine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of engine detection, and particularly relates to a liquid rocket engine centroid dynamic measurement system based on ultrasonic waves. BACKGROUND

[0002] In the development and production of liquid rocket engines, liquid level monitoring during the filling and storage of liquid fuel and liquid oxidant storage tanks is very important. Due to the application characteristics of flammability, explosiveness, ultralow temperature and high pressure, the measured liquid must be in a large-scale, sealed, low-temperature and high-pressure environment, avoiding contact with electricity and magnetism, and cannot collide, so higher requirements are put forward for the measurement method and principle of the liquid level of liquid fuel and liquid oxidant. During the storage process of the rocket engine, the centroid of the liquid fuel and the liquid oxidant generally does not change, but during the running process of the rocket, the liquid level of the liquid fuel and the liquid oxidant will gradually decrease and tilt, and the centroid position of the liquid rocket engine as a whole will change accordingly, which affects the stability of the rocket to some extent. Dynamic measurement of the centroid of the liquid fuel and the liquid oxidant of the rocket engine can greatly help monitor the running condition of the rocket and analyze the stability of the rocket during running. There are many traditional methods for measuring the centroid of liquid, but these methods generally need to install the measurement device inside the equipment, and for the liquid rocket engine involved in the present application, the traditional measurement method is not applicable, because it not only easily leads to leakage of liquid fuel and liquid oxidant, but also has a high maintenance cost after failure, so a new wireless and non-destructive measurement technology needs to be found to solve this problem.

[0003] The ultrasonic wireless detection technology can realize truly non-contact and non-immersed measurement, does not damage the structural integrity and sealing of the engine, and avoids the leakage problem of the liquid fuel and the liquid oxidant; the artificial neural network is a mathematical model of algorithm that simulates the behavior characteristics of animal neural networks for distributed parallel information processing. This network relies on the complexity of the system to adjust the relationship between a large number of nodes connected to each other, so as to achieve the purpose of processing information, and has the ability of self-learning and self-adaptation. Therefore, if the ultrasonic wave and the neural network are applied to the centroid position detection of the liquid rocket engine, the safety of the detection can be greatly improved. SUMMARY

[0004] The present application overcomes the defects that the existing measurement technology will damage the structural integrity of the engine and be affected by the internal structure of the engine, and solves the technical problem of providing a liquid rocket engine centroid dynamic measurement system based on ultrasonic waves and CNN neural networks to realize dynamic monitoring of the centroid of the liquid rocket engine.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: an ultrasonic-based liquid rocket engine center of mass dynamic measurement system, comprising a first ultrasonic transducer array, a second ultrasonic transducer array, a signal processing module and a computing unit, wherein the first ultrasonic transducer array and the second ultrasonic transducer array are both arranged on the engine casing, the first ultrasonic transducer array is arranged at a position corresponding to the position of the liquid fuel storage tank, and the second ultrasonic transducer array is arranged at a position corresponding to the position of the liquid oxidizer storage tank; the first ultrasonic transducer array and the second ultrasonic transducer array each include a plurality of ultrasonic transducers arranged in the same vertical plane, and each ultrasonic transducer array is arranged in a different vertical plane, the ultrasonic transducers are used to transmit ultrasonic waves to different positions of the liquid surface in the engine casing within the vertical plane, and receive reflected echoes, which are then sent to the computing unit through the signal processing module;

[0006] The calculation unit is used to calculate the coordinates of each liquid surface echo point based on the reflected echoes received by each ultrasonic transducer array; it is also used to calculate the center of mass coordinates of the liquid rocket engine based on the coordinates of each liquid surface echo point corresponding to the first ultrasonic transducer array and the second ultrasonic transducer array.

[0007] The number of ultrasonic transducers in the first ultrasonic transducer array and the second ultrasonic transducer array is greater than or equal to 4.

[0008] The ultrasonic transducer comprises an arched packaging shell, a backing and a piezoelectric ceramic layer located in the middle. The surface of the arched packaging shell is a concave surface that matches the outer surface of the engine casing.

[0009] The calculation unit is used to calculate the coordinates of the center of mass of the liquid fuel and the liquid oxidizer based on the coordinates of each liquid surface echo point corresponding to the first ultrasonic transducer array and the second ultrasonic transducer array, and then calculate the coordinates of the center of mass of the liquid rocket engine; the specific method for calculating the coordinates of the center of mass of the liquid fuel and the liquid oxidizer is:

[0010] Step 1: Establish a three-dimensional coordinate system with the center of the engine casing as the coordinate origin, the vertical direction as the Z-axis, and the direction through the origin and perpendicular to the vertical plane where the corresponding ultrasonic transducer array is located as the X-axis. Determine the coordinates of the liquid surface echo point corresponding to each ultrasonic transducer based on the real-time distance from each ultrasonic transducer to the corresponding liquid surface echo point and the ultrasonic transmission direction of the ultrasonic transducer.

[0011] Step 2: Perform parabola fitting based on the coordinates of the liquid surface echo points corresponding to each ultrasonic transducer, and use the fitted parabola as the liquid surface curve;

[0012] Step 3: determining the centroid coordinates of the liquid fuel and the liquid oxidizer according to the liquid surface curves obtained by the first ultrasonic transducer array and the second ultrasonic transducer array.

[0013] In step 3, the specific method for determining the centroid coordinates of the liquid fuel and the liquid oxidizer according to the liquid surface is as follows:

[0014] Step 3.1: determining the coordinates of the two intersection points A and B of the liquid surface curve of the liquid fuel and the engine shell by the first group of ultrasonic transducer arrays, determining the cross section of the liquid fuel according to the intersection point coordinates, and calculating the cross-sectional area of the liquid fuel;

[0015] Step 3.2: calculating the static moment of the liquid fuel cross section relative to the Y-axis and the Z-axis;

[0016] Step 3.3: calculating the centroid coordinates of the liquid fuel on the Y-axis and the Z-axis according to the static moment, and further determining the centroid coordinates of the liquid fuel.

[0017] Step 3.4: calculating the centroid coordinates of the liquid oxidizer on the Y-axis and the Z-axis by the second group of ultrasonic transducer arrays and the above calculation steps.

[0018] The liquid rocket engine centroid dynamic measurement system based on ultrasonic waves comprises two first ultrasonic transducer arrays and two second ultrasonic transducer arrays, wherein the two first ultrasonic transducer arrays are located in different and intersecting vertical planes, and the two second ultrasonic transducer arrays are located in different and intersecting vertical planes.

[0019] The calculation unit is used to calculate the coordinates of each liquid surface echo point of the liquid fuel according to each reflected echo received by the two first ultrasonic transducer arrays, and to calculate the coordinates of each liquid surface echo point of the liquid oxidizer according to each reflected echo received by the two second ultrasonic transducer arrays, and to calculate the centroid coordinates of the liquid fuel and the liquid oxidizer according to the coordinates of each liquid surface echo point of the liquid fuel and the liquid oxidizer.

[0020] The vertical planes where the two first ultrasonic transducer arrays are located are perpendicular, and the vertical planes where the two second ultrasonic transducer arrays are located are perpendicular.

[0021] The specific method for calculating the centroid coordinates of the liquid rocket engine by the calculation unit is as follows:

[0022] Step 1: Establish a three-dimensional coordinate system with the engine shell core as the coordinate origin, the vertical direction as the Z-axis direction, and the direction passing through the origin and perpendicular to the vertical plane where one of the corresponding ultrasonic transducer arrays is located as the direction of the X-axis; determine the coordinates of the liquid surface echo points corresponding to each ultrasonic transducer in the ultrasonic transducer array according to the real-time distances from the ultrasonic transducers to the corresponding liquid surface echo points and the ultrasonic wave transmission directions of the ultrasonic transducers;

[0023] Step 2: Perform parabolic fitting according to the coordinates of the liquid surface echo points corresponding to each ultrasonic transducer in one of the ultrasonic transducer arrays to obtain the liquid surface curve in the vertical plane; similarly, obtain the liquid surface curve in the vertical plane of the other ultrasonic transducer array;

[0024] Step 3: Determine the centroid coordinates in the Y-axis and Z-axis directions according to the liquid surface curve obtained from one of the ultrasonic transducer arrays, and determine the centroid coordinates in the X-axis and Z-axis directions according to the liquid surface curve obtained from the other ultrasonic transducer array;

[0025] Step 4: Calculate the centroid coordinates of the overall liquid inside the engine according to the centroid coordinates of the liquid fuel and the liquid oxidizer; obtain the centroid coordinates of the engine shell; calculate the centroid coordinates of the liquid rocket engine at the current time according to the centroid coordinates of the liquid inside the engine at the current time and the centroid coordinates of the engine shell.

[0026] The specific method for calculating the centroid coordinates of the liquid rocket engine by the calculation unit according to each liquid surface echo point coordinate is as follows:

[0027] Step 2-1: Use the first ultrasonic transducer array and the second ultrasonic transducer array to perform multi-point measurement on the liquid surfaces of the liquid fuel storage tank and the liquid oxidizer storage tank in the engine shell to obtain real-time coordinate data of each liquid surface echo point;

[0028] Step 2-2: Design and train a CNN model suitable for calculating the centroid of a liquid rocket engine; the training data set consists of historical measurement data and simulation data, and the label is the known centroid coordinates; the CNN model structure includes multiple convolution layers, pooling layers, and fully connected layers connected in one go;

[0029] Step 2-3: Perform transfer learning using the ImageNet pre-trained model to reduce training time and improve model performance;

[0030] Step 2-4: Output the real-time coordinate data of each liquid surface echo point to the CNN model, use the trained CNN model to predict the preprocessed real-time coordinate data of the liquid surface echo points, and obtain the centroid coordinates of the engine under the current liquid surface.

[0031] The signal processing module comprises a pulse excitation module, a transceiver isolation module and an analog-to-digital conversion module; the pulse excitation module is used for sending a pulse signal to excite an ultrasonic transducer to send ultrasonic waves; the transceiver isolation module is used for receiving echo signals collected by the ultrasonic transducer and sending the echo signals to the analog-to-digital conversion module; and the analog-to-digital conversion module is used for sending the echo signals to the computing unit after conditioning and analog-to-digital conversion of the echo signals.

[0032] Compared with the prior art, the application has the following beneficial effects:

[0033] The application provides an ultrasonic liquid rocket engine centroid dynamic measurement system, which uses the acoustic-electric conversion characteristics of an ultrasonic piezoelectric transducer to fit echoes received by multiple ultrasonic transducers to detect the positions of liquid fuel and liquid oxidizer surfaces in the engine in real time, calculates centroid coordinates of the liquid fuel and the liquid oxidizer according to the real-time positions of the liquid fuel and the liquid oxidizer surfaces, and dynamically measures the centroid position of the liquid rocket engine in real time according to the centroid positions of the liquid fuel and the liquid oxidizer under multiple liquid levels. Finally, based on data driving, the application can also accurately predict and optimize the centroid position of the liquid rocket engine based on a CNN neural network, and the accuracy and speed of engine centroid calculation can be improved. The detection method is safe and reliable, and the method is not affected by the internal structure of the liquid rocket engine. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A structure schematic diagram of an ultrasonic liquid rocket engine centroid dynamic measurement system provided by the first embodiment of the application is shown in the figure.

[0035] Figure 2 A liquid fuel and liquid oxidizer position distribution diagram of a liquid rocket engine is shown in the figure.

[0036] Figure 3 A mounting schematic diagram of a first ultrasonic transducer array and a second ultrasonic transducer array is shown in the figure.

[0037] Figure 4 A liquid surface fitting processing schematic diagram in the first embodiment of the application is shown in the figure.

[0038] Figure 5 A three-dimensional coordinate system schematic diagram of an engine established in the second embodiment of the application is shown in the figure.

[0039] Figure 6 A structure schematic diagram of an ultrasonic liquid rocket engine centroid dynamic measurement system provided by the third embodiment of the application is shown in the figure.

[0040] In the figure: 1 is an ultrasonic transducer, 2 is an engine casing, 11 is an arched packaging shell, 12 is a backing, 13 is a piezoelectric ceramic layer, 10 is a first ultrasonic transducer array, and 20 is a second ultrasonic transducer array. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] like Figures 1-5 As shown, the first embodiment of the present invention provides an ultrasonic-based liquid rocket engine center of mass dynamic measurement system, comprising a first ultrasonic transducer array 10, a second ultrasonic transducer array 20, a signal processing module and a computing unit. The first ultrasonic transducer array 10 and the second ultrasonic transducer array 20 are both arranged on the engine casing 2. The first ultrasonic transducer array 10 is arranged at a position corresponding to the position of the liquid fuel storage tank, and the second ultrasonic transducer array 20 is arranged at a position corresponding to the position of the liquid oxidizer storage tank. The first ultrasonic transducer array 10 and the second ultrasonic transducer array 20 each include a plurality of ultrasonic transducers 1 arranged in the same vertical plane, and each ultrasonic transducer array is arranged in a different vertical plane. The ultrasonic transducers 1 are used to transmit ultrasonic waves to different positions of the liquid surface in the engine casing 2 in the vertical plane and receive reflected echoes, which are then sent to the computing unit through the signal processing module.

[0044] The calculation unit is used to calculate the coordinates of each liquid surface echo point based on the reflected echoes received by each ultrasonic transducer array; it is also used to calculate the center of mass coordinates of the liquid rocket engine based on the coordinates of each liquid surface echo point corresponding to the first ultrasonic transducer array 10 and the second ultrasonic transducer array 20.

[0045] In this embodiment, the number of ultrasonic transducers 1 in the first ultrasonic transducer array 10 and the second ultrasonic transducer array 20 is greater than or equal to 4. Figure 3 As shown, in this embodiment, the number of ultrasonic transducers 1 in the first ultrasonic transducer array and the second ultrasonic transducer array is 4. Further, as Figure 3 As shown, in this embodiment, in each ultrasonic transducer array, each ultrasonic transducer 1 is symmetrically distributed at the bottom of the liquid fuel storage tank and the liquid oxidizer storage tank of the engine housing 2.

[0046] Specifically, ifFigure 3 As shown, the ultrasonic transducer 1 comprises an arched encapsulating housing 11, a backing 12, and a piezoelectric ceramic layer 13 located in between. The surface of the arched encapsulating housing 11 is concave, matching the outer surface of the engine housing 2. Encapsulating the ultrasonic transducer in the arched encapsulating housing 11, which matches the engine's external dimensions, eliminates an air layer between the ultrasonic transducer probe and the engine housing. This prevents acoustic energy attenuation caused by strong reflections from the probe into the air, thereby improving detection accuracy.

[0047] Furthermore, if Figure 1 As shown, in this embodiment, the signal processing module includes a pulse excitation module, a transceiver isolation module and an analog-to-digital conversion module; the pulse excitation module is used to send a pulse signal to excite the ultrasonic transducer 1 to send ultrasonic waves; the transceiver isolation module is used to receive the echo signal collected by the ultrasonic transducer 1 and send it to the analog-to-digital conversion module, and the analog-to-digital conversion module is used to condition and convert the echo signal into analog-to-digital and then send it to the calculation unit.

[0048] Specifically, in this embodiment, the effective data in the raw data collected by the ultrasonic transducer 1 mainly includes ultrasonic signals reflected from the engine housing and the hydraulic surface inside the engine. The signal reflected from the engine housing 2 is called the housing echo, and the signal reflected from the hydraulic surface is called the liquid surface echo. Because the reflected echo carries a large amount of noise signals and multiple reflections from the same interface, it is first necessary to obtain the envelope of the original waveform to facilitate the identification of the first reflected housing echo and the liquid surface echo signal; then, the Kalman filter algorithm is used to filter out the internal spike noise of the raw data to improve the smoothness of the waveform; because the peak value of the housing echo is the largest in the original ultrasonic echo signal, the center position of the housing echo is then determined by searching for the maximum signal peak position with a fixed position on the left side of the echo signal; the end face wave is located after the housing wave, so after finding the housing echo, the echo tracking algorithm is used to find the signal with the largest peak value, and then the position of the liquid surface echo can be determined.

[0049] Specifically, in this embodiment, the calculation unit calculates the coordinates of the center of mass of the liquid fuel and the liquid oxidizer based on the coordinates of each liquid surface echo point corresponding to the first ultrasonic transducer array and the second ultrasonic transducer array, and then calculates the coordinates of the center of mass of the liquid rocket engine. The specific method for calculating the coordinates of the center of mass of the liquid fuel and the liquid oxidizer is:

[0050] Step 1: Establish a three-dimensional coordinate system with the center of the engine casing as the coordinate origin, the vertical direction as the Z-axis, and the direction through the origin and perpendicular to the vertical plane where the corresponding ultrasonic transducer array is located as the X-axis. Determine the coordinates of the liquid surface echo point corresponding to each ultrasonic transducer 1 based on the real-time distance from each ultrasonic transducer 1 to the corresponding liquid surface echo point and the ultrasonic transmission direction of the ultrasonic transducer 1.

[0051] Step 2: According to the coordinates of the liquid surface echo points corresponding to each ultrasonic transducer 1, a parabolic fitting is performed, and the fitted parabola is taken as the liquid surface curve, as shown in Figure 4

[0052] In this embodiment, specifically, four ultrasonic transducers 1 are used, and the four ultrasonic transducers are simultaneously excited to work by pulse signals, and ultrasonic waves are emitted to the engine. The ultrasonic waves are reflected at the engine shell and the liquid fuel surface, and the shell echo signals and the liquid fuel surface echo signals are sent to the computing unit after being received by the ultrasonic transducers 1. The computing unit filters out the noise of the original data by Kalman filtering algorithm, and then plots the time delay difference within a period. When the liquid surface changes, the liquid surface echo time difference obtained by the front and rear can be used to obtain the real-time position of the liquid surface echo point under the condition of known sound speed. Since the engine shell and the liquid fuel surface are both arc-shaped, the liquid fuel surface echo position detected by the ultrasonic transducers 1 in this embodiment is subjected to parabolic fitting processing. By using the least square method for parabolic fitting, the real-time position of the entire liquid surface change can be obtained.

[0053] Specifically, in this embodiment, the ultrasonic transducers 1 are symmetrically distributed at the bottom of the engine shell 2, which can make the fitting result of the parabola better.

[0054] Step 3: The centroid coordinates of the liquid fuel and the liquid oxidizer are determined according to the liquid surface curves obtained by the first ultrasonic transducer array and the second ultrasonic transducer array, respectively.

[0055] Further, in step 3, the specific method for determining the centroid coordinates of the liquid fuel and the liquid oxidizer according to the liquid surface is as follows:

[0056] Step 3.1: The coordinates of the two intersection points A and B of the liquid fuel surface curve and the engine shell are determined by the first group of ultrasonic transducer arrays, and the cross section of the liquid fuel is determined according to the intersection point coordinates, and the cross-sectional area of the liquid fuel is calculated.

[0057] Step 3.2: The static moment of the liquid fuel cross section relative to the Y-axis and the Z-axis is calculated.

[0058] In step 3.2, the calculation method of the static moment is: the integral of the product of the microelement area of the liquid fuel cross section and the distance from each microelement to the corresponding coordinate axis is taken as the static moment of the liquid fuel cross section relative to the corresponding coordinate axis.

[0059] Step 3.3: The centroid coordinates of the liquid fuel in the Y-axis and the Z-axis are calculated according to the static moment, and the centroid coordinates of the liquid fuel are determined.

[0060] ​In step 3.3, the centroid of the liquid fuel in the Y-axis and Z-axis coordinates is equal to the corresponding static moment divided by the cross-sectional area of the liquid fuel.

[0061] Step 3.4: The centroid coordinates of the liquid oxidizer in the Y-axis and Z-axis can be calculated by the second set of ultrasonic transducer arrays and the above calculation steps.

[0062] As shown in Figure 5 In this embodiment, a three-dimensional coordinate system is established with the engine shell center as the coordinate origin. The Z-axis is in the vertical direction, and each ultrasonic transducer 1 is installed in the YZ plane. When the engine liquid fuel burns, as the fuel level gradually drops, the centroid of the liquid fuel in the Z-axis direction will continuously drop. The liquid rocket engine will accelerate or decelerate during operation, which will cause the liquid fuel to shake in a certain direction. When the fuel liquid shakes in the Y-axis direction, the centroid of the liquid fuel in the Y-axis direction will change. If the engine shell structure is symmetrical and the density of the liquid fuel is uniform, the centroid of the liquid fuel in the X-axis direction will remain at the origin. In this way, the centroid of the liquid fuel can be equivalent to the centroid of the liquid fuel cross section. The liquid surface curve obtained by parabolic fitting can determine the two intersection points A and B with the engine shell. According to the two intersection points, the cross-sectional area of the fuel liquid can be calculated. The integral of the infinitesimal area of the liquid fuel cross section and the distance from each infinitesimal to the corresponding axis (Y-axis and Z-axis) is the static moment of the liquid fuel cross section in the Y-axis and Z-axis. After calculating the static moment of the cross section in the Y-axis and Z-axis, divide it by the cross-sectional area of the fuel liquid to get the centroid coordinates of the fuel liquid in the Y-axis and Z-axis.

[0063] By using the centroid calculation method of the liquid fuel in the Z-axis and Y-axis introduced in this embodiment, the centroid of the liquid oxidizer in the Z-axis and Y-axis can be calculated, and further the centroid change of the liquid stored in the engine in the Z-axis and Y-axis can be calculated.

[0064] Example Two

[0065] The embodiment two of the present application provides a liquid rocket engine centroid dynamic measurement system based on ultrasonic waves, which comprises a first ultrasonic transducer array, a second ultrasonic transducer array, a signal processing module and a calculation unit. Different from the embodiment one, the embodiment two comprises two first ultrasonic transducer arrays and two second ultrasonic transducer arrays, wherein the two first ultrasonic transducer arrays are located in different and intersected vertical planes, and the two second ultrasonic transducer arrays are located in different and intersected vertical planes; the calculation unit is used to calculate the coordinates of each liquid surface echo point of the liquid fuel according to each reflected echo received by the two first ultrasonic transducer arrays; is also used to calculate the coordinates of each liquid surface echo point of the liquid oxidizer according to each reflected echo received by the two second ultrasonic transducer arrays; and is also used to calculate the centroid coordinates of the liquid fuel and the liquid oxidizer according to the coordinates of each liquid surface echo point of the liquid fuel and the liquid oxidizer.

[0066] When the fuel liquid shakes in the X-axis and Y-axis directions, the second ultrasonic transducer group comprising a plurality of ultrasonic transducers is also installed at the intersection position of the engine bottom and the XZ plane in the embodiment, and the centroid of the liquid fuel and the liquid oxidizer liquid surface in the X-axis and Z-axis directions can be calculated by using the method proposed in the embodiment one of the present application. Then, the centroid coordinates of the liquid fuel and the liquid oxidizer are fused into the centroid coordinates of the whole liquid stored in the engine according to the fusion calculation method of the partition centroid. Further, the centroid coordinates of the engine shell are calculated according to the centroid coordinates of the liquid under a plurality of liquid levels. Finally, the centroid position of the whole engine at the current moment is obtained by combining the centroid position of the whole liquid at the current moment. Thus, the centroid coordinates of the liquid rocket engine at the current moment can be obtained. Therefore, the liquid surface change parameters measured by the ultrasonic transducers in the embodiment can realize the real-time and dynamic measurement of the centroid of the liquid rocket engine.

[0067] Further, in the embodiment, the vertical planes where the two first ultrasonic transducer arrays are located are perpendicular, and the vertical planes where the two second ultrasonic transducer arrays are located are perpendicular.

[0068] Specifically, in the embodiment, the specific method for the calculation unit to calculate the centroid coordinates of the liquid rocket engine is as follows:

[0069] Step 1: taking the centroid of the engine shell as the coordinate origin, taking the vertical direction as the Z-axis direction, and taking the direction passing through the origin and perpendicular to the vertical plane where one corresponding ultrasonic transducer array is located as the direction of the X-axis, to establish a three-dimensional coordinate system; determining the coordinates of each liquid surface echo point corresponding to each ultrasonic transducer 1 in the ultrasonic transducer array according to the real-time distance from each ultrasonic transducer 1 to the corresponding liquid surface echo point and the ultrasonic wave transmission direction of the ultrasonic transducer 1;

[0070] Step 2: Perform parabola fitting based on the coordinates of the liquid surface echo points corresponding to each ultrasonic transducer 1 in one of the ultrasonic transducer arrays, and use the fitted parabola as the liquid surface curve in the vertical plane. Similarly, obtain the liquid surface curve in the vertical plane where the other ultrasonic transducer array is located.

[0071] Step 3: Determine the center of mass coordinates in the Y-axis and Z-axis directions based on the liquid surface curve obtained by one of the ultrasonic transducer arrays, and determine the center of mass coordinates in the X-axis and Z-axis directions based on the liquid surface curve obtained by the other ultrasonic transducer array;

[0072] Step 4: Calculate the center of mass coordinates of the entire liquid inside the engine based on the center of mass coordinates of the liquid fuel and liquid oxidizer; obtain the center of mass coordinates of the engine casing; calculate the center of mass coordinates of the liquid rocket engine at the current moment based on the center of mass coordinates of the liquid inside the engine and the center of mass coordinates of the engine casing at the current moment.

[0073] Specifically, the coordinates of the center of mass of the engine casing can be calculated based on the coordinates of the center of mass of the liquid stored inside the engine under multiple sets of liquid level conditions.

[0074] Example 3

[0075] like Figure 6 As shown, the third embodiment of the present invention provides a liquid rocket engine center of mass dynamic measurement system based on a convolutional neural network (CNN) algorithm, including a signal processing module and a computing unit module. Unlike the second embodiment, this embodiment introduces a CNN neural network algorithm to learn the complex relationship between the fuel liquid level and the center of mass, thereby improving the accuracy and speed of the center of mass calculation.

[0076] Specifically, in this embodiment, the calculation unit uses a CNN neural network algorithm to perform deep learning and analysis on the coordinates of the liquid surface echo points, establishes a complex liquid surface and center of mass relationship model, and thus performs accurate prediction and optimization on a data-driven basis. The specific method by which the calculation unit calculates the center of mass coordinates of the liquid rocket engine based on the coordinates of each liquid surface echo point is as follows:

[0077] Step 2-1: Use the first ultrasonic transducer array and the second ultrasonic transducer array to perform multi-point measurements on the liquid levels of the liquid fuel storage tank and the liquid oxidizer storage tank in the engine casing, respectively, to obtain the real-time coordinate data of each liquid surface echo point; input these coordinate data into the signal processing module for preprocessing, filtering out noise and performing normalization processing.

[0078] Step 2-2: Design and train a CNN model suitable for liquid rocket engine center of mass calculation; the training dataset consists of historical measurement data and simulation data, labeled with known center of mass coordinates, and the CNN model structure includes multiple convolutional layers, pooling layers, and fully connected layers connected at once to extract and learn features and patterns in the coordinates of liquid surface echo points.

[0079] Step 2-3: Use the ImageNet pre-trained model for transfer learning to reduce training time and improve model performance;

[0080] Step 2-4: Output the real-time coordinate data of each liquid surface echo point to the CNN model, use the trained CNN model to predict the real-time coordinate data of the preprocessed liquid surface echo point, and obtain the center of mass coordinates of the engine under the current liquid surface.

[0081] Through the CNN neural network algorithm in this embodiment, the position of the center of mass of a liquid rocket engine under complex liquid surface conditions can be accurately predicted and optimized on a data-driven basis, which not only improves the accuracy of the center of mass calculation, but also significantly accelerates the calculation speed, realizing real-time and dynamic measurement.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultrasonic-based liquid rocket engine center of mass dynamic measurement system, characterized in that: The invention comprises a first ultrasonic transducer array, a second ultrasonic transducer array, a signal processing module and a computing unit, wherein the first ultrasonic transducer array and the second ultrasonic transducer array are both arranged on an engine casing, the arrangement position of the first ultrasonic transducer array corresponds to the position of a liquid fuel storage tank, and the arrangement position of the second ultrasonic transducer array corresponds to the position of a liquid oxidant storage tank; the first ultrasonic transducer array and the second ultrasonic transducer array both comprise a plurality of ultrasonic transducers (1) arranged in the same vertical plane, and each ultrasonic transducer array is arranged in a different vertical plane, the ultrasonic transducers (1) being used to transmit ultrasonic waves to different positions of the liquid surface in the engine casing (2) in the vertical plane and receive reflected echoes, which are then sent to the computing unit through the signal processing module; The calculation unit is used to calculate the coordinates of each liquid surface echo point based on the reflected echoes received by each ultrasonic transducer array; it is also used to calculate the center of mass coordinates of the liquid rocket engine based on the coordinates of each liquid surface echo point corresponding to the first ultrasonic transducer array and the second ultrasonic transducer array.

2. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 1, characterized in that: The number of ultrasonic transducers (1) in the first ultrasonic transducer array and the second ultrasonic transducer array is greater than or equal to 4.

3. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 1, characterized in that: The ultrasonic transducer (1) comprises an arched packaging shell (11), a backing (12) and a piezoelectric ceramic layer (13) located in the middle; the surface of the arched packaging shell (11) is a concave surface that matches the outer surface of the engine housing (2).

4. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 1, characterized in that: The calculation unit calculates the coordinates of the center of mass of the liquid fuel and the liquid oxidizer based on the coordinates of each liquid surface echo point corresponding to the first ultrasonic transducer array and the second ultrasonic transducer array, and then calculates the coordinates of the center of mass of the liquid rocket engine. The specific method for calculating the coordinates of the center of mass of the liquid fuel and the liquid oxidizer is: Step 1: Establish a three-dimensional coordinate system with the center of the engine housing as the coordinate origin, the vertical direction as the Z-axis direction, and the direction through the origin and perpendicular to the vertical plane where the corresponding ultrasonic transducer array is located as the X-axis direction; determine the coordinates of the liquid surface echo point corresponding to each ultrasonic transducer (1) based on the real-time distance from each ultrasonic transducer (1) to the corresponding liquid surface echo point and the ultrasonic transmission direction of the ultrasonic transducer (1); Step 2: performing parabola fitting according to the coordinates of the liquid surface echo points corresponding to each ultrasonic transducer (1), and using the fitted parabola as the liquid surface curve; Step 3: Determine the center of mass coordinates of the liquid fuel and the liquid oxidizer respectively based on the liquid surface curves obtained by the first ultrasonic transducer array and the second ultrasonic transducer array.

5. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 4, characterized in that: In step 3, the specific method for determining the center of mass coordinates of the liquid fuel and the liquid oxidant according to the hydraulic surface is: Step 3.1: Determine the coordinates of two intersection points A and B of the fuel liquid surface curve and the engine housing using the first set of ultrasonic transducer arrays, determine the cross-section of the liquid fuel based on the intersection coordinates, and calculate the cross-sectional area of ​​the fuel liquid; Step 3.2: Calculate the static moments of the liquid fuel cross section with respect to the Y and Z axes; Step 3.3: Calculate the center of mass coordinates of the liquid fuel on the Y and Z axes based on the static moment, and then determine the center of mass coordinates of the liquid fuel; Step 3.4: The center of mass coordinates of the liquid oxidant on the Y and Z axes can be calculated using the second set of ultrasonic transducer arrays and the above calculation steps.

6. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 1, characterized in that: The invention comprises two first ultrasonic transducer arrays and two second ultrasonic transducer arrays, wherein the two first ultrasonic transducer arrays are located in different and intersecting vertical planes, and the two second ultrasonic transducer arrays are located in different and intersecting vertical planes; The calculation unit is used to calculate the coordinates of each liquid surface echo point of the liquid fuel based on the respective reflected echoes received by the two first ultrasonic transducer arrays; it is also used to calculate the coordinates of each liquid surface echo point of the liquid oxidizer based on the respective reflected echoes received by the two second ultrasonic transducer arrays; it is also used to calculate the center of mass coordinates of the liquid fuel and the liquid oxidizer based on the coordinates of each liquid surface echo point of the liquid fuel and the liquid oxidizer.

7. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 6, characterized in that: The vertical planes where the two first ultrasonic transducer arrays are located are perpendicular, and the vertical planes where the two second ultrasonic transducer arrays are located are perpendicular.

8. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 6, characterized in that: The specific method for the calculation unit to calculate the coordinates of the center of mass of the liquid rocket engine is: Step 1: Establish a three-dimensional coordinate system with the center of the engine casing as the coordinate origin, the vertical direction as the Z-axis direction, and the direction through the origin and perpendicular to the vertical plane where one of the corresponding ultrasonic transducer arrays is located as the X-axis direction; determine the coordinates of the liquid surface echo point corresponding to each ultrasonic transducer (1) based on the real-time distance from each ultrasonic transducer (1) in the ultrasonic transducer array to the corresponding liquid surface echo point, and the ultrasonic wave transmission direction of the ultrasonic transducer (1); Step 2: performing parabola fitting based on the coordinates of the liquid surface echo points corresponding to each ultrasonic transducer (1) in one of the ultrasonic transducer arrays, and using the fitted parabola as the liquid surface curve in the vertical plane where the parabola is located; similarly, obtaining the liquid surface curve in the vertical plane where the other ultrasonic transducer array is located; Step 3: Determine the center of mass coordinates in the Y-axis and Z-axis directions based on the liquid surface curve obtained by one of the ultrasonic transducer arrays, and determine the center of mass coordinates in the X-axis and Z-axis directions based on the liquid surface curve obtained by the other ultrasonic transducer array; Step 4: Calculate the center of mass coordinates of the entire liquid inside the engine based on the center of mass coordinates of the liquid fuel and liquid oxidizer; obtain the center of mass coordinates of the engine casing; calculate the center of mass coordinates of the liquid rocket engine at the current moment based on the center of mass coordinates of the liquid inside the engine and the center of mass coordinates of the engine casing at the current moment.

9. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to any one of claims 1 to 6, characterized in that: The specific method for the calculation unit to calculate the coordinates of the center of mass of the liquid rocket engine according to the coordinates of each liquid surface echo point is as follows: Step 2-1: Using the first ultrasonic transducer array and the second ultrasonic transducer array, perform multi-point measurement of the liquid levels of the liquid fuel storage tank and the liquid oxidizer storage tank within the engine casing, respectively, to obtain real-time coordinate data of each liquid surface echo point; Step 2-2: Design and train a CNN model suitable for liquid rocket engine center of mass calculation; The training dataset consists of historical measurement data and simulated data, with labels as known centroid coordinates. The CNN model structure includes multiple convolutional layers, pooling layers, and fully connected layers connected at once. Step 2-3: Use the ImageNet pre-trained model for transfer learning to reduce training time and improve model performance; Step 2-4: Output the real-time coordinate data of each liquid surface echo point to the CNN model, use the trained CNN model to predict the real-time coordinate data of the preprocessed liquid surface echo point, and obtain the center of mass coordinates of the engine under the current liquid surface.

10. The liquid rocket engine center of mass dynamic measurement system based on ultrasound according to claim 1, characterized in that: The signal processing module includes a pulse excitation module, a transceiver isolation module and an analog-to-digital conversion module; the pulse excitation module is used to send a pulse signal to excite the ultrasonic transducer (1) to send ultrasonic waves; the transceiver isolation module is used to receive the echo signal collected by the ultrasonic transducer (1) and send it to the analog-to-digital conversion module, and the analog-to-digital conversion module is used to condition and convert the echo signal into analog-to-digital and then send it to the calculation unit.

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