Propellant remaining amount measurement system and method based on liquid sloshing power

Abstract

The present application belongs to the field of spacecraft propellant measurement technology, and discloses a propellant residual quantity measurement system based on liquid sloshing power, which comprises a sloshing platform, a propellant tank installed on the sloshing platform, a vibrator top rod of a vibrator fixedly connected with the sloshing platform, and a three-axis force sensor installed at the center of the bottom of the propellant tank; a signal generator, a power amplifier and the vibrator are sequentially signal connected, and the three-axis force sensor, a strain amplifier, a data acquisition instrument and a data processing unit are sequentially signal connected. The present application also discloses a propellant residual quantity measurement method, wherein a step signal output by the signal generator is transmitted to the vibrator through the power amplifier, the vibrator gives the sloshing platform an excitation parallel to the X axis, the three-axis force sensor collects an analog signal of the sloshing power and converts the analog signal into a data signal through the data acquisition instrument to send to the data processing unit to obtain the propellant residual quantity. The present application provides a new propellant residual quantity measurement method and idea.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft propellant measurement technology, specifically relating to a propellant remaining quantity measurement system and method based on liquid sloshing dynamics. Background Technology

[0002] Propellant remaining quantity is one of the key technologies for on-orbit management of spacecraft. During on-orbit operation, spacecraft sometimes need to maintain their orbit, which consumes the propellant they carry. The on-orbit lifespan of a spacecraft largely depends on its orbit-maintaining capability; therefore, the propellant consumption status of the spacecraft plays a crucial role in predicting its on-orbit lifespan. To achieve accurate measurement of the propellant remaining quantity of spacecraft in microgravity and thus accurately predict their on-orbit operational lifespan, numerous technologies have been developed for predicting propellant remaining quantity, including flow meter technology, pressure-volume-temperature (PVT) technology, radioactive tracer technology, bookkeeping (BK) technology, and gas pressure injection technology.

[0003] Currently, after satellites are positioned in orbit, my country uses the PVT method to estimate the remaining propellant, with an error typically ranging from 1% to 2%. This results in a satellite lifetime prediction error of 6 to 12 months, failing to meet the international commercial satellite requirement of less than 3 months. Furthermore, the enhanced capabilities of communication satellites have increased the demands for propellant quantity measurement and efficient propellant utilization. Low-precision measurement methods lead to excessive propellant waste, while the inability to accurately predict remaining propellant can potentially impact satellite deorbiting. Existing propellant quantity measurement methods based on differential pressure and temperature control using the gas equation of state require the installation of self-locking valves, pressure stabilizing containers, pressure sensors, and differential pressure sensors on the propellant tank, resulting in complex testing equipment that consumes valuable space resources. Therefore, it is necessary to develop a simpler method for accurately determining the remaining propellant quantity in spacecraft. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a propellant remaining quantity measurement system and method based on liquid sloshing dynamics, so as to accurately estimate the remaining propellant quantity of spacecraft in orbit.

[0005] To solve the above-mentioned technical problems, the present invention provides a propellant remaining quantity measurement system based on liquid sloshing force, comprising: an excitation generation unit, a sloshing platform, a signal collection unit, and a data processing unit;

[0006] The excitation unit includes a signal generator, a power amplifier, and an exciter connected in sequence; the propellant tank is installed on the swaying platform and is fixedly connected to the swaying platform to realize five degrees of freedom of motion along the positive and negative X and Y axes and around the Z axis; the exciter push rod of the exciter is fixedly connected to the swaying platform to provide the swaying platform with excitation parallel to the X axis;

[0007] The signal acquisition unit includes a triaxial force sensor, a strain amplifier, and a data acquisition instrument connected in sequence; the data acquisition instrument is connected to the data processing unit via a network.

[0008] As an improvement to the propellant remaining quantity measurement system based on liquid sloshing force of the present invention:

[0009] The triaxial force sensor is installed at the center of the bottom of the propellant tank. A reference coordinate system is established with the center of the bottom of the propellant tank as the origin. The exciter is located on the left side of the YZ plane of the reference coordinate system.

[0010] The present invention also provides a method for measuring propellant remaining quantity using a propellant remaining quantity measurement system based on liquid sloshing force, characterized in that:

[0011] S1, The signal generator emits an excitation signal f i (t) = a(t);

[0012] S2. The power amplifier increases the amplitude of the excitation signal and transmits it to the exciter;

[0013] S3. The exciter outputs the excitation to the swaying platform to the right through the exciter push rod, giving the propellant tank a horizontal excitation to the right parallel to the X-axis of the reference coordinate system;

[0014] S4. The propellant tank shakes under the action of horizontal excitation, and the propellant generates a shaking force on the propellant tank wall.

[0015] S5. The triaxial force sensor measures and outputs an analog signal that is proportional to the magnitude of the swaying force;

[0016] S6. The data acquisition instrument converts the analog signal into dynamic swaying force data signals F1, F2 and F3 along the X, Y and Z axes, and sends the process data of the dynamic swaying force data signals F1, F2 and F3 changing with time until the steady state value is reached to the data processing unit in real time.

[0017] S7. The data processing unit plots the time response curve of the output swaying force as a function of time and obtains the maximum peak value x. tmax steady-state value x t (∞) and peak time t pThen calculate and output the remaining propellant amount M:

[0018]

[0019] Among them, M p This represents the difference between the maximum peak value and the steady-state value.

[0020] As an improvement to the method for measuring the remaining propellant amount of the present invention:

[0021] The derivation process of the remaining propellant amount is as follows:

[0022] (1) Setting: The spring oscillator model is used to make the propellant tank model equivalent, and the propellant in the propellant tank is set to be an incompressible liquid;

[0023] (2) Plot the time response curve x0(t) of the dynamic swaying force F1 in the x-axis direction, and obtain the maximum peak value x of the swaying force. tmax steady-state value x t (∞), peak time t p ;

[0024] (3) According to Newton's second law, we have:

[0025]

[0026] Where k represents the elastic stiffness of the equivalent system, D represents the viscous damping coefficient of the equivalent system, and M represents the mass of the equivalent system;

[0027] Applying the Laplace transform to equation (2) above and rearranging, we get:

[0028] (Ms 2 +Ds+k)X0(s)=F i (s) (3)

[0029] Set the maximum overshoot:

[0030]

[0031] Where Δx represents the difference between the maximum peak value and the steady-state value, Δx = x tmax -x t (∞), where ξ is the damping ratio;

[0032] set up:

[0033] Furthermore:

[0034]

[0035] From equation (3) after the Laplace transform, we can know that:

[0036]

[0037] By the final value theorem:

[0038]

[0039] Furthermore:

[0040] inherent:

[0041] Combining equations (3) to (10) above, we obtain equation (1).

[0042] The beneficial effects of this invention are mainly reflected in:

[0043] The propellant remaining quantity measurement system and method based on liquid sloshing force of this invention calculates the remaining propellant quantity by inputting an excitation and using a triaxial force sensor to measure the dynamic sloshing force data generated by the propellant during forced vibration of the propellant tank. Compared with existing propellant remaining quantity measurement methods based on pressure difference and temperature control using the gas state equation, this method requires less data and has a simpler testing process. Existing propellant measurement methods do not utilize the sloshing force generated by liquid propellant to measure the remaining propellant quantity. This invention provides a novel approach to propellant remaining quantity measurement, offering a completely new perspective. Attached Figure Description

[0044] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0045] Figure 1 This is a schematic diagram of the propellant remaining quantity measurement system based on liquid sloshing force according to the present invention;

[0046] Figure 2 The response curve of the propellant sloshing force as a function of time in this invention is shown.

[0047] Figure 3 This is the response curve of the propellant sloshing force as a function of time in the experiment. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0049] Example 1: A propellant remaining quantity measurement system based on liquid sloshing force, such as... Figure 1 As shown, it includes an excitation generation unit, a shaking platform, a signal collection unit, and a data processing unit.

[0050] The excitation unit includes a signal generator, a power amplifier, and an exciter. The signal generator, power amplifier, and exciter are sequentially connected to generate the step signal f output by the signal generator. i The excitation force (t) = a(t) is transmitted to the vibrator through a power amplifier. The vibrator is a device used to generate excitation force, enabling the excited object to obtain a certain form and magnitude of vibration. The vibrator includes a vibrator push rod, through which the excitation is output. Vibrators are existing technology and can be commercially available; for example, the HEV-200 vibrator from Nanjing Founeng Technology Industry Co., Ltd. can be used.

[0051] The swaying platform is a vibration table with five degrees of freedom, including positive and negative X and Y axes and rotation around the Z axis. The propellant tank is fixedly installed on the swaying platform by bolts, and the swaying platform realizes the five degrees of freedom of movement. The swaying platform is existing technology and can be purchased commercially or customized. For example, the RX / ZDT-6 series six-degree-of-freedom vibration table of Liaoning Ruixin Precision Machinery Co., Ltd. can be used.

[0052] A reference coordinate system is established with the bottom center of the propellant tank installation location as the origin. On the left side of the YZ plane, the signal generator, power amplifier, and exciter are sequentially connected. The exciter push rod is fixedly connected to the swaying platform via a push rod mounting pad, providing excitation to the swaying platform parallel to the X-axis. The push rod mounting pad is a rigid cylindrical connector, fixedly connected to the swaying platform. A mounting hole is provided on the push rod mounting pad; the head end of the exciter push rod extends into the mounting hole and is locked in place with a locking screw. This allows the excitation generated by the exciter to be transmitted to the swaying platform through the exciter push rod and the push rod mounting pad, causing the propellant tank to sway.

[0053] The signal acquisition unit includes a triaxial force sensor, a strain amplifier, and a data acquisition instrument connected in sequence. The triaxial force sensor is installed at the center of the bottom of the propellant tank and is fixedly connected to the propellant tank. It is used to collect the electrical signals corresponding to the dynamic swaying forces F1, F2, and F3 generated by the propellant during swaying along the X-axis, Y-axis, and Z-axis of the reference coordinate system.

[0054] The strain amplifier is used to amplify the signal transmitted by the triaxial force sensor and transmit it to the data acquisition instrument.

[0055] The data acquisition unit is used to convert the force signals collected by the above-mentioned triaxial force sensors into data signals and send them to the data processing unit via wired or wireless network.

[0056] The data processing unit is deployed on a computer to receive data collected by the data acquisition instrument, plot time response curves, and utilize the remaining propellant mass M and peak time t. p Maximum overshoot M p steady-state value x t(∞), Input signal f i The functional relationship between f(M,t) and (t) p M p ,x t (∞),f i (t) is used to measure the remaining amount of propellant.

[0057] The specific method for measuring the remaining propellant amount based on liquid sloshing force is as follows:

[0058] 1. The signal generator sends an excitation signal f i (t) = a(t), which provides a step signal input to the power amplifier. The power amplifier is in working condition and records the data of the step signal for subsequent calculation of the remaining propellant.

[0059] 2. The power amplifier amplifies the excitation signal power of the signal generator, increases the amplitude of the given step signal input, increases the power of the input step signal, and then transmits the amplified step signal to the exciter.

[0060] 3. After receiving the amplified step signal, the exciter outputs the excitation to the shaking platform to the right through the exciter push rod, giving the propellant tank a rightward excitation parallel to the X-axis of the reference coordinate system, so that the propellant tank carrying the propellant is excited to shake, so as to collect data.

[0061] 4. The propellant tank shakes under horizontal excitation, and the propellant inside the tank exerts a shaking force on the tank wall.

[0062] 5. The triaxial force sensor measures the analog signals corresponding to the dynamic swaying forces generated by the propellant along the X, Y and Z axes in the propellant tank, and then sends them to the data acquisition instrument in real time;

[0063] 6.d Convert the analog signal input in step 5 into dynamic swaying force data signals F1, F2, and F3 on the X, Y, and Z axes that can be recognized by the computer. When the dynamic swaying force data signals F1, F2, and F3 fluctuate within a very small range, it means that the swaying force response over time has reached a steady state value.

[0064] The data acquisition unit sends the process data of the dynamic swaying force data signals F1, F2 and F3 changing over time until the steady state value is reached to the data processing unit in real time;

[0065] 7. The data processing unit processes the process data obtained in step 6, which shows the dynamic swaying force changing over time until it reaches a steady-state value. First, it uses commercial software Origin to plot the time response curve of the swaying force over time, such as... Figure 2 As shown, the maximum peak value of the swaying force x is obtained. tmax steady-state value x t(∞) and peak time t p Then based on the peak time t p Maximum overshoot M p steady-state value x t (∞), Input signal f i The functional relationship between f(M,t) and (t) p M p ,x t (∞),f i (t) is used to calculate and determine the remaining amount of propellant:

[0066]

[0067] Where M represents the remaining amount of propellant in the propellant tank, f i (t) represents the numerical value of the input step force (i.e., the numerical value of the excitation signal emitted by the signal generator in step 1), t p The peak time, x, represents the time when the time response curve first reaches its peak value. t (∞) represents the steady-state value reached by the swaying force over time, M p This represents the difference between the maximum peak value and the steady-state value.

[0068] The derivation process of the formula for remaining propellant is as follows:

[0069] (1) Setting: The spring oscillator model is used to make the propellant tank model equivalent, ensuring that the elastic stiffness, swaying fundamental frequency, damping coefficient, swaying force of the equivalent model are equal to those of the system consisting of the propellant tank and the propellant it carries; the propellant in the propellant tank is set to be an incompressible liquid.

[0070] (2) Plot the time response curve x0(t) of the dynamic swaying force F1 along the x-axis to obtain the response curve of the propellant swaying force as a function of time under a step signal, as shown below. Figure 2 As shown, the maximum peak value x of the sloshing force is then obtained from the response curve of the propellant sloshing force as a function of time. tmax steady-state value x t (∞) and peak time t p ;

[0071] (3) According to Newton's second law, we have:

[0072]

[0073] Where k represents the elastic stiffness of the equivalent system, D represents the viscous damping coefficient of the equivalent system, and M represents the mass of the equivalent system.

[0074] Applying the Laplace transform to equation (2) above and rearranging, we get:

[0075] (Ms 2 +Ds+k)X0(s)=F i (s) (3)

[0076] Where s is a complex variable, X0(s) is the image function, and F i (s) is the original function.

[0077] Set the maximum overshoot:

[0078]

[0079] Where Δx represents the difference between the maximum peak value and the steady-state value, Δx = x tmax -x t (∞), where ξ is the damping ratio;

[0080] set up:

[0081] Furthermore:

[0082]

[0083] From equation (3) after the Laplace transform, we can know that:

[0084]

[0085] By the final value theorem:

[0086]

[0087] Furthermore:

[0088] inherent:

[0089] Substituting equations (4), (5), (6), and (9) into equation (10) yields the formula for calculating the remaining propellant mass:

[0090]

[0091] This invention provides a propellant remaining quantity measurement system and method based on liquid sloshing force. Compared to existing propellant remaining quantity measurement systems and methods based on pressure difference and temperature control, both predict the remaining propellant quantity using formulas, but their underlying principles are completely different. The pressure difference and temperature control-based systems and methods utilize the gas state equation, requiring measurements of equilibrium pressure and temperature before and after the experiment. They also require multiple pressure-stabilizing gas containers, self-locking valves, and multiple pressure and temperature sensors. This invention, however, utilizes the sloshing force generated by the propellant during propellant tank sloshing to predict the remaining propellant quantity. Compared to this invention, existing pressure difference and temperature control-based propellant remaining quantity measurement systems and methods involve more complex testing equipment and more testing steps, while this invention only requires measuring the sloshing force generated by the propellant during propellant tank sloshing, thus simplifying the measurement method.

[0092] experiment:

[0093] The effectiveness of the present invention was verified by simulating the propellant residual quantity measurement system and method based on liquid sloshing force proposed in Example 1 in a laboratory environment.

[0094] The experiment used a liquid container to simulate a propellant tank. The liquid container was fixedly mounted on a swaying platform, which had five degrees of freedom: positive and negative X and Y axes and rotation along the Z axis. A reference coordinate system was established with the bottom center of the propellant tank as its origin. On the left side of the YZ plane, a signal generator, power amplifier, and exciter were connected in sequence. The exciter's push rod was connected to the swaying platform via a push rod mounting pad. A triaxial force sensor was installed at the bottom center of the propellant tank and connected to a strain amplifier, data acquisition unit, and computer in sequence. The signal generator output a step signal, the exciter caused the tank to sway, and the triaxial sensor collected the dynamic swaying force data generated by the propellant swaying. Finally, the data processing unit in the computer processed the dynamic swaying force data and derived the remaining force. Specifically:

[0095] The liquid container on the shaking platform has a volume of V = 1136 L and a mass of 100 kg. The density of the propellant N₂O₄ loaded in the liquid container is ρ = 1444 kg / m³. 3 The propellant N2O4 is filled to 96% of the liquid container's capacity. The signal generator emits a horizontal signal to the right with a magnitude of f. i A step force signal of 76 kN (t) was measured, and the dynamic swaying force response curve over time was plotted as follows: Figure 3 Then from Figure 3 The steady-state value x can be obtained. t (∞) = 40.82001N, maximum peak value x tmax = 40.95028N, peak time t p=6s, and then the maximum overshoot is obtained from equation (4):

[0096]

[0097] Therefore, from equation (1), the predicted value of the propellant mass in the liquid container can be obtained as follows:

[0098]

[0099] The theoretical value of the propellant mass in the liquid container is:

[0100] M1 = 0.96ρV = 1574.8 kg

[0101] error

[0102] This demonstrates that the measurement method of the present invention has high accuracy and meets the needs of actual measurement. In contrast, existing propellant measurement methods do not utilize the sloshing force generated by the liquid propellant during the sloshing process to measure the propellant balance. Therefore, the present invention provides a completely new direction and approach for the field of spacecraft propellant prediction, adding more possibilities to the work in this field.

[0103] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for measuring propellant remaining quantity using a propellant remaining quantity measurement system based on liquid sloshing force, characterized in that: The propellant remaining quantity measurement system based on liquid sloshing force includes an excitation generation unit, a sloshing platform, a signal collection unit, and a data processing unit; The excitation unit includes a signal generator, a power amplifier, and an exciter connected in sequence; the propellant tank is installed on the swaying platform and is fixedly connected to the swaying platform to realize five degrees of freedom of motion along the positive and negative X and Y axes and around the Z axis; the exciter push rod of the exciter is fixedly connected to the swaying platform to provide the swaying platform with excitation parallel to the X axis; The signal acquisition unit includes a triaxial force sensor, a strain amplifier, and a data acquisition instrument connected in sequence; the data acquisition instrument is connected to the data processing unit via a network. The triaxial force sensor is installed at the center of the bottom of the propellant tank. A reference coordinate system is established with the center of the bottom of the propellant tank as the origin. The exciter is located on the left side of the YZ plane of the reference coordinate system. The method for measuring the remaining propellant amount involves the following steps: S1, The signal generator emits an excitation signal. The excitation signal is a step signal; S2. The power amplifier increases the amplitude of the excitation signal and transmits it to the exciter; S3. The exciter outputs the excitation to the swaying platform to the right through the exciter push rod, giving the propellant tank a horizontal excitation to the right parallel to the X-axis of the reference coordinate system; S4. The propellant tank shakes under the action of horizontal excitation, and the propellant generates a shaking force on the propellant tank wall. S5. The triaxial force sensor measures and outputs an analog signal that is proportional to the magnitude of the swaying force; S6. The data acquisition instrument converts the analog signal into dynamic swaying force data signals along the X, Y, and Z axes. , and Dynamic swaying force data signal , , When fluctuations are within a very small range, it indicates that the swaying force has reached a steady-state value over time, and the dynamic swaying force data signal is displayed. , , The process data, which changes over time until a steady-state value is reached, is sent to the data processing unit in real time. S7. The data processing unit plots the time response curve of the swaying force over time and obtains the maximum peak value. steady-state value and peak time Then calculate and output the remaining propellant amount M: （1） in, This represents the difference between the maximum peak value and the steady-state value.

2. The method for measuring the remaining propellant amount according to claim 1, characterized in that: The derivation process of the remaining propellant amount is as follows: (1) Setting: The spring oscillator model is used to make the propellant tank model equivalent, and the propellant in the propellant tank is set to be an incompressible liquid; (2) Take the dynamic swaying force in the x-axis direction Plotting time response The curve is obtained, and the maximum peak value of the swaying force is obtained. steady-state value Peak time ; (3) According to Newton's second law, we have: （2） in, This represents the elastic stiffness of the equivalent system. This represents the viscous damping coefficient of the equivalent system. Indicates the quality of the equivalent system; Applying the Laplace transform to equation (2) above and rearranging, we get: （3） Set the maximum overshoot: （4） in This represents the difference between the maximum peak value and the steady-state value. , The damping ratio; set up: (5) Furthermore: （6） From the Laplace transform equation (3), we can see that: （7） By the final value theorem: （8） Furthermore: (9) Unique: (10) Combining the above equations (3) to (10), we obtain equation (1).

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