An online monitoring method for external leakage of an aircraft hydraulic system based on a mechanism model

Abstract

This invention discloses an online monitoring method for external leakage in aircraft hydraulic systems based on a mechanistic model, belonging to the field of hydraulic system technology. It aims to solve the technical bottlenecks of existing aircraft hydraulic system external leakage monitoring, such as poor real-time performance, high false alarm rate, and inability to detect the leakage amount and rate. The method includes the following steps: First, a mechanistic model is constructed based on the law of conservation of mass. Combined with temperature and pressure data monitored by airborne sensors, the oil volume inside each hydraulic component outside the tank is calculated according to volumetric deformation characteristics, deriving the theoretical value of the oil volume inside the self-pressurized tank. Second, the mechanistic model is corrected by comparing the theoretical value with the actual monitored value using flight parameter data under leak-free conditions, eliminating inherent errors. Finally, real-time flight parameter data is input to recalculate the theoretical value, and compared with the real-time monitoring value from the level sensor to determine if the system is leaking. If leakage occurs, the leakage amount and rate are calculated, and an early warning result is output. This invention relies on existing airborne sensors, requiring no additional equipment or sensors. It can effectively distinguish between normal oil fluctuations and actual leakage, improving monitoring accuracy and real-time performance. It provides data support for the handling and maintenance of aircraft hydraulic system leakage faults and has certain engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic system fault diagnosis technology, specifically relating to an online monitoring method for external leakage in aircraft hydraulic systems based on a mechanism model. It is applicable to real-time leakage monitoring, fault early warning, and parameter quantification evaluation of various aircraft hydraulic systems. Background Technology

[0002] Hydraulic systems play an irreplaceable role in aerospace and other fields. As the core power source for aircraft, hydraulic systems undertake critical tasks such as driving the main flight control surfaces, retracting and extending the landing gear, and braking the wheels. Facing extreme environments such as high pressure, wide temperature range, and high-frequency alternating loads, they are highly susceptible to external oil leakage due to a combination of factors, including mechanical wear, aging of seals, and structural fatigue cracks. Leakage not only degrades the performance of the hydraulic system but can also lead to pressure instability, actuator jamming, and even control failure, directly threatening flight safety.

[0003] Currently, leakage monitoring in aircraft hydraulic systems faces the following major technical bottlenecks: First, insufficient real-time performance and monitoring accuracy. Traditional monitoring methods rely on manual inspections and offline sampling, which have significant time lags and cannot meet the real-time monitoring needs throughout the entire flight process. Second, complex interference factors and a high false alarm rate. In actual flight, drastic fluctuations in oil temperature and pressure, as well as frequent reversals of actuators, cause dynamic changes in the oil volume within the system, increasing the difficulty of leak identification and easily leading to misjudgments. Third, existing technologies are mostly targeted at single technologies or specific components, lacking a holistic analysis of the leakage characteristics of hydraulic systems. They can only provide vague early warning information such as low hydraulic system pressure or abnormal operation, and cannot accurately output key parameters such as leakage rate and leakage volume. This makes it difficult to achieve early identification and handling of minor leakage faults, limiting the autonomous decision-making capability and maintenance efficiency of airborne hydraulic systems.

[0004] Therefore, developing an online monitoring method that can adapt to complex working conditions and has leakage early warning capabilities has become an urgent need to improve the intelligent operation and maintenance level of aviation equipment and strengthen flight safety assurance capabilities. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide an online monitoring method for external leakage in aircraft hydraulic systems based on a mechanistic model. This method enhances the real-time early warning capability for leakage faults during aircraft flight, reduces maintenance costs, and provides technical support for online monitoring of aircraft hydraulic systems.

[0006] The technical solution of the present invention includes the following steps:

[0007] The first step is to construct a mechanistic model and calculate the theoretical value V1 of the oil volume in the self-pressurizing tank. Based on the law of conservation of mass, the mechanistic model is constructed, where the oil mass in the self-pressurizing tank is the difference between the initial total oil mass of the hydraulic system and the sum of the oil masses in the hydraulic components outside the tank. The initial total oil mass of the hydraulic system can be directly obtained from the refueling data; combined with the temperature T monitored by the onboard sensors... a Pressure P a The array can be used to calculate the sum of the oil mass in each hydraulic component except the oil tank step by step, and then derive the theoretical value V1 of the oil volume in the booster tank.

[0008] To facilitate the construction of mechanistic models, hydraulic components in a hydraulic system are classified into three categories based on their volumetric deformation characteristics: rigid components, micro-deformation components, and large-deformation components. Rigid components include various valves, hydraulic pipelines, filters, radiators, etc. Micro-deformation components mainly include piston pumps, hoses, etc., while large-deformation components include actuators, accumulators, buffer bottles, etc.

[0009] The volume of a rigid component is almost constant, and the mass of the hydraulic fluid can be expressed as m1=(ρ0+Δρ)‧V0; where V0 is the initial volume of the component, ρ0 is the initial density of the hydraulic fluid, and Δρ is the density change under the influence of pressure P1 and temperature T1.

[0010] The micro-deformation element undergoes a small volumetric elastic deformation under pressure. The mass of the oil can be expressed as m2=(ρ0+Δρ)‧(V0+dV); where dV is the volume change under the influence of pressure P2 and temperature T2.

[0011] Large deformation elements have a large volume change. Considering that the volume change is ΔV, the oil mass can be expressed as m3=(ρ0+Δρ)‧(V0+ΔV).

[0012] Calculate the total mass of hydraulic fluid in all components of the hydraulic system, m= And obtain the total system mass m0 based on the initial refueling data.

[0013] The mass of oil in the self-pressurized oil tank is m 油箱 =m-m0, thus the theoretical value of the oil volume in the self-pressurizing oil tank, V1=m, can be calculated. 油箱 / ρ.

[0014] The second step involves correcting the flight parameter data based on a leak-free operating condition using a mechanism model. Temperature and pressure data from this leak-free condition are input into the mechanism model, and the theoretical value V1 is compared with the actual oil volume V measured by the onboard level sensor under leak-free conditions. a If the absolute value of the difference between the two is |V1-V a If the error exceeds the allowable range, the mechanism model is corrected and recalculated until the calculation result meets the allowable range before proceeding to the next step.

[0015] In the third step, online monitoring of external leakage of the hydraulic system is realized, and the status and prediction results of the hydraulic system are output. The real-time flight parameter data T b , P b are input into the calibrated mechanism model, and the theoretical value V2 of the oil volume in the self-pressurizing fuel tank is recalculated. The theoretical value V2 is compared with the actual value V of the oil volume monitored by the liquid level sensor in real time b and compared with the preset warning threshold ξ. The logic for judging the working status of the hydraulic system is as follows:

[0016] If |V2 - V b | ≤ ξ, it is determined that the hydraulic system has no leakage and is in normal working condition. Continuously collect real-time data and repeat the above monitoring process;

[0017] If |V2 - V b | > ξ, it is determined that the hydraulic system has external leakage. Immediately calculate the leakage amount through the formula ΔV = V2 - V b and calculate the leakage rate through the formula v q = ΔV / t;

[0018] According to the magnitude of the leakage rate, divide the leakage fault levels (minor leakage v q < k1, medium leakage k1 ≤ v q < k2, severe leakage v q ≥ k2; where k1 and k2 are set according to actual requirements), and synchronously output the system status, leakage amount, leakage rate, leakage fault level and warning information, providing reliable data support for fault handling and maintenance decision-making.

[0019] Among them, the leakage rate warning threshold ξ is determined according to the type and working parameters of the aircraft hydraulic system, combined with ground test data, ensuring accurate identification of leakage faults and effectively avoiding false alarms and false warnings caused by normal oil volume fluctuations, and ensuring the reliability of monitoring results.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) The present invention constructs a mechanism model of the hydraulic system based on the law of conservation of mass, solves the hydraulic oil volume in combination with basic physical laws, laying a theoretical foundation for leakage monitoring; at the same time, hydraulic components are divided into three categories of rigid, micro-deformation, and large-deformation according to volume deformation characteristics, and the hydraulic oil volume in the fuel tank is inversely solved through the mass conservation relationship;

[0022] (2) This invention introduces non-leakage flight parameter data to correct the mechanism model. By comparing the theoretical calculation value with the actual monitoring value and iteratively optimizing until the error meets the allowable range, the inherent error of the model and the initial error of the airborne sensor are effectively eliminated, the accuracy of the mechanism model is improved, and misjudgment and omission caused by model deviation are avoided.

[0023] (3) This invention realizes online real-time monitoring of external leakage in aircraft hydraulic systems. The theoretical value of oil volume can be quickly calculated through real-time flight parameter data. The calculation method and logic are consistent with the characteristics of the actual working process of aircraft hydraulic systems. The system status is judged by comparing with the real-time monitoring value of the liquid level sensor. The leakage fault can be identified in a timely manner. At the same time, the leakage amount and leakage rate can be accurately calculated and the prediction results can be output. The early detection, early warning and early assessment of leakage faults are realized, providing data support for the handling and maintenance of leakage faults in aircraft hydraulic systems.

[0024] (4) The mechanism model in this invention can distinguish between normal oil volume fluctuations in the hydraulic system and volume changes caused by external leakage, effectively avoid false alarms caused by pressure and temperature changes and normal component deformation, improve the accuracy and stability of leakage monitoring, and ensure the effectiveness of aircraft hydraulic system monitoring and flight safety. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating an online monitoring method for external leakage in an aircraft hydraulic system based on a mechanistic model, provided by the present invention.

[0026] Figure 2 This is a schematic diagram of the mechanism model of the present invention.

[0027] Figure 3 This is a simulation model diagram of the aircraft hydraulic system of the present invention.

[0028] The markings in the diagram are explained below:

[0029] 1 is a hydraulic pump; 2 is a check valve; 3 is a buffer bottle; 4 is filter 1; 5 is an accumulator 1; 6 is a pressure sensor; 7 is a temperature sensor; 8 is a load; 9 is filter 2; 10 is an accumulator 2; 11 is a hydraulic oil tank; 12 is a heat exchanger; 13 is a throttle valve. Detailed Implementation

[0030] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings.

[0031] The working process of a hydraulic system is simulated using a simulation model, such as... Figure 3As shown, the hydraulic system includes a hydraulic pump 1, a check valve 2, a buffer bottle 3, a high-pressure filter 4, a system accumulator 5, multiple pressure sensors 6, multiple temperature sensors 7, a load 8, a return oil filter 9, an oil tank booster accumulator 10, a self-boosting oil tank 11, a heat exchanger 12, and a throttle valve 13 for simulating leakage.

[0032] In this embodiment, the specific execution steps of the online monitoring method are as follows:

[0033] In the simulation model, parameters are set according to the physical characteristics of each component. For rigid components such as valves, filters, and pipelines, the initial oil volume is determined based on the inner diameter and length of the pipeline and the dead zone volume of the internal flow channel of the component. For micro-deformable components such as plunger pumps and hoses, parameters such as length and diameter are used. For large-deformable components such as actuators and accumulators, accurate models are established based on parameters such as stroke, cross-sectional area, charging pressure, and initial volume. The type of hydraulic oil and parameters such as the oil volume expansion coefficient α and compressibility coefficient β are determined.

[0034] Simulate typical aircraft flight profiles (takeoff, cruise, and landing), and collect flight parameter data under leak-free conditions, including the temperature T at each key node. a Pressure P a Such as pump outlet, actuator chamber, accumulator, etc., and the measured oil volume V of the self-pressurizing oil tank level sensor. a Data, etc. Based on the mechanism model described in the first step of this invention, the sum of the oil volumes of each hydraulic component outside the oil tank is calculated. The theoretical value V1 of the oil volume in the self-pressurized oil tank is derived according to the law of conservation of mass, and compared with |V1-V a If the error exceeds the allowable range of ±2%, the mechanism model is corrected and recalculated until the accuracy requirements are met, and the model calibration is completed.

[0035] A leakage simulation unit was installed at the branch line of the high-pressure pipeline. By adjusting the opening of the throttle orifice 13, three different leakage conditions were simulated: a small leakage of 0.1 L / min, a moderate leakage of 0.5 L / min, and a severe leakage of 1 L / min. Real-time flight parameter data under the leakage conditions were collected, including real-time temperature T. b Pressure P b The self-pressurized oil tank level sensor measures the actual oil volume V. b The leakage flow rate was simultaneously calibrated using a flow meter for subsequent verification.

[0036] Real-time temperature T b Pressure P bData such as load type are input into the calibrated mechanism model. Based on the model and formula in this invention, the oil mass in rigid elements, micro-deformation elements and large-deformation elements are solved respectively, thereby calculating the sum of the oil mass of all hydraulic components outside the oil tank. Combined with the initial total oil mass of the system, the theoretical value V2 of the oil volume in the self-pressurizing oil tank is calculated.

[0037] Comparing the theoretical value V2 with the measured value V from the liquid level sensor b If |V2-V b If |V2-V| < the warning threshold, the system is determined to be leak-free and in normal working condition; if |V2-V| < the warning threshold, the system is considered to be leak-free and in normal working condition. b The warning threshold is used to determine if an external leak has occurred in the system, and then the following formula is used: ΔV = V² - V b The leakage amount is calculated using the formula v. q =ΔV / t calculates the leakage rate and outputs the system status (normal / leaking), leakage amount, leakage rate, leakage fault level (minor / moderate / severe) and early warning information.

[0038] Model verification results show that under normal operating conditions with drastic temperature and pressure fluctuations and frequent actuator reversals, the false alarm rate of the system is ≤2%. The method of this invention can effectively distinguish between normal oil volume fluctuations and actual leakage. It can stably monitor leakage under different leakage conditions and realize early warning of faults. The leakage calculation error is ≤5% and the leakage rate calculation error is ≤8%, which meets the real-time requirements of online monitoring throughout the flight process.

[0039] In summary, the online monitoring method for external leakage of aircraft hydraulic systems of the present invention achieves accurate and reliable monitoring under complex operating conditions through mechanism modeling, correction of flight parameter data under leak-free conditions, and real-time comparison and judgment. It has certain engineering application value for online monitoring of external leakage of aircraft hydraulic systems.

Claims

1. A method for online monitoring of external leakage in aircraft hydraulic systems based on a mechanistic model, characterized in that, Includes the following steps: The first step is to construct a mechanistic model and calculate the theoretical value V1 of the oil volume in the self-pressurizing tank. Based on the law of conservation of mass, the mechanistic model is constructed, where the oil mass in the self-pressurizing tank is the difference between the initial total oil mass of the hydraulic system and the sum of the oil masses in the hydraulic components outside the tank. The initial total oil mass of the hydraulic system is directly obtained from the refueling data, combined with the temperature T monitored by the onboard sensors. a Pressure P a The data is used to calculate the sum of the oil mass in each hydraulic component outside the oil tank, and then the theoretical value V1 of the oil volume in the booster tank is derived. The second step involves developing a correction mechanism model based on flight parameter data under leak-free operating conditions. This model compares the theoretical value V1 with the actual oil volume V measured by the onboard level sensor under leak-free conditions. a If the absolute value of the difference between the two is |V1-V a If the error exceeds the allowable range, the mechanism model is corrected and recalculated until the calculation result meets the allowable range before proceeding to the next step. The third step is to achieve online monitoring of external leaks in the hydraulic system and output the hydraulic system status and prediction results. This involves transmitting real-time flight parameter data (T). b P b Input the corrected mechanism model, recalculate the theoretical value V2 of the oil volume in the self-pressurizing oil tank, and compare the theoretical value V2 with the actual value V of the oil volume monitored in real time by the level sensor. b Compare; if |V2-V b If the warning threshold is not exceeded, the hydraulic system is considered normal; if |V2-V b If the warning threshold is exceeded, it is determined that a leak has occurred in the hydraulic system. The leakage amount and leakage rate are then calculated, and relevant prediction results are output.

2. The online monitoring method for external leakage of an aircraft hydraulic system according to claim 1, characterized in that, In the first step, a hydraulic system mechanism model is constructed based on the law of conservation of mass. The hydraulic components, except for the self-pressurizing tank, are divided into three categories according to their volumetric deformation characteristics: rigid components, micro-deformation components, and large-deformation components. The mass of oil in each type of component is calculated, and then the sum of the mass of oil in each hydraulic component except for the self-pressurizing tank is solved.

3. The online monitoring method for external leakage of an aircraft hydraulic system based on a mechanistic model according to claim 1, characterized in that, The rigid components include various valves, hydraulic pipelines, filters, radiators, etc. The formula for calculating the oil mass in rigid components is m1=(ρ0+Δρ)‧V0; Where V0 is the initial volume of the element, ρ0 is the initial density, and Δρ is the density change under the influence of pressure and temperature.

4. The online monitoring method for external leakage of an aircraft hydraulic system based on a mechanistic model according to claim 1, characterized in that, The micro-deformation element includes a plunger pump and a hose; its oil mass calculation formula is m2=(ρ0+Δρ)‧(V0+dV), where dV is the small volumetric elastic deformation generated by the element under pressure.

5. The online monitoring method for external leakage of an aircraft hydraulic system based on a mechanistic model according to claim 1, characterized in that, The large deformation element includes an actuator, an accumulator, and a buffer bottle; its oil mass calculation formula is m3=(ρ0+Δρ)‧(V0+ΔV); where ΔV is the real-time volume change calculated based on the element's motion state or inflation pressure.

6. The online monitoring method for external leakage of an aircraft hydraulic system according to claim 1, characterized in that, In the second step, the error is set as needed; in the third step, the leakage amount is determined by the formula ΔV=V²-V. b The leakage rate is calculated using the formula v. q =ΔV / t, where t is the monitoring time.

7. The online monitoring method for external leakage of an aircraft hydraulic system according to claim 1, characterized in that, The flight parameters include temperature, pressure, and the actual volume of fuel in the self-pressurizing fuel tank.

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