An APU health deviation evaluation method based on state-standardized residual fusion

Abstract

The application provides an APU health deviation evaluation method based on state standardized residual fusion, and belongs to the technical field of health diagnosis of an auxiliary power unit of an airplane. The application is used to solve the problems of discontinuous APU health evaluation results, incomparable cross-working conditions, single information and lack of maintenance verification. The steps of the application comprise the following steps: S1: obtaining A13 samples and health reference responses; S2: calculating EGT health reference residuals; S3: state internal residual standardization and forward thermal deviation extraction; S4: auxiliary variable state internal deviation calculation; S5: multi-parameter health deviation index construction; S6: life cycle trend analysis and replacement window verification.

Description

Technical Field

[0001] This invention relates to an APU health deviation assessment method based on state-standardized residual fusion, belonging to the field of aircraft auxiliary power unit health diagnosis technology. Background Technology

[0002] The aircraft auxiliary power unit (APU) is a critical onboard support system for civil aircraft, and its operational status affects the reliability of ground power supply, bleed air, main engine starting, and flight release. Airline ACARS A13 messages record exhaust temperature, bleed air pressure, guide vane opening, generator load, ambient temperature, and lifecycle information of the APU during wing operation, which can be used for APU health status assessment. In actual maintenance scenarios, maintenance personnel not only need to determine whether the APU is abnormal, but also need to obtain an indicator that continuously characterizes the degree of health deviation to describe changes in health status, identify trends of increased risk before replacement, and assist in maintenance plan development.

[0003] Defects and shortcomings of existing technology: 1. The results of anomaly assessment are not continuous enough. Existing methods mostly output normal / abnormal assessments, making it difficult to form a sortable and traceable continuous health deviation.

[0004] 2. The original residuals are not comparable across operating conditions. The normal fluctuation scale of EGT is different under different operating conditions. If the original residuals are directly compared, it is easy to misjudge changes under normal operating conditions as health degradation.

[0005] 3. Insufficient information from a single EGT residual. Changes in APU health are not only reflected in the increase in exhaust temperature, but may also be reflected in auxiliary variables such as bleed air pressure, load, guide vane opening, and air path pressure. Relying solely on EGT residuals is insufficient to fully characterize changes in the coupled state of multiple parameters.

[0006] 4. Health indicators lack verification through maintenance events. Some health indicators only show trend changes and do not verify their engineering applicability in conjunction with the 30-day, 60-day, and 90-day windows before replacement, making it difficult to prove their supporting value for maintenance decisions. Summary of the Invention

[0007] To address the problems of discontinuous APU health assessment results, incomparability across operating conditions, limited information, and lack of maintenance verification in existing APU health assessments, this invention proposes an APU health deviation assessment method based on state-standardized residual fusion.

[0008] The technical solution adopted by the present invention to solve the above problems is as follows: The present invention includes the following steps: Step 1: Based on the aircraft auxiliary power unit on-wing operation message, obtain the actual exhaust temperature, operating status descriptor, auxiliary variables, and health reference exhaust temperature; Step 2: Obtain the health reference residual based on the actual exhaust temperature and the health reference exhaust temperature; Step 3: Based on the distribution characteristics of the health reference residual within the potential operating states represented by the operating state descriptor, obtain the state-standardized residual, and obtain the positive thermal response deviation based on the state-standardized residual; Step 4: Based on the distribution characteristics of the auxiliary variables within the potential operating states, obtain the in-state deviation of the auxiliary variables; Step 5: Obtain multi-parameter health deviation indicators based on the deviation of the positive thermal response and the intra-state deviation of the auxiliary variables; Step 6: Sort the multi-parameter health deviation indicators by time, obtain the health deviation sequence of a single aircraft auxiliary power unit within an installation life cycle, and verify it.

[0009] Furthermore, step 1 specifically includes: Obtain airline A13 message samples, which include actual exhaust temperature, operating status descriptor, auxiliary variables, message time, aircraft number, auxiliary power unit serial number, and lifecycle information; Based on the operating status descriptor, obtain the health reference exhaust temperature corresponding to the potential operating status.

[0010] Furthermore, the formula for calculating the health reference residual in step 2 is as follows: (1); In formula (1), Let be the EGT health reference residual for the t-th sample. For the actual EGT, This is a reference value for healthy EGT.

[0011] Furthermore, step 3 specifically includes: Based on the mean and standard deviation of the health reference residuals of the health reference samples under potential operating conditions, the health reference residuals of the current sample are standardized to obtain the state-standardized residuals. The positive thermal response deviation is obtained based on the positive part of the state-standardized residual. When multiple EGT-related channels exist, the thermal response health deviation term is calculated based on the positive thermal response deviation. ; The formula for calculating the state-standardized residual is: (2); In formula (2), and Let be the mean and standard deviation of the health reference residuals under the k-th potential operating state, respectively. To prevent small constants with a denominator of zero; The formula for calculating the deviation of the positive thermal response is: (3); Thermal response health deviation The calculation formula is: (4); In formula (4), M This refers to the number of channels related to EGT.

[0012] Furthermore, step 4 specifically includes: Based on the mean and standard deviation of each auxiliary variable in the health reference sample under potential operating conditions, the auxiliary variables of the current sample are standardized to obtain the in-state deviation of the auxiliary variables; The formula for calculating the intra-state deviation of the auxiliary variable is: (5); In formula (5), For the first t The first sample l Auxiliary variables, and The first k The first potential operating state l The mean and standard deviation of each auxiliary variable in the healthy reference sample.

[0013] Furthermore, step 5 specifically includes: Based on the preset fusion weights, the positive thermal response deviation and the intra-state deviation of the auxiliary variable are weighted and fused to obtain a multi-parameter health deviation index. The multi-parameter health deviation index is: (6); In formula (6), For the first t Multi-parameter health deviation indicators for each sample To integrate weights, This represents the number of auxiliary variables.

[0014] Furthermore, step 6 specifically includes: Based on the aircraft number, auxiliary power unit serial number, and installation cycle, the multi-parameter health deviation indicators are sorted by time to obtain the auxiliary power unit life cycle health deviation sequence. Based on the life cycle health deviation sequence and with the actual replacement date as a reference, the changing trends of multiple health deviation indicators are verified within a preset time window before replacement.

[0015] The beneficial effects of this invention are: (1) This invention constructs a continuous health deviation index. This invention outputs a continuous health deviation index, rather than a simple normal / abnormal judgment, which can be used to compare the health status between different APUs or different life cycle stages.

[0016] (2) This invention improves comparability across operating conditions. This invention performs residual standardization within the same potential operating state, reducing the interference of changes in environment, load and control state on the judgment of health deviation.

[0017] (3) This invention enhances the ability to characterize multiple parameters of health. This invention not only utilizes the positive residual of EGT, but also integrates the bias of auxiliary variables such as PT, IGV, GLA, P2A, and WB, which can more comprehensively reflect the changes in the multi-parameter coupling state of APU.

[0018] (4) This invention has the capability to verify maintenance events. This invention combines the verification of health deviation indicators at 30 days, 60 days and 90 days before replacement, making the evaluation results closer to the actual maintenance decision-making scenario. Attached Figure Description

[0019] Figure 1 This is a flowchart of an APU health deviation assessment method based on state-standardized residual fusion; Figure 2 A graph showing the effect of health deviation indicators. Detailed Implementation

[0020] In this embodiment, APU refers to the aircraft auxiliary power unit, and EGT refers to the engine exhaust temperature. Figure 1 As shown in this embodiment, the steps of an APU health deviation assessment method based on state-standardized residual fusion include: S1: Acquisition of A13 samples and health reference responses; Acquire airline A13 message samples, including actual EGT, operating status descriptor, auxiliary variables, message time, aircraft number, APU serial number, and lifecycle information. Simultaneously, acquire the healthy EGT reference value for each sample under the corresponding operating condition. This health reference value represents the normal thermal response level of the APU under the current operating conditions.

[0021] S2: EGT health reference residual calculation; The difference between the actual EGT and the healthy EGT reference value is calculated to obtain the healthy EGT reference residual. This residual is used to represent the degree of deviation of the current sample's thermal response from the healthy reference response.

[0022] The health reference residuals are: (1); In formula (1), Let be the EGT health reference residual for the t-th sample. For the actual EGT, This is a reference value for healthy EGT.

[0023] S3: In-state residual standardization and positive thermal deviation extraction; Within the same potential operating state, the current residual is standardized based on the mean and standard deviation of the residuals of the healthy reference sample, and the positive part of the standardized residual is extracted to obtain the positive thermal response deviation.

[0024] The formula for calculating the state-standardized residual is: (2); In formula (2), and Let be the mean and standard deviation of the health reference residuals under the k-th potential operating state, respectively. To prevent small constants with a denominator of zero; The formula for calculating the deviation of the positive thermal response is: (3); When multiple EGT-related channels exist, the thermal response health deviation term can be further calculated: (4); In formula (4), M This refers to the number of channels related to EGT.

[0025] S4: Calculation of intra-state deviation of auxiliary variables; Auxiliary variables such as PT, IGV, GLA, P2A, and WB are selected, and their standardized deviations relative to the mean of the healthy reference sample are calculated within the same potential operating state to obtain the auxiliary variable deviation term.

[0026] The intra-state deviation of the auxiliary variable is: (5); In formula (5), For the first t The first sample l Auxiliary variables, and The first k The first potential operating state l The mean and standard deviation of each auxiliary variable in the healthy reference sample.

[0027] S5: Construction of multi-parameter health deviation indicators; The positive thermal response deviation term and the auxiliary variable deviation term are weighted according to... The data is then fused to obtain multi-parameter health deviation indicators for each A13 message. During implementation, appropriate indicators can be selected based on the verification results. Values.

[0028] The multi-parameter health deviation index is: (6); In formula (6), For the first t Multi-parameter health deviation indicators for each sample To integrate weights, This represents the number of auxiliary variables.

[0029] S6: Lifecycle Trend Analysis and Replacement Window Verification; Health deviation indicators will be determined according to aircraft number, APU serial number, and installation cycle. Arranged chronologically, an APU lifecycle health deviation sequence is formed. Using the actual replacement date as a reference, windows of 30 days, 60 days, and 90 days before replacement are set to analyze the increasing trend and concentration of high values ​​of health deviation indicators in different windows.

[0030] Furthermore, to verify the technical effect of the present invention, this embodiment was verified based on the APU A13 message data of a certain airline, and the results are as follows. Figure 2 As shown, during the stable health phase, the health deviation index remains at a low level; as the replacement phase approaches, the health deviation index shows an increase or a concentration of high values, indicating that this method can form a continuous index reflecting the degree of APU health deviation, and the health deviation index shows good maintenance event indication ability within the 30-day, 60-day, and 90-day windows (grey areas of different depths).

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for assessing APU health deviation based on state-standardized residual fusion, characterized in that, include: Step 1: Based on the aircraft auxiliary power unit on-wing operation message, obtain the actual exhaust temperature, operating status descriptor, auxiliary variables, and health reference exhaust temperature; Step 2: Obtain the health reference residual based on the actual exhaust temperature and the health reference exhaust temperature; Step 3: Based on the distribution characteristics of the health reference residual within the potential operating states represented by the operating state descriptor, obtain the state-standardized residual, and obtain the positive thermal response deviation based on the state-standardized residual; Step 4: Based on the distribution characteristics of the auxiliary variables within the potential operating states, obtain the in-state deviation of the auxiliary variables; Step 5: Obtain multi-parameter health deviation indicators based on the deviation of the positive thermal response and the intra-state deviation of the auxiliary variables; Step 6: Sort the multi-parameter health deviation indicators by time, obtain the health deviation sequence of a single aircraft auxiliary power unit within an installation life cycle, and verify it.

2. The APU health deviation assessment method based on state-standardized residual fusion according to claim 1, characterized in that, Step 1 specifically includes: Obtain airline A13 message samples, which include actual exhaust temperature, operating status descriptor, auxiliary variables, message time, aircraft number, auxiliary power unit serial number, and lifecycle information; Based on the operating status descriptor, obtain the health reference exhaust temperature corresponding to the potential operating status.

3. The APU health deviation assessment method based on state-standardized residual fusion according to claim 1, characterized in that, The formula for calculating the health reference residual in step 2 is: （1）； In formula (1), Let be the EGT health reference residual for the t-th sample. For the actual EGT, This is a reference value for healthy EGT.

4. The APU health deviation assessment method based on state-standardized residual fusion according to claim 1, characterized in that, Step 3 specifically includes: Based on the mean and standard deviation of the health reference residuals of the health reference samples under potential operating conditions, the health reference residuals of the current sample are standardized to obtain the state-standardized residuals. The positive thermal response deviation is obtained based on the positive part of the state-standardized residual. When multiple EGT-related channels exist, the thermal response health deviation term is calculated based on the positive thermal response deviation. ; The formula for calculating the state-standardized residual is: （2）； In formula (2), and Let be the mean and standard deviation of the healthy reference residuals under the k-th potential operating state, respectively. To prevent small constants with a denominator of zero; The formula for calculating the deviation of the positive thermal response is: （3）； Thermal response health deviation The calculation formula is: （4）； In formula (4), M This refers to the number of channels related to EGT.

5. The APU health deviation assessment method based on state-standardized residual fusion according to claim 1, characterized in that, Step 4 specifically includes: Based on the mean and standard deviation of each auxiliary variable in the health reference sample under potential operating conditions, the auxiliary variables of the current sample are standardized to obtain the in-state deviation of the auxiliary variables; The formula for calculating the intra-state deviation of the auxiliary variable is: （5）； In formula (5), For the first t The first sample l Auxiliary variables, and The first k The first potential operating state l The mean and standard deviation of each auxiliary variable in the healthy reference sample.

6. The APU health deviation assessment method based on state-standardized residual fusion according to claim 1, characterized in that, Step 5 specifically includes: Based on the preset fusion weights, the positive thermal response deviation and the intra-state deviation of the auxiliary variable are weighted and fused to obtain a multi-parameter health deviation index. The multi-parameter health deviation index is: （6）； In formula (6), For the first t Multi-parameter health deviation indicators for each sample To integrate weights, This represents the number of auxiliary variables.

7. The APU health deviation assessment method based on state-standardized residual fusion according to claim 1, characterized in that, Step 6 specifically includes: Based on the aircraft number, auxiliary power unit serial number, and installation cycle, the multi-parameter health deviation indicators are sorted by time to obtain the auxiliary power unit life cycle health deviation sequence. Based on the life cycle health deviation sequence and with the actual replacement date as a reference, the changing trends of multiple health deviation indicators are verified within a preset time window before replacement.

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