PARKING FREE SYSTEM VALVE CHECK PROCEDE

Abstract

Method for diagnosing a health status of an actuator of an electro-hydraulic valve (110A; 110B) of a first hydraulic control circuit (100A; 100B) of a parking braking system of an aircraft, comprising: - determining a delay (Δt, Δt') called "actuation delay" between a determined instant following an activation or a deactivation of said valve (110A; 110B) and another instant of exceeding a given pressure threshold measured on a given pressure sensor (121A; 121B) downstream of said valve, - comparing said "actuation delay" (Δt, Δt') with a predetermined threshold value (Anomaly_threshold_A; Anomaly_threshold_B) called "anomaly detection threshold". Figure for the abstract: 1

Description

Title of the invention: METHOD FOR CONTROLLING A PARKING BRAKE SYSTEM VALVE TECHNICAL FIELD AND PRIOR ART

[0001] The present invention relates to the field of aircraft brake systems and more specifically concerns that of electro-hydraulic valves in such systems, in particular those used in parking brake systems and commonly called PBSELV or PBSV (from the English "Park Brake Selector Valve") or PBSOV (from the English "Park Brake Shut-off Valve").

[0002] It relates both to a method for diagnosing the state of health of such valves and to a device for implementing such a method.

[0003] Generally speaking, an aircraft wheel brake comprises friction elements, some of which are secured to the wheel and others to a stator, and a brake cylinder arranged to exert sufficient force on the friction elements to prevent an aircraft wheel from rotating. When parking, a brake cylinder is activated by a dedicated control system called a parking brake system or parking brake system and typically provided with elements distinct from those of the brake cylinder control system during landing.

[0004] The parking brake system comprises in particular a hydraulic distributor commonly called a PBSELV valve (from the English "Park Brake Selector Valve"). This valve is formed of an actuator typically formed of at least one electric torque motor. The PBSELV valve sometimes remains stuck in the open or closed position despite the triggered actuation of the parking brake system by the pilot. This can lead to operationally problematic cases of an aircraft that is not stabilized, or stuck on the ground.

[0005] In parking brake systems, operational faults often originate from failures of the PBSELV valve actuators, and in particular of the actuator motor(s). This is sometimes due to a deposit of particles on the electrical contacts.

[0006] Maintenance tests consisting of checking the correct movement of a brake cylinder under control of the PBSELV valve exist but they only allow the detection of a possible failure of the electric control motor(s).

[0007] Document FR 3076267 presents a method for diagnosing a state of wear of a parking brake system actuator.

[0008] Generally speaking, current methods for monitoring the operation of PBSELV valves are not sufficiently reliable due to unavailable data. or invalid, insufficient sampling frequency, or detection thresholds that are too high.

[0009] The problem arises of finding a new means of evaluating the health status of a valve actuator for an aircraft braking system. Statement of the invention

[0010] An aim of the present invention is to provide a method for diagnosing an operating state of an actuator of an electro-hydraulic valve of a first hydraulic control circuit of a parking braking system of an aircraft, this method comprising steps consisting of:

[0011] - determine a delay called “actuation delay” between a determined instant following a command to activate or deactivate said valve and another instant of exceeding a given pressure threshold measured on a given pressure sensor downstream of said valve,

[0012] - compare said “actuation delay” to a predetermined threshold value called “anomaly detection threshold”.

[0013] According to a first embodiment of the method, another electrohydraulic valve of a second hydraulic circuit of said parking braking system is activated or deactivated concomitantly with said valve, said determined instant being an instant of exceeding said given pressure threshold measured on another pressure sensor downstream of said other valve of the second hydraulic circuit.

[0014] Advantageously, following the activation or deactivation command of said valve, the method may comprise steps consisting of:

[0015] - estimate a first time interval Atl between an instant of exceeding a first threshold Th_Pa of pressure measured on said given sensor and an instant of exceeding said first threshold Th_Pa of pressure measured on said other pressure sensor,

[0016] - estimate a second time interval At2 between an instant of exceeding a second pressure threshold measured on said given sensor and an instant of exceeding said second pressure threshold measured on said other pressure sensor,

[0017] - estimate a third time interval At3 between an instant of exceeding a third pressure threshold Th_Pc measured on said given sensor and an instant of exceeding said third pressure threshold measured on said other pressure sensor,

[0018] said actuation delay At corresponding to the lowest estimated delay, between the first time interval, the second time interval and the third time interval, in other words at At = min (Atl; At2; At3).

[0019] According to a second mode of implementation of the method, said given instant is determined from an electrical signal from a parking brake system control switch. Such a switch is typically located in the aircraft cockpit.

[0020] Advantageously, the method may further comprise, following said comparison: the recording of so-called “monitoring” data associating an actuation delay value with calendar data dating the determination of this actuation delay.

[0021] According to a particular implementation, the method may further comprise a classification of the monitoring data into at least a first class of monitoring data called “normal” when the comparison is lower than said threshold value and into at least a second class of monitoring data called “abnormal” when the comparison is higher than said threshold value.

[0022] The method may further comprise, by means of a display device and on a graphical interface, the display of a set of data resulting from said classification according to a first graphical representation when the data of said set belongs to the first class of monitoring data and according to a second graphical representation when the data of said set belongs to the second class of monitoring data.

[0023] The display on the software graphical interface and via said display device may also include that of another set of data associating an actuation delay value evaluated by another method with calendar data dating this evaluation.

[0024] According to a particular implementation, said actuation of said valve by said actuation control signal is carried out when said aircraft is in operation on the ground: the method further comprising, following said comparison, steps of:

[0025] - incrementation of a first counter called “anomaly detection”, and of a second counter called “theft or cycle detection having suffered an anomaly”,

[0026] - calculation from the first counter and a number of determinations made, of an average m of abnormal delays detected,

[0027] - calculation from the second counter and a number of flights carried out, of a percentage p of flights having suffered an anomaly,

[0028] - evaluate a linear combination PBESELV_wi = m + a*p, with a coefficient determined non-zero,

[0029] - compare the linear combination PBESELV_wi = m + a *p with a threshold called threshold determined alert Aller_Thres, to trigger a maintenance operation when PBESELV_wi > Aller_Thres.

[0030] According to another aspect, the present application relates to a diagnostic device provided with of a computer processing system for implementing a method as defined above. Brief description of the drawings

[0031] The present invention will be better understood on the basis of the following description and the attached drawings in which:

[0032] - [Fig.l] represents an example of a parking braking system provided with one or several valves, in particular of the PBSELV type, whose operating condition we wish to check.

[0033] - [Fig.2] illustrates a first method of determining actuation delay between two valves of two separate hydraulic circuits of the same braking system and evaluated from pressure measurements taken on these two separate hydraulic circuits.

[0034] - [Fig.3] illustrates a second method of determining actuation delay valve evaluated from pressure measurements taken on a hydraulic circuit and an electrical control signal.

[0035] - [Fig.4] illustrates a display of actuation delay data classified into different categories.

[0036] - [Fig.5] represents a schematic diagram of a diagnostic device according to a particular mode of the invention.

[0037] - [Fig.6] represents an example of a sequence of steps in a method of diagnostics of the operating status of an aircraft parking brake system valve.

[0038] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0039] We now refer to [Fig.l] which serves to illustrate, in a schematic manner, a braking system of an aircraft, and in particular a part dedicated to the control of parking brakes also called parking brakes.

[0040] The system is composed, in this example, of two independent hydraulic circuits 10A, 10A forming two sources of hydraulic energy independent of each other. In the illustrated braking system, the circuits 10A, 10B are used together, each controlling a group of wheels in the left and right landing gears 2L, 2R.

[0041] According to a possible embodiment, on each landing gear 2R (resp. 2L), the two brakes of the front wheels are controlled by the first hydraulic circuit 10A and the two brakes of the rear wheels by the second circuit 10B. The first circuit 10A and the second circuit 10B are typically provided with the same functions and may be identical.

[0042] The circuits 10A, 10B are each provided with a control sub-circuit 100A, 100B hydraulic dedicated to controlling the aircraft parking brake, and each equipped in particular with a 110A, 110B parking brake selection valve PBSV or PBSELV (for “Park Brake Selector Valve”) which is of particular interest here.

[0043] We wish to be able to detect possible operating problems with this valve 110A, 110B PBSELV and in particular with its electric actuator.

[0044] To check the operating state of this actuator, one method consists of using a measurement of hydraulic pressure downstream of the parking brake selection valve PBSELV following a command to activate or deactivate the valve. An indicator determined according to a dynamic of rise or fall in hydraulic pressure downstream of the valve 110A or 110B PBSELV is monitored and then compared to a threshold.

[0045] In the specific case of [Fig.l], where the system is composed of two hydraulic circuits 100A, 100B for parking brake control, it is advantageous to carry out a comparison of hydraulic pressure data between the two independent circuits 100A, 100B.

[0046] More specifically, a hydraulic pressure measurement is used, carried out on the first circuit 100A following a command to activate or deactivate a first PBSELV valve 110A. The measurement can be carried out by means of a pressure sensor 121A located downstream of the first parking brake selection valve 110A coupled to the first PBSELV valve 110A.

[0047] Insofar as the activation or deactivation command of the PBSELV valves 110A, 110B is here concomitant, a hydraulic pressure measurement is also carried out on the second circuit 100B following this same activation or deactivation command. The measurement can be carried out by means of a pressure sensor 121B coupled to the second valve 110B of the PBSELV type.

[0048] According to a first phase, one then determines, following the command to activate or deactivate the valves 110A, 110B simultaneously, for the first circuit 110A: an instant tA where a given pressure threshold, for example 130 bars, measured by the sensor 121A, is reached, and for the second circuit 110B: an instant tB where an excess of the same given pressure threshold, for example 130 bars, measured by the sensor 121B is reached.

[0049] In this way we deduce a delay At = ] tb - ta\ between these two instants ta and tb, which we will call “actuation delay”.

[0050] The detection of the reaching of the pressure threshold and the determination of the delay At can advantageously be carried out by means of a processing unit 150, for example in the form of a computer or a processor or a calculator using pressure measurement data from the pressure sensors 121A, 121B. Such a processing unit 150 may be internal to the aircraft itself, and for example associated with, or integrated into, or be part of, a brake system control unit commonly called BSCU (for "Brake System Control Unit") of the aircraft. Alternatively, such a processing unit 150 may belong to a ground maintenance system interfaced with the aircraft or with the braking system itself, from the activation or deactivation control status data of the PBSELV valves 110A, 110B and from the pressure measurements from the pressure sensors 121 A, 121B transmitted by the aircraft or the braking system itself.

[0051] The actuation delay or delay At can then be compared to a predetermined delay threshold ANOMALY_th in order to detect a possible actuation anomaly of one of the two valves 110A, 110B. When the delay At exceeds the predetermined threshold ANOMALY_th, an anomaly indicator can be generated and this delay can then be considered abnormal and may be due to a malfunction of the PBSELV valve actuator.

[0052] The comparison with the ANOMALY_th threshold can be carried out by means of the same processing unit 150 or a separate processing unit, for example itself equipped with at least one processor or computer or calculator. Similarly, the anomaly indicator can be produced by the processing unit 150 or at least one other separate processing unit. For example, the anomaly indicator can be generated from a flag signal in a status register.

[0053] The estimated delay At as well as the time at which the measurements are carried out can typically be recorded, for example in a memory of the processing unit 150 or associated with this processing unit 150.

[0054] In order in particular to rule out the case of a hydraulic problem on one of the circuits 100A, 100B, a plurality of trigger delay measurements can be carried out for different pressure thresholds.

[0055] Thus, in a particular embodiment illustrated in [Fig.2], the curves C i2ia, C121B respectively give a change in the pressure measured by the sensor 121A, and a change in the pressure measured by the sensor 121B, following simultaneous activation of the valves. We then determine:

[0056] - a first delay Atl between an instant tAi of exceeding a first threshold Th_Pa given, for example 40 bars (4 MPa), by the pressure measured by the sensor 121A and an instant tBi of exceeding the first threshold given by the pressure measured by the sensor 121B;

[0057] - a second delay At2 between an instant tA2 of exceeding a second threshold given Th_Pb (with Th_Pb greater than Th_Pa) and for example 100 bars (10 MPa), by the pressure measured by the sensor 121A and an instant tB2 of exceeding the first given threshold, by the pressure measured by the sensor 121B,

[0058] - a third delay At3 between an instant tA3 of exceeding a third given threshold pressure, Th_Pc (with Th_Pc greater than Th_Pa and Th_Pb) for example 130 bars (13 MPa), by the pressure measured by the sensor 121A and an instant tB2 of exceeding the third given threshold, by the pressure measured by the sensor 121B.

[0059] The actuation delay selected At can then correspond here to the shortest delay selected between several delays, here between the first delay At1, the second delay At2, and the third delay At3, so that At = min (At1; At2; At3). This calculation, or selection of the shortest delay can, here again, be carried out by the processing unit 150 or a separate processing unit.

[0060] It should be noted that in the particular embodiment illustrated in [Fig.2], detections of reaching or exceeding pressure thresholds Th_Pa, Th_Pb, Th_Pc are carried out on the basis of an increasing pressure change following activation of the valves. It is possible, as a variant or in combination, to determine a delay on the basis of pressure drops measured respectively on the first sensor 121A and the second sensor 121B following, for example, a simultaneous command to deactivate the valves 110A, 110B.

[0061] In certain cases, in particular where several independent hydraulic circuits are not available, it is possible, according to an alternative embodiment, to carry out an actuation delay measurement from a single pressure sensor.

[0062] In this case, the actuation delay can be determined from a single hydraulic circuit and by measuring a delay At' between, on the one hand, a switching time of an electrical signal Scom for controlling the activation or deactivation of the PBSELV valves 110A, 110B of a parking control switch which can be located at the cockpit, and a time of exceeding a given pressure threshold measured on a pressure sensor downstream of the PBSELV type valve.

[0063] In the embodiment illustrated in [Fig. 3], the curves C41, C42 are respectively representative of an electrical signal from the parking control switch and of a measurement of the pressure measured downstream of the PBSELV valve. The delay At' is here determined for a pressure threshold Th_P of 130 bars (13 MPa).

[0064] As indicated previously, after the first phase of determining the delay At or At', a comparison of this difference with a determined anomaly threshold is carried out in a second phase.

[0065] A different anomaly threshold is typically used depending on whether the first phase was carried out by determining a delay At on the basis of pressure measurements taken from two separate hydraulic circuits or by determining a delay At' on the basis of pressure measurements taken from a single separate hydraulic circuit and an electrical signal.

[0066] The delay At determined using two hydraulic circuits is thus compared to a first anomaly threshold Anomaly_threshold_A, is adjustable, and typically more precise. This first anomaly threshold Anomaly_threshold_A can be programmed for example at 0.5 seconds. A delay At, measured greater than the anomaly threshold, here At > Anomaly_threshold_A, is considered abnormal and can correspond to abnormal operation of the electric actuator of the valve 110A or of the electric actuator of the valve 110B.

[0067] In the case where the measurement of the delay At' has been carried out on the basis of a switching instant of an electrical signal, in particular of a parking control switch which may be located at the cockpit, and the indicator of a moment of activation or deactivation of the parking brake or of a moment of reaching a pressure threshold measured on a single hydraulic circuit, the delay At' is compared to a second anomaly threshold Anomaly_threshold_B different from the first threshold Anomaly_threshold_A. This other anomaly threshold Anomaly_threshold_B is also adjustable and can be for example programmed at 2 seconds. When At' > Anomaly_threshold_B then can be diagnosed as abnormal.

[0068] Flight-to-flight monitoring and observation of the trends in the evolution of the delay At, At' from one flight to another can then make it possible to better anticipate a possible operational failure of the PBSELV electric valve actuator. For this, a recording of so-called "monitoring" data associating a determined delay value At with calendar data making it possible to date the determination of the delay At can be carried out, for example in one or more memories of a computer system of the aircraft, possibly from one or more memories associated with the processing unit 150.

[0069] A step of classifying the monitoring data into at least a first class of data called “normal” when At is lower than the threshold Anomaly_threshold_A (or At is lower than the threshold Anomaly_threshold_B) and into at least a second class of data called “abnormal” can also be implemented, by means of a conventional classification algorithm.

[0070] Monitoring the PBESLV valve actuator(s) may include displaying on a software graphical interface and via a display device coupled to a computer processing system, a set of monitoring data.

[0071] Thus, in the display example illustrated in [Fig.4], data belonging to the “normal” data class are displayed according to a first graphic representation, for example PNOrm disks, while data belonging to the “abnormal” data class are displayed according to a second graphic representation, for example Panorm squares •

[0072] In the particular embodiment illustrated, other data belonging to a class of “abnormal” data but originating from a known alternative detection method may also be displayed and have a third representation graphic for example of crosses or points Panorm_ait.

[0073] A method as described previously, with a lowered threshold, in this example of 0.5 seconds, makes it possible in the present case to be able to detect anomalies very early on compared to a conventional detection method.

[0074] An alert indicator can then be generated based on the frequency and amplitude of the delays At, At' detected.

[0075] Thus, it is possible to provide in particular an incrementation of a first counter XI called “anomaly detection”, each time a threshold is exceeded, in particular each time that At > Anomaly_threshold_A or each time that At' > Anomaly_threshold_B.

[0076] A second counter X2 called “detection of flight having suffered an anomaly”, can be incremented as soon as for a given flight, an exceeding of threshold At > Anomaly_threshold_A or At' > Anomaly_threshold_B is detected.

[0077] From the first counter XI and a number NI (with NI a non-zero integer) of determinations made, we calculate an average m = Xl / Nl of the abnormal delays detected.

[0078] From the second counter X2 and a total number N2 of flights carried out, a percentage p = X2 / N2 of flights having suffered an anomaly is calculated. We can choose, depending on the particular example, to carry out this calculation on a number N2 of 180 flights.

[0079] We then evaluate a linear combination PBESELV_wi of the mean m and the percentage p, in particular such that PBESELV_wi = m + a*p.

[0080] The result is then compared with a determined so-called "alert" threshold Aler_Thres. Exceeding this alert threshold (i.e. PBESELV_wi > Aler_Thres) can then trigger an alert signal indicating that a maintenance operation is necessary.

[0081] It may be provided that at least one of the steps of classifying the monitoring data, of incrementing the first counter XI and the second counter X2, of calculating the average m and the percentage p, of evaluating PBESELV_wi, of comparing with the “alert” threshold Aler_Thres, are carried out by means of a processing unit installed in the aircraft.

[0082] According to another possible implementation, several diagnostic steps can be carried out by means of a computer system of which at least one processing unit (computer, processor, calculator, etc.) is external to the aircraft.

[0083] Thus, in [Fig. 5], a diagnostic device 6 external to the aircraft 1 is shown schematically. The aircraft comprises a parking brake system 2 provided with at least one hydraulic valve of the PBSV or PBSELV type (“Park Brake Selector Valve”) whose operating state, and in particular that of its electric actuator, is to be diagnosed.

[0084] An example of a device for diagnosing the operating state of the valves is here represented in the form of the device 6, here connected by a wired connection 7 to means 4 for recording measurement data from the braking system and / or flight recording.

[0085] The apparatus 6, for example in the form of a terminal, is provided with at least one computer processing or calculation unit 9 comprising for example one or more microprocessors and / or microcontrollers. The diagnostic device is also typically provided with storage and recording means 10 including a main memory provided for example with a volatile memory and a non-volatile memory. The volatile memory can be implemented for example in the form of synchronous dynamic random access memory (SDRAM), dynamic random access memory (DRAM), dynamic random access memory. The non-volatile memory can be implemented for example in the form of a flash memory or a memory controller. The storage means also comprise one or more software and data storage elements. Examples of mass storage elements include for example a hard disk, a digital versatile disk (DVD), a memory card, a USB key.

[0086] Coded instructions which, when executed, cause a diagnostic method as described above to be executed may be stored in the memory of the apparatus 6. The apparatus 6 comprises one or more input / output devices 11 allowing a user to enter data and commands into the processing unit 9. The input device(s) may be implemented, for example, by a keyboard, a mouse, a touch screen, a voice recognition system. Information concerning the treatment and in particular a treatment result may be displayed via a display 12.

[0087] Thus, the flight-to-flight monitoring and the observation of the trends in the evolution of the delay At, At' can be carried out by means of the device 6 and the latter can be configured to execute one or more, or even all of the steps of: classification of the monitoring data, display of the classified monitoring data, calculation of the average m and of the percentage p, evaluation of the indicator PBESELV_wi, comparison with the alert threshold Aler_Thres, generation of an alert signal indicating that a maintenance operation is necessary.

[0088] In [Fig.6], an example of a sequence of steps for implementing a diagnostic method for checking the health status of a PBESELV valve is given in the form of a flowchart.

[0089] According to a first step S1, a parking brake trigger request is detected.

[0090] Then, the control parameters and measurement data linked to the activation or deactivation of the PBESLV valve actuator are recorded (step S2).

[0091] It is then checked (step S3) whether the parking brake control system comprises two hydraulic circuits. If this is the case, the delay At is evaluated (step S42).

[0092] Otherwise, and if the electrical parking switch signal is available, the delay At' is evaluated (step S41).

[0093] From one or more delay values ​​At' or At, for different flights, the indicator PBESELV_wi is then evaluated and this data is compared to the alert threshold Aller_Thres (step S5). If this alert threshold Aller_Thres is exceeded, an alert is triggered (step S6), which results in a maintenance operation.

Claims

Claims

1. Method for diagnosing an operating state of an actuator of an electro-hydraulic valve (110A; 110B) of a first hydraulic control circuit (100A; 100B) of a parking braking system of an aircraft, comprising: - determining a delay (At, At') called "actuation delay" between a determined instant following an activation or a deactivation of said valve (110A; 110B) and another instant of exceeding a given pressure threshold measured on a given pressure sensor (121A; 121B) downstream of said valve, - comparing said "actuation delay" (At, At') with a predetermined threshold value (Anomaly_threshold_A; Anomaly_threshold_B) called "anomaly detection threshold".

2. Method according to claim 1, in which another electrohydraulic valve (110B; 110A) of a second hydraulic circuit (100B; 100A) of said parking braking system is activated or deactivated concomitantly with said valve (110A; 110B), said determined instant being an instant of exceeding said given pressure threshold measured on another pressure sensor (121B; 121A) downstream of said other valve (110B; 110A) of the second hydraulic circuit (100B; 100A).

3. Method according to claim 2, wherein following the activation or deactivation of said valve (110A; 110B) steps consisting of: - estimating a first time interval (Atl) between an instant of exceeding a first threshold (Th_Pa) of pressure measured on said given sensor (121A; 121B) and an instant of exceeding said first threshold (Th_Pa) of pressure measured on said other pressure sensor (121B; 121A), - estimating a second time interval (At2) between an instant of exceeding a second threshold (Th_Pb) of pressure measured on said given sensor (121A; 121B) and an instant of exceeding said second threshold of pressure measured on said other pressure sensor (121B; 121A), - estimating a third time interval (At3) between an instant of exceeding a third threshold (Th_Pc) of pressure measured on said sensor given (121A;121B) and an instant of exceeding said third pressure threshold measured on said other pressure sensor; (121B; 121A), said actuation delay (At) corresponding to the lowest estimated delay (At = min (Atl; At2; At3)) between the first time interval, the second time interval and the third time interval.

4. Method according to claim 1, wherein said given instant is determined from an electrical signal of a parking control switch of the parking brake system and in particular located at the cockpit of the aircraft.

5. Method according to one of the preceding claims, further comprising, following said comparison: - the recording of so-called "monitoring" data associating an actuation delay value (At, At') with calendar data dating the determination of this actuation delay.

6. Method according to claim 5, further comprising the implementation: - of a classification of the monitoring data into at least a first class of monitoring data called "normal" when the comparison is lower than said threshold value (Anomaly_threshold_A; Anomaly_threshold_B) and into at least a second class of monitoring data called "abnormal" when the comparison is higher than said threshold value (Anomaly_threshold_A; Anomaly_threshold_B).

7. The method of claim 6, further comprising: via a display device and on a graphical interface, displaying a set of data resulting from said classification according to a first graphical representation when the data of said set belongs to the first class of monitoring data and according to a second graphical representation when the data of said set belongs to the second class of monitoring data.

8. A method according to claim 7, wherein the display on the software graphical interface and via said display device comprises that of another set of data associating an actuation delay value evaluated by another method with calendar data dating this evaluation.

9. A method according to one of claims 1 to 8, wherein said actuation of said valve (110A; 110B) by said actuation control signal is performed when said aircraft is in ground operation: the method further comprising, following said com- parison, stages of: - incrementing a first counter called “anomaly detection”, and a second counter called “theft or cycle detection having suffered an anomaly”, - calculation from the first counter and a number of determinations made, of an average m of abnormal delays detected, - calculation from the second counter and a number of flights carried out, of a percentage p of flights having suffered an anomaly, - evaluate a linear combination PBESELV_wi = m + a*p, with a a determined non-zero coefficient, - compare the linear combination PBESELV_wi = m + a*p with a threshold called the alert threshold determined Aller_Thres, to trigger a maintenance operation when PBESELV_wi > Aller_Thres.

10. Diagnostic device provided with a computer processing system for implementing a method according to one of claims 1 to 9.

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