PROCEDE DE CONTROLE DE VALVE DE SYSTEME DE FREIN DE PARKING

Abstract

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

Description

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

[0001] The present invention relates to the field of aircraft braking systems and more specifically to 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 health status of such valves and to a device for implementing such a method.

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

[0004] The parking brake system includes, in particular, a hydraulic distributor commonly called a PBSELV valve (Park Brake Selector Valve). This valve consists of an actuator typically comprising at least one electric torque motor. The PBSELV valve sometimes remains stuck in the open or closed position despite the pilot's activation of the parking brake system. This can lead to operationally problematic situations where the aircraft is unstabilized 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 proper movement of a brake cylinder under the 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 wear condition of a parking brake system actuator.

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

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

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

[0011] - determine a time interval called "actuation delay" between a determined instant following an activation or deactivation command of said valve and another instance 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 electro-hydraulic 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 exceedance of 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 include steps consisting of:

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

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

[0017] - estimate a third time interval At3 between an overshooting instant of a third pressure threshold Th_Pc measured on said given sensor and an instant of exceedance of 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 = min (Atl ; At2 ; At3).

[0019] According to a second embodiment 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 include, 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 include a classification of the monitoring data into at least a first class of monitoring data called "normal" when the comparison is less than said threshold value and into at least a second class of monitoring data called "abnormal" when the comparison is greater than said threshold value.

[0022] The method may further include, 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 through 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 embodiment, said actuation of said valve by said actuation control signal is performed when said aircraft is in operation on the ground: the method further comprising, following said comparison, the steps of:

[0025] - incrementing a first counter called the "anomaly detection" counter, and a second counter, referred to as the "flight or cycle anomaly detection" counter,

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

[0027] - calculation from the second counter and a number of flights performed, of a percentage p of flights that experienced an anomaly,

[0028] - evaluate a linear combination PBESELV_wi = m + a*p, with a 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 equipped with a computer processing system for the implementation of a process 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 accompanying drawings in which:

[0032] - Fig. 1 represents an example of a parking braking system equipped with a or several valves, in particular of the PBSELV type, whose operating condition we wish to verify.

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

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

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

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

[0037] - Figure 6 represents an example of a sequence of steps in a process of diagnostic of the operating status of an aircraft parking brake system valve.

[0038] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0039] Reference is now made to [Fig. 1], which serves to illustrate schematically a aircraft braking system, and in particular a part dedicated to the control of parking brakes also called parking brakes.

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

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

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

[0043] We wish to be able to detect any problems in the operation of this 110A, 110B PBSELV valve and in particular of its electric actuator.

[0044] To verify the operating status of this actuator, one method consists of using a hydraulic pressure measurement downstream of the parking brake selector valve PBSELV following an activation or deactivation command for the valve. An indicator determined according to a dynamic increase or decrease in hydraulic pressure downstream of the PBSELV valve 110A or 110B is monitored and then compared to a threshold.

[0045] In the specific case of [Fig.1], where the system consists of two hydraulic parking brake control circuits 100A, 100B, it is advantageous to perform a comparison of hydraulic pressure data between the two independent circuits 100A, 100B.

[0046] More specifically, a hydraulic pressure measurement is used on the first circuit 100A following an activation or deactivation command of 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 110A PBSELV valve.

[0047] Since the activation or deactivation command for the PBSELV valves 110A and 110B is simultaneous, a hydraulic pressure measurement is also performed on the second circuit 100B following this same activation or deactivation command. The measurement can be carried out using a pressure sensor 121B coupled to the second PBSELV-type valve 110B.

[0048] According to a first phase, following the simultaneous activation or deactivation command of valves 110A, 110B, for the first circuit 110A, an instant tA is determined where a given pressure threshold, for example 130 bars, measured by sensor 121A, is reached, and for the second circuit 110B, an instant tB is determined where an exceedance of the same given pressure threshold, for example 130 bars, measured by 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 pressure threshold being reached 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 pressure sensors 121A, 121B. Such a processing unit 150 may be internal to the aircraft itself, and for example associated with, integrated into, or forming part of, a brake system control unit commonly referred to as a 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 brake system itself, based on the activation or deactivation command status data of the PBSELV valves 110A, 110B and on the pressure measurements from pressure sensors 121A, 121B transmitted by the aircraft or the brake system itself.

[0051] The actuation 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 valve actuator PBSELV.

[0052] The comparison at the ANOMALY_th threshold can be performed using the same processing unit 150 or a separate processing unit, for example, one that itself has at least one processor, computer, or calculator. Similarly, the anomaly indicator can be generated by the processing unit 150 or by 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 time At and the time at which the measurements can be taken are typically recorded, for example in a memory of the processing unit 150 or associated with this processing unit 150.

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

[0055] Thus, in a particular embodiment illustrated in [Fig. 2], curves C121A and C121B respectively show the evolution of the pressure measured by sensor 121A and the evolution of the pressure measured by sensor 121B, following simultaneous activation of the valves. We then determine:

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

[0057] - a second delay At2 between a time 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 sensor 121A and an instant tB2 of exceeding the first given threshold, by the pressure measured by sensor 121B,

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

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

[0060] It should be noted that, in the particular embodiment illustrated in [Fig. 2], detection of the attainment or exceedance of pressure thresholds Th_Pa, Th_Pb, Th_Pc is performed based on an increasing pressure trend following activation of the valves. Alternatively, or in combination, a delay can be determined based on pressure drops measured respectively on the first sensor 121A and the second sensor 121B following, for example, a simultaneous command to deactivate valves 110A and 110B.

[0061] In certain cases, particularly 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 an instant of switching of an electrical signal Scom of control of activation or deactivation of the PBSELV 110A, 110B valves of a parking control switch which may be located at the cockpit level, and an instant 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], curves C41 and C42 represent, respectively, an electrical signal from a parking control switch and a pressure measurement taken downstream of the PBSELV valve. The delay At' is determined here for a pressure threshold Th_P of 130 bar (13 MPa).

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

[0065] A different anomaly threshold is typically used depending on whether the first phase was carried out by determining a delay At based on pressure measurements taken from two separate hydraulic circuits or by determining a delay At' on the pressure measurement based on 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, which is adjustable and typically more precise. This first anomaly threshold Anomaly_threshold_A can, for example, be programmed to 0.5 seconds. A measured delay At greater than the anomaly threshold, here At > Anomaly_threshold_A, is considered abnormal and may correspond to abnormal operation of the electric actuator of valve 110A or of the electric actuator of valve 110B.

[0067] In the case where the measurement of the delay At' was performed based on the switching instant of an electrical signal, in particular a parking control switch that may be located in the cockpit, and the indicator of the activation or deactivation instant of the parking brake or the reaching of a pressure threshold measured on a single hydraulic circuit, the delay At' is compared to a second anomaly threshold Anomaly_threshold_B, which is different from the first threshold Anomaly_threshold_A. This second anomaly threshold Anomaly_threshold_B is also adjustable and can, for example, be programmed to 2 seconds. When At' > Anomaly_threshold_B, then it 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 allow for better anticipation of a possible malfunction of the PBSELV electric valve actuator. For this purpose, a recording of so-called "monitoring" data associating a determined delay value At with calendar data allowing the determination of the delay At to be dated can be carried out, for example in one or more memories of an aircraft computer system, 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 less than the threshold Anomaly_threshold_A (or At is less 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] The monitoring of the PBESLV valve actuator(s) may include displaying on a software graphical interface and through 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 graphical representation, for example, of PNORm disks, while data belonging to the "Abnormal" data classes are displayed according to a second graphical 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 can also be displayed and have a third graphical representation, for example, of crosses or points. PanOrm_ait-

[0073] A method such as described above, with a lowered threshold, in this example of 0.5 seconds, makes it possible in the present case to detect anomalies much earlier than with a conventional detection method.

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

[0075] Thus, we can foresee in particular an incrementation of a first counter XI called "anomaly detection", at each threshold exceedance, in particular each time that At > Anomaly_threshold_A or each time that At' > Anomaly_threshold_B.

[0076] A second counter X2, called "flight detection anomaly", can be incremented as soon as, for a given flight, an exceedance of the 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, an average m = Xl / Nl of the abnormal delays detected is calculated.

[0078] From the second counter X2 and a total number N2 of flights performed, a percentage p = X2 / N2 of flights that experienced an anomaly is calculated. Depending on the specific example, this calculation can be performed 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 so-called "alert" threshold determined 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 classification of the monitoring data, incrementation of the first counter XI and the second counter X2, calculation of the average m and the percentage p, evaluation of PBESELV_wi, comparison with the "alert" threshold Aler_Thres, are carried out by means of a processing unit implanted in the aircraft.

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

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

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

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

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

[0087] Thus, flight-to-flight monitoring and observation of the trends in the evolution of the delay At, At' can be carried out using the device 6 and the latter can be configured to perform one or more, or even all of the steps of: classification of monitoring data, display of classified monitoring data, calculation of the average m and the percentage p, evaluation of the indicator PBESELV_wi, comparison to 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 the implementation of a diagnostic method to check the health status of a PBESELV valve is given in the form of a flowchart.

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

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

[0091] We then check (step S3) whether the parking brake control system has two hydraulic circuits. If so, we evaluate the delay At (step S42).

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

[0093] Based on 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 leads to a maintenance operation.

Claims

Demands

1. A method for diagnosing the operating state of an actuator of an electro-hydraulic valve (110A; 110B) of a first hydraulic control circuit (100A; 100B) of an aircraft parking brake system, comprising the following steps: - determining a delay (At, At') referred to as the "actuation delay" between a specified instant following the activation or 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, said specified instant being an instant of exceeding said given pressure threshold measured on another pressure sensor (121B; 121A) downstream of another electro-hydraulic valve (110B; 110A) of a second hydraulic circuit (100B; 100A) of said braking system. parking and activated or deactivated simultaneously with said valve (110A;110B) or said determined instant being determined from an electrical signal from a parking control switch of the parking brake system and in particular located at the level of the aircraft cockpit, - compare said "actuation delay" (At, At') to a predetermined threshold value (Anomaly_threshold_A; Anomaly_threshold_B) called "anomaly detection threshold".;

2. A method according to claim 1, wherein, following the activation or deactivation of said valve (110A; 110B), the steps consist of: - estimating a first time interval (At1) 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), - estimate a third time interval (At3) between an instant of exceeding a third threshold (Th_Pc) of pressure measured on said given sensor (121A; 121B) and an instant of exceeding said third threshold of pressure 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.

3. A method according to any 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.

4. A method according to claim 3, 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 less than said threshold value (Anomaly_threshold d_A; Anomaly_threshold_B) and into at least a second class of monitoring data called "abnormal" when the comparison is greater than said threshold value (Anomaly_threshold d_A; Anomaly_threshold_B).

5. A method according to claim 4, further comprising: 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.

6. A method according to claim 5, wherein the display on the software graphical interface and by means of said display device includes that of another set of data associating an actuation delay value evaluated by another method with calendar data dating this evaluation.

7. A method according to any one of claims 1 to 6, wherein said actuation of said valve (110A; 110B) by said signal of

8. The actuation command is executed when the aircraft is in operation on the ground; the method further comprising, following the said comparison, the steps of: - incrementing a first counter called the "anomaly detection" counter, and a second counter called the "flight or cycle detection" counter, - calculation, based on the first counter and a number of determinations performed, of an average m of abnormal delays detected, - Calculate, based on the second counter and the number of flights performed, a percentage p of flights that experienced 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. Diagnostic device equipped with a computer processing system for implementing a method according to any one of claims 1 to 7.

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