Method for controlling the valve of a parking brake system

Abstract

The invention relates to a method for diagnosing a state of health of an actuator of an electro-hydraulic valve (110A; 110B) of a first hydraulic control circuit (100A; 100B) of a parking brake system of an aircraft, which comprises: - determining a delay (Δt, Δt'), referred to as "actuation delay", between a determined instant following an activation or a deactivation of the valve (110A; 110B) and another instant of exceeding a given pressure threshold measured on a given pressure sensor (121A; 121B) downstream of the valve; - comparing the actuation delay (Δt, Δt') with a predetermined threshold value (Anomaly_threshold_A; Anomaly_threshold_B) referred to as "anomaly detection threshold".

Description

[0001] PARKING BRAKE SYSTEM VALVE CONTROL METHOD

[0002] DESCRIPTION

[0003] TECHNICAL FIELD AND PRIOR ART

[0004] 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").

[0005] It relates both to a method for diagnosing the state of health of such valves and to a device for implementing such a method.

[0006] 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 equipped with elements separate from those of the brake cylinder control system during landing.

[0007] The parking brake system includes in particular a hydraulic distributor commonly called PBSELV valve (from the English "Park Brake Selector Valve"). This valve is formed by an actuator typically formed by 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 unstabilized aircraft, or stuck on the ground.

[0008] In parking brake systems, operational faults often originate from failures of the PBSELV valve actuators, and in particular the actuator motor(s). This is sometimes due to a deposit of particles on the electrical contacts. Maintenance tests consisting of checking the correct 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).

[0009] Document FR 3076267 presents a method for diagnosing a state of wear of a parking brake system actuator.

[0010] Generally speaking, current methods for monitoring the operation of PBSELV valves are not sufficiently reliable due to unavailable or invalid data, insufficient sampling frequency, or excessively high detection thresholds.

[0011] The problem arises of finding a new way to assess the health status of a valve actuator for an aircraft braking system.

[0012] STATEMENT OF THE INVENTION

[0013] 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:

[0014] - determine a delay known as an “actuation delay” between a given instant following an activation or deactivation command of said valve and another instant of exceeding a given pressure threshold measured on a given pressure sensor downstream of said valve,

[0015] - compare said “actuation delay” to a predetermined threshold value called “anomaly detection threshold”.

[0016] 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 exceeding said given pressure threshold measured on another pressure sensor downstream of said other valve of the second hydraulic circuit.

[0017] Advantageously, following the activation or deactivation command of said valve, the method may comprise 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 and an instant of exceeding said first threshold Th_Pa of pressure measured on said other pressure sensor,

[0018] - 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,

[0019] - estimate a third time interval At3 between an instant of exceeding a third threshold Th_Pc of pressure measured on said given sensor and an instant of exceeding said third threshold of pressure measured on said other pressure sensor, said actuation delay At corresponding to the shortest 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).

[0020] According to a second embodiment of the method, said given instant is determined from an electrical signal from a control switch of the parking brake system. Such a switch is typically located in the cockpit of the aircraft.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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:

[0026] - incrementation of a first counter called “anomaly detection”, and of a second counter called “theft or cycle detection having suffered an anomaly”,

[0027] - calculation from the first counter and a number of determinations made, of an average m of abnormal delays detected,

[0028] - calculation from the second counter and a number of flights carried out, of a percentage p of flights having suffered an anomaly,

[0029] - evaluate a linear combination PBESELV_wi = m + a * p, with a determined non-zero coefficient,

[0030] - 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.

[0031] According to another aspect, the present application relates to a diagnostic device provided with a computer processing system for implementing a method as defined above.

[0032] BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be better understood on the basis of the description which follows and the attached drawings in which: - figure 1 represents an example of a parking braking system provided with one or more valves, in particular of the PBSELV type, the operating state of which it is desired to check.

[0034] - Figure 2 illustrates a first method for determining the 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.

[0035] - Figure 3 illustrates a second method for determining valve actuation delay evaluated from pressure measurements made on a hydraulic circuit and an electrical control signal.

[0036] - Figure 4 illustrates a display of actuation delay data classified into different categories.

[0037] - figure 5 represents a schematic diagram of a diagnostic device according to a particular embodiment of the invention.

[0038] - figure 6 represents an example of a sequence of steps in a method for diagnosing the operating status of a valve in an aircraft parking brake system.

[0039] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0040] We now refer to Figure 1 which serves to illustrate, in a schematic manner, an aircraft braking system, and in particular a part dedicated to the control of parking brakes also called parking brakes.

[0041] The system is composed, in this example, of two independent hydraulic circuits 10A, 10A forming two independent hydraulic energy sources. In the illustrated braking system, the circuits IDA, 10B are used together, each controlling a group of wheels in the left and right landing gears 2L, 2R.

[0042] According to a possible embodiment, on each 2R (resp. 2L) landing gear, 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 are typically equipped with the same functions and may be identical.

[0043] The circuits 10A, 10B are each equipped with a hydraulic control sub-circuit 100A, 100B dedicated to controlling the aircraft parking brake, and each equipped in particular with a parking brake selection valve 110A, 110B PBSV or PBSELV (for “Park Brake Selector Valve”) which is of particular interest here.

[0044] We want to be able to detect any possible operating problems with this 110A, 110B PBSELV valve and in particular its electric actuator.

[0045] To check the operating status of this actuator, one method consists of using a measurement of hydraulic pressure downstream of the PBSELV parking brake selection valve following a command to activate or deactivate the valve. An indicator determined according to a dynamic rise or fall in hydraulic pressure downstream of the PBSELV valve 110A or 110B is monitored and then compared to a threshold.

[0046] In the specific case of Figure 1, 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.

[0047] 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.

[0048] To the extent that 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. According to a first phase, it is then determined, following the simultaneous activation or deactivation command of the valves 110A, 110B, for the first circuit 110A: an instant ÎA where a given pressure threshold, for example 130 bars, measured by the sensor 121A, is reached, and for the second circuit 110B: an instant ts 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 can be internal to the aircraft itself, and for example associated with, or integrated into, or be part of, a braking 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, based on the activation or deactivation control status data of the PBSELV valves 110A, 110B and on the pressure measurements from the pressure sensors 121A, 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 time At as well as the time at which the measurements are carried out may typically be recorded, for example in a memory of the processing unit 150 or associated with this processing unit 150.

[0054] In particular, in order 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 Figure 2, the curves C121A, 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 t*i of exceeding a first given threshold Th_Pa, for example 40 bars (4 MPa), by the pressure measured by the sensor 121A and an instant ÎBI of exceeding the first given threshold by the pressure measured by the sensor 121B;

[0057] - a second delay At2 between an instant tA2 of exceeding a second given threshold 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 tAa of exceeding a third given pressure threshold, 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, again, be carried out by the processing unit 150 or a separate processing unit. It should be noted that in the particular exemplary 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 change in pressure following activation of the valves. Alternatively or in combination, provision may be made 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.

[0060] 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.

[0061] 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 instant 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 cockpit level, and a moment of exceeding a given pressure threshold measured on a pressure sensor downstream of the PBSELV type valve.

[0062] In the embodiment illustrated in Figure 3, curves C41, C42 are respectively representative of an electrical signal from the parking control switch and 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).

[0063] As indicated previously, after the first phase of determining the delay At or At', a second phase is used to compare this difference with a determined anomaly threshold.

[0064] 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.

[0065] 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 to 0.5 seconds. A delay At, measured higher than the anomaly threshold, here At > Anomaly_threshold_A, is considered abnormal and can correspond to an abnormal operation of the electric actuator of the valve 110A or of the electric actuator of the valve 110B.

[0066] In the case where the measurement of the delay At' was 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 to 2 seconds. When At' > Anomaly_threshold_B then can be diagnosed as abnormal.

[0067] Flight-to-flight monitoring and observation of 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.

[0068] 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.

[0069] 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. Thus, in the display example illustrated in Figure 4, data belonging to the “normal” data class is displayed according to a first graphical representation, for example PNORM disks, while data belonging to the “abnormal” data class is displayed according to a second graphical representation, for example P NO M squares.

[0070] 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 P anorm_alt-

[0071] A method as described previously, with a lowered threshold, in this example of 0.5 seconds, makes it possible in this case to detect anomalies very early compared to a conventional detection method.

[0072] An alert indicator can then be generated based on the frequency and amplitude of the detected delays At, At'.

[0073] Thus, it is possible to provide in particular an incrementation of a first counterXl 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.

[0074] 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.

[0075] 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.

[0076] From the second counter X2 and a total number N2 of flights carried out, we calculate a percentage p = X2 / N2 of flights having suffered an anomaly. We can choose, depending on the particular example, to carry out this calculation on a number N2 of 180 flights.

[0077] 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. 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.

[0078] It may be provided that at least one of the steps of classifying the monitoring data, incrementing the first counter XI and the second counter X2, calculating the average m and the percentage p, evaluating PBESELV_wi, comparing with the “alert” threshold Aler Thres, are carried out by means of a processing unit installed in the aircraft.

[0079] According to another implementation possibility, several diagnostic steps can be carried out using a computer system of which at least one processing unit (computer, processor, calculator, etc.) is external to the aircraft.

[0080] Thus, in Figure 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.

[0081] An example of a device for diagnosing the operating state of the valve(s) is represented here 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.

[0082] The device 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.

[0083] 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.

[0084] Thus, flight-to-flight monitoring and observation of trends in the evolution of the delay At, At' can be carried out using 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 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.

[0085] In Figure 6, an example of a sequence of steps for implementing a diagnostic method to check the health status of a PBESELV valve is given in the form of a flowchart.

[0086] According to a first step IF we detect a request to trigger parking braking.

[0087] Then, the control parameters and measurement data related to the activation or deactivation of the PBESLV valve actuator are recorded (step S2).

[0088] We then check (step S3) whether the parking brake control system has two hydraulic circuits. If this is the case, the delay At is evaluated (step S42).

[0089] Otherwise, and if the electrical signal from the parking switch is available, the delay At' is evaluated (step S41).

[0090] From one or more delay values ​​At' or At, for different flights, the PBESELV_wi indicator 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

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 the following steps: - 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, said determined 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 parking brake system and activated or deactivated concomitantly with said valve (110A; 110B) or said determined instant being 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, - compare said “actuation delay” (At, At') to a predetermined threshold value (Anomaly_threshold_A; Anomaly_threshold_B) called “anomaly detection threshold”.

2. Method according to claim 1, in which following the activation or deactivation of said valve (110A; 110B) steps consisting of: - estimate 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), - estimate 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 pressure threshold 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 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 shortest estimated delay (At = min (Atl; At2; At3)) between the first time interval, the second time interval and the third time interval.

3. 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.

4. The method of claim 3, further comprising implementing: - 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).

5. The method of claim 4, further comprising: by means of 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 data of monitoring and according to a second graphical representation when the data of said set belongs to the second class of monitoring data.

6. Method according to claim 5, in which 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.

7. Method according to one of claims 1 to 6, wherein said actuation of said valve (110A; 110B) 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: - 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 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.

8. Diagnostic device provided with a computer processing system for implementing a method according to one of claims 1 to 7.

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