Method and device for monitoring a rotating machine using a vibration signal

Abstract

The present invention relates to a method for monitoring a rotating machine (RM) using a vibration signal (VS). The rotating machine (RM) comprises a plurality of subsystems (S, B) of rotating mechanical parts (LA1-L1N, LB1-LB2), and the vibration signal (VS) comprises vibration contributions from the subsystems (S, B). The method comprises, for at least one said subsystem (S), steps consisting of: estimating (S210) the vibration contribution of said subsystem (S) from a set of synchronous averages of the vibration signal (VS) associated with rotational frequencies (FA1-FA2) of the parts (LA1-LA2) of said subsystem (S) and multiples of these rotational frequencies (FA1-FA2); and determining (S310) whether said subsystem (S) is defective by comparative analysis of a so-called health indicator corresponding to the estimated vibration contribution (EVS) of said subsystem (S). subsystem (SA). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Method and device for monitoring a rotating machine from a vibration signal Technical field

[0001] The present invention relates to the field of monitoring mechanical systems. More particularly, the present invention relates to a method for monitoring a rotating machine, a monitoring device, a system, an aircraft, and an associated program. The present invention finds a particularly advantageous, although in no way limiting, application for the implementation of engine monitoring systems for aircraft. Prior art

[0002] The invention falls within the particular context of monitoring rotating machines by analyzing vibration signals. The vibration signals generated by a rotating machine advantageously make it possible to monitor the operation of the rotating machine. Indeed, these signals include a great deal of information on the faults that may affect the various mechanical parts of the rotating machine.

[0003] In this context, a monitoring system aims to detect, from a measured vibration signal, a defect in the rotating machine (e.g. damage to a part). Also, the reliability of such a monitoring system represents a major challenge for many applications such as aeronautics. However, monitoring a rotating machine by vibration analysis requires the use of a vibration signal comprising a multitude of contributions from different vibration sources.

[0004] In fact, a rotating machine (e.g. an aircraft engine) is composed of numerous subsystems comprising several rotating mechanical parts. The measured vibration signal thus includes the vibration contributions of each of the different parts of the rotating machine which, in addition, can interfere with each other. Random contributions linked to various noises can also be added to the measured vibration signal. Also, to monitor in particular the operation of a subsystem of interest of the rotating machine, it is necessary to extract the contribution of this subsystem from the vibration signal.

[0005] Existing solutions for separating sources in a vibration signal are divided into two categories. On the one hand, some solutions are based on an assumption of statistical independence between the different vibration sources to separate them from each other. For example, document CN102519582B illustrates such a solution using a component analysis. main ones. However, the strong correlations between the vibrational contributions of the different sources imply that the hypothesis of statistical independence is not verified, and make these solutions imprecise.

[0006] On the other hand, state-of-the-art solutions exploit the frequency components of the measured vibration signal to separate different vibration sources. Such a solution is for example presented in document CN105910701A. To separate the vibration sources, these solutions assume that the frequency components of the different sources are disjoint. However, this is not the case. The parts of a rotating machine interfere with each other and, as such, the vibration contributions of different parts include common frequency components. Thus, the assumption used by these solutions leads to errors in the estimation of the vibration contribution of a source of interest.

[0007] Ultimately, existing solutions do not allow the contribution of one of the vibration sources of a rotating machine to be accurately estimated. As a result, the reliability of existing solutions for detecting, by vibration analysis, a fault in a subsystem of a rotating machine is not fully satisfactory.

[0008] Therefore, there is a need for a monitoring solution that allows, from a vibration signal of a rotating machine, to reliably determine whether a subsystem of the rotating machine is defective. Statement of the invention

[0009] The present invention aims to remedy all or part of the drawbacks of the prior art, in particular those set out above.

[0010] According to one aspect of the invention, there is proposed a method for monitoring a rotating machine from a vibration signal, the rotating machine comprising a plurality of subsystems of rotating mechanical parts and the vibration signal comprising vibration contributions from the subsystems, the method comprising for at least one said subsystem steps consisting of: - estimate the vibrational contribution of said subsystem from a set of synchronous averages of the vibrational signal comprising: • first synchronous averages (of the vibration signal) associated with rotation frequencies of the parts of said subsystem; and • one or more second synchronous averages (of the vibration signal) associated with multiples of the rotation frequencies of the parts of said subsystem, these multiples being common to at least two parts of said subsystem; - determine whether said subsystem is defective by comparative analysis of a so-called health indicator corresponding to the estimated vibration contribution of said subsystem.

[0011] In the context of the invention, we designate, by "vibration signal", a signal representative of the vibration of the rotating machine monitored. For example, the vibration signal can be acquired via an accelerometer mounted on the rotating machine.

[0012] It should be noted that the rotation frequencies (i.e. rotation speeds) of the mechanical parts of the rotating machine can be defined absolutely (e.g. 10,000 rpm) or relatively to the rotation frequency of a reference shaft (e.g. 2xfref ). Hereinafter, the ratio between the rotation frequency of any part and the rotation frequency of the reference shaft is designated by the term "order".

[0013] Furthermore, by "multiple of a rotation frequency" we mean a product of the rotation frequency by an integer strictly greater than 1. A multiple of a rotation frequency is also referred to hereinafter as "harmonic". Furthermore, a multiple f is said to be common to two parts, the respective rotation frequencies of which are / } and / 2, if there are two integers £ and P greater than 1 such that / = k- f and f = p ■ f 2 + e, with < A a margin of error linked to a numerical approximation.

[0014] To estimate the vibration contribution of a subsystem of the rotating machine comprising several rotating mechanical parts, the present invention proposes to use the synchronous averages of the vibration signal respectively associated with the rotation frequencies of the parts of the subsystem - called first synchronous averages. Each of these synchronous averages makes it possible to extract the frequency components (i.e. the fundamental frequency and the harmonics) of the vibration contribution of one of the parts of the subsystem. Furthermore, it is proposed to use the synchronous averages of the vibration signal associated with multiples of the rotation frequencies (i.e. the harmonics, the orders) common to several parts of the subsystem - called second synchronous averages, which makes it possible to take into account the interferences between the vibration contributions of these parts.

[0015] Unlike the aforementioned existing solutions, the present invention is not based on an assumption of statistical independence between the vibration sources, nor on an assumption of disjoint frequency components between the vibration sources. In this sense, the proposed solution can be described as a non-parametric source separation solution and makes it possible to take into account interference between the parts of the rotating machine. Consequently, in comparison with existing solutions, the proposed solution makes it possible to estimate more precisely the vibration contribution of a subsystem of a rotating machine.

[0016] Thus, the proposed solution makes it possible to extract (i.e., to isolate), from the measured vibration signal, the vibration contribution of a subsystem of the rotating machine. As a result, the proposed solution makes it possible to reliably determine (in particular in terms of probability of correct detection and probability of false alarm) whether this subsystem is defective (e.g., includes a damaged part).

[0017] The present invention is particularly advantageous in that it makes it possible to detect a fault in the rotating machine early and, thus, to avoid the propagation of damage from one part to other parts of the rotating machine.

[0018] According to one embodiment, the monitoring method comprises, for each of the subsystems of the rotating machine, steps consisting of: estimating the vibration contribution of said subsystem from the acquired vibration signal; and determining whether said subsystem is defective by comparative analysis of a so-called health indicator corresponding to the estimated contribution of said subsystem.

[0019] This embodiment is particularly advantageous in that it allows each of the subsystems of the rotating machine to be individually monitored. If the rotating machine has a fault, this embodiment allows the defective subsystem(s) to be identified and suitable maintenance to be scheduled.

[0020] According to one embodiment, the vibrational contribution of said subsystem is estimated from a difference between: a sum of said first synchronous averages; and a sum of said one or more second synchronous averages.

[0021] In this embodiment, it is proposed to use the sum of said first synchronous averages of the vibration signal associated with the rotation frequencies of the parts of the subsystem. This sum makes it possible to extract the frequency components (i.e. the fundamental frequency and the harmonics) of the vibration contributions of the parts of the subsystem.

[0022] Furthermore, it is proposed to eliminate the replication of interference between the parts of the subsystem, by subtracting said second synchronous averages of the vibratory signal of the rotating machine associated with the common harmonics (i.e. with the common orders). Indeed, by summing the vibratory contributions of each of the parts of the subsystem, the frequency components common to several parts (characterizing the interference between these parts) are taken into account several times.

[0023] This embodiment makes it possible to precisely estimate the vibrational contribution of a subsystem of the vibrational signal of the rotating machine.

[0024] According to one embodiment, the estimated contribution of said subsystem is expressed by: / J. «), avec: “ indice T i cp^ff J, the smallest multiple frequency of f. and f; and m the average synchronous with the vibration signal x(u) associated with the frequency / , and defined by: / r \_ \ where N is a number of averaged samples of the mx \Jf M ~ n ( w - n ■ ivi j, vibration signal x(u), and Mf is a number of samples of the vibration signal x(u) for a period associated with the frequency f..

[0025] The synchronous average associated with (p^ff J, the smallest multiple frequency of the rotation frequencies f. and f. of two parts of the subsystem, allows to extract the common harmonics (i.e. common orders) to these two parts. These common harmonics are representative of the interferences between the vibrational contributions of these parts.

[0026] Therefore, according to this embodiment, the vibrational contribution of the subsystem is obtained by summing the vibrational contributions of each of the parts, then eliminating the replication of the interferences between them.

[0027] According to one embodiment, the monitoring method comprises, for at least one part of said subsystem, steps consisting of: - estimate the vibration contribution of said part from a set of synchronous averages of the estimated vibration contribution of said subsystem including: • a third synchronous average (of the estimated vibrational contribution of said subsystem) associated with a rotation frequency of said part; and • one or more fourth synchronous averages (of the estimated vibrational contribution of said subsystem) associated with multiples of the rotation frequency of said part, these multiples being common to said part and to at least one other part of said subsystem; - determining whether said part is defective by comparative analysis of a so-called health indicator corresponding to the estimated contribution of said part.

[0028] In this embodiment, to estimate the vibration contribution of one of the parts of the subsystem, it is proposed to use the synchronous average of the vibration signal associated with the rotation frequency of this part - called third synchronous average. This synchronous average makes it possible to extract the frequency components (i.e. the fundamental frequency and the harmonics) of the vibration contribution of the part considered.

[0029] Furthermore, it is proposed to use the synchronous averages of the vibration signal associated with multiples of the rotation frequency (i.e. the harmonics, the orders) common to the said part considered and to the other parts of the subsystem - called second synchronous averages. This allows for interference between the part in question and other parts of the subsystem to be taken into account.

[0030] This embodiment makes it possible to extract, from the vibration signal of the rotating machine, the exclusive contribution of one of the parts of a subsystem of the rotating machine and to reliably determine whether this part is defective.

[0031] According to one embodiment, the monitoring method comprises, for each of the parts of the subsystem, steps consisting of: estimating the vibration contribution of the part from the estimated vibration contribution of the subsystem; and determining whether the part is defective by comparative analysis of a so-called health indicator corresponding to the estimated contribution of said part.

[0032] This embodiment is particularly advantageous in that it allows each of the parts of the subsystem to be individually monitored. In this way, if the subsystem is defective, this embodiment allows the defective part(s) of the subsystem to be identified.

[0033] According to one embodiment, the vibrational contribution of said part is estimated from a difference between: said third synchronous average; and a sum of said one or more fourth synchronous averages.

[0034] In this embodiment, said third synchronous average associated with the rotation frequency of the part considered is used to extract the frequency components (i.e. the fundamental frequency and the harmonics) of the vibrational contribution of the part.

[0035] It is further proposed, in order to isolate the exclusive vibrational contribution of the part considered, to eliminate the interferences between the part considered and the other parts of the subsystem, and this by subtracting said fourth synchronous averages associated with common harmonics (i.e. common orders).

[0036] Thus, this embodiment makes it possible to precisely estimate the vibrational contribution of a part of a subsystem of the rotating machine from the vibrational contribution of the subsystem.

[0037] According to one embodiment, the estimated contribution of said part is expressed by: u} h)™* = “ time index or angular; fAp the rotation frequency of said part; FA, the rotation frequencies of the parts of said subsystem; ffl, the smallest multiple frequency Al' J j) of / and of fj; and mx yu), the synchronous average of the estimated vibrational contribution XA(ll) of said subsystem (SA) associated with the frequency f. and defined by: ( r \ IVW ( m \ where N is a number of averaged samples of mXA( f. u) = L^a\un- Mf.) the estimated vibration contribution xA(li), and Mf. is a number of samples of the estimated vibration contribution xA(ll) for a period associated with the frequency f..

[0038] The synchronous average associated with f / ■ \, the smallest multiple frequency of the P\J Ai' J j) rotation frequencies fAi and f allow the extraction of common harmonics (i.e. common orders) to the part considered and to another part of the subsystem and representative of the interferences between these two parts.

[0039] The exclusive vibrational contribution of the part considered is, according to this embodiment, obtained by: determining the vibrational contribution of the part considered (including interference with other parts); then eliminating interference with the other parts of the subsystem.

[0040] According to one embodiment, if a defect in a said subsystem is detected, the monitoring method comprises, for each of the parts of the subsystem, a step consisting of determining whether the part is defective by comparative analysis of a so-called health indicator corresponding to the estimated contribution of said part.

[0041] This embodiment is advantageous in that it makes it possible to precisely locate a fault in the rotating machine. Indeed, if a subsystem of the rotating machine is defective, this embodiment makes it possible to identify the part(s) of the subsystem exhibiting a fault.

[0042] According to one embodiment, a defect is detected if a quadratic mean of a said estimated contribution is greater than a threshold.

[0043] More specifically, a subsystem is determined to be defective if a quadratic mean of the estimated vibration contribution of said subsystem is greater than a threshold; and a part is determined to be defective if a quadratic mean of the estimated vibration contribution of said part is greater than a threshold.

[0044] According to this embodiment, a health indicator corresponding to an estimated vibration contribution of a subsystem or a part is a quadratic average of the estimated vibration contribution of the subsystem or the part. Thus, a defect is detected if this health indicator is greater than a threshold.

[0045] This embodiment makes it possible to reliably detect whether a subsystem or part has a defect by comparative analysis of a so-called health indicator corresponding to its estimated vibration contribution. Indeed, if a part or subsystem is defective, the defect will cause greater vibration.

[0046] According to one embodiment, the monitoring method comprises a step of angular resampling of the vibration signal by interpolation of the vibration signal with respect to a reference signal representative of the rotation of a reference shaft of the rotating machine. In particular, it should be noted that the rotations of the parts of said subsystem are linked to the rotation of the reference shaft.

[0047] The periodicity of the vibration signal of the rotating machine is intrinsically linked to the rotation of the rotating machine. In stationary operation, the rotation of the rotating machine is regular and the periodicity of the vibration signal is constant over time. However, in practice, the rotation speed of the rotating machine undergoes fluctuations. Also, if these fluctuations are not taken into account when analyzing the vibration signal, this may result in errors in the estimation of the vibration contribution of a subsystem or a part.

[0048] For this reason, it is proposed in this embodiment to resample the vibration signal by interpolating it with respect to the signal representative of the rotation of a reference shaft. This embodiment makes it possible to take into account the fluctuations in the rotation speed of the rotating machine when estimating a vibration contribution of a subsystem or a part.

[0049] This embodiment makes it possible to improve the accuracy of the estimation of a vibration contribution of a subsystem or a part from the vibration signal of the rotating machine.

[0050] According to one embodiment, the monitoring method comprises, if a fault in a subsystem is detected, a step consisting of providing an alarm signal comprising at least one identifier and the estimated vibration contribution of the faulty subsystem.

[0051] The alarm signal may further comprise: an identifier and the estimated vibration contribution of a defective part of said subsystem.

[0052] This embodiment makes it possible to signal the presence of a fault in the rotating machine and to identify the defective subsystem, and in particular the defective part. In addition, by providing the vibration contribution associated with the detected fault, this embodiment makes it easier to characterize the latter.

[0053] For example, the alarm signal may be provided to a restitution device comprising a screen, which makes it easier to characterize a defect affecting the subsystem or the part. Indeed, the vibration contribution of a damaged part may be representative of repetitive shocks, which may be easily identifiable on a screen.

[0054] Alternatively, it could also be envisaged to provide the alarm signal to a control device of the rotating machine.

[0055] According to one aspect of the invention, there is provided a device for monitoring a rotating machine from a vibration signal, the device comprising: - an estimation module configured to estimate the vibration contribution of a subsystem of the rotating machine from a set of averages synchronous vibration signal including: • first synchronous averages (of the vibration signal) associated with rotation frequencies of the parts of said subsystem; and • one or more second synchronous averages (of the vibration signal) associated with multiples of the rotation frequencies of the parts of said subsystem, these multiples being common to at least two parts of said subsystem; and - a fault detection module configured to determine whether a said subsystem is defective by comparative analysis of a so-called health indicator corresponding to the estimated contribution of said subsystem.

[0056] According to one embodiment, the monitoring device implements all or part of the steps of the proposed monitoring method.

[0057] According to one aspect of the invention, there is provided a monitoring system comprising: an acquisition device configured to acquire a vibration signal; and a monitoring device according to the invention.

[0058] The monitoring system may further comprise a restitution device comprising: a screen; and / or a loudspeaker. Such a restitution device is configured to restore an alarm signal provided by the monitoring device if a fault is detected.

[0059] According to one embodiment, the acquisition device comprises: an accelerometer; and / or a microphone. For example, the accelerometer may be mounted on a fixed part of the rotating machine being monitored, or the microphone may be placed near it.

[0060] The acquisition device may further comprise a tachometer making it possible to measure the rotation frequency of a reference shaft of the rotating machine.

[0061] According to one aspect of the invention, there is provided an aircraft comprising a rotating machine and a surveillance system according to the invention.

[0062] In the context of the invention, the term aircraft designates any device capable of rising and moving in the air, such as an airplane, a helicopter, a drone, etc.

[0063] According to one embodiment, the rotating machine is a combustion engine or an internal combustion engine.

[0064] According to one aspect of the invention, there is provided a computer program comprising instructions for implementing steps of a monitoring method according to the invention, when the computer program is executed by at least one processor or computer.

[0065] The computer program may be formed of one or more sub-parts stored in the same memory or in separate memories. The program may use any programming language, and be in the form of source code, code object, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0066] According to one aspect of the invention, there is provided a computer-readable information medium comprising a computer program according to the invention.

[0067] The information carrier may be any entity or device capable of storing the program. For example, the carrier may comprise a storage means, such as a non-volatile memory or ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a floppy disk or a hard disk. Furthermore, the storage medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by a telecommunications network or by a computer network or by other means. The program according to the invention may in particular be downloaded onto a computer network. Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

[0068] The proposed monitoring device, monitoring system, aircraft, computer program and information medium have the advantages described above in connection with the proposed monitoring method. Brief description of the drawings

[0069] Other characteristics and advantages of the present invention will emerge from the description provided below, illustrating embodiments of the invention given by way of example and without any limiting character, with reference to the attached drawings:

[0070] [Fig.l] represents an example of software and hardware architecture of an aircraft comprising a rotating machine and a monitoring system according to an embodiment of the invention;

[0071] [Fig.2] represents steps of a method for monitoring a rotating machine according to an embodiment of the invention;

[0072] [Fig.3A] and [Fig.3B] represent steps of a method for monitoring a rotating machine according to an embodiment of the invention; and

[0073] [Fig.4] represents an example of functional architecture of a device for monitoring a rotating machine according to an embodiment of the invention. Description of the embodiments

[0074] The present invention applies, in particular, to the monitoring of rotating machines on board aircraft. The following description of the invention will refer to this particular context, which is given only as an illustrative example and does not must not limit the invention, which applies to the monitoring of any rotating machine.

[0075] [Fig.l] represents an example of software and hardware architecture of an aircraft comprising a rotating machine and a monitoring system according to an embodiment of the invention.

[0076] The aircraft AC illustrated in [Fig.l] comprises: a rotating machine MAC; and a monitoring system SYS configured to monitor the operation of the rotating machine MAC.

[0077] The rotating machine MAC comprises: a plurality of subsystems SA-SB. Each of the subsystems SA-SB comprising a plurality of rotating mechanical parts LArL A2, LB1-LB2.

[0078] For information purposes, the rotating machine MAC may be a combustion engine (e.g. a turbojet), an internal combustion engine, a compressor, etc. A subsystem SA-SB may in particular be a gearbox, a gearbox of an airplane, or a rear reducer of a helicopter. And, the parts LAi-LA2 may for example belong to the following set of parts: a transmission shaft, an alternator, a toothed wheel, a bearing, or a blade.

[0079] For simplicity, only two two-part subsystems are illustrated in [Fig.l]. However, the present invention is, of course, applicable to any number of subsystems in the rotating machine and to any number of rotating parts in a subsystem.

[0080] It is important to emphasize that the rotating machine MAC is associated with a kinematics and that this kinematics defines the different frequencies (i.e. speeds) of rotation of the mechanical parts of the rotating machine MAC. Typically, the rotation frequencies of the parts of the rotating machine MAC are expressed in an integer number of revolutions per minute.

[0081] In particular, it should be noted that the rotations of the parts of the rotating machine MAC are linked to the rotation of a reference shaft of the rotating machine MAC. For this reason, the rotation frequencies of the parts can be defined relatively to the rotation frequency of the reference shaft. For example, / 41 ~ Lit ' / ref with: f 4P the rotation frequency of a part LAi; and / f, the rotation frequency of the reference shaft (in particular constant in stationary mode, and potentially variable in transient mode). In this case, we designate by the term "order" the ratio Lu between the rotation frequency / 41 of a part LAi and the rotation frequency / f of the reference shaft.

[0082] Thus, each part of the rotating machine MAC is characterized by a rotation frequency (i.e. speed). More particularly, when a rotating part has a defect, then the defect manifests itself within the SIG vibration signal at the rotation frequency of the part as well as at its harmonics (i.e. multiples of the rotation frequency). For example, if a gear wheel has a defect (e.g. a broken or damaged tooth), then the defect induces an increase in the vibration of the gear wheel observable at the rotation frequency of the gear wheel and at the harmonics.

[0083] However, it should be emphasized that certain harmonics may be common to several LAi-LA2 parts of a subsystem SA and thus characterize the interferences between the vibrational contributions of these LArLA2 parts. As an example, consider a subsystem SA comprising: a first LAi part whose rotation frequency is 2 / ; and a second LA2 part whose rotation frequency is 3 / . So, according to this example, the harmonics common to the vibrational contributions of the pieces A[ and A2 are the following: 6f, 12 / f, 18 / ... < Fÿ / 2; or, of equivalently, the common orders of the vibrational contributions of the pieces LA[ and LA2 are the following: 6, 12, 18, ... < Fs / 2f .

[0084] The monitoring system SYS comprises: an acquisition device SENS configured to acquire a vibration signal SIG from the rotating machine MAC; and a monitoring device APP configured to monitor the operation of the rotating machine MAC from the vibration signal SIG.

[0085] In the context of the invention, it may be envisaged to use the monitoring system SYS to monitor different types of rotating machines, for example on board an aircraft as illustrated in [Fig.l] or on a test bench.

[0086] More particularly, the monitoring device APP is configured to detect a fault in the rotating machine MAC (e.g. a damaged part). For this purpose, the monitoring device APP is configured to: take as input the vibration signal SIG of the rotating machine MAC; and if a fault is detected, provide as output an alarm signal ALM. The operation of the monitoring device APP is described in more detail below with reference to FIGS. 2 and 3A-3B.

[0087] According to the embodiment illustrated by [Fig.l], the monitoring system SYS further comprises a restitution device DISP configured to restore the alarm signal ALM provided by the monitoring device APP.

[0088] The SENS acquisition device is configured to acquire (i.e. measure) over a determined period a vibration signal SIG generated by the rotating machine MAC during its operation.

[0089] It should be emphasized that the measured vibration signal SIG includes the vibration contributions of the different parts LAi-LA2, LBi-LB2 of the rotating machine MAC and, in addition, random contributions linked to various noises, coming from for example from aerodynamic or electromagnetic sources.

[0090] In particular, the SENS acquisition device may comprise an accelerometer mounted on a fixed part, or a microphone placed close to the rotating machine MAC. However, in the context of the invention, it could be envisaged to use any type of signal acquired by a sensor and representative of the vibration of the rotating machine MAC during its operation.

[0091] The SENS acquisition device notably comprises an acquisition chain capable of digitizing (or even amplifying and filtering) the (analog) signal acquired by the accelerometer or the microphone.

[0092] Hereinafter we denote x(t) the digital SIG vibration signal available at the output of the SENS acquisition device. The signal x(t) is a time signal sampled with a sampling frequency Fs and the length of the signal x(t) depends on the duration of the measurement carried out by the SENS acquisition device.

[0093] According to one embodiment, the acquisition device SENS further comprises a tachometer for measuring the frequency (i.e. speed) of rotation of the reference shaft. The acquisition device SENS is thus configured to provide, to the monitoring device APP, a reference signal REF (also called tachometric signal) noted .^.^( / ) and representative of the rotation of the reference shaft. The reference signal REF can in particular be used to resample the vibration signal SIG as described below with reference to [Fig.2].

[0094] The DISP restitution device is configured to restore the ALM alarm signal provided by the APP monitoring device if a fault in the MAC rotating machine is detected.

[0095] According to one embodiment, the ALM alarm signal comprises at least one element among the following: an identifier of a defective subsystem; the vibration contribution associated with the defective subsystem; an identifier of a defective part; and the vibration contribution associated with the defective part.

[0096] The DISP restitution device may comprise a screen for displaying the identifier of the subsystem and / or the part having a defect and for viewing the vibration contribution associated with this defect. The DISP restitution device may further comprise a loudspeaker.

[0097] However, in the context of the invention, embodiments could also be envisaged according to which the monitoring device APP provides, if a fault is detected, an alarm signal ALM to a control device of the rotating machine MAC or of the aircraft AC.

[0098] The APP monitoring device comprises, according to the embodiment illustrated by [Fig.l]: at least one processing unit or processor PROC; and at least one MEM memory.

[0099] More particularly, the monitoring device APP has, according to one embodiment, the hardware architecture of a computer. As such, the monitoring device APP may comprise a processor PROC, a random access memory, a read-only memory MEM, and a non-volatile memory. The memory MEM associated with the device APP constitutes an information medium in accordance with the invention, readable by a computer and by the processor PROC, on which is recorded a computer program PROG in accordance with the invention. The computer program PROG comprises instructions for carrying out steps of a monitoring method in accordance with the invention and implemented by the monitoring device APP, when the computer program PROG is executed by the processor PROC.

[0100] The computer program PROG defines functional and software modules of the APP monitoring device described below with reference to [Fig.4].

[0101] As illustrated by [Fig. 1], according to one embodiment, the APP device has a communication module COM configured to communicate with the acquisition device SENS and / or the restitution device DISP. No limitation is attached to the nature of the communication interfaces between these devices, which may be wired or wireless, and may implement any protocol known to those skilled in the art.

[0102] [Fig.2] represents steps of a method for monitoring a rotating machine according to an embodiment of the invention. More specifically, this figure presents the operation of the APP monitoring device introduced with reference to [Fig.l].

[0103] As illustrated by [Fig.2], and according to one embodiment, the proposed monitoring method comprises at least one of the steps S100 to S400 described below and implemented by the proposed monitoring device APP.

[0104] In step S100, the monitoring device APP obtains the vibration signal SIG from the rotating machine MAC. In particular, step S100 comprises, according to one embodiment, at least one of the following steps S110 to S130.

[0105] In step SI 10, the monitoring device APP receives the vibration signal SIG, coming from the acquisition device SENS, and in particular via its communication module COM.

[0106] Alternatively, the monitoring device APP could, in step SI 10, read the vibration signal from a memory shared with the acquisition device SENS.

[0107] In step S120, the monitoring device APP obtains the reference signal REF (also called the tachometric signal) representative of the rotation of the reference shaft. For example, the monitoring device APP receives the reference signal REF, from the acquisition device SENS, and in particular via its COM communication module.

[0108] As previously mentioned, the reference signal REF can be acquired by a tachometer and thus represent the rotation of the reference shaft over time, and more particularly the frequency (i.e. speed) of rotation of the reference shaft.

[0109] In step S130, the monitoring device APP performs an angular resampling of the vibration signal x(t) by interpolating it with respect to the reference signal Tref(0'). The angular vibration signal thus obtained is noted x(3)-

[0110] The angular resampling is carried out as a function of the rotation of the reference shaft to take into account possible variations in the frequency (i.e. speed) of rotation of the rotating machine MAC during the acquisition time of the vibration signal x (t).

[0111] Since the proposed method can be applied to both a temporal or angular vibration signal, we hereinafter use the notation x(lt) to designate the temporal vibration signal x(t) or the angular vibration signal x(ff), 11 being a temporal index? or an angular index G.

[0112] In the context of the invention, embodiments could also be envisaged according to which the acquisition device SENS directly provides an angular vibration signal x(0) as output, for example by carrying out the acquisition of samples at a fixed angular pitch of the rotating machine MAC.

[0113] In step S200, the monitoring device APP, for at least one set of one or more parts of the rotating machine MAC, estimates the vibration contribution of the set of parts from the vibration signal SIG. In other words, the monitoring device APP carries out a separation of the vibration sources during this step.

[0114] Step S200 comprises at least one of steps S210 and S220. Note that the monitoring method may comprise one or more iterations of steps S200, S210 and S220.

[0115] In step S210, the monitoring device APP estimates, for at least one subsystem SA-SB of the rotating machine MAC, the vibration contribution SIGA of the subsystem SA from the vibration signal SIG. The implementation of the estimation carried out in step S210 is described in more detail with reference to [Fig.3A].

[0116] In particular, according to one embodiment, the monitoring device APP estimates the vibration contribution of each of the SA-SB subsystems of the rotating machine MAC.

[0117] In step S220, the monitoring device APP estimates, for at least one part LAi of a subsystem SA, the vibration contribution SIGA[ of the part LAi from the estimated vibration contribution SIGA of the subsystem SA. The implementation of the estimation carried out in step S220 is described in more detail with reference to [Fig.3B].

[0118] According to one embodiment, the monitoring device APP estimates the vibration contribution SIGAi-SIGA2 of each of the parts LArLA2 of a subsystem SA. In addition, the monitoring device APP can estimate the vibration contribution of each of the parts LArLA2, LBi-Lb2 of each of the subsystems SA-SB of the rotating machine MAC.

[0119] It should be emphasized that the APP monitoring device uses the kinematics F a-Fb of the rotating machine MAC to estimate the vibration contribution of a subsystem SA and / or a part LAb. In particular, this kinematics FA-FB defines the different rotation frequencies (absolutely or relatively) of the mechanical parts of the rotating machine MAC.

[0120] In step S300, the monitoring device APP determines whether the rotating machine MAC is defective. In other words, the monitoring device APP detects during this step the presence of a defect in the rotating machine MAC (e.g., a damaged part). For this purpose, step S300 comprises at least one of steps S310 and S320.

[0121] In step S310, the monitoring device APP determines, for at least one subsystem SA of the rotating machine MAC, whether the subsystem SA is defective by comparative analysis of the health indicator corresponding to the estimated vibration contribution SIGA of the subsystem SA.

[0122] According to one embodiment, to detect a fault in a subsystem SA, the monitoring device APP determines, from the estimated contribution SIGA of the subsystem SA, at least one health indicator representative of the presence of a fault in the subsystem SA and compares said at least one health indicator to a threshold.

[0123] For example, a health indicator that can be used is the root mean square (or "Root Mean Square" in English) of the vibration contribution. Indeed, the vibration of a damaged part is greater. For this reason, and according to one embodiment, the monitoring device APP determines that a subsystem SA is defective if the root mean square (over a given number of samples L) of the estimated vibration contribution SIGA of the subsystem SA is greater than a threshold, e'g' -O2 >

[0124] Alternatively, the APP monitoring device could use, as health indicators, the kurtosis and / or the coefficient of asymmetry (“skewness” in English) of the estimated vibration contribution SIGA (on a given number of samples). However, no limitation is attached to the nature of the health indicators used by the APP monitoring device.

[0125] According to one embodiment, the monitoring device APP determines, for each of the subsystems SA-SB of the rotating machine MAC, whether this subsystem SA, SB is defective.

[0126] According to one embodiment, if (and only if) a fault of the subsystem SA is detected in step S310, the monitoring device APP implements step S320. In other words, the detection of a fault of a subsystem SA triggers the implementation of step S320.

[0127] In step S320, the monitoring device APP determines, for at least one part LAi of a subsystem SA, whether the part LAi is defective by comparative analysis of the health indicator corresponding to the estimated vibration contribution SIGA[ of the part LAb

[0128] According to one embodiment, to detect a defect in a part LAi, the monitoring device APP determines, from the estimated vibration contribution SIGA[, at least one so-called health indicator representative of the presence of a defect in the part LAi and compares said at least one health indicator to a threshold.

[0129] In particular, the monitoring device APP can detect a defect of a part by using a health indicator based on the quadratic mean as described above. However, in the context of the invention, embodiments could also be envisaged in which different health indicators are used depending on the part analyzed during step S320.

[0130] According to one embodiment, the monitoring device APP determines, for each of the parts LArLA2 of a subsystem SA, whether this part LAb LA2 is defective, in particular if a defect of the subsystem SA is detected in step S310.

[0131] According to one embodiment, the monitoring device APP determines, for each of the parts LArLA2, LBi-LB2 of the rotating machine MAC, whether this part is defective.

[0132] In step S400, if a fault of the rotating machine MAC is detected in step S300, the monitoring device APP provides at least one alarm signal ALM.

[0133] According to one embodiment, if a defect of a subsystem SA is detected in step S310, said at least one alarm signal ALM comprises: an identifier of the defective subsystem SA; and the vibration contribution SIGA of the defective subsystem SA. Furthermore, according to one embodiment, if a defect of a part LAi of a subsystem SA is detected in step S320, said at least one alarm signal ALM comprises: an identifier of the defective part LAi; and the vibration contribution SIG A of the defective part LAb

[0134] Preferably, the ALM alarm signal comprises: an identifier of the subsystem and the vibration contribution SIGA of the defective subsystem SA; and an identifier and the vibration contribution SIGA of the defective part LAp In this sense, the ALM alarm signal can be described as a two-level alarm signal, with a subsystem level and a part level.

[0135] As previously described, and according to one embodiment, the monitoring device APP transmits the alarm signal ALM to the restitution device DISP, in particular via its communication module COM.

[0136] In addition, according to one embodiment, the APP monitoring device outputs the health indicators determined during steps S310 and S320.

[0137] [Fig.3A] represents steps of a method for monitoring a rotating machine according to an embodiment of the invention. This figure details step S210 of estimating the vibration contribution SIGA of a subsystem SA from the vibration signal SIG.

[0138] We recall here that, to separate the different sources of vibrations, the monitoring device APP uses the kinematics of the rotating machine MAC and that this kinematics defines the different frequencies (i.e. speeds) of rotation of the mechanical parts of the rotating machine MAC. In particular, we denote FA the set of rotation frequencies FAi-FA2 of the parts LAi-LA2 of a subsystem SA.

[0139] Furthermore, the rotation frequencies FAi-FA2 of the parts LAi-LA2 can be defined in a relative manner with respect to the rotation frequency of a machine reference shaft. For example, fAi = iA\ ■ ff with: f AV the rotation frequency FA[ of a part LAi; and / f, the rotation frequency of the reference shaft; and said order associated with the part LAp

[0140] In step S210, the monitoring device APP estimates, for at least one subsystem SA of the rotating machine MAC, the vibration contribution SIGA of the subsystem SA from the vibration signal SIG. To do this, according to the embodiment illustrated by [Fig.3A], step S210 comprises at least one of steps S211 to S213.

[0141] In step S211, the monitoring device APP determines a signal sA(li) associated with the subsystem SA considered and expressed by: sA(u)= u), Eq. ( 1 )

[0142] with the synchronous average of the vibration signal x(u) associated with the frequency / . defined by: mx ( f ? u) =~ ( u - n ■ Mft ), Eq. (2)

[0143] where N is a number of averaged samples (i.e. a number of averaged sections) of the SIG vibration signal, and Mf. is the number of samples of the SIG vibration signal per period associated with the frequency / For example, the number of samples Mf.~ FJ f., with Fs the sampling frequency of the SIG vibration signal.

[0144] In the above expression, the synchronous averages MArMA2 make it possible to extract the frequency components (i.e. the fundamental frequency and the harmonics) of

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] the vibration contribution of each of the LAi-LA2 parts of the SA subsystem. However, it should be emphasized that certain frequency components are common to several LArLA2 parts of the SA subsystem, thus characterizing the interference between these parts as previously discussed. Thus, by summing the vibration contributions of each of the LArLA2 parts of the SA subsystem as described in equation 1, the frequency components common to several parts are taken into account several times. In other words, the interferences between the LArLA2 parts of the SA subsystem are replicated. Therefore, the signal sA(Ü) obtained includes: the vibrational contribution of the sub- SA system considered; and the replication of interference between the LArLA2 parts of the SA subsystem. In step S212, the monitoring device APP determines a signal rA(u) in using the following expression: rA(u)^ Eq- (3) with (p^ f / J ' the Smallest multiple frequency of f. and f.. More precisely, We have : f, with k an integer greater than 1; and I i with P an integer greater than 1 and |g| < A a margin of error linked to a numerical approximation. The synchronous average MA,A2 associated with the smallest frequency (or order) multiple of the rotation frequencies FAi and FA2 of two parts LAi and LA2 of the subsystem SA makes it possible to extract the frequency components common to the two parts LA[ and LA2. In fact, the rA(u) signal is representative of the interference between the LArLA2 parts of the SA subsystem. Typically, for LArLA2 parts of an SA subsystem, the values I ff \ if cF fc= r \ are stored in a matrix called orders common. As shown in equation 3, only the values are used such that the common order matrix is ​​an upper triangular matrix. When the LArLA2 parts of an SA subsystem are mechanically linked to the reference shaft by means of one or more gears, the values f )} Can be obtained (especially analytically) by the number of teeth of the LArLA2 parts of the SA subsystem and by the rotation frequency of the reference shaft / y ret

[0153] Alternatively, for two parts LAi and LA2 of a subsystem SA, the value ff) Can be determined by the rotation frequencies / A1 and f A2 of the parts using a numerical search algorithm.

[0154] In step S213, the monitoring device APP estimates the vibration contribution SIGA of the subsystem SA denoted XA(li) using the following expression: xA(u) = sA(u)-rA(u), Eq. (4).

[0155] We recall here that the signal sA(li) includes both the vibrational contribution of the SA subsystem considered and the replication of the interferences between the parts LArLA2 of the SA subsystem. Thus, by eliminating from the signal sA(li) the replication of the interferences r4(u), an estimate of the vibrational contribution SIGA of the SA subsystem considered is obtained.

[0156] The vibration contribution SIGA of the SA subsystem is then used in step S310 to determine whether the SA subsystem considered is defective.

[0157] [Fig.3B] represents steps of a method for monitoring a rotating machine according to an embodiment of the invention. This figure details in particular step S220 of estimating the vibration contribution of a part LAi from the vibration contribution of a SIGA subsystem.

[0158] In step S220, the monitoring device APP estimates, for at least one part LAi of a subsystem SA of the rotating machine MAC, the vibration contribution SIGAi of the part LA[ from the estimated vibration contribution SIGA of the subsystem SA. For this purpose, according to the embodiment illustrated by [Fig.3B], step S220 comprises at least one of steps S221 to S223.

[0159] In step S221, the monitoring device APP determines a signal 5'A1(w) associated with the part LA[ considered and expressed by: SA}(ll) = Ecl- (5)' x ni /

[0160] with: f AV the rotation frequency of the part LAi; and the average synchronous NA[ of the vibrational contribution XA(u) of said subsystem associated with the frequency fM and defined by: Eq. (6).

[0161] The synchronous average NAi makes it possible to extract the frequency components of the vibration contribution of the part LAp. However, certain frequency components are common to the part LAi and to other parts LA2 of the subsystem SA, thus characterizing the interference between these parts.

[0162] In fact, the signal sA ^Û) obtained includes: the vibrational contribution of the part LAi considered; and the interferences between the part LAi and the other parts of the subsystem Its-

[0163] In step S222, the monitoring device APP determines a signal r^ll) representative of the interference between the part LAi considered and the other parts of the subsystem SA. The signal rA£u) is obtained by using the following expression: rAI(u) = Eq. (7).

[0164] with ff , the smallest frequency multiple of and of f ..

[0165] The synchronous mean NAi,a2 associated with the smallest multiple frequency of the rotation frequencies FAi and FA2 of the part LAi and another part LA2 of the subsystem SA makes it possible to extract the frequency components common to the two parts LAi and LA2. Thus, the signal () makes it possible to describe the interferences between the part LAi considered and the other parts LA2 of the subsystem SA.

[0166] In step S223, the monitoring device APP estimates the vibration contribution SIGai of the part LAi noted ,^(^) using the following expression: XaM =sAi(u) -rAi(u), Eq. (8).

[0167] As mentioned above, the signal 54j(w) makes it possible to extract the frequency components of the vibration contribution of the part LAb but some of these frequency components are common to the part LAi and to other parts LA2 of the subsystem SA. For this reason, it is proposed here to eliminate the interference from the signal which makes it possible to isolate the exclusive vibration contribution SIGAi of the part LAi considered.

[0168] The vibration contribution SIGAi of the part LAi is then used in step S320 to determine whether the part LAi considered is defective.

[0169] According to one embodiment, if a defect in the part LAi considered is detected, the monitoring device APP uses the signal f4[(m) representative of the interferences to determine whether the defect propagates (i.e. emerges) on other parts LA2 of the subsystem SA. For this purpose, the monitoring device APP determines at least one health indicator for the signal rAi(u) and compares said at least one health indicator to a threshold.

[0170] [Fig.4] represents an example of functional architecture of a device for monitoring a rotating machine according to an embodiment of the invention.

[0171] Generally, the APP monitoring device comprises modules respectively configured to implement each of the steps of a monitoring method according to the invention.

[0172] In particular, and as illustrated by [Fig.4], the proposed APP monitoring device comprises, according to one embodiment, at least one of the following modules: - an Ml00 obtaining module configured to obtain a SIG vibration signal from the rotating machine, comprising in particular: • a resampling module Ml30 configured to carry out an angular resampling S130 of the SIG vibration signal by interpolation of the SIG vibration signal with respect to the reference signal REF representative of the rotation of a reference shaft; - an M200 estimation module configured to estimate the vibration contribution of a set of one or more parts of the MAC rotating machine from the SIG vibration signal, comprising at least one of the following modules: • a vibration estimation module of an M210 subsystem configured to estimate the SIGA vibration contribution of an SA-SB subsystem of the MAC rotating machine from the SIG vibration signal; and • a vibration estimation module of a part M220 configured to estimate the vibration contribution SIGAi of a part LA[ of a subsystem SA of the rotating machine MAC from the vibration contribution SIGA of the subsystem SA; - a fault detection module M300 configured to detect a fault in the rotating machine MAC, comprising at least one of the following modules: • a fault detection module of a subsystem M310 configured to determine whether a subsystem SA-SB of the rotating machine MAC is defective by comparative analysis of the health indicator corresponding to the estimated vibration contribution SIGA-SIGB of the subsystem SA-SB; and • a part defect detection module M320 configured to determine whether a part LArLA2 of a subsystem SA of the rotating machine MAC is defective by comparative analysis of the health indicator corresponding to the estimated vibration contribution SIGAi-SIGA2 of the part LArLA2; and - an M400 supply module configured to provide one or more ALM alarm signals if a fault in the MAC rotating machine is detected.

[0173] The term module can correspond to a software component as well as to a hardware component or a set of hardware and software components, a software component itself corresponding to one or more computer programs or sub-programs or more generally to any element of a program capable of implementing a function or a set of functions as described for the modules concerned. In the same way, a hardware component corresponds to any element of a hardware assembly capable of implementing a function or set of functions for the module concerned (integrated circuit, smart card, memory card, etc.).

[0174] It should be noted that the order in which the steps of a method according to the invention are carried out, in particular with reference to the attached drawings, constitutes only an example of embodiment without any limiting character, variants being possible. In particular, a method according to the invention may comprise one or more iterations of the steps described above, in particular with reference to the attached drawings. Furthermore, the reference signs are not limiting of the scope of the protection, their sole function being to facilitate the understanding of the claims.

Claims

Claims

1. Method for monitoring a rotating machine (MAC) from a vibration signal (SIG), the rotating machine (MAC) comprising a plurality of subsystems (SA-SB) of rotating mechanical parts (LAi -LA2, LBi-Lb2) and the vibration signal (SIG) comprising vibration contributions of the subsystems (SA-SB), the method comprising for at least one said subsystem (SA) steps consisting of: - estimating (S210) the vibration contribution of said subsystem (SA) from a set of synchronous averages of the vibration signal (SIG) comprising: • first synchronous averages (MArMA2) associated with rotation frequencies (FArFA2) of the parts of said subsystem (LArLA2); and • one or more second synchronous averages (MA[jA2) associated with multiples of the rotation frequencies (FArFA2) of the parts of said subsystem (LAi -LA2), these multiples being common to at least two parts of said subsystem (LArLA2);and to - determine (S310) whether said subsystem (SA) is defective by comparative analysis of a so-called health indicator corresponding to the estimated vibration contribution (SIGA) of said subsystem (SA).;

2. Method according to claim 1, wherein the vibration contribution (SIGA) of said subsystem (SA) is estimated (S310) from a difference between: a sum of said first synchronous averages (MArMA2); and a sum of said one or more second synchronous averages (MAijA2).

3. Method according to claim 2, in which the estimated contribution (SIGA) of said subsystem (SA) is expressed by: xA(li) = mjj m), with: “ l ' ' ' l ' f -1 Z- . f \ \ [ If J a temporal or angular index; FA, the rotation frequencies (FArFA2 ) of the parts (LArLA2) of said subsystem (SA) (pi ff J, the smallest multiple frequency of / . and of fj; and f the synchronous average of the vibration signal x(u) associated with the frequency f. and defined by: mx ( f. U ) = 77 ( u - n ■ Mf. ), where N is a number of averaged samples, and Mf is a number of samples for a period associated with the frequency

4. Method according to one of claims 1 to 3, comprising for at least one part (LAi) of said subsystem (SA) steps consisting in: - estimating (S220) the vibration contribution (SIGA[) of said part (LAi) from a set of synchronous averages of the estimated vibration contribution (SIGA) of said subsystem (SA) comprising: • a third synchronous average (NAi) associated with a rotation frequency (FAi) of said part (LAi); and • one or more fourth synchronous averages (N AijA2) associated with multiples of the rotation frequency (FAi) of said part (LA[), these multiples being common to said part (LAi) and to at least one other part (LA2) of said subsystem (SA); and to - determine (S320) whether said part (LAi) is defective by comparative analysis of a so-called health indicator corresponding to the estimated contribution (SIGA[) of said part (LAi).

5. Method according to claim 4, in which the vibration contribution (SIGAi) of said part (LAi) is estimated (S220) from a difference between: said third synchronous average (NAi); and a sum of said one or more fourth synchronous averages (NAi>A2).

6. Method according to claim 5, in which the estimated contribution (SIGAi) of said part (LAi) is expressed by: / \ with: u, a temporal or angular index uw); fla rotation frequency of said part (LAi); FA, the rotation frequencies (FArFA2) of the parts of said subsystem (LArLA2); ff 1, the smallest multiple frequency of / .. and f.; and mi M y\, the synchronous average of the vibration contribution x^ll) of said subsystem (SA) associated with the frequency f. and defined by: ( f? 11 ) = (un- Mf. ), where N is a number of averaged samples, and Mf is a number of samples for a period associated with the frequency

7. Method according to one of claims 4 to 6, in which if a defect of a said subsystem (SA) is detected (S310), the method comprises for each of the parts (LArLA2) of the subsystem a step (S320) consisting of: determining whether said part (LAi) is defective by comparative analysis of a so-called health indicator corresponding to the estimated contribution (SIGA[) of said part.

8. Method according to one of claims 1 to 7, comprising a step of angular resampling (S 130) of the vibration signal (SIG) by interpolation of the vibration signal with respect to a reference signal (REF) representative of the rotation of a reference shaft of the rotating machine (MAC).

9. Method according to one of claims 1 to 8, comprising, if a fault of a said subsystem (SA) is detected (S310), a step consisting of providing (S400) an alarm signal (ALM) comprising at least one identifier and the estimated contribution (SIGA) of the faulty subsystem (SA).

10. Device for monitoring a rotating machine (MAC) from a vibration signal (SIG), the device (APP) comprising: - an estimation module (M210) configured to estimate the vibration contribution of a subsystem (SA) of the rotating machine (MAC) from a set of synchronous averages of the vibration signal (SIG) comprising: • first synchronous averages (MArMA2) associated with rotation frequencies (FArFA2) of the parts of said subsystem (LArLA2); and • one or more second synchronous averages (MA[jA2) associated with multiples of the rotation frequencies (FAi-FA2) of the parts of said subsystem (LAi -LA2), these multiples being common to at least two parts of said subsystem (LArLA2); and - a fault detection module (M310) configured to determine whether a said subsystem (SA) is defective by analysis comparative of a so-called health indicator corresponding to the estimated contribution (SIGA) of said subsystem (SA).

11. Monitoring system (SYS) comprising an acquisition device (SENS) configured to acquire a vibration signal (SIG) and a monitoring device (APP) according to claim 10.

12. System (SYS) according to claim 11, wherein the acquisition device (SENS) comprises an accelerometer or a microphone.

13. Aircraft (AC) comprising a rotating machine (MAC) and a surveillance system (SYS) according to claim 11 or 12.

14. Aircraft (AC) according to claim 13, wherein the rotating machine (MAC) is a combustion engine or an internal combustion engine.

15. Computer program (PROG) comprising instructions for implementing steps (S100-S400) of a monitoring method according to any one of claims 1 to 9, when said computer program (PROG) is executed by at least one processor (PROC).

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