Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
  • G01M5/0066—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by exciting or detecting vibration or acceleration
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M15/00—Testing of engines
  • G01M15/14—Testing gas-turbine engines or jet-propulsion engines
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
  • G01M5/0016—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings of aircraft wings or blades
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M7/00—Vibration-testing of structures; Shock-testing of structures

Definitions

• the present invention belongs to the general field of monitoring the operation, and therefore the state of health, turbomachines. It relates more particularly to a method for monitoring a turbomachine by analyzing vibration signals. It also relates to a monitoring device configured to implement said monitoring method.
• the invention finds a particularly advantageous application, although in no way limiting, in the application field of aeronautics, more particularly in the context of monitoring the operation of a turbomachine equipping an aircraft.
• Turbomachines are used in a wide variety of applications, such as for example transport (in particular transport by air), civil engineering, industrial production, energy, etc. They are designed to transform the kinetic energy of a fluid into mechanical energy (and vice versa) so as to fulfill different functions (turbines, pumps, compressors, turbochargers, etc.).
• a turbomachine conventionally comprises a rotating assembly called a "rotor” (i.e. a wheel mounted on a shaft), this rotating assembly being coupled, via bearings (with rolling bearings for example), to a fixed casing called the “stator”.
• the rotor (as well as possibly the stator) is equipped with blades (also called “vanes”) distributed over one or more circumferential lines. These blades, like any mechanical structure, are subject to vibration when excited.
• the sources of excitation can be diverse: rotary forces intrinsic to the operation of the turbomachine, mechanical defect of the blade, excitation of origin external to the turbomachine (for example an aerodynamic excitation such as turbulence), etc.
• the blade As a mechanical structure, responds to these excitations, which generates stresses that can lead to its damage, or even to its rupture (destruction). Such consequences are of course harmful for the blade in question, but also potentially for the entire turbomachine.
• the strain gauge sensor affects the modal characteristics thereof, which can induce an error in the analysis of the vibration behavior of the blade,
• BTT a non-intrusive technique
• This BTT technique consists, for a speed regime, in measuring the real instants of passage of a blade in front of a fixed proximity sensor (typically arranged on the stator) and in comparing these instants with reference instants obtained for a blade of the same type not subject to vibration (for example a sound blade, that is to say a blade not showing any mechanical defect).
• reference instants can for example be obtained theoretically by digital simulation or even further to tests carried out beforehand (for example on a test bench).
• the BTT technique is nonetheless deficient in certain aspects. Indeed, given its principle of implementation, it makes it possible to obtain only one sample of the vibratory deformation (ie only one evaluation of deflection) per revolution of the blade and per sensor. Consequently, and in practice, the temporal deflection signal generated over time, due to the successive rotations of the blade, is very strongly under-sampled (the average sampling frequency of the deflection signal is equal to the rotor rotation frequency multiplied by the number of sensors used). This is detrimental to the precision of the evaluation of the vibratory behavior of the blade, and therefore ultimately to the monitoring of the operation of the turbomachine.
• the present invention aims to remedy all or part of the drawbacks of the prior art, in particular those set out above, by proposing a solution which makes it possible to monitor the vibratory behavior of the blades of a turbomachine in a more efficient than the solutions of the prior art.
• the invention relates to a method for monitoring a turbomachine, said method comprising, for at least one blade of a rotor equipping the turbomachine, steps of:
• the response time of said at least one proximity sensor (also known as the "rise time") is sufficiently low, for example of the order of a thousandth of a second at most, so that said at least one acquired time signal translates the progressive rise/fall of the physical quantity measured by said at least one proximity sensor.
• the response time of said at least one proximity sensor is here sufficiently low to prevent said at least one acquired time signal from taking on the appearance of a square wave (slot).
• a square signal (corresponding in fine to an “all or nothing” signal) does not in fact make it possible to represent the progressiveness of the passage of said at least one blade in front of said at least one proximity sensor. Consequently, such a square signal does not make it possible to obtain information on a possible offset between the dynamics of said at least one blade and that of a reference blade of the same type.
• the monitoring method according to the invention therefore advantageously differs from the state of the art, and more particularly from the BTT method, in that it proposes to combine at least one proximity sensor characterized by a time low response with the obtaining of a plurality of samples of said at least one acquired time signal.
• This combination in fact makes it possible to have samples that are distinct from each other since said at least one acquired signal has a bell-shaped profile and not a square-shaped profile.
• the fact of being able to transcribe the progressiveness of the passage of said at least one blade in front of said at least one proximity sensor advantageously makes it possible to obtain samples whose values, distinct from each other, make it possible to finely characterize the vibratory behavior of said at least one blade, by accurately calculating said deflection values. This then results in great precision in the evaluation of parameters (frequency, amplitude, phase) of the acquired time signal.
• the acquired signal was a square signal, as is the case in the BTT method, then it would be necessary to be satisfied with a single and unique sample since all the values taken on the upper part of the slot would be identical. between them.
• the number of proximity sensors is less than or equal to three.
• the monitoring method may also comprise one or more of the following characteristics, taken in isolation or in all technically possible combinations.
• said method further comprises a step of calculating, from samples of said at least time signal, a quantity characterizing the duration of the passage of said at least one blade in front of said at least one proximity sensor, the monitoring step also being performed using said quantity.
• Said quantity relating to the passage time forms an indicator of the vibratory behavior of said at least one blade. Indeed, in the event of vibration in said at least one acquired time signal, it provides information on the direction of the vibratory displacement at the moment when said at least one blade passes in front of said at least one sensor. Therefore, if the passage time is small compared to that obtained theoretically for a reference signal, this means that the vibratory movement of said at least one blade is in the same direction as the rotation of the rotor (and vice versa, in the opposite direction, if the passage time is long compared to that of the reference signal).
• said method further comprising a step of calculating a quantity characterizing an advance or a delay of said at least one time signal with respect to a reference signal representative of a passage in front of said at least one blade proximity sensor not undergoing vibration and of the same type as said at least one blade from which said at least one time signal was acquired, the calculation of said quantity being implemented at from samples of said at least one time signal as well as said reference signal, and the monitoring step also being performed using said quantity.
• Said quantity relating to the advance or delay of said at least one time signal also forms an indicator of the vibratory behavior of said at least one blade. Indeed, if this indicator is positive, this means that said at least one blade arrived earlier (i.e. ahead) in said at least one time signal acquired than in a reference signal.
• said two quantities make it possible to obtain information on the overall speed of said at least one blade (speed of rotation and speed of vibration) as well as on the position of said at least one blade in the vibration cycle.
• the difference between said calculated deflections and said approximation signal is evaluated by means of a norm Ip, p being a strictly positive real.
• the index p of the standard Ip is strictly between 0 and 2.
• the minimization of the cost function includes the execution of an iteratively reweighted least squares algorithm.
• said at least one sensor is an optical sensor.
• a plurality of analog time signals are acquired due to a plurality of passages of said at least one blade in front of each proximity sensor.
• the inventors have found that the fact of considering a plurality of turns of the rotor (and therefore a plurality of passages of said at least one blade in front of the same proximity sensor) was advantageous in that it makes it possible to estimate with great precision the amplitudes of the frequencies retained for the approximation signal, and therefore ultimately the vibration frequencies of said at least one blade.
• the invention relates to a computer program comprising instructions for the implementation of a monitoring method according to the invention when said computer program is executed by a computer.
• This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in no any other desirable shape.
• the invention relates to an information or recording medium readable by a computer on which is recorded a computer program according to the invention.
• the information or recording medium can be any entity or device capable of storing the program.
• the medium may include a storage medium, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or even a magnetic recording medium, for example a diskette (floppy disk) or a disk hard.
• the information or recording medium can be a transmissible medium such as an electrical or optical signal, which can be conveyed via an electrical or optical cable, by radio or by other means.
• the program according to the invention can in particular be downloaded from an Internet-type network.
• the information or recording medium 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.
• the invention relates to a device for monitoring a turbomachine, said device comprising:
• an obtaining module configured to obtain a plurality of samples of at least one analog time signal acquired by means of at least one fixed proximity sensor and representative of a passage of at least one blade of a rotor equipping the turbomachine in front of said at least one proximity sensor, said at least one proximity sensor being characterized by a response time adapted to the fact that the time signal is representative of the progressive appearance and disappearance of said at least one blade during its passage,
• a calculation module configured to calculate a deflection of said at least one blade for each of said samples
• a determination module configured to determine, in the form of a linear combination of sinusoidal signals, a signal, called "approximation signal", minimizing a cost function evaluating a difference between said calculated deflections and said approximation signal,
• a monitoring module configured to monitor the vibratory behavior of said at least one blade from frequencies and/or amplitudes and/or phases of the sinusoidal signals forming said approximation signal.
• the invention relates to a turbomachine monitoring system, said system comprising acquisition means comprising at least one fixed proximity sensor and configured to:
• At least proximity sensor acquiring at least one analog time signal representative of a passage of at least one blade of a rotor equipping the turbomachine in front of said at least one proximity sensor, said at least proximity sensor being characterized by a response time adapted to that the time signal is representative of the progressive appearance and disappearance of said at least one blade during its passage in front of said sensor,
• the invention relates to an aircraft comprising a turbine engine equipped with a rotor provided with blades as well as a monitoring system according to the invention.
• FIG. 1 schematically represents, in its environment, an embodiment of a monitoring system according to the invention, said system being configured to monitor the operation of a turbine engine equipped with a rotor;
• FIG. 2 is a graph showing an example of an analog time signal acquired using a proximity sensor and following the passage of a blade of the rotor in front of said proximity sensor;
• FIG. 3 schematically represents an example of hardware architecture of a monitoring device belonging to the surveillance system of FIG. 1;
• FIG. 4 represents, in the form of a flowchart, the main steps of a monitoring method according to the invention, as they are implemented by the surveillance system of FIG. 1;
• FIG. 5 is a graph representing an example of a shift between, on the one hand, an analog time signal acquired using a proximity sensor and following the passage of a blade of the rotor in front, and on the other hand a signal reference ;
• FIG. 6 figure 6 schematically represents a particular mode of implementation of the monitoring method of figure 4.
• the present invention finds its place in the field of monitoring the operation of a turbomachine.
• turbomachine of the turbojet type fitted to an aircraft such as for example a civil aircraft capable of transporting passengers
• aircraft such as for example a civil aircraft capable of transporting passengers
• the invention remains applicable, with regard to the field of aeronautics, whatever the type of turbomachine considered (turboengine, a turbofan, etc.), as well as for any type of aircraft ( plane, helicopter, etc.).
• the invention can be applied to any type of turbomachine, regardless of the industrial field for which this turbomachine is intended to be operated.
• FIG. 1 schematically shows, in its environment, an embodiment of a monitoring system 10 according to the invention.
• said monitoring system 10 is implemented in the aircraft, for example integrated into the full authority regulation system commonly referred to as FADEC (acronym of the English expression "Full Automatic Digital Engine Control) regulating the operation of the turbomachine.
• FADEC full authority regulation system
• no limitation is attached to the location of said surveillance system 10 within the aircraft.
• Said monitoring system 10 is configured to determine, when the turbomachine is in operation, one or more quantities characteristic of the vibratory behavior of one or more blades equipping the rotor of said turbomachine.
• the fact of determining such quantities amounts in particular to carrying out, when the turbomachine is in operation, a modal analysis of said blade or blades, thus making it possible to monitor the appearance and/or degradation of pre-existing faults.
• the monitoring system 10 comprises acquisition means 11 configured to acquire at least one analog time signal representative of a passage of at least one blade of the rotor in front of at least one proximity sensor (again known as the “presence detector”).
• the number of proximity sensors is less than or equal to three.
• two proximity sensors belong to the acquisition means 11 and are distributed circumferentially so as to be spaced apart by 95° counterclockwise.
• the acquisition means 11 comprise a single proximity sensor CAP.
• the invention is now described for a single given PAL blade of the turbine engine rotor. It is nevertheless important to note that all of the technical considerations described below can be applied without distinction to each of the blades of the rotor. It emerges from these wording choices that the expression "at least one analogue time signal acquired” refers to the signal or signals acquired following one or more revolutions of the rotors (and therefore one or more passages of the blade PAL in front of the CAP proximity sensor).
• Said CAP proximity sensor is mounted fixed on the turbomachine.
• said CAP proximity sensor is fixedly arranged on the stator, so that the part of the blade which passes in front of the CAP sensor, at each turn of the rotor, corresponds to the distal end of the blade PAL (i.e. the opposite part at the foot of the PAL blade) seen along a line of sight orthogonal to the axis of rotation of the rotor.
• the CAP proximity sensor forms a sensitive element configured to supply an electric signal according to the variations of a physical quantity with which said CAP sensor is associated. Said at least one analog time signal is then obtained in a manner known per se from said at least one electric signal.
• the proximity sensor CAP used to detect the passage of the blade PAL is an optical sensor (or, equivalently, an optical probe).
• the physical quantity associated with such an optical sensor corresponds to the light intensity reflected by the blade PAL towards said optical sensor, the light directed towards the blade PAL coming from a light beam according to arrangements known per se. .
• optical sensor only constitutes a variant implementation of the invention. Also, other variants are possible, considering for example an inductive sensor, a capacitive sensor, an ultrasonic sensor, a magnetic sensor, etc.
• the proximity sensor CAP is characterized by a response time adapted to the fact that the time signal acquired is representative of the progressive appearance and disappearance of the blade PAL during its passage in front of the CAP proximity sensor (ie in the field of said CAP sensor for the present embodiment).
• the response time of the proximity sensor CAP also known as the "rise time”
• the response time of the proximity sensor CAP is sufficiently low for the time signal acquired (which ultimately corresponds to the image of the relative position of the end of the blade PAL relative to the position (or field) of the sensor CAP) translates the progressive rise/fall of the physical quantity measured by the proximity sensor CAP.
• the response time of the proximity sensor CAP is less than 35 nanoseconds. Of course, nothing excludes considering a response time greater than 35 nanoseconds, the choice of such a value essentially depending on the rotational speed of the blade PAL
• FIG. 2 is a graph showing an example of an analog time signal acquired using the proximity sensor CAP.
• the signal of FIG. 2 corresponds to the signal acquired following a single passage of the blade PAL in front of the proximity sensor CAP.
• the abscissa and ordinate axes of the graph in figure 2 respectively represent the time and the light intensity reflected by the blade towards the proximity sensor CAP (in the present case, the light intensity is normalized so as to be between 0 and 1).
• the acquired time signal takes on the appearance of a bell, with an ascending/descending phase (oblique and not vertical slope) corresponding to the progressive entry/exit of the blade PAL of the CAP proximity sensor field.
• the response time of the proximity sensor CAP is here sufficiently low to prevent the acquired time signal from taking on the aspect of a square signal (slot).
• a square signal (corresponding in fine to an “all or nothing” signal) does not make it possible to represent the progressiveness of the passage of the blade PAL in the field of the proximity sensor CAP. Consequently, such a square signal does not make it possible to obtain information on a possible shift between the dynamics of the blade PAL and that of a reference blade of the same type.
• the invention for its part, due to the very fact of the profile of the signal acquired by means of the proximity sensor CAP (see FIG. 2), makes it possible to characterize such a shift, as will be described in more detail later.
• the acquisition means 11 are not limited to the CAP proximity sensor. Indeed, and in a conventional manner, the acquisition means 11 comprise an acquisition chain in which the proximity sensor CAP is integrated. Said acquisition chain also comprises an acquisition card configured to condition said at least electrical signal supplied by the proximity sensor CAP, so as to finally deliver said at least one analog time signal corresponding to the variation in light intensity reflected by the blade PAL as it passes through the field of said proximity sensor CAP.
• the conditioning implemented by the acquisition card comprises for example an amplification and/or a filtering.
• Said acquisition means 11 also comprise, at the output of the acquisition chain, an analog/digital converter configured to digitize said at least one analog time signal. This digitization of said at least one analog time signal makes it possible to obtain a plurality of samples of the latter.
• each sample is presented as a pair, a first component of which corresponds to an instant of acquisition, and the second component of which corresponds to the light intensity reflected by the PAL blade. to the proximity sensor CAP at said instant of acquisition.
• the invention advantageously differs from the state of the art, and more particularly from the BTT method, in that it therefore proposes to combine a proximity sensor characterized by a low response time with obtaining a plurality of samples of said at least one acquired time signal.
• This combination in fact makes it possible to have samples that are distinct from each other since said at least one acquired signal has a bell-shaped profile and not a square-shaped profile.
• the fact of being able to transcribe the progressiveness of the passage of the blade PAL in front of the proximity sensor CAP advantageously makes it possible to obtain samples whose values, distinct from each other, will make it possible to characterize the vibratory behavior of the PAL blade as described below. If, on the contrary, the signal acquired was a square signal, as is the case in the BTT method, then it would be necessary to be satisfied with a single and unique sample since all the values taken on the upper part of the slot would be identical to each other.
• the field of the proximity sensor CAP corresponds to a disc (“spot” in English) whose radius is equal to 1.5 mm.
• the monitoring system 10 also comprises a monitoring device 12 configured to perform processing allowing, from the samples acquired in said at least one time signal, to monitor the vibration behavior of the blade PAL, by implementing steps of a monitoring method according to the invention.
• the monitoring device 12 is integrated into the aircraft. Note, however, that this is only a variant implementation of the invention, and nothing excludes considering the case where the monitoring device 12 is implemented on the ground, by example in a room managed by personnel belonging to the company responsible for the design/control/monitoring of the turbine engine.
• FIG 3 schematically shows an example of hardware architecture of the monitoring device 12 belonging to the monitoring system 10 of Figure 1.
• the monitoring device 12 has the hardware architecture of a computer.
• said monitoring device 12 comprises, in particular, a processor 1, a random access memory 2, a read only memory 3 and a non-volatile memory 4. It also has communication means 5.
• the read only memory 3 of the monitoring device 12 constitutes a recording medium in accordance with the invention, readable by the processor 1 and on which is recorded a computer program PROG in accordance with the invention, comprising instructions for the execution of steps of the monitoring method according to the invention.
• the program PROG defines functional modules of the monitoring device 12, which are based on or control the hardware elements 1 to 5 of the aforementioned monitoring device 12, and which include in particular:
• MOD_OBT configured to obtain the plurality of samples of said at least one analog time signal acquired by the acquisition means 11,
• a calculation module MOD_CALC configured to calculate a deflection of the blade PAL for each of the samples acquired
• a determination module MOD_DET configured to determine, in the form of a linear combination of sinusoidal signals, a signal, called “approximation signal", minimizing a cost function evaluating a difference between said calculated deflections and said approximation signal ,
• a monitoring module MOD_SUR configured to monitor the vibratory behavior of the blade PAL from (i.e. using) frequencies and/or amplitudes and/or phases of the sinusoidal signals forming said approximation signal.
• the communication means 5 allow the monitoring device 12 in particular to receive data from other entities, in particular samples of said at least one time signal, after these samples have been acquired by said acquisition means. 11, themselves provided in this case with means of communication suitable for transmission. These means of communication 5 are based, in a manner known per se, on a communication interface capable of exchanging data between the monitoring device 12 and another entity.
• the term “obtaining” of the MOD_OBT module refers to the reception, coming directly from the acquisition means 11, of the samples acquired for said at least one time signal. Consequently, in the present embodiment, the MODJOBT obtaining module is integrated into the means of communication 5.
• the monitoring device 12 obtains, via its MOD_OBT obtaining module, the samples after the latter have been stored in storage means, such as for example a dedicated database, placed between the acquisition means 11 and said monitoring device 12.
• the present invention also covers other embodiments in which the acquisition means 11 are integrated into the monitoring device 12.
• the term "obtaining" means then reference to the acquisition as such of the samples of said at least one time signal.
• FIG. 4 represents, in the form of a flowchart, the main steps of the monitoring method according to the invention, as they are implemented by the monitoring system 10 of FIG. 1.
• a reference signal SIG_REF has been obtained beforehand and is stored by the monitoring device 12, for example in the non-volatile memory 4.
• This reference signal SIG_REF is representative of a passage of the PAL blade in front of the CAP sensor when said PAL blade is not subjected to vibration. More particularly, in the present embodiment, the reference signal SIG_REF is associated with a sound blade (ie devoid of design defects, and having undergone no mechanical fatigue) of the same type as said blade PAL, and is generated by numerical simulation. None, however, precludes considering other modes of obtaining said reference signal SIG_REF, following a campaign of tests on a test bench.
• the monitoring method initially comprises a step E10 of acquisition of a plurality of samples E j (j is an integer index). Said step E10 is implemented by the acquisition means 11.
• the monitoring method also comprises a step E20 of transmission (transmission) of the samples E j acquired from the acquisition means 11 to the monitoring device 12.
• Said step E20 is implemented by suitable communication means equipping the means of acquisition 11.
• the monitoring method also includes a step E30 of obtaining (receiving), by the monitoring device 12, said plurality of samples E j .
• Said step E30 is implemented by the MOD_OBT obtaining module equipping the monitoring device 12.
• the monitoring method also comprises a step E60 of calculation, by the monitoring device 12, of a deflection of the blade PAL for each of the samples E j .
• Said step E60 is implemented by the MOD_CALC module equipping the monitoring device 12.
• the transmission of the samples E j acquired, from the acquisition means 11 to the monitoring device 12 can be carried out in different ways. For example, as soon as a sample is acquired, it is transmitted to the monitoring device 12 (ie the samples are transmitted one by one), and a deflection of the blade PAL is calculated for this transmitted sample.
• G “obtaining said plurality of samples” results from the iteration, for each of the samples, of the reception of said sample and the calculation of a deflection for said sample.
• a plurality of samples can be transmitted at one time to the monitoring device 12.
• the deflection of the blade PAL, for a sample E j is calculated in accordance with the principles described in document WO 2018/002818 already mentioned previously.
• t j the instant of acquisition associated with a sample E j of the signal SIG
• t jr represents the instant of the reference signal SIG_REF in correspondence with said instant t j of the signal SIG
• ie t jr is the instant of the reference signal SIG_REF in which the luminous intensity is equal to the luminous instant associated with the sample E j .
• the quantity At makes it possible to evaluate, at constant light intensity, the offset between the signals SIG and SIG_REF.
• FIG. 5 schematically represents an example of offset between the signals SIG and SIG_REF.
• Points are represented on the rising parts of the curves associated with said signals SIG and SIG_REF. These points, as far as the SIG signal is concerned, correspond to the samples acquired on said rising part. The other points, as far as the reference signal SIG_REF is concerned, refer to the points in correspondence with the samples of the signal SIG.
• the monitoring method includes a step E70 for determining, in the form of a linear combination of sinusoidal signals, a signal, called an "approximation signal » SIG_APPROX, minimizing a cost function evaluating a difference between said calculated deflections dj and said approximation signal SIG_APPROX.
• Said step E70 is implemented by the determination module MOD_DET equipping the monitoring device 12.
• - 1 is the time variable taking its values in an interval representative of the duration of the passage of the blade PAL in front of the proximity sensor CAP, for example an interval bounded by the minimum and the maximum of the acquisition times associated with the samples E j of the SIG signal,
• the determination of the approximation signal SIG_APPROX is conventionally carried out by means of an interpolation and extrapolation algorithm by Discrete Fourier transformation, for example with a high temporal resolution.
• F has a finite cardinality, and can be chosen according to the knowledge we have of the dynamics of blades such as the PAL blade (we understand that the larger the cardinality of F, the more the determination of SIG_APPROX consumes computing resources),
• - Ci corresponds to the amplitude of the sinusoidal signal having frequency f.
• the exponent p is for example between 0 and 2.
• the inventors have in fact observed that choosing such an exponent p makes it possible to cancel a non-negligible part of the coefficients q, which contributes to reducing the calculation load.
• the coefficient p is equal to 1.
• the cost function can be minimized in accordance with any suitable optimization technique known to those skilled in the art.
• the minimization of the cost function includes the execution of an algorithm of iteratively reweighted least squares, also called the IRLS algorithm (acronym of the Anglo-Saxon expression “Iterative Reweighted Least-Squares”).
• said approximation signal SIG_APPROX in that it makes it possible to approximate the deflections d j calculated during rotation of the rotor (and therefore of the blade PAL), characterizes the vibratory behavior of said blade PAL. It is therefore possible to access the frequencies and/or amplitudes and/or phases of the sinusoidal signals forming said approximation signal SIG_APPROX.
• the monitoring method comprises a step E80 of monitoring the blade PAL from frequencies and/or amplitudes and/or phases of the sinusoidal signals forming said approximation signal SIG_APPROX.
• Said step E80 is implemented by the module MOD_SUR equipping the monitoring device 12.
• said monitoring step E80 comprises an extraction of parameters (frequencies, amplitudes, phases) considered to be of interest in the approximation signal SIG_APPROX.
• parameters frequencies, amplitudes, phases
• the extraction of the parameters can also be supplemented by an analysis of the latter, in order to determine whether the vibratory behavior of the PAL blade is faulty or not.
• This analysis of the parameters comprises for example a comparison of the quantitative parameters (amplitudes and/or phases) with given thresholds.
• the monitoring step E80 can also include the transmission of an alert in the event that one or more anomalies (example threshold overrun) are observed for one or more parameters extracted from the approximation signal SIG_APPROX .
• calculation E60, determination E70 and monitoring E80 can be executed during a flight of the aircraft, but also, according to another example, in a deferred manner (for example if the samples are stored by the monitoring device 12 in its non-volatile memory 4).
• the monitoring device 12 determines a single approximation signal SIG_APPROX by taking into account all the deflections calculated from the samples of all the signals SIG_1, SIG_2 , etc.
• the set of deflections forms a signal defined by pieces in time (each piece corresponds to a passage of the blade PAL in front of the proximity sensor CAP), an approximation of which is sought via the determination of said approximation signal SIG_APPROX.
• step E10 can be seen as a “step for obtaining a plurality of samples” within the meaning of the invention.
• the invention also covers other modes in which, when the acquisition means 11 are distinct from (and therefore not integrated into) the monitoring device 12, said steps E10 and E20 do not belong to the monitoring method. , and are carried out prior to the implementation of said monitoring method.
• step E30 described above can be seen as a "step for obtaining a plurality of samples" within the meaning of the invention, and the monitoring method is then implemented by the single monitoring device 12.
• monitoring step E80 being carried out by an operator on the ground rather than by the monitoring device 12.
• FIG. 6 schematically represents a particular mode of implementation of the monitoring method of FIG. 4.
• the monitoring method further comprises a step E40 of calculating, from (ie by using) samples of the signal SIG (ie the samples obtained by the monitoring device 12 following on execution of step E30), a quantity Q1 characterizing the duration of the passage of the blade PAL in front of the proximity sensor CAP (ie the duration of crossing of the field of said proximity sensor CAP by the blade PAL).
• the monitoring step E80 is also executed using said quantity Q1.
• said calculation step E40 comprises:
• the determination of the input time tjni (respectively of the output time t_fin) can for example consist in selecting, among the samples E j of the signal SIG and by traversing these samples E j by acquisition times increasing, the first sample (respectively the last sample) whose associated light intensity value is non-zero.
• the determination of the entry time tjni (respectively of the exit time t_fin) consists in selecting, among the samples E j of the signal SIG and by traversing these samples E j at increasing acquisition instants, the first sample (respectively the last sample) whose associated light intensity value is greater than a given threshold.
• step E40 is not limited to determining the entry instant tjni (respectively the exit instant t_fin) among the samples E j acquired. Indeed, nothing excludes considering a sample of the signal SIG not corresponding to a sample acquired during step E10, and obtained for example by interpolation between two samples chosen from among said samples E j .
• step E40 smoothing the measured signal SIG (for example by means of an adapted filtering), so as to prevent the profile of the signal SIG presents several instants of rise and/or exit for a single and same passage of the blade PAL in front of the proximity sensor CAP. Such false instants can result from noise likely to complicate the implementation of step E40.
• Said quantity Q1 forms an indicator of the vibratory behavior of the blade PAL.
• it provides an indication of the direction of the vibratory displacement at the time of the crossing of the field of the sensor CAP by the blade PAL. Consequently, if the crossing time of the signal SIG is small compared to that of the signal of reference SIG_REF, this means that the vibratory movement of the blade PAL takes place in the same direction as the rotation of the rotor (and conversely, in the opposite direction, if the crossing time of the SIG signal is long compared to that of the signal of reference SIG_REF).
• the quantity Q1 it is also possible to determine, when the signals are normalized, an indicator corresponding to the area of the surface located below the curve of the signal SIG and comprised between the instants input tjni and output t_fin.
• This indicator is “similar” to the quantity Q1 in that it also makes it possible to provide information on the direction of the vibratory movement of the blade PAL (by comparison with the corresponding area located under the curve of the reference signal SIG_REF).
• the monitoring method also comprises a step E50 of calculating a quantity Q2 characterizing an advance or a delay of the time signal SIG with respect to the reference signal SIG_REF, the calculation of said quantity Q2 being implemented from samples of said signals SIG and SIG_REF. Moreover, the monitoring step E80 is also executed using said quantity Q2.
• Said advance or delay of the signal SIG relative to the reference signal SIG_REF is also referred to as the “order of arrival” of the blade PAL in the field of the proximity sensor CAP.
• said calculation step E50 comprises:
• sub-step E50_l a determination (sub-step E50_l), for the time signal SIG, of an entry instant tjni of the blade PAL in the field of said proximity sensor CAP (in this case, this is a sub-step identical to sub-step E40_l described above),
• the input time tjni_r represents the time of the reference signal SIG_REF in correspondence with said input time tjni of the signal SIG, i.e. tjni_r is the time of the reference signal SIG_REF at which the light intensity is equal to the light instant measured by the signal SIG at said input instant tjni.
• Said quantity Q2 also forms an indicator of the vibratory behavior of the blade PAL. Indeed, if this indicator is positive, this means that the blade PAL arrived earlier (ie in advance) in the signal SIG than in the reference signal SIG_REF (and vice versa).
• the two quantities Q1 and Q2 make it possible to obtain information on the overall speed of the blade PAL (speed of rotation and speed of vibration) as well as on the position of the blade PAL in the vibration cycle. This information is deduced and analyzed during the monitoring step E80.
• the calculations of said quantities Q1 and Q2 are also advantageous in the case where the speed regime is constant and where the vibrations affecting the blade PAL are mono-frequency vibrations (i.e. uni-modal vibrations). Indeed, in this case, the quantities Q1 and Q2 make it possible to determine whether said vibrations are synchronous or indeed asynchronous.
• the duration of crossing the field of the proximity sensor CAP that is to say the quantity Q1
• the order of arrival of the blade PAL that is to say the quantity Q2
• the order of arrival of the blade PAL is constant and of the same sign during the various revolutions of the rotor.
• the crossing time of the field of the proximity sensor CAP that is to say the quantity Q1
• the order of arrival of the blade PAL are variable.
• the monitoring method of FIG. 6 has been described by considering that the steps E40 and E50 are executed before the steps the calculation steps E60 and the determination steps E70. However, this is only a variant implementation of the invention, and other variants are possible provided that the quantities Q1 and Q2 are calculated after obtaining the samples E j (step E30) and before the monitoring step E80.
• the monitoring method of FIG. 6 has also been described considering that the quantities Q1 and Q2 were both calculated.
• the invention nevertheless remains applicable in cases where only one of said two quantities Q1, Q2 is calculated.
• the invention covers embodiments in which only step E40 or only step E50 is implemented.
• the monitoring system 10 also comprises, with respect to the system illustrated by FIG. 1, a calculation module configured to calculate said quantity Q1 (respectively a calculation module configured to calculate said quantity Q2).
• This calculation module is defined by specific additional instructions of the PROG program.
• the calculation module configured to calculate said quantity Q1 is a dedicated module, distinct from the calculation module MOD_CALC configured to calculate the deflections d j .
• the calculation module MOD_CALC configured to calculate the deflections d j is also configured to calculate the quantity Q1 (respectively the quantity Q2).

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• 2021
  • 2021-07-06 FR FR2107299A patent/FR3125122B1/fr active Active
• 2022
  • 2022-06-24 WO PCT/FR2022/051257 patent/WO2023281183A1/fr not_active Ceased
  • 2022-06-24 CN CN202280048324.5A patent/CN118043637A/zh active Pending
  • 2022-06-24 US US18/576,645 patent/US20240328892A1/en active Pending
  • 2022-06-24 EP EP22744277.9A patent/EP4367492A1/de active Pending

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