Mechanical system equipped with a device for monitoring a moving element of that mechanical system and method for monitoring such a moving element of a mechanical system.
The monitoring device with magnetic dipoles and signal comparison technology allows real-time detection of defects in mechanical systems, addressing the inefficiencies of post-operation analysis by identifying abnormalities in moving elements.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Utility models
- Current Assignee / Owner
- EUROCOPTER FRANCE SA
- Filing Date
- 2024-06-13
- Publication Date
- 2026-06-05
AI Technical Summary
Existing mechanical systems lack real-time monitoring capabilities to detect abnormal wear or defects in moving elements, relying on post-operation analysis that is complex and inefficient.
A monitoring device equipped with magnetic dipoles that generate a magnetic field synchronized with moving elements, coupled with a measuring device and computer system to compare measurement signals against reference signals, detecting defects by identifying differences exceeding predefined thresholds.
Enables real-time detection of defects such as wear, degradation, or breakage in mechanical systems, allowing immediate fault identification without requiring post-operation analysis.
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Abstract
Description
Title of the invention: Mechanical system equipped with a device for monitoring a moving element of this mechanical system and method for monitoring such a moving element of a mechanical system.
[0001] The present invention is in the field of monitoring mechanical systems.
[0002] The present invention relates to a mechanical system equipped with a device for monitoring a moving element of this mechanical system and to a method for monitoring such a moving element.
[0003] A mechanical system may include one or more moving elements relative to a support or housing, such as, for example, a shaft, a piston or a connecting rod.
[0004] A mechanical system may, for example, include at least one rotating component guided in rotation by one or more bearings. A bearing includes, for example, a bearing equipped with one or more rows of rolling elements such as balls, rollers or the like.
[0005] A rotating part of a mechanical system can also be a gear or pinion in order to provide a reduction or increase in the speed of rotation between the input and output shafts of the mechanical system.
[0006] A mechanical system may, for example, be equipped with an epicyclic gear train that provides a high speed reduction ratio between two rotating parts. Such a mechanical system may be a gearbox or a power transmission unit of a vehicle, particularly an aircraft.
[0007] A mechanical system can also be an electric motor comprising a fixed stator and a rotating rotor.
[0008] Each moving element of a mechanical system, whether in rotation or translation, can be subject to abnormal wear or degradation.
[0009] Preventive maintenance operations can be implemented to periodically inspect the mechanical system and detect any potential defects or abnormal wear. Alternatively or in addition, a mechanical system monitoring system can be used to detect such defects or wear during operation.
[0010] Some monitoring systems designated by the acronym HUMS for "Health and Usage Monitoring System" are intended to monitor a system Mechanical processes are analyzed using various sensors by monitoring the evolution of a set of indicators. These sensors might include, for example, an accelerometer, a tachometer, or a strain gauge. The number of indicators can be significant, making the analysis complex. Such an analysis is not performed in real time, but rather after the mechanical system has finished operating.
[0011] The present invention aims to provide an alternative and innovative solution for monitoring a mechanical system, and in particular the moving parts of this mechanical system, in order to detect as early as possible the appearance of abnormal wear or defects.
[0012] The present invention relates, for example, to a mechanical system equipped with a monitoring device, the mechanical system comprising at least one moving element relative to a support, relative to a displacement axis AX, said at least one moving element being ferromagnetic.
[0013] Said at least one moving element relative to a support may, for example, be rotating about the axis of displacement AX, or be translating about this axis of displacement AX, or even a combination of rotational and translational movements relative to this axis of displacement AX. Said at least one moving element may be made partially or entirely of a ferromagnetic material.
[0014] The mechanical system according to the invention is remarkable in that the monitoring device comprises a computer and at least one magnetic dipole moving with said at least one moving element, relative to the axis of displacement AX, the monitoring device comprising a measuring device fixed relative to the support and emitting at least one measurement signal SM relative to a magnetic field generated by said at least one magnetic dipole, the computer comparing said at least one measurement signal SM with at least one reference signal SR and detecting a fault in the mechanical system in the presence of a difference between said at least one measurement signal SM and said at least one reference signal SR greater than a threshold.
[0015] Since the magnetic dipole(s) move with the moving element(s), the magnetic field generated by a magnetic dipole is substantially fixed relative to the associated moving element(s). The effect of a moving element on the magnetic field generated by the associated magnetic dipole is therefore independent of the movements of that moving element and the magnetic dipole, and in particular of any possible variations in these movements. This effect is consequently linked solely to the moving element itself, and in particular to its mechanical, electromagnetic, or dimensional characteristics.
[0016] The measuring device is traversed by the magnetic field generated by the magnetic dipole(s) and impacted by the moving element. This measuring device then emits at least one measurement signal SM carrying information relating to this magnetic field. This at least one measurement signal SM may be emitted continuously or alternately during periods of monitoring of the mechanical system.
[0017] The measuring device is for example positioned on said at least one moving element to be monitored.
[0018] Alternatively, the measuring device can be positioned on the mechanical system such that the at least one moving element to be monitored is located between the at least one magnetic dipole and the measuring device. The measuring device is, for example, positioned on the support of the mechanical system or on another fixed part of that mechanical system.
[0019] Furthermore, said at least one reference signal SR includes information relating to a reference magnetic field generated by said at least one magnetic dipole under known operating conditions, and in particular when the mechanical system does not have any defects affecting its operation. Said at least one reference signal SR and the reference magnetic field thus correspond to a new mechanical system, therefore without defects, or one that has undergone maintenance guaranteeing its integrity and the absence of defects. Said at least one reference signal SR was, for example, emitted by the measuring device when the mechanical system was new, or following such maintenance.
[0020] This at least one reference signal SR can be stored in a memory of the computer or in a memory linked to the computer, or even in a memory of the measuring device.
[0021] Consequently, a difference between said at least one measurement signal SM and said at least one reference signal SR may be characteristic of a change in the mechanical system, and in particular in said at least one moving element. Such a difference may be observed following the occurrence of abnormal or significant wear, degradation, or even breakage. Indeed, the circulation of the magnetic flux(s) resulting from the magnetic field generated by one or more magnetic dipoles through an associated moving element is significantly modified following the occurrence of abnormal or significant wear, degradation, or even breakage.
[0022] Therefore, if the difference between said at least one measurement signal SM and said at least one reference signal SR is greater than the predetermined threshold, the measurement system deduces the possible occurrence of a defect, or even a breakage, on said at least one reference signal SR. minus one moving element. The threshold can be predetermined, for example by simulations and / or tests, and validated by tests.
[0023] The mechanical system according to the invention can thus be advantageously monitored, substantially in real time, during its operation. The occurrence of a fault can be detected immediately, without waiting for further processing and analysis.
[0024] The mechanical system according to the invention may include one or more of the following features, taken alone or in combination.
[0025] According to one possibility, said at least one magnetic dipole may be attached to said at least one moving element and for example fixed to said at least one moving element.
[0026] When the mechanical system comprises several moving elements having similar, or even identical, movements relative to the axis of displacement AX, a single moving element may include said at least one magnetic dipole. For example, said at least one magnetic dipole may be attached to the moving element furthest from the measuring device, such that the magnetic field generated by said at least one magnetic dipole passes through all the moving elements before reaching the measuring device.
[0027] Alternatively, the measuring device can be positioned as close as possible to the moving element carrying said at least one magnetic dipole in order to specifically monitor this moving element without being possibly disturbed by other moving elements or other parts of the mechanical system.
[0028] According to another possibility compatible with the preceding ones, said at least one magnetic dipole may comprise a single magnetic dipole.
[0029] Alternatively, said at least one magnetic dipole may comprise several magnetic dipoles jointly generating the magnetic field. In this case, the magnetic dipoles are preferably attached to the same moving element. Furthermore, the magnetic dipoles are preferably distributed regularly with respect to the axis of movement AX.
[0030] For example, when said at least one moving element and the magnetic dipoles are rotating around the displacement axis AX, the magnetic dipoles can be equally distributed in azimuth around the displacement axis AX.
[0031] When said at least one moving element and the magnetic dipoles are in translation parallel to the displacement axis AX, the magnetic dipoles can be equidistant in pairs parallel to the displacement axis AX.
[0032] The use of several magnetic dipoles advantageously multiplies the number of periods of the magnetic field, particularly compared to the number of periods of displacement of the moving element. The use of several magnetic dipoles also makes it possible to differentiate a mechanical problem from a magnetic or electrical problem. The number of periods of the magnetic field is thus a multiple of the number of periods of movement of the moving element, thus allowing better detection of the possible presence of a defect, whether mechanical, magnetic or electrical, or of abnormal wear.
[0033] A magnetic dipole may include a permanent magnet that can be attached to a moving element. Alternatively, a magnetic dipole may include magnetic powder, designated for example as "plastic magnet," attached to a moving element and then magnetized, typically by being placed in a strong magnetic field. Alternatively, a magnetic dipole may include an electromagnet, attached to a moving element and electrically powered, for example by a battery.
[0034] Alternatively, a magnetic dipole may comprise two permanent magnets placed close to each other, and magnetically crossed to jointly create a magnetic field loop.
[0035] According to another possibility compatible with the preceding ones, the monitoring device may include an alarm in communication with the computer to signal the detection of a fault. This alarm generates an alert to inform an operator of the detection of a fault in the mechanical system. The alarm may emit, in a known manner, an audible, visual, or even haptic alert via a control device, such as a lever, for example.
[0036] According to another possibility compatible with the preceding ones, the measuring device can emit three measurement signals SM1-SM3 relating to the magnetic field generated by said at least one magnetic dipole, respectively, along three distinct and non-coplanar measurement directions AXM1-AXM3. The three measurement signals SM1-SM3 can, for example, each contain information relating to coordinates along the three measurement directions AXM1-AXM3 of the generated magnetic field in order to characterize it in three dimensions. The three measurement signals SM1-SM3 can then be compared respectively to three reference signals SR1-SR3.
[0037] Each measurement signal SM1-SM3 is thus compared independently of the other measurement signals SM1-SM3 to a reference signal SR1-SR3. For each measurement direction AXM1-AXM3, a difference between the measurement signal SM1-SM3 and the reference signal SR1-SR3 is thus determined and compared to the threshold, which may be specific to each measurement direction AXM1-AXM3. In this way, when such a difference exceeds the threshold corresponding to the measurement direction AXM1-AXM3 concerned, a fault is detected in the mechanical system, or even in the moving element itself.
[0038] According to another possibility compatible with the preceding ones, said at least one measurement signal SM emitted by the measuring device may include at least one time-domain measurement signal SMtemp, and the computer is then configured to transform said at least one time-domain measurement signal SMtemp in a known manner into at least one spectral measurement signal SMspec. Similarly, said at least one reference signal SR may include at least one spectral reference signal SRspec having at least one reference line at a reference frequency with a reference amplitude. Said at least one spectral reference signal SRspec may have been obtained by transforming a time-domain reference signal SRtemp.
[0039] The threshold also includes at least one frequency threshold and one amplitude threshold so that the computer is configured to compare said at least one measurement spectral signal SMspec with said at least one reference spectral signal SRspec and to determine the presence of a defect on the mechanical system, or even on the moving element, when said at least one measurement spectral signal SMspec includes at least one spectral line whose spectral amplitude has a difference with the reference amplitude greater than the amplitude threshold or whose spectral frequency has a difference with the reference frequency greater than the frequency threshold.
[0040] According to another possibility compatible with the preceding ones, the mechanical system may comprise, or even constitute, an electric motor equipped with a stator and a rotor, said at least one moving element comprising the rotor, the rotor comprising several magnetic dipoles and being free to rotate relative to the stator. For example, the mechanical system is a permanent magnet synchronous electric motor, the rotor comprising the permanent magnets, the support comprising the stator.
[0041] The present invention also relates to a method for monitoring a mechanical system having at least one moving element, relative to a support, with respect to a displacement axis AX, said at least one moving element being ferromagnetic. The monitoring method comprises the following steps: - generating a magnetic field moving with said at least one moving element, relative to the displacement axis AX, using at least one magnetic dipole, - measurement of the magnetic field using a measuring device fixed relative to the support, - emission of at least one measurement signal SM relating to the magnetic field by the measuring device, - determination of at least one difference between said at least one measurement signal SM and at least one reference signal SR using a calculator, - detection of a fault on the mechanical system, using the computer, when a difference between said at least one measurement signal SM and said at least one reference signal SR is greater than a threshold.
[0042] Similar to the monitoring device described above, the monitoring method makes it possible to identify the presence of a defect, such as abnormal wear or a crack, for example, or even a break or rupture, on said at least one moving element, following a change in the magnetic field detected by the measuring device. The presence of such a defect is identified by comparing said at least one measurement signal SM and said at least one reference signal SR, using the threshold.
[0043] The monitoring method according to the invention may include one or more of the following features, taken alone or in combination.
[0044] According to one possibility, the method may include generating an alert, using an alerter connected to the computer, following the detection of a fault in the mechanical system. The alert may be emitted audibly, visually, or even haptically.
[0045] According to another possibility compatible with the preceding ones, said at least one magnetic dipole may comprise a single magnetic dipole or several magnetic dipoles jointly generating the magnetic field.
[0046] In the latter case, the magnetic dipoles can be attached to the same moving element, and for example distributed regularly relative to the axis of displacement AX.
[0047] In particular, when said at least one moving element and the magnetic dipoles are rotating around the displacement axis AX, the magnetic dipoles are preferably equally distributed in azimuth around the displacement axis AX.
[0048] In addition, a magnetic dipole may include a permanent magnet, magnetic powder, or even an electromagnet, fixed on a moving element.
[0049] According to another possibility compatible with the previous ones, when emitting at least one measurement signal SM relating to the magnetic field, three measurement signals SM1-SM3 relating to the magnetic field generated by said at least one magnetic dipole can be emitted by the measuring device respectively in three distinct and non-coplanar measurement directions AXM1-AXM3.
[0050] Said at least one reference signal comprises three reference signals SR1-SR3 carrying information relating to coordinates of a reference magnetic field according to these three measurement directions AXM1-AXM3.
[0051] Thus, when determining at least one difference between said at least one measurement signal SM and at least one reference signal SR, the three measurement signals SM1-SM3 are compared respectively to the three reference signals SR1-SR3 for determine three differences according respectively to the three measurement directions AXM1-AXM3.
[0052] The three differences are then compared to at least one threshold. As soon as one of them is greater than the threshold corresponding to the measurement direction AXM1-AXM3 concerned, a fault is detected on the mechanical system, or even on the said moving element.
[0053] According to another possibility compatible with the preceding ones, said at least one measurement signal SM emitted by the measuring device may comprise at least one time-domain measurement signal SMtemp, the method then comprising a transformation of said at least one time-domain measurement signal SMtemp into at least one spectral measurement signal SMspec, using calculation and a known transformation law stored in a memory of the computer or connected to the computer. Said at least one reference signal SR then comprises at least one spectral reference signal SRspec having at least one reference line at a reference frequency with a reference amplitude
[0054] Therefore, during the determination of at least one difference between said at least one measurement signal SM and at least one reference signal SR, at least one difference can be determined between said at least one measurement spectral signal SMspec and said at least one reference spectral signal SRspec.
[0055] This at least one difference may, for example, include a difference in frequencies between the reference frequency of the reference line and a spectral frequency of a spectral line of the SMspec measurement spectral signal. This at least one difference may include a difference in amplitudes between the reference amplitude of the reference line and a spectral amplitude of a spectral line of the SMspec measurement spectral signal.
[0056] In this embodiment of the method according to the invention, the threshold may include a frequency threshold and an amplitude threshold. Then, during the determination of at least one difference, the computer can determine an amplitude difference and a frequency difference between the measurement spectral signal SMspec and the reference spectral signal SRspec. Then, during fault detection on the mechanical system, the computer compares the amplitude difference with the amplitude threshold and the frequency difference with the frequency threshold. A fault is considered detected on the mechanical system when the amplitude difference exceeds the amplitude threshold or when the frequency difference exceeds the frequency threshold. An alert may then be issued by the alarm device.
[0057] The invention and its advantages will become apparent in more detail in the following description, with illustrative examples given by reference to the accompanying figures, which represent: - [Fig. 1], a cross-sectional view of a mechanical system according to the invention, - [Fig.2], a partially exploded view of the mechanical system of [Fig.1], - [Fig.3], a partial cross-sectional view of the mechanical system of [Fig.1], - [Fig. 4], a view of a moving element of a mechanical system according to the invention, - [Fig. 5], a diagram illustrating a method according to the invention, - [Fig. 6], a graph illustrating signals processed by a system mechanical according to the invention, and - [Fig.7], a graph illustrating signals processed by a mechanical system according to the invention.
[0058] Elements present in several separate figures are assigned one and the same reference.
[0059] Fig. 1 represents a mechanical system 10 comprising one or more moving elements 1 movable relative to a support 18 or a housing, relative to a displacement axis AX, the moving element(s) 1 comprising a ferromagnetic material.
[0060] The moving element(s) 1 may be in rotation or translation relative to a displacement axis AX, or may even have combined rotational and translational movements.
[0061] The mechanical system 10 can, for example, be an electric motor 40, as shown in [Fig. 1], comprising a fixed stator 41, integral with the support 18, and a rotating rotor 11. Such an electric motor 40 can thus comprise several moving elements 1 rotating about the axis of movement AX. The electric motor 40 shown in [Fig. 1] comprises, for example, as moving elements 1, the rotor 11, a splined shaft end 12, and two bearings 13, 14.
[0062] Reference "1" thus designates in general a moving element while references 11-15 designate a particular moving element.
[0063] The electric motor 40 also includes windings 42 fixed to the stator 41, and therefore fixed relative to the support 18 and the axis of movement AX. Finally, the electric motor 40 includes two covers 43, 44 fixed to the support 18 and therefore fixed relative to the axis of movement AX.
[0064] Alternatively, a mechanical system 10 according to the invention may also be a power transmission device or a vehicle gearbox, equipped, for example, with rotating input and output shafts, as well as gears and pinions forming moving elements 1. Figure 4 shows an example of a gear 15 of such a mechanical system 10 rotating about the axis of movement AX. The gear 15 comprises a toothed ring 151 and a hollow shaft 152.
[0065] In addition, a mechanical system 10 may include an epicyclic gear train enabling a large reduction ratio of rotational speed between rotating input and output shafts of the mechanical system.
[0066] Alternatively, a mechanical system 10 according to the invention may also be a linear motor comprising one or more elements in translational motion.
[0067] The mechanical system 10 according to the invention also includes a monitoring device 20 configured to monitor one or more moving elements 1 of the mechanical system in order to detect the occurrence of defects. The monitoring device 20 is equipped with a computer 5 and one or more magnetic dipoles 2 moving with at least one of the moving elements 1 relative to the axis of movement AX. The computer 5 may be integrated into the mechanical system 10 or located outside the mechanical system 10.
[0068] The monitoring device 20 may comprise a single magnetic dipole 2 generating a magnetic field. Alternatively, the monitoring device 20 may comprise several magnetic dipoles 21-26 jointly generating the magnetic field. The reference numeral "2" thus generally designates a magnetic dipole, while the reference numerals 21-26 designate a particular magnetic dipole.
[0069] Regardless of the number of magnetic dipoles 2, the magnetic dipole(s) 2 may be attached to the same moving element 1. Therefore, the magnetic field generated by the magnetic dipole(s) 2 moves with the moving element 1, relative to the axis of displacement AX.
[0070] For example, in the example shown in Figures 1 to 3, the rotor 11 may comprise four magnetic dipoles 21-24, each magnetic dipole 21-24 being provided with two adjacent permanent magnets 61-68. For clarity, only four permanent magnets 61-64, forming two magnetic dipoles 21, 22, are shown in [Fig. 2].
[0071] The magnetic dipoles 21-24 are thus fixed to the rotor 11 and free to rotate relative to the stator 4L. The two permanent magnets 61-68 forming a magnetic dipole 2 are placed side by side and end-to-end, their magnetic poles reversed, as shown in [Fig. 3]. The north pole of one of these two permanent magnets 61-68 is, for example, oriented towards the axis of movement AX, while the south pole of the other of these two permanent magnets 61-68 is oriented towards this same axis of movement AX. Consequently, the field lines jointly generated by these two permanent magnets 61-68 forming a magnetic dipole 21-24 loop back on themselves, thus forming a magnetic field loop for this magnetic dipole 21-24.
[0072] Alternatively, in the example shown in [Fig. 4], the toothed wheel 15 can support eight magnetic dipoles 21-28, each comprising a single magnet permanent 61-68. The permanent magnets 61-68 are in this case oriented identically around the axis of displacement AX.
[0073] Alternatively, a magnetic dipole 2 may include pre-magnetized magnetic powder, or even an electromagnet.
[0074] Furthermore, when the monitoring device 20 comprises several magnetic dipoles 2, these magnetic dipoles 2 are possibly distributed regularly with respect to the axis of displacement AX. For example, in Figures 1 to 4, the magnetic dipoles 21-28 are arranged equally around the axis of displacement AX.
[0075] The magnetic dipoles can alternatively be distributed irregularly around the axis of displacement AX on a moving element 1.
[0076] According to another aspect, the monitoring device 20 comprises at least one measuring device 3 fixed relative to the support 18 and configured to measure a magnetic field passing through or circulating in the mechanical system 10, and in particular the magnetic field generated by the magnetic dipole(s) 3. The measuring device 3 can then emit at least one measurement signal SM carrying information relating to this magnetic field generated by the magnetic dipole(s) 2.
[0077] To this end, the measuring device 3 may include one or more sensors capable of measuring a magnetic field, in particular Hall effect sensors or magnetoresistive sensors. For example, the measuring device 3 may include three sensors capable of measuring values of a magnetic field in three distinct and non-coplanar measurement directions, for example the three measurement directions AXM1-AXM2-AXM3 shown in [Fig. 4].
[0078] The measuring device 3 can be connected by a wired or wireless link to the computer 5. The measuring device 3 can be arranged on the mechanical system 10 so that the magnetic field emitted by the magnetic dipole(s) 2 passes through or circulates in the moving element(s) 1 to be monitored before being measured by the measuring device 3. For example, the measuring device 3 can be arranged so that the moving element(s) 1 to be monitored are positioned between the measuring device 3 and the magnetic dipole(s) 2.
[0079] The monitoring device 20 may include a single measuring device 3. Alternatively, the monitoring device 20 may include several measuring devices 3, used in redundancy to compensate for a possible failure of one of the measuring devices 3.
[0080] The measuring device(s) 3 can be fixed to the support 18 or to a part attached to the support 18. For example, in the case of the electric motor 40 shown in Figures 1 to 3, two measuring devices 3 can be fixed to the cover 44, which is itself fixed to the support 18.
[0081] The monitoring device 20 may also include an alarm 9, in wired or wireless communication with the computer 5, to alert an operator when a fault is detected on a moving element 1 of the mechanical system 10.
[0082] The alert device 9 may include one or more indicator lights to visually signal such an alert. Alternatively or in addition, the alert device 9 may include at least one screen to display a message relating to this alert.
[0083] Alternatively or additionally, the alarm 9 may include a loudspeaker to audibly emit such an alert. Alternatively or additionally, the alarm 9 may emit this alert haptically, via a control device, such as a lever for example.
[0084] Furthermore, the computer 5 of the monitoring device 20 may include at least one processor and at least one memory, at least one integrated circuit, at least one programmable system, at least one processing unit, or at least one logic circuit; these examples do not limit the scope given to the term "computer." The term "processor" may refer to a central processing unit known by the acronym CPU, a graphics processing unit (GPU), a digital signal processing unit (DSP), a microcontroller, etc.
[0085] The calculator 5 can also be connected to a memory by a wired or wireless connection.
[0086] The memory can, for example, store instructions or algorithms executed by the computer 5 to implement the monitoring method of the invention. The memory can thus store a computer program intended to be executed by the computer 5 in order to implement such a monitoring method.
[0087] This monitoring method comprises the following steps illustrated in [Fig.5].
[0088] This process thus comprises a generation 110 of a magnetic field. During this step, the magnetic dipole(s) 2 generate a magnetic field that moves with the moving element(s) 1, relative to the axis of movement AX. This magnetic field thus passes through the moving element(s) 1 and can be modified by the geometry, dimensions, and mechanical or electromagnetic characteristics of each moving element 1 it passes through.
[0089] Then, during a measurement step 120, the measuring device 3 measures the magnetic field generated by the magnetic dipole(s) 2 and modified by the moving element(s) 1. The measuring device 3 measures the magnetic field possibly using the sensor(s) it includes.
[0090] Then, during an emission step 130, the measuring device 3 emits one or more measurement signals SM relating to the previously measured magnetic field. The measurement signal(s) SM are thus transmitted to the computer 5 for processing, via a wired or wireless connection. The measurement signal(s) SM can be formed by raw measurements of the magnetic field carried out by the measuring device 3, or by measurements obtained by a more or less complex signal processing carried out by a computer integrated into the measuring device 3, or even by the computer 5, from such raw measurements, for example via a filtering or a usual sampling, or even the application of transformations.
[0091] A measurement signal SM may include one or more pieces of information relating to the measured magnetic field, chosen for example from one or more norms or amplitudes, one or more orientations, one or more frequencies or even coordinates, for example according to the three measurement directions AXM1-AXM2-AXM3.
[0092] The measuring device 3 can for example emit a single SM signal containing one or more pieces of information relating to the measured magnetic field.
[0093] Alternatively, the measuring device 3 can emit several SM signals, each containing one or more pieces of information relating to the measured magnetic field. For example, the measuring device 3 can emit three SM1-SM3 measurement signals relating to the magnetic field generated by the magnetic dipole(s) 2, respectively along three measurement directions AXM1-AXM3.
[0094] Then, during a determination step 140, the calculator 5 calculates one or more differences between, on the one hand, the measurement signal(s) SM and, on the other hand, one or more reference signals SR. The difference(s) may include, for example, a difference in amplitude between each measurement signal SM and the associated reference signal SR and / or a difference in periods or frequencies between each measurement signal SM and the associated reference signal SR.
[0095] Each reference signal SR has been previously determined and stored in the memory of the computer 5 or in the memory connected to the computer 5. Each reference signal SR contains information relating to a reference magnetic field relative to the fault-free mechanical system 10. A reference signal SR may contain one or more pieces of information relating to the reference magnetic field, chosen, for example, from one or more norms or amplitudes, one or more orientations, one or more frequencies, or even coordinates, for example, along the three measurement directions AXM1-AXM2-AXM3.
[0096] Such a reference signal SR can for example be defined by simulations, in particular using a finite element calculation, then verified and validated during tests.
[0097] Such a reference signal SR may alternatively have been measured on the mechanical system 10 in its new condition, or after a maintenance operation ensuring its proper functioning as well as the proper functioning and condition of the moving element(s) 1.
[0098] The memory can store a single SR reference signal. Alternatively, the memory can store several SR reference signals, each comprising one or several pieces of information relating to the reference magnetic field, for example three reference measurement signals SR 1 -SR 3 relating to the reference magnetic field respectively according to three measurement directions AXM1-AXM3.
[0099] Finally, during a detection step 150, the presence of a fault on the mechanical system 10 is sought. The computer 5 compares said at least one difference between, on the one hand, the measurement signal(s) SM and, on the other hand, respectively, one or more reference signals SR with a predetermined threshold stored in the memory of the computer 5 or in the memory connected to the computer 5. The threshold has been previously established by tests and / or simulations.
[0100] Thus, a difference between a measurement signal SM and a corresponding reference signal SR greater than a threshold is interpreted by the computer 5 as reflecting the presence of a defect on the mechanical system 10, and in particular on one or more moving elements 1. Indeed, any defect on a moving element 1, whether dimensional, resulting for example in significant wear or spalling, or whether it concerns the appearance of a crack, or even a break, will modify the path of the magnetic field through this moving element 1, and consequently modify the magnetic field measured by the measuring device 3. Thus, a significant difference between the measurement signal SM, characteristic of the current measured magnetic field, and a reference signal SR, characteristic of the reference magnetic field present within a mechanical system 10 without a defect, indicates the presence of a defect.
[0101] Conversely, the fact that each difference between on the one hand the measurement signal(s) SM and on the other hand respectively the reference signal(s) SR is less than or equal to the threshold, may indicate an absence of known defects on the mechanical system 10.
[0102] The measurement signal SM and the reference signal SR can be compared over time. For this purpose, the computer 5 directly uses a measurement time signal SMtemp, as emitted by the measuring device 3, possibly after a filtering step to remove measurement noise. The previously determined and stored reference signal SR then includes at least one reference time signal SR temp. The computer 5 compares this measurement time signal SMtemp with the reference time signal R temp and determines at least one difference, for example, an amplitude difference and a period shift. The presence of a fault can then be identified, and possibly reported, when the amplitude difference exceeds an amplitude threshold and the period shift exceeds a period threshold.
[0103] Figure [Fig.6] represents, for example, a graph showing on one hand three measurement signals SM1-SM3 and three reference signals SR1-SR3, all varying over time. The three measurement signals SM1-SM3 are emitted by the measuring device 3 and correspond to measurements of the magnetic field measured along the three measurement directions AXM1-AXM3.
[0104] In the graph of [Fig. 6], a significant period shift is observed between the first measurement signal SMI and the first reference signal SRI, exceeding a period threshold, as well as a significant amplitude difference between the second measurement signal SM2 and the second reference signal SR2, exceeding an amplitude threshold. The third measurement signal SM3 and the third reference signal SR3 appear closer to each other, and their differences, both in amplitude and period shift, are less than or equal to the amplitude and period thresholds, respectively.
[0105] Consequently, these differences between the first measurement signal SMI and the first reference signal SRI, and between the second measurement signal SM2 and the second reference signal SR 2, therefore make it possible to determine the presence of a defect on the mechanical system 10.
[0106] The measurement signal SM and the reference signal SR can alternatively be compared spectrally. For this purpose, the method includes a transformation 135, performed by the computer 5, to transform at least one time-domain measurement signal SMtemp, as emitted by the measuring device 3, into at least one spectral measurement signal SMspec, optionally after a filtering step of this at least one time-domain measurement signal SMtemp to remove measurement noise.
[0107] The previously determined and stored reference signal SR then comprises at least one reference spectral signal SR spec ec. Such a reference spectral signal SR spec, visible in [Fig.7], comprises at least one reference line, characterized by a reference frequency FR and a reference amplitude AR.
[0108] The calculator 5 compares the measurement spectral signal SMspec with the corresponding reference spectral signal SRspec and determines at least one difference, for example, an amplitude difference and a frequency shift between a spectral line of the measurement spectral signal SMspec and a reference line of the reference spectral signal SRspec. The presence of a defect can then be identified, and possibly reported, when the amplitude difference exceeds an amplitude threshold and the frequency shift exceeds a frequency threshold.
[0109] Figure 7 shows a graph displaying, on the one hand, a measurement spectral signal SMspec and, on the other hand, a reference spectral signal SRspec. The reference spectral signal SRspec comprises a single reference spectral line characterized by a reference frequency FR and a reference amplitude AR, whereas the measurement spectral signal SMspec comprises three measurement spectral lines characterized respectively by three measured spectral frequencies F Ml-FM3 and three measured spectral amplitudes AM1-AM3.
[0110] The graph in [Fig. 7] shows a small frequency shift between the first measurement spectral line and the reference spectral line, less than a frequency threshold, as well as a significant amplitude difference between this first measurement spectral line and the reference spectral line, but greater than an amplitude threshold. This amplitude difference, exceeding an amplitude threshold, therefore allows the presence of a defect in the mechanical system 10 to be determined.
[0111] The presence of a second and third spectral measurement lines is also observed. Since the reference spectral signal has only one reference spectral line, it can be deduced that a significant amplitude difference between this second spectral measurement line and a non-existent reference spectral line, and therefore one of zero amplitude, exceeds the amplitude threshold. The same is true for the third spectral measurement line. Consequently, the appearance of the second and third spectral measurement lines, which are absent from the reference spectral signal, can also be used to determine the presence of a defect in the mechanical system 10.
[0112] Furthermore, the type of difference exceeding a threshold can help identify a specific type of defect. The direction(s) among the measurement directions AXM1-AXM3 along which the threshold is exceeded can also help identify a type of defect.
[0113] For example, when the bearings 13,14 are ball or roller bearings, excessive radial play in one of these bearings 13,14 can be detected and identified by the calculator 5 when the spectral measurement signal has several spectral measurement lines, simultaneously along the three measurement directions AXM1-AXM3, the spectral measurement frequencies associated respectively with these spectral measurement lines corresponding to harmonics 2, 3 and 5 with respect to the reference spectral frequency of the corresponding reference spectral signal.
[0114] On the other hand, the appearance of axial play in one of these bearings 13,14 can be detected and identified when a similar phenomenon occurs only in the direction AXM1, namely parallel to the axis of displacement AX for these bearings 13,14.
[0115] The appearance of a mechanical imbalance, also referred to as "unbalance", can also be detected and identified by the monitoring device 20 by the presence of two spectral measurement lines in the spectral measurement signal, simultaneously along the three measurement directions AXM1-AXM3, and whose amplitude depends on the level of imbalance.
[0116] In the case where the mechanical system 10 is an electric motor 40, for example a permanent magnet motor 61-68, the monitoring device 20 according to the invention advantageously makes it possible to detect and identify a demagnetization of at least one, or even all, of the permanent magnets 61-68. The monitoring device 20 according to the invention also makes it possible to detect and identify a break in one of the permanent magnets 61-68.
[0117] A demagnetization or a break of a single permanent magnet can be detected and identified by the appearance of several spectral measurement lines in the spectral measurement signal, simultaneously along the three measurement directions AXM7-AXM3, and whose amplitude is influenced by the level of demagnetization.
[0118] In addition, a demagnetization of all permanent magnets can be detected and identified by a decrease in the amplitude of the fundamental measurement spectral line in the measurement spectral signal, simultaneously along the three measurement directions AXM7-AXM3.
[0119] Finally, following the detection 150 of a fault on the mechanical system 10, the method may include generating an alert 160, using the alerter 9, to notify an operator of the presence of this fault. For example, upon such detection, the computer 5 may transmit, via a wired or wireless connection, to the alerter 9 a signal, optical or electrical, digital or analog, carrying information relating to the detection of a fault, or even the type of fault detected. Upon receiving this signal, the alerter 9 may issue an alert to indicate the detection of this fault. Optionally, the alerter 9 may issue a specific alert to indicate the type of fault detected, for example, by displaying a specific message on a screen of the alerter 9.
[0120] Alternatively or in addition, following the detection 150 of the presence of such a fault, the method may include a storage 170 in a memory of the computer 5 or linked to the computer 5 of information relating to this detection of the presence of such a fault.
[0121] When each difference between on the one hand the measurement signal(s) SM and on the other hand respectively the reference signal(s) SR is less than or equal to the threshold, confirming the absence of a defect on the mechanical system 10, the process may include a signaling of information, using the alerter 9, in order to signal this absence of a defect to the operator and / or a memorization of this information of absence of a defect.
[0122] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments. It is, of course, conceivable to replace a described means with an equivalent means without departing from the scope of the present invention.
Claims
Demands
1. Mechanical system (10) equipped with a monitoring device (20), said mechanical system (10) comprising at least one moving element (1) relative to a support (18) with respect to a displacement axis (AX), said at least one moving element (1) being ferromagnetic, characterized in that said monitoring device (20) comprises a computer (5) as well as at least one magnetic dipole (2) moving with said at least one moving element (1), relative to said displacement axis (AX), said monitoring device (20) comprising a measuring device (3) fixed with respect to said support (18) and emitting at least one measurement signal (SM) relating to a magnetic field generated by said at least one magnetic dipole (2),said computer (5) comparing said at least one measurement signal (SM) with said at least one reference signal (SR) and detecting a fault of said mechanical system (10) in the presence of a difference between said at least one measurement signal (SM) and said at least one reference signal (SR) greater than a threshold.
2. Mechanical system (10) according to claim 1, wherein said measuring device (3) emits three said measurement signals (SM1-SM3) relating to said magnetic field generated by said at least one magnetic dipole (2) respectively along three distinct and non-coplanar measurement directions (AXM1-AXM3), the three said measurement signals (SM1-SM3) being compared respectively to three said reference signals (SR1-SR3) relating to said three measurement directions (AXM1-AXM3).
3. Mechanical system (10) according to any one of claims 1 to 2, wherein said at least one magnetic dipole (2) is integral with said moving element (1).
4. Mechanical system (10) according to any one of claims 1 to 3, wherein said at least one magnetic dipole (2) comprises a single magnet (61-68).
5. Mechanical system (10) according to any one of claims 1 to 3, in which said at least one magnetic dipole (2) comprises two magnets (61-68).
6. Mechanical system (10) according to any one of claims 1 to 5, wherein said at least one moving element (1) and said at least one magnetic dipole (2) are rotating about said axis of displacement (AX).
7. Mechanical system (10) according to claim 6, wherein said monitoring device (20) comprises several said magnetic dipoles (2) equally distributed in azimuth around said axis of displacement (AX), and jointly generating said magnetic field.
8. Mechanical system (10) according to any one of claims 1 to 7, wherein said monitoring device (20) includes an alarm (9) in communication with said computer (5) to signal said fault.
9. Mechanical system (10) according to any one of claims 1 to 8, wherein said mechanical system (10) comprises an electric motor (40) equipped with a stator (41) and a rotor (11), said rotor (11) comprising permanent magnets (46,47) and being rotationally movable relative to said stator (41), said at least one moving element (1) comprising said rotor (11), said at least one magnetic dipole (2) comprising said permanent magnets (46,47), said support (18) comprising said stator (41).
10. Mechanical system (10) according to any one of claims 1 to 9, wherein said at least one measurement signal (SM) emitted by said measurement device (3) comprises at least one measurement time signal (SMtemp), said at least one reference signal (SR) comprises at least one reference spectral signal (SRspec) having at least one reference line at a reference frequency (FR) with a reference amplitude (AR), said threshold comprises a frequency threshold and an amplitude threshold, said computer (5) being configured to transform said at least one measurement time signal (SMtemp) into at least one measurement spectral signal (SMspec) compared with said at least one reference spectral signal (SRspec) and to determine the presence of a defect on the mechanical system (10) when said at least one spectral measurement signal (SMspec) has at least one spectral line whose amplitude has a difference with said reference amplitude greater than said amplitude threshold or whose frequency has a difference with said reference frequency greater than said frequency threshold.
11. A method for monitoring a mechanical system (10) having at least one moving element (1) relative to a support (18) with respect to a displacement axis (AX), said at least one moving element (1) being ferromagnetic, said monitoring method comprising the following steps: - generation (110) of a magnetic field moving with said at least one moving element (1), relative to the axis of displacement (AX), using at least one magnetic dipole (2), - measurement (120) of said magnetic field using a measuring device (3) fixed relative to said support (18), - emission (130) of at least one measurement signal (MS) relating to said magnetic field by said measuring device (3), - determination (140) of at least one difference between said at least one measurement signal (MS) and at least one reference signal (RS) using a calculator (5), - detection (150) of a fault on said mechanical system (10), using said computer (5), when a difference between said at least one measurement signal (SM) and said at least one reference signal (SR) is greater than a threshold.
12. A monitoring method according to claim 11, wherein during said emission (130), three said measurement signals (SM1-SM3) relating to said magnetic field generated by said at least one magnetic dipole (2) are emitted by said measuring device (3) respectively along three distinct and non-coplanar measurement directions (AXM1-AXM3), and during said determination (140), said three measurement signals (SM1-SM3) are compared respectively to three said reference signals (SR1-SR3) relating to said three measurement directions (AXM1-AXM3) to determine at least three differences along said three measurement directions (AXM1-AXM3) respectively.
13. A monitoring method according to any one of claims 11 to 12, wherein said at least one moving element (1) and said at least one magnetic dipole (21-26) are rotating about said axis of displacement (AX).
14. A monitoring method according to claim 13, wherein said at least one magnetic dipole (2) comprises several said magnetic dipoles (2) equally distributed in azimuth around said axis of displacement (AX), and jointly generating said magnetic field.
15. A monitoring method according to any one of claims 11 to 14, wherein said method comprises a generation (160) of an alert, using an alerter (9), following said detection (150) of said fault on said mechanical system (10).
16. A monitoring method according to any one of claims 11 to 15, wherein said at least one measurement signal (SM) emitted by said measuring device (3) comprises at least one measurement time signal (SMtemp), said method comprising a transformation (135) of said at least one measurement time signal (SMtemp) into at least one measurement spectral signal (SMspec), and during said determination (140), said at least one reference signal (SR) comprising at least one reference spectral signal (SRspec) having at least one reference line at a reference frequency with a reference amplitude, at least one difference is determined between said at least one measurement spectral signal (SMspec) and said at least one reference spectral signal (SRspec), and during said detection (150), said threshold comprising a frequency threshold and an amplitude threshold,said defect is detected on said mechanical system (10) when said at least one spectral measurement signal (SMspec) comprises at least one spectral line whose amplitude differs from said reference amplitude by a factor greater than said amplitude threshold, or whose frequency differs from said reference frequency by a factor greater than said frequency threshold.