Device and method for monitoring the health status of an electromechanical actuator

Abstract

The invention relates to a computer-implemented method (100) for monitoring the health status of an electromechanical actuator (1) comprising an electric motor powered by a three-phase power supply (2) delivering three currents. The method comprises the following steps: - S10) the intensities ia(t), ib(t) and ic(t) of the three currents across the terminals of the electric motor are measured; - S20) by applying the Clarke-Concordia transform to the measured intensities ia(t), ib(t) and ic(t), a contour (S) representative in the Clarke domain of the operation of the electromechanical actuator (1) is determined; - S30) an indicator (K), called the shape indicator, is calculated, representing a deviation between a shape of the contour (S) and a circle; and - S40) an action, for example an alert, is triggered based on at least one value of the shape indicator (K). Figure for the abbreviation: Figure 4

Description

Title of the invention: Device and method for monitoring the health status of an electromechanical actuator TECHNICAL FIELD OF THE INVENTION

[0001] Electromechanical actuators of the EMA type (for "Electro-Mechanical Actuator" in English) are subject to a set of degradations depending on their field of use.

[0002] Examples of degradation that can lead to malfunctions may include, in particular:

[0003] - of power electronics: short circuit at the component level, loss of electrical contact;

[0004] - of the electric motor: Short circuit at the stator windings, rotor demagnetization, misalignment;

[0005] - of the reducer: deformation and degradation of the gears.

[0006] - bearings: deformation and degradation of bearings, rings or the cage.

[0007] These degradations can be monitored by specific instrumentation (source of weight and loss of reliability) or by monitoring currents (MCSA approaches (“Motor Current Signature Analysis” in English)).

[0008] The invention falls within this context and relates to methods for monitoring failures based on current monitoring. By ultimately improving the health of EMA-type electromechanical actuators, particularly those integrated into aircraft or other means of air transport, the invention contributes to increasing the efficiency of air transport and thus contributes to reducing greenhouse gas emissions in this sector. STATE OF THE ART

[0009] In fault tracking methods based on current monitoring, we consider here more specifically the monitoring of electromechanical actuators including an electric motor powered by three-phase currents. Such actuators are increasingly used in the aeronautical field due to current technical developments and decarbonization objectives aimed at reducing the use of current hydraulic actuators.

[0010] Electromechanical actuators are generally controlled by an electronic device that can, for example, regulate the power supply to obtain the desired position, speed, or torque. However, this electronic device does not always allow for correction of the setpoint values ​​in case of deviations. It can It can be beneficial in many situations to implement preventive maintenance systems and methods to detect critical changes.

[0011] The invention aims to provide such a solution. Description of the invention

[0012] To this end, the following method is proposed in accordance with this disclosure. This method is a computer-implemented method for monitoring the health status of an electromechanical actuator comprising an electric motor powered by a three-phase supply delivering three currents, the method comprising the following steps: - S10) we measure the intensities of the three currents at the terminals of the electric motor; - S20) by applying the Clarke-Concordia transform to the intensities measured, a representative contour is determined in the Clarke domain of the operation of the electromechanical type actuator; - S30) we calculate an indicator called a shape indicator and representative of a difference between a shape of the outline and a circle; - S40) an action is triggered, for example an alert, depending on at least of a value of the form indicator.

[0013] Thus, thanks to the method according to the invention, it is possible to determine, based on measurements of the current intensities delivered by the three-phase power supply and the subsequent calculation of the form indicator, the deviations in the operation of an electromechanical actuator from ideal operation, that is, when the electromechanical actuator is balanced or non-faulty. Another advantage is that the form indicator according to the invention can be determined independently of the operating regime of the electromechanical actuator. Furthermore, a form indicator such as that according to the present disclosure appears to be a lever for integrating electromechanical actuators into the next generations of aircraft, in that it allows, depending on its value, the triggering of an action such as a maintenance alert.

[0014] In certain embodiments, - The electric motor includes a rotor, - We measure an angular position of the electric motor rotor, - We determine the representative contour using in addition the measured angular position.

[0015] Thus, measuring the angular position of the rotor makes it possible to isolate the two components of the Clarke-Concordia transform, which are periodic signals, over one or more periods.

[0016] In other examples, the angular position of the magnetic flux or the position of a top turn could be used to isolate these two components over one or more periods.

[0017] In some embodiments, the perimeter and area of ​​the representative contour are calculated.

[0018] In some embodiments, the shape indicator is a function of the area and perimeter of the contour.

[0019] Thus, advantageously, the method according to the invention exploits in a simple and efficient way the results of the tool represented by the Clarke transform to determine the shape indicator.

[0020] In some embodiments, the shape indicator is a function of the ratio between the area and the perimeter of the contour.

[0021] In some embodiments, to calculate the perimeter of the contour, the contour is considered as a polygon whose each vertex is defined by a pair of two intensities obtained by applying the Clarke transform to the intensities measured at a given time instant, the perimeter being equal to the sum of the lengths of the sides of the polygon.

[0022] Thus, according to this assumption of considering the contour as a polygon, the calculation of the perimeter of the contour is simplified. The determination of the shape indicator is thereby further simplified.

[0023] In some embodiments, to calculate the area of ​​the contour, the contour is considered as a polygon whose each vertex is defined by a pair of two intensities, obtained by applying the Clarke transform to the intensities measured at a given time instant, the area being equal to the area of ​​the polygon, and being calculated for example by the so-called Shoelace method.

[0024] Thus, according to this assumption of considering the contour as a polygon, the calculation of the contour area is simplified. The determination of the shape indicator is thereby further simplified.

[0025] In some embodiments, at step S40, the action is triggered further depending on at least one achievement of a criterion, the criterion being defined according to at least one value among a position, a speed, a torque.

[0026] Thus, advantageously, the action is triggered once the value of the form indicator is confirmed by the achievement of the criterion, in other words, the action is triggered by a double check.

[0027] In some embodiments, the criterion is an exceedance of a threshold value by at least one value.

[0028] For example, advantageously, the action can be triggered when the value of an operating parameter of the electromechanical actuator deviates from an operating range considered to be non-degraded.

[0029] The various steps of the method for monitoring the health status of an electromechanical actuator according to this disclosure can be determined by computer program instructions.

[0030] Accordingly, the present disclosure also relates to a computer program comprising instructions which, when the instructions are executed by at least one processor, cause said at least one processor to execute the steps of one of the methods presented above.

[0031] This program may use any programming language, and be in the form of source code, object code, or code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0032] This disclosure also relates to a non-volatile, computer-readable storage medium on which the previously described computer program is stored. The information medium can be any entity or device capable of storing the program. For example, the medium can include a storage means, such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a floppy disk or a hard disk drive. Alternatively, the information medium can 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 process in question. BRIEF DESCRIPTION OF THE FIGURES

[0033] Other advantages, purposes and particular features of the present invention will become apparent from the following non-limiting description of at least one particular embodiment of the devices and methods of the present invention, with reference to the accompanying drawings, in which:

[0034] [Fig.1] is a schematic view of an example of an electromechanical type actuator and its three-phase power supply;

[0035] [Fig.2] is a flowchart showing the steps of a method for monitoring the health status of an electromechanical actuator as illustrated in [Fig.1] according to this disclosure;

[0036] [Fig.3] is a schematic view of a device configured to implement all or part of the steps that can be implemented within the framework of the method for monitoring the health status of an electromechanical type actuator according to this disclosure;

[0037] [Fig.4] is a representation of a representative contour in the Clarke domain of the operation of a healthy electromechanical actuator determined during the implementation of the method for monitoring the health status of an electromechanical actuator according to this disclosure;

[0038] [Fig.5] is a representation of a representative contour in the Clarke domain of the operation of another degraded electromechanical actuator determined during the implementation of the method for monitoring the health status of an electromechanical actuator according to this disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present description is given as a non-limiting example of an embodiment.

[0040] The methods according to this disclosure will be presented in the case of an implementation on an electromechanical actuator 1 used in the architecture of an aircraft. For example, the electromechanical actuator 1 is a three-phase permanent magnet synchronous motor supplied with current by a power supply 2 delivering three three-phase currents ia(t), ib(t) and ic(t) as illustrated in [Fig. 1].

[0041] The method 100 for monitoring the health status of the electromechanical actuator 1 described herein comprises a set of steps illustrated in [Fig.2] which will be described below, among which are: a step S10 of measuring the intensities of the currents supplying the electromechanical actuator, a step S20 of determining a signature of the operation of the electromechanical actuator 1, a step S30 of calculating an indicator on the basis of this signature and a step S40 of triggering an action on the basis of the calculated indicator.

[0042] Some or all of the steps performed during the implementation of Method 100 can be carried out by a device 200 shown in [Fig. 3]. This device comprises a circuit 201 and memories 202 and 203 for storing program instructions that can be loaded into the circuit 801 and causing this circuit to execute at least some of the steps of Method 100 for monitoring the health status of an electromechanical actuator according to the invention illustrated in [Fig. 2]. When the program instructions are executed by the circuit 201, the memories 202 and 203 can also store data and information useful for executing the steps of the present invention as described herein.

[0043] Circuit 201 can be, for example: - a processor or processing unit adapted to interpret instructions in a computer language; the processor or processing unit may understand, be associated with, or be attached to a memory containing the instructions, or - the combination of a processor / processing unit and memory, the processor or processing unit being adapted to interpret instructions in a computer language, the memory containing said instructions, or - an electronic circuit board in which the steps of the invention are described in silicon, or - a programmable electronic chip such as an FPGA chip (for "Field-Programmable Gate Array").

[0044] The device 200 may also include input and output interfaces 807 for receiving input data and providing output data, which will be detailed later.

[0045] The device 200 may also include a graphical interface 205 for viewing information, such as part of the data from the method 100 for monitoring the health status of an electromechanical actuator according to the invention.

[0046] Method 100 for monitoring the health status of the electromechanical type actuator 1 will be described below.

[0047] During step S10, the intensities of the three-phase currents ia(t), ib(t) and ic(t) supplying the electromechanical actuator 1 are measured synchronously at the terminals of the electric motor of the electromechanical actuator 1. For example, the intensities of the three-phase currents ia(t), ib(t) and ic(t) can be measured at the windings of the electric motor of the electromechanical actuator 1. Indeed, it is known that the most frequent degradations on EMA type actuators have impacts on the currents measured at these locations.

[0048] During step S20, a representative contour S in the Clarke domain of the operation of the electromechanical actuator 1 is determined. For example, this determination is performed by the circuit 201 of the device 200. More specifically, the measured currents ia(t), ib(t), and ic(t) are projected onto a Clarke frame by applying a Clarke-Concordia transform. The Clarke transform is a mathematical transformation that converts a three-phase system to a two-phase model by changing the reference frame. The Clarke transform is a mathematical tool used in circuit theory and signal processing. It simplifies the analysis of three-phase circuits by transforming them into a two-phase system that can be represented in a two-dimensional plane called the "Clarke domain."Thus, the Clarke-Concordia transform of a triplet of signals a(t), b(t), c(t) is a pair of projected signals id(t), iq(t) defined, from the signals a(t), b(t),c(t) by the following equations: .

[0049] = _^c(t) [00501 i,(t)=^ïb(t)-$c(r)

[0051] In the Clarke domain, the component id(t) represents the projection of the three-phase system onto the real axis, the component iq(t) represents the projection of the three-phase system onto the imaginary axis, in quadrature with id (t).

[0052] Thus, when a Clarke-Concordia transform is applied to the measured intensities of the three-phase currents ia(t), ib(t) and ic(t), we obtain the transformed quantities Id(t), Iq(t) defined by: -Jï ic(t)

[0053]

[0054] The projection of the intensities ia(t), ib(t) and ic(t) onto the Clarke frame results in a two-dimensional pattern in the plane Id(t), Iq(t). This two-dimensional pattern constitutes the contour S representing, in the Clarke domain, the operation of the electromechanical actuator 1.

[0055] According to one example, N triplets of intensity values ​​ia(t), ib(t), and ic(t), are measured at N time instants ti, where i is an integer between 1 and N. The signature is thus formed by a set of N points in the Clarke coordinate system, with coordinates (Id(ti), Iq(ti)). For example, the number N of triplets can be between 10 and 100. In another example, an average can be calculated over a given number of rotations, which can be on the order of 10 rotations.

[0056] It is advantageous to note that the contour S of a balanced three-phase system, i.e., one without malfunctions, is a circle. Figure 4 shows an example of the signature of such a balanced three-phase system. This observation will be advantageously used in Method 100 for monitoring the health status of the electromechanical actuator 1.

[0057] Indeed, when a system malfunctions, its representative contour S deviates from a perfect circle, as illustrated in [Fig. 5], which shows the representative contour S of a degraded EMA actuator. Examples of malfunctions include power supply problems, misalignment, demagnetization, and bearing defects.

[0058] During step S30, an indicator K called the shape indicator is calculated on the basis of the contour S obtained in step S20. The shape indicator K is representative of a deviation between the shape of the contour S and a circle.

[0059] In some embodiments, the calculation of the shape indicator K is based on the determination of the perimeter ps of the signature S and the area As formed by the signature S.

[0060] We are here considering the case where the contour includes N points with coordinates (Id(t; ), Iq(ti)) in the Clarke domain, where i is an integer ranging from 1 to N and f represents a given time instant. As an example, these N points can be considered as forming a polygon. The perimeter of the contour S can then be obtained by calculating the sum of the lengths of the segments forming the contour of the polygon, i.e.: IK J - 'A) ) 2 + ( / ÀJ - ijfù ) 2

[0061] In this case, the area formed by the contour S can be considered as the area of ​​the polygon formed by the N points. The area formed by the contour S can be determined by any method for calculating the area of ​​a polygon. For example, the so-called Shoelace method can be used.

[0062] To estimate the difference between the shape of the contour S and a circle, several methods are possible. One method relies on the use of the isoperimetric inequality. The isoperimetric inequality is an inequality satisfied between the surface A and the perimeter p defined by a geometric domain. In Euclidean space, the isoperimetric inequality is written: 4jtA <

[0063] Equality is obtained only in the case of a domain defining a disk, in other words, whose contour is a circle.

[0064] Thus, in certain embodiments, the shape indicator K is defined by:

[0065] with As Faire defined by the contour S and ps the perimeter defined by the contour S.

[0066] It may be noted that with this definition the K-shaped indicator is less than or equal to at 1, therefore can also be expressed as a percentage (%).

[0067] Thus, in the case where the electromechanical actuator 1 was degraded and / or unbalanced, the shape of its representative contour S would move away, as seen previously, from a circle, reducing at the same time the value of the shape indicator K.

[0068] After calculating the value of the shape indicator K, during step S40, an action is triggered based on at least one value of the shape indicator K.

[0069] For example, if the value of the K-shape indicator is less than a percentage threshold value, the triggered action may be sending a maintenance alert.

[0070] In certain embodiments, the action is triggered further depending on at least one occurrence of a criterion. For example, the criterion is defined based on a value of one of the operating parameters of the electromechanical actuator 1. Examples of operating parameters applied The parameters of the actuator are position, speed, or torque. It may be necessary to condition the consideration of the K-shape indicator on certain ranges of torque, speed, and position values ​​of the actuator whose health is being monitored. For example, when the actuator is in regeneration mode, i.e., with a negative speed or torque, the K-shape indicator is no longer relevant. Advantageously, the value of the shape indicator is confirmed (where applicable) by measuring an operating parameter of the electromechanical actuator 1 and determining, for example, whether this operating parameter is outside the operating range imposed on the electromechanical actuator 1. In other words, the K-shape indicator can be compared to the operating acceptability criteria of the electromechanical actuator 1.

[0071] Advantageously, the steps of method 100 according to this disclosure and in particular of determining the K-shape indicator can be integrated into a predictive maintenance process to generate alerts and possibly lead to maintenance operations.

Claims

Demands

1. A computer-implemented method (100) for monitoring the health status of an electromechanical actuator (1) comprising an electric motor supplied by a three-phase power supply (2) delivering three currents, the method comprising the following steps: - S10) the intensities ia(t), ib(t) and ic(t) of the three currents at the terminals of the electric motor are measured; - S20) by applying the Clarke-Concordia transform to the measured intensities ia(t), ib(t) and ic(t), a contour (S) representative in the Clarke domain of the operation of the electromechanical actuator (1) is determined; - S30) an indicator (K) called a shape indicator and representative of a deviation between a shape of the contour (S) and a circle is calculated; - S40) an action, for example an alert, is triggered as a function of at least one value of the shape indicator (K).

2. Method (100) according to claim 1 wherein: - the electric motor comprises a rotor, - an angular position of the rotor of the electric motor is measured, - the representative contour (S) is determined using further the measured angular position.

3. Method (100) according to claim 1 or 2, wherein the perimeter (ps) and area (As) of the representative contour (S) are calculated.

4. Method (100) according to any one of claims 1 to 3, wherein the shape indicator (K) is a function of the area (As) and the perimeter (ps) of the contour (S).

5. Method (100) according to claim 4, wherein the shape indicator is a function of the ratio between the area (As) and the perimeter (ps) of the contour (S).

6. Method (100) according to any one of the preceding claims, wherein to calculate the perimeter (ps) of the contour (S), the contour (S) is considered as a polygon whose each vertex is defined by a pair of two intensities, obtained by applying the Clarke transform to the intensities measured at a given time instant, the perimeter (ps) being equal to the sum of the lengths of the sides of the polygon.

7. Method (100) according to any one of the preceding claims, wherein, to calculate the area (As) of the contour (S), the contour (S) as a polygon whose each vertex is defined by a pair of two intensities, obtained by applying the Clarke transform to the intensities measured at a given time instant, the area (As) being equal to the area of ​​the polygon, and being calculated for example by the so-called Shoelace method.

8. Method (100) according to any one of claims 1 to 3, wherein at step S40, the action is triggered further depending on at least one achievement of a criterion, the criterion being defined as a function of at least one value among a position, a speed, a torque.

9. A computer program comprising instructions which, when executed on a computer, cause the computer to perform all or part of the steps of method (100) according to any one of claims 1 to 8.

10. A non-volatile, computer-readable storage medium on which a computer program according to claim 9 is recorded.

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