Determining states of an apparatus using support vector machines

Abstract

The invention relates to a system and to a method for determining a state of a device by means of a trained support-vector machine. According to the invention, an operating parameter space is divided into classification volumes, at least one of which indicates a normal state and at least one other of which indicates a fault state of the device. A current state of the device can therefore be determined by determining where a current operating parameter point is to be arranged in the operating parameter space. The invention further relates to methods and to variants of the system in order to facilitate a cause evaluation and to determine particularly relevant operating parameters for the fault determination.

Claims

1. A system for determining a state of an apparatus, the system comprising: a capture device configured to capture at least two operating parameters of the apparatus during operation of the apparatus; and a computing device configured to implement an operating point module, a trained support vector machine (SVM), and an output module, wherein the operating point module is configured to generate an operating point in an n-dimensional operating parameter space from the at least two captured operating parameters, where n is greater than or equal to two, wherein the trained SVM is configured and trained to divide the n-dimensional operating parameter space into at least three classification volumes, each of the at least three classification volumes indicating different states of the apparatus, wherein a first classification volume indicates a normal state of the apparatus, and a second classification volume and a third classification volume indicate different fault states of the apparatus, wherein the trained SVM is further configured to assign the operating point generated by the operating point module to one classification volume of the at least three classification volumes, wherein the output module is configured to: determine a state of the apparatus according to the one classification volume to which the generated operating point is assigned by the trained SVM; and output an output signal indicating at least the determined state of the apparatus, and wherein the computing device is further configured to implement an evaluation module, the evaluation module being configured to: determine a respective normal vector to every plane or hyperplane that separates the first classification volume, which identifies the normal state of the apparatus, from one of the classification volumes that indicate a fault state of the apparatus; and determine and output, for each of the determined normal vectors, a value of an entry with a greatest absolute value for the normal vector.

2. The system of claim 1, wherein the at least two operating parameters captured by the capture device comprise: an electrical voltage; an electrical current intensity; an acceleration; a linear acceleration; a rotational speed; a rotational acceleration; a temperature; or any combination thereof.

3. The system of claim 1, wherein the SVM is configured to use a linear kernel.

4. The system of claim 1, wherein the capture device is configured to capture the at least two captured operating parameters as parts of a respectively corresponding operating parameter maximum value.

5. An apparatus comprising: a system for determining a state of the apparatus, the system comprising: a capture device configured to capture at least two operating parameters of the apparatus during operation of the apparatus; and a computing device configured to implement an operating point module, a trained support vector machine (SVM), and an output module, wherein the operating point module is configured to generate an operating point in an n-dimensional operating parameter space from the at least two captured operating parameters, where n is greater than or equal to two, wherein the trained SVM is configured and trained to divide the n-dimensional operating parameter space into at least three classification volumes, each of the at least three classification volumes indicating different states of the apparatus, wherein a first classification volume indicates a normal state of the apparatus, and a second classification volume and a third classification volume indicate different fault states of the apparatus, wherein the trained SVM is further configured to assign the operating point generated by the operating point module to one classification volume of the at least three classification volumes, wherein the output module is configured to: determine a state of the apparatus according to the one classification volume to which the generated operating point is assigned by the trained SVM; and output an output signal indicating at least the determined state of the apparatus, and wherein the computing device is further configured to implement an evaluation module, the evaluation module being configured to: determine a respective normal vector to every plane or hyperplane that separates the first classification volume, which identifies the normal state of the apparatus, from one of the classification volumes that indicate a fault state of the apparatus; and determine and output, for each of the determined normal vectors, a value of an entry with a greatest absolute value for the normal vector.

6. A method for determining a state of an apparatus the method comprising: operating the apparatus; capturing at least two operating parameters of the apparatus during operation of the apparatus; generating an operating point in an n-dimensional operating parameter space based on the at least two captured operating parameters, where n is greater than or equal to two; dividing the n-dimensional operating parameter space into at least three classification volumes using a trained support vector machine (SVM), each of the at least three classification volumes indicating different states of the apparatus, wherein a first classification volume of the at least three classification volumes indicates a normal state of the apparatus, and a second classification volume and a third classification volume of the at least three classification volumes indicate different fault states of the apparatus; assigning the generated operating point to a classification volume of the at least three classification volumes; determining a state of the apparatus according to the classification volume to which the generated operating point is assigned; outputting an output signal indicating at least the determined state of the apparatus; determining a respective normal vector to every plane or hyperplane that separates the first classification volume from one of the classification volumes that indicate a fault state of the apparatus; and determining and outputting a value of an entry with a greatest absolute value for each determined normal vector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic block diagram of a system for determining a state of an apparatus according to one embodiment of a first aspect;

(2) FIG. 2 shows a schematic illustration of an exemplary operating parameter space with training data;

(3) FIG. 3 shows a schematic flowchart for explaining a method for determining a state of an apparatus according to one embodiment of a second aspect; and

(4) FIG. 4 shows a further schematic illustration of an exemplary operating parameter space with training data.

DETAILED DESCRIPTION

(5) The accompanying figures are intended to convey a further understanding of the embodiments of the invention. The drawings illustrate embodiments and are used, in conjunction with the description, to explain principles and concepts of the invention. Other embodiments and many of the advantages mentioned emerge with regard to the drawings. The elements in the drawings are not necessarily shown in a manner true to scale with respect to one another.

(6) In the figures, same, functionally same, and same acting elements, features, and components are each provided with the same reference signs, unless stated otherwise. The numbering of the method acts is used for better clarity and is not intended to be understood as a chronological sequence, unless explicitly or implicitly stated otherwise. For example, some method acts may also be carried out at the same time or in a reverse sequence.

(7) FIG. 1 shows a schematic block diagram of one embodiment of a system 100 for determining a state of an apparatus 200. The apparatus 200 may be, for example, an electrical machine (e.g., an electric motor and/or generator). Alternatively, the apparatus 200 may also be a pump or a drive train of a vehicle (e.g., of an electric vehicle or a hybrid vehicle).

(8) Although the system 100 and the apparatus 200 are shown separately from one another in FIG. 1, the apparatus 200 may include the system 100 for determining the state of the apparatus 200 in some embodiments. According to the present embodiments, it is also possible to provide a vehicle that includes both the system 100 and the system 200.

(9) The system 100 is explained in more detail below using the example of an electric motor as the apparatus 200, where the described concepts are not restricted to such an apparatus 200.

(10) The system 100 includes a capture device 10 that is configured to capture at least two operating parameters of the apparatus 200 during operation of the apparatus 200. For this purpose, the capture device 10 may respectively include, for example, a sensor 11, 12 that is respectively configured to capture the respective operating parameter.

(11) As already described above, it is advantageous if the operating parameters are captured as parts of a respective operating parameter maximum value. The individual sensors 11, 12 may be configured, for example, such that the sensors 11, 12 already output the measured values as such parts.

(12) Alternatively, the capture device 10 may also include a conversion unit (e.g., implemented by a processor, a microcontroller, an ASIC, or an FPGA) that is configured to convert the raw sensor data captured by the sensors 11, 12 into the corresponding parts. In the example of an electric motor as the apparatus 200, a first sensor 11 may be configured to capture a current applied to the electric motor 200, and a second sensor 12 may be configured to capture a voltage applied to the electric motor 200, for example.

(13) The system 100 also includes a computing device 20 that is configured to implement an operating point module 21, a trained support vector machine 22, and an output module 23. The operating point module 21, the trained support vector machine 22, and the output module 23 may be implemented as software modules that are executed by the computing device 20. Optionally, the computing device 20 may also be configured to implement the evaluation module described above.

(14) The computing device 20 may be, for example, a processor with an associated memory, a cloud computing platform, a microcontroller, an application-specific integrated circuit (ASIC), and/or the like.

(15) The operating point module 21 is configured to generate an operating point in an n-dimensional operating parameter space from the at least two captured operating parameters (e.g., voltage and current intensity), where n≥2. This operating point, which, if the captured operating parameters are instantaneous operating parameters, constitutes an instantaneous operating point, may be used, according to the present embodiments, to indicate an instantaneous state of the apparatus 200.

(16) For this purpose, the trained support vector machine 22 is configured and trained to divide the n-dimensional operating parameter space into at least two classification volumes that each indicate different states of the apparatus 200. Depending on the dimensionality of the n-dimensional operating parameter space, the class boundaries between classification volumes are straight lines (for n=2), planes (for n=3), or hyperplanes (n≥4).

(17) For this purpose, the support vector machine is provided with training data having corresponding labels y.sub.i that assign a respective state (e.g., normal state, fault state 1, fault state 2, . . . ) to each of the training points x.sub.i.

(18) FIG. 2 shows a schematic illustration of an operating parameter space with training data using the example of n=2 with two operating parameters x1, x2. In this case, a first operating parameter x1 is illustrated on the horizontal axis and indicates or represents a current intensity applied to the electric motor 200, for example. A second operating parameter x2 is plotted on the vertical axis and indicates or represents a voltage applied to the electric motor 200, for example.

(19) First training points 61, which indicate a normal state of the apparatus 200, for example, are represented by circles in FIG. 2. Second training points 62, which indicate a fault state of the apparatus 200, are represented by rhombuses in FIG. 2. When training the support vector machine 22, an optimum straight line, plane, or hyperplane 65, which may divide the training points 61, 62 from one another such, that a maximum distance d1, d2 to the training points 61, 62 results, is determined.

(20) The data points 63, both of the first training data 61 and of the second training data 62, which all have the shortest possible distance to the optimum straight line, plane or hyperplane 65, as illustrated in FIG. 2, are referred to as support vectors since the data points 63 would fundamentally suffice to train the support vector machine. The support vector machine also gets its name from these support vectors.

(21) According to the statements above, the optimum straight line, plane, or hyperplane 65 divides the operating parameter space, which is spanned by the x1 axis and the x2 axis, into a first classification volume 51, which indicates a normal state, and a second classification volume 52, which indicates a fault state.

(22) According to various known variants and developments of support vector machines, the support vector machine 22 may be configured as a soft margin support vector machine or a hard margin support vector machine, for example.

(23) The trained support vector machine 22 is now able to assign any desired instantaneous operating point, which was formed by the operating point module, to one of the existing classification volumes 51, 52.

(24) The methods described here may also be used with more than two classification volumes (e.g., three or more classification volumes 51, 52), where the first classification volume 51 always indicates the normal state, and where further classification volumes usually classify different fault states. It is also possible for there to be a plurality of classification volumes that are separate from one another and each indicate different normal states of the apparatus 200 (e.g., states that, although differing greatly in terms of operating parameters, are both acceptable during operation of the apparatus 200).

(25) Referring again to FIG. 1, the output module 23 is configured to determine a state of the apparatus 200 according to the classification volume 51, 52 to which the generated operating point is assigned by the support vector machine, and to output an output signal 71 that indicates at least the determined state of the apparatus 200.

(26) For example, as information, the output signal 71 may have a logic zero in order to indicate a normal state of the apparatus 200 and a logic one in order to indicate a fault state of the apparatus 200. In the case of more than one fault state of the apparatus 200 (e.g., more than three classification volumes 51, 52), the output signal 71 may have, for example, an item of binary-coded numerical information that clearly identifies and characterizes the state of the apparatus 200 (e.g., 0 (“00”)-normal state, 1 (“01”)-first fault state, 2 (“10”)-second fault state, and so on).

(27) The output module 23 may also be configured to determine, over a predetermined period or continuously, a trajectory of the operating point over the course of time in the n-dimensional operating parameter space and to extrapolate progression of the trajectory in the future.

(28) On the basis of this, it is possible to determine the first time in the temporal progression at which the operating point presumably assumes a position in the n-dimensional operating parameter space that should be assigned to a state of the apparatus 200 other than the instantaneous state.

(29) For example, it is possible to determine that, according to the extrapolated trajectory of the operating point, the operating point will change, in X minutes (e.g., four minutes), from the first classification volume 51, which indicates the normal state, into a position belonging to the second classification volume 52 that indicates a fault state. In other words, it is possible to extrapolate that the indicated fault state will accordingly occur in X minutes.

(30) On the basis of this, the output signal 71 may include, for example, a time specification that indicates when at least a particular fault state will occur, when a change will take place between determined classification volumes 51, 52 (and which classification volumes), and/or what this change means.

(31) For example, the different classification volumes 51, 52, that indicate different fault states of the apparatus 200 may indicate consecutively more serious fault states of the apparatus 200. The extrapolated trajectory may therefore indicate for each class boundary (e.g., the optimum straight line, plane, or hyperplane 65 that separates two classification volumes 51, 52 from one another) whether and when the operating point will intersect this according to the extrapolated trajectory, and may output a corresponding list.

(32) This makes it possible to indicate to a user, for example, when a slight impairment in the function of the apparatus 200 will presumably occur (e.g., first fault state—operating point is assigned to the second classification volume 52), when a greater impairment will occur (e.g., second fault state—operating point is assigned to the third classification volume), and when a definitive failure of the function of the apparatus 200 will occur (e.g., third fault state—operating point is assigned to the fourth classification volume).

(33) FIG. 3 shows a schematic flowchart for explaining a method for determining a state of an apparatus 200 according to one embodiment of the second aspect of the present embodiments. The method according to FIG. 3 may be carried out, for example, by the system according to the first aspect of the present embodiments (e.g., using the system 100 according to FIG. 1).

(34) The method according to FIG. 3 may therefore be adapted according to all variants, modifications, and options described with respect to the system according to the first aspect of the present embodiments and vice versa. In the description of the method according to FIG. 3, reference is sometimes also made to reference signs in FIG. 1 and FIG. 2 without this being intended to be understood as a restriction to the use with the system 100 according to FIG. 1.

(35) In act S10, the apparatus 200 is operated. For example, an electric motor or a pump is switched on or the like.

(36) In act S20, the at least two operating parameters x1, x2 of the apparatus 200 are captured during operation (e.g., as described above with respect to the capture device 10). For example, one operating parameter x1, x2 of the apparatus 200 may each be captured by a corresponding sensor 11, 12.

(37) In act S30, an operating point is generated in an n-dimensional operating parameter space based on the at least two captured operating parameters, where n≥2. The operating point may be generated S30 as explained above with respect to the operating point module 21.

(38) In act S40, the n-dimensional operating parameter space is divided into at least two classification volumes 51, 52 that each indicate different states of the apparatus (e.g., using a trained support vector machine 22). The division S40 of the n-dimensional operating parameter space may alternatively also be described as the generation of classification boundaries 65.

(39) The support vector machine 22 may be trained, for example, as described above, with the result that a method for training a support vector machine for use in a system for determining a state of an apparatus 200 is also provided in the present case.

(40) The n-dimensional operating parameter space is divided S40 such that a first classification volume 51 indicates a normal state of the apparatus 200 and a second classification volume 52 indicates a fault state of the apparatus 200. The n-dimensional operating parameter space may also be divided into further classification volumes that may indicate further fault states of the apparatus 200. The n-dimensional operating parameter space is divided S40, as is conventional with support vector machines, by calculating an optimum straight line, a plane, or a hyperplane 65, in each case, based on the dimension n of the operating parameter space.

(41) The support vector machine may be, for example, in the form of a hard margin support vector machine (e.g., if the training data used may be linearly separated; if an (n−1)-dimensional class boundary may be drawn in the n-dimensional operating parameter space and defines the classification volumes 51, 52 such that each classification volume 51, 52 precisely and only includes the training data 61, 62 respectively assigned to this classification volume 51, 52).

(42) In other cases, for example, if the training data 61, 62 cannot be linearly separated, the support vector machine may be, for example, in the form of a soft margin support vector machine (e.g., in the form of an L1 soft margin support vector machine or an L2 support vector machine).

(43) In act S50, the support vector machine 22 determines that the generated operating point is assigned to one of the classification volumes 51, 52. This is usually carried out using a decision function.

(44) In act S60, a state of the apparatus 200 is determined according to that classification volume 51, 52 in which the generated operating point is arranged.

(45) In act S70, an output signal 71 indicating at least the determined state of the apparatus 200 is finally generated and output. As described above, the output signal 71 may contain further information (e.g., an expected time at which the instantaneous operating point will change from the classification volume in which the instantaneous operating point is currently situated to another classification volume and the like).

(46) The method may also be used to more accurately determine the influences of the different operating parameters on the fault states of the apparatus 200. For this purpose, a respective normal vector that is perpendicular to the corresponding class boundary is determined (e.g., normalized to a length of 1) for each classification boundary (e.g., optimum straight line, plane, or hyperplane 65). The term “normal vector” does not relate to the normal state of the apparatus 200, for example, but rather, to the perpendicular arrangement with respect to the class boundary.

(47) The individual entries for the normal vector at the different indices of the normal vector provide information on the direction in which the normal vector points in the operating parameter space, with the result that the absolute values thereof provide information on changes in which operating parameters x1, x2 cause a change between classification volumes in a particularly rapid manner.

(48) Therefore, in an optional act S80, it is possible to determine a respective normal vector to each plane or hyperplane that separates the first classification volume from a classification volume that indicates a fault state of the apparatus.

(49) In an optional act S90, the value of the entry with the greatest absolute value for each determined normal vector, together with the corresponding index value, may then be determined and output, with the result that it is clear (e.g., when processing a fault state of the apparatus 200 in a workshop or in a laboratory) which operating parameter x1, x2 should be checked as a matter of priority in order to find the cause of the fault state.

(50) Acts S80 and S90 may be carried out, for example, by an evaluation module implemented by the computing device 20. Alternatively, acts S80 and S90 may also be carried out by an external evaluation device that is part of the system 100 and may be connected to the computing device 20 of the system.

(51) If, as described above, a ranking of entries for the normal vector is output, the corresponding operating parameters x1, x2 may be checked in this order in order to provide that the most likely causes of faults are checked first. This makes it possible to considerably shorten a time needed to find causes of faults.

(52) This procedure is particularly advantageous if the n-dimensional operating parameter space is divided by the trained support vector machine 22 into at least three classification volumes, where the first classification volume 51 indicates the normal state of the apparatus and the second classification volume 52 and a third classification volume indicate different fault states of the apparatus 200.

(53) In act S80, it is possible in this case to determine a respective normal vector to each plane or hyperplane 65 that separates the first classification volume 51 from a classification volume 52 that indicates a fault state of the apparatus 200. The normal vectors therefore indicate on account of primarily which operating parameters x1, x2 the operating point would cross from the first classification volume (e.g., normal state) to in each case one of the classification volumes 52, which indicates a fault state of the apparatus 200.

(54) In FIG. 2, for example, the normal vector N1 may be arranged such that the normal vector N1 points from the first classification volume 51 in the direction of the second classification volume 52. Since the classification boundary in FIG. 2 is an optimum straight line 65 that is defined, by way of example, by x1=x2, the normal vector is, for example, (1/√2, −1/√2).sup.T, where the root of the scalar product of the vector with itself was used to determine the length of a vector and therefore of the normal vector. In another normalization scheme, the normal vector may be normalized such that the absolute values of entries of the normal vector add up to one.

(55) Since a ranking of the absolute values of the entries for the normal vectors is used in the present case, it is not necessary to normalize the normal vector to a length of one. However, as described above, the captured operating parameters may each be captured as parts (e.g., as fractional parts) of a respectively corresponding operating parameter maximum value, where the respective operating parameter maximum values may be determined in advance and may be stored in the capture device 10 and/or the computing device 20. In other words, the operating parameters may each be captured as values between 0 and 1, both inclusive.

(56) In the example in FIG. 2, the result is therefore that both operating parameters x1, x2 each have the same influence on possible migration of the instantaneous operating point from the first classification volume 51 to the second classification volume 52.

(57) FIG. 4 schematically shows a variant of the situation illustrated in FIG. 2, in which the first training data 61 and the second training data 62 are such that the classification boundary (e.g., optimum straight line, plane, or hyperplane 65; a straight line in the present case) extends parallel to the vertical axis x2.

(58) The normal vector N2 that is depicted in FIG. 4 and points from the first classification volume 51 in the direction of the second classification volume 52 is defined by N2=(1,0).sup.T. In the analysis, it therefore emerges that only the first operating parameter x1 is decisive for a movement of the instantaneous operating point from the first classification volume 51 to the second classification volume 52.

(59) When checking the cause of a fault, it may therefore be possible in this case to completely dispense with checking the second operating parameter x2. Two extreme examples are illustrated in FIG. 2 and FIG. 4. Operating parameter spaces with a dimensionality of considerably more than n=2 will occur in reality, and a number of operating parameters x1, x2 will influence whether an instantaneous operating point will move from the first classification volume 51 in the direction of a classification volume 52 that indicates a fault state of the apparatus 200.

(60) In the detailed description above, various features have been combined in one or more examples in order to improve the rigorousness of the illustration. However, the above description is of a merely illustrative but in no way restrictive nature. The above description is used to cover all alternatives, modifications, and equivalents of the various features and exemplary embodiments. Many other examples will be immediately and directly clear to a person skilled in the art on the basis of expert knowledge in view of the above description.

(61) The exemplary embodiments were selected and described in order to be able to describe the principles on which the invention is based and possible applications in practice in the best possible manner. As a result, experts may modify and use the invention and various exemplary embodiments of the invention in an optimum manner with respect to the intended purpose.

(62) The elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent. Such new combinations are to be understood as forming a part of the present specification.

(63) While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.