Method for identifying a rotor position of a rotor element, computer program product, and sensor device

Abstract

The invention proposes a method for identifying a rotor position of a rotor element (30) of a motor vehicle depending on a sensor signal from a sensor unit (32). The method comprises an initialization phase (10) and a subsequent determination phase (20), wherein the initialization phase (10) comprises the following steps: a) determining the first angular position (13) of the rotor element depending on the sensor signal (11), b) ascertaining a raw value (14) of the first angular position (13), c) storing (15) the sensor signal (11) in a data collection area (17) depending on the raw value of the first angular position (13), d) repeating steps a) - c) until the raw value of the first angular position has covered at least a portion of a rotation region (R), and e) ascertaining (22) a correction value (21) depending on the data collection area (17), and wherein the determination phase (20) comprises the following steps: I) determining the first angular position (13) of the rotor element depending on the sensor signal (11), II) ascertaining error information (19) relating to an expected angular error depending on the raw value of the first angular position and the correction value (21), and III) determining (18) the rotor position of the rotor element (30) depending on the error information (19).

Description

[0001] Method for detecting a rotor position of a rotor element, computer program product and sensor device

[0002] Description

[0003] The invention relates to a method for detecting a rotor position of a rotor element as a function of a sensor signal of a sensor unit, a computer program product and a sensor device.

[0004] It is well known from the state of the art to use sensors as motor position sensors (MPS). In some cases, the sensors are not mounted at the end of a shaft (end-of-shaft), but rather enclose the electric motor or shaft. This requires sensors with a large diameter.

[0005] State-of-the-art sensors often provide output signals that are not unambiguous over 360°. Furthermore, after a restart of the sensors and / or electronics, the current angular position of the target may be unknown.

[0006] It is an object of the present invention to at least partially remedy the above-mentioned disadvantages known from the prior art. In particular, it is an object of the present invention to improve the accuracy in detecting a rotor position of a rotor element. Furthermore, it is an object of the present invention to enable precise detection of a rotor position of a rotor element with as little external information as possible, i.e., information from components external to the system.

[0007] The above object is achieved by a method having the features of claim 1, by a computer program product having the features of claim 14, and by a sensor device having the features of claim 15. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the computer program product and / or the sensor device, and vice versa, so that reciprocal reference is or can always be made to the individual aspects of the invention with regard to the disclosure.

[0008] Embodiments of the invention can advantageously provide an improved method. Such a method eliminates the need for additional information, such as from the customer or from an additional index sensor. This makes the method according to the invention more cost-effective.

[0009] A first aspect of the present invention relates to a method for detecting a rotor position of a rotor element of a motor vehicle based on a sensor signal from a sensor unit. The method comprises an initialization phase and a subsequent determination phase.

[0010] The initialization phase comprises the following steps: a) determining the first angular position of the rotor element as a function of the sensor signal, b) determining a raw value of the first angular position, c) storing the sensor signal as a function of the raw value of the first angular position in a data collection field, d) repeating steps a) - c) until the raw value of the first angular position has covered at least part of a rotation range, and e) determining a correction value as a function of the data collection field,

[0011] The determination phase includes the following steps:

[0012] I) Determining the first angular position of the rotor element as a function of the sensor signal, II) Determining error information of an expected angular error as a function of the raw value of the first angular position and the correction value and

[0013] IV) Determining the rotor position of the rotor element depending on the error information.

[0014] In other words, a method can be provided in which the information required to reliably and accurately determine the rotor position can be obtained from an initialization phase. The initialization phase can be a repeating command sequence. While the initialization phase is running, a rotor position of the rotor element can still be determined, whereby a user is preferably informed that the method is still in the initialization phase, which is why the determination of the rotor position may not yet have the expected accuracy.

[0015] The rotor element can preferably be part of a motor, preferably an electric motor. The rotor element can be, for example, an axle or a shaft. The rotor position can be understood as a rotational position of the rotor element, preferably with respect to a specified zero position. The zero position can be defined in particular by the rotor element and / or the sensor unit. Furthermore, the zero position can be predetermined mechanically and / or electronically. The rotor position can thus, in particular, be related to the entire rotation range. By taking the angular error into account, the rotor position can preferably also be referred to as the corrected, absolute angular position of the rotor element.

[0016] The sensor unit is preferably designed as a motor position sensor (MPS). The sensor unit can be designed, in particular, for contactless detection of the first angular position. This can reduce wear on components of the sensor unit and / or the rotor element. The sensor signal can be a continuous or discontinuous and / or a digital or analog signal. Furthermore, it is conceivable for the sensor signal to comprise a singular signal, through which only a single value of the first angular position is transmitted. Thus, the first angular position and / or the rotor position can be determined at a specific point and / or as a curve. When determining the first angular position, the first angular position can be calculated based on the sensor signal. For example, the sensor signal can be transformed and / or sampled to determine the first angular position.However, it is also conceivable for the sensor signal to include information about the first angular position. The sensor signal preferably has a cosine and a sine signal, which can be stored in the data collection field. An amplitude signal can be determined based on the sine and cosine raw signals and also stored in the data collection field. When determining the first angular position, an angular value within a subsection can be determined, wherein, in the context of the present disclosure, the subsection can be a measuring range of a sensor unit. The subsection can, for example, comprise a predetermined angular range that can be detected by the sensor unit. Accordingly, the first angular position can be an angular value between, for example, 0° and 36°. The first angular position can comprise a rotational position of the rotor element in the subsection, in particular measured using the angular error.In particular, the first angular position can therefore also be referred to as a relative, measured angular position.

[0017] In contrast, the raw value of the first angular position is preferably an angular value between 0° and 360°, i.e. in the rotation range.

[0018] At least part of the rotation range can be a sub-range of the rotation range from 0° to 360°. In principle, it can prove advantageous to repeat steps a) to c) until the entire rotation range has been covered. However, this can be time-consuming, which is why it can also prove advantageous to cover only part of the rotation range, approximately 70% to 80% of the rotation range. This can save time without significantly reducing the accuracy of detecting the rotor position.

[0019] The expected angular error can be a periodic error, for example, a sinusoidal error. The expected angular error can be determined at a specific point and / or as a curve. In particular, the expected angular error exhibits a correlation with the first angular position and / or the location of the first angular position in the rotation range. The correction value can be used to determine the positioning of the first angular position in the rotation range, which can then be used to determine the expected angular error.

[0020] The error information may include a, preferably predetermined, value of the expected angular error. However, it is also conceivable for the error information to include the associated rotor position, in particular a value of the rotor position assigned as a function of the position information of the first angular position.

[0021] In the determination phase, determining error information about an expected angular error can involve reading a database. The rotor position can be determined based on the angular error and the first angular position. For example, the first angular position can be corrected by the angular error. Provision can be made for the rotor position to be provided for controlling the rotor element. For example, an electric motor can be controlled based on the rotor position.

[0022] Such a method can improve the accuracy of detecting the rotor position by taking the angular error into account.

[0023] According to one embodiment of the method, the initialization phase is performed once, in particular once when starting the motor vehicle. According to one embodiment of the method, when determining the raw value of the first angular position, the first angular position is related to the rotation range. In other words, the first angular position can refer to the partial section, while the raw value of the first angular position can refer to the rotation range. Accordingly, the raw value can assume a value in the entire rotation range from 0° to 360°. It should be noted that the term "raw value" in the context of the present disclosure is intended to indicate that the angular value provided by the raw value of the first angular position has not (yet) been corrected. Based on the determined raw value, it can be determined where, or at which support point, the sensor signal should be stored in the data collection field.

[0024] According to one embodiment of the method, when determining the correction value, a first phase position is determined in the current operating cycle. In addition, a second phase position is determined or retrieved in a simulated operating cycle. For this purpose, it can be provided that a moving average of the stored raw value of the first angular position is determined over a predefined range, or for each of the first angular positions of a predefined range of the entire rotation range. The predefined range of the rotation range can then be moved over the entire rotation range in order to derive a curve therefrom. In other words, an amplitude curve can be derived from the large number of determined raw values ​​over a predefined range of the rotation range.

[0025] A characteristic minimum can be determined or ascertained from the amplitude curve. From this characteristic minimum, the first phase position in the current operating cycle can be determined.

[0026] To determine the second phase position, a similar procedure can be used as for determining the first phase position, with the difference that the curve progression can be obtained from simulated vehicle situations. The simulated vehicle situations are preferably measurement sequences, as described above, which can be carried out in production or during the manufacture of the vehicle.

[0027] According to one embodiment of the method, the correction value is determined based on the difference between the first phase position and the second phase position. In other words, the difference between the first phase position and the second phase position can be calculated, from which the correction value can be determined.

[0028] According to one embodiment of the method, the difference between the first phase position and the second phase position is rounded to a multiple of the subsection. In other words, the difference can be rounded to a multiple of the physical measuring range of the sensor. The correction value is derived from this.

[0029] According to one embodiment of the method, the data collection field is divided into a predefined number of support points. Each support point can be assigned to a raw value corresponding to an angular value of at least one part of the rotation range. The size of the data collection field can therefore be determined by a resolution of the rotation range. The higher the resolution of the subsection, the more support points the data collection field can have. In other words, support points can be provided over the entire 0° to 360° range. The number of support points can determine the effort and memory requirements. In other words, the data collection field can have a matrix having a predefined number of vectors, each vector having attributes.Attributes of the vector are preferably the difference between the raw value of the determined first angular position and the nominal value of the support point, a verification value, and the sensor signals. The verification value is preferably a binary value. The verification value can be used to determine whether the vector or the support point has already been filled. If no values ​​have yet been stored for a specific angular position, the verification value can reflect this. According to one embodiment of the method, in step d), it is monitored, in particular by a monitoring unit, whether the data collection field, in particular each support point of the data collection field, has been filled by storing a sensor signal.Since the data collection field can have a number of support points corresponding to a resolution of at least part of the rotation range, the initialization phase can already be completed if the rotation range has not been completely covered, but only, for example, 70% to 80%. Alternatively, the data collection field can have a number of support points corresponding to a resolution of the entire rotation range. In such an embodiment of the data collection field, it is conceivable to already complete the initialization phase when approximately between 70% and 80% of the support points of the data collection field have been filled.

[0030] According to one embodiment of the method, a status signal is output when the initialization phase has been completed, and in particular, is . This allows a user to be informed whether the initialization phase has been completed, so that the user can assume the expected accuracy in detecting the rotor position when the initialization phase is completed.

[0031] According to one embodiment of the method, the initialization phase further comprises the following step: f) determining the rotor position of the rotor element relative to the subsection as a function of the first angular position.

[0032] According to one embodiment of the method, a calibration process is performed in which the expected angular error is determined over the rotation range, and the error information is entered into a database. In other words, a database, also referred to as a look-up table, can be populated using a calibration process. The calibration process can be separated from the initialization phase. According to one embodiment of the method, the sensor unit is designed as an inductive sensor. Furthermore, the sensor unit comprises a conductor element that is rotationally fixedly connected to the rotor element, and a sensor element for inductively detecting the conductor element to detect the first angular position.

[0033] According to one embodiment of the method, the rotor element is a shaft of a vehicle. The present invention can also relate to such a vehicle having a rotor element, wherein the rotor position of the rotor element can be detected using a method as described above and below.

[0034] A second aspect of the present invention relates to a computer program product comprising instructions which, when executed by a control unit, cause the control unit to execute a method as described above and below.

[0035] Thus, a computer program product according to the invention brings with it the same advantages as have already been described in detail with reference to a method according to the invention. The method can in particular be a computer-implemented method. The computer program product can be implemented as computer-readable instruction code. Furthermore, the computer program product can be stored on a computer-readable storage medium such as a data disk, a removable drive, a volatile or non-volatile memory, or a built-in memory / processor. Furthermore, the computer program product can be provided or made available in a network such as the Internet, from which it can be downloaded by a user or executed online as needed. The computer program product can be implemented both by means of software and by means of one or more special electronic circuits, i.e., in hardware, or in any hybrid form, i.e., using software components and hardware components. A third aspect of the present invention relates to a sensor device for detecting a rotor position of a rotor element in a rotation range. The sensor device has a sensor unit for detecting a first angular position in at least a partial section of a rotor element, and a control unit for executing a method as described above and below.

[0036] According to one embodiment of the sensor device, the rotor element has rotor blades and is rotationally asymmetric. In particular, the rotor element has a special rotor blade that differs from the other rotor blades. This allows a curve profile or amplitude curve profile to be obtained, as explained in more detail above and below. In other words, the rotor element can have a rotor blade that has a unique characteristic compared to the other rotor blades. The blade can have a different geometry than the other rotor blades. Such a special rotor blade can, for example, have a slope or be smaller than the other rotor blades.

[0037] Thus, a sensor device according to the invention brings with it the same advantages as have already been described in detail with reference to a method according to the invention and / or a computer program product according to the invention. The sensor device can, for example, be designed for integration in a vehicle and / or in an engine. The control unit can be integrated into a central control unit of the vehicle, e.g. in the form of an ECU and / or an engine control unit. However, it is also conceivable for the control unit to be integrated into a decentralized control unit for the sensor unit. The control unit can comprise a processor and / or a microprocessor. The control unit can in particular also be referred to as a computing unit. Furthermore, the control unit can have a memory unit for providing the database.

[0038] The invention is explained in more detail below with reference to the accompanying drawings. Fig. 1 shows a method according to the invention with a schematic representation of the method steps,

[0039] Fig. 2 shows a method according to the invention with a schematic representation of the method steps,

[0040] Fig. 3 shows a sensor device according to the invention for carrying out the method,

[0041] Fig. 4 shows an amplitude curve in the current operating cycle, and Fig. 5 shows an amplitude curve in simulated operating cycles.

[0042] In the following description of some embodiments of the inventions, the same reference numerals are used for the same technical features even in different embodiments.

[0043] Fig. 1 shows a method according to the invention with a schematic representation of the method steps. The method according to the invention for detecting a rotor position of a rotor element of a motor vehicle as a function of a sensor signal from a sensor unit can be divided into two phases. The method has an initialization phase 10 and a determination phase 20. In Figs. 1 and 2, the initialization phase 10 is schematically represented by dashed lines and the determination phase 20 by dotted lines (which is why the reference numerals 10 and 20 appear twice). Elements of Figs. 1 and 2 represented by solid lines can belong to both the initialization phase 10 and the determination phase 20.

[0044] In the initialization phase 10, which is preferably carried out when the motor vehicle is started, the first angular position 13 of the rotor element is determined 12 in a first method step as a function of the sensor signal 11. Appropriate processing units (“Offset corr”, “Amp corr”, “arctan”, etc.) can be provided for this purpose. The sensor signal 11 can be provided by a sensor unit 32. This takes place in the main signal path. The sensor signal 11 is preferably a cosine and a sine signal. Furthermore, the sensor signal can be processed into an amplitude signal. In the main signal path, the sensor signal 11 can be further processed to determine 14 a raw value of the first angular position 13. The raw value of the first angular position 13 is an uncorrected angular value which is related to at least part of the rotation range R.The sensor signal is then stored 15 in a data collection field 17 as a function of the raw value of the first angular position 13. This is done based on the angle or the raw value of the first angular position, which the main signal path supplies after the "angle tracker" (i.e., after determining the raw value of the first angular position 14). In other words, based on the raw value of the first angular position, it can be determined where in the data collection field the sensor signal should be stored. The data collection field 17 contains memory locations for a defined number of support points 25 (see Fig. 2). In each case, it can also be stored how far the specific angular value lies from the ideal value of the support point.In other words, a deviation value can be stored in the data collection field, whereby this indicates the difference between the angular value to which the support point has been assigned and the angular position of the raw value with which this support point has actually been filled. This makes it possible to replace the stored values ​​later on if a new value is closer to the ideal angular value, i.e. to the angular value to which the support point has been assigned. Furthermore, it can be stored in the data collection field whether a support point has been filled or not. In other words, it is indicated in a field provided for this purpose in the data collection field whether measured values ​​are available for a support point.

[0045] The steps explained above are repeated until the raw value of the first angular position 13 could cover at least part of the rotation range. In other words, the steps explained above are repeatedly carried out until measured values ​​for all or for a predetermined number of support points could be stored in the data collection field 17. If this is the case, the data collection can be stopped and a correction value 21 can be determined 22 depending on the data collection field 17. After the initialization phase 10, the determination phase 20 can begin. Depending on the first angular position and the correction value 21, error information 19 of an expected angular error can be determined. In other words, a database based on the first angular position and the correction value can be read in order to determine or ascertain the error information. The database can be referred to as a look-up table.The look-up table can be calibrated and / or filled into such a database by means of a calibration process 24. Through the initialization phase 10 and in particular the determination of the correction value 21, the angle value or the angular position output by the angle tracker 14 can be corrected with the correction value 21, so that the corrected angular position can correspond to an angular value that can form the basis for reading the look-up table over the entire rotation range R (i.e., over 360°). This means that as soon as the correction value 21 has been determined, i.e., the initialization phase 10 has been completed, a switch 16 can be switched so that the database can be read, which in turn allows the error information 19 to be determined. By switching the switch 16, the accuracy of the output signal 28 can be improved. The switching of the switch 16 can be signaled to a higher-level control unit.For this purpose, a corresponding status signal 26 can be output.

[0046] Subsequently, the rotor position of the rotor element 30 can be determined depending on the error information 19, which can be determined from the database. In a further optional step 18, the rotor position of the rotor element 30 can be related (back) to the sub-section. This can prove advantageous for the user, since the output signal 28 is expected in a predefined angular range, which can correspond to the sub-section. In other words, in an optional step of 360°, the actual measuring range of the sensor unit can be calculated back. In Fig. 2, the initialization phase is shown in more detail than in Fig. 1. The initialization phase can further comprise the step of determining 18 the rotor position of the rotor element (30) related to the sub-section as a function of the first angular position 13.In other words, the output signal 28 is output even if the switch has not yet been switched because the initialization phase 10 has not yet been completed.

[0047] When determining 22 the correction value 21, a first phase position PB is determined in the current operating cycle. A second phase position PEOL is also determined in a simulated operating cycle. Alternatively, the second phase position PEOL can already have been determined and stored in a storage medium, so that the second phase position PEOL can be retrieved in the initialization phase 10.

[0048] To determine the correction value 21, the first step is to determine the difference between the first phase position PB and the second phase position PEOL. The difference is then rounded to a multiple of the subsection.

[0049] Fig. 3 shows a sensor device 100 according to the invention for carrying out the method. The sensor device 100 has a sensor unit 32 for detecting a first angular position 13 at least in a partial section T of a rotor element 30. The sensor device 100 further has a control unit 34, which is designed to carry out a method as schematically illustrated in Figs. 1 and 2. The sensor unit 32 can have a sensor element. Such a sensor element is designed, in particular, to detect only a repeating partial section T of a rotation of the rotor element 30 within the rotation range R.

[0050] The rotor element 30 has multiple rotor blades. The rotor element 30 is rotationally asymmetric, as the rotor element 30 preferably has a unique rotor blade 33 that differs from the other rotor blades 31. It is conceivable that the unique rotor blade 33 is a missing rotor blade. This allows an amplitude curve to be obtained, as shown in Figs. 4 and 5.

[0051] Fig. 4 and 5 are intended to serve to explain in more detail by way of example the method step of determining the correction value 21 of the initialization phase 10. This method step is initiated when the data collection is stopped, i.e. when the data collection field 17 has been filled to a predefined degree (approximately 70%, for example). In order to be able to determine or determine the correction value 21, a one-time "phase detection" is carried out. For this purpose, the moving average 52 of the raw value of the first angular position 13 is shifted over a predefined range of the rotation range R in the current operating cycle over the entire rotation range (including overlap). The result is a curve profile 50 in the current operating cycle. The solid line 50 in Fig. 5 shows a typical amplitude profile in the current operating cycle, from which the curve profile 52 can be determined using the method step described.The curve (the moving average 52) exhibits a characteristic minimum 51, which is characteristic of the amplitude profile and thus of the position of the target's special feature. This value is the first phase position PB in the current operating cycle.

[0052] A second phase position PEOL is also determined at the EOL (end-of-line tester). For this purpose, the data collection process in the data collection field, as described above, can also be performed at the EOL. From this, one or more curve profiles for simulated operating cycles 42 can be determined. These can be saved for the second phase position so that they can be used to determine the difference.

[0053] Additionally, it should be noted that the terms "comprising" and "having" do not exclude other elements, and the indefinite articles "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features and steps described with reference to one of the above embodiments may also be used in combination with other features and steps of other embodiments described above. Reference signs in the claims are not to be considered limitations.

[0054] List of reference symbols

[0055] 100 sensor device

[0056] 10 Initialization phase

[0057] 11 Sensor signal

[0058] 12 Determining the first angular position

[0059] 13 the first angular position

[0060] 14 Determining a raw value

[0061] 15 Saving the sensor signal

[0062] 16 switches

[0063] 17 Data collection field

[0064] 18 Determining the rotor position of the rotor element

[0065] 19 Error information

[0066] 20 Determination phase

[0067] 21 Correction value

[0068] 22 Determining the correction value

[0069] 24 Calibration process

[0070] 26 Status signal

[0071] 30 rotor element

[0072] 31 rotor blades

[0073] 32 Sensor unit

[0074] 33 special rotor blades

[0075] 34 Control unit

[0076] 42 Curve progression in a simulated operating cycle

[0077] 50 Curve progression in the current operating cycle

[0078] 51 characteristic minimum

[0079] 52 moving average

[0080] PB first phase position

[0081] PEOL second phase position

[0082] T section

[0083] R rotation range

Claims

Method for detecting a rotor position of a rotor element, computer program product and sensor device Patent claims 1. A method for detecting a rotor position of a rotor element (30) of a motor vehicle as a function of a sensor signal from a sensor unit (32), comprising an initialization phase (10) and a subsequent determination phase (20), wherein the initialization phase (10) comprises the following steps: a) determining the first angular position (13) of the rotor element as a function of the sensor signal (11), b) determining a raw value (14) of the first angular position (13), c) storing (15) the sensor signal (11) as a function of the raw value of the first angular position (13) in a data collection field (17), d) repeating steps a) - c) until the raw value of the first angular position (13) has covered at least part of a rotation range (R), and e) determining (22) a correction value (21) as a function of the data collection field (17), and wherein the determination phase (20) comprises the following steps: I) determining the first angular position (13) of the rotor element as a function of the sensor signal (11), II) Determining error information (19) of an expected angular error as a function of the raw value of the first angular position and the correction value (21) and III) Determining the rotor position of the rotor element (30) depending on the error information (19).

2. Method according to claim 1, wherein the initialization phase (10) is carried out once, in particular once during Starting the motor vehicle.

3. Method according to one of the preceding claims, wherein when determining the raw value of the first angular position (13), the first angular position (13) is related to the rotation range (R).

4. Method according to one of the preceding claims, wherein, when determining (22) the correction value (21), a first phase position (PB) is determined (23) in the current operating cycle and a second phase position (PEOL) is determined or retrieved in a simulated operating cycle.

5. The method according to claim 4, wherein the correction value (21) is determined based on the difference between the first phase position (PB) and the second phase position (PEOL).

6. The method according to claim 5, wherein the difference between the first phase position (PB) and the second phase position (PEOL) is rounded to a multiple of a subsection (T), from which the correction value (21) is derived.

7. Method according to one of the preceding claims, wherein the data collection field (17) is divided into a predefined number of support points (25), wherein each support point (25) can be assigned a raw value corresponding to an angle value of at least a part of the rotation range (R).

8. Method according to one of the preceding claims, wherein in step d) it is monitored whether the data collection field (17), in particular each support point (25) of the data collection field, has been filled by storing (15) a sensor signal.

9. Method according to one of the preceding claims, wherein a status signal (26) is output when the initialization phase has been completed.

10. Method according to one of the preceding claims, wherein the initialization phase (10) further comprises the following step: f) determining (18) the rotor position of the rotor element relative to the subsection as a function of the first angular position (13).

11. Method according to one of the preceding claims, wherein a calibration process (24) is carried out in which the expected angular error over the rotation range is determined and the error information (19) is entered into a database.

12. Method according to one of the preceding claims, wherein the sensor unit (32) is designed as an inductive sensor, and wherein the sensor unit (32) comprises a conductor element which is connected to the rotor element (30) in a rotationally fixed manner, and a sensor element for inductive detection of the conductor element for detecting the first angular position (13).

13. Method according to one of the preceding claims, wherein the rotor element (30) is a shaft of a vehicle.

14. A computer program product comprising instructions which, when executed by a control unit (34), cause the control unit (34) to execute a method according to one of the preceding claims.

15. Sensor device (100) for detecting a rotor position of a rotor element (30) in a rotation range, comprising a sensor unit (32) for detecting a first angular position (13) at least in a partial section (T) of a rotor element (30), and a Control unit (34) for carrying out a method according to one of claims 1 - 13.

16. Sensor device (100) according to claim 15, wherein the rotor element (30) has rotor blades (31) and is rotationally asymmetric, wherein the rotor element (30) in particular has a special rotor blade (33) which differs from the other rotor blades (31).

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