Method for detecting free ends of plug-in coils in a stator and device for detecting hairpin positions with a profile sensor

Abstract

Method for detecting the position of free ends (14, 15) of plug-in coils (12) in a stator (10), the method comprising: I. Placing the stator (10) in a detection area (24) of a profile sensor (18) such that a surface of the stator (10) with free ends (14, 15) is located in the detection area (24) of the profile sensor (18); II. Detection of a respective 3-dimensional position of the stator surface relative to the profile sensor (18) for a total quantity (34) of measuring points (32) using the profile sensor (18); III Determining a direction indicator (38), in particular a surface normal, for each measurement point (32) of at least a subset of the total set (34) of the recorded measurement points (32), wherein the direction indicator (38) is an indicator of the local orientation of the measured surface in the area of ​​the measurement point (32); IV Identifying the measuring points (32) belonging to the free ends (14, 15) of the plug-in coils (12), the identification comprising: a) Identifying all measurement points (32) in the total set (34) of recorded measurement points (32) whose height value lies within a tolerance range around a presumed position of the free ends (14, 15) in the height direction; b) Assigning these identified measurement points (32) to a set of candidates (44) for points of the free ends (14, 15); c) Grouping the candidates (44) into possible free ends (46), further candidates (44) being grouped with a candidate (44) to a possible free end (46) if they have a distance to the candidate (44) or to a candidate (44) already grouped with it that is equal to or less than a first maximum distance; d) for each possible free end (46) which includes a minimum set (Y) of assigned candidates (44), selecting at least one candidate (44) whose directional indicator (38) lies within a target range, as the identified measurement point (48) on the respective free end; e) For each of the identified measurement points (48): Assigning further measurement points (32) from the total set (34) of measurement points (32) from step II to the free end (14, 15) of the identified measurement point (48), whereby further measurement points (32) are assigned to the free end (14, 15), e1) if they are at a distance to the identified measuring point (48) or to another measuring point (32) associated with the free end (14, 15) that is equal to or less than a second maximum distance; and e2) if its direction indicator (38) is within a target value range.

Description

[0001] The present invention relates to a method for detecting plug-in coil positions in a stator or for detecting the position of their free ends.

[0002] The stator comprises a laminated core and plug-in coils. The plug-in coils have free ends that protrude from the laminated core. Plug-in coils can be single pins or, for example, hairpins. Hairpins are typically U-shaped plug-in coils with two legs, each with a free end, and a connecting section that joins these legs. This connecting section is located opposite the free ends.

[0003] DE 10 2005 016 525 A1 describes a general method for the three-dimensional shape acquisition of a general body. DE 10 2005 016 525 A1 specifies certain criteria for using only measurements from certain angles.

[0004] DE 10 2017 116 853 A1 provides for a system for the automatic selection of 3D alignment algorithms.

[0005] The invention is based on the objective of providing a method for detecting the position of the plug-in coils that is as reliable and accurate as possible.

[0006] The problem is solved by a method according to claim 1 and a device according to claim 12. The dependent claims and parts of the description describe advantageous embodiments of the invention.

[0007] The position of the plug-in coils, as described in this method, can be determined at various points during stator processing. Position measurement can be performed after the stator has been fitted with the plug-in coils, for example, before connecting or welding the free ends of the coils together. This measurement allows for verification of the correct alignment and position of the plug-in coils. This can be done before and / or after further processing steps. For instance, it ensures that the plug-in coils are correctly positioned for subsequent welding. Measuring the position of the plug-in coils, and potentially also the shape of their free ends, can also be used to check weld quality. The position measurement involves determining the surface profile of the free ends in space.

[0008] The method according to the invention comprises the following steps: Step 1: Placing the stator in a measuring area a profile sensor, such that a surface of the stator with free ends is located within the measuring range of the profile sensor;

[0009] The use of various measuring devices as profile sensors is possible. For example, a laser line sensor can be used. A laser line sensor can determine the distance of individual measuring points along a line to the sensor by means of triangulation. The use of several individual sensors that together measure the surface as a profile sensor is also in line with the invention.

[0010] When using a laser line sensor, the stator can be rotated beneath the laser line sensor, allowing the individual pin-bearing areas of the stator to move through the line-shaped detection area of ​​the line sensor. The individual line measurements (series of points) are then combined to create a two-dimensional measurement area with distance information (distance to the sensor) or height information for each measurement point. The profile sensor can comprise multiple measuring devices or sensors, such as several laser line sensors. It can also include a stereoscopic measuring device and / or one or more other types of measuring devices.

[0011] Step II: Capturing a respective 3-dimensional position of the stator surface relative to the profile sensor for a total number of measuring points using the profile sensor;

[0012] In this step, the three-dimensional position of each measuring point (typically its position within the measuring field—which is essentially a two-dimensional field with measuring points—and distance information) is recorded. For a line sensor where the stator rotates, the position within the measuring range can be determined, for example, by recording the stator's rotational position during a specific line measurement. The individual line measurements are then concatenated according to their respective rotation angles to obtain the complete measuring range.

[0013] In a laser line sensor, for example, the distance to the sensor for each measuring point along the measurement line (detection area) is determined by measuring the time of flight of the laser signal. The position of the measuring points along the sensor's measurement line is used together with information about the rotation of the stator under the sensor to assign the position of each measuring point within the measurement field.

[0014] A surface sensor can measure parts of the stator's surface or be dimensioned to measure the entire surface in a single measurement step. A point sensor can be used to scan each measurement point within the desired measurement range step by step and measure the respective height value.

[0015] Step III Determining a direction indicator, in particular a surface normal, for each measurement point of at least a subset of the total set of recorded measurement points, wherein the direction indicator is an indicator of the local orientation of the measured surface in the area of ​​the measurement point;

[0016] Typically, the direction indicator of a measuring point is determined by also considering surrounding measuring points or their position in the measuring field and the elevation information. However, this is not mandatory; other methods of determination are possible within the scope of the invention. For example, a sensor can be used that, in addition to the elevation information, also captures a value for the local surface orientation (e.g., by considering the intensity of the reflected signal or similar).

[0017] The direction indicator can, for example, be the local surface normal. To determine the direction indicator or the surface normal, a surface profile of the measured surface in the area of ​​the considered measurement points can be determined or approximated using the surrounding measurement points, and the direction indicator can be derived from this. For example, a surface can be approximated using the points in the neighborhood, and the normal of this fictitious surface can then be determined, which can then be used as the normal at the considered point. For approximation, for example, a surface function can be iteratively fitted to the points in the neighborhood. In another embodiment, a linear surface profile between the individual measurement points can be assumed. Other approximations of the surface profile are also within the scope of the invention.

[0018] Step IV Identifying the measuring points that belong to the free ends of the plug-in coils, whereby identification includes: This step comprises several sub-steps and serves to select those measurement points from the total set of recorded measurement points that represent the measurement data regarding the free ends of the plug-in coils.

[0019] A sub-step belonging to step IV a) comprises identifying all measurement points in the total set of recorded measurement points whose height value lies within a tolerance range around a presumed position of the free ends in the height direction.

[0020] The presumed position of the free ends can be based on knowledge of the stator geometry. It can also be based on an evaluation of the measurement data. For example, by checking in which plane a certain number of measurement points are located vertically, it can be concluded that the free ends are located near this plane. In substep a), all points are identified that lie within a tolerance range around the presumed position of the free ends. This also includes measurement points in vertical ranges that lie around the actual position of the ends.

[0021] In substep b), these identified measurement points are assigned to a set of candidates for points on the free ends. The identified measurement points are thus treated as candidates that could represent measurement points on the surface of the free ends. Since a tolerance range was considered in step a), the candidates also include measurement points that lie below the actual surface of the free ends and are located, for example, on the side faces of the conductor segments that transition into the surfaces of the free ends. Therefore, the candidates do not only include measurement points that are actually located on the surfaces of the free ends.

[0022] In substep c), the candidates are grouped into possible free ends. Additional candidates are grouped with a candidate at a possible free end if their distance to that candidate, or to a candidate already grouped with it, is equal to or less than a first maximum distance (calculated using the recorded 3-dimensional position of the candidates). Here, the candidates are grouped together by selecting measurement points from the set of candidates that lie within the first maximum distance of each other, or that are connected to each other via other candidates that are each within the first maximum distance of each other. The distance between two candidates can be determined, in particular, based on the previously determined 3-dimensional position of the corresponding measurement point.

[0023] This groups together all candidates corresponding to measurement points on the surface of a given free end. Since the candidates only include measurement points within a tolerance range around the presumed vertical position of the free ends, they do not include measurement points located in the spaces between the surfaces of the free ends (i.e., no measurement points at positions where, viewed from above, there are no conductor segments but rather the stator lamination stack). Candidates at the edges of the free ends or on the side faces of the conductor segments therefore have no adjacent candidates within the first maximum distance from them, pointing away from the surface of the free end. This ensures that the candidates for each end of the conductor segments are grouped separately from one another.

[0024] Thus, a group of candidates is formed for each free end or each contiguous free surface (a free end can also include the tops of two conductor pieces connected to each other, e.g., by welding).

[0025] In a substep d), for each possible free end that includes at least a minimum number of assigned candidates, at least one candidate is selected whose direction indicator lies within a target value range (surface locally exhibits target orientation) as an identified measurement point on the respective free end.

[0026] From the groups formed in step c) (these correspond to the free ends), at least one candidate or measurement point is selected in step d), and this is subsequently treated as an identified measurement point. To be selected in step d), the candidate's direction indicator must lie within a target value range. The surface described by the measurement point must therefore have a specific orientation. For example, if the stator is positioned with its free ends facing upwards within the measurement range of the profile sensor, the surface of the free ends typically extends horizontally. The corresponding surface normal would therefore point vertically. Accordingly, a candidate whose surface normal points vertically (within the target value range) would be selected as the identified measurement point (if the surface normal is used as the direction indicator).

[0027] In sub-step e), for each of the identified measurement points, the remaining measurement points from the total set of measurement points from step II are assigned to the free end of the respective identified measurement point. The grouping in this step requires that the remaining measurement points assigned to the free end meet both of the following criteria: Criterion e1): the further measuring points have a distance to the identified measuring point or to another measuring point already assigned to the free end that is equal to or smaller than a second maximum distance. This criterion corresponds to the criterion used in substep c) for grouping candidates. In other words, measurement points from contiguous areas are grouped together.

[0028] As a further criterion e2), only measurement points whose direction indicator lies within a target value range are assigned to a free end. For example, only those points with a surface normal pointing vertically (within the target value range) are assigned to the free end. In this way, the assignment of measurement points to a free end is effectively terminated at the surface edges, and only those measurement points belonging to the surface are grouped. The measurement points for the side faces of the conductor segments that merge into the surface are not assigned, as their direction indicator does not lie within the target value range. For example, their surface normal points horizontally.

[0029] As already stated, part of the invention also includes a device for detecting hairpin positions with a profile sensor having a detection range, wherein the device is designed and configured to carry out a method as described above and below. The descriptions of the methods are also to be understood as referring to the device.

[0030] Part of the invention also includes the use of a device according to the invention for carrying out one of the methods according to the invention.

[0031] Points from the total set of measurement points from step II that are not assigned to any of the identified measurement points and therefore not to any free end in substep e) can be explicitly identified as not belonging to a free end.

[0032] The above descriptions detail the method according to the invention. The method can also be described in simplified terms in broad strokes. However, this simplified description should not be understood as limiting the scope of the method according to the invention described above.

[0033] In simple terms, the process involves roughly placing the stator within the measuring range of the profile sensor. The profile sensor then captures a three-dimensional profile of the stator "from above" (looking at the upward-protruding plug-in coils), allowing the position of the individual plug-in coils and their free ends to be determined.

[0034] The measurement points that characterize the surface of the free ends of the individual plug-in coils are then identified in the acquired measurement data. This is done by carrying out the further steps performed within the framework of the method according to the invention.

[0035] In simplified terms, the process begins by examining the measurement points located around a presumed position of the free ends. These points are then checked to determine if they actually belong to a free end. This is done by verifying that a sufficient number of surrounding measurement points are at the same height. From the points that, along with a sufficient number of surrounding points, are at the correct height, one point is selected for each free end, provided that the surface at the position of this point extends in the appropriate direction (typically horizontally).

[0036] Starting from this selected point, the remaining points that actually belong to a free end are identified. This involves checking which surrounding measurement points are sufficiently close to each other. During this check, the points must also meet the criterion that the measured surface at the respective location (the measurement point) has a suitable direction (normally extending horizontally). By checking the direction of the surface's extension, the edges of the free ends can be reliably identified, and thus the surfaces of the free ends of the plug-in coils can be recognized.

[0037] Before sub-step a) in step IV, the position of the stator laminated core in the vertical direction can be determined. Specifically, in sub-step a) of step IV, the presumed position of the free ends and the tolerance range relative to the position of the stator laminated core can be taken into account. This allows information about the stator geometry to be used to improve the accuracy of the measurement. Positioning inaccuracies can also be compensated for.

[0038] The method can also include a step in which the rotational position of the stator is detected within the measuring range or with respect to a detection range of the profile sensor. For this purpose, the stator typically includes a marking that indicates a specific position on its circumference. Such a marking can, for example, be arranged on the stator's laminated core. Depending on the stator, the rotational position of the stator can also be derived from the arrangement of the plug-in coils, as required by the method. In a step to determine the rotational position, a rough measurement of the plug-in coil positions can be performed, although this does not yet achieve the accuracy of the measurement method according to the invention. By detecting the rotational position, high accuracy can be achieved with simple and easy-to-use sensor technology.

[0039] As previously explained, the measuring range of the profile sensor can be composed of multiple individual measurements taken during the stator measurement process. For example, the measuring range can be composed of a series of linear measurement points measured along the stator, offset by a specific rotational angle. The detection range encompasses the number of measurement points that can be acquired by the profile sensor in a single measurement. The measuring range, in turn, comprises the total number of measurement points used to measure the stator or its surface as a whole, which may have been acquired in several individual measurement processes. Thus, the measuring range can include multiple individual measurements acquired at different times, which, taking into account any changes in the relative position between the stator and the detection range of the profile sensor, are combined to form a single overall measurement that constitutes the measuring range.This allows for the use of a simple and reliable sensor.

[0040] It is specifically intended that the detection area comprises a linear series of measuring points extending across the width of one side of the stator. A linear detection area particularly encompasses the radial extent of the plug-in coils, arranged essentially on concentric circular paths, on one side of the stator, as viewed from a rotational axis of the stator.

[0041] The measuring range, when viewed in a planar dimension, can particularly have the shape of a circular ring disk. A region around the stator's axis of rotation can therefore be specifically excluded from the measurement. In this way, the measuring range is limited to relevant areas, and the measurement resolution can be increased while maintaining the same metrological effort for the profile sensor.

[0042] The detection range of the profile sensor can be configured to capture a linear series of measurement points in a single measurement process. This allows for the rapid and reliable measurement of line profiles, and the detection range of the profile sensor can be moved across the stator. When capturing the 3-dimensional position of the stator surface in step II, multiple measurement processes can be performed with a stationary profile sensor, and the stator can be moved relative to the profile sensor between each measurement, for example, by rotating it. This allows for precise control of the profile sensor's position. It is also possible for the stator to remain stationary while the profile sensor is moved.

[0043] The profile sensor can include at least one measuring device that detects the 3-dimensional position of the stator surface using laser triangulation. This allows for high measurement speed and accuracy.

[0044] In sub-step e) of step IV, when checking criterion e1), a distance in the vertical direction may be weighted differently than a distance in the horizontal plane. For example, positional differences in the vertical direction may be assigned a higher weight. Therefore, deviations in the vertical direction could, for example, lead to a termination if they are small, i.e., to a failure to assign the result to a free end.

[0045] A free end can be a single free end of a single plug-in coil. In particular, the position of a special pin can be checked here.

[0046] At least one free end can be a common free end, encompassing at least the individual free ends of two plug-in coils. In this case, the position of the individual ends themselves, as well as their alignment relative to each other, can be checked. For example, the overall outline of the common free end can be determined and checked to detect any offset in the horizontal plane. A vertical offset can also be checked.

[0047] At least one free end can be a common free end comprising welded individual free ends from at least two plug-in coils. This can be used for weld seam inspection. In particular, a shape analysis can also be performed, taking into account the height profile of the weld seam. Figures

[0048] The invention will now be explained with reference to the accompanying drawings. The drawings show: Fig. 1 a schematic perspective view of a stator with inserted and twisted plug-in coils; Fig. 2 a schematic representation of a detection of the position of free ends of plug-in coils in a symbolically represented stator by means of a profile sensor; Fig. 3 a schematic representation of the measuring range of the profile sensor Fig. 1; Fig. 4 a schematic representation of a flow chart of the method according to the invention; Fig. 5 a schematic representation of a subset of measurement points whose height value lies within a tolerance range around a presumed position of the free ends in the height direction; Fig. 6 an illustration of the procedure for processing the measured values; and Fig. 7 an alternative formation of a measuring range.

[0049] In the figures, corresponding elements and areas bear the same reference symbols. Not all reference symbols are shown in all figures.

[0050] Fig. Figure 1 shows a schematic perspective view of a stator 10 with twisted plug-in coils 12 inserted into a laminated core 11. The plug-in coils 12 are arranged on circular tracks extending in the circumferential direction U. Each plug-in coil 12 has stripped individual free ends 14, which are oriented in a vertical direction H. The individual free ends 14 are arranged such that predominantly two individual free ends 14 are positioned together and effectively form a common free end 15, which is subsequently welded together. The plug-in coils 12 are predominantly designed as hairpins with a generally U-shaped profile (the U-shape is not shown in the figure). However, the stator 10 also includes individual special pins 16, which have a different geometry, e.g.Longer legs with individual free ends 14, wherein these individual free ends 14 are partially arranged individually and not in pairs. Various pin shapes and types are possible within the scope of the invention.

[0051] A free end 14 within the meaning of the invention can be a single free end 14, i.e., the end of a leg of a single plug-in coil 12, or it can be a common free end 15 within the meaning of the invention, which can be formed from several adjacent single free ends 14.

[0052] Fig. Figure 2 shows a schematic representation of the detection of the position of free ends 14, 15 of plug-in coils 12 in a symbolically represented stator 10 by means of a profile sensor 18, which is arranged at a distance 20 from the surface of the stator 10. The distance 20 varies across the surface of the stator 10, depending on the stator geometry.

[0053] The profile sensor 18 is designed as a laser line sensor and emits a fan-shaped laser signal onto the surface of the stator 10, resulting in a linear direct detection area 24. This means that several measuring points along the detection area 24 are measured in a single measurement process. The laser signal reflected from the surface of the stator 10 in the area of ​​the linear direct detection area 24 is received point by point in the profile sensor 18, and the respective distance at each measuring point 32 in the detection area 24 is determined by measuring the signal transit time. Fig. Figure 1 also shows an alternative extent 25 of a possible detection area 24, which captures the width of one side of the stator 10. To capture the entire surface of the stator 10, the stator 10 is rotated about a rotation axis 26, as indicated by the arrow 28. In this way, in the present example, the different areas of the surface of the stator 10 are supplied to the linear direct detection area 24.

[0054] The stator can include a marking 29 by means of which its rotational position with respect to the direct detection range 24 or its position in an overall measuring range or measuring range 30 can be uniquely identified. Taking into account the respective rotational position of the stator 10 in the measuring range 30 of the profile sensor 18, the individual line-like arranged measuring points 32 are combined to form an overall measurement. An example of such a combined measuring range 30 with all measuring points 32 is shown in the Fig. 3 and Fig. Figure 7 (for the alternative extension 25) is shown. Other arrangements of the measuring points 32 in the measuring range 30 are conceivable within the scope of the invention.

[0055] In the example of Fig. The measuring points 32, which are arranged on a line 36 extending radially outwards from the center of the measuring area 30, each correspond to a measurement of the profile sensor 18 in a specific angular position. The individual radially extending lines 36 are each offset by a specific rotation angle and together cover a complete rotation (360° in specific rotational steps).

[0056] After the 3-dimensional position of the stator surface relative to the profile sensor 18 has been recorded for the total set 34 at measuring points 32 (in each intended angular position) using the profile sensor 18 (step II of the procedure), a direction indicator 38, in particular a surface normal, is determined for each measuring point 32 or at least a subset of the total set 34 of recorded measuring points 32 (step III of the procedure). The direction indicator 38 is an indicator for the local orientation of the measured surface in the area of ​​the respective measuring point 32. Fig. For clarity, only directional indicators 38 are shown at some of the measuring points 32.

[0057] In step IV of the procedure, the measuring points 32 belonging to the free ends 15 of the plug-in coils 12 are identified. This identification takes place in several sub-steps, which in Fig. 4 is shown in a flowchart. Identification includes: a) Identifying all measurement points 32 in the total set 34 of recorded measurement points 32 whose height value lies within a tolerance range around a presumed position of the free ends 14, 15 in the height direction H.

[0058] This results in a subset 40 of measuring points 32 as schematically represented in Fig. Figure 5 is shown. This subset 40 mainly comprises measuring points 32 that are assigned to the surface of the free ends 15. Since a tolerance range is also taken into account in substep a), the subset 40 also includes measuring points 32 that are assigned to the surface on the side faces 42 descending from the free ends 15 (see Figure 5). Fig. 1) are assigned to the plug-in coils 12.

[0059] In sub-step b), these identified measuring points 32, i.e., the measuring points 32 identified in sub-step a) within the tolerance range in the vertical direction, are assigned to a set of candidates 44 for measuring points 32 of the free ends 15.

[0060] In sub-step c), the candidates 44 are grouped into possible free ends 46. Such grouping is in Fig. 6 for part of the in Fig. The process is illustrated by the five candidates 44 shown. Further candidates 44 are grouped with a candidate 44 at a possible free end 46 if their distance to the candidate 44 or to a candidate 44 already grouped with it is equal to or less than a first maximum distance. The distance is calculated using the recorded 3-dimensional position of the respective candidates 44 or the measurement points 32 that have been identified as candidates 44.

[0061] In step d), for each possible free end 46 that comprises a minimum number of assigned candidates 44 or more, at least one candidate 44 is selected whose direction indicator 38 lies within a target value range (surface locally exhibits target orientation) as an identified measurement point 48 on the respective free end 15. By requiring the minimum number, only those possible free ends 46 are considered or treated as actual free ends that comprise a sufficiently large number of measurement points 32 or candidates 44. This results in smaller groups 50 (see Fig. 6) Candidates 44 or adjacent measurement points 32 were not considered further. It can be assumed that these smaller groups 50 do not represent actual free ends, as they comprise too few measurement points 32 at the level of the free ends 15 of the plug-in coils and are usually due to measurement inaccuracies or artifacts.

[0062] In sub-step e), for each of the identified measuring points 48: the further measuring points 32 from the total set 34 of measuring points from step II are assigned to the free end 15 of the identified measuring point 48, whereby further measuring points are assigned to the free end if the two criteria e1) and e2) are met.

[0063] Criterion e1) is fulfilled for further measurement points 32 from the total set 34 of measurement points 32 if they have a distance to the identified measurement point 48 or another measurement point 32 already assigned to the free end 15 that is equal to or less than a second maximum distance. The distance is calculated using the recorded 3-dimensional position of the candidates 44 or measurement points 32.

[0064] The criterion e2) is fulfilled for further measuring points 32 from the total set 34 at measuring points 32 if their direction indicator 38 lies within a target value range.

[0065] Criteria e1) and e2) ensure that, with a suitable selection of maximum distance and setpoint range, only those additional measuring points 32 are assigned to the free end 15 of an identified measuring point 48 that have a specific surface orientation and a maximum distance. Typically, these are adjacent measuring points 32 at essentially the same height and with a horizontally extended surface. This is the typical configuration for the surfaces of the free ends 15.

[0066] The measuring range 30 can, as in Fig. Figure 7, viewed purely in its planar extent, exhibits in particular the shape of a circular annular disk. A region around the rotation axis 26 of the stator 10 can therefore be specifically excluded during measurement.

Claims

[1] Method for detecting the position of free ends (14, 15) of plug-in coils (12) in a stator (10), the method comprising: I. Placing the stator (10) in a detection area (24) of a profile sensor (18) such that a surface of the stator (10) with free ends (14, 15) is located in the detection area (24) of the profile sensor (18); II. Detection of a respective 3-dimensional position of the stator surface relative to the profile sensor (18) for a total quantity (34) of measuring points (32) using the profile sensor (18); III Determining a direction indicator (38), in particular a surface normal, for each measurement point (32) of at least a subset of the total set (34) of the recorded measurement points (32), wherein the direction indicator (38) is an indicator of the local orientation of the measured surface in the area of ​​the measurement point (32); IV Identifying the measuring points (32) belonging to the free ends (14, 15) of the plug-in coils (12), the identification comprising: a) Identifying all measurement points (32) in the total set (34) of recorded measurement points (32) whose height value lies within a tolerance range around a presumed position of the free ends (14, 15) in the height direction; b) Assigning these identified measurement points (32) to a set of candidates (44) for points of the free ends (14, 15); c) Grouping the candidates (44) into possible free ends (46), further candidates (44) being grouped with a candidate (44) to a possible free end (46) if they have a distance to the candidate (44) or to a candidate (44) already grouped with it that is equal to or less than a first maximum distance; d) for each possible free end (46) which includes a minimum set (Y) of assigned candidates (44), selecting at least one candidate (44) whose directional indicator (38) lies within a target range, as the identified measurement point (48) on the respective free end; e) For each of the identified measurement points (48): Assigning further measurement points (32) from the total set (34) of measurement points (32) from step II to the free end (14, 15) of the identified measurement point (48), whereby further measurement points (32) are assigned to the free end (14, 15), e1) if they are at a distance to the identified measuring point (48) or to another measuring point (32) associated with the free end (14, 15) that is equal to or less than a second maximum distance; and e2) if its direction indicator (38) is within a target value range. [2] Method according to claim 1, characterized by, that before sub-step a) in step IV a position of the stator stack (11) in the vertical direction (H) is determined and that in particular in sub-step a) in step IV the presumed position of the free ends (14, 15) and the tolerance range from the position of the stator stack (11) (10) are taken into account. [3] Method according to any of the preceding claims, characterized by , that it includes a step in which a rotational position of the stator (10) is detected in the measuring range (30) or with respect to a detection range (24) of the profile sensor (18). [4] Method according to any of the preceding claims, characterized by , that the measuring range (30) comprises several individual measurements which are recorded at different times and which are combined to form a total measurement taking into account a change in the relative position between stator (10) and detection area (24) of the profile sensor (18), forming the measuring range (30). [5] Method according to any of the preceding claims, characterized by , that the detection range (24) of the profile sensor (18) detects a linear series of measurement points (32) in a measurement process. [6] Method according to any of the preceding claims, characterized by , that when capturing the 3-dimensional position of the stator surface in step II, several measurement processes are carried out with a stationary profile sensor (18) and the stator (10) is moved relative to the profile sensor (18) between each measurement process. [7] Method according to any of the preceding claims, characterized by , that the profile sensor (18) comprises at least one measuring device which detects the 3-dimensional position of the stator surface by means of laser triangulation. [8] Method according to any of the preceding claims, characterized by, that in sub-step e) of step IV, when testing criterion e1), the distance is weighted differently for a distance in the vertical direction (H) than for a distance in a horizontal plane orthogonal to the vertical direction (H). [9] Method according to any of the preceding claims, characterized by , that at least one free end (14, 15) is a single free end (14) of a single plug-in coil (12). [10] Method according to any of the preceding claims, characterized by , that at least one free end (14, 15) is a common free end (15) which includes at least the individual free ends (14) of two plug-in coils (12). [11] Method according to any of the preceding claims, characterized by , that at least one free end (14, 15) is a common free end (15) which comprises welded individual ends of at least two plug-in coils (12). [12] Device for detecting hairpin positions with a profile sensor (18) having a detection area (24), wherein the device is designed and configured to perform a method according to any one of claims 1 to 11.

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