Method and measuring device for determining the arrangement of a track component

Abstract

The invention relates to a method for determining the arrangement of a track component (12), in particular a track sleeper (6), of a track (4) mounted in a ballast bed (7), wherein a region (14) of the track (4) is detected by means of an optical sensor device (17). The track (4) is lifted in the detected region (14), in which the track component (12) is hidden under ballast grains (11), the position of ballast grains (11) being changed, and the arrangement of the track component (12) is determined on the basis of the position changes (16) of the ballast grains (11) detected by means of the sensor device (17). In this way, the arrangement of the ballasted track component (12) is indirectly determined.

Description

[0001] METHOD AND MEASURING DEVICE FOR DETERMINING THE ARRANGEMENT OF A TRACK COMPONENT

[0002] The invention relates to a method for determining the arrangement of a track component, in particular a track sleeper, of a track bed embedded in ballast, wherein a section of the track is detected by means of an optical sensor device. Furthermore, the invention relates to a corresponding measuring device comprising the optical sensor device and an evaluation device for determining the arrangement based on measurement signals from the sensor device, as well as a system with the measuring device.

[0003] A method for controlling a track construction machine is known from AT 519739 A4. Positional data of track objects, in particular track sleepers and rails, and of obstacles are acquired using an optical sensor device. The optical sensor device can comprise a laser scanner or a camera for this purpose. The reliability and precision with which the positional data of the track objects can be acquired depends on the nature of the object to be acquired and its surroundings. Furthermore, the method can only determine the arrangement of track objects that are visible to the optical sensor device.

[0004] The invention is based on the objective of improving the aforementioned method in such a way that the arrangement of track components covered with ballast grains can also be determined. A further objective of the invention is to provide a corresponding measuring device and a system for using the measuring device. These objectives are achieved by the features of independent claims 1, 9, and 12. Dependent claims specify advantageous embodiments of the invention.

[0005] According to the invention, the track in the detected area is lifted along with the track component concealed beneath ballast grains, thereby changing the position of the ballast grains. The arrangement of the track component is determined based on these positional changes of the ballast grains detected by the sensor device. The lifted track section can also extend beyond the area detected by the sensor device. In this way, the arrangement of the ballasted track component is determined indirectly. Positional changes of the ballast grains also include changes in orientation due to minor rolling or tilting movements. In these cases, the edges and surface segments of the respective ballast grains also change their position in space. The movement of the track component during the track lifting process causes the detected positional changes of the ballast grains. The ballast grains positioned directly above the track component are lifted along with the track component.Other ballast grains, such as those positioned in a sleeper bay between two track sleepers, remain unchanged. In a transition zone, ballast grains slide sideways. This trickling movement is also detected by the sensor system and used to determine the position of the track component.

[0006] By recording the changes in position, that is, the movements of the ballast grains, conclusions can be drawn, in particular, about the arrangement of the track component in the longitudinal direction of the track. In the simplest case, this is done by evaluating height differences along the recorded ballast grain surface. For this purpose, for example, images are taken using a 3D scanner before and after lifting the track section. Preferably, a line or grid pattern is projected onto the ballast surface using a laser and recorded with a camera. The height differences can be derived from local distortions of the pattern when the track section is lifted.

[0007] The optical sensor device, in particular a camera, is directed from above or from an oblique angle onto the area of ​​the track with the track component hidden under ballast grains. The movement of the ballast grains at the edges of the raised track component is evaluated using computational image analysis, for example, by means of image correlation or optical flow analysis of two or more successive 2D or 3D images.

[0008] Advantageously, the position of the gravel grains is recorded using a so-called event camera. This is a camera whose event-based image sensor is designed to detect changes within a recorded area. If no changes occur within the area the event camera is pointed at, the recorded image shows a uniform gray area. However, as soon as an event occurs in the area—that is, an optical change—the event camera's image indicates this through altered gray values, ranging from gray to white and black in the corresponding areas. The display of these events is independent of the absolute brightness of the recorded scene. Therefore, even movements of objects whose brightness or darkness lie outside the dynamic range of a conventional camera can be recorded.Furthermore, an event camera features asynchronous refresh rates in the range of 1 MHz, enabling the capture of even very fast events with high resolution and without motion blur. The latency of an event camera is also significantly lower than that of a conventional camera. This allows for real-time event recording.

[0009] In the event camera, specific sensor pixels of an image sensor output a measurement signal that detects a change in brightness at their respective location within the captured area. The assignment of the captured area to the respective sensor pixel is determined by the imaging optics, specifically the lens of the event camera. The pixel size and the properties of the imaging optics determine the size of the area imaged by a single sensor pixel at each location. In any case, the movement of a gravel grain is detected immediately when a brightness value on the surface of the gravel grain changes. This occurs when the corresponding surface changes its position relative to an existing light source. Brightness changes resulting from movement are detectable in both daylight and artificial light.

[0010] In a further advantageous improvement, the respective output measurement signal is fed to an evaluation unit, where measurement signals received over a detection period are evaluated to determine the position of the track component. The detection period corresponds to an accumulation time for the respective received measurement signal. This means that a value proportional to the measurement signal is accumulated during this period. The accumulation time affects the reaction speed and detection accuracy when determining the position of the track component. A shorter accumulation time increases the evaluation speed. However, the accumulation time must be sufficiently long to allow enough relevant image information resulting from detected brightness differences to be evaluated. Preferably, the accumulation time lies in a range between 10 milliseconds and 33 milliseconds.

[0011] Advantageously, measurement signals received from the sensor pixels during the recording period are evaluated as event values. For example, each change in brightness from light to dark or from dark to light results in an event value of one. Either the initial event value for each sensor pixel remains constant for the duration of the recording period, or the event values ​​for each sensor pixel are accumulated. In the latter case, the respective event value is higher the more changes in brightness resulting from movements are detected at the point on the track assigned to the corresponding sensor pixel.

[0012] Advantageously, the measurement signals from the sensor pixels, which are arranged on a common detection axis (ideally parallel to a track transverse direction), are evaluated as a single summed event value. For each detection axis, only this single summed event value is needed for further evaluation. This allows the efficient determination of the position of track components with a longitudinal orientation parallel to the selected detection axis. A corresponding evaluation algorithm can be implemented with minimal computing resources and a short evaluation time, thus enabling a

[0013] Evaluation results are available almost in real time.

[0014] In a further advantageous embodiment of the method, the elevation of a ballast surface relative to the sensor device is detected, whereby the arrangement of the track component is determined, in particular, based on an elevation profile of the ballast surface. The sensor device detects the result of positional changes of the ballast grains. As soon as individual ballast grains exhibit a changed elevation relative to the sensor device, this change in the surface profile is used for subsequent evaluation to determine the arrangement of a track component. A 2D or 3D laser scanner or a lidar sensor (Light Detection and Ranging Sensor) can be used as the sensor device, for example.

[0015] Preferably, the sensor system is controlled synchronously with a lifting unit of a track construction machine. The term "lifting unit" also refers to a lifting and aligning unit. This improvement allows the sensor system to be activated specifically when a track section is set in motion by the lifting unit. Outside of these operations, the sensor system and computer-aided evaluation require no resources, resulting in an overall efficient execution of the process.

[0016] In the measuring device according to the invention for determining the arrangement of a track component, in particular a track sleeper, of a track bed supported in ballast, comprising an optical sensor device for detecting a section of the track and an evaluation device for determining the arrangement based on measurement signals from the sensor device, the sensor device is configured to detect changes in the position of the ballast grains during a lifting operation of a section of the track with the track component hidden under ballast grains, and the evaluation device is configured to determine the arrangement of the track component based on the detected changes in the position of the ballast grains. With this measuring device, a reliable determination of the position of a track component hidden under ballast is possible in real time.

[0017] Advantageously, the sensor system includes an event camera. Such an event camera enables the detection of gravel movements regardless of the prevailing lighting conditions, for example, in high contrast ranges, with high accuracy and without delays.

[0018] In a further improvement, the sensor system includes a distance measuring device, in particular a lidar sensor or a time-of-flight (TOF) camera. This distance measuring device can detect the distance between the ballast surface and the sensor. In a simple version, this allows the location of a hidden track component to be determined based on a change in the surface profile. Together with an event camera, the distance measuring device serves to define a reference plane for determining the position of a track component within a coordinate system assigned to the sensor. This is useful if the event camera is positioned at an oblique angle, i.e., with a sharp viewpoint onto the ballast surface. Then, by comparing the data acquired by the event camera and the distance measuring device, a specific position of the surface captured by the event camera in space can be determined.The positions of characteristic surface features subsequently lead to the spatial determination of the arrangement of a track component located based on these surface features. Such characteristic surface features are, in particular, the positional changes of the ballast grains, captured by the event camera and statistically evaluated. For example, clustered positional changes of the ballast grains indicate a track component located beneath them.

[0019] A system according to the invention with the described measuring device is characterized by a lifting unit for lifting a track section towards which the sensor device is directed. Such a system comprises all components necessary for the efficient detection of a track component hidden under ballast. As soon as a track section towards which the measuring device is directed is moved by means of the lifting unit, the moved ballast grains are detected, followed by an evaluation to determine the position of characteristic surface features caused by the moving track component.

[0020] Preferably, a control unit for the synchronous control of the lifting unit and the measuring device is arranged as a system component. This control unit is, for example, coupled as a separate component to the machine control of a tamping machine or integrated into this machine control. This allows the measuring device to be activated as soon as the lifting unit causes movement of the track section under consideration.

[0021] Advantageously, the system is designed as a track construction machine that can be moved along the track using rail-mounted chassis and includes the lifting unit and the measuring device. The measuring device is an integral component of the track construction machine.

[0022] The track construction machine includes, in particular, a tamping unit for tamping under track sleepers, wherein the respective track sleeper has an arrangement relative to the track construction machine determined by the measuring device, and wherein a machine control system is provided, in particular for automatically positioning the tamping unit over the respective track sleeper. Such a track construction machine can be operated as an autonomous machine for automatically tamping under the track sleepers. The measuring device provides the machine control system with all the necessary position data for the automated positioning of the tamping unit over the respective track sleeper.

[0023] The invention is explained below by way of example with reference to the accompanying figures. These show, in schematic representation:

[0024] Fig. 1 Track construction machine on a track;

[0025] Fig. 2 Track component under ballast;

[0026] Fig. 3 Track section and measuring device;

[0027] Fig. 4 Sensor device;

[0028] Fig. 5 Image from an event camera showing an initial recording period;

[0029] Fig. 6 captured events according to the recording in Fig. 5;

[0030] Fig. 7 Recording of an event camera with a second

[0031] Collection period;

[0032] Fig. 8 recorded events according to the recording in Fig. 6.

[0033] The track construction machine 1 shown in Fig. 1 is a

[0034] The tamping machine comprises a machine frame 2, which is movable on rail carriages 3 on a track 4. This track construction machine 1 serves to restore the intended position of a track grid formed from track rails 5 and track sleepers 6, which is supported in a ballast bed 7. A lifting unit 8 is arranged on the machine frame 2 for lifting and lateral adjustment. A tamping unit 10, arranged behind it with respect to a working direction 9, serves to fix the raised track grid by pushing ballast grains 11 under the raised track sleepers 6 and compacting them.

[0035] Especially during track relocation, track components 12, particularly the sleepers 6 as well as balises or components of a turnout, are completely ballasted because significant lifting forces are required to bring the track 4 into its desired final position. A sufficient quantity of ballast is needed to fill the correspondingly large voids under the sleepers resulting from these large lifting forces. With such ballasting, rail fastenings are also buried deep beneath the ballast layer, rendering sensors for detecting these metallic rail fastenings ineffective. Therefore, it is impossible to determine the position of a sleeper 6 based on the position of its associated rail fastening.In practice, the positioning of the tamping unit 10 over a track sleeper 6 is carried out by an operator who, based on sufficient experience and known sleeper spacing, can estimate the arrangement of the respective track sleeper 6 under the ballast grains 11.

[0036] To relieve the operator and subsequently automate the track construction machine 1, a measuring device 13 is arranged according to the invention, by means of which the arrangement of a respective track component 12 under a layer of ballast can be determined. This measuring device 13 is directed at an area 14 of the track 4 and detects the corresponding surface. In this area, a section of the track 4 is lifted by means of the lifting unit 8. During this lifting process 15, ballast grains 11 are set in motion and change their position. In particular, the ballast grains 11 resting on hidden track components 12 are lifted upwards. The ballast grains 11 located in between retain their position. In a transition area, partially lifted ballast grains 11 slide laterally. These changes in position 16 of the ballast grains 11 are detected by means of an optical sensor device 17 of the measuring device 13.This results in characteristic features of the recorded ballast surface 18, which allow clear conclusions to be drawn about the arrangement of the respective hidden track component 12.

[0037] In an evaluation unit 19, these characteristic features of the recorded ballast surface 18 are computationally evaluated. A corresponding algorithm is implemented in the evaluation unit 19 for this purpose. Preferably, a trainable algorithm is used, which, based on past and evaluated work processes, forms a continuously improved mathematical model based on artificial intelligence (AI model) for determining the position of a track component 12 from the recording data of the sensor device 17. An artificial neural network implemented in a processor of the evaluation unit 19 is trained with data from the sensor device 17. Preferably, the so-called Machine Learning Operations (MLOps) method is used for this training of the AI ​​model. The advantage lies in consistent and reproducible results.This is achieved through expert-supervised training and the selective input of controlled, high-quality data. The corresponding AI uses the so-called deep learning method of neural networks.

[0038] The trickling movements 20 of the ballast grains 11 at the edges of the upwardly moving track component 12 are detected by means of an image analysis system set up in the evaluation unit 19. For this purpose, digital image correlation (DIC) or optical flow analysis is performed on two or more successive 2D or 3D images to determine the movement vectors. In Fig. 2, the position changes 16 of the ballast grains 11 detected by the image analysis are shown as hatched areas. It can be seen that the lifting process 15 produces a characteristic pattern of the detected position changes 16. This results in a height profile 21 of the ballast surface 18, from which the arrangement of the hidden track component 12 can be derived.

[0039] To detect the position changes 16 of the gravel grains 11, the sensor system 17 includes, for example, a lidar sensor, a time-of-flight sensor, or a digital camera for capturing color or monochrome images. Images are captured with a sufficiently high frame rate (frames per second, FPS) using the digital camera and then processed for image analysis. A 2D laser scanner can also be used to capture the resulting height profile 21.

[0040] In Fig. 3, the measuring device 13 is shown with an extended

[0041] Sensor assembly 17 is shown. This assembly includes the evaluation unit 19, to which an event camera 22 and a distance measuring device 23 are connected. Unlike conventional cameras, the event camera 22 only detects actual movements within the observed area 14, with these movements being detected in the form of local changes in brightness. Other names include neuromorphic camera, silicon retina, or dynamic vision sensor. The sensor pixels 25 arranged on an image sensor 24 operate independently and asynchronously and only provide an output signal when a change in brightness occurs at a location 27 of the detected area 14, which is assigned by means of an imaging optic 26 (Fig. 4).

[0042] Preferably, a light source 28 is arranged with an oblique incidence of light onto the observed area 14. In this way, even slight movements of a ballast grain 11 lead to perceptible changes in brightness on the surface. Optimal illumination is achieved by producing maximum contrast changes even with minimal ballast movements. Additionally, the illumination can be spectrally restricted to create a defined lighting situation. The optical detection devices 22, 23 are equipped with appropriate optical filters.

[0043] The distance measuring device 23 comprises, for example, a lidar sensor or a time-of-flight (TOF) sensor for detecting a distance to a height h of the respective gravel grain 11. For example, the height h is detected as a distance between a zero point of the distance measuring device 23 and a reference plane 29, which is approximated to the irregular gravel surface 18. Due to the known fixed arrangement of the distance measuring device 23 and the event camera 22 within a housing or a support frame of the measuring device 13, the height h of the respective gravel grain 11 with respect to the image sensor 24 of the event camera 22 is also known.

[0044] In Fig. 3, the lifting process 15 is illustrated by arrows. The lifting unit 8 grips the track rails 5 at a lifting point 30 with lifting rollers or lifting hooks and pulls them upwards together with the track components 12 connected to the track rails 5. These are essentially the track sleepers 6 located in the lifted section of the track 4. The lifting of the track sleepers 6 is greatest in the immediate vicinity of the lifting point 30 and decreases with increasing distance from the lifting point 30. Therefore, the measuring device 13 is arranged on the track construction machine 1 such that the detected area 14 is close to the lifting point 30. Preferably, the lifting point 30 lies within the detected area 14. The lifting height for detecting the position changes 16 of the gravel grains 11 is preferably in a range between 5 mm and 40 mm, in particular between 5 mm and 20 mm, for example at 10 mm .After the recording process, the lifting can continue without interruption if a larger lifting value is specified to achieve a target position of track 4.

[0045] The determination of the position of a point 27 on the surface of a gravel grain 11 with a detected change in brightness is explained with reference to Fig. 4. A fixed coordinate system XYZ of the measuring device 13 serves, for example, as the reference system. The height h of the gravel surface 18 is measured using the distance measuring device 23. From this measured height h, a current distance of the event camera 22 to the gravel surface 18 can be derived. Subsequently, the position of the surface point 27, detected by a sensor pixel 25, is determined via a projection axis 31 according to a pinhole camera model. This surface point 27 lies at the intersection between the projection axis 31 and the reference plane 29, which approximates the irregular gravel surface 18. The position of this reference plane 29 in the XYZ coordinate system is thus derived from the height h of the gravel surface 18 recorded by means of the distance measuring device 23.

[0046] The image sensor 24 of the event camera 22 has sensor pixels 25 arranged in a two-dimensional coordinate system. Each sensor pixel 25 has a first coordinate on a first coordinate axis a and a second coordinate on a second coordinate axis b in this coordinate system. A coordinate transformation performed in the evaluation unit 19 yields the position of each sensor pixel 25 in the three-dimensional XYZ coordinate system of the measuring device 13. Using the known position of the projection axis 31 of each sensor pixel 25 and the measured height h of the ballast surface 18, the coordinates of the recorded surface point 27 in the three-dimensional XYZ coordinate system can also be calculated by the evaluation unit 19. Subsequently, the arrangement of each track object 12 can be determined in the form of coordinates.

[0047] In a simpler version, the event camera 22 is pointed directly down onto the gravel surface. If the distance to the gravel surface is sufficiently large relative to the given lifting values, determining the elevation h is unnecessary. The coordinates of the respective recorded point 27 are derived directly from the

[0048] Position of the event camera 22 about the respective projection axis 31. For the geometric relationships, a constant distance to a fictitious gravel surface plane 29 is assumed. The reduction of the distance due to the lifting process 15 is disregarded because a corresponding horizontal displacement of the intersection point of the respective projection axis 31 with the fictitious gravel surface plane 29 is negligible.

[0049] Fig. 5 shows a recording 32 from the event camera 22 with an initial recording period. During this period, changes in brightness are visible, resulting from a lifting operation 15 of the track 4, which in turn causes movement of the ballast grains 11 resting on the track components 12. In this exemplary representation of recording 32, the white pixels indicate a recorded change in brightness from dark to light. Recorded changes in brightness from light to dark are represented by black pixels. The consistently gray pixels are assigned to track sections without recorded movement. However, the representation of the recorded data can be flexibly implemented. For example, the same raw data can lead to different representations with different accumulation times.

[0050] The arrangement of the respective track sleeper 6 is already visible in this image 32. For example, the event camera 22 is directed towards the area of ​​track 4 below the tamping unit 10. Vibrating tamping picks 33 are then also visible in the image 32. Based on this image 32, an operator can position the tamping unit 10 above the visible track sleeper 6. For this purpose, a monitor is installed in an operator's cabin 34 to display the current image 32. In other preferred variants, the event camera 22 is arranged on the machine frame 2 or on the lifting unit 8 and forms an acute viewing angle α with respect to the reference plane 29. When the event camera 22 is arranged on or in the area of ​​the lifting unit 8, the viewing direction is directed forward with respect to the working direction 9.The viewing direction of the event camera 22 can also be directed backwards with respect to the working direction 9 if the event camera 22 is mounted in front of the lifting unit 8 and, in particular, in front of the tamping unit 10. In any case, the event camera 22 is directed towards an observation area that lies within the track section raised by means of the lifting unit 8.

[0051] For automated position determination, the data from the event camera 22 are further processed by the evaluation unit 19. The current recording 32 is evaluated based on the two-dimensional coordinate system of the image sensor 24. In the example shown, the origin of the coordinate system is located in the upper left corner of the recording 32. The first coordinate axis a points to the right and the second coordinate axis b points downwards.

[0052] In this example, the evaluation for determining the position of the track sleepers 6 is performed along the second coordinate axis b, because the first coordinate axis a and the track sleepers 6 are essentially aligned parallel to the transverse direction of the track. Distances between the track sleepers 6 are determined taking into account the given distortion along the coordinate axis b. Therefore, to simplify data processing, the measurement signals from the sensor pixels 25, which are arranged on a detection axis 35 running parallel to the first coordinate axis a, are evaluated together.

[0053] Each image 32 is acquired during a predefined acquisition period, which corresponds to an accumulation time for the measurement signal of the respective sensor pixel 25. This acquisition period is the time span between the beginning and the end of an acquisition process, comparable to the exposure time of a conventional camera. For example, 20 milliseconds are specified for the accumulation. If a sensor pixel 25 detects a change in brightness during this acquisition period, an event value e equal to one is assigned to this sensor pixel 25. These event values ​​e are shown in Fig. 5. Otherwise, the event value of the sensor pixel 25 remains zero, and the image shows a constant gray. A longer acquisition period generally results in more sensor pixels 25 acquiring events and thus more accumulated event values ​​e.

[0054] For further evaluation, all event values ​​e occurring along a common detection axis 35 are summed. The result is a progression of a summed event value Le along the second coordinate b, as shown in Fig. 6. For clarity, only one corresponding detection axis 35 is shown in Figures 5 and 6. The diagram according to Fig. 6 is an exemplary result of the automated data processing using the evaluation unit 23. From this, in particular after filtering based on local maximum values, the arrangement of the respective track sleepers 6 can be determined. The respective spacing of the track sleepers 6 in the longitudinal direction 36 of the track is obtained via the geometric relationships described with reference to Fig. 4.

[0055] Fig. 7 shows another recording 32 from the event camera 22 with a second recording period that is longer than the first recording period. Here, the lifting process 15 has already progressed further. The corresponding diagram of the summed event values ​​Le over the second coordinate axis b is shown in Fig. 8.

[0056] Preferably, several recordings 32 taken during a lifting operation 15 are used for an evaluation process. First, the arrangement of the respective track component 2 is determined for each recording 32, and the most probable result is determined using statistical methods.

[0057] In a further development of the invention, a control device 37 is arranged for the synchronous control of the lifting unit 8 and the measuring device 13. Preferably, this control device 37 is integrated into a machine control 38 of the track construction machine 1. The control device 37 activates the measuring device 13 as soon as a lifting process 15 is initiated by means of the lifting unit 8. In particular, an evaluation by the evaluation device 23 only takes place when the lifting process 15 has already exceeded a predetermined minimum time and an increased movement of the ballast grains occurs. A corresponding result can be seen in Figures 7 and 8.

[0058] Coupling the measuring device 13 with the machine control 38 has the additional advantage that the tamping unit 10 can be automatically positioned above the respective track sleeper 6. Forward movement of the tamping machine or a tamping satellite from track sleeper 6 to track sleeper 6 is based on the arrangement of the ballasted track sleepers 6 with respect to the moving coordinate system XYZ, as determined by the measuring device 13.

[0059] A simplified positioning of the tamping unit 10 is achieved when the event camera 22 is positioned on the tamping machine in the track center above the lifting unit 8, facing in the direction of travel 9. This results in images 32 as shown in Figures 5 or 7. From the corresponding diagrams in Figures 6 and 8, a position control signal for the tamping machine can then be directly derived from the values ​​of the second coordinate axis b. Only the distortion resulting from the acute viewing angle a of the event camera 22 and the resulting perspective view needs to be taken into account. The position control signal is used to control the traction drives 39, thus moving the tamping unit 10 from track sleeper 6 to track sleeper 6.

Claims

Patent claims 1. Method for determining the arrangement of a track component (12), in particular a track sleeper (6), of a track (4) laid in a ballast bed (7), wherein an area (14) of the track (4) is detected by means of an optical sensor device (17), characterized in that the track (4) in the detected area (14) with the track component (12) hidden under ballast grains (11) is lifted and ballast grains (11) are thereby changed in their position and that the arrangement of the track component (12) is determined on the basis of the position changes (16) of the ballast grains (11) detected by means of the sensor device (17).

2. Method according to claim 1 or 2, characterized in that the position changes (16) of the gravel grains (11) are detected by means of an event camera (22).

3. Method according to claim 2, characterized in that in the event camera (22) those sensor pixels (25) of an image sensor (24) output a measurement signal which detect a change in brightness at the associated location (27) of the detected area (14).

4. Method according to claim 3, characterized in that the respective output measurement signal is supplied to an evaluation device (19) and that measurement signals received in the evaluation device (19) over a recording period are evaluated to determine the position of the track component (12).

5. Method according to claim 4, characterized in that measurement signals received over the recording period of the Sensor pixels (25) are evaluated as event values ​​(e).

6. Method according to claim 4 or 5, characterized in that the measurement signals of the sensor pixels (25) which are arranged on a common detection axis (35) which is in particular aligned parallel to a track transverse direction are evaluated as a summed event value (Le).

7. Method according to one of claims 1 to 6, characterized in that a height (h) of a ballast surface (18) is detected in relation to the sensor device (17) and that the arrangement of the track component (12) is determined in particular on the basis of a height profile (21) of the ballast grains.

8. Method according to one of claims 1 to 7, characterized in that the sensor device (17) is controlled synchronously to a lifting unit (8) of a track construction machine (1).

9. Measuring device (13) for determining the arrangement of a track component (12), in particular a track sleeper (6), of a track (4) supported in a ballast bed (7), comprising an optical sensor device (17) for detecting an area (14) of the track (4) and an evaluation device (19) for determining the arrangement on the basis of measurement signals from the sensor device (17), characterized in that the sensor device (17) is configured to detect changes in position of the track component (12) during a lifting operation (15) of a section of the track (4) with the track component (12) hidden under ballast grains. to capture gravel grains (11) and that the The evaluation unit (19) is designed to determine the arrangement of the track component (12) based on the recorded changes in position of the ballast grains (11).

10. Measuring device (13) according to claim 9, characterized in that the sensor device (19) comprises an event camera (22).

11. Measuring device (13) according to claim 9 or 10, characterized in that the sensor device (19) comprises a distance measuring device (23), in particular a lidar sensor or a TOF camera.

12. System with a measuring device (13) according to one of claims 9 to 11, characterized by a lifting unit (8) to lift a section of track towards which the sensor device (17) is directed.

13. System according to claim 12, characterized by a control device (37) for synchronous control of the lifting unit (8) and the measuring device (13) .

14. System according to claim 12 or 13, characterized by a track construction machine (1) which is movable on the track (4) with rail carriages (3) and comprises the lifting unit (8) and the measuring device (13).

15. System according to claim 14, characterized in that the track construction machine (1) comprises a tamping unit (10) for tamping under track sleepers (6), that the respective track sleeper (6) has an arrangement relative to the track construction machine (1) determined by means of the measuring device (13), and that a machine control (38) in particular is set up for automatically positioning the tamping unit (10) above the respective track sleeper (6).

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