MEASURING DEVICE FOR DETERMINING THE POSITION OF THE OVERHEAD WIRE

Description

[0001] For the trouble-free operation of electric railways on tracks with an overhead line system, compliance with the contact wire position is particularly important. The contact wire height above the top of the rail and the contact wire lateral position relative to the track centerline are therefore subject to standards. For example, according to DIN EN 50119, for the Re 330 overhead line type, the minimum contact wire height is 5070 mm and the standard contact wire height is 5300 mm above the top of the rail. The contact wire lateral position may deviate by ± 300 mm from the track centerline—particularly due to the zigzag pattern of the contact wire. Contact wires that are positioned outside a specified range can lead to arcing at the interface between the pantograph and contact wire and to malfunctions, which can cause serious damage to components of the overhead line system and the pantograph.

[0002] To check the current overhead wire position, special measuring vehicles are available, whose measuring devices only permit speeds of, for example, 120 km / h. In addition, paths—i.e., time slots in the timetable—must be reserved for the measuring vehicles alongside regular passenger and freight traffic, which is often problematic given current track occupancy.

[0003] Patent DE 10 2013 217 160 B3 discloses a method for measuring the height and lateral position of the overhead contact wire of a track. Using the rotating mirrors of two or more fan lasers installed on the roof of a rail vehicle, the environmental profile is recorded within a predefined scanning area, from which the contact wire position of the detected contact wire is filtered out using suitable filter algorithms. After each scanning cycle, the scanners generate data telegrams containing angle and distance values ​​to detected surfaces or objects. The scanning angles of the scanning laser beams exhibit a phase shift of 360° per number of fan lasers used.

[0004] EP 2 966 400 A1 discloses a measuring vehicle with a device for contactless, three-dimensional measurement of the position of an overhead line. The position-measuring device comprises two laser scanners arranged side by side in the direction of travel for determining the overhead line position based on acquired angle and distance data. The device further comprises two line-scan cameras, also arranged side by side in the direction of travel, whose sensor pixel rows extend along the camera connecting line and each acquire image data of a one-dimensional image. Based on the acquired angle and distance data, an image region of interest is defined in the one-dimensional images, and the image region outside the image region of interest is masked. The successively acquired, masked image data is accumulated in a memory.A two-dimensional image is generated from accumulated masked one-dimensional image data of the two line scan cameras, from which the overhead line position is determined.

[0005] EP 3 199 910 A1 discloses a line-scan measuring device with three line-scan cameras for recording overhead lines. The line-scan cameras are arranged centrally and side by side on a vehicle to capture images of the overhead line. The captured overhead line images are processed to determine the height and lateral position of the overhead line using stereo measurements. For this purpose, the centrally arranged line-scan camera has an image capture range that covers the entire area within which an overhead line may be present, while the two laterally arranged line-scan cameras each capture half of this range.

[0006] WO 02 / 21445 A2 describes an arrangement for detecting a change in a reference object assigned to a track. Four optical recording systems of the arrangement are located on the roof of an inspection vehicle. During an inspection run, these systems acquire contactless, related images of all elements of an overhead line and their surfaces from different directions at specified recording locations. One of the four optical recording systems is used to monitor and inspect the contact wire. A reference image comparison is performed to evaluate the recorded images.

[0007] Fan lasers are very expensive to purchase due to the lidar sensors they use, and are vulnerable and maintenance-intensive during high-speed operation due to moving components such as the rotating mirror. The acquisition rate is limited by the line-by-line image construction of the scanning laser beam.

[0008] The invention is therefore based on the object of providing an improved measuring device of the type mentioned at the outset, which is capable of detecting the contact wire position even in high-speed operation of a rail vehicle carrying the measuring device of up to 400 km / h.

[0009] The problem is solved by a generic measuring device with the features specified in patent claim 1. The measuring device is suitable and intended for determining the relative position of a contact wire of an overhead line system assigned to a track to a rail vehicle traveling on the track. The measuring device comprises a time-of-flight camera arrangement arranged on the rail vehicle for acquiring image data with depth information of a detection area containing the contact wire. Furthermore, the measuring device comprises an evaluation unit configured to estimate position data of the contact wire using various estimation methods and to determine the relative position of the contact wire by spatial and temporal fusion of the position data.

[0010] The arrangement comprises several time-of-flight cameras. Time-of-flight cameras are known per se and comprise an illumination unit for emitting light pulses that illuminate the contact wire, an optical unit for projecting the light reflected from the contact wire onto a sensor array, and control electronics for synchronously controlling the illumination unit and the sensor array. The sensor array comprises a matrix-like arrangement of sensor pixels for collecting incoming light pulses and measuring the time of flight between the emission of a light pulse and its incidence on the respective sensor pixels. A bandpass filter tuned to the frequency of the light pulse can be used to eliminate interfering background light.

[0011] Class 1 laser diodes with high intensities at a wavelength of 850 nm are preferably used as the illumination unit in order to achieve the shortest possible integration times for the sensor pixels. By using several time-of-flight cameras, a detection area extending sufficiently laterally and upwards can be created through the mutual arrangement and alignment of their fields of view, so that contact wires at different heights and lateral positions can be detected. For one time-of-flight camera recording, several, for example four, individual images are captured and superimposed to minimize the noise component. The image data with depth information is fed as raw data to an evaluation unit, which is designed to estimate the position data of the contact wire using various estimation methods. For example, geometric, machine learning-based and filter-based methods can be used.Each estimation method estimates the position data of the contact wire. Finally, by spatially and temporally fusing the position data, the relative position of the contact wire is determined in the form of polar or Cartesian coordinates relative to a reference point. The use of a time-of-flight camera achieves a cost advantage over fan lasers. Robust calibration of the time-of-flight camera arrangement enables a long operating time until the next maintenance, which is also helped by the fact that, unlike fan lasers, there are no moving parts.

[0012] The time-of-flight camera arrangement comprises a plurality of time-of-flight cameras, each time-of-flight camera having a sensor arrangement with a matrix-like arrangement of sensor pixels, and the number of rows of sensor pixels to be read out being adaptable to reduce the recording time for high travel speeds of the rail vehicle. The use of the measuring device according to the invention in rail vehicles in regular operation, for example in passenger trains, requires its functionality even at high travel speeds of, for example, over 200 km / h up to 400 km / h. Due to the relative movement between the measuring device and the contact wire, each sensor pixel collects light reflected by a speed-dependent longitudinal section of the contact wire.The readout and integration times for a full sensor resolution of, for example, 352 x 288 sensor pixels are too long for high driving speeds, as this leads to motion blur in the recorded image data. Therefore, a region of interest of sensor pixels is defined, which limits the number of rows of sensor pixels to be read out, for example, to 32 x 288 sensor pixels. The 32 rows are arranged in a row along the vehicle's longitudinal direction. This significantly reduces readout times and avoids blurring effects.

[0013] The time-of-flight camera assembly comprises a first time-of-flight camera, which is arranged in the center of the vehicle and has an optical unit with a vertical optical axis and a focal length for detecting contact wires that run in a near, lower section of the detection area. It further comprises a second time-of-flight camera, which is arranged in the center of the vehicle and has an optical unit with a vertical optical axis and a focal length for detecting contact wires that run in a far, upper section of the detection area.The time-of-flight camera arrangement also includes a third time-of-flight camera and a fourth time-of-flight camera, which are arranged symmetrically outside the vehicle center and have an optical unit with optical axes tilted outward at an acute angle toward the vehicle center and with a focal length for detecting contact wires that run along the lateral edges of the near, lower section of the detection zone. Due to the different aperture angles and axis alignments of the camera fields of view, as well as the different focal lengths, the contact wire is imaged with different spatial resolutions (ground sampling distance, or GSD) depending on its position within the detection zone.Assuming a contact wire diameter of 19 mm, contact wires at approximately the maximum contact wire height are mapped to one row of sensor pixels, while lower contact wires at approximately the nominal contact wire height are mapped to two rows of sensor pixels. Contact wires even lower and laterally positioned, down to the minimum contact wire height, are mapped to three rows of sensor pixels.

[0014] In a preferred embodiment, the measuring device according to the invention comprises at least one video camera for capturing image data with color information of the detection area containing the contact wire, and an evaluation device for the image data for checking for faults in the time-of-flight camera arrangement. The video camera can be used to easily determine whether the image data capture of the time-of-flight cameras is disrupted by dirt or foreign objects in their field of view.

[0015] In a further preferred embodiment of the measuring device according to the invention, the time-of-flight camera arrangement has a control unit for sequentially triggering the time-of-flight cameras in a master-slave arrangement. To avoid mutual interference between the lighting units assigned to the time-of-flight cameras, the time-of-flight cameras are not triggered simultaneously, but sequentially in a master-slave arrangement. After system start-up, the first time-of-flight camera, configured as the master, receives a trigger signal. If an image is received, it sends a trigger signal to the second, third, and fourth time-of-flight cameras, configured as slaves. If four images are received, the master and slaves operate cyclically at a repetition frequency of, for example, 30 Hz. This achieves a measurement value rate for sufficient spatial resolution even at high driving speeds.

[0016] In a further preferred embodiment of the measuring device according to the invention, time-of-flight cameras arranged at a distance from one another form a stereo base, wherein the evaluation unit is designed to combine image data from time-of-flight cameras of a stereo base into stereo image data and to determine stereo position data of the contact wire therefrom. Based on the stereo position data, the position data of the time-of-flight cameras is checked for plausibility. Short integration times of the time-of-flight cameras combined with a suitable image format lead to an image overlap below a certain driving speed. This image overlap can be used to verify the plausibility of the contact wire position of each of the time-of-flight cameras using a stereoscopic basis of the time-of-flight cameras as a second independent measurement principle.

[0017] In a further preferred embodiment of the measuring device according to the invention, the time-of-flight camera arrangement, the evaluation unit, and the control unit are arranged in a sealed housing with a cover plate having camera openings and illumination openings and with an interface for connection to the rail vehicle. The housing is connected to a subframe that can be screwed to the roof structure of the rail vehicle. The housing is water- and dust-tight and has a cover plate, for example, which is square and extends seamlessly through a roof scoop of the rail vehicle when installed. The center of the cover plate can serve as a reference point for the measuring device. The cover plate has illumination openings for the light output of the illumination units and camera openings for the light input to the sensor arrangements of the time-of-flight cameras and the video cameras.On the bottom, the housing has cable passages for data and power supply cables.

[0018] In a further preferred embodiment of the measuring device according to the invention, the evaluation unit is connected to a motion sensor for detecting an operational movement of the reference point relative to the top of the rail and / or the track center. The motion sensor can detect roll, pitch, yaw, and heave movements of the rail vehicle body relative to the top of the rail, whereby the position data of the contact wire related to the reference point can be corrected and related to the top of the rail. This enables a direct comparison of the measured relative position with standardized contact wire heights and lateral positions.

[0019] In a further preferred embodiment of the measuring device according to the invention, the evaluation unit is connected to a position sensor for detecting the current position of the rail vehicle. The position sensor can have a receiver of a satellite system for determining the position of the rail vehicle. This allows the detected contact wire position data to be combined with the associated vehicle position in order to display the position data along a track section being traveled.

[0020] The invention also relates to a rail vehicle with a measuring device according to one of claims 1 to 9.

[0021] Further features and advantages of the invention will become apparent from the following description of an embodiment with reference to the drawings, in which FIG. 1 shows a section of a perspective view of a rail vehicle with an integrated measuring device according to the invention, FIG. 2 shows a perspective view of the measuring device according to the invention, FIG. 3 shows a cross-section through the detection range of the measuring device according to the invention, and FIG. 4 shows diagrams of contact wire lateral positions and contact wire heights determined with the measuring device according to the invention along the path traveled by the rail vehicle. are illustrated schematically.

[0022] According to FIG 1 A measuring device 1 for determining the relative position of a contact wire 2 of a not further shown overhead line system to a rail vehicle 3 traveling on the track is integrated in the roof area of ​​the rail vehicle 3 and is flush with a roof scoop 4. The rail vehicle 3 can be a high-speed train with a pantograph 5a that can contact the contact wire 2 for power supply.

[0023] The measuring device 1 has according to FIG 2 a sealed housing 5 with a square cover plate 6, which has camera openings and lighting openings. The housing 5 is connected to a base frame 8, which can be screwed to the roof structure of the rail vehicle 3. The center of the cover plate 6 serves as a reference point R for the measuring device 1. Light pulses from lighting units 7 in the form of laser diodes with a wavelength of 850 nm emerge through the lighting openings. These pulses are reflected from the contact wire 2 and, through the camera openings of a first time-of-flight camera 11, a second time-of-flight camera 12, a third time-of-flight camera 13, and a fourth time-of-flight camera 14, impinge on the sensor arrangements assigned to them, respectively. The cover plate 6 also has two camera openings for video cameras 15 for capturing image data with RGB color information of the detection area containing the contact wire 2.

[0024] The time-of-flight cameras 11, 12, 13, 14, with their lighting units and with an evaluation unit and control unit - also arranged in the housing 5 - form a multiple time-of-flight camera arrangement for capturing image data with depth information of a detection area 16 of width S containing the contact wire 2.

[0025] According to FIG 3 The first time-of-flight camera 11 and the second time-of-flight camera 12 are arranged one behind the other in the vehicle center M and have an optical unit with vertical optical axes A1 and A2, respectively. The focal length of the first time-of-flight camera 11 enables detection of contact wires 19 in a near, lower section 16U of the detection area 16 between a minimum contact wire height Hmin and a nominal contact wire height Hnom in a field of view with an aperture angle of 80°. The focal length of the second time-of-flight camera 12 enables detection of contact wires 19 in a far, upper section 16O of the detection area 16 between the nominal contact wire height Hnom and a maximum contact wire height Hmax in a field of view with an aperture angle of 48°.The third time-of-flight camera 13 and the fourth time-of-flight camera 14 are arranged symmetrically outside the vehicle center M and offset in the vehicle's longitudinal direction L and have optical units with optical axes A3, A4 tilted outwards by an angle of 36° relative to the vehicle center M. The focal lengths of the third and fourth time-of-flight cameras 13, 14 enable detection of contact wires 19 in fields of view with an aperture angle of 60°. These contact wires run in the lateral edge regions 16S of the near, lower section 16U of the detection zone 16. Due to the different aperture angles and axis alignments of the camera fields of view as well as the different focal lengths, the contact wire 2 is imaged with different spatial resolutions (ground sampling distance, GSD for short) depending on its position in the detection zone 16.Assuming a contact wire diameter of 19 mm, contact wires 2 in resolution area P1 (hatching to the bottom right) are mapped to one row of sensor pixels at approximately the maximum contact wire height Hmax, while lower-lying contact wires 2 in resolution area P2 (hatching to the top right) are mapped to two rows of sensor pixels at approximately the nominal contact wire height Hnom. Even lower-lying contact wires 2 and also laterally located contact wires 2 down to the minimum contact wire height Hmin in resolution area P3 (cross-hatching) are mapped to three rows of sensor pixels.

[0026] The image data with depth information captured by the time-of-flight camera arrangement is fed to an evaluation unit in order to estimate the position data of the contact wire 2 using various estimation methods and to determine the relative position of the contact wire 2 by spatial and temporal fusion of the position data. The video cameras 15 can easily determine whether the image data acquisition of the time-of-flight cameras 11, 12, 13, 14 is disrupted by dirt or foreign objects in their field of view. For a recording by a time-of-flight camera 11, 12, 13, 14, several, for example four, individual images are captured and superimposed to minimize the noise component. Geometric, machine learning-based, and filter-based methods are used. Each estimation method estimates the position data of the contact wire 2.Finally, the relative position of the contact wire is determined in the form of polar or Cartesian coordinates relative to a reference point through spatial and temporal fusion of the position data. To reduce the acquisition time for high travel speeds of rail vehicle 3, the number of rows of sensor pixels to be read can be adapted. A region of interest of sensor pixels is defined, which limits the number of rows of sensor pixels to be read, for example, to 32 x 288 sensor pixels. The 32 rows are arranged in a row in the vehicle's longitudinal direction L. This significantly reduces the readout time and avoids blurring.

[0027] The evaluation unit is connected to a position sensor for detecting the current position of the rail vehicle, for example a receiver of a satellite system, in order to FIG 4to be able to display the recorded contact wire lateral positions X and the recorded contact wire heights Z as a function of the route length S covered by the rail vehicle 3.

Claims

1. Measuring device (1) for ascertaining the position of a contact wire (2) of an overhead contact line system assigned to a track relative to a rail vehicle (3) travelling on the track, comprising - a time-of-flight camera arrangement arranged on the rail vehicle (3) for detecting image data with depth information of a capture region (16) containing the contact wire (2), - wherein the time-of-flight camera arrangement has a plurality of time-of-flight cameras (11, 12, 13, 14), characterised in that - each time-of-flight camera (11, 12, 13, 14) has a sensor arrangement with a matrix-type arrangement of sensor pixels, - wherein in order to reduce the recording time for high travel speeds of the rail vehicle (3), the number of rows of sensor pixels to be read out can be adapted, - wherein the time-of-flight camera arrangement - comprises a first time-of-flight camera (11), which is arranged in the centre of the vehicle (M) and has an optical unit with a vertical optical axis (A1) and with a focal length for capturing contact wires (2), which run in a close, lower section (16U) of the capture region (16), - comprises a second time-of-flight camera (12), which is arranged in the centre of the vehicle (M) and has an optical unit with a vertical optical axis (A2) and with a focal length for capturing contact wires (2), which run in a remote, upper section (160) of the capture region (16), and - comprises a third time-of-flight camera (13) and a fourth time-of-flight camera (14), which are arranged in symmetry outside of the centre of the vehicle (M) and have an optical unit with optical axes (A3, A4) tilted outward about an acute angle with respect to the centre of the vehicle (M) and with a focal length for detecting contact wires (2), which run in lateral edge regions (16S) of the close, lower section (16U) of the capture region (16), and - wherein the measuring device (1) comprises an evaluation unit, which is embodied to estimate position data of the contact wire (2) using different estimation methods and to determine the relative position (X, Z) of the contact wire (2) by spatial and temporal fusion of the position data.

2. Measuring device (1) according to claim 1, further having - at least one video camera (15) for capturing image data with colour information of the capture region (16) containing the contact wire (2) and an evaluation facility for the image data for monitoring the interruption of the time-of-flight camera arrangement.

3. Measuring device (1) according to claim 1 or 2, - wherein the time-of-flight camera arrangement has a control unit for sequential trigging of the time-of-flight camera (11, 12, 13, 14) in the manner of a master-slave arrangement.

4. Measuring device (1) according to one of claims 1 to 3, - wherein time-of-flight cameras (11, 12, 13, 14) arranged at a distance from one another form a stereo base, - wherein the evaluation unit is embodied to combine image data of time-of-flight cameras (11, 12, 13, 14) of a stereo base to form stereo image data and therefrom to ascertain stereo position data of the contact wire (2), and to check the position data of the time-of-flight cameras (11, 12, 13, 14) for plausibility using the stereo position data.

5. Measuring device (1) according to one of claims 1 to 4, - wherein the time-of-flight camera arrangement, the evaluation unit and the control unit are arranged in a sealed housing (5) with a cover plate (6) having camera openings and lighting openings and with an interface for connection to the rail vehicle (3).

6. Measuring device (1) according to one of the preceding claims, - wherein the evaluation unit is connected to a motion sensor for capturing an operational movement of the reference point (R) relative to the rail top edge and / or to the centre of the track (M).

7. Measuring device (1) according to one of the preceding claims, - wherein the evaluation unit is connected to a position sensor for capturing a current position of the rail vehicle (3).

8. Rail vehicle (3) with a measuring device (3) according to one of the preceding claims.