SYSTEM FOR MONITORING A RAILWAY CROSSING

Description

[0001] The invention relates to a system for monitoring a level crossing according to the preamble of claim 1.

[0002] Laser scanners are often used to monitor flat areas. A light beam generated by a laser is directed into a field of view via a light deflection unit, where it is reflected or remitted by any object present. The reflected or remitted light returns to the laser scanning unit and is detected there by a receiver. The light deflection unit is usually designed to be pivotable or rotatable, so that the light beam generated by the laser sweeps across a field of view created by the rotational movement. If a reflected light signal from the field of view is received by the receiver, the angular position of the deflection unit can be used to determine the angular position of the object in the field of view.If the propagation time of, for example, pulsed laser light is also monitored, the propagation time can be used to determine the distance of the object from the laser scanner and thus the location of the object in the field of view using the speed of light. If two-dimensional protective fields are also defined in the field of view, violations of the protective fields by the laser scanner can be fully monitored. If an unauthorized object is located in the protective field, the receiver unit can output a corresponding safety signal, e.g., a warning or control signal. Such laser scanners are described, for example, in DE 4340756C2. The evaluation of protective fields of these laser scanners is described, for example, in EP 0967492A1 and EP 0520247A2.

[0003] Such laser scanners are also used in generic systems for monitoring a level crossing, as disclosed in DE102007060303B4, JP2003011824A or DE202012101250U1.

[0004] Such a system must be designed to be fail-safe and therefore meet high safety requirements in order to achieve the so-called Performance Level d (PLd) or Safety Integrity Level 3 (SIL3). Previously, such safety was achieved, among other things, by using a safety laser scanner, such as the one described in DE4340 756A1, which complies with the relevant standards, such as EN13849 for machinery safety and EN61496 for electro-sensitive protective equipment (ESPE). To meet these safety standards, a number of measures must be implemented in the laser scanner, such as secure electronic evaluation through redundant, diverse electronics, function monitoring or, specifically, monitoring for contamination of optical components, particularly a front screen, and / or providing individual test targets with defined reflectances that must be detected at the corresponding scanning angles.These safety measures are even more important when used outdoors, exposed to negative environmental influences such as fog, rain and snow.

[0005] There is a requirement to also secure level crossings or other outdoor railway areas with safety systems that meet Performance Level d (PLd) or Safety Integrity Level 3 (SIL3). At level crossings, for example, cars must be reliably detected before the train is cleared. Or, switch areas must be secured in such a way that no switch can be adjusted while a train is on them (otherwise, derailment would result, with significant consequential damage, including to personnel).

[0006] As mentioned above, systems with laser scanners are occasionally used for this purpose, but as a complete system, they are not certified for any PL or SIL level. Only one radar system is known that, although it meets the Performance Level or Safety Integrity Level, is very expensive and its frequencies are not available in many countries. Furthermore, installation and maintenance are very complex. Conventional laser scanner systems, based on two redundant laser scanners, have not been able to achieve the safety levels, primarily due to a lack of evidence of the laser scanners' detection capability. For example, black cars are not reliably detected.

[0007] Based on this prior art, the object of the invention is to provide an improved system for securing a level crossing which can in particular meet the aforementioned safety levels.

[0008] This object is achieved by a system having the features of claim 1. The system according to the invention for monitoring a level crossing comprises a laser scanner with a light transmitter generating a scanning beam and a light receiver receiving reflections of the scanning beam at locations within the field of view, and with a deflection unit that periodically deflects the scanning beam so that it sweeps over the level crossing, and with an angle detection unit for detecting the angular position of the deflection unit, an evaluation unit that determines a distance from the light travel time between the emission of the light and the reception of a reflection and, together with the angular position, can determine the location of the reflection, naturally present objects in the field of view and within the visual range of the laser scanner, which form a reference contour and delimit the field of view, and a contour field boundary can be defined in the evaluation unit, which lies in front of the reference contour as seen from the laser scanner and defines a contour field between the reference contour and the contour field boundary, and whose shape is freely definable,wherein the level crossing is located between the laser scanner and the contour field and the evaluation unit is designed to output a safety signal at a safety output if no reflection signal from the reference contour or from the contour field is received by the laser scanner when passing over the level crossing.

[0009] In the system according to the invention, no protective field of the laser scanner is defined, and it is irrelevant how well or poorly objects are detected by the laser scanner. Nevertheless, every object is reliably detected, regardless of its remission properties. According to the invention, objects are not detected based on their diffuse reflection of the laser beams emitted by the laser scanner. Instead, the contour located in the field of view and a contour field in front of it, whose extent can be configured, are used to detect an object indirectly, namely through the absence of a reflection from the reference contour or from any objects in the contour field.The contour field, which in actual use can be extremely deep depending on the distance from the reference contour, has the advantage of effectively preventing false triggering of the laser scanner, i.e. incorrect triggering of the safety signal, for example due to permissible objects between the reference contour and the level crossing. The contour itself can also change without affecting the safety functions of the laser scanner, because as long as the changes in the contour do not change the contour field boundary, this has no effect on its functionality. Only when an object is located between the contour field and the laser scanner does the laser scanner detect the area as violated, because the object will then shadow part of the contour field, resulting in a reflection signal from the contour (incomplete contour) or from the contour field being missing. This missing signal therefore results in indirect object detection.

[0010] Thanks to this detection strategy with contour and contour field, every object between the contour field and the laser scanner is reliably detected, regardless of its reflectance properties. Even shiny black objects or slanted surfaces are no longer a problem.

[0011] Furthermore, a loss of detection of objects from the contour field, e.g., due to weather conditions or because the object's surface does not reflect enough laser light, does not result in a loss of safety. The system still issues a safety signal in this case. Outputs can then be deactivated (no release to the higher-level control system).

[0012] Proof of the system's detection capability is no longer necessary, because if object detection fails (due to the object itself or external influences such as weather or the like, or due to other malfunctions), the system always defaults to the safe side, i.e., it issues a safety signal. If the contour is not detected across the entire field of view, or if at least a reflected signal is emitted from the contour field, the system will not issue a release. This allows Safety Performance Level d (PLd) or Safety Integrity Level 3 (SIL3) to be achieved.

[0013] In a further development of the invention, the scanning beam sweeps the level crossing essentially horizontally, and the naturally occurring objects are formed by buildings or other immobile structures. The invention thus makes it possible to use natural landmarks as reference contours, which can be located up to the maximum visibility of the laser scanner, often up to 100 m away. Additional reference markers are no longer necessary.

[0014] If there are no suitable landmarks within the laser scanner's field of view that could serve as reference contours, a further development of the invention allows the laser scanner's scanning beam to be directed slightly downward, and the naturally present objects are formed by the ground. In this case, the always present ground forms the reference contour, so no additional landmarks are necessary.

[0015] Advantageously, the contour field boundary is located well in front of the actual reference contour visible to the laser scanner, while the contour field boundary remains unchanged, so that a change in the location of the reference contour within the contour field does not affect the functionality of the laser scanner. This allows even temporary structures, such as construction containers in front of a house, to serve as a reference contour, regardless of whether the construction container is present or not.

[0016] In a further embodiment of the invention, the total viewing angle range is composed of several unconnected individual viewing angle ranges located horizontally adjacent to each other at different viewing angles. Each individual viewing angle range is assigned its own reference contour with a contour field and contour field boundary. This allows larger areas with gaps to be monitored. This embodiment can also be useful when the naturally present objects are not connected from the perspective of the laser scanner.

[0017] To increase safety, two laser scanners can be provided, each of whose scanning beams covers the level crossing. Both of these scanners form a system according to the invention, and their triggering areas overlap as completely as possible in a bird's eye view. With two redundant systems according to the invention, the requirements for Safety Performance Level d (PLd) or Safety Integrity Level 3 (SIL3) can be met much more easily.

[0018] The invention will be explained in detail below using exemplary embodiments with reference to the drawings. The drawings show: Fig. 1 is a schematic view of a system according to the invention with a level crossing from above; Figs. 2 to 4 are schematic views as Fig. 1 of further application situations; Fig. 5 a schematic representation of a laser scanner.

[0019] The system 10 according to the invention comprises, among other things, a laser scanner 12 which is constructed in a known manner, as described, for example, in the above-mentioned DE 4340756C2 and in Fig. 5 shown schematically. In such a laser scanner 12, a light transmitter 100 is provided for emitting a scanning beam 101, which is sent into a field of view 14 via a deflection unit, here a deflecting mirror 102, which rotates continuously. The field of view 14 thus has a fan-shaped extension. If an object 104 is located within the field of view 14, the light 106 reflected by the object 104 is sent back along the same path and fed from the deflecting mirror 102 via a receiving optics 108 to a light receiver 110. As a rule, such laser scanners 12 operate with short light pulses of a few nsec, so that the location of the reflection on the object 104 in the field of view 14 can be determined via the angular position of the deflecting mirror 102, which is determined by means of an angle detection unit 114, and the propagation time of the light pulse.

[0020] Furthermore, the laser scanner 12 has an evaluation unit 112, to which the received signals from the light receiver are fed in order to perform the aforementioned evaluation to determine the location of the reflection. The evaluation unit 112 evaluates the information and, depending on this, can output a safety signal at a safety output 116. For example, an emergency stop signal can be output to an operator via a display device, or a train signaling device can be directly controlled. In the exemplary embodiment shown, the evaluation unit 112 is an integral component of the laser scanner 10. This does not necessarily have to be the case. The evaluation unit 112 could also be provided in a separate control system. Likewise, the evaluation unit 112 could also be designed in several parts.

[0021] The system 10 according to the invention for monitoring a railroad crossing 16 comprises, in addition to the laser scanner 12, naturally occurring objects 18 in the field of view 14 and within the visual range of the laser scanner 10, which form a reference contour 20 and delimit the field of view 14. These naturally occurring objects 18 can be buildings, immobile structures, such as posts, or similar landmarks. However, they must extend across the entire relevant field of view 14 of the laser scanner 12 and thus delimit the field of view 14.

[0022] Furthermore, the system 10 according to the invention comprises a manually definable contour field boundary 22, which, as seen from the laser scanner, lies in front of the reference contour 20 and defines a contour field 24 between the reference contour 20 and the contour field boundary 22. The shape of the contour field boundary 22 is freely definable, so that the contour field 24 is delimited on the one hand by the reference contour 20 and, on the other hand, by the contour field boundary 22 in the direction of the laser scanner 10. It is, of course, clear that the contour field 24 is always located within the field of view 14, i.e., is delimited laterally by the minimum and maximum viewing angles. The definition or configuration of the contour field boundary 22 generally takes place in the evaluation unit 112.

[0023] The evaluation unit 112 is further configured to output a safety signal at a safety output 116 if the laser scanner 10 does not receive a reflection signal from the reference contour 20 or from objects in the contour field 24 when scanning the level crossing 16. The scanning beam 101 preferably scans the level crossing 16 essentially horizontally.

[0024] In Fig. 1 A schematic bird's-eye view of a typical application of the system 10 according to the invention is shown. A railroad crossing 16 is to be secured with the system 10 according to the invention so that the presence of objects 28, such as vehicles 28-1 or people 28-2, located in the intersection area of ​​railway tracks 32 and road 34, is reliably detected.

[0025] This happens as follows. If no objects 28 are present within the field of view 14, the laser scanner 12 sees only the naturally present object 18 with its contour, which is stored in the laser scanner as the reference contour 20. This ensures that even if no object 28 is present, at least the reference contour 20 is seen by the laser scanner 12. Thus, in the "good case," the laser scanner 12 always receives a reflection from the field of view 14 and thus a received signal.

[0026] In addition, the aforementioned contour field boundary 22 is stored in the evaluation unit 112. This defines the contour field 24, whereby any reflection from the contour field 24, for example, from an object 30-1 located in the contour field 24, is permitted, thus counting as a "good case." Reflections from the contour field 24 therefore do not trigger the safety signal.

[0027] However, if a reflection from the contour field 24 or from the reference contour 20 fails to occur within the resolution of the laser scanner 12, so that the laser scanner 12 does not receive a signal in an angular range, then either the contour field in this angular range has been shadowed by an object between the laser scanner 12 and the contour field boundary 22, or a malfunction has occurred. Both are critical cases and lead to the triggering of the safety signal. Shadowing by an object 28-2 is in Fig. 1 shown schematically. The object 28-2 is located in front of the contour field boundary 22, so that a reflection from the object 28-2 is detected as coming from outside the contour field 24. This also includes cases in which the object 28-2 specularly reflects the transmitted light beam 101 in a direction other than back to the laser scanner 12 or completely absorbs the transmitted light beam 101, so that in both cases no reflection returns to the laser scanner 12.

[0028] The area 36 of the field of view 24 between the laser scanner 12 and the contour field boundary 22 can thus be referred to as the triggering area 24, because every object in this triggering area 24 triggers a safety signal, regardless of the object's remission properties (apart from the trivial case of transparent objects, which are irrelevant here). However, the essential significance for the function of the system according to the invention lies in the contour field 24, because the safety signal is only not triggered if, at every angular step across the entire angular range of the field of view 14, some reflection from the contour field 24 or from the reference contour 20 returns to the laser scanner 12.

[0029] In Fig. 2 is another similar application situation as in Fig. 1 This figure illustrates that once the contour field boundary 22 has been defined and stored, the further "fate" of the reference contour is irrelevant. The reference contour can therefore change as long as it remains within the field of view and range of the laser scanner 12. For example, if the reference contour 20 changes such that a construction container 38 is placed in front of the building 18, this change in the reference contour 20 has no effect on the functioning of the system 10 according to the invention, since the scanning beam 101 is then reflected by the construction container 38 instead of the reference contour 20.

[0030] In a further embodiment of the invention as described in Fig. 3 As shown, the total viewing angle range 40 is composed of several unconnected individual viewing angle ranges 40-1, 40-2, and 40-3, which lie horizontally next to one another at different viewing angles. Each individual viewing angle range is assigned its own reference contour based on an associated, naturally occurring object with a contour field and contour field boundary. Object 18-1, for example, is a building with an associated contour field 24-1. Objects 18-2 and 18-3 can be artificially created landmarks in the form of posts or the like with associated contour fields 24-2 and 24-3. This allows a larger area to be monitored overall, although gaps may occur between the individual viewing angle ranges. However, if these gaps are small enough that objects to be detected can still be detected, such as a vehicle 28-1, the gaps are acceptable.This embodiment can also be useful if the naturally existing objects, here building 18-1 and landmarks 18-2 and 18-3, are not connected from the perspective of the laser scanner.

[0031] Another advantageous feature of the system according to the invention is also Fig. 3 shown schematically. A tree, bush, or other plant 18-4 is shown there as an example that even such objects in the contour field 24, here 24-1, are irrelevant, because the transmitted light beam is either reflected by the plant 18-4 itself or, if the transmitted light beam passes through gaps in the leaves, by the reference contour 20-1. Temporary objects, such as people 30-1, are also unproblematic in the contour field, because they provide a reflection of the scanning light beam 101 to the laser scanner 10.

[0032] In Fig. 4 An embodiment is shown in which the scanning beam 101 of the laser scanner 10 is directed slightly diagonally downwards and the naturally present objects 18 are formed by the ground 18-5. The reference contour 20 in this case is the line on which the scanning beam 101 strikes the ground 18-5. In this example, this is essentially the track bed. Just as in the previous examples, a contour field boundary 22 and thus a contour field 24 is defined, wherein the contour field boundary 22 is at a sufficient distance from the reference contour 20 so that minor ground irregularities in the contour field 24 are insignificant, similar to the above in Fig. 2 The case explained with the construction container. Thus, even in this case, where there are no landmarks rising from the ground, such as buildings or the like, the system 10 according to the invention can still be used.

[0033] To facilitate the achievement of Safety Performance Level d (PLd) or Safety Integrity Level 3 (SIL3), the system according to the invention can be provided redundantly, wherein each of the redundant systems can be designed according to one of the previously described embodiments. At least two laser scanners are then provided, whose scanning beams both sweep the level crossing and which both form a system according to the invention and whose triggering areas overlap as completely as possible in a bird's eye view. The overlap only has to be present in a bird's eye view, because the scanning beams and thus the scanning fields of the laser scanners can be spaced apart in the vertical direction without restricting functionality, since typical objects such as vehicles or people always have a noticeable vertical extension.The safety signals of the two redundant systems are logically linked "OR" so that a critical situation is indicated as soon as at least one of the systems indicates an inadmissible object in the triggering area.

Claims

1. A system for monitoring a level crossing (16), said system comprising - a laser scanner (10) having a light transmitter (100) generating a scanning beam (101) and a light receiver (110) receiving reflections of the scanning beam (101) at locations in the field of view (14) and having a deflection unit (102), which periodically deflects the scanning beam (101) such that it sweeps over the level crossing (16), and having an angle detection unit (114) for detecting the angular position of the deflection unit (102), - an evaluation unit (112) which determines a distance from the time of flight between the transmission of the light and the reception of a reflection and which can determine the location of the reflection together with the angular position, - naturally existing objects (18, 18-1, 18-2, 18-3, 18-5) in the field of view (14) and within the range of vision of the laser scanner (10) that form a reference contour (20, 20-1, 20-2, 20-3) and limit the field of view (14), characterized in that - a contour field boundary (22) can be defined in the evaluation unit (112), which contour field boundary (22), viewed from the laser scanner (10), lies in front of the reference contour (20, 20-1, 20-2, 20-3), defines a contour field (24, 24-1, 24-2, 24-3) between the reference contour (20, 20-1, 20-2, 20-3) and the contour field boundary (22) and can be freely defined in terms of its shape, wherein the level crossing (16) is disposed between the laser scanner (10) and the contour field (24, 24-1, 24-2, 24-3), and - the evaluation unit (112) is configured to output a safety signal at a safety output (116) if neither a reflection signal (106) from the reference contour (20, 20-1, 20-2, 20-3) nor a reflection signal from the contour field (24, 24-1, 24-2, 24-3) is received by the laser scanner (10) when sweeping over the level crossing (16).

2. A system according to claim 1, characterized in that the scanning beam sweeps over the level crossing substantially horizontally and the naturally existing objects are formed by buildings or other immobile structures.

3. A system according to claim 1, characterized in that the scanning beam of the laser scanner is directed slightly obliquely downwardly and the naturally existing objects are formed by the ground.

4. A system according to any one of the preceding claims, characterized in that the contour field boundary remains unchanged on a location change of the reference contour.

5. A system according to any one of the preceding claims, characterized in that two laser scanners are provided whose scanning beams both sweep over the level crossing and which both make up a system in accordance with the invention according to any one of the preceding claims and whose triggering regions overlap as completely as possible in a bird's eye view.

6. A system according to any one of the preceding claims, characterized in that the total angle of view range is composed of a plurality of unconnected individual angle of view ranges, which lie horizontally next to one another at different angles of view, and each individual angle of view range is assigned an associated reference contour having a contour field and a contour field boundary.