Method and device for determining estimated actual dimensions of an elevator car - Patents.com

Abstract

A method for determining the estimated actual dimensions of an elevator car (7) and a calculation unit (29) for carrying out such a method are described. The method includes the following steps: (a) acquiring a virtual two-dimensional map of the elevator car (7) based on data provided by a lidar sensor (17), the virtual two-dimensional map representing reflective surfaces (33) from which laser light emitted by the lidar sensor (17) is reflected; (b) defining a starting area as a rectangular area at a location within the actual dimensions of the elevator car (7); (c) continuously expanding the rectangular area by one pixel in each of four expansion directions orthogonal to edges of the rectangular area, wherein if any pixel in one of the expansion directions corresponds to one of the reflective surfaces (33) shown in the virtual two-dimensional map, the expansion of the rectangular area is stopped in this expansion direction, and the rectangular area is continuously expanded by one pixel only in each of the remaining expansion directions until the rectangular area is fully expanded to its maximum in each of the expansion directions; and (d) determining the fully expanded rectangular area as the estimated actual dimensions of the elevator car (7).

Description

[Technical field]

[0001] The invention relates to a method and a device for determining the estimated actual dimensions of an elevator car. Furthermore, the invention relates to a maintenance arrangement applied when maintaining an elevator. Finally, the invention relates to a computer program product arranged to implement the proposed method and to a computer readable medium having stored thereon such a computer program product. [Background technology]

[0002] Chinese Utility Model No. 207908967 discloses a method and calculation device for determining the estimated actual dimensions of an elevator car using a laser radar device used in an automated guided vehicle.

[0003] In an elevator, an elevator car may be moved between various levels, for example to transport passengers and / or goods between different floors of a building. Elevators are typically configured to perform various functions. Such functions may relate to normal operation of the elevator and may include, for example, controlling the intended movement of the elevator car, controlling the precise stopping of the elevator car at the floors, providing information to passengers, etc. Other functions may relate to emergency operations and may include, for example, controlling emergency operations such as activating an emergency brake of the elevator car, arranging for emergency rescue and maintenance, etc. Further functions may relate to routine maintenance of the elevator.

[0004] All functions of an elevator may have to be tested before normal operation of the elevator can actually begin. Traditionally, specialized maintenance technicians may have to perform such tests. Such tests may involve, for example, intentionally moving the elevator car to various positions using various control mechanisms, such as activating hall operating panels at various floors and / or car operating panels at the elevator car. For such purposes, technicians may have to spend a lot of time and effort, for example, using the elevator to travel throughout the building.

[0005] To reduce the effort and time for such testing, new approaches are currently being developed in which at least some of the tests may be performed by a machine, such as a robot. For example, a robot may be configured to travel throughout a building using an elevator. The robot may test the functionality of the elevator, for example, by performing actions that are later performed by a crew member or technician during normal operation or maintenance. In doing so, the robot may have to enter and exit the elevator car at various floors, operate hall operating panels and / or car operating panels, etc.

[0006] For such purposes, the robot may need to be able to autonomously navigate throughout a building and its elevators. Therefore, the robot may need some information about its environment. In particular, the robot may need information about the positions and dimensions of floors, elevator doors, elevator cars, etc.

[0007] It has been observed that, especially for a robot that can use an elevator and check its functioning, the robot may need precise information about the dimensions of the elevator car. Such information may be necessary to enable the robot to move throughout the elevator car. In particular, such information may help the robot to move to a position in the elevator car where it does not obstruct the occupants in the elevator car, i.e., to "behave" in a "social" manner. For example, the robot may move to a position on the wall or in a corner of the elevator cabin, instead of standing upright in the center of the elevator car or blocking the entrance / exit areas of the elevator car.

[0008] To enable the robot to navigate throughout the building and its elevators, the robot may be equipped with one or more sensors. In particular, the robot may be equipped with a lidar system with a lidar sensor to determine information about its environment. "Lidar" is an abbreviation for light detection and ranging. In general, lidar is an optical technology in which light is emitted and then detected when reflected at a target. In particular, lidar is a surveying method that can measure the distance to a target by illuminating the target with a laser light and measuring the reflected light with a sensor. In addition, the robot may be equipped with other types of sensors, such as ultrasonic sensors, mechanical sensors, as well as actuators to operate, for example, elevator functions.

[0009] However, when using a lidar system to sense the environment, erroneous observations may occur under at least some conditions. For example, when using a lidar system, it has been observed that the robot may have problems accurately determining the dimensions of the elevator car. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] China Utility Model No. 207908967 Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, what may be needed is a method and a computing device for determining the actual dimensions of an elevator car in a reliable and / or accurate manner. Additionally, what may be needed is a maintenance arrangement that applies such a method and computing device, as well as a computer program product and a computer readable medium that stores the computer program product that implements the method. [Means for solving the problem]

[0012] Such a need may be met by the subject matter of one of the independent claims. Advantageous embodiments are defined in the dependent claims and in the following description.

[0013] According to a first aspect of the invention, a method for determining an estimated actual size of an elevator car is proposed, the method comprising at least the following steps, preferably in the given order: (a) obtaining a virtual two-dimensional map of the elevator car based on data provided by a lidar sensor, the virtual two-dimensional map representing reflective surfaces from which laser light emitted by the lidar sensor is reflected; (b) defining a starting area as a rectangular area at a location within the actual dimensions of the elevator car; (c) continuously expanding the rectangular area by one pixel in each of four expansion directions perpendicular to the edges of the rectangular area, including stopping the expansion of the rectangular area in one of the expansion directions if any pixel in that expansion direction corresponds to one of the reflective surfaces depicted in the virtual two-dimensional map, and continuously expanding the rectangular area by one pixel only in each of the remaining expansion directions until the rectangular area is fully expanded to its maximum in each of the expansion directions; (d) determining the fully expanded rectangular area as the estimated actual dimensions of the elevator car.

[0014] According to a second aspect of the invention, a computing device for determining estimated actual dimensions of an elevator car is proposed, the computing device being configured to perform a method according to an embodiment of the first aspect of the invention.

[0015] According to a third aspect of the present invention, a maintenance arrangement is proposed for providing support in maintaining an elevator arrangement. The maintenance arrangement comprises a mapping robot and a computing device according to an embodiment of the second aspect of the present invention. The mapping robot comprises a mobilization unit and a lidar sensor. The robot is configured to move along an accessible space driven by the mobilization unit and to obtain a virtual two-dimensional map of the robot's surroundings using the lidar sensor. The computing device is then configured to determine estimated actual dimensions of the elevator car based on the virtual two-dimensional map of the elevator car obtained by the lidar sensor of the robot.

[0016] According to a fourth aspect of the invention, a computer program product is proposed, the computer program product comprising computer readable instructions for instructing a processor to perform or control a method according to an embodiment of the first aspect of the invention.

[0017] Finally, according to a fifth aspect of the invention, a computer readable medium is proposed having stored thereon a computer program product according to an embodiment of the fourth aspect of the invention.

[0018] The concepts underlying the embodiments of the present invention can be construed as being based, inter alia, on the following observations and realizations.

[0019] Furthermore, as already briefly indicated above, lidar systems sometimes provide erroneous or inaccurate results when detecting their environment, especially when mirrors are present in the environment, which generate mirrored representations of the environment that can interfere with the lidar system.

[0020] In particular, the lidar system used by the robot to determine the environment in an elevator configuration can often be obstructed by mirrors covering parts of the walls of the elevator car. Thus, based on the information provided by the lidar system, the robot may infer that the estimated dimensions of the elevator car are larger than they actually are.

[0021] To overcome such erroneous or inaccurate detection and analysis of the environment based on the lidar signal, a certain approach is proposed herein. Such approach is particularly applicable to determine the estimated actual dimensions of an elevator car, since it may benefit from certain assumptions and / or assumptions applicable to such elevator cars. For example, an elevator car may be generally assumed to have a substantially rectangular horizontal cross-section (sometimes also called a footprint). Furthermore, it may be generally assumed that mirrors cover only partial areas of the entire wall within the elevator car, leaving other areas without mirrors. For example, a mirror may be surrounded by an area without mirrors or held by a frame without mirrors.

[0022] The method proposed herein for determining the estimated actual dimensions of an elevator car starts with obtaining a virtual two-dimensional map of the elevator car based on data provided by a lidar sensor. Such a two-dimensional map may be obtained by the lidar sensor when emitting a laser beam along a plane, in particular along a horizontal plane. For example, a laser beam may be emitted by a laser source. Such a laser beam may then be deflected, for example using a mirror, into a direction contained in the horizontal plane. The mirror may be rotated such that the laser beam is deflected in all directions along the horizontal plane, i.e. such that the laser beam is deflected continuously 360° in the horizontal plane. Upon reflection at a target, the reflection of the laser beam may be detected at the lidar sensor. By analyzing such reflections, in particular by analyzing the time of flight (TOF) between emitting the laser beam and detecting the reflection, information may be obtained about the distance of the target relative to the lidar sensor. Based on such information, a virtual two-dimensional map of the environment of the lidar sensor may be generated. If the lidar sensor is located in the elevator car, such a two-dimensional map may represent the reflective surfaces from which the laser light emitted by the lidar sensor is reflected. Such reflective surfaces typically correspond to the surfaces of the vertical walls of an elevator car.

[0023] However, if at least one of these walls is partially covered by a mirror, the lidar sensor will generally not detect the distance to this wall, but rather the mirror will reflect an image of the wall on the opposite side of the elevator car, and the lidar sensor may detect an incorrect distance to the reflected wall.

[0024] Therefore, in order to obtain reliable information about the actual dimensions of the elevator car, the method proposed herein proceeds to specifically analyze the obtained virtual two-dimensional map.

[0025] In the algorithm proposed for such purpose, first a starting area is defined. The starting area may correspond to one pixel in the image representing the virtual two-dimensional map. In other words, the starting area may be the smallest area for which information can be provided in the virtual two-dimensional map. Such a pixel or starting area is or may be generally interpreted as being rectangular.

[0026] For the algorithm proposed herein to be successful, the starting area should be defined at a location within the actual dimensions of the elevator car. In other words, the starting area should not be defined within a virtual space created when reflecting the walls of the elevator car in a mirror that covers one of the walls of the elevator car, such a virtual space being outside the actual footprint of the elevator car. Instead, the starting area should be defined somewhere within the actual dimensions of the elevator car, i.e., within the actual footprint of the elevator car.

[0027] To ensure that the starting area is defined within the actual dimensions of the elevator car, the starting area may be defined based on prior knowledge data that indicates additional information about the actual dimensions of the elevator car.

[0028] In other words, other sources of information about the actual dimensions of the elevator car may be used when defining the location of the start area. Typically, such additional information is not included in or cannot be analytically derived from the virtual two-dimensional map itself. For example, prior knowledge data indicative of such additional information may be obtained from a map or floor plan representing the layout or footprint of the building in which the elevator is located. Using such a layout or footprint, it may be estimated where the elevator car is located and where its actual dimensions roughly end. Thus, the start area may be defined within such estimated actual dimensions of the elevator car.

[0029] For example, a human technician may determine the location of the starting area based on prior knowledge data and / or based on other criteria, and the technician may then input information about such location into a computing device configured to perform other steps of the methods proposed herein.

[0030] Alternatively, the computing device itself may run an algorithm that may analyze prior knowledge data to locate the starting area within the actual dimensions of the elevator car. For example, the computing device may use image analysis to analyze a map or floor plan representing the layout or footprint of the building that houses the elevator to determine a location within the actual dimensions of the elevator car.

[0031] Preferably, the starting area may be defined at or near the geometric center of the elevator car.

[0032] In other words, the starting area should preferably not be defined at or near one of the walls surrounding the interior space of the elevator car, but should be defined sufficiently away from such walls. Thus, the starting area should be defined sufficiently away from any mirrors that cover a portion of such walls. In this regard, "at or near the geometric center of the elevator car" may be interpreted as closer to the geometric center of the elevator car than to one of the walls. By defining the starting area at or near such a geometric center, the likelihood of receiving accurate results of the estimated actual dimensions of the elevator car using the proposed method may be increased.

[0033] Furthermore, the starting area should preferably be defined such that the edges of the rectangular area are parallel to the walls of the elevator car.

[0034] Expressed differently, the starting area, which itself has a rectangular geometry, should preferably be oriented such that its edges are parallel to the walls of the elevator car, which also has a rectangular geometry. Preferably, the misalignment of such parallel arrangement should be less than 20°, more preferably less than 10°, or even less than 5°. Having such an orientation of the starting area, i.e., matched to the geometry of the elevator car, may increase the likelihood of receiving accurate results of the estimated actual dimensions of the elevator car using the proposed method.

[0035] Having defined the starting area, in the next step of the proposed method the rectangular area of ​​the starting area is successively expanded by one pixel in each of four expansion directions, each expansion direction being perpendicular to one of the edges of the rectangular starting area. In other words, in the first step the starting area may be one pixel in the virtual two-dimensional map of the elevator car, but the rectangle defining the starting area is expanded in each expansion direction to include one pixel above, one pixel below, one pixel to the left and one pixel to the right of the initial pixel defining the starting area. Furthermore, in order to keep the expanded area rectangular, the entire expanded area of ​​the rectangle includes the corner pixels connecting the mentioned expanded pixels. Expressed differently, the edges of the rectangular starting area are moved in parallel by the width of one pixel in each of the four expansion directions.

[0036] Such expansion of the rectangular area may be repeated several times, in particular said expansion of the rectangular area in all expansion directions may be repeated until at least one of the edges of the rectangular area reaches one of the reflective surfaces represented in the virtual two-dimensional map.

[0037] Thus, if any pixel in one of the expansion directions corresponds to one of the reflective surfaces depicted in the virtual two-dimensional map, the expansion of the rectangular area in this direction should be stopped, i.e. not performed in the subsequent steps of expanding the rectangular area, instead, in such subsequent steps the rectangular area should be expanded by one pixel only in each of the remaining expansion directions.

[0038] Thus, the overall procedure for successively expanding a rectangular area generally begins by expanding the rectangular area in all four directions of expansion until such expansion is "blocked" in at least one of the directions of expansion by the expanded rectangular area reaching one of the reflective surfaces representing the walls, i.e., lateral limits, of the elevator car, and then the rectangular area is successively expanded further in the remaining directions of expansion until the expansion action is also "blocked" sooner or later when another of the reflective surfaces representing one of the other walls of the elevator car is reached.

[0039] Finally, the rectangular area is fully expanded to its maximum in each of the expansion directions, so that such fully expanded rectangular area represents the estimated actual dimensions of the elevator car as determined in the proposed method.

[0040] The proposed method allows to determine the estimated real dimensions of the elevator car with high accuracy: in fact, the fully expanded rectangle obtained when maximally expanding the initial starting area in each of the four expansion directions generally corresponds well to the exact real dimensions of the elevator car.

[0041] The results of the proposed method are particularly robust as long as some prerequisites and / or assumptions hold. In particular, it is generally necessary that the starting area is selected such that its location lies within the actual dimensions of the elevator car. Furthermore, it may be useful that the starting area is positioned at a suitable starting location, preferably far enough away from the mirrored walls of the elevator car, and / or that the orientation of the rectangular starting area is made to match the approximately rectangular footprint of the elevator car.

[0042] However, in some cases and / or in some starting conditions, the proposed algorithm may sometimes not provide accurate results: for example, if the position of the starting area is not set far enough away from the mirrored walls of the elevator car, the algorithm may cause areas shown in the virtual 2D map but actually outside the actual dimensions of the elevator car to be wrongly interpreted as being part of the actual dimensions of the elevator car.

[0043] To overcome such deficiencies, the method proposed herein may be further modified. In particular, according to one embodiment, steps (b) to (c) of the proposed method may be repeated iteratively by defining the starting area in step (b) at various positions within the actual dimensions of the elevator car.

[0044] In other words, when obtaining reliable results indicative of the estimated actual dimensions of the elevator car, it may be useful not only to successively expand the initial starting area once until this rectangular area is fully expanded, but to repeat this procedure several times, i.e., in multiple iterations, while varying the starting positions of each of the starting areas, so that the final resulting fully expanded rectangular area is developed from different initial starting areas that differ at least with respect to their position within the actual dimensions of the elevator car.

[0045] In particular, it may be useful in each such subsequent iteration to define a starting area at a location that is completely within the extended rectangle determined in the first iteration.

[0046] In other words, in a first iteration, the starting area may be successively expanded until it reaches a fully expanded rectangular area. Then, in one or more subsequent iterations, the position of the starting area may be set to be located within this fully expanded rectangular area of ​​the first iteration. This may increase the likelihood that the final result of the proposed method is accurate.

[0047] In particular, according to one embodiment, in step (d) of the proposed method, if all iterations result in the same fully expanded rectangular area, then such fully expanded rectangular area may be determined to represent the estimated actual dimensions of the elevator car.

[0048] In other words, if multiple starting areas are set at different locations and expanded to a fully expanded rectangular area in each of multiple successive iterations, in a best case scenario, all iterations will result in the same fully expanded rectangular area. In other words, all iterations will converge to produce the same fully expanded rectangular area. In such a case, the resulting fully expanded rectangular area will very likely represent the actual dimensions of the determined elevator car.

[0049] According to an alternative embodiment, in step (d) of the proposed method, if the iterations result in different fully extended rectangular areas, the most likely solution may be selected from among the different fully extended rectangular areas taking into account additional prior knowledge, and the most likely solution may be determined as the estimated actual dimensions of the elevator car.

[0050] In other words, in a scenario where different iterations of the proposed method do not result in the same fully extended rectangular area, the most likely solution among the different resulting fully extended rectangular areas may be selected by considering further information. Such further information may be, for example, prior knowledge about typical geometries of elevator cars, typical artifacts contained in the virtual two-dimensional map obtained based on the lidar data, etc. For example, if different iterations result in fully extended rectangular areas with different rectangular geometries, the most likely solution may be selected based on the most reasonable aspect ratio of such rectangular geometries and / or the most reasonable size of the rectangular geometries.

[0051] Furthermore, according to another particular embodiment, each of the multiple determined fully expanded areas that do not include the starting area defined in the first iteration may be ignored when determining the estimated actual dimensions of the elevator car.

[0052] This may mean that, for at least the first iteration, the location of the starting area is known to be located within the actual dimensions of the elevator car. If a fully extended rectangular area obtained in one of the subsequent iterations of the proposed method does not include this location, this fully extended rectangular area obviously does not represent the entire actual dimensions of the elevator car, but instead represents only a part of this entire actual dimensions or even lies at least partially within a mirror image part of the virtual two-dimensional map of the elevator car. Thus, such a fully extended rectangular area may be ignored when finding the actual dimensions of the elevator car.

[0053] One embodiment of the computing device according to the second aspect of the present invention may comprise a processor for processing computer-readable instructions and a memory for storing such computer-readable instructions and / or for storing data to be processed. Furthermore, the computing device may comprise interfaces or data communication lines, through which data and / or signals may be exchanged with other devices, such as, for example, lidar sensors and / or other components in a larger device or robot. In particular, the computing device is configured to perform or control the methods proposed herein. Thus, by operating the computing device, the estimated actual dimensions of the elevator car may be determined.

[0054] Such a computing device may be part of a maintenance arrangement according to one embodiment of the third aspect of the present invention. Such a maintenance arrangement may provide support in maintaining the elevator arrangement. For example, such a maintenance arrangement may provide support in the checking function of the elevator arrangement.

[0055] For such purposes, the maintenance configuration comprises a mapping robot and the proposed computing device. The mapping robot comprises a mobilization unit that allows the robot to move in the environment. The mobilization unit may comprise one, two or more wheels that may be controllably driven by actuators such as motors. Using the mobilization unit, the robot may move in the accessible space in an elevator configuration. The mapping robot further comprises a lidar sensor. Using the lidar sensor, the robot may obtain a virtual two-dimensional map of the surroundings.

[0056] Thus, the mapping robot may move through the elevator configuration and obtain a virtual two-dimensional map of the elevator configuration. Based on this virtual two-dimensional map, the computing device may then determine the estimated actual dimensions of the elevator cars. Thus, the proposed maintenance configuration may determine the estimated actual dimensions of the elevator cars, preferably in a fully or at least partially automated manner.

[0057] In a further developed embodiment of the maintenance arrangement, a mapping robot or an optional maintenance robot with its own mobilization unit may be configured to carry out maintenance procedures in the elevator car. For example, the mapping robot or the maintenance robot may be configured to move through the entire elevator arrangement to activate and check some of its functions. As a particular example, such a robot may activate the hall operating panel and / or the car operating panel, detect deterioration or contamination in the elevator arrangement, intentionally block the elevator doors and check the reaction of the elevator. In so doing, the robot may be configured to move through the elevator car taking into account the estimated actual dimensions of the elevator car determined by the computing device.

[0058] An embodiment of a computer program product according to the fourth aspect of the invention comprises computer readable instructions which, when executed by, for example, a processor in the proposed computing unit, result in the proposed method being performed or controlled such that the estimated actual dimensions of the elevator car are determined.

[0059] Such a computer program product may be stored in a computer readable medium according to one embodiment of the fifth aspect of the present invention. Such a computer readable medium may be any memory device that can store data in a persistent or non-persistent manner. For example, the computer readable medium may be a flash memory, a CD, a DVD, a RAM or a ROM, etc. Alternatively, the computer readable medium may be part of a computer, a server or a data cloud, to which the computer program product may be downloaded.

[0060] It should be noted that possible features and advantages of embodiments of the present invention are described herein partly with respect to a method and partly with respect to a device for determining an estimated actual dimension of an elevator car or with respect to a maintenance arrangement implementing or using such an approach. Those skilled in the art will recognize that features may be suitably transferred from one embodiment to another, that features may be modified, adapted, combined and / or substituted, etc., to arrive at further embodiments of the present invention.

[0061] In the following, advantageous embodiments of the present invention will be described with reference to the accompanying drawings. However, the drawings and the description should not be construed as limiting the present invention. [Brief description of the drawings]

[0062] [Figure 1] FIG. 1 illustrates a maintenance arrangement comprising a computing device for determining estimated actual dimensions of an elevator car according to one embodiment of the present invention. [Diagram 2] FIG. 2 illustrates an example of a virtual two-dimensional map of an elevator car provided by a lidar sensor for use in a method according to one embodiment of the present invention. [Diagram 3] FIG. 1 is a visualization of the steps of a method according to one embodiment of the invention. [Figure 4] 3 is a visualization of the steps of a method according to an alternative embodiment of the invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] The figures are only schematic and not to scale. Same reference signs denote the same or similar features.

[0064] 1 shows a maintenance arrangement 1 that may provide support in maintaining an elevator arrangement 3. The maintenance arrangement 1 comprises a mapping robot 5 located in an elevator car 7 of the elevator arrangement 3. In the illustrated example, the elevator car 7 comprises four walls 9 arranged at a perpendicular angle to one another, so that the elevator car 7 has a rectangular horizontal cross section. At least one of these walls 9 is partially covered by a mirror 11.

[0065] The mapping robot 5 comprises a mobilization unit 13. In the shown example, the mobilization unit 13 comprises a number of controllably driven wheels 15. The mapping robot 5 may thus move along the entire elevator car 7 and / or adjacent floors in a building (not shown). Furthermore, the mapping robot 5 is configured to perform maintenance procedures within the elevator car 7, such as for example to test or check the functionality of the elevator arrangement 3.

[0066] The maintenance arrangement 3 further comprises a lidar system including a lidar sensor 17. The lidar sensor 17 comprises a laser source 19 for emitting a laser beam 21 and a detector 23 for detecting the reflection of the laser beam 21. Furthermore, the lidar system comprises a rotating mirror 25 for deflecting the laser beam 21 into a horizontal portion of the laser beam 27 that is part of a horizontal detection plane. When emitting pulses of the laser beam 21 and detecting the returning pulses when reflected at a target such as one of the walls 9 of the elevator car 7, the lidar sensor 17 can be used to prepare a virtual two-dimensional map representing a reflecting surface 33 extending in the detection horizontal plane and corresponding to the surface of the wall 9 of the elevator car 7.

[0067] The maintenance arrangement 3 further comprises a calculation unit 29. The calculation unit 29 is configured to obtain a virtual two-dimensional map of the elevator car 7 based on the data provided by the lidar sensor 17 and to determine estimated actual dimensions of the elevator car 7 using such virtual two-dimensional map.

[0068] 2 shows an example of a virtual two-dimensional map 30 including a representation of an elevator car 7. Here, a white portion 31 in the map 30 represents an area that appears virtually accessible by the laser beams 21, 27 of the lidar sensor 17. This white portion 31 is surrounded by black lines that represent a reflective surface 33 from which the laser beams 21, 27 are reflected. Outside the reflective surface 33 there is a shaded area 35 that is inaccessible by the laser beams 21, 27.

[0069] Within the white portion 31, which virtually represents the accessible area of ​​the elevator car 7, there appear to be several linear structures 37. In fact, these linear structures 37 represent a mirror-free portion of one of the walls 9 adjacent to one or more mirrors 11, which cover other portions of the walls 9 of the elevator car 7. Thus, these linear structures 37 indicate the actual location of the walls 9, whereas the portion 39 with the dotted hatching is only virtually accessible and in fact represents a part of the white portion 31 shown without the dotted hatching, as it is reflected in one of the mirrors 11.

[0070] Thus, in the example shown in FIG. 2, only the upper part of the white area 31, i.e. the part without the dotted slashes, corresponds to the actual dimensions of the elevator car 7, whereas the lower part with the dotted slashes is only virtual and corresponds to a reflection of the upper part.

[0071] The steps of an exemplary embodiment of a method for determining the estimated actual dimensions of an elevator car 7 will now be described with reference to FIGS.

[0072] As a first step shown in Fig. 3(a), a starting area 41 is defined. The starting area 41 shall form a rectangular area 45 and be located within the actual dimensions of the elevator car 7. Additional information obtained from prior knowledge data may be used to know approximately where these actual dimensions are. For example, there may be a map or drawing showing the layout or footprint of the entire building including the elevator arrangement 3, from which a rough location of the elevator car 7 may be derived relative to which the starting area 41 may be positioned. The starting area 41 may be a single pixel of the virtual two-dimensional map 30. The rectangular starting area 41 is positioned such that its edge 43 is parallel to one of the walls 9 of the elevator car 7.

[0073] 3(b), the starting area 41 forming a rectangular area 45 is expanded by one pixel in each of the four expansion directions 47, thereby forming a larger rectangular area 45, the edges 43 of which are moved towards the walls 9 of the elevator car 7 compared to the starting area 41.

[0074] This process of expanding the rectangular area 45 by one pixel in each expansion direction 47 is repeated until one of the pixels thus expanded corresponds to one of the reflective surfaces 33, i.e. until the position of the pixel overlaps with the position of the reflective surface 33. Such a situation is shown in Fig. 3(c), where the lower edge 43 of the rectangular area 45, after being expanded multiple times in the downward expansion direction 47, coincides with the reflective surface 33 formed by one of the linear structures 37 representing the non-mirror wall portion. The expansion of the rectangular area 45 in this downward expansion direction 47 is then stopped.

[0075] However, in each of the remaining expansion directions 47 the rectangular area 45 is expanded further in successive steps until the entire white portion 31 , representing the actual accessible area, is completely filled by the rectangular area 45 .

[0076] At that stage, the rectangular area 45 is fully expanded to its full extent and can be taken to represent the estimated actual dimensions of the elevator car 7.

[0077] 4 shows an example where the start area 41 is not originally set in the correct location. Instead, the start area 41 is set too close to one of the mirrors 11 of the elevator car 7.

[0078] Thus, as shown in the sequence of Figures 4(a)-(c), during the continuous expansion of the rectangular area 45, the rectangular area 45 enters into the virtually only accessible area 39 "behind" the mirror 11. Obviously, the fully expanded rectangular area 45, as shown in Figure 4(c), does not ultimately correspond to the actual dimensions of the elevator car 7.

[0079] To reduce the risk of obtaining such erroneous results, the method steps of defining the starting area 41 and then successively expanding the rectangular area 45 may be repeated in multiple iterations, where in each iteration the starting area 41 may be set to a different position.

[0080] In particular, as shown in the sequence of Figures 4(d)-(f), in a second iteration, the starting area 41 may be set within the fully expanded rectangular area 45 determined in the preceding first iteration. Starting at such an alternative location, the rectangular area 45 may then be successively expanded until the fully expanded rectangular area 45 precisely fills the entire actual dimensions of the elevator car 7.

[0081] Finally, it should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Also, elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

1. A method for determining the estimated actual dimensions of an elevator car (7), the method comprising the following steps: (a) obtaining a virtual two-dimensional map (30) of the elevator car (7) based on data provided by a lidar sensor (17), the virtual two-dimensional map (30) representing reflective surfaces (33) onto which laser light emitted by the lidar sensor (17) is reflected; (b) defining a starting area (41) as a rectangular area (45) at a location within the actual dimensions of the elevator car (7); (c) continuously expanding the rectangular area (45) by one pixel in each of four expansion directions (47) perpendicular to the edge (43) of the rectangular area (45), including stopping the expansion of the rectangular area (45) in one of the expansion directions (47) if any pixel in this expansion direction (47) corresponds to one of the reflecting surfaces (33) shown in the virtual two-dimensional map (30) and continuously expanding the rectangular area (45) by one pixel only in each of the remaining expansion directions (47) until the rectangular area (45) is fully expanded to its maximum in each of the expansion directions (47); (d) determining the fully expanded rectangular area (45) as the estimated actual dimensions of the elevator car (7).

2. 2. The method of claim 1, wherein the starting area (41) is defined based on prior knowledge data indicating additional information about the actual dimensions of the elevator car (7).

3. 3. The method according to claim 1 or 2, wherein the starting area is defined at or near the geometric center of the elevator car (7).

4. 4. The method according to any one of claims 1 to 3, wherein the starting area (41) is defined such that an edge (43) of the rectangular area (45) is parallel to a wall (9) of the elevator car (7).

5. 5. The method according to claim 1, wherein steps (b) to (c) are repeated iteratively by defining a starting area (41) in step (b) at various positions within the actual dimensions of the elevator car (7).

6. 6. The method of claim 5, wherein in each subsequent iteration, a starting area (41) is defined at a location that is within the complete extended rectangular area (45) determined in the first iteration.

7. 7. The method according to claim 5 or 6, wherein in step (d), if all the iterations result in the same fully expanded rectangular area (45), the fully expanded rectangular area (45) is provided as the estimated actual size of the elevator car (7).

8. 7. The method according to claim 5 or 6, wherein in step (d), if the iterations result in different fully expanded rectangular areas (45), selecting the most likely solution among the different fully expanded rectangular areas taking into account additional prior knowledge, and determining the most likely solution as the estimated actual size of the elevator car (7).

9. 9. The method according to claim 5, wherein each determined fully extended rectangular area (45) that does not include the starting area (41) defined in the first iteration is ignored when determining the estimated actual dimensions of the elevator car (7).

10. A calculation device (29) for determining estimated actual dimensions of an elevator car (7), comprising: A computing device (29), characterized in that the computing device (29) is configured for one of carrying out and controlling the method according to any one of claims 1 to 9.

11. A maintenance arrangement (1) for providing support in maintaining an elevator arrangement (3), the maintenance arrangement (1) comprising: a mapping robot (5) comprising a mobilization unit (13) and a lidar sensor (17), the mapping robot (5) being configured to move along an accessible space in an elevator configuration driven by the mobilization unit (13) and to acquire a virtual two-dimensional map (30) of a surrounding of the mapping robot (5) using the lidar sensor (17); A computing device (29) according to claim 10, A maintenance arrangement (1), wherein a computing device (29) is configured to determine estimated actual dimensions of an elevator car (7) based on a virtual two-dimensional map (30) of the elevator car (7) acquired by a lidar sensor (17) of a mapping robot (5).

12. At least one of a mapping robot (5) and an optional maintenance robot with a mobilization unit is configured to perform a maintenance procedure in the elevator car (7); 12. The maintenance arrangement according to claim 11, wherein at least one of the mapping robot (5) and the maintenance robot is configured to move within the elevator car (7) taking into account the determined estimated actual dimensions of the elevator car (7).

13. A computer program product comprising computer readable instructions instructing a processor to one of perform and control the method of any one of claims 1 to 9.

14. A computer readable medium having stored thereon the computer program product of claim 13.

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