Monitoring of elevator doors

Abstract

Embodiments of the present disclosure relate to monitoring of an elevator door. The invention relates to an apparatus (120, 140, 150) for detecting a state of an elevator door, the apparatus (120, 140, 150) being configured to determine (210), based on pressure data, at least one indicator value indicative of a change in pressure, compare (220) the at least one indicator value to a respective reference value, and set (230) a detection result to represent one of (i) the elevator door is open, (ii) the elevator door is closed, in dependence on the comparison between the at least one indicator value and the respective reference value. Furthermore, the invention relates to a method, a computer program product and an elevator system.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to the field of elevator technology. More specifically, the present invention relates to monitoring of elevators. BACKGROUND

[0002] Elevator cars travelling in a hoistway comprise several doors to improve safety by not allowing passengers to enter the hoistway, e.g. during travel. The operation of the elevator car doors is controlled with high precision and the status of the doors is constantly monitored. For example, an elevator car shall not start a trip unless the doors are closed, and thus the status of the car doors is linked to other entities in the elevator system with the purpose of maintaining and improving the safety of using the elevator system.

[0003] In prior art solutions, the monitoring of the status of the elevator car doors is based on obtaining measurement data from one or more sensors coupled to the door frame or the elevator door to generate data about the position of one or more door leaves relative to the frame. The sensors applied in prior art solutions are based on detection generated in response to electrical contact or in response to a photoelectric phenomenon, e.g. infrared sensors.

[0004] A drawback of prior art solutions is that the sensors can get dirty and their operation can be disturbed. Further, the sensors of the described type are coupled to moving parts of the elevator car door, where the mechanical stress experienced by the sensors can break the sensors, thereby challenging the entire elevator system. Further, in prior art solutions the sensors belong to the safety chain of the elevator system, which does not necessarily allow external entities to access the sensor data.

[0005] There is thus a need to introduce new methods for monitoring the operation of elevator car doors that at least partly alleviate the determinations of prior art solutions. SUMMARY

[0006] In order to provide a basic understanding of some aspects of various inventive embodiments, a brief summary of the invention is set forth below. The summary is not an extensive overview of the disclosure. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The sole purpose of the following summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description of the embodiments of the invention that is to follow.

[0007] It is an object of the present invention to present a device, a method, a computer program product and an elevator system for detecting the status of an elevator door.

[0008] It is an object of the present invention to be achieved by the device, the method, the computer program product and the elevator system defined in the respective disclosure.

[0009] According to a first aspect, there is provided an apparatus for detecting a state of an elevator door, the apparatus being configured to: determine, based on pressure data, at least one indicator value indicative of a pressure change; compare the at least one indicator value to a respective reference value; and set, in dependence on the comparison between the at least one indicator value and the respective reference value, a detection result to represent one of: (i) the elevator door is open, (ii) the elevator door is closed.

[0010] The apparatus can be configured to determine the at least one indicator value indicative of the pressure change by applying a statistical analysis to the pressure data within a predefined time window. For example, the apparatus can be configured to perform the statistical analysis by determining a variance within the predefined time window to determine the at least one indicator value indicative of the pressure change. Also, the apparatus can be configured to perform the determination of the variance by at least one of: on a first order, on a second order.

[0011] The apparatus can further be configured to, in response to the detection result representing that the elevator door is open, generate a control signal to at least one entity for calibrating an operation of the entity. For example, the apparatus can be configured to generate the control signal to at least one of: a positioning system of an elevator car in the elevator shaft, an accelerometer associated with the elevator car.

[0012] Furthermore, the apparatus can be at least one of: a measurement device coupled to the elevator car, an elevator controller, a server device residing in a communication network.

[0013] The apparatus can further be configured to receive the pressure data from at least one pressure sensor configured to measure a pressure from at least one of: the elevator shaft; within the elevator car. For example, the apparatus can be configured to receive the pressure data representing a pressure in the elevator shaft from at least one pressure sensor arranged in at least one of: on top of the elevator car; on a wall of the elevator shaft; in a vent arranged to transfer air between the elevator car and the elevator shaft.

[0014] According to a second aspect, there is provided a method for detecting a state of an elevator door, the method performed by an apparatus comprising: determining, based on pressure data, at least one indicator value indicative of a pressure change; comparing the at least one indicator value to a respective reference value; and setting, in dependence on the comparison between the at least one indicator value and the respective reference value, a detection result to represent one of: (i) the elevator door is open, (ii) the elevator door is closed.

[0015] The at least one indicator value indicative of a pressure change can be determined by applying a statistical analysis to the pressure data within the predefined time window. For example, the statistical analysis can comprise determining a variance within the predefined time window to determine the at least one indicator value indicative of a pressure change. Likewise, the determination of the variance can be performed by at least one of: on a first order, on a second order.

[0016] Further still, the method can further comprise, in response to the detection result representing that the elevator door is open, generating a control signal to at least one entity for calibrating operation of the entity. For example, the at least one entity can be at least one of: a positioning system of an elevator car in the elevator shaft, an accelerometer associated with the elevator car.

[0017] The method can further comprise receiving pressure data from at least one pressure sensor configured to measure pressure from at least one of: the elevator shaft; within the elevator car. The pressure data representing pressure in the elevator shaft can for example be received from at least one pressure sensor arranged in at least one of: on top of the elevator car; on a wall of the elevator shaft; in a vent arranged to transfer air between the elevator car and the elevator shaft.

[0018] According to a third aspect, there is provided a computer program product for detecting a state of an elevator door, which, when executed by at least one processor, causes an apparatus to perform the method according to the second aspect as defined in the preceding description.

[0019] According to a fourth aspect, there is provided an elevator system comprising: at least one elevator car and an apparatus according to the first aspect as defined in the preceding description.

[0020] The expression “several” refers here to any positive integer number starting from 1, for example 1, 2 or 3.

[0021] The expression “several” refers here to any positive integer number starting from 1, for example 1, 2 or 3.

[0022] The various illustrative and non-limiting embodiments of the present application in terms of construction and methodology and additional objects and advantages thereof will be understood and appreciated by those skilled in the art upon reading of the following description of the various illustrative and non-limiting embodiments taken concomitantly with the drawings.

[0023] The verbs “comprise” and “include” are used as open-ended limitations that neither excludes nor requires the existence of also un-recited features. The features of the various aspects described herein are combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, does not exclude a plurality, but rather means “one or more”, unless explicitly stated otherwise. BRIEF DESCRIPTION OF DRAWINGS

[0024] Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

[0025] Figure 1 An elevator system according to an example is schematically illustrated.

[0026] Figure 2 A method according to an example is schematically illustrated.

[0027] Figures 3A to 3C A chart related to a method according to an example is schematically illustrated.

[0028] Figure 4 An apparatus according to an example is schematically illustrated. DETAILED DESCRIPTION

[0029] The specific examples provided in the description given below should not be construed as limiting the scope and / or applicability of the claims appended hereto. The list and groups of examples provided in the description given below are not exhaustive, unless explicitly stated otherwise.

[0030] Some aspects of the invention are described below by reference to the example schematically illustrated in Figure 1 Fig. 1, wherein it is illustrated as some elevator entities as well as other entities of an elevator system. According to an example, there is provided an elevator car 100 comprising several elevator doors 110. In the context of Fig. 1, the elevator doors 110 are to be understood as covering at least one of the following: elevator car door, landing door. In case of two doors being installed, a door system can be implemented such that the elevator doors 110 are opened and closed in a synchronized manner, for example by utilizing a so-called door coupler solution, connecting the doors together when in operation. Figure 1

[0031] ​Furthermore, the elevator system includes a measuring device 120 associated with the elevator car 100, for example, by coupling the measuring device 120 to the top of the elevator car 100, such that the measuring device 120 can travel with the elevator car 100 in a path of travel, such as in a shaft. The measuring device 120 may include at least one sensor 130 suitable for measuring the pressure of the environment. Suitable sensors 130 may be pressure sensors, such as barometers. At least one pressure sensor 130 may be mounted within the measuring device 120 or it may be external to the housing of the measuring device 120, but communicatively connected to the measuring device 120 via wired or wireless means. Thus, the measuring device 120 may include a communication interface for communicating with the pressure sensor 130, but also for communicating with other entities, such as the elevator controller 140 or entities residing in a cloud computing environment, but at least serving the measuring device 120 in the manner described above (such as server device 150). The implementation of the elevator doors is advantageously considered when selecting the location of the pressure sensor 130. For example, selection can be made to place it at a location where pressure can be measured, and based on the state of the elevator door, possible detection of pressure changes can be performed. For example, the applicable location could be inside the elevator car 100 or on the outer surface of the elevator car 100, such as... Figure 1 The diagram is schematically shown on the top of the elevator car 100. In some examples, pressure sensors 130 may be located in the elevator shaft, for example near the opening from the elevator shaft to the ground (e.g., covered by a landing door), and each pressure sensor 130 may be configured to communicate, for example wirelessly, with a measuring device 120 to transmit data representing the pressure experienced at the location of the pressure sensor 130 in question.

[0032] Also as from Figure 1 As derived from this, communication with the elevator controller 140 and / or the service device 150 residing in the communication network and the measuring device 120 can be performed in a wired or wireless manner. The wireless implementation for the server device 150 can be implemented at least in part by utilizing wireless communication resources provided by a mobile communication network in the area where the elevator system is set to operate and therefore the measuring device 120 is set to operate. For clarity, it is worth mentioning that in some examples, the measuring device 120 can be configured to perform its tasks without a communication connection to the server device 150 or at least directly to the elevator controller 140. Further, in some examples, communication between the measuring device 120 and the server device 150 can be configured to be performed via the elevator controller 140. Even further, in addition to the pressure sensor 130, the measuring device 120 can be configured to receive measurement data from other types of sensors, such as from accelerometers and position sensors, which can be implemented at least in part within the housing of the measuring device 120.

[0033] According to embodiments, the processing of the measurement data obtained from the pressure sensor 130 can be performed by the measurement device 120, or the raw measurement data can be sent by the measurement device 120 to another entity, such as the elevator controller 140 or the server device 150, for processing. When describing examples of the method schematically illustrated in Figure 2 the entity performing the data processing is now referred to as the apparatus.

[0034] Figure 2Figures illustrate non-limiting examples regarding the processing of data for determining the state of an elevator door. As previously described, the elevator door corresponds here to at least one of the following: the elevator car door, the landing door, and where one or more respective doors are opened, creating an air flow between at least the space in question, such as the hoistway or the elevator car 100 or even both, and the door hall of the landing. In other words, the location of the at least one pressure sensor 130 can be chosen according to the implementation of the elevator door, in order to allow detecting the pressure of the measurement location, and detecting changes therein according to the state of the elevator door. For example, if the pressure sensor 130 resides on the hoistway side, for example on the top of the elevator car 100 or on the hoistway wall, then at least the landing door needs to be open in order to perform any detection, due to the path established for the air flow between the hoistway and the door hall. Similarly, if the pressure sensor 130 resides within the elevator car 100, then the elevator door set between the volume of the elevator car 100 and the door hall needs to be open in order to perform any detection representing the state of the door, due to the path established for the air flow between the elevator car 100 and the door hall. Further, the pressure sensor 130 can also be set in a vent set to transfer air between the elevator car 100 and the elevator hoistway, where the pressure sensor 130 can receive data representing the state of the pressure at least in the hoistway. As derived from the previous description, the at least one pressure sensor 130 is configured to collect pressure data in the elevator environment, and the apparatus is set to determine 210 an indicator value indicative of a change in pressure in the elevator environment, such as in the elevator hoistway, based on the pressure data. The indicator value can be any applicable mathematical parameter derived from the measurement data, i.e. from the raw measurement data, which contains consecutive pressure values received with the sampling frequency of the measurement system. In advantageous examples, the indicator value can be determined such that it reacts quickly to changes in the measurement data. In some examples, the change can be determined between two consecutive data values, but from the reliability point of view of the solution, such implementation is not necessarily optimal. Thus, a more complex solution can be based on determining the indicator value by applying statistical analysis to the pressure data within a pre-defined window. The pre-defined window can be defined within a time corresponding to a pre-defined number of data values, as the sampling rate can depend on the applied system, i.e. at least on the pressure sensor 130 capabilities and the communication channels and processing resources in the apparatus 120.

[0035] According to at least some advantageous examples, a statistical analysis can be performed in order to determine an indicator value representing a variance of data values within a predefined time window. The determination of the variance can be performed by applying a rolling method in determining the variance, i.e. a rolling variance, in order to determine the variance for pressure data values measured within consecutive time windows, such that disturbances due to environmental changes, at least including pressure changes within the respective time window, can be detected. The determination of the rolling variance can be performed in consecutive time windows, e.g. such that at least some pressure data values occur in the consecutive time windows. In other words, the time windows are at least partially overlapping. According to some examples, the determination of the variance can advantageously be performed by calculating a variance of a certain order, such as a first order, a second order or a third order, from the pressure data values. These orders can be considered in the context of the present solution in the way that the first order represents a noise level in the raw data, i.e. the measured data values, the second order represents a variability of the noise level, e.g. a speed, and the variance of the third order represents an acceleration of the noise level. An advantage of using the variance of the selected order in the method in the described way is that any deviations in the measured pressure data are easier to detect than from the raw data.

[0036] In response to determining 210 the indicator value, the apparatus 120 can be arranged to compare 220 the indicator value with a reference value. The reference value is advantageously defined in advance, e.g. as a fixed value, e.g. obtained by trial and error, and it defines a reference value allowing the comparison to be performed such that a conclusion can be drawn with an acceptable accuracy. For example, the reference value can define a value of the change in the predetermined time window in order to draw a conclusion that the elevator door 110 is open if the indicator value exceeds the reference value. In some examples, the reference value can be dynamically defined, e.g. based on previous measurements received from the at least one pressure sensor 130. In other words, the reference value is not necessarily fixed, but can be dynamically defined, e.g. such that it relates to a regular noise level learned from previous samples derived from previous time windows. As is clear from the context, the at least one reference value is selected and / or defined depending on the representation of the indicator value, i.e. depending on how the indicator value is calculated.

[0037] Finally, in step 230, the apparatus 120 can perform a conclusion by setting a detection result to represent one of the following depending on the comparison of the indicator value and the reference value: (i) the elevator door 110 is open, (ii) the elevator door 110 is closed. The apparatus 120 can be arranged to communicate the detection result to at least one other entity, such as the elevator controller 140, for further use.

[0038] Further, in some embodiments, the method can be implemented so as to determine a plurality of indicator values from the raw data, such as a first order and a second order variance. Further, respective reference values are defined for two of these indicator values. As a result, the two indicator values are compared to their respective reference values and a conclusion can be performed based on the comparison. It is also worth mentioning that in case a plurality of indicator values is determined, it is not necessarily required that the respective indicator values are determined from the same set of raw data, but from a time window, so that for determining the respective indicator values, several samples can be different. For example, if both indicator values exceed their respective reference values, a conclusion can be drawn that the elevator door 110 is open. Of course, other decision rules can be defined. Such an implementation in combination with a plurality of comparison paths can be advantageous if an increased precision is required.

[0039] According to an example, in case the device 120 generates an expression that the elevator door 110 is open based on measurement data obtained from the at least one pressure sensor 130, the device 120 or any other entity that receives information about the elevator door 110 being open can be configured to generate a control signal to at least one other entity belonging to the elevator system. The generation of the control signal can cause a calibration of the at least one other entity, which can be an entity that generates information about the state of the elevator system or the elevator car 100. This is possible because it is detected that the elevator door 110 is open, it is confirmed that the elevator car 100 resides at the landing, and the information can for example be used to calibrate a positioning system of the elevator car in the elevator shaft or an accelerometer associated with the elevator car. The positioning system can be such, for example, so that it generates position information of the elevator car 100 in the shaft based on detections of magnetic sensors installed in the shaft within a known interval.

[0040] Figures 3A to 3C An example of determining variances of different orders from pressure data values received from the pressure sensor 130 (130) is schematically illustrated as a chart. In other words, Figure 3A An example of determining variances of different orders from pressure data values received from the pressure sensor 130 (130) is schematically illustrated as a chart. In other words, Figure 3A The magnitude of pressure data values received from the pressure sensor 130 over a period of time is schematically illustrated. By applying a rolling variance over the first or second order, a clear deviation in the chart is generated, and based on at least one of these deviations, a conclusion can be drawn that the elevator door 110 is open. For the sake of clarity, it is worth mentioning that Figures 3A to 3C the x-axis in the chart represents time, and the y-axis represents the intensity of the respective signal. However, Figures 3A to 3C the intensity of the signal in the chart is not necessarily the same scale. Further, as Figure 3B and Figure 3C indicated, respective parameter values can be defined for the parameters in question. In Figure 3B and Figure 3CIn the middle, reference values are marked with Ref1 (for variance of the first order; see Figure 3B ) and Ref2 (for variance of the second order, Figure 3C ). Further, a moment of detection is denoted with Td, which is plotted against Figures 3A to 3C All plots in Fig. 4 are common for all.

[0041] For example, the device can refer to a computing device, such as a server device, a laptop, a PC or any similar data processing device, like Figure 4 schematically illustrated. Figure 4 A non-limiting example of a device suitable for performing the method in cooperation with other entities, such as sensors, is schematically illustrated as a block diagram. The device can thus be, for example, the measurement device 120, the elevator controller 140 or the server device 150 discussed in the preceding description. For the sake of clarity, it is worth mentioning that Figure 4 The block diagram of Fig. 5 depicts some components of a device that can be used to implement the operations of the device. The device comprises a processor 410 and a memory 420. The memory 420 can store data and computer program code 425. The device can further comprise a communication component 430 for wired and / or wireless communication with other entities, such as at least one pressure sensor 130, and other sensors, but also with other entities. Furthermore, an I / O (input / output) component 440 can be provided with the processor 410 and parts of the computer program code 425 to provide a user interface for receiving input from a user, such as a technician of the elevator system, and / or providing output to a user of the system, if necessary. In particular, the user I / O component can comprise user input components, such as one or more keys or buttons, a keyboard, a touch screen or a touch pad, etc. The user I / O component can comprise output components, such as a display or a touch screen. The components of the device can be communicatively coupled to each other by a bus 450, which enables the transfer of data and control information between the components.

[0042] The memory 420 and parts of the computer program code 425 stored therein can also be provided with the processor 410 to cause the device, i.e. the apparatus, to perform the method described in the preceding description. The processor 410 can be configured to read from and write to the memory 420. Although the processor 410 is depicted as a single component each, it can be implemented as one or more separate processing components each. Similarly, although the memory 420 is depicted as a single component each, it can be implemented as one or more separate components, some or all of which can be integrated / removable, and / or can provide permanent / semi-permanent / dynamic / cached storage.

[0043] The computer program code 425 can comprise computer executable instructions which, when loaded into the processor 410, implement the functions corresponding to the steps of the method. As an example, the computer program code 425 can comprise a computer program consisting of one or more sequences of one or more instructions which, when executed by the processor 410, cause the apparatus to carry out the described method. The processor 410 is thereby enabled to load and execute the computer program by reading the one or more sequences of one or more instructions included in the computer program from the memory 420. The one or more sequences of one or more instructions can be configured such that, when executed by the processor 410, the apparatus performs the described method. The apparatus can therefore comprise at least one processor 410 and at least one memory 420 including the computer program code 425 of one or more programs, the at least one memory 420 and the computer program code 425 configured to, with the at least one processor 410, cause the apparatus to perform the described method.

[0044] The computer program 425 can be provided, for example, as a computer program product including at least one computer-readable non-transitory medium having stored thereon the computer program code 425, which, when executed by the processor 410, causes the apparatus to carry out the method. The computer-readable non-transitory medium can include memory devices or recording media such as CD-ROMs, DVDs, Blu-ray discs, or another article of manufacture that tangibly embodies the computer program. As another example, the computer program can be provided as a signal configured to reliably transfer the computer program.

[0045] Further, the computer program code 425 can comprise a proprietary application such as a computer program code for causing the method to be carried out in the described manner.

[0046] Any of the programming functions mentioned can also be performed in firmware or hardware, as desired.

[0047] Furthermore, as mentioned above, the functions of the apparatus can be shared between a plurality of devices as a distributed computing environment. For example, the distributed computing environment can include a plurality of devices schematically illustrated in Figure 4 arranged to cooperate in a predetermined manner to implement the method. For example, each device can be arranged to perform one or more method steps and, in response to the completion of its specialized steps, it can hand over the continuation of the process to the next device. The devices can be, for example, the measurement device 120, the elevator controller 140 and the server device 150 or any combination thereof, provided that the measurement data from the at least one pressure sensor 130 can be transferred to the respective entity.

[0048] According to some aspects, therefore, there is provided an elevator, wherein the elevator system comprises an apparatus for carrying out the described method.

[0049] In some examples, the detection result obtained by the method can be confirmed with information from other systems. For example, in some embodiments, the detection result is confirmed by obtaining measurement data from the accelerometer and by detecting, on the basis of the measurement data from the accelerometer, that the elevator car is stationary while the pressure data indicates that the elevator door 110 is open, from which it can be concluded that the expression about the state of the elevator door 110 is correct. Position information can be used in the same way to confirm the result of the method.

[0050] In cases where the apparatus is implemented as a separate device, it can be associated with the elevator car 100 as a separate unit to provide information about the state of the elevator system, in particular information about the state of the elevator door 110, to an external entity, such as a server device residing in a communication network. This implementation can be advantageous if the elevator system is old and it is not possible to integrate monitoring devices in the elevator system itself, but only to introduce these monitoring devices to the elevator system as separate units. In this way, data can be generated to monitor the elevator system in question.

[0051] The solution described in the foregoing description can be applied in cases where it is necessary to know the state of the elevator door and to use this information for any additional use. For example, the information about the state of the elevator door derivable in the described manner can be used to detect that the elevator car has entered a floor, as a non-limiting example.

[0052] The specific examples provided in the description given above should not be construed as limiting the scope and / or applicability of the appended claims. The lists and groups of examples provided in the description given above are not exhaustive, unless explicitly stated otherwise.

Claims

1. A device for detecting the status of an elevator door, the device comprising: At least one processor (410); At least one memory (420) includes computer program code (425); Communication component (430); I / O components (440); The at least one processor (410), the at least one memory (420), the communication component (430), the I / O component (440), and the bus (450) are communicatively coupled to each other. Characterized in that the at least one memory (420) and the computer program code (425) are configured together with the at least one processor (410) to cause the device to: - Based on the pressure data, at least one index value indicating a change in the pressure is determined (210) by applying statistical analysis to the pressure data within a predefined time window; - Compare the at least one indicator value with its respective reference value (220); and - Based on the comparison between the at least one index value and the respective reference value, the detection result is set (230) to indicate that one of the following is true: (i) the elevator door is open, (ii) the elevator door is closed.

2. The apparatus of claim 1, wherein the apparatus is configured to perform the statistical analysis by determining the variance within the predefined time window to determine the at least one index value indicating the change in pressure.

3. The apparatus of claim 2, wherein the apparatus is configured to perform the determination of the variance by at least one of the following: at a first order representing the noise level in the pressure data, at a second order representing the variability of the noise level, and at a third order representing the acceleration of the noise level.

4. The apparatus according to any one of the preceding claims, further configured to: In response to the detection result indicating that the elevator door is open, a control signal for calibration is generated to at least one of the following: a positioning system of the elevator car (100) in the elevator shaft, and an accelerometer associated with the elevator car (100).

5. The apparatus according to any one of claims 1 to 3, wherein the apparatus is at least one of the following: a measuring device (120) coupled to an elevator car (100); an elevator controller (140); or a server device (150) residing in a communication network.

6. The apparatus according to any one of claims 1 to 3, wherein the apparatus is configured to receive pressure data from at least one pressure sensor (130), the at least one pressure sensor being configured to measure pressure from at least one of: an elevator shaft, or in an elevator car (100).

7. The apparatus of claim 6, wherein the apparatus is configured to receive pressure data representing pressure in the elevator shaft from at least one pressure sensor (130), the at least one pressure sensor (130) being arranged in at least one of the following ways: on the top of the elevator car (100); on the wall of the elevator shaft; or in a vent arranged to transfer air between the elevator car (100) and the elevator shaft.

8. A method for detecting the state of an elevator door, the method being performed by a device, comprising: - Based on the pressure data, at least one index value indicating the change of the pressure is determined (210) by applying statistical analysis to the pressure data within a predefined time window; - Compare the at least one indicator value with its respective reference value (220); and - Based on the comparison between the at least one index value and the respective reference value, the detection result is set (230) to indicate that one of the following is true: (i) the elevator door is open, (ii) the elevator door is closed.

9. The method of claim 8, wherein the statistical analysis comprises determining the variance within the predefined time window to determine the at least one index value indicating the change in pressure.

10. The method of claim 9, wherein the determination of the variance is performed by at least one of the following: at a first order representing the noise level in the pressure data, at a second order representing the variability of the noise level, and at a third order representing the acceleration of the noise level.

11. The method according to any one of claims 8-10, wherein the method further comprises: In response to the detection result indicating that the elevator door is open, at least one of the following generates a control signal for calibration: a positioning system for the elevator car in the elevator shaft, and an accelerometer associated with the elevator car.

12. The method according to any one of claims 8 to 10, further comprising: The pressure data is received from at least one pressure sensor (130), which is configured to measure the pressure from at least one of the following: elevator shaft, or in elevator car (100).

13. The method of claim 12, wherein the pressure data representing the pressure in the elevator shaft is received from at least one pressure sensor (130), the at least one pressure sensor (130) being arranged in at least one of the following ways: on the top of the elevator car (100); on the wall of the elevator shaft; or in a vent arranged to transfer air between the elevator car (100) and the elevator shaft.

14. A computer program product for detecting the state of an elevator door (110), said computer program product causing a device to perform the method according to any one of claims 8 to 13 when executed by at least one processor.

15. An elevator system, comprising: At least one elevator car (100). as well as The apparatus according to any one of claims 1 to 7.

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