METHOD FOR DETECTING CHANGES IN AN AREA TO BE MONITORED

Description

[0001] The present invention relates to a method for detecting changes in a monitored area of ​​a conveying system, a method for detecting an empty monitored area of ​​a conveying system, a system with a sound sensor and an evaluation unit connected to the sound sensor for detecting changes in a monitored area of ​​a conveying system, and a conveying system.

[0002] Transportation systems can include, for example, elevators, escalators, and moving walkways. Such systems are used for both passenger and freight transport.

[0003] Elevators are used, among other things, to transport passengers between different floors within a building. There are various reasons for detecting changes within an elevator car. In this case, the elevator car can constitute the area to be monitored according to the invention. Changes within the elevator car can include: A change in the number of people in the elevator car; a change in the number of movable objects, such as luggage, suitcases, or any other items. Items may include, for example, items lost or left behind by a person, such as a set of keys, a mobile phone, an envelope, tools such as a hammer, screwdriver, etc.; a handrail, mirror, seat, etc., of the elevator car's interior fittings that are no longer in their intended position due to wear and tear, aging, or vandalism.

[0004] Besides recognizing changes, it can also be useful or necessary to determine whether an elevator car is empty or occupied. "Occupied" here is broadly understood as "an elevator car that is not empty." An elevator car that is not empty can be: If a person is in the elevator car; and / or if an object, especially a movable object, is in the elevator car.

[0005] There are various reasons why it's necessary to detect changes in an elevator car or to know whether it's "empty" or "occupied." For example, when empty, the car's lights and / or ventilation may be switched off. Furthermore, access to a specific floor may only be permitted when the car is empty, not when occupied. Similarly, in an elevator car with multiple doors, opening one or more doors simultaneously may only be allowed when the car is empty. Such requirements are necessary for elevator systems that travel between different security zones, as is common in airports, government buildings, or hospitals.

[0006] An area to be monitored within an elevator system can also be the access area to the elevator system, meaning an accessible area around the elevator shaft door on a given floor. The size of this monitored area depends on the specific requirements, but is typically an area with a radius of up to several meters around the shaft door, for example, up to 5 meters, preferably up to 3 meters, and most preferably up to 2 meters. The shape of the area can, of course, also be rectangular, such as square.

[0007] For escalators and moving walkways, the area to be monitored can be the entrance or access area to the escalator or moving walkway, as well as the exit or egress area. The size of this monitored area depends on the specific requirements.

[0008] Various systems for monitoring areas are known in the prior art. US 5,761,155 A discloses a method according to the preamble of claim 1. US 5,761,155 A discloses a system with a sound sensor and an evaluation unit connected to the sound sensor.

[0009] For example, there are sensors that can detect the presence of people in a room. These are based, for instance, on ultrasound and utilize the Doppler effect for person detection. However, this requires minimal movement of the people, such as their hands or head. Completely stationary people or objects cannot be detected by these Doppler-based sensors. Other sensors are based on infrared. These can detect people, but are poorly suited or completely unsuitable for detecting objects.

[0010] Systems for detecting changes in an elevator car are also known, based on the analysis of optical images, such as photos or videos. However, these systems are poorly suited for elevator cars with one or more transparent side walls or a transparent floor, as the environment outside the car changes. Similarly, screens displaying moving content are now common in elevator cars and can lead to inaccurate information during optical analysis.

[0011] Another system and method for detecting changes in a room is known as "UltraSense: A Self-Calibrating Ultrasound-Based Room Occupancy Sensing System", Abbass Hammoud, Michel Deriaz, Dimitri Konstantas, Procedia Computer Science 109C (2017) 75-83. This known method is based on emitting an ultrasound pulse, recording a response signal to the ultrasound pulse, and directly calculating a Fourier transform of the response signal for further evaluation of a frequency spectrum of the response signal with respect to Doppler shifts.

[0012] The object of the present invention is to provide a robust system and a robust method for detecting changes of any kind in a monitored area. This includes reliably detecting whether one or more stationary objects and / or persons are present or not, and / or whether their number and / or position has changed.

[0013] Another object of the present invention is to provide a robust system and a robust method for detecting an empty area to be monitored, as well as a conveying system with such a system.

[0014] These tasks are solved by the subject matter of independent claims.

[0015] Advantageous embodiments of the invention are described by the dependent claims and / or specified in the further description of the invention.

[0016] The inventive method for detecting changes in a monitored area of ​​a conveying system comprises a sound sensor and an evaluation unit connected to the sound sensor. The method is characterized by Emitting an acoustic pulse into the area to be monitored, recording an acoustic response signal of the pulse as the actual signal, determining an envelope of the actual signal, detecting changes based on the envelope, wherein the detection of changes based on the envelope is further characterized by determining a spectrum of the envelope of the actual signal as an actual measurement.

[0017] This inventive method enables reliable detection of changes in the monitored area, which may, for example, be an elevator car. By determining the envelope, the detection of changes is made largely independent of the frequency of the acoustic pulse. Furthermore, it has been experimentally verified that the detection of changes based on the envelope functions reliably.

[0018] In contrast to the state of the art, which is based on the Doppler effect for detecting changes, this method also makes it possible to detect stationary persons and objects.

[0019] Furthermore, it is advantageous that the data used, in particular the actual signal, does not allow the identification of a specific person.

[0020] According to another preferred embodiment of the invention, a reference measurement is compared with the actual measurement in order to detect a change.

[0021] This advantageous embodiment allows the actual measurement to be compared with a reference measurement, which has proven advantageous in the tests.

[0022] According to a preferred embodiment of the invention, a frequency spectrum is used as the spectrum.

[0023] According to another preferred embodiment of the invention, an amplitude spectrum, for example an amplitude-frequency spectrum, is used as the spectrum.

[0024] This advantageous embodiment allows, in particular, the comparison of amplitude spectra. Compared to other spectra in the frequency domain, such as a phase spectrum, real-part spectrum, or imaginary-part spectrum, amplitude spectra are advantageous in that they are independent of any time shift of the actual signal or partial time shifts of its constituent parts. Here, "amplitude" is defined as the square root of the sum of the squares of the real and imaginary parts.

[0025] For example, test measurements revealed that despite unchanged test conditions in the monitored area, a certain variation in the signal—that is, in both the actual signal and the reference signal—could be observed. It is suspected that these variations are due to air turbulence or temperature fluctuations in the monitored area. Turbulence could be caused, for example, by people entering, leaving, crossing, or even just briefly entering and leaving the monitored area. However, the test measurements showed that, despite these variations in the signal, the amplitude spectra for different signals under identical conditions in the monitored area were largely the same.

[0026] According to a preferred embodiment of the invention, a difference between the reference measurement and the actual measurement is determined during comparison.

[0027] According to a preferred embodiment of the invention, a comparative value is determined by summing the differences or by summing values ​​determined from the differences.

[0028] According to a preferred embodiment of the invention, the actual measurement is recognized as different from the reference measurement if the comparison value exceeds a tolerance threshold.

[0029] According to a preferred embodiment of the invention, the acoustic impulse is emitted over an angular range or an opening angle of at least 90 degrees.

[0030] This advantageous embodiment allows the area to be geometrically determined by the angular range of the emitted pulse.

[0031] For example, an access area to or from a transport system is typically open, meaning it is not structurally separated from the rest of the space. However, it can be desirable to monitor the access area. In the case of an elevator, it can be useful to obtain information about whether a person, object, or even a robot is in front of a shaft door. For instance, it sometimes happens that people trigger elevator calls, but before the elevator car can reach the floor from which the call was made, the person moves away from the elevator. In such a case, monitoring the access area allows a call to be canceled as soon as no one is present in the monitored area, i.e., the elevator access area.

[0032] This advantageous embodiment also allows for the detection of objects that are deposited in the access area or in the area to be monitored and that could endanger the safety of persons.

[0033] According to a preferred embodiment of the invention, the evaluation unit comprises a processor, at least one memory connected to the processor via a bus, and at least one interface connected via the bus for communication.

[0034] According to a preferred embodiment of the invention, the determination and detection of changes are carried out by the evaluation unit.

[0035] Another aspect of the invention relates to a method for detecting an empty area to be monitored in a conveying system, wherein the reference signal is determined for an empty area to be monitored.

[0036] According to a preferred embodiment of the invention, the area to be monitored is recognized as empty if the actual signal is recognized as being essentially equal to the reference signal.

[0037] Another aspect of the invention relates to a system with a sound sensor and an evaluation unit connected to the sound sensor for detecting changes in a monitored area of ​​a conveying system for carrying out one of the methods described above.

[0038] Another aspect of the invention relates to a conveying system with the system described above.

[0039] Exemplary embodiments of the invention are described below with reference to the accompanying drawings, whereby neither the drawings nor the description are to be interpreted as limiting the invention.

[0040] Further preferred embodiments of the invention are also described with reference to the exemplary embodiments. Fig. 1 shows a purely schematic representation of an elevator car. Fig. 2 shows a purely schematic representation of an elevator system. Fig. 3 shows, purely schematically, for a reference measurement, an acoustic pulse, a response signal to the pulse and its envelope, as well as a corresponding spectrum. Fig. 4 shows, purely schematically, for an actual measurement, the acoustic pulse, a response signal to the pulse and its envelope, as well as a corresponding spectrum. Fig. 5 shows, purely schematically, a section of an elevator system in which the area to be monitored is located in front of a shaft door of the elevator system. Fig. 6 shows, purely schematically, a method for detecting changes in an area to be monitored.

[0041] The figures are merely schematic and not to scale. Identical reference symbols in the different figures denote identical or equivalent features.

[0042] Fig. 1 shows an elevator cabin 10 for a in Fig. 2 The elevator system 20 shown, which, as described at the outset, is a conveying system within the meaning of this patent application. How Fig. 2 Figure 20 shows that the elevator system includes the elevator car 10, which can be moved between different floors by means of a drive system. A traction elevator is shown as the drive system, but any drive system can be used for an elevator system. Wire ropes are shown as the suspension element 22, but belts or the like can also be used. Alternative drive systems such as a hydraulic elevator, rack and pinion elevator, a vacuum elevator, or a ropeless elevator, for example, one implemented using a linear motor, can also be used.

[0043] How Fig. 1 As shown, the elevator car 10 is equipped with a detection module 30. This module comprises a transmitter 32, a receiver 34, and an evaluation unit 36 ​​connected to the transmitter 32 and the receiver 34. In this embodiment, the elevator car 10 forms a monitored area 11. This area is bounded by the side walls, floor, ceiling, and car door of the elevator car 10.

[0044] The evaluation unit 36 ​​typically has a processor, at least one memory connected to the processor via a bus, and at least one interface for communication connected via the bus.

[0045] The detection module 30 serves to detect changes within the elevator car 10. A change could be an added object 42, such as a forgotten package. A change within the elevator car could also be a person 44 newly entering the elevator car 10. An object removed from the elevator car 10, such as a handrail, could also constitute a change. The object of the invention is to detect any changes in the interior of the elevator car 10 or in the area 11 to be monitored.

[0046] For this purpose, transmitter 32 emits an acoustic pulse 40, specifically a sound pulse of approximately 48 kHz and a duration of approximately 0.3 ms. The duration of 0.3 ms corresponds to several oscillations at 48 kHz, whereby it should be noted that transmitter 32 also has an attack and a decay period. The frequency was chosen so that it is inaudible to both humans and pets, such as dogs. If a frequency other than 48 kHz is chosen, the duration must be adjusted accordingly. Ultrasound at a frequency of 16 kHz or higher is preferably used as the sound source, so that the pulse and its response signal are inaudible or only faintly audible to humans.

[0047] The emission occurs over an angular range of at least 90°, preferably at least 120°, and particularly preferably at least 150°. Angular range here refers to the opening angle over which the impulse is emitted. With an angular range of 180°, the entire interior of the cabin can normally be covered by the impulse or sound signal 40. The angular range is defined in Fig. 1 represented by dashed lines. In Fig. 1 Transmitter 32 is located centrally on the ceiling of elevator car 10. Alternatively, if transmitter 32 were located in a corner of elevator car 10, a pulse 40 emitted over an angle of 90° would also cover the entire interior of elevator car 10.

[0048] The impulse 40 is reflected by surfaces of the elevator car 10 as well as by any objects or items 42 or persons 44 and animals inside the car 10. Objects can be movable items such as packages, but also fixed objects inside the car such as handrails and the like. The reflected sound signal of the in Fig. 1 The object 42 shown is represented by a wave packet 46. The reflected sound signal of the object 42 is represented by a wave packet 46. Fig. 1 Person 44 shown is represented by wave packet 48.

[0049] The reflected sound signals 46, 48 are detected by the receiver 34 as an acoustic response signal to the impulse 40 and forwarded to the evaluation unit 36 ​​for evaluation.

[0050] Fig. 1 Figure 32 shows both a transmitter 32 and a receiver 34. In an alternative embodiment, the functions of the transmitter and the receiver can be combined in one device that can be operated as both a transmitter and a receiver. In English, such a device is called a transducer, a term also commonly used in German.

[0051] The following describes in detail the procedure for detecting changes in a monitored area using an elevator car as the area to be monitored.

[0052] The inventive method serves to detect changes. The aim is not to detect what has changed, but rather whether a change has occurred.

[0053] According to one embodiment of the invention, the evaluation unit 36 ​​requires at least one in Fig. 3 The reference measurement shown (50) is recorded in the elevator car's state against which changes are to be detected. The reference measurement and the actual measurement are essentially analogous, but taken at different times.

[0054] To determine the reference measurement 50, as described in Fig. 3 shown, an acoustic impulse 52, which in Fig. 1 The signal, represented as pulse 40, is emitted as described above. The acoustic response signal of the emitted pulse is received by the receiver 34 and designated as reference signal 54. The frequency of the response signal essentially corresponds to that of the emitted pulse, but may also shift slightly. However, the duration and amplitude of the response signal differ from the emitted pulse. Subsequently, the envelope of reference signal 54 is determined, which is designated as reference envelope 56. From reference envelope 56, an amplitude spectrum 50' of the envelope is determined by means of a Fourier transform and stored as reference measurement 50.

[0055] For example, the reference measurement 50 can be stored in the memory of the evaluation unit 36. Alternative storage locations, such as saving in a [missing information], are possible.

[0056] A data communication network with interconnected data storage is also conceivable. The data storage can be local or decentralized.

[0057] Various methods are known in acoustics for determining the envelope 56. The envelope of a signal represents the course of the signal's amplitude.

[0058] In the present case, the envelope 56 of the reference signal 54 represents the amplitude profile of the reference signal 54.

[0059] In general, the envelope of a signal, for example an amplitude-mode modulated signal, can be determined as follows. Demodulation, or rather the determination of the envelope, is achieved by rectifying the signal using a diode. The rectified signal is charged into a capacitor, which can then be discharged through a resistor. This results in the envelope of the signal. This is described, for example, in the book "The Audio Encyclopedia: A Reference Work for Sound Engineers," ISBN 3598117744, page 13. Mathematically, this can be implemented as follows: First, the absolute values ​​are determined. Alternatively, only the positive values ​​of the signal can be used. Then, the values ​​are averaged over a certain period of time to determine the envelope.Averaging can be done, for example, by summation and calculation of the mean, in particular a moving average, or by means of a corresponding integral.

[0060] As an alternative to averaging, the individual maxima of the signal can also be combined to obtain the signal's envelope. These individual maxima can then be further combined using interpolation.

[0061] The Fourier transform is suggested above for determining the amplitude spectrum 50'. The computationally more suitable Fast Fourier transform can also be used instead. Other methods and / or transformations for frequency analysis, or more generally for function analysis, are also applicable, such as a wavelet transform.

[0062] In order to detect any change in and / or on the elevator car 10 at any time after the recording of the reference measurement 50, the inventive method is carried out as follows. The method steps are shown schematically in Fig. 6 depicted.

[0063] As in Fig. 4 As shown, in a process step S 1, an acoustic pulse 62 is emitted as described above. The pulse 62 propagates within the cabin 10, the interior of which forms the area 11 to be monitored, and is reflected by reflective surfaces. The acoustic response signal of this pulse 62 is in Fig. 1 represented by sound waves 46, 48.

[0064] This acoustic response signal is received or recorded by the sound sensor 34, also referred to as the receiver, in a process step S2, analogous to the procedure of the reference measurement 50. The received signal is referred to as the actual signal 64. Subsequently, in a process step S3, the envelope of the actual signal 64, the actual envelope 66, is determined from it as described above.

[0065] In this embodiment, as already described above, an amplitude spectrum 60' of the actual envelope 66, which represents the actual measurement 60, is determined from the actual envelope 66 in a process step S4 using a Fourier transform. Since the individual values ​​of the spectrum are generally complex numbers, the amplitude is understood to be the square root of the sum of the squares of the real and imaginary parts of the complex number. The alternatives to the Fourier transform described above can also be applied analogously to the envelope of the actual signal.

[0066] As a next step, in process step S5, a detection of changes based on the envelope 66 is carried out.

[0067] In this embodiment, the actual measurement 60 is compared with the reference measurement 50.

[0068] Comparison can be achieved, for example, by determining the difference between the reference measurement 50 and the actual measurement 60 as a function of frequency. The absolute values ​​of these differences can be summed over a frequency range to obtain a comparative value, also known as a measure, for the equality of the reference measurement 50 with the actual measurement 60. Instead of the absolute values, the squares of the differences can also be summed over the frequency range. Of course, integration can also be used instead of summation. Other comparison operations, by which the equality or similarity of two functions can be determined, can naturally also be applied. For example, zero crossings can be used for this purpose.

[0069] The obtained measure of equality can be compared in a subsequent step with a tolerance threshold to detect a change in the elevator car 10: the interior of the elevator car is recognized as unchanged if the measure is less than the tolerance threshold; otherwise, a change within the elevator car is detected. If the measure is less than the tolerance threshold, the actual measurement 60 is essentially the same as the reference measurement 50.

[0070] Further embodiments and configurations are described below, focusing only on differences from those already described.

[0071] Furthermore, it has been found that the measurement results appear to differ at various temperatures. It is also assumed that air turbulence within the elevator car 10 influences the measurements. In order to reliably detect changes in the elevator car 10 as well as in a monitored area 11, a further embodiment of the invention involves carrying out a large number of reference measurements, for example, over a longer period, such as a 24-hour period.

[0072] Reference measurements can also be carried out additionally or alternatively as follows. If changes compared to an empty elevator car are to be detected, several reference measurements of the empty elevator car are carried out over a certain period of time, for example after a person has left the elevator car, so that reference measurements are recorded under different turbulence conditions inside the elevator car.

[0073] It has also been shown that reference measurements should be recorded not only after a single person leaves the elevator, but also when several people exit the elevator car. Furthermore, reference measurements can be recorded after a person has left the elevator car with a pet, such as a dog.

[0074] In the case of a large number of reference measurements, the actual measurement is compared with each reference measurement, and the reference measurement with the smallest deviation from the actual measurement is used for further evaluation.

[0075] In a Fig. 5In the illustrated embodiment, the transmitter 32 and the receiver 34 are located on a floor outside the elevator car and the shaft. The evaluation unit 36 ​​can also be located on the same floor, or at any other location, for example, in the casing of a shaft door 80. The beam angle and direction of the pulse are selected such that only waves of the pulse 52, 62 are emitted into the area to be monitored in front of the shaft door 80 for the actual measurement 60 and the reference measurement 50, respectively. The area in front of the shaft door can be open, meaning it is not separated by special structural measures such as partitions or the like. Of course, the area to be monitored can be appropriately marked, for example, with floor markings, railings, or balustrades that partially delineate the area. However, this is not strictly necessary.

[0076] According to another embodiment, the transport system is designed as an escalator or moving walkway. In the case of an escalator or moving walkway, the access or exit area can be monitored for changes, or to determine whether it is empty or occupied by at least one person, object, or animal. For example, an operating mode of the escalator or moving walkway could be triggered based on this monitoring. It would be conceivable, for instance, that the escalator or moving walkway starts moving as soon as a change in the access area is detected. It would also be conceivable that an escalator or moving walkway only starts moving if the exit area is empty at that time.

[0077] According to a further embodiment, as well as another configuration, the area to be monitored can also be limited by the transit time of the emitted pulses and their reflected response signals. For example, only measured values ​​greater than a minimum duration and less than a maximum duration can be used from the actual signal. The area to be monitored can be restricted by the transit time.

[0078] According to another embodiment, a reference measurement at a specific time or in a predetermined state of the conveying system can be omitted. In this case, the conveying system is continuously monitored for changes. Instead of the reference measurement(s) used in the other embodiments, one or more actual measurements are used as reference measurements and continuously monitored for any changes that occur.

[0079] According to a further embodiment, as well as another embodiment, the detection of changes based on the envelope is carried out by a neural network. For this purpose, the neural network is trained, for example, with envelopes that were determined in the state of the area to be monitored, against which changes are to be detected. In this embodiment, the process step S4 described above, in which the spectrum of the envelope is determined, can be omitted. However, it is equally possible to first determine the spectrum of the envelope and train the neural network with spectra of the space to be monitored, and then base the detection of changes on this.

[0080] According to another embodiment, as well as a further embodiment, changes are detected by analyzing the envelope in order to determine a property parameter for the monitored space and compare it with an associated reference parameter. For example, zero crossings can be counted in an envelope that has been high-pass filtered during the analysis, particularly in the time domain. The number of zero crossings allows conclusions to be drawn about the (current) state of the monitored space. The more features or property parameters that are determined from the envelope, the more accurately the space monitoring can be performed.

Claims

1. Method for detecting changes in an area (11) to be monitored of a conveying system (20) having a sound sensor (30) and an evaluation unit (36) connected to the sound sensor (34), by - - emitting (S 1) an acoustic pulse (62) into the area to be monitored, - - recording (S2) an acoustic response signal of the pulse as an actual signal (64), - - determining (S3) an envelope (66) of the actual signal (64), - - detecting (S5) changes on the basis of the envelope (66), wherein detecting changes on the basis of the envelope (66) is characterized by - - determining (S4) a spectrum of the envelope (66) of the actual signal (64) as an actual measurement (60).

2. Method according to claim 1, wherein detecting changes on the basis of the envelope (66) is further characterized by - - comparing a reference measurement (50) with the actual measurement (60).

3. Method according to either claim 1 or claim 2, wherein the spectrum is a frequency spectrum, preferably an amplitude-frequency spectrum.

4. Method according to either claim 2 or claim 3, wherein a difference between the reference measurement (50) and the actual measurement (60) is determined during the comparison.

5. Method according to claim 4, wherein a comparison value is determined by summing the differences or by summing values determined from the differences.

6. Method according to claim 5, wherein the actual measurement (60) is detected as being different from the reference measurement (50) if the comparison value exceeds a tolerance threshold.

7. Method according to any of the preceding claims, wherein the acoustic pulse is emitted over an angular range of at least 90 degrees.

8. Method according to any of the preceding claims, wherein the evaluation unit (36) has a processor, at least one memory connected to the processor via a bus, and at least one interface for communication connected via the bus.

9. Method according to any of the preceding claims, wherein the determinations and the detection of changes are carried out by the evaluation unit (36).

10. Method for detecting an empty area (11) to be monitored of a conveying system (20) by means of a method according to any of claims 1 to 9, wherein the reference measurement (50) is determined when the area (11) to be monitored is empty.

11. Method according to claim 10, wherein the area (11) to be monitored is detected as being empty if the actual measurement (60) is detected as being substantially equal to the reference measurement (50).

12. System having a sound sensor (32) and an evaluation unit (36) connected to the sound sensor for detecting changes in an area (11) to be monitored of a conveying system (20) for carrying out any of the methods according to claims 1 to 11.

13. Conveying system having a system according to claim 12.