METHOD FOR DETECTING CHANGES IN AN AREA TO BE MONITORED

Abstract

A method for detecting changes in an area to be monitored of a conveying system utilizes a sound sensor and an evaluation unit connected to the sound sensor. The method includes emitting an acoustic pulse into the area to be monitored, recording an acoustic response signal of the pulse as an actual signal, determining an envelope of the actual signal, and detecting changes on the basis of the envelope.

Claims

1-13. (canceled)

14. A method for detecting changes in an area to be monitored of a conveying system, the conveying system having a sound sensor and an evaluation unit connected to the sound sensor, the method comprising the steps of: emitting an acoustic pulse into the area to be monitored; recording an acoustic response signal as an actual signal, the acoustic response signal being detected by the sound sensor as a reflection of the acoustic pulse in the area; determining an envelope of the actual signal; detecting changes in the area based upon the envelope; and wherein the detecting changes is performed by determining a spectrum of the envelope of the actual signal as an actual measurement.

15. The method according to claim 14 wherein the spectrum is a frequency spectrum.

16. The method according to claim 14 wherein the spectrum is an amplitude-frequency spectrum.

17. The method according to claim 14 wherein the detecting changes is further performed by comparing a reference measurement with the actual measurement.

18. The method according to claim 17 wherein all differences between the reference measurement and the actual measurement are determined during the comparison.

19. The method according to claim 18 wherein a comparison value is determined by summing the differences or by summing values determined from the differences.

20. The method according to claim 19 wherein the actual measurement is detected as being different from the reference measurement when the comparison value exceeds a tolerance threshold.

21. The method according to claim 14 wherein the acoustic pulse is emitted over an angular range of at least 90 degrees.

22. The method according to claim 14 wherein the evaluation unit includes a processor, at least one memory connected to the processor via a bus, and at least one interface for communication connected via the bus.

23. The method according to claim 14 wherein the determining steps and the detecting changes step are performed by the evaluation unit.

24. A method for detecting an empty area to be monitored of a conveying system, the method comprising the steps of: performing the method according to claim 14; performing the detecting changes step by comparing a reference measurement with the actual measurement; and determining the reference measurement when the area to be monitored is empty.

25. The method according to claim 24 wherein the area to be monitored is detected as being empty when the actual measurement is detected as being substantially equal to the reference measurement.

26. A system for monitoring an area to be monitored of a conveyor system, the system comprising: a sound sensor; an evaluation unit connected to the sound sensor for detecting changes in the area to be monitored; and wherein the system is adapted to perform the method according to claim 14.

27. A conveying system having an area to be monitored and the system according to claim 26 monitoring the area to be monitored.

Description

DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1 shows purely schematically an elevator car.

[0051] FIG. 2 shows purely schematically an elevator system.

[0052] FIG. 3 shows purely schematically for a reference measurement an acoustic pulse, a response signal of the pulse and its envelope as well as an associated spectrum.

[0053] FIG. 4 shows purely schematically for an actual measurement the acoustic pulse, a response signal of the pulse and its envelope as well as an associated spectrum.

[0054] FIG. 5 shows purely schematically a section of an elevator system in which an area to be monitored is located in front of a shaft door of the elevator system.

[0055] FIG. 6 shows purely schematically a method for detecting changes in an area to be monitored.

[0056] The drawings are merely schematic, and not to scale. In the different figures, identical reference signs denote identical or similar features.

DETAILED DESCRIPTION

[0057] FIG. 1 shows an elevator car 10 for an elevator system 20 shown in FIG. 2, which elevator system, as described above, is a conveying system within the meaning of this patent application. As shown in FIG. 2, the elevator system 20 has the elevator car 10 which can be moved between different floors by means of a drive system. A traction sheave elevator is shown as the drive system, but any desired drive system for an elevator system can be used. Wire ropes are shown as support means 22, but support belts or the like can also be used. Alternative drive systems such as a hydraulic elevator, a rack and pinion hoist, a vacuum elevator or a cable-free elevator implemented by means of a linear motor, for example, can also be used.

[0058] As shown in FIG. 1, the elevator car 10 is equipped with a detection module 30. The detection module has a transmitter 32, a receiver 34 and an evaluation unit 36 connected to the transmitter 32 and the receiver 34. In this exemplary embodiment, an area 11 to be monitored is formed by the elevator car 10. The area is delimited by side walls, a floor surface, a ceiling surface and a car door of the elevator car 10.

[0059] 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.

[0060] The detection module 30 serves to detect changes within the elevator car 10. A change can be an added object 42, such as a forgotten package. Furthermore, a change within the elevator car can also be a new person 44 in the elevator car 10. An object removed from the elevator car 10, such as a handrail, can also be a change. The aim of the invention is to detect any changes in the interior of the elevator car 10 or in the area 11 to be monitored.

[0061] For this purpose, the transmitter 32 emits an acoustic pulse 40, in particular a sound pulse of approximately 48 kHz and a duration of approximately 0.3 ms. The duration of 0.3 ms corresponds to some oscillations at 48 kHz, wherein it is to be observed that the transmitter 32 also has a rise time and a decay time. The frequency was selected such that it is neither audible for humans nor pets, such as dogs. If a frequency other than 48 kHz is selected, the duration must be adapted accordingly. Ultrasound is preferably used as the sound at a frequency of 16 kHz or more, so that the pulse and its response signal are not audible or only weakly audible, at least for humans.

[0062] The transmission takes place over an angular range of at least 90, preferably of at least 120 and particularly preferably of at least 150. The angular range is understood here to mean the opening angle over which the pulse is emitted. In the case of an angular range of 180, the entire interior of the car can normally be detected by the pulse or sound signal 40. The angular range is shown in FIG. 1 by dashed lines. In FIG. 1, the transmitter 32 is arranged centrally on the ceiling of the elevator car 10. Alternatively, if the transmitter 32 were arranged in a corner of the elevator car 10, a pulse 40 that is emitted over an angular range of 90 would also cover the entire interior of the elevator car 10.

[0063] The pulse 40 is reflected by surfaces of the elevator car 10 as well as by any objects 42 or persons 44 and animals within the car 10. Objects can be movable objects such as packages, but also objects that are fixed in the interior of the car, such as handrails and the like. The reflected sound signal of the object 42 shown in FIG. 1 is represented by a wave packet 46. The reflected sound signal of the person 44 shown in FIG. 1 is represented by the wave packet 48.

[0064] The reflected sound signals 46, 48 are detected by the receiver 34 as an acoustic response signal of the pulse 40 and forwarded to the evaluation unit 36 for evaluation.

[0065] FIG. 1 shows both a transmitter 32 and a receiver 34. In an alternative embodiment, the function of the transmitter and the receiver can be combined in one device which can be operated both as a transmitter and as a receiver. Such a device is referred to as a transducer.

[0066] The method for detecting changes in an area to be monitored is described in detail below on the basis of an elevator car as the area to be monitored.

[0067] The method according to the invention serves to detect changes. The aim is not to detect what has changed, but rather whether a change has taken place.

[0068] According to an exemplary embodiment of the invention, the evaluation unit 36 requires at least one reference measurement 50 shown in FIG. 3, which is recorded in that state of the elevator car in relation to which changes are to be detected. In principle, the reference measurement and the actual measurement are carried out analogously to one another, but at different points in time.

[0069] To determine the reference measurement 50, as shown in FIG. 3, an acoustic pulse 52, shown as pulse 40 in FIG. 1, is emitted as described above. The acoustic response signal of the emitted pulse is received by the receiver 34 and referred to as the reference signal 54. The frequency of the response signal substantially corresponds to that of the emitted pulse, but can also be slightly different. However, the duration and the amplitude of the response signal differ from the emitted pulse. The envelope which is referred to as the reference envelope 56 is then determined from the reference signal 54. An amplitude spectrum 50 of the envelope is determined from the reference envelope 56 using a Fourier transform and stored as a reference measurement 50.

[0070] For example, the reference measurement 50 can be stored in the memory of the evaluation unit 36. Alternative storage locations such as storage in a data memory connected via a data communication network are also conceivable. The data memory can be local or else decentralized.

[0071] Various methods are known in acoustics for determining the envelope 56. The envelope of a signal reflects the course of the amplitude of the signal.

[0072] In the present case, the envelope 56 of the reference signal 54 reflects the amplitude profile of the reference signal 54.

[0073] In general, the envelope of a signal, for example an amplitude mode modulated signal, can be determined, for example, as follows. The demodulation or the determination of the envelope is carried out by rectifying the signal with the aid of a diode. The rectified signal is charged into a capacitor, which in turn can be discharged through a resistor. This results in the envelope of the signal. This is described, for example, in the book Die Audio-Enzyklopdie: ein Nachschlagewerk fr Tontechniker (The Audio Encyclopedia: A Reference Guide for Sound Engineers), ISBN 3598117744, page 13. This can be implemented mathematically, for example, as follows. First, the absolute values are determined. Alternatively, only the positive values of the signal can be taken. The values are then averaged over a certain period of time in order to determine the envelope. The averaging can take place, for example, via summation and calculation of the mean value, in particular a sliding mean value, or by means of a corresponding integral.

[0074] As an alternative to averaging, the individual maxima of the signal can also be connected in order to obtain the envelope of the signal. The individual maxima can also be connected to one another by means of interpolation.

[0075] A Fourier transform is proposed above for determining the amplitude spectrum 50. Instead of a Fourier transform, a fast Fourier transform, which is more suitable in terms of computation, can also be used. Other methods and/or transforms for frequency analysis or more generally for function analysis can also be used, such as a wavelet transform.

[0076] In order to be able to detect a change from the point in time of the reference measurement 50 in and/or on the elevator car 10 at any point in time after the recording of the reference measurement 50, the method according to the invention is carried out as follows. The method steps are shown purely schematically in FIG. 6.

[0077] As shown in FIG. 4, in a method step S1, an acoustic pulse 62 is emitted as described above. The pulse 62 propagates in the car 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 shown in FIG. 1 by sound waves 46, 48.

[0078] This acoustic response signal is again received or recorded analogously to the method of reference measurement 50, in a method step S2 by the sound sensor 34, which is also referred to as the receiver. The received signal is referred to as the actual signal 64. Then, in a method step S3, the envelope of the actual signal 64, the actual envelope 66, is determined as described above.

[0079] In this exemplary embodiment, an amplitude spectrum 60 of the envelope 66, which forms the actual measurement 60, is determined from the actual envelope 66 in a method step S4, again using a Fourier transform, as also already described above. Since the individual values of the spectrum are generally complex numbers, the amplitude is 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.

[0080] As the next step, changes are detected on the basis of the envelope 66 in a method step S5.

[0081] For this purpose, the actual measurement 60 is compared with the reference measurement 50 in this exemplary embodiment.

[0082] The comparison can be determined, for example, by determining the difference between the reference measurement 50 and the actual measurement 60 as a function of the frequency. The absolute values of the differences can be summed over a frequency range in order to obtain a comparison value, also referred to as a measure, for the equality of the reference measurement 50 to the actual measurement 60. Instead of the absolute values, the squares of the differences can also be summed over the frequency range. Instead of a summation, an integration can also be carried out, of course. Other comparison operations by means of which the equality or similarity of two functions can be determined can of course also be used. For example, zero crossings can be used for this purpose.

[0083] The measure of equality obtained can be compared with a tolerance threshold in a subsequent step in order to detect a change in the elevator car 10: the interior of the elevator car is detected as being unchanged if the measure is smaller 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 substantially equal to the reference measurement 50.

[0084] Further exemplary embodiments and embodiments are described below, wherein only differences from the exemplary embodiments already described will be discussed.

[0085] It has also been found that the measurement results appear to be different at different temperatures. It is further assumed that turbulences in the air within the elevator car 10 influence the measurements. In order nevertheless to reliably detect changes in the elevator car 10 and in an area 11 to be monitored, a plurality of reference measurements is carried out, for example over a longer period of time, for example over a time range of 24 hours, in a further exemplary embodiment and also a further embodiment of the invention.

[0086] Furthermore, reference measurements can additionally or alternatively be carried out as follows. If changes to an empty elevator car are to be detected, a plurality of reference measurements of the empty elevator car is carried out over a certain period of time after, for example, a person has left the elevator car so that reference measurements are recorded in the case of different turbulences within the elevator car.

[0087] It has also been shown that reference measurements should not only be recorded after just one person has left the elevator car, but also when multiple persons have left the elevator car. Furthermore, reference measurements can be recorded after a person has left the elevator car with a pet, such as a dog.

[0088] In the case of the plurality of reference measurements, the actual measurement is compared with each reference measurement and that reference measurement which has the smallest deviation from the actual measurement is used for further evaluation.

[0089] In an exemplary embodiment shown in FIG. 5, the transmitter 32 and the receiver 34 are arranged on a floor, outside the elevator car 10 and the shaft. The evaluation unit 36 can also be arranged on the floor or also at any other location, for example in a cladding of a shaft door 80. The emission angle as well as the emission direction of the pulse is selected such that only waves of the pulse 52, 62 for the actual measurement 60 or for the reference measurement 50 are emitted into the area 11 to be monitored in front of the shaft door 80. The area 11 in front of the shaft door can be open, i.e., not delimited by special structural measures, partition walls or the like. Of course, the area to be monitored can be marked appropriately, for example by floor markings, railings or balustrades that partially delimit the area. However, this is not absolutely necessary.

[0090] According to a further exemplary embodiment and a further embodiment, the conveying system is designed as an escalator or moving walkway. In the case of an escalator or moving walkway, for example, the access area or the output area can be monitored for changes or 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 on the basis of the monitoring. It would be conceivable, for example, for the escalator or moving walkway to be started as soon as a change in the access area is detected. It would also be conceivable for an escalator or moving walkway to be started only if the output area is empty at this time.

[0091] According to a further exemplary embodiment as well as a further embodiment, the area to be monitored can also be limited by the propagation 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 by the actual signal. The area to be monitored can be restricted by the propagation duration.

[0092] According to a further exemplary embodiment as well as a further embodiment, a reference measurement at a specific point in time or in a predetermined state of the conveying system can be dispensed with. In this case, the conveying system is continuously monitored for changes. Instead of the reference measurement or the reference measurements used in the other exemplary embodiments, one or more actual measurements are used as reference measurements and continuously monitored for changes that occur.

[0093] According to a further exemplary embodiment as well as a further embodiment, the detection of changes on the basis of the envelope is detected by a neural network. For this purpose, for example, the neural network is trained with envelopes that were determined in that state of the area to be monitored in relation to which changes are to be detected. The method step S4 described above, in which the spectrum of the envelope is determined, can be dispensed with in this exemplary embodiment. However, it is also possible to first determine the spectrum of the envelope and to train the neural network with spectra of the space to be monitored, as well as to base the detection of changes thereon.

[0094] According to a further exemplary embodiment as well as a further embodiment, in order to detect changes on the basis of the envelope, the envelope is analyzed in order to determine a property parameter for the space to be monitored and to compare it with an associated reference parameter. For example, zero crossings can be counted in the case of an envelope that has previously been high-pass filtered as part of the analysis, in particular in the time domain. The (current) state of the monitored space can be concluded on the basis of the number. The more features or property parameters are determined from the envelope, the more precisely the space monitoring can be carried out.

[0095] In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.