DE102020128501A1 - Method and device for contactless monitoring of a space to be monitored - Google Patents

Abstract

The invention relates to a method and a device for contactless monitoring of a room to be monitored, sound signals being emitted by a signal source and detected by a sensor device. The method includes the emission of sound measurement signals by means of the signal source in a room area to be monitored and the detection of sound response signals from the room to be monitored by means of the sensor device in response to the emission of the sound measurement signals. The following is also provided in an evaluation device, which is connected at least to the sensor device: determining an envelope for the recorded sound response signals; determining a property parameter for the space to be monitored from an envelope analysis; providing reference data indicative of a reference parameter for the space to be monitored; and determining a change in the space to be monitored when the property parameter differs from the reference parameter.

Description

The relates to a method and a device for contactless monitoring of a space to be monitored.

background

In connection with various applications, there is a need to monitor a room or a room area to determine whether there has been a change in the room compared to a (previous) comparison or reference situation, for example to check whether a person has entered the room or left it. In this way, for example, it can be detected for the monitored room whether it is empty or whether there are objects or people in the room.

Such monitoring can be provided, for example, in transportation systems such as elevators, escalators or moving walks. Such transport systems are used both for the transport of people and for the transport of goods. Elevators are used, among other things, to transport passengers between different floors within a building. There are a wide variety of reasons for recognizing changes in the elevator car of the elevator.

Various systems are known from the prior art for monitoring spatial areas. For example, sensors are known which can detect the presence of people in a room. These are based, for example, on ultrasound and use the Doppler effect to identify people. However, this requires minimal movement of the people, for example the hands or the head. These sensors, which are based on the Doppler effect, cannot detect people or objects that are absolutely still. Other sensors are based on infrared. These can recognize people, but are only poorly or not at all suitable for recognizing objects.

Also known are systems for detecting changes in a spatial area, for example an elevator car, which are based on the evaluation of optical images, for example photos or video images. However, these systems are ill-suited to elevator cars with one or more transparent side walls or a transparent floor, since the environment outside the elevator car changes. Likewise, nowadays screens can be found in elevator cabins, which show moving content and can lead to incorrect information in the case of a visual evaluation.

In a method for detecting changes in a room, ultrasonic pulses are emitted (Hammoud et al., Procedia Computer Science 109C(2017)75-83). Response signals of the ultrasonic pulses are then recorded. A Fourier transform is performed on the response signal to examine the frequency spectrum of the response signal for Doppler shifts.

summary

The object of the invention is to specify a method and a device for contactless monitoring of a space to be monitored, with which a change in the monitored space can be determined in a robust and reliable manner.

A method and a device for contactless monitoring of a room to be monitored according to independent claims 1 and 10 are created for the solution. Configurations are the subject of dependent subclaims.

According to one aspect, a method for contactless monitoring of a room to be monitored is created, which has the following: providing a signal source that is set up to emit sound signals; Providing a sensor device that is set up to detect sound signals; Transmission of sound measurement signals by means of the signal source in a spatial area to be monitored; and detecting sound response signals from the room to be monitored by means of the sensor device upon the transmission of the sound measurement signals. The following is also provided in an evaluation device, which is connected at least to the sensor device: determining an envelope for the recorded sound response signals; determining a property parameter for the space to be monitored from an envelope analysis; providing reference data indicative of a reference parameter for the space to be monitored; and determining a change in the space to be monitored when the property parameter differs from the reference parameter.

According to a further aspect, a device for contactless monitoring of a space to be monitored is created, which has the following: a signal source which is set up to emit sound signals; a sensor device that is set up to detect sound signals; and an evaluation device which is connected at least to the sensor device. The evaluation device is set up to evaluate sound response signals detected by the sensor device in response to the emission of sound measurement signals by the signal source into a room to be monitored and to carry out the following: determining an envelope for the detected sound response signals; determining a property parameter for the space to be monitored from an envelope analysis; providing reference data indicative of a reference parameter for the space to be monitored; and determining a change in the space to be monitored when the property parameter differs from the reference parameter.

With the proposed technology, a robust system and a robust method for the contactless detection of changes of any kind in a spatial area to be monitored are created. A change in the monitored room can also be reliably detected if one or more stationary objects and/or people are present in the room or not.

It can also be detected, for example, when the monitored room has emptied (again), for example because one or more people have left the room (again).

Provision can be made for an unchanged state of the monitored space to be determined if the property parameter does not differ from the reference parameter, or if a deviation in the parameters is only determined within predetermined tolerance limits. In this or other exemplary embodiments, the reference or comparison data can indicate a reference state of the monitored space at an (earlier) reference point in time.

A room to be monitored within the meaning of the present application is any spatial area, be it for example inside or outside of buildings, which can be spatially detected or monitored contactlessly by means of the arrangement with the at least one signal source and the at least one sensor device Except for the space in an elevator car. The wording “room to be monitored” within the meaning of the present application also does not include vestibules or waiting rooms of the elevator system assigned to an elevator system, in particular waiting areas in front of an elevator car door.

The acoustic response signals can be detected as time-resolved acoustic response signals in the time domain and a time-resolved envelope can be determined. The envelope is then an enveloping curve over the sound response signals recorded during the measurement (along the time axis).

Determining the property parameter for the space to be monitored may further comprise: determining a transformed envelope, the transformed envelope being determined using at least one of the following transformations on the envelope: transforming the envelope into the frequency domain and wavelet transforming; and determining the property parameter for the space to be monitored from the transformed envelope. The change can be determined in an improved manner by means of the transformed envelope curve. The transformation is part of the envelope analysis. The property parameter is determined from an analysis of the transformed envelope.

Alternatively or additionally, the envelope curve analysis can include an analysis of the (non-transformed) envelope curve in order to determine a property parameter for the space to be monitored and to compare it with an assigned reference parameter. In the case of an envelope curve that has previously been high-pass filtered as part of the envelope curve analysis, in particular in the time domain, zero crossings, for example, can be counted in order to determine the property parameter. Based on the number, the (current) status of the monitored room can be inferred. The more features or property parameters are determined from the envelope and/or the transformed envelope, the more accurately the space monitoring can be performed.

In the case of transforming the envelope into the frequency domain, the property parameter for the space to be monitored can be determined from the transformed envelope into the frequency domain. For example, the Fourier transform or the fast Fourier transform can be used to transfer the envelope into the frequency domain and thus determine a frequency spectrum (transformed envelope) for it. In the frequency domain (further) analysis of the transformed envelope can be performed, for example filtering.

The property parameter can be determined in the envelope curve analysis in the frequency domain from a frequency-dependent amplitude distribution (amplitude spectrum) of the transformed envelope curve.

Furthermore, the following can be provided: determining at least one further property parameter for the space to be monitored from the envelope analysis and determining the change in the space to be monitored, if the property parameter differs from the reference parameter and/or the at least one further property parameter differs from a further reference parameter which is indicated by the reference data. In connection with the at least one further property parameter, the explanations given in connection with the property parameter regarding configurations apply accordingly. This applies to the further reference parameter and the reference parameter in a comparable manner.

When determining the change taking into account the property parameter and the reference parameter, at least one of the following parameter operations can be performed: summation and difference formation. For example, amplitude values (frequency dependent) can be added or subtracted.

The change in the space to be monitored can be determined if the property parameter and the reference parameter differ by at least a threshold value. It is determined that there is no change if the difference between the property parameter and the reference parameter does not exceed the threshold value.

At least one of the following room changes can be determined as a change in the room to be monitored: empty room, presence of a person, absence of a person, change of location of a person, change of position of an object in the room and dangerous situation.

The envelope curve is an enveloping curve over the sound response signals recorded during the measurement. When determining the envelope, the following method can be provided, for example: determination of absolute values for the recorded sound response signals, and subsequent calculation of a moving average. Alternatively, the individual maxima of the recorded sound response signals can be connected, with or without absolute value formation beforehand. Here, the maxima can be connected by means of interpolation.

Further configurations are described below.

In an alternative exemplary embodiment, a method for contactless detection of a change in a spatial area to be monitored can be provided, in which a sound sensor and an evaluation unit connected to the sound sensor are used. The method comprises the following: emitting an acoustic pulse (sound measurement signal); recording an acoustic response signal of the impulse (acoustic response signals) as an actual signal; Determining an envelope of the actual signal and detecting changes based on the envelope.

In one embodiment, the detection of changes based on the envelope provides for the determination of a (frequency) spectrum of the envelope of the actual signal. This spectrum is determined by transforming the envelope (actual measurement) into the frequency domain. A reference measurement (reference data) is compared with the actual measurement to detect a change.

An amplitude spectrum can be evaluated in the frequency domain, for example an amplitude-frequency spectrum. This allows amplitude spectra to be compared with one another. Amplitude spectra in the frequency domain are independent of a time shift in the actual signal or partial time shifts in partial signals of the actual signal. During test measurements it was found that in this way adverse effects of air turbulence and/or temperature fluctuations in the area to be monitored on the evaluation of monitoring measurements can be avoided.

When determining the change, a difference between the reference measurement and the actual measurement can be determined. A comparison value for determining the change can be calculated by summing the differences or summing values determined from the differences. The actual measurement can be recognized as different from the reference measurement if the comparison value exceeds a tolerance threshold (threshold value).

Provision can be made for acoustic impulses (sound measurement signals) to be emitted over an angular range of at least approximately 90 degrees (aperture angle) into the space to be monitored. This allows the area to be monitored to be determined geometrically by means of the angular range of the emitted pulse. For example, an access area can be open towards or away from buildings, i.e. not separated from the rest of the room by structural measures. Provision can be made for monitoring the access area, for example in order to obtain information as to whether a person, an object or even a robot is in front of a door of the access area. This advantageous embodiment also makes it possible to recognize objects that are deposited in the access area or in the area to be monitored and endanger the safety of the people.

The evaluation unit has a processor and a memory device connected thereto in order to evaluate the sound response signals or sound response data derived therefrom. An interface for data communication is also provided.

It can be provided that a model for the room to be monitored or the room surveillance that has been trained within the framework of the use of artificial intelligence can be used in the envelope curve analysis to detect the change(s) in the evaluation device, for example in connection with a neural network. For this purpose, for example, the neural network is trained using envelope curves and/or transformed envelope curves, which were determined for different states of the space to be monitored.

character list

• 1 eine schematische Darstellung einer Aufzugskabine;
• 2 eine schematisch Darstellung einer Aufzugsanlage;
• 3 zeigten für eine Ist-Messung einen akustischen Impuls, ein Antwortsignal des Impulses und dessen Hüllkurve sowie ein zugehöriges Spektrum;
• 4 zeigten für eine Referenz-Messung den akustischen Impuls, ein Antwortsignal des Impulses und dessen Hüllkurve sowie ein zugehöriges Spektrum;
• 5 schematisch einen Ausschnitt einer Aufzugsanlage, bei welcher ein zu überwachender Bereich vor einer Schachttüre der Aufzugsanlage liegt; und
• 6 schematisch eine Blockdarstellung für ein Verfahren zum Erkennen einer Veränderung in einem zu überwachenden Bereich.

According to the following further exemplary embodiments are explained in more detail with reference to figures of a drawing. Here show:

• 1 a schematic representation of an elevator car;
• 2 a schematic representation of an elevator system;
• 3 showed an acoustic impulse, a response signal of the impulse and its envelope as well as an associated spectrum for an actual measurement;
• 4 showed the acoustic impulse, a response signal of the impulse and its envelope as well as an associated spectrum for a reference measurement;
• 5 schematically a section of an elevator installation, in which an area to be monitored is located in front of a shaft door of the elevator installation; and
• 6 schematically shows a block diagram for a method for detecting a change in an area to be monitored.

A method and a device for contactless monitoring of a space to be monitored are explained below by way of example, in particular with reference to an elevator installation and spaces to be monitored that are related thereto. The aspects of the technology can be transferred in the same way to any spatial areas for which contactless surveillance is to be carried out, for example to detect the presence or absence of objects and/or people in the monitored space.

1 shows an elevator car 10 for an in 2 Elevator system 20 shown. This is a transport system.

According to 2 the elevator system 20 includes 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 drive system for an elevator installation can be used. Wire ropes are shown as the suspension means 22, but suspension belts or the like can also be used. Alternative drive systems such as a hydraulic elevator, a rack and pinion elevator, a vacuum elevator or a cable-free elevator realized by means of a linear motor, for example, can also be used.

To 1 1, the elevator car 10 is equipped with a detection module 30. This has a transmitter 32 (signal source), a receiver 34 (sensor device) and an evaluation unit 36 connected to the transmitter 32 and the receiver 34 . In this exemplary embodiment, an area to be monitored is formed by the interior of the elevator car 10 . The area is delimited by side walls, a floor area, a ceiling area and a car door of the elevator car 10.

The detection module 30 is used to detect changes within the elevator car 10 . A change here can be an added item 42, such as a forgotten package. Furthermore, a change within the elevator car 10 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 bring about a change.

In order to detect a change in the elevator car 10 (room to be monitored), the transmitter 32 emits an acoustic pulse 40 (sound measurement signal), in particular a sound pulse of approximately 48 kHz and a pulse duration of approximately 0.3 ms. The duration of 0.3 ms corresponds to a few oscillations at 48 kHz, whereby it should be noted that the transmitter also has an attack time and a decay time. The frequency can be chosen in such a way that neither humans nor pets such as dogs can hear it. If a frequency other than 48 kHz is selected, the duration must be adjusted accordingly. The sound used is preferably ultrasound at a frequency of 16 kHz or more, so that the impulse and the response signal are not audible or only weakly audible, at least for humans.

The transmission takes place over an angular range of at least approximately 90°, preferably at least 120° and particularly preferably at least 150°. With an angular range of 180 °, the entire interior of the Cabin are detected by the sound signal 40. The angular range is in 1 represented by dashed lines. In 1 the transmitter 32 is arranged centrally on the ceiling of the elevator car 10 . If, alternatively, the transmitter 32 were arranged in a corner of the elevator car, a pulse which is emitted over an angular range of 90° would also cover the entire interior of the elevator car.

The pulse 40 reflects off surfaces of the cabin as well as any objects 42 or people 44 inside the cabin 10, as well as animals. Objects 42 can be movable objects such as packages, but also objects fixed in the interior of the cabin, such as handrails and the like. The reflected sound signal of the in 1 The object 42 shown is represented by a wave packet 46 . The reflected sound signal in the 1 shown person 44 is represented by the wave packet 48. The reflected sound signals 46, 48 are detected by the receiver 34 as an acoustic response signal of the impulse 40 and forwarded to the evaluation unit 36 for evaluation.

1 shows both the transmitter 32 (signal source or transmitter) and the receiver 34 (sensing device). In an alternative embodiment, the function of the transmitter and the receiver can be combined in one device that can be operated both as a transmitter and as a receiver. In English, such a device is called a transceiver, which is also common in German.

The method for detecting or determining a change in a spatial area to be monitored is described below by way of example using the monitoring of the interior of the elevator car 10 as the area to be monitored. The technology can be used in a comparable manner in other spatial areas, for example a room or an office in a building, a storage room, a room in a means of transport or a spatial area outside of a building, without this exemplary enumeration being in any way exhaustive.

In the method, it is monitored or determined whether something has changed in the monitored room with regard to objects and/or people located therein (compared to a comparative or reference state). For this purpose, at least one in 3 reference measurement 50 shown as an example (reference data) is provided, which is recorded for the comparison or reference state of the space to be monitored, compared to which changes are to be detected.

To determine the reference measurement 50, as in 3 shown, an acoustic pulse 52 (sound measurement signal) emitted as described above. The acoustic response signal of the emitted pulse is received by the receiver 34 and is referred to as the reference signal 54 . The frequency of the response signal can essentially correspond to that of the transmitted pulse. However, the length of time and/or the amplitude of the response signal differ from the transmitted pulse. Thereafter, the envelope of the reference signal 54 is determined, which is referred to as the reference envelope 56 . In the exemplary embodiment shown, an amplitude spectrum 50 ′ of the envelope (transformed reference envelope) is determined from the reference envelope 56 by means of Fourier transformation and stored as a reference measurement 50 .

Various methods are known as such in acoustics for determining the envelope curve 56 . The envelope of an amplitude mode modulated signal can be determined, for example, as follows. The envelope is determined by rectifying the signal using 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 "The Audio Encyclopedia: A Reference Guide for Audio 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 averaging or by means of an integral.

The Fourier transform can be used to determine the amplitude spectrum 50' in the frequency domain. Instead, the computationally less complex Fast Fourier Transform (fast Fourier Transform) can also be used. Other methods of transforming the envelope (transformed envelope) in order to subsequently analyze it can be used, for example a wavelet transform. Alternatively, a transformed envelope can be generated using a mathematical unfolding operation applied to the envelope.

In order to be able to detect a change compared to the 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 is carried out as follows in one exemplary embodiment.

6 shows a schematic block diagram for a method for detecting a change in an area to be monitored. In a step S1 an acoustic pulse 62 is emitted as described above. The acoustic pulse 62 propagates in the elevator car 10 and is reflected from reflective surfaces. The acoustic response signal (sound response signal) of the acoustic pulse 62 is in 1 represented by sound waves 46,48.

Analogously to the method of the reference measurement 50, this acoustic response signal is in turn received by the receiver 34 (step S2). The signal received is referred to as the actual signal 64 . Then, in step S3, the envelope of the actual signal 64 (as described above), the actual envelope 66, is determined. In step S4, an amplitude spectrum of the envelope (transformed envelope) which forms the actual measurement 60 is determined from the actual envelope 66 by means of Fourier transformation.

In step S4, an amplitude spectrum 60' of the envelope curve 66, which forms the actual measurement 60, is again determined from the actual envelope curve 66 by means of Fourier transformation. Since the individual values of the spectrum are generally complex numbers, the amplitude can be understood as the square root of the sum of the squares of the real and imaginary parts of the complex number.

In the next step S5, the actual measurement 60 is compared with the reference measurement 50 in order to determine possible changes for the envelope curve 66. For this purpose, the actual measurement 60 is compared with the reference measurement 50 in this exemplary embodiment.

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 frequency. The absolute amounts of the differences can be summed up over a frequency range in order to obtain a comparison value, which is also referred to as a measure, for the equality of the reference measurement 50 with the actual measurement 60 . Instead of the absolute amounts, the squares of the differences over the frequency range can also be summed up. Instead of a summation, an integration can of course also take place. Other mathematical comparison operations, by means of which the equality or similarity of two functions can be determined, can of course also be used.

The measure of equality obtained can be compared with a tolerance threshold in a following step in order to detect a change in the elevator car: the interior of the elevator car 10 is recognized as unchanged if the measure is smaller than the tolerance threshold, otherwise a change within of the elevator car 10 recognized.

In order to take into account changes occurring in the elevator car 10 during a monitoring period, a large number of reference measurements are carried out in one exemplary embodiment, for example over a longer period of time, for example over a time range of 24 hours.

Furthermore, reference measurements can additionally or alternatively be carried out as follows. If changes from an empty elevator car are to be detected, several reference measurements of the empty elevator car are taken over a certain period of time after, for example, a person has left the elevator car, so that reference measurements are recorded at different turbulences within the elevator car.

It has also been shown that reference measurements should be recorded not only after just one person has left the elevator car 10, but also when several people have left it. Furthermore, reference measurements can be recorded after a person with a pet, such as a dog, has left the elevator car 10 .

In the case of a large number 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 the further evaluation.

In an alternative embodiment 5 the transmitter 32 and the receiver 34 are located on a floor, outside the elevator car 10 and the shaft. The evaluation unit 36 can also be arranged on the floor, or at any other location, for example in a paneling of a shaft door 80. The angle of radiation as well as the direction of radiation of the acoustic impulse is selected in such a way that only waves of the impulse 52, 62 are present measurement 60 or for reference measurement 50 in the area to be monitored in front of the shaft door 80. The area 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, such as floor markings, railings or balustrades that partially delimit the area. However, this is not absolutely necessary.

According to a further exemplary embodiment, the space to be monitored is formed outside and separately from the elevator car, for example as an entrance area or the exit area of a building.

According to a further embodiment, the area to be monitored can also be limited by the propagation time of the emitted acoustic pulses and their reflected response signals. For example, only measured values greater than a minimum time period and less than a maximum time period can be used from the actual signal. The area to be monitored can be restricted via the runtime.

A reference measurement can be dispensed with at a certain point in time or in a predetermined state of the room to be monitored. In this case, the room to be monitored 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.

The aspects of the technology explained above, in particular with reference to an elevator system, can be transferred in the same way to any spatial areas for which contactless monitoring is to be carried out.

Reference List

10

elevator car

20

elevator system

22

carrying means

30

detection module

32

Channel

34

recipient

36

evaluation unit

40

pulse

42

object

44

person

46

wave packet

48

wave packet

50

reference measurement

50'

Amplitude spectrum of the reference envelope

52

acoustic impulse

54

reference signal

56

reference envelope

60

actual measurement

60'

Amplitude spectrum of the actual envelope

62

acoustic impulse

64

actual signal

66

actual envelope

Claims (10)

Method for contactless monitoring of a space to be monitored, with - Providing a signal source that is set up to emit sound signals; - Providing a sensor device that is set up to detect sound signals; - Transmission of sound measurement signals by means of the signal source in a room area to be monitored; and - Detection of sound response signals from the room to be monitored by means of the sensor device on the emission of the sound measurement signals; wherein the following is also provided in an evaluation device, which is connected at least to the sensor device: - determining an envelope for the detected sound response signals; - determining a property parameter for the space to be monitored from an envelope analysis; - providing reference data indicative of a reference parameter for the space to be monitored; and - determining a change in the space to be monitored when the property parameter differs from the reference parameter. procedure after claim 1 , characterized in that the sound response signals are detected as time-resolved sound response signals in the time domain and a time-resolved envelope is determined. procedure after claim 1 or 2 , characterized in that determining the property parameter for the space to be monitored further comprises the following: - determining a transformed envelope, the transformed envelope being determined using at least one of the following transformations on the envelope: transforming the envelope into the frequency domain and wavelet Transformation; and - determining the property parameter for the space to be monitored from the transformed envelope. procedure after claim 3 , characterized in that in the case of the transformation of the envelope in the frequency domain the property parameters for the space to be monitored are determined from the transformed envelope in the frequency domain. procedure after claim 4 , characterized in that the property parameter is determined from a frequency-dependent amplitude distribution of the transformed envelope. Method according to at least one of the preceding claims, characterized in that the following is also provided: - determining at least one further property parameter for the space to be monitored from the envelope analysis and - determining the change in the space to be monitored if the property parameter differs from the reference parameter and / or distinguish at least one further property parameter from a further reference parameter, which is indicated by the reference data. Method according to at least one of the preceding claims, characterized in that when determining the change, taking into account the property parameter and the reference parameter, at least one of the following parameter operations is carried out: summation and difference formation. Method according to at least one of the preceding claims, characterized in that the change in the space to be monitored is determined if the property parameter and the reference parameter differ by at least a threshold value. Method according to at least one of the preceding claims, characterized in that at least one of the following room changes is determined as a change in the room to be monitored: empty room, presence of a person, absence of a person, change of location of a person, change in position of an object in the room and dangerous situation . Device for contactless monitoring of a space to be monitored, with - A signal source that is set up to emit sound signals; - A sensor device which is set up to detect sound signals; and - An evaluation device which is connected at least to the sensor device; wherein the evaluation device is set up to evaluate sound response signals detected by the sensor device for the emission of sound measurement signals by the signal source into a room to be monitored and to carry out the following: - determining an envelope for the detected sound response signals; - determining a property parameter for the space to be monitored from an envelope analysis; - providing reference data indicative of a reference parameter for the space to be monitored; and - determining a change in the space to be monitored when the property parameter differs from the reference parameter.

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