KR20150028106A - Indoor positioning based on inaudible sound's droppler effects - Google Patents

Abstract

The present invention relates to a method for an electronic product like a mobile device existing indoor to receive a sinusoidal signal of inaudible frequency band generated in a speaker (Beacon) installed in a specific indoor position in advance, and to estimate its own position accurately by sensing Doppler effect generated in motion. More specifically, The electronic product like a mobile device etc has to know an indoor map and the position of the speaker (Beacon) in the map in advance, and the speaker is attached to the ceiling or the wall in the indoor space. If the electronic product like a mobile device moves in the indoor space, the sinusoidal wave from the speaker attached in the indoor space is distorted, and this distortion is caused by the Doppler effect. Finally, the indoor positioning technology enables the mobile device to grasp its own position accurately on the basis of the degree of distortion of the sinusoidal wave.

Description

[0001] INDOOR POSITIONING BASED ON INAUDIBLE SOUND'S DROPPER EFFECTS [0002]

The present invention relates to a self-position recognition in a room, and more particularly, to a method for enabling accurate electronic position recognition (navigation) through a speaker (beacon) installed in a room in an electronic product such as a mobile device equipped with a microphone. It can be used for all indoor location-based services, typically using indoor maps, and the range can range from the telecommunications industry to the robotics industry.

The Doppler effect was discovered by CJ Doppler in 1842 and is caused when one or more of the excitation (speaker) and the observer (electronic device such as mobile device) The wave frequency is higher when the distance is narrowed, and the wave frequency is lower when the distance is longer. The technique used in the present invention is based on detecting the frequency variation of a wave by extending it from a one-dimensional space to a three-dimensional space.

High-precision indoor location-based services, which were impossible due to limitations in accuracy due to the conventional technology, can help inform the disabled and the elderly more precisely about the coordinates of the location. . In addition, if location-based services such as museums, hospitals, and expositions are applied to important public facilities, it can be used as a base service for providing new information to users as well as estimating a simple location.

Currently, Wi-Fi (Wi-Fi), Inertial Measurement Unit (IMU), laser, ultrasound, RFID and other sensors are used for self-location recognition. Indoor location-based services are currently being prepared for commercialization. FIG. 8 shows an indoor location tracking technique using the latest Wi-Fi fingerprint technology, which guarantees an accuracy within a few meters in an advanced manner than the initial technology RSSI (Received Signal Strength Indication). However, in the case of indoor location based service using Wi-Fi, there is a disadvantage that the infrastructure is considerably expensive to construct and the accuracy is unexpectedly inaccurate and accurate location recognition is not possible. In the case of self-location recognition using other methods, it is required that the observer not only have a facility infrastructure, but also carry the separate equipment or tag. Therefore, it is a reality that the cost of constructing an inexpensive infrastructure, compatibility with all mobile devices and electronic products, and technology capable of more precise location recognition are required.

On three dimensions, different Doppler effects from three speakers (Beacons) that generate three different base frequencies in space-orthogonal relation as the observer moves can accurately estimate the current position in space.

FIG. 1 illustrates an example in a two-dimensional space. The different sine waves generated by the first speaker (Beacon [101] and the second Beacon [102]) proceed in a forward direction concentrically. In this case, observers moving in arbitrary directions [103] will be able to observe different Doppler effects of the first Beacon [101] and the second Beacon [102], since the tangent angles of the two concentric circles are different . Finally, the ratio of the two Doppler frequencies is a measure of the approximate location, and the magnitude of the Doppler frequency determines the speed. In addition to using the ratio of the two Doppler frequencies, it is also possible to determine the final position by integrating the magnitude of the frequency. If it is used in combination with a geomagnetic sensor or the like as needed, more accurate position estimation becomes possible.

FIG. 2 shows an example in a one-dimensional environment such as a corridor. Like FIG. 1, different signals generated in the first Beacon [201] and the second Beacon [202] are echoed in a certain direction along the corridor . The observer can obtain a measure of the approximate position through the directions of the two Doppler signals and can also determine the final position by integrating the magnitude of the Doppler frequency.

In general, the temporal resolution (hereinafter referred to as a sampling rate) of a microphone mounted on an electronic device such as a mobile device is 44.1 KHz, and 44100 signals can be input per second. Since the sine-wave frequency of the non-audible frequency band generated by Beacon is required to be 19KHz or more according to the Nyquist sampling theory, the final sinusoidal signal generated by Beacon is 22KHz to 22KHz . It is impossible to determine the correct Doppler frequency with limited signal bandwidth and limited sampling rate. To overcome this, frequency axis interpolation is used as a solution.

Fig. 3 shows an example of a method of accurately estimating a frequency using an interpolation method in a frequency-axis signal with a limited resolution. FIG. 4 shows the frequency variation due to the Doppler effect actually input, in which [401] is the Doppler frequency to be actually generated theoretically, [402] is the Doppler shift amount estimated using only the existing FFT (Fast Fourier Transform) Shows the actual output frequency of the Doppler change amount to be actually used in the present invention through the frequency axis interpolation. It is possible to accurately detect the frequency change due to the Doppler effect through a sufficient interpolation algorithm even with a limited sampling rate and limited frequency axis resolution Show.

In the conventional indoor location-based service using Wi-Fi, since it uses radio waves close to the speed of light, it is impossible to track the position using time difference tracking and Doppler effect in the current technology. Instead, To ensure accuracy. In addition, since the transmission and reception of radio waves are assumed, a basic infrastructure cost such as a dedicated processor and a highly-precisely designed antenna is inevitably high. However, the present invention using a non-audible frequency can sufficiently transmit and receive through a general speaker and a microphone, and it is possible to detect a time difference tracking and a Doppler effect sufficiently with the present technology because the speed of the wave is relatively slow. There is a strength. In addition, most of the mobile devices and electronic devices carried by most users are equipped with microphones, so it is possible to guarantee high accuracy within a few centimeters due to low infrastructure cost, and finally to improve the quality of indoor location based service .

FIG. 1 is a diagram illustrating position tracking on a two-dimensional plane according to an embodiment of the present invention.
2 is a diagram illustrating an example in a one-dimensional view according to an embodiment of the present invention.
3 is a diagram illustrating an example of frequency axis interpolation according to an embodiment of the present invention.
4 is a diagram illustrating a result of an accurate frequency estimation using an interpolation method according to an embodiment of the present invention.
5 is a diagram illustrating a configuration of a beacon according to an embodiment of the present invention.
6 is a diagram showing a configuration of an observation device according to an embodiment of the present invention.
7 is a flowchart of a main processor of an observation instrument according to an embodiment of the present invention.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

On three dimensions, different Doppler effects from three speakers (Beacons) that generate three different base frequencies in space-orthogonal relation as the observer moves can accurately estimate the current position in space.

FIG. 1 illustrates an example in a two-dimensional space. The different sine waves generated by the first speaker (Beacon [101] and the second Beacon [102]) proceed in a forward direction concentrically. In this case, observers [103] moving in an arbitrary direction can observe the different Doppler effects of the first Beacon [101] and the second Beacon [102], because the tangent angles of the two concentric circles . Finally, the ratio of the two Doppler frequencies is a measure of the approximate location, and the magnitude of the Doppler frequency determines the speed. In addition to using the ratio of the two Doppler frequencies, it is also possible to determine the final position by integrating the magnitude of the frequency. If it is used in combination with a geomagnetic sensor or the like as needed, more accurate position estimation becomes possible.

FIG. 2 shows an example in a one-dimensional environment such as a corridor. As in FIG. 1, different signals generated in the first Beacon [201] and the second Beacon [202] resonate in a certain direction along the corridor. The observer can obtain a measure of the approximate position through the directions of the two Doppler signals and can also determine the final position by integrating the magnitude of the Doppler frequency.

In general, the temporal resolution (hereinafter referred to as a sampling rate) of a microphone mounted on an electronic device such as a mobile device is 44.1 KHz, and 44100 signals can be input per second. Since the sine-wave frequency of the non-audible frequency band generated by Beacon is required to be 19KHz or more according to the Nyquist sampling theory, the final sinusoidal signal generated by Beacon is 22KHz to 22KHz . It is impossible to determine the correct Doppler frequency with limited signal bandwidth and limited sampling rate. To overcome this, frequency axis interpolation is used as a solution.

3 shows an example of a method for accurately estimating a frequency using an interpolation method in a frequency-axis signal having a generally limited resolution. FIG. 4 shows the frequency variation due to the Doppler effect actually input, in which [401] is the Doppler frequency to be actually generated theoretically, [402] is the Doppler shift amount estimated using only the existing FFT (Fast Fourier Transform) Shows the actual output frequency of the Doppler change amount to be actually used in the present invention through the frequency axis interpolation. It is possible to accurately detect the frequency change due to the Doppler effect through a sufficient interpolation algorithm even with a limited sampling rate and limited frequency axis resolution Show.

A plurality of beacons for reproducing signal components of different sine waves in the indoor space are constructed as shown in FIG. 5. A signal generator 501 for constantly generating one of the sine waves of 19 KHz to 22 KHz, which is a non-audible frequency band, A signal amplifying unit 502 for amplifying the signal to a sufficient size, and a speaker 503 for radiating the signal amplifying unit 502 in space. If the observer moves at a maximum speed of 4 Km / h regardless of direction, the maximum speed change is 4 Km / h at -4 Km / h, and the maximum Doppler frequency that can be distorted at 19 Khz sine wave is given by Therefore, the signal generator can generate one of the base frequencies (hereinafter, referred to as "channels") of about 50 kHz of the signals of 19 KHz to 22 KHz, which can be defined by the maximum velocity of the observer.

The sinusoidal wave generated by the Beacon is input to a microphone of an electronic device (hereinafter, referred to as an observation device) such as a mobile device carried by an observer, and estimates the final indoor position. This is shown in FIG. 6, and a single sinusoidal wave An amplifier 602 for amplifying a received signal, an ADC (Analog to Digital Converter) 603 for digitizing the received signal to the main processor, and a main processor 604 for executing a series of algorithms ], Which is also a minimum requirement of the instrument.

The main processor of the observation device basically undergoes a series of processes as shown in FIG. 7 and includes a digital filter 701, windowing 702, discrete Fourier transform (DFT) 703, maximum peak detection 704, ], An integration unit [706], and a final positioning unit [707].

A series of digital signals input to the main processor through the ADC [603] are removed from signals other than the Beacon signal through the digital filter [701], and the digital filter removes signals other than the channels of each of the known beacons It is designed as BandPass Filter type. In order to pass only the desired sinusoidal wave regardless of the ambient noise, the signal passing through the digital filter 701 is divided into channels and then converted into a frequency axis through the DFT [703] To detect. Before the DFT [703] is performed, it goes through windowing [702], in order to minimize the leakage error that may occur in the conversion to the frequency axis. Since the DFT [704] is performed at a limited sampling rate, it is difficult to know the exact frequency only by the maximum peak detection [704]. Therefore, the maximum point can be estimated through the maximum peak detection [704] and the interpolation [705]. Assuming that the estimated maximum point is the frequency variation due to the Doppler effect, it is possible to trace the final position as shown in FIG. 1 through the integration unit [706]. This is due to the fact that the spatial source always spreads in the form of a spherical wave. If we know in advance a number of Beacon [101-102] channels and locations in the interior space, then the integration of the frequency variation due to the Doppler effect The value is mathematically because it means absolute distance from Beacon [101-102]. In addition, in order to prevent spatial errors caused by noise, the observing device [103] finds its position based on the maximum of three beacons closest to itself at all times based on the integral value, The effect of correcting the error by itself is also obtained.

A high-precision indoor location-based service, which was impossible due to limitations in accuracy of the prior art, can help inform the disabled and the elderly more precisely about the coordinates of the location, which can guide the convenience of facilities such as doorways and elevators Can be applied. In addition, if location-based services such as museums, hospitals, and expositions are applied to important public facilities, it can be used as a base service for providing new information to users as well as estimating a simple location.

In future applications to the robot industry, which is not a technical field of the present invention, it can be widely used for unmanned system building of buildings requiring precise coordinates.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA) A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

101, 102: Beacon
103: Observer

Claims (1)

Indoor location based technology using Doppler effect of non - audible frequency band.

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