KR20110059336A - Method of discriminating environmental noise for ultrasonic distance measurement - Google Patents

Abstract

PURPOSE: A method for discriminating environmental noise in ultrasonic distance measurement is provided to increase reliability of position tracking data by preventing an error due to an ultrasonic wave included in environmental noise. CONSTITUTION: An ultrasonic signal is inputted in a plurality of channels(S10). A first reference frequency(F1) is detected from the received signal and an output for a corresponding state is periodically updated(S20). A second reference(F2) signal is detected from the received signal and an output for a corresponding state is periodically updated(S30). An output state of the first reference frequency is compared with an output state of the second reference frequency and a normal signal is determined(S40).

Description

Method of discriminating environmental noise for ultrasonic distance measurement

The present invention relates to a method for distinguishing environmental noise during ultrasonic distance measurement, and more specifically, to an ultrasonic distance measurement environment for improving reliability of measurement data by preventing an error due to ultrasonic waves included in environmental noise in a distance measuring system using ultrasonic waves. It is about noise classification method.

This study was conducted as part of the IT core technology development project of the Ministry of Knowledge Economy and ICT Research Promotion Agency.

[2008-S033-01, Development of Indoor and Outdoor Wide Area Localization Sensor]

In general, various methods are used to reduce the distance error generated when acquiring the distance data by using ultrasonic waves, and a method for reducing the distance error is also required in tracking a location using beacons and tags. Beacon is a device for transmitting or receiving the ultrasonic wave is installed on the wall or ceiling, the tag is a device for transmitting or receiving the ultrasonic wave is installed on the moving object to determine the position. The method of reducing the distance error corresponding to such an environment can be largely classified into (1) software method, (2) hardware method, and (3) system configuration method.

(1) In the S / W method, the first method is to set the maximum / minimum value at which the distance value can be measured and ignore the distance value outside this range. Second, the distance value acquired in the past and the current distance value Using the difference and the difference between the time at which the past distance value is obtained and the current distance value, the maximum variation value of the distance value according to the time difference is set to ignore the exceeded distance value. Third, the Kalman filter There is a method of correcting a distance value using a method such as an average.

(2) The H / W method uses the amplification and filter circuit at the ultrasonic receiver to reduce errors caused by electrical noise generated inside the apparatus. (3) The method by the system configuration is to install as much as possible to avoid the interference of the obstacle between the transmitter and receiver of the ultrasonic wave, and to add a beacon in the area where it is difficult to receive the ultrasonic wave by the obstacle.

In the case of the above method (1), since it is a method for reducing the error that has already occurred, it cannot be corrected up to the same value as the actual distance value. That is, the error is reduced but not disappeared. In the case of the method (2), the filter circuit is used to remove the electrical noise inside the apparatus and amplify the received ultrasonic signal to efficiently receive the ultrasonic signal to be obtained. This is to detect a weak ultrasonic signal to obtain a distance value to a farther distance, but to prevent an error due to electrical noise of an internal device. In the case of method (3), the occurrence of distance value error caused by obstacles, that is, distance value error caused by distance data being measured longer than actually received when ultrasonic waves reflected from other places are not received. This is a way to reduce it.

As another example, according to "Ultrasound reception signal detector using a difference of peak values" of Korean Patent Publication No. 0442640, including a comparator 3 for comparing the ultrasound signal received at the receiver with a DC voltage source 2 as a reference. An ultrasonic reception signal detector for measuring a reception time of an ultrasonic signal, comprising: a peak detector 6 for receiving a received ultrasonic signal and detecting peak values of a predetermined number of ultrasonic signals; and an output terminal of the comparator 3 ( And a main signal processor 5 for distinguishing the noise signal from the ultrasonic signal from the width of the pulse signal by comparing the width of the pulse signal output through 4) with the peak value of the ultrasonic signal output from the peak value detector 6. To start the configuration.

Although the accurate ultrasonic arrival time can be known by installing a peak detector that distinguishes a noise signal from an ultrasonic signal, high reliability cannot be expected in tracking a moving object moving in a beacon-installed area.

An object of the present invention for improving the conventional problems as described above, the environment of the ultrasonic distance measurement to increase the reliability of the position tracking data by preventing the error caused by the ultrasonic wave included in the environmental noise when measuring the distance of the ultrasonic method for the moving object To provide a way to distinguish noise.

In order to achieve the above object, the present invention provides a method for distinguishing a noise source during the distance measurement of the ultrasonic method using the transmission sensor and the reception sensor: a first step of inputting the ultrasonic signal into a plurality of channels; Determining whether a first reference frequency is detected in the received signal, and periodically updating an output of a corresponding state; Determining whether a second reference frequency is detected in the received signal, and periodically updating an output for a corresponding state; And a fourth step of determining whether the signal is a normal signal by comparing the output states of the first reference frequency and the second reference frequency.

Further, according to the present invention, the first step is characterized by using a reference receiving sensor and an auxiliary receiving sensor having different specific frequency ranges.

Further, according to the present invention, the first step is characterized by using a reference reception sensor having one wideband frequency domain and a plurality of bandpass filters having different specific frequency domains.

In addition, according to the present invention, the second and third steps are characterized by using two or more reference frequencies in the ultrasonic frequency range and outputting a detection result of the reference frequency as a flag.

In addition, according to the present invention, the fourth step may be determined as a normal signal by the originating sensor only when there is only a first reference frequency and no second reference frequency exists.

As described above, according to the present invention, by separating the sound waves corresponding to a specific frequency of the ultrasonic transmitting sensor and the sound waves of the same frequency band included in the environmental noise by eliminating the frequency of occurrence of the distance value error due to noise generated in real life distance data Can increase the reliability.

In addition, by increasing the reliability of the distance data, it is also possible to increase the reliability of the ultrasonic positioning system that calculates the position data using the distance data.

In addition, by eliminating errors due to environmental noise, it is possible to stably use the distance measurement using ultrasonic waves and the position detection system using ultrasonic waves in various environments.

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

1 is a schematic diagram showing a hardware configuration according to a first embodiment of the present invention, FIG. 2 is a flowchart showing a main operation procedure according to FIG. 1, and FIG. 3 is a schematic diagram showing a hardware configuration according to a second embodiment of the present invention. 4 is a flowchart showing the main operation sequence of FIG. 3.

The present invention relates to a method for distinguishing the noise source (N) when the distance measurement of the ultrasonic method using the transmission sensor 10 and the reception sensor. In particular, it is a method for reducing the probability of occurrence of positioning error of a moving object having a tag in an area where a plurality of beacons are installed. As described above, even though the error is reduced by the S / W method, there is a difference from the actual distance value, and the H / W method is only an effect of reducing the probability of error occurrence. And when the frequency of error occurs a lot there is a limit to deal with the prior art. If the S / W method has more abnormal distance values due to errors than the normal distance value, the difference between the calculated value and the actual distance value becomes larger, and the conventional H / W or system configuration method generates an error corresponding to a specific condition. Only works.

One of the causes for the increased frequency of error is a noise source (N) that causes environmental noise. In addition to the sound waves of human beings (human voice, music through speakers, etc.), environmental noise generally has sound waves corresponding to ultrasonic frequencies. For example, the sound of applause, tearing off the tape, and noise generated when loading an object. These sound waves make it difficult to reliably use a range finder using ultrasonic waves, and furthermore, a system that uses this distance value to locate a device in real life.

According to the present invention, a first step (S10) of inputting the ultrasonic signal through a plurality of channels is performed. When a beacon or a tag transmits an RFID signal and transmits an ultrasonic wave, the distance between the tag and the beacon is measured by measuring the time of flight (TOF) of the ultrasonic flight time from when the tag or beacon receives the RFID to receiving the ultrasonic wave. Calculate At this time, the present invention inputs the normal ultrasonic signal by the transmitting sensor 10 and the abnormal ultrasonic signal by the noise source N through a plurality of channels (hardware).

In this way, the method of distinguishing the sound wave of the ultrasonic frequency band included in the environmental noise of the noise source (N) and the ultrasonic wave transmitted by the transmitting sensor 10 in the distance measuring method using ultrasonic waves is largely implemented in two embodiments.

As a first embodiment of the present invention (see FIG. 1), the first step S10 uses a reference receiving sensor 20 and an auxiliary receiving sensor 30 having different specific frequency ranges. The reference receiving sensor 20 responds at a specific ultrasonic frequency (narrow band) and uses the same frequency as the transmitting sensor 10. The auxiliary reception sensor 30 uses what is sensitive to an ultrasonic frequency different from that of the reference reception sensor 20. In the distance measuring system using ultrasonic waves, when the ultrasonic receiver receives sound waves in the ultrasonic frequency band (more than 20KHz) included in the environmental noise, the sound waves are mistaken for the ultrasonic wave transmitted by the ultrasonic transmitter. The reference receiving sensor 20 and the auxiliary receiving sensor 30 are the minimum hardware resources for preventing such an error by distinguishing the ultrasonic wave transmitted by the transmitting sensor 10.

As a second embodiment of the present invention (see FIG. 3), the first step S10 includes a plurality of band pass filters having a specific frequency region different from that of the reference reception sensor 40 having one broadband frequency region. 42) (44). Only one reference receiving sensor 40, which senses the frequency of the broadband, uses a plurality of band pass filters 42 and 44 in circuit. The band pass filters 42 and 44 analyze sound wave components of different frequency bands to distinguish environmental noise. The band pass filter 42 on one side passes through the first reference frequency F1, and the band pass filter 44 on the other side passes through the second reference frequency F2. The second embodiment of the present invention has the advantage of preventing an increase in appearance caused by mounting two or more ultrasonic receiving sensors together on the moving body.

Of course, the above-described reference reception sensor 20 and the auxiliary reception sensor 30 of the first embodiment also have the functions of the band pass filters 42 and 44 according to the second embodiment.

In addition, according to the present invention, a second step S20 of determining whether a first reference frequency F1 is detected in the received signal and a third step of determining whether a second reference frequency F2 is detected in the received signal Go through (S30). The second step S20 and the third step S30 periodically update the output of the corresponding state. The detection states of the reference frequencies F1 and F2 are output and stored to enable access by a microcomputer (not shown).

As illustrated in FIG. 1A of the first embodiment, the ultrasonic signal of the first reference frequency F1 transmitted by the ultrasonic transmitting sensor 10 is detected by the reference receiving sensor 20 but not by the auxiliary receiving sensor 30. As shown in (b) of FIG. 1, ultrasonic noise of the noise source N is detected by both the reference reception sensor 20 and the reference reception sensor 40. 3 (a) of the second embodiment, the ultrasonic signals of the first reference frequency F1 transmitted by the transmitting sensor 10 are all detected by the reference receiving sensor 40 and pass through one side band pass filter 42, but the other side. It does not pass through the band pass filter 44. As illustrated in FIG. 3B, ultrasonic noise of the noise source N passes through all of the band pass filters 42 and 44.

In this case, the second step S20 and the third step S30 use two or more reference frequencies F1 and F2 within the ultrasonic frequency range, and flag the detection result of the reference frequencies F1 and F2. Will output The present invention shows and describes the means for detecting one first reference frequency F1 and the means for detecting one second reference frequency F2, but the latter means in the upper and lower ranges of the first reference frequency F1. A plurality of second reference frequencies F2 may be installed to detect the plurality of second reference frequencies F2. The detection states of the reference frequencies F1 and F2 are indicated by flags to enable reading by the microcomputer.

Further, according to the present invention, a fourth step S40 of comparing the output states of the first reference frequency F1 and the second reference frequency F2 to determine whether the signal is a normal signal is performed. The fourth step S40 determines that the signal is normal by the transmitting sensor 10 only when the first reference frequency F1 is present and the second reference frequency F2 is not present.

For example, the transmitting sensor 10 transmits an ultrasonic signal of 40 KHz, the reference receiving sensor 20 responds to the first reference frequency F1 signal of 40 KHz, and the auxiliary receiving sensor 30 receives the second reference frequency of 20 KHz ( F2) Set to respond to a signal. If the environmental noise such as clapping sound is generated, the sound wave of 40 KHz or 20 KHz corresponding to the ultrasonic wave is included as well as the sound wave of the audible frequency band that can be heard by humans, as shown in FIGS. 1B and 3B. All kinds of channels detect sound waves. Therefore, in this case, it is determined that the ultrasonic wave sensor 10 of 40KHZ receives the sound wave by the noise source N instead of the sound wave transmitted by the ultrasonic wave sensor 10. When one type of ultrasonic receiving sensor is used as in the related art, when such an environmental noise occurs, a distance data error occurs because it is mistaken that the ultrasonic transmitting sensor has received the ultrasonic wave.

If the microcomputer determines that the input signal is a sound wave by the noise source N in the fourth step S40, the microcomputer ignores the distance value and performs the following sampling.

In this way, by separating the sound wave source that transmits only a specific frequency and the sound waves of the same ultrasonic frequency band that can occur in the surrounding environment, it is possible to obtain a more stable distance value by reducing the frequency data error occurrence frequency.

It is apparent to those skilled in the art that the present invention is not limited to the described embodiments, and that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, such modifications or variations will have to belong to the claims of the present invention.

1 is a schematic diagram showing a hardware configuration according to a first embodiment of the present invention;

2 is a flowchart showing a main operation sequence according to FIG. 1;

3 is a schematic diagram showing a hardware configuration according to a second embodiment of the present invention;

4 is a flowchart showing the main operation sequence of FIG. 3.

* Description of the symbols for the main parts of the drawings *

10: outgoing sensor 20: reference receiving sensor

30: auxiliary receiving sensor 40: reference receiving sensor

42, 44: band pass filter N: noise source

F1: first reference frequency F2: second reference frequency

Claims (5)

In the method of distinguishing the noise source (N) in the distance measurement of the ultrasonic method using the transmitting sensor 10 and the receiving sensor: A first step (S10) of inputting the ultrasonic signal into a plurality of channels; A second step (S20) of determining whether a first reference frequency (F1) is detected in the received signal and periodically updating an output of a corresponding state; A third step (S30) of determining whether a second reference frequency (F2) is detected in the received signal and periodically updating an output of a corresponding state; And And comparing the output state of the first reference frequency (F1) and the second reference frequency (F2) to determine whether the signal is a normal signal (S40); environmental noise of the ultrasonic distance measurement characterized in that it comprises a How to distinguish. The method of claim 1, The first step (S10) is the environmental noise classification method of the ultrasonic distance measurement, characterized in that using the reference receiving sensor 20 and the auxiliary receiving sensor 30 having a different specific frequency range. The method of claim 1, The first step (S10) is an ultrasonic distance, characterized in that using the reference receiving sensor 40 having a single broadband frequency domain and a plurality of band pass filters 42, 44 having a different specific frequency range How to distinguish environmental noise in measurement. The method of claim 1, In the second step S20 and the third step S30, two or more reference frequencies F1 and F2 are used in the ultrasonic frequency range, and the detection results of the reference frequencies F1 and F2 are output as flags. Method for distinguishing environmental noise of ultrasonic distance measurement, characterized in that. The method of claim 1, In the fourth step (S40), ultrasonic distance measurement, which is determined as a normal signal by the transmitting sensor 10 only when the first reference frequency F1 exists and the second reference frequency F2 does not exist. How to distinguish environmental noise

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