JP2013185856A - Methods for measuring position and wind speed utilizing doppler effect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring a position, compensating for sound velocity change due to wind and having high measurement accuracy.SOLUTION: A method for measuring a position by compensating for sound velocity change on the basis of a measurement result of wind velocity utilizing a Doppler effect, includes: transmitting an acoustic wave having a predetermined frequency from an object 1 to be measured in position to allow an object 2 measuring a position to receive the acoustic wave, and calculating a propagation time of the acoustic wave from the reception time and the transmission time; and compensating for sound velocity change due to wind on the basis of a Doppler effect to calculate a distance from the object 2 measuring a position to the object 1 to be measured in position to measure a position.

Description

  The present invention relates to a position measuring method and a wind speed measuring method using the Doppler effect capable of measuring a position with high accuracy in the measurement field.

  In recent years, labor reduction and cost reduction of agricultural production, management work, etc. are becoming more and more important issues in agriculture in Japan as the number of agricultural workers decreases and the population ages. Among the tasks that are not being automated, weeding on the shore is one example. In particular, rice terraces and terraced fields in hilly and mountainous areas depend on human power such as brush cutters, and the development of small weeding robots is underway to automatically perform this heavy labor and dangerous weeding work. Yes.

  When the robot automatically performs mowing work, it is conceivable to use GPS for route generation and position detection. However, high-accuracy GPS is expensive, and it may not always be possible to supplement the required number of GPS satellites in hilly and mountainous areas, so it is difficult to aim for a low-priced practical aircraft.

  In addition, when performing position measurement using sound waves outdoors or the like, there is a decrease in measurement accuracy due to changes in sound speed due to wind in an environment where wind blows, and position measurement cannot be performed accurately.

  As a result of patent research, it has been proposed to cancel the influence of wind speed by transmitting and receiving sound waves between devices as in Japanese Patent Application Publication No. 2005-516190. It is also known to measure wind speed by utilizing the Doppler effect.

JP-T-2005-516190

  However, in the former, since sound waves are transmitted and received between the devices, the devices and processing become complicated, and the cost increases. In the latter method of measuring the wind speed by the Doppler effect, the speaker and the microphone are fixed, and the speaker and the microphone need to be fixed. Therefore, it is difficult to apply the method to a moving object position measurement system.

  Therefore, it has been a problem to accurately measure the position and the like of a moving object without degrading the measurement accuracy associated with the change in sound speed due to the wind even in an environment where the wind blows, such as outdoors.

  The present invention has been made in view of the above points, and in order to solve the above problems, the present invention is a position measurement method for compensating for a change in sound speed based on a wind speed measurement result using the Doppler effect. A sound wave of a predetermined frequency is transmitted from the measurement body and received by the position measurement body, and the propagation time of the sound wave is calculated from the reception time and the transmission time, and the position of the sound wave is compensated for by the wind based on the Doppler effect. An object of the present invention is to provide a position measuring method using the Doppler effect, characterized in that the position is measured by calculating the distance of the position measuring body from the measuring body.

  In addition, the sound wave for position measurement and the sound wave of constant frequency for wind speed compensation are alternately transmitted from the speaker from the moving position measurement object and received by the microphone of the position measurement object, and the distance of the position measurement object is calculated sequentially. The present invention provides a position measuring method using the Doppler effect for position measurement.

  Further, the position measurement sound wave transmitted from the position measurement object is an M-sequence code sound wave of spread spectrum sound, and the distance calculation method performed by the position measurement body that has received the sound wave is the M-sequence code of the sound wave. An object of the present invention is to provide a position measurement method using the Doppler effect, which performs a correlation process and performs a synchronization process.

  Still another object of the present invention is to provide a position measuring method using the Doppler effect that is installed at a position where the number of position measuring bodies is one or more and the distance from the moving position measuring body is several tens of meters or more.

  Furthermore, a sound wave having a predetermined frequency is transmitted from a sound wave transmitting body including a position measurement body and received by a sound wave receiving body including a position measurement body, and the sound wave is frequency-analyzed and transmitted from the bandwidth of the spectral component. An object of the present invention is to provide a wind speed measuring method using the Doppler effect, characterized by measuring a wind speed between a body and a sound wave receiver.

  The position measurement method using the Doppler effect according to the present invention is a position measurement method for compensating for the change in sound speed based on the measurement result of the wind speed using the Doppler effect, as in claim 1. A sound wave having a predetermined frequency is transmitted from the position measurement body and received by the position measurement body. The propagation time of the sound wave is calculated from the reception time and the transmission time, and the change in the sound speed due to the wind based on the Doppler effect is compensated. By calculating the position of the position measurement object from the position measurement object and measuring the position, it is possible to measure the position of the position measurement object without complicating the apparatus, and the wind based on the Doppler effect Measures the position of the object to be measured accurately without compromising measurement accuracy due to changes in sound speed due to wind, even in environments where the wind blows outdoors, etc. Rukoto can.

  According to another aspect of the present invention, a sound wave for position measurement and a sound wave having a constant frequency for wind speed compensation are alternately transmitted from a speaker and received by a microphone of the position measurement body. By calculating the distance of the measuring body sequentially and measuring the position, the device can be simplified, and as described above, the compensation of the sound speed change due to the wind based on the Doppler effect is performed, even under the wind blowing environment such as outdoors, The position of the moving position-measuring object can be accurately measured without degrading the measurement accuracy associated with the change in sound velocity due to the wind.

  Further, according to a third aspect of the present invention, there is provided a distance calculation method performed by the position measurement body that receives the sound wave when the position measurement sound wave transmitted from the position measurement body is an M-sequence code sound wave of spread spectrum sound. By performing correlation processing on the M-sequence code of the sound wave and performing synchronization processing, the excellent autocorrelation characteristics and noise resistance of the M-sequence code of the spread spectrum sound can be used, even under the noise of the wind blowing environment such as outdoors. In addition to being able to measure the position with high accuracy as described above, since it is a wireless network, it is easy to add or remove the measuring object, and the position can be measured freely.

  Furthermore, as described in claim 4, when the number of position measuring bodies is one or more, and the distance from the moving position measuring body is several tens of meters or more, the measuring distance is several tens of meters. Even in the case of measurement of m or more, it is possible to measure the position of the position measuring body that moves at the calculated distance from the position measuring body, and to measure the position with an error of several centimeters.

  Furthermore, as described in claim 5, a sound wave having a predetermined frequency is transmitted from a sound wave transmitting body including a position measuring body and received by a sound wave receiving body including a position measuring body, and the sound wave is subjected to frequency analysis and its spectrum is obtained. By measuring the wind speed between the sound wave transmitter and the sound wave receiver from the bandwidth of the component, the wind speed between the sound wave transmitter and the sound wave receiver can be measured using the Doppler effect.

Outline explanatory drawing of the position measuring system of the present invention, Overview of distance calculation same as above, Illustration of the principle of sound velocity change due to wind force of Doppler effect as above, Frequency characteristic explanatory diagrams (a), (b), (c), Frequency characteristics explanatory diagram of sound speed change due to wind, Relationship diagram of frequency and power spectrum Relationship diagram between wind speed and power spectrum indoors Relationship diagram of wind speed and power spectrum in outdoor Relationship diagram of wind speed and power spectrum Relationship diagram of wind speed and power spectrum The experimental result figure of the sound speed change by the wind for a reference.

  The position measurement method of the present invention is a position measurement method that compensates for changes in sound speed based on the measurement result of wind speed using the Doppler effect, and transmits a sound wave of a predetermined frequency from the position measurement object to the position measurement object. Calculate the propagation time of the sound wave from the reception time and transmission time, and compensate for the change in sound velocity due to the wind based on the Doppler effect to calculate the distance of the position measurement object from the position measurement object It is characterized by doing.

  In the position measuring method using the Doppler effect, one or more (four in the figure) position measuring bodies 2 are arranged at a predetermined distance around the position measuring body 1 moving as shown in FIG. The position measuring body 1 is measured by sequentially measuring the distance from the position measuring body 2 to the position measuring body 1.

  As shown in FIG. 2, the moving position-measurement body 1 alternately creates a sound wave including a spectrum-spread sound for position measurement and a sound wave having a constant frequency for wind speed compensation by a processor 3 attached thereto. The signal is converted and amplified by the audio amplifier 4 and transmitted from the speaker 5 to the position measuring body 2 side. At this transmission timing, a synchronization signal is output from the processor 3 to the wireless device 6 and transmitted to the position measuring body 2 side for notification.

  The position measuring body 2 receives and detects the synchronization signal by the wireless device 7 attached as shown in FIG. 2, outputs the synchronization signal to the processor 8, detects the synchronization signal, and then detects the synchronization signal from the microphone 9. The sound wave signal to be output is A / D converted. Then, when the sound wave data accumulates in the buffer, correlation processing is performed and necessary processing such as correlation peak detection is performed, and the distance between the speaker 5 and the microphone 9 is calculated by the processor 8 using sound waves such as spread spectrum sound, The result is transmitted and notified to the position measuring body 1 via the wireless device 7, and the position of the position measuring body 1 is measured by multiplying the sound speed by the propagation time based on the distance information. ing.

  In one dimension, the position can be measured with one position measuring body 2, and in two dimensions, the position can be measured with two position measuring bodies 2. In this case, the position can be measured by selecting one position of the intersection of two circles. In the case of three or more as shown in FIG. 1, the positions are measured as intersections of these circles or overlapping neighboring points.

  Sound waves have the advantage that they can easily go around even if there are obstacles, and the measuring means is inexpensive. Spread spectrum sound has noise tolerance and can measure the position with high accuracy. By using the M-sequence code as a sound wave, it has excellent autocorrelation characteristics and noise tolerance of the M-sequence code. Measurement accuracy and noise resistance can be improved. Further, by performing the correlation process and the distance calculation on the position measuring device 2 side, it is possible to distribute the calculation cost of the correlation process and the like, the load on the position measuring body 1 is reduced, and the entire processor can be constructed at low cost. Furthermore, since the position measurement body 1 and the position measurement body 2 are synchronously controlled using the wireless devices 6 and 7 as described above, position measurement can be performed with high accuracy.

  However, where there is an influence of wind, such as outdoors, an error occurs in the measurement when the position is measured by the sound wave as described above. The main error factor is that the sound speed changes due to the wind and the measurement accuracy decreases. For this reason, it is necessary to compensate for the change in sound velocity due to the wind.

In an environment where wind blows, the distance D (m) by sound waves is the sound propagation time ΔT (s) from the speaker 5 to the microphone 9, the sound speed Vs (m / s), the temperature t (° C.), and the wind speed Vw ( m / s), the following equation is obtained.
D = Vs × ΔT
Vs = 331.5 + 0.61 × t + Vw
Here, the wind speed Vw becomes positive when the wind is blown from the speaker 5 to the microphone 9, and becomes negative when the wind is reversed.

  In order to improve the accuracy of the distance D from the above equation, it is necessary to accurately measure the wind speed Vw and temperature, and it can be corrected to the sound speed Vs (m / s) including the influence of the wind speed and temperature, and compensated by the change in the wind speed of the sound wave Is possible.

In the present invention, the change in the sound speed due to the wind speed using the Doppler effect is compensated, and FIG. 3 shows the principle thereof. As shown in FIG. 3, the microphone 9 and the speaker 5 are arranged, and sound waves having a frequency f are emitted from the speaker 5. At this time, the sound velocity c is scattered and reflected by the fine particles moving at the velocity V, and the frequency f ″ received by the microphone 9 by the Doppler phenomenon is obtained as follows. Here, f ′ is the frequency of the sound when colliding with the fine particles.

(C−Vcos θ ₁ ) c
f '= ────────────f f''= ──────────── f'
c (c−Vcos θ ₂ )

(C−Vcos θ ₁ )
f '' = ──────────── f
(C−Vcos θ ₂ )

From the above formula, if the frequencies f, f ″, c, θ ₁ , θ ₂ are known or measurable, the wind speed V can be obtained. However, when the position is measured, the position of the speaker 5 or the microphone 9 is not determined, and thus θ ₁ and θ ₂ are not constant values. Therefore, when a sound having a constant frequency is output, the microphone 9 is assumed to receive a sound in which the Doppler effect occurs within the range of 0 ° <θ ₁ <90 ° and 0 ° <θ ₂ <90 °. How the frequency changes depending on the wind speed was calculated by substituting into the above equation. For example, if the distance is measured using the sound from the speaker 5 installed in the robot, the sound in which the Doppler effect occurs within the range of 0 ° <θ ₁ <90 ° and 0 ° <θ ₂ <90 ° is obtained. It is thought that the microphone 9 is picking up. Here, the speed of sound c = 340 m / s and the frequency of the transmitted sound wave f = 24 KHz.

The results are shown in FIGS. 4A, 4B, and 4C. In each graph, the x-axis represents θ ₁ , the y-axis represents θ ₂ , and the z-axis represents the reception frequency. FIG. 5 shows the maximum and minimum values of the wind speed and the reception frequency at that time. As the wind speed increases as shown in FIGS. 4 and 5, the width of the measurement frequency increases.

As a result, for example, the wind speed Vw can be obtained from the relationship shown in FIG.
1 1
Vw = ------ fmax-342.8 Vw = ------- fmin + 342.8
70 70

fmax and fmin are values of a maximum frequency and a minimum frequency that are equal to or higher than a certain value in the power spectrum when the received sound wave signal is Fourier-transformed.

However, since it is impossible to receive all the ranges of θ ₁ and θ ₂ at the same sound pressure level, it is difficult to uniquely determine the maximum frequency and the minimum frequency. Therefore, the received sound wave signal is subjected to frequency analysis such as Fourier transform, the power spectrum Fm of the frequency fm with the maximum difference value with respect to the power spectrum Fc of the center frequency fc is obtained, and the difference value is used as the feature value df. The wind speed Vw was calculated as follows:

Fm- Fc df -1.69
df ＝ ─────── Vw = ─────────
fm-fc -0.173

  Therefore, the present invention can measure the wind speed by utilizing the Doppler effect, and transmits a sound wave having a predetermined frequency from the sound wave transmitter including the speaker of the position measurement body as described above to thereby measure the microphone of the position measurement body. The sound wave receiving body including the sound wave is received, the sound wave is subjected to frequency analysis, and the average wind speed in a wide range between the sound wave transmitting body and the sound wave receiving body can be measured from the bandwidth of the spectral component. It is possible to measure the wind speed with an inexpensive device such as a sound wave transmitter such as a speaker and a sound wave receiver such as a microphone as described above, and without adding a separate device, frequency analysis of the sound wave received by the processor An inexpensive wind speed measurement system can be constructed.

  In addition, by outputting the sound wave for wind speed measurement immediately after the output of the sound wave for position measurement as described above, it is possible to measure the influence of almost the same wind received by the sound wave for position measurement. By alternately outputting the sound wave for measurement and the sound wave for wind speed measurement, the position of the moving position-measurement body 1 can be sequentially measured. A thermometer can be provided to compensate for the speed of sound.

  Experiments were conducted to confirm the Doppler effect. As shown in FIG. 6, the speaker 5 and the microphone 9 are installed at a distance of 1 m, and 4.46 m / s, 2.99 m / s, 2.23 m / s of wind is directed from the speaker 5 side to the microphone 9 using a fan. It was generated toward. A sound wave having a frequency of 24 KHz was transmitted from the speaker 5, and the sound wave received by the microphone 9 was subjected to frequency analysis. FIG. 6 shows the received frequency components. From FIG. 6, the frequency width of the received sound wave increases as the wind speed increases in accordance with the principle. Therefore, by utilizing the Doppler effect, the wind speed Vw can be determined from the calculation formula described above for the wind speed from the frequency bandwidth. Table 1 shows a comparison between the wind speed Vw calculated in this way and the wind speed measured using an off-the-shelf anemometer, and it is sufficiently possible to measure the wind speed using the Doppler effect of the present invention. It was proved that there was.

Table 1 Wind speed measurement using the Doppler effect and wind speed results from an anemometer of a ready-made product

  In addition, a spectrum spread sound and a constant frequency sound with a fixed frequency of 24 KHz were alternately emitted from the speaker 5 and experimented indoors and outdoors. As a result, the relationship between the frequency of the sound received by the microphone 9 of each pattern with different wind speeds in the room and the power spectrum thereof is that shown in FIGS. 7 and 8, respectively. Thereby, it turns out that the width of a frequency has spread, so that the wind speed becomes strong. FIG. 9 shows the result of paying attention to the point that the difference of the power spectrum from the peak of 24 KHz becomes the largest, and there is a correlation between the wind speed and the difference.

  FIG. 10 shows the results of an outdoor experiment. The wind direction was blowing from the microphone 9 toward the speaker 5. As described above, a correlation is seen indoors, and a correlation is seen between wind speed and difference even outdoors. In the outdoors, the anemometer was placed on the speaker and microphone for synchronization, so it was considered that there was a deviation from the actual wind speed, but it was found that there was a change in sound speed due to the wind speed, and compensation is performed. It can be judged that this is effective.

  For reference, the experiment was performed with a background noise of 40 dB (F), an output sound pressure level of 80 dB (F), and a measurement distance of 0.5, 5, 10, 20, 0, 40, and 50 m. The sound wave of the M series code of the spread spectrum sound, the sound wave of frequency 24KHz, and the synchronization signal were created by a personal computer and outputted by the media processor. As described in FIGS. 1 and 2, the spread spectrum sound is output from the speaker through the audio amplifier of the moving position-measurement body 1. The synchronization signal is input to the wireless device and transmitted to the position measurement body 2 side for notification.

  In the position measurement body 2, after receiving and detecting the synchronization signal by the wireless device, the synchronization signal is output to the processor, and when the synchronization signal is recognized, the sound wave signal output from the microphone 9 is A / D converted. When sound wave data accumulates in the recording buffer, correlation processing is performed, the distance between the speaker 5 and the microphone 9 is calculated, and the result is transmitted to the personal computer of the position measuring body 1 via the wireless device and displayed. The distance acquisition interval is 350 ms.

  The result is shown in FIG. □ is an actual measurement error, and ◇ is a measurement error when compensated by using wind speed data. For □, the error after 20m becomes linearly worse. This is because the wind was blowing about 0.3 m / s from the microphone toward the speaker between 20 and 50 m. The result of recalculation by adding this wind speed to the sound speed is a plot of ◇. If the influence of wind is taken into consideration, the error is within 20 mm even within 50 m, and the position can be measured with considerable accuracy by compensating for the change in sound velocity due to the wind.

  This can be applied to a position measurement method that compensates for a change in sound speed based on the measurement result of wind speed using the Doppler effect described above, and in particular, a sound wave for position measurement transmitted from a position measurement object is spread spectrum. A sound wave of an M-sequence code of a sound, and a distance calculation method performed by a position measurement body that has received the sound wave performs a correlation process on the M-sequence code of the sound wave and performs a synchronization process, thereby obtaining an M-sequence code as a spread spectrum sound. The position can be measured with high accuracy by utilizing the excellent autocorrelation characteristics and noise resistance.

  As described above, the construction of the wireless network makes it easy to add and remove position measuring bodies, and can freely place them. In addition, an appropriate number of position measuring bodies are installed at predetermined positions on obstacles. Can be dealt with.

  As described above, the position measuring body may be one position measuring body in one dimension, and two position measuring bodies can be measured in two dimensions. In addition, by using sound waves of different M-sequence codes, it is possible to perform position measurement of two or more moving position measurement objects at the same time. And even if the position-measuring object is moved several tens of meters or more as described above, the position can be accurately measured with an error of several centimeters.

  The present invention enables accurate position measurement and wind speed measurement, weeding treatment by robots, etc. on terraced rice fields and terraced fields and terraced fields in agricultural fields, dome, logistics in the factory and outdoors, transportation self-propelled Widely used for bogie running and cleaning robots, self-running cart delivery and cleaning robots at airports, weeding robots, other navigation systems, indoor and outdoor wind circulation monitoring, meteorological data observation, road traffic wind speed information system, etc. be able to.

      DESCRIPTION OF SYMBOLS 1 ... Position measuring body 2 ... Position measuring body 3 ... Processor 5 ... Speaker 6, 7 ... Wireless device 8 ... Processor 9 ... Microphone

Claims (5)

  A position measurement method that compensates for changes in sound speed based on wind speed measurement results using the Doppler effect, and transmits a sound wave of a predetermined frequency from a position measurement body to be received by the position measurement body, and its reception time and transmission The Doppler effect is characterized in that the propagation time of the sound wave is calculated from the time, and the distance from the position measurement body is calculated and the position is measured by compensating for the change in sound velocity due to the wind based on the Doppler effect. Position measurement method using   A sound wave for position measurement and a sound wave with a constant frequency for wind speed compensation are alternately transmitted from a speaker from a moving position measurement object, received by a microphone of the position measurement object, and the distance of the position measurement object is sequentially calculated. The position measuring method using the Doppler effect according to claim 1, wherein the position is measured.   The position measurement sound wave transmitted from the position measurement object is an M-sequence code sound wave of spread spectrum sound, and the distance calculation method performed by the position measurement body that has received the sound wave correlates the M-sequence code of the sound wave. The position measurement method using the Doppler effect according to claim 1 or 2, wherein the synchronization processing is performed by performing the steps.   The position measurement using the Doppler effect according to any one of claims 1 to 3, wherein at least one position measurement body is provided, and the position measurement body is installed at a position where the distance from the moving position measurement body is several tens of meters or more. Method.   A sound wave having a predetermined frequency is transmitted from a sound wave transmitting body including a position measuring body and received by a sound wave receiving body including a position measuring body, and the sound wave is subjected to frequency analysis, and the sound wave is transmitted from the sound wave transmitting body based on the bandwidth of the spectral component. A wind speed measuring method using the Doppler effect, characterized by measuring the wind speed between receivers.

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