CN111965653A - Distance measurement method and system based on linear sweep frequency sound wave - Google Patents
Distance measurement method and system based on linear sweep frequency sound wave Download PDFInfo
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- CN111965653A CN111965653A CN202010671957.4A CN202010671957A CN111965653A CN 111965653 A CN111965653 A CN 111965653A CN 202010671957 A CN202010671957 A CN 202010671957A CN 111965653 A CN111965653 A CN 111965653A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
- G01S15/06—Systems determining the position data of a target
- G01S15/08—Systems for measuring distance only
- G01S15/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S15/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
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- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
Abstract
The invention discloses a distance measurement method and system based on linear sweep frequency sound waves, and belongs to the field of sound wave distance measurement. The method comprises the following steps: the generated sweep frequency period is T, and the lower limit of the frequency is fminAnd an upper frequency limit of fmaxThe linear sweep frequency sound wave is used as a transmitting signal, and a section of linear sweep frequency signal is generated by using the same sweep frequency parameters and is used as a reference signal; intercepting the received signals with the same time length and performing cross-correlation operation with the reference signals, and acquiring the corresponding position of the peak value as a signal alignment point; framing the received signals by time length T from a signal alignment point, mixing each frame of received signals with reference signals with the same time length, performing low-pass filtering on the mixed signals, and obtaining frequency difference through frequency spectrum analysis; and acquiring the target distance at the current moment by using the relation between the distance and the frequency difference of the target changed in any two frame times. The invention is not affected by the clock inconsistency of the transmitting and receiving ends, and can realize centimeter-level distance measurement on common audio equipment based on the accurate measurement and calculation of the target distance change quantity.
Description
Technical Field
The invention belongs to the field of acoustic ranging, and particularly relates to a ranging method and system based on linear sweep frequency acoustic waves.
Background
The traditional sound wave ranging principle is similar to the radar ranging principle, and the target distance is calculated by measuring the flight time delay of signals in the air, but the method requires the clocks of the signal receiving and transmitting devices to be strictly synchronized. Currently, a commonly applied method is to use a radio frequency signal as an inter-node synchronization signal, and calculate the inter-node distance by measuring the arrival time difference between a sound wave and the radio frequency signal, and in such a method, a custom module must be added to synchronize through a wireless signal, so that additional hardware cost is increased. In addition, with the TDOA technique, which measures the time difference between two nodes reaching a target node to obtain the distance difference between the two nodes and the target node, the TDOA-based ranging method has a lower requirement on time synchronization, but may have a higher requirement on the measurement accuracy of the time difference due to the smaller distance between the nodes.
The frequency of the sweep frequency signal in a single period changes linearly with the change of time, has good autocorrelation and is also commonly used in a radar ranging system. The method generally comprises the steps of carrying out frequency mixing processing on reflected waves and transmitted waves of frequency sweep signals, obtaining beat signals with frequencies in direct proportion to signal flight time delay, and obtaining the frequencies through frequency spectrum analysis so as to calculate target distances. However, the above method still requires that the clocks at the signal transmitting and receiving ends are strictly synchronous, and has certain limitations in application.
Disclosure of Invention
Aiming at the defects of the related art, the invention aims to provide a distance measuring method and system based on linear sweep frequency sound waves, and aims to solve the technical problem that clocks are not synchronous in the existing sound wave distance measuring technology.
In order to achieve the above object, an aspect of the present invention provides a distance measuring method based on linear sweep frequency acoustic waves, including the following steps:
the generated sweep frequency period is T, and the lower limit of the frequency is fminAnd an upper frequency limit of fmaxThe linear sweep frequency sound wave is used as a transmitting signal, and a section of linear sweep frequency signal is generated by using the same sweep frequency parameters and is used as a reference signal;
intercepting the received signals with the same time length and performing cross-correlation operation with the reference signals, and acquiring the position corresponding to the peak value of the cross-correlation result as a signal alignment point;
framing the received signal with a time duration T from the signal alignment point, mixing each frame of received signal with the reference signal of the same time duration,after low-pass filtering the mixing signal, obtaining the signal frequency difference through spectrum analysis
Wherein n is the current frame number;
and acquiring the target distance at the current moment by utilizing the relation between the distance of the target changed in any two frame times and the signal frequency difference.
Further, the relationship between the distance of the target changing in any two frame times and the signal frequency difference is
Wherein R isnIs the target distance, R, at the current time0And
respectively, a known initial position and a corresponding signal frequency difference, c is the propagation speed of sound in the air, T is the sweep frequency period, and B is the sweep frequency bandwidth.
Further, the time length of intercepting the received signal is 2T, and T is the sweep frequency period.
Further, the spectral analysis is FFT.
Further, before the received signal is intercepted, a butterworth filter is used for filtering the received signal, and normalization processing is performed.
According to another aspect of the present invention, there is provided a linear swept acoustic wave based ranging system comprising
A generating unit for generating a sweep frequency with a sweep period of T and a lower frequency limit of fminAnd an upper frequency limit of fmaxThe linear sweep frequency sound wave is used as a transmitting signal, and a section of linear sweep frequency signal is generated by using the same sweep frequency parameters and is used as a reference signal;
the pseudo-synchronization unit intercepts the received signals with the same time length and performs cross-correlation operation with the reference signals, and acquires the position corresponding to the peak value of the cross-correlation result as a signal alignment point;
a frequency difference obtaining unit for framing the received signals with a time length T from the signal alignment point, mixing each frame of the received signals with the reference signals with the same time length, low-pass filtering the mixed signals, and obtaining the signal frequency difference through spectrum analysis
Wherein n is the current frame number;
and the distance acquisition unit is used for acquiring the target distance at the current moment by utilizing the relation between the distance of the target changed in any two frame times and the signal frequency difference.
Further, in the distance obtaining unit, the relationship between the distance of the target changing in any two frame times and the signal frequency difference is
Wherein R isnIs the target distance, R, at the current time0And
respectively, a known initial position and a corresponding signal frequency difference, c is the propagation speed of sound in the air, T is the sweep frequency period, and B is the sweep frequency bandwidth.
Further, in the pseudo synchronization unit, the time length for intercepting the received signal is 2T, where T is the frequency sweep period.
Further, the spectral analysis is FFT.
Further, before the pseudo-synchronization unit intercepts the received signal, the received signal is filtered by using a butterworth filter and normalized.
Compared with the prior art, the technical scheme of the invention does not need to use other wireless signals to carry out clock synchronization, but utilizes the correlation of the frequency sweep signals to carry out pseudo synchronization on the received signals, thereby obtaining the target change distance in each frequency sweep period, and obtaining the absolute distance of the target relative to the transmitting end at any moment by obtaining the initial reference distance. The invention is not affected by the clock inconsistency of the transmitting and receiving ends, can realize centimeter-level distance measurement on common audio equipment based on the accurate measurement and calculation of the target distance change quantity, and the measurement range can meet the measurement requirement of common indoor scenes.
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FIG. 1 is a schematic diagram of the basic principle of an embodiment of the present invention;
fig. 2 is a schematic diagram of the relationship between the transmission signal, the reference signal and the difference frequency signal in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In order to achieve the above object, an embodiment of the present invention provides a distance measurement method based on linear sweep frequency acoustic waves, including the following steps:
the generated sweep frequency period is T, and the lower limit of the frequency is fminAnd an upper frequency limit of fmaxThe linear sweep frequency sound wave is used as a transmitting signal, and a section of linear sweep frequency signal is generated by using the same sweep frequency parameters and is used as a reference signal;
intercepting the received signals with the same time length and performing cross-correlation operation with the reference signals, and acquiring the position corresponding to the peak value of the cross-correlation result as a signal alignment point;
framing the received signals by time length T from the signal alignment point, mixing each frame of received signals with the reference signals with the same time length, low-pass filtering the mixed signals, and obtaining signal frequency difference through spectrum analysis
Wherein n isThe current frame number;
and acquiring the target distance at the current moment by utilizing the relation between the distance of the target changed in any two frame times and the signal frequency difference.
Further, the relationship between the distance of the target changing in any two frame times and the signal frequency difference is
Wherein R isnIs the target distance, R, at the current time0And
respectively, a known initial position and a corresponding signal frequency difference, c is the propagation speed of sound in the air, T is the sweep frequency period, and B is the sweep frequency bandwidth.
Further, the time length of intercepting the received signal is 2T, and T is the sweep frequency period.
Further, the spectral analysis is FFT.
Further, before the received signal is intercepted, a butterworth filter is used for filtering the received signal, and normalization processing is performed.
The principles of the above embodiments are described below:
the generated sweep frequency period is T, the sweep frequency bandwidth is B (the lower limit of frequency is f)minUpper limit of frequency fmax) The linear frequency modulation continuous wave is used as a transmitting signal; a linear swept frequency signal with only two consecutive periods is generated with the same parameters as a reference signal, as shown in fig. 1. The time when the receiving end receives the signal is taken as the starting point of the time shaft, and 0, 2T is intercepted]Performing cross correlation on the received signal in the interval and a reference signal, finding a corresponding point on a time axis according to a corresponding position of a cross correlation peak value, and taking the point as a received signal alignment point (shown in figure 2), thereby completing signal pseudo-synchronization;
the signal is framed with a duration T starting from the signal alignment point,mixing each frame signal with a monocycle reference signal, performing low-pass filtering on the mixed signal, and acquiring a signal frequency difference by using FFT (fast Fourier transform)
Where n is the current frame number, as shown in FIG. 2. According to the relation between the distance of the target changing in any two frame time and the signal frequency difference
Calculating the linear distance R of the target at the current momentnWherein R is0And
respectively, the known initial position and the corresponding signal frequency difference, c is the speed of sound propagation in air.
Just as the time of transmission of the signal is unknown to the receiving end, a reference signal is constructed locally at the receiving end, which differs from the actual transmitted signal by an unknown fixed time t0. The distance corresponding to any time is
Further can obtain
The contents of the above embodiments will be described with reference to a preferred embodiment.
Example one
Loudspeaker with FsThe sampling frequency of 44.1KHz generates a linear sweep frequency (chirp) signal with a frequency range of 14.5KHz-17KHz (sweep frequency bandwidth B of 2.5KHz) and a period T of 40ms, and the total duration is 2 minutes, so as to serve as a transmission signal.
The receiving equipment with the audio sampling frequency of 44.1KHz is adopted and is arranged at a determined distance R away from the signal transmitting end0In the position of (a). After the speaker transmits the signal, the receiving apparatus starts receiving the signal and stands still for 5s at the initial position. Then, the straight line distance of the opposite signal transmitting ends is changed until the signal acquisition is finished.
The distance measuring method comprises the following steps:
step one, filtering a received signal by using a Butterworth filter, and performing normalization processing;
intercepting the front 3528 sampling points (signals with the length of 2 periods) of the received signal, locally generating linear sweep frequency signals with the same length as reference signals, performing cross-correlation operation on the linear sweep frequency signals and the reference signals, and finding out signal alignment points according to the positions corresponding to cross-correlation peak values;
and thirdly, framing the received signal from the signal alignment point, wherein the length of a frame of signal is the same as the period of the chirp signal, and each frame of signal comprises 1764 sampling points. Mixing each frame of received signal with single-period standard chirp signal, low-pass filtering, removing DC component, and using FFT to obtain signal frequency difference
(n is the current frame number);
step four, obtaining the initial distance R0And the frequency difference of the original signal
On the basis of a formula
The distance R of the relative transmitting end at any subsequent time can be obtainedn. Wherein an initial distance R is obtained0And the frequency difference of the original signal
The method of (a) may be various methods known in the art and will not be described in detail herein.
The results of one test of this example are as follows:
| true distance/m | 0.5 | 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 |
| Estimate distance/m | 0.50 | 0.99 | 1.48 | 1.98 | 2.50 | 3.01 | 3.51 | 4.02 | 4.51 | 5.03 |
As can be seen from the above table, the error of the ranging method based on the linear sweep acoustic wave is only within 3 cm.
In another aspect, an embodiment of the present invention provides a distance measurement system based on linear swept-frequency acoustic waves, including
A generating unit for generating a sweep frequency with a sweep period of T and a lower frequency limit of fminAnd an upper frequency limit of fmaxThe linear sweep frequency sound wave is used as a transmitting signal, and a section of linear sweep frequency signal is generated by using the same sweep frequency parameters and is used as a reference signal;
the pseudo-synchronization unit intercepts the received signals with the same time length and performs cross-correlation operation with the reference signals, and acquires the position corresponding to the peak value of the cross-correlation result as a signal alignment point;
a frequency difference obtaining unit for framing the received signals with a time length T from the signal alignment point, mixing each frame of the received signals with the reference signals with the same time length, low-pass filtering the mixed signals, and obtaining the signal frequency difference through spectrum analysis
Wherein n is the current frame number;
and the distance acquisition unit is used for acquiring the target distance at the current moment by utilizing the relation between the distance of the target changed in any two frame times and the signal frequency difference.
The functions of each unit can be referred to the description of the foregoing method embodiments, and are not described herein again.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A distance measurement method based on linear sweep frequency sound waves is characterized by comprising the following steps:
the generated sweep frequency period is T, and the lower limit of the frequency is fminAnd an upper frequency limit of fmaxThe linear sweep frequency sound wave is used as a transmitting signal, and a section of linear sweep frequency signal is generated by using the same sweep frequency parameters and is used as a reference signal;
intercepting the received signals with the same time length and performing cross-correlation operation with the reference signals, and acquiring the position corresponding to the peak value of the cross-correlation result as a signal alignment point;
framing the received signals by time length T from the signal alignment point, mixing each frame of received signals with the reference signals with the same time length, low-pass filtering the mixed signals, and obtaining signal frequency difference through spectrum analysis
Wherein n is the current frame number;
and acquiring the target distance at the current moment by utilizing the relation between the distance of the target changed in any two frame times and the signal frequency difference.
2. The ranging method of claim 1, wherein the relationship between the distance of the target changing in any two frame times and the signal frequency difference is
Wherein R isnIs the target distance, R, at the current time0And
respectively, a known initial position and a corresponding signal frequency difference, c is the propagation speed of sound in the air, T is the sweep frequency period, and B is the sweep frequency bandwidth.
3. The ranging method according to claim 1 or 2, wherein the duration of intercepting the received signal is 2T, T being the sweep period.
4. A ranging method according to claim 1 or 2, characterized in that the spectral analysis is FFT.
5. A ranging method as claimed in claim 1 or 2, characterized in that the received signal is filtered using a butterworth filter and normalized before being intercepted.
6. A distance measuring system based on linear sweep frequency sound wave is characterized by comprising
A generating unit for generating a sweep frequency with a sweep period of T and a lower frequency limit of fminAnd an upper frequency limit of fmaxThe linear sweep frequency sound wave is used as a transmitting signal, and a section of linear sweep frequency signal is generated by using the same sweep frequency parameters and is used as a reference signal;
the pseudo-synchronization unit intercepts the received signals with the same time length and performs cross-correlation operation with the reference signals, and acquires the position corresponding to the peak value of the cross-correlation result as a signal alignment point;
a frequency difference obtaining unit for framing the received signals with a time length T from the signal alignment point, mixing each frame of the received signals with the reference signals with the same time length, low-pass filtering the mixed signals, and obtaining the signal frequency difference through spectrum analysis
Wherein n is the current frame number;
and the distance acquisition unit is used for acquiring the target distance at the current moment by utilizing the relation between the distance of the target changed in any two frame times and the signal frequency difference.
7. The ranging system according to claim 6, wherein the distance obtaining unit obtains the relationship between the distance of the target changing in any two frame times and the signal frequency difference as
Wherein R isnIs the target distance, R, at the current time0And
respectively, a known initial position and a corresponding signal frequency difference, c is the propagation speed of sound in the air, T is the sweep frequency period, and B is the sweep frequency bandwidth.
8. The ranging system according to claim 6 or 7, wherein the pseudo-synchronization unit intercepts the received signal for a duration of 2T, T being the sweep period.
9. The ranging system according to claim 6 or 7, wherein the spectral analysis is an FFT.
10. The ranging system according to claim 6 or 7, wherein the pseudo-synchronization unit filters the received signal using a butterworth filter and performs normalization processing before truncating the received signal.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2024106106A1 (en) * | 2022-11-14 | 2024-05-23 | 株式会社デンソー | Object detecting device |
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