Near-ultrasonic high-precision arrival time estimation method based on speed compensation

Abstract

The invention discloses a near-ultrasonic high-precision arrival time estimation method based on speed compensation. The method comprises the following steps of: transmitting a customized signal by adopting a static loudspeaker, and receiving a return signal through a microphone of the smart phone in a moving state; filtering the return signal to obtain a rising / falling linear frequency modulation signal; respectively carrying out cross-correlation processing on the time offset and a customized signal to output respective cross-correlation results, and extracting corresponding time offset; adjusting the customized signal according to the two time offsets to generate a reference signal of a rising / falling linear frequency modulation signal; according to the rising / falling linear frequency modulation signal and the corresponding reference signal, frequency mixing, filtering and fast Fourier transform processing are carried out in sequence, and then joint analysis and calculation processing is carried out to obtain arrival time estimation. The method does not depend on an additional sensor, carries out accurate arrival time estimation on the moving target, and can realize accurate arrival time estimation on the moving target in a complex indoor scene.

Description

Technical Field

[0001] The invention belongs to the technical field of indoor positioning, and in particular relates to a near-ultrasonic high-precision arrival time estimation method based on velocity compensation. Background Art

[0002] In recent years, with the continuous expansion of application fields, indoor positioning technology has attracted much attention. In areas such as public space navigation, it can not only provide services based on location information, but also be used to control indoor drones and industrial robots. Acoustic positioning technology transmits ultrasonic waves through a base station, and the receiving device receives the signal for positioning. This technology has strong anti-interference ability and uses methods such as filtering and cross-correlation to achieve high-precision positioning in a noisy environment. Acoustic positioning technology relies on high-precision arrival time estimation. However, when estimating the arrival time of a moving target, the Doppler effect will cause a certain offset in the estimated value. The positioning result calculated based on this arrival time has a large error. Therefore, it is of great significance for acoustic positioning to eliminate the influence of the Doppler effect and perform high-precision arrival time estimation for moving targets.

[0003] Some algorithms estimate the speed of moving targets in real time by adding sensors or emitting additional signals, and use the measured speed to correct the estimated arrival time. However, additional sensors often require strict data calibration and complex processing algorithms. In addition, it is difficult to estimate the speed of moving targets in real time using additional signals, and the deviation of speed estimation is large, resulting in poor estimation accuracy of arrival time.

[0004] Some other algorithms eliminate the influence of the Doppler effect through unique signal design, but the existing algorithms are limited in the accuracy of speed and arrival time estimation, making it difficult to achieve high-precision arrival time estimation for high-speed moving objects.

[0005] In summary, there is an urgent need for a high-precision arrival time estimation algorithm that can effectively compensate for Doppler shift. Summary of the invention

[0006] In view of the above problems existing in the prior art, the present invention provides a near-ultrasonic high-precision arrival time estimation algorithm based on velocity compensation, which does not rely on additional sensors and can accurately estimate the arrival time of a moving target.

[0007] The present invention adopts the following technical solutions:

[0008] The near-ultrasonic high-precision arrival time estimation method based on velocity compensation of the present invention comprises:

[0009] S1. A stationary speaker transmits a customized signal to the surrounding environment, and a smartphone microphone in motion receives the customized signal as a return signal.

[0010] S2, filtering and separating the return signal to separate the rising linear frequency modulation signal and the falling linear frequency modulation signal in the return signal;

[0011] S3, cross-correlating the rising linear frequency modulation signal and the falling linear frequency modulation signal with the custom signal respectively to output respective cross-correlation results, and extracting the time offset corresponding to the respective maximum values ​​in the two cross-correlation results;

[0012] S4, performing time shift adjustment and frequency expansion on the customized signal according to the two time offsets to generate two different reference signals, which are used as reference signals of the rising linear frequency modulation signal and the falling linear frequency modulation signal respectively;

[0013] S5. Perform mixing, filtering, and fast Fourier transform processing in sequence according to each linear frequency modulation signal in the up-linear frequency modulation signal and the down-linear frequency modulation signal and its corresponding reference signal, and then perform joint analysis and calculation processing in combination with the two time offsets to obtain an arrival time estimate.

[0014] The custom signal in S1 is set according to the following formula:

[0015] s(t)=s up (t)+s down (t)

[0016]

[0017] The customized signal is mainly composed of an ascending linear frequency modulation signal and a descending linear frequency modulation signal, wherein and Denote the starting frequencies of the rising linear frequency modulation signal and the falling linear frequency modulation signal, B up and B down They represent the bandwidth of the rising linear FM signal and the falling linear FM signal respectively, T represents the duration of the signal, t represents time, t∈[0,T].

[0018] The cross-correlation in step S3 adopts generalized cross-correlation.

[0019] In S4, the customized signal is time-shifted and frequency-extended according to the following settings:

[0020] The starting time of the reference signal corresponding to the rising linear frequency modulation signal is A represents the time shift adjustment parameter, and the frequency is Expand in a way that the ratio remains unchanged;

[0021] The starting time of the reference signal corresponding to the falling linear frequency modulation signal is Frequency according to The expansion is performed in a way that the ratio remains unchanged.

[0022] The specific steps of S5 are:

[0023] S5.1. For each linear frequency modulation signal in the rising linear frequency modulation signal and the falling linear frequency modulation signal and its corresponding reference signal, mixing, filtering, and fast Fourier transform processing are performed in sequence to obtain respective intermediate frequency signal spectrum diagrams;

[0024] S5.2, jointly analyzing the intermediate frequency signal spectrograms of the ascending linear frequency modulation signal and the descending linear frequency modulation signal to obtain the average frequency of the direct signal;

[0025] S5.3. Based on the frequency mean and time offset of the customized signal and direct signal and The computation process obtains an arrival time estimate.

[0026] The specific steps of S5.1 are:

[0027] S5.1.1, mixing the up-linear frequency modulation signal and the down-linear frequency modulation signal with their corresponding reference signals to obtain respective mixed signals, and then filtering them to obtain respective intermediate frequency signals;

[0028] S5.1.2. Perform fast Fourier transform on the respective intermediate frequency signals to obtain the intermediate frequency signal spectrum diagram of the respective linear frequency modulation signals.

[0029] The specific steps of S5.2 are:

[0030] S5.2.1. Perform peak detection on the intermediate frequency signal spectra of the rising linear frequency modulation signal and the falling linear frequency modulation signal respectively;

[0031] S5.2.2. In the intermediate frequency signal spectrum of the rising linear frequency modulation signal / falling linear frequency modulation signal, extract the frequency corresponding to the peak with the largest power after satisfying the following formula as the direct signal peak frequency

[0032]

[0033] in and They represent the starting frequencies of the rising linear FM signal and the falling linear FM signal, respectively, and v max Indicates the maximum speed of the smartphone microphone.

[0034] S5.3.3. Perform a weighted average of the direct signal peak frequencies of the ascending linear frequency modulation signal and the descending linear frequency modulation signal to obtain a direct signal frequency mean.

[0035] The arrival time estimation in S5.3 is obtained specifically by the following formula:

[0036]

[0037] Among them, τ d represents the estimated arrival time, Indicates the time offset corresponding to the maximum value in the result of the cross-correlation between the rising linear frequency modulation signal and the custom signal, represents the time offset corresponding to the maximum value in the cross-correlation result between the down-converted linear frequency modulation signal and the customized signal, A represents the time shift adjustment parameter, B up represents the bandwidth of the rising linear FM signal, and T represents the duration of the signal.

[0038] The beneficial effects of the present invention are:

[0039] A mixed signal of 16-19kHz and 22-19kHz is used as the transmitting signal; a bandpass filter is used to separate the upchirp and downchirp linear frequency modulation signals in the received signal; the GCC is used to roughly estimate the arrival time and the FMCW algorithm is used to jointly estimate the peak frequency corresponding to the direct signal, thus achieving accurate arrival time estimation of mobile targets in complex indoor scenarios.

[0040] The invention proposes a near-ultrasonic high-precision arrival time estimation algorithm based on velocity compensation, which has high precision and good robustness and can accurately estimate the arrival time of a moving target. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 It is a flow chart of a near-ultrasonic high-precision arrival time estimation algorithm based on velocity compensation described in the present invention;

[0043] Figure 2 It is the waveform diagram and spectrogram of the customized signal;

[0044] Figure 3 is a schematic diagram of the design scheme of the reference signal;

[0045] Figure 4 is a spectrum diagram of the intermediate frequency signal of the rising linear frequency modulation signal and the falling linear frequency modulation signal; DETAILED DESCRIPTION

[0046] The following describes the embodiments of the present invention through specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0047] like Figure 1 As shown, the specific embodiment of the near-ultrasonic high-precision arrival time estimation method of the present invention includes the following steps:

[0048] S1. A stationary speaker transmits a customized signal to the surrounding environment, and the customized signal is received as a return signal by the microphone of a smartphone in motion; the return signal includes a direct signal;

[0049] like Figure 2 and Figure 3 As shown, the custom signal in S1 is set according to the following formula:

[0050] s(t)=s up (t)+s down (t)

[0051]

[0052] The customized signal is mainly composed of a rising linear frequency modulation signal s up (t) and the falling linear frequency modulation signal s down (t) is composed of and Denote the starting frequencies of the rising linear frequency modulation signal and the falling linear frequency modulation signal, B up and B down They represent the bandwidth of the rising linear FM signal and the falling linear FM signal respectively, T represents the duration of the signal, t is the time, t∈[0,T].

[0053] like Figure 2 As shown, the customized signal mainly consists of an ascending linear frequency modulation signal and a descending linear frequency modulation signal;

[0054] In this embodiment, the duration of the customized signal is 40 ms, the frequency of the up-FM signal is 16-19 kHz, the spectrum of the down-FM signal is 22-19 kHz, the sampling frequency is 48 kHz, and the signal refresh rate is 5 Hz.

[0055] Indoor positioning technology based on near-ultrasound often adopts TDOA algorithm, and the acoustic signal needs to select a signal with inaudible frequency band and good correlation. Linear sweep signal meets the above requirements, its frequency changes linearly with time, and the signal has good correlation.

[0056] In this embodiment, the upper and lower cutoff frequencies of the bandpass filter for separating the rising linear frequency modulation signal are 15.9kHz and 19.1kHz respectively, and the order is 20; the upper and lower cutoff frequencies of the bandpass filter for separating the falling linear frequency modulation signal are 18.9kHz and 22.1kHz respectively, and the order is 20.

[0057] S2, using a filter to perform bandpass filtering and separation processing on the return signal to separate the rising linear frequency modulation signal and the falling linear frequency modulation signal in the return signal;

[0058] Ignoring multipath propagation, the return signal s r (t) is:

[0059]

[0060] The moving microphone separates the received signal into an ascending linear frequency modulation signal through a bandpass filter. and down-converting linear FM signals

[0061]

[0062] where t d is the delay time of signal propagation, and α is the attenuation coefficient.

[0063] Where h up (t) and h down (t) represent the separated rising linear frequency modulation signal and down-converting linear FM signals The bandpass filter, * represents the convolution operation. The above formula represents filtering the received signal to separate the received rising linear frequency modulation signal and the falling linear frequency modulation signal.

[0064] Since the transmission signal is a mixed signal of an upchirp signal and a downchirp signal, in order to avoid mutual interference between the two, a bandpass filter must be designed to effectively separate them.

[0065] S3, cross-correlate the rising linear frequency modulation signal and the falling linear frequency modulation signal with the custom signal respectively, output their respective cross-correlation results, and extract the time offset corresponding to the respective maximum values ​​in the two cross-correlation results and

[0066] The cross-correlation adopts generalized cross-correlation (GCC).

[0067] and is the time offset corresponding to the respective maximum values ​​in the two cross-correlation results:

[0068]

[0069] Where R up (τ) and R down (τ) represent the results of upchirp and downchirp cross-correlation, respectively.

[0070] S4. Based on two time offsets and Performing time shift adjustment and frequency extension on the customized signal to generate two different reference signals, which are used as reference signals of the rising linear frequency modulation signal and the falling linear frequency modulation signal respectively;

[0071] The custom signal is time-shifted and frequency-extended according to the following settings:

[0072] The starting time of the reference signal corresponding to the rising linear frequency modulation signal is A represents the time shift adjustment parameter, and the frequency is The frequency is expanded in a manner that the ratio remains unchanged; in this embodiment, the frequency expansion is 16-20.5kHz;

[0073] The starting time of the reference signal corresponding to the falling linear frequency modulation signal is Frequency according to The frequency is expanded in a manner that the ratio remains unchanged. In this embodiment, the frequency is expanded to 22-17.5kHz, and A is taken as 10ms.

[0074] In this embodiment, the starting time of the reference signal corresponding to the rising linear frequency modulation signal is The duration is 60ms, and the frequency is extended to 16-20.5kHz; the start time of the reference signal corresponding to the falling linear FM signal is The duration is 60ms and the frequency is extended to 22-17.5kHz.

[0075] Reference signal design: By optimizing the start time and bandwidth of the reference signal, the algorithm's estimation accuracy of delay is enhanced.

[0076] S5. Perform mixing, filtering, and fast Fourier transform processing in sequence according to each linear frequency modulation signal in the up-linear frequency modulation signal and the down-linear frequency modulation signal and its corresponding reference signal, and then perform joint analysis and calculation processing in combination with the two time offsets to obtain an arrival time estimate.

[0077] The specific steps of S5 are:

[0078] S5.1. For each linear frequency modulation signal in the rising linear frequency modulation signal and the falling linear frequency modulation signal and its corresponding reference signal, mixing, filtering, and fast Fourier transform processing are performed in sequence to obtain respective intermediate frequency signal spectrum diagrams;

[0079] S5.1 The specific steps are:

[0080] S5.1.1, mixing the up-linear frequency modulation signal and the down-linear frequency modulation signal with their corresponding reference signals to obtain respective mixed signals, and then filtering them with a low-pass filter to obtain respective intermediate frequency signals;

[0081] S5.1.2. Perform fast Fourier transform on the respective intermediate frequency signals to obtain the intermediate frequency signal spectrum diagram of the respective linear frequency modulation signals.

[0082] This step will obtain the intermediate frequency signal and corresponding spectrum diagram of the rising linear frequency modulation signal, and the intermediate frequency signal and corresponding spectrum diagram of the falling linear frequency modulation signal;

[0083] like Figure 4 As shown, mixing is performed without considering the Doppler effect. Using the formula And use the low-pass filter to obtain the intermediate frequency signal of the rising linear frequency modulation signal

[0084]

[0085] Consider that the signal speaker is stationary, the microphone moves at a speed v relative to the speaker, and the distance between the microphone and the speaker is R. At this time, the intermediate frequency signal can be expressed as:

[0086]

[0087] Where c is the propagation speed of the sound signal in the air. Ignore the higher-order terms and consider The frequency of the intermediate frequency signal can be expressed as:

[0088]

[0089] The arrival time between the microphone and the speaker can be obtained by estimating the frequency of the intermediate frequency signal. However, it can be concluded from the above formula that the frequency of the intermediate frequency signal is affected by the movement speed of the microphone, which in turn affects the final arrival time estimation.

[0090] The intermediate frequency signal corresponding to the down-converted linear frequency modulation signal The frequency should be:

[0091]

[0092] In the proposed signal design scheme, the custom signal we designed satisfies This condition. Therefore, the following formula is obtained:

[0093]

[0094] S5.2, jointly analyzing the intermediate frequency signal spectrograms of the ascending linear frequency modulation signal and the descending linear frequency modulation signal to obtain the average frequency of the direct signal;

[0095] S5.2 The specific steps are:

[0096] S5.2.1. Perform peak detection on the intermediate frequency signal spectra of the rising linear frequency modulation signal and the falling linear frequency modulation signal respectively;

[0097] S5.2.2. When jointly analyzing the frequency spectra of the intermediate frequency signals corresponding to the rising linear frequency modulation signal and the falling linear frequency modulation signal, the proposed customized constraint condition is used to find the peak frequency.

[0098] In the intermediate frequency signal spectrum of the rising linear frequency modulation signal / falling linear frequency modulation signal, extract the frequency corresponding to the peak with the largest power after satisfying the following formula as the direct signal peak frequency

[0099]

[0100] in and They represent the starting frequencies of the rising linear FM signal and the falling linear FM signal, respectively, and v max Indicates the maximum speed of the smartphone microphone.

[0101] In this embodiment, the maximum speed of the moving target is 1.5 m / s, and the speed of sound is 346.15 m / s. 22kHz, The calculated frequency difference is 164.67 Hz. To enhance the robustness of the algorithm, the threshold is amplified by 1.5 times, that is, 247.01 Hz. In this embodiment, B is 247.01 Hz.

[0102] Joint analysis: In order to improve the robustness of the algorithm and accurately estimate the arrival time of the faster microphone, the set constraints are used. The constraints refer to the above formulas. The peak values ​​of the intermediate frequency spectra of the rising linear FM signal and the falling linear FM signal that meet the conditions are extracted respectively.

[0103] S5.2.3. Perform a weighted average of the direct signal peak frequencies of the ascending linear frequency modulation signal and the descending linear frequency modulation signal to obtain a direct signal frequency mean.

[0104] Speed ​​compensation: To eliminate the influence of Doppler effect on arrival time estimation, the peak frequencies of the up-line FM signal and the down-line FM signal are added together to eliminate the influence of speed on arrival time estimation in the frequency domain. When the microphone moves fast, the peak frequencies of the up-line FM signal and the down-line FM signal differ too much, such as Figure 4 As shown, direct addition will result in the generation of erroneous peaks.

[0105] S5.3. Based on the frequency mean and time offset of the customized signal and direct signal and The computation process obtains an arrival time estimate.

[0106] The arrival time estimation is obtained by the following formula:

[0107]

[0108] Among them, τ d represents the estimated arrival time, Indicates the time offset corresponding to the maximum value in the result of the cross-correlation between the rising linear frequency modulation signal and the custom signal, represents the time offset corresponding to the maximum value in the cross-correlation result between the down-converted linear frequency modulation signal and the customized signal, A represents the time shift adjustment parameter, B up represents the bandwidth of the rising linear FM signal, and T represents the duration of the signal.

[0109] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A near-ultrasonic high-precision arrival time estimation method based on velocity compensation, characterized in that: Includes steps: S1. A stationary speaker transmits a customized signal to the surrounding environment, and a smartphone microphone in motion receives the customized signal as a return signal. S2, filtering and separating the return signal to separate the rising linear frequency modulation signal and the falling linear frequency modulation signal in the return signal; S3, cross-correlating the rising linear frequency modulation signal and the falling linear frequency modulation signal with the custom signal respectively to output respective cross-correlation results, and extracting the time offset corresponding to the respective maximum values ​​in the two cross-correlation results; S4, performing time shift adjustment and frequency expansion on the customized signal according to the two time offsets to generate two different reference signals, which are used as reference signals of the rising linear frequency modulation signal and the falling linear frequency modulation signal respectively; S5. Perform mixing, filtering, and fast Fourier transform processing in sequence according to each linear frequency modulation signal in the up-linear frequency modulation signal and the down-linear frequency modulation signal and its corresponding reference signal, and then perform joint analysis and calculation processing in combination with the two time offsets to obtain an arrival time estimate.

2. The method for near-ultrasonic high-precision arrival time estimation based on velocity compensation according to claim 1, characterized in that: The custom signal in S1 is set according to the following formula: s(t)=s up (t)+s down (t) The customized signal is mainly composed of an ascending linear frequency modulation signal and a descending linear frequency modulation signal, wherein and Denote the starting frequencies of the rising linear frequency modulation signal and the falling linear frequency modulation signal, B up and B down They represent the bandwidth of the rising linear FM signal and the falling linear FM signal respectively, T represents the duration of the signal, t represents time, t∈[0,T].

3. The method for near-ultrasonic high-precision arrival time estimation based on velocity compensation according to claim 1, characterized in that: The cross-correlation in step S3 adopts generalized cross-correlation.

4. The method for near-ultrasonic high-precision arrival time estimation based on velocity compensation according to claim 1, characterized in that: In S4, the customized signal is time-shifted and frequency-extended according to the following settings: The starting time of the reference signal corresponding to the rising linear frequency modulation signal is A represents the time shift adjustment parameter, and the frequency is Expand in a way that the ratio remains unchanged; The starting time of the reference signal corresponding to the falling linear frequency modulation signal is Frequency according to The expansion is performed in a way that the ratio remains unchanged.

5. The method for near-ultrasonic high-precision arrival time estimation based on velocity compensation according to claim 1, characterized in that: The specific steps of S5 are: S5.

1. For each linear frequency modulation signal in the rising linear frequency modulation signal and the falling linear frequency modulation signal and its corresponding reference signal, mixing, filtering, and fast Fourier transform processing are performed in sequence to obtain respective intermediate frequency signal spectrum diagrams; S5.2, jointly analyzing the intermediate frequency signal spectrograms of the ascending linear frequency modulation signal and the descending linear frequency modulation signal to obtain the average frequency of the direct signal; S5.

3. Based on the frequency mean and time offset of the customized signal and direct signal and The computation process obtains an arrival time estimate.

6. The method for near-ultrasonic high-precision arrival time estimation based on velocity compensation according to claim 5, characterized in that: The specific steps of S5.1 are: S5.1.1, mixing the up-linear frequency modulation signal and the down-linear frequency modulation signal with their corresponding reference signals to obtain respective mixed signals, and then filtering them to obtain respective intermediate frequency signals; S5.1.

2. Perform fast Fourier transform on the respective intermediate frequency signals to obtain the intermediate frequency signal spectrum diagram of the respective linear frequency modulation signals.

7. The method for near-ultrasonic high-precision arrival time estimation based on velocity compensation according to claim 5, characterized in that: The specific steps of S5.2 are: S5.2.

1. Perform peak detection on the intermediate frequency signal spectra of the rising linear frequency modulation signal and the falling linear frequency modulation signal respectively; S5.2.

2. In the intermediate frequency signal spectrum of the rising linear frequency modulation signal / falling linear frequency modulation signal, extract the frequency corresponding to the peak with the largest power after satisfying the following formula as the direct signal peak frequency in and They represent the starting frequencies of the rising linear FM signal and the falling linear FM signal, respectively, and v max Indicates the maximum speed of the smartphone microphone. S5.3.

3. Perform a weighted average of the direct signal peak frequencies of the ascending linear frequency modulation signal and the descending linear frequency modulation signal to obtain a direct signal frequency mean.

8. The method for near-ultrasonic high-precision arrival time estimation based on velocity compensation according to claim 7, characterized in that: The arrival time estimation in S5.3 is obtained specifically by the following formula: Among them, τ d represents the estimated arrival time, Indicates the time offset corresponding to the maximum value in the result of the cross-correlation between the rising linear frequency modulation signal and the custom signal, represents the time offset corresponding to the maximum value in the cross-correlation result between the down-converted linear frequency modulation signal and the customized signal, A represents the time shift adjustment parameter, B up represents the bandwidth of the rising linear FM signal, and T represents the duration of the signal.

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