JP2023031336A - Signal processing device, sound wave system, and vehicle - Google Patents

Abstract

To detect reflected waves with good accuracy even when the number of transmitted sound waves is small.SOLUTION: A signal processing device (1) comprises: a transmission wave signal generation unit (161) configured to generate a transmission wave signal for transmission of a sound wave; reception wave signal output units (13, 14, 15) configured to output a reception wave signal based on reception of the sound wave; a reference data storage unit (162) configured to store reference data; and detection units (163, 164, 165) configured to detect the reflected wave of the transmitted wave that is included in the received wave, on the basis of a correlation between the reception wave signal and the reference data. The reference data represents the output signal of the reception wave signal output unit in a first period in which the transmission wave generation unit outputs the transmission wave signal and a second period of a prescribed length that continues following the first period in succession.SELECTED DRAWING: Figure 4

Description

The invention disclosed in this specification provides a signal processing device for processing a transmission signal for transmitting sound waves and a reception signal based on reception of sound waves, a sound wave system including the signal processing device, and It relates to a vehicle equipped with the sound wave system.

2. Description of the Related Art Conventionally, an ultrasonic system is known that measures the distance to an obstacle by measuring the time TOF (Time Of Flight) from the time an ultrasonic wave is generated until the reflected wave from the obstacle returns. Such ultrasonic systems are often installed in vehicles, and one example is known as an in-vehicle clearance sonar.

WO2020/004609

For example, the ultrasonic system described in Patent Document 1 prepares waveform data (reference data) expected to be received, and detects a reflected wave based on the correlation between the reference data and the actually received signal. do.

However, the ultrasonic system described in Patent Literature 1 has a problem that the accuracy of detection of reflected waves deteriorates when the number of transmitted ultrasonic waves is small. For example, in the ultrasonic system described in Patent Document 1, in order to distinguish between a received signal with a frequency of 58 kHz and a received signal with a frequency of 59 kHz, the number of waves of ultrasonic waves to be transmitted is set to 29 waves at the minimum, and the mutual phase must be shifted by one period or more.

The signal processing device disclosed herein includes a transmission signal generation unit configured to generate a transmission signal for transmitting a sound wave, and a reception signal based on reception of the sound wave. a reference data storage unit configured to store reference data; and based on the correlation between the received wave signal and the reference data, included in the received wave and a detector configured to detect a reflected wave of the transmitted wave obtained, wherein the reference data is generated during a first period during which the transmitted wave signal generator outputs the transmitted wave signal and during the first period. It is the output signal of the received wave signal output section in a second period of a predetermined length that continues continuously.

The acoustic wave system disclosed in the present specification includes the signal processing device configured as described above and an acoustic wave transmitting/receiving device configured to be directly or indirectly connected to the signal processing device. .

The vehicle disclosed herein is configured to include the acoustic wave system configured as described above.

According to the signal processing device, the sound wave system, and the vehicle disclosed in this specification, reflected waves can be accurately detected even if the number of transmitted sound waves is small.

FIG. 1 is a diagram schematically showing a vehicle equipped with an ultrasonic system according to an embodiment and an object. FIG. 2 is a diagram for explaining an example of correlation processing. FIG. 3 is a diagram for explaining an example of correlation processing. FIG. 4 is a diagram showing the configuration of the ultrasound system according to the embodiment. FIG. 5 is a diagram for explaining the operation during transmission of the ultrasound system according to the embodiment. FIG. 6 is a time chart showing signals appearing on the secondary side of the transformer during transmission of the ultrasound system according to the embodiment. FIG. 7 is a diagram for explaining the operation of the ultrasound system according to the embodiment when receiving waves.

An embodiment of the present invention will be described below with reference to the drawings. The ultrasonic system according to the embodiment described below is assumed to be mounted on a vehicle as an example, and measures the distance between the vehicle and an object to provide an alarm function, an automatic braking function, and an automatic It can be used for parking functions, etc.

<Correlation processing>
First, an outline of correlation processing used in the ultrasound system according to the embodiment will be described. FIG. 1 shows a vehicle 200 equipped with an ultrasound system 100 (hereinafter referred to as “ultrasound system 100”) according to an embodiment, and an object (obstacle) 300 . Ultrasonic waves transmitted from the ultrasonic system 100 are reflected by the object 300 and received by the ultrasonic system 100 as reflected waves. At this time, the ultrasound system 100 also receives environmental noise N. FIG.

Here, correlation processing will be described using FIGS. 2 and 3. FIG. In FIG. 2, reference data Dref is prepared in advance. The reference data Dref is waveform data of a reflected wave expected to be received, and is waveform data having the same frequency as the frequency of the sound wave to be transmitted. The frequency of the received reflected wave Rs1 shown in FIG. 2 is the same as the transmission frequency. Therefore, in the correlation result C1 obtained by the correlation processing of multiplying the reference data Dref and the reflected wave Rs1, the correlation value is always a positive value as shown in FIG. As a result, the convolution integral value obtained by temporally integrating the correlation result C1 becomes large, and the reflected wave is emphasized.

On the other hand, the frequency of the received environmental noise N shown in FIG. 3 is shifted from the transmission frequency. That is, the frequency of the environmental noise N deviates from the frequency of the reference data Dref. Therefore, as shown in FIG. 3, in the correlation result C2, there is a period in which the correlation value is negative, and the convolution integral value is smaller than in FIG. In this way, it is possible to distinguish between transmitted and reflected waves and environmental noise.

<Ultrasonic system>
Next, the ultrasound system 100 will be described. FIG. 4 is a diagram showing the configuration of the ultrasound system 100. As shown in FIG.

The ultrasound system 100 includes a signal processing device 1 , a transformer Tr, and an ultrasound transmission/reception device 2 . The ultrasonic transmission/reception device 2 is externally connected to the signal processing device 1 via a transformer Tr. Note that the transformer Tr may not necessarily be provided.

The signal processing device 1 is a semiconductor integrated circuit device. The signal processing device 1 includes a DAC (Digital to Analog Converter) 11, a driver 12, an LNA (Low Noise Amplifier) 13, an LPF (Low Pass Filter) 14, an ADC (Analog to Digital Converter) 15, and a digital processing It includes a portion 16 and external terminals T1 to T5.

The DAC 11 D/A converts the transmission signal output from the transmission signal generation unit 161 included in the digital processing unit 16 from a digital signal to an analog signal, and outputs the signal after the D/A conversion to the driver 12 .

The output terminals of the differential pair of the driver 12 are connected to the primary side of the transformer Tr via external terminals T1 and T2. An ultrasonic transmission/reception device 2 is connected to the secondary side of the transformer Tr. A driver 12 drives the ultrasonic transmission/reception device 2 based on the output signal of the DAC 11 .

The ultrasonic transmission/reception device 2 has a piezoelectric element (not shown) and transmits and receives ultrasonic waves. That is, the ultrasonic transmission/reception device 2 functions both as a sound source and as a reception section.

The input terminals of the differential pair of LNA 13 are connected to the secondary side of transformer Tr via external terminals T3 and T4. The output signal of LNA 13 is supplied to ADC 15 via LPF 14 . The ADC 15 A/D-converts the output signal of the LNA 13 from an analog signal to a digital signal, and outputs the A/D-converted signal to the reference data storage section 162 and the correlation processing section 163 included in the digital processing section 16 .

The LNA 13, the LPF 14, and the ADC 15 are an example of a received wave signal output unit configured to output a received wave signal based on received ultrasonic waves.

The digital processing unit 16 includes a transmission signal generation unit 161, a reference data storage unit 162, a correlation processing unit 163, a correlation value summation unit 164, a threshold determination unit 165, a TOF measurement unit 166, and an interface 167. , provided.

The transmission signal generator 161 is configured to generate a transmission signal for transmitting ultrasonic waves. More specifically, upon receiving a wave transmission command from an ECU (Electronic Control Unit) (not shown) mounted on the vehicle 200 (see FIG. 1) via the interface 47, the wave transmission signal generator 161 generates a predetermined wave number. A transmission signal containing the signal is generated, and the transmission signal is output to the DAC 11 .

The reference data storage unit 162 is configured to store reference data. Details of the reference data will be described later. For example, a register can be used for the reference data storage unit 162 .

The correlation processing unit 163 performs correlation processing based on the received wave signal output from the ADC 15 and the reference data stored in the reference data storage unit 162 at a predetermined cycle.

Correlation value summation section 164 outputs a correlation convolution integral value by calculating the sum of the correlation processing results by correlation processing section 163 . It should be noted that the correlation convolution integral value to be output may be a value obtained by truncating a negative value such that the negative value of the calculated result is 0.

A threshold determination unit 165 compares the correlation convolution integral value with a predetermined threshold. The threshold determination unit 165 detects a reflected wave from the object 300 when the correlation convolution integral value exceeds a predetermined threshold.

The correlation processing unit 163, the correlation value summation unit 164, and the threshold determination unit 165 are configured to detect a reflected wave of the transmitted wave that may be included in the received wave, based on the correlation between the received wave signal and the reference data. 1 is an example of a reflected wave detection unit.

The TOF measuring unit 166 uses a counter 166A to measure the time (TOF) from when the ultrasonic wave is transmitted until when the reflected wave from the object 300 is received.

The interface 47 conforms to LIN (Local Interconnect Network), for example, and communicates with an ECU (not shown) mounted on the vehicle 200 (see FIG. 1) via an external terminal T5.

Next, the operation of the ultrasound system 100 configured as described above during wave transmission will be described with reference to FIG. First, when the transmitted wave signal generation unit 161 receives a wave transmission command from an ECU (not shown) mounted on the vehicle 200 (see FIG. 1) via the interface 167, the transmitted wave signal generation unit 161 generates a predetermined number of waves (for example, 16 waves) is output to the DAC 11 . As a result, ultrasonic waves are transmitted from the ultrasonic transmission/reception device 2 . Also, the TOF measurement unit 166 starts counting by the counter 166A at the timing when the wave transmission command is received.

It is desirable to change the frequency of the transmission signal for each transmission. For example, the transmission signal generation unit 161 may change the frequency of the transmission signal in order of, for example, 56 kHz, 57 kHz, 58 kHz, 59 kHz, 60 kHz, 61 kHz, 56 kHz, 57 kHz, 58 kHz, . For example, random numbers may be used to randomly change between 56 kHz, 57 kHz, 58 kHz, 59 kHz, 60 kHz, and 61 kHz. The ultrasonic system 100 changes the frequency of the transmission signal for each transmission, so that, for example, an ultrasonic wave transmitted from another vehicle of the same type as the vehicle 200 (see FIG. 1) can be transmitted from the vehicle 200 (see FIG. 1). It is possible to reduce the possibility of erroneously recognizing that it is a reflected wave of a transmitted ultrasonic wave.

Then, a first period P1 (see FIG. 6 described later) during which the transmitted wave signal generation unit 161 outputs the transmitted wave signal, and a second period P2 (see FIG. 6 described later) having a predetermined length continuously following the first period P1 ), the LNA 13, LPF 14, and ADC 15, that is, the received wave signal output unit operates, and the reference data storage unit 162 stores the received wave signal output unit in the first period P1 and the second period P2 (see FIG. 6 described later). Store the output signal as reference data. During the second period (see FIG. 6, which will be described later), reverberation occurs in the ultrasonic transmission/reception device 2 . Therefore, the reference data is data corresponding to the transmitted wave signal and reverberation.

FIG. 6 is a time chart showing signals appearing on the secondary side of the transformer Tr when the ultrasound system 100 transmits waves. The horizontal axis of FIG. 6 indicates time, and the vertical axis of FIG. 6 indicates the frequency of the signal. FIG. 6 shows signals appearing on the secondary side of the transformer Tr when the frequencies of the transmission signals are set to 56 kHz, 57 kHz, 58 kHz, 59 kHz, 60 kHz and 61 kHz. As can be seen from FIG. 6, even if the frequencies of the transmitted wave signals are different, the trajectories of the reverberant frequencies are almost the same. The reverberation frequency trajectory is determined by the characteristics of external components such as the transformer Tr and the ultrasonic transmission/reception device 2 . Therefore, the reverberant frequency locus is unique to the ultrasound system 100 .

FIG. 7 is a diagram for explaining the operation of the ultrasound system 100 when receiving waves. When the ultrasound system 100 receives waves, the LNA 13 , LPF 14 and ADC 15 , that is, the received wave signal output section first outputs the received wave signal to the correlation processing section 163 . Correlation processing section 163 performs correlation processing based on the received wave signal and the reference data. Further, the correlation value summation unit 164 calculates the sum of the correlation processing results by the correlation processing unit 163 and outputs a correlation convolution integral value. Then, threshold determination section 165 compares the correlation convolution integral value with a predetermined threshold. The TOF measurement unit 166 causes the counter 166A to continue counting when the threshold determination unit 165 determines that the correlation convolution integral value is equal to or less than the predetermined threshold value, and the threshold determination unit 165 determines that the correlation convolution integration value exceeds the predetermined threshold value. When it is determined that it exceeds, the count value of the counter 166A at that timing is held. The count value held by the TOF measurement unit 166 corresponds to the TOF, and the distance to the object can be specified by the TOF and the velocity of the ultrasonic waves transmitted from the ultrasonic transmitter/receiver. The count value held by TOF measurement unit 166 is sent via interface 47 to an ECU (not shown) mounted on vehicle 200 (see FIG. 1).

In the ultrasound system 100, as described above, the reference data is data corresponding not only to the transmitted wave signal but also to the reverberation. can be detected with high accuracy.

As described above, the reverberation frequency trajectory is determined by the characteristics of external components such as the transformer Tr and the ultrasonic transmission/reception device 2 . The characteristics of the external parts may change, for example, depending on whether or not foreign matter (for example, raindrops, mud, etc.) adheres to the ultrasonic transmitter/receiver 2 . Therefore, the reference data storage unit 162 is preferably configured to store the reference data each time the transmission signal generator outputs the transmission signal. As a result, the ultrasonic system 100 can accurately detect reflected waves even when the characteristics of the external component have changed.

Also, it is desirable that the length of the second period P2 is equal to or shorter than the length of the first period P1. As can be seen from FIG. 6, the frequency becomes unstable in the second half of the reverberation. By setting the lengths of the first period P1 and the second period P2 so that the length of the second period P2 is equal to or less than the length of the first period P1, the part where the reverberation frequency is unstable can be referred to. You can avoid being included in the data. Thereby, the detection accuracy of the reflected wave can be further improved.

Also, it is desirable that the length of the second period P2 is at least half the length of the first period P1. By setting each length of the first period P1 and the second period P2 so that the length of the second period P2 is half or more of the length of the first period P1, if the reference data is only the transmission signal, Since the data also correspond to the reverberation, the effect of improving the detection accuracy of the reflected wave can be obtained more reliably.

<Others>
In addition to the above-described embodiment, the configuration of the present invention can be modified in various ways without departing from the gist of the invention. The above embodiments should be considered illustrative in all respects and not restrictive, and the technical scope of the present invention is indicated by the scope of claims rather than the description of the above embodiments. It should be understood that all modifications that fall within the meaning and range of equivalents of the claims are included.

For example, the correlation processing unit 163, the correlation value summation unit 164, and the threshold determination unit 165 may be used not only as a reflected wave detection unit, but also as a situation change detection unit configured to detect a situation change. good.

When the signal processing device 1 is configured to include a situation change detection section, the reference data storage section 162 is configured to store a plurality of reference data generated at different timings. The situation change detection unit is configured to detect a situation change based on the correlation between the plurality of reference data.

For example, the correlation processing unit 163 performs correlation processing based on the latest reference data and past reference data having the same transmission signal frequency as the latest reference data. Further, the correlation value summation unit 164 calculates the sum of the correlation processing results by the correlation processing unit 163 and outputs a correlation convolution integral value. Then, threshold determination section 165 compares the correlation convolution integral value with a predetermined threshold. When the threshold value determination unit 165 determines that the correlation convolution integral value exceeds the predetermined threshold value, the threshold value determination unit 165 sends a signal from the interface 47 to the vehicle to indicate that there is no change in the situation such as a change in the characteristics of the external components. 200 (see FIG. 1) is transmitted to an ECU (not shown). On the other hand, when the threshold value determination unit 165 determines that the correlation convolution integral value is equal to or less than the predetermined threshold value, the threshold value determination unit 165 outputs a signal indicating that a situation change such as a characteristic change of an external component has occurred. 47 to an ECU (not shown) mounted on vehicle 200 (see FIG. 1).

The signal processing device 1 can detect a situation change such as foreign matter (for example, raindrops, mud, etc.) adhering to the ultrasonic transmitter/receiver 2 by including the above-described situation change detection unit. It should be noted that although the reflected wave detection unit and the situation change detection unit can be provided as separate circuits, by using a common circuit as described above, the size and cost of the signal processing device 1 can be reduced. be able to.

In the above embodiment, the ultrasonic system 100 that transmits ultrasonic waves (sound waves with a high frequency exceeding audible sound) has been described, but the present invention is also applicable to a sound wave system that transmits sound waves other than ultrasonic waves. can do.

The signal processing apparatus (1) described above includes a transmission signal generator (161) configured to generate a transmission signal for transmitting a sound wave, and a reception signal based on the reception of the sound wave. a reference data storage unit (162) configured to store reference data; and a correlation between the received wave signal and the reference data a detector (163, 164, 165) configured to detect a reflected wave of the transmitted wave that may be included in the received wave based on the reference data, the transmitted wave signal generator is the output signal of the received wave signal output section in a first period for outputting the transmitted wave signal and a second period of a predetermined length following the first period continuously (first configuration).

Since the signal processing device having the first configuration can include reverberation in the reference data, it is possible to accurately detect reflected waves even if the number of transmitted sound waves is small.

In the signal processing device having the first configuration, the reference data storage unit is configured to store the reference data each time the transmission signal generation unit outputs the transmission signal (second 2 configuration).

In the signal processing device having the second configuration, reflected waves can be detected with high accuracy even when the characteristics of external parts attached to the signal processing device change.

In the signal processing device having the first or second configuration, the length of the second period may be shorter than or equal to the length of the first period (third configuration).

The signal processing device having the third configuration can further improve the detection accuracy of the reflected wave.

In the signal processing device having the third configuration, the length of the second period may be half or more of the length of the first period (fourth configuration).

In the signal processing device having the fourth configuration, the reference data is data corresponding not only to the transmitted wave signal but also to the reverberation, so that the effect of improving the detection accuracy of the reflected wave can be obtained more reliably.

The signal processing device having any one of the first to fourth configurations further includes a situation change detection unit (163, 164, 165) configured to detect a situation change, wherein the reference data storage unit is different A configuration ( 5th configuration).

The signal processing device having the fifth configuration can detect a situation change such as foreign matter (for example, raindrops, mud, etc.) adhering to an external component.

The sound wave system (100) described above includes a signal processing device having any one of the first to fifth configurations, and a sound wave transmitting/receiving device (2) configured to be directly or indirectly connected to the signal processing device. ) and a configuration (sixth configuration).

The sound wave system having the sixth configuration can accurately detect reflected waves even when the number of transmitted sound waves is small.

The vehicle (200) described above has a configuration (seventh configuration) including the sound wave system of the sixth configuration.

In the vehicle having the seventh configuration, it is possible to use the detection result of the sound wave system that can accurately detect reflected waves even if the number of transmitted sound waves is small.

1 signal processing device 2 ultrasonic transmission/reception device 11 DAC
12 driver 13 LNA
14LPF
15 ADCs
16 digital processing unit 161 transmission signal generation unit 162 reference data storage unit 163 correlation processing unit 164 correlation value summation unit 165 threshold determination unit 166 TOF measurement unit 166A counter 167 interface 100 ultrasonic system according to the embodiment 200 vehicle 300 object (Obstacle)
T1 to T5 External terminal Tr Transformer

Claims (7)

a transmit signal generator configured to generate a transmit signal for transmitting an acoustic wave;
a received wave signal output unit configured to output a received wave signal based on received sound waves;
a reference data store configured to store reference data;
a reflected wave detector configured to detect a reflected wave of the transmitted wave that may be included in the received wave based on the correlation between the received wave signal and the reference data;
with
The reference data is the output signal of the received wave signal output section during a first period during which the transmitted wave signal generation section outputs the transmitted wave signal and a second period of a predetermined length following the first period. There is a signal processor. 2. The signal processing apparatus according to claim 1, wherein said reference data storage unit is configured to store said reference data each time said transmission signal generation unit outputs said transmission signal. 3. The signal processing device according to claim 1, wherein the length of said second period is equal to or shorter than the length of said first period. 4. The signal processing device according to claim 3, wherein the length of said second period is half or more of the length of said first period. further comprising a situation change detection unit configured to detect a situation change;
The reference data storage unit is configured to store a plurality of the reference data generated at different timings,
The signal processing device according to any one of claims 1 to 4, wherein the situation change detection unit is configured to detect the situation change based on a correlation between a plurality of the reference data. A signal processing device according to any one of claims 1 to 5;
a sound wave transceiver configured to be directly or indirectly connected to the signal processing device. A vehicle comprising the acoustic wave system of claim 6 .

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