Sound wave processing device and ultrasonic system

Abstract

This sonicator (1) comprises: a wave transmission signal generation unit (41) which generates a transmission signal for transmitting a sound wave; a received wave signal output unit (3) which outputs a received wave signal based on the received wave of the sound wave; a correlation convolution integration processing unit (43) which performs a correlation convolution integration process in parallel for each of the reference wave data on the basis of the received wave signal and a plurality of pieces of reference wave data (Ref1 to RefN); and a self-wave identification unit (44) which determines whether the received sound wave is a self-wave which is a reflected wave of the sound wave that is transmitted by the wave transmission signal generation unit, on the basis of a correlation convolution integral value that is output from the correlation convolution integration processing unit.

Description

Technical Field

[0001] The present disclosure relates to a sound wave processing device and an ultrasonic system.

Background Art

[0002] Conventionally, an ultrasonic system that measures the distance to an obstacle by generating a sound wave and measuring the time of flight (TOF) until the reflected wave from the obstacle returns is known. Conventionally, such an ultrasonic system is often mounted on a vehicle, and as an example, an in-vehicle clearance sonar is known.

[0003] As an example of such a conventional ultrasonic system, there is a method of preparing waveform data (reference wave data) that is expected to be received, and performing correlation convolution integration processing based on the reference wave data and the actually received signal to enhance the reflected wave. Such a method is also called a pulse compression method and can improve the S / N ratio. The pulse compression method is described in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in an ultrasonic system, it is necessary to distinguish between a reflected wave (self-wave) transmitted from its own ultrasonic system and reflected by an object, and an ultrasonic wave (other-wave) transmitted from another ultrasonic system.

[0006] In particular, in-vehicle clearance sonars have recently increased in the types of vehicles they are mounted on and the purposes for which they are mounted, and interference by ultrasonic waves transmitted from other sonars has become a problem.

[0007] In view of the above circumstances, this disclosure aims to provide an acoustic wave processing device that achieves self-wave identification through an effective configuration. [Means for solving the problem]

[0008] The sound wave processing device relating to this disclosure is A transmission signal generation unit that generates a transmission signal for transmitting sound waves, A receiving signal output section that outputs a receiving signal based on the reception of sound waves, A correlation convolution integration processing unit performs correlation convolution integration processing in parallel for each of the reference wave data based on the received signal and a plurality of reference wave data, A self-wave identification unit determines whether the received sound wave is a self-wave, which is a reflected sound wave of the sound wave transmitted by the transmission signal generation unit, based on the correlation convolution integral value output from the correlation convolution integral processing unit. It has a configuration that includes the following: [Effects of the Invention]

[0009] According to the sound wave processing device of this disclosure, self-wave identification can be achieved with an effective configuration. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with an ultrasonic system and an object. [Figure 2] Figure 2 is a diagram illustrating an example of correlation processing. [Figure 3] Figure 3 is a diagram illustrating an example of correlation processing. [Figure 4] Figure 4 shows the configuration of the receiving processing unit in the comparative example. [Figure 5A] Figure 5A shows the received signal from the simulation results for the comparative example (number of samples = 128). [Figure 5B] Figure 5B shows the correlation convolution integral values ​​of the simulation results for the comparative example (sample size = 128). [Figure 6A]FIG. 6A is a diagram showing a received signal of a simulation result according to a comparative example (number of samples = 256). [Figure 6B] FIG. 6B is a diagram showing a correlation convolution integral value of a simulation result according to a comparative example (number of samples = 256). [Figure 7] FIG. 7 is a diagram showing a configuration of an ultrasonic system according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing a specific configuration example of a correlation processing unit and a correlation processing value summation unit. [Figure 9] FIG. 9 is a table showing an example of a correlation maximum value. [Figure 10] FIG. 10 is a schematic diagram showing a state where a vehicle equipped with an ultrasonic system moves. [Figure 11A] FIG. 11A is a diagram showing a received signal of a simulation result according to a comparative example (when the vehicle is stopped). [Figure 11B] FIG. 11B is a diagram showing a correlation convolution integral value of a simulation result according to a comparative example (when the vehicle is stopped). [Figure 12A] FIG. 12A is a diagram showing a received signal of a simulation result according to a comparative example (when the vehicle is moving). [Figure 12B] FIG. 12B is a diagram showing a correlation convolution integral value of a simulation result according to a comparative example (when the vehicle is moving). [Figure 13] FIG. 13 is a diagram showing a configuration of an ultrasonic system according to the third embodiment. [Figure 14] FIG. 14 is a schematic diagram showing an example in which a plurality of ultrasonic systems are mounted on a vehicle.

MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, exemplary embodiments will be described with reference to the drawings. Note that the ultrasonic system according to the embodiments described below is assumed to be mounted on a vehicle as an example, and can be used for an alarm function, an automatic braking function, an automatic parking function, etc. by measuring the distance between the vehicle and an object.

[0012] <1. About correlation processing> First, let's explain the overview of the correlation processing used in the ultrasonic system. Figure 1 shows a vehicle 500 equipped with an ultrasonic system (not shown) and an object (obstacle) 1000. The ultrasonic waves transmitted from the ultrasonic system are reflected by the object 1000 and received by the ultrasonic system as reflected waves.

[0013] Here, the correlation process will be explained using Figures 2 and 3. In Figure 2, the reference wave data Dref is prepared in advance. The reference wave data Dref is the waveform data of the reflected wave that is expected to be received, and it is waveform data with the same frequency as the frequency of the transmitted sound wave. The frequency of the received reflected wave Rs1 shown in Figure 2 is the same as the transmitted frequency. That is, the reflected wave Rs1 is the self-wave. Therefore, in the correlation result C1 obtained by the correlation process of multiplying the reference wave data Dref and the reflected wave Rs1, the correlation processed value is always a positive value, as shown in Figure 2. As a result, the convolution integral value obtained by integrating the correlation result C1 over time becomes large.

[0014] On the other hand, the frequency of the received reflected wave Rs2, shown in Figure 3, is different from the transmission frequency. That is, the reflected wave Rs2 is a different wave, and its frequency is different from the frequency of the reference wave data Dref. Therefore, as shown in Figure 3, the correlation result C2 will have a period in which the correlation processing value is negative, and the convolution integral value will be smaller than that in Figure 2. In this way, the local wave and other waves can be distinguished.

[0015] <2. Comparative Examples> Before describing the embodiments, a comparative example for comparison with the embodiments will be described. Figure 4 shows the configuration of the receiving processing unit 10 according to the comparative example. The receiving processing unit 10 shown in Figure 4 includes an A / D conversion unit 6, a reference wave storage unit 7, a correlation convolution integration processing unit 8, and a comparator 9.

[0016] The A / D conversion unit 6 performs A / D (analog-to-digital) conversion on the received signal Rsv based on the received ultrasound. The reference wave storage unit 7 stores reference wave data that has the same frequency as the ultrasound transmitted from the ultrasound system, including the receiving processing unit 10.

[0017] The correlation convolution integral processing unit 8 comprises a correlation processing unit 81 and a correlation processing value summing unit 82. The correlation processing unit 81 has a buffer (not shown) capable of storing a predetermined number of samples of the received signal Rsv converted by the A / D conversion unit 6. The correlation processing unit 81 calculates a correlation processing value by multiplying the received signal Rsv stored in the buffer with the reference wave data for each sample. The correlation processing value summing unit 82 calculates the correlation convolution integral value by calculating the sum of the sample-by-sample correlation processing values ​​calculated by the correlation processing unit 81.

[0018] The comparator 9 compares the correlation convolution integral value output from the correlation processing value summing unit 82 with a threshold Th and outputs a determination signal Cmpout as a result of the comparison. If the correlation convolution integral value exceeds the threshold Th, a determination signal Cmpout is output indicating that a reflected wave (self-wave) based on ultrasound transmitted from the ultrasound system including the receiving processing unit 10 has been received.

[0019] In this manner, the receiving processing unit 10 sequentially stores the received signal Rsv in a buffer, calculates the correlation convolution integral value, and compares the calculated correlation convolution integral value with a threshold value. Here, an example of the simulation results of the receiving processing unit 10 will be explained using Figures 5A, 5B and 6A, 6B.

[0020] Figures 5A and 5B show the simulation results when an ultrasonic system including a receiving processing unit 10 transmits an ultrasonic wave at 58 kHz as an example, and the reflected wave based on the transmitted ultrasonic wave is received. Figure 5A shows the waveform of the received signal Rsv. Figure 5B shows the result of correlation convolution integration processing based on the received signal Rsv. Note that Figures 5A and 5B show the case where the number of samples used for correlation convolution integration processing is 128, and since there are 8 samples for one wave transmitted, 128 / 8 = 16 waves of ultrasonic waves are transmitted. However, the left side of Figure 5B shows the case where the reference wave data is 57 kHz, and the right side shows the case where the reference wave data is 58 kHz. The correlation convolution integral value is a waveform that oscillates between positive and negative.

[0021] As shown in Figure 5A, the received wave is a reflected wave with ambient noise superimposed on the transmitted ultrasound (S / N ratio = 3dB in Figure 5A). Due to this ambient noise, as shown in Figure 5B, the difference between the maximum value (positive value) of the correlation convolution integral based on the 57kHz reference wave data, which is a frequency shifted from the frequency of the transmitted ultrasound, and the maximum value of the correlation convolution integral based on the 58kHz reference wave data, which is the frequency of the transmitted ultrasound, is small. Therefore, it is difficult to set a threshold Th between the two maximum values.

[0022] In contrast, Figures 6A and 6B show the simulation results when the number of samples is set to 256 (number of transmitted waves = 256 / 8 = 32). Figure 6A shows the received signal Rsv, and Figure 6B shows the result of the correlation convolution integral processing. As shown above, by increasing the number of samples from 128 to 256, the difference in the maximum values ​​of the correlation convolution integral becomes larger, as shown in Figure 6B, making it easier to set a threshold Th between the two maximum values.

[0023] However, increasing the number of samples necessitates increasing the buffer capacity. Increasing the buffer capacity leads to increased costs for the circuitry used for correlation convolution integration. Furthermore, from the perspective of the lifespan of the ultrasonic system, a lower wavenumber is preferable.

[0024] Furthermore, as the distance between the ultrasonic system and the object increases, the power of the transmitted ultrasonic waves attenuates before they are reflected by the object and received, causing the absolute value of the correlation convolution integral to decrease. For example, the amplitude of the waveforms shown in Figures 5B and 6B decreases. This necessitates control to dynamically change the threshold Th according to the distance.

[0025] <3. First Embodiment> To solve the problems in the above comparative example, the first embodiment described below is implemented. Figure 7 shows the configuration of the ultrasonic system 100 according to the first embodiment.

[0026] The ultrasonic system 100 includes a sound wave processing device 1, an ultrasonic transceiver 5, and a transformer Tr. The ultrasonic transceiver 5 is externally connected to the sound wave processing device 1 via the transformer Tr. Note that the transformer Tr is not necessarily required.

[0027] The sound wave processing device 1 is a semiconductor device that integrates a driver unit 2, an analog front end 3, and a digital processing unit 4 onto a single chip. The driver unit 2 has a DA circuit 21. The DA circuit 21 performs D / A conversion from a digital signal to an analog signal using the transmission signal output from the transmission signal generation circuit 41 included in the digital processing unit 4. The DA circuit 21 is connected to the primary side of the transformer Tr via external terminals T1 and T2.

[0028] An ultrasonic transceiver 5 is connected to the secondary side of the transformer Tr. The ultrasonic transceiver 5 has a piezoelectric element (not shown) and transmits and receives ultrasonic waves. In other words, the ultrasonic transceiver 5 functions as both a sound source and a receiver.

[0029] The analog front end 3 (receiving signal output section) includes an LNA (low-noise amplifier) ​​31, an LPF (low-pass filter) 32, and an A / D converter 33. The primary side of the transformer Tr is connected to the LNA 31 via external terminals T3 and T4. The output of the LNA 31 is input to the A / D converter 33 via the LPF 32.

[0030] The digital processing unit 4 includes a transmission signal generation circuit 41, a register (reference wave storage unit) 42, a correlation convolution integration processing unit 43, a self-wave identification unit 44, a BPF (bandpass filter) 45, an envelope detection unit 46, a comparator 47, a TOF measurement unit 48, and a serial interface 49.

[0031] Register 42 stores reference wave data Ref1 to RefN (N: an integer of 2 or more). In other words, register 42 stores multiple reference wave data. Reference wave data Ref1 to RefN are waveform data of neighboring frequencies, including the frequency of the ultrasonic waves transmitted from the ultrasonic transceiver 5 by the transmission signal generation circuit 41 (hereinafter referred to as the transmission frequency). For example, the above neighboring frequencies include frequencies shifted by 1 kHz from the transmission frequency. For example, if the transmission frequency is 58 kHz, one example of reference wave data could be Ref1=55 kHz, Ref2=56 kHz, Ref3=57 kHz, Ref4=58 kHz, Ref5=59 kHz, Ref6=60 kHz, Ref7=61 kHz (N=7). Note that the above 1 kHz is just one example of a shift between adjacent frequencies, but it may be possible to select the shift.

[0032] The BPF45 extracts and outputs a signal within a predetermined bandwidth from the received signal output from the A / D converter 33. This predetermined bandwidth includes the transmission frequency. This allows for the removal of received signals with frequencies significantly different from the transmission frequency. The predetermined bandwidth may be selectable. For example, it may be selectable between the transmission frequency ±1kHz and the transmission frequency ±8kHz.

[0033] The envelope detection unit 46 detects the envelope of the received signal output from the BPF 45 and outputs the detected envelope. The comparator 47 compares the detected envelope with a predetermined threshold Th 47 and outputs the comparison result. The envelope detection unit 46 and the comparator 47 can detect when an ultrasonic wave with a certain amount of power has been received, and as will be described later, self-wave determination during no-signal periods can be avoided.

[0034] The correlation convolution integration processing unit 43 includes a correlation processing unit 431 and a correlation processing value summing unit 432.

[0035] The correlation processing unit 431 has a buffer (not shown) capable of storing a predetermined number of samples of the received signal output from the BPF 45. The correlation processing unit 431 calculates a correlation processing value by multiplying the received signal stored in the buffer with each of the reference wave data Ref1 to RefN for each sample. That is, a correlation processing value is calculated for each of the reference wave data Ref1 to RefN. The correlation processing value summing unit 432 calculates a correlation convolution integral value for each of the reference wave data Ref1 to RefN by summing the individual correlation processing values ​​calculated by the correlation processing unit 431. That is, a correlation convolution integral value is calculated for each of the reference wave data Ref1 to RefN.

[0036] Here, Figure 8 shows a specific configuration example of the correlation processing unit 431 and the correlation processing value summing unit 432. As shown in Figure 8, the correlation processing unit 431 has a shift register SR and multiplication units M0 to Mn. The shift register SR functions as a buffer.

[0037] The shift register SR has a group of flip-flops DF0 to DFn. Each of the flip-flop groups DF0 to DFn consists of a number of D flip-flops equal to the number of bits in the received signal fin(t). For example, if the received signal fin(t) is 12 bits, each of the flip-flop groups DF0 to DFn consists of 12 D flip-flops.

[0038] The flip-flop groups DF0 to DFn are arranged in order from the preceding stage. The input terminal of the flip-flop group DF0 is connected to the received signal fin(t). In the flip-flop groups DF0 to DFn, the output terminal of the preceding stage is connected to the input terminal of the succeeding stage. The clock terminal of each of the flip-flop groups DF0 to DF is connected to the clock signal CK.

[0039] This shift register SR causes each output of the flip-flop group DF0 to DFn to be bit-shifted from the preceding stage to the succeeding stage each time a pulse of the clock signal CK is input. The outputs fin(t-0) to fin(tn) of the flip-flop group DF0 to DFn are input to the multipliers M0 to Mn, respectively. The reference wave data Table(0) to Table(n), stored in register 42, are also input to the multipliers M0 to Mn. Therefore, the bit data of the received signals fin(t-0) to fin(tn), stored (n+1 times) by the shift register SR, and the reference wave data Table(0) to Table(n) are multiplied by the multipliers M0 to Mn to output the correlated values ​​fconv(t-0) to fconv(tn).

[0040] The number of (n+1) sensors is set based on the transmission time (number of waves) of the transmitted signal and the sampling frequency of the received signal, and it is desirable to set it so that at least the received signal for the duration of the transmission time can be captured.

[0041] As shown in Figure 8, the correlation processing value summing unit 432 has a sum calculation unit SUM. The sum calculation unit SUM outputs the correlation convolution integral value by calculating the sum of the obtained correlation processing values ​​fconv(t-0) to fconv(tn).

[0042] The multiplication units M0 to Mn and the summation unit SUM are provided for each of the reference wave data Ref1 to RefN. In other words, N multiplication units M0 to Mn and summation units SUM are provided. This allows the correlation convolution integral value to be calculated for each of the reference wave data Ref1 to RefN.

[0043] In this manner, the correlation convolution integration processing unit 43 performs correlation convolution integration processing in parallel for each of the reference wave data Ref1 to RefN.

[0044] The self-wave identification unit 44 (Figure 7) includes a correlation maximum value acquisition unit 44A and a determination unit 44B. Based on the output from the comparator 47, the correlation maximum value acquisition unit 44A acquires the maximum value of the correlation convolution integral output from the correlation processing value summing unit 432 (correlation maximum value) during the period when the envelope detected by the envelope detection unit 46 exceeds the threshold Th47 (the period from when the envelope exceeds the threshold Th47 until it becomes less than or equal to the threshold Th47). The correlation maximum value is acquired for each reference wave data Ref1 to RefN. It is desirable to acquire the maximum value of the absolute value of the correlation convolution integral value. However, it is also acceptable to acquire the maximum value of only the positive values ​​of the correlation convolution integral value, or the maximum value of only the absolute value of the negative values.

[0045] The determination unit 44B determines, based on the maximum correlation value obtained by the maximum correlation value acquisition unit 44A, whether or not the ultrasonic waves received by the ultrasonic transceiver 5 are reflected waves (self-waves) based on the ultrasonic waves transmitted from the ultrasonic transceiver 5 by the transmission signal generation circuit 41.

[0046] As a first determination method by the determination unit 44B, the determination unit 44B determines whether or not a wave is the local wave by checking whether the frequency of the reference wave data with the maximum value among the maximum correlation values ​​for each reference wave data Ref1 to RefN matches the transmission frequency.

[0047] Here, Figure 9 is a table showing an example of the maximum correlation obtained when the self-wave is received with a transmission frequency of 58 kHz, and the reference wave data Ref1 to RefN are reference wave data from 55 kHz to 61 kHz (N=7). Note that Figure 9 shows the results for combinations of sample size conditions (sample size = 128 or 256) and noise conditions superimposed on the received signal (no noise, S / N = 3 dB, S / N = 0.5 dB).

[0048] Thus, even with a sample size of 128, which is less than 256, and even when noise is superimposed (S / N = 3dB or 0.5dB), the frequency at which the maximum value ("94" or "86") is obtained among the maximum correlation values ​​for each reference wave data Ref1 to RefN is 58kHz, which is the transmission frequency, making it possible to determine that it is the local wave.

[0049] Furthermore, as a second determination method by the determination unit 44B, the determination unit 44B obtains the top three maximum correlation values ​​from each of the reference wave data Ref1 to RefN, and if the frequencies of the obtained maximum correlation values ​​are three adjacent frequencies, it determines whether or not it is the local wave by checking whether the frequency midway between those adjacent frequencies is the transmission frequency.

[0050] For example, if the transmission frequency is 58kHz, the determination is made based on whether the top three frequencies of the acquired maximum correlation values ​​are adjacent frequencies of 57kHz, 58kHz, and 59Hz. In the example shown in Figure 9, even if the number of samples is 128, which is less than 256, and even if noise is superimposed (S / N = 3dB or 0.5dB), the frequencies of the top three maximum correlation values ​​("72, 94, 84" and "66, 86, 78") are adjacent frequencies of 57kHz, 58kHz, and 59Hz, so it can be determined that it is the local wave.

[0051] In particular, with this second determination method, the maximum correlation value of the transmission frequency and the maximum correlation value of the transmission frequency and adjacent frequencies fluctuate up and down, so even if the maximum correlation value of the transmission frequency is not the maximum correlation value for each reference wave data Ref1 to RefN, misidentification as not being the local wave is suppressed.

[0052] Thus, in this embodiment, instead of an absolute evaluation comparing the correlation convolution integral value with a threshold as in the comparative example, a relative evaluation is performed on the correlation convolution integral value for each reference wave data Ref1 to RefN. This makes it possible to identify the self-wave even with a small number of samples and even when noise is superimposed on the received signal. Since the required number of samples is reduced, the circuit cost for correlation convolution integration processing can be reduced. Furthermore, even when the distance between the ultrasonic system 100 and the object increases and the correlation convolution integral value becomes small, the self-wave can still be identified by the relative evaluation described above. This eliminates the need for dynamic control of the threshold as explained in the comparative example.

[0053] The TOF measurement unit 48 uses a counter 481 to measure the time (TOF) from the time it takes to transmit an ultrasonic wave until the reflected wave is received from the target object. The counter 481 starts counting when the transmission signal generation circuit 41 starts transmitting. The TOF measurement unit 48 continues counting with the counter 481 until the determination unit 44B determines that it is the local wave. If the determination unit 44B determines it is the local wave, the counter 481 retains the count value at that time. The retained count value corresponds to the TOF, and the distance to the target object can be determined by the TOF and the speed of sound.

[0054] The serial interface 49, for example, conforms to DSI3 and communicates with an external ECU (vehicle electronic control unit) (not shown) via the external terminal T5. The count value held above is sent to the ECU by interface 49.

[0055] <4. Second Embodiment> The method of comparing a threshold value with a correlation convolution integral value using a single reference wave data and a received signal, as shown in the comparative example above (Figure 4), has the following problems. As shown in Figure 10, when the vehicle 500 equipped with the ultrasonic system including the receiving processing unit 10 according to the comparative example is moving, or when the object 1000 is moving, a phenomenon occurs (Doppler shift) in which ultrasonic waves with a frequency shifted from the frequency of the transmitted ultrasonic waves are received due to the Doppler effect.

[0056] The frequency variation due to the Doppler effect is expressed by the following equation (1). f=((V-v0)(V+vs) / (V+v0)(V-vs))·f0 (1) However, f: received frequency, V: speed of sound, vs: speed of sound source, v0: speed of object, f0: transmitted frequency

[0057] Here, Figures 11A and 11B show the simulation results when a vehicle equipped with an ultrasonic system including a receiving processing unit 10 is stopped (the target object is also stopped), and the ultrasonic system transmits ultrasonic waves at, for example, 58 kHz (transmission frequency = 58 kHz), and the reflected waves based on the transmitted ultrasonic waves are received. Figure 11A shows the waveform of the received signal Rsv. Figure 11B shows the result of correlation convolution integration processing based on the received signal Rsv. However, in Figure 11B, the left side shows the case when the reference wave data is 58 kHz, and the right side shows the case when the reference wave data is 59 kHz.

[0058] In this case, the frequency of the received signal equals the transmission frequency of 58 kHz. As shown in Figure 11B, the maximum value of the correlation convolution integral based on the 58 kHz reference wave data (stored in the reference wave storage unit 7) becomes large, and it can be determined that it is the local wave by comparing it with the threshold Th.

[0059] On the other hand, Figures 12A and 12B show the simulation results when a vehicle is approaching an object at 20 km / h (the object is stationary). Figure 12A shows the waveform of the received signal Rsv. Figure 12B shows the result of correlation convolution integration processing based on the received signal Rsv. However, in Figure 12B, the left side shows the case when the reference wave data is 58 kHz, and the right side shows the case when the reference wave data is 59 kHz.

[0060] In this case, due to the Doppler effect, the frequency of the received signal becomes 58.9 kHz, which is a deviation from the transmission frequency of 58 kHz. As a result, as shown in Figure 12B, the maximum value of the correlation convolution integral based on the 58 kHz reference wave data becomes smaller, and there is a risk that it may be misidentified as not being the local wave when compared with the threshold Th.

[0061] As shown in the comparative example, the Doppler effect may cause a misidentification of a signal as not being the local wave, even though it is actually the local wave being received. The second embodiment described below is implemented to solve this problem.

[0062] The configuration of the ultrasonic system according to the second embodiment is the same as that of the first embodiment described above (Figure 7). In the second embodiment, two transmissions are performed, and the processing by the self-wave identification unit 44 is as follows.

[0063] The correlation maximum value acquisition unit 44A acquires the maximum correlation value for each reference wave data during the first transmission, similar to the first embodiment. The determination unit 44B identifies the frequency of the reference wave data for which the acquired maximum correlation value is maximized.

[0064] The correlation maximum value acquisition unit 44A acquires the maximum correlation value for each reference wave data during the second transmission, similar to the first embodiment. The determination unit 44B identifies the frequency of the reference wave data for which the acquired maximum correlation value is the largest. The determination unit 44B then determines that the received ultrasonic wave is the local wave if the frequency identified during the first transmission and the frequency identified during the second transmission are the same.

[0065] In the example mentioned earlier, where the vehicle is moving at 20 km / h, both the frequency identified during the first transmission and the frequency identified during the second transmission will be 59 kHz, making it possible to determine that it is the vehicle's own signal.

[0066] The processing in self-wave identification 44 may also be carried out as follows.

[0067] The correlation maximum value acquisition unit 44A acquires the correlation maximum value for each reference wave data during the first transmission, similar to the first embodiment. The determination unit 44B identifies the frequency in the middle of the three frequencies if the top three frequencies among the acquired correlation maximum values ​​are three adjacent frequencies.

[0068] The correlation maximum value acquisition unit 44A acquires the correlation maximum value for each reference wave data during the second transmission, similar to the first embodiment. The determination unit 44B identifies the frequency of the acquired correlation maximum value, similar to the first transmission. The determination unit 44B then determines that the received ultrasonic wave is the local wave if the frequency identified during the first transmission is the same as the frequency identified during the second transmission.

[0069] Thus, according to the second embodiment, even if the relative speed between the vehicle and the object is unknown, the influence of the Doppler effect in self-wave detection can be suppressed. Note that the number of transmissions is not limited to two, but may be three or more.

[0070] <5. Third Embodiment> The third embodiment described here, like the second embodiment, is implemented to solve the problems caused by the Doppler effect. Figure 13 shows the configuration of the ultrasonic system 100 according to the third embodiment. The configuration shown in Figure 13 differs from the second embodiment (Figure 7) in that it does not have an envelope detection unit 46 and a comparator 47, and the configuration of the self-wave identification unit 44 is different. In this embodiment, the self-wave identification unit 44 has a comparator 44C and a determination unit 44D.

[0071] In this embodiment, the transmitting signal generation circuit 41 transmits ultrasonic waves of a first frequency (e.g., 58 kHz) and ultrasonic waves of a second frequency (e.g., 56 kHz) different from the first frequency in succession from the ultrasonic transmitting / receiving device 5.

[0072] The comparator 44C compares the correlation convolution integral value for each reference wave data output from the correlation processing value summing unit 432 with a predetermined threshold. The determination unit 44D determines that the received ultrasonic wave is the local wave if the frequency shifts of the reference wave data whose correlation convolution integral value exceeds the threshold are in the same direction and by the same amount.

[0073] For example, if the first frequency is 58kHz and the second frequency is 56kHz, and the reflected waves received due to the Doppler effect shift from the first and second frequencies to 59kHz and 57kHz, then since each shift is in the same direction and by the same amount (+1kHz), it can be determined that these are the original waves.

[0074] According to this embodiment, the self-wave can be identified with a single transmission while suppressing the effects of the Doppler effect. Furthermore, the self-wave can be identified by a combination of the first and second frequencies. Note that the frequencies of the continuously transmitted ultrasonic waves may be three or more frequencies.

[0075] <6. Multiple Ultrasound Systems> Figure 14 shows, as an example, a state in which multiple ultrasonic systems, including the ultrasonic systems 100 according to each embodiment described above, are mounted on the front end of a vehicle 30. In addition to ultrasonic system 100, ultrasonic systems 301 to 303 are mounted on the vehicle 30. Although ultrasonic system 100 and ultrasonic systems 301 to 303 may each perform ultrasonic wave transmission and TOF measurement in sequence, in that case the frequency of distance measurement to the object by the same ultrasonic system decreases, and there is a risk that, for example, the vehicle 30 may approach the object unnecessarily.

[0076] Therefore, it is preferable that the ultrasonic system 100 and ultrasonic systems 301-303 perform ultrasonic wave transmission and TOF measurement in parallel. In such a case, as shown in Figure 14, for example, there is a risk that the ultrasonic system 100 will receive not only the reflected waves from the ultrasonic waves transmitted from the ultrasonic system 100 that are reflected by the object 351, but also the reflected waves from the ultrasonic waves transmitted from the other ultrasonic systems 301 and 302 that are reflected by the object 352 and 353, respectively.

[0077] However, even in this case, the ultrasonic waves transmitted from the ultrasonic systems 301 and 302 have a different frequency (or, in the third embodiment, a combination of different frequencies) than the transmission frequency set for their own ultrasonic system 100, so interference from ultrasonic waves from the other ultrasonic systems 301 and 302 can be avoided by determination by the self-wave identification unit 44.

[0078] <7. Other> Although embodiments have been described above, various modifications to the embodiments are possible within the scope of the spirit of the present invention.

[0079] For example, the driver unit 2 may be connected to an ultrasonic transmitter for sending waves, and the analog front end 3 may be connected to an ultrasonic receiver separate from the ultrasonic transmitter. In other words, the sound source and the receiver do not have to be the same device.

[0080] Furthermore, ultrasonic systems, including sound wave processing devices, can be mounted on mobile objects other than vehicles, such as unmanned transport robots or service robots used for carrying goods. Alternatively, ultrasonic systems can be mounted on stationary objects rather than mobile ones.

[0081] <8. Addendum> As described above, for example, the sound wave processing device (1) according to this disclosure includes a transmission signal generation unit (41) that generates a transmission signal for transmitting sound waves, A receiving signal output unit (3) outputs a receiving signal based on the reception of sound waves, A correlation convolution integration processing unit (43) performs correlation convolution integration processing in parallel for each of the reference wave data (Ref1 to RefN) based on the received signal and a plurality of reference wave data, A self-wave identification unit (44) determines whether the received sound wave is a self-wave, which is a reflected sound wave of the sound wave transmitted by the transmitting signal generation unit, based on the correlation convolution integral value output from the correlation convolution integral processing unit, The configuration includes the following (first configuration).

[0082] Furthermore, in the first configuration described above, the self-wave identification unit (44) may be configured to include a correlation maximum value acquisition unit (44A) that acquires the maximum value of the correlation convolution integral value (correlation maximum value) for each of the reference wave data over a predetermined period, and a determination unit (44B) that determines whether it is the self-wave based on the relative evaluation of the acquired correlation maximum value (second configuration).

[0083] Furthermore, in the second configuration described above, the determination unit (44B) may be configured to identify the frequency of the reference wave data that yields the maximum value of the acquired correlation (third configuration).

[0084] Furthermore, in the second configuration described above, the determination unit (44B) may be configured to identify the frequency midway between the three adjacent frequencies when the frequencies of the reference wave data in the top three of the acquired maximum correlation values ​​are three adjacent frequencies (fourth configuration).

[0085] Furthermore, in any of the second to fourth configurations described above, the system may further include an envelope detection unit (46) that extracts an envelope from the received signal, and a comparator (47) that compares the extracted envelope with a predetermined threshold, wherein the predetermined period is the period from when the envelope exceeds the threshold to when it falls below the threshold (fifth configuration).

[0086] Furthermore, in the fifth configuration described above, the system may further include a bandpass filter (45) that extracts a signal of a predetermined bandwidth from the received signal and outputs it to the envelope detection unit (sixth configuration).

[0087] Furthermore, in any of the second to sixth configurations described above, the maximum correlation value may be the maximum absolute value of the correlation convolution integral (seventh configuration).

[0088] Furthermore, in any of the first to seventh configurations described above, the transmitting signal generation unit (41) may perform multiple transmissions, and the self-wave identification unit (44) may determine that the frequency of the reference wave data that increases the correlation convolution integral value is the same for all of the multiple transmissions (eighth configuration).

[0089] Furthermore, in any of the first to seventh configurations described above, the transmitting signal generation unit (41) may transmit sound waves of multiple frequencies in succession, and the self-wave identification unit (44) may determine that the frequency of the reference wave data that increases the correlation convolution integral value is the self-wave if it is shifted from the multiple frequencies in the same direction and by the same amount (the ninth configuration).

[0090] Furthermore, in any of the first to ninth configurations described above, the device may have a configuration that includes a first external terminal (T1, T2) that enables connection between the transmitting signal generation unit (41) and an external ultrasonic transmitting / receiving device (5), and a second external terminal (T3, T4) that enables connection between the ultrasonic transmitting / receiving device and the receiving signal output unit (3) (the tenth configuration).

[0091] Furthermore, the ultrasonic system (100) relating to this disclosure has a configuration comprising the sound wave processing device (1) of the 10th configuration described above and the ultrasonic transmitting and receiving device (5) (11th configuration).

[0092] Furthermore, the sound wave processing device (1) according to any of the first to ten configurations described above may be mountable on a vehicle (the twelfth configuration).

[0093] Furthermore, the ultrasonic system according to this disclosure is an ultrasonic system that can be mounted on the vehicle and comprises a first ultrasonic system (100) including the sound wave processing device (1) of the configuration of the 12th configuration described above, and at least one other second ultrasonic system (301, 302, 303), and the first ultrasonic system and the second ultrasonic system may be configured to perform ultrasonic wave transmission and TOF (Time of Flight) measurement in parallel. [Industrial applicability]

[0094] This disclosure can be used, for example, in an in-vehicle ultrasonic system. [Explanation of symbols]

[0095] 1. Acoustic device 2. Driver section 3 Analog Front End 4. Digital Processing Unit 5. Ultrasonic Transceiver 6 A / D conversion section 7 Reference wave storage section 8. Correlation Convolution Integration Processing Unit 9 Comparator 10 Receiving Processing Unit 21 DA circuit 30 vehicles 31 Low-noise amplifier 32 Low-pass filters 33 A / D converters 41 Transmission signal generation circuit 42 registers 43 Correlation Convolution Integration Processing Unit 44 Self-wave identification unit 44A Correlation Maximum Value Acquisition Unit 44B Judgment section 44C comparator 44D Judgment section 46 Envelope detection unit 47 Comparator 48 TOF Measurement Unit 49 Serial Interface 81 Correlation Processing Unit 82 Correlation Processing Value Sum Unit 100 Ultrasonic Systems 301-303 Ultrasonic System 351-353 Objects 431 Correlation Processing Unit 432 Correlation Processing Value Sum Unit 481 counter 500 vehicles 1000 objects DF0~DFn Flip-flop group M0~Mn Multiplication section SR Shift Register SUM (Total Sum Calculation Unit) T1~T5 External terminals Tr transformer

Claims

1. A transmission signal generation unit that generates a transmission signal for transmitting sound waves, A receiving signal output section that outputs a receiving signal based on the reception of sound waves, A correlation convolution integration processing unit performs correlation convolution integration processing in parallel for each of the reference wave data based on the received signal and a plurality of reference wave data, A self-wave identification unit determines whether the received sound wave is a self-wave, which is a reflected sound wave of the sound wave transmitted by the transmission signal generation unit, based on the correlation convolution integral value output from the correlation convolution integral processing unit. It has, The aforementioned wave identification unit is A correlation maximum value acquisition unit that acquires the maximum value (correlation maximum value) of the correlation convolution integral value over a predetermined period for each of the aforementioned reference wave data, A determination unit that determines whether the obtained correlation maximum value is the local wave based on a relative evaluation of the correlation maximum value, by identifying the frequency of the reference wave data that maximizes the obtained correlation maximum value, A sound wave processing device having

2. A transmission signal generation unit that generates a transmission signal for transmitting sound waves, A receiving signal output section that outputs a receiving signal based on the reception of sound waves, A correlation convolution integration processing unit performs correlation convolution integration processing in parallel for each of the reference wave data based on the received signal and a plurality of reference wave data, A self-wave identification unit determines whether the received sound wave is a self-wave, which is a reflected sound wave of the sound wave transmitted by the transmission signal generation unit, based on the correlation convolution integral value output from the correlation convolution integral processing unit. It has, The aforementioned wave identification unit is A correlation maximum value acquisition unit that acquires the maximum value (correlation maximum value) of the correlation convolution integral value over a predetermined period for each of the aforementioned reference wave data, A determination unit determines whether the reference wave is the local wave based on a relative evaluation of the maximum correlation value, by identifying the midpoint frequency of the three adjacent frequencies when the frequencies of the top three reference wave data with the highest obtained correlation values ​​are three adjacent frequencies. A sound wave processing device having

3. An envelope detection unit that extracts an envelope from the received signal, The system further comprises a comparator that compares the extracted envelope with a predetermined threshold, The sound wave processing apparatus according to claim 1 or claim 2, wherein the predetermined period is the period from when the envelope exceeds the threshold to when it falls below the threshold.

4. The sound wave processing apparatus according to claim 3, further comprising a bandpass filter that extracts a signal of a predetermined bandwidth from the received signal and outputs it to the envelope detection unit.

5. The sound wave processing apparatus according to claim 1 or claim 2, wherein the maximum correlation value is the maximum absolute value of the correlation convolution integral.

6. The aforementioned transmission signal generation unit performs multiple transmissions, The sound wave processing apparatus according to claim 1 or 2, wherein the self-wave identification unit determines that the frequency identified by the determination unit is the same for the multiple transmissions.

7. A first external terminal that enables connection between the wave transmission signal generation unit and an external ultrasonic transceiver, The sound wave processing apparatus according to claim 1 or claim 2, further comprising a second external terminal that enables connection between the ultrasonic transmitting and receiving device and the wave receiving signal output unit.

8. An ultrasonic system comprising the sound wave processing device described in claim 7 and the ultrasonic transmitting and receiving device.

9. A sound wave processing device according to claim 1 or claim 2 that can be mounted on a vehicle.

10. An ultrasonic system that can be mounted on the vehicle, comprising a first ultrasonic system including the sound wave processing device described in claim 9, and at least one other second ultrasonic system, The first ultrasonic system and the second ultrasonic system are ultrasonic systems that perform ultrasonic wave transmission and TOF (Time of Flight) measurement in parallel.

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