Signal processing equipment, sound wave systems, and vehicles

Abstract

This signal processing device is provided with: a transmission signal generation unit which generates a transmission signal for transmission of sound waves and which includes a first and second chirp signal (TX1, TX3) in the transmission signal; a received signal output unit which outputs a received signal based on the reception of sound waves; and a derivation unit which derives a velocity relative to a target on the basis of a first timing, at which a part (RX1) of the received signal that corresponds to the first chirp signal (TX1) is detected, and a second timing at which a part (RX3) of the received signal that corresponds to the second chirp signal (TX3) is detected. The frequency of one of the first and second chirp signal increases with time, and the frequency of the other decreases with time.

Description

Technical Field

[0001] The invention disclosed in this specification relates to a signal processing device that processes a transmission signal for transmitting sound waves and a reception signal based on the reception of sound waves, a sound wave system including the signal processing device, and a vehicle including the sound wave system.

Background Art

[0002] Conventionally, an ultrasonic system that measures the distance to an object (obstacle) by measuring the time of flight (TOF) from the generation of ultrasonic waves until the reflected wave from the obstacle returns is known (see, for example, Patent Document 1). Such an ultrasonic system is often mounted on a vehicle, and as an example, an in-vehicle clearance sonar is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional ultrasonic systems can measure the distance from the ultrasonic system to an object, but cannot measure the relative speed between the ultrasonic system and the object.

Means for Solving the Problems

[0005] The signal processing apparatus disclosed herein comprises: a transmission signal generation unit configured to generate a transmission signal for transmitting sound waves and to include a first chirp signal and a second chirp signal in the transmission signal; a reception signal output unit configured to output a reception signal based on the reception of sound waves; and a derivation unit configured to derive the relative velocity with an object based on a first timing for detecting a portion of the reception signal corresponding to the first chirp signal and a second timing for detecting a portion of the reception signal corresponding to the second chirp signal, wherein one of the first chirp signal and the second chirp signal is a signal whose frequency increases over time, and the other of the first chirp signal and the second chirp signal is a signal whose frequency decreases over time.

[0006] The sound wave system disclosed herein comprises a signal processing device having the above configuration and a sound wave transceiver configured to be directly or indirectly connected to the signal processing device.

[0007] The vehicles disclosed herein are configured to include the acoustic system described above. [Effects of the Invention]

[0008] According to the signal processing device, sound wave system, and vehicle disclosed herein, the relative speed with respect to an object can be measured. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with an ultrasonic system according to an embodiment 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 ultrasonic system according to the embodiment. [Figure 5] Figure 5 shows an example of a control signal for transmission. [Figure 6] Figure 6 is a schematic diagram showing an example of a received signal. [Figure 7] Figure 7 shows an example of the first reflected wave detection unit. [Figure 8] Figure 8 is a time chart showing the results of the correlation process. [Modes for carrying out the invention]

[0010] One embodiment of the present invention will be described below with reference to the drawings. The ultrasonic system according to the embodiment described below is intended to be mounted on a vehicle as an example, and can be used for alarm functions, automatic braking functions, and automatic parking functions by measuring the distance between the vehicle and an object.

[0011] <Correlation Processing> First, an overview of the correlation processing used in the ultrasonic system according to the embodiment will be described. Figure 1 shows a vehicle 200 equipped with the ultrasonic system 100 according to the embodiment (hereinafter referred to as "ultrasonic system 100") 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 ultrasonic system 100 also receives environmental noise N.

[0012] Here, the correlation process will be explained using Figures 2 and 3. In Figure 2, reference data Dref is prepared in advance. Reference 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 transmission frequency. Therefore, the correlation result C1 obtained by the correlation process, which multiplies the reference data Dref and the reflected wave Rs1, always has a positive correlation value, as shown in Figure 2. As a result, the convolution integral value obtained by integrating the correlation result C1 over time becomes large, and the reflected wave is emphasized.

[0013] On the one hand, the frequency of the received environmental noise N shown in FIG. 3 is deviated from the transmission frequency. That is, the frequency of the environmental noise N is deviated from the frequency of the reference data Dref. Therefore, as shown in FIG. 3, in the correlation result C2, a period in which the correlation value becomes negative occurs, and the convolution integral value becomes smaller than that in FIG. 2. In this way, the reflected wave based on the transmitted wave and the environmental noise can be distinguished.

[0014] <Ultrasonic System> Next, the ultrasonic system 100 will be described. FIG. 4 is a diagram showing the configuration of the ultrasonic system 100.

[0015] The ultrasonic system 100 includes a signal processing device 1, a transformer Tr, and an ultrasonic transmission / reception device 2. The ultrasonic transmission / reception device 2 is externally connected to the signal processing device 1 via the transformer Tr. Note that the transformer Tr does not necessarily have to be provided.

[0016] 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, a digital processing unit 16, and external terminals T1 to T5.

[0017] The DAC 11 performs D / A conversion on 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 D / A conversion to the driver 12.

[0018] The output terminals of the differential pair of the driver 12 are connected to the primary side of the transformer Tr via the external terminals T1 and T2. The ultrasonic transmission / reception device 2 is connected to the secondary side of the transformer Tr. The driver 12 drives the ultrasonic transmission / reception device 2 based on the output signal of the DAC 11.

[0019] The ultrasonic transceiver 2 has a piezoelectric element (not shown) and transmits and receives ultrasonic waves. In other words, the ultrasonic transceiver 2 functions as both a sound source and a receiver.

[0020] The differential pair input terminals of LNA13 are connected to the secondary side of transformer Tr via external terminals T3 and T4. The output signal of LNA13 is supplied to ADC15 via LPF14. ADC15 performs A / D conversion of the output signal of LNA13 from an analog signal to a digital signal, and outputs the converted signal to the first reflected wave detection unit 162, the second reflected wave detection unit 163, and the third reflected wave detection unit 164, which are included in the digital processing unit 16.

[0021] LNA13, LPF14, and ADC15 are examples of a received signal output unit configured to output a received signal based on the reception of ultrasonic waves.

[0022] The digital processing unit 16 includes a transmission signal generation unit 161, a first reflected wave detection unit 162, a second reflected wave detection unit 163, a third reflected wave detection unit 164, a Doppler frequency calculation unit 165, a relative velocity calculation unit 166, a TOF measurement unit 167, and an interface 168.

[0023] The transmission signal generation unit 161 is configured to generate a transmission signal for the transmission of ultrasonic waves. More specifically, the transmission signal generation unit 161 receives transmission commands from an ECU (Electronic Control Unit) (not shown) mounted on the vehicle 200 (see Figure 1) via interface 168. Upon receiving the signal, it generates a transmission signal and outputs that transmission signal to DAC11.

[0024] The transmission signal generation unit 161 is configured to include the first chirp signal TX1, the constant frequency signal TX2, and the second chirp signal TX3 shown in Figure 5 in the transmission control signal in the order of the first chirp signal TX1, the constant frequency signal TX2, and the second chirp signal TX3. The transmission signal generation unit 161 is configured to generate a transmission signal based on the transmission control signal. The transmission signal has a waveform that is roughly the same as the transmission control signal, but it has a distorted waveform due to the effects of the circuit's responsiveness, etc.

[0025] In the example shown in Figure 5, the first chirp signal TX1 is an 8-wave chirp signal whose frequency increases in 1kHz increments from 53kHz to 60kHz, the constant frequency signal TX2 is an 11-wave signal with a frequency of 60kHz, and the second chirp signal TX3 is an 8-wave chirp signal whose frequency decreases in 1kHz increments from 60kHz to 53kHz. Note that the frequency and number of waves of the transmission control signal are not limited to the example shown in Figure 5.

[0026] However, it is desirable that the frequency variation range of the first chirp signal TX1 and the second chirp signal TX3 are the same. If the frequency variation ranges of the first chirp signal TX1 and the second chirp signal TX3 are the same, the overall frequency variation range of the transmitted signal can be minimized. This simplifies circuit design and component selection.

[0027] The first reflected wave detection unit 162 detects a portion RX1 (see Figure 6) of the received signal corresponding to the first chirp signal of the received signal, based on the correlation between the received signal output from the ADC 15 and the first reference data composed of the first chirp signal TX1.

[0028] The second reflected wave detection unit 163 detects a portion RX3 (see Figure 6) of the received signal that corresponds to the second chirp signal of the received signal, based on the correlation between the received signal output from the ADC 15 and the second reference data composed of the second chirp signal TX3.

[0029] The third reflected wave detection unit 164 detects a portion RX3 (see Figure 6) of the received signal corresponding to the second chirp signal of the received signal, based on the correlation between the received signal output from the ADC 15 and third reference data consisting of a first chirp signal TX1, a frequency signal TX2, and a second chirp signal TX3.

[0030] Figure 7 shows an example of the first reflected wave detection unit 162. The first reflected wave detection unit 162 in the example shown in Figure 7 includes a reference data storage unit 162A, a correlation processing unit 162B, a correlation value summing unit 162C, and a threshold determination unit 162D. The reference data storage unit 162A is configured to store the first reference data. For example, a register can be used for the reference data storage unit 162A.

[0031] The correlation processing unit 162B performs correlation processing at a predetermined period based on the received signal output from the ADC 15 and the first reference data stored in the reference data storage unit 162A.

[0032] The correlation value summing unit 162C outputs a correlation convolution integral value by calculating the sum of the correlation processing results from the correlation processing unit 162B. Note that the output correlation convolution integral value may be calculated by truncating negative values, where negative values ​​are treated as zero.

[0033] The threshold determination unit 162D compares the correlation convolution integral value with a predetermined threshold. As shown in Figure 8, the threshold determination unit 162D detects a portion RX1 (see Figure 6) corresponding to the first chirp signal of the received signal when the correlation convolution integral value becomes larger than the predetermined threshold and reaches a local maximum.

[0034] Examples of the second reflected wave detection unit 163 and the third reflected wave detection unit 164 are the same as the example of the first reflected wave detection unit 162. However, in the second reflected wave detection unit 163, the second reference data is used instead of the first reference data, and in the third reflected wave detection unit 164, the third reference data is used instead of the first reference data. In addition, in the example of the second reflected wave detection unit 163 and the example of the third reflected wave detection unit 164, the portion RX3 (see Figure 6) corresponding to the second chirp signal of the received signal is detected instead of the portion RX1 (see Figure 6) corresponding to the first chirp signal of the received signal.

[0035] The Doppler frequency calculation unit 165 includes a storage unit (not shown) that stores the time TREF from the first termination timing when the first chirp signal TX1 of the transmitted signal ends to the second termination timing when the second chirp signal TX3 of the transmitted signal ends. The Doppler frequency calculation unit 165 measures the time TM1 (Figure 8) from the first timing when a portion RX1 corresponding to the first chirp signal of the received signal is detected to the second timing when a portion RX3 corresponding to the second chirp signal of the received signal is detected. The Doppler frequency calculation unit 165 may have a built-in counter and measure the time TM1 using the built-in counter, or it may measure the time TM1 using the counter 167A in the TOF measurement unit 167.

[0036] Furthermore, if only one of the second reflected wave detection unit 163 or the third reflected wave detection unit 164 detects the portion RX3 corresponding to the second chirp signal of the received signal, it is desirable for the Doppler frequency calculation unit 165 to consider that the portion RX3 corresponding to the second chirp signal of the received signal was not detected and not measure time TM1. This can suppress erroneous measurement of time TM1. Also, the detection timing of the portion RX3 corresponding to the second chirp signal of the received signal by the second reflected wave detection unit 163. and It is desirable not to measure time TM1 if the detection timing of the portion RX3 corresponding to the second chirp signal of the received signal by the third reflected wave detection unit 164 is shifted by more than a predetermined time. This can suppress erroneous measurement of time TM1.

[0037] Detection timing of the portion RX3 corresponding to the second chirp signal of the received signal by the second reflected wave detection unit 163 and If the detection timing of the portion RX3 corresponding to the second chirp signal of the received signal by the third reflected wave detection unit 164 is shifted from each other by less than the predetermined time, the Doppler frequency calculation unit 165 may use either of them to measure time TM1, or it may use the average of the two to measure time TM1.

[0038] The Doppler frequency calculation unit 165 calculates the Doppler frequency of the received signal from the difference between time TREF and time TM1. Calculate the Plural frequency.

[0039] The relative speed calculation unit 166 calculates the relative speed between the vehicle 200 (see Figure 1) and the object 300 (see Figure 1) from the Doppler frequency of the received signal calculated by the Doppler frequency calculation unit 165.

[0040] The first reflected wave detection unit 162, the second reflected wave detection unit 163, the third reflected wave detection unit 164, the Doppler frequency calculation unit 165, and the relative velocity calculation unit 166 described above are examples of derivation units configured to derive the relative velocity with respect to the object 300 (see Figure 1) based on a first timing for detecting a portion RX1 (see Figures 6 and 8) corresponding to the first chirp signal of the received signal and a second timing for detecting a portion RX3 (see Figures 6 and 8) corresponding to the second chirp signal of the received signal.

[0041] The TOF measurement unit 167 uses a counter 167A to measure the time (TOF) from the time it takes to transmit ultrasonic waves until the reflected waves from the object 300 are received. In this embodiment, the TOF measurement unit 167 stops the counting operation of the counter 167A based on the detection result of the third reflected wave detection unit 164. However, the detection result of the second reflected wave detection unit 163 may be used instead of the detection result of the third reflected wave detection unit 164, or the detection results of both the third reflected wave detection unit 164 and the second reflected wave detection unit 163 may be used.

[0042] Interface 168, for example, conforms to LIN (Local Interconnect Network) and communicates with an unshown ECU mounted on the vehicle 200 (see Figure 1) via external terminal T5. For example, interface 168 sends the calculation results of the relative speed calculation unit 166 and the measurement results of the TOF measurement unit 167 to the unshown ECU mounted on the vehicle 200 (see Figure 1).

[0043] <Other> Furthermore, the configuration of the present invention can be modified in various ways without departing from the spirit of the invention, in addition to the embodiments described above. The embodiments described above should be considered to be illustrative and not restrictive in all respects, and the technical scope of the present invention is indicated by the claims, not by the description of the embodiments described above, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims.

[0044] For example, the transmitted signal does not necessarily have to include a constant frequency signal TX2. However, it is desirable for the transmitted signal to include a constant frequency signal TX2 because the detection accuracy of the third reflected wave detection unit 164 is improved when the transmitted signal includes a constant frequency signal TX2.

[0045] Alternatively, instead of the second or third reference data described above, reference data consisting of a constant frequency signal TX2 and a second chirp signal TX3 may be used.

[0046] For example, the order of the first chirp signal TX1 and the second chirp signal TX3 in the transmitted signal may be swapped.

[0047] In the above embodiment, an ultrasonic system 100 that transmits ultrasonic waves (sound waves with high frequencies exceeding audible sound) was described, but the present invention can also be applied to sound wave systems that transmit sound waves other than ultrasonic waves.

[0048] The signal processing device (1) described above comprises: a transmission signal generation unit (161) configured to generate a transmission signal for transmitting sound waves and to include a first chirp signal and a second chirp signal in the transmission signal; a reception signal output unit (13, 14, 15) configured to output a reception signal based on the reception of sound waves; and a derivation unit (162, 163, 164, 165, 166) configured to derive the relative velocity with respect to an object based on a first timing for detecting the portion of the reception signal corresponding to the first chirp signal and a second timing for detecting the portion of the reception signal corresponding to the second chirp signal, wherein one of the first chirp signal and the second chirp signal is a signal whose frequency increases over time, and the other of the first chirp signal and the second chirp signal is a signal whose frequency decreases over time (first configuration).

[0049] The signal processing device, which is the first configuration described above, can measure the relative speed with respect to the object.

[0050] In the signal processing device having the first configuration described above, the derivation unit may be configured to derive the relative speed based on a comparison result between the time from the first termination timing when the first chirp signal of the transmitted signal ends to the second termination timing when the second chirp signal of the transmitted signal ends and the time from the first timing to the second timing. (Second configuration)

[0051] The signal processing device, which is the second configuration described above, can calculate the relative velocity with respect to an object from the Doppler frequency of the received signal.

[0052] In the signal processing device having the first or second configuration described above, the transmitting signal generation unit may be configured to include the first chirp signal, a constant frequency signal, and the second chirp signal in the transmitting signal in the order of the first chirp signal, the constant frequency signal, and the second chirp signal (third configuration).

[0053] The signal processing device, which is the third configuration described above, can improve the accuracy of the relative speed with respect to the object.

[0054] In a signal processing device having any of the first to third configurations described above, the derivation unit may be configured to detect the portion of the received signal corresponding to the second chirp signal based on the correlation between the received signal and each of the plurality of reference data (fourth configuration).

[0055] The signal processing device, which is the fourth configuration described above, can suppress erroneous measurement of the relative velocity with respect to the object.

[0056] In a signal processing device having any of the first to fourth configurations described above, there may also be a configuration in which the frequency change width of the first chirp signal and the frequency change width of the second chirp signal are the same (fifth configuration).

[0057] The signal processing device, which is the fifth configuration described above, can minimize the frequency variation range of the entire transmitted signal. This simplifies circuit design and component selection.

[0058] The sound wave system (100) described above has a configuration (sixth configuration) comprising a signal processing device having one of the first to fifth configurations described above, and a sound wave transmitting and receiving device (2) configured to be directly or indirectly connected to the signal processing device.

[0059] The sixth configuration described above, the sound wave system, can measure the relative velocity with respect to an object.

[0060] The vehicle (200) described above is configured to include the sound wave system of the sixth configuration described above (seventh configuration).

[0061] In the seventh configuration of the vehicle described above, the relative velocity with respect to an object measured by the sound wave system can be used. [Explanation of symbols]

[0062] 1. Signal Processing Device 2. Ultrasonic Transceiver 11 DAC 12 drivers 13 LNA 14 LPF 15 ADC 16 Digital Processing Unit 161 Wave transmission signal generation unit 162 First Reflected Wave Detection Unit 162A Reference data storage unit 162B Correlation Processing Unit 162C Correlation Value Sum Unit 162D Threshold determination unit 163 Second Reflected Wave Detection Unit 164 Third Reflected Wave Detection Unit 165 Doppler frequency calculation unit 166 Relative velocity calculation unit 167 TOF Measurement Unit 167A Counter 168 Interfaces 100 Ultrasonic system according to the embodiment 200 vehicles 300 Objects (obstacles) T1~T5 External terminals Tr transformer

Claims

1. A transmission signal generation unit is configured to generate a transmission signal for transmitting sound waves, and to include a first chirp signal and a second chirp signal in the transmission signal. A receiving signal output unit configured to output a receiving signal based on the reception of sound waves, A derivation unit is configured to derive the relative velocity with respect to an object based on a first timing for detecting the portion of the received signal corresponding to the first chirp signal and a second timing for detecting the portion of the received signal corresponding to the second chirp signal. Equipped with, One of the first chirp signal and the second chirp signal is a signal whose frequency increases over time, and the other of the first chirp signal and the second chirp signal is a signal whose frequency decreases over time. The derivation unit is configured to derive the relative speed based on a comparison result between the time from a first termination timing when the first chirp signal of the transmitted signal ends to a second termination timing when the second chirp signal of the transmitted signal ends and the time from the first timing to the second timing.

2. The signal processing apparatus according to claim 1, wherein the transmitting signal generation unit is configured to include the first chirp signal, a constant frequency signal, and the second chirp signal in the transmitting signal in the order of the first chirp signal, the constant frequency signal, and the second chirp signal.

3. The signal processing apparatus according to claim 1, wherein the derivation unit is configured to detect the portion of the received signal corresponding to the second chirp signal based on the correlation between the received signal and each of the plurality of reference data.

4. The signal processing apparatus according to claim 1, wherein the frequency change width of the first chirp signal and the frequency change width of the second chirp signal are the same.

5. A signal processing apparatus according to any one of claims 1 to 4, A sound wave system comprising a sound wave transceiver configured to be directly or indirectly connected to the signal processing device.

6. A vehicle comprising the sound wave system described in claim 5.

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