Drive device, sound wave sensor, and moving body
By generating transmission signals with a distinct frequency from the resonant frequency, the ultrasonic system effectively differentiates between reverberation and reflected waves, enhancing the detection of nearby obstacles and improving distance measurement accuracy.
Patent Information
- Application Number
- JP2024124465
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-07-31
- Publication Date
- 2026-02-13
AI Technical Summary
Ultrasonic systems face challenges in detecting nearby obstacles due to overlapping reverberation waves and reflected waves, making it difficult to accurately measure distance using the envelope of the received signal.
The ultrasonic system employs a signal processing device that generates transmission signals with a frequency different from the resonant frequency of the ultrasonic transducer, allowing the detection circuit to differentiate between reverberation and reflected waves by monitoring frequency changes during the reverberation period.
This approach enables accurate detection of nearby obstacles by distinguishing between reverberation and reflected waves based on frequency fluctuations, improving the system's ability to measure short distances accurately.
Smart Images
Figure 2026022876000001_ABST
Abstract
Description
[Technical Field]
[0001] The present disclosure relates to a drive unit, an acoustic wave sensor, and a moving body. [Background technology]
[0002] Conventionally, ultrasonic systems have been known that measure the distance to an obstacle by measuring the time of flight (TOF) between generating ultrasonic waves and the return of the reflected waves from the obstacle. Such ultrasonic systems are often installed in vehicles, and an example is an in-vehicle clearance sonar (see, for example, Patent Document 1). [Prior art documents] [Patent documents]
[0003] [Patent Document 1] International Publication No. 2020 / 004609
[0004] [overview] Generally, in an ultrasonic system, the vibration of the ultrasonic transducer element continues for a period of time after the element is deactivated, which period of time is commonly referred to as the reverberation period.
[0005] In an ultrasonic system in which a single ultrasonic transducer both transmits and receives ultrasonic waves, the reflected waves from nearby obstacles overlap with the reverberation waves, making it difficult to detect nearby obstacles by the envelope of the received signal.
[0006] The signal processing device disclosed in this specification includes a transmission signal generation circuit configured to generate a transmission signal, a drive circuit configured to drive an acoustic transducer based on the transmission signal, a reception circuit configured to generate a reception signal based on a reflected wave that is an acoustic wave transmitted from the acoustic transducer and reflected by an object, and a detection circuit configured to detect the presence or absence of the object based on a change in frequency of the reception signal during the reverberation period of the acoustic transducer. The transmission signal generation circuit is configured to make the frequency of the transmission signal different from the resonant frequency of the acoustic transducer.
[0007] The ultrasonic sensor disclosed in this specification comprises the signal processing device configured as described above and the ultrasonic sensor element.
[0008] The moving body disclosed in this specification is equipped with the acoustic wave sensor having the above-described configuration. [Brief explanation of the drawings]
[0009] [Figure 1] FIG. 1 is a diagram schematically illustrating a vehicle equipped with a sonic wave system and an object. [Figure 2] FIG. 2 is a diagram showing the configuration of a sound wave system according to a comparative example. [Figure 3] FIG. 3 is a diagram showing schematic waveforms of a transmitted wave, a reverberation wave, and a reflected wave processed by the ultrasonic system shown in FIG. 2 when an object is present in the near distance. [Figure 4] FIG. 4 is a diagram showing the configuration of a sound wave system according to an embodiment. [Figure 5] FIG. 5 is a diagram showing schematic waveforms of a transmitted wave, a reverberation wave, and a reflected wave processed by the ultrasonic system shown in FIG. 4 when an object is present in the near distance. [Figure 6] FIG. 6 is a diagram illustrating an example of the configuration of a part of the reflection detection unit.
[0010] [Detailed explanation] Comparative examples and embodiments will be described below with reference to the drawings. The ultrasonic system described below is assumed to be mounted on a vehicle as an example, and can be used for warning functions, automatic braking functions, automatic parking functions, etc. by measuring the distance between the vehicle and an object. FIG. 1 is a schematic diagram showing a vehicle 200 equipped with an 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. The ultrasonic system 100 is, for example, ultrasonic system 100A or 100B described below.
[0011] The ultrasonic system 100 may be mounted on a moving body other than the vehicle 200. Examples of moving bodies other than the vehicle 200 include a self-propelled vacuum cleaner and a ship.
[0012] <Ultrasound system (comparison example)> FIG. 1 is a diagram showing the configuration of an ultrasound system 100A according to a comparative example (=a general configuration to be compared with the embodiments described later).
[0013] The ultrasonic system 100A includes a signal processing device 1A, a transformer Tr, capacitors C1 and C2, and an ultrasonic vibration element 2. The ultrasonic vibration element 2 is externally connected to the signal processing device 1A via the transformer Tr and the capacitors C1 and C2. Note that the transformer Tr and the capacitors C1 and C2 do not necessarily have to be provided.
[0014] The signal processing device 1A is a semiconductor integrated circuit device and includes a DAC (Digital to Analog Converter) 11, a driver 12, an LNA (Low Noise Amplifier) 13, a PGA (Programmable Gain Amplifier) 14, an ADC (Analog to Digital Converter) 15, a digital processing unit 16, and external terminals T1 to T5.
[0015] The DAC 11 converts the digital wave signal output from the transmission wave signal generating unit 161 included in the digital processing unit 16 into an analog signal, and outputs the D / A converted signal to the driver 12.
[0016] The output terminals of the differential pair of the driver 12 are connected to the primary side of a transformer Tr via external terminals T1 and T2. The secondary side of the transformer Tr is connected to the ultrasonic vibration element 2. The driver 12 drives the ultrasonic vibration element 2 based on the output signal of the DAC 11.
[0017] The ultrasonic vibration element 2 transmits and receives ultrasonic waves, that is, the ultrasonic vibration element 2 functions as both a sound source and a receiver.
[0018] The input terminals of the differential pair of the LNA 13 are connected to the secondary side of the transformer Tr via external terminals T3 and T4 and capacitors C1 and C2. The LNA 13 amplifies the differential signal received from the external terminals T3 and T4, converts it to a single-ended signal, and outputs it to the PGA 14. The LNA 13 also performs clipping to prevent the single-ended signal from exceeding a predetermined level. The PGA 14 amplifies the signal received from the LNA 13 and outputs it to the ADC 15. The ADC 15 A / D converts the output signal of the PGA 14 from an analog signal to a digital signal, and outputs the A / D converted signal to the BPF 162.
[0019] The digital processing unit 16 includes a transmission signal generating unit 161, a BPF (Band Pass Filter) 162, an ABS (Absolute value processing unit) 163, an envelope unit 164, a reflected wave detecting unit 165, a TOF measuring unit 166, and an interface 167.
[0020] The transmission signal generating unit 161 is configured to generate a transmission signal for transmitting ultrasonic waves. More specifically, when the transmission signal generating unit 161 receives a wave transmission command from an ECU (Electronic Control Unit) (not shown) mounted on the vehicle 200 (see FIG. 1) via the interface 167, the transmission signal generating unit 161 generates a transmission signal including a predetermined wave number and outputs the transmission signal to the DAC 11.
[0021] The BPF 162 passes only a predetermined frequency band of the output signal of the ADC 15 and attenuates frequency bands other than the predetermined frequency band. The BPF 162 has frequency characteristics according to the frequency setting of the transmission signal. For example, the predetermined frequency band is set to match the frequency band of the transmission signal.
[0022] The ABS 163 performs absolute value processing on the output signal of the BPF 162. That is, the ABS 163 performs inversion processing on the negative output signal of the BPF 162 to convert it into a positive signal.
[0023] The envelope unit 164 outputs a signal obtained by envelope detection of the output signal of the ABS 163, which is the received signal.
[0024] The reflected wave detection unit 165 detects the reflected wave reflected by the object 300 when the envelope detection signal output from the envelope unit 164 exceeds a threshold value.
[0025] The TOF measurement unit 166 measures the time from when an ultrasonic wave is transmitted until when a reflected wave reflected by the object 300 is received (TOF) using the counter 166A.
[0026] FIG. 3 is a diagram showing schematic waveforms of a transmitted wave W1, a reverberation wave W2, and a reflected wave W3 processed by the ultrasound system 100A when an object 300 is present in the near distance.
[0027] When the object 300 is located close by, the LNA 13 receives a differential signal in a state where the reverberation wave W2 and the reflected wave W3 overlap. When the reverberation wave W2 and the reflected wave W3 overlap, the reverberation wave W2 and the reflected wave W3 strengthen or weaken each other depending on their phase relationship. Therefore, when the reverberation wave W2 and the reflected wave W3 overlap, it is difficult to detect the object 300 based on the envelope of the received signal.
[0028] <Ultrasound system (embodiment)> Fig. 4 is a diagram showing the configuration of an ultrasonic system 100B according to an embodiment. Fig. 5 is a diagram showing schematic waveforms of a transmitted wave W1, a reverberation wave W2, and a reflected wave W3 processed by the ultrasonic system 100B when an object 300 is present in the short distance. Fig. 5 also shows the frequency F1 of the output signal of ABS163, which is a received signal.
[0029] The ultrasound system 100B differs from the ultrasound system 100A in that it includes a signal processing device 1B instead of the signal processing device 1A, but is otherwise basically the same as the ultrasound system 100A.
[0030] The signal processing device 1B differs from the signal processing device 1A in the frequency of the transmitted wave signal and the processing content of the reflected wave detection unit 165, but is otherwise basically the same as the signal processing device 1A.
[0031] The transmission signal generating unit 161 provided in the signal processing device 1B shown in FIG. 4 is configured to make the frequency of the transmission signal different from the resonant frequency of the ultrasonic transducer element 2. On the other hand, the reverberation wave W2 shown in FIG. 5 has the characteristic of vibrating at the resonant frequency of the ultrasonic transducer element 2. Because the frequency of the reflected wave W3 is the same as the frequency of the transmission signal, the reverberation wave W2 and the reflected wave W3 have different frequencies. Therefore, during the period when the reverberation wave W2 and the reflected wave W3 overlap, the frequency F1 of the output signal of the ABS 163, which is the reception signal, fluctuates relative to the frequency of the reverberation wave W2. The degree of fluctuation in frequency F1 varies depending on the phase relationship between the reverberation wave W2 and the reflected wave W3. However, regardless of the phase relationship between the reverberation wave W2 and the reflected wave W3, the frequency F1 always fluctuates relative to the frequency of the reverberation wave W2 during the period when the reverberation wave W2 and the reflected wave W3 overlap.
[0032] Therefore, the reflected wave detection unit 165 provided in the signal processing device 1B shown in Fig. 4 is configured to detect the presence or absence of the object 300 based on a change in frequency F1 during the reverberation period of the acoustic transducer 2. This allows the signal processing device 1B shown in Fig. 4 to detect the object 300 located at a close distance. After the reverberation period of the acoustic transducer 2 has ended, the reflected wave detection unit 165 provided in the signal processing device 1B shown in Fig. 4 detects a reflected wave reflected by the object 300 when the envelope detection signal output from the envelope unit 164 exceeds a threshold value, similar to the reflected wave detection unit 165 provided in the signal processing device 1A shown in Fig. 2.
[0033] The length of the reverberation period is determined by the characteristics of the acoustic transducer 2, the transformer Tr, etc. For this reason, it is preferable that the length of the reverberation period calculated based on the characteristics of the acoustic transducer 2, the transformer Tr, etc. assumed to be externally connected to the signal processing device 1B shown in Fig. 4 be stored in a non-volatile manner in a register or the like provided in the reflected wave detection unit 165. Note that, for example, if there is a possibility that the acoustic transducer 2, the transformer Tr, etc. assumed to be externally connected to the signal processing device 1B shown in Fig. 4 can be selected from a plurality of types, the length of the reverberation period stored in a non-volatile manner in a register or the like provided in the reflected wave detection unit 165 may be rewritable via the interface 167.
[0034] More specifically, the reflected wave detection unit 165 provided in the signal processing device 1B shown in FIG. 4 is configured to divide the reverberation period into a first period and a second period following the first period, not to detect the presence or absence of the object 300 during the first period, and to detect the presence or absence of the object 300 based on a change in frequency F1 during the second period. The end timing of the first period is set, for example, to the timing when clipping in the LNA 13 is expected to end or the timing when a predetermined time has elapsed since the timing when clipping in the LNA 13 is expected to end. During the period when clipping in the LNA 13 is being performed, the amplitude of the reverberation wave W2 is much larger than the amplitude of the reflected wave W3. Therefore, even if the reverberation wave W2 and the reflected wave W3 overlap, the variation of frequency F1 relative to the frequency of the reverberation wave W2 becomes small, making it difficult to detect the presence or absence of the object 300. Therefore, it is preferable to exclude the period when clipping in the LNA 13 is being performed from the period for detecting the presence or absence of the object 300.
[0035] Fig. 6 is a diagram showing an example of the configuration of a portion of the reflection detection unit 165. The reflected wave detection unit 165 provided in the signal processing device 1B shown in Fig. 4 includes a quadrature detection circuit 165A, a differentiation circuit 165B, and an LPF (Low Pass Filter) 165C.
[0036] The quadrature detection circuit 165A performs quadrature detection on the output signal of the ABS 163, which is the received signal, and detects the phase of the output signal of the ABS 163, which is the received signal.
[0037] The differentiation circuit 165B performs differentiation processing on the phase detected by the quadrature detection circuit 165A to find the instantaneous frequency of the output signal of the ABS 163, which is the received signal.
[0038] The LPF 165C performs filtering, more specifically, low-pass filtering, on the instantaneous frequency calculated by the differentiation circuit 165B. The reflected wave detection unit 165 provided in the signal processing device 1B shown in Fig. 4 detects the presence or absence of the object 300 based on the instantaneous frequency after filtering. The filtering smoothes the instantaneous frequency and suppresses false detections when detecting the presence or absence of the object 300 based on changes in the frequency F1, more specifically, changes in the instantaneous frequency after filtering.
[0039] The reflected wave detection unit 165 provided in the signal processing device 1B shown in Figure 4 is configured to detect the presence or absence of an object 300 when the difference between the minimum and maximum values of the instantaneous frequency of the output signal of ABS163, which is the received signal, during the above-mentioned second period is equal to or greater than a first threshold value, as an example of a method for detecting the presence or absence of an object 300 based on a change in frequency F1.
[0040] Furthermore, the reflected wave detection unit 165 provided in the signal processing device 1B shown in FIG. 4 is configured to detect at least one of an abnormality in the ultrasonic vibration element 2, an abnormality in the receiving circuit, and reception of ultrasonic waves from sources other than the driver 12 when the difference is equal to or greater than the first threshold but greater than the second threshold. This makes it possible to suppress false detections when detecting the presence or absence of an object 300 based on changes in frequency F1. The receiving circuit includes an LNA 13, a PGA 14, an ADC 15, a BPF 162, and an ABS 163. Ultrasonic waves from sources other than the driver 12 are, for example, ultrasonic waves transmitted from another ultrasonic system. The second threshold is a value greater than the first threshold, and may be set to, for example, the theoretical value of the difference in the phase relationship between the reverberation wave W2 and the reflected wave W3 at which the difference is greatest.
[0041] As another example of a method for detecting the presence or absence of an object 300 based on a change in frequency F1, the reflected wave detection unit 165 provided in the signal processing device 1B shown in Figure 4 may be configured to divide the second period into multiple intervals, calculate the interval average value of the instantaneous frequency of the output signal of ABS163, which is the received signal in each interval, and detect the presence of an object 300 if there is an interval average value whose difference from the resonant frequency of the ultrasonic vibration element 2 is equal to or greater than a predetermined value.
[0042] <Other> The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The technical scope of the present disclosure is indicated by the claims, not by the description of the above-described embodiments, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims.
[0043] In the above embodiment, the ultrasonic system 100 that transmits ultrasonic waves (sound waves with a high vibration frequency exceeding audible sound) has been described, but the ultrasonic system 100 may be modified into a sonic system that transmits sound waves other than ultrasonic waves.
[0044] <Additional Notes> A supplementary note will be provided for the present disclosure, the specific configuration examples of which have been shown in the above-described embodiments.
[0045] The signal processing device (1B) of the present disclosure comprises a transmission signal generating circuit (162) configured to generate a transmission signal, a drive circuit (12) configured to drive an acoustic vibration element (2) based on the transmission signal, a receiving circuit (13, 14, 15, 162, 163) configured to generate a reception signal based on a reflected wave, which is an acoustic wave sent from the acoustic vibration element and reflected by an object, and a detection circuit (165) configured to detect the presence or absence of the object based on a change in frequency of the reception signal during the reverberation period of the acoustic vibration element, and the transmission signal generating circuit is configured to make the frequency of the transmission signal different from the resonant frequency of the acoustic vibration element (first configuration).
[0046] According to the signal processing device of the first configuration, it is possible to detect an object located at a short distance.
[0047] In the signal processing device of the first configuration described above, the detection circuit may be configured to determine the instantaneous frequency of the received signal, perform filtering processing on the instantaneous frequency, and detect the presence or absence of the object based on the instantaneous frequency after the filtering processing (second configuration).
[0048] In the signal processing device of the second configuration, the detection circuit may be configured to perform quadrature detection on the received signal to detect the phase of the received signal, and to perform differential processing on the phase to obtain the instantaneous frequency (third configuration).
[0049] In any of the first to third configurations of the signal processing device, the detection circuit may be configured to detect the presence of the object when the difference between the minimum and maximum values of the instantaneous frequency of the received signal is equal to or greater than a first threshold value (fourth configuration).
[0050] In the signal processing device of the above fourth configuration, the detection circuit is configured to detect that at least one of an abnormality in the ultrasonic vibration element, an abnormality in the receiving circuit, and reception of ultrasonic waves from a source other than the driving circuit has occurred when the difference is greater than the first threshold value, even if the difference is greater than the second threshold value, and the second threshold value may be greater than the first threshold value (fifth configuration).
[0051] In any of the first to fifth configurations of the signal processing device, the detection circuit may be configured (sixth configuration) to divide the reverberation period into a first period and a second period following the first period, not to detect the presence or absence of the object in the first period, and to detect the presence or absence of the object in the second period.
[0052] An ultrasonic sensor (100B) of the present disclosure has a configuration (seventh configuration) including the signal processing device of any one of the first to sixth configurations and the ultrasonic sensor element.
[0053] The moving body (200) of the present disclosure has a configuration (eighth configuration) including the acoustic wave sensor of the seventh configuration. [Explanation of symbols]
[0054] 1A, 1B Signal processing device 2 Ultrasonic vibration element 11 DAC 12 Drivers 13 LNA 14 PGA 15 ADC 16 Digital Processing Section 161 Transmission signal generator 162 BPF 163 ABS 164 Envelope section 165 Reflected wave detection unit 165A Quadrature detection circuit 165B Differential circuit 165C LPF 166 TOF measurement unit 166A Counter 167 Interface 100, 100A, 100B Ultrasonic Systems 200 vehicles 300 Object (Obstacle) C1 and C2 capacitors T1~T5 external terminals Tr transformer
Claims
1. a transmit signal generating circuit configured to generate a transmit signal; a drive circuit configured to drive the acoustic wave vibration element based on the transmission signal; a receiving circuit configured to generate a receiving signal based on a reflected wave, which is an acoustic wave transmitted from the acoustic wave vibration element and reflected by an object; a detection circuit configured to detect the presence or absence of the object based on a change in frequency of the received signal during a reverberation period of the acoustic transducer; Equipped with The signal processing device, wherein the transmission signal generating circuit is configured to make the frequency of the transmission signal different from the resonance frequency of the acoustic wave vibration element.
2. 2. The signal processing device according to claim 1, wherein the detection circuit is configured to determine an instantaneous frequency of the received signal, perform filtering on the instantaneous frequency, and detect the presence or absence of the object based on the instantaneous frequency after the filtering.
3. 3. The signal processing device according to claim 2, wherein the detection circuit is configured to detect the phase of the received signal by performing quadrature detection on the received signal, and to obtain the instantaneous frequency by performing a differentiation process on the phase.
4. The signal processing device according to claim 1 , wherein the detection circuit is configured to detect the presence of the object when a difference between a minimum value and a maximum value of the instantaneous frequency of the received signal is equal to or greater than a first threshold value.
5. The signal processing device described in claim 4, wherein the detection circuit is configured to detect that at least one of an abnormality in the ultrasonic vibration element, an abnormality in the receiving circuit, and reception of ultrasonic waves from a source other than the driving circuit has occurred when the difference is greater than the first threshold value, even if the difference is greater than the second threshold value, and the second threshold value is a value greater than the first threshold value.
6. 2. The signal processing device according to claim 1, wherein the detection circuit is configured to divide the reverberation period into a first period and a second period subsequent to the first period, not to detect the presence or absence of the object in the first period, and to detect the presence or absence of the object in the second period.
7. An ultrasonic sensor comprising: the signal processing device according to any one of claims 1 to 6; and the ultrasonic sensor element.
8. A moving object comprising the ultrasonic sensor according to claim 7.
Citation Information
Patent Citations
Acoustic wave processing device and ultrasonic system
WO2020004609A1