Signal processor, ultrasonic sensor, and vehicle
The signal processing device for ultrasonic sensors addresses the issue of false detection by extracting amplitude and phase signals from reflected waves and using these to generate a detection signal that distinguishes ground reflections from object reflections, thereby improving sensor reliability.
Patent Information
- Application Number
- JP2023198278
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-22
- Publication Date
- 2025-06-03
AI Technical Summary
Ultrasonic sensors mounted on vehicles often experience false detection due to ultrasonic waves being reflected by the ground and received by the sensor.
A signal processing device that includes a receiving circuit to output reflected wave signals, an extractor to separate amplitude and phase signals, and a detection unit that generates a detection signal based on the time change of these signals, thereby distinguishing reflections from objects and the ground.
The proposed solution effectively suppresses false detection by accurately differentiating between reflections from objects and the ground, enhancing the reliability of ultrasonic sensors in vehicle applications.
Smart Images
Figure 2025084400000001_ABST
Abstract
Description
[Technical field]
[0001] The present disclosure relates to a signal processing device. [Background technology]
[0002] Conventionally, the time it takes for an ultrasonic wave to be emitted and reflected back from an obstacle is called the Time of Flight (TOF). Ultrasonic sensors are known that measure the distance to an obstacle by measuring the distance of the obstacle. Such ultrasonic sensors are often mounted on vehicles, and an example of such sensors is an on-board clearance sonar. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] International Publication No. 2020 / 004609
[0004] [overview] When an ultrasonic sensor is attached to a vehicle or the like, there is a possibility that false detection may occur if the transmitted ultrasonic waves are reflected by the ground and received by the ultrasonic sensor.
[0005] In view of the above circumstances, an object of the present disclosure is to provide a signal processing device capable of suppressing false detection caused by reflection of ultrasonic waves on the ground.
[0006] A signal processing device according to an embodiment of the present disclosure includes: A receiving circuit configured to output a reflected wave signal based on an output of the ultrasonic sensor element; an extractor configured to extract an amplitude signal and a phase signal of the reflected wave signal; a detection unit configured to generate a detection signal as a detection result of the reflected wave signal based on a time change of the phase signal and the amplitude signal; The configuration is provided with the following. [Brief description of the drawings]
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[0008] [Detailed Description] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
[0009] [Ultrasonic Sensor Mounted on a Vehicle] FIG. 1 shows a vehicle 200 equipped with an ultrasonic sensor 10X and an object (obstacle) 300. The ultrasonic wave transmitted from the ultrasonic sensor 10X is reflected by the object 300 and received by the ultrasonic sensor 10X as a reflected wave. The ultrasonic sensor 10X measures the distance by measuring the time from when the ultrasonic wave is transmitted until it is received. As the ultrasonic sensor 10X, various ultrasonic sensors described below can be applied, but the application target of the ultrasonic sensor is not limited to vehicles.
[0010] [Reflection of Ultrasonic Waves] Here, the reflection of ultrasonic waves will be described. FIG. 2 is a schematic diagram showing the transmission and reception of ultrasonic waves by an ultrasonic sensor. FIG. 2 shows an ultrasonic sensor 10X, an object 300, and the ground 400. Note that FIG. 2 is a schematic diagram viewed from the side. The ultrasonic sensor 10X is provided, for example, on a bumper of a vehicle and is arranged at a position at a height H from the ground 400. The object 300 is an object to be detected (for example, a pole or a wall). The ultrasonic sensor 10X includes an ultrasonic sensor element (not shown in FIG. 2), and ultrasonic waves are transmitted from the ultrasonic sensor element.
[0011] The ultrasonic wave US1 transmitted from the ultrasonic sensor 10X in the front direction is reflected by the object 300 and becomes a reflected wave US2, which is received by the ultrasonic sensor 10X. The reflected wave US2 due to being reflected by the object 300 is concentrated in a narrow range as viewed from the ultrasonic sensor 10X (ultrasonic sensor element). Therefore, the reflected wave US2 basically becomes one Sin (sine) wave. FIG. 3 shows an example of the reflected wave signal RS due to the reflected wave US2. As shown in FIG. 3, the reflected wave signal RS is one Sin wave. The phase of the reflected wave signal RS is constant over time.
[0012] On the other hand, ultrasonic waves are also transmitted from the ultrasonic sensor 10X toward the ground 400. The ultrasonic wave US11 transmitted toward the ground 400 is reflected by the ground 400 and becomes a reflected wave US12, which is received by the ultrasonic sensor 10X. Generally, the ground 400 (such as an asphalt road surface) has fine holes (unevenness), and has a deep structure as viewed from the ultrasonic sensor 10X. Since retroreflection occurs in the deep structure, the ultrasonic wave is reflected relatively strongly.
[0013] FIG. 4 is a schematic perspective view showing the ultrasonic sensor 10X and the ground 400. The ultrasonic sensor 10X is arranged at a position with a height H from the ground 400. Therefore, a plurality of reflected waves US12 due to the unevenness of the ground 400 at an equal distance from the ultrasonic sensor 10X are received by the ultrasonic sensor 10X, and the reflected wave signals of each reflected wave US12 are synthesized.
[0014] FIG. 5 shows examples of each waveform of the reflection signals RS1 to RSN due to each reflected wave US12 and the reflection signal RS obtained by synthesizing the reflection signals RS1 to RSN. Due to the subtle difference in the distance to each unevenness, a difference in phase occurs in each reflected wave US12. Since the transmission of the ultrasonic wave is performed by burst transmission of a plurality of waves such as 16 waves, the intensity of the transmitted ultrasonic wave changes over time. Since the intensities of the reflection wave signals RS1 to RSN due to the reflected waves US12 from each direction change over time, the intensity and phase of the synthesized reflection wave signal RS change over time.
[0015] <Comparative Example> FIG. 6 is a diagram showing the configuration of the ultrasonic sensor 100 according to the comparative example. The ultrasonic sensor 100 includes an ultrasonic sensor element (hereinafter, sensor element) 1 and a signal processing device 100A. The signal processing device 100A is an IC (integrated circuit) that integrates a drive circuit 2, a reception circuit 3, an ADC 4, a detection unit 5, a threshold generation unit 6, a comparator 7, and a communication terminal 8.
[0016] The sensor element 1 is composed of a piezoelectric element and is externally connected to the signal processing device 100A.
[0017] The drive circuit 2 is a circuit that drives the sensor element 1. When the sensor element 1 is pulse-driven by the drive circuit 2, the sensor element 1 vibrates and ultrasonic waves are transmitted from the sensor element 1. When the sensor element 1 vibrates, for example, by receiving a reflected wave of ultrasonic waves, the sensor outputs a sensor output signal SS.
[0018] The reception circuit 3 is a circuit that receives and processes the sensor output signal SS. The reception circuit 3 includes an LNA (low noise amplifier) and an LPF (low pass filter), etc. The LNA can amplify the weak sensor output signal SS. The reception circuit 3 outputs a reflected wave signal RS as a processing result of the sensor output signal SS.
[0019] The ADC (AD converter) 4 converts the reflected wave signal RS, which is an analog signal, into a digital signal DS.
[0020] The detection unit 5 performs detection processing on the digital signal DS to generate an amplitude signal AS. For example, envelope detection is used as the detection method. The amplitude signal AS is generated as an envelope of the digital signal DS. However, the amplitude signal AS may have a waveform other than the envelope.
[0021] The threshold value generation unit 6 generates a threshold value TH to be input to the comparator 7. The comparator 7 compares the amplitude signal AS with the threshold value TH and outputs an output signal OUT as a comparison result. The output signal OUT can take a high level or a low level as its level. The output signal OUT is output to the outside via the communication terminal 8.
[0022] FIG. 7 is a diagram showing an example of a reflected wave signal RS when receiving a reflected wave US2 due to reflection in the object 300 and an amplitude signal AS with respect to the reflected wave signal RS. The reflected wave signal RS in FIG. 7 is the same as that in FIG. 3. As shown in FIG. 7, the amplitude signal AS exceeds the threshold value TH, and the object 300 can be detected.
[0023] On the other hand, FIG. 8 is a diagram showing an example of reflected wave signals RS1 to RSN due to reflection on the ground 400, a reflected wave signal RS obtained by synthesizing the reflected wave signals RS1 to RSN, and an amplitude signal AS with respect to the reflected wave signal RS. Each reflected wave signal shown in FIG. 8 is the same as that in FIG. 5. Also, FIG. 8 shows the amplitude signal AS with respect to the reflected wave signal RS. As shown in FIG. 8, the amplitude signal AS exceeds the threshold value TH. Therefore, in the configuration according to the comparative example shown in FIG. 6, there is a possibility of misdetecting the reflection on the ground 400 as the reflection in the object 300 by comparing the amplitude signal AS and the threshold value TH in the comparator 7.
[0024] It is also possible to adjust the mounting angle of the ultrasonic sensor or to adopt a measure to reduce the vertical directivity of the ultrasonic sensor. The vertical directivity is represented by a vertical directivity angle θ in FIG. 2, for example. The reception sensitivity is maximum at the center of the range of the vertical directivity angle θ, and the reception sensitivity decreases as the distance from the center increases. However, such a measure also has limitations, and the influence due to reflection on the ground cannot be completely suppressed.
[0025] <First Embodiment> In view of the above problems, embodiments of the present disclosure are implemented as follows. Here, FIG. 9 is a diagram showing waveform examples of the reflected wave signal RS due to reflection in the object 300 and the phase PH of the reflected wave signal RS. The reflected wave signal RS in FIG. 9 is the same as that in FIG. 3. The phase PH is constant over time. On the other hand, FIG. 10 is a diagram showing waveform examples of the reflected wave signals RS1 to RSN due to reflection on the ground 400, the reflected wave signal RS obtained by synthesizing the reflected wave signals RS1 to RSN, and the phase PH of the reflected wave signal RS. Each reflected wave signal in FIG. 10 is the same as that in FIG. 5. Thus, the phase PH changes over time. In the present embodiment, based on such a phase difference, the reflection in the object 300 and the reflection on the ground 400 are discriminated.
[0026] FIG. 11 is a diagram showing the configuration of the ultrasonic sensor 101 according to the first embodiment. The ultrasonic sensor 101 includes a sensor element 1 and a signal processing device 101A.
[0027] The difference from the above-described comparative example lies in the configuration of the signal processing device 101A. The signal processing device 101A includes a drive circuit 2, a reception circuit 3, an ADC 4, a threshold value generation unit 6, a comparator 7, and a communication terminal 8 as in the comparative example, and further includes an extraction unit 9 and a detection unit 15. Note that the comparator 7 may be provided outside the signal processing device 101A.
[0028] The digital signal DS output from the ADC 4 is input to the extraction unit 9. The extraction unit 9 outputs a phase signal PS and an amplitude signal AS by performing detection processing on the digital signal DS. That is, the extraction unit 9 extracts the phase signal PS and the amplitude signal AS of the reflected wave signal RS. As the detection method, for example, quadrature demodulation or FFT (Fast Fourier Transform) is used. The phase signal PS and the amplitude signal AS are respectively input to the detection unit 15.
[0029] The detection unit 15 includes a differentiator 10, an absolute value output unit 11, a moving average unit 12, a detection sensitivity output unit 13, and a multiplier 14.
[0030] The differentiator 10 performs a differentiation process on the phase signal PS and outputs a differential signal DF. The absolute value output unit 11 outputs an absolute value signal AV as the absolute value of the differential signal DF. The moving average unit 12 performs a moving average process on the absolute value signal AV and outputs an average value signal MA. The moving average process is a process of obtaining the average value of data in a predetermined interval up to the present. That is, the average value of a predetermined number of data up to the present is calculated.
[0031] The detection degree output unit 13 generates a detection degree DD based on the average value signal MA and outputs the detection degree DD. The detection degree DD is data representing the degree of detection of the object 300. The multiplier 14 multiplies the amplitude signal AS by the detection degree DD to output a detection signal DT. The detection signal DT is the detection result of the reflected wave signal RS. The comparator 7 compares the detection signal DT with a threshold TH and outputs an output signal OUT.
[0032] Note that the detection unit 15 includes a detection degree determination unit 151. The detection degree determination unit 151 includes the absolute value output unit 11, the moving average unit 12, and the detection degree output unit 13.
[0033] FIG. 12 is a diagram showing waveform examples of various signals in the signal processing apparatus 101A according to the present embodiment. FIG. 12 is a diagram when the sensor element 1 receives a reflected wave due to reflection by the object 300. Here, a case where the reflected wave signal RS is the same as in FIG. 9 is shown. In FIG. 12 and FIG. 13 described later, the amplitude signal AS, the phase signal PS, the absolute value signal AV, the average value signal MA, the detection degree DD, and the detection signal DT are shown in order from the upper stage. The average value signal MA is generated by an exponential moving average that decreases the weight as it goes from the most recent to the past. However, other methods than the exponential moving average may be used for the moving average.
[0034] As shown in FIG. 12, the phase signal PS is constant and the absolute value signal AV is zero. Here, the detection degree output unit 13 obtains the detection degree DD by, for example, inverse proportion calculation based on the average value signal MA. As a result, for example, the detection degree DD takes a value from 0 to 1, and the larger the value, the higher the degree of detection of the object 300. Note that the detection degree DD = 1 may be calculated as the upper limit value. Also, as another example, the detection degree output unit 13 may obtain the detection degree DD as a value in a plurality of steps between 0 and 1 by using the value of the average value signal MA and a table.
[0035] In the case of FIG. 12, since the average value signal MA becomes almost 0, the detection degree DD is output as, for example, the maximum value of 1. At this time, the amplitude signal AS is multiplied by the detection degree DD by the multiplier 14, and the detection signal DT is output. In the case of FIG. 12, since the detection signal DT is almost the same as the amplitude signal AS, the detection signal DT exceeds the threshold value TH. Therefore, the comparator 7 can detect the reflection at the object 300.
[0036] On the other hand, FIG. 13 is a diagram showing waveform examples of various signals in the signal processing apparatus 101A according to the present embodiment, similar to FIG. 12, but is a diagram when the sensor element 1 receives a reflected wave due to reflection from the ground 400. Here, the reflected wave signal RS shows the same case as FIG. 10.
[0037] In the case of FIG. 13, a change occurs in the phase signal PS, and the value of the absolute value signal AV increases at the changed location. As a result, a relatively high value occurs in the average value signal MA, and a relatively low value occurs in the detection degree DD. Therefore, the detection signal DT becomes a low value with respect to the amplitude signal AS, and even if the value of the amplitude signal AS exceeds the threshold value TH, the detection signal DT does not exceed the threshold value TH. Therefore, it is possible to suppress the misdetection of the reflection from the ground 400 as the reflection at the object 300.
[0038] <Second Embodiment> FIG. 14 is a diagram showing the configuration of the ultrasonic sensor 102 according to the second embodiment. The ultrasonic sensor 102 includes a signal processing device 102A. The difference in the configuration of the signal processing device 102A from the first embodiment is that it has an amplitude output unit 140 instead of the multiplier 14.
[0039] In this embodiment, the detection degree output unit 13 outputs the detection degree DD as 0 or 1 according to whether the value of the average value signal MA is equal to or greater than a predetermined threshold. In this case, the detection degree DD is binary. When the detection degree DD is 1, the amplitude output unit 140 outputs the amplitude signal AS as the detection signal DT as it is, and when the detection degree DD is 0, the amplitude output unit 140 outputs the detection signal DT as 0. That is, the amplitude output unit 140 determines whether to output the amplitude signal AS according to the detection degree DD.
[0040] As in the example of FIG. 13, when the value of the average value signal MA increases, the detection degree DD is output as 0, and the amplitude signal AS is not output from the amplitude output unit 140. Thereby, it is possible to suppress the detection signal DT from exceeding the threshold TH and suppress false detection.
[0041] <Supplementary Note> As described above, the signal processing device (101A) according to one aspect of the present disclosure includes a receiving circuit (3) configured to output a reflected wave signal (RS) based on the output of the ultrasonic sensor element (1), an extraction unit (9) configured to extract an amplitude signal (AS) and a phase signal (PS) of the reflected wave signal, and a detection unit (15) configured to generate a detection signal (DT) as a detection result of the reflected wave signal based on the time change of the phase signal and the amplitude signal (a first configuration).
[0042] Further, in the above first configuration, it may further include a comparator (7) configured to compare the detection signal (DT) with a threshold (TH) (a second configuration).
[0043] Also, in the above first or second configuration, the detection unit (15) has a detection degree determination unit (151) configured to determine a detection degree (DD) representing the detection degree of ultrasonic wave reflection at the object (300) based on the temporal change of the phase information. The detection signal (DT) may be configured to be generated based on the detection degree (third configuration).
[0044] Also, in the above third configuration, the detection unit (15) has a differentiator (10) configured to perform a differentiation process on the phase signal and output a differentiation signal (DF). The detection degree determination unit (151) may be configured to output the detection degree (DD) based on the differentiation signal (fourth configuration).
[0045] Also, in the above fourth configuration, the detection degree determination unit (151) may have an absolute value output unit (11) configured to output an absolute value signal (AV) by taking the absolute value of the differentiation signal (fifth configuration).
[0046] Also, in the above fifth configuration, the detection degree determination unit (151) may have a moving average unit (12) configured to output an average value signal (MA) by the moving average of the absolute value signal (sixth configuration).
[0047] Also, in the above sixth configuration, the detection degree determination unit (151) may have a detection degree output unit (13) configured to determine the detection degree (DD) based on the average value signal by calculation or using a table (seventh configuration).
[0048] Also, in any of the above third to seventh configurations, the detection unit (15) may have a multiplier (14) configured to output the detection signal (DT) by multiplying the detection degree (DD) and the amplitude signal (AS) (eighth configuration).
[0049] Further, in any one of the third to seventh configurations, the detection unit (15) may be configured to include an amplitude output unit (140) that outputs the detection signal (DT) by determining the presence or absence of output of the amplitude signal (AS) according to the detection degree (DD) (ninth configuration).
[0050] Moreover, an ultrasonic sensor (101) according to an aspect of the present disclosure includes a signal processing device (101A) having any one of the first to ninth configurations and the ultrasonic sensor element (1) (tenth configuration).
[0051] Further, a vehicle (200) according to an aspect of the present disclosure includes the ultrasonic sensor (10X) having the tenth configuration (eleventh configuration).
Industrial Applicability
[0052] The present disclosure can be used, for example, in ultrasonic sensors for vehicle-mounted applications and the like.
Explanation of Reference Numerals
[0053] 1 Sensor element 2 Driving circuit 3 Receiving circuit 4 ADC 5 Detection unit 6 Threshold value generation unit 7 Comparator 8 Communication terminal 9 Extraction unit 10 Differentiator 11 Absolute value output unit 12 Moving average unit 13 Detection degree output unit 14 Multiplier 140 Amplitude output unit 15 Detection unit 151 Detection degree determination unit 10X Ultrasonic sensor 100, 101, 102 Ultrasonic sensors 100A, 101A, 102A Signal processing devices 200 Vehicle 300 Object 400 Ground
Claims
1. A receiving circuit configured to output a reflected wave signal based on the output of an ultrasonic sensor element; An extraction unit configured to extract an amplitude signal and a phase signal of the reflected wave signal; A detection unit configured to generate a detection signal as a detection result of the reflected wave signal based on a temporal change of the phase signal and the amplitude signal; A signal processing device comprising the above.
2. The signal processing device according to claim 1, further comprising a comparator configured to compare the detection signal with a threshold value.
3. The detection unit has a detection degree determination unit configured to determine a detection degree representing a detection degree of reflection of ultrasonic waves at an object based on a temporal change of the phase information, The signal processing device according to claim 1, wherein the detection signal is generated based on the detection degree.
4. The detection unit has a differentiator configured to perform differentiation processing on the phase signal and output a differential signal, The signal processing device according to claim 3, wherein the detection degree determination unit outputs the detection degree based on the differential signal.
5. The signal processing device according to claim 4, wherein the detection degree determination unit has an absolute value output unit configured to output an absolute value signal by taking an absolute value of the differential signal.
6. The signal processing device according to claim 5, wherein the detection degree determination unit has a moving average unit configured to output an average value signal by a moving average of the absolute value signal.
7. The signal processing device according to claim 6, wherein the detection degree determination unit has a detection degree output unit configured to determine the detection degree based on the average value signal by calculation or using a table.
8. The signal processing device according to claim 3, wherein the detection unit has a multiplier configured to output the detection signal by multiplying the detection degree and the amplitude signal.
9. The signal processing device according to claim 3, wherein the detection unit has an amplitude output unit configured to output the detection signal by determining presence or absence of output of the amplitude signal according to the detection degree.
10. An ultrasonic sensor comprising the signal processing device according to any one of claims 1 to 9 and the ultrasonic sensor element.
11. A vehicle comprising the ultrasonic sensor according to claim 10.
Citation Information
Patent Citations
Acoustic wave processing device and ultrasonic system
WO2020004609A1