Drive device, signal-processing device, ultrasonic sensor, and vehicle

Abstract

A drive device (4) according to the present disclosure is provided with a transmission signal generation circuit (41) configured to generate a transmission signal, and a drive circuit (42) configured to drive an ultrasonic vibration element (2) on the basis of the transmission signal. The drive circuit (42) is provided with: an initial drive sequence for generating the transmission signal having an initial frequency (f0); a first transition sequence for generating the transmission signal making a transition from the initial frequency (f0) to a first frequency (f1); and a second transition sequence for generating the transmission signal making a transition from the first frequency (f0) to a second frequency (f1). The initial frequency (f0) and the second frequency (f2) are closer to the resonance frequency (fc) of the ultrasonic vibration element (2) than the first frequency (f1). The time (Tt1) of the first transition sequence is longer than the time (Tt2) of the second transition sequence.　According to the present disclosure, it is possible to improve the followability of the vibration frequency change of the ultrasonic vibration element with respect to a frequency change in the transmission signal while suppressing an increase in the drive period of the ultrasonic vibration element. Thus, even if the drive period of the ultrasonic vibration element is short, the accuracy of identifying reflected waves can be improved.

Description

Drive unit, signal processing device, ultrasonic sensor, and vehicle

[0001] The invention disclosed in this specification relates to a drive unit, a signal processing unit, an ultrasonic sensor, and a vehicle.

[0002] The ultrasonic sensor generates ultrasonic waves, measures the time it takes for the generated ultrasonic waves to hit an object and return to the ultrasonic sensor, and uses the measured time to determine the distance from the ultrasonic sensor to the object.

[0003] International Publication No. 2020 / 004609

[0004] However, if it is not possible to distinguish between ultrasonic waves transmitted from other ultrasonic sensors and ultrasonic waves (reflected waves) transmitted from one's own ultrasonic sensor and reflected by an object, there is a risk of erroneous detection of distance.

[0005] Therefore, the ultrasonic sensor disclosed in Patent Document 1 changes the frequency of the transmitted wave signal and identifies the reflected wave by determining how the frequency changes. However, the frequency of the ultrasonic vibration element does not immediately change in response to the frequency change of the transmitted wave signal. In this way, if the vibration frequency change of the ultrasonic vibration element does not follow the frequency change of the transmitted wave signal well, the accuracy of identifying the reflected wave may deteriorate unless the frequency change is made gradually and the driving period of the ultrasonic vibration element is extended.

[0006] A drive device according to the present disclosure includes a transmit signal generating circuit configured to generate a transmit signal and a drive circuit configured to drive an ultrasonic vibration element based on the transmit signal. The drive circuit includes an initial drive sequence that generates the transmit signal at an initial frequency, a first transition sequence that generates the transmit signal from the initial frequency until it transitions to a first frequency, and a second transition sequence that generates the transmit signal until it transitions from the first frequency to a second frequency. The initial frequency and the second frequency are closer to a resonant frequency of the ultrasonic vibration element than the first frequency. The duration of the first transition sequence is longer than the duration of the second transition sequence.

[0007] The signal processing device according to the present disclosure includes a driving device having the above-described configuration, a receiving circuit configured to generate a received signal based on a reflected wave, which is an ultrasonic wave transmitted from the ultrasonic vibration element and reflected by an object, and an identification circuit configured to identify the reflected wave from the received signal.

[0008] An ultrasonic sensor according to the present disclosure includes the signal processing device configured as described above and an ultrasonic transmitting / receiving device including the ultrasonic vibration element.

[0009] A vehicle according to the present disclosure includes an ultrasonic sensor having the above-described configuration.

[0010] According to the present disclosure, it is possible to improve the tracking ability of the vibration frequency change of the ultrasonic vibration element in response to the frequency change of the transmission signal while suppressing an increase in the drive period of the ultrasonic vibration element, thereby improving the accuracy of identifying reflected waves even if the drive period of the ultrasonic vibration element is short.

[0011] FIG. 1 is a diagram showing a schematic configuration of an ultrasonic sensor according to an embodiment. FIG. 2 is a diagram showing a waveform of a drive signal and a frequency transition of a transmission signal. FIG. 3 is a diagram showing another waveform of a drive signal and a frequency transition of a transmission signal. FIG. 4 is a diagram showing a first pattern of frequency transition of a transmission signal and an ultrasonic wave. FIG. 5 is a diagram showing a second pattern of frequency transition of a transmission signal and an ultrasonic wave. FIG. 6 is a diagram showing a third pattern of frequency transition of a transmission signal and an ultrasonic wave. FIG. 7 is a diagram showing a fourth pattern of frequency transition of a transmission signal and an ultrasonic wave. FIG. 8 is a diagram showing a fifth pattern of frequency transition of a transmission signal and an ultrasonic wave. FIG. 9 is an external view of a vehicle.

[0012] 1 is a diagram showing a schematic configuration of an ultrasonic sensor 1 according to an embodiment. The ultrasonic sensor 1 includes an ultrasonic vibration element 2 and a signal processing device 3.

[0013] The ultrasonic vibration element 2 is composed of a piezoelectric element, and emits ultrasonic waves and receives ultrasonic waves reflected by an object (waves reflected from an object). In other words, the ultrasonic vibration element 2 is an ultrasonic transmission / reception device that transmits and receives ultrasonic waves. Unlike the present embodiment, the ultrasonic sensor may be configured to include an ultrasonic vibration element dedicated to transmitting ultrasonic waves and an ultrasonic vibration element dedicated to receiving ultrasonic waves.

[0014] The signal processing device 3 processes the drive signals supplied to the ultrasonic vibration elements 2 and the signals received from the ultrasonic vibration elements 2. In this embodiment, no transformer is provided between the ultrasonic vibration elements 2 and the signal processing device 3.

[0015] The signal processing device 3 includes a driving device 4 , a receiving circuit 5 , and an identification circuit 6 .

[0016] The driving device 4 drives the ultrasonic vibration element 2. The driving device 4 includes a wave transmission signal generating circuit 41, a driving circuit 42, and a boosting circuit 43.

[0017] The transmission signal generating circuit 41 generates a transmission signal. The transmission signal generating circuit 41 has a plurality of frequency change patterns for the transmission signal, and selects one pattern from the plurality of frequency change patterns.

[0018] The drive circuit 42 supplies a drive signal, which is an amplified transmission signal, to the ultrasonic vibration element 2 to drive (vibrate) the ultrasonic vibration element 2 .

[0019] The boost circuit 43 boosts the received voltage Vin to generate the power supply voltage Vcp for the drive circuit 42. The boost circuit 43 is configured, for example, by a charge pump circuit. If the drive period of the ultrasonic vibration element 2 is long, the power supply voltage Vcp decreases, and the power of the ultrasonic waves emitted from the ultrasonic vibration element 2 decreases. For this reason, in an ultrasonic sensor 1 that does not include a transformer, it is particularly useful to be able to shorten the drive period of the ultrasonic vibration element.

[0020] The receiving circuit 5 receives the signal output from the ultrasonic transducer 2 and generates a received signal based on the wave reflected from the object.

[0021] The discrimination circuit 6 discriminates reflected waves by discriminating between frequency change patterns selected by the transmission signal generation circuit 41 and frequency change patterns not selected by the transmission signal generation circuit 41. In other words, the discrimination circuit 6 discriminates (detects) reflected waves when the frequency change pattern of the received signal supplied from the reception circuit 5 corresponds to (matches or is similar to) the frequency change pattern selected by the transmission signal generation circuit 41. The discrimination process in the discrimination circuit 6 makes it possible to distinguish between ultrasonic waves transmitted from other ultrasonic sensors and ultrasonic waves (reflected waves) transmitted from its own ultrasonic sensor and reflected by an object.

[0022] The multiple frequency change patterns provided by the transmission signal generating circuit 41 include a pattern in which the frequency transitions from the initial frequency f0 to the first frequency f1 and then to the second frequency f2. The drive circuit 42 includes an initial drive sequence that generates a transmission signal of the initial frequency f0, a first transition sequence that generates a transmission signal from the initial frequency f0 to the first frequency f1, and a second transition sequence that generates a transmission signal from the first frequency f1 to the second frequency f2. When the transmission signal generating circuit 41 selects a pattern in which the frequency transitions from the initial frequency f0 to the first frequency f1 and then to the second frequency f2, the drive circuit 42 executes the initial drive sequence, the first transition sequence, and the second transition sequence. Note that the initial frequency f0 and the second frequency f2 are closer to the resonant frequency fc of the ultrasonic vibration element 2 than the first frequency f1.

[0023] FIG. 2 is a diagram showing the waveform of the drive signal and the frequency transition of the transmission signal when the transmission signal generating circuit 41 selects a pattern in which the frequency transitions in the order of the initial frequency, the first frequency, and the second frequency.

[0024] In Figure 2, the waveform of the drive signal and the frequency transition of the transmission signal are depicted from top to bottom. In the waveform of the drive signal, the horizontal axis represents time and the vertical axis represents voltage. In the frequency transition of the transmission signal, the horizontal axis represents time and the vertical axis represents frequency.

[0025] The drive circuit 42 sets the time Tt1 of the first transition sequence longer than the time Tt2 of the second transition sequence. The drive circuit 42 also sets the time Ti of the initial drive sequence to the time required for the vibration of the ultrasonic vibration element 2 at the initial frequency f0 to stabilize.

[0026] The ultrasonic vibration element 2 has a structure that easily vibrates at the resonance frequency fc. Therefore, when the frequency of the transmission signal is transitioned from a value close to the resonance frequency fc to a value far from the resonance frequency fc, the vibration frequency of the ultrasonic vibration element 2 has difficulty tracking changes in the transmission signal. Therefore, the drive circuit 42 lengthens the time Tt1 of the first transition sequence as described above to improve the ability of the ultrasonic vibration element 2 to track changes in the vibration frequency of the ultrasonic vibration element 2 to track changes in the transmission signal in the first transition sequence. On the other hand, when the frequency of the transmission signal is transitioned from a value far from the resonance frequency fc to a value close to the resonance frequency fc, the vibration frequency of the ultrasonic vibration element 2 easily tracks changes in the transmission signal. Therefore, the drive circuit 42 shortens the time Tt2 of the second transition sequence as described above to prevent the drive period of the ultrasonic vibration element from becoming longer.

[0027] That is, the driving device 4 can improve the ability of the ultrasonic vibration element 2 to follow changes in the vibration frequency of the ultrasonic vibration element 2 in response to changes in the frequency of the transmission signal while preventing the driving period of the ultrasonic vibration element 2 from becoming longer. This makes it possible to improve the accuracy of identifying reflected waves in the identification circuit 6 even if the driving period of the ultrasonic vibration element 2 is short.

[0028] In the frequency transition of the transmission signal shown in Fig. 2, the first frequency f1 is higher than the second frequency f2, but conversely, the second frequency f2 may be higher than the first frequency f1. Also, in the frequency transition of the transmission signal shown in Fig. 2, the initial frequency f0 is lower than the resonant frequency fc of the ultrasonic vibration element 2, but conversely, the initial frequency f0 may be higher than the resonant frequency fc of the ultrasonic vibration element 2. Also, the initial frequency f0 may match the resonant frequency fc of the ultrasonic vibration element 2. Also, in the frequency transition of the transmission signal shown in Fig. 2, the second frequency f2 is different from the initial frequency f0, but conversely, the second frequency f2 may match the initial frequency f0.

[0029] 2, the drive circuit 42 may include a first continuation sequence that continuously generates a transmission signal of the first frequency f1, and the time Tk1 of the first continuation sequence may be set between the time Tt1 of the first transition sequence and the time Tt2 of the second transition sequence. Note that the drive circuit 42 does not necessarily have to include the first continuation sequence.

[0030] 2, the drive circuit 42 may include a second continuation sequence that continuously generates a transmission signal of the second frequency f2, and the time Tk2 of the second continuation sequence may be set after the time Tt2 of the second transition sequence. Note that the drive circuit 42 does not necessarily have to include the second continuation sequence.

[0031] 2, it is desirable that the drive circuit 42 reduce the drive amount immediately before starting the first transition sequence. In the example shown in FIG. 2, the drive circuit 42 starts a period Ts1 in which the duty of the drive signal supplied to the ultrasonic vibration element 2 is reduced immediately before starting the first transition sequence. This causes the frequency transition to start in a state in which the ultrasonic vibration element 2 is temporarily weakened, resulting in a smooth frequency change of the ultrasonic vibration element 2. In other words, it is possible to further improve the ability of the ultrasonic vibration element 2 to follow the vibration frequency change of the transmission signal.

[0032] 2, it is desirable that the drive circuit 42 reduce the drive amount immediately before starting the second transition sequence. In the example shown in FIG. 2, the drive circuit 42 starts a period Ts2 in which the duty of the drive signal supplied to the ultrasonic vibration element 2 is reduced immediately before starting the second transition sequence. This causes the frequency transition to start in a state in which the ultrasonic vibration element 2 is temporarily weakened, resulting in a smooth frequency change of the ultrasonic vibration element 2. In other words, it is possible to further improve the ability of the ultrasonic vibration element 2 to follow the vibration frequency change of the transmission signal.

[0033] As shown in the example of FIG. 3, the drive amount may be reduced by reducing the amplitude of the drive signal supplied to the ultrasonic vibration element 2.

[0034] 4 to 8 are examples of frequency change patterns provided by the transmission signal generation circuit 41. In FIGS. 4 to 8, the horizontal axis represents time, and the vertical axis represents frequency. In FIGS. 4 to 8, a frequency transition FT1 of the transmission signal and a vibration frequency transition FT2 of the ultrasonic vibration element 2 are depicted. As shown in FIGS. 4 to 8, reverberation occurs in which the ultrasonic vibration element 2 continues to vibrate for a while even after the transmission signal has stopped.

[0035] The first pattern shown in Fig. 4 and the second pattern shown in Fig. 5 are examples of patterns in which the frequency transitions in the order of the initial frequency f0, the first frequency f1, and the second frequency f2. The third pattern shown in Fig. 6, the fourth pattern shown in Fig. 7, and the fifth pattern shown in Fig. 8 are examples of patterns in which the frequency transitions not in the order of the initial frequency f0, the first frequency f1, and the second frequency f2.

[0036] <Vehicle Sonar> Figure 9 is an external view of a vehicle. Front sonars X1 (L, R, C) are provided at the left and right corners and in the center of the front bumper of vehicle XX. Rear sonars X2 (L, R, C) are also provided at the left and right corners and in the center of the rear bumper of vehicle XX (however, for convenience of illustration, rear sonars X2R and X2C are not shown).

[0037] In this way, by installing the front sonar X1 (L, R, C) and the back sonar X2 (L, R, C) in the vehicle XX, it is possible to detect the approach of or measure the distance to objects (i.e., obstacles, other vehicles, or pedestrians) around the vehicle XX, thereby assisting the driver in driving safely.

[0038] The ultrasonic sensor 1 described above can be applied to the front sonar X1 (L, R, C) and the back sonar X2 (L, R, C).

[0039] <Others> Various modifications can be made to the embodiments of the present disclosure as appropriate within the scope of the technical ideas set forth in the claims. The various embodiments described so far may be combined as appropriate within a consistent scope. The above-described embodiments are merely examples of embodiments of the present disclosure, and the meanings of the terms in the present disclosure and each constituent element are not limited to those described in the above embodiments.

[0040] In this embodiment, no transformer is provided between the ultrasonic vibration element 2 and the signal processing device 3, but a transformer may be provided between the ultrasonic vibration element 2 and the signal processing device 3. When a transformer is provided between the ultrasonic vibration element 2 and the signal processing device 3, it is possible to omit the boost circuit 43.

[0041] <Supplementary Note> Supplementary notes are provided for the present disclosure, the specific configuration examples of which have been shown in the above-described embodiments.

[0042] The drive device (4) of the present disclosure comprises a transmission signal generating circuit (41) configured to generate a transmission signal, and a drive circuit (42) configured to drive an ultrasonic vibration element based on the transmission signal, wherein the drive circuit includes an initial drive sequence that generates the transmission signal at an initial frequency, a first transition sequence that generates the transmission signal until it transitions from the initial frequency to a first frequency, and a second transition sequence that generates the transmission signal until it transitions from the first frequency to a second frequency, wherein the initial frequency and the second frequency are closer to the resonant frequency of the ultrasonic vibration element than the first frequency, and the time period of the first transition sequence is longer than the time period of the second transition sequence (first configuration).

[0043] In the driving device of the first configuration described above, the driving circuit may include a first continuation sequence that continuously generates the transmission signal of the first frequency, and the first continuation sequence may be configured (second configuration) to be provided between the first transition sequence and the second transition sequence.

[0044] In the driving device of the first or second configuration, the driving circuit may include a second continuation sequence that continuously generates the transmission signal of the second frequency, and the second continuation sequence may be provided after the second transition sequence (third configuration).

[0045] The drive device of any of the first to third configurations may be configured (fourth configuration) to include a boost circuit (43) configured to boost the received voltage and generate a power supply voltage for the drive circuit.

[0046] In the driving device of any of the first to fourth configurations described above, the driving circuit may be configured to reduce the driving amount immediately before starting the first transition sequence (fifth configuration).

[0047] In the driving device of the fifth configuration described above, the driving circuit may be configured to reduce the duty of the driving signal supplied to the ultrasonic vibration element immediately before starting the first transition sequence (sixth configuration).

[0048] In the driving device of any of the first to sixth configurations described above, the driving circuit may be configured to reduce the driving amount immediately before starting the second transition sequence (seventh configuration).

[0049] In the driving device of the seventh configuration described above, the driving circuit may be configured to reduce the duty of the driving signal supplied to the ultrasonic vibration element immediately before starting the second transition sequence (eighth configuration).

[0050] The signal processing device (3) of the present disclosure has a configuration (ninth configuration) including a driving device of any one of the first to eighth configurations described above, a receiving circuit (5) configured to generate a received signal based on a reflected wave, which is an ultrasonic wave sent from the ultrasonic vibration element and reflected by an object, and an identification circuit (6) configured to identify the reflected wave from the received signal.

[0051] In the signal processing device of the ninth configuration, the transmission signal generating circuit may be configured to have a plurality of frequency change patterns of the transmission signal, and the plurality of frequency change patterns may include a pattern in which the initial frequency, the first frequency, and the second frequency transition in that order, and to select one pattern from the plurality of frequency change patterns (tenth configuration).

[0052] In the signal processing device of the above-mentioned tenth configuration, the identification circuit may be configured to identify the reflected wave by distinguishing between the frequency change pattern selected by the transmission signal generation circuit and the frequency change pattern not selected by the transmission signal generation circuit (eleventh configuration).

[0053] The ultrasonic sensor (1) of the present disclosure has a configuration (twelfth configuration) including a signal processing device of any one of the ninth to eleventh configurations and an ultrasonic transmitting / receiving device including the ultrasonic vibration element.

[0054] A vehicle (XX) of the present disclosure has a configuration (thirteenth configuration) that includes the ultrasonic sensor of the twelfth configuration described above.

[0055] REFERENCE SIGNS LIST 1 ultrasonic sensor 2 ultrasonic vibration element 3 signal processing device 4 drive device 41 transmission signal generating circuit 42 drive circuit 43 boost circuit 5 receiving circuit 6 identification circuit XX vehicle X1 front sonar X2 rear sonar

Claims

1. a transmit signal generating circuit configured to generate a transmit signal; a drive circuit configured to drive the ultrasonic vibration element based on the transmission signal; Equipped with The drive circuit an initial drive sequence for generating the transmit signal at an initial frequency; a first transition sequence for generating the transmit signal from the initial frequency to a first frequency; a second transition sequence for generating the transmit signal to transition from the first frequency to a second frequency; Including, the initial frequency and the second frequency are closer to a resonant frequency of the ultrasonic vibration element than the first frequency; A driving device, wherein the duration of the first transition sequence is longer than the duration of the second transition sequence.

2. The drive circuit a first continuous sequence for continuously generating the transmit signal at the first frequency; The drive device according to claim 1 , wherein the first continuation sequence is provided between the first transition sequence and the second transition sequence.

3. The drive circuit a second continuing sequence for continuously generating the transmit signal at the second frequency; The drive device of claim 1 , wherein the second continuation sequence is provided after the second transition sequence.

4. The drive device according to claim 1 , further comprising a boost circuit configured to boost a received voltage to generate a power supply voltage for the drive circuit.

5. The drive circuit The drive device according to claim 1 , configured to reduce the drive amount immediately before starting the first transition sequence.

6. The drive circuit The driving device according to claim 5 , wherein the driving device is configured to reduce a duty of the driving signal supplied to the ultrasonic vibration element immediately before starting the first transition sequence.

7. The drive circuit The drive device according to claim 1 , configured to reduce the drive amount immediately before starting the second transition sequence.

8. The drive circuit The driving device according to claim 7 , wherein the driving device is configured to reduce the duty of the driving signal supplied to the ultrasonic vibration element immediately before starting the second transition sequence.

9. The drive device according to claim 1 ; a receiving circuit configured to generate a receiving signal based on a reflected wave, which is an ultrasonic wave transmitted from the ultrasonic vibration element and reflected by an object; an identification circuit configured to identify the reflected wave from the received signal; A signal processing device comprising:

10. The transmission signal generating circuit includes: A plurality of frequency change patterns of the transmission signal are provided, the plurality of frequency change patterns includes a pattern in which the initial frequency, the first frequency, and the second frequency transition in this order; The signal processing device according to claim 9 , wherein one pattern is selected from a plurality of said frequency change patterns.

11. 11. The signal processing device according to claim 10, wherein the identification circuit is configured to identify the reflected wave by distinguishing between the frequency change pattern selected by the transmission signal generation circuit and the frequency change pattern not selected by the transmission signal generation circuit.

12. A signal processing device according to any one of claims 9 to 11; an ultrasonic transmitting / receiving device including the ultrasonic vibration element; An ultrasonic sensor comprising:

13. A vehicle comprising the ultrasonic sensor of claim 12.