JP2015010888A - Ultrasonic sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic sensor device for which the performance of detecting an object at a short distance is improved, even when the vibration characteristic of an ultrasonic vibrator changes.SOLUTION: An ultrasonic vibrator 1 transmits an ultrasonic pulse and receives a reflection wave reflected at an object. An amplification unit 2 amplifies an electric signal outputted from the ultrasonic vibrator 1. A first measurement unit 4 measures, on the basis of the electric signal outputted from the ultrasonic vibrator 1, a Q value of reverberating vibration generated in the ultrasonic vibrator 1 due to that the ultrasonic pulse is transmitted. A second measurement unit 5 measures the frequency of reverberating vibration on the basis of the electric signal outputted from the ultrasonic vibrator 1. A prediction unit 6 predicts the output amplitude of the amplification unit 2 on the basis of the Q value measured by the first measurement unit 4, the frequency measured by the second measurement unit 5, and the output amplitude in a non-saturated state outputted from the amplification unit 2. A comparison unit 7 compares the output amplitude outputted from the amplification unit 2 at a given point of time and the output amplitude predicted by the prediction unit 6 at that point of time, and a determination unit 8 determines, on the basis of the result of comparison, whether or not the object is present.

Description

  The present invention relates to an ultrasonic sensor device.

  Conventionally, an ultrasonic transducer that transmits and receives ultrasonic pulses has been provided. The ultrasonic transducer transmits ultrasonic pulses, and whether reflected waves from objects appear in the signals received by the ultrasonic transducers. There is an ultrasonic sensor device that detects the presence or absence of an object by determining whether or not (see Patent Document 1).

  In this type of ultrasonic sensor device, a signal due to reverberation appears in the received signal of the ultrasonic transducer immediately after transmitting an ultrasonic pulse, so the detection gate is opened after the time when the reverberation converges. The presence or absence of reflected waves is detected. Even if an object is present at a short distance, the presence of the object can be detected if a reflected wave is input after the detection gate is opened by multiple reflection, but there is no multiple reflection, and the reflected wave is generated before the reverberation vibration converges. When input, there is a possibility that an object at a short distance cannot be detected.

  In the ultrasonic sensor device described in Patent Document 1, an abnormality in a reverberation waveform is detected in order to detect a short-distance object to which a reflected wave is input before the detection gate is opened. That is, if the reflected wave is input before the reverberation vibration converges, it takes a longer time for the reverberation vibration on which the reflected wave signal is superimposed to converge. Therefore, in the ultrasonic sensor device described in Patent Document 1, the presence / absence of a reflected wave is determined based on a change in the length of reverberation vibration caused by superimposition of a reflected wave signal.

Japanese Patent Laid-Open No. 5-232240

  In the ultrasonic sensor device disclosed in Patent Document 1 described above, the presence or absence of a reflected wave is determined from the change in the length of reverberation vibration, and an object at a short distance is detected. By the way, since the length of reverberation vibration may change when the vibration characteristics of an ultrasonic transducer (ultrasonic vibrator) generated by reverberation change due to temperature and individual variations, this is disclosed in Patent Document 1. The detection performance of an object at a short distance is low in the ultrasonic sensor device.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic sensor device that improves the detection performance of an object at a short distance even when the vibration characteristics of the ultrasonic transducer change. Is to provide.

  An ultrasonic sensor device of the present invention converts an input pulse signal into an ultrasonic pulse, transmits the ultrasonic pulse, receives an ultrasonic pulse reflected by an object, and converts it into an electric signal; Generated in the ultrasonic transducer by amplifying an electrical signal output from the ultrasonic transducer and transmitting an ultrasonic pulse based on the electrical signal output from the ultrasonic transducer A first measurement unit for measuring a Q value of the reverberation vibration, a second measurement unit for measuring a frequency of the reverberation vibration based on an electric signal output from the ultrasonic transducer, and the first measurement unit. A prediction unit that predicts an output amplitude of the amplification unit based on a measured Q value, a frequency measured by the second measurement unit, and an output amplitude in a non-saturated state output from the amplification unit; The output amplitude output from the unit and the prediction unit predicts And a comparing unit for comparing the output amplitude at that time, characterized by comprising a determination unit based on the presence or absence of an object the comparison result by the comparison unit.

  The ultrasonic sensor device includes a switching unit that switches the amplification factor of the amplification unit from a plurality of preset amplification factors to a maximum amplification factor within a range in which the output of the amplification unit is not saturated. It is also preferable that the unit is configured to set the timing for switching the amplification factor of the amplification unit based on the Q value measured by the first measurement unit.

  The ultrasonic sensor device includes an attenuator that attenuates an electric signal output from the ultrasonic transducer, and the first measurement unit receives an electric signal of the ultrasonic transducer attenuated by the attenuator. It is also preferable to measure the Q value of the reverberation vibration.

  According to the present invention, the first measurement unit measures the Q value of reverberation vibration, and the second measurement unit measures the frequency of reverberation vibration. Since the prediction unit predicts the output amplitude of the amplification unit using the measurement result of the Q value and frequency of the reverberation vibration, even when the reverberation vibration changes due to temperature and individual variations, the output amplitude of the amplification unit is determined. It can be predicted accurately. When an object exists at a short distance of the ultrasonic sensor device and the reflected wave reflected by this object is superimposed on the reverberation vibration, the actual output amplitude output from the amplifying unit is based on the output amplitude predicted by the prediction unit. It will shift. Therefore, the determination unit superimposes the reflected wave reflected by the object on the reverberation vibration based on the comparison result of the output amplitude of the amplification unit at a certain time and the output amplitude predicted by the prediction unit. It is possible to determine whether or not there is an object at a short distance.

It is a block diagram of the ultrasonic sensor apparatus of this embodiment. It is a flowchart explaining operation | movement same as the above. (A) (b) is a wave form diagram explaining operation | movement same as the above. It is a wave form diagram explaining operation | movement same as the above. It is a block diagram of the other form same as the above. It is a wave form diagram explaining operation | movement same as the above. (A)-(c) is a wave form diagram explaining the operation | movement same as the above. It is a block diagram of another form same as the above. It is a wave form diagram explaining operation | movement same as the above.

  An embodiment of an ultrasonic sensor device according to the present invention will be described with reference to the drawings.

  The ultrasonic sensor device of this embodiment includes an ultrasonic transducer 1, an amplification unit 2, a first measurement unit 4, a second measurement unit 5, a prediction unit 6, a comparison unit 7, and a determination unit 8. Is provided. In addition to the above configuration, the ultrasonic sensor device of the present embodiment further includes a voltage measurement unit 3, a drive circuit 9, and a transformer 10. The ultrasonic sensor device according to the present embodiment is attached to, for example, the vicinity of bumpers before and after an automobile, and is used to detect an object around the automobile during parking.

  The drive circuit 9 outputs a pulse signal having a predetermined frequency at regular time intervals in order to output ultrasonic waves from the ultrasonic transducer 1 in a pulsed manner.

  A drive circuit 9 is connected to the primary side of the transformer 10, and the ultrasonic transducer 1 is connected to the secondary side of the transformer 10. The transformer 10 boosts the pulse signal input from the drive circuit 9 and applies the pulse signal to the ultrasonic transducer 1. The transformer 10 vibrates the ultrasonic transducer 1 and applies ultrasonic pulses having a predetermined frequency to the ultrasonic transducer 1. Output from.

  The ultrasonic transducer 1 converts the pulse signal input from the transformer 10 into an ultrasonic pulse and transmits the ultrasonic pulse. When an object exists around the ultrasonic sensor device, the ultrasonic wave transmitted from the ultrasonic transducer 1 is reflected by the object and received by the ultrasonic transducer 1. When receiving the ultrasonic wave reflected by the object, the ultrasonic vibrator 1 vibrates by the received ultrasonic wave, converts the vibration into an electric signal S1, and outputs the electric signal S1.

  The amplifying unit 2 amplifies the electric signal S1 output from the ultrasonic transducer 1 and outputs the signal S2 obtained by the amplification to the voltage measuring unit 3.

  The voltage measurement unit 3 measures the peak value for each period of the signal S2 output from the amplification unit 2, that is, the output amplitude of the signal S2.

  The first measuring unit 4 transmits the ultrasonic pulse based on the electric signal S1 output from the ultrasonic vibrator 1 and the Q value (attenuation constant) of reverberation vibration generated in the ultrasonic vibrator 1. Measure.

  FIG. 3A is a waveform diagram of the electric signal S1 output from the ultrasonic transducer 1, and FIG. 3B is a waveform diagram of the signal S2 output from the amplifying unit 2. When an ultrasonic pulse is transmitted from the ultrasonic transducer 1 at time t0, reverberation vibration is generated in the ultrasonic transducer 1 by transmitting the ultrasonic pulse. A corresponding electrical signal S1 is output. Since the electrical signal output from the ultrasonic vibrator 1 due to reverberation vibration is very large compared to the electrical signal generated by receiving the reflected wave, the output of the amplifying unit 2 reaches a saturation level due to attenuation of the reverberation vibration. The output S2 of the amplification unit 2 is saturated until the time t4 when it falls below. On the other hand, the output signal S1 of the ultrasonic transducer 1 before being amplified by the amplifying unit 2 is saturated at the beginning of the occurrence of reverberation vibration, but decreases with the decay of the reverberation vibration, and is earlier than time t4. It is smaller than the saturation level at t1.

  The first measurement unit 4 calculates the Q value of the ultrasonic transducer 1 based on the non-saturated output signal S1 output from the ultrasonic transducer 1. In other words, the first measuring unit 4 uses the following formula (1) based on the first peak voltage V1 (time t2) and the second peak voltage V2 (time t3) after becoming non-saturated. ) To obtain the Q value.

Q = −2 × π / ln (V2 / V1) (1)
The second measuring unit 5 measures the frequency of the output signal based on the output signal S1 output from the ultrasonic transducer 1. For example, the second measuring unit 5 obtains the peak time interval or zero-crossing time interval of the output signal S1, and obtains the frequency from the reciprocal of this time interval.

  The prediction unit 6 includes a Q value measured by the first measurement unit 4, a frequency measured by the second measurement unit 5, and an unsaturated output amplitude (that is, the voltage measurement unit 3) output from the amplification unit 2 at a certain time. ) And the amplification factor of the amplification unit 2, the output amplitude of the amplification unit 2 is predicted. The output amplitude of the amplification unit 2 measured by the voltage measurement unit 3 is input to the prediction unit 6, and in the example of FIG. 3B, the output S2 of the amplification unit 2 decreases from the saturation level after time t4. doing. Therefore, the predicting unit 6 employs the output amplitude V3 at the time t5 when the desaturation state is reached as the reference amplitude, and predicts the output amplitude of the amplifying unit 2 at the subsequent time t using the output amplitude V3. Specifically, assuming that the Q value measured by the first measurement unit 4 is Q1, the frequency measured by the second measurement unit 5 is f1, and the output amplitude of the amplification unit 2 in the non-saturated state is V3, the prediction unit 6 The predicted value V (t) of the output amplitude at time t is obtained using equation (2).

V (t) = V3 × exp (−π × f1 × t / Q1) (2)
Note that the prediction unit 6 employs the output amplitude V3 of the amplifying unit 2 that has become non-saturated as the reference amplitude, but may employ the signal V3p before amplification by the amplifying unit 2 as the reference amplitude. Here, when the gain of the amplification unit 2 is G1, V3 = V3p × G1. Therefore, the predicted value V (t) of the output amplitude at time t is obtained by the following equation (3).

V (t) = V3p × G1 × exp (−π × f1 × t / Q1) (3)
When the comparison unit 7 takes in the output amplitude S (t) of the amplification unit 2 from the voltage measurement unit 3 at time t after time t5, the comparison unit 7 and the prediction unit 6 predict the current amplitude. The output amplitude V (t) is compared. The comparison unit 7 sets a predetermined allowable error δ for the output amplitude V (t) predicted by the prediction unit 6. The comparison unit 7 determines that the absolute value (| S (t) −V (t) |) of the error between the output amplitude S (t) at the time t and the output amplitude V (t) predicted by the prediction unit 6 is an allowable error δ. If it is smaller than “0”, “0” is output. On the other hand, if the absolute value of the error between the output amplitude S (t) at time t and the output amplitude V (t) predicted by the prediction unit 6 is greater than or equal to the allowable error δ, the comparison unit 7 outputs “1”. Output.

  The determination unit 8 determines the presence or absence of a reflected wave by the object based on the comparison result of the comparison unit 7. If the output of the comparison unit 7 is “1”, the reflection by the object is in a period in which reverberation vibration exists. It is determined that a wave has been input, and a determination result that an object is present at a short distance is output to the outside. On the other hand, if the output of the comparison unit 7 is “0”, the determination unit 8 determines that the reflected wave from the object is not input during the period in which reverberation vibration exists, and the determination result that there is no object at a short distance. Is output to the outside.

  FIG. 2 is a flowchart for explaining the detection operation of the ultrasonic sensor. When ultrasonic waves are transmitted from the ultrasonic transducer 1, reverberation vibration is generated in the ultrasonic transducer 1 by the transmitted ultrasonic waves. For example, the second measurement unit 5 measures the frequency of the reverberation vibration by measuring the time interval of the zero crossing of the signal S1 output from the ultrasonic transducer 1 (step ST1).

  When the reverberation vibration generated in the ultrasonic vibrator 1 is attenuated and the vibration amplitude of the output signal S1 falls below the saturation level, the first measurement unit 4 measures the vibration amplitude of the reverberation vibration, and based on the measurement result. Using the above equation (1), the Q value of the reverberation vibration is obtained by calculation (step ST2).

  Thereafter, the prediction unit 6 takes in the output amplitude V3 in the non-saturated state from the voltage measurement unit 3 as a reference amplitude, and uses the output amplitude V3, the frequency f1 of the reverberation vibration, and the Q value Q1, the above equation (2). From this, the predicted value V (t) of the output amplitude at time t is obtained (step ST3).

  Next, the comparison unit 7 compares the output amplitude S (t) at time t with the output amplitude V (t) predicted by the prediction unit 6 (step ST4). If the absolute value of the error between the output amplitude S (t) and the output amplitude V (t) is within the allowable error δ, the comparison unit 7 sets the output to “0”.

  4 is a waveform diagram of the output S2 of the amplifying unit 2, and when the reflected wave from the object is superimposed on the reverberation vibration as illustrated, the output amplitude S (t) output from the voltage measuring unit 3 is The output amplitude V (t) predicted by the prediction unit 6 becomes a different value. When the absolute value of the difference between the actual output amplitude S (t) and the output amplitude V (t) predicted by the prediction unit 6 is equal to or greater than the allowable error δ, the comparison unit 7 sets the output to “1”.

  Based on the comparison result of the comparison unit 7, the determination unit 8 determines whether there is an object at a short distance where the reflected wave is incident before the reverberation vibration is attenuated (step ST5). Here, if the output of the comparison unit 7 is “0”, the determination unit 8 determines that there is no object at a short distance, and outputs the determination result to the outside. If the output of the comparison unit 7 is “1”, the determination unit 8 determines that an object is present at a short distance, and outputs the determination result to the outside.

  Further, the determination unit 8 outputs the output amplitude S (t) measured by the voltage measurement unit 3 when a necessary time elapses from when the ultrasonic transducer 1 transmits ultrasonic waves until the reverberation vibration sufficiently attenuates. And a predetermined threshold level are compared. Here, the period from the time when the ultrasonic transducer 1 transmits ultrasonic waves until the time required until the reverberation vibration sufficiently attenuates is referred to as a mask period, and the next period after the mask period ends. A period until the ultrasonic transducer 1 transmits ultrasonic waves is referred to as a detection gate period. In this detection gate period, when the output amplitude S (t) of the voltage measurement unit 3 exceeds the threshold level, the determination unit 8 determines that the reflected wave from the object has been input, and reflects the reflected wave from the time when the ultrasonic pulse is transmitted. The judgment result that the object exists at a distance corresponding to the time until receiving the signal is output to the outside.

  As described above, the ultrasonic sensor device of the present embodiment includes the ultrasonic transducer 1, the amplification unit 2, the first measurement unit 4, the second measurement unit 5, the prediction unit 6, and the determination unit 8. It is characterized by comprising. The ultrasonic transducer 1 converts an input pulse signal into an ultrasonic pulse and transmits it, receives an ultrasonic pulse reflected by an object, and converts it into an electrical signal. The amplifying unit 2 amplifies the electric signal output from the ultrasonic transducer 1. The first measurement unit 4 measures the Q value of reverberation vibration generated in the ultrasonic transducer 1 by transmitting an ultrasonic pulse based on the electrical signal output from the ultrasonic transducer 1. The second measurement unit 5 measures the frequency of the signal due to reverberation vibration based on the electrical signal output from the ultrasonic transducer 1. The predicting unit 6 determines the output amplitude of the amplifying unit 2 based on the Q value measured by the first measuring unit 4, the frequency measured by the second measuring unit 5, and the unsaturated output amplitude output from the amplifying unit 2. Predict. The comparison unit 7 compares the output amplitude output from the amplification unit 2 at a certain point in time with the output amplitude at that point predicted by the prediction unit 6. The determination unit 8 determines the presence / absence of an object based on the comparison result by the comparison unit 7.

  In the ultrasonic sensor device of the present embodiment, the first measurement unit 4 measures the Q value of reverberation vibration, and the second measurement unit 5 measures the frequency f1 of reverberation vibration. Since the prediction unit 6 predicts the output amplitude of the amplification unit 2 using the measurement result of the Q value and frequency of the reverberation vibration, even if the reverberation vibration changes due to temperature and individual variations, the prediction unit 6 The output amplitude can be accurately predicted. When an object exists at a short distance of the ultrasonic sensor device and the reflected wave reflected by this object is superimposed on the reverberation vibration, the actual output amplitude output from the amplifying unit 2 is predicted by the predicting unit 6 Deviation from amplitude. Therefore, the determination unit 8 determines whether the reflected wave reflected by the object is reverberation vibration based on the result of the comparison unit 7 comparing the output amplitude of the amplification unit 2 and the output amplitude predicted by the prediction unit 6 at a certain time. It is possible to determine whether or not the object is superimposed on the object and to detect an object at a short distance.

  By the way, in the ultrasonic sensor device of this embodiment, as shown in FIG. 5, the waveform of the envelope of the signal output from the amplification unit 2 is transferred to the voltage measurement unit 3 between the amplification unit 2 and the voltage measurement unit 3. A detection circuit 11 for outputting may be provided. FIG. 6 is a waveform diagram of the signal S2 output from the amplification unit 2 and the signal S3 output from the detection circuit 11. The waveform of the output signal S3 of the detection circuit 11 is the waveform of the envelope of the output signal S2. The voltage measurement unit 3 measures the voltage value of the signal S3 input from the detection circuit 11 and outputs the voltage value to the prediction unit 6. The prediction unit 6 captures the measurement results of the voltage measurement unit 3, the first measurement unit 4, and the second measurement unit 5 at a predetermined sampling interval. When the reverberation vibration is attenuated after the ultrasonic wave is transmitted and the measurement result of the voltage measurement unit 3 is lower than the saturation level, the prediction unit 6 uses the voltage value at that time to use the voltage measurement unit 3 at a certain time thereafter. Predict the measured value of. Then, the comparison unit 7 compares the actual measurement value output from the voltage measurement unit 3 at a certain point of time with the voltage value at the point of time predicted by the prediction unit 6, and determines the determination unit 8 based on the comparison result. Determines whether there is an object at a short distance.

  In addition, although the period for which the prediction unit 6 samples the measurement results of the voltage measurement unit 3, the first measurement unit 4, and the second measurement unit 5 is arbitrary, for example, the period (1 of reverberation vibration generated in the ultrasonic transducer 1). It is also preferable to sample at / f1).

  Further, the prediction unit 6 detects the zero cross of the reverberation vibration, counts the number of times the zero cross is detected within the unit time, obtains the zero cross cycle, and actually shifts by (1/4) cycle from the zero cross point. The comparison unit 7 may compare the voltage measured in step 1 and the prediction value predicted by the prediction unit 6. FIG. 7A is a diagram illustrating waveforms of the output signal S2 of the amplification unit 2 and the output S3 of the detection circuit 11. FIG. 7B is a waveform diagram showing a zero cross of the output signal S2 (a waveform diagram obtained by binarizing the output signal S2 at a zero level), and FIG. 7C is a waveform diagram showing sampling timing. A point deviated by (1/4) period from the zero cross point becomes a peak of reverberation vibration, and the vicinity of the peak of reverberation vibration is a time zone in which the amount of change in voltage with respect to time change is smallest in one period. In the example of FIG. 7, the comparison unit 7 measures the voltage measurement unit 3 at the timing when (¼) cycle has elapsed from the zero cross point at which the output signal S2 switches from negative to positive, that is, near the positive peak of reverberation vibration. Sample the results. Then, the comparison unit 7 compares the actual voltage value measured by the voltage measurement unit 3 at the above timing with the voltage value at this timing predicted by the prediction unit 6, and based on the comparison result, the determination unit 8 The presence / absence of an object at a short distance is determined.

  Since FIG. 7A schematically shows the output S2 of the amplifying unit 2, the time width in which the output S2 is positive and the output S2 become negative in the zero-cross waveform of FIG. 7B. Although the time width varies, the output S2 is actually substantially equal to the positive time width and the negative time width.

  Further, in the ultrasonic sensor device of the present embodiment, as shown in FIG. 8, the amplification factor of the amplification unit 2 is maximized within a range in which the output of the amplification unit 2 is not saturated from among a plurality of preset amplification factors. It is also preferable to provide a switching unit 13 that switches to the amplification factor. The switching unit 13 is configured to set the timing for switching the amplification factor of the amplification unit 2 based on the Q value measured by the first measurement unit 4.

  Since the signal level of the signal S1 output from the ultrasonic transducer 1 by receiving the reflected wave from the object is smaller than the signal generated by the reverberation vibration, it is preferable to increase the amplification factor of the amplification unit 2 as much as possible. . When the amplification factor of the amplification unit 2 is set to a large value, the output of the amplification unit 2 is saturated by the amplification unit 2 amplifying the signal due to the reverberation vibration in the mask period in which the signal due to the reverberation vibration remains. There is a possibility that. When the output of the amplifying unit 2 is saturated, the reflected wave from the object cannot be detected. Therefore, it is preferable to set the amplification factor as large as possible within the range where the output of the amplifying unit 2 is not saturated.

  For example, when three types of amplification factors g1, g2, and g3 (g1 <g2 <g3) are preset as the amplification factors of the amplification unit 2, the switching unit 13 attenuates a signal due to reverberation vibration in the mask period T1. Accordingly, the amplification factor of the amplification unit 2 is switched so as to increase the amplification factor. In the example of FIG. 9, the switching unit 13 divides the mask period T1 into three periods T11, T12, and T13, sets the amplification factor to the minimum value g1 in the first period T11, and sets the amplification factor to an intermediate value in the subsequent period T12. The gain is set to the maximum value g3 in the last period T13. In the period T11, the amplification factor of the amplification unit 2 is set to the minimum value g1 of the three set values, and the output of the amplification unit 2 is excluded except the period in which the signal S1 itself is saturated (the first half of the period T11). S2 is no longer saturated. In the subsequent period T12, the switching unit 13 switches the amplification factor of the amplification unit 2 to a value g2 larger than g1, and the output of the amplification unit 2 can be increased without saturating the output S2 of the amplification unit 2. . Further, in the last period T13 of the mask period T1, the switching unit 13 switches the amplification factor of the amplification unit 2 to the maximum value g3 among the three values g1 to g3, and the output S2 of the amplification unit 2 also in the period T13. The output of the amplifying unit 2 can be increased without saturating.

  In the example of FIG. 9, the reflected wave by the object is superimposed on the signal waveform due to the reverberation vibration from the second half of the period T12 to the first half of the period T13. When the amplification factor of the amplification unit 2 is set to g3 in the entire mask period T1, the output S2 of the amplification unit 2 becomes a waveform A1 indicated by a two-dot chain line in FIG. 9, and the amplification unit 2 until the end of the period T12. Since the output S2 is saturated, the signal due to the reflected wave cannot be detected. On the other hand, when the amplification factor of the amplification unit 2 is set to g1 in the entire mask period T1, the output S2 of the amplification unit 2 becomes a waveform A3 indicated by a broken line in FIG. 2, the signal component of the reflected wave included in the output S <b> 2 becomes small, and it becomes difficult to detect the signal due to the reflected wave.

  Therefore, the switching unit 13 sets the amplification factor of the amplifying unit 2 to the maximum value g2 within a range in which the output S2 of the amplifying unit 2 is not saturated in the period T12, and the output S2 of the amplifying unit 2 is shown in FIG. A waveform A2 indicated by a one-dot chain line is obtained. Thereby, the signal of the reflected wave by the object superimposed on the signal due to reverberation vibration can be reliably detected.

  Note that the switching unit 13 determines the timing for switching the amplification factor of the amplification unit 2 based on the Q value measured by the first measurement unit 4. When the Q value is small, the time until the reverberation vibration converges is shortened. Therefore, when the Q value is small, the switching unit 13 advances the timing for switching the amplification factor of the amplification unit 2 to a large value. As long as the output S2 is not saturated, the output of the amplifying unit 2 can be amplified to a value as large as possible.

  Note that in the detection gate period after the mask period T1 ends, the switching unit 13 does not change the amplification factor of the amplification unit 2, and keeps the amplification factor g3 in the last period T13 of the mask period T1.

  Further, as shown in FIG. 5, the ultrasonic sensor device of the present embodiment includes an attenuator 12 that attenuates an electric signal output from the ultrasonic transducer 1, and the first measuring unit 4 is an attenuator 12. It is also preferable to measure the Q value of the reverberation vibration based on the attenuated electric signal of the ultrasonic vibrator 1.

  When measuring the Q value of the reverberation vibration based on the output of the amplifying unit 2, the output of the amplifying unit 2 amplifies the output of the ultrasonic transducer 1, and therefore the period during which the output is saturated is long. It takes a relatively long time before the Q value can be measured. If an object is present in the vicinity of the ultrasonic sensor device, a reflected wave from the object is superimposed on the reverberation vibration, and the signal waveform due to the reverberation vibration changes, so that the Q value of the reverberation vibration may not be accurately measured. On the other hand, if the first measurement unit 4 measures the Q value of the reverberation vibration based on the signal obtained by attenuating the output of the ultrasonic transducer 1 with the attenuator 12, the time point when the ultrasonic wave is transmitted. Thus, the Q value of the reverberation vibration can be measured in a shorter time. Therefore, since the Q value of the reverberation vibration can be measured in a time zone where the influence of the reflected wave reflected by the object at a short distance is small, the Q value of the reverberation vibration can be measured more accurately.

DESCRIPTION OF SYMBOLS 1 Ultrasonic transducer 2 Amplification part 4 1st measurement part 5 2nd measurement part 6 Prediction part 7 Comparison part 8 Judgment part 9 Drive circuit 10 Transformer 11 Detection circuit 12 Attenuator 13 Switching part

Claims (3)

An ultrasonic transducer that converts an input pulse signal into an ultrasonic pulse, transmits the ultrasonic pulse, receives an ultrasonic pulse reflected by an object, and converts it into an electrical signal;
An amplifying unit for amplifying an electrical signal output from the ultrasonic transducer;
A first measurement unit that measures a Q value of reverberation vibration generated in the ultrasonic transducer by transmitting an ultrasonic pulse based on an electrical signal output from the ultrasonic transducer;
A second measurement unit that measures the frequency of the reverberation vibration based on an electrical signal output from the ultrasonic transducer;
A prediction unit that predicts an output amplitude of the amplification unit based on a Q value measured by the first measurement unit, a frequency measured by the second measurement unit, and an output amplitude in a non-saturated state output from the amplification unit; ,
A comparison unit that compares the output amplitude output from the amplification unit at a certain point in time with the output amplitude at the point predicted by the prediction unit;
An ultrasonic sensor device comprising: a determination unit that determines presence or absence of an object based on a comparison result by the comparison unit. A switching unit that switches the amplification factor of the amplification unit to a maximum amplification factor within a range in which the output of the amplification unit is not saturated from a plurality of preset amplification factors,
2. The ultrasonic sensor device according to claim 1, wherein the switching unit is configured to set a timing for switching an amplification factor of the amplification unit based on a Q value measured by the first measurement unit. . An attenuator for attenuating the electrical signal output from the ultrasonic transducer;
The said 1st measurement part measures the Q value of the said reverberation vibration based on the electrical signal of the said ultrasonic transducer | vibrator attenuate | damped by the said attenuator, The any one of Claim 1 or 2 characterized by the above-mentioned. The ultrasonic sensor device according to item.

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