JP2019196942A - Object detecting device - Google Patents

Abstract

To provide an object detecting device capable of improving detection precision of an object.SOLUTION: An object detecting device includes: transmission parts 1, 2 for transmitting ultrasonic waves in which a frequency changes in a predetermined pattern with a lapse of time as probing waves; reception parts 1, 5 for receiving ultrasonic waves; a frequency coincidence degree calculation part 11 for calculating coincidence between a frequency of a reception wave and a predetermined pattern; an amplitude peak detection part 10 for detecting a peak of amplitude of a reception wave; and a distance determination part 4 for determining distance to an object on the basis of the degree of coincidence calculated by the frequency coincidence degree calculation part 11 and a detection result of a peak of amplitude by the amplitude peak detection part 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an object detection device.

  For vehicle-mounted object detection devices that detect obstacles by sending and receiving ultrasonic waves, change the frequency of the exploration wave with time, compare the frequency of the received wave and the exploration wave, and send other vehicles traveling around A technique for avoiding interference with ultrasonic waves has been proposed (see, for example, Patent Document 1).

European Patent No. 2373434

  However, in an object detection apparatus that transmits and receives ultrasonic waves using a resonance type microphone, the frequency waveform of the received signal may change in the same manner as the exploration wave when reception of the reflected wave starts and when reception ends. Therefore, in the method of identifying the received wave only by comparing the frequencies, there is a possibility that the object detection accuracy is lowered.

  In view of the above points, an object of the present invention is to provide an object detection device capable of improving the detection accuracy of an object.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided an object detection device for detecting an object outside the vehicle mounted on the vehicle, wherein the ultrasonic wave changes in a predetermined pattern over time. Transmitting units (1, 2) that transmit the wave as the exploration wave, receiving units (1, 5) that receive the ultrasonic waves, and using the ultrasonic waves received by the receiving unit as the received waves, the frequency of the received waves and a predetermined frequency A frequency coincidence calculating unit (11) that calculates the degree of coincidence with the pattern, an amplitude peak detecting unit (10) that detects an amplitude peak of the received wave, a coincidence calculated by the frequency coincidence calculating unit, and A distance determination unit (4) for determining a distance from the object based on the detection result of the amplitude peak by the amplitude peak detection unit;

  The frequency pattern included in the exploration wave appears in the reflected wave when the amplitude of the reflected wave increases to some extent. Therefore, by determining the distance from the object based on the frequency coincidence and the amplitude peak detection result, the object detection accuracy can be improved.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows an example of a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a figure which shows the structure of the object detection apparatus concerning 1st Embodiment. It is a figure which shows the frequency of an upstream chirp signal. It is a figure which shows the frequency of a downstream chirp signal. It is a figure which shows the frequency of an upstream chirp signal. It is a figure for demonstrating an amplitude threshold value and receiving time. It is a figure for demonstrating the method of calculating a coincidence using a frequency offset. It is a flowchart of the object detection process in 1st Embodiment. It is a flowchart of the amplitude peak detection process in 1st Embodiment. It is a figure for demonstrating the effect of 1st Embodiment. It is a flowchart of the object detection process in 2nd Embodiment. It is a figure for demonstrating the calculation method of the residual sum of squares in 3rd Embodiment. It is a flowchart of the amplitude peak detection process in 3rd Embodiment. It is a figure for demonstrating the calculation method of the residual sum of squares in 4th Embodiment. It is a flowchart of the amplitude peak detection process in 4th Embodiment. It is a figure which shows the structure of the object detection apparatus concerning 5th Embodiment. It is a figure which shows the frequency of the chirp signal in other embodiment. It is a figure which shows the frequency of the chirp signal in other embodiment. It is a figure which shows the frequency of the chirp signal in other embodiment. It is a figure which shows the frequency of the chirp signal in other embodiment. It is a figure which shows the frequency of the chirp signal in other embodiment. It is a figure which shows the frequency of the chirp signal in other embodiment. It is a figure which shows the frequency of the chirp signal in other embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment will be described. The object detection device of the present embodiment is an ultrasonic sonar device that is mounted on a vehicle and detects an object outside the vehicle.

  As shown in FIG. 1, the object detection apparatus includes a microphone 1, a transmission circuit 2, a signal generation unit 3, and a control unit 4. In addition, the object detection device includes a reception circuit 5, a signal processing unit 6, an amplitude generation unit 7, a frequency generation unit 8, an amplitude threshold determination unit 9, an amplitude peak detection unit 10, a frequency determination unit 11, And a reference wave storage unit 12.

  The control unit 4, the signal processing unit 6, and the like are configured by a known microcomputer including a CPU, a ROM, a RAM, an I / O, and the like, and execute processes such as various calculations according to a program stored in the ROM or the like. Further, the control unit 4 or the like may be configured by an ASIC including a signal processing circuit.

  The microphone 1 is arranged facing the outer surface of the vehicle, and transmits an ultrasonic wave that is an exploration wave for detecting an object toward the outside of the vehicle. Specifically, the microphone 1 includes a piezoelectric element (not shown) having a configuration in which a piezoelectric layer is disposed between two electrodes facing each other. The two electrodes are connected to the transmission circuit 2, and an ultrasonic voltage is transmitted from the microphone 1 to the outside of the vehicle by applying an AC voltage from the transmission circuit 2 and deforming the piezoelectric layer.

  The transmission circuit 2 performs processing such as boosting on the input signal and outputs it. The transmission circuit 2 is connected to a signal generation unit 3 that generates a pulse signal. The transmission circuit 2 converts the pulse signal input from the signal generation unit 3 into an AC signal, and then boosts the signal to generate the pulse signal. An alternating voltage is applied to the microphone 1.

  As described above, the microphone 1 and the transmission circuit 2 are configured to transmit a search wave having a frequency corresponding to the frequency of the pulse signal when the pulse signal as the AC signal generated by the signal generation unit 3 is input. Corresponds to the transmitter.

  Note that the signal generation unit 3 generates a pulse signal including a chirp signal whose frequency changes in a predetermined pattern with time in response to a transmission instruction from the control unit 4. Thereby, an ultrasonic wave including a chirp signal whose frequency changes with time in a predetermined pattern is transmitted from the microphone 1 as an exploration wave. Further, a plurality of patterns of exploration waves including different types of chirp signals are transmitted from the microphone 1, and the exploration wave pattern is determined by a transmission instruction issued from the control unit 4 to the signal generation unit 3. . In order to make the amplitude of the exploration wave constant, the signal generator 3 and the transmission circuit 2 are controlled so that the amplitude of the pulse signal and the amplitude of the AC voltage input to the microphone 1 are constant.

  In the present embodiment, a chirp signal whose frequency monotonously increases with time and a chirp signal whose frequency monotonously decreases are used.

  Specifically, when the control unit 4 issues a first pattern transmission instruction to the signal generation unit 3, the signal generation unit 3 generates a pulse signal whose frequency increases linearly over time as shown in FIG. 2. Generate. As a result, the first exploration wave including the upstream chirp signal whose frequency increases with time is transmitted from the microphone 1.

  When the second pattern transmission instruction is issued from the control unit 4 to the signal generation unit 3, the signal generation unit 3 generates a pulse signal whose frequency decreases linearly with the passage of time as shown in FIG. As a result, the second exploration wave including the downstream chirp signal whose frequency decreases with time is transmitted from the microphone 1.

If the resonance frequency of the microphone 1 is f ₀ , the signal generator 3 starts sweeping the frequency of the pulse signal from a frequency different from the resonance frequency f ₀ . Specifically, the signal generation unit 3 sweeps the frequency of the pulse signal between a frequency lower than the resonance frequency f ₀ and a higher frequency. The frequency of the pulse signal generated by the signal generator 3 and the frequency of the exploration wave may change continuously, or may change discretely as shown in FIG.

  The microphone 1 is configured to transmit ultrasonic waves, receive ultrasonic waves, and output a voltage corresponding to the sound pressure of the received ultrasonic waves. Specifically, the two electrodes of the piezoelectric element included in the microphone 1 are also connected to the reception circuit 5, and a voltage generated between the two electrodes when the piezoelectric layer is deformed by receiving an ultrasonic wave is a reception circuit. 5 is input. The receiving circuit 5 amplifies the weak voltage input from the microphone 1 with an amplifier (not shown) so as to be a desired voltage, and removes noise with a band-pass filter as necessary, and then performs A / D conversion. The receiving circuit 5 outputs the signal generated thereby.

  Thus, the microphone 1 and the receiving circuit 5 are configured to receive an ultrasonic wave and output a signal corresponding to the amplitude and frequency of the received ultrasonic wave, and correspond to a wave receiving unit. The ultrasonic wave received by the microphone 1 is used as a received wave.

  The signal processing unit 6 detects the frequency and amplitude of the received wave from the signal generated by the receiving circuit 5 through A / D conversion.

Specifically, the signal processing unit 6 calculates I and Q from the mixing signal of the reference signal generated by the signal generation unit 3 and the reception signal using orthogonal demodulation. The frequency of the reference signal generated by the signal generation unit 3 is f _p , t is time, and I is the frequency of 2f _p or more after multiplying the output signal of the receiving circuit 5 by sin (2πf _p t). This is the magnitude of the signal obtained by removing the component. Q is the magnitude of a signal obtained by multiplying the output signal of the receiving circuit 5 by cos (2πf _p t) and then removing a component having a frequency of 2 f _p or more. The frequency f _p is a value close to the resonance frequency f ₀ in the resonance band of the microphone 1. In _addition, it may be as _f p = f _0.

Amplitude generator 7 calculates the _{A r} by ^{_{A r = (I 2 + Q}} 2) 1/2 the amplitude of the received wave as _{A r.} Further, the frequency generator 8 calculates P by P = atan (Q / I), where P is the phase of the received wave, and f _r is the frequency of the received wave, and f _r = 1 / (2π) · dP / dt + f to calculate the _{f r} by _p.

The amplitude generation unit 7 generates a waveform of the amplitude _Ar based on the calculated amplitude _Ar . Frequency generator 8, on the basis of the calculated frequency f _r, and generates a waveform of a frequency f _r. The amplitude waveform generated by the amplitude generation unit 7 is transmitted to the amplitude threshold value determination unit 9 and the amplitude peak detection unit 10. Further, the frequency waveform generated by the frequency generation unit 8 is transmitted to the frequency determination unit 11.

  The amplitude threshold determination unit 9 determines whether or not the amplitude of the received wave is larger than a predetermined amplitude threshold based on the amplitude waveform generated by the amplitude generation unit 7. The determination result of the amplitude threshold determination unit 9 is transmitted to the control unit 4. Note that the amplitude threshold value may be a constant value or may be changed according to the time elapsed since the transmission of the exploration wave. For example, as shown in FIG. 5, the amplitude threshold value may be discretely decreased with time.

  The time when the microphone 1 transmits the exploration wave is the transmission time, the time when the microphone 1 receives the reflected wave of the exploration wave is the reception time, the propagation time from the transmission time to the reception time is T, If the distance between and is D and the speed of sound is c, then T = 2D / c. In the object detection device, a predetermined amplitude threshold is set for the propagation time T, and the amplitude threshold determination unit 9 detects the reflected wave by comparing the amplitude of the received wave with the amplitude threshold. The amplitude threshold value determination unit 9 determines whether or not a reflected wave is detected during a predetermined time after the exploration wave is transmitted.

  The transmission time is, for example, a time when an AC signal starts to be input from the signal generation unit 3 to the transmission circuit 2. The reception time is, for example, a time when the amplitude of the reception wave becomes larger than the amplitude threshold as at time t1 in FIG. 5 or a time when the amplitude of the reception wave becomes maximum as at time t2 in FIG. The In FIG. 5, a time other than t1 when the amplitude of the received wave becomes larger than the amplitude threshold or a time other than t2 when the amplitude of the received wave becomes maximum may be set as the received time.

  As will be described later, the amplitude peak detection unit 10 compares the slope of the amplitude of the received wave with the slope threshold, but the time when the absolute value of the slope of the amplitude is smaller than the slope threshold may be used as the reception time. Further, as described later, the frequency determination unit 11 compares the frequency coincidence with the coincidence threshold, but the time when the coincidence becomes larger than the coincidence threshold may be set as the reception time. The time when the coincidence takes a peak may be set as the reception time.

  The determination result of the amplitude threshold value determination unit 9, the propagation time, and the like are transmitted to the control unit 4. The peak value is also transmitted to the control unit 4. As the peak value, the maximum value of the amplitude of the received wave, the amplitude value of the received time, and the amplitude value compared with the amplitude threshold can be used. Further, when the amplitude threshold value is changed with time, the amplitude threshold value at the reception time may be a peak value.

  The control unit 4 calculates the distance to the object based on the information transmitted from the amplitude threshold value determination unit 9, determines whether the object exists within a predetermined distance from the vehicle, and drives according to the determination result. Notification to the person. The control unit 4 corresponds to a distance determination unit.

  The amplitude peak detector 10 detects the peak of the amplitude of the received wave from the amplitude waveform generated by the amplitude generator 7. In the present embodiment, the amplitude peak detector detects the peak of the amplitude of the received wave by comparing the gradient of the amplitude of the received wave with a predetermined gradient threshold.

  Note that the amplitude waveform of the reception wave varies depending on the frequency characteristics of the microphone 1, the transmission circuit 2, and the reception circuit 5. For this reason, the inclination threshold is set based on the frequency characteristics of one or both of the transmission unit configured by the microphone 1 and the transmission circuit 2 and the reception unit configured by the microphone 1 and the reception circuit 5. For example, the inclination threshold is decreased as the resonance band of the microphone 1 is narrowed, and the inclination threshold is increased as the band is widened.

  Based on the waveform generated by the frequency generation unit 8, the frequency determination unit 11 determines whether or not the received wave includes a signal whose frequency changes in the same manner as the search wave. The frequency determination unit 11 has a function as a frequency coincidence calculation unit that calculates the coincidence between the frequency of the received wave and a predetermined pattern, and the frequency changes in a predetermined pattern based on the calculated coincidence. It is determined whether or not the signal is included in the received wave.

Note that when the reflected wave of the exploration wave is received, the microphone 1 changes in frequency in the opposite direction to the exploration wave with time, or after the frequency changes more slowly than the exploration wave, and then the frequency changes in the same manner as the exploration wave Output a signal. This is because when the AC voltage starts to be applied from the transmitting circuit 2 microphones 1 begins to minutely vibrate at around the resonance frequency f _0, also it takes time to reach a state where the microphone 1 is vibrated at the frequency of the pulse signal This is probably because of this. Similarly, it is considered that when the microphone 1 receives the reflected wave, it starts to vibrate slightly near the resonance frequency f ₀ and it takes time until the microphone 1 vibrates at the frequency of the reflected wave.

  For example, when the microphone 1 transmits a first exploration wave including an upstream chirp signal, the frequency of the received wave monotonously increases more gently than the pulse signal before the upstream chirp signal whose frequency changes in the same manner as the pulse signal. Appears. Alternatively, a signal whose frequency monotonously decreases appears before an upstream chirp signal whose frequency changes in the same manner as the pulse signal.

  When the microphone 1 transmits the second exploration wave including the downstream chirp signal, a signal whose frequency increases monotonously appears in the reception wave before the downstream chirp signal whose frequency changes like the pulse signal. Alternatively, a signal whose frequency monotonously decreases more gently than the pulse signal appears before the downstream chirp signal whose frequency changes as in the case of the pulse signal.

  Therefore, in the present embodiment, the received wave is determined using the chirp signal included in the received wave and the portion before the chirp signal. Specifically, the reference wave storage unit 12 stores a chirp signal and a reference wave corresponding to a portion before the chirp signal for each chirp signal. Then, the frequency determination unit 11 calculates the degree of coincidence between the waveform transmitted from the frequency generation unit 8 and the waveform of the reference wave stored in the reference wave storage unit 12, and determines the chirp signal included in the received wave. .

  Note that such a resonant microphone 1 outputs a signal similar to the above signal at the start of reception of reflected waves, at the end of reception, at the time of reception of noise, and the like. In order to distinguish between this signal and the chirp signal corresponding to the exploration wave, in this embodiment, the received wave is determined using the frequency coincidence and the amplitude peak as described later.

  As the waveform of the reference wave corresponding to the upstream chirp signal, for example, a waveform whose frequency increases more slowly than the pulse signal generated by the signal generation unit 3 and then increases at the same rate of change as the pulse signal is used. Further, for example, a waveform whose frequency increases at the same rate of change as the pulse signal after the frequency decreases is used.

  As the waveform of the reference wave corresponding to the downlink chirp signal, for example, a waveform whose frequency decreases more slowly than the pulse signal generated by the signal generation unit 3 and then decreases at the same rate of change as the pulse signal is used. Further, for example, a waveform whose frequency decreases at the same rate of change as the pulse signal after the frequency is increased is used.

  As described above, the reference wave storage unit 12 stores a reference wave including a frequency change pattern similar to that of the exploration wave. The frequency determination unit 11 determines that a chirp signal is included in the received wave when the degree of coincidence between the waveform generated by the frequency generation unit 8 and the reference wave is greater than a predetermined coincidence threshold.

The frequency determination unit 11 obtains the degree of coincidence using, for example, a frequency offset. FIG. 6 shows an uplink chirp signal where the reference wave frequency is R (t), the frequency offset is Δf, and Δf is used to approximate the reference wave frequency R (t) to the received wave frequency f _r (t). Then, a method is shown in which the degree of coincidence is obtained by evaluating the correlation between R (t) + Δf and f _r (t) by the residual sum of squares.

  When the number of samples is N and the standard deviation is σ, the residual sum of squares E is as shown in Equation 1.

  The residual sum of squares E is minimized when Equation 2 holds, and Δf at this time is as shown in Equation 3.

  Substituting this Δf into Equation 1 and substituting the residual sum of squares E obtained thereby into Equation 4, the degree of coincidence M is obtained.

  For the downlink chirp signal, the matching degree M can be similarly obtained using the reference wave for the downlink chirp signal.

  The frequency determination unit 11 compares the coincidence degree M with the coincidence degree threshold value, and determines that the chirp signal is included in the received wave when the coincidence degree M is larger than the coincidence degree threshold value. Specifically, the frequency determination unit 11 determines that the uplink chirp signal is included in the received wave when the coincidence M for the uplink chirp signal is greater than the coincidence threshold. Moreover, the frequency determination part 11 determines with the downlink chirp signal being contained in the received wave, when the coincidence degree M about a downlink chirp signal is larger than a coincidence threshold.

  In the present embodiment, the determination result of the frequency determination unit 11 is transmitted to the amplitude peak detection unit 10, and the amplitude peak detection unit 10 detects the amplitude peak using the determination result of the frequency determination unit 11. To do. The detection result of the amplitude peak detection unit 10 is transmitted to the amplitude threshold determination unit 9, and the amplitude threshold determination unit 9 determines the amplitude based on the detection result of the amplitude peak detection unit 10.

  Specifically, the amplitude peak detection unit 10 performs amplitude peak detection processing when the frequency determination unit 11 determines that the received wave includes a signal whose frequency changes in a predetermined pattern. The amplitude peak detection unit 10 sets an amplitude peak detection range, which is a time range, based on the time when the coincidence calculated by the frequency determination unit 11 is greater than the coincidence threshold. Then, the amplitude peak detection unit 10 calculates the amplitude gradient in the amplitude peak detection range, and determines whether or not the absolute value of the calculated gradient is smaller than the gradient threshold value.

  The amplitude threshold determination unit 9 compares the amplitude of the received wave with the amplitude threshold when the amplitude peak detection unit 10 determines that the absolute value of the amplitude gradient of the received wave is smaller than the inclination threshold.

  The operation of the object detection device will be described. When the control unit 4 sends a transmission instruction to the signal generation unit 3, the signal generation unit 3 starts generating a pulse signal. The pulse signal generated by the signal generator 3 is converted into an AC signal by the transmission circuit 2, an AC voltage is applied from the transmission circuit 2 to the microphone 1, and an exploration wave is transmitted from the microphone 1. At this time, the signal generation unit 3 changes the frequency of the pulse signal to be generated with time in accordance with the transmission instruction from the control unit 4. As a result, the first exploration wave or the second exploration wave is transmitted from the microphone 1.

  Thereafter, when the control unit 4 issues a wave receiving instruction to the signal processing unit 6, the processes of steps S1 to S7 shown in FIG. 7 are executed. In step S1, received wave data is updated. Specifically, the receiving circuit 5 amplifies the output voltage of the microphone 1, performs A / D conversion, and outputs it to the signal processing unit 6. Then, the signal processing unit 6 performs a filter process or the like on the signal input from the receiving circuit 5 in response to the reception instruction.

  The amplitude generator 7 generates an amplitude waveform from the output of the signal processor 6. Further, the frequency generation unit 8 generates a frequency waveform from the output of the signal processing unit 6.

  The object detection apparatus proceeds from step S1 to step S2, and determines whether the frequency waveform of the received wave matches the waveform of the reference wave. Specifically, the frequency determination unit 11 compares the frequency waveform generated by the frequency generation unit 8 with the waveform of the reference wave stored in the reference wave storage unit 12 to obtain the degree of coincidence, and the degree of coincidence is the degree of coincidence. It is determined whether or not it is larger than the threshold value. If it is determined that the coincidence is greater than the coincidence threshold, the object detection apparatus proceeds to step S3. If it is determined that the coincidence is equal to or less than the coincidence threshold, the object detection apparatus proceeds to step S1.

  In step S <b> 3, the amplitude peak detector 10 detects an amplitude peak from the amplitude waveform generated by the amplitude generator 7. In step S3, the process shown in FIG. 8 is performed in detail. That is, the amplitude peak detector 10 normalizes the amplitude waveform in step S31, calculates the amplitude gradient in step S32, and determines whether the gradient is within a predetermined range in step S33. To do. If it is determined that the slope value is within the predetermined range, the object detection device proceeds to step S4 assuming that the amplitude of the received wave is near the maximum, and if it is determined that the slope value is not within the predetermined range. The object detection device proceeds to step S1.

  In step S31 of the present embodiment, specifically, the amplitude waveform is normalized as follows. That is, the amplitude peak detection range is set based on the time when the frequency waveforms match in step S2. A value obtained by dividing the amplitude value of the sample included in the amplitude peak detection range by the representative amplitude value is set as a new amplitude value. In step S32, an inclination is calculated from the new amplitude value, and the calculated inclination is compared with an inclination threshold value in step S33.

  Since the slope of the amplitude of the reflected wave changes depending on the amplitude level, when the slope is determined using the amplitude waveform generated by the amplitude generator 7 as it is, it is necessary to change the slope threshold according to the amplitude level of the reflected wave. Yes, processing becomes complicated. On the other hand, by normalizing the amplitude of the received wave, it is possible to make a determination while keeping the inclination threshold constant.

  As the amplitude peak detection range, for example, a time range before and after the reference time is used with the time when the frequency coincidence becomes larger than the coincidence threshold as the reference time. Further, a time range from a predetermined time before the reference time to the reference time, a time range between two times before the reference time, a time range after the reference time, or the like may be used. Also, the time at which the process of step S31 is started may be set as the reference time.

  As the representative amplitude value, for example, the amplitude at the reference time, the amplitude before the reference time for a predetermined time, and the amplitude after the predetermined time from the reference time can be used. Further, as the representative amplitude value, the maximum value and minimum value of the amplitude within the amplitude peak detection range, the amplitude of the first sample within the amplitude peak detection range, and the amplitude of the last sample may be used. Further, as the representative amplitude value, an average value or a median value of amplitudes within the amplitude peak detection range may be used.

In step S32 in the present embodiment, the amplitude of the first sample of the amplitude peak detection range set to A _1, the amplitude of the last sample and A _N, the length of the amplitude peak detection range and T _slope, the slope as S, S is obtained by S = (A _N −A ₁ ) / T _slope . It is assumed that the first sample and the last sample are acquired at the start time and end time of the amplitude peak detection range, respectively.

  In step S33, it is determined that the inclination is within the predetermined range when the absolute value of the inclination S is smaller than the inclination threshold, and the inclination is not within the predetermined range when the absolute value of the inclination S is equal to or greater than the inclination threshold. It is determined.

  In step S4 of FIG. 7, the amplitude threshold value determination unit 9 determines whether or not the amplitude value of the received wave is larger than the amplitude threshold value. If it is determined that the amplitude value of the received wave is greater than the amplitude threshold value, the object detection apparatus proceeds to step S5, and the determination result in step S4 is stored in the amplitude threshold value determination unit 9. On the other hand, if it is determined that the amplitude value of the received wave is not larger than the amplitude threshold value, the object detection device proceeds to step S1.

  Note that the amplitude value to be compared with the amplitude threshold value in step S4 is, for example, the maximum value of the amplitude of the received wave in the amplitude value determination range that is the time range set based on the reference time described above. If not, the maximum value within the amplitude value determination range may be used. Further, as an amplitude value to be compared with the amplitude threshold value, an average value of two or more amplitude values within the amplitude value determination range may be used.

  Further, the amplitude value determination range may be the same as the amplitude peak detection range or may be different from the amplitude peak detection range. For example, the amplitude value determination range may be a time range after the amplitude peak detection range.

  The object detection apparatus proceeds from step S5 to step S6, and determines whether or not the measurement end time has elapsed. The measurement end time is a time that is a predetermined time after the transmission of the exploration wave is started. If it is determined that the measurement end time has elapsed, the object detection device proceeds to step S7, and if it is determined that the measurement end time has not elapsed, the object detection device proceeds to step S1.

  In step S <b> 7, the amplitude threshold value determination unit 9 transmits the determination result of the amplitude value, the peak value of the reflected wave, the reception time, the detection result of the chirp signal, and the like to the control unit 4. The control unit 4 performs notification to the driver according to the determination result of the amplitude value and the magnitude of the peak value.

  The effect of this embodiment will be described. When the microphone 1 transmits the first exploration wave including the upstream chirp signal and the amplitude generator 7 and the frequency generator 8 generate, for example, the amplitude waveform and the frequency waveform shown in FIG. 9, the chirp signal is generated as follows. Detected.

  That is, at time t3 in FIG. 9, the waveform of the reference wave of the uplink chirp signal indicated by the alternate long and short dash line and the frequency waveform of the received wave are in good agreement. The object detection apparatus proceeds to step S3. As indicated by the one-dot chain line of the amplitude graph, the amplitude gradient is small at time t3. Therefore, it is determined in step S3 that the amplitude is close to the peak, and the object detection apparatus proceeds to step S4, depending on the magnitude of the amplitude. Is detected.

  On the other hand, the frequency waveform of the reference wave and the received wave of the downlink chirp signal indicated by a two-dot chain line at time t4 in FIG. 9 is in good agreement, so when step S2 is executed at time t4, the frequency coincidence degree Increases, and the object detection apparatus proceeds to step S3. However, as indicated by the two-dot chain line in the amplitude graph, the amplitude gradient is large at time t4. Therefore, it is determined in step S3 that the amplitude is not near the peak, and the object detection processing by the amplitude threshold value determination unit 9 is not performed. The detection device proceeds to step S1.

  Thus, in this embodiment, even if the frequency coincidence increases, the process returns to step S1 without performing the distance determination if the amplitude gradient is large.

  The chirp signal included in the exploration wave appears when the received signal becomes large to some extent, and the propagation time and the distance to the object can be accurately measured by detecting the chirp signal. However, apart from this chirp signal, a waveform similar to the chirp signal may appear at the frequency at the start of reception of the reflected wave, at the end of reception, and at the time of noise generation, and when receiving time is determined based on this waveform The measurement accuracy of the propagation time and the distance to the object is lowered.

  While the amplitude changes greatly at the start of reception of the reflected wave, at the end of reception, and when noise is generated, the change in amplitude is small near the peak of the amplitude. Therefore, the amplitude peak can be detected from the amplitude gradient. As described above, by determining the reception time based on the time when the frequency coincidence is large and the amplitude is near the peak, the measurement accuracy of the propagation time and the distance to the object can be improved. it can. In addition, it is possible to avoid interference and perform simultaneous measurement with a plurality of microphones, thereby improving measurement reliability and measurement cycle.

(Second Embodiment)
A second embodiment will be described. In the present embodiment, the received wave determination method is changed with respect to the first embodiment, and the others are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  As shown in FIG. 10, in this embodiment, the object detection apparatus proceeds from step S1 to step S3, and detects an amplitude peak. When the amplitude peak detection unit 10 determines that the amplitude is near the peak, the object detection apparatus proceeds from step S3 to step S2.

  In step S2 of the present embodiment, the frequency determination unit 11 compares the frequency coincidence at the time when the amplitude is near the peak with the coincidence threshold. If it is determined in step S2 that the degree of coincidence is greater than the coincidence degree threshold, the object detection apparatus proceeds from step S2 to step S4, and determines the amplitude value.

  In this embodiment in which the order of step S2 and step S3 is thus changed, the same effect as that of the first embodiment can be obtained.

  In this embodiment, the order of step S2 and step S3 is changed. However, the order of steps S2 to S4 may be changed. For example, after step S1, the process may be executed in the order of steps S4, S2, and S3. That is, the amplitude of the received wave is compared with the amplitude threshold, and the frequency coincidence is compared with the coincidence threshold at the time when the amplitude is larger than the amplitude threshold. If the coincidence is greater than the coincidence threshold, it is determined whether or not the amplitude is near the peak. If the amplitude is near the peak, the driver is notified according to the peak value or the like.

  Moreover, you may process in order of step S4, S3, S2 after step S1. That is, the amplitude of the received wave is compared with the amplitude threshold value, and it is determined whether or not the amplitude is near the peak at the time when the amplitude is larger than the amplitude threshold value. When the amplitude is near the peak, the frequency coincidence is calculated. If the coincidence is greater than the coincidence threshold, the driver is notified according to the peak value or the like.

(Third embodiment)
A third embodiment will be described. In this embodiment, the method of detecting the amplitude peak is changed from that of the first embodiment, and the others are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  In the present embodiment, the amplitude peak detector 10 stores an amplitude reference waveform for detecting an amplitude peak from the amplitude waveform of the received wave. As shown in FIG. 11, the amplitude reference waveform is a waveform that matches the portion near the peak in the normalized amplitude waveform, and the amplitude peak detector 10 determines the amplitude waveform and amplitude of the received wave. The peak of the amplitude of the received wave is detected by comparing with the reference waveform.

  For example, when manufacturing an object detection device, an upstream chirp signal and a downstream chirp signal are transmitted with an object placed around the object detection device, and the amplitude near the peak of the amplitude waveform of the received wave at that time is an amplitude reference. The waveform is stored in the amplitude peak detector 10 as a waveform.

As shown in FIG. 12, in step S3 of the present embodiment, the object detection apparatus proceeds from step S31 to step S34, and calculates the residual sum of squares of the normalized amplitude waveform and the amplitude reference waveform. Specifically, an amplitude peak detection range that is a time range is set based on the time when step S3 is started or the time when the frequency coincidence becomes greater than the coincidence threshold. Then, the amplitude of the i th sample contained in the amplitude peak detection range and A _i, what the amplitude A _i and normalized with A _{i ',} the amplitude of the portion corresponding to the i th sample of the amplitude reference waveform As R _Ai , a residual sum of squares E _A is calculated by Equation 5.

Object detection apparatus proceeds from step S34 to step S35, determines whether the residual sum of squares E _A is less than the predetermined residual sum of squares threshold. If it is determined that the residual sum of squares E _A is less than the residual sum of squares threshold, the object detecting device proceeds to step S4 as the amplitude of the received wave is around the peak, the residual sum of squares E _A is the residual square If it determines with it being more than a sum threshold value, an object detection apparatus will progress to step S1.

  As described above, also in the present embodiment in which the amplitude waveform of the received wave is compared with the amplitude reference waveform to detect the amplitude peak, the same effect as that of the first embodiment can be obtained.

  Note that the method for detecting an amplitude peak in the present embodiment may be applied to the second embodiment. In this case, the same effect as that of the second embodiment can be obtained.

(Fourth embodiment)
A fourth embodiment will be described. In this embodiment, the method of calculating the residual sum of squares is changed with respect to the third embodiment, and the others are the same as those in the third embodiment. Therefore, only different parts from the third embodiment will be described. .

  As shown in FIG. 13, the amplitude peak detection unit 10 of the present embodiment detects the amplitude peak by comparing the amplitude waveform of the received wave with the amplitude reference waveform multiplied by the amplitude magnification.

Specifically, the object detecting device proceeds from step S2 to step S3, as shown in FIG. 14, at step S36, the amplitude peak detector 10 calculates the amplitude ratio k _A. The amplitude peak detector 10 proceeds from step S36 to step S34, and calculates the residual sum of squares _{E A} by Equation 6.

The amplitude magnification k _A is calculated so that the residual sum of squares E _A is minimized. The residual sum of squares E _A is minimized when Equation 7 holds, and the amplitude magnification k _{A at} this time is as shown in Equation 8.

  The amplitude peak detection unit 10 proceeds from step S34 to step S35, and performs the same determination as in the third embodiment.

  In this embodiment that calculates the residual sum of squares using the amplitude magnification in this way, the same effect as the first embodiment that normalizes the amplitude can be obtained.

(Fifth embodiment)
A fifth embodiment will be described. In this embodiment, a wave receiving unit is added to the first embodiment, and the other parts are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  As shown in FIG. 15, the object detection device of this embodiment includes a reception circuit 13 in addition to the reception circuit 5, and the output of the microphone 1 is input to the reception circuit 5 and the reception circuit 13. Similarly to the reception circuit 5, the reception circuit 13 performs processing such as amplification, noise removal, and A / D conversion on the output signal of the microphone 1, but the gain is lower than that of the reception circuit 5. The microphone 1 and the receiving circuit 13 correspond to a low gain receiving unit.

  A signal generated by the receiving circuit 5 and a signal generated by the receiving circuit 13 are transmitted to the signal processing unit 6. The signal processing unit 6 and the amplitude generation unit 7 generate two amplitude waveforms based on the two input signals, and the two amplitude waveforms are transmitted to the amplitude peak detection unit 10.

  The amplitude peak detection unit 10 detects an amplitude peak based on the amplitude waveform generated from the output signals of the microphone 1 and the reception circuit 2 when the amplitude of the reception wave is equal to or less than a predetermined value. The amplitude peak detector 10 detects the amplitude peak based on the amplitude waveform generated from the output signal of the receiving circuit 13 when the amplitude of the received wave is larger than a predetermined value.

  In the case where only one receiving unit is provided, if the amplitude of the received wave is large, the output of the receiving unit exceeds the upper limit of the signal that can be input to the signal processing unit 6, and waveform information is lost. May decrease. On the other hand, when the amplitude of the received wave is larger than a predetermined value, the amplitude peak detecting unit 10 detects the amplitude peak based on the output of the low gain receiving unit, thereby reducing the amplitude peak detection accuracy. Can be suppressed.

(Other embodiments)
In addition, this invention is not limited to above-described embodiment, In the range described in the claim, it can change suitably.

  For example, in the first embodiment, the chirp signal whose frequency increases linearly and the chirp signal whose frequency decreases linearly are used. However, as shown in FIGS. 16 and 17, the chirp signal and frequency whose frequency increases nonlinearly as shown in FIGS. A chirp signal with a non-linear decrease may be used. For example, the frequency of the AC signal may be changed logarithmically with time. In this case, as shown in FIG. 18, the frequency of the AC signal may be changed discretely.

  Further, as shown in FIGS. 19 and 20, a chirp signal that changes after the frequency is kept constant for a predetermined time may be used. In this case, the frequency of the chirp signal may be changed linearly or non-linearly. Further, it may be constant for a predetermined time after changing the frequency of the chirp signal. Further, the frequency of the chirp signal may be changed discretely.

  Further, as shown in FIGS. 21 and 22, a chirp signal that increases after the frequency decreases and a chirp signal that decreases after the frequency increases may be used. In this case, the frequency of the chirp signal may be changed linearly or non-linearly. Moreover, you may use combining these patterns.

  In the first embodiment, one microphone 1 functions as a transmission unit and a reception unit. However, a microphone that functions as a reception unit may be arranged separately from the microphone that functions as a transmission unit. .

  Further, the amplitude gradient may be obtained by a method different from that of the first embodiment. For example, the amplitude gradient between the newest sample and the previous sample may be obtained for each sampling, and the average of the gradients obtained for the samples included in the amplitude peak detection range may be used as the amplitude gradient in the entire amplitude peak detection range. . In this case, if the amplitude peak detection range is the same, the same value as that of the first embodiment is calculated. However, by obtaining the inclination for each sampling, it becomes easy to cope with the change of the amplitude peak detection range. Alternatively, the slope may be obtained by approximating the amplitude waveform to a linear regression model by the least square method. Further, the amplitude peak detection range may be changed according to the elapsed time from the transmission time.

  In the third embodiment, one or both of the amplitude reference waveform and the residual sum of squares threshold value may be set based on the frequency characteristics of one or both of the transmission unit and the reception unit.

  When the chirp signal and the amplitude peak are detected in steps S2 and S3 for the received waves at two times within a predetermined time, the absolute value of the amplitude gradient of the received waves at the two times is small. The distance from the object may be determined based on the amplitude of the received wave. Alternatively, the distance to the object may be determined based on the amplitude of the received wave having the smaller residual amplitude sum of squares.

In the first embodiment, the amplitude of the received wave is normalized by dividing it by the representative amplitude value. However, the amplitude of the received wave may be corrected by another method. For example, a representative amplitude value of the received wave and _{A d,} representative amplitude value of the amplitude reference waveform and _{R Ad,} as ΔA _{= R} Ad -A _d, may be the amplitude of the corrected _{A i} + _ΔA. Alternatively, ΔA = (1 / N) Σ (R _Ai −A _i ) may be used. Here, Σ means the sum from 1 to N for i. Further, E _A = Nσ _A ² = Σ ((A _i + ΔA) −R _Ai ) ² and from the condition that ∂E _A / ∂ (ΔA) = 0, ΔA = (1 / N) Σ (A _i − R _Ai ). Alternatively, k _A = A _d / R _Ad , (1 / N) Σ (A _i / R _Ai ), and ΣA _i / ΣR _Ai may be used, and A _i / k _A may be the corrected amplitude. Further, E _A = Nσ _A ² = Σ (A _i / k _A −R _Ai ) ^2, and from the condition that ＡE _A / ∂k _A = 0, k _A = Σ (A _i R _Ai ) / Σ ( R _Ai ² ).

In the fourth embodiment, k _A = A _d / R _Ad may be set. Alternatively, k _A = (1 / N) Σ (A _i / R _Ai ) may be used. Alternatively, k _A = ΣA _i / ΣR _Ai may be set.

Further, in the fourth embodiment, and ΔA _{= R} Ad -A _d, may be compared with _{A i} and _{R Ai -ΔA.} Alternatively, ΔA = (1 / N) Σ (R _Ai −A _i ) may be used. Further, E _A = Nσ _A ² = Σ (A _i − (R _Ai −ΔA)) ^2, and ΔA = (1 / N) Σ (A _i from the condition that な る E _A / ∂ (ΔA) = 0. -R _Ai ).

DESCRIPTION OF SYMBOLS 1 Microphone 2 Transmission circuit 4 Control part 5 Reception circuit 10 Amplitude peak detection part 11 Frequency determination part

Claims (16)

An object detection device that is mounted on a vehicle and detects an object outside the vehicle,
A transmission unit (1, 2) for transmitting an ultrasonic wave whose frequency changes in a predetermined pattern over time as an exploration wave;
A receiving unit (1, 5) for receiving ultrasonic waves;
A frequency coincidence calculating unit (11) for calculating the coincidence between the frequency of the received wave and the predetermined pattern using the ultrasonic wave received by the wave receiving unit as a received wave;
An amplitude peak detector (10) for detecting an amplitude peak of the received wave;
A distance determination unit (4) that determines a distance from an object based on the degree of coincidence calculated by the frequency coincidence degree calculation unit and the amplitude peak detection result by the amplitude peak detection unit. .   The object detection apparatus according to claim 1, wherein the amplitude peak detection unit detects the amplitude peak of the received wave by comparing the amplitude waveform of the received wave with a predetermined amplitude reference waveform.   The amplitude peak detection unit determines the peak of the amplitude of the received wave when the residual sum of squares of the amplitude waveform of the received wave and the amplitude reference waveform is smaller than a predetermined residual sum of square threshold. The object detection device according to claim 2 to detect. When it is determined that the coincidence is greater than a predetermined coincidence threshold for the received waves at two times within a predetermined time, and the amplitude peak detection unit detects the amplitude peak of the received wave ,
The distance determination unit determines the distance to the object based on the amplitude of the received wave having a smaller residual sum of squares of the amplitude waveform and the amplitude reference waveform among the received waves at the two times. The object detection apparatus according to claim 3.   5. The one or both of the amplitude reference waveform and the residual sum of squares threshold value are set based on frequency characteristics of one or both of the transmitting unit and the receiving unit. Object detection device.   The object detection apparatus according to claim 1, wherein the amplitude peak detection unit detects an amplitude peak of the received wave by comparing an amplitude gradient of the received wave with a predetermined gradient threshold.   The object detection device according to claim 6, wherein the amplitude peak detection unit detects the peak of the amplitude of the received wave when the absolute value of the amplitude of the received wave becomes smaller than the tilt threshold.   The object detection apparatus according to claim 7, wherein the amplitude peak detection unit compares the inclination of the amplitude of the received wave with the inclination threshold after normalizing the amplitude of the received wave. For the received wave at two times within a predetermined time, it is determined that the degree of coincidence is greater than the coincidence threshold, and the amplitude peak detector determines the absolute value of the slope of the amplitude of the received wave as the slope. When it is determined that it is smaller than the threshold,
The distance determination unit according to claim 7 or 8, wherein the distance determination unit determines a distance from an object based on an amplitude of the received wave having a smaller absolute value of an amplitude gradient of the received waves at the two times. Object detection device.   The object detection device according to claim 7, wherein the inclination threshold is set based on one or both frequency characteristics of the transmission unit and the reception unit.   The distance determination unit determines a distance from an object based on the amplitude of a received wave when the degree of coincidence is greater than a predetermined coincidence threshold and an amplitude peak is detected by the amplitude peak detection unit. The object detection device according to claim 1. A predetermined time range from before to after the time when the coincidence becomes larger than the coincidence threshold is set as an amplitude peak detection range,
The object detection device according to claim 1, wherein the amplitude peak detection unit detects an amplitude peak of the received wave based on an amplitude of the received wave in the amplitude peak detection range. A low gain receiver (1, 13) having a lower gain than the receiver;
The amplitude peak detector detects an amplitude peak based on an amplitude of an ultrasonic wave received by the low gain receiver when the amplitude of the received wave is larger than a predetermined value. The object detection apparatus according to one.   The object detection device according to claim 1, wherein the frequency of the exploration wave monotonously increases or decreases monotonically with time.   The receiving unit, when receiving a reflected wave of the exploration wave, outputs a signal whose frequency changes in the same manner as the exploration wave after the frequency has changed in the opposite direction to the exploration wave with time. Item 15. The object detection device according to Item 14. A reference wave storage unit (12) for storing a reference wave including a waveform whose frequency changes in the predetermined pattern;
The frequency coincidence degree calculating unit calculates the degree of coincidence by comparing the frequency of the reference wave stored in the reference wave storage unit with the frequency of the received wave. The object detection apparatus described in 1.

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