JPH1073657A - Velocity measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge whether an ultrasonic wave includes noise and perform velocity operation only when noise is not included. SOLUTION: Whether each zone signal Se from a band-pass filter 8 satisfies predetermined conditions is judged with a detector 9 and only when it satisfies the predetermined conditions, the device outputs a detection signal Sf of a superior level. It judges that the detection signal Sf having the superior level is one or two and noise is not included when they are detection signal Sf from adjacent zones and that noise is included and it outputs the judgment as a noise judgment signal Sj to an operator in the other cases. Based on the noise judgment signal Sj, an operator 13 operates velocity only when noise is not included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting whether or not an ultrasonic wave received by a receiver contains the noise and detecting the noise. The present invention relates to a speed measuring device that enables highly reliable speed measurement by performing speed calculation processing only when the speed is not included.

[0002]

2. Description of the Related Art Conventionally, a speed measuring device utilizing the Doppler effect is sometimes used for measuring the speed of a moving object. FIG. 10 is a block diagram showing a configuration of such a speed measuring device. Hereinafter, for convenience of explanation, the speed measuring device will be roughly divided into a transmitting system, a receiving system, and a signal processing system.

The transmission system includes a reference oscillator for generating a reference signal having a frequency Fout, an output amplifier for amplifying the reference signal, and a transmitter 3 for emitting an ultrasonic wave based on a signal from the output amplifier 2. ing.

[0004] The receiving system includes a receiver 4 for receiving an ultrasonic wave having a frequency Fin and converting it into an electric signal, a preamplifier for amplifying a signal from the receiver 4 and outputting the amplified signal as a received signal. 5 is comprised.

[0005] Further, the signal processing system receives a reference signal and a received signal, mixes them, detects a signal from the mixer 6, and detects a signal having a difference frequency Fd between the reference signal and the received signal. A detector 7 that outputs a differential frequency signal, a bandpass filter 801 that extracts a Doppler signal by passing a Doppler frequency band signal from the differential frequency signal output from the detector 7, and measures the frequency of the Doppler signal. The frequency measuring device 12 determines whether or not the ultrasonic wave contains noise based on the signal from the noise band bandpass filter 802 that passes the noise band component of the difference frequency signal. A signal detector 901 for outputting a noise determination signal, it is determined whether or not a valid operation is possible based on the noise determination signal. Fd = 2 · V · Fout / (C−V) ······················ (1) The speed of the moving object is calculated based on the frequency of the signal. It comprises a display 14 for displaying the calculated speed of the moving object. Note that V in Equation 1 indicates the speed of the moving object, and C indicates the speed of sound.

[0006]

However, the above-described configuration is a configuration that can detect only when the noise is outside the measurement frequency band. Therefore, when the noise appears within the measurement frequency band, the noise is removed. There was a problem that it was not possible to detect and it was difficult to increase the reliability of the measurement result.

That is, many noise sources are present in various familiar environments such as applause, collision between metals, and turning or rolling of paper. The frequency components included in these noises are not single frequency components but include a plurality of frequency components.

For this reason, depending on the type of noise, it may appear in the frequency band of the ultrasonic wave to be used for measurement, and in such a case, it cannot be determined whether or not the ultrasonic wave contains noise. Speed measurement is performed based on a signal containing noise. Therefore, there is a problem that the reliability of the obtained operation result is low.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a speed measuring device capable of detecting noise even when it exists in a measurement frequency band, thereby improving measurement accuracy and reliability.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to an ultrasonic wave emitting means for emitting ultrasonic waves based on a reference signal of a predetermined frequency, and an ultrasonic wave receiving means for receiving ultrasonic waves. And a speed calculating means for calculating the speed of the moving object from the reference signal and the received signal, wherein the speed calculating means comprises: A difference frequency detection unit that obtains a difference in frequency from a signal and outputs the difference frequency signal as a difference frequency signal, and a frequency band that separates the difference frequency signal into two or more predetermined frequency bands and outputs the result as a band signal When the separation unit and the time when the band signal or the detection signal of the band signal exceeds a threshold value or a time when it can be considered to have exceeded the threshold value continue for a preset first determination time,
A band signal determination unit that outputs a detection signal of a superior level, and outputs a valid signal when a time exceeding the threshold or a time that can be regarded as exceeding the threshold continues for a second determination time longer than the first determination time. , The band signal and the detection signal are input, and a band signal selection unit that selects one of the band signals from the plurality of band signals based on the detection signal; A noise presence / absence determining unit that determines whether or not the ultrasonic wave includes noise and outputs a noise determination signal, and measures the frequency of the band signal selected by the band signal selecting unit, and based on the measurement result, When calculating the velocity of a moving object, only when it is determined based on the noise determination signal that the received ultrasonic wave does not include noise, and when the band signal is determined to be valid based on the valid signal. And having a measurement calculation unit for performing time calculation processing.

That is, from the received signal including various frequencies,
In order to measure the speed of the moving object with high accuracy by processing only the signal of the sound wave reflected by the moving object, the received signal is separated into band signals of a plurality of frequency bands by the frequency band separation unit.

If the time when the band signal is larger than the threshold value or the time when the band signal is considered to be larger than the threshold value is longer than the first judgment time set in advance, the detection signal having the dominant level indicating that is determined. When the time when the band signal exceeds the threshold value or the time when the band signal is considered to have exceeded the threshold value is longer than the second judgment time set in advance by a predetermined amount, an effective signal indicating that fact is output.

The first judgment time is set to be shorter than the second judgment time, and is set to be longer than the time of the band signal in the case where the start region of the band signal is disturbed in frequency or the like.

The second judgment time is a judgment time for removing the region from the frequency measurement and measuring the frequency when the frequency of the end region of the band signal is disturbed.

[0015] When at least one or more detection signals having a superior level are present by the band signal selection unit, the band signal corresponding to the detection signal having the highest frequency is selected.

The noise presence / absence determination section determines whether or not the ultrasonic wave received by the wave receiving means contains noise based on the detection signal, and outputs a noise determination signal.

The frequency of the band signal is measured by the measuring and calculating means, and the frequency is determined only when it is determined that the received ultrasonic wave does not include noise and when the band signal is determined to be valid based on the valid signal. The calculation of the speed of the moving object is performed by the measurement calculation unit based on the measurement result.

The above-mentioned superior level refers to a signal level effective in the subsequent judgment processing. For example, when a "High" level pulse signal is output when the band signal is larger than the threshold, the "High" level is output. Level becomes the dominant level.

According to a second aspect of the present invention, the noise presence / absence determining unit determines one or two detection signals having a superior level when the quality factor of the frequency band separation unit is high and the level of the differential frequency signal is low. If one is detected,
Alternatively, when the quality factor of the frequency band separation unit is low and the level of the differential frequency signal is high, one to three detection signals having a superior level are detected, and two or more superior levels are detected. When detection signals are detected, it is determined that the received ultrasonic waves do not include noise only when these detection signals are output from adjacent bands.

That is, when the quality factor of the frequency band separation unit is high and the level of the differential frequency signal is low, one or two detection signals having a superior level are detected, and the two superior levels are detected. When the detection signals are detected, it is determined that the received ultrasonic waves do not include noise only when these detection signals are output from adjacent bands.

Further, when the quality factor of the frequency band separation unit is low and the level of the differential frequency signal is high, one to three detection signals having a superior level are detected, and two or three superior levels are detected. Is detected, it is determined that the received ultrasonic waves do not include noise only when these detection signals are output from adjacent bands.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a speed measuring device according to the present embodiment. The velocity measuring device includes: an ultrasonic wave emitting unit that emits an ultrasonic wave based on a reference signal; a wave receiving unit that receives an ultrasonic wave reflected by a moving object or the like and outputs a received signal; It comprises speed calculation means for calculating the speed of the moving object based on the signal.

The speed calculating means includes a differential frequency detecting section for obtaining a differential frequency signal between the received signal and the reference signal, a frequency band separating section for separating and outputting the differential frequency signal into a plurality of frequency band band signals, A band signal judging unit for judging whether the band signal satisfies a predetermined condition and outputting a detection signal and a valid signal, and a band for selecting a band signal corresponding to a specific detection signal from the detection signals having a plurality of superior levels A signal selection unit, a noise presence / absence determination unit that detects whether or not the received ultrasonic wave contains noise based on the detection signal and outputs a noise determination signal, and measures a frequency of the band signal selected by the band signal selection unit And based on the frequency only when the ultrasonic wave received based on the noise determination signal contains no noise and the band signal measured by the effective signal is valid. It consists a measurement calculator for calculating the velocity of a moving object.

To explain the above configuration in detail, the transmitting means includes a reference oscillator for generating a reference signal S1 having a frequency Fout, an output amplifier for amplifying the power of the reference signal S1, and an ultrasonic amplifier S2 for amplifying the reference signal S1. And a wave transmitter 3 that emits light.

The receiving means 4 receives the ultrasonic wave S3, converts it into an electric signal, and outputs it. The signal from the receiver 4 is amplified, and the amplified signal is output as a received signal S4. It comprises an operational amplifier 5.

The difference frequency detecting section in the speed calculating means extracts a frequency difference between the received signal S4 and the reference signal S1 from the mixers 6 and 6 for mixing the received signal S4 and the reference signal S1, and extracts the difference. It comprises a detector 7 that outputs the frequency signal S5.

Further, the frequency band separating section separates the differential frequency signal S5 from the detector 7 into five adjacent narrow band frequency components and outputs it as band signals Se (SeHH to SeLL). (8a to 8e). Note that the number of divisions of the bandpass filter 8 is not limited to five, and can be set as appropriate.

The band signal judging section has signal detectors 9 (9a to 9e) provided corresponding to each band pass filter 8, and when each band signal Se satisfies a condition 1 described later, it has an advantage. Level detection signal Sf (SfHH to Sf
LL), and outputs an effective signal Si when the condition 2 is satisfied.

The band signal selecting section selects and outputs a band signal Se corresponding to the detection signal Sf having the highest frequency band from among the plurality of detection signals Sf having a superior level from the signal detecting section 9. have. The selected band signal Se is referred to as a band signal Sh.

The noise presence / absence determining unit receives the detection signal Sf from the signal detector 9, determines whether or not the received ultrasonic wave S3 contains noise based on the detection signal Sf, and determines this. It has a noise detector 15 that outputs it as a noise determination signal Sj.

The measurement calculation unit includes a frequency measuring unit 12 for measuring the frequency of the selected band signal Sh, a noise determination signal Sj
It is determined whether or not the received ultrasonic wave S3 contains noise based on the above, and whether or not the band signal Sh is valid based on the valid signal Si from the signal detector 9, and the noise is included. And an arithmetic unit 13 for calculating the speed of the moving object based on the frequency measured by the frequency measuring unit 12 only when the signal is not valid and is a valid signal.

The measurement calculation unit is provided with a temperature measuring device 15 for measuring the outside air temperature in consideration of the fact that the sound speed changes depending on the temperature. The temperature measuring device 15 appropriately corrects the temperature and displays the speed of the moving object. A display unit 14 is provided.

In the following description, the band-pass filter 8 (8a to 8e) and the signal detector 9 (9a to 9e)
9e) and the like consisting of a plurality of means having the same function are described as appropriate, such as a band-pass filter 8, a signal detector 9, etc., using a general number unless otherwise mentioned. .

FIG. 2 shows output signals of each block, and the operation will be described with reference to FIG. A reference signal S 1 having a frequency Fout is oscillated from the reference oscillator 1 and amplified by the output amplifier 2. Then, the ultrasonic wave S2 is transmitted from the transmitter 3.
Is injected.

The emitted ultrasonic wave S2 is reflected by the moving object and is subjected to the Doppler effect.
The reflected wave S3 is received by the receiver 4 as n reflected waves S3.

The ultrasonic wave S3 received by the receiver 4
It is necessary to pay attention that the frequency of the received signal S4 is not a single frequency and the waveform is not a clean waveform as shown in the emitted ultrasonic wave S2 because ultrasonic waves reflected or the like are incident under various conditions. .

For example, when measuring the ball speed of a ball thrown by a pitcher, the ultrasonic wave S3 received by the receiver 4 includes a reflected wave from the ball and a moving object other than the ball such as the body of the pitcher. The reflected wave includes a reflected wave, a direct wave that the ultrasonic wave emitted from the transmitter 3 directly wraps around and is received, and a reflected wave reflected by a stationary object. For the purpose of measuring the ball speed, all ultrasonic waves other than the ultrasonic waves reflected by the ball become noise.

Furthermore, many noise sources are present in various familiar environments, such as when clapping, collision between metals, and turning or rolling paper. The frequency components included in these noises are not single frequency components but include a plurality of frequency components.

The signal from the receiver 4 is amplified by the preamplifier 5 to become a received signal S4, then mixed with the reference signal S1 by the mixer 6, detected by the detector 7 to become the differential frequency signal S5, and Input to the pass filter 8.

The band-pass filter 8 is 5
Is divided into three bands (HH, HL, M, LH, LL), and the input difference frequency signal S5 is divided into each band signal Se (S
eHH to SeLL) and output to the signal detector 9 and the signal selector 10.

Since the bandpass filter 8 has transient characteristics, the frequencies of the start region and the end region of the band signal Se are modulated to frequencies different from the original frequency. Therefore, an accurate result cannot be obtained by performing measurement and calculation processing using such a band signal Se. Therefore, in order to eliminate the influence of the transient characteristics, the signal detector 9 is used.
Has made various decisions.

That is, the signal detector 9 determines whether or not the input band signal Se is larger than a threshold value set in advance for the signal detector 9, and determines whether the band signal Se becomes larger than the threshold value. Alternatively, when the time that can be regarded as being longer than the first determination time (condition 1), the detection signal Sf (SfHH to SfLL) having the superior level is output to the signal selector 10.

When the time when the band signal becomes larger than the threshold value or the time when the band signal can be considered larger than the second judgment time (condition 2), the band signal Se is not at least an unnatural signal such as noise, Further, an effective signal Si indicating that the frequency can be measured without including the modulated area in the end area of the band signal Se due to the transient characteristic is output to the arithmetic unit 13.

Then, the signal selector 10 detects the band signal Sh having the highest frequency band from the detection signal Sf having the superior level.
And outputs it to the frequency measuring device 12.

The reason for selecting a high-frequency band signal from a plurality of band signals Se is that, for example, when comparing the frequency of the ultrasonic wave reflected from the pitcher with the ultrasonic wave reflected from the ball, This is because the frequency of the reflected ultrasonic wave is high (the Doppler frequency is high).

Therefore, when the above relationship is not established, a reference to be selected by the signal selector 10 may be appropriately provided.

The arithmetic unit 13 receives the signal from the frequency measuring unit 12, the valid signal Si from the signal detector 9, and the outside air temperature signal from the temperature measuring unit 15. Based on these, the arithmetic unit 13 determines the sound speed C as the outside air temperature t by using a relational expression of C = 331.5 + 0.6t (2). Is calculated, and the display 14 displays this result.

Next, referring to FIG.
Will be described in detail. When the intermittent difference frequency signal S5 is input to the bandpass filter 8, the bandpass filter 8 modulates the start and end regions of the difference frequency signal S5 to a frequency different from the original frequency in the start region and the end region by a transient characteristic. Output as Therefore, the frequencies of the start region and the end region of the band signal Se are modulated by the transient characteristics and become different from the original frequency.

Hereinafter, the signal area transiently modulated by the band-pass filter 8 is referred to as a transient modulation area, and particularly, the modulation area at the start of a signal is referred to as a start modulation area, and the modulation area at the end is referred to as an end modulation area. The durations of the start modulation area and the end modulation area are described as Δts and Δte, respectively.

FIG. 3A shows a differential frequency signal S5 inputted from the detector 7 to the band-pass filter 8, and FIG.
(B) shows the band signal Se output from the band pass filter 8. FIG. 3 (c) is a diagram for facilitating the understanding of the frequency characteristics of the band signal Se that has been transiently modulated, and shows a waveform when the band signal Se is subjected to frequency / voltage conversion (F / V conversion). Is shown.

Now, assume that the center frequency in a certain band of the band-pass filter 8 is Fc, and the frequency of the difference frequency signal S5 is F.

At this time, if the frequency F of the differential frequency signal S5 is lower than the center frequency Fc (F <Fc), the frequency Fe of the band signal Se output from the band-pass filter 8 with the input of the differential frequency signal S5 is , Gradually increases to a frequency close to the center frequency Fc, and thereafter, a region gradually settles to the frequency F of the differential frequency signal S5 (start modulation region), and when the differential frequency signal S5 ends,
The output gradually increases to a frequency close to the center frequency Fc, and thereafter the output ends gradually (end modulation region).

Therefore, the F / V converted band signal Se
As shown in FIG. 3C, peaks are formed at both ends of the signal.

When the frequency F of the differential frequency signal S5 is higher than the center frequency Fc (F> Fc), the frequency Fe of the band signal Se is increased with the input of the differential frequency signal S5.
Gradually reaches the frequency F of the differential frequency signal S5 via the center frequency Fc (start modulation area), and when the differential frequency signal S5 ends, gradually decreases via the center frequency Fc (end modulation area), and the output ends. I do.

Accordingly, the F / V converted band signal Se is
Is a signal having a gentle mountain shape at both ends of the signal as shown in FIG.

On the other hand, when the frequency F of the difference frequency signal S5 is equal to the center frequency, the band signal Se gradually becomes the center frequency Fc (start modulation area), and the difference frequency signal S5
With the end of the period, the frequency gradually decreases (end modulation region), and the output is stopped.

Since the band-pass filter 8 has the transient characteristic as described above, a transiently modulated start modulation region and an end modulation region are generated, and frequency measurement and the like are performed using a signal region including these modulation regions. Therefore, accurate frequency measurement cannot be performed. Therefore, the error in the speed of the moving object becomes large, and the reliability is significantly reduced.

Therefore, in the signal detector 9, it is determined whether or not signal processing is possible by excluding the influence of the transient characteristic. This will be described with reference to FIG.

FIG. 4A is a block diagram showing a schematic configuration of the signal detector 9. The band signal Se is compared with a preset threshold value Vth to determine a predetermined pulse signal (judgment signal).
Based on the comparison block 9A that outputs S11 and the determination signal from the comparison block 9A, the detection signal Sf of the superior level is output when the band signal Se satisfies the condition 1, and the valid signal Si is output when the band signal Se satisfies the condition 2. The determination block 9B is configured to perform the determination.

FIG. 4B shows each signal waveform in the comparison block 9A, and FIG.
3 shows the respective signal waveforms.

The comparison block 9A receives a band signal Se and a threshold Vth, and outputs a trigger signal S10 when the band signal Se becomes larger than the threshold Vth. The comparator 9a has a predetermined width corresponding to the trigger signal S10. It is composed of a retrigger type circuit (retriggerable one-shot circuit) 9b for outputting the judgment signal S11.

The re-trigger type circuit 9b is provided with a trigger signal S1 input when the re-trigger type circuit 9b is in a metastable state.
0, each time the retrigger circuit 9b
Becomes a new metastable state. Therefore, if a plurality of trigger signals S10 are input continuously at intervals within the metastable state of the retrigger circuit 9b, a single wide square wave pulse signal S11 is output. This metastable state is characterized by a time constant τ, and the time constant is set to be larger by a predetermined amount than the cycle of the lower cutoff frequency of each bandpass filter 8.

The decision signal S11 obtained in this way
Is input to the decision block 9B. Decision block 9B
Is composed of a first judgment system and a second judgment system, and their operations are the same, but ultimately obtain different actions because of different set values.

These first and second decision systems are provided with a decision signal S11.
Are output from the first and second integrators 9c (9ca, 9cb) and the first and second Schmitt trigger circuits 9d which output integrated signals S15 (S15a, S15b) obtained by integrating the above to the first and second Schmitt trigger circuits 9d (9da, 9db). Trigger signal S1
6 (S16a, S16b), the first and second one-shot circuits 9e (9ea, 9eb) for outputting a pulse of a predetermined width
It is composed of

In the above configuration, the first integrator 9ca integrates the decision signal S11 and outputs an integrated signal S15a.
When the integration signal S15a becomes equal to or higher than the predetermined level V1, the first Schmitt trigger circuit 9da activates the trigger signal S1.
6a, and the first one-shot circuit 9ea detects the detection signal Sf with the rising of the trigger signal S16a as a trigger.
Is output.

The time width of this detection signal Sf is t2,
This time is a time required for the frequency measurement device 12 to measure the frequency of the band signal Se (hereinafter, referred to as a frequency measurement time).

Needless to say, the output of the first integrator 9ca is the level V
If it does not reach 1, the first Schmitt trigger circuit 9d
Since the trigger signal S16a is not output from a, the detection signal Sf is a signal of a non-order level.

The first integrator 9ca is designed so that the time t1 until the integration signal S15a reaches the predetermined level V1 is slightly longer than the duration Δts of the start modulation area.
Is set.

Therefore, the first Schmitt trigger circuit 9da
Is output after the start modulation area has elapsed since the input of the band signal Se. Therefore, when the frequency is measured by the frequency measuring device 12, it is possible to exclude at least the signal in the start modulation area.

However, in this case, the end modulation area may be included in the frequency measurement time t2. Therefore, the second determination system determines whether or not the end modulation area is included in the frequency measurement time t2, and outputs an effective signal Si if the end modulation area is not included.

That is, the second integrator 9cb outputs the judgment signal S11
And outputs an integrated signal S15b. When the integration signal S15b becomes equal to or higher than the predetermined level V2, the second Schmitt trigger circuit 9db outputs a trigger signal S16b. The second one-shot circuit 9eb outputs a valid signal Si having a predetermined width with the rising of the trigger signal S16b as a trigger.

A time t3 from the end of the detection signal Sf to the time when the integration signal S15b reaches the predetermined level V2.
Is set to be slightly longer than the duration Δte of the end modulation area.

Therefore, if the time t3 can be secured during the time width t0 of the band signal Se, the frequency measurement time t2
Does not include the end modulation area.

To summarize the above, when t0 ≧ t1 (condition 1), a detection signal Sf having a superior level of the time width t2 is output, and when t0 ≧ t1 + t2 + t3, (condition 2)
An effective signal Si is output.

Next, the signal selector 10 will be described with reference to FIG. The signal selector 10 has input terminals D1 to D5 having priorities, and selects a specific band signal Se based on a signal from the priority encoder 10A to which the detection signal Sf is input to the input terminals D1 to D5 and a signal from the priority encoder 10A. And an analog multiplexer 10B for output.

The detection signal Sf from the signal detector 9 is
Are configured to be input to the input terminal of the higher priority in order from the detection signal Sf of the higher frequency band.

For example, since the detection signal SfHH has the highest frequency band, the input terminal D5 having the highest priority
, And the detection signal SfLL is input to the input terminal D1 having the lowest priority since the frequency band is the lowest.

In response to the input having the priority, the output is output as a control signal to the analog multiplexer 10B according to the logic table shown in FIG. 5B, and the analog multiplexer 10B outputs a plurality of band signals based on the control signal. A specific band signal is selected from Se and output. FIG.
In (b) and (c), the superior level is “H”.

Next, the noise detector 15 will be described with reference to the drawings. As described above, the ultrasonic waves received by the receiver 4 include ultrasonic waves from various sources. However, except for the ultrasonic waves reflected by the moving object, the ultrasonic waves are generated by noise for the purpose. is there.

FIG. 6 shows signal waveforms when noise is included and when noise is not included. In FIG. 6, range A indicates the case where noise is not included, and range B indicates the case where noise is included. Is shown. A range C indicates a noise region.

In FIG. 6, the frequency of the differential frequency signal S5 when no noise is included belongs to the band HL.
The frequency of the differential frequency signal S5 when noise is included is such that the original signal belongs to the band M and the noise is in the bands HH and HH.
L and LH are shown.

When the ultrasonic wave S2 corresponding to the reference signal S1 is transmitted from the transmitter S3, the ultrasonic wave S2 is reflected by the moving object under the Doppler effect and becomes a reflected wave S3.

At this time, if no noise is included, the difference frequency signal S5 is a signal having a single frequency,
When noise is included, the difference frequency signal S5 is a signal having a plurality of frequencies.

Accordingly, when no noise is included, the detection signal SfHL is selected by the signal selector 10 and the band signal SfHL is selected.
h is output to the frequency measuring device 12. When the band signal Sh satisfies the above-described conditions (1) and (2), the valid signal Si is output to the arithmetic unit 13.

On the other hand, when noise is included, the detection signals SfHH, SfHL, Sf
Since M and SfLF are both signals of superior levels, the signal selector 10 detects the detection signals SfHH, SfHL, Sf
It cannot be determined which of M and SfLF is a signal due to noise.

Therefore, the signal selector 10 selects and outputs the detection signal SfHH having the highest frequency band among them according to the principle. As a result, the frequency measuring device 12 measures the frequency of the noise, and There is a disadvantage that the calculation of the speed is performed by the calculator 13 based on the frequency.

Therefore, in order to avoid such inconveniences, the noise detector 15 determines whether or not the received ultrasonic wave S3 contains noise based on the detection signal Sf, that is, the difference frequency signal S5 includes a signal due to noise. Is determined.

The procedure for determining the presence or absence of noise will be described with reference to the Bode diagram of FIG. FIGS. 7A and 7B show a differential frequency signal S5 when the ultrasonic wave does not contain noise, and FIG. 7C shows a differential frequency signal S5 when the ultrasonic wave contains noise. I have. Note that the alternate long and short dash line in the figure indicates the frequency characteristic of each bandpass filter 8.

In the case of FIG. 7 (a), the detection signal SfLH is output only from the band LH.
It can be determined that LH is not noise.

In the case of FIG. 7B, the difference frequency signal S5 (shown by a dotted line in the figure) is located between the band M and the band HL. In this case, the detection signal SfM and the detection signal SfHL Is output. Therefore, 2
If two detection signals Sf are output, it can be determined that it is not noise.

However, as shown in FIG.
In cases where (a) and (b) do not apply, that is, when the detection signal Sf is output from two or more bands, it can be determined that the differential frequency signal S5 contains noise.

Therefore, the noise detector 15 determines that noise is not included when the detection signal Sf is output only from one band and when the detection signal Sf is output only from two adjacent bands. Then, a noise determination signal Sj indicating that is output, and otherwise, it is determined that noise is included.

The structure of the noise detector 15 for making such a determination will be described with reference to FIG. FIG. 8A shows a configuration of the noise detector 15 and includes a diode Da (Da1).
To Da5), Db (Db1 to Db), resistors Ra (Ra1 to Ra5), Rb (Rb1 to Rb6) connected in series to the diodes Da and Db, and the other end of which is connected in common.
A resistor Rc connected in series with the resistors Ra and Rb and having the other end grounded, compares the potential of the connection between the resistor Rc and the resistors Ra and Rb with a reference potential Vref, and compares the potential with the reference potential Vref.
Is small, the “Low” level noise determination signal S
j, and in the opposite case, a comparator C that outputs a "High" level noise determination signal Sj.

In such a configuration, assuming that the dominant level of the detection signal Sf is 5 V and the voltage drop at each of the diodes Da and Db is 0.6 V, a detection signal having a dominant level as shown in FIG. The number of conducting diodes Da and Db varies depending on the number of Sf and the like, and accordingly, the input voltage of the comparator C takes a different value.

In the case of FIG. 8 (b), it is assumed that noise is not included only when there is one detection signal of a dominant level or two detection signals having a dominant level from an adjacent band.
The reference voltage Vref is a voltage between 2.93V and 3.3V,
For example, if the voltage is set to 3.12 V, the signal level of the noise determination signal Sj can be made to correspond to "L" or "H" depending on the presence or absence of noise.

Thus, when the "H" level noise determination signal Sj is input to the arithmetic unit 13, the arithmetic unit 13 determines that the signal measured by the frequency measuring unit 12 is noise,
No subsequent speed calculation is performed. Therefore, the speed displayed on the display 14 does not include the speed due to noise, and the reliability can be improved.

In the above description, it is assumed that the signal level of the differential frequency signal S5 is low and the quality factor (Q value) of the bandpass filter 8 is high, and the noise detector 15 determines the presence or absence of noise. Was explained.

However, for various reasons (for example, the cost of components used for the bandpass filter 8 is reduced), Q
Sometimes the value cannot be increased. That is, when the signal level of the differential frequency signal S5 input to the bandpass filter 8 is high and the Q value is low, it is necessary to provide a new criterion instead of the above-described determination procedure.

This will be described with reference to FIG. FIG.
FIG. 9A is a Bode diagram showing a case where the Q value of the band-pass filter 8 is high and the signal level of the difference frequency signal S5 is low, and FIG. FIG. 9 shows a Bode diagram when the signal level of the frequency signal S5 is large. Note that FIG.
(B) Both show the case where the difference frequency signal S5 is in the frequency band of the band M.

In the case of FIG. 9A, the bandpass filter 8
Is high and the signal level of the differential frequency signal S5 is low, so that the signal levels of the band signals Se other than the band signal SeM are low. Therefore, only the detection signal SfM is a signal having a superior level.

On the other hand, in the case of FIG. 9B, since the Q value of the band-pass filter 8 is low and the level of the differential frequency signal S5 is large, the output level of each band signal Se is only the band signal SeM. Adjacent band signals SeLH, S
eHL also increases. Therefore, in addition to the detection signal SfM,
The detection signals SfLH and SfHL are also signals having a superior level.

Of course, depending on the frequency position of the differential frequency signal S5, one detection signal SfM may be output, and the detection signal SfM, SfLH or the detection signal SfM may be output.
There may be a case where two detection signals are output like M and SfHL.

Therefore, even if the ultrasonic wave received by the receiver 4 contains no noise, a maximum of three detection signals Sf may appear. In this case, the detection signal output from the signal detector 9 is output. It is determined that no signal Sf has a dominant level is within 3 when the signal Sf is output from an adjacent band, and that the signal Sf contains noise in other cases. to decide.

As described above, it is detected whether or not the clapping, the collision between metals, the noise generated when the paper is turned or rolled, etc. are present in the measurement frequency band, and the frequency band concerned is detected. In the case where it exists, the speed calculation processing is not performed, so that the reliability of the obtained result can be improved.

As a method of avoiding the transient characteristics of the bandpass filter 8, the avoiding means is constituted by using a delay circuit, a one-shot circuit or the like. According to the method according to the present embodiment, for example, Band signal SeH in FIG.
Even when the signal level is substantially equal to the threshold value Vth of the signal detector 9 as in H, and as a result, the pulse width of the detection signal SfHH is narrow and noise-like (shown by a dotted line in FIG. 2), the signal is output as the detection signal Sf. There are features that are not.

The frequency of each band divided by the band pass filter 8 is equal to the reference frequency Fo of the reference oscillator 1.
ut and the measurement speed range of the apparatus. If, for example, the frequency Fout of the reference signal is 40 kHz and the speed range is 20 to 150 km / h, the frequency of the reflected wave reflected by the moving object is about 41.3-50.9
3 kHz, and the frequency of the differential frequency signal S5 is 1.3
It becomes 10.93 kHz.

In such a case, the difference frequency signal S5
Is changed to five band-pass filters 8 (8a to 8a).
If divided equally in e), the frequency width of each band will be about 2
kHz, the center frequencies of the band-pass filters 8a to 8e are set to 2.3 kHz, 4.2 kHz, and 6.1 kHz.
z, 8.0 kHz and 10.0 kHz.

[0108]

According to the present invention, it is determined whether or not the received ultrasonic wave contains noise, and the speed calculation processing is performed only when the received ultrasonic wave does not contain noise. It has become possible to improve the reliability of the obtained result.

[Brief description of the drawings]

FIG. 1 is a block diagram of a speed measuring device applied to the description of a first embodiment of the present invention.

FIG. 2 is a timing chart showing output waveforms from each block of the speed measuring device.

3A and 3B are diagrams illustrating the transient characteristics of a band-pass filter, wherein FIG. 3A shows a differential frequency signal S5, FIG.
(C) is a diagram showing an F / V waveform.

4A and 4B are diagrams applied to the description of the signal detector, where FIG. 4A is a block diagram, FIG. 4B is a signal waveform of a comparison block, and FIG.
FIG. 4 is a diagram showing a signal waveform of a decision block.

5A and 5B are diagrams applied to the description of the signal selector, wherein FIG. 5A is a block diagram, FIG. 5B is a logic table of a priority encoder, and FIG. 5C is a logic table of an analog multiplexer.

FIG. 6 is a timing chart showing output waveforms from each block of the speed measurement device when noise is included and when noise is not included.

FIG. 7 shows that the signal level of the differential frequency signal is small and
FIGS. 7A and 7B are diagrams for explaining a method of determining whether or not noise is included when the Q value is high. FIG. 10A shows a case where a signal appears only in one detection signal, and FIG. FIG. 7C shows a case where two or more detection signals appear.

8A and 8B are diagrams illustrating the configuration and the like of a noise detector, where FIG. 8A is a configuration diagram and FIG. 8B is a diagram illustrating conditions for noise determination.

FIG. 9 shows that the signal level of the differential frequency signal is large and
FIGS. 7A and 7B are diagrams for explaining a method of determining whether or not noise is included when the Q value is low. FIG. 10A is a diagram illustrating a frequency position of a differential frequency signal, and FIG. FIG. 9 is a diagram showing three detection signals output from adjacent bands based on the above.

FIG. 10 is a block diagram of a speed measuring device applied to the description of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reference oscillator 2 Output amplifier 3 Transmitter 4 Receiver 5 Preamplifier 6 Mixer 7 Detector 8 Bandpass filter 9 Signal detector 10 Signal selector 12 Frequency measuring device 13 Computing device 14 Display 15 Noise detector

Claims (2)

[Claims] 1. An ultrasonic wave emitting means for emitting an ultrasonic wave based on a reference signal of a predetermined frequency, a wave receiving means for receiving an ultrasonic wave and outputting it as a received signal, and a moving object based on the reference signal and the received signal. A speed calculating device having a speed calculating means for calculating a speed of the signal, wherein the speed calculating means obtains a frequency difference between the received signal and the reference signal, and outputs a difference frequency signal as a difference frequency signal; A frequency band separation unit that separates the difference frequency signal into two or more predetermined frequency bands and outputs the band signal as a band signal, and a time period when the band signal or a detection signal of the band signal exceeds a threshold value. If the time that can be regarded as exceeding the predetermined first judgment time continues, the detection signal of the superior level is output, and the time when the threshold value is exceeded or the time when it can be considered that the threshold value is exceeded is determined. If the second determination time is longer than the first determination time, a band signal determination unit that outputs a valid signal, the band signal and the detection signal are input, and the plurality of band signals are determined based on the detection signal. A band signal selecting section for selecting one of the band signals from the above, and a noise for outputting a noise judgment signal by judging whether or not the ultrasonic wave received by the wave receiving means contains noise based on the detection signal. The presence / absence determining unit, and measuring the frequency of the band signal selected by the band signal selecting unit, and calculating the speed of the moving object based on the measurement result; A speed measurement device comprising: a measurement calculation unit that performs a speed calculation process only when it is determined that noise is not included and the band signal is determined to be valid based on the valid signal. 2. The method according to claim 1, wherein the noise presence / absence determination unit detects one or two detection signals having a superior level when the quality factor of the frequency band separation unit is high and the level of the difference frequency signal is low, or This is a case where, when the quality factor of the frequency band separation unit is low and the level of the differential frequency signal is large, one to three detection signals having a superior level are detected, and two or more superior levels are detected. 2. The speed according to claim 1, wherein, when a signal is detected, it is determined that the received ultrasonic wave does not include noise only when the detection signal is output from an adjacent band. measuring device.