JPH0823917B2 - Ultrasonic Doppler type moving object detector - Google Patents

Description

The present invention relates to an ultrasonic Doppler type moving object detection device.

<Prior art> For example, at an intersection where the traffic volume on the secondary road intersecting with the traffic volume on the main road is very small, the traffic light on the main road side is always kept blue and the vehicle etc. When a traffic signal arrives, a control method (semi-sensitive control) is adopted so that traffic at an intersection can be smoothed by detecting this and changing a traffic signal.

An ultrasonic Doppler type moving object detection device is used as a vehicle detector on the secondary road side.

A conventional example of such an ultrasonic Doppler type moving object detecting device will be described with reference to FIG.

In the figure, reference numeral 1 denotes a handset having an ultrasonic transducer, which is driven by an AC voltage output from a drive circuit 2. 3 is a receiving amplifier, 4 is a mixer, 5 is a local oscillator, 6 is a bandpass filter, 7 is an amplifier, 8 is a signal processing circuit, and 9 is a sensing output circuit.

In this configuration, the ultrasonic wave (for example, 25 kHz) from the handset 1 is transmitted for 20 ms by the drive output from the drive circuit 2.
Is radiated at a constant period (60 to 90 ms), the reflected wave is taken in through the handset 1 during the transmission period, amplified by the receiving amplifier 3, and output from the local oscillator 5 by the mixer 4. The frequency band (for example, 24.4 kHz) is demodulated and the band filter 6 extracts only the Doppler shift component. That is, when there is no vehicle, the frequency of the reflected wave is the same as the transmission frequency, and the beat frequency of 600 Hz is obtained from the mixer 4 in this case, which is cut as the cutoff point of the bandpass filter 6. On the other hand, when the vehicle is approaching, the frequency of the reflected wave becomes higher than the transmission frequency (the higher the vehicle speed, the higher). In this case, a beat frequency higher than 600 Hz is obtained and extracted by the bandpass filter 6. Then, the amplifier 7 outputs the frequency signal corresponding to the extracted Doppler shift.
Then, the signal processing circuit 8 determines whether or not the wave number is equal to or more than a predetermined value within a certain period of time. Is output.

As described above, conventionally, the presence or absence of the vehicle is determined by the band filter 6 based on whether or not the reception frequency is higher than the transmission frequency, and the influence of a sudden frequency change such as wind is detected by the signal processing circuit 8. I try to remove it.

<Problems to be Solved by the Invention> By the way, the lower the speed of the approaching vehicle is, the smaller the Doppler shift amount is. For example, in the case of a vehicle having a speed of 5 km / h, the Doppler shift is about 200 Hz with respect to a transmission wave of 25 kHz. Therefore, in order to detect such a vehicle at a low speed, a bandpass filter having a sharp cutoff characteristic is required, and at present, it is difficult to detect a vehicle approaching at a speed lower than 5 km / h.

For this reason, there is a fear that the vehicle detection function will not operate during traffic congestion.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrasonic Doppler type moving object detection apparatus capable of detecting a vehicle approaching at an ultra-low speed.

<Means for Solving Problems> Therefore, the present invention radiates an ultrasonic wave of a constant frequency and receives a reflected wave from a moving object passing through the radiating region, and In an ultrasonic Doppler type moving object detecting device for detecting a moving object based on a frequency change, a waveform shaping means for converting the reflected wave into a pulse signal, and a pulse oscillating a pulse signal having the same transmission frequency as the radiated ultrasonic wave. Oscillating means, pulse wave number difference measuring means for measuring the difference between the pulse wave numbers generated at the same time of both means at predetermined intervals, storage means for storing the measured value of the pulse wave number difference measuring means, and the storing means. Determining means for determining whether or not the difference between the previous value and the current value stored in is within a predetermined value, and integrating means for integrating the measurement values of the measuring means when the determining means determines that the difference is within the predetermined value And a detection output generating means for generating a detection output of the moving object when the integrated value of the integrating means exceeds a predetermined value within a predetermined time set in advance.

<Operation> According to the above configuration, in an object that moves at high speed, the transit time in the radiation region is short and the number of integrations is small, but the difference between the transmission frequency of ultrasonic waves and the frequency of reflected waves (Doppler shift)
Is large and the measured value of the wave number difference for each time is large, so that the integrated value can be sufficiently detected to exceed the determination value under normal conditions. On the other hand, an object moving at a low speed has a small Doppler shift and a small measurement value per time, but since the transit time in the radiation region is long and the number of integrations is large, the integration value also exceeds the determination value. . Therefore, by appropriately setting the integration time and the determination value, it is possible to detect a moving object that is slower than ever before. Also, if the difference between the current and previous wave number differences is compared and the difference is abnormally large, the measured value at that time is set to an abnormal value, and the reflected wave from the stationary object suddenly changes due to wind, etc. It can be distinguished from the case.

<Example> An example of the present invention will be described below.

In FIG. 1 showing the configuration of the present embodiment, reference numeral 11 is a drive circuit for transmitting a transmission output of a constant frequency (for example, 25 kHz) for driving an ultrasonic transducer to a handset 13 via a transmission amplifier 12. The handset 13 emits ultrasonic waves toward a certain area and receives reflected waves from the area. Received reflected wave is received amplifier 14, band filter for noise removal
It is input to the comparator 16 via 15. comparator
Reference numeral 16 indicates an H level output when the reflected wave exceeds a predetermined reference value, where the reflected wave is converted into a pulse signal and corresponds to a waveform shaping means. 17 is a pulse width verification circuit that verifies the pulse interval output by the comparator 16 and outputs an abnormality determination signal when the pulse interval is equal to or greater than the pulse interval corresponding to the frequency of the reflected wave from the stationary object (40 μs when the transmission frequency is 25 kHz). is there. 18 is an oscillation circuit that outputs a pulse signal of the same frequency (25 kHz) as the transmission output frequency of the drive circuit 11, 1
9 is the comparator 1 input through the inverter 20
A first counter that counts 6 pulses and generates a count-up output when the number reaches a predetermined number N, and a first counter 21 that counts the pulses of the pulse oscillation circuit 18 and generates a count-up output when the number reaches a predetermined number N as well. 2 counters.

Reference numeral 22 is an SR flip-flop (hereinafter referred to as SRFF) which is set by the output of the first counter 19 and reset by the output of the second counter 21, and its Q terminal output is The pulse signal having a frequency of 1 MHz, for example, from the oscillator circuit 24 is input to the other input of the AND circuit 23. These pulse oscillating circuit 18, first and second counters 19, 20, S / R / F / F22, AND circuit
A pulse wave number difference measuring means is configured to include the 23 and the oscillation circuit 24, and measures the difference between the pulse wave number generated at the same time between the transmitted wave and the reflected wave.

Reference numeral 25 is an AND circuit to which the pulse output of the comparator 16 and the reset signal output when the count value from the second counter 21 becomes N + α are input, and 26 is the abnormality determination signal of the AND circuit 25 and the pulse width verification circuit 17. OR circuit to input, 27 is OR
When the output of the circuit 26 and the count-up output of the second counter 21 are input, and either of the inputs becomes H, the S / R-
It is an OR circuit that outputs a reset signal to F / F22.

31 is a D-flip-flop (hereinafter referred to as D-F-F) in which the output of S-R-F-F22 is input to the CP input terminal.
The Q terminal output is input to the AND circuits 32 and 35, and the terminal output is input to the D input terminal and the AND circuits 33 and 34. The other input of the AND circuits 32 and 34 has an AND circuit
The output of 23 is input, and the outputs of the AND circuits 32 and 34 are first and second as storage means for alternately storing the wave number difference measurement values.
Input to the CK input terminals of memories 36 and 37. The reset outputs of the OR circuit 26 are input to the other inputs of the AND circuits 33 and 35, and the outputs of the AND circuits 33 and 35 are input to the R (reset) terminals of the first and second memories 36 and 37. ing.

38 is a judging circuit as a judging means for comparing the stored values of the first memory 36 and the second memory 37 and judging whether or not the difference is within a predetermined value, and 39 is a judgment result of the judging circuit 38 is larger than a predetermined value. When the count value reaches a predetermined number M, the OR circuit 40
The reset signal of the third counter 41 is output via the.

The third counter 41 constitutes an integrating means for integrating the wave number difference measurement value output from the AND circuit 23, and the integration time is controlled by the timer 42 which is driven in synchronization with the drive circuit 11, and the timer 42 When the integrated value becomes equal to or more than a predetermined value within the time between the reset signals output in a predetermined cycle from, a count-up output is generated. Reference numeral 43 is a detection output circuit as a detection output generating means for generating a detection output of a moving object when the count-up output of the third counter 41 is input.

 Next, the operation will be described.

When a transmission output of, for example, 25 kHz is output from the drive circuit 11 at a constant cycle (for example, 60 to 90 ms), the transmission amplifier 12 widens the ultrasonic transducer of the handset 13 to oscillate ultrasonic waves in a predetermined area. The emitted ultrasonic waves are reflected by an object in the area, and the reflected waves are input from the handset (see FIG. 2). The input reflected wave is amplified by the receiving amplifier 14 and pulse-shaped noise is removed by the bandpass filter 15, and then input to the comparator 16, where it is converted into a pulse signal (digital signal) as shown in FIG. 3 (A). Can be replaced. The output of the comparator 16 is input to the first counter 19 via the inverter 20,
The number of pulses is counted. At this time, the pulse signal (FIG. 3 (B)) having the same frequency (25 kHz) as the transmission frequency is also output from the pulse oscillation circuit 18, and the second counter 21 starts counting at the same time as the first counter 19. . Each of the counters 19 and 21 outputs a count-up output when counting a predetermined number N (see FIGS. 3C and 3D).

In this case, when the reflected wave from an approaching moving object,
Since the frequency becomes higher than the transmission frequency due to the Doppler effect, the pulse interval becomes (40-a) μm shorter than the transmission wave interval 40 μm. It should be noted that a varies depending on the speed of the moving object and becomes larger as the speed becomes higher.

Therefore, according to the Doppler shift amount, the first counter 19
The count-up time is faster than the count-up time of the second counter 21, and the S / R / F / F22 outputs a pulse signal having a pulse width corresponding to the time (see FIG. 3 (E)).

The pulse output of S / R / F / F22 is input to the AND circuit 23, and the frequency of the oscillation circuit 24 is 1 MHz only while the AND circuit 23 is input.
A pulse is output from the AND circuit 23 to the third counter 41 in synchronism with the pulse output (see FIG. 3 (F)).

Then, when the count value of the second counter 21 becomes N + α, a reset signal is output to the AND circuit 25, and when a pulse is output from the comparator 16 thereafter, the AND circuit 25 and O
The pulse oscillation circuit 18, the first and second counters 19 and 21 are simultaneously reset via the R circuit 26 (FIG. 3 (G)), and the same counting operation as described above is repeated until the reflected wave disappears.

On the other hand, the third counter 41 is a timer that is output in synchronization with the start of transmission of the drive circuit 11 in every predetermined cycle (for example, four cycles).
It is designed to be reset by the reset signal of 42, and during the period between resets (predetermined time), AN
The number of pulses input from the D circuit 23 is integrated and counted. Then, when the integrated value becomes equal to or more than a predetermined value within a predetermined time from the reset to the reset, a count-up signal is output to the detection output circuit 43, and the detection output circuit 43 generates a detection output with a moving object ( (See Fig. 4). Further, if the integrated value does not reach the predetermined value, it is determined that there is no moving object and no detection output is issued. The third counter 41 is reset by the reset signal from the timer 42 to prepare for the next detection operation.

By the way, in this device, S / R
-The set time of F / F22, that is, the previous value and the current value of the output pulse width are constantly compared, and if the difference is large, it is determined that the frequency change of the reflected wave is sudden due to wind, etc. and the integrated value is reset. The operation will be described below with reference to FIG.

Every time an output is generated from S ・ R ・ F ・ F22, DF
・ F31 Q terminal and terminal output are switched. The output of the Q terminal is connected to the CK terminal of the first memory 36 and the AND circuit 32,
Input to the AND circuit 35 connected to the R terminal of the second memory 37,
It is an enable signal for the clock reception of the first memory 36 and the reset reception of the second memory 37, and the terminal output is the opposite, and is input to the AND circuits 33 and 34 to input the first memory 36.
It is an enable signal for the reset acceptance and the second memory 37 clock acceptance.

Therefore, when the Q terminal output becomes H, the
The count signal from the oscillator circuit 24 is input to the CK terminal of the AND circuit 2
It is input via 3, 32 and the number is stored. Next SR
-When the terminal output becomes H due to the output of F / F22, the second memory 37 can now receive the clock and the oscillation circuit
The count signal from 24 is input and stored. Then, the value stored in the first memory 36 and the current value stored in the second memory 37 are compared by the judgment circuit 38, and when the difference is equal to or more than a predetermined value, it is judged as abnormal and the abnormality number counter 39 Count up the count value. When the count value of the abnormality counter 39 reaches the predetermined value M, the reset signal is ORed by the OR circuit 40.
It is output to the third counter 41 via the and resets the third counter 41. At this time, the first and second memories 36 and 37 are also reset by the reset signal to the third counter 41.

By doing so, when the reflected wave has a large frequency change, the detection output is not output because it is not due to the moving object but due to the wind or the like, and malfunction is prevented. Also,
When the frequency of the reflected wave is lower than the transmission frequency, the interval between the pulses output from the comparator 16 becomes long and the pulse width verification circuit 17 detects this and outputs an abnormality determination signal to stop the pulse counting operation.

At the same time that the current value is stored in the second memory 37, the first memory 36 becomes resettable by the terminal output of DF / F31, and after the current value is stored in the second memory 37. The first memory 36 is reset by a reset signal from the OR circuit 26 shown in FIG. 5 to prepare for the next value storage operation. Similarly, the second memory 37 is reset after the storage operation of the first memory 36. In this way, the previous value and the current value are exchanged and stored in the first and second memories 36 and 37 while the previously stored values are reset.

In the first and second memories 36, 37, when there is no stored value in both memories 36, 39, such as immediately after power-on or when reset by a reset signal to the third counter 41, compare with the first. Since the determination is always an abnormality determination because there is no stored value in one of the memories, the count value of the reset signal generation of the abnormality counter 39 must be at least 2 or more.

According to the configuration as described above, the determination is made only by the velocity of the moving object, that is, the frequency difference between the transmitted wave and the reflected wave (Doppler shift amount) in the related art. It uses the fact that a slow moving object can take a long area transit time, in other words, a long sensing time by adding the transit time to the determination factor, that is, it is determined by the integrated value within a fixed time of the Doppler shift. Therefore, it is possible to detect an ultra-low speed, which has been difficult to detect in the past, for example, a moving object up to 2 km / h. Further, for example, when an ultrasonic Doppler type moving object detection device is applied for road traffic control, there are many demands for detecting two or more vehicles but not humans. In this case, since the time required to pass through the sensing area is the same as that of a two-wheeled vehicle or more when the speed is the same, the method of the present invention integrates the Doppler shift amount at the same speed. Since the value of two or more wheels is greater than that of human by the length of the vehicle, there is also an effect that it is possible to distinguish a human from two or more wheels with a higher probability than in the conventional method.

Further, in the past, the analog circuit was the main focus, the demodulation circuit configuration such as the filter circuit, the mixer, etc. was complicated, and there were many unstable elements due to the need for temperature compensation. Except for the system and simple filters, it is composed of digital circuits except for the stability, and the digital circuit part can be made compact by making it IC.

In this embodiment, when the difference between the stored values in the first and second memories is abnormal, the third counter is reset to reset the integrated value up to that point. When an abnormality is determined through a processing circuit such as a memory, the measurement value at that time may be invalidated (not integrated) without being taken into the third counter.

<Effects of the Invention> As described above, according to the present invention, the presence or absence of a moving object is determined by the integrated value of the Doppler shift amount within a fixed time. It was difficult to move even a moving object approaching at a very low speed,
Since the passage time of the sensing area is long, the integrated value of the Doppler shift becomes large, and it is possible to sufficiently detect by setting the determination value appropriately. Further, the previous value and the current value of the Doppler shift amount are compared, and if the difference is large, it is determined to be abnormal, and therefore malfunction due to wind or the like can be prevented. Furthermore, since the circuit configuration is mainly composed of a digital circuit, it has good stability and can be miniaturized by using an IC.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a transmission / reception state of a transmitted wave and a reflected wave of the same embodiment, and FIG. 3 is a diagram for explaining a counting operation of a Doppler shift amount. An output time chart, FIG. 4 is a time chart for explaining the integration operation of the Doppler shift, and FIG. 5 is an output time chart for explaining the storage operation of the measured value of the Doppler shift.
FIG. 6 shows a schematic configuration diagram of a conventional example. 11 …… Drive circuit, 13 …… Transmitter, 16 …… Comparator,
18 ... Pulse oscillator circuit, 19 ... First counter, 21 ... Second counter, 22 ... S / R / F, 23 ... AND circuit, 2
4 …… Oscillation circuit, 26 …… OR circuit, 31 …… DF ・ F, 32
~ 35 …… AND circuit, 36 …… first memory, 37 …… second memory, 38 …… decision circuit, 39 …… abnormality counter, 41 ……
3rd counter, 42 ... Timer, 43 ... Detection output circuit

Claims (1)

[Claims] Claim: What is claimed is: 1. A method for radiating an ultrasonic wave having a constant frequency, receiving a reflected wave from a moving object passing through the radiation area, and detecting the moving object based on a frequency change of the reflected wave with respect to the transmission frequency. In a sound wave Doppler type moving object detection device, a waveform shaping means for converting the reflected wave into a pulse signal, a pulse oscillating means for oscillating a pulse signal having the same transmission frequency as the radiated ultrasonic waves, and at the same time of both means. Between the pulse wave number difference measuring means for measuring the difference in the generated pulse wave number for each predetermined cycle, the storing means for storing the measured value of the pulse wave number difference measuring means, and the previous value and the current value stored in the storing means. Determination means for determining whether the difference is within a predetermined value,
Integrating means for integrating the measured values of the measuring means when the determining means determines that the measured value is within a predetermined value, and a moving object when the integrated value of the integrating means exceeds a predetermined value within a predetermined time set in advance. An ultrasonic Doppler-type moving object detection device, comprising: a detection output generation unit that generates a detection output.