JPS5938555B2 - Moving object detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a moving object detection device that detects a Doppler signal and activates a switch, in which the phase difference between a reference signal and a received signal is maintained at a constant phase difference in a normal state. The purpose is to control and maintain stable operation of the device in a steady state.

Ultrasonic waves are emitted into space, and the sound waves are generated as the objects move as they receive signals reflected from objects in the monitoring space.

Various devices have been proposed and implemented in the past that detect a so-called Doppler signal and operate a switch to detect a moving object, particularly a human body, present in a monitoring space.

This device is particularly important for intruder alarms used in Joe rooms, museums, vaults, etc., to prevent unauthorized persons from entering at night and to prevent important items from being taken away. play a role.

However, conventionally, this type of device has been unable to generate false alarms due to external ultrasonic waves such as the sound of keys, the sound of metal touching, falling impact, air blowing from an air nozzle, etc. This has the disadvantage of causing false alarms.

One of the causes of these false alarms is that large amplitude fluctuations occur in the received signal, making it impossible to clearly distinguish between the signal from the moving object and the disturbance noise. It is in.

In order to prevent this problem, conventionally used methods use so-called filter technology to determine the Doppler shift frequency band that occurs when the human body moves through experiments or calculations, and remove unnecessary bands. An attempt was made to avoid the effects of Marunan by using technology to cut off the existing components.

However, the biggest drawback of this method is that the spectrum of external noise cannot be generally defined, and the frequency f of the transmitted signal.

This method is effective if the noise of the disturbance happens to be outside the band of the prepared film. If it does, it cannot be prevented.

In addition, in order to avoid the influence of disturbances, another proposed method is to process the received signal by converting the signal component to the frequency f of the transmitted signal.

A device that separates and separately detects higher and lower components, and operates a switch only when one of these components is detected or one component is overwhelmingly larger than the other. It is.

The principle of this second method is that the Doppler shift caused by the movement of the object is f.

Using the well-known fact that f0 is either north or below fo, it is further assumed that the spectrum of noise generally occurs equally on both sides above and below fo.

It was built based on these two principles.

If this method is followed, it is true that far more disturbances can be avoided than in the first method mentioned above, but if the principle is followed, disturbances will occur asymmetrically above and below with respect to fo. This can be said to be a drawback as it is not effective against noise.

Yet another drawback of this method is its complication due to the technical difficulty of separating fo into its lower components.

As is well known, the Dotsupura component is the energy wave used,
It occurs in proportion to the propagation speed of ultrasonic waves or radio waves and the moving speed of a moving object, but for example, if you try to detect a person walking for a 40 KHz ultrasonic wave, the difference is ±20
It must be possible to detect the frequency below about Hz, and a filter must be used that has an extremely high frequency deviation ratio of 0.05%.

Therefore, it is difficult to achieve this with commonly used filters.
In order to realize this, it was necessary to use technology such as quadrature detection, for example.

The present invention has been made in view of this point, and will be explained in detail below with reference to Examples.

In Figure 1, 1 is an oscillator that oscillates a high frequency signal,
The signal is amplified by the amplifier 2 and then applied to the transmitter 3.

The frequency is, for example, 40 KHz. The transmitter 3 emits ultrasonic waves corresponding to the applied signal toward the monitoring space,
The ultrasonic wave is reflected by an object in the monitoring space, reaches the receiver 4 as a signal synthesized in the space, is converted into an electrical signal, is amplified by the amplifier 5, and is applied to the phase difference detection circuit A. .

A phase shift circuit 6 shifts the phase of the output of the oscillator 1 and is applied to the other input of the phase difference detection circuit A as a reference signal.

The output of the amplifier 5 is a signal k, and the output of the phase shift circuit 6 is a signal g, and the phase difference detection circuit A acts as a detector of a pure phase difference between the signal g and the signal.

As a method for detecting this phase difference, for example, the signals g, k
are converted into rectangular waves by limiters 7.9 and the rising edges of these rectangular waves are detected by differentiating circuits 8.10, respectively, and the outputs of the differentiating circuits 8 and 10 correspond to the rising edge of the signal g, respectively. This pulse s
When used as the set pulse and reset pulse of the R rough flip-flop 11, the rectangular wave output from the flip-flop 7°11 has a duty just proportional to the phase difference between the signal g and the signal g.

Therefore, the output of this flip-flop 11 is transferred to the integrating circuit 12.
When integrated by , a signal representing the phase difference of the input signal can be obtained as the integrated output, and the signal processing circuit 13 can issue an alarm.

On the other hand, the phase difference when the received signal includes a reflection from a moving object, that is, a trap shift signal, will be explained.

A certain part of the received signal is a received signal component from a fixed object, and since the frequency of this component is not known as the transmitted signal, there is a certain phase difference θ with the calibration signal σt as shown in FIG.

Exists with . The other part is a deviation component and becomes a rotation vector that rotates at a period corresponding to the difference from the transmitted signal.

OA is a vector of fixed reflection component composite components.

Since t is a vector of the Doppler shift component and rotates with the length of radius AB around point A, the combined vector OB of the reflected waves is a vector that rotates around point 0 and with arc BJ: as the end point. Become.

Conventional detection methods use envelope detection or phase detection to extract the signal as a Doppler component, but the present invention is independent of the amplitude and uses σ
Only the phase difference θ between t and σt is extracted.

If the t vector, that is, the deviation component, has a higher frequency component than the calibration signal, this vector rotates counterclockwise, and the temporal change in its phase becomes as shown in FIG. 3A.

On the other hand, if it has low frequency components, the change will be as shown in Figure 3.

Naturally, when there is no deviation component, it will be like (c).

The reason why there is a slight fluctuation in C is that the phase of the gold component fluctuates slightly due to fluctuations in temperature, etc. 6 Now, the characteristics of the signal obtained in this way are as clear from Fig. 3, as the deviation frequency is f.

If it is north of fo, a sawtooth wave going to the right will be obtained, and if it is below fo, a sawtooth wave going down to the right will be obtained.More importantly, no filter is used to obtain this wave. It is a point.

Next, the response of this circuit to disturbance will be explained.

First, when ultrasonic waves arrive from the outside, especially in the case of external noise that occurs in nature, it is random with respect to the calibration signal, so the reset signal R that controls the flip-flop 11 is completely random.

Therefore, the signal output that has passed through the integrating circuit 12 has a value representative of the fixed reflection component, or a signal with a slight fluctuation around this value, and this fluctuation is slight.

In addition, the main component of the influence of wind etc. is thought to be fluctuations in amplitude due to changes in conditions along the propagation path.

As a well-known fact, what is shown in FIG. 4 is an explanatory diagram using a vector of an amplitude-modulated waveform.

According to the same figure, the amplitude modulated wave has a vector that rotates in a balanced manner in both right and left directions around g within the carrier signal and gS2.
It has been expressed as a composite signal pt with gr.

According to this theory, it is clear that no matter how the amplitude changes, the phase of the composite wave with respect to the reference signal does not change at all and remains constant.

Since this vector g S 2g r appears as north, bottom, and sideband waves, it is natural that it will be detected by using a filter. Although it is clear that the Doppler signal appears, it is completely unnecessary for the purpose of Doppler signal detection, and it is completely unnecessary and even nonsensical to need to cancel it again at the north where the lower sideband waves are separated. It is.

As is clear from Kitaki's explanation, the present invention can detect the deviation contained in the signal by examining what phase difference the received signal component has with the reference signal and what kind of time change it shows. Although it is possible to detect the component, there are some problems, namely, the fixed phase component is 0 with respect to the reference signal.
There is a problem when the angle exists at 360 degrees or near 360 degrees.

This is because, as shown in Figure 5, when there is a slight fluctuation in the steady state, there is almost no problem, but as shown in Figure 6, when the difference is near 0 degrees or 360 degrees, the phase difference A jump occurs in the detection output.

This is a contradiction caused by expressing 0 degrees to 360 degrees as a voltage change of 0-V (volt).

Therefore, even though there is actually a slight change in angle, the output appears as if a sudden change has occurred.

In other words, in order for the output of the phase difference detection circuit A to have a waveform corresponding to that shown in FIG.
The phase difference with the received signal when there is no moving object) is 36
It is necessary that the angle is not at or near 0°.

That is, when the phase difference between the reference signal σt as shown in Fig. 8 and the received signal (fixed reflecting object) OA is small, the input/output characteristics of the phase difference detection circuit as shown in Fig. 9 will occur. The sixth problem mentioned above is due to disturbances such as air fluctuations and noise.
When a jumping phenomenon as shown in the figure occurs, it appears as if a phase rotation from 0° to 360° and from 360° to 00 has occurred, causing malfunction.

The present invention is intended to prevent such a jumping phenomenon, and the basic principle of the present invention is to detect the phase difference when no moving object is present from the output of the phase difference detection circuit A, and to detect this phase difference from the output of the phase difference detection circuit A. When the phase difference is around 00 or 36 (f), the phase of the reference signal OR is shifted by the phase shift circuit 6, and ideally the phase difference is controlled to be, for example, 180° (not necessarily 180°). That's true.

Specifically, the input and output of the phase difference detection circuit is input to an integrator 14 with a time constant sufficiently large compared to the speed of the moving body, and this output is input to a phase shift circuit 6 to shift the phase and perform the jump described in It removes.

In other words, if the phase is A2 shown in FIG. 10, the phase shift amount of the phase shift circuit 6 is increased so that it becomes O from ■, and conversely, if the phase is A1, the phase shift amount is increased from @ to 0. The amount of phase shift is decreased so that the state of .

That is, the phase shift is controlled so that the steady state is O, and in this case, the phase shift amount of the phase shift circuit 6 only needs to be 3600.

Since the phase difference detection circuit A having the characteristics shown in FIG. 9 detects the phase difference between the received signal and the reference signal σt, increasing the phase shift amount of the phase shift circuit 6 will decrease the phase amount. By decreasing the phase shift amount of the advanced phase shift circuit 6, the phase amount is controlled by increasing the phase amount, and the above-mentioned jump can be eliminated.

FIG. 11 is a vector diagram showing the phase shift of the phase shift circuit 6.

FIG. 7 shows an example of the phase shift circuit 6, where Q is a variable resistance element,
For example, in a FET, the amount of phase shift between input and output changes depending on the control input.

However, if the output of the phase difference detection circuit A is used as this control input, the jumping phenomenon as shown in FIG. 6 will be eliminated in a steady state, and stable operation can be expected.

By the way, as mentioned above, the output of the integrator 14 is transferred to the phase shift circuit 6.
Since the output of the integrator 14 is shifted by the comparator 151,1 as shown in
52 to each comparator and the aforementioned phase A1. A2 may be detected respectively, and the phase shift amount of the phase shift circuit 6 may be controlled using the detection output.

Note that the above-mentioned phase control is not performed when a moving object is present or when a disturbance such as noise is present, and the integrator 14 is configured to operate only when a moving object is not present.

Next, in order to operate the switch using the obtained output signal of the phase difference detection circuit A, there is a method in which the signal processing circuit 13 performs amplification detection on the alternating current component of the phase difference detection output to operate it, and There are methods such as a method of performing switching using a signal obtained by performing DC amplification of these signals after differentiation to obtain the slope, or a method of performing switching using a jump pulse.

As described above, the present invention emits ultrasonic waves into a monitoring space using a transmitter using the output of an oscillator, and a reference signal is obtained by shifting the phase of the received signal received by a receiver and the output of the oscillator using a phase shift circuit. Since the system detects the rotation of the phase difference with the signal and issues an alarm, the operation is extremely stable against external noise,
It is extremely stable in operation due to wind, etc., does not use any filters, has no adjustment points, can be constructed with a very small number of parts, and can phase-shift the input signal using the output signal of the phase difference detection circuit. Since the detection phase difference is always controlled to a constant value, there is no jump phenomenon even when the fixed phase component exists near 0 degrees or 360 degrees with respect to the calibration signal, and the operation is stable. Since the direction of rotation is detected, the output of this rotation is differentially amplified and detected, and an alarm is issued, stable operation is possible at all times.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram of an embodiment of the moving object detection method of the present invention, Fig. 2 is a vector diagram of the same as above, Fig. 3 is a detection signal waveform diagram of the same as above, and Fig. 4 is an amplitude modulated diagram of the same as above. A vector explanatory diagram of waveforms, FIG. 5 is a phase difference detection output waveform diagram in a steady state, and FIG. 6 is a phase difference detection output waveform diagram in a jumping state.
FIG. 7 is a specific circuit diagram of the same phase shift circuit, FIG. 8 is a vector diagram explaining the jumping phenomenon, FIG. 9 is a characteristic diagram of the phase difference detection circuit used in the above, and FIGS. 10 and 11. This figure is an explanatory diagram of the operation of the phase shift circuit used in the above, and FIG. 12 is a block diagram showing another example of a circuit for preventing jumps. 1... Oscillator, 3... Transmitter, 4...
...Receiver, 6...Phase shift circuit, 13...
...Signal processing circuit, A...Phase difference detection circuit.

Claims (1)

[Scope of Claims] 1. An oscillator that oscillates a frequency signal in the ultrasonic range, a transmitter that emits ultrasonic waves driven by the frequency signal from the oscillator toward a monitoring space, and an output from the oscillator that outputs a predetermined phase. a phase shift circuit that generates a signal whose phase is shifted by a phase shifter, a receiver that receives ultrasonic waves reflected from an object in the monitoring space, and a first wave receiver that converts the signal from the phase shift circuit into a rectangular wave. a second limiter that converts the received signal converted into an electric signal by the limiter and the receiver into a rectangular wave; a first differentiation circuit that differentiates the output of the first limiter; A second differentiating circuit that differentiates the fluctuation of the output; a flip-flop that uses the output of the first differentiating circuit as a reset signal and the output of the second differentiating circuit as a set signal; and an integrating circuit that integrates the output of the flip-flop. A moving object detection device comprising: a phase difference detection circuit comprising: and a signal processing circuit that detects rotation of the phase difference from an integrated output of the integration circuit. 2. The moving object detection device according to claim 1, wherein the phase shift circuit is controlled by the output signal of the phase difference detection circuit so that the detected phase difference is constant.