JP4886395B2 - Moving object detection device - Google Patents

Description

  The present invention relates to a moving object detection device that detects the presence of an object moving in a monitoring space by radiating ultrasonic waves to the monitoring space and detecting a frequency shift of a reflected wave caused by the movement of the object in the monitoring space. It is about.

  In recent years, since vehicle theft and on-the-car theft of automobiles have increased, in-vehicle theft alarm devices that sound an alarm sound when a suspicious person enters a parked vehicle have become widespread. The apparatus is equipped with a moving object detection device for detecting the presence or absence of a moving object (person) in the monitoring space (inside the vehicle) (for example, see Patent Document 1).

  This kind of moving object detection device radiates ultrasonic waves of a predetermined frequency into the monitoring space, and detects the frequency shift of the reflected wave that occurs as a Doppler effect accompanying the movement of the object existing in the monitoring space. (See, for example, Patent Documents 2 and 3).

  FIG. 5 shows an example of a conventional moving object detection apparatus. By receiving a transmission signal of a predetermined frequency oscillated by the oscillator 1 and the transmission circuit 2 driving the transmitter 3, an ultrasonic wave having the same frequency as the oscillation frequency of the oscillator 1 is transmitted to the monitoring space. The reflected wave generated by the reflection of the ultrasonic wave on the object O existing inside is received by the wave receiver 4. In the receiver 4, the received reflected wave is converted into a received signal Ein, and the received signal Ein is input to the first and second phase detection circuits 6 </ b> A and 6 </ b> B, respectively, and the same frequency as the oscillation frequency of the oscillator 1. Are mixed with the reference signals E0 and E0 '. Here, one reference signal E0 is an output of the phase shift circuit 10, and is set so that the phases of both reference signals E0 and E0 'are different from each other. Therefore, the pair of Doppler signals E and E 'obtained as beat signals at the outputs of the first and second phase detection circuits 6A and 6B also have different phases. The Doppler signals E and E ′ are binary signals (hereinafter referred to as “axis code signals”) X and X corresponding to the positive and negative of the signals in the comparators 9A and 9B after the harmonic components are removed by the low-pass filters 7A and 7B, respectively. Converted to Y. Since each of the axis code signals X and Y has two values (high level and low level), four states can be represented by a combination of both, and these four states represent the Doppler signals E and E ′. Of the four quadrants of the vector plane serving as the basic axis, it indicates in which quadrant the vector corresponding to the received signal Ein exists. Therefore, considering four states (positive, positive, negative, negative, negative) according to the combination of the polarities of the Doppler signals E and E ′, it is made to correspond to each quadrant (first quadrant to fourth quadrant) on the vector plane. It can be done. In short, if the four states are classified by combining the polarities of the Doppler signals E and E ′ having both positive and negative polarities, a quadrant (first quadrant) in which vectors having signal values of both Doppler signals E and E ′ exist as components. Thru | or 4th quadrant) and said each state respond | correspond one-to-one. This vector moves in a quadrant in the vector plane in accordance with the frequency shift of the received signal Ein with respect to the reference signals E0 and E0 ′, depending on whether the frequency becomes lower or higher, that is, whether the object O moves away or approaches. The quadrant is moved clockwise or counterclockwise.

  Therefore, in this conventional example, the detection circuit 8 is configured by the quadrant signal generation circuit 80, the memory 81, the transition direction detection circuit 82, the arithmetic circuit 83, and the threshold circuit 84, and the following processing is performed. However, the functions of the quadrant signal generation circuit 80, the transition direction detection circuit 82, the arithmetic circuit 83, and the threshold circuit 84 can be realized by configuring the detection circuit 8 by a microcomputer and executing a program in the microcomputer.

  The quadrant signal generation circuit 80 detects the quadrant in which the received signal Ein exists on the vector plane by the signal processing described above and outputs a corresponding quadrant signal Q. At the same time, the received signal Ein is a boundary line of each quadrant. A transition signal Z is generated when transitioning beyond. Since the quadrant signal Q only needs to represent four states, it may be 2 bits or more. Further, the quadrant signal Q is temporarily stored in the memory 81 every time the transition signal Z is generated, and is also input to the transition direction detection circuit 82. Here, the quadrant signal Q stored in the memory 81 is updated every time the transition signal Z is generated.

In the transition direction detection circuit 82, a vector corresponding to the received signal Ein is input from the quadrant signal generation circuit 80 as the transition signal Z is generated by shifting to the adjacent quadrant (first quadrant to fourth quadrant). The current quadrant signal Q (that is, the quadrant signal Q after the transition) and the previous quadrant signal Q (that is, the quadrant signal Q before the transition) stored in the memory 81 when the previous transition signal Z is generated. Are compared to determine whether the quadrant has shifted clockwise or counterclockwise. Here, the output of the transition direction detection circuit 82 is added when the vector corresponding to the received signal Ein crosses the quadrant boundary line (basic axis) counterclockwise around the origin, and the quadrant boundary clockwise. It is set so that a direction signal instructing subtraction is output when the line is crossed. Thus, when the direction signal that is the output of the transition direction detection circuit 82 is obtained, the contents of the memory 81 are updated. The direction signal, which is the output of the transition direction detection circuit 82, and the transition signal Z, which is the output of the quadrant signal generation circuit 80, are input to the arithmetic circuit 83. The arithmetic circuit 83 generates a transition direction detection circuit each time the transition signal Z is generated. 82 is read, and 1 is added to the value stored in the arithmetic circuit 83 if the direction signal is counterclockwise, and 1 if it is clockwise. Therefore, when the vector corresponding to the received signal Ein moves along a locus from the first quadrant through the second quadrant to the third quadrant, if the initial value of the arithmetic circuit 83 is 0, the final value is It becomes 3. Thus, when the absolute value of the output value of the arithmetic circuit 83 exceeds the threshold value preset in the threshold circuit 84, the threshold circuit 84 sends out a detection signal. The detection signal is input to the alarm drive circuit 11, and the presence of the moving object O is appropriately notified by the alarm.

According to the above configuration, since the ultrasonic wave is transmitted and the frequency shift of the reflected wave is detected, if the frequency of the transmitted signal is f0, the moving speed of the object is v, and the propagation speed of the ultrasonic wave is c. The frequency Δf of the Doppler signals E and E ′ is | Δf | ≈2vf0 / c (generally v << c), and the frequency of the Doppler signals E and E ′ is proportional to the moving speed v of the object. Further, since the wave number N of the Doppler signals E and E ′ generated when the object moves by a unit distance is N = 2f0 / c, the ultrasonic wave propagation speed c and the transmission frequency f0 are constant. For example, the wave number N is constant regardless of the moving speed v of the object. Therefore, the number of quadrant transitions on the vector plane of the vector corresponding to the received signal Ein is also constant. In other words, if expressed in four quadrants as described above, the number of quadrant transitions is 4 × N, which is proportional to the moving distance of the object. In addition, since the direction of quadrant transition represents the direction in which the object moves, if the number of transitions is added or subtracted according to the direction of the transition when quadrant transition occurs, the moving distance and direction of the object can be known. is there. In other words, the moving distance of the object O in the monitoring space becomes the determination criterion of the threshold circuit 84, and the presence of the object can be detected regardless of the time for which the object O moves in the monitoring space.
JP-A-9-272402 Japanese Examined Patent Publication No. 62-43507 Japanese Patent Publication No. 6-16085

  By the way, when the moving object detection device as described above is mounted on an in-vehicle burglar alarm device, vibrations and sounds generated when other vehicles (cars, trains, motorcycles, etc.) pass by the side ( The window glass of the vehicle, the transmitter 3 or the receiver 4 may vibrate with a minute amplitude when transmitted to the automobile), and the ultrasonic propagation path fluctuates with time due to the minute vibration. Phase modulation is applied to the reflected wave.

  Here, when the periodic signal output from the oscillator 1 is sin (ωt + φ) and the minute vibration is fmsinω0t, the modulation signal f output from the receiving circuit 5 is f = sin (ωt + φ + fmsinω0t). Therefore, the Doppler signals E and E ′ output from the phase detection circuits 6A and 6B are expressed by the following equations, respectively.

E = sin (ωt + φ + fmsinω0t) sinωt
≒ 1 / 2fmsinφsinω0t
E '= sin (ωt + φ + fmsinω0t) cosωt
≒ 1 / 2fmcosφsinω0t
However, fm << 1
As is clear from the above equation, if φ is 0 or π / 2, one of the Doppler signals E and E ′ is zero, and if φ is π / 4 or 3π / 4, the Doppler signals E and E ′. Are in reverse phase (ie, phase difference is π ) or in phase (phase difference is zero).

  For example, when the Doppler signals E and E ′ are in phase, the axis code signals X and Y obtained by binarizing the Doppler signals E and E ′ have a cycle of (1, 1) and (−1, −1). (Refer to Fig. 6 (a)), and because the transition direction cannot be detected from the quadrant signal Q before and after the transition, it is not possible to erroneously detect an object (such as a window glass) that vibrates slightly as a moving object. There should be no.

  However, in the case where the thresholds of the comparators 9A and 9B that convert the Doppler signals E and E ′ into the axis code signals X and Y have hysteresis for preventing chattering, as shown in FIG. When the amplitudes of the signals E and E ′ are different (for example, when the amplitude of the Doppler signal E ′ is small), there is a position between the axis code signals X and Y as shown in FIGS. A phase difference occurs, and the quadrant signal Q periodically shifts in the order of (1, 1) → (−1,1) → (−1, −1) → (1, −1) → (1,1). There is a possibility that an object that vibrates slightly will be erroneously detected as an object that moves in the direction of approach (see FIG. 6B).

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a moving object detection device capable of suppressing erroneous detection of a minute vibrating object as a moving object.

In order to achieve the above object, an invention according to claim 1, an oscillating means that oscillates at a predetermined frequency, a wave sending means that sends an ultrasonic wave to a monitoring space by a wave sending signal output from the oscillating means, Detecting a phase difference between a wave receiving means for receiving a reflected wave generated by reflection of a sound wave on an object existing in a monitoring space, and a received signal output from the wave receiving means and a reference signal having the same frequency as the wave transmission signal. Phase detecting means, binary signal converting means for converting the phase detection signal output from the phase detecting means into a binary signal by comparing with a predetermined threshold value, and binary signal output from the binary signal converting means Detection means for detecting the presence or absence of a moving object in the monitoring space, and the phase detection means mixes a reference signal and a reception signal having the same frequency as the transmission signal and different phases from each other to obtain a phase difference from each other. A pair of different positive and negative polarities The binary signal converting means compares the Doppler signals output from the pair of phase detection circuits with a predetermined first threshold value having hysteresis, respectively. A pair of first comparators for converting into an axis code signal , and the detecting means is based on the axis code signal and is in a quadrant of a vector plane in which the signal values of the respective Doppler signals are taken on the vertical and horizontal axes. In the moving body detection apparatus, the binary signal converting means further includes a quadrant signal generating unit that generates a quadrant signal corresponding to a quadrant in which a vector whose components are signal values of both Doppler signals exists. a pair of second ratio to convert to the discrimination signal by comparing the Doppler signal with a predetermined second threshold value also is smaller absolute value than and the first threshold value having respective hysteresis Has a vessel, I said detecting means, said pre-Symbol doppler signal at the comparison result of the first comparator are both exceeded the first threshold value, and the phase difference of the determination signal is the first if the threshold and greater than the difference reference value corresponding to the second threshold value, generates the quadrant signal, to detect the presence or absence of a moving object based on the temporal change of the quadrant signals It is characterized by.

According to a second aspect of the present invention, in the first aspect of the invention, the second threshold value is set to a half of the first threshold value, and the phase difference in the comparison result of the second comparator is calculated . The reference value is set to π / 4.

A pair of Doppler signals obtained by receiving a reflected wave reflected on a moving object such as a person or a reflected wave reflected on a stationary object usually has the same or slightly different amplitude value. Since only a Doppler signal obtained by receiving a reflected wave reflected by a minutely vibrating object should have a large difference in amplitude value between the two, according to the present invention, either one of the Doppler signals quadrant value exceeds the first threshold in the first comparator, and the value of the other of the Doppler signal is speculated that the reflected wave reflected on the object to fine vibration is less than the first threshold value The false detection can be suppressed by not generating the signal, and the comparison result of the second comparator even when the values of the pair of Doppler signals are both equal to or higher than the first threshold value in the first comparator. (Binarized A quadrant signal is generated only when the phase difference in the discrimination signals α, β) is larger than a reference value corresponding to the difference between the first threshold value and the second threshold value, and the second comparator compares When the phase difference in the result is less than the reference value, by not performing the moving object detection process, it is possible to suppress erroneous detection of a slightly vibrating object as a moving object.

  FIG. 1 shows a block diagram of this embodiment. However, since the basic configuration and basic operation of this embodiment are the same as those of the conventional example shown in FIG. 5, the same reference numerals are given to common components, and the description thereof is omitted.

In the present embodiment, comparators 9C and 9D (second comparator) different from the comparators 9A and 9B (first comparator) are connected in parallel to the output terminals of the low-pass filters 7A and 7B. The comparison results (hereinafter referred to as discrimination signals) α and β in the comparators 9C and 9D are taken into the quadrant signal generation circuit 80 of the detection circuit 8 made of a microcomputer. Here, in the comparators 9A and 9B, hysteresis is given to the threshold value. When the Doppler signals E and E ′ exceed the larger threshold value Th1 (+), the smaller threshold value Th1 (−). When the Doppler signals E and E ′ fall below the smaller threshold value Th1 (−), the switching to the larger threshold value Th1 (+) prevents chattering. Similarly, the comparators 9C and 9D added in this embodiment also have hysteresis in the threshold value, and when the Doppler signals E and E ′ exceed the larger threshold value Th2 (+), the smaller one is obtained. The threshold value Th2 (-) is switched, and when the Doppler signals E and E 'fall below the smaller threshold value Th2 (-), the larger threshold value Th2 (+) is switched. The threshold values (second threshold values) Th2 (+) in the comparators 9C and 9D are compared with the threshold values (first threshold values) Th1 (+) and Th1 (-) in the comparators 9A and 9B. , Th2 (-) has a smaller absolute value, that is, the second threshold value Th2 (+) so as to satisfy the relationship Th2 (+) <Th1 (+) and Th2 (-)> Th1 (- ). , Th2 (−) are set, and when the values of the Doppler signals E, E ′ are larger than the second threshold value Th2 (+), the determination signals α 1 , β become high level, and the Doppler signals E, E When the value of 'is smaller than the second threshold value Th2 (-), the discrimination signals α and β become low level.

On the other hand, in the quadrant signal generation circuit 80, the amplitude value of one of the Doppler signals E and E ′ is the first threshold value Th1 (+), in the first comparator (comparator 9A or 9B). When smaller than Th1 (−) and the other amplitude value is larger than the first threshold value Th1 (+), Th1 (−) in the first comparator (comparator 9A or 9B) , the comparator 9A, 9B sets 2 Processing for generating quadrant signals from the digitized axis code signals X and Y is not performed. That is, a pair of Doppler signals E and E ′ obtained by receiving a reflected wave reflected on a moving object such as a person or a reflected wave reflected on a stationary object usually has the same amplitude value or Only a slight difference should occur, and Doppler signals E and E ′ obtained by receiving reflected waves reflected on a slightly vibrating object (for example, a window glass of a vehicle that vibrates as a vehicle passes). since it is believed to occur a large difference in the amplitude value of each other, the Doppler signal E, is one of E ', the first threshold Th1 which those of the first comparator (+), Th1 - from () When the other Doppler signal is smaller and larger than the first threshold values Th1 (+) and Th1 (-) in the first comparator , the received signal Ein is caused by a reflected wave reflected by a slightly vibrating object. Quadrant signal generation circuit can be guessed 0 can be suppressed to be erroneously detected as an object the moving object minutely vibrate by not generating a quadrant signal.

Here, it is by the reflected wave reflected on the object reception signal Ein is minutely vibrate, the Doppler signal E, E 'values are all first comparator (comparator 9A or 9B) in the first of Since the threshold values Th1 (+) and Th1 (-) may be exceeded, the first threshold values Th1 (+) and Th1 (-) in the first comparator (comparator 9A or 9B ) Only the comparison processing cannot sufficiently suppress erroneous detection of an object that vibrates slightly.

Therefore, even if the values of the Doppler signals E and E ′ exceed the first threshold values Th1 (+) and Th1 (−) in the first comparator (comparator 9A or 9B ), The phase difference between the discrimination signals α and β is less than the reference value corresponding to the difference between the first threshold values Th1 (+) and Th1 (−) and the second threshold values Th2 (+) and Th2 (−). If so, it can be assumed that the Doppler signals E and E ′ are substantially in phase or out of phase, and the received signal Ein is due to a reflected wave reflected by a slightly vibrating object .

For example, a second threshold Th2 (+), Th2 (- ) the first threshold value Th1 (+), Th1 (- ) 1 times the half of the (Th2 (+) = Th1 ( +) × 1/2 , Th2 (−) = Th1 (−) × 1/2 ), the values of the Doppler signals E, E ′ are set to the first threshold values Th1 (+), Th1 as shown in FIG. (-) discrimination signal when exceeding the alpha, the phase difference Δφ of β is a maximum at 30 ° (= [pi / 6), determines that the phase if the phase difference Δφ is 30 ° or less, fine vibrations It can be inferred that this is due to the reflected wave reflected by the object. As shown in FIG. 3, the time t2 when the determination signal β changes from the low level to the high level from the time t1 when the determination signal α changes from the low level to the high level (quadrant signal Q = (1, −1)). Time T1 (= t2−t1) until (quadrant signal Q = (1,1)) and time t3 (quadrant signal Q = (− 1,1) when the determination signal α changes from high level to low level from time t2. )) Until the time T2 (= t3-t2) is compared in the arithmetic circuit 83, and the ratio (T1: T2) of the two times T1, T2 is within the range of 1: 3 to 3: 1, in other words, the two The arithmetic circuit 83 reads and stores the output signal of the transition direction detection circuit 82 only when the phase difference Δφ between the determination signals α and β corresponding to the time difference between the times T1 and T2 is 45 ° (= π / 4) or more. Add 1 if the direction signal is counterclockwise to the value, and turn clockwise If the phase difference Δφ between the discrimination signals α and β corresponding to the time difference between the two times T1 and T2 is less than 45 °, the arithmetic circuit 83 adds or subtracts the stored value. Not performed. That is, the ratio (T1: T2) of the two times T1 and T2 is outside the range of 1: 3 to 3: 1. In other words , the phase difference Δφ between the determination signals α and β corresponding to the time difference between the two times T1 and T2 is If the angle is less than 45 °, the arithmetic circuit 83 determines whether the actual received signal Ein moves between the first quadrant and the third quadrant (when the Doppler signals E and E ′ are in phase) as shown in FIG. Alternatively, it is estimated that the movement is between the second quadrant and the fourth quadrant (when the Doppler signals E and E ′ are in reverse phase), so that the moving object detection process is not performed.

Here, the reference value (= 45 °) that the arithmetic circuit 83 compares with the phase difference Δφ between the discrimination signals α and β is the first threshold Th1 (+), Th1 (−) and the second threshold value. A value corresponding to the difference between the threshold values Th2 (+) and Th2 (-), that is, a value determined by estimating a slight margin value for the maximum value (= 30 °) of the phase difference Δφ between the discrimination signals α and β. It is. However, the values exemplified in this embodiment are merely examples, and the present invention is not limited to these values.

Thus, according to the present embodiment, one of the values of the Doppler signals E and E ′ becomes the first threshold values Th1 (+) and Th1 (− in the comparators 9A and 9B ( first comparator). ) And the value of the other Doppler signal is equal to or greater than the first threshold value Th1 (+), Th1 (−), it is assumed that the reflected wave is reflected by a slightly vibrating object, and the quadrant signal generation circuit 80 Since the quadrant signal Q is not generated, false detection can be suppressed, and the values of the Doppler signals E and E ′ are both equal to or higher than the first threshold values Th1 (+) and Th1 (−) in the comparators 9A and 9B . Even in some cases, the phase difference Δφ between the discrimination signals α and β is the difference between the first threshold values Th1 (+) and Th1 (−) and the second threshold values Th2 (+) and Th2 (−). is generated only quadrant signal Q when greater than the corresponding reference value, determination signal alpha, when the phase difference Δφ of β is less than the reference value calculation times By 83 it does not perform the processing of the moving object detection (addition or subtraction processing on the stored value), in which more reliably suppressed from being erroneously detected as the moving object an object minutely vibrate.

It is a block diagram which shows embodiment of this invention. It is a wave form diagram for operation explanation same as the above. It is explanatory drawing of the axis code signal in the same as the above. It is explanatory drawing of the quadrant signal in the same as the above. It is a block diagram which shows a prior art example. It is operation | movement explanatory drawing same as the above. It is a wave form diagram for operation explanation same as the above.

DESCRIPTION OF SYMBOLS 1 Oscillator 2 Transmitter circuit 3 Transmitter 4 Receiver 5 Receiver circuit 6A, 6B Phase detector circuit 8 Detector circuit 9A, 9B Comparator (1st comparator)
9C, 9D comparator (second comparator)
80 quadrant signal generation circuit 83 arithmetic circuit

Claims (2)

An oscillating unit that oscillates at a predetermined frequency, a transmitting unit that transmits an ultrasonic wave to the monitoring space by a transmission signal output from the oscillating unit, and a reflected wave that is generated when the ultrasonic wave is reflected by an object existing in the monitoring space Receiving means for receiving the signal, phase detecting means for detecting the phase difference between the received signal output from the receiving means and the reference signal having the same frequency as the transmitted signal, and the phase detecting signal output from the phase detecting means A binary signal converting means for converting the signal into a binary signal by comparing the signal with a predetermined threshold, and a detecting means for detecting the presence or absence of a moving object in the monitoring space based on the binary signal output from the binary signal converting means And
The phase detection means mixes a reference signal and a reception signal having the same frequency as the transmission signal and different phases, and converts them into a pair of Doppler signals having positive and negative polarities having different phases. Have
The binary signal converting means converts the Doppler signals output from the pair of phase detection circuits to a predetermined first threshold value having hysteresis, thereby converting the signals into a pair of axis code signals . Having a comparator of
The detection means is based on the pair of axis code signals in a quadrant in which a vector whose component is the signal value of both Doppler signals is present among quadrants of the vector plane in which the signal values of the Doppler signals are taken in the vertical and horizontal axes. In the mobile object detection device having a quadrant signal generation unit for generating a corresponding quadrant signal,
The binary signal converting means further compares the pair of Doppler signals with a predetermined second threshold value having hysteresis and having an absolute value smaller than the first threshold value, thereby making a pair of determinations. a second comparator of the pair to be converted into a signal,
The detection means, the pre-Symbol doppler signal at the comparison result of the first comparator are both exceeded the first threshold value, and the pair of phase difference of the first threshold of the discrimination signal If the value is greater than the reference value corresponding to the difference between the second threshold value, it generates the quadrant signal, to detect the presence or absence of a moving object based on the temporal change of the quadrant signals A moving object detection device. The second threshold value is set to a half of the first threshold value, and the reference value of the phase difference in the comparison result of the second comparator is set to π / 4. The moving object detection device according to claim 1.

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