JP2008145255A - Detector for moving object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detector for moving object capable of preventing misdetection of moving objects. <P>SOLUTION: When a determination circuit 86 makes a transmitter 3 output a transmission signal of a first frequency f1 from an oscillation circuit 1, and detects the moving object, the determination circuit makes the transmitter 3 output a transmission signal of a second frequency f2 that is different from the first frequency f1, from the oscillation circuit 1. When the moving object is also detected from the transmission signal of the second frequency f2, in other words, only when the moving object is detected from the transmission signals of all the frequencies (first frequency f1 and second frequency f2), a detection signal is output from the determination circuit 86. As a result, misdetection of the moving object can be prevented, even if high-energy waves (sound waves whose sound pressure level is very high) arrives from outside a monitoring space, for example. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention radiates continuous energy waves such as ultrasonic waves and radio waves to the monitoring space, and detects the frequency shift of the reflected wave caused by the movement of the object in the monitoring space, thereby the presence of an object moving in the monitoring space. The present invention relates to a moving object detection device that detects the above.

  In recent years, vehicle theft and on-the-car theft have increased, so that 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) (see, for example, Patent Document 1).

  This type of moving object detection device radiates a continuous energy wave (for example, an ultrasonic wave) of a predetermined frequency into a monitoring space, and a reflected wave generated as a Doppler effect accompanying the movement of an object existing in the monitoring space. (See, for example, Patent Documents 2 and 3).

FIG. 7 shows an example of a conventional moving object detection apparatus. By driving the transmitter 3 with a transmission signal having a predetermined frequency that the oscillator 1 oscillates, an ultrasonic wave having the same frequency as the oscillation frequency of the oscillator 1 is transmitted to the monitoring space, and the object O existing in the monitoring space is transmitted to the object O. A reflected wave generated by reflecting the ultrasonic wave 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. And reference signals E ₀ and E ₀ ′. Here, one reference signal E ₀ is an output of the phase shift circuit 10 and is set so that the phases of both reference signals E ₀ and E ₀ ′ 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 according to the frequency shift of the received signal Ein with respect to the reference signals E ₀ and E ₀ ′, and whether the frequency becomes lower or higher, that is, whether the object O moves away or approaches. In response to this, 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 with 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, the 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 detection circuit 80, are input to the arithmetic circuit 83. The arithmetic circuit 83 causes the transition direction detection circuit 82 every time the transition signal Z is generated. 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 the locus from the first quadrant, the second quadrant, and the third quadrant to the fourth quadrant in order, the initial value of the arithmetic circuit 83 is 0. In this case, the final value is 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, the frequency of the transmission signal is f ₀ , the moving speed of the object is v, and the propagation speed of the ultrasonic wave is c. For example, the frequency Δf of the Doppler signals E and E ′ is | Δf | ≈2 vf ₀ / 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 = 2f ₀ / c, the ultrasonic wave propagation speed c and the transmission frequency f ₀ are constant. If so, 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 very small amplitude, and the propagation path of the ultrasonic wave fluctuates over time due to the vibration. The wave will be phase modulated.

Here, when the periodic signal output from the oscillator 1 is sin (ωt + φ) and the vibration is f _m sinω ₀ t, the modulation signal f output from the receiver 4 is f = sin (ωt + φ + f _m sinω ₀ t), the Doppler signals E and E ′ output from the phase detection circuits 6A and 6B are respectively expressed by the following equations.

E = sin (ωt + φ + f _m sinω ₀ t) sinωt
≒ 1 / 2f _m sinφsinω ₀ t
E '= sin (ωt + φ + f _m sinω ₀ t) cosωt
≒ 1 / 2f _m cosφsinω ₀ t
However, f _m ≪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 / 2) 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). (See FIG. 8A), and since the transition direction cannot be detected from the quadrant signal Q before and after the transition, a vibrating object (such as a window glass) is not erroneously detected as a moving object. It should be.

  However, when the thresholds of the comparators 9A and 9B that convert the Doppler signals E and E ′ into the axis code signals X and Y are provided with 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 a vibrating object may be erroneously detected as an object that moves in a direction approaching (see FIG. 8B).

  Therefore, the present inventors have already proposed what is shown in FIG. 10 to prevent the above-described erroneous detection. In the configuration shown in FIG. 10, comparators 9C and 9D (second comparator) different from the comparators 9A and 9B (first comparator) are connected in parallel to the output ends of the low-pass filters 7A and 7B. The comparison results (hereinafter referred to as discrimination signals) α, β in these comparators 9C, 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, in the comparators 9C and 9D added in this configuration, hysteresis is given to the threshold value. When the Doppler signals E and E ′ exceed the larger threshold value Th2 (+), the smaller value is obtained. The threshold value Th2 (-) is switched, and when the Doppler signals E and E 'fall below the smaller threshold value Th2 (-), the 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 larger absolute value, that is, the second threshold value Th2 (+) so as to satisfy the relationship of Th1 (+) <Th2 (+) and Th1 (−)> Th2 (−). , Th2 (−) are set, and when the amplitude value of the Doppler signals E, E ′ is larger than the second threshold value Th2 (+), the determination signal α becomes a high level, and the Doppler signals E, E ′. Is smaller than the second threshold value Th2 (−), the determination signal β is at a high level, and at other times, the determination signals α and β are both at a low level.

  On the other hand, in the quadrant signal generation circuit 80, when at least one of the determination signals α and β is at a low level, the quadrant signal is generated from the axis code signals X and Y binarized by the comparators 9A and 9B. 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). Only the amplitude value of the Doppler signals E and E ′ is the second threshold value Th2 (+), Th2 in the second comparator (comparator 9C or 9D). If the received signal Ein is less than (−), it can be assumed that the received signal Ein is due to a reflected wave reflected by an object that vibrates slightly, and in that case, the quadrant signal generation circuit 80 does not generate a quadrant signal, and thus it vibrates slightly. object Can be prevented from being erroneously detected as a moving object.

  Here, even if the received signal Ein is a reflected wave reflected by an object that vibrates slightly, the amplitude values of the Doppler signals E and E ′ are the second values in the second comparator (comparator 9C or 9D). Since the threshold values Th2 (+) and Th2 (-) may be exceeded, the comparison with the second threshold values Th2 (+) and Th2 (-) in the second comparator (comparator 9C or 9D). The processing alone cannot sufficiently suppress erroneous detection of an object that vibrates slightly.

  Therefore, even if the amplitude values of the Doppler signals E and E ′ exceed the second threshold values Th2 (+) and Th2 (−) in the second comparator (comparator 9C or 9D), the axis The phase difference between the code signals X and Y is below a reference value corresponding to the difference between the first threshold values Th1 (+) and Th1 (-) and the second threshold values Th2 (+) and Th2 (-). If so, the Doppler signals E and E ′ are almost in phase or out of phase, and the absolute value of the amplitude value is considered to be different. Therefore, it is assumed that the received signal Ein is due to a reflected wave reflected by a slightly vibrating object. be able to. That is, the fact that the phase difference between the Doppler signals E and E ′ (= phase difference between the axis code signals X and Y) is equal to or smaller than the reference value exists in the quadrant before the transition when the quadrant transition occurs. This indicates that the time was extremely short, and it is very difficult for a moving object (eg, a person) to change the direction of movement in such a short period of time, so in this case the received signal Ein Can be assumed to be due to a reflected wave reflected by a slightly vibrating object.

  For example, the second threshold values Th2 (+) and Th2 (-) are twice the first threshold values Th1 (+) and Th1 (-) (Th2 (+) = Th1 (+) × 2, Th2). When (−) = Th1 (−) × 2) is set, the amplitude values of the Doppler signals E and E ′ exceed the second threshold values Th2 (+) and Th2 (−) as shown in FIG. The phase difference φ between the axis code signals X and Y at the time is 30 ° (= π / 6) at the maximum. Then, as shown in FIG. 12, the axis code signal Y changes from the low level to the high level from the time t1 (quadrant signal Q = (1, −1)) when the axis code signal X changes from the low level to the high level. Time T1 (= t2−t1) until time t2 (quadrant signal Q = (1, 1)) and time t3 (quadrant signal Q = (−) when the axis code signal X changes from high level to low level from time t2. 1, 1)) is compared with the time T2 (= t3-t2) 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. The arithmetic circuit 83 reads and stores the output signal of the transition direction detection circuit 82 only when the time difference between the two times T1 and T2 (phase difference between the axis code signals X and Y) is 45 ° (= π / 4) or more. 1 if the direction signal is counterclockwise to the current value If it is clockwise, a process of subtracting 1 is executed, and when the time difference between the two times T1 and T2 is less than 45 °, the arithmetic circuit 83 does not perform addition or subtraction on the stored value. 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 time difference between the two times T1 and T2 (the phase difference between the axis code signals X and Y) is 45. If it is less than 0 °, the arithmetic circuit 83 causes the actual received signal Ein to move between the first quadrant and the third quadrant (when the Doppler signals E and E ′ are in phase), as shown in FIG. It is estimated that the second quadrant and the fourth quadrant move (when the Doppler signals E and E ′ are in reverse phase), and the moving object detection process is not performed.

  Here, the reference values (= 45 °) that the arithmetic circuit 83 compares with the phase difference between the axis code signals X and Y are the first threshold values Th1 (+) and Th1 (−) and the second threshold value. It is determined by estimating a slight margin value for the value corresponding to the difference between the threshold values Th2 (+) and Th2 (-), that is, the maximum value (= 30 °) of the phase difference φ between the axis code signals X and Y. Value.

  Thus, according to this configuration, the amplitude values of the Doppler signals E and E ′ are less than the second threshold values Th2 (+) and Th2 (−) in the comparators 9C and 9D (second comparator). For example, it can be assumed that the reflected wave is reflected from an object that vibrates slightly, and the quadrant signal Q is not generated from the quadrant signal generation circuit 80, so that erroneous detection can be suppressed. Further, the amplitude values of the Doppler signals E and E ' Even when the second threshold values Th2 (+) and Th2 (-) are equal to or larger than the first threshold values Th1 (+) and Th1 (-), The quadrant signal Q is generated only when it is larger than the reference value corresponding to the difference between the second threshold values Th2 (+) and Th2 (-), and the phase difference φ between the axis code signals X and Y is below the reference value. In this case, the arithmetic circuit 83 does not perform the moving object detection process (addition or subtraction process for the stored value). Are those that can more reliably suppress be erroneously detected as the moving object an object minutely vibrate.

  However, when a large energy wave (a sound wave with a very high sound pressure level) arrives from outside the monitoring space, the above-mentioned phase-modulated reflected waves overlap with each other in a complicated manner due to multiple reflections, and as a result, will be detected originally. The quadrant signal Q is (1,1) → (−1,1) → (−1, −1) → (1, −1) → (1, as in the case of receiving the reflected wave with respect to the moving object. It has been found that there is a possibility that a moving object may be erroneously detected due to periodic transition in the order of 1).

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

  In order to achieve the above object, the invention of claim 1 transmits an oscillation means whose oscillation frequency is variable and a continuous energy wave whose amplitude periodically changes by a transmission signal output from the oscillation means to a monitoring space. Transmitting means for receiving, a receiving means for receiving a reflected wave generated when the continuous energy wave is reflected by an object existing in the monitoring space, and a reference signal and a receiving signal having the same frequency as the transmitting signal but different in phase from each other And a phase detection means for obtaining a pair of Doppler signals having an amplitude corresponding to the phase difference from the reference signal and having a phase different from each other, and a signal processing of the pair of Doppler signals to move in the monitoring space Detection means for detecting an object and outputting a detection signal. The detection means outputs a transmission signal having a fundamental frequency from the oscillation means to the transmission means to detect a moving object. A transmission signal having a plurality of types of frequencies is output from the oscillation unit to the transmission unit, and a detection signal is output only when a moving object is detected for all the transmission signals of the one to a plurality of types of frequencies. And

  According to a second aspect of the present invention, in the first aspect of the invention, the wave transmitting means has a mountain-shaped output characteristic having a peak at the center frequency at which the energy of the continuous energy wave is maximum, and the detecting means has a fundamental frequency and The one or more types of frequencies are set to be divided into a higher frequency and a lower frequency than the center frequency.

  According to a third aspect of the present invention, in the second aspect of the present invention, the detection means is configured such that the fundamental frequency and the one or more types of frequencies are such that the energy of the continuous energy wave transmitted from the transmission means is substantially the same. It is characterized by being set.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the detection means moves until a predetermined standby time elapses from the time when the frequency of the transmission signal output from the oscillation means is switched. The object is not detected.

  According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the detection means is configured so that the continuous energy wave transmitted from the transmission means is not shorter than the maximum time required for reciprocating in the monitoring space. The waiting time is set.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the detection means includes the moving direction of the moving object detected at the fundamental frequency and the moving object detected at one or more types of frequencies. A detection signal is output when the movement direction of each coincides.

  According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, when the detection means does not detect a moving object at one or a plurality of types of frequencies, a predetermined non-detection time has elapsed. The moving object detection process is initialized.

  According to the first aspect of the present invention, the detection means outputs a transmission signal having a fundamental frequency from the oscillation means to the transmission means to detect a moving object, and transmits one or more types of frequencies different from the fundamental frequency. Since a wave signal is output in order from the oscillating means to the transmitting means, and a detection signal is output only when a moving object is detected for all transmission signals of the one or more types of frequencies, if it is a real moving object Even if the frequency of the transmitted signal is switched, it will be detected as a moving object at all frequencies, but if there is no moving object, it will not be detected by switching the frequency of the transmitted signal, thus preventing false detection of moving objects it can.

  According to the second aspect of the present invention, the frequency to be switched, that is, the fundamental frequency and the other frequencies are set so as to be divided into a higher frequency and a lower frequency than the center frequency in the output characteristics of the transmission means. Variations in the detectable distance due to the size of can be suppressed.

  According to the invention of claim 3, since the detection means is set to a frequency at which the energy of the continuous energy wave transmitted from the transmission means is substantially the same as the fundamental frequency and the one or more types of frequencies. Variations in the detectable distance due to the magnitude of energy for each frequency can be further suppressed.

  According to the invention of claim 4, there is a possibility that it cannot be detected accurately until the characteristics of the hardware constituting each means are stabilized when the frequency is switched, and until a predetermined standby time elapses, that is, Misdetection can be prevented by the detection means not detecting the moving object until the characteristics of the hardware are stabilized.

  According to the invention of claim 5, there is a possibility of erroneous detection that the continuous energy wave of the frequency before switching remains in the monitoring space, but the continuous energy wave transmitted from the wave transmitting means passes through the monitoring space. After the elapse of the waiting time set to a time not shorter than the maximum time required for reciprocating, erroneous detection due to a continuous energy wave at a frequency before switching can be prevented.

  According to the sixth aspect of the present invention, for example, when a swinging object such as a pendulum is detected, the moving direction is periodically reversed. Therefore, the detecting means moves the moving object detected at the fundamental frequency. If the detection signal is output when the moving direction of the moving object detected at one or more types of frequencies coincides, it is possible to prevent erroneous detection of the moving object as described above. it can.

  According to the seventh aspect of the present invention, the detection means initializes the detection process of the moving object when a predetermined non-detection time has elapsed unless a moving object is detected at one or more types of frequencies. If the detected moving object is not detected again within the predetermined non-detection time, the first detection can be regarded as a false detection. In that case, the detection means initializes the detection process so that the next detection can be performed. Can be provided.

  Hereinafter, an embodiment using ultrasonic waves as continuous energy waves as in the conventional example will be described in detail with reference to the drawings. However, the technical idea of the present invention can also be applied when radio waves are used instead of ultrasonic waves.

(Embodiment 1)
FIG. 1 shows a block diagram of this embodiment. However, since the basic configuration and the basic operation of the present embodiment are the same as those of the conventional example shown in FIG.

  The oscillation circuit 1 is composed of a voltage controlled oscillator (VCO), the oscillation frequency can be switched from the outside, and the oscillation frequency is determined by a frequency setting signal (DC voltage signal) output from the frequency switching circuit 85 included in the detection circuit 8. That is, the frequency of the transmission signal is switched. In the present embodiment, the frequency switching circuit 85 is configured to selectively switch between two types of frequencies, the first frequency (reference frequency) f1 and the second frequency f2, and the detection circuit 8 includes the determination circuit 86. In response to the instruction, either the frequency setting signal set to the first frequency f1 or the frequency setting signal set to the second frequency f2 is output, and the frequency of the transmission signal output from the oscillation circuit 1 is set to the first frequency f1. Alternatively, the frequency is switched to the second frequency f2.

  The determination circuit 86 responds to the comparison result between the absolute value of the output value of the arithmetic circuit 83 and the threshold value by the threshold circuit 84, that is, if the absolute value of the output value of the arithmetic circuit 83 exceeds the threshold value, the frequency switching circuit 85. Is instructed to switch from the first frequency f1 to the second frequency f2, and as will be described later, at all frequencies (first frequency f1 and second frequency f2) set by switching by the frequency switching circuit 85, the arithmetic circuit Only when the comparison result that the absolute value of the output value 83 exceeds the threshold is output from the threshold circuit 84, the detection signal is sent to the alarm drive circuit 11.

  Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

First, the frequency switching circuit 85 of the detection circuit 8 outputs a frequency setting signal to set the oscillation frequency of the oscillation circuit 1 to the first frequency f1. Then, by driving the transmitter 3 with a transmission signal of the first frequency f1 oscillated by the oscillator 1, an ultrasonic wave having the same frequency as the oscillation frequency (first frequency f1) of the oscillator 1 is transmitted to the monitoring space. The reflected wave generated by the ultrasonic wave reflected from the object O existing in the monitoring space is received by the 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. And reference signals E ₀ and E ₀ ′. The pair of Doppler signals E and E ′ output from the first and second phase detection circuits 6A and 6B are respectively removed from the harmonic components by the low-pass filters 7A and 7B, and then the axis code signals X and X in the comparators 9A and 9B. It is converted into Y and taken into the detection circuit 8.

  As in the conventional example, in the detection circuit 8, the quadrant signal generation circuit 80 outputs the quadrant signal Q corresponding to the combination of the polarities of the Doppler signals E and E ', and at the same time, the received signal Ein crosses the boundary line of each quadrant. A transition signal Z is generated when transitioning. 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. The transition direction detection circuit 82 generates a current quadrant signal Q (that is, a quadrant signal Q after transition) input from the quadrant signal generation circuit 80 as the transition signal Z is generated, and the generation of the previous transition signal Z. At the same time, the previous quadrant signal Q (that is, the quadrant signal Q before transition) stored in the memory 81 is compared to determine whether the quadrant has shifted clockwise or counterclockwise. However, the output of the transfer 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 line is added clockwise. It is set to output a direction signal instructing subtraction when crossing. 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 detection circuit 80, are input to the arithmetic circuit 83. The arithmetic circuit 83 causes the transition direction detection circuit 82 every time the transition signal Z is generated. The signal is processed so that 1 is added to the value stored in the arithmetic circuit 83 if the direction signal is counterclockwise and 1 is subtracted if it is clockwise. When the absolute value of the output value of the arithmetic circuit 83 exceeds a threshold value preset in the threshold circuit 84, the output of the threshold circuit 84 changes from L level to H level.

  When the output of the threshold circuit 84 becomes H level, the determination circuit 86 sets the detection flag stored in the memory 81 to 1, and the frequency switching circuit 85 changes from the first frequency f1 to the second frequency f2. Switching is instructed and counting of a predetermined standby time is started. The frequency switching circuit 85 sets the oscillation frequency of the oscillation circuit 1 to the second frequency f2 in response to an instruction from the determination circuit 86. Here, in the detection circuit 8, signal processing (detection processing) by the quadrant signal generation circuit 80, the transition direction detection circuit 82, the arithmetic circuit 83, and the threshold circuit 84 is stopped until the standby time count is completed. That is, when the frequency of the ultrasonic wave transmitted from the transmitter 3 is switched from the first frequency f1 to the second frequency f2, the ultrasonic wave of the first frequency f1 before switching remains in the monitoring space. Since there is a possibility that a moving object exists because the ultrasonic wave of the first frequency f1 and the ultrasonic wave of the second frequency f2 coexist during the interval, a predetermined waiting time elapses in the monitoring space. By stopping the signal processing until it can be assumed that there is no ultrasonic wave having the first frequency f1, the above-described erroneous detection is prevented. Note that the standby time may be a time that can be considered that there is no ultrasonic wave having the first frequency f1 in the monitoring space. For example, when the ultrasonic wave transmitted from the transmitter 3 reciprocates in the monitoring space. What is necessary is just to set it as the time which is not shorter than the maximum value of required time. In addition, since the charged charges of the capacitors used in the low-pass filters 7A, 7B and the like are completely discharged within the standby time, malfunction (false detection) due to the charges remaining in the capacitors can be prevented.

  When the counting of the standby time is completed, the determination circuit 86 initializes the quadrant signal Q and the transition signal Z stored in the memory 81 and the output value of the arithmetic circuit 83 and starts counting a predetermined non-detection time. If the output of the threshold circuit 84 becomes H level again until the count of the non-detection time is completed, the determination circuit 86 outputs a detection signal to the alarm drive circuit 11 and the presence of the moving object O Is appropriately notified by an alarm. On the other hand, if the output of the threshold circuit 84 does not become H level before the count of the non-detection time is completed, a detection signal is not output from the determination circuit 86 to the alarm drive circuit 11, and the determination is made. The circuit 86 resets the detection flag stored in the memory 81 to 0, and then instructs the frequency switching circuit 85 to switch from the second frequency f2 to the first frequency f1. However, the detection flag of the memory 81 may be simply reset to 0 instead of instructing the frequency switching circuit 85 to perform switching. That is, since the direction in which the frequency is switched may be any direction, the reference frequency may be changed from the first frequency f1 to the second frequency f2, and processing may be performed starting from the second frequency f2 and switching to the first frequency f1. .

  Thus, if the object is a real moving object (for example, a person moving in the monitoring space), all frequencies (the first frequency f1 and the second frequency f2) even if the frequency of the transmission signal (ultrasound) is switched. In FIG. 10, the quadrant signal Q is sequentially transferred between adjacent quadrants to be detected as a moving object, and similarly to the configuration shown in FIG. 10, an object that is erroneously detected as a moving object although it does not move, for example, vibrates. If it is an object (such as a window glass of an automobile), it will not be detected erroneously. Furthermore, when a large energy wave (sound wave with a very high sound pressure level) arrives from outside the monitoring space, a transmitted signal (ultrasonic wave) For example, the quadrant signal Q is shifted between the quadrants where the quadrant signal Q is not adjacent (the first quadrant and the third quadrant or the second quadrant and the fourth quadrant). for No longer detected as an animal body.

  As described above, in the present embodiment, when a moving object is detected by outputting the transmission signal of the first frequency f1 from the oscillation circuit 1 to the transmitter 3, the transmission signal of the second frequency f2 different from the first frequency f1 is detected. Is output from the oscillation circuit 1 to the transmitter 3 and a moving object is detected also for the transmission signal of the second frequency f2, in other words, the transmission signals of all frequencies (the first frequency f1 and the second frequency f2). Since a detection signal is output from the detection circuit 8 only when a moving object is detected, erroneous detection of the moving object can be prevented. The above-described non-detection time is determined according to the minimum value of the moving speed of the moving object to be detected. That is, as described above, when a moving object is detected by transmitting an ultrasonic wave of the first frequency f1, if the candidate is a real moving object, the moving object is again detected before the non-detection time elapses. Since it is considered that the object is detected, if no moving object is detected again before the non-detection time elapses, detection of the moving object with respect to the ultrasonic transmission of the first frequency f1 is ignored, and detection processing in the detection circuit 8 Is initialized and a new detection process is started.

Here, the wave transmitter 3, as shown in FIG. 3 has the output characteristics of the mountain-type energy (sound pressure) becomes the maximum (W _MAX) at the center frequency f _S, for example, the center frequency f _S A higher predetermined frequency is the first frequency f1, and a lower predetermined frequency than the center frequency f _S is the second frequency f2. Thus, if the first frequency f1 and the second frequency f2 are distributed to a frequency higher and lower than the center frequency f _S in the output characteristics of the transmitter 3, the energy (sound pressure) of each frequency f1, f2 is distributed. Variations in the distance at which a moving object can be detected due to the size can be suppressed. At this time, in order to further suppress variation in the detectable distance, energy (sound pressure) of the same degree as the first frequency f1 and the second frequency f2, for example, −3 dB with respect to the maximum value W _{MAX at the} center frequency f _S It is desirable to select a frequency that is within the range. In this embodiment, the number of frequencies to be switched is two types (first frequency f1 and second frequency f2). However, three or more types of frequencies may be switched, and four or more types and even types of frequencies may be switched. When switching between, it is desirable to select the same number from a frequency band higher than the center frequency f _S and a frequency band lower than the center frequency f _S.

(Embodiment 2)
FIG. 4 shows a block diagram of the present embodiment. However, components that are functionally common to the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate.

The transmitter 3 is driven by the transmission signal output from the oscillation circuit 1, and an ultrasonic wave having the same frequency as the oscillation frequency (the first frequency f1 or the second frequency f2) of the oscillation circuit 1 is transmitted to the monitoring space for monitoring. The reflected wave generated by the reflection of the ultrasonic wave on the object O existing in the space is received by the 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 A and 6 B, respectively, so as to be the same as the oscillation frequency of the oscillation circuit 1. Mixing (mixing) with the frequency reference signals E ₀ and E ₀ ′. Here, one reference signal E ₀ is an output of the phase shift circuit 10 and is set so that the phases of both reference signals E ₀ and E ₀ ′ 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. Then, the pair of Doppler signals E and E ′ are amplified by the amplification circuits 13A and 13B, respectively, and then taken into the detection circuit 8.

In the detection circuit 8, a pair of Doppler signals E and E 'are sampled and quantized by the sampling circuit 87 at a predetermined sampling period, and converted from an analog value to a digital value. Further, the converted digital value is converted into a nonvolatile memory. 81 are sequentially stored. Here, a digital value (digital data) obtained by converting one Doppler signal E by the sampling circuit 87 is X _n , and a digital value (digital data) obtained by converting the other Doppler signal E ′ by the sampling circuit 87 is Y _n (n is A vector R _n is defined which starts at the origin of the two-dimensional orthogonal coordinate system and ends at (X _n , Y _n ). Note that the magnitude of the vector R _n corresponds to the amplitudes of the Doppler signals E and E ′.

An angle formed by the vector R _{n −1} obtained by the previous sampling and stored in the memory 81 and the vector R _n obtained by the current sampling (this angle is referred to as a vector rotation angle) φ _n is detected. Calculation is performed by the vector rotation angle calculation circuit 88 of the circuit 8 (see FIG. 5). The vector rotation angle calculation circuit 88 calculates the rotation angle φ _n by the following equation.

φ _n = arctan {(X _n-1 Y _n -Y _n-1 X _n ) / (X _n-1 X _n -Y _n-1 Y _n )}
Therefore, when the object O approaches, the vector R _n rotates counterclockwise, so the polarity of the rotation angle φ _n becomes positive. When the object O moves away, the vector R _n rotates clockwise, so that the rotation angle φ _n Polarity is negative. Then, if the rotation angle φ _n obtained by the vector rotation angle calculation circuit 88 is integrated by the rotation angle integration circuit 89, the integrated value (= φ ₁ + φ ₂ +... + Φ _n +...) Is proportional to the moving distance of the object O. Will do. Further, the integrated value integrated by the rotation angle integrating circuit 89 is compared with a predetermined threshold value by the threshold circuit 84, and when the integrated value exceeds the threshold value, the output of the threshold circuit 84 changes from L level to H level. The output of the threshold circuit 84 (H and L binary signals) is taken into the determination circuit 86.

Here, when a reflected wave subjected to phase modulation is received by the receiver 4, noise components due to phase modulation are included in the amplitude level values X _n and Y _n obtained by sampling the Doppler signals E and E ′. As a result, a large difference occurs between the two, and as a result, the locus of the vector R _n moves on the ellipse as shown by the one-dot dashed line B or the two-dot broken line C in FIG. There is a risk that. Therefore, in the present embodiment, when the amplitude level values X _n and Y _n of the pair of Doppler signals E and E ′ are compared and the difference between the amplitude level values X _n and Y _n exceeds a predetermined value. Since the locus of the vector R _n is moving on the ellipse as described above, it is regarded as not a reflected wave by the moving object O, and the rotation angle φ _n corresponding to the Doppler signals E and E ′ is zero. Alternatively, by providing an amplitude level determination unit that sets a predetermined minimum value, erroneous detection of a reflected wave from an object other than a moving object, for example, a vibrating object (such as a window glass) is prevented.

In the present embodiment, an amplitude level determination unit is configured by the amplitude calculation circuit 800 and the amplitude determination circuit 801 provided in the detection circuit 8. In the amplitude calculation circuit 800, the effective values of the amplitude level values X _n and Y _n obtained by sampling the pair of Doppler signals E and E ′ by the sampling circuit 85 are calculated and output to the amplitude determination circuit 801. The amplitude determination circuit 801 obtains a ratio (amplitude ratio) between the effective values of the amplitude level values X _n and Y _n and sets the ratio to an upper limit value sufficiently larger than 1 and sufficiently smaller than 1. compared with the lower limit value, larger than and the lower limit value smaller than the upper limit value, permits the calculation of the rotation angle phi _n to the vector rotation angle calculation circuit 88, if less than the upper limit or lower limit, the rotation The vector rotation angle calculation circuit 88 is instructed to set the value of the angle φ _n to zero or a predetermined minimum value.

That is, when the ratio of the effective values of the amplitude level values X _n and Y _n is equal to or higher than the upper limit value or lower than the lower limit value, noise components due to phase modulation are superimposed on the amplitude level values X _n and Y _n . Assuming that the rotation angle φ _n calculated from the amplitude level values X _n and Y _{n is set} to zero or the minimum value, the influence of noise on the integrated value of the rotation angle φ _n is reduced, and erroneous detection of an object is prevented. be able to.

  When the output of the threshold circuit 84 changes to H level, the determination circuit 86 instructs the frequency switching circuit 85 to switch from the first frequency f1 to the second frequency f2, and the frequency switching circuit 85 is the same as in the first embodiment. When the threshold value circuit 84 outputs a comparison result that the integrated value integrated by the rotation angle integrating circuit 89 exceeds the threshold value at all frequencies (the first frequency f1 and the second frequency f2) that are switched and set at Only the detection signal is sent to the alarm drive circuit 11. 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. Since the operation of the determination circuit 86 is the same as that of the first embodiment, a detailed description is omitted.

Here, in the conventional example and the first embodiment, the moving object is detected by the number of quadrant transitions. Therefore, when the object moves only to the extent that the vector corresponding to the received signal Ein remains within the same quadrant, the object is moved. It cannot be detected. On the other hand, in the present embodiment, in the two-dimensional Cartesian coordinate system, the vector R _n having the origin as the starting point and the amplitude level values X _n and Y _n of the pair of Doppler signals E and E ′ as the ending point increases with time. Since the rotation angle φ _n is calculated by integrating the rotation angle φ _{n and} the integrated value of the rotation angle φ _n is compared with a predetermined threshold value by the threshold circuit 84, as in the conventional example and the first embodiment. Changes in the Doppler signals E and E ′ can be examined in detail including information that is lost when the pair of Doppler signals E and E ′ is binarized. As a result, it is possible to detect an object that moves only a little, such as an object that does not move in the same quadrant as in the conventional example and the first embodiment.

Further, when the moving object O is detected in this embodiment, ideally, the locus of the vector R _n moves on the circumference centered at the origin as shown by the solid line A in FIG. Is phase-modulated, the amplitude level values X _n and Y _n obtained by sampling the Doppler signals E and E ′ are superposed with noise due to phase modulation, resulting in a large difference between them. As a result, the locus of the vector R _n moves on the ellipse as shown by the one-dot dashed line B or the two-dot broken line C in FIG. However, as described above, when the ratio of the effective values of the amplitude level values X _n and Y _n is equal to or higher than the upper limit value or lower than the lower limit value, the amplitude level values X _n and Y _n contain noise due to phase modulation. Since the rotation angle φ _n calculated from the amplitude level values X _n and Y _n is set to zero or the minimum value, the influence of noise on the integrated value of the rotation angle φ _n is reduced to reduce the influence of the object. False detection can be prevented.

Furthermore, when a large energy wave (sound with a very high sound pressure level) arrives from outside the monitoring space, the frequency of the transmission signal (ultrasound) is switched to change the distribution of the ultrasound in the monitoring space. , for example, even if the locus of the vector R _n is the first frequency f1 has moved on a circle as shown by the solid line b in FIG. 6, for the second frequency f2 is the locus of the vector R _n As shown by the solid line B in FIG. 6, the movement changes on the ellipse, and as a result, it is not detected as a moving object.

  In both the first and second embodiments, it is possible to determine the moving direction of the object (the direction toward or away from the transmitter 3 and the receiver 4), so the first frequency f1. In addition, the moving object may be detected for the transmission signal of the second frequency f2, and the detection signal may be output from the determination circuit 86 only when the moving directions of the respective moving objects coincide. For example, since it is not desirable to detect a swinging object such as a pendulum as a moving object, such as amulets and accessories suspended in the passenger compartment, as described above, “the moving directions of the respective moving objects match”. If a condition is added, it is possible to prevent erroneous detection of a moving object as described above as a moving object.

1 is a block diagram illustrating a first embodiment. It is a flowchart for operation | movement description same as the above. It is an output characteristic figure of a transmitter in the same as the above. FIG. 6 is a block diagram illustrating a second embodiment. It is operation | movement explanatory drawing same as the above. It is operation | movement explanatory drawing 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 operation | movement explanatory drawing same as the above. It is a block diagram which shows another prior art example. 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oscillator 3 Transmitter 4 Receiver 5 Receiver 6A, 6B Phase detection circuit 8 Detection circuit 84 Threshold circuit 85 Frequency switching circuit 86 Determination circuit

Claims (7)

Oscillation means having a variable oscillation frequency, transmission means for transmitting a continuous energy wave whose amplitude periodically changes by a transmission signal output from the oscillation means to the monitoring space, and the continuous energy wave is present in the monitoring space The receiving means for receiving the reflected wave that is reflected by the object to be transmitted, and the reference signal having the same frequency as the transmitted signal and the phase of the received signal are mixed to correspond to the phase difference from the reference signal. Phase detection means for obtaining a pair of Doppler signals having amplitude and different phases, and detection means for processing the pair of Doppler signals to detect a moving object in the monitoring space and outputting a detection signal ,
The detection means outputs a transmission signal having one or more types of frequencies different from the fundamental frequency from the oscillation means when the moving means is detected by outputting the transmission signal of the fundamental frequency from the oscillation means to the transmission means. And a detection signal is output only when a moving object is detected for all the transmission signals of the one or more types of frequencies. The wave transmitting means has a mountain-shaped output characteristic having a peak at the center frequency where the energy of the continuous energy wave is maximum,
2. The moving object detection apparatus according to claim 1, wherein the detection means is configured to assign the fundamental frequency and the one or more types of frequencies to a frequency higher and lower than the center frequency.   3. The detection means according to claim 2, wherein the fundamental frequency and the one or more types of frequencies are set to frequencies at which the energies of continuous energy waves transmitted from the transmission means are substantially the same. Moving object detection device.   4. The detection unit according to claim 1, wherein the detection unit does not detect a moving object until a predetermined standby time has elapsed from a time point when the frequency of the transmission signal output from the oscillation unit is switched. The moving object detection apparatus described in 1.   The detection means is characterized in that the waiting time is set to a time that is not shorter than the maximum value of the time required for the continuous energy wave transmitted from the wave transmission means to reciprocate in the monitoring space. 5. A moving object detection device according to 4.   The detection means outputs a detection signal when the moving direction of the moving object detected at the fundamental frequency matches the moving direction of the moving object detected at one or more types of frequencies. The moving object detection device according to any one of 1 to 5.   7. The detection unit according to claim 1, wherein if a moving object is not detected at one or more types of frequencies, the detection unit initializes the detection process of the moving object when a predetermined non-detection time has elapsed. The moving object detection device according to claim 1.

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