JPH01227085A - Ultrasonic type anti-carthief apparatus - Google Patents

Abstract

PURPOSE:To enable positive detection of a slight opening of a door or a window glass for a vehicle, by storing an inclination of a reflected wave in each time zone to make a judgement in comparison with a new reflected wave pattern received at a fixed interval per time zone. CONSTITUTION:A burst-like transmission signal coming from a transmitting circuit 3 as controlled with a reference signal generator 2 is sent to an ultrasonic microphone 1a for transmission to generate a burst-like ultrasonic signal. The ultrasonic wave as reflected back from a seat, window glass and the like in a car room is converted into an electrical signal with an ultrasonic microphone 1b for reception. Then, after amplified 4, the electrical signal is detected through a detection circuit 5 and a level judgement on a pulse-like waveform corresponding to a pulse-like envelope line is performed in a time sharing manner with a sampling/holding circuit 6 in terms of a time zone specified by a reference signal generator 2 and the electrical signal is converted into digital from analog. Inclination of waveforms is compared between the ultrasonic signal and a new reflected wave received at a fixed interval. The reflected wave is passed only when the inclination thereof coincide with each other. Then, the number of the reflected waves is divided by a time shared number of those of non-coincidence to calculate a ratio. When the ratio exceeds a fixed value, an alarm is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an ultrasonic vehicle theft system that uses an ultrasonic microphone to detect disturbances in reflected waves that occur when a door or window glass is slightly opened inside a vehicle. This relates to preventers.

2. Description of the Related Art Conventionally, most of this type of ultrasonic vehicle anti-theft device utilizes the Doppler effect. To briefly explain the detection principle, first, ultrasonic waves with a frequency of f0, which is a warning target, are continuously sent out inside the vehicle interior, and the ultrasonic waves reflected from the seats and window glass inside the vehicle interior are received again, and the transmitted signal and the received The signals are mixed by a heterodyne detector and the difference component between the two signal frequencies is extracted. In this case, if everything in the vehicle is stationary, there will be no Doppler effect, the frequencies of both signals will be exactly the same, the difference will be zero, and the output will be only the DC component. In a vehicle, when a door or window is opened, the frequency of the reflected ultrasonic wave changes by Δf from fo due to the Doppler effect depending on the speed of movement. Then, when the heterodyne detector extracts the difference between the image frequencies of transmission and reception, a frequency component of Δf is extracted. This component output is amplified and used as an alarm output.

The above-mentioned method that uses the Dra-Prah effect has a simple detection circuit and high sensitivity, but it must be detected while the object to be detected (opening/closing a door or window glass) is moving. When this speed is slow, it has the disadvantage of being susceptible to the effects of air fluctuations.

In view of these drawbacks of the Doppler one-way system, we developed a transmitter that emits pulsed ultrasonic waves into the vehicle interior, a receiver that receives the ultrasonic waves reflected from the vehicle interior, and a reflected wave pattern under normal conditions. A method that compares the reflected wave pattern during normal operation with the reflected wave pattern during alarm (doors and windows are open), and determines whether there is an abnormality based on the presence or absence of a difference. has been devised. To make a comparative judgment using this method, first, an ultrasonic pulse is sent out from a transmitter, the reflected wave is received, and the reception period is time-divided into many parts, and the reception level for each time period is memorized. However, a method has been devised that subtracts this memory pattern for each time period. In this case, assuming that there is no change in the interior of the vehicle, the reflected pattern is the same as the pattern stored in the memory during normal operation, so the result of subtraction will be approximately zero at any time. becomes. If a warning situation occurs, the reflected level and phase will shift, so the received level in a certain time period will change, and therefore, in that time period, a certain numerical level with a sign that is not zero will remain as the result of subtraction. When this level exceeded a set value, an alarm was output.

Problems that the invention aims to solve In such a conventional configuration, the phase shift of the reflected waves.

It is highly sensitive to changes in level, and even when only the level changes without much phase shift due to air fluctuations, it outputs a subtracted output, which can cause malfunctions.

The present invention solves these problems, and aims to provide an ultrasonic anti-theft device for a vehicle that is less affected by air fluctuations and therefore less likely to malfunction.

Means for Solving the Problem In order to solve this problem, the present invention emits pulsed ultrasonic waves at regular intervals from an ultrasonic microphone installed in a vehicle interior, receives the reflected waves, and sets the reception period. Time-divided into multiple waves, and the slope of the reflected wave in each time period is e, o,
The reflected wave pattern is stored as a reference pattern in e, and compared with new reflected wave patterns received at regular intervals for each time period.

Function: With this configuration, it is possible to reliably detect an abnormality caused by a slight opening of a door or window glass in the vehicle interior, and to reduce malfunctions caused by air fluctuations.

Embodiment FIG. 1 is a block diagram of an ultrasonic vehicle anti-theft device according to an embodiment of the present invention. In FIG. 1, 1& is a transmitting ultrasonic microphone, and 1b is a receiving ultrasonic microphone. , 2 is a reference signal generator, 3 is an oscillation circuit, 4 is an amplifier circuit, 6 is a detection circuit, 6 is a sample and hold circuit, 7 is a MU/D converter, 8 is a storage circuit, and 〇 is a microcomputer. The computer 9 performs slope determination based on level comparison after Mu/D conversion, slope comparison between each reflected wave, and control of abnormality determination.

Figure 2 shows the detected waveforms of the reflected waves in the sealed state of the vehicle interior, that is, normal state (solid line), and the open state of the doors and windows, that is, abnormal state (dotted line), and further divides the wave reception period into 30. (1, to t30). Each of these waveforms is out of phase, and this is expressed as the slope (e) of the waveform in each time period.

Comparing o and e), it is t5 out of 30 divisions.

t8. tll・t, 5・t141 t15”+6.t
47't18"19・t21・t25.t24・t25
- Inconsistent time periods occur in 18 time periods: t26, t27, t29 It50.

Figure 3 shows an example of a waveform obtained by detecting a reflected wave when the temperature inside the vehicle interior is increased and the air fluctuates in a closed state inside the vehicle interior, and the reception period is further divided into 30 (1, to ). In this way, the slope of the waveform (flD) in each time period is defined as a waveform in which only level fluctuations occur in the same phase.

0, e), the time period that does not match is '+4
．． There are only three time periods: t231 and t27.

As described above, by time-divisioning the received reflected waves into a large number of waves during the reception period and comparing the slopes of the reflected waves in each time period, it is possible to reduce the influence of air fluctuations and to detect the effects of abnormalities such as doors and window glass. It is possible to reliably detect a shift in the phase of the reflected waveform due to the state where the mirror is slightly opened. Note that this reflected waveform is actually an ultrasonic signal (approximately 4oxaz) that is emitted in a pulsed manner as shown in Figure 4 (2L), which is reflected inside the vehicle interior, and is reflected as shown in Figure 4 (b). As a result, the ultrasonic component is removed, resulting in a waveform corresponding to a pulsed envelope as shown in FIG. 4(C) and FIGS. 2 and 3.

The above operation will be explained using the block diagram shown in FIG.

First, it is desirable to use piezoelectric ceramic ultrasonic microphones as the transmitting ultrasonic microphone 1a and the receiving ultrasonic microphone 1b from the viewpoints of reliability, stability of transmission and reception, and sensitivity. Now, this transmitting ultrasonic microphone 1a is controlled by a reference signal generator 2, and a transmitting circuit 3
A burst-like transmission signal is sent from the
1 burst-like ultrasound generation). The generated ultrasonic waves are reflected by the seats, window glass, etc. inside the vehicle, and the returned ultrasonic waves are converted into electrical signals by the receiving ultrasonic microphone 1b. In this state, the received waveform is as shown in Fig. 4(b), and since the ultrasonic signal of approximately 40 KHz becomes the carrier wave, it is amplified by the amplifier circuit 4, then detected by the detection circuit 5, and the pulse A pulse-like waveform corresponding to the shaped envelope is shown in FIG. 4(C). The sample and hold circuit 6 determines the level of this in time series in a time period specified by the reference signal generator 2, and the M/D converter 7 performs M/D conversion. Furthermore, in order to determine this time-series level change as the slope of the waveform, the level is compared for each winter time period (for example, to-t,) If O, then $, t; if -t2<O, then 9
．． If t2-t3=o, then 0) Determine the slope and store it in the storage circuit 8. After that, the slope of the waveform is compared with new reflected waves received at regular intervals, and only when the slopes match is OK, other e++e, ■ →
The number of discrepancies such as 0, 94-)O is divided by the time-divided number to calculate the ratio, and when this ratio exceeds a certain value, it is determined to be abnormal and an alarm is output.

Effects of the Invention As described above, according to the present invention, a new reflected wave pattern is created in which the receiving period of the reflected wave waveform is time-divided into a large number of periods, the slope of the reflected wave in each time period is stored, and the reflected wave is received at regular intervals. By comparing and determining each time period, it is possible to reliably detect the slightest opening of a door or window glass in a vehicle, and it is a highly reliable ultrasonic method that does not malfunction due to air fluctuations in the vehicle interior. The effect of providing a vehicle anti-theft device is obtained.

[Brief explanation of the drawing]

The first page shows a block diagram of an ultrasonic vehicle anti-theft device according to an embodiment of the present invention, and the second page shows the closed state inside the vehicle, that is, the normal state, and the abnormal state when the door or window is slightly opened. Figure 3 shows the waveform of detected reflected waves from the state.
The figure shows the detected waveform of the reflected wave when air fluctuations occur in a closed vehicle interior, Figure 4 (IL) is a diagram of the transmitted waveform radiated at regular intervals, and Figure 4 (b) shows the reflected wave. A waveform diagram of the received wave is shown in FIG. 3(c), which shows a waveform corresponding to the envelope when the received reflected wave is detected and removed from the carrier wave. 11L...Transmission ultrasonic microphone, 1b...
...Receiving ultrasonic microphone, 2...Reference signal generator, 3...Oscillation circuit, 4...
Amplifier circuit, 5...Detection circuit, 6...Sample hold circuit, 7...Music/D converter, 8
...Memory circuit, 9...Microcomputer. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure tn -tn-t > 0-■-time to ~f30t
/Itbe-ni0-θtn-mut<o---e! ! :Ki φ5? Itejru Figure 3 ShiL Mugi Motion Example - Time Reading ~ t3
゜

Claims (1)

[Claims] An ultrasonic microphone installed in the vehicle interior emits pulsed ultrasonic waves at regular intervals, the reflected waves are received by the ultrasonic microphone, and the reception period is time-divided into multiple units.
By storing the slope of the reflected wave in each time period as a reference pattern in ■, 0, and ■, and comparing it with new reflected wave patterns received at regular intervals for each time period, it is possible to reduce Detects abnormalities caused by opening windows or window glass,
An ultrasonic vehicle anti-theft device configured to output a detection signal.