JPS63298599A - Ultrasonic discriminating method for car kind - Google Patents

Abstract

PURPOSE:To exactly discriminate a car kind of a vehicle running at a high speed by using two ultrasonic handsets whose resonance points are different, driving alternately each ultrasonic handset by two frequencies, respectively, and also, shifting a phase for driving them. CONSTITUTION:A first ultrasonic handset 1 is driven alternately by a prescribed period of, for instance, 35msec by two frequencies f1, f2, avoids malfunction caused by respective double reflected waves and executes car form sampling. Also, a second ultrasonic handset 11 is driven alternately by a prescribed period of, for instance, 35msec by two frequencies f3, f4, avoids malfunction caused by the respective double reflected waves and executes car form sampling. Also, phases of driving of the two ultrasonic handsets 1, 11 are shifted by, for instance, 12msec. Accordingly, respective ultrasonic handsets 1, 11 can execute car form sampling at every 12msec. In such a way, even with respect to a vehicle running at a high speed of about 120km/h, the sampling measurement of the lowest number required for deciding a card kind can be executed, and correct car form recognition can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention receives and processes reflected waves of ultrasonic pulses emitted toward a road surface, samples the shape of a passing vehicle, and stores the measurement results. This relates to a method for determining the type of vehicle passing by by comparing it with a standard value.

Prior art and its disadvantages This type of ultrasonic vehicle type identification method is disclosed in Japanese Patent Application Laid-Open No. 57-3639.
It is described in Publication No. 8. This prior technology transmits ultrasonic pulses toward the road surface at regular intervals, sequentially measures and stores the time from transmission until the arrival of the reflected waves, calculates the vehicle height from the accumulated time data, and calculates the vehicle height. The calculated vehicle height is converted from moment to moment as the vehicle moves forward into a certain amount of standardized vehicle shape, and the standardized vehicle shape is compared with pre-stored vehicle shape data for each vehicle type. This is to determine the model of the vehicle.

However, in the above-mentioned prior art, the vehicle shape sampling period performed using the ultrasonic transceiver was set to 35 m5ec, making it difficult to identify the type of vehicle traveling at a high speed of 60 km/h or more.

In view of this point, the applicant filed the patent application No. 61-29622.
In the specification No. 3, we proposed an ultrasonic vehicle type identification device that uses a broadband ultrasonic transceiver and performs multi-frequency sampling in a transmitting/receiving separation method to shorten the sampling period to 17.5 m5ec or less.

However, the ultrasonic transceiver used in the ultrasonic vehicle type identification device is
Since the ability to recognize the shape of a car with high resolution is required, it is necessary to use a device with sharp directivity, but since it is currently difficult to obtain broadband ultrasonic transducers at low prices, It is difficult to commercialize a vehicle type identification device that uses a sonic transceiver to separate transmission and reception.

Technical Problems to be Solved In view of the above points, the present invention uses two ultrasonic transceivers, each transmitting two different frequencies (four frequencies in total), and furthermore, By shifting the phase of the drive, it is possible to shorten the sampling period at low cost and without mutual interference.
The present invention aims to provide an ultrasonic vehicle type identification method that can accurately identify the type of vehicle that travels at high speeds up to around 20 km/h.

Means for Solving Problems In order to solve the above problems, the present invention emits ultrasonic pulses from an ultrasonic transceiver toward a road surface at a constant period, until the reflected waves from the road surface or the vehicle are received by the ultrasonic transceiver. By repeating at high speed the measurement of the time required to obtain the equivalent distance to the vehicle from the measured value, the external shape of the passing vehicle is sampled, and the measured value is compared with the stored standard value. In the ultrasonic classification method for determining the vehicle type, first, two ultrasonic transceivers are used, and one resonance point
The ultrasonic transceiver with the resonance point F2 has two frequencies f1 and f2, and the other ultrasonic transceiver with the resonance point F2 has the other two frequencies f1 and f2.
4, and secondly, by shifting the driving phase of the two ultrasonic transceivers, the shape of the passing vehicle can be continuously sampled and measured at four frequencies.

The first ultrasonic transceiver has two frequencies of f and f2, for example 3
Car shape sampling is performed by alternately driving at a constant cycle of 5 msec to avoid malfunctions due to double reflected waves. Further, the second ultrasonic transceiver is driven alternately at two frequencies f and f4 at a constant frequency of, for example, 35m5eC, thereby performing car-shaped sampling while avoiding malfunctions due to double reflected waves. The driving phases of the two ultrasonic transceivers are shifted by, for example, 12 msec. This allows each ultrasonic transceiver to perform wheel-shaped sampling every 12 msec. Therefore, even for a vehicle traveling at a high speed of about 120 km/h, it is possible to perform the minimum number of sampling measurements necessary for vehicle type determination, and accurate vehicle shape recognition is possible.

Examples of this invention Next, one embodiment of the present invention will be described.

As shown in FIG. 1, the ultrasonic vehicle type identification device using the method of this invention includes two ultrasonic transceivers 1 and 10 with different resonance points, Fl and F2, and for each ultrasonic transceiver, Drive systems 3 and 5.1 that drive alternately at two different frequencies (f , f , f 1 2 3, f 4) and shift both ultrasonic transceiver drives by a predetermined phase.
3.14, and malfunction prevention systems 3 to 9.11 to 18 for eliminating malfunctions due to multifrequency multiple reflected wave reception outputs.

The reason why two ultrasonic transceivers with different resonance points are used, each ultrasonic transceiver is driven alternately at two frequencies, and the driving phases are shifted is as follows.

That is, as shown in Fig. 2, the vehicle shape sampling period by ultrasonic waves is Ts (msec), and the speed of the passing vehicle is V.
(km/h), the vehicle length is L〈m), the sensing area of the vehicle sensor is La (m), and the number of samplings is N (pieces), then Ts = (L + La) / (N-V) - ■On the other hand In order to recognize the correct vehicle shape, the number N of vehicles sampled must be at least 8 in order to reliably identify various vehicle shapes.

Now, assuming that the vehicle length of a regular passenger car traveling at 120 km/h is 4 (m) and the sensing area La is 0.8 (m), and substituting it into the above equation 0, Ts = 18 (msec).
・・・・・・・・・・・・・・・■.

That is, in order to obtain eight samples of a regular passenger car traveling at a speed of 120 km/h and accurately determine the type of vehicle as a regular passenger car, the vehicle shape sampling period Ts must be 18 m5ec.

As mentioned above, by using two ultrasonic transceivers with different resonance points, driving each ultrasonic transceiver alternately at two frequencies, and shifting the driving phases, it is possible to generate such a short-cycle vehicle. This makes shape sampling possible.

The two systems 3 to 9 and 11 to 18 connected to the first ultrasonic transceiver 1 and the second ultrasonic transceiver 10 are completely different, except that the driving frequency of each ultrasonic transceiver is different. Since they have the same configuration, only the system corresponding to one ultrasonic transceiver 1 will be explained.

The resonance point F1 of the ultrasonic transceiver 1 is 22.4 kHz. The ultrasonic transceiver 1 receives a transmission command signal from a control device 19 configured as a microbussor at a timing of period T (-36 m5ec as an example), as shown in FIGS. 3(a) and 3(b). 2 of fl and f2 through the transmission drive circuit 5 and the transmission/reception separation diode 3 which are supplied with af and af2.
Frequency (-as an example, f, = 21°4, kHz, f2
= 23-4 kHz) for a certain period of time Ts (for example, 5
ms e c ).

Ultrasonic waves received from the ultrasonic transceiver 1 are amplified to a required level by a receiving amplifier 4 and then input to a mixer 5.

This mixer mixes and receives the received waves from the receiving amplifier 4 at a local oscillation frequency fo1 (eg, 16°4 kHz). Reception output is fl.

The mixer output frequency f1'' when f2.

f2'' are 5 kHz and 7 kHz, respectively.

The output of the mixer is the output of each subsequent stage fl''.

The signal is output to two bandpass filters 6.7 whose center frequency is f2''.

A comparator 8.9 is connected to each of the bandpass filters 6 and 7, and each comparator compares the output of the bandpass filter with a standard value, and when the output of the filter is above a predetermined level, controls a signal to that effect. Output to the device 10.

The control device 10 controls the output of each comparator as shown in FIG.
As shown in ~(f), the reception gate timings of Gf1 to Gf4 are set, respectively.

In this way, from the mixer 5, at the reception gate timing Gf1 when fl is emitted, the output ff'' (5kHz) when the first reflected wave from the vehicle is received,
Output sf when receiving the second reflected wave in the previous cycle
2" (7kHz) is output. Also, at reception gate timing Gf2 when f2 is emitted, ff2" (7kHz) when the first reflected wave from the vehicle is received.
and sf when receiving the second reflected wave in the previous cycle
” (5kHz) is output.

The bandpass filter 6.7 makes only the first reflected wave ff1'' valid during the period in which fl is emitted from the ultrasonic transceiver 1 of the mixer 5, and rejects the second reflected wave sf of other frequencies.
Similarly, in the period in which f2 is emitted from the ultrasonic transceiver 1, only the first reflected wave ff2 is effective, and the second reflected wave s f 1'' of the other frequency is to separate the mixer outputs.

When one ultrasonic transceiver is used to drive at two frequencies, the mixer output includes, for example, the second reflected wave Sf2'' of f2 in the period in which fl is emitted, as shown in Figure 3. , f
2 is emitted, the second reflected wave sft'' of f is present.

When driving at two frequencies using one ultrasonic transceiver in this way, the received output of the second reflected wave of the other frequency is mixed in the mixer output, so it is necessary to separate this well with the bandpass filter 6.7. There is a need to.

To explain this in detail, although double reflected waves coexist and malfunction occurs, this occurs only when a vehicle with a vehicle height of less than 1.5 m arrives under the ultrasonic transceiver. The reason for this is that, as shown in FIG. 3 (c), there is a time period of Td = 47 msec before the reception gate Gf of the next cycle starts, and from then on, only the mixed double reflected waves can be received.
This is because it does not affect malfunction.

Focusing on this point, the bandpass filters 6.7 have 5kHz and 7kHz frequencies, respectively, as shown in FIGS. 4(a) and 4(b).
A device with normal characteristics such as a maximum output of 20 dB at kHz is used, and the output level is attenuated when the second reflected wave is received.

As a result, for example, as shown in FIG.
The level of is -10th of the level of the first reflected wave Aff3.
This is much lower than the level of the reflected wave Bff3 from a 200 mm diameter vinyl chloride ball 5 meters in front. Therefore, as shown in Fig. 6, if the level of the reflected wave Bff3 from the vinyl chloride ball 5 m ahead is set to 20 V with a margin of 20 dB and the sensing threshold level is set to 2■, then the level of the second reflected wave from the vehicle is becomes 4■ and malfunctions.

However, in this invention, the bandpass filter 6.7 attenuates the mixer output level so that, for example, 4■ becomes 0.4V, so if the received output of the second reflected wave is passed through the bandpass filter, the second reflected wave can be removed. Therefore,
Even when one ultrasonic transceiver 1 is used and driven at two frequencies, even if the second reflected wave of another frequency is mixed in the mixer output, it can be well separated and removed by the bandpass filter 6.7. can do.

A bandpass filter with the above characteristics can be easily realized using an LC filter.

Furthermore, as shown in Fig. 2 (a), the transmission time Ts is set to 5 m.
When transmitting as 5ec, mixer output 5k) Iz
(period: 0.2 m5 ec), a wave number of 25 waves is obtained.

The other one! The sound wave transceiver 11 has a resonance point F2 of 27.4k.
Hz, f3=26, 4 kHz, and f4
It is driven alternately by two frequencies of =28.4kHz. Also,
The local oscillation frequency of the mixer 14 is 21.4 kHz, and the mixer output frequency f3'' is 5k when the reflected wave is received when the ultrasonic wave of 'f3 is emitted. In this case, the mixer output level f4'' is 7kHz. These are separated by bandpass filters 16.17. As shown in FIG. 3, each comparator 18.
The control device 10 also controls the output from the third
As shown in the figure, the reception gate timings of Gf and Gf4 are set respectively.

As mentioned above, the ultrasonic waves emitted from the first ultrasonic transceiver 1 and the second ultrasonic transceiver 11 have a frequency difference of at least 3 kHz or more, so mutual interference is unlikely to occur. do not have.

The first ultrasonic transceiver transmits 3
By driving alternately at a constant cycle of 5 m5 ec, vehicle-shaped sampling is performed while avoiding malfunctions due to double reflected waves.
By driving alternately at a constant cycle of 35 m5ec using two frequencies, vehicle shape sampling is performed while avoiding malfunctions due to double reflected waves.
By shifting the output timing of the transmission command signal to the system, the driving of the first ultrasonic transceiver 1 and the driving of the second ultrasonic transceiver 10 can be performed for 12 m as illustrated in FIG.
It is performed with a shift of sec. This changes the car shape to 12
Sampling can be performed every msec, and even for an ordinary passenger car traveling at or around 120 km/h, at least 8 samplings can be obtained and the correct vehicle shape can be recognized.

A vehicle passing at a speed higher than 120 km/h can be presumed to belong to the type of ordinary passenger car, so if it cannot be identified even by the vehicle type discrimination method according to the present invention, it is treated as a regular passenger car. Even if you do, in fact,
It is thought that there will be no problem.

Effects of the Invention As described above, according to the present invention, two ultrasonic transceivers with different resonance points are used, each ultrasonic transceiver is alternately driven at two frequencies, and the driving phase of the two ultrasonic transceivers is alternately driven. By shifting, it is possible to sample the vehicle shape in a short period, so even vehicles traveling at high speeds of 60 km/h to around 120 km/h can obtain a sufficient number of vehicle shape samples to accurately identify the vehicle type. It became so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a device that implements the method of the present invention, FIG. 2 is an explanatory diagram of the vehicle shape sampling period for high-speed vehicles, and FIG. 3 is a diagram showing the transmission timing, reception gate, A time chart showing the temporal relationship of the mixer output, Fig. 4 is a graph explaining the necessary characteristics of the bandpass filter, Fig. 5 is a graph showing the reception level of the ultrasonic wave reflected by the reflector, and Fig. 6 is the sensing FIG. 7 is a graph explaining the required attenuation degree of the level and the second reflected wave level, and is a schematic diagram showing wheel-shaped sampling in the case of four-frequency drive.

Claims (1)

[Scope of Claims] Ultrasonic pulses are emitted from an ultrasonic transceiver toward a road surface at regular intervals, and the time required for the ultrasonic transceiver to receive reflected waves from the road surface or a vehicle is measured, and the measured value is An ultrasonic vehicle model that measures the external shape of a passing vehicle by repeatedly obtaining the equivalent distance from the vehicle at high speed, and then compares the measured value with a stored standard value to determine the vehicle type. In the determination method, (a) Two ultrasonic transceivers are used, one ultrasonic transceiver at resonance point F_1 is used at two frequencies f_1 and f_2, and the other ultrasonic transceiver at resonance point F_2 is used at f_3 and f_4. An ultrasonic vehicle model characterized by: (b) continuously sampling and measuring the shape of a passing vehicle at four frequencies by shifting the driving phase of the two ultrasonic transceivers, respectively, alternately at two frequencies; Discrimination method.