JPS5916231B2 - Inter-vehicle distance measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inter-vehicle distance measuring method, and particularly to a fail-safe method thereof.

The vehicle is equipped with a transmitter and receiver that transmits and receives ultrasonic waves,
It is known that when an ultrasonic wave transmitted from the other vehicle is received, the ultrasonic signal is sent back to the other vehicle, and the inter-vehicle distance is measured based on this transmission/reception cycle.

This method is called the transmitter-receiver time difference measurement method.

On the other hand, it is also well known to measure the inter-vehicle distance by projecting ultrasonic waves toward the other vehicle and measuring the time until the reflected waves are obtained.

This method is called a reflective time difference measurement method.

Since ultrasonic waves have a weaker attenuation than media such as light and radio waves, the measurement range in the reflective time difference measurement method is about 25 meters.

On the other hand, the transmitting/receiving time difference measurement method transmits ultrasonic waves to the other vehicle by receiving the ultrasonic waves, so the measurement range can be expanded to about twice as much.

Therefore, it is desirable to adopt a transmitter-receiver type time difference measurement method.
This method has the disadvantage that it is more expensive than the reflective time difference measurement method.

The present invention has been made for the purpose of providing a fail-safe function to the transmitter-receiver type time difference measuring method and thereby making effective use of the system.

To achieve this purpose, the frequencies of the ultrasonic waves transmitted from the vehicles are made approximately equal to each other for both vehicles.
The receiver can receive both ultrasonic waves transmitted from the other vehicle and the own vehicle.

Then, the pulse width of the ultrasonic signals transmitted from both vehicles is made different, and the distance between vehicles is normally measured by receiving the ultrasonic waves transmitted from the other vehicle. The distance between vehicles is measured by receiving the reflected waves of the transmitted ultrasonic signals.

Hereinafter, the present invention will be described in detail with reference to illustrated embodiments.

Two vehicles are shown in FIG. 1 as 1 and 2.

The vehicle 1 is provided with transducers 3, 4, 5, and 6.

The vehicle 2 is provided with transducers 7, 8, 9, and 10.

Normally, when the transducer 5 of the forward vehicle 1 receives an ultrasonic signal transmitted from the transducer 7 of the rear vehicle 2, the transducer 3
The ultrasonic signal is transmitted from the transmitter/receiver 9 toward the transducer 9.

The transducers 3, 7 and the transducers 5, 9 are designated by the same reference numerals in FIG.

A monostable multi-circuit, indicated as 11, is provided for transmitting ultrasound signals with a pulse width of 2T from the rear vehicle 2.

A monostable multi 12 is provided in the vehicle ahead, and this monostable multi outputs a pulse signal with a pulse width IT.

The output signal of the OR circuit 13 is added to the monostable multi-circuit 11, and when this output signal becomes HIGH, a signal with a pulse width of 2T is generated at its output terminal.

A transmit control circuit is shown as 14. Transmission control circuit 14
is composed of a pulse modulator, a power amplifier, etc., and while the output signal of the monostable multicircuit 11 is being generated, it is controlled at a frequency f.
1 signal and drives the transducer 7 via the analog gate 15.

The signal output from the transducer 7 is shown as A in FIG.

When an ultrasonic wave is transmitted from the transducer 7 at time t1 shown in FIG. 3, it is received by the transducer 5 of the vehicle ahead 1 at time t2.

Transducer/receiver 5 converts the ultrasonic signal into an electrical signal and applies it to a receiving circuit shown as 16.

The signal converted by the transducer 5 is shown as B in FIG.

The wave receiving circuit 16 is composed of a filter, a preamplifier, etc., and removes and amplifies components other than the frequency f1, and outputs the result to a pulse width determination circuit shown as 11.

The pulse width judgment circuit 17, like the pulse width judgment circuits 18 and 19, is composed of a combination of a monostable multi-circuit and a logic gate circuit, or a pulse counting circuit, and these are composed of a pulse width judgment circuit shown below. When a signal is input, a signal HIGH is output.

When the output signal of the wave receiving circuit 16 is generated at time t2 in FIG.
7 produces an output signal.

This output signal is led to a monostable multicircuit 12.

Reference numeral 20 indicates a wave transmission control circuit, which has the same configuration as 14.

The output signal of the monostable multi-circuit 12 is transmitted to this wave transmission control circuit 2.
0 and outputs a transmission signal shown as C in FIG.
The transducer 3 is driven.

Therefore, the ultrasonic signal of frequency f1 is transmitted at time t3 shown in FIG.

The ultrasonic signal transmitted from the transducer 3 at time t3 (Figure 3) is received by the transducer 9 at time t4.The ultrasonic signal is converted into an electrical signal (as shown in Figures 2-3). (denoted as D)
, to a receiving circuit shown as block 21 via an analog gate 22 and a limiter 23.

The wave receiving circuit 21 has the same configuration as the wave receiving circuit 16.

The output signal of the wave receiving circuit 21 is sent to the pulse width judgment circuit 18.19.
guided by.

Therefore, at time t5, which is a time IT after time t4, the pulse width determination circuit 18 produces an output signal.

This output signal is guided to the input terminal of the OR gate 13 via an AND gate 24, and at the holding time t5, the monostable multicircuit 11 is driven and the transducer 7 transmits ultrasonic waves again.

The period of the signal output from this monostable multi-circuit 11'
l'□5ec (the time from time t1 to time t5 shown in FIG. 3) is measured by the arithmetic processing unit 25, and the following calculation is performed to calculate the inter-vehicle distance LOm.

V: Ultrasonic velocity (m/5eC) In FIG. 2, what is shown as block 26 is an abnormality detection device.

The abnormality detection device 26 includes a disconnection detection circuit and a transducer failure detection circuit.

Since the disconnection detection circuit is well known, a detailed explanation will be omitted, but when the line 27 to the transducer 7 and the line 28 to the transducer 9 are disconnected, this is detected based on a change in resistance value, and each output signal is Set E and F (Figure 3) to LOW.

The transducer failure detection circuit detects a failure of the transducer by identifying the presence or absence of a reverberation signal generated after the transducer is driven, and sets the output signals B and F to LOW.

Shown as 29 is a switching circuit.

The switching circuit is composed of a group of logic gates.

The switching circuit 29 receives the output signals E, F from the abnormality detection device 26 and switches the analog gates 15, 22 . One of the input signals (gate signal) of the AND gate 24, the analog gates 30 and 31, and the AND gate 32 is switched ON or OFF as follows.

One of the input sides of the analog gate 30 is connected to the wave transmission control circuit 14
, and the output side is guided to the transducer 9.

One input side of the analog gate 31 is connected to the transducer 7, and the output side is connected to the input side of the microphone 23.

The other input side of the AND gate 32 is the pulse width determination circuit 1
9 output signals are added.

Therefore, if an abnormality occurs in either the transducer 7 or 9, an ultrasonic signal with a pulse width of 2'T is transmitted from the remaining transducer, and the ultrasonic signal reflected by the vehicle 1 in front is transmitted and received in the same way. The monostable multi-circuit 11 is driven by the output signal received by the pulse width detector and output from the pulse width determination circuit 19.

FIG. 3 shows a case where an abnormality occurs in the transducer T.

In this case, since the signal E is LOW and the signal F is HIGH, the ultrasonic signal is transmitted from the transducer 9 at time tll.

When the transducer 9 receives this reflected wave at time t12, the pulse width determination circuit 19 generates an output signal at time t13 after a time 2T, the monostable multi-circuit 11 is driven, and the transducer 9 outputs an output signal from the transducer 9 again. Sound waves are transmitted.

The inter-vehicle distance in this case is also determined based on observing the output signal of the monostable multi-circuit 11 and measuring the time from time ill to t12.

As described above, according to the present invention, the distance between vehicles is normally measured using the transceiver type time difference measurement method using two transducers, so it is possible to measure distances over a long distance, and even if one transducer has an abnormality. When this occurs, the remaining transducer can be used to measure the inter-vehicle distance using the reflective time difference measurement method, so although there is a problem that the measurement range is approximately %, it is still possible to measure the inter-vehicle distance.

Therefore, the system can be used effectively.

Although the monostable multicircuit and the pulse width determination circuit are configured as independent electric circuits in the above-described embodiment, this function may also be provided in the arithmetic processing device.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of installing a transducer in a vehicle, Fig. 2 is an electrical block diagram showing an embodiment of the present invention, and Fig. 3 is an explanation of the operation of the electrical block diagram shown in Fig. 2. It is a diagram. 1: Front vehicle, 2: Rear vehicle, 3', 4, 5, 6
゜7.8, 9, 10: Transducer, 15, 22, 30゜3
1: analog gate, 25: arithmetic processing unit, 26: abnormality detection device, 29: switching device.

Claims (1)

[Claims] 1. A vehicle is provided with first and second ultrasonic transducers, the first transducer transmits an ultrasonic signal with a predetermined pulse width toward the other vehicle, and the other vehicle transmits the ultrasonic signal. A second transducer receives an ultrasonic signal having a pulse width different from the ultrasonic signal that has been transmitted, and the ultrasonic signal having a predetermined pulse width is transmitted again from the first transducer. At the same time, an abnormality detection device for detecting an abnormality in the ultrasonic transducer is provided, and in response to the output signal of the abnormality detection device, a predetermined pulse is output from the remaining transducer among the first and second transducers. An inter-vehicle distance measuring method characterized in that the ultrasonic signal having a predetermined pulse width is transmitted toward the other vehicle, and the ultrasonic signal having a predetermined pulse width reflected by the other vehicle is received by the remaining transducer. . 2. The inter-vehicle distance measuring method according to claim 1, wherein the first and second transducers and the wave transmission control circuit/wave reception circuit are connected by an analog gate.