JPS594673B2 - Inter-vehicle distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inter-vehicle distance measuring device using ultrasonic waves.

There are two methods for measuring inter-vehicle distance using ultrasonic waves: a transceiver time difference measurement method and a reflection time difference measurement method.

Since the reflection type time difference measurement method may not be able to identify whether the received wave is reflected from a vehicle or an obstacle, the transmission/reception time difference measurement method is used to accurately measure the inter-vehicle distance.

However, since the transmitter-receiver time difference measurement method cannot detect obstacles, it is particularly difficult to apply to unmanned vehicles.

Therefore, an object of the present invention is to provide an inter-vehicle distance measuring device suitable for application to unmanned vehicles.

FIG. 1 shows a conventional example using a transmitting/receiving time difference measuring method, and FIG. 2 shows a conventional example using a reflective time difference measuring method.

In Figure 1, the vehicle in front is designated as 1, and the vehicle in the rear is designated as 2.
It will be shown shortly.

A wave transmitter 3 and a wave receiver 4 are installed on the front side of the rear vehicle 2, and a wave transmitter 5 and a wave receiver 6 are installed on the rear side of the front vehicle.

The wave receiver 6 is installed facing the wave transmitter 3, and the wave receiver 4 is installed facing the wave transmitter 5.

Ultrasonic waves of frequency f1 are transmitted from the transmitter 3 of this rear vehicle.

When the receiver 6 of the vehicle ahead receives this, the transmitter 5 immediately sends back the ultrasonic wave of frequency f2.

When the rear vehicle also receives the ultrasonic wave with frequency f2 at the receiver 4, it immediately transmits the next ultrasonic wave (frequency fl).

In other words, the transmit-receive time difference measurement method constantly sends ultrasonic waves back and forth between the vehicle in front and the vehicle behind, measures the time from one ultrasound transmission to the next transmission, and converts the measurement into the inter-vehicle distance.

In FIG. 2, a wave transmitter 8 and a wave receiver 9 are installed in front of the vehicle 7.

The transmitter 8 emits ultrasonic waves, and the receiver 9 receives reflected waves from the vehicle 10 in front.

The flight time is measured and the distance between vehicles is calculated.

The transmitting/receiving time difference measurement method shown in Figure 1 has the advantage of being able to expand the measurement range up to twice as much as the reflection time difference measurement method, as well as being able to distinguish received signals from reflected signals from other objects. Since it is possible to receive only the transmission signal from the other vehicle, an accurate inter-vehicle distance can be calculated.

However, on the other hand, it cannot detect obstacles.

The reflective time difference measurement method shown in FIG. 2 cannot distinguish between reflected waves from a vehicle and reflected waves from other objects.

3 and 4 show electrical block diagrams in which the present invention is implemented.

In FIG. 3, a receiver 13 is installed in front of the vehicle 11 to receive ultrasonic waves of frequency f2 emitted from the vehicle 12.

The receiver 13 is shown with the same reference numerals in FIG.

The wave receiving amplification circuit 14 is for amplifying the weak signal obtained by the wave receiver 11.

The output of the wave receiving amplification circuit 14 is input to a PLL circuit shown as a block 15.

The PLL circuit 15 combines a filter and a DC amplification function, and converts the ultrasonic pulse into a DC pulse by excluding frequency components other than f1.

The output signal of the PLL circuit 15 is input to a differentiating circuit 16.

The signal obtained at the output of the differentiating circuit 16 is input to an automatic synchronization circuit indicated as 17.

When the automatic synchronization circuit 17 receives this differential signal, it drives the monomulti circuit 18.

As a result, an output signal is generated from the monomulti circuit 18 for a certain period of time, and this output signal is input to the pulse modulation circuit 19.

This pulse modulation circuit modulates the output signal of the monomulti circuit 18 at the frequency f1.

The output signal of the pulse modulation circuit 19 is amplified by a wave transmitting amplifier circuit 20 and drives a wave transmitter 21.

In this way, ultrasonic waves of frequency f1 are transmitted from the transmitter 21 provided in front of the vehicle 11 shown in FIG.

In FIG. 5, the ultrasonic wave emitted from the transmitter 21 is shown as 22, and the wave received by the receiver 13 is shown as 23.

The wave received by the receiver 24 installed at the rear of the vehicle 12 is shown as 25 in FIG. 5, and the ultrasonic wave emitted from the transmitter 26 is shown as 27.

As mentioned above, the output signal of the monomulti circuit 18 is generated after receiving the received wave shown as 23 in FIG.
This is input to the calculation circuit 28.

The calculation circuit 28 calculates the interval T between the output signals of the monomulti circuit 18.
(sec), and the inter-vehicle distance between the vehicle 11 and the vehicle 12 is calculated as being equal to or greater than the vehicle distance.

Note that the block designated as 29 is a reference pulse generation circuit, and is equipped with a timer.
A pulse is generated every time IJ seconds are counted.

The circuit is configured to receive the output signal of the monomulti circuit 18 and reset the timer when this output signal is generated.

When the wave receiver 13 does not receive the wave, the output signal of the reference pulse generation circuit 29 is applied to the automatic synchronization circuit 17, and the ultrasonic wave is transmitted from the wave transmitter 21 every 350 m.

In other words, the output of the automatic periodic circuit 17 is used when there is no vehicle ahead within a certain distance.

Receiver 24 and transmitter 2, shown as 30 in FIG.
The control device for controlling 6 has the same structure as that shown in FIG. 4 except for this automatic periodic circuit.

Now, in this invention, another receiver 31 is installed in front of the rear vehicle 11.

This receiver 31 receives the frequency f transmitted from the transmitter 21.
It receives ultrasonic waves of 1.

The received signal of the wave receiver 31 is amplified by a wave receiving amplification circuit 32 (having the same configuration as the wave receiving amplification circuit 14 ) shown as 32 and inputted to a PLL circuit 33 .

This PLL circuit 33 removes and amplifies frequency components other than f1, and outputs the amplified signals to a differentiating circuit shown as a block 34.

The output of the differentiating circuit 34 is input to an arithmetic circuit shown as a block 35.

The arithmetic circuit 35 receives the output of the monomulti circuit 18 as well as data indicating the inter-vehicle distance calculated by the calculation circuit 28 .

The received wave obtained by the wave receiver 31 is shown as 36 in FIG.

This calculation circuit 35 compares data based on the time from when the output of the monomulti circuit 18 is generated until the output of the differentiation circuit 34 is obtained with the inter-vehicle distance data calculated by the calculation circuit 28. Whether the reflected wave obtained by the receiver 31 is from the vehicle 12 in front or from the vehicle 12 in front
Determine if the source is from an obstacle between the

That is, the reflected wave obtained by the receiver 31 is transmitted to the transmitter 21.
Since the ultrasonic wave passed through the triangular ridgeline connecting → the inverter surface → the receiver 31, the arithmetic circuit 35 first obtained the received wave 36 from the point at which the output signal of the monomultiplier 18 was generated. Based on the time T1 until then, a correction value AT1, which is expressed as the vertical distance between the reflector surface and the vehicle, is calculated.

Next, this correction value AT1 and the inter-vehicle distance data given from the calculation circuit 28 (hereinafter referred to as "correction value AT1").

). The result of this comparison is:

is significantly larger than ATl, it is determined that the reflected wave is not from the end face of the vehicle 12 ahead, and it is detected that there is a reflector, that is, an obstacle between the vehicle 12 and the vehicle 12 ahead. .

As described above, according to the present invention, there is an effect that an obstacle existing in front of the vehicle can be identified as the vehicle ahead.

Therefore, it is possible to achieve the objective of applying the inter-vehicle distance based on the transmission/reception type time difference measurement method to the driving control of an unmanned vehicle.

In the above embodiment, the presence of an obstacle is detected by calculating the flight time of the reflected wave and the inter-vehicle distance. However, the signal received by the receiver 31 is delayed by a predetermined time. The presence of an obstacle may be detected based on a time difference between the received signal and the signal received by the receiver 13.

[Brief explanation of the drawing]

Fig. 1 is a drawing showing a conventional example of inter-vehicle distance measuring using a transmitting and receiving time difference measuring method, Fig. 2 is a drawing showing a conventional example of an inter-vehicle distance measuring device using a reflective time difference measuring method, and Fig. 3 is a drawing showing a conventional example of an inter-vehicle distance measuring device using a transceiver type time difference measuring method. FIG. 4 is an electrical block diagram showing an embodiment of the present invention, and FIG. 5 is an explanatory diagram of the operation of the electrical block diagram shown in FIG. 4. 11...Rear car, 12...Front car, 2
1.26...Transmitter, 13,24...
Receiver, 31... Receiver, 28... Calculation circuit, 36... Arithmetic circuit.

Claims (1)

[Scope of Claims] 1. The transmitter of the rear car and the receiver of the car in front are installed so as to face each other, and the transmitter of the car in front and the receiver of the car behind are installed so as to face each other. , in response to the receiver of the forward vehicle receiving the ultrasonic wave transmitted from the transmitter of the rear vehicle, transmitting the ultrasonic wave from the transmitter of the forward vehicle; In response to the rear vehicle receiving the ultrasonic waves, the rear vehicle transmits the ultrasonic waves again, and the inter-vehicle distance between the front vehicle and the rear vehicle is measured based on measuring the transmission/reception cycle of the ultrasonic waves. At the same time, a receiver is installed in the rear car to receive the reflected waves of the ultrasonic waves transmitted from the rear car, and the flight time of the reflected waves is measured. Based on this measurement value and the inter-vehicle distance, An inter-vehicle distance measuring device characterized in that it detects obstacles present in the vehicle. 2. The inter-vehicle distance measuring device according to claim 1, wherein the frequency of the ultrasonic waves transmitted from the rear vehicle and the frequency of the ultrasonic waves transmitted from the vehicle ahead are different.