JPS633267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the inter-vehicle distance between two vehicles in succession.

Logistics systems are being developed in which cargo is loaded onto vehicles and the vehicles are operated unmanned to transport the cargo from station to station. In this goods transportation system, vehicle operation is centrally controlled at a center. By the way, in order to increase the efficiency of transporting goods, it is necessary to operate a large number of vehicles at the same time and to reduce the distance between the vehicles. However, if the service interval is shortened and the number of vehicles running is increased, the control device at the center will become huge, making economical operation difficult in terms of equipment and maintenance costs. Therefore,
A large number of vehicles are run as a single formation without being physically linked, and the leading vehicle of each formation is controlled by a center, while each subsequent vehicle runs independently while maintaining a constant distance from the preceding vehicle. It is conceivable to perform control to reduce the control burden at the center. Such a travel control system requires a device that accurately and continuously measures the distance between vehicles.

One of the devices for measuring the inter-vehicle distance between a preceding vehicle and a following vehicle is a device that uses ultrasonic waves. This measuring device is suitable for short-distance measurements of about 1 to several tens of meters. The ultrasonic distance measuring device is
As shown in FIG. 1, it consists of ultrasonic transmitting and receiving devices 9 and 7 mounted on each of the preceding vehicle 4 and the following vehicle (measuring vehicle) 1, and an inter-vehicle distance calculation device 8 mounted on the measuring vehicle 1. ing. The transmitting/receiving devices 7 and 9 each include transmitters 2 and 6 that transmit ultrasonic waves toward the opposing vehicle, and receivers 3 and 5 that receive the ultrasonic waves sent from the opposing vehicle. . Referring to FIG. 2, an ultrasonic wave having a frequency f1 (for example, 25 KHz) is transmitted from the transmitter 2 of the measuring vehicle 1 toward the preceding vehicle 4. When this ultrasonic wave is received by the receiver 5 of the preceding vehicle 4, the transmitting/receiving device 9 immediately transmits the signal at the frequency f2 (for example, 20K).
Hz) is transmitted from a transmitter 6 toward the measurement vehicle 1. This ultrasonic wave of frequency f2 is transmitted to the measurement vehicle 1.
When the ultrasonic wave is received by the wave receiver 3, the transmitting/receiving device 7 similarly immediately transmits the ultrasonic wave of the frequency f1. In this way, the ultrasonic waves of frequencies f1 and f2 constantly reciprocate between the vehicles 1 and 4. This method of repeatedly transmitting and receiving ultrasonic waves between the vehicles 1 and 4 that follow one another is called a sing-around method. The reason why ultrasonic waves with different frequencies f1 and f2 are used is to prevent mutual interference.

Ignoring the time delay between receiving and transmitting ultrasonic waves by the transmitting/receiving devices 7 and 9, the transmission period T of the ultrasonic waves by the transmitting and receiving device 7 of the measuring vehicle 1 is as long as the ultrasonic waves travel back and forth between the vehicles 1 and 4. equal to the time it takes to Therefore, the inter-vehicle distance D between the preceding vehicle 4 and the measurement vehicle 1 is expressed as follows using the wave transmission period T: D=T/2·v. Here, V is the speed of sound. The calculation device 8 measures the wave transmission period T and calculates the inter-vehicle distance D based on the above formula. Even when both vehicles 1 and 4 or one of the vehicles is stopped, and even when both vehicles 1 and 4 are running, the inter-vehicle distance D can be accurately measured by the above measuring device. It is done.

Even if the ultrasonic wave is not immediately transmitted from the transmitter 2 when the ultrasonic wave is received by the receiver 3 of the measurement vehicle 1, but the ultrasonic wave is transmitted by the transmitting/receiving device 7 at a fixed cycle. good. In this case, the inter-vehicle distance is calculated based on the time from when the ultrasonic wave is transmitted from the transmitter 2 until when the wave is detected by the receiver 3. However, in the single-around method,
The sing-around method is preferable because the wave transmission period in the measurement vehicle 1 changes depending on the inter-vehicle distance, and when the inter-vehicle distance becomes small, the wave transmission period becomes shorter and more distance information can be obtained.

By the way, the transducer 2 of both vehicles 1 and 4 may be damaged due to the large inter-vehicle distance between the two vehicles 1 and 4, attenuating the ultrasonic waves, or due to fluctuations in the ultrasonic waves, or because the vehicles are traveling on a curved route. 5, and 6 and 3 do not face each other, the ultrasonic waves may not be received by the receivers 3 and 5. Since the calculation device 8 starts timing operation after the ultrasonic wave is transmitted by the transmitter 2, if the wave is not detected by the receiver 3, the calculation device 8 continues the timing operation and calculates the incorrect inter-vehicle distance. Become.

This invention makes it possible to continue transmitting and receiving ultrasonic waves between vehicles in succession even if no reception is detected after a certain period of time has passed after transmitting the ultrasonic waves, and in the above-mentioned cases. An object of the present invention is to provide an inter-vehicle distance measuring device that does not output erroneous inter-vehicle distance data.

The inter-vehicle distance measuring device according to the present invention includes an ultrasonic transmitting/receiving device mounted on each of two vehicles in succession, and an inter-vehicle distance calculating device mounted on at least one vehicle. Both of the above two ultrasonic transmitting and receiving devices include an ultrasonic transmitter, an ultrasonic receiver, a wave transmission drive circuit that drives the ultrasonic transmitter to transmit pulsed ultrasonic waves,
a wave reception detection circuit that detects a signal component of a predetermined frequency from the output signal of the ultrasonic wave receiver; and a wave transmission drive circuit that transmits pulsed ultrasonic waves in response to the detection signal of the wave reception detection circuit. The first activating means is provided for activating the . Either one of the ultrasonic transmitting/receiving devices transmits a pulsed ultrasonic wave when a detection signal is not output from the wave reception detection circuit within a first fixed time after the ultrasonic wave is transmitted by the wave transmission drive circuit. A second circuit for activating the wave transmitting drive circuit so as to
It has a means of starting. The inter-vehicle distance calculation device measures the time from ultrasonic wave transmission by the wave transmission drive circuit to detection signal output by the wave reception detection circuit, and outputs a signal representing the inter-vehicle distance between two vehicles in succession. Prohibition means for stopping the operation of the inter-vehicle distance calculation circuit when the detection signal is not output from the wave reception detection circuit within a second fixed time after ultrasonic waves are transmitted by the inter-vehicle distance calculation circuit and the wave transmission drive circuit. It is equipped with

According to this invention, ultrasonic transmitting/receiving devices are mounted on two vehicles in succession, and ultrasonic waves are repeatedly transmitted and received between these devices, so that the process from ultrasonic wave transmission to reception in one vehicle is It is possible to measure the distance between vehicles based on time. If for some reason the ultrasonic wave reception is not detected during the first fixed time after the ultrasonic wave, the second activation means activates the wave transmission drive circuit, so that both vehicles The transmission and reception of ultrasonic waves between the two vehicles is not interrupted and is carried out continuously, so that inter-vehicle distance control will not become impossible. Furthermore, if no ultrasonic reception is detected during the second fixed period of time after the ultrasonic wave is transmitted, the measured inter-vehicle distance data will be cleared by the prohibition means and will not become regular data. Erroneous data will not be output, making it possible to always accurately measure the distance between vehicles.

Embodiments of the present invention will be described in detail below with reference to FIGS. 3 to 6.

Referring to FIGS. 3 and 4, in the ultrasonic transmitter/receiver 7 mounted on the measurement vehicle 1, the reference pulse generation circuit 11 operates for a certain period of time T1 (for example,
360 (ms)), and generates a reference pulse A every fixed time T1. This timer is reset by the output pulse (transmission pulse) B of the monostable multivibrator 13. As will become clear from what will be described later, if the ultrasonic wave from the preceding vehicle 4 is not detected within a certain time T1 after transmitting the ultrasonic wave from the measuring vehicle 1, the generating circuit 11 performs the measurement again. It generates a reference pulse A for transmitting ultrasonic waves from the vehicle 1. The reference pulse A is the automatic synchronization circuit 12.
The signal is sent to the monostable multivibrator 13 via the . The monostable multivibrator 13 has a pulse width T when a pulse signal is input from the synchronous circuit 12.
2 transmission pulse B is output. This pulse width T2
is the transmission width of the ultrasonic wave. The transmitted pulse B is sent to the pulse modulation circuit 14, where it is modulated by a signal of frequency f1 to become an ultrasonic signal. This ultrasonic signal is voltage amplified by the wave transmission control circuit 15 to a magnitude corresponding to the output of the voltage control circuit 18 . On the other hand, the output B of the monostable multivibrator 13 is also sent to a reset pulse circuit 17, and this circuit 17 detects its fall. The voltage control circuit 18 is
Each reset pulse output from circuit 17 generates a voltage that increases linearly with time from that point on. Except when the monostable multivibrator 13 is activated based on the reference pulse A, the period T of the transmitted pulse B is equal to the time for the ultrasonic waves to travel back and forth between the two vehicles 1 and 4, and is proportional to the inter-vehicle distance D. There is. Therefore, the final voltage of the voltage control circuit 18 immediately before being reset is proportional to the inter-vehicle distance D, and the voltage of the modulation circuit 14 is proportional to the inter-vehicle distance D.
Since the voltage of the ultrasonic signal from the transmission control circuit 15 is amplified to a magnitude proportional to the output voltage of the voltage control circuit 18, an ultrasonic signal having an amplitude proportional to the inter-vehicle distance D can be obtained. This compensates for the ultrasonic path loss that increases with the inter-vehicle distance D. The ultrasonic signal thus amplified according to the inter-vehicle distance D is amplified in current by the transmitting amplification circuit 16 and then sent to the transmitter 2, from which it is transmitted toward the preceding vehicle 4. Ultrasonic waves are transmitted.

The ultrasonic waves transmitted from the measurement vehicle 1 are transmitted to the preceding vehicle 4.
When the wave is received by the receiver 5, the transmitter/receiver 9 generates a transmit pulse E synchronized with the reception, and based on this transmit pulse E, an ultrasonic wave with a frequency f2 is transmitted from the transmitter 6. The wave is transmitted toward the measurement vehicle 1. When the ultrasonic wave from the preceding vehicle 4 is received by the receiver 3 of the measuring vehicle 1, this received signal is amplified by the amplification circuit 19, and the frequency f2 component by the band amplification circuit 20. Then, the gain adjustment circuit 21 controls the PLL circuit (phase locked) in the subsequent stage 21.
loop) 22 is adjusted to a voltage level suitable for operation. The PLL circuit 22 detects the received signal,
The output is waveform-shaped by a pulse width shaping circuit 23 and becomes a received pulse F. The rising edge of this received pulse F is detected by the next-stage differentiation and rectification circuit 24, and is sent to the monostable multivibrator 13 as a trigger pulse via the automatic synchronization circuit 12. In this way, the monostable multivibrator 13 outputs the transmission pulse B synchronized with the reception pulse F. It will be understood that the period T of the transmitted pulse B is equal to the time required for the ultrasonic waves to travel back and forth between the vehicles 1 and 4. If the received pulse F is not obtained before the above-mentioned fixed time T1 has elapsed after transmitting the ultrasonic wave, the reference pulse A is generated from the reference pulse generation circuit 11 and input to the monostable multivibrator 13. Therefore, transmission and reception of ultrasonic waves between both vehicles 1 and 4 is continuously performed without interruption.

Ultrasonic transmitting/receiving device 9 mounted on the preceding vehicle 4
except that it does not include a reference pulse generation circuit and an automatic synchronization circuit, that the modulation frequency of the pulse modulation circuit 34 is f2, and that the frequency selectively amplified by the band amplification circuit 40 is f1. , since it has the same configuration as the ultrasonic transmitter/receiver 7,
It will be easily understood that when the receiver 5 receives a thermal sound wave, the transmitter 6 transmits an ultrasonic wave synchronized with the reception.

The inter-vehicle distance calculating device 8 measures the period T of the ultrasonic wave transmitted from the transmitter 2, converts it into an inter-vehicle distance D, and displays the result, and the transmitting pulse B of the monostable multivibrator 13 is I am typing. The propagation speed of ultrasound changes depending on temperature. Arithmetic circuit 8
includes a circuit that generates clock pulses for distance calculations at a temperature-dependent frequency. In addition, when the receiving pulse F is not obtained even after a predetermined time T3 (for example, 350 ms, which corresponds to about 60 m in inter-vehicle distance) after transmitting the ultrasonic wave from the transmitter 2, the arithmetic circuit 8 It is equipped with a circuit that processes the inter-vehicle distance data at that time as missing.

Now, the oscillator 51 generates pulses of a constant frequency, and these pulses are sent to the PLL circuit 53. The temperature setting circuit 52 sets the temperature when measuring the distance between vehicles, and includes a digital switch. Even if this setting circuit 52 can set the temperature finely in 1°C increments,
It may also be set at intervals. The PLL circuit 53 is
Used as a frequency synthesizer, it is preferable to mix the frequency of the voltage controlled oscillator with the frequency of the local oscillator, beat down the mixture, and divide the frequency using a programmable counter. The base number of the programmable counter is changed by the code input sent from the temperature setting circuit 52. Therefore, from the PLL circuit 53,
A clock pulse N having a frequency corresponding to the temperature set by the setting circuit 52 is output, and this clock pulse N is output.
The pulse N is sent to the arithmetic counter circuit 53 as a pulse signal P via a timing circuit 55, as will be described later.

An example of a specific circuit of each block other than the above-mentioned three circuits 51 to 53 of the arithmetic unit 8 is shown in FIG. Referring to FIGS. 5 and 6, the arithmetic processing circuit 54 is composed of a binary counter 61 and a NOR circuit 62. Monostable multivibrator 1
The transmission pulse B of No. 3 is transmitted by these binary counters 61 and
Input to NOR circuit 62. The binary counter 61 has two outputs G and H that are alternately inverted each time the transmission pulse B is input, and one output G is a NOR
circuit 62 and timer circuit 56. The period during which this output G is at the "H" level is the measurement period. Since the NOR circuit 62 receives the transmission pulse B and the output G as input signals, the output U of the NOR circuit 62 is at the "H" level only during the period when the transmission pulse B is not present and not during the measurement period. The timer circuit 56 is connected to a monostable multivibrator circuit 63.
It is composed of an OR circuit 64. This circuit 6
The period of the metastable state of No. 3 is the above-mentioned predetermined time T3. The output G of the binary counter 61 is input to this monostable multivibrator 63, and the monostable multivibrator 63 is triggered every time the output G is inverted. After being triggered, the above predetermined time T3
If the trigger is triggered again within this period, the output J of the circuit 63 will be held at the "L" level, but will become the "H" level after the time T3 has elapsed. Output signal J of circuit 63
is sent to data latch circuit 58 as a reset signal. The OR circuit 64 includes the output U of the NOR circuit 62 and the output J of the monostable multivibrator 63.
is input. The output W of the OR circuit 64 is used as a reset signal for the arithmetic counter circuit 57. The timing circuit 55 is sent from the PLL circuit 53. AND circuit 65 and flip-flop 66 that act with the gate circuit of clock pulse N
and an AND circuit 67. AND
The circuit 67 has the other output H of the binary counter 61.
Since the and transmission pulse B are input, the AND circuit 67 outputs a pulse I synchronized with the transmission pulse B at the end of the measurement period. This pulse signal I is sent to data latch circuit 58 as a read signal and is also input to flip-flop 66 as its reset signal. The set signal of flip-flop 66 is the output J of monostable multivibrator 63. Flip-flop 66 is normally reset, and its inverted output M is input to AND circuit 65. When the flip-flop 66 is set, its non-inverted output K goes to the "H" level and is sent to the data display drive circuit 59 as an inhibition signal. The output G of the binary counter 61 is further input to the AND circuit 65. Therefore, AND circuit 65 normally (when flip-flop 66 is reset)
opens its gate only when the output G is at the “H” level, that is, during the measurement period, and outputs the clock pulse N.
is sent to the calculation counter 57 as a clock pulse P. Furthermore, when the flip-flop 66 is set, the gate of the AND circuit 65 is closed even during the measurement period, so the clock pulse is sent to the counter 57.
will no longer be sent to

Now, while the output G of the binary counter 61 is at the "H" level, the gate of the AND circuit 65 is open as long as the flip-flop 66 is reset, so the clock pulse N from the PLL circuit 53 is The signal is input to the calculation counter 57 through the circuit 65. Furthermore, since the reset signal W of the counter 57 is at the "L" level during the measurement period, the counter 57 continues its counting operation. When the output G of the binary counter 61 is inverted to the "L" level, the gate of the AND circuit 65 is closed and the clock pulse N is no longer sent to the counter 57. At this point, the read signal is activated by the latch circuit 58.
The count value of the counter 57 is read into the latch circuit 58. The read count value of the counter 57 represents the inter-vehicle distance. Counter 57 is reset by signal W after this reading. The data regarding the inter-vehicle distance stored in the latch circuit 58 is displayed on the display of the data display circuit 60 by the data table drive circuit 59. This display is preferably performed using a value obtained by converting the count value of the counter 57 into an inter-vehicle distance.

After the output G of the binary counter 61 rises to the "H" level and the counter 57 starts counting, if the transmission pulse B is still not input even after the set time T3 has elapsed, the output from the monostable multivibrator 63 is J is generated, the signal W goes to the "H" level, the counter 57 is reset, and the flip-flop 66 is set, so the gate of the AND circuit 65 is closed and no clock pulse is sent to the counter 57. Further, since the output K of the flip-flop 66 is inputted to the data display drive circuit 59 as an inhibition signal, no measurement data is displayed. Thereafter, the transmission pulse B is output based on the reference pulse A of the reference pulse generation circuit 11, so the arithmetic unit 8 returns to its original state, and when the signal G is reversed to the "H" level, the following distance is calculated. The calculation process is performed again.

[Brief explanation of the drawing]

Figures 1 and 2 show the principle of inter-vehicle distance measurement. Figure 1 is an explanatory diagram showing two vehicles and how ultrasonic waves are transmitted and received, and Figure 2 is a time diagram showing transmission and reception of waves.・Chart, FIG. 3 is a block diagram showing an embodiment of the present invention, FIG. 4 is a time chart showing the output signals of each block of the ultrasonic transmitter/receiver in the circuit shown in FIG. 3, and FIG. A circuit diagram showing a specific example of a part of the distance calculation device in more detail,
FIG. 6 is a time chart showing the output signals of each circuit in FIG. 1...Following vehicle (measurement vehicle), 4...Leading vehicle,
2, 6... Transmitter, 3, 5... Receiver, 7, 9...
...Ultrasonic transmitting and receiving device, 8...Following distance calculation device,
56...Timer circuit.

Claims (1)

[Claims] 1. Consists of an ultrasonic transmitting/receiving device mounted on each of two vehicles in front and behind each other, and an inter-vehicle distance calculation device mounted on at least one vehicle, the ultrasonic transmitting/receiving device comprising: An ultrasonic transmitter, an ultrasonic receiver, a wave transmission drive circuit that drives the ultrasonic transmitter to transmit pulsed ultrasonic waves, and a signal component of a predetermined frequency from the output signal of the ultrasonic receiver. a wave reception detection circuit that detects the wave reception detection circuit; and a first activation means that activates the wave transmission drive circuit to transmit the pulsed ultrasonic wave in response to the detection signal of the wave reception detection circuit, The ultrasonic transmitting/receiving device is configured to transmit pulsed ultrasonic waves when the detection signal is not output from the wave reception detection circuit within a first fixed time after the ultrasonic wave transmission by the wave transmission drive circuit. The inter-vehicle distance calculating device includes a second starting means for starting the wave driving circuit, and the inter-vehicle distance calculating device measures the time from ultrasonic wave transmission by the wave transmission driving circuit to detection signal output by the wave reception detection circuit, an inter-vehicle distance calculation circuit that outputs a signal representing an inter-vehicle distance between two vehicles; and a detection signal is not output from the wave reception detection circuit within a second fixed period of time after the ultrasonic wave is transmitted by the wave transmission drive circuit. An inter-vehicle distance measuring device, comprising a prohibition means that sometimes stops the operation of the inter-vehicle distance calculation circuit.