JPH1164513A - Inter-vehicle distance alarm system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a highly reliable inter-vehicle distance alarm system, by reducing influences of radio interference and of multi-path. SOLUTION: An actual inter-vehicle distance at a present point of time is computed as a distance an electromagnetic wave propagates in a period of time equating to a time difference between a time signal (in a signal processing part 30) by a clocking means possessed by an own vehicle and a time signal (received by a transreceiver 10) representing the same time and received from another vehicle, and an alarm is sent out when the actual inter-vehicle distance value is smaller than a predetermined safety inter-vehicle distance value. As for the frequency of the electromagnetic wave, a different frequency is allotted to every traffic lane by a frequency control signal produced by receiving and decoding a light signal received by a light receiver 20 and therefore radio interference is avoided. In order to prevent a time error from being produced between the two vehicles, a time reset signal is received by the light receiver and supplied to the signal processing part 30 and a time counter in the signal processing part 30 is reset with appropriate timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention compares a safe inter-vehicle distance set for a vehicle or the like with an actual inter-vehicle distance at the time when the comparison result reaches a value within a predetermined range. The present invention relates to an inter-vehicle distance warning system which issues a warning to a driver of the vehicle or the like, and more particularly to an improvement of such a system having improved reliability.

[0002]

2. Description of the Related Art Conventionally, a collision prevention system (collision warning system) has been proposed in which a warning is issued to a driver to prevent a collision in advance when an inter-vehicle distance between traveling vehicles is abnormally close to each other. Have been. FIG. 4 is a block diagram showing an outline of a conventional collision warning system of this kind. still,
The system shown in FIG. 4 is of the same type as that proposed in Japanese Patent Application Laid-Open No. 8-80793.

In FIG. 4, an antenna / front-end unit 1 provided at a front end of a passenger car or the like (vehicle or the like in the Road Traffic Act) is provided with a predetermined directivity from itself (own vehicle) to the front. An electromagnetic wave fT (for example, a transmission wave such as a millimeter wave) is emitted, and the electromagnetic wave fT receives a reflected wave fR reflected by another vehicle or an obstacle or the like as a reception wave. The reflected wave fR (millimeter wave) received by the antenna front end unit 1 as described above is converted into an IF by a signal processing unit 2 further including an IF circuit and the like. The inter-vehicle distance is calculated based on the phase difference and the like.

The data of the following distance obtained by the signal processing section 2 is supplied to an alarm determination section 3 at the next stage. In addition to the data of the inter-vehicle distance, the alarm determination unit 3 outputs the ground speed data of the vehicle at that time from the vehicle speed sensor 4 and the sensor 5
(A plurality of sensors are collectively represented as a sensor 5 for convenience.) Data relating to the movement of various vehicles such as the degree of braking of the vehicle, the steering angle, and the angular velocity related to the movement of the vehicle are supplied. It has been made. The alarm determination unit 3 calculates the safe inter-vehicle distance by the calculation based on the various data supplied as described above, and calculates the safe inter-vehicle distance by the signal processing unit 2 at the time. When it is determined that the latter is smaller than the former, an alarm signal is supplied to the alarm output unit 6 in the next stage. Upon receiving this alarm signal, the alarm output unit 6 gives a predetermined display and / or an alarm to the driver.

The system described above with reference to FIG. 4 detects an inter-vehicle distance by projecting a beam of electromagnetic waves and receiving a reflected wave from the object, and determines the inter-vehicle distance by a so-called radar principle. Things.

Japanese Unexamined Patent Publication No. 4-157392 discloses a vehicular collision warning device of a type that detects an inter-vehicle distance based on the principle of a radar as described above. The device disclosed in this publication is of a type that determines the inter-vehicle distance based on the beat between an electromagnetic wave projected on a target and a reflected wave thereof. By comparing the actual inter-vehicle distance at this time thus determined with a preset safe inter-vehicle distance, when the former becomes smaller than the latter, an alarm is issued to the driver. It is configured to emit.

In the case of this device, the driver sets the above-mentioned safe inter-vehicle distance when the driver reaches a certain inter-vehicle distance in accordance with the actual driving feeling according to the vehicle speed or the like at the time. When the button is operated, the actual inter-vehicle distance at that time is stored in the storage means (alarm distance storage) as a safe inter-vehicle distance, and thereafter, the distance based on the storage becomes the safe inter-vehicle distance. The troublesome operation for setting the optimal safe inter-vehicle distance according to the vehicle speed and acceleration (degree of acceleration and deceleration) is eliminated, and the appropriate safe inter-vehicle distance according to various driving situations can be set. It is an apparatus aiming at the following.

[0008]

The above-mentioned conventional collision warning system or vehicle collision warning system has the following problems. That is, first, there is a problem of electromagnetic wave interference due to adopting the radar system. When an electromagnetic wave is emitted from the front of the vehicle on a multi-lane road or an up-and-down road, and this electromagnetic wave is reflected back by a vehicle ahead in the same lane as the vehicle, the vehicle returns There is a possibility that an electromagnetic wave returning from a vehicle or the like ahead of the vehicle and an electromagnetic wave emitted and received from a vehicle or the like traveling in an adjacent lane interfere with each other to cause a malfunction of the system. In order to avoid such a fear, it is conceivable that the frequencies of the electromagnetic waves to be used are variously changed, but it is actually difficult to assign different frequencies to all the persons concerned.

Second, there is a problem of multipath when electromagnetic waves are reflected from the vehicle or other objects and returned. FIG. 5 is a conceptual diagram for explaining a situation in which this multipath occurs. Electromagnetic waves (transmitted waves) emitted from the own vehicle are reflected in random directions when projected on a target (such as a partner vehicle). A part of this reflected wave returns to the vehicle as it is, but the other part is reflected back on the road surface, guardrails, other installations, buildings on the side of the road, etc., and returns to the vehicle. . Under such a situation where multipaths returning in various propagation paths occur, it becomes difficult to discriminate which electromagnetic wave is the reflected wave from the original target, and the inter-vehicle distance is calculated in multiple ways. As a result, it is difficult to recognize the correct inter-vehicle distance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and provides a reliable inter-vehicle distance alarm system of this kind which reduces the effects of interference and multipath and has high reliability. The purpose is to:

[0011]

Means for Solving the Problems and Actions One aspect of the present invention for solving the above-mentioned problems is as follows: (1) The safety inter-vehicle distance set for a vehicle or the like and the actual inter-vehicle distance at that time are determined An inter-vehicle distance warning system adapted to issue a warning to a driver of the vehicle or the like when the comparison result reaches a value within a predetermined range, under the control of the inter-vehicle distance warning system. Frequency-use identification means provided for each vehicle or the like to receive frequency information transmitted from the outside and identify frequencies to be used in the corresponding vehicle, etc .; A time signal generating means for performing an operation to generate a time signal corresponding to a time counting result of the time counting operation; and a use frequency discriminating means provided for each of the corresponding vehicles and the like and transmitting the time signal to an external vehicle and the like. Time signal transmitting means for wirelessly transmitting using the frequency identified by, and a time signal receiving means provided for each corresponding vehicle and the like, and receiving the time signal transmitted by the time signal transmitting means, The actual inter-vehicle distance between the vehicles is calculated based on the reception time signal provided by the time signal reception means provided for each of the vehicles and the time signal generated by the time signal generation means of the own vehicle. And means for calculating an inter-vehicle distance calculated by

Another aspect of the present invention is: (2) In (1), the time signal transmitting means and / or the time signal transmitting means of the vehicle or the like depends on the lane of travel of the vehicle or the like.
Alternatively, there is provided a frequency setting means for transmitting frequency setting information for setting a frequency to be applied to communication in the time signal receiving means.

Still another aspect of the present invention is: (3) In (1), the reception frequency of the time signal receiving means is scanned to transmit a transmission frequency from the time signal transmitting means of another vehicle or the like. And a transmission frequency adjusting unit configured to match the transmission frequency from its own time signal transmitting unit to the recognized frequency.

Still another aspect of the present invention is as follows: (4) In (1), means is provided for changing a mode of issuing the alarm in accordance with a traveling speed of the corresponding vehicle or the like.

Still another aspect of the present invention is as follows: (5) In (1), the time signal generating means provided for each of the corresponding vehicles or the like is provided with a predetermined time reset signal transmitted from the outside. These are reset at the same time.

Still another aspect of the present invention is: (6) In (1), the time signal transmitting means and the time signal receiving means are arranged at a front end portion and a rear end portion of the vehicle or the like.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing embodiments of the present invention in detail with reference to the drawings.

Before describing the details, the principle of the present invention will be outlined. That is, in the system of the present invention,
The actual inter-vehicle distance at the time is calculated based on the time difference between the time signal of the own vehicle's timekeeping means and the time signal received from another vehicle and indicating the same time (the electromagnetic wave which is substantially constant to this time difference). A value corresponding to the inter-vehicle distance is calculated by multiplying by the propagation speed.) When the actual inter-vehicle distance value is smaller than a predetermined safe inter-vehicle distance, an alarm is issued.

FIG. 1 is a block diagram showing a configuration of a device provided in a vehicle under control of an inter-vehicle distance warning system according to an embodiment of the present invention. In FIG. 1, a vehicle or the like under the control of this frequency projects (transmits) an electromagnetic wave such as a millimeter wave toward an external object such as another vehicle and receives an electromagnetic wave transmitted from the other vehicle. Transceiver 10
Is provided. The transceiver 10 includes a front vehicle antenna 1 provided at a front end portion of the vehicle or the like for mainly projecting and receiving an electromagnetic wave to a vehicle or the like ahead of the vehicle.
1 is connected to a rear vehicle antenna 12 provided at a rear end portion of the vehicle or the like mainly for projecting / receiving electromagnetic waves to a vehicle or the like behind the vehicle.

The transceiver 10 includes an optical receiver 20 described later.
A frequency control signal generated as a result of receiving and decoding the electromagnetic wave frequency allocation signal is supplied, and the frequency of the electromagnetic wave projected or received toward an external object such as another vehicle is set by the frequency control signal. Has been made. The transceiver 10 receives the electromagnetic wave from the other vehicle through the above-described antenna, decodes the time signal from the other vehicle, and supplies the resulting time signal to the subsequent signal processing unit 30.

The signal processing unit 30 has a clock means for performing a clock operation inside itself and generates a time signal. The time signal generated in this manner is compared with the time signal indicating the same time received from the partner vehicle and supplied from the transceiver 10 as described above to determine the time difference between the two time signals. The actual inter-vehicle distance (measured inter-vehicle distance) at that time is calculated as the distance over which the electromagnetic wave propagates in time. The signal processing unit 30 supplies an alarm signal to a subsequent alarm display unit 40 when the actually measured inter-vehicle distance is shorter than a preset safe inter-vehicle distance.

When the alarm display unit 40 receives the alarm signal from the signal processing unit 30, the driver uses a visual display (eg, an LED display), a voice message, an alarm sound, or a combination of these methods. A warning is issued to the effect that the inter-vehicle distance has been reduced.

The signal processing unit 30 is supplied with a time reset signal from the optical receiver 20 and, for example, every predetermined period,
Alternatively, the time difference between the vehicles and the like is reset to zero by resetting the time value of its own time counting means at every fixed time. Therefore, it is possible to sufficiently reduce the error in determining the inter-vehicle distance based on the time difference between the time signals as described above.

As shown in FIG. 1, a frequency search signal from a lane change information sensor 50 described later is supplied to the transceiver 10 so that a frequency to be applied to transmission and reception of electromagnetic waves in the transceiver 10 can be detected. The vehicle speed signal indicating the ground speed of the vehicle or the like at that time is supplied from the vehicle speed sensor 60 to the signal processing unit 30.
The configuration is such that the generation of an alarm signal and the mode of the alarm according to the vehicle speed can be selected.

FIG. 2 is a timing chart for explaining the operation of determining the inter-vehicle distance in the signal processing section 30 of FIG. As described above, the system of the present invention uses the time difference between the time signal (time reference signal) of the own vehicle and the time signal (time reference signal) indicating the same time received from another vehicle as the value of the electromagnetic wave. It is based on the principle of determining the actual inter-vehicle distance at the time by multiplying the propagation speed.

The signal processing units 30 of all the vehicles and the like under the control of the system of this embodiment form a time reference signal every 0.1 second. Then, the time difference between the time reference signal of the own vehicle and the time reference signal received from another vehicle is measured by the clock signal. For example, if the distance between the vehicles is 100 meters, the above-mentioned time difference due to this distance is about 0.3 microseconds, and it is necessary to calculate this time by 20 minutes.
By using a clock signal of MHz, measurement with sufficient accuracy can be performed. In the case of the system of the specification of FIG.
When there is a time difference of 0.167 microseconds, the distance is converted to 50 meters between vehicles, and when there is a time difference of 0.33 microseconds, it is converted to 100 meters of the distance between vehicles.
In the case of this system, the error relating to the distance is equivalent to one clock in the circuit configuration. In this case, the error (maximum value) of the calculated distance is 15 meters corresponding to one clock (0.05 microsecond) from the relationship between the time reference signal and the clock signal.

FIG. 3 is a conceptual diagram for explaining a case where a vehicle or the like under control of the system of the present invention travels on a two-lane road on one side. In the figure, a to g are vehicles under the control of the system, a to e are traveling in the up lane,
f and g are traveling in the down lane. At the front end and the rear end of each vehicle, a front vehicle antenna 11 and a rear vehicle antenna 12 as described above with reference to FIG. 1 are provided. These antennas transmit time signals by electromagnetic waves, and receive signals from other vehicles. Receives electromagnetic waves (time signals). For example, an electromagnetic wave emitted from a rear portion of the vehicle a is input to a transceiver (see FIG. 1) of the vehicle b via an antenna at a front portion of the vehicle b. Also, the electromagnetic wave emitted from the front of the vehicle b
Is input to the transceiver of the same vehicle a via the antenna at the rear of the vehicle.

An optical transmitter 70 is provided so as to cross the up and down lanes. The optical transmitter 70 is configured to project an electromagnetic wave frequency assignment signal for allocating another unique electromagnetic wave frequency to each of the up lane and the down lane to each vehicle or the like by an optical signal. The optical receiver 20 (FIG. 1) for each vehicle is configured to receive and decode the electromagnetic wave frequency assignment signal from the optical transmitter 70, generate a frequency control signal as a result of the decoding, and To supply. FIG.
As described above, the transceiver 10 adjusts the operating frequency so as to match the frequency of the electromagnetic wave projected onto or received from an external object such as another vehicle with the frequency represented by the frequency control signal ( Settings).

In the system according to the present embodiment, the frequency of the electromagnetic wave to be used is assigned to each lane by the optical transmitter 70, so that the electromagnetic wave is emitted from, for example, the front part (front vehicle antenna 11) of the vehicle c on the up lane (outside). The electromagnetic wave is transmitted to the rear of the vehicle a in the forward lane (inside) of the adjacent lane (inside) and the front of the vehicle f in the down lane (inside) (antenna 11 for the front vehicle).
However, since the electromagnetic waves have different frequencies, they are not received and decoded, and therefore there is no risk of interference.
Similarly, the electromagnetic waves emitted from the front part (front vehicle antenna 11) of the vehicle f in the down lane (inside) are the vehicles b to
e, but the frequency of the electromagnetic wave is different,
There is no risk of interference without being decoded.

In a vehicle such as the vehicle e shown in FIG. 3 which intends to change lanes, the lane change information sensor 50 shown in FIG. 1 outputs a frequency search signal based on a detection signal from a direction indicator, an acceleration sensor or the like. This signal is input to the transceiver 10. Upon receiving the frequency search signal, the transceiver 10 temporarily resets its own reception unit, scans the reception frequency, and identifies the transmission frequency of the electromagnetic wave assigned to the relevant lane by the reception intensity. To detect. Thereafter, the transceiver 10 automatically sets the frequency of the electromagnetic wave used for transmission / reception to the detected frequency.

As described above, the signal processing unit 30 shown in FIG. 1 is supplied with the vehicle speed signal indicating the ground speed of the vehicle or the like at that time from the vehicle speed sensor 60 to generate a warning signal according to the vehicle speed or to generate a warning signal. The configuration is such that selection of the mode and the like can be made. Further, in response to the warning signal, the warning display unit 40 reduces the inter-vehicle distance to the driver by a method such as a visual display (eg, an LED display), a voice message, a warning sound, or a combination thereof. For example, when the inter-vehicle distance calculated by the signal processing unit 30 is in a range of 200 to 30 meters, a warning signal is issued every 50 meters in a section of 200 to 100 meters. , 100 meters to 3
It is emitted every 10 meters in a section of 0 meters. During high-speed driving (continuous 100 km / h or more), an alarm is issued when the inter-vehicle distance becomes 100 m or less, and when traveling at low speed (50 km / h or less), the inter-vehicle distance becomes 30 m or less. An alert is issued in a manner different from the alert.

Although the time signal in each vehicle or the like is always counted up (timed operation) by the signal processing unit 30 in FIG. 1, an error occurs depending on the precision of the clock. In order to prevent this error from increasing between the vehicles, the system of the present embodiment employs the following configuration. That is,
For example, a time reset signal by an optical signal is transmitted from the optical transmitter 70 of FIG. 3 at a predetermined cycle or at a fixed time to each vehicle or the like under the control of this system. The time reset signal based on this optical signal is transmitted to the optical receiver 2 of each vehicle or the like.
0 is received. The optical receiver 20 decodes the time reset signal based on the optical signal, converts the signal into a time reset signal as an electronic signal, and supplies it to the signal processing unit 30. The signal processing unit 30 resets (synchronizes) the time counter circuit with the time reset signal, thereby maintaining a sufficiently small time error between vehicles.

In the embodiment described above, the front vehicle antenna 11 is provided at a front end portion of the vehicle or the like in order to project / receive an electromagnetic wave to a vehicle or the like in front of the vehicle.
In addition, since the rear vehicle antenna 12 is provided at a rear end portion of the vehicle or the like in order to project / receive an electromagnetic wave to a vehicle or the like behind the vehicle, the drivers can mutually communicate with each other at a corner or the like. Even when the vehicle is in a positional relationship where the vehicle cannot be seen, it is possible to maintain the contribution for safe driving.

In the above-described present invention, the inter-vehicle distance is calculated based on the time difference between the time reference signal of the own vehicle and the time reference signal received from outside indicating the same time. Instead of using the time reference signal as in the system, the inter-vehicle distance may be calculated based on the degree of the phase shift of the sub-carrier by the FM modulation method using the sub-carrier.

As described above, according to the present invention, it is possible to reduce the influence of interference and multipath, and to realize this kind of highly reliable inter-vehicle distance warning system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a device provided in a vehicle or the like under control of an inter-vehicle distance warning system as an embodiment of the present invention.

FIG. 2 is a timing chart for explaining an operation of calculating an inter-vehicle distance in a signal processing unit in FIG. 1;

FIG. 3 is a conceptual diagram illustrating a case where a vehicle or the like under control of the system of the present invention travels on a two-lane road on one side.

FIG. 4 is a block diagram showing an outline of a conventional collision warning system.

FIG. 5 is a conceptual diagram for explaining a situation in which multipath occurs.

[Description of Signs] 1 Antenna / front end unit 2 Signal processing unit 3 Alarm determination unit 4 Vehicle speed sensor 5 Sensor 6 Alarm output unit 10 Transceiver 11 Antenna for front vehicle 12 Antenna for rear vehicle 20 Optical receiver 30 Signal processing unit 40 Warning display section 50 Lane change information sensor 60 Vehicle speed sensor 70 Optical transmitter

Claims (6)

[Claims] The present invention relates to a driver of a vehicle or the like when a result of comparison between the safe distance between vehicles set for the vehicle or the like and an actual distance between the vehicles at that time is within a predetermined range. An inter-vehicle distance alarm system configured to issue an alarm to a vehicle, which receives operating frequency information transmitted from outside provided for each vehicle or the like under the control of the inter-vehicle distance alarm system and receives the corresponding vehicle. Use frequency identification means for identifying a frequency to be used for each, etc., and time signal generation means provided for each of the corresponding vehicles and the like for performing a timekeeping operation and generating a time signal corresponding to a result of the timekeeping operation. A time signal transmitting means provided for each of the vehicles and the like to transmit the time signal to an external vehicle or the like wirelessly using a frequency identified by the use frequency identifying means; A time signal receiving unit provided for each of the corresponding vehicles and the like for receiving the time signal transmitted by the time signal transmitting unit; and a reception provided for each of the corresponding vehicles and the like and received by the time signal receiving unit. Inter-vehicle distance calculating means for calculating an actual inter-vehicle distance between the vehicles based on a time signal and a time signal generated by the own time signal generating means. Alarm system. 2. Frequency setting information for setting a frequency to be applied to communication in the time signal transmitting means and / or the time signal receiving means of the vehicle or the like depending on a lane in which the vehicle or the like travels. 2. The inter-vehicle distance warning system according to claim 1, further comprising a frequency setting means for transmitting the distance. 3. The transmission frequency from the time signal transmitting means of the other vehicle or the like is recognized by scanning the reception frequency of the time signal receiving means, and the transmission frequency from the own time signal transmitting means is recognized. The inter-vehicle distance warning system according to claim 1, further comprising a transmission frequency adjusting means configured to match the frequency. 4. The inter-vehicle distance warning system according to claim 1, further comprising means for changing a mode of issuing the warning in accordance with a traveling speed of the vehicle. 5. The time signal generating means provided for each of the vehicles and the like is adapted to be simultaneously reset at a predetermined timing by a time reset signal transmitted from the outside. The inter-vehicle distance warning system according to claim 1, wherein 6. The inter-vehicle distance warning system according to claim 1, wherein the time signal transmitting means and the time signal receiving means are arranged at a front end portion and a rear end portion of the vehicle or the like.