JPH08226964A - Monitor for distance-between-two vehicles - Google Patents

Abstract

PURPOSE: To stepwisely alter the receiving amplification factor and to accurately calculate the relative speed based on the rangefinding result before or after the factor is varied by reading a previous distance between two vehicles obtained by the same receiving amplification factor as a new suitable receiving amplification factor from reference-distance-between two vehicles preserving means, and giving it to relative speed calculating means. CONSTITUTION: A received signal is amplified at a suitable receiving amplification factor by a signal amplifier 1d to calculate the relative speed of the respective times, binarized by a signal processor 2, then synchronously added and preserved in a memory 3e. Then, the received signal is amplified by altering the factor to the amplification factor raised or lowered by one stage from the suitable receiving amplification factor, binarized, and the distance between two vehicles obtained by totally three times of rangefinding operations for synchronously adding the signal is preserved in the memory 3e. In order to calculate the relative speed, if the suitable receiving amplification factors at the previous time of one set three times of rangefinding operations and at this time of one set three times of the rangefinding operations are altered, a relative speed calculator 3 calculates the relative speed by using the distance between the two vehicles obtained by rangefinding at the suitable receiving amplification factor of this time and the distance between the two vehicles obtained by the same factor of the previous time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention constantly monitors an inter-vehicle distance, a relative speed, and an own vehicle speed between a preceding vehicle and an own vehicle, and automatically detects when the distance between the preceding vehicle and the preceding vehicle becomes too dangerous. The present invention relates to an inter-vehicle distance monitoring device that gives a warning to inform a driver.

[0002]

2. Description of the Related Art Conventionally, a certain vehicle emits a pulsed optical signal forward, and the signal from the direction in which the signal is reflected and returned to the front target is received and processed to the front target. For example, Japanese Patent Application Nos. 6-146752 and 6-248438 have been proposed as vehicle radar devices for automatically detecting a distance.

The vehicle radar devices of these inventions have a structure as shown in FIG. 13 in principle, and are composed of a distance sensor head 1, a signal processing unit 2 and a computer. The distance calculation unit 3 is included.

The distance sensor head 1 is composed of an LED or a laser light emitting diode, and a light transmitting section 1a for transmitting a pulsed optical signal to the outside at a predetermined cycle, and the light transmitting section 1a having a predetermined pulse width and pulse. A drive circuit 1b driven at intervals (cycles) and an optical signal from a direction in which an optical signal sent from the light transmitting unit 1a is reflected back to a target in front (even if this signal contains noise). Light receiving section 1c for continuously receiving and converting the received signal to an electric signal, and a signal amplifying section 1d for amplifying the received signal.

Under the control of the inter-vehicle distance calculating section 3, the signal processing section 2 binarizes the signal from the signal amplifying circuit 1d in accordance with the signal strength thereof, and outputs a plurality of signals after the signal transmission timing of the light transmitting section 1a. This is a part for sampling at each sampling point with a different time, performing synchronous addition, and storing the added value for each sampling point. The inter-vehicle distance calculation section 3 is based on the signal processing result of the signal processing section 2, This is a part for calculating the inter-vehicle distance to the target.

The operation of the proposed vehicle radar device will be described below. During one distance measurement operation, the light transmitting unit 1
From a, a predetermined number of times N (for example, 8192 times) is transmitted at a predetermined pulse width Pwd (for example, 130 nsec) and a pulse interval Pds (for example, 6 μsec), and this optical signal is reflected from the target and returned. The light receiving unit 1c receives the optical signal,
The signal is amplified by the signal amplification circuit 1d and output to the signal processing unit 2.

FIG. 14 shows a flow of signal processing executed by the signal processing section 2 and the distance calculating section 3 for digitizing light-receiving signals, sampling processing, and distance calculating processing. First, the amplitude-amplified received light signal b1 (
Not only the reflected signal of the actual light-transmitting signal but also a lot of noise is mixed) is binarized into "0" and "1" by comparison with a predetermined reference value wref, and the binarized signal sequence b2 is obtained. Become. Then, for this binarized signal sequence b2, one sampling process is started in synchronization with the pulse transmission timing of the light transmitting unit 1a, and at a constant sampling period Δt (for example, 67 nsec: equivalent to 10 m in distance conversion). By sampling, digital data b3 having a preset number of bits is obtained and stored. Then, during one distance measuring operation, sampling processing is performed a predetermined number of times N and the digital data b3 group is subjected to synchronous addition processing for each bit.

In this way, the characteristic data b4 of the added value level with respect to the distance is obtained by the light transmitting operation of the predetermined number N and the sampling processing of N times executed in synchronization with it. In this added value level characteristic, the probability that the binarized data will be "0" and "1" is 1/2 each if the received light signal is the noise level.
The added value of the predetermined number of times N is approximately N / 2. However, if the received light signal includes the reflected signal that the transmitted light signal reflected back to the target in front, the signal level of the bit corresponding to the round-trip distance of the optical signal becomes higher than the noise level,
The probability that the binarized data becomes “1” becomes higher than 1/2, and the added value of the predetermined number N becomes a value between N and N / 2.

Therefore, a threshold level TH slightly higher than N / 2 is set, a bit indicating an added value exceeding this is found, and the corresponding distance point is indexed as the inter-vehicle distance to the target and output. To do.

However, since the sampling points (corresponding to each bit) are in steps of 10 m, the inter-vehicle distance at the intermediate point cannot be accurately calculated. Therefore, the sampling point at which the added value has a peak and the four points v1 before and after the sampling point v1,
v2, v3, v4 are taken out, these are divided into two sets, and the intersection A of the straight lines ln1 and ln2 connecting each set is obtained, and this intersection A
The distance B corresponding to is determined as the inter-vehicle distance to the target and is output.

[0011]

However, in such a proposed vehicle radar device, it has been necessary to further improve the following points. That is, when trying to measure a wide range with one type of signal strength,
In particular, the signal strength becomes too strong at the time of detecting the short-distance target, and as shown in FIG. 15A, there are some sampling points where the added value is almost equal to the total number of times of addition N near the peak sampling point. It may occur (that is, addition saturation may occur), and the above-described peak detection process cannot accurately determine the inter-vehicle distance. On the other hand, when detecting a long-distance target, the received light signal intensity is low as shown in FIG. 15B, and only an added value level characteristic that is so low as to be indistinguishable from the noise level is obtained, and the S / N deteriorates to detect the distance. The accuracy is low.

In view of these problems, in the invention of the above-mentioned application, as a measure for improving the accuracy of distance measurement, the light transmission signal output level and the reception amplification factor are previously set after one distance measurement operation is completed. A method has been proposed in which the added value peak is controlled to fall within a predetermined range by gradually changing the set change amount.

However, even when the distance measurement is performed by these methods, it is necessary to further improve the accuracy. This is because, as shown in FIG. 16 (a), the distances d1, d2, ... To the target change at every distance measurement timing t1, t2 ,. Since the phase characteristic of the receiving circuit element changes when the distance is changed to, the distance measurement values d4 and d5 may be different between the respective reception amplification factors even if the distance measurement is performed on the same target.
Therefore, as shown in FIG. 9B, when the reception amplification factor is switched, relative velocity calculation, for example, Vr, is performed between the distance measurement values d4 and d5 by the reception amplification factor at different stages at timings t4 and t5 before and after the switching. = (Di−di−1) / θ where θ is the distance measurement cycle and di is the distance measurement value at the timing ti, the relative speed calculation accuracy may be degraded.

By the way, the radar device for a vehicle judges whether or not an appropriate inter-vehicle distance is maintained between the preceding vehicle and the preceding vehicle by using the result of the distance measurement, and warns the driver when the vehicle is too close and dangerous. Although an inter-vehicle distance warning device is provided, the warning inter-vehicle distance calculation takes into account the inter-vehicle distance, the own vehicle speed, and the relative speed with respect to the preceding vehicle. This is because even if the inter-vehicle distance is short, the vehicle speed is slow, the preceding vehicle is accelerating, and the relative speed goes to +, that is, if the inter-vehicle distance tends to increase, there is no need to issue an alarm, and conversely This is because if the vehicle speed is large even if the vehicle speed is large and the inter-vehicle distance tends to decrease abruptly when the relative speed becomes negative, it is necessary to issue an alarm.

Therefore, it is necessary to keep the relative speed calculation accuracy high, but the accuracy is good when no correction is made to the distance measurement values obtained before and after the reception amplification factor is changed as described above. Since the relative speed cannot be obtained, the reliability of the inter-vehicle distance warning is impaired.

Therefore, as a method for solving the problem of deterioration of the relative speed calculation accuracy due to the stepwise change of the reception amplification factor,
As shown in FIGS. 17A and 17B, a correction value for the distance measurement value is registered in advance in a specific memory for each reception amplification factor, and the correction value in this memory is referred to after the distance measurement operation. A method of correcting the distance measurement value can be considered.

However, in this method, since it is necessary to register the correction value in the memory for each step of the reception amplification rate, there is a problem that the same number of correction value memories as the number of steps of the reception amplification rate are required. is there.

Further, if the distance measurement range based on the reception amplification factor at the same stage is corrected by one correction value, there is a problem that an error that affects the relative speed calculation occurs at the end where the reception amplification factor is switched. . This is because the phase characteristic of the receiving circuit changes according to the distance to the target even if the distance is measured with the same reception amplification factor. That is, as shown in FIG. 17 (b), the distance measurement characteristics Dn-1, Dn, D having inclinations slightly different from the ideal characteristic C in which the distance measurement value and the true value match over the entire area.
Because it has n + 1, ...

In order to solve this problem, a method is conceivable in which the distance measuring range with the same reception amplification factor is subdivided to narrow the distance range covered by one-step reception amplification factor. There is a problem that the number of memories increases.

Further, in order to realize highly accurate distance measurement characteristics, in the case of the above method, it is necessary to set a different correction value for each radar device due to individual differences. There is a problem that productivity is extremely low.

The above problems similarly apply when variable control of the output level of the transmitted light signal is performed.

The present invention was invented to solve such a technical problem, and the reception amplification factor can be changed stepwise, and the relative velocity based on the distance measurement results before and after the reception amplification factor is changed. It is an object of the present invention to provide an inter-vehicle distance monitoring device that can perform calculation with high accuracy.

The present invention also provides an inter-vehicle distance monitoring device capable of changing the output level of a transmission signal in a stepwise manner and accurately calculating the relative speed based on the distance measurement results before and after changing the signal output level. To aim.

[0024]

According to a first aspect of the present invention, there is provided speed detection means for detecting the speed of the host vehicle, and signal transmission means for transmitting a pulsed signal to the outside at a predetermined transmission cycle.
The receiving means for continuously receiving the signal from the direction in which the signal sent by the signal sending means is reflected by the target and returned, and the signal received by the receiving means is binarized in each sending cycle of the signal sending means. Adder means for adding a predetermined number of times for each of a plurality of sampling points with different elapsed times from the signal sending timing; peak value detecting means for obtaining a peak value of the added value at each sampling point of the adding means; An inter-vehicle distance calculating means for calculating the distance corresponding to the sampling point giving the peak value obtained by the value detecting means as an inter-vehicle distance to the target in front, and a distance measurement value saving for saving the inter-vehicle distance calculated by the inter-vehicle distance calculating means Means and the inter-vehicle distance calculating means calculates a new inter-vehicle distance, and reads out the previously calculated inter-vehicle distance stored in the distance-measuring value storage means. Relative speed calculating means for calculating the relative speed between the vehicle and the target in front, relative speed calculated by the speed detecting means for detecting the speed of the own vehicle and the inter-vehicle distance calculating means for calculating the relative distance between the vehicle and the relative speed calculating means. The vehicle-to-vehicle distance determining means determines whether or not the current vehicle-to-vehicle distance is appropriate based on the speed, and the alarm output means that outputs a warning to the driver when the vehicle-to-vehicle distance determining means determines that the current vehicle-to-vehicle distance is inappropriate. In an inter-vehicle distance monitoring device, a reception amplification rate control means for stepwise controlling an appropriate reception amplification rate of the reception means so that the peak value detected by the peak value detection means falls within a predetermined level, and a reception amplification of the reception means. The rate is one step higher than the proper reception amplification rate adjusted by the reception amplification rate control means,
One step down, the reference inter-vehicle distance storage means for changing the reception amplification factor of each to obtain the inter-vehicle distance and storing these inter-vehicle distances, and the proper reception amplification factor adjusted by the reception amplification factor control means are changed. When the inter-vehicle distance is obtained, a relative speed calculation assisting means for reading out the previous inter-vehicle distance obtained at the same reception amplification factor as the new appropriate reception amplification factor from the reference inter-vehicle distance storage means and giving it to the relative speed calculation means is provided. Be prepared.

According to a second aspect of the present invention, in place of the reference inter-vehicle distance storage means in the inter-vehicle distance monitoring apparatus of the first aspect,
From the relative speed calculated by the relative speed calculation means, when the own vehicle is approaching the target ahead, the proper reception amplification factor of the reception means is lowered by one step, and when the own vehicle is leaving, the proper reception amplification factor is obtained. Is used to obtain the inter-vehicle distance, and the inter-vehicle distance is stored, and the reference inter-vehicle distance storage means is used.

According to a third aspect of the present invention, there are provided a speed detecting means for detecting the speed of the host vehicle, a signal sending means for sending a pulsed signal to the outside at a predetermined sending cycle, and a signal sent by the signal sending means. The receiving means for continuously receiving the signal from the direction in which the signal is reflected back to the target and the signal received by the receiving means are binarized, and the elapsed time from the signal sending timing in each sending cycle of the signal sending means is shown. Addition means for adding a predetermined number of times of transmission for each of a plurality of different sampling points, peak value detection means for obtaining the peak value of the added value at each sampling point of the addition means, and peak value obtained by the peak value detection means And an inter-vehicle distance calculating means for calculating a distance corresponding to a sampling point as an inter-vehicle distance to a target ahead, and a distance measurement value saving means for saving the inter-vehicle distance calculated by the inter-vehicle distance calculating means, When the inter-vehicle distance calculation means calculates a new inter-vehicle distance, the previously-calculated inter-vehicle distance stored in the distance-measurement value storage means is read, and the difference between these inter-vehicle distances is used to calculate the distance between the host vehicle and the target ahead. Relative speed calculating means for calculating the relative speed of the vehicle, the speed of the own vehicle detected by the speed detecting means and the inter-vehicle distance calculated by the inter-vehicle distance calculating means, and the current inter-vehicle distance based on the relative speed calculated by the relative speed calculating means. A vehicle-to-vehicle distance monitoring device comprising an inter-vehicle distance determining means for determining suitability and an inter-vehicle distance monitoring means for outputting an alarm to a driver when the inter-vehicle distance determining means determines that the current inter-vehicle distance is unsuitable. The signal output control means for stepwise controlling the appropriate signal output level of the signal sending means so that the peak value detected by the means falls within a predetermined level, and the signal output level of the signal sending means Against the proper signal output level control means is adjusted, one step on than, 1
Reference inter-vehicle distance storage means that changes the signal output level of each step to determine the inter-vehicle distance and saves these inter-vehicle distances, and the appropriate signal output level adjusted by the signal output control means are changed, and the new inter-vehicle distance is changed. And a relative speed calculation assisting means for reading out the previous inter-vehicle distance obtained at the same signal output level as the new appropriate signal output level from the reference inter-vehicle distance storing means and giving it to the relative speed calculating means. It is a thing.

According to a fourth aspect of the present invention, in place of the reference inter-vehicle distance storing means in the inter-vehicle distance monitoring device of the third aspect,
From the relative speed calculated by the relative speed calculating means, the appropriate signal output level of the signal sending means is lowered by one step when the own vehicle is approaching the target ahead, and when the own vehicle is leaving the appropriate signal output level. Is used to obtain the inter-vehicle distance, and the inter-vehicle distance is stored, and the reference inter-vehicle distance storage means is used.

[0028]

According to the inter-vehicle distance monitoring apparatus of the present invention, a pulsed signal is sent to the outside at a predetermined sending cycle, and a signal from the direction in which the sent signal is reflected back to the target is continuously sent. , The received signal is binarized, the binarized received signal is added by a predetermined number of times at each of a plurality of sampling points with different elapsed times from the signal sending timing in each signal sending cycle, and each sampling is performed. The peak value of the added value of the points is obtained by the peak value detecting means, the distance corresponding to the sampling point giving this peak value is calculated as the inter-vehicle distance to the target in front, and this inter-vehicle distance is temporarily stored in the inter-vehicle distance storage means. Save to.

When a new inter-vehicle distance is calculated,
The previous vehicle-to-vehicle distance stored in the relative speed calculation means is read, and the relative speed between the host vehicle and the target in front of the vehicle is calculated from the difference between the previous and current vehicle-to-vehicle distances. The suitability of the current inter-vehicle distance is determined based on the vehicle speed and the current inter-vehicle distance, and an alarm is output to the driver when the current inter-vehicle distance is unsuitable.

Here, the proper reception amplification rate of the reception means is controlled stepwise by the reception amplification rate control means so that the peak value detected by the peak value detection means falls within a predetermined added value level. The reception amplification factor is always variably adjusted to an appropriate value.

At the same time, along with the distance measurement by the proper reception amplification rate adjusted by the reception amplification rate control means, the reference inter-vehicle distance storage means makes the reception amplification rate of the reception means one step above and one step below the proper reception amplification rate. Change them to obtain inter-vehicle distances and save these inter-vehicle distances. When the proper reception amplification factor is newly changed and a new inter-vehicle distance is obtained, the relative speed calculation assisting unit obtains a reception amplification factor corresponding to the new proper reception amplification factor, and the inter-vehicle distance is saved. The distance is read from the reference inter-vehicle distance storage means and given to the relative speed calculation means as the previous inter-vehicle distance to calculate the relative speed.

As a result, even if the reception amplification factor is changed and adjusted, the relative speed can be calculated using the inter-vehicle distance measured with the same reception amplification factor before and after the adjustment, and the relative speed can be calculated with high accuracy. To improve the reliability of issuing the inter-vehicle distance warning.

According to the inter-vehicle distance monitoring device of the invention of claim 2,
Send a pulsed signal to the outside at a predetermined sending cycle,
Multiple sampling points that continuously receive signals from the direction in which the transmitted signal is reflected back to the target, binarize the received signal, and change the elapsed time from the signal transmission timing in each signal transmission cycle. The binarized reception signals are added for each predetermined number of times of transmission, the peak value of the added value at each sampling point is obtained by the peak value detecting means, and the distance corresponding to the sampling point giving this peak value is the front target. Is calculated as the inter-vehicle distance, and the inter-vehicle distance is temporarily stored in the inter-vehicle distance storage means.

When a new inter-vehicle distance is calculated,
The previous vehicle-to-vehicle distance stored in the relative speed calculation means is read, and the relative speed between the host vehicle and the target in front of the vehicle is calculated from the difference between the previous and current vehicle-to-vehicle distances. The suitability of the current inter-vehicle distance is determined based on the vehicle speed and the current inter-vehicle distance, and an alarm is output to the driver when the current inter-vehicle distance is unsuitable.

Here, the proper reception amplification rate of the reception means is controlled stepwise by the reception amplification rate control means so that the peak value detected by the peak value detection means falls within a predetermined added value level. The reception amplification factor is always variably adjusted to an appropriate value.

At the same time, along with the distance measurement based on the proper reception amplification rate adjusted by the reception amplification rate control means, the host vehicle approaches the target ahead from the relative speed calculated by the relative speed calculation means by the reference inter-vehicle distance storage means. If so, the proper reception amplification factor is decreased by one step, and conversely, if the vehicle is departing, the proper reception amplification factor is increased by one step to obtain the inter-vehicle distance, and the inter-vehicle distance is stored. When the proper reception amplification factor is newly changed and a new inter-vehicle distance is obtained, the relative speed calculation assisting unit obtains a reception amplification factor corresponding to the new proper reception amplification factor, and the inter-vehicle distance is saved. The distance is read from the reference inter-vehicle distance storage means and given to the relative speed calculation means as the previous inter-vehicle distance to calculate the relative speed.

As a result, even if the reception amplification factor is changed and adjusted, the relative speed can be calculated using the inter-vehicle distance measured with the same reception amplification factor before and after the adjustment, and the relative speed can be calculated with high accuracy. To improve the reliability of issuing the inter-vehicle distance warning.

In addition, in each distance measuring operation, a response is obtained by measuring the distance with only two kinds of reception amplification factors, that is, the proper reception amplification factor and the reception amplification factor which is changed by one step up or down by one step. Speed up.

According to the inter-vehicle distance monitoring device of the invention of claim 3,
Send a pulsed signal to the outside at a predetermined sending cycle,
Multiple sampling points that continuously receive signals from the direction in which the transmitted signal is reflected back to the target, binarize the received signal, and change the elapsed time from the signal transmission timing in each signal transmission cycle. The binarized reception signals are added for each predetermined number of times of transmission, the peak value of the added value at each sampling point is obtained by the peak value detecting means, and the distance corresponding to the sampling point giving this peak value is the front target. Is calculated as the inter-vehicle distance, and the inter-vehicle distance is temporarily stored in the inter-vehicle distance storage means.

When a new inter-vehicle distance is calculated,
The previous vehicle-to-vehicle distance stored in the relative speed calculation means is read, and the relative speed between the host vehicle and the target in front of the vehicle is calculated from the difference between the previous and current vehicle-to-vehicle distances. The suitability of the current inter-vehicle distance is determined based on the vehicle speed and the current inter-vehicle distance, and an alarm is output to the driver when the current inter-vehicle distance is unsuitable.

Here, the signal output level of the signal output means is controlled stepwise by the signal output control means so that the peak value detected by the peak value detection means falls within a predetermined added value level, and the signal output level is changed. Always variably adjust to the appropriate one.

At the same time, along with the distance measurement based on the proper signal output level adjusted by the signal output control means, the reference inter-vehicle distance storage means makes the signal output level of the signal sending means one step above and one step below the appropriate signal output level. Change them to obtain inter-vehicle distances and save these inter-vehicle distances. Then, when the appropriate signal output level is newly changed and a new inter-vehicle distance is obtained, the relative speed calculation assisting means obtains a signal output level corresponding to the new appropriate signal output level, and the inter-vehicle distance is saved. The distance is read from the reference inter-vehicle distance storage means and given to the relative speed calculation means as the previous inter-vehicle distance to calculate the relative speed.

As a result, even if the signal output level is changed and adjusted, the relative speed can be calculated using the inter-vehicle distance measured at the same signal output level before and after the adjustment,
It calculates the relative speed with high accuracy and improves the reliability of the inter-vehicle distance warning.

According to the inter-vehicle distance monitoring device of the invention of claim 4,
Send a pulsed signal to the outside at a predetermined sending cycle,
Multiple sampling points that continuously receive signals from the direction in which the transmitted signal is reflected back to the target, binarize the received signal, and change the elapsed time from the signal transmission timing in each signal transmission cycle. The binarized reception signals are added for each predetermined number of times of transmission, the peak value of the added value at each sampling point is obtained by the peak value detecting means, and the distance corresponding to the sampling point giving this peak value is the front target. Is calculated as the inter-vehicle distance, and the inter-vehicle distance is temporarily stored in the inter-vehicle distance storage means.

When a new inter-vehicle distance is calculated,
The previous vehicle-to-vehicle distance stored in the relative speed calculation means is read, and the relative speed between the host vehicle and the target in front of the vehicle is calculated from the difference between the previous and current vehicle-to-vehicle distances. The suitability of the current inter-vehicle distance is determined based on the vehicle speed and the current inter-vehicle distance, and an alarm is output to the driver when the current inter-vehicle distance is unsuitable.

Here, the appropriate signal output level of the signal sending means is controlled stepwise by the signal output control means so that the peak value detected by the peak value detecting means falls within a predetermined added value level, and the signal sending means is controlled. Always variably adjust the signal output level of to an appropriate level.

At the same time, along with the distance measurement based on the appropriate signal output level adjusted by the signal output control means, the host vehicle approaches the target ahead from the relative speed calculated by the relative speed calculation means by the reference inter-vehicle distance storage means. The appropriate signal output level is lowered by one step when the vehicle is leaving, and conversely, the appropriate signal output level is raised by one step when the host vehicle is leaving to obtain the inter-vehicle distance, and the inter-vehicle distance is stored. Then, when the appropriate signal output level is newly changed and a new inter-vehicle distance is obtained, the relative speed calculation assisting means obtains a signal output level corresponding to the new appropriate signal output level, and the inter-vehicle distance is saved. The distance is read from the reference inter-vehicle distance storage means and given to the relative speed calculation means as the previous inter-vehicle distance to calculate the relative speed.

As a result, even if the signal output level is changed and adjusted, the relative speed can be calculated using the inter-vehicle distance measured at the same signal output level before and after the adjustment.
It calculates the relative speed with high accuracy and improves the reliability of the inter-vehicle distance warning.

In addition, in each distance measuring operation, the response is obtained by measuring the distance with only two kinds of signal output levels, that is, the appropriate signal output level and the signal output level which is changed by one step up or down by one step. Speed up.

[0050]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a circuit configuration of an embodiment of the invention of claim 1, and an inter-vehicle distance monitoring apparatus of this embodiment is roughly divided into a distance sensor head 1, a signal processing unit 2 and a computer. Inter-vehicle distance calculation unit 3 and vehicle speed sensor 4
And an alarm buzzer 5 for alarming an improper inter-vehicle distance.

The distance sensor head 1 is composed of an LED or a laser light emitting diode, and has a light transmitting section 1a for transmitting an optical signal to the front, and a driving circuit 1b for causing the light transmitting section 1a to emit light with a constant pulse width at a constant cycle. And a photodiode that receives an optical signal, converts it into an electrical signal, and outputs it, and continuously outputs an optical signal from the direction in which the optical signal from the light transmitting unit 1a is reflected back to the target in front. A light receiving portion 1c for receiving light, a signal amplification circuit 1d of variable amplification factor for amplifying the signal of the light receiving portion 1c, and an amplification factor control circuit 1e for variably controlling the amplification factor of the signal amplification circuit 1d in stages. Has been done.

The signal processing section 2 compares the output signal of the signal amplifying circuit 1d with a certain reference value to obtain a binarized signal, and further, at every predetermined number N times of pulse signal transmission timings of the light transmitting section 1a, the transmission timing thereof. Sampling is started in synchronism, the binarized signal is sampled at each sampling point at a plurality of different times, and a binary value of "0" or "1" is added a predetermined number of times N times at each sampling point. It is a part. This configuration is disclosed in Japanese Patent Application No. 6-
The same materials as those used in No. 146752 and Japanese Patent Application No. 6-248438 are used.

The inter-vehicle distance calculation unit 3 is composed of a computer. When the functions of each calculation process are decomposed and shown, the distance measurement order control unit 3a which controls the distance measurement process sequence and gives a control signal to each unit, and the optical distance calculation unit 3a. A signal processing control unit 3b that controls signal transmission timing control and light-receiving signal processing timing, an inter-vehicle distance calculation unit 3c that performs inter-vehicle distance calculation, and a reception amplification rate change that determines the necessity of changing the amplification rate of a reception signal. The determination unit 3d,
A memory 3e that stores various distance measurement data, a relative speed calculation unit 3f that calculates a relative speed, an alarm distance that calculates an alarm distance based on the vehicle speed from the vehicle speed sensor 4 and the relative speed from the relative speed calculation unit 3f. Comparing the calculation unit 3g with the warning distance calculated by the warning distance calculation unit 3g and the current inter-vehicle distance calculated by the inter-vehicle distance calculation unit 3c, the necessity of issuing a warning is determined.
The alarm buzzer 5 is composed of an alarm issuance determination unit 3h that controls the alarm issuance.

The vehicle speed sensor 4 inputs vehicle speed data to the inter-vehicle distance calculating section 3.

The alarm buzzer 5 is installed in the driver's seat, and notifies the driver by issuing a warning when it is determined that the distance is a dangerous inter-vehicle distance.

Next, the operation of the inter-vehicle distance monitoring device having the above configuration will be described. The signal processing control unit 3b gives a distance measurement command to the signal processing unit 2 based on the command of the distance measurement order control unit 3a of the inter-vehicle distance calculation unit 3, and the signal processing unit 2 controls the drive circuit 1b of the distance sensor head 1. Then, a driving signal having a constant pulse width is given to the light transmitting section 1a at a predetermined number of times N times during one distance measuring operation, and the light transmitting section 1a is forwarded a predetermined number of times N times.
Once, an optical signal having a constant pulse width is transmitted at a predetermined cycle.

On the other hand, the light receiving section 1c continuously receives optical signals from the front. When the received light signal does not include the reflected signal from the preceding vehicle, which is the target in the front, that is, when there is no vehicle ahead, the optical signal at the noise level is received and converted into an electric signal. The signal is output to the amplifier circuit 1d, where it is amplified by a predetermined amplification factor and output to the signal processing unit 2. However, in this case, since the received light signal has a noise level, the signal binarized by the signal processing unit 2 is a signal in which “0” and “1” appear at almost the same probability, and the binarized signal is transmitted. Even if the addition processing is performed for each sampling point N times a predetermined number of times in synchronization with the optical timing, the added value at each sampling point becomes a noise level of approximately N / 2, and the inter-vehicle distance cannot be obtained.

However, when there is a vehicle ahead and the light signal reflected by the preceding vehicle and returned is received by the light receiving section 1c, the signal processing section 2 performs binarization processing,
The added value level characteristic obtained by the synchronous addition processing is shown in FIG.
B4.

This added value data is output to the inter-vehicle distance calculation unit 3c, and as described in the conventional example based on FIG. 14, the sampling point indicating the added peak value is obtained, and the sampling point indicating the added peak value is calculated. The peak point A is obtained from the added value data v1, v2, v3, v4 of four surrounding points in the same manner as in the conventional example, and the distance point B corresponding to the peak point A is calculated.
The memory D of the memory 3e is temporarily used as a distance measurement value (inter-vehicle distance) at the current reception amplification factor Gn (hereinafter, referred to as main amplification factor).
Save to _hold. At the same time, the measured distance value is also output to the relative speed calculation unit 3f. It is assumed that the memory D_hold can store data for at least two times like a shift register, and if new data is written, the data written immediately before is shifted as the data for the previous time. The same applies to memories D_down and D_up described later.

At the timing when the distance measuring operation at a certain main amplification factor Gn ends, the distance measurement order control unit 3a causes the amplification factor control circuit 1e to lower the amplification factor Gn- by one step from the main amplification factor Gn.
The next distance measuring operation is executed by giving a command to change to 1 and at the same time the next distance measuring operation command to the signal processing control section 3b, and the amplification factor Gn which is one step lower than the main amplification factor Gn is executed.
The inter-vehicle distance calculation unit 3c obtains the inter-vehicle distance from the synchronous addition value data at n-1 and stores it in the memory D_down of the memory 3e.

Next, the distance measurement order control unit 3a causes the amplification factor control circuit 1e to increase the amplification factor Gn + by one step from the main amplification factor Gn.
By giving a command to change to 1 and simultaneously giving the next distance measurement operation command to the signal processing control unit 3b, the next distance measurement operation is executed, and the amplification factor Gn + 1 is increased by one step from the main amplification factor Gn. The inter-vehicle distance calculating unit 3c obtains the inter-vehicle distance from the synchronous added value data and stores it in the memory D_up of the memory 3e.

Distance measuring operation with the above main amplification factor Gn and amplification factor Gn-1 one step lower than that and amplification factor G one step higher than that
A total of three distance measuring operations including the distance measuring operation for each of n + 1
It is repeatedly executed to calculate the relative speed once.

In a total of three distance measuring operations for one relative speed calculation, the peak value of the added value data at the main amplification factor Gn obtained by the inter-vehicle distance calculation unit 3c is sent to the reception amplification factor change determination unit 3d. Is also output. Here, the added peak value is compared with the proper range, and if it exceeds the proper range, it is determined that the added value data is saturated, and a command to reduce the received signal amplification factor by one step is output to the amplification factor control circuit 1e. Conversely, if it is lower than the proper range, a command to increase the reception signal amplification factor by one step is output to the amplification factor control circuit 1e.

When it is determined that the main amplification factor is within the proper range and does not need to be changed, when a new set of three distance measuring operations is started, the following distance calculation unit 3c determines that the current amplification factor is present. Memory G for new distance measurement value (distance between vehicles) D in Gn
It is stored in _hold and also output to the relative speed calculation unit 3f.

When a new distance measurement value D is input, the relative speed calculation unit 3f calls the previous distance measurement value stored in the memory D-hold in the memory 3e, and the difference from the current distance measurement value is obtained. Calculates the relative speed between the target object and the vehicle ahead (the preceding vehicle) and outputs it to the alarm distance calculation unit 3g.

The following formula is used as the relative velocity calculation formula in the relative velocity calculation unit 3f. That is, the previous distance measurement value stored in the memory D_hold is D
_hold, the current distance measurement value is D, and the time from the last distance measurement operation to the current distance measurement operation is 3 · ΔT, the current relative speed Vr is calculated based on the following equation (1).

[0067]

## EQU00001 ## Vr = (DD-hold) /3.multidot..DELTA.T (1) where .DELTA.T is the time from one distance measurement to the next distance measurement, that is, the distance measurement cycle (for example, set to 50 msec). Yes,
In this embodiment, one set of three distance measuring operations is performed to calculate one relative speed, so that the time between the last distance measurement with the main amplification factor and the current distance measurement with the main amplification factor is three.・ It becomes ΔT.

However, now, the peak value of the synchronous addition value obtained in a certain distance measuring operation deviates from the proper range,
When the reception amplification factor change determination unit 3d outputs a command to decrease or increase the main amplification factor by one step to the amplification factor control circuit 1e, the amplification factor change command is the relative speed calculation unit 3f.
Also given to.

When the amplification factor change command is output, the amplification factor control circuit 1e controls the received signal amplification factor of the signal amplification circuit 1d to be lowered or raised by one step based on the change command. Then, the above-mentioned one set of three distance measuring operations are newly started, and the distance measuring results are stored as new distance measuring values in the memories D_hold, D_down, and D_up in the memory 3e.

When the one set of three distance measuring operations after the change of the amplification rate is completed, the relative speed calculating section 3f changes the inter-vehicle distance calculating section 3c.
Using the distance measurement value D at the new main amplification rate that is calculated by and the previous distance measurement value stored in the memory D_down if the main amplification rate is one step lower than the previous time,
The relative speed is calculated based on the following equation (1) ′.

[0071]

## EQU00002 ## Vr = (DD-down) /2..DELTA.T (1) 'On the contrary, if the main amplification factor has been raised by one step from the previous one in the current distance measurement, the new main amplification factor Distance measurement value,
Using the previous distance measurement value stored in the memory D_up, the relative speed is calculated based on the following equation (1) ″.

[0072]

## EQU00003 ## Vr = (D-D_up) /. DELTA.T (1) "The relative speed calculated by the relative speed calculation unit 3f is output to the alarm distance calculation unit 3g, where an alarm based on the following equation (2) is generated. The inter-vehicle distance Dw is calculated and given to the warning issuance determination unit 3h.

[0073]

## EQU00004 ## Dw = Vf * t1 + Vr * t2 (2) where Vf is the vehicle speed input from the vehicle speed sensor 4, and Vf
r is the relative speed input from the relative speed calculator 3f, t
1 and t2 are coefficients determined experimentally.

For example, when the current vehicle distance D is large, the own vehicle speed Vf is also large, and the relative speed Vr is large at-,
In other words, if there is a tendency to suddenly approach the preceding vehicle, there is a high risk of a rear-end collision, so it is necessary to issue an alarm. Conversely, even if the current inter-vehicle distance D is small, if the vehicle speed Vf is small and the relative speed Vr is + There is no need to issue an alarm because the risk of a rear-end collision is low because the car tends to leave. Therefore, the warning inter-vehicle distance Dw under the actual traveling condition is determined in real time in consideration of the own vehicle speed Vf and the relative speed Vr based on the equation (2).

In the warning issuing determination unit 3h, the warning inter-vehicle distance Dw input from the warning distance calculation unit 3g and the distance measurement value (current inter-vehicle distance) D input from the inter-vehicle distance calculation unit 3c are compared to determine the current inter-vehicle distance. If D is smaller than the warning inter-vehicle distance Dw, it is determined that the vehicle is too close to the preceding vehicle, an alarm issuance command is output to the alarm buzzer 5, and an inter-vehicle distance alarm is issued to alert the driver.

The relative velocity calculation processing in the series of distance measuring operations described above will be described in detail with reference to the flowcharts of FIGS. In the following processing, a situation in which a vehicle ahead is present and the vehicle is following and traveling will be described as a starting point.

When there is no change in the reception amplification factor between the last distance measurement operation and the newly executed current distance measurement operation, the value of the reception amplification factor change flag G_FLG is 0 (no step change). The step value GAIN is not changed (step S1).

The reception gain of the receiving circuit is set to the main gain GA
Control to IN (step S2). The time ΔT from the last distance measurement operation (this distance measurement cycle is set to, for example, 50 msec, and the timing is adjusted by timer management)
After the lapse of time (step S3), the current distance measuring operation is executed (step S4).

The distance measurement value (inter-vehicle distance) and the added peak value obtained by the distance measurement operation this time are stored in the memory D and the memory PK, respectively (steps S5 and S6).

In this case, since the main amplification factor is not changed, the relative velocity VR is calculated based on the obtained distance measurement value D and the previous distance measurement value D_hold based on the formula shown in step S11, and stored in the memory VR. Store (steps S7, S9, S1
1).

Then, for the next relative velocity calculation, the main amplification factor of this time is lowered by one step, and the distance measurement is performed at each of the increased amplification factors, and the distance measurement values are stored in the memory ( Steps S12 to S20).

Therefore, first, the contents of the memory D are changed to D_hol.
It is stored in d (step S12), the reception amplification factor of the reception circuit is lowered by one step and controlled to the amplification factor GAIN-1 (step S13), and the distance measurement cycle Δ from the previous distance measurement operation of step S4.
After the elapse of T (step S14), the distance measurement operation is performed (step S15), and the distance measurement value with the reception amplification factor reduced by one step is stored in the memory D_down (step S16).

Then, the amplification factor of the receiving circuit is controlled to the gain factor GAIN + 1, which is one step higher than the main amplification factor GAIN (step S17), and similarly, the distance measurement period ΔT elapses from the previous distance measurement operation of step S15. (Step S18), the distance measurement operation is performed (step S19), and the distance measurement value with the reception amplification factor increased by one step is stored in the memory D.
It is stored in _up (step S20).

Next, in order to keep the added peak value PK within the predetermined range, that is, when the proper range lower limit value TH_L and the proper range upper limit value TH_H are set, TH_L <PK <TH_.
Change control of the main amplification factor is performed so that it becomes H (steps S21 to S25).

For this reason, first, if the added peak value PK obtained by the distance measuring operation performed this time is smaller than the proper range lower limit value TH_L, the main amplification factor is set in the distance measuring operation for the next relative speed calculation. The value +1 is stored in G_FLG to increase (steps S21 and S22). Conversely, the added peak value PK
Is larger than the appropriate range upper limit value TH_H, the value -1 is stored in G_FLG in order to lower the main amplification factor in the distance measuring operation for the next relative speed calculation (steps S21, S).
23, S24). If the added peak value PK is within the proper range, it is not necessary to change the reception amplification factor.
The value 0 is stored in FLG (step S25).

Up to this point, one cycle for calculating the relative speed is returned to step S1 again, and the distance measuring operation for calculating a new relative speed is started.

Now, when there is a step change in the reception amplification factor due to the approach or departure from the preceding vehicle, the main amplification is performed according to the value of the reception amplification factor change flag G_FLG determined from the added peak value in the previous distance measurement cycle. The value of the memory GAIN in which the step value of the rate is stored is changed (step S
1) The gain of the receiving circuit is controlled to the main gain GAIN (step S2).

After the time ΔT has passed since the last distance measuring operation (step S3), a new distance measuring operation is performed (step S3).
4) The obtained distance measurement value and added peak value are stored in the memory D and the memory PK, respectively (steps S5 and S6).

Here, if the main amplification factor is lowered by one step from the previous time, that is, the reception amplification factor change flag G_FL.
If G = -1, then the distance measurement value D of this time and the value of the memory D_down measured in the previous cycle with the same amplification factor as this time are used,
The relative speed is calculated based on the arithmetic expression shown in step S8 and stored in the memory VR (steps S7 and S8). On the contrary, if the main amplification factor is increased by one step from the previous time, that is, if the reception amplification factor change flag G_FLG = + 1, the distance measurement is performed this time in the current distance measurement value D and the previous amplification period. Using the value of the memory D_up, step S10
The relative speed is calculated based on the arithmetic expression shown in
Store in R (steps S9 and S10).

Subsequently, the distance measurement value by the main amplification factor is further calculated for the relative speed calculation in the next cycle, and the distance measurement value at each amplification factor which is lowered by one step from the main amplification factor and increased is obtained, and each is stored in the memory D_hold. , Memory D_down, and memory D_up (steps S12 to S20). Then, the adequacy of the added peak value is judged, if it is improper, the reception amplification factor is changed again, and if it is adequate, an allowance is made to leave the reception amplification factor as it is. It will be performed (steps S21 to S25).

In this way, the inter-vehicle distance of the preceding vehicle changes during traveling, it becomes necessary to automatically change the amplification factor of the receiving circuit, and an error occurs in the distance measurement value due to the reception amplification factor before and after the change of the reception amplification factor. However, even after the reception amplification factor is changed, the value obtained by measuring the distance with the same reception amplification factor as that after the change in the previous relative speed calculation cycle is obtained, so the previous measurement with the same reception amplification factor was obtained. It becomes possible to calculate the relative speed using the distance value and the distance measurement value this time, and an accurate relative speed can be obtained.
Therefore, the warning distance calculated on the basis of this also becomes highly accurate, and the reliability of the inter-vehicle distance warning can be increased.

Next, an embodiment of the invention of claim 2 will be described with reference to FIGS.
It will be described with reference to FIG. The inter-vehicle distance monitoring device of this embodiment controls the signal amplification factor of the received light signal to increase or decrease, and obtains an accurate value even when calculating the relative speed using the distance measurement values obtained before and after the amplification factor is changed. On the other hand, when the inter-vehicle distance tends to approach, the distance is measured with the amplification factor which is one step smaller than that when the distance is measured with the main amplification factor. Conversely, when the inter-vehicle distance tends to be separated, the distance is measured with the main amplification factor. Than that 1
When the relative speed is calculated in the next distance measurement operation after the amplification rate is changed, the previous distance measurement value with the same amplification rate as this time is used. It is characterized by being calculated.

The inter-vehicle distance monitoring apparatus of this embodiment has the structure shown in FIG. 4, and most of it is common to the first embodiment shown in FIG. 1, and the common parts are designated by the same reference numerals. Although shown, there is a slight change in the internal configuration of the inter-vehicle distance calculation unit 3. That is, the distance measurement order control unit 3a, which controls the distance measurement processing sequence and gives a control signal to each unit, determines to the amplification factor control circuit 1e the approach tendency and the departure tendency of the inter-vehicle distance after the distance measurement operation at the main amplification factor. It has a function of performing the distance measuring operation by changing the reception amplification factor one step down or up. The memory 3e for storing various distance measurement data is obtained by changing the memory D_main for storing the distance measurement value at the main amplification rate and the reception amplification rate by one step up or down one step. And a memory D_sub for storing the measured distance value.

Next, the operation of the inter-vehicle distance monitor of the second embodiment will be described. The signal processing control unit 3b gives a distance measurement command to the signal processing unit 2 based on the command of the distance measurement order control unit 3a of the inter-vehicle distance calculation unit 3, and the signal processing unit 2 controls the drive circuit 1b of the distance sensor head 1. Then, a drive signal having a constant pulse width is given to the light transmitting section 1a a predetermined number of times N times during one distance measuring operation, and a predetermined number of times N times forward of the light transmitting section 1a is given a constant pulse width at a predetermined period. Is transmitted.

On the other hand, the light receiving section 1c continuously receives an optical signal from the front, converts it into an electric signal and outputs it to the signal amplifying circuit 1d, and amplifies it at a preset amplification factor to the signal processing section 2. Output.

As described in the conventional example with reference to FIG. 14, the signal processing unit 2 binarizes the received light amplified signal and performs the synchronous addition process. The obtained added value data is output to the inter-vehicle distance calculation unit 3c, the sampling point indicating the added peak value is obtained, and the added value data v1, v2, v3, v4 of four points around the sampling point indicating the added peak value are calculated. As in the conventional example, the peak point A is obtained, the corresponding distance point B is indexed, and the current reception amplification factor, that is, the distance measurement value (inter-vehicle distance) at the main amplification factor is temporarily stored in the memory D of the memory 3e.
Save it in _main. At the same time, the measured distance value is also output to the relative speed calculation unit 3f. Note that the memory D_main can store data for at least two times like a shift register, and if new data is written, the data written immediately before is shifted as the data for the previous time. The same applies to the memory D_sub described later.

At the timing when the distance measuring operation at a certain main amplification factor Gn is completed, the distance measurement order control unit 3a determines whether the main amplification factor has changed between the last distance measurement and the current distance measurement. If the distance measurement amplification factor of this time is executed with the same main amplification factor as the distance measurement of the previous time, the relative velocity calculation unit 3f is caused to perform relative velocity calculation. However, if there is a step change between the main amplification factor of the previous distance measurement and the main amplification factor of this distance measurement, the distance measurement was performed last time with the same amplification factor as the current distance measurement value and this time main amplification factor. The relative velocity calculation is executed using the distance measurement value. Then, from the sign of the relative velocity obtained, if it is + or 0, there is a tendency to leave (even if the relative velocity is 0, there is a tendency to leave), so the amplification factor is
If a command to increase the amplification rate is given to the amplification factor control circuit 1e and conversely if the sign of the previous relative speed is −, there is an approaching tendency, so a command to decrease the amplification factor by one step is given to the amplification factor control circuit 1e to change the amplification factor. Then, the distance measurement operation is executed with the changed amplification factor, and the distance measurement value is stored in the memory D_sub of the memory 3e.

Thus, two distance measuring operations, that is, the distance measuring with the main amplification factor Gn and the distance measuring with the amplification factor one step lower or higher than that, constitute one set of distance measuring operations for relative velocity calculation. Is repeatedly executed as.

The peak value of the added value data at the main amplification factor Gn obtained by the inter-vehicle distance calculation unit 3c is also output to the reception amplification factor change determination unit 3d, where the added peak value is compared with the proper range to determine the proper range. If it exceeds, it outputs a command to lower the received signal amplification factor by one step to the amplification factor control circuit 1e on the assumption that the added value data is saturated, and conversely, if it is lower than the proper range, increases the received signal amplification factor by one step. Gain control circuit 1
output to e.

When a new distance measurement value with the main amplification factor is input, the relative speed calculation unit 3f calculates the relative speed according to the following calculation formula (11) or (11) ', and the alarm distance calculation unit 3g receives it. Output.

That is, when there is no change in the main amplification factor between the previous time and this time, the previous distance measurement value D_main stored in the memory D_main, the distance measurement value D at the current main amplification factor D
The current relative velocity Vr is calculated using the following equation (11).

[0102]

Vr = (DD−main) / 2 · ΔT (11) Here, ΔT is the time from one distance measurement to the next distance measurement, that is, the distance measurement cycle (for example, set to 50 msec). Yes,
Since the distance measurement is repeated twice from the last distance measurement with the main amplification rate to the current distance measurement with the main amplification rate, the elapsed time between the two distance measurement values is 2 · ΔT.

However, when there is a change between the previous main amplification factor and the current main amplification factor, measurement with the previous distance measurement value D_sub stored in the memory D_sub and the current main amplification factor are performed. Using the distance value D, the current relative velocity Vr is calculated based on the following equation (11) '.

[0104]

[Equation 6] Vr = (DD−sub) / ΔT (11) ′ Here, from the distance measurement with the amplification factor changed by one step from the previous main amplification factor to the distance measurement with the current main amplification factor. Since the elapsed time is one cycle of the distance measuring operation, it is ΔT.

The relative speed Vr calculated by the relative speed calculation unit 3f is output to the warning distance calculation unit 3g, and the warning inter-vehicle distance Dw is calculated based on the equation (2) as in the first embodiment.
Is calculated and given to the warning issuance determination unit 3h.

In the warning announcement determination unit 3h, the warning inter-vehicle distance Dw input from the warning distance calculation unit 3g is compared with the distance measurement value (current inter-vehicle distance) D input from the inter-vehicle distance calculation unit 3c, and the current inter-vehicle distance is compared. If D is smaller than the warning inter-vehicle distance Dw, it is determined that the vehicle is too close to the preceding vehicle, an alarm issuance command is output to the alarm buzzer 5, and an inter-vehicle distance alarm is issued to alert the driver.

The relative velocity calculation process in the series of distance measuring operations of the above second embodiment will be described in detail with reference to the flowcharts of FIGS. 5 and 6. In the following processing, a situation in which a vehicle ahead is present and the vehicle is following and traveling will be described as a starting point.

When there is no change in the reception amplification factor between the previous distance measurement operation and the newly executed current distance measurement operation, the value of the reception amplification factor change flag G_FLG is 0 (no step change). The step value GAIN is not changed (step S31).

The receiving gain of the receiving circuit is set to the main gain GA.
Control to IN (step S32). Then, after the time ΔT (the distance measuring cycle is set to, for example, 50 msec and the timing is adjusted by timer management) from the last distance measuring operation (step S33), the current distance measuring operation is executed (step S34). .

The distance measurement value (vehicle distance) and the added peak value obtained by the current distance measurement operation are stored in the memory D and the memory PK, respectively (steps S35 and S36).

In this case, since the main amplification factor is not changed, the relative velocity VR is calculated from the obtained distance measurement value D and the previous distance measurement value D_main based on the formula shown in step S39, and stored in the memory VR. Store (steps S37, S3
9).

Next, it is judged from the obtained relative speeds whether the inter-vehicle distance tends to approach or depart, and if there is an approach tendency, distance measurement is performed with an amplification factor that is one step lower than the main amplification factor. On the contrary, if there is a tendency to leave, distance measurement is performed with an amplification factor that is one step higher than the main amplification factor, and the distance measurement value is stored in memory (steps S40 to S45).

Therefore, first, the contents of the memory D are changed to D_mai.
It is stored in n (step S40), whether the relative speed VR is positive or negative is determined (step S41), and if the relative speed VR is + or 0 because there is a tendency to leave (even if the relative speed is 0, there is a tendency to leave. G) to increase the amplification rate by one step
AIN + 1 is controlled (step S42), and conversely, if the relative speed VR is-because of the approaching tendency, GAIN-1 is controlled to lower the amplification factor by one step (step S4).
3), distance measuring cycle ΔT from the last distance measuring operation in step S34
Is waited for (step S44), the distance measurement operation is performed (step S45), and the distance measurement value with the one-step reception amplification factor changed is stored in the memory D_sub (step S46).

Next, in order to keep the added peak value PK within the predetermined range, that is, when the proper range lower limit value TH_L and the proper range upper limit value TH_H are set, TH_L <PK <TH_.
Change control of the main amplification factor is performed so that it becomes H (steps S47 to S51).

For this reason, first, if the added peak value PK obtained by the distance measuring operation performed this time is smaller than the proper range lower limit value TH_L, the main amplification factor is set in the distance measuring operation for the next relative speed calculation. The value +1 is stored in G_FLG to increase (steps S47 and S48). Conversely, the added peak value PK
Is larger than the appropriate range upper limit value TH_H, the value -1 is stored in G_FLG in order to lower the main amplification factor in the distance measuring operation for the next relative speed calculation (steps S47, S).
49, S50). If the added peak value PK is within the proper range, it is not necessary to change the reception amplification factor.
The value 0 is stored in FLG (step S51).

Up to this point, one cycle for calculating the relative speed is returned to step S31, and the distance measuring operation for calculating a new relative speed is started.

Now, if there is a step change in the reception amplification factor due to the approach or departure from the preceding vehicle, the main amplification is performed according to the value of the reception amplification factor change flag G_FLG determined from the added peak value in the previous distance measurement cycle. The value of the memory GAIN in which the step value of the rate is stored is changed (step S
31), the gain of the receiving circuit is set to the main gain GAIN
Control (step S32).

After the time ΔT has passed since the last distance measuring operation (step S33), a new distance measuring operation is performed (step S34), and the obtained distance measuring value and added peak value are stored in the memory D and the memory PK, respectively. (Steps S35, S3
6).

Here, if the main amplification factor is changed by one step from the previous time, that is, the reception amplification factor change flag G_FLG.
If it is not = 0, the relative velocity VR is calculated based on the arithmetic expression shown in step S38 using the current distance measurement value D and the value of the memory D_sub measured at the same amplification factor as the current cycle in the previous cycle. , Memory VR (steps S37, S3)
8).

Then, the distance measurement value based on the main amplification factor is calculated for the relative speed calculation in the next cycle, and the distance measurement value at the amplification ratio one step higher or lower than the main amplification factor according to whether the relative speed is positive or negative. It is obtained and stored in the memory D_sub (steps S40 to S46). Then, the adequacy of the added peak value is judged, and if it is improper, the reception amplification factor is changed again, and if it is adequate, an allowance is made to leave the reception amplification factor as it is. It will be performed (steps S47 to S51).

As described above, according to the second embodiment, the inter-vehicle distance of the preceding vehicle changes while the vehicle is running, and it is necessary to automatically change the amplification factor of the reception circuit. The reception amplification factor before and after the reception amplification factor is changed. Even if there is an error in the distance measurement value due to, even if the reception amplification rate is changed, the value obtained with the same reception amplification rate as the reception amplification rate after the change to the previous relative speed calculation cycle is obtained. , It becomes possible to calculate the relative speed by using the previous distance measurement value and the current distance measurement value with the same reception amplification rate, and the accurate relative speed can be obtained. Therefore, the alarm distance calculated based on this can also be calculated. The accuracy becomes high and the reliability of the inter-vehicle distance warning can be increased.

In addition, in the case of the second embodiment, the main amplification factor and 1 are used to calculate the relative speed once.
Since it suffices to measure the distance twice each with the amplification factor changed up or down, the response time can be made shorter than the response time when the distance is measured three times as in the first embodiment.

Next, one embodiment of the invention of claim 3 will be described with reference to FIGS.
This will be described with reference to FIG. In the first embodiment shown in FIG. 1, the main amplification factor is calculated every relative velocity measurement cycle so that the relative velocity can be calculated using the distance measurement value of the same amplification factor before and after the change of the proper reception amplification factor. In the third embodiment, the distance measurement is performed at a total of three times together with the distance measurement with the amplification factor changed by one step above and below.
In the light transmission circuit with the function of variably adjusting the signal output level, the relative speed can be calculated each time using the distance measurement value at the same signal output level before and after changing the appropriate signal output level. It is characterized by performing the distance measurement at the proper output level for each relative speed measurement cycle, lowering it by one step, and measuring the distance at the increased output level for a total of three times.

Therefore, most of the circuit structure is common to that of the first embodiment shown in FIG. 1, and the common parts are designated by the same reference numerals. There is a slight change in the internal configuration of the calculation unit 3. That is, the distance sensor head 1 is composed of an LED or a laser light emitting diode, and is a light transmitting unit 1a that forwards an optical signal.
And a drive circuit 1b 'with an output adjusting function capable of causing the light transmitting section 1a to emit light with a constant pulse width at a constant cycle and variably adjusting the light emission output level in a stepwise manner, and receiving an optical signal to receive an electrical signal. A light receiving section 1c which is composed of a photodiode which converts the light into a light and outputs the light signal from the light transmitting section 1a, which continuously receives the light signal from the direction in which the light signal is reflected and returned to the target in front, and the light receiving section 1c It is composed of a signal amplifier circuit 1d 'for amplifying the signal of the section 1c and a drive current control circuit 1f for stepwise controlling the drive current for adjusting the output of the drive circuit 1b'.

The inter-vehicle distance calculation unit 3 is composed of a computer. When the functions of each calculation process are decomposed and shown, the distance measurement order control unit 3a which controls the distance measurement process sequence and gives a control signal to each unit, A signal processing control unit 3b that controls the timing of transmitting an optical signal and a processing timing of a received light signal, an inter-vehicle distance calculating unit 3c that performs an inter-vehicle distance calculation, and a drive that determines the necessity of changing the signal output level of the light transmission signal. A current change determination unit 3j, a memory 3e for storing various ranging data,
The relative speed calculator 3f for calculating the relative speed, the alarm distance calculator 3g for calculating the alarm distance based on the vehicle speed from the vehicle speed sensor 4 and the relative speed from the relative speed calculator 3f, and the alarm distance calculator 3g. An alarm issue determination unit 3h is configured to compare the required alarm distance with the current inter-vehicle distance determined by the inter-vehicle distance calculation unit 3c to determine the necessity of issuing an alarm and control the alarm buzzer 5 to issue an alarm.

The signal processing unit 2, the vehicle speed sensor 4, and the alarm buzzer 5 are the same as those in the first and second embodiments.

Next, the operation of the inter-vehicle distance monitoring system of the third embodiment having the above construction will be described. Based on a command from the ranging order control unit 3a of the inter-vehicle distance calculation unit 3, the signal processing control unit 3
A distance measurement command is given to the signal processing unit 2 from b, and the signal processing unit 2 activates the drive circuit 1b ′ of the distance sensor head 1 to
A drive signal having a constant pulse width is given to the light transmitting section 1a a predetermined number of times N times during the distance measurement operation, and an optical signal having a constant pulse width is given a predetermined number of times N times forward from the light transmitting section 1a. Is sent. At this time, the drive current of the light transmitting unit 1a by the drive circuit 1b 'is controlled to an appropriate value by the drive current control circuit 1f.

On the other hand, the light receiving section 1c continuously receives optical signals from the front. When the received light signal does not include the reflected signal from the preceding vehicle, which is the target in the front, that is, when there is no vehicle ahead, the optical signal at the noise level is received and converted into an electric signal. The signal is output to the amplifier circuit 1d ′, amplified here and output to the signal processing unit 2. However, in this case, since the received light signal has a noise level, the signal binarized by the signal processing unit 2 is a signal in which “0” and “1” appear at almost the same probability, and the binarized signal is transmitted. Even if the addition processing is performed for each sampling point N times a predetermined number of times in synchronization with the optical timing, the added value at each sampling point becomes a noise level of approximately N / 2, and the inter-vehicle distance cannot be obtained.

However, when there is a vehicle ahead and the light signal reflected by the preceding vehicle and returned is received by the light receiving section 1c, the signal processing section 2 performs binarization processing,
The added value level characteristic obtained by the synchronous addition processing is shown in FIG.
B4.

This added value data is output to the inter-vehicle distance calculation unit 3c, and as described in the conventional example based on FIG. 14, the sampling point indicating the added peak value is obtained, and the sampling point indicating the added peak value is calculated. The peak point A is obtained from the added value data v1, v2, v3, v4 of four surrounding points in the same manner as in the conventional example, and the distance point B corresponding to the peak point A is calculated.
The memory 3 is temporarily stored as the distance measurement value (inter-vehicle distance) at the current light transmission signal output level Pn (hereinafter referred to as the main output level).
It is stored in the memory D_hold of e. At the same time, the measured distance value is also output to the relative speed calculation unit 3f. It is assumed that the memory D_hold can store data for at least two times like a shift register, and if new data is written, the data written immediately before is shifted as the data for the previous time. Memory D_down and memory D_u described later
The same is true for p.

At the timing when the distance measuring operation at a certain main output level Pn is completed, the distance measuring order control unit 3a instructs the drive current control circuit 1f to change the main output level Pn to the output level Pn-1 which is one step lower. And at the same time the next distance measuring operation command is given to the signal processing control unit 3b, the next distance measuring operation is executed, and the main output level Pn becomes 1
The inter-vehicle distance calculation unit 3c obtains the inter-vehicle distance from the synchronous added value data at the step-down output level Pn-1 and stores it in the memory D_down of the memory 3e.

The distance measurement sequence control section 3a then gives a command to the drive current control circuit 1f to change from the main output level Pn to the output level Pn + 1 increased by one step, and at the same time, the signal processing control section 3b receives the next measurement. A distance measurement operation is executed one after another by giving a distance operation command, and the vehicle distance calculation unit 3c obtains the vehicle distance from the synchronous addition value data at the output level Pn + 1 which is one step higher than the main output level Pn, and the memory 3e is obtained. Save to memory D_up of.

The distance measurement operation at the main output level Pn and the output level Pn-1 which is one step lower than that, and the distance measurement operation at the output level Pn + 1 which is one step lower than that are performed three times in total. The distance operation is repeatedly executed for one relative velocity calculation.

In a total of three distance measuring operations for one relative speed calculation, the peak value of the additional value data at the main output level Pn obtained by the inter-vehicle distance calculating section 3c is also supplied to the drive current change judging section 3j. The output peak value is compared with the appropriate range, and if it exceeds the appropriate range, it is determined that the additional value data is saturated, and a command to decrease the signal output level by one step is output to the drive current control circuit 1f, and the reverse operation is performed. If it is lower than the proper range, a command to increase the signal output level by one step is output to the drive current control circuit 1f.

When it is determined that the main output level is within the proper range and does not need to be changed, when a new set of three distance measuring operations is started, the following distance calculation unit 3c is started.
Stores a new distance measurement value (inter-vehicle distance) D at the current output level Pn in the memory D_hold, and at the same time, the relative speed calculation unit 3f
Also output.

When a new distance measurement value is input, the relative speed calculation unit 3f calls the previous distance measurement value stored in the memory D_hold in the memory 3e, and detects the difference from the current distance measurement value to the front. The relative speed with respect to the target (preceding vehicle) is calculated and output to the alarm distance calculation unit 3g.

As the relative speed calculation formula in the relative speed calculation unit 3f, the formula (1) shown in the first embodiment is used.

However, the synchronous addition peak value obtained by a certain distance measuring operation deviates from the proper range, and the drive current change judging section 3j issues a command to lower or raise the main output level by one step. When the output is output to, the output level change command is also given to the relative speed calculator 3f.

When the output level change command is output, the drive current control circuit 1f performs control to lower or increase the signal output level of the drive circuit 1b 'by one step based on the change command. Then, the above-mentioned one set of three distance measuring operations are newly started, and the distance measuring results are stored as new distance measuring values in the memories D_hold, D_down, and D_up in the memory 3e.

When the one set of three distance measuring operations after the output level change is completed, the relative speed calculation unit 3f calculates the distance measurement value D at the new main output level obtained by the inter-vehicle distance calculation unit 3c,
If the main output level is one step lower than the previous one, the relative speed is calculated based on the above equation (1) 'using the previous distance measurement value stored in the memory D_down. On the contrary, if the main output level is one step higher than the previous one in the current distance measurement, the distance measurement value at the new main output level and the previous distance measurement value stored in the memory D_up are used. Then, the relative speed is calculated based on the above-mentioned formula (1) ″.

The relative speed thus calculated by the relative speed calculation unit 3f is output to the warning distance calculation unit 3g, where the warning inter-vehicle distance Dw is calculated based on the above equation (2) and given to the warning issuance determination unit 3h. To be

In the warning issuing determination unit 3h, the warning inter-vehicle distance Dw input from the warning distance calculation unit 3g and the distance measurement value (current inter-vehicle distance) D input from the inter-vehicle distance calculation unit 3c are compared to determine the current inter-vehicle distance. If D is smaller than the warning inter-vehicle distance Dw, it is determined that the vehicle is too close to the preceding vehicle, an alarm issuance command is output to the alarm buzzer 5, and an inter-vehicle distance alarm is issued to alert the driver.

The relative velocity calculation processing in the series of distance measuring operations described above will be described in detail with reference to the flowcharts of FIGS. 8 and 9. In the following processing, a situation in which a vehicle ahead is present and the vehicle is following and traveling will be described as a starting point.

When there is no change in the output level between the previous distance measuring operation and the newly executed current distance measuring operation, the value of the output level change flag L_FLG is 0 (no step change), so the main output level step value LEVEL is not changed (step S61).

The output level of the light transmitting circuit is controlled to the main output level LEVEL (step S62). The time ΔT from the last distance measurement operation (this distance measurement cycle is, for example, 50 ms
After ec is set and the timing is adjusted by timer management (step S63), the current distance measuring operation is executed (step S64).

The distance measurement value (vehicle distance) and the added peak value obtained by the distance measurement operation this time are stored in the memory D and the memory PK, respectively (steps S65 and S66).

In this case, since the main output level is not changed, the relative speed VR is calculated from the obtained distance measurement value D and the previous distance measurement value D_hold based on the formula shown in step S71, and stored in the memory VR. Store (steps S67, S69,
S71).

Then, for the next relative velocity calculation, the distance is measured at each of the output levels raised or lowered by one step with respect to the main output level of this time, and the distance measurement values are stored in the memory ( Steps S72 to S80).

For that purpose, first, the contents of the memory D are changed to D_hol.
The value is stored in d (step S72), the output level of the light transmitting circuit is lowered by one step to control the output level LEVEL-1 (step S73), and the distance measurement period ΔT elapses from the previous distance measurement operation of step S64. Wait (step S74),
A distance measurement operation is performed (step S75), and the distance measurement value with the one-step output level lowered is stored in the memory D_down (step S76).

Subsequently, the output level LEV obtained by raising the output level of the light transmitting circuit by one step from the main output level LEVEL.
EL + 1 is controlled (step S77), and similarly, waiting for the distance measurement period ΔT to elapse from the previous distance measurement operation of step S75 (step S78), the distance measurement operation is performed (step S79), and this one-stage output is performed. The distance measurement value with the level raised is stored in the memory D_up (step S80).

Next, in order to keep the added peak value PK within the predetermined range, that is, when the proper range lower limit value TH_L and the proper range upper limit value TH_H are set, TH_L <PK <TH_.
The main output level is controlled to be changed to H (steps S81 to S85).

For this reason, first, if the added peak value PK obtained by the distance measuring operation performed this time is smaller than the proper range lower limit value TH_L, the main output level is set in the distance measuring operation for the next relative speed calculation. The value +1 is stored in L_FLG to increase (steps S81 and S82). On the contrary, if the added peak value PK is larger than the appropriate range upper limit value TH_H, the value -1 is stored in L_FLG in order to lower the main output level in the distance measuring operation for the next relative speed calculation (step S).
81, S83, S84). If the added peak value PK is within the proper range, it is not necessary to change the output level, so the value 0 is stored in L_FLG (step S85).

The processing up to this point is regarded as one cycle for calculating the relative speed, and the process returns to step S61 again to start the distance measuring operation for calculating the new relative speed.

If there is a step change in the output level due to the approaching or leaving of the preceding vehicle, the main output level of the main output level is changed according to the value of the output level change flag L_FLG determined from the added peak value in the previous distance measurement cycle. The value of the memory LEVEL in which the step value is stored is changed (step S61), and the output level of the light transmitting circuit is controlled to this main output level LEVEL (step S62).

After the time ΔT has elapsed from the last distance measuring operation (step S63), a new distance measuring operation is performed (step S64), and the obtained distance measuring value and added peak value are stored in the memory D and the memory PK, respectively. (Steps S65, S6
6).

If the main output level is lowered by one step from the previous time, that is, the output level change flag L_
If FLG = -1, the relative speed is calculated based on the arithmetic expression shown in step S68 using the current distance measurement value D and the value of the memory D_down measured at the same output level as this time in the previous cycle. And stores it in the memory VR (step S6).
7, S68). Conversely, the main output level is 1 more than the previous time
If it is stepped up, that is, the output level change flag L
If _FLG = + 1, the relative speed is calculated based on the calculation formula shown in step S70 using the current distance measurement value D and the value of the memory D_up measured at the same output level as this time in the previous cycle. , Memory VR (step S6)
9, S70).

Then, the distance measurement value at the main output level is lowered by one step and the distance measurement value at each output level raised for the relative speed calculation in the next cycle is calculated, and the distance measurement value at each output level is calculated. , Memory D_dow
n, stored in the memory D_up (steps S72 to S8)
0). Then, the adequacy of the added peak value is judged, if it is improper, the output level is changed again, and if it is adequate, an allowance is made to leave the output level as it is, and the process returns to step S61 to perform distance measurement in the next cycle. (Steps S81-
S85).

Thus, according to the third embodiment, the inter-vehicle distance of the preceding vehicle changes during traveling, and it becomes necessary to automatically change the output level of the light transmitting circuit. Even if there is an error in the distance measurement value, the value measured at the same output level as the output level after the change to the previous relative speed calculation cycle is obtained even after the output level is changed. It is now possible to calculate the relative speed using the previous distance measurement value and the current distance measurement value, and the accurate relative speed can be obtained. Therefore, the alarm distance calculated based on this can be highly accurate. The reliability of the inter-vehicle distance warning can be increased.

Next, an embodiment of the invention of claim 4 is shown in FIG.
~ It demonstrates based on FIG. The inter-vehicle distance monitoring apparatus of this embodiment controls the signal output level of the light transmission signal to increase or decrease, and obtains an accurate value even when calculating the relative speed using the distance measurement values obtained before and after the output level change. Therefore, when the inter-vehicle distance tends to approach, the distance is measured at the main output level even when the output level is one step smaller than that at the main output level, and conversely when the inter-vehicle distance tends to leave, the distance is measured at the main output level. Sometimes, even if the output level is increased by one step, the distance is measured and saved, and when calculating the relative speed in the distance measurement operation after the next output level change, the previous measurement of the same output level as the current output level is performed. The feature is that calculation is performed using a distance value.

The inter-vehicle distance monitoring system of this embodiment has the structure shown in FIG. 10, and most of it is common to the third embodiment shown in FIG. 7, and the common parts are designated by the same reference numerals. Although shown, there is a slight change in the internal configuration of the inter-vehicle distance calculation unit 3. That is, the distance measurement order control unit 3a, which controls the distance measurement processing sequence and gives a control signal to each unit, determines to the driving current control circuit 1f whether the inter-vehicle distance is approaching or leaving after the distance measuring operation at the main output level. It has a function of changing the output level by one step or up to perform the distance measuring operation. The memory 3e for storing various distance measurement data is obtained by changing the memory D_main for storing the distance measurement value at the main output level and the output level by one step up or down. It has a memory D_sub for storing distance measurement values.

Next, the operation of the inter-vehicle distance monitoring system of the fourth embodiment will be described. Based on the command from the distance measurement order control unit 3a of the inter-vehicle distance calculation unit 3, the signal processing control unit 3b gives a distance measurement command to the signal processing unit 2, and the signal processing unit 2 drives the drive circuit 1b ′ of the distance sensor head 1. A driving signal having a constant pulse width is given to the light transmitting section 1a a predetermined number of times N times during one distance measuring operation by controlling, and a predetermined number of times N times of constant pulses are transmitted forward from the light transmitting section 1a at a predetermined period. The width of the optical signal is transmitted.

On the other hand, the light receiving section 1c continuously receives an optical signal from the front, converts it into an electrical signal, and a signal amplifier circuit 1d '.
To the signal processing unit 2.

As described in the conventional example with reference to FIG. 14, the signal processing unit 2 binarizes the received light amplified signal and performs the synchronous addition process. The obtained added value data is output to the inter-vehicle distance calculation unit 3c, the sampling point indicating the added peak value is obtained, and the added value data v1, v2, v3, v4 of four points around the sampling point indicating the added peak value are calculated. As in the conventional example, the peak point A is obtained, the distance point B corresponding to the peak point A is determined, and the distance measurement value (inter-vehicle distance) at the current output level, that is, the main output level is temporarily stored in the memory D_main of the memory 3e. To do. At the same time, the measured distance value is also output to the relative speed calculation unit 3f. The memory D_main
Like a shift register, the data can be stored at least twice, and when new data is written, the data written immediately before is shifted as the data for the previous time. The same applies to the memory D_sub described later.

At the timing when the distance measuring operation at a certain main output level Pn is completed, the distance measuring order control unit 3a determines whether or not the main output level is changed between the last distance measuring and the current distance measuring. If the current distance measurement output level is being executed at the same main output level as the previous distance measurement, the relative speed calculation unit 3f is caused to execute the relative speed calculation.
However, if there is a step change between the main output level of the previous distance measurement and the main output level of the current distance measurement, the previous distance measurement was performed at the same output level as this measurement value and this main output level. The relative velocity calculation is executed using the distance measurement value. From the sign of the relative speed obtained, if it is + or 0, there is a tendency to leave (even if the relative speed is 0, there is a tendency to leave). Therefore, an instruction to increase the output level by one step is issued to the drive current control circuit 1f. On the contrary, if the sign of the previous relative speed is −, there is a tendency to approach, so a command to lower the output level by one step is given to the drive current control circuit 1f to change the output level, and the output level after the change is applied. The distance measurement operation is executed, and the distance measurement value is stored in the memory D_sub of the memory 3e.

Thus, two distance measuring operations, that is, the distance measuring at the main output level Pn and the distance measuring at the output level one step lower or higher than that, constitute one set of distance measuring operations for relative velocity calculation. Is repeatedly executed as.

The peak value of the added value data at the main output level Pn obtained by the inter-vehicle distance calculation section 3c is also output to the drive current change determination section 3j, where the added peak value is compared with the appropriate range to determine the appropriate range. If it exceeds, it is considered that the added value data is saturated and a command to decrease the signal output level by one step is output to the drive current control circuit 1f. Conversely, if it is lower than the appropriate range, a command to increase the signal output level by one step is issued. Output to the control circuit 1f.

When a new distance measurement value at the main output level is input, the relative speed calculator 3f calculates the relative speed by the calculation formula (11) or (11) 'used in the second embodiment, Output to the alarm distance calculation unit 3g.

That is, when there is no change in the main output level between the previous time and this time, the previous distance measurement value D_main stored in the memory D_main and the distance measurement value D at the current main output level are used. The current relative speed Vr is calculated based on the equation (11), and if there is a change between the previous main output level and the current main output level, the memory D_sub
Using the previous distance measurement value D_sub and the current distance measurement value D at the main output level, the current relative velocity Vr is calculated based on the equation (11) '.

The relative speed Vr calculated by the relative speed calculation unit 3f is output to the warning distance calculation unit 3g, and the warning inter-vehicle distance Dw is calculated based on the equation (2) as in the first embodiment.
Is calculated and given to the warning issuance determination unit 3h.

In the warning issuing determination section 3h, the warning inter-vehicle distance Dw input from the warning distance calculation section 3g and the distance measurement value (current inter-vehicle distance) D input from the inter-vehicle distance calculation section 3c are compared to determine the current inter-vehicle distance. If D is smaller than the warning inter-vehicle distance Dw, it is determined that the vehicle is too close to the preceding vehicle, an alarm issuance command is output to the alarm buzzer 5, and an inter-vehicle distance alarm is issued to alert the driver.

The relative velocity calculation processing in the series of distance measuring operations of the above fourth embodiment will be described in detail with reference to the flowcharts of FIGS. 11 and 12. In the following processing, a situation in which a vehicle ahead is present and the vehicle is following and traveling will be described as a starting point.

When there is no change in the output level between the previous distance measurement operation and the newly executed current distance measurement operation, the value of the output level change flag L_FLG is 0 (no step change), so the main output level step value LEVEL is not changed (step S91).

The output level of the light transmitting circuit is controlled to an appropriate main output level LEVEL (step S92). The time ΔT from the last distance measurement operation (this distance measurement cycle is, for example,
After the time is set to 50 msec and the timing is adjusted by the timer management) (step S93), the current distance measuring operation is executed (step S94).

The distance measurement value (vehicle distance) and the added peak value obtained by the distance measurement operation this time are stored in the memory D and the memory PK, respectively (steps S95 and S96).

In this case, since the main output level is not changed, the relative speed VR is calculated from the obtained distance measurement value D and the previous distance measurement value D_main based on the formula shown in step S99, and stored in the memory VR. Store (steps S97, S9
9).

Subsequently, it is judged from the obtained relative speeds whether the inter-vehicle distance tends to approach or leave, and if there is an approach tendency, distance measurement is performed at an output level that is one step lower than the main output level. Conversely, if there is a tendency to leave, distance measurement is performed at an output level that is one step higher than the main output level, and the measured distance value is stored in memory (steps S100 to S1).
05).

Therefore, first, the contents of the memory D are changed to D_mai.
The value is stored in n (step S100), and whether the relative speed VR is positive or negative is determined (step S101). If the relative speed VR is + or 0 because the vehicle has a tendency to leave (even if the relative speed is 0, the tendency to leave is detected. LEVEL + 1 to raise the output level by one level (assuming that there is) (step S102),
On the contrary, if the relative velocity VR is negative due to the approaching tendency, the output level is controlled to LEVEL-1 to decrease by one step (step S103), and the distance measuring cycle ΔT elapses from the previous distance measuring operation of step S104. Wait for (step S
104), the distance measurement operation is performed (step S105), and the distance measurement value in the state in which the one-step output level is changed is stored in the memory D_sub (step S106).

Next, in order to keep the added peak value PK within the predetermined range, that is, when the proper range lower limit value TH_L and the proper range upper limit value TH_H are set, TH_L <PK <TH_.
The main output level is controlled to change to H (steps S107 to S111).

For this reason, first, if the added peak value PK obtained in the distance measuring operation performed this time is smaller than the proper range lower limit value TH_L, the main output level is set in the distance measuring operation for the next relative speed calculation. The value +1 is stored in L_FLG to increase (steps S107 and S108). Conversely, if the added peak value PK is larger than the appropriate range upper limit value TH_H, the value -1 is stored in L_FLG in order to lower the main output level in the distance measurement operation for the next relative speed calculation (steps S107 and S109). , S110). Then, if the added peak value PK is within the proper range, there is no need to change the output level, so the value 0 is stored in L_FLG (step S111).

The process up to this point is regarded as one cycle for calculating the relative speed, and the process returns to step S91 again to start the distance measuring operation for calculating the new relative speed.

If there is a step change in the output level due to the approaching or leaving of the preceding vehicle, the main output level of the main output level is changed according to the value of the output level change flag L_FLG determined from the added peak value in the previous distance measurement cycle. The value of the memory LEVEL in which the step value is stored is changed (step S91), and the output level of the light transmitting circuit is controlled to this main output level LEVEL (step S92).

After the time ΔT has passed since the last distance measuring operation (step S93), a new distance measuring operation is performed (step S94), and the obtained distance measuring value and added peak value are stored in the memory D and the memory PK, respectively. (Steps S95, S9
6).

Here, if the main output level is changed by one step from the previous time, that is, the output level change flag L_F.
If LG = 0, the relative velocity VR is calculated based on the arithmetic expression shown in step S98 using the current distance measurement value D and the value of the memory D_sub measured at the same output level as this time in the previous cycle. And stores it in the memory VR (step S9).
7, S98).

Subsequently, the distance measurement value based on the main output level for the calculation of the relative speed in the next cycle, and the distance measurement value at the output level one step above or below the main output level depending on whether the relative speed is positive or negative. It is obtained and stored in the memory D_sub (steps S100 to S106). Then, the adequacy of the added peak value is judged, if it is improper, the output level is changed again, and if it is adequate, the output level is kept as it is, and the process returns to step S91 to perform the distance measurement in the next cycle. (Steps S107 to S111).

As described above, according to the fourth embodiment, the inter-vehicle distance of the preceding vehicle changes during traveling, and it becomes necessary to automatically change the output level of the light transmitting circuit. The output level before and after the output level is changed. Even if there is an error in the distance measurement value due to, even if the output level is changed, the value is measured at the same output level as the output level after the change to the previous relative speed calculation cycle, so the same output The relative speed can now be calculated using the previous distance measurement value and the current distance measurement value at the level, and the accurate relative speed can be obtained. Therefore, the alarm distance calculated based on this can be highly accurate. Therefore, it becomes possible to increase the reliability of the inter-vehicle distance warning.

In addition, in the case of the fourth embodiment, the distance is measured twice each with the main output level and the output level changed one step above or below for calculating the relative speed once. Therefore, the response time can be made faster than in the case where the distance measurement is performed three times as in the third embodiment.

[0187]

As described above, in the inter-vehicle distance monitoring apparatus according to the first aspect of the present invention, the distance measurement for amplifying the received signal at the proper reception amplification factor for each relative speed calculation, binarizing it, and then synchronously adding it. Along with the operation, it is increased by one step from the proper reception amplification rate, and it is changed to the lowered amplification rate and the reception signal is amplified in the same way.
The inter-vehicle distance obtained in each of the three distance measuring operations including the binarizing and the synchronous addition operation is stored, and the relative speed is calculated by calculating the relative speed of one set of three times. If the proper reception amplification factor has been changed between the distance measurement operation for this purpose and this time of one set of three times the distance measurement operation, the inter-vehicle distance obtained by distance measurement with the current proper reception amplification factor and the previous time Since the relative speed calculation is performed using the inter-vehicle distance obtained by distance measurement with the same reception amplification factor of, even if the proper reception amplification factor is changed and adjusted,
The relative speed can be calculated using the inter-vehicle distance obtained by measuring the distance with the same reception amplification factor before and after the adjustment, and the relative speed can be calculated with high accuracy, improving the reliability of the inter-vehicle distance warning. You can

According to the inter-vehicle distance monitoring system of the invention of claim 2,
Along with the distance measurement operation that amplifies the received signal with an appropriate reception amplification factor for each relative speed calculation, binarizes it, and then synchronously adds,
If the inter-vehicle distance tends to approach, the level is lowered by one step from the proper reception amplification rate. Conversely, if the inter-vehicle distance tends to leave, the level is increased by one step from the proper reception amplification rate. A total of two distance-measuring operations including a distance-measuring operation of amplifying, binarizing, and then synchronously adding are repeated, and the inter-vehicle distances obtained in each are stored, and in calculating the relative speed, one set of 2
If the proper reception amplification factor is changed between the distance measurement operation for calculating the relative speed of one time and the distance measurement operation of this set of two times, the distance is measured with the current proper reception amplification ratio. Since the relative speed calculation is performed using the obtained inter-vehicle distance and the inter-vehicle distance obtained by changing the previous proper amplification factor by one step, even if the proper reception amplification factor is changed and adjusted, The relative speed can be calculated using the inter-vehicle distance obtained by distance measurement with the same reception amplification factor before and after the adjustment, and the relative speed can be calculated with high accuracy, and the reliability of the inter-vehicle distance warning can be improved. it can.

Further, in the case of the invention of claim 2, in each distance measuring operation, one set of the proper reception amplification rate and the reception amplification rate which is changed by one step up or down by one step are used to set the reception amplification rate twice. Since the relative speed is calculated by using the inter-vehicle distance obtained by each of the distance measurement operations in step 1, the response speed can be increased.

According to the inter-vehicle distance monitoring device of the invention of claim 3,
It outputs a signal at an appropriate output level for each relative speed calculation, receives the reflected signal from the target, binarizes the amplified signal, and then adds the signals synchronously with the distance measurement operation, and one step higher than the appropriate output level. Change the output level to raised or lowered, send out the same signal, receive the reflected signal from the target, and add the distance synchronously. Save it and calculate the relative speed.
If the proper output level is changed between the previous distance measurement operation for calculating the relative speed of one set and three times and the current distance measurement operation of one set of three times, the measurement is performed at the appropriate output level of this time. Since the relative speed is calculated using the inter-vehicle distance obtained by distance measurement and the inter-vehicle distance obtained by distance measurement at the same output level of the previous time, even if the appropriate output level is changed and adjusted, before and after the adjustment. The relative speed can be calculated using the inter-vehicle distance obtained by distance measurement at the same output level, and the relative speed can be calculated with high accuracy, and the reliability of the inter-vehicle distance warning can be improved.

According to the inter-vehicle distance monitoring apparatus of the invention of claim 4,
A signal is sent at an appropriate output level for each relative speed calculation, the reflected signal from the target is received, and the amplified signal is binarized and then added synchronously. For example, if the inter-vehicle distance tends to deviate from the proper output level by one step, and conversely, the output level is raised by one step from the proper output level and the same signal is sent, and the reflected signal from the target is received. Then, a total of two distance measurement operations including the distance measurement operation of synchronously adding and repeating are performed, and the inter-vehicle distances obtained in each are stored, and the previous one set 2
If the proper output level is changed between the distance measurement operation for calculating the relative speed of one time and the distance measurement operation of one set and two times this time, the distance measurement is performed at the appropriate output level this time. Since the relative speed calculation is performed using the inter-vehicle distance and the inter-vehicle distance when the distance is measured by changing the previous appropriate output level by one step, even if the appropriate output level is changed and adjusted, before and after the adjustment. The relative speed can be calculated using the inter-vehicle distance obtained by distance measurement at the same output level, the relative speed can be calculated with high accuracy, and the reliability of the inter-vehicle distance warning can be improved.

Further, in the case of the invention of claim 4, in each distance measuring operation, a set of the proper output level and the output level which is changed by one step up or down by one step is measured by two sets of output levels. Since the relative speed is calculated using the inter-vehicle distance obtained by each distance operation, the response speed can be increased.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a first embodiment of the present invention.

FIG. 2 is a first half flowchart of a relative speed calculation process according to the first embodiment.

FIG. 3 is a flowchart of the latter half of the relative speed calculation process of the first embodiment.

FIG. 4 is a circuit block diagram of a second embodiment of the present invention.

FIG. 5 is a flowchart of the first half of the relative velocity calculation process of the second embodiment.

FIG. 6 is a flowchart of the latter half of the relative speed calculation process of the second embodiment.

FIG. 7 is a circuit block diagram of a third embodiment of the present invention.

FIG. 8 is a flowchart of the first half of the relative velocity calculation process of the third embodiment.

FIG. 9 is a second half flow chart of the relative speed calculation process of the third embodiment.

FIG. 10 is a circuit block diagram of a fourth embodiment of the present invention.

FIG. 11 is a flowchart of the first half of the relative speed calculation process of the fourth embodiment.

FIG. 12 is a flowchart of the latter half of the relative speed calculation process of the fourth embodiment.

FIG. 13 is a circuit block diagram of a conventional example.

FIG. 14 is a waveform diagram illustrating a signal processing operation of a conventional example.

FIG. 15 is a waveform diagram illustrating a reception amplification factor change determination processing operation of a conventional example.

FIG. 16 is a waveform chart showing a change in distance measurement accuracy before and after a reception amplification factor is changed in the conventional example.

FIG. 17 is a waveform diagram showing an error caused by a correction process after the reception amplification factor is changed in the conventional example.

[Explanation of symbols]

 1 distance sensor head 1a light transmitter 1b drive circuit 1b 'drive circuit 1c light receiver 1d signal amplification circuit 1d' signal amplification circuit 1e amplification factor control circuit 1f drive current control circuit 2 signal processing unit 3 relative speed calculation unit 3a distance measurement order Control unit 3b Signal processing control unit 3c Inter-vehicle distance calculation unit 3d Reception amplification rate change judgment unit 3e Memory 3f Relative speed calculation unit 3g Warning distance calculation unit 3h Warning announcement judgment unit 3j Driving current change judgment unit 4 Vehicle speed sensor 5 Warning buzzer

Claims (4)

[Claims] 1. A speed detecting means for detecting the speed of the host vehicle, a signal sending means for sending a pulsed signal to the outside at a predetermined sending cycle, and a signal sent by the signal sending means reflected on a target. The receiving means for continuously receiving the signal from the returning direction and the signal received by the receiving means.
Addition means for digitizing and adding a predetermined number of times of transmission for each of a plurality of sampling points with different elapsed times from the signal transmission timing in each transmission cycle of the signal transmission means, and for each sampling point of the addition means A peak value detecting means for obtaining a peak value of the added value, an inter-vehicle distance calculating means for calculating a distance corresponding to a sampling point giving the peak value obtained by the peak value detecting means as an inter-vehicle distance to a target in front, Distance measurement value storage means for storing the inter-vehicle distance calculated by the inter-vehicle distance calculation means, and the previously calculated inter-vehicle distance stored in the distance measurement value storage means when the inter-vehicle distance calculation means calculates a new inter-vehicle distance Read the distance,
Relative speed calculating means for calculating the relative speed between the host vehicle and the target in front of the vehicle based on the difference in these inter-vehicle distances, the speed of the host vehicle detected by the speed detecting means, and the inter-vehicle distance calculated by the inter-vehicle distance calculating means. An inter-vehicle distance determining means for determining suitability of the current inter-vehicle distance based on the distance and the relative speed calculated by the relative speed calculating means, and for the driver when the inter-vehicle distance determining means determines that the current inter-vehicle distance is unsuitable. In an inter-vehicle distance monitoring device comprising an alarm output means for outputting an alarm, the proper reception amplification factor of the receiving means is stepwise so that the peak value detected by the peak value detecting means falls within a predetermined level. The reception amplification rate control means for controlling, and the reception amplification rate of the reception means, which is one step higher and one step lower than the proper reception amplification rate adjusted by the reception amplification rate control means. When a new inter-vehicle distance is obtained by changing the appropriate inter-vehicle distance and saving the inter-vehicle distance by reference inter-vehicle distance storage means, the proper reception amplification rate adjusted by the reception amplification rate control means is changed. An inter-vehicle distance including a relative speed calculation assisting means for reading out the previous inter-vehicle distance obtained with the same reception amplification factor as the new proper reception amplification factor from the reference inter-vehicle distance storage means and giving it to the relative speed calculation means. Monitoring equipment. 2. A speed detecting means for detecting the speed of the host vehicle, a signal sending means for sending a pulsed signal to the outside at a predetermined sending cycle, and a signal sent by the signal sending means reflected on a target. The receiving means for continuously receiving the signal from the returning direction and the signal received by the receiving means.
Addition means for digitizing and adding a predetermined number of times of transmission for each of a plurality of sampling points with different elapsed times from the signal transmission timing in each transmission cycle of the signal transmission means, and for each sampling point of the addition means A peak value detecting means for obtaining a peak value of the added value, an inter-vehicle distance calculating means for calculating a distance corresponding to a sampling point giving the peak value obtained by the peak value detecting means as an inter-vehicle distance to a target in front, Distance measurement value storage means for storing the inter-vehicle distance calculated by the inter-vehicle distance calculation means, and the previously calculated inter-vehicle distance stored in the distance measurement value storage means when the inter-vehicle distance calculation means calculates a new inter-vehicle distance Read the distance,
Relative speed calculating means for calculating the relative speed between the host vehicle and the target in front of the vehicle based on the difference in these inter-vehicle distances, the speed of the host vehicle detected by the speed detecting means, and the inter-vehicle distance calculated by the inter-vehicle distance calculating means. An inter-vehicle distance determining means for determining suitability of the current inter-vehicle distance based on the distance and the relative speed calculated by the relative speed calculating means, and for the driver when the inter-vehicle distance determining means determines that the current inter-vehicle distance is unsuitable. In an inter-vehicle distance monitoring device comprising an alarm output means for outputting an alarm, the proper reception amplification factor of the receiving means is stepwise so that the peak value detected by the peak value detecting means falls within a predetermined level. When the host vehicle is approaching the target ahead from the relative speed calculated by the relative speed calculating means and the relative speed calculating means for controlling, the proper receiving amplification rate of the receiving means is one step lower. With the amplification factor, when the own vehicle is leaving, a reference inter-vehicle distance storage unit that stores the inter-vehicle distance by obtaining the inter-vehicle distance with an amplification factor that is one step higher than the proper reception amplification factor, and the reception amplification factor control When the proper reception amplification factor adjusted by the means is changed and a new inter-vehicle distance is obtained, the inter-vehicle distance stored in the reference inter-vehicle distance storage means as the previous inter-vehicle distance is read and given to the relative speed calculation means. An inter-vehicle distance monitoring device comprising relative speed calculation assisting means. 3. A speed detecting means for detecting the speed of the host vehicle, a signal sending means for sending a pulsed signal to the outside at a predetermined sending cycle, and a signal sent by the signal sending means reflected on a target. The receiving means for continuously receiving the signal from the returning direction and the signal received by the receiving means.
Addition means for digitizing and adding a predetermined number of times of transmission for each of a plurality of sampling points with different elapsed times from the signal transmission timing in each transmission cycle of the signal transmission means, and for each sampling point of the addition means A peak value detecting means for obtaining a peak value of the added value, an inter-vehicle distance calculating means for calculating a distance corresponding to a sampling point giving the peak value obtained by the peak value detecting means as an inter-vehicle distance to a target in front, Distance measurement value storage means for storing the inter-vehicle distance calculated by the inter-vehicle distance calculation means, and the previously calculated inter-vehicle distance stored in the distance measurement value storage means when the inter-vehicle distance calculation means calculates a new inter-vehicle distance Read the distance,
Relative speed calculating means for calculating the relative speed between the host vehicle and the target in front of the vehicle based on the difference in these inter-vehicle distances, the speed of the host vehicle detected by the speed detecting means, and the inter-vehicle distance calculated by the inter-vehicle distance calculating means. An inter-vehicle distance determining means for determining suitability of the current inter-vehicle distance based on the distance and the relative speed calculated by the relative speed calculating means, and for the driver when the inter-vehicle distance determining means determines that the current inter-vehicle distance is unsuitable. In an inter-vehicle distance monitoring device comprising an alarm output means for outputting an alarm, the appropriate signal output level of the signal transmission means is stepwise so that the peak value detected by the peak value detection means falls within a predetermined level. The signal output control means for controlling the signal output control means and the signal output level of the signal sending means are one step above and one step below the proper signal output level adjusted by the signal output control means. Reference inter-vehicle distance storage means for changing these signal output levels to obtain inter-vehicle distances and storing these inter-vehicle distances, and the appropriate signal output level adjusted by the signal output control means are changed, and new inter-vehicle distances are changed. Is calculated, the relative speed calculation assisting means for reading out the previous inter-vehicle distance obtained at the same signal output level as the new appropriate signal output level from the reference inter-vehicle distance storing means and giving it to the relative speed calculating means. An inter-vehicle distance monitoring device provided. 4. A speed detecting means for detecting the speed of the host vehicle, a signal sending means for sending a pulsed signal to the outside at a predetermined sending cycle, and a signal sent by the signal sending means reflected on a target. The receiving means for continuously receiving the signal from the returning direction and the signal received by the receiving means.
Addition means for digitizing and adding a predetermined number of times of transmission for each of a plurality of sampling points with different elapsed times from the signal transmission timing in each transmission cycle of the signal transmission means, and for each sampling point of the addition means A peak value detecting means for obtaining a peak value of the added value, an inter-vehicle distance calculating means for calculating a distance corresponding to a sampling point giving the peak value obtained by the peak value detecting means as an inter-vehicle distance to a target in front, Distance measurement value storage means for storing the inter-vehicle distance calculated by the inter-vehicle distance calculation means, and the previously calculated inter-vehicle distance stored in the distance measurement value storage means when the inter-vehicle distance calculation means calculates a new inter-vehicle distance Read the distance,
Relative speed calculating means for calculating the relative speed between the host vehicle and the target in front of the vehicle based on the difference in these inter-vehicle distances, the speed of the host vehicle detected by the speed detecting means, and the inter-vehicle distance calculated by the inter-vehicle distance calculating means. An inter-vehicle distance determining means for determining suitability of the current inter-vehicle distance based on the distance and the relative speed calculated by the relative speed calculating means, and for the driver when the inter-vehicle distance determining means determines that the current inter-vehicle distance is unsuitable. In an inter-vehicle distance monitoring device comprising an alarm output means for outputting an alarm, the appropriate signal output level of the signal transmission means is stepwise so that the peak value detected by the peak value detection means falls within a predetermined level. And a proper signal output level of the signal sending means when the own vehicle is approaching the target ahead from the relative speed calculated by the relative speed calculating means. A reference inter-vehicle distance storage means for saving the inter-vehicle distance by obtaining an inter-vehicle distance at an output level that is one step lower than the appropriate signal output level when the own vehicle is leaving with an output level that is one step lower When the appropriate signal output level adjusted by the signal output control means is changed and a new inter-vehicle distance is obtained, the inter-vehicle distance stored in the reference inter-vehicle distance storage means as the previous inter-vehicle distance is read to read the relative speed. An inter-vehicle distance monitoring device, comprising: relative speed calculation assisting means provided to calculating means.