JP3206412B2 - Inter-vehicle distance measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-vehicle distance measuring device for distinguishing a preceding vehicle from a stationary object ahead and outputting a signal indicating the inter-vehicle distance or a stationary object. The present invention relates to an inter-vehicle distance measuring device which is preferably applied to a vehicle running control device or the like which controls the vehicle to automatically follow a preceding vehicle.

[0002]

2. Description of the Related Art In recent years, with the spread of constant-speed traveling devices that allow a vehicle to travel at a constant set speed, the constant-speed traveling device is operated for the purpose of preventing rear-end collision with a preceding vehicle and improving driving operability. Various devices have been proposed that control the running speed of a host vehicle to automatically follow the host vehicle while keeping a safe inter-vehicle distance.

[0003] This type of vehicle travel control device is equipped with a radar device (inter-vehicle distance measuring device) for measuring the distance to an object ahead of the host vehicle in the traveling direction. It is extremely important in performing automatic tracking control to accurately identify whether the preceding object is a preceding vehicle as a tracking target or a simple stationary object. Especially when traveling on a curved road, the radar device may or may not catch the preceding vehicle, and if a stationary object is mistaken for the preceding vehicle, unnecessary deceleration may occur, or conversely, If the vehicle is erroneously recognized as a stationary object, it becomes impossible to maintain the optimum safe inter-vehicle distance.

For this reason, for example, Japanese Patent Application Laid-Open No.
In the vehicle traveling control device disclosed in Japanese Patent Publication No. 31, the distance signal measured by the radar device is an inter-vehicle distance signal with a preceding vehicle traveling ahead of the own vehicle, or a roadside corner reflector, a guide sign, or the like. Is determined by the following method.

That is, when the radar device captures the roadside reflector while the vehicle is traveling at the speed Vs, the distance signal output from the radar device has a macro waveform shown in FIG. . FIG. 4 shows that the vehicle 5 is
3 illustrates a distance signal when three reflectors 7 on the curve road side are sequentially captured. In this figure, before the radar device captures the roadside reflector 7, an indefinite distance signal is output (indicated by "A" in FIG. 4), but when the roadside reflector 7 is captured, that is, when the distance is determined, the instant Is output, and then the own vehicle 5
As the vehicle travels, the distance from the roadside reflector 7 gradually decreases, and a corresponding distance signal B → C is output.

Since the distance signal detected by the radar device is read at a constant sampling time T, the inclination of the distance signal B → C is enlarged as shown in FIG. In FIG. 5, the distance signal at the instant t ₀ when the roadside reflector 7 is captured is d ₀ , and when the _eighth sampling is performed from the time t ₀ , the distance signal at t ₈ is d ₈ . The relative velocity V _ref between the vehicle 5 and the roadside reflector 7 in this _{case, V ref = (d 8 -d} 0) / (t 8 -t 0) becomes ≒ -Vs.

Here, at least k times the vehicle speed (0 <k <1)
Is determined to be a stationary object, that is, when | _Vref |> kVs (1), it is determined that the radar apparatus has captured the roadside reflector 7. On the other hand, when Expression (1) is not satisfied, it is determined that the preceding vehicle 6 traveling ahead of the host vehicle 5 is being captured.

[0008]

However, in the above-mentioned conventional inter-vehicle distance measuring apparatus, there is no problem when one roadside reflector is captured one by one. If the measurement is performed such that the roadside reflector 7 is captured or a plurality of roadside reflectors 7, 7 are simultaneously captured, the obtained distance signal becomes an ideal waveform having a substantially constant slope as shown in FIG. It is rare.

That is, as shown in FIG. 6, the "rounding" X of the waveform which is considered to be caused by the detection accuracy of the inter-vehicle distance measuring device, or the distance that occurs when different roadside reflectors are continuously detected without time intervals. In many cases, a "jump" Y of a signal, or a "jump" of a distance signal caused when a plurality of roadside reflectors are detected alternately and simultaneously, as shown in FIGS. 7 and 8, are often observed.

When the relative speed V _ref is obtained from the distance signals at two points using such a waveform, the expression (1) is often not satisfied even when the roadside reflector is captured, and the actual response is obtained. It may not be possible to accurately recognize whether the object is a preceding vehicle or a stationary object. For this reason, if such an inter-vehicle distance measuring device is used for the automatic following control, a stationary object may be erroneously recognized as a preceding vehicle, and unnecessary deceleration may occur, and smooth following may not be realized. Note that this problem is not solved even if an average value is obtained from the following several distance signals using the least squares method in order to obtain the relative speed _Vref .

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has as its object to provide an inter-vehicle distance measuring apparatus capable of reliably distinguishing a preceding vehicle from a stationary object.

[0012]

In order to achieve the above object, an inter-vehicle distance measuring apparatus according to the present invention is characterized in that the object in front of the own vehicle is a preceding vehicle traveling in front of the own vehicle or a stopped object. An inter-vehicle distance measuring device that outputs an inter-vehicle distance when the vehicle is a preceding vehicle and outputs an indefinite distance signal when the vehicle is a stationary object, and detects a distance to an object in front of the own vehicle. Distance detecting means for outputting a distance signal, a vehicle speed detecting means for detecting a speed of the own vehicle and outputting a vehicle speed signal, and a plurality of distance signals detected by the distance detecting means in a time axis direction. A relative speed calculating unit that extracts a plurality of groups while sequentially shifting a plurality of adjacent distance signals, and calculates a relative speed between the host vehicle and the object in each of the distance signal groups; a vehicle speed from the vehicle speed detecting unit; Based on signal A reference range of the relative speed to be determined as the preceding vehicle is set, and when all the relative speeds of the respective distance signal groups calculated by the relative speed calculation unit are within the reference range, the relative speed is detected by the distance detection unit. The determined distance signal is determined as an inter-vehicle distance to the preceding vehicle and output, and if any one of the relative velocities of the distance signal groups is not within the reference range, the distance signal is detected by the distance detecting means. And a stop object determining unit that determines the distance signal obtained as a distance signal to a stop object and outputs an indefinite distance signal.

In the present invention, when the object captured by the distance detecting means is a preceding vehicle, first, there is no jump in the distance signal, and second, the relative speed is lower than when the object is a stationary object. It is small. That is, jumps occur in the distance signal when different stationary objects are detected consecutively without time intervals or when multiple stationary objects are detected alternately at the same time. In the case of, a large jump does not occur between adjacent distance signals. Therefore, when no jump occurs in the distance signal, the captured object is either the preceding vehicle or the same stationary object, and both can be easily identified by the magnitude of the relative speed with respect to the own vehicle. . In other words, when the vehicle is a preceding vehicle, the relative speed with respect to the own vehicle is small, and when the vehicle is a stationary object, the relative speed with respect to the own vehicle is approximately the running speed of the own vehicle.

Based on such knowledge, the inter-vehicle distance measuring apparatus of the present invention sequentially shifts a plurality of distance signals adjacent in the time axis direction from a plurality of distance signals detected by the distance detecting means. A plurality of groups are extracted, and the relative velocities between the host vehicle and the object in each distance signal group are calculated. If all of these relative velocities are within the reference range, the captured object is determined to be the preceding vehicle.

A plurality of groups of adjacent distance signals are extracted while sequentially shifting them, and the relative speed between the own vehicle and the object in each distance signal group is calculated. , Its relative speed will be outside the reference range. This makes it possible to identify whether or not the distance signal has jumped. Further, by setting the reference range of the relative speed to be determined as the preceding vehicle based on the vehicle speed signal from the vehicle speed detecting means, it is possible to identify whether the captured object is the preceding vehicle or the same stationary object.

If at least one of the relative velocities of each distance signal group is not within the reference range, a jump occurs in the distance signal. Is output.

The distance detecting means according to the present invention detects a distance to an object in front of the vehicle and outputs a distance signal, and is, for example, a radar device using a laser, an ultrasonic wave, or a radio wave.

Further, the vehicle speed detecting means according to the present invention detects the speed of the own vehicle and outputs a vehicle speed signal, and a vehicle speed sensor or the like equipped with a vehicle may be used.

When the relative speed between the vehicle and the object is calculated by the relative speed calculating means according to the present invention, the number of distance signals detected by the distance detecting means is not limited as long as they are adjacent to each other. However, if the number of distance signals extracted is small, the number of distance signals increases, so that the calculation time becomes long.If the number of distance signals extracted is large, the accuracy of detecting the jump of the distance signal decreases. It is desirable to set an appropriate number in relation to the set value of the reference range and the like. It is preferable that the number of groups extracted by sequentially shifting the plurality of distance signals adjacent to each other includes at least all of the distance signals detected by the distance detection unit.

In the stationary object determining means according to the present invention,
The reference range of the relative speed to be determined as the preceding vehicle is set based on the vehicle speed signal of the own vehicle detected by the vehicle speed detecting means, and this serves as a reference whether the captured object is the preceding vehicle or the stopped object.

In the stationary object determining means according to the present invention,
When the difference between adjacent distance signals in each of the distance signal groups is equal to or greater than a predetermined value, the distance signal detected by the distance detection unit is determined as a distance signal to a stationary object, and the distance is determined. An indefinite signal can be output.

In the inter-vehicle distance measuring apparatus according to the present invention, the distance detecting means detects the distance to the object in front of the own vehicle and outputs a distance signal. The object captured by the distance detecting means is detected by the preceding vehicle. In some cases or in the case of the same stationary object, it can be said that a large jump does not occur in adjacent distance signals. In other words, when different stationary objects are continuously detected without time intervals or when multiple stationary objects are detected alternately at the same time, a jump occurs in the distance signal. The difference between adjacent distance signals in the signal group is determined. If the difference is equal to or greater than a predetermined value, it is determined that the distance signal has jumped, and the captured object is recognized as a stationary object. I do. By adding this function, a stationary object may be recognized without calculating the relative speed, so that the recognition processing speed can be increased.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an inter-vehicle distance measuring device according to an embodiment of the present invention. As shown in the drawing, the inter-vehicle distance measuring device according to the present embodiment includes a distance detecting means 1, a vehicle speed detecting means 2. , Relative speed calculating means 3 and stationary object determining means 4, and can be applied, for example, as an inter-vehicle distance measuring device of an automatic following device.

The distance detecting means 1 detects a distance to an object ahead of the host vehicle and outputs a distance signal. The distance detecting means 1 can be constituted by a radar device using a laser, an ultrasonic wave or a radio wave. For example, it is provided on the front of a car so as to easily catch an object. The distance signal detected by the distance detecting means 1 is sent to the relative speed calculating means 3, where it is temporarily stored and used for calculating the relative speed.

The vehicle speed detecting means 2 detects the speed of the host vehicle and outputs a vehicle speed signal, and a vehicle speed sensor or the like mounted on the vehicle can be used. The vehicle speed signal detected by the vehicle speed detecting means 2 is sent to the stationary object determining means 4, where it is temporarily stored and used for setting a relative speed reference range.

The relative velocity calculating means 3 extracts a plurality of groups of adjacent distance signals from the plurality of distance signals detected by the distance detecting means 1 while sequentially shifting the plurality of distance signals. The hardware for calculating the relative speed between the vehicle and the object includes an input port for inputting a distance signal from the distance detecting means 1, a RAM for temporarily storing the distance signal input from the distance detecting means 1, RO storing a program for extracting a plurality of distance signal groups from the distance signal and a relative speed calculation program
M, a CPU that performs the actual calculation, and an output port that outputs the calculation result to the stationary object determination means 4.

The stopped object determining means 4 has mainly two functions. That is, first, based on the vehicle speed signal from the vehicle speed detecting means 2, a reference range of a relative speed to be determined as a preceding vehicle is set. Secondly, when the relative speeds of the respective distance signal groups calculated by the relative speed calculating means 3 are all within the reference range, the distance signal detected by the distance detecting means 1 is determined as the inter-vehicle distance to the preceding vehicle. If any one of the relative velocities of the distance signal groups is not within the reference range, the distance signal detected by the distance detecting means 1 is determined to be a distance signal to the stationary object, and the distance is undefined. Output a signal. As hardware, an input port for inputting a vehicle speed signal from the vehicle speed detecting means 2 and a relative speed from the relative speed calculating means 3, a RAM for temporarily storing such information, a reference range setting program, and determination of relative speed ROM in which a program is stored, CPU for performing actual setting and determination calculation,
And an output port for outputting the operation result to the outside.

In the present embodiment, the relative speed calculating means 3 and the stationary object judging means 4 have different structures. However, they may be formed as a single hardware having both of these means 3 and 4. It is.

Next, the operation will be described. FIG. 2 is an explanatory diagram of signal processing in the embodiment, and FIG. 3 is a flowchart showing a signal processing procedure in the embodiment. In the following description, among the plurality of continuous distance signals detected by the distance detecting means 1 at the sampling interval T, the relative speed calculating means 3 outputs eight continuous distance signals d ₀ , d ₁ ,.
.., D ₇ are stored, and four adjacent distance signals are extracted from the eight distance signals to form one distance signal group. A case where a distance signal group is extracted will be described. However, in the inter-vehicle distance measuring apparatus of the present invention, the number of distance signals (8) stored in the relative speed calculating means 3 and the number of adjacent distance signals used for calculating the relative speed (4)
) And the number of distance signal groups (five), which is the number of times of calculation of the relative speed, are not particularly limited and can be changed as appropriate.

As shown in FIGS. 2 and 3, first, adjacent distance signals d ₀ ,
d _1, ..., stores d ₇ to the relative speed calculation unit 3 (step 1). While the distance signal d ₀ is not determined, that is, while there is no captured object in the distance detecting means 1, the distance detecting means 1
, The stationary object determining means 4 outputs a distance indefinite signal to the outside (step 2 →
7).

When the distance signal d ₀ is determined, the stationary object determining means 4 determines whether or not the difference between the adjacent distance signals d ₀ , d ₁ ,..., D ₇ is within a predetermined value (step 2 →).
3). That is, the maximum value and the minimum value of the allowable range of the difference between the adjacent distance signals are determined in advance, and before calculating the relative speed, it is determined whether or not the distance signal has a large jump outside the allowable range. . In the depicted embodiment, the maximum value D _max = 4m tolerance, the minimum value _{D min = -4m, D min <} d 7 -d 6 <D max, ..., D min <d i + 1
−d _i <D _max ,..., D _min <d ₁ −d ₀ <D _max (0
.Ltoreq.i.ltoreq.6, i is an integer) (step 3), and if even one does not satisfy the allowable range, the stationary object determining means 4 outputs an indefinite distance signal to the outside (step 7).

In this processing, when the distance detecting means 1 is capturing a preceding vehicle traveling ahead of the host vehicle or capturing the same stationary object, a large distance signal is output to the adjacent distance signal. By performing this processing before calculating the relative speed, at least a jump occurs in the distance signal, that is, a case where different stationary objects are continuously detected without time intervals or a plurality of It is possible to identify a case where a stationary object is detected alternately at the same time. As a result, the captured object can be immediately recognized as a stationary object, and the recognition processing speed can be increased.

In step 3, when all the differences between the adjacent distance signals are within the allowable range, the waveform of the distance signal from the distance detecting means 1 is considered to be the ideal case shown in FIG. 4 or FIG. In addition to the case where the captured object is the preceding vehicle, the case where the same stationary object is captured is also included. Therefore, in order to identify this, first, the relative speed is calculated by the relative speed calculating means 3 (step 4), and the calculation result is sent to the stationary object determining means 4, and the stationary object determining means 4 A final determination is made as to whether the vehicle is a stationary object or not (step 5).

[0034] The relative velocity V _ref between the vehicle and the capture object in the relative speed calculating means 3, the phase four adjacent distance signal _{d i, d i + 1,} d i + 2, d i + 3 (0 ≦ i ≦ 4, i is an integer) using the least squares method. In this case, since a total of eight distance signals are used, when extracting one distance signal group consisting of four adjacent distance signals, the distance signal group is formed while shifting the start points of the distance signals one by one. I do. That is, in the present embodiment, the five distance signal groups [d ₀ , d ₁ , d ₂ ,
d ₃ ], [d ₁ , d ₂ , d ₃ , d ₄ ], [d ₂ , d ₃ ,
d ₄ , d ₅ ], [d ₃ , d ₄ , d ₅ , d ₆ ], [d ₄ ,
d ₅ , d ₆ , d ₇ ] are extracted, and the relative velocities V _ref0 , V _ref1 , V _ref2 , V _ref of each of these five distance signal groups are extracted.
_ref3 and _Vref4 are calculated.

The five relative speeds calculated by the relative speed calculating means 3 are sent to the stationary object determining means 4, and the stationary object determining means 4 transfers the five relative speeds from the vehicle speed detecting means 2. Thresholds (reference ranges) V _max and V _min for determining whether or not the vehicle is a stationary object based on the vehicle speed Vs of the vehicle
And the five relative velocities V calculated earlier.
_{ref0, V ref1, V ref2,} V ref3, V ref4 is determined whether there are any within the reference range (Step 5). In this embodiment, the maximum value V _max of the reference range -100 (miles /
h), the minimum value V _{min is set} to 0.7 · Vs (km / h).

The five relative speeds V _ref0 , V _ref1 ,
_Only when V _ref2 , V _ref3 , and V _ref4 are all within the reference range, it is determined that the captured object is the preceding vehicle, and the closest distance signal d ₇ at the time of output is output to the outside as an inter-vehicle distance (step 6). . In addition, five relative speeds V _ref0 ,
If any one of V _ref1 , V _ref2 , V _ref3 , and V _ref4 is out of the reference range, it is determined that the captured object is a stationary object, and a distance indefinite signal is output to the outside (step 7).

As described above, according to the inter-vehicle distance measuring apparatus of the present embodiment, the jump of the distance signal can be immediately determined, and whether the preceding vehicle or the stationary object can be accurately determined. . The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0038]

As described above, according to the present invention, a plurality of groups of distance signals adjacent to each other are extracted while sequentially shifting them, and the relative speed between the host vehicle and the object in each distance signal group is calculated. Therefore, the presence or absence of the jump of the distance signal can be accurately identified. Further, by setting the reference range of the relative speed to be determined as the preceding vehicle based on the vehicle speed signal from the vehicle speed detecting means, it is possible to accurately identify whether the captured object is the preceding vehicle or the same stationary object.

In the present invention, the difference between adjacent distance signals in each distance signal group is determined before the relative speed is determined. If the difference is greater than a predetermined value, the distance signal jumps. Since the object is determined to be present and the captured object is recognized as a stationary object, the recognition processing speed is increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an inter-vehicle distance measuring apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining signal processing of an inter-vehicle distance measuring device according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a signal processing procedure of the inter-vehicle distance measuring apparatus according to the embodiment of the present invention.

FIG. 4 is a graph showing a waveform of a distance detection signal with respect to time when a stationary object is detected.

FIG. 5 is a graph showing an enlarged waveform of a distance detection signal with respect to time when a stationary object is detected.

FIG. 6 is a graph illustrating an example of a defect in a distance detection signal waveform with respect to time when a stationary object is detected.

FIG. 7 is a graph showing a failure example of a distance detection signal waveform with respect to time when a stationary object is detected.

FIG. 8 is a graph showing a failure example of a distance detection signal waveform with respect to time when a stationary object is detected.

FIG. 9 is a schematic diagram showing a detection state of an object stopped ahead when traveling on a curved road.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Distance detection means 2 ... Vehicle speed detection means 3 ... Relative speed detection means 4 ... Stopping object determination means 5 ... Own vehicle 6 ... Previous vehicle 7 ... Roadside corner reflector (stopping object)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-80154 (JP, A) JP-A-6-138234 (JP, A) JP-A-5-256943 (JP, A) 138588 (JP, A) JP-A-62-130500 (JP, A) Patent 3044524 (JP, B2) Patent 2789437 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S 7 / 00-17/88 B60R 21/00

Claims (2)

(57) [Claims] An object in front of a host vehicle is determined whether it is a preceding vehicle or a stationary object traveling in front of the host vehicle. An inter-vehicle distance measurement device that outputs an indefinite distance signal in some cases, a distance detection unit that detects a distance to an object in front of the own vehicle and outputs a distance signal, and detects a speed of the own vehicle. Vehicle speed detection means for outputting a vehicle speed signal, and from a plurality of distance signals detected by the distance detection means,
A relative speed calculating means for extracting a plurality of groups while sequentially shifting a plurality of distance signals adjacent in a time axis direction, and calculating a relative speed between the host vehicle and the object in each distance signal group; Setting a reference range of the relative speed to be determined as the preceding vehicle based on the vehicle speed signal from the means, and when all the relative speeds of the distance signal groups calculated by the relative speed calculation means are within the reference range. Determines and outputs the distance signal detected by the distance detection means as an inter-vehicle distance to the preceding vehicle, and when any one of the relative speeds of the distance signal groups is not in the reference range. A stop object determining unit that determines the distance signal detected by the distance detecting unit as a distance signal to a stationary object and outputs an indeterminate distance signal. 2. The method according to claim 1, further comprising the step of determining the distance signal detected by the distance detecting means when a difference between adjacent distance signals in each of the distance signal groups is equal to or greater than a predetermined value. The inter-vehicle distance measurement device according to claim 1, wherein the distance signal is determined based on a distance signal to a stationary object and an indefinite distance signal is output.