JPH09257927A - Radar equipment for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure generation of alarm at a proper timming by calculating a relative speed only at the time when the distance of target substance is in a range of specified distance or below. SOLUTION: Distance calculating means 7 detects a distance R to a target substance. The value of the distance R is determined and the determination of whether relative speed calculation means 10 is operated or not is made. Namely, a specified value R-limit set to the maximum detection distance R-max or below and the actual distance R are compared with each other, and only in the case of R<R-limit the calculation means 10 is operated. Since the relative speed is calculated in the case that the distance with the target substance is only in the range of not more than the specified distance set not more than the maximum detection distance of radar, the calculated relative speed becomes the same as the true value, whereby after the application of LPF almost the same value is obtained. Accordingly there occurs no delay in generation of alarm, thereby ensuring the generation at a proper timming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes it possible to inexpensively construct a processing apparatus for a received signal by using a wave having a pulse width longer than a sampling period, while suppressing a decrease in distance measurement accuracy due to a long pulse wave. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle radar device, and particularly to a technique for solving the problems of alarm stability and alarm time delay when applied to an inter-vehicle distance alarm device.

[0002]

2. Description of the Related Art As a conventional vehicle radar device, for example, there is one described in Japanese Patent Application Laid-Open No. 7-84031 (prior application of the present applicant). This is a straight line that connects the sampling point and its surroundings or other sampling points by arranging the output obtained by sampling and adding the reflected waves from the target object in time series, using a pulse wave longer than the sampling period. Is obtained and the time corresponding to the intersection is used for distance calculation. With this configuration, it is possible to obtain a high distance resolution equal to or longer than the sampling period without increasing the speed of the circuit.

[0003]

However, such a conventional vehicle radar device has the following problems. In the case of a vehicular radar device, it is desirable to be able to detect an object as far as possible in view of application to an inter-vehicle distance warning device or the like. Therefore, in such a vehicle radar device, the maximum detection distance required is determined, and the time of the latest sampling point is determined so that the maximum detection distance can be calculated. For example, in order to calculate the distance up to 120 m, the time of the latest sampling point is
The time is set to correspond to 120 m. With this setting, it is possible to detect the distance to the target object within the range of 0 to 120 m. Further, in the case of such a vehicle radar device, in order to prevent erroneous detection due to road surface reflection or ambient light, it is determined that the detected object exists only when the value of the sampling data is a predetermined value or more, Generally, the level of the pulse to be transmitted or the sensitivity of the element to be detected is set so that the level of the reflected wave from the target object (vehicle) within the maximum detection distance is equal to or higher than the predetermined value.

However, the maximum detection distance (for example, 120
Even if the target object is farther than m), if the reflection level of the preceding vehicle is very high, the sampling data at the maximum detection distance (120 m) position shows the maximum value, and the value is Since it exceeds the specified value for detection,
The distance to the target object is calculated. And 120
Since the sampling point does not exist at the time of m or more, the calculated value shows 120 m.

Therefore, as shown in FIG. 10, when a target object having a very high reflection level is approaching at a constant relative speed from the maximum detection distance or more, the true distance to the target object is greater than the maximum detection distance. In the scene (area 1) of
The detected distance continuously indicates the value of the maximum detection distance, and then, after entering the scene (area 2) in which the true distance is less than the maximum detection distance, the correct distance is output. When the relative velocity of the target object is calculated based on the value of this output distance,
Since the distance does not change in the area 1, the relative speed becomes zero, and the correct value of the relative speed is output after entering the area 2.

Considering the application of such a vehicle radar device to an inter-vehicle distance warning device or the like, the following problems occur. Generally, the inter-vehicle distance to the preceding vehicle measured by the vehicle radar device is easily changed due to noise. Then, in order to calculate the relative speed necessary for the alarm judgment, the operation of taking the time derivative of the detected inter-vehicle distance is performed. However, if such time derivative is taken, it is calculated due to the noise of the inter-vehicle distance. The relative speed is also noisy. If the alarm distance is calculated using the relative speed with such noise as it is, the value of the alarm distance becomes unstable, and the magnitude relationship with the actual inter-vehicle distance becomes unstable, and the alarm generation becomes unstable. There is a possibility of becoming.

In order to prevent such alarm instability, a method is generally used in which the calculated relative speed is passed through a low-frequency band-pass filter (low-pass filter) to reduce fluctuations in the relative speed due to noise. To be This low-pass filter has the effect of blocking high-frequency fluctuation components above a certain cut-off frequency (cut-off frequency) of the input signal and passing only low-frequency fluctuation components below it, so that the necessary signal By determining a cutoff frequency so as to cut off a high-frequency fluctuation component equal to or higher than the component frequency, and designing a low-pass filter based on the cutoff frequency, it is possible to effectively remove the noise of the relative speed.

However, in general, a low-pass filter is
It has the characteristic of phase delay. This is a problem that the necessary change of the signal itself is slightly delayed in time because the high-pass signal component is blocked by the low-pass filter. Due to the problem of the phase delay, in a scene approaching a target object with a high reflection level from a distance farther than the maximum detection distance as described above, a scene (region The erroneous relative velocity value (= zero) calculated in 1) is retained for a while even if the distance to the target object is less than the maximum detection distance (region 2), so the calculated relative velocity value is The value is smaller than the actual value, and the alarm distance calculated accordingly becomes small, so the alarm issuance is delayed.

The problem of the phase delay due to the low-pass filter characteristically occurs in the vehicle radar device of such a sampling / adding system. The reason is,
The sampling / addition type radar device has a long sampling period, and in order to detect the distance more accurately than the long sampling period, the position of the peak point is estimated using a mathematical method. This is because the periodic noise is likely to be included in the error, and in order to suppress the error fluctuation in the relative speed due to the periodic noise, it is essential to use the low-pass filter having a relatively small cutoff frequency.

The problem relating to the characteristic low-pass filter in such a sampling / adding type vehicle radar device will be described in detail below. FIG. 11 is a diagram showing detection distance accuracy in the first and third embodiments of the conventional example (Japanese Patent Application No. 5-233091) (FIG. 1 of the conventional example.
The same figure as 1.). Looking at the characteristics of the first example of the conventional example, the error of the detection distance is about 4 m at the maximum,
Within one sampling interval of 10 m (10 m), a point that is approximately 4 m larger than the actual distance (about 38 m)
There is a point (around 34 m) that is slightly smaller than approximately 4 m (around 34 m) and shows a periodic fluctuation within this 10 m. In the third embodiment, the maximum error value is at most 0.
It is about 5 m, which is smaller than that of the first embodiment.
Similar to the embodiment, the periodic fluctuation is shown within 10 m.

The detection error of 0.5 m at maximum is an accuracy with no particular problem if the data is simply used as a distance for determination. However, when a periodic error variation occurs with respect to the actual distance in this way, a problem arises when this is used for relative velocity calculation. That is, as the distance changes with time, the value of the detection error fluctuates periodically, and the relative velocity calculated using this also fluctuates cyclically. Further, the fluctuation amplitude of this relative speed becomes relatively large.

FIG. 12 shows a case where the maximum amplitude of the error of the detection distance is 0.5 m and the vibration is generated in a cycle of 10 m (the third example of the conventional example
The relative amplitude error amplitude (corresponding to the example) is shown with respect to the true relative speed at that time. The relative speed error amplitude is proportional to the value of the true relative speed and is equal to the true relative speed of 30
The error amplitude is not less than%, for example, when the relative speed is 100 km / h, the error amplitude is 31.4 km / h.

A low-pass filter is effective for reducing a relative velocity error having an amplitude proportional to the true relative velocity due to such a periodic distance error. The reason is that the low-pass filter has a higher amplitude attenuation effect as the input frequency is higher. The frequency of the relative velocity error fluctuation due to the detection distance error is a value obtained by dividing the true relative velocity by the sampling interval (10 m). Therefore, the larger the true relative velocity is, the higher the input frequency is, and the greater the effect of damping the error amplitude is. Become.

In FIG. 13, the cutoff frequency is 0.4H.
7 shows the damping effect of the relative velocity error amplitude when set to z. With this setting, the vibration of the relative speed due to the periodic noise of the detection distance can be suppressed to be small regardless of the value of the true relative speed. For example, the maximum value of the relative speed error is 3 km / h when the true relative speed is about 15 km / h.
Indicates a value of degree. As described above, in order to accurately calculate the relative velocity of the target object using the sampling / adding type radar device, the low-pass filter is essential. Further, it is desirable that the cutoff frequency of the low pass filter is as small as possible with respect to the assumed input frequency.

On the other hand, however, when the low-pass filter having a small cutoff frequency is used, the above-mentioned problem of the phase delay becomes more remarkable. In FIG. 14, 100k
The output result when a relative speed is calculated by applying a low-pass filter having a cutoff frequency of 0.4 Hz when approaching a stopped vehicle at m / h is shown. As shown in the figure, from the initial value 0 km / h to the true relative speed 100 km / h
The time delay required to converge to 1.3 seconds is 1.3 seconds, which is a very large time delay for application to an inter-vehicle distance warning device.

As described above, in the case of the vehicle radar of the sampling / adding type, a unique distance error is generated due to the distance detecting method, so that simply changing the setting of the low-pass filter causes a relative error. There is a problem that it is difficult to satisfy both the alarm stability problem due to the error vibration of the speed and the alarm time delay problem.

The present invention has been made to solve the above problems, and when applied to an inter-vehicle distance warning device, it solves the problem of warning stability due to error vibration of relative speed, and gives a warning. An object of the present invention is to provide a vehicle radar device capable of solving the problem of time delay.

[0018]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, in the invention described in claim 1, the reflected waves from the target object are sampled and added, and the outputs thereof are arranged in time series to form a straight line connecting the sampling point and the sampling points before and after or other sampling points. In a vehicular radar device that obtains an intersection and uses the time corresponding to this intersection for distance calculation, the relative velocity calculation means for calculating the relative velocity from continuously detected distances, and the distance between the target object and the maximum detection of the radar. Selection means for activating the relative speed calculating means when the distance is within a predetermined distance set to a value equal to or less than the distance.

As described above, according to the present invention, the relative speed is calculated only in the range where the distance to the target object is equal to or less than the predetermined distance set to the maximum detection distance of the radar or less, so the calculated relative speed is a true value. Since it shows the same value as, it becomes almost the same value after the low-pass filter. Therefore, the warning distance shows a value that is almost the same as the true value after the relative speed is calculated, and is constant thereafter, so that the warning can be issued at an appropriate timing.

The invention according to claim 2 is configured such that the predetermined distance of the selecting means is variable. With such a configuration, more appropriate measurement can be performed according to the traveling state of the vehicle and the like. The variable means is, for example, as described in claim 3, a running state of the vehicle (for example, vehicle speed) or a change in the output state sampled and added as described in claim 4 (for example, presence or absence of saturation). ), The predetermined distance is changed.

Further, in the invention according to claim 5,
Instead of changing the predetermined distance in the selection means,
The selecting means is configured to selectively actuate the relative speed calculating means in response to a change in the state of the sampled / added output. For example, when the state of the sampled / added output is saturated, it is detected that the sampling / added output at the slowest sampling point is no longer the first and second peaks, and the relative speed calculation means is activated. It may be configured as described above (details will be described later in the embodiment).

[0022]

According to the present invention, in a situation where the target object is approaching from a distance farther than the maximum detection distance, the relative velocity is not erroneously calculated as zero, and the low pass for noise removal is eliminated. Even if the filter is applied, the correct relative speed is calculated at a distance shorter than the predetermined distance,
It is possible to obtain the effect that the alarm can be issued at an appropriate timing without delay.

When the predetermined distance of the selecting means is changed according to the traveling condition of the vehicle as described in claims 2 and 3, the higher the traveling vehicle speed, the greater the traveling speed. By setting it so that it becomes smaller as the speed decreases, it is possible to warn from a distance that is not much different from the maximum detection distance during high speed running when the warning distance of the inter-vehicle distance warning becomes long, and at the time of low speed running when the warning distance is short. Therefore, it is possible to reduce the probability that an erroneous relative speed output is generated.

Further, as described in claims 2 and 4, when the predetermined distance of the selection means is changed according to the change of the state of the sampled / added output, the reflection from the target object is prevented. Accurate measurement can be performed even when the output that is strongly sampled and added is saturated.

Further, as described in claim 5, the selecting means may be configured so as to directly control the operation of the relative speed calculating means in accordance with the change in the state of the sampled / added output. An effect similar to that of 4 can be obtained.

[0026]

FIG. 1 is a block diagram showing a first embodiment of the present invention. First, the configuration will be described.
In FIG. 1, reference numeral 3 denotes a radar device, which comprises a pulse signal transmitting means 1 and a reflected pulse signal receiving means 2. Also, 4
Is a control means for controlling the pulse signal transmission timing, 6
Is a sampling / adding means, 8 is a peak detecting means for sampling / adding signals, 7 is a distance calculating means using a microcomputer or the like, 10 is a relative speed calculating means for calculating a relative speed from the distance, and 9 is a relative speed calculating means. It is a selection means for selectively operating. That is, the selection means 9 activates the relative speed calculation means 10 only under certain conditions according to the distance detected by the distance calculation means 7.

FIG. 2 is a block diagram showing the configuration of a system in which the radar device shown in FIG. 1 is applied to an inter-vehicle distance warning device. The device of FIG. 2 includes a radar device 11 that detects an inter-vehicle distance R and a relative speed V _r with respect to a preceding vehicle, a vehicle speed sensor 12 that detects a vehicle speed V _f , an inter-vehicle distance R from the radar device 11, and a relative speed V _{r. r} and the vehicle speed V _f from the vehicle speed sensor 12
The information processing circuit 13 determines whether or not to generate an alarm according to the above, and generates an alarm signal, and an alarm generation device 14 that receives the alarm signal and generates an alarm.

Next, the operation will be described. The radar device 11 detects the distance R to the target object in front (the preceding vehicle) and the relative speed V _r of the preceding vehicle, and the vehicle speed sensor 12 detects the own vehicle speed V _f . These three types of signal values are input to the information processing circuit 13, and the information processing circuit 13 calculates the warning distance R _s according to the relative speed V _r and the vehicle speed V _f . After that, by comparing the warning distance R _s and the inter-vehicle distance R, the degree of approach to the preceding vehicle is determined, and an alarm signal is output to issue an alarm when it is determined that the vehicle is excessively close. In response to this alarm signal, the alarm generator 14 issues an alarm. As a method of issuing this alarm, for example, visual presentation using an alarm lamp or the like, and auditory presentation such as generation of an alarm sound are performed.

Next, the detailed operation of the radar device 11 will be described based on the processing flow shown in FIG. First, in step 101, the inter-vehicle distance R is detected. The method of detecting the inter-vehicle distance R here is the same as the method described in the conventional example, and in the distance calculating means 7 of FIG. 1, the peak value of the sampling addition output and its front and rear are connected by a straight line to form an intersection point. Then, using this as the reflected wave reception time, the required time T from the transmission of the distance measurement wave to the reception of the reflected wave from the target object is calculated. Further, the distance R from the required time T to the target object is detected. Next, at step 102, it is judged whether or not there is a current detection distance, and the current detection distance R
If there is not, the processing of this time is ended, but the detection distance R
If there is, the process proceeds to step 103 and thereafter.

In step 103, the value of the detection distance R is judged, and the relative speed calculating means 10 is selected by the selecting means 9 in FIG.
Decide whether to activate. That is, assuming that the maximum detection distance of the radar device is R _max , a predetermined value R _limit set to R _max or less is compared with the current detection distance R, and the current detection distance R is smaller than the predetermined value R _limit. In this case, the relative speed calculating means 10 is operated in step 104 and thereafter, and if not, the current processing is ended without operating the relative speed calculating means 10. Here, the maximum detection distance R _max corresponds to the fastest sampling point. The time of the last sampling point is T from the transmission of the wave for distance measurement.
if a _post-max seconds, the maximum detection distance R _{m ax} is R _max =
C × T _max / 2 (where C is the speed of the distance measuring wave, and in the case of light, the speed of light).

The predetermined value R _limit is preferably as large as possible in order to detect a target object as far as possible, which is the original purpose of the radar device. However, in order to secure the relative velocity calculation accuracy, the maximum value is required. It is necessary to secure a certain degree of difference between the detection distance R _max and the predetermined value R _limit . For example, when the maximum detection distance R _max is 120 m, the predetermined value R _lim
It may be set to about 110 m.

In step 104, the relative speed V _r0 is calculated by _{obtaining the} change over time in the detection distance R. As the calculation method, a least square method with high stability and accuracy is used. However, for calculation, in addition to the current detection distance, for example, the past three data are required, and if the past detection distance data are not available, the relative speed cannot be calculated. In addition, even if the past detection distance data are available, if the current detection distance data is significantly different from the previous distance data (for example, it is changed by 10 m or more during the measurement cycle dt of 100 msec). in case of,
Since there is a high possibility that a target object different from the previous time has started to be detected, the distance data of the past three times recorded so far are reset, and a new memory is made from this time. In this way, when the relative speed V _r0 cannot be calculated, step 1
The processing of this time is ended at 05, and the process returns to the beginning.

As a formula for calculating the relative velocity V _r , for example, the following formula (1) using the least square method can be used.

[0034]

[Equation 1]

However, R ₀ : the value of the current detection distance R R _{1 to} R ₃ : the value of the detection distance R in the past 1 to 3 cycles before dt: the measurement cycle If the relative speed V _r0 can be calculated, the step Proceeding to 106, the following (Equation 2) is applied to the calculated value of the relative speed V _r0.
A low-pass filter like the formula is applied to obtain the corrected relative velocity V _r0L .

[0036]

[Equation 2]

However, V _{r0 to} V _r2 : relative velocities for the present and past two cycles without the low pass filter V _{r1L to} V _r2L : relative velocities for the past two cycles after the low pass filter A ₁ , A ₂ , B _{0 to} B ₂ : constants determined by the setting of the low-pass filter The values of the above-mentioned constants A ₁ , A ₂ , B _{0 to} B ₂ are, for example, a measurement cycle dt of 0.1 second, and a cut-off frequency of the low-pass filter ( When the cutoff frequency) fc is set to 1.5 Hz, it becomes as shown in the following (Equation 3). A ₁ = -0.823865 A ₂ = 0.294220 B ₀ = 0.1117589 (Equation 3) B ₁ = 0.2335177 B ₂ = 0.1117589 Further, this low-pass filter is expressed by the above (Equation 2). As can be seen, the value of the relative speed after the low-pass filter for the past two cycles is required, and therefore the expression (2) is used after the third cycle from the start of detection. If there is no past relative velocity data for 2 cycles from the beginning of detection,
The value before applying the low-pass filter may be used as it is. Then, in step 107, the detected distance R and the corrected relative speed V _r0L are output to the information processing circuit 13, and the processing of this time is ended. The information processing circuit 13 makes an alarm judgment as to whether or not an alarm should be issued. The details will be described below.

FIG. 4 is a flow chart showing the processing of warning judgment. First, in step 121, the radar device 11
Each data such as the detected distance R and the relative speed V _r0L detected by the vehicle speed V _f detected by the vehicle speed sensor 12 is read. Next, in step 122, the warning distance is calculated. As the alarm distance, the alarm distance R _s1 for the primary alarm and the alarm distance R _s2 for the secondary alarm are calculated. The warning distance R _s1 for the primary warning is a warning distance with some margin, and the warning distance R _s2 for the secondary warning is a warning distance for the emergency warning. These alarm distances are calculated based on, for example, the following (Formula 4) and (Formula 5). (Primary alarm distance)

[0039]

(Equation 4)

(Secondary alarm distance)

[0041]

(Equation 5)

[0042] However, V _a: speed of the preceding vehicle α _1, α _2: deceleration T _d1, T _d2: sky run time T _x1, T _x2: spare time It should be noted that the speed V _a of the above-mentioned preceding vehicle, step The relative speed V _r0L read in step 121 and the own vehicle speed V _{f are} calculated by the following equation (6). V _a = V _r0L + V _f ( _Equation 6) However, in the equation (Equation 6), the value of the relative speed V _r0L is
A positive value is used when the inter-vehicle distance is increased, and a negative value is used when the inter-vehicle distance is decreased. Further, the idle running time is the time from when the general driver determines that the vehicle is excessively approaching until the deceleration or braking actually operates, and a statistically obtained value is used.

Next, at step 123, the inter-vehicle distance R and 1
The next alarm distance R _s1 is compared and the degree of excessive approach is determined by the following equation (7). R ≦ R _s1 (Equation 7) If the equation (Equation 7) is satisfied, it means that the distance is equal to or less than the primary alarm distance, and the primary alarm or the secondary alarm is generated after step 124. If the expression (7) is not satisfied, no alarm is generated and the process returns to the next step.

In step 124, the secondary warning distance R _s2 and the inter-vehicle distance R are further compared, and the necessity of the emergency warning is determined by the following equation (8). R ≦ R _s2 (Equation 8) When the above (Equation 8) is satisfied, it means that the inter-vehicle distance R is equal to or less than the secondary warning distance R _s2 , and step 1
Proceed to step 25 and issue an emergency secondary alarm. When the inter-vehicle distance R is larger than the secondary warning distance R _{s2, the routine} proceeds to step 127, where the primary warning is generated.

The primary alarm and the secondary alarm are, for example, the following alarms. First, in the primary alarm, in step 127, it is determined whether the alarm time Δt has elapsed from the current time Tn and the alarm generation time T _F1 , and if it is within the alarm time Δt, the primary alarm is issued in step 128. Is generated, and a command signal is output to the alarm generation device 14 to turn on the alarm lamp for the primary alarm in step 129. Alarm time Δ
If it exceeds t, the alarm sound for the primary alarm is stopped in step 130, and only the alarm lamp is turned on.
That is, in the primary alarm, even if the state corresponding to the primary alarm continues, the alarm sound is stopped after a predetermined time, and only the alarm lamp is kept on.

In step 125, an alarm sound for a secondary alarm is generated, and in step 126, a command signal is output to the alarm generator 14 so as to turn on the alarm lamp for the secondary alarm. That is, in the secondary alarm, the alarm sound and the alarm lamp continue to be activated while the state corresponding to the secondary alarm continues. After both the primary alarm and the secondary alarm are generated, the process returns to the beginning and the next process is repeated.

By the above processing, for example, a predetermined value R for the maximum detection distance R _max = 120 m
_When setting _limit = 110 m, the calculated relative speed, change in warning distance, and the status of warning issuance are as follows.
It becomes as shown in FIG. In FIG. 5, first, when the true distance to the target object is larger than the predetermined value R _limit = 110 m, the relative speed calculation means is not operated,
The relative velocity value is not calculated. In the conventional case, when the maximum detection distance R _max = 120 m or more, the relative speed was an erroneous value of zero.

Next, the calculation of the relative speed is started from the time when it becomes less than the predetermined value R _limit . Since the relative speed calculated there is the same value as the true value (for example, 100 km / h), it is almost the same value (10
0 km / h). Conventionally, since the initial relative speed was zero, it took time for the relative speed after the low-pass filter to rise with a delay and reach a true value (100 km / h). Therefore, the rising of the warning distance was delayed and the warning was also delayed, but according to the present embodiment, the warning distance shows almost the same value as the true value after the calculation of the relative speed is started, and thereafter it is constant. Therefore, the warning can be issued at an appropriate timing.

Further, in the present embodiment, the predetermined value R _limit for selectively operating the relative speed calculating means 10 is described as a constant value, but the means for detecting the running condition of the host vehicle is used. Is provided, and the predetermined value R _limit is changed according to the situation, it is possible to obtain an operation that matches the purpose of the apparatus. For example, when the traveling speed of the vehicle is detected as the traveling condition of the vehicle, the inter-vehicle distance warning is set by setting the value of R _limit to be larger as the traveling vehicle speed is higher and smaller as the traveling speed is lower. It is possible to warn from a distance that is not much different from the maximum detection distance when driving at high speeds where the warning distance becomes long, and it is possible to reduce the probability that an incorrect relative speed output will occur when driving at low speeds when the warning distance is short. .

Next, a second embodiment will be described. This embodiment differs from the first embodiment in the operation of the selection means 9. That is, in the first embodiment, the relative speed calculation means 1 is used according to the value of the detection distance R.
While 0 is selectively operated, in the present embodiment, the relative speed calculation means 10 is selectively operated based on the results of sampling and addition.

FIG. 6 is a block diagram showing the configuration of the second embodiment. The configuration is almost the same as that of the first embodiment shown in FIG. 1, but the selecting means 9 for selectively operating the relative speed calculating means 10 is the sampling / adding means 6
The difference is that it is performed based on the sampling addition output in.

Next, the operation will be described. First, FIG.
The relationship between the sampling / addition output and the distance measurement accuracy will be described with reference to FIG. FIG. 7 is a diagram showing a change in the sampling / addition output when the target object approaches from a distance farther than the maximum detection distance, and shows a case where the sampling / addition output is not saturated. In FIG. 7, the distance to the target object becomes smaller in the order of (1) to (4). Here, the slowest sampling point of the radar device corresponds to a distance to the target object of 120 m, and the sampling point is arranged every 10 m.
In addition, in (1) to (4), the numerals, respectively, indicate the first and second peaks of the sampling / addition output, and the outputs on both sides of these two outputs are connected by a straight line, and the intersection point Calculate the distance from the position to the target object.

As in the cases (1) and (2), when the output value at the slowest sampling point is the first or second peak, sampling at a point farther than the slowest sampling point is performed. Since there is no additional value output, it is not possible to directly connect a straight line and the distance cannot be calculated. However, instead of directly connecting a straight line, the slope at the farthest sampling point is estimated based on the slope on the opposite side of the peak [the slope on the side in (1)], as shown by the broken line. Since it is possible to draw a straight line, it is possible to detect the distance. However, in this case, the accuracy of the detected distance becomes worse as compared with the scenes of (3) and (4).

In the above case, the predetermined value R smaller than the maximum detection distance is used as in the first embodiment.
_limit (for example, 110 m) is set, and a predetermined value R _limit
If the relative speed calculation means 10 is selectively operated according to the magnitude relationship between the detected distance and the detected distance, a correct relative speed output can be obtained.

On the other hand, FIG. 8 shows a scene in which the sampling / addition output is saturated due to the high reflection level of the target object. (1) and (2) show a case where one saturation occurs, and (3) and (4) show a case where two saturations occur. When the saturation is one and the farthest sampling point is at the first or second peak as in (1), the error in the detection distance is large. (2)
As described above, the detection distance accuracy improves when the first and second peaks disappear, so in this case, the predetermined value R _limit is
It should be set to a value smaller than 110 m (for example, 105 m).

Similarly, when there are two saturations and the farthest sampling point is at the first or second peak as in (3), the error in the detection distance is large,
If the first and second peaks are eliminated as shown in (4), the detection distance accuracy is improved. In this case, the predetermined value R
_{The limit} needs to be set to a value (for example, 100 m) that is smaller than that when there is only one saturation.

As described above, the detection accuracy can be improved by changing the predetermined value R _limit according to the saturation state in the sampling / addition output. In the present embodiment, the above-mentioned processing is performed.

The detailed operation will be described below based on the processing flow shown in FIG. In FIG. 9, first, step 2
At 01, the inter-vehicle distance R is detected. Then, in step 202, the presence or absence of the current detection distance R is determined, and if the current detection distance R is not present, the current processing ends, but
If there is the detection distance R, the process proceeds to step 203 and subsequent steps.

In step 203, a predetermined value R _limit is determined according to the state of sampling / addition output. Specifically, as described above, it is detected whether or not the sampling / addition output is saturated, and when the saturation is not generated, the predetermined value 110m as usual is set, and when the saturation is generated, the Depending on the number of sampling points at which saturation occurs, the predetermined value R _limit is set to be smaller as the number of saturation points increases. For example, if there is one saturation point 105m
In the two cases, it may be set to 100 m.

Since the processing contents after step 204 are the same as the processing after step 103 in FIG. 3, the description thereof will be omitted. Further, since the processing contents after the relative speed calculation and the alarm output are the same as those in the first embodiment described in FIG. 4, the description thereof will be omitted.

By the above processing, the predetermined value R for selectively operating the relative speed calculating means 10 is obtained.
By changing the _limit to an appropriate value according to the state of the sampling / addition output, for example, even when the sampling / addition output is saturated due to a very high reflection level of the target object, Only the correct relative speed can be calculated and the alarm can be issued at an appropriate timing.

Further, in the present embodiment, sampling /
The predetermined value R _limit for selectively operating the relative speed calculating means 10 is changed based on the state of the added output. For example, the determination as to whether to operate the relative speed calculating means 10 is performed by sampling. -The same effect can be obtained even if the configuration is performed directly from the result of addition output. For example, it is detected that the sampling / addition output at the latest sampling point is no longer the first and second peaks, that is, the state of (2) in FIG. The speed calculation means 10 may be configured to operate.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration when the present invention is applied to an inter-vehicle distance warning device.

FIG. 3 is a flowchart showing a distance calculation process according to the first embodiment.

FIG. 4 is a flowchart showing an alarm process according to the first embodiment.

FIG. 5 is an operation diagram showing measurement and alarm states according to the first embodiment.

FIG. 6 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 7 is a diagram showing an example of changes in sampling / addition output when saturation does not occur in the sampling / addition output.

FIG. 8 is a diagram showing an example of changes in sampling / addition output when saturation occurs in the sampling / addition output.

FIG. 9 is a flowchart showing distance calculation processing according to the second embodiment.

FIG. 10 is an operation diagram showing an example of measurement and alarm states in the conventional example.

FIG. 11 is a characteristic diagram showing an example of detection distance accuracy in a conventional example.

FIG. 12 is a characteristic diagram showing an example of the relationship between the relative amplitude error amplitude and the true relative speed in the conventional example.

FIG. 13: The cutoff frequency of the low pass filter is set to 0.
The characteristic view which shows the damping effect of relative velocity error amplitude when it sets to 4 Hz.

FIG. 14 shows a case where a stopped vehicle is approaching at a predetermined speed,
The characteristic view which shows the output result at the time of calculating a relative velocity by applying a low pass filter having a cutoff frequency of 0.4 Hz.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pulse signal sending means 2 ... Reflected pulse signal receiving means 3 ... Radar device 4 ... Control means for controlling pulse signal sending timing 6 ... Sampling / adding means 7 ... Distance calculating means 8 ... Sampling / adding signal peak detecting means 9 ... Selection means 10 ... Relative speed calculation means 11 ... Radar device 12 ... Vehicle speed sensor 13 ... Information processing circuit 14 ... Warning generator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G08G 1/16 G08G 1/16 E

Claims (5)

[Claims] 1. A pulse of an electromagnetic wave, light or a sound wave is transmitted,
A straight line connecting the sampling point and the sampling points and the sampling points and the output that is sampled and added to the reflected wave of the transmitted electromagnetic wave, light or sound wave from the target object and arranged in time series. In the vehicle radar device that uses the time corresponding to this intersection for distance calculation, the relative speed calculation means that calculates the relative speed from the continuously detected distance and the distance between the target object and the maximum A vehicle radar device comprising: a selection unit that operates the relative speed calculation unit when the range is equal to or less than a predetermined distance set to a value equal to or less than the detection distance. 2. The vehicle radar apparatus according to claim 1, further comprising means for varying a predetermined distance of the selecting means. 3. The vehicle radar device according to claim 2, wherein the means for varying the predetermined distance changes the predetermined distance according to a traveling state of the vehicle. 4. The radar device for a vehicle according to claim 2, wherein the means for varying the predetermined distance changes the predetermined distance according to a change in the state of the output sampled and added. 5. Transmitting pulses of electromagnetic waves, light or sound waves,
A straight line connecting the sampling point and the sampling points and the sampling points and the output that is sampled and added to the reflected wave of the transmitted electromagnetic wave, light or sound wave from the target object and arranged in time series. In the vehicle radar device that uses the time corresponding to this intersection to calculate the distance, the relative velocity calculation means that calculates the relative velocity from the continuously detected distance, and the change in the state of the output sampled and added And a selecting means for selectively operating the relative speed calculating means in accordance with the above.