JP3346867B2 - Stationary object identification type mobile radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stationary object discriminating type mobile station which continuously radiates radio waves forward while changing the frequency, receives reflected waves, and measures the distance to a stationary object or a moving object ahead. Related to body radar devices.

[0002]

2. Description of the Related Art An FM-CW (frequency modulation type continuous wave) for continuously radiating radio waves forward while changing a frequency, receiving a reflected wave from a target (target), and measuring a distance to the target. A wave-type mobile radar device has been researched and developed. The FM-CW method can be manufactured at low cost because the configuration of the high-frequency circuit is simpler than the conventional pulse method.

[0003] A mobile radar device of the FM-CW system is mounted on an automobile to measure and display an inter-vehicle distance to a preceding vehicle instantaneously, or to operate an automatic driving system such as auto cruise according to the inter-vehicle distance. A proposal has been made.

The FM-CW radar device can measure not only the distance to the target but also the moving speed of the target. The distance to the target is calculated by measuring the required time of a radio wave reciprocating between the radar device and the target, that is, the detection delay time (corresponding to a frequency difference) of the reflected wave with respect to the transmitted wave. On the other hand, the moving speed of the target measures the Doppler effect of the reflected wave generated in accordance with the moving speed of the target, that is, the frequency shift amount (corresponding to the frequency difference) of the received reflected wave with respect to the frequency of the transmitted wave. Is calculated.

In the FM-CW radar device, for example, a millimeter-wave band FM-modulated wave is transmitted in a range of several tens of MHz around a center frequency of several tens of GHz. Also,
As a method of calculating the distance and the moving speed of the target from the frequency difference between the transmitted wave and the received wave, a frequency analysis method using fast Fourier transform (FFT) is employed.

[0006] Here, beat signals of a transmitted wave and a reflected wave are collected for a rising section and a falling section of the frequency of the FM modulation cycle, respectively. The extracted beat signals are respectively subjected to fast Fourier transform and converted into two types of frequency spectra. By reading the frequencies of the corresponding peaks on the two types of frequency spectrums, the distance and moving speed of the target are calculated. After the A / D conversion of the beat signal of the analog signal, all the operations are digital arithmetic processing.

FIG. 5 is an explanatory diagram of an on-vehicle radar device of the FM-CW system. In the figure, (a) shows the running state, (b) shows the transmitted and received radio waves, (c) shows the beat signal, and (d) shows the frequency spectrum. Here, reflected waves from a plurality of front targets including a stationary object are received in a superimposed manner.

In FIG. 5A, a radio wave 50 is transmitted forward from an own vehicle 51 by the FM-CW system.
The radio wave 50 is reflected by a plurality of targets existing ahead, that is, the preceding vehicles 52 and 53, and a guardrail 54 installed along a curve to form a reflected wave.

In FIG. 5B, the transmission wave 55 shown in FIG.
Is around the center frequency f _0, the modulation width [Delta] F, is FM-modulated at a repetition period 1 / f _m. The reflected waves of the respective targets are received by the vehicle 51 with a time delay as a distance component and a Doppler shift as a relative speed component.
The RF signal of the reflected wave received is mixed with the RF signal of the transmitted wave to form a beat signal as shown in FIG.

In FIG. 5C, the frequency f of the beat signal
_b is own vehicle 51 and the target of the relative distance R, using the relative velocity _{V, f b = (4 ·} ΔF · f m / c) · R ± (2 · f 0 · V / c) = f r ± f _d (1) Here, _fr is a beat frequency according to the relative distance, and f _d is a beat frequency according to the Doppler shift.

Then, during the FM modulation cycle, the beat frequency f _up = f _r −f _d in the up beat section where the frequency rises,
Beat frequency f _dn in the down beat section where the frequency falls
= The relation f _r + f _d, the relative distance R and the relative velocity v
Is expressed as _{R = (c / 2ΔFf m)} · (f dn + f up) v = (c / f 0) · (f dn -f up) ... (2). That is, the relative distance R and the relative speed v are obtained by measuring the frequencies f _dn and f _up of the beat signal in the upbeat section and the downbeat section, respectively.

As a method of measuring a beat signal, a method of frequency analysis by fast Fourier transform (FFT) is employed. Beat signals are collected in the upbeat section and the downbeat section, and each beat signal is
And converted into respective frequency spectra. Then, among the peaks appearing in the two kinds of frequency spectrums, peaks having similar peak frequencies are regarded as being due to the same target, and the frequencies f _dn and f _up of the beat signal are obtained.

In FIG. 5D, a frequency spectrum obtained by performing a fast Fourier transform of a beat signal using a DSP has spectrum data arranged one by one at discrete frequency points (calculation points or data points). It is a discrete function. The interval between the data points is determined by balancing the measurement range of the inter-vehicle distance, the measurement resolution of the distance and the relative speed, the calculation capability of the DSP, and the like. In a practical example, the measurement range is set to a maximum of 200 m, the bandwidth of the frequency spectrum is determined, and the resolution of the distance is set to several meters and the resolution of the relative speed is set to about 5 to 15 km without significantly increasing the calculation load. .

For example, a peak P1 on the frequency spectrum in the downbeat section and a peak P2 on the frequency spectrum in the upbeat section are considered to correspond to the same target. The frequency of peak P1 is f _DN , peak P
When the frequency of frequency 2 is measured as f _UP , the relative distance R between the vehicle 51 and the target is given by the following equation (2): R = k ₁ (f _DN + f _UP ) / 2 k ₁ = c / ΔFf _m ... (3). Further, the relative speed v between the vehicle 51 and the target is as follows: v = k ₂ (f _DN −f _UP ) / 2 k ₂ = 2c / f ₀ (4)

A typical procedure for analyzing the frequency of a beat signal to form a frequency spectrum is as follows: the beat signal is band-limited by a low-pass filter, sampled by an A / D converter, and used by a DSP (Digital Signal Processor). This is a procedure for performing matrix operation processing of fast Fourier transform.

[0016]

The main purpose of the vehicle-mounted radar apparatus shown in FIG. 5 is to measure the inter-vehicle distance to the nearest preceding vehicle 52. If there are stationary objects, there is a possibility that reflected waves from these stationary objects may hinder the measurement of the inter-vehicle distance to the preceding vehicle 52.

In the case where two peaks having similar peak frequencies in the two kinds of frequency spectra are regarded as being caused by the same target, as long as the preceding vehicle traveling in the same direction on the same lane in a normal traveling state is regarded as the target. Even if there are a plurality of targets, the possibility of erroneously recognizing a combination of peaks of another target as a combination of the same target is extremely low.

However, when the preceding vehicle is stopped and the relative speed is close to 100 km / h, the influence of the beat frequency f _d according to the Doppler shift cannot be ignored, and the running preceding vehicle in two kinds of frequency spectrums is required. In the interval between the vehicle peaks, a peak of the stopped preceding vehicle may be formed. In this case, the peaks of different targets are confused with the peaks of the same target, and a relative distance R far from the actual value of the preceding vehicle running is output.

Further, while the peak of the preceding vehicle is a single point, in the case of a continuous large stationary object such as the guardrail 54, as shown in the peaks Q1 and Q2 in FIG. , And a number of unstable peaks are formed on this peak.

Therefore, the preceding vehicles 52, 53 running
May be buried in the peak of the guardrail 54 and cannot be identified. Further, the peaks of the preceding vehicles 52 and 53 may be confused with the unstable peak above the peak of the guardrail 54. In such a case, the inter-vehicle distance R, which is far from the actual value up to the preceding vehicles 52 and 53, is of course
Is output.

If the outputted inter-vehicle distance R is different from the actual value, the on-vehicle radar device for ensuring the safety during traveling may adversely increase the danger by erroneously determining the driver. . Further, in a system that issues an alarm for a short inter-vehicle distance, there is a problem that the alarm continues to sound due to a malfunction. Further, when an automatic driving function such as cruise control for controlling the speed of the vehicle 51 while maintaining a constant inter-vehicle distance is introduced, reliability of speed control cannot be ensured.

By the way, on the two kinds of frequency spectra, the matching of the peak height and the peak shape (degree of coincidence) may be examined to find the corresponding peak. However, if an arithmetic program for examining the peak height and the shape of the peak shape in detail is adopted, the load on the arithmetic element increases. Also,
When examining the degree of matching of the peak shape, it is possible to avoid confusing a continuous long stationary object with a preceding vehicle, but inevitably confusing a stopped preceding vehicle with a running preceding vehicle.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a stationary object identification type mobile radar device capable of distinguishing a stationary object from a moving object by simple arithmetic processing and measuring a distance to the moving object without being confused by the stationary object. And

[0024]

Means for Solving the Problems In FIG.
The stationary object identification type mobile radar device includes: a transmitting unit 11 that transmits a radio wave whose frequency is regularly changed toward an object to be measured; and a high-frequency signal that receives a reflected wave from the object to be measured. The receiving means 12 integrates the high-frequency signals of the transmitted radio waves to form a beat signal, and the beat signal is subjected to fast Fourier transform in a section where the frequency rises and a section where the frequency falls, thereby forming two types of frequency spectra. And a calculating means 14 for making necessary peaks correspond to the two kinds of frequency spectra and calculating a distance from the frequency of each peak to the object to be measured. In the mounted mobile radar device, a measuring means 15 for measuring the moving speed of the moving object itself and a frequency spectrum of a stationary object peak caused by the moving speed are provided. Calculated based on the shift amount on the moving velocity vector, the correction means 1 having at least one of the correction, adjusting means for adjusting the frequency resolution the shift amount of the two kinds of frequency spectrum in the shift amount
And identification means 17 for identifying the effect of the correction on the corresponding peaks on the two kinds of frequency spectra, at least one of which is corrected, and identifying whether the peak is a stationary object or a moving object. It is.

According to a second aspect of the present invention, there is provided a stationary object identification type mobile radar apparatus according to the first aspect, wherein the adjusting means divides the calculated shift amount by frequency resolution to obtain a decimal number. Adjustment means for adjusting the shift amount by rounding the following.

According to a third aspect of the present invention, there is provided the stationary object identification type mobile radar device according to the first aspect, wherein the correcting means divides the calculated shift amount by a frequency resolution. Correction means for shifting one of the two types of frequency spectrums with respect to the two shift amounts sandwiched therebetween, and the identification means includes two frequency spectra obtained by correcting one of the two types of frequency spectra and the other frequency spectrum. And an identification means for identifying whether the peak is a stationary object by identifying the effect of the correction.

According to a fourth aspect of the present invention, there is provided the stationary object identification type mobile radar device according to the first aspect, wherein the correction means divides the calculated shift amount by a frequency resolution. Correction means for shifting one of the frequency spectrums with respect to the two shift amounts sandwiched therebetween, interpolating the two shifted spectrum values sandwiching the respective frequency points to obtain an interpolated frequency spectrum, and the identification means comprises: And identification means for identifying the effect of the correction in the interpolated frequency spectrum and the other of the two types of frequency spectrum, and identifying whether or not the peak is a stationary object.

According to a fifth aspect of the present invention, there is provided a stationary object identification type mobile radar device according to the first aspect, wherein the correction means accumulates a plurality of the two types of frequency spectrums, and stores each of the two types of frequency spectra. Correction means for determining a weighted average value of the spectrum value at the frequency point which goes back in the past to form a comparison frequency spectrum,
The identification means is an identification means for identifying the effect of the correction in the comparison frequency spectrum and the other of the two types of frequency spectrum, and identifying whether or not the peak is a stationary object.

[0029] The stationary object identification type mobile radar device according to claim 6 is the stationary object identification type mobile radar device according to claim 1, wherein the correction means includes one frequency point for each of the two types of frequency spectrums. Correction means for forming an enhanced frequency spectrum with a value obtained by adding the spectrum values of the frequency points on both sides to the spectrum value of the frequency point, and the identification means, An identification means for identifying the effect of the correction and identifying whether or not the peak is a stationary object.

A still object identifying type mobile radar device according to a seventh aspect of the present invention is the stationary object identifying type mobile radar device according to the first aspect, wherein the two types of frequency spectrums identified as a stationary object separately from a moving object. Calculating means for detecting the frequency of the corresponding peak above and calculating the distance to the stationary object, and output means for outputting data of the calculated distance to the stationary object separately from the moving object are provided. It is a thing.

For example, in the stationary object-identifying mobile radar device of the first aspect, the second display means is provided separately from the first display means for displaying the distance data to the moving object, and is capable of displaying the distance data as a numerical value. Calculating means for detecting the frequency of the corresponding peak on the two types of frequency spectrums identified as stationary objects and calculating the distance to the stationary object; and displaying the calculated distance to the stationary object in a second display And control means for causing the means to display.

[0032]

In FIG. 1, in the stationary object identification type mobile radar apparatus according to the first aspect, at least one frequency axis of the two types of frequency spectrums is shifted uniformly, and the moving speed of the mobile body itself in the two types of frequency spectrums Cancels out the Doppler effect due to As a result, on two types of frequency spectrums, at least one of which is corrected,
The peak positions (frequency) of the corresponding stationary objects match, and the stationary objects can be identified by a simple operation using data of two types of frequency spectra.

Further, by canceling the peak of a long stationary object such as the guardrail 54 in FIG. 5A, the peak of a moving object which has been buried in the peak of the stationary object and which has become difficult to distinguish is made more noticeable. It becomes possible to detect accurately. The calculation of the relative distance and the relative speed using the peak frequency of the moving object detected from the result of the calculation operation is obtained by a calculation formula from which the influence of the shift is removed.

In the correction means 16, for example, (1) two types of frequency spectrums, at least one of which is corrected, are subtracted from each other (subtraction is performed at corresponding individual frequency points). At this time, the identification means 17 identifies a peak at which the amplitude of the subtraction becomes substantially zero as a stationary object. Correction means 1
In (6), two types of frequency spectrums of which at least one is corrected may be divided. At this time, the identification means 17 identifies a peak where the answer of the division becomes almost 1 as a stationary object.

The two types of frequency spectra used by the identification means 17 may be formed one by one from beat signals within one cycle of the frequency change of the transmitted radio wave. However, since the frequency change is continuously repeated in the same manner at short time intervals of 500 to 1 kHz, an average frequency spectrum is calculated for each of a section in which the frequency of a plurality of cycles rises and a section in which the frequency falls, and correction is performed for this. , Identification may be performed.

The calculating means 14 can calculate the distance only for the moving object, assuming that the peak of the identified stationary object did not exist on the original frequency spectrum. Thus, the distance calculation of the moving object (for example, the preceding vehicle) is not erroneously interrupted by the stationary object. However, with respect to the identified peak of the stationary object, the distance of the stationary object may be separately calculated to be used for alarming or the like.

The measuring means 15 is constituted by a speed sensor provided independently of the stationary object identifying type mobile radar device itself. In the case of a car, an existing ground sensor or wheel speed sensor may be used. The correction unit 16 calculates the Doppler effect of the reflected wave of the stationary object from the moving speed, and performs a correction process using the amount of frequency shift due to the Doppler effect.

In the calculation of the distance by the calculating means 14, as shown in FIG. 1, a conventional calculation formula may be applied by using the frequency spectrum formed by the converting means 13, but the correcting means may be used. It is also possible to use the frequency spectrum corrected at 16. In this case, a correction corresponding to the shift amount is added to the conventional formula.

In the stationary object identification type mobile radar device according to claims 2 to 6, in consideration of the fact that the frequency spectrum is a discrete data array at a constant data interval,
A preferred calculation method for the correction means and the identification means is proposed. That is, without increasing the load on the DSP and the arithmetic element, the stability of peak identification is ensured, and the identification of stationary objects and the measurement resolution (accuracy of distance and relative speed) of moving objects are ensured.

Here, when at least one of the two types of frequency spectrums is shifted, the data points (operational points on the frequency axis) of the two are made to coincide with each other, thereby enabling the operation of operation between discrete data arrays. This is because data points of two kinds of frequency spectra rarely coincide with each other when shifted by the speed obtained by the measuring means. This is because if the data points are not matched, it is not possible to execute an operation between frequency spectra that are discrete functions.

According to the stationary object identification type mobile radar device of the second aspect, when one of the two kinds of frequency spectrums is shifted to cancel out the Doppler effect component relating to the stationary object, the deviation between the calculation points of the two is rounded off. Align. That is, if the shift amount exceeds the frequency resolution of 0.5, the frequency spectrum is shifted to the next data point. If less than 0.5 increments, then shift to the next lower data point.

According to the third aspect of the present invention, when the one of the two kinds of frequency spectrums is shifted to offset the Doppler effect for the stationary object,
Two kinds of frequency spectra are formed corresponding to two kinds of shift amounts (two data points) sandwiching the "interval between data points" with the calculated value. These two types of frequency spectra are respectively subtracted (or divided) from the other frequency spectrum. Then, (1) a stationary object adopts a frequency spectrum that is more clearly identified, (2) all peaks and continuous peaks determined to be a stationary object in any of the two types of frequency spectra are regarded as a stationary object, And the like.

According to the fourth aspect of the present invention, the data of two data points is interpolated for one of the frequency spectrum shifted by the calculated shift amount or the other of the other frequency spectrum. hand,
The data located at the frequency point of the other frequency spectrum is formed. By repeating this operation for all data points, a frequency spectrum is formed for subtraction (or division).

At this time, it is desirable to perform the interpolation calculation processing on the frequency spectrum having the larger peak power before the interpolation calculation. This is because, when the interpolation calculation process is performed, the peak sharpness is reduced by averaging data of two adjacent frequency points. If subtraction (division) is performed after reducing the difference in peak sharpness between the two types of frequency spectrums, the answer at the portion of the stationary object becomes close to 0 (1), and the stationary object can be erroneously determined. Is less effective.

According to the stationary object identification type mobile radar device of the present invention, the frequency change of the transmitted radio wave is continuously and similarly repeated at short time intervals, and is corrected from a plurality of periods retroactively from the present to the past. , Two kinds of frequency spectrums for identification are formed. As a result, an error in identifying a stationary object is reduced as compared with a case where only two frequency spectra extracted from a frequency change in one cycle are used, and the peak of a moving object is confused with the effect of temporary noise. The likelihood decreases.

Then, instead of performing simple averaging of the data at each frequency point in each of the sections in which the frequency of a plurality of cycles going back from the present to the past rises and the sections in which the frequencies fall, the present invention goes from the present to the past. Weighted averaging with reduced weight is employed. This allows the current stationary,
The effects of moving objects are emphasized.

In the stationary object identification type mobile radar device according to the sixth aspect, the low peak (moving object or stationary object) on the frequency spectrum is emphasized so that the peak is not lost. Since the peak of a stationary object or a moving object is formed over a plurality of frequency points (the sampling frequency is selected so that a peak is formed over a plurality of frequency points), three consecutive frequencies are formed. By executing the process of adding the data of the points to obtain the data of the center frequency point at all the frequency points, the amplitude (data) of the peak portion is emphasized compared to the amplitude (data) of the non-peak location. .

In the stationary object identification type mobile radar device according to the seventh aspect, for example, a display element for numerically displaying the distance to the moving object is arranged in addition to a display element for numerically displaying the distance to the moving object. Then, by detecting the frequencies of the corresponding peaks on the two kinds of frequency spectra identified as the stationary object, the distance to the stationary object is calculated, and the distance to the stationary object is displayed along with the distance to the moving object.

The distance to the stationary object may be output as data to another device. It functions as one sensor of an autonomous driving system such as auto cruise and measures the distance to a vehicle waiting for a traffic light or a parked vehicle on the road. The operation of reading the peak frequency from the frequency spectrum and calculating the distance may be performed in the same manner as in the case of a moving object.

[0050]

FIG. 2 is an explanatory diagram of an FM-CW radar device of an embodiment, FIG. 3 is an explanatory diagram of an FM-CW radar device of an embodiment, and FIG. 4 is an explanatory diagram of signal processing. 2, (a) shows a hardware configuration, (b) shows signal processing, and (c) shows a display unit. FIG.
Among them, (a) shows subtraction processing, (b) shows interpolation processing, and (c) shows enhancement processing. Here, a radar device for measuring an inter-vehicle distance to a preceding vehicle which is mounted on a vehicle is shown, and a frequency spectrum of a section where the frequency of a transmitted radio wave rises is shifted by the own vehicle speed, and a frequency spectrum of a section where the frequency decreases is reduced Subtract.

In FIG. 2A, the signal processing recognition unit 24
Are integrated as an ECU (Electronic Control Unit). The signal processing recognition unit 24 includes a low-pass filter 24A, an A / D converter 24B, a DSP (Di
gital Signal Processor) 24C, microcomputer circuit 24
E, a sequence circuit 24D, and a plurality of memory elements (not shown).

The low-pass filter 24A narrows the band of the beat signal output as an analog signal from the radar sensor 22 in conformity with the sampling frequency (several 100 kHz) of the A / D converter 24B. A / D conversion is performed on the banded beat signal, and from the A / D-converted beat signal, predetermined time periods of an UP beat section and a DOWN beat section are respectively extracted and temporarily stored in a memory (not shown). DSP
24C performs (1) fast Fourier transform on the AD conversion data temporarily stored in the memory to form frequency spectra in an UP beat section and a DOWN beat section, respectively.

The microcomputer circuit 24E calculates the ground speed of the vehicle from the output of the vehicle speed sensor 25 and inputs the data to the DSP 24C. Then, it receives the distance data calculated by the DSP 24C and the identification result of the moving object / stationary object. Then, an inter-vehicle distance and the like are displayed through the display unit 28.

The microcomputer circuit 24E calculates a safe inter-vehicle distance and a braking distance from the vehicle speed and the like, and issues an alarm when the distance to the preceding vehicle or the obstacle ahead of the vehicle falls below these distances. Alternatively, the throttle opening may be controlled so as to keep the inter-vehicle distance constant, and the speed of the host vehicle may be adjusted.

The DSP 24C further calculates (2) the shift amount of the frequency spectrum corresponding to the ground speed, (3) corrects one of the frequency spectra with the shift amount, and performs subtraction processing with the other. A stationary object and a moving object are identified from the result of the subtraction processing, and the frequency of the nearest peak adjacent to the moving object on two types of frequency spectrums is read to calculate the inter-vehicle distance. (5) The distance to the stationary object is also calculated separately for the stationary object.However, since the own vehicle speed is accurately measured, it is not necessary to check the correspondence between the peaks in both frequency spectra. It is only necessary to detect the frequency of the peak read above.

In the DSP 24C, the calculation load of (1) fast Fourier transform is large, but the calculation load of (3) correction to (5) distance calculation is considerably large. Therefore, there are restrictions on the sampling frequency of the beat signal, the number of quantization bits, the bandwidth of the frequency spectrum, the number of data points, and the like. In addition, the arithmetic processing for comparing the peaks of the same target on two types of frequency spectra is required. A simple method is also required.

The vehicle speed sensor 25 detects the teeth of a gear-shaped rotating body which is formed of a magnetic material and interlocks with the wheels by a magnetic sensor and outputs ON / OFF of the magnetic flux as a digital signal. The vehicle speed sensor 25 is provided, for example, on the axle of the rear wheel, and outputs a digital signal that changes according to the rotation speed of the wheel. The microcomputer circuit 24E detects the ON-OFF frequency of the digital signal and calculates the ground speed of the vehicle. Vehicle speed sensor 25
Introduces several automatic control functions of the car, such as cruise control that maintains a constant speed, and ABS (Anti-Lock Breaking Sys
tem) can also be used.

The radar sensor 22 is the same as that described in the conventional example of FIG. 5, and emits a transmission radio wave whose frequency repeatedly rises and falls linearly at a constant period toward the front of the vehicle. Then, a reflected radio wave from a moving object or a stationary object ahead is detected, and a high-frequency signal of the reflected radio wave is integrated with a high-frequency signal of the transmitted radio wave at that time to form a beat signal and output.

The sequence circuit 24D controls the frequency of the radio wave transmitted from the radar sensor 22, and operates the A / D converter 24B in response to the frequency change.
Synchronize the operation of P24C. Thereby, the range in which the fast Fourier transform of the beat signal is performed is positioned in the section where the frequency increases and the section where the frequency decreases.

In FIG. 2B, the beat signal output from the radar sensor 22 shown in FIG. 2A has an UP section in which the frequency of the transmitted radio wave rises linearly, and a linear decrease in the frequency of the transmitted radio wave. And down-converted into down-sampled data, and A / D converted to quantized data (amplitude-time signal) 32U, 32D. Quantized data 32U, 32
D is cut out of a predetermined time by an appropriate window function, and is subjected to fast Fourier transform to obtain UP section spectrum data 33U and DOWN section spectrum data 33D indicating the distribution of frequency components.

UP section spectrum data 33U and DO
Peak extraction processing is performed for each of the WN section spectrum data 33D, and the UP section peak frequency 3
4U and DOWN section peak frequency 34D are obtained.
Here, peak frequencies 34U and 34D were extracted from the individual spectrum data 33U and 33D by the complex frequency interpolation method. The complex frequency interpolation method is a frequency identification method using phase information, and can be executed by a relatively simple vector operation. According to this method, the peak position between two data points can be specified with high accuracy without increasing the number of spectrum data (= increase in calculation load).

The extraction results of the peak frequencies 34U and 34D are temporarily stored in a memory (not shown). An inter-vehicle distance calculation 35 is executed based on the UP section peak frequency 34U and the DOWN section peak frequency 34D.

On the other hand, in the stationary object identification processing 36, the data obtained by shifting the UP section spectrum data 33U and the DO
By subtracting the WN section spectrum data 33D, a stationary object and a moving object are identified. The identification result of the stationary object and the moving object is used when specifying a combination of the UP section peak frequency 34U and the DOWN section peak frequency 34D used for the distance calculation. That is, the frequencies of all the moving object peaks in the UP section spectrum data 33U and the DOWN section spectrum data 33D are read, and the combination of the peaks adjacent on the two frequency axes is determined to be the same moving object (preceding vehicle). Is done.

In FIG. 2C, the display unit 28 shown in FIG.
Is provided with a buzzer 28A for generating an alarm, a volume control knob 28B for the buzzer 28A, and a setting knob 28C for setting the alarm distance in a plurality of steps. When the preceding vehicle is detected by the radar device, the lamp 37A is turned on. The inter-vehicle distance to the preceding vehicle measured by the radar device is numerically displayed on the display 37B.

On the other hand, when a stationary object such as a guardrail is detected by the radar device, the lamp 38A is turned on.
The distance to the stationary object measured by the radar device is numerically displayed on the display 38B. Switch 38C
Accordingly, the operator can arbitrarily set whether or not to perform the detection of the stationary object and the distance measurement of the stationary object by the radar device. When the changeover switch 38C is set to "OFF", only the display of the preceding vehicle by the lamp 37A and the display 37B maintains the function, and the data relating to the stationary object is not used.

In FIG. 3, the signal processing recognizing section 24 shown in FIG. 2A first performs a fast Fourier transform on a beat signal in an UP beat section in which the frequency rises and a DOWN beat section in which the frequency falls, and obtains a frequency spectrum S _UP ,
An _SDN is formed. In parallel with this, the own vehicle speed is calculated from the output of the vehicle speed sensor, and the shift amount Δf of the frequency spectrum S _UP corresponding to the own vehicle speed is calculated. Then, a corrected frequency spectrum S _{SH in} which the frequency spectrum S _UP in the UP beat section is shifted to the higher side by Δf is formed.

Next, the corrected frequency spectrum S _SH is subtracted from the frequency spectrum S _DN in the DOWN beat section, and the frequency spectrum S which cancels the peak of the stationary object is obtained.
_X is formed. Further, peak data P _UP and P _DN are extracted from the frequency spectrum S _{UP in the UP} beat section and the frequency spectrum S _{DN in the} DOWN beat section, respectively. In step 30, peak data P _UP and P _DN are searched for on the frequency spectrum S _X , and are determined to be a stationary object (clutter) if they are eliminated and eliminated, but if they remain without being eliminated, they are moving objects. (Target).

Finally, the relative distance is calculated separately for each of the stationary object and the moving object, and the relative speed is calculated for the moving object. The distance between the stationary object and the moving object is separately displayed and output.

In FIG. 4A, a corrected frequency spectrum S _SH obtained by shifting the frequency spectrum S _UP in the UP beat section according to the vehicle speed is subtracted from the frequency spectrum S _{DN in the} DOWN beat section to obtain a frequency spectrum S _X. Is formed. In this case the peak of the stationary object is offset, peak a value of around 0 disappeared on the frequency spectrum S _X is determined to be a stationary object.

Incidentally, the subtraction processing of the frequency spectrum S _DN and the corrected frequency spectrum S _SH may be replaced with division processing. Two frequency spectra S _DN , S
Approximately equal spectrum data located at the same sampling position of _SH becomes a value close to 1 by the division process. On the other hand, for a moving object having no peak corresponding to the same sampling position, the answer of division is 2, 3, 0.3,
0.6 mag. A stationary object can be determined by identifying the answer of the division by a band-shaped threshold level centered at 1.

In FIG. 4B, in the present embodiment, the correction frequency spectrum S _SH is subjected to an interpolation process in order to align the sampling positions of the frequency spectrum S _DN and the correction frequency spectrum S _SH . That is, when the frequency spectrum S _UP is shifted by the shift amount calculated from the own vehicle speed, the position (frequency) of the spectrum data of the frequency spectrum S _DN and the corrected frequency spectrum S _SH is reduced by a small number of the answers obtained by dividing the shift amount by the frequency resolution. Deviations and subtraction errors increase. Therefore, the correction frequency spectrum S
_From two adjacent spectrum data of _SH , spectrum data at a sampling position equal to the frequency spectrum S _DN is interpolated.

The interpolation data 42A and the interpolation data 42A are set at sampling positions that match the frequency spectrum S _{DN in the} DOWN beat section.
42B, 42C and 42D are formed. Interpolation data 42
A is linear interpolation of data 41A and 41B, interpolation data 42B is linear interpolation of data 41B and 41C, interpolation data 42C is linear interpolation of data 41C and 41D, and interpolation data 42D is data 41D and 41E.
Are calculated by the linear interpolation. A corrected frequency spectrum S _SH obtained by interpolation correction of the frequency spectrum S _DN is subtracted.

Referring to FIG. 4C, in this embodiment, when detecting the peak position (frequency), the entire frequency spectrum is emphasized to make the peak stand out on the frequency spectrum. That is, three consecutive spectrum data are added to obtain the spectrum data at the central sampling position. As a result, a slow peak becomes a sharp peak, and when a peak is identified at a certain threshold level, the possibility that the peak is overlooked is low.

[0074]

According to the stationary object identification type mobile radar device of the first aspect, it is possible to identify the stationary object (clutter) and the moving object (target) with high accuracy in the FM-CW radar device. This identification can be realized, for example, only by a slight change in the processing program in the arithmetic unit. Therefore, in the on-vehicle radar device, it is possible to reduce malfunctions of the system (alarm or follow-up running) caused by recognizing the clutter (stationary object) as the target (the preceding vehicle).

Further, since a stationary object and a moving object can be distinguished by a simple computation operation, the computational load for identification is light, and
Even if the sampling frequency of the beat signal is not increased, the interval between operation points (data points) in the fast Fourier transform is reduced, and the total number of spectrum data is not increased, distance and relative speed can be measured with high accuracy. Therefore, it is easy to improve the accuracy of the measurement of the distance between vehicles and the like and to improve the responsiveness.

According to the stationary object identification type mobile radar device of the second aspect, even if the frequency spectrum is formed by discrete spectrum data, the two types of frequency spectrums are subtracted (divided) to obtain the stationary object. Can be identified. Then, the fractional part of the answer obtained by dividing the shift amount by the frequency resolution can be identified more accurately than when simple round-up or round-down processing is performed. Further, since the calculation is simple, it is not necessary to increase the load on the arithmetic element and the storage element, and high-speed processing can be performed.

According to the third aspect of the present invention, two types of comparison are performed in parallel.
The stationary object identification accuracy is higher than in the case of the stationary object identification type mobile radar device.

According to the stationary object identification type mobile radar device of the fourth aspect, the fractional part of the answer obtained by dividing the shift amount by the frequency resolution is used as it is in the interpolation processing for the two frequency spectra to be compared and calculated. You do not have to round up or down the points. Therefore, an error that occurs when the frequency points of the two frequency spectra are matched is reduced, and the identification accuracy of the stationary object is higher than in the case of the stationary object identification type mobile radar device of the second and third aspects.

According to the stationary object identification type mobile radar device of the fifth aspect, since a plurality of frequency spectrums are synthesized (averaged) in each of the section where the frequency rises and the section where the frequency falls, one by one. Compared to the case where the frequency spectrum is used, it is less susceptible to temporary noise and environmental changes in the radio wave radiation space. In addition, since weighting (filtering processing) is performed giving priority to the present time, identification of a stationary object having a high response speed and distance measurement of a phase object can be performed in real time.

According to the stationary object identification type mobile radar apparatus of the sixth aspect, a slow peak becomes a sharp peak, and the possibility that a peak is overlooked when a peak is identified with a certain threshold value is low.

According to the stationary object identification type mobile radar device of the present invention, the distance to the stationary object is displayed separately from the distance of the moving object. It can alert the operator.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory diagram of an FM-CW radar device according to an embodiment.

FIG. 3 is an explanatory diagram of a processing routine.

FIG. 4 is an explanatory diagram of signal processing.

FIG. 5 is an explanatory diagram of an on-vehicle radar device of the FM-CW system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Sending means 12 Receiving means 13 Conversion means 14 Arithmetic means 15 Measurement means 16 Correction means 17 Identification means

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor: Tokio Shinagawa 1-2-2, Goshodori, Hyogo-ku, Kobe City, Hyogo Prefecture Inside Fujitsu Ten Limited (56) References JP-A-4-315083 (JP, A) JP-A-4-305184 (JP, A) JP-A-7-98375 (JP, A) JP-A-5-232214 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S7 / 00-7/42 G01S 13/00-13/95

Claims (7)

(57) [Claims] A transmitting means for transmitting a transmission radio wave whose frequency is regularly changed toward an object to be measured; and a transmitting means for transmitting a reflected wave from the object to a high-frequency signal received at that time. Receiving means (12) for integrating a high frequency signal of a radio wave to form a beat signal; and a conversion for forming two kinds of frequency spectrums by performing a fast Fourier transform on the beat signal in a section where the frequency rises and a section where the frequency falls. Means (13), and calculating means (14) for associating required peaks with the two kinds of frequency spectrums and calculating a distance from the frequency of each peak to the object to be measured. In the mounted mobile radar device, measuring means (15) for measuring a moving speed of the mobile body itself
And calculating a shift amount on a frequency spectrum that a stationary object peak has due to the moving speed based on the moving speed,
Correcting means (16) having an adjusting means for correcting at least one of the two kinds of frequency spectrums with the shift amount and adjusting the shift amount with a frequency resolution; and adjusting the at least one of the two kinds of frequency spectra. A stationary object identifying type mobile radar device, characterized in that an identification means (17) for identifying whether the peak is a stationary object or a moving object is provided by identifying the effect of the correction on the corresponding peak of (i). 2. The stationary object identifying type mobile radar device according to claim 1, wherein the adjusting means adjusts the shift amount by dividing the calculated shift amount by a frequency resolution and rounding a decimal fraction. A stationary object identification type mobile radar device characterized by the following. 3. The mobile radar apparatus according to claim 1, wherein the correction unit is configured to determine the two shift amounts sandwiching a value obtained by dividing the calculated shift amount by frequency resolution.
Correction means for shifting one of the two types of frequency spectra, and the identification means identifies the effect of the correction on the two frequency spectra obtained by correcting one of the two types of frequency spectra and the other frequency spectrum. A stationary object identification type mobile radar device, wherein the identification means identifies whether or not the peak is a stationary object. 4. The stationary-object-identifying mobile radar device according to claim 1, wherein the correction unit shifts one of the frequency spectra for two shift amounts sandwiching a value obtained by dividing the calculated shift amount by frequency resolution. Correction means for performing complementary operation on two shifted spectrum values sandwiching each frequency point to obtain a complementary frequency spectrum, and the identification means includes the complementary frequency spectrum and the two kinds of frequencies. A stationary object identification type mobile radar device, characterized by identifying means for identifying whether or not the peak is a stationary object by identifying the effect of the correction with the other of the spectrums. 5. The stationary-object-identifying mobile radar device according to claim 1, wherein the correction means accumulates a plurality of the two types of frequency spectra, and weights the spectrum values at respective frequency points in the past. Correction means for determining an average value to form a comparison frequency spectrum, and the identification means identifies the effect of the correction in the comparison frequency spectrum and the other of the two types of frequency spectrums, and determines a peak. A stationary object identifying type mobile radar device, characterized in that: is a stationary object. 6. The stationary-object-identifying mobile radar device according to claim 1, wherein the correction unit includes:
Correction means for forming an emphasized frequency spectrum in which a value obtained by adding the spectrum value of both frequency points to the spectrum value of one frequency point is the spectrum value of the frequency point; A stationary object identifying type mobile radar device, characterized by identifying means for identifying the effect of the correction on the type frequency spectrum and identifying whether or not the peak is a stationary object. 7. The stationary object identification type mobile radar device according to claim 1, wherein, apart from a moving object, a frequency of a corresponding peak on the two kinds of frequency spectra identified as a stationary object is detected, A stationary object identification type moving body, comprising: a calculating means for calculating a distance to a stationary object; and an output means for outputting data of the calculated distance to the stationary object separately from a moving object. Radar equipment.