JP4910955B2 - Radar equipment for vehicles - Google Patents

Description

  The present invention relates to a vehicular radar apparatus that detects an object existing around a vehicle by transmitting and receiving radar waves.

  Conventionally, a monopulse radar device has been known as a vehicle radar device (see, for example, Patent Document 1). This monopulse radar device receives a reflected wave of a radar wave by two antennas arranged at a predetermined interval, and based on the phase difference between the received signals, the direction of the object that caused the reflected wave is generated. Is calculated. The direction calculation principle will be briefly described.

  For example, as shown in FIG. 13, radar waves having a wavelength λ reflected by a target (object) M at an angle (azimuth) θ formed by the perpendiculars of the antennas A1 and A2 are arranged with an interval D 2 Assume that the signals are received by the antennas A1 and A2. In this case, a difference Δd occurs between the path lengths of the radar waves received by the antennas A1 and A2. This path length difference Δd changes in accordance with the angle θ between the perpendicular of the antennas A1 and A2 and the arrival direction of the radar wave reflected by the target M. Therefore, the path length difference Δd is obtained as the phase difference Δφ between the two received signals, and the azimuth (angle θ) of the target M can be obtained from the phase difference Δφ. Here, the relationship between the phase difference Δφ and the angle θ between the two received signals is expressed by the following formula 1.

(Equation 1)
Δφ = (2π / λ) Dsinθ
When the angle θ is sufficiently small, sin θ≈θ. Therefore, when Equation 1 is transformed with respect to the angle θ, Equation 2 is obtained.

(Equation 2)
θ = Δφ · λ / (2π · D)
Next, a method for calculating the phase difference Δφ will be described. First, a triangular wave transmission signal having an ascending portion where the frequency rises and a descending portion where the frequency falls is transmitted as a radar wave, and the radar wave reflected by the object is received by the two antennas A1 and A2. Generate a received signal. Then, for each of the ascending part and the descending part, the transmission signal and the reception signal are mixed and a frequency signal corresponding to the difference between the frequency of the transmission signal and the frequency of the reception signal (the ascending part beat signal and the descending part beat signal). ) Further, frequency analysis is performed on each of the rising part beat signal and the falling part beat signal by fast Fourier transform (FFT), and the frequency is increased for each section of the rising part where the frequency of the transmission signal rises and the falling part where the frequency decreases. Obtain spectral data. This frequency spectrum data is obtained as a complex vector for each frequency.

  And the peak of each frequency spectrum is detected from the absolute value of the complex vector for each frequency in each frequency spectrum data of the ascending part and the descending part, and the ascending part peak frequency and the descending part peak frequency are specified. In addition, these rising part peak frequency and falling part peak frequency generate | occur | produce by the radar wave reflected by the target object, and become a frequency according to the distance and relative velocity with the said target object.

  When the rising peak frequency and the falling peak frequency are specified, the phase of the beat signal at the rising peak frequency and the falling peak frequency is calculated. This phase can be obtained, for example, from the angle formed by the complex vector and the real axis. Then, by subtracting the phases at the rising peak frequency of the beat signal calculated for each received signal and subtracting the phases at the falling peak frequency, the phase difference of the rising peak frequency and the falling peak frequency The phase difference can be obtained.

When the phase difference is calculated in this way, one of the phase difference at the rising peak frequency and the phase difference at the falling peak frequency is appropriately selected as the phase difference Δφ for azimuth calculation. Then, based on the selected phase difference Δφ, the orientation of the object is calculated using Equation 2 above.
JP-A-9-152478

  Here, the ascending part peak frequency and the descending part peak frequency are used for calculating the distance and relative speed of the object in addition to calculating the direction of the object. Below, the calculation method of the distance and relative speed based on the rising part peak frequency and the falling part peak frequency is demonstrated.

  As shown in FIG. 14A, when the moving speeds of the vehicle to which the radar device is attached and the object that reflects the radar wave are equal (relative speed V = 0), the radar wave reflected by the object is the target. The distance D between the objects is delayed by the time required for the round trip. In this case, the reception signal fr is shifted along the time axis from the transmission signal fs by the delay time, and the rising peak frequency fbu and the falling peak frequency fbd are equal (fbu = fbd).

  On the other hand, when the moving speed of the vehicle to which the radar apparatus is attached and the object are different (relative speed V ≠ 0), the radar wave reflected by the object undergoes a Doppler shift corresponding to the relative speed V with respect to the object. For this reason, the reception signal fr is shifted along the frequency axis by the amount of the Doppler component due to the relative speed V in addition to the shift for the delay time corresponding to the distance D to the object. In this case, as shown in FIGS. 14A and 14B, the rising peak frequency fbu and the falling peak frequency fbd are different (fb1 ≠ fb2).

  Thus, the reception signal fr is shifted in the time axis and frequency axis directions according to the distance D to the object and the relative speed V. In other words, the frequency difference on the time axis between the transmission signal fs and the reception signal fr corresponds to the distance D from the object, and the frequency difference on the frequency axis corresponds to the relative speed V. Each frequency can be obtained from the following Equation 3 and Equation 4.

(Equation 3)
Frequency fb = (| fbu | + | fbd |) / 2 corresponding to the distance D

(Equation 4)
Frequency fd = (| fbu | − | fbd |) / 2 corresponding to the relative velocity V
From the frequencies fb and fd corresponding to the distance D and the relative speed V, the distance D to the object and the relative speed V can be calculated by the following formulas 5 and 6.

(Equation 5)
D = {C / (4 × ΔF × fm)} × fb

(Equation 6)
V = {C / (2 × f0)} × fd
ΔF is the frequency modulation width of the transmission signal fs, f0 is the center frequency of the transmission signal fs, fm is the repetition frequency, and C is the speed of light.

  However, when there are a plurality of objects that reflect the radar wave, the ascending portion peak frequency fbu and the descending portion peak frequency fbd appear in a number corresponding to the object. Therefore, in order to calculate the distance D and the relative speed V with each object, it is necessary to combine the ascending peak frequency fbu and the descending peak frequency fbd for each object (pair match).

  As a pair matching method, it is conceivable to combine the rising peak frequency fbu and the falling peak frequency fbd on condition that the above-described phase difference Δφ is approximate. This is because the rising peak frequency fbu and the falling peak frequency fbd are considered to be generated by the same object when having an approximate phase difference Δφ.

  However, when the peak frequencies of a plurality of objects are overlapped, if a phase at the peak frequency is calculated, a combined phase in which the phases of the reflected waves from the plurality of objects are combined is calculated. Therefore, in this case, correct pair matching cannot be performed from the phase difference between the rising peak frequency and the falling peak frequency. As a result, there is a possibility that the distance and the relative speed are erroneously calculated including the direction of the object.

  The present invention has been made in view of the above points, and in a situation where the orientation of the object cannot be correctly calculated from the peak frequencies of the ascending part beat signal and the descending part beat signal, the orientation of the object is erroneously calculated. An object of the present invention is to provide a vehicular radar apparatus that can reliably prevent this.

In order to achieve the above-mentioned object, the vehicular radar device according to claim 1,
Transmitting means for transmitting a transmission signal, which is frequency-modulated by a modulated signal having a waveform having at least an ascending part and a descending part, as a radar wave;
Two receiving means arranged at a predetermined interval and receiving a reflected wave and generating a received signal when the transmitted radar wave is reflected by an object;
In a vehicular radar apparatus comprising signal processing means for calculating the direction of an object based on received signals generated by two receiving means,
Each of the two receiving means includes beat signal generating means for generating a beat signal corresponding to the frequency difference between the reception signal and the transmission signal for each of the rising and falling parts of the transmission signal,
The signal processing means includes azimuth calculating means for calculating the azimuth of the object based on the phase difference at the peak frequency of at least one beat signal of the ascending part and the descending part respectively generated from the reception signals of the two receiving means. ,
Abort to determine the accuracy of the waveform indicating the peak frequency of the beat signal of at least one of the rising part and the falling part, and to stop calculating the azimuth by the azimuth calculating means when the accuracy does not satisfy the predetermined standard and means,
The stopping means determines that the accuracy of the waveform indicating the peak frequency does not satisfy a predetermined criterion when the integral value of at least one of the beat signal of the rising part and the falling part is equal to or greater than a predetermined threshold value, The calculation of the direction by the direction calculation means is stopped .

  As described above, when the accuracy of the waveform indicating the peak frequency of at least one of the beat signal of the ascending part and the descending part does not satisfy the predetermined standard, the calculation of the azimuth by the azimuth calculating unit is stopped, thereby It is possible to reliably prevent the direction of the object from being erroneously calculated.

Specifically, the canceling means does not satisfy the predetermined standard for the accuracy of the waveform indicating the peak frequency when the integrated value of at least one beat signal of the rising part and the falling part is equal to or greater than a predetermined threshold value. determined to a, it cancels the orientation calculation of by azimuth calculating means. When the integral value of the beat signal is equal to or greater than a predetermined threshold, a large number of peaks may be generated due to the reflected wave from the roadside reflector, or the level of the entire beat signal may be increased due to the influence of noise or the like. Conceivable. In such a case, since it becomes difficult to accurately detect the peak frequency itself, the calculation of the azimuth is stopped.

(Reference example)
First, before describing an embodiment of the present invention, a reference example serving as a basis of the present embodiment will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a vehicular radar apparatus according to a reference example.

  As shown in FIG. 1, the radar apparatus 2 according to the reference example includes a transmitter 4 that transmits a millimeter wave band radar wave via a transmission antenna AS. The transmitter 4 includes a D / A converter 12 for digital / analog (D / A) conversion of a signal having a pattern in which the frequency gradually increases, gradually decreases, and is constant with respect to the time output from the microcomputer 10, and the D / A A signal output from the converter 12 is input as a modulation signal, a voltage-controlled oscillator 14 that generates a millimeter-wave band high-frequency signal modulated by the modulation signal, and an output of the power-controlled oscillator 14 is a transmission signal fs and a local signal. And a distributor 16 that distributes power to L. The transmission signal fs is supplied to the transmission antenna AS, and the local signal L is supplied to the receiver 6.

  In addition, the radar device 2 according to the reference example includes two receiving antennas AR1 and AR2 that receive a radar wave (hereinafter referred to as a reflected wave) reflected by an object such as a preceding vehicle and are arranged at a predetermined interval. I have. When the reflected waves are received by the two antennas AR 1 and AR 2, the antennas AR 1 and AR 2 generate reception signals fr 1 and fr 2 corresponding to the reflected waves and give them to the receiver 6.

  The receiver 6 mixes the received signals fr1 and fr2 and the local signal L corresponding to the antennas AR1 and AR2, and generates two beat signals B1 and B2 corresponding to the frequency of the difference between these signals. Mixers MX1 and MX2 and two amplifiers AMP1 and AMP2 for amplifying beat signals B1 and B2 generated by the mixers MX1 and MX2, respectively. The amplifiers AMP1 and AMP2 also have a filter function for removing unnecessary high frequency components from the beat signals B1 and B2.

  The beat signals B1 and B2 amplified by the amplifiers AMP1 and AMP2 are given to the A / D conversion unit 8. The A / D converter 8 includes two A / D converters AD1 and AD2 that sample the beat signals B1 and B2 and convert them into digital data D1 and D2. Digital data D1 and D2 of the beat signals B1 and B2 converted by the A / D converters AD1 and AD2 are given to the microcomputer 10.

  The microcomputer 10 is composed mainly of a CPU, a ROM, and a RAM, and detects the distance, relative speed, and direction from an object such as a preceding vehicle based on the digital data D1 and D2 from the A / D conversion unit 8. Perform detection processing. Further, the microcomputer 10 includes a digital signal processor or the like for performing a fast Fourier transform (FFT) process on the digital data D1 and D2 when performing these processes.

  In the vehicle radar device 2 configured as described above, as shown in FIG. 3, as a result of modulation by a modulation signal having a pattern in which the frequency gradually increases, gradually decreases, and is constant, a frequency increase unit, a frequency decrease unit, and a frequency constant unit Is transmitted by the transmitter 4 via the transmission antenna AS. When the radar wave is reflected by an object such as a preceding vehicle, the reflected wave is received by the receiving antennas AR1 and AR2. At that time, the reception signals generated by the reception antennas AR1 and AR2 are mixed with the local signal L by the mixers MX1 and MX2 of the receiver 6, whereby each reception signal and the local signal L (transmission signal fr) are mixed. Beat signals B1 and B2 corresponding to the frequency component of the difference between the two are generated. Each of the A / D converters AD1 and AD2 samples the beat signals B1 and B2 by a predetermined number of times and performs A / D conversion for each of the frequency increasing portion, the frequency decreasing portion, and the constant frequency portion of the transmission signal fs. As a result, beat signals are generated by the frequency increasing unit, the frequency decreasing unit, and the frequency constant unit, respectively.

  Next, detection processing executed by the microcomputer 10 to detect the distance to the object, the relative speed, and the direction will be described based on the flowchart shown in FIG.

  First, in step S100, the digital data D1 and D2 of the beat signals B1 and B2 output from the receiver 6 by receiving a radar wave reflected by an object such as a preceding vehicle are respectively a frequency increasing unit and a frequency decreasing unit. In addition, a predetermined number is read in the fixed frequency part and temporarily stored in the RAM.

  In the subsequent step S110, frequency analysis processing (fast Fourier transform processing) is executed on each digital data D1 and D2 stored in the RAM as beat signals B1 and B2 of the frequency increasing portion and frequency decreasing portion. As a result of the fast Fourier transform process, complex vectors for each frequency of the beat signals B1 and B2 are obtained. The absolute value of this complex vector indicates the amplitude (intensity) of each corresponding frequency. That is, spectrum data indicating the intensity for each frequency is obtained for each of the beat signals B1 and B2 by the fast Fourier transform process. This fast Fourier transform process is performed separately for beat signals B1 and B2 in the frequency increasing section and beat signals B1 and B2 in the frequency decreasing section.

  Next, in step S120, the frequency spectrum data calculated for each beat signal B1, B2 is averaged for each of the frequency increasing part and the frequency decreasing part. In step S130, the common rising part peak frequency UPF and falling part peak frequency DPF of the beat signals B1 and B2 are extracted from the averaged rising part spectrum data and falling part spectrum data. In this case, all the frequency components that are peaks on the spectrum are extracted from the ascending spectrum data and the descending spectrum data, and the frequency is specified as the peak frequency.

  Here, different noises are superimposed on the beat signals B1 and B2, and since the performance of the reception channels and the antennas AR1 and AR2 are slightly different, the peak frequencies of the beat signals B1 and B2 are different. Deviation may occur. Therefore, the spectrum data indicating the intensity of each frequency component of each beat signal B1 and B2 is averaged as described above, and the common peak frequencies UPF and DPF are extracted from the result. Thereby, since the noise is random, the intensity of the noise component becomes smaller than the intensity of the peak frequencies UPF and DPF by the averaging process, and the S / N ratio can be improved. Theoretically, when receiving a reflected wave reflected by the same object, each of the beat signals B1 and B2 should have a peak frequency component at the same frequency. For this reason, spectrum data of one beat signal B1, B2 is obtained, a peak frequency is extracted from the spectrum data, and it can be estimated that the same peak frequency is generated in the other beat signals B1, B2. .

  As a result of the processing in step S130, the common rising peak frequency UPF and falling peak frequency DPF are extracted for each of the beat signals B1 and B2. As a method of detecting the peak frequency, for example, the change in the amplitude of each frequency is obtained sequentially, and the peak of the frequency at which the sign of the change in amplitude is reversed from positive to negative before and after that is peaked. What is necessary is just to specify as a frequency.

  In step S140, the phase difference between the beat signals B1 and B2 at the common rising and falling peak frequencies UPF and DPF is calculated. As a method for calculating this phase difference, the phase difference between the beat signals B1 and B2 at the peak frequency may be calculated from the angle formed by the complex vector and the real axis as in the prior art. . When there are peaks at a plurality of frequencies of the rising and falling beat signals B1 and B2, the phase difference between the beat signals B1 and B2 is calculated at each peak frequency.

  In step S150, the difference between the phase difference between the beat signals B1 and B2 at the rising peak frequency UPF calculated at step S140 and the phase difference between the beat signals B1 and B2 at the falling peak frequency DPF is less than a predetermined value, and The combination of the rising part peak frequency UPF and the falling part peak frequency DPF in which the difference in peak intensity is less than a predetermined value is determined. In this combination determination, when a combination that approximates the phase difference and the peak intensity is found, the ascending portion peak frequency UPF and the descending portion peak frequency DPF are pair matched.

  When there are a plurality of objects that reflect radar waves, ascending part peak frequencies UPF and descending part peak frequencies DPF appear according to the number of the objects, and therefore the ascending part peak frequency UPF and descending part peak frequency DPF Must be combined (pair match) for each object. In this reference example, when the rising part peak frequency UPF and the falling part peak frequency DPF are generated by reflected waves from the same object, the phase difference between the rising part and the falling part peak frequencies UPF and DPF is substantially the same. Focusing on the fact that the phase difference between the beat signals B1 and B2 at the rising and falling peak frequencies UPF and DPF2 is approximate, pair matching is performed.

  However, the condition for this pair match is not based only on the above-described phase difference and peak intensity difference, but may include other conditions such as the relative speed belonging to the range of −200 km / h to 100 km / h. good.

  For the combination of the rising part peak frequency UPF and the falling part peak frequency DPF pair-matched in step S150, in step S200, the beat signal B1, at the rising part or falling part peak frequencies UPF, DPF is calculated using the above-described equation 2. The direction θ of the object is calculated from the phase difference of B2. Thereafter, the process proceeds to step S210, and the distance D and the relative speed V from the object are calculated from the pair-matched ascending part peak frequency UPF and descending part peak frequency DPF using Equation 5 and Equation 6 described above. In step S220, the calculated azimuth θ, distance D, and relative speed V are stored as history data. The history data is composed of a plurality of azimuths θ, distances D, and relative speeds V calculated in the past. When there are a plurality of objects, the history data is classified and stored for each object. .

  On the other hand, if there is an ascending part peak frequency UPF and a descending part peak frequency DPF that are not pair-matched in step S150, the peak frequencies generated by the reflected waves from a plurality of objects coincide with each other due to the processing after step S160. It is determined whether or not a pair match has been made, and in such a case, an ascending part peak frequency UPF and a descending part peak frequency DPF to be pair matched are specified, and the azimuth θ of the object, the distance D, and The relative speed V is calculated.

  Here, an example of a situation in which peak frequencies generated by reflected waves from a plurality of objects overlap will be described with reference to FIG. FIG. 4 shows a situation where two vehicles A and B are traveling in front of the own vehicle when the own vehicle equipped with the radar device 2 is traveling on a road composed of a plurality of lanes. ing. At this time, the preceding vehicle A travels at a speed of a relative speed −v2 with respect to the own vehicle at a point that is a distance r away from the own vehicle, and the preceding vehicle B is at a point that is a distance R (> r) away from the own vehicle. It is assumed that the vehicle is traveling at a relative speed −v1 (| v1 | <| v2 |) with the host vehicle.

  In such a situation, as shown in FIG. 5, both the vehicles A and B have a relative speed with the own vehicle, so that the ascending portion peak frequencies UPF1, UPF2 and the descending portion peak frequency DPF are shifted. However, since the absolute value of the relative speed −v2 of the vehicle A is larger than the absolute value of the relative speed −v1 of the vehicle B, the deviation amount between the rising part peak frequency UPF1 and the falling part peak frequency DPF is large. Furthermore, since the distance R of the vehicle B is longer than the distance r of the vehicle A, the rising portion peak frequency UPF2 and the falling portion peak frequency DPF due to the reflected wave from the vehicle B appear in a higher frequency range. At this time, if the descending portion peak frequency DPF of the vehicle A moves to a high frequency range by Doppler shift, the descending portion peak frequency DPF of the vehicle A and the descending portion peak frequency DPF of the vehicle B may overlap.

  In such a case, the phases of the beat signals B1 and B2 at the descending peak frequency DPF are a phase obtained by combining the phase due to the reflected wave from the vehicle A and the phase due to the reflected wave from the vehicle B. For this reason, even if the phase difference between the beat signals B1 and B2 at the descending portion peak frequency DPF is calculated, it is different from the phase difference between the beat signals B1 and B2 at any of the ascending portion peak frequencies UPF1 and UPF2 of the vehicles A and B. Become.

  However, as shown in FIG. 6, when the frequency spectrum data is calculated by performing the fast Fourier transform on the beat signal of the constant frequency part, the relative speeds of the vehicle A and the vehicle B are different. , A peak occurs at the frequency corresponding to −v2. In this way, a plurality of objects having different relative velocities can be identified by referring to the frequency spectrum data of the beat signal of the constant frequency portion.

  Therefore, in step S160, frequency spectrum data is calculated by performing fast Fourier transform on the beat signal of the constant frequency portion. Thereafter, in step S170, it is determined whether or not there is a combination of the rising peak frequency UPF and the falling peak frequency DPF shifted by the relative speed corresponding to the peak frequency of the frequency spectrum data calculated in step S160. By such collation, it can be confirmed that the peak frequency is generated by the object having the same relative speed in the beat signal of the constant frequency part and the beat signal of the ascending part and the descending part.

  For example, in the example shown in FIG. 5, first, the rising peak frequency UPF and the falling are shifted by an amount corresponding to the relative speed (−v2) corresponding to the peak frequency generated in the spectrum data of the constant beat signal by the vehicle A. It is determined whether there is a combination with the partial peak frequency DPF. In this case, the rising portion peak frequency UPF1 and the falling portion peak frequency DPF satisfy the condition. Next, there is a combination of an ascending portion peak frequency UPF and a descending portion peak frequency DPF shifted by an amount corresponding to the relative speed (−v1) corresponding to the peak frequency generated in the spectrum data of the constant portion beat signal by the vehicle B. It is determined whether to do it. In this case, the rising part peak frequency UPF2 and the falling part peak frequency DPF satisfy the condition.

  If such confirmation is made, the process proceeds to step S180, and the corresponding rising part peak frequency UPF and falling part peak frequency DPF are pair matched. In step S190, the azimuth θ of the object is calculated from the phase difference at the peak frequency of the beat signal of the constant frequency portion. Thereafter, in the same manner as described above, in step S210, the distance D to the object and the relative speed V are calculated, and in step 220, the calculated distance D and relative speed V are stored as history data.

  As described above, according to the vehicle radar device according to the reference example, even when the peak frequency due to the plurality of objects overlaps in the ascending part beat signal or the descending part beat signal, While calculating the azimuth | direction of a target object, the pair matching of a rising part peak frequency and a falling part peak frequency is attained. Therefore, the object can be detected continuously without losing sight of the object such as the preceding vehicle.

(Embodiment)
A vehicle radar apparatus according to an embodiment will be described. The configuration of the vehicular radar apparatus according to the present embodiment is the same as that of the vehicular radar apparatus according to the above-described reference example, and thus the description thereof is omitted.

  When the accuracy of the waveform indicating the peak frequency of at least one beat signal of the ascending part and the descending part is inferior, the vehicular radar apparatus according to the present embodiment is subject to the object by other means as in the above-described reference example. Is not calculated, but the calculation of the azimuth using the beat signal is stopped, thereby reliably preventing the azimuth of the object from being erroneously calculated.

  FIG. 7 is a flowchart showing detection processing for detecting the distance to the object, the relative speed, and the direction according to the present embodiment. In this flowchart, most of the processing is common to the flowchart of FIG. For this reason, the same reference numbers are assigned to the same processes, and the description thereof is omitted.

  The processes that are characteristic in the flowchart of FIG. 7 are the processes of steps S121 and S122. Step S121 is executed after step S120 in which the frequency spectrum data calculated for each of the beat signals B1 and B2 is averaged for each frequency increasing portion and frequency decreasing portion. Then, an integration process is performed for each of the average spectrum data of the frequency increasing unit and the average spectrum data of the frequency decreasing unit calculated in step S120, and the ascending unit integration value and the descending unit integration value are calculated.

  In step S122, the ascending part integrated value and the descending part integrated value calculated in step S121 are compared with a predetermined threshold value. Then, when both the ascending part integral value and the descending part integral value are equal to or less than the predetermined threshold, the process proceeds to step S130 and the subsequent steps, and the direction θ, the distance D, and the relative speed V of the object are calculated. On the other hand, if one of the ascending part integral value and the descending part integral value is greater than the threshold value, the process returns to step S100 without calculating the orientation θ of the object.

  The above-mentioned ascending part integral value or descending part integral value exceeds a predetermined threshold value because a number of peak frequencies occur due to reflections from roadside reflectors such as guardrails in addition to the preceding vehicle to be detected and obstacles on the road. Or when the level of the entire beat signal is high due to the influence of noise or the like. FIG. 8 shows spectral data when there is reflection from a roadside reflector such as a guardrail and spectral data when there is no such reflection.

  When there is reflection from a roadside reflector, it is difficult to accurately detect the peak frequency from the object such as the preceding vehicle or perform the above-described pair match. There is a possibility of calculation. In this embodiment, the accuracy of the waveform indicating the peak frequency of the beat signal is increased by using the above-described ascending part integration value and the descending part integration value. If it is determined that the accuracy is inferior, the calculation of the bearing or the like is stopped.

(Modification 1)
In the embodiment described above, the peak of the beat signal is obtained using the ascending part integrated value and the descending part integrated value calculated by performing the integration process on each of the average spectrum data of the frequency increasing part and the average spectrum data of the frequency decreasing part. The accuracy of the waveform indicating the frequency was determined. On the other hand, in the first modification, the number of total peak frequencies in the ascending part spectrum data and the descending part spectrum data calculated by performing the fast Fourier transform processing on the ascending part beat signal and the descending part beat signal is as follows. The accuracy of the waveform indicating the peak frequency is determined based on the ratio of the number of peak frequencies matched in pairs.

  That is, as shown in the flowchart of FIG. 9, in step S141, the phase difference between the beat signals B1 and B2 at each rising portion peak frequency UPF calculated at step S140 and the beat signals B1 and B2 at each falling portion peak frequency DPF are calculated. All combinations of rising part peak frequency UPF and falling part peak frequency DPF that are less than a predetermined value are extracted. In step S142, the ratio of the number of pair matched peak frequencies is calculated based on the number of all peak frequencies in the ascending spectrum data or the descending spectrum data, and whether the ratio is equal to or greater than a predetermined threshold value. To determine.

  In the determination of step S142, if it is determined that the ratio of the number of pair matched peak frequencies is equal to or greater than a predetermined threshold, the process proceeds to step S143, and based on the pair matched ascending peak frequency UPF and descending peak frequency DPF, The azimuth θ, distance D, and relative speed V of the object are calculated. On the other hand, if it is determined in step S142 that the ratio of the number of pair-matched peak frequencies is smaller than a predetermined threshold, the calculation of the orientation θ and the like is stopped for all the objects.

  Thus, the accuracy of the waveform indicating the peak frequency can also be determined based on the ratio of the number of pair-matched peak frequencies. This is because, when there are many peak frequencies that are not pair-matched, a large number of peak frequencies are generated by roadside reflectors, and they overlap each other or contain many noise components.

(Modification 2)
In the second modification, the peak frequency density in the ascending part spectral data and the descending part spectral data calculated by performing the fast Fourier transform process on the ascending part beat signal and the descending part beat signal (that is, in a predetermined frequency range). The accuracy of the waveform indicating the peak frequency is determined based on the number of peak frequencies.

  That is, as shown in the flowchart of FIG. 10, in step S131, after the common rising part peak frequency UPF and falling part peak frequency DPF are extracted for each of the beat signals B1 and B2 in step S130, a predetermined frequency is obtained. The number of rising part peak frequencies UPF and the number of falling part peak frequencies DPF in the region are calculated, and these are compared with a predetermined threshold.

  In the determination of step S131, when it is determined that the number of rising part peak frequencies UPF and the number of falling part peak frequencies DPF are equal to or less than a predetermined threshold value, the process proceeds to step S140 and subsequent steps, and the direction θ, distance D, and The relative speed V is calculated. On the other hand, if it is determined in step S131 that the number of rising part peak frequencies UPF or the number of falling part peak frequencies DPF is greater than a predetermined threshold, the calculation of the orientation θ and the like for all objects is stopped.

  Thus, the accuracy of the waveform indicating the peak frequency can also be determined by the numbers of the rising peak frequency UPF and the falling peak frequency. This is because it is very unlikely that the number of peak frequencies exceeding the threshold value is generated by an object to be detected such as a preceding vehicle. When such a large number of peak frequencies occur, a large number of roadside reflectors This is because the possibility of receiving the reflected wave is high.

(Modification 3)
In the third modification, a change in the peak frequency of the ascending and descending beat signals is predicted based on the history data including the azimuth θ, the distance D, and the relative speed V of each object, and a plurality of objects are predicted by the prediction. When there is a high possibility that the peak frequencies overlap, it is determined that the accuracy of the waveform indicating the peak frequency does not satisfy a predetermined standard, and calculation of the azimuth and the like is stopped.

  That is, as shown in the flowchart of FIG. 11, in step S10, the reflected wave of each object is stored based on the history data that is stored in step S220 and includes the orientation θ, distance D, and relative velocity V of each object. The frequency at which the peak frequency is generated is predicted, and it is determined whether or not the peak frequency is generated by a plurality of objects in the same frequency band. The frequency at which this peak frequency is generated is obtained by predicting the distance D and the relative speed V by adding or subtracting the change in the distance D and the relative speed V in the history data to the latest distance D and the relative speed V, and the predicted distance. It calculates | requires by carrying out the back calculation of Numerical formula 3-Numerical formula 6 mentioned above from D and relative speed V.

  In this step S10, when it is determined that the peak frequencies due to the plurality of objects overlap, in step S20, the process waits for the time until the frequency bands where the peak frequencies due to the plurality of objects differ. After the standby, the process proceeds to step S100 and subsequent steps, and detection processing for each object is started.

  As described above, when the peak frequencies of a plurality of objects overlap, the phases of the beat signals B1 and B2 at the peak frequencies are combined phases. Therefore, for example, a beat signal of a certain part is used to perform pair matching. Such treatment is necessary. For this reason, in such a case, it may be determined that the accuracy of the waveform indicating the peak frequency is poor, and the calculation processing of the azimuth or the like may be stopped.

  As described above, the peak frequency may be predicted from the history data including the orientation θ, the distance D, and the relative speed V of each object. However, the rising peak frequency UPF and the falling peak frequency DPF are included in the history data. Is added, the processing for predicting the peak frequency becomes easy.

(Modification 4)
The fourth modification includes at least one of an imaging device that captures an image in a direction in which a radar wave is transmitted, a navigation device that detects the traveling position of the vehicle, and a detection device that detects the steering angle of the steering wheel of the vehicle, When the vehicle radar device detects an inappropriate situation for performing the object detection process by these devices, it is considered that the accuracy of the waveform indicating the peak frequency is lowered, and the direction of the object Etc. are to be canceled.

  That is, as shown in the flowchart of FIG. 12, in step S30, the image in the direction in which the radar wave ahead of the traveling direction of the vehicle is transmitted, the traveling position of the vehicle detected by the navigation device, or the steering angle of the steering wheel is It is determined whether or not the radar apparatus is suitable for performing the object detection process.

  Here, regarding the image, when it is recognized that a specific object (for example, a wall surface of a guard rail or a tunnel) having a high radar wave reflection intensity exists on the road side, calculation of the direction and the like is stopped. This is because when a guardrail is present on the roadside or a tunnel wall is present, it is difficult to accurately detect the peak frequency due to the object to be detected due to the reflected wave of the radar wave from them.

  Further, even when the traveling position of the vehicle detected by the navigation device is in the tunnel, the calculation of the direction of the object is stopped for the same reason.

  Further, regarding the steering angle of the steering wheel, the calculation of the orientation of the object is stopped when the steering angle is equal to or greater than a predetermined angle. This is because when the steering angle of the steering wheel is greater than or equal to a predetermined angle, the radar device mounted on the vehicle may receive a lot of reflected waves from a card rail or the like existing on the roadside. The steering angle may be detected by providing a detector such as a rotary encoder on the rotating shaft of the steering wheel. For example, the steering angle may be detected at the indirect seat from the difference in the rotational speed of the rolling wheels.

  Only when the situation detected by such a device is determined to be suitable for the object detection process by the radar device, the object detection process in step S100 and subsequent steps is executed, thereby executing the object detection. It is possible to reliably prevent erroneous detection.

  In the reference example described above, a radar wave including a frequency increasing unit, a frequency decreasing unit, and a constant frequency unit is used. However, the embodiment and the first to fourth modified examples are not limited to such a radar wave. Alternatively, a radar wave composed simply of a frequency increasing portion and a frequency decreasing portion may be used.

It is a block diagram showing the whole block diagram of the vehicle radar apparatus in a reference example. It is a flowchart which shows the detection process which detects with the microcomputer 10 of a reference example, the distance with a target object, a relative speed, and an azimuth | direction. It is a wave form diagram which shows the waveform of the radar wave transmitted from a transmitter in a reference example. It is explanatory drawing for demonstrating an example of the condition where the some peak frequency produced by the some target object overlaps. FIG. 5 is a waveform diagram for explaining a principle in which descending portion peak frequencies DPF generated by reflected waves from vehicles A and B overlap in the situation shown in FIG. 4. FIG. 5 is a waveform diagram showing a peak frequency of a beat signal of a constant frequency portion generated by a reflected wave from vehicles A and B in the situation shown in FIG. 4. It is a flowchart which shows the detection process which detects the distance, relative speed, and direction with a target object in embodiment. It is a wave form diagram which shows the frequency spectrum data of the beat signal when there is reflection from roadside reflectors, such as a guardrail, and the frequency spectrum data of the beat signal when there is no such reflection. It is a flowchart which shows the detection process in the modification 1 which detects the distance, relative speed, and direction with a target object. 12 is a flowchart illustrating a detection process for detecting a distance from a target object, a relative speed, and an orientation in Modification 2. 14 is a flowchart showing a detection process for detecting a distance from a target object, a relative speed, and an azimuth in Modification 3. It is a flowchart which shows the detection process in the modification 4 which detects the distance, relative speed, and direction with a target object. It is explanatory drawing for demonstrating the detection principle of a direction in the radar apparatus of a monopulse system. The principle of detecting an object in a conventional FMCW radar device will be described. (A) is a graph showing a transmission signal fs and a reception signal fr, and (b) is a graph showing the transmission signal fs and the reception signal fr. It is a graph which shows the beat frequency equivalent to the difference of a frequency.

Explanation of symbols

2 Radar device 4 Transmitter 6 Receiver 8 A / D converter 10 Microcomputer 12 D / A converter 14 Power control oscillator 14 Power distributor AS Transmit antenna AR1, AR2 Receive antenna AMP1, AMP2 Amplifier MX1, MX2 Mixer AD1, AD2 A / D converter

Claims (1)

Transmitting means for transmitting a transmission signal, which is frequency-modulated by a modulated signal having a waveform having at least an ascending part and a descending part, as a radar wave;
Two receiving means which are arranged with a predetermined interval and receive the reflected wave and generate a reception signal when the transmitted radar wave is reflected by an object;
A vehicle radar apparatus comprising: signal processing means for calculating an orientation of the object based on reception signals generated by the two receiving means;
Each of the two receiving means includes a beat signal generating means for generating a beat signal corresponding to a frequency difference between the reception signal and the transmission signal for each rising part and falling part of the transmission signal,
The signal processing means calculates an orientation of the object based on a phase difference at a peak frequency of at least one beat signal of an ascending portion and a descending portion respectively generated from reception signals of the two receiving means. A calculation means;
Determine the accuracy of the waveform indicating the peak frequency of at least one beat signal of the ascending and descending portions, and cancel the azimuth calculation by the azimuth calculating means when the accuracy does not satisfy a predetermined standard includes a stop means for, the,
The cancellation means determines that the accuracy of the waveform indicating the peak frequency does not satisfy a predetermined criterion when an integral value of at least one of the rising and falling beat signals is equal to or greater than a predetermined threshold value. Then , the vehicle radar apparatus is characterized in that the calculation of the azimuth by the azimuth calculation means is stopped .

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