JP2007003476A - Object detector and object detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a static object with an object detector of FM-CW (frequency modulate continuous wave) radar type. <P>SOLUTION: The object detector comprises a transmitting means 1, a receiving means 2, a speed detecting means 10 for detecting a speed of a moving object, a frequency offset amount calculating means 5 for calculating the offset amount of the frequency based on the speed information, a frequency offset means 5 that determines a rising offset frequency spectrum by adding the frequency offset amount to the frequency spectrum of a received IF signal in the frequency rising part of a transmitted signal and determines a lowering offset frequency spectrum by subtracting the frequency offset amount from the frequency spectrum of the frequency spectrum of a received IF signal in the frequency lowering part of the transmitted signal, an adding means 6 for determining an adding frequency spectrum by adding the rising offset frequency spectrum to the lowering offset frequency spectrum, and a static object detecting means 7 for detecting the static object based on the adding frequency spectrum. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an object detection apparatus and an object detection method using the FM-CW method, and more particularly to an apparatus and method for detecting a stationary object.

 With respect to this type of invention, the frequency spectrum obtained from the frequency rising modulation part of the FM-CW radar and the frequency spectrum obtained from the frequency falling modulation part are calculated, and the reflected signal from the stationary object is removed to detect only the moving object. A frequency modulation radar device for detection is known (see Patent Document 1). According to this apparatus, even if a stationary object and a moving object are mixed in the radar beam, only the moving object can be extracted and the distance and moving speed between the moving objects can be detected. It is possible to make a risk determination on the positional relationship with the other vehicle.

However, in this device, since the moving object is detected by eliminating the frequency spectrum of the stationary object that is relatively stationary and leaving the frequency spectrum of the moving object, it is impossible to detect the stationary object. was there. In particular, in a situation where there are many stationary objects such as parked vehicles and stationary vehicles at the end of a traffic jam, as well as moving objects such as traveling vehicles, there are object detection devices that can detect stationary objects. It was sought after.
Japanese Patent Laid-Open No. 6-214017

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an FM-CW radar type object detection apparatus and an object detection method capable of detecting a stationary object.

 According to the present invention, a transmission unit that is mounted on a moving body and transmits a frequency-modulated transmission signal, and a reception unit that receives a reflection signal generated by reflecting the transmission signal transmitted by the transmission unit on an object as a reception signal. Means for detecting an object based on a reception IF signal obtained from a transmission signal and a reception signal, a speed detection means for detecting the speed of a moving body, A frequency offset amount calculating unit that calculates a frequency offset amount based on a Doppler shift amount corresponding to the velocity information of the moving object detected by the detecting unit, and a reception IF signal obtained from the transmission signal and the reception signal are acquired and transmitted. The frequency offset amount is added to the frequency spectrum of the reception IF signal in the frequency rising portion of the signal to obtain the rising offset frequency spectrum, and The frequency offset means for subtracting the frequency offset amount from the frequency spectrum of the received IF signal in the descending portion to obtain the descending offset frequency spectrum, and the summed frequency by adding the ascending offset frequency spectrum and the descending offset frequency spectrum obtained by the frequency offset means An object detection apparatus is provided that includes an adding means for obtaining a spectrum and a stationary object detecting means for detecting a stationary object based on the added frequency spectrum obtained by the adding means.

 Thereby, in the FM-CW radar type object detection device, it is possible to detect a stationary object based on the added frequency spectrum.

  Hereinafter, the object detection apparatus 100 according to the first to third embodiments will be described with reference to the drawings. The object detection device 100 is mounted on a vehicle (moving body) on which a user is boarded, and the presence of a target around the vehicle, the direction of the target, the distance from the vehicle, the characteristics of the target (whether it is a moving body or a stationary object). ) Is detected.

<First Embodiment>
FIG. 1 is a block diagram of an object detection apparatus 100 according to the first embodiment. As shown in FIG. 1, the object detection device 100 includes a radar head 200 and a signal processing device 300.

 The radar head 200 has at least a transmission unit 1 that transmits a transmission signal to a front space and a reception unit 2 that receives a reflection signal from a front target, and FM-CW (Frequency Modulate Continuous) that frequency-modulates a triangular wave or a sawtooth wave. Wave: a frequency-modulated continuous wave radar system). The FM-CW system is a system that uses a triangular wave modulated transmission signal as a radio wave radar, and detects the distance and relative speed of the reflecting object from the difference between the reflected signal frequency at the time of frequency rising modulation and the reflected signal frequency at the frequency falling modulation. It is.

  The transmission means 1 includes a transmission antenna 11, a power distributor 12, and a VCO (Voltage Controlled Oscillator) 13. A VCO (Voltage Controlled Oscillator) 13 generates a transmission signal modulated by a triangular wave signal sent from the triangular wave generating means 301 on the signal processing device 300 side. The power distributor 12 distributes the transmission signal generated by the VCO 13 into two branches at a predetermined power ratio. One is transmitted from the transmission antenna 11 as a transmission signal, and one is used as a reference signal. The transmission antenna 11 sends a transmission signal to the front space.

 The receiving unit 2 includes a receiving antenna 21, a mixer circuit 22, and an amplifier circuit 23. The receiving antenna 21 receives the reflected signal returned from the transmission signal transmitted from the transmitting antenna 11 after being reflected by the front target. The mixer circuit 22 mixes a part of the transmission signal branched by the power distributor 12 and the reception signal, and generates a reception IF signal (IF: Intermediate Frequency). The amplifier circuit 23 amplifies the reception IF signal generated by the mixer circuit 22 and outputs the amplified signal to the FFT (Fast Fourier Transform) processing means 302 on the signal processing device 300 side.

 The radar head 200 of this embodiment includes a transmission / reception azimuth scanning unit 3. The transmission / reception azimuth scanning means 3 is directed to different directions by mechanically turning the transmission antenna 11 and the reception antenna 21 along the horizontal direction with respect to the traveling surface of the vehicle so that signals can be transmitted and received in different directions. The transmission signal is transmitted and the reception signal is received from different directions. The turning directions (angles) of the transmission antenna 11 and the reception antenna 21 are sent to the frequency offset amount calculation means 4 as transmission azimuth information of the transmission signal or reception azimuth information of the reception signal.

 Note that the azimuth detection type FM-CW radar head is not limited to one in which the radar head 200 is mechanically turned to change the transmission / reception azimuth axis, and has a mechanism for turning the transmission antenna 11 alone. Alternatively, a circulator may be added to perform transmission and reception of signals with a single transmission / reception antenna, and the transmission / reception antenna may be turned in the horizontal direction to change the transmission / reception direction. In addition, a transmission / reception antenna may have an array antenna structure, and a phased array antenna that controls the beam direction using a phase shifter for each array may be used.

  The signal processing device 300 has an object detection function of a general FM-CW radar. The signal processing apparatus 100 of the present example extracts the reception IF signal by multiplying the reception signal and the transmission signal (reference signal) and passing through an LPF (low pass filter), and Fourier-transforms the reception IF signal. The frequency of the reflected signal included in the reception IF signal is obtained from the obtained spectrum peak. Since the received IF signal includes a frequency component proportional to the distance to the target and a Doppler frequency shift caused by the relative speed between the radar device and the target, the received IF signal when the frequency is increased and the received signal when the frequency is decreased These are obtained from the frequency difference of the IF signal, and based on this, the distance to the target object and the relative speed can be obtained.

  The signal processing apparatus 300 according to the present embodiment includes at least a speed detection unit 10, a frequency offset amount calculation unit 4, a frequency offset unit 5, an addition unit 6, and a stationary object detection unit 7. Although not particularly limited, it is preferable to have the difference calculation means 8 and the moving object detection means 9. Furthermore, the signal processing apparatus 300 according to the present embodiment preferably includes a storage unit 15 and an editing unit 16. Note that the signal processing device 300 preferably includes a triangular wave generation unit 301 that generates a triangular wave, and an FFT processing unit 302 that performs frequency analysis of a reception IF signal output from the amplifier circuit 23.

  Specifically, the signal processing device 300 executes a program that detects a stationary object, a ROM (Read Only Memory) that stores a program that detects a moving object, and the program stored in the ROM. Frequency offset means 5, addition means 6, stationary object detection means 7, difference calculation means 8, moving object detection means 9, CPU (Central Processing Unit) functioning as editing means 16, and RAM functioning as accessible storage means (Random Access Memory) and the like (memory 50). In the present embodiment, for convenience of explanation, the adding means 6, the difference calculating means 8, the stationary object detecting means 7, and the moving object detecting means will be described as separate configurations, but these are an adding function, a difference calculating function, a stationary object, You may comprise as 1 or 2 or more arithmetic devices (CPU etc.) which have a detection function, a moving object detection function, and an edit function.

  Hereinafter, each unit of the signal processing device 300 will be described.

  The speed detection means 10 detects the speed of the host vehicle (moving body). A speedometer mounted on the vehicle may be used.

  The frequency offset amount calculation means 4 calculates a frequency offset amount based on the Doppler shift amount corresponding to the speed of the host vehicle detected by the speed detection means 10.

  The frequency offset unit 5 calculates an ascending offset frequency spectrum and a descending offset frequency spectrum using the frequency offset amount calculated by the frequency offset amount calculating unit 4. Specifically, the frequency offset means 5 acquires the reception IF signal obtained from the transmission signal and the reception signal, and is calculated by the frequency offset amount calculation means 4 into the frequency spectrum of the reception IF signal in the frequency rising portion of the transmission signal. The rising offset frequency spectrum is obtained by adding the obtained frequency offset amount, and the falling offset frequency spectrum is obtained by subtracting the frequency offset amount calculated by the frequency offset amount calculating means from the frequency spectrum of the reception IF signal in the frequency falling portion of the transmission signal. .

  The adding unit 6 adds the ascending offset frequency spectrum and the descending offset frequency spectrum obtained by the frequency offset unit 5 to obtain an adding frequency spectrum. The stationary object detection unit 7 detects a stationary object based on the addition frequency spectrum obtained by the addition unit 6. Specifically, assuming that the spectrum showing a characteristic peak in the sum frequency spectrum is a reflected signal from a stationary object, the presence of the stationary object is detected, and the direction of the stationary object is detected from the direction in which the signal is received. The distance can be obtained from the frequency value to be performed.

 The object detection apparatus 100 of this embodiment further includes a difference calculation unit 8 and a moving object detection unit 9. The difference calculation means 8 calculates a difference between the rising offset frequency spectrum and the falling offset frequency spectrum obtained by the frequency offset means 5 to obtain a difference frequency spectrum. The moving object detection means 9 detects a moving object based on the difference frequency spectrum calculated by the difference calculation means. Specifically, the spectrum showing a pair of positive and negative peaks characteristic in the differential frequency spectrum is a reflected signal from the moving object, and detects the presence of the moving object, and determines the direction of the moving object from the reception direction of the signal, The distance and the moving speed can be obtained from the central frequency value and the difference between the positive and negative peaks of the received IF signal.

 Although not particularly limited, the object detection apparatus 100 according to the present embodiment includes a storage unit 15 that stores the detection result of the stationary object detection unit 7 and / or the detection result of the moving object detection unit 9, and the detection stored in the storage unit 15. Editing means 16 for editing object detection information based on the result. The editing unit 16 is preferably configured to be incorporated in the stationary object detection unit 7 or the moving object detection unit 9. However, for convenience of explanation, in this example, the editing unit is combined with the stationary object detection unit 7 and the moving object detection unit 9. Were configured independently. The editing unit 16 extracts a spectrum corresponding to the stationary object from the addition frequency spectrum obtained by the adding unit 6, and based on the transmission direction of the transmission signal or the reception direction of the reception signal, the spectrum information of the extracted stationary object is obtained. A two-dimensional map projected on a predetermined projection plane is edited. The stationary object detection means 7 detects the two-dimensional shape of the stationary object based on the edited two-dimensional map.

 Further, the editing unit 16 extracts the spectrum corresponding to the stationary object and the intensity thereof from the addition frequency spectrum obtained by the adding unit 6, and transmits the transmission direction of the transmission signal or the reception direction of the reception signal and the spectrum corresponding to the stationary object. Based on the intensity, a three-dimensional map of the extracted stationary object spectrum is edited. The stationary object detection means 7 detects the shape of the stationary object based on the edited two-dimensional map.

Next, the operation of the object detection apparatus 100 according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing a control procedure of the object detection apparatus 100 of the present embodiment.
The object detection apparatus 100 of this embodiment has a general FM-CW radar function, and detects the presence / absence of an object, the distance to the object, and the speed of the object.

  First, the transmission means 1 sends a transmission signal via the transmission antenna 11 (S1). The receiving unit 2 receives a reflected signal generated by reflecting the transmission signal transmitted by the transmitting unit 1 on an object as a received signal (S2). The frequency offset unit 5 acquires a reception IF signal obtained from the transmission signal and the reception signal. Incidentally, the received IF signal acquired by the frequency offset means 5 is mixed with a part of the transmission signal branched by the power distributor 12 and the reception signal by the mixer circuit 22, amplified by the amplifier circuit 23, and FFT (fast Fourier). Information obtained by Fourier transformation by the transformation means 302.

 FIG. 3 shows a signal example when a reflected signal from an object having a relative velocity of zero or near zero is observed. 3 (1) shows a triangular wave signal generated by the triangular wave generator 301, FIG. 3 (2) shows a transmission signal output from the VCO 13 after frequency conversion with the triangular wave signal, and FIG. 3 (3) is a forward object. A reception signal (reflection signal) and a transmission signal (shown by a dotted line) reflected by the mark and FIG. 3 (4) show a reception IF signal obtained by mixing the transmission signal and the reception signal. Since the slope of the frequency modulation is known, by detecting the frequency f0 shown in FIG. 3 (4), the time delay according to the distance can be calculated, and the distance to the object ahead can be detected.

 FIG. 4 shows an example of a signal obtained by observing a reflected signal from an object having a relative speed (relative speed is not zero). The titles of the graphs (1) to (4) in FIG. 4 are the same as those in FIG. As shown in FIG. 4 (3), the received signal reflected from the front object having a relative velocity has a time delay corresponding to the distance and a frequency shift due to the Doppler effect due to the relative velocity. As shown in FIG. 4 (4), the frequency of the reception IF signal at the time of frequency increase modulation is observed as f1, and the frequency of the reception IF signal at the time of frequency decrease modulation is observed as f2. Based on the average value of the two frequencies f1 and f2, the amount of time delay can be detected to detect the distance to the front object. Further, the Doppler frequency is calculated from the frequency difference between the two frequencies f1 and f2, and the relative speed can be detected.

  In parallel with the processing from S1 to S3, the speed detecting means 10 detects the speed of the host vehicle (moving body) (S21). The frequency offset amount calculation means 4 obtains a Doppler shift amount based on the speed of the host vehicle detected by the speed detection means 10 (S22), and calculates a frequency offset amount based on the Doppler shift amount (S23). Specifically, the frequency offset amount calculation means 4 calculates the relative speed of the stationary object based on the speed V of the host vehicle detected by the speed detection means 10 and the transmission direction θ of the transmission signal acquired from the transmission / reception direction scanning means 3. (= V · cos θ) is calculated, and the frequency offset amount Δf based on the Doppler shift amount corresponding to the relative speed is calculated from the following equation 1 and output to the frequency offset means 4.

Δf = F · V · cos θ / C (1), where F is the frequency of the transmission signal and C is the speed of light
The frequency offset means 5 acquires the reception IF signal of the rising portion of the transmission frequency (S4), and acquires the reception IF signal of the lower portion of the transmission frequency (S5). The frequency offset means 5 adds the frequency offset amount calculated by the frequency offset amount calculation means 4 to the reception IF signal at the rising portion of the transmission frequency to obtain the rising offset frequency spectrum, and receives the reception IF signal at the frequency falling portion of the transmission signal. A descending offset frequency spectrum is obtained by subtracting the frequency offset amount calculated by the frequency offset amount calculating means 4 from the frequency spectrum of the signal (S6).

 FIG. 5 shows an ascending frequency spectrum A and a descending frequency spectrum B when a reflected signal reflected from a forward target is received while the host vehicle is traveling. Two peaks P1 and P2 are observed near the frequency X1, and two peaks Q1 and Q2 are observed near the frequency X2.

 FIG. 6 shows an ascending offset frequency spectrum and a descending offset frequency spectrum offset by the frequency offset amount by the frequency offset means 5. As shown in FIG. 6, the frequencies of the peaks P1 and P2 after the offset processing are almost the same, and it can be estimated that the peaks P1 and P2 correspond to the reflected signal from the stationary object. On the other hand, the frequencies of the peaks Q1 and Q2 are different, and it can be inferred that they correspond to the reflected signal from the moving object.

 The frequency offset unit 5 outputs the offset ascending offset frequency spectrum and the descending offset frequency spectrum that are offset toward the adding unit 6 and / or the difference calculating unit 8.

 The adding means 6 adds the ascending offset frequency spectrum and the descending offset frequency spectrum obtained by the frequency offset means 5 to obtain an adding frequency spectrum (S7). FIG. 7 is an addition frequency spectrum obtained by adding the rising offset frequency spectrum and the falling frequency spectrum obtained by the frequency offset means 5. The peaks of the reflected signals Q1 and Q2 from the moving object at a long distance observed in FIGS. 5 and 6 are not noticeable, but the peaks of the reflected signals P1 and P2 from the stationary object at a short distance are almost doubled. P3, and a frequency spectrum in which the signal level of a stationary object is emphasized can be obtained. The adding means 6 outputs the obtained addition frequency spectrum toward the stationary object detecting means 7.

 The stationary object detection means 7 detects a stationary object based on the peak P of the addition frequency spectrum as shown in FIG. 7 (S8), and stores the detection result in the storage device 11 (S11). Since the peak (eg, Q1, Q2) of the moving object is not emphasized in the added frequency spectrum, the stationary object can be detected separately from the moving object. The stationary object detection means 7 detects the stationary object, calculates the distance to the stationary object, stores the result in the storage means 15, or sends it to the vehicle control device that controls the running of the vehicle.

 The difference calculating means 8 calculates a difference frequency spectrum by calculating a difference between the rising offset frequency spectrum and the falling offset frequency spectrum obtained by the frequency offset means 5 (S9). FIG. 8 is a difference frequency spectrum obtained by calculating the difference between the rising offset frequency spectrum and the falling frequency spectrum obtained by the frequency offset means 5. The peaks of the reflected signals P1 and P2 from the stationary object at a short distance observed in FIGS. 5 and 6 cancel each other and the peaks are not noticeable. However, the peaks of the reflected signals Q1 and Q2 from the moving object at a long distance are not observed. The peak remains, and a frequency spectrum in which the signal level of the moving object is enhanced can be obtained. The difference calculation means 8 outputs the obtained difference frequency spectrum to the moving object detection means 7.

 In this way, by calculating the addition frequency spectrum and / or the difference frequency spectrum based on the ascending offset frequency spectrum and the descending offset frequency spectrum offset according to the frequency offset amount, the reflected wave from the stationary object is emphasized, Or the reflected wave from a moving object can be emphasized correctly.

 There is no problem when there is a single forward object, but when there are multiple forward objects and multiple objects are observed at the same time, the reflected signals of frequency rising modulation and frequency falling modulation have multiple frequency components. In order to perform accurate distance measurement, it is necessary to appropriately pair the frequency components received at the time of frequency increase and frequency decrease modulation. In particular, in a scene where many reflected signals from a stationary object such as an urban area are observed, many false detections and undetections occur due to pairing mistakes, and thus there is a high demand for accurate pairing processing. In this embodiment, a stationary object and a moving object are distinguished and detected by performing an offset process for obtaining an ascending offset frequency spectrum and a descending offset frequency spectrum, and an addition process and a difference process for obtaining an addition frequency spectrum and a difference frequency spectrum therefrom. can do. That is, it is possible to detect not only a preceding traveling vehicle having a relative speed but also a parked and stopped vehicle and a preceding vehicle that is traveling but has a relative speed of zero due to traffic jams or the like. In addition, it is possible to suppress a pairing error of the received signal that occurs when there are a plurality of front objects.

 The moving object detection means 7 detects a moving object based on the peaks Q1 and Q2 of the difference frequency spectrum as shown in FIG. 8 (S10), and at least temporarily stores it in the storage means 15 (S11). In the difference frequency spectrum, since the peak (for example, P1 and P2) of the stationary object is canceled, the moving object can be detected separately from the stationary object. The moving object detecting means 9 detects the moving object, calculates the distance to the moving object and the moving speed, stores the result in the storage means 15, or to a vehicle control device (not shown) for controlling the running of the vehicle. Send out.

 Incidentally, S7 and S8 and S9 and S10 may be processed in parallel or may be processed independently.

 As described above, the stationary object is detected based on the added frequency spectrum in which the reflected reception signal from the stationary object is enhanced, and the reflected reception signal from the moving object is enhanced (the reflected signal from the stationary object is removed). By detecting a moving object based on the difference frequency spectrum, both a stationary object and a moving object can be detected simultaneously, or either one can be detected alone.

 It is determined whether or not scanning of the transmission antenna 11 and the reception antenna 21 has been completed for all directions (S13). If not completed, S1 to S13 and S21 to S23 are repeated until the process is completed.

 Next, the editing means 16 edits the two-dimensional map (S14). The two-dimensional map is a two-dimensional spectral intensity distribution obtained by projecting extracted spectral information of a stationary object onto a predetermined projection plane. The two-dimensional map extracts a spectrum corresponding to a stationary object from the addition frequency spectrum obtained by the adding means 6, and uses the extracted spectrum information of the stationary object based on the transmission direction of the transmission signal or the reception direction of the reception signal. Projected onto a predetermined projection plane. The two-dimensional map may include spectral information of the moving object. That is, the spectrum corresponding to the moving object is extracted from the difference frequency spectrum obtained by the difference calculating means 8, and the spectrum information of the extracted moving object is determined based on the transmission direction of the transmission signal or the reception direction of the reception signal. Information projected onto the projection plane may be included in the two-dimensional map.

 An example of a two-dimensional map will be described with reference to FIGS. FIG. 9A is a detection image in which the ascending offset frequency spectrum calculated by the frequency offset means 5 is arranged on two-dimensional coordinates defined based on each transmission / reception direction. FIG. 9B is a detected image in which the descending offset frequency spectrum calculated by the frequency offset means 5 is arranged on two-dimensional coordinates defined based on each transmission / reception direction. The intensity of the detected frequency spectrum is shown by shading based on the background density. A region having a large density difference from the background density has a high reflection intensity and is an object existing at a relatively close position. In addition, for the region showing a predetermined density difference (absolute value), the outline was cut out to clearly show the boundary of the object. FIG. 10 shows the difference calculation processing result of the ascending offset frequency spectrum and the descending offset frequency, that is, the difference frequency spectrum calculated by the difference calculating means 8 on the same two-dimensional coordinates as FIG. As shown in FIG. 10, the images of the rectangular objects that existed on the left and right have disappeared. This is because the spectrum corresponding to the stationary object has been removed by the processing of the difference calculation means 8.

 FIG. 11 is an example of a two-dimensional map edited by the editing means 16. FIG. 11 shows the result of the addition operation processing of the rising offset frequency spectrum and the falling offset frequency, that is, the addition frequency spectrum calculated by the adding means 6 on the same two-dimensional coordinates as in FIG. The intensity of the spectrum is shown as ½ along with the addition process. As shown in FIG. 11, the image of the rectangular object existing on the left and right is emphasized, and the image of the circular object at the center is inconspicuous. This is because the spectrum corresponding to the stationary object is emphasized as compared with the other spectra by the processing of the addition calculation means 8. Thereby, the position of the object on the two-dimensional coordinate defined based on the direction can be detected (S16). Image data that can visually recognize a forward object may be edited based on a two-dimensional map in which a coordinate system is defined.

 Further, the editing unit edits the three-dimensional map as necessary (S15). FIG. 12 is an example of a three-dimensional map edited by the editing means 16. This three-dimensional map shows an addition frequency spectrum on three-dimensional coordinates obtained by adding spectrum intensity as a third coordinate axis to two-dimensional coordinates based on transmission and reception directions. The three-dimensional map shown in FIG. 12 is edited based on the information of the two-dimensional map shown in FIG. The change in intensity is expressed by the change in color (wavelength). The wavelength from red to purple was made to correspond to the value of the reflection intensity so that the higher reflection intensity was red and the lower reflection intensity was purple. According to this three-dimensional map, the position where the reflection spectrum is generated (the position where the object is present) and the reflection intensity of the spectrum can be expressed, so that the position and shape of the target can be expressed visually. If the reflection intensity can be detected continuously on the coordinates, the state of the object surface can be predicted, and the surface shape of the object can be predicted based on the locus of points with the same reflection intensity. can do. In other words, when there is a stationary object such as a guardrail on the travel route, when the sum frequency spectrum is obtained based on the received signal reflected by the guardrail, the travel is performed based on the locus of the point where the reflection intensity of the same value continues. The extended state of the guard rail extended to the left and right ends of the road can be estimated, and a pseudo three-dimensional map of the traveling road can be generated and displayed from the extended state of the guard rail. As a result, the position and shape of the object can be detected on the three-dimensional coordinates defined based on the azimuth and the reflection intensity.

 The detection result is output toward the vehicle control device 400 (S17).

 Depending on the weather (fog, rain) and time zone (nighttime), when the field of view is poor, or when traveling on mountain roads, a CCD or the like may not be able to obtain a high quality captured image. According to this, a stationary object (and / or a moving object) can be detected based on a reflected signal (received signal) from a stationary object (such as a guardrail or a side wall) on the roadside. Can be accurately recognized, information on the travel route of the host vehicle can be provided, and travel lane protrusion prevention control can be performed.

 Incidentally, the stationary object detection information detected in S8 and the moving object detection information detected in S9 may be output to the vehicle control device 400 without undergoing an editing process. The edited two-dimensional map may be output to the moving object detection means 9 and / or the stationary object detection means 7 for object detection, or may be output as it is.

 As described above, according to the present embodiment, in the FM-CW radar that detects a target by transmitting / receiving an electromagnetic wave that is frequency-modulated with a triangular wave, the frequency spectrum of the received IF signal in the frequency increasing portion is obtained from the speed information of the own vehicle. By offsetting (shifting) based on the frequency offset amount, the frequency components of the IF signal in the frequency increasing portion and the frequency decreasing portion caused by the reflected signal from a stationary object (an object having a relative speed equal to the speed of the host vehicle) are equal. By adding the two frequency spectra, the addition frequency spectrum that suppresses the reflected signal from the moving object can be obtained, and only the stationary object is detected separately from the moving object. be able to. Also, by performing the difference calculation process in parallel, a difference frequency spectrum that suppresses the reflection signal from the stationary object can be obtained, and the detection of the moving object together with the stationary object can be performed simultaneously with one measurement. .

Second Embodiment
A second embodiment will be described based on FIGS. 13 and 14. FIG. 13 shows a block configuration of the object detection apparatus 101 of the present embodiment. As shown in FIG. 13, the present embodiment differs from the first embodiment in that the difference calculation unit 8 includes an absolute value calculation unit 81 and an addition unit 61 that performs processing different from that in the first embodiment. . Since these points are basically the same as those in the first embodiment, different points will be mainly described here, and overlapping portions will be omitted.

 The difference calculation means 8 obtains the absolute frequency value of the difference frequency spectrum. This function may be provided by the adding means 61. That is, the adding means 6 may calculate the frequency absolute value based on the difference frequency spectrum.

 The adding unit 61 adds the ascending offset frequency spectrum and the descending offset frequency spectrum obtained by the frequency offset unit 5 and subtracts the absolute frequency value of the difference frequency spectrum obtained by the difference calculating unit 8. Ask for. In addition to the process of adding the rising offset frequency spectrum and the falling offset frequency spectrum, the adding means 61 of the present embodiment performs a process of subtracting the frequency absolute value of the difference frequency spectrum from the added frequency spectrum. The difference frequency spectrum is obtained by removing the frequency spectrum corresponding to the stationary object and leaving the frequency spectrum corresponding to the moving object. On the other hand, in the addition frequency spectrum, the frequency spectrum corresponding to the stationary object is emphasized, but the frequency spectrum indicating the moving object is a weak peak such as peaks Q1 and Q2 shown in FIG. In the present embodiment, the spectrum corresponding to the moving object is subtracted from the added frequency spectrum. Since the difference frequency spectrum appears as a positive spectrum peak and a negative spectrum peak as shown in FIG. 8, in this example, the absolute frequency value is subtracted from the added frequency spectrum.

 FIG. 14 is a flowchart showing the control procedure of this embodiment. Since it is basically the same as the control procedure of the first embodiment shown in FIG. 2, different processing (S71 and S72) will be described here. In S <b> 71, the adding unit 6 acquires the absolute difference value of the difference frequency spectrum calculated by the difference calculating unit 8. In S72, the adding means 6 subtracts (subtracts) the difference absolute value from the added frequency spectrum calculated in S7. What was obtained in S72 is the addition frequency spectrum of this embodiment.

 Although not particularly limited, it is preferable that the adding means 6 obtains an absolute value spectrum obtained by converting the signal intensity to half at all frequencies based on the absolute value of the difference frequency spectrum, and subtracts it from the added frequency spectrum. Thus, by subtracting (difference processing) the absolute value spectrum, the reflected signal of the moving object can be removed without impairing the characteristics of the reflected signal of the emphasized stationary object, and the stationary object can be more accurately detected. Detection can be performed.

<Third Embodiment>
A third embodiment will be described based on FIGS. 15 and 16. In the present embodiment, the movement vector of the own vehicle is obtained from the behavior information such as the traveling speed and steering angle of the own vehicle, and the Doppler shift amount and the frequency offset amount are calculated from the speed component obtained by vector decomposition into the transmission direction of the transmission signal. It is characterized by

 FIG. 15 shows a block configuration of the object detection apparatus 101 of the present embodiment. As shown in FIG. 15, this embodiment is the first in that it has behavior information acquisition means 20 that detects the behavior of a moving body (own vehicle), and that the offset amount calculation means 4 includes a movement vector calculation unit 41. Different from the embodiment. Since these points are basically the same as those in the first embodiment, different points will be mainly described here, and overlapping portions will be omitted.

  The transmission means 1 of this embodiment includes a scanning transmission antenna 11 that transmits transmission signals in a plurality of transmission directions while reciprocatingly rotating along a substantially horizontal direction with the traveling surface of the moving body.

  The behavior information acquisition unit 20 acquires behavior information related to the behavior of the moving body, such as steering angle information and left and right wheel speed difference, which affects the speed component of the moving body in each sending direction.

  The frequency offset amount calculation unit 4 calculates the velocity component of the moving body for each transmission direction in which the transmission antenna 11 transmits the transmission signal, based on the behavior information of the moving body acquired by the behavior information acquisition unit 20, and transmits the transmission direction. The frequency offset amount is calculated based on the velocity component of each moving body. The movement vector calculation unit 41 has a function of calculating a movement vector including information on the traveling direction of the own vehicle that changes according to the behavior of the moving body based on the speed information of the own vehicle and the behavior information of the own vehicle.

 For example, when detected as the traveling speed V of the host vehicle and the moving direction φ, the frequency offset amount Δf corresponding to the Doppler shift amount in the transmission direction θ of the transmission signal is expressed by the following equation.

Δf = F · V · cos (θ−φ) / C (2) (where F is the transmission signal frequency and C is the speed of light)
FIG. 16 is a flowchart showing the control procedure of this embodiment. Since it is basically the same as the control procedure of the first embodiment shown in FIG. 2, different processing (S201 to S203) will be described here. In S201, the behavior information acquisition unit 20 acquires behavior information such as the steering angle of the host vehicle. In S202, the movement vector calculation unit 41 calculates a movement vector including information on the traveling direction of the host vehicle based on the speed information of the host vehicle and the behavior information of the host vehicle.

In S203, the frequency offset amount calculation means 4 calculates the frequency offset amount based on the movement vector for each transmission direction in which the transmission antenna 11 transmits the transmission signal calculated from the velocity information of the moving body and the behavior information of the moving body. calculate.

  Thus, since the Doppler shift amount and the frequency offset amount are calculated from the speed component obtained by vector decomposition into the transmission direction of the transmission signal from the traveling speed and behavior information of the own vehicle, even if the own vehicle does not go straight, The speed component of the own vehicle can be accurately calculated for each sending direction. Based on the exact relative speed between the stationary object and the host vehicle, it is possible to calculate the exact frequency offset amount, difference frequency spectrum, and addition frequency spectrum, and even when the host vehicle is turning on a curved road, etc. And / or the reflected signal of the moving object can be accurately classified.

  The embodiment described above is described in order to facilitate understanding of the present invention, and is not described in order to limit the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

It is a figure which shows the block configuration of the object detection apparatus of 1st Embodiment. It is a figure which shows the control procedure of the object detection apparatus which concerns on 1st Embodiment. (1)-(4) is a figure for demonstrating each state of the signal sent toward the stationary object. (1)-(4) is a figure for demonstrating each state of the signal sent toward the moving object. It is a figure which shows the rising frequency spectrum A and the falling frequency spectrum B at the time of receiving the reflective signal reflected from the front target when the own vehicle is drive | working. The ascending offset frequency spectrum and the descending offset frequency spectrum offset by the frequency offset amount by the frequency offset means 5. It is an addition frequency spectrum obtained by adding the rising offset frequency spectrum and the falling frequency spectrum obtained by the frequency offset means 5. It is the difference frequency spectrum which calculated the difference of the rising offset frequency spectrum and the falling frequency spectrum which the frequency offset means 5 calculated | required. FIG. 9A is a detection image in which the ascending offset frequency spectrum calculated by the frequency offset means 5 is arranged on two-dimensional coordinates defined based on each transmission / reception direction. FIG. 9B is a detected image in which the descending offset frequency spectrum calculated by the frequency offset means 5 is arranged on two-dimensional coordinates defined based on each transmission / reception direction. It is a figure which shows the difference calculation process result of a raise offset frequency spectrum and a fall offset frequency. It is a figure which shows an example of the two-dimensional map edited by the edit means. 3 is an example of a three-dimensional map edited by an editing unit 16. It is a figure which shows the block configuration of the object detection apparatus 101 of 2nd Embodiment. It is a figure which shows the control procedure of the object detection apparatus which concerns on 2nd Embodiment. It is a figure which shows the block configuration of the object detection apparatus of 3rd Embodiment. It is a figure which shows the control procedure of the object detection apparatus which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Object detection apparatus 200 ... Radar head 1 ... Transmission means 11 ... Transmission antenna 12 ... Power divider 13 ... VOC
2 ... Receiving means 21 ... Receiving antenna 22 ... Mixer circuit 23 ... Amplifying circuit 3 ... Transmission / reception direction scanning means 300 ...
DESCRIPTION OF SYMBOLS 301 ... Triangular wave generation part 302 ... FFT processing part 4 ... Frequency offset amount calculation means 5 ... Frequency offset means 6 ... Addition means 7 ... Stationary object detection means 8 ... Difference calculation means 9 ... -Moving object detection means 10 ... speed detection means 15 ... storage means 16 ... editing means 400 ... vehicle control device

Claims (7)

A transmission unit mounted on a mobile body for transmitting a frequency-modulated transmission signal; and a reception unit for receiving, as a reception signal, a reflection signal generated by reflecting a transmission signal transmitted by the transmission unit on an object, An FM-CW radar type object detection device that detects an object based on a reception IF signal obtained from a transmission signal and a reception signal,
Speed detecting means for detecting the speed of the moving body;
A frequency offset amount calculating means for calculating a frequency offset amount based on a Doppler shift amount corresponding to the speed information of the moving object detected by the speed detecting means;
A reception IF signal obtained from the transmission signal and the reception signal is acquired, and the frequency offset amount calculated by the frequency offset amount calculation means is added to the frequency spectrum of the reception IF signal in the frequency increase portion of the transmission signal to increase the offset. A frequency offset means for obtaining a frequency spectrum, and subtracting the frequency offset amount calculated by the frequency offset amount calculation means from the frequency spectrum of the reception IF signal in the frequency drop portion of the transmission signal to obtain a fall offset frequency spectrum;
Adding means for adding the rising offset frequency spectrum and the falling offset frequency spectrum obtained by the frequency offset means to obtain an added frequency spectrum;
An object detection apparatus comprising: a stationary object detection unit configured to detect a stationary object based on the addition frequency spectrum obtained by the addition unit. Difference calculating means for calculating a difference frequency spectrum by calculating a difference between the rising offset frequency spectrum and the falling offset frequency spectrum obtained by the frequency offset means;
The object detection apparatus according to claim 1, further comprising: a moving object detection unit that detects a moving object based on the difference frequency spectrum calculated by the difference calculation unit. The adding means adds the ascending offset frequency spectrum and the descending offset frequency spectrum obtained by the frequency offset means, and subtracts the absolute value of the difference frequency spectrum obtained by the difference calculating means from the addition result to add Find the frequency spectrum,
The object detection apparatus according to claim 2, wherein the stationary object detection unit detects a stationary object based on the addition frequency spectrum obtained by the addition unit. It further comprises behavior information acquisition means for acquiring behavior information indicating the behavior of the mobile object,
The transmission means includes a transmission antenna that transmits a transmission signal toward a plurality of transmission directions while reciprocatingly rotating along a substantially horizontal direction with the mounting surface of the moving body,
The frequency offset amount calculating means transmits the transmission signal from the transmitting antenna based on the speed information of the moving object detected by the speed detecting means and the behavior information of the moving object acquired by the behavior information acquiring means. The object detection device according to claim 1, wherein a speed component of the moving body for each sending direction is calculated, and an offset amount of the frequency is calculated based on the speed component of the moving body for each sending direction. .  The stationary object detection means extracts a spectrum corresponding to a stationary object from the addition frequency spectrum obtained by the adding means, and uses the extracted spectrum information of the stationary object as a transmission direction of the transmission signal or reception of the reception signal. 5. An editing function for editing a two-dimensional map projected on a predetermined projection surface based on a direction, and detecting the shape of a stationary object based on the edited two-dimensional map. The object detection apparatus in any one of.  The stationary object detection means extracts the spectrum corresponding to the stationary object and its intensity from the addition frequency spectrum obtained by the adding means, and corresponds to the transmission direction of the transmission signal or the reception direction of the reception signal and the stationary object. An editing function for editing a three-dimensional map of the spectrum of the extracted stationary object based on the intensity of the spectrum is provided, and the shape of the stationary object is detected based on the edited three-dimensional map. The object detection apparatus according to claim 1. A reception IF signal obtained from the transmission signal and the received signal, which is mounted on the mobile body, transmits a frequency-modulated transmission signal, receives a reflection signal generated by reflecting the transmission signal on an object as a reception signal, and FM-CW radar type object detection method for detecting an object based on
Detecting the speed of the moving body;
Calculating a frequency offset amount based on a Doppler shift amount corresponding to the detected speed information of the moving body;
Obtaining a reception IF signal obtained from the transmission signal and the reception signal, obtaining the rising offset frequency spectrum by adding the frequency offset amount to the frequency spectrum of the reception IF signal in the frequency rising portion of the transmission signal, and transmitting the transmission signal Subtracting the frequency offset amount from the frequency spectrum of the received IF signal in the frequency falling portion of
Adding the rising offset frequency spectrum and the falling offset frequency spectrum to obtain an added frequency spectrum;
Calculating a difference between the rising offset frequency spectrum and the falling offset frequency spectrum to obtain a difference frequency spectrum;
Detecting a stationary object based on the pre-added frequency spectrum;
Detecting a moving object based on the difference frequency spectrum;
An object detection method comprising: