JP4396436B2 - Target detection device - Google Patents

Description

  The present invention relates to a target detection apparatus using a radar.

  Conventionally, it is known that a low-power millimeter-wave radar using millimeter waves as electromagnetic waves can detect a situation of about 100 meters from the radar, and can be used even in fog, rain, and snow. The current antenna power of millimeter wave radar is 10 mm watts or less, and radio waves of 60 GHz band, 76 GHz band or 90 GHz band are used.

  Such a radar is usually installed in front of the vehicle, detects the inter-vehicle distance and relative speed with the preceding vehicle, displays the detected inter-vehicle distance and relative speed, and displays such measured values. Based on the collision prevention. In addition, by appropriately changing the radar mounting position, it is possible to perform backward monitoring, side monitoring, blind spot monitoring, or issue an alarm based on such monitoring.

  Alternatively, inter-vehicle distance control, automatic brake control, and the like can be performed based on the radar measurement values. This radar is an ACC (auto-vehicle controller), PBA (pre-crash / brake assist), PSB (pre-crash seat belt). ) Can be applied to the system.

  Thus, the radar can support safe driving of the vehicle, and is expected as an important system constituting an ITS (Intelligent Road Traffic System). Conventionally, such radar is also used for military use.

  FM-CW (Frequency Modulated-Continuous Wave) radar uses a frequency-modulated continuous wave. The electromagnetic waves radiated from the transmitting antenna are set so that the frequency increases linearly and / or decreases with time. That is, the frequency and time of the transmission signal (electromagnetic wave: radio wave, light) are proportional. In short, the frequency of the transmission signal becomes higher as time passes if the frequency is increased.

  When a transmission signal is sent out from an antenna and hits a target at a distance R, it is reflected and returned to the receiving antenna. Since the speed of electromagnetic waves is constant at any frequency (c = speed of light), the graph showing the relationship between the time and frequency of the reflected wave is shifted slightly to the right with the separation. This deviation amount is the electromagnetic wave delay time τ1.

  Note that the round-trip time τ1 = 2R / c of the electromagnetic wave to the target separated by the distance R. Here, the electromagnetic wave delay time τ1 increases as the distance R to the target increases. Since the frequency increases / decreases with the passage of time within the frequency sweep time, the delay time τ1 of the reception signal with respect to the transmission signal is proportional to the frequency difference between the transmission signal and the reception signal at the time of reception.

When the frequency of these differences is the beat frequency fb, the sweep time is Δt, and the sweep frequency width is Δf, the delay time τ1 = (1 / c) × 2R × (ε _r ) ^1/2 = Δt / Δf = fb∝ There is a relationship of Kfb. K is a constant, ε _r is a dielectric constant in the propagation medium of electromagnetic waves, and is 1 in air. Therefore, if the beat frequency fb is measured, the delay time τ1 is found, and if the delay time τ1 is known, the distance R is found. This is the conceptual operation principle of FM-CW radar.

  The output signal of the receiving antenna of the FM-CW radar is a time domain waveform. When the transmission signal is mixed with the reception signal output from the reception antenna, a beat signal can be obtained. The Fourier transform is a transform that decomposes a given waveform into many simple sine waves and indicates the frequency components of each sine wave. When Fourier transform is applied to the time domain waveform of the beat signal, the frequency component can be extracted.

  When the beat signal is sampled and AD-converted, this is a set of discontinuous values, so that discrete Fourier transform (DFT) can be used as digital Fourier transform. When the discrete Fourier transform (DFT) is performed on the beat signal within the frequency sweep time, the frequency amplitude of the beat signal appears like a frequency spectrum.

  The discrete Fourier transform (DFT) can be performed using a fast Fourier transform (FFT) algorithm. Note that Fast Fourier Transform (FFT) is a technique for reducing the amount of calculation and performing conversion at high speed, focusing on the symmetry of discrete Fourier transform. As described above, when fast Fourier transform (FFT) is performed on the beat signal, a peak appears at a position corresponding to the beat frequency fb on the frequency axis.

  As described above, since the distance R to the target is proportional to the delay time τ1, and the delay time τ1 is proportional to the beat frequency fb, the position of the beat frequency fb on the frequency axis is the distance R to the target. It will correspond. This spectrum on the frequency axis is called “distance power spectrum” in the sense that the frequency corresponds to the distance. When there are a plurality of targets, a plurality of beat frequency peaks appear on the distance power spectrum in accordance with the reflectance. In addition, when both the frequency increase period and the frequency decrease period are set at the time of frequency sweep, the relative speed between the target and the target can be obtained from the difference in beat frequency in both periods.

  Such FM-CW radars are described, for example, in Patent Documents 1 to 5 below. In the FM-CW radar, a DBF (digital beam forming) radar is used. A DBF radar does not scan an electromagnetic wave of a transmission signal as a beam in real space, but receives interference waves from all directions by a plurality of receiving antenna elements, and physically separates the receiving antenna elements. This is a method of obtaining data obtained when a transmission signal is virtually scanned by recombining reception signals from only a specific direction by adjusting a phase difference between reception signals based on distance.

  A monopulse radar using a phase difference between received signals is described in, for example, Patent Document 6 below.

  Furthermore, a super resolution algorithm radar that exceeds the limits of the DBF method is also known. The super resolution algorithm is used for estimating the direction of arrival of a signal using an array antenna and identifying a radar target. It is a general term for techniques that achieve high resolution beyond the limits of the forming method and Fourier transform. As the super-decomposition algorithm, the MUSIC method, ESPRIT method, MODE method and the like are known.

  By the way, when the radar apparatus is applied to, for example, a vehicle system, it is important to detect and control an object as soon as possible. On the other hand, when applied to such a system, noise may be detected as an object, and a method of determining an object from a plurality of detection results is used to improve the reliability of the detection results.

  An FM-CW radar for detecting an object without being affected by noise is described in, for example, Patent Document 7 below. This document sets a determination threshold value in order to appropriately detect the peak frequency of a beat signal. A method of setting appropriately is disclosed.

  For example, Patent Document 8 discloses a technique that eliminates malfunctions by appropriately changing the detection sensitivity according to the level of background noise included in the output of the receiver or performing data interpolation.

Furthermore, in Patent Document 9 below, a value representing the correlation between the position and speed of the preceding vehicle detected by the distance sensor and the image sensor, and a value related to the reliability of the calculated position and speed, respectively, are calculated. Whether or not these vehicles are one vehicle to be monitored is determined by sensor fusion based on the calculated value.
JP 11-133142 A JP 2000-75028 A JP 2003-270341 A JP 2000-258524 A JP 2000-9831 A JP-A-9-152478 JP-A-8-226963 JP-A-8-184666 JP 2002-99906 A

  However, in the above-described conventional target detection device, in particular, the target detection device described in Patent Document 9, since the sensor fusion using different types of radar is performed, the target detection accuracy is increased. On the other hand, if the detection results of the respective radars do not match, the final result cannot be obtained, and there is a possibility that the detection cycle becomes long.

  This invention is made | formed in view of such a subject, and it aims at providing the target detection apparatus which can detect a target at high speed.

A target detection apparatus according to a first aspect of the invention has a first radar that has a first detection range and a calculation for obtaining a distance power spectrum for a long time, and a second detection range that overlaps the first detection range. The second radar having a short calculation time for obtaining the distance power spectrum, the first determination means for determining the presence of the target based on the calculation result of the first radar, and the target based on the calculation result of the second radar. a second judging means for performing presence determination of a presence determining means for determining the presence from the presence determination result of the target of the first determining means, is target object to the presence of the last is confirmed by the presence determining means, existence determination previous When the existence of the first and second radars in the overlapping range is determined , the second radar calculation result is input to the second determination unit, and the second determination unit determines the previous target after the determination. With a specifying means to make this presence determination And wherein the door.

  Note that the terms “short calculation time” and “long calculation time” are defined as relative time lengths.

  The calculation result of each radar is, for example, a distance power spectrum in an area in front of the radar, and target presence determination can be made based on whether or not the spectrum level at a specific distance exceeds a threshold value.

  The calculation result of the first radar can be obtained in a shorter time than the calculation result of the second radar.

  In this target detection apparatus, when the presence of a target is determined in the overlapping range of the first and second radars, the presence or absence of the next target can be determined even with low accuracy. When the target whose existence has been determined by the presence determination means exists in the overlapping range, the calculation result of the second radar with a short calculation time is input to the second determination means, and the current presence after the previous determination of the target Is determined by the second determination means. Thereby, a target can be detected at high speed. The target data determined by the current presence determination can be used for the current control. In the overlap area, if the target was confirmed in the previous time, the target can be confirmed at this time by the second radar and the second determination means using this result. In the non-overlap area, Even if the target after the previous determination has moved and entered, it is preferable that the control target is not controlled only by the detection result of the second radar.

A target detection apparatus according to a second invention includes a first radar having a long calculation time having a first detection range, a second radar having a second calculation range having a second detection range overlapping with the first detection range, First determination means for determining the presence of a target based on the calculation result of one radar, second determination means for determining the presence of a target based on the calculation result of the second radar, and presence determination result of the first determination means When the presence determination means for determining the presence of the target and the target for which the previous presence has been determined by the presence determination means have been determined in the overlapping range of the first and second radars by the previous presence determination. , A second means for inputting the calculation result of the second radar to the second determination means, and a second specifying means for performing the current presence determination after the previous target is determined by the second determination means. When the existence is confirmed, the designation means calculates the calculation result of the first radar. Is input to the first determination means, the presence determination of the target is performed by the first determination means, and the second determination means performs a plurality of targets while the first determination means performs one target presence determination. While performing the presence determination, the control target is controlled based on the determination result of the second determination means.

  Here, the “control target” refers to a system such as ACC or PBA, for example.

  Since the first radar has a long calculation time, it can relatively accurately perform the calculation as compared with the second radar. When the presence of the target is confirmed in the overlapping range, the calculation result of the second radar is input to the second determination means, and the calculation is performed at a relatively high speed. When the target presence determination is performed, the designation unit inputs the calculation result of the first radar to the first determination unit and causes the first determination unit to perform the presence determination of the target, so that a more accurate determination result is obtained. Can be obtained.

  That is, basically, when the presence of a target is determined in the overlapping range, high-speed target presence determination is performed using the second radar and the second determination means, and the calculation of the first radar is performed in parallel. If the calculation result of the first radar is obtained, the target presence is accurately determined by the first radar and the first determination means, and both high speed and accuracy are achieved.

  The target detection apparatus according to the third aspect of the present invention is the determination of the first determination means when the presence of the target is confirmed in the overlapping range, or when the first determination means performs one target presence determination. Control of the controlled object is performed based on the result. In other words, the determination results include the results of the first determination means and the results of the second determination means. If the first determination means performs one target presence determination, this result is used for control. By using it, relatively accurate control can be performed.

  The target detection apparatus according to the fourth aspect of the present invention is based on the calculation result of the second radar when the presence of the target is confirmed in the overlapping range, or when the first determination means performs one target presence determination. It is characterized by comprising correction means for correcting the target-related physical quantity (relative speed, direction, etc.) obtained with the target-related physical quantity obtained from the calculation result of the first radar. Note that “obtained from a calculation result” not only means that it is obtained directly, but also means that it is obtained by processing data for obtaining a calculation result.

  That is, in the overlapping range, the same target is detected by the first and second radars, but the target related physical quantity obtained from the calculation result of the second radar is based on the more accurate target related physical quantity by the correcting means. The accuracy of the target related physical quantity obtained on the second radar side can be improved.

  A target detection apparatus according to a fifth invention is characterized in that the first detection range of the first radar in the overlap range is limited based on a target-related physical quantity obtained from the calculation result of the second radar in the overlap range. To do.

  In other words, when the target-related physical quantity is obtained from the second radar, the first detection range of the first radar necessary for target detection can be narrowed down. Therefore, the calculation time can be reduced by limiting the first detection range. Can be shortened and high-speed calculations can be performed.

In the target detection apparatus according to the sixth aspect of the invention, the presence determination means detects the presence of an object from the determination results of the first determination means and the second determination means in the overlapping range of the detection ranges of the first radar and the second radar. It is characterized by being confirmed.
Since the target determined by the determination results (sensor fusion) of both radars in the overlapping range has high accuracy and reliability of the detection result, the target determination by the second radar is performed after the target is determined. Even if the presence determination of the target is performed by the two determination means, the accuracy can be kept high.
A target detection apparatus according to a seventh aspect of the invention includes a first radar having a first detection range, a second radar having a second detection range that overlaps the first detection range, and lower detection accuracy than the first radar. In the overlapping range of the first and second detection ranges, when the difference between the target related physical quantities obtained from the calculation results of the first and second radars is equal to or greater than a specified value, the target relation obtained from the calculation results of the second radar The target detection apparatus includes a correction unit that corrects the physical quantity with the target-related physical quantity obtained from the calculation result of the first radar , and the second radar is a millimeter wave radar including a plurality of receiving antenna elements. The physical quantity related to the target is the distance to the target and the direction toward the target, and the correction means can obtain the phase of the signal output from the plurality of receiving antenna elements from the calculation result of the first radar. Second radar performance on target-related physical quantities By standard related physical quantity those obtained from the results of phase-shifting to match, and performs a correction.

  According to this target detection apparatus, the same target is detected by the first and second radars in the overlapping range, but when the difference between the physical quantities related to the target is equal to or larger than the specified value, the second correction unit corrects the second target. The accuracy of the target related physical quantity obtained on the second radar side is improved by correcting the target related physical quantity obtained from the radar calculation result based on the more accurate target related physical quantity from the first radar. be able to.

In the target detection apparatus according to the eighth aspect of the invention, the target-related physical quantity obtained from the calculation result of the first radar is such that an error caused by a predetermined physical quantity due to an external factor has already been corrected. To do. Here, the predetermined physical quantity is a physical quantity that affects electronic equipment such as temperature. Since the first radar outputs the calculation result in which the error due to the predetermined physical quantity is corrected, if the calculation result of the second radar and the target related physical quantity are corrected based on this, the first radar target in the overlapping range is corrected. If the target-related physical quantity of the second radar is matched with the related physical quantity, the target-related physical quantity of the second radar can be made accurate.

  In the target detection apparatus according to the ninth aspect of the present invention, the correction means performs correction when there is no other target around the target detected by the first or second radar.

  In this target detection apparatus, when other targets exist around the target, that is, when roadside objects, obstacles, or vehicles exist, noise based on these targets is included in the calculation result. . Therefore, when these targets are present, the correction time is not necessarily suitable. Therefore, the correction means performs correction when it is not such time, and performs more accurate correction.

  When the correcting means adjusts the phase between the signals output from the receiving antenna elements, the directivity of the radar changes. That is, if the signals are in phase, the signal intensity is high, but in order to increase the signal intensity from a target existing in a specific direction, the signal intensity of the reflected wave from the target is increased. What is necessary is just to adjust the phase between signals. The target related physical quantity obtained from the second radar, in this case, the azimuth, may deviate from an accurate value due to the influence of temperature or the like. In this case, accurate correction is performed by shifting the phase of the signal until the target-related physical quantity of the second radar matches the target-related physical quantity of the first radar that provides a more accurate value. be able to.

  According to the target detection apparatus of the present invention, a target can be detected at high speed.

  Hereinafter, the target detection apparatus according to the embodiment will be described. In addition, the same code | symbol shall be used for the same element and the overlapping description is abbreviate | omitted.

  FIG. 1 is a block diagram of a target detection apparatus 100 according to an embodiment.

  The target detection apparatus 100 includes a first radar 100a having a detection range R1, a second radar 100b having a detection range R2, and a calculation unit 100c that performs calculation based on the outputs of both radars 100a and 100b. ing. The fan-shaped long-distance narrow-angle detection range R1 and the sector-shaped short-distance wide-angle detection range R2 partially overlap with each other in common. In the long-distance narrow-angle detection range R1, the non-overlap detection range is R2a, and the overlap detection range (overlap range) is R1b. In the short-distance wide-angle detection range R2, the left and right non-overlapping detection ranges are R1a and R1c, and the central overlapping detection range is R2b.

  The first radar 100a having the detection range R1 is a DBF (digital beam forming) FM-CW radar, and the second radar 100b having the detection range R2 is a two-channel detecting phase difference of the received signal.・ It is a monopulse radar.

First, the FM-CW type radar as the first radar 100a will be described, then the two-channel monopulse type radar 100b as the second radar 100b will be described, and then an object using these plural radars. An embodiment of the mark detection apparatus will be described.
(First radar)

  FIG. 2 is a block diagram of an FM-CW radar as the first radar 100a.

  This FM-CW radar is a DBF radar with 1 transmission channel and 8 reception channels. Therefore, the receiving array antenna 1 includes eight receiving antenna elements CH1 to CH8 corresponding to each channel. The antenna elements CH1 to CH8 are connected to the corresponding mixers 11-1 to 11-8 via individual isolators constituting the isolator group 12.

  The mixers 11-1 to 11-8 mix a part of the transmission signal with the reception signal that has reached each antenna element to obtain a beat signal. The transmission signal component as a local signal is given to the mixers 11-1 to 11-8. More specifically, this transmission signal component is given from the voltage controlled oscillator (VCO) 14 to the mixers 11-1 to 11-8 via the branch circuit 15 and the isolator group 13.

  The voltage-controlled oscillator 14 is a varactor-controlled gun oscillator having a center frequency of f0 (for example, 60 GHz), and outputs a modulated wave up to f0 ± ΔF by a control voltage output from the modulation DC power supply 22. That is, when the control voltage input to the voltage controlled oscillator 14 increases, the frequency of the voltage output from the voltage controlled oscillator 14 increases, and when the control voltage input to the voltage controlled oscillator 14 decreases, the voltage control The frequency of the voltage output from the type oscillator 14 is lowered.

  The DC power source 22 periodically changes the output voltage value under the control of the modulation signal source 23. It is assumed that the control voltage input to the voltage controlled oscillator 14 is a triangular wave.

  The FM modulated wave output from the voltage controlled oscillator 14 is radiated as a transmission signal given to the transmitting antenna 21 via the branch circuit 15. Since the time waveform of the frequency of the transmission signal output from the transmitting antenna 21 is proportional to the control voltage input to the voltage controlled oscillator 14, it becomes a triangular wave.

  On the other hand, the FM modulated wave output from the voltage controlled oscillator 14 is branched into 8 channels by the branch circuit 15 to become a local signal, and is mixed with the received signals of 8 channels in the mixers 11-1 to 11-8, respectively. The beat signal for each channel is generated. The beat signal for each channel changes according to the distance to the target and the relative speed. That is, the distance and relative speed can be obtained from the beat signal. The details will be described below.

  First, the beat frequency change when the relative speed of the target is zero will be described.

  FIG. 3A shows the change in the transmission signal frequency (= proportional to the control voltage to VCO) output from the voltage controlled oscillator 14 (transmitting antenna 21), and the relative speed is zero at the distance R. It is the graph which showed the change of the received signal frequency re-radiated from a target object and output from each antenna element CH1-CH8. In this graph, the vertical axis represents frequency and the horizontal axis represents time.

  Note that the solid line in FIG. 3A indicates the temporal change in the transmission signal frequency, and the broken line indicates the temporal change in the reception signal frequency. FIG. 3B is a graph showing the frequency (beat frequency) of the output voltage (beat signal) of each mixer when the relative speed of the target is zero, and the time axis (horizontal axis) is shown in FIG. ) And the timing are matched. Note that the difference between the transmission signal frequency and the reception signal frequency is the beat frequency.

  As can be seen from this graph, a modulation signal obtained by multiplying a continuous wave by triangular frequency modulation is used as the transmission signal. The center frequency of the modulated wave is f0, the frequency shift width is ΔF, and the repetition frequency of the triangular wave is fm.

  As shown in FIG. 3A, between the transmission timing of the transmission signal and the reception timing of the reception signal, when the relative speed of the target is zero, the delay time τ1 corresponding to the distance R to the target (Τ1 = 2R / c: c is the speed of light).

  Next, the beat frequency change when the relative speed of the target is V will be described.

  FIG. 4A shows a change in the transmission frequency output from the voltage-controlled oscillator 14, and the radiation is re-radiated from the target at the distance R and the relative speed is V, and is output from the antenna elements CH1 to CH8. It is the graph which showed the change of receiving frequency, and shows a frequency on a vertical axis and time on a horizontal axis.

  Note that the solid line in FIG. 4A indicates a temporal change in the transmission signal frequency, and the broken line indicates a temporal change in the reception signal frequency. FIG. 4B is a graph showing the frequency (beat frequency) of the output voltage (beat signal) of each mixer when the relative speed of the target is V, and the time axis (horizontal axis) is shown in FIG. And the timing is matched.

  Between the transmission timing of the transmission signal and the reception timing of the reception signal, when the relative speed of the target is V, the delay time τ1 (τ1 = 2R / c: c is light based on the distance R to the target And a frequency shift D corresponding to the relative speed V. Note that the example shown in FIG. 4A shows a case where the received signal frequency is shifted upward in the graph and the target approaches. This is due to the Doppler effect.

The beat frequency when the relative speed is zero is fr, the Doppler frequency when the relative speed is V, fd, the beat frequency in the section where the frequency increases (up section) is fb1, and the beat frequency in the section where the frequency decreases (down section) If fb2 is satisfied, fb1 = fr−fd and fb2 = fr + fd are established. If this is solved for fr and fd, fr = (fb1 + fb2) / 2 and fd = (fb1−fb2) / 2 are obtained. The distance R and the speed V can be obtained by the following equations.
R = (C / (4 ・ ΔF ・ fm)) ・ fr = (C / (4 ・ ΔF ・ fm)) ・ (fb1 + fb2) / 2
V = (C / (2 ・ f0)) ・ fd = (C / (2 ・ f0)) ・ (fb1-fb2) / 2

  That is, if the beat frequency fb1 in the frequency up section and fb2 in the frequency down section are measured, the distance R and the relative velocity V of the target can be obtained in an arbitrary beam direction. If the velocity V is calculated sequentially, the azimuth, distance, and velocity of the target can be detected.

  Referring to FIG. 2 again, a low-noise amplifier 24, a high-speed A / D converter 25, a DBF signal are provided after the high-frequency circuit 10 including the mixer group 11, the isolator groups 12 and 13, the oscillator 14, and the branch circuit 15. A processing unit 26 and a complex FFT operation unit 27 are provided.

  The low noise amplifier (amplifier) 24 amplifies the 8-channel beat signals output from the mixers 11-1 to 11-8 in parallel. The amplifier 24 has a built-in low-pass filter with a cutoff frequency of 77 kHz for anti-aliasing.

  The high-speed A / D converter 25 is a circuit that performs A / D conversion on the 8-bit beat signals in parallel and simultaneously, and samples the beat signals at 200 kHz. With this sampling frequency, 128 points are sampled in the frequency up and down sections of the triangular wave in FM modulation.

  The DBF signal processing unit 26 acquires a digital beat signal for each channel from the high-speed A / D converter 25, performs DBF processing and distance / speed calculation, and performs target (target) recognition processing. The complex FFT calculation unit 27 is a calculation unit that performs a complex FFT calculation in a series of processes in the DBF signal processing unit 26, receives a digital beat signal for each channel from the DBF signal processing unit 26, and receives it. The complex FFT operation is performed on the result and the result is returned to the DBF signal processing unit 26. A power spectrum obtained by performing a complex FFT operation on a beat signal obtained for each channel is called a “distance power spectrum” because the frequency corresponds to the distance. An example of the distance power spectrum is shown in FIG.

  The DBF signal processing unit 26 adjusts beam scanning and sidelobe characteristics in a digital state by performing the function of the phase shifter of the phased array antenna radar by digital signal processing. Are received once after AD conversion, and then the distance R and velocity V in the azimuth θ of the target are calculated based on the beat signal of each channel. The direction of beam scanning can be arbitrarily set.

  That is, when a radio wave arriving from the direction of the angle θ with respect to the traveling direction X of the vehicle transmitting the beam is received by an array antenna composed of n antenna elements arranged at intervals d (n = 8 in this example). ), And the propagation path length of the radio wave for the antenna element (CH1) as a reference, the propagation path lengths for the antenna element (CH2),..., And the antenna element (CHn) are dsin θ,. Only get longer. Therefore, the phase of the radio wave reaching the antenna element (CH2) is delayed from that of the radio wave reaching the antenna element (CH1).

  The delay amounts are (2πdsinθ) / λ,..., (2 (n−1) πdsinθ) / λ, respectively. Here, λ is the wavelength of the radio wave. By synthesizing with the phase being advanced for each channel by this delay, radio waves from the θ direction are the same as those received in the same phase by all antenna elements, and directivity is directed in the θ direction. That is, if the phase of the signal of each channel is adjusted so that the received signal from the target angle θ can be detected, this adjustment amount corresponds to the angle θ.

  Thus, the major feature of DBF is that once the signals of all antenna elements (all receiving channels) are captured as digital signals, beam synthesis can be performed in any direction based on the signals, so that a single signal capture is performed. The digital processing is executed by the DBF signal processing unit 26 because a plurality of beams can be formed.

  The DBF signal processing unit 26 acquires a digital beat signal for each channel from the high-speed A / D converter 25, performs DBF processing and distance / speed calculation, and performs target (target) recognition processing. The beam swing width of this embodiment is from −10 degrees to +10 degrees, and 40 beams are formed with an angular resolution of 0.5 degrees.

  From the beam signals synthesized for each angle, the relative velocity and the relative distance for each angle are calculated by the above-described equations, and the target recognition process is performed from these information. For the target recognition process, a conventional technique may be applied depending on the application.

  As described above, the DBF signal processing unit 26 acquires the channel-specific digital beat signal from the high-speed A / D converter 25, the complex FFT operation unit 27 performs the complex FFT operation on the channel-specific signal, and the result of the FFT operation. By calculating the distance power spectrum and taking into account the phase delay amount, the beam for the angle θ is synthesized, and the distance R and the velocity V are calculated for the synthesized beam, so that the object in the desired direction θ is obtained. The distances R and V of the mark are calculated to recognize the target.

  As described above, the complex FFT calculation unit 27 is a calculation unit that performs the complex FFT calculation in the series of processes in the DBF signal processing unit 26 on behalf of the DBF signal processing unit 26. Is subjected to a complex FFT operation and the result is returned to the DBF signal processing unit 26.

As described above, when each channel beat signal is sampled and AD-converted, this is a set of discontinuous values. Therefore, when this is DFT processed by fast Fourier transform (FFT), the beat frequency on the frequency axis A peak appears at a position corresponding to fb, but the position of the beat frequency fb on the frequency axis corresponds to the distance R to the target. When the frequency spectrum of each channel is obtained, the distance power spectrum at a specific directivity angle can be obtained by adjusting the phase between the channels.
(Second radar)

  FIG. 6 is a block diagram of a two-channel monopulse radar as the second radar 100a.

  The two-channel monopulse radar receives a reflected wave Ref from a target M as a target by two reception antenna elements A1 and A2 that are spaced apart from each other. When the distance between the antennas A1 and A2 is D, the angle from the front of the vehicle, that is, the incident angle θ of the received signal is x = Dsinθ≈Dθ where the path difference between the two received signals is “x”. Is given by the phase difference Δφ = 2π (x / λ) based on this path difference “x”, and is given by θ≈Δφ · λ / (2π · D).

  The processing circuit 50 is reduced by an oscillator 53 that transmits a signal to the transmitting antenna 52, a mixing circuit MX1 and MX2 that mixes an output of the oscillator 53 with a signal from the receiving antenna elements A1 and A2, and a mixing circuit MX1 and MX2. And a calculation unit 51 to which a frequency-reception received signal is input. If the calculation unit 51 measures the phase difference Δφ between two input reception signals, the angle θ can be obtained. The phase difference Δφ can be obtained by converting two received signals into a square wave, taking an exclusive OR between the square waves, and counting the output period with a counter.

  Further, when the oscillator 53 is a voltage-controlled oscillator and a triangular wave control voltage is input to the transmission signal, the FM-modulated transmission signal is output from the transmission antenna 21, and the transmission signal and the reception signal are mixed. When the beat signal becomes a fast Fourier transform, it becomes a power spectrum corresponding to the distance to the target. When the distance power spectrum at the angle θ is necessary, the spectrum whose phase has advanced by the phase difference Δφ corresponding to the angle θ of the power spectra of the two received signals may be delayed and amplified in phase.

When angle information is not added, the distance power spectrum of the azimuth average of all azimuth detection values within the wide-angle detection range can be obtained from the received signal. Compared with DBF radar, this two-channel monopulse radar has a smaller amount of computation than DBF's FM-CW radar, and can output at high speed and provide sufficient detection accuracy. Then, detection accuracy is inferior.
(First embodiment)

  FIG. 7 is a diagram illustrating a vehicle state for explaining a detection algorithm of the target detection device according to the first embodiment.

  A state in which the host vehicle S1 is traveling while scanning the long-distance narrow-angle detection range R1 with the first radar 100a and scanning the short-distance wide-angle detection range R2 with the second radar 100b is shown. In the figure, a state in which the preceding vehicle S3 is traveling is shown in front of the host vehicle S1. The rear position of the preceding vehicle S3 in the short-distance wide-angle detection range R2 is P2.

  The azimuth average distance power spectrum (calculation result) obtained from the second radar 100b (detection range R2) indicates the relationship between the distance to the target (reception signal frequency) and the reception level (dBsm) (not shown). In this spectrum, a peak is observed at the rear position P2 of the preceding vehicle S3. That is, this spectrum means that a target (target) from which a reflected wave is obtained exists at the position P2.

  Therefore, an appropriate threshold value is set for the spectrum from the radar, and it can be determined that the target exists when the peak of the spectrum, for example, at the position P2 exceeds the threshold value. This is the presence detection. However, since the accuracy of existence is low in a single detection, the presence is confirmed when detection is performed several times.

  The azimuth average distance power spectrum (calculation result) obtained from the first radar 100a (detection range R1) also shows the relationship between the distance to the target (reception signal frequency) and the reception level (dBsm) (not shown). In this spectrum, a peak is observed at the rear position P2 of the preceding vehicle S3. In other words, this spectrum also means that a target (target) from which a reflected wave is obtained exists at the position P2.

  A spectrum (calculation result) of the first radar 100a is input to the calculation unit 100c, and target presence detection is performed by the threshold determination (first determination unit).

  The spectrum of the second radar 100b (calculation result) is input to the calculation unit 100c, and each target presence detection is performed by the threshold determination (second determination unit).

  As described above, the first radar 100a has a large calculation amount, and the second radar 100b has a small calculation amount. This is relative. Therefore, the calculation time of the first radar 100a is long, and the calculation time of the second radar 100b is short. Of course, this is also a relative one, and in this example, even if it is a long time, it is not on the order of several tens of minutes.

  When a highly accurate calculation result is required, it is preferable to use the calculation result of the first radar 100a, and when performing high-speed calculation, it is preferable to perform data processing with a tendency to use the calculation result of the second radar 100b. When the presence of the target is confirmed within the overlapping range R2b, the reliability of the second determination unit based on the calculation result of the second radar 100b is increased. In this case, the calculation of the second radar 100b is performed. The result is selected and the presence determination of the target is performed by the second determination means (designating means).

  As described above, the target detection apparatus includes the first radar 100a having a long calculation time having the long-distance narrow-angle detection range R1, and the short-distance wide-angle detection range R2 overlapping the long-distance narrow-angle detection range R1. A second radar 100b having a short calculation time, a first determination unit for determining the presence of a target based on the calculation result of the first radar 100a, and a first determination for determining the presence of a target based on the calculation result of the second radar 100b. 2 determination means, presence determination means for determining the presence of a target from the presence determination result of the first determination means, and a target whose previous presence has been determined by the presence determination means (after calculation period T5 in FIG. 8B) ) When the first and second radars are present in the overlapping range R2b, the calculation result of the second radar 100b is input to the second determination means, and the second determination means determines the previous target after the previous determination. This time the presence determination (Fig. 8 And a designation means for) causing in computation period t1~t5 operational period in T6 of b). Note that the terms “short calculation time” and “long calculation time” are definitions of relative time lengths.

In this target detection device, if the presence of a target is determined in the overlapping range R2b of the first and second radars, the presence or absence of the next target can be determined even with low accuracy. The means inputs the calculation result of the second radar 100b having a short calculation time to the second determination means when the target whose existence is determined by the presence determination means exists in the overlapping range, and this time after the previous determination of the target. Is determined by the second determination means. Thereby, a target can be detected at high speed. Of course, the second determination means can achieve both higher speed and accuracy by performing sensor fusion with the first determination means. The target data determined by the current presence determination can be used for the current control. In the overlap area, if the target has been confirmed in the previous time, the target can be confirmed at this time by the second radar 100b and the second determination means using this result. In the non-overlap area, Even if the target after the previous determination has moved and entered, it is preferable that the control target is not controlled only by the detection result of the second radar 100b.
That is, even when the confirmed target moves and enters the detection ranges R1a and R2c (non-overlapping areas) in FIG. 1, the control target is controlled only by the detection result of the second radar 100b. It is preferable not to do so. On the other hand, in the detection range R1a, when a target is detected by the first radar 100a with high accuracy, control can be performed using this result. In addition, when the target that has existed only in the outer detection ranges R2a and R2c is not determined and the target enters the overlapping region, the information on the detection ranges R2a and R2c is used to determine the overlapping range. It is preferable to set a focused detection range near the boundary with the non-overlapping range and narrow the detection range, thereby reducing the amount of calculation and shortening the calculation time until the target is determined, so that control can be performed. . Even in such a case, it is possible to determine the target with the first radar 100a without determining the presence or absence of the target with the second radar 100b alone. That is, in the above-described embodiment, the presence of the target is determined in the overlapping region R2b, but the presence of the target can also be determined in the region R1a.

  Further, in the above-described apparatus, for example, collision determination can be performed at a calculation cycle four to five times that of the conventional one. Therefore, for example, when applied to a collision avoidance system using this, the collision prediction time used for this is shortened. It can be calculated in time. As a result, alarms, brakes, seat belts, and the like during control can be controlled in real time.

  The details will be described below.

  FIG. 8 is a time chart showing the timings of “detection” and “determination” of the target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. Since whether or not “detection” is performed in each calculation period varies depending on the case, it is indicated as “during determination” in FIG.

  FIG. 6A shows a time chart in which the determination is performed only by the first radar (DBF-FM-CW radar), and FIG. 6B shows the determination using the first and second radars (monopulse radar). The time chart to perform is shown.

  DBF's FM-CW radar (inspection of detection range R1) has a large amount of calculation (long calculation time for obtaining a distance power spectrum) and high detection accuracy, and monopulse radar (inspection of detection range R2) ) Has a characteristic that the calculation amount is small (the calculation time for obtaining the distance power spectrum is short) and sufficient detection accuracy is obtained, but the detection accuracy is inferior to that of the DBF method.

  In the example of FIG. 6A, according to the determination results in the calculation periods T1 to T4, “presence” of the target is made in the calculation period T5, and “determination” is performed in the calculation period T6 after this determination, Control of a control target (such as an ACC system) is performed at the end of each fixed calculation period. Examples of vehicle control include inter-vehicle distance control, automatic brake control, PBA (pre-crash / brake assist), and PSB (pre-crash / seat belt) system control.

  The control cycle in FIG. 10A is relatively long compared to the control cycle in FIG.

  In the example of FIG. 5B, in a single calculation period (for example, T1) of the FM-CW radar that scans the long-distance narrow-angle detection range R1, 5 is used for the monopulse radar that scans the short-range wide-angle detection range R2. Two calculation periods (t1 to t5) are set. That is, while the first radar 100a (DBF FM-CW radar: see FIG. 1) generates one output (distance power spectrum), the second radar 100b (monopulse radar: see FIG. 1) Five outputs (distance power spectrum) are generated.

  The calculation unit 100c (see FIG. 1) sets a threshold value for the distance power spectrum output from each, and determines that the target is present when the reception level exceeds this threshold value. Detection is performed.

  In FIG. 5B, when the presence of the target is detected once within one calculation period of the short-range wide-angle detection range R2, the “high-speed detection flag (detection flag: accuracy level L)” is set to 1. , The number of calculation periods in which the high-speed detection flag is 1 (in this example, number = 5 (t1, t2, t3, t4, t5) is one calculation period (= T1) in the long-distance narrow-angle detection range R1. ).

  If the presence of a target is detected once within the one-time calculation period of the long-range narrow-angle detection range R1 (when the reception level of the distance power spectrum exceeds the threshold), the “high-precision detection flag (detection Flag: Accuracy level M) ”is set to 1, and the number of calculation periods in which the high-precision detection flag is 1 is counted. If the count value exceeds a specified value, the presence of the target is confirmed, The (detection flag (accuracy level H)) becomes 1 (the determination flag is met at the calculation time T5).

  That is, within a certain calculation period (T1), there are more than a specified number of detection flags with an accuracy level L, and there are also detection flags with an accuracy level M. When the value is exceeded, there is a detection flag of accuracy level H, that is, a confirmation flag (see calculation period T5). The accuracy levels L, M, and H indicate a low accuracy state, an intermediate state, and a high state, respectively. When the confirmation flag H is set, it is confirmed that the same target is located within the overlapping range.

  When the presence of the target is “determined” in the calculation period T5, the calculation result of the second radar 100b is adopted in the next calculation period T6, and control is performed for each calculation period. That is, the control cycle is shorter than that in FIG.

  In other words, when the presence of the target is confirmed in the overlapping range R2b, the designation unit inputs the calculation result of the first radar 100a to the first determination unit (the calculation period T6 of R1), and the target is detected by the first determination unit. While the first determination unit performs one target presence determination, the second determination unit performs the target presence determination a plurality of times while the second determination unit (the calculation period T6 of R2). The control target is controlled based on the determination results of each of the calculation periods t1, t2, t3, t4, and t5).

  Since the first radar 100a has a long calculation time, relatively accurate calculation can be performed in comparison with the second radar 100b. When the presence of the target is confirmed in the overlapping range R2b, the calculation result of the second radar 100b is input to the second determination unit, and the calculation is performed at a relatively high speed. When performing the target presence determination for the first time (calculation period T6), the designation unit inputs the calculation result of the first radar 100a to the first determination unit and causes the first determination unit to perform the target presence determination. Thus, a more accurate determination result can be obtained.

  That is, basically, when the presence of the target is determined in the overlapping range R2b, the first radar 100a performs the calculation while performing the high-speed target presence determination using the second radar 100b and the second determination unit. If the calculation result of the first radar 100a is obtained in parallel, the target presence is accurately determined by the first radar and the first determination means, and the control is performed at the end of the calculation period T6. Both high speed and accuracy are achieved.

  In other words, when the presence of the target is confirmed in the overlapping range R2b (calculation period T5), when the first determination unit performs one target presence determination (calculation period T6), this first determination The control target is controlled based on the determination result of the means. The target presence determination result includes the result of the first determination means and the result of the second determination means. If the first determination means performs one target presence determination, this result is By using it for control, relatively accurate control can be performed.

  In addition, the sensor-fusion method in the case of using two conventionally known radars can also be employed. Also, the calculation results of the radar can be supplemented with each other.

  FIG. 9 is a flowchart for performing a target recognition process in the short-distance wide-angle detection range R2 while the vehicle is traveling.

  First, it is determined whether or not the same target as the long-distance narrow-angle detection range R1 is detected in the overlapping range R2b (S101). That is, regarding an object whose existence is determined in the overlapping region R2b, if the relative speed and direction of both radars match (the difference is within a specified value), it can be determined that they are the same object. If the determination result is “Yes”, the process proceeds to step S102. If the determination result is “No”, the current process ends.

  In step S102, it is determined whether or not the object confirmation flag (H) is set. If the determination result is “Yes”, vehicle control is performed (S103). If the determination result is “No”, the current process is terminated.

  FIG. 10 is a flowchart for performing a target recognition process in the long-distance narrow-angle detection range R1 during vehicle travel. First, it is determined whether or not a target is detected in the long-distance narrow-angle detection range R1 (S201). If the determination result is “Yes”, the process proceeds to step S202. If the determination result is “No”, the current process ends.

  In step S202, it is determined whether the same target is continuously detected and has been detected a predetermined number of times or more. If the determination result is “Yes”, the target determination flag is set (S203). If the determination result is “No”, the current process is terminated. When the target determination flag is set, vehicle control is performed based on the target related physical quantity (direction, relative speed, etc.) obtained from the calculation result (S204).

  FIG. 11 is a time chart showing the timings of “detection” and “determination” of the target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. Since whether or not “detection” is performed in each calculation period varies depending on the case, it is indicated as “during determination” in FIG. There are a plurality of calculation periods t1 to t5 of the second determination means in each of the calculation periods T1 to T7 of the first determination means. In the first determination means for determining the presence of the target in the long-distance narrow-angle detection range R1, when the presence of the target is determined (calculation period T5), five calculations are performed in the short-distance wide-angle detection range R2 within this calculation period. A period is set, and the position of the target (preceding vehicle) S3 within each calculation period is indicated by b1 to b5. Further, the positions of the preceding vehicle S3 in the calculation period T6 after the presence of the target is determined are indicated by c1 to c5.

  FIG. 12 is a diagram illustrating a state of a running vehicle. In the figure, there is a preceding vehicle S3 in front of the host vehicle S1, and the preceding vehicle S1 is relatively close to the host vehicle.

  When the presence of the target is determined within the overlapping range R2b (calculation period T5), the second radar 100b is calculated in the subsequent calculation period (corresponding to positions b5, c1 to c5) of the second radar 100b (see FIG. 1). The target-related physical quantities (azimuth and relative speed) obtained from the respective calculation results are corrected based on the target-related physical quantities (azimuth and relative speed) obtained in the calculation period T5 of the first radar 100a (see FIG. 1). Is done. That is, in this example, the target-related physical quantity of the first radar 100a is updated at the position b4, and the second radar after the position b5 is based on the target-related physical quantity obtained by the first radar 100a. The target related physical quantity obtained in 100b is corrected.

  For example, the target-related physical quantity of the second radar 100a at the position b4 calculates a correction amount that matches the target-related physical quantity of the first radar 100a at this time, and this correction amount is obtained by the second radar after the position b5. The obtained target-related physical quantity and the calculation result are corrected.

  For example, when the target related physical quantity is the azimuth of the target, the azimuth obtained by the first radar 100a is 10.5 degrees and the azimuth obtained by the second radar 100b is 10 degrees at the time corresponding to the position b4. In this case, a deviation of + 5% becomes the correction amount, and at the position b5, the azimuth obtained by the second radar 100b may be multiplied by 5%.

  In addition, about the method of taking correction amount, the difference of each target related physical quantity can be taken, or the estimated value from the change rate of the difference until now can also be used. The target related physical quantity includes the direction of the target (distance in the front direction of the vehicle, distance in the lateral direction of the vehicle) and the relative speed. Correction can be performed in consideration of the update timing of this information. In the above-described example, the target-related physical quantity of the first radar 100a is updated at the position b4, and the target-related physical quantity is updated at the same timing in the next calculation period.

  In order to perform the correction, the second object 100 is determined so that the target-related physical quantity obtained by the second radar 100b at the position b4 matches the target-related physical quantity obtained by the first radar 100a. The phase of the signal from the receiving antenna element of the radar 100b may be shifted. In the above example, the correction amount is obtained as a ratio, and this is multiplied by the target related physical quantity in the subsequent calculation period (b5 and thereafter), and the signal is shifted by the amount corresponding to this.

  FIG. 13 is a flowchart for performing the target recognition process in the short-distance wide-angle detection range R2 during vehicle travel using the above-described correction.

  Steps S101 to S103 are the same as those shown in FIG. In this example, correction steps S301 and S302 are provided between step S102 and step S103.

  That is, when the target determination flag is set (S102), the target-related physical quantity (distance, relative speed) in the long-distance narrow-angle detection range R1 and the target-related physical quantity (distance, relative speed) in the short-distance wide-angle detection range R2. It is determined whether the difference from the (relative speed) is a specified value or more (S301). When the determination result is “No”, the vehicle control is performed by trusting the current physical quantity related to the target of the second radar 100b (S103). When the determination result is “Yes”, the target related physical quantity in the short-distance wide-angle detection range R2 is corrected (S302), and vehicle control is performed using the corrected target related physical quantity (S103). The correction method is as described above.

  As described above, in this target detection device, when the presence of the target is determined in the overlapping range R2b, or when the first determination unit performs one target presence determination, the calculation result of the second radar 100b. Is provided with a correction means for correcting the target related physical quantity (relative speed, direction, etc.) obtained from the target physical quantity obtained from the calculation result of the first radar 100a.

  That is, in the overlapping range R2b, the same target is detected by the first radar 100a and the second radar 100b, but the target-related physical quantity obtained from the calculation result of the second radar 100b is corrected more accurately by the correcting means. By correcting based on the target related physical quantity, the accuracy of the target related physical quantity obtained on the second radar side can be improved.

  FIG. 14 is a time chart showing the timings of “detection” and “determination” of the target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. Whether or not “detection” or “determination” is performed in each calculation period differs depending on the case, and is shown as “determining” in FIG.

  FIG. 15 is a diagram illustrating a state of a running vehicle.

  The preceding vehicle S3 is moving in a direction relatively close to the host vehicle S1. As time elapses, the relative position of the preceding vehicle S3 with respect to the host vehicle S1 becomes b1, b2, b3, b4, b5, and C. Since the calculation of the first radar 100a takes time, when the target is confirmed after the calculation of the first radar 100a is completed, the target moves from moment to moment, so literally the first radar 100a. It can be considered that the target presence determination result by is still being determined.

  Therefore, by limiting the first detection range R1 of the first radar 100a, which takes time to calculate, the time for calculating the calculation result is shortened. Since the reliability of the calculation result of the radar 100b is improved, the control can be performed using the calculation result. Note that the calculation time of the second radar 100b is, for example, ¼ of the calculation time of the first radar 100a.

  In the restriction of the first detection range R1, the target related physical quantity obtained in the second detection range R2 is used. That is, since it is considered that the target is present in the target-related physical quantity (azimuth, distance) of the second radar 100b, the first detection range R1 is reduced to an area including the target that seems to exist. At this time, the steering angle information can also be used. For example, in a DBF-FM-CW radar, a DFT scan or a DFT calculation range is set. When the distance power spectrum within this range (FFT calculation result) has a peak greater than or equal to the threshold value, a power spectrum depending on the direction can be obtained from the distance power spectrum of each channel.

  In this target detection device, the first detection range of the first radar in the overlap range R2b is limited based on the target-related physical quantity obtained from the calculation result of the second radar in the overlap range R2b. When the target-related physical quantity is obtained from the second radar 100b, the first detection range R1 of the first radar 100a necessary for target detection can be narrowed down. By limiting the first detection range R1, Calculation time can be shortened and high-speed calculations can be performed.

  Next, a procedure for determining the presence of a target will be described in detail.

  FIG. 16 is a time chart showing the timings of “detection” and “determination” of a target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2.

  The result of the target presence determination calculation in the first calculation period T1 of the long-distance narrow-angle detection range R1 indicates “detection” (high-precision detection flag = 1), and the short-distance wide-angle detection is performed during the calculation period T1. When the target presence determination calculation (t1 to t5) is performed five times in the range R2, the presence of the target is determined by sensor fusion.

  That is, in sensor fusion, at least one target is “detected (accuracy level L)” by the first and second radars, and, for example, a predetermined number of times within one calculation period T1 (second radar) ( (For example, 3 times) When the “high-speed detection flag” is reached, it is determined that the target is “detected (accuracy level M)” within the calculation period T1, and if this condition is not satisfied, The mark is determined to be “undetected”.

  In this example, since the presence of the target is “detected (meeting the accuracy level L)” in the first radar in the calculation period T1, the target is “detected” for the entire calculation period T1. It is determined that As a result of the calculation period T1, it is assumed that the target exists (detection), and the high accuracy detection flag is set to 1.

  Subsequently, the target is not detected in the next calculation period T2 of the long-distance narrow-angle detection range R1 (high accuracy detection flag = 0), and five objects are detected in the short-range wide-angle detection range R2 during the calculation period T2. When target detection is performed (high-speed detection flag = 1 × 5), the presence of the target is determined by sensor fusion.

  In this case, since the above condition is not satisfied, “not detected” is determined and the high-precision detection flag is set to 0.

  When the determination result by sensor fusion indicates “detection: accuracy level M”, the target presence determination result (high accuracy detection flag = 1) in the long-distance narrow-angle detection range R1 is performed a predetermined number of times (for example, four times). The temporary confirmation state (accuracy level M) of the presence of the target becomes the final confirmation state (accuracy level H), and vehicle control is performed based on the detection result. As described above, vehicle control includes inter-vehicle distance control, automatic brake control, PBA (pre-crash / brake assist), and PSB (pre-crash / seat belt) system control.

  That is, the state of “high accuracy detection flag” = 1 within one calculation period (for example, T1) can be “tentatively determined: accuracy level M” by sensor fusion, and if this state overlaps several times, The presence of the target is “final determination: accuracy level H”.

  When the presence of the target is “final determination: accuracy level H”, the reliability of the detection result of the short-distance wide-angle detection region R2 is also high. Therefore, the short-distance wide-angle detection by the second radar is performed after the calculation period T6. For each calculation period of range R2, the calculation unit 100c (see FIG. 1) outputs the presence / absence of the target, the distance to the target, the relative speed, and the direction at this time, and performs vehicle control based on this output. .

  In addition, after the calculation period T6, the calculation unit 100c uses the output of the first radar that outputs an accurate value within the last minute period in each period (T6, T7...) Presence / absence, relative speed, and direction are output, and vehicle control is performed based on the output.

  FIG. 17 is a time chart showing the timing of target detection and determination in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2.

  In this example, after “detection” (high-precision detection flag = 1) of the presence of the target in the calculation period T1, “not detected” (high-precision detection flag = 0) every calculation period T2, T3, T4, “Detection” (high accuracy detection flag = 1: accuracy level M) and “not detected” (high accuracy detection flag = 0) continue, followed by “detection” (high accuracy detection flag = 1: accuracy level M). As a result, the presence of the target is “determined: accuracy level H”.

  That is, it is determined whether or not “detection” is included in two calculation periods among the four calculation periods T2, T3, T4, and T5 after “detection” in the calculation period T1. After “high accuracy detection flag = 1”, “final determination flag = 1”. After the calculation period T6, the control is the same as that described above.

  FIG. 18 is a time chart showing the timing of target detection and determination in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2.

  In this example, after “detection” (high accuracy detection flag = 1: accuracy level M) of the presence of the target in the calculation period T1, “not detected” (high accuracy detection flag) every calculation period T2, T3, T4. = 0), "not detected" (high accuracy detection flag = 0), "detected" (high accuracy detection flag = 1: accuracy level M), followed by "detection", but "not detected" Therefore, the presence of the target is not determined, and “detection” continues after the calculation period T6.

  FIG. 19 is a time chart showing the timing of target detection and determination in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2.

  In this example, after “detection” (high-precision detection flag = 1) of the presence of the target in the long-distance narrow-angle detection range R1, “detection: accuracy level M” and “detection” are performed every calculation periods T2, T3, and T4. : “Accuracy level M” and “Detection: Accuracy level M” continue, and then “Undetected” is performed in the calculation period T5. However, since “Not detected” in the calculation period T5, “Detection: Accuracy level” The number of “M” satisfies the condition, but “the final determination flag = 0” at the time of the calculation period T5.

  In this example, since “detection: accuracy level M” is included three times in four consecutive calculation periods T2, T3, T4, and T5, the second radar corresponding to the calculation period T5 by the sensor fusion “ When “detection: accuracy level L” is output more than the specified number of times, when “detection: accuracy level M” is performed by the first radar in the calculation period T6, this is indicated by “determining flag = 1: accuracy”. Level H ”.

  FIG. 20 is a flowchart showing the target recognition process R1 including the interpolation process.

  First, it is determined whether or not the presence of a target has been detected within the long-distance narrow-angle detection range R1 (including the case where the detection range is limited) (accuracy level H) (S501). If the presence of the target is detected in step S501 (accuracy level H), then in the overlap detection range R1b (R2b) between the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2, It is determined whether or not the presence of the mark is detected (accuracy level H) (S502). Note that sensor fusion is possible in the overlap detection range.

  When the target does not exist in the overlap detection range (No), interpolation processing for data that does not exist can be performed. In the present embodiment, the interpolation process is performed by predicting the position of the current target from the relative speed of the detection result up to the previous time and using this as the detection result. Note that the interpolation processing method in the present invention is not limited to this, and the current detection result may be predicted from the detection results up to the previous time by using a known method such as linear prediction, for example. As a simpler method, the previous result may be the current detection result.

  If Yes in step S502, that is, if the target exists in the overlap detection range and sensor fusion is possible, the interpolation flag is reset in step S503 (interpolation flag = 0), and the process proceeds to the next step S504. move on.

  In step S504, “high accuracy detection flag = 1: accuracy level M” indicating that the same target exists (condition (1)) within several consecutive detection cycles (for example, calculation period T1 × 5). It is counted whether or not it is counted more than the specified number of times (confirmation flag = 1: accuracy level H) and (condition (2)) whether the interpolation flag is set (interpolation flag = 0).

  That is, in the sensor fusion state without interpolation processing, when “detection flag: accuracy level M” of a specified number or more is included, “determining flag: accuracy level H” of the presence of the target is set (S505), Vehicle control is executed as described above (S506).

  If “No” in step S501, that is, if the presence of the target is not detected within the long-range narrow angle detection range R1 (priority detection range Rx), the target exists only within the short-range wide-angle detection range R2. It is determined whether or not the “R2 single target determination flag” indicating that it is to be set is set (= 1) (see S611) (S507). Note that the target presence determination flag alone in the short-distance wide-angle detection range is set when the count number of “high-speed detection flag = 1” in the detection cycle exceeds a specified value.

  If “Yes” in step S507, it is determined whether the target is the same target. That is, in step S508, the difference between the distance and relative speed of the target in the short-distance wide-angle detection range R2 and the distance and relative speed of the target in the previous long-distance narrow-angle detection range R1 are both specified values. It is determined whether it is within the range.

  That is, it is determined whether or not the detection error between the radar outputs is within a certain range. If the detection error is within a certain range, that is, if “Yes” in step S508, it can be determined that they are the same target, so the process proceeds to step S509, and if it is “No”, the process ends. To do.

  In step S509, it is determined whether the specified number of continuous detections is not zero. That is, when the high-speed detection flag is set once, the specified continuous detection count is incremented by one. In other words, it is determined whether or not at least one high-speed detection flag is currently set, and a target determination flag is set for this target.

  If the specified number of continuous detections is zero (“No” in step S509), the accuracy of the presence of the target at the current time decreases, and if not, the presence of the target is determined. In step S507, when the target determination flag for the short-range wide-angle detection range R2 alone is set, the target is the same target (S508), and the target is currently detected (S509), the current short-range wide-angle Interpolation processing of data (target related physical quantity) in the detection range R2 is performed.

  That is, when the target is not detected in the narrow-angle detection range R1 (S501), but the object confirmation flag for the short-distance wide-angle detection range alone is set in the short-distance wide-angle detection range R2 (S507). ), The previous value (distance / velocity or target information) of the long-distance narrow-angle detection range R1 and the current value (distance / velocity or target information) set with the short-distance wide-angle single target determination flag. In comparison, if this error is within the specified value, it is determined that these are the same target, and if it is determined that they are the same target, it is determined whether the previous interpolation processing is performed (S510). If the previous time is not an interpolation process, an interpolation process is performed. An initial interpolation process is also performed.

  The initial interpolation processing means that the target is detected by the long-distance narrow-angle detection range R1 when the target is not detected in the long-distance narrow-angle detection range R1 before the object is determined. Since it can be detected at a cycle faster than the calculation cycle of the short-distance wide-angle detection range R2 before it is not in the state, the short-distance wide-angle detection range R2 is continuously detected multiple times, and the long-distance narrow-angle detection range R1 happens to be detected. By adopting the result of being able to detect continuously at a high speed when interpolating the data of the long-distance narrow-angle detection range R1 to the target detection state, It is possible to reduce the processing time required for confirmation. Note that the detection state by this interpolation processing is preferably not added to the prescribed number of continuous detections. For example, it is possible to detect three consecutive times before confirmation and to prevent the number of continuous detections from being reset to 0 when it happens to be in the state where it cannot be detected due to something in the fourth time. The state can be maintained, and the processing time required for confirmation is shortened. Note that continuous interpolation processing is not performed.

  If “Yes” in step S510, it is determined whether or not interpolation processing has been performed in the previous calculation period (S510). Is reset (S513). If interpolation processing has not been performed last time, interpolation processing is performed and an interpolation flag is set (S511). An initial interpolation process is also performed. However, continuous interpolation processing is not performed.

  When interpolation processing is performed here, when the target moves from the short-distance wide-angle detection range R2 to the overlap detection range with the long-distance narrow-angle detection range R1 (S501, S502), the interpolation flag is set. The condition (2) in step S504 cannot be satisfied, and the confirmation flag in step S506 is not set (S506).

  FIG. 21 is a flowchart for performing a target recognition process in the short-distance wide-angle detection range R2 during vehicle travel.

  First, in step S604, whether or not the same target is detected by each of the first radar and the second radar within the overlapping detection range R2b of the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. judge. If it is determined in step S604 that the same target has been detected, it is determined whether the target presence determination flag (accuracy level H) is set (S605). If the confirmation flag is set, step S606 is executed, and if it is not set, the process ends.

  In step S606, it is determined whether or not the difference between the distance / relative speed obtained from the first radar and the distance / relative speed obtained from the second radar is greater than or equal to a specified value. If it is greater than or equal to the specified value, the distance and relative speed obtained from the second radar (low accuracy) are corrected (S607). The correction method is as described above.

  Through step S606 or S607, vehicle control is performed using the distance and relative speed at which the difference between the radar outputs is within the specified value (S608).

  If it is determined as “No” in step S604, it is determined whether or not the target is detected only by the second radar in the overlap detection range R2b (S609). If the determination result is “No”, the process is terminated, and if it is “Yes”, step S610 is subsequently executed. In step S610, it is determined whether or not the same target is continuously detected by the second radar (S610).

  When only the second radar detects the same target continuously (“Yes” in S610), the short-distance wide-angle detection indicating that the target is detected by the short-distance wide-angle detection region R2 alone. The single target confirmation flag in the region R2 is set (S611), and the process is terminated. If only the second radar has not detected the same target continuously (No in S610), the process is terminated. This R2 single target confirmation flag is used for the determination in step S507 of FIG.

  As described above, in order to determine whether or not a target exists, that is, in order to set a determination flag, several detections are required. That is, in several detection cycles, when the high-precision detection flag is set a number of times greater than or equal to the specified value, the confirmation flag is set.

  As described above, this target detection device, when the difference between the target-related physical quantities obtained from the calculation results of the first and second radars in the overlapping range R2b of the first and second detection ranges is equal to or greater than a specified value, Correction means for correcting the target related physical quantity obtained from the calculation result of the second radar with the target related physical quantity obtained from the calculation result of the first radar is provided.

  According to this target detection apparatus, the same target is detected by the first and second radars in the overlapping range, but when the difference between the physical quantities related to the target is equal to or larger than the specified value, the second correction unit corrects the second target. The accuracy of the target related physical quantity obtained on the second radar side is improved by correcting the target related physical quantity obtained from the radar calculation result based on the more accurate target related physical quantity from the first radar. be able to.

  Here, it is assumed that the output of the first radar 100a is corrected for errors due to external factors such as temperature. When the same target is detected by the first and second radars, the target-related physical quantity of the second radar 100b may be corrected with the target-related physical quantity of the first radar 100a. There is a case where it is difficult to judge whether or not it is a mark. Hereinafter, a method for solving this will be described.

  FIG. 22 is a diagram illustrating a state of a running vehicle. It is assumed that the first radar 100a (see FIG. 1) accurately detects the position of the target (target related physical quantity: azimuth, distance). That is, the target exists at the peak position of the calculation result (distance power spectrum) of the first radar 100a, and the temperature characteristic data of the distance power spectrum of each channel is stored in the storage device, and the stored temperature characteristic data The distance power spectrum is corrected (corrected). For example, when the orientation is deviated by a specified amount due to the temperature difference from the reference temperature, the temperature difference is calculated from the output of the temperature sensor, and the calculation result is corrected by the amount of deviation.

  The position of the target obtained from the first radar 100a is P1. If the target detected by the second radar 100b is the same target as this, it should be located within the “same target recognition range” RS including the position P1.

  However, the target position P2 obtained from the second radar 100b may be located outside the same target recognition range RS. This is because the position of the target detected by the second radar 100b has shifted due to the influence of temperature or the like. Here, it is assumed that the azimuth is shifted. The reason why the azimuth is shifted is because the phase difference of the signal obtained from the receiving antenna element is shifted. 'And. When the position of the target detected by the second radar 100b is in the same target recognition range RS ′ in consideration of the phase difference, it can be determined that this is a different target. In the present example, the same target recognition range RS ′ in consideration of the phase difference deviation is a variation range of the short-distance wide-angle monopulse radar stored in advance in the ROM.

  When the position P2 of the target detected by the second radar 100b is outside the same target recognition range RS and within the same target recognition range RS ′ considering phase difference deviation, each radar These are the same target only if the difference in relative speeds of the targets detected in (1) is within the specified value, and only if it can be determined that there are no other targets that can cause noise. And the position (target related physical quantity) P2 obtained from the second radar 100b is corrected to coincide with the position P1 obtained from the first radar 100a.

  FIG. 23 is a flowchart for performing the above control.

First, in step S701, it is determined whether all of the conditions (A), (B), and (C) are satisfied.
(Condition (A)) In the overlap region R2b, the difference in the distance (position) and direction to the target obtained from both radars is greater than or equal to the specified value, so the position P2 is located outside the same target recognition range. .
(Condition (B)) The position P2 obtained from the second radar 100b is located inside the same target recognition range RS ′ in consideration of the phase difference.
(Condition (C)) The difference in relative speed from the target obtained from both radars is within a specified value.

  If “Yes” in step S701, it is determined whether there is a roadside object or a parallel running vehicle that causes noise within a predetermined distance from the position P1 or P2 (S702). This can be determined, for example, by the presence or absence of a level increase in the distance power spectrum within a desired detection range set as necessary. If there is a level increase, it is determined that an object causing noise exists. can do.

  If there is no object that causes noise, it is determined whether or not the above-described conditions (B) and (C) are satisfied continuously for a specified number of times (S703). If established, the target position P2 by the second radar 100b in the short-distance wide-angle detection range R2, that is, the phase difference between the received signals is corrected. The correction method is as described above.

  Note that in steps S701 to S703, if the determination condition is not satisfied, the process ends.

  As described above, in this target detection apparatus, the error due to the predetermined physical quantity is already corrected in the target related physical quantity (relative speed, relative distance, relative position) obtained from the calculation result of the first radar 100a. It is what. The predetermined physical quantity is a physical quantity that affects electronic equipment such as temperature. Since the first radar 100a outputs the calculation result in which the error due to the predetermined physical quantity is corrected, if the calculation result of the second radar 100b and the target related physical quantity are corrected based on this, the first radar in the overlapping range R2b. By matching the target-related physical quantity of the second radar with the target-related physical quantity of 100a, the target-related physical quantity of the second radar 100b can be made accurate.

  In addition, the correction unit performs correction when there is no other target around the target detected by the first or second radar (S702). If there are other targets around the target, that is, if a roadside object, an obstacle, or a vehicle is present, the calculation result includes noise based on these targets. Therefore, when these targets are present, the correction time is not necessarily suitable, so the correction means performs correction when it is not such time, and performs more accurate correction.

  In the above preferred target detection apparatus, the second radar 100b is a millimeter wave radar (including a monopulse radar) having a plurality of receiving antenna elements, and the target related physical quantity is the same as that of the target. The correction unit is configured to calculate the phase of the signal output from the plurality of receiving antenna elements to the physical quantity related to the target obtained from the calculation result of the first radar. Correction is performed by shifting the phase until the target-related physical quantities obtained from the results match.

  When the correcting means adjusts the phase between the signals output from the receiving antenna elements, the directivity of the radar changes. That is, if the signals are in phase, the signal intensity is high, but in order to increase the signal intensity from a target existing in a specific direction, the signal intensity of the reflected wave from the target is increased. What is necessary is just to adjust the phase between signals. The target-related physical quantity obtained from the second radar 100b, in this case, the azimuth, may deviate from an accurate value due to the influence of temperature or the like. In this case, accurate correction is performed by shifting the phase of the signal until the target-related physical quantity of the second radar matches the target-related physical quantity of the first radar that provides a more accurate value. be able to.

  Furthermore, the combination of radars may be composed of radar groups with different combinations as long as the effects of the present invention can be obtained.

  That is, a relatively high-precision super-decomposition algorithm radar is used to detect the first detection range R1, and a relatively low-precision DBF-FM-CW radar is used to detect the second detection range R2. The effect of the present invention can also be obtained when using. Radars using the MUSIC method, ESPRIT method, MODE method, etc. are known as radars for super-resolution algorithms.

  For example, a MUSIC radar is applied to the first detection range R1, a DBF-FM-CW radar is applied to the second detection range R2, or an ESPRIT radar is detected to the second detection range R1. A monopulse radar can be applied to the range R2.

  In the target detection apparatus described above, the determination result of the first determination means and the second determination means (determination in FIG. 8B) in the overlapping range R2b of the detection ranges of the first radar 100a and the second radar 100b. The existence of the object is determined. In the overlapping range R2b, since the target determined by the determination results (sensor fusion) of both radars has high accuracy and reliability of the detection result, after the target is determined (after the calculation period T5 in FIG. 8B) However, even if the presence determination of the target is performed by the second determination unit that performs the target determination in the second radar 100b (calculation period t1, t2,... T5), the accuracy can be kept high. In this case, any radar may have high target presence detection accuracy. However, since the first radar 100a functions as a correction reference, the correction reference radar has a relatively high detection accuracy. Is preferred.

  For example, rather than using a detection method that detects a front range relatively close to the vehicle, such as when the detection range of each radar is a combination of a short-range wide-angle detection range and a long-range narrow-angle detection range, It is preferable to detect a detection range relatively far from the vehicle with a highly accurate radar.

  Furthermore, according to a preferred aspect, the overlapping area, that is, a target whose presence is detected by a high-precision detection method, is less susceptible to noise than a high-precision sensor. By relaxing the condition, it is possible to continue detection without losing sight of the confirmed target. In addition, the threshold value can be lowered only in the case of a target detected with high accuracy. In this case, even if there is noise, detection can be continued without lowering the reliability of the detection result.

  Furthermore, although there are two detection ranges described above, these may be three or more as long as they have overlapping ranges, those having the same detection range limit distance, different ones, and detectable openings. Various combinations such as those having the same or different angles can be used.

  The present invention can be used for a target detection apparatus.

1 is a block diagram of a target detection apparatus 100 according to an embodiment. It is a block diagram of the FM-CW system radar as the first radar 100a. A change in the transmission signal frequency (= proportional to the control voltage to the VCO) output from the voltage controlled oscillator 14 (transmitting antenna 21) and a re-radiation from a target at a distance R and having a relative speed of zero. It is the graph which showed the change of the received signal frequency output from each antenna element CH1-CH8. A change in transmission frequency output from the voltage-controlled oscillator 14 and a change in reception frequency output from each antenna element CH1 to CH8 after being re-radiated from a target at a distance R and having a relative speed of V are shown. The frequency is plotted on the vertical axis and the time is plotted on the horizontal axis. It is a graph which shows a result when FFT is performed with respect to the data which performed 0 pad process. It is a block diagram of a 2-channel monopulse radar as the second radar 100a. It is a figure which shows the state of the vehicle for demonstrating the detection algorithm of the target detection apparatus which concerns on 1st Embodiment. It is a time chart which shows the timing of "detection" and "determination" of the target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. It is a flowchart which performs the target recognition process in the short distance wide angle detection range R2 during vehicle travel. It is a flowchart which performs the target recognition process in the long-distance narrow-angle detection range R1 during vehicle travel. It is a time chart which shows the timing of "detection" and "determination" of the target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. It is a figure which shows the state of the vehicle in driving | running | working. It is a flowchart which performs the target recognition process in the short distance wide angle detection range R2 during vehicle travel using the above-mentioned correction. It is a time chart which shows the timing of "detection" and "determination" of the target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. It is a figure which shows the state of the vehicle in driving | running | working. It is a time chart which shows the timing of "detection" and "determination" of the target in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. It is a time chart which shows the timing of target detection and determination in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. It is a time chart which shows the timing of target detection and determination in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. It is a time chart which shows the timing of target detection and determination in the long-distance narrow-angle detection range R1 and the short-distance wide-angle detection range R2. It is a flowchart which shows the target recognition process R1 containing an interpolation process. It is a flowchart which performs the target recognition process in the short distance wide angle detection range R2 during vehicle travel. It is a figure which shows the state of the vehicle in driving | running | working. It is a flowchart for performing the object recognition process of short-distance wide-angle detection range R2.

Explanation of symbols

100a... First radar, 100b... Second radar, 100c.

Claims (9)

In the target detection device,
A first radar having a first detection range and a long calculation time for calculating a distance power spectrum;
A second radar having a second detection range overlapping the first detection range and having a short calculation time to obtain a distance power spectrum;
First determination means for determining the presence of a target based on the calculation result of the first radar;
Second determination means for determining the presence of a target based on the calculation result of the second radar;
Presence determination means for determining the presence of a target from the presence determination result of the first determination means;
When the target whose previous presence has been determined by the presence determination means has been determined to exist in the overlapping range of the first and second radars in the previous presence determination, the calculation result of the second radar is used as the second radar. A designation unit that inputs to the determination unit and causes the second determination unit to perform the current presence determination after the previous target is determined;
A target detection apparatus comprising: In the target detection device,
A first radar with a long computation time having a first detection range;
A second radar having a short calculation time and having a second detection range overlapping the first detection range;
First determination means for determining the presence of a target based on the calculation result of the first radar;
Second determination means for determining the presence of a target based on the calculation result of the second radar;
Presence determination means for determining the presence of a target from the presence determination result of the first determination means;
When the target whose previous presence has been determined by the presence determination means has been determined to exist in the overlapping range of the first and second radars in the previous presence determination, the calculation result of the second radar is used as the second radar. A designation unit that inputs to the determination unit and causes the second determination unit to perform the current presence determination after the previous target is determined;
With
When the presence of the target is confirmed in the overlapping range, the designation unit inputs the calculation result of the first radar to the first determination unit and causes the first determination unit to determine the presence of the target,
While the first determination means performs one target presence determination, the second determination means performs a plurality of target presence determinations, and controls the control target based on the determination result of the second determination means. The target detection apparatus characterized by performing.   When the presence of the target is confirmed in the overlapping range, and the first determination unit performs one target presence determination, the control target is controlled based on the determination result of the first determination unit. The target detection apparatus according to claim 2, wherein the target detection apparatus performs the target detection.   When the presence of the target is confirmed in the overlapping range, when the first determination unit performs one target presence determination, the target-related physical quantity obtained from the calculation result of the second radar, The target detection apparatus according to claim 2, further comprising a correction unit that corrects the target-related physical quantity obtained from the calculation result of the first radar.   5. The first detection range of the first radar in the overlapping range is limited based on a calculation result of the second radar in the overlapping range. 5. Target detection device.   The presence determination means uses the result of the previous presence determination by the first determination means and the second determination means in the overlapping range of the detection ranges of the first radar and the second radar, and the presence of the current object The target detection apparatus according to any one of claims 1 to 5, wherein the target is detected. In the target detection device,
A first radar having a first detection range;
A second radar having a second detection range overlapping the first detection range and having a detection accuracy lower than that of the first radar;
If the difference between the target-related physical quantities obtained from the calculation results of the first and second radars in the overlapping range of the first and second detection ranges is equal to or greater than a specified value, the difference is obtained from the calculation results of the second radar. A target detection apparatus comprising correction means for correcting a target related physical quantity with a target related physical quantity obtained from a calculation result of the first radar ,
The second radar is a millimeter wave radar having a plurality of receiving antenna elements,
The target-related physical quantity is a distance between the target and a direction toward the target,
The correction means converts a phase between signals output from the plurality of receiving antenna elements into a target relation physical quantity obtained from the calculation result of the first radar, and a target relation obtained from the calculation result of the second radar. A target detection apparatus characterized in that the correction is performed by shifting the phase until the physical quantities match . 8. The target detection according to claim 7, wherein the target-related physical quantity obtained from the calculation result of the first radar has already been corrected for an error caused by a predetermined physical quantity due to an external factor. apparatus. The target according to claim 7 or 8, wherein the correction means performs the correction when there is no other target around the target detected by the first or second radar. Detection device.

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