JP2009092410A - Radar system and target detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To predict the distance up to a target so as not to deviate from a distance value of the target to be detected actually in the next scanning, even if the speed of the target changes suddenly in scanning wherein frequency modulation of a radar wave is not performed. <P>SOLUTION: By the use of a radar system having a target distance prediction means for predicting the present distance of the target based on its distance and speed in the past, a continuity decision means for counting the number of times of detection of the target corresponding to a predicted distance, when no targets corresponding to the predicted distance are detected, and outputting the detected distance of the target when the count number reaches a specified number, and a target presumption means for presuming that the target corresponding to the predicted distance and a speed detected by the scanning has been detected when a second radar wave without frequency modulation is transmitted/received, it becomes possible to predict the distance not deviating from the distance to be detected by the next scanning. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radar apparatus and a target detection method for scanning a predetermined area by transmitting and receiving a frequency-modulated radar wave and detecting the distance or speed of the target for each scan, and in particular, detecting by a past scan. A target distance prediction means for predicting the distance of the target in the current scan based on the distance and speed of the target, and a target corresponding to the predicted distance in the current scan is not detected Includes target estimation means for performing target estimation processing for estimating that a target corresponding to the predicted distance and the speed detected in the past scan has been detected, and the prediction in the current scan. A radar apparatus comprising: a continuity determination unit that counts the number of times a target corresponding to the detected distance is detected and outputs the distance of the detected target when the count value reaches a specified number And a target detection method.

  There is known an in-vehicle radar device that scans the front of a vehicle such as an automobile and detects a target such as a preceding vehicle. Such a radar apparatus receives a reflected wave of a transmitted radar wave and detects a preceding vehicle that has reflected the radar wave at an azimuth angle at which the peak of the reflected wave is formed. Also, when transmitting a radar wave, such a radar device modulates the frequency using an FM-CW (Frequency Modulated-Continuous Wave) method, and detects the distance and speed of the preceding vehicle from the frequency difference between the transmitted and received waves. To do. Then, the radar apparatus outputs information such as the azimuth angle, distance, and speed of the preceding vehicle to a vehicle ECU (Electronic Control Unit) that controls the operation of the vehicle. Then, the vehicle ECU performs follow-up running control so as to keep the inter-vehicle distance constant based on these pieces of information.

  The in-vehicle radar device outputs only target information that has been detected continuously in a continuous scan, that is, has a history of continuity, in order to ensure the reliability of the target information output to the vehicle ECU. To do. Specifically, the radar device predicts the distance of the current target from the distance and speed of the target (hereinafter referred to as “previous detection target”) detected in the previous scan, and matches the predicted distance. Alternatively, when a target corresponding to a distance with a small error is detected in the current scan, it is determined that the target detected in the current scan (hereinafter referred to as “currently detected target”) has continuity. The radar apparatus outputs information such as the latest azimuth angle, speed, and distance of the target when the number of times determined to have continuity reaches a specified number.

  In the continuity determination procedure as described above, a target having a certain degree of continuity history may not be detected due to a decrease in the reception level of the reflected wave due to a change in the angle of the reflection surface. That is, the target may be lost. Then, since the continuity history is interrupted at that time, if the same target is detected again in a future scan, it is detected as a new target. Then, in order for the radar apparatus to output the target information, a history of continuity is required again until the specified number of times, and therefore the timing at which the target information is output to the vehicle ECU is delayed.

Therefore, in order to prevent such a situation, a method for estimating a lost target from a previously detected target has been proposed. Specifically, it is estimated that a target corresponding to the azimuth angle, speed, and predicted distance of the target detected last time has been detected. The target in this scan estimated in this way is hereinafter referred to as “currently estimated target”. According to this method, when the target is lost, the distance of the target in the next scan can be predicted based on the estimated target, and the continuity is detected when the target is detected again in the next scan. A history can be maintained. Therefore, delay in output timing can be prevented. As an example, Patent Document 1 describes an example of a radar apparatus that estimates the position of a target in the current scan from the position and speed of the target detected last time.
JP 2004-226120 A

  By the way, the on-vehicle radar device periodically performs its own fault diagnosis in order to ensure the reliability of its operation. Specifically, the radar apparatus executes a scan that does not perform frequency modulation of the radar wave at a frequency of once every 10 to 20 scans. Then, the radar apparatus diagnoses the normality / abnormality of its own operation depending on whether the reception level of the reflected wave from the road surface exceeds a preset threshold value. Then, since the conventional radar apparatus pauses the detection of the target in the scan for performing the fault diagnosis process, the estimation process when the target is detected in the past is performed, and the next scan is performed. When the same target is detected again, the continuity history can be maintained.

  However, in this case, for example, if the speed of the preceding vehicle suddenly changes due to sudden braking, the distance predicted from the current estimated target and the distance of the target actually detected in the next scan are greatly different. The continuity history may be interrupted. Then, the time for outputting the target information is delayed.

  Accordingly, an object of the present invention is to provide a distance that does not deviate from the distance of the target that is actually detected in the next scan, even if the speed of the target changes suddenly during a scan that does not perform frequency modulation of the radar wave. An object of the present invention is to provide a radar apparatus capable of performing prediction and a target detection method thereof.

  In order to achieve the above object, the radar apparatus according to the first aspect of the present invention scans a predetermined area by transmitting and receiving the first radar wave subjected to frequency modulation, and the distance of the target is determined for each scan. A radar apparatus for detecting a speed, the target distance predicting means for predicting the distance of the target in the current scan based on the distance and speed of the target detected in the past scan, and the current scan Counting the number of times the target corresponding to the predicted distance is detected, and when the count value reaches a specified number, continuity determining means for outputting the distance of the detected target; When the target corresponding to the predicted distance is not detected in the current scan, it is estimated that the target corresponding to the predicted distance and the speed detected in the past scan has been detected. First target And a target estimator to perform a constant process. When the target estimation unit detects the velocity of the target by transmitting and receiving the second radar wave not subjected to the frequency modulation in the current scan, the target distance and the current scan And performing a second estimation process for estimating that a target corresponding to the speed detected in step (b) is detected.

  According to a preferred embodiment of the above aspect, the target estimation means is detected when the speed of the target is detected by transmitting and receiving a second radar wave not subjected to the frequency modulation in the current scan. The second target estimation process is performed when the speed is a specified speed.

  According to another preferred embodiment of the above aspect, when the target estimation means detects the speed of the target by transmitting and receiving a second radar wave that is not subjected to the frequency modulation in the current scan, The second target estimation process is performed when a prescribed number of targets having an azimuth angle that matches the azimuth angle of the target detected in the past scan is detected. The azimuth angle that coincides with the azimuth angle of the target detected in the past scan includes an azimuth angle in which an error from the azimuth angle of the target detected in the past scan is included in a predetermined allowable range.

  According to a further preferred embodiment of the above aspect, the target estimation means receives the second radar wave that is not subjected to the frequency modulation in the current scan and detects the speed of the target. The second target estimation process is performed by weighting the detected speed based on the level of the second radar wave.

  According to the above aspect, when the target estimation unit detects the velocity of the target by transmitting and receiving the second radar wave not subjected to the frequency modulation in the current scan, Since it is estimated that the target corresponding to the speed detected in the current scan has been detected, even if the speed of the target suddenly changes after the previous scan, this is used for the estimation process in this scan. Can be reflected. Therefore, based on the estimation result, it is possible to predict a distance that does not deviate from the distance detected in the next scan. Therefore, it is possible to prevent a delay in outputting the target information due to the interruption of the continuity history.

  According to the preferred embodiment, the target estimation means performs the target estimation process when the detected speed is a specified speed, that is, when the speed is not a speed corresponding to a road surface or a stationary object. It can prevent detecting a road surface or a stationary object as a target. If a road surface or a stationary object is erroneously estimated as a target, the history of the continuity of the target detected in the next scan may be interrupted. However, according to this embodiment, such a situation can be avoided.

  According to another preferred embodiment, the target estimating means detects the target when a specified number of targets having an azimuth angle that matches the azimuth angle of the target detected in a past scan is detected. A second target estimation process is performed. Here, if the specified number is set to singular, the target estimation process can be stopped when multiple targets with different velocities are detected even if the azimuth is approximate. By estimating a plurality of different targets corresponding to the target, it is possible to prevent a situation in which continuity is determined between different targets and information on the wrong target is output.

  According to the further preferred embodiment, the target estimating means performs the target estimating process by weighting the detected speed based on the level of the received second radar wave. That is, when the level of the received wave is low, it is easily affected by interference by various reflected waves from various targets and various noises, and the reliability of the speed of the detected target becomes low. Therefore, in such a case, it is possible to avoid a decrease in the reliability of the estimation result by reducing the rate of reflecting the speed detected this time in the target estimation process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

  FIG. 1 is a diagram for explaining a usage situation when the radar apparatus according to the present embodiment is mounted on a vehicle. The radar device 10 according to the present embodiment is mounted in a front front grill of the vehicle 1 and transmits and receives radar waves through a radome provided on the front side of the vehicle 1 such as a bumper, a front grill, and a license plate plate, A region defined by an angle range α centered on the front F of the vehicle 1 (for example, ± 8 degrees centered on the front F) is scanned.

  In the present embodiment, the radar apparatus 10 is an example of a mechanical scan type radar apparatus that scans the angle range α by swinging an antenna that transmits and receives radar waves. It may be an electronic scan type radar apparatus that performs scanning using the phase difference between the two.

  FIG. 2 is a diagram for explaining the frequency modulation mode of the radar wave transmitted by the radar apparatus 10. In the present embodiment, the period during which the radar apparatus 10 scans the angle range α in front of the vehicle 1 once is one scan. FIG. 2 shows a change in frequency with respect to time of the radar wave.

  The CW mode scan is executed to detect the level of the reflected wave from the road surface for the purpose of failure detection. Therefore, in order to ensure an opportunity for failure detection, the radar apparatus 10 periodically switches and executes these two modes of scanning. Specifically, the CW mode scan is executed at a frequency of once every time the FM-CW mode scan is executed, for example, 10 to 20 times.

FIG. 3 is a diagram for explaining the principle of detecting the target distance and the like in each scan mode.
In the FM-CW mode scan, the azimuth, distance, and speed of a target that reflects a radar wave are detected.

  First, as shown by the solid line W1 in FIG. 3A, the frequency of the radar wave gradually increases during the rising period UP and gradually decreases during the falling period DN in accordance with a triangular wave having a frequency fm and an amplitude ΔF. When this radar wave is reflected by the target, as indicated by a dotted line W2, a time delay ΔT corresponding to the distance of the target and a Doppler frequency ΔD corresponding to the speed (relative speed) of the target are obtained. A corresponding frequency shift is received by the radar device 10.

  Here, the azimuth angle of the target is detected as follows. When the radar apparatus 10 scans the angular range α, the radar wave is transmitted / received so that a pair of rising period UP and falling period DN correspond to each unit azimuth angle (for example, 1 degree). Then, at the adjacent azimuths where the reflected waves are obtained, the reception level of the reflected waves corresponding to the rising period UP and the reception level of the reflected waves corresponding to the falling period DN, for example, average azimuth angles that form peaks, respectively. The azimuth angle is detected as the azimuth angle of the target.

The distance and speed of the target are detected as follows. The frequency of the beat signal obtained by mixing the transmission / reception wave as described above changes with time as shown by the solid line B1 in FIG. That is, the frequency is fu during the rising period UP and the frequency fd during the falling period DN. From these frequencies, the distance R and the speed Vf of the target are calculated by the following equations (where C is the speed of light and f0 is the center frequency of the transmitted radar wave).
R = C · (fu + fd) / (8 · ΔF · fm)
Vf = C · (fd−fu) / (4.f0)
In the CW mode scan, the azimuth and velocity of the target are detected.

  In the CW mode scan, the angle range α is scanned at a constant frequency, so that the azimuth angle of the target is detected from the arrival direction of the reflected wave. The speed of the target is detected as follows.

  The frequency of the radar wave is fixed at a constant frequency fc as shown by a solid line C1 in FIG. When this radar wave is reflected by the target, the frequency of the received wave is shifted by the Doppler frequency fp corresponding to the speed of the target, as indicated by a dotted line C2.

Then, the frequency of the beat signal obtained by mixing the transmission / reception wave at this time becomes the Doppler frequency fp as indicated by the solid line BS2 in FIG. From the Doppler frequency fp, the target velocity Vc is calculated by the following equation.
Vc = C · fp / (2 · fc)
Further, the radar apparatus 10 performs failure diagnosis using the above principle when scanning in the CW mode. The method is as follows.

  In an in-vehicle radar device, problems such as a decrease in antenna sensitivity and poor connection of circuit components appear as a decrease in the reception level of reflected waves. Therefore, such a problem can be detected by periodically monitoring the level change of the reflected wave obtained from the same target. In this regard, in the on-vehicle radar device, attention is paid to the fact that the level of the reflected wave from the road surface is the most stable, and the level is monitored.

  In the scan in the CW mode, as described above, the beat signal based on the reflected wave from the target is processed to detect the Doppler frequency component corresponding to the speed of the target. Here, since the road surface is stationary, the speed is obtained from the speed of the host vehicle. Therefore, the level of the component corresponding to the Doppler frequency, that is, the reception level of the reflected wave from the road surface is detected from the beat signal by obtaining the Doppler frequency corresponding to the speed of the host vehicle as a parameter by map calculation or the like. The The radar apparatus 10 diagnoses a failure when the level falls below a threshold set in advance based on experimental results or the like.

  Furthermore, in the present embodiment, the radar apparatus 10 further detects the speed of a target such as a preceding vehicle when in the CW mode.

  Here, FIG. 4 shows the types of target information detected by the radar apparatus 10 in each mode scan. That is, the radar apparatus 10 detects the target Ob_n at the azimuth angle A_n by the FM-CW mode scan fS_n (n = 1, 2, 3,...). The radar apparatus 10 detects the distance R_n and the velocity V_n of the target Ob_n by the method described with reference to FIGS. Further, the radar apparatus 10 detects the target Ob_n at the azimuth angle A_n by the scan cS_n in the CW mode. The radar apparatus 10 detects the velocity V_n of the target Ob_n by the method described with reference to FIGS.

  FIG. 5 shows the configuration of the radar apparatus according to this embodiment. The operation of the radar apparatus 10 is integrally controlled by the control unit 30. The control unit 30 includes, for example, a special purpose integrated circuit, and the transmission control unit 32 and the target detection unit 34 are realized by a processor that operates according to a control program or a processing program stored in a memory inside the control unit 30. .

  The transmission control unit 32 instructs the triangular wave generation unit 12 to switch between the FM-CW mode scan and the CW mode scan. Then, in response to the instruction, the triangular wave generator 12 generates a triangular wave voltage signal in the FM-CW mode and a constant bias voltage signal in the CW mode, and inputs the voltage signal to the voltage control oscillator 14. . Then, the voltage control transmitter 14 generates a radar wave that is frequency-modulated according to the input signal. Then, the generated radar wave is transmitted from the antenna 20 oscillated by the antenna driving unit 18 via the circulator 16. A part of the radar wave is also input to the mixer 22.

  At this time, the transmission control unit 32 controls the antenna driving unit 18 so as to swing the antenna 20 by reciprocating the angle range α around the front F of the vehicle 1. At this time, the operating speed of the antenna 20 is controlled with respect to the frequency modulation period of the radar wave so that a pair of rising period UP and falling period DN correspond to each unit azimuth angle. The radar wave reflected by the target is received by the antenna 20.

  The received radar wave is input to the mixer 22 by the circulator 16. The mixer 22 mixes the transmission / reception wave for each scan, and generates a beat signal having a frequency corresponding to the frequency difference between the two. Then, the generated beat signal has high frequency noise removed by the band pass filter 24 and is input to the AD conversion unit 26 of the control unit 30.

  The AD converted beat signal is input to the target detection unit 34. In addition, the speed of the host vehicle is input from the vehicle speed sensor to the target detection unit 34. And the target detection part 34 performs a series of processing procedures shown in FIG. And the target detection part 34 outputs this to an audio | voice / display output device, when a failure and operation | movement abnormality are detected. In addition, the target detection unit 34 outputs information such as the azimuth angle, distance, and speed of the detected target to the vehicle ECU.

[First embodiment]
FIG. 6 is a flowchart for explaining the procedure of the main operation by the radar apparatus 10 in the first example of the present embodiment. The procedure shown in FIG. 6 is executed by the target detection unit 34 for each scan. First, when the target detection unit 34 completes the digital data acquisition of the AD-converted beat signal (YES in S2), the target detection unit 34 determines the frequency modulation mode in the current scan (S4).

When the frequency modulation mode is the FM-CW mode, steps S6 to S10 are executed. The target detection unit 34 first performs an FFT (Fast Fourier Transform) process on the beat signal for each unit azimuth, and the beat signal peaks in the azimuth direction during the frequency rise period UP of the transmission wave and the fall period DN. The beat signal peak in the azimuth angle direction is extracted (S6).
And the target detection part 34 extracts the peaks in which the azimuth angle at which the peak is formed is approximated between the peak in the ascending period UP and the peak in the descending period DN, and associates them, that is, performs pairing. Do. Thus, the frequency in the rising period UP of the beat signal having a high probability obtained from the same target is associated with the frequency in the falling period DN. By doing so, one target is detected at, for example, an average azimuth angle of each azimuth in which each peak is formed (S8).

  Then, the target detection unit 34 calculates the distance and speed of the target from the frequencies of the ascending period UP and the descending period DN associated with each other (S10). In this way, the azimuth, distance, and speed of the target are detected from the beat signal.

  Next, the target detection unit 34 performs continuity determination processing (S12) of the detected target according to a procedure described later. And the target detection part 34 is preset among the information including the azimuth angle, speed, and distance of the target when the number of times determined to have continuity reaches a specified number (for example, three times). Information that meets the output conditions is selected (S16), and the information is output to the vehicle ECU (S18). Here, for example, the output condition is set for the distance, the speed, and the like on the basis that the inter-vehicle distance is equal to or less than a certain distance and is subject to follow-up traveling control or collision response control.

  On the other hand, if the result of determination in step S4 is that the frequency modulation mode is CW mode, steps S20 to S24 are executed. Here, the scan in the CW mode is executed for the purpose of detecting the failure of the radar apparatus 10 as described above. Therefore, the target detection unit 34 performs FFT processing on the beat signal, and detects a Doppler frequency component included in the received wave from each target. Then, the target detection unit 34 obtains the Doppler frequency corresponding to the speed of the own vehicle acquired from the vehicle speed sensor by map calculation or the like, and extracts the level of the reflected wave component from the road surface corresponding to the magnitude of the Doppler frequency. To do. Then, failure diagnosis is performed by comparing the level with a threshold (S20). It should be noted that detection results such as failure and abnormal operation are notified to the user by voice or display output.

  Next, the target detection unit 34 detects the peak of the beat signal in the azimuth direction (S22). This procedure will be described in detail with reference to FIG. And the target detection part 34 detects the target in the azimuth | direction angle in which each peak is formed, and detects a speed from the Doppler frequency of the peak component (S24). Thus, in the CW mode, the azimuth and speed of the target are detected.

  FIG. 7 is a flowchart for explaining the detailed operation procedure of the peak detection process when the radar wave frequency modulation mode is the CW mode. The procedure shown in FIG. 7 corresponds to the procedure S22 of FIG.

  First, the target detection unit 34 obtains the frequency components of the beat signal for each unit azimuth by FFT processing (S32), and sorts the components of the same frequency in the order of level intensity (S34). And the target detection part 34 extracts the frequency component sorted in order of the intensity | strength in each azimuth direction in order with a big level.

  Here, each peak is formed at an azimuth angle at which the reflected wave from the target is at the maximum level. Therefore, the target detection unit 34 determines whether the extracted frequency component corresponds to a level that can be adopted as a peak. If not applicable (NO in S38), this is excluded, and if applicable (YES in S38), the azimuth angle and the level of the frequency component are stored in the memory in the control unit 30 (S40). This process is repeated until the number of extracted peaks reaches a specified number (S36, S42). The azimuth angle corresponding to the peak extracted in this way is detected as the azimuth angle of the target.

  FIG. 8 is a flowchart for explaining the detailed operation procedure of the continuity determination processing by the target detection unit 34. The procedure of FIG. 8 corresponds to the procedure S12 of FIG.

  The target detection unit 34 performs the processing from steps S52 to S60 to determine whether one target is detected at this time for all the previously detected targets (S50, S62).

  First, the target detection unit 34 determines the frequency modulation mode in the current scan (S52). In the FM-CW mode, the target detection unit 34 uses the detected distance and speed and the elapsed time for one scan for the previously detected target being processed, and the target in the current scan. Predict the distance of the mark. Here, the target detection unit 34 that executes such a procedure corresponds to “target distance prediction means”.

  Then, among the current detection target, the target whose azimuth angle coincides with the previous detection target or within a predetermined error range is extracted, and the difference between the distance of the extracted current detection target and the predicted distance is allowable. If it is within the range, it is determined that the current detection target has continuity (S54). Then, the continuity history of the current detection target is updated, and information such as the azimuth angle, distance, and speed of the current detection target is stored in the memory in the control unit 30.

  However, if there is no target whose azimuth is the same as the previously detected target or within the specified error range, and there is no target whose distance from the predicted distance is within the allowable range, or the previous detection If there is no target whose azimuth is the same as the target or within the predetermined error range, it is determined that the target detected this time has no continuity. In that case, without updating the continuity history from the previous detection target, information such as the azimuth angle, distance, and speed of the current detection target is newly stored in the memory in the control unit 30 as the current detection target. Store.

  Here, the target detection unit 34 that executes such a procedure corresponds to “continuity determination means”.

  Then, the target detection unit 34, when the previously detected target being processed is also detected this time, that is, when it is determined that there is continuity among the currently detected targets (YES in S56). Ends the process, and performs the same process for the next previously detected target.

  However, if the previously detected target is not detected this time, that is, if there is no current detected target determined to have continuity and the previously detected target is lost (NO in S56), the previous detection is performed. Assuming that a target having the distance predicted from the target and the azimuth angle and speed of the previously detected target has been detected, the target is estimated as the current detection target. Here, the target detection unit 34 that executes such a procedure corresponds to “target estimation means”. And the target detection part 34 stores the information of this estimation target estimated in this way in a memory (S66), and updates the history of continuity from the previous detection target for this estimation target. .

If the determination result is CW mode in step S52, the continuity of the target is determined as to whether the previously detected target is detected this time according to the following procedure (S64).
FIG. 9 is a flowchart for explaining in detail the continuity determination procedure of the target detected in the CW mode. The procedure in FIG. 9 corresponds to the procedure S64 in FIG.

  First, the target detection unit 34 ends the process when a plurality of current detection targets have the same speed (YES in S70). In the CW mode, when a reflected wave from the same target forms a plurality of peaks, and a plurality of azimuth angles correspond to the same velocity, the target is specified based on the azimuth angle at which the peak is formed. It becomes difficult. Therefore, by interrupting the process in such a case, a single target is prevented from being erroneously detected as a plurality of targets.

  In step S70, it may be added to a condition for determining whether or not the detected speed corresponds to the specified speed. Here, the prescribed speed is set to a speed that is not confused with the road surface based on the speed of the road surface or the stationary object on the road side corresponding to the speed of the host vehicle. By doing so, it can prevent detecting a road surface and a stationary object accidentally.

  Then, when the speed is different for each target detected this time as the “target distance predicting means” (NO in S70), the target detection unit 34 determines the current target distance from the distance, speed, and elapsed time of the target detected last time. The distance of the target is predicted (S72).

  Next, the target detection unit 34 detects, as “target estimation means”, the current detection in which the difference in peak level of reflected waves, the difference in azimuth, and the difference in velocity are minimized for all the previously detected targets. A target is extracted (S74, S76, S78).

  Here, in step S76, it is possible not to provide a speed difference condition when extracting the detection target this time. By doing so, continuity can be determined based on the azimuth angle and the reception level of the reflected wave, and the suddenly changed speed can be reflected in the current estimated target even if the speed changes suddenly.

  Then, the target having the speed and azimuth of the target and the distance predicted from the previous detection target is estimated as the current detection target, and stored in the memory as the current estimation target (S80). At this time, the target detection unit 34 determines, as “continuity determination means”, that the extracted current detection target, that is, the current estimation target, has continuity from the previous detection target. Update the history of.

  Here, the procedure of FIGS. 6 to 9 will be described in detail with reference to FIGS. Each of FIGS. 10 to 12 shows information such as the distance and speed of the target detected in each scan with respect to time, the distance in the next scan predicted from these, and the continuity determination result in each scan. The relationship is shown schematically.

  FIG. 10 shows a case where a target is detected without being lost in a plurality of consecutive FM-CW mode scans. The radar apparatus 10 detects the azimuth angle A_1, the distance R_1, and the velocity V_1 of the new target Ob_1 in the scan fS_1 (steps S4 to S10 in FIG. 6).

  Next, the continuity of the current detection target Ob_1 is determined (step S12 in FIG. 6, steps S50 to S62 in FIG. 8). At this time, since the same target is not detected in the previous scan, the current target Ob_1 does not have continuity. Therefore, the target detection unit 34 processes the current detection target Ob_1 having the azimuth A_1, the distance R_1, and the velocity V_1 as a new detection target, and the value of the counter variable storing the continuity history is “1”. (Procedures S50, S52, S54, and S62 in FIG. 8).

  In the next scan fS_2, when the target detection unit 34 detects the target Ob_2 at the azimuth angle A_2, the target R_2 and the speed V_2 are detected (procedures S4 to S10 in FIG. 6). Then, the continuity of the target detected this time is determined (procedure S12 in FIG. 6 and procedures S50 to S62 in FIG. 8).

  At this time, since the scan fS_2 is in the FM-CW mode (S52 in FIG. 8), the target detection unit 34 uses the distance R_1 of the previous detection target Ob_1, the velocity V_1, and the elapsed time for one scan, The target distance pR_2 in the scan fS_2 is predicted. If the difference between the azimuth angle A_1 of the previous detection target Ob_1 and the azimuth angle A_2 of the current detection target Ob_2 is within the allowable range, the detected distance R_2 is compared with the predicted distance pR_2. If the error is within a predetermined allowable range, it is determined that the current detection target Ob_2 in the scan fS_2 has continuity. Then, the value of the counter variable storing the continuity history is incremented by “1” to “2”, and the azimuth A_2, the distance R_2, and the velocity V_2 are stored in the memory (S54 in FIG. 8).

  Further, in the next scan fS_3, when the target detection unit 34 detects the target Ob_3 at the azimuth angle A_3, the target R_3 and the speed V_3 are detected (steps S4 to S10 in FIG. 6). Then, the continuity of the current detection target Ob_3 is determined (step S12 in FIG. 6, steps S50 to S62 in FIG. 8).

  At this time, since the scan fS_3 is in the FM-CW mode (S52 in FIG. 8), the target detection unit 34 calculates the distance pR_2 from the distance R_2 and speed V_2 of the previous detection target Ob_2 and the elapsed time for one scan. Predict. If the difference between the azimuth angle A_2 of the previous detection target Ob_2 and the azimuth angle A_3 of the current detection target Ob_3 is within an allowable range, the detected distance R_3 is compared with the predicted distance pR_3. If the error is within a predetermined allowable range, it is determined that the current detection target Ob_3 in the scan fS_3 has continuity. Then, the value of the counter variable storing the continuity history is incremented by “1” to “3”, and the azimuth A_3, the distance R_3, and the speed V_3 are stored in the memory (S54 in FIG. 8).

  Since the value of the counter variable has reached “3”, the target detection unit 34 outputs the azimuth angle A_3, the distance R_3, and the speed V_3 of the current detection target Ob_3 to the vehicle ECU (step S16 in FIG. 6). , S18).

  FIG. 11 shows a case where a target is lost in one scan among a plurality of consecutive FM-CW mode scans. The operation in the scan fS_1 is the same as that in FIG. Note that the following procedure is also applied when the target detected in the scan fS_1 is not a new target but a target for which continuity has already been determined.

  In the next scan fS_2, since there is no current detection target whose difference from the azimuth angle A_1 of the previous detection target Ob_1 is within the allowable range (NO in S56 of FIG. 8), the target detection unit 34 detects the previous detection target. The target object Ob_2 corresponding to the target object distance pR_n + 1, which is obtained from the distance R_n and the speed V_n of the target Ob_1, and the elapsed time for one scan, and the azimuth angle A_1 and speed V_1 of the previously detected target Ob_1 are as follows. It is estimated that it has been detected (S66 in FIG. 8), and this is stored as an estimated target this time.

  Then, in the next scan fS_3, the target detection unit 34 predicts the distance pR_3 from the distance pR_2 and speed V_1 of Ob_2 estimated as the previous detection target and the elapsed time for one scan. Then, if the difference between the azimuth angle A_1 of Ob_2 estimated as the previous detection target and the azimuth angle A_3 of the current detection target Ob_3 is within the allowable range, the detected distance R_3 is compared with the predicted distance pR_3. To do. If the error is within a predetermined allowable range, it is determined that the current detection target Ob_3 in the scan fS_3 has continuity. Then, the value of the counter variable storing the continuity history is incremented by “1” to “3”, and the azimuth A_3, the distance R_3, and the speed V_3 are stored in the memory (S54 in FIG. 8).

  Then, since the value of the counter variable has reached “3”, the target detection unit 34 outputs the azimuth angle A_3, distance R_3, and speed V_3 of the current detection target Ob_3 to the vehicle ECU (step S16 in FIG. 6). , S18).

  In this way, when the target is lost, the distance in the next scan is predicted using the current detection target estimated from the previous detection target. In the next scan, the continuity is determined using the predicted distance. By doing so, the continuity is maintained in the next scan without being interrupted by the lost target.

  Next, FIG. 12 illustrates a case where a scan cS_n in the CW mode is executed between a plurality of consecutive FM-CW mode scans fS_n. The operation in the scan fS_1 is the same as that in FIG. Note that the following procedure is also applied when the target detected in the scan fS_1 is not a new target but a target for which continuity has already been determined.

  The radar apparatus 10 first detects the target Ob_2 at the azimuth angle A_2 in the scan cS_2 in the CW mode. The radar apparatus 10 detects the velocity V_2 of the current target Ob_2 by the method described in FIGS. 3C and 3D (steps S4, S20, S22, and S24 in FIG. 6). Then, the continuity of the current detection target Ob_2 is determined (step S12 in FIG. 6, steps S50, S52, and S64 in FIG. 8).

  Here, since the distance is not detected in the scan cS_2, the radar apparatus 10 compares the azimuth angle A_1 of the previous detection target Ob_1 with the azimuth angle A_2 of the current detection target, and the error is within a predetermined range. For example, the target Ob_2 is determined to have continuity, and the value of the counter variable storing the continuity history is incremented by "1" to "2" (steps S70 to S78 in FIG. 9). The target Ob_2 is estimated as the current detection target of the azimuth A_2, the distance pR_2, and the speed V_2 (S80 in FIG. 9).

  In the next scan fS_3, the target detection unit 34 predicts the distance pR_3 from the distance pR_2 and speed V_2 of Ob_2 estimated as the previous detection target and the elapsed time for one scan. If the difference between the azimuth angle A_2 of Ob_2 estimated as the previous detection target and the azimuth angle A_3 of the current detection target Ob_3 is within an allowable range, the detected distance R_3 is compared with the predicted distance pR_3. To do. If the error is within a predetermined allowable range, it is determined that the current detection target Ob_3 in the scan fS_3 has continuity. Then, the value of the counter variable storing the continuity history is incremented by “1” to “3”, and the azimuth A_3, the distance R_3, and the speed V_3 are stored in the memory (S54 in FIG. 8).

  Since the value of the counter variable has reached “3”, the target detection unit 34 outputs the azimuth angle A_3, the distance R_3, and the speed V_3 of the current detection target Ob_3 to the vehicle ECU (step S16 in FIG. 6). , S18).

  As described above, in the present embodiment, when the CW mode scan is executed, not only the failure detection but also the azimuth angle and speed of the target are detected. Then, continuity is determined based on the azimuth angle of the target, and the currently detected target is estimated based on the detected speed (current estimated speed). Then, the distance in the next FM-CW mode scan is predicted from the estimated target this time.

  By doing so, even if the speed of the target changes suddenly during the CW mode, this can be reflected in the predicted distance in real time. Therefore, the next FM-CW is accurately estimated compared to the case in which the current estimated target is estimated only from the previous detection target detected in the previous FM-CW mode, and the distance in the next FM-CW mode is predicted based on this target. The distance in the mode can be predicted. Therefore, the target detected in the next FM-CW mode can maintain continuity with high accuracy.

  In a preferred modification of the first embodiment, in the case of determining continuity in the CW mode, in order to ensure the reliability of the detected information, the detection target is detected according to the reception level of the reflected wave. Weight the distance. FIG. 13 is a diagram for explaining such a procedure.

  The flowchart in FIG. 13A is added between S56 and S60 in FIG. 8, and when the result of step S56 is “YES”, that is, the current detection target having continuity with the previous detection target is detected. It is executed when

  The target detection unit 34 obtains the weight a (S562) for the reception level of the reflected wave in the current scan from the correspondence shown in FIG. Then, the weight b corresponding to the difference between the reception level of the reflected wave in the previous scan and the reception level of the reflected wave in the current scan is set to “1” (S566). Then, the reception level Wm of the current reflected wave is multiplied by a and b, and the result W is used as a weight to calculate the velocity V_n of the currently detected target by the following equation (S568).

Vn = (1−W) V_n−1 + W · V_n (where V_n−1 is the speed of the previously detected target)
Then, the target detection unit 34 employs the speed V_n as the speed of the target detected this time (S569).

  Thus, the higher the reception level of the current reflected wave, the higher the reliability of the speed of the target detected this time, and the higher the level of the reflected wave that can be detected this time. Therefore, the speed of the target detected this time with high reliability can be output to the vehicle ECU, or can be used for the prediction of the next distance. This procedure is executed when the scan mode is the FM-CW mode and the detected target has continuity this time and when it is in the CW mode. Therefore, by reflecting the reception level of the reflected wave in the accuracy of the detection distance reflected in the estimated target this time in the CW mode scan, a more reliable detection distance can be used for the estimation. Can be improved.

  By the way, in the FM-CW mode scan, a plurality of reflection peaks may be obtained depending on the shape of the reflection surface even for the same target. In such a case, it is difficult to uniquely specify the azimuth angle of the target. Therefore, in the next CW mode scan, the reliability of the azimuth angle is lowered when the continuity between the previous detection target and the current detection target is determined based on the azimuth angle.

  In that regard, in the second example of the present embodiment, when a plurality of peaks are formed from the same target, the speed corresponding to each peak is the same, and the previous detection in the FM-CW mode is performed. As a standard for determining the continuity between the target and the current detection target in the CW mode, velocity is used instead of the azimuth. When the speed difference is within the allowable range, it is determined that the current detection target has continuity with the previous detection target. The procedure in such a case is shown in FIGS.

[Second embodiment]
FIG. 14 is a flowchart for explaining the procedure of the main operation by the radar apparatus 10 in the second example of the present embodiment. The flowchart of FIG. 14 is obtained by adding a process (step S14) for grouping the currently detected targets at the same speed to the procedure of the first main operation shown in the flowchart of FIG. The added part is surrounded by a dotted line. The detailed procedure of step S14 is shown in the flowchart of FIG.

  First, the target detection unit 34 sorts the current detection target in the order of the peak level corresponding to the azimuth (S142). And the target detection part 34 performs the next procedure (S146) about all the present detection targets in the sorted order (S144, S156).

  The target detection unit 34 compares the current detection target being processed with all other current detection targets, and groups the current detection targets having the same speed (S146). This grouping process is executed until there is no current detection target for which grouping determination has not been performed (S148, S150, S152, S154).

  In this way, among the plurality of current detection targets detected from the same target, the current detection targets having the same speed are grouped. In the following, the plurality of current detection targets grouped will be referred to as a current detection group. In the next scan, this is called the previous detection group.

  FIG. 16 is a flowchart in which steps S73, S82, S84, S86, S88, and S90 are added to the flowchart of FIG. 9 showing the continuity determination procedure in the CW mode scan. The added part is surrounded by a dotted line.

  The target detection unit 34 predicts the distance of the current target from the distance, speed, and elapsed time of the target previously detected in step S72, and then executes the same speed grouping process described above (in S73). YES), for all the previously detected targets, the current detected target that minimizes the difference in peak level of reflected waves and the difference in velocity is extracted (S82, S84, S86).

  Then, a target having the speed and azimuth of the extracted target and the distance predicted from the previous detection target is estimated as the current detection target, and stored in the memory as the current estimation target (S88). Furthermore, the target detection unit 34 associates the currently estimated target with the previous detection group, and a plurality of peaks are detected from the same target even in the next FM-CW mode scan, and the target of the same speed is grouped. In this case, the continuity between the newly grouped detection target group and the current estimation target is maintained (S90).

  FIG. 17A is obtained by adding steps S564 and S570 to the procedure of FIG. 13 in which weighting is performed according to the reception level of the reflected wave in the CW mode. The added part is surrounded by a dotted line. When the previous detection group having the same speed is determined (YES in S564), the target detection unit 34 responds to the difference between the reception level of the reflected wave in the previous scan and the reception level of the reflected wave in the current scan. The weight b to be obtained is obtained from the correspondence relationship in FIG. 17B (S570).

  At this time, as the reception level of the previous reflected wave, the representative value of the reception level of the previous detection group in which the current detection target has continuity is used. Here, if the difference between the reception level of the previous detection group and the reception level of the current detection target is large, it means that the reliability of the distance of the current detection target is low. Therefore, in such a case, it is possible to increase the estimation accuracy of the current estimated target by reducing the ratio of reflecting the distance of the currently detected target in the current estimated target.

  In the above description, the distance between the detected targets indicates the linear distance between the radar apparatus 10 and the target. However, a coordinate plane with the forward direction of the host vehicle and a direction perpendicular thereto as coordinate axes may be assumed, and the forward coordinate of the preceding vehicle on the coordinate plane may be used as the distance.

  In recent years, in addition to follow-up control for a preceding vehicle, anti-collision control that activates a safety control device when a danger of rear-end collision is detected has been demanded. Such anti-collision control requires that a failure diagnosis of the radar device is periodically performed and that the distance be reliably detected in a situation where the vehicle approaches the preceding vehicle. In that respect, according to the above-described embodiment, the target in the CW mode scan can be accurately estimated while performing the failure diagnosis periodically in the CW mode scan. Sex can be maintained. Therefore, the speed of the preceding vehicle can be detected quickly.

  Furthermore, in the above description, the on-vehicle radar device that detects the preceding vehicle has been described as an example. However, the present embodiment can also be applied to a radar device for monitoring the rear or side of the vehicle, and the same effects as those described above can be achieved. Further, the radar apparatus of the present embodiment has the same effects even when mounted on a moving body other than a vehicle.

  As described above, according to the present embodiment, even if the speed of the target changes suddenly during the CW mode can, this can be reflected in the estimation process. Therefore, based on the estimation result, it is possible to predict a distance that does not deviate from the distance detected in the next scan. Therefore, it is possible to prevent a delay in outputting the target information due to the interruption of the continuity history.

It is a figure explaining the use condition when the radar apparatus in this embodiment is mounted in the vehicle. It is a figure which shows the frequency change with respect to time of the radar wave which the radar apparatus 10 transmits. It is a figure explaining the principle which detects the distance etc. of the target in each scan mode. It is a figure explaining the information which the radar apparatus detects about the target detected by the scan of each mode. It is a figure which shows the structure of the radar apparatus in this embodiment. It is a flowchart figure explaining the main operation | movement procedure of a radar apparatus in the 1st Example of this embodiment. It is a flowchart explaining the detailed operation | movement procedure of a peak detection process when the frequency modulation mode of a radar wave is CW mode. It is a flowchart figure explaining the detailed operation | movement procedure of the continuity determination process by the target detection part. It is a flowchart figure explaining the continuity determination procedure of the target detected in CW mode in detail. It is a figure which shows the case where a target is detected without being lost by the scan of a continuous FM-CW mode. It is a figure which shows the case where a target is lost in the scan of a continuous FM-CW mode. It is a figure which shows the case where the scan of CW mode is performed between the scans of FM-CW mode. It is a flowchart figure explaining the procedure which weights the distance of a detection target according to the reception level of a reflected wave. It is a flowchart figure explaining the main operation | movement procedure of a radar apparatus in the 2nd Example of this embodiment. It is a flowchart figure which shows in detail the process which groups this detection target of the same speed. It is a flowchart figure explaining the continuity determination procedure of the target detected in CW mode in a 2nd Example in detail. It is a flowchart figure explaining the procedure which weights the distance of a detection target according to the reception level of a reflected wave in a 2nd Example.

Explanation of symbols

10: Radar device, 30: Control unit, 34: Target detection unit

Claims (5)

In a radar device that scans a predetermined area by transmitting and receiving a first radar wave subjected to frequency modulation, and detects the distance and speed of a target for each scan,
A target distance prediction means for predicting the distance of the target in the current scan based on the distance and speed of the target detected in the past scan;
Counts the number of times the target corresponding to the predicted distance is detected in the current scan, and outputs the distance of the detected target when the count value reaches a specified number A determination means;
When the target corresponding to the predicted distance is not detected in the current scan, it is estimated that the target corresponding to the predicted distance and the speed detected in the past scan has been detected. A target estimation means for performing a first target estimation process,
The target estimating means detects the predicted distance and the current scan when the speed of the target is detected by transmitting and receiving the second radar wave not subjected to the frequency modulation in the current scan. A radar apparatus that performs a second estimation process that estimates that a target corresponding to the detected speed has been detected. In claim 1,
The target estimation means, when detecting the speed of the target by transmitting and receiving a second radar wave not subjected to the frequency modulation in the current scan, when the detected speed is a specified speed, A radar apparatus that performs the second target estimation process. In claim 1,
Further detecting the azimuth of the target for each scan,
When the target estimation means detects the velocity of the target by transmitting and receiving the second radar wave not subjected to the frequency modulation in the current scan, the target azimuth angle detected in the past scan A radar apparatus that performs the second target estimation process when a specified number of targets having an azimuth angle that coincides with the target angle is detected. In claim 1,
If the target estimation means detects the velocity of the target by transmitting and receiving the second radar wave that is not subjected to the frequency modulation in the current scan, the target estimation means sets the level of the received second radar wave. A radar apparatus, wherein the second target estimation process is performed by weighting the detected speed based on the second target estimation process. In a target detection method of a radar apparatus that scans a predetermined region by transmitting and receiving a first radar wave subjected to frequency modulation, and detects a distance or speed of the target for each scan,
A target distance prediction step for predicting the distance of the target in the current scan based on the distance and speed of the target detected in the past scan;
When the target corresponding to the predicted distance is not detected in the current scan, it is estimated that the target corresponding to the predicted distance and the speed detected in the past scan has been detected. A target estimation step for performing a first target estimation process;
Counts the number of times the target corresponding to the predicted distance is detected in the current scan, and outputs the distance of the detected target when the count value reaches a specified number A determination step,
In the target estimation step, when the speed of the target is detected by transmitting and receiving the second radar wave not subjected to the frequency modulation in the current scan, the target distance is detected by the current scan. And performing a second estimation process for estimating that a target corresponding to the speed is detected.

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