JP3761888B2 - In-vehicle radar system - Google Patents

Description

  The present invention relates to an on-vehicle radar device that is mounted on a vehicle and is used to search for obstacles such as other vehicles traveling ahead in the vicinity of the vehicle, for example, and to ensure safety of traveling.

  Conventionally, an in-vehicle radar device that searches for obstacles such as the traveling direction of a vehicle has been developed. As an on-vehicle radar device, the beat signal is extracted from the beat component of the frequency generated by the exploration wave, which is a continuous transmission wave that is frequency-modulated with a triangular wave as the modulation signal, and the reflected wave from the target, and the target is based on the frequency of the beat signal. The FM-CW method is used to obtain the relative speed and relative distance between the two. Prior arts related to FM-CW radar are disclosed in, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4. In particular, in Patent Document 2, it is possible to change the irradiation direction of a beam-shaped radio wave transmitted from an in-vehicle radar device, and for example, to search for a target such as a vehicle traveling diagonally forward during a curved run or the like. The structure to perform is disclosed.

  FIG. 16 shows a schematic configuration of a conventional FM-CW in-vehicle radar device 1. The in-vehicle radar device 1 searches the target 2 and transmits a radio wave for searching from the antenna 3 in order to calculate the relative speed between the distance to the target 2 and the target 2. The antenna 3 receives the reflected radio wave reflected by the target 2. Since the antenna 3 is formed so that a high gain range has a sharp beam shape, the scanning mechanism 4 performs scanning to change the beam direction, and the target from the beam direction when the reflected signal from the target 2 is received. Two directions can also be detected. If the distance and direction to the target 2 are known, the position of the target 2 can be relatively obtained with reference to the own vehicle.

  In the FM-CW system search, a search signal that is frequency-modulated with a triangular wave is applied from the transmission circuit 5 to the antenna 3 for transmission, and the reflected signal received by the antenna 3 is amplified and frequency-converted by the reception circuit 6 to be analog. / Digital conversion (hereinafter abbreviated as “A / D”) circuit 7 converts it into a digital signal, and Fast Fourier Transform (hereinafter abbreviated as “FFT”) circuit 8 converts it into a frequency component. The target detection circuit 9 calculates the distance R to the target 2 and the relative speed V based on the frequency component from the FFT circuit 8.

  FIG. 17 shows the principle by which the target detection circuit 9 shown in FIG. 16 searches for the target 2 and calculates the distance R and the relative velocity V by the FM-CW method. The antenna 3 in FIG. 16 transmits a search signal 10 of a continuous wave (CW) that is FM-modulated so that the frequency continuously changes on the triangular wave at a constant change rate. Since the search signal 10 is reflected by the target 2 and received by the antenna 3, the reflected signal 11 is delayed by a time corresponding to the distance R as shown in FIG. A difference in frequency occurs with respect to the search signal 10 whose frequency is changing. In addition, since a relative velocity V is generated between the target 2 and the target signal 2, a Doppler shift effect is also generated in the reflected signal 11, which causes the frequency to differ from the search signal 10.

  In the FM-CW system, an upbeat signal 12 that is a beat signal in a frequency rising section where the frequency shift amount of frequency modulation increases, and a downbeat signal 13 that is a beat signal in a falling section where the frequency shift amount decreases. As shown in FIG. 17B, the change in frequency due to the Doppler shift effect is reflected differently. For this reason, the frequency fub of the upbeat signal 12 and the frequency fdb of the downbeat signal 13 are expressed by the following equations 1 and 2 using the range frequency fr and the Doppler shift frequency fd, which are the frequencies of the standard beat signal. Can be expressed as:

fub = fr−fd (1)
fdb = fr + fd (2)

  Here, the range frequency fr is proportional to the distance R to the target 2, and if the amplitude of the frequency shift as a triangular wave of the FM-CW search signal 10 is Δf, the modulation frequency fm as a triangular wave, and the speed of light as C, then It is expressed by the following formula 3. Further, the Doppler shift frequency fd is expressed by the following Expression 4 where V is the relative velocity with the target 2 and λ is the wavelength of the search signal 10. The distance R and the relative speed V can also be calculated from the range frequency fr and the Doppler shift frequency fd using the relationship of Expression 3 and Expression 4, respectively.

  As shown in FIG. 16, prior art relating to an on-vehicle radar device that performs scanning in the beam direction of the antenna 3 is disclosed in, for example, Patent Document 5, Patent Document 6, Patent Document 7, or Patent Document 8. Patent Document 9 discloses a configuration in which a range for searching for a target is switched between short range and long range. Patent Document 10 discloses a prior art in which a target such as a flying object is specified using a part of data obtained during radar exploration. Patent Document 11 discloses a prior art for recognizing an obstacle three-dimensionally using an on-vehicle radar.

JP-A 52-111395 JP-A-7-120549 JP-A-9-80148 JP-A-9-145824 JP-A-11-64499 JP-A-11-72651 JP-A-11-84001 JP 11-231053 JP-A-8-82679 JP 10-282220 A JP-A-11-38141

  Among the prior arts that scan the beam direction of the antenna, for example, in Patent Document 7 and Patent Document 8, a reflected signal level obtained by performing a plurality of searches in one scanning period and corresponding to changes in the beam direction. The idea of estimating the direction of the target from the peak of is shown. In order to increase the search accuracy with respect to the direction of the target by using the idea like these prior arts, it is necessary to make the search direction within one scan fine and increase the number of times of search. However, in such a method, calculation processing and the like are added, and hardware for high-speed signal processing is required for high-speed processing. Increasing the speed of signal processing causes problems such as heat generation as well as cost, necessitating an appropriate circuit scale for smooth use, and increases the system configuration.

  Further, although there is a method of narrowing the angle range in which the search is performed in a specific section where the target exists, the hardware configuration becomes complicated and there are not many merit in cost.

  In target recognition, when a reflected signal from a guardrail, a tunnel, a soundproof wall, or the like is also received, it is necessary to assemble complicated logic to extract a true target. For example, in the case of a guardrail, the relative speed calculated after the pairing process combining the frequency of the frequency rising section and the frequency falling section in the FM-CW method is never the same value as the own vehicle speed. It looks like a moving object, not a stationary object. Further, since the distance movement amount does not coincide with the value obtained from the relative speed, it can be determined that the distance is a guardrail based on these values. However, if the frequency of exploration increases, the data update rate becomes faster and the distance travel distance decreases, so that even if the relative speed is obtained from the distance travel distance, the accuracy becomes rough and it becomes difficult to compare the relative speeds.

  Further, in the case of the FM-CW method, the distance and the relative speed are calculated by combining the frequency rising section and the falling section. However, since the Doppler shift effect is large for an object approaching at a high relative speed, the rising speed is increased. The frequency difference between the section and the descending section becomes large. In addition, in the case of an approaching target, the beat signal in the frequency increasing section shifts to a lower frequency side, and processing of a very low beat signal becomes difficult, so the minimum distance at which the target can be detected is far compared to the stationary state. turn into. As a result, it is not possible to track the approaching target, and it is impossible to obtain information about whether the target is approaching as it is or whether the direction is deviating.

In addition, when it is determined that the target detected during the travel is a stationary object, an object that the vehicle can step over and pass through is also included. Conventionally, there is no particular criterion for these objects, and even objects that can be stepped over are subject to warning and deceleration control. For these, it is conceivable to take a method of excluding a stationary object from the control target without determining it as a target, but in the case of an object that cannot be stepped over or passed through, a method of excluding it from the control target the adoption Rukoto can not.

  An object of the present invention is to provide an in-vehicle radar device capable of accurately recognizing the position and property of a target.

The present invention is an on-vehicle radar device that is mounted on a vehicle and searches for targets around the vehicle.
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
The distance to the target is calculated based on the reflected signal from the target received by the antenna and the search signal transmitted from the antenna, and the target is recognized based on the beam direction of the antenna detected by the distance and direction detecting means. The effect of multipath does not show up in the change due to the distance of the reflected signal level in the specific frequency range, and it is stationary based on the change state in which the power suddenly decreases until the distance approaches. The vehicle-mounted radar device includes target recognition means for determining the height of the target.

According to the present invention, when approaching a stationary target, it is determined whether or not the target can be stepped over based on a change in the level of the reflected signal from the target due to the distance. Reflected signals from the target, a signal received directly to the antenna, there is a signal received reflected on the road surface, in a multi-path phase difference arising based on the path difference of the reflected signals are received by the antenna The signal level fluctuates. When the height of the target is low, the level fluctuation of the reflected signal due to multipath is small, and there is a high possibility that it can be stepped over. Since it is determined whether it is possible or not overstep based on a change in the level of the reflected signal by the distance from the target, Ru can be performed reliably determined with a simple configuration.

  Further, in the present invention, the target recognizing means determines that the target can be stepped over when the level of the reflected signal from the stationary target suddenly decreases from the middle of the approach. To do.

  According to the present invention, when the level of the reflected signal from the stationary target decreases rapidly from the middle of the approach, it is determined that the target can be stepped over. A target that can be stepped over has a low height from the road surface, and when the distance to the antenna becomes small, it does not fall within the range of the beam direction of the antenna, so the level of the reflected signal rapidly decreases. Therefore, when the level of the reflected signal decreases rapidly from the middle of the approach, there is a high possibility that the target is at least lower than the position of the antenna, and there is a high possibility that the target can be stepped over.

  In the present invention, the target recognizing means has data indicating a change in a threshold value of a reflected signal level with respect to a distance in advance for a recognized stationary target, and the reflected signal level from the stationary target is within the predetermined distance range. When the value is smaller than the target, it is judged that the target can be stepped over.

  According to the present invention, a map indicating a change in the threshold value of the reflected signal level with respect to the distance is formed in advance for the recognized stationary target, so if the reflected signal level when approaching the stationary target falls below the threshold value, It can be determined that there is a high possibility that the stationary target is low in height and can be stepped over.

Furthermore, the present invention is an in-vehicle radar device that is mounted on a vehicle and searches for a target around the vehicle.
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
The distance to the target is calculated based on the reflected signal from the target received by the antenna and the search signal transmitted from the antenna, and the target is recognized based on the beam direction of the antenna detected by the distance and direction detecting means. For the stationary target to be recognized, data having a threshold value of the reflected signal level with respect to the distance in advance is included, and the change due to the distance of the reflected signal level from the stationary target is not affected by multipath, and the distance is And target recognition means for determining the height of the target based on a distance where the reflected signal level in a changing state where the power is once increased and then rapidly decreases until approaching is reached. This is an on-vehicle radar device.

  According to the present invention, the distance at which the drop in the reflected signal level when approaching the stationary target is smaller than the threshold drawn on the map corresponds to the height of the stationary target. It can be determined that the height is higher when the height is lower and the height falls after approaching relatively.

  In the present invention, the target recognizing means may determine whether or not the stationary target can be stepped over based on a state in which the reflected signal level decreases as the distance approaches.

  According to the present invention, when the drop in the reflected signal level when approaching the stationary target becomes a certain level or more than the level at a long distance, it is determined that the signal can be stepped over, and the reflected signal level due to the difference in the material of the target, etc. To avoid the effects of changes.

Furthermore, the present invention is an in-vehicle radar device that is mounted on a vehicle and searches for a target around the vehicle.
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
The distance to the target is calculated based on the reflected signal from the target received by the antenna and the search signal transmitted from the antenna, and the target is recognized based on the beam direction of the antenna detected by the distance and direction detecting means. The effect of multipath does not appear in the change in the reflected signal level due to the distance , and the reflected signal level in the changing state where the power once increases and suddenly decreases until the distance approaches An on-vehicle radar device comprising target recognition means for determining the height of a stationary target based on a distance that suddenly decreases.

  According to the present invention, the height of the stationary target is estimated according to the distance at which the drop amount of the reflected signal level when approaching the stationary target becomes a certain level or more from the reflected signal level at a long distance. When the height of the stationary target is relatively low, the target moves out of the range of the beam from the antenna even at a relatively long distance, and a drop in the received signal level is avoided. If the height of the target is relatively high, the drop in the reflected signal level increases after the distance becomes short. Since the target to be compared is the reflection signal level at a long distance of the target itself, the influence of the difference in the material of the target can be reduced and the target height can be accurately estimated.

Furthermore, the present invention is an in-vehicle radar device that is mounted on a vehicle and searches for a target around the vehicle.
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
A target recognition unit that calculates a distance to the target based on a reflected signal from the target received by the antenna and a search signal transmitted from the antenna, and recognizes the target based on the calculation result;
When the target recognition means recognizes a target stationary at a distance greater than a predetermined distance, the level of the reflected signal at the time of recognition is greater than a predetermined reference and is closer than the vehicle position at the time of recognition In addition, the effect of multipath does not appear in the change due to the distance of the reflected signal level, and the drop in the level of the reflected signal in the changing state where the power suddenly decreases until the distance approaches is large, An on-vehicle radar device that recognizes that the target is not a target of a height that should be wary of traveling of the vehicle.

  According to the present invention, when a target stationary at a distance greater than a predetermined distance is recognized, the level of the reflected signal at the time of recognition is higher than a predetermined reference and closer to the position at the time of recognition. When the drop of the reflected signal level is large, the target is recognized not to be a target having a height that should be wary of driving of the vehicle. For example, when a reflected signal is received from an object above a road surface on which a vehicle passes, such as a signboard, a sign, or a three-dimensional intersection, the antenna is approached to some extent even if it is in the antenna beam direction range far away. Thus, the reflected signal level drops greatly. When detecting such an object that does not interfere with traveling, it is recognized that the target is not a target to be warned, so that control such as unnecessary warning and braking can be prevented.

  In the present invention, the height of the target is the height of the highest part of the target.

  According to the present invention, the possibility of stepping over can be determined based on the height of the highest part of the target.

  In the present invention, the target recognizing means determines whether the target can be stepped over based on the determined height.

  According to the present invention, it is determined whether or not it is possible to step over at the highest part of the target, so that a reliable determination can be made.

  In the present invention, the height of the target is the height of the lowest part of the target.

  According to the present invention, it is possible to determine the possibility of passing through the height at the lowest portion of the target.

  In the present invention, the target recognizing means determines whether or not the target can pass through based on the determined height.

  According to the present invention, since it is determined whether or not it is possible to pass through at the lowest part of the target, a reliable determination can be made.

  Further, in the present invention, the target recognition unit performs the determination of the height of the target in a plurality of sections according to the distance from the target, and determines a predetermined alarm and / or based on the determination result for each section. A signal for braking is derived.

  According to the present invention, the height of the target is determined based on the presence or absence of multipath effects in a plurality of sections while approaching a stationary target. Therefore, multiple determinations are made while approaching the target. If it is determined that the target can be overcome in an early period, unnecessary warnings and braking can be avoided.

Moreover, in the present invention, the search for the target is performed by the FM-CW method.
The target recognizing means estimates the distance to the target and the relative speed using only the data of the frequency decrease section when determining that the relative speed with respect to the target is larger than the reference speed.

  According to the present invention, accurate detection can be performed even for a rapidly approaching target.

  According to the present invention, since the target height is determined based on the multipath effect that becomes noticeable when the target height is high, it is possible to step over a target that does not cause the multipath effect. Therefore, it is possible to avoid unnecessary deceleration and generation of an alarm.

  Further, according to the present invention, the position of the antenna that transmits the exploration signal and receives the reflected signal has a certain height from the road surface, and a target lower than this height, if the distance to the target is close to some extent, Using a phenomenon that deviates from the beam direction of the antenna, it is possible to reliably determine whether or not a stationary target can be stepped over with a simple configuration.

  In addition, according to the present invention, it is possible to easily determine whether or not a stationary target can be stepped over based on a threshold value in a map created in advance.

  Furthermore, according to the present invention, a threshold map for the reception level is provided in advance for a distance that is a criterion for determining a drop in the reception level of the reflected signal from the target based on the target being below the beam direction of the antenna. Since the height of the target is determined based on the distance at which the reflected signal level from the target becomes smaller than the threshold value, the target height can be quickly determined.

  Further, according to the present invention, when the drop amount of the reflected signal level when approaching the stationary target reaches a constant value compared with the reflected signal level at a distance, it is determined that the target can be stepped on. Therefore, it is possible to make a high-probability judgment regardless of the material of the target.

  Further, according to the present invention, the height of the target is estimated based on the distance at which the drop amount of the reflected signal level that changes in accordance with the distance from the stationary target becomes a certain amount or less compared to the distance. For a target with a low height, even if the distance is relatively long, the probe beam deviates from the target, and a drop in the reflected signal level is avoided. For a relatively high target, the beam direction deviates from the target only after approaching a short distance, and the distance at which the reflected signal level starts to drop decreases. Since the target height is estimated according to the distance, the target height can be easily and easily estimated, and the target height is not affected by changes in the reflected signal level due to the target material. Can be accurately estimated.

  Furthermore, according to the present invention, an appropriate judgment is made for a target that is detected at a relatively far distance and has a position sufficiently higher than the road surface of the vehicle, such as a signboard, in which the reflected signal level drops sharply when approaching. And avoid unnecessary alarms and braking.

  Further, according to the present invention, it is possible to determine the possibility of stepping over the highest portion of the target as the height.

  Further, according to the present invention, since the possibility of stepping over is determined at the highest part of the target, a highly accurate determination can be made.

  Further, according to the present invention, it is possible to determine the possibility of skipping by setting the lowest portion of the target as the height.

  According to the present invention, since the possibility of passing through is determined at the lowest part of the target, a highly accurate determination can be made.

  Further, according to the present invention, the possibility of stepping over is determined in a plurality of sections approaching the target. Therefore, if it is determined that the possibility of stepping over even relatively far is high, control such as deceleration is not performed. In addition, it can pass over the target amount.

  In addition, according to the present invention, it is possible to accurately estimate the distance, position, etc., even for a target that approaches rapidly.

  FIG. 1 shows a schematic electrical configuration of an in-vehicle radar device 21 used in each embodiment of the present invention. The on-vehicle radar device 21 has an antenna 23 for searching for the target 22. The beam direction 23a of the antenna 23 can be changed in the horizontal plane by the scanning mechanism 24. The scanning mechanism 24 can swing the beam direction 23a of the antenna 23 within a certain angle range with respect to the traveling direction.

  From the antenna 23, an FM-CW radio wave generated by the transmission circuit 25 is transmitted as an exploration signal. When the exploration signal hits the target 22, it is reflected on the surface of the target 22 and becomes a reflected signal. When the reflected signal is received by the antenna 23, a beat signal generated between the reflected signal and the search signal is electrically processed by the receiving circuit 26, converted into a digital signal by the A / D circuit 27, and a frequency component is converted by the FFT circuit 28. Extracted. The target detection circuit 29 detects a target corresponding to the target 22 based on the frequency component extracted by the FFT circuit 28. The target recognition circuit 30 recognizes the target 22 based on the target detection results in a plurality of search directions within one scan and the target detection results obtained from a plurality of scans. A plurality of search results in one scan and a search result in a plurality of scans are stored in the memory 31.

  The in-vehicle radar device 21 is mounted on a vehicle 32, and the position of the antenna 23 is higher than the road surface 33 on which the vehicle 32 travels. The result recognized by the target recognition circuit 30 of the in-vehicle radar device 21 is given to the alarm device 34 and the cruise control device 35. The alarm device 34 generates an alarm when the distance to the target 22 becomes shorter than a predetermined distance and a danger of collision occurs. When it is determined that the distance to the target 22 is short in consideration of the relative speed, the cruise control device 35 performs control to brake the vehicle 32 and reduce the traveling speed. If braking is unnecessary, control is performed so as to continue traveling at a preset speed. The beam direction 23 a of the antenna 23 can be detected by the direction detection device 36.

  FIG. 2 shows a processing procedure of the target recognition circuit 30 as the first embodiment of the present invention. When the target is recognized, the procedure from step a1 is started. In step a2, it is determined whether or not the scan that is the scan of the antenna 23 by the scanning mechanism 24 has been completed for one scan. When it is determined that the search is completed, in step a3, the beam direction 23a of the antenna 23 is directed in one direction and there are three or more beams in a state in which the search signal is transmitted, and the reflected signal from the target 22 Whether or not is detected is determined. When it is determined that three or more beams are not detected, it is determined in step a4 whether or not the target recognized in the previous scan has been detected. If not detected, the process returns to step a2. If it is determined in step a4 that the target 22 detected in the previous scan is recognized, the angle is calculated from the data of the previous and current two scans in step a5. If it is determined in step a3 that three or more beams have been detected, an angle is calculated from one scan data in step a6.

  When the calculation process in step a5 or step a6 is completed, a pairing process is performed in step a7. In the pairing process, the frequency increase period and the frequency decrease period of the FM-CW method are combined. In step a8, it is determined whether or not the pairing process was possible in step a7. When it is determined that the pairing process is not possible, the frequency data is shifted in step a9, the data is divided for each specific section in step a10, the position in each section is calculated in step a11, and the road shoulder position in step a12. Judgment is made. For data that could be paired in step a8, the processing from step a9 to step a12 is not performed. The contents of each process from step a9 to step a12 will be described later.

  In step a13, it is determined whether or not there is a target outside the road shoulder. When it is determined that there is a target, the target outside the shoulder is deleted in step a14. When it is determined in step a13 that there is no target outside the shoulder, or when step a14 is completed, it is determined in step a15 whether there is a stationary target object. If it is determined that there is no stationary object target, a signal representing the target recognition result is output in step a16.

  When it is determined in step a15 that there is a stationary object target, the probability that the stationary object target can be stepped over is calculated in step a17 and subsequent steps. In step a17, the probability value is initialized to zero. In step a18, it is determined whether or not the power that is the reception intensity of the stationary object at a long distance is large. When it is determined that the power is large, the probability value is set to 50 in step a19. If the power at a long distance is large, the stationary object target is determined to have a high height from the road surface, and if it travels as it is, there is a high possibility that it cannot get over, so the probability value is set to 50. When it is determined in step a18 that the power at a long distance is not large, or when step a19 is completed, it is determined in step a20 whether or not the power rapidly decreases in a relatively long distance. When it is determined that the stationary target will be lowered, the probability that the stationary object target is present at a relatively high position such as a signboard is increased, and the possibility that the stationary object target cannot be stepped on is also reduced. In step a21, the probability value is decreased by 30.

  When it is determined in step a20 that the power at a long distance does not suddenly decrease, or when step a21 ends, the process proceeds to step a22. In step a22, the power as the received signal strength varies as the distance approaches, and it is determined whether or not the maximum value in one section A is greater than the minimum value in the next section B. When the received signal level fluctuates due to the multipath phenomenon with respect to the stationary object target, the relationship as in step a22 is established, reflecting the fluctuation period, and the process proceeds to step a23. In step a23, the probability value is increased by 20. When it is determined in step a22 that the relationship is not established, or when step a23 ends, the process proceeds to step a24. In step a24, it is determined whether the maximum value of section C is greater than the minimum value of section D in the next section C determined in step a22 and further in the next section D. When it is determined that the condition of step a24 is satisfied, the probability value is increased by 20 in step a25. When it is determined in step a24 that the condition is not satisfied, or when step a25 ends, the process proceeds to step a16, and the calculated probability value is output to the alarm device 34, the cruise control device 35, or the like in FIG.

  As judged by comparing the “maximum value” and the “minimum value” in the adjacent section, the power suddenly decreases in the same way according to the “maximum variation width” and “deviation amount from the average value”. Judgment can be made.

  After the target output in step a16, or when it is determined in step a2 that one scan has not ended, the procedure moves to step a26 and the procedure is ended. When it is determined in step a2 that one scan is not completed, the target is searched until one scan is completed, and if a reflection signal is detected, the target is recognized. In the next scan, the beam angle is shifted by a predetermined angle. In addition, the angle of the beam can be complemented more finely by dividing into three or more scans. The alarm device 34 in FIG. 1 issues a warning when the probability given by the target output at step a16 becomes 50% or more, for example. In addition, the cruise control device 35 performs braking to limit the traveling speed of the vehicle 33 when the probability is about 70 to 80%.

FIG. 3 is a related embodiment of the present invention. While the operation mechanism 24 of FIG. 1 detects the beam direction 23a of the antenna 23 as an angle by the direction detection device 36, the search signal is transmitted and the reflected signal is received at every fixed angle. An example of a change in the reflected signal level obtained by performing the above is shown. FIG. 3A shows a change when scanning is performed in one direction, and FIG. 3B shows a search result when the angle of the beam to be searched in the reciprocating direction is shifted by a predetermined angle. In FIG. 3B, the solid line indicates the detection result in the current scan, and the broken line indicates the detection result in the previous scan.

When determining the direction of the target based on the detection result as shown in FIG. 3, since the target is detected only at two angles in FIG. 3A, the reflected signal power B is larger. Must be determined to be the direction of the target. As shown in FIG. 3B, when the data of two scans are used with the angle shifted, the original angle where the target exists is between the previous B angle and the current A angle. I understand that. In this related form, even if the search angle is relatively long, the search angle is shifted between the first scan and the second scan. As a result, the search is performed at a small angle interval. High-accuracy exploration results can be obtained.

  FIG. 4 shows an example of a relative position change when the target 22 is searched by a plurality of scans. There is generally a speed difference between the target 22 and the vehicle 32. The scanning mechanism 24 scans the antenna 23 in a range of ± 4 degrees, for example, in a time of about 100 ms per scan. Therefore, when the search is performed with two scans, there is a relative movement of about 0.2 seconds between the position of the first vehicle 32 and the final position of the vehicle 32. The target 22 moves. In step a9 of FIG. 2, the Doppler shift frequency is calculated from the relative speed difference based on the above-described Expression 4, and the upbeat frequency and the downbeat frequency based on Expression 1 and Expression 2 are calculated based on the calculated Doppler shift frequency. To correct. In step a10, the data corrected with the change of the Doppler shift frequency is divided for each specific section. In step a11, calculation is performed based on the distance R obtained from the above-described Expression 3 and the direction at that time in each specific section. In step a12, the part where the target positions are gathered as a result of the position calculation in step a11 is determined to be a road shoulder.

  In the procedure from step a9 to step a12, data that cannot be paired in step a8 is processed as an unnecessary reflector such as a guide rail and used for determining the shoulder position. However, since unnecessary reflectors do not become a major obstacle to the running of the vehicle, the data determined to be unpairable in step a8 may be removed from the processing target and not treated as a target. it can. In this way, the processing burden can be reduced.

FIG. 5 shows a procedure for estimating the position and relative speed of the target 22 when the vehicle 32 approaches the target 22 at a high speed as a related form of the present invention. After recognizing the target in step b1, it is determined in step b2 whether or not the distance is smaller than the reference standard. If it is determined that the speed is smaller, it is determined in step b3 whether or not the relative speed is greater than the reference speed. When it is determined in step b2 that the distance is not smaller than the reference distance, or when it is determined in step b3 that the relative speed is not larger than the reference speed, the frequency is determined in step b4 as in the normal FM-CW system. The distance to the target 22 and the relative speed are calculated using the data of the rising section and the frequency falling section. When it is determined in step b3 that the relative speed is greater than the reference speed, in step b5, the distance to the target 22 and the relative speed are estimated using only the data in the frequency decrease section. When step b4 or step b5 ends, the procedure ends at step b6.

  FIG. 6 shows a change depending on the distance between the upbeat frequency fub and the downbeat frequency fdb when searching for a target by the FM-CW method. From Equation 1 and Equation 2, it can be seen that the difference between the downbeat frequency fdb and the upbeat frequency fub is twice the Doppler shift frequency fd. From Equation 4, the Doppler shift frequency fd corresponds to the relative velocity V. It can be seen that the difference between fdb and fub is proportional to the relative speed V. Therefore, when the relative speed is relatively large, the upbeat frequency fab becomes considerably small when the distance to the target is small. In the receiving circuit 26 as shown in FIG. 1, processing for a very low frequency becomes difficult. Therefore, in this embodiment, when the distance to the target is closer than a reference distance that is, for example, d1, the relative speed is increased. When the speed is higher than the reference speed V1, the distance to the target and the relative speed are determined using only the downbeat frequency fdb in the frequency decreasing section without using the upbeat frequency fub in the frequency increasing section. As the relative speed, the value obtained by the FM-CW method similar to the normal in step b4 is used as it is, the Doppler shift frequency fd of Expression 4 is obtained, and the range frequency fr is obtained from the relationship with the downbeat frequency fdb of Expression 2. , And the distance R is calculated from the expression 3 to estimate the relative speed V and the distance R.

FIG. 7 shows an example of the concept of determining whether or not an object that can be stepped over is approached when approaching an object that is stationary on the road as a second embodiment of the present invention. When the height of the target 42 reflected by the reflected signal 41 from the search signal 40 transmitted from the antenna 23 of the vehicle 32 is relatively higher than the road surface 43, a multipath phenomenon occurs. That is, among the reflected signals 41, a signal directly received by the antenna 23 and a signal reflected by the one circuit plane 43 and then received by the antenna 23 are generated, and between the reflected signals 41 received based on the path difference. Produces a phase difference. Due to this phase difference, the reflected signal level decreases when the reflected signals 41 cancel each other.

  FIG. 8 shows the difference due to the influence of the height of the target 42 from the road surface 43 when the signal level of the reflected signal 41 according to the distance is expressed as power. FIG. 8A shows a change in the power of the reflected signal 41 from the relatively high target 42. FIG. 8B shows the change in the power of the reflected signal for the relatively low target 42. When the height of the target 42 is high, the power fluctuation with respect to the distance is large due to the influence of multipath.

  Step a22 in FIG. 2 compares, for example, section A and section B in FIG. 8, and comparison in step a24 compares section C and section D in FIG. An example of the distance between each of the A, B, C, and D sections is 20 m. Thus, if the power fluctuates due to the influence of the multipath, it can be determined that the target 42 is high and the probability that the vehicle can get over is very small. In the change in power when the height of the target 42 shown in FIG. 8B is small, the power increases as the distance gets closer to a certain distance. Therefore, A, B, C, and D in FIG. The conditions of step a22 and step a24 for comparison in the sections corresponding to the sections are not satisfied.

FIG. 9 shows a procedure for determining whether or not a stationary object can be stepped over as a related embodiment of the present invention. That is, when a stationary object target is detected in step c1, it is determined in step c2 whether or not the vehicle is in an interval for determining whether or not it can be stepped over based on the distance. In step c3, it is determined whether or not the reflected signal level from the target fluctuates depending on the distance, and the influence of multipath occurs as in steps a22 and a24 in FIG. If it is determined that there is a multipath effect, the probability value is increased in step c4. After increasing the probability value in step c4, or after not increasing the probability value because there is no multipath effect in step c3, target output is performed in step c5 in the same manner as step a16 in FIG. 1 is issued from the warning device 34 in FIG. 1, or the braking control is performed by the cruise control device 35 in FIG. After the target output in step c5 is completed, or when it is determined in step c2 that it is not the determination section, the procedure is ended in step c6. In this related form, determination sections can be provided in a plurality of sections as they approach from the far side, and determination can be performed from an early stage, ensuring safety and making a reliable determination at the next distance determination.

  Note that the height of the target can also be detected from the occurrence state of the multipath and the distance to the target.

FIG. 10 shows the concept of determining the height of a stationary target as a third embodiment of the present invention. FIG. 10A shows a state in which the vehicle 32 approaches the targets 44 and 45 existing in front of the road surface 43 in the traveling direction. It is assumed that the target 44 is lower in height from the road surface 43 than the target 45. As shown in FIG. 10 (a), the beam direction 23a from the antenna 23 of the vehicle 32 extends in a certain range, so that when the distance to the targets 44 and 45 is relatively large, both targets The search signals hit 44 and 45, and the reflected signal is received by the antenna 23. As shown in FIG. 10 (b), when the vehicle 32 approaches the targets 44 and 45, the beam direction 23a of the antenna 23 extends forward from a position spaced from the road surface 43. It will deviate from the range of the direction 23a.

  FIG. 11A shows a change in the reception power of the reflected signal with respect to the distance when the vehicle 32 as shown in FIG. 10 approaches the targets 44 and 45. The solid line shows the power change of the reflected signal from the low target 44, and the broken line shows the power change of the reflected signal from the high target 45. Even a high target 45 may have a height that does not cause multipath effects as shown in FIG. 8 at a long distance. In this embodiment, if the target 44 or 45 is approached, the difference in height is recognized from the difference in reception level due to the difference in height, and the target 44 or 44 is determined based on the mounting position of the antenna 23 or the like. A height of 45 can also be estimated. Whether or not the vehicle 32 can step over the target 44 is determined, for example, by setting a relationship map as a threshold value such as a change of the reception level with respect to the height at which the vehicle 32 can be stepped over, as indicated by a one-dot chain line. It can be determined that the signal can be stepped over if the reflected signal level is lowered. In addition, the height of the target 44 can be estimated based on the height that can be stepped over, which is a threshold value.

  As shown in FIG. 11B, if a plurality of maps having different heights are prepared, the approximate height of the target can be determined from a map that is close to the depressed state. In addition, as shown in FIG. 11C, the height may be obtained from the distance R when the reception level falls below a predetermined threshold P on the short distance side (out of the detection range below the beam). it can.

  FIG. 12 shows a procedure for determining whether or not it can be stepped over based on the concept of the present embodiment. When a stationary object target is detected in step d1, it is determined in step d2 whether or not the distance to the stationary object target is shorter than a certain value. When it is determined that the distance is short, it is determined in step d3 whether or not the reflected signal level is smaller than a certain value. If not, the possibility that the stationary object target can be stepped over is small, and the probability value is increased in step d4. When the reflected signal level has fallen below a certain value in step d3, there is a high possibility that the stationary object target can be stepped over, and the probability value is reduced in step d5. After step d4 or step d5, target output is performed in step d6 as in step a16 in FIG. If the probability value is, for example, 50% or more at the target output, an alarm is generated from the alarm device 34 in FIG. 1, and when the probability value further increases to about 70 to 80%, braking is applied by the cruise control device 35. After the target output in step d6 is completed, or when it is determined in step d2 that the distance is not smaller than a certain value, the procedure is terminated in step d7. The fixed value for determining the distance in step d2 is a distance at which the low target 44 deviates from the range of the beam direction 23a of the antenna 23 as shown in FIG.

  The determination process as shown in FIG. 12 is performed after step a25 in FIG. Depending on whether or not it can be stepped over, the probability value can be increased or decreased to make a more appropriate judgment.

FIG. 13 shows, as a fourth embodiment of the present invention, a conceptual procedure for determining the drop in the reflected signal level as shown in FIG. 11 on the basis of the level at a distance. After detecting the stationary object target in step e1, in step e2, it is determined whether or not the target is already stored. When not stored, in step e3, the distance to the stationary object target and the reflected signal level are stored in the memory 31 of FIG. If the target is already stored in step e2, the process proceeds to step e4. In step e4, the reflected signal level is compared with the stored signal level. In step e5, it is determined whether or not a certain level of drop has occurred in the comparison result. If it is determined that there is no drop above a certain level, it is determined in step e6 whether or not the distance is smaller than a reference value. This distance is determined in accordance with the distance at which the target 44 as shown in FIG. When it is determined in step e6 that the distance is smaller than the reference value, the probability value is increased in step e7. When it is determined in step e5 that a certain drop or more has occurred, the probability value is decreased in step e8. The target output of step e9 is performed with the probability value changed in step e7 or step e8. This target output is performed in the same manner as in step a16 in FIG. When it is determined in step e6 that the distance is not smaller than the reference value, or after target output is performed in step e9, the procedure is terminated in step e10.

  In the present embodiment, the reflected signal level itself is not subject to determination, and in step e4, it is determined whether or not a certain level of drop has occurred with reference to the far reflected signal level. Although the reflected signal level varies depending on the material of the target and the like, in the present embodiment, it can be made less susceptible to the influence of the material. In this embodiment, whether or not the stationary object target can be stepped over is determined by whether or not a certain amount of depression occurs before the distance becomes shorter than the reference value. In other words, the distance at which the amount of sagging is more than a certain amount corresponds to the height of the stationary object target, so it is also possible to estimate the height of the stationary object target from the distance when the amount of sagging more than a certain amount occurs It becomes.

  This embodiment is also basically executed following step a25 in FIG. However, it is necessary to store the reflected signal level with respect to the distance in step e2 in each stationary target.

FIG. 14 shows the concept of determining a stationary target that does not hinder the traveling of the vehicle as a fifth embodiment of the present invention. If there is a signboard 46 or the like near the road surface 43 on which the vehicle 32 is traveling, the signboard 46 enters the beam direction 23a of the antenna 23 at a relatively long distance, as shown in FIG. Can be received with a large reflected signal level. As shown in FIG. 14B, when the vehicle 32 approaches the signboard 46, the beam direction 23a of the antenna 23 deviates from the signboard 46, so that the reflected signal level rapidly decreases.

  FIG. 15 shows the relationship between the power of the reflected signal and the distance when the vehicle 32 approaches the sign 46 as shown in FIG. In the state shown in FIG. 14A, the power of the reflected signal is relatively large, and when the state shown in FIG. As shown in FIG. 15, when approaching a high target, the distance at which the power of the reflected signal suddenly decreases is far beyond the distance at which a drop occurs when approaching a low target. . Based on the idea of the present embodiment, if the power at a relatively long distance drops rapidly in the determination at step a20 in FIG. 2, the probability value is reduced at step a21. In this embodiment, the height of the lowest part of the target is detected and it is confirmed that the vehicle can pass through. On the other hand, the above-described determination as to whether or not it can be stepped over is made based on the height of the highest portion.

  Also in the present embodiment, the height of the target can be obtained by using the maps as shown in FIGS. 11B and 11C.

The present invention can be modified to the following related forms.
(1) In an in-vehicle radar device mounted on a vehicle and searching for a target around the vehicle, the gain is increased in a predetermined beam direction, and a search signal is transmitted in the beam direction. An antenna that receives the reflected signal of the antenna, a scanning unit that performs scanning that changes the beam direction of the antenna within a predetermined range, a direction detection unit that detects a beam direction of the antenna that is changed by the scanning unit, and a scanning unit. Search control that repeatedly scans the beam direction within the predetermined range, and controls to perform target search in a plurality of directions in which the beam direction detected by the direction detection unit has different angles between the repeated scans. Means and based on the reflected signal from the target received by the antenna and the exploration signal transmitted from the antenna It calculates the distance to the target, based on the beam direction of the antenna which is detected by the distance and direction detection means, vehicle radar device which comprises a target recognition unit for recognizing a target.

  An on-vehicle radar device that is mounted on a vehicle and searches for a target around the vehicle transmits a search signal from an antenna in a predetermined beam direction and receives a reflection signal from the target. The beam direction of the antenna is scanned within a predetermined range by the scanning means, and is detected by the direction detecting means. The scanning control unit repeatedly scans the beam direction of the antenna within a predetermined range, and performs control so that the target is searched in a plurality of directions in which the beam directions detected by the direction detection unit are different between repeated scannings. . The target recognition means calculates the distance to the search signal based on the reflection signal from the target received by the antenna and the search signal transmitted from the antenna. Target recognition is performed based on the calculated distance and the beam direction of the antenna detected by the direction detection means. The beam direction for exploring the target can be obtained by the scanning control means so as to have a plurality of different directions for each scanning of the antenna. Therefore, by combining the exploration results obtained by the plurality of scannings, for each finer angle difference It is possible to perform a highly accurate search equivalent to the result obtained by performing the search. Since the angle between explorations in one scan does not have to be as fine as the final angle, the target direction can be obtained with the same accuracy as when the processing speed is increased.

  (2) The target recognizing means recognizes a target based on a search result for a plurality of beam directions for each scan, and when the number of beam directions in which a reflected signal is received is smaller than a predetermined reference value, An on-vehicle radar device that recognizes a target based on a combination of search results obtained by a plurality of scanning operations.

  When a sufficient number of search results cannot be obtained by one scan, the target can be recognized based on the search results obtained by a plurality of scans, so that the target recognition accuracy can be improved.

  (3) The target recognizing unit calculates a Doppler shift frequency based on a search result obtained by the plurality of scans from a frequency shift amount accompanying the movement of the target, and generates a reflection signal combined for target recognition according to the calculation result. An on-vehicle radar device characterized by being changed.

  Considering the time lag between a plurality of scans, it is possible to perform recognition with high accuracy by combining target search results.

  (4) The target recognizing means recognizes a reflected signal having a frequency that is out of the combination target according to the calculation result, as a reflected signal from an unnecessary reflection object, as a reflected signal from the target. An on-vehicle radar device that is not handled.

  Reflected signals with frequencies that cannot be combined among multiple search results are recognized as unnecessary reflectors and are not treated as reflected signals from the target, so do not place a processing load on targets that do not actually need attention. In this way, it is possible to cause a focused process to be performed on a target that needs attention.

  (5) The search for the target is performed by the FM-CW method, and the target recognition unit includes peak data obtained from a reflected signal having a frequency that is not included in the combination according to the calculation result among the search results. In-vehicle radar apparatus, wherein the distance and direction are calculated by subtracting the Doppler shift for the own vehicle speed between the frequency increase interval and the decrease interval of the FM-CW method.

  Calculates the distance and direction by subtracting the Doppler shift for the own vehicle speed in the FM-CW frequency up and down sections, even for exploration results that are not subject to combination for a specific target. Therefore, the position of the search target can be obtained effectively.

  (6) The target recognizing unit recognizes the calculation result of the distance and the direction as data on the unnecessary reflection object, obtains a position where the unnecessary reflection object gathers from the distance and the direction, and determines the position as a road shoulder. An on-vehicle radar device characterized by that.

  The calculation result based on the exploration results that could not be combined is recognized as data about unnecessary reflectors, and the position where unnecessary reflectors gather is judged as the road shoulder, so the road shoulder and objects outside it are subject to attention. To reduce the processing burden.

It is a block diagram which shows schematic electrical structure of the vehicle-mounted radar apparatus 21 used by each embodiment of this invention. It is a flowchart which shows the operation | movement procedure of the target recognition circuit 30 as 1st Embodiment of this invention. It is a figure which shows the view which detects the direction of a target by several scan as a related form of this invention. It is a figure which shows the view which considers the relative moving amount | distance of a target, when utilizing the data obtained by multiple scans. It is a flowchart which shows the procedure which estimates distance and relative speed with respect to the target which approaches at high relative speed as a related form of this invention. It is a graph which shows the reason which estimates distance and relative speed using the frequency fall section with respect to the target which approaches at high relative speed. As a second embodiment of the present invention, it is a diagram showing a concept of determining whether or not it can be stepped over depending on whether or not the reception level of the reflected signal varies due to the influence of multipath. It is a graph which shows the state in which the difference in the influence of a multipath arises according to the difference in the height of a target. It is a flowchart which shows the procedure which determines in a some area, when approaching from a long distance side whether it can step on a stationary object target as a related form of this invention. It is a figure which shows the principle which can judge by the fall of the reflected signal level at the time of approaching whether it can step on a stationary object target as 3rd Embodiment of this invention. It is a graph which shows the relationship between the distance when approaching the stationary object target which can be stepped on, and a reflected signal level. It is a flowchart which shows the procedure of the other idea which judges whether a stationary object target can step over using the idea shown in FIG. It is a graph which shows the other way of thinking as 4th Embodiment of this invention from the amount of drop of the level at the time of approach with respect to the reflected signal level in a long distance whether a stationary object target can step over. As a fifth embodiment of the present invention, it is a diagram illustrating a concept of determining that a stationary object target is at a position higher than a position where a vehicle travels, such as a signboard. It is a graph which shows the change by the distance of the reflected signal level with respect to the stationary target object of a high position as shown in FIG. It is a block diagram which shows schematic electrical structure of the conventional vehicle-mounted radar apparatus. It is a graph which shows the operation principle of the radar apparatus of FM-CW system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Car-mounted radar apparatus 22 Target 23 Antenna 23a Beam direction 24 Scanning mechanism 25 Transmission circuit 26 Reception circuit 29 Target detection circuit 30 Target recognition circuit 31 Memory 32 Vehicle 33,43 Road surface 34 Alarm device 35 Cruise control device 36 Direction detection device 40 Search signal 41 Reflection signal 44, 45 Target 46 Signboard

Claims (13)

In an on-vehicle radar device that is mounted on a vehicle and explores targets around the vehicle,
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
The distance to the target is calculated based on the reflected signal from the target received by the antenna and the search signal transmitted from the antenna, and the target is recognized based on the beam direction of the antenna detected by the distance and direction detecting means. The effect of multipath does not show up in the change due to the distance of the reflected signal level in the specific frequency range, and it is stationary based on the change state in which the power suddenly decreases until the distance approaches. And an on-vehicle radar device comprising target recognition means for determining the height of the target.   2. The target recognizing unit determines that the target can be stepped over when the level of a reflected signal from the stationary target rapidly decreases from the middle of the approach. In-vehicle radar system. The target recognizing unit has data indicating a change in a threshold value of a reflected signal level with respect to a distance in advance for a recognized stationary target, and the reflected signal level from the stationary target is smaller than the threshold value within a predetermined distance range. in-vehicle radar device according to claim 1, characterized in that it is determined that the target can be overstep. In an on-vehicle radar device that is mounted on a vehicle and explores targets around the vehicle,
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
The distance to the target is calculated based on the reflected signal from the target received by the antenna and the search signal transmitted from the antenna, and the target is recognized based on the beam direction of the antenna detected by the distance and direction detecting means. For the stationary target to be recognized, data having a threshold value of the reflected signal level with respect to the distance in advance is included, and the change due to the distance of the reflected signal level from the stationary target is not affected by multipath, and the distance is And target recognition means for determining the height of the target based on a distance where the reflected signal level in a changing state in which the power once increases before approaching and then rapidly decreases is smaller than the threshold value. An on-vehicle radar device.   5. The on-vehicle radar device according to claim 4, wherein the target recognizing unit determines whether or not the stationary target can be stepped over based on a state in which the reflected signal level decreases as the distance approaches. In an on-vehicle radar device that is mounted on a vehicle and explores targets around the vehicle,
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
The distance to the target is calculated based on the reflected signal from the target received by the antenna and the search signal transmitted from the antenna, and the target is recognized based on the beam direction of the antenna detected by the distance and direction detecting means. The effect of multipath does not appear in the change in the reflected signal level due to the distance , and the reflected signal level in the changing state where the power once increases and suddenly decreases until the distance approaches A vehicle-mounted radar device comprising: target recognition means for determining the height of a stationary target based on a distance that suddenly decreases. In an on-vehicle radar device that is mounted on a vehicle and explores targets around the vehicle,
An antenna configured to increase gain in a predetermined beam direction, transmit a probe signal in the beam direction, and receive a reflected signal from a target with respect to the probe signal;
A target recognition unit that calculates a distance to the target based on a reflected signal from the target received by the antenna and a search signal transmitted from the antenna, and recognizes the target based on the calculation result;
When the target recognition means recognizes a target stationary at a distance greater than a predetermined distance, the level of the reflected signal at the time of recognition is greater than a predetermined reference and is closer than the vehicle position at the time of recognition In addition, the effect of multipath does not appear in the change due to the distance of the reflected signal level, and when the drop in the reflected signal level is large in the changing state where the power suddenly decreases until the distance approaches , An in-vehicle radar device that recognizes that the target is not a target of a height that should be wary of traveling of the vehicle.   8. The on-vehicle radar device according to claim 1, wherein the height of the target is a height of a highest portion of the target.   9. The on-vehicle radar device according to claim 8, wherein the target recognizing unit determines whether or not the target can be stepped over based on the determined height.   The on-vehicle radar device according to claim 4, wherein the height of the target is a height of a lowest portion of the target.   11. The on-vehicle radar device according to claim 10, wherein the target recognizing unit determines whether or not the target can pass through based on the determined height.   The target recognizing means determines the height of the target in a plurality of sections according to the distance from the target, and signals for warning and / or braking determined in advance based on the determination results for each section. The in-vehicle radar device according to claim 8, wherein the in-vehicle radar device is derived. The exploration of the target is performed by FM-CW method,
The target recognizing means estimates the distance to the target and the relative speed using only the data of the frequency decrease section when determining that the relative speed with respect to the target is larger than the reference speed. The vehicle-mounted radar apparatus in any one of -12.

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