JP4163695B2 - Leading vehicle recognition device - Google Patents

Description

  The present invention relates to a transmission / reception means for transmitting an electromagnetic wave toward a predetermined area in the traveling direction of the own vehicle and receiving a reflected wave from an object existing in the predetermined area; Object information calculating means for calculating the position of the object with respect to the object, integration means for combining the plurality of objects as one object based on at least the position of the object when the plurality of objects are detected in the predetermined area; The present invention relates to a preceding vehicle recognition apparatus including detection position calculation means for calculating the center of a reflected wave from an object collected by an integration means as a detection position.

Even when a target like a preceding vehicle is located at the end of the scanning range of the radar beam, in order to accurately determine the direction of the target, the reception level when the center of the beam is irradiated on the target, The effective reflection cross section is obtained based on the antenna gain value at the center of the beam and the distance to the detected target. If the target exists slightly outside the scanning range of the beam, the effective reflection cross section is obtained. Is known from Japanese Patent Application Laid-Open Publication No. 2004-259259, which obtains the antenna gain from the received signal level and obtains the direction of the target from the obtained antenna gain and the angle-gain characteristics of the beam registered in advance.
JP-A-11-64500

  By the way, the above-mentioned conventional one requires complicated signal processing such as calculation of effective reflection cross section when obtaining the direction of the target located at the end of the scanning range of the radar beam, and the calculation load of the CPU is reduced. There was a problem of increasing.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to improve the detection accuracy of the lateral position of an object at the end of a predetermined area where the transmission / reception means transmits and receives electromagnetic waves by a simple calculation.

In order to achieve the above object, according to the first aspect of the present invention, an electromagnetic wave is transmitted toward a predetermined region in the traveling direction of the host vehicle, and a reflected wave from an object existing in the predetermined region is received. Based on transmission / reception means, object information calculation means for calculating at least the position of the object with respect to the own vehicle based on the transmission / reception result of the transmission / reception means, and based on at least the position of the object when a plurality of objects are detected in the predetermined area In the preceding vehicle recognition apparatus, comprising: an integrating unit that combines the plurality of objects as a single object; and a detection position calculating unit that calculates a center of a reflected wave from the object collected by the integrating unit as a detection position. based on the waveform indicated by the reflected waves from, whether only part of the object enters from the left or right edge of its said predetermined area, than all of the object enters the predetermined area Since it is determined that only a portion of the object has entered the predetermined region by the region-end decision means and the area end determination means for determining a correction of the detection position to the whole of the object enters the predetermined area A preceding vehicle recognizing device including a detecting position correcting means is proposed.

According to the second aspect of the present invention, in addition to the configuration of the first aspect, the detection position correcting unit may cause the region end determining unit to cause only a part of the object to fall within the predetermined region . If it is determined that the vehicle has entered from the right end , a preceding vehicle recognition device is proposed in which the detection position of the object calculated by the detection position calculation means is corrected laterally outward by a predetermined distance. Is done.

  According to a third aspect of the present invention, in addition to the configuration of the second aspect, in the case where the detection position correcting unit continuously corrects the previously corrected object, the detected object The preceding vehicle recognition is characterized in that the lateral movement amount between the previous detection position and the current detection position is corrected, and the detection position of the object is corrected based on the calculated lateral movement amount and the predetermined distance for the correction. A device is proposed.

  According to the invention described in claim 4, in addition to the configuration of claim 3, the detection position correcting means may calculate the lateral movement when the object is approaching in the traveling direction of the own vehicle. Based on the value obtained by subtracting the amount from the predetermined distance, and when the object is separated from the traveling direction of the vehicle, the detection of the object is performed based on the value obtained by adding the calculated lateral movement amount to the predetermined distance. A preceding vehicle recognition device is proposed which is characterized by correcting the position.

According to the invention described in claim 5, in addition to any one of claims 1 to 4, before Symbol transmitting and receiving means are radar apparatus, the detection area of the predetermined region is a radar device A preceding vehicle recognition device characterized by the above is proposed.

  The radar device 14 of the embodiment corresponds to the transmission / reception means of the present invention.

According to the first aspect of the invention, the object information calculation means calculates the positions of the objects in the predetermined area based on the transmission / reception result of the transmission / reception means, and the integration means calculates the positions of the plurality of objects in the predetermined area. Summary of the object of the plurality as one object, in the preceding vehicle detection device for calculating the center of the reflected wave from the detection position calculating unit has been summarized objects as the detection position, only a portion of the object of that within a predetermined area If the area edge determination means determines whether or not the object has entered from the left end or right edge before the entire object enters the predetermined area , the determination is made until the entire object enters the predetermined area. Since the detection position correction means corrects the detection position, even if only a part of the preceding vehicle enters the predetermined area and is detected before the entire preceding vehicle enters the predetermined area , the detected part Is mistaken for the whole preceding car Position detection accuracy can be prevented from decreasing, thus, also in the transverse direction across a predetermined area of the position of only enters preceding vehicle part in a predetermined area, it can be correctly recognized by a simple calculation It becomes. This makes it possible to quickly recognize a vehicle that cuts in front of the host vehicle from a close range as a preceding vehicle, and enables smooth vehicle speed control and alarm with sufficient time, improving the reliability of the system in a complicated traffic environment. To do.

According to the invention of claim 2, when it is determined by the region end determination means that only a part of the object has entered the predetermined region from the left end or the right end, the region end determination unit is the detection position calculation unit. Since the calculated detection position of the object is corrected laterally outward by a predetermined distance, only a part of the preceding vehicle has been detected within the predetermined area before the entire preceding vehicle has entered the predetermined area . Even in this case, the lateral center position of the preceding vehicle can be correctly recognized as the position of the preceding vehicle.

  According to the third aspect of the present invention, the lateral movement amount between the previous detection position and the current detection position of the detected object when the correction is performed continuously for the previously corrected object is calculated, and the calculated lateral movement is calculated. Since the detection position of the object is corrected based on the amount and the predetermined distance, it is possible to recognize the lateral position of the preceding vehicle to be interrupted ahead of the host vehicle with higher accuracy.

  According to the invention of claim 4, when the object is approaching in the traveling direction of the own vehicle, the detection position of the object is corrected based on the value obtained by subtracting the lateral movement amount from the predetermined distance, and the object is traveling in the own vehicle. When the distance is away from the direction, the detection position of the object is corrected based on the value obtained by adding the lateral movement amount to the predetermined distance, so the lateral position of the preceding vehicle that is going to interrupt the front of the host vehicle is further increased. It can be recognized with high accuracy.

According to the invention of claim 5, sending the receiving means constituted by a radar device, since the detection area to a predetermined area, can be reliably determined preceding vehicle by a radar device.

  Embodiments of the present invention will be described below based on the embodiments of the present invention shown in the accompanying drawings.

  FIGS. 1 to 13 show an embodiment of the present invention. FIG. 1 is a block diagram of a control system of an ACC system, FIGS. 2 to 4 are first to third partial diagrams and diagrams of the operation. 5 is an explanatory diagram for explaining why a lateral position detection error occurs when the vehicle enters the end of the detection area, FIG. 6 is an explanatory diagram corresponding to steps S5 and S6 of the flowchart, and FIG. 7 corresponds to step S9 of the flowchart. FIG. 8 is an explanatory diagram corresponding to step S12 of the flowchart, FIG. 9 is an explanatory diagram corresponding to step S17 of the flowchart, FIG. 10 is an explanatory diagram of operation when the preceding vehicle interrupts (conventional example), and FIG. FIG. 12 is an operation explanatory diagram when the preceding vehicle interrupts (example), FIG. 12 is an operation explanatory diagram when the preceding vehicle stops trying to interrupt (conventional example), and FIG. 13 is an intermediate when the preceding vehicle tries to interrupt. Canceled Kino is an operation explanatory diagram (Example).

  As shown in FIG. 1, an ACC (adaptive cruise) that keeps a preset inter-vehicle distance and follows the preceding vehicle when there is a preceding vehicle, and runs at a constant speed at a preset vehicle speed when there is no preceding vehicle. The control system includes a predicted trajectory estimation unit M1, a control target region setting unit M2, a control target determination unit M3, an object information calculation unit M4, an integration unit M5, a detection position calculation unit M6, and a region end determination. Means M7, detection position correction means M8, control target value determination means M9, and vehicle control means M10 are provided.

  A vehicle speed sensor 11 and a yaw rate sensor 12 are connected to the predicted trajectory estimation means M1, a radar device 14 is connected to the object information calculation means M4, and a display 15, a deceleration actuator 16 and an acceleration actuator 17 are connected to the vehicle control means M10. Is done.

  The predicted trajectory estimation means M1 estimates the future predicted trajectory of the host vehicle based on the vehicle speed detected by the vehicle speed sensor 11 and the yaw rate of the host vehicle detected by the yaw rate sensor 12. That is, the turning radius of the own vehicle is calculated from the current vehicle speed and the yaw rate, and the future predicted trajectory of the own vehicle is estimated by connecting the arc of the turning radius to the current traveling direction of the own vehicle.

  The control target area setting unit M2 has a width obtained by adding a predetermined width (2 m in the embodiment) to the left and right sides of the future predicted trajectory of the host vehicle estimated by the predicted trajectory estimating unit M1, and is a predetermined front part of the host vehicle. A band-like control target region having a length up to a distance (100 m in the embodiment) is set. The predetermined width of 2 m corresponds to a half of the lane width 4 m, and thus the width of the control target area corresponds to the lane width 4 m. The predetermined distance of 100 m corresponds to a distance at which the radar device 14 can reliably detect the preceding vehicle.

  The control object determining unit M3 determines, as a control object, any preceding vehicle existing in the control object region set by the control object region setting unit M2 among the plurality of preceding vehicles detected by the radar device 14.

  The object information calculation means M4 calculates the relative distance, lateral position and relative speed of the object detected by the radar device 14.

  The integration unit M5 integrates a plurality of objects collected as a single vehicle among a plurality of objects detected in the detection area spreading in a fan shape of the radar device 14. Since the vehicle has a portion that strongly reflects the electromagnetic wave transmitted by the radar device 14 and a portion that reflects weakly, the reflected wave from one target is detected as being divided into a plurality of objects. In some cases, the integration unit M5 can recognize the plurality of objects as one target.

  The detection position calculation means M6 calculates the center position of the width of one target integrated by the integration means M5 as the vehicle detection position. When the entire target is in the detection area, the detection position calculated by the detection position calculation means M6 substantially matches the center position of the actual target width (see FIG. 5A). Is partially included in the left and right ends of the detection area, the detection position calculated by the detection position calculation means M6 does not coincide with the center position of the actual target width (see FIG. 5B). .

  The region end determination means M7 determines a state where only a part of the target is in the right or left end of the detection area. When the entire target is in the detection area, the reception intensity of the reflected wave received by the radar device 14 is highest in the center and gradually lowers on both the left and right sides, but only the end of the target is in the detection area. If it is present, it can be determined because the received intensity of the reflected wave suddenly drops at the end of the detection area.

  In view of the fact that the detection position correction means M8 cannot accurately calculate the position of the target when only a part of the target is in the right or left end of the detection area (see FIG. 5B), The target position calculated by the detection position calculation means M6 is corrected so as to approach the correct position. The corrected target position is output to the control target determining means M3, where any target is determined as a preceding vehicle to be controlled.

  The control target value determining means M9 determines a target vehicle speed, a target acceleration / deceleration, a target inter-vehicle distance, and the like, which are parameters for causing the host vehicle to follow and follow the preceding vehicle to be controlled. Then, the vehicle control means M10 drives the deceleration actuator 16 and the acceleration actuator 17 based on the control target value determined by the control target value determination means M9, and opens / closes the throttle valve or operates the brake device to follow the traveling control. In addition to executing the constant speed running control, the current control state of the vehicle is displayed on the display 15 to notify the driver.

  Next, the functions of the region edge determination unit M7 and the detection position correction unit M8 will be described mainly based on the flowcharts of FIGS. 2 to 4 and the operation explanatory diagrams of FIGS.

  First, the reflected wave from the target is detected by the radar device 14 in step S1, and the relative distance, the lateral position and the relative velocity of the target are calculated by the object information calculation means M4, the integration means M5 and the detection position calculation means M6 in step S2. In the following step S3, it is determined that the reflected wave is from the end of the detection area, and in the subsequent step S4, the reflected wave is from the right end of the detection area of the radar device 14 by the region end determination means M7. If it is determined that there is, that is, if a part of the target is located at the right end of the detection area, the lateral position of the target is detected to the right by 0.9 m corresponding to half the vehicle width from the lateral position detected in step S5. If it is determined in step S4 that the reflected wave is from the left end of the detection area of the radar device 14 by the region end determination means M7, that is, a part of the target enters the left end of the detection area. If so, the lateral position of the target is shifted to the left by 0.9 m corresponding to half the vehicle width from the lateral position detected in step S6.

  This will be described in detail with reference to FIG. 6. For example, when a part of the target enters the right end of the detection area, the horizontal position of the target is detected as the A position at the left end, but the actual horizontal position of the target is Since it is the B position in the center of the vehicle width, the B position, which is shifted to the right by 0.9 m corresponding to half the vehicle width, is set as the lateral position of the target, so that the target at the end of the detection area is The lateral position detection accuracy can be increased.

  In the subsequent step S7, the takeover confirmation with the previous target is performed. If the current target takes over the previous target in step S8, the difference between the horizontal position of the previous target and the current target is determined in step S9. After the horizontal position is corrected by subtracting or adding to the horizontal position shifted by 0.9 m, the target continuation counter is incremented in step S10. If the answer to step S8 is NO, the process proceeds to step S11 described later.

  The reason for performing the correction in step S9 is that the lateral movement amount of the target that moves laterally toward the front of the host vehicle after entering the end of the detection area is twice the detected lateral movement amount of the target. This is due to the fact that it corresponds. That is, as shown in FIG. 7A, when the lateral position of the current target moves 0.3 m laterally inward with respect to the lateral position of the previous target, the true lateral movement amount at the center position of the target is 0. It will be 0.6m, twice the 3m. That is, even if the actual lateral movement amount of the target is 0.6 m, the detected lateral movement amount is half of 0.3 m.

  As shown in FIG. 7B, even if the correction in step S5 (correction by shifting the lateral position of the target by 0.9 m which is half the vehicle width) is performed, the corrected lateral position of the previous target and the corrected lateral position of the current target are corrected. The lateral movement amount, which is the difference between the two, is still 0.3 m, which is half of the actual lateral movement amount of 0.6 m.

  Therefore, in this embodiment, as shown in FIG. 7C, the lateral position of the current target is shifted by 0.3 m from 0.3 m which is the difference between the lateral position a of the previous target and the lateral position b of the current target. The true lateral position d of the target this time is obtained by subtracting from the lateral position c. When the target moves laterally away from the front of the host vehicle, the difference between the horizontal position a of the previous target and the horizontal position b of the current target is set to 0.3 m, and the horizontal position of the current target is set to 0. The true lateral position d of the current target can be obtained by adding to the lateral position c shifted by .9 m.

  In the subsequent step S11, if the target lateral position corrected in step S9 falls within the detection area, the lateral position of the target is corrected again on the edge of the detection area (strictly outside the edge). That is, in FIG. 8, the lateral position e of the target detected first is corrected to the f position 0.9 m outside by the correction of FIG. 6, and further corrected to the g position 0.3 m inside by the correction of FIG. As a result, if the lateral position g of the target enters the detection area, the lateral position of the target is moved to the h position on the end of the detection area in step S12. As a result, it is possible to prevent the target normally detected (detected without correction) in the detection area from being indistinguishable from the target detected at the end of the detection area. If the answer to step S11 is NO, the process proceeds to step S19 described later.

  If it is determined in step S3 that the reflected wave is not from the edge of the detection area, step S13 confirms that the previous target has been taken over, and step S14 indicates that the current target is the target that has taken over the previous target. In S15, the previous target is the target at the end of the detection area, and in step S16, the difference between the correction position of the previous target (position on the end of the detection area) and the calculated position of the current target is a predetermined value (this embodiment). If it is 1.5 m) or more, when the correction position of the previous target is returned to the current target calculation position in step S17, the position where the movement amount becomes 2/3 is set as the current target position, and in subsequent step S18. Increment the target continuation counter. If the answer to step S14 is NO, the process proceeds to step S19 described later, and if the answer to steps S15 and S16 is NO, the process proceeds to step S18.

  The meaning of step S17 will be described with reference to FIG. In step S12, the lateral position of the target is set to the i position on the edge of the detection area, and when the current target completely enters the detection area and the true position becomes the j position, the true position of the previous target is set. Since the position is the k position, the lateral movement amount becomes excessive because the target lateral movement amount of the target is calculated from the i position to the j position even though the target is the k position → j position. . Therefore, when the lateral movement amount is 1.5 m or more, the lateral movement amount is prevented from being excessive by moving the current target position from the true position j to the outer m position. To do. In this embodiment, the m position is set to a position that is two-thirds the amount of movement from the i position to the j position.

  Thus, when the relative distances, lateral positions and relative speeds of all targets are calculated in step S19, the predicted trajectory estimation means M1 automatically calculates from the vehicle speed detected by the vehicle speed sensor 11 and the yaw rate detected by the yaw rate sensor 12 in step S20. Estimate the future prediction trajectory of the car. In step S21, the stored target data is called. In step S22, the target is a target having a target continuation counter of 3 or more. In step S23, the target is the control object area setting means M2 is a predicted trajectory of the vehicle. In step S24, the preceding vehicle candidate buffer has a preceding vehicle candidate in the preceding vehicle candidate buffer, and in step S25, the target is the preceding vehicle candidate buffer. If the target is shorter than the vehicle candidate, the target is placed in the preceding vehicle candidate buffer in step S26.

  If the answer to step S19 is NO, the process returns to step S2. If the answer to step S24 is NO, the process proceeds to step S26. If the answer to steps S22, S23, and S25 is NO, the process is described later. Control goes to step S27.

  When all the target data are called in step S27, the target in the preceding vehicle candidate buffer is output as the preceding vehicle in step S28, and follow-up running control for the preceding vehicle is executed. If the answer to step S27 is NO, the process returns to step S21.

  Next, the operation when the target cuts in front of the host vehicle will be described with reference to FIGS.

  FIG. 10 shows a conventional example. When a part of the target enters the detection area, it is not detected (see FIGS. 10A to 10C), and when the target almost completely enters the detection area. Detected (see FIG. 10D). If the target is detected three times in succession after the first detection of the target, the target is determined, and thereafter it is recognized as a preceding vehicle from the relationship between the target position and the predicted trajectory (see FIG. 10E). . When it is recognized that the target is a preceding vehicle, deceleration control of the own vehicle is started to increase the inter-vehicle distance, but the recognition of the preceding vehicle is delayed and the inter-vehicle distance is clogged (see FIG. 10 (F)). The deceleration for widening the jammed inter-vehicle distance increases and the ride comfort deteriorates (see FIG. 10G).

  FIG. 11 is an example, and the target starts an interruption in front of the vehicle (see FIG. 11A), and when a part of the vehicle body enters the detection area, it is detected immediately. The target detection position is corrected laterally outward (see FIG. 11B). When the target further approaches the front of the vehicle and half of the vehicle enters the detection area, the detection position corrected laterally outside reaches the end of the detection area, so the target position is output as the end of the detection area. In the meantime, it is detected three times in succession and the target is determined (see FIG. 11C). When almost the entire target enters the detection area, the detected position itself becomes the horizontal position of the target, and since it has already been determined as the target, it is recognized as a preceding vehicle (see FIG. 11D). When the target is recognized as the preceding vehicle, deceleration control of the host vehicle is started to increase the inter-vehicle distance. The ride comfort is improved (see FIGS. 11E to 11G).

Next, the operation in the case where the target has interrupted in front of the own vehicle but has been canceled and returned to the original will be described with reference to FIGS. 12 and 13.
FIG. 12 shows a conventional example, where the target starts interrupting in front of the vehicle (see FIG. 12 (A)), and when a part of the vehicle body enters the detection area, it is detected immediately. The detection position of the target is a part that has entered the detection area, and is detected as many times as the target is determined during that time (see FIG. 12B). When half of the vehicle enters the detection area and the detected position is output, it is already determined as a target, so it is recognized as a preceding vehicle, and deceleration control is started to increase the inter-vehicle distance (FIG. 12C). reference). Even if the preceding vehicle cancels the lane change and returns to the original lane, the detection continues and the deceleration control is continued (see FIG. 12D). When the preceding vehicle goes out of the detection area, it is recognized that there is no preceding vehicle, acceleration control is started, the vehicle is accelerated to the set vehicle speed, and the vehicle continues to travel at the set vehicle speed (see FIGS. 12E and 12F). . Thus, in the conventional example, since acceleration and deceleration are repeated, there is a problem that riding comfort is deteriorated.

  FIG. 13 is an example, and the target starts an interruption in front of the vehicle (see FIG. 13A), and when a part of the vehicle body enters the detection area, it is detected immediately. The target detection position is corrected laterally outward (see FIG. 13B). Even if the target further approaches the front of the vehicle and half of the vehicle body enters the detection area, the detection position corrected laterally outside remains at the end of the detection area, so the target position becomes the end of the detection area. Even if it continues to be output and is detected three times in the meantime and the target is determined, it is not recognized as a preceding vehicle (see FIG. 13C). If the target cancels the lane change and tries to return to the original lane, the detection continues, but the detection position is outside the own lane and the vehicle is not recognized as a preceding vehicle. Continue (see FIG. 13D). When the preceding vehicle goes out of the detection area, it is recognized that there is no preceding vehicle, and the traveling at the set vehicle speed continues (see FIG. 13E). In this way, in the embodiment, unnecessary acceleration and deceleration are not performed, so that riding comfort is improved.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, although the ACC system has been described in the embodiment, the present invention can be applied to a preceding vehicle recognition device for a vehicle for any use other than the ACC system.

ACC system control system block diagram First part of the flowchart explaining the operation Second part of the flowchart explaining the operation Third part of the flowchart explaining the operation Explanatory diagram of why horizontal position detection error occurs when the vehicle enters the end of the detection area Explanatory drawing corresponding to step S5, S6 of a flowchart Explanatory drawing corresponding to step S9 of the flowchart Explanatory drawing corresponding to step S12 of a flowchart Explanatory drawing corresponding to step S17 of the flowchart Action explanatory diagram when the preceding vehicle interrupts (conventional example) Action explanatory diagram when the preceding vehicle interrupts (Example) Action explanation diagram when the preceding vehicle is interrupted and tries to interrupt (conventional example) Action explanation diagram when the preceding vehicle is interrupted and tries to interrupt (Example)

Explanation of symbols

M4 Object information calculation means M5 Integration means M6 Detection position calculation means M7 Area edge determination means M8 Detection position correction means 14 Radar device (transmission / reception means)

Claims (5)

Transmitting / receiving means (14) for transmitting an electromagnetic wave toward a predetermined area in the traveling direction of the vehicle and receiving a reflected wave from an object existing in the predetermined area;
Object information calculating means (M4) for calculating at least the position of the object relative to the own vehicle based on the transmission / reception result of the transmitting / receiving means (14);
An integration unit (M5) for combining the plurality of objects as one object based on at least the position of the object when the plurality of objects are detected in the predetermined region;
A preceding vehicle recognition apparatus comprising: a detection position calculation means (M6)) that calculates, as a detection position, a center of a reflected wave from the object collected by the integration means (M5);
Based on the waveform indicated by the reflected waves from an object, whether only part of the object enters from the left or right edge of its said predetermined area, than all of the object enters the predetermined area An area edge determination means (M7) to be determined before ;
Detection position correction means for correcting the detection position until it is determined that only part of the object has entered the predetermined area by the area edge determination means (M7) until the entire object enters the predetermined area. M8) and a preceding vehicle recognition device. The detection position correction means (M8)
By the region-end decision means (M7), when only part of the object is determined to have entered from the left or right edge to the predetermined region, the detection position calculating means objects calculated by (M6) The preceding vehicle recognition apparatus according to claim 1, wherein the detection position is corrected laterally outward by a predetermined distance. The detection position correction means (M8)
When the correction is performed continuously on the previously corrected object, the lateral movement amount between the previous detection position and the current detection position of the detected object is calculated, and the calculated lateral movement amount and the correction are performed. The preceding vehicle recognition apparatus according to claim 2, wherein the detection position of the object is corrected based on the predetermined distance. The detection position correction means (M8)
When the object is approaching in the traveling direction of the own vehicle, based on a value obtained by subtracting the calculated lateral movement amount from the predetermined distance, and when the object is separated from the traveling direction of the own vehicle. The preceding vehicle recognition apparatus according to claim 3, wherein the detected position of the object is corrected based on a value obtained by adding the calculated lateral movement amount to the predetermined distance. Before Symbol receiving means (14) is a radar device, the predetermined region is characterized by a detection area of the radar device, the preceding vehicle detection device according to any one of claims 1 to 4.

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