WO2005091015A1

WO2005091015A1 - Radar

Info

Publication number: WO2005091015A1
Application number: PCT/JP2005/003842
Authority: WO
Inventors: Yuji Hirogari; Motoi Nakanishi
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2004-03-23
Filing date: 2005-03-07
Publication date: 2005-09-29
Also published as: JPWO2005091015A1

Abstract

A beam scan is performed over a search range of a predetermined azimuth/direction and predetermined distance range and information on a plurality of objects obtained at each scan are compared, so that an object detected according to the same object is followed with a higher reliability and the following reliability is lowered when the detection is unsuccessful. That is, when the following reliability exceeds a first threshold value (S1), the object is detected as a target and when the reliability is below a second threshold value, the object is detected not as a target. This eliminates the problems that erroneous information indicating presence of a target actually not existing is outputted when a small threshold value is set or judgment of an object coming into the radar search range is delayed when a large threshold value is set.

Description

Radar

Technical field

The present invention relates to a radar that detects a target and tracks the target.

[0002] For example, in the case of an on-vehicle radar, in order to secure the safety of the own vehicle and other vehicles, it is necessary to simply detect distances and relative speeds of a plurality of targets within a detection range. It is necessary to set the position of the target as a target to be tracked (hereinafter simply referred to as “target”!) And to have a function to track that target. This target tracking function is a function that continues tracking the target by repeating the process of extracting the target being tracked from a plurality of targets detected in each measurement cycle. It informs the driver and performs control according to the presence of the target. For example, if the target has a dangerous relationship with the vehicle, the engine and brakes are automatically controlled as necessary.

[0003] Conventionally, the probability that a target is detected at the same position in each measurement cycle is calculated, and when the probability exceeds a predetermined threshold value, it is assumed that the target actually exists. ! / For example, in Patent Document 1, when a target has been successfully detected at a target position for N times out of M detection operations, the target is regarded as a tracking target. Then, in this patent document 1, in order to improve the detection performance near the maximum detection distance of the radar, the threshold value of N out of M times, that is, the value of N Is changing.

[0004] Further, in Patent Document 2, the position of a target (detected target) detected by measurement is compared with the position of an already stored target (memory target), and the position of the detected target is stored. The value increases when it is determined that the position of the target corresponds, and decreases when it is determined that the position does not correspond. Then, when a long-term loss occurs in which the certainty falls below a predetermined threshold, the data relating to the target is erased in the storage means, and the shortfall occurs when the certainty does not fall below the predetermined threshold. Losing time, the target Related data is not erased.

Patent document 1: JP-A-11-38119

Patent Document 2: Japanese Patent No. 3065821

Disclosure of the invention

Problems to be solved by the invention

[0005] However, as shown in Patent Document 1, by lowering the sign and the value N, it becomes easier to output an erroneous tracking result due to noise, a pairing error of a stationary object, or the like. That is, when N is reduced, the possibility that the detected target is the target being tracked decreases, but the risk of collision or the like can be reduced by determining that the target is the target being tracked. When noise is detected as a target (a target target to be tracked) even though the target does not actually exist, unnecessary braking is often applied to the vehicle by automatic control. Driving comfort is impaired. Further, Patent Document 1 corresponds to processing relating to tracking of a target in the vicinity of the maximum detection distance, and does not allow quick response to, for example, preventing collision with another vehicle trying to approach the own vehicle. For example, if another vehicle enters the vicinity of the maximum detection distance, the threshold N can be set to a small value to quickly detect the entry. Even if the target moves out of the radar detection range, the target is not present in the radar detection range because it tries to determine the presence or absence of the target with a small threshold N. Information may be output as if it were running. Conversely, if the threshold value N is increased, it can be quickly determined that the target has gone out of the radar detection range, but the judgment of other vehicles trying to enter the radar detection range will be delayed and safety will be easily impaired. Problems arise.

[0006] The certainty factor shown in Patent Document 2 is not a measure for measuring the reliability of signal processing for force / target tracking, which can be one of the judgment factors for controlling the own vehicle. This is clear from Patent Document 2 that, for example, an object approaching a high speed is increased by increasing the degree of certainty of the object! /. In this way, since the same scale can always be used, it is not possible to immediately and accurately respond to sudden changes in the situation.

[0007] It is an object of the present invention to provide a radar that solves the above-mentioned problem in performing signal processing for target tracking and enables target tracking suitable for various situations. Means for solving the problem (1) According to the present invention, transmission of an electromagnetic wave to a predetermined detection range and reception of a reflected wave from the target are repeatedly performed at each predetermined observation timing, and the target information including at least the position information of the target is obtained. When the target information detecting means to be detected is compared with the target information detected at a plurality of different observation timings by the target information detecting means, when the target information caused by the same target is detected. Means for increasing the tracking reliability of the target, reducing the tracking reliability when the target information derived from the same target is not detected, and means for setting the first and second thresholds, respectively. Means for judging the target as a target when the tracking reliability exceeds the first threshold, and judging that the target is not a target when the tracking reliability falls below the second threshold. It is characterized by:

[0009] (2) In (1), the first and second thresholds are determined according to a received signal condition such as a received signal strength and a noise strength.

[0010] (3) In (1), the first and second thresholds are determined according to the relative motion situation such as the relative position and the relative speed of the target.

(4) In (1), the radar is an on-vehicle radar, and includes means for detecting a state of a road on which the vehicle runs, and determines first and second threshold values according to the road environment. .

(5) In (1), the radar is an on-vehicle radar, and includes means for detecting vehicle conditions such as a running speed, acceleration / deceleration, a steering angle, a yaw rate, and a tilt angle of the vehicle, and a threshold setting means. Sets the first and second thresholds according to these vehicle conditions.

(6) In (1)-(5), the threshold value setting means increases or decreases the first and second threshold values in the same direction.

(7) In (1)-(5), the threshold value setting means increases or decreases the first and second threshold values in different directions.

The invention's effect

(1) According to the present invention, the first threshold value for determining that the target to be tracked exists, and the determination that the tracking target has no longer need to be the target are determined. By defining the second threshold value, the degree of freedom in signal processing for target tracking increases, and signal processing for target tracking according to the purpose becomes possible. For example, as the first threshold value (hereinafter, referred to as S1) is set smaller, the time until the detected target is determined as the target can be shortened. This makes it possible to respond quickly when another vehicle enters the vicinity of the own vehicle. Also, for example, if the second threshold value (hereinafter, referred to as S2) is set to a large value, for example, when the target is far away from the own vehicle, its tracking reliability falls below S2 earlier. Other vehicles traveling in a distant place with a low vehicle speed can be quickly released from the target. As a result, information that does not hinder driving is quickly deleted, and the burden on the driver can be reduced. In other words, the signal from the radar increases the driving comfort without the automatic cruise control (hereinafter referred to as ACC) function that frequently controls the engine and brakes.

[0016] (2) By determining the first and second thresholds according to the received signal condition such as the received signal strength and the noise strength, for example, the stronger the received signal strength, the more the noise may be Since the probability is low, the determination of the target can be made early and the determination of the cancellation of the target can be made earlier by setting S2 smaller than S1. Conversely, when the received signal strength is weak, increasing the value of S1 and decreasing S2 reduces the probability that noise is erroneously detected as a target, and the signal strength of the target once targeted is weak. However, tracking can be continued without fail.

(3) By setting the first and second thresholds according to the relative motion situation such as the relative position and the relative speed of the target, optimization according to the motion situation of the target can be achieved. For example, if this radar is an in-vehicle radar, S1 is small when the relative speed of the approaching vehicle to the own vehicle is high and S1 is large when the relative speed is low. Can be determined early. If the relative speed in the approaching direction is low, there is time to spare, so by increasing S1, the probability of erroneously detecting a non-existent target or a target that does not need to be tracked as a target target is increased. Can be reduced.

(4) A signal for target tracking according to the road condition is detected by detecting the condition of the road on which the vehicle travels and determining the first and second thresholds according to the condition of the road. Optimization of processing becomes possible.

[0019] (5) By detecting vehicle conditions such as vehicle speed, acceleration / deceleration, steering angle, yaw rate, and inclination angle, and determining first and second threshold values according to the vehicle conditions, It is possible to optimize signal processing for target tracking according to vehicle conditions. (6) By increasing and decreasing the first and second threshold values in the same direction, the first and second threshold values can be determined according to the weight of safety and comfort. For example, if both the first and second thresholds are reduced, the omission of setting as a target to be tracked is reduced, and safety can be improved. Conversely, if the first and second threshold values are both increased, the probability of tracking an unnecessary target as a target is reduced, and comfort is improved without unnecessary braking by the ACC.

(7) By increasing / decreasing the first and second threshold values in different directions, the start timing of the target tracking is advanced when the relationship between the first and second threshold values is satisfied. In addition, it becomes possible to track only targets that need to be continuously tracked as targets. Conversely, when the relationship of the first threshold value> the second threshold value is satisfied, it is possible to reduce erroneous detection and to reliably track a target that has once started tracking.

Brief Description of Drawings

FIG. 1 is a block diagram showing a hardware configuration of a radar.

FIG. 2 is a functional block diagram relating to signal processing of the radar.

FIG. 3 is a diagram in which positions of a plurality of detected targets at a certain timing are plotted.

FIG. 4 is a diagram showing first and second thresholds and the effects of setting values.

FIG. 5 is a flowchart relating to a target tracking process.

FIG. 6 is a flowchart relating to threshold value setting processing.

FIG. 7 is a diagram showing an example of setting thresholds / values according to the state of a road on which the own vehicle is traveling.

FIG. 8 is a diagram showing a setting example of a threshold value according to the vehicle condition of the own vehicle.

FIG. 9 is a diagram showing a setting example of a threshold value according to a detected relative movement state of a target.

FIG. 10 is a diagram showing an example of setting a threshold value according to a received signal state and other states. Explanation of symbols

[0023] 4 antennas

30-Tracking control unit

SA-Detection range

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] A radar according to an embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the entire system including the vehicle-mounted radar and various units connected to it. FIG. 3 is a block diagram showing the configuration of FIG. In FIG. 1, a portion indicated by reference numeral 20 is a radar front end, and includes a control circuit 1, a millimeter wave circuit 2, a scan unit 3, an antenna 4, and the like. Here, the millimeter wave circuit 2 modulates the oscillation frequency with a modulation signal provided from the control circuit 1 as described later, and outputs a transmission signal to the antenna 4 via the scan unit 3. Also, the received signal is supplied to the control circuit 1 as an intermediate frequency signal (IF signal). The scanning unit 3 scans the beam direction of the antenna 4 over a predetermined range by, for example, mechanical reciprocation.

The control circuit 1 supplies a modulation signal to the millimeter wave circuit 2 and obtains the distance to the target and the relative speed based on the IF signal from the millimeter wave circuit 2. Further, the control circuit 1 outputs a control signal to the scan cut 3 to scan the azimuth direction of the detection range by directing the beam of the antenna 4 to a predetermined azimuth, thereby obtaining the azimuth of the target. . This detects the relative movement status of the target. Further, the control circuit 1 detects a received signal status such as a received signal intensity and a noise intensity.

[0026] The mode switch 10 is a switch for switching whether to control the AC C in the force following mode in which the ACC is controlled in the collision prevention mode. The tracking processing control unit 30 reads the state of the mode switch 10 and sets the first and second threshold values as described later. The tracking processing control unit 30 receives signals from a vehicle speed sensor 11, a car navigation (car navigation device) 12, an ETC (Electronic Toll Collection System) 13, and various other sensors 14 to drive the own vehicle. Detects the road environment and the status of the vehicle. Then, the information of the target is given to the ACC controller 15.

The ACC controller 15 performs automatic cruise control based on the vehicle speed obtained by the vehicle speed sensor 11 and the relative position and relative speed given from the control circuit 1. For example, control data is given to the engine control unit 16 and the brake control unit 17 so that the distance between the vehicle and the preceding vehicle is always kept constant. It also gives control data for avoiding collision with a target ahead such as a preceding vehicle.

[0028] The engine control unit 16 and the brake control unit 17 perform engine control and brake control based on control data given from the ACC controller 15. FIG. 2 is a block diagram of signal processing of tracking processing control section 30 shown in FIG. Here, the information input means 35 is a signal processing section for inputting information from the mode switch 10, the vehicle speed sensor 11, the car navigation 12, the ETC 13, and the various sensors 14 shown in FIG.

[0030] The tracking processing unit 31 inputs target characteristic information such as the distance, relative speed, and azimuth of each target input from the radar front end 20, and determines whether the force is the target being tracked, that is, It is determined whether or not the force is a signal generated due to the same target as the target being tracked.

The tracking reliability calculation unit 32 obtains “tracking reliability”, which is an index of reliability that can be regarded as being correctly tracked, based on the result of the tracking processing unit 31.

The threshold setting unit 33 sets a value based on various information input via the information input unit 35 by a method described later.

The threshold determination unit 34 determines whether the tracking reliability calculated by the tracking reliability calculation unit 32 exceeds the first threshold set by the threshold setting unit 33. If the target is exceeded, the target is determined to be the target, and if the target falls below the second threshold, it is determined that the target is no longer the target. Then, the relative position and the relative motion information of the plurality of targets are output. The ACC controller 15 shown in FIG. 1 controls the engine control unit 16 or the brake control unit 17 based on this information.

FIG. 3 is an example in which the positions of a plurality of targets detected by the radar front end 20 shown in FIG. 2 at a certain timing are plotted. In Fig. 3, O indicates the radar antenna position (the position of the vehicle), and SA indicates the radar detection range. In this way, by repeatedly performing scanning over the radar position O as a center over the left and right sides in front of the vehicle, detection is performed over an angle Θ in the azimuth direction and over a distance L in the distance direction. CI and C2 are other vehicles existing in front of the own vehicle, respectively. In addition, the positions of many targets in the range surrounded by LW and RW are obtained by detecting each point on the side walls provided on the left and right of the road as targets. When such side walls LW, RW are detected as targets, those targets are stationary objects, and therefore, the target is detected at the vehicle speed.

RU

FIG. 4 shows the effect of setting the first and second threshold values. When the tracking reliability exceeds the first threshold value S1, the target is set as the target to be tracked.If the threshold value S1 is set to a small value, the tracking of the target is accelerated, while the relative speed of the side wall is reduced. Erroneously detected and The possibility of tracking this as a moving object also increases. Conversely, when the threshold value S1 is increased, the possibility of erroneously tracking a target such as a side wall is reduced, but the tracking of a target that should be tracked tends to be delayed. For example, in FIG. 4A, LW and RW are the left and right side walls, C3 is the target position of the vehicle traveling in front of the vehicle, and C2 is the vehicle traveling on the right side of the vehicle! Indicates the target position. As shown in this figure, even if a certain part of the side wall is detected as a target CW due to a pairing error or the like at a certain timing (one of a certain scanning cycle), such erroneous detection occurs every time scanning is performed. In other words, its continuity is poor, so the tracking reliability does not increase. Therefore, erroneous tracking can be prevented by appropriately increasing S1. On the other hand, if the first threshold value S1 is set to a small value, a false target cannot be prevented.If a new target C2 enters the detection range SA in front of the vehicle, The tracking start of the target C2 can be hastened.

FIG. 4B shows the second threshold! / And the effect of the setting of the value S2! /. Here, N indicates the range of the target that is likely to be erroneously detected due to the influence of fixed pattern noise such as the clock of the switching power supply circuit and signal processing circuit of the radar and the driving signal of the scanning mechanism. In such a region where the influence of the fixed pattern noise is large, the detection of the position and the relative speed of the target becomes inaccurate, so that the tracking of the target fails and the tracking reliability tends to decrease. C4 'is the position of the target detected under the influence of the noise. C3 indicates the target position of the vehicle running ahead of the own vehicle, and C5 indicates the target position of the vehicle that is going down to the right rear of the own vehicle.

In such a case, the value S2 is set to a small value for the second threshold for the range N. As a result, it is possible to reduce the tendency that the target is canceled even though it actually exists.

Note that the vehicle (C5) that has moved to the outside of the detection range SA force does not set a target for the target regardless of the tracking reliability (the target is released).

Next, the processing contents of the tracking processing control unit 30 shown in FIGS. 1 and 2 will be described based on FIGS.

FIG. 5 is a flowchart relating to the target tracking process. First, target information such as the relative position, relative speed, and received signal strength profile in the azimuth direction of the target, and the target A determination is made as to whether or not the force is capable of associating with the Dell (information that allows the position and speed of the target to be predicted at the next scan, such as the position, moving speed, and scattering cross section of the target) (ST1). ). If a new target is detected without being able to be associated with the target currently being tracked, an initial value is set for the tracking reliability RC for that target, and the target is set to that target. Next, create all models (ST2 → ST3 → ST4).

[0039] In step ST1, if the association between the new target information in the current scan and the information of the model of the target being tracked is successful, the tracking reliability RC for that target is increased (S T1 → ST2 → ST5). For example, it is assumed that the tracking reliability RC takes an integer value, and +1 is given in step ST5. Then, the information of the target model of the target is updated (ST6). For example, information such as the position, relative velocity, and scattering cross section is updated to the latest values. Subsequently, when the tracking reliability RC exceeds the first threshold value S1, the valid flag of the target is set (ST7 → ST8). That is, the target is determined as one of the goals.

[0040] In step ST1, among the plurality of tracking target models, the tracking reliability RC of the tracking target model that does not correspond to the new target information by the current scan is reduced. (ST1 → ST2 → ST9). For example, do 1 RC. When the tracking reliability RC falls below the second threshold value S2, the valid flag of the target is reset (ST10 → ST11). That is, the target is removed from the target.

As described above, the tracking reliability RC of each of the detected targets is increased or decreased, and the plurality of tracking targets are compared by comparing the first and second thresholds S1 ′ S2 with the tracking reliability RC. Of the tracking targets of, the target exceeding the first threshold value S1 is extracted as a target. In addition, in the second threshold, the tracking target that falls below the value is released from the target.

FIG. 6 shows a threshold setting process. In the example shown in (A), the first and second thresholds SI and S2 are determined according to the received signal strength for each target and the signal (noise) strength that can be regarded as noise for target detection. . In the example of (B), the first and second thresholds SI and S2 are determined for each target according to the relative movement of the target. In the example shown in (C), the first and second thresholds SI and S2 are determined according to the road condition detected based on the car navigation system, ETC, inclination angle, steering angle, and yaw rate. In the example shown in (D), the first and second thresholds SI and S2 are determined according to the vehicle information such as the vehicle speed of the vehicle and the health condition of the driver. Shown in (E) In the example, the first and second thresholds SI and S are set according to the state of the mode switch that switches between the collision prevention mode that emphasizes safety and the following mode in which the vehicle automatically follows the preceding vehicle. Set 2.

Next, a specific example of setting the first and second threshold values SI and S2 will be described with reference to FIGS. 7 to 10. FIG. Depending on the value, the setting method of the value is shown.

(A) of FIG. 7 is an example of setting the thresholds! / And the values according to the planar shape of the road on which the own vehicle runs. When the radius of curvature of the road is larger than a predetermined value, that is, while the vehicle is traveling on a curve, the preceding vehicle is irradiated with a diagonally backward force beam, so that the radar scattering cross-section (hereinafter, RCS) becomes smaller. The probability that a reflected signal cannot be detected in each scanning cycle is likely to occur, and the probability of erroneous detection that is processed as if it is another target increases due to changes in the reflection position within the same target. . Therefore, when the curvature radius of the road is smaller than the predetermined value, S2 is set to be smaller than the average value. Alternatively, the smaller the radius of curvature, the smaller S2 is. As a result, it is possible to reliably catch the target. In a curve with a small radius of curvature, the probability of erroneously detecting a stationary object as a moving object increases. Therefore, when the radius of curvature is smaller than a predetermined value, S1 is made larger than the average value. Or, increase S1 as the radius of curvature is smaller. This can reduce the probability of the erroneous detection.

[0044] On the other hand, when the vehicle is traveling on a road with a large radius of curvature, erroneous detection is small because the signal strength of other vehicles traveling ahead is high and the relative position is stable. . Therefore, when the radius of curvature is larger than the predetermined value, S1 is made smaller than the average value. Alternatively, the larger the radius of curvature, the smaller S1 is. As a result, targets that fall within the detection range can be processed as targets at an early stage. When the radius of curvature is larger than a predetermined value, S2 is made larger than the average value. Or, increase S2 as the radius of curvature increases. As a result, a target that has gone out of the detection range can be quickly removed from the target, unnecessary tracking can be suppressed, and the processing capacity can be devoted to the necessary signal processing accordingly.

[0045] Such a planar shape of the road can be detected based on the steering angle of the own vehicle, the output of the yaw rate sensor, or the map information from the car navigation system. FIG. 7B shows a method of setting a threshold value according to the vertical shape of the road on which the vehicle runs, that is, the inclination angle of the road. On a slope, the gain decreases according to the directivity of the antenna in the vertical direction, and the received signal strength decreases, so that the probability of continuity of target detection in each scanning cycle increases. Therefore, when the inclination angle of the road on which the vehicle travels is more than a predetermined angle, S2 is made smaller than the average value. Or, decrease S2 as the inclination angle increases. As a result, the target once detected as a target can be reliably captured. Also, on such a slope, the frequency at which a target newly entering the detection range cannot be detected increases, so S1 is also set to be smaller than the average value. Alternatively, S 1 is reduced as the inclination angle increases. As a result, a target within the detection range can be set as a target at an early stage.

On the other hand, on a flat ground, the received signal strength is high and the number of erroneous detections is small. Therefore, when the inclination angle of the road is gentler than the predetermined angle, S1 is made smaller than the average value. Or make S1 smaller as it is slower. This allows early detection of targets that are within the detection range on flat ground. Also, since there are few false detections on flat ground, S2 is set to be larger than the average value as in the case of traveling on a straight road. Or, increase S2 as it is flatter. As a result, a target that has come out of the detection range can be quickly removed from the target, unnecessary tracking can be suppressed, and the processing capacity can be devoted to the necessary signal processing accordingly.

FIG. 7 (C) is an example of setting thresholds // according to the type of the road on which the own vehicle runs. While driving on a highway, the situation of the target ahead changes relatively slowly. In such a situation, it is not necessary to set the target as a target so early that S1 is made larger than the average value in order to be less affected by noise. As a result, the target can be detected as a target when the existence of the target is surely established. Since the target can be detected stably while driving on the highway, S2 is set to be smaller than the average value. By reducing S2, even if the tracking reliability of the target once captured is reduced to some extent, it can be continuously captured as the target.

On the other hand, when traveling on a general road, S1 is made smaller than the average value, and S2 is made larger than the average value. As a result, a new target is regarded as a target at an early stage, and when the tracking reliability of the target starts to decrease (that is, when the existence of the target becomes suspicious), the target is promptly observed. You can remove it from the mark.

It should be noted that the type of road on which the vehicle is traveling may be detected by car navigation or ETC information.

FIG. 7D is an example of setting values according to the weather conditions during traveling. In bad weather, the strength of the received signal decreases, and continuity in each scanning cycle may not be maintained. Therefore, if the weather is worse than the previously determined condition, S2 is made smaller than the average value. Or make S2 smaller as bad weather. As a result, the target once detected as the target can be reliably kept. Also, in such bad weather, the probability of an accident such as a slip accident increases, so S1 is also made smaller than the average value. Or make S1 smaller as bad weather. Even if the probability of erroneous detection increases in this way, early response is possible by reducing S1. Such weather information can be obtained by receiving a weather sensor provided on the vehicle or broadcasted information.

FIG. 8 shows a setting method according to the vehicle condition of the own vehicle!

(A) of FIG. 8 shows a method of setting thresholds and values according to the physical condition (health state) of the driver. The driver's mental and physical health is judged based on the driver's self-report and driving conditions obtained from external sensors and other factors. Physical condition that tends to slow down the response to dangerous conditions (e.g., reduced limb motor ability due to injuries, injured or illness such as bird's eye or visual impairment such as narrowing of the visual field, continuous operation for a long time, lack of sleep) When S1 is small in the state of hunger, hunger, mental depression, etc., it is possible to respond quickly to the target (by ACC). In addition, by reducing S2, targets with low tracking reliability can be considered as targets, and safety is enhanced.

FIG. 8B shows an example of setting values for a truck or the like according to the loading amount! If the load is large, set both SI and S2 small. If the load is large, the brakes will be less effective. In such a case, by reducing S1, it is possible to respond to a new target earlier. Also, by making S2 small, it becomes possible to cautiously deal with targets with low tracking reliability. It should be noted that this loading amount may be a force that also provides a sensor force, or may be input externally. FIG. 8C shows an example of setting a threshold value for the traveling speed of the own vehicle. As described above, when the traveling speed of the own vehicle is higher than the predetermined speed, S1 is made larger than the average threshold value. Or, increase S1 as the speed increases. This prevents sudden activation due to detection of an incorrect target. Also, by making S2 smaller than S1, it is possible to reliably catch and detect the target detected as the target.

On the other hand, during low-speed traveling, S1 is set smaller than the average threshold value. Or make S1 smaller at lower speeds. This makes it possible to quickly detect targets moving in the direction transverse to the radar beam irradiation direction, such as overtaking vehicles and crossing vehicles and traversing vehicles, as a target, enabling early response. Further, by making S2 larger than S1, the target cancellation of the target grasped as the target is hastened, and prompt response to the miscellaneous target is possible.

FIG. 9 shows an example in which a threshold value is set according to the detected relative movement state of the target.

(A) of FIG. 9 is an example of setting thresholds // according to the distance from the vehicle to the target. When the distance to the target is farther than the predetermined distance, S1 is increased. When the distance is short, S1 is decreased. Or, increase S1 as the distance increases. Decrease S1 as the distance decreases. In this way, the farther the distance to the target, the more time it takes to determine whether or not the target is the target force.Therefore, it is possible to reduce false detections by increasing S1 accordingly. it can. Conversely, if the distance becomes short, S1 becomes small, and safety is more important than false detection, and collision determination can be performed quickly.

FIG. 9 (B) shows the relative speed of the target, the rule of thumb, and how to set the values! When a target is approaching the host vehicle at high speed, there is not enough time to detect the target as a target. Therefore, when approaching faster than the predetermined speed, S1 is set smaller. Or make S1 smaller as you approach faster. By reducing S1 in this way, the target can be set earlier, and the collision determination can be performed quickly. Conversely, when the relative speed is small in the approaching direction or when the vehicle is moving away from the vehicle, S1 is increased because there is ample time to determine whether or not to target the target. I do. This can reduce false detections accordingly. FIG. 9C is an example of setting a threshold value according to the RCS of the target. In general, around a target with a large RCS, the level of the received signal strength rises over a wide azimuth, and the peak of the received signal strength of a target with a small RCS tends to be covered and hidden. That is, a target with a small RCS is detected. Therefore, if a target with a large RCS exists in the vicinity, S2 is determined according to the size of the RCS of the nearby target. For example, the larger the RCS of a nearby target, the smaller S2. As a result, the target once detected as the target can be reliably tracked.

In general, a virtual image due to noise or side lobes tends to appear around a target having a large RCS. Therefore, when there is a target with a large RCS in the vicinity, S1 is determined according to the size of the RCS of the target in the vicinity. In other words, the larger the RCS of the nearby target, the larger S1 is, and the smaller the RCS of the nearby target, the smaller S1. This reduces the probability that the RCS will falsely detect a virtual image around a large target.

FIG. 9D is an example of setting a threshold value for the driving temper of a driver of another vehicle around the own vehicle. If the driving temper of another driver is “impatient”, set S1 to be smaller than the average value. For example, the degree of impatientness is evaluated based on the frequency of overtaking vehicles, the distance between vehicles when being overtaken, the acceleration at the time of overtaking, and the value of S1 is reduced when the evaluation point exceeds a predetermined evaluation point. Or make S1 smaller as it exceeds. In this way, early action can be taken when high-risk vehicles are nearby.

FIG. 10 shows an example in which a threshold value is set according to a received signal condition or other conditions.

FIG. 10A shows an example of setting a threshold value for the received signal strength. When the received signal strength is weaker than the specified value, or as the received signal strength is weaker, S1 is set larger. This can reduce false detection of noise as a target. If the received signal strength is weaker or weaker, S2 is set smaller. As a result, the target once detected as the target can be maintained more reliably. Conversely, for a target with a high received signal strength, it is unlikely to be due to noise, so S1 is reduced accordingly. Alternatively, as the received signal strength becomes stronger, the time until detection as a target can be shortened by reducing S1. Also, the received signal strength is strong! ヽ Set S2 large for the target. Or the received signal strength is strong! Increase S2. For such a target with a strong received signal strength, tracking can be continued reliably, and by increasing S2, a target that is no longer the target can be quickly eliminated.

FIG. 10B is an example of setting a threshold value according to the noise intensity. In a radar that obtains the distance to a target by frequency analysis, there is an area that is affected by the noise of the fixed pattern, as shown in Fig. 4 (B). In such a position, the frequency of erroneous detection increases, and thus, by setting S1 large, the erroneous detection can be reduced. Also, by setting S 2 to be small in that region, it becomes possible to more reliably track a target that is difficult to continue tracking.

FIG. 10C shows a method of setting a threshold value inside and outside the radar detection range. Since the target information is not necessarily required for the target outside the detection range, both SI and S2 are set to be higher than the upper limit of the tracking reliability. As a result, tracking reliability is updated outside the detection guarantee range, but is not treated as a target.

FIG. 10 (D) shows a method of setting a value according to a gain that changes according to the beam direction. In this example, SI and S2 are both set to be smaller as they are outside the scanning range. By reducing S2 in this way, it becomes easier to maintain the tracking of the target in the azimuth where the gain of the antenna is small. In addition, by making S1 smaller, an interrupting vehicle of another vehicle enters near the outside of the detection range, so that it is possible to respond quickly to those targets.

FIG. 10E shows an example of setting a threshold value according to a time zone. Taking statistics of the probability of road traffic accidents by time zone shows a certain distribution, and there are time zones with high accident occurrence rates. For example, at 4:00 pm or 6:00 in the evening, or when the toll on the expressway is approaching soon. In such a time zone, SI and S2 are both set smaller than the average value. Thus, safety-oriented operation control becomes possible.

[0065] In addition to the above, for example, information on the accident occurrence rate at each point or each section of the road, which is statistically obtained from the outside, is obtained from the outside, and the high accident occurrence rate! When traveling, both SI and S2 may be set small. This enables safety-oriented operation control.

[0066] In any of the cases shown in Figs. 7 to 10, the tracking reliability exceeds S1 because of S1 <S2. If the target cannot be detected by the measurement timing before the tracking reliability exceeds S2, the target force is immediately removed at that point. Alternatively, a process may be performed in which the target is regarded as a target until the tracking reliability falls below S1.

Note that in the examples shown in Fig. 6 to Fig. 10, the forces that indicate how to set the first and second thresholds for various conditions are not applied to these conditions alone. SI and S2 may be determined so as to satisfy multiple conditions at the same time. For example, the upper right column of each table shown in Fig. 7-Fig. 10 is the antecedent part, and the table contents are the consequent part, and finally SI and S2 are generated one by one by fuzzy inference using min-max centroid method etc. You may make it.

Claims

The scope of the claims

[1] Detecting target information including at least target position information by repeating transmission of electromagnetic waves to a predetermined detection range and reception of reflected waves from the target at each predetermined observation timing Means,

By comparing the target information detected at a plurality of different observation timings by the target information detecting means, when the target information originating from the same target is detected, the tracking reliability of the target is increased. Means for lowering the tracking reliability when target information derived from the same target is not detected,

Means for determining the first and second threshold values, respectively;

When the tracking reliability exceeds a first threshold value, the target is determined as a target target, and when the tracking reliability falls below the second threshold, the target is determined as a target target. When,

A radar comprising:

2. The radar according to claim 1, wherein the threshold and the value setting means determine the first and second thresholds and values in accordance with a received signal condition such as the strength of the received signal and the strength of noise.

3. The threshold value setting means according to claim 1, wherein the threshold value setting means sets the first and second threshold values according to a relative movement situation such as a relative position and a relative speed of the tracking target. Radar.

[4] The radar is provided in the vehicle and includes means for detecting the condition of the road on which the vehicle runs, and the threshold and the value setting means are adapted to the first and the second in accordance with the environment of the road. The radar according to claim 1, wherein a threshold value is determined.

[5] The radar is provided in a vehicle, and further includes means for detecting a vehicle condition such as a traveling speed, acceleration / deceleration, a steering angle, a yaw rate, an inclination angle, and the like of the vehicle. 2. The radar according to claim 1, wherein the first and second thresholds are determined according to a situation.

[6] The radar according to any one of claims 15 to 15, wherein the threshold value setting means increases or decreases the first and second threshold values in the same direction.

[7] The radar according to any one of claims 15 to 15, wherein the threshold value setting means increases / decreases the first and second threshold values in different directions.