JP2013257249A - Object detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object detection device that discriminates a vehicle from a feature.SOLUTION: An object detection device 100 that transmits a radio wave to the surroundings of a vehicle to detect an object on the basis of a reflection wave reflected from the object around the vehicle comprises: reflection power identifying means 34 for identifying the reflection power of the reflection wave; and other-vehicle detection means 33 for detecting the object as another vehicle on the basis of a change in the reflection power.

Description

  The present invention relates to an object detection device that transmits radio waves to the periphery of a vehicle and detects the presence of an object based on a reflected wave reflected from the object around the vehicle.

  2. Description of the Related Art An object detection device is known that monitors a blind spot from a driver's seat with a radar to notify a driver of other vehicles that travel in adjacent driving lanes and approach from the rear side. For example, when the driver turns on the blinker switch, when the object detection device detects that there is an obstacle on the rear side, the driver notifies the driver by sounding an alarm sound.

  By the way, in the radar monitoring range, not only other vehicles but also features such as guard rails often exist. The driver does not change lanes to the adjacent guardrail immediately adjacent to the host vehicle, but if the turn signal switch is turned on because of a right or left turn before the intersection or the vehicle is You may be parked close to In these cases, it is often unnecessary for the object detection device to sound an alarm sound. For this reason, in the object detection device, it is desired to exclude features such as guardrails from other alarm targets for other vehicles.

  There is a technology that uses a guardrail pole to detect a guardrail (see, for example, Patent Document 1). Patent Document 1 discloses a stationary object determination device that determines a series of targets whose peak density with respect to a frequency of a beat spectrum is a predetermined value or more as a guardrail pole.

Japanese Patent Laid-Open No. 11-211811

  However, the stationary object determination device disclosed in Patent Document 1 has a problem that the guardrail cannot be detected depending on the shape of the guardrail.

  FIG. 1 is an example of a diagram schematically showing a guardrail and other vehicles detected by a radar apparatus. Since the guard rail of FIG. 1A has an iron plate stretched around the roadway by a pole (hereinafter referred to as a guard rail with an iron plate), the object detection device always receives the radar reflected by the iron plate. For this reason, it is observed that the iron plate is moving at zero relative speed with respect to the host vehicle (the dotted line in FIG. 1A represents another vehicle).

  FIG.1 (b) has shown the case where the other vehicle is running in parallel with the relative speed zero with respect to the own vehicle. Also in this case, the object detection device always receives the radar reflected by the other vehicle. Thus, in the case of a guard rail with an iron plate, it may be difficult to distinguish the guard rail with an iron plate from other vehicles, and it is difficult to exclude only the guard rail. The same is true for features other than guard rails with iron plates.

  In view of the above problems, an object of the present invention is to provide an object detection device capable of distinguishing other vehicles from features.

  The present invention is an object detection device that transmits radio waves to the periphery of a vehicle and detects the presence of an object based on a reflected wave reflected from an object around the vehicle, and reflects the reflected power of the reflected wave. It has an identification means, and another vehicle detection means for detecting that the object is another vehicle based on the fluctuation of the reflected power.

  It is possible to provide an object detection device capable of distinguishing other vehicles from features.

It is an example of the figure which shows typically the guardrail and other vehicle which a radar apparatus detects. It is an example of the figure explaining the schematic characteristic of the radar apparatus in a present Example. It is a figure which shows the structural example of the vehicle-mounted system containing a radar apparatus. It is an example of the schematic block diagram of a radar apparatus. It is an example of the figure which illustrates typically the frequency of a transmission signal, a reception signal, and a beat signal. It is an example of the figure explaining determination of an azimuth | direction. It is an example of the figure explaining the electric power of the beat signal obtained by Fourier transform. It is an example of the functional block diagram of a radar apparatus. It is a figure which shows the example of a measurement of the change of the position of a target. It is an example of the figure which shows the example of the shape of a guardrail. It is an example of the flowchart figure which shows the procedure in which a radar apparatus determines whether a target is a guardrail. It is an example of the functional block diagram of a radar apparatus (Example 2). It is a figure which shows the example of a measurement of the change of reflected electric power. FIG. 10 is an example of a flowchart illustrating a procedure in which a radar apparatus determines whether a target is a guardrail (Example 2). It is an example of the functional block diagram of a radar apparatus (Example 3). FIG. 10 is an example of a flowchart illustrating a procedure in which a radar apparatus determines whether a target is a guardrail (third embodiment). It is a figure which shows an example of weighting (alpha) and (beta).

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 2 is an example of a diagram illustrating the schematic features of the radar apparatus according to the present embodiment. In FIG. 2A, a guard rail is laid on the left side of the host vehicle substantially parallel to the traveling lane. There may be other lanes between the own vehicle and the guard rail (however, in this case, it is often possible to determine whether the guard rail of the own vehicle lane or the guard rail of another adjacent lane is based on the distance). The object detection device transmits a radar within a predetermined angle from the side of the host vehicle to the rear side, and analyzes the reflected wave to detect an obstacle.

  Since the guardrail is installed, the object detection device mainly detects the reflected wave from the guardrail, and detects the distance to the guardrail, the relative speed, and the azimuth (lateral position y) for each radar scan. To do. Since the guardrail is fixed, even if the host vehicle moves in the width direction in the lane, the fluctuation width Δya of the lateral position y of the guardrail is small.

  In FIG. 2 (b), another vehicle is traveling on the lane on the left side of the host vehicle at substantially the same speed as the host vehicle with respect to the road surface. Which other vehicles are subject to warning depends on the irradiation range of the radar and the design policy, but is mainly a parallel running vehicle and a rear side vehicle. In this embodiment, hereinafter, it is simply referred to as a parallel running vehicle. A parallel running vehicle is a parallel running vehicle in which the front portion is slightly behind the host vehicle or a part of the vehicle body is superimposed in the vehicle length direction of the host vehicle and the relative speed with the host vehicle is substantially zero.

  When the object detection device transmits a radar, the parallel running vehicle reflects the radar, so the object detection device detects the distance, relative speed, and direction (lateral position) to the parallel running vehicle for each scan. The parallel running vehicle moves in the width direction within or beyond the lane, and the relative speed is not always zero, so the relative position (vehicle width direction, traveling direction) varies. For this reason, together with the movement of the host vehicle in the width direction, the amount of change in the position of the parallel running vehicle (only the amount of change Δyb in the y direction is shown in the figure) increases.

  Theoretically, Δyb should be about twice as large as Δya. However, since the relative positions of the parallel running vehicle and the host vehicle are not always the same, the reflected wave is not constant, and Δyb is actually Δya. More than twice.

  Therefore, it is possible to determine whether the detected obstacle is a guardrail or a feature such as a parallel running vehicle by monitoring a temporal change in relative position and comparing it with a predetermined threshold value. In addition, since the position of the target is obtained from the distance and the azimuth, it may be determined based on the amount of change in at least one of the distance and the azimuth.

[Configuration example]
FIG. 3 is a diagram illustrating a configuration example of an in-vehicle system 300 including a radar device. The radar apparatus 100 corresponds to the object detection apparatus recited in the claims. The radar device 100 and a driving support ECU (Electronic Control Unit) 200 are connected via an in-vehicle network such as a CAN (Controller Area Network). As will be described later, the radar apparatus 100 periodically transmits the distance to the target, the relative speed, and the direction (hereinafter, collectively referred to as target information) to the driving support ECU 200. Note that any object that reflects the radar can be a target. In addition to a three-dimensional object, a planar object such as a manhole, road surface, or wall can also be a target. Intended for vehicles.

  The radio wave transmission / reception unit of the radar apparatus 100 according to the present embodiment is disposed inside the left end corner and the right end corner of the rear bumper of the vehicle made of a material that allows radio waves to pass, such as resin. The center of the radar transmission direction is arranged to be about 45 to 70 degrees with respect to the direction parallel to the axle. The irradiation angle (radar detection range) can be designed to be 90 to 120 degrees, for example. The elevation angle is almost zero (parallel to the road surface).

  In addition to the radar apparatus 100 that detects a parallel running vehicle, the radar apparatus 100 may be attached in front of the host vehicle.

  The driving assistance ECU 200 provides various driving assistances such as BSM (Blind Spot Monitoring-System) and CTW (Cross Traffic Warning) based on the target information. A blinker switch 201, a wheel speed sensor 202, a steering angle sensor 203, and an operation device 204 are connected to the driving support ECU 200. The blinker switch 201 detects the operation direction of the blinker lever. The wheel speed sensor 202 detects the rotation of the rotor arranged on each wheel as a wheel pulse by a sensor on the vehicle body side taking out from a magnetic flux change or the like. The rotational speed is obtained from the number of wheel pulses per unit time, and the vehicle speed can be obtained by further considering the tire diameter. The steering angle sensor 203 is a sensor that detects the rotation angle of the steering shaft. There are various detection principles. For example, S pole and N pole magnetic bodies are arranged on the steering shaft side, the periphery of the steering shaft is enclosed in a ring shape, and a change in magnetism is detected on the ring side. Thus, the rotation angle is detected.

  The operation device 204 is various in-vehicle devices used for driving support for avoiding abnormal approach to a target. Examples of the operation device 204 include an alarm buzzer, an audio output device, and a steering motor. The alarm buzzer warns that there is a risk of abnormally approaching the target if the lane is changed by blowing the buzzer on the meter panel, and the audio output device will give a message (for example, “There is another vehicle on the rear side.” ) Is output from the speaker. The steering motor applies a rotational torque to the steering shaft so as to increase the load in the steering direction when the driver steers the steering wheel when there is another vehicle on the rear side. Since the driver requires a larger steering force than before, the driver can be alerted to the presence of the parallel running vehicle.

  FIG. 4 shows an example of a schematic configuration diagram of the radar apparatus 100. The radar apparatus 100 is configured to include a VCO (voltage controlled oscillator) 16, an ASIC 17, and a microcomputer 18 on a substrate 11 connected to a plurality of antennas. The configuration diagram shown is an example, and the function of the ASIC 17 may be implemented by the microcomputer 18 or the function of the microcomputer 18 may be implemented by the ASIC 17. Moreover, you may provide DSP other than showing in figure.

  The antenna includes a transmitting antenna 12 and a plurality of receiving antennas 14-1 to 14-n. The transmission antenna 12 transmits a radar wave modulated to a predetermined frequency by the transmission circuit 13. As will be described later, the frequency of the transmission wave is controlled to increase or decrease in a triangular wave shape, and the beat signal is measured in each of the rising and falling intervals. Such a radar is called FMCW (Frequency-modulated continuous-wave), but in this embodiment, a pulse radar that switches the irradiation direction of the radar every short time may be used.

  The transmission circuit 13 converts, for example, a high-frequency signal in the millimeter wave band generated by the VCO 16 into a voltage and supplies the voltage to the transmission antenna 12 as a transmission signal. The transmission circuit 13 has a distribution circuit that distributes the transmission signal (high-frequency signal) generated by the VCO 16 to the reception circuits 15-1 to 15-n of the n reception antennas 14-1 to 14-n. Yes.

  Although the number of receiving antennas is n in the figure, it is sufficient to have at least two receiving antennas in order to detect the azimuth. The reception antennas 14-1 to 14-n have the same configuration including the reception circuits 15-1 to 15-n (a group of one reception antenna and reception circuit may be referred to as a channel). The receiving antennas 14-1 to 14-n receive the reflected waves reflected by the target and output them to the receiving circuits 15-1 to 15-n. The reception circuits 15-1 to 15-n mix and amplify the reception signals acquired from the reception antennas 14-1 to 14-n and the transmission signals acquired from the transmission circuit 13 with a mixer, and then remove unnecessary frequency components. Remove and output to the substrate 11 side. The mixed signal is a beat signal generated by the difference in frequency between the transmission signal and the reception signal. The frequency of the beat signal is called the beat frequency.

  Each of the receiving circuits 15-1 to 15-n receives the beat signal and sends it to the substrate 11 side. Although not shown in the figure, each receiving circuit 15-1 to 15-n and the substrate 11 are connected via a switch, and at the same time, one receiving circuit 15-1 to 15-n is connected to a beat signal. Is supposed to generate.

  The VCO 16 on the substrate 11 side is controlled by the microcomputer 18 and modulates a high frequency signal by a triangular wave having an ascending section and a descending section. Further, the ASIC 17 is provided at the subsequent stage of the A / D conversion circuits 21-1 to 21-n and the A / D conversion circuits 21-1 to 21-n provided corresponding to the receiving circuits 15-1 to 15-n. The provided buffers 22-1 to 22-n and the FFT processing unit 23 are provided.

  The A / D conversion circuits 21-1 to 21-n convert the beat signals into digital data and store them in the subsequent buffers 22-1 to 22-n for each channel. Each of the buffers 22-1 to 22-n is divided into an ascending section buffer and a descending section buffer. Beat signals received by the receiving antennas 14-1 to 14-n in the rising section are stored in the rising section buffer, and beat signals received by the receiving antennas 14-1 to 14-n in the falling section are stored in the falling section buffer. .

  The FFT processing unit 23 performs FFT processing on the beat signal for each channel. The beat signal is converted into data of a relationship between frequency and power by FFT processing. The radio waves received by the receiving antennas 14-1 to 14-n contain components other than the reflected wave, but the frequency at which the power is peak can be estimated as the beat frequency by FFT processing.

  The microcomputer 18 is an information processing apparatus including a CPU, a ROM, a RAM, an input / output interface, and other general circuits. The microcomputer 18 performs characteristic processing of this embodiment described later.

[Distance, relative speed, direction]
The radar apparatus 100 calculates the distance and the relative speed based on the processing result processed by the FFT processing unit 23, and calculates the azimuth based on the phase of the beat signal having the peak frequency obtained by the FFT processing.

  FIG. 5 is an example of a diagram schematically illustrating frequencies of a transmission signal, a reception signal, and a beat signal. FIG. 5A shows a case where the relative speed of the host vehicle and the target is zero, and FIG. 5B shows a case where the speeds of the host vehicle and the target are different from each other.

The transmission signal S repeatedly increases and decreases in frequency. A frequency variation amount is ΔF, a center frequency is f ₀ , and 1 / fm is a repetition period of an ascending section and a descending section. From the time when the transmission antenna 12 transmits a transmission signal to the time when the reception antennas 14-1 to 14-n receive the reception signal R, the time required for radio waves to reciprocate at the speed of light C through the distance to the target. Is required. Therefore, when the relative speed is zero, there is a difference between the frequency of the transmission signal and the reception signal according to the distance from the target and fm. When this difference is reflected in the beat frequency fb and the relative speed is zero, the beat frequency fb1 in the rising section and the beat frequency fb2 in the falling section are equal.

  When the relative velocity is not zero, the frequency of the transmission signal S is Doppler shifted according to the relative velocity when reflected by the target, so the frequency of the reception signal R is more than the change due to the distance to the target and fm. (Or the change is reduced). Let the Doppler frequency be fd. When the host vehicle is approaching the target, the frequency of the consultation signal is shifted (increased) by the Doppler frequency fd in the ascending section, so the difference between the frequency of the received signal and the transmitting signal is small, and in the descending section, The difference in frequency between the received signal and the transmitted signal becomes large. Therefore, the beat frequency fb1 in the rising section and the beat frequency fb2 in the falling section are not equal.

If the beat frequency when the relative speed is zero is fr, the beat frequencies fb1 and fb2 can be expressed as follows.
fb1 = fr−fd
fb2 = fr + fd
When this is transformed, the following equation is obtained.
fr = (fb1 + fb2) / 2
fd = (fb2-fb1) / 2
The distance R and the relative speed V of the target can be obtained from the following expressions.
R = (C / (4 · ΔF · fm)) · fr
V = (C / (2 · f ₀ )) · fd
FIG. 6 is an example of a diagram illustrating the determination of the azimuth. FIG. 6A is a diagram schematically showing a received signal when a target is present in front of the radar apparatus 100. When the target is in front, there is almost no path difference between the target and the two receiving antennas 14-1 and 14-2. Are in phase. Note that the radar apparatus 100 processes the beat signal, but if the received signal has the same phase, the beat signal also has the same phase.

FIG. 6B shows a path difference when the target is present in the direction of the angle θ with respect to the front of the radar apparatus 100. A path difference x occurs between the target and the receiving antennas 1 and 2. When the distance between the antennas is d, the path difference x is d · sin θ. There is the following relationship between the phase difference Δφ and the direction θ. λ is the wavelength of the received signal.
Δφ = 2π × (d · sinθ / λ)
Therefore, if the phase difference Δφ is obtained, since λ and d are fixed values, the azimuth θ can be obtained from the following equation.
θ = arcsin (λ · Δφ / (2 · π · d))
The phase difference Δφ is obtained from the result of Fourier transform performed by the FFT processing unit 23 for each reception channel.

  As shown in FIG. 7, a power peak appears at a frequency with many frequency components by performing Fourier transform for each rising and falling interval of each reception channel. The frequency at which this peak is obtained is the beat frequency. As described above, the distance R and the relative speed V are obtained from the beat frequency fb1 in the rising section and the beat frequency fb2 in the falling section.

Further, the frequency function of the beat frequency is obtained as a complex number including a real number and an imaginary number by Fourier transform. Since the amplitude of the complex number (Z = a + ib) is √ (a ² + b ² ) and the phase is arctan (b / a), the phase of the beat frequency can be calculated for each receiving antenna. The difference between the phase φ of the reception channel 14-1 and the phase φ of the reception channel 14-2 is the phase difference Δφ.

  This method of obtaining the orientation is called a monopulse method. In this embodiment, the determination of the azimuth by the monopulse method has been described. However, methods for obtaining the azimuth are known such as DBF (Digital Beam Forming) processing, MUSIC (Multiple Signal Classification) analysis, Capon analysis, etc., and are limited to the monopulse method. is not.

[Function of microcomputer]
FIG. 8A shows an example of a functional block diagram of the radar apparatus 100. The radar apparatus 100 includes a position determination unit 31, a position change calculation unit 32, and a guardrail determination unit 33.

  The position determination unit 31 determines the position of the target from the distance R and the azimuth θ. FIG. 8B is an example of a diagram for explaining how to obtain the position. In the figure, the radar mounting position (for example, the left corner of the bumper) is the origin, the vehicle width direction is the X axis, and the traveling direction is the Y axis. Further, the reference position of the azimuth is Y axis, and the counterclockwise direction is positive.

  FIG.8 (c) shows an example of the front view of a guardrail. Since the guard rail in which the strip-shaped iron plate along the roadway is fixed to the plurality of poles uniformly reflects the radar, the radar apparatus 100 calculates that the target is present beside the shortest distance when viewed from the vehicle. Is often output. That is, with the Y axis as a reference, the azimuth is 90 degrees, and the distance R is about the same as the distance to the guardrail.

  The position determining unit 31 determines the x coordinate and the y coordinate of the target from the distance R and the azimuth θ. When a target is detected at an azimuth of 90 degrees and a distance R, the position (x, y) of the target is (−R, 0). For example, the position determination unit 31 determines the x coordinate and the y coordinate each time the FFT processing unit 23 performs the FFT process.

The position change calculation unit 32 calculates the amount of change in the x-coordinate and y-coordinate of the target from the target positions (x, y) for a predetermined number or a predetermined time. The position change calculation unit 32 calculates the following change amount, for example.
The difference between the maximum and minimum values of the x coordinate, the difference between the maximum and minimum values of the y coordinate,
-X-coordinate standard deviation, y-coordinate standard deviation-x-coordinate variance, y-coordinate variance The guardrail determination unit 33 compares the threshold value with the amount of change to determine whether the target is a guardrail or a guardrail. . The guardrail is a representative feature, and it is determined whether or not the feature reflects a radio wave extending in the road direction.

  FIG. 9 is a diagram illustrating a measurement example of a change in the position of the target. FIG. 9A shows a case where the target is a guardrail, and FIG. 9B shows a case where the target is a parallel running vehicle. FIG. 9 shows only the y coordinate. The y coordinate of the guardrail is substantially zero (straight side), and even if it is not zero, there is no change exceeding ± y1 [m]. The absolute value of the change is about half of y1.

  On the other hand, the y coordinate of the parallel running vehicle greatly varies around zero (right side). The distribution range of the y-coordinate is approximately ± y1 [m], but there are some measurement points exceeding ± y1 [m].

  Therefore, it is possible to determine whether the target is the guard rail or not by appropriately setting the threshold and the guard rail determination unit 33 comparing the threshold with the amount of change. When the absolute value of the difference between the maximum value and the minimum value is to be determined, the threshold value is, for example, y1 [m]. The measurements in FIGS. 9A and 9B are obtained by traveling about 10 [m], and it is possible to determine whether or not the vehicle is a guardrail only by traveling about 10 [m].

  Similarly, it can be determined whether or not the x-coordinate is a guardrail by comparing with the threshold value. Since the x coordinate is the distance between the left end of the host vehicle (radar device) and the guard rail, the center value does not become zero (the general distance depends on the driver and the width, for example, 0.5 to 2 [m 〕degree). However, since the values vary around the center value and the magnitude of the variation is greater for a parallel-running vehicle than for a guardrail, the determination can be made in the same manner.

  The guardrail determination unit 33 determines whether or not the target is a guardrail, paying attention to at least the y coordinate. You may focus only on x-coordinate or you may focus on both y-coordinate and x-coordinate. Whether to focus on the y-coordinate or the x-coordinate or both should be determined according to the characteristics and settings of the radar apparatus 100 (radar irradiation range, x-direction, y-direction distance accuracy, etc.). Good. When paying attention to both the y-coordinate and the x-coordinate, it may be determined as a guardrail only when one change amount exceeds the threshold value, or may be determined as a guardrail when both change amounts exceed the threshold value. .

The guardrail is not limited to that shown in FIG.
10A to 10D are examples of diagrams illustrating examples of the shape of the guardrail. In the guard rail of FIG. 10A, a plurality of pipes (three in the figure) along the roadway are fixed in parallel to a plurality of poles fixed perpendicular to the road surface. Compared to a guardrail with a fixed iron plate, the reflected area of radio waves is reduced, but the reflected area of radio waves is almost uniform while the vehicle is running. Easy to stabilize. Therefore, it can be similarly determined whether it is a guardrail. In some cases, a rope-like member is used instead of a pipe.

  Moreover, in the guardrail of FIG.10 (b), the shape of the pipe arrange | positioned along a roadway is curving. The design is given by the curved shape. Compared to a guardrail as shown in FIG. 10A, the reflected area of radio waves is not uniform during traveling of the vehicle, but the position (x, y) of the target is more stable than a parallel-running vehicle. . Therefore, it can be similarly determined whether it is a guardrail. In addition, the design which consists of a pipe of a straight line and a curve etc. may be given to the whole between perpendicular pipes, without using a pipe parallel to a roadway.

  Further, in the guard rail of FIG. 10C, two pipes along the roadway are fixed to a plurality of poles fixed perpendicularly to the road surface, and a plurality of pipes perpendicular to the road surface are provided between the two pipes. It is fixed. Depending on the density of the vertical pipe, the reflection area of the radio wave becomes substantially uniform during traveling of the vehicle, so that the position (x, y) of the target is more stable than that of the parallel traveling vehicle. Therefore, it can be similarly determined whether it is a guardrail.

  Further, in the guard rail of FIG. 10D, a net is stretched between a plurality of poles fixed perpendicular to the road surface. That is, a net is fixed to the pole instead of the iron plate in FIG. Also in this case, since the reflection area of the radio wave is substantially uniform during the traveling of the vehicle, the position (x, y) of the target is more stable than that of the parallel traveling vehicle. Therefore, it can be similarly determined whether it is a guardrail. In the case of a guardrail using a net, there may be no explicit vertical pole.

  The guardrails in FIG. 10 are all made of metal (for example, iron, aluminum, etc.). However, there is no intention to limit the material of the guard rail as long as it can reflect radio waves. Further, in this embodiment, the discrimination between the guardrail and the parallel running vehicle is described. However, for a feature (for example, a wall surface of a tunnel, a building, etc.) that continuously reflects radio waves even when the vehicle runs. However, it can be distinguished from a parallel running vehicle.

[Operation procedure]
FIG. 11 is an example of a flowchart illustrating a procedure in which the radar apparatus 100 according to the present embodiment determines whether or not a target is a guardrail. The procedure of FIG. 11 is repeatedly executed every time a beat signal is obtained from each channel.

  As described above, in the radar apparatus 100, the reception antenna receives (captures) the reflected wave, and the FFT processing unit 23 performs the FFT processing to generate the beat signal. Then, the distance R, the relative speed V, and the direction are calculated from the beat signal (S10).

  Next, the position determining unit 31 calculates the position (x, y) of the target from the distance R and the azimuth (S20).

  The position change calculation unit 32 calculates the amount of change in position when a predetermined number or positions (x, y) of a predetermined time or more are obtained (S30).

  And the guardrail determination part 33 determines whether the variation | change_quantity of the position of a target is less than a threshold value (S40). The threshold value is determined in each of the x direction and the y direction. Here, it is determined whether or not the amount of change is less than the threshold value in both the x direction and the y direction.

  When the amount of change in the position of the target is not less than the threshold (No in S40), the guardrail determination unit 33 determines that the target is not a guardrail (S60). In this case, the radar apparatus 100 transmits the distance R, the relative speed V, and the direction θ to the driving support ECU 200.

  When the amount of change in the position of the target is less than the threshold (Yes in S40), the guardrail determination unit 33 determines that the target is a guardrail (S50). In this case, the radar apparatus 100 does not transmit the distance R, the relative speed V, and the direction θ to the driving support ECU 200. Therefore, since the driving assistance ECU 200 does not detect the presence of the target, the operation device is not operated. Therefore, it can suppress calling a driver's attention considering a guardrail as a parallel running vehicle. Note that the radar apparatus 100 may transmit to the driving support ECU 200 that the guardrail is detected together with the distance R, the relative speed V, and the direction θ, or alone.

  As described above, the radar apparatus 100 according to the present embodiment can distinguish features such as guardrails and parallel running vehicles by paying attention to the stability of the position of the target.

  In the present embodiment, a radar apparatus 100 that determines whether or not a target is a guardrail by focusing on the reflected power from the guardrail will be described.

  As described with reference to FIG. 7, the FFT processing unit 23 can acquire the power of the beat frequency by performing Fourier transform for each of the rising and falling intervals of the reception channels 1 and 2. Since this electric power is considered to correlate with the amount of reflection of millimeter waves reflected by the target, a target having a uniform reflection area such as a guardrail is more stable than a parallel running vehicle. Therefore, in this embodiment, it is determined whether or not it is a guardrail based on this power.

  FIG. 12 shows an example of a functional block diagram of the radar apparatus 100 of the present embodiment. In FIG. 12, the position determination unit 31 of the first embodiment is replaced with a reflected power determination unit 34, and the position change calculation unit 32 is replaced with a power change calculation unit 35.

  The reflected power determination unit 34 determines the reflected power of the target from the power of the beat frequency obtained by Fourier transform. For example, only peak values may be extracted and used as reflected power data, or power values at several to about 10 frequencies before and after the peak may be extracted, and an average thereof may be used as reflected power data.

The power change calculation unit 35 calculates the amount of change in reflected power from the reflected power data for a predetermined number or a predetermined time. The power change calculation unit 35 calculates the following change amount, for example.
・ Frequency component of reflected data ・ Average of difference between adjacent reflected power data ・ Difference between maximum and minimum reflected power ・ Standard deviation of reflected power ・ Dispersion of reflected power The guardrail determination unit 33 compares the threshold value and the amount of change. Then, it is determined whether the target is a guardrail (feature) or a guardrail (feature).

  Since the reflected power increases or decreases depending on the distance R to the target, the absolute value of the reflected power is affected by the distance R. Even if the distance R changes, the amount of change in the reflected power of the guardrail is small, and the amount of change in the reflected power of the parallel running vehicle is large. You may normalize by R. For example, the influence of the distance R included in the change amount can be reduced by dividing the reflected power data by the distance R.

  FIG. 13 is a diagram illustrating a measurement example of a change in reflected power. FIG. 13A shows a case where the target is a guardrail, and FIG. 13B shows a case where the target is a parallel running vehicle. The reflected power of the guardrail is distributed between P5 and P7, with P6 as the center. Further, the reflected power of the guardrail tends to change uniformly (it is difficult to decrease or increase), and there is a feature that the difference between the immediately preceding reflected power and the next reflected power is small.

  On the other hand, the center value of the reflected power of the parallel running vehicle is not clear, and the distribution range is wide as P2 to P7. Moreover, the reflected power of a parallel running vehicle tends to repeatedly decrease or increase, and there is a characteristic that the difference between the immediately preceding reflected power and the next reflected power is large. When the reflected powers of FIGS. 13A and 13B are compared, it can be said that the reflected power of the parallel running vehicle has more high frequency components than the reflected power of the guardrail.

  For this reason, paying attention to the high frequency component, the frequency component of the reflected power can be determined as a variation amount. In this case, the reflected power data is subjected to FFT to obtain the intensity for each frequency component, and the frequency at which the intensity shows a peak is compared with a threshold value. If this frequency is greater than or equal to the threshold, the target is a parallel running vehicle.

  Further, focusing on the high frequency component, the average difference between adjacent reflected power data may be used as a determination target as the amount of change. In this case, the reflected power of the guardrail and the parallel running vehicle can be determined by setting the threshold value to be less than one of the scales Pn (for example, about 30% to 100%).

  Further, the amount of change in the reflected power of the parallel running vehicle may be affected by the vehicle speed with respect to the road surface of the host vehicle. For example, there is an effect that the change amount of the parallel running vehicle increases or decreases as the vehicle speed increases. For this reason, it is also effective to classify the vehicle speed into, for example, 10 levels and set a threshold value for each level. By doing so, it becomes possible to accurately distinguish between the guardrail and the parallel running vehicle according to the vehicle speed.

  FIG. 14 is an example of a flowchart illustrating a procedure in which the radar apparatus 100 according to the present embodiment determines whether or not a target is a guardrail. The procedure in FIG. 14 is repeatedly executed every time a beat signal is obtained from each channel.

  As described above, the radar apparatus 100 generates a beat signal by the reception antenna receiving the reflected wave and the FFT processing unit 23 performing the FFT processing. Then, the distance R, the relative speed V, and the direction are calculated from the beat signal (S110).

  Next, the reflected power determination unit 34 calculates the power of the beat frequency as reflected power data (S120).

  When the reflected power data of a predetermined number or a predetermined time or more is obtained, the power change calculation unit 35 calculates the amount of change in the reflected power (S130).

  And the guardrail determination part 33 determines whether the variation | change_quantity of reflected electric power is less than a threshold value (S140).

  When the amount of change in reflected power is not less than the threshold (No in S140), the guardrail determination unit 33 determines that the target is not a guardrail (S160). In this case, the radar apparatus 100 transmits the distance R, the relative speed V, and the direction θ to the driving support ECU 200.

  When the amount of change in the reflected power is less than the threshold (Yes in S140), the guardrail determination unit 33 determines that the target is a guardrail (S150). In this case, the radar apparatus 100 does not transmit the distance R, the relative speed V, and the direction θ to the driving support ECU 200. Therefore, since the driving assistance ECU 200 does not detect the presence of the target, the operation device is not operated. Therefore, it can suppress calling a driver's attention considering a guardrail as a parallel running vehicle. Note that the radar apparatus 100 may transmit to the driving support ECU 200 that the guardrail is detected together with the distance R, the relative speed V, and the direction θ, or alone.

  As described above, the radar apparatus 100 according to the present embodiment can discriminate features such as a guardrail and a parallel running vehicle by paying attention to, for example, a high frequency component of the reflected power.

  In the present embodiment, a radar apparatus 100 capable of combining the determination of the first embodiment and the determination of the second embodiment will be described.

  FIG. 15 is an example of a functional block diagram of the radar apparatus 100 of the present embodiment. It has the functions of the radar apparatus 100 of the first and second embodiments. A description of each function is omitted.

  FIG. 16 is an example of a flowchart illustrating a procedure in which the radar apparatus 100 according to the present embodiment determines whether a target is a guardrail. The procedure of FIG. 16 is repeatedly executed every time a beat signal is obtained from each channel.

  As described above, the radar apparatus 100 generates a beat signal by the reception antenna receiving the reflected wave and the FFT processing unit 23 performing the FFT processing. Then, the distance R, the relative speed V, and the direction are calculated from the beat signal (S210).

  Next, the position determining unit 31 calculates the position (x, y) of the target from the distance R and the azimuth, and the reflected power determining unit 34 calculates the power of the beat frequency as reflected power data (S220).

  The position change calculation unit 32 calculates the amount of change in position when a predetermined number or positions (x, y) of a predetermined time or more are obtained, and the power change calculation unit 35 calculates reflected power data of the predetermined number or predetermined time or more. Is obtained, the amount of change in the reflected power is calculated (S230).

  Then, the guardrail determination unit 33 determines whether “α × change amount of target position + β × change amount of reflected power” is less than a threshold value (S240). α is a weight for the amount of change in position, and β is a weight for the amount of change in reflected power. Since whether the position or reflected power is likely to vary depends on the characteristics of the radar device 100 (position variation tendency, reflected power variation tendency, etc.) and the scene (vehicle speed, country / region, weather, etc.), α , Β can be determined according to the characteristics of the radar device 100 and the scene.

FIG. 17 is a diagram showing an example of weights α and β set according to the scene. In FIG. 17A, α and β can be switched according to whether the vehicle speed is equal to or higher than the vehicle speed V ₀ . In this way, appropriate weighting can be performed according to the vehicle speed. In FIG. 17B, α and β are switched for each of rain, fog, and other weather conditions. Since millimeter wave radar may have low detection accuracy due to rain or fog, appropriate weighting is possible according to the weather. In FIG. 17C, α and β are switched according to the country / region. By doing so, appropriate weighting is possible in cold regions with a lot of snow and fog, and in countries and regions where the material and shape of the guardrail are special.

  Each of these scenes can be specified by a wheel speed sensor, GNSS (Global Navigation Satellite Systems) position information, a raindrop sensor, or the like.

  The guardrail determination unit 33 determines whether or not “α × target position change amount + β × reflected power change amount” is less than a threshold value (S240). The subsequent processing is the same as in the first and second embodiments.

  As described above, the radar apparatus 100 according to the present embodiment can discriminate features such as guardrails and parallel running vehicles by paying attention to the stability of the position and the high-frequency component of the reflected power.

DESCRIPTION OF SYMBOLS 12 Transmission antenna 14-1-14-n Reception antenna 18 Microcomputer 23 FFT processing part 31 Position determination part 32 Position conversion calculation part 33 Guardrail determination part 34 Reflected power determination part 35 Power change calculation part 100 Radar apparatus

Claims (6)

An object detection device that transmits radio waves to the periphery of a vehicle and detects the presence of an object based on a reflected wave reflected from the object around the vehicle,
Reflected power specifying means for specifying the magnitude of the reflected power of the reflected wave from the object;
Other vehicle detection means for detecting that the object is another vehicle based on the fluctuation of the reflected power;
An object detection apparatus having Having position specifying means for analyzing the reflected power of the reflected wave and specifying the relative position of the object with respect to the host vehicle,
The other vehicle detection means weights each of the reflected power fluctuations and the relative position fluctuations according to a traveling situation, and detects that the object is the other vehicle.
The object detection apparatus according to claim 1.   3. The object detection device according to claim 1, wherein the other vehicle detection unit detects that the object is another vehicle when the frequency of the reflected power fluctuation is equal to or higher than a first threshold value.   3. The object detection device according to claim 1, wherein the other vehicle detection unit detects that the target is another vehicle when the amount of change in the reflected power is equal to or greater than a second threshold value.   The other vehicle is a parallel running vehicle in which the front portion of the other vehicle is behind the host vehicle or at least a part of the vehicle body is superimposed in the vehicle length direction of the host vehicle and the relative speed with the host vehicle is substantially zero. The object detection apparatus according to claim 1, wherein the object detection apparatus is provided.   The object detection according to any one of claims 1 to 5, wherein the other vehicle detection means outputs detection information of the object only when it is detected that the object is the other vehicle. apparatus.

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