JP7045648B2 - Vehicle object detector - Google Patents

Description

The present disclosure relates to an object detection device for a vehicle.

Patent Document 1 describes an object detection device for a vehicle. This vehicle is equipped with a millimeter wave radar sensor and a CPU. The millimeter wave radar sensor sends a transmitted wave, which is a continuous electromagnetic wave (FM-CW) in the millimeter wave band with frequency modulation of a triangular wave, toward a predetermined angle in the traveling direction from the front end of the vehicle at regular time intervals. It fires at the frequency and receives the received wave, which is the reflected wave from the object existing in front of the vehicle, and detects the object. Subsequently, a beat signal is generated by mixing the transmitted wave and the received wave, and the generated beat signal is frequency-analyzed by a fast Fourier transform (FFT). The object information calculation processing unit of the CPU combines the peak frequency Fu on the up side and the peak frequency Fd on the down side for a plurality of objects detected by the millimeter-wave radar sensor, thereby increasing the distance L between the object and the vehicle, respectively. Calculate the relative velocity V.

Japanese Unexamined Patent Publication No. 2012-185084

However, the object detection device described in Patent Document 1 for a vehicle provided with an automatic braking system or the like that automatically decelerates the vehicle when the distance to the object (object) in front of the vehicle becomes less than a predetermined distance. When is applied, the object detection device does not detect the height of the object, so that the object is placed above the vehicle and is an upper structure that can slip through, but the vehicle and the upper structure When the distance becomes less than or equal to the predetermined distance, the upper structure may be determined as an obstacle (erroneous detection), and unnecessary control such as deceleration of the vehicle speed may be performed. If a camera or the like that captures the front of the vehicle is provided in order to prevent such false detection, the number of parts may increase and the processing may become complicated.

Therefore, an object of the present disclosure is to provide a vehicle object detection device capable of detecting that the structure is an upper structure and suppressing erroneous detection with a simple configuration.

In order to solve the above problems, the first aspect of the present invention is when a frequency-modulated electromagnetic wave is irradiated in front of the traveling direction of the own vehicle as a transmitted wave, and the irradiated transmitted wave is reflected by an object in front of the own vehicle. It is a vehicle object detection device that can receive the reflected wave of the above as a received wave and measure the distance and relative speed from the own vehicle to a predetermined object based on the beat signal generated by mixing the transmitted wave and the received wave. Further, it is provided with a distance intensity information generation means, a frequency analysis means, and a determination means. The distance strength information generating means generates distance strength information indicating a change in signal strength for each unit distance from the beat signal. The frequency analysis means takes the distance intensity information within a predetermined distance from the own vehicle among the distance intensity information generated by the distance intensity information generation means as the target information, and frequency-analyzes the target information. The determination means determines whether or not the predetermined object is an upper structure arranged above the predetermined reference height position based on the analysis information frequency-analyzed by the frequency analysis means.

In the above configuration, the distance intensity information generating means generates the distance intensity information indicating the change in the signal intensity for each unit distance from the beat signal, and the frequency analysis means has the range of the predetermined distance from the own vehicle in the distance intensity information. The distance intensity information in the inside is used as the target information, and the target information is frequency-analyzed. When a radar that transmits and receives electromagnetic waves (for example, a millimeter wave radar) is installed at a predetermined height position on the front surface of the vehicle, the characteristic of the analysis information obtained by frequency-analyzing the above target information (for example, a strong spectrum) is the height position. Since it differs for each different object, the determination means determines whether or not the object is an upper structure arranged above the reference height position based on the characteristics of the analysis information frequency-analyzed by the frequency analysis means. It can be determined. In this way, it is possible to determine whether or not the structure is an upper structure by a radar that transmits and receives electromagnetic waves, and since a camera or the like that captures the front of the vehicle is not required, it is possible to determine that the structure is an upper structure with a simple configuration. It can be detected and false detection can be suppressed.

The second aspect of the present invention is the object detection device of the first aspect, and the determination means is based on the detection peak frequency which is the peak frequency within the predetermined target range of the analysis information. It is determined whether or not the object of is an upper structure.

Here, in the analysis information analyzed by the frequency analysis means, a strong spectrum in a low frequency region is likely to be generated regardless of the height position of the object. In the above configuration, the determination means determines whether or not the predetermined object is an upper structure based on the detection peak frequency within the predetermined target range of the analysis information. Therefore, by setting the range excluding the strong spectrum generated regardless of the height position of the object to the target range (for example, the range above the predetermined frequency or the range below the predetermined intensity), the height of the object is set. The characteristics of the analysis information depending on the position are clarified, and the determination accuracy of the determination means can be improved. In addition, the peak frequency within the target range excluding the strong spectrum that occurs regardless of the height position of the object tends to be higher as the height position of the object is higher, so the object is based on the detected peak frequency. Can be determined whether or not is an upper structure.

The third aspect of the invention is the object detection device of the second aspect, which comprises a storage means. The storage means frequency-analyzes the distance intensity information within the range of the predetermined distance when the object at the reference height position is irradiated with the transmitted wave, and within the target range of the frequency-analyzed analysis information. The threshold value set based on the reference peak frequency, which is the peak frequency of the above, is stored in advance. When the detection peak frequency is higher than the threshold value, the determination means determines that the predetermined object is an upper structure.

In the above configuration, the determination means determines that the predetermined object is an upper structure when the detection peak frequency is higher than the threshold value stored in advance in the storage means. The threshold is determined by frequency-analyzing the distance intensity information within the range of the predetermined distance when the object at the reference height position is irradiated with the transmitted wave, and within the target range of the frequency-analyzed analysis information. It is set based on the reference peak frequency, which is the peak frequency. As described above, the peak frequency within the above target range excluding the strong spectrum generated regardless of the height position of the object in the analysis information tends to be higher as the height position of the object is higher. By setting a threshold value based on the reference peak frequency corresponding to the object at the reference height position and comparing the detection peak frequency with the threshold value by the determination means, it is possible to determine whether or not the structure is an upper structure. False positives can be suppressed.

In addition, the peak frequency obtained by frequency-analyzing the target information of the distance strength information indicating the signal strength for each unit distance is the theory even if the speeds of objects having the same height are different if the conditions other than the speed are the same. Since the values are substantially the same, the threshold value of the reference height position can be easily set.

A fourth aspect of the present invention is the object detection device of the third aspect, wherein the storage means stores in advance a plurality of threshold values corresponding to a plurality of distance ranges different from each other. When the detection peak frequency is higher than the threshold value corresponding to the predetermined distance range of the target information among the plurality of threshold values, the determination means determines that the predetermined object is an upper structure.

In the above configuration, the storage means stores in advance a plurality of threshold values corresponding to a plurality of different distance ranges of the object at the reference height position, and the determination means determines the predetermined distance of the target information among the plurality of threshold values. The threshold value corresponding to the range is compared with the detected peak frequency to determine whether or not the structure is an upper structure. Therefore, for example, after determining whether or not the upper structure is in the first distance range (140 m to 120 m, etc.), is the upper structure in the second distance range (120 m to 100 m, etc.)? Since it can be determined again whether or not it is a superstructure, it can flexibly respond to an object that enters the detection range in front of the vehicle or moves out of the detection range. Can be determined.

According to the present disclosure, it is possible to detect that the structure is an upper structure and suppress erroneous detection with a simple configuration.

It is a block diagram of the automatic braking system including the object detection device which concerns on one Embodiment of this invention. It is a table which shows the correspondence relationship between a distance range and a threshold value. It is explanatory drawing of the multipath relationship between a millimeter wave radar apparatus and an object. It is a figure which shows the relationship between the distance and the signal strength. It is explanatory drawing of the result of frequency analysis of the distance intensity information. It is a flowchart for demonstrating automatic braking processing. It is a flowchart for demonstrating the height determination process.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a vehicle (own vehicle) 1 equipped with an automatic braking system 40 including an object detection device 10 according to the present embodiment. As shown in FIG. 1, the vehicle 1 according to the present embodiment includes a millimeter-wave radar device 11, an ECU (Electronic Control Unit) 20, and a brake 2. In the automatic braking system 40 of the present embodiment, the first collision margin time TTC (Time to Collection) obtained by dividing the distance L between the vehicle 1 and the object in front of the vehicle 1 by the relative speed V is set in advance. When the predetermined time t1 or less is reached, the brake 2 is controlled to slowly decelerate the vehicle 1, and then the brake is applied when the second predetermined time t2 or less, which is shorter than the first predetermined time t1. 2 is controlled to stop the vehicle 1 to avoid a collision with an object. That is, a relatively long time during which the vehicle 1 can be stopped with a margin is set in the first predetermined time t1, and the vehicle 1 is stopped in the second predetermined time t2 while avoiding a collision with an object. The minimum required time is set to make it work. In the present embodiment, the automatic braking system 40 controls the brake 2 to slowly decelerate the vehicle 1 when the collision margin time TTC becomes the first predetermined time t1 or less. The brake 2 In addition to the control of the brake 2 or the control of the brake 2, the automatic braking system 40 may issue an alarm to the driver by sound or the like.

The millimeter-wave radar device 11 is an FSK-type millimeter-wave radar device 11 having a signal generation unit 12, an oscillator 13, a transmitting antenna 14, a receiving antenna 15, a mixer 16, and an A / D converter 17. The transmitting antenna 14 and the receiving antenna 15 are arranged at a predetermined installation height position (for example, a height position of 0.8 m from the road surface) of the front end portion of the vehicle 1. The signal generation unit 12 generates a signal that is a continuous electromagnetic wave in the millimeter wave band. The oscillator 13 generates a signal having two frequencies from the signal generated by the signal generation unit 12. The signal generated in the oscillator 13 is distributed to the transmitting antenna 14 and the mixer 16 as a transmitting wave. The millimeter-wave radar device 11 alternately switches signals of two frequencies generated by the oscillator 13 and irradiates the signal from the transmitting antenna 14 in front of the traveling direction of the vehicle 1 as a transmitted wave. The transmitted wave is a continuous wave that is alternately switched to signals having two frequencies, fu and fd, centered on the center frequency _f0 . The receiving antenna 15 receives the reflected wave when the transmitted wave emitted from the transmitting antenna 14 is reflected by the object in front of the vehicle 1 as the received wave. The received wave is received with a delay with respect to the transmitted wave according to the distance between the vehicle 1 and the object, and is shifted in the vertical direction (frequency direction) with respect to the transmitted wave due to the Doppler effect. The mixer 16 mixes the transmitted wave from the oscillator 13 and the received wave from the receiving antenna 15 to generate a beat signal. The beat signal generated by the mixer 16 is input to the A / D converter 17 via a switch (not shown), a filter (not shown), or the like. The A / D converter 17 A / D-converts the beat signal from the mixer 16 side into a digital signal in synchronization with the sampling signal, and sequentially converts the beat signal into a digital signal in the storage unit 21 described later of the ECU 20 as the signal strength for each unit time. Remember. That is, the beat signal is information indicating a change in signal strength with time.

The ECU 20 has a storage unit 21 and a CPU 22, and controls the brake 2 according to the result of the collision margin time TTC and the height determination of the object described later.

The storage unit 21 is composed of a recording medium such as a ROM (Read Only Memory) 23 or a RAM (Random Access Memory) 24, for example.

The ROM 23 includes various programs (including an automatic control program and a height determination program) read by the CPU 22 and various data (the first predetermined time t1, the second predetermined time t2, and a plurality (this) described later. In the embodiment, three threshold values k1 to k3 and the like are stored in advance. The various data stored in the ROM 23 are set based on the measured values and theoretical values obtained by experiments, simulations, calculations, and the like. Further, these data may be stored in a state of being included in each program.

The threshold values k1 to k3 stored in the ROM 23 are the specifications of the millimeter-wave radar device 11, the predetermined installation height position where the millimeter-wave radar device 11 is installed, and the predetermined height as a reference for determining the height. It is a theoretical value calculated by determining a position (hereinafter referred to as a reference height position), and is a plurality of values from the vehicle 1 to the object (in the present embodiment, as shown in FIG. 2). It is stored in the ROM 23 in correspondence with each of the distance ranges M1 to M3 (hereinafter, simply referred to as distance ranges M1 to M3) of (3). Specifically, the threshold value k1 is associated with the distance range M1 (range of 80 m or more and less than 100 m in this embodiment), and the threshold value k2 is associated with the distance range M2 (range of 100 m or more and less than 120 m in this embodiment). Corresponding, the threshold value k3 is associated with the distance range M3 (in this embodiment, the range of 120 m or more and less than 140 m) and stored in the ROM 23.

Next, a method of setting the threshold values k1 to k3 will be described with reference to FIG. FIG. 3 is an explanatory diagram of a case where a transmitted wave and a received wave propagate in a plurality of paths (multipath). As shown in FIG. 3, a position L away from the millimeter wave radar device 11 in which the transmitting antenna 14 and the receiving antenna 15 are arranged at the predetermined installation height position h and a predetermined height position in front of the vehicle 1. When transmitting a transmitted wave to an object X arranged in H and receiving a received wave from the object X, the path of the transmitted wave and the received wave includes a direct path R _AB and a road surface reflection path R _ACB . There is. Generally, the radar equation for obtaining the received power P is expressed by the following equation (1).

ここで、Ｐｔは送信電力、Ｇｔは送信アンテナゲイン、Ｇｒは受信アンテナゲイン、λはミリ波の波長、σは反射断面積をそれぞれ示す。

Here, Pt indicates the transmission power, Gt indicates the transmission antenna gain, Gr indicates the reception antenna gain, λ indicates the wavelength of the millimeter wave, and σ indicates the reflection cross section.

The radar equation (2) in the case where the above-mentioned transmitted wave and received wave propagate in a plurality of paths (direct path R _AB and road surface reflection path R _ACB ) is described below using the above radar equation (1). It is represented by the equation (2).

ここで、Ｋはクーロン定数、φは経路長差による位相差、ρは路面の反射率、Ｒ_ＡＢはＡ－Ｂ間の経路長、Ｒ_ＡＣＢはＡ－Ｃ－Ｂ間の経路長（Ｒ_ＡＣ＋Ｒ_ＣＢ）をそれぞれ示す。Ｒ_ＡＢ及びＲ_ＡＣＢは、ミリ波レーダ装置１１の設置高さ位置ｈ、対象物Ｘの高さ位置Ｈ、及びミリ波レーダ装置１１と対象物Ｘとの距離Ｌによって定まる。

Here, K is the Coulomb constant, φ is the phase difference due to the path length difference, ρ is the reflectance of the road surface, R _AB is the path length between AB, and R _ACB is the path length between A and B ( _{RA AC} ). + R _CB ) are shown respectively. R _AB and R _ACB are determined by the installation height position h of the millimeter wave radar device 11, the height position H of the object X, and the distance L between the millimeter wave radar device 11 and the object X.

When setting the threshold value k1 corresponding to the distance range M1, first, each constant in the radar equation (2) is set based on the specifications of the millimeter wave radar device 11. Then, the installation height position h is set to the installation height position of the millimeter wave radar device 11 (for example, 0.8 m from the road surface), and the height position H of the object X is set to the reference height position (for example, 5 m from the road surface). ), The change in the received power P (signal strength) with respect to the distance L within the distance range M1 (for example, a range of 80 m or more and less than 100 m) (hereinafter referred to as distance strength information) is plotted (FIG. 4). See the broken line in the middle distance range M1). Next, the distance intensity information within the distance range M1 is frequency-analyzed by fast Fourier transform (FFT) (see FIG. 5), and the peak in the region r2 (hereinafter referred to as the target range r2) having a predetermined frequency f1 or higher. The frequency (reference peak frequency (f3 in FIG. 5)) is set as the threshold k1. Similar to the threshold value k1, the threshold values k2 and k3 corresponding to the distance ranges M2 and M3 also perform frequency analysis of the distance intensity information within the distance ranges M2 and M3, and set the peak frequency (reference peak frequency) of the target range r2 to the threshold value k2. , K3. That is, the threshold values k1 to k3 are within the predetermined distance range (M1, M2, M3) when the transmitted wave is applied to the object (object X) at the reference height position H in front of the vehicle 1. The distance intensity information is frequency-analyzed, and is set based on the reference peak frequency, which is the peak frequency within the target range r2 of the frequency-analyzed analysis information. In the present embodiment, the reference height position H is set higher than the height of the vehicle 1, and the upper structure is an object through which the vehicle 1 can pass below. Further, the predetermined frequency f1 is a value set by an experiment, a simulation, or the like, and is set to a value equal to or higher than an upper limit value in a frequency region in which a strong spectrum is likely to be generated regardless of the height position of the object.

The RAM 24 is preset with a data storage area for readable and writable storage of various data such as beat signals digitally converted by the A / D converter 17. Further, the RAM 24 functions as a program expansion area read from the ROM 23, a temporary storage area of the calculation result of the CPU 22, and the like, in addition to the temporary storage area of the various data.

As shown in FIG. 1, the CPU 22 executes an automatic control process and a height determination process by executing various programs (automatic control program and height determination program) stored in the ROM 23. The CPU 22 includes a distance / speed detection unit 25, a distance intensity information generation unit (distance intensity information generation means) 26, a frequency analysis unit (frequency analysis means) 27, a determination unit (determination means) 28, and a brake control unit 29. And have. That is, the CPU 22 includes an object detection device 10 that executes a height determination process. The function of the object detection device 10 may be extracted from the CPU 22 and provided in another information processing device.

The distance / speed detection unit 25 frequency-analyzes the beat signal digitally converted by the A / D converter 17, and the Doppler shift frequencies fus, fds and Doppler shifts of the received waves for the two frequency fu and fd components of the transmitted wave. The phase difference φ of both received waves is obtained by ) Or (4-b). When there are a plurality of objects in front of the vehicle 1, the distance L and the relative speed V between the vehicle 1 and the object are detected for each object.

ここで、Ｃは光速度、φは位相差、Δｆは送信波の周波数変調幅、ｆｕは高い方の送信波の周波数、ｆｄは低い方の送信波の周波数、ｆｕｓはｆｕに対する受信波のドップラーシフト周波数、ｆｄｓはｆｄに対する受信波のドップラーシフト周波数をそれぞれ示す。

Here, C is the optical velocity, φ is the phase difference, Δf is the frequency modulation width of the transmitted wave, fu is the frequency of the higher transmitted wave, fd is the frequency of the lower transmitted wave, and fus is the Doppler of the received wave with respect to fu. The shift frequency and fds indicate the Doppler shift frequency of the received wave with respect to fd, respectively.

The distance intensity information generation unit 26 uses information indicating changes in signal intensity over time using the distance L with the object (predetermined object) detected by the distance / speed detection unit 25 and the relative velocity V with the object. From the beat signal, which is, distance strength information indicating a change in signal strength for each unit distance (for example, 0.1 m) is generated. When there are a plurality of objects in front of the vehicle 1, the distance intensity information generation unit 26 generates distance intensity information for each object from the beat signal for each object. As shown in FIG. 4, the distance intensity information theoretically has a different waveform depending on the height position of the object. That is, the waveform of the distance intensity information theoretically becomes the same waveform when the height position of the object is the same, and becomes a different waveform when the height position of the object is different. In FIG. 4, the distance intensity information when the height position of the object is 1.5 m is shown by a solid line, and the distance intensity information when the height position of the object is 5 m is shown by a broken line.

When the distance L between the moving vehicle 1 and the object in front becomes the distance of the lower limit value of the distance range M1, M2, M3 (lower limit value 80m, 100m, 120m), the frequency analysis unit 27 raises the lower limit value. The distance intensity information of the distance range (distance range corresponding to the lower limit value) up to the distance of is used as the target information, and the frequency analysis of these target information is performed in the distance direction by the high-speed Fourier transform (FFT). That is, the frequency analysis unit 27 uses the distance intensity information of the distance ranges M1, M2, and M3 from the vehicle 1 among the distance intensity information generated by the distance intensity information generation unit 26 as the target information, and performs frequency analysis in the distance direction. When there are a plurality of objects in front of the vehicle 1, the frequency analysis unit 27 frequency-analyzes the target information of the distance intensity information for each object. As shown in FIG. 5, among the analysis information obtained as a result of frequency analysis, a strong spectrum is generated in the low frequency region r1 lower than the predetermined frequency f1 regardless of the height position of the object, and the predetermined frequency f1 is described. In the target range r2 having a frequency f1 or higher, a peak frequency that differs depending on the height position of the object tends to occur (see FIG. 5). That is, the peak frequency of the target range r2 of the analysis information is theoretically substantially the same for objects having the same height, even if the relative velocities V are different, if the conditions other than the relative velocities V are the same. .. In FIG. 5, the analysis information when the height position of the object is 1.5 m is shown by a solid line, and the analysis information when the height position of the object is 5 m is shown by a broken line.

The determination unit 28 is the above-mentioned analysis information among the analysis information frequency-analyzed by the frequency analysis unit 27 when the distance L between the traveling vehicle 1 and the object in front reaches the lower limit of the distance ranges M1, M2, and M3. The peak frequency in the target range r2 (hereinafter referred to as the detected peak frequency) is compared with the threshold value (k1 to k3) corresponding to the distance range (M1 to M3) of the analysis information. Then, when the detection peak frequency in the target range r2 of the analysis information frequency-analyzed by the frequency analysis unit 27 is higher than the threshold value, the determination unit 28 places the object at the reference height position (in this embodiment, a height of 5 m). It is determined that the structure is above the upper structure (position). When there are a plurality of objects in front of the vehicle 1, the determination unit 28 determines whether or not each object is an upper structure. The determination unit 28 stores the determination result in the RAM 24 of the storage unit 21 in correspondence with the object.

The brake control unit 29 calculates the collision margin time TTC by the following equation (5) using the distance L and the relative speed V with the object detected by the distance / speed detection unit 25, and the calculated collision margin time TTC is calculated in advance. When the time becomes t1 or less for the first predetermined time set and the determination unit 28 does not determine that the object is an upper structure, the brake 2 is controlled to decelerate. Further, when the calculated collision margin time TTC becomes equal to or less than the preset second predetermined time t2, the brake control unit 29 controls the brake 2 to stop the vehicle 1 and cause a collision with the object. To avoid.

ここで、ＴＴＣは衝突余裕時間、Ｌは車両１と対象物との距離、Ｖは車両１と対象物との相対速度を示す。なお、対象物が上方構造物であると判定されていない場合には、対象物が上方構造物ではないと判定されている場合の他に、対象物が上方構造物であるか否か不明である場合も含まれる。第１の所定時間ｔ１及び第２の所定時間ｔ２は、実験やシミュレーション等により求められる。

Here, TTC indicates the collision margin time, L indicates the distance between the vehicle 1 and the object, and V indicates the relative speed between the vehicle 1 and the object. If the object is not determined to be an upper structure, it is unclear whether the object is an upper structure or not, in addition to the case where the object is determined not to be an upper structure. In some cases it is included. The first predetermined time t1 and the second predetermined time t2 are obtained by experiments, simulations, and the like.

Next, the automatic control process and the height determination process executed by the CPU 22 will be described with reference to the flowcharts shown in FIGS. 6 and 7. In this embodiment, the automatic control process and the height determination process are executed separately.

The automatic control process is started at the start of the vehicle 1 and is repeatedly executed at predetermined time intervals. As shown in FIG. 6, when this process is started, the brake control unit 29 calculates the collision margin time TTC from the distance L and the relative speed V detected by the distance / speed detection unit 25 with the object. The collision margin time TTC and the second predetermined time t2 are compared (step S11). When the collision margin time TTC with the object is longer than the second predetermined time t2 (step S11: NO), the process proceeds to step S12. On the other hand, when the collision margin time TTC with the object is the second predetermined time t2 or less (step S11: YES), the brake 2 is controlled to stop the vehicle 1 to avoid the collision with the object (step S14). ).

In step S12, the collision margin time TTC with the object and the first predetermined time t1 are compared, and when the collision margin time TTC with the object is the first predetermined time t1 or less (step S12: YES), the step. Move to S13. On the other hand, when the collision margin time TTC with the object is longer than the first predetermined time t1 (step S12: NO), this process is terminated.

In step S13, the determination result of the object by the determination unit 28 is read from the storage unit 21, and when the object is not determined to be an upper structure (step S13: YES), the brake 2 is controlled to control the vehicle 1. Decelerate slowly. On the other hand, when it is determined that the object is an upper structure (step S13: NO), this process is terminated.

The height determination process is started when the vehicle 1 is started, and is repeatedly executed at predetermined time intervals. As shown in FIG. 7, when this process is started, the distance intensity information generation unit 26 receives a distance intensity indicating a change in signal intensity for each unit distance from a beat signal which is information indicating a change in signal intensity with time. Information is generated (step S21), and the process proceeds to step S22.

In step S22, the frequency analysis unit 27 sets the distance L between the moving vehicle 1 and the object in front to the distance of the lower limit value of the predetermined distance range M1, M2, M3 (for example, the lower limit value 120 m of the distance range M3). At that time, the distance intensity information in the predetermined distance range (for example, 140 m to 120 m (distance range M3)) among the distance intensity information up to that point is frequency-analyzed as the target information, and the process proceeds to step S23.

In step S23, the determination unit 28 performs frequency analysis by the frequency analysis unit 27 when the distance L between the traveling vehicle 1 and the object in front reaches the lower limit of the predetermined distance ranges M1, M2, and M3. Among the analyzed information, the detection peak frequency in the target range r2 having the predetermined frequency f1 or more is compared with the threshold value (for example, the threshold value k3) corresponding to the distance range (for example, the distance range M3) of the analysis information. The determination unit 28 determines that the object is an upper structure located above the reference height position when the detection peak frequency is higher than the threshold value, and determines that the object is an upper structure located above the reference height position, and when the detection peak frequency is equal to or less than the threshold value, the object object. Is not an upper structure. Then, the determination unit 28 stores the determination result in the RAM 24 of the storage unit 21.

In the object detection device 10 configured as described above, the distance intensity information generation unit 26 obtains distance intensity information indicating a change in signal intensity for each unit distance from a beat signal which is information indicating a change in signal intensity with time. The frequency analysis unit 27 generates the distance intensity information in the predetermined distance range M1, M2, M3 from the vehicle 1 among the distance intensity information generated by the distance intensity information generation unit 26, and sets these target information as the frequency. To analyze. The characteristics (for example, strong spectrum) of the analysis information obtained by frequency-analyzing the above-mentioned target information when the millimeter-wave radar device 11 is installed at a predetermined height position (for example, a height position of 0.8 m from the road surface) are shown in FIG. As shown in 5, since the height position tends to be different for each object having a different height position, the determination unit 28 determines that the object is from the reference height position based on the characteristics of the analysis information frequency-analyzed by the frequency analysis unit 27. Can also be determined whether or not it is an upper structure arranged above. In this way, the millimeter-wave radar device 11 can determine whether or not the structure is an upper structure. Therefore, for example, the structure is a simple structure without the need for a camera or the like for capturing the front of the vehicle 1. It is possible to detect that and suppress false detection.

Further, the determination unit 28 determines whether or not the object is an upper structure based on the detection peak frequency within the target range r2 having a predetermined frequency f1 or more in the analysis information frequency-analyzed by the frequency analysis unit 27. judge. The predetermined frequency f1 is set to be equal to or higher than the upper limit of the frequency region in which a strong spectrum is likely to be generated regardless of the height position of the object. That is, since the target range r2 for detecting the detection peak frequency is set to a range excluding the low frequency region where a strong spectrum is generated regardless of the height position of the object, analysis based on the height position of the object is performed. The characteristics of the information (difference in peak frequency) are clarified, and the determination accuracy of the determination by the determination unit 28 can be improved.

Further, the peak frequency in the target range r2 excluding the low frequency region where a strong spectrum is generated regardless of the height position of the object becomes higher as the height position of the object is higher, and is based on the detected peak frequency. It is possible to determine whether or not the object is an upper structure.

Further, the thresholds k1 to k3 are the above-mentioned analysis information among the analysis information obtained by frequency-analyzing the distance intensity information within the distance range M1 to M3 when the transmitted wave is applied to the object at the reference height position H. It is set based on the reference peak frequency, which is the peak frequency within the target range r2. As described above, the peak frequency within the target range r2 of the analysis information obtained by frequency analysis of the distance intensity information tends to be higher as the height position of the object is higher, so that the determination unit 28 detects it. By comparing the peak frequency with the threshold value (k1 to k3), it is possible to determine whether or not the object is an upper structure, and false detection can be suppressed.

Further, the peak frequency in the target range r2 of the analysis information obtained by frequency analysis of the distance intensity information in the predetermined distance range is such that the conditions other than the velocity V are the same among the objects having the same height. For example, even if the speed V is different, it is theoretically substantially the same, so that the threshold value of the reference height position can be easily set.

Further, the storage unit 21 stores in advance a plurality of threshold values k1 to k3 corresponding to the plurality of distance ranges M1 to M3 from the vehicle 1 to the object. Then, when the distance L between the moving vehicle 1 and the object in front becomes the distance of the lower limit value of the distance range M1, M2, M3, the determination unit 28 detects in the distance range corresponding to the lower limit value. The peak frequency is compared with the threshold value corresponding to the distance range to determine whether or not the structure is an upper structure. Therefore, for example, after determining whether or not the predetermined object is an upper structure in the distance range M3 (140 m to 120 m, etc.), the upper structure is formed in the distance range M2 (120 m to 100 m, etc.). Since it can be determined again whether or not the structure is present, whether or not the structure is an upper structure flexibly responds to an object that enters the detection range in front of the vehicle 1 or moves out of the detection range. It can be determined whether or not.

Further, in the present embodiment, the reference height position H is set higher than the height of the vehicle 1 (for example, 5 m), so that the viaduct or the traffic sign through which the vehicle 1 can pass below is set to the reference height position H. It can be determined that the upper structure is higher than the above. By appropriately setting the reference height position H in this way, it is possible to reliably determine whether or not the object in front of the vehicle 1 is an upper structure such as a viaduct that can pass at least below. .. For example, it is possible to reliably distinguish between a preceding vehicle (another vehicle) having a height position of about 1.5 m and an upper structure such as a viaduct having a height position of 5 m or more.

Further, in the present embodiment, the distance intensity information generation unit 26, the frequency analysis unit 27, and the determination unit 28 for executing the height determination process detect the distance L and the relative speed V between the vehicle 1 and the object. It is provided in the ECU 20 of the millimeter wave radar device 11 for this purpose. In this way, since the algorithm for the height determination process can be incorporated into the ECU 20 of the existing millimeter wave radar device 11, the existing millimeter wave radar device 11 can be easily provided with the height determination function. can. Further, even when an object detection device capable of executing the height determination process is provided separately from the ECU 20 of the existing millimeter wave radar device 11, the vehicle can be easily used by using the existing millimeter wave radar device 11. An object detection device can be provided in 1.

Therefore, according to the present embodiment, it is possible to detect that the structure is an upper structure and suppress erroneous detection with a simple configuration.

Further, since false detection can be suppressed, an upper structure that allows the object to pass below when the collision margin time TTC with the object in front of the vehicle 1 becomes t1 or less for the first predetermined time. It is possible to avoid unnecessary control such that the automatic braking system 40 decelerates the vehicle 1 in spite of being a thing.

In the present embodiment, the distance range M1 is set to a range of 80 m or more and less than 100 m, the distance range M2 is set to a range of 100 m or more and less than 120 m, and the distance range M3 is set to a range of 120 m or more and less than 140 m. It is possible to set a desired distance range instead of a thing.

Further, in the present embodiment, the plurality of distance ranges M1 to M3 are set to a range that does not overlap each other, but the distance ranges M1 to M3 may be a range that partially overlaps each other. For example, the distance range M1 may be set to 100 m or more and 120 m or less, the distance range M2 may be set to 110 m or more and 130 m or less, and the distance range M3 may be set to 120 m or more and 140 m or less.

Further, in the present embodiment, a plurality of threshold values (k1 to k3) corresponding to a plurality of distance ranges (M1 to M3) are set, and whether or not the object is an upper structure is determined for each of the plurality of distance ranges. Judgment was made, but it is not limited to this. For example, one threshold value corresponding to one distance range may be set, and it may be determined whether or not the object is an upper structure in the distance range.

Further, in the present embodiment, the threshold value (k1 to k3) is calculated using the above formula (2), but the above formula (2) is an example, and the threshold value may be calculated using another formula. Further, in the present embodiment, the threshold value is calculated by calculation, but the threshold value may be derived by simulation on a computer, or the threshold value may be derived by experiment.

Further, in the present embodiment, the peak frequency of the reference height position H is set as the threshold value, but the threshold value is not limited to this and may be set based on the peak frequency of the reference height position H. For example, a frequency slightly higher than the peak frequency of the reference height position H may be set as the threshold value.

Further, in the present embodiment, a threshold value is set for an object (object X) at the reference height position H in front of the vehicle 1, but the reference height is set for each predetermined lateral angle (azimuth) in front of the vehicle 1. The threshold of the distance range with respect to the object at the position H may be set. In this case, the millimeter-wave radar device 11 may detect the azimuth angle of the object and compare the threshold value corresponding to the detected azimuth angle with the detected peak frequency.

Further, in the present embodiment, since the strong spectrum generated regardless of the height position of the object is not used as the peak frequency, the target range r2 for detecting the peak frequency is set to a region of a predetermined frequency f1 or higher. However, for example, the target range r2 may be set to a region equal to or lower than the intensity of a predetermined spectrum.

Further, in the present embodiment, the reference height position H is set higher than the height of the vehicle 1, but the reference height position H is not limited to this. That is, a desired reference height position H can be set, and the height of the object can be determined with the reference height position H as a reference.

Although the present invention has been described above based on the above-described embodiment, the present invention is not limited to the contents of the above-described embodiment, and can be appropriately modified without departing from the present invention. That is, it goes without saying that all other embodiments, examples, operational techniques, and the like made by those skilled in the art based on this embodiment are included in the scope of the present invention.

For example, in the above embodiment, the object detection device 10 for determining whether or not the structure is an upper structure based on the beat signal generated by the FSK type millimeter wave radar device 11 has been described, but the FM-CW type millimeter wave has been described. It may be an object detection device that determines whether or not it is an upper structure based on a beat signal generated by a radar device.

Further, in the above embodiment, the object detection device 10 is applied to the vehicle 1 equipped with the automatic braking system 40, but the object detection device 10 is not limited to this. The object detection device 10 may be applied to a vehicle 1 equipped with an inter-vehicle distance warning device that issues an alarm, an ACC (Adaptive Cruise Control) that travels at a constant speed while ensuring a predetermined inter-vehicle distance, and the like.

1: Vehicle (own vehicle)
10: Object detection device 20: ECU
21: Storage unit (memory means)
22: CPU
26: Distance strength information generation unit (distance strength information generation means)
27: Frequency analysis unit (frequency analysis means)
28: Judgment unit (judgment means)

Claims (1)

The frequency-modulated electromagnetic wave is irradiated as a transmission wave in front of the traveling direction of the own vehicle, and the reflected wave when the irradiated transmission wave is reflected by the object in front of the own vehicle is received as a reception wave, and the transmission wave and the said An object detection device for a vehicle capable of measuring the distance and relative speed from the own vehicle to a predetermined object based on a beat signal generated by mixing the received wave.
From the beat signal, a distance strength information generating means for generating distance strength information indicating a change in signal strength for each unit distance, and a distance strength information generating means.
Of the distance intensity information generated by the distance intensity information generating means, the frequency analysis means for frequency-analyzing the target information by using the distance intensity information within a predetermined distance from the own vehicle as the target information.
The predetermined object is arranged above the predetermined reference height position based on the detection peak frequency which is the peak frequency within the target range of the predetermined frequency or higher in the analysis information frequency-analyzed by the frequency analysis means. A determination means for determining whether or not the structure is an upper structure,
When the object at the reference height position is irradiated with the transmitted wave, the distance intensity information within the predetermined distance range is frequency-analyzed, and the peak frequency within the target range of the frequency-analyzed analysis information is used. A storage means for pre-storing a threshold set based on a certain reference peak frequency is provided .
The storage means pre-stores a plurality of the threshold values corresponding to a plurality of distance ranges different from each other.
When the detection peak frequency is higher than the threshold value corresponding to the predetermined distance range of the target information among the plurality of threshold values, the determination means determines that the predetermined object is the upper structure. do
A vehicle object detection device characterized by this.

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