JP2012229948A - Pedestrian detection device, pedestrian detection method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pedestrian detection device, a pedestrian detection method and a program capable of more reliably detecting a pedestrian.SOLUTION: A pedestrian detection device comprises: a transmission section 11 which transmits a radio wave in an anterior direction of an own vehicle; a receiving section 12 which receives a reflected radio wave, the radio wave reflected from a target existing ahead of the own vehicle; a storage section 22 which preliminarily stores a pedestrian reflected radio wave property, a property of the radio wave reflected from the pedestrian; and an information processing section 21 which determines whether or not the target reflecting the radio wave is the pedestrian by comparing the property of the reflected radio wave received by the receiving section 12 with the pedestrian reflected radio wave property stored in the storage section. The pedestrian detection device can determine whether or not the target is the pedestrian regardless of presence or absence of a movement of the target as well as a moving direction of the target by determining whether or not the target reflecting the radio wave is the pedestrian through comparison between the property of the reflected radio wave received by the receiving section 12 and the pedestrian reflected radio wave property stored in the storage section 22.

Description

  The present invention relates to a pedestrian detection device, a pedestrian detection method, and a program suitable for use in a vehicle.

  In recent years, various driving support technologies for reducing the burden on the driver when driving a vehicle, and technologies for reducing collision damage when a vehicle collision is inevitable or close to it have been proposed. For example, a collision avoidance system using a target detection device such as a radar that detects a target existing in front of a vehicle using a 76 GHz band radio wave (hereinafter referred to as “millimeter wave”), or damage caused by a collision. A system for reducing the above has also been proposed (see, for example, Patent Document 1).

  In the case of the above-described collision avoidance system or damage reduction system, it is desirable to determine the type of target existing in front of the vehicle in order for the system to function effectively. In other words, it is desirable that the type of the target in front of the vehicle, for example, whether it is a vehicle or a human pedestrian, can be determined by a radar or the like.

  Specifically, since a pedestrian may cross the front of the vehicle, if it can be determined that the target in front of the vehicle is a pedestrian, It is desirable to perform control to issue a warning so as to pay attention to the pedestrian ahead. By performing such control, pedestrian safety can be ensured.

  In the obstacle detection device (radar) described in Patent Document 1, in principle, a target moving in a lateral direction (crossing direction) with respect to a traveling path of a vehicle is determined as a pedestrian. . Further, Patent Document 1 describes a technique for avoiding erroneous discrimination that occurs when discriminating as described above, that is, discriminating an object that is not a pedestrian as a pedestrian.

JP 2000-249754 A

  However, the obstacle detection device described in Patent Document 1 is not a pedestrian because it determines the type of target (whether it is a pedestrian) or not based on whether or not the vehicle travels laterally with respect to the travel path of the vehicle. There has been a problem that there is a high possibility that an object will be misidentified as a pedestrian. In other words, there is a problem that it is difficult to reliably detect a pedestrian walking along a traveling path or a pedestrian that is stopped.

  SUMMARY An advantage of some aspects of the invention is that it provides a pedestrian detection device, a pedestrian detection method, and a program that can detect a pedestrian more reliably.

In order to achieve the above object, the present invention provides the following means.
The pedestrian detection device according to the present invention includes a transmitter that transmits radio waves toward the front of the vehicle, and a reflected radio wave that is reflected by a target existing in front of the vehicle among the radio waves transmitted from the transmitter. , A pedestrian reflected radio wave characteristic that is a characteristic of the radio wave reflected by the pedestrian, and a reflected radio wave characteristic received by the receiving part are stored in the storage part. An information processing unit for determining whether or not the target reflecting the radio wave is the pedestrian by comparing with the pedestrian reflected radio wave characteristic is provided.

  According to the pedestrian detection device of the present invention, the target reflecting the radio wave is a pedestrian by comparing the characteristic of the reflected radio wave received by the receiving unit with the pedestrian reflected radio wave characteristic stored in the storage unit. A determination is made whether or not. Therefore, it can be determined whether or not the target is a pedestrian regardless of whether the target is moving or not.

  The characteristics of the reflected radio wave described above can exemplify the intensity of the reflected radio wave, a change in intensity, and the like. This characteristic changes based on various factors such as the material and shape of a target that reflects radio waves and the presence or absence of the shape change of the target itself. That is, the characteristic of the reflected radio wave when the target is a vehicle is different from the characteristic of the reflected radio wave when the target is a pedestrian. Pedestrians wear various articles that are more complicated in shape than structures such as vehicles and utility poles, whose shapes change greatly over time, and whose radio wave reflectivity varies greatly. . Therefore, the characteristic of the reflected radio wave in a pedestrian has a feature that the fluctuation of the reflected radio wave is severe compared to the characteristic of the reflected radio wave in a vehicle or the like. By paying attention to this point, it is possible to more reliably determine whether or not the target is a pedestrian.

  In the above invention, the characteristic of the reflected radio wave is the intensity of the reflected radio wave reflected by the target, and a predetermined intensity threshold value that is a value of the intensity of the reflected radio wave related to the pedestrian reflected radio wave characteristic is stored in the storage unit. It is desirable.

  Thus, by determining whether the target is a pedestrian based on the intensity of the reflected radio wave, it is possible to more reliably determine whether the target is a pedestrian. That is, when comparing a pedestrian and a structure such as a vehicle or a utility pole, the intensity of the reflected pedestrian when the radio wave having the same intensity is irradiated is weaker than the intensity of the reflected radio wave of the structure. Based on this characteristic, even a pedestrian who moves in the traveling direction of the vehicle or a pedestrian who is stationary can be easily distinguished from a structural part such as a vehicle or a power pole.

  In the above invention, the information processing unit walks the target reflecting the radio wave based on whether or not the intensity value of the reflected radio wave received by the receiving unit is equal to or less than a predetermined intensity threshold stored in the storage unit. It is desirable to determine whether or not the person is a person.

  In this way, a predetermined intensity threshold is set as a boundary between the intensity of the reflected radio wave from a pedestrian and the intensity of the reflected radio wave from a vehicle that is not a pedestrian, and the intensity value of the reflected radio wave reflected by the target is By determining the target as a pedestrian if it is equal to or less than a predetermined intensity threshold, it is possible to easily and reliably distinguish between a pedestrian and a non-pedestrian.

  In the above invention, the storage unit stores in advance a plurality of predetermined intensity threshold values related to at least the distance from the vehicle to the target, the information processing unit acquires information on the distance from the vehicle to the target, and the receiving unit Whether the target reflecting the radio wave is a pedestrian based on whether the value of the intensity of the reflected radio wave received by the vehicle is equal to or greater than a predetermined intensity threshold corresponding to the distance from the vehicle to the target It is desirable to perform the determination.

  In this manner, a plurality of predetermined intensity thresholds that differ according to at least the distance from the vehicle to the target are prepared in advance, and a plurality of predetermined intensity thresholds corresponding to the distance from the vehicle to the target acquired by the information processing unit are provided. If the value of the intensity of the reflected radio wave selected from the predetermined intensity threshold and reflected by the target is equal to or less than the selected predetermined intensity threshold, the target is determined to be a pedestrian, and the pedestrian walks. Can be easily and reliably distinguished from non-persons. More specifically, since the intensity of the reflected radio wave from the target varies greatly depending on the distance from the vehicle to the target, a predetermined intensity threshold corresponding to the distance from the vehicle to the target is used. Thus, it is possible to reliably distinguish between a pedestrian and a non-pedestrian.

  In the above invention, the characteristic of the reflected radio wave is the value of the fluctuation range of the intensity of the reflected radio wave reflected by the target, and the storage unit is the value of the fluctuation range of the intensity of the reflected radio wave according to the pedestrian reflected radio wave characteristic. A predetermined fluctuation threshold value is stored, and the information processing unit determines whether the value of the fluctuation range of the intensity of the reflected radio wave received by the receiving unit is equal to or larger than the predetermined fluctuation threshold value stored in the storage unit. It is desirable to determine whether the target reflecting the radio wave is a pedestrian.

  Thus, by determining whether the target is a pedestrian based on the fluctuation range of the intensity of the reflected radio wave, it is possible to reliably determine whether the target is a pedestrian. That is, when comparing a pedestrian and a structure such as a vehicle, the intensity of the reflected radio wave greatly varies with time. This is considered because a pedestrian has a complicated shape as compared with a structure such as a vehicle, and the shape changes greatly with the passage of time. Based on this characteristic, even a pedestrian who moves in the traveling direction of the vehicle or a pedestrian who is stationary can be easily distinguished from a structural part such as a vehicle or a power pole.

  Furthermore, a predetermined fluctuation threshold is set as a boundary between the fluctuation range of the intensity of the reflected radio wave from the pedestrian and the intensity fluctuation band of the reflected radio wave from a vehicle that is not a pedestrian, and the reflected radio wave reflected by the target If the value of the fluctuation range of the intensity is equal to or greater than a predetermined fluctuation threshold, it is possible to easily and reliably distinguish the pedestrian from the non-pedestrian by determining the target as a pedestrian.

  Here, the fluctuation range of the intensity of the reflected radio wave is a known method for obtaining the fluctuation range such as a difference value that is a difference in intensity value of the reflected radio wave at a certain time interval or an amplitude value of the intensity of the reflected radio wave that fluctuates. The obtained value can be used.

  In the above invention, the characteristic of the reflected radio wave is a total value of intensity deviations in the reflected radio wave measured at a plurality of different times, and the storage unit includes the reflected radio wave characteristic in the reflected radio wave characteristic. A predetermined deviation threshold value that is a value obtained by summing intensity deviations is stored, and the information processing unit stores a value obtained by summing intensity deviations in the reflected radio waves received by the receiving unit in the storage unit. It is desirable to determine whether or not the target that has reflected the radio wave is the pedestrian based on whether or not it is greater than or equal to the predetermined deviation threshold.

  Thus, by determining whether the target is a pedestrian based on the total value of intensity deviations in the reflected radio wave, it is possible to reliably determine whether the target is a pedestrian. Furthermore, a predetermined deviation threshold is set as a boundary between the total deviation of the intensity of reflected radio waves from pedestrians and the total deviation of the intensity of reflected radio waves from non-pedestrian vehicles, etc., and reflected by the target. If the total deviation of the reflected radio wave intensity is equal to or greater than a predetermined deviation threshold, it is possible to easily and reliably distinguish between a pedestrian and a non-pedestrian by determining the target as a pedestrian. it can.

  In the above invention, the information processing unit repeatedly determines whether or not the target reflecting the radio wave at a predetermined cycle is a pedestrian, and when the target is determined to be a pedestrian, the predetermined period is: It is desirable to hold the determination result that the target is a pedestrian regardless of the determination result thereafter.

  When it is determined that the target is a pedestrian in this way, even if it is determined that the target is not a pedestrian, the determination result that the target is a pedestrian is By continuing to output, it is possible to suppress making an erroneous determination that a target that is a pedestrian is not a pedestrian.

  In general, the intensity of reflected radio waves from pedestrians fluctuates greatly, and the variation mode is not constant. For this reason, even if the target is a pedestrian, the target may be determined to be a pedestrian or may not be determined to be a pedestrian depending on the determination timing in the information processing unit. Even in this case, once the target is determined to be a pedestrian for a certain period of time, the target is determined to be a pedestrian regardless of the result of the determination. It can suppress making a wrong judgment that a target is not a pedestrian.

  In the above invention, the characteristic of the reflected radio wave is a dispersion value of the intensity of the reflected radio wave measured at a plurality of different times, and the storage unit stores the intensity of the reflected radio wave according to the pedestrian reflected radio wave characteristic. A predetermined dispersion threshold value that is a dispersion value is stored, and the information processing unit is configured such that an intensity dispersion value in the reflected radio wave received by the reception unit is equal to or greater than the predetermined dispersion threshold value stored in the storage unit. It is desirable to determine whether or not the target reflecting the radio wave is the pedestrian based on whether or not it is.

  Thus, by determining whether the target is a pedestrian based on the intensity dispersion value in the reflected radio wave, it is possible to reliably determine whether the target is a pedestrian. Furthermore, a predetermined dispersion threshold is set as a boundary between the dispersion value of the intensity of the reflected radio wave from the pedestrian and the dispersion value of the intensity of the reflected radio wave from a vehicle that is not a pedestrian, and is reflected by the target. If the dispersion value of the intensity of the reflected radio wave is equal to or greater than a predetermined dispersion threshold, it is possible to easily and reliably distinguish between a pedestrian and a non-pedestrian by determining the target as a pedestrian.

  In the above invention, the information processing unit calculates the moving speed of the target based on the radio wave transmitted from the transmitting unit and the reflected radio wave received by the receiving unit, and the calculated moving speed of the target is calculated in advance. It is desirable to determine that the target is not the pedestrian when the predetermined moving speed is exceeded.

  Thus, when the moving speed of the target is equal to or higher than the predetermined moving speed, it is determined that the target is not a pedestrian, so that the pedestrian is compared with the case where the target is determined based only on the characteristics of the reflected radio wave. It is possible to reduce the probability of misjudging a target that is not a pedestrian. Here, examples of the predetermined moving speed may include about 12 km / h to about 18 km / h, which is the speed when the pedestrian runs with full power.

  In the above invention, the receiving unit further detects a direction in which the reflected radio wave enters, and the information processing unit calculates a direction in which the target exists based on a direction in which the reflected radio wave enters the receiving unit, and transmits The distance from the transmitter and receiver to the target is calculated based on the radio wave transmitted from the receiver and the reflected radio wave received by the receiver, and the calculated distance to the target and the direction in which the target exists The movement direction of the target is calculated based on the time change of the vehicle, and if the calculated movement direction of the target intersects the traveling direction of the vehicle, whether the target reflecting the radio wave is a pedestrian or not It is desirable to increase the probability that a target that reflects radio waves is determined to be a pedestrian by changing the reference used when determining.

  Whether the target in the information processing unit is a pedestrian when the movement direction of the target obtained by the calculation intersects with the traveling direction of the vehicle, in other words, when the target crosses the traveling direction of the vehicle, By changing the criterion for determining whether or not the target is a pedestrian, it is possible to reliably distinguish between a pedestrian and a non-pedestrian.

  For example, when a target that reflects radio waves moves, it is unlikely that the target is a fixed structure such as a utility pole. Further, when the moving direction of the moving target is a direction crossing the traveling direction of the vehicle, the target is unlikely to be a preceding vehicle traveling on the same roadway. That is, when the moving direction of the target intersects with the traveling direction of the vehicle, the possibility that the target is a pedestrian is higher than in other cases. In this case, by changing the reference value and increasing the probability that the target is determined to be a pedestrian, the probability of erroneously determining that the target is a pedestrian can be reduced. On the other hand, the probability of misjudging a target that is not a pedestrian as a pedestrian is difficult to increase.

  Here, the criteria for determining whether the target is a pedestrian include the intensity value of the reflected radio wave, the fluctuation range of the intensity of the reflected radio wave, the total deviation value of the intensity of the reflected radio wave, The value of the variance of the intensity can be exemplified.

  In the above invention, the information processing unit, when the calculated moving direction of the target intersects the traveling direction of the vehicle, based on the radio wave transmitted from the transmitting unit and the reflected radio wave received by the receiving unit. In addition, if the calculated moving speed of the target is within a predetermined predetermined crossing speed range, it is determined whether the target reflecting the radio wave is a pedestrian. It is desirable to increase the probability of determining that a target that reflects radio waves is a pedestrian by changing the reference used in doing so.

  In this way, when the moving direction of the target intersects the traveling direction of the vehicle and the moving speed of the target is within a predetermined crossing speed range, whether or not the target in the information processing unit is a pedestrian By changing the criterion for determining the target and increasing the probability that the target is determined to be a pedestrian, the pedestrian and the non-pedestrian can be reliably distinguished.

  Here, as a predetermined crossing speed range, the walking speed range of a pedestrian can be illustrated, and a lower limit can mention about 4 km / h which is a walking speed of elderly people, and an upper limit is pedestrian. From 12 km / h to 18 km / h, which is the speed when running at full power.

  In the pedestrian detection method of the present invention, a detection step of transmitting a radio wave toward the front of the vehicle and receiving a reflected radio wave reflected from a target existing in front of the vehicle, characteristics of the received reflected radio wave, A comparison step of comparing characteristics stored in a radio wave reflected from a pedestrian stored in advance, and a determination step of determining whether the target is a pedestrian based on the comparison result. To do.

  The program of the present invention transmits a radio wave toward the front of the vehicle to the computer, receives a reflected radio wave reflected from a target existing in front of the vehicle, characteristics of the received reflected radio wave, Realizing a comparison function that compares the characteristics of radio waves reflected from pedestrians stored in advance, and a determination function that determines whether a target is the pedestrian based on the comparison result Features.

  According to the pedestrian detection method or program of the present invention, the reflected wave characteristic received by the receiving unit is compared with the pedestrian reflected wave characteristic stored in advance, so that the target reflecting the radio wave is a pedestrian. A determination is made whether or not. Therefore, it can be determined whether or not the target is a pedestrian regardless of whether the target is moving or not.

  According to the pedestrian detection device, the pedestrian detection method and the program of the present invention, the radio wave is reflected by comparing the characteristic of the reflected radio wave received by the receiving unit with the pedestrian reflected radio wave characteristic stored in advance. A determination is made as to whether the target is a pedestrian. Therefore, it is possible to determine whether or not the target is a pedestrian regardless of whether or not the target is moving, and the moving direction, and it is possible to more reliably detect the pedestrian.

It is a block diagram explaining the structure of the pedestrian detection apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart explaining the determination method whether the detected target in the pedestrian detection apparatus 1 of FIG. 1 is a pedestrian. It is a graph explaining the relationship between the prescribed threshold value in the intensity threshold and the threshold value for pedestrian determination. It is a flowchart explaining the determination method whether the detected target in the pedestrian detection apparatus which concerns on the 1st modification of the 1st Embodiment of this invention is a pedestrian. It is a flowchart explaining the determination method whether the detected target in the pedestrian detection apparatus which concerns on the 2nd modification of the 1st Embodiment of this invention is a pedestrian. It is a flowchart explaining the determination method whether the detected target in the pedestrian detection apparatus which concerns on the 3rd modification of the 1st Embodiment of this invention is a pedestrian.

[First Embodiment]
Hereinafter, a pedestrian detection apparatus 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 6. FIG. 1 is a block diagram illustrating a configuration of a pedestrian detection device 1 according to the present embodiment.

  The pedestrian detection device 1 according to the present invention is a target detection device that detects a target existing in front of a vehicle, and also performs a determination as to whether or not the detected target is a pedestrian. . When it is determined that the target detected by the pedestrian detection device 1 is a pedestrian, a pedestrian detection signal indicating that a pedestrian has been detected in front of the vehicle is output from the pedestrian detection device 1. Is done.

  The pedestrian detection signal output from the pedestrian detection device 1 is an alarm unit that informs the driver of the vehicle of the presence of a pedestrian, an automatic that controls the vehicle traveling speed or stops the vehicle according to the distance from the pedestrian. It is input to the traveling control unit or the like.

  The pedestrian detection apparatus 1 is a millimeter wave sensor using a radar that detects a target existing in front of a vehicle using a so-called millimeter wave. In this embodiment, the distance and relative speed between the vehicle on which the pedestrian detection device 1 is provided and the target are detected by an FM-CW (Frequency Modulation-Continuous Wave) method, and the direction in which the target with respect to the vehicle exists is present. The description will be made by applying to the case where (azimuth) is detected by a DBF (Digital Beam Forming) method. Note that the method for detecting the distance and relative speed between the vehicle and the target and the method for detecting the direction in which the target is present with respect to the vehicle may be other methods different from the above-described methods, It is not limited.

  Moreover, the pedestrian detection apparatus 1 may detect a target using only the millimeter wave sensor as described above and determine whether or not the target is a pedestrian. In addition to this, a video acquisition unit such as a camera and a video processing unit that processes the acquired video may be used together to detect a target and determine whether the target is a pedestrian or not. There is no particular limitation.

As shown in FIG. 1, the pedestrian detection apparatus 1 is mainly provided with a millimeter wave transmission / reception unit 10, a signal processing unit 20, and an output I / F unit 30.
The millimeter wave transmission / reception unit 10 transmits millimeter waves (radio waves) toward the front of the vehicle and receives reflected millimeter waves (reflected radio waves) reflected by a target existing in front. The millimeter wave transmitter / receiver 10 is mainly provided with a millimeter wave signal transmitter (transmitter) 11 and a millimeter wave signal receiver (receiver) 12.

  The millimeter wave signal transmission unit 11 transmits a millimeter wave. Specifically, the millimeter wave signal transmission unit 11 transmits a millimeter wave whose frequency is changed (modulated) with time. As the configuration of the millimeter wave signal transmission unit 11, a known configuration can be used and is not particularly limited. When the frequency of the millimeter wave is represented by a graph in which the vertical axis represents frequency and the horizontal axis represents time, the millimeter wave frequency is modulated so as to draw a shape in which a right-handed hypotenuse and a right-hand hypotenuse are continuous.

  The millimeter wave signal receiver 12 receives the reflected millimeter wave reflected by the target and outputs a received signal, and detects the incident direction of the reflected millimeter wave. In the present embodiment, description will be made by applying to an example of a millimeter wave signal receiving unit 12 having a plurality of, for example, five arranged antennas. In this case, the length of the path of the reflected millimeter wave that reaches each of the five antennas varies depending on the direction in which the reflected millimeter wave enters the millimeter wave signal receiving unit 12. Therefore, the incident direction of the reflected millimeter wave can be detected by detecting the phase between the reflected millimeter waves detected by the respective antennas.

  The signal processing unit 20 controls transmission of the millimeter wave from the millimeter wave signal receiving unit 12 and processes a reception signal output from the millimeter wave signal receiving unit 12 that has received the reflected millimeter wave. The signal processing unit 20 is mainly provided with a signal processing microcomputer (information processing unit, computer) 21 and a storage unit 22.

The signal processing microcomputer 21 is an electronic circuit that performs signal calculation processing, and performs calculations related to various controls in the signal processing unit 20, calculation processing of input received signals, and the like.
The storage unit 22 is a semiconductor storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and stores a program used for arithmetic processing in the signal processing microcomputer 21. Furthermore, as will be described later, the storage unit 22 stores various threshold values used for determining whether or not the target is a pedestrian.

  The output I / F unit 30 is output from the signal processing unit 20 when the signal processing unit 20 detects a pedestrian in front of the vehicle, in other words, when the target is determined to be a pedestrian. It is an interface for outputting a pedestrian detection signal to the outside of the pedestrian detection device 1.

  Next, a pedestrian detection method in the pedestrian detection apparatus 1 having the above configuration will be described. FIG. 2 is a flowchart illustrating a method for determining whether or not the detected target in the pedestrian detection apparatus 1 of FIG. 1 is a pedestrian.

  First, when the power supply state of the vehicle is in an ACC (accessory) on state, in other words, when power is supplied to the pedestrian detection device 1, the millimeter wave signal is sent from the signal processing unit 20 to the millimeter wave signal transmission unit 11. A control signal for transmitting is output. The millimeter wave is transmitted from the millimeter wave signal transmission unit 11 to which the control signal is input toward the front of the vehicle. The millimeter wave may be transmitted continuously, or may be transmitted discretely at regular intervals, and is not particularly limited.

  When the target exists in front of the vehicle, the millimeter wave transmitted from the millimeter wave signal transmission unit 11 is reflected by the target and becomes a reflected millimeter wave. The reflected millimeter wave is reflected from the target toward the vehicle, and a part of the reflected millimeter wave is received by the millimeter wave signal receiving unit 12. In other words, the reflected millimeter wave is detected by the millimeter wave signal receiving unit 12 (S11: detection step). The millimeter wave signal receiving unit 12 outputs a reflected millimeter wave reception signal received from each of the five antennas.

  The reception signal output from the millimeter wave signal reception unit 12 is input to the signal processing microcomputer 21 of the signal processing unit 20. Based on the input received signal, the signal processing microcomputer 21 determines whether or not the target reflecting the millimeter wave crosses the traveling direction of the vehicle (S12).

  Specifically, first, the signal processing microcomputer 21 obtains a phase difference between the reception signals related to the five antennas input from the millimeter wave signal reception unit 12 by calculation. Based on the obtained phase difference, the signal processing microcomputer 21 calculates the incident direction of the reflected millimeter wave, in other words, the direction of the target reflecting the millimeter wave with respect to the vehicle by calculation.

  Further, the signal processing microcomputer 21 calculates the phase difference between the millimeter wave transmitted from the millimeter wave signal transmitter 11 and the reflected millimeter wave received by the millimeter wave signal receiver 12 by calculation. Based on the obtained phase difference, the signal processing microcomputer 21 obtains the distance between the target reflecting the millimeter wave and the vehicle by calculation. A calculation method for obtaining the distance between the target and the vehicle based on the phase difference between the millimeter wave and the reflected millimeter wave can be a known calculation method, and is not particularly limited.

  The signal processing microcomputer 21 causes the storage unit 22 to store the target azimuth and the distance to the target obtained by calculation. At predetermined time intervals, the signal processing microcomputer 21 obtains the direction of the target and the distance to the target again by calculation. Here, the signal processing microcomputer 21 acquires the value of the target orientation and the distance to the target previously stored from the storage unit 22, and the target orientation determined by the current calculation from the acquired value. Based on the change to the value of the distance to the target, the moving direction and moving speed of the target are obtained by calculation.

  When the moving direction and moving speed of the target are obtained by calculation, the signal processing microcomputer 21 crosses the traveling direction of the obtained target and the moving speed is equal to the crossing threshold (crossing speed range). ), In other words, whether the moving direction of the target and the traveling direction of the vehicle intersect, and whether the moving speed is within the range of the crossing threshold is determined. When the moving direction of the target intersects the traveling direction of the vehicle and the moving speed is within the range of the crossing threshold value (in the case of YES), the target is set to various threshold values to be used later in the processing. Setting is made as a threshold for pedestrian determination that increases the probability of determining that the user is a pedestrian (S13). On the other hand, when the moving direction of the target does not intersect the traveling direction of the vehicle or the moving speed is outside the range of the crossing threshold value (in the case of NO), various threshold values used in the subsequent processing are defined. Setting as a value is performed (S14).

  Here, as the crossing threshold, the walking speed range of the pedestrian can be exemplified, the lower limit can be about 4 km / h which is the walking speed of the elderly, and the upper limit is the pedestrian running at full power. About 12 km / h to 18 km / h.

  In addition, the prescribed values in the various threshold values are values that are set when the pedestrian detection device 1 is shipped from the factory, for example, in a state where there is no prediction as to whether or not the target is a pedestrian. It is a value that determines whether the target is a pedestrian or a structure such as a vehicle or a utility pole. The threshold for pedestrian determination is a value that is used when the target is predicted to be a pedestrian (highly likely). Compared to the specified value, the threshold is set lower or higher. It is a value that increases the probability of determining a target as a pedestrian.

FIG. 3 is a graph for explaining the relationship between a prescribed threshold value and a threshold value for pedestrian determination in the intensity threshold value.
As an example, a predetermined threshold and a threshold for pedestrian determination in the intensity threshold used for determining whether or not the target is a pedestrian based on the intensity value of the reflected millimeter wave will be described with reference to FIG. . In the case of the determination using the intensity threshold, it is determined that the target is a pedestrian if the intensity value of the reflected millimeter wave is equal to or less than the intensity threshold. Therefore, the intensity threshold for pedestrian determination that increases the probability of determining the target as a pedestrian is higher than the prescribed intensity threshold. In FIG. 3, the prescribed intensity threshold is indicated by a bold line graph, and the intensity threshold for pedestrian determination is indicated by a thin dotted line graph.

  When various threshold values are set as described above, the signal processing microcomputer 21 determines whether the intensity value of the reflected millimeter wave received by the millimeter wave signal receiving unit 12 is equal to or less than the intensity threshold value. Perform (S15: contrast step). The intensity threshold value is stored in advance in the storage unit 22, and is divided into whether the target reflecting the millimeter wave is a pedestrian or a non-pedestrian (for example, a vehicle) depending on the magnitude of the value of the reflected millimeter wave intensity. A value that defines the boundary. As shown in FIG. 3, the intensity threshold decreases as the distance between the vehicle and the target increases, and takes a substantially constant value when the distance exceeds a certain distance.

  When the signal processing microcomputer 21 performs the determination of S15, the pedestrian determination intensity threshold set in S13 corresponding to the distance to the target obtained by the immediately preceding calculation, or set in S14 A prescribed intensity threshold is acquired from the storage unit 22. The signal processing microcomputer 21 that has acquired the intensity threshold value compares the acquired intensity threshold value with the intensity value of the reflected millimeter wave that has been input most recently. When the intensity of the reflected millimeter wave is less than the acquired intensity threshold value (in the case of NO), the signal processing microcomputer 21 determines that the target is not a pedestrian (S16: determination step).

  On the other hand, when the intensity of the reflected millimeter wave is equal to or greater than the acquired intensity threshold value (in the case of YES), the signal processing microcomputer 21 has a fluctuation range in the intensity of the reflected millimeter wave, in other words, a difference value equal to or greater than the fluctuation threshold value. (S17: comparison step). The fluctuation threshold value is stored in advance in the storage unit 22, and whether the target reflecting the millimeter wave according to the magnitude of the difference value in the intensity of the reflected millimeter wave is a pedestrian or a non-pedestrian (for example, a vehicle). It is a value that determines the boundary to divide.

  If YES is determined in S15 described above, the certain period (predetermined period) after the YES determination is a case where the intensity of the reflected millimeter wave is less than the acquired intensity threshold and NO is determined. In addition, the signal processing microcomputer 21 maintains the YES determination.

By doing in this way, it can suppress making the wrong judgment that the target which is a pedestrian is not a pedestrian.
That is, the intensity of the reflected radio wave from the pedestrian varies greatly, and the variation mode is not constant. Therefore, even if the target is a pedestrian, it may be determined that the target is a pedestrian, or may be erroneously determined not to be a pedestrian, depending on the determination timing in the signal processing microcomputer 21. Even in this case, once the target is determined to be a pedestrian for a certain period of time, the target is determined to be a pedestrian regardless of the result of the determination. It can suppress making a wrong judgment that a target is not a pedestrian.

  The signal processing microcomputer 21 obtains the pedestrian determination variation threshold set in S13 or the specified variation threshold set in S14 from the storage unit 22 when performing the determination in S17. The signal processing microcomputer 21 that has acquired the fluctuation threshold obtains a difference value between the most recently input reflected millimeter wave intensity value and the reflected millimeter wave intensity value input the previous time or a predetermined time ago by calculation. . Then, the difference value obtained by calculation, in other words, the reflected millimeter wave fluctuation is compared with the obtained fluctuation threshold. If the reflected millimeter wave fluctuation is less than the obtained fluctuation threshold (in the case of NO), the signal processing microcomputer 21 determines that the target is not a pedestrian (S16).

  On the other hand, when the reflected millimeter wave fluctuation is greater than or equal to the obtained fluctuation threshold (in the case of YES), the signal processing microcomputer 21 determines whether or not the moving speed of the target is equal to or higher than the speed threshold. (S18: contrast step). The speed threshold value is stored in advance in the storage unit 22, and is a value that defines a boundary that divides whether the target reflecting the millimeter wave according to the moving speed of the target is a pedestrian or a non-pedestrian (for example, a vehicle). It is. For example, examples of the speed threshold include 12 km / h to 18 km / h, which is the speed when a pedestrian runs with full power.

  The signal processing microcomputer 21 acquires the pedestrian determination speed threshold set in S13 or the specified speed threshold set in S14 from the storage unit 22 when performing the determination in S18. The signal processing microcomputer 21 that has acquired the speed threshold calculates the phase difference between the most recently transmitted millimeter wave and the received reflected millimeter wave, and determines the moving speed of the target based on the calculated phase difference. calculate. And when the moving speed calculated | required is more than the acquired speed threshold value (in the case of YES), the signal processing microcomputer 21 determines with the target not being a pedestrian (S16). On the other hand, when the moving speed obtained by calculation is less than the acquired speed threshold value (in the case of NO), the signal processing microcomputer 21 determines that the target is a pedestrian (S19: determination step). ).

  When the signal processing microcomputer 21 determines that the target is a pedestrian, a pedestrian detection signal is output from the signal processing microcomputer 21 to the outside of the pedestrian detection device 1 via the output I / F unit 30. The

  According to said structure, the target which reflected the millimeter wave by contrasting the characteristic of the reflected millimeter wave received by the millimeter wave signal receiving part 12 and the pedestrian reflected radio wave characteristic memorize | stored in the memory | storage part 22 is compared. A determination is made whether is a pedestrian. Therefore, the determination as to whether or not the target is a pedestrian can be detected more reliably regardless of whether the target is moving or not.

  By determining whether or not the target is a pedestrian based on the intensity of the reflected millimeter wave, it is possible to more reliably determine whether or not the target is a pedestrian. That is, when comparing a pedestrian and a structure such as a vehicle or a power pole, the intensity of the reflected millimeter wave of the pedestrian when the millimeter wave of the same intensity is irradiated is weaker than the intensity of the reflected millimeter wave of the structure. Based on this characteristic, even a pedestrian who moves in the traveling direction of the vehicle or a pedestrian who is stationary can be easily distinguished from a structural part such as a vehicle or a power pole.

  A plurality of intensity thresholds different according to the distance from the vehicle to the target are prepared in advance, and the intensity threshold corresponding to the distance from the vehicle to the target acquired by the signal processing microcomputer 21 is selected from the plurality of intensity thresholds. If the intensity value of the reflected millimeter wave reflected by the target is equal to or less than the selected intensity threshold, the target is determined to be a pedestrian (S15), thereby distinguishing between a pedestrian and a non-pedestrian. It can be done easily and reliably. More specifically, since the intensity of the reflected millimeter wave from the target varies greatly depending on the distance from the vehicle to the target, by using an intensity threshold corresponding to the distance from the vehicle to the target, A distinction can be made between pedestrians and non-pedestrians.

  By determining whether the target is a pedestrian based on the intensity fluctuation range in the reflected millimeter wave (S17), it is possible to reliably determine whether the target is a pedestrian. That is, when comparing a pedestrian and a structure such as a vehicle, the intensity in the reflected millimeter wave greatly varies with time. This is considered because a pedestrian has a complicated shape as compared with a structure such as a vehicle, and the shape changes greatly with the passage of time. Based on this characteristic, even a pedestrian who moves in the traveling direction of the vehicle or a pedestrian who is stationary can be easily distinguished from a structural part such as a vehicle or a power pole.

  Furthermore, a fluctuation threshold is set as a boundary between the fluctuation range of the intensity of the reflected millimeter wave from the pedestrian and the intensity fluctuation range of the reflected millimeter wave from the vehicle that is not the pedestrian, and the reflection millimeter wave reflected by the target is set. If the value of the fluctuation width of the wave intensity is equal to or greater than the fluctuation threshold, it is possible to easily and reliably distinguish the pedestrian from the non-pedestrian by determining the target as a pedestrian.

  When the movement speed of the target is equal to or higher than the speed threshold as in the determination in S18, it is determined that the target is not a pedestrian, compared with the case where the determination is based only on the characteristics of the reflected millimeter wave, The probability that a target that is not a pedestrian is erroneously determined to be a pedestrian can be reduced.

  As shown in S12 to S14, when the moving direction of the target obtained by calculation intersects the traveling direction of the vehicle, in other words, when the target crosses the traveling direction of the vehicle, the object in the signal processing microcomputer 21 Those that are not pedestrians and pedestrians by changing the various thresholds for determining whether a target is a pedestrian to thresholds for determining pedestrians and increasing the probability that the target is determined to be a pedestrian Can be reliably distinguished.

  For example, when a target that reflects millimeter waves moves, it is unlikely that the target is a fixed structure such as a utility pole. Further, when the moving direction of the moving target is a direction crossing the traveling direction of the vehicle, the target is unlikely to be a preceding vehicle traveling on the same roadway. That is, when the moving direction of the target intersects with the traveling direction of the vehicle, the possibility that the target is a pedestrian is higher than in other cases. In this case, by changing the threshold value to the threshold value for pedestrian determination and increasing the probability of determining that the target is a pedestrian, the probability of erroneously determining that the target is a pedestrian is reduced. be able to. On the other hand, the probability of misjudging a target that is not a pedestrian as a pedestrian is difficult to increase.

  Furthermore, when the moving speed of the target is within a predetermined crossing threshold range, various thresholds for determining whether or not the target in the signal processing microcomputer 21 is a pedestrian are set as thresholds for crossing the pedestrian. By changing to and increasing the probability that the target is determined to be a pedestrian, the pedestrian and the non-pedestrian can be reliably distinguished.

  In the determination in S15 described above, the intensity value of the reflected millimeter wave received when the distance between the vehicle and the target is a predetermined distance, and the intensity when the distance between the vehicle and the pedestrian is also the predetermined distance. The determination may be performed by comparing with a threshold value. By doing in this way, the amount of calculation processing at the time of determination in S15 decreases, and a pedestrian and a non-pedestrian can be distinguished easily and rapidly.

  Further, in the determination in S17, the determination may be made by comparing the value obtained by summing the intensity deviations in the reflected millimeter wave over a predetermined period with the deviation threshold, or the intensity dispersion value in the reflected millimeter wave and the variance The determination may be made by comparing with a threshold value. In this way, even if it is difficult to determine whether a target is a pedestrian or not, it is difficult to determine whether the target is a pedestrian by evaluating the fluctuation range by a method different from the intensity difference value in the reflected millimeter wave. The determination can be made stably.

  Here, the deviation threshold value is stored in the storage unit 22 in advance, and whether the target reflecting the millimeter wave according to the magnitude of the intensity deviation value in the reflected millimeter wave is a pedestrian or a non-pedestrian. It is a value that determines the boundary to divide. Similarly, the dispersion threshold is pre-stored in the storage unit 22, and a boundary that divides a target that reflects the millimeter wave into a pedestrian or a non-pedestrian according to the magnitude of the dispersion value in the reflected millimeter wave. It is a value to be determined.

[First Modification of First Embodiment]
Next, a first modification of the first embodiment of the present invention will be described with reference to FIG.
The basic configuration of the pedestrian detection device of this embodiment is the same as that of the first embodiment, but the pedestrian detection method is different from that of the first embodiment. Therefore, in this embodiment, only the detection method of a pedestrian is demonstrated using FIG. FIG. 4 is a flowchart illustrating a method for determining whether or not the detected target in the pedestrian detection apparatus 1 of the present modification is a pedestrian.

  As shown in FIG. 4, after the power is supplied to the pedestrian detection device 1, whether the signal processing microcomputer 21 has a fluctuation width in the intensity of the reflected millimeter wave, in other words, a difference value is not less than a fluctuation threshold value. Until this determination is made, in other words, S11 to S17 are the same as the pedestrian detection method in the first embodiment. If it is determined in S17 that the reflected millimeter wave fluctuation is greater than or equal to the obtained fluctuation threshold (YES), the signal processing microcomputer 21 determines that the target is a pedestrian (S19). In other words, the signal processing microcomputer 21 is different from the first embodiment in that it does not determine whether the target moving speed is equal to or lower than the speed threshold.

  In this way, when determining whether or not the target is a pedestrian based only on the characteristics of the reflected millimeter wave, the determination based on the moving speed of the target is also performed. Can reduce the amount of computation required.

[Second Modification of First Embodiment]
Next, a second modification of the first embodiment of the present invention will be described with reference to FIG.
The basic configuration of the pedestrian detection device of this embodiment is the same as that of the first embodiment, but the pedestrian detection method is different from that of the first embodiment. Therefore, in this embodiment, only the detection method of a pedestrian is demonstrated using FIG. FIG. 5 is a flowchart illustrating a method for determining whether or not the detected target in the pedestrian detection apparatus 1 according to the present modification is a pedestrian.

  As shown in FIG. 5, the process from when power is supplied to the pedestrian detection apparatus 1 until the detection of reflected millimeter waves (S11) is the same as in the first embodiment. Thereafter, the signal processing microcomputer 21 determines whether or not the intensity value of the reflected millimeter wave received by the millimeter wave signal receiving unit 12 is equal to or lower than the intensity threshold value (S15). It is determined whether or not the above is true (S18). Based on the results of these determinations, the signal processing microcomputer 21 determines that the target is not a pedestrian (S16) or determines that the target is a pedestrian (S19).

  The determination from S15 to S18 described above is different from the first embodiment in that only prescribed threshold values are used. As a result, the number of various threshold values stored in the storage unit 22 can be halved, and the amount of calculation required for performing the determination can be reduced.

[Third Modification of First Embodiment]
Next, a third modification of the first embodiment of the present invention will be described with reference to FIG.
The basic configuration of the pedestrian detection device of this embodiment is the same as that of the first embodiment, but the pedestrian detection method is different from that of the first embodiment. Therefore, in this embodiment, only the detection method of a pedestrian is demonstrated using FIG. FIG. 6 is a flowchart illustrating a method for determining whether or not the detected target in the pedestrian detection apparatus 1 of the present modification is a pedestrian.

  As shown in FIG. 6, the process from when power is supplied to the pedestrian detection device 1 until the detection of the reflected millimeter wave (S11) is the same as in the first embodiment. Thereafter, the signal processing microcomputer 21 determines whether or not the intensity value of the reflected millimeter wave received by the millimeter wave signal receiving unit 12 is equal to or less than the intensity threshold (S15). Then, it is determined whether or not the variation threshold value is exceeded (S17). Based on the results of these determinations, the signal processing microcomputer 21 determines that the target is not a pedestrian (S16) or determines that the target is a pedestrian (S19).

  DESCRIPTION OF SYMBOLS 1 ... Pedestrian detection apparatus, 11 ... Millimeter wave signal transmission part (transmission part), 12 ... Millimeter wave signal reception part (reception part), 21 ... Signal processing microcomputer (information processing part, computer), 22 ... Memory | storage part, S11: Detection step, S15: Comparison step, S16: Determination step, S17: Comparison step

Claims (13)

A transmitter that transmits radio waves toward the front of the vehicle;
Of the radio waves transmitted from the transmission unit, a reception unit that receives a reflected radio wave that is a radio wave reflected by a target existing in front of the vehicle;
A storage unit in which pedestrian reflected radio wave characteristics, which are characteristics of radio waves reflected by pedestrians, are stored in advance;
Whether the target reflecting the radio wave is the pedestrian by comparing the characteristic of the reflected radio wave received by the receiving unit with the pedestrian reflected radio wave characteristic stored in the storage unit. An information processing unit for determining
A pedestrian detection device characterized by being provided. The characteristic of the reflected radio wave is the intensity of the reflected radio wave reflected by the target,
The pedestrian detection device according to claim 1, wherein a predetermined intensity threshold value that is an intensity value of the reflected radio wave related to the pedestrian reflected radio wave characteristic is stored in the storage unit.   The information processing unit reflects the radio wave based on whether the intensity value of the reflected radio wave received by the receiving unit is equal to or less than the predetermined intensity threshold stored in the storage unit. The pedestrian detection device according to claim 2, wherein it is determined whether or not a target is the pedestrian. In the storage unit, a plurality of the predetermined intensity thresholds related to at least a distance from the vehicle to the target are stored in advance.
The information processing unit acquires information on a distance from the vehicle to the target,
The object that reflects the radio wave based on whether or not the intensity value of the reflected radio wave received by the receiving unit is equal to or greater than the predetermined intensity threshold corresponding to the distance from the vehicle to the target. The pedestrian detection device according to claim 2, wherein it is determined whether or not a mark is the pedestrian. The characteristic of the reflected radio wave is a value of a fluctuation range of intensity in the reflected radio wave reflected by the target,
The storage unit stores a predetermined fluctuation threshold value that is a value of a fluctuation range of intensity in the reflected radio wave related to the pedestrian reflected radio wave characteristic,
The information processing unit receives the radio wave based on whether or not the value of the fluctuation range of the intensity of the reflected radio wave received by the receiving unit is equal to or greater than the predetermined fluctuation threshold stored in the storage unit. The pedestrian detection device according to claim 1, wherein it is determined whether or not the reflected target is the pedestrian. The characteristic of the reflected radio wave is a total value of intensity deviations in the reflected radio wave measured at a plurality of different times,
The storage unit stores a predetermined deviation threshold value that is a total value of intensity deviations in the reflected radio waves related to the pedestrian reflected radio wave characteristics,
The information processing unit is configured to determine whether the radio wave is based on whether a value obtained by summing the intensity deviations in the reflected radio waves received by the reception unit is equal to or greater than the predetermined deviation threshold stored in the storage unit. The pedestrian detection device according to claim 1, wherein it is determined whether or not the target reflecting the object is the pedestrian. The information processing unit repeatedly determines whether the target that reflected the radio wave at a predetermined period is the pedestrian,
When it is determined that the target is the pedestrian, a predetermined period holds a determination result that the target is the pedestrian regardless of a result of the determination thereafter. Item 7. The pedestrian detection device according to Item 5 or 6. The characteristic of the reflected radio wave is a value of dispersion of intensity in the reflected radio wave measured at a plurality of different times,
In the storage unit, a predetermined dispersion threshold value that is a value of intensity dispersion in the reflected radio wave related to the pedestrian reflected radio wave characteristic is stored,
The information processing unit reflects the radio wave based on whether a value of intensity dispersion in the reflected radio wave received by the receiving unit is equal to or greater than the predetermined dispersion threshold stored in the storage unit. The pedestrian detection device according to claim 1, wherein it is determined whether or not the target is the pedestrian. The information processing unit
Based on the radio wave transmitted from the transmitter and the reflected radio wave received by the receiver, the moving speed of the target is calculated,
further,
The pedestrian detection device according to claim 1, wherein when the calculated moving speed of the target is equal to or higher than a predetermined moving speed, the target is not the pedestrian. . The receiver further detects a direction in which the reflected radio wave is incident,
The information processing unit
Calculate the direction in which the target is present based on the direction in which the reflected radio wave is incident on the receiver,
Based on the radio wave transmitted from the transmitter and the reflected radio wave received by the receiver, the distance from the transmitter and the receiver to the target is calculated,
Based on the calculated distance to the target and the temporal change in the direction in which the target exists, calculate the moving direction of the target,
When the calculated moving direction of the target intersects the traveling direction of the vehicle,
The reference used when determining whether or not the target reflecting the radio wave is the pedestrian is changed to increase the probability of determining the target reflecting the radio wave as the pedestrian. The pedestrian detection apparatus according to claim 1, wherein the pedestrian detection apparatus is a pedestrian detection apparatus. The information processing unit
When the calculated moving direction of the target intersects the traveling direction of the vehicle,
Based on the radio wave transmitted from the transmitter and the reflected radio wave received by the receiver, the moving speed of the target is calculated,
further,
When the calculated moving speed of the target is within a predetermined predetermined crossing speed range, it is used when determining whether the target reflecting the radio wave is the pedestrian or not. The pedestrian detection device according to claim 10, wherein the pedestrian detection device according to claim 10, wherein the probability of determining the target reflecting the radio wave as the pedestrian is increased by changing a reference. A detection step of transmitting a radio wave toward the front of the vehicle and receiving a reflected radio wave reflected from a target existing in front of the vehicle;
A comparison step for comparing the characteristic of the received reflected radio wave with the characteristic of the radio wave reflected from a pedestrian stored in advance;
A determination step of determining whether or not the target is the pedestrian based on a contrasted result;
A pedestrian detection method characterized by comprising: On the computer,
A detection function for transmitting a radio wave toward the front of the vehicle and receiving a reflected radio wave reflected from a target existing in front of the vehicle;
A comparison function for comparing the characteristic of the received reflected radio wave with the characteristic of the radio wave reflected from a pedestrian stored in advance;
A determination function for determining whether the target is the pedestrian based on the contrasted results;
A program to realize

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