JP2008039581A - Onboard radar system and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an onboard radar system, capable of enhancing the possibility of avoidance of accident, even when detection of a target by own radar system is difficult. <P>SOLUTION: The onboard radar system 100 performs transmission from a transmitting antenna 103, receives reflected waves reflected by the target with receiving antennas 104, 105, and detects its distance from the target and a relative speed. Even when own vehicle can not recognize the target, and cannot perform collision avoidance operation adequately, the possibility of being involved in an accident is reduced by making other radar systems recognize own vehicle. More specifically, by a signal processing part 109; (1) an electric wave reflector 112 is revolved for a detected target via the use of a drive device 111, and the radar device of the target is made to detect the presence of own vehicle; (2) an alarm is given to its driver with an annunciator arrangement 110. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an in-vehicle radar device used in an inter-vehicle distance warning system, an adaptive cruise control system, a pre-crash system, and the like, and a control method thereof.

  In recent years, there has been a great interest in automobile safety technology. In response, various systems have begun to be put into practical use mainly by automobile-related companies. In particular, a system for avoiding a collision and a system for reducing an impact at the time of a collision such as an inter-vehicle distance warning system, an adaptive cruise control system, and a pre-crash system are well known.

  For example, as disclosed in Patent Document 1, the inter-vehicle distance alarm system uses a warning light, an alarm sound, or the like when the inter-vehicle distance from a target (vehicle, obstacle, etc.) in front of the host vehicle is too close. This system informs the driver of the danger.

  Further, for example, as disclosed in Patent Document 2, the adaptive cruise control system controls the vehicle traveling speed to the planned vehicle speed without the intervention of the driving vehicle, or the vehicle that travels in front of the host vehicle. This is a system that keeps the inter-vehicle distance at a predetermined interval.

  Further, for example, as disclosed in Patent Document 3, the pre-crash system applies a brake when a collision with a target approaching the host vehicle from the front, side, rear, or the like of the host vehicle cannot be avoided. This system is operated to reduce the impact of collision. Furthermore, there is a system that can cope with such as reducing the impact on the occupant due to a collision by appropriately fastening the seat belt.

  As one of the inter-vehicle distance detection devices that measure the distance to the target, the relative speed, and the like when constructing these systems, for example, there is an in-vehicle radar device as disclosed in Non-Patent Document 1. This in-vehicle radar device emits radio waves and receives reflected waves from targets such as vehicles and obstacles, detects the propagation time of the radio waves, the signal intensity of the reflected waves, the Doppler shift of the frequency, etc. Measure the distance and relative speed to the target based on

However, in such an on-vehicle radar device, there are the following (1) to (3) as factors that deteriorate the target detection performance.
(1) Depending on the direction of the target, the signal intensity of the reflected wave cannot be obtained sufficiently. In particular, when the target is a vehicle, the reflection cross-sectional area of the radio wave with respect to the oblique direction of the vehicle becomes small.
(2) When the target is present at the end of the transmitted radio wave, the signal strength of the reflected wave cannot be obtained sufficiently. As is clear from the directivity of the antenna, considering the relationship between the angular direction and the antenna gain, when the target is present at the end of the transmission wave, both the transmission antenna gain and the reception antenna gain are reduced. In general, the signal intensity of the reflected wave, the reflection cross-sectional area, and the antenna gain have a relationship represented by Expression (1). Therefore, when the reflection cross-sectional area is small and the antenna gain is small, the signal strength of the reflected wave is reduced.

Here, Pr is the received power (signal intensity of the reflected wave), Pt is the transmission power, Gt is the transmission antenna gain, Gr is the reception antenna gain, σ is the reflection cross section, Range is the distance, and K is the proportional coefficient.
(3) The signal intensity of the reflected wave cannot be sufficiently obtained because the radio wave transmitted / received due to rain, fog, etc. is attenuated.

  In such a case, since the signal intensity of the reflected wave from the target cannot be obtained sufficiently, it is difficult to detect the presence of the target despite the presence of the target. In the inter-vehicle distance warning system, adaptive cruise control system, and pre-crash system, appropriate control according to each system is performed based on the distance and relative speed of the target around the host vehicle detected by the on-vehicle radar device. Do. For this reason, it is difficult to ensure sufficient system reliability without solving the above-described problems.

  For example, as disclosed in Patent Document 4, as a solution to these problems, the reliability of the camera and the millimeter wave radar are compared, the one with the higher reliability is used to detect the inter-vehicle distance, It is known to always detect the correct inter-vehicle distance according to the situation.

JP-A-10-95291 JP-A-11-39586 JP 2000-95130 A JP-A-6-230115 Journal of the Institute of Electronics, Information and Communication Engineers October 1996 issue (pp977-981), “Trends in the development of millimeter-wave radars for automobiles”

  In the conventional inter-vehicle distance detection device described above, when the reliability of the camera cannot be sufficiently ensured due to rain or fog, the signal strength of the reflected wave cannot be sufficiently obtained depending on the direction of the target, or the radio wave transmitted by the target. It is unlikely that a sufficient effect will be obtained if it is present at the end of the film.

  Furthermore, the point of interest in the above-mentioned conventional inter-vehicle distance detection device is to improve performance and accuracy when recognizing the surrounding environment only with the device mounted on the host vehicle. For this reason, in a situation where the target cannot be detected by the inter-vehicle distance detection device of the own vehicle, the system for avoiding the collision and the system for reducing the impact at the time of the collision do not work at all.

  a) The signal strength of the reflected wave cannot be obtained sufficiently depending on the direction of the target, b) The target exists at the end of the transmitted radio wave, or c) The radio wave transmitted / received is attenuated by rain, fog, etc. In either case, it is difficult for the radar device to detect the target accurately.

  An object of the present invention is to provide an on-vehicle radar device or a control method thereof that can reduce the possibility of being involved in an accident even when it is difficult to accurately detect a target with the own radar device.

  Another object of the present invention is to provide an in-vehicle radar device or a control method thereof that can reduce the possibility of being involved in an accident even when the collision avoidance operation with the target on the own vehicle side is insufficient. There is.

  The present invention provides a vehicle-mounted radar device that receives a reflected wave reflected from a target by outputting a transmission wave from a transmission unit, and detects a distance and relative speed with the target based on the reflected wave. The main feature is that a means for reflecting a transmission wave transmitted from another radar apparatus is provided.

  Thus, even when the radar device of the own vehicle cannot accurately grasp the presence of the target, the risk of an accident is avoided by causing the target radar device to detect the presence of the own vehicle.

  In a preferred embodiment of the present invention, the in-vehicle radar device includes means for directing (turning) the reflecting means in the direction of the detected target.

  Further, in a preferred embodiment of the present invention, in the on-vehicle radar device, a means for determining which target among the detected plural targets is most likely to collide, and the most likely collision by the means. Means for directing the reflecting means in the direction of the target determined to be high.

  In a preferred embodiment of the present invention, the in-vehicle radar device includes a notification unit that notifies the driver that the reflection unit is directed to another target.

  According to the present invention, even when it is difficult for the own radar device to detect the target or when the collision avoiding operation with the target is insufficient on the own vehicle side, the other radar device detects the presence of the own vehicle. Therefore, the possibility of being involved in an accident can be reduced.

  Other objects and features of the present invention will become apparent from the following description of the embodiments.

  An in-vehicle radar device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of an in-vehicle radar device according to Embodiment 1 of the present invention.

  In FIG. 1, the on-vehicle radar device 100 includes a modulation processing unit 101, a signal generation device 102, and a transmission antenna 103. In addition, reception antennas 104 and 105, a mixer 106, a demodulation processing unit 107, an A / D converter 108, and a signal processing unit 109 are provided. Furthermore, a notification device 110 and a driving device 111 controlled by the signal processing unit 109 and a radio wave reflector 112 driven by the driving device 111 are provided. Hereinafter, the role of each block and the like will be described by taking as an example a case where the radar method is a two-frequency CW (Continuous Wave) method and the angle detection method is a phase comparison monopulse method.

  The modulation processing unit 101 applies two different voltages v <b> 1 and v <b> 2 to the signal generator 102. The signal generator 102 generates high-frequency signals having two different frequencies f1 and f2 corresponding to the voltages v1 and v2. This high-frequency signal is input to the transmission antenna 103, and transmission radio waves having frequencies f1 and f2 are radiated into the space. The transmission radio wave is reflected by a target such as a vehicle or an obstacle (not shown) and received by the reception antennas 104 and 105 as a reception radio wave.

  At this time, a received high-frequency signal (hereinafter referred to as a received signal) is added with a Doppler frequency (fd) generated by a relative speed with respect to a target with respect to a transmitted high-frequency signal (hereinafter referred to as a transmitted signal). The frequencies of the received signals are f1 + fd and f2 + fd, respectively.

  In addition, since the phase difference φd is generated between the reception signal received by the reception antenna 104 and the reception signal received by the reception antenna 105 due to the optical path difference, the phases of the reception signals are φ and φ + φd, respectively.

  The reception signals input to the reception antennas 104 and 105 are input to the mixer 106, and the transmission signal and the reception signal are mixed to generate an intermediate frequency signal, which is then input to the demodulation processing unit 107. The signal demodulated by the demodulation processing unit 107 is input to the A / D converter 108 and input to the signal processing unit 109. As the signal processing unit 109, for example, a processor such as a DSP (Digital Signal Processor) specialized for processing of sound, images, and the like is suitable.

  Next, specific processing of the signal processing unit 109 provided in the in-vehicle radar device 100 according to the first embodiment of the present invention will be described with reference to FIG.

  FIG. 2 is a flowchart of a routine executed by the signal processing unit 109 according to the first embodiment of the present invention, which is repeatedly activated at predetermined time intervals.

  When the routine is started, first, FFT (Fast Fourier Transform) processing in step 201 is executed, and an FFT signal including frequency spectrum information is generated. Note that the FFT processing can be selected from processing by software or processing by a dedicated circuit such as an ASIC (Application Specific Integrated Circuit).

  Next, the physical value conversion process of step 202 is executed, and the target distance is calculated by Equation (2) based on the FFT signal.

  Here, Range is the target distance, C is the speed of light, φ is the phase difference between f1 and f2 in the received radio wave, and Δf is the frequency difference between f1 and f2.

  Further, the relative speed of the target is calculated by Expression (3).

  Here, Rate is the relative speed of the target, C is the speed of light, fd is the Doppler frequency, and f is the transmission frequency.

  Further, the angle of the target is calculated by Expression (4).

  Here, Azimuth is the angle of the target, φd is the phase difference between the reception signal of the reception antenna 104 and the reception signal of the reception antenna 105, λ is the wavelength of the transmission signal, and d is the distance between the reception antennas 104 and 105.

  Next, the target detection status determination process of step 203 is executed, and it is determined whether there is a target that is in danger of collision around the host vehicle.

  Next, when step 204 is executed and it is confirmed that there is a target at risk of collision in the vicinity of the host vehicle, the drive device operation process in step 205 and the notification process in step 206 are activated. If the presence of a target at risk of collision in the vicinity of the host vehicle is not confirmed, the drive device initialization process in step 207 is started.

  Here, the contents of the target detection status determination process in step 203 will be described. In this step, a target having a high risk of colliding with the host vehicle is determined from information on a plurality of targets detected by the in-vehicle radar device 100, that is, Range, Rate, and Azimuth. At this time, if a plurality of targets having a high risk of collision are detected at the same time, one target having the highest risk of collision is selected from them.

  A method of selecting a target having the highest risk of collision will be described with reference to FIG.

  FIG. 3 is a diagram illustrating an example of a target detection status of the in-vehicle radar device 100 according to the first embodiment of the present invention.

  The in-vehicle radar device 100 can detect a target within the beam range 301. The actual target 302 is a moving body traveling in the adjacent lane, the target 303 is a moving body traveling in the own lane, and the stationary object 304 is a stationary object such as a telephone pole. In this case, the stationary object 304 without the risk of collision with the host vehicle is excluded from the target. Of the remaining two targets, one is the target 302 traveling in the adjacent lane, the other is the target 303 traveling in the own lane, and the target with the highest risk of collision is the target 303. Is determined.

  Next, the contents of the drive device operation process in step 205 in FIG. 2 will be described. When this process is started, the drive unit 111 necessary for directing (turning) the radio wave reflector 112 of FIG. 1 in the direction in which the target 303 having the highest risk of collision selected in step 203 exists is provided. Command value is determined.

  Next, the contents of the notification process in step 206 will be described. When this process is activated, a signal is sent to the notification device 110, so that the driver can be notified that the presence of the dangerous target 303 is confirmed around the host vehicle. In addition, as the alerting | reporting apparatus 110, there exists the method by the display on a display by LED, or a warning sound.

  Next, the drive device initialization process in step 207 will be described. When this process is started, an operation to return the state of the radio wave reflector 112 from the state in which the direction of the radio wave reflector 112 is changed according to the direction of the target to the initial state is executed by the drive device operation process in step 205. Thereby, even when a dangerous target no longer exists around the host vehicle, it is possible to avoid a situation in which the radio wave reflector 112 faces an unexpected direction. As the initial state, the front direction of the in-vehicle radar device 100 is appropriate, but can be arbitrarily changed for each application.

  Next, the drive device 111 provided in the in-vehicle radar device 100 according to the first embodiment of the present invention will be described. The driving device 111 drives the radio wave reflector 112 to turn at predetermined time intervals based on the command value calculated in the processing step 205 or 207 of FIG. Note that the power of the driving device 111 includes, for example, a motor.

  Next, the radio wave reflector 112 provided in the in-vehicle radar device 100 according to the first embodiment of the present invention will be described with reference to FIG.

  FIG. 4 is an example of the shape of the radio wave reflector 112 according to the first embodiment of the present invention. The radio wave reflector 112 has a shape excluding one surface of the triangular pyramid, and has a structure in which the radio wave traveling straight from the target is reflected as it is toward the target by directing its opening toward the target. In FIG. 4, it is the figure seen from the downward direction rather than the center. The radio wave reflector (reflector) 112 having such a shape can efficiently reflect the radio wave incident from the front direction in the front direction. However, such a reflector 112 has a lower reflection efficiency for radio waves incident from other than the front direction.

  FIG. 5 is a block diagram of an in-vehicle radar device 500 according to the second embodiment of the present invention.

  In this embodiment, when compared with the configuration of the on-vehicle radar device 100 of the first embodiment described above, only the driving device 511 and the radio wave reflector 512 are added for convenience, but a plurality of radio wave reflectors 112 to 512 capable of turning are added. It is different in having. Accordingly, the processing contents of the signal processing unit 509 in the present configuration with slight changes, and the driving devices 111 to 511 and the radio wave reflectors 112 to 512 will be described.

  FIG. 6 is a flowchart of a routine executed by the signal processing unit 509 provided in the in-vehicle radar device 500 according to the second embodiment of the present invention, which is repeatedly activated at predetermined time intervals. Basically, it is the same as the processing of the signal processing unit 109 of FIG. 1 described with reference to FIG.

  If it is confirmed in step 204 that there is a target having a collision risk, the process proceeds to step 601 to start target risk calculation processing. When this process is started, the risk of collision is calculated for each target selected in step 203 first. Then, according to the calculated degree of risk, in the drive device operation process of step 205, among the plurality of radio wave reflectors 112 to 512 provided in the in-vehicle radar device 500, how many radio wave reflectors should be directed to the target. Determine whether. Then, command values to the respective driving devices 111 to 511 are determined so as to turn the necessary radio wave reflectors 112 to 512 toward the respective targets.

  FIG. 7 is a block diagram of an in-vehicle radar device 700 according to the third embodiment of the present invention.

  In the present embodiment, when compared with the configuration of the on-vehicle radar device 500 of FIG. 5 described above, the driving devices (1 to n) 711 to 721 and the radio wave reflectors 712 to 722 are included in the signal processing unit of the on-vehicle radar device 700. It is characterized in that it operates independently from the processing result 109. The difference from Example 2 of FIG. 5 by this is demonstrated.

  In the on-vehicle radar device 700 according to the third embodiment of the present invention, the driving devices 711 to 721 are repeatedly operated at regular time intervals regardless of the target detection status of the on-vehicle radar device 700. Accordingly, the radio wave reflectors 712 to 722 scan the front direction of the in-vehicle radar device 700 within a certain range (scanning angle range) at regular time intervals.

  In addition, the repetition operation period of the drive apparatuses 711-721 and the electromagnetic wave reflectors 712-722, a scanning angle range, etc. can be arbitrarily set according to the application to be used.

  FIG. 8 is a block diagram of an in-vehicle radar device 800 according to the fourth embodiment of the present invention.

  In the present embodiment, when compared with the configuration of the on-vehicle radar device 500 of the second embodiment of FIG. 5 described above, the radio wave reflection device 810 in which the drive devices 811 to 812 and the radio wave reflectors 813 to 814 are combined is an on-vehicle radar. It is characterized in that it is separate from the device 800. Each of the driving devices 811 to 812 in the radio wave reflection device 810 is controlled by a command from the signal processing unit 809 in the in-vehicle radar device 800.

  According to this embodiment, the radio wave reflection device 810 can be attached to any place of the vehicle.

  FIG. 9 is an example of attachment of the in-vehicle radar device according to the second or third embodiment of the present invention to a vehicle. The vehicle 900 includes an in-vehicle radar device 910 for rear monitoring. In addition, radio wave reflection devices 921 and 922 that are separate from the in-vehicle radar device 910 are mounted in rear bumpers on the left and right sides of the vehicle as shown in the figure.

  According to this embodiment, it is possible to prevent the signal intensity from being lowered when viewed from another radar apparatus, and to secure a reflection cross-sectional area obliquely behind the vehicle.

  In the above-described embodiment, the two-frequency CW system is described as an example, but the same effect can be obtained by other modulation systems such as an FMCW system that modulates the frequency of radio waves into a triangle in terms of time. Although the amplitude comparison monopulse method has been described as an example, the same effect can be obtained by other angle detection methods such as a phase comparison monopulse method and a mechanical scan method. Furthermore, although the 76 GHz band has been described, the same effect can be obtained in other frequency bands.

  According to the embodiment of the present invention described above, when the collision avoidance operation with the target is insufficient in the own vehicle, the possibility of being involved in an accident is reduced by making the other radar apparatus recognize the existence of the own vehicle. can do.

1 is a block configuration diagram of an in-vehicle radar device according to Embodiment 1 of the present invention. The flowchart of the process routine of the signal processing part in Example 1 of this invention. 1 is a diagram illustrating an example of a target detection status of an in-vehicle radar device according to Embodiment 1 of the present invention. An example figure of the shape of radio wave reflector 112 in Example 1 of the present invention. The block block diagram of the vehicle-mounted radar apparatus 500 by Example 2 of this invention. The flowchart of the routine which the signal processing part by Example 2 of this invention performs. The block block diagram of the vehicle-mounted radar apparatus 700 by Example 3 of this invention. The block block diagram of the vehicle-mounted radar apparatus 800 by Example 4 of this invention. An example figure of attachment to a vehicle of an in-vehicle radar device by one example of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100,500,700,800,910 ... Vehicle-mounted radar apparatus, 101 ... Modulation processing part, 102 ... Signal generation apparatus, 103 ... Transmission antenna, 104, 105 ... Reception antenna, 106 ... Mixer, 107 ... Demodulation processing part, 108 ... A / D converter, 109,509,809 ... Signal processing unit, 110 ... Notification device, 111,511,711-721,811-812 ... Drive device, 112-512,712-722,813-814 ... Radio wave reflection Reflector, 810, 921, 922 ... Radio wave reflection device, 301 ... Beam range, 302, 303 ... Target, 304 ... Stationary object, 900 ... Vehicle.

Claims (11)

  A transmission means for transmitting a transmission wave toward the periphery of the vehicle, a reception means for receiving a reflected wave reflected from the target by this transmission, and a distance from the target based on the reflected wave received by the reception means; An in-vehicle radar apparatus having a calculation means for calculating a relative speed, comprising: a reflection means capable of turning and reflecting a transmission wave from the outside; and a drive means for driving the reflection means to turn. Radar equipment.   2. The in-vehicle radar device according to claim 1, wherein the driving unit includes a direction setting unit that sets a turning direction of the reflecting unit in a target direction detected by the radar device of the own vehicle.   3. The driving means according to claim 1, wherein said driving means determines which target has the highest possibility of collision among a plurality of targets detected by the radar device of the own vehicle, and the determination means causes the most collision. An in-vehicle radar device comprising: direction setting means for setting a turning direction of the reflecting means in the direction of the target that is determined to be highly likely.   4. The on-vehicle radar device according to claim 1, wherein the driving means includes a motor that outputs a turning driving force for turning the reflecting means.   5. The in-vehicle radar device according to claim 1, further comprising an informing unit that informs a driver that the reflecting unit is driven to turn toward an external target. 6.   6. The method according to claim 1, further comprising initialization setting means for initializing a turning direction of the reflecting means to a predetermined direction when a target is not detected by the radar device of the host vehicle. An on-vehicle radar device.   An on-vehicle radar device that transmits a transmission wave toward the surroundings of the vehicle, receives a reflected wave reflected from the target by this transmission, and calculates a distance and a relative speed from the target based on the received reflected wave A control method for an in-vehicle radar device, characterized in that the reflecting means for reflecting the transmission wave from the outside is turned.   8. The method of controlling an in-vehicle radar device according to claim 7, wherein the turning direction of the reflecting means is set in the direction of the target detected by the radar device of the own vehicle.   9. The method according to claim 7, wherein a target that has the highest possibility of collision among the plurality of targets detected by the radar device of the host vehicle is determined, and the direction of the target that is determined to have the highest possibility of collision is determined. A control method for an in-vehicle radar device, wherein a turning direction of the reflecting means is set.   The method for controlling an on-vehicle radar device according to claim 7, wherein the driver is notified that the reflecting means is turning-driven toward an external target.   The on-vehicle radar device according to any one of claims 7 to 10, wherein when the target is not detected by the radar device of the own vehicle, the turning direction of the reflecting means is initialized to a predetermined direction. Control method.

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