JP2010091490A - Automotive radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that conventional techniques cannot have determined the reliability of target detection information in real time. <P>SOLUTION: An automotive radar system includes: a transmission means for transmitting first radio waves; a reception means for receiving second radio waves, reflected first radio waves from a target, and acquiring reception signals; a computation means for computing the distance, relative speed, and angle to the target on the basis of the reception signals; and first and second radars having a first region capable of detecting the distance, relative speed, and angle to the target and a second region capable of detecting only the distance and relative speed to the target. The computation means computes the distance, relative speed, and angle to the target in a third region in which the second region of the first radar and the second region of the second radar are superimposed on each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an on-vehicle radar system used in a preventive safety system.

  In recent years, interest in automobile safety technology has increased, and research and development of collision avoidance systems such as inter-vehicle distance warning systems, adaptive cruise control systems, pre-crash systems, and systems that reduce impact during collisions have been actively promoted. ing.

  When constructing these systems, an in-vehicle radar is one of sensors that measure the distance, relative speed, and angle with a target. This in-vehicle radar radiates radio waves and receives reflected waves from targets such as vehicles and obstacles, detects the propagation time of radio waves, signal intensity of reflected waves, Doppler shift of frequency, etc. A modulation method for measuring a distance to a target and a relative speed based on the above is known. Particularly, a two-frequency CW (Continuous Wave) method and an FMCW (Frequency Modulated Continuous Wave) method are well known.

  Here, there is known a vehicle object detection device in which a region where an object can be detected with high accuracy using an array antenna is expanded (see Patent Document 1).

JP 2006-292518 A

  According to Patent Document 1, in order to determine whether or not the relative position of an object detected in an indeterminate region (side lobe or grating lobe) is reliable based on a preliminarily estimated relative movement locus, The reliability of the target detection information in the uncertain area cannot be determined unless the target is detected in advance in the fixed area of the own radar or the fixed area of another radar and the relative movement locus is estimated. That is, there is a problem that the reliability of the target detection information cannot be determined in real time.

  Therefore, an object of the present invention is to provide an in-vehicle radar system that can expand a region for detecting a target distance, relative speed, and angle in real time by using side lobes and grating lobes that lead to false detection of the target. There is to do.

  In order to solve the above problems, one of the desirable embodiments of the present invention is as follows.

  The in-vehicle radar system includes: a transmission unit that transmits a first radio wave; a reception unit that receives a second radio wave reflected from a target and obtains a reception signal; and Calculation means for calculating the distance, relative speed, and angle to the target, a first area that can detect the distance, relative speed, and angle to the target, and a second that can detect only the distance and relative speed to the target The first and second radars having a first area and a second radar area, and the calculation means includes a target in a third area where the second area possessed by the first radar and the second area possessed by the second radar overlap. Distance, relative speed, and angle.

  According to the present invention, there is provided an in-vehicle radar device system capable of expanding an area for detecting a target distance, relative speed, and angle in real time by using a side lobe and a grating lobe that lead to erroneous detection of the target. be able to.

  The on-vehicle radar system according to the present embodiment will be described below with reference to FIGS. In the drawings and the following description, the same reference numerals or the same reference symbols are used for the same components.

  The vehicle-mounted radar described below will describe a case where a two-frequency CW method is used as a modulation method and a phase comparison monopulse method using an array antenna is used as an angle detection method.

  FIG. 1 is a diagram showing a system configuration of an in-vehicle radar system. A vehicle-mounted radar (1) 101 and a vehicle-mounted radar (2) 102 are mounted in front of the vehicle 100. The on-vehicle radar (1) 101 and the on-vehicle radar (2) 102 are connected to the integrated controller 104 via a communication network 103, and target information detected by each of the on-vehicle radars is connected to the integrated controller 104 via the communication network 103. 104 is transmitted. Hereinafter, the configuration of the on-vehicle radar (1) 101 will be described first, but the same applies to the on-vehicle radar (2) 102.

  FIG. 2 shows an area where the distance, relative speed and angle of the target (hereinafter referred to as target information determination area) in the in-vehicle radar (1) 101 can be detected, and an area where only the distance and relative speed between the target can be detected (hereinafter referred to as the following). It is a figure which shows typically a target information uncertain area | region. The main difference between the two areas is whether the angle with the target can be calculated. Hereinafter, the reason will be described.

  FIG. 3 is a diagram showing the relationship between the phase difference of the received signal and the angle with the target in the target information determination area and the target information indetermination area. The vertical axis represents the phase difference of the received signal, and the horizontal axis represents the angle with the target. In this embodiment, the angle with the target is 0 degree in the front direction, plus in the right direction and minus in the left direction. As can be seen from the figure, there are a region where the relationship between the phase difference of the received signal and the angle of the target is one-to-one, and a region which is not one-to-one and has uncertainty. Since the phase comparison monopulse method using an array antenna calculates the angle with the target by detecting the phase difference of the received signal, the region where the phase difference of the received signal and the angle with the target are not one-to-one This is an area where the angle cannot be determined. In this embodiment, this area is called a target information indeterminate area. An area where the phase difference of the received signal and the angle between the target is one to one is called a target information determination area.

  Furthermore, from the figure, even in the target information uncertain area, the angle with the target cannot be calculated uniquely, but the target exists in the right direction area or the left direction area based on the phase difference of the received signal. It turns out that it is possible to judge whether to do. In the present embodiment, they are referred to as a right direction target uncertainty region and a left direction target uncertainty region, respectively.

  Note that conventional in-vehicle radars generally use only the target information fixed area, and exclude target information calculated in the target information undefined area. On the other hand, in this embodiment, target information calculated in the target information indeterminate region is also used.

  FIG. 4 is a block diagram showing the on-vehicle radar (1) 101. As shown in FIG.

  The on-vehicle radar (1) 101 includes a modulation processing unit 401, a signal generator 402, a transmission antenna 403, a reception antenna (1) 404, a reception antenna (2) 405, a mixer (1) 406, a mixer (2) 407, A / D converter (1) 408, A / D converter (2) 409, and signal processor 410 are provided.

  Hereinafter, the role of each block will be described.

  The modulation processing unit 401 applies two different voltages v 1 and v 2 to the signal generator 402. The signal generator 402 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 403, 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 input to the reception antenna (1) 404 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.

  The received signal input to the receiving antenna (1) 404 is input to the mixer (1) 406, mixes the transmission signal and the received signal, generates an intermediate frequency signal, and then inputs to the A / D converter (1) 408. And input to the signal processing unit 410. A similar received signal is also generated from the receiving antenna (2) 405 and input to the signal processing unit 410.

  The signal processing unit 410 is a processor such as a DSP.

  Next, specific processing of the signal processing unit 410 included in the in-vehicle radar (1) 101 will be described with reference to FIG. This figure is a flowchart of a routine executed by the signal processing unit 410 and is repeated at predetermined time intervals.

  When the routine is started, first, the FFT processing in step 500 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.

  Next, the distance calculation process of step 501 is executed, and the distance to the target is calculated by equation (1) based on the FFT signal.

  Here, Range is the distance, C is the speed of light, φ is the phase difference between the received signals f1 and f2 at the receiving antenna (1), and Δf is the frequency difference between f1 and f2.

  Next, the relative speed calculation process of step 502 is executed, and the relative speed with respect to the target is calculated by equation (2).

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

  Subsequently, the received signal phase difference calculation process in step 503 is executed, and the phase difference between the received signal received by the receiving antenna (1) 404 and the received signal received by the receiving antenna (2) 405 is calculated. .

は受信アンテナ（１）４０４の受信信号、

は受信アンテナ（２）４０５の受信信号である。 Where Δφ is the phase difference of the received signal,

Is the received signal of the receiving antenna (1) 404,

Is a received signal of the receiving antenna (2) 405.

  Subsequently, the target detection area determination in step 504 is executed. As described above, it is possible to determine whether the target information is determined from the phase difference of the received signal or whether the target information is determined from the target information determined area. When the process is executed and it is determined that the target information is in the uncertain target information area, the right / left determination process of step 506 is executed.

  When the angle calculation process of step 505 is executed, the relationship between the phase difference of the received signal and the target angle as shown in FIG. 2 is used, and the angle with the target is calculated from the phase difference of the received signal calculated in step 503. Is calculated. At this time, the fact that the target information is information calculated in the target detection information determination area is also recorded as target detection area information.

  When the left and right region determination processing in step 506 is executed, the relationship between the phase difference of the received signal and the angle with the target as shown in FIG. 2 is used, and the target is moved to the right from the phase difference of the received signal calculated in step 503. It is determined whether it exists in the direction target information indeterminate area or in the left direction target information indeterminate area. At this time, this determination result is also recorded as target detection area information.

  Note that the relationship between the phase difference of the received signal used in step 504 to step 506 and the angle between the target and the target follows formula (4), and can be calculated by calculation processing.

  Here, θ is the angle with the target, Δφ is the phase difference of the received signal, λ is the wavelength of the received wave, and d is the distance between the antennas.

  As another method, the relationship between the phase difference of the received signal used in steps 504 to 506 and the angle between the target and the target can be obtained by collecting data in advance and storing it in a memory or the like.

  Next, target information transmission processing in step 507 is executed, and the distance, relative speed, angle, target detection area information, in-vehicle radar identification information, and the like calculated in steps 500 to 506 to the integrated controller 104. Send. Here, the radar identification information is information used by the integrated controller 104 to identify at which position the target information is provided by the radar.

  Next, a description will be given of the entire vehicle-mounted radar system.

  FIG. 6 is a diagram illustrating an example of an arrangement method of the in-vehicle radar (1) 101 and the in-vehicle radar (2) 102 in the in-vehicle radar system. As shown in the figure, the target information indeterminate region of the in-vehicle radar (1) 101 and the target information indeterminate region of the in-vehicle radar (2) 102 are arranged so as to overlap each other, so that the distance from the target and the relative An area where the speed and angle can be calculated (hereinafter referred to as a target information confirmation area) can be formed. Specifically, the angle of the target can be determined by triangulation using the distance from the target detected by each in-vehicle radar in this superimposed region. This process is executed by the integrated controller 104 in FIG.

  Next, signal processing provided in the integrated controller 104 in the in-vehicle radar system will be described with reference to FIG. The flowchart shown in the figure is repeated at predetermined time intervals.

  When the routine is started, first, in the detection area determination in step 701, it is determined which radar the target information currently being processed is detected and in which detection area the target information is detected. Determine the processing. Here, the detection area refers to either a target information confirmation area, a right direction target information uncertain area, or a left direction target information uncertain area. As a specific determination method, first, if the information is detected in the target detection information determination area regardless of the location of the radar, the process proceeds to step 704. In the case of target information detected in other target detection information indeterminate areas, as described above, in the case of target information indeterminate areas in the direction in which the target information indeterminate areas are superimposed, step 703 is executed. Otherwise, step 702 is executed.

  For example, when the target information to be processed is information detected in the right direction target information indeterminate region of the in-vehicle radar (1) 101, step 702 is executed. If the target information currently being processed is information detected in the left target information indeterminate region of the in-vehicle radar (1) 101, step 703 is executed.

  Next, when the target information discarding process in step 702 is executed, it is determined that the angle with the target cannot be determined, and the target detection information is discarded.

  Next, when the angle recalculation process of step 703 is executed, the angle with the target is confirmed by executing triangulation based on the distance to the target calculated in each target uncertain region. Go to step 704.

  Hereinafter, the triangulation method will be specifically described with reference to FIG. As shown in the figure, when the detection target 800 exists in the aforementioned target information confirmation area, the on-vehicle radar (1) detects the distance R1 and the relative speed V1 with the target in the right target uncertain area. In the on-vehicle radar (2), the distance R2 to the target and the relative speed V2 are detected. Since the distances R1 and R2 with respect to the targets detected by the respective on-vehicle radars are detection results for the same target, considering the mounting interval dr between the on-vehicle radar (1) and the on-vehicle radar (2), The angle θ1 with respect to the target detected by the on-vehicle radar (1) can be calculated by equation (5).

  At this time, since the relative speed of the target detected in each region detects the same object, naturally, by adding a process that takes into account that an approximately equal value should be detected, Accuracy is improved when determining the angle.

  In the target information transmission process in step 704, the distance, relative speed, and angle with the target calculated in the target information determination area and the target information determination area are transmitted to the host controller. As the upper controller, there are controllers such as an inter-vehicle distance warning system, an adaptive cruise control system, and a pre-crash system.

  In the present embodiment, an example in which two on-vehicle radars are mounted will be described, but it goes without saying that the same applies to the case where three or more radars are mounted. In addition, in the present embodiment, the system in the case of having a controller that controls the system has been described, but without using the overall controller, by exchanging target information directly between each in-vehicle radar via a communication network, It is also possible to establish a system.

The figure which shows the system configuration | structure of a vehicle-mounted radar system. The figure which shows typically the target information fixed area | region and target information uncertain area | region in vehicle-mounted radar (1). The figure which shows the relationship between the phase difference of the received signal in a target information definite area | region and a target information uncertain area | region, and the angle of a target. The figure which shows the block configuration of the vehicle-mounted radar (1). The flowchart of the routine which the signal processing part of vehicle-mounted radar (1) performs. The figure which shows an example of the arrangement | positioning method of the vehicle-mounted radar (1) and vehicle-mounted radar (2) in a vehicle-mounted radar system. The flowchart of the signal processing with which the integrated controller in a vehicle-mounted radar system is equipped. The figure which shows an example in case a detection target exists in a target information confirmation area | region.

Explanation of symbols

100 Vehicle 101 On-vehicle radar (1)
102 On-vehicle radar (2)
103 Communication Network 104 Integrated Controller 401 Modulation Processing Unit 402 Signal Generator 403 Transmitting Antenna 404 Receiving Antenna (1)
405 Receiving antenna (2)
406 Mixer (1)
407 Mixer (2)
408 A / D converter (1)
409 A / D converter (2)
410 Signal Processing Unit 800 Detection Target

Claims (3)

A transmission means for transmitting the first radio wave;
Receiving means for receiving a second radio wave reflected from the target and obtaining a received signal;
Calculation means for calculating a distance to the target, a relative speed, and an angle based on the received signal;
A first radar and a second radar having a first area capable of detecting a distance to the target, a relative speed and an angle; and a second area capable of detecting only the distance to the target and the relative speed;
The calculation means calculates a distance to the target, a relative speed, and an angle in a third region where the second region of the first radar and the second region of the second radar overlap. In-vehicle radar system. The receiving means represents an array antenna;
The first region shows a main lobe in the array antenna;
The in-vehicle radar system according to claim 1, wherein the second region indicates a grating lobe or a side lobe in the array antenna.   The in-vehicle radar system according to claim 1, wherein the calculation unit calculates a distance to the target, a relative speed, and an angle based on triangulation.

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