JP2013164385A - Radar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect timing for receiving a reflection wave obtained by the reflection of a transmission wave from a target outside a vehicle with high accuracy while taking the influence of a return wave into consideration.SOLUTION: In a radar system 11, a distance calculation unit 22 calculates an intermediate point between rising timing surpassing a threshold set on the basis of a sampling maximum value and falling timing falling below the threshold among reception signal waveforms composed of a plurality of sampling values obtained in an AD converter 21 as reception timing. The distance calculation unit 22 determines to have received a fusion wave between reflection light of a detection object and return light in the case where a return light fusion determination unit 23 recognizes that both waveforms of the reflection light and the return light are not the same even though they are approximate to each other by comparing reception timing and peak intensity in the reception signal waveforms (reflection light) with return light information. Then, a return light removal distance calculation unit uses a relation between the peak intensity and pulse width to offset the rising timing in the reception signal waveforms.

Description

  The present invention relates to a radar device mounted on a vehicle.

  Conventionally, a transmission wave having a predetermined pulse waveform is transmitted, a reception signal including a reflection wave received within a predetermined time from the transmission timing of the transmission wave is sampled, and reception of the reflection wave is performed based on the sampling value. An on-vehicle radar device that detects timing is known. According to this in-vehicle radar device, by measuring the time difference from the transmission timing of the transmission wave to the reception timing of the reflected wave (that is, the round-trip time of the transmission wave), the distance from the target reflecting the transmission wave is obtained. Can do.

  In this type of radar device, the transmission timing of the transmission wave is known, whereas the reception timing of the reflected wave reflected from the target outside the vehicle cannot be known in advance. High detection accuracy is required for the reception timing. On the other hand, in order to realize such high-accuracy detection, high resolution in the sampling of the received signal is required, and the cost of equipment (for example, AD converter) related to this is increased. That is, in the radar apparatus, the detection accuracy and the cost are in a trade-off relationship.

  Therefore, the maximum value of the sampling value obtained from the received signal is detected, a value obtained by multiplying the maximum value by a coefficient less than 1 (for example, 0.5) is set as a threshold value, and the sampling value exceeds this threshold value. By calculating the timing and the falling timing at which the sampling value falls below this threshold value, a detection method is adopted in which the intermediate point between the two timings is the reception timing of the reflected wave (for example, Patent Document 1). reference). According to this detection method, the detection accuracy of the reception timing can be improved without necessarily requiring high-resolution sampling.

JP 2005-257405 A

  By the way, a conventional radar apparatus is mounted on a vehicle in a form exposed to the outside, but in recent radar apparatuses, in order to prevent deterioration in detection accuracy due to attachments due to wind and rain or dust, A mode of being installed in the vicinity of the windshield) is beginning to be adopted.

  As described above, in the radar apparatus installed in the vehicle interior, the transmission wave is reflected from a part of the vehicle such as the windshield, although it is not necessary to consider the influence of noise caused by the reflection of the transmission wave from the deposit. It is constantly affected by the reflected wave (referred to as “return wave”).

  However, since the conventional radar apparatus employs only a configuration for removing noise as described in Patent Document 1, there is no way to deal with a return wave. Such a problem can be ignored for a target located far from the vehicle because the reception timing of the return wave and the reception timing of the reflected wave from the target are significantly different, but PCS (Pre- Like Crash Safety), there is a vehicle control that has a high demand for detection of a target close to the vehicle, which is becoming a problem that cannot be ignored.

  In order to solve the above problems, the present invention is a radar capable of accurately detecting the reception timing of a reflected wave in which a transmitted wave is reflected from a target outside the vehicle while taking into account the influence of a return wave. An object is to provide an apparatus.

  The radar apparatus according to claim 1, which is an invention made to achieve the above object, is an apparatus installed in a vehicle interior, wherein a transmission wave of a pulse waveform is transmitted by a transmission / reception means, and the transmission wave is transmitted. A reception signal is generated by receiving a signal including the reflected wave, and the reception signal generated by the transmission / reception means is sampled by the sampling means. Then, the threshold setting means sets the sampling maximum value, which is the maximum value of the sampling values, among the pulse waveforms composed of a plurality of sampling values obtained by the sampling means within a predetermined time from the transmission timing of the transmission wave by the transmission / reception means. Based on this, a threshold for determining the reception timing of the reflected wave is set.

  Further, the timing calculation means calculates the rising timing at which the sampling value exceeds the threshold set by the threshold setting means, and the falling timing at which the sampling value falls below the sampling value, and the reception timing detection means calculates by the timing calculation means An intermediate point between the rising timing and the falling timing is detected as the reception timing of the reflected wave.

  In the present invention, in such a configuration, the storage means uses the reflected wave obtained by reflecting the transmission wave from a part of the vehicle within the predetermined time as a return wave, and the reception timing and sampling maximum corresponding to the return wave. The return wave information including the value is stored.

  When the return wave determination unit can regard that the reception timing of the reflected wave detected by the reception timing detection unit approximates the reception timing corresponding to the return wave stored in the storage unit, the return wave information is used. Then, it is determined whether or not the pulse waveform including the maximum sampling value is the same as the waveform of the return wave.

  Further, when the timing correction unit determines that the pulse waveform including the maximum sampling value is not the same as the waveform of the return wave by the return wave determination unit, the timing calculation unit uses the pulse width based on the maximum sampling value. The rise timing calculated in step 1 is corrected.

  In the present invention, since a part of the vehicle in which the transmission wave is reflected as the return wave is located at a predetermined distance from the radar apparatus, the reception timing and the maximum sampling value in the return wave information are stored as known information. The point that can be kept, and the reflected wave (the reflected wave to be detected) from which the transmitted wave is reflected from the target and the reflected wave (the returned wave) from which a transmitted wave is reflected from a part of the vehicle, The focus is on the similar relationship to the shape of the transmitted wave.

  In other words, in the present invention, by comparing the reception timing and pulse waveform in the received signal (reflected wave) with this return wave information, if the reflected wave and the return wave are approximate but not the same, It is assumed that the reflected wave with the return wave (specifically, the reflected wave with the reflected wave of the detection object fused in time behind the return wave) is received, and in this case, the reflected wave of the detection object or Rise timing is offset using a pulse width based on the maximum sampling value of the return wave.

  Therefore, according to the present invention, it is possible to remove the influence of the return wave from the rising timing with respect to the fusion wave as described above, thereby transmitting from the target outside the vehicle while taking the influence of the return wave into account. The reception timing of the reflected wave reflected from the wave can be detected with high accuracy.

  In the radar apparatus of the present invention, as described in claim 2, when the return wave determining means determines that the pulse waveform including the maximum sampling value is the same as the waveform of the return wave, An update means for updating the return wave information stored in the storage means based on the rising timing and the falling timing calculated by the timing calculating means may be provided.

  With this configuration, the sampling maximum value and the reception timing in the return wave information can be held at the latest values. For example, dust or dirt adheres to a part of the vehicle, or radar in the vehicle interior. Even when the position of the device is shifted and the return wave information varies somewhat, it is possible to cope with it appropriately.

  Further, in the radar device of the present invention, as described in claim 3, the maximum sampling value obtained by the sampling means is the actual measurement maximum value, and the maximum sampling value included in the return wave information is the comparison maximum value, When the return wave determination means determines that the pulse waveform including the maximum sampling value is not the same as the waveform of the return wave, the difference value between the measured maximum value and the comparison maximum value exceeds the preset allowable difference value May include correction prohibiting means for prohibiting correction of the rise timing by the timing correcting means.

  With this configuration, when the actual measured maximum value is much larger than the comparative maximum value, i.e., when there is no influence of the return wave on the rise timing calculation, the detection target is not subjected to unnecessary correction. The reception timing of the reflected wave can be detected appropriately. The allowable difference value can be set, for example, as a value that makes the comparison maximum value smaller than a threshold value based on the actual measurement maximum value.

  In the radar apparatus according to claim 3, as described in claim 4, the timing correction unit is configured such that the difference value between the actual measurement maximum value and the comparison maximum value is non-negative and equal to or less than the allowable difference value. In some cases, the rise timing can be corrected using the pulse width based on the actually measured maximum value.

  That is, in the reflected wave (fused wave) that is a combination of the reflected wave and the return wave of the detection target, if the reflected wave of the detection target is relatively stronger than the return wave, the actual measurement maximum value of the detection target Since a value corresponding to the reflected wave is detected, the rising timing is offset using the pulse width based on the actually measured maximum value.

  Alternatively, in the radar apparatus according to the present invention, as described in claim 5, the timing correction unit, when it can be considered that the actual measurement maximum value matches the comparison maximum value, sets the comparison maximum value included in the return wave information. The rising timing can be corrected by using the pulse width based on it.

  That is, in the fusion wave, since the reflected wave of the detection target is relatively weaker than the return wave, if the value corresponding to the reflected wave of the detection target is not detected as the actual measurement maximum value, the pulse based on the actual measurement maximum value is bothered. Since the rise timing is offset using the pulse width based on the return wave information without calculating the width, the reception timing of the reflected wave to be detected can be efficiently obtained.

  In the radar apparatus of the present invention, as described in claim 6, the transmission / reception means transmits transmission waves to a plurality of areas on the traveling direction side of the vehicle, and the storage means returns corresponding to each of these areas. Wave information can also be stored. In this case, the detection range of the spatial reflected wave can be suitably expanded.

  Further, in the radar apparatus of the present invention, as described in claim 7, the target outside the vehicle is based on the transmission timing of the transmission wave by the transmission / reception means and the reception timing detected by the reception timing detection means. It is also possible to provide a distance measuring means for measuring the distance to In this case, since ranging can be performed by one apparatus, it is possible to reduce the processing load of another apparatus that cooperates with the radar apparatus of the present invention.

(A) is explanatory drawing which shows schematic structure of the driving assistance system to which the radar apparatus of this invention is applied, (b) is a side view of the vehicle which shows the example of arrangement | positioning of a radar apparatus. It is a schematic diagram which shows an example of the irradiation area | region of the transmission wave in a radar apparatus. (A) is a functional block diagram which shows the structure of a radar control part, (b) is a functional block diagram which shows the structure of a distance calculation part among the structures of a radar control part. It is a flowchart which shows the procedure of the pre-process process which a radar control part performs. (A) is a flowchart which shows the procedure of the normal distance calculation process which a radar control part performs, (b) is a flowchart which shows the procedure of the return light removal calculation process which a radar control part performs. It is a graph for demonstrating correction | amendment of the rise timing in a return light removal calculation process. It is a flowchart which shows the procedure of the return light fusion determination process which a radar control part performs. It is the 1st explanatory view for explaining the judgment method in return light fusion judgment processing. It is the 2nd explanatory view for explaining the judgment method in return light fusion judgment processing.

Hereinafter, a driving support system to which a radar apparatus according to an embodiment of the present invention is applied will be described with reference to the drawings.
[Schematic configuration of the system]
As shown in FIG. 1A, the driving support system 1 of the present embodiment is based on a radar device 10 that detects an object 50 such as another vehicle or a pedestrian outside the vehicle, and a detection result by the radar device 10. And a vehicle control unit 30 that performs various vehicle controls. The driving support system 1 is mounted on a vehicle 100 such as a passenger car, for example, and the radar apparatus 10 is installed so as to transmit a transmission wave to the traveling direction side of the vehicle 100 in the passenger compartment.

  In the present embodiment, the radar apparatus 10 is configured to irradiate a laser beam as a transmission wave on the front side as the traveling direction side of the vehicle 100, and as shown in FIG. It is installed near the windshield (hereinafter referred to as “front glass”).

  As shown in FIG. 1A, the radar apparatus 10 includes a radar control unit 11, a scanning drive unit 12, and an optical unit 13. The radar control unit 11 includes a well-known microcomputer 20 including a CPU 17 and a memory 18 such as a ROM, a RAM, and a flash memory, and an AD converter 21 (see FIG. 3) described later. The CPU 17 executes various processes such as a distance calculation process described later according to a program stored in the memory 18 such as a ROM.

  The scanning drive unit 12 is configured by, for example, an actuator or a motor, and can receive the command from the microcomputer 20 of the radar control unit 11 so that the optical unit 13 can be directed in any direction in the horizontal direction and the vertical direction. It is configured.

  The optical unit 13 emits a laser beam having a predetermined pulse waveform in response to a command from the microcomputer 20 of the radar control unit 11, and a laser beam from the light emitting unit 14 (FIG. 1A). In FIG. 1, a solid line arrow) includes a light receiving unit 15 for receiving a reflected wave (indicated by a broken line arrow in FIG. 1A) when reflected by an object 50 outside the vehicle 100. Specifically, the light receiving unit 15 is configured to receive a reflected wave (reflected light) of laser light and generate a signal including a waveform corresponding to the reflected light as a received signal (analog signal).

  As a result, the scanning drive unit 12 may be configured to be changed so that the emission direction of the laser light from the light emitting unit 14 is the same as the direction in which the light receiving unit 15 can receive the reflected light. For example, instead of the optical unit 13, the scan driving unit 12 may be configured to drive a mirror that reflects laser light and reflected light in an arbitrary direction.

  In this case, the laser beam is scanned in the horizontal direction by rotating a mirror having a plurality of reflecting surfaces by the scanning drive unit 12 and the angles of the reflecting surfaces are set to different angles, so that the laser beam is also vertically aligned. A configuration for scanning while shaking light may be employed. Further, a mechanism for directing a mirror having one reflecting surface in an arbitrary direction may be employed.

  As described above, the radar apparatus 10 intermittently irradiates a predetermined region in the traveling direction of the host vehicle (frontward in this embodiment) with laser light that is an electromagnetic wave while scanning, and the reflected wave (reflected light). ) To detect the target ahead of the host vehicle as each detection point. When the host vehicle moves rearward or sideward, the radar apparatus 10 may irradiate laser light in that direction and receive the reflected wave.

  Here, in the radar apparatus 10 of the present embodiment, the microcomputer 20 of the radar control unit 11 scans the laser light emitted from the optical unit 13 within a predetermined region using the scan driving unit 12 as described above. . Note that the direction in which the radar apparatus 10 is directed can be specified by dividing the entire area irradiated with the laser light into a matrix for each area irradiated with the laser light and assigning a number to each area. For example, as shown in FIG. 2, numbers are assigned in order from the left in the horizontal direction, and these numbers are called orientation numbers. Also, numbers are assigned in order from the top in the vertical direction, and these numbers are referred to as layer numbers.

  When scanning with laser light, as shown in FIG. 2, only the azimuth number is increased by 1 from the upper left corner (layer number 1, azimuth number 1) of this region, and the upper right corner (layer number 1, azimuth number N). The laser beam is irradiated intermittently at equal intervals (equal angles) while changing the range in which the laser beam is irradiated to the right in the horizontal direction (see the solid line in layer number 1 in FIG. 2).

  When the laser beam reaches the upper right corner, the layer number is increased by 1 from the upper left corner, and the irradiation range of the laser beam is changed to a region (layer number 2, azimuth number 1) below the upper left corner by a predetermined angle. (Refer to the broken line between the layer number 1 and the layer number 2 in FIG. 2), the laser beam is irradiated again while changing the range (azimuth number) in which the laser beam is irradiated from this region to the right in the horizontal direction.

  As described above, when the range in which the laser beam is irradiated to the right corner (azimuth number N) moves in each layer number, the layer number is increased by 1, and the laser beam is irradiated again from the region of the orientation number 1. By repeating this operation, the radar apparatus 10 divides the area on the traveling direction side of the host vehicle into a plurality of areas in two dimensions, and acquires object information in which the distance to the object existing in each divided area is detected. It will be. In this way, when the laser beam up to the region in the lower right corner (layer number K, azimuth number N) is irradiated, scanning for one cycle (one scan) is completed.

  The microcomputer 20 (CPU 17) of the radar apparatus 10 detects the distance to the target (detection point) based on the timing at which the reflected light is detected (the time from when the laser light is applied until the reflected light is detected). The distance calculation process is executed, and the direction of the target is detected based on the direction in which the laser beam is irradiated.

  The radar apparatus 10 detects the position of the target (detection point) each time the laser beam is irradiated (corresponding to the coordinates of the object (direction / layer) and the distance to the object). Each time a result is obtained, the result is stored in a memory 18 such as a RAM of the radar control unit 11.

  Next, the vehicle control unit 30 is configured as a well-known microcomputer including a CPU, a memory, and the like, and performs processing for controlling the behavior of the host vehicle according to a program stored in the ROM and the like, and notification to the driver. Various processes such as performing are executed. For example, when the vehicle control unit 30 receives a command from the radar apparatus 10 to perform driving support such as changing the behavior of the host vehicle (or urging the behavior to be changed), the vehicle control unit 30 sends a control signal corresponding to the command. What is necessary is just to make it output to any of a display apparatus, an audio | voice output apparatus, a braking device, a steering apparatus, etc.

  More specifically, the vehicle control unit 30 can be configured as a control unit for realizing ACC (Adaptive Cruise Control), LKA (Lane Keep Assist), and PCS (Pre-Crash Safety). For example, when the vehicle control unit 30 is caused to function as part of the ACC, the vehicle control unit 30 performs throttle control and brake control in order to control the vehicle speed and the inter-vehicle distance based on the information about the position of the preceding vehicle. It is only necessary to issue a command to it.

  When the vehicle control unit 30 is caused to function as a part of the LKA, the vehicle control unit 30 uses an alarm device, steering control, and brake control in order to travel safely on the own lane based on information on the position of the own lane. A command may be issued to When the vehicle control unit 30 is caused to function as a part of the PCS, the vehicle control unit 30 performs throttle control or reduction in order to reduce or avoid a collision based on information on the position of an obstacle such as a preceding vehicle or a person. A command may be issued to the brake control, the seat belt, and the airbag.

  In the radar apparatus 10, since the optical unit 13 is installed in the passenger compartment, the light receiving unit 15 reflects light from a target to be detected such as a preceding vehicle, a person, or a lane (including curbstones and guardrails). Not only that, the return light (corresponding to the return wave) that is reflected and returned from the windshield as a part of the host vehicle without being transmitted is received.

  For this reason, in the radar apparatus 10 of this embodiment, the radar control unit 11 employs a configuration necessary for dealing with such return light. Hereinafter, the functional configuration of the radar control unit 11 will be described.

[Functional configuration of radar control unit]
As shown in FIG. 3A, the radar control unit 11 includes an AD converter 21 that samples the reception signal generated by the light receiving unit 15 (see FIG. 1) for each irradiation region of the laser light, and the AD converter. Based on the received signal waveform sampled at 21, the distance calculation unit 22 calculates the distance between the detection target and the host vehicle.

  The AD converter 21 receives a signal (analog signal) generated by the light receiving unit 15 (see FIG. 1) during a measurement period set in advance from the transmission timing of the radar light by the light emitting unit 14 (see FIG. 1). A plurality of sampling values (digital signals) sampled at predetermined intervals are output in order. The measurement period only needs to be set longer than the time required for the laser beam to reciprocate at least the maximum detection distance of the radar apparatus 10.

  The distance calculation unit 22 is a component that functionally represents a distance calculation process executed by the microcomputer 20, and receives waveforms (received signal waveforms) indicated by a plurality of sampling values sampled by the AD converter 21, A calculation result related to the distance between the detection target and the host vehicle is output to the vehicle control unit 30.

  Further, as shown in FIG. 3B, the distance calculation unit 22 converts the return light information 28 (corresponding to the return wave information) stored in the memory 18 and the received signal waveform obtained by the AD converter 21. Based on the return light fusion determination unit 23 that determines whether or not the return light and the reflected light to be detected are fused, and a function that is realized according to the determination result by the return light fusion determination unit 23, the normal distance A calculation unit 24, a return light feature calculation unit 25, and a return light removal distance calculation unit 26 are provided.

  The return light information 28 includes the reception timing and peak intensity of the return light (pulse waveform) because the windshield on which the radar light is reflected as the return light is located at a predetermined distance from the radar device 10. Information to be represented is included as at least known information.

[Pre-processing]
Here, as a process before functioning as the return light fusion determination unit 23, the normal distance calculation unit 24, the return light feature calculation unit 25, and the return light removal distance calculation unit 26, a pre-process process executed by the microcomputer 20 is performed. This will be described with reference to the flowchart shown in FIG. In addition, when the power supply of the radar apparatus 10 main body is turned on, the preprocess process is repeatedly executed at predetermined intervals (cycles based on the measurement period) until the power supply is turned off.

  When this processing is started, the microcomputer 20 (specifically, the CPU 17) increases (rises) and decreases (falls) a sampling value of a predetermined value or more in the received signal waveform sampled by the AD converter 21. The maximum sampling value (sampling maximum value) is extracted from the pulse waveform indicating (S110), and a value obtained by multiplying the sampling maximum value by a coefficient less than 1 (0.5 in this embodiment) is used as a threshold value. Set (S120).

  Then, in the pulse waveform in S110, the timing at which the sampling value exceeds the threshold set in S120 is calculated as the rising timing (S130), and the timing at which the sampling value falls below the threshold (peak detection threshold) set in S120 The timing is calculated (S140).

[Normal distance calculation processing]
Next, normal distance calculation processing executed by the microcomputer 20 as the normal distance calculation unit 24 will be described with reference to the flowchart of FIG. The normal distance calculation process is started in accordance with a command from the return light fusion determination unit 23.

  When this process is started, the microcomputer 20 (specifically, the CPU 17) determines the temporal intermediate point between the rising timing calculated in S130 and the falling timing calculated in S140 of the reflected light to be detected. Detection is made as reception timing (S160). Then, the radar light emitted from the light emitting unit 14 is reflected on the detection target from the transmission timing of the radar light corresponding to the reflected light to the reception timing detected in S160, and the reflected light is received by the light receiving unit. A round trip time required to reach 15 is calculated, and a value obtained by multiplying half the round trip time by the speed of light is calculated as the distance between the host vehicle and the detection target (S170). As for the details of the normal distance calculation process, various additional processes can be performed as described in Patent Document 1.

  The normal distance calculation processing described above is not performed only on the reflected light of the detection target when the return light fusion determination unit 23 determines that the return light and the reflected light of the detection target are not fused. It is also performed for the return light.

[Return light feature calculation processing]
Specifically, in the return light feature calculation process executed by the microcomputer 20 as the return light feature calculation unit 25, the reception timing detected in S160 in the normal distance calculation process performed on the return light is the return light reception timing. The maximum sampling value extracted in S110 in the previous process is stored in the memory 18 as the peak intensity of the return light.

  The return light feature calculation unit 25 then calculates the average value (return light) of the round trip time of the radar light required for each of the plurality of reception timings accumulated in the memory 18 until the radar light is irradiated and received as return light. Average distance time) and the standard deviation are calculated, and the average distance time and the standard deviation of the return light are stored in the memory 18 in a form including the return light information 28. Further, the return light feature calculation unit 25 calculates an average value (average peak value of return light) and a standard deviation of a plurality of peak intensities accumulated in the memory 18, and calculates the average peak value and standard deviation of the return light. The data is stored in the memory 18 in a manner included in the return light information 28.

  That is, the memory 18 stores the average distance time and standard deviation of the return light and the average peak value and standard deviation of the return light as the return light information 28. In the memory 18, in addition to the return light information 28, a correlation map 27 representing the relationship between the peak intensity of the pulse waveform of the radar light generated by the light emitting unit 14 and the pulse width (see FIG. 3B). Is remembered. This correlation map 27 is used by the return light removal distance calculation unit 26 described later by utilizing the relationship in which the reflected light and return light waveforms to be detected are similar in shape to the radar light pulse waveform. is there.

[Return light removal distance calculation processing]
Next, the return light removal distance calculation process executed by the microcomputer 20 as the return light removal distance calculation unit 26 will be described with reference to the flowchart shown in FIG. Note that the return light removal distance calculation process is started in accordance with a command from the return light fusion determination unit 23.

  When this process is started, the microcomputer 20 (specifically, the CPU 17) corrects the rising timing calculated in S130 in the previous process based on the sampling maximum value extracted in S110 in the previous process (S150), A temporal intermediate point between the corrected rising timing and the falling timing calculated in S140 is detected as the reception timing of the reflected light to be detected (S160). Then, as in the normal distance calculation process described above, the distance between the host vehicle and the detection target is calculated based on the time from the radar light transmission timing to the reception timing detected in S160 (S170).

Here, the correction of the rising timing in S150 will be described with reference to FIGS. 6 (a) and 6 (b).
First, in FIG. 6A and FIG. 6B, each sampling point obtained by sampling each point represented by a square on the solid line by the AD converter 21 (that is, this solid line is a received signal waveform), on the broken line Each point represented by a rhombus is a sampling value corresponding to the return light.

  The sampling value corresponding to the return light is the sampling value sampled for the return light when the return light fusion determination unit 23 determines that the return light and the reflected light to be detected are not fused. It is. Each sampling value is a value corresponding to the intensity of the reflected light. In FIGS. 6A and 6B, a value obtained by averaging the values before and after the rise in the pulse waveform is set to zero. Yes.

  6 (a) and 6 (b), the received signal waveform represented by the solid line is returned from the reflected light (reflected light of the detection target) reflected from the target of the laser light. A pulse waveform formed by the fusion of light is shown. FIG. 6A shows a case where the received light intensity of the reflected light of the detection target is larger than the received light intensity of the return light, and FIG. 6B shows that the received light intensity of the reflected light of the detection object is higher than the received light intensity of the return light. Also shows a small case.

  Note that the reflected light of the detection target appears temporally after the return light, whereas the reflected light reflected from a part of the host vehicle (the windshield) is reflected from the detection target. Is due to the reflected light reflected from the target outside the vehicle. Such fusion of reflected light and return light to be detected can occur when reflected light from an obstacle close to the host vehicle is received. For example, the vehicle control unit 30 functions as a part of the PCS. In this case, it becomes necessary to measure the distance to such an obstacle.

  First, when the received light intensity of the reflected light to be detected is larger than the received light intensity of the return light, the microcomputer 20 (specifically, the CPU 17) performs the sampling extracted in S110 in the pre-process as shown in FIG. Using the maximum value as the peak intensity of the pulse waveform, the correlation map 27 stored in the memory 18 is referenced, and the pulse width corresponding to this peak intensity is acquired.

  Then, as shown in FIG. 6A, instead of the rising timing T1 calculated in S130 in the previous process, the falling timing T2 calculated in S140 is used as a starting point, and the correction time based on the acquired pulse width is T1. The time offset to the side is calculated as the corrected rising timing T1 ′. In the present embodiment, since the peak detection threshold is set to a half value of the maximum sampling value, the time corresponding to the pulse width can be set as the correction time.

  Next, when the light reception intensity of the reflected light to be detected is smaller than the light reception intensity of the return light, the microcomputer 20 (specifically, the CPU 17) extracts it in S110 in the previous process as shown in FIG. 6B. Since the maximum sampling value is substantially equal to the average peak value in the return light information, the pulse width corresponding to the average peak value (peak intensity) in the return light information is acquired from the correlation map 27 stored in the memory 18.

  Then, as shown in FIG. 6B, the rising timing T1 calculated in S130 in the previous process is set as a starting point, and the time offset to the T2 side by the correction time based on the acquired pulse width is the corrected rising timing. Calculated as T1 ′. In the present embodiment, since the peak detection threshold is set to a half value of the maximum sampling value, the time corresponding to the pulse width can be set as the correction time.

  Hereinafter, as shown in FIG. 6A, when the received light intensity of the reflected light to be detected is larger than the received light intensity of the return light, the return light removal distance calculation process performed by the microcomputer 20 is the first return light. The return light removal distance calculation process performed by the microcomputer 20 when the received light intensity of the reflected light to be detected is smaller than the received light intensity of the return light as shown in FIG. This is referred to as return light removal distance calculation process 2.

[Return light fusion judgment processing]
Finally, return light fusion determination processing executed by the microcomputer 20 as the return light fusion determination unit 23 will be described with reference to the flowchart shown in FIG. Note that the return light fusion determination process is started together with the start of the previous process.

  When this process is started, in S210, the microcomputer 20 (specifically, the CPU 17) causes the peak intensity P, which is the maximum sampling value extracted in S110 in the previous process, the rising timing T1 calculated in S130, and S140. Input waveform information including the calculated fall timing T2 is acquired. The input waveform information is represented as a data string corresponding to a received signal waveform having one or more peak intensities P.

  In subsequent S220, based on the input waveform information corresponding to the received signal waveform acquired in S110, it is determined whether or not the condition of the following equation (1) is satisfied. In the following equation (1), μrt represents the average distance time of the return light in the return light information stored in the memory 18, and σrt represents the standard deviation of the average distance time of the return light (FIG. 8A). )reference).

(T1 + T2) / 2 <(μrt + 10σrt) (1)
That is, in S220, using the condition of the above equation (1), the round trip time of the radar light corresponding to the first pulse waveform in the received signal waveform is the round trip time (average distance time) of the radar light corresponding to the return light. It is determined whether or not it is less than the time obtained by adding a predetermined first margin time 10σrt to μrt.

  If the condition of the above equation (1) is satisfied, it is assumed that the reception timing of the reflected light approximates (or is close to) the reception timing corresponding to the return light, and the process proceeds to S230. On the other hand, when the condition of the above equation (1) is not satisfied, the reception timing of the reflected light (pulse waveform including the maximum sampling value) and the reception timing corresponding to the return light are compared, and the time interval between them is sufficient. (See FIG. 8B), the normal distance calculation process described above is started for this pulse waveform.

  Next, in S230, based on the input waveform information corresponding to the received signal waveform acquired in S110, it is determined whether or not the condition of the following equation (2) is satisfied. In the following equation (2), μrp represents the average peak value of the return light in the return light information stored in the memory 18, and σrp represents the standard deviation of the average peak value of the return light (FIG. 8 (a)). )reference).

P> (μrp + 4σrp) (2)
That is, in S230, using the condition of the above equation (2), the peak intensity P corresponding to the first pulse waveform in the received signal waveform is obtained by adding a predetermined margin intensity 4σrp to the peak intensity μrp corresponding to the return light. Determine whether the value is exceeded.

  When the condition of the above equation (2) is satisfied, the received light intensity (sampling maximum value) of the reflected light and the received light intensity corresponding to the return light are not the same, and the reflected light and return light of the detection target Assuming that the fused wave is fused, the process proceeds to S250. On the other hand, when the condition of the above equation (2) is not satisfied, the received light intensity (sampling maximum value) of the reflected light is regarded as the same as the received light intensity corresponding to the return light (see FIG. 8C). ), The process proceeds to S240.

In S240, based on the input waveform information corresponding to the received signal waveform acquired in S110, it is determined whether or not the condition of the following equation (3) is satisfied.
(T1 + T2) / 2> (μrt + 4σrt) (3)
That is, in S240, using the condition of the above equation (3), the round trip time of the radar light corresponding to the first pulse waveform in the received signal waveform is the round trip time (average distance time) of the radar light corresponding to the return light. It is determined whether or not a time obtained by adding a predetermined second margin time 4σrt to μrt is reached. Note that the second margin time 4σrt is a time shorter than at least the first margin time 10σrt in S210 described above.

  When the condition of the above equation (3) is satisfied, the reflected light reception timing and the reception timing corresponding to the return light are approximate but non-identical. As a result, the second return light removal calculation process described above is started with respect to the pulse waveform of the fused wave. The reason for starting the second return light removal calculation process is that the received light intensity of the reflected light (sampling maximum value) and the received light intensity corresponding to the returned light are the same in S230, and the reflected light This is because since the reception timing and the reception timing corresponding to the return light are not the same, the light reception intensity of the reflected light to be detected in the fusion wave can be said to be smaller than the light reception intensity of the return light.

  On the other hand, when the condition of the above equation (3) is not satisfied, the return light information calculation process described above is executed assuming that the reflected light (pulse waveform including the maximum sampling value) is the same as the waveform of the return light. To do. In this case, the normal distance calculation process described above may be executed for the second and subsequent pulse waveforms in the received signal waveform.

  Finally, in S250, based on the input waveform information corresponding to the received signal waveform acquired in S110, it is determined whether or not the condition of the following equation (4) is satisfied. However, it is assumed that the peak intensity P is not saturated. In the following equation (4), k represents a coefficient (for example, 0.5) by which the sampling maximum value is multiplied when the peak detection threshold is set in S120.

(P × k) <2 μrp (4)
That is, in S250, whether or not the value obtained by multiplying the peak intensity P corresponding to the first pulse waveform by the coefficient k in the received signal waveform is smaller than twice the peak intensity μrp corresponding to the return light. to decide.

  When the above equation (4) is satisfied (or when the peak intensity P is saturated), the received light intensity (sampling maximum value) of the reflected light is larger than the received light intensity corresponding to the return light, and The first return light removal calculation process described above is executed on the assumption that the difference value between the received light intensity (maximum sampling value) of the reflected light and the received light intensity corresponding to the return light is smaller than a predetermined allowable difference value. .

  The allowable difference value is set in advance as a value that can appropriately detect the reception timing of the reflected light to be detected without correcting the rising timing (see FIG. 9B). On the other hand, when the above difference value is smaller than the allowable difference value, the influence of the return light appears on the detection of the reception timing in the reflected light to be detected (see FIG. 9C).

  Therefore, when the above formula (4) is not established, the first return light removal calculation process described above is executed because it is not necessary to correct the rising timing. In other words, if the difference between the received light intensity (maximum sampling value) of the reflected light and the received light intensity corresponding to the return light exceeds the allowable difference value, the reflected light and return light to be detected are fused. Even so, since the influence of the return light does not appear on the detection of the reception timing in the reflected light to be detected, the execution of the return light removal calculation process is prohibited.

[effect]
As described above, in the radar apparatus 10 according to the present embodiment, the waveform of both the reflected light and the return light is approximated by comparing the reception timing and peak intensity in the received signal waveform (reflected light) with the return light information. If they are not the same, it is assumed that the reflected wave in which the reflected light and the return light to be detected are fused, and the rising timing is offset using the pulse width based on the maximum sampling value at this time.

  Therefore, according to the radar apparatus 10 of this embodiment, it is possible to remove the influence of the return wave from the rising timing with respect to the fusion wave. The reception timing of the reflected wave in which the transmission wave is reflected from the external target) can be accurately detected, and as a result, the distance from the external target close to the vehicle can be appropriately measured.

  When the radar apparatus 10 can assume that the reflected light and the return light have the same waveform, the radar apparatus 10 calculates the average peak value and the average distance time of the return light according to the sampling maximum value and the reception timing at this time. Since it is updated, it is possible to learn the return light information, thereby making it possible to make a determination according to the state of the windshield of the vehicle (raindrops, dust, etc. may adhere).

  Furthermore, in the radar apparatus 10, the reflected light and the return light have the same peak intensity (that is, the actual measurement maximum value and the comparison maximum value are the same), and the reception timings of the reflected light and the return light are approximate but not the same. In the case where it can be considered, the rising timing is offset using the pulse width based on the average peak value in the return light information.

  For this reason, according to the radar apparatus 10, even when the peak intensity corresponding to the reflected light to be detected (and the rising timing) cannot be detected, the influence of the return wave is removed from the rising timing with respect to the fusion wave. As a result, the detection accuracy of an external target close to the vehicle can be improved.

[Correspondence with Invention]
In this embodiment, the optical unit 13 is a transmission / reception unit, the AD converter 21 is a sampling unit, the microcomputer 20 that performs the processing of S110 to S120 is a threshold setting unit, and the microcomputer 20 that performs the processing of S130 to S140 is a timing calculation unit. The microcomputer 20 that performs the process of S160 is a reception timing detection unit, the memory 18 is a storage unit, the return light fusion determination unit 23 is a return wave determination unit, the microcomputer 20 that performs the process of S150 is a timing correction unit, and the return light feature calculation unit 25 is The updating means, the microcomputer 20 that performs the processes of S230 and S150, each corresponds to an example of a correction prohibiting means, and the microcomputer 20 that performs the process of S170 corresponds to an example of a distance measuring means.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  In the radar apparatus 10 of the above-described embodiment, the configuration is such that radar light is transmitted and received by the optical unit 13, but the configuration is not limited to radar light, and other electromagnetic waves such as ultrasonic waves may be transmitted and received.

  In the radar apparatus 10 of the above embodiment, the return light fusion determination process is performed using the reflected light from the windshield of the host vehicle as the return light. However, depending on the installation position of the radar apparatus 10 in the host vehicle, the windshield For example, return light fusion determination processing may be performed using reflected light from a door window, a hood, or the like as return light.

  In the radar apparatus 10 of the above-described embodiment, the radar control unit 11 performs the distance measurement process of S170. Alternatively, the vehicle control unit 30 may perform the distance measurement process of S170.

  DESCRIPTION OF SYMBOLS 1 ... Driving support system, 10 ... Radar apparatus, 11 ... Radar control part, 12 ... Scanning drive part, 13 ... Optical unit, 14 ... Light emission part, 15 ... Light receiving part, 17 ... CPU, 18 ... Memory, 20 ... Microcomputer, DESCRIPTION OF SYMBOLS 21 ... AD converter, 22 ... Distance calculation part, 23 ... Return light fusion determination part, 24 ... Normal distance calculation part, 25 ... Return light feature calculation part, 26 ... Return light removal distance calculation part, 27 ... Correlation map, 28 ... return light information, 30 ... vehicle control unit, 50 ... object, 100 ... vehicle.

Claims (7)

A radar device installed in a vehicle room,
Transmitting / receiving means for transmitting a transmission wave of a pulse waveform, receiving a signal including a reflection wave of the transmission wave, and generating a reception signal;
Sampling means for sampling the received signal generated by the transmitting / receiving means;
Based on the sampling maximum value which is the maximum value of the sampling value among the pulse waveforms consisting of a plurality of sampling values obtained by the sampling means within a predetermined time from the transmission timing of the transmission wave by the transmission / reception means, Threshold setting means for setting a threshold for determining the reception timing of the reflected wave;
Timing calculating means for calculating a rising timing at which the sampling value exceeds the threshold set by the threshold setting means, and a falling timing at which the sampling value falls below the threshold;
Reception timing detection means for detecting an intermediate point between the rise timing and fall timing calculated by the timing calculation means as the reception timing of the reflected wave;
A storage for storing return wave information including the reception timing corresponding to the return wave and the sampling maximum value as a return wave obtained by reflecting the transmission wave from a part of the vehicle within the predetermined time Means,
When the reception timing of the reflected wave detected by the reception timing detection unit can be regarded as at least approximate to the reception timing corresponding to the return wave stored in the storage unit, the return wave information is used, Return wave determination means for determining whether or not the pulse waveform including the maximum sampling value is the same as the waveform of the return wave;
When the return wave determination means determines that the pulse waveform including the maximum sampling value is not the same as the waveform of the return wave, the timing calculation means uses the pulse width based on the maximum sampling value. Timing correction means for correcting the calculated rise timing;
A radar apparatus comprising:   When the return wave determining means determines that the pulse waveform including the sampling maximum value is the same as the waveform of the return wave, the sampling maximum value and the rising timing and falling timing calculated by the timing calculating means, The radar apparatus according to claim 1, further comprising an update unit that updates the return wave information stored in the storage unit based on the information. The sampling maximum value obtained by the sampling means is the actual measurement maximum value, the sampling maximum value included in the return wave information is the comparison maximum value,
When the return wave determination means determines that the pulse waveform including the maximum sampling value is not the same as the waveform of the return wave, a difference value between the actual measurement maximum value and the comparison maximum value is set in advance. The radar apparatus according to claim 1, further comprising a correction prohibiting unit that prohibits correction of the rising timing by the timing correcting unit when the difference value is exceeded.   The timing correction means uses the pulse width based on the measured maximum value when the difference value between the measured maximum value and the comparative maximum value is non-negative and equal to or less than the allowable difference value. The radar apparatus according to claim 3, wherein the rising timing is corrected. The sampling maximum value obtained by the sampling means is the actual measurement maximum value, the sampling maximum value included in the return wave information is the comparison maximum value,
The timing correction means corrects the rising timing using a pulse width based on the comparison maximum value when the actual measurement maximum value can be regarded as coincident with the comparison maximum value. The radar device according to claim 4. The transmission / reception means transmits the transmission wave to a plurality of regions on the traveling direction side of the vehicle,
The radar apparatus according to claim 1, wherein the storage unit stores the return wave information corresponding to each of the areas.   Ranging means for measuring the distance to the target outside the vehicle based on the transmission timing of the transmission wave by the transmission / reception means and the reception timing detected by the reception timing detection means is provided. The radar apparatus according to any one of claims 1 to 6.