JP6824761B2 - Radar device and road surface detection method - Google Patents

Description

The present invention relates to a radar device and a road surface detection method.

Conventionally, for example, there is a radar device mounted on a vehicle and detecting a target such as a preceding vehicle based on a reflected wave in which a transmitted wave transmitted from the vehicle hits the target and is reflected.

Such a radar device detects a target that hinders the running of the vehicle and outputs it to a collision avoidance support device such as a PCS (Pre-Crash Safety System) (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-215273

However, in the conventional technology, the road surface may be erroneously detected as an obstacle, which may lead to a malfunction of the collision avoidance support device. Therefore, in the radar device, it is desired to improve the detection accuracy of the road surface.

The present invention has been made in view of the above, and an object of the present invention is to provide a radar device and a road surface detection method capable of improving the detection accuracy of the road surface.

The radar device according to the embodiment includes a lead-out unit, a continuity determination unit, and a road surface determination unit. The derivation unit derives the observation data of the target including the distance to the target and the depression angle based on the reflected wave reflected by the transmitted wave transmitted from the own vehicle. The continuity determination unit determines whether or not the observation data previously derived by the derivation unit and the observation data derived this time are observation data of the same target that are continuous in time. Based on the observation data determined by the continuity determination unit to be the same target, the road surface determination unit satisfies the determination condition that the distance is constant when the own vehicle travels among the targets indicating the depression angle. The target is judged to be the road surface.

According to the present invention, the detection accuracy of the road surface can be improved.

FIG. 1A is a diagram showing a mounting example of a radar device. FIG. 1B is a diagram showing an outline of a road surface detection method. FIG. 2 is a block diagram of the radar device. FIG. 3A is a schematic view showing the relative speed of the road surface. FIG. 3B is a diagram showing changes over time in the horizontal angle of the road surface. FIG. 4 is a diagram illustrating processing by the determination unit. FIG. 5 is a flowchart showing a processing procedure executed by the radar device. FIG. 6 is a flowchart showing a processing procedure of the road surface determination process executed by the radar device.

Hereinafter, embodiments of the radar device and the road surface detection method disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

First, the outline of the road surface detection method by the radar device according to the embodiment will be described with reference to FIGS. 1A and 1B. FIG. 1A is a diagram showing a mounting example of the radar device 1, and FIG. 1B is a diagram showing an outline of a road surface detection method.

Such a road surface detection method is executed by the radar device 1 shown in FIG. 1A. Here, a case where the radar device 1 is provided in the center of the front grill of the own vehicle MC will be described.

The position where the radar device 1 is provided is not limited to this, and may be any position such as the rear part, the side surface, and the rearview mirror of the own vehicle MC.

The radar device 1 transmits a transmission wave SW centered on a transmission axis RA substantially parallel to the traveling direction of the own vehicle MC traveling on the road surface G. When a target exists in the transmission range of the transmission wave SW, the reflected wave by the transmission wave SW arrives from the target. The radar device 1 receives the reflected wave and derives observation data such as an angle, a distance, and a relative velocity at which the target exists based on the received signal.

As shown in FIG. 1A, the transmission range of the transmission wave SW transmitted by the radar device 1 includes the road surface G. Therefore, the road surface G is included in the target detected by the radar device 1.

However, the conventional radar device does not have sufficient accuracy to discriminate between the road surface G and an obstacle existing on the road surface G (hereinafter referred to as "lower object"), and the road surface G is erroneously detected as a lower object. There was a case.

Therefore, the radar device 1 according to the embodiment is determined to improve the detection accuracy of the road surface G by improving the recognition accuracy of the road surface G and the lower object. In the following, for the sake of simplicity, it is assumed that the own vehicle MC is traveling straight at a constant traveling speed.

First, the radar device 1 determines whether or not the observation data obtained in the previous scan and the observation data obtained in the current scan are observation data of the same target that are continuous in time.

The radar device 1 determines that the observation data of this time, which is the closest to the prediction data predicted from the past scan, is the same target having temporal continuity with the observation data derived last time.

Here, the transmitted wave SW is reflected by the road surface G existing at a substantially constant distance from the radar device 1, and the radar device 1 receives the reflected wave by the road surface G. That is, the distance to the road surface G detected by the radar device 1 is substantially constant.

Then, when the own vehicle MC travels, the radar device 1 detects the road surface G at different positions at a substantially constant distance from the radar device 1, but the distance of the previous observation data corresponding to the road surface G and the current time. The distance of the observation data is approximately a constant distance.

Therefore, the predicted data predicted from the previous observation data corresponding to the road surface G and the current observation data are close to each other, and the radar device 1 uses the same target with temporal continuity for both observation data. Judge that there is.

Subsequently, the radar device 1 extracts a target indicating the depression angle, that is, a target indicating below the transmission axis RA of the transmission wave SW, based on the observation data having continuity in time. Here, the target extracted by the radar device 1 is the road surface G or a lower object.

Subsequently, the radar device 1 determines the road surface G and the lower object based on the time course of the distance between the road surface G and the lower object when the own vehicle MC is traveling. Specifically, as shown in FIG. 1B, a target whose distance is constant when the own vehicle MC is traveling is determined to be the road surface G.

Here, "the distance is constant" does not require that the values exactly match. That is, as long as the time-series observation data is in a continuous range, a predetermined error (for example, 50 cm) is allowed, and "distance is constant" and "distance is substantially constant" are synonymous. It shall be.

On the other hand, as shown in FIG. 1B, in the case of a downward object, when the own vehicle MC travels, the distance gradually decreases according to the travel distance. Therefore, the radar device 1 determines that the target whose distance changes is the lower target among the targets indicating the lower side of the transmission axis RA. Then, the radar device 1 determines that the target whose distance is constant among the targets indicating below the transmission axis RA is the road surface G.

In this way, the radar device 1 can appropriately determine the road surface G and the lower object based on the change with time of the observation data. Therefore, according to the radar device 1 according to the embodiment, the detection accuracy of the road surface G can be improved.

By the way, the radar device 1 can also derive the relative velocity and the horizontal angle with the target as observation data, and can also detect the road surface G based on the relative velocity and the horizontal angle. Details of this point will be described later with reference to FIGS. 3A and 3B.

Further, the road surface G is detected in a wider range than the lower object. Therefore, the radar device 1 can also determine that the target that is detected over a wide range is the road surface G among the targets that satisfy the above conditions. Details of this point will be described later with reference to FIG.

In the following, the case where the radar device 1 is of the FM-CW (Frequency Modulated-Continuous Wave) method will be described, but the FCM (Fast Chirp Modulation) method may be used.

Next, the configuration of the radar device 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram of the radar device 1. Note that FIG. 2 also shows the vehicle control device 2.

The vehicle control device 2 controls a vehicle such as a PCS (Pre-crash Safety System) or an AEB (Advanced Emergency Braking System) based on the detection result of a target by the radar device 1.

The transmission unit 10 includes a signal generation unit 11, an oscillator 12, a horizontal transmission antenna 13a, a vertical transmission antenna 13b, and a switch 14. The signal generation unit 11 generates a modulated signal whose voltage changes in a triangular wave shape and supplies it to the oscillator 12.

The oscillator 12 generates a transmission signal ST whose frequency changes with the passage of time based on the modulated signal generated by the signal generation unit 11, and outputs the transmission signal ST to the horizontal transmission antenna 13a or the vertical transmission antenna 13b.

The horizontal transmission antenna 13a and the vertical transmission antenna 13b convert the transmission signal ST from the oscillator 12 into a transmission wave TW, and output the transmission wave SW to the outside of the own vehicle MC.

The transmission wave SW output by the horizontal transmission antenna 13a and the vertical transmission antenna 13b is an FM-CW whose frequency fluctuates in a predetermined cycle. The transmitted wave SW transmitted from the horizontal transmitting antenna 13a and the vertical transmitting antenna 13b in front of the own vehicle MC is reflected by another vehicle or a target such as the road surface G to become a reflected wave RW.

Further, the horizontal transmission antennas 13a are arranged at equal intervals in the horizontal direction and output the transmission wave SW in the horizontal direction, and the vertical transmission antennas 13b are arranged at equal intervals in the vertical direction and transmit in the vertical direction. Output wave SW.

The switch 14 connects any of the horizontal transmitting antenna 13a and the vertical transmitting antenna 13b to the oscillator 12. The switch 14 operates at a predetermined timing under the control of the transmission control unit 31 described later, and switches the connection between either the horizontal transmission antenna 13a or the vertical transmission antenna 13b and the oscillator 12.

The receiving unit 20 comprises a plurality of horizontal receiving antennas 21a forming an array antenna, a plurality of vertical receiving antennas 21b, and a plurality of individual receiving units 22 connected to the plurality of horizontal receiving antennas 21a and the vertical receiving antenna 21b. Be prepared.

Each horizontal receiving antenna 21a and each vertical receiving antenna 21b receives the reflected wave from the target and converts the reflected wave into a received signal. Each individual receiving unit 22 processes the received signal obtained by the corresponding receiving antenna 21.

The number of the horizontal receiving antenna 21a and the number of the vertical receiving antenna 21b shown in FIG. 2 are four, respectively, but may be three or less or five or more.

Each individual receiving unit 22 includes an amplifier 23, a mixer 24, and an A / D (Analog / Digital) converter 25. The received signal obtained from the reflected wave received by the horizontal receiving antenna 21a and the vertical receiving antenna 21b is amplified by the amplifier 23 (for example, a low noise amplifier) and then sent to the mixer 24. The mixer 24 mixes a part of the transmission signal ST and the reception signal to remove unnecessary signal components to generate a beat signal.

As a result, a beat signal indicating a beat frequency that is the difference between the frequency of the transmission signal ST and the frequency of the reception signal is generated. The beat signal generated by the mixer 24 is converted into a digital signal by the A / D converter 25 and then output to the signal processing unit 30.

In the following, the beat signal obtained from the reflected wave received by the horizontal receiving antenna 21a is referred to as a horizontal beat signal, and the beat signal obtained from the reflected wave received by the vertical receiving antenna 21b is referred to as a vertical beat signal.

The signal processing unit 30 includes a transmission control unit 31, a Fourier transform unit 32, and a data processing unit 33. The signal processing unit 30 is, for example, a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output port, and the like, and controls the entire radar device 1.

When the CPU of the microcomputer reads and executes the program stored in the ROM, it functions as a transmission control unit 31, a Fourier transform unit 32, and a data processing unit 33. The transmission control unit 31, the Fourier transform unit 32, and the data processing unit 33 can all be configured by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

The transmission control unit 31 controls the signal generation unit 11 of the transmission unit 10 to output a modulated signal whose voltage changes in a triangular wave shape from the signal generation unit 11 to the oscillator 12. As a result, the transmission signal ST whose frequency changes with the passage of time is output from the oscillator 12 to the transmission antenna 13. Further, the transmission control unit 31 controls the switching of the switch 14.

The Fourier transform unit 32 performs a fast Fourier transform (FFT) process on each of the horizontal beat signal and the vertical beat signal output from each of the plurality of individual receiving units 22.

As a result, the Fourier transform unit 32 converts the horizontal beat signal and the vertical beat signal output from each of the plurality of individual receiving units 22 into frequency spectrum data, respectively.

The frequency spectrum converted by the Fourier transform unit 32 is output to the data processing unit 33. The frequency spectrum data includes signal level information for each frequency bin (BIN) set at frequency intervals according to the frequency resolution of the Fourier transform unit 32.

In the following, a frequency spectrum based on a horizontal beat signal may be referred to as a horizontal frequency spectrum, and a frequency spectrum based on a vertical beat signal may be referred to as a vertical frequency spectrum.

The data processing unit 33 includes a derivation unit 41, a continuity determination unit 42, a road surface determination unit 43, a filter processing unit 44, a target classification unit 45, an unnecessary target determination unit 46, a combination processing unit 47, and a combination processing unit 47. The output target selection unit 48 is provided. The data processing unit 33 derives observation data of the distance, speed, and angle from the target based on the frequency spectrum data converted by the Fourier transform unit 32, and controls the vehicle with the target information according to the observation data. Output to device 2. The vehicle control device 2 controls the behavior of the own vehicle MC based on the target information acquired from the radar device 1.

The derivation unit 41 performs an observation data derivation process for deriving observation data including data on the distance, velocity, and angle from the target based on the frequency spectrum data converted by the Fourier transform unit 32. The observation data derivation process is repeatedly executed by the derivation unit 41 every predetermined cycle (for example, 1/20 second), and the derivation observation data is output from the derivation unit 41 to the continuity determination unit 42 at each predetermined cycle. ..

The lead-out unit 41 includes a peak detection unit 41a, an angle estimation unit 41b, and a pairing unit 41c. Since the derivation unit 41 performs basically the same processing on the horizontal frequency spectrum and the vertical frequency spectrum, a case where the derivation unit 41 derives observation data from the horizontal frequency spectrum will be described as an example.

In the horizontal frequency spectrum converted by the Fourier transform unit 32, the peak detection unit 41a has an up section in which the frequency of the transmission signal ST rises and a down section in which the frequency of the transmission signal ST falls for peaks exceeding a predetermined signal level. Extract in each section of and. Hereinafter, the frequency extracted in this way is referred to as a "peak frequency".

Since the reflected wave from the same target is received by the four horizontal receiving antennas 21a, the peak frequencies extracted are the same between the frequency spectra of the four beat signals. Further, when a plurality of targets are present at different angles in the same frequency bin, the signal of one peak frequency in the frequency spectrum contains information about the plurality of targets.

Since the positions of the four receiving antennas 21 are different from each other, the phases of the reflected waves received by the four horizontal receiving antennas 21a are different from each other. Therefore, the phase information of the received signals having the same frequency bin is different for each horizontal receiving antenna 21a.

The angle estimation unit 41b separates information about a plurality of targets existing in the same frequency bin from a signal of one peak frequency by a predetermined angle calculation process for each of the up section and the down section, and those plurality of objects. Estimate the angle of each mark.

The angle estimation unit 41b pays attention to signals in the same frequency bin (hereinafter referred to as peak signals) corresponding to each peak frequency in all frequency spectra of the four beat signals, and is based on the phase information of those peak signals. Estimate the angle of the marker. In the following, the angle of the target estimated by the derivation unit 41 will be referred to as “peak angle”, and the signal power of such peak angle will be referred to as “angle power”.

The angle estimation unit 41b derives such a peak angle for all peak frequencies in the horizontal frequency spectrum and the vertical frequency spectrum in the up section and the down section. The angle estimation unit 41b uses a predetermined angle estimation method such as ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques), DBF (Digital Beam Forming), or MUSIC (Multiple Signal Classification). Is done.

As a result, the angle estimation unit 41b can estimate a plurality of peak angles and the power of each of these peak angles from a signal of one frequency.

Through the above processing, the peak detection unit 41a and the angle estimation unit 41b derive peak data corresponding to each of a plurality of targets existing in front of the own vehicle MC in each of the up section and the down section.

The peak data includes data such as the above-mentioned peak frequency, peak angle, and signal power of the peak angle (hereinafter, referred to as angular power).

The pairing unit 41c sets the peak of the up section and the peak of the down section based on the degree of coincidence between the peak angle and the angle power of the up section calculated by the angle estimation unit 41b and the peak angle and the angle power of the down section. Perform pairing to associate.

For example, the pairing unit 41c pairs peaks having peak angles and angular powers within a predetermined range among the peak angle estimation results for the up section and the down period. For example, the pairing unit 41c calculates the Mahalanobis distance using the peak angles and angular powers of the frequency peaks of the up section and the down section, respectively, and sets the peak of the up section and the peak of the down section where the Mahalanobis distance is the minimum value. To associate. A well-known technique can be used to calculate the Mahalanobis distance.

In this way, the pairing unit 41c associates peaks related to the same target with each other. As a result, the pairing unit 41c derives observation data for each of the plurality of targets existing in front of the own vehicle MC. Since such observation data is obtained by associating two peaks, it is also called "pair data".

The pairing unit 41c derives data indicating instantaneous values of the speed and distance of each target with respect to the own vehicle MC (radar device 1) as observation data from the peaks of the paired up section and down section. For example, the pairing unit 41c derives the velocity from the difference between the peak frequencies of the two peak data in the up section and the down section, which are the sources of the observation data (pair data), and derives the velocity from the sum of the peak frequencies of these two peak data. The distance can be derived. Further, the pairing unit 41c determines the angle of each target with respect to the own vehicle MC (radar device 1) from the average value of the peak angles of the two peak data of the up section and the down section, which are the sources of the observation data (pair data). Data showing instantaneous values is derived as observation data.

The derivation unit 41 performs the above processing in the same manner for the vertical frequency spectrum. The observation data derived from the horizontal frequency spectrum by the derivation unit 41 is data indicating the position of the target in the horizontal direction, and the observation data derived from the vertical frequency spectrum is data indicating the position of the target in the vertical direction.

Then, the derivation unit 41 specifies a combination of observation data corresponding to the same target based on the angular power and the like derived from the horizontal frequency spectrum and the vertical frequency spectrum, respectively. Thereby, it is possible to associate the direction in which each target exists (hereinafter referred to as horizontal angle) and the vertical angle (hereinafter referred to as elevation / depression angle).

Here, of the elevation / depression angles, the elevation angle indicates an angle on the upper side with respect to the transmission axis RA shown in FIG. 1A, and the depression angle indicates an angle on the lower side with respect to the transmission axis RA. If the target is a road surface G or a downward object, the depression angle will be indicated.

The continuity determination unit 42 determines whether or not the instantaneous value of the target being determined by this scan has continuity with the target detected up to the previous scan. The continuity determination unit 42 calculates the current predicted position from the position of the target until the previous scan, and if there is an instantaneous value close to the predicted position in this scan, it determines that the instantaneous value has continuity. ..

Then, the continuity determination unit 42 outputs the observation data determined to have continuity to the road surface determination unit 43. The observation data determined by the continuity determination unit 42 to have no continuity is the new data newly observed this time.

Such new data is basically not output to the vehicle control device 2. Therefore, erroneous control (emergency braking, etc.) of the vehicle control device 2 based on the new data basically does not occur. Therefore, the road surface determination unit 43 can omit the road surface determination process for new data.

The road surface determination unit 43 determines the road surface G based on the observation data input from the continuity determination unit 42. Further, the road surface determination unit 43 includes an extraction unit 43a and a determination unit 37b.

The extraction unit 43a extracts the observation data of the target that satisfies the determination condition described later as a candidate target from the observation data determined by the continuity determination unit 42 to have continuity, and determines the extracted observation data. Output to 43b. In addition, the extraction unit 43a also outputs observation data other than the extracted candidate markers to the determination unit 43b.

The determination unit 43b determines the road surface G based on the observation data extracted by the extraction unit 43a. The determination unit 43b turns on the road surface flag of the observation data regarding the target determined as the road surface G and outputs the output to the filter processing unit 44. The details of the processing by the extraction unit 43a and the determination unit 43b will be described later with reference to the drawings of FIGS. 3A and after.

The filter processing unit 44 is a processing unit that corrects variations in instantaneous values by performing filter processing that averages the instantaneous values of a plurality of times processed in time series for each target. The filter processing unit 44 outputs the information regarding the target after the filter processing to the target classification unit 45.

The target classification unit 45 classifies each target into a moving object and a stationary object based on the filtering result of the filtering unit 44. The target classification unit 45 turns on the moving object flag for the target determined to be a moving object. Further, the target classification unit 45 outputs the classified classification result to the unnecessary target determination unit 46.

The target classification unit 45 can further subdivide and classify the preceding vehicle, the adjacent vehicle traveling in front of the adjacent traveling lane, and the like from the targets classified as moving objects. For example, the target classification unit 45 turns on the preceding vehicle flag for a target that has moved in the same direction as the own vehicle MC even once in the past in front of the traveling lane in which the own vehicle MC travels.

Further, the target classification unit 45 turns on the adjacent vehicle flag for the target that has moved in the same direction as the own vehicle MC even once in the past in front of the lane adjacent to the traveling lane in which the own vehicle MC travels. The preceding vehicle flag and the adjacent vehicle flag are held until the radar device 1 loses sight of the target.

Then, when the preceding vehicle flag or the adjacent vehicle flag is turned on, the target classification unit 45 outputs information (relative speed, distance, horizontal angle, etc.) regarding the preceding vehicle or the adjacent vehicle to the road surface determination unit 43.

In addition, the target classification unit 45 outputs the processing result of the target classification process to the unnecessary target determination unit 46. The processing result of the target classification process is information indicating the state of the moving object flag and the preceding vehicle flag of each target, the estimated angle of the target (including the horizontal angle and the vertical angle), the distance to the target, and the own vehicle. Includes information indicating the relative speed with respect to the MC (radar device 1).

The unnecessary target determination unit 46 determines whether or not the target is unnecessary in terms of system control, and transfers control to the coupling processing unit 47. Unnecessary targets are road surface G, structures, wall reflections, and the like. It should be noted that the unnecessary target is basically not output to the vehicle control device 2, but may be retained internally.

The coupling processing unit 47 groups a plurality of targets that are presumed to be reflection points from the same object into one target. The output target selection unit 48 selects a target that needs to be output to the vehicle control device 2 for system control. Further, the output target selection unit 48 outputs the target information (including the distance, relative speed, etc.) of the selected target to the vehicle control device 2.

Next, the details of the road surface determination process by the road surface determination unit 43 will be described with reference to FIGS. 3A, 3B, and 4. First, the extraction process by the extraction unit 43a will be described with reference to FIGS. 3A and 3B.

FIG. 3A is a schematic view showing the relative speed of the road surface G. FIG. 3B is a diagram showing changes over time in the horizontal angle of the road surface G. In addition, the road surface determination unit 43 shall perform the following processing on the observation data indicating below the transmission axis RA (see FIG. 1A).

As shown in FIG. 3A, when the own vehicle MC travels straight at a constant speed V, the relative speed between the own vehicle MC and the road surface G is a speed −V which is the opposite value of the speed V. Here, the target whose relative velocity is velocity −V includes a stationary lower object in addition to the road surface G.

If it is a stationary downward object, the distance to the own vehicle MC becomes shorter when the own vehicle MC travels. Therefore, it is possible to determine that the target exhibiting such behavior is a lower object.

On the other hand, as described above, the radar device 1 continuously detects the road surface G at a position separated by a substantially constant distance as the own vehicle MC travels. As a result, the distance D to the road surface G detected by the radar device 1 becomes substantially constant. Therefore, although the road surface G is observed as a stationary object as an instantaneous value, the distance is substantially constant even when the own vehicle MC travels, and the amount of change in the distance in time series is small.

Therefore, the extraction unit 43a acquires, for example, a signal indicating the traveling speed of the own vehicle MC from the vehicle speed sensor (not shown), and extracts a target corresponding to a stationary object based on the signal.

Subsequently, the extraction unit 43a measures the time course of the distance of the observation data corresponding to the stationary object. Then, the extraction unit 43a extracts the observation data whose distance is substantially constant as a candidate target as a candidate for the road surface G, and outputs the observation data of the candidate target to the determination unit 43b.

In this way, since the extraction unit 43a extracts the candidate target based on the change in relative velocity with time in addition to the distance, it is possible to reliably eliminate the stationary lower object. Therefore, the detection accuracy of the road surface G can be improved.

The determination conditions for extracting the candidate markers are not limited to this. For example, as shown in FIG. 3B, the extraction unit 43a can also extract, among the targets satisfying the above-mentioned determination conditions, the targets having a large variation with time of the horizontal angle as the candidate targets.

This is because the range of reflection points that the transmission wave SW can reflect is limited in the case of a lower object, whereas the road surface G has an infinite number of reflection points that the transmission wave SW can reflect. ..

Therefore, as shown in FIG. 3B, although the road surface G is determined by the continuity determination unit 42 to be the same target having continuity in each scan, the variation in the horizontal angle tends to be large.

For example, the extraction unit 43a obtains the standard deviation of the horizontal angle in a plurality of scans for the target satisfying the above-mentioned determination condition, and the value of the standard deviation is equal to or more than a predetermined value, that is, the target having a large variation in the horizontal angle. It can also be extracted as a candidate marker.

As a result, the extraction unit 43a can improve the extraction accuracy of the candidate target, and can improve the detection accuracy of the road surface G by the radar device 1.

Next, the process of determining the road surface G by the determination unit 43b will be described with reference to FIG. FIG. 4 is a diagram showing a determination process of the road surface G by the determination unit 43b. The black circle shown in FIG. 4 indicates the position of the candidate marker extracted by the extraction unit 43a.

When a candidate marker exists, the determination unit 43b determines such a plurality of candidate markers as the road surface G. This is because, on the road surface G, there are innumerable reflection points of the transmitted wave SW, and innumerable candidate markers.

In other words, since the road surface G is detected over a wide range, it is unlikely that only one target corresponding to the road surface G is detected. Therefore, the determination unit 43b determines such a plurality of candidate markers as the road surface G on condition that there are a plurality of candidate markers having different horizontal angles, that is, positions in the left-right direction in the figure.

As a result, the radar device 1 can suppress erroneous detection of the road surface G and improve the detection accuracy. Note that FIG. 4 shows a case where there are four target target candidates, but this is an example and does not limit the number of target target candidates.

By the way, when the radar device 1 detects a target related to a stopped vehicle at a relatively low position in a state where the own vehicle MC and the stopped vehicle are close to each other, the radar device 1 mistakenly mistakes the target as a target related to the road surface G. May be judged.

Therefore, when the distance between the own vehicle MC and the stopped vehicle is relatively long, the radar device 1 relates to the vehicle when the target related to the stopped vehicle is detected as a target existing at a position higher than the road surface G. Turn on the flag indicating that it is a target.

As a result, even when the own vehicle MC approaches the stopped vehicle, it is possible to prevent the target regarding the stopped vehicle from being erroneously determined as the road surface by determining the state of the flag.

In other words, the radar device 1 can exclude the target related to the stopped vehicle from the judgment target of the road surface G by confirming the state of the preceding vehicle flag and the adjacent vehicle flag described above, and suppresses erroneous detection of the road surface G. can do.

Next, the processing procedure executed by the radar device 1 will be described with reference to FIGS. 5 and 6. FIG. 5 is a flowchart showing a processing procedure executed by the radar device 1. Further, FIG. 6 is a flowchart showing a processing procedure of the road surface determination process executed by the radar device 1.

As shown in FIG. 6, first, the peak detection unit 41a performs the peak detection process (step S101). Then, the angle estimation unit 41b performs the angle estimation process based on the processing result of the peak detection process (step S102).

Then, the pairing unit 41c performs the pairing process based on the processing results up to the angle estimation process (step S103). Subsequently, the continuity determination unit 42 performs the continuity determination process based on the process results up to the pairing process (step S104).

Subsequently, the road surface determination unit 43 performs the road surface determination process based on the processing results up to the continuity determination process (step S105). The processing procedure of the road surface determination process in step S105 will be described later with reference to FIG.

Subsequently, the filter processing unit 44 performs the filter processing based on the processing results up to the road surface determination processing (step S106). Then, the unnecessary target determination unit 46 performs the unnecessary target determination process based on the processing results up to the filter process (step S107).

Subsequently, the combination processing unit 47 performs the combination process based on the processing results up to the unnecessary target determination process (step S108). Then, the output target selection unit 48 performs the output target selection process based on the processing results up to the combination process (step S109).

Next, the processing procedure of the road surface determination process of step S105 shown in FIG. 5 will be described with reference to FIG. First, the extraction unit 43a determines whether or not the observation data has continuity (step S201).

Subsequently, when the observation data has continuity (step S201, Yes), the extraction unit 43a determines whether or not the observation data shows a depression angle (step S202).

Subsequently, the extraction unit 43a determines whether or not the distance to the target is substantially constant with respect to the observation data indicating the depression angle (step S202, Yes) (step S203).

Subsequently, when the extraction unit 43a has a substantially constant distance to the target (step S203, Yes), it determines whether or not the relative velocity is equivalent to a stationary object (step S204).

Then, when the relative velocity is equivalent to that of a stationary object (step S204, Yes), the extraction unit 43a extracts as a candidate target (step S205). Subsequently, the determination unit 43b determines whether or not there are a plurality of candidate markers having different horizontal angles (step S206).

Then, when the determination unit 43b has a plurality of candidate markers having different horizontal angles (steps S206, Yes), the determination unit 43b determines the plurality of candidate markers as the road surface G (step S207), and ends the process. ..

On the other hand, when the determination conditions of steps S201 to S204 and step S206 are not satisfied (step S201, No / step S202, No / step S203, No / step S204, No / step S206, No), the road surface determination unit 43 , The process is terminated without determining the road surface G.

As described above, the radar device 1 according to the embodiment includes a lead-out unit 41, a continuity determination unit 42, and a road surface determination unit 43. The derivation unit 41 derives the observation data of the target including the distance to the target and the depression angle based on the reflected wave reflected by the transmitted wave SW transmitted from the own vehicle MC.

The continuity determination unit 42 determines whether or not the observation data previously derived by the derivation unit 41 and the observation data derived this time are observation data of the same target that are continuous in time. Based on the observation data determined by the continuity determination unit 42 as the same target, the road surface determination unit 43 selects a target that satisfies the determination condition that the distance is constant when the own vehicle MC travels, among the targets indicating the depression angle. Judged as road surface G. Therefore, according to the radar device 1, the detection accuracy of the road surface G can be improved.

By the way, the vehicle is often a strong reflector having a stronger reflection intensity of the reflected wave than the road surface G. Therefore, the angular power corresponding to the vehicle tends to take a higher value than the angular power corresponding to the road surface G.

Therefore, the road surface determination unit 43 may set a threshold value based on the angular power of the vehicle and determine the road surface G for a target whose angular power is lower than the applied threshold value. In other words, the road surface determination unit 43 can also determine the road surface G by excluding the reflected wave based on the vehicle.

As a result, the road surface G can be detected with high accuracy while suppressing the processing load by the road surface determination unit 43. The reflected intensity of the reflected wave by the road surface G differs depending on the road surface conditions (type of road surface, presence or absence of rain) of the road surface G and the like. Therefore, the road surface determination unit 43 can change such a threshold value according to the road surface conditions.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments expressed and described as described above. Therefore, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

1 Radar device 2 Vehicle control device 41 Derivation unit 41a Peak detection unit 41b Angle estimation unit 41c Pairing unit 42 Continuity determination unit 43 Road surface determination unit 43a Extraction unit 43b Determination unit 44 Filter processing unit 45 Target classification unit 46 Unnecessary target Judgment unit 47 Coupling processing unit 48 Output target selection unit G Road surface SW transmission wave

Claims (6)

A derivation unit that derives observation data of the target including the distance to the target and the depression angle based on the reflected wave reflected by the transmitted wave transmitted from the own vehicle.
A continuity determination unit that determines whether or not the observation data derived last time by the derivation unit and the observation data derived this time are observation data of the same target that are continuous in time,
Based on the observation data determined to be the same target by the continuity determination unit, among the targets indicating the depression angle, the target that satisfies the determination condition that the distance becomes constant when the own vehicle travels is defined as the road surface. A radar device including a road surface determination unit for determination. The out-licensing unit
Further deriving the relative velocity with the target as the observation data,
The road surface determination unit
The radar device according to claim 1, wherein a target whose relative velocity is derived by the derivation unit and corresponds to a stationary object is determined as the road surface. The out-licensing unit
Further deriving the direction of the target as the observation data,
The road surface determination unit
The radar device according to claim 1 or 2, wherein a target whose directional variation derived by the derivation unit is equal to or greater than a reference value is determined as the road surface. The road surface determination unit
An extraction unit that extracts the target that satisfies the determination condition based on the observation data,
Among the targets extracted by the extraction unit, when there are a plurality of the targets derived by the derivation unit having different directions, the target is provided with a determination unit for determining the plurality of targets as the road surface. The radar device according to claim 3, wherein the radar device is characterized by the above. The road surface determination unit
The road surface is determined for a target whose reception intensity of the reflected wave used for the derivation process of the observation data is lower than a threshold value set based on the reception intensity of the reflected wave when it is reflected by the vehicle. The radar device according to any one of claims 1 to 4, wherein the radar device is characterized. A derivation process for deriving observation data of the target including the distance to the target and the depression angle based on the reflected wave of the transmitted wave transmitted from the own vehicle reflected on the target.
A continuity determination step of determining whether or not the observation data derived last time by the derivation step and the observation data derived this time are observation data of the same target that are continuous in time,
Based on the observation data determined to be the same target by the continuity determination step, among the targets showing the depression angle, the target that satisfies the determination condition that the distance becomes constant when the own vehicle travels is defined as the road surface. A road surface detection method including a road surface determination step for determination.

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