Radar device and target height estimation method

There is provided a radar device configured to detect a target by executing signal processing on the basis of a transmission wave and a reflection wave of the transmission wave reflected on the target. An antenna unit having a plurality of antennas arranged in a vertical direction. A calculation unit configured to calculate vertical azimuths of the target on the basis of the reflection waves with respect to the transmission waves transmitted from each of the antennas, and to accumulate calculation results. An estimation unit configured to calculate moving average values of maximum values of the vertical azimuths on the basis of the calculation results accumulated by the calculation unit, and to estimate the moving average values of the maximum values, as a height of the target.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2017-44023 filed on Mar. 8, 2017.

BACKGROUND

Technical Field

The present disclosure relates to a radar device and a target height estimation method.

Related Art

In the related art, a radar device has been known which is mounted in a vehicle or the like and is configured to receive a reflection wave, which is formed as a transmission wave transmitted from the vehicle collides with a target and is reflected from the target, and to detect the target on the basis of the obtained received signal.

As the radar device, there is a radar device that includes a plurality of antennas configured to two-dimensionally scan a distance and a horizontal azimuth of a target and arranged in a vertical direction, and is configured to estimate a vertical angle, at which the target is estimated to exist, i.e., a height of the target, based on a received signal with respect to transmission waves from each antenna (for example, refer to Patent Document 1). Thereby, it is possible to detect a superjacent object such as a road sign and a signboard.Patent Document 1: JP-A-H09-288178

However, the above technology has room for further improvement in estimating the height of the target with accuracy.

Specifically, according to the radar device, when it is intended to detect the superjacent object, the direct reflection waves from the superjacent object and the reflection waves from the superjacent object via a road surface or the like interfere with each other, so that a so-called multipath occurs and a signal level and the like with respect to the superjacent object are likely to be unstable. For this reason, the estimation accuracy of the height of the target, which is the superjacent object, may be lowered.

SUMMARY

It is therefore an object of the disclosure to provide a radar device and a target height estimation method capable of estimating a height of a target with accuracy.

According to an aspect of the embodiments of the present invention, there is provided a radar device configured to detect a target by executing signal processing on the basis of a transmission wave and a reflection wave of the transmission wave reflected on the target, the radar device including: an antenna unit having a plurality of antennas arranged in a vertical direction; a calculation unit configured to calculate vertical azimuths of the target on the basis of the reflection waves with respect to the transmission waves transmitted from each of the antennas, and to accumulate calculation results, and an estimation unit configured to calculate moving average values of maximum values of the vertical azimuths on the basis of the calculation results accumulated by the calculation unit, and to estimate the moving average values of the maximum values, as a height of the target.

According to the above configuration, it is possible to estimate the height of the target with accuracy.

DETAILED DESCRIPTION

Hereinafter, an illustrative embodiment of the radar device and the target height estimation method of the present disclosure will be described in detail with reference to the accompanying drawings. In the meantime, the present disclosure is not limited to the illustrative embodiment to be described later.

Also, in the below, after describing an outline of a target height estimation method in accordance with the illustrative embodiment with reference toFIGS. 1A and 1B, a radar device1to which the target height estimation method of the illustrative embodiment is applied will be described with reference toFIGS. 2A to 7B.

Meanwhile, in the below, an example where the radar device1adopts an FM-CW (Frequency Modulated Continuous Wave) method and is mounted to an own vehicle MC is described.

First, an outline of the target height estimation method in accordance with the illustrative embodiment is described with reference toFIGS. 1A to 1D.FIG. 1Adepicts a situation where a target TG is a superjacent object.FIG. 1Bdepicts calculation results of a height of the target TG, based on reflection waves from the superjacent object.FIGS. 1C and 1Dillustrate an outline of the target height estimation method in accordance with the illustrative embodiment.

First, the radar device1of the illustrative embodiment includes a vertical direction antenna (hereinafter, referred to as “vertical antenna”) having a plurality of antennas arranged in a vertical direction. The radar device1can receive reflection waves, which are formed as transmission waves transmitted from the vertical antenna collide with the target TG and are reflected from the target, and perform calculation for estimating an arrival direction of the reflection waves on the basis of the obtained received signals, thereby obtaining an angle of the vertical direction (hereinafter, referred to as “vertical azimuth”) at which the target TG is estimated to exist.

In the meantime, as shown inFIG. 1A, in case the target TG is a superjacent object, a so-called multipath occurs, so that a synthetic wave of a reflection wave W1(hereinafter, referred to as “direct wave W1”) directly arriving from the target TG and a reflection wave W2(hereinafter, referred to as “via wave W2”) arriving from the target TG via a road surface100is incident on the radar device1.

Therefore, the radar device1is required to calculate the vertical azimuth of the target TG from the synthetic wave. However, a vertical azimuth of a virtual image G of the target TG corresponding to the via wave W2is obtained or an SN (Signal-Noise) ratio based on a distance between the own vehicle MC and the target TG is deteriorated, so that the calculation results become unstable, as shown inFIG. 1B.

As can be seen fromFIG. 1B, within a range in which the distance between the own vehicle MC and the target TG is up to 30 m, the calculation results in which the height of the target TG is substantially stable about 3 m are obtained. However, when the distance is far away from 30 m, the variations increase, so that the calculation results are unstable.

Therefore, in the target height estimation method of the illustrative embodiment, target height estimation processing of accumulating, in a buffer33a(refer toFIG. 2A), calculation values of the vertical azimuths, which are obtained in azimuth calculation processing that is periodically executed in correspondence to one scan of radio waves, including a calculation value of this time and calculation values of previous constant periods, and estimating a height of the target TG on the basis of the accumulated time-series data, not instantaneous values, is performed.

Specifically, as shown inFIG. 1C, in the target height estimation processing, the vertical azimuths of previous constant periods including the vertical azimuth of this time are acquired from the buffer33a(step S1). Then, effective data is extracted from the acquired data (step S2).

Herein, the effective data indicates data except a calculation result, which is clearly ineffective, such as values deviating from a beam range of the radar device1. As can be seen fromFIG. 1B, calculation values that can be determined to clearly deviate from the beam range such as the height 10 m may be included in the calculation results. By the processing of step S2, it is possible to exclude such data.

Subsequently, as shown inFIG. 1C, in the target height estimation processing, for the effective data, moving average values of maximum values are calculated (step S3). Then, the calculated moving average values are set as estimated target height values (step S4). Therefore, in other words, in the target height estimation processing, the processing of normalizing the calculation results of the vertical azimuths and averaging the maximum values in the vertical direction and in the time axis direction is performed.

FIG. 1Ddepicts an example of the processing result of the target height estimation processing. As can be seen fromFIG. 1D, the height of the target TG, which is the superjacent object, becomes the stable estimated target height values by obtaining the moving average values of the maximum values from the previous calculation results having variations.

Therefore, according to the target height estimation method of the illustrative embodiment, it is possible to estimate the height of the target with accuracy. In the meantime, the example of obtaining the moving average values of the maximum values has been described. However, moving average values of minimum values may be obtained. The moving average values of minimum values correspond to estimated virtual image height values, which are the vertical azimuth of the virtual image G. The estimated virtual image height values are obtained without variations, so that it is possible to accurately determine the virtual image G as an unnecessary target in unnecessary target determination processing, which will be described later.

Also, based on a difference between the estimated target height value and the estimated virtual image height value, a subjacent object fallen on the road surface100may be determined. This will be described later with reference toFIGS. 6A to 6C.

In the below, the radar device1to which the target height estimation method is applied is described in more detail.

FIG. 2Ais a block diagram of the radar device1in accordance with the illustrative embodiment.FIG. 2Bdepicts a configuration example of the antenna unit.FIG. 2Cillustrates operations of the antenna unit, which are to be performed when calculating the horizontal azimuth and the vertical azimuth. Meanwhile, inFIG. 2A, only constitutional elements necessary to describe features of the illustrative embodiment are shown as functional blocks, and the descriptions of the general constitutional elements are omitted.

In other words, the respective constitutional elements shown inFIG. 2Aare functionally conceptual, and are not necessarily required to be physically configured, as shown. For example, the specific form of distribution/integration of the respective functional blocks is not limited to the shown example, and all or some of the functional blocks may be distributed/integrated functionally or physically in an arbitrary unit, depending on diverse loads, using situations and the like.

As shown inFIG. 2A, the radar device1includes a transmission unit10, a receiving unit20, and a processing unit30, and is connected to a vehicle control device2configured to control behaviors of the own vehicle MC.

The vehicle control device2is configured to perform vehicle control such as PCS (Pre-crash Safety System), AEB (Advanced Emergency Braking System) and the like, based on a detection result of the target TG by the radar device1. In the meantime, the radar device1may also be used for a variety of utilities (for example, monitoring of an airplane or a ship), in addition to the in-vehicle radar device.

The transmission unit10includes a signal generator11, an oscillator12, a switch13, and transmission antennas14. The signal generator11is configured to generate a modulation signal for transmitting millimeter waves frequency modulated by triangular waves under control of a transmission/receiving controller31, which will be described later.

The oscillator12is configured to generate a transmission signal on the basis of the modulation signal generated by the signal generator11, and to output the same to the switch13. The switch13is configured to output the transmission signal input from the oscillator12, to any one of the plurality of transmission antennas14.

Specifically, the switch13can set the transmission antenna14, to which the transmission signal is to be input, to any one transmission antenna or sequentially switch the transmission antennas in time division manner, based on the control of the transmission/receiving controller31. In the meantime, as shown inFIG. 2A, the transmission signal generated by the oscillator12is also distributed to mixers22, which will be described later.

The transmission antenna14is configured to convert the transmission signal from the switch13into a transmission wave, and to output the transmission wave to an outside of the own vehicle MC. The transmission wave output by the transmission antenna14is a continuous wave frequency modulated by a triangular wave. The transmission wave transmitted from the transmission antenna14to the outside of the own vehicle MC, for example, in front of the own vehicle MC is reflected on the target TG such as the other vehicle and becomes a reflection wave.

The receiving unit20includes a plurality of receiving antennas21to form an array of antennas, a plurality of mixers22, and a plurality of A/D converters23. The mixer22and the A/D converter23are provided for each of the receiving antennas21.

Each receiving antenna21is configured to receive the reflection wave from the target TG, as a reception wave, to convert the reception wave into a received signal and to output the received signal to the mixer22. In the meantime, the number of the receiving antennas21shown inFIG. 2Ais four. However, three or less or five or more antennas may also be provided.

A configuration example of the antenna unit40where the respective transmission antennas14and the respective receiving antennas21are arranged is described. As shown inFIG. 2B, in the antenna unit40of the illustrative embodiment, the transmission antennas14are arranged in the vertical direction, for example. Also, the receiving antennas21are arranged in the horizontal direction.

As shown inFIG. 2C, upon the horizontal azimuth calculation, any one of the transmission antennas14transmits the transmission wave, for example, and each receiving antenna21receives the reception wave.

Upon the vertical azimuth calculation, the respective transmission antennas14are sequentially switched in the time division manner and transmit the transmission waves, and any one of the receiving antennas21receives the reception wave, for example.

Returning toFIG. 2A, the received signal output from the receiving antenna21is amplified by an amplifier (for example, a low noise amplifier) (not shown) and is then input to the mixer22. The mixer22is configured to mix parts of the distributed transmission signal and the received signal input from the receiving antenna21, to remove an unnecessary signal component to generate a beat signal, and to output the beat signal to the A/D converter23.

The beat signal is a differential wave between the transmission wave and the reflection wave, and has a beat frequency, which is a difference between a frequency of the transmission signal (hereinafter, referred to as “transmission frequency”) and a frequency of the received signal (hereinafter, referred to as “receiving frequency”). The beat signal generated in the mixer22is converted into a digital signal in the A/D converter23, which is then output to the processing unit30.

The processing unit30includes a transmission/receiving controller31, a signal processor32, and a storage33. The signal processor32includes a frequency analysis unit32a, a peak extraction unit32b, an azimuth calculation unit32c, a pairing unit32d, a continuity determination unit32e, a horizontal filter unit32f, a target height estimation unit32g, a target classification unit32h, an unnecessary target determination unit32i, a grouping unit32j, and an output target selection unit32k.

The storage33has a buffer33a, an estimated target height value33b, and an estimated virtual image height value33c. In the buffer33a, vertical azimuths of previous constant periods including a vertical azimuth of this time are accumulated. As the estimated target height value33band the estimated virtual image height value33c, processing results of the target height estimation unit32gare stored.

The processing unit30is a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory) corresponding to the storage33, a register, input/output ports, and the like, and is configured to control the entire radar device1.

The CPU (microcomputer) reads out and executes a program stored in the ROM, so that it functions as the transmission/receiving controller31, the signal processor32and the like. In the meantime, both the transmission/receiving controller31and the signal processor32may be configured by hardware such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array) and the like.

The transmission/receiving controller31is configured to control the transmission unit10including the signal generator11, and the receiving unit20. The signal processor32is configured to periodically execute a series of signal processing. Subsequently, the respective constitutional elements of the signal processor32are described with reference toFIGS. 3 to 5G.

FIG. 3illustrates processing from pre-processing of the signal processor32to peak extraction processing in the signal processor32.FIG. 4Aillustrates azimuth calculation processing.FIGS. 4B and 4Cillustrate pairing processing.

The frequency analysis unit32ais configured to perform Fast Fourier Transform (FFT) processing (hereinafter, referred to as “FFT processing”) for the beat signal input from each A/D converter23, and to output a result thereof to the peak extraction unit32b. The result of the FFT processing is a frequency spectrum of the beat signal, and is a power value (signal level) for each frequency of the beat signal (for each of frequency bins set at frequency intervals corresponding to a frequency resolution).

The peak extraction unit32bis configured to extract peak frequencies, which become peaks of the result of the FFT processing executed by the frequency analysis unit32a, to reflect the peak frequencies in target data, and to output the same to the azimuth calculation unit32c. In the meantime, the peak extraction unit32bis configured to extract the peak frequencies for each of an “UP section” and a “DN section” of the beat signal, which will be described later.

The azimuth calculation unit32cis configured to calculate an arrival azimuth and a power value of the reflection wave corresponding to each of the peak frequencies extracted in the peak extraction unit32b. At this time, since the arrival azimuth is an azimuth at which the target TG is estimated to exist, the arrival azimuth may be hereinafter referred to as “estimated azimuth”. The estimated azimuth includes a horizontal azimuth and a vertical azimuth.

Also, the azimuth calculation unit32cis configured to accumulate the calculated vertical azimuths of previous constant periods including a vertical azimuth of this time in the buffer33a. Also, the azimuth calculation unit32cis configured to output the calculated estimated azimuth and the power value to the pairing unit32d.

The pairing unit32dis configured to determine the correct association of the peak frequencies of each of the “UP section” and the “DN section”, based on the calculation result of the azimuth calculation unit32c, and to calculate a distance and a relative speed of each target TG from the determination result. Also, the pairing unit32dis configured to reflect the estimated azimuth, distance and relative speed of each target TG in the target data, and to output the same to the continuity determination unit32e.

The flow from the pre-processing of the signal processor32to this processing in the signal processor32is shown inFIGS. 3 to 4C. In the meantime,FIG. 3is divided into three parts by two thick downward white arrows. In the below, the respective parts are referred to as an upper part, a middle part and a lower part in order.

As shown in the upper part ofFIG. 3, after the transmission signal fs(t) is transmitted from the transmission antenna14, as the transmission wave, it is reflected on the target TG, arrives as the reflection wave, and is received at the receiving antenna21, as the received signal fr(t).

At this time, as shown in the upper part ofFIG. 3, the received signal fr(t) is delayed with respect to the transmission signal fs(t) by a time difference τ, in correspondence to a distance between the own vehicle MC and the target TG. By the time difference τ and a Doppler effect based on the relative speeds of the own vehicle MC and the target TG, the beat signal is obtained as a signal in which a frequency fup of “UP section” where the frequency increases and a frequency fdn of “DN section” where the frequency decreases are repeated (refer to the middle part ofFIG. 3)

The lower part ofFIG. 3pictorially depicts a result of the FFT processing that was performed for the beat signal by the frequency analysis unit32a, for “UP section” and “DN section”.

As shown in the lower part ofFIG. 3, after the FFT processing, waveforms are obtained in the respective frequency regions of “UP section” and “DN section”. The peak extraction unit32bextracts the peak frequencies that become peaks in the waveforms.

For example, in the example shown in the lower part ofFIG. 3, a peak extraction threshold is used, so that peaks Pu1to Pu3are respectively determined as peaks and peak frequencies fu1to fu3are respectively extracted, in “UP section”.

Also, in “DN section”, the peak extraction threshold is also used, so that peaks Pd1to Pd3are respectively determined as peaks and peak frequencies fd1to fd3are respectively extracted.

In the frequency component of each peak frequency extracted by the peak extraction unit32b, the reflection waves from a plurality of targets TG may be mixed. Therefore, the azimuth calculation unit32cis configured to perform the azimuth calculation for each of the peak frequencies, and to interpret the existence of the target TG corresponding each peak frequency.

In the meantime, the azimuth calculation of the azimuth calculation unit32cmay be performed using the well-known arrival direction estimation method such as ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques), for example.

FIG. 4Apictorially depicts the azimuth calculation result performed by the azimuth calculation unit32c. The azimuth calculation unit32ccalculates the estimated azimuths of the respective targets TG corresponding to the peaks Pu1to Pu3, from the peaks Pu1to Pu3of the azimuth calculation result. Also, magnitudes of the respective peaks Pu1to Pu3are the power values. The azimuth calculation unit32cperforms the azimuth calculation processing for each of “UP section” and “DN section”, as shown inFIG. 4B.

Also, although not shown inFIG. 4A, which is a pictorial plan view, a horizontal azimuth and a vertical azimuth, which are required to be combined so as to correspond to the same target, of the horizontal azimuths and the vertical azimuths included in the estimated azimuths of the respective targets TG calculated by the azimuth calculation unit32care combined on the basis of a difference of the power values, and the like.

The pairing unit32dis configured to perform a pairing of associating the respective peaks of which the estimated azimuths and the power values are close to each other in the azimuth calculation result performed by the azimuth calculation unit32c, as shown inFIG. 4B. Also, the pairing unit32dis configured to calculate a distance and a relative speed of each target G corresponding to each of the associated peaks.

The distance can be calculated on the basis of a relation of “distance∝(fup+fdn)”. The relative speed can be calculated on the basis of a relation of “speed∝(fup−fdn)”. As a result, as shown inFIG. 4C, the pairing processing result indicative of the estimated azimuth, distance and relative speed of each target TG relative to the own vehicle MC is obtained.

Subsequently, the continuity determination unit32eis described. The continuity determination unit32eis configured to determine temporal continuity between the target data detected up to the previous scans and the target data of the latest period (this scan), to reflect a result of the determination in the target data, and to output the same to the horizontal filter unit32f.

Specifically, as shown inFIG. 5A, the continuity determination unit32ecalculates a predicted position LP of this time on the basis of the previous values, for example, the previous position and the previous speed corresponding to the target TG1′ detected up to the previous scans. Then, the continuity determination unit32edetermines the target TG, which is closest to the predicted position LP of this time, of the targets TG under determination in this scan, as a target TG1that is temporally continuous to the target TG1′ up to the previous time (refer to M1inFIG. 5A).

Subsequently, the horizontal filter unit32fis described. The horizontal filter unit32fis configured to perform horizontal filter processing of smoothing the target data in the horizontal direction and in the time axis direction, to reflect a result thereof in the target data, and to output the same to the target classification unit32h.

FIG. 5Bpictorially depicts the horizontal filter processing that is to be executed by the horizontal filter unit32f. That is, as shown inFIG. 5B, in the filter processing, the targets of this prediction and the target TG of this time based on the continuous targets TG′ up to the previous time are smoothed, i.e., the plurality of times of instantaneous value data is averaged to suppress the variations of the instantaneous value data and to increase the detection accuracy of the target TG.

Subsequently, the target height estimation unit32gis described. The target height estimation unit32gis configured to execute target height estimation processing including steps S1to S4(refer toFIG. 1C). That is, the target height estimation unit32gis configured to acquire the vertical azimuths of previous constant periods including the vertical azimuth of this time from the buffer33a. Also, the target height estimation unit32gis configured to extract effective data by excluding ineffective data from the data acquired from the buffer33a.

Also, the target height estimation unit32gis configured to calculate moving average values of maximum values for the extracted effective data, and to store the calculated moving average values in the storage33, as the estimated target height value33b. Here, the other processing to be included in the target height estimation processing is described with reference toFIGS. 6A to 6C.FIGS. 6A to 6Cillustrate the other processing of the target height estimation processing.

As shown inFIG. 6A, the target height estimation unit32gcalculates moving average values of minimum values for the extracted effective data (step S5). Also, the target height estimation unit32gstores the calculated moving average values of minimum values in the storage33, as the estimated virtual image height value33c(step S6).

FIG. 6Bdepicts an example of the calculation processing result of the moving average values of the minimum values. As can be seen fromFIG. 6B, the estimated virtual image height values33c, which are the vertical azimuths of the virtual image G, are smoothed in the vertical direction and in the time axis direction, and the variations thereof are suppressed.

The estimated virtual image height values33care obtained without variations, so that it is possible to accurately determine the virtual image G, as an unnecessary target, in unnecessary target determination processing, which will be described later.

Also, as shown inFIG. 6C, the target height estimation unit32gcompares the estimated target height value33band the estimated virtual image height value33c, determines the target TG, as a subjacent object, when a difference of the estimated values is equal to or smaller than a predetermined value (step S7), and adopts the estimated virtual image height value33c, as a height of the target TG (step S8).

When the target TG is a subjacent object fallen on the road surface100, the multipath does not occur. Therefore, the decrease in difference between the estimated target height values33band the estimated virtual image height values33cis used as the determination material. The reason to adopt the estimated virtual image height value33cis described. Since the estimated target height value33bis the moving average value of the maximum value and the estimated virtual image height value33cis the moving average value of the minimum value, it is thought that the estimated virtual image height value33chas the higher degree of certainty, as the height of the subjacent object fallen on the road surface100.

In this way, the subjacent object and the height thereof are investigated, so that it is possible to accurately determine the target TG, as the subjacent object, in the unnecessary target determination processing, which will be described later.

Returning toFIG. 2A, the target classification unit32his described. The target classification unit32his configured to perform target classification processing of classifying types of the target data, to reflect a result thereof in the target data, and to output the same to the unnecessary target determination unit32i.

FIGS. 5C and 5Dpictorially depict a classification example performed by the target classification unit32h. As shown inFIG. 5C, the target classification unit32hcan classify the target TG, as a moving object such as a preceding vehicle LC and an oncoming vehicle OC, for example.

Specifically, the target classification unit32hclassifies the target TG of which relative speed is greater than a reverse direction of the own vehicle speed of the own vehicle MC, as the preceding vehicle LC. Also, the target classification unit32hclassifies the target TG of which relative speed is smaller than the reverse direction of the own vehicle speed of the own vehicle MC, as the oncoming vehicle OC.

Also, as shown inFIG. 5D, the target classification unit32hcan classify the target TG, as a stationary object S, for example. Specifically, the target classification unit32hclassifies the target TG of which relative speed is substantially reverse to the own vehicle speed of the own vehicle MC, as the stationary object S.

Subsequently, the unnecessary target determination unit32iis described. The unnecessary target determination unit32iis configured to perform unnecessary target determination processing of determining whether a target is an unnecessary target TG with respect to the system control, to reflect a result thereof in the target data, and to output the same to the grouping unit32j.

FIG. 5Epictorially depicts an example of a target that is determined as an unnecessary target by the unnecessary target determination unit32i. As shown inFIG. 5E, the unnecessary target determination unit32idetermines a “superjacent object” such as a road sign, “rains”, and a “subjacent object”, which does not cause any problem to the traveling of the own vehicle MC, for example, as the unnecessary target.

Upon the determination, the estimated target height value33bor the estimated virtual image height value33coutput from the target height estimation unit32gand stored in the storage33can be used. The unnecessary target includes a structure, road surface reflection, wall reflection, a reflection ghost, the virtual image G and the like, in addition to the above examples. The target TG determined as an unnecessary target is not basically an output target of the radar device1.

Subsequently, the grouping unit32jis described. The grouping unit32jis configured to perform grouping processing of aggregating a plurality of target data based on the same object to one data, to reflect a result thereof in the target data, and to output the same to the output target selection unit32k.

FIG. 5Fpictorially depicts the grouping processing that is performed by the grouping unit32j. That is, as shown inFIG. 5F, the grouping unit32jregards targets, which are estimated as reflected points from the same object (for example, a truck TR), of a plurality of detected targets, as divided targets TD, and aggregates the same to one target TG. This grouping is performed on the basis of conditions that detected positions are close to each other, the speeds are similar to each other, and the like, for example.

Subsequently, the output target selection unit32kis described. The output target selection unit32kis configured to perform output target selection processing of selecting a target TG that is required to be output to the vehicle control device2with respect to the system control, and to output the target data of the selected target TG to the vehicle control device2.

FIG. 5Gpictorially depicts the output target selection processing that is performed by the output target selection unit32k. Basically, the output target selection unit32kpreferentially selects the target TG detected at a position close to an own lane.

Therefore, as shown inFIG. 5G, for example, when the target TG1on the own lane, the target TG2on an opposite lane (or an adjacent lane) and the target TG3at a position deviating from the own lane are respectively detected, the output target selection unit32kdoes not select the target TG3, for example (refer to M2inFIG. 5G).

In this case, the output target selection unit32kselects the target TG1and the target TG2, which are thought to be necessary for PCS or AEB (refer to frames FR inFIG. 5G).

Subsequently, a processing sequence that is to be executed by the processing unit30of the radar device1of the illustrative embodiment is described with reference toFIGS. 7A and 7B.FIG. 7Ais a flowchart depicting a processing sequence that is to be executed by the processing unit30of the radar device1in accordance with the illustrative embodiment.FIG. 7Bis a flowchart depicting a processing sequence of the target height estimation processing. In the meantime, here, a processing sequence of a series of signal processing corresponding to one scan is shown.

As shown inFIG. 7A, the frequency analysis unit32afirst executes the frequency analysis processing (step S101). Then, the peak extraction unit32bexecutes the peak extraction processing (step S102).

Then, the azimuth calculation unit32cexecutes the azimuth calculation processing (step S103), and the pairing unit32dexecutes the pairing processing on the basis of the result thereof (step S104).

Then, the continuity determination unit32eexecutes the continuity determination processing (step S105), and the horizontal filter unit32fexecutes the horizontal filter processing (step S106).

Then, the target height estimation unit32gexecutes the target height estimation processing (step S107). In the target height estimation processing, as shown inFIG. 7B, the target height estimation unit32gacquires the vertical azimuths of previous constant periods including the vertical azimuth of this time from the buffer33a(step S201).

Then, the target height estimation unit32gextracts the effective data by excluding the ineffective data from the acquired data (step S202). Then, the target height estimation unit32gcalculates the moving average values of the maximum values for the extracted effective data (step S203).

Then, the target height estimation unit32gsets the calculated moving average values, as the estimated target height value33b(step S204). Then, the target height estimation unit32gcalculates the moving average values of the minimum values for the extracted effective data (step S205).

Then, the target height estimation unit32gsets the calculated moving average values, as the estimated virtual image height value33c(step S206). In the meantime, although not shown, the target height estimation unit32gmay subsequently execute processing of determining whether the target is a subjacent object on the basis of the difference between the estimated target height value33band the estimated virtual image height value33cand processing of determining the height of the subjacent object when the target is the subjacent object (refer to step S7and step S8ofFIG. 6C).

Then, the target height estimation unit32gends the target height estimation processing. Returning toFIG. 7A, the target classification unit32hsubsequently executes the target classification processing (step S108).

Then, the unnecessary target determination unit32iexecutes the unnecessary target determination processing (step S109), and the grouping unit32jexecutes the grouping processing (step S110). Then, the output target selection unit32kexecutes the output target selection processing (step S111), so that the series of signal processing corresponding to one scan is over.

As described above, the radar device1of the illustrative embodiment is the radar device1configured to detect the target TG by executing the signal processing on the basis of the transmission wave and the reflection wave of the transmission wave reflected on the target TG, and includes the antenna unit40, the azimuth calculation unit32c(corresponding to an example of “calculation unit”), and the target height estimation unit32g(corresponding to an example of “estimation unit”).

The antenna unit40includes the plurality of transmission antennas14(corresponding to an example of “antennas”) arranged in the vertical direction. The azimuth calculation unit32cis configured to calculate the vertical azimuths of the target TG on the basis of the reflection waves with respect to the transmission waves transmitted from the transmission antennas14, and to accumulate the calculation results.

The target height estimation unit32gis configured to calculate the moving average values of the maximum values of the vertical azimuths on the basis of the calculation results accumulated by the azimuth calculation unit32c, and to estimate the moving average values of the maximum value, as the height of the target TG.

Therefore, according to the radar device1of the illustrative embodiment, it is possible to estimate the height of the target TG with accuracy.

Also, the target height estimation unit32gis configured to calculate the moving average values of the maximum values for the effective data obtained by excluding the ineffective data from the calculation results accumulated by the azimuth calculation unit32c.

Therefore, according to the radar device1of the illustrative embodiment, since the height of the target TG is estimated on the basis of the normalized data, it is possible to further increase the accuracy of the height of the target TG to be estimated.

Also, the target height estimation unit32gis configured to calculate the moving average values of the minimum values of the vertical azimuths on the basis of the calculation result, and to estimate the moving average values of the minimum values, as the height of the virtual image G corresponding to the target TG.

Therefore, according to the radar device1of the illustrative embodiment, it is possible to estimate the height of the virtual image G corresponding to the target TG with accuracy.

Also, when the difference between the height of the target TG and the height of the virtual image G estimated is equal to or smaller than the predetermined value, the target height estimation unit32gdetermines that the target TG is a subjacent object, and adopts the height of the virtual image G, as the height of the subjacent object.

Therefore, according to the radar device1of the illustrative embodiment, it is possible to estimate the subjacent object, which is fallen on the road surface100and should be determined as an unnecessary target, and the height thereof with accuracy.

Meanwhile, in the above illustrative embodiment, the radar device1adopts the FM-CW method. However, the present disclosure is not limited thereto. For example, an FCM (Fast Chirp Modulation) method can also be adopted. In the meantime, when the FCM method is adopted, since the pairing processing is not required, it is possible to exclude the pairing unit32dfrom the constitutional elements.

Also, in the above illustrative embodiment, the ESPRIT has been exemplified as the arrival direction estimation method that is used by the radar device1. However, the present disclosure is not limited thereto. For example, a DBF (Digital Beam Forming), a PRISM (Propagator method based on an Improved Spatial-smoothing Matrix), a MUSIC (Multiple Signal Classification) and the like can also be used.

Also, in the above illustrative embodiment, the radar device1is provided to the own vehicle MC. However, the radar device1may be provided to a moving object except for a vehicle, such as a ship, an airplane and the like.

The additional effects and modified embodiments can be easily conceived by one skilled in the art. For this reason, the wider aspects of the present disclosure are not limited to the specific and representative illustrative embodiment as described above. Therefore, a variety of changes can be made without departing from the concepts or scope of the general inventions defined by the appended claims and equivalents thereof.