Radar apparatus and signal processing method

A radar apparatus includes: a derivation portion that derives an instantaneous value of a target; a tracking portion that tracks a single target based on a derivation result of the derivation portion; a lost process portion that performs a lost process to stop the single target from being tracked by the tracking portion; and a target classification portion that classifies the single target into a standstill target or a moving target; and, when the single target is the standstill target, the lost process portion suppresses generation of the lost process more greatly than when the single target is the moving target.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2018-122868 filed on Jun. 28, 2018.

FIELD OF THE INVENTION

The present invention relates to a technique for tracking a target detected by a radar apparatus.

BACKGROUND OF THE INVENTION

Normally, a radar apparatus determines continuity about an instantaneous value of a target to thereby track the target. A continuity determination process executed in the radar apparatus is a process for determining whether there is continuity or not between an instantaneous value of a currently detected target and an instantaneous value of a previously detected target to thereby track the same target. In other words, the continuity determination process is a process for determining whether the currently detected target and the previously detected target are the same target or not to thereby track the same target. Incidentally, the continuity may be often determined not based on the previously detected instantaneous value per se but based on a processing result of various kinds of filtering performed thereon.

When it is determined that there is no continuity in the continuity determination process, an extrapolation process for virtually deriving an instantaneous value of a currently undetected target by prediction etc. using a kinetic model to thereby continue tracking of the same target is executed based on the previous processing result (e.g. see JP-A-2014-202678). When the instantaneous value of the target derived by the extrapolation process is data indicating that the target is present out of afield of view (FOV) of the radar apparatus, a lost process for stopping the tracking of the same target is executed.

SUMMARY OF THE INVENTION

Information of the target subjected to the lost process is not set as an output subject to an external system of AEB (Autonomous Emergency Braking) etc. Therefore, there is a problem that when a standstill object such as a parking block or a wall which has been once detected by the radar apparatus, for example, during backward parking falls out of the FOV, the standstill object cannot be recognized by the external system side.

In addition, the standstill object such as the parking block or the wall which has been detected once by the radar apparatus, for example, during the backward parking may fall out of the FOV and then fall into the FOV again. Since the lost process is executed as soon as the standstill object falls out of the FOV, the standstill object is detected as a new target when the standstill object falls into the FOV again. Therefore, there is a problem that priority as an output object to the external system may be lowered.

In consideration of the aforementioned problem, an object of the present invention is to improve tracking (standstill target tracking) performance for tracking a standstill target that is a tracking subject to be detected by a radar apparatus.

A radar apparatus according to the invention comprises: a derivation portion that derives an instantaneous value of a target; a tracking portion that tracks the same target based on a derivation result of the derivation portion; a lost process portion that performs a lost process to stop the same target from being tracked by the tracking portion; and a target classification portion that classifies the same target into a standstill target or a moving target; wherein: when the same target is the standstill target, the lost process portion suppresses generation of the lost process more greatly than when the same target is the moving target (first configuration).

In the radar apparatus of the first configuration, it may be that, when the same target is the standstill target and a tracking position of the same target falls out of a detection region of the radar apparatus, the lost process portion prohibits generation of the lost process (second configuration).

In the radar apparatus of the second configuration, it may be that the radar apparatus is mounted on a mobile object together with another radar apparatus; and even when the same target is the standstill target and the tracking position of the same target falls out of the detection region of the radar apparatus, the lost process portion exceptionally does not prohibit generation of the lost process if the tracking position of the same target falls into a detection region of the other radar apparatus (third configuration).

In the radar apparatus of the second or third configuration, it may be that even when the same target is the standstill target and the tracking position of the same target falls out of the detection region of the radar apparatus, the lost process portion exceptionally does not prohibit generation of the lost process if the same target is not a fixture to a land (fourth configuration).

The radar apparatus of any one of the first to fourth configurations may further comprises: a non-volatile storage portion that stores information of the standstill target detected by the radar apparatus immediately before the radar apparatus is powered OFF; wherein: when the radar apparatus is powered ON again, the tracking portion uses the information stored in the non-volatile storage portion (fifth configuration).

The radar apparatus of the fifth configuration may further comprises: a change determination portion that determines whether a position of the radar apparatus has changed or not between immediately before the radar apparatus is powered OFF and when the radar apparatus has been powered ON again; wherein: when determination is made by the change determination portion that the position of the radar apparatus has changed, the tracking portion exceptionally does not use the information stored in the non-volatile storage portion even if the radar apparatus has been powered ON again (sixth configuration).

A signal processing method according to the invention is a signal processing method of a radar apparatus comprising a derivation step of deriving an instantaneous value of a target; a tracking step of tracking the same target based on a derivation result of the derivation step; a lost process step of performing a lost process to stop the same target from being tracked by the tracking step; and a target classification step of classifying the same target into a standstill target or a moving target; wherein: when the same target is the standstill target, the lost process step suppresses generation of the lost process more greatly than when the same target is the moving target (seventh configuration).

According to the present invention, it is possible to improve tracking (standstill target tracking) performance for tracking a standstill target that is a tracking subject to be detected by the radar apparatus.

DETAILED DESCRIPTION OF THE INVENTION

1. Configuration of Radar Apparatus According to First Embodiment

FIG. 1is a view showing the configuration of a radar apparatus1according to a first embodiment. The radar apparatus1is mounted on a mobile object such as a vehicle. The vehicle on which the radar apparatus is mounted will be hereinafter referred to as “own vehicle”. In addition, a straight travelling direction of the own vehicle, that is also a direction going from a driver's seat toward steering will be referred to as “front”. Moreover, a straight travelling direction of the own vehicle, that is also a direction going from the steering toward the driver's seat will be referred to as “rear”. In addition, a direction perpendicular to the straight travelling direction of the own vehicle and a vertical line, that is also a direction going from a right side of a driver facing the front toward a left side of the driver will be referred to as “leftward”. Moreover, a direction perpendicular to the straight travelling direction of the own vehicle and the vertical line, that is also a direction going from the left side of the driver facing the front toward the right side of the driver will be referred to as “rightward”.

The radar apparatus1uses an FMCW (Frequency Modulated Continuous Wave) to acquire target data relevant to any target present on a left front side of the own vehicle.

The radar apparatus1derives target data having parameters including a distance from reflection of the FMCW on the target to reception of the reflected wave thereof by each of reception antennas of the radar apparatus1(hereinafter referred to as “target distance”) [m], relative velocity [km/h] of the target to the own vehicle, a target distance in the front/rear direction of the own vehicle (hereinafter referred to as “longitudinal position”) [m], a target distance in the right/left direction of the own vehicle (hereinafter referred to as “lateral position”) [m], etc. The longitudinal position is expressed as follows. When, for example, a position at which the radar apparatus1is mounted on the own vehicle is set as an origin O, the longitudinal position in front of the own vehicle is expressed by a positive value, and the longitudinal position at the rear of the own vehicle is expressed by a negative value. The lateral position is expressed as follows. When, for example, the position at which the radar apparatus1is mounted on the own vehicle is set as the origin O, the lateral position on the right side of the own vehicle is expressed by a positive value, and the lateral position on the left side of the own vehicle is expressed by a negative value.

As shown inFIG. 1, the radar apparatus1is mainly provided with a transmission portion2, a reception portion3, and a signal processing device4.

The transmission portion2is provided with a signal generation portion21and a transmitter22. The signal generation portion21generates a modulation signal in which voltage changes in the shape of a triangular wave, and supplies the generated modulation signal to the transmitter22. The transmitter22frequency-modulates a signal of a continuous wave based on the modulation signal generated by the signal generation portion21, generates a transmission signal in which frequency changes with the lapse of time, and outputs the generated transmission signal to a transmission antenna23.

The transmission antenna23outputs a transmission wave TW based on the transmission signal from the transmitter22. The transmission wave TW outputted by the transmission antenna23is the FMCW whose frequency fluctuates in a predetermined cycle. The transmission wave TW transmitted from the transmission antenna23to the left front side of the own vehicle is reflected as a reflected wave RW by an object such as a person or another vehicle.

The reception portion3is provided with a plurality of reception antennas31that form an array antenna, and a plurality of individual reception portions32that are connected to the plurality of reception antennas31respectively. In the present embodiment, for example, the reception portion3is provided with four reception antennas31and four individual reception portions32. The four individual reception portions32correspond to the four reception antennas31respectively. Each of the reception antennas31receives the reflected wave RW from the object to acquire a reception signal. Each of the individual reception portions32processes the reception signal obtained by a corresponding one of the reception antennas31.

Each of the individual reception portions32is provided with a mixer33and an A/D converter34. The reception signal obtained by the reception antenna31is amplified by a low noise amplifier (not shown) and then sent to the mixer33. The transmission signal sent from the transmitter22of the transmission portion2is inputted to the mixer33, and the transmission signal and the reception signal are mixed in the mixer33. Thus, a beat signal having a beat frequency as a difference between a frequency of the transmission signal and a frequency of the reception signal is generated. The beat signal generated by the mixer33is converted into a digital signal by the A/D converter34, and then outputted to the signal processing device4.

The signal processing device4is provided with a microcomputer including a CPU (Central Processing Unit) and a memory41etc. The signal processing device4stores various data into the memory41that is a storage device. The various data are set as subjects to be calculated. For example, the memory41is an RAM (Random Access Memory) etc. The signal processing device4is provided with a transmission control portion42, a Fourier transform portion43, and a data processing portion44as functions which are implemented as software by the microcomputer. The transmission control portion42controls the signal generation portion21of the transmission portion2.

The Fourier transform portion43executes fast Fourier transform (FFT) on the beat signals outputted from the individual reception portions32respectively. Thus, the Fourier transform portion43converts each of the beat signals relevant to the reception signals of the reception antennas31respectively into a frequency spectrum that is data of a frequency region. The frequency spectrum obtained by the Fourier transform portion43is inputted to the data processing portion44.

As shown inFIG. 1, the data processing portion44is provided with a peak extraction portion44a, an azimuth calculation portion44b, a pairing portion44c, a continuity determination portion44d, a filter process portion44e, a target classification portion44f, an unnecessary target determination portion44g, a coupling process portion44hand an output target selection portion44ias main functions.

The peak extraction portion44aextracts peak frequencies as peaks in a fast Fourier transform result performed by the Fourier transform portion43, to output the extracted peak frequencies to the azimuth calculation portion44b. Incidentally, the peak extraction portion44aextracts the peak frequencies as for each of an UP section (section in which frequency of the transmission wave TW rises) and a DOWN section (section in which the frequency of the transmission wave TW drops).

The azimuth calculation portion44bestimates an arrival angle of the reflected wave corresponding to each of the peak frequencies extracted in the peak extraction portion44a, and calculates signal intensity (a reception level) at the peak frequency.

The pairing portion44cobtains a correct combination of the UP section and the DOWN section based on the estimation result and the calculation result of the azimuth calculation portion44b, and calculates a distance and relative velocity of each of the targets from the combination result. In addition, the pairing portion44coutputs information (an instantaneous value of the target) including the estimated angle, the distance and the relative velocity of the target to the continuity determination portion44d.

The continuity determination portion44ddetermines whether there is continuity or not between the instantaneous value of the currently detected target and a previous processing result of the filter process portion44e. The continuity determination portion44doutputs the information about the target of the continuity determination portion to the filter process portion44e. The continuity determination portion44dis provided with a tracking portion45and a lost process portion46. Details of processings executed by the tracking portion45and the lost process portion46respectively will be described later.

As for each detected target, the filter process portion44esmooths the current instantaneous value whose continuity has been taken, and a prediction value by a predetermined weighting factor. When an α-β filter is used, the following expression is established. Incidentally, α is larger than 0 and smaller than 1. As for a new target whose continuity has not been taken, the prediction value is absent. Therefore, prediction value data in the following expression is replaced with the instantaneous value data.
Filtered Target Data=α×prediction value data+(1−α)×instantaneous value data

The filter process portion44emay use any other filter than the α-β filter, such as a Kalman filter, an extended Kalman filter, an unscented Kalman filter or a particle filter. When, for example, the particle filter is used, the filter process portion44eweights particles to more heavily weight a particle which is longer in distance between the current instantaneous value whose continuity has been taken and a predicted position of the particle. The filter process portion44ethen resamples the particles to delete particles weighted lightly and duplicate particles weighted heavily. A weighted average of the particles subjected to the resampling process is set as filtered target data. Incidentally, the distance between the current instantaneous value whose continuity has been taken and the predicted position of the particle may be any of an Euclidean distance and a statistical distance.

The filter process portion44eoutputs information about the filtered targets to the target classification portion44f.

The target classification portion44fclassifies each of the targets into a moving object or a standstill object based on a filter process result etc. of the filter process portion44e. The target classification portion44foutputs the classification result to the unnecessary target determination portion44g.

The unnecessary target determination portion44gdetermines whether each target is an unnecessary target or not from a viewpoint of system control. For example, the unnecessary target is a phase wrap-around ghost etc. Incidentally, information of the target determined as unnecessary by the unnecessary target determination portion44gis basically not outputted to an external apparatus but may be held internally. The unnecessary target determination portion44goutputs the information of the target not determined as unnecessary, to the coupling process portion44h.

Of the targets not determined as unnecessary by the unnecessary target determination portion44g, the coupling process portion44hgroups targets each estimated as a reflection point from the same object into one target, and outputs the grouping result to the output target selection portion44i.

The output target selection portion44iselects any target that is required to be outputted to the external apparatus from the viewpoint of system control. For example, the output target selection portion44iselects any target that has been tracked for a long period by the tracking portion45with priority, and minimizes the degree of priority of any newly detected target. The output target selection portion44ioutputs target information about the selected target to the external apparatus.

For example, the external apparatus is a vehicle control ECU5. For example, the vehicle control ECU5is electrically connected to a vehicle velocity sensor6, a steering angle sensor7, a throttle8, and a brake9. The vehicle control ECU5performs vehicle control such as AEB, ACC (Adaptive Cruise Control) or PCS (Pre-Crash Safety System) based on the target information acquired from the radar apparatus1.

2. Operation of Signal Processing Device

Next, operation of the signal processing device4will be described.FIG. 2is a flow chart showing the operation of the signal processing device4. The signal processing device4iterates processing shown inFIG. 2cyclically every predetermined time (e.g. 1/20 second).

Before start of the processing shown inFIG. 2, control of the signal generation portion21performed by the transmission control portion42is completed. First, the Fourier transform portion43executes fast Fourier transform on beat signals outputted respectively from the individual reception portions32(step S1). A frequency spectrum of both the UP section and the DOWN section about each of the four reception antennas31is inputted from the Fourier transform portion43to the data processing portion44.

Next, the peak extraction portion44aextracts a peak frequency from the frequency spectrum (step S2). The peak extraction portion44aextracts a frequency in which a peak having power exceeding a predetermined threshold appears as the peak frequency, from the frequency spectrum.

Next, the azimuth calculation portion44bestimates angles of targets relevant to the signal of the extracted peak frequency by an azimuth calculation process. In the azimuth calculation process, angles and signal powers for the angles are derived from one peak frequency signal. Any well-known azimuth calculation process such as ESPRIT, MUSIC or PRISM can be used as the azimuth calculation process.

FIG. 3is a graph conceptually showing angles estimated by the azimuth calculation process as an angle spectrum. InFIG. 3, the abscissa expresses angle (deg) and the ordinate expresses signal power. The angle (deg) is an angle between a frontward straight travelling direction of the own vehicle and a direction going from the radar apparatus1toward the target. Each of the angles estimated by the azimuth calculation process appears as a peak Pa in the angle spectrum. The angle estimated by the azimuth calculation process will be hereafter referred to as “peak angle” and the signal power for the peak angle will be hereinafter referred to as “angle power”. The peak angles simultaneously derived thus from one peak frequency signal indicate angles of targets present at the same distance (distance corresponding to the peak frequency) from the radar apparatus1.

The pairing portion44cderives the peaks angles and the angle powers of the targets present at the same distance from the radar apparatus1. Thus, the pairing portion44cderives section data respectively corresponding to the targets present on the left front side of the own vehicle. The pairing portion44cderives the section data having parameters including the peak frequency, the peak angle and the angle power, for each of the UP section and the DOWN section. The pairing portion44cassociates the section data of the UP section with the section data of the DOWN section to thereby obtain a correct combination of the UP section and the DOWN section (step S4). For example, the pairing portion44cuses calculation using a Mahalanobis distance to associate two section data having similar parameters (peak frequency, peak angle and signal power).

Successively, the continuity determination portion44dperforms a continuity determination process based on a processing result of the pairing portion44c(step S5). Then, the filter process portion44eperforms a filter process based on a processing result of the continuity determination process (step S6).

Successively, the target classification portion44fperforms a target classification process based on a processing result of the filter process (step S7). Then, the unnecessary target determination portion44gperforms an unnecessary target determination process based on a processing result of the target classification process (step S8).

The coupling process portion44hperforms a coupling process based on a processing result of the unnecessary target determination process (step S9). Finally, the output target selection portion44iperforms an output target selection process based on a processing result of the coupling process (step S10), and outputs target information of the targets selected as output subjects to the external apparatus. Then, the processing is terminated.

3. Outline of Continuity Determination Process

FIG. 4is a flow chart showing an outline of the continuity determination process. The flow chart shown inFIG. 4is executed on each of a previous processing result of the filter process portion44eand a target subjected to a previous extrapolation process.

First, the tracking portion45calculates a predicted position in current detection of the previous processing result of the filter process portion44eor the target subjected to the previous extrapolation process (hereinafter referred to as previous target) (step S110). That is, the current position is predicted based on a position and relative velocity of the previous target data.

Next, the tracking portion45sets an allocation region including the aforementioned predicted position (step S120). The allocation region may be shaped like a rectangle in which, for example, the aforementioned predicted position is the center of gravity in a two-dimensional plane when the own vehicle is looked down on.

When a currently detected target is within the allocation region (YES in the step S130), the tracking portion45determines that the currently detected target has continuity with the previous target (is the same target) (step S140). When the process of the step S140is completed, the flow operation shown inFIG. 4is terminated. Incidentally, when the currently detected target within the allocation region is also within another allocation region and allocated to the other allocation region, the flow operation may be shifted not to the step S140but to a step S160.

On the other hand, when the currently detected target is not within the allocation region (NO in the step S130), the tracking portion45determines whether the aforementioned predicted position falls into an FOV or not (step S150).

When the aforementioned predicted position falls into the FOV (YES in the step S150), the tracking portion45performs an extrapolation process (the step S160). Specifically, the tracking portion45determines that the same target as the previous processing result of the filter process portion44eis present in the aforementioned predicted position. Incidentally, the aforementioned predicted position used in the extrapolation process is not handled as an instantaneous value of the target in the filter process performed by the filter process portion44e. When the process of the step S160is completed, the flow operation shown inFIG. 4is terminated.

On the other hand, when the aforementioned predicted position falls out of the FOV (NO in the step S150), the tracking portion45determines whether the previous target is a standstill target or a moving target (step S170). Incidentally, the tracking portion45uses a classification result of the target classification portion44fto perform a determination process of the step S170.

When the previous target is a moving target (NO in the step S170), the lost process portion46performs a lost process (step S180). Specifically, the lost process portion46determines that the same target as the previous target has not been detected currently, so that the lost process portion46deletes the aforementioned predicted position from the memory41. By the lost process, the tracking of the same target by the tracking portion45is stopped. When the process of the step S180is completed, the flow operation shown inFIG. 4is terminated.

On the other hand, when the previous target is a standstill target (YES in the step S170), the lost process portion46performs a lost process if a predetermined condition is satisfied, and the tracking portion45performs an extrapolation process if the predetermined condition is not satisfied (step S190). For example, a condition that the continuity determination portion44dacquires information about a travelling locus of the vehicle from the vehicle control ECU5, calculates a distance between the radar apparatus1and the previous target based on the acquired information, and concludes that the calculated distance is longer than a predetermined distance can be enumerated as the predetermined condition. In addition, a condition that the extrapolation process in the step S190continues a predetermined number of times can be enumerated as another example of the predetermined condition. Incidentally, when the extrapolation process in the step S190has been executed, the continuity determination portion44dmay acquire the information about the travelling locus of the vehicle from the vehicle control ECU5in the step S110in a next cycle and the tracking portion45may calculate a predicted position based on the acquired information. When the process of the step S190is completed, the flow operation shown inFIG. 4is terminated.

Incidentally, the lost process may be executed when the extrapolation process continues the predetermined number of times. In addition, a currently detected target having no continuity with all previously detected targets and all previously extrapolated targets is a new target.

When the same target that is the tracking subject of the tracking portion45is a standstill target, the lost process portion46can suppress generation of the lost process by the processes of the aforementioned steps170to S190more greatly than when the same target that is the tracking subject of the tracking portion45is a moving target. Accordingly, it is possible to improve tracking (standstill target tracking) performance for tracking a standstill target that is a tracking subject to be detected by the radar apparatus1.

Thus, it is possible to solve a problem that when a standstill object such as a parking block or a wall which has been once detected by the radar apparatus, for example, during backward parking falls out of the FOV, the standstill object cannot be recognized by the external system side.

In addition, the standstill object such as the parking block or the wall which has been detected once by the radar apparatus, for example, during backward parking may fall out of the FOV and then fall into the FOV again. Since the lost process is executed as soon as the standstill object falls out of the FOV, the standstill object is detected as a new target when the standstill object falls into the FOV again. Therefore, there is a problem that priority as an output object to the external system may be lowered. This problem can be also solved.

Incidentally, the tracking portion45may always perform the extrapolation process in place of the process of the step S190. That is, the lost process portion46may prohibit generation of the lost process when the aforementioned predicted position falls out of the FOV (NO in the step S150) and the previous target is a standstill target (YES in the step S170). It is possible to improve the performance for tracking the standstill target more greatly by such modification.

Here, a plurality of radar apparatuses may be mounted on the vehicle. For example, five radar apparatuses are mounted on the vehicle shown inFIG. 5. A dotted-line rectangle inFIG. 5designates each of the radar apparatuses. An FOV101inFIG. 5is an FOV of the radar apparatus detecting any target present on the left rear side of the vehicle. An FOV102inFIG. 5is an FOV of the radar apparatus detecting any target present on the right rear side of the vehicle. An FOV103inFIG. 5is an FOV of the radar apparatus detecting any target present in the front of the vehicle. An FOV104inFIG. 5is an FOV of the radar apparatus detecting any target present on the left front of the vehicle. An FOV105inFIG. 5is an FOV of the radar apparatus detecting any target present on the right front of the vehicle.

A region that is out of an FOV of one radar apparatus but is within an FOV of another radar apparatus is present inFIG. 5. When a target within such a region is not tracked by the one radar apparatus but detected by the other radar apparatus, target data can be derived more accurately. Accordingly, although the tracking portion45performs an extrapolation process in principle in place of the process of the step S190, the lost process portion46may perform a lost process as an exception when the aforementioned predicted position is within the FOV of the other radar apparatus.

In the aforementioned first embodiment and the modification thereof, it is determined whether the previous target is a standstill target or a moving target in the step S170. However, there are two kinds of standstill targets, i.e. an object that can change to a moving target in the future, such as a parked vehicle, and a fixture to a land such as a parking block or a wall. It is not preferable to prohibit a lost process on the object which can change to the moving target in the future, such as the parked vehicle, because a ghost of the standstill target may continuously remain after the standstill target has changed to the moving target.

Accordingly, although the tracking portion45performs the extrapolation process in principle in place of the process of the step S190, the lost process portion46may perform the lost process as an exception when the previous target is not the fixture to the land but satisfies the predetermined condition. For example, a condition in which the extrapolation process performed in principle in place of the process of the step S190continues a predetermined number of times may be used as the predetermined condition in this modification.

The method for determining whether the target determined as the standstill target in the step S170is the fixture to the land or not is not particularly limited. For example, determination may be made with reference to the contents of grouping by the coupling process portion44h, or determination may be made with reference to an image taken by a camera mounted on the vehicle.

4. Second Embodiment

FIG. 6is a view showing the configuration of a radar apparatus1′ according to a second embodiment. The radar apparatus1′ is configured to include a signal processing device4′ with which the signal processing device4in the radar apparatus1according to the first embodiment is replaced. The signal processing device4′ has a configuration in which a change determination portion47is added to the signal processing device4. In addition, at least a portion of a memory41belonging to the radar apparatus1′ is a non-volatile such as a flash memory.

When an ignition switch or a power switch of an own vehicle is turned from ON to OFF, the radar apparatus1′ is also powered from ON to OFF. A data processing portion44non-volatilely stores information of a standstill target detected by the radar apparatus1′ into the memory41immediately before the radar apparatus1′ is powered OFF. Examples of the information of the standstill target include instantaneous data of the standstill target, extrapolation data (data obtained by an extrapolation process) of the standstill target, filter data (data obtained by a filter process) of the standstill target, etc. Incidentally, a predetermined flag is included in the information of the standstill target non-volatilely stored in the memory41immediately before the radar apparatus1′ is powered OFF. The predetermined flag is a flag meaning that the information of the standstill target has been non-volatilely stored in the memory41immediately before the radar apparatus1′ is powered OFF.

When the ignition switch or the power switch of the own vehicle is turned ON again, the radar apparatus ′1is also powered ON again. When the radar apparatus is powered ON again, a tracking portion45uses the information of the standstill target that has been non-volatilely stored in the memory41. Accordingly, when the information of the standstill target has been non-volatilely stored in the memory41immediately before the radar apparatus1′ is powered OFF, the standstill target whose information has been non-volatilely stored in the memory41is processed as a previous target in a flow chart shown inFIG. 4of a first cycle after the radar apparatus1′ is powered ON again. Therefore, a standstill target having continuity with the previous target can be detected in the first cycle after the radar apparatus1′ is powered ON again.

For example, the ignition switch or the power switch of the own vehicle is turned OFF after the own vehicle has entered a parking lot. The ignition switch or the power switch of the own vehicle is then turned ON again in order to enable the own vehicle to leave the parking lot. Thus, performance for tracking the standstill target in such a case can be improved.

However, when, for example, the own vehicle is towed away after the ignition switch or the power switch of the own vehicle has been turned OFF and until the ignition switch or the power switch of the own vehicle is turned ON again, an erroneous extrapolation process is performed by the flow chart that is executed as shown inFIG. 4after the radar apparatus1′ is powered ON again.

Therefore, in the embodiment, the change determination portion47determines whether the position of the radar apparatus1′ has changed or not between immediately before the radar apparatus1′ is powered OFF and when the radar apparatus1′ has been powered ON again. When determination is made by the change determination portion47that the position of the radar apparatus has changed, the tracking portion45is configured exceptionally not to use the information of the standstill target including the aforementioned predetermined flag even if the radar apparatus has been powered ON again.

The determination method performed by the change determination portion47is not particularly limited. For example, position information of the own vehicle may be acquired from a navigation apparatus10mounted on the own vehicle as shown inFIG. 6, and determination as to whether the position of the radar apparatus1′ has changed or not may be made by use of the acquired position information. In addition, determination may be made that the position of the radar apparatus1′ has not changed, for example, when detection results of an ambient state detection sensor (the radar apparatus1′ itself, an on-vehicle camera, an LIDAR (Light Detection and Ranging), a clearance sonar, or the like) mounted on the own vehicle are similar between immediately before the radar apparatus1′ is powered OFF and when the radar apparatus1′ has been powered ON again. Setting of a similarity range in the determination depends on estimation of probability as to presence of a moving target around the own vehicle or detection characteristics of the ambient state detection sensor. For example, when a detection result of the on-vehicle camera is used, an object taken in a photographic image is recognized by image recognition technology. When the same standstill object is present between immediately before the radar apparatus1′ is powered OFF and when the radar apparatus1′ has been powered ON again, determination may be made that the standstill object falls into the similarity range.

Various technological features disclosed in the description of the present invention can have various changes added without departing from the gist of technical creation of the present invention, in addition to the aforementioned embodiments. In addition, the embodiments and the modifications disclosed in the description of the present invention may be combined in a feasible range and carried out.

For example, the radar apparatus1,1′ in each of the aforementioned embodiments is an FMCW-type radar apparatus. However, another type radar apparatus may be used. For example, an FCM (Fast-Chirp Modulation)-type radar apparatus may be used.

For example, the radar apparatus1,1′ in each of the aforementioned embodiments is mounted on the vehicle. However, the radar apparatus1,1′ may be mounted on another mobile object than the vehicle, such as a vessel or a flying object.