Source: https://patents.google.com/patent/US9869761B2/en
Timestamp: 2020-01-18 03:21:17
Document Index: 476217648

Matched Legal Cases: ['art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18', 'art 18']

US9869761B2 - Radar apparatus - Google Patents
US9869761B2
US9869761B2 US14/564,599 US201414564599A US9869761B2 US 9869761 B2 US9869761 B2 US 9869761B2 US 201414564599 A US201414564599 A US 201414564599A US 9869761 B2 US9869761 B2 US 9869761B2
US14/564,599
US20150204971A1 (en
Keishi YOSHIMURA
2014-01-22 Priority to JP2014-009227 priority
2014-12-09 Application filed by Denso Ten Ltd filed Critical Denso Ten Ltd
2014-12-09 Assigned to FUJITSU TEN LIMITED reassignment FUJITSU TEN LIMITED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ISHIMORI, HIROYUKI, YOSHIMURA, KEISHI
2015-07-23 Publication of US20150204971A1 publication Critical patent/US20150204971A1/en
2018-01-16 Publication of US9869761B2 publication Critical patent/US9869761B2/en
239000000203 mixtures Substances 0 description 137
Next, the radar apparatus 10 is explained. The radar apparatus 10 includes an antenna 101, a mixer 13 (including 13 a to 13 d), an analog-to-digital (AD) converter 14 (including 14 a to 14 d), a signal generator 15, an oscillator 16, a switch SW, a memory 17, and a signal processor 18.
The antenna 101 includes a transmitting antenna 11 and a receiving antenna 12. The transmitting antenna 11 includes a transmitting antenna 11 a and a transmitting antenna 11 b. The transmitting antenna 11 a and the transmitting antenna 11 b are switched to each other in a predetermined cycle. Thus, at least one of the two transmitting antennas outputs a transmission wave.
The receiving antenna 12 includes four receiving antennas 12 a, 12 b, 12 c and 12 d. The four receiving antennas receive reflection waves reflected by the target and output reception signals of the received waves to the mixers 13.
Transmission ranges of the transmitting antenna 11 a and the transmitting antenna 11 b are explained with reference to FIG. 2. FIG. 2 shows the transmission ranges of the transmission waves from the transmitting antenna 11 a and the transmitting antenna 11 b. Directions are described by x, y and z coordinate axes in FIG. 2. The x, y and z coordinate axes are fixed relative to a host vehicle CA (hereinafter referred to as “vehicle CA”). The x axis corresponds to a width direction of the vehicle CA, and the y axis corresponds to a traveling direction of the vehicle CA. Moreover, the z axis corresponds to a height direction (direction showing a height of a vehicle) of the vehicle CA. FIG. 2 illustrates a view looked downward (−z side) from a point above (+z side) the vehicle CA in the height direction (z-axis direction).
A transmission range Tr1 shows a reach of the transmission wave output from the transmitting antenna 11 a. A transmission axis Ce running in a substantial center of the transmission range Tr1 shows a transmission direction of the transmission wave. Given that the transmission axis Ce is ±0 degree, a horizontal angle of the transmission range Tr1 is approx. ±7 degrees, i.e. approx. 14 degrees, to the transmission axis Ce. Moreover, a transmission distance of the transmission wave is approx. 150 m. In a case where the vehicle CA is located substantially in a center of a current traffic lane RC, a horizontal angle range of the transmission range Tr1 includes a width (approx. 3.6 m) of the current traffic lane RC.
A transmission range Tr2 shows a reach of the transmission wave output from the transmitting antenna 11 b. Given that the transmission axis Ce is ±0 degree, a horizontal angle of the transmission range Tr2 is approx. ±30 degrees, i.e. approx. 60 degrees, to the transmission axis Ce. Moreover, a transmission distance of the transmission wave is approx. 70 m. In a case where the vehicle CA is located substantially in the center of the current traffic lane RC, a horizontal angle range of the transmission range Tr2 includes a width (approx. 10.8 m) of the current traffic lane RC, a left traffic lane RL that is a traffic lane left to the current traffic lane RC and a right traffic lane RR that is a traffic lane right to the current traffic lane RC.
The transmission waves output from the transmitting antenna 11 b are used to properly derive an azimuth direction of the target in azimuth direction calculation of the target, described later, even if a phase ghost occurs. Herein, the term “phase ghost” refers to a phenomenon in which an angle different from a true angle of the target is derived due to a 360-degree rotation of a phase of the reflection wave from the target. Even in a case where the phase ghost occurs, the radar apparatus 10 derives an accurate angle of the target based on a difference in reception levels of two reflection waves, one of which is the transmission wave reflected by the target after being transmitted to the transmission range Tr1 and the other of which is the transmission wave reflected by the target after being transmitted to the transmission range Tr2.
In reference back to FIG. 1, the mixer 13 includes the four mixers 13 a, 13 b, 13 c and 13 d. Each of the four mixers is electrically connected to each of the receiving antennas and all of the four receiving antennas are electrically connected to the mixer 13. The mixer 13 mixes the reception signal corresponding to the reflection wave received by the receiving antenna 12 with a transmission signal corresponding to the transmission wave. In other words, the mixer 13 derives a beat signal that is a signal of a difference between the reception signal and the transmission signal. The derived beat signal is outputs to the AD converter 14.
The AD converter 14 includes the four AD converters 14 a, 14 b, 14 c and 14 d. Each of the four AD converters is electrically connected to each of the receiving antennas via the mixer, and all of the four receiving antennas are electrically connected to the AD converters via the mixer. The AD converter 14 converts an analogue signal input from the mixer 13 into a digital signal. Concretely, the AD converter 14 samples an analogue beat signal in a predetermined cycle. Then, the AD converter 14 quantizes and converts the sampled analogue beat signal into a digital beat signal, and outputs the converted digital beat signal to the signal processor 18.
The switch SW electrically connects one of the transmitting antenna 11 a and the transmitting antenna 11 b to the oscillator 16. In other words, the switch SW switches connection to the oscillator 16 between one of the two transmitting antennas (e.g. the transmitting antenna 11 a) and the other antenna (e.g. the transmitting antenna 11 b). The switch SW switches the connection, for example, for every 5 msec.
The transmission signal TS has a period in which a frequency of the transmission signal TS goes up to the first frequency (hereinafter referred to as “up period”). For example, a period U1 (a time period from t0 to t1) and a period U2 (a time period from t2 to t3) are the up periods. Moreover, the transmission signal TS has a period in which the frequency of the transmission signal TS goes down to the second frequency (hereinafter referred to as “down period”). For example, a period D1 (a time period from the t1 to the t2) and a period D2 (a time period from the t3 to t4) are the down periods. Further, a first transmission period Tx1 (a time period from the t0 to the t2) is a period when the transmitting antenna 11 a transmits the transmission wave and a second transmission period Tx2 (a time period from the t2 to the t4) is a period when the transmitting antenna 11 b transmits the transmission wave.
With reference back to FIG. 1, the memory 17 stores an execution program for various arithmetic processing performed by the signal processor 18. Moreover, the memory 17 stores plural target information derived by the signal processor 18. The memory 17 stores, for example, target information 17 a derived in a previous process and a current process. The previous process and the current process are temporally consecutive processes. The target information 17 a includes a position and the speed of the target. Position information includes the distance from the target to a point where the receiving antenna 12 receives the reflection wave reflected by the target (hereinafter referred to as “longitudinal distance”) and also a distance from the target to the transmission axis Ce in a lateral direction (vehicle width direction) (hereinafter referred to as “lateral distance”). The lateral distance is derived by the signal processor 18 that calculates an angle of the target, using trigonometric functions. Moreover, the speed includes an absolute speed and the relative speed of the target to the vehicle CA.
The signal processor 18 derives the target information based on the foregoing beat signal BS derived based on the transmission signal TS and the reception signal RS. The signal processor 18 includes a deriving part 18 a, a setting part 18 b, a determination part 18 c and a history pairing part 18 d and performs various functions. With reference to process flowcharts in FIG. 4 and FIG. 5, the various functions performed by the signal processor 18 are hereinafter explained.
The signal processor 18 processes the digital beat signal BS in each of the up period and the down period, by using FFT (a step S102). As a result, the signal processor 18 obtains a frequency spectrum including a signal level value and phase information for each frequency relating to the beat signal BS in each of the up period and the down period. Moreover, the frequency spectrum of each of the receiving antennas 12 a to 12 d is obtained.
A process using ESPRIT (hereinafter referred to as “ESPRIT process”) is explained. FIG. 6 illustrates details of the ESPRIT process. The ESPRIT is a method of predicting an arrival direction of an arrival wave (reflection wave) based on a phase difference between two sub-arrays, disposed at positions slightly different from each other, of the receiving antennas 12 a to 12 d.
FIG. 7 illustrates a flowchart explaining the history pairing process, the stationary target pairing process and the additional pairing process. The history pairing part 18 d of the signal processor 18 performs the history pairing process, using the history peak signals extracted in the history peak extraction (a step S121). For example, Mahalanobis distance is used for the history pairing process. Concretely, the signal processor 18 derives an index, based on a formula (2), for determining whether or not the angle peak signals in a combination are associated with a same reflection point, by using two parameter values of an “angle difference” and an “angle signal level difference” between the angle peak signals derived based on the history peak signals in the up period and in the down period. In the formula (2), the Mahalanobis distance is referred to as RD. The angle difference is referred to as θdg. The angle signal level difference is referred to as θpg.
In a case of where the Mahalanobis distance is equal to or less than a predetermined value (e.g. 60), the history pairing part 18 d determines that there is a high possibility that the angle peak signals in the up period and the down period of the combination are associated with the same reflection point and finalizes the combination as a history pair data set. In a case where the Mahalanobis distance of the combination exceeds the predetermined value, in other words, in a case where there is a low possibility that the angle peak signals of the combination are associated with a same reflection point, the history pairing part 18 d examines whether or not another combination of other angle peak signals can be finalized as the history pair data set. This process is described later.
Next, the deriving part 18 a of the signal processor 18 performs a next process prediction that is a process of deriving a prediction peak signal (a step S111). The prediction peak signal includes parameters, such as a prediction frequency and prediction angle, and is used in the history peak extraction process and/or another process in the step S104 in a next process performed next after the current process. Concretely, the deriving part 18 a derives the prediction peak signal of a high-priority filtered data set, in each of the up period and the down period, for the vehicle control, among the filtered data sets derived in the current process.
The history pairing part 18 d performs the history pairing based on the prediction frequency and the prediction angle of the prediction peak signal, as described later. The prediction frequency in the up period may be different from the prediction frequency in the down period, depending on the relative speed of the target. The prediction angle in the up period is the same as the prediction angle in the down period because of one target.
FIG. 8 illustrates the history peak extraction. A longitudinal axis and a horizontal axis of FIG. 8 represent signal level [dB] and frequency [kHz], respectively. FIG. 8A illustrates the history peak extraction in the up period and FIG. 8B illustrates the history peak extraction in the down period. The deriving part 18 a derives the prediction peak signal in each of the up period and the down period. Then the setting part 18 b sets a prediction region based on the prediction peak signals. The angle peak signal to be processed (hereinafter referred to as “object signal”) for the history pairing is derived in the prediction region.
Concretely, the setting part 18 b defines a prediction frequency range as a range of three bins higher to three bins lower than a reference frequency that is the prediction frequency of the prediction peak signal derived by the deriving part 18 a in the next process prediction in the previous process (the step S111 in FIG. 5). Then, the frequency peak signal in the prediction frequency range is extracted as the history peak signal. One bin is approx. 468 Hz.
In FIG. 8B, a frequency peak signal Pd (a frequency fdn and a signal level value L1 a) exists in a down-period prediction frequency range that has a prediction frequency fde as the reference frequency, and a frequency of the frequency peak signal Pd is the closest to the prediction frequency fde. The frequency peak signal Pd is one of the signals that exceed the threshold signal level L0 and that have been extracted in the peak extraction process in the step S103. Therefore, the frequency peak signal Pd is extracted as the history peak signal Pd in the down period.
Next, the setting part 18 b defines a prediction angle range of ±4 degrees from the prediction angle of the prediction peak signal serving as a reference angle. Then, the angle peak signal in the prediction angle range is deemed as the object signal for the history pairing.
In this embodiment of the invention, the history pairing part 18 d deems the angle peak signal Pu2 in the up period and the angle peak signal Pd1 in the down period that have the angles closest to the prediction angle θe, as the signals for the history pairing. Then, in a case where the Mahalanobis distance based on a combination of the angle peak signal Pu2 and the angle peak signal Pd1 (hereinafter referred to as “first combination”) is equal to or less than a predetermined value, the history pairing part 18 d finalizes the first combination as a pair of the angle peak signals that have the highest possibility of being associated with a same reflection point.
However, in a case where the Mahalanobis distance based on the first combination exceeds the predetermined value, the determination part 18 c of the signal processor 18 determines whether or not a plurality of the angle peak signals exist in at least one of the periods. In a case where the plurality of angle peak signals exist in at least one of the periods, the history pairing part 18 d selects, as signals for the history pairing, a second combination of the angle peak signals that is different from the first combination of the angle peak signals that have the angles closest to the prediction angle θe.
When taking FIG. 9A as an example, the two different angle peak signals Pu1 and Pu2 exist in the up period. Therefore, the history pairing part 18 d selects the angle peak signal Pu1 and the angle peak signal Pd1 in the down period as the second combination. Then, in a case where a signal level difference of the second combination is equal to or less than a predetermined value, the history pairing part 18 d finalizes the second combination as the history pair data set.
As described above, in the case where the combination of the angle peak signals first selected as a first combination having the angles closest to the prediction angle θe does not satisfy a pairing approval condition based on the Mahalanobis distance, the determination part 18 c determines whether or not a plurality of the angle peak signals exist in at least one of the up period and the down period. Then, in the case where the plurality of angle peak signals exist in at least one of the periods, the history pairing part 18 d selects a second combination of different angle peak signals from the periods between which the angle peak difference is a smallest difference, except the first combination having the angles closest to the prediction angle θe. Then, the history pairing part 18 d determines whether or not the signal level difference between the angle peak signals of the second combination is equal to or less than the predetermined value. In a case where the difference is equal to or less than the predetermined value, the history pairing part 18 d finalizes the second combination as the history pair data set.
As described above, in a case where the first combination does not satisfy the pairing approval condition, the history pairing part 18 d determines whether or not the second combination satisfies re-pairing approval conditions.
The history pairing process of the embodiment mentioned above is explained below with reference to FIG. 10. FIG. 10 illustrates a flowchart that explains the history pairing process. As shown in FIG. 10, the setting part 18 b defines the prediction angle range based on the prediction angle θe in each of the up period and the down period. Then, the signal processor 18 determines whether or not one or more angle peak signals exist in the angle range (in approx. ±4 degrees) (a step S131). In a case where no angle peak signal exists in the prediction angle range in one of the up period and the down period (No in the step S131), the history pairing part 18 d ends the process without finalizing the history pair data set. In the case where the history pair data set is not finalized, the signal processor 18 performs the extrapolation process in the step S108 for determining the continuity. The extrapolation process is a process of temporarily securing the time continuity by replacing the history pair data set in the current process with the prediction data set obtained by predicting the history pair data set in the current process based on the filtered data set in the previous process.
Then, the history pairing part 18 d determines whether or not the combination paired based on the Mahalanobis distance is finalized as the history pair data set, in other words, whether or not the pairing approval condition is satisfied (a step S133). For example, the history pairing part 18 d determines whether or not a combination as shown in FIG. 11 is finalized as the pair data set. FIG. 11 illustrates a combination of the angle peak signals having the angles closest to the prediction angle θe. A prediction region Su in the up period is defined as a substantially rectangle range of approx. ±3 bins in a frequency direction (y-axis direction) and of approx. ±4 degrees in an angle direction (x-axis direction) from a prediction position that is an intersection of the frequency fu of the frequency peak signal Pu and the prediction angle θe.
With reference back to the step S133 in FIG. 10, the signal processor 18 determines, based on the Mahalanobis distance, whether or not there is a high possibility that the angle peak signals of the combination are associated with a same reflection point. Concretely, using the formula (2) mentioned above, the signal processor 18 derives the Mahalanobis distance based on the angle difference (θu2−θd1) and on the angle signal level difference (R2−R1 a) between the angle peak signal Pu2 in the up period and the angle peak signal Pd1 in the down period. In a case where the Mahalanobis distance is equal to or less than the predetermined value (Yes in the step S133), the history pairing part 18 d deems that the pairing approval condition is satisfied and finalizes the combination of the angle peak signals Pu2 and Pd1 as the history pair data set (a step S134).
In a case where the Mahalanobis distance exceeds the predetermined value in the step S133 (No in the step S133), the history pairing part 18 d determined that the combination of the angle peak signals Pu2 and Pd1 is wrong, in other words, that there is a low possibility that the angle peak signals of the combination are not associated with the same reflection point. As a result, the history pairing part 18 d does not finalize the combination of the angle peak signals as the history pair data set. Moreover, the history pairing part 18 d determines whether or not another combination satisfies the pairing approval condition.
Concretely, the determination part 18 c determines whether or not a plurality of angle peak signals exist in at least one of the up period and the down period (a step S135). In a case where the plurality of angle peak signals exist in at least one of the periods (Yes in the step S135), the signal processor 18 selects the combination of the angle peak signals between which the angle difference is a smallest difference, from the periods, except the combination of the angle peak signals having the angles closest to the prediction angle θe (a step S136).
Then, the history pairing part 18 d determines whether or not the signal level difference of the combination of the angle peak signals between which the angle difference is the smallest difference is equal to or less than a predetermined value (e.g. 3.5 dB) (a step S137). In a case where the angle signal level difference is equal to or less than the predetermined value (Yes in the step S137), the history pairing part 18 d finalizes the combination as the history pair data set (the step S134).
Concretely, the history pairing part 18 d finalizes the combination as the history pair data set as shown in FIG. 12. FIG. 12 illustrates the combination of which the angle difference is a smallest difference and of which the angle signal level difference is equal to or less than the predetermined value. The two angle peak signals Pu1 and Pu2 exist in the prediction region Su of the up period, and the angle peak signal Pd1 exists in the prediction region Sd of the down period. In such a case, the condition of the plurality of angle peak signals in at least one of the periods, mentioned in the step S135 in FIG. 10, is satisfied. Then, the history pairing part 18 d determines whether or not the angle peak signals Pu1 and Pd2, between which the angle difference is the smallest difference, satisfy the re-pairing approval condition, excluding the angle peak signal Pu2 that has been determined as the signal that does not satisfy the pairing approval condition, from the angle peak signals in the prediction region Su and the prediction region Sd.
In a case where the angle signal level difference between the angle peak signals Pu1 and Pd1 is equal to or less than the predetermined value, the condition that the signal level difference between the angle peak signals is equal to or less than the predetermined value, mentioned in the step S137 in FIG. 10 is satisfied, and the history pairing part 18 d finalizes the combination as the history pair data set. Thus, in the case where the plurality of angle peak signals exist in the prediction region, use of the extrapolation process is minimized and, at the same time, the combination of the angle peak signals having the highest possibility to be associated with a same reflection point is finalized as the history pair data set. Thus, an actual position of the target can be derived.
In a case where the plurality of angle peak signals do not exist in either of the up period and the down period in the step S135 (No in the step S135) or in a case where the angle signal level difference between the angle peak signals exceeds the predetermined value in the step S137 (No in the step S137), the history pairing part 18 d ends the process without finalizing the history pair data set. As a result, the signal processor 18 performs the extrapolation process.
Generally, as the longitudinal distance becomes greater, a distance corresponding to a prediction angle range that is the angle range of the prediction region becomes greater. As the longitudinal distance becomes greater, even if the angle range is fixed (e.g. ±4 degrees), a lateral distance becomes greater. Thus, in a case where a target exists in a current traffic lane in a relatively long distance, a process of re-pairing of a different combination performed by a history pairing part 18 d in the first embodiment may include an angle peak signal of a target existing outside a range of the current traffic lane, such as a next traffic lane of the current traffic lane, in the prediction region. Therefore, the angle peak signal outside the range of the current traffic lane may become a candidate for a combination with an angle peak signal in the current traffic lane and the combination of the angle peak signals may be finalized as the history pair data set. The process described in the second embodiment is a process of preventing from finalizing a wrong combination as the history pair data set.
Next explained is a case where the angle peak signal exists in a relatively long distance from the vehicle CA. FIG. 14 illustrates a prediction region Su2 where the angle peak signal exists in the relatively long distance. The angle peak signals Pu1, Pu2 and Pu3 in the up period in FIG. 14 are signals generated based on a frequency peak signal of a frequency fu2 equivalent to the longitudinal distance of 60 m. The prediction region Su2 is defined as a range of approx. ±3 bins in the frequency direction (y-axis direction) and approx. ±4 degrees in the angle direction (x-axis direction) from a prediction position of an intersection of the frequency fu2 and the prediction angle θe. Given that the prediction angle θe is the lateral distance of ±0 m, the lateral distance of the prediction region Su2 is approx. ±4.2 m, i.e. approx. 8.4 m, which includes the current traffic lane RC and the next traffic lanes of the right traffic lane RR and a left traffic lane RL. Therefore, the prediction region Su2 includes the angle peak signals Pu1 and Pu2 of the front vehicle Ta in the current traffic lane RC and also the angle peak signal Pu3 of the near vehicle Tb traveling in the right traffic lane RR. Since the angle peak signals not only of the front vehicle Ta but also of the near vehicle Tb are included as the object signals for re-pairing, a wrongly-paired history pair data set may be finalized in the process of re-pairing performed by the history pairing part 18 d.
Therefore, as the longitudinal distance of the angle peak signal becomes greater, the history pairing part 18 d performs a process of narrowing the angle range in the prediction region. FIG. 15 illustrates a situation where as the longitudinal distance of the angle peak signal becomes greater, the angle range is narrowed. As shown in FIG. 15, the signal processor 18 selects the angle peak signal that is a candidate for the process of re-pairing, from a prediction region Su3 of which the angle range is approx. ±2 degrees narrower than the angle range of approx. ±4 degrees of the prediction region Su1. A setting part 18 b adjusts the angle range of the prediction region.
FIG. 16 illustrates a flowchart of the process performed in the second embodiment. In a case where a Mahalanobis distance exceeds a predetermined value (No in a step S133), the history pairing part 18 d sets the prediction angle range according to the longitudinal distance of the angle peak signal. The signal processor 18 selects the angle peak signal in the set prediction angle range (a step S141). In other words, the signal processor 18 selects the angle peak signal in a predetermined angle range (e.g. in the angle of approx. ±4 degrees) in each of the up period and the down period, in the step S131. In the step S141, the signal processor 18 selects the angle peak signal in the prediction angle range according to the longitudinal distance of the angle peak signal. For example, in a case where the longitudinal distance of the angle peak signal is 30 m, the prediction angle range is approx. ±4 degrees. Therefore, an angle peak signal same as the angle peak signals selected in the step S131 is selected. Moreover, in a case where the longitudinal distance of the angle peak signal is 60 m, the prediction angle range is approx. ±2 degrees. Therefore, the angle peak signal existing in a range narrower than the angle range for the longitudinal distance of 30 m is selected.
A structure and a function of the radar apparatus 10 in the third embodiment is the same as the structure and the function of the radar apparatus 10 in the first embodiment, except that the signal processor 18 in the third embodiment includes a detector 18 e. However, a history pairing process in the third embodiment is partially different. A difference is mainly hereinafter explained with reference to FIG. 17 to FIG. 18.
FIG. 17A illustrates a block diagram of a vehicle control system 1 in the third embodiment. The signal processor 18 of the radar apparatus 10 includes the detector 18 e. The detector 18 e detects whether or not a combination of the angle peak signals in a previous process exists in a short distance range that is a range in a relatively short distance from the vehicle CA, in a current traffic lane region that is a range of the current traffic lane RC in which the vehicle CA is traveling.
In a case where the angle peak signal is derived in the current process, the detector 18 e determines whether or not a position represented by a filtered data set that has been derived in the previous process (hereinafter referred to as “previous filtered data set”) and that has continuity with the angle peak signal, is in the current traffic lane region ML. In a case where the angle peak signal in the current process (hereinafter referred to as “current angle peak signal”) is in the current traffic lane region ML, the signal processor 18 performs the process of re-pairing. Concretely, in FIG. 17B, angle peak signals Pu1 and Pu2 of a front vehicle Ta exist in a prediction region Su11 defined by a prediction frequency range based on a frequency fu11 and by a prediction angle range based on a prediction angle θe. In a case where the detector 18 e detects the previous filtered data set that has continuity with the angle peak signals Pu1 and Pu2 in the current traffic lane region ML, the angle peak signals Pu1 and Pu2 are deemed as the object signals for re-pairing.
On the other hand, an angle peak signal Pu12 of a near vehicle Tb exists in a prediction region Su12 defined by the prediction frequency range based on a frequency fu12 and by the prediction angle range based on a prediction angle (e.g. approx. +4 degrees). However, since the detector 18 e does not detect any previous filtered data set that has the continuity with the angle peak signal Pu12 in the current traffic lane region ML, the angle peak signal Pu12 is not deemed as the object signal for re-pairing.
As described above, in order to decide whether or not the position of the target is in the current traffic lane region ML, the signal processor 18 does not use the angle peak signal but uses the previous filtered data set because the process of pairing the angle peak signals has not been completed so that the longitudinal distance and the lateral distance to the target have not been calculated precisely. Therefore, the detector 18 e detects whether or not the target is in the current traffic lane region ML by using the filtered data set generated after the previous pairing process.
FIG. 18 illustrates a flowchart of the process performed in the third embodiment. When the Mahalanobis distance exceeds a predetermined value (No in the step S133), the signal processor 18 determines whether or not the detector 18 e has detected the previous filtered data set in the current traffic lane region ML (a step S142). In other words, the signal processor 18 determines whether or not the previous filtered data set is a most prioritized data set for vehicle control, such as ACC.
In a case where the previous filtered data set is in the current traffic lane region ML (Yes in the step S142), the history pairing part 18 d performs of the process of re-pairing a combination different from a combination including the angle peak signal having an angle closest to the prediction angle θe (the steps S135 to S137). Thus, the radar apparatus 10 can reduce the processing load in the derivation of the target information and also can prevent from finalizing a wrong combination as the history pair data set. Moreover, in a case where the previous filtered data set does not exist in the current traffic lane region ML (No in the step S142), the signal processor 18 ends the process and performs the extrapolation process.
A structure and the process of the radar apparatus 10 in the fourth embodiment is the same as the structure and the process of the radar apparatus 10 in the first embodiment, except that the signal processor 18 in the fourth embodiment includes an obtaining part 18 f and a computing part 18 g. However, a history pairing process in the fourth embodiment is partially different. A difference is mainly hereinafter explained with reference to FIG. 19 to FIG. 21. In this embodiment, the process performed in an up period is described as an example. However, the process is also performed for a down period.
FIG. 19A illustrates a block diagram of a vehicle control system 1 in the fourth embodiment. The signal processor 18 of the radar apparatus 10 includes the obtaining part 18 f and the computing part 18 g. The obtaining part 18 f obtains the radius value of the curve of a traffic lane in which the vehicle CA is traveling. The computing part 18 g calculates the relative lateral distance for any targets represented by target information based on the obtained radius value of the curve.
The signal processor 18 in the fourth embodiment selects a candidate for the combination based on a prediction region defined based on the relative lateral distance. The obtaining part 18 f obtains the radius value of the curve from the vehicle controller 20. In other words, the obtaining part 18 f obtains the radius value of the curve of the traffic lane in which the vehicle CA is traveling. Then the computing part 18 g derives the relative lateral distance based on a formula (5) below. In the formula (5), Srd refers to the relative lateral distance and Sad refers to the absolute lateral distance and CR refers to the curve radius. The absolute lateral distance is derived based on the formula (1) mentioned above and an angle of a pair data set, using trigonometric functions. Therefore, the relative lateral distance of a previous filtered data set that has continuity with a current angle peak signal is used as the relative lateral distance of the angle peak signal.
In the case where the angle peak signal exists in the prediction angle ranges (Yes in the step S131), the signal processor 18 determines whether or not a combination having a Mahalanobis distance equal to or less than a predetermine value (e.g. 60 or less) exists among all the possible combinations of all angle peak signals in the up period and all angle peak signals in the down period (a step S144). In a case where the combination having the Mahalanobis distance equal to or less than the predetermined value exists (Yes in the step S144), a history pairing part 18 d finalizes the combination as the history pair data set (a step S134). In a case where no combination having the Mahalanobis distance equal to or less than the predetermined value exists (No in the step S144), the history pairing part 18 d ends the process. Moreover, in a case where plural combinations having the Mahalanobis distances equal to or less than the predetermined value exist, the history pairing part 18 d finalizes the combination having the smallest Mahalanobis distance, as the history pair data set. Thus, even in a case where plural angle peak signals exist in the prediction region, the radar apparatus 10 can surely finalize a correctly-paired combination as the pair data set and can derive an actual position of an target.
A structure and a function of the radar apparatus 10 in the sixth embodiment is the same as the structure and the function of the radar apparatus 10 in the first embodiment, except that the signal processor 18 includes a divider 18 h. However, a history pairing process in the sixth embodiment is partially different. A difference is mainly hereinafter explained with reference to FIG. 24 to FIG. 25.
FIG. 24A illustrates a block diagram of a vehicle control system 1 of the sixth embodiment. The signal processor 18 of the radar apparatus 10 includes the divider 18 h. The divider 18 h divides the prediction region into the plurality of areas based on an angle.
FIG. 24B illustrates a situation where the prediction regions in an up period and a down period are divided into the plurality of areas. The divider 18 h divides a prediction region Su in the up period and a prediction region Sd in the down period into three areas of a center area TE, a left area LE, and a right area RE, respectively, based on angles. The center area TE, the left area LE and the right area RE are in a same frequency range (approx. ±3 bins) in the prediction region Su (Sd) and are divided based on the angles that are different from one another. Concretely, an angle range of the center area TE is from −2 degrees to +2 degrees. Angle ranges of the left area LE and he right area RE are −2 degrees to −4 degrees and +2 degrees to +4 degrees, respectively.
In a case where the process of re-pairing is performed, the divider 18 h divides the prediction region into the plurality of areas. Then, in a case where the angle peak signal exists in the center areas TE in one of the periods, a signal processor 18 selects an angle peak signal in one of the center area TE, the left area LE and the right area RE in the other period as a candidate for a combination with the angle peak signal in the center area TE. Moreover, in a case where the angle peak signal exists in the left area LE in one of the periods, the signal processor 18 selects an angle peak signal in one of the left area LE and the center area TE in the other period as a candidate for a combination with the angle peak signal in the left area LE and does not select an angle peak signal in the right area RE in the other period as the candidate for the combination with the angle peak signal in the left area LE.
Concretely, as shown in FIG. 24, in a case where a Mahalanobis distance of a combination of angle peak signals Pu2 and Pd1 closest to a prediction angle (θe) in the up period and in the down period, respectively, exceeds a predetermined value, the divider 18 h divides the prediction region Su (Sd) into the three areas.
Then, the signal processor 18 selects a candidate combination different from the combination of the angle peak signals Pu2 and Pd1. In other words, the signal processor 18 selects a candidate for the angle peak signal in the down period based on the left area LE in which the angle peak signal Pu1 exists. The signal processor 18 selects the angle peak signal Pd1 in the left area LE of the down period as the candidate for the combination with the angle peak signal Pu1. Then in a case where an angle signal level of the combination of the angle peak signals Pu1 and Pd1 is equal to or less than the predetermined value, the history pairing part 18 d finalizes the combination as the history pair data set.
FIG. 25 illustrates a flowchart of the process performed in the sixth embodiment. In the case where the Mahalanobis distance exceeds the predetermined value (No in a step S133), the determination part 18 c determines whether or not a plurality of angle peak signals exist in at least one of the up period and the down period in a process of re-pairing (a step S135). In the a where the plurality of angle peak signals exist in at least one of the periods (Yes in the step S135), the divider 18 h divides the prediction region Su (Sd) into the plurality of areas (the center area TE, the left area LE and the right area RE) based on angles (a step S145).
Then, the signal processor 18 selects a combination having the smallest angle difference between the angle peak signals in the up period and the down period, from amongst the angle peak signals in the areas in which a combination can be made (a step S146). In a case where the angle signal level difference is equal to or less than the predetermined value (Yes in a step S137), the history pairing part 18 d finalizes the combination as the pair data set. Thus, the radar apparatus 10 can exclude the combination of the angle peak signals in a relatively long lateral distance and can finalize the combination of the angle peak signals in a relatively short distance in the lateral direction as the history pair data set.
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