Object detection device

Abstract

The present invention relates to an object detection device, and an object of the present invention is to optimize a detection cycle. The object detection device includes a transmission unit that transmits a transmission wave; a reception unit that receives a reception wave that is returned after the transmission wave is reflected by an object until a prescribed measurement time elapses; a detection unit that detects the object based on distance information based on the reception wave received by the reception unit; and a reception control unit that makes the measurement time after the object is detected shorter than the measurement time after the object is not detected. The reception control unit sets the measurement time to a time corresponding to a position that is farther than a distance to the nearest existing object by a prescribed distance.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an object detection device. BACKGROUND

[0002] In a device that detects a distance to an object or the like, a TOF (Time Of Flight) method is used. The TOF method is a technique that calculates a distance to an object based on a difference between a time at which a transmission wave such as an ultrasonic wave is transmitted and a time at which a reception wave that is a reflection wave of the transmission wave reflected by the object is received.

[0003] In a device that detects an object using the TOF method, a technique is disclosed in which a received signal is quadrature-demodulated using a sine wave signal synchronized with a burst signal (Patent Literature 1). In addition, a technique is disclosed in which a CFAR (Constant False Alarm Rate) process is performed in which an influence of a clutter is suppressed by subtracting a moving average from a received signal (Patent Literature 2).

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2005-249770

[0005] Patent Literature 2: Japanese Patent Application Publication No. 2006-292597

[0006] In the TOF method, the shorter the detection period from when a detection result (TOF, distance, or the like) is acquired until a next detection result is acquired, the greater the number of detection results (number of samples) that can be acquired per unit time, and thus the detection accuracy can be improved. However, in the related art, optimization of a measurement time from when a transmission wave is transmitted until a reception wave is received and a processing time required for processing of the reception wave is insufficient, and thus there are cases in which the detection period is unnecessarily long. SUMMARY

[0007] Therefore, one of the objects of the present disclosure is to optimize a detection period.

[0008] An object detection device that is one example of the present disclosure includes a transmission unit that transmits a transmission wave, a reception unit that receives a reception wave that is a reflection wave of the transmission wave reflected by an object from when the transmission wave is transmitted until a prescribed measurement time elapses, a detection unit that detects the object based on distance information based on the reception wave received by the reception unit, and a reception control unit that makes a measurement time after the object is detected shorter than a measurement time after the object is not detected.

[0009] According to the above structure, the measurement time is shortened in the case where an object is detected, and the detection cycle is optimized. For example, in a system for detecting an obstacle or the like, there are cases where it is sufficient to detect an object that is present in the vicinity, and the necessity of expanding the detection range to a region farther than the detected object is low. In such a case, as in the above structure, the detection cycle is accelerated by reducing the measurement time for detecting a region farther than the detected object, and thus the detection accuracy of a region closer than the detected object can be improved.

[0010] Further, in the object detection device as one example described above, the reception control section can set the measurement time to a time corresponding to a position that is farther than the distance to the nearest existing object by a predetermined distance.

[0011] According to the above structure, the region to be detected can be narrowed to a region closer than the surrounding region of the detected object.

[0012] Further, the object detection device as one example described above can further include a transmission control section that sets a transmission interval from the transmission of a transmission wave until the transmission of a next transmission wave, and makes the transmission interval after the detection of an object shorter than the transmission interval after the non-detection of an object, and the transmission section can transmit the transmission wave in accordance with the transmission interval.

[0013] As described above, in the case where an object is detected, not only the measurement time but also the transmission interval is shortened, and thus the detection cycle can be effectively optimized.

[0014] Further, the object detection device as one example described above can further include a CFAR processing section that performs CFAR processing on a signal corresponding to a reception wave received by the reception section using an average value of values of a plurality of signals corresponding to a predetermined moving average time, and the farther the distance to the detected object, the shorter the moving average time.

[0015] According to the above structure, the moving average time is shortened in the case where the distance to the detected object is relatively far, and the processing time required for the CFAR processing is shortened. For a region where the distance to the object is relatively far, the clutter removal effect based on the CFAR processing does not need to be at such a high level in many cases. Therefore, as in the above structure, the farther the distance to the detected object, the shorter the moving average time, and thus the detection cycle can be optimized.

[0016] Further, an object detection device as another example of the present disclosure includes: a transmission unit that transmits a transmission wave; a reception unit that receives a reception wave returned by reflection of the transmission wave by an object; a detection unit that detects the object based on distance information based on the reception wave received by the reception unit; and a CFAR processing unit that performs CFAR processing using an average value of values of a plurality of signals corresponding to the reception wave received by the reception unit, the average value corresponding to a prescribed moving average time, and that makes the moving average time after detection of the object shorter than the moving average time after non-detection of the object.

[0017] According to the above structure, the moving average time is shortened in a case where the distance of the detected object is relatively long, and the processing time required for the CFAR processing is shortened. In a region where the distance of the object is relatively long, in many cases, the clutter removal effect based on the CFAR processing does not need to be at such a high level. Therefore, as in the above structure, the farther the distance of the detected object, the shorter the moving average time, and thus the detection period can be optimized.

[0018] Further, the object detection device as the above another example can further include a reception control unit that sets a prescribed measurement time after transmission of the transmission wave, and that makes the measurement time after detection of the object shorter than the measurement time after non-detection of the object, and the reception unit receives the reception wave from after the transmission of the transmission wave until the measurement time elapses.

[0019] According to the above structure, the measurement time is shortened in a case where the object is detected, and the detection period is optimized. For example, in a system for detecting an obstacle or the like, there are cases where it is sufficient to detect an object that exists closest, and cases where the necessity of expanding the detection range to a region farther than the detected object are low are more frequent. In such a case, as in the above structure, the detection period is accelerated by reducing the measurement time for detecting a region farther than the detected object, and thus the detection accuracy of a region closer than the detected object can be improved.

[0020] Further, in the object detection device as the above another example, the reception control unit can set the measurement time to a time corresponding to a position that is farther than the distance to the object that exists closest by a prescribed distance.

[0021] According to the above structure, the region to be detected can be narrowed to a region closer than the surrounding region of the detected object.

[0022] Further, the object detection device of the above another example can be configured to further include a transmission control section that sets a time from transmission of a transmission wave until transmission of a next transmission wave, i.e., a transmission interval, and makes the transmission interval after detection of an object shorter than the transmission interval after no detection of an object, and the transmission section transmits the transmission wave in accordance with the transmission interval.

[0023] As described above, in the case where an object is detected, not only the measurement time but also the transmission interval is shortened, so that the detection cycle can be effectively optimized. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a plan view showing one example of an appearance of a vehicle provided with the object detection system according to the first embodiment.

[0025] Figure 2 is a block diagram showing one example of a hardware structure of the ECU and the object detection device according to the first embodiment.

[0026] Figure 3 is a diagram for explaining an outline of the TOF method.

[0027] Figure 4 is a block diagram showing one example of a functional structure of the object detection device according to the first embodiment.

[0028] Figure 5 is a diagram showing one example of control of the measurement time based on the reception control section according to the first embodiment.

[0029] Figure 6 is a flowchart showing one example of processing in the object detection device according to the first embodiment.

[0030] Figure 7 is a block diagram showing one example of a functional structure of the object detection device according to the second embodiment.

[0031] Figure 8 is a diagram for illustratively explaining one example of the CFAR processing according to the second embodiment.

[0032] Figure 9 is a diagram showing one example of a signal that becomes a source of a difference signal in the CFAR processing according to the second embodiment.

[0033] Figure 10 is a diagram showing one example of a difference signal obtained as a result of the CFAR processing according to the second embodiment.

[0034] Figure 11is a flowchart showing one example of processing in the object detection device according to the second embodiment.

[0035] Figure 12 is a block diagram showing one example of a functional structure of the object detection device according to the third embodiment.

[0036] Explanation of Reference Numerals

[0037] 1 vehicle; 2 vehicle body; 3F front wheels; 3R rear wheels; 100 ECU; 110 input / output device; 120 storage device; 130 processor; 200, 200', 200", 201 to 204 object detection device; 210 transceiver section; 211 transducer; 220 control section; 221 input / output device; 222 storage device; 223 processor; 301 transmission section; 302 transmission control section; 311 reception section; 312 pre-processing section; 313 threshold processing section; 314 detection section; 315 reception control section; 321 CFAR processing section; 511, 512, 520, 530, 540 arithmetic unit; O obstacle; RS road surface; t50 detection time; t51 first moving average time; t52 second moving average time. DETAILED DESCRIPTION

[0038] Hereinafter, the embodiments of the present disclosure will be described based on the drawings. The structure of the embodiments described below, and the effects and advantages brought about by the structure are merely one example, and are not limited to the description below.

[0039] (First Embodiment)

[0040] Figure 1 is a plan view showing one example of the appearance of a vehicle 1 equipped with the object detection system according to the first embodiment. The object detection system exemplified below is a system that performs transmission and reception of sound waves (ultrasonic waves) and the like, and detects information (distance from an object, presence or absence of an object, and the like) about an object (another vehicle, an obstacle on a road, a person, an animal, and the like) present in the surroundings of the vehicle 1 based on information such as a time difference (TOF) of the signal transmission and reception.

[0041] As shown in Figure 1 , the object detection system is equipped with an ECU (Electronic Control Device) 100 mounted inside the vehicle 1 of four wheels including a pair of front wheels 3F and a pair of rear wheels 3R, and object detection devices 201 to 204 mounted outside the vehicle 1.

[0042] In the example shown in Figure 1 , the object detection devices 201 to 204 are provided at mutually different positions at the rear end portion (for example, a rear bumper or the like) of the vehicle body 2 outside the vehicle 1.

[0043] Further, in the present embodiment, the hardware structures and the functions of the object detection devices 201 to 204 are respectively the same. Therefore, in the following, in order to simplify, the object detection devices 201 to 204 are sometimes collectively described as the object detection device 200.

[0044] In addition, in the present embodiment, the setting positions of the object detection device 200 are not limited to Figure 1 the example shown in the drawing. The object detection device 200 can be provided at the front end portion of the vehicle body 2 (for example, a front bumper or the like), can be provided at the side surface portion of the vehicle body 2, and can be provided at two or more of the rear end portion, the front end portion, and the side surface portion. In addition, the number of the object detection devices 200 is not limited to Figure 1 the example shown in the drawing.

[0045] Figure 2 is a block diagram showing one example of the hardware structure of the ECU 100 and the object detection device 200 according to the first embodiment.

[0046] As shown in Figure 2 , the ECU 100 has the same hardware structure as a general-purpose computer. More specifically, the ECU 100 has an input-output device 110, a storage device 120, and a processor 130.

[0047] The input-output device 110 is an interface for realizing the transmission and reception of information between the ECU 100 and the outside (in the example shown in the drawing, the object detection device 200). Figure 1

[0048] The storage device 120 includes a main storage device such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and / or a secondary storage device such as an HDD (Hard Disk Drive) and an SSD (Solid State Drive).

[0049] The processor 130 is responsible for various processes executed in the ECU 100. The processor 130 includes, for example, a CPU (Central Processing Unit) or the like. The processor 130 realizes various functions such as automatic driving, alarm output, and the like by reading and executing a program stored in the storage device 120.

[0050] The object detection device 200 has a transmission-reception section 210 and a control section 220.

[0051] ​The transceiving section 210 has a vibrator 211 such as a piezoelectric element, and transmits and receives ultrasonic waves through the vibrator 211.

[0052] More specifically, the transceiving section 210 transmits an ultrasonic wave generated in accordance with the vibration of the vibrator 211 as a transmission wave, and receives the vibration of the vibrator 211 caused by the ultrasonic wave transmitted as the transmission wave being reflected by an object existing outside and returning. In Figure 2 In the example shown, as an object that reflects the ultrasonic wave from the transceiving section 210, an obstacle O provided on the road surface RS is exemplified.

[0053] Further, in Figure 2 In the example shown, a structure in which both the transmission of the transmission wave and the reception of the reception wave are implemented by the single transceiving section 210 having the single vibrator 211 is exemplified, but the embodiment is not limited thereto. For example, a structure in which the first vibrator for the transmission of the transmission wave and the second vibrator for the reception of the reception wave are provided separately, and the structure on the transmission side and the structure on the reception side are separated, can also be employed.

[0054] The control section 220 has the same hardware structure as a general-purpose computer. More specifically, the control section 220 has an input / output device 221, a storage device 222, and a processor 223.

[0055] The input / output device 221 is an interface for implementing the transmission and reception of information between the control section 220 and the outside (in Figure 2 In the example shown, the ECU 100 and the transceiving section 210).

[0056] The storage device 222 includes a main storage device such as a ROM, a RAM, and / or a secondary storage device such as an HDD, an SSD.

[0057] The processor 223 is responsible for various processing performed in the control section 220. The processor 223 includes, for example, a computing device such as a CPU. The processor 223 implements various functions by reading and executing a program stored in the storage device 333.

[0058] The object detection device 200 according to the present embodiment detects the distance to an object (for example, the obstacle O or the like) by a technique called a so-called TOF method. As described in detail below, the so-called TOF method is a technique for calculating the distance to an object from the difference between the time at which the transmission wave is transmitted (more specifically, the start of transmission) and the time at which the reception wave is received (more specifically, the start of reception).

[0059] Figure 3 is a diagram for explaining the outline of the TOF method. More specifically, Figure 3is a graph that illustrates and schematically represents a time variation of a signal level (e.g., amplitude) of the ultrasonic wave transmitted and received by the object detection device 200 according to the present embodiment. In Figure 3 In the graph shown, the horizontal axis corresponds to time, and the vertical axis corresponds to a signal level of the signal transmitted and received by the object detection device 200 via the transmitting and receiving unit 210 (the vibrator 211).

[0060] In Figure 3 In the graph shown, the solid line L11 represents a signal level of the signal transmitted and received by the object detection device 200, that is, an envelope line of a time variation of the degree of vibration of the vibrator 211. From the solid line L11, it can be known that the vibrator 211 is vibrated for a time Ta from the time t0, and thus the transmission of the wave is completed at the time t1, and thereafter, the vibration of the vibrator 211 continues while being attenuated due to inertia during a time Tb until the time t2. Therefore, in Figure 3 In the graph shown, the time Tb corresponds to a so-called reverberation time.

[0061] The solid line L11 reaches a peak at which the degree of vibration of the vibrator 211 exceeds (or becomes above) a prescribed threshold value represented by the dotted line L21 at the time t4 that has elapsed a time Tp from the time t0 at which the transmission of the wave is started. The threshold value is a value that is set in advance in order to identify whether the vibration of the vibrator 211 is vibration caused by the reception of the reception wave that is the transmitted wave returned as reflected by the object to be detected (e.g., the obstacle O) shown in Figure 2 or vibration caused by the reception of the reception wave that is the transmitted wave returned as reflected by the object (e.g., the road surface RS) outside the object to be detected shown in Figure 2

[0062] Further, in Figure 3 the example shown in

[0063] Here, the vibration having the peak that exceeds (or is above) the threshold value represented by the dotted line L21 can be regarded as vibration caused by the reception of the reception wave that is the transmitted wave returned as reflected by the object to be detected. On the other hand, the vibration having a peak that is below (or less than) the threshold value can be regarded as vibration caused by the reception of the reception wave that is the transmitted wave returned as reflected by the object outside the object to be detected.

[0064] Therefore, from the solid line L11, it can be known that the vibration of the vibrator 211 at the time t4 is vibration caused by the reception of the reception wave that is the transmitted wave returned as reflected by the object to be detected.

[0065] ​Further, in the solid line L11, the vibration of the vibrator 211 attenuates after the time t4. Therefore, the time t4 corresponds to a time at which the reception of the reception wave that is the transmitted wave returned by reflection of the object of detection is completed, in other words, a time at which the transmitted wave that was transmitted last at the time t1 returns as the reception wave. The time t4 is a time at which the signal level of the reception wave exceeds the threshold value.

[0066] Further, in the solid line L11, the time t3 that is the start point of the peak at the time t4 corresponds to a time at which the reception of the reception wave that is the transmitted wave returned by reflection of the object of detection is started, in other words, a time at which the transmitted wave that was transmitted first at the time t0 returns as the reception wave. Therefore, in the solid line L11, the time ΔT between the time t3 and the time t4 is equal to the time Ta that is the transmission time of the transmitted wave.

[0067] According to the above, in order to find the distance to the object of detection by the TOF method, it is necessary to find the time Tf between the time t0 at which the transmitted wave is started to be transmitted and the time t3 at which the reception of the reception wave is started to be received. This time Tf can be found by subtracting the time ΔT that is equal to the time Ta that is the transmission time of the transmitted wave from the time Tp that is the difference between the time t0 and the time t4 at which the peak of the signal level of the reception wave exceeds the threshold value.

[0068] The time t0 at which the transmitted wave is started to be transmitted can be easily determined as the time at which the object detection device 200 starts to operate, and the time Ta that is the transmission time of the transmitted wave is determined in advance by setting or the like. Therefore, in order to find the distance to the object of detection by the TOF method, as a result, it is important to determine the time t4 at which the peak of the signal level of the reception wave exceeds the threshold value. Also, in order to determine this time t4, it is important to detect the reception wave that is the transmitted wave returned by reflection of the object of detection with high precision.

[0069] Figure 4 is a block diagram showing one example of the functional structure of the object detection device 200 according to the first embodiment. Further, in the example shown in Figure 4 In the example shown in the drawing, the structure on the transmission side and the structure on the reception side are separated, but such a manner of illustration is merely for the convenience of explanation. In the present embodiment, as described above, both the transmission of the transmitted wave and the reception of the reception wave are implemented by the single transceiver 210 having the single vibrator 211. However, as described above, a structure in which the structure on the transmission side and the structure on the reception side are separated can also be applied.

[0070] As shown in Figure 4 The object detection device 200 has the transmission section 301 and the transmission control section 302 as the structure on the transmission side. Also, the object detection device 200 has the reception section 311, the pre-processing section 312, the threshold processing section 313, the detection section 314, and the reception control section 315 as the structure on the reception side.

[0071] Further, in the present embodiment, Figure 4 At least a part of the structures shown can be implemented by a dedicated hardware (analog circuit), and the remaining part can be implemented as a result of cooperation of hardware and software, more specifically, as a result of the processor 223 of the object detection device 200 reading and executing a program from the storage device 222. In addition, in the present embodiment, Figure 4 Each of the structures shown can act under the control of the control section 220 of the object detection device 200 itself, or can act under the control of the external ECU 100.

[0072] First, the structure on the transmission side will be described.

[0073] The transmission section 301 transmits a transmission wave to the outside by vibrating the vibrator 211 described above at a prescribed transmission interval. The transmission interval is a time interval from after the transmission of the transmission wave until the next transmission of the transmission wave. The transmission section 301 can be constituted, for example, of a circuit that generates a carrier wave, a circuit that generates a pulse signal corresponding to identification information to be imparted to the carrier wave, a multiplier that modulates the carrier wave in accordance with the pulse signal, an amplifier that amplifies a transmission signal output from the multiplier, and the like.

[0074] The transmission control section 302 controls the transmission interval in accordance with a detection result (distance from an object, presence or absence of an object, and the like) based on the detection section 314 described later. Specifically, the transmission control section 302 sets the transmission interval after the detection of an object to be shorter than the transmission interval after the non-detection of an object. The transmission section 301 transmits a transmission wave in accordance with the transmission interval controlled (set) by the transmission control section 302.

[0075] Next, the structure on the reception side will be described.

[0076] The reception section 311 receives a reception wave that is returned from the transmission wave transmitted from the transmission section 301 by being reflected by an object until a prescribed measurement time elapses after the transmission of the transmission wave. The measurement time is a standby time set in order to receive a reception wave that is a reflection wave of the transmission wave after the transmission of the transmission wave.

[0077] The pre-processing section 312 performs pre-processing of generating an envelope line that indicates the similarity of the transmission wave and the reception wave received by the reception section 311. The pre-processing can include, for example, amplification processing of amplifying a reception signal corresponding to the reception wave, filter processing of reducing noise contained in the amplified reception signal, correlation processing of acquiring a correlation value that indicates the similarity of the transmission signal and the reception signal, envelope line processing of generating an envelope line that indicates the waveform of the time variation of a correlation value signal based on the correlation value, and the like.

[0078] The threshold processing section 313 performs determination as to whether the transmission wave and the reception wave are similar in level of the threshold or more, based on the comparison result of the value of the envelope generated by the pre-processing section 312 and the threshold.

[0079] The detection section 314 detects the object based on the TOF (distance information) based on the reception wave received by the reception section. The detection section 314 according to the present embodiment determines the timing at which the similarity of the transmission wave and the reception wave becomes the level of the threshold or more, that is, the timing at which the peak of the signal level of the reception wave exceeds the threshold (for example, the timing t4 in FIG. 13) based on the processing result of the threshold processing section 313, and detects the distance from the object (including the presence or absence of the object) by the TOF method. Figure 2

[0080] The reception control section 315 controls the measurement time based on the detection result of the detection section 314. Specifically, the reception control section 315 sets the measurement time after the detection of the object to be shorter than the measurement time after the non-detection of the object. The reception section 311 receives the reception wave based on the measurement time set by the reception control section 315.

[0081] Figure 5 is a graph showing one example of the control of the measurement time by the reception control section 315 according to the first embodiment. In the graph shown in FIG. 14, the horizontal axis corresponds to time, and the vertical axis corresponds to the signal level of the reception signal. Figure 5 Figure 5 In FIG. 14, the reference measurement time Tl, the shortened measurement time T2, the peak P corresponding to the object, and the TOF corresponding to the peak P are shown.

[0082] In a case where the peak P corresponding to the object is detected by the detection section 314 in a certain detection period, the reception control section 315 according to the present embodiment shortens the measurement time in the next detection period based on the TOF corresponding to the peak P. In the example shown in FIG. 14, the measurement time is shortened from the reference measurement time Tl to the measurement time T2 which is longer than the TOF corresponding to the nearest object (peak P) by a predetermined time. In addition, the transmission control section 302 shortens the transmission interval in conjunction with such shortening of the measurement time. Figure 5

[0083] In the object detection system mounted on the vehicle 1 and the like, there are many cases where the necessity of expanding the detection range to a region farther than the nearest object is low as long as the nearest object can be detected. Therefore, as described above, the measurement time is shortened based on the position of the object after the detection of the object, and thus it is possible to reduce the waste of the detection period. In addition, it is possible to speed up the detection period for a region closer than the detected object, and it is possible to improve the detection accuracy in the region.

[0084] ​​​Further, the prescribed time (difference between TOF and measurement time T2) is a value that should be appropriately set in accordance with the usage environment, performance of the vibrator 211, and the like, and for example, is preferably a time corresponding to a distance of less than 1 m.

[0085] Figure 6 is a flowchart showing one example of processing in the object detection device 200 according to the first embodiment. If the detection section 314 detects an object (TOF corresponding to the object) (S101: YES), the transmission control section 302 shortens the transmission interval in accordance with the TOF corresponding to the object, and the reception control section 315 shortens the measurement time in accordance with the TOF (S102). On the other hand, if no object is detected (S102: NO), the transmission control section 302 sets the transmission interval to the reference value, and the reception control section 315 sets the measurement time to the reference value (T1) (S103).

[0086] The transmission section 301 outputs a transmission wave in accordance with the shortened transmission interval set in step S102 or the transmission interval set as the reference value in step S103 (S104). The reception section 311 receives a reception wave in accordance with the shortened measurement time (T2) set in step S102 or the measurement time (T1) set as the reference value in step S103 (S105).

[0087] Then, the pre-processing section 312 performs pre-processing on the reception signal in an amount corresponding to the measurement time (T1 or T2) set as described above (S106), and the threshold processing section 313 performs threshold processing on the reception signal after the pre-processing by the pre-processing section 312 (S107). The detection section 314 detects an object in accordance with the result of the threshold processing by the threshold processing section 313 (S101).

[0088] According to the above-described embodiment, optimization of the detection cycle for detecting an object is possible, and it is possible to improve the detection accuracy in a region where the necessity of detecting an object is high (for example, a region close to a detected object).

[0089] Other embodiments will be described below with reference to the drawings, but for portions that play the same or similar role as the first embodiment, the same reference numerals are assigned and the description thereof is omitted.

[0090] (Second Embodiment)

[0091] Figure 7is a block diagram showing one example of a functional configuration of the object detection device 200' according to the second embodiment. The object detection device 200' according to the present embodiment differs from the object detection device 200 according to the first embodiment in that it has a mechanism for optimizing the CFAR processing in accordance with the detection result of the object. The object detection device 200' according to the present embodiment has, as a receiving-side configuration, a CFAR processing section 321 in addition to the configuration of the object detection device 200 according to the first embodiment shown in FIG. 2. Figure 4

[0092] The CFAR processing section 321 generates a difference signal by performing CFAR processing on the envelope generated by the pre-processing section 312. The CFAR processing is roughly processing for generating a difference signal that represents the difference between the value (signal level) of the envelope and the average value of the values of the envelope in order to reduce the clutter contained in the envelope. The CFAR processing section 426 generates a difference signal by performing CFAR processing on the value of the envelope corresponding to the received wave, the difference signal being based on the difference between the value of one sample corresponding to the received wave received at a certain detection time and the average value of the values of a plurality of samples corresponding to the received wave received at least one of the first moving average time and the second moving average time existing before and after the detection time.

[0093] ​Further, as the CFAR processing, a plurality of processes having different properties such as a CA-CFAR (Cell Averaging Constant False Alarm Rate) process, a GO-CFAR (Greatest Of Constant False Alarm Rate) process, and a SO-CFAR (Smallest Of Constant False Alarm Rate) process are considered. The CA-CFAR process is a process of generating a difference signal based on a difference between a value of one sample amount corresponding to a reception wave received at a certain detection time and an average value of values of a plurality of sample amounts corresponding to reception waves received at both a first moving average time and a second moving average time. The GO-CFAR process is a process of generating a difference signal based on a difference between a value of one sample amount corresponding to a reception wave received at a certain detection time and a larger one of an average value of values of a plurality of sample amounts corresponding to reception waves received at a first moving average time and an average value of values of a plurality of sample amounts corresponding to reception waves received at a second moving average time. The SO-CFAR process is a process of generating a difference signal based on a difference between a value of one sample amount corresponding to a reception wave received at a certain detection time and a smaller one of an average value of values of a plurality of sample amounts corresponding to reception waves received at a first moving average time and an average value of values of a plurality of sample amounts corresponding to reception waves received at a second moving average time.

[0094] The CFAR processing section 321 according to the present embodiment sets a moving average time in the CFAR processing based on a detection result of the detection section 314. Specifically, the farther the distance (TOF) of the detected object, the shorter the moving average time made by the CFAR processing section 321. The specific method for achieving such setting of the moving average time is not particularly limited, and for example, the moving average time in a case where the TOF (distance) corresponding to the object is greater than a threshold value can be made shorter than the moving average time in a case where the TOF is equal to or less than the threshold value. With such processing, in a case where the object exists at a relatively far distance or in a case where the object does not exist within the detectable range, the processing time required for the CFAR processing can be shortened. If the moving average time is shortened, the number of samples decreases and the effect of removing clutter decreases, but in a case where the object exists at a relatively far distance or in a case where the object does not exist within the detectable range, the effect of removing clutter does not need to be at such a high level in many cases. Therefore, as described above, the farther the distance of the object, the shorter the moving average time, and thus the waste of the processing time required for the CFAR processing can be reduced.

[0095] The threshold processing unit 313 in this embodiment compares the value of the differential signal generated by the CFAR processing unit 321 with a threshold, and determines whether the identification information of the transmitted wave and the received wave is similar at a predetermined level or above based on the comparison result.

[0096] Similar to the first embodiment, the detection unit 314 determines, based on the processing result of the threshold processing unit 313, the moment when the similarity between the transmitted wave and the received wave reaches a predetermined level, i.e., the moment when the signal level of the received wave exceeds the threshold (e.g., the moment when the peak value of the received wave exceeds the threshold). Figure 2 At time t4, the distance to the object (including whether the object exists) is detected using the Time-of-Flight (TOF) method.

[0097] Figure 8 This is a diagram illustrating an example of the CFAR processing involved in the second embodiment. Figure 8 In the illustrated CFAR processing, firstly, the received signal (the signal corresponding to the envelope generated by the preprocessing unit 312) is sampled at predetermined time intervals. The arithmetic unit 511 of the CFAR processing unit 321 calculates the sum of the values ​​of the N samples corresponding to the received wave received at a first moving average time t51 prior to the detection time t50. Additionally, the arithmetic unit 512 of the CFAR processing unit 321 calculates the sum of the values ​​of the N samples corresponding to the received wave received at a second moving average time t52 after the detection time t50. The arithmetic unit 520 of the CFAR processing unit 321 sums the calculation results of the arithmetic units 511 and 512. The arithmetic unit 530 of the CFAR processing unit 321 divides the calculation result of the arithmetic unit 520 by the sum of the number of samples N in the first moving average time t51 and the number of samples N in the second moving average time t52, i.e., 2N, to calculate the average value of the first moving average time t51 and the second moving average time t52. Furthermore, the arithmetic unit 540 of the CFAR processing unit 321 subtracts the average value of the calculation result of the arithmetic unit 530 from the value corresponding to the detection time t50 to generate a differential signal.

[0098] Figure 9 This is a diagram illustrating an example of a signal that becomes the source of the differential signal in the CFAR processing according to the second embodiment.

[0099] exist Figure 9 In the example shown, the solid line L700 represents the value of the envelope; specifically, in... Figure 8 The example shown illustrates the time variation of the signal value (signal level) input to the + side of the arithmetic unit 540 at each detection time t50. The dotted line L701 represents the average value calculated in the CFAR processing, specifically... Figure 8 The example shown illustrates the time variation of the value of the signal input to one side of the arithmetic unit 540.

[0100] If the CFAR processing is performed, the value of the signal represented by the solid line L700 is subtracted from the value of the signal represented by the dotted line L701 in each time, thereby obtaining a difference signal in each time. Further, in the present embodiment, the value of the difference signal does not become a negative value, but is always processed as a value of zero or more. Therefore, for example, the value of the difference signal in an interval in which the value represented by the dotted line L701 is larger than the value represented by the solid line L700 is not calculated as a negative value, but is calculated as zero. Further, it goes without saying that in an interval in which the value represented by the solid line L700 is a value of zero or less, the value of the difference signal is calculated as a value of zero or more.

[0101] Figure 10 is a graph representing one example of a difference signal obtained as a result of the CFAR processing involved in the second embodiment.

[0102] In the example illustrated in Figure 10 , the solid line L801 represents an example of a time variation of the value of the difference signal. As illustrated by this solid line L801, the value of the difference signal comes to a peak P801 exceeding a threshold value L811 at a certain time t80, and varies in a value range smaller than the threshold value L811 during a period T81, T82 before and after the time t80.

[0103] The time t80 corresponds to a timing at which the signal level of the reception wave reflected by the object of the detection target, which is extracted as a result of the reduction of the clutter by the CFAR processing, comes to a peak (the timing t4 illustrated in Figure 3 The period T81 and the period T82 correspond to periods in which the clutter, which is reduced by the CFAR processing, due to reflection by a road surface or the like, is detected.

[0104] By the above-described processing, the time t80 (TOF) at which the peak P801 corresponding to the object of the detection target is reached can be accurately detected without detecting the periods T81, T82 corresponding to the clutter.

[0105] Figure 11 is a flowchart representing one example of processing in the object detection device 200' involved in the second embodiment. Figure 11 The flowchart illustrated is a chart for explaining the features of the processing based on the CFAR processing section 321, and the processing related to the transmission control section 302 and the reception control section 315 (setting of the transmission interval and the measurement time, etc.) is omitted (for the processing related to the transmission control section 302 and the reception control section 315, refer to steps S102 to S106 in Figure 6 ).

[0106] If the detection section 314 detects an object (TOF corresponding to the object) (S201: Yes), the CFAR processing section 321 determines whether the distance (TOF) from the object is equal to or greater than a threshold value (S202). In a case where the distance from the object is equal to or greater than the threshold value (S202: Yes), the CFAR processing section 321 sets the first moving average time t51 and the second moving average time t52 to be shorter than the reference values (S203). On the other hand, in a case where the distance from the object is not equal to or greater than the threshold value (smaller than the threshold value) (S202: No), the CFAR processing section 321 sets the first moving average time t51 and the second moving average time t52 to be the reference values (S204).

[0107] The CFAR processing section 321 performs CFAR processing in accordance with the first moving average time t51 and the second moving average time t52 that are set to be shorter in step S203, or the first moving average time t51 and the second moving average time t52 that are set to be the reference values in step S204 (S205). Then, the threshold processing section 313 performs threshold processing on the difference signal generated based on the CFAR processing by the CFAR processing section 321 (S206). The detection section 314 detects an object in accordance with the result of the threshold processing by the threshold processing section 313 (S201).

[0108] According to the above-described embodiment, the moving average time in the CFAR processing can be optimized in accordance with the distance of the object. By performing such CFAR processing together with the optimization of the transmission interval and the measurement time of the transmission control section 302 and the reception control section 315 described in the first embodiment, the detection period for detecting an object can be further optimized.

[0109] (Third Embodiment)

[0110] Figure 12 is a block diagram showing one example of a functional structure of an object detection device 200" according to the third embodiment. The object detection device 200" according to the present embodiment differs from the object detection device 200' according to the second embodiment shown in Figure 7 the transmission control section 302 and the reception control section 315. That is, the object detection device 200" according to the present embodiment does not perform the optimization of the transmission interval and the measurement time based on the transmission control section 302 and the reception control section 315, but performs the optimization of the moving average time based on the CFAR processing section 321. Even in such a structure, it is possible to reduce the waste of processing time required for the CFAR processing, and thus it is possible to obtain the effect of the optimization of the detection period for detecting an object.

[0111] The above-described embodiments of the present disclosure are merely examples and are not intended to limit the scope of the application. The above-described new embodiments can be implemented in various ways and various omissions, substitutions, and changes can be made thereto without departing from the scope of the present application. The above-described embodiments are included within the scope and spirit of the present application and are included within the scope of the present application and equivalents thereof recited in the claims.

Claims

1.An object detection device characterized by comprising: a transmission section that transmits a transmission wave; a reception section that receives a reception wave that has returned as a result of the transmission wave being reflected by an object, from after the transmission of the transmission wave until a prescribed measurement time elapses; a detection section that detects the object based on distance information based on the reception wave received by the reception section; and a reception control section that makes the measurement time after the object is detected shorter than the measurement time after the object is not detected, the reception control section sets the measurement time to a time corresponding to a position that is a prescribed distance farther than a distance to the closest existing object, the object detection device further comprises a CFAR processing section that performs CFAR processing based on a prescribed moving average time on a signal corresponding to the reception wave received by the reception section, and the farther the distance to the detected object, the shorter the moving average time. 2.The object detection device according to claim 1, characterized in that the object detection device further comprises a transmission control section that sets a transmission interval from after the transmission of the transmission wave until the next transmission wave is transmitted, and makes the transmission interval after the object is detected shorter than the transmission interval after the object is not detected, the transmission section transmits the transmission wave in accordance with the transmission interval. 3.An object detection device characterized by comprising: a transmission section that transmits a transmission wave; a reception section that receives a reception wave that has returned as a result of the transmission wave being reflected by an object; a detection section that detects the object based on distance information based on the reception wave received by the reception section; and a CFAR processing section that performs CFAR processing based on a prescribed moving average time on a signal corresponding to the reception wave received by the reception section, and the farther the distance to the detected object, the shorter the moving average time. 4.The object detection device according to claim 3, characterized in that the object detection device further comprises a reception control section that sets a prescribed measurement time after the transmission of the transmission wave, and makes the measurement time after the object is detected shorter than the measurement time after the object is not detected, the reception section receives the reception wave from after the transmission of the transmission wave until the measurement time elapses. 5.The object detection device according to claim 4, characterized in that the object detection device further comprises a transmission control section that sets a time from after the transmission of the transmission wave until the next transmission wave is transmitted, that is, a transmission interval, and makes the transmission interval after the object is detected shorter than the transmission interval after the object is not detected, the transmission section transmits the transmission wave in accordance with the transmission interval. ​ ​ ​ ​

Images