Object detection device

Abstract

The present invention provides an object detection device that appropriately reduces clutter regardless of the environment and accurately detects a received wave that is a transmission wave reflected and returned by an object as a detection target. The object detection device, as an example of the present disclosure, includes: a signal processing unit that samples a first processing target signal corresponding to a first received wave reflected and returned by an object as a first transmission wave, and obtains a differential signal based on the difference between the value of at least one sample of the first processing target signal corresponding to the first received wave received at a certain detection timing and the average value of the first processing target signal for multiple samples corresponding to the first received wave received during at least one of a first period and a second period of a predetermined length before and after the detection timing; and a threshold setting unit that sets a threshold value to be compared with the value of the differential signal based on the deviation of the values of the multiple samples of the first processing target signal.

Description

Technical Field

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

[0002] Conventional radar-based technologies for transmitting and receiving information related to objects have a known process called CFAR (Constant False Alarm Rate) for reducing noise, known as clutter, caused by reflections from objects not intended for detection. CFAR processing, in general, involves obtaining a differential signal based on the difference between the value (signal level) of a signal to be processed corresponding to a received wave and the average value of that signal. Conventional technologies utilizing this CFAR process detect received waves, which are transmitted waves reflected from an object, by comparing the differential signal value with a fixed threshold.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-292597

[0004] Here, in the conventional technology described above, the fixed threshold used as the comparison target for the value of the differential signal obtained as a result of CFAR processing is preferably set to a level that detects the received wave of the transmitted wave reflected by the object to be detected but does not detect clutter.

[0005] However, the level of clutter is generally not constant and can vary depending on the environment, such as the condition of the ground (road surface) on which the object to be detected is placed. Therefore, in the above-mentioned conventional technology that uses a fixed threshold as the basis for comparison of the differential signal value, depending on the environment, clutter may also be detected in addition to the received wave that is the transmitted wave reflected back from the object to be detected. Summary of the Invention

[0006] Therefore, one of the objects of the present disclosure is to provide an object detection device that can appropriately reduce clutter regardless of the environment and accurately detect a received wave of a transmitted wave reflected and returned by an object to be detected.

[0007] An object detection device as an example of the present disclosure includes: a transmitting unit that transmits a first transmission wave; a receiving unit that receives a first reception wave that is reflected by an object and returned as the first transmission wave; a signal processing unit that samples a first processing object signal corresponding to the first reception wave and obtains a differential signal, the differential signal being a signal based on the difference between the value of at least one sample portion of the first processing object signal corresponding to the first reception wave received at a certain detection timing and the average value of the values of multiple sample portions of the first processing object signal corresponding to the first reception wave received during at least one of a first period and a second period of a prescribed time length before and after the detection timing; a threshold setting unit that sets a threshold value as a comparison object with the value of the differential signal based on a deviation in the values of the multiple sample portions of the first processing object signal; and a detection unit that detects information related to the object at the detection timing based on a comparison result of the value of the differential signal and the threshold value.

[0008] With this configuration, even under changing environmental conditions, an appropriate threshold can be dynamically set based on variations in the value of the first processing target signal, such that, for example, the received wave of the transmitted wave reflected off the object being detected is detected, while clutter is not detected. Therefore, with this configuration, regardless of the environmental conditions, clutter can be appropriately reduced, and the received wave of the transmitted wave reflected off the object being detected can be accurately detected.

[0009] In the object detection device described above, the signal processing unit selectively executes multiple CFAR processes, including CA-CFAR (Cell Averaging Constant False Alarm Rate) and GO-CFAR (Greatest Of Constant False Alarm Rate) processes, according to settings. The CA-CFAR process acquires a differential signal based on the difference between the value of the first processing target signal for at least one sample corresponding to the first reception wave received at the detection timing and the average value of the first processing target signal for multiple samples corresponding to the first reception wave received in both the first period and the second period. The GO-CFAR process acquires a differential signal based on the difference between the value of the first processing target signal for at least one sample corresponding to the first reception wave received at the detection timing, the average value of the first processing target signal for multiple samples corresponding to the first reception wave received in the first period, and the average value of the first processing target signal for multiple samples corresponding to the first reception wave received in the second period, whichever is greater. This configuration allows for improved flexibility by utilizing multiple CFAR processes separately.

[0010] In this case, when the signal processing unit performs CA-CFAR processing, the threshold setting unit sets the threshold based on the standard deviation, which is an indicator of the deviation in the values of the first processing target signal for multiple samples corresponding to the first received wave received in both the first period and the second period. When the signal processing unit performs GO-CFAR processing, the threshold setting unit sets the threshold based on the standard deviation corresponding to the larger average value of the standard deviation, which is an indicator of the deviation in the values of the first processing target signal for multiple samples corresponding to the first received wave received in the first period, and the standard deviation, which is an indicator of the deviation in the values of the first processing target signal for multiple samples corresponding to the first received wave received in the second period. With this configuration, it is possible to set an appropriate threshold by taking into account an appropriate standard deviation depending on the type of CFAR processing.

[0011] Furthermore, in the above-described object detection device, the transmitting unit encodes the first transmission wave to include predetermined identification information before transmitting it, and the signal processing unit uses, as the first processing target signal, a correlation value signal based on a correlation value indicating the similarity between the identification information of the first transmission wave and the first reception wave to obtain a difference signal. With this configuration, the correlation value signal can be used as the first processing target signal to obtain a difference signal in a format that facilitates determination of the similarity between the first transmission wave and the first reception wave.

[0012] In the object detection device described above, the transmitting unit transmits the second transmission wave before transmitting the first transmission wave, and the receiving unit receives the second reception wave, which is the second transmission wave and is reflected by the road surface, serving as the object, before receiving the first reception wave. The object detection device further includes a set value acquisition unit that estimates the shape of the road surface based on information regarding the second processing target signal corresponding to the second reception wave and acquires a set value corresponding to the road surface shape based on the estimation result. The signal processing unit acquires a differential signal based on the difference between the value of at least one sample of the first processing target signal corresponding to the first reception wave received at the detection timing and the average value of the first processing target signal corresponding to a plurality of samples of the first reception wave received during at least one of the first and second periods, and the set value, whichever is greater. With this configuration, by constantly subtracting a value at least equal to the set value from the value of the first processing target signal, a differential signal can be acquired in which clutter corresponding to, for example, the shape of the road surface is appropriately reduced.

[0013] In this case, the set value acquisition unit estimates the shape of the road surface based on coding information indicating whether the second transmitted wave and the second received wave are coded, which is information related to the second processing target signal; an average characteristic based on a moving average of the values of the second processing target signal; and a deviation between the value of the second processing target signal and the value of the signal represented by the empirical formula that best approximates the second processing target signal among a plurality of pre-set empirical formulas. The set value is then acquired based on the estimation result. With this configuration, the road surface shape can be appropriately estimated based on the three types of information: coding information, average characteristic, and deviation, and the set value can be appropriately acquired based on the estimation result.

[0014] In this case, the set value acquisition unit estimates the road surface shape using pre-stored first set information indicating the correspondence between the coded information, average characteristics, differential deviation, and road surface shape, and acquires the set value using pre-stored second set information indicating the correspondence between the road surface shape and the set value. With this configuration, the road surface shape can be easily estimated simply by referring to the first set information based on the three types of information: coded information, average characteristics, and deviation, and the set value can be easily acquired simply by referring to the second set information based on the estimation result.

[0015] In the above-described object detection device, the transmitter and receiver can be integrally configured as a transmitter and receiver including a single transducer capable of transmitting and receiving sound waves. This configuration simplifies the configuration for transmitting and receiving waves.

[0016] In the above-mentioned object detection device, the detection unit detects the distance to the object as information related to the object. With such a configuration, the distance to the object can be detected as one of the information related to the object. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is an exemplary and schematic diagram showing the appearance of a vehicle equipped with the object detection system according to the embodiment when viewed from above.

[0018] Figure 2 This is an exemplary and schematic block diagram showing a general hardware configuration of an ECU (electronic control unit) and an object detection device according to the embodiment.

[0019] Figure 3 This is an exemplary and schematic diagram for explaining the outline of a technique used by the object detection device according to the embodiment to detect the distance to an object.

[0020] Figure 4This is an exemplary and schematic block diagram showing the detailed structure of the object detection device according to the embodiment.

[0021] Figure 5 This is an exemplary and schematic diagram for explaining the outline of CA-CFAR (Cell Averaging Constant False Alarm Rate) processing and threshold value setting processing that can be executed in the embodiment.

[0022] Figure 6 This is an exemplary and schematic diagram for explaining the outline of a GO-CFAR (Greatest Of Constant False Alarm Rate) process and a threshold value setting process that can be executed in the embodiment.

[0023] Figure 7 is an illustrative and schematic diagram showing an example of a signal that forms the basis of a differential signal obtained as a result of CFAR processing according to an embodiment.

[0024] Figure 8 is an illustrative and schematic diagram showing an example of a differential signal obtained as a result of the CFAR process according to the embodiment.

[0025] Figure 9 It is an exemplary and schematic diagram for explaining setting values that can be set in the embodiment.

[0026] Figure 10 This is an illustrative and schematic diagram showing an example of the data structure of a road surface estimation table used to estimate the shape of a road surface in the embodiment.

[0027] Figure 11 This is an illustrative and schematic diagram showing an example of the data structure of a setting value table used to acquire setting values in the embodiment.

[0028] Figure 12 This is an exemplary and schematic flowchart showing a series of processes executed by the object detection device according to the embodiment to detect the distance to an object.

[0029] Description of Reference Numerals

[0030] 200, 201, 202, 203, 204…Object detection device; 210…Transmitter / receiver; 211…Oscillator; 220…Control unit; 411…Transmitter (transmitter); 421…Receiver (receiver); 426…CFAR processing unit (signal processing unit); 428…Threshold setting unit; 429…Detection unit; 430…Setting value acquisition unit; 430a…Road surface estimation table (first setting information); 430b…Setting value table (second setting information) DETAILED DESCRIPTION

[0031] Hereinafter, embodiments and modifications of the present disclosure will be described with reference to the accompanying drawings. The structures of the embodiments and modifications described below, as well as the functions and effects of the structures, are merely examples and are not intended to limit the scope of the present disclosure.

[0032] <Implementation Method>

[0033] Figure 1 This is an exemplary and schematic diagram showing the appearance of a vehicle 1 equipped with an object detection system according to an embodiment when viewed from above. As described below, the object detection system according to the embodiment detects objects including people (such as those described later) in the surrounding area by transmitting and receiving sound waves (ultrasonic waves) and obtaining the time difference between the transmission and reception. Figure 2 The on-board sensor system provides information about the obstacle O shown.

[0034] like Figure 1 As shown, the object detection system includes an ECU (electronic control unit) 100 mounted inside a four-wheeled vehicle 1 including a pair of front wheels 3F and a pair of rear wheels 3R, and object detection devices 201 to 204 mounted as external equipment of the vehicle 1 .

[0035] exist Figure 1 In the illustrated example, the object detection devices 201 to 204 are provided at different positions from each other in, for example, a rear bumper at the rear end of the vehicle body 2 as exterior equipment of the vehicle 1 .

[0036] In the embodiment, object detection devices 201 to 204 have the same hardware configuration and functions. Therefore, for simplicity, object detection devices 201 to 204 may be collectively referred to as object detection device 200 hereinafter.

[0037] In addition, in the embodiment, the installation position of the object detection device 200 is not limited to Figure 1The object detection device 200 can be installed at the front end of the vehicle body 2, such as the front bumper, or at the side of the vehicle body 2, or at least at the rear bumper, front bumper, and side. In addition, in the embodiment, the number of object detection devices 200 is not limited to Figure 1 Example shown.

[0038] Figure 2 This is an exemplary and schematic block diagram showing the hardware configuration of ECU 100 and object detection device 200 according to the embodiment.

[0039] like Figure 2 As shown, the ECU 100 has the same hardware configuration as a general computer. More specifically, the ECU 100 includes an input / output device 110 , a storage device 120 , and a processor 130 .

[0040] The input and output device 110 is used to realize the communication between the ECU 100 and the outside (in Figure 1 In the example shown, it is an interface for sending and receiving information between the object detection device 200).

[0041] The storage device 120 includes a main storage device such as a ROM (Read Only Memory) or a RAM (Random Access Memory) and / or an auxiliary storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0042] Processor 130 is responsible for various processes executed in ECU 100. Processor 130 includes a computing device such as a CPU (Central Processing Unit). Processor 130 reads and executes computer programs stored in storage device 120 to implement various functions such as automatic parking.

[0043] On the other hand, Figure 2 As shown, object detection device 200 includes a transceiver 210 and a control unit 220 .

[0044] The transceiver 210 includes a transducer 211 such as a piezoelectric element, and transmits and receives ultrasonic waves using the transducer 211 .

[0045] More specifically, the transceiver 210 transmits ultrasonic waves generated by the vibration of the vibrator 211 as transmission waves, and receives vibrations of the vibrator 211 caused by the ultrasonic waves transmitted as the transmission waves being reflected by an external object and returning as reception waves. Figure 2In the illustrated example, an obstacle O provided on the road surface RS is illustrated as an object that reflects ultrasonic waves from the transmitting and receiving unit 210 .

[0046] In addition, Figure 2 The illustrated example illustrates a configuration in which both transmission of transmission waves and reception of reception waves are achieved by a single transceiver 210 having a single transducer 211. However, the techniques of the embodiments are also applicable to configurations in which the transmission side and reception side are separated, such as a configuration in which a first transducer for transmitting transmission waves and a second transducer for receiving reception waves are separately provided.

[0047] The control unit 220 has the same hardware configuration as a general computer. More specifically, the control unit 220 includes an input / output device 221 , a storage device 222 , and a processor 223 .

[0048] The input and output device 221 is used to realize the communication between the control unit 220 and the outside (in Figure 1 In the example shown, it is an interface for transmitting and receiving information between the ECU 100 and the transceiver 210 .

[0049] The storage device 222 includes a main storage device such as a ROM and a RAM and / or an auxiliary storage device such as an HDD and an SSD.

[0050] The processor 223 is responsible for various processes executed in the control unit 220. The processor 223 includes, for example, a computing device such as a CPU. The processor 223 realizes various functions by reading and executing computer programs stored in the storage device 333.

[0051] Here, object detection device 200 according to the embodiment detects the distance to an object using a technique known as the TOF (Time of Flight) method. As described in detail below, the TOF method calculates the distance to an object as information related to the object by taking into account the difference between the timing when a transmission wave is transmitted (more specifically, the start of transmission) and the timing when a reception wave is received (more specifically, the start of reception).

[0052] Figure 3 This is an exemplary and schematic diagram for explaining the outline of the technology used by the object detection device 200 according to the embodiment to detect the distance to the object. More specifically, Figure 3 This is a graph that schematically and exemplarily shows how the signal level (e.g., amplitude) of ultrasonic waves transmitted and received by the object detection device 200 according to the embodiment changes over time. Figure 3In the graph shown, the horizontal axis corresponds to time, and the vertical axis corresponds to the signal level of the signal transmitted and received by the object detection device 200 via the transmitting and receiving unit 210 (transducer 211 ).

[0053] exist Figure 3 In the graph shown, the solid line L11 represents the signal level of the signal transmitted and received by the object detection device 200. In other words, it represents an example of the envelope curve of the degree of vibration of the vibrator 211 changing with time. From this solid line L11, it can be seen that the vibrator 211 is driven and vibrates for a time Ta starting at timing t0, and the transmission of the transmission wave is completed at timing t1. Thereafter, during a time Tb until reaching timing t2, the vibration of the vibrator 211 caused by inertia continues while attenuating. Therefore, at Figure 3 In the diagram shown, the time Tb corresponds to the so-called reverberation time.

[0054] At time t4, which is a time Tp elapsed from time t0 when the transmission wave was transmitted, the vibration level of the vibrator 211 reaches a peak value exceeding a predetermined threshold value Th1 (or above) indicated by the dashed dotted line L21. The threshold value Th1 is used to identify whether the vibration of the vibrator 211 is caused by an object to be detected (e.g., Figure 2 Is it caused by the reception of the transmitted wave reflected by the obstacle (shown as an obstacle) or by the reception of the received wave by an object outside the subject (such as Figure 2 The value set in advance is caused by the reception of the received wave of the transmitted wave reflected and returned by the road surface RS) shown.

[0055] In addition, Figure 3 , an example is shown in which the threshold value Th1 is set to a constant value that does not change regardless of the passage of time. However, in the embodiment, the threshold value Th1 may be set to a value that changes with the passage of time.

[0056] Here, vibrations with a peak value exceeding (or exceeding) the threshold value Th1 can be considered to be caused by the reception of the received wave of the transmitted wave reflected and returned by the object being detected. On the other hand, vibrations with a peak value below (or less than) the threshold value Th1 can be considered to be caused by the reception of the received wave of the transmitted wave reflected and returned by an object other than the object being detected.

[0057] Therefore, it can be understood from the solid line L11 that the vibration of the transducer 211 at the timing t4 is caused by the reception of the reception wave of the transmission wave reflected and returned by the object to be detected.

[0058] Furthermore, in the solid line L11, the vibration of the transducer 211 decays after timing t4. Therefore, timing t4 corresponds to the timing at which the reception of the transmitted wave reflected by the object being detected is completed. In other words, the transmitted wave last transmitted at timing t1 returns as a received wave.

[0059] Furthermore, in solid line L11, timing t3, which is the starting point of the peak at timing t4, corresponds to the start of reception of the transmitted wave reflected from the object being detected. In other words, it is the timing at which the transmitted wave initially transmitted at timing t0 returns as a received wave. Therefore, in solid line L11, the time ΔT between timing t3 and timing t4 is equal to time Ta, which is the transmission time of the transmitted wave.

[0060] Based on the above, in order to determine the distance to the object to be detected using the TOF method, it is necessary to determine the time Tf between the timing t0 at which the transmission wave starts to be transmitted and the timing t3 at which the reception wave starts to be received. This time Tf can be determined by subtracting a time ΔT equal to the time Ta (the transmission time of the transmission wave) from the time Tp (the difference between the timing t0 and the timing t4 at which the signal level of the received wave reaches a peak exceeding the threshold Th1).

[0061] The timing t0 at which transmission of the transmission wave begins can be easily determined as the timing at which object detection device 200 begins operation. The time Ta, which is the transmission time of the transmission wave, is predetermined by settings or the like. Therefore, to determine the distance to the detection target object using the TOF method, it is ultimately important to determine the timing t4 at which the signal level of the received wave reaches a peak exceeding the threshold Th1. Furthermore, to determine this timing t4, it is important to accurately detect the received wave, which is the transmitted wave reflected back from the detection target object.

[0062] However, conventionally, in technologies that transmit and receive information about objects using waves such as radar and sound waves, CFAR (Constant False Alarm Rate) processing is known as a process for reducing noise, known as clutter, caused by reflections from objects other than the detection target. CFAR processing, in general, involves obtaining a differential signal based on the difference between the value (signal level) of the processing target signal corresponding to the received wave and the average value of the processing target signal. Conventional technologies utilizing this CFAR processing detect received waves, which are transmitted waves reflected from the detection target object, by comparing the value of the differential signal with a fixed threshold.

[0063] Here, in the conventional technology described above, the fixed threshold used as the comparison target for the value of the differential signal obtained as a result of the CFAR process is preferably set to a level that detects the received wave of the transmitted wave reflected by the object to be detected but does not detect clutter.

[0064] However, the level of clutter is generally not constant and can vary depending on the environment, such as the condition of the road surface on which the detection target object is located. Therefore, in the above-mentioned conventional technology that uses a fixed threshold as the basis for comparison of the differential signal value, depending on the environment, clutter may be detected in addition to the received wave reflected from the detection target object.

[0065] Therefore, the embodiment configures object detection device 200 as follows to appropriately reduce clutter regardless of the environment and accurately detect received waves of transmitted waves reflected and returned by an object to be detected.

[0066] Figure 4 2 is an exemplary and schematic block diagram showing the detailed structure of the object detection device 200 according to the embodiment. Figure 4 In the example shown, the transmission side and reception side structures are separated, but this is for ease of illustration only. Therefore, in the embodiment, as described above, both the transmission of the transmission wave and the reception of the reception wave are achieved by a single transceiver 210 having a single transducer 211. However, as described above, the technology of the embodiment can also be applied to a structure in which the transmission side and reception side structures are separated.

[0067] like Figure 4 As shown, object detection device 200 includes a wave transmitter 411, a code generator 412, a carrier output unit 413, a multiplier 414, and an amplifier circuit 415 as a transmission-side configuration. Wave transmitter 411 is an example of a "transmitting unit."

[0068] Furthermore, object detection device 200 includes a receiver 421, an amplifier circuit 422, a filter processing unit 423, a correlation processing unit 424, an envelope processing unit 425, a CFAR processing unit 426, a threshold processing unit 427, a threshold setting unit 428, a detector 429, and a set value acquisition unit 430 as a receiving-side configuration. Receiver 421 is an example of a "receiving unit," and CFAR processing unit 426 is an example of a "signal processing unit."

[0069] Furthermore, in an embodiment, Figure 4At least a portion of the structure shown is implemented by dedicated hardware (analog circuit), and the remaining portion can be implemented as a result of the cooperation between hardware and software. More specifically, the processor 223 of the object detection device 200 reads a computer program from the storage device 222 and executes it. In addition, in the embodiment, Figure 4 Each of the components shown may operate under the control of the control unit 220 of the object detection device 200 itself, or may operate under the control of the external ECU 100 .

[0070] First, the configuration of the transmission side will be briefly described.

[0071] The wave transmitter 411 is constituted by the aforementioned oscillator 211 , and transmits a transmission wave corresponding to the transmission signal output (after amplification) from the amplifier circuit 415 via the oscillator 211 .

[0072] Here, in the embodiment, the wave transmitter 411 encodes the transmission wave into identification information including a predetermined code length based on the configuration described below and then transmits the encoded transmission wave.

[0073] The code generation unit 412 generates a signal corresponding to identification information to be added to the transmission wave, for example, a pulse signal corresponding to a bit string consisting of consecutive 0 or 1 bits.

[0074] The carrier output unit 413 outputs a carrier wave of a signal to which identification information is to be assigned. For example, the carrier output unit 413 outputs a sine wave of a predetermined frequency as a carrier wave.

[0075] Multiplier 414 modulates the carrier wave to impart identification information by multiplying the output from code generator 412 by the output from carrier wave output unit 413. The modulation method can utilize a single method or a combination of multiple methods, such as phase modulation, amplitude modulation, and frequency modulation. Multiplier 414 then outputs the modulated carrier wave, endowed with identification information, to amplifier circuit 415 as a transmission signal, serving as the basis for the transmission wave.

[0076] The amplifier circuit 415 amplifies the transmission signal output from the multiplier 414 and outputs the amplified transmission signal to the wave transmitter 411 .

[0077] Next, the configuration of the receiving side will be briefly described.

[0078] The wave receiver 421 is composed of the aforementioned transducer 211 , and receives the transmission wave reflected by an object via the transducer 211 as a reception wave.

[0079] The amplifier circuit 422 amplifies the reception signal that is a signal corresponding to the reception wave received by the wave receiver 421 .

[0080] The filter processing unit 423 performs filtering processing to reduce noise on the received signal amplified by the amplifier circuit 422. In addition, in an embodiment, the filter processing unit 423 may also obtain information related to the frequency of the transmitted signal and further perform frequency correction on the received signal to match the frequency of the transmitted signal.

[0081] The correlation processing unit 424 obtains a correlation value corresponding to the similarity between the identification information of the transmitted and received waves based on, for example, the transmitted signal obtained from the transmitting side structure and the received signal processed by the filter processing unit 423. The correlation value can be obtained based on a generally known correlation function or the like.

[0082] The envelope processing unit 425 obtains an envelope of the waveform of the correlation value signal, which is a signal based on the correlation value acquired by the correlation processing unit 424 , and outputs the envelope to the CFAR processing unit 426 as a processing target signal.

[0083] The CFAR processing unit 426 obtains a difference signal by performing CFAR processing on the processing target signal output from the envelope processing unit 425. As previously mentioned, CFAR processing is generally a process of obtaining a difference signal based on the difference between the value (signal level) of the processing target signal and the average value of the processing target signal in order to reduce noise contained in the processing target signal.

[0084] The CFAR processing unit 426 involved in the embodiment samples the processing object signal corresponding to the received wave by performing CFAR processing, and obtains a differential signal based on the difference between the value of (at least) one sample of the processing object signal corresponding to the received wave received at a certain detection timing and the average value of the values of multiple sample portions of the processing object signal corresponding to the received wave received during at least one of the first period and the second period of a specified time length before and after the detection timing.

[0085] Furthermore, CFAR processing can include multiple processes of varying nature, such as CA-CFAR (Cell Averaging Constant False Alarm Rate), GO-CFAR (Greatest of Constant False Alarm Rate), and SO-CFAR (Smallest of Constant False Alarm Rate). In this regard, the CFAR processing unit 426 of the embodiment selectively executes multiple CFAR processes based on settings, allowing for the separate use of at least CA-CFAR and GO-CFAR. The details of CA-CFAR and GO-CFAR will be discussed later, and therefore will not be described here.

[0086] The threshold processing unit 427 compares the value of the differential signal acquired by the CFAR processing unit 426 with the threshold value, and determines based on the comparison result whether the identification information of the transmission wave and the reception wave is similar to a predetermined level or more.

[0087] Here, as described above, if a fixed threshold is used as the comparison target for the difference signal value, depending on the environment, not only the received wave of the transmitted wave reflected and returned by the object to be detected but also clutter may be detected.

[0088] Therefore, in order to solve the above-mentioned inconvenience, the threshold processing unit 427 according to the embodiment uses the threshold value dynamically set by the threshold setting unit 428 according to the environment as a comparison target with the value of the differential signal.

[0089] Specifically, the threshold setting unit 428 of this embodiment dynamically sets an appropriate threshold value corresponding to the environment, taking into account the deviation in the value of the processing target signal, which is the subject of CFAR processing. More specifically, the threshold setting unit 428 sets the threshold value, which is used as the basis for comparison with the value of the difference signal, based on the deviation in the value of the processing target signal for a plurality of samples corresponding to received waves received during at least one of the first and second periods of a predetermined length of time before and after the aforementioned detection timing. Furthermore, as described in detail later, the index representing the deviation is calculated using different criteria depending on the type of CFAR processing performed by the CFAR processing unit 426.

[0090] Furthermore, the detection unit 429 determines the timing when the similarity between the identification information of the transmission wave and the reception wave reaches a predetermined level or higher, based on the processing result of the threshold processing unit 427, that is, the timing when the signal level of the reception wave returned by the reflection reaches a peak value exceeding the threshold value (for example, Figure 2 The distance to the object is detected by the TOF method (timing t4 shown).

[0091] Here, an overview of the CFAR processing and threshold setting process performed in the embodiment will be described. As previously described, the CFAR processing unit 426 of the embodiment selectively executes multiple CFAR processes based on settings, so as to selectively utilize at least the CA-CFAR process and the GO-CFAR process. Furthermore, the threshold setting unit 428 of the embodiment calculates an index representing the deviation of the value of the processing target signal according to different criteria depending on the type of CFAR process performed by the CFAR processing unit 426. Based on the calculation results, the threshold value is dynamically set according to the environment, such as the road surface condition, which is a significant factor in clutter.

[0092] First, the CA-CFAR process and the threshold value setting process based on the CA-CFAR process will be described.

[0093] as follows Figure 5 As shown, the CA-CFAR processing is a process for obtaining a differential signal based on the difference between the value of a processing target signal of one sample corresponding to a received wave received at a certain detection timing and the average value of the values of the processing target signal of multiple samples corresponding to received waves received in the first period and the second period before and after the detection timing.

[0094] Figure 5 This is an exemplary and schematic diagram for explaining an outline of a CA-CFAR process that can be executed in the embodiment and a threshold value setting process based on the CA-CFAR process.

[0095] like Figure 5 As shown, in CA-CFAR processing, a processing target signal 510 is first sampled at predetermined time intervals. Then, a calculation unit 511 of the CFAR processing unit 426 calculates the sum of N sample values of the processing target signal corresponding to a received wave received during a first period T51 prior to a certain detection timing t50. Furthermore, a calculation unit 512 of the CFAR processing unit 426 calculates the sum of N sample values of the processing target signal corresponding to a received wave received during a second period T52 subsequent to detection timing t50.

[0096] The arithmetic unit 520 of the CFAR processing unit 426 sums the arithmetic results of the arithmetic units 511 and 512. The arithmetic unit 530 of the CFAR processing unit 426 divides the arithmetic result of the arithmetic unit 520 by 2N, which is the sum of the number N of samples of the processing target signal in the first period T51 and the number N of samples of the processing target signal in the second period T52, to calculate the average value of the values of the processing target signal in both the first period T51 and the second period T52.

[0097] Then, the calculator 540 of the CFAR processing unit 426 subtracts the average value of the calculation results of the calculator 530 from the value of the processing target signal at the detection timing t50 to obtain a difference signal 550 .

[0098] On the other hand, the operator 560 of the threshold setting unit 428 subtracts the average value of the calculation results of the operator 530 from the values of the processing target signal for each of the 2N samples in the first period T51 and the second period T52. Furthermore, the operator 570 of the threshold setting unit 428 calculates the standard deviation, which serves as an indicator of the difference in the values of the processing target signal for both the first period T51 and the second period T52, by calculating the square root of the sum of the squares of the calculation results of the operator 560 for the 2N samples divided by 2N. Furthermore, the threshold setting unit 428 sets the threshold 580 to be compared with the difference signal 550 by performing processing such as multiplying the calculation result of the operator 570 by a predetermined gain.

[0099] In addition, Figure 5 In the example shown, the first period T51 and the second period T52 can be set with no time gap before and after detection timing t50, or they can be set with a time interval of several samples before and after detection timing t50. The latter setting ignores the information immediately before and after detection timing t50, thereby achieving a processing result that emphasizes the information at detection timing t50.

[0100] Next, the GO-CFAR process and the threshold value setting process based on the GO-CFAR process will be described.

[0101] as follows Figure 6 As shown, the GO-CFAR processing is a process for obtaining a differential signal based on the difference between the value of a processing target signal of one sample corresponding to a received wave received at a certain detection timing, the average value of the first processing target signal of multiple sample portions corresponding to a received wave received in a first period existing before the detection timing, and the average value of the processing target signal of multiple sample portions corresponding to a received wave received in a second period existing after the detection timing, whichever is larger.

[0102] Figure 6 This is an exemplary and schematic diagram for explaining an outline of a GO-CFAR process that can be executed in the embodiment and a threshold value setting process based on the GO-CFAR process.

[0103] like Figure 6As shown, in GO-CFAR processing, similar to CA-CFAR processing, the processing target signal 610 is first sampled at predetermined time intervals. The calculation unit 611 of the CFAR processing unit 426 then calculates the sum of the values of the processing target signal for N samples corresponding to the received wave received during the first period T61 before a certain detection timing t60. Furthermore, the calculation unit 612 of the CFAR processing unit 426 calculates the sum of the values of the processing target signal for N samples corresponding to the received wave received during the second period T62 after the certain detection timing t60.

[0104] The arithmetic unit 621 of the CFAR processing unit 426 divides the calculation result of the arithmetic unit 611 by the number N of samples of the processing target signal in the first period T61, thereby calculating the average value of the processing target signal in the first period T61. Furthermore, the arithmetic unit 622 of the CFAR processing unit 426 divides the calculation result of the arithmetic unit 612 by the number N of samples of the processing target signal in the second period T62, thereby calculating the average value of the processing target signal in the second period T62.

[0105] The CFAR processing unit 426 then extracts the larger average value 630 between the average value of the calculation results of the calculator 621 and the average value of the calculation results of the calculator 622. The calculator 640 of the CFAR processing unit 426 then subtracts the extracted larger average value 630 from the value of the processing target signal at detection timing t50 to obtain a difference signal 650.

[0106] On the other hand, the calculation unit 661 of the threshold setting unit 428 subtracts the average value of the calculation results of the calculation unit 621 from each of the N samples of the processing target signal in the first period T61. Furthermore, the calculation unit 671 of the threshold setting unit 428 calculates the standard deviation, which is an indicator of the variation in the value of the processing target signal in the first period T61, by calculating the square root of the value obtained by dividing the square of the calculation results of the calculation unit 661 for N samples by N.

[0107] Furthermore, the operator 662 of the threshold setting unit 428 subtracts the average value of the calculation results of the operator 622 from each of the N samples of the processing target signal in the second period T62. Furthermore, the operator 672 of the threshold setting unit 428 calculates the standard deviation, which is an indicator of the variation in the value of the processing target signal in the second period T62, by calculating the square root of the value obtained by dividing the square of the calculation results of the N samples of the processing target signal by the operator 662 by N.

[0108] The threshold setting unit 428 then extracts the standard deviation corresponding to the larger average value 630 extracted by the CFAR processing unit 426, from the standard deviation of the calculation result of the calculation unit 661 and the standard deviation of the calculation result of the calculation unit 662. The threshold setting unit 428 then performs processing such as multiplying the extracted result by a predetermined gain, and sets a threshold value 680 based on the standard deviation corresponding to the larger average value 630 as a comparison target for the difference signal 550.

[0109] In addition, Figure 6 In the example shown, Figure 5 Similar to the example shown, the first period T61 and the second period T62 may be set without a time gap before and after the detection timing t60, or may be set with a time interval of several samples before and after the detection timing t60.

[0110] In this manner, the CFAR processing unit 426 according to the embodiment selectively executes multiple CFAR processes according to settings, thereby selectively utilizing at least the CA-CFAR process and the GO-CFAR process. Furthermore, the threshold setting unit 428 according to the embodiment calculates an index representing the deviation in the value of the processing target signal using different criteria depending on the type of CFAR process executed by the CFAR processing unit 426. Based on the calculation results, the threshold value is dynamically set according to the environment, such as the road surface condition, which is a significant factor in clutter.

[0111] In addition, the SO-CFAR process is also mentioned in the above description, but the SO-CFAR process is basically the same as the GO-CFAR process except that the smaller of the value related to the first period and the value related to the second period is extracted, so further description is omitted here.

[0112] The differential signal obtained as a result of the CFAR process will be described in more detail below.

[0113] First, two signals serving as a basis for a differential signal will be described with reference to specific waveform examples.

[0114] Figure 7 is an illustrative and schematic diagram showing an example of a signal that forms the basis of a differential signal obtained as a result of CFAR processing according to an embodiment.

[0115] exist Figure 7 In the example shown, a solid line L700 shows a processing target signal which is one of the signals that form the basis of the differential signal, and more specifically, shows the signal at Figure 5 In the example shown, the signal input to the positive side of the operator 540 at each detection timing t50 and the signal input to the positive side of the operator 540 at each detection timing t50 are Figure 6The example shown is an example of temporal change in the value (signal level) of the signal on the positive side input to the operator 640 at each detection timing t60.

[0116] In addition, Figure 7 In the example shown, a dashed line L701 indicates a target signal that is differentiated from a target signal in the CA-CFAR process, and more specifically, indicates the signal at the time of Figure 5 In the example shown, the time variation of the value of the signal input to the negative side of the operator 540 is shown. In addition, the double-dashed line L702 shows the target signal that is differentiated from the target signal in the GO-CFAR process, and more specifically, shows the signal of the target signal. Figure 6 In the example shown, the value of the signal input to the negative side of the operator 640 is changed over time.

[0117] In an embodiment, when CA-CFAR processing is performed, the differential signal at each time is obtained by subtracting the value of the signal shown by the dotted line L701 from the value (signal level) of the signal shown by the solid line L700 at each time. When GO-CFAR processing is performed, the differential signal is obtained by subtracting the value of the signal shown by the double-dotted line L702 from the value of the signal shown by the solid line L700 at each time.

[0118] Furthermore, in the embodiment, the value of the differential signal does not become a negative value, but is always processed as a value greater than zero. Therefore, in the embodiment, for example, in an interval where the value indicated by the dashed line L701 (the same applies to the double-dashed line L702) is greater than the value of the signal indicated by the solid line L700, the value of the differential signal is not calculated as a negative value, but is calculated as zero. Furthermore, of course, in an interval where the value of the signal indicated by the solid line L700 is greater than the value indicated by the dashed line L701 (the same applies to the double-dashed line L702), the value of the differential signal is calculated as a value greater than zero.

[0119] Based on the above calculation, in the embodiment, the temporal change of the value (signal level) of the differential signal is, for example, as follows: Figure 8 In the form shown.

[0120] Figure 8 is an illustrative and schematic diagram showing an example of a differential signal obtained as a result of the CFAR process according to the embodiment.

[0121] exist Figure 8 In the example shown, solid line L801 illustrates the temporal variation of the differential signal value. As shown by solid line L801, the differential signal value reaches a peak value P801 at a certain time t80 and fluctuates within a range of values less than the peak value P801 during periods T81 and T82 before and after time t80.

[0122] Furthermore, time t80 corresponds to the timing when the signal level of the received wave, which is the transmission wave reflected and returned by the object to be detected and extracted as a result of clutter reduction by the CFAR process, reaches a peak ( Figure 3 The timing t4 shown in FIG. 1 ) and the periods T81 and T82 correspond to the clutter generated by reflection from the road surface etc. which is reduced by the CFAR process.

[0123] Here, in the embodiment, as described above, at least two CFAR processes, CA-CFAR process and GO-CFAR process, are used separately. Figure 8 In the example of the change in the value of the differential signal, only one solid line L801 is shown. However, as described below, in the embodiment, since a differential signal showing a time change as shown by the solid line L801 is obtained regardless of whether CA-CFAR processing or GO-CFAR processing is performed, Figure 8 In FIG, the differential signal obtained as a result of the GO-CFAR process and the differential signal obtained as a result of the CA-CFAR process are not distinguished and illustrated.

[0124] More specifically, if Figure 7 As shown, the values of the signal (see dashed-dotted line L701) used for differentiation from the processing target signal (see solid line L700) in CA-CFAR processing and the values of the signal (dashed-double-dashed line L702) used for differentiation from the processing target signal (see solid line L700) in GO-CFAR processing show approximately the same temporal variations, except that the former tends to be smaller than the latter. Therefore, differential signals showing approximately the same temporal variations are obtained regardless of whether CA-CFAR or GO-CFAR processing is used.

[0125] However, as described above, in GO-CFAR processing, since a larger value tends to be subtracted from the value of the processing target signal compared to CA-CFAR processing, the differential signal obtained as a result of GO-CFAR processing tends to be zero more often than the differential signal obtained as a result of CA-CFAR processing.

[0126] exist Figure 8 In the example shown, if the threshold value shown by the solid line L811 is set, the periods T81 and T82 corresponding to the interference will not be detected, but the time t80 when the value of the differential signal reaches the peak value P801 corresponding to the timing when the signal level of the received wave of the transmitted wave reflected and returned by the object to be detected reaches the peak value can be detected.

[0127] Here, as described above, if the level of clutter does not change, even if a fixed threshold is used as the threshold, no particular inconvenience will occur. However, since the level of clutter is not constant but may vary depending on the environment, it may also be possible to change the level of clutter, for example, depending on the environment. Figure 8 As shown in the example, the noise value (signal level) in the period T81 reaches Figure 8 In this case, if the threshold value shown by the solid line L811 is not changed, not only the peak P801 that is the original detection target but also the peak P802 corresponding to the clutter will be detected.

[0128] Therefore, in the embodiment, the threshold setting unit 428 dynamically sets an appropriate threshold value corresponding to the environment, taking into account the variation in the value of the target signal to be processed, as described above. Since the variation in the value of the target signal affects the degree of clutter, dynamically setting (changing) the threshold value in consideration of this variation allows for an appropriate threshold value to be set that detects only the intended target signal and not clutter.

[0129] For example, in Figure 8 In the example shown, when an environment in which the noise value during period T81 reaches peak value P802 is reached, threshold setting unit 428 sets the threshold value indicated by the dot-dashed line L812 to correspond to this environment. Since the threshold value indicated by the dot-dashed line L812 is greater than peak value P802, the threshold value indicated by the dot-dashed line L812 can be used to accurately detect only the intended detection target without detecting noise.

[0130] However, as mentioned above, the differential signal at a certain detection timing is obtained based on the value obtained by subtracting the average value of the value of the processing target signal in at least one period before and after the detection timing from the value of the processing target signal at the detection timing. In addition, when the value of the processing target signal is less than the average value, the value of the differential signal is calculated as zero. In view of this, if the calculation method for obtaining the differential signal is adjusted so that the following value is always subtracted from the value of the processing target signal Figure 9 By setting the value to be equal to or greater than the set value and having a magnitude equal to or greater than zero as shown, the time for the difference signal to become zero can be prolonged, and noise can be effectively reduced.

[0131] Figure 9 It is an exemplary and schematic diagram for explaining setting values that can be set in the embodiment.

[0132] exist Figure 9In the example shown, solid line L900 illustrates an example of temporal variation in the value (signal level) of the target signal. Furthermore, line L901, comprised of a dashed line L901a and a dotted line L901b, illustrates an example of temporal variation in the value of the target signal, which is differentiated from the target signal in order to obtain a differential signal during CA-CFAR processing. Furthermore, line L902, comprised of a dashed double-dashed line L902a and a dotted line L902b, illustrates an example of temporal variation in the value of the target signal, which is differentiated from the target signal in order to obtain a differential signal during GO-CFAR processing. Furthermore, solid line L903 illustrates an example of a setting value for effectively reducing noise by extending the time it takes for the differential signal to reach zero.

[0133] Similar to the previous example, Figure 9 In the example shown, the basic calculation method for obtaining the differential signal is to subtract the value shown by line L901 or L902 from the value shown by solid line L900. However, in the embodiment, in order to extend the time it takes for the differential signal value to reach zero and effectively reduce noise, the calculation method for obtaining the differential signal is adjusted based on the set value so that a value greater than the set value shown by solid line L903 is always subtracted from the value shown by solid line L900. Furthermore, the set value is set to be smaller than the peak value shown by solid line L900, but larger than the surrounding values that fluctuate within a smaller range of values closer to zero than the peak value.

[0134] That is, in Figure 9 In the example shown, in the interval where the value shown by line L901 becomes the value shown by the dotted line L901a higher than the set value shown by the solid line L903, the differential signal based on the CA-CFAR processing is obtained based on the result obtained by subtracting the value shown by the dotted line L901a from the value shown by the solid line L900, and in the interval where the value shown by line L901 becomes the value shown by the dotted line L901b lower than the set value shown by the solid line L903, the differential signal based on the CA-CFAR processing is obtained based on the result obtained by subtracting the value shown by the solid line L903 from the value shown by the solid line L900.

[0135] Similarly, in Figure 9 In the example shown, in the interval where the value shown in line L902 becomes the value shown in double-dashed line L902a that is higher than the set value shown in solid line L903, a differential signal based on GO-CFAR processing is obtained based on the result obtained by subtracting the value shown in double-dashed line L902a from the value shown in solid line L900, and in the interval where the value shown in line L902 becomes the value shown in dotted line L902b that is lower than the set value shown in solid line L903, a differential signal based on GO-CFAR processing is obtained based on the result obtained by subtracting the value shown in solid line L903 from the value shown in solid line L900.

[0136] Here, in Figure 9 In the example shown, the set value indicated by the solid line L903 is shown as a fixed value. However, the degree of fluctuation in the value indicated by the solid line L900 varies depending on the road surface shape. In other words, depending on the road surface shape, a situation may occur where the value indicated by the solid line L900 is always higher than the set value indicated by the solid line L903, causing the set value to be dynamically adjusted according to the road surface shape.

[0137] Therefore, return to Figure 2 In the embodiment, wave transmitter 411 transmits a transmission wave for estimating road shape before transmitting the transmission wave for distance detection using the TOF method described above. Furthermore, set value acquisition unit 430 acquires a set value based on a processing target signal output from envelope processing unit 425, which is a received wave reflected from the transmission wave for estimating road shape and received by wave receiver 421.

[0138] The transmission wave used for distance detection and the transmission wave used for road shape estimation are essentially the same wave, depending on whether or not they are encoded. However, in the following text, the transmission wave used for distance detection may be referred to as the first transmission wave, and the transmission wave used for road shape estimation may be referred to as the second transmission wave, as needed, to clearly distinguish between the two. Furthermore, the received wave resulting from the reflection of the first transmission wave may be referred to as the first received wave, while the received wave resulting from the reflection of the second transmission wave may be referred to as the second received wave. Furthermore, the processing target signal corresponding to the first received wave may be referred to as the first processing target signal, while the processing target signal corresponding to the second received wave may be referred to as the second processing target signal.

[0139] In the embodiment, setting value acquisition unit 430 estimates the road surface shape by referring to road surface estimation table 430a based on information related to the second processing target signal corresponding to the second received wave. Based on the estimation result, setting value table 430b is referred to to acquire setting values corresponding to the road surface shape. Road surface estimation table 430a is an example of "first setting information," and setting value table 430b is an example of "second setting information."

[0140] More specifically, upon acquiring the second processing target signal, the setting value acquisition unit 430 determines an empirical formula that best approximates the second processing target signal. This empirical formula is selected by, for example, calculating the degree of agreement with each of a plurality of pre-set empirical formulas. Furthermore, the empirical formula-based approximation targets not the entire section of the second processing target signal, but rather a specific section estimated based on the installation position and orientation of the object detection device 200, where a portion of the second received wave, which is the second transmitted wave reflected from an object outside the detection target, such as the road surface, is received.

[0141] Then, once the set value acquisition unit 430 has determined the empirical formula that best approximates (a specific interval of a portion of the temporal variation of) the second processing target signal, it calculates an indicator (e.g., a standard deviation) representing the deviation of the difference between the value of the signal represented by the empirical formula and the value of the second processing target signal. Furthermore, the set value acquisition unit 430 also calculates an average characteristic based on a moving average of the values of the second processing target signal.

[0142] Furthermore, the setting value acquisition unit 430 considers the coding information indicating whether the second transmission wave and the second reception wave are coded as information related to the second processing target signal in addition to the average characteristic and the deviation calculated by the above calculation, and refers to the following Figure 10 The road surface estimation table 430a having the data structure shown above estimates the shape of the road surface. In addition, the coded information is determined in advance when the second transmission wave is transmitted.

[0143] Figure 10 1 is an illustrative and schematic diagram showing an example of the data structure of the road surface estimation table 430 a used to estimate the shape of the road surface in the embodiment.

[0144] like Figure 10 As shown, in the embodiment, road surface estimation table 430a contains data indicating a correspondence relationship between encoding information indicating whether the second transmitted wave and the second received wave are encoded, an average characteristic based on a moving average of the values of the second processing target signal, a deviation between the difference between the value of the signal represented by the empirical formula that best approximates (a specific interval of a portion of the temporal variation of) the second processing target signal among a plurality of pre-set empirical formulas and the value of the second processing target signal, and the shape of the road surface. Road surface estimation table 430a is fixed data determined through experiments, etc., and is pre-stored in set value acquisition unit 430.

[0145] Therefore, if the coded information determined in advance when the second transmission wave is transmitted is determined, and the average characteristics and deviation calculated based on the reception of the second reception wave are determined, the setting value acquisition unit 430 can estimate the shape of the appropriate road surface by referring to the road surface estimation table 430a based on the determination result.

[0146] When the estimation of the road shape based on the road estimation table 430a is completed, the setting value acquisition unit 430 refers to the following Figure 11 The setting value table 430b having the data structure shown above acquires setting values corresponding to the shape of the road surface.

[0147] Figure 11 1 is an illustrative and schematic diagram showing an example of the data structure of the setting value table 430 b used to acquire the setting values in the embodiment.

[0148] like Figure 11 As shown, in the embodiment, the setting value table 430b is data indicating the correspondence between the road surface shape and the setting value. The setting value table 430b is stored in advance in the setting value acquisition unit 430 as fixed data determined by experiments or the like.

[0149] Therefore, if the shape of the road surface is estimated with reference to the road surface estimation table 430 a , the setting value acquisition unit 430 can acquire appropriate setting values by further referring to the setting value table 430 b based on the estimation result.

[0150] Return to Figure 2 The set value acquisition unit 430 outputs the set value acquired based on the road surface estimation table 430a and the set value table 430b to the CFAR processing unit 426. Thus, the CFAR processing unit 426 can consider the set value when acquiring the differential signal, thereby acquiring a differential signal with effectively reduced clutter.

[0151] Hereinafter, the flow of processing executed in the embodiment will be described.

[0152] Figure 12 This is an exemplary and schematic flowchart showing a series of processes executed by the object detection device 200 according to the embodiment to detect information related to an object.

[0153] like Figure 12 As shown, in the embodiment, first, in S1201, the wave transmitter 411 transmits a transmission wave corresponding to the transmission signal generated by the code generator 412, the carrier output unit 413, the multiplier 414, and the amplifier circuit 415 toward the outside of the vehicle 1. The transmission wave transmitted in S1201 is a second transmission wave for estimating the shape of the road surface.

[0154] Then, in S1202, the wave receiver 421 receives the received wave. The received wave received in S1202 is a second received wave resulting from the second transmitted wave transmitted in S1201 being reflected by an object outside the vehicle 1. The received signal corresponding to the second received wave undergoes amplification by the amplifier circuit 422, noise suppression by the filter processing unit 423, and acquisition of a correlation value by the correlation processing unit 424, and is then output to the envelope processing unit 425.

[0155] Then, in S1203, envelope processing unit 425 calculates the envelope of the waveform of the correlation value signal based on the correlation value obtained by correlation processing unit 424, and generates a processing target signal corresponding to the temporal change in the value of the envelope. The processing target signal generated in S1203 is the second processing target signal corresponding to the second received wave received in S1202.

[0156] Furthermore, in S1204, the set value acquisition unit 430 acquires information necessary for estimating the road surface shape based on the second signal to be processed generated in S1203. As described above, the information necessary for estimating the road surface shape includes three types of information: encoding information indicating whether the second transmitted wave and the second received wave are encoded; average characteristics based on a moving average of the values of the second signal to be processed; and the deviation between the value of the second signal to be processed and the value of the signal represented by the empirical formula that best approximates (a specific interval of a portion of the temporal variation of) the second signal to be processed, among a plurality of pre-set empirical formulas.

[0157] Then, in S1205, the set value acquisition unit 430 estimates the shape of the road surface using the road surface estimation table 430a. More specifically, the set value acquisition unit 430 estimates the shape of the road surface corresponding to the information acquired in S1203 by referring to the road surface estimation table 430a based on the information acquired in S1203.

[0158] Furthermore, in S1206, the set value acquisition unit 430 acquires the set value using the set value table 430b. More specifically, the set value acquisition unit 430 refers to the set value table 430b based on the estimation result in S1205 to acquire the set value corresponding to the road surface shape. Furthermore, the set value acquired in S1206 is output to the CFAR processing unit 426 and utilized in the CFAR processing in S1210 described below.

[0159] Then, in S1207, the wave transmitter 411 transmits a transmission wave corresponding to the transmission signal generated by the code generator 412, the carrier output unit 413, the multiplier 414, and the amplifier circuit 415 toward the outside of the vehicle 1. The transmission wave transmitted in S1207 is a first transmission wave for detecting the distance to an object existing outside the vehicle 1.

[0160] Then, in S1208, the wave receiver 421 receives the received wave. The received wave received in S1208 is a first received wave received as a result of the first transmitted wave transmitted in S1207 being reflected by an object outside the vehicle 1. The received signal corresponding to the first received wave undergoes amplification by the amplifier circuit 422, noise suppression by the filter processing unit 423, and acquisition of a correlation value by the correlation processing unit 424, and is then output to the envelope processing unit 425.

[0161] Then, in S1209, envelope processing unit 425 calculates the envelope of the waveform of the correlation value signal based on the correlation value obtained by correlation processing unit 424, and outputs a processing target signal corresponding to the temporal change in the value of the envelope. The processing target signal generated in S1209 is the first processing target signal corresponding to the first received wave received in S1208.

[0162] Furthermore, in S1210, the CFAR processing unit 426 performs CFAR processing. More specifically, the CFAR processing unit 426 obtains a differential signal based on the difference between the value (signal level) of the first processing target signal generated in S1209 and the average value of the value of the first processing target signal. However, in the case where the average value of the value of the first processing target signal is lower than the set value obtained in S1206, the object of the difference from the value of the first processing target signal is not the average value but the set value. In addition, the method for calculating the average value of the value of the first processing target signal differs depending on whether CA-CFAR processing, GO-CFAR processing, or other CFAR processing is performed, but the specific example of the method for calculating the average value has been explained, so further explanation is omitted here.

[0163] Meanwhile, in S1211, the threshold setting unit 428 obtains the deviation in the value of the processing target signal. More specifically, the threshold setting unit 428 calculates a standard deviation, which serves as an indicator of the deviation in the value of the first processing target signal generated in S1209, using different criteria depending on the type of CFAR processing performed in S1210. A specific example of how the standard deviation is calculated depending on the type of CFAR processing has already been described, and further explanation is omitted here.

[0164] Furthermore, in S1212, the threshold setting unit 428 sets a threshold value to be compared with the value of the difference signal obtained in S1210 based on the deviation of the value of the processing target signal obtained in S1211. More specifically, the threshold setting unit 428 sets the threshold value by performing processing such as multiplying the standard deviation of the value of the processing target signal obtained in S1211 by a predetermined gain.

[0165] Then, in S1213 , the threshold processing unit 427 performs threshold processing to compare the value of the differential signal acquired in S1210 with the threshold set in S1212 .

[0166] Then, in S1214, detection unit 429 detects the distance to the object that caused the transmission wave to be reflected based on the results of the threshold processing in S1213. More specifically, detection unit 429 deems the timing at which the differential signal acquired in S1210, determined as a result of the threshold processing in S1213, exceeds the threshold set in S1212 as the timing at which the received wave, a result of the first transmission wave being reflected and returned by the detection target object, is received. Using the TOF method, detection unit 429 detects the distance to the object. Processing then terminates.

[0167] As described above, the object detection device 200 according to the embodiment includes a wave transmitter 411, a wave receiver 421, a CFAR processing unit 426, a threshold setting unit 428, and a detection unit 429. The wave transmitter 411 transmits a first transmission wave. The wave receiver 421 receives a first reception wave, which is the first transmission wave reflected by an object. The CFAR processing unit 426 samples the first processing target signal corresponding to the first reception wave and obtains a difference signal based on the difference between the value of at least one sample of the first processing target signal corresponding to the first reception wave received at a certain detection timing and the average value of the first processing target signal for multiple samples corresponding to the first reception wave received during at least one of a first period and a second period of a predetermined length before and after the detection timing. The threshold setting unit 428 sets a threshold value to be compared with the value of the difference signal based on the deviation between the values of the multiple samples of the first processing target signal. The detection unit 429 detects information related to the object at the detection timing based on the comparison result of the difference signal value and the threshold value.

[0168] With this configuration, even under changing environmental conditions, an appropriate threshold value can be dynamically set based on variations in the value of the first processing target signal, for example, to detect received waves of transmitted waves reflected from an object being detected, while ignoring clutter. Therefore, with this configuration, regardless of the environmental conditions, clutter can be appropriately reduced, and received waves of transmitted waves reflected from an object being detected can be accurately detected.

[0169] In an embodiment, the CFAR processing unit 426 selectively executes multiple CFAR processes, including CA-CFAR processing and GO-CFAR processing, according to settings. CA-CFAR processing is a process for obtaining a differential signal based on the difference between the value of the first processing target signal for at least one sample corresponding to the first received wave received at the detection timing and the average value of the first processing target signal for multiple samples corresponding to the first received wave received in both the first period and the second period. In addition, GO-CFAR processing is a process for obtaining a differential signal based on the difference between the value of the first processing target signal for at least one sample corresponding to the first received wave received at the detection timing, the average value of the first processing target signal for multiple samples corresponding to the first received wave received in the first period, and the average value of the first processing target signal for multiple samples corresponding to the first received wave received in the second period, whichever is larger. According to this structure, by using multiple CFAR processes separately, flexibility can be improved.

[0170] Furthermore, in the embodiment, when the CFAR processing unit 426 performs CA-CFAR processing, the threshold setting unit 428 sets the threshold based on the standard deviation, which serves as an indicator of the deviation in the values of the first processing target signal for multiple samples corresponding to the first received wave received during both the first and second periods. Furthermore, when the CFAR processing unit 426 performs GO-CFAR processing, the threshold setting unit 428 sets the threshold based on the standard deviation corresponding to the larger average value of the standard deviation, which serves as an indicator of the deviation in the values of the first processing target signal for multiple samples corresponding to the first received wave received during the first period, and the standard deviation, which serves as an indicator of the deviation in the values of the first processing target signal for multiple samples corresponding to the first received wave received during the second period. With this configuration, it is possible to set an appropriate threshold by taking into account the appropriate standard deviation depending on the type of CFAR processing.

[0171] In this embodiment, the wave transmitter 411 encodes the first transmission wave to include predetermined identification information before transmitting it. Furthermore, the CFAR processing unit 426 uses a correlation value signal based on a correlation value indicating the similarity between the identification information of the first transmission wave and the first reception wave as the first processing target signal to obtain a difference signal. With this configuration, the correlation value signal can be used as the first processing target signal to easily determine whether the first transmission wave and the first reception wave are similar.

[0172] Furthermore, in the embodiment, the wave transmitter 411 transmits the second transmission wave before transmitting the first transmission wave. Furthermore, the wave receiver 421 receives the second reception wave, which is the second transmission wave reflected by the road surface, serving as an object, before receiving the first reception wave. Object detection device 200 further includes a set value acquisition unit 430 that estimates the shape of the road surface based on information regarding the second processing target signal corresponding to the second reception wave and acquires a set value corresponding to the road surface shape based on the estimation result. Furthermore, CFAR processing unit 426 acquires a differential signal based on the difference between the value of at least one sample of the first processing target signal corresponding to the first reception wave received at the detection timing and the average value of the first processing target signal corresponding to multiple samples of the first reception wave received during at least one of the first and second periods, or the set value, whichever is greater. With this configuration, by always subtracting a value equal to or greater than the set value from the value of the first processing target signal, a differential signal can be acquired that appropriately reduces noise corresponding to, for example, the shape of the road surface.

[0173] Furthermore, in the embodiment, the set value acquisition unit 430 estimates the road surface shape based on coding information indicating whether the second transmitted wave and the second received wave are coded, which is information related to the second processing target signal; an average characteristic based on a moving average of the values of the second processing target signal; and a deviation between the value of the signal represented by the empirical formula that best approximates the second processing target signal among a plurality of pre-set empirical formulas and the value of the second processing target signal, and acquires the set value based on the estimation result. With this configuration, the road surface shape can be appropriately estimated based on the three types of information: coding information, average characteristic, and deviation, and the set value can be appropriately acquired based on the estimation result.

[0174] Furthermore, in the embodiment, set value acquisition unit 430 estimates the road surface shape using a pre-stored road surface estimation table 430a, which indicates the correspondence between coded information, average characteristics, differential deviations, and road surface shape, and acquires the set value using a pre-stored set value table 430b, which indicates the correspondence between the road surface shape and the set value. With this configuration, the road surface shape can be easily estimated simply by referring to road surface estimation table 430a based on the three types of information: coded information, average characteristics, and deviations, and the set value can be easily acquired simply by referring to set value table 430b based on the estimation result.

[0175] Modifications

[0176] In addition, in the above-mentioned embodiment, the technology disclosed in the present invention is applied to a structure for detecting information related to an object by transmitting and receiving ultrasonic waves, but the technology disclosed in the present invention can also be applied to a structure for detecting information related to an object by transmitting and receiving sound waves, millimeter waves, electromagnetic waves, etc. which are fluctuations other than ultrasonic waves.

[0177] In the above-described embodiment, an object detection device that detects the distance to an object is exemplified as an object to which the technology of the present disclosure is applied. However, the technology of the present disclosure can also be applied to an object detection device that only detects the presence or absence of an object as information related to the object.

[0178] Furthermore, in the above-described embodiment, the road surface estimation table 430a, an example of the first setting information, and the setting value table 430b, an example of the second setting information, are configured as separate data. However, both may be configured as a single data set. In other words, the disclosed technology can also perform road surface shape estimation and setting value acquisition based on a single data set representing the correspondence between five types of information: coded information, average characteristics, deviation, road surface shape, and setting values.

[0179] The embodiments and modifications of the present disclosure have been described above, but the above-mentioned embodiments and modifications are merely examples and are not intended to limit the scope of the invention. The above-mentioned new embodiments and modifications can be implemented in various ways and can be omitted, replaced, or changed in various ways without departing from the scope of the invention. The above-mentioned embodiments and modifications are included in the scope and spirit of the invention, and are included in the invention described in the claims and their equivalents.

Claims

1. An object detection device comprising: A transmitting unit, configured to transmit a first transmission wave; a receiving unit for receiving a first reception wave that is the first transmission wave and is reflected by an object and returned; a signal processing unit that samples a first processing target signal corresponding to the first received wave and acquires a differential signal based on a difference between a value of at least one sample of the first processing target signal corresponding to the first received wave received at a certain detection timing and an average value of values of a plurality of sample first processing target signals corresponding to the first received wave received during at least one of a first period and a second period of a predetermined length before and after the detection timing; a threshold setting unit that sets a threshold value to be compared with the value of the difference signal based on a deviation in the values of the first processing target signal of the plurality of samples; as well as a detection unit that detects information related to the object at the detection timing based on a comparison result of the value of the differential signal and the threshold value, The transmitting unit transmits the second transmission wave before transmitting the first transmission wave. The receiving unit receives a second received wave as the second transmitted wave, which is reflected by the road surface as the object and returns, before receiving the first received wave. The object detection device further includes a set value acquisition unit that estimates the shape of the road surface based on information related to the second processing target signal corresponding to the second received wave, and acquires a set value corresponding to the shape of the road surface based on the estimation result. The signal processing unit obtains the differential signal based on a difference between the value of the first processing target signal for the at least one sample corresponding to the first reception wave received at the detection timing and the average value of the first processing target signal for the plurality of samples corresponding to the first reception wave received in at least one of the first period and the second period, whichever is larger, and the set value. The above-mentioned setting value acquisition unit estimates the shape of the above-mentioned road surface based on the coding information, average characteristics, and differential deviation, and acquires the above-mentioned setting value based on the estimation result, wherein the above-mentioned coding information is information related to the above-mentioned second processing object signal, indicating whether the above-mentioned second transmission wave and the above-mentioned second reception wave are encoded; the above-mentioned average characteristics are characteristics based on the moving average of the value of the above-mentioned second processing object signal; and the above-mentioned differential deviation is the deviation of the difference between the value of the signal represented by the experimental formula that best approximates the above-mentioned second processing object signal among a plurality of pre-set experimental formulas and the value of the above-mentioned second processing object signal.

2. The object detection device according to claim 1, wherein: The signal processing unit selectively executes a plurality of CFAR processes including CA-CFAR process and GO-CFAR process according to the setting. In the CA-CFAR processing, the differential signal is obtained based on the difference between the value of the first processing target signal for at least one sample corresponding to the first reception wave received at the detection timing and the average value of the first processing target signal for the plurality of samples corresponding to the first reception wave received in both the first period and the second period. In the above-mentioned GO-CFAR processing, the above-mentioned differential signal is obtained based on the difference between the value of the first processing object signal of the above-mentioned at least one sample portion corresponding to the above-mentioned first reception wave received at the above-mentioned detection timing, the average value of the value of the first processing object signal of the above-mentioned multiple sample portions corresponding to the above-mentioned first reception wave received in the above-mentioned first period, and the average value of the value of the first processing object signal of the above-mentioned multiple sample portions corresponding to the above-mentioned first reception wave received in the above-mentioned second period, among any larger average values.

3. The object detection device according to claim 2, wherein: When the signal processing unit performs the CA-CFAR processing, the threshold setting unit sets the threshold based on a standard deviation that is an indicator of deviations in values of a plurality of samples of the first processing target signal corresponding to the first received wave received in both the first period and the second period. When the signal processing unit performs the GO-CFAR processing, the threshold setting unit sets the threshold based on a standard deviation corresponding to the larger average value, of the standard deviations representing the deviations in the values of the first processing object signal for the plurality of sample portions corresponding to the first reception wave received during the first period and the standard deviations representing the deviations in the values of the first processing object signal for the plurality of sample portions corresponding to the first reception wave received during the second period.

4. The object detection device according to any one of claims 1 to 3, wherein: The transmitting unit encodes the first transmission wave to include predetermined identification information and then transmits it. The signal processing unit acquires the difference signal using, as the first processing target signal, a correlation value signal based on a correlation value indicating a degree of similarity between the identification information of the first transmission wave and the first reception wave.

5. The object detection device according to claim 1, wherein: The setting value acquisition unit estimates the shape of the road surface using first setting information stored in advance as information indicating a correspondence relationship between the coding information, the average characteristic, the deviation of the difference, and the shape of the road surface. The set value acquisition unit acquires the set value using second setting information stored in advance as information indicating a correspondence relationship between the shape of the road surface and the set value.

6. The object detection device according to any one of claims 1 to 3, wherein: The transmitting unit and the receiving unit are integrally configured as a transmitting and receiving unit including a single transducer capable of transmitting and receiving sound waves.

7. The object detection device according to any one of claims 1 to 3, wherein: The detection unit detects the distance to the object as information on the object.

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