Object detection device

Abstract

To provide an object detection device that can minimize an effect of a Doppler shift, reduce variations in correlation results after correlation processing, and stabilize detection performance of an object regardless of the relative speed.SOLUTION: An object detection device that is mounted on a moving body and detects an object existing around the moving body, includes: a transmitter that transmits a transmission wave according to a transmission signal; a receiver that receives a transmission wave reflected by the object as a receiving wave; a relative speed estimation unit that estimates a relative speed between the moving body and the object; a correlation processing unit that, when acquiring a correlation value corresponding to similarity between the transmission signal and a receiving signal according to the receiving wave, changes a window width of a reference window determining a pulse number of the transmission signal for taking a correlation for the receiving signal depending on the relative speed; and a detection unit that, when it is determined that the similarity is at a level of a predetermined threshold value or more, detects information on the object.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Conventionally, an object detection device is known that transmits ultrasonic waves as transmission waves and receives received waves, which are transmission waves reflected by an object and returned, to detect information about the object, such as the distance to the object. For example, Patent Document 1 proposes a technique that enables changing the range of the relative speed of an object to be detected according to the speed of a moving body while improving the reception signal SN ratio when the object detection device is mounted on the moving body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional object detection device, it is known to transmit a burst wave with a long pulse length, receive the reflected wave reflected by the object, and then perform correlation processing using a reference signal equivalent to the transmission wave. When the object detection device is mounted on a moving body (such as a vehicle) to acquire information about the object, when performing correlation processing on the received wave using a burst transmission wave with a long pulse length as the reference signal, the influence of the Doppler shift generated between the moving body and the object becomes large, and the variation in the correlation result after the correlation processing tends to increase. In particular, the faster the relative speed, the greater the variation. In the technique of Patent Document 1 described above, demodulation is performed for each code according to the relative speed. However, when demodulating for each code, there is a problem that it cannot sufficiently cope with changes in the relative speed and sufficient object detection accuracy cannot be obtained.

[0005] Therefore, one of the problems of the present disclosure is to minimize the influence of Doppler shift between a moving body and an object, reduce the variation in the correlation result after correlation processing, and stabilize the detection performance of the object, regardless of the magnitude of the relative speed, when affected by Doppler shift. An object detection device capable of this is provided.

Means for Solving the Problem

[0006] An object detection device as an example of the present disclosure is an object detection device mounted on a moving body and detecting an object existing around the moving body, including a transmitter that transmits a transmission wave corresponding to a transmission signal, a receiver that receives the transmission wave reflected by the object as a reception wave, a relative speed estimation unit that estimates the relative speed between the moving body and the object, and a reference window for determining the number of pulses of the transmission signal for taking correlation with the reception signal when obtaining a correlation value corresponding to the similarity between the transmission signal and the reception signal corresponding to the reception wave. The window width of the reference window is changed according to the relative speed. Width and narrowness It further includes a correlation processing unit that changes the window width according to the relative speed, and a detection unit that detects information about the object when the correlation value is determined to be similar at a level equal to or higher than a predetermined level. According to this configuration, the window width of the reference window when obtaining the correlation value is changed according to the relative speed between the moving body (object detection device) and the object. That is, the number of reference pulses when taking correlation is changed. As a result, the signal-to-noise ratio can be improved regardless of the magnitude of the relative speed, contributing to the stabilization of the object detection performance.

[0007] Also, the correlation processing unit of the above object detection device may change the window width in units of the code length of the transmission signal. According to this configuration, the correlation processing is simplified, contributing to the reduction of the processing burden.

Brief Description of the Drawings

[0008]

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[0009] Hereinafter, embodiments and modifications of the present disclosure will be described with reference to the drawings. The configurations of the embodiments and modifications described below, as well as the operations and effects brought about by the configurations, are merely examples and are not limited to the following description.

[0010] FIG. 1 is an exemplary and schematic diagram showing an appearance of a vehicle 1 equipped with an object detection system including an object detection device according to the embodiment as viewed from above.

[0011] As shown in FIG. 1, the object detection system includes an ECU (Electronic Control Unit) 100 mounted inside a four-wheel vehicle 1 including a pair of front wheels 3F and a pair of rear wheels 3R, and object detection devices 201 to 208 mounted on the exterior of the vehicle 1.

[0012] In the example shown in FIG. 1, as an example, the object detection devices 201 to 204 are installed (arranged) at different positions at predetermined intervals in the vehicle width direction, for example, in a rear bumper of a vehicle body 2 as an exterior of the vehicle 1. Further, the object detection devices 205 to 208 are installed (arranged) at different positions at predetermined intervals in the vehicle width direction, for example, in a front bumper of the vehicle body 2.

[0013] Here, in this embodiment, the hardware configurations and functions of the object detection devices 201 to 208 are the same respectively. Therefore, hereinafter, for simplicity, the object detection devices 201 to 208 may be collectively referred to as the object detection device 200. Also, the predetermined intervals between the object detection devices 200 can be appropriately adjusted according to the shape of the bumper or the like, and do not need to be exactly the same. Also, in the vertical direction, as long as it is within the formation range of the bumper, it does not need to be exactly the same as the vehicle width direction, and some deviation may occur.

[0014] Also, in this embodiment, the installation position of the object detection device 200 is not limited to the example shown in FIG. 1. The object detection device 200 may be installed on at least one of the rear bumper and the front bumper, and may also be installed on the side surface of the vehicle body 2. Also, the object detection device 200 may be installed at any position of the rear bumper or the front bumper. Also, in the embodiment, the number of the object detection devices 200 is not limited to the example shown in FIG. 1.

[0015] Also, for example, two imaging units 102 and 104 are provided on the vehicle body 2. The imaging units 102 and 104 are, for example, digital cameras incorporating imaging elements such as CCD (charge coupled device) and CIS (CMOS image sensor). The imaging units 102 and 104 can output moving image data (imaging image data) at a predetermined frame rate. Each of the imaging units 102 and 104 has a wide-angle lens or a fish-eye lens, and can photograph, for example, a range of 140° to 220° in the horizontal direction. Therefore, the imaging units 102 and 104 can sequentially photograph the road surface on which the vehicle 1 can move, stop lines, parking frame lines, division lines, etc. attached to the road surface, and objects (for example, walls, trees, humans, bicycles, vehicles, etc.) existing around and far away from the vehicle 1, and output them as imaging image data.

[0016] The imaging unit 102 is provided, for example, inside the rear window on the rear side of the vehicle body 2, or on the rear bumper or the like. The imaging unit 104 is provided, for example, inside the front window on the front side of the vehicle body 2, or on the front bumper, front grille, or the like. The captured imaging image data is subjected to arithmetic processing and image processing, and can be used for generating an image with a wider viewing angle and for generating a virtual viewpoint image viewed from above. Further, the imaging image data captured by the imaging unit 102 or the imaging unit 104 can be used for estimating the relative speed between the object included in the imaging image data and the host vehicle (vehicle 1) based on the imaging image data and the host vehicle speed, and can be used for correlation processing in the object detection device 200.

[0017] Based on the configuration as described below, the object detection system according to the present embodiment transmits and receives ultrasonic waves, and acquires the time difference of the transmission and reception, etc., thereby detecting information regarding objects (for example, the object O shown in FIG. 2 described later) including other vehicles and humans existing around.

[0018] FIG. 2 is an exemplary and schematic block diagram showing the hardware configurations of the ECU 100 and the object detection device 200 of the object detection system according to the embodiment.

[0019] As shown in FIG. 2, the ECU 100 has a hardware configuration similar to that of a normal computer. More specifically, the ECU 100 includes an input / output device 110, a storage device 120, and a processor 130.

[0020] The input / output device 110 is an interface for realizing the transmission and reception of information between the ECU 100 and the outside (the object detection device 200 in the example shown in FIG. 1).

[0021] 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).

[0022] The processor 130 is in charge of various processes executed in the ECU 100. The processor 130 includes an arithmetic unit such as a CPU (Central Processing Unit) for example. By reading and executing the computer program stored in the storage device 120, the processor 130 realizes various functions such as parking assistance for example.

[0023] On the other hand, as shown in FIG. 2, the object detection device 200 includes a transceiver 210 and a control unit 220. With these configurations, the object detection device 200 is configured as an in-vehicle sonar as an example of an in-vehicle sensor that detects the distance to an object (object O) existing around the vehicle 1.

[0024] The transceiver 210 has a vibrator 211 such as a piezoelectric element, and the vibrator 211 realizes transmission and reception of ultrasonic waves.

[0025] More specifically, the transceiver 210 transmits the ultrasonic wave generated in response to the vibration of the vibrator 211 as a transmission wave, and receives the vibration of the vibrator 211 brought about by the ultrasonic wave transmitted as the transmission wave being reflected by an object existing outside and returning. In the example shown in FIG. 2, as an object that can reflect the ultrasonic wave from the transceiver 210, the road surface RS and an object O installed on or movable on the road surface RS are exemplified.

[0026] Note that in the example shown in FIG. 2, a configuration in which both transmission of the transmission wave and reception of the reception wave are realized by a single transceiver 210 having a single vibrator 211 is exemplified. However, the technology of the embodiment is naturally applicable to a configuration in which the transmission-side configuration and the reception-side configuration are separated, such as a configuration in which a vibrator for transmitting the transmission wave and a vibrator for receiving the reception wave are provided separately for example.

[0027] The control unit 220 has a hardware configuration similar to that of a normal computer. More specifically, the control unit 220 includes an input / output device 221, a storage device 222, and a processor 223.

[0028] The input / output device 221 is an interface for realizing the transmission and reception of information between the control unit 220 and the outside (in the example shown in FIG. 1, the ECU 100 and the transceiver 210). Also, vehicle speed information acquired by the vehicle speed sensor 10 is input to the input / output device 221. Further, imaging image data captured by the imaging unit 102 or the imaging unit 104 is input to the input / output device 221 via the input / output device 110, and is used for estimating the relative speed between the vehicle 1 and the object O based on the vehicle speed information and the imaging image data.

[0029] The storage device 222 includes a main storage device such as a ROM or a RAM, and / or an auxiliary storage device such as an HDD or an SSD.

[0030] The processor 223 controls various processes executed in the control unit 220. The processor 223 includes an arithmetic unit such as a CPU, for example. The processor 223 realizes various functions by reading and executing a computer program stored in the storage device 222.

[0031] Here, the object detection device 200 according to the embodiment detects the distance to an object as one of the information regarding the object by a technique called the so-called TOF (Time Of Flight) method. As will be described in detail below, the TOF method is a technique for calculating the distance to an object in consideration of the difference between the timing when a transmission wave is transmitted (more specifically, when transmission starts) and the timing when a reception wave is received (more specifically, when reception starts).

[0032] FIG. 3 is an exemplary and schematic diagram for explaining the outline of the technique used by the object detection device 200 according to the embodiment to detect the distance to an object.

[0033] In the example shown in FIG. 3, the temporal change in the signal level (e.g., amplitude) of the ultrasonic wave transmitted and received by the object detection device 200 according to the embodiment is represented in a graph format. In the graph shown in FIG. 3, 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 transmitter / receiver 210 (vibrator 211).

[0034] In the graph shown in FIG. 3, the solid line L11 represents an example of an envelope (envelope waveform) that represents the temporal change in the signal level of the signal transmitted and received by the object detection device 200, that is, the degree of vibration of the vibrator 211. From this solid line L11, it can be read that the vibrator 211 is driven to vibrate for a time Ta from the timing t0, and the transmission of the transmission wave is completed at the timing t1, and then the vibration of the vibrator 211 continues while decaying due to inertia during the time Tb until the timing t2 is reached. Therefore, in the graph shown in FIG. 3, the time Tb corresponds to the so-called reverberation time.

[0035] The solid line L11 reaches a peak where the degree of vibration of the vibrator 211 exceeds (or is equal to) a predetermined threshold Th1 represented by the dashed-dotted line L21 at the timing t4 when a time Tp has elapsed from the timing t0 when the transmission of the transmission wave started. This threshold Th1 is a value preset to identify whether it is caused by the reception of the received wave as the transmission wave reflected by the object to be detected (e.g., the object O shown in FIG. 2) and returned, or whether it is caused by the reception of the received wave as the transmission wave reflected by an object outside the detection target (e.g., the road surface RS shown in FIG. 2) and returned.

[0036] Note that FIG. 3 shows an example in which the threshold Th1 is set as a constant value that does not change with the passage of time, but in the embodiment, the threshold Th1 may be set as a value that changes with the passage of time.

[0037] Here, vibrations having peaks exceeding (or equal to) the threshold Th1 can be regarded as being caused by the reception of a received wave as a transmitted wave reflected back by the object to be detected. On the other hand, vibrations having peaks below (or less than) the threshold Th1 can be regarded as being caused by the reception of a received wave as a transmitted wave reflected back by an object other than the object to be detected.

[0038] Therefore, from the solid line L11, it can be read that the vibration of the vibrator 211 at timing t4 is caused by the reception of a received wave as a transmitted wave reflected back by the object to be detected.

[0039] Note that in the solid line L11, after timing t4, the vibration of the vibrator 211 is attenuating. Therefore, timing t4 corresponds to the timing when the reception of the received wave as a transmitted wave reflected back by the object to be detected is completed, in other words, the timing when the transmitted wave finally transmitted at timing t1 returns as a received wave.

[0040] Also, in the solid line L11, the timing t3 as the start point of the peak at timing t4 corresponds to the timing when the reception of the received wave as a transmitted wave reflected back by the object to be detected starts, in other words, the timing when the transmitted wave first transmitted at timing t0 returns as a received wave. Therefore, in the solid line L11, the time ΔT between timing t3 and timing t4 is equal to the time Ta as the transmission time of the transmitted wave.

[0041] Based on the above, in order to obtain the distance to the object to be detected by the TOF method, it is necessary to obtain the time Tf between the timing t0 when the transmitted wave starts to be transmitted and the timing t3 when the received wave starts to be received. This time Tf can be obtained by subtracting the time ΔT equal to the time Ta as the transmission time of the transmitted wave from the time Tp as the difference between the timing t0 and the timing t4 when the signal level of the received wave reaches a peak exceeding the threshold Th1.

[0042] The timing t0 when the transmission wave starts being transmitted can be easily specified as the timing when the object detection device 200 starts operating, and the time Ta as the transmission time of the transmission wave is determined in advance by settings or the like. Therefore, ultimately, in order to obtain the distance to the object to be detected by the TOF method, it is important to specify the timing t4 when the signal level of the received wave reaches a peak exceeding the threshold Th1.

[0043] Therefore, conventionally, a correlation value corresponding to the similarity between the transmission wave and the received wave is obtained (calculated), and based on the comparison result between the correlation value and a predetermined threshold, it is determined whether the similarity is at a level of a predetermined value or more, and the timing determined to be at a level of a predetermined value or more in similarity is specified as the timing t4 when the received wave reaches a peak exceeding the threshold Th1. The correlation value is a value that reaches a peak when the waveforms of the transmission wave and the received wave are similar (matched) at a level of a predetermined value or more, which is calculated based on a generally well-known autocorrelation function or the like.

[0044] By the way, when at least one of the vehicle 1 equipped with the object detection device 200 and the object O is moving, the received wave is affected by the Doppler shift, the variation of the correlation result after the correlation processing becomes large, and it may be difficult to accurately compare with the threshold Th1. In addition, since the relative speed changes depending on the moving states of the vehicle 1 and the object O, there is a possibility that the comparison accuracy with the threshold Th1 further decreases.

[0045] Therefore, in the present embodiment, by configuring the object detection device 200 as follows, when taking the correlation between the transmission wave and the received wave, the influence of the Doppler shift is reduced, and obtaining an accurate correlation value is realized.

[0046] FIG. 4 is an exemplary and schematic block diagram showing the detailed configuration of the object detection device 200 according to the embodiment. In the example shown in FIG. 4, the configuration of the transmission side and the configuration of the reception side are separated, but the illustrated mode is for convenience of explanation only. In the embodiment, as described above, both the transmission of the transmission wave and the reception of the reception wave are realized by a (single) transceiver 210 having a (single) vibrator 211.

[0047] As shown in FIG. 4, the object detection device 200 includes, as a configuration on the transmission side, a transmitter 311, a code generation unit 312, a carrier wave output unit 313, a multiplier 314, and an amplifier circuit 315. Further, the object detection device 200 includes, as a configuration on the reception side, a receiver 321, an amplifier circuit 322, a filter processing unit 323, a correlation processing unit 324, a relative speed estimation unit 324a, an envelope processing unit 325, a threshold processing unit 326, and a detection unit 327.

[0048] Note that a part of the configuration shown in FIG. 4 is realized by dedicated hardware (analog circuit), and the remaining part can be realized as a result of cooperation between hardware and software, more specifically, as a result of the processor 223 of the control unit 220 reading and executing a computer program from the storage device 222.

[0049] First, the configuration on the transmission side will be briefly described.

[0050] The transmitter 311 is composed of the above-described vibrator 211, and the vibrator 211 transmits a transmission wave (for example, ultrasonic wave) corresponding to the (amplified) transmission signal output from the amplifier circuit 315. As will be described below, in the embodiment, an encoded signal generated by attaching identification information of a predetermined code length to a carrier wave is output as a transmission signal that is the basis of the transmission wave.

[0051] The code generation unit 312 generates a signal (pulse signal) corresponding to a code of a bit string composed of a continuous series of bits of 0 or 1, for example. The length of this bit string corresponds to the code length of the identification information given to the transmission signal.

[0052] The carrier wave output unit 313 outputs a carrier wave as a signal to which identification information is to be added. The carrier wave is configured as, for example, a sine wave of an arbitrary frequency.

[0053] The multiplier 314 multiplies the output from the code generation unit 312 and the output from the carrier wave output unit 313 to perform modulation of the carrier wave so as to add identification information. Then, the multiplier 314 outputs the modulated carrier wave with the identification information added thereto as a transmission signal that serves as the basis of the transmission wave to the amplifier circuit 315. Note that as the modulation method, a single modulation method that is generally well-known, such as an amplitude modulation method, a phase modulation method, or a frequency modulation method, or a combination of two or more thereof can be used.

[0054] In this way, in the embodiment, the combination of the code generation unit 312, the carrier wave output unit 313, and the multiplier 314 functions as a transmission signal output unit that outputs, as a transmission signal that serves as the basis of the transmission wave, an encoded signal generated by adding identification information of a predetermined code length to the carrier wave to the transmitter 311 side. Since the identification information is basically not lost due to reflection, based on the identification information, it is possible to more easily or more reliably determine the similarity between the transmission signal and the reception signal corresponding to the reception wave received when the transmission wave corresponding to the transmission signal returns due to reflection.

[0055] The amplifier circuit 315 amplifies the transmission signal output from the multiplier 314 and outputs the amplified transmission signal to the transmitter 311. Note that the amplifier circuit 315 also supplies the amplified transmission signal to the correlation processing unit 324 and uses it as a reference signal when performing correlation processing.

[0056] Next, the configuration of the receiving side will be briefly described.

[0057] The receiver 321 is composed of the above-described vibrator 211, and the vibrator 211 receives the transmission wave reflected by the object as a reception wave. As described above, since the transmission wave contains identification information, the reception wave also contains the same identification information.

[0058] The amplifier circuit 322 amplifies the received signal as a signal corresponding to the received wave received by the receiver 321.

[0059] The filter processing unit 323 performs filtering processing on the received signal amplified by the amplifier circuit 322 to suppress noise.

[0060] The correlation processing unit 324 obtains the above-described correlation value corresponding to the similarity between the transmitted wave and the received wave. More specifically, the correlation processing unit 324 uses the transmission signal output from the amplifier circuit 315 as a reference signal for performing correlation processing on the received signal, and obtains a correlation value. As described above, the correlation value is generally calculated based on a well-known correlation function or the like.

[0061] FIG. 5 is a diagram schematically showing the waveform of the received signal SI received by the receiver 321 when a transmission signal with a code such as "1110010" of 7-bit length is output as identification information from the transmitter 311. As described above, since the identification information is basically maintained, a similar code also exists in the received signal SI.

[0062] For example, when performing correlation processing in normal processing, correlation is taken for all waveforms of the 7-bit length "1110010". That is, the correlation processing unit 324 obtains the correlation value of the received signal SI using the 7-bit length waveform (reference signal) based on the transmission signal provided from the amplifier circuit 315. In this case, the window width of the reference window that determines the pulse length W1 (number of pulses) of the reference signal at the time of correlation is set to a window width corresponding to the 7-bit length. As a result, when the received signal SI is affected by the Doppler shift, the correlation result may also be greatly affected by the Doppler shift, and the SN ratio may be good or bad, which causes a large variation in the correlation result (correlation value).

[0063] FIG. 6 is a diagram showing the correlation result when correlation processing is performed. The horizontal axis represents the frequency, and the vertical axis represents the amount of drop in the correlation value (signal level) when affected by the Doppler shift. In this case, since the pulse length to be subjected to the correlation processing is long (for 7 symbol lengths), a peak value appears at the center frequency HC. However, when affected by the Doppler shift, at the position of the frequency HF shifted by ΔH (for example, several kHz) from the center frequency HC, the signal level may drop significantly (for example, the amount of drop is -a dB). That is, the correlation can only be obtained near the center frequency HC, resulting in low peak detection accuracy. Note that the relationship between -a indicating the amount of drop and -b and -c to be described later is that -a has a larger drop than -b, and -b has a larger drop than -c.

[0064] On the other hand, in the correlation processing unit 324 of the present embodiment, the window width of the reference window M for determining the number of pulses of the reference signal during correlation is changeable. For example, FIG. 7 shows that the window width of the reference window M is set to the reference window M1 corresponding to 1 symbol length (for example, 5 pulses). In this case, since the pulse length W2 for taking the correlation becomes shorter than the pulse length W1 shown in FIG. 5, even when the received signal SI is affected by the Doppler shift, the influence of the Doppler shift on the correlation result is reduced, and the SN ratio is improved.

[0065] FIG. 8 is a diagram showing the correlation result when correlation processing is performed using the reference window M1. In this case, since the pulse length for the correlation target becomes shorter than the pulse length when the entire symbol length is used, it is difficult to be affected by the Doppler shift during correlation, and the drop in the signal level at the position of the frequency HF shifted by ΔH (for example, several kHz) from the center frequency HC due to the influence of the Doppler shift is reduced (for example, the amount of drop is -b dB). That is, the peak detection accuracy during correlation is improved.

[0066] The window width of the reference window M shown in FIG. 9 is set to be even shorter than the reference window M1 (for example, 1 pulse). In this case, since the pulse length W3 for taking the correlation becomes shorter than the pulse length W2 shown in FIG. 7, even when the received signal SI is affected by the Doppler shift, the influence of the Doppler shift on the correlation result is further reduced, and the SN ratio is further improved.

[0067] FIG. 10 is a diagram showing the correlation result when correlation processing is performed using the reference window M2. In this case, since the pulse length to be correlated is 1 pulse, it is less susceptible to the influence of Doppler shift during correlation, and the signal level drop at the position of the frequency HF shifted by ΔH (for example, several kHz) from the center frequency HC due to the influence of Doppler shift is further reduced (for example, the drop amount is -cdB). That is, the peak detection accuracy during correlation is further improved.

[0068] Thus, by changing the window width of the reference window M (for example, shortening the window width), it is possible to make it less susceptible to the influence of Doppler shift. Note that the Doppler shift increases as the relative speed increases. In other words, according to the speed of the relative speed, by changing the window width of the reference window M, the influence of the Doppler shift received during correlation processing can be adjusted. For example, when the relative speed is high, the window width of the reference window M is narrowed as shown in FIG. 9. As a result, correlation processing can be performed in a state less susceptible to the influence of Doppler shift. That is, it can contribute to the improvement of the SNR. Conversely, when the relative speed is low, the window width of the reference window M is widened. In this case, since the relative speed is low, the influence of Doppler shift is small. In addition to the small signal level drop at the position of the frequency HF shifted by ΔH (for example, several kHz) from the above-mentioned center frequency HC, it is possible to improve the SNR by increasing the pulse length to be correlated. As a result, the SNR of the entire correlation processing can be improved.

[0069] As described above, the correlation processing unit 324 can obtain information regarding the relative speed from the relative speed estimation unit 324a and determine the window width of the reference window M, thereby realizing correlation processing that is less susceptible to the influence of Doppler shift.

[0070] Note that, in FIG. 7, the case of setting a reference window M1 (e.g., 5 pulse lengths) corresponding to one code length is shown, and in FIG. 9, the case of setting a reference window M2 corresponding to one pulse length is shown. In the present embodiment, the set value of the window width of the reference window M is not limited to this. For example, as shown in FIG. 11, the pulse length (the number of pulses captured in the reference window M) can be set as appropriate. In the case of FIG. 11, the reference window M3 shows the case of a pulse length W4 (e.g., 3 pulse lengths). The relationship between the relative speed and the window width of the reference window M may be determined in advance by tests or the like, for example, mapped, or may be calculated each time by a predetermined calculation formula.

[0071] Also, in FIG. 7, the case of setting a reference window M1 (e.g., 5 pulse lengths) with a window width corresponding to one vehicle code length is shown. In other embodiments, the window width of the reference window M may vary (be set) in units of code length, such as two vehicle body code lengths or three code lengths. In this case, the setting of the window width of the reference window M becomes easy, the correlation processing is simplified, and it can contribute to reducing the processing load. Note that the window width of M can also be set as appropriate in units of the number of pulses regardless of the code length, and it can contribute to realizing correlation processing that is less affected by the Doppler shift.

[0072] Returning to FIG. 4, the envelope processing unit 325 obtains the envelope of the waveform of the signal corresponding to the correlation value obtained by the correlation processing unit 324.

[0073] The threshold processing unit 326 compares the value of the envelope obtained by the envelope processing unit 325 with a predetermined threshold.

[0074] Based on the comparison result by the threshold processing unit 326, the detection unit 327 identifies the timing (the timing t4 shown in FIG. 3) when the signal level of the received wave reaches a peak exceeding the threshold, and detects the distance to the object by the TOF method.

[0075] An example of the processing flow related to object detection of the object detection device 200 (object detection system) configured as described above will be described using the flowchart of FIG. 12.

[0076] First, the object detection device 200 uses a code generation unit 312, a carrier wave output unit 313, and a multiplier 314 to set the transmitted signal, which is generated by attaching identification information of a predetermined code length to a carrier wave, as the transmitted wave that serves as the basis for the transmitted signal. Then, the transmitted signal is amplified by an amplifier circuit 315 and provided to a transmitter 311. The transmitter 311 transmits a transmitted wave corresponding to the transmitted signal as ultrasonic waves outward from the vehicle 1 (S100).

[0077] Then, the receiver 321 receives, as a received wave, a reflected wave that returns to the vehicle 1 side as a transmitted wave reflected by an object (object O) existing outside the vehicle 1 (S102).

[0078] Then, the received received wave is amplified by an amplifier circuit 322, filtered by a filter processing unit 323 (S104), and supplied to a correlation processing unit 324.

[0079] In accordance with the acquisition of the received wave, the correlation processing unit 324 acquires the relative speed between the vehicle 1 and the object (object O) from a relative speed estimation unit 324a (S106).

[0080] In the correlation processing unit 324, as described above, the window width of the reference window M corresponding to the relative speed is set, correlation processing is executed, and a correlation value is acquired (S108).

[0081] Then, in an envelope processing unit 325, an envelope of the waveform of the signal corresponding to the correlation value acquired by the correlation processing unit 324 is calculated. A threshold processing unit 326 compares the value of the envelope with a predetermined threshold and executes threshold processing to determine whether or not the identification information of the transmitted wave and the received wave is similar at a level equal to or higher than a predetermined level based on the comparison result. Then, the detection unit 327 identifies the timing at which the similarity of the identification information of the transmitted wave and the received wave reaches a level equal to or higher than a predetermined level, that is, the timing at which the signal level of the received wave as the transmitted wave returned by reflection exceeds the threshold (for example, the timing t4 shown in FIG. 3), and executes TOF conversion processing for detecting the distance to the object by the TOF method (S112).

[0082] Then, the object detection device 200 checks whether the object detection process end condition is satisfied. For example, when the ignition switch of the vehicle 1 is turned off or an end operation of the object detection process by the user is confirmed and the object detection process end condition is satisfied (Yes in S114), this flow is temporarily terminated. On the other hand, when the object detection process end condition is not satisfied (No in S114), the process returns to the process of S100, and the above-described process is repeatedly executed to continue the object detection process.

[0083] As described above, according to the object detection device 200 (object detection system) of the present embodiment, when affected by the Doppler shift between the vehicle 1 (moving body) and the object O (object), regardless of the magnitude of the relative speed, the influence of the Doppler shift can be minimized, the variation in the correlation result after the correlation process can be reduced, and the detection performance of the object can be stabilized.

[0084] In the above-described embodiment, the technology of the present disclosure is applied to a configuration that detects information about an object by transmitting and receiving ultrasonic waves. However, the technology of the present disclosure can also be applied to a configuration that detects information about an object by transmitting and receiving waves other than ultrasonic waves, such as sound waves, millimeter waves, or electromagnetic waves.

[0085] As described above, the present embodiment and the modified example have been described. However, the above-described embodiment and the modified example are merely examples and are not intended to limit the scope of the invention. The above-described novel embodiment and the modified example can be implemented in various forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The above-described embodiment and the modified example are included in the scope and gist of the invention and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0086] 1…Vehicle, 10…Vehicle speed sensor, 200…Object detection device, 210…Transceiver, 211…Vibrator, 220…Control unit, 221…Input / output device, 222…Memory device, 223…Processor, 311…Transmitter, 321…Receiver, 324…Correlation processing unit, 324a…Relative speed estimation unit, M, M1, M2, M3…Reference window.

Claims

**Claim 1** An object detection device mounted on a moving body for detecting an object existing around the moving body, comprising: a transmitter that transmits a transmission wave corresponding to a transmission signal; a receiver that receives the transmission wave reflected by the object as a reception wave; a relative velocity estimator that estimates a relative velocity between the moving body and the object; a correlation processing unit that changes the window width of a reference window for determining the number of pulses of the transmission signal for correlating with the reception signal according to the relative velocity when obtaining a correlation value corresponding to the similarity between the transmission signal and the reception signal corresponding to the reception wave; a detection unit that detects information about the object when the correlation value is determined to be similar at a level equal to or higher than a predetermined level; An object detection device comprising the above components. **Claim 2** The object detection device according to claim 1, wherein the correlation processing unit changes the window width in units of the code length of the transmission signal.

Images