Object detection device

Abstract

To provide an object detection device further improved in code determination accuracy.SOLUTION: An object detection device (10) includes a transmission signal generation unit (12), correlation signal generation units (134), and a signal determination unit (14). The transmission signal generation unit can generate a plurality of types of transmission signal whose frequency changes with time, and outputs one of the plurality of types of transmission signal to a transmission unit (111) that transmits a probe wave that is an ultrasonic wave whose frequency has been modulated based on a frequency change mode of the transmission signal. The correlation signal generation units each generate a correlation signal indicating a correlation between a reference signal and a received signal. A plurality of the correlation signal generation units is provided corresponding to the plurality of types of transmission signal. Based on the correlation signal, the signal determination unit performs signal determination, which is determination of whether or not the received wave has a frequency change mode corresponding to the frequency change mode of the probe wave. The signal determination unit performs the signal determination by comparing the plurality of correlation signals.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] The object detection device described in Patent Document 1 includes a transmitting unit, a receiving unit, a frequency matching degree calculation unit, an amplitude peak detection unit, and a distance determination unit. The transmitting unit transmits an ultrasonic wave whose frequency changes in a predetermined pattern over time as a probing wave. The receiving unit receives the ultrasonic wave. The frequency matching degree calculation unit calculates the matching degree between the frequency of the received wave and the predetermined pattern. The amplitude peak detection unit detects the peak of the amplitude of the received wave. Specifically, for example, the amplitude peak detection unit detects the peak of the amplitude of the received wave by comparing the slope of the amplitude of the received wave with a predetermined slope threshold value. The distance determination unit determines the distance to the object based on the matching degree calculated by the frequency matching degree calculation unit and the detection result of the amplitude peak by the amplitude peak detection unit.

[0003] The pattern of the frequencies included in the probing wave appears in the reflected wave when the amplitude of the reflected wave becomes large enough. Therefore, the object detection device described in Patent Document 1 can improve the detection accuracy of the object by determining the distance to the object based on the matching degree of the frequency and the detection result of the amplitude peak.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In this type of object detection device, there is a need to improve the code determination accuracy, that is, the accuracy of determining whether the received wave is a reflected wave from an object of the probe wave transmitted by the device itself, as much as possible. The present invention has been made in view of the circumstances exemplified above. That is, the present invention provides, for example, an object detection device in which the code determination accuracy is further improved. [Means for solving the problem]

[0006] The object detection device (10) described in claim 1 is A transmitting signal generation unit (12) outputs one of the multiple types of transmitting signals to a transmitting unit (111) which can generate multiple types of transmitting signals whose frequency changes over time and transmits a probe wave that is frequency-modulated ultrasound based on the frequency change pattern of the transmitting signal. A correlation signal generation unit (134) generates a correlation signal that shows the correlation between a reference signal corresponding to the transmission signal and a received signal output by the receiving unit (112) in accordance with the received wave, which is an ultrasonic wave received by the receiving unit. A signal determination unit (14) performs a code determination, which is a determination of whether the received wave has a frequency change pattern corresponding to the frequency modulation pattern of the probe wave, based on the correlation signal. An amplitude signal generation unit (132) converts the received signal into an amplitude signal, Equipped with, The correlation signal generation unit is provided in multiple units to correspond to multiple types of the transmission signals, The signal determination unit, In the sign determination range, which is a time range set based on the amplitude signal, Multiple correlation signals By comparing, The aforementioned signal is then evaluated.

[0007] In addition, each element in the application documents may be given a reference numeral in parentheses. However, such reference numerals merely indicate one example of the correspondence between the element and the specific means described in the embodiments described later. Therefore, the present invention is not limited in any way by the notation of the above reference numerals. [Brief explanation of the drawing]

[0008] [Figure 1]This is a block diagram showing the schematic functional configuration of an object detection device according to the first embodiment of the present invention. [Figure 2A] Figure 1 is a graph showing an example of a transmission signal output from the transmission signal generation unit. [Figure 2B] This graph shows another example of a transmission signal output from the transmission signal generation unit shown in Figure 1. [Figure 2C] This graph shows yet another example of a transmission signal output from the transmission signal generation unit shown in Figure 1. [Figure 3] Figure 1 is a graph showing an example of a reference signal used in the correlation signal generation unit. [Figure 4] Figure 1 is a time chart showing an example of code determination by the signal determination unit. [Figure 5] Figure 1 is a flowchart showing an example of code determination by the signal determination unit. [Figure 6A] Figure 4 shows another example of the code determination range method, and Figure 6B shows a time chart. [Figure 6B] Figure 4 shows another example of the code determination range method, and Figure 6A shows a time chart. [Figure 7] Figure 4 is a time chart showing another example of the sign determination range method. [Figure 8A] Figure 4 is a time chart showing yet another example of the method for determining the sign determination range. [Figure 8B] Figure 4 is a time chart showing yet another example of the method for determining the sign determination range. [Figure 8C] Figure 4 is a time chart showing yet another example of the sign determination range method. [Figure 9] Figure 1 is a time chart showing another example of the code determination method by the signal determination unit. [Figure 10] This flowchart shows another example of the code determination method used by the signal determination unit shown in Figure 1. [Figure 11]It is a block diagram showing a schematic functional configuration of an object detection apparatus according to a second embodiment of the present invention. [Figure 12] It is a block diagram showing a schematic functional configuration of an object detection apparatus according to a third embodiment of the present invention. [Figure 13] It is a time chart showing an example of a code determination method by the signal determination unit shown in FIG. 12. [Figure 14] It is a flowchart showing an example of a code determination method by the signal determination unit shown in FIG. 12. [Figure 15] It is a time chart showing another example of a code determination method by the signal determination unit shown in FIG. 12. [Figure 16] It is a flowchart showing another example of a code determination method by the signal determination unit shown in FIG. 12.

MODE FOR CARRYING OUT THE INVENTION

[0009] (Embodiment) Hereinafter, embodiments of the present invention will be described based on the drawings. Note that various modifications applicable to one embodiment may interfere with the understanding of the embodiment if inserted in the middle of the series of explanations regarding the embodiment. For this reason, the modifications will be collectively described after the description of the embodiment.

[0010] (First Embodiment: Configuration) Figure 1 shows a schematic configuration of the object detection device 10 according to the first embodiment. Referring to Figure 1, the object detection device 10 is configured to be mounted on a moving body such as a vehicle and to detect objects B present around the moving body. Here, the object B that the object detection device 10 is to be detected is a tangible object that may obstruct the movement of the moving body on which the object detection device 10 is mounted, and may also be referred to as an "obstacle," "candidate obstacle object," or "target." Furthermore, "detecting" object B means at least detecting the presence of object B, i.e., an obstacle, and may also include measuring the distance to object B, and determining the type of object B (e.g., pedestrian, other vehicle, building, etc.) and shape. For example, obtaining a valid measurement of the distance to object B may indicate the presence of object B corresponding to that measurement. Therefore, even if, for example, the object detection device 10 measures the distance to object B and outputs it to an external device (not shown) mounted on the vehicle, and such output does not include information that directly indicates the presence or absence of object B, the object detection device 10 can still be said to be a device that "detects" object B. "Information that directly indicates the presence or absence" of object B refers to signals or data such as "1" or "HI" if object B is within a predetermined detection range, and "0" or "LO" if it is not. The same applies to the determination of the type and shape of object B; if these are effectively determined, it can indicate the presence of object B corresponding to such determination results.

[0011] In this embodiment, the moving object is a vehicle, specifically an automobile. The vehicle equipped with the object detection device 10 will be referred to as "the vehicle" below. The object detection device 10 is configured to detect object B that has reflected ultrasonic waves by transmitting a probe wave, which is an ultrasonic wave, into the space outside the vehicle and receiving a received wave that includes a reflected wave of the probe wave from an object B present in that external space. The "received wave" may include noise and interference in addition to the reflected wave of the probe wave from object B. The "interference" includes ultrasonic waves transmitted from other devices different from the object detection device 10 mounted on the vehicle, and is typically a probe wave from a similar device mounted on another vehicle, or a reflected wave of such a probe wave from the exterior wall of a building, etc. The object detection device 10 comprises a transmitting / receiving unit 11, a transmitting signal generation unit 12, a receiving signal processing unit 13, a signal determination unit 14, and a control unit 15. The configuration of each part of the object detection device 10 will be described below.

[0012] The transmitting / receiving unit 11 is a component for transmitting probe waves and receiving receiver waves, and comprises a transmitting unit 111 and a receiving unit 112. The transmitting unit 111 is provided to transmit probe waves, which are ultrasonic waves frequency-modulated in correspondence with the transmitting signal ST input from the transmitting signal generation unit 12, into the space outside the vehicle. The receiving unit 112 receives the received ultrasonic waves and is configured to generate a received signal SD according to the reception state of the received waves (i.e., reception strength, frequency, etc.) and output it to the received signal processing unit 13. In this embodiment, the transmitting / receiving unit 11 has a so-called "integrated transmitting and receiving" configuration. That is, the transmitting unit 111 comprises a single transducer 113 having ultrasonic wave transmission and reception functions, and a transmitting circuit 114 electrically connected to the transducer 113. The receiving unit 112 comprises a single transducer 113 common to the transmitting unit 111, and a receiving circuit 115 electrically connected to the transducer 113. The transducer 113 incorporates an electromechanical energy conversion element such as a piezoelectric element and has a predetermined resonant frequency, thus functioning as a so-called resonant ultrasonic microphone.

[0013] The transmitting circuit 114 is configured to drive the transducer 113 based on the input transmitting signal ST, thereby causing the transducer 113 to emit a probe wave in the ultrasonic band. Specifically, the transmitting circuit 114 has a circuit configuration such as a digital / analog conversion circuit and a driver circuit for generating a drive signal to drive the transducer 113 based on the transmitting signal ST. That is, the transmitting circuit 114 is configured to perform processing such as digital / analog conversion on the transmitting signal ST output from the transmitting signal generation unit 12, and to apply the resulting AC voltage, which is the drive signal, i.e., the drive voltage, to the transducer 113. The receiving circuit 115 is configured to generate a received signal SD corresponding to the reception result of the received wave in the transducer 113, and to output the generated received signal SD to the received signal processing unit 13. Specifically, the receiving circuit 115 has a circuit configuration such as an amplification circuit and an analog / digital conversion circuit for converting the element generated voltage, which is an AC voltage generated in the transducer 113 by the reception of the received wave, into the received signal SD. In other words, the receiving circuit 115 is configured to generate and output a received signal SD corresponding to the frequency and amplitude of the received wave by performing signal processing such as amplification and analog / digital conversion on the element generated voltage, which is a voltage signal input from the transducer 113.

[0014] The transmission signal generation unit 12 is configured to generate a transmission signal ST whose frequency changes over time and output it to the transmission unit 111. That is, the transmission signal generation unit 12 has a circuit configuration such as an oscillator circuit that can generate an AC signal (e.g., a pulsed signal) of any frequency within a predetermined frequency range with variable frequency. In this embodiment, the transmission signal generation unit 12 is configured to generate a plurality of types of transmission signals ST with different frequency change patterns, and to output one of these plurality of types of transmission signals ST to the transmission unit 111. Specifically, as shown in Figure 2A, the transmission signal generation unit 12 is configured to generate and output an up transmission signal ST1 which has the characteristic of increasing frequency, and a down transmission signal ST2 which has the characteristic of decreasing frequency. In Figure 2A, the horizontal axis t represents time, and the vertical axis f represents frequency. One of the up transmission signal ST1 and the down transmission signal ST2 corresponds to the "first transmission signal," and the other corresponds to the "second transmission signal." In other words, the transmission signal ST that the transmission signal generation unit 12 can generate and output includes an up transmission signal ST1 and a down transmission signal ST2. In this embodiment, the transmission signal generation unit 12 is configured to selectively generate and output either the up transmission signal ST1 or the down transmission signal ST2. For the sake of simplicity, the up transmission signal ST1 will be referred to as the "first transmission signal" and the down transmission signal ST2 as the "second transmission signal". However, as will be discussed later, it goes without saying that the present invention should not be limited to this embodiment.

[0015] For example, as shown in Figure 2A, the up transmission signal ST1 and the down transmission signal ST2 can be set as signals whose frequency changes curvilinearly and continuously. In this case, the up transmission signal ST1 and the down transmission signal ST2 are set to have a relationship where the frequency change pattern is inverted in the figure. That is, the pattern of frequency increase over time in the up transmission signal ST1 and the pattern of frequency decrease over time in the down transmission signal ST2 are set to be the same. Specifically, the up transmission signal ST1 is set so that its frequency increases over time from a predetermined lower limit frequency fd to a predetermined upper limit frequency fu, and the amount of frequency increase increases over time. On the other hand, the down transmission signal ST2 is set so that its frequency decreases over time from the upper limit frequency fu to the lower limit frequency fd, and the amount of frequency decrease increases over time. Furthermore, when the elapsed time from the starting point, i.e., t=0, is the same, the slope of the up transmission signal ST1, i.e., the amount of frequency increase per unit time, and the slope of the down transmission signal ST2, i.e., the amount of frequency decrease per unit time, are set to be the same. The center frequency fc shown in Figure 2A is the midpoint, or average value, between the lower frequency limit fd and the upper frequency limit fu, and is typically the resonant frequency. The waveforms of the up transmission signal ST1 and the down transmission signal ST2 are set to intersect at the center frequency fc.

[0016] Alternatively, as shown in Figure 2B, for example, the up-transmission signal ST1 and the down-transmission signal ST2 can be set as so-called linear chirp signals, where the frequency changes linearly. In this case, the up-transmission signal ST1 is set so that its frequency increases linearly over time from the lower frequency limit fd to the upper frequency limit fu. On the other hand, the down-transmission signal ST2 is set so that its frequency decreases linearly over time from the upper frequency limit fu to the lower frequency limit fd. Furthermore, the slope of the up-transmission signal ST1, i.e., the frequency increase per unit time, and the slope of the down-transmission signal ST2, i.e., the frequency decrease per unit time, are set to have the same absolute value but opposite signs. Thus, in the example in Figure 2B, as in the example in Figure 2A, the up-transmission signal ST1 and the down-transmission signal ST2 are set to have a relationship where the frequency change pattern is inverted vertically in the figure. In addition, the waveform of the up-transmission signal ST1 and the waveform of the down-transmission signal ST2 are set to have an intersection point at the center frequency fc.

[0017] In the example of the transmission signal ST shown in Figures 2A and 2B, the frequency bandwidth of the up transmission signal ST1 (i.e., fd~fu) and the frequency bandwidth of the down transmission signal ST2 are set to coincide. In contrast, for example, as shown in Figure 2C, the up transmission signal ST1 and the down transmission signal ST2 can be set as so-called shift chirp signals. In this case, the frequency bandwidth of the up transmission signal ST1 and the frequency bandwidth of the down transmission signal ST2 are set to overlap in part and not overlap in the remainder. Specifically, in the example in Figure 2C, the up transmission signal ST1 is set so that its frequency increases linearly over time from the lower limit frequency fd to the upper intermediate frequency fmu. The upper intermediate frequency fmu is the frequency between the upper limit frequency fu and the center frequency fc. On the other hand, the down transmission signal ST2 is set so that its frequency decreases linearly over time from the upper limit frequency fu to the lower intermediate frequency fmd. The lower intermediate frequency fmd is the frequency between the lower limit frequency fd and the center frequency fc. The upper intermediate frequency fmu and the lower intermediate frequency fmd can be set such that their midpoint, or average value, becomes the center frequency fc. The overlapping frequency band is located near the center frequency fc (i.e., from fmd to fmu).

[0018] Referring again to Figure 1, the received signal processing unit 13 is configured to generate an amplitude signal SA and a correlation signal by performing various signal processing, such as filtering, on the received signal SD output from the receiving circuit 115, and output them to the signal determination unit 14. The received signal processing unit 13 has the configuration of an in-vehicle microcomputer equipped with a CPU that performs predetermined functions by executing a program, and / or a hardware circuit configured to perform predetermined processing functions such as filtering. Specifically, the received signal processing unit 13 includes a filter unit 131, an amplitude signal generation unit 132, a reference signal output unit 133, and a correlation signal generation unit 134.

[0019] The filter unit 131 is configured to perform filtering (e.g., bandpass filtering) on ​​the received signal SD and output the filtered signal SF, which is the received signal SD after filtering, to the amplitude signal generation unit 132 and the correlation signal generation unit 134. The amplitude signal generation unit 132 is provided to convert the filtered signal SF into an amplitude signal SA. The "amplitude signal SA" is a signal that indicates the magnitude of the amplitude (e.g., the amplitude envelope) of the received signal SD, which is an AC signal, i.e., the filtered signal SF. Specifically, the amplitude signal generation unit 132 is configured to generate the amplitude signal SA based on the filtered signal SF using a well-known method such as envelope detection and output it to the signal determination unit 14. In the case of the I and Q signals after quadrature detection (i.e., complex signals), applying a low-pass filter can be used to obtain the same effect as applying a bandpass filter to the original signal.

[0020] The reference signal output unit 133 is configured to output a reference signal to the correlation signal generation unit 134 for use in correlation calculations in the correlation signal generation unit 134. "Correlation calculation" refers to calculating the correlation, or similarity, of two signals, or in other words, the "degree of agreement" in the above-mentioned Patent Document 1. The correlation signal, which is the result of the calculation, indicates that the correlation, or similarity, is high if the value is large. The reference signal is a reference signal used for comparison with the frequency characteristics of the received signal SD, or the filtered signal SF, for correlation calculations, and has frequency characteristics corresponding to the frequency characteristics of the transmitted signal ST. That is, the reference signal output unit 133 is configured to determine the reference signal to output to the correlation signal generation unit 134 based on the transmitted signal ST output from the transmitted signal generation unit 12. Specifically, the reference signal output unit 133 outputs a first reference signal SR1 corresponding to the up-transmission signal ST1, or the first-transmission signal, and outputs a second reference signal SR2 corresponding to the down-transmission signal ST2, or the second-transmission signal.

[0021] Here, considering that the transmitted signal ST does not equal the received signal SD due to the microphone characteristics, i.e., the frequency characteristics of the transmitting / receiving unit 11, in this embodiment, as shown in Figure 3, the reference signal is set to a narrower frequency band than the transmitted signal ST. More specifically, Figure 3 shows the correspondence between the transmitted signal ST and the reference signal when both the up-transmitted signal ST1 and the down-transmitted signal ST2 are linear chirp signals. In Figure 3, the transmitted signal ST on the left is the same as in Figure 2B, and SR on the right represents the reference signal. As shown in Figure 3, the first reference signal SR1 is set to a frequency band corresponding to a part of the frequency characteristics of the up-transmitted signal ST1, specifically, approximately half of the frequency band of the up-transmitted signal ST1 centered at the center frequency fc. Furthermore, the first reference signal SR1 has the same slope as the slope of the up-transmitted signal ST1, i.e., the amount of frequency change per unit time. Similarly, the second reference signal SR2 is set to a frequency band corresponding to a part of the frequency characteristics of the down-transmitted signal ST2, specifically, approximately half of the frequency band of the down-transmitted signal ST2 centered at the center frequency fc. Furthermore, the second reference signal SR2 has the same slope as the down-transmit signal ST2.

[0022] Referring again to Figure 1, the correlation signal generation unit 134 is provided to generate a correlation signal that indicates the correlation between the reference signal corresponding to the transmitted signal ST and the filtered signal SF, i.e., the similarity of their frequency characteristics. Specifically, the correlation signal generation unit 134 is configured to generate a correlation signal based on the filtered signal SF using a well-known method and output it to the signal determination unit 14. The correlation signal generation unit 134 has a configuration as a correlation filter (e.g., a matched filter) for correlation processing calculation between the received signal SD, i.e., the filtered signal SF, and the reference signal. As a method for generating the correlation signal, i.e., calculating the correlation, for example, there is a method of vector rotation of the complex received signal based on the reference signal and adding them (see, for example, Japanese Patent Application Publication No. 2022-124824). Correlation filters such as matched filters are already well-known technology at the time of filing this application (see, for example, Japanese Patent Application Publication No. 2008-256568). Therefore, further details regarding the configuration of the correlation signal generation unit 134 and the correlation signal calculation method using it will be omitted.

[0023] In this embodiment, the correlation signal generation unit 134 is provided in multiple units corresponding to the multiple types of transmission signals ST that the transmission signal generation unit 12 can generate and output. That is, the correlation signal generation unit 134 is provided with N correlation filters when the transmission signal generation unit 12 has a configuration that enables it to generate and output N types of transmission signals ST. Specifically, corresponding to the transmission signal generation unit 12 selectively outputting one of two types of transmission signals ST, an up transmission signal ST1 and a down transmission signal ST2, the correlation signal generation unit 134 has a first correlation signal generation unit 134a and a second correlation signal generation unit 134b as correlation filters. The first correlation signal generation unit 134a is provided corresponding to the up transmission signal ST1. The second correlation signal generation unit 134b is provided corresponding to the down transmission signal ST2. Accordingly, the reference signal output unit 133 outputs a first reference signal SR1 to the first correlation signal generation unit 134a and outputs a second reference signal SR2 to the second correlation signal generation unit 134b. The first correlation signal generation unit 134a is configured to generate a first correlation signal SC1, which shows the correlation between the first reference signal SR1 and the filtered signal SF, and output it to the signal determination unit 14. Similarly, the second correlation signal generation unit 134b is configured to generate a second correlation signal SC2, which shows the correlation between the second reference signal SR2 and the filtered signal SF, and output it to the signal determination unit 14.

[0024] The signal determination unit 14 is configured to perform code determination based on the correlation signal generated and output by the correlation signal generation unit 134. "Code determination" is a determination of whether the received wave currently received has a frequency change pattern that corresponds to the frequency modulation pattern of the probe wave transmitted this time (i.e., immediately before the reception of the received wave). In other words, code determination is a determination of whether the received wave currently received by the receiving unit 112 of the object detection device 10 is a reflected wave from object B of the probe wave transmitted from the transmitting unit 111 of the object detection device 10. If the determination is YES, that is, if the received wave currently received by the receiving unit 112 of the object detection device 10 is a reflected wave from object B of the probe wave transmitted from the transmitting unit 111 of the object detection device 10, the received wave will be referred to as a "normal wave" below. Conversely, if the determination is NO, it will be referred to as "interference" below. The signal determination unit 14 has a configuration as an in-vehicle microcomputer equipped with a CPU or the like that performs predetermined functions by the execution of a program, and / or as a hardware circuit configured to perform predetermined functions.

[0025] In this embodiment, the signal determination unit 14 is configured to perform sign determination by comparing multiple correlated signals. Specifically, when the transmission signal generation unit 12 outputs an up transmission signal ST1 as the first transmission signal, the signal determination unit 14 determines that the first correlated signal SC1 is a normal wave if it shows a higher correlation than the second correlated signal SC2, while determining that it is interference if it shows a lower correlation.

[0026] More specifically, the signal determination unit 14 is configured to perform sign determination by comparing multiple correlated signals within a sign determination range, which is a time range set based on the amplitude signal SA. Specifically, the signal determination unit 14 determines at least the starting point of the sign determination range, which is the starting point and time width, based on the amplitude signal SA. The signal determination unit 14 then determines whether the signal is a normal wave or interference based on the comparison result of the maximum value of the first correlated signal SC1 and the maximum value of the second correlated signal SC2 detected within the determined sign determination range. That is, when the transmitted signal ST is an up-transmitting signal ST1, the signal determination unit 14 determines that the received wave is a normal wave if the maximum value of the first correlated signal SC1 is greater, while determining that it is interference if the maximum value of the second correlated signal SC2 is greater. Similarly, when the transmitted signal ST is a down-transmitting signal ST2, the signal determination unit 14 determines that the received wave is a normal wave if the maximum value of the second correlated signal SC2 is greater, while determining that it is interference if the maximum value of the first correlated signal SC1 is greater.

[0027] The control unit 15 is provided to control the overall operation of the object detection device 10. The control unit 15 has the configuration of an in-vehicle microcomputer equipped with a CPU that performs predetermined functions by executing a program, and / or a hardware circuit configured to perform predetermined functions. The control unit 15 is also electrically connected to an external device (not shown) mounted on the vehicle so as to be able to communicate with information. Such an external device is, for example, an electronic control device (i.e., an automatic driving ECU, etc.) that performs driving control of the vehicle using the object detection results from the object detection device 10. ECU stands for Electronic Control Unit. The control unit 15 outputs setting signals to the transmission signal generation unit 12 for setting, i.e., selecting, the transmission signal ST to be output to the transmission unit 111, and transmission instruction signals to control the start and stop of the transmission of the search wave. The control unit 15 also receives the code determination result from the signal determination unit 14. Based on the received code determination result, the control unit 15 generates a detection signal corresponding to the detection result of object B and outputs this detection signal to the external device.

[0028] (First Embodiment: Operation Overview) The following describes the operational overview of the configuration of this embodiment, along with the effects achieved by this configuration, with reference to the drawings. In the following description, the device configuration of the object detection device 10 according to this embodiment, and the object detection method and computer program executed thereunder, may be collectively referred to simply as "this embodiment."

[0029] When predetermined object detection conditions are met, the control unit 15 outputs a setting signal and a transmission instruction signal to the transmission signal generation unit 12. The "predetermined object detection conditions" include, for example, the driving state of the vehicle (i.e., shift position, vehicle speed, etc.). The transmission signal generation unit 12 then generates one of several types of transmission signals ST that can be generated based on the setting signal and outputs it to the transmission unit 111. The transmission unit 111 transmits a probe wave, which is an ultrasonic wave frequency-modulated based on the frequency change pattern of the input transmission signal ST, toward the space outside the vehicle. The probe wave is encoded by frequency modulation based on the transmission signal ST.

[0030] When the receiving unit 112 receives a received wave, which is an ultrasonic wave, it generates a received signal SD, which is a signal corresponding to the amplitude and frequency of the received wave, and outputs it to the received signal processing unit 13. In the received signal processing unit 13, the filter unit 131 performs filtering on the received signal SD to generate a filtered signal SF. The generated filtered signal SF is input to the amplitude signal generation unit 132 and the correlation signal generation unit 134. The amplitude signal generation unit 132 converts the filtered signal SF into an amplitude signal SA and outputs this amplitude signal SA to the signal determination unit 14. The correlation signal generation unit 134 generates a correlation signal showing the correlation between the reference signal output from the reference signal output unit 133 and the filtered signal SF, and outputs it to the signal determination unit 14.

[0031] The signal determination unit 14 performs sign determination based on the amplitude signal SA and correlation signal generated by the received signal processing unit 13. Specifically, the signal determination unit 14 sets a sign determination range based on the amplitude signal SA. The "sign determination range" is the time range used for sign determination in the amplitude signal SA and correlation signal, whose values ​​fluctuate over time; specifically, it is the time range in which the values ​​used for sign determination are detected or extracted. For example, as shown in Figure 4, the signal determination unit 14 sets a predetermined time width W as the sign determination range, starting from the point tA when the amplitude signal SA rises and reaches the amplitude threshold THA. In this specific example, the amplitude threshold THA is set to be variable over time. That is, the amplitude threshold THA has the characteristic of being held constant at a low value, then rising to a high value, being held at the high value for a predetermined period, and then decreasing. The signal determination unit 14 then performs sign determination based on the correlation signal within the set sign determination range.

[0032] Here, for example, if the sign determination range deviates significantly from the center of the reflected wave, there is a possibility of incorrect sign determination. Such problems typically occur when the amplitude of the reflected wave is very large and the amplitude saturates, or when the amplitude signal waveform is distorted by multiple reflected waves. Therefore, in this embodiment, the transmission signal generation unit 12 is provided to selectively output one of several types of transmission signals ST. In addition, multiple correlation signal generation units 134 are provided to correspond to the multiple types of transmission signals ST. The signal determination unit 14 then performs sign determination by comparing the multiple correlation signals generated by the correlation signal generation unit 134.

[0033] Specifically, in the example shown in Figure 4, the amplitude signal SA is assumed to have a sub-amplitude peak PA1 corresponding to interference and a main amplitude peak PA2 corresponding to the normal wave. In this case, the first correlation signal SC1 has a first sub-correlation peak PC11 corresponding to the sub-amplitude peak PA1 and a first main correlation peak PC12 corresponding to the main amplitude peak PA2. The first sub-correlation peak PC11 is a peak that does not exceed the correlation threshold THC. The first main correlation peak PC12 is a peak that exceeds the correlation threshold THC. On the other hand, the second correlation signal SC2 has a second sub-correlation peak PC21 corresponding to the sub-amplitude peak PA1 and a second main correlation peak PC22 corresponding to the main amplitude peak PA2. The second sub-correlation peak PC21 is a peak that exceeds the correlation threshold THC. The second main correlation peak PC22 is a peak that does not exceed the correlation threshold THC. In this regard, as shown in Figure 4, the sign determination range is set to include the first main correlation peak PC12 and the second main correlation peak PC22, while excluding the first sub-correlation peak PC11 and the second sub-correlation peak PC21. Within the set sign determination range, the first principal correlation peak PC12 exceeds the correlation threshold THC, while the second principal correlation peak PC22 does not. That is, the first principal correlation peak PC12 > the second principal correlation peak PC22. Therefore, in this case, the signal determination unit 14 determines that the principal amplitude peak PA2 corresponding to the first principal correlation peak PC12 is due to a reflected wave corresponding to a normal wave. In other words, in this case, the signal determination unit 14 determines that the received wave corresponding to the principal amplitude peak PA2 is a normal wave.

[0034] Figure 5 shows a flowchart corresponding to the determination method described above. In this example of operation, the transmission signal ST is assumed to be the first transmission signal, i.e., the up transmission signal ST1. Also, in the flowchart of Figure 5, "S" is an abbreviation for "step". The same applies to other flowcharts described later.

[0035] Referring to Figure 5, first, in step 501, the signal determination unit 14 detects the rising edge of the amplitude signal SA (i.e., tA shown in Figure 4). Next, in step 502, the signal determination unit 14 sets the sign determination range based on the rising edge of the amplitude signal SA detected in step 501. Subsequently, in step 503, the signal determination unit 14 detects the peaks of the correlation signals within the sign determination range set in step 502. Specifically, the signal determination unit 14 detects peak 1, which is the peak of the first correlation signal SC1, and peak 2, which is the peak of the second correlation signal SC2, within the sign determination range. Then, in step 504, the signal determination unit 14 compares the peaks of the multiple correlation signals detected in step 503. Specifically, the signal determination unit 14 compares the magnitude of peak 1 and peak 2. If peak 1 > peak 2 (i.e., step 504 = YES), the signal determination unit 14 executes the process in step 505. In step 505, the signal determination unit 14 determines that the code included in the received wave is its own code, that is, that the received wave is a normal wave. "Own code" refers to the code, or frequency modulation pattern, included in the probe wave that was actually transmitted. Specifically, for example, if the code of the up transmission signal ST1 is "1" and the code of the down transmission signal ST2 is "0", then if the transmission signal ST corresponding to the probe wave actually transmitted this time is the up transmission signal ST1, then the own code is "1". On the other hand, if peak 1 < peak 2 (i.e., step 504 = NO), the signal determination unit 14 executes the process in step 506. In step 506, the signal determination unit 14 determines that the code included in the received wave is not its own code, that is, that the received wave is interference.

[0036] In this embodiment, code determination is performed by comparing multiple correlation signals (i.e., the first correlation signal SC1 and the second correlation signal SC2) corresponding to multiple transmission signals ST (i.e., the first transmission signal and the second transmission signal). This further improves the accuracy of code determination. Furthermore, by performing code determination based on the rising edge of the amplitude signal SA, misdetermination caused by received waves with small amplitudes, such as road surface reflections, can be effectively suppressed. Moreover, the accuracy of code determination can be further improved by using a so-called shift chirp, as shown in Figure 2C.

[0037] Incidentally, according to the microphone characteristics of the transducer 113, which is a resonant ultrasonic microphone, i.e., the frequency characteristics of the transmitting / receiving unit 11, the transmitted signal ST does not equal the received signal SD. That is, for example, the further the frequency of the drive signal deviates from the resonant frequency, the lower the frequency tracking ability of the probe wave. Therefore, a deviation occurs between the frequency characteristics of the transmitted signal ST and the frequency characteristics of the probe wave that is actually transmitted. Consequently, a deviation also occurs between the frequency characteristics of the received signal SD, which is generated due to the reflected wave of the probe wave, and the frequency characteristics of the transmitted signal ST. For this reason, the frequency bandwidth of the transmitted signal ST can be set wider than the microphone frequency bandwidth. The "microphone frequency bandwidth" is the frequency range from 0 to -3 dB when the gain of the transmitting / receiving unit 11 at the resonant frequency is 0 dB. In this regard, as shown in Figure 3, the accuracy of code determination can be further improved by correcting the reference signal and setting it to a narrower frequency bandwidth than the transmitted signal ST.

[0038] Furthermore, delays occur during filtering and correlation calculations. Specifically, as shown in Figure 4, a time-axis shift can typically occur between the waveform of the amplitude signal SA, the waveform of the first correlation signal SC1, and the waveform of the second correlation signal SC2. Therefore, the signal determination unit 14 corrects for the delays generated during filtering and correlation calculations used to generate at least the correlation signals used for sign determination, and then performs the sign determination. Figure 4 shows the relationship between waveforms after such correction has compensated for the delay. Such corrections can be performed, for example, using a conformance correction value obtained through conformance tests using experiments or computer simulations. This can further improve the accuracy of the sign determination.

[0039] (First embodiment: Modification 1) The following describes a modified example that may be applied to the first embodiment described above. In this modified example, the following description will mainly focus on the parts that differ from the first embodiment. In addition, parts that are the same or equivalent in the first embodiment and this modified example are denoted by the same reference numerals. Therefore, in this modified example, with respect to components that have the same reference numerals as those in the first embodiment, the description in the first embodiment may be appropriately applied unless there is a technical inconsistency or additional explanation is required. The same applies to other modified examples, as well as the second and third embodiments described later.

[0040] In the peak detection in step 503, only peaks that are greater than or equal to the correlation threshold THC may be detected. Furthermore, if no peaks are found during such peak detection, the maximum value within the sign determination range is used. In this case, the maximum value detected may be only those greater than or equal to the correlation threshold THC. Here, the amplitude signal SA and the correlation signal behave differently. Therefore, the signal determination unit 14 may use different values ​​for the amplitude threshold THA, which is the threshold for determining the amplitude signal SA, and the correlation threshold THC, which is the threshold for determining the correlation signal. Specifically, for example, the amplitude threshold THA may be set to change over time. In contrast, the correlation threshold THC may be set as a constant value that does not change over time. By changing the way the amplitude threshold THA and the correlation threshold THC change over time in this way, the accuracy of sign determination can be further improved.

[0041] Furthermore, the signal length of the transmitted signal ST may be changed depending on the specifications of the device and the scene. In this modified example, the signal determination unit 14 sets the time width W of the code determination range based on the signal length of the transmitted signal ST, i.e., the number of pulses. Specifically, Figure 6A shows the case where the signal length is long (for example, 64 pulses). On the other hand, Figure 6B shows the case where the signal length is short (for example, 16 pulses). Referring to Figures 6A and 6B, the time width W of the code determination range is set wider (i.e., longer) when the signal length is long than when the signal length is short. This can further improve the accuracy of code determination. Note that the time width W may be set in two stages, for long and short signal lengths, that is, by selecting a value when the signal length is longer than a predetermined value and a value when the signal length is less than or equal to a predetermined value. Alternatively, the time width W may be set in multiple stages according to the length of the signal.

[0042] (First embodiment: Modification 3) The following describes other modifications with reference to Figures 1 and 7. In this modification, the starting point of the sign determination range can be set to a time tM that is shifted, or corrected, from the time tA at which the amplitude signal SA rises and reaches the amplitude threshold THA. The shift amount (i.e., correction amount), Δt = tA - tM, can be obtained, for example, by fitting tests using experiments or computer simulations, taking the above delay into consideration. Alternatively, Δt can be set variably according to driving conditions such as vehicle speed. Alternatively, Δt can be set, for example, based on the rate of change of the amplitude signal SA at time tA at which the amplitude signal SA rises and reaches a predetermined amplitude threshold THA, as will be described later. This can further improve the accuracy of sign determination.

[0043] (First embodiment: Modification 4) Further modifications will be described below with reference to Figures 1, 8A, 8B, and 8C. In these modifications, the signal determination unit 14 sets the sign determination range based on the rate of change dA of the amplitude signal SA at time tA, when the amplitude signal SA rises and reaches a predetermined amplitude threshold THA. Specifically, Figure 8A shows the case where the rate of change dA is large. On the other hand, Figures 8B and 8C show the case where the rate of change dA is small. As shown in Figures 8A and 8B, the time width W of the sign determination range can be set wider (i.e., longer) when the rate of change dA is large than when it is small. The time width W may be set in two stages, for the case where the rate of change dA is large and the case where it is small, or it may be set in multiple stages. Alternatively, as shown in Figures 8A and 8C, when the rate of change dA is small, the sign determination range may be shifted to the "earlier side" on the time axis, that is, to the side going back in time. Either the change in time width W or the time shift may be used, or they may be used in combination. In this way, by setting the time width W and timing of the sign determination range based on the rate of change dA, the accuracy of sign determination can be further improved.

[0044] (First embodiment: Modification 5) Further modifications will be explained below with reference to Figures 1, 9, and 10. For reference, the amplitude signal SA is also shown as a dotted line in the correlation signal time chart in Figure 9. In this modification, the signal determination unit 14 sets the code determination range based on the point in time when the correlation signal rises and reaches the correlation threshold THC. Specifically, when the transmitted signal ST is the up-transmitted signal ST1, i.e., the first transmitted signal, the signal determination unit 14 detects the point in time tC1 where the correlation threshold THC is reached at the rising portion of the first principal correlation peak PC12, as shown in Figure 9. The signal determination unit 14 also sets a predetermined time width W starting from this point in time tC1 as the code determination range. Then, the signal determination unit 14 performs code determination based on the correlation signal within the set code determination range. Specifically, the signal determination unit 14 performs code determination by comparing the first principal correlation peak PC12 and the second principal correlation peak PC22 within the set code determination range, or by determining whether the first principal correlation peak PC12 is equal to or greater than the correlation threshold THC. This could further improve the accuracy of code determination.

[0045] Figure 10 shows a flowchart corresponding to the above determination method. Referring to Figure 10, first, in step 1001, the signal determination unit 14 detects the rising edge of the correlation signal (i.e., tC1 shown in Figure 9). Next, in step 1002, the signal determination unit 14 sets the sign determination range based on the rising edge of the correlation signal detected in step 1001. Subsequently, in step 1003, the signal determination unit 14 detects the peak of the correlation signal within the sign determination range set in step 1002. The peak detection in step 1003 is the same as step 503 in Figure 5. The processing contents of steps 1004 to 1006 are the same as the processing contents of steps 504 to 506 in Figure 5, respectively.

[0046] (Second embodiment) In the filter section 131 shown in Figure 1, a lower Q value is preferable when determining correlation, but a higher Q value is preferable when generating amplitude signals SA. For this reason, it is preferable to use different filter Q values ​​for generating amplitude signals SA and for generating correlation signals, i.e., the first correlation signal SC1 and the second correlation signal SC2. Figure 11 shows a schematic configuration of an object detection device 10 according to a second embodiment, which is a modification of the first embodiment from this viewpoint. Referring to Figure 11, the object detection device 10 comprises a first filter section 135 and a second filter section 136. That is, this embodiment corresponds to a configuration in which the filter section 131 in the first embodiment is divided into sections for generating amplitude signals SA and sections for generating correlation signals. Furthermore, the Q values ​​of the first filter section 135 and the second filter section 136 are different. Specifically, the Q value of the first filter section 135 is set higher than that of the second filter section 136.

[0047] In this embodiment, the first filter unit 135 is configured to perform filtering on the received signal SD and output the first filtered signal SF1, which is the received signal SD after filtering, to the amplitude signal generation unit 132. The second filter unit 136 is configured to perform filtering on the received signal SD and output the second filtered signal SF2, which is the received signal SD after filtering, to the correlation signal generation unit 134.

[0048] In this configuration, the amplitude signal generation unit 132 generates an amplitude signal SA based on the first filtered signal SF1 obtained by filtering the received signal SD with a first filter unit 135 that has a high Q value. On the other hand, the correlation signal generation unit 134 generates correlation signals, namely the first correlation signal SC1 and the second correlation signal SC2, based on the second filtered signal SF2 obtained by filtering the received signal SD with a second filter unit 136 that has a low Q value. Thus, in this embodiment, it is possible to use different filter Q values ​​for generating the amplitude signal SA and the correlation signals with the simplest possible device configuration. Therefore, according to this embodiment, the accuracy of sign determination can be further improved.

[0049] (Third embodiment) Figure 12 shows a schematic configuration of the object detection device 10 according to the third embodiment. In this embodiment, the signal determination unit 14 performs sign determination based on a normalized correlation signal calculated by normalizing the first filtered signal SF1 output from the first filter unit 135 so that its amplitude is constant, and comparing it with a reference signal. That is, the received signal processing unit 13 includes a normalized correlation signal generation unit 137 that performs so-called normalized correlation processing. The normalized correlation signal is a signal obtained by removing (i.e., reducing) the effect of the amplitude of the received signal SD from the correlation signal. Specifically, corresponding to the fact that the transmission signal generation unit 12 can generate and output two types of transmission signals ST, an up transmission signal ST1 and a down transmission signal ST2, the normalized correlation signal generation unit 137 has a first normalized correlation signal generation unit 137a and a second normalized correlation signal generation unit 137b. The first normalized correlation signal generation unit 137a is provided in correspondence with the up transmission signal ST1, i.e., the first correlation signal generation unit 134a. The first normalized correlation signal generation unit 137a is configured to generate a first normalized correlation signal SN1 by calculating the correlation between the signal obtained by normalizing the second filtered signal SF2 and the first reference signal SR1, and output it to the signal determination unit 14. The second normalized correlation signal generation unit 137b is provided in correspondence with the down transmission signal ST2, i.e., the second correlation signal generation unit 134b. The second normalized correlation signal generation unit 137b is configured to generate a second normalized correlation signal SN2 by calculating the correlation between the signal obtained by normalizing the second filtered signal SF2 and the second reference signal SR2, and output it to the signal determination unit 14.

[0050] In this embodiment, in order to suppress the occurrence of delays due to correlation and normalization calculations as much as possible, the first normalized correlation signal generation unit 137a is provided in parallel with the first correlation signal generation unit 134a. That is, the first normalized correlation signal generation unit 137a is configured to take the first reference signal SR1 and the second filtered signal SF2 as inputs, normalize the amplitude of the second filtered signal SF2, perform a correlation calculation, and output the first normalized correlation signal SN1, which is the result of the calculation, to the signal determination unit 14. In other words, the received signal processing unit 13 has a configuration that allows the generation of correlation signals in the first correlation signal generation unit 134a and the generation of normalized correlation signals in the first normalized correlation signal generation unit 137a to be performed in parallel. Similarly, the second normalized correlation signal generation unit 137b is provided in parallel with the second correlation signal generation unit 134b.

[0051] Figures 13 and 14 show an example of operation in which a sign determination is performed within a sign determination range based on the rising edge of the amplitude signal SA, similar to the first embodiment described above. In Figure 13, the first normalized correlation signal SN1 is obtained by normalizing the second filtered signal SF2 output from the first filter unit 135 so that its amplitude is constant, and then performing a correlation calculation with the first reference signal SR1. Similarly, the second normalized correlation signal SN2 is obtained by normalizing the second filtered signal SF2 and then performing a correlation calculation with the second reference signal SR2. In this example of operation, as shown in Figure 13, the signal determination unit 14 sets a predetermined time width W as the sign determination range, starting from the point tA at which the amplitude signal SA rises and reaches the amplitude threshold THA. The signal determination unit 14 then performs a sign determination based on the correlation signal within the set sign determination range and the normalized correlation signal obtained by normalizing it. Specifically, the signal determination unit 14 detects the peak of the correlation signal within the sign determination range, compares its magnitude, and checks the normalized correlation signal. If the normalized correlation signal is greater than or equal to a predetermined normalization threshold THN, the sign is determined.

[0052] The amplitude of the correlation signal changes not only with the degree of correlation between the received signal SD and the reference signal, but also with the amplitude of the received signal SD; the larger the amplitude of the received signal SD, the larger the amplitude of the correlation signal. For this reason, when a reflected wave with a very large amplitude is received, the amplitude of the correlation signal becomes large, sometimes exceeding the threshold and causing misjudgment. However, by using a correlation signal that excludes the effect of the amplitude of the received signal SD, the judgment accuracy can be improved.

[0053] (Variation 1 of the third embodiment) The normalized correlation signal may also be the signal obtained by dividing the correlation signal by the amplitude signal SA. In this case, the first normalized correlation signal SN1 is obtained by dividing the first correlation signal SC1 by the amplitude signal SA and normalizing it. That is, SN1 = SC1 / SA. Similarly, the second normalized correlation signal SN2 is obtained by dividing the second correlation signal SC2 by the amplitude signal SA and normalizing it. Through normalization processing, a signal independent of the amplitude of the received signal SD can be obtained.

[0054] (Variation 2 of the third embodiment) The normalized correlation signal may be a signal obtained by normalizing the correlation signal using the maximum value of the correlation signal. In this case, the first normalized correlation signal SN1 is obtained by normalizing the maximum value of the first correlation signal SC1 by setting it to "1". That is, SN1 = SC1 / SC1(MAX). Similarly, the second normalized correlation signal SN2 is obtained by normalizing the maximum value of the second correlation signal SC2 by setting it to "1". Through normalization processing, even when the amplitude of the received signal SD is large, a signal can be obtained in which the maximum value of the correlation signal is set to 1. Note that the normalization method is already publicly known or well known at the time of filing of this application, as described in Japanese Patent Application Publication No. 2022-124824, etc. Therefore, further details on the normalization method will be omitted.

[0055] Figure 14 shows a flowchart corresponding to the sign determination method described above. The processing contents of steps 1401 to 1403 shown in Figure 14 are the same as the processing contents of steps 501 to 503 shown in Figure 5. In step 1404, the signal determination unit 14 obtains a normalized correlation signal from the normalized correlation signal generation unit 137. Subsequently, in step 1405, the signal determination unit 14 compares the peaks of the multiple correlation signals detected in step 1403, similar to step 504 shown in Figure 5. Specifically, the signal determination unit 14 compares the magnitudes of peak 1 and peak 2. If peak 1 > peak 2 (i.e., step 1405 = YES), the signal determination unit 14 executes the processing in step 1406. In step 1406, the signal determination unit 14 determines whether the normalized correlation signal corresponding to peak 1 is greater than or equal to the normalization threshold THN, that is, whether the normalized value of the first principal correlation peak PC12 in Figure 13 is greater than or equal to the normalization threshold THN. If the normalized correlation signal is greater than or equal to the normalization threshold THN (i.e., step 1406 = YES), the signal determination unit 14 executes the process in step 1407. In step 1407, the signal determination unit 14 determines that the code included in the received wave is its own code, that is, the received wave is a normal wave. On the other hand, if peak 1 < peak 2 (i.e., step 1405 = NO) or if the normalized correlation signal is less than the normalization threshold THN (i.e., step 1406 = NO), the signal determination unit 14 executes the process in step 1408. In step 1408, the signal determination unit 14 determines that the received wave is interference.

[0056] Figures 15 and 16 show an example of operation in which sign determination is performed within a sign determination range based on the rising edge of the correlation signal. Specifically, in this example, when the transmitted signal ST is the up-transmitted signal ST1, i.e., the first transmitted signal, the signal determination unit 14 detects the time tC1 when the correlation threshold THC is reached at the rising edge of the first principal correlation peak PC12, as shown in Figure 15. The signal determination unit 14 also sets a predetermined time width W starting from the detected time tC1 as the sign determination range. Then, the signal determination unit 14 performs sign determination based on the correlation signal and the normalized correlation signal within the set sign determination range. This can further improve the accuracy of sign determination.

[0057] Figure 16 shows a flowchart corresponding to the above-described code determination method. Referring to Figure 16, first, in step 1601, the signal determination unit 14 detects the rising edge of the correlation signal (i.e., tC1 shown in Figure 15). Next, in step 1602, the signal determination unit 14 sets the code determination range based on the rising edge of the correlation signal detected in step 1601. That is, the processing contents of steps 1601 and 1602 are the same as the processing contents of steps 1001 and 1002 shown in Figure 10, respectively. Also, the processing contents of steps 1603 to 1608 are the same as the processing contents of steps 1403 to 1408 shown in Figure 14, respectively.

[0058] In peak detection in step 1403 and step 1603, only peaks greater than or equal to the correlation threshold THC may be detected. Furthermore, in such peak detection, if no peaks are found, the maximum value within the sign determination range is used. In this case, the maximum value detected may be only those greater than or equal to the correlation threshold THC. Here, the amplitude signal SA, the correlation signal, and the normalized correlation signal each behave differently. Therefore, the signal determination unit 14 may use different values ​​for the amplitude threshold THA, which is the threshold for determining the amplitude signal SA; the correlation threshold THC, which is the threshold for determining the correlation signal; and the normalization threshold THN, which is the threshold for determining the normalized correlation signal. Specifically, for example, as shown in Figure 13, the amplitude threshold THA may be set to change over time. In contrast, the correlation threshold THC and the normalization threshold THN may be set as constant values ​​that do not change over time. Also, in Figures 13 and 15, the normalization threshold THN may be set to a value different from the ratio of the height of the correlation threshold THC to the height of the first principal correlation peak PC12. This can further improve the accuracy of sign determination.

[0059] For example, if an oncoming vehicle equipped with another company's sonar approaches the vehicle, and the ultrasonic waves transmitted from that oncoming vehicle are received as a received wave by the receiving unit 112 of the object detection device 10 in the vehicle, the amplitude of the received wave becomes very large. As a result, the correlation signal on the incorrect code side, which is not the vehicle's own code, becomes large, which may lead to misjudgment. In this respect, according to this embodiment, by using a normalized correlation signal, it is possible to effectively suppress the occurrence of misjudgment.

[0060] (Other variations) The present invention is not limited to the embodiments and modifications described above. In other words, further modifications can be made to the embodiments and modifications described above.

[0061] The present invention is not limited to the device configurations described in the embodiments and modifications above. Specifically, for example, the object detection device 10 is not limited to an in-vehicle configuration (i.e., a configuration mounted on a vehicle). Therefore, for example, the object detection device 10 can be mounted on watercraft such as ships, or on aircraft such as airplanes.

[0062] The transmitting / receiving unit 11 is not limited to a so-called "integrated transmitting and receiving" configuration in which ultrasonic waves can be transmitted and received by a single transducer 113. That is, for example, a transmitting transducer 113 electrically connected to a transmitting circuit 114 and a receiving transducer 113 electrically connected to a receiving circuit 115 may be provided separately.

[0063] As described above, all or part of the part of the object detection device 10 that performs calculations and decisions may be configured as an in-vehicle microcomputer equipped with a CPU, ROM, RAM, non-volatile memory, interface, etc. "Non-volatile memory" is a type of memory that allows the contents to be rewritten when the power is on, but retains the contents when the power is off, and includes flash memory and hard disks. Alternatively, all or part of such a part may be configured with hardware circuits (e.g., ASIC or FPGA) configured to enable the above-described operation. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array.

[0064] Thus, each of the above functional configurations and methods may be implemented by a dedicated computer provided by configuring a processor and memory programmed to execute one or more functions embodied by a computer program. Alternatively, each of the above functional configurations and methods may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, each of the above functional configurations and methods may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer in a computer-readable non-transitional substantial storage medium. That is, each of the above functional configurations and methods can also be expressed as a computer program including procedures for implementing it, or as a non-transitional substantial storage medium storing said program. Examples of non-transitional substantial storage media include ROM, RAM, non-volatile memory, DVD, CD-ROM, etc. The program can be downloaded or upgraded via V2X communication. V2X is an abbreviation for Vehicle to X. Alternatively, such programs may be downloaded or upgraded via terminal equipment installed at manufacturing plants, maintenance facilities, dealerships, etc., for mobile devices such as vehicles.

[0065] The transmission signal generation unit 12 and the reception signal processing unit 13 can be integrated as a module by being provided on the same board. The same applies to the reception signal processing unit 13 and the signal determination unit 14. The same also applies to the signal determination unit 14 and the control unit 15. Therefore, for example, the transmission signal generation unit 12, the reception signal processing unit 13, the signal determination unit 14 and the control unit 15 can be integrated as a module on the same board, and specific signal processing units such as the filter unit 131 can be implemented as hardware circuits, while the remaining parts can be realized by at least one CPU or MPU.

[0066] The filter unit 131 may filter the received signal SD using a well-known FIR filter or IIR filter. Alternatively, the received signal SD may be converted into frequency components (i.e., complex vectors) using quadrature detection, discrete Fourier transform, FFT, etc., before being filtered. If the signal is converted to a complex vector and filtered, the subsequent amplitude signal generation unit 132, correlation signal generation unit 134, and normalized correlation signal generation unit 137 also perform various processing on the complex vector. Processing with a complex vector of frequency components can reduce the size of the hardware circuitry or reduce the computational load on the CPU or MPU.

[0067] The correlation signal generation unit 134 may have a built-in reference signal. That is, the reference signal output unit 133 can be omitted. Also, the same number of correlation signal generation units 134 are provided as there are types of transmission signals ST. For example, if there are four types of transmission signals ST that the transmission signal generation unit 12 can generate and output, then four correlation signal generation units 134 may be provided. However, providing multiple correlation signal generation units 134 does not necessarily mean providing multiple correlation signal generation units 134 individually and in parallel. That is, for example, by switching the input of the reference signal to a single common correlation signal generation unit 134, it is possible to realize multiple correlation signal generation units 134 in a time-division multiplexing manner. In other words, in Figure 1, the first correlation signal generation unit 134a and the second correlation signal generation unit 134b can be integrated. The same applies to the normalized correlation signal generation unit 137 in Figure 12.

[0068] The normalized correlation signal generation unit 137 can also be applied to the configuration shown in Figure 1. That is, the normalized correlation signal generation unit 137 may take the filtered signal SF, which is the output of the filter unit 131, as input. Also, referring to Figure 12, the normalized correlation signal generation unit 137 may be configured to normalize the correlation signal generated by the correlation signal generation unit 134. That is, the first normalized correlation signal generation unit 137a may be configured to take the first correlation signal SC1 output from the first correlation signal generation unit 134a as input and normalize it. Similarly, the second normalized correlation signal generation unit 137b may be configured to normalize the second correlation signal SC2 output from the second correlation signal generation unit 134b.

[0069] The present invention is not limited to the operating modes described in the embodiments and modifications above. Specifically, for example, the frequency change mode in the transmitted signal ST is not limited to monotonically increasing or decreasing as shown in Figure 2A, etc., but may be step-like or the like. Also, the up-transmitted signal ST1 only needs to have the characteristic of increasing frequency overall, and may have a portion in the initial stage where the frequency decreases for a short time from the center frequency fc or a starting frequency near it. The same applies to the down-transmitted signal ST2. Furthermore, the shift chirp signal shown in Figure 2C can be transformed into a curve-like frequency change mode as shown in Figure 2A. Also, in the shift chirp signal shown in Figure 2C, the frequency band of the up-transmitted signal ST1 may be fmd~fu, while the frequency band of the down-transmitted signal ST2 may be fmu~fd. Furthermore, it is possible to set a multi-bit code sequence in which multiple codes are arranged when transmitting a single probe wave. In other words, for example, if the code of the first transmitted signal is set to "1" and the code of the second transmitted signal is set to "0", then the search wave may be assigned a code such as "1010" or "1101". The present invention can be suitably applied to such cases as well.

[0070] In various judgment processes, "greater than or equal to..." and "greater than..." are interchangeable. Similarly, "less than..." and "less than or equal to..." are interchangeable. Furthermore, terms with common or similar meanings, such as "detection," "detection," "measurement," "calculation," and "acquisition," are interchangeable as long as they do not contradict each other technically. That is, for example, "acquiring" a certain characteristic value may include "calculating" the same value and having the same value input.

[0071] It goes without saying that the elements constituting the above embodiments are not necessarily essential unless explicitly stated as particularly essential or considered fundamentally essential. Furthermore, when numerical values ​​such as the number, quantity, or range of components are mentioned, the present invention is not limited to those specific numerical values ​​unless explicitly stated as particularly essential or considered fundamentally limited to those specific numerical values. Similarly, when the shape, direction, positional relationship, etc., of components are mentioned, the present invention is not limited to those shape, direction, positional relationship, etc., unless explicitly stated as particularly essential or considered fundamentally limited to those specific shape, direction, positional relationship, etc.

[0072] Modifications are not limited to the examples given above. That is, all or part of one embodiment may be combined with all or part of another embodiment, to the extent that it is not technically contradictory. Multiple modifications may also be combined with each other. Furthermore, all or part of the above embodiments may be combined with all or part of the modifications.

[0073] (Perspectives included in this disclosure) This disclosure includes at least the following aspects: [First point of view] Object detection device (10), A transmitting signal generation unit (12) outputs one of the multiple types of transmitting signals to a transmitting unit (111) which can generate multiple types of transmitting signals whose frequency changes over time and transmits a probe wave that is frequency-modulated ultrasound based on the frequency change pattern of the transmitting signal. A correlation signal generation unit (134) generates a correlation signal that shows the correlation between a reference signal corresponding to the transmission signal and a received signal output by the receiving unit (112) in accordance with the received wave, which is an ultrasonic wave received by the receiving unit. A signal determination unit (14) performs a signal determination, which is to determine whether the received wave has a frequency change pattern corresponding to the frequency modulation pattern of the probe wave, based on the correlation signal. Equipped with, The correlation signal generation unit is provided in multiple units to correspond to multiple types of the transmission signals, The signal determination unit performs the signal determination by comparing a plurality of the correlation signals. Object detection device. [Second perspective] The multiple types of transmission signals include a first transmission signal and a second transmission signal, Of the first transmission signal and the second transmission signal, one has a monotonically increasing frequency, and the other has a monotonically decreasing frequency. The correlation signal generation unit generates a correlation signal that shows the correlation between the reference signal corresponding to the first transmission signal and the received signal, and a correlation signal that shows the correlation between the reference signal corresponding to the second transmission signal and the received signal. The object detection device described in the first perspective. [Third perspective] The frequency band of the first transmission signal and the frequency band of the second transmission signal are set so that they partially overlap and the remainder does not overlap. The object detection device described in the second perspective. [Fourth perspective] The unit further comprises an amplitude signal generation unit (132) that converts the received signal into an amplitude signal, The signal determination unit performs the signal determination by comparing a plurality of the correlation signals within a sign determination range, which is a time range set based on the amplitude signal. An object detection device described in any one of the three perspectives. [Fifth perspective] The signal determination unit sets the sign determination range based on the rate of change of the amplitude signal at the point when the amplitude signal increases and reaches a predetermined amplitude threshold. The object detection device described in the fourth perspective. [Sixth perspective] Different values ​​are used for the amplitude threshold, which is the threshold for determining the amplitude signal, and the correlation threshold, which is the threshold for determining the correlation signal. An object detection device as described in the fourth or fifth aspect. [Seventh perspective] The amplitude signal generation unit generates the amplitude signal based on the signal obtained by filtering the received signal by the first filter unit (135). The correlation signal generation unit generates the correlation signal based on the signal obtained by filtering the received signal by the second filter unit (136). The first filter section and the second filter section have different Q values. An object detection device described in any one of the 4th to 6th aspects. [Perspective 8] The signal determination unit sets the time width of the code determination range based on the signal length of the transmitted signal. An object detection device described in any one of the four to seven points. [Perspective 9] The signal determination unit performs the signal determination based on a normalized correlation signal obtained by removing the effect of the amplitude of the received signal from the correlation signal. An object detection device described in any one of the eight perspectives. [Perspective 10] The signal determination unit performs the signal determination after correcting the delay that occurs in the filtering process and correlation calculation used to generate the correlation signal used for the signal determination. An object detection device described in any one of the 1st to 9th perspectives. [Perspective 11] The aforementioned transmission signal is a linear chirp signal. An object detection device described in any one of the ten points from the first to the tenth. [Perspective 12] The aforementioned reference signal is set in a frequency band narrower than that of the aforementioned transmission signal. An object detection device described in any one of the 1st to 11th perspectives. [Explanation of symbols]

[0074] 10. Object detection device 111 Transmitter 112 Receiving Unit 12. Transmission signal generation unit 134 Correlation signal generation unit 134a First Correlation Signal Generation Unit 134b Second Correlation Signal Generation Unit 135 First filter section 136 Second filter section 14 Signal determination unit

Claims

1. An object detection device (10), A transmitting signal generation unit (12) outputs one of the multiple types of transmitting signals to a transmitting unit (111) which can generate multiple types of transmitting signals whose frequency changes over time and transmits a probe wave that is frequency-modulated ultrasound based on the frequency change pattern of the transmitting signal. A correlation signal generation unit (134) generates a correlation signal that shows the correlation between a reference signal corresponding to the transmission signal and a received signal output by the receiving unit (112) in response to the received wave, which is an ultrasonic wave received by the receiving unit. A signal determination unit (14) performs a signal determination, which is to determine whether the received wave has a frequency change pattern corresponding to the frequency modulation pattern of the probe wave, based on the correlation signal. An amplitude signal generation unit (132) converts the received signal into an amplitude signal, Equipped with, The correlation signal generation unit is provided in multiple units to correspond to multiple types of the transmission signals, The signal determination unit performs the signal determination by comparing a plurality of the correlation signals within a sign determination range, which is a time range set based on the amplitude signal. Object detection device.

2. The multiple types of transmission signals include a first transmission signal and a second transmission signal, Of the first transmission signal and the second transmission signal, one has a monotonically increasing frequency, and the other has a monotonically decreasing frequency. The correlation signal generation unit generates a correlation signal that shows the correlation between the reference signal corresponding to the first transmission signal and the received signal, and a correlation signal that shows the correlation between the reference signal corresponding to the second transmission signal and the received signal. The object detection device according to claim 1.

3. The frequency band of the first transmission signal and the frequency band of the second transmission signal are set so that they partially overlap and the remainder does not overlap. The object detection device according to claim 2.

4. The signal determination unit sets the sign determination range based on the rate of change of the amplitude signal at the point when the amplitude signal increases and reaches a predetermined amplitude threshold. The object detection device according to claim 1.

5. Different values ​​are used for the amplitude threshold, which is the threshold for determining the amplitude signal, and the correlation threshold, which is the threshold for determining the correlation signal. The object detection device according to claim 1.

6. The amplitude signal generation unit generates the amplitude signal based on the signal obtained by filtering the received signal by the first filter unit (135). The correlation signal generation unit generates the correlation signal based on the signal obtained by filtering the received signal by the second filter unit (136). The first filter section and the second filter section have different Q values. The object detection device according to claim 1.

7. The signal determination unit sets the time width of the code determination range based on the signal length of the transmitted signal. The object detection device according to claim 1.

8. The signal determination unit performs the signal determination based on a normalized correlation signal obtained by removing the effect of the amplitude of the received signal from the correlation signal. An object detection device according to any one of claims 1 to 7.

9. The signal determination unit performs the signal determination after correcting the delay that occurs in the filtering process and correlation calculation used to generate the correlation signal used for the signal determination. The object detection device according to claim 1.

10. The aforementioned transmission signal is a linear chirp signal. The object detection device according to claim 1.

11. The aforementioned reference signal is set in a frequency band narrower than that of the aforementioned transmission signal. The object detection device according to claim 1.

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