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 technology]

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

[0003] The frequency pattern contained in the search wave appears in the reflected wave when the amplitude of the reflected wave becomes large to a certain extent. Therefore, the object detection device described in Patent Document 1 can improve the object detection accuracy by determining the distance to the object based on the frequency match and the detection result of the amplitude peak. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7000981 Summary of the Invention [Problem to be solved by the invention]

[0005] In this type of object detection device, it is required to improve as much as possible the code determination accuracy, i.e., the accuracy of determining whether the currently received wave is a reflection wave of the search wave transmitted by the device itself by an object. The present invention has been made in consideration of the above-mentioned circumstances. That is, the present invention provides an object detection device with, for example, further improved code determination accuracy. [Means for solving the problem]

[0006] The object detection device (10) according to claim 1 comprises: a transmission signal generating unit (12) capable of generating a plurality of types of transmission signals whose frequencies change over time, and outputting one of the plurality of types of transmission signals to a transmitting unit (111) that transmits a search wave that is an ultrasonic wave whose frequency is modulated based on the frequency change mode of the transmission signal; a correlation signal generating unit (134) that generates a correlation signal indicating a correlation between a reference signal corresponding to the transmission signal and a reception signal output in response to a reception wave, which is an ultrasonic wave received by a receiving unit (112); a signal determination unit (14) that performs code determination based on the correlation signal to determine whether or not the received wave has a frequency change pattern corresponding to the frequency modulation pattern of the search wave; Equipped with A plurality of correlation signal generators are provided corresponding to a plurality of types of the transmission signals, The signal determination unit performs the code determination by comparing a plurality of the correlation signals.

[0007] In addition, in each section of the application documents, each element may be given a reference number in parentheses. However, such a reference number merely indicates an example of the correspondence between the element and the specific means described in the embodiment described later. Therefore, the present invention is not limited in any way by the description of the reference numbers above. [Brief description of the drawings]

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

[0009] (Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that various modified examples applicable to one embodiment may be hindered from understanding the embodiment if they are inserted in the middle of a series of explanations related to the embodiment. For this reason, the modified examples are described together after the explanation of the embodiment.

[0010] (First embodiment: configuration) FIG. 1 shows a schematic configuration of an object detection device 10 according to a first embodiment. Referring to FIG. 1, the object detection device 10 is configured to be mounted on a moving body such as a vehicle and detect an object B present around the moving body. Here, the object B, which is the detection target of the object detection device 10, is a tangible object that may be an obstacle to the movement of the moving body on which the object detection device 10 is mounted, and may also be referred to as an "obstacle", an "obstacle candidate object", or a "target". In addition, "detecting" the object B means detecting at least the presence of the object B, i.e., an obstacle, and may also include measuring the distance to the object B, determining the type (e.g., pedestrian, other vehicle, building, etc.) and shape of the object B, and the like. For example, the fact that a valid measurement value of the distance to the object B has been obtained may indicate the presence of the object B corresponding to the measurement value. Therefore, for example, even if the object detection device 10 measures the distance to object B and outputs the measured distance to an external device (not shown) mounted on the vehicle, and such output does not include information directly indicating the presence or absence of object B, such object detection device 10 can be said to be a device that "detects" object B. The "information directly indicating the presence or absence" of object B is, for example, a signal or data that is "1" or "HI" when object B is present within a predetermined detection range, and is "0" or "LO" when object B is not present. The same applies to the determination of the type and shape of object B, and the fact that these have been effectively determined can indicate the presence of object B corresponding to such determination result.

[0011] In this embodiment, the moving body is a vehicle, specifically an automobile. In addition, a vehicle equipped with the object detection device 10 is hereinafter referred to as the "own vehicle". The object detection device 10 is configured to transmit an ultrasonic search wave to the external space of the own vehicle and to receive a received wave including a reflected wave of the search wave by an object B present in the external space, thereby detecting the object B that has reflected the reflected wave. The "received wave" may include noise and interference in addition to the reflected wave of the search wave by the object B. The "interference" includes ultrasonic waves transmitted from another device different from the object detection device 10 mounted on the own vehicle, and is typically a search wave from a device of the same type mounted on another vehicle, or a reflected wave of the search wave by an outer wall of a building or the like. The object detection device 10 includes a transmission / reception unit 11, a transmission signal generation unit 12, a reception signal processing unit 13, a signal determination unit 14, and a control unit 15. The configuration of each unit in the object detection device 10 will be described below.

[0012] The transmitting / receiving unit 11 is a component for transmitting a search wave and receiving a received wave, and includes a transmitting unit 111 and a receiving unit 112. The transmitting unit 111 is provided so as to be capable of transmitting a search wave, which is an ultrasonic wave frequency-modulated in response to a transmission signal ST input from the transmission signal generating unit 12, to the external space of the vehicle. The receiving unit 112 is configured to receive the received wave, which is an ultrasonic wave, and to generate a received signal SD corresponding to the reception state (i.e., reception strength, frequency, etc.) of the received wave and output it to the received signal processing unit 13. In this embodiment, the transmitting / receiving unit 11 has a so-called "integrated transmitting / receiving type" configuration. That is, the transmitting unit 111 includes one transducer 113 having an ultrasonic transmission function and a receiving function, and a transmitting circuit 114 electrically connected to the transducer 113. The receiving unit 112 includes one transducer 113 common to the transmitting unit 111, and a receiving circuit 115 electrically connected to the transducer 113. The transducer 113 has a built-in electromechanical energy conversion element such as a piezoelectric element, and has a configuration as a so-called resonance type ultrasonic microphone having a predetermined resonance frequency.

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

[0014] The transmission signal generating unit 12 is provided to generate a transmission signal ST whose frequency changes with time and output it to the transmitting unit 111. That is, the transmission signal generating unit 12 has a circuit configuration such as an oscillator circuit capable of generating an AC signal (e.g., a pulse-shaped signal) of any frequency within a predetermined frequency range with a variable frequency. In this embodiment, the transmission signal generating unit 12 is configured to generate a plurality of types of transmission signals ST whose frequency change manners are different, and to output one of the plurality of types of transmission signals ST to the transmitting unit 111. Specifically, as shown in FIG. 2A and the like, the transmission signal generating unit 12 is configured to generate and output an up transmission signal ST1 whose frequency is increased and a down transmission signal ST2 whose frequency is decreased. In FIG. 2A and the like, the horizontal axis t indicates time, and the vertical axis f indicates 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". That is, the transmission signal ST that the transmission signal generating unit 12 can generate and output includes an up transmission signal ST1 and a down transmission signal ST2. In this embodiment, the transmission signal generating unit 12 is configured to selectively, i.e., alternatively, generate and output either the up transmission signal ST1 or the down transmission signal ST2. Hereinafter, for the sake of simplicity of explanation, the up transmission signal ST1 corresponds to the "first transmission signal" and the down transmission signal ST2 corresponds to the "second transmission signal". However, as will be described later, it goes without saying that the present invention should not be limited to such an embodiment.

[0015] For example, as shown in FIG. 2A, the up transmission signal ST1 and the down transmission signal ST2 may be set as signals whose frequencies change continuously and in a curved manner. In this case, the up transmission signal ST1 and the down transmission signal ST2 are set in a relationship in which the change manner of the frequency is upside down in the figure. That is, the frequency increase manner of the up transmission signal ST1 over time and the frequency decrease manner of the down transmission signal ST2 over time are set to match. Specifically, the up transmission signal ST1 is set so that the frequency increases from a predetermined lower limit frequency fd to a predetermined upper limit frequency fu over time, and the frequency increase amount increases over time. On the other hand, the down transmission signal ST2 is set so that the frequency decreases from the upper limit frequency fu to the lower limit frequency fd over time, and the frequency decrease amount increases over time. And, when the elapsed time from the start point, i.e., the point of t=0, is the same, the slope of the up transmission signal ST1, i.e., the frequency increase amount per unit time, and the slope of the down transmission signal ST2, i.e., the frequency decrease amount per unit time, are set to be the same. The center frequency fc shown in Fig. 2A is the intermediate value, i.e., the average value, between the lower limit frequency fd and the upper limit frequency fu, and is typically a resonant frequency. The waveform of the up transmission signal ST1 and the waveform of the down transmission signal ST2 are set to have an intersection at the center frequency fc.

[0016] Alternatively, for example, as shown in FIG. 2B, the up transmission signal ST1 and the down transmission signal ST2 may be set as so-called linear chirp signals whose frequencies change linearly. In this case, the up transmission signal ST1 is set so that the frequency increases linearly from the lower limit frequency fd to the upper limit frequency fu over time. On the other hand, the down transmission signal ST2 is set so that the frequency decreases linearly from the upper limit frequency fu to the lower limit frequency fd over time. The slope of the up transmission signal ST1, i.e., the frequency increase amount per unit time, and the slope of the down transmission signal ST2, i.e., the frequency decrease amount per unit time, are set so that their absolute values ​​are the same and their signs, i.e., their positive and negative signs are opposite. In this way, in the example of FIG. 2B as in the example of FIG. 2A, the up transmission signal ST1 and the down transmission signal ST2 are set so that their frequency change modes are upside down in the figure. Also, the waveform of the up transmission signal ST1 and the waveform of the down transmission signal ST2 are set so that they have an intersection at the center frequency fc.

[0017] Here, in the example of the transmission signal ST shown in FIG. 2A and FIG. 2B, the frequency band in the up transmission signal ST1 (i.e., fd to fu) and the frequency band in the down transmission signal ST2 are set to coincide with each other. In contrast, for example, as shown in FIG. 2C, the up transmission signal ST1 and the down transmission signal ST2 can be set as so-called shifted chirp signals. In this case, the frequency band in the up transmission signal ST1 and the frequency band in the down transmission signal ST2 are set to overlap partially and not overlap the remaining portions. Specifically, in the example of FIG. 2C, the up transmission signal ST1 is set so that the frequency increases linearly from the lower limit frequency fd to the upper intermediate frequency fmu over time. The upper intermediate frequency fmu is a 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 the frequency decreases linearly from the upper limit frequency fu to the lower intermediate frequency fmd over time. The lower intermediate frequency fmd is a 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 so that the intermediate value, i.e., the average value, of the two is the center frequency fc. The overlapping frequency band portion is provided near the center frequency fc (i.e., fmd to fmu).

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

[0019] The filter unit 131 is configured to perform a filter process (e.g., band-pass filter process) on the received signal SD, and output a filtered signal SF, which is the received signal SD after the filter process, 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 indicating the magnitude of the amplitude (e.g., the amplitude envelope) of the received signal SD, which is an AC signal, that is, the filtered signal SF. Specifically, the amplitude signal generation unit 132 is configured to generate the amplitude signal SA using a well-known method such as envelope detection based on the filtered signal SF, and output it to the signal determination unit 14. Note that in the case of I, Q signals (i.e., complex signals) after quadrature detection, applying a low-pass filter can achieve the same effect as applying a band-pass filter to the original signal.

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

[0021] Here, taking into consideration that the transmission signal ST does not equal the reception signal SD due to the microphone characteristics, i.e., the frequency characteristics of the transmission / reception unit 11, in this embodiment, as shown in FIG. 3, the reference signal is set to a frequency band narrower than that of the transmission signal ST. More specifically, FIG. 3 shows the correspondence relationship between the transmission signal ST and the reference signal when the up transmission signal ST1 and the down transmission signal ST2 are both linear chirp signals. In FIG. 3, the transmission signal ST on the left side is the same as that in FIG. 2B, and SR on the right side indicates the reference signal. As shown in FIG. 3, the first reference signal SR1 is set to a part of the frequency characteristics in the up transmission signal ST1, specifically, a frequency band corresponding to approximately half of the frequency band in the up transmission signal ST1 with the center frequency fc as the center. In addition, the first reference signal SR1 has the same slope as the slope in the up transmission signal ST1, i.e., the amount of frequency change per unit time. Similarly, the second reference signal SR2 is set to a part of the frequency characteristics in the down transmission signal ST2, specifically, a frequency band corresponding to approximately half of the frequency band in the down transmission signal ST2 with the center frequency fc as the center. Moreover, the second reference signal SR2 has the same gradient as the gradient of the down transmission signal ST2.

[0022] Referring again to FIG. 1, the correlation signal generating unit 134 is provided to generate a correlation signal indicating the correlation between the reference signal corresponding to the transmission signal ST and the filtered signal SF, i.e., the similarity of the frequency characteristics. Specifically, the correlation signal generating 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 determining unit 14. The correlation signal generating 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. Examples of methods for generating a correlation signal, i.e., calculating the correlation, include a method of vector rotating and adding a complex received signal based on a reference signal (see, for example, JP 2022-124824 A, etc.). Correlation filters such as matched filters are already well-known technologies at the time of filing the present application (see, for example, JP 2008-256568 A, etc.). Therefore, further detailed explanation of the configuration of the correlation signal generating unit 134 and the correlation signal calculation method used thereby will be omitted.

[0023] In this embodiment, a plurality of correlation signal generators 134 are provided corresponding to a plurality of types of transmission signals ST that the transmission signal generator 12 can generate and output. That is, when the transmission signal generator 12 has a configuration capable of generating and outputting N types of transmission signals ST, the correlation signal generator 134 is provided with N correlation filters. Specifically, the correlation signal generator 134 has a first correlation signal generator 134a and a second correlation signal generator 134b as correlation filters in response to the transmission signal generator 12 selectively outputting one of two types of transmission signals ST, the up transmission signal ST1 and the down transmission signal ST2. The first correlation signal generator 134a is provided corresponding to the up transmission signal ST1. The second correlation signal generator 134b is provided corresponding to the down transmission signal ST2. In response to this, the reference signal output unit 133 outputs the first reference signal SR1 to the first correlation signal generator 134a and outputs the second reference signal SR2 to the second correlation signal generator 134b. The first correlation signal generator 134a is configured to generate a first correlation signal SC1 indicating the correlation between the first reference signal SR1 and the filtered signal SF, and output the first correlation signal SC1 to the signal determiner 14. Similarly, the second correlation signal generator 134b is configured to generate a second correlation signal SC2 indicating the correlation between the second reference signal SR2 and the filtered signal SF, and output the second correlation signal SC2 to the signal determiner 14.

[0024] The signal determination unit 14 is provided to perform code determination based on the correlation signal generated and output by the correlation signal generation unit 134. The "code determination" is a determination of whether or not the currently received received wave has a frequency change pattern corresponding to the frequency modulation pattern of the search wave transmitted this time (i.e., immediately before the reception of the received wave). In other words, the code determination is a determination of whether or not the currently received received wave received by the receiving unit 112 in the object detection device 10 is a reflected wave by the object B of the search wave transmitted from the transmitting unit 111 in the object detection device 10. If the determination is YES, that is, if the currently received received wave received by the receiving unit 112 in the object detection device 10 is a reflected wave by the object B of the search wave transmitted from the transmitting unit 111 in the object detection device 10, the received wave will be referred to as a "normal wave" below. On the other hand, if the determination is NO, the received wave will be referred to as a "interference" below. The signal determination unit 14 is configured as an on-board microcomputer including a CPU or the like that performs a predetermined function by executing a program, and / or as a hardware circuit configured to perform a predetermined function.

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

[0026] More specifically, the signal determination unit 14 is configured to perform code determination by comparing a plurality of correlation signals in a code determination range, which is a time range set based on the amplitude signal SA. Specifically, the signal determination unit 14 is configured to determine at least the start point of the code determination range and the time width based on the amplitude signal SA. Then, the signal determination unit 14 is configured to determine whether the received wave is a normal wave or interference based on a comparison result between the maximum value of the first correlation signal SC1 and the maximum value of the second correlation signal SC2 detected in the determined code determination range. That is, when the transmission signal ST is an up transmission signal ST1, the signal determination unit 14 determines that the received wave is a normal wave if the maximum value of the first correlation signal SC1 is larger, while determining that the received wave is interference if the maximum value of the second correlation signal SC2 is larger. Similarly, when the transmission signal ST is a down transmission signal ST2, the signal determination unit 14 determines that the received wave is a normal wave if the maximum value of the second correlation signal SC2 is larger, while determining that the received wave is interference if the maximum value of the first correlation signal SC1 is larger.

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

[0028] (First embodiment: operation overview) Below, an overview of the operation of the configuration of this embodiment will be described together 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 thereby may be collectively referred to simply as "this embodiment."

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

[0030] When the receiving unit 112 receives a received wave that is an ultrasonic wave, it generates a received signal SD that 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 executes a filter process on the received signal SD to generate a filtered signal SF. The generated filtered signal SF is input to the amplitude signal generating unit 132 and the correlation signal generating unit 134. The amplitude signal generating unit 132 converts the filtered signal SF to an amplitude signal SA and outputs the amplitude signal SA to the signal determining unit 14. The correlation signal generating unit 134 generates a correlation signal indicating 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 determining unit 14.

[0031] The signal determination unit 14 executes code determination based on the amplitude signal SA and the correlation signal generated by the reception signal processing unit 13. Specifically, the signal determination unit 14 sets a code determination range based on the amplitude signal SA. The "code determination range" is a time range used for code determination in the amplitude signal SA and the correlation signal whose values ​​vary with time, specifically, a time range in which a value used for code determination is detected or extracted. For example, as shown in FIG. 4, the signal determination unit 14 sets a predetermined time width W starting from a time tA at which the amplitude signal SA rises and reaches the amplitude threshold THA as the code determination range. In this specific example, the amplitude threshold THA is set to be variable according to the passage of time. That is, the amplitude threshold THA has a 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 of time, and then falling. Then, the signal determination unit 14 executes code determination based on the correlation signal in the set code determination range.

[0032] Here, for example, if the code determination range is significantly shifted from the center of the reflected wave, there is a possibility that the code determination will be erroneous. Such a defect typically occurs when the amplitude of the reflected wave is very large and saturated, or when the amplitude signal waveform is disturbed by multiple reflected waves. Therefore, in this embodiment, the transmission signal generation unit 12 is provided to selectively output one of multiple types of transmission signals ST. Also, multiple correlation signal generation units 134 are provided corresponding to the multiple types of transmission signals ST. Then, the signal determination unit 14 performs code determination by comparing the multiple correlation signals generated by the correlation signal generation unit 134.

[0033] Specifically, in the example shown in FIG. 4, the amplitude signal SA has a sub-amplitude peak PA1 corresponding to interference and a main amplitude peak PA2 corresponding to a 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 FIG. 4, the sign determination range is set to not include the first sub-correlation peak PC11 or the second sub-correlation peak PC21, but to include the first main correlation peak PC12 and the second main correlation peak PC22. In the set code judgment range, the first main correlation peak PC12 exceeds the correlation threshold THC, while the second main correlation peak PC22 does not exceed the correlation threshold THC. That is, the first main correlation peak PC12>the second main correlation peak PC22. In this case, the signal judgment unit 14 judges that the main amplitude peak PA2 corresponding to the first main correlation peak PC12 is due to a reflected wave corresponding to a normal wave. In other words, in this case, the signal judgment unit 14 judges that the received wave corresponding to the main amplitude peak PA2 is a normal wave.

[0034] Fig. 5 shows a flowchart corresponding to the above-mentioned determination mode. In this operation example, the transmission signal ST is the first transmission signal, that is, the up transmission signal ST1. In addition, in the flowchart of Fig. 5, "S" is an abbreviation of "step". The same applies to other flowcharts described later.

[0035] 5, first, in step 501, the signal determination unit 14 detects the rising edge of the amplitude signal SA (i.e., tA shown in FIG. 4). Next, in step 502, the signal determination unit 14 sets a code determination range based on the rising edge of the amplitude signal SA detected in step 501. Then, in step 503, the signal determination unit 14 detects a peak of the correlation signal in the code determination range set in step 502. Specifically, the signal determination unit 14 detects peak 1, which is a peak in the first correlation signal SC1, and peak 2, which is a peak in the second correlation signal SC2, in the code determination range. Then, in step 504, the signal determination unit 14 compares the peaks of the 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 of step 505. In step 505, the signal determination unit 14 determines that the code included in the current received wave is the own code, that is, the current received wave is a normal wave. The "own code" is the code, that is, the frequency modulation mode, included in the actually transmitted search wave. 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", when the transmission signal ST corresponding to the search wave actually transmitted this time is the up transmission signal ST1, 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 of step 506. In step 506, the signal determination unit 14 determines that the code included in the current received wave is not the own code, that is, the current received wave is interference.

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

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

[0038] In addition, a delay occurs in the filtering process and the correlation calculation. That is, referring to FIG. 4, a shift along the time axis may usually 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 performs the code determination after correcting the delay occurring in the filtering process and the correlation calculation used to generate at least the correlation signal used in the code determination. FIG. 4 shows the relationship between the waveforms in a state where the delay is compensated by such correction. Such correction may be performed, for example, using an adaptive correction value obtained by an adaptive test using an experiment or a computer simulation. This may further improve the accuracy of the code determination.

[0039] (First embodiment: Modification 1) A modified example that can be applied to the first embodiment will be described below. In the following description of this modified example, the differences from the first embodiment will be mainly described. In addition, the same reference numerals are used for the same or equivalent parts in the first embodiment and this modified example. Therefore, in the following description of this modified example, the description of the first embodiment may be appropriately used for components having the same reference numerals as those in the first embodiment, unless there is a technical contradiction or a special additional description. The same applies to other modified examples, the second embodiment, the third embodiment, and the like described later.

[0040] In the peak detection in step 503, only peaks equal to or greater than the correlation threshold THC may be detected. In addition, in the case where there is no peak in the peak detection, the maximum value in the code determination range is used. In this case, the maximum value to be detected may be only a value equal to or greater than 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 a threshold for determining the amplitude signal SA, and the correlation threshold THC, which is a threshold for determining the correlation signal. Specifically, for example, the amplitude threshold THA may be set so as to change with time. In contrast, the correlation threshold THC may be set as a constant value that does not change with time. In this way, by changing the manner of change over time between the amplitude threshold THA and the correlation threshold THC, the accuracy of the code determination may be further improved.

[0041] Also, the signal length of the transmission signal ST may be changed according to the specifications of the device, the scene, and the like. Therefore, in this modification, the signal determination unit 14 sets the time width W of the code determination range based on the signal length of the transmission signal ST, i.e., the number of pulses. Specifically, FIG. 6A shows a case where the signal length is long (e.g., 64 pulses). Meanwhile, FIG. 6B shows a case where the signal length is short (e.g., 16 pulses). With reference to FIGS. 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 the code determination. Note that the time width W may be set in two stages, when the signal length is long and when it is short, that is, by selecting a value when the signal length is longer than a predetermined value and a value when the signal length is equal to or less than the predetermined value. Alternatively, the time width W may be set in multiple stages according to the length of the signal length.

[0042] (First embodiment: Modification 3) Hereinafter, another modified example will be described with reference to Fig. 1 and Fig. 7. In this modified example, the start point of the sign determination range can be set to a time tM shifted, i.e., corrected, from a time tA when the amplitude signal SA rises and reaches an amplitude threshold THA. The shift amount (i.e., correction amount) Δt=tA-tM can be obtained, for example, by a compatibility test using an experiment or a computer simulation, taking into account the above-mentioned delay. Alternatively, Δt can be set variably according to, for example, driving conditions such as vehicle speed. Alternatively, Δt can be set, for example, based on the rate of change (i.e., the slope of the tangent) of the amplitude signal SA at a time tA when the amplitude signal SA rises and reaches a predetermined amplitude threshold THA, as will be described later. This can further improve the accuracy of the sign determination.

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

[0044] (First embodiment: Modification 5) Hereinafter, another modified example will be described with reference to FIG. 1, FIG. 9, and FIG. 10. For reference, the amplitude signal SA is also shown by a dotted line in the correlation signal time chart in FIG. 9. In this modified example, the signal determination unit 14 sets the code determination range based on the time when the correlation signal rises and reaches the correlation threshold value THC. Specifically, when the transmission signal ST is an up transmission signal ST1, i.e., a first transmission signal, the signal determination unit 14 detects the time tC1 when the correlation threshold value THC is reached at the rising part of the first main correlation peak PC12, as shown in FIG. 9. In addition, the signal determination unit 14 sets a predetermined time width W starting from the time tC1 as the code determination range. Then, the signal determination unit 14 executes the code determination based on the correlation signal in the set code determination range. Specifically, the signal determination unit 14 performs the code determination by comparing the first main correlation peak PC12 and the second main correlation peak PC22 in the set code determination range and by determining whether the first main correlation peak PC12 is equal to or greater than the correlation threshold value THC. This can further improve the accuracy of the code determination.

[0045] Fig. 10 shows a flow chart corresponding to the above-mentioned determination mode. Referring to Fig. 10, first, in step 1001, the signal determination unit 14 detects the rising edge of the correlation signal (i.e., tC1 shown in Fig. 9). Next, in step 1002, the signal determination unit 14 sets a code determination range based on the rising edge of the correlation signal detected in step 1001. Then, in step 1003, the signal determination unit 14 detects a peak of the correlation signal within the code determination range set in step 1002. The peak detection in step 1003 is the same as step 503 in Fig. 5. The process contents of steps 1004 to 1006 are the same as the process contents of steps 504 to 506 in Fig. 5, respectively.

[0046] Second Embodiment The Q value in the filter unit 131 shown in FIG. 1 is preferably low when correlation is sought, but is preferably high when the amplitude signal SA is generated. For this reason, it is preferable to use different filter Q values ​​for generating the amplitude signal SA and for generating the correlation signals, i.e., the first correlation signal SC1 and the second correlation signal SC2. FIG. 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 FIG. 11, the object detection device 10 includes a first filter unit 135 and a second filter unit 136. That is, this embodiment corresponds to a configuration in which the filter unit 131 in the first embodiment is divided into one for generating the amplitude signal SA and one for generating the correlation signal. The first filter unit 135 and the second filter unit 136 have different Q values. That is, the Q value of the first filter unit 135 is set higher than that of the second filter unit 136.

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

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

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

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

[0051] 13 and 14 show an operation example in which the sign determination is performed in a sign determination range based on the rising edge of the amplitude signal SA, as in the first embodiment. In FIG. 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 the 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 operation example, as shown in FIG. 13, the signal determination unit 14 sets a predetermined time width W starting from a time tA at which the amplitude signal SA rises and reaches an amplitude threshold THA as the sign determination range. Then, the signal determination unit 14 performs sign determination based on the correlation signal in the set sign determination range and the normalized correlation signal obtained by normalizing the correlation signal. Specifically, the signal determination unit 14 detects the peak of the correlation signal in the sign determination range, performs a magnitude comparison, and checks the normalized correlation signal, and determines the sign if the normalized correlation signal is equal to or greater than a predetermined normalization threshold THN.

[0052] The amplitude of the correlation signal changes not only depending on the correlation between the received signal SD and the reference signal, but also on 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, exceeding the threshold and resulting in an erroneous judgment; however, by using a correlation signal that eliminates the influence of the amplitude of the received signal SD, the judgment accuracy is improved.

[0053] (Modification 1 of the third embodiment) The normalized correlation signal may be a 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. The normalization process makes it possible to obtain a signal that is not dependent on the amplitude of the received signal SD.

[0054] (Modification 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 as "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 as "1". By the normalization process, a signal with the maximum value of the correlation signal set to 1 can be obtained even when the amplitude of the received signal SD is large. Note that the normalization method is already publicly known or well-known at the time of filing of the present application, as described in JP 2022-124824 A and the like. For this reason, further details regarding the normalization method will be omitted.

[0055] FIG. 14 shows a flowchart corresponding to the above-mentioned code determination mode. The process contents of steps 1401 to 1403 shown in FIG. 14 are the same as the process contents of steps 501 to 503 shown in FIG. 5, respectively. In step 1404, the signal determination unit 14 acquires a normalized correlation signal from the normalized correlation signal generation unit 137. Next, 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 FIG. 5. Specifically, the signal determination unit 14 compares the magnitude of peak 1 with that of peak 2. If peak 1>peak 2 (i.e., step 1405=YES), the signal determination unit 14 executes the process of step 1406. In step 1406, the signal determination unit 14 determines whether the normalized correlation signal corresponding to peak 1 is equal to or larger than the normalization threshold value THN, that is, whether the value obtained by normalizing the first main correlation peak PC12 in FIG. 13 is equal to or larger than the normalization threshold value THN. If the normalized correlation signal is equal to or greater than the normalized threshold THN (i.e., step 1406=YES), the signal judgment unit 14 executes the process of step 1407. In step 1407, the signal judgment unit 14 judges that the code contained in the currently received wave is the own code, that is, that the currently received wave is a normal wave. In contrast, if peak 1<peak 2 (i.e., step 1405=NO) or if the normalized correlation signal is less than the normalized threshold THN (i.e., step 1406=NO), the signal judgment unit 14 executes the process of step 1408. In step 1408, the signal judgment unit 14 judges that the currently received wave is interference.

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

[0057] Fig. 16 shows a flow chart corresponding to the above-mentioned code determination mode. Referring to Fig. 16, first, in step 1601, the signal determination unit 14 detects the rising edge of the correlation signal (i.e., tC1 shown in Fig. 15). Next, in step 1602, the signal determination unit 14 sets a code determination range based on the rising edge of the correlation signal detected in step 1601. That is, the process contents of steps 1601 and 1602 are respectively similar to the process contents of steps 1001 and 1002 shown in Fig. 10. Moreover, the process contents of steps 1603 to 1608 are respectively similar to the process contents of steps 1403 to 1408 shown in Fig. 14.

[0058] In the peak detection in step 1403 or step 1603, only peaks equal to or greater than the correlation threshold THC may be detected. In addition, in the peak detection, if there is no peak, the maximum value in the sign determination range is used. In this case, the maximum value to be detected may be only a value equal to or greater than the correlation threshold THC. Here, the amplitude signal SA, the correlation signal, and the normalized correlation signal behave differently. Therefore, the signal determination unit 14 may use different values ​​for the amplitude threshold THA, which is a threshold for determining the amplitude signal SA, the correlation threshold THC, which is a threshold for determining the correlation signal, and the normalized threshold THN, which is a threshold for determining the normalized correlation signal. Specifically, for example, as shown in FIG. 13, the amplitude threshold THA may be set to change with time. In contrast, the correlation threshold THC and the normalized threshold THN may be set as constant values ​​that do not change with time. In addition, in FIG. 13 and FIG. 15, the normalized 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 main correlation peak PC12. This may further improve the accuracy of the sign determination.

[0059] For example, when an oncoming vehicle equipped with a sonar from another company approaches the vehicle, the ultrasonic waves transmitted from the oncoming vehicle are received as received waves by the receiver 112 of the object detection device 10 in the vehicle, and the amplitude of the received waves becomes very large. This may result in an erroneous determination due to the increase in the correlation signal of the incorrect code, which is not the own code. In this regard, according to the present embodiment, the occurrence of erroneous determination can be effectively suppressed by using a normalized correlation signal.

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

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

[0062] The transmitting / receiving unit 11 is not limited to a so-called "integrated transmitting / receiving type" configuration capable of transmitting and receiving ultrasonic waves 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 parts that perform calculations and judgments in the object detection device 10 may be configured as an in-vehicle microcomputer equipped with a CPU, ROM, RAM, non-volatile memory, an interface, and the like. "Non-volatile memory" is a memory that has the function of rewriting stored contents while the power is on, while retaining stored contents while the power is off, and includes flash memory and hard disks. Alternatively, all or part of such parts may be configured to include hardware circuits (e.g., ASIC and FPGA) that are configured to enable the above-mentioned operations. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array.

[0064] In this way, each of the above functional configurations and methods may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, each of the above functional configurations and methods may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, each of the above functional configurations and methods may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transient tangible storage medium as instructions executed by a computer. That is, each of the above functional configurations and methods can also be expressed as a computer program including a procedure for realizing the same, or a non-transient tangible storage medium storing the program. Examples of the non-transient tangible storage medium include a ROM, a RAM, a non-volatile memory, a DVD, a CD-ROM, and the like. The program can be downloaded or upgraded via V2X communication. V2X is an abbreviation for Vehicle to X. Alternatively, such a program may be downloaded or upgraded via a terminal device provided at a manufacturing plant, a repair shop, a dealer, or the like of a mobile object such as a vehicle.

[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 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 may be integrated as a module on the same board, with a specific signal processing unit such as the filter unit 131 being implemented as a hardware circuit, and the remaining units being realized by at least one CPU or MPU.

[0066] The filter unit 131 may perform filtering on the received signal SD using a known FIR filter or IIR filter. Alternatively, the received signal SD may be converted into frequency components (i.e., complex vectors) by quadrature detection, discrete Fourier transform, FFT, or the like, and then filtered. When the signal is converted into a complex vector and filtered, the amplitude signal generator 132, correlation signal generator 134, and normalized correlation signal generator 137 in the subsequent stages also perform various processes using complex vectors. By performing processing using complex vectors of frequency components, the scale of the hardware circuit can be reduced, or the amount of calculations in the CPU or MPU can be reduced.

[0067] The correlation signal generating unit 134 may include a reference signal. That is, the reference signal output unit 133 may be omitted. The correlation signal generating unit 134 is provided in the same number as the types of the transmission signals ST. Therefore, for example, when the transmission signal generating unit 12 can generate and output four types of transmission signals ST, four correlation signal generating units 134 may be provided. However, providing a plurality of correlation signal generating units 134 does not necessarily mean providing a plurality of correlation signal generating units 134 individually and in parallel. That is, for example, by switching the input of the reference signal to one common correlation signal generating unit 134, it is possible to realize a plurality of correlation signal generating units 134 in a time-division manner. In other words, in FIG. 1 and the like, the first correlation signal generating unit 134a and the second correlation signal generating unit 134b may be integrated. The same applies to the normalized correlation signal generating unit 137 in FIG. 12.

[0068] The normalized correlation signal generator 137 may be applied to the configuration shown in Fig. 1. That is, the normalized correlation signal generator 137 may receive the filtered signal SF, which is the output of the filter unit 131, as an input. Also, referring to Fig. 12, the normalized correlation signal generator 137 may be provided to normalize the correlation signal generated by the correlation signal generator 134. That is, the first normalized correlation signal generator 137a may be provided to receive the first correlation signal SC1 output from the first correlation signal generator 134a as an input and normalize the first correlation signal SC1. Similarly, the second normalized correlation signal generator 137b may be provided to normalize the second correlation signal SC2 output from the second correlation signal generator 134b.

[0069] The present invention is not limited to the operation modes described in the above embodiments and modifications. Specifically, for example, the frequency change mode in the transmission signal ST is not limited to monotonically increasing or decreasing as shown in FIG. 2A and the like, and may be step-like or the like. Also, the up transmission signal ST1 may have a characteristic that the frequency increases as a whole, and may have a part in which the frequency decreases for a short time from the center frequency fc or a start frequency in the vicinity of the center frequency fc at the beginning. The same applies to the down transmission signal ST2. Also, the shifted chirp signal shown in FIG. 2C may be transformed into a curved frequency change mode as shown in FIG. 2A. Also, in the shifted chirp signal shown in FIG. 2C, the frequency band of the up transmission signal ST1 may be fmd-fu, while the frequency band of the down transmission signal ST2 may be fmu-fd. Furthermore, when transmitting a single search wave, it is possible to set a code string of multiple bits in which multiple codes are arranged. That is, for example, if the code of the first transmission signal is "1" and the code of the second transmission signal is "0", 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 determination processes, "greater than" and "exceed" are interchangeable. Similarly, "less than" and "equal to or less than" are interchangeable. Furthermore, terms with a common or similar meaning, such as "detect," "sens," "measure," "calculate," and "obtain," are interchangeable as long as there is no technical contradiction. That is, for example, "obtaining" a certain characteristic value can include "calculating" the same value and inputting the same value.

[0071] Needless to say, the elements constituting the above-mentioned embodiment are not necessarily essential, except when expressly stated as essential or when considered to be obviously essential in principle. Furthermore, when the numbers, amounts, ranges, etc. of the components are mentioned, the present invention is not limited to the specific values, except when expressly stated as essential or when clearly limited to a specific value in principle. Similarly, when the shapes, directions, positional relationships, etc. of the components are mentioned, the present invention is not limited to the shapes, directions, positional relationships, etc., except when expressly stated as essential or when clearly limited to a specific shape, direction, positional relationship, etc. in principle.

[0072] The modified examples are not limited to the above examples. That is, all or part of one embodiment and all or part of another embodiment may be combined with each other within a range that does not cause technical contradiction. In addition, multiple modified examples may be combined with each other. Furthermore, all or part of the above embodiment and all or part of the modified examples may be combined with each other.

[0073] (Aspects included in this disclosure) The present disclosure includes at least the following aspects. [First viewpoint] An object detection device (10), a transmission signal generating unit (12) capable of generating a plurality of types of transmission signals whose frequencies change over time, and outputting one of the plurality of types of transmission signals to a transmitting unit (111) that transmits a search wave that is an ultrasonic wave whose frequency is modulated based on the frequency change mode of the transmission signal; a correlation signal generating unit (134) that generates a correlation signal indicating a correlation between a reference signal corresponding to the transmission signal and a reception signal output in response to a reception wave, which is an ultrasonic wave received by a receiving unit (112); a signal determination unit (14) that performs signal determination based on the correlation signal to determine whether or not the received wave has a frequency change pattern corresponding to the frequency modulation pattern of the search wave; Equipped with A plurality of correlation signal generators are provided corresponding to a plurality of 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 viewpoint] the plurality of types of transmission signals include a first transmission signal and a second transmission signal; one of the first transmission signal and the second transmission signal has a monotonically increasing frequency and the other has a monotonically decreasing frequency; the correlation signal generation unit generates the correlation signal indicating a correlation between the reference signal corresponding to the first transmission signal and the received signal, and the correlation signal indicating a correlation between the reference signal corresponding to the second transmission signal and the received signal. 13. An object detection device according to a first aspect. [Third Perspective] The frequency band of the first transmission signal and the frequency band of the second transmission signal are set to have a part that overlaps with each other and a remaining part that does not overlap with each other. The object detection device according to a second aspect. [Fourth viewpoint] The receiving signal is converted into an amplitude signal by an amplitude signal generating unit (132), the signal determination unit performs the signal determination by comparing a plurality of the correlation signals in a code determination range, which is a time range set based on the amplitude signal. The object detection device according to any one of the first to third aspects. [Fifth viewpoint] the signal determination unit sets the sign determination range based on a rate of change of the amplitude signal at a point in time when the amplitude signal increases and reaches a predetermined amplitude threshold value. An object detection device according to a fourth aspect. [Sixth viewpoint] an amplitude threshold for judging the amplitude signal and a correlation threshold for judging the correlation signal are different from each other; 13. An object detection device according to claim 12, wherein the object detection device is a [Seventh viewpoint] the amplitude signal generating unit generates the amplitude signal based on a signal obtained by filtering the received signal using a first filter unit (135); The correlation signal generating unit generates the correlation signal based on a signal obtained by filtering the received signal using a second filter unit (136); The first filter section and the second filter section have different Q values. The object detection device according to any one of the fourth to sixth aspects. [Eighth viewpoint] the signal determination unit sets a time width of the code determination range based on a signal length of the transmission signal. The object detection device according to any one of the fourth to seventh aspects. [Ninth viewpoint] The signal determination unit performs the signal determination based on a normalized correlation signal obtained by removing an influence of the amplitude of the received signal from the correlation signal. The object detection device according to any one of the first to eighth aspects. [10th viewpoint] the signal determination unit performs the signal determination after correcting a delay occurring in a filtering process and a correlation calculation used to generate at least the correlation signal used in the signal determination. The object detection device according to any one of the first to ninth aspects. [Eleventh viewpoint] The transmit signal is a linear chirp signal. The object detection device according to any one of the first to tenth aspects. [12th viewpoint] The reference signal is set in a frequency band narrower than that of the transmission signal. The object detection device according to any one of the first to eleventh aspects. [Explanation of symbols]

[0074] 10 Object detection device 111 Transmitter 112 Receiving unit 12 Transmission signal generator 134 Correlation signal generator 134a First correlation signal generator 134b Second correlation signal generator 135 First filter section 136 Second filter section 14 Signal Judgment Section

Claims

1. An object detection device (10), a transmission signal generating unit (12) capable of generating a plurality of types of transmission signals whose frequencies change over time, and outputting one of the plurality of types of transmission signals to a transmitting unit (111) that transmits a search wave that is an ultrasonic wave whose frequency is modulated based on the frequency change mode of the transmission signal; a correlation signal generating unit (134) that generates a correlation signal indicating a correlation between a reference signal corresponding to the transmission signal and a reception signal output in response to a reception wave, which is an ultrasonic wave received by a receiving unit (112); a signal determination unit (14) that performs signal determination based on the correlation signal to determine whether or not the received wave has a frequency change pattern corresponding to the frequency modulation pattern of the search wave; an amplitude signal generating unit (132) for converting the received signal into an amplitude signal; Equipped with A plurality of correlation signal generators are provided corresponding to a plurality of types of the transmission signals, the signal determination unit performs the signal determination by comparing a plurality of the correlation signals in a code determination range, which is a time range set based on the amplitude signal. Object detection device.

2. the plurality of types of transmission signals include a first transmission signal and a second transmission signal; one of the first transmission signal and the second transmission signal has a monotonically increasing frequency and the other has a monotonically decreasing frequency; the correlation signal generation unit generates the correlation signal indicating a correlation between the reference signal corresponding to the first transmission signal and the received signal, and the correlation signal indicating a 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 to have a part that overlaps with each other and a remaining part that does not overlap with each other. The object detection device according to claim 2 .

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

5. an amplitude threshold for judging the amplitude signal and a correlation threshold for judging the correlation signal are different from each other; The object detection device according to claim 1 .

6. The amplitude signal generating unit generates the amplitude signal based on a signal obtained by filtering the received signal using a first filter unit (135); The correlation signal generating unit generates the correlation signal based on a signal obtained by filtering the received signal using a 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 a time width of the code determination range based on a signal length of the transmission 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 an influence 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 a delay occurring in a filtering process and a correlation calculation used to generate at least the correlation signal used in the signal determination. The object detection device according to claim 1 .

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

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

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