Object detection device and object detection method

Abstract

The present invention provides an object detection device and an object detection method. A drive signal generating unit (3) generates a first drive signal and a second drive signal and outputs them toward a transmitting unit (20A). The first drive signal is a drive signal corresponding to a first transmission wave. The second drive signal is a drive signal corresponding to a second transmission wave. The first transmission wave and the second transmission wave are included in a plurality of transmission waves that are continuously transmitted from the start of the transmission process of the transmission wave to the end of the transmission process and are respectively encoded according to a waveform pattern. The second transmission wave is transmitted after the first transmission wave. A detection unit (52) is configured to detect an object based on a reception signal corresponding to a reception result of a receiver (21), the receiver receiving a reception wave including a reflected wave where the transmission wave is reflected by an object. The detection unit makes a reception determination of the reflected wave based on a frequency signal corresponding to the waveform pattern in the reception signal and a reference signal corresponding to the waveform pattern in the first drive signal.

Description

Technical Field

[0001] The present disclosure relates to an object detection device and an object detection method for detecting an object around a moving object. Background Art

[0002] There are known devices that detect objects using ultrasonic sensors. When such an object detection device is mounted on a vehicle and used for obstacle detection, the object detection accuracy may be reduced due to crosstalk or the like. Crosstalk can be generated, for example, by an ultrasonic sensor mounted on the vehicle receiving ultrasonic waves transmitted from ultrasonic sensors mounted on other vehicles that exist around the vehicle. Alternatively, crosstalk can be generated, for example, by one of a plurality of ultrasonic sensors mounted on the vehicle receiving ultrasonic waves transmitted from another ultrasonic sensor.

[0003] However, Patent Document 1 discloses an ultrasonic multi-sensor array. The ultrasonic multi-sensor array described in Patent Document 1 has at least two transmitting units and at least one receiving unit. Several transmitting units can operate in parallel.

[0004] In the ultrasonic multi-sensor array described in Patent Document 1, ultrasonic pulses are encoded in order to enable parallel operation. Specifically, the frequency of the carrier signal is linearly modulated in order to encode the pulses of each of the multiple transmitting units that operate simultaneously. That is, the frequency of the carrier signal of the first transmitting unit increases linearly during the pulse duration. On the other hand, the frequency of the carrier signal of the second transmitting unit decreases linearly during the pulse duration.

[0005] Patent Document 1: German Patent Application Publication No. 10106142

[0006] By using the technology disclosed in Patent Document 1, the ultrasonic sensor mounted on the vehicle can identify whether the received wave is a reflected wave of its own transmitted wave. Specifically, such identification is based on whether the frequency change that is the same as the frequency change of its own transmitted wave is included in the received wave. If the desired identification accuracy is obtained, the above-mentioned crosstalk problem can be solved.

[0007] However, in the object detection device and object detection method using ultrasonic transmission and reception as described above, further improvement in recognition accuracy is required. The present disclosure is completed in view of the above-mentioned exemplified matters, etc. That is, the present disclosure, for example, provides a device configuration and method that can improve recognition accuracy more than before. Summary of the invention

[0008] The object detection device is mounted on a moving body and is configured to detect objects around the moving body.

[0009] According to one aspect of the present disclosure, an object detection device comprises:

[0010] a drive signal generating unit configured to generate a drive signal for driving the transmitting unit and output the drive signal to the transmitting unit, wherein the transmitting unit includes a transmitter for transmitting a transmission wave as an ultrasonic wave to the outside; and

[0011] a detection unit configured to detect the object based on a reception signal corresponding to a reception result of a receiver, wherein the receiver receives a reception wave including a reflection wave resulting from the transmission wave being reflected by the object,

[0012] The drive signal generating unit generates a first drive signal and outputs it toward the transmitting unit, and generates a second drive signal and outputs it toward the transmitting unit, wherein the first drive signal is the drive signal corresponding to a first transmission wave, and the second drive signal is the drive signal corresponding to a second transmission wave, the first transmission wave is included in a plurality of transmission waves that are continuously transmitted during a period from the start of the transmission process of the transmission wave to the end of the transmission process and are respectively encoded according to a waveform pattern, and the second transmission wave is included in the plurality of transmission waves and is transmitted after the first transmission wave.

[0013] The detection unit makes a reception determination of the reflected wave based on a frequency signal corresponding to the waveform pattern in the received signal and a reference signal corresponding to the waveform pattern in the first drive signal.

[0014] According to another aspect of the present disclosure, an object detection method for detecting an object around a moving body is an object detection method using a drive signal generating unit and a detecting unit, wherein:

[0015] The drive signal generating unit is configured to generate a drive signal for driving the transmitting unit and output the drive signal to the transmitting unit. The transmitting unit includes a transmitter for transmitting a transmission wave as an ultrasonic wave to the outside.

[0016] The detection unit is configured to detect the object based on a reception signal corresponding to a reception result of a receiver, wherein the receiver receives a reception wave including a reflection wave of the transmission wave reflected by the object,

[0017] The object detection method comprises the following steps:

[0018] The drive signal generating unit generates a first drive signal and outputs it toward the transmitting unit, and generates a second drive signal and outputs it toward the transmitting unit, wherein the first drive signal is the drive signal corresponding to a first transmission wave, and the second drive signal is the drive signal corresponding to a second transmission wave, the first transmission wave is included in a plurality of transmission waves that are continuously transmitted during a period from the start of transmission processing of the transmission wave to the end of transmission processing and are respectively encoded according to waveform patterns, and the second transmission wave is included in the plurality of transmission waves and is transmitted after the first transmission wave.

[0019] The detection unit determines whether the reflected wave has been received based on the frequency signal corresponding to the waveform pattern in the received signal and the reference signal corresponding to the waveform pattern in the first drive signal.

[0020] In addition, in various parts of the application documents, each element is marked with a reference figure mark in brackets. However, such a reference figure mark is only a simple example of the correspondence between the element and the specific unit described in the embodiment described later. Therefore, the present disclosure is not limited in any way by the above-mentioned reference figure mark. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a block diagram showing a schematic configuration of an object detection device according to the first embodiment.

[0022] Figure 2 Yes means Figure 1 FIG. 1 is a timing diagram of a frequency characteristic of an example of a drive signal output by the drive signal generating unit shown in FIG.

[0023] Figure 3 It means stored in Figure 1 A timing chart of an example of a reference signal of the reference signal storage unit shown.

[0024] Figure 4 Yes means Figure 1 FIG. 1 is a timing chart showing an overview of frequency shift amount detection by the frequency shift detection unit.

[0025] Figure 5 Yes means Figure 1 A timing chart showing an overview of an example of reception determination processing performed by a detection unit shown.

[0026] Figure 6 It is a timing chart showing an example of the driving signal according to the second embodiment.

[0027] Figure 7 This is a timing chart showing an example of a reference signal according to the second embodiment.

[0028] Figure 8 This is a time chart showing an overview of an example of the reception determination process according to the second embodiment.

[0029] Fig. 9 This is a timing chart showing an overview of another example of the reception determination process according to the second embodiment.

[0030] Fig.10 This is a timing chart showing an example of a reference signal according to the third embodiment.

[0031] Fig.11 This is a timing chart showing an overview of an example of the reception determination process according to the third embodiment.

[0032] Fig.12 It is a timing chart showing an example of the driving signal and the reference signal according to the fourth embodiment.

[0033] Fig.13 This is a timing chart showing an overview of an example of the reception determination process according to the fourth embodiment.

[0034] Fig.14 This is a block diagram showing a schematic configuration of an object detection device according to a fifth embodiment.

[0035] Fig.15 Yes means Fig.14 FIG. 1 is a timing diagram of a frequency characteristic of an example of a drive signal output by the drive signal generating unit shown in FIG.

[0036] Fig.16 Yes means Fig.14 A timing chart showing an overview of an example of reception determination processing performed by a detection unit shown.

[0037] Fig.17 Yes means Figure 1 as well as Fig.14 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0038] Fig.18 Yes means Figure 1 as well as Fig.14 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0039] Fig.19 Yes means Figure 1 as well as Fig.14 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0040] Fig. 20Yes means Figure 1 as well as Fig.14 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0041] Fig.21 Yes means Figure 1 as well as Fig.14 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0042] Fig. 22 Yes means Figure 1 as well as Fig.14 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0043] Fig.23 Yes means Figure 1 as well as Fig.14 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit. DETAILED DESCRIPTION

[0044] (Implementation Method)

[0045] The following describes the embodiments of the present disclosure based on the accompanying drawings. In addition, if various modifications that can be applied to an embodiment are inserted in the middle of a series of descriptions related to the embodiment, it may hinder the understanding of the embodiment. Therefore, the modifications are collectively recorded after the description of the embodiment.

[0046] (First Embodiment: Configuration)

[0047] Reference Figure 1 The object detection device 1 is configured to be mounted on a vehicle V as a moving body to detect an object B around the vehicle V. Hereinafter, the state in which the object detection device 1 is mounted on the vehicle V is referred to as the "vehicle-mounted state". In addition, the vehicle V in which the object detection device 1 according to the present embodiment is mounted is referred to as the "own vehicle" hereinafter.

[0048] The object detection device 1 has a configuration as a so-called ultrasonic sensor. Specifically, the object detection device 1 is configured to transmit a transmission wave as an ultrasonic wave toward the outside. In addition, the object detection device 1 is configured to detect a surrounding object B and obtain distance measurement information corresponding to the object B by receiving a reflected wave caused by the object B of the transmission wave transmitted to the outside.

[0049] Object detection device 1 includes transceiver 2, drive signal generator 3, reception signal processor 4, and control unit 5. Object detection device 1 has a configuration in which transceiver 2, drive signal generator 3, reception signal processor 4, and control unit 5 are supported by one sensor housing.

[0050] In the present embodiment, the object detection device 1 has a structure of an integrated transceiver. That is, the object detection device 1 is configured to have a transceiver unit 2 so that the transceiver unit 2 performs the transceiver function. Specifically, the transceiver unit 2 has a transmitting unit 20A and a receiving unit 20B. In addition, the transceiver unit 2 has a transducer 21. The transmitting unit 20A and the receiving unit 20B are configured to respectively realize the transmitting function and the receiving function using the common transducer 21.

[0051] The transducer 21 has a function as a transmitter that transmits a transmission wave to the outside, and a function as a receiver that receives a reception wave including a reflection wave of the transmission wave caused by the object B. Specifically, the transducer 21 is configured as an ultrasonic microphone in which an electrical-mechanical energy conversion element such as a piezoelectric element is built into a substantially cylindrical microphone frame.

[0052] When mounted on a vehicle, the transducer 21 is arranged to face the outer surface of the vehicle, so that it is configured to transmit the transmission wave to the outside of the vehicle and to receive the reflected wave from the outside of the vehicle. Specifically, the transducer 21 is mounted on the outer panel member V1 when mounted on the vehicle, so that the transmitting and receiving surface 21a is exposed to the external space of the vehicle from the through hole, i.e., the mounting hole V2, formed in the outer panel member V1 of the vehicle. The outer panel member V1 is, for example, a bumper or a body panel, and is formed of a plate made of synthetic resin or metal. The transmitting and receiving surface 21a is the outer surface of the microphone frame in the transducer 21, and is configured to function as a transmitting surface for transmitting waves and a receiving surface for receiving waves.

[0053] The transceiver 2 includes a transducer 21, a transmission circuit 22, and a reception circuit 23. The transducer 21 is electrically connected to the transmission circuit 22 and the reception circuit 23. The transmission unit 20A is composed of the transducer 21 and the transmission circuit 22. The reception unit 20B is composed of the transducer 21 and the reception circuit 23.

[0054] The transmitting circuit 22 is configured to drive the transducer 21 based on the input drive signal, so as to utilize the transducer 21 to emit a transmission wave of a frequency corresponding to the frequency of the drive signal. Hereinafter, the frequency of the drive signal is referred to as the "drive frequency". Specifically, the transmitting circuit 22 has a digital / analog conversion circuit, etc. That is, the transmitting circuit 22 is configured to generate an element input signal by performing signal processing such as digital / analog conversion on the drive signal output from the drive signal generating unit 3. The element input signal is an AC voltage signal for driving the transducer 21, that is, the electrical-mechanical energy conversion element provided in the transducer 21. Moreover, the transmitting circuit 22 is configured to drive the electrical-mechanical energy conversion element in the transducer 21 by applying the generated element input signal to the transducer 21, so as to excite the transceiver surface 21a and transmit the transmission wave to the outside.

[0055] The receiving circuit 23 is configured to generate a receiving signal corresponding to the reception result of the receiving wave of the transducer 21 and output it to the receiving signal processing unit 4. Specifically, the receiving circuit 23 has an amplifier circuit and an analog / digital conversion circuit. That is, the receiving circuit 23 is configured to generate a receiving signal by performing signal processing such as amplification and analog / digital conversion on the element output signal output by the transducer 21. The element output signal is an AC voltage signal generated by the electrical-mechanical energy conversion element provided in the transducer 21 when the receiving wave excites the transceiver surface 21a. In addition, the receiving circuit 23 is configured to output the generated receiving signal containing information related to the amplitude and frequency of the receiving wave to the receiving signal processing unit 4.

[0056] In this way, the transceiver 2 is configured to generate a reception signal corresponding to the frequency of the reception wave and the distance between the transducer 21 and the object B by transmitting a transmission wave through the transducer 21 and receiving a reflected wave from the object B as a reception wave. Hereinafter, the reception wave when the transducer 21 as a transceiver receives the reflected wave of the transmission wave transmitted by itself is referred to as a "normal wave". In contrast, the reception wave caused by the transmission wave from other devices is referred to as an "abnormal wave" below. "Other devices" also include other transducers 21 mounted on the vehicle.

[0057] The drive signal generating unit 3 is configured to generate a drive signal based on a control signal received from the control unit 5 and output the drive signal to the transmitting unit 20A. The drive signal is a signal for driving the transmitting unit 20A and causing the transmission wave to be transmitted from the transducer 21, for example, a pulse signal having a frequency within the ultrasonic frequency band. A specific example of the drive signal is described in the operation overview section described later. The control signal is a signal for controlling the output of the drive signal from the drive signal generating unit 3 to the transmitting unit 20A.

[0058] The drive signal generating unit 3 is configured to generate and output a drive signal corresponding to the waveform pattern in the transmission wave encoded according to the waveform pattern. In addition, the drive signal generating unit 3 is configured to selectively generate and output a plurality of drive signals having mutually different waveform patterns. Furthermore, the drive signal generating unit 3 is configured to continuously generate and output a plurality of drive signals during the period from the start of the transmission process of the transmission wave to the end of the transmission process. Hereinafter, each of the plurality of drive signals output during the period from the start of the transmission process of the transmission wave to the end of the transmission process is referred to as a "differentiation drive signal". The details of differentiating the drive signals are described in the operation overview description section described later.

[0059] In the present embodiment, the drive signal generating unit 3 generates a drive signal in which at least the front-end transmission wave is encoded by frequency modulation. The "front-end transmission wave" is the transmission wave that is initially transmitted among the multiple transmission waves that are continuously transmitted during the period from the start of the transmission process to the end of the transmission process. The transmission wave that is transmitted after the front-end transmission wave among the multiple transmission waves that are continuously transmitted during the period from the start of the transmission process to the end of the transmission process is called the "subsequent transmission wave". The front-end transmission wave corresponds to the "first transmission wave". The subsequent transmission wave corresponds to the "second transmission wave". Hereinafter, the front-end transmission wave and the subsequent transmission wave that are continuously transmitted during the period from the start of the transmission process of a transmission wave to the end of the transmission process are collectively referred to as "differentiation of transmission waves". The details of differentiation of transmission waves are described in the operation overview description section described later.

[0060] Specifically, the drive signal generating unit 3 generates a drive signal such that the front-end transmission wave becomes a chirped wave and the subsequent transmission wave becomes a chirped wave or a CW wave. A chirped wave is a wave whose frequency increases or decreases over time. A CW wave is a wave with a constant frequency. CW is the abbreviation of continuous waveform. CW wave is also called CF wave. CF is the abbreviation of continuous frequency.

[0061] In this way, the drive signal generating unit 3 generates and outputs a drive signal that encodes each of a plurality of distinguished transmission waves that are continuously transmitted from the start of the transmission process to the end of the transmission process according to the frequency modulation method. That is, the drive signal generating unit 3 encodes the transmission wave with a plurality of bits corresponding to the number of distinguished transmission waves. In addition, in the present embodiment, the drive signal generating unit 3 generates and outputs a drive signal in which the front end transmission wave becomes a V-shaped chirp wave. The V-shaped chirp wave refers to a wave whose frequency changes in a V-shaped or inverted V-shaped shape over time.

[0062] The received signal processing unit 4 is configured to generate an amplitude signal and a frequency signal by performing processing such as FFT on the received signal. FFT is the abbreviation of Fast Fourier Transform. The amplitude signal is a signal corresponding to the amplitude of the received wave. The frequency signal is a signal corresponding to the frequency of the received wave. In other words, the frequency signal is a signal corresponding to the waveform pattern of the encoding in the received signal.

[0063] The control unit 5 is configured to control the overall operation of the object detection device 1. Specifically, in the present embodiment, the control unit 5 is a well-known microcomputer having a CPU, a ROM, a non-volatile rewritable memory, a RAM, an input / output interface, and the like. That is, the control unit 5 is configured to perform various processes by reading and executing programs stored in the ROM or the non-volatile rewritable memory. CPU is the abbreviation of Central Processing Unit. ROM is the abbreviation of Read Only Memory. Examples of non-volatile rewritable memories include EPROM, EEPROM, and flash memory. EPROM is the abbreviation of Erasable Programmable Read Only Memory. EEPROM is the abbreviation of Electrically Erasable Programmable Read Only Memory. RAM is the abbreviation of Random access memory. ROM, non-volatile rewritable memory, and RAM are non-transitional physical storage media.

[0064] The control unit 5 is configured to control the transmission of the transmission wave and detect the object B based on the reception wave. Specifically, the control unit 5 includes a transmission control unit 51 and a detection unit 52 as functional structures realized on a microcomputer.

[0065] The transmission control unit 51 is configured to control the transmission state of the transmission wave from the transmission unit 20A by outputting a control signal to the drive signal generation unit 3. Specifically, the transmission control unit 51 sets the waveform pattern and output timing of the drive signal generated and output by the drive signal generation unit 3 using the control signal.

[0066] The detection unit 52 is configured to detect the object B based on the reception signal output from the receiving circuit 23. Specifically, the detection unit 52 determines whether the received wave is a normal wave based on the frequency signal output from the reception signal processing unit 4 and a predetermined reference signal. In addition, when the received wave is a normal wave, the detection unit 52 detects the existence of the object B and the distance between the transducer 21 and the object B based on the amplitude signal output from the reception signal processing unit 4. Specifically, in the present embodiment, the detection unit 52 includes a reference signal storage unit 521, a frequency shift detection unit 522, a reception determination unit 523, and a detection determination unit 524.

[0067] The reference signal storage unit 521 stores a reference signal corresponding to the waveform pattern in the drive signal. The details of the reference signal are described in the operation overview section described later. The frequency shift detection unit 522 detects the frequency shift amount between the transmission wave and the reflected wave based on the relative speed accompanying the relative movement of the vehicle and the object B. The details of the detection of the frequency shift amount are described in the operation overview section described later.

[0068] The reception determination unit 523 performs reception determination of the reflected wave based on the reference signal, the frequency signal corresponding to the waveform pattern in the received signal, and the frequency shift amount detected by the frequency shift detection unit 522. Specifically, the reception determination unit 523 performs pattern matching of the waveform of the frequency signal and the waveform of the reference signal while considering the detected frequency shift amount, thereby determining whether the received wave is a normal wave. The details of the determination operation of the reception determination unit 523 are described in the operation overview description section described later.

[0069] When the reception determination unit 523 determines that the received wave is a normal wave and the amplitude signal is equal to or greater than a predetermined determination threshold, the detection determination unit 524 detects the presence of the object B. In addition, when the presence of the object B is detected, the detection determination unit 524 generates distance measurement information corresponding to the distance between the transducer 21 and the object B based on the amplitude signal.

[0070] (First Embodiment: Operation Overview)

[0071] Hereinafter, an overview of the operation based on the configuration of the present embodiment, typical operation examples, and effects achieved by the configuration will be described with reference to the drawings.

[0072] If the specified object detection conditions are met, the object detection device 1 starts the object detection operation. The object detection conditions include, for example, that the vehicle's travel speed is within a specified range, that the vehicle's gear position is a travel position including reverse, etc. If the object detection conditions are not met, the object detection device 1 ends the object detection operation.

[0073] In the object detection operation, the transmission control unit 51 determines the arrival of the timing for starting the transmission process at a predetermined period. The predetermined period is, for example, a period of several hundred milliseconds. The arrival of the timing for starting the transmission process is determined using a timing means such as a timer. If the timing for starting the transmission process arrives, the transmission control unit 51 outputs a control signal to the drive signal generating unit 3. Thus, the transmission process is executed.

[0074] Specifically, if a control signal is input to the drive signal generating unit 3, a drive signal is generated and outputted toward the transmitting unit 20A, i.e., the transmitting circuit 22. The transmitting circuit 22 drives the transducer 21 based on the input drive signal. Then, the transducer 21, which functions as a transmitter, transmits a transmission wave as an ultrasonic wave of a frequency corresponding to the frequency of the drive signal toward the outside of the vehicle. In this way, the object detection device 1 repeatedly transmits the transmission wave at a prescribed period during the object detection operation. Therefore, the above-mentioned prescribed period is also referred to as a "transmission period". In addition, ideally, the frequency of the transmission wave is roughly consistent with the frequency of the drive signal. Among them, according to the relationship between the followability of the transmitting unit 20A including the transducer 21 to the drive frequency, a slight difference or delay is generated between the frequency of the transmission wave and the drive frequency.

[0075] Figure 2 FIG. 2 shows an example of the drive signal SD output from the drive signal generating unit 3 from the start of the transmission process to the end of the transmission process in one transmission process. Figure 2 In the above, the vertical axis f represents frequency and the horizontal axis T represents time. Figure 2 As shown, in this operation example, the drive signal SD includes three distinguishing drive signals SD1 to SD3 during the period from the transmission process start timing TT0 to the transmission process end timing TTE. That is, in this operation example, the drive signal generating unit 3 outputs the drive signal SD including the three distinguishing drive signals SD1 to SD3 at a predetermined period. The distinguishing drive signal SD1 and the like are equivalent to the signal obtained by subdividing the drive signal SD that continues during the period from the transmission process start timing TT0 to the transmission process end timing TTE into the number of coded bits equivalent to the number of transmission waves. According to the above, the transmission process start timing TT0 arrives repeatedly at a predetermined period during the period when the object detection condition is satisfied. The time interval between the moments TT0 and TT1, the time interval between the moments TT1 and TT2, and the time interval between the moments TT2 and TTE are approximately equal.

[0076] The plurality of differentiated drive signals SD1 and the like are outputted continuously in time. That is, there is no interval period between mutually adjacent signals in the plurality of differentiated drive signals SD1 and the like. The details will be described later. In addition, the plurality of differentiated drive signals SD1 and the like are encoded according to the frequency modulation method. For example, in Figure 2In the specific example shown, the front end drive signal SD1 between time TT0 and time TT1 has a drive frequency characteristic in which the frequency changes in a V-shape as time passes.

[0077] Specifically, the driving frequency in the front-end drive signal SD1 changes as follows. At time TT0, the driving frequency is the intermediate frequency fc. The intermediate frequency fc is approximately equal to the resonant frequency f0 of the transceiver 2, i.e., the transducer 21. The driving frequency temporarily drops from the intermediate frequency fc to the lowest frequency fmin and then turns to rise. At time TT1, the driving frequency is the highest frequency fmax. fmax>f0. The frequency reduction speed from the intermediate frequency fc to the lowest frequency fmin and the frequency increase speed from the lowest frequency fmin to the highest frequency fmax are approximately equal. Compared with the frequency reduction time from the intermediate frequency fc to the lowest frequency fmin, the frequency rise time from the lowest frequency fmin to the highest frequency fmax is longer. Therefore, although the front-end drive signal SD1 temporarily drops from the intermediate frequency fc to the lowest frequency fmin, it actually has a frequency change mode in the form of "up chirp". The front-end drive signal SD1, which is the first bit and is the front-end bit, is assigned a code "1" corresponding to the frequency change mode in the form of up chirp.

[0078] At TT1, the drive signal SD is switched from the front drive signal SD1 to the intermediate drive signal SD2. That is, the front drive signal SD1 and the intermediate drive signal SD2 are continuous in time. In other words, the end time of the front drive signal SD1 coincides with the start time of the intermediate drive signal SD2. The intermediate drive signal SD2 between time TT1 and TT2 has a drive frequency characteristic in which the frequency changes in a V shape over time.

[0079] The driving frequency variation mode in the intermediate drive signal SD2 is the same as the driving frequency variation mode in the front-end drive signal SD1. That is, the driving frequency variation in the intermediate drive signal SD2 is as follows. At time TT1, the driving frequency is the intermediate frequency fc. The driving frequency turns to rise after temporarily decreasing from the intermediate frequency fc to the lowest frequency fmin. At time TT2, the driving frequency is the highest frequency fmax. The frequency reduction speed from the intermediate frequency fc to the lowest frequency fmin and the frequency increase speed from the lowest frequency fmin to the highest frequency fmax are roughly equal. Compared with the frequency reduction time from the intermediate frequency fc to the lowest frequency fmin, the frequency increase time from the lowest frequency fmin to the highest frequency fmax is longer. Therefore, although the intermediate drive signal SD2 temporarily decreases from the intermediate frequency fc to the lowest frequency fmin, it actually has a frequency variation mode of "up chirping". The intermediate drive signal SD2 as the second bit is given a code "1" corresponding to the frequency variation mode of up chirping.

[0080] At time TT2, the drive signal SD switches from the intermediate drive signal SD2 to the final drive signal SD3. That is, the intermediate drive signal SD2 and the final drive signal SD3 are continuous in time. The final drive signal SD3 between time TT2 and time TTE has a drive frequency characteristic in which the frequency changes in an inverted V shape over time.

[0081] The driving frequency change mode in the terminal drive signal SD3 is opposite to the driving frequency change mode in the front end drive signal SD1. That is, the driving frequency in the terminal drive signal SD3 changes as follows. At time TT2, the driving frequency is the intermediate frequency fc. The driving frequency temporarily rises from the intermediate frequency fc to the maximum frequency fmax and then decreases. At time TTE, the driving frequency is the minimum frequency fmin. fmin<f0. The frequency rise speed from the intermediate frequency fc to the maximum frequency fmax is roughly equal to the frequency decrease speed from the maximum frequency fmax to the minimum frequency fmin. Compared with the frequency rise time from the intermediate frequency fc to the maximum frequency fmax, the frequency decrease time from the maximum frequency fmax to the minimum frequency fmin is longer. Therefore, although the terminal drive signal SD3 temporarily rises from the intermediate frequency fc to the maximum frequency fmax, it actually has a frequency change mode of "down chirp". The code "0" corresponding to the frequency change mode of down chirp is assigned to the terminal drive signal SD3 as the third bit.

[0082] like Figure 2 As shown, the frequency band in the lower chirp-like frequency change mode corresponding to the code "0" is called the lower chirp frequency band fbd. The lower chirp frequency band fbd is a frequency range from the highest frequency fmax to the lowest frequency fmin. In addition, the frequency band in the upper chirp-like frequency change mode corresponding to the code "1" is called the upper chirp frequency band fbu. The upper chirp frequency band fbu is also a frequency range from the lowest frequency fmin to the highest frequency fmax. That is, the lower chirp frequency band fbd and the upper chirp frequency band fbu are set to be approximately the same. In addition, the upper chirp frequency band fbu and the lower chirp frequency band fbd are set to include the resonance frequency f0 respectively.

[0083] The transmitting circuit 22 drives the transducer 21 based on the input drive signal SD to cause the transducer 21 to emit a transmission wave within the ultrasonic frequency band. As described above, the drive signal SD has a plurality of differentiated drive signals SD1, etc. The plurality of differentiated drive signals SD1, etc. are respectively encoded according to a frequency modulation method. Therefore, the differentiated transmission waves respectively corresponding to the plurality of differentiated drive signals SD1, etc. have a frequency modulation method corresponding to the modulation method of the drive frequency in the differentiated drive signal SD1, etc. That is, the differentiated transmission waves are encoded according to the frequency modulation method in the differentiated drive signal SD1, etc. The differentiated transmission waves are transmission waves corresponding to the differentiated drive signals. That is, the differentiated transmission waves are equivalent to a series of transmission waves transmitted in one transmission process during the period from the transmission process start timing TT0 to the transmission process end timing TTE, and the transmission waves are subdivided corresponding to the differentiated drive signals.

[0084] Thus, in the present embodiment, the drive signal generating unit 3 generates a front-end drive signal SD1 and outputs it toward the transmitting unit 20A, and the front-end drive signal SD1 is a drive signal corresponding to the front-end transmission wave included in the plurality of differentiated transmission waves. In addition, the drive signal generating unit 3 generates a drive signal corresponding to the subsequent transmission wave included in the plurality of differentiated transmission waves, namely, an intermediate drive signal SD2 and a terminal drive signal SD3, and outputs them toward the transmitting unit 20A. Thus, the transmitting unit 20A transmits a transmission wave including a plurality of differentiated transmission waves during the period from the start of the transmission process to the end of the transmission process. The plurality of differentiated transmission waves are continuously transmitted during the period from the start of the transmission process to the end of the transmission process, and are respectively encoded according to the waveform pattern. Thus, the transmission wave is encoded as a code sequence having multiple bits.

[0085] In this operation example, a series of transmission waves transmitted from the transmission process start timing TT0 to the transmission process end timing TTE includes three segmented transmission waves corresponding to the three segmented drive signals SD1 to SD3. The three segmented transmission waves are chirped in accordance with the frequency variation patterns of the three segmented drive signals SD1 to SD3.

[0086] For example, in Figure 2 In the specific example shown, the front transmission wave corresponding to the front drive signal SD1 as the first bit is encoded by the code "1" corresponding to the waveform pattern of the front drive signal SD1, that is, the up-chirp. In addition, the distinction transmission wave corresponding to the intermediate drive signal SD2 as the second bit is encoded by the code "1" corresponding to the waveform pattern of the intermediate drive signal SD2, that is, the up-chirp. And the distinction transmission wave corresponding to the terminal drive signal SD3 as the third bit is encoded by the code "0" corresponding to the waveform pattern of the terminal drive signal SD3, that is, the down-chirp.

[0087] Figure 2The transmission wave corresponding to the driving signal SD shown has a 3-bit code such as "110". That is, the codes of the first bit, the second bit, and the third bit are "1", "1", and "0", respectively. Similarly, in this embodiment, the transmission wave can be given a 3-bit code such as "100", "111", "010", "011", and "001". In this way, according to the object detection device 1 involved in this embodiment and the object detection method executed by it, the transmission wave can be encoded with multiple bits, thereby improving the recognition accuracy more than before.

[0088] The receiving unit 20B performs a receiving operation during a predetermined receivable period in the object detection operation. The receivable period is a period between the transmission processing end timing TTE and the next transmission processing start timing TT0 that comes immediately after, excluding a dead zone caused by the influence of reverberation, etc., in the configuration of this embodiment as an integrated transmitter and receiver. The transducer 21 as a receiver outputs an AC voltage signal corresponding to the amplitude and frequency of the received wave, that is, an element output signal, during the receivable period.

[0089] The receiving circuit 23 generates a received signal by performing signal processing such as amplification and analog / digital conversion on the element output signal. The received signal processing unit 4 generates an amplitude signal and a frequency signal by performing processing such as FFT on the received signal. The received signal processing unit 4 outputs the generated amplitude signal and frequency signal to the control unit 5.

[0090] As described above, the plurality of distinguishing drive signals SD1 and the like included in the drive signal SD are frequency modulated corresponding to the codes. In addition, the frequency of the transmission wave corresponds to the drive frequency which is the frequency of the drive signal SD. Therefore, the transmission wave has a frequency change corresponding to the time change of the drive frequency as a feature corresponding to the identification. Therefore, when the received wave is a normal wave, the frequency modulation state of the received signal should have the same feature as the transmitted wave.

[0091] Therefore, the detection unit 52 in the control unit 5 determines whether the received wave is a normal wave based on the frequency signal output from the received signal processing unit 4. Specifically, the reception determination unit 523 performs reception determination of the reflected wave by comparing the frequency signal corresponding to the waveform pattern in the received signal with the reference signal stored in the reference signal storage unit 521.

[0092] Figure 3 FIG. 5 shows a specific example of the reference signal SS stored in the reference signal storage unit 521. The down-chirp reference signal SSD corresponding to the code "0" has a driving frequency characteristic in which the frequency changes in an inverted V shape over time. The waveform of the down-chirp reference signal SSD is similar to Figure 2Specifically, the down-chirp reference signal SSD has a frequency characteristic in which the frequency temporarily rises from the resonance frequency f0 and then decreases toward a frequency lower than the resonance frequency f0.

[0093] In contrast, the up-chirp reference signal SSU corresponding to the code "1" has a driving frequency characteristic in which the frequency changes in a V-shape over time. Figure 2 Specifically, the up-chirp reference signal SSU has a frequency characteristic in which the frequency temporarily decreases from the resonance frequency f0 and then increases toward a frequency higher than the resonance frequency f0.

[0094] When both the host vehicle and the object B are stopped, the frequency of the transmitted wave and the frequency of the received wave, which is the reflected wave of the transmitted wave caused by the object B, are almost identical. In this case, the waveform of the frequency signal in the received wave and the waveform of the reference signal are almost identical on a time graph with the vertical axis being the frequency f and the horizontal axis being the time T.

[0095] However, in reality, at least one of the vehicle and object B often moves. Typically, at least the vehicle moves. Alternatively, the vehicle and object B move in different ways. The moving way includes the speed, acceleration, and direction during the movement. The moving way also includes stopping. When the moving ways of the vehicle and object B are different, a frequency shift between the transmitted wave and the received wave is generated. Figure 4 Such a frequency shift is schematically shown. Figure 4 In FIG. 1 , the solid line schematically shows the frequency characteristic of the reception signal SR, that is, the above-mentioned frequency signal. In addition, the dotted line schematically shows the frequency characteristic of the reference signal SS.

[0096] For example, when object B approaches the vehicle, Figure 4 As shown, the frequency of the received signal SR is higher than the frequency of the reference signal SS. In this case, the frequency shift is generated in such a way that one of the received signal SR and the reference signal SS is shifted toward the other by Δf. Δf is the frequency shift amount. The frequency shift amount Δf can be considered to be almost equal to the Doppler frequency shift amount.

[0097] The frequency shift amount Δf is expressed by the following formula (1). In formula (1), N is the number of samples, fr is the frequency of the received signal, and R is the frequency of the reference signal SS. The frequency shift detection unit 522 calculates the frequency shift amount Δf between the transmission wave and the reflected wave caused by the relative speed accompanying the relative movement of the host vehicle and the object B using formula (1).

[0098] [Formula 1]

[0099]

[0100] The relative speed Δv between the object B and the host vehicle is expressed by the following equation (2). In equation (2), c is the speed of sound. In addition, the relative speed between the host vehicle and the object B is simply referred to as "relative speed" hereinafter.

[0101] [Formula 2]

[0102]

[0103] The reception determination unit 523 performs reception determination of the reflected wave based on the frequency signal corresponding to the waveform pattern in the received signal SR, the frequency shift amount Δf detected by the frequency shift detection unit 522, and the reference signal SS. Specifically, the reception determination unit 523 determines whether the received wave is a normal wave by performing pattern matching of the waveform of the frequency signal and the waveform of the reference signal SS while taking the detected frequency shift into consideration.

[0104] In this embodiment, the reception decision unit 523 performs pattern matching using the mean square error MSE. That is, the reception decision unit 523 calculates the mean square error MSE using the following equation (3).

[0105] [Formula 3]

[0106]

[0107] In addition, when the mean square error MSE is less than a predetermined code determination threshold, the reception determination unit 523 determines that a chirp signal having a code corresponding to the frequency change pattern in the reference signal SS is included in the received wave. Furthermore, when the predetermined code sequence such as "110" included in the transmitted wave is also included in the received wave, the reception determination unit 523 determines that the received wave is a normal wave. Furthermore, when the received wave is a normal wave, the detection determination unit 524 detects the object B based on the amplitude signal output from the received signal processing unit 4.

[0108] Figure 5 Shown with Figure 2 The following is an overview of the reception determination process when the reflected wave of the transmission wave corresponding to the driving signal SD caused by the object B is received as a normal wave. Figure 5 In the diagram, the uppermost time diagram shows a frequency signal corresponding to the received signal SR.

[0109] Figure 5The middle time diagram in shows the relative speed Δv calculated by the above formula (2). That is, Δv_UP in the second time diagram from the top is the calculation result of the relative speed Δv when the up-chirp reference signal SSU corresponding to the code "1" is used as the reference signal SS. Δv_DN in the third time diagram from the top is the calculation result of the relative speed Δv when the down-chirp reference signal SSD corresponding to the code "0" is used as the reference signal SS.

[0110] Figure 5 The time diagram shown at the bottom of the figure shows the mean square error MSE calculated by the above formula (3). MSE_UP shown by the solid line is the calculation result of the mean square error MSE when the up-chirp reference signal SSU corresponding to the code "1" is used as the reference signal SS. MSE_DN shown by the dotted line is the calculation result of the mean square error MSE when the down-chirp reference signal SSD corresponding to the code "0" is used as the reference signal SS. MSE_TH shown by the horizontal dotted line is the code judgment threshold. In addition, TR1 shown by the arrow on the horizontal axis shows the time when the mean square error MSE is less than the code judgment threshold MSE_TH and becomes a minimum. In particular, the earliest time TR1 corresponding to the front-end drive signal SD1 and the front-end transmission wave is also called the "receiving time".

[0111] like Figure 2 As shown, in this operation example, the drive signal SD has a front drive signal SD1 having an up-chirp waveform pattern corresponding to the code "1". In addition, the drive signal SD has an intermediate drive signal SD2 having an up-chirp waveform pattern corresponding to the code "1". Furthermore, the drive signal SD has a terminal drive signal SD3 having a down-chirp waveform pattern corresponding to the code "0". Thus, the transmission wave is given the code "110".

[0112] like Figure 5 As shown in FIG. 1 , at time TR1, the mean square error MSE_UP corresponding to the up-chirp waveform pattern is less than the code determination threshold MSE_TH and is a minimum value. Therefore, it is determined that the waveform pattern of the first bit corresponding to time TR1 in the received wave contains a waveform pattern corresponding to code "1". In addition, the calculated value Δv_UP of the relative speed corresponding to the value of the mean square error MSE_UP at time TR1 is substantially consistent with the actual relative speed Δv=0 km / h.

[0113] Similarly, at time TR2 after time TR1, the mean square error MSE_UP corresponding to the up-chirp waveform pattern is less than the code determination threshold MSE_TH and is a minimum value. Here, the speed of sound, which is the propagation speed of the transmission wave and the reflected wave, is sufficiently faster than the moving speed of the vehicle and the object B around it. Therefore, it can be considered that the frequency shift amount Δf, that is, the relative speed Δv, is almost unchanged at time TR1 and time TR2. Therefore, the calculated value Δv_UP of the relative speed corresponding to the value of the mean square error MSE_UP at time TR2 should be almost consistent with the relative speed Δv calculated by the first bit.

[0114] At this point, the calculated value Δv_UP of the relative speed corresponding to the value of the mean square error MSE_UP at time TR2 falls within the range of the determination window Δvw. The determination window Δvw is a relative speed range of a predetermined width with the relative speed Δv=0 km / h calculated by the first bit as the center. Therefore, it is determined that the waveform pattern of the second bit corresponding to time TR2 in the received wave includes a waveform pattern corresponding to the code "1".

[0115] In addition, at time TR3 after time TR2, the mean square error MSE_DN corresponding to the down-chirp waveform pattern is less than the code decision threshold MSE_TH and is a minimum value. Here, similarly to the above, it can be considered that the frequency shift amount Δf, that is, the relative speed Δv, is almost unchanged at time TR1 and time TR3. Therefore, the calculated value Δv_DN of the relative speed corresponding to the value of the mean square error MSE_DN at time TR3 should be almost consistent with the relative speed Δv calculated by the first bit.

[0116] At this point, the calculated value Δv_DN of the relative speed corresponding to the value of the mean square error MSE_DN at time TR3 falls within the range of the determination window Δvw. Therefore, it is determined that the waveform pattern of the third bit corresponding to time TR3 in the received wave includes a waveform pattern corresponding to code "0".

[0117] However, in Figure 5 The portion surrounded by the dotted line in the top time diagram of generates a frequency variation pattern of a waveform similar to the waveform pattern in the down-chirp reference signal SSD. This portion is the portion between the reflected wave corresponding to the front transmission wave and the reflected wave corresponding to the subsequent transmission wave transmitted immediately after the front transmission wave. In addition, at time TRF, the mean square error MSE_DN is less than the code determination threshold MSE_TH and is a minimum value. Therefore, corresponding to time TRF, it seems that the waveform pattern corresponding to the code "0" is included in the received wave immediately after the waveform pattern corresponding to the front code "1".

[0118] However, such a frequency variation pattern is caused by Figure 2That is, such a frequency change pattern is not caused by the division transmission wave to which the code "0" is intentionally given by the division driving signal for down-chirping.

[0119] However, the transmitter 20A including the transducer 21 has a predetermined resonance frequency f0. In such a resonance-type transmitter 20A, the frequency followability is poor in the driving frequency away from the resonance frequency f0. Therefore, the driving frequency rises toward the maximum frequency fmax before the time TT1, and discontinuously decreases to the intermediate frequency fc at the time TT1, and further decreases toward the minimum frequency fmin, thereby generating the above-mentioned frequency change pattern.

[0120] In this way, the frequency change pattern generated independently of the coding intention is called "pseudo code". Figure 2 to Figure 5 In the operation example shown, if such a pseudo code is mistakenly determined as a down-chirping code "0" between the code "1" corresponding to the time TR1 and the code "1" corresponding to the time TR2, the recognition accuracy is reduced. The pseudo code is generated, for example, at the switching portion between two consecutive distinguishing drive signals. Alternatively, the pseudo code is generated, for example, when two reflected waves are received consecutively.

[0121] In this regard, in this operation example, it is determined that the waveform pattern of the first bit corresponding to the time TR1 in the received wave contains a waveform pattern corresponding to the code "1". In addition, based on the determination result of the first bit, the relative speed Δv=0 km / h is calculated. On the other hand, the calculated value Δv_DN of the relative speed corresponding to the time TRF does not enter the range of the determination window Δvw. Therefore, it is determined that the waveform pattern of the received wave corresponding to the time TRF is a pseudo code.

[0122] As described in detail above, in this embodiment, the reception judgment of the first bit is performed based on the frequency signal corresponding to the waveform pattern in the received signal SR and the reference signal SS corresponding to the waveform pattern in the front-end drive signal SD1. In addition, based on the reception judgment result of the first bit, the reception judgment of the second and subsequent bits is performed. That is, the relative speed judgment using the relative speed Δv calculated from the first bit as a reference is combined in the pattern matching. In this way, the pseudo code is well identified.

[0123] Specifically, the frequency shift amount Δf is calculated by the reception judgment of the first bit. In addition, the relative speed Δv is calculated based on the calculated frequency shift amount Δf. Moreover, the code judgment of the second and subsequent bits is performed by whether the calculated value of the relative speed Δv of the second and subsequent bits enters the relative speed range set based on the calculated value of the relative speed Δv in the first bit, that is, the judgment window Δvw. In addition, as mentioned above, pseudocodes may also be generated when multiple reflected wave signals are received in an overlapping manner. In this case, by using the non-overlapping front end bit with high reliability as a reference to judge the subsequent bits, a high-precision judgment can be made. Therefore, according to the object detection device 1 involved in this embodiment and the object detection method executed thereby, it is possible to well suppress the erroneous judgment caused by pseudocodes, and therefore, the recognition accuracy can be improved more than before.

[0124] In this embodiment, the detection unit 52 performs reception determination of the reflected wave corresponding to the front-end transmission wave based on the reference signal SS corresponding to the waveform pattern in the front-end drive signal SD1. In addition, the detection unit 52 performs reception determination of the reflected wave corresponding to the subsequent transmission wave based on the reference signal SS corresponding to the waveform pattern in the subsequent distinguishing drive signal SD2, etc.

[0125] In such a configuration and method, a reception determination of a reflected wave corresponding to a front transmission wave encoded according to the waveform pattern in the front drive signal SD1 is performed based on a reference signal SS corresponding to a waveform pattern in the front drive signal SD1. In addition, a reception determination of a reflected wave corresponding to a subsequent transmission wave encoded according to the waveform pattern in the intermediate drive signal SD2 is performed based on a reference signal SS corresponding to a waveform pattern in the intermediate drive signal SD2. Similarly, a reception determination of a reflected wave corresponding to a subsequent transmission wave encoded according to the waveform pattern in the terminal drive signal SD3 is performed based on a reference signal SS corresponding to a waveform pattern in the terminal drive signal SD3. Therefore, according to the object detection device 1 involved in this embodiment and the object detection method executed thereby, the reception determination accuracy can be further improved.

[0126] In the present embodiment, the detection unit 52 includes a frequency shift detection unit 522. The frequency shift detection unit 522 detects a frequency shift amount Δf between a transmission wave and a reflected wave based on the relative speed between the vehicle and the object B. In addition, the detection unit 52 makes a reception determination of a reflected wave corresponding to a subsequent transmission wave based on the frequency shift amount Δf detected from the reflected wave corresponding to the front transmission wave.

[0127] Specifically, the frequency shift detection unit 522 calculates the frequency shift amount Δf based on the reception determination result of the reflected wave corresponding to the front transmission wave as the first bit. In addition, the detection unit 52 calculates the relative speed Δv based on such frequency shift amount Δf. Moreover, the detection unit 52 performs code determination on the second and subsequent bits by whether the calculated value of the relative speed Δv of the second and subsequent bits enters the determination window Δvw set based on such calculated value of the relative speed Δv.

[0128] In such a configuration, the frequency shift amount Δf caused by the relative speed between the host vehicle and the surrounding object B is detected based on the reflected wave corresponding to the front transmission wave. Moreover, based on the frequency shift amount Δf detected based on the reflected wave corresponding to the front transmission wave, that is, the relative speed Δv, the reception judgment of the reflected wave corresponding to the subsequent transmission wave is performed. As a result, the chirp coding in the front transmission wave can be used to well perform the Doppler shift correction when the reception judgment of the reflected wave corresponding to the subsequent transmission wave. Therefore, according to the object detection device 1 involved in this embodiment and the object detection method executed by it, the reception judgment accuracy in the case where the host vehicle and the surrounding object B move relative to each other can be further improved.

[0129] In this embodiment, at least the front-end transmission wave is encoded by frequency modulation. That is, at least the front-end transmission wave is chirped and encoded so that the frequency changes over time. Specifically, according to Figure 2 In the specific example shown, at least the front transmission wave is encoded by a V-shaped chirp wave. This can further improve the reception judgment accuracy. In particular, the detection accuracy of the frequency shift amount Δf, that is, the relative speed Δv, is improved. In addition, the detection or identification accuracy of the reception time TR1 is improved.

[0130] (Second Embodiment)

[0131] Below, refer to Figure 6 to Figure 9 The second embodiment is described. In the following description of the second embodiment, the parts different from the first embodiment are mainly described. In addition, in the first embodiment and the second embodiment, the same or equivalent parts are marked with the same reference numerals. Therefore, in the following description of the second embodiment, for the components with the same reference numerals as the first embodiment, as long as there is no technical contradiction or special additional description, the description in the first embodiment can be appropriately cited. The same is also true in the third embodiment described later.

[0132] Figure 6An example of the drive signal SD in this embodiment is shown. In this embodiment, the front end drive signal SD1 is formed in an up-chirp frequency band fbu formed by the first minimum frequency fmin1 and the first maximum frequency fmax1, and the frequency changes over time. The up-chirp frequency band fbu corresponds to the "first frequency band".

[0133] Specifically, the driving frequency change mode in the front-end drive signal SD1 is as follows. At time TT0, the driving frequency is the first intermediate frequency fc1. fc1<f0. The driving frequency temporarily decreases from the first intermediate frequency fc1 to the first minimum frequency fmin1 and then turns to rise. At time TT1, the driving frequency is the first maximum frequency fmax1. fmax1>f0. The frequency reduction speed from the first intermediate frequency fc1 to the first minimum frequency fmin1 is approximately equal to the frequency increase speed from the first minimum frequency fmin1 to the first maximum frequency fmax1. Compared with the frequency reduction time from the first intermediate frequency fc1 to the first minimum frequency fmin1, the frequency rise time from the first minimum frequency fmin1 to the first maximum frequency fmax1 is longer. Therefore, although the front-end drive signal SD1 temporarily decreases from the first intermediate frequency fc1 to the first minimum frequency fmin1, it actually has a frequency change mode in the form of "up chirp". The front-end drive signal SD1 as the first bit is given a code "1" corresponding to the frequency change mode in the form of up chirp.

[0134] The driving frequency variation mode in the intermediate driving signal SD2 is the same as the driving frequency variation mode in the front driving signal SD1. That is, the intermediate driving signal SD2 is also formed so that the frequency in the up-chirp frequency band fbu varies with time. The code "1" corresponding to the up-chirp frequency variation mode is given to the intermediate driving signal SD2 as the second bit.

[0135] On the other hand, the end drive signal SD3 is formed so that the frequency changes with time in the down-chirp frequency band fbd formed by the second minimum frequency fmin2 and the second maximum frequency fmax2. The down-chirp frequency band fbd corresponds to the "second frequency band".

[0136] The driving frequency change in the terminal drive signal SD3 is as follows. At time TT2, the driving frequency is the second intermediate frequency fc2. fc2>f0. The driving frequency temporarily rises from the second intermediate frequency fc2 to the second maximum frequency fmax2 and then turns to decrease. At time TTE, the driving frequency is the second minimum frequency fmin2. fmin2<f0. The frequency rise speed from the second intermediate frequency fc2 to the second maximum frequency fmax2 is approximately equal to the frequency decrease speed from the second maximum frequency fmax2 to the second minimum frequency fmin2. Compared with the frequency rise time from the second intermediate frequency fc2 to the second maximum frequency fmax2, the frequency decrease time from the second maximum frequency fmax2 to the second minimum frequency fmin2 is longer. Therefore, although the terminal drive signal SD3 temporarily rises from the second intermediate frequency fc2 to the second maximum frequency fmax2, it actually has a frequency change mode of "down chirp". The terminal drive signal SD3 as the third bit is given a code "0" corresponding to the frequency change mode of down chirp.

[0137] In the first embodiment, the down-chirp frequency band fbd and the up-chirp frequency band fbu are set to coincide with each other, that is, to overlap each other entirely. In contrast, in the present embodiment, the down-chirp frequency band fbd and the up-chirp frequency band fbu are set to overlap each other partially.

[0138] Specifically, the down-chirp frequency band fbd and the up-chirp frequency band fbu are formed so that the second minimum frequency fmin2 is higher than the first minimum frequency fmin1. Also, the down-chirp frequency band fbd and the up-chirp frequency band fbu are formed so that the second maximum frequency fmax2 is higher than the first maximum frequency fmax1.

[0139] In this way, the upper chirp frequency band fbu in the present embodiment is equivalent to the frequency band after the upper chirp frequency band fbu in the above-mentioned first embodiment is shifted or offset to the low frequency side. The shift amount or offset amount is equivalent to the difference between the first intermediate frequency fc1 and the resonance frequency f0. Similarly, the lower chirp frequency band fbd in the present embodiment is equivalent to the frequency band after the lower chirp frequency band fbd in the above-mentioned first embodiment is shifted or offset to the high frequency side. The shift amount or offset amount is equivalent to the difference between the second intermediate frequency fc2 and the resonance frequency f0. In addition, the lower chirp frequency band fbd and the upper chirp frequency band fbu are set to approximately the same bandwidth. That is, fmax1-fmin1≈fmax2-fmin2. In addition, the upper chirp frequency band fbu and the lower chirp frequency band fbd are set to include the resonance frequency f0.

[0140] However, the transducer 21 of the resonant ultrasonic microphone has the same characteristics as a bandpass filter. That is, the frequency band that can be well transmitted and received by the transmitter 20A is actually limited to a width of ±several % with the resonant frequency f0 as the center. At a driving frequency far from the resonant frequency f0, the followability of the transmitter 20A is poor.

[0141] Therefore, a predetermined transmission and reception frequency band is set for the transmitting unit 20A. Such a transmission and reception frequency band is a range of S=0 to Sb[dB] when the output or sensitivity is S and S=0[dB] at the resonant frequency f0. That is, the transmission and reception frequency band as a frequency range in which the transmission and reception unit 2 can transmit and receive well is a frequency band of S=0 to Sb[dB] between the upper limit frequency fu and the lower limit frequency fd. Typically, Sb is, for example, -3[dB]. The sensitivity is the sensitivity when the transducer 21 is used as a receiver. In addition, such a transmission and reception frequency band can also be called a "resonance frequency band", "-3dB band" or "3dB band".

[0142] Therefore, in this embodiment, the lower chirp frequency band fbd and the upper chirp frequency band fbu are set within the transmission and reception frequency band between the upper limit frequency fu and the lower limit frequency fd. Specifically, the first minimum frequency fmin1 is set to coincide with the lower limit frequency Fd. In addition, the second maximum frequency fmax2 is set to coincide with the upper limit frequency Fu.

[0143] Figure 7 FIG. 5 shows a specific example of the reference signal SS stored in the reference signal storage unit 521. The up-chirped reference signal SSU corresponding to the code "1" has a driving frequency characteristic in which the frequency changes in a V-shape over time. The waveform of the up-chirped reference signal SSU is similar to Figure 6 The waveform of the distinguishing drive signal corresponding to the code "1" such as the front end drive signal SD1 in the specific example shown is formed accordingly. Specifically, the up-chirp reference signal SSU has a frequency characteristic in which the frequency temporarily decreases from the frequency side slightly lower than the resonance frequency f0 and then rises to the frequency side higher than the resonance frequency f0. That is, the up-chirp reference signal SSU in this embodiment is equivalent to the signal after the up-chirp reference signal SSU in the above-mentioned first embodiment is shifted or offset to the low frequency side. The shift amount or offset amount is equivalent to the difference between the resonance frequency f0 and the first intermediate frequency fc1.

[0144] On the other hand, the down-chirp reference signal SSD corresponding to the code "0" has a driving frequency characteristic in which the frequency changes in an inverted V shape over time. Figure 6The waveform of the distinguishing drive signal corresponding to the code "0" such as the terminal drive signal SD3 in the specific example shown is formed accordingly. Specifically, the down-chirp reference signal SSD has a frequency characteristic in which the frequency temporarily rises from the frequency side slightly higher than the resonance frequency f0 and then decreases to the frequency side lower than the resonance frequency f0. That is, the down-chirp reference signal SSD in this embodiment is equivalent to a signal after the down-chirp reference signal SSD in the first embodiment is shifted or offset to the high frequency side. The shift amount or offset amount is equivalent to the difference between the second intermediate frequency fc2 and the resonance frequency f0.

[0145] Figure 8 as well as Fig. 9 Shown with Figure 6 The following is an overview of the reception determination process when the reflected wave of the transmission wave corresponding to the driving signal SD is received as a normal wave. Figure 8 as well as Fig. 9 The time diagrams shown are Figure 5 The same as the time diagrams shown. Figure 8 In the specific example shown, the actual relative speed is 0 km / h. Fig. 9 In the specific example shown, the actual relative speed is -10 km / h. Fig. 9 In the specific example shown, object B is moving away from the vehicle at a speed of 10 km / h. Fig. 9 In the top time diagram, the double-dotted line shows Figure 8 The specific example shown is the frequency characteristic of the received signal SR when the relative speed is 0 km / h. Fig. 9 The difference between the solid line and the two-dot chain line in corresponds to the frequency shift amount Δf.

[0146] like Figure 8 as well as Fig. 9 As shown by the dotted line in the uppermost time diagram of FIG, a pseudo code-like waveform pattern similar to the waveform pattern in the down-chirped reference signal SSD may be generated in the received signal SR. In this specific example, such a pseudo code-like waveform is generated in the portion between the reflected wave corresponding to the front transmission wave and the reflected wave corresponding to the subsequent transmission wave transmitted immediately after the front transmission wave.

[0147] In this regard, in the present embodiment, an offset is provided between the upper chirp frequency band fbu and the lower chirp frequency band fbd. That is, the shift direction of the center frequency in the upper chirp frequency band fbu from the resonance frequency f0 is opposite to the shift direction of the center frequency in the lower chirp frequency band fbd from the resonance frequency f0. Similarly, the shift direction of the upper chirp reference signal SSU from the resonance frequency f0 is opposite to the shift direction of the lower chirp reference signal SSD from the resonance frequency f0.

[0148] Therefore, the calculated value of the frequency shift amount Δf or the relative speed Δv corresponding to the above pseudo-code waveform and the calculated value of the frequency shift amount Δf or the relative speed Δv corresponding to other parts of the reflected wave are less compatible. Figure 8 as well as Fig. 9 As shown, the calculated value Δv_DN of the relative speed corresponding to the time TRF does not enter the range of the determination window Δvw with the relative speed Δv calculated at the first bit as the center. In particular, in this embodiment, the calculated value Δv_DN of the relative speed corresponding to the time TRF is further away from the range of the determination window Δvw than in the first embodiment described above.

[0149] Thus, according to this embodiment, the calculated value of the relative speed Δv corresponding to the pseudo code can be further away from the calculated value of the relative speed Δv calculated at the first bit. Therefore, the pseudo code based on the relative speed determination using the first bit as a reference can be better identified. Therefore, the reception determination accuracy can be further improved.

[0150] In the present embodiment, the up-chirp frequency band fbu and the down-chirp frequency band fbd are set to include the resonance frequency f0. This improves the sound pressure of the transmission wave and the reception sensitivity of the reflected wave.

[0151] In this embodiment, the upper chirp frequency band fbu and the lower chirp frequency band fbd are set so that the second minimum frequency fmin2 is higher than the first minimum frequency fmin1. In addition, the upper chirp frequency band fbu and the lower chirp frequency band fbd are set so that the second maximum frequency fmax2 is higher than the first maximum frequency fmax1. Thus, the offset between the frequency bands can be well set.

[0152] In this embodiment, at least the front-end transmission wave is also encoded by frequency modulation. That is, at least the front-end transmission wave is chirped and encoded so that the frequency changes over time. Specifically, according to Figure 6 In the specific example shown, at least the front transmission wave is encoded by a V-shaped chirp wave. This can further improve the reception judgment accuracy.

[0153] (Third Embodiment)

[0154] Below, refer to Fig.10 as well as Fig.11 The third embodiment is described below. In this embodiment, before calculating the frequency shift amount Δf or the relative speed Δv of the first bit, the initial up-chirp reference signal SSU0 and the initial down-chirp reference signal SSD0 are used as the reference signal SS. Fig.10 In the specific example shown, the drive signal SD is Figure 6In addition, the initial up-chirp reference signal SSU0 and the initial down-chirp reference signal SSD0 are the same as those of the second embodiment shown in FIG. Figure 7 The up-chirp reference signal SSU and the down-chirp reference signal SSD in the second embodiment described above are identical.

[0155] After calculating the frequency shift amount Δf or the relative speed Δv of the first bit, the modified up-chirp reference signal SSU1 and the modified down-chirp reference signal SSD1 are used as the reference signal SS. The modified up-chirp reference signal SSU1 is obtained by correcting the initial up-chirp reference signal SSU0 based on the calculation result of the frequency shift amount Δf or the relative speed Δv of the first bit. The modified down-chirp reference signal SSD1 is obtained by correcting the initial down-chirp reference signal SSD0 based on the calculation result of the frequency shift amount Δf or the relative speed Δv of the first bit.

[0156] exist Fig.10 as well as Fig.11 In the specific example shown, the actual relative speed is -10 km / h. Fig.10 as well as Fig.11 In the specific example shown, the object B is relatively moving away from the host vehicle at a speed of 10 km / h.

[0157] like Fig.11 As shown in FIG. 1 , at time TR1, the mean square error MSE_UP corresponding to the up-chirp waveform pattern is less than the code determination threshold MSE_TH and is a minimum value. Therefore, it is determined that the waveform pattern of the first bit corresponding to time TR1 in the received wave contains a waveform pattern corresponding to code "1". In addition, the frequency shift amount Δf and the relative speed Δv of the first bit are calculated.

[0158] Next, in this embodiment, the reference signal SS is corrected based on the calculated value of the frequency shift amount Δf or the relative speed Δv of the first bit. In the mean square error MSE_DN calculated using the corrected up-chirp reference signal SSU1 and the corrected down-chirp reference signal SSD1 as the corrected reference signal SS, the minimum value at the time TRF is not less than the code determination threshold MSE_TH. That is, the pseudo code and the reference signal SS are inconsistent. Therefore, the code corresponding to the time TRF is not recognized.

[0159] Thus, according to the present embodiment, the erroneous determination caused by the pseudo code can be further suppressed. Therefore, the reception determination accuracy can be further improved. In addition, it is not necessary to use the relative speed determination using the determination window Δvw set based on the calculated value of the relative speed Δv. That is, in the present embodiment, instead of the relative speed determination using the first bit as the reference in the above-mentioned first embodiment, etc., the reference signal SS is corrected based on the reception determination result of the first bit. Thus, the processing load can be reduced well.

[0160] (Fourth Embodiment)

[0161] Below, refer to Fig.12 as well as Fig.13 A fourth embodiment will be described. Fig.12 In FIG. 1 , an upper section shows an example of a drive signal SD, and a lower section shows an example of a synthesized reference signal SSM which is a reference signal corresponding to the drive signal SD. Fig.12 The driving signal SD shown is Figure 6 The drive signals SD shown are identical. Fig.13 Shown with Fig.12 The schematic diagram of the reception determination process is shown in FIG. 1 when the reflected wave of the transmission wave corresponding to the driving signal SD caused by the object B is received as a normal wave. Fig.13 In the specific example shown, the actual relative speed is -10 km / h. Fig.13 In the specific example shown, the object B is relatively moving away from the host vehicle at a speed of 10 km / h.

[0162] In the present embodiment, the detection unit 52 performs reception determination of the reflected wave based on the synthetic reference signal SSM. The synthetic reference signal SSM is obtained by integrating the reference signals corresponding to the distinguishing drive signal SD1 and the like. The synthetic reference signal SSM can be stored in the reference signal storage unit 521. Alternatively, the frequency shift detection unit 522 can perform processing of reading the reference signals corresponding to the distinguishing drive signal SD1 and the like from the reference signal storage unit 521 and integrating them.

[0163] exist Fig.12 In the specific example shown, the synthesized reference signal SSM is obtained by integrating the up-chirped reference signal SSU of the first bit, the up-chirped reference signal SSU of the second bit, and the down-chirped reference signal SSD of the third bit. Figure 7 The second bit of the up-chirp reference signal SSU is the same as that shown in FIG. Figure 7 The third bit of the down-chirp reference signal SSD corresponds to the intermediate drive signal SD2. Figure 7The same as shown, corresponding to the end drive signal SD3.

[0164] During the period from the transmission processing start timing TT0 to the transmission processing end timing TTE, a transmission wave including a plurality of differentiated transmission waves respectively encoded according to the waveform pattern in the differentiated drive signal SD1, etc. is transmitted. These plurality of differentiated transmission waves include a front-end transmission wave encoded according to the waveform pattern in the front-end drive signal SD1. In addition, these plurality of differentiated transmission waves include a subsequent transmission wave encoded according to the waveform pattern in the subsequent differentiated drive signal SD2, etc. and transmitted after the front-end transmission wave. Therefore, when the transmission wave including these plurality of differentiated transmission waves is reflected by the object B and the reflected wave generated is received as a received wave by the receiving unit 20B, the received wave includes a reflected wave corresponding to the front-end transmission wave and a reflected wave corresponding to the subsequent transmission wave.

[0165] Here, in this embodiment, when judging the reception of the reflected wave, a synthetic reference signal SSM reflecting the waveform pattern of the entire transmission wave is used. That is, the reception judgment is made based on whether the mean square error MSE calculated using the synthetic reference signal SSM is smaller than the code judgment threshold MSE_TH and is a minimum value.

[0166] Fig.13 The time TR shown at the bottom of the time chart is the earliest time when the mean square error MSE is less than the code decision threshold MSE_TH and is a minimum value. Such a time TR is also called a "reception time".

[0167] According to this embodiment, by using a synthetic reference signal SSM that reflects the waveform pattern of the entire transmission wave, the reception judgment accuracy can be further improved. Alternatively, by calculating the relative speed only in the portion corresponding to the front-end bit in the synthetic reference signal SSM, and applying the relative speed to the entire synthetic reference signal SSM for pattern matching processing, the calculation load can be reduced as much as possible.

[0168] (Fifth Embodiment)

[0169] Below, refer to Figure 14 to Figure 16 The fifth embodiment is described. Fig.14 As shown, the detection unit 52 includes a reference signal storage unit 521 , a frequency shift detection unit 522 , a reception determination unit 523 , a detection determination unit 524 , a reference time setting unit 525 , and a timing setting unit 526 .

[0170] Fig.15 An example of the drive signal SD in this embodiment is shown. Fig.15 The driving signal SD shown is Figure 6 The drive signals SD shown are identical. Fig.16 Shown with Fig.15The following is an outline of the reception determination process when the reflected wave of the transmission wave corresponding to the driving signal SD caused by the object B is received as a normal wave.

[0171] The reference time setting unit 525 sets the reference time TS1 based on the reception determination result of the reflected wave corresponding to the front-end transmission wave. The reference time TS1 is the time when the frequency signal extracted from the received signal corresponding to the front-end transmission wave and the reference signal have a maximum value or above a predetermined value, also called the "reception time". Fig.16 In the specific example shown, the reference time setting unit 525 sets the earliest time TR1 among the times when the mean square error MSE is less than the code determination threshold MSE_TH and is a minimum value as the reference time TS1. As described later, the minimum value of the mean square error MSE corresponds to the maximum value of the consistency M, that is, the degree of consistency between the frequency signal and the reference signal.

[0172] The timing setting unit 526 sets the determination timing TS2 of the subsequent transmission wave based on the reference timing TS1 set by the reference timing setting unit 525. Specifically, the timing setting unit 526 sets the determination timings TS2, TS3, etc. based on the reference timing TS1 and the output interval of the distinguishing drive signal SD1, etc.

[0173] exist Fig.15 as well as Fig.16 In the specific example shown, the timing setting unit 526 sets the time Tint1 after the reference time TS1 as the determination time TS2. Tint1 is the transmission interval, that is, the time interval between the times TT0 and TT1. In addition, the timing setting unit 526 sets the time Tint2 after the determination time TS2 as the determination time TS3. Tint2 is the transmission interval, that is, the time interval between the times TT1 and TT2.

[0174] The reception determination unit 523 performs reception determination of the reflected wave corresponding to the subsequent transmission wave at the determination timing set by the timing setting unit 526. In the present embodiment, the reception determination unit 523 determines whether the mean square error MSE is less than the code determination threshold MSE_TH within the determination time window Tw with the determination timing TS2 as the center. In addition, the reception determination unit 523 determines whether the mean square error MSE is less than the code determination threshold MSE_TH within the determination time window Tw with the determination timing TS3 as the center.

[0175] In this embodiment, at time TR2 within the determination time window Tw with determination timing TS2 as the center, the mean square error MSE_UP corresponding to the up-chirp waveform pattern is less than the code determination threshold MSE_TH and is a minimum value. Thus, it is determined that the waveform pattern of the second bit corresponding to time TR2 includes a waveform pattern corresponding to code "1".

[0176] Similarly, at time TR3 within the determination time window Tw with determination timing TS3 as the center, the mean square error MSE_DN corresponding to the down-chirp waveform pattern is smaller than the code determination threshold MSE_TH and is a minimum value. Thus, it is determined that the waveform pattern of the third bit corresponding to time TR3 includes a waveform pattern corresponding to code "0".

[0177] On the other hand, at the time TRF between the reference time TS1 and the decision time TS2, the mean square error MSE_DN corresponding to the down-chirp waveform pattern is less than the code decision threshold MSE_TH and is a minimum value. However, the decision time and decision time window corresponding to the time TRF are not set. Fig.16 In the pseudo-code waveform shown by the portion surrounded by the dotted line in the top time chart, no code determination is performed.

[0178] Thus, in the present embodiment, at the determination time using the reference time TS1 set based on the reception determination result of the reflected wave corresponding to the front-end transmission wave as the reference, the reception determination of the reflected wave corresponding to the subsequent transmission wave is performed. That is, the front-end transmission wave has the function of being a code, and also has the synchronization function when the reception determination of the reflected wave corresponding to the subsequent transmission wave is performed. Thus, the identification function of the reflected wave and the noise is improved. In addition, the generation of the false determination caused by the pseudo-code-shaped waveform generated between the reflected wave corresponding to the distinguished transmission wave and the reflected wave corresponding to the distinguished transmission wave sent immediately thereafter can be well suppressed. Therefore, the reception determination accuracy can be further improved. And, since the determination of whether the mean square error MSE is less than the code determination threshold MSE_TH is performed in the determination time window Tw using the determination time TS2 etc. as the center, the calculation load can be reduced as much as possible.

[0179] (Variation Example)

[0180] The present disclosure is not limited to the above-mentioned embodiments. Therefore, the above-mentioned embodiments can be appropriately changed. Representative modified examples are described below. In the following description of the modified examples, the differences from the above-mentioned embodiments are mainly described. In addition, in the above-mentioned embodiments and the modified examples, the same or equivalent parts are marked with the same figure marks. Therefore, in the description of the following modified examples, for the constituent elements with the same figure marks as the above-mentioned embodiments, as long as there is no technical contradiction or special additional description, the description in the above-mentioned embodiment can be appropriately quoted.

[0181] The object detection device 1 is not limited to a vehicle-mounted configuration, that is, a configuration mounted on the vehicle V. Therefore, specifically, for example, the object detection device 1 can also be mounted on a ship or an aircraft. In addition, the object detection device 1 is not limited to a configuration in which the transceiver 2, the drive signal generating unit 3, the received signal processing unit 4, and the control unit 5 are supported by a sensor frame. That is, for example, all or at least a part of the functional configurations provided in the drive signal generating unit 3, the received signal processing unit 4, and the control unit 5 can be provided in a sonar ECU not shown. ECU is an abbreviation of Electronic Control Unit. The sonar ECU is mounted on this vehicle so as to be connected to the ultrasonic sensor having a configuration in which the transceiver 2 is supported on the sensor frame via an on-board communication line so as to be able to communicate.

[0182] The object detection device 1 is not limited to Figure 1 As shown in the figure, the structure includes one transceiver 2 and one drive signal generator 3. That is, the object detection device 1 may include a plurality of transceivers 2. In this case, the drive signal generator 3 and the transceiver 2 are provided in the same number.

[0183] The object detection device 1 is not limited to a structure of an integrated transmitter and receiver. That is, the object detection device 1 is not limited to a structure capable of transmitting and receiving ultrasonic waves through a single transducer 21. Therefore, for example, a transducer 21 for transmission electrically connected to a transmission circuit 22 and a transducer 21 for reception electrically connected to a reception circuit 23 may be provided in parallel. In other words, the transmission unit 20A and the reception unit 20B may each include a transducer 21. In this case, the transmission unit 20A and the reception unit 20B may each be supported by their own sensor frames.

[0184] There may be a case where the two-dimensional position of object B relative to the vehicle is detected by triangulation using multiple transducers 21. In this case, for example, transmission waves having the same frequency characteristics, i.e., code sequences, can be emitted from multiple transducers 21 mounted on the vehicle. At this time, a "normal wave" refers to a received wave when the vehicle receives a reflected wave of a transmission wave transmitted from the vehicle. In contrast, an "abnormal wave" refers to a received wave when the vehicle receives a reflected wave of a transmission wave transmitted from another vehicle. Thus, the influence caused by crosstalk between multiple vehicles can be well suppressed. Alternatively, for example, transmission waves having different frequency characteristics, i.e., code sequences, can be emitted from multiple transducers 21 mounted on the vehicle. Thus, the transducer 21 on the transmitting side and the transducer 21 on the receiving side can easily distinguish between the same direct wave and different indirect waves, and therefore, erroneous recognition caused by the influence of multiple reflections and the like can be well suppressed.

[0185] The configuration of each part such as the transmitting circuit 22 and the receiving circuit 23 is not limited to the specific example shown in the above embodiment. That is, for example, a digital / analog conversion circuit may be provided in the driving signal generating part 3 instead of the transmitting circuit 22. That is, the driving signal may be the element input signal itself for the transducer 21.

[0186] The code sequence in the drive signal SD may be changeable or unchangeable. That is, for example, the transmission control unit 51 may also be configured to change the code sequence in the drive signal SD, i.e., the transmission wave, when the detection unit 52 detects crosstalk. Alternatively, the drive signal generation unit 3 may also be configured to output only one drive signal SD to one transceiver unit 2. In this case, for example, the drive signal generation unit 3 in the object detection device 1 mounted on the vehicle only outputs a drive signal SD corresponding to a 3-bit code such as "110". In addition, the drive signal generation unit 3 in the object detection device 1 mounted on a certain other vehicle only outputs a drive signal SD corresponding to a 3-bit code such as "100". Furthermore, the drive signal generation unit 3 in the object detection device 1 mounted on another other vehicle only outputs a drive signal SD corresponding to a 3-bit code such as "111".

[0187] When a plurality of transceiver units 2 are provided, the drive signal generating unit 3 can be configured to input a drive signal SD of a different code sequence to each of the plurality of transceiver units 2. Specifically, for example, when two transceiver units 2 are provided, a drive signal SD corresponding to a 3-bit code such as "110" is input to one of the transceiver units, and a drive signal SD corresponding to a 3-bit code such as "100" is input to the other of the transceiver units.

[0188] The processing content in the detection unit 52 is also not limited to the above-mentioned specific examples. For example, the reception determination unit 523 may determine whether the degree of match M is greater than a predetermined reference value instead of determining whether the mean square error MSE is less than a predetermined code determination threshold MSE_TH.

[0189] That is, the receiving determination unit 523 may also determine that the chirp signal of the code corresponding to the reference signal is included in the received wave when the consistency M is greater than a predetermined reference value. The consistency M is an indicator indicating the degree of consistency between the frequency signal in the received signal and the reference signal, and is shown in the following formula (4). In short, the consistency M is equivalent to the opposite concept of error.

[0190] [Formula 4]

[0191]

[0192] The method for calculating the frequency shift amount and the relative speed is not limited to the above specific example. For example, the frequency shift amount k in the following equation (5) can be used instead of the frequency shift amount Δf in the above equation (1).f .

[0193] [Formula 5]

[0194]

[0195] The degree to which the influence of Doppler shift appears in the frequency of the received signal corresponds to the ratio of the relative velocity to the speed of sound. Therefore, for the frequency shift, it is more accurate to express it by a ratio as in the above equation (5) rather than by a difference as in the above equation (1).

[0196] When the above-mentioned equation (5) is used, the relative speed Δv is expressed by the following equation (6).

[0197] [Formula 6]

[0198]

[0199] In addition, the frequency shift k f It can also be approximately calculated by the following formula (7). This further reduces the calculation load.

[0200] [Formula 7]

[0201]

[0202] When the above-mentioned equations (5) to (7) are used, the pattern matching of the reception determination unit 523 is performed using the following equation (8) instead of the above-mentioned equation (3).

[0203] [Formula 8]

[0204]

[0205] The error sum of squares S calculated by formula (8) E is N times the mean square error MSE. Therefore, even when using formula (8), it is possible to perform the same Figure 5 Wait for the same code judgment.

[0206] In addition, in formula (8), the error square sum S E When is a minimum value, the following formula (9) holds.

[0207] [Formula 9]

[0208]

[0209] The following equation (10) is derived from the above equations (8) and (9). The frequency shift amount k shown in the equation (10) can also be expressed as f As the detection result of the frequency shift detection unit 522.

[0210] [Formula 10]

[0211]

[0212] The code determination method is not limited to using the sum of squared errors, mean squared errors, or consistency. That is, for example, correlation operations can be used. In this case, the code determination is performed by determining whether the correlation value obtained by the correlation operation based on the received signal and the reference signal is above a threshold.

[0213] exist Figure 6 In the specific example shown, the lower chirp frequency band fbd and the upper chirp frequency band fbu are formed so that the second lowest frequency fmin2 is higher than the first lowest frequency fmin1. In addition, the lower chirp frequency band fbd and the upper chirp frequency band fbu are formed so that the second highest frequency fmax2 is higher than the first highest frequency fmax1. However, the present disclosure is not limited to such a mode. That is, for example, the second lowest frequency fmin2 may be lower than the first lowest frequency fmin1, and the second highest frequency fmax2 may be lower than the first highest frequency fmax1.

[0214] The waveform of the differentiation drive signal is not limited to the above-mentioned specific examples. That is, for example, the frequency rise speed and the frequency decrease speed in the V-shaped chirp wave may be different. In addition, the frequency rise time and the frequency decrease time may be the same or different. Instead of the V-shaped chirp wave, a chirp wave whose frequency rises or decreases monotonically may be used. The frequency rise or decrease may be linear or non-linear such as a Sigmaid curve. Furthermore, an interval period may be set between mutually adjacent differentiation drive signals SD1 among a plurality of differentiation drive signals SD1.

[0215] In the above specific example, a differentiated driving signal and a differentiated transmission wave having an up-chirp frequency variation pattern and a differentiated driving signal and a differentiated transmission wave having a down-chirp frequency variation pattern are used. However, the present disclosure is not limited to such a pattern.

[0216] Specifically, a CW wave can also be used as a distinguishing driving signal and a distinguishing transmission wave. In this case, for example, a code "1" can be assigned to the frequency change mode of the up-chirp, a code "0" can be assigned to the CW wave, and a code "-1" can be assigned to the frequency change mode of the down-chirp. Alternatively, a binary number can be used based on installation considerations, and a code "01" can be assigned to the frequency change mode of the up-chirp, a code "11" can be assigned to the CW wave, and a code "10" can be assigned to the frequency change mode of the down-chirp.

[0217] Even when using CW waves, it is preferred that at least the front-end transmission wave and the corresponding front-end drive signal SD1 are encoded by frequency modulation. This is because the front-end bit is not easily affected by interference, so it is suitable as a reference bit. In addition, by using frequency modulation coding, the waveform of the mean square error MSE becomes sharper during pattern matching, and the variability of the consistent point, i.e., the minimum point, on the time axis is small. In particular, chirp coding in which the frequency changes in a V-shape or an inverted V-shape over time is preferred. As a result, the reception judgment accuracy can be further improved. In particular, the detection accuracy of the frequency shift amount is improved. Alternatively, the setting accuracy of the judgment timing, i.e., the reception time TR, TR1, and the judgment time window Tw is improved.

[0218] In the above specific example, the number of distinguishing drive signals included in the drive signal SD is 3. However, the present disclosure is not limited to such a mode. That is, the number of distinguishing drive signals included in the drive signal SD can be 2 or more than 4. As required, the number of bits or bytes in the code sequence of the drive signal SD is not particularly limited.

[0219] Figure 17 to Figure 22 An example of the drive signal SD is shown in the case where the drive signal SD includes two division drive signals. Fig.23 An example of the drive signal SD is shown in the case where the number of the division drive signals included in the drive signal SD is four or more.

[0220] like Figures 17 to 23 As shown, in a preferred example, the signal of the front end among the plurality of distinguishing driving signals has a certain frequency modulation that is not a CW wave. Correspondingly, the front end transmission wave as the transmission wave of the front end among the plurality of distinguishing transmission waves also has a certain frequency modulation that is not a CW wave. On the other hand, the signal that is not the front end among the plurality of distinguishing driving signals may also be a CW wave. Alternatively, the signal that is not the front end among the plurality of distinguishing driving signals may also be encoded other than chirp encoding, for example, by phase modulation, frequency offset modulation, or ON-OFF modulation.

[0221] "Above a threshold value" and "exceeding a threshold value" can be interchanged with each other. Similarly, "less than a threshold value" and "below a threshold value" can be interchanged with each other.

[0222] The elements constituting the above-mentioned embodiments are not necessarily required, except for the cases where they are specifically indicated as required and the cases where they are clearly considered to be required in principle. In addition, when the numerical values ​​of the number, value, amount, range, etc. of the constituent elements are mentioned, the present disclosure will not be limited to the specific number, except for the cases where they are specifically indicated as required and the cases where they are clearly limited to a specific number in principle. Similarly, when the shapes, directions, positional relationships, etc. of the constituent elements are mentioned, the present disclosure will not be limited to their shapes, directions, positional relationships, etc., except for the cases where they are specifically indicated as required and the cases where they are limited to a specific shape, direction, positional relationship, etc. in principle.

[0223] The modification examples are not limited to the above-mentioned examples. In addition, a plurality of modification examples can be combined with each other. Furthermore, all or part of the above-mentioned embodiment and all or part of the modification examples can be combined with each other.

[0224] The above-mentioned functional configurations and methods can also be implemented by a dedicated computer provided by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the above-mentioned functional configurations and methods can also be implemented by a dedicated computer provided by a processor constituted by one or more dedicated hardware logic circuits. Alternatively, the above-mentioned functional configurations and methods can also be implemented by one or more dedicated computers constituted by a combination of a processor and a memory programmed to execute one or more functions and a processor constituted by one or more hardware logic circuits. Specifically, the control unit 5 is not limited to a well-known microcomputer having a CPU, etc. That is, all or part of the control unit 5 can also be a digital circuit configured to realize the above-mentioned functions, such as an ASIC or FPGA such as a gate array. ASIC is the abbreviation of Application Specific Integrated Circuit: Application Specific Integrated Circuit. FPGA is the abbreviation of Field Programmable Gate Array: Field Programmable Gate Array. In addition, the computer program can also be stored as an instruction executed by a computer in a non-transitional substantial storage medium that can be read by a computer. That is, the device or method disclosed in the present invention can also be expressed as a computer program including steps for realizing the above-mentioned functions or methods, or a non-transitional substantial storage medium storing the program.

[0225] (Summarize)

[0226] The present disclosure shown by the above-mentioned embodiments and modifications includes the following viewpoints. In addition, the following viewpoints can be applied in combination with each other as long as there is no technical contradiction.

[0227] According to a first aspect, an object detection device configured to detect an object around the mobile body by being mounted on a mobile body includes a drive signal generating unit and a detection unit. The drive signal generating unit is configured to generate a drive signal for driving a transmission unit including a transmitter that transmits a transmission wave as an ultrasonic wave toward the outside, and output the drive signal toward the transmission unit. The drive signal generating unit generates a first drive signal and a second drive signal and outputs them toward the transmission unit. The first drive signal is a drive signal corresponding to the first transmission wave. The second drive signal is a drive signal corresponding to the second transmission wave. The first transmission wave and the second transmission wave are included in a plurality of transmission waves that are continuously transmitted from the start of the transmission process of the transmission wave to the end of the transmission process and are respectively encoded according to a waveform pattern. That is, the first transmission wave is one of these plurality of transmission waves. In addition, the second transmission wave is another one of these plurality of transmission waves that is transmitted after the first transmission wave. The detection unit is configured to detect the object based on a reception signal corresponding to a reception result of a receiver that receives a reception wave including a reflection wave caused by an object of the transmission wave. The detection unit performs reception determination of the reflection wave based on a frequency signal corresponding to the waveform pattern in the reception signal and a reference signal corresponding to the waveform pattern in the first drive signal. This makes it possible to improve recognition accuracy more than ever before.

[0228] Specifically, in such a configuration, the drive signal generating unit generates a first drive signal corresponding to a first transmission wave encoded according to a waveform pattern and outputs it toward the transmitting unit. In addition, the drive signal generating unit generates a second drive signal corresponding to a second transmission wave encoded according to a waveform pattern and transmitted after the first transmission wave and outputs it toward the transmitting unit. Thus, a plurality of transmission waves including the first transmission wave and the second transmission wave are continuously transmitted during the period from the start of the transmission process to the end of the transmission process. In addition, these plurality of transmission waves are respectively encoded according to the waveform pattern in the drive signal. The detection unit detects an object based on a received signal corresponding to the reception result of the receiver. At this time, the detection unit performs reception determination of the reflected wave based on a frequency signal corresponding to the waveform pattern in the received signal and a reference signal corresponding to the waveform pattern in the drive signal.

[0229] That is, according to such a configuration, during the period from the start of the transmission process to the end of the transmission process, a plurality of transmission waves respectively encoded according to the waveform pattern in the drive signal are transmitted. These plurality of transmission waves include a first transmission wave encoded according to the waveform pattern in the first drive signal. In addition, these plurality of transmission waves include a second transmission wave encoded according to the waveform pattern in the second drive signal and transmitted after the first transmission wave. Therefore, when the reflected waves generated by the reflection of these plurality of transmission waves by the object are received by the receiver as received waves, the received waves include the reflected waves corresponding to the first transmission wave and the reflected waves corresponding to the second transmission wave transmitted after the first transmission wave. Here, when the reception determination of the reflected waves is performed, at least a reference signal corresponding to the waveform pattern in the first drive signal, i.e., the first transmission wave, is used.

[0230] According to the second aspect, the detection unit in the first aspect performs reception determination of the reflected wave corresponding to the first transmission wave based on the first reference signal, which is a reference signal corresponding to the waveform pattern in the first drive signal. In addition, the detection unit performs reception determination of the reflected wave corresponding to the second transmission wave based on the second reference signal, which is a reference signal corresponding to the waveform pattern in the second drive signal.

[0231] In such a configuration, a reception determination of a reflected wave corresponding to a first transmission wave encoded according to a waveform pattern in the first drive signal is performed based on a first reference signal corresponding to a waveform pattern in the first drive signal. In addition, a reception determination of a reflected wave corresponding to a second transmission wave encoded according to a waveform pattern in the second drive signal is performed based on a second reference signal corresponding to a waveform pattern in the second drive signal. Thus, the reception determination accuracy can be further improved.

[0232] According to the third aspect, the detection unit in the first and second aspects has a frequency shift detection unit. The frequency shift detection unit detects the frequency shift amount between the transmission wave and the reflected wave caused by the relative speed between the moving body and the object. In addition, the detection unit performs reception determination of the reflected wave corresponding to the second transmission wave based on the frequency shift amount detected from the reflected wave corresponding to the first transmission wave.

[0233] In such a configuration, the frequency shift amount caused by the relative speed between the moving body and the objects around it is detected based on the reflected wave corresponding to the first transmission wave. Here, the speed of sound, which is the propagation speed of the transmission wave and the reflected wave, is sufficiently faster than the moving speed of the moving body and the objects around it. Therefore, when the first transmission wave is transmitted and received and when the subsequent second transmission wave is transmitted and received, the frequency shift amount, that is, the relative speed, can be regarded as unchanged. Therefore, the detection unit performs reception judgment of the reflected wave corresponding to the subsequent second transmission wave based on the frequency shift amount detected based on the reflected wave corresponding to the first transmission wave. That is, through the encoding in the first transmission wave, the Doppler frequency shift correction can be well performed when the reception judgment of the reflected wave corresponding to the subsequent second transmission wave is made. As a result, the reception judgment accuracy in the case where the moving body and the objects around it move relative to each other can be further improved.

[0234] According to a fourth aspect, the detection unit in the first to third aspects includes a reference time setting unit, a timing setting unit, and a reception determination unit. The reference time setting unit sets the reference time based on the reception determination result of the reflected wave corresponding to the first transmission wave. The timing setting unit sets the determination timing using the reference time set by the reference time setting unit as a reference. The reception determination unit performs reception determination of the reflected wave corresponding to the second transmission wave at the determination timing set by the timing setting unit.

[0235] In such a configuration, the reception determination of the reflected wave corresponding to the second transmission wave is performed at the determination timing using the reference time set based on the reception determination result of the reflected wave corresponding to the first transmission wave as the reference. That is, the first transmission wave has the function of being a code, and also has the synchronization function when the reception determination of the reflected wave corresponding to the subsequent transmission wave is performed. Thus, the identification function of the reflected wave and the noise is improved. In addition, the generation of erroneous determination caused by the pseudo code generated between the reflected wave corresponding to the first transmission wave and the reflected wave corresponding to the transmission wave sent after the first transmission wave can be well suppressed. Moreover, the pseudo code can also be generated in the case of receiving multiple reflected waves in an overlapping manner. In this case, by using the non-overlapping leading end bit with high reliability as the reference to determine the subsequent bit, a high-precision determination can be performed. Therefore, the reception determination accuracy can be further improved.

[0236] According to the fifth aspect, in the first to fourth aspects, at least the first transmission wave is encoded by frequency modulation. This can further improve the reception determination accuracy. In particular, the detection accuracy of the frequency shift amount and the setting accuracy of the determination timing are improved.

[0237] According to the sixth aspect, in the fifth aspect, at least the first transmission wave is chirped so that the frequency changes in a V-shape or an inverted V-shape over time. This can further improve the reception determination accuracy. In particular, the detection accuracy of the frequency shift amount and the setting accuracy of the determination timing are improved.

[0238] According to the seventh aspect, in the fifth and sixth aspects, the first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes over time. In addition, the second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency, and the frequency changes over time. Furthermore, the first frequency band and the second frequency band are set to partially overlap each other.

[0239] It is possible that a pseudo-code-like waveform similar to the waveform pattern in the first drive signal or the second drive signal is generated between the reflected wave corresponding to the first transmission wave and the reflected wave corresponding to the second transmission wave transmitted immediately after the first transmission wave. For this point, in such a configuration, an offset is set between the frequency band in the first drive signal, i.e., the first frequency band, and the frequency band in the second drive signal, i.e., the second frequency band. Therefore, for example, the consistency of the above-mentioned pseudo-code-like waveform with the reference signal corresponding to the first transmission wave or the second transmission wave is reduced. Or, the matching of the calculated value of the frequency shift or relative speed corresponding to the above-mentioned pseudo-code-like waveform and the calculated value of the frequency shift or relative speed corresponding to other parts in the reflected wave is reduced. As a result, the generation of erroneous judgments caused by pseudo-codes can be well suppressed. Therefore, the reception judgment accuracy can be further improved.

[0240] According to the eighth aspect, the first frequency band and the second frequency band in the seventh aspect are set to include the resonance frequency of the transmission unit. This improves the sound pressure of the transmission wave and the reception sensitivity of the reflected wave.

[0241] According to the ninth aspect, in the seventh and eighth aspects, the second lowest frequency is a high frequency compared to the first lowest frequency, and the second highest frequency is a high frequency compared to the first highest frequency. Alternatively, the second lowest frequency is a low frequency compared to the first lowest frequency, and the second highest frequency is a low frequency compared to the first highest frequency. Thus, the offset between the frequency band in the first drive signal, that is, the first frequency band, and the frequency band as the frequency band in the second drive signal can be well set.

[0242] According to the tenth aspect, the detection unit in the first aspect performs reception determination of the reflected wave based on a synthetic reference signal obtained by integrating a reference signal corresponding to the first drive signal and a reference signal corresponding to the second drive signal.

[0243] In such a configuration, during the period from the start of the transmission process to the end of the transmission process, a plurality of transmission waves encoded according to the waveform pattern in the drive signal are transmitted. These plurality of transmission waves include a first transmission wave encoded according to the waveform pattern in the first drive signal. In addition, these plurality of transmission waves include a second transmission wave encoded according to the waveform pattern in the second drive signal and transmitted after the first transmission wave. Therefore, when the reflected waves generated by the reflection of these plurality of transmission waves by an object are received by the receiver as received waves, the received waves include the reflected waves corresponding to the first transmission wave and the reflected waves corresponding to the second transmission wave transmitted after the first transmission wave. Here, when determining the reception of the reflected waves, a synthetic reference signal obtained by integrating the reference signal corresponding to the first drive signal and the reference signal corresponding to the second drive signal is used. Therefore, the accuracy of the reception determination can be further improved.

[0244] According to the 11th aspect, the detection unit in the 10th aspect includes a frequency shift detection unit. The frequency shift detection unit detects the frequency shift amount between the transmission wave and the reflected wave caused by the relative speed between the moving body and the object. In addition, the detection unit performs reception determination of the reflected wave based on the frequency shift amount detected from the reflected wave.

[0245] In such a configuration, the frequency shift amount caused by the relative speed between the moving body and the objects around it is detected based on the reflected wave corresponding to the transmission wave. Here, the speed of sound, which is the propagation speed of the transmission wave and the reflected wave, is sufficiently faster than the moving speed of the moving body and the objects around it. Therefore, in the transmission and reception corresponding to the multiple transmission waves transmitted continuously, it can be regarded that the frequency shift amount, that is, the relative speed, does not change. Therefore, the detection unit makes a reception judgment of the reflected wave based on the frequency shift amount detected based on the reflected wave corresponding to the transmission wave. Thus, the reception judgment accuracy in the case where the moving body and the objects around it move relative to each other can be further improved. In addition, the frequency shift amount, that is, the relative speed, is detected using the front end bit portion in the synthetic reference signal, that is, the reference signal corresponding to the first drive signal, and the subsequent bits are judged based on this, so that the calculation load can be reduced as much as possible.

[0246] According to the twelfth aspect, in the tenth and eleventh aspects, at least the first transmission wave is encoded by frequency modulation. This can further improve the reception determination accuracy. In particular, the detection accuracy of the frequency shift amount is improved.

[0247] According to the 13th aspect, in the 12th aspect, at least the first transmission wave is chirped so that the frequency changes in a V-shape or an inverted V-shape over time. This can further improve the reception determination accuracy. In particular, the detection accuracy of the frequency shift amount is improved.

[0248] According to the 14th aspect, in the 12th and 13th aspects, the first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes over time. In addition, the second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency, and the frequency changes over time. Furthermore, the first frequency band and the second frequency band are set to partially overlap each other.

[0249] It is possible that a pseudo-code-like waveform similar to the waveform pattern in the first drive signal or the second drive signal is generated between the reflected wave corresponding to the first transmission wave and the reflected wave corresponding to the transmission wave transmitted immediately after the first transmission wave. For this point, in such a configuration, an offset is provided between the frequency band in the first drive signal, i.e., the first frequency band, and the frequency band as the frequency band in the second drive signal. Therefore, the consistency of the above-mentioned pseudo-code-like waveform with the reflected wave corresponding to the first transmission wave or the second transmission wave is reduced. Alternatively, the matching of the calculated value of the frequency shift or relative speed corresponding to the above-mentioned pseudo-code-like waveform and the calculated value of the frequency shift or relative speed corresponding to other parts in the reflected wave is reduced. Therefore, the generation of erroneous judgment caused by the pseudo-code can be well suppressed. Therefore, the reception judgment accuracy can be further improved.

[0250] According to the fifteenth aspect, the first frequency band and the second frequency band in the fourteenth aspect are set to include the resonance frequency of the transmission unit. This improves the sound pressure of the transmission wave and the reception sensitivity of the reflected wave.

[0251] According to the 16th viewpoint, in the 14th and 15th viewpoints, the second lowest frequency is a high frequency compared to the first lowest frequency, and the second highest frequency is a high frequency compared to the first highest frequency. Alternatively, the second lowest frequency is a low frequency compared to the first lowest frequency, and the second highest frequency is a low frequency compared to the first highest frequency. Thus, the offset between the frequency band in the first drive signal, that is, the first frequency band, and the frequency band as the frequency band in the second drive signal can be well set.

[0252] According to the 17th aspect, an object detection method for detecting an object around a moving body uses a drive signal generating unit and a detection unit. The drive signal generating unit generates a drive signal for driving a transmitting unit and outputs the drive signal toward the transmitting unit, wherein the transmitting unit has a transmitter that transmits a transmission wave as an ultrasonic wave toward the outside. The drive signal generating unit generates a first drive signal and a second drive signal and outputs them toward the transmitting unit. The first drive signal is a drive signal corresponding to the first transmission wave. The second drive signal is a drive signal corresponding to the second transmission wave. The first transmission wave and the second transmission wave are included in a plurality of transmission waves that are continuously transmitted during the period from the start of the transmission process of the transmission wave to the end of the transmission process and are respectively encoded according to a waveform pattern. The second transmission wave is transmitted after the first transmission wave. The detection unit detects an object based on a received signal corresponding to a reception result of a receiver, wherein the receiver receives a received wave including a reflected wave caused by an object of the transmission wave. The detection unit performs a reception judgment of the reflected wave based on a frequency signal corresponding to the waveform pattern in the received signal and a reference signal corresponding to the waveform pattern in the first drive signal. Thus, the recognition accuracy can be improved compared with the past.

[0253] Specifically, according to such a method, during the period from the start of the transmission process to the end of the transmission process, a plurality of transmission waves respectively encoded according to the waveform pattern in the drive signal are transmitted. These plurality of transmission waves include a first transmission wave encoded according to the waveform pattern in the first drive signal. In addition, these plurality of transmission waves include a second transmission wave encoded according to the waveform pattern in the second drive signal and transmitted after the first transmission wave. Therefore, when the reflected waves generated by the reflection of these plurality of transmission waves by an object are received by the receiver as received waves, the received waves include a reflected wave corresponding to the first transmission wave and a reflected wave corresponding to the second transmission wave transmitted after the first transmission wave. Here, when determining the reception of the reflected wave, at least the first drive signal, i.e., a reference signal corresponding to the waveform pattern in the first transmission wave, is used.

[0254] According to the 18th aspect, the method involved in the 17th aspect performs the following processing by the detection unit. Based on the first reference signal, which is a reference signal corresponding to the waveform pattern in the first drive signal, a reception determination of the reflected wave corresponding to the first transmission wave is performed. In addition, based on the second reference signal, which is a reference signal corresponding to the waveform pattern in the second drive signal, a reception determination of the reflected wave corresponding to the second transmission wave is performed.

[0255] In such a method, a reception determination of a reflected wave corresponding to a first transmission wave encoded according to a waveform pattern in the first drive signal is performed based on a first reference signal corresponding to a waveform pattern in the first drive signal. In addition, a reception determination of a reflected wave corresponding to a second transmission wave encoded according to a waveform pattern in the second drive signal is performed based on a second reference signal corresponding to a waveform pattern in the second drive signal. Thus, the reception determination accuracy can be further improved.

[0256] According to the 19th aspect, in the method according to the 17th and 18th aspects, the following processing is performed by the detection unit. The frequency shift amount between the transmission wave and the reflected wave caused by the relative speed between the moving body and the object is detected. In addition, the reception determination of the reflected wave corresponding to the second transmission wave is performed based on the frequency shift amount detected from the reflected wave corresponding to the first transmission wave.

[0257] In such a method, the frequency shift amount caused by the relative speed of the moving body and the objects around it is detected based on the reflected wave corresponding to the first transmission wave. Here, the speed of sound, which is the propagation speed of the transmission wave and the reflected wave, is sufficiently faster than the moving speed of the moving body and the objects around it. Therefore, it is possible to regard the frequency shift amount, that is, the relative speed, as unchanged when the first transmission wave is transmitted and received and when the subsequent second transmission wave is transmitted and received. Therefore, such a method is based on the reception judgment of the reflected wave corresponding to the subsequent second transmission wave based on the frequency shift amount detected based on the reflected wave corresponding to the first transmission wave. That is, the first transmission wave has the function of serving as a code, and also has the Doppler shift correction function when the reception judgment of the reflected wave corresponding to the subsequent transmission wave is made. Thereby, the reception judgment accuracy in the case where the moving body and the objects around it move relative to each other can be further improved.

[0258] According to the 20th aspect, in the method according to the 17th to 19th aspects, the following processing is performed by the detection unit. A reference time is set based on the reception determination result of the reflected wave corresponding to the first transmission wave. In addition, the determination timing is set using the set reference time as a reference. In addition, the reception determination of the reflected wave corresponding to the second transmission wave is performed at the set determination timing.

[0259] In such a method, the reception determination of the reflected wave corresponding to the second transmission wave is performed at the determination timing using the reference time set based on the reception determination result of the reflected wave corresponding to the first transmission wave as the reference. That is, the first transmission wave has the function of being a code, and also has the synchronization function when the reception determination of the reflected wave corresponding to the subsequent transmission wave is performed. Thus, the identification function of the reflected wave and the noise is improved. In addition, the generation of false determination caused by the pseudo code generated between the reflected wave corresponding to the first transmission wave and the reflected wave corresponding to the transmission wave sent immediately after the first transmission wave can be well suppressed. Moreover, the pseudo code may also be generated when multiple reflected waves are received in an overlapping manner. In this case, by using the non-overlapping front end bit with high reliability as the reference to determine the subsequent bit, it is possible to perform a high-precision determination. Therefore, the reception determination accuracy can be further improved.

[0260] According to the 21st aspect, in the method according to the 17th to 20th aspects, at least the first transmission wave is encoded by frequency modulation. This can further improve the reception determination accuracy. In particular, the detection accuracy of the frequency shift amount and the setting accuracy of the determination timing are improved.

[0261] According to the 22nd aspect, in the method according to the 21st aspect, at least the first transmission wave chirp is encoded so that the frequency changes in a V-shape or an inverted V-shape over time. This can further improve the reception determination accuracy. In particular, the detection accuracy of the frequency shift amount and the setting accuracy of the determination timing are improved.

[0262] According to the 23rd aspect, the method involved in the 21st and 22nd aspects performs the following processing: The first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes over time. The second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency and partially overlapping the first frequency band, and the frequency changes over time.

[0263] It is possible that a pseudo-code-like waveform similar to the waveform pattern in the first drive signal or the second drive signal is generated between the reflected wave corresponding to the first transmission wave and the reflected wave corresponding to the transmission wave transmitted immediately after the first transmission wave. For this point, in such a method, an offset is provided between the frequency band in the first drive signal, that is, the first frequency band and the frequency band as the frequency band in the second drive signal. Therefore, the consistency of the above-mentioned pseudo-code-like waveform with the reflected wave corresponding to the first transmission wave or the second transmission wave is reduced. Alternatively, the matching of the calculated value of the frequency shift or relative speed corresponding to the above-mentioned pseudo-code-like waveform and the calculated value of the frequency shift or relative speed corresponding to other parts in the reflected wave is reduced. Therefore, the generation of erroneous judgment caused by the pseudo-code can be well suppressed. Therefore, the reception judgment accuracy can be further improved.

[0264] According to a 24th aspect, in the method according to the 23rd aspect, the first frequency band and the second frequency band are set to include the resonance frequency of the transmission unit. This improves the sound pressure of the transmission wave and the reception sensitivity of the reflected wave.

[0265] According to the 25th viewpoint, in the methods involved in the 23rd and 24th viewpoints, the second lowest frequency is set to a frequency higher than the first lowest frequency, and the second highest frequency is set to a frequency higher than the first highest frequency. Alternatively, in such a method, the second lowest frequency is set to a frequency lower than the first lowest frequency, and the second highest frequency is set to a frequency lower than the first highest frequency. Thus, the offset between the frequency band in the first drive signal, i.e., the first frequency band, and the frequency band in the second drive signal, i.e., the frequency band, can be well set.

[0266] According to the 26th aspect, in the method according to the 17th aspect, the detection unit makes a reception determination of the reflected wave based on a synthetic reference signal obtained by integrating a reference signal corresponding to the first drive signal and a reference signal corresponding to the second drive signal.

[0267] In such a method, during the period from the start of the transmission process to the end of the transmission process, multiple transmission waves encoded according to the waveform pattern in the drive signal are transmitted. These multiple transmission waves include a first transmission wave encoded according to the waveform pattern in the first drive signal. In addition, these multiple transmission waves include a second transmission wave encoded according to the waveform pattern in the second drive signal and transmitted after the first transmission wave. Therefore, when the reflected waves generated by the reflection of these multiple transmission waves by the object are received by the receiver as received waves, the received waves include the reflected waves corresponding to the first transmission wave and the reflected waves corresponding to the second transmission wave transmitted after the first transmission wave. Here, when the reception judgment of the reflected waves is performed, a synthetic reference signal obtained by integrating the reference signal corresponding to the first drive signal and the reference signal corresponding to the second drive signal is used. Therefore, the reception judgment accuracy can be further improved.

[0268] According to the 27th aspect, the method according to the 17th aspect performs the following processing by the detection unit: Detecting the frequency shift amount between the transmission wave and the reflected wave caused by the relative speed between the moving body and the object. Based on the frequency shift amount detected from the reflected wave corresponding to the first transmission wave, performing reception determination of the reflected wave corresponding to the second transmission wave.

[0269] In such a method, the frequency shift amount caused by the relative speed of the moving body and the objects around it is detected based on the reflected wave corresponding to the transmission wave. Here, the sound speed, which is the propagation speed of the transmission wave and the reflected wave, is sufficiently fast compared to the moving speed of the moving body and the objects around it. Therefore, in the transmission and reception corresponding to multiple transmission waves transmitted continuously, the frequency shift amount, that is, the relative speed, can be regarded as unchanged. Therefore, such a method makes a reception judgment of the reflected wave based on the frequency shift amount detected based on the reflected wave corresponding to the transmission wave. As a result, the reception judgment accuracy in the case where the moving body and the objects around it move relative to each other can be further improved. In addition, the frequency shift amount, that is, the relative speed, is detected using the front end bit portion in the synthetic reference signal, that is, the reference signal corresponding to the first drive signal, and the subsequent bits are judged based on this, so that the calculation load can be reduced as much as possible.

[0270] According to the 28th aspect, the method according to the 26th and 27th aspects encodes at least the first transmission wave by frequency modulation. This can further improve the reception determination accuracy. In particular, the setting accuracy of the detection accuracy of the frequency shift amount is improved.

[0271] According to the 29th aspect, the method according to the 28th aspect encodes at least the first transmission wave chirp so that the frequency changes in a V-shape or an inverted V-shape over time. This can further improve the reception determination accuracy. In particular, the detection accuracy of the frequency shift amount is improved.

[0272] According to the 30th aspect, the method according to the 28th and 29th aspects performs the following processing: The first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes over time. The second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency and partially overlapping the first frequency band, and the frequency changes over time.

[0273] It is possible that a pseudo-code-like waveform similar to the waveform pattern in the first drive signal or the second drive signal is generated between the reflected wave corresponding to the first transmission wave and the reflected wave corresponding to the transmission wave transmitted immediately after the first transmission wave. For this point, in such a method, an offset is provided between the frequency band in the first drive signal, that is, the first frequency band and the frequency band as the frequency band in the second drive signal. Therefore, the consistency of the above-mentioned pseudo-code-like waveform with the reflected wave corresponding to the second transmission wave is reduced. Alternatively, the matching of the calculated value of the frequency shift or relative speed corresponding to the above-mentioned pseudo-code-like waveform and the calculated value of the frequency shift or relative speed corresponding to other parts in the reflected wave is reduced. Therefore, the generation of erroneous judgment caused by the pseudo-code can be well suppressed. Therefore, the reception judgment accuracy can be further improved.

[0274] According to the 31st aspect, the first frequency band and the second frequency band in the 30th aspect are set to include the resonance frequency of the transmission unit. This improves the sound pressure of the transmission wave and the reception sensitivity of the reflected wave.

[0275] According to the 32nd viewpoint, in the method involved in the 30th and 31st viewpoints, the second lowest frequency is set to a frequency higher than the first lowest frequency, and the second highest frequency is set to a frequency higher than the first highest frequency. Alternatively, in such a method, the second lowest frequency is set to a frequency lower than the first lowest frequency, and the second highest frequency is set to a frequency lower than the first highest frequency. Thus, the offset between the frequency band in the first drive signal, that is, the first frequency band, and the frequency band as the frequency band in the second drive signal can be well set.

Claims

1. An object detection device is an object detection device configured to detect an object around the moving body by being mounted on the moving body, comprising: a drive signal generating unit that generates a drive signal for driving a transmitting unit and outputs the drive signal to the transmitting unit, wherein the transmitting unit includes a transmitter that transmits a transmission wave as an ultrasonic wave to the outside; and a detection unit configured to detect the object based on a reception signal corresponding to a reception result of a receiver that receives a reception wave including a reflected wave resulting from the transmission wave being reflected by the object, The drive signal generating unit generates a first drive signal and outputs it toward the transmitting unit, and generates a second drive signal and outputs it toward the transmitting unit, the first drive signal is the drive signal corresponding to a first transmission wave, the second drive signal is the drive signal corresponding to a second transmission wave, the first transmission wave is included in a plurality of transmission waves that are continuously transmitted during a period from the start of transmission processing of the transmission wave to the end of transmission processing and are respectively encoded according to a waveform pattern, and the second transmission wave is included in the plurality of transmission waves and is transmitted after the first transmission wave. The detection unit performs reception determination of the reflected wave based on a frequency signal corresponding to the waveform pattern in the received signal and a reference signal corresponding to the waveform pattern in the first drive signal. The detection unit includes a frequency shift detection unit that detects a frequency shift amount between the transmission wave and the reflected wave based on a relative speed between the moving body and the object. The detection unit makes a reception determination of the reflected wave corresponding to the second transmission wave based on the frequency shift amount detected from the reflected wave corresponding to the first transmission wave.

2. The object detection device according to claim 1, wherein: The detection unit performs a reception determination of the reflected wave corresponding to the first transmission wave based on a first reference signal, and performs a reception determination of the reflected wave corresponding to the second transmission wave based on a second reference signal, wherein the first reference signal is a reference signal corresponding to a waveform pattern in the first drive signal, and the second reference signal is a reference signal corresponding to a waveform pattern in the second drive signal.

3. The object detection device according to claim 1 or 2, wherein: The detection unit has: a reference time setting unit that sets a reference time based on a reception determination result of the reflected wave corresponding to the first transmitted wave; a timing setting unit that sets a determination timing based on the reference time set by the reference time setting unit; as well as The reception determination unit performs reception determination of the reflected wave corresponding to the second transmission wave at the determination timing set by the timing setting unit.

4. The object detection device according to claim 1 or 2, wherein: At least the first transmission wave is encoded by frequency modulation.

5. The object detection device according to claim 4, wherein: At least the first transmission wave is chirp-coded so that the frequency changes in a V-shape or an inverted V-shape over time.

6. The object detection device according to claim 4, wherein: The first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes with time. The second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency, and the frequency changes with time. The first frequency band and the second frequency band are set to partially overlap each other.

7. The object detection device according to claim 6, wherein: The first frequency band and the second frequency band are set to include a resonance frequency of the transmission unit.

8. The object detection device according to claim 6, wherein: One of the second lowest frequency is higher than the first lowest frequency, and one of the second highest frequency is higher than the first highest frequency. or, One of the second lowest frequency is lower than the first lowest frequency, and one of the second highest frequency is lower than the first highest frequency.

9. The object detection device according to claim 1 or 2, wherein: The detection unit performs reception determination of the reflected wave based on a synthetic reference signal obtained by integrating the reference signal corresponding to the first drive signal and the reference signal corresponding to the second drive signal.

10. An object detection device, configured to be mounted on a moving body to detect an object around the moving body, comprising: a drive signal generating unit that generates a drive signal for driving a transmitting unit and outputs the drive signal to the transmitting unit, wherein the transmitting unit includes a transmitter that transmits a transmission wave as an ultrasonic wave to the outside; as well as a detection unit configured to detect the object based on a reception signal corresponding to a reception result of a receiver that receives a reception wave including a reflected wave resulting from the transmission wave being reflected by the object, The drive signal generating unit generates a first drive signal and outputs it toward the transmitting unit, and generates a second drive signal and outputs it toward the transmitting unit, the first drive signal is the drive signal corresponding to a first transmission wave, the second drive signal is the drive signal corresponding to a second transmission wave, the first transmission wave is included in a plurality of transmission waves that are continuously transmitted during a period from the start of transmission processing of the transmission wave to the end of transmission processing and are respectively encoded according to a waveform pattern, and the second transmission wave is included in the plurality of transmission waves and is transmitted after the first transmission wave. The detection unit performs reception determination of the reflected wave based on a frequency signal corresponding to the waveform pattern in the received signal and a reference signal corresponding to the waveform pattern in the first drive signal. The detection unit has: a reference time setting unit that sets a reference time based on a reception determination result of the reflected wave corresponding to the first transmitted wave; a timing setting unit that sets a determination timing based on the reference time set by the reference time setting unit; as well as The reception determination unit performs reception determination of the reflected wave corresponding to the second transmission wave at the determination timing set by the timing setting unit.

11. The object detection device according to claim 10, wherein: The detection unit performs a reception determination of the reflected wave corresponding to the first transmission wave based on a first reference signal, and performs a reception determination of the reflected wave corresponding to the second transmission wave based on a second reference signal, wherein the first reference signal is a reference signal corresponding to a waveform pattern in the first drive signal, and the second reference signal is a reference signal corresponding to a waveform pattern in the second drive signal.

12. The object detection device according to claim 10 or 11, wherein: At least the first transmission wave is encoded by frequency modulation.

13. The object detection device according to claim 12, wherein: At least the first transmission wave is chirp-coded so that the frequency changes in a V-shape or an inverted V-shape over time.

14. The object detection device according to claim 12, wherein: The first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes with time. The second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency, and the frequency changes with time. The first frequency band and the second frequency band are set to partially overlap each other.

15. The object detection device according to claim 13, wherein: The first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes with time. The second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency, and the frequency changes with time. The first frequency band and the second frequency band are set to partially overlap each other.

16. The object detection device according to claim 14, wherein: The first frequency band and the second frequency band are set to include a resonance frequency of the transmission unit.

17. The object detection device according to claim 15, wherein: The first frequency band and the second frequency band are set to include a resonance frequency of the transmission unit.

18. The object detection device according to claim 14, wherein: One of the second lowest frequency is higher than the first lowest frequency, and one of the second highest frequency is higher than the first highest frequency. or, One of the second lowest frequency is lower than the first lowest frequency, and one of the second highest frequency is lower than the first highest frequency.

19. The object detection device according to claim 15, wherein: One of the second lowest frequency is higher than the first lowest frequency, and one of the second highest frequency is higher than the first highest frequency. or, One of the second lowest frequency is lower than the first lowest frequency, and one of the second highest frequency is lower than the first highest frequency.

20. The object detection device according to claim 12, wherein: The detection unit performs reception determination of the reflected wave based on a synthetic reference signal obtained by integrating the reference signal corresponding to the first drive signal and the reference signal corresponding to the second drive signal.

21. The object detection device according to claim 13, wherein: The detection unit performs reception determination of the reflected wave based on a synthetic reference signal obtained by integrating the reference signal corresponding to the first drive signal and the reference signal corresponding to the second drive signal.

22. An object detection device, configured to be mounted on a moving body to detect an object around the moving body, comprising: a drive signal generating unit that generates a drive signal for driving a transmitting unit and outputs the drive signal to the transmitting unit, wherein the transmitting unit includes a transmitter that transmits a transmission wave as an ultrasonic wave to the outside; and a detection unit configured to detect the object based on a reception signal corresponding to a reception result of a receiver that receives a reception wave including a reflected wave resulting from the transmission wave being reflected by the object, The drive signal generating unit generates a first drive signal and outputs it toward the transmitting unit, and generates a second drive signal and outputs it toward the transmitting unit, the first drive signal is the drive signal corresponding to a first transmission wave, the second drive signal is the drive signal corresponding to a second transmission wave, the first transmission wave is included in a plurality of transmission waves that are continuously transmitted during a period from the start of transmission processing of the transmission wave to the end of transmission processing and are respectively encoded according to a waveform pattern, and the second transmission wave is included in the plurality of transmission waves and is transmitted after the first transmission wave. The detection unit performs reception determination of the reflected wave based on a frequency signal corresponding to the waveform pattern in the received signal and a reference signal corresponding to the waveform pattern in the first drive signal. The first transmission wave and the second transmission wave are encoded by frequency modulation. The first drive signal is formed in a first frequency band formed by a first minimum frequency and a first maximum frequency, and the frequency changes with time. The second drive signal is formed in a second frequency band formed by a second minimum frequency and a second maximum frequency, and the frequency changes with time. The first frequency band and the second frequency band are set to partially overlap each other. The first frequency band and the second frequency band are set to include a resonance frequency of the transmission unit.

23. The object detection device according to claim 22, wherein: The detection unit performs a reception determination of the reflected wave corresponding to the first transmission wave based on a first reference signal, and performs a reception determination of the reflected wave corresponding to the second transmission wave based on a second reference signal, wherein the first reference signal is a reference signal corresponding to a waveform pattern in the first drive signal, and the second reference signal is a reference signal corresponding to a waveform pattern in the second drive signal.

24. The object detection device according to claim 22 or 23, wherein: At least the first transmission wave is chirp-coded so that the frequency changes in a V-shape or an inverted V-shape over time.

25. The object detection device according to claim 22 or 23, wherein: One of the second lowest frequency is higher than the first lowest frequency, and one of the second highest frequency is higher than the first highest frequency. or, One of the second lowest frequency is lower than the first lowest frequency, and one of the second highest frequency is lower than the first highest frequency.

26. The object detection device according to claim 22 or 23, wherein: The detection unit performs reception determination of the reflected wave based on a synthetic reference signal obtained by integrating the reference signal corresponding to the first drive signal and the reference signal corresponding to the second drive signal.

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