Object detection device

Abstract

An object detection device (200) according to an embodiment comprises: a transmission unit (301) that transmits a transmission wave obtained by multiplexing a plurality of ultrasound waves of different frequencies; a reception unit (303) that receives a reflected wave generated as a result of the transmission wave being reflected by an object; a frequency analysis unit (305) that generates reflected wave frequency information representing a plurality of frequency components included in the reflected wave and separated echo information indicating a temporal change in an amplitude value for each of the plurality of frequency components included in the reflected wave; a distance information generation unit (306) that generates distance information relating to the distance to the object, on the basis of the separated echo information; a Doppler detection unit (307) that calculates a Doppler frequency on the basis of the reflected wave frequency information, transmission wave frequency information representing a plurality of frequency components included in the transmission wave, and frequency interval information indicating an interval of the plurality of frequency components included in the transmission wave; and a correction unit (309) that corrects the distance information on the basis of the Doppler frequency.

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to an object detection device. [Background technology]

[0002] 2. Description of the Related Art In a system for assisting a moving body such as a vehicle in traveling, an object detection device is used that detects obstacles present around the moving body by transmitting and receiving ultrasonic waves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 141370 Summary of the Invention [Problem to be solved by the invention]

[0004] In an object detection device that uses ultrasonic waves, multipath waves may occur, whereby reflected waves from the same obstacle travel different paths and are received by the receiver, due to the shape of the obstacle and the surrounding environment. When such multipath waves occur, the accuracy of obstacle detection may be reduced due to phenomena such as a decrease in amplitude value caused by anti-phase waves.

[0005] Therefore, one of the problems to be solved by the embodiments of the present invention is to provide an object detection device that can reduce the influence of multipath and improve the accuracy of obstacle detection. [Means for solving the problem]

[0006] An object detection device according to one embodiment of the present invention comprises a transmitting unit that transmits a transmission wave in which multiple ultrasonic waves of different frequencies are multiplexed; a receiving unit that receives a reflected wave generated when the transmission wave is reflected by an object; a frequency analysis unit that generates reflected wave frequency information indicating the multiple frequency components contained in the reflected wave and separated echo information indicating the change in amplitude value over time for each of the multiple frequency components contained in the reflected wave; a distance information generation unit that generates distance information regarding the distance to the object based on the separated echo information; a Doppler detection unit that calculates a Doppler frequency based on the reflected wave frequency information, transmission wave frequency information indicating the multiple frequency components contained in the transmission wave, and frequency interval information indicating the interval between the multiple frequency components contained in the transmission wave; and a correction unit that corrects the distance information based on the Doppler frequency.

[0007] According to the above configuration, distance information can be generated using multiple frequency components, and the distance information can be corrected based on the Doppler frequency calculated with high accuracy using frequency interval information, thereby reducing the influence of multipath and improving the accuracy of obstacle detection.

[0008] The Doppler detection unit may also interpolate missing frequency components contained in the reflected wave based on frequency interval information, and calculate the Doppler frequency based on the difference between the frequency components of the interpolated reflected wave and the frequency components of the transmitted wave.

[0009] This allows the Doppler frequency to be calculated with high accuracy.

[0010] The distance information generating section may generate the distance information based on the largest amplitude value among a plurality of amplitude values ​​detected for each frequency component at the same time, which are acquired from the separated echo information.

[0011] This makes it possible to generate highly accurate distance information even if some of the multiple frequency components are lost due to the influence of multipath.

[0012] The distance information generating section may generate the distance information based on corrected echo information indicating a change in the maximum amplitude value over time.

[0013] By using the corrected echo information as described above, the influence of multipath can be effectively reduced and highly accurate distance information can be generated.

[0014] Furthermore, a common oscillator may be used to transmit the transmitted wave and receive the reflected wave.

[0015] This minimizes the paths of the transmitted and received waves, reducing the possibility of multipath occurrence. Also, since there is no need to provide individual transducers for each frequency component, costs can be reduced. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a top view showing an example of the configuration of a vehicle according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of a hardware configuration of the vehicle control system according to the embodiment. [Figure 3] FIG. 3 is a perspective view illustrating an example of the configuration of the vibrator according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a method for calculating distance using the TOF method. [Figure 5] FIG. 5 is a block diagram illustrating an example of a functional configuration of the object detection device according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of separated echo information according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of corrected echo information according to the embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of an FFT analysis result for a reflected wave according to the embodiment. [Figure 9] FIG. 9 is a flowchart illustrating an example of processing in the object detection device according to the embodiment. [Figure 10]FIG. 10 is a perspective view showing an example of the configuration of a vibrator according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The configurations of the embodiments described below and the actions and effects brought about by the configurations are merely examples, and the present invention is not limited to the following description.

[0018] 1 is a top view showing an example of the configuration of a vehicle 1 according to an embodiment. The vehicle 1 is an example of a moving body on which an object detection device according to this embodiment is mounted. The object detection device according to this embodiment is a device that detects obstacles present around the vehicle 1 based on information such as TOF (Time Of Flight) and Doppler shift acquired by transmitting a transmission wave (ultrasound wave) from the vehicle 1 and receiving a reflected wave generated when the transmission wave is reflected by an object.

[0019] The object detection device of this embodiment includes a plurality of transceivers 21A to 21L (hereinafter, abbreviated to transceivers 21 when there is no need to distinguish between the plurality of transceivers 21A to 21L). Each transceiver 21 is installed on a vehicle body 2 that serves as the exterior of a vehicle 1, transmits a transmission wave toward the outside of the vehicle body 2, and receives a reflected wave from an object present outside the vehicle body 2. In the example shown in FIG. 1, four transceivers 21A to 21D are arranged at the front end of the vehicle body 2, four transceivers 21E to 21H are arranged at the rear end, two transceivers 21I and 21J are arranged on the right side, and two transceivers 21K and 21L are arranged on the left side. Note that the number and installation locations of the transceivers 21 are not limited to this example.

[0020] 2 is a block diagram showing an example of a hardware configuration of a vehicle control system 50 according to an embodiment. The vehicle control system 50 performs processing for controlling the vehicle 1 based on information output from an object detection device 200. The vehicle control system 50 of this embodiment includes an ECU 100 and the object detection device 200.

[0021] The object detection device 200 includes multiple transmitter / receivers 21 and a control unit 220. Each transmitter / receiver 21 includes a vibrator 511 configured using a piezoelectric element or the like, an amplifier, etc., and realizes transmission and reception of ultrasonic waves by the vibration of the vibrator 511. Specifically, each transmitter / receiver 21 transmits ultrasonic waves generated in response to the vibration of the vibrator 511 as a transmission wave Wt, and detects the vibration of the vibrator 511 caused by a reflected wave Wr generated when the transmission wave Wt is reflected by an object such as an obstacle O or a road surface RS. The vibration of the vibrator 511 is converted into an electrical signal, and based on the electrical signal, it is possible to obtain information such as a time of flight (TOF) corresponding to the distance from the transmitter / receiver 21 to the obstacle O and Doppler shift information corresponding to the relative speed of the obstacle O.

[0022] 2 illustrates a configuration in which a common oscillator 511 is used to transmit the transmission wave Wt and receive the reflected wave Wr, but the configuration of the transmitter / receiver 21 is not limited to this. For example, an oscillator for transmitting the transmission wave Wt and an oscillator for receiving the reflected wave Wr may be provided separately.

[0023] The control unit 220 includes an input / output device 221, a storage device 222, and a processor 223. The input / output device 221 is an interface device that enables transmission and reception of information between the control unit 220 and the outside (transmitter / receiver 21, ECU 100, etc.). The storage device 222 includes a main storage device such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a HDD (Hard Drive), etc. The processor 223 is an integrated circuit that executes various processes to realize the functions of the control unit 220, and includes, for example, a CPU (Central Processing Unit) that operates according to a program, a RAM (RAM) for a specific purpose, and the like. The processor 223 may be configured using a designed ASIC (Application Specific Integrated Circuit), etc. The processor 223 reads and executes programs stored in the storage device 222 to perform various types of arithmetic processing and control processing.

[0024] The ECU 100 is a unit that executes various processes for controlling the vehicle 1 based on various information acquired from the object detection device 200 and the like. The ECU 100 has an input / output device 110, a storage device 120, and a processor 130. The input / output device 110 is an interface device that enables transmission and reception of information between the ECU 100 and external mechanisms (such as the object detection device 200, drive mechanism, braking mechanism, steering mechanism, transmission mechanism, in-vehicle display, speakers, and various sensors). The storage device 120 includes a main storage device such as a ROM or RAM, and an auxiliary storage device such as an HDD or SSD. The processor 130 is an integrated circuit that executes various processes for realizing the functions of the ECU 100, and may be configured using, for example, a CPU, an ASIC, or the like. The processor 130 reads programs stored in the storage device 120 and executes various arithmetic and control processes.

[0025] 3 is a perspective view showing an example of the configuration of a vibrator 511 according to the embodiment. The vibrator 511 has an upper electrode 521, an upper wiring 522, a piezoelectric body 523, a lower electrode 524, and a lower wiring 525.

[0026] Upper electrode 521 is provided on the upper surface of piezoelectric body 523 and is used as an electrode for applying voltage. Upper wiring 522 is connected to upper electrode 521 and a predetermined AC power supply. Lower electrode 524 is provided on the lower surface of piezoelectric body 523 and is used as a ground electrode. Lower wiring 525 is connected to lower electrode 524 and a predetermined ground electrode. When AC voltage is applied, piezoelectric body 523 vibrates due to the piezoelectric effect, generating an ultrasonic wave (transmission wave) that travels in the direction shown by the arrow in the figure.

[0027] The above configuration is an example, and is not limited to this configuration of the vibrator 511. For example, the upper electrode 521 may be a ground electrode, and the lower electrode 524 may be an electrode for applying a voltage.

[0028] Fig. 4 is a diagram showing an example of a distance calculation method using the TOF method. Fig. 4 illustrates an envelope L11 that indicates changes over time in the amplitude value (signal strength) of ultrasonic waves transmitted and received by the transmitting and receiving unit 210. In the graph shown in Fig. 4, the horizontal axis corresponds to time (TOF), and the vertical axis corresponds to the amplitude value (the magnitude of vibration of the transducer 511) of the ultrasonic waves transmitted and received by the transmitting and receiving unit 210.

[0029] Envelope L11 shows the change over time in amplitude values ​​indicating the magnitude of vibration of oscillator 511. From envelope L11 shown in Fig. 4, it can be seen that oscillator 511 is driven to vibrate for time Ta from time t0, completing transmission of the transmission wave at time t1, and then the vibration of oscillator 511 due to inertia continues while attenuating for time Tb until time t2. Therefore, in the graph shown in Fig. 4, time Tb corresponds to the so-called reverberation time.

[0030] The envelope L11 reaches a peak at time t4, which is a time Tp after time t0 when the transmission of the transmission wave starts, at which time the magnitude of the vibration of the vibrator 511 reaches or exceeds the detection threshold Ith. This detection threshold Ith is a value set to distinguish whether the vibration of the vibrator 511 is caused by the reception of a reflected wave from an obstacle O (another vehicle, a structure, a pedestrian, etc.) or by the reception of a reflected wave from an object other than the obstacle O (for example, a road surface RS, etc.). Note that although the detection threshold Ith is shown as a constant value here, the detection threshold Ith may also be a variable value that changes depending on the situation. Vibrations having a peak equal to or greater than the detection threshold Ith can be considered to be caused by the reception of a reflected wave from the obstacle O.

[0031] The envelope L11 in this example shows that the vibration of the vibrator 511 is attenuated after timing t4. Therefore, timing t4 corresponds to the timing at which reception of the reflected wave from the obstacle O is completed, in other words, the timing at which the transmitted wave last transmitted at timing t1 returns as a reflected wave.

[0032] Furthermore, in envelope L11, timing t3, which is the start point of the peak at timing t4, corresponds to the timing when reception of the reflected wave from obstacle O begins, in other words, the timing when the transmitted wave first transmitted at timing t0 returns as a reflected wave. Therefore, the time ΔT between timing t3 and timing t4 is equal to the time Ta, which is the transmission time of the transmitted wave.

[0033] From the above, in order to use TOF to find the distance from the source of transmission and reception of ultrasonic waves to the obstacle O, it is necessary to find the time Tf between the time t0 when the transmission wave begins and the time t3 when the reflected wave begins to be received. This time Tf can be found by subtracting the time ΔT, which is equal to the time Ta for transmitting the transmitted wave, from the time Tp, which is the difference between the time t0 and the time t4 when the intensity of the reflected wave exceeds the detection threshold Ith and reaches its peak.

[0034] The time t0 when the transmission wave starts to be transmitted can be easily identified as the time when the object detection device 200 starts to operate, and the time Ta as the transmission time of the transmission wave is determined in advance by settings, etc. Therefore, by identifying the time t4 when the intensity of the reflected wave reaches a peak and becomes equal to or greater than the detection threshold Ith, the distance from the source of transmission and reception to the obstacle O can be obtained.

[0035] 5 is a block diagram showing an example of the functional configuration of an object detection device 200 according to an embodiment. The object detection device 200 of this embodiment includes a transmitter 301, a transmission control unit 302, a receiver 303, a signal processing unit 304, a frequency analysis unit 305, a distance information generation unit 306, a Doppler detection unit 307, a storage unit 308, and a correction unit 309. These functional components 301 to 309 can be realized, for example, by cooperation between hardware components such as those shown in FIG. 2 and software components such as programs and firmware. Furthermore, at least some of these functional components 301 to 309 may be realized by dedicated hardware (circuits, etc.).

[0036] The transmitting unit 301 transmits a transmission wave Wt in which a plurality of ultrasonic waves with different frequencies are multiplexed. That is, the transmission wave Wt is an ultrasonic wave containing a plurality of frequency components. The transmission wave Wt may be, for example, an ultrasonic wave in which sine waves with different frequencies in a frequency range of 20 kHz or higher are multiplexed. The transmitting unit 301 is configured using the above-described transducer 511, etc.

[0037] The transmission control unit 302 performs processing to cause the transmission unit 301 to transmit the transmission wave Wt including the above-described multiple frequency components. The transmission control unit 302 of this embodiment includes a carrier wave generation unit 311 and a multiplexing processing unit 312.

[0038] The carrier wave generation unit 311 generates a plurality of carrier waves that are the source of the transmission wave Wt. The carrier wave generation unit 311 generates, for example, a plurality of sine waves with different frequencies. The multiplexing processing unit 312 generates an audio signal by multiplexing a plurality of carrier waves (sine waves) with different frequencies. The multiplexing method is not particularly limited, but methods such as OFDM (Orthogonal Frequency Division Multiplexing) and FDM (Frequency Division Multiplexing) can be used. The transmission unit 301 outputs a transmission wave Wt that includes a plurality of frequency components in accordance with the audio signal thus generated.

[0039] The receiving unit 303 receives a reflected wave Wr generated when the transmitted wave Wt is reflected by an object. The reflected wave Wr is an ultrasonic wave containing multiple frequency components, just like the transmitted wave Wt. The receiving unit 303 is configured using a vibrator 511, an AD conversion circuit, etc., and generates an audio signal of the received reflected wave Wr.

[0040] The transmitting unit 301 and receiving unit 303 of this embodiment are configured using a common oscillator 511. That is, the transmission of the transmission wave Wt and the reception of the reflected wave Wr in each transmitting / receiving unit 21 (each of the transmitting / receiving units 21A to 21L) are performed using the common oscillator 511. This minimizes the paths of the transmission wave Wt and the reflected wave Wr, thereby reducing the possibility of multipath occurrence compared to when multiple oscillators are used. Furthermore, since there is no need to provide an oscillator for each frequency component, an increase in costs can be suppressed.

[0041] The signal processing unit 304 performs predetermined signal processing on the audio signal of the reflected wave Wr. The signal processing may include filtering for noise removal, correlation processing for determining the similarity between the transmitted wave Wt and the reflected wave Wr, and the like.

[0042] The frequency analysis unit 305 performs frequency analysis on the audio signal of the reflected wave Wr after signal processing, and generates reflected wave frequency information indicating multiple frequency components contained in the reflected wave Wr. The frequency analysis unit 305 also generates separated echo information indicating changes over time in amplitude value for each of the multiple frequency components contained in the reflected wave Wr. The frequency analysis may be, for example, FFT (Fast Fourier Transform) or the like.

[0043] Fig. 6 is a diagram showing an example of separated echo information 411 according to the embodiment. In Fig. 6, an audio signal 401 of the transmitted wave Wt, an audio signal 402 of the reflected wave Wr, and separated echo information 411 are illustrated.

[0044] Here, an example is shown in which the transmitted wave Wt contains four types of frequency components A to D, and the reflected wave Wr contains four types of frequency components A' to D'. That is, it is assumed that a Doppler shift occurs between the transmitted wave Wt and the reflected wave Wr due to movement of the transmitter / receiver 21 or obstacle O. The frequency difference (e.g., A'-A) between a frequency component (e.g., A) contained in the transmitted wave Wt and the corresponding frequency component (e.g., A') contained in the reflected wave Wr is referred to as the Doppler frequency. The reflected wave frequency information in this embodiment is information indicating the frequency components A' to D' after the Doppler shift.

[0045] The separated echo information 411 is generated based on the results of FFT analysis of the audio signal 402 of the reflected wave Wr. In the graph of the separated echo information 411, the horizontal axis corresponds to the time elapsed since the transmission wave Wt was transmitted, and the vertical axis corresponds to the amplitude value of the reflected wave Wr. The separated echo information 411 shows the change over time in the amplitude value for each of the four frequency components A' to D' contained in the reflected wave Wr.

[0046] The separated echo information 411 shows that there is variation in the amplitude values ​​of each frequency component. Such variation in amplitude values ​​is thought to be due to the influence of multipath of the reflected wave Wr (for example, cancellation of amplitudes due to opposite phase waves). The object detection device 200 of this embodiment is provided with means for reducing such influence of multipath.

[0047] 5, the distance information generating unit 306 generates distance information relating to the distance from a reference position (e.g., the installation position of the transmitting / receiving unit 21) to an object (obstacle O) based on the separated echo information 411. The distance information is output to, for example, the ECU 100 (see FIG. 2) and is used for automatic driving control, danger avoidance control, etc. of the vehicle 1.

[0048] The distance information generating unit 306 of this embodiment includes a corrected echo information generating unit 321. The corrected echo information generating unit 321 generates corrected echo information based on the largest maximum amplitude value among multiple amplitude values ​​detected for each frequency component at the same time, which are acquired from the separated echo information 411. The corrected echo information may be, for example, information indicating a change over time in the maximum amplitude value.

[0049] 7 is a diagram showing an example of corrected echo information 421 according to an embodiment. The corrected echo information 421 is generated by generating a maximum value line L1 that indicates changes over time in multiple maximum amplitude values ​​(amplitude values ​​corresponding to the positions of dots in FIG. 7) acquired from the separated echo information 411. For example, the maximum amplitude value corresponding to timing t1 is the amplitude value A' (solid line), and the maximum amplitude value corresponding to timing t2 is the amplitude value C' (dotted line). The maximum value line L1 can be generated by acquiring multiple such maximum amplitude values ​​at predetermined time intervals.

[0050] In the corrected echo information 421 shown in Fig. 7, the maximum value line L1 is compared with a reference line Lref (the line corresponding to frequency component B in this example) which shows the change over time in the amplitude value of a single frequency component. As shown by the reference line Lref, with a single frequency component, there is a time period in which the amplitude value drops significantly due to the influence of multipath, but such a time period does not exist with the maximum value line L1. By using this maximum value line L1 to calculate the TOF corresponding to the obstacle O (the TOF corresponding to the peak exceeding the detection threshold Ith) using, for example, a method such as that shown in Fig. 4, the distance to the obstacle O can be calculated with high accuracy.

[0051] Returning to FIG. 5 , the Doppler detection unit 307 calculates the Doppler frequency based on the reflected wave frequency information, the transmitted wave frequency information, and the frequency interval information 308. As described above, the reflected wave frequency information is information indicating the multiple frequency components A' to D' included in the reflected wave Wr. The transmitted wave frequency information is information indicating the multiple frequency components A to D included in the transmitted wave Wt. The frequency interval information is information indicating the intervals between the multiple frequency components A to D included in the transmitted wave Wt (the frequency difference between two adjacent frequency components). The intervals may be constant or may vary over the entire intervals between the multiple frequency components A to D. The transmitted wave frequency information and the frequency interval information may be stored in advance in the storage unit 308 or may be acquired from the transmission control unit 302. For example, the Doppler detection unit 307 interpolates missing frequency components A' to D' included in the reflected wave Wr based on the frequency interval information, and calculates the Doppler frequency based on the difference between the interpolated frequency components A' to D' and the frequency components A to D of the transmitted wave Wt.

[0052] The correction unit 309 corrects the distance information generated by the distance information generation unit 306 based on the Doppler frequency detected by the Doppler detection unit 307 .

[0053] Here, when calculating the Doppler frequency, it is necessary to accurately detect the frequency components of the reflected wave Wr, but as described above, if a drop in amplitude value occurs due to the influence of multipath (see reference line Lref in FIG. 7), the frequency components of the reflected wave Wr may not be accurately detected. Therefore, the Doppler detection unit 307 of this embodiment uses frequency interval information to interpolate frequency components that are missing due to the influence of multipath, etc., and calculates the Doppler frequency using the interpolated frequency components.

[0054] Fig. 8 is a diagram showing an example of an FFT analysis result for a reflected wave Wr according to an embodiment. The graph shown in Fig. 8 is an example of an analysis result corresponding to one time window in an FFT analysis of the reflected wave Wr. Here, an example is shown in which peaks Pa to Pd are detected for each of four frequency components A' to D' contained in the reflected wave Wr. Δf indicates the interval (frequency difference) between the multiple frequency components A to D contained in the transmitted wave Wt. This interval Δf is a value that can also be applied to the interval between the multiple frequency components A' to D' of the reflected wave Wr.

[0055] 8 illustrates a state in which the peak Pb of frequency component B' drops significantly below the original peak Pb'. This phenomenon can occur due to the effects of multipath interference, as described above. When this occurs, the amplitude value of peak Pb falls below the threshold, increasing the possibility that frequency component B' will not be detected.

[0056] Therefore, the Doppler detection unit 307 of this embodiment complements the missing frequency component B' by using the interval Δf. For example, the missing frequency component B' can be interpolated by adding or subtracting the interval Δf using the frequency components A', C', and D' of the other detected peaks Pa, Pc, and Pd as references. Then, by calculating the difference between the frequency component of the reflected wave Wr thus interpolated and the frequency component of the transmitted wave Wt, the Doppler frequency can be calculated with high accuracy.

[0057] It is also possible that, for example, frequency component A' falls below the original peak Pa. In such cases, the amount of Doppler shift can be predicted from the vehicle speed, and the frequency component A' of the missing peak Pa can be interpolated by adding or subtracting an interval Δf based on the frequency components B', C', and D' of the other detected peaks Pb, Pc, and Pd. For frequency component A', the value of the predicted amount of Doppler shift A' is compared with the value of the interval Δf from frequency component B' to determine consistency, making it possible to calculate the Doppler frequency with high accuracy.

[0058] 9 is a flowchart showing an example of processing in the object detection device 200 according to the embodiment. When execution of the object detection processing is started, the transmitter 301 transmits a transmission wave Wt (S101), and the receiver 303 receives a reflected wave Wr (S102). At this time, the transmission of the transmission wave Wt and the reception of the reflected wave Wr are preferably performed by a common oscillator 511 (one transmitter / receiver 21).

[0059] The signal processing unit 304 performs filtering on the audio signal 402 of the reflected wave Wr (S103). The frequency analysis unit 305 performs frequency analysis on the filtered reflected wave Wr to generate separated echo information 411 indicating changes in amplitude over time for each frequency component contained in the reflected wave Wr (S104). The distance information generation unit 306 (corrected echo information generation unit 321) generates corrected echo information 421 indicating changes in maximum amplitude over time based on the separated echo information 411 (S105). Then, the distance information generation unit 306 generates distance information relating to the distance to the obstacle O based on the corrected echo information 421 (S106).

[0060] The Doppler detection unit 307 calculates the Doppler frequency based on the reflected wave frequency information, transmitted wave frequency information, and frequency interval information (S107). At this time, the Doppler detection unit 307 interpolates, for example, frequency components missing from the multiple frequency components contained in the reflected wave Wr due to the influence of multipath or the like using frequency interval information (interval Δf), and calculates the Doppler frequency based on the difference between the frequency components of the interpolated reflected wave Wr and the frequency components of the transmitted wave Wt. Then, the correction unit 309 corrects the frequency distance information based on the Doppler frequency (S108).

[0061] As described above, according to this embodiment, the Doppler frequency can be calculated with high accuracy by using frequency interval information indicating the intervals between multiple frequency components contained in the transmission wave, and highly accurate distance information can be generated. This reduces the influence of multipath and improves the accuracy of obstacle detection.

[0062] (Variation) 10 is a perspective view showing an example of the configuration of a vibrator 551 according to a modified example. The vibrator 551 of this modified example has nine (3×3) upper electrodes 521a-521i, nine upper wires 522a-522i, a piezoelectric body 523, a lower electrode 524, and a lower wire 525. The nine upper electrodes 521a-521i are provided in different regions on the surface of the upper side of the piezoelectric body 523 and are electrically insulated from each other. The nine upper wires 522a-522i are connected to the upper electrodes 521a-521i, respectively.

[0063] With the above configuration, by applying different voltages to the nine upper electrodes 521a-521i, ultrasonic waves of different frequencies can be output from each of the upper electrodes 521a-521i. That is, with the transducer 551 configured as above, by inputting an audio signal of a single frequency to each of the upper electrodes 521a-521i, it is possible to generate the transmission wave Wt containing the above-mentioned multiple frequency components. This makes it possible to omit a mechanism for generating a multiplexed signal in which multiple frequencies are multiplexed.

[0064] The programs that cause a computer (for example, the processor 223) to execute processes for realizing the various functions in the above-described embodiments are stored in the form of installable or executable files on a CD (Compact Disc)-ROM, a flexible disk (FD), a CD The program can be provided by recording it on a computer-readable recording medium such as a Recordable Disk (R), a Digital Versatile Disk (DVD), etc. The program may also be provided or distributed via a network such as the Internet.

[0065] Although the embodiments of the present disclosure have been described above, the above-described embodiments and their modifications are merely examples and are not intended to limit the scope of the invention. The novel embodiments and modifications described above can be implemented in various forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above-described embodiments and modifications are included within the scope and spirit of the invention, and are also included in the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0066] 1...vehicle, 2...vehicle body, 21, 21A to 21L...transmitter / receiver unit, 50...vehicle control system, 100...ECU, 110...input / output device, 120...storage device, 130...processor, 200...object detection device, 220...control unit, 221...input / output device, 222...storage device, 223...processor, 301...transmitter unit, 302...transmission control unit, 303...receiver unit, 304...signal processing unit, 305...frequency analysis unit, 306...distance information generator generation unit, 311...carrier wave generation unit, 312...multiplexing processing unit, 321...corrected echo information generation unit, 411...separated echo information, 421...corrected echo information, 511, 551...vibrators, 521, 521a to 521i...upper electrodes, 522, 522a to 522i...upper wiring, 523...piezoelectric body, 524...lower electrode, 525...lower wiring, L1...maximum value line, O...obstacle, RS...road surface, Wt...transmitted wave, Wr...reflected wave, Δf...interval

Claims

1. a transmitting unit that transmits a transmission wave in which a plurality of ultrasonic waves having different frequencies are multiplexed; a receiving unit that receives a reflected wave generated when the transmitted wave is reflected by an object; a frequency analysis unit that generates reflected wave frequency information indicating a plurality of frequency components included in the reflected wave and separated echo information indicating a change over time in amplitude value for each of the plurality of frequency components included in the reflected wave; a distance information generating unit that generates distance information regarding the distance to the object based on the separated echo information; a Doppler detection unit that calculates a Doppler frequency based on the reflected wave frequency information, transmission wave frequency information indicating a plurality of frequency components included in the transmission wave, and frequency interval information indicating intervals between the plurality of frequency components included in the transmission wave; a correction unit that corrects the distance information based on the Doppler frequency; Equipped with The Doppler detection unit interpolates missing frequency components contained in the reflected wave based on the frequency interval information, and calculates the Doppler frequency based on the difference between the frequency components of the reflected wave after interpolation and the frequency components of the transmitted wave.

2. a transmitting unit that transmits a transmission wave in which a plurality of ultrasonic waves having different frequencies are multiplexed; a receiving unit that receives a reflected wave generated when the transmitted wave is reflected by an object; a frequency analysis unit that generates reflected wave frequency information indicating a plurality of frequency components included in the reflected wave and separated echo information indicating a change over time in amplitude value for each of the plurality of frequency components included in the reflected wave; a distance information generating unit that generates distance information regarding the distance to the object based on the separated echo information; a Doppler detection unit that calculates a Doppler frequency based on the reflected wave frequency information, transmission wave frequency information indicating a plurality of frequency components included in the transmission wave, and frequency interval information indicating intervals between the plurality of frequency components included in the transmission wave; a correction unit that corrects the distance information based on the Doppler frequency; Equipped with The object detection device, wherein the distance information generation unit generates the distance information based on the largest maximum amplitude value among multiple amplitude values ​​detected for each frequency component at the same time obtained from the separated echo information, and in that case generates the distance information based on corrected echo information that indicates changes in the maximum amplitude value over time.

3. The transmission of the transmission wave and the reception of the reflected wave are performed using a common oscillator. The object detection device according to claim 1 or 2.

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