Object detection device

Abstract

To provide an object detection device capable of determining the height of an object with good accuracy.SOLUTION: An object detection device (1) is configured to detect the height of an object (B) based on a waveform area which is an area of an amplitude waveform in a received signal corresponding to a received wave including a reflected wave of a transmission wave on the object (B) which is an ultrasonic wave. The object detection device includes a phase detection unit (61) and an area correction unit (75). The phase detection unit detects a phase of the received signal with reference to a reference signal corresponding to the transmission wave. The area correction unit corrects the waveform area according to the phase.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a technology for determining whether a detected obstacle is a tall obstacle by utilizing the fact that the intensity characteristics of reflected waves vary depending on the height of the obstacle. Specifically, for example, when detecting a curb, a sonar transmits a wave toward the road surface (i.e., diagonally downward), which is reflected by the curb and then reflected back onto the road surface, and the sonar receives the reflected wave. On the other hand, a horizontally transmitted wave passes above the curb and is not received by the sonar. Therefore, the intensity characteristics of the reflected wave received by the sonar at this time have one peak that exceeds the obstacle detection threshold. In contrast, when detecting a wall, a horizontally transmitted wave is reflected by the wall, and the sonar receives the reflected wave as is. Therefore, the sonar receives both the reflected wave of the transmitted wave emitted diagonally downward and the reflected wave of the transmitted wave emitted horizontally. Therefore, the intensity characteristics of the reflected waves received by the sonar at this time have two peaks exceeding the obstacle detection threshold within a short period of time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5846316 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the technology disclosed in Patent Document 1 determines whether a detected obstacle is a tall obstacle based on the number of received wave peaks that exceed a detection threshold. However, if a tall obstacle is located far away, two overlapping peaks may be erroneously recognized as a single peak. Therefore, the technology disclosed in Patent Document 1 has a problem in that the accuracy of determining the height of a distant object is low.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, etc. That is, the present invention provides an object detection device that can determine the height of an object with high accuracy, for example. [Means for solving the problem]

[0006] The object detection device (1) is configured to detect the height of an object (B) based on a waveform area, which is the area of ​​the amplitude waveform in a received signal corresponding to a received wave including a reflected wave of an ultrasonic wave transmitted by the object (B). The object detection device according to claim 1 a phase detection unit (61) that detects the phase of the received signal relative to a reference signal corresponding to the transmitted wave; an area correction unit (75) that corrects the waveform area in accordance with the phase; Preparation picture, the phase detection unit detects a phase gap, which is a difference between one of the plurality of flat portions and another of the plurality of flat portions, when a plurality of flat portions in which the phase waveform is flat exists within a predetermined range; The area correction unit corrects the waveform area with a correction value according to the phase gap. .

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

[0008] [Figure 1] 1 is a plan view showing a schematic configuration of a vehicle equipped with an in-vehicle system that constitutes an object detection device according to an embodiment. [Figure 2] 2 is a block diagram showing a schematic functional configuration of the in-vehicle system shown in FIG. 1. FIG. [Figure 3] 1 is a graph showing amplitude and phase waveforms used to determine the height of an object. [Figure 4] 10 is a time chart showing an example of a phase gap that appears in a phase waveform. [Figure 5] 10 is an amplitude waveform graph showing an example of setting a predetermined range for detecting a phase gap from a phase waveform. [Figure 6] FIG. 10 is a conceptual diagram showing an example of setting a predetermined range for detecting a phase gap from a phase waveform. [Figure 7] 3 is a flowchart showing a specific example of an object detection operation by the in-vehicle system shown in FIG. 2. [Figure 8] 8 is a flowchart showing a specific example of the waveform area calculation process shown in FIG. 7. [Figure 9] 10A and 10B are amplitude waveform graphs and phase waveform graphs showing an example of setting a predetermined range for calculating a phase feature value from a phase waveform. [Figure 10] 10 is a flowchart showing another specific example of the waveform area calculation process performed by the in-vehicle system shown in FIG. 2. [Figure 11] FIG. 10 is a block diagram showing a schematic functional configuration of an in-vehicle system according to a third embodiment. [Figure 12] FIG. 12 is a conceptual diagram showing an outline of pulse compression performed by the correlation detection unit shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that various modifications applicable to one embodiment may be hindered from being understood if they are introduced in the middle of a series of explanations relating to the embodiment. Therefore, the modifications will be described together after the explanation of the embodiment.

[0010] (In-vehicle system configuration) Referring to FIG. 1, the in-vehicle system 1 is mounted on a vehicle C as a moving body. The vehicle C is a so-called four-wheeled automobile, and has a box-like body C1 formed in a substantially rectangular shape in a plan view. The shape of each part of the vehicle C in a "plan view" refers to the shape of that part when viewed from the line of sight in the same direction as the direction of gravity, with the vehicle C stably placed on a horizontal surface so that it can travel. The vehicle C equipped with the in-vehicle system 1 according to this embodiment will be referred to as the "host vehicle" hereinafter.

[0011] Hereinafter, the imaginary line that passes through the center of the host vehicle in the vehicle width direction in a plan view and is parallel to the vehicle length direction of the host vehicle will be referred to as the vehicle center line LC. The vehicle length direction is a direction that is perpendicular to the vehicle width direction and perpendicular to the vehicle height direction. The vehicle height direction is a direction that defines the vehicle height of the host vehicle and is a direction parallel to the direction of gravity when the host vehicle is stably placed on a horizontal surface so that it can travel. In addition, "front," "rear," "left," "right," and "up" are defined as shown by the arrows in Figure 1. In other words, the vehicle length direction is synonymous with the front-to-rear direction. In addition, the vehicle width direction is synonymous with the left-to-right direction.

[0012] The in-vehicle system 1 includes an electronic control unit 2 and an ultrasonic sensor 3. The electronic control unit 2 is an in-vehicle microcomputer that may also be referred to as an ECU, and includes a CPU, ROM, RAM, non-volatile rewritable memory, etc. (not shown). ECU stands for Electronic Control Unit. The non-volatile rewritable memory is a storage device that allows information to be rewritten while the power is on but retains information in an unrewritable manner while the power is off, such as a flash ROM. The ROM, RAM, and non-volatile rewritable memory are non-transient physical storage media. The electronic control unit 2 is mounted inside a vehicle body C1.

[0013] The electronic control unit 2 is connected to the ultrasonic sensors 3 via an on-board information communication line so as to be able to send and receive information. In this embodiment, the host vehicle is equipped with a plurality of ultrasonic sensors 3. The electronic control unit 2 is configured to read and execute a control program stored in a ROM or a non-volatile rewritable memory, thereby controlling the overall operation of the on-board system 1, including the timing of the transmission and reception of ultrasonic waves by each of the plurality of ultrasonic sensors 3. In other words, the on-board system 1 constituting the object detection device according to this embodiment is configured to detect an object B around the host vehicle based on the results of transmission and reception of ultrasonic waves by the ultrasonic sensors 3 while mounted on the host vehicle.

[0014] The front bumper of the host vehicle, i.e., the bumper C2 on the front side of the vehicle body C1, is equipped with a first front sensor 3A, a second front sensor 3B, a third front sensor 3C, and a fourth front sensor 3D as ultrasonic sensors 3. Similarly, the rear bumper of the host vehicle, i.e., the bumper C2 on the rear side of the vehicle body C1, is equipped with a first rear sensor 3E, a second rear sensor 3F, a third rear sensor 3G, and a fourth rear sensor 3H as ultrasonic sensors 3.

[0015] The first front sensor 3A is provided at the right end of the front bumper so as to emit a transmission wave to the right front of the vehicle. The second front sensor 3B is disposed between the first front sensor 3A and the vehicle center line LC in the vehicle width direction so as to emit a transmission wave substantially ahead of the vehicle. The third front sensor 3C is disposed in a position substantially symmetrical to the second front sensor 3B across the vehicle center line LC. The third front sensor 3C is disposed between the vehicle center line LC and the fourth front sensor 3D in the vehicle width direction so as to emit a transmission wave substantially ahead of the vehicle. The fourth front sensor 3D is disposed in a position substantially symmetrical to the first front sensor 3A across the vehicle center line LC. The fourth front sensor 3D is provided at the left end of the front bumper so as to emit a transmission wave to the left front of the vehicle.

[0016] The first rear sensor 3E is provided at the right end of the rear bumper so as to emit a transmission wave to the right rear of the vehicle. The second rear sensor 3F is disposed between the first rear sensor 3E and the vehicle center line LC in the vehicle width direction so as to emit a transmission wave to approximately rear of the vehicle. The third rear sensor 3G is disposed in a position approximately symmetrical to the second rear sensor 3F across the vehicle center line LC. The third rear sensor 3G is disposed between the vehicle center line LC and the fourth rear sensor 3H in the vehicle width direction so as to emit a transmission wave to approximately rear of the vehicle. The fourth rear sensor 3H is disposed in a position approximately symmetrical to the first rear sensor 3E across the vehicle center line LC. The fourth rear sensor 3H is provided at the left end of the rear bumper so as to emit a transmission wave to the left rear of the vehicle.

[0017] (ultrasonic sensor) The schematic configuration of the ultrasonic sensor 3 will be described below with reference to Fig. 2. Note that, for simplicity of illustration, Fig. 2 shows only one of the multiple ultrasonic sensors 3 connected to the electronic control device 2, and the others are omitted.

[0018] The ultrasonic sensor 3 is configured to transmit ultrasonic waves as transmission waves toward the outside of the vehicle, and to receive reception waves including reflection waves of the transmitted transmission waves from the object B, thereby detecting the object B present in the vicinity and acquiring the distance to the object B.

[0019] Specifically, the ultrasonic sensor 3 includes a transmitter / receiver 4, a drive signal generator 5, a received signal processor 6, and a sensor controller 7. In this embodiment, the transmitter / receiver 4, drive signal generator 5, received signal processor 6, and sensor controller 7 are supported by a single sensor housing made of synthetic resin or the like.

[0020] In this embodiment, the ultrasonic sensor 3 is provided with only one transmitter / receiver 4, and is configured to perform the transmission and reception functions using this transmitter / receiver 4. That is, the transmitter / receiver 4 has a function as a transmitter 40A that transmits transmission waves to the outside, and a function as a receiver 40B that receives reception waves. Specifically, one transmitter / receiver 4 has one transducer 41. The transmitter 40A and receiver 40B are configured to use the common transducer 41 to perform the transmission function and the reception function, respectively.

[0021] The transducer 41 is configured to function as a transmitter that transmits transmitted waves to the outside and as a receiver that receives reflected waves. The transducer 41 has a configuration as a so-called resonant ultrasonic microphone that incorporates an electromechanical energy conversion element such as a piezoelectric element. Specifically, the transducer 41 is configured by joining the electromechanical energy conversion element to the bottom plate of a substantially cylindrical casing with a bottom. When mounted on the vehicle, the casing is inserted into a through-hole C3 formed in the bumper C2, so that the transmitting / receiving surface 41a, which is the outer surface of the bottom plate that constitutes the diaphragm, faces the space outside the vehicle.

[0022] The transmitter / receiver unit 4 includes a transducer 41, a transmission circuit 42, and a reception circuit 43. That is, the transmitter unit 40A includes the transducer 41 and the transmission circuit 42. The receiver unit 40B includes the transducer 41 and the reception circuit 43. The transducer 41 is electrically connected to the transmission circuit 42 and the reception circuit 43.

[0023] The transmission circuit 42 is configured to drive the transducer 41 based on the input drive signal, thereby causing the transducer 41 to emit a transmission wave in the ultrasonic band. Specifically, the transmission circuit 42 has a digital / analog conversion circuit and the like. That is, the transmission circuit 42 is configured to perform processing such as digital / analog conversion on the drive signal output from the drive signal generation unit 5, and apply the AC voltage generated thereby to the transducer 41.

[0024] The receiving circuit 43 is configured to generate a receiving signal corresponding to the reception result of the ultrasonic waves at the transducer 41, and to output the generated receiving signal to the receiving signal processing unit 6. Specifically, the receiving circuit 43 has an amplifier circuit, an analog / digital conversion circuit, etc. That is, the receiving circuit 43 is configured to perform signal processing such as amplification and analog / digital conversion on the voltage signal input from the transducer 41, thereby generating and outputting a receiving signal corresponding to the frequency, phase, and amplitude of the received ultrasonic waves.

[0025] The drive signal generating unit 5 is configured to generate a drive signal for driving the transmitting unit 40 A. The drive signal is a signal for driving the transmitting unit 40 A to transmit a transmission wave from the transducer 41, and is, for example, a pulsed signal in the ultrasonic band.

[0026] The received signal processing unit 6 is configured to output a phase signal and an amplitude signal by performing signal processing such as quadrature detection processing on the received signal output from the receiving circuit 43. Specifically, the received signal processing unit 6 includes a phase detection unit 61 that detects the phase of the received signal and outputs a phase signal, and an amplitude detection unit 62 that detects the amplitude of the received signal, i.e., the reflected wave, and outputs an amplitude signal.

[0027] The phase signal is a signal corresponding to the phase of the received signal relative to a reference signal corresponding to the transmitted wave. The reference signal is a signal having a waveform corresponding to the waveform of the transmitted wave or drive signal, specifically, a signal having a constant transmission frequency fc. The reference signal can be generated internally in the received signal processing unit 6 or received from the drive signal generating unit 5 or the sensor control unit 7. The phase signal is a signal corresponding to the difference between the phase of the reference signal and the phase of the received signal. For this reason, the "phase" or "phase signal" can also be referred to as the "phase difference" or "phase difference signal." The waveform of the phase signal is referred to as the "phase waveform." The amplitude signal is a signal corresponding to the amplitude, i.e., intensity, of the received signal. The waveform of the amplitude signal is referred to as the "amplitude waveform."

[0028] FIG. 3 shows an example of an amplitude signal and a phase signal. In FIG. 3, the horizontal axis D represents the converted distance. The converted distance D is the propagation distance calculated by multiplying the propagation time (i.e., TOF) by the speed of sound, and can be evaluated as the reception time converted into distance. TOF stands for Time of Flight, and is the elapsed time from the transmission time of the transmitted wave to the reception time of the reflected wave. The reception time can also be referred to as the "reception time." In the upper graph of FIG. 3, the vertical axis Va represents the amplitude. In the lower graph of FIG. 3, the vertical axis θ represents the phase. FIG. 4 shows a phase signal with the horizontal axis representing the reception time t. As mentioned above, the converted distance D is obtained by converting the reception time t using the speed of sound. Therefore, even if the horizontal axis in FIG. 3 is represented as the reception time t, the waveforms will be similar. Therefore, the horizontal axis of each waveform in FIG. 3 and the like may represent either the converted distance D or the reception time t.

[0029] (First embodiment) The configuration of the first embodiment will be described below with reference to FIGS.

[0030] The sensor control unit 7 is communicably connected to the electronic control unit 2 so as to cooperate with the electronic control unit 2 to control the operation of the ultrasonic sensor 3. That is, the sensor control unit 7 is configured to control the output of the drive signal from the drive signal generation unit 5 to the transmission unit 40A, and to detect the object B based on the processed signal output from the received signal processing unit 6.

[0031] The sensor control unit 7 is configured as an in-vehicle microcomputer including a CPU, ROM, RAM, non-volatile rewritable memory, etc. (not shown). That is, the sensor control unit 7 is configured to control the operation of the ultrasonic sensor 3 by reading and executing a control program stored in the ROM or non-volatile rewritable memory.

[0032] In this embodiment, an in-vehicle system 1 equipped with an electronic control device 2 and an ultrasonic sensor 3 is configured to detect the height of an object B based on a waveform area, which is the area of ​​an amplitude waveform. Specifically, the sensor control unit 7 includes a drive control unit 71, an amplitude determination unit 72, an area calculation unit 73, a phase feature detection unit 74, an area correction unit 75, and an object detection unit 76 as functional components realized on an in-vehicle microcomputer.

[0033] The drive control unit 71 is configured to control the emission state of the transmission wave from the transmitter 40A by outputting a control signal to the drive signal generation unit 5. The control signal is a signal for controlling the output characteristics of the drive signal output from the drive signal generation unit 5 to the transceiver 4, specifically, the output timing, frequency, number of pulses, etc. In other words, the drive control unit 71 controls the output timing, frequency, number of pulses, etc. of the drive signal generated and output by the drive signal generation unit 5. In this embodiment, the drive control unit 71 outputs a control signal to the drive signal generation unit 5 to cause the transceiver 4 to generate a transmission wave having a constant transmission frequency fc.

[0034] The amplitude determination unit 72 is configured to determine the presence or absence of an object B based on the amplitude signal. Specifically, when the amplitude Va exceeds an object determination threshold Va_th, the amplitude determination unit 72 determines that the object B is present, assuming that the received signal contains a wave reflected by the object B.

[0035] The area calculation unit 73 is configured to calculate the waveform area of ​​the amplitude waveform when the amplitude determination unit 72 determines that the received signal contains a wave reflected by the object B. Specifically, the area calculation unit 73 calculates the area of ​​the portion of the amplitude waveform that exceeds the object determination threshold Va_th. Furthermore, in this embodiment, in order to suppress the influence of area fluctuations due to changes in the distance between the ultrasonic sensor 3 and the object B, the area calculation unit 73 calculates a waveform area normalized based on a characteristic value of the amplitude waveform (for example, the peak value or peak width at the maximum peak).

[0036] The phase feature detection unit 74 is configured to analyze the phase waveform and obtain a phase feature value, which is the result of the analysis. The phase feature value is a feature value that indicates the change in phase θ of the portion of the phase signal that corresponds to the reflected wave from object B, rather than the noise portion. In this embodiment, when multiple flat portions (e.g., the portion surrounded by the dashed ellipse in FIG. 4 ) where the phase waveform is flat exist within a predetermined range, the phase feature detection unit 74 detects a phase gap Δθ, which is the difference between one of the multiple flat portions. The “predetermined range” is a range of reception time t or converted distance D that includes a reflected wave from one object B but does not include a reflected wave from another object B at a different distance, resulting from the transmission of a single transmitted wave and the reception of the reflected wave from the transmitted wave by object B. This range may also be referred to as a “reflected wave region.” Specific examples of the predetermined range, i.e., the reflected wave region, will be described later.

[0037] The area correction unit 75 is configured to correct the waveform area calculated by the area calculation unit 73 in accordance with the phase θ. In this embodiment, the area correction unit 75 corrects the waveform area with a correction value in accordance with the change in the phase θ corresponding to the reflected wave. Specifically, the area correction unit 75 corrects the waveform area with a correction value in accordance with the phase gap Δθ, which is the phase feature value acquired by the phase feature detection unit 74.

[0038] In this embodiment, the area correction unit 75 is configured to perform different processing depending on whether the phase gap Δθ is undetectable (i.e., substantially zero) or less than a predetermined value, or a second case. Specifically, the area correction unit 75 corrects the waveform area using a correction value for undetection in the first case, and corrects the waveform area using a correction value for detection in the second case. The correction value for undetection is a constant value. In contrast, the correction value for detection is a correction value using cosΔθ, and more specifically, is K / (1+cosΔθ), where K is a constant value (e.g., 1).

[0039] The object detection unit 76 is configured to detect the presence or absence of object B and the height of object B if object B is present, based on the determination result from the amplitude determination unit 72 and the correction result from the area correction unit 75 of the waveform area calculated by the area calculation unit 73. Specifically, in this embodiment, if the waveform area is equal to or greater than the height determination threshold, object B is determined to be a tall object (e.g., a pole), whereas if the waveform area is less than the height determination threshold, object B is determined to be a short object (e.g., a curb).

[0040] (Operation overview) In the following description, the device configuration, the object detection method, and the object detection program according to this embodiment will be simply referred to as "this embodiment." Below, an overview of the operation of this embodiment will be described together with the effects achieved by this embodiment with reference to FIGS.

[0041] 2, drive control unit 71 outputs a control signal to drive signal generation unit 5. Drive signal generation unit 5 then generates a drive signal based on the control signal and outputs the generated drive signal to transmitter 40A. Transmitter 40A is driven by the drive signal. That is, transmission circuit 42 excites transducer 41 based on the input drive signal. As a result, a transmission wave is transmitted from transducer 41, which functions as a transmitter, to the outside of the vehicle.

[0042] When the received waves, including the reflected waves generated when the transmitted waves are reflected by the object B, reach the transducer 41, the transducer 41 is excited. That is, the received waves are received by the transducer 41. Then, a voltage signal according to the excited state, i.e., the receiving state, is output from the transducer 41. The receiving circuit 43 performs signal processing such as amplification and analog-to-digital conversion on the voltage signal to generate a received signal, and outputs the received signal to the received signal processing unit 6.

[0043] The received signal processing unit 6 performs signal processing such as quadrature detection processing on the received signal, thereby outputting a phase signal and an amplitude signal. Specifically, the phase detection unit 61 generates a phase signal and outputs it to the sensor control unit 7. Furthermore, the amplitude detection unit 62 generates an amplitude signal and outputs it to the sensor control unit 7. Various signal processing methods such as quadrature detection processing for generating phase signals and amplitude signals were already publicly known or well-known at the time of filing of this application, and such publicly known or well-known techniques can also be used in this embodiment. For this reason, detailed explanation of such signal processing will be omitted in this specification.

[0044] The sensor control unit 7 detects the presence or absence of object B and, if object B is present, the height of object B, based on the phase signal and amplitude signal output from the received signal processing unit 6. Specifically, first, the amplitude determination unit 72 determines the presence or absence of object B based on the amplitude signal. Specifically, the amplitude determination unit 72 determines the presence of object B when the amplitude Va exceeds an object determination threshold Va_th. When the amplitude determination unit 72 determines that object B is present and that the received signal contains a wave reflected by object B, the area calculation unit 73 calculates the waveform area used to determine the height of object B.

[0045] Incidentally, Japanese Patent Application Laid-Open Publication No. 2014-74665, filed by the applicant of the present application, discloses a technology for determining the height of object B from the area of ​​a reflected wave. Specifically, this technology determines the height of object B by utilizing the tendency that the larger the area of ​​the reflected wave, the higher the height of object B. The relationship between area and height can be defined using a map or lookup table created in advance by experiment or computer simulation. This technology improves the accuracy of height determination compared to the technology disclosed in Patent Document 1. However, the inventor of the present application analyzed various reflected wave waveforms and discovered the following technical problem.

[0046] The waveform area is affected by the distance to object B. Specifically, the longer the distance to object B, the smaller the waveform area. Therefore, the area calculation unit 73 calculates a normalized waveform area based on a characteristic value of the amplitude waveform (for example, the peak value or peak width at the maximum peak). Specifically, the area calculation unit 73 normalizes the amplitude waveform by setting the peak value at the maximum peak to "1". Then, the area calculation unit 73 calculates the waveform area based on the normalized amplitude waveform. In this way, by detecting the height of object B based on the normalized waveform area, it is possible to suppress the influence of area fluctuations due to changes in the distance between the ultrasonic sensor 3 and object B.

[0047] As described in Patent Document 1, when object B is a tall object, two waves reach the ultrasonic sensor 3: a base reflected wave, which is a wave reflected from the base of object B, and an upper reflected wave, which is a wave reflected from the top end of object B or a position at approximately the same height as the mounting height of ultrasonic sensor 3. Specifically, the upper reflected wave, which has a shorter propagation distance, reaches the ultrasonic sensor 3 first, and then the base reflected wave, which has a longer propagation distance, reaches the ultrasonic sensor 3.

[0048] When object B is located in the medium to short distance range, the upper reflected wave and the root reflected wave can be clearly distinguished from each other on the amplitude waveform. However, when object B is located far away, the upper reflected wave and the root reflected wave overlap. When such overlap occurs, the overlapping portions may reinforce or weaken each other depending on the phase relationship between the two. Specifically, for example, the example in FIG. 3(a) shows an example in which the upper reflected wave and the root reflected wave are out of phase, and the overlapping portions weaken each other. On the other hand, the example in FIG. 3(b) shows an example in which the upper reflected wave and the root reflected wave are approximately in phase, and the overlapping portions reinforce each other. When the upper reflected wave and the root reflected wave overlap in this way, the area calculation result is affected by the phase relationship between the two.

[0049] Therefore, in this embodiment, the phase feature detection unit 74 analyzes the phase waveform and detects the phase gap Δθ, which is a phase feature value, within a predetermined search range, i.e., the reflected wave region. FIGS. 5 and 6 conceptually illustrate a method for setting the reflected wave region Dr. FIG. 5 shows an amplitude waveform. In FIG. 5, Dmin indicates the minimum value of the reflected wave region Dr, and Dmax indicates the maximum value of the reflected wave region Dr. That is, the reflected wave region Dr is defined as the converted distance D between the minimum value Dmin and the maximum value Dmax. The peak distance Dc is the converted distance D corresponding to the maximum value of the reflected wave peak within the reflected wave region Dr. FIG. 6 is a conceptual diagram for setting the reflected wave region Dr. In FIG. 6, R indicates the road surface, h1 indicates the mounting height of the ultrasonic sensor 3, i.e., the transducer 41, and h2 indicates the height of the facing position F from the road surface R. The facing position F is the position on the object B directly facing the ultrasonic sensor 3, i.e., the transducer 41. In this specific example, h1 = h2. D1 is the distance between the transducer 41 and the directly facing position F. D2 is the distance between the transducer 41 and the base of the object B.

[0050] The minimum value Dmin is the converted distance D corresponding to D1 (i.e., Dmin=2×D1) when the peak distance Dc is associated with D2 (i.e., Dc=2×D2). The maximum value Dmax is the converted distance D corresponding to D2 (i.e., Dmax=2×D2) when the peak distance Dc is associated with D1 (i.e., Dc=2×D1).

[0051] In this way, the phase feature detection unit 74 sets a reflected wave region Dr and detects a phase gap Δθ within the set reflected wave region Dr. Specifically, although the reflected wave from object B may have a phase θ shift, theoretically it has the same waveform as the transmitted wave, i.e., the reference signal. Therefore, the value of the phase θ should be approximately constant for a single reflected wave. However, when multiple reflected waves are received from a single object B, a phase gap Δθ may occur between the multiple reflected waves. Therefore, the phase feature detection unit 74 searches for flat sections (e.g., the areas surrounded by dashed ellipses in Figure 4) where the phase waveform is flat within the reflected wave region Dr. If multiple flat sections are detected, the phase representative value for each flat section is calculated. The "phase representative value" is the average value, median value, or value at the center position in the increasing direction of the reception time t or the converted distance D of the flat sections. The phase gap Δθ is the difference between the phase representative values ​​of adjacent flat sections in the increasing direction of the reception time t or the converted distance D.

[0052] The area correction unit 75 corrects the waveform area calculated by the area calculation unit 73 in accordance with the phase θ (i.e., the change in the phase θ corresponding to the reflected wave). Specifically, the area correction unit 75 corrects the waveform area with a correction value in accordance with the phase gap Δθ. Here, the constructive or destructive effect of the amplitudes of two interfering waves can be calculated by the dot product of vectors. Therefore, in this embodiment, the area correction unit 75 multiplies the waveform area calculated by the area calculation unit 73 by a correction value M=K / (1+cosΔθ).

[0053] The object detection unit 76 detects the presence or absence of object B and, if object B is present, the height of object B, based on the determination result from the amplitude determination unit 72 and the correction result from the area correction unit 75 of the waveform area calculated by the area calculation unit 73. Specifically, in this embodiment, if the waveform area is equal to or greater than the height determination threshold, object B is determined to be a tall object, whereas if the waveform area is less than the height determination threshold, object B is determined to be a short object. This makes it possible to determine the height of object B with high accuracy.

[0054] (Example of operation) 7 and 8 are flowcharts showing a specific example of the object detection process executed by the sensor control unit 7. In FIGS. 7 and 8, "S" is an abbreviation for "step." While a predetermined object detection condition is met, the electronic control unit 2 causes each of the multiple ultrasonic sensors 3 to repeatedly execute an object detection operation at a predetermined cycle. That is, the sensor control unit 7 of a certain ultrasonic sensor 3 repeatedly executes the object detection process shown in FIG. 7 at a predetermined cycle based on a command signal from the electronic control unit 2. The above-mentioned CPU (not shown) provided in the sensor control unit 7 will hereinafter be simply referred to as "CPU."

[0055] When the object detection process starts, first, in step 701, the CPU determines whether or not an object B is present based on whether the amplitude Va exceeds an object determination threshold Va_th. If object B is present (i.e., step 701=YES), the CPU proceeds with the process from step 702 onwards. On the other hand, if object B is not present (i.e., step 701=NO), the CPU skips the process from step 702 onwards and temporarily ends the current object detection process.

[0056] In step 702, the CPU calculates the waveform area Wa. Details of the calculation process of the waveform area Wa will be described later. Subsequently, in step 703, the CPU determines whether the waveform area Wa is equal to or greater than the height determination threshold Wa_th. If the waveform area Wa is equal to or greater than the height determination threshold Wa_th (i.e., step 703=YES), the CPU determines in step 704 that the object B corresponding to this waveform area Wa is a tall object, and temporarily ends the current object detection process. On the other hand, if the waveform area Wa is less than the height determination threshold Wa_th (i.e., step 703=NO), the CPU determines in step 705 that the object B corresponding to this waveform area Wa is a short object, and temporarily ends the current object detection process.

[0057] A specific example of the calculation process of the waveform area Wa in step 702 will be described with reference to the flowchart shown in FIG. 8. First, in step 801, the CPU detects peaks in the amplitude waveform. Next, in step 802, the CPU normalizes the amplitude waveform. Subsequently, in step 803, the CPU calculates the pre-correction area Wa_r based on the normalized amplitude waveform. The pre-correction area Wa_r is the value calculated by the area calculation unit 73 before correction by the area correction unit 75. Thereafter, the CPU causes the process to proceed to steps 804 and 805.

[0058] In step 804, the CPU analyzes the phase waveform to detect the phase gap Δθ. In step 805, the CPU determines whether the current phase waveform corresponds to a first case in which the phase gap Δθ is not detected (i.e., is approximately zero) or is less than a predetermined value, or a second case otherwise.

[0059] In the first case (i.e., step 805=NO), the CPU proceeds to step 806. In step 806, the CPU calculates the waveform area Wa by correcting the pre-correction area Wa_r using a predetermined non-detection correction value M1. In contrast, in the second case (i.e., step 805=YES), the CPU proceeds to step 807. In step 807, the CPU calculates the waveform area Wa by correcting the pre-correction area Wa_r using a detection correction value M2=K / (1+cosΔθ).

[0060] Second Embodiment A second embodiment, which is a partial modification of the first embodiment, will be described below. The following description of the second embodiment will mainly focus on the differences from the first embodiment. In the first and second embodiments, identical or equivalent parts are designated by the same reference numerals. Therefore, in the following description of the second embodiment, the description of the first embodiment can be appropriately applied to components having the same reference numerals as those in the first embodiment, unless there is a technical contradiction or a special additional explanation. The same applies to the third and subsequent embodiments described below.

[0061] In this embodiment, the phase feature detector 74 detects a phase feature value, which is a statistical value corresponding to the variation in the phase θ, instead of the phase gap Δθ. In this case, the phase feature value is, for example, the standard deviation, variance, or existence range of the phase θ within the reflected wave region Dr. Then, the area corrector 75 corrects the waveform area in accordance with the phase feature value.

[0062] As shown in FIG. 9, the reflected wave region Dr in this embodiment is the region where the amplitude Va in the normalized amplitude signal exceeds the object determination threshold Va_th. FIG. 9(a) shows a case where no interference of reflected waves occurs, and FIG. 9(b) shows a case where interference between reflected waves occurs. As shown in FIG. 9(a), when no interference of reflected waves occurs, the fluctuation or variation in the phase θ within the reflected wave region Dr is small. In contrast, as shown in FIG. 9(b), when interference of reflected waves occurs, the fluctuation or variation in the phase θ within the reflected wave region Dr becomes large. Therefore, the area correction unit 75 corrects the waveform area using a correction value M corresponding to the state of the fluctuation or variation in the phase θ within the reflected wave region Dr. This can achieve the same effects as the first embodiment.

[0063] The flowchart shown in Fig. 10 shows a specific example of the process of calculating the waveform area Wa according to this embodiment, and is a partial modification of the flowchart shown in Fig. 8. That is, steps 1001 to 1003 in Fig. 10 are the same as steps 801 to 803 in Fig. 8. Therefore, the process from step 1004 onwards will be explained below.

[0064] In step 1004, the CPU analyzes the phase waveform to detect a phase feature value α, which is a statistical value corresponding to the variation state of the phase θ. Next, in step 1005, the CPU acquires a correction value M(α) based on the phase feature value α detected in step 1004. The correction value M(α) can be acquired using a map, lookup table, or calculation formula with the phase feature value α as a parameter. The map, lookup table, or calculation formula is created by experiment or computer simulation and is stored in advance in the above-mentioned ROM or non-volatile rewritable memory (not shown) in the sensor control unit 7. Then, in step 1006, the CPU calculates the waveform area Wa by correcting the pre-correction area Wa_r using the correction value M(α).

[0065] (Third embodiment) A third embodiment will be described below. In this embodiment, the in-vehicle system 1 uses pulse compression to stably detect phase feature values ​​such as the phase gap Δθ, thereby enabling the height of the object B to be determined with even greater accuracy.

[0066] 11, the sensor control unit 7 includes a drive control unit 71, an amplitude determination unit 72, an area calculation unit 73, a phase feature detection unit 74, an area correction unit 75, and an object detection unit 76, as well as a correlation detection unit 77. The correlation detection unit 77 is configured to detect the correlation between a reference signal corresponding to the transmitted wave and the received signal.

[0067] Fig. 12 shows an overview of pulse compression performed by the correlation detection unit 77 shown in Fig. 11. In Fig. 12, Sa indicates the received signal, Sr indicates the reference signal, Sa indicates the amplitude signal, Sθ indicates the phase signal, Pa indicates the amplitude signal after pulse compression, and Pθ indicates the phase signal after pulse compression.

[0068] Based on the received signal Ss and the reference signal Sr, a phase signal Sθ and an amplitude signal Sa are obtained by signal processing such as quadrature detection. Then, a pulse-compressed phase signal Pθ and an amplitude signal Pa are obtained by pulse compression, i.e., correlation detection using a predetermined reference signal. Note that pulse compression techniques themselves were already publicly known or well-known at the time of filing this application, and such publicly known techniques can also be used in this embodiment. Therefore, detailed descriptions of pulse compression techniques will be omitted in this specification. Then, a phase feature value can be detected, i.e., calculated, using the value of the pulse-compressed phase signal Pθ corresponding to the peak value of the pulse-compressed amplitude signal Pa.

[0069] According to this embodiment, the S / N ratio is improved, so that peak values ​​can be detected well even in the waveform of a reflected wave with a relatively small amplitude that is likely to be buried in noise, thereby enabling stable detection of phase feature values.

[0070] (Variation) The present invention is not limited to the above-described embodiment. Therefore, the above-described embodiment can be modified as appropriate. Representative modifications will be described below. In the following description of the modifications, differences from the above-described embodiment will be mainly described. Furthermore, the same reference numerals are used for parts that are identical or equivalent to each other in the above-described embodiment and the modifications. Therefore, in the following description of the modifications, the description of the above-described embodiment can be used as appropriate for components that have the same reference numerals as the above-described embodiment, unless there is a technical contradiction or special additional explanation.

[0071] The present invention is not limited to the specific device configurations shown in the above embodiments. That is, for example, all or part of the electronic control unit 2 may be configured to include a digital circuit configured to enable the above-described operations, such as an ASIC or FPGA. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. That is, in the electronic control unit 2, an on-board microcomputer portion and a digital circuit portion may coexist.

[0072] The ultrasonic sensor 3 is not limited to a configuration capable of transmitting and receiving ultrasonic waves using a single transducer 41 as shown in Fig. 2. That is, for example, a transmitting transducer 41 electrically connected to a transmitting circuit 42 and a receiving transducer 41 electrically connected to a receiving circuit 43 may be provided in parallel.

[0073] The configurations of the components such as the transmission circuit 42 and the reception circuit 43 are not limited to the specific examples shown in the above embodiment. That is, for example, the digital / analog conversion circuit may be provided in the drive signal generation unit 5 instead of the transmission circuit 42. Furthermore, the transmission circuit 42 may be integrated with the drive signal generation unit 5. Similarly, the reception circuit 43 may be integrated with the reception signal processing unit 6.

[0074] As long as there is no technical contradiction, all or part of the functional components of the sensor control unit 7 may be provided in the received signal processing unit 6 or the electronic control unit 2. In other words, the object detection device according to the present invention may be configured by at least either the electronic control unit 2 or the ultrasonic sensor 3.

[0075] All or part of the sensor control unit 7 may be configured with a digital circuit, such as an ASIC or FPGA, configured to enable the above-described operations. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. In other words, the sensor control unit 7 may include both an on-board microcomputer and a digital circuit.

[0076] The program according to the present invention, which enables the execution of the various operations, procedures, or processes described in the above embodiments, can be downloaded or upgraded via V2X communication. V2X stands for Vehicle to X. Alternatively, the program can be downloaded or upgraded via a terminal device installed in a manufacturing plant, a repair shop, a dealer, or the like of vehicle C. The program can be stored on a memory card, an optical disk, a magnetic disk, or the like.

[0077] In this manner, each of the above functional configurations and methods may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, each of the above functional configurations and methods may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, each of the above functional configurations and methods may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, a computer program may be stored in a computer-readable, non-transitory storage medium as instructions to be executed by a computer. In other words, each of the above functional configurations and methods may be expressed as a computer program including procedures for implementing the same, or as a non-transitory storage medium storing the program.

[0078] 2 are merely functional blocks set up for the sake of convenience in order to facilitate understanding of the present invention. Therefore, even if these functional blocks are not actually implemented as subroutines or hardware, the requirements of the present invention can be met as long as the functions or processes specified in the present invention are implemented.

[0079] The correlation detection unit 77 may calculate a frequency signal indicating frequency characteristics from the received signal based on the phase signal, and then determine whether the received reflected wave is a normal wave by detecting the correlation between this frequency signal and the frequency characteristics of the transmitted wave. Alternatively, the received signal processing unit 6 may include a frequency detection unit that detects and outputs a frequency signal based on the received signal. A "normal wave" refers to a wave received when the transducer 41, acting as a transceiver, receives a reflected wave of its own transmitted wave. In contrast, a received wave resulting from a transmitted wave from another device is hereinafter referred to as an "irregular wave." The "other device" includes not only an ultrasonic sensor 3 mounted on a vehicle other than the subject vehicle, but also other ultrasonic sensors 3 mounted on the subject vehicle. In this case, if the reflected wave included in the currently received wave is a normal wave, the amplitude determination unit 72 determines the presence or absence of object B based on the amplitude signal. Furthermore, if the reflected wave included in the currently received wave is a normal wave, the area calculation unit 73 calculates the waveform area.

[0080] The present invention is not limited to the specific operation or processing examples shown in the above embodiment. That is, for example, the normalization process of step 802 may be omitted. In this case, a value corresponding to the measured distance is used as the height determination threshold Wa_th.

[0081] In step 806, the non-detection correction value M1 may be 1. Alternatively, step 806 may be omitted. Alternatively, steps 805 and 806 may be omitted by appropriately setting the value of K in M2 (for example, K≠1).

[0082] Regarding the method of setting the reflected wave region Dr, a method different from the above specific examples can also be used.

[0083] The height determination is not limited to distinguishing between tall and short objects. For example, it may be distinguished between tall, medium, and short objects, or the height of object B may be classified into four or more levels. Alternatively, an approximate value of the height of object B may be calculated.

[0084] Even in the first case where the phase gap Δθ is undetectable (i.e., substantially zero) or less than a predetermined value, it is possible to perform different correction processes depending on whether interference between two reflected waves occurs as shown in FIG. 3(b) or whether there is only one reflected wave and no interference occurs as shown in FIG. 9(a). The two cases can be distinguished, for example, by determining whether the length of the flat portion in the normalized amplitude waveform is equal to or greater than a predetermined value. Specifically, for example, no correction process is performed when there is only one reflected wave and no interference occurs as shown in FIG. 9(a), whereas correction is performed when there is interference between two reflected waves as shown in FIG. 3(b).

[0085] The transmitted wave may be encoded by frequency modulation, which improves the accuracy of detecting the presence or absence and height of object B.

[0086] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential unless expressly stated as essential or clearly considered essential in principle. Furthermore, when numerical values ​​such as the number, amount, range, etc. of components are mentioned, the present invention is not limited to those specific numerical values ​​unless expressly stated as essential or clearly limited to specific numerical values ​​in principle. Similarly, when the shape, direction, positional relationship, etc. of components are mentioned, the present invention is not limited to those shapes, directions, positional relationship, etc. unless expressly stated as essential or clearly limited to specific shapes, directions, positional relationship, etc. in principle.

[0087] The modified examples are not limited to the above examples. That is, a part of one embodiment and a part of another embodiment may be combined with each other. Also, multiple modified examples may be combined with each other. Furthermore, all or part of the above embodiment and all or part of the modified examples may be combined with each other. [Explanation of symbols]

[0088] 1. In-vehicle system (object detection device) 2. Electronic control device 3 Ultrasonic Sensor 6. Received signal processing section 61 Phase detection unit 7 Sensor control unit 75 Area correction section 77 Correlation detection unit B Object C vehicle

Claims

1. An object detection device (1) configured to detect the height of an object (B) based on a waveform area, which is an area of ​​an amplitude waveform in a received signal corresponding to a received wave including a reflected wave by the object (B) of a transmitted ultrasonic wave, a phase detection unit (61) that detects the phase of the received signal relative to a reference signal corresponding to the transmitted wave; an area correction unit (75) that corrects the waveform area according to the phase; Equipped with the phase detection unit detects a phase gap, which is a difference between one of the plurality of flat portions and another of the plurality of flat portions, when a plurality of flat portions in which the phase waveform is flat exists within a predetermined range; the area correction unit corrects the waveform area with a correction value according to the phase gap; Object detection device.

2. The area correction unit calculates the correction value using cos Δθ, where Δθ is the phase gap. The object detection device according to claim 1 .

3. the area correction unit corrects the waveform area using a non-detection correction value as the correction value in a first case where the phase gap is not detected or is less than a predetermined value; In a second case different from the first case, the waveform area is corrected using a detection-time correction value as the correction value. The object detection device according to claim 1 or 2.

4. The height of the object is detected based on the waveform area normalized based on a characteristic value in the amplitude waveform. The object detection device according to any one of claims 1 to 3.

5. Further comprising a correlation detection unit (77) for detecting a correlation between a reference signal corresponding to the transmission wave and the reception signal, The object detection device according to any one of claims 1 to 4.

6. The transmission wave is frequency modulated. The object detection device according to any one of claims 1 to 5.

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