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 an object (B) based on a received signal corresponding to a reflected wave of a transmission wave on the object (B) which is an ultrasonic wave. The object detection device includes a distance acquisition unit (72), a feature quantity acquisition unit (73), and a determination unit (75). The distance acquisition unit acquires a distance to the object based on the received signal. The feature quantity acquisition unit acquires a plurality of feature quantities of the waveform of the received signal. The determination unit determines the height of the object by performing calculation while weighting the plurality of feature quantities acquired by the feature quantity acquisition unit with different weights according to the distance acquired by the distance acquisition unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an object detection device configured to detect an object based on a received signal corresponding to a transmitted ultrasonic wave reflected by the object. [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 differ 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 received by the sonar. Meanwhile, 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 wave received by the sonar at this time have two peaks that exceed 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 object is a tall object such as a wall or a short object such as a curb based on the number of received wave peaks that exceed the detection threshold. However, if a tall object is located far away, the peak of the base reflection from the diagonal downward direction and the peak of the front reflection from the horizontal direction may overlap, which may result in the object being mistakenly recognized as a single reflected wave peak. Therefore, the technology disclosed in Patent Document 1 has a problem in that it is not very accurate in determining the height of distant objects.

[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 an object (B) based on a received signal corresponding to a transmitted ultrasonic wave reflected by the object (B). The object detection device according to claim 1 a distance acquisition unit (72) that acquires a distance to the object based on the received signal; a feature acquisition unit (73) that acquires a plurality of feature amounts of the waveform of the received signal; a determination unit (75) that determines the height of the object by performing a calculation on the plurality of feature amounts acquired by the feature amount acquisition unit while weighting the feature amounts with different weights according to the distance acquired by the distance acquisition unit; Equipped with picture, The feature acquisition unit acquires, as the plurality of feature amounts, at least two of a waveform area, which is the area of ​​an amplitude waveform in the received signal, a peak number in the amplitude waveform, a peak ratio, which is an intensity ratio between the maximum peak and other peaks in the amplitude waveform, and a phase feature of the received signal relative to a reference signal corresponding to the transmitted wave. .

[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] 10 is a graph showing a schematic relationship between the waveform area and the object height and the measured distance. [Figure 4] 10 is a graph showing a rough relationship between the number of peaks and the object height and the measured distance. [Figure 5] 10 is a graph showing a schematic relationship between the peak ratio and the object height and the distance measurement distance. [Figure 6] 10 is a graph schematically showing the relationship between the phase feature and the object height and the ranging distance. [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] 10 is a flowchart showing another specific example of the object detection operation by the in-vehicle system shown in FIG. 2. [Figure 9] 10 is a flowchart showing yet another specific example of the object detection operation by the in-vehicle system shown in FIG. 2. [Figure 10] FIG. 10 is a conceptual diagram showing an outline of the synchronous addition waveform calculation process 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 detect an object B present in the vicinity and acquire the distance to the object B based on a reception signal corresponding to the reception result of the reception wave including the reflected wave of the transmission wave by 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 wave 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 wave.

[0025] The drive signal generating unit 5 is provided 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 cause the transducer 41 to transmit a transmission wave.

[0026] The received signal processing unit 6 is configured to perform various signal processing such as filtering and quadrature detection on the received signal output from the receiving circuit 43. The received signal processing unit 6 is also configured to output a processed signal, which is a result of the various signal processing, to the sensor control unit 7.

[0027] 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.

[0028] 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.

[0029] 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. Specifically, the sensor control unit 7 includes a drive control unit 71, a distance acquisition unit 72, a feature amount acquisition unit 73, a coefficient setting unit 74, and a determination unit 75 as functional components realized on an in-vehicle microcomputer.

[0030] The drive control unit 71 controls 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 transmitter / receiver 4, specifically, the output timing, frequency, etc. In other words, the drive control unit 71 controls the output timing, frequency, etc. of the drive signal generated and output by the drive signal generation unit 5.

[0031] The distance acquisition unit 72 is configured to acquire the measured distance, which is the distance to the object B, based on the received signal. Specifically, in this embodiment, for example, the distance acquisition unit 72 is configured to calculate the measured distance based on the reception time of a peak in the amplitude signal included in the processed signal output from the received signal processing unit 6.

[0032] The feature acquisition unit 73 acquires multiple feature quantities of the waveform of the received signal. Specifically, the feature acquisition unit 73 acquires at least two of the multiple feature quantities: the waveform area, the number of peaks, and the peak ratio of the amplitude waveform, and the phase feature of the received signal. The amplitude waveform is the waveform of the amplitude signal, which is a signal corresponding to the amplitude, i.e., the intensity, of the received signal. The peak ratio is the intensity ratio between the maximum peak and another peak (e.g., the second largest peak) in the amplitude waveform. The phase feature is a feature of the phase signal (e.g., a phase-flat portion). 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 the 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 generation 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 a "phase difference" or a "phase difference signal." The waveform of the phase signal is called a "phase waveform."

[0033] The coefficient setting unit 74 sets a weighting coefficient for weighting each of the plurality of feature amounts acquired by the feature amount acquiring unit 73 with a weight according to the ranging distance acquired by the distance acquiring unit 72. Details of the weighting will be described later.

[0034] The determination unit 75 determines the height of the object B by performing a calculation on the plurality of feature amounts (i.e., typically two feature amounts) acquired by the feature amount acquisition unit 73 while weighting them with different weights according to the measured distance acquired by the distance acquisition unit 72. Specifically, the determination unit 75 determines the height of the object B by assigning j an integer of 1 or more, K an integer of 2 or more, and dividing the plurality of feature amounts into X1 to X K The weighting coefficient w for the j-th feature Xj is set as a value w according to the distance measurement distance d. j (d) Then, the feature Xj is weighted by a weighting coefficient w jThe coefficient setting unit 74 calculates the determination amount Y by adding or multiplying the values ​​multiplied by (d) for j=1 to K. K Two of them are X j1 ,X j2 Let j1 and j2 be different natural numbers, then w j1 (d) and w j2 The weighting coefficient w(d) is set so that the change tendency with an increase in the distance measurement distance d differs between (a) and (b). The determination unit 75 then determines the height of the object B by comparing the calculated determination amount Y with a determination threshold value.

[0035] (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.

[0036] 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.

[0037] 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.

[0038] The received signal processing unit 6 performs various signal processing such as filtering and quadrature detection on the received signal to generate a processed signal including an amplitude signal, and outputs the processed signal to the sensor control unit 7. Specifically, for example, the received signal processing unit 6 generates and outputs a phase signal and an amplitude signal by quadrature detection. Various signal processing methods, such as quadrature detection, for generating a phase signal and an amplitude signal 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. Therefore, further details of such signal processing will not be described in this specification.

[0039] 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 processed signals such as the amplitude signal output from the received signal processing unit 6. Specifically, first, the distance acquisition unit 72 determines the presence or absence of object B based on the amplitude signal. That is, the distance acquisition unit 72 determines the presence of object B when the amplitude exceeds the object detection threshold. Then, the distance acquisition unit 72 calculates the ranging distance based on the reception time of the amplitude peak that exceeds the object detection threshold.

[0040] The feature amount acquiring unit 73 acquires a plurality of feature amounts of the waveform of the received signal that are necessary for detecting the height of the object B. Specifically, the feature amount acquiring unit 73 acquires at least two of the waveform area, the number of peaks, the peak ratio, and the phase feature.

[0041] Here, the behavior of feature quantities when the object height or the measured distance changes differs depending on the type of feature quantity. Figures 3 to 6 schematically show the relationship between object height and measured distance for each of multiple feature quantities, namely, waveform area, number of peaks, peak ratio, and phase feature. In Figures 3 to 6, 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 time the transmitted wave is transmitted to the time the reflected wave is received. The reception time can also be referred to as the "reception time." The converted distance D is a value corresponding to the measured distance d. In the amplitude waveforms shown in Figures 3 to 5, the vertical axis M represents amplitude. In the phase waveforms shown in Figure 6, the vertical axis θ represents phase.

[0042] Japanese Patent Application Laid-Open Publication No. 2014-74665, which has already been filed and published by the applicant of the present application, discloses a technique for determining the height of object B from the waveform area. Specifically, this technique determines the height of object B by utilizing the tendency that the larger the waveform area, the higher the height of object B. The relationship between waveform area and height can be specified using a map or lookup table created in advance by experiment or computer simulation.

[0043] FIG. 3 shows an example of determining object height by calculating the waveform area based on an amplitude waveform normalized by setting the peak value at the maximum peak to "1." The reason for normalizing the waveform area is as follows: The waveform area is affected by the distance to object B. Specifically, the waveform area decreases as the distance to object B increases. Therefore, the feature acquisition unit 73, which functions as an area calculation unit, calculates a waveform area normalized based on the peak value at the maximum peak. By detecting the height of object B based on the normalized waveform area in this way, it is possible to suppress the influence of area fluctuations due to changes in the distance between the ultrasonic sensor 3 and object B. Note that normalization can also be performed using the peak width at the maximum peak. In FIG. 3, the dashed-dotted line parallel to the horizontal axis indicates the object detection threshold. As shown in FIG. 3, when object B is located close (e.g., the measurement distance is approximately 1 m or less), the intensity of the frontal reflection is high. Therefore, there is no significant difference in the normalized waveform area between a tall object with two peaks, one corresponding to the frontal reflection and the other to the base reflection, and a short object with only one peak. On the other hand, when the measurement distance is long (for example, about 3 m or more), the waveform area tends to become large for tall objects due to the combination of two peaks. Therefore, when the measurement distance is long, a large difference can occur in the waveform area after normalization between short and tall objects.

[0044] FIG. 4 shows an example of determining object height based on the number of peaks. In FIG. 4, the dashed-dotted line parallel to the horizontal axis indicates the object detection threshold, and the apex of the detected peak is indicated by a black dot. As described above, if object B is a tall object such as a wall or pole, two peaks, one for the front reflection and one for the base reflection, are detected. As shown in the waveforms in the upper right corners of FIGS. 3 and 4, the amplitude peak corresponding to the front reflection and the amplitude peak corresponding to the base reflection occur in this order in chronological order. On the other hand, if object B is a short object such as a curb, there is only one reflected wave peak. Therefore, as described in Patent Document 1, it is possible to determine the height of object B based on the peak count, which is the number of amplitude peaks that exceed the object detection threshold.

[0045] As shown in Figure 4, when the measurement distance is short, the two peaks of a tall object are clearly separated. In contrast, when the measurement distance is long, the two peaks of a tall object are combined into approximately one peak. Therefore, determining the height of an object based on the number of peaks is easy at short distances, but difficult at long distances.

[0046] Similarly, as shown in Figure 5, when the measurement distance is short, the two peaks of a tall object are clearly separated, making it easy to detect with high accuracy. In contrast, when the measurement distance is long, the two peaks of a tall object are combined into almost a single peak, which means that the other peaks to be compared with the maximum peak may be erroneously detected. Therefore, while determining the height of an object using the peak ratio is easy at short distances, it becomes difficult at long distances.

[0047] The phase feature is explained in detail below. Theoretically, the reflected wave from object B has a waveform similar to the transmitted wave, i.e., the reference signal. However, a phase θ deviation can occur depending on the positional relationship between the ultrasonic sensor 3 and object B. For this reason, the value of the phase θ should be approximately constant for a single reflected wave. Therefore, when a reflected wave whose amplitude peak exceeds the object detection threshold is received, a corresponding phase flat portion (i.e., the bold line portion in the figure) occurs, as shown in Figure 6. A "phase flat portion" is a continuous section in which the amount of change in phase θ is within a predetermined range for a predetermined period or a predetermined converted distance. When multiple reflected waves are received from a single object B, multiple phase flat portions occur. Specifically, a phase flat portion corresponding to the base reflection and a phase flat portion corresponding to the front and top reflections usually occur. Therefore, the height of object B can be estimated by geometric calculation using the mounting height of the ultrasonic sensor 3, the measured distance in the phase flat portion corresponding to the base reflection (i.e., the converted distance D), and the measured distance in the phase flat portion corresponding to the front and top reflections. The "measured distance in the phase flat portion" is, for example, a converted distance D corresponding to the position of the start point or center point in the horizontal axis direction of the phase flat portion.

[0048] Here, when the measurement distance is short, for a tall object, a phase flat portion corresponding to the front reflection and a phase flat portion corresponding to the base reflection occur in this order in time series, as shown in the waveform in the upper right of Figure 6. In this case, for a short object, a phase flat portion corresponding to the base reflection and a phase flat portion corresponding to the top / front reflection may occur separately in time series, as shown in the waveform in the upper left of Figure 6. In this case, there will be no significant difference in the phase characteristics between the two.

[0049] In contrast, when the measurement distance is long, for tall objects, phase flat portions occur in two places: the base reflection and the front reflection. On the other hand, for short objects, the base reflection and the top reflection can be considered essentially the same, so only one phase flat portion occurs. Therefore, determining the object height using phase features is easy at long distances, but difficult at short distances.

[0050] Therefore, the coefficient setting unit 74 sets a weighting coefficient for each of the multiple feature amounts acquired by the feature amount acquiring unit 73, so as to weight the feature amount with a different weight depending on the ranging distance acquired by the distance acquiring unit 72. Specifically, for example, when determining the height of an object using two types of feature amounts, the waveform area and the number of peaks, the coefficient setting unit 74 sets a larger weighting coefficient for the waveform area as the ranging distance increases, and sets a larger weighting coefficient for the number of peaks as the ranging distance decreases. Alternatively, for example, when determining the height of an object using two types of feature amounts, the number of peaks and phase features, the coefficient setting unit 74 sets a larger weighting coefficient for the number of peaks as the ranging distance decreases, and sets a larger weighting coefficient for the phase features as the ranging distance increases.

[0051] The determination unit 75 determines the height of object B by performing calculations on the multiple feature amounts acquired by the feature amount acquisition unit 73 while weighting them in accordance with the measured distance acquired by the distance acquisition unit 72. Specifically, the determination unit 75 determines the height of object B by adding or multiplying the multiple feature amounts while weighting them with different weights in accordance with the measured distance. In other words, the determination unit 75 performs object height determination using the weighting in accordance with the measured distance as the reliability of the object height determination based on each feature amount.

[0052] As described above, this embodiment focuses on the fact that the way features appear depending on the distance from object B varies among multiple feature amounts, and performs comprehensive object height determination using multiple feature amounts, while changing the weighting of the feature amounts according to the distance. In other words, this embodiment changes the feature amount that is given importance according to the distance. This makes it possible to determine the height of object B with good accuracy over a wide range from close distances to long distances.

[0053] (Example of operation) Fig. 7 is a flowchart showing a specific example of the object detection process executed by the sensor control unit 7. In Fig. 7, "S" is an abbreviation for "step." The same applies to Fig. 8 and subsequent figures.

[0054] While a predetermined object detection condition is met, the electronic control unit 2 causes each of the 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 acquires, i.e., calculates, the measured distance. Next, in step 702, the CPU acquires a plurality of feature amounts. Subsequently, in step 703, the CPU sets a weighting coefficient corresponding to each of the plurality of feature amounts acquired in step 702 according to the measured distance acquired in step 701. Then, in step 704, the CPU determines the height of object B using the feature amounts acquired in step 702 and the weighting coefficients set in step 703. Specifically, the CPU assigns a weighting coefficient w to the j-th feature amount Xj. j The value multiplied by (d) is added or multiplied for j=1 to K to calculate a judgment quantity Y, and the calculated judgment quantity Y is compared with a judgment threshold to determine whether object B is a tall object or not.

[0056] (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.

[0057] 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.

[0058] 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.

[0059] 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. The reception signal processing unit 6 may be provided in the sensor control unit 7.

[0060] 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 and / 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.

[0061] 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. That is, the sensor control unit 7 may include both an on-board microcomputer and a digital circuit. In other words, each process in the present invention may be performed by hardware or software.

[0062] 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.

[0063] 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 computer program, or as a non-transitory storage medium storing the program.

[0064] As is clear from the above, the functional blocks shown in Fig. 2 are merely functional blocks set up for the sake of convenience to facilitate understanding of the contents of the present invention. Therefore, even if these functional blocks are not actually realized as subroutines or hardware, the requirements of the present invention can be satisfied as long as the predetermined functions or processes of the present invention are realized.

[0065] The present invention is not limited to the specific operational examples or processing examples described in the above embodiment. For example, the distance acquisition unit 72 may acquire the measured distance based on the first time the amplitude signal exceeds the object detection threshold. Specifically, if only one peak exceeding the object detection threshold is present in the amplitude waveform acquired in one reception process, the measured distance is acquired based on the time corresponding to the intersection of the rising edge of that peak and the object detection threshold. In contrast, if multiple peaks exceeding the object detection threshold are present in the amplitude waveform acquired in one reception process, the measured distance is acquired based on the time corresponding to the intersection of the rising edge of the first peak and the object detection threshold. The weighting factor may change stepwise or continuously (e.g., linearly) as the measured distance changes. Regarding the feature value, the acquired value may be used as is or may be converted into an N-value value stepwise. The feature value used for height determination is not limited to two feature values: one feature value whose weighting coefficient increases as the distance increases, and another feature value whose weighting coefficient decreases as the distance increases, but may be three or more feature values. In this case, three or more features may be used, for example, a feature whose weighting coefficient increases as the distance increases, a feature whose weighting coefficient decreases as the distance increases, and a feature whose weighting coefficient remains constant even when the distance changes.

[0066] In the long distance range, the S / N ratio becomes poor, making it difficult to capture the feature amount. Therefore, the determination unit 75 may determine the height of the object B based on the feature amount weighted according to the acquisition history of the feature amount. That is, the coefficient setting unit 74 sets the weighting coefficient according to the acquisition history of the feature amount. In this way, by using data from multiple times with weighting according to the distance, it is possible to improve the determination accuracy.

[0067] 8 shows a flowchart corresponding to such a modified example. When the object detection process starts, first, in step 801, the CPU acquires, i.e., calculates, the measured distance. Next, in step 802, the CPU acquires a plurality of feature amounts. Subsequently, in step 803, the CPU sets a weighting coefficient corresponding to each of the plurality of feature amounts according to the measured distance acquired in step 801. Then, in step 804, the CPU determines whether the processes of steps 801 to 803 have been repeated N times.

[0068] Until the processing of steps 801 to 803 has been repeated N times (i.e., step 804=NO), the CPU returns the processing to step 801. On the other hand, when the processing of steps 801 to 803 has been repeated N times (i.e., step 804=YES), the CPU advances the processing to steps 805 and 806.

[0069] In step 805, the CPU calculates the decision amount Y from the weights for N times. Specifically, the CPU calculates the decision amount Y using the following formula (1). In the following formula (1), y n is the weighting coefficient w according to the distance d j (d) is multiplied by the feature value Xj, and the result is added or multiplied for j=1 to K, that is, the decision value Y based on the n-th (1≦n≦N) data. n is the weight for N times, that is, a coefficient for weighting each of N times according to the value of n. Specifically, in this example, in a scene where the vehicle is approaching the object B, on the premise that an object with a small value of n (i.e., measured in the past) is far away, a weighting coefficient W for multiple times determination according to the number of times n is set. n That is, in the following formula (1), each of the determination amounts for multiple times is multiplied by a weighting coefficient for multiple determinations, and the sum is calculated. Also, in this example, the coefficient W n are normalized so that the sum is 1. n Alternatively, the coefficient W may be set to a value according to the distance measurement distance d. nmay be a constant value. In step 806, the CPU determines the height of the object B by comparing the calculated determination amount Y with a determination threshold value.

number

[0070] Note that indirect waves may also be used in calculating the determination amount Y. An "indirect wave" is a reflected wave when a wave transmitted from one of a plurality of ultrasonic sensors 3 mounted on the same vehicle C is reflected by an object B and received by another of the plurality of ultrasonic sensors 3. In contrast, a reflected wave received by the same ultrasonic sensor 3 as the one that transmitted the transmitted wave is called a "direct wave." In this case, in step 805, the CPU can calculate the determination amount Y using the following formula (2). The following formula (2) shows an example of calculation when one direct wave and one indirect wave are used. In the following formula (2), Yd in the first item indicates the determination amount based on the direct wave, and Yid in the second item indicates the determination amount based on the indirect wave. Yd and Yid are each calculated using the above formula (1). Furthermore, a generalized formula that can be used when a plurality of indirect waves are used is shown in the following formula (3). y in the following formula (3) d_n is the y in the above equation (1) for the direct wave n and y id1_n ~y idM_n is the y in the above equation (1) for each of the M indirect waves. n In the following formulas (2) and (3), the proportion of direct waves to indirect waves is set equal, but they may be unequal, for example, by increasing the proportion of direct waves.

number

number

[0071] As described above, the S / N ratio deteriorates in the long distance range. Therefore, the determination unit 75 determines the height of the object B based on a synchronously added waveform obtained by synchronously adding the waveforms of the received signals according to the distance acquired by the distance acquisition unit 72. By using the synchronously added waveform, the S / N ratio can be improved. In addition, the number of feature quantities to be used can be increased.

[0072] Fig. 9 shows a flowchart corresponding to this modified example. In the object detection process, the processes of steps 901 to 905 are executed in order. In step 901, the CPU receives reflected waves N times. Next, in step 902, the CPU calculates a synchronously added waveform. Fig. 10 shows an overview of the calculation of the synchronously added waveform. The superposition is performed by aligning peak positions by tracking using the waveforms, vehicle movement amount, etc., or by aligning the entire waveforms based on waveform cross-correlation.

[0073] In step 903, the CPU acquires a plurality of feature amounts based on the synchronously added waveform calculated in step 902. In step 904, the CPU sets a weighting coefficient corresponding to each of the plurality of feature amounts. The weighting method may be, for example, a simple sum (i.e., equivalent to the amount of determination for each time). Alternatively, the weight may be changed according to the amount of movement. This is because the more distant the object, the less information can be obtained from the feature. Specifically, it is possible to increase the weight for one determination for a closer object. In step 905, the CPU determines the height of object B using the feature amounts acquired in step 903 and the weighting coefficients set in step 904.

[0074] 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.

[0075] The transmitted wave may be encoded by frequency modulation, which improves the accuracy of detecting the presence or absence and height of object B. In particular, when both direct and indirect waves are used, as in the above-described modified example, it becomes easy to distinguish between the direct and indirect waves.

[0076] 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.

[0077] 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]

[0078] 1. In-vehicle system (object detection device) 2. Electronic control device 3 Ultrasonic Sensor 7 Sensor control unit 72 Distance acquisition part 73 Feature acquisition unit 74 Counting judgment section 75 Judgment section B Object C vehicle

Claims

1. An object detection device (1) configured to detect an object (B) based on a received signal corresponding to a reflected wave of an ultrasonic transmission wave by the object (B), a distance acquisition unit (72) that acquires a distance to the object based on the received signal; a feature acquisition unit (73) that acquires a plurality of feature amounts of the waveform of the received signal; a determination unit (75) that determines the height of the object by performing a calculation on the plurality of feature amounts acquired by the feature amount acquisition unit while weighting the feature amounts with different weights according to the distance acquired by the distance acquisition unit; Equipped with the feature amount acquiring unit acquires, as the plurality of feature amounts, at least two of a waveform area, which is an area of ​​an amplitude waveform in the received signal, a peak number in the amplitude waveform, a peak ratio, which is an intensity ratio between a maximum peak and other peaks in the amplitude waveform, and a phase feature of the received signal relative to a reference signal corresponding to the transmission wave. Object detection device.

2. the determination unit determines the height of the object based on the feature amounts weighted according to an acquisition history of the feature amounts. The object detection device according to claim 1 .

3. the determination unit determines the height of the object based on a synchronously added waveform obtained by synchronously adding waveforms of the received signals in accordance with the distance acquired by the distance acquisition unit. The object detection device according to claim 1 or 2.

4. the determination unit determines the height of the object by adding or multiplying the plurality of feature amounts acquired by the feature amount acquisition unit while weighting them with different weights according to the distance acquired by the distance acquisition unit. The object detection device according to any one of claims 1 to 3.

5. the determination unit determines the height of the object using a weighting according to the distance acquired by the distance acquisition unit as a reliability. The object detection device according to any one of claims 1 to 4.

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