Object detection device

Abstract

To provide an object detection device capable of improving object detection accuracy.SOLUTION: An object detection device is provided with an ultrasonic sensor 2 having: a transmitting unit 40A that transmits ultrasonic waves in response to a transmission signal; a receiving unit 40B that receives reflected waves reflected by an object and outputs a received signal in response to the reflected waves; an amplitude signal generating unit 6 that generates an amplitude signal from the received signal that indicates the lapse of transmission time and the change in amplitude of the ultrasonic waves; a threshold setting unit 7 that sets a determination threshold that is a predetermined threshold for determining whether or not the object is present; and an object determination unit 8 that determines whether or not an object is present based on the amplitude signal and the determination threshold. The threshold setting unit sets a boundary BD that divides a region of the transmission time of the amplitude signal into a first region where the amplitude fluctuation in the amplitude signal is large and a second region where the amplitude fluctuation is small, and sets a first threshold for the amplitude signal in the first region and sets a second threshold for the amplitude signal in the second region.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, there is known an object detection device that transmits and receives a search wave from a transmitting / receiving unit and detects an object present within the irradiation range of the search wave by removing noise due to road surface reflection contained in the reflected wave of the received search wave (for example, see Patent Document 1). This object detection device calculates an object determination threshold for determining the presence or absence of an object based on a signal processed by a low-pass filter unit for a signal output from a receiving circuit unit and a reference value of a dark noise level output from a reference setting unit. Then, when the object detection device determines that the peak value of the output from the receiving circuit unit exceeds the object determination threshold, it determines that an object is present within the irradiation range of the search wave. In this way, the object detection device described in Patent Document 1 suppresses the influence of noise due to road surface reflection when determining the presence or absence of an object by determining the presence or absence of an object using the object determination threshold calculated based on the signal processed by the low-pass filter unit and the reference value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-59764 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the object detection device described in Patent Document 1, the object determination threshold used when determining the presence or absence of an object is calculated by adding a constant reference value of a background noise level to an output signal based on a signal output by a receiving circuit unit.

[0005] However, the noise fluctuation amount differs between road surface reflection noise and background noise, so if a determination threshold for determining the presence or absence of an object is set by adding a certain reference value to an output signal, the determination threshold cannot be set according to the respective fluctuation amounts of the road surface reflection noise and background noise.

[0006] For example, when two noises with different fluctuation amounts are present in the output signal, if the judgment threshold is set to correspond to the side with the larger noise fluctuation amount, it is difficult to make the judgment threshold correspond to the side with the smaller noise fluctuation amount. Also, if the judgment threshold is set to correspond to the side with the smaller noise fluctuation amount, it is difficult to make the judgment threshold correspond to the side with the larger noise fluctuation amount. For this reason, if the presence or absence of an object is determined based on the judgment threshold set by adding a certain reference value to the output signal, the object detection device may erroneously detect an object or fail to detect an object.

[0007] In view of the above, an object of the present disclosure is to provide an object detection device capable of improving the accuracy of object detection. [Means for solving the problem]

[0008] According to one aspect of the disclosure, An object detection device that detects an object by transmitting and receiving ultrasonic waves, The ultrasonic sensor (2) includes a transmitting section (40A) that transmits ultrasonic waves in response to a transmission signal, a receiving section (40B) that receives the reflected waves reflected by an object and outputs a received signal in response to the reflected waves, an amplitude signal generating section (6) that generates an amplitude signal indicating the passage of transmission time of the ultrasonic waves and a change in amplitude from the received signal, a threshold setting section (7) that sets a determination threshold that is a predetermined threshold for determining the presence or absence of an object, and an object determining section (8) that determines the presence or absence of an object based on the amplitude signal and the determination threshold, The threshold setting unit sets a boundary (B) that divides the transmission time region of the amplitude signal into a first region where the amplitude fluctuation in the amplitude signal is large and a second region where the amplitude fluctuation is small, and sets a first threshold that is a judgment threshold for the first region based on the amplitude of the amplitude signal in the first region, and sets a second threshold that is a judgment threshold for the second region based on the amplitude of the amplitude signal in the second region.

[0009] There are cases where two types of noise occurring in the amplitude signal have different amounts of fluctuation and are present at positions with different distances from the ultrasonic sensor. Therefore, by setting the first threshold based on the magnitude of the amplitude signal in the first region and setting the second threshold based on the magnitude of the amplitude signal in the second region, the judgment threshold can correspond to the amount of fluctuation of the noise in each of the first and second regions. Therefore, it is possible to suppress erroneous detection of an object or non-detection of an object, and to improve the object detection accuracy in the object detection device.

[0010] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram of an object detection device according to a first embodiment. [Diagram 2] 4 is a diagram illustrating an example of the directivity of ultrasonic waves transmitted by an ultrasonic sensor. FIG. [Diagram 3] 10A and 10B are diagrams for explaining a road surface reflection region and a region outside the road surface reflection region of an amplitude signal. [Figure 4] FIG. 4 is a diagram showing characteristics of road noise and background noise. [Diagram 5] 4 is a flowchart showing a control process executed by the object detection device according to the first embodiment. [Figure 6] 13 is a flowchart showing details of a boundary setting process. [Figure 7]4 is a diagram for explaining a method of setting a boundary set by a threshold setting unit according to the first embodiment. FIG. [Figure 8] 10 is a flowchart showing details of a determination threshold setting process. [Figure 9] FIG. 4 is a diagram for explaining a smoothing process executed by a threshold setting unit according to the first embodiment. [Figure 10] FIG. 4 is a diagram for explaining thresholds set by a threshold setting unit according to the first embodiment. [Figure 11] FIG. 11 is a diagram for explaining thresholds set by a threshold setting unit according to a second modified example of the first embodiment. [Figure 12] 10 is a flowchart showing a control process executed by an object detection device according to a second embodiment. [Figure 13] FIG. 11 is a diagram for explaining thresholds set by a threshold setting unit according to the second embodiment. [Figure 14] 1 is a diagram showing an example of the directivity of ultrasonic waves transmitted by an ultrasonic sensor when the ultrasonic sensor is parallel to a road surface; [Figure 15] 10A and 10B are diagrams illustrating an example of the directivity of ultrasonic waves transmitted by an ultrasonic sensor when the ultrasonic sensor is inclined downward with respect to a road surface. [Figure 16] 10A and 10B are diagrams illustrating an example of the directivity of ultrasonic waves transmitted by an ultrasonic sensor when the ultrasonic sensor is inclined upward with respect to a road surface. [Figure 17] 13 is a flowchart showing a control process executed by an object detection device according to a third embodiment. [Figure 18] FIG. 13 is a diagram for explaining thresholds set by a threshold setting unit according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same reference numerals are used for parts that are the same as or equivalent to those described in the preceding embodiments, and the description thereof may be omitted. In addition, in the embodiments, when only a part of the components is described, the components described in the preceding embodiments can be applied to the other parts of the components. In the following embodiments, each embodiment can be partially combined with each other, even if not specifically stated, as long as it does not cause any trouble in combination.

[0013] (First embodiment) A first embodiment will be described. An object detection device 1 of this embodiment shown in Fig. 1 is mounted on a vehicle, which is a moving body (not shown) that travels on a road, and is configured to detect an object B around the vehicle. The vehicle on which the object detection device 1 is mounted is hereinafter referred to as "host vehicle." The vehicle (not shown) is, for example, an automobile.

[0014] The object detection device 1 detects an object B by transmitting and receiving ultrasonic waves, and includes an ultrasonic sensor 2 and a control unit 3 that controls the operation of the ultrasonic sensor 2. The ultrasonic sensor 2 is configured to detect an object B by transmitting a search wave, which is an ultrasonic wave, and receiving the search wave reflected by the object B. The ultrasonic sensor 2 is an ultrasonic sonar that transmits ultrasonic waves.

[0015] The ultrasonic sensor 2 includes a transmitter / receiver 4, a transmission signal generator 5, an amplitude signal generator 6, a threshold setting unit 7, and an object determiner 8.

[0016] The transmitting / receiving unit 4 has a transmitting unit 40A and a receiving unit 40B. The transmitting unit 40A is provided so as to be capable of transmitting a search wave to the outside. The receiving unit 40B is provided so as to be capable of receiving ultrasonic waves including a wave reflected by an object B of the search wave transmitted from the transmitting unit 40A.

[0017] The transmitting / receiving unit 4 includes a transducer 41, a transmitting circuit 42, and a receiving circuit 43. The transmitting unit 40A includes the transducer 41 and the transmitting circuit 42. The receiving unit 40B includes the transducer 41 and the receiving circuit 43.

[0018] The transducer 41 has a function as a transmitter that transmits a search wave to the outside and a function as a receiver that receives a reflected wave, and is electrically connected to a transmission circuit 42 and a reception circuit 43. In other words, the ultrasonic sensor 2 has a so-called integrated transmission and reception configuration.

[0019] Specifically, the transducer 41 is configured as an ultrasonic microphone incorporating an electromechanical energy conversion element such as a piezoelectric element. The transducer 41 is disposed at a position facing the outer surface of the vehicle so as to be able to transmit a search wave to the outside of the vehicle and to receive a reflected wave from the outside of the vehicle.

[0020] The transmission circuit 42 is configured to drive the transducer 41 based on the input transmission signal, thereby causing the transducer 41 to emit a search wave. Specifically, the transmission circuit 42 has a digital / analog conversion circuit and the like. That is, the transmission circuit 42 is configured to generate an element input signal by performing signal processing such as digital / analog conversion on the transmission signal output from the transmission signal generation unit 5. The element input signal is an AC voltage signal for driving the transducer 41. The transmission circuit 42 is configured to apply the generated element input signal to the transducer 41 to excite the electro-mechanical energy conversion element in the transducer 41, thereby generating a search wave.

[0021] The receiving circuit 43 is provided to generate a receiving signal corresponding to the result of receiving the ultrasonic wave by the transducer 41 and output the signal to the amplitude signal generating unit 6. Specifically, the receiving circuit 43 has an amplifier circuit, an analog / digital conversion circuit, and the like. That is, the receiving circuit 43 is configured to perform signal processing such as amplification and analog / digital conversion on the element output signal output by the transducer 41 to generate a receiving signal including information on the amplitude and frequency of the received wave. The element output signal is an AC voltage signal generated by an electromechanical energy conversion element provided in the transducer 41 upon receiving the ultrasonic wave.

[0022] The transmission signal generating unit 5 is provided to generate a transmission signal and output it to the transmission circuit 42. The transmission signal is a signal for driving the transducer 41 to cause the transducer 41 to emit a search wave.

[0023] The amplitude signal generating unit 6 processes the received signal output by the receiving circuit 43 to generate an amplitude signal used for setting a judgment threshold value in the threshold setting unit 7, which will be described later, and also generates an amplitude signal used for detecting object B in the object judgment unit 8.

[0024] For example, the amplitude signal generating unit 6 generates an amplitude signal with the intensity of the received signal as the amplitude. Alternatively, the amplitude signal generating unit 6 performs quadrature detection on the received signal, and generates an amplitude signal with the amplitude of the complex signal generated by this as the amplitude of the received signal. Alternatively, the amplitude signal generating unit 6 generates an amplitude signal by calculating the correlation between the received signal and a reference signal set based on the transmitted signal. When the amplitude signal is generated by such a correlation calculation, the signal width of the amplitude signal is reduced due to the effect of pulse compression, the SN ratio is improved, and the detection accuracy of the reflected signal is improved. The amplitude signal generating unit 6 generates an amplitude signal indicating the transmission time, which is the time elapsed since the transducer 41 transmitted the search wave from the received signal, and the change in amplitude corresponding to the intensity of the received signal, and outputs the signal to the threshold setting unit 7 and the object determination unit 8.

[0025] The threshold setting unit 7 sets a judgment threshold for the object determination unit 8 to determine the presence or absence of the object B based on the amplitude signal. The threshold setting unit 7 has a memory 71 that stores threshold parameters (to be described later) for setting the judgment threshold, and sets the judgment threshold based on the threshold parameters stored in the memory 71.

[0026] The object determination unit 8 determines the presence or absence of an object B to be detected, based on the amplitude signal output from the amplitude signal generation unit 6 and the determination threshold set by the threshold setting unit 7. The object determination unit 8 detects an amplitude peak from the amplitude signal generated based on the reflected signal of the wave reflected by the object B, and determines that the object B is present when this peak exceeds the determination threshold set by the threshold setting unit 7.

[0027] Incidentally, ultrasonic waves transmitted from an ultrasonic sonar such as the ultrasonic sensor 2 have directivity as shown by hatching in Fig. 2. When ultrasonic waves are transmitted horizontally toward the front of the vehicle, the directivity of the ultrasonic waves is strongest toward the front of the vehicle, which is the transmission direction, and has a component that spreads in a diagonal direction toward the front of the vehicle with respect to the vertical direction of the vehicle, so as to diffuse from the transmission direction.

[0028] 2, even if the ultrasonic sensor 2 transmits ultrasonic waves ahead of the vehicle, a part of the transmitted ultrasonic waves is reflected by the road surface R of the road. Therefore, the reflected waves received by the ultrasonic sensor 2 include waves reflected by the road surface R. Note that the directivity of ultrasonic waves changes depending on the height at which the ultrasonic sensor 2 is mounted on the vehicle, the mounting orientation, the sensor characteristics of the ultrasonic sensor 2, and the like, and the directivity shown in FIG. 2 is an example of the directivity of ultrasonic waves.

[0029] Then, when the ultrasonic sensor 2 does not receive a reflected wave from the object B and the amplitude signal generating unit 6 generates an amplitude signal, the amplitude signal is generated based on the reflected wave from the road surface R. The amplitude of such an amplitude signal generated based on the reflected wave from the road surface R becomes an unnecessary amplitude, i.e., noise, when determining the presence or absence of the object B based on the amplitude signal.

[0030] For this reason, when determining the presence of object B based on the determination threshold set by the threshold setting unit 7, it is desirable to set the determination threshold larger than the amplitude of the amplitude signal generated based on the wave reflected from the road surface R, so as not to erroneously detect the wave reflected from the road surface R as the wave reflected from object B. However, if the determination threshold is set significantly larger than the amplitude of the amplitude signal generated based on the wave reflected from the road surface R, there is a risk that the presence of object B will not be detected when the amplitude of the amplitude signal generated based on the wave reflected from object B is relatively small. For this reason, it is necessary to appropriately set the determination threshold set for determining the presence or absence of object B based on the amplitude of the amplitude signal generated based on the wave reflected from the road surface R.

[0031] As described above, the ultrasonic waves transmitted from the ultrasonic sensor 2 have directionality. For this reason, for example, when the ultrasonic sensor 2 transmits ultrasonic waves in the horizontal direction ahead of the vehicle, the ultrasonic waves are reflected relatively strongly in a range from a position slightly away from the installation position of the ultrasonic sensor 2 on the road surface R to a position a predetermined distance ahead of the vehicle, as shown in Fig. 3. The ultrasonic waves are not easily reflected by the road surface R that is farther away from the ultrasonic sensor 2 than the portion where the ultrasonic waves are reflected relatively strongly.

[0032] 3, the amplitude of the amplitude signal based on the reflected wave from the road surface R increases or decreases depending on the distance from the ultrasonic sensor 2 in the transmission direction in which the ultrasonic sensor 2 transmits ultrasonic waves. According to the inventors' careful consideration, the range of increase or decrease in amplitude, i.e., the amount of fluctuation, differs depending on the distance from the ultrasonic sensor 2. Hereinafter, the distance from the ultrasonic sensor 2 in the direction in which the ultrasonic sensor 2 transmits ultrasonic waves will be simply referred to as the distance from the ultrasonic sensor 2.

[0033] Specifically, the amplitude signal based on the reflected wave from the road surface R tends to have a large amplitude increase / decrease range for the portion based on the reflected wave reflected at a portion on the road surface R that is relatively close to the ultrasonic sensor 2. In contrast, the amplitude signal based on the reflected wave from the road surface R tends to have a small amplitude increase / decrease range for the portion based on the reflected wave reflected at a portion on the road surface R that is relatively far from the ultrasonic sensor 2. In other words, the amplitude signal based on the reflected wave from the road surface R tends to have a large amplitude fluctuation range for the reflected signal reflected at a position relatively close to the ultrasonic sensor 2 and a small amplitude fluctuation range for the reflected signal reflected at a position relatively far from the ultrasonic sensor 2.

[0034] In this way, the amplitude signal based on the reflected wave from a portion of the road surface R where the ultrasonic wave is relatively strongly reflected tends to have a large range of increase or decrease in amplitude. On the other hand, the amplitude signal based on the reflected wave from a portion of the road surface R that is farther away from the ultrasonic sensor 2 than the portion of the road surface R where the ultrasonic wave is relatively strongly reflected tends to have a small range of increase or decrease in amplitude.

[0035] This is because the ultrasonic waves transmitted from the ultrasonic sensor 2 are hardly reflected at all at locations on the road surface R that are farther away from the ultrasonic sensor 2 than locations on the road surface R where the ultrasonic waves are relatively strongly reflected. However, the amplitude signal contains dark noise that is generated when the receiving circuit 43 outputs a received signal, for example. For this reason, the amplitude of the amplitude signal based on the reflected waves from locations on the road surface R that are farther away from the ultrasonic sensor 2 than locations on the road surface R where the ultrasonic waves are relatively strongly reflected is almost entirely due to the dark noise. The amplitude due to the dark noise is much smaller than the amplitude of the amplitude signal based on the reflected waves from locations on the road surface R where the ultrasonic waves are relatively strongly reflected.

[0036] The dark noise is also included in the amplitude signal based on the reflected wave from a portion of the road surface R where the ultrasonic wave is reflected relatively strongly. The amplitude signal generated by the amplitude signal generating unit 6 indicates the transmission time that has elapsed since the exploration wave was transmitted and the amplitude of the received signal, and the time from the transmission of the exploration wave to the reception of the reflected wave can be calculated by the TOF method. Therefore, the transmission time in the amplitude signal can be regarded as the distance from the ultrasonic sensor 2 that transmits the exploration wave to the road surface R or the object B. Note that TOF is an abbreviation for Time of Flight.

[0037] 3, of the transmission time regions of the amplitude signal generated by the amplitude signal generating unit 6, a region based on reflected waves from a portion on the road surface R where ultrasonic waves are relatively strongly reflected is referred to as a road surface reflection region R1. Also, of the amplitude signal generated by the amplitude signal generating unit 6, a region based on reflected waves from a portion on the road surface R that is farther away from the ultrasonic sensor 2 than the portion on the road surface R where ultrasonic waves are relatively strongly reflected is referred to as outside the road surface reflection region R2. Also, the amplitude signal based on reflected waves from the road surface R may be referred to as road surface noise.

[0038] The road surface reflection region R1 is an area that contains more road surface noise than the outside road surface reflection region R2. The road surface reflection region R1 is an area that contains more road surface noise than background noise. The outside road surface reflection region R2 is an area that contains almost no road surface noise and is mostly occupied by background noise.

[0039] According to the inventors' intensive study, the road surface noise and the dark noise have the characteristics and tendencies shown in Fig. 4. Specifically, the road surface noise occupies a higher proportion than the dark noise in a road surface reflection region R1 close to the ultrasonic sensor 2. In contrast, the dark noise occupies a higher proportion than the road surface noise in an area outside the road surface reflection region R2 far from the ultrasonic sensor 2. That is, of the entire area of ​​the amplitude signal, the area where the road surface noise is dominant is the road surface reflection region R1. Also, of the entire area of ​​the amplitude signal, the area where the dark noise is dominant is the area outside the road surface reflection region R2.

[0040] Furthermore, the road noise has a larger amplitude fluctuation amount, which indicates the difference between the maximum and minimum values ​​of the amplitude, compared to the dark noise. The road noise has a larger trend, which indicates the amount of change in the maximum point and the amount of change in the minimum point with respect to the amount of change in the distance from the ultrasonic sensor 2, compared to the dark noise. That is, the road noise has a larger change in the average amplitude value per unit change in the distance from the ultrasonic sensor 2 compared to the dark noise. The road reflection area R1 corresponds to a first area, which is the side of the amplitude signal where the amount of amplitude fluctuation is large and is the side where the distance from the ultrasonic sensor 2 to the road surface R is short. The outside road reflection area R2 corresponds to a second area, which is the side of the amplitude signal where the amount of amplitude fluctuation is small and is the side where the distance from the ultrasonic sensor 2 to the road surface R is long.

[0041] The threshold setting unit 7 sets the judgment thresholds using different calculation methods for the road surface reflection area R1 and the outside road surface reflection area R2 based on the amplitude signal including the road surface noise and dark noise having such characteristics and tendencies. A specific method for setting the judgment thresholds will be described later.

[0042] The threshold setting unit 7 outputs threshold information, which is information about the set judgment threshold, to the object determination unit 8. The object determination unit 8 determines the presence or absence of the object B based on the amplitude signal output from the amplitude signal generation unit 6 and the threshold information output from the threshold setting unit 7.

[0043] Specifically, when the object determination unit 8 determines that the peak of the amplitude signal is equal to or greater than the determination threshold, it determines that object B is present within the transmission range of the ultrasonic waves. In contrast, when the object determination unit 8 does not determine that the peak of the amplitude signal is equal to or greater than the determination threshold, it determines that object B is not present within the transmission range of the ultrasonic waves. In other words, when the amplitude signal has a peak that exceeds the determination threshold, the object determination unit 8 determines that object B is present within the transmission range of the ultrasonic waves, and when the amplitude signal does not have a peak that exceeds the determination threshold, it determines that object B is not present within the transmission range of the ultrasonic waves.

[0044] The transmission signal generating unit 5, the amplitude signal generating unit 6, the threshold setting unit 7, and the object determining unit 8 are each composed of a DSP programmed with functions such as transmission signal generation, amplitude signal generation, threshold setting, object detection and determination, etc. DSP is an abbreviation for Digital Signal Processor.

[0045] The control unit 3 is connected to the ultrasonic sensor 2 via an in-vehicle communication line so as to be capable of communicating information with the ultrasonic sensor 2, and is configured to control the transmission and reception operation of the ultrasonic sensor 2. The control unit 3 is provided as a so-called sonar ECU, and includes an in-vehicle microcomputer having a CPU, ROM, RAM, non-volatile rewritable memory, etc. (not shown). ECU is an abbreviation for Electronic Control Unit. Examples of non-volatile rewritable memory include EEPROM and flash ROM. EEPROM is an abbreviation for Electronically Erasable and Programmable Read Only Memory.

[0046] As described above, the object detection judgment result is transmitted from the object determination unit 8 to the control unit 3. This judgment result is used for processing such as warning of an obstacle and automatic parking. For example, when the vehicle is moving due to automatic parking, if the object detection judgment result indicating the presence of object B is received from the object determination unit 8, the control unit 3 reduces the speed of the vehicle or stops the vehicle from traveling.

[0047] Next, the operation of the object detection device 1 will be described. The object detection device 1 repeatedly executes an object detection process including the process shown in Fig. 5. In the object detection process, a transmission instruction is issued from the control unit 3 to the transmission signal generation unit 5, and a search wave is transmitted from the transducer 41 based on the transmission signal generated by the transmission signal generation unit 5. Then, when reception of an ultrasonic signal by the transmission / reception unit 4 is detected, the object detection device 1 executes the process shown in Fig. 5.

[0048] First, in step S10, the received signal is processed in the amplitude signal generation unit 6. Specifically, the amplitude signal generation unit 6 generates an amplitude signal based on the received signal output from the transducer 41, and outputs the generated amplitude signal to the threshold setting unit 7 and the object determination unit 8. The amplitude signal generation unit 6 generates an amplitude signal every time the transmission / reception unit 4 receives a reflected wave, and outputs the amplitude signal to the threshold setting unit 7 and the object determination unit 8 every time an amplitude signal is generated. The threshold setting unit 7 sets a determination threshold every time an amplitude signal is received, and outputs information on the determination threshold to the object determination unit 8.

[0049] In addition, in step S10, when the amplitude signal generating unit 6 outputs the amplitude signal to the threshold setting unit 7 and the object determination unit 8, the amplitude signal generating unit 6 may perform an averaging process on the received signals repeatedly acquired from the receiving circuit 43 to perform a process of removing noise in advance before outputting the amplitude signal. In addition, if the object detection device 1 is configured to have an object detection unit other than the ultrasonic sensor 2, such as a camera, and the camera can detect that the reflected wave received by the transmitter / receiver 4 is a reflected wave from object B, the amplitude signal generating unit 6 may generate an amplitude signal and output the amplitude signal each time it acquires a received signal from the receiving circuit 43, without performing noise removal processing such as averaging processing.

[0050] In the next step S20, the threshold setting unit 7 sets a boundary BD shown in Fig. 7 for setting a judgment threshold for the transmission time region of the amplitude signal. Specifically, the threshold setting unit 7 executes the process shown in Fig. 6 to set a boundary BD for dividing the amplitude signal into a road surface reflection region R1 and a non-road surface reflection region R2.

[0051] First, in step S100, the threshold setting unit 7 performs a smoothing process on each amplitude signal repeatedly acquired from the amplitude signal generating unit 6, and makes a smooth signal waveform of the amplitude signal that varies according to the distance from the ultrasonic sensor 2. The threshold setting unit 7 smoothes the amplitude signal, for example, by performing a moving average process on the amplitude signal.

[0052] When performing moving average processing, as shown in Fig. 7, the threshold setting unit 7 calculates a moving average value Avm, which is the average value for each moving window Wm, while shifting the moving window Wm having a preset time width, and determines the tendency of the amplitude to change according to the distance from the ultrasonic sensor 2. Specifically, the threshold setting unit 7 calculates the average value of the magnitude of each amplitude included in the moving window Wm, and sets the calculated average value as the average value of the distance from the ultrasonic sensor 2 at the intermediate position of the moving window Wm. Note that in Fig. 7, the average value of the moving window Wm is indicated by a black circle.

[0053] The threshold setting unit 7 calculates the average value for each moving window Wm by moving the moving window Wm from a position where the distance from the ultrasonic sensor 2 is 0 to a position where the distance from the ultrasonic sensor 2 is maximum so that the average value of the magnitude of each amplitude can be calculated in the entire region of the amplitude signal. In this way, the threshold setting unit 7 calculates the smoothed signal by performing a smoothing process on the amplitude signal.

[0054] The smoothing process may be performed by a method other than the moving average process.

[0055] In the following steps S110 and S120, the threshold setting unit 7 sets a boundary BD based on the amount of fluctuation in the smoothed signal. Specifically, the threshold setting unit 7 obtains a maximum value and a minimum value from the average value for each calculated moving window Wm. Then, the threshold setting unit 7 sets a boundary BD for dividing the amplitude signal into a road surface reflection region R1 and an area outside the road surface reflection region R2 based on the difference between the obtained maximum and minimum values. As a result, the area of ​​the amplitude signal is divided into a road surface reflection region R1 and an area outside the road surface reflection region R2, as shown in FIG. 7.

[0056] Here, the maximum value of the average values ​​calculated by the threshold setting unit 7 is maximum value A1, the distance from the ultrasonic sensor 2 at which maximum value A1 occurs is maximum value distance L1, the minimum value of the average values ​​is minimum value A2, and the distance from the ultrasonic sensor 2 at which minimum value A2 occurs is minimum value distance L2. In addition, the magnitude of the amplitude at the boundary BD between the road surface reflection region R1 and the outside road surface reflection region R2 is boundary value A3, and the distance from the ultrasonic sensor 2 at which boundary value A3 occurs is boundary distance L3.

[0057] The threshold setting unit 7 calculates the boundary value A3 by using the maximum value A1 and the minimum value A2 as the boundary value A3=minimum value A2+(maximum value A1-minimum value A2)×coefficient k, and obtains the distance from the ultrasonic sensor 2 at which the average value becomes the boundary value A3 as the boundary distance L3. The coefficient k is set to a value smaller than 1 so that the change in the average value of the amplitude per unit change in the distance from the ultrasonic sensor 2 in the road surface reflection region R1 is larger than the change in the average value of the amplitude per unit change in the distance from the ultrasonic sensor 2 outside the road surface reflection region R2. The boundary distance L3 is set to a value larger than the maximum value distance L1 and smaller than the minimum value distance L2 so as to be the distance between the maximum value distance L1 and the minimum value distance L2. The threshold setting unit 7 uses the boundary BD set in this way to divide the region of the transmission signal in the amplitude signal into the road surface reflection region R1 and the outside road surface reflection region R2.

[0058] In addition, the boundary BD may be set based on the difference between the amplitude at the position in the amplitude signal that is closest to the ultrasonic sensor 2 and the amplitude at the position that is farthest from the ultrasonic sensor 2, rather than the difference between the maximum and minimum values.

[0059] Returning to FIG. 5, in step S30, the threshold setting unit 7 acquires from the memory 71 threshold parameters used to set a judgment threshold in step S40 described later. The details of the threshold parameters will be described later. Then, in step S40, the threshold setting unit 7 sets a judgment threshold. Specifically, the threshold setting unit 7 executes the process shown in FIG. 8 to set a judgment threshold for the road surface reflection region R1 and a judgment threshold for the outside road surface reflection region R2 used by the object determination unit 8 to determine the presence or absence of an object B. Hereinafter, the judgment threshold for the road surface reflection region R1 is also referred to as a reflection region threshold Th1, and the judgment threshold for the outside road surface reflection region R2 is also referred to as an outside reflection region threshold Th2. In this embodiment, the road surface reflection region R1 corresponds to the first threshold, and the outside reflection region threshold Th2 corresponds to the second threshold.

[0060] First, in step S200, the threshold setting unit 7 acquires information on the boundary BD set in step S20. Then, in step S210, the threshold setting unit 7 starts setting the reflection region threshold Th1. Specifically, in step S220, the threshold setting unit 7 performs a smoothing process on the amplitude signal of the road surface reflection region R1 for each amplitude signal repeatedly acquired from the amplitude signal generating unit 6, and makes the amplitude signal of the road surface reflection region R1, which varies depending on the distance from the ultrasonic sensor 2, into a blunt signal waveform. For example, the threshold setting unit 7 smoothes the amplitude signal by performing a moving average process on the amplitude signal of the road surface reflection region R1.

[0061] 9, when performing the moving average process, the threshold setting unit 7 calculates the reflection area average value Av1 for each reflection area window W1 while shifting the reflection area window W1 having a preset predetermined time width, and finds the tendency of the amplitude to change according to the distance from the ultrasonic sensor 2. Specifically, the threshold setting unit 7 calculates the reflection area average value Av1 of the magnitude of each amplitude included in the reflection area window W1, and sets the calculated reflection area average value Av1 as the reflection area average value Av1 of the distance from the ultrasonic sensor 2 at the intermediate position of the reflection area window W1. Information on the preset time width of the reflection area window W1 is stored in advance in the memory 71 as a threshold parameter.

[0062] The threshold setting unit 7 calculates the average value for each amplitude in the entire region of the amplitude signal of the road surface reflection region R1 by moving the reflection region window W1 from a position where the distance from the ultrasonic sensor 2 is 0 to a position where the distance from the ultrasonic sensor 2 is the boundary BD, and obtains the average value for each reflection region window W1. In this way, the threshold setting unit 7 obtains the smoothed signal by performing a smoothing process on the amplitude signal of the road surface reflection region R1.

[0063] In the next step S230, the threshold setting unit 7 calculates the reflection area threshold Th1 by using the threshold parameter. Specifically, the threshold setting unit 7 calculates the reflection area threshold Th1 for each distance from each ultrasonic sensor 2 by using the reflection area coefficient for the smoothed signal corresponding to the reflection area average value Av1 for each reflection area window W1 calculated in step S220.

[0064] The reflection area coefficient is a value set so that the reflection area threshold Th1 is greater than the reflection area average value Av1 calculated by the threshold setting unit 7, and is set to a value that can ensure a sufficient difference between the reflection area threshold Th1 and the amplitude signal. For example, when the reflection area threshold Th1 is calculated by multiplying the reflection area average value Av1 by the reflection area coefficient, the reflection area coefficient is set to a value greater than 1. The reflection area coefficient may be set by adding the reflection area coefficient to the reflection area average value Av1. Information on the reflection area coefficient is stored in advance in the memory 71 as a threshold parameter. The reflection area coefficient corresponds to a first coefficient for calculating the reflection area threshold Th1 of the road surface reflection area R1.

[0065] When the threshold setting unit 7 has calculated the reflection area threshold value Th1 for each distance from each ultrasonic sensor 2 in the entire road surface reflection area R1, the process proceeds to step S240.

[0066] In step S240, the threshold setting unit 7 starts setting the outside reflection area threshold Th2. Specifically, in step S250, the threshold setting unit 7 performs a smoothing process on the amplitude signal outside the road surface reflection area R2 for each amplitude signal repeatedly acquired from the amplitude signal generating unit 6, and makes the amplitude signal outside the road surface reflection area R2, which varies depending on the distance from the ultrasonic sensor 2, into a blunt signal waveform. The threshold setting unit 7 smoothes the amplitude signal by, for example, performing a moving average process on the amplitude signal outside the road surface reflection area R2.

[0067] 9, when performing the moving average process, the threshold setting unit 7 calculates the outside reflection area average value Av2 for each outside reflection area window W2 while shifting the outside reflection area window W2 having a preset predetermined time width, and determines the tendency of the amplitude to change according to the distance from the ultrasonic sensor 2. Specifically, the threshold setting unit 7 calculates the outside reflection area average value Av2 of the magnitude of each amplitude included in the outside reflection area window W2, and sets the calculated outside reflection area average value Av2 as the outside reflection area average value Av2 of the distance from the ultrasonic sensor 2 at the intermediate position of the outside reflection area window W2. Information on the predetermined time width of the outside reflection area window W2 is stored in advance in the memory 71 as a threshold parameter.

[0068] The threshold setting unit 7 calculates the average value for each window W2 outside the reflection area by moving the window W2 outside the reflection area from a position where the distance from the ultrasonic sensor 2 is the boundary BD to a position where the distance from the ultrasonic sensor 2 is maximum so that the average value of the magnitude of each amplitude can be calculated in the entire region of the amplitude signal outside the road surface reflection area R2. In this way, the threshold setting unit 7 calculates the smoothed signal by performing a smoothing process on the amplitude signal outside the road surface reflection area R2.

[0069] As described above, the road surface reflection region R1, where road surface noise is dominant, has a larger amplitude fluctuation amount than the outside road surface reflection region R2, where dark noise is dominant. The road surface noise in the road surface reflection region R1 has a larger trend showing the amount of change in the maximum point and the amount of change in the minimum point with respect to the amount of change in the distance from the ultrasonic sensor 2 than the dark noise in the outside road surface reflection region R2. That is, the amount of change in the amplitude of the amplitude signal that changes according to the distance from the ultrasonic sensor 2 in the outside road surface reflection region R2 tends to be smaller than the amount of change in the amplitude of the amplitude signal that changes according to the distance from the ultrasonic sensor 2 in the road surface reflection region R1.

[0070] For this reason, when moving average processing is performed on the amplitude signal with the width of the reflection area window W1 and the width of the outside reflection area window W2 set to the same size, the amount of change in the average value for each outside reflection area window W2 is smaller than the amount of change in the average value for each reflection area window W1. Therefore, even if the width of the outside reflection area window W2 is made larger than the width of the reflection area window W1 when performing moving average processing on the amplitude signal, it is possible to adequately obtain the tendency of change in the amplitude of the amplitude signal outside the road surface reflection area R2.

[0071] For this reason, in this embodiment, the width of the outside reflection area window W2 is set larger than the width of the reflection area window W1, which reduces the processing load when the threshold setting unit 7 executes the smoothing process on the outside road surface reflection area R2 and can speed up the process.

[0072] The smoothing process performed in steps S220 and S250 may be performed by a method other than the moving average process. For example, the smoothing process may be performed by CFAR (Constant False Alarm Rate), that is, a constant false alarm rate.

[0073] In the next step S260, the threshold setting unit 7 calculates the outside-reflection-area threshold Th2 by using the threshold parameter. Specifically, the threshold setting unit 7 calculates the outside-reflection-area threshold Th2 for each distance from each ultrasonic sensor 2 by using the outside-reflection-area coefficient for the smoothed signal corresponding to the outside-reflection-area average value Av2 for each outside-reflection-area window W2 calculated in step S250.

[0074] The outside reflection area coefficient is a value set so that the outside reflection area threshold Th2 is greater than the outside reflection area average value Av2 calculated by the threshold setting unit 7, and is set to a value that can ensure a sufficient difference between the outside reflection area threshold Th2 and the amplitude signal. For example, when the outside reflection area threshold Th2 is calculated by multiplying the outside reflection area average value Av2 by the outside reflection area coefficient, the outside reflection area threshold Th2 is set to a value greater than 1. The outside reflection area threshold Th2 may be set by adding the outside reflection area coefficient to the outside reflection area average value Av2 calculated by the threshold setting unit 7. Information on the outside reflection area coefficient is stored in advance in the memory 71 as a threshold parameter. The outside reflection area coefficient corresponds to a second coefficient for calculating the outside reflection area threshold Th2 for the road surface reflection area R2.

[0075] As described above, the road surface reflection region R1 is a region of amplitude signals based on reflected signals including waves reflected at a portion of the road surface R that is relatively close to the ultrasonic sensor 2, and is dominated by road surface noise. The amplitude of the road surface noise is larger than that of the background noise, and the amount of fluctuation is larger than that of the background noise.

[0076] For this reason, if the reflection area threshold Th1 is set to a value close to the amplitude of the road noise, when the peak of the road noise becomes larger than the reflection area threshold Th1 due to fluctuations in the road noise, there is a risk that the object detection device 1 will erroneously detect the reflected wave from the road surface R as the reflected wave from the object B. Therefore, it is necessary to set the reflection area threshold Th1 to be sufficiently large compared to the amplitude of the road noise. This makes it possible to suppress erroneous detection due to the reflected wave from the road surface R in the road reflection area R1.

[0077] Moreover, if an object B is present in the road surface reflection region R1, the ultrasonic sensor 2 receives a reflected wave from the object B that is present at a relatively short distance from the ultrasonic sensor 2. The signal of the reflected wave from a relatively short distance from the ultrasonic sensor 2 tends to be large. Therefore, the amplitude signal based on the reflected wave from the object B in the road surface reflection region R1 has a large amplitude.

[0078] In this case, the amplitude signal of the road surface reflection region R1 is an amplitude signal based on the reflected waves from the object B and the road surface R, and so the amplitude peak is likely to be large. Therefore, even if the reflection region threshold Th1 is set sufficiently large compared to the amplitude of the road surface noise, the object B in the road surface reflection region R1 can be detected without any problem based on the peak.

[0079] In contrast, the outside road surface reflection region R2 is a region of amplitude signals including waves reflected at a portion of the road surface R that is relatively far from the ultrasonic sensor 2, and is dominated by dark noise. The magnitude of the amplitude of the dark noise is smaller than the magnitude of the amplitude of the road surface noise, and the amount of fluctuation is smaller than the amount of fluctuation of the road surface noise.

[0080] For this reason, even if the outside reflection area threshold Th2 is set to a value close to the amplitude of the road surface noise, the peak of the dark noise is unlikely to exceed the outside reflection area threshold Th2 due to fluctuations in the dark noise. Therefore, there is a low possibility that the peak of the dark noise will exceed the outside reflection area threshold Th2, causing the object detection device 1 to erroneously detect a wave reflected from the road surface R as a wave reflected from the object B. Therefore, the outside reflection area threshold Th2 can be made closer to the amplitude of the amplitude signal than the reflection area threshold Th1.

[0081] Furthermore, if an object B exists outside the road surface reflection area R2, the ultrasonic sensor 2 receives a reflected wave from the object B that exists at a relatively long distance from the ultrasonic sensor 2. The signal of the reflected wave from a relatively long distance from the ultrasonic sensor 2 tends to be small. Therefore, the amplitude signal based on the reflected wave from the object B outside the road surface reflection area R2 has a small amplitude.

[0082] In this case, the amplitude signal based on the reflected wave from object B has a smaller amplitude outside the road surface reflection area R2 compared to when object B is present in the road surface reflection area R1. Therefore, the amplitude signal has the amplitude based on the reflected wave from object B superimposed on the dark noise, but the amplitude peak is unlikely to become large. In other words, there is little difference in the magnitude of the peak of the amplitude signal between when object B is present outside the road surface reflection area R2 and when object B is not present. In particular, when object B is a low-profile object with a relatively small height, the amplitude of the reflected wave from the low-profile object is small, so that it is difficult to detect the peak of the amplitude signal even if a low-profile object is present outside the road surface reflection area R2.

[0083] However, by bringing the outside reflection area threshold Th2 closer to the amplitude of the dark noise, even if the peak of the amplitude signal based on the reflected wave from object B outside the road surface reflection area R2 is relatively small, object B outside the road surface reflection area R2 can be detected without any problems based on the peak.

[0084] For this reason, in this embodiment, in which the reflection area threshold Th1 is calculated by multiplying the reflection area average value Av1 by the reflection area coefficient, and the reflection area threshold Th2 is calculated by multiplying the reflection area average value Av2 by the reflection area coefficient, the reflection area coefficient is set to be smaller than the reflection area coefficient. That is, in this embodiment, the reflection area coefficient and the reflection area coefficient are set so that the difference between the reflection area threshold Th1 in the road surface reflection area R1 and the road surface noise is larger than the difference between the reflection area threshold Th2 in the road surface reflection area R2 and the dark noise. This makes it possible to suppress erroneous detection of the object B in the road surface reflection area R1, and to suppress non-detection of the object B in the road surface reflection area R2.

[0085] The threshold setting unit 7 outputs to the object determination unit 8 information on the reflection area threshold Th1 calculated in step S230 and information on the outside reflection area threshold Th2 calculated in step S260.

[0086] Returning to FIG. 5, in step S50, the object determination unit 8 determines whether the peak of the amplitude signal is equal to or greater than the determination threshold. Specifically, the object determination unit 8 determines whether the peak of the amplitude signal in the road surface reflection region R1 is equal to or greater than the reflection region threshold Th1, and determines whether the peak of the amplitude signal in the outside road surface reflection region R2 is equal to or greater than the outside reflection region threshold Th2. If it is determined that either the peak of the amplitude signal in the road surface reflection region R1 is equal to or greater than the reflection region threshold Th1 or the peak of the amplitude signal in the outside road surface reflection region R2 is equal to or greater than the outside reflection region threshold Th2, the process proceeds to step S60. On the other hand, if neither the peak of the amplitude signal in the road surface reflection region R1 is equal to or greater than the reflection region threshold Th1 nor the peak of the amplitude signal in the outside road surface reflection region R2 is equal to or greater than the outside reflection region threshold Th2, the process proceeds to step S70.

[0087] In step S60, the object determination unit 8 determines that the object B is present within the transmission range of the ultrasonic waves, and ends the process. In contrast, in step S70, the object determination unit 8 determines that the object B is not present within the transmission range of the ultrasonic waves, and ends the process. When the process shown in FIG. 5 ends, the object determination unit 8 transmits the object determination detection result to the control unit 3.

[0088] The effects of this embodiment will be described. As a method for detecting object B within the transmission range of ultrasonic waves, a method of determining whether or not the peak value of the amplitude signal is equal to or greater than a predetermined threshold value is considered. For example, if the peak value of the amplitude signal is smaller than the threshold value, it is determined that object B is not within the transmission range of ultrasonic waves, and if the peak value of the amplitude signal is equal to or greater than the threshold value, it is determined that object B is within the transmission range of ultrasonic waves. However, if the signal received by the transducer 41 contains road surface noise and background noise, it is necessary to set the threshold value taking these noises into consideration.

[0089] However, the magnitude of the road surface noise changes depending on the distance from the ultrasonic sensor 2 to the road surface R. Moreover, the background noise is approximately constant regardless of the distance from the ultrasonic sensor 2. Therefore, the amount of fluctuation in the amplitude signal caused by noise differs depending on the distance from the ultrasonic sensor 2. Therefore, if a threshold is set without taking into consideration the difference between road surface noise and background noise, there is a risk that the object B will be erroneously detected or not detected.

[0090] However, as described above, in this embodiment, the reflection area threshold Th1 is set based on the magnitude of the amplitude signal in the road surface reflection area R1, and the outside reflection area threshold Th2 is set based on the magnitude of the amplitude signal in the outside road surface reflection area R2. Therefore, the reflection area threshold Th1 can be made to correspond to the road noise in the road surface reflection area R1 close to the ultrasonic sensor 2, and the outside road surface reflection area R2 can be made to correspond to the dark noise in the outside road surface reflection area R2 far from the ultrasonic sensor 2. Therefore, it is possible to suppress erroneous detection of the object B or non-detection of the object B, and to improve the detection accuracy of the object B in the object detection device 1.

[0091] As described above, in the object detection device 1 of this embodiment, the threshold setting unit 7 sets a boundary BD that divides the transmission time region of the amplitude signal into a road surface reflection region R1 on the side where the amount of amplitude fluctuation in the amplitude signal is large and an outside road surface reflection region R2 on the side where the amount of amplitude fluctuation is small. Furthermore, the threshold setting unit 7 sets a reflection region threshold Th1 for the road surface reflection region R1 based on the magnitude of the amplitude signal for the road surface reflection region R1, and sets an outside reflection region threshold Th2 for the outside road surface reflection region R2 based on the magnitude of the amplitude signal for the outside road surface reflection region R2.

[0092] This makes it possible to suppress erroneous detection of object B or non-detection of object B, thereby improving the detection accuracy of object B by the object detection device 1.

[0093] Furthermore, according to the above embodiment, the following effects can be obtained.

[0094] (1) In the above embodiment, the threshold setting unit 7 sets the reflection area threshold Th1 and the outside-reflection area threshold Th2 every time the transceiver unit 4 receives a reflected wave.

[0095] According to this, since the reflection area threshold Th1 and the outside reflection area threshold Th2 can be set for each amplitude signal, the detection accuracy of the object B of the object detection device 1 can be further improved.

[0096] (2) In the above embodiment, the threshold setting unit 7 obtains a smoothed signal by smoothing processing that obtains an average value for each moving window Wm for the amplitude signal, and sets the boundary BD based on the amount of fluctuation in the obtained smoothed signal.

[0097] According to this, even if the amount of fluctuation in the amplitude of the amplitude signal is relatively large, the boundary BD can be easily found.

[0098] (3) In the above embodiment, the threshold setting unit 7 determines the reflection area threshold Th1 using the magnitude of the amplitude signal of the road surface reflection area R1 and the reflection area coefficient. The threshold setting unit 7 also determines the outside reflection area threshold Th2 using the magnitude of the amplitude signal of the road surface reflection area R2 and the outside reflection area coefficient. The outside reflection area coefficient is set so that the outside reflection area threshold Th2 is greater than the outside reflection area average value Av2. The reflection area coefficient is set so that the reflection area threshold Th1 is greater than the reflection area average value Av1. The reflection area coefficient is also set so that the difference between the reflection area threshold Th1 in the road surface reflection area R1 and the road surface noise is greater than the difference between the outside reflection area threshold Th2 in the road surface reflection area R2 and the dark noise.

[0099] As described above, in the road surface reflection region R1, the amplitude of the road surface noise is larger than that of the background noise, and the fluctuation of the road surface noise is larger than that of the background noise. In addition, in the road surface reflection region R1, the amplitude signal based on the reflected wave from the object B tends to have a large amplitude.

[0100] In contrast, the outside road surface reflection area R2 is an area that does not include road surface noise and is occupied by dark noise. Also, the amount of variation in dark noise in the outside road surface reflection area R2 is smaller than the amount of variation in road surface noise in the road surface reflection area R1. Also, in the outside road surface reflection area R2, the amplitude signal based on the reflected wave from the object B tends to have a small amplitude.

[0101] Therefore, by setting the reflection area coefficient so that the difference between the reflection area threshold Th1 and road surface noise in the road surface reflection area R1 is larger than the difference between the outside reflection area threshold Th2 and dark noise outside the road surface reflection area R2, it is possible to suppress erroneous detection due to waves reflected from the road surface R in the road surface reflection area R1, and to improve the detection accuracy of object B even if the peak of the amplitude signal based on the waves reflected from object B outside the road surface reflection area R2 is relatively small.

[0102] (4) In the above embodiment, the threshold setting unit 7 obtains smoothed signals for the road surface reflection region R1 and the outside road surface reflection region R2 by smoothing processing that obtains an average value for each of the reflection region window W1 and the outside reflection region window W2 for the amplitude signal. The threshold setting unit 7 also sets the reflection region threshold Th1 based on the amount of fluctuation in the smoothed signal for the road surface reflection region R1, and sets the outside reflection region threshold Th2 based on the amount of fluctuation in the smoothed signal for the outside road surface reflection region R2.

[0103] According to this, even if the amount of fluctuation in the amplitude of the amplitude signal in the road surface reflection region R1 and the amount of fluctuation in the amplitude of the amplitude signal outside the road surface reflection region R2 are relatively large, the reflection region threshold Th1 and the outside reflection region threshold Th2 can be easily determined.

[0104] (5) In the above embodiment, the outside reflection area window W2 for obtaining the smoothed signal outside the road surface reflection area R2 is set larger than the reflection area window W1 for obtaining the smoothed signal in the road surface reflection area R1.

[0105] As described above, the amount of change in the amplitude of the amplitude signal that changes depending on the distance from the ultrasonic sensor 2 outside the road surface reflection area R2 tends to be smaller than the amount of change in the amplitude of the amplitude signal that changes depending on the distance from the ultrasonic sensor 2 in the road surface reflection area R1. Therefore, when performing moving average processing on the amplitude signal, even if the width of the outside reflection area window W2 is made larger than the width of the reflection area window W1, it is possible to adequately obtain the tendency of change in the amplitude of the amplitude signal outside the road surface reflection area R2. This reduces the processing load when the threshold setting unit 7 performs smoothing processing on the outside road surface reflection area R2, and enables the processing to be speeded up.

[0106] (First modified example of the first embodiment) In the above-described first embodiment, an example has been described in which the threshold setting unit 7 executes the process of step S20 to set the boundary every time the transmitting / receiving unit 4 receives an ultrasonic signal, but the present invention is not limited to this.

[0107] For example, the threshold setting unit 7 may execute the process of step S20 as appropriate, rather than executing the process of step S20 every time the transceiver unit 4 receives an ultrasonic signal. For example, the threshold setting unit 7 may execute the process of step S20 every time a predetermined time elapses.

[0108] Furthermore, the threshold setting unit 7 may be configured not to execute the processes of steps S100 and S110 in step S20. In this case, the threshold setting unit 7 may store in advance in the memory 71 position information from the ultrasonic sensor 2 that is the position of the boundary BD, and may perform boundary setting in step S120 based on the position information of the boundary BD stored in the memory 71.

[0109] (Second modified example of the first embodiment) In the above-described first embodiment, an example has been described in which the threshold setting unit 7 sets the reflection area threshold Th1 for the road surface reflection area R1 based on the magnitude of the amplitude signal for the road surface reflection area R1, and sets the outside reflection area threshold Th2 for the outside road surface reflection area R2 based on the magnitude of the amplitude signal for the outside road surface reflection area R2, but this is not limited to this.

[0110] For example, as shown in Fig. 11, when the change amount of the reflection area threshold Th1 around the boundary BD in the road surface reflection area R1 is larger than that of other parts, the reflection area threshold Th1 around the boundary BD may be corrected to approach the outside reflection area threshold Th2. The reflection area threshold Th1 around the boundary BD in the road surface reflection area R1 may be set based on the reflection area threshold Th1 around the boundary BD and the outside reflection area threshold Th2 around the boundary BD.

[0111] 11, for example, the reflection area threshold Th1 of the first periphery R3 may be set by adding a value obtained by multiplying the reflection area threshold Th1 of the first periphery R3 by a first correction coefficient smaller than 1 (e.g., 0.9) to a value obtained by multiplying the outside reflection area threshold Th2 of the second periphery R4 by a second correction coefficient smaller than the first correction coefficient (e.g., 0.1). In this case, the first correction coefficient and the second correction coefficient may be set so that the sum of the first correction coefficient and the second correction coefficient is 1.0.

[0112] In addition, when the change amount of the outside reflection area threshold Th2 around the boundary BD in the outside road surface reflection area R2 is larger than that of other parts, the outside reflection area threshold Th2 around the boundary BD may be corrected to approach the reflection area threshold Th1. The outside reflection area threshold Th2 around the boundary BD in the outside road surface reflection area R2 may be set based on the reflection area threshold Th1 around the boundary BD and the outside reflection area threshold Th2 around the boundary BD.

[0113] 11, for example, the reflection area outside threshold Th2 of the second periphery R4 may be set by adding a value obtained by multiplying the reflection area threshold Th1 of the first periphery R3 by a first correction coefficient smaller than 1 (e.g., 0.1) to a value obtained by multiplying the reflection area outside threshold Th2 of the second periphery R4 by a second correction coefficient larger than the first correction coefficient (e.g., 0.9). In this case, the first correction coefficient and the second correction coefficient may be set so that the sum of the first correction coefficient and the second correction coefficient is 1.0.

[0114] The reason for correcting the reflection area threshold Th1 around the boundary BD to approach the outside reflection area threshold Th2 and correcting the outside reflection area threshold Th2 around the boundary BD to approach the reflection area threshold Th1 in this manner will be described.

[0115] When the amount of change in the reflection area threshold Th1 around the boundary BD in the road surface reflection area R1 is larger than that in other areas, and the amount of change in the outside reflection area threshold Th2 around the boundary BD outside the road surface reflection area R2 is larger than that in other areas, the difference between the reflection area threshold Th1 around the boundary BD and the outside reflection area threshold Th2 becomes large, which may cause the object detection device 1 to erroneously detect or not detect the object B around the boundary BD.

[0116] In response to this, by correcting the reflective area threshold Th1 around the boundary BD to approach the outside reflective area threshold Th2, and correcting the outside reflective area threshold Th2 around the boundary BD to approach the reflective area threshold Th1, it is possible to suppress false detection of object B around the boundary BD or non-detection of object B.

[0117] Second embodiment Next, the second embodiment will be described with reference to Figs. 12 and 13. In this embodiment, a part of the object detection process is different from that in the first embodiment. The rest is the same as in the first embodiment. Therefore, in this embodiment, the parts different from the first embodiment will be mainly described, and the description of the parts similar to the first embodiment may be omitted.

[0118] The control process executed by the object detection device 1 of this embodiment will be described with reference to Fig. 12. The control process executed by the object detection device 1 of this embodiment is different from the control process executed by the object detection device 1 of the first embodiment in that steps S11, S12, and S13 are added. Note that the processes of steps S10, S20, S30, S40, S50, S60, and S70 shown in Fig. 12 are similar to the processes of the respective steps described with reference to Fig. 5 of the first embodiment, and therefore description thereof will be omitted.

[0119] After the amplitude signal generating unit 6 processes the received signal in step S10, the threshold setting unit 7 acquires air temperature information, which is information on the ambient temperature of the vehicle through which the ultrasonic sensor 2 propagates, in step S11. The threshold setting unit 7 acquires the air temperature information, for example, from an outside temperature sensor provided in the vehicle. In this embodiment, the threshold setting unit 7 corresponds to the temperature acquiring unit.

[0120] In the next step S12, the threshold setting unit 7 determines whether the outside temperature is equal to or higher than a preset judgment temperature based on the acquired temperature information. If it is determined that the outside temperature is equal to or higher than the judgment temperature, the process proceeds to step S20. On the other hand, if it is not determined that the outside temperature is equal to or higher than the judgment temperature, the process proceeds to step S12.

[0121] In the process of step S20, as described in the first embodiment, the threshold setting unit 7 sets a boundary BD for dividing the amplitude signal into a road surface reflection region R1 and an outside road surface reflection region R2. Then, by executing the processes of steps S30 and S40, the threshold setting unit 7 sets a reflection region threshold Th1 which is a determination threshold for the road surface reflection region R1, and sets an outside reflection region threshold Th2 which is a determination threshold for the outside road surface reflection region R2.

[0122] In contrast, in the process of step S12, the threshold setting unit 7 does not set a boundary BD for dividing the amplitude signal into a road surface reflection region R1 and an outside road surface reflection region R2.

[0123] In this case, the threshold setting unit 7 executes the processing of steps S30 and S40, so as to set no judgment threshold for each of the road surface reflection area R1 and the outside road surface reflection area R2, as shown in FIG. 13, and sets a low temperature judgment threshold Th3 for the entire area of ​​the amplitude signal.

[0124] In this case, the threshold setting unit 7 sets the low temperature judgment threshold Th3, which is the judgment threshold for outside the road surface reflection area R2, to a value larger than the outside reflection area threshold Th2 for outside the road surface reflection area R2 that is set when the external air temperature is equal to or higher than the judgment temperature. In other words, the threshold setting unit 7 sets the low temperature judgment threshold Th3, which is the judgment threshold for outside the road surface reflection area R2, so that the difference between the dark noise in outside the road surface reflection area R2 and the low temperature judgment threshold Th3 approaches the difference between the reflection area threshold Th1 in the road surface reflection area R1 and the road surface noise.

[0125] In this embodiment, the threshold setting unit 7 performs processing similar to that of steps S210 to S230, and performs a smoothing process on the entire range of the amplitude signal for each amplitude signal repeatedly acquired from the amplitude signal generating unit 6, and determines the tendency of the amplitude to change depending on the distance from the ultrasonic sensor 2.

[0126] The threshold setting unit 7 calculates the average value for each amplitude magnitude in the entire region of the amplitude signal by moving a window (not shown) from a position where the distance from the ultrasonic sensor 2 is 0 to a position where the distance from the ultrasonic sensor 2 is maximum. The width of the window when the threshold setting unit 7 performs the smoothing process when the outside air temperature is not determined to be equal to or higher than the determination temperature is set to the same size as the width of the reflection region window W1 when the threshold setting unit 7 performs the smoothing process when the outside air temperature is determined to be equal to or higher than the determination temperature.

[0127] Then, the threshold setting unit 7 calculates the low temperature judgment threshold Th3 for each distance from each ultrasonic sensor 2 by using a predetermined coefficient for the average value for each window. The magnitude of the predetermined coefficient is set to the same magnitude as the reflection area coefficient. In this way, the threshold parameter used to set the low temperature judgment threshold Th3 when the outside air temperature is not determined to be equal to or higher than the judgment temperature is set to the same parameter as the threshold parameter used to set the reflection area threshold Th1 when the outside air temperature is determined to be equal to or higher than the judgment temperature. Information on the window width and the predetermined coefficient are stored in advance in the memory 71 as threshold parameters.

[0128] When the low temperature determination threshold Th3 is set for the entire range of the amplitude signal by a predetermined coefficient, the difference between the low temperature determination threshold Th3 and the road surface noise is approximately the same as the difference between the low temperature determination threshold Th3 and the background noise.

[0129] The reason why the low temperature determination threshold value Th3 is set uniformly using a predetermined coefficient for the entire range of the amplitude signal when the outside air temperature is not determined to be equal to or higher than the determination temperature will be described below.

[0130] The search wave transmitted from the ultrasonic sensor 2 and the reflected wave from object B are attenuated as the propagation distance in the air increases. However, the amount of attenuation during propagation decreases as the air temperature decreases. In other words, the amplitude signal based on the search wave transmitted from the ultrasonic sensor 2 and the reflected wave from object B is less likely to become small as the outside air temperature decreases. For this reason, when the outside air temperature is relatively low, even if object B is located at a relatively long distance from the ultrasonic sensor 2, the peak of the amplitude signal based on the reflected wave from object B tends to be large, as shown in FIG. 13. However, the dark noise does not vary substantially with the outside air temperature.

[0131] Therefore, even if the low temperature judgment threshold Th3 is set to be higher than the outside reflection area threshold Th2 which is set when the outside air temperature is equal to or higher than the judgment temperature, and even if a judgment threshold is set for the amplitude signal outside the road surface reflection area R2 which is similar to the judgment threshold set for the amplitude signal in the road surface reflection area R1, object B located at a location relatively far from the ultrasonic sensor 2 can be detected without any problems.

[0132] Furthermore, by setting the magnitude of the predetermined coefficient to be the same as that of the reflection area coefficient, it is possible to prevent the reflected wave from the road surface R, which is relatively close to the ultrasonic sensor 2, from being mistakenly detected as the reflected wave from the object B.

[0133] (Modification of the second embodiment) In the above-described second embodiment, an example was described in which the low temperature judgment threshold Th3 is set so that the difference between the low temperature judgment threshold Th3 and road surface noise is approximately the same magnitude as the difference between the low temperature judgment threshold Th3 and background noise, but this is not limited to this.

[0134] For example, if the difference between the low temperature judgment threshold Th3 and background noise is set to approach the difference between the low temperature judgment threshold Th3 and road surface noise, the low temperature judgment threshold Th3 may be set so that the difference between the low temperature judgment threshold Th3 and road surface noise is a different magnitude than the difference between the low temperature judgment threshold Th3 and background noise.

[0135] Third embodiment Next, a third embodiment will be described with reference to Figs. 14 to 18. In this embodiment, a part of the object detection process is different from that in the first embodiment. The rest is the same as in the first embodiment. Therefore, in this embodiment, the parts different from the first embodiment will be mainly described, and the description of the parts similar to the first embodiment may be omitted.

[0136] The ultrasonic waves transmitted from the ultrasonic sensor 2 have directionality, and if the road surface R is inclined in the transmission direction of the exploration wave, the way in which the exploration wave hits the road surface R changes depending on the inclination. For example, let us assume that the road surface R is parallel to the horizontal direction as shown in FIG. 14. In contrast, as shown in FIG. 15, if the road surface R is inclined downward and the part beyond the inclined part is parallel to the horizontal direction, the exploration wave reaches a position on the road surface R farther away from the ultrasonic sensor 2 than when the road surface R is parallel to the horizontal direction. Therefore, compared to when the road surface R is parallel to the horizontal direction, the ultrasonic sensor 2 receives the reflected wave from a position on the road surface R farther away from the ultrasonic sensor 2.

[0137] 16, when the road surface R is inclined upward and the part beyond the inclined portion is parallel to the horizontal direction, it is more difficult for the exploration wave to hit the road surface R than when the road surface R is parallel to the horizontal direction. Therefore, it is more difficult for the ultrasonic sensor 2 to receive the reflected wave from the road surface R than when the road surface R is parallel to the horizontal direction. Note that in FIGS. 14 to 16, the directivity of the exploration wave transmitted from the ultrasonic sensor 2 is indicated by hatching.

[0138] Therefore, when the road surface R is inclined, the object detection device 1 of this embodiment changes the position of the boundary BD set by the threshold setting unit 7 in accordance with the inclination. The control process executed by the object detection device 1 of this embodiment will be described with reference to Fig. 17. Compared to the control process executed by the object detection device 1 of the first embodiment, the control process executed by the object detection device 1 of this embodiment includes the additional process of step S14. Note that the processes of steps S10, S20, S30, S40, S50, S60, and S70 shown in Fig. 17 are similar to the processes of the respective steps described with reference to Fig. 5 of the first embodiment, and therefore description thereof will be omitted.

[0139] After the amplitude signal generating unit 6 processes the received signal in step S10, the threshold setting unit 7 acquires inclination information, which is information on the inclination of the traveling direction of the vehicle, i.e., the transmission direction of the exploration wave, in step S14. The threshold setting unit 7 may acquire the inclination information, for example, from an imaging camera, Lidar, or gyro sensor provided on the vehicle, or from map information included in a navigation device. In this embodiment, the threshold setting unit 7 functions as an inclination information acquiring unit that acquires information on the inclination of the road surface R. Note that Lidar is an abbreviation for Laser Imaging Detection and Ranging.

[0140] In the following step S20, the threshold setting unit 7 sets a boundary BD for dividing the amplitude signal into a road surface reflection region R1 and a non-road surface reflection region R2, based on the acquired gradient information.

[0141] Specifically, in the processing of step S120 described in the first embodiment, the threshold setting unit 7 sets a boundary BD for dividing the amplitude signal into a road surface reflection region R1 and an outside road surface reflection region R2 based on the difference between the maximum and minimum values ​​obtained from the moving average value Avm for each moving window Wm.

[0142] Here, when the road surface R is inclined downward, the threshold setting unit 7 sets the boundary BD so that the road surface reflection area R1 is larger than the outside road surface reflection area R2 compared to when the road surface R is parallel to the horizontal direction and when it is inclined upward. For example, as shown in Fig. 18, the threshold setting unit 7 sets the boundary BD so that the road surface reflection area R1 is the entire area of ​​the amplitude signal. In other words, the threshold setting unit 7 sets the position where the distance from the ultrasonic sensor 2 is maximum as the boundary BD. As a result, the entire area of ​​the amplitude signal is set as the road surface reflection area R1.

[0143] In contrast, when the road surface R is inclined upward, the threshold setting unit 7 sets the boundary BD so that the outside road surface reflection area R2 is larger than the road surface reflection area R1 compared to when the road surface R is parallel to the horizontal direction and when it is inclined downward. For example, as shown in Fig. 18, the threshold setting unit 7 sets the boundary BD so that the outside road surface reflection area R2 is the entire area of ​​the amplitude signal. In other words, the threshold setting unit 7 sets the position where the distance from the ultrasonic sensor 2 is 0 as the boundary BD. As a result, the entire area of ​​the amplitude signal is set as the outside road surface reflection area R2.

[0144] Then, the threshold setting unit 7 executes the processes of steps S30 and S40 to set a reflection area threshold Th1, which is a judgment threshold for the road surface reflection area R1, and sets an outside reflection area threshold Th2, which is a judgment threshold for the outside road surface reflection area R2.

[0145] When the boundary BD is set so that the entire region of the amplitude signal is the road surface reflection region R1, the threshold setting unit 7 calculates the reflection region average value Av1 for each reflection region window W1 while shifting the reflection region window W1 in the road surface reflection region R1 which is the entire region of the amplitude signal. Then, the threshold setting unit 7 calculates the reflection region threshold value Th1 for the road surface reflection region R1 which is the entire region of the amplitude signal by using the reflection region coefficient for the calculated reflection region average value Av1 for each reflection region window W1.

[0146] Furthermore, when the boundary BD is set so that the entire region of the amplitude signal is outside the road surface reflection region R2, the threshold setting unit 7 calculates the outside reflection region average value Av2 for each outside reflection region window W2 while shifting the outside reflection region window W2 in the outside road surface reflection region R2 which is the entire region of the amplitude signal.Then, the threshold setting unit 7 calculates the outside reflection region threshold value Th2 for the outside road surface reflection region R2 which is the entire region of the amplitude signal by using the outside reflection region coefficient for the outside reflection region average value Av2 for each outside reflection region window W2 calculated.

[0147] In this manner, in this embodiment, the boundary BD is changed according to the inclination of the road surface R. By changing the boundary BD, the determination threshold is changed according to the inclination of the road surface R. The reason for changing the boundary BD according to the inclination of the road surface R will be described.

[0148] As described above, if there is a slope in the transmission direction of the exploration wave on the road surface R, the way in which the exploration wave hits the road surface R changes depending on the slope, and this changes the distance from the ultrasonic sensor 2 to the road surface R of the reflected wave from the road surface R that can be received by the ultrasonic sensor 2.

[0149] For example, when a road surface R is inclined downward as shown in Fig. 18, the distance from the ultrasonic sensor 2 to the road surface R for the reflected wave from the road surface R tends to be large. Therefore, of the entire region of the amplitude signal, the road surface reflection region R1 where the road surface noise is dominant becomes large, while the outside road surface reflection region R2 where the dark noise is dominant becomes small. Therefore, by increasing the proportion of the reflection region threshold Th1 in the judgment threshold in accordance with the size of the larger road surface reflection region R1, it is possible to suppress the erroneous detection of the reflected wave from the road surface R as the reflected wave from the object B.

[0150] 18, the distance from the ultrasonic sensor 2 to the road surface R of the reflected wave from the road surface R tends to be smaller. Therefore, of the entire region of the amplitude signal, the road surface reflection region R1 where road surface noise is dominant becomes smaller, whereas the outside road surface reflection region R2 where dark noise is dominant becomes larger. Therefore, by increasing the proportion of the outside reflection region threshold Th2 in the judgment threshold in accordance with the increasing size of the outside road surface reflection region R2, it is possible to detect object B even if the peak of the amplitude signal based on the reflected wave from object B is relatively small.

[0151] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as described below.

[0152] In the above embodiment, the object detection device 1 is provided in a vehicle, which is a moving body, but the present invention is not limited to this. For example, the object detection device 1 may be provided in something other than a moving body.

[0153] In the above embodiment, the transducer 41 has a function as a transmitter and a function as a receiver, and the ultrasonic sensor 2 has an integrated transmission and reception configuration, but the present invention is not limited to this. For example, the transducer 41 constituting the transmission unit 40A and the transducer 41 constituting the reception unit 40B may be provided separately.

[0154] In the above embodiment, an example has been described in which the width of the outer reflection area window W2 is set to be larger than the width of the reflection area window W1, but the present invention is not limited to this.

[0155] For example, the width of the outer reflection area window W2 may be set to be equal to or smaller than the width of the reflection area window W1.

[0156] In the above-described embodiment, an example was described in which the threshold setting unit 7 calculates an average value by performing a smoothing process on the amplitude signal, and sets the boundary BD based on the maximum and minimum values ​​of the calculated average value, but this is not limited to the example.

[0157] For example, the threshold setting unit 7 may set the boundary BD based on the attitude of the ultrasonic sensor 2 and the directivity of the ultrasonic waves transmitted by the transducer 41. In this case, the threshold setting unit 7 may calculate an expected distance to the road surface R based on the attitude of the ultrasonic sensor 2 and the directivity of the ultrasonic waves transmitted by the transducer 41, and set the boundary BD based on the calculated expected distance.

[0158] In the above embodiment, an example has been described in which the threshold setting unit 7 acquires the temperature information from an outside temperature sensor provided in the host vehicle, but the present invention is not limited to this.

[0159] For example, the threshold setting unit 7 can receive temperature information from a server or cloud outside the vehicle. Alternatively, it can obtain related information related to the temperature information from a server or cloud outside the vehicle, and estimate the temperature information from the obtained related information.

[0160] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is particularly expressly stated that they are essential or where they are clearly considered to be essential in principle.

[0161] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless it is specifically stated as required or unless it is clearly limited to a specific number in principle.

[0162] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., there is no limitation to those shapes, positional relationships, etc., unless specifically stated or in principle limited to a specific shape, positional relationship, etc.

[0163] The control unit 3 and the method of the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. The control unit 3 and the method of the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. The control unit 3 and the method of the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. The computer program may also be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0164] 2. Ultrasonic Sensor 6 Amplitude signal generation section 7 Threshold setting section 8 Object determination section 40A Transmitter 40B Receiver B boundary

Claims

1. An object detection device that detects an object by transmitting and receiving ultrasonic waves, an ultrasonic sensor (2) having a transmitting section (40A) for transmitting the ultrasonic wave in response to a transmission signal, a receiving section (40B) for receiving a reflected wave reflected by the object and outputting a received signal in response to the reflected wave, an amplitude signal generating section (6) for generating an amplitude signal indicating the passage of a transmission time of the ultrasonic wave and a change in amplitude from the received signal, a threshold setting section (7) for setting a judgment threshold which is a predetermined threshold for judging the presence or absence of the object, and an object judging section (8) for judging the presence or absence of the object based on the amplitude signal and the judgment threshold, The threshold setting unit sets a boundary (B) that divides the transmission time region of the amplitude signal into a first region where the amplitude fluctuation in the amplitude signal is large and a second region where the amplitude fluctuation is small, and sets a first threshold that is the judgment threshold for the first region based on the amplitude of the amplitude signal in the first region, and sets a second threshold that is the judgment threshold for the second region based on the amplitude of the amplitude signal in the second region.

2. The object detection device according to claim 1 , wherein the threshold setting unit sets at least one of the first threshold and the second threshold every time the receiver receives the reflected wave.

3. The object detection device according to claim 2 , wherein the threshold setting unit obtains a smoothed signal by performing a smoothing process for obtaining an average value for each predetermined time width for the amplitude signal, and sets the boundary based on an amount of fluctuation in the obtained smoothed signal.

4. The object detection device according to claim 1 , wherein the threshold setting unit sets the boundary based on an attitude of the ultrasonic sensor and a directivity of the ultrasonic wave transmitted by the transmission unit.

5. the threshold setting unit determines the first threshold using a magnitude of the amplitude signal in the first region and a predetermined first coefficient, and determines the second threshold using the magnitude of the amplitude signal in the second region and a second coefficient different from the first coefficient; the second coefficient is set to a value such that the second threshold is greater than the average value of the amplitude signal in the second region; 2. The object detection device according to claim 1, wherein the first coefficient is set to a value such that the first threshold is greater than an average value of the amplitude signal in the first region, and the difference between the first threshold and the magnitude of the amplitude signal in the first region is greater than the difference between the second threshold and the magnitude of the amplitude signal in the second region.

6. The ultrasonic sensor is provided on a moving body that travels on a road surface of a travel path, The object detection device according to claim 5, wherein the threshold setting unit sets the boundary of the amplitude signal so that the region of the amplitude signal where the distance from the ultrasonic sensor to the road surface is closer is the first region, and the region of the amplitude signal where the distance from the ultrasonic sensor to the road surface is farther is the second region.

7. The ultrasonic sensor has a temperature acquisition unit (6) that acquires information on an ambient temperature through which the ultrasonic waves propagate, 7. The object detection device of claim 6, wherein the threshold setting unit sets the second threshold based on the magnitude of the amplitude signal in the second region when the ambient temperature is equal to or higher than a predetermined judgment temperature, and when the ambient temperature is lower than the judgment temperature, sets the second threshold to a magnitude greater than the second threshold set when the ambient temperature is equal to or higher than the judgment temperature.

8. The object detection device according to claim 7 , wherein the threshold setting unit sets the second threshold so that a difference between the second threshold and the magnitude of the amplitude signal in the second region approaches a difference between the first threshold and the magnitude of the amplitude signal in the first region.

9. The ultrasonic sensor has an inclination information acquisition unit (6) that acquires information on the inclination of the road surface, The object detection device of claim 6, wherein the threshold setting unit sets the first area larger and the second area smaller when the road surface is inclined downward than when the road surface is inclined upward, and sets the second area smaller and the second area larger when the road surface is inclined upward than when the road surface is inclined downward.

10. 10. The object detection device according to claim 9, wherein the threshold setting unit sets the entire range of the amplitude signal to the first range when the road surface is inclined downward, and sets the entire range of the amplitude signal to the second range when the road surface is inclined upward.

11. The object detection device according to any one of claims 1 to 10, wherein the threshold setting unit obtains smoothed signals for the first region and the second region by performing a smoothing process to obtain an average value for the amplitude signal for each predetermined time width, sets the first threshold based on the amount of fluctuation in the smoothed signal for the first region obtained, and sets the second threshold based on the amount of fluctuation in the smoothed signal for the second region obtained.

12. 12. The object detection device according to claim 11, wherein the predetermined time width for obtaining the smoothed signal of the second region is set to be larger than the predetermined time width for obtaining the smoothed signal of the first region.

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