Obstacle detection device

Abstract

To improve the reliability of a detection result of the height of an obstacle.SOLUTION: An obstacle detection device (1) which is mounted on a vehicle includes: at least one transmission unit (10A) that transmits a survey wave; at least one reception unit (10B) that is arranged at a different position from the transmission unit and receives a reflected wave; a decision unit (53) which decides a detectable distance in which the height of the obstacle can be detected from the current position of the vehicle by using the propagation time in which the receiving intensity of a road surface reflected wave is greater than or equal to a first threshold, which can be obtained by using the first threshold for the receiving intensity which is determined according to the propagation time until a top-end reflected wave is received, and data showing the time series change of the receiving intensity of the road surface reflected wave among the reflected waves received by the reception unit; an obstacle detection unit (51) that detects a distance to an obstacle on the basis of the reflected wave received by the reception unit; and a height detection unit that detects the height of the obstacle on the basis of the reflected wave received by the reception unit when the detected distance is less than or equal to the detectable distance.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an obstacle detection device.

Background Art

[0002] In the technology described in Patent Document 1, the height of an obstacle existing around a vehicle is detected using an ultrasonic sensor provided in the vehicle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to estimate the height of an obstacle, the intensity of the reflected wave reflected from the upper end of the obstacle is used. For example, when the height of the obstacle is low, such as a curb or a vehicle stopper, the intensity of the reflected wave reflected from the upper end of the obstacle tends to be weaker than when the height of the obstacle is high. Therefore, when the height of the obstacle is low, the road surface reflected wave may be erroneously determined as the reflected wave at the upper end of the obstacle. As a result, the estimated height of the obstacle may be inaccurate. Thus, it has been desired to improve the reliability of the detection result.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms.

[0006] According to one embodiment of the present disclosure, an obstacle detection device (1) is provided. This obstacle detection device is mounted on a vehicle and comprises at least one transmitting unit (10A) that transmits a probe wave, at least one receiving unit (10B) positioned differently from the transmitting unit and that receives a reflected wave generated when the probe wave is reflected by an object, and a first threshold value for the received intensity which is determined according to the propagation time until the reflected wave reflected at the upper end of the obstacle is received, and data showing the time-series change in the received intensity of the road surface reflected wave that is reflected from the road surface among the reflected waves received by the receiving unit, wherein the received intensity of the road surface reflected wave is obtained using the first threshold value The system includes: a determination unit (53) that determines a detectable distance from the vehicle's current position to the obstacle's height using the aforementioned propagation time; an obstacle detection unit (51) that detects the distance to the obstacle based on the reflected wave received by the receiving unit; and a height detection unit (53) that detects the height of the obstacle, which detects the height of the obstacle based on the reflected wave received by the receiving unit when the detected distance is less than or equal to the detectable distance, and does not detect the height of the obstacle when the detected distance is greater than the detectable distance.

[0007] In this embodiment, the obstacle detection device can determine a detectable distance from the current vehicle position that allows it to detect the height of the obstacle. Based on the detectable distance, the obstacle detection device 1 determines that it is possible to detect the height of the obstacle from the vehicle's current position, and then detects the height of the obstacle. In this way, the reliability of the estimation result can be improved compared to an embodiment in which it is not determined whether it is possible to detect the height of the obstacle. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows the positional relationship between a distance sensor mounted on a vehicle and an object. [Figure 2] This is a block diagram illustrating the schematic configuration of an obstacle detection device. [Figure 3] This is an explanatory diagram of the peak in the reflected wave received by the distance sensor. [Figure 4] This is an explanatory diagram showing how to calculate the distance to an object and the height of the object. [Figure 5] This is an explanatory diagram about reflected waves that occur when reflected by a tall obstacle. [Figure 6] This figure shows an example of reflected waves, including road surface reflected waves. [Figure 7] This is an explanatory diagram illustrating the advantages of placing ultrasonic sensors in different locations. [Figure 8] This is a flowchart of the height calculation process. [Figure 9] This is an explanatory diagram on how to identify the scope of exclusion. [Figure 10] This is an explanatory diagram of the method for calculating the detectable distance. [Figure 11] This is a cross-sectional view of the obstacle. [Figure 12] This diagram shows an example of a vehicle equipped with two pairs of ultrasonic sensors. [Figure 13] This diagram shows a vehicle moving while turning. [Figure 14] This is an explanatory diagram of the control of vehicle A1 using the calculated detectable distance. [Modes for carrying out the invention]

[0009] A1. Embodiment The vehicle A1 shown in Figure 1 is equipped with a function to detect an object M1 in its vicinity. In Figure 1, a left-handed Cartesian coordinate system is set up, with the X-axis being the direction parallel to the width direction of vehicle A1, the Y-axis being the direction parallel to the front-rear direction of vehicle A1, and the Z-axis being the direction parallel to the vertical direction. The rear of vehicle A1 is defined as the positive Y-axis direction, and the vertically upward direction is defined as the positive Z-axis direction. In this embodiment, the assumed object M1 is a wheel stop composed of two blocks. Each block has a roughly rectangular parallelepiped shape extending in the X-axis direction. Note that one of the two blocks is located on the +X side of the other and is therefore not shown in Figure 1. In this embodiment, it is assumed that object M1 is a low-height object. Object M1 is also called an obstacle.

[0010] As shown in Figure 2, the obstacle detection device 1 comprises an injection unit 10A, a receiving unit 10B, a transmitting circuit 20, a receiving circuit 30, and a processing unit 50. As shown in Figure 1, the injection unit 10A and the receiving unit 10B are installed on the rear bumper of vehicle A1. The injection unit 10A and the receiving unit 10B are positioned at a distance from each other in the X-axis direction of vehicle A1. Note that the receiving unit 10B is positioned on the +X side of the injection unit 10A and is therefore not shown in Figure 1. Assume that the positions of the injection unit 10A and the receiving unit 10B are the same on the Y-axis and Z-axis.

[0011] The ejection unit 10A and the receiving unit 10B are ultrasonic sensors using piezoelectric elements. The ejection unit 10A transmits ultrasonic waves as probe waves. For example, the ejection unit 10A transmits ultrasonic waves in the horizontal direction. The receiving unit 10B receives reflected waves that are reflected by objects around the vehicle A1 from the probe waves. The ejection unit 10A is also called the transmitter. The receiving unit 10B is also called the receiver. In this embodiment, the ejection unit 10A is not used for receiving reflected waves. Also, the receiving unit 10B is not used for transmitting probe waves. The reason for using two ultrasonic sensors positioned at different locations for transmitting probe waves and receiving reflected waves will be explained later.

[0012] As shown in Figure 2, the transmitting circuit 20 drives the ejection unit 10A according to the control of the processing unit 50, causing the ejection unit 10A to transmit ultrasonic waves at a preset frequency. The receiving circuit 30 supplies the processing unit 50 with a received signal indicating the reflected wave received by the receiving unit 10B. The ejection unit 10A, the receiving unit 10B, the transmitting circuit 20, and the receiving circuit 30 constitute the sonar mounted on vehicle A1.

[0013] The processing unit 50 detects the position and height of the object M1 using the injection unit 10A and the receiving unit 10B. The processing unit 50 includes, as functional units, an obstacle detection unit 51, a height detection unit 53, and a storage unit 55. Each function provided in the processing unit 50 is realized by a computer mounted on the vehicle A1, which includes a processor, a memory, etc. This computer can communicate with an ECU (Electronic Control Unit) provided in the vehicle A1.

[0014] The obstacle detection unit 51 determines whether there is an obstacle around the vehicle A1 based on the reception intensity of the reflected wave received by the receiving unit 10B. Further, the obstacle detection unit 51 detects the distance on the Y-axis from the vehicle A1 to the obstacle based on the reception intensity of the received reflected wave. A specific method for obtaining the distance on the Y-axis from the vehicle A1 to the obstacle will be described below.

[0015] As shown in FIG. 3, the received reflected wave includes two peaks. A peak is a point in the waveform representing the time-series change of the reception intensity of the reflected wave where the value indicating the slope changes from a positive value to a negative value, and the reception intensity indicated by the wave having that point as the maximum point exceeds a preset threshold value. A peak is also referred to as a maximum point. The reflected wave having a peak at time Tpk1 is the reflected wave reflected from the upper end of the object. The reflected wave having a peak at time Tpk2 is the reflected wave reflected from the lower end of the object. Ultrasonic waves are reflected at the boundary between the object and the air around the object at the upper end, so the reflected wave at the upper end of the object appears as a peak. Also, ultrasonic waves are reflected at the boundary between the object and the road surface at the lower end, so the reflected wave at the lower end of the object appears as a peak. Thus, the reflected wave reflected at the boundary between one substance and a different substance appears as a peak.

[0016] Also, the reception intensity of the reflected wave reflected from the upper end of the object is smaller than that of the reflected wave reflected from the lower end. This is because the area of the surface facing the receiving unit 10B is smaller at the upper end of the object M1 than at the lower end of the object in contact with the road surface. Whether the two peaks are reflected waves from the same object is determined as follows. For example, in the example shown in FIG. 3, when the time T12 indicating the difference between the time Tpk1 and the time Tpk2 is less than or equal to a preset value, it is determined that the peak at time Tpk1 and the peak at time Tpk2 are reflected waves from the same object M1.

[0017] The obstacle detection unit 51 obtains the time Tr2 as the time from the time T0 when the emission unit 10A transmits the detection wave to the time T2 when the reception intensity of the reflected wave exceeds a preset threshold value Vth2. As shown in FIG. 4, let the distance between the emission unit 10A and the reception unit 10B and the reflection point at the lower end of the object M1 be the distance L2. The obstacle detection unit 51 calculates the distance L2 by dividing the value obtained by multiplying the speed of sound by the time Tr2 by 2.

[0018] As shown in FIG. 4, assume a right triangle having the hypotenuse of the distance L2. The distance D1 of one side sandwiching the right angle is the distance on the Z axis between the emission unit 10A and the reception unit 10B and the ground. The distance D1 is a value determined at the time of designing the vehicle A1 and is known. The distance D2 of the other side sandwiching the right angle is the distance on the Y axis between the emission unit 10A and the reception unit 10B and the reflection point at the lower end of the object M1. The distance D2 can be calculated using the distance L2 and the distance D1.

[0019] As shown in Figure 2, the height detection unit 53 determines the detectable distance. The detectable distance is the distance from vehicle A1 to the obstacle at which the height of the obstacle can be detected. Being able to detect the height of an obstacle means that the height of the obstacle can be detected with a predetermined detection accuracy. The height detection unit 53 is also called the determination unit. As will be described in detail later, the reception intensity of the reflected wave reflected from the upper end of a low-height obstacle is weak, so the distance from vehicle A1 to the obstacle at which the height of the obstacle can be detected is limited. The height of the obstacle is detected when the distance from vehicle A1 to the obstacle is less than or equal to the detectable distance. On the other hand, if the distance from vehicle A1 to the obstacle exceeds the detectable distance, the height of the obstacle is not detected. The method for determining the detectable distance will be described later. The height of the obstacle is determined as follows.

[0020] As shown in Figure 3, the obstacle detection unit 51 determines time Tr1 as the time from time T0, which is the time when the ejection unit 10A transmits the search wave, to time T1, which is the time when the received intensity of the reflected wave exceeds a preset threshold Vth1. As shown in Figure 4, distance L1 is the distance between the ejection unit 10A and the receiving unit 10B and the reflection point at the upper end of object M1. The obstacle detection unit 51 calculates distance L1 by multiplying the speed of sound by time Tr1 and dividing the resulting value by 2.

[0021] As shown in Figure 4, a right-angled triangle with a hypotenuse of distance L1 is assumed. The distance D2 of one of the sides enclosing the right angle is the distance on the Y-axis between the injection unit 10A and the receiving unit 10B and the reflection point at the lower end of object M1. Distance D2 can be calculated using the method described above. Distance D3 is the distance on the Z-axis between the injection unit 10A and the receiving unit 10B and the upper end of object M1. The height detection unit 53 calculates distance D3 using distance L1 and distance D2. Furthermore, the height detection unit 53 calculates the value obtained by subtracting distance D3 from the known distance D1 as the height D4 of the upper end of object M1. In this embodiment, the height of the upper end of object M1 is taken as the height of object M1.

[0022] The storage unit 55 stores data used for various processes in the obstacle detection device 1. For example, the storage unit 55 stores the threshold values ​​Vth1 and Vth2 mentioned above. The storage unit 55 also stores a first threshold value used by the height detection unit 53 in the process of determining the detectable distance. The first threshold value will be described later.

[0023] The following explains why the injection unit 10A and the receiving unit 10B are positioned in different locations.

[0024] Generally, the reception strength of reflected waves reflected by low-height obstacles is weaker than the reception strength of reflected waves reflected by high-height obstacles. In this specification, an obstacle whose upper end is lower than the height of the location where the injection unit 10A and the receiving unit 10B are installed is called a low-height obstacle. An obstacle whose upper end is higher than the height of vehicle A1 is called a high-height obstacle. As shown in Figure 1, the upper end of object M1 is lower than the location where the injection unit 10A is installed. Object M1 is a low-height obstacle. As shown in Figure 5, the upper end of object M2 is higher than the height of vehicle A1. Object M2 is a high-height obstacle. For the sake of ease of understanding the technology, the width of object M2 is assumed to be greater than the width of vehicle A1.

[0025] In the example shown in Figure 1, some of the probe waves transmitted from the launch unit 10A pass over object M1, while other parts are reflected by object M1. On the other hand, in the example shown in Figure 5, the probe waves transmitted from the launch unit 10A are reflected without passing over object M2. Therefore, most of the probe waves are reflected by object M1. This difference occurs because the surface area of ​​object M1 directly facing the launch unit 10A is smaller than the surface area of ​​object M2 directly facing the launch unit 10A. Therefore, the received intensity of the reflected waves reflected by object M1, which is a low-height obstacle, is smaller than the received intensity of the reflected waves reflected by object M2, which is a taller obstacle.

[0026] As shown in Figure 6, the receiving unit 10B receives a composite wave WC, which is a combination of the reflected wave WA reflected by object M1 and the road surface reflected wave WB. This is because a portion of the search wave transmitted from the emission unit 10A is reflected by the road surface. Hereinafter, the reflected wave reflected by the road surface will be called the road surface reflected wave. In the waveform shown, the wave represented by the dashed line is the reflected wave WA reflected by the obstacle. The wave represented by the dashed line is the road surface reflected wave WB. The wave represented by the solid line is the composite wave WC. Since what the obstacle detection device 1 should detect is the reflected wave WA reflected by the obstacle, the road surface reflected wave WB is a noise component.

[0027] Furthermore, the upper end of a low-height obstacle is closer to the road surface than the upper end of a high-height obstacle. Therefore, depending on the received intensity of the road surface reflected wave, it is expected that the received intensity of the reflected wave reflected by a low-height obstacle and the received intensity of the road surface reflected wave will be close. In such a case, it becomes difficult for the receiving unit 10B to extract the reflected wave reflected at the upper end of the obstacle from the reflected wave received. Therefore, it is necessary to increase the signal-to-noise ratio (S / N ratio) of the received reflected wave. In this embodiment, in order to improve the S / N ratio, the emission unit 10A that transmits the exploration wave and the receiving unit 10B that receives the reflected wave are arranged in different positions. The reason why the S / N ratio can be improved by arranging the transmitting unit that transmits the exploration wave and the receiving unit that receives the reflected wave in different positions will be explained below.

[0028] Referring to Figure 7, we compare the case where the probe wave transmitter and the reflected wave receiver are located in the same position (hereinafter referred to as Case C1) and the case where the probe wave transmitter and the reflected wave receiver are located in different positions (hereinafter referred to as Case C2). In Case C1, the same ultrasonic sensor S1 transmits the probe wave and receives the reflected wave. In Case C2, ultrasonic sensor S1 transmits the probe wave, and ultrasonic sensor S2, which is different from ultrasonic sensor S1, receives the reflected wave. In Case C2, ultrasonic sensor S1 does not receive the reflected wave. Ultrasonic sensors S1 and S2 are located in the same position on the Y axis, but in different positions on the X and Z axes. In both Case C1 and Case C2, it is assumed that the intensity of the transmitted probe wave is the same. In the example shown in Figure 7, it is assumed that there are no obstacles within the detectable range of ultrasonic sensors S1 and S2, and that the probe wave is reflected only by the road surface. Furthermore, it is assumed that the road surface is asphalt, and that the probe wave is isotropically scattered on the road surface.

[0029] The dashed-dotted curve H1 represents the reflection position of the probe wave on the road surface when the time elapsed from the probe wave transmitted simultaneously from the ultrasonic sensor S1 to the road surface is time T10. As shown in the figure, curve H1 is a semicircle with the origin at the position obtained by projecting the position of the ultrasonic sensor S1 in the vertical direction.

[0030] The solid curve H2 represents the reflection position of the probe wave on the road surface when the elapsed time T10 from the probe wave transmitted simultaneously from ultrasonic sensor S1 to ultrasonic sensor S2 is the same for both probe waves. For the sake of easier understanding of the technology, ultrasonic sensors S1 and S2 are assumed to be positioned such that the curve H2, which shows the reflection position of the probe wave on the road surface, forms a semicircle.

[0031] The region of curve H1 (excluding the area inside the curve) represents the area where the probe wave is reflected from the road surface in case C1. The region of curve H2 (excluding the area inside the curve) represents the area where the probe wave is reflected from the road surface in case C2. The length of the curved portion of curve H2 is shorter than the length of the curved portion of curve H1. In other words, the reflection area of ​​the reflected wave on the road surface received simultaneously is smaller in case C2 compared to case C1. This means that when the transmitter and receiver are located in different positions, the reflection intensity of the road surface reflected wave received at the same time is smaller compared to when the transmitter and receiver are located in the same position. Therefore, when the transmitter and receiver are located in different positions, the signal-to-noise ratio (S / N ratio) of the received reflected wave can be improved compared to when the transmitter and receiver are located in the same position.

[0032] Furthermore, if the ultrasonic sensor S1, which is the transmitting unit that sends out probe waves, also functions as the receiving unit that receives reflected waves, reverberation vibrations will occur as a result of transmitting probe waves, making it difficult to distinguish whether the received signal represents a reflected wave or reverberation vibrations. However, if the transmitting unit and the receiving unit are located in different positions, they will not be affected by reverberation vibrations.

[0033] For the reasons mentioned above, in this embodiment, the ejection unit 10A that transmits the probe wave and the receiving unit 10B that receives the reflected wave are placed in different positions. For example, if the receiving unit is placed higher than the transmitting unit, the reception strength of the reflected wave from obstacles on the road surface tends to be weaker compared to when the height of the receiving unit and the transmitting unit are the same. Therefore, in this embodiment, the ejection unit 10A and the receiving unit 10B are placed in the same position in the Z-axis direction and at a distance from each other in the X-axis direction.

[0034] The height calculation process for determining the height of an obstacle, as shown in Figure 8, starts when predetermined starting conditions are met. These starting conditions include, for example, vehicle A1 beginning to move backward at a predetermined speed or less. The predetermined speed is, for example, 10 kilometers per hour.

[0035] In step S101, the processing unit 50 causes the ejection unit 10A to transmit a probe wave via the transmission circuit 20. The probe wave is, for example, a pulse signal. At this time, the processing unit 50 stores the transmission time of the probe wave in memory.

[0036] In step S102, the processing unit 50 causes the receiving unit 10B to receive the reflected wave via the receiving circuit 30 for a certain period of time from the time of transmission of the probe wave. This certain period of time is, for example, 15 milliseconds. For example, if vehicle A1 is traveling at 10 kilometers per hour, the distance traveled in 15 milliseconds is approximately 42 millimeters. Therefore, the received reflected wave can be processed in the same way as when the probe wave is transmitted and the reflected wave is received while vehicle A1 is stationary. The processing unit 50 stores the received signal of the reflected wave received by the receiving unit 10B in memory. The period from the time of transmission of the probe wave until a certain period of time has elapsed is also called a predetermined time interval after the transmission of the probe wave.

[0037] In step S103, the processing unit 50 determines whether the received reflected wave is solely a road surface reflection. This is because the received reflected wave may include not only road surface reflections but also reflections generated by some obstacle around the vehicle. Specifically, the processing unit 50 determines that the received reflected wave is solely a road surface reflection if the received intensity of the received reflected wave does not exceed a preset obstacle detection threshold ThA. On the other hand, the processing unit 50 determines that the received reflected wave includes both road surface reflections and reflections from some obstacle if the received intensity of the received reflected wave exceeds the obstacle detection threshold ThA. The obstacle detection threshold ThA is a predetermined value for the received intensity used to determine the presence or absence of an obstacle. The obstacle detection threshold ThA is determined according to the time elapsed since the exploration wave was emitted. The obstacle detection threshold ThA is also called the second threshold. The obstacle detection threshold ThA is set to have a value greater than the first threshold, which will be described later.

[0038] The signal waveform shown in Figure 9 represents the received intensity of the reflected wave received within a certain time period from the time the probe wave was transmitted. The signal waveform shown contains multiple peaks. In Figure 9, the peak that occurred at time Tpk10 exceeds the obstacle detection threshold ThA, which is represented by the dashed line. In such a case, the processing unit 50 determines that the received reflected wave includes both a road surface reflection and a reflection reflected by some obstacle.

[0039] As shown in Figure 8, if it is determined in step S103 that the received reflected wave is solely a road surface reflected wave (step S103; YES), the process in step S105 is executed. On the other hand, if the received reflected wave is not solely a road surface reflected wave (step S103; NO), the process in step S104 is executed.

[0040] In step S104, the processing unit 50 identifies the range of the received reflected wave to be used for calculating the detectable distance. Specifically, the processing unit 50 identifies the range that includes peaks exceeding the obstacle detection threshold ThA and has the same time width as the pulse width of the pulse signal transmitted as the probe wave as an exclusion range for calculating the detectable distance. The processing unit 50 also identifies the range excluding the exclusion range as the target range to be used for calculating the detectable distance. Peaks exceeding the obstacle detection threshold ThA are reflected waves generated when the probe wave is reflected by some obstacle. The time width during which such reflected waves occur corresponds to the pulse width of the probe wave's pulse signal. In this way, the target range can be easily identified. The target range is also called the first range.

[0041] In the example shown in Figure 9, the range containing the peak that occurred at time Tpk10 and having the same time width as the pulse width of the probe wave is identified as the exclusion range Ex1. The range excluding the exclusion range Ex1 is identified as the target range used to calculate the detectable distance. The reason for identifying the target range in this way will be explained later.

[0042] In the waveform shown in Figure 9, the received signal strength exceeds the obstacle detection threshold ThA approximately 1.5 milliseconds after transmission and approximately 3 milliseconds after transmission. These are reflected waves from the ground almost directly below the ejection unit 10A, where the probe wave transmitted from the ejection unit 10A was reflected. Therefore, reflected waves received within a predetermined period after the probe wave is transmitted are not used in the calculation of the detectable distance. The predetermined period can be set, for example, to 20 percent of the time that the receiving unit 10B receives the reflected wave. In Figure 9, reflected waves within a predetermined period after the probe wave is transmitted are set as the excluded range Ex0, which is not used in the calculation of the detectable distance. After step S104 is executed, step S105, shown in Figure 8, is executed.

[0043] In step S105, the processing unit 50 calculates the detectable distance L5. If the received reflected waves consist only of road surface reflected waves, the processing unit 50 uses all of the received reflected waves to calculate the detectable distance L5. If the received reflected waves consist of more than just road surface reflected waves, the processing unit 50 uses the target range identified in step S104 to calculate the detectable distance L5.

[0044] The detectable distance is calculated using the propagation time at which the received intensity of the road surface reflected wave exceeds a first threshold. The first threshold is a threshold for received intensity determined according to the propagation time until the reflected wave reflected off the upper end of an obstacle (upper end reflected wave) is received. More specifically, the first threshold is determined based on data (distance-dependent data) that shows the relationship between the received intensity of the reflected wave reflected off the upper end of a pre-prepared obstacle and the distance to the pre-prepared obstacle.

[0045] As shown in Figure 10, the processing unit 50 identifies the position on the time axis where waveform W1, which represents the time-series change of the received reflected wave, and waveform W2, which represents the first threshold, intersect. Since there may be two or more intersection points between waveform W1 and waveform W2, the processing unit 50 identifies the position on the time axis where the first intersection point P1 is located within the target range. The processing unit 50 calculates the elapsed time from the transmission time of the probe wave to the time corresponding to the position of intersection point P1. Then, the processing unit 50 calculates the detectable distance L5 by multiplying the value obtained by dividing the elapsed time by 2 by the speed of sound.

[0046] As shown in Figure 8, if an obstacle is detected in step S106 (step S106; YES), the process in step S107 is executed. Note that in the process in step S103, if it is determined that the received reflected wave is not solely a road surface reflected wave, an obstacle is considered to have been detected. On the other hand, if no obstacle is detected (step S106; NO), the height calculation process is terminated.

[0047] In step S107, the processing unit 50 calculates the distance L2 to the obstacle using the method described above. In step S108, if the distance L2 is less than or equal to the detectable distance L5 (step S108; YES), the processing unit 50 executes the process in step S109. On the other hand, if the distance L2 is greater than the detectable distance L5 (step S108; NO), the height calculation process is terminated.

[0048] In step S109, the processing unit 50 calculates the height D4 of the obstacle using the distance L1 and the distance D2. The distance L1 is calculated by the method described above. The processing unit 50 stores the calculated height D4 of the obstacle in memory. After that, the height calculation process is completed.

[0049] For example, when vehicle A1 is moving backward to enter a parking space, the distance between vehicle A1 and the obstacle gradually decreases. Therefore, the processing unit 50 may repeat the above process at predetermined time intervals until, for example, vehicle A1 stops. As shown in Figure 1, object M1 is a low-height obstacle that is difficult for the driver of vehicle A1 to see from the driver's seat. As shown in Figure 1, for example, when vehicle A1 moves backward (+Y direction), depending on the height of object M1, the bumper portion of vehicle A1 may come into contact with object M1. When the above process is repeated while vehicle A is moving, height detection is not performed when the distance D2 is greater than the detectable distance L5. When the distance D2 becomes less than or equal to the detectable distance L5, that is, when vehicle A1 approaches object M1 to a distance where the height can be detected, the height D4 of the obstacle is detected. For example, the height detection unit 53 notifies the ECU of vehicle A1 of the detected height. This may result in the output of an alarm indicating that a low-height obstacle has been detected.

[0050] Next, we will explain how to determine the first threshold. For example, the first threshold can be determined by training a neural network. In this case, with a pre-prepared object of known height placed on the road surface, a probe wave is transmitted, and the received signal representing the reflected wave generated when the probe wave reflects off the object is input to the neural network to estimate the height of the object. Furthermore, by repeating the above process while changing the road surface on which the object is placed, for example, multiple height estimates can be obtained. In addition, the received intensity of the reflected wave reflected from the upper end of the object and the road surface reflection intensity are determined from each received signal. The received intensity of the reflected wave reflected from the upper end of the object can be determined, for example, from the difference between the waveform of the reflected wave generated when a probe wave transmitted without an object placed on the road surface reflects off the road surface and the waveform of the reflected wave generated when a probe wave transmitted with an object placed on the road surface reflects off the road surface.

[0051] Furthermore, for example, 3σ is calculated from the standard deviation σ of the height estimate. For each received signal whose height estimate falls within the 3σ range, the largest value among the ratios of the received intensity of the reflected wave reflected from the upper end of the object to the road surface reflected intensity is determined as the coefficient α. Then, with a pre-prepared object of known height placed on a certain road surface, a probe wave is transmitted, and the value obtained by multiplying the received intensity of the resulting reflected wave by the coefficient α is taken as the first threshold. In this way, the first threshold is determined based on the received intensity, which is determined according to the propagation time until the upper end reflected wave is received.

[0052] As shown in Figure 10, beyond intersection P1, the received intensity of the reflected wave represented by waveform W1 exceeds the first threshold represented by waveform W2. This means that, on the time axis, beyond intersection P1, the upper end reflected wave is buried by the road surface reflected wave. Therefore, in this embodiment, the distance corresponding to the position of intersection P1 on the time axis is determined as the detectable distance.

[0053] Furthermore, as described above, the range of the received reflected wave that includes peaks whose received intensity exceeds the obstacle detection threshold ThA, and excludes the exclusion range which has the same time width as the pulse width, is used to determine whether the height of the obstacle can be detected from the vehicle's current position. In this way, since waves other than road surface reflected waves are not used in the calculation of the detectable distance, it is possible to avoid inaccuracies in the calculated detectable distance. This improves the accuracy of determining whether or not it is possible to detect the height of an obstacle from the vehicle's current position.

[0054] Furthermore, the obstacle detection device 1 uses the position on the time axis where the intersection of the waveform representing the time-series change in the received intensity of the reflected wave and the waveform representing the first threshold set based on distance-dependent data is located to determine the propagation time at which the received intensity of the road surface reflected wave exceeds the first threshold. In addition, the obstacle detection device 1 calculates the detectable distance using the propagation time at which the received intensity of the road surface reflected wave exceeds the first threshold. Therefore, for obstacles of similar height to pre-prepared obstacles, it is possible to calculate the distance to an obstacle at which the reflected wave from the upper end of the obstacle is not buried by the road surface reflected wave. The calculated detectable distance indicates the distance between the vehicle and the obstacle at which it is possible to distinguish between the reflected wave reflected from the upper end of the obstacle and the road surface reflected wave.

[0055] Furthermore, the obstacle detection device 1 detects the height of an obstacle if it determines that it is possible to detect the height of the obstacle from the vehicle's current position based on the detectable distance. In this way, the reliability of the estimation result can be improved compared to a configuration in which it does not determine whether it is possible to detect the height of the obstacle.

[0056] B1. Other Embodiments 1 The pre-prepared object used to obtain the first threshold is preferably an object installed in the parking space where vehicle A1 is parked. For example, a wheel stop or a curb. However, the pre-prepared object is not limited to these and may also be an embankment, a step, etc.

[0057] As shown in Figure 11, the shape of the upper end of the wheel stop M5 and the shape of the upper end of the curb M6 are different. Therefore, the received intensity of the reflected wave will be different depending on whether the probe wave is reflected at the upper end of the wheel stop M5 or at the curb M6. In the figure, the upper ends are enclosed by dashed lines. Therefore, it is desirable to prepare separate waveforms for the first threshold for the wheel stop and the first threshold for the curb. For this reason, a wheel stop, or an object with a height that simulates a wheel stop, can be prepared in advance, and the first threshold for the wheel stop can be determined based on the received intensity of the reflected wave reflected at the upper end of the prepared object. Furthermore, a curb, or an object with a height that simulates a curb, can be prepared in advance, and the first threshold for the curb can be determined based on the received intensity of the reflected wave reflected at the upper end of the prepared object.

[0058] Assume that vehicle A1 is equipped with a camera that takes pictures of the rear. When vehicle A1 is moving backward, the camera takes pictures of at least the upper end of any obstacles in the direction of vehicle A1's movement. The processing unit 50 determines whether the obstacle is a wheel stop or a curb based on the image data output by the camera. The camera is also called an image sensor.

[0059] Whether an obstacle is a wheel stop or a curb is determined as follows. As shown in Figure 11, the cross-sectional shape of the upper end of the curb M6 is more gently curved than the cross-sectional shape of the upper end of the wheel stop M5. Therefore, of the wheel stop M5 and the curb M6, the degree of change in the brightness value per pixel is greater in the range where the upper ends of each are visible in the captured image than in the other. Thus, the processing unit 50 can determine whether the captured object is a wheel stop M5 or a curb M6 based on the degree of change in brightness in the range where the upper ends are visible in the captured image.

[0060] Specifically, the processing unit 50 calculates a value representing the degree of brightness change by dividing the brightness in the range where the upper end is visible by the number of pixels in that range. The processing unit 50 determines that the object is a wheel stop M5 if the calculated value representing the degree of brightness change is the same as a pre-set reference value representing the degree of brightness change for the wheel stop M5, or if the difference from the reference value is less than or equal to a certain value. The processing unit 50 also determines that the object is a curb M6 if the calculated value representing the degree of brightness change is the same as a pre-set reference value representing the degree of brightness change for the curb M6, or if the difference from the reference value is less than or equal to a certain value.

[0061] If it is determined to be a wheel stop, the detectable distance L5 can be calculated using the first threshold value for wheel stops. On the other hand, if it is determined to be a curb, the detectable distance L5 can be calculated using the first threshold value for curbs.

[0062] In this manner, the detectable distance L5 is calculated using a first threshold value set from the measured value of the received intensity of reflected waves reflected by pre-prepared obstacles such as wheel stops and curbs, or objects of similar height. Similar to the embodiment, if the distance to the obstacle is less than or equal to the detectable distance L5, the height of the obstacle is calculated. Therefore, the detection accuracy of the height of wheel stops or curbs can be improved.

[0063] B2. Other Embodiments 2 Furthermore, three or more types of first thresholds can be prepared. For example, a first threshold may be predetermined for each radius of curvature of the cross-section of the upper end of the object. In addition, for each radius of curvature of the object's cross-section, the degree of brightness change for each pixel in the upper end range of the captured image is predetermined. Here, the cross-section is the cross-section obtained when the rear end of vehicle A1 is facing the object, as shown in Figure 1, and is cut by a plane passing through the center of the front end and the center of the rear end of vehicle A1. The processing unit 50 identifies the radius of curvature of the object's cross-section from the degree of brightness change in the upper end range of the captured image. The storage unit 55 is assumed to have data pre-stored that shows the correspondence between the degree of brightness change in the image and the radius of curvature. The storage unit 55 is also assumed to have data pre-stored that shows the first threshold determined for each radius of curvature of the cross-section of the upper end of the obstacle. The processing unit 50 determines the detectable distance L5 using the first threshold corresponding to the identified radius of curvature. Since a first threshold value defined for each radius of curvature of the cross-section at the upper end is used, the detectable area can be calculated with high accuracy.

[0064] B3. Other Embodiments 3 In this embodiment, the range containing peaks exceeding the obstacle detection threshold ThA and having the same time width as the pulse width of the pulse signal transmitted as a search wave was identified as an excluded range for the detection distance calculation process. The remaining range was identified as an included range for the detection distance calculation process. However, the method for identifying the excluded range and the included range is not limited to this. It is sufficient to exclude at least the range where the received intensity exceeds the obstacle detection threshold ThA, so the entire range where the received intensity exceeds the obstacle detection threshold ThA may be considered an excluded range. Alternatively, the entire range where the received intensity does not exceed the obstacle detection threshold ThA may be considered an included range for the detection distance calculation process.

[0065] B4. Other Embodiments 4 In this embodiment, an example was described in which one pair of injection and receiving parts are arranged at the rear end of vehicle A1, but two or more pairs of injection and receiving parts may be arranged. As shown in Figure 12, injection parts 10A-1 and 10A-2 and receiving parts 10B-1 and 10B-2 may be arranged at the rear end of vehicle A1. The rear end refers to the part of vehicle A1 from which there is nothing behind that position. Injection part 10A-1 and receiving part 10B-1 are arranged at different positions on the -Y side from the vehicle center in the vehicle width direction. In the figure, the position of the vehicle center in the vehicle width direction is shown by the dashed line F1. Injection part 10A-2 and receiving part 10B-2 are arranged at different positions on the +Y side from the vehicle center in the vehicle width direction.

[0066] Generally, parking spaces often have two wheel stops spaced apart, aligned with the position of the rear wheels of vehicle A1. When vehicle A1 moves backward, there will be an area behind vehicle A1 where the wheel stops (object M1) are installed and an area where the wheel stops are not installed.

[0067] As shown in Figure 12, the injection unit 10A-1 and the receiving unit 10B-1 are positioned on one side of the vehicle center in the vehicle width direction. The injection unit 10A-2 and the receiving unit 10B-2 are positioned on the other side of the vehicle center in the vehicle width direction. The distance between the injection unit 10A-1 and the receiving unit 10B-1 in the vehicle width direction is less than half the vehicle width. The same applies to the injection unit 10A-2 and the receiving unit 10B-2. By arranging them in this way, for example, if two wheel chocks are installed with a gap between them to match the position of the rear wheels of the vehicle, the wheel chocks, which are obstacles, can be reliably detected.

[0068] Alternatively, the ejection units 10A-1 and 10A-2 and the receiving units 10B-1 and 10B-2 may be located at the front of the vehicle A1 instead of the rear. The front is defined as the portion of the vehicle A1 that is free of obstructions in front of it. Alternatively, two pairs of transmitting and receiving units may be located at both the front and rear of the vehicle A1.

[0069] B5. Other Embodiments 5 As shown in Figure 12, when two pairs of ejection and receiving units are arranged at the rear end of the vehicle, the detectable distance can be calculated as follows. The ejection unit 10A-1 and receiving unit 10B-1 are also referred to as the first pair. The ejection unit 10A-2 and receiving unit 10B-2 are also referred to as the second pair. In other embodiments 5, it is assumed that the reflected wave of the probe wave transmitted from the ejection unit 10A-1 is received by the receiving unit 10B-1, and the reflected wave of the probe wave transmitted from the ejection unit 10A-2 is received by the receiving unit 10B-2.

[0070] For example, the ejection units 10A-1 and 10A-2 each transmit probe waves at different frequencies. Therefore, the source can be identified based on the frequency of the reflected wave. The receiving circuit 30 treats only the reflected probe wave transmitted from ejection unit 10A-1 as the received signal for the receiving unit 10B-1 from among the reflected waves received by the receiving unit 10B-1. Furthermore, the receiving circuit 30 treats only the reflected probe wave transmitted from ejection unit 10A-2 as the received signal for the receiving unit 10B-2 from among the reflected waves received by the receiving unit 10B-2.

[0071] Alternatively, the ejection units 10A-1 and 10A-2 transmit search waves at the same frequency at the same time. The receiving circuit 30 may determine, based on the elapsed time since the transmission of the search wave, whether the reflected wave received by the receiving unit 10B-1 is a reflected wave of the search wave transmitted from the ejection unit 10A-1. Hereinafter, the object M1 located on the -Y side as shown in Figure 12 will be referred to as the left object M1. As shown in Figure 12, for example, the time it takes for the search wave transmitted from the ejection unit 10A-1 to reach the left object M1 is shorter than the time it takes for the search wave transmitted from the ejection unit 10A-2 to reach the left object M1. Therefore, the time it takes for the search wave transmitted from the ejection unit 10A-1 to be reflected by the left object M1 and reach the receiving unit 10B-1 is shorter than the time it takes for the search wave transmitted from the ejection unit 10A-2 to be reflected by the left object M1 and reach the receiving unit 10B-1. In this way, the source can be identified based on the elapsed time since the transmission of the probe wave. The same applies to the reflected wave received by the receiving unit 10B-2.

[0072] The processing unit 50 determines the position on the time axis where the intersection point is located when the waveform of the road surface reflected wave received by the receiving unit 10B-1 and the waveform W2 representing the first threshold are superimposed. The processing unit 50 calculates the first detectable distance L5-1 using the position on the time axis of the intersection point. Furthermore, the processing unit 50 determines the position on the time axis where the intersection point is located when the waveform of the road surface reflected wave received by the receiving unit 10B-2 and the waveform W2 representing the first threshold are superimposed. The processing unit 50 calculates the second detectable distance L5-2 using the position on the time axis of the intersection point.

[0073] Subsequently, the processing unit 50 calculates the average value of the detectable distance L5-1 and the detectable distance L5-2 as the detectable distance L5. Since the waveforms of road surface reflected waves received by multiple receiving units are used, the detectable distance can be calculated with high accuracy even if there is variation in the received intensity of the road surface reflected waves.

[0074] The same applies when two pairs of transmitters and receivers are located at the front of the vehicle. The processing unit 50 calculates the detectable distance using data showing the time-series change in the received intensity of the road surface reflected waves received by each receiver and a first threshold value, and then calculates the average of the two calculated detectable distances. Similarly, the average of the calculated detectable distances can be calculated when three or four pairs of transmitters and receivers are located at the front or rear of the vehicle.

[0075] B6. Other Embodiments 6 In another embodiment 5, an example was described in which the vehicle is equipped with two pairs of transmitters and receivers (see Figure 12). Alternatively, the rear or front end of the vehicle may be equipped with one ejector unit and two receiving units, each positioned at different locations.

[0076] The processing unit 50 calculates the first detectable distance L5-3 using the position on the time axis where the intersection point is located when the waveform of the road surface reflected wave received by one receiving unit and the waveform W2 representing the first threshold are superimposed. Furthermore, the processing unit 50 calculates the second detectable distance L5-4 using the position on the time axis where the intersection point is located when the waveform of the road surface reflected wave received by the other receiving unit and the waveform W2 representing the first threshold are superimposed. Subsequently, the processing unit 50 calculates the average value of the detectable distances L5-3 and L5-4 as the detectable distance L5. Since the waveforms of the road surface reflected waves received by multiple receiving units are used, the detectable distance can be calculated with high accuracy even if there is variation in the received intensity of the road surface reflected waves.

[0077] Furthermore, the detectable distance can be similarly determined when one ejection unit and three or more receiving units are arranged at the rear or front end of the vehicle.

[0078] B7. Other Embodiments 7 Furthermore, as shown in Figure 13, when vehicle A1 is moving backward while turning, it is desirable to calculate the detectable distance using a distance sensor located on the side closer to the inner wheel of vehicle A1. It is assumed that two pairs of injection and receiving parts are located at the rear end of vehicle A1. The two pairs of injection and receiving parts are located at different positions. The injection part 10A-1 and receiving part 10B-1 are also called the first pair. The injection part 10A-1 and receiving part 10B-1 are also called the second pair.

[0079] As shown in Figure 13, suppose vehicle A1 is moving backward while turning between parking spaces where vehicles B1 and B2 are parked. In this case, the reflected wave generated when the probe wave transmitted from the ejection unit 10A-1 is reflected by vehicle B1 may be received by the receiving unit 10B-1. In such a case, if the reflected wave received by the receiving unit 10B-1 is used, it may be possible that vehicle B1 parked in the adjacent parking space is mistakenly recognized as an obstacle in the surroundings before object M1, which is a wheel stop, is detected.

[0080] Therefore, when vehicle A1 is moving backward while turning, it is desirable to calculate the detectable distance using data showing the time-series change in the received intensity of the reflected wave received by a pair of receivers located on the side closer to the inner wheel of the vehicle, and a first threshold. This makes it possible to suppress the erroneous detection of objects outside the route that vehicle A1 is traveling.

[0081] Furthermore, two pairs of transmitters and receivers are positioned at the front of the vehicle, and it is desirable to calculate the detectable distance using the distance sensor located closer to the inner wheel of vehicle A1, even when vehicle A1 is moving forward while turning.

[0082] B8. Other Embodiments 8 As shown in the embodiment, let's assume that vehicle A1 is equipped with a pair of ejection units 10A and receiving units 10B. In the embodiment, a search wave was transmitted once, and the detectable distance was determined using the received reflected wave. Alternatively, for example, the processing unit 50 may transmit a new search wave after a predetermined time has elapsed since the transmission time of the previously transmitted search wave. In this case, the waveform synthesized by averaging the received intensity of the reflected wave of the previously transmitted search wave and the received intensity of the reflected wave of the later transmitted search wave may be used as the waveform of the reflected wave. When synthesizing the waveform, the range in which the received intensity exceeds the obstacle detection threshold ThA is excluded. Therefore, even if there is variation in the received intensity of the road surface reflected wave, the detectable distance can be calculated with accuracy. The waveform synthesized by averaging the received intensity is also called the waveform obtained by averaging the waveform of the reflected wave received earlier and the waveform of the reflected wave received later.

[0083] B9. Other Embodiments 9 In the embodiment, an example was described in which a waveform W1 representing the time-series change of the reflected wave and a waveform W2 representing the first threshold have an intersection point (see Figure 10). However, there are also cases where the waveform W1 representing the time-series change of the reflected wave and the waveform W2 representing the first threshold do not have an intersection point. In such cases, the processing unit 50 calculates the height of the detected obstacle, assuming there is no limitation on the detectable distance.

[0084] For example, if vehicle A1 is equipped with an automatic parking function, the calculated detectable distance can be used to control vehicle A1. The following control of vehicle A1 is performed in conjunction with, for example, the obstacle detection device 1 and the ECU installed in vehicle A1.

[0085] As shown in Figure 14, in state (A), the detectable distance is calculated to be 2 meters from the intersection of waveform W1, which represents the time-series change of the reflected wave, and waveform W2, which represents the first threshold. At this time, the received reflected wave does not contain any peaks exceeding the obstacle detection threshold ThA, and object M1 is not detected. In this case, vehicle A1 is controlled to move further backward at a speed below a predetermined speed.

[0086] In state (B), assume that the detectable distance is calculated to be 2 meters from the intersection of waveform W1, which represents the time-series change of the reflected wave, and waveform W2, which represents the first threshold. Also assume that the received reflected wave contains a peak that exceeds the obstacle detection threshold ThA, and that object M1 is detected. Furthermore, assume that the distance to object M1 is calculated to be 3 meters. However, since the distance to object M1 is greater than the detectable distance, the height of object M1 is not detected. In this case, the vehicle A1 is controlled to decelerate and move further backward.

[0087] In state (C), assume that the detectable distance is calculated to be 2 meters from the intersection of waveform W1, which represents the time-series change of the reflected wave, and waveform W2, which represents the first threshold. Assume that object M1 is detected from the received reflected wave. Assume that the distance to object M1 is calculated to be 2 meters. Since the distance to object M1 is less than or equal to the detectable distance, the height of object M1 is calculated. The height of object M1 is compared with a predetermined reference value, and if it is determined that it is difficult for vehicle A1 to go over object M1, vehicle A1 is controlled to move further backward to a position where it will not collide with object M1 before stopping.

[0088] B10. Other Embodiments 10 In this embodiment, an example was described in which the detectable distance L5 is calculated using the position on the time axis at the intersection point P1 of a waveform W1 representing the time-series change of the received reflected wave and a waveform W2 representing the first threshold. However, the method for calculating the detectable distance L5 is not limited to this.

[0089] For example, the detectable distance L5 can also be determined using a trained machine learning model. In the training phase, machine learning is performed using waveform data representing road surface reflected waves and a first threshold for received intensity, which is determined according to the propagation time until the reflected wave reflected off the top of an obstacle is received, as training data, and a machine learning model is generated. In the inference phase, the trained machine learning model is input with the received intensity for each predetermined period included in the waveform of the reflected wave, and the time information corresponding to each received intensity, and the detectable distance L5 is output.

[0090] B11. Other Embodiments 11 The method for detecting the height of an obstacle is not limited to the method described in the embodiment. The height of an obstacle can also be estimated using a trained machine learning model. A waveform within a certain range, including peaks, is extracted from the waveform representing the received signal. When the received intensity for each predetermined period, and the time information corresponding to each received intensity, which are included in the extracted waveform, are input to the trained machine learning model, the machine learning model outputs the height of object M1.

[0091] Furthermore, a neural network can be used that, for example, takes a waveform representing a reflected wave signal as input and outputs an estimated value of the obstacle's height. For example, the neural network may include not only a three-layer neural network, but also a four-layer or more DNN (Deep Neural Network), a CNN (Convolutional Neural Network) having convolutional and pooling layers, etc.

[0092] B12. Other Embodiments 12 Furthermore, the ejection unit 10A and the receiving unit 10B may be positioned at a distance from each other in the vehicle height direction (Z-axis direction) of the vehicle A1. Alternatively, the ejection unit 10A and the receiving unit 10B may be positioned at a distance from each other in the vehicle width direction (X-axis direction) and also at a distance from each other in the vehicle height direction (Z-axis direction) of the vehicle A1. When the receiving unit is positioned higher than the transmitting unit, the reception strength of reflected waves from obstacles on the road surface tends to be weaker compared to when the height of the receiving unit and the transmitting unit are the same. However, by positioning the ejection unit that transmits the search wave and the receiving unit that receives the reflected wave at different locations, the signal-to-noise ratio can be improved. Therefore, it is possible to suppress the upper end reflected wave from being buried by the road surface reflected wave and to detect the upper end reflected wave.

[0093] In this embodiment, an example in which ultrasound is used as the probe wave was described, but radio waves may also be used as the probe wave.

[0094] The control unit and method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control unit and method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0095] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0096] 1...Obstacle detection device, 10A, 10A-1, 10A-2...Ejection unit, 10B, 10B-1, 10B-2...Receiving unit, 20...Transmission circuit, 30...Receiving circuit, 50...Processing unit, 51...Obstacle detection unit, 53...Height detection unit, 55...Storage unit, A1...Vehicle, B1...Vehicle, B2...Vehicle, D1, D2, D3...Distance, Ex0...Exclusion range, Ex1...Exclusion range, F1...Dashed line, H1, H2...Curve, L1, L2...Distance, L 5, L5-1, L5-2…Detectable distance, M1, M2…Object, M5…Wheel stop, M6…Curb, P1…Intersection, S1, S2…Ultrasonic sensor, T0…Time, T1…Time, T2…Time, ThA…Obstacle detection threshold, Tpk1, Tpk2, Tpk10…Time, Tr1…Time, Tr2…Time, Vth1…Threshold, Vth2…Threshold, W1…Waveform, W2…Waveform, WA…Reflected wave, WB…Road surface reflected wave, WC…Composite wave

Claims

1. Obstacle detection device (1) mounted on a vehicle, A transmitter (10A) that transmits a probe wave, At least one receiving unit (10B) is positioned differently from the transmitting unit and receives reflected waves generated when the probe wave is reflected by an object, A determination unit (53) determines a detectable distance from the vehicle's current position to the height of the obstacle, using a first threshold for reception intensity, which is determined according to the propagation time until the reflected wave reflected off the upper end of the obstacle is received, and data showing the time-series change in reception intensity of the road surface reflected wave among the reflected waves received by the receiving unit, and using the propagation time at which the reception intensity of the road surface reflected wave is equal to or greater than the first threshold, An obstacle detection unit (51) detects the distance to the obstacle based on the reflected wave received by the receiving unit, A height detection unit (53) for detecting the height of the obstacle, If the detected distance is less than or equal to the detectable distance, the receiving unit detects the height of the obstacle based on the reflected wave it has received. A height detection unit that does not detect the height of the obstacle when the detected distance is greater than the detectable distance, An obstacle detection device equipped with [a specific feature].

2. Obstacle detection device according to claim 1, The first threshold is set based on distance-dependent data that shows the relationship between the received intensity of the reflected wave reflected at the upper end of a pre-prepared obstacle and the distance to the pre-prepared obstacle. The determination unit finds one of the intersection points between the waveform representing continuous data on the time axis of the received intensity of the reflected wave received by the receiving unit and the waveform representing the first threshold, and uses the position on the time axis where the intersection point is located to determine the detectable distance at which the height of the obstacle can be detected. Obstacle detection device.

3. Obstacle detection device according to claim 2, The aforementioned pre-prepared obstacle is an object with a height that is assumed to be a wheel stop or curb. Obstacle detection device.

4. An obstacle detection device according to any one of claims 1 to 3, In a predetermined time interval after the transmission of the exploration wave, if the received intensity of the reflected wave received by the receiving unit exceeds a second threshold that is greater than the first threshold, The determination unit determines a detectable distance from the vehicle's current position to the height of the obstacle, using the first threshold and a first range of data showing the time-series change in the received intensity of the reflected wave received by the receiving unit, excluding at least the range in which the received intensity exceeds the second threshold. Obstacle detection device.

5. Obstacle detection device according to claim 4, A pulse signal is transmitted as the aforementioned exploration wave. The determination unit, when the waveform representing the time-series change in the received intensity of the reflected wave received by the receiving unit includes a maximum point, and the received intensity at the maximum point exceeds the second threshold, uses the range including the maximum point, excluding the pulse width range of the pulse signal, as the first range. Obstacle detection device.

6. Obstacle detection device according to claim 1, The transmitting unit and the receiving unit are, Both are located at the front end of the vehicle, or both are located at the rear end of the vehicle. In the vehicle width direction, on one side from the vehicle center, the following are arranged at different positions in the vehicle width direction: Obstacle detection device.

7. Obstacle detection device according to claim 1, It comprises a first pair of the transmitting unit and the receiving unit, and a second pair of the transmitting unit and the receiving unit, The first pair of transmitting units is positioned differently from the second pair of transmitting units. The receiving unit of the first pair is positioned differently from the receiving unit of the second pair. The receiving unit of the first pair receives the reflected wave generated by the reflection of the probe wave transmitted by the transmitting unit of the first pair. The receiving unit of the second pair receives the reflected wave generated by the reflection of the probe wave transmitted by the transmitting unit of the second pair. The aforementioned determination unit, For each of the receiving units, the detectable distance is calculated using the position on the time axis where the intersection point of the waveform representing the time-series change in the received intensity of the reflected wave and the waveform representing the first threshold is located. The average value of the detectable distance calculated for each of the aforementioned receiving units is determined. The height detection unit is If the detected distance is less than or equal to the average value of the detectable distance, the height of the obstacle is detected. If the detected distance is greater than the average value of the detectable distance, the height of the obstacle is not detected. Obstacle detection device.

8. Obstacle detection device according to claim 1, The receiving unit comprises two or more of the above-mentioned receiving units, Each of the aforementioned receiving units is: The transmitting unit and the other receiving units are located in different positions. The transmitting unit receives the reflected wave that is generated when the probe wave transmitted by the transmitting unit is reflected. The aforementioned determination unit, For each of the receiving units, the detectable distance is calculated using the position on the time axis where the intersection point of the waveform representing the time-series change in the received intensity of the reflected wave and the waveform representing the first threshold is located. The average value of the detectable distance calculated for each of the aforementioned receiving units is determined. The height detection unit detects the height of the obstacle when the detected distance is less than or equal to the average value of the detectable distances. If the detected distance is greater than the detectable distance, the height of the obstacle is not detected. Obstacle detection device.

9. Obstacle detection device according to claim 1, The transmitting unit transmits a pulse signal as the probe wave, and then, after a predetermined time has elapsed, transmits another pulse signal. The determination unit determines the intersection point between the waveform obtained by averaging the waveform of the reflected wave received earlier and the waveform of the reflected wave received later, and the waveform representing the first threshold, and uses the position on the time axis where the intersection point is located to determine the detectable distance. Obstacle detection device.

10. Obstacle detection device according to claim 3, An image sensor that photographs the upper end of the obstacle in the direction of travel of the vehicle and outputs image data, A storage unit that stores a first threshold value, which is set in advance for each size of the radius of curvature of the cross-section passing through the central position of the front and rear ends of the vehicle at the upper end of the obstacle, and data indicating the correspondence between the degree of brightness change of the image data output by the image sensor and the radius of curvature. Furthermore, The transmitting unit and the receiving unit are both located at the front end of the vehicle, or both are located at the rear end of the vehicle. The determination unit determines the detectable distance using the first threshold defined for each radius of curvature, which is determined from the degree of brightness change of the image data output by the image sensor. Obstacle detection device.

11. Obstacle detection device according to claim 1, It comprises a first pair of the transmitting unit and the receiving unit, and a second pair of the transmitting unit and the receiving unit, The first pair of transmitting units is positioned differently from the second pair of transmitting units. The receiving unit of the first pair is positioned differently from the receiving unit of the second pair. The first pair of transmitting units and receiving units, and the second pair of transmitting units and receiving units are arranged at the rear end of the vehicle. The first pair of transmitting and receiving units are arranged on one side of the vehicle center in the vehicle width direction, and the second pair of transmitting and receiving units are arranged on the other side of the vehicle center in the vehicle width direction. The aforementioned determination unit, When the vehicle is moving backward while turning, the detectable distance is determined using the propagation time obtained using data showing the time-series change in the received intensity of the road surface reflected wave included in the reflected wave received by the receiving unit located closer to the inner wheel of the vehicle among the first pair and the second pair, and the first threshold. Obstacle detection device.

Images