Distance measuring device, distance measuring method, program, and automatic parking control method

Abstract

The present invention provides a distance measuring device, distance measuring method, program, and automatic parking control method that can accurately measure the distance to an object even when interference of reflected waves occurs. [Solution] The distance measuring device of the present disclosure includes a detection unit that detects the maximum point of the received wave intensity in a graph showing the relationship between the received wave intensity when the transmitted ultrasonic wave is reflected by an object and received, and the flight time of the ultrasonic wave, and a distance measuring unit that, in the graph, if there are multiple maximum points in the range where the received wave intensity is above a predetermined threshold, calculates the distance to the object based on the flight time at the maximum point with the lowest received wave intensity among the multiple maximum points.

Description

Technical Field

[0001] The present disclosure relates to a distance measuring device, a distance measuring method, a program, and an automatic parking control method for a vehicle equipped with the distance measuring device that measures the distance to a surrounding object based on the reflected wave of transmitted ultrasonic waves.

Background Art

[0002] Patent Document 1 discloses a parking assist device that detects a wheel stopper, which is a structure capable of stopping a vehicle by abutting against a wheel of the vehicle, and automatically parks the vehicle in accordance with the detected wheel stopper.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Some wheel stoppers have a shape including an inclined surface whose surface facing the wheel of the wheel stopper is inclined with respect to the ground and a vertical surface perpendicular to the ground. When ultrasonic waves are irradiated onto a wheel stopper having such a shape, the ultrasonic waves reflected by the inclined surface and the ultrasonic waves reflected by the vertical surface may interfere with each other. When interference of the reflected waves occurs, it may be difficult to accurately measure the distance from the vehicle to the wheel stopper.

[0005] The present disclosure contributes to providing a distance measuring device, a distance measuring method, a program, and an automatic parking control method that can accurately measure the distance to an object even when interference of the reflected waves occurs.

Means for Solving the Problems

[0006] A distance measuring device according to one aspect of the present disclosure includes a detection unit that detects a maximum point of received wave intensity from the received wave intensity of a reflected wave received when a transmitted ultrasonic wave is reflected by an object, and a distance measuring unit that, if there are multiple maximum points in a range where the received wave intensity is above a predetermined threshold, calculates the distance to the object based on the flight time of the ultrasonic wave at the maximum point with the lowest received wave intensity among the multiple maximum points.

[0007] A distance measuring method according to one aspect of the present disclosure includes the following steps: a computer performs the process of detecting a maximum point of received wave intensity from the received wave intensity of a reflected wave received after a transmitted ultrasonic wave is reflected by an object; and, if there are multiple maximum points within a range where the received wave intensity is above a predetermined threshold, the computer performs the process of calculating the distance to the object based on the flight time of the ultrasonic wave at the maximum point with the lowest received wave intensity among the multiple maximum points.

[0008] A program according to one aspect of this disclosure causes a computer to perform the following steps: a step of detecting a maximum point of received wave intensity from the received wave intensity of a reflected wave received after a transmitted ultrasonic wave is reflected by an object; and a step of calculating the distance to the object based on the flight time of the ultrasonic wave at the maximum point with the lowest received wave intensity among the multiple maximum points, if there are multiple maximum points in the range where the received wave intensity is above a predetermined threshold.

[0009] An automatic parking control method relating to one subject of this disclosure includes the following processes: a computer performs the following: a process of detecting a maximum point of received wave intensity from the received wave intensity of a reflected wave received after a transmitted ultrasonic wave is reflected by an object; if there are multiple maximum points in a range where the received wave intensity is above a predetermined threshold, a process of calculating the distance to the object based on the flight time of the ultrasonic wave at the maximum point with the lowest received wave intensity among the multiple maximum points; and a process of automatically driving the vehicle to park it in accordance with the position of the object based on the distance. [Effects of the Invention]

[0010] According to this disclosure, the distance to an object can be measured accurately even when interference of reflected waves occurs. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram illustrating how reflected waves interfere. [Figure 2] A diagram illustrating an example of the vehicle configuration according to the first embodiment. [Figure 3] Block diagram illustrating an example of the functional configuration of a distance measuring device according to the first embodiment. [Figure 4] This figure shows an example of a graph illustrating the relationship between wave intensity and flight time. [Figure 5] A flowchart illustrating an example of operation of the distance measuring device according to the first embodiment. [Figure 6] Block diagram showing an example of the functional configuration of a parking assistance device according to the first embodiment. [Figure 7] A flowchart illustrating an example of the overall operation of a vehicle when automatic parking control is performed by a parking assist device in a vehicle according to the first embodiment. [Figure 8A] This figure illustrates how the received intensity at multiple maximum points in a graph showing the relationship between received intensity and flight time changes due to disturbance factors. [Figure 8B] This figure illustrates how the received intensity at multiple maximum points in a graph showing the relationship between received intensity and flight time changes due to disturbance factors. [Figure 9] A diagram showing an example of the vehicle configuration according to the second embodiment. [Figure 10] Block diagram showing an example of the functional configuration of a distance measuring device according to the second embodiment. [Figure 11] A flowchart illustrating an example of operation of a distance measuring device according to the second embodiment. [Figure 12] A diagram illustrating the hardware configuration of a computer. [Modes for carrying out the invention]

[0012] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. However, detailed descriptions that are not necessary, such as detailed descriptions of well-known matters or redundant descriptions of substantially the same configurations, may be omitted.

[0013] <Overview> In a TOF (Time Of Flight) distance measuring device that transmits ultrasonic waves and receives the ultrasonic waves reflected by an object, and calculates the distance to the object using the flight time of the ultrasonic waves and the speed of sound, when the object has a plurality of surfaces that reflect ultrasonic waves, it is known that the reflected waves from each surface interfere with each other and the distance measuring accuracy decreases.

[0014] In a vehicle having an automatic parking function, in order to accurately park the vehicle at a desired parking position, it has been studied to accurately measure the position from the vehicle to the wheel stopper. There are some wheel stoppers whose shape includes an inclined surface with a surface facing the wheel being inclined with respect to the ground and a vertical surface perpendicular to the ground. When irradiating such a wheel stopper with ultrasonic waves, it has been found through experiments or simulations that interference of reflected waves is likely to occur.

[0015] FIG. 1 is a schematic diagram showing a state in which reflected waves cause interference in a wheel stopper including an inclined surface with a surface facing the wheel being inclined with respect to the ground and a vertical surface perpendicular to the ground. FIG. 1 shows a cross section in a plane perpendicular to the long side of the wheel stopper.

[0016] When ultrasonic waves are irradiated onto a wheel stopper including an inclined surface and a vertical surface and interference of reflected waves occurs, the measured flight time of the ultrasonic waves may deviate from the actual flight time, and it may be difficult to accurately calculate the distance to the wheel stopper using the flight time. Specifically, from past experience, it is known that when ultrasonic waves are irradiated onto a wheel stopper including an inclined surface and a vertical surface and interference of reflected waves occurs, the distance calculated based on the flight time becomes longer than the actual distance.

[0017] This disclosure provides a distance measuring device, distance measuring method, program, and automatic parking control method that can accurately measure the distance to a wheel stop even when interference of reflected waves occurs due to a wheel stop including an inclined surface and a vertical surface.

[0018] <First Embodiment> First, a first embodiment of this disclosure will be described.

[0019] (Overall structure) Figure 2 is a diagram illustrating an example of the configuration of a vehicle 100 according to the first embodiment. The vehicle 100 includes a first monitoring sensor 10, a distance measuring device 20, a parking assist device 30, and an in-vehicle network 40. The first monitoring sensor 10 and the distance measuring device 20, the first monitoring sensor 10 and the parking assist device 30, and the distance measuring device 20 and the parking assist device 30 are connected to each other in a manner that allows them to communicate with one another via the in-vehicle network 40. In the example shown in Figure 2, the distance measuring device 20 and the parking assist device 30 are shown as independent devices, but these functional configurations may be provided in the same device.

[0020] The first monitoring sensor 10 is a sonar sensor that transmits ultrasonic waves, receives ultrasonic waves reflected by objects surrounding the vehicle 100, and outputs the received ultrasonic wave intensity (wave height) and the ultrasonic wave flight time (TOF: Time of Flight) at predetermined intervals. The predetermined interval is, for example, a very short interval of time. Hereinafter, the information including the received ultrasonic wave intensity and ultrasonic wave flight time at the predetermined interval may be referred to as distance measurement event information. The first monitoring sensor 10 transmits ultrasonic waves from the vehicle 100 at least toward the rear of the vehicle 100. The first monitoring sensor 10 is installed, for example, on the rear bumper of the vehicle 100. The first monitoring sensor 10 may also be installed on the front bumper or left and right sides of the vehicle, and may transmit ultrasonic waves forward, to the left, or to the right.

[0021] The distance measuring device 20 measures the distance from the vehicle 100 to surrounding objects based on distance measurement event information acquired from the first monitoring sensor 10. The distance measuring device 20 is, for example, a computer mounted on the vehicle 100.

[0022] The parking assist device 30 performs automatic parking control on the vehicle 100, instructing it to park automatically in a parking space based on the distance to surrounding objects measured by the distance measuring device 20. The parking assist device 30 is, for example, a computer mounted on the vehicle 100.

[0023] (Functional configuration of the distance measuring device 20) Figure 3 is a block diagram illustrating an example of the functional configuration of a distance measuring device 20 according to the first embodiment. The distance measuring device 20 comprises a determination unit 21, a detection unit 22, and a distance measuring unit 23.

[0024] The determination unit 21 determines whether or not automatic parking control for the vehicle 100 is being performed by the parking assist device 30. The determination unit 21 can make this determination by, for example, receiving a signal from the parking assist device 30 via the in-vehicle network 40 indicating whether or not automatic parking control is being performed.

[0025] Based on the distance measurement event information acquired from the first monitoring sensor 10, the detection unit 22 creates a graph at predetermined intervals showing the relationship between the received signal strength included in the distance measurement event information and the flight time, and detects the maximum point of the received signal strength in the range where the received signal strength in the graph is equal to or greater than a predetermined threshold.

[0026] The predetermined threshold is a value set in advance to distinguish between the road surface and surrounding objects other than the road surface. The predetermined threshold is set in advance during the design phase of the parking assistance device 30, for example, by experiment or simulation. The point of maximum wave intensity at wave intensity above the predetermined threshold is likely to be caused by ultrasonic waves reflected by surrounding objects other than the road surface.

[0027] Figure 4 shows an example of a graph illustrating the relationship between wave intensity and flight time. In Figure 4, the horizontal axis represents flight time, and the vertical axis represents wave intensity. Figure 4 is a graph created based on distance measurement event information acquired when the surrounding object is a wheel stopper (see Figure 1) whose wheel-stopping surface (the surface facing the wheel) includes both an inclined surface and a vertical surface.

[0028] When the surrounding objects are wheel stops that include inclined and vertical surfaces, ultrasonic interference can cause multiple maximum points of received wave intensity to occur within a range where the received wave intensity is above a predetermined threshold, as shown in Figure 4. In the example shown in Figure 4, two maximum points, MP1 and MP2, are present.

[0029] Past experience has shown that when the surrounding objects are wheel stops that include both inclined and vertical surfaces, the received intensity at the maximal point MP2, which has a longer flight time, is higher than the received intensity at the maximal point MP1, which has a shorter flight time, as shown in Figure 4.

[0030] Based on the distance measurement event information, the detection unit 22 detects the maximum point of the received wave intensity within a range where the received wave intensity is above a predetermined threshold, based on the relationship between the received wave intensity and the flight time, as illustrated in Figure 4. In the following description, the maximum point of the received wave intensity within a range where the received wave intensity is above a predetermined threshold may be simply referred to as the maximum point.

[0031] Returning to the explanation of Figure 3, the distance measuring unit 23 calculates the distance from the vehicle 100 to the surrounding object at predetermined intervals, using the flight time at the maximum point, based on the distance measuring event information acquired from the first monitoring sensor 10.

[0032] The distance measuring unit 23 calculates the distance to surrounding objects using the flight time at the maximum point if there is only one maximum point in the graph showing the relationship between wave intensity and flight time.

[0033] If there are multiple maximum points in the graph showing the relationship between wave intensity and flight time, the distance measuring unit 23 calculates the distance to surrounding objects using the flight time at the maximum point with the lowest wave intensity among the multiple maximum points.

[0034] (Example of operation of the rangefinder 20) Figure 5 is a flowchart illustrating an example of the operation of the rangefinder 20. In the example of the operation of the entire vehicle 100 described later, the processing of the rangefinder 20 shown in the example of operation in Figure 5 is described as the processing of measuring the distance of surrounding objects.

[0035] In step S1, the distance measuring device 20 determines whether or not automatic parking control is being performed for the vehicle 100. If it is determined that automatic parking control is being performed for the vehicle 100 (step S1:Y), the process proceeds to step S3. If it is determined that automatic parking control is not being performed for the vehicle 100 (step S1:N), the process proceeds to step S2.

[0036] In step S2, the distance measuring device 20 calculates the distance to surrounding objects using the flight time at the maximum point with the highest wave intensity among multiple maximum points in a graph showing the relationship between wave intensity and flight time.

[0037] In step S3, the distance measuring device 20 calculates the distance to surrounding objects using the flight time at the point with the lowest wave intensity among multiple maximum points in a graph showing the relationship between wave intensity and flight time.

[0038] In Figure 5, within the dashed lines associated with steps S2 and S3, specific examples of flight times at the maximum points used to calculate distance in each step are shown in thick lines. In this way, the distance measuring device 20 changes the maximum points used to calculate distance depending on whether or not automatic parking control for the vehicle 100 is being performed. This results in the following effects.

[0039] If automatic parking control is not being performed for the vehicle 100, the distance measuring device 20 calculates the distance to surrounding objects using the flight time at the maximum point with the highest received wave intensity among multiple maximum points, for example, the maximum point with the highest received ultrasonic wave intensity. When automatic parking control is not being performed, it is not necessary to consider ultrasonic interference caused by wheel stops with inclined surfaces, so the distance to surrounding objects can be calculated as the distance with the highest received wave intensity and the highest probability of an object being present.

[0040] On the other hand, when automatic parking control is being performed for the vehicle 100, the distance measuring device 20 calculates the distance to surrounding objects using the flight time at the maximum point with the lowest wave intensity among multiple maximum points. As mentioned above, it is known that if the distance to surrounding objects where ultrasonic interference is likely to occur is calculated using the flight time at the maximum point with the highest wave intensity, the calculated distance will be longer than the actual distance. According to the distance measuring device 20 of the first embodiment, since the distance is calculated using the flight time at the maximum point with the lowest wave intensity, taking into account ultrasonic interference caused by wheel stops including inclined and vertical surfaces, such a situation can be avoided.

[0041] (Functional configuration of the parking assistance device 30) Figure 6 is a block diagram showing an example of the functional configuration of the parking assistance device 30. The parking assistance device 30 comprises a self-position estimation unit 31, a coordinate generation unit 32, a parking space detection unit 33, a path generation unit 34, a vehicle control unit 35, a collision determination unit 36, and a storage unit 37. In this embodiment, after the start of parking assistance (automatic parking) control, the parking assistance device 30 extracts a parking space as the target parking position from an image captured by a camera mounted on the vehicle 100, generates a path for the vehicle to travel from a predetermined position (parking start position) to the target parking position, compares and corrects the generated path with the actual travel position, and drives the vehicle to the target parking position.

[0042] The self-position estimation unit 31 estimates the position and orientation of the vehicle 100 when the parking assist device 30 performs automatic parking control on the vehicle 100. For example, the self-position estimation unit 31 reads feature point information from the surrounding environment map read from the storage unit 37 and, during playback driving, estimates the position and orientation of the vehicle 100 by comparing it with feature points based on information indicating the surrounding environment acquired by the first monitoring sensor 10 and surrounding images acquired by cameras mounted on the vehicle 100.

[0043] The coordinate generation unit 32 generates coordinate information of surrounding objects relative to the vehicle 100, based on distance information to surrounding objects obtained from the distance measuring device 20.

[0044] The coordinate information is, for example, information in the XY coordinate system. The X coordinate is the position coordinate of the vehicle 100 in the direction of travel during automatic parking (hereinafter also referred to as the X direction). The Y coordinate is the position coordinate in the direction perpendicular to the direction of travel and perpendicular to the side of the vehicle 100 (hereinafter also referred to as the Y direction).

[0045] For example, the coordinate generation unit 32 generates coordinate information of surrounding objects using the principle of triangulation.

[0046] The parking space detection unit 33 detects a space (parking space) in which the vehicle 100 will be parked by automatic parking control, based on information indicating the surrounding environment acquired by the first monitoring sensor 10 and surrounding images acquired by a camera mounted on the vehicle 100.

[0047] The path generation unit 34 generates a path that moves the vehicle 100 from its current position to the parking space without colliding with surrounding objects, based on the position information of the vehicle 100 estimated by the self-position estimation unit 31, the coordinate information of surrounding objects generated by the coordinate generation unit 32, and the position information of the parking space detected by the parking space detection unit 33. If any of the information changes while the vehicle control unit 35 is automatically driving the vehicle 100 according to the generated path, the path generation unit 34 may update the path based on the changed information.

[0048] The vehicle control unit 35 controls the vehicle 100 to automatically drive according to the route generated by the route generation unit 34.

[0049] The collision determination unit 36 ​​determines whether a collision will occur with a surrounding object during automatic driving by the vehicle control unit 35. The collision determination unit 36 ​​determines whether a collision has occurred based on distance information to the surrounding object obtained from the distance measuring device 20.

[0050] If the collision detection unit 36 ​​determines that a collision with a surrounding object is imminent, the vehicle control unit 35 stops automatic driving or slows down the vehicle. Based on the distance to the wheel stop measured by the distance measuring device 20, the vehicle control unit 35 slows down the vehicle 100 as it approaches the wheel stop. The vehicle control unit 35 controls automatic driving so that, for example, the wheels of the vehicle 100 stop in front of the wheel stop. Whether or not the surrounding object whose distance has been measured by the distance measuring device 20 is a wheel stop can be determined, for example, based on the surrounding image acquired by a camera mounted on the vehicle 100.

[0051] The memory unit 37 stores various information when the parking assist device 30 performs automatic parking control on the vehicle 100.

[0052] (Example of operation when automatic parking control is performed in vehicle 100) Figure 7 is a flowchart illustrating an example of the overall operation of the vehicle 100 when automatic parking control is performed by the parking assist device 30 in the vehicle 100 according to the first embodiment.

[0053] In step S11, the parking assist device 30 detects a parking space based on information about the surrounding environment acquired from the first monitoring sensor 10, or on surrounding images acquired from a camera mounted on the vehicle 100.

[0054] In step S12, the parking assist device 30 generates a movement path for the vehicle 100 based on the vehicle's position information, the coordinate information of surrounding objects, and the position information of the parking space.

[0055] In step S13, the parking assist device 30 controls the vehicle 100 to drive automatically based on the route generated in step S12. Even while the parking assist device 30 is controlling the vehicle 100 to drive automatically, if any of the information used to generate the route changes, it may update the route based on the updated information and perform automatic driving control based on the updated route.

[0056] In step S14, the distance measuring device 20 performs a distance measuring process to measure the distance to surrounding objects. The details of the distance measuring process in step S14 are as explained in Figure 5.

[0057] In step S15, the parking assist device 30 performs automatic driving control to stop the vehicle 100 in line with the wheel stop, based on the distance to the wheel stop acquired in step S14.

[0058] This operation enables the vehicle 100 to automatically park precisely in line with the position of the wheel stop. In the distance measurement process of step S14, as explained in conjunction with Figure 5, the distance measuring device 20 calculates the distance to the wheel stop using the flight time of the maximum point with the lowest received wave intensity when automatic parking control is in progress. This allows the distance measuring device 20 to accurately calculate the distance to the wheel stop even when the wheel stop includes inclined and vertical surfaces and interference occurs in the ultrasonic waves reflected by the wheel stop.

[0059] <Second Embodiment> Next, a second embodiment of the present disclosure will be described. In the description of the second embodiment, components similar to those in the first embodiment will be denoted by the same reference numerals and their description will be omitted. Also, in the description of the second embodiment, if a component has the same configuration as in the first embodiment but operates differently, it will be denoted by the reference numeral "A" and described accordingly.

[0060] It is known that external disturbances such as wind can affect ultrasound propagating through the air. For example, when external disturbances such as wind are present, the received intensity of ultrasound reflected from an object at the same location may be lower or higher compared to when no external disturbances are present.

[0061] In this second embodiment, taking into consideration the presence of such disturbance factors, the ranging device measures the distance to surrounding objects using the flight time of the maximum point with the shortest flight time among multiple maximum points in a graph showing the relationship between received signal strength and flight time.

[0062] Figures 8A and 8B illustrate how the received intensity at multiple maximum points in a graph showing the relationship between received intensity and flight time changes due to disturbance factors. Similar to Figure 4, Figures 8A and 8B are graphs created based on distance measurement event information acquired when the surrounding object is a wheel stopper (see Figure 1) whose wheel-stopping surface (the surface facing the wheel) includes both an inclined surface and a vertical surface. Figures 8A and 8B are graphs obtained by transmitting ultrasonic waves to a wheel stopper from the same distance and receiving the reflected ultrasonic waves.

[0063] Figure 8A is a graph similar to Figure 4 described above, and is based on measurement results in an environment where external disturbances such as wind can be ignored. In Figure 8A, within the range where the received wave intensity is above a predetermined threshold, the received wave intensity at the maximum point MP1, which has a shorter flight time, is lower than the received wave intensity at the maximum point MP2, which has a longer flight time.

[0064] On the other hand, Figure 8B is a graph based on measurement results in an environment where the influence of external disturbances such as wind is greater than in the example in Figure 8A. In Figure 8B, within the range where the received wave intensity is above a predetermined threshold, the received wave intensity at the maximum point MP3, which has a shorter flight time, is lower than the received wave intensity at the maximum point MP4, which has a longer flight time.

[0065] Thus, even under the same measurement conditions, the received wave intensity can change due to external disturbances such as wind.

[0066] Here, we consider calculating the distance to surrounding objects using the distance measurement method of the distance measuring device 20 described in the first embodiment, when external disturbance factors such as wind are large, as shown in Figure 8B. As shown in Figure 8B, if the received intensity of the maximum point MP3, which has a shorter flight time, is lower than the received intensity of the maximum point MP4, which has a longer flight time, then, as described in the first embodiment, if we try to calculate the distance using the maximum point with the lowest received intensity among the multiple maximum points, the distance will be calculated using the flight time of the maximum point MP4, which has a longer flight time. When calculating the distance using the maximum point with a longer flight time, there is a risk that the calculated distance to surrounding objects will be longer than the actual distance.

[0067] Therefore, in the second embodiment, considering the case where external disturbances such as wind are large, the distance is calculated using the flight time at the maximal point with the shortest flight time among multiple maximal points. As a result, in the example shown in Figure 8A, the flight time at maximal point MP1 is used, which is the same as the description of the first embodiment. Also, in the example shown in Figure 8B, the flight time at maximal point MP3 is used, which allows for a distance that is more in line with the actual distance than when the flight time at maximal point MP4 is used to calculate the distance.

[0068] However, the distance measurement method that uses the flight time of the maximal point with the shortest flight time among multiple maximal points to measure the distance to surrounding objects is applicable when the wheel stopper has inclined and vertical surfaces, as shown in Figure 1, and interference with reflected ultrasonic waves is likely to occur. However, it has been found that it is difficult to apply when the overall shape of the wheel stopper is such that interference with reflected ultrasonic waves is unlikely to occur, such as when the overall shape of the wheel stopper is approximately a rectangular parallelepiped. This is because if a distance measurement method that uses the flight time of the maximal point with the shortest flight time to measure the distance to surrounding objects with shapes that do not easily interfere is likely to calculate a distance that is shorter than the actual distance.

[0069] Therefore, in the second embodiment, the shape of the surrounding object is identified from the surrounding image acquired from the camera to determine whether or not it is a wheel stopper including inclined and vertical surfaces, and the maximum point used for distance calculation is changed based on the identification result. The configuration and operation of the second embodiment will be described below.

[0070] Figure 9 shows an example of the configuration of a vehicle 100A according to the second embodiment. As shown in Figure 9, the vehicle 100A according to the second embodiment includes a first monitoring sensor 10, a distance measuring device 20A, a parking assist device 30, an in-vehicle network 40, and a second monitoring sensor 50.

[0071] The second monitoring sensor 50 has a camera that takes pictures of the area around the vehicle 100A and outputs images of the area around the vehicle 100A.

[0072] Figure 10 is a block diagram showing an example of the functional configuration of the distance measuring device 20A according to the second embodiment.

[0073] As shown in Figure 10, the distance measuring device 20A according to the second embodiment has an identification unit 24.

[0074] The identification unit 24 identifies surrounding objects in the direction of travel of the vehicle 100 based on the surrounding image acquired from the second monitoring sensor 50 (camera). The identification unit 24 identifies whether the surrounding object is a wheel stopper, with the surface facing the wheel including an inclined surface and a vertical surface (see Figure 1).

[0075] The distance measuring unit 23A calculates the distance to surrounding objects using the flight time at the maximum point when there is only one maximum point in the graph showing the relationship between received signal strength and flight time.

[0076] If there are multiple maximum points in the graph showing the relationship between received signal strength and flight time, the distance measuring unit 23A changes the maximum point used to calculate the distance based on the identification result by the identification unit 24.

[0077] If the distance measuring unit 23A determines, based on the identification by the identification unit 24, that the surrounding object is a wheel stopper including inclined and vertical surfaces, it calculates the distance to the surrounding object using the flight time at the maximum point with the shortest flight time among multiple maximum points.

[0078] Furthermore, if the distance measuring unit 23A determines, based on the identification by the identification unit 24, that the surrounding object is not a wheel stopper including an inclined surface and a vertical surface, it calculates the distance to the surrounding object using the flight time at the maximum point with the lowest wave reception intensity among multiple maximum points.

[0079] Figure 11 is a flowchart illustrating an example of operation of the distance measuring device 20A according to the second embodiment.

[0080] In step S21, the distance measuring device 20A determines whether or not automatic parking control is being performed for the vehicle 100. If it is determined that automatic parking control is being performed for the vehicle 100 (step S21:Y), the process proceeds to step S22. If it is determined that automatic parking control is not being performed for the vehicle 100 (step S21:N), the process proceeds to step S23.

[0081] In step S22, the distance measuring device 20A determines whether the surrounding object is identified as a wheel stop (see Figure 1) that includes an inclined surface and a vertical surface. If the surrounding object is identified as a wheel stop that includes an inclined surface and a vertical surface (step S22:Y), the process proceeds to step S24. If the surrounding object is identified as not being a wheel stop that includes an inclined surface and a vertical surface (step S22:N), the process proceeds to step S25.

[0082] Furthermore, if a surrounding object is identified as not being a wheel stopper that includes inclined and vertical surfaces, this includes, for example, cases where the overall shape is a rectangular parallelepiped and the surface facing the wheel is a vertical surface (a wheel stopper that does not include inclined surfaces).

[0083] In step S23, the distance measuring unit 23 calculates the distance to the object using the flight time at the point with the highest wave intensity among multiple maximum points with wave intensity above a predetermined threshold, in a graph showing the relationship between wave intensity and flight time.

[0084] In step S24, the distance measuring unit 23 calculates the distance to the object using the flight time at the maximum point with the shortest flight time among multiple maximum points with a reception intensity above a predetermined threshold, in a graph showing the relationship between reception intensity and flight time.

[0085] In step S25, the distance measuring unit 23 calculates the distance to the object using the flight time at the point with the lowest wave intensity among multiple maximum points with wave intensity above a predetermined threshold, in a graph showing the relationship between wave intensity and flight time.

[0086] In Figure 11, within the dashed lines associated with steps S23, S24, and S25, specific examples of the flight time of the maximum point used to calculate the distance in each step are shown in thick lines. Thus, the distance measuring device 20A changes the maximum point used to calculate the distance depending on whether or not automatic parking control for the vehicle 100A is being performed. Furthermore, the distance measuring device 20A also changes the maximum point used to calculate the distance depending on whether or not the surrounding objects are wheel stops including inclined and vertical surfaces. This results in the following effects.

[0087] When automatic parking control is not being performed for the vehicle 100A, the distance measuring device 20A calculates the distance to surrounding objects using the flight time at the point with the highest received wave intensity among multiple maximum points, for example, the point with the highest received ultrasonic wave intensity. When automatic parking control is not being performed, it is not necessary to consider ultrasonic interference caused by wheel stops with inclined surfaces, so the distance to surrounding objects can be calculated as the distance with the highest received wave intensity and the highest probability of surrounding objects being present.

[0088] When automatic parking control is being performed for the vehicle 100A, and the surrounding object is a wheel stop that includes both an inclined surface and a vertical surface, the distance measuring device 20A calculates the distance to the surrounding object using the flight time at the maximum point with the shortest flight time among multiple maximum points. As described above, when external disturbance factors such as wind are large, calculating the distance using the flight time at the maximum point with the lowest wave intensity, as in the first embodiment, may result in calculating a distance that is longer than the actual distance. The distance measuring device 20A of the second embodiment takes into account cases where external disturbance factors are large and calculates the distance to the surrounding object using the flight time at the maximum point with the shortest flight time, thereby enabling accurate calculation of the distance to the wheel stop.

[0089] Furthermore, if automatic parking control is being performed for vehicle 100A, and the surrounding object is not a wheel stop including an inclined surface and a vertical surface, the distance measuring device 20A calculates the distance to the surrounding object using the flight time at the maximum point with the lowest wave reception intensity among multiple maximum points. If the distance to the surrounding object is measured using the flight time of the maximum point with the shortest flight time when the surrounding object is not a wheel stop including an inclined surface and a vertical surface, the calculated distance may be shorter than the actual distance. The distance measuring device 20A can prevent such a situation.

[0090] <Example of computer hardware configuration> The distance measuring devices 20, 20A and the parking assistance device 30 described in the above embodiments are computers, and their functional configuration is realized by the computer executing a predetermined program. Below, we will describe examples of the hardware configuration of the computer that realizes each of the functions of the distance measuring devices 20, 20A and the parking assistance device 30.

[0091] Figure 12 illustrates the hardware configuration of computer 2100. As shown in Figure 12, computer 2100 includes input devices 2101 such as input buttons and a touchpad, output devices 2102 such as a display and speakers, a CPU (Central Processing Unit) 2103, ROM (Read Only Memory) 2104, and RAM (Random Access Memory) 2105. Computer 2100 also includes storage devices 2106 such as a hard disk drive and SSD (Solid State Drive), a reader 2107 that reads information from recording media such as DVD-ROM (Digital Versatile Disk Read Only Memory) and USB (Universal Serial Bus) memory, and a transceiver 2108 that communicates via a network. The above components are connected by a bus 2109.

[0092] The reading device 2107 reads the program for realizing the functions of each of the above-mentioned parts from the recording medium on which the program is recorded and stores it in the storage device 2106. Alternatively, the transmitting / receiving device 2108 communicates with a server device connected to the network and stores the program for realizing the functions of each of the above-mentioned parts downloaded from the server device in the storage device 2106.

[0093] The CPU 2103 copies the program stored in the memory device 2106 to the RAM 2105, and then sequentially reads and executes the instructions contained in that program from the RAM 2105, thereby realizing the functions of each of the above-mentioned parts. Furthermore, when the program is executed, information obtained from the various processes described in each embodiment is stored in the RAM 2105 or the memory device 2106 and used as appropriate. [Industrial applicability]

[0094] This disclosure is useful for a distance measuring device that performs distance measurement processing by transmitting and receiving ultrasonic waves. [Explanation of Symbols]

[0095] 100, 100A Vehicles 10. First monitoring sensor 20,20A distance measuring device 21 Judgment section 22 Detection unit 23,23A distance measuring section 23A Distance measurement section 24 Identification Unit 30 Parking assist system 31 Self-position estimation part 32 Coordinate generator 33 Parking space detection unit 34 Path generation unit 35 Vehicle Control Unit 36 Collision determination section 37 Memory section 40 In-vehicle network 50 Second monitoring sensor

Claims

1. A detection unit that detects the point of maximum reception intensity from the reception intensity of the reflected wave received when the transmitted ultrasonic wave is reflected by an object, If there are multiple maximum points within a range where the received wave intensity is above a predetermined threshold, a distance measuring unit calculates the distance to the object based on the flight time of the ultrasonic waves at the maximum point with the lowest received wave intensity among the multiple maximum points. A distance measuring device equipped with the following features.

2. The distance measuring unit calculates the distance to the object based on the maximum point with the lowest wave reception intensity among the plurality of maximum points, or the flight time at the maximum point with the shortest flight time. The distance measuring device according to claim 1.

3. The system further includes a determination unit that determines whether or not automatic parking control for the vehicle is currently being performed. The distance measuring unit is If the automatic parking control is not in operation, the distance from the vehicle to the object is calculated based on the flight time at the maximum point with the highest wave intensity among the plurality of maximum points. If the automatic parking control is in operation, the distance is calculated based on the flight time at the maximum point with the lowest wave reception intensity or the maximum point with the shortest flight time among the plurality of maximum points. The distance measuring device according to claim 1.

4. The distance measuring unit is If the object is a wheel stopper, and the surface of the wheel stopper facing the wheel does not include an inclined surface with respect to the ground, the distance is calculated based on the flight time at the maximum point with the lowest wave reception intensity among the plurality of maximum points. If the object is a wheel stopper, and the surface of the wheel stopper facing the wheel includes the inclined surface, the distance is calculated based on the flight time at the maximum point with the shortest flight time among the plurality of maximum points. The distance measuring device according to claim 3.

5. Computers A process to detect the maximum point of the received wave intensity from the received wave intensity of the reflected wave that is received after the transmitted ultrasonic wave is reflected by an object, If there are multiple maximum points within a range where the received wave intensity is above a predetermined threshold, the process of calculating the distance to the object is performed based on the flight time of the ultrasonic waves at the maximum point with the lowest received wave intensity among the multiple maximum points. A distance measurement method that performs this operation.

6. The calculation process involves calculating the distance to the object based on the flight time at the maximum point with the lowest wave reception intensity or the maximum point with the shortest flight time among the plurality of maximum points. The distance measurement method according to claim 5.

7. The system further includes a process to determine whether or not automatic parking control for the vehicle is currently being performed. The calculation process described above is: If the automatic parking control is not in operation, the distance from the vehicle to the object is calculated based on the flight time at the maximum point with the highest wave intensity among the plurality of maximum points. If the automatic parking control is in operation, the distance is calculated based on the flight time at the maximum point with the lowest wave reception intensity or the maximum point with the shortest flight time among the plurality of maximum points. The distance measurement method according to claim 5.

8. The calculation process described above is: If the object is a wheel stopper, and the surface of the wheel stopper facing the wheel does not include an inclined surface with respect to the ground, the distance is calculated based on the flight time at the maximum point with the lowest wave reception intensity among the plurality of maximum points. If the object is a wheel stopper, and the surface of the wheel stopper facing the wheel includes the inclined surface, the distance is calculated based on the flight time at the maximum point with the shortest flight time among the plurality of maximum points. The distance measurement method according to claim 7.

9. A procedure for detecting the maximum point of the received wave intensity from the received wave intensity of the reflected wave received after the transmitted ultrasonic wave is reflected by an object, If there are multiple maximum points within a range where the received wave intensity is above a predetermined threshold, a procedure for calculating the distance to the object based on the flight time of the ultrasonic waves at the maximum point with the lowest received wave intensity among the multiple maximum points, A program that causes a computer to execute something.

10. Computers A process to detect the maximum point of the received wave intensity from the received wave intensity of the reflected wave that is received after the transmitted ultrasonic wave is reflected by an object, If there are multiple maximum points within a range where the received wave intensity is above a predetermined threshold, the process of calculating the distance to the object is performed based on the flight time of the ultrasonic waves at the maximum point with the lowest received wave intensity among the multiple maximum points. A process to automatically drive the vehicle to park it in accordance with the position of the object based on the distance, An automatic parking control method that performs this operation.

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