Method for determining the position of an object using ultrasound and driver assistance system for determining the position of an object in the surroundings of a vehicle

Abstract

The invention relates to a method for determining the position of an object using ultrasound waves, wherein ultrasound pulses are emitted by at least two ultrasound sensors (11, 12, 13, 14) arranged at a distance from one another and ultrasound echoes reflected at the object are received, wherein provision is made for determining possible object positions using a raster map (200), wherein the cells (210) of the raster map (200) represent specific regions in the surroundings, each cell (210) being assigned a counter, the counters of those cells (210) being incremented which intersect a circular arc or a spherical surface defined by the distance assigned to a direct echo in the case of reception of a direct echo, and the counters of those cells (210) being incremented which intersect an elliptical arc or an ellipsoidal surface defined by the distance assigned to a cross echo and the relative position of the ultrasound sensors (11, 12, 13, 14) involved in the case of reception of a cross echo, wherein possible object positions are determined by the positions of those cells (210) whose counters are above a predefined boundary value. Further aspects of the invention relate to a computer program and a driver assistance system (300) which are designed to implement the method.

Description

Technical Field

[0001] This invention relates to a method for determining the position of an object using ultrasound, wherein at least two ultrasonic sensors arranged spaced apart from each other emit ultrasonic pulses and then receive ultrasonic echoes reflected by the object. Another aspect of the invention relates to a computer program and a driver assistance system configured to implement this method. Background Technology

[0002] Different driver assistance systems are known that assist a vehicle driver in performing various driving maneuvers, provide advance warnings of danger, and / or at least temporarily guide the vehicle automatically. To achieve these functions, these driver assistance systems rely on accurate data about objects in the surrounding environment (such as other road users and obstacles such as trees or pillars). Accurately determining the position of these objects relative to the vehicle is particularly important.

[0003] Least squares can be used to determine the location of an object. In least squares, multiple spatially spaced sensors are used to determine the distance between each sensor and the object. For example, ultrasonic distance sensors can be used for location determination based on least squares.

[0004] When multiple objects exist in the surrounding environment, the challenge arises in assigning the measured distances to the correct objects so that the correct circles or ellipses intersect. This mainly occurs in scenes with a large number of different objects, due to incorrect tangent points leading to incorrect locations or objects being inferred from places where no objects are present. The more sensors used, the more complex the selection of intersecting circles and ellipses becomes.

[0005] DE 100 27 828 A1 describes an active ultrasonic observation device that enables the identification of objects invisible in a medium due to smoke or fog. This active ultrasonic observation device includes at least one transmitter for emitting a transmitted signal and at least one receiver arranged at a known position relative to the transmitter. A grid is used to determine the spatial position, and the amplitude value of a reflected point is input into the grid. Here, the relative position is first determined by analyzing the echo, and then the reflected point is input into the grid.

[0006] EP 3 398 824 A1 discloses a braking system for an automated vehicle, comprising a distance sensor, a brake actuator, and a control unit. The control unit determines a "region of interest" within the field of view and defines an occupancy grid that divides the field of view into an array of grid cells. Objects identified by the distance sensor are assigned to grid cells, which are characterized in terms of repeatability for object recognition. The control unit determines whether a stationary object with repeatability for object recognition above a boundary value is located within the "region of interest," and upon identification of such a stationary object, the control unit activates the brake actuator.

[0007] Document DE 10 2013 018 315 A1 describes an environment model with an adaptive grid, in which data is received from at least one sensor system for environmental detection, and an environment model in the form of a grid map is created. Data from sensor systems, such as ultrasonic sensors, can be used for this purpose, and data from other sensor systems can be fused and confidence-checked if necessary. In this grid map, the size and / or arrangement of cells in the grid can vary according to driving conditions. Summary of the Invention

[0008] A method for determining the location of an object using ultrasound is proposed, wherein ultrasonic pulses are emitted by at least two ultrasonic sensors arranged spaced apart from each other, and ultrasonic echoes reflected at the object are received. In this setup, possible object locations are determined using a grid map, where cells of the grid map represent specific areas in the surrounding environment, and each cell is associated with a counter. Upon receiving a direct echo as an ultrasonic echo, the counters of those cells intersecting with arcuate or spherical surfaces, defined by distances associated with the direct echo, are incremented. Upon receiving a cross echo, the counters of those cells intersecting with elliptical or ellipsoidal surfaces, defined by distances associated with the cross echo and the relative positions of the participating ultrasonic sensors, are incremented. The possible object locations are then determined by the positions of those cells whose counters exceed a pre-given boundary value.

[0009] The object can be, for example, a traffic participant such as a vehicle or pedestrian, or an obstacle such as a tree or pillar.

[0010] To determine the location of an object, at least one of the ultrasonic sensors can, for example, emit an ultrasonic pulse, wherein two or more ultrasonic sensors can receive the ultrasonic echoes reflected by the object in the surrounding environment. Here, the ultrasonic echo received by the ultrasonic sensor that originally emitted the ultrasonic pulse is called the direct echo, while the ultrasonic echo received by one or more other ultrasonic sensors is called the cross echo. The distance to the object can be determined by the propagation time from the emission of the ultrasonic pulse to the reception of the ultrasonic echo and by the known speed of sound. Depending on the situation, especially when there are multiple objects in the surrounding environment, multiple ultrasonic echoes may be received by a single ultrasonic sensor for the emitted ultrasonic pulse.

[0011] Each ultrasonic sensor can emit ultrasonic pulses sequentially. Alternatively, two or more ultrasonic sensors can be configured to emit ultrasonic pulses simultaneously, wherein the ultrasonic pulses are preferably encoded for differentiation. For encoding, the ultrasonic pulses can be modulated and / or different frequencies can be used.

[0012] Raster maps can be configured in two or three dimensions, where each cell in the raster map represents a specific area of ​​the surrounding environment. Accordingly, each of these raster cells is associated with a location within a two-dimensional or three-dimensional area of ​​the surrounding environment. For example, the raster map could represent a spatial area with dimensions of 2.5m × 2.5m × 1m (length × width × height), using a 5cm grid. For this example, a raster map with 50 × 50 × 20 = 50,000 elements would be obtained.

[0013] The counter assigned to the cell can, for example, be represented as a variable in the memory of a computer device or controller, whereby the raster map can be represented accordingly as a two-dimensional or three-dimensional array. If an integer with a value range of 0-255 is chosen as the type of this variable, only one byte of storage space is needed for the counter. In the example above with a raster map of size 50×50×20 elements, only 50,000 bytes of memory would be required. Obviously, additional attributes—such as the obtained ultrasonic echo signal level—can also be assigned to each raster cell, and these attributes can be stored in memory accordingly.

[0014] Preferably, the length and width (road surface) dimensions are selected within the range of 1m to 10m, more preferably 2m to 5m, while the height dimension is selected within the range of 0.5m to 5m, more preferably 1m to 2m. The mesh size is preferably selected within the range of 1cm to 25cm, more preferably 2cm to 10cm. It is possible to consider using the same or different mesh sizes for different dimensions.

[0015] If the grid map is two-dimensional, circular and elliptical arcs are used to determine the cells representing the possible locations of objects. If the grid map is three-dimensional, spherical and ellipsoidal surfaces are used to determine these cells. In the case of direct echo, the radius of the circular or spherical surface is determined based on the distance obtained from the propagation time, wherein the ultrasonic sensor is located at the center of the circle or sphere. In the case of elliptical or ellipsoidal surfaces, the transmitting ultrasonic sensor is located at one focus, and the receiving ultrasonic sensor is located at the other focus. Here, for example, a method similar to the gardener's method can be used. Construct an elliptical arc, where the sum of the distances between points on the elliptical arc is given by the distance determined by the signal propagation time of the cross echo.

[0016] To determine the cells intersected by circular and / or elliptical arcs, or by spherical and / or ellipsoidal surfaces, the corresponding arcs or surfaces can be analytically represented and their intersections with cells in the raster map can be calculated. One possibility for determining the intersecting cells is an algorithm based on the Bresenham algorithm, which enables the rasterization of geometries such as circles.

[0017] If the cell counters increment by 1, then in the case of a 2D raster map, it is preferable to select a pre-given boundary value of 1 (≥1), while in the case of a 3D raster map, it is preferable to select ≥2. The higher the boundary value, the lower the probability of recognizing an object, even if no real object exists at that location. Conversely, as the boundary value increases, sensitivity decreases, thus increasing the probability of "not recognizing a real object as an object."

[0018] Not every region of an arc or surface is considered as an object location because the ultrasonic sensor can generally only receive ultrasonic echoes from a specific direction. Therefore, it is preferable that, upon receiving an echo, the counter of only the units representing physically capable of receiving the echo is incremented. Accordingly, it is preferable that the counter of a unit is incremented only if the unit is located within the area defined by the field of view of the ultrasonic sensor that has received the ultrasonic echo. Here, the field of view can be defined, for example, by a cone, where it can be checked, for example, whether each unit is within or tangent to the volume of the cone.

[0019] Furthermore, it is preferable to divide the field of view of the ultrasonic sensor into at least two partial regions, each of which is assigned a minimum signal level. The counter of a unit is incremented only when the unit is located in a partial region of that field of view where the minimum signal level is exceeded by the signal level of the received ultrasonic echo. For this purpose, the signal level of the received ultrasonic echo is determined in addition to the propagation time of the ultrasonic echo. The partial regions may, for example, be defined as nested cones, where, for example, a first cone represents the complete field of view, while a second cone with a smaller opening angle represents the core region. Ultrasonic echoes with high signal levels can only be reflected by objects located within the corresponding core region of the ultrasonic sensor. Accordingly, it is preferable to pre-define a minimum signal level for the core region that is higher than that for the field of view outside the core region.

[0020] Preferably, when incrementing the unit counter, the unit is associated with the received ultrasonic echo for further analysis and processing. Preferably, it stores which ultrasonic echoes have been received by the ultrasonic sensors, and preferably stores other attributes, such as distance determined by the propagation time of the ultrasonic echo and / or the signal level of the ultrasonic echo.

[0021] To more accurately determine the object's location, the least squares method can be additionally used. In the least squares method, the distance between each sensor and the object is determined using multiple spatially spaced sensors. Typically, the ultrasonic echoes received by two different sensors are sufficient for determination in two-dimensional space, while the ultrasonic echoes received by three different sensors are sufficient for determination in three-dimensional space. Potential ambiguities can usually be resolved by eliminating the possibility of objects located inside the vehicle or on the side facing away from the sensors.

[0022] Preferably, the possible object locations determined by the positions of those cells with counters having values ​​above the boundary values ​​are pre-selected for subsequent determination of the target object location using the least squares method. This is particularly advantageous if such cells are associated with received ultrasonic echoes, allowing the selection of either the ultrasonic echo or the distance associated with it for the least squares method. The location determination accuracy achieved through this least squares method can be superior to that of the grid size of a raster map.

[0023] Preferably, the location of objects is determined by applying filtering and / or machine learning methods to the created raster map. In particular, the locations of adjacent raster cells with counters above the boundary values, or those assigned to these raster cells, can be considered.

[0024] Such filtering can, for example, provide a weighted average of clusters of neighboring cells from counters with values ​​higher than a pre-given boundary, and the location of an object can be determined from this average.

[0025] By applying machine learning methods, it is possible to group specific structures composed of units with counters above a boundary value into objects. Furthermore, machine learning can be used to perform object classification. For example, in such object classification, it is possible to distinguish between vehicles, pedestrians, pillars, walls, etc.

[0026] Preferably, after one measurement cycle or a predetermined number of measurement cycles, the counters of all cells in the raster map are reset. Specifically, all cells are reset to the neutral value "0".

[0027] Preferably, a measurement cycle is considered complete after the ultrasonic sensor has emitted an ultrasonic pulse and received a corresponding ultrasonic echo, or after a maximum predetermined waiting time for receiving an ultrasonic echo has elapsed. For example, one ultrasonic sensor may send a signal and, for example, up to 12 ultrasonic sensors may receive the signal within a measurement cycle. Since each ultrasonic sensor can receive multiple ultrasonic echoes, for example, up to 20 ultrasonic echoes, up to 240 echoes can be received within a single measurement cycle.

[0028] Preferably, the proposed method is repeated continuously, so that the object position is obtained or updated in the same continuous manner. The obtained object and its determined position are preferably available for use by a driver assistance system.

[0029] According to the present invention, a computer program is also provided, wherein the methods described herein are implemented when the computer program is executed on a programmable computer device. The computer program may, for example, be a module for implementing a driver assistance system or its subsystems in a vehicle. The computer program may be stored on a machine-readable storage medium, such as a permanent or rewritable storage medium, or attached to a computer device, or stored on a removable CD-ROM, DVD, Blu-ray disc, or USB strip. Alternatively or additionally, the computer program may be provided on the computer device (e.g., on a server) for download, for example via a data network (such as the Internet) or via a communication connection (e.g., a telephone line or wireless connection).

[0030] Furthermore, according to the present invention, a driver assistance system for determining the position of objects in the environment surrounding a vehicle is provided, wherein the driver assistance system includes a plurality of ultrasonic sensors. Here, the driver assistance system is configured to implement one of the methods described herein.

[0031] Advantages of the present invention

[0032] This invention is particularly capable of accurately and reliably determining the location of an object using multiple ultrasonic sensors that receive object echoes, thereby providing an accurate two-dimensional or three-dimensional environmental map. By using a grid map, the computational overhead required for location determination increases only slightly with the increase in the number of sensors and / or the number of objects in the surrounding environment, thus enabling the method to be implemented resource-efficiently. This particularly allows the method to be implemented in conventional control equipment used to operate driver assistance systems. Attached Figure Description

[0033] The embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0034] The attached diagram shows:

[0035] Figure 1 : A schematic diagram of the transmission and reception of ultrasonic waves used to identify objects in the environment surrounding a vehicle;

[0036] Figure 2 A schematic diagram of a first example of a raster map of the vehicle's surroundings; and

[0037] Figure 3 : A schematic diagram of the field of view of the ultrasonic sensor in a vehicle. Detailed Implementation

[0038] In the following description of embodiments of the invention, the same reference numerals are used to denote the same or similar elements, and in some cases, repeated descriptions of said elements are omitted. The drawings are for illustrative purposes only, showing the subject matter of the invention.

[0039] Figure 1 The front of a vehicle 1 with a driver assistance system 300 is shown, which is used to determine the position of an object 2 in the surrounding environment of the vehicle 1.

[0040] exist Figure 1 In the illustrated embodiment, the driver assistance system 300 includes four ultrasonic sensors 11, 12, 13, and 14, all of which are arranged at the front of the vehicle 1. For example, the ultrasonic sensors 11, 12, 13, and 14 can be arranged in the bumper of the vehicle 1. The driver assistance system 300 further includes a controller 100 connected to the ultrasonic sensors 11, 12, 13, and 14. The controller 100 is configured to manipulate the connected ultrasonic sensors 11, 12, 13, and 14 to emit ultrasonic pulses 20 and to process the received ultrasonic echoes 31 and 43.

[0041] exist Figure 1In the situation shown, object 2 is located in front of vehicle 1. Obviously, there could be more than one object 2 in the surrounding environment, but for clarity, the process of this method is described with a single object 2.

[0042] To identify object 2 in the surrounding environment and determine its location, ultrasonic sensors 11, 12, 13, and 14 emit ultrasonic pulses 20 and receive ultrasonic echoes 31 and 43 reflected by object 2. For greater clarity, in Figure 1 Only the first ultrasonic sensor 11 is shown emitting ultrasonic pulse 20. Obviously, the other ultrasonic sensors 12, 13, and 14 are also capable of emitting ultrasonic pulse 20.

[0043] The ultrasonic pulse 20 is reflected by object 2. Here, the ultrasonic echo received by the first ultrasonic sensor 11 is called the direct echo 31, because the original ultrasonic pulse 20 was emitted by the first ultrasonic sensor 11. The ultrasonic echoes received by the other ultrasonic sensors 12, 13, and 14 are called cross echoes 43, wherein, for simplicity... Figure 1 The indication only indicates that the cross echo 43 is received through the third ultrasonic sensor 13.

[0044] Based on the propagation time from the emission of the ultrasonic pulse 20 to the reception of the direct echo 31, and based on the known speed of sound, the distance from the object 2 to the first ultrasonic sensor 11 can be determined. A distance can also be assigned to the cross echo 43 using the propagation time. In existing position determination methods, after obtaining the distance, the position of the object 2 relative to the ultrasonic sensors 11, 12, 13, and 14 is determined using the least squares method.

[0045] In the case of direct echo 31, the radius of arc 51 is determined based on the distance obtained from the propagation time; this arc describes the possible position of object 2. Here, the first ultrasonic sensor 11 is located at the center of arc 51. In the case of cross echo 43, the possible position of object 2 is described by elliptical arc 63, where the transmitting first ultrasonic sensor 11 is located at one focus, and the receiving third ultrasonic sensor 13 is located at another focus. For example, elliptical arc 63 can be constructed similarly to the gardener's method, where the sum of the distances to points on elliptical arc 63 is given by the distance determined from the signal propagation time of cross echo 43. The position of object 2 is given by the intersection of arc 51 and elliptical arc 63.

[0046] If multiple objects 2 are in the surrounding environment of vehicle 1, or if multiple ultrasonic sensors 11, 12, 13, and 14 emit ultrasonic pulses 20 and receive ultrasonic echoes 31 and 43 to determine distance, the number of distances to be considered in the least squares method increases. Here, it is not possible to determine which of the arcs 51 or elliptical arcs 63 must intersect each other for position determination solely from the obtained distances. Especially in scenarios with a large number of different objects 2, incorrect positions may be determined due to incorrect intersection points. Therefore, according to the present invention, after determining the distance by the propagation time of the received ultrasonic echoes 31 and 43, the distance is determined by the grid map 200 (see...). Figure 2 This determines the possible locations of objects.

[0047] against Figure 2 The situation shown, Figure 2 A grid map 200 is shown. In the example shown, the grid map 200 is a two-dimensional grid map with 10×10 elements or cells 210, which represent the surrounding environment area located in front of the vehicle 1.

[0048] In order to target Figure 1 The situation shown determines the possible location of object 2, and each cell in unit 210 is associated with a counter. If the arc 51 associated with the direct echo 31 intersects with the corresponding cell 210, the counter is incremented by a value of 1. Figure 2 In the illustration, these first units 211 are marked with a first shaded line. Similarly, for those assigned to cross echo 43 (see... Figure 1 For those units 210 where the elliptical arc 63 intersects, the counter also increments by a value of 1. Figure 2 In the illustration, these second units 213 are marked with a second shading line.

[0049] exist Figure 2 In the example shown, there are two overlapping units 215, which are marked not only by a first shading line but also by a second shading line. The counter of the overlapping unit 215 is incremented twice and therefore has the value "two". If a pre-given boundary value of 1 is given, only the counters of these overlapping units 215 exceed that boundary value and are considered as possible locations of object 2.

[0050] Figure 3 The field of view 81, 83 of the first ultrasonic sensor 11 and the third ultrasonic sensor 13 are schematically shown for a vehicle equipped with a driver assistance system 300. The second ultrasonic sensor 12 and the fourth ultrasonic sensor 14 also obviously have corresponding fields of view; for clarity, these fields of view are not shown in the diagram. Figure 3As shown in the diagram, fields of view 81 and 83 represent the following areas of the environment surrounding vehicle 1: within these areas, the ultrasonic sensors 11, 12, 13, and 14 are able to detect object 2 by receiving ultrasonic echoes 31 and 43. This can be used, for example, when creating a grid map 200 (see...). Figure 2 The counter is incremented only for the following units 210: the units are located within the fields of view 81, 83 of the ultrasonic sensors 11, 12, 13, 14 that receive the corresponding ultrasonic echoes 31, 43.

[0051] Additionally, it can be configured to divide the field of view (81, 83) into multiple sub-regions. Figure 2 In the example, each of the fields of view 81 and 83 is also assigned a core region 71 and 73, which are located entirely within the corresponding field of view 81 and 83, but are relatively small. When analyzing the received ultrasonic echoes 31 and 43, it is utilized that ultrasonic echoes 31 and 43 with high signal levels are only reflected by objects 2 located within the core regions 71 and 73 of the corresponding ultrasonic sensors 11, 12, 13, and 14. Accordingly, it is preferably configured that a minimum signal level is pre-given for each partial region, wherein a higher minimum signal level is pre-given for the core regions 71 and 73 than for the portions of the fields of view 81 and 83 located outside the core regions 71 and 73. Accordingly, the counter of unit 210 is incremented only when unit 210 is located in a partial region of the fields of view 81 and 83 where the minimum signal level of that partial region is exceeded by the signal level of the received ultrasonic echoes 31 and 43.

[0052] This invention is not limited to the embodiments described herein and the aspects emphasized therein. Rather, various modifications that are within the scope of the claims and are of skill to those skilled in the art can be implemented.

Claims

1. A method for determining the position of an object (2) using ultrasound, wherein, The ultrasonic sensors (11, 12, 13, 14) arranged spaced apart from each other emit ultrasonic pulses (20) and receive ultrasonic echoes (31, 43) reflected at the object (2), characterized in that possible object locations are determined using a grid map (200), wherein cells (210) of the grid map (200) represent specific areas in the surrounding environment, each cell (210) is equipped with a counter, and those cells intersecting with arcs (51) or spherical surfaces are counted upon receiving a direct echo (31). The counter of 210 is incremented, the arc or spherical surface is defined by the distance associated with the direct echo (31), and in the case of receiving a cross echo (43), the counters of those units (210) intersecting with the elliptical arc (63) or ellipsoidal surface are incremented, the elliptical arc or ellipsoidal surface is defined by the distance associated with the cross echo (43) and the relative position of the participating ultrasonic sensors (11, 12, 13, 14), wherein the possible object position is determined by the position of those units (210) whose counters are higher than a pre-given boundary value. The field of view (81, 83) of the ultrasonic sensors (11, 12, 13, 14) is divided into at least two partial regions, each of which is assigned a minimum signal level, and the counter of the unit (210) is incremented only when the unit (210) is located in the partial region of the field of view (81, 83) where the minimum signal level of the partial region is exceeded by the signal level of the received ultrasonic echo (31, 43), wherein the at least two partial regions are defined as cones arranged nested to each other.

2. The method according to claim 1, characterized in that, The counter of the unit (210) is incremented only when the unit (210) is located within the area defined by the field of view (81, 83) of the ultrasonic sensors (11, 12, 13, 14) that have received the ultrasonic echo (31, 43).

3. The method according to claim 1 or 2, characterized in that, As the counter of unit (210) is incremented, the unit (210) is associated with the received ultrasonic echoes (31, 43) for further analysis and processing.

4. The method according to claim 1 or 2, characterized in that, The possible object locations determined by the positions of those units (210) with counters having values ​​higher than the boundary value are used as a preselection for subsequently determining the position of object (2) using the least squares method.

5. The method according to claim 1 or 2, characterized in that, The location of object (2) is determined by applying filtering and / or machine learning methods to the created raster map (200).

6. The method according to claim 1 or 2, characterized in that, After one measurement cycle or a pre-given number of measurement cycles, the counters of all cells (210) of the raster map (200) are reset.

7. The method according to claim 6, wherein, A measurement cycle ends after one of the ultrasonic sensors (11, 12, 13, 14) has emitted an ultrasonic pulse (20) and received the corresponding ultrasonic echo (31, 43) by the ultrasonic sensor (11, 12, 13, 14).

8. A computer program that, when run on a computer, implements the method according to any one of claims 1 to 7.

9. A driver assistance system (300) for determining the position of an object (2) in the surrounding environment of a vehicle (1), wherein, The vehicle (1) includes a plurality of ultrasonic sensors (11, 12, 13, 14), characterized in that the driver assistance system (300) is configured to implement the method according to any one of claims 1 to 7.

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