DE102020205683A1 - Method for determining the position of objects using ultrasound and a driver assistance system for determining the position of an object in the vicinity of a vehicle - Google Patents

Abstract

The invention relates to a method for determining the position of objects using ultrasound, with ultrasound pulses being transmitted and ultrasound echoes reflected on objects being received again by at least two spaced apart ultrasound sensors (11, 12, 13, 14). It is provided that possible object positions are determined using a grid map (200), with one cell (210) of the grid map (200) representing a specific area in the vicinity, each cell (210) being assigned a counter, and in the case of one received direct echoes the counters are increased for those cells (210) which intersect an arc or a spherical surface which is defined by a distance assigned to the direct echo, and in the case of a received cross echo, the counters are increased for those cells (210) which have a Cut an elliptical arc or an ellipsoid surface, which is defined by a distance assigned to the cross echo and the relative position of the ultrasonic sensors (11, 12, 13, 14) involved, with possible object positions being determined via the positions of those cells (210) whose counters are above a predetermined limit value is. Further aspects of the invention relate to a Computerp rogram and a driver assistance system (300), which are set up to carry out the method.

Description

The invention relates to a method for determining the position of an object using ultrasound, with ultrasound pulses being transmitted and ultrasound echoes reflected from objects being received again by at least two ultrasound sensors arranged at a distance from one another. Further aspects of the invention relate to a computer program and a driver assistance system which are set up to carry out the method.

State of the art

Various driver assistance systems are known which support a driver of a vehicle in the execution of various driving maneuvers, warn a driver of dangers and / or can automatically guide a vehicle at least at times. For their function, the driver assistance systems are dependent on precise data about objects such as other road users and obstacles such as trees or posts in the vicinity. The exact determination of the position of objects relative to the vehicle is particularly important.

To determine the position of an object, lateration methods can be used in which the distance between the respective sensor and the object is determined using a plurality of spatially spaced sensors. For example, distance sensors based on ultrasound can be used for a position determination based on lateration methods.

If there are several objects in the vicinity, it is a challenge to assign the individual measured distances to the correct object for the application of the lateration method, so that the correct circles or ellipses are intersected with one another. Especially in scenarios with a large number of different objects, it can happen that incorrect points of intersection create incorrect positions or that objects are assumed to be in places where there is no object. The more sensors are used, the more complex the selection of the circles and ellipses to be intersected with one another becomes.

DE 100 27 828 A1 describes an active ultrasonic vision device which makes objects in a medium recognizable, which are not visible through smoke or fog. The active ultrasonic viewing device comprises at least one transmitter for transmitting a transmission signal and at least one receiver arranged in a known position relative to the transmitter. To determine a position in space, a grid is used in which the amplitude values for reflection points are entered. First, the relative position is determined by evaluating the echoes and then the reflection point is entered in the grid.

EP 3 398 824 A1 discloses a braking system for an automated vehicle that includes a distance sensor, a brake actuator and a control unit. The control unit determines a “region of interest” in a field of view and defines an occupancy grid which divides the field of view into an array of grid cells. Objects recognized by the distance sensor are assigned to a grid cell and the grid cells are characterized by means of an indication of the repeatability of an object detection. The control unit determines whether a solid object with a repeatability of the object detection is located in the “region of interest” above a limit value and the control unit activates the brake actuator when such a solid object is detected.

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 detecting the environment and an environment model is created in the form of a grid map. For this purpose, data from sensor systems such as ultrasonic sensors can be used and, if necessary, fused with data from other sensor systems and checked for plausibility. In the case of the grid map, the size and / or the arrangement of the cells in the grid can be changed depending on the driving situation.

Disclosure of the invention

A method is proposed for determining the position of an object using ultrasound, with ultrasound pulses being transmitted and ultrasound echoes reflected on objects being received again by at least two ultrasound sensors arranged at a distance from one another. It is provided that possible object positions are determined using a grid map, with a cell of the grid map representing a specific area in the vicinity and a counter being assigned to each cell. In the case of a received direct echo as ultrasonic echoes, the counters are incremented for those cells which intersect an arc of a circle or a spherical surface which is defined by a distance assigned to the direct echo, and in the case of a received cross echo, the counters are incremented for those cells which have an elliptical arc or intersect an ellipsoid surface which is defined by a distance assigned to the cross echo and the relative position of the ultrasonic sensors involved. Possible object positions are then based on the positions of those Cells whose count is above a predetermined limit.

The objects can be, for example, road users such as vehicles or pedestrians or obstacles such as trees or posts.

For a determination of the position of an object, for example, at least one of the ultrasonic sensors can emit an ultrasonic pulse, wherein ultrasonic echoes reflected from an object in the vicinity can be received by two or more ultrasonic sensors. The ultrasonic echo received by the ultrasonic sensor that originally transmitted the ultrasonic pulse is called the direct echo and the ultrasonic echo received by the other ultrasonic sensor (s) is called the cross echo. The distance to the object can then be determined from the transit time, which elapses from the transmission of the ultrasonic pulse to the reception of the ultrasonic echo, and the known speed of sound. Depending on the situation, in particular if there are several objects in the vicinity, several ultrasonic echoes can also be received by a single ultrasonic sensor for a transmitted ultrasonic pulse.

The individual ultrasonic sensors can each emit ultrasonic pulses one after the other. Additionally or alternatively, it can be provided that two or more ultrasonic sensors transmit ultrasonic pulses at the same time, these being preferably coded for differentiation. For coding, the ultrasonic pulses can be modulated and / or can use different frequencies.

The grid map can in particular be designed two-dimensionally or three-dimensionally, with each of the cells of the grid map representing a specific area of the environment. Correspondingly, each of the grid cells is assigned a position in the two-dimensional or three-dimensional area of the environment. The grid map can represent, for example, a spatial area with the dimensions 2.5 mx 2.5 mx 1 m (length x width x height), a grid of 5 cm being used. This example results in a grid map with 50 x 50 x 20 = 50,000 elements.

The counter assigned to a cell can be represented, for example, as a variable in a memory of a computer device or a control device, in which case the grid map can accordingly be represented as a two- or three-dimensional array. If an integer with the value range 0 to 255 is selected as the type for the variable, only one byte of storage space is required for the counter. In the above-mentioned example with a grid map measuring 50 x 50 x 20 elements, only 50,000 bytes of memory would be required accordingly. Of course, it is possible to assign further attributes to each grid cell and to store them accordingly in a memory, such as, for example, a determined signal level of the ultrasonic echo.

The dimensions in length and width (street level) in the range from 1 m to 10 m, preferably from 2 m to 5 m and in height in the range from 0.5 m to 5 m, preferably from 1 m to 2 m, are preferred chosen. The grid size is preferably selected in the range from 1 cm to 25 cm, preferably in the range from 2 cm to 10 cm. It is conceivable to use the same or different grid sizes for the different dimensions.

If the grid map is two-dimensional, arcs of circles and arcs of ellipses are used to determine the cells which represent possible positions of an object. If the grid map is three-dimensional, spherical surfaces and ellipsoidal surfaces are used to determine the cells. In the case of a direct echo, the distance determined on the basis of the transit time determines the radius of the circle or the surface of the sphere, the ultrasonic sensor being in the center of the circle or sphere. In the case of an ellipse or an ellipsoidal surface, the transmitting ultrasonic sensor is in one focal point and the receiving ultrasonic sensor is in the other focal point. The elliptical arc can be constructed in analogy to the gardening method, the sum of the distances between the points of the elliptical arc being given over the distance determined from the signal propagation time of the cross echo.

To determine the cells which are intersected by the circular arcs and / or elliptical arcs or by the spherical surfaces and / or ellipsoidal surfaces, the corresponding arc or the corresponding surface can be displayed analytically and points of intersection with the cells of the grid map can be determined. One possibility for determining the cut cells is an algorithm based on the Bresenham algorithm, which enables geometric shapes such as circles to be rasterized.

The counter of a cell increases by the value 1 is increased, the predetermined limit value is preferably selected to be 1 in the case of a two-dimensional grid map and preferably 2 is selected in the case of a three-dimensional grid map. The higher the selected limit, the lower the probability of recognizing an object even though there is no real object at this point. Conversely, the sensitivity decreases when the limit value is increased, so that the probability increases that a real object will not be recognized as such.

Not every area of an arc or a surface can be used as an object position, since the ultrasonic sensors can only receive ultrasonic echoes from certain directions. Therefore, when an echo is received, only the counters of those cells are preferably incremented which represent an area from which it is physically possible to receive an echo. Accordingly, it is preferably provided that the counter of a cell is only increased when the cell is in an area defined by a field of view of the ultrasonic sensor that received the ultrasonic echo. The field of vision can be defined, for example, by means of a cone, in which case it can then be checked, for example, whether the respective cell lies within the volume of the cone or touches this cone.

It is also preferably provided that the field of view of an ultrasonic sensor is divided into at least two sub-areas, each of the sub-areas being assigned a minimum signal level and the counter of a cell is only increased if the cell is in a sub-area of the viewing area whose minimum signal level is through the signal level of the received ultrasonic echo is exceeded. For this purpose, it is provided that, in addition to the transit time of an ultrasonic echo, the signal level of the received ultrasonic echo is also determined. The partial areas can be defined, for example, as cones arranged one inside the other, with a first cone representing the complete field of vision and a second cone with a smaller opening angle representing a core area. An ultrasonic echo with a high signal level can only be reflected by an object that is located in the core area of the respective ultrasonic sensor. Accordingly, it is preferably provided that the minimum signal level is specified higher for a core area than for the viewing area outside the core area.

If the counter of a cell is increased, this cell is preferably linked to the received ultrasonic echo for further evaluation at a later date. It is preferably stored through which of the ultrasonic sensors the respective ultrasonic echo was received and further attributes such as, for example, the distance determined from the transit time of the ultrasonic echo and / or the signal level of the ultrasonic echo are preferably stored.

In order to determine the position of an object more precisely, lateration methods can also be used, in which the distance between the respective sensor and the object is determined using several spatially spaced sensors. Ultrasonic echoes received from two different sensors are usually sufficient for a determination in 2D space and ultrasonic echoes received from three different sensors for a determination in 3D space. Any existing ambiguities can generally be resolved in that a possible position for an object, which is located inside the vehicle or on a side facing away from the sensors, can be discarded.

The possible object positions determined via the positions of the cells with a counter above the limit value are preferably used as a preselection for a subsequent determination of the position of an object using a lateration method. If received ultrasound echoes have been assigned to such a cell, in particular these ultrasound echoes or the distances assigned to these ultrasound echoes can be selected for carrying out the lateration. The accuracy achieved via such a lateration can be better than the grid size of the grid map.

The position of an object is preferably determined by applying a filter method and / or a machine learning method to the grid map created. In particular, adjacent grid cells can be taken into account with a counter above the limit value or their assigned positions.

With such a filtering, for example, weighted mean values for clusters of neighboring cells can be formed with counters above the predetermined limit value and a position of an object can be determined therefrom.

By applying machine learning methods, certain structures from cells can be combined into objects with a counter above the limit value. Furthermore, machine learning methods can be used to carry out an object classification. For example, with such an object classification, a distinction can be made between vehicles, pedestrians, posts, walls and so on.

The counters of all cells of the grid map are preferably reset after running through a measuring cycle or a predetermined number of measuring cycles. In particular, all cells are set back to the neutral value "0".

A measurement cycle is preferably considered to be completed after an ultrasound sensor has sent an ultrasound pulse and the associated ultrasound echoes have been received by the ultrasound sensors or the maximum predetermined waiting time for receiving one Ultrasonic echoes has been exceeded. For example, one ultrasonic sensor can transmit in one measurement cycle and, for example, up to 12 ultrasonic sensors can receive the signal. Because each ultrasonic sensor can receive several ultrasonic echoes, for example up to 20 ultrasonic echoes, up to 240 echoes, for example, could be received in a single measurement cycle.

The proposed method is preferably repeated continuously, so that the object positions are also continuously determined or updated. The determined objects and their determined positions are preferably made available to a driver assistance system.

According to the invention, a computer program is also proposed according to which one of the methods described herein is carried out when the computer program is executed on a programmable computer device. The computer program can be, for example, a module for implementing a driver assistance system or a subsystem thereof in a vehicle. The computer program can be stored on a machine-readable storage medium, for example on a permanent or rewritable storage medium or in association with a computer device or on a removable CD-ROM, DVD, Blu-Ray disc or a USB stick. Additionally or alternatively, the computer program can be made available for download on a computer device such as a server, for example via a data network such as the Internet or a communication connection such as a telephone line or a wireless connection.

According to the invention, a driver assistance system for determining the position of objects in the vicinity of a vehicle is also proposed, the driver assistance system comprising a plurality of ultrasonic sensors. The driver assistance system is set up to carry out one of the methods described herein.

Advantages of the invention

In particular when using a large number of ultrasonic sensors which receive echoes from objects, the invention enables an exact and reliable determination of the position of the objects and in this way provides an accurate two-dimensional or three-dimensional map of the surroundings. Using the grid map increases the number of sensors and / or objects in the area and the computing effort required for determining the position increases only slightly, so that the method can be implemented in a way that conserves resources. In particular, this enables the method to be implemented in conventional control units which are used to operate driver assistance systems.

Figure list

Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

• 1 Eine schematische Darstellung des Aussendens und Empfangens von Ultraschall zur Erkennung eines Objekts in der Umgebung eines Fahrzeugs,
• 2 eine schematische Darstellung einer Gitterkarte der Umgebung des Fahrzeugs und
• 3 eine schematische Darstellung der Sichtbereiche von Ultraschallsensoren des Fahrzeugs.

Show it:

• 1 A schematic representation of the transmission and reception of ultrasound to detect an object in the vicinity of a vehicle,
• 2 a schematic representation of a grid map of the surroundings of the vehicle and
• 3 a schematic representation of the viewing areas of ultrasonic sensors of the vehicle.

Embodiments of the invention

In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference numerals, a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

1 shows a front of a vehicle 1 with a driver assistance system 300 for determining the position of objects 2 in the vicinity of the vehicle 1 .

The driver assistance system 300 includes in the in 1 embodiment shown four ultrasonic sensors 11 , 12th , 13th , 14th all of which are at the front of the vehicle 1 are arranged. The ultrasonic sensors 11 , 12th , 13th and 14th can for example in a bumper of the vehicle 1 be incorporated. The driver assistance system 300 also includes a control unit 100 , which with the ultrasonic sensors 11 , 12th , 13th , 14th connected is. The control unit 100 is set up for this purpose, the connected ultrasonic sensors 11 , 12th , 13th , 14th for sending ultrasonic pulses 20th to control and received ultrasonic echoes 31 , 43 to process.

In the In 1 there is an object 2 in front of the vehicle 1 . Of course, there can also be more than one object 2 are located in the area, however, for a better overview, the procedure is carried out on a single object 2 described.

To objects 2 to recognize in the environment and to determine their position, send the Ultrasonic sensors 11 , 12th , 13th , 14th Ultrasonic pulses 20th from and receiving objects 2 reflected ultrasonic echoes 31 , 43 . For a better overview, the 1 just sending out an ultrasonic pulse 20th by a first ultrasonic sensor 11 shown. Of course, the other ultrasonic sensors can also 12th , 13th , 14th also ultrasonic pulses 20th send out.

The ultrasound pulse 20th is from the object 2 reflected. One of the first ultrasonic sensors 11 received ultrasonic echo as direct echo 31 as the original ultrasound pulse 20th through the first ultrasonic sensor 11 was sent out. From another of the ultrasonic sensors 12th , 13th , 14th received ultrasonic echoes are called cross echoes 43 referred to, in order to simplify the representation of the 1 only the reception of the cross echo 43 by a third ultrasonic sensor 13th is drawn.

Based on the transit time from the transmission of the ultrasonic pulse 20th until the direct echo is received 31 passes, as well as the known speed of sound can then be the distance of the object 2 to the first ultrasonic sensor 11 to be determined. Also the cross echo 43 a distance can be assigned over the running time. In the case of the position determination methods known from the prior art, the position of the object is provided directly after the distances have been determined by means of a lateration method 2 relative to the ultrasonic sensors 11 , 12th , 13th , 14th to determine.

With the direct echo 31 the distance determined on the basis of the running time determines the radius of a circular arc 51 , the possible positions of the object 2 describes. The first ultrasonic sensor is located here 11 in the center of the circular arc 51 . At the cross echo 43 are the possible positions of the object 2 through an elliptical arc 63 described, wherein the transmitting first ultrasonic sensor 11 in a focal point and the receiving third ultrasonic sensor 13th is in the other focal point. The elliptical arc 63 can be constructed, for example, in analogy to the gardening method, with the sum of the distances between the points of the elliptical arc 63 from the signal propagation time of the cross echo 43 a certain distance is given. The position of the object 2 is through the intersection of the circular arc 51 with the elliptical arc 63 given.

If there are multiple objects 2 in the vicinity of the vehicle 1 or are used to determine distances by several of the ultrasonic sensors 11 , 12th , 13th , 14th Ultrasonic pulses 20th emitted and ultrasonic echoes 31 , 43 received again, the number of distances to be taken into account during lateration increases. It is not clear from the obtained distances alone which of the arcs of the circle 51 or elliptical arcs 63 have to be cut with each other for position determination. Especially in scenarios with a lot of different objects 2 it can happen that incorrect positions are formed due to incorrect intersection points. Therefore, according to the invention, provision is made after determining the distances via the transit times of the received ultrasonic echoes 31 , 43 , possible object positions via a grid map 200 , compare 2 to determine.

2 shows for the in 2 the situation shown is a grid map 200 . The grid map 200 is in the example shown a two-dimensional grid map with 10 x 10 elements or cells 210 which one in front of the vehicle 1 represents the lying area of the environment.

To determine possible positions of the object 2 for those in the in 1 situation shown is each of the cells 210 assigned a counter. This counter is around the value 1 increased if the direct echo 31 assigned circular arc 51 the corresponding cell 210 cuts. In the representation of the 2 these were the first cells 211 marked with a first hatching. Likewise is the counter for those cells 210 about the value 1 increases which of the cross echo 43 , compare 1 , associated elliptical arc 63 get cut. In the representation of the 2 became these second cells 213 marked with a second hatching.

In the in 2 In the example shown, there are two overlapping cells 215 , which are marked with both the first hatching and the second hatching. The counter of these overlapping cells 215 has been raised twice and is therefore equal to two. If a limit value of 1 is specified, only the counters of these overlapping cells are exceeded 215 this limit value and come as possible positions for the object 2 in question.

3 shows schematically for the vehicle 1 with the driver assistance system 300 Viewing areas 81 , 83 of the first ultrasonic sensor 11 and the third ultrasonic sensor 13th . Of course, a second ultrasonic sensor also has 12th and a fourth ultrasonic sensor 14th corresponding viewing areas, which are shown in the representation of the 3 are not shown for a better overview. The viewing areas 81 , 83 represent those areas around the vehicle 1 represent in which the respective ultrasonic sensors 11 , 12th , 13th , 14th Objects 2 by receiving ultrasonic echoes 31 , 43 can detect. This can be used, for example, when creating the grid map 200 , compare 2 , just the counters for those cells 210 to increase which is within the field of view 81 , 83 of the ultrasonic sensor 11 , 12th , 13th , 14th lie, the corresponding ultrasonic echo 31 , 43 received.

In addition, the viewing areas can be provided 81 , 83 to be divided into several sub-areas. In the example of the 2 is to each of the viewing areas 81 , 83 another core area 71 , 73 assigned, which each completely within the corresponding field of view 81 , 83 but is smaller. When evaluating received ultrasound echoes 31 , 43 is then exploited that an ultrasonic echo 31 , 43 with a high signal level only from one object 2 reflected in the core area 71 , 73 of the respective ultrasonic sensor 11 , 12th , 13th , 14th is located. Accordingly, provision is preferably made for minimum signal levels to be specified for each of the individual sub-areas, the minimum signal level for the core areas 71 , 73 is specified higher than for the part of the viewing areas 81 , 83 that is outside the core areas 71 , 73 lies. An increment in a cell's counter 210 is made accordingly only if the cell 210 in a part of the field of vision 81 , 83 whose minimum signal level is determined by the signal level of the received ultrasonic echo 31 , 43 is exceeded.

The invention is not restricted to the exemplary embodiments described here and the aspects emphasized therein. Rather, a large number of modifications are possible within the range specified by the claims, which are within the scope of expert action.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 10027828 A1 [0005]
• EP 3398824 A1 [0006]
• DE 102013018315 A1 [0007]

Claims (10)

Method for determining the position of objects (2) using ultrasound, with ultrasound pulses (20) being transmitted and ultrasound echoes (31, 43) reflected on objects (2) from at least two spaced apart ultrasound sensors (11, 12, 13, 14) ) are received again, characterized in that possible object positions are determined using a grid map (200), wherein a cell (210) of the grid map (200) represents a specific area in the environment, a counter is assigned to each cell (210), and in the case of a received direct echo (31) the counters are incremented for those cells (210) which intersect an arc (51) or a spherical surface which is defined by a distance assigned to the direct echo (31), and in the case of a received cross echo (43) the counters are incremented for those cells (210) which intersect an elliptical arc (63) or an ellipsoidal surface which d A distance assigned to the cross echo (43) and the relative position of the ultrasonic sensors (11, 12, 13, 14) involved are defined, with possible object positions being determined via the positions of those cells (210) whose counter is above a predetermined limit value. Procedure according to Claim 1 , characterized in that the counter of a cell (210) is only increased when the cell (210) is in a field of view (81, 83) of the ultrasonic sensor (11, 12, 13, 14) that detects the ultrasonic echo (31, 43) has received the defined area. Procedure according to Claim 2 , characterized in that the viewing area (81, 83) of an ultrasonic sensor (11, 12, 13, 14) is divided into at least two sub-areas, each of the sub-areas being assigned a minimum signal level and an increase in the counter of a cell (210) only made when the cell (210) lies in a partial area of the viewing area (81, 83) whose minimum signal level is exceeded by the signal level of the received ultrasonic echo (31, 43). Method according to one of the Claims 1 until 3 , characterized in that when the counter of a cell (210) is increased, this cell (210) is linked to the received ultrasonic echo (31, 43) for further evaluation at a later date. Method according to one of the Claims 1 until 4th , characterized in that the possible object positions determined via the positions of the cells (210) with a counter above the limit value are used as a preselection for a subsequent determination of the position of an object (2) using a lateration method. Method according to one of the Claims 1 until 5 , characterized in that the position of an object (2) is determined by applying a filter method and / or a machine learning method to the grid map (200) created. Method according to one of the Claims 1 until 6th , characterized in that the counters of all cells (210) of the grid map (200) are reset after running through a measuring cycle or a predetermined number of measuring cycles. Procedure according to Claim 7 , a measurement cycle being completed after one of the ultrasonic sensors (11, 12, 13, 14) has transmitted an ultrasonic pulse (20) and the associated ultrasonic echoes (31, 43) have been received by the ultrasonic sensors (11, 12, 13, 14) . Computer program that executes the method according to one of the Claims 1 until 8th when it runs on a computer. Driver assistance system (300) for determining the position of objects (2) in the vicinity of a vehicle (1), the vehicle (1) comprising a plurality of ultrasonic sensors (11, 12, 13, 14), characterized in that the driver assistance system ( 300) is set up to perform one of the methods according to one of the Claims 1 until 8th to execute.

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