METHOD FOR DETERMINING THE LOCATION OF AN OBJECT

Description

[0001] The invention relates to a method and a system for determining the position of an object in the surrounding area of ​​a vehicle.

[0002] It is generally known to determine the position of objects in the surrounding area of ​​a vehicle using several sensors that only allow distance measurement but not direction determination, and a tracking method in which several reflections are determined in several consecutive transmission-reception cycles.

[0003] When detecting a reflection at a second sensor resulting from a transmission signal from a first sensor located at a different location than the second sensor, it is often assumed that the object is located on a circle. This is an approximate consideration, since the potentially possible positions of the object where the reflection occurred lie on an ellipse around the first and second sensor positions. Since the calculations required for tracking methods become very complex when using ellipses and therefore require considerable computing power, this ellipse is approximated by a circle whose center lies centrally on the connecting line between the first and second sensor positions.

[0004] DE 10 2016 105 022 A1 discloses a method for detecting at least one object in the environment of a motor vehicle. For this purpose, a first sensor is controlled to emit a sensor signal, and a second sensor receives sensor data that describes the sensor signal reflected by the at least one object. Furthermore, it is provided that a fuzzy feature is determined from the sensor data as an object feature for describing the at least one object, wherein the fuzzy feature describes a distance between the at least one object and a position of the first sensor and / or a position of the second sensor. The fuzzy feature is described as an ellipse, wherein focal points of the ellipse are determined based on the position of the first sensor and the second sensor.Furthermore, a major semi-axis of the ellipse is determined based on a travel time of the sensor signal and a length of a minor semi-axis of the ellipse is determined based on the focal points and the length of the major semi-axis.

[0005] WO 2020 / 012852 A1 discloses a positioning assistance device for enabling improvement of the positioning accuracy of an object by calculating the position according to the shape of the object. The device includes a unit for identifying the position of the peripheral object based on an intersection point calculated by an intersection point position calculation unit. The peripheral object position identification unit determines a first line segment connecting intersection points of a circle and an ellipse obtained when a specific distance measuring sensor is driven to receive a self-transmitted signal.Further, the peripheral object position identification unit determines a second line segment connecting intersection points of a circle and an ellipse obtained when the specific distance measuring sensor is driven to receive a cross echo. The object position is then determined based on the first line segment and the second line segment.

[0006] The article by D. Bank and T. Kampke, "High-Resolution Ultrasonic Environment Imaging," in IEEE Transactions on Robotics, vol. 23, no. 2, pp. 370-381, April 2007, describes a method for obtaining high-resolution images of a vehicle's environment by determining line-shaped segments that describe the boundaries of geometric environmental objects.

[0007] Approximating the ellipse with a circle has the disadvantage of reducing the calculation accuracy, resulting in inaccurate and unstable contours of an object in the vehicle's surroundings. These calculation inaccuracies sometimes lead to reflections being incorrectly assigned to an object.

[0008] Based on this, it is the object of the invention to provide a method for calculating the position of an object which has a high degree of accuracy and, at the same time, a low computational complexity.

[0009] This object is achieved by a method having the features of independent patent claim 1. Preferred embodiments are the subject of the dependent claims. A system for calculating the position of an object is the subject of independent patent claim 7.

[0010] According to a first aspect, the invention relates to a method for determining the position of an object using a sensor system of a vehicle. The vehicle has at least a first sensor with a first sensor position and a second sensor with a second sensor position, different from the first sensor position. The method comprises the following steps: First, at least a partial area of ​​an ellipse is calculated, wherein the ellipse is formed by points at which the distance from the first sensor position via the respective point to the second sensor position is constant. In other words, the points at which a signal transmitted at the first sensor must be reflected in order to be received at the second transmitter and the signal propagation time is constant lie on an ellipse around the first and second sensor positions.

[0011] Subsequently, an ellipse segment is determined that lies within the detection range of both the first sensor and the second sensor. The ellipse segment has a first and a second ellipse endpoint.

[0012] An intermediate point of the ellipse segment is then determined, which is located on a perpendicular bisector to the connecting line between the first and second ellipse endpoints.

[0013] A circular segment is then determined that passes through the first and second ellipse endpoints and the ellipse segment intermediate point.

[0014] Finally, the position of the object is determined based on the circle segment.

[0015] The technical advantage of the method according to the invention is that the ellipse is approximated by a circle that is adapted as precisely as possible to the shape of the ellipse in the area detectable by both sensors. This significantly reduces inaccuracies in position determination due to the approximation of the ellipse by a circle or circular segment.

[0016] According to one embodiment, the ellipse segment extends along the entire overlap area of ​​the detection range of the first sensor with the detection range of the second sensor. This optimizes the approximation of the ellipse by the circle or circular segment over the entire area in which the potential reflection location may be located.

[0017] According to one embodiment, determining the circle or the circular segment comprises calculating the radius of the circular segment and determining a center point of this circle or this circular segment.

[0018] According to one embodiment, the center of the circle or circular segment is determined by determining the point on the perpendicular bisector of the connecting line between the first and second ellipse endpoints that is at a distance equal to the radius of the circle or circular segment from the intermediate point of the ellipse segment. This results in a circle or circular segment approximating the ellipse, passing through the two ellipse endpoints and the intermediate point of the ellipse segment, and thus approximating the ellipse within the detection range of both sensors.

[0019] According to one embodiment, the first and second sensors are ultrasonic sensors. In principle, other sensors are also conceivable, in particular those that provide distance measurement without direction determination (1D sensors).

[0020] According to one embodiment, the position of the object relative to the vehicle is determined by iteratively repeating the method steps of one of the preceding embodiments over multiple transmission and reception cycles of the first and second sensors (so-called tracking algorithms). Such methods allow the position of an object to be determined even if the sensors do not allow the direction in which the reflection occurred to be determined.

[0021] According to a further aspect, the invention relates to a system for determining the position of an object. The system comprises a sensor system arranged on a vehicle. The sensor system has at least a first sensor with a first sensor position and a second sensor with a second sensor position different from the first sensor position. The system also has a computing unit configured to perform the following steps: Calculating at least a partial area of ​​an ellipse, wherein the ellipse is formed by points at which the distance from the first sensor position via the respective point to the second sensor position is constant; determining an ellipse section that lies both in the detection range of the first sensor and in the detection range of the second sensor, wherein the ellipse section has a first and a second ellipse end point; determining an ellipse section intermediate point that is located on a mid-perpendicular to the connecting line between the first and second ellipse end points; determining a circle or circle section that runs through the first and second ellipse end points and the ellipse section intermediate point; and determining the position of the object based on the circle or circle section.

[0022] According to one embodiment of the system, the ellipse segment extends along the entire overlap area of ​​the detection range of the first sensor with the detection range of the second sensor. This optimizes the approximation of the ellipse by the circle or circular segment over the entire area in which the potential reflection location may be located.

[0023] According to one embodiment of the system, the computing unit is configured to determine the circle or the circular segment by calculating a radius of the circle or the circular segment and determining a center point of this circle or this circular segment.

[0024] According to one embodiment of the system, the computing unit is configured to determine the center point of the circle or circular segment by determining the point on the perpendicular bisector to the connecting line between the first and second ellipse endpoints that is at a distance equal to the radius of the circle or circular segment from the intermediate point of the ellipse segment. This results in a circle or circular segment approximating the ellipse, which passes through the two ellipse endpoints and the intermediate point of the ellipse segment, thus approximating the ellipse within the detection range of both sensors.

[0025] According to one embodiment of the system, the first and second sensors are ultrasonic sensors. In principle, other sensors are also conceivable, in particular those that provide distance measurement without direction determination (1D sensors).

[0026] According to one embodiment of the system, the computing unit is configured to determine the position of an object relative to the vehicle by iteratively determining a circle or a segment of a circle over multiple transmission and reception cycles of the first and second sensors (so-called tracking algorithms). Such methods allow the position of an object to be determined even if the sensors do not allow the direction in which the reflection occurred to be determined.

[0027] The terms "approximately", "substantially" or "about" mean, in the sense of the invention, deviations from the exact value by + / - 10%, preferably by + / - 5% and / or deviations in the form of changes that are insignificant for the function.

[0028] Further developments, advantages, and possible applications of the invention will become apparent from the following description of exemplary embodiments and from the figures. All described and / or illustrated features, individually or in any combination, are fundamentally the subject of the invention, regardless of their summary in the claims or their reference back to them. The content of the claims is also incorporated into the description.

[0029] The invention is explained in more detail below with reference to exemplary embodiments and the figures. They show: Fig. 1 an example of a top view of a vehicle with an environmental detection system having a plurality of sensors; Fig. 2 by way of example, a schematic representation of a detection situation with two sensors spaced apart from one another, in which the ellipse on which the reflecting object could be located is approximated by circles whose centers lie centrally between the sensor positions; Fig. 3 by way of example and schematically the determination of a segment of an ellipse which is to be approximated by a circle or segment of a circle; Fig. 4 exemplary and schematically the determination of an ellipse segment intermediate point and the determination of the circle radius and the circle center for the ellipse segment according to Fig. 3 ; and Fig. 5 An example of a block diagram that illustrates the process steps for determining the position of an object.

[0030] Figur 1 shows, by way of example and in a roughly schematic manner, a vehicle F which has a plurality of sensors. In particular, the vehicle has a first sensor S1 and a second sensor S2 which are provided at different positions on the vehicle. Preferably, the vehicle F has more than two sensors which are provided distributed around the vehicle F. The sensors can in particular be distance-measuring sensors, for example ultrasonic sensors. Alternatively, the sensors can also be radar sensors or LIDAR sensors. However, the sensors preferably do not have the ability to determine the direction from which a received, reflected signal component of the transmitted signal originates. Such sensors are often referred to as 1D sensors. The determination of the distance of an object at which the reflection occurs can be based on the propagation time between the transmission time and the reception time.

[0031] The sensors are coupled to a computer unit R, which has at least one processor and at least one memory unit. This computer unit R is configured to perform the method sequences disclosed in this document and thus achieve improved distance determination of detected objects.

[0032] Fig. 2 shows a schematic plan view of a detection situation in which, for example, a first sensor S1, which is arranged at a first sensor position SP1, transmits a transmission signal, a reflection occurs at an object O and a second sensor S2, which is provided at a second sensor position SP2 which is different from the first sensor position SP1, receives a reflected portion of this transmission signal.

[0033] Assuming a linear propagation of the transmitted signal in the environment of the vehicle, the possible points at which the reflection occurred lie on an ellipse E, which is Fig. 2 is shown as a solid line. This is because the distance between the first sensor position SP1, any point on the ellipse E, and the second sensor position SP2 is constant, and thus, based on the detected signal propagation time, the reflecting object could be located at any point on the ellipse E.

[0034] The first sensor has a first detection range EB1 and the second sensor S2 has a second detection range EB2.

[0035] Since the calculation of the position of the reflecting object, which is preferably performed using a tracking method based on information obtained in several consecutive transmit-receive cycles, is more complex based on ellipses and thus requires more computing time, the ellipse E is often approximated by a circle or a circular segment. The center of the circle or circular segment is often assumed to be a point on the connecting line between the first and second sensor positions SP1, SP2, which is equidistant from the first and second sensor positions SP1, SP2, i.e., the center of the connecting line.

[0036] In Fig. 2 A first circle K1 and a second circle K2 are shown, by means of which the ellipse E can be approximated. The first circle K1 has a radius equal to the longer semi-axis a of the ellipse E and is therefore tangent to the ellipse E on the outside; the second circle K2 has a radius equal to the shorter semi-axis b of the ellipse E and is therefore tangent to the ellipse E on the inside.

[0037] A disadvantage of this method is that the approximation of the ellipse E by both the first circle K1 and the second circle K2 leads to sometimes significant inaccuracies in determining the distance to the detected object. As a result, tracking algorithms cannot determine an accurate and stable contour of an object. The inaccuracies increase the further the first and second sensor positions SP1, SP2 are separated, as this causes the semi-axes a, b of the ellipse E to differ more in length.

[0038] The following is based on the Figuren 3 and 4 A method is described by which the inaccuracies occurring when approximating the ellipse E by a circle or a circle segment can be reduced. A detection scenario is used that is similar to that of Fig. 1 is identical.

[0039] First, an ellipse segment EA of the ellipse E is determined, which can be detected by the two sensors S1 and S2. The ellipse segment EA is determined based on the intersection of the detection areas EB1, EB2 of the first and second sensors S1, S2. The detection areas EB1, EB2 create intersection points with the ellipse E. The ellipse segment EA is determined by those intersection points that lie in both the first and second detection areas EB1, EB2. The ellipse segment EA is in Fig. 3 indicated by the thickened line. The ellipse segment EA has a first ellipse endpoint EP1 and a second ellipse endpoint EP2.

[0040] The following procedural steps serve to approximate the ellipse segment EA by a circle or a circle segment. In other words, a circle segment is determined that replicates the ellipse segment EA as closely as possible, i.e., with the smallest possible deviations.

[0041] First, as in Fig. 4 As shown, an intermediate point Z of the ellipse segment is determined. This is done by first determining a connecting line VG between the first ellipse endpoint EP1 and the second ellipse endpoint EP2. Subsequently, the perpendicular bisector is formed on this connecting line VG, and the intersection point of this perpendicular bisector with the ellipse segment EA is determined. This intersection point between the perpendicular bisector and the ellipse segment EA forms the intermediate point Z of the ellipse segment.

[0042] Subsequently, a circle or a circular segment KA is determined which passes through the first ellipse end point EP1, the second ellipse end point EP2 and the ellipse segment intermediate point Z.

[0043] The triangle with the corners EP1, EP2 and Z is an isosceles triangle, based on which the radius r of the circle or the radius of the circular segment KA can be determined using geometric relationships known to the person skilled in the art.

[0044] The radius r is determined in particular by the following formula: r = sin γ 2 sin α ;

[0045] The center M of the circle or circular segment KA is determined based on the calculated radius r by determining the point on the center line that is at a distance r from the ellipse segment intermediate point Z. It should be noted that the distance of the center M to the connecting line VG is smaller than the distance to the ellipse segment intermediate point Z.

[0046] As in Fig. 4 As can be seen, the center point M is not centrally located between the sensor positions SP1, SP2, so that the approximation accuracy is improved by the method.

[0047] Fig. 5 shows a diagram that illustrates the process steps for determining the position of an object.

[0048] After completing a transmit-receive cycle, a sensor receives a reflection resulting from a transmitted signal sent by another sensor. The travel time of the signal between transmission and reception can be used to determine a distance traveled.

[0049] Subsequently, at least a partial area of ​​an ellipse is calculated, wherein the ellipse is formed by points for which the distance from the first sensor position via the respective point to the second sensor position is constant and corresponds to the aforementioned propagation time of the signal (S10).

[0050] Subsequently, an ellipse segment is determined that lies within the detection range of both the first sensor and the second sensor (S11). The ellipse segment has a first and a second ellipse endpoint.

[0051] Subsequently, an intermediate point of the ellipse segment is determined, which is located on a perpendicular bisector to the connecting line between the first and second ellipse endpoints (S12).

[0052] A circular segment is then determined which passes through the first and second ellipse endpoints and the ellipse segment intermediate point (S13).

[0053] Finally, the position of the object where the reflection occurred is determined based on the circular segment (S14).

[0054] The invention has been described above using exemplary embodiments. It is understood that numerous changes and modifications are possible without departing from the scope of protection defined by the patent claims. List of reference symbols

[0055] a, b Semi-axes of the ellipse EEllipse EAEllipse section EB1 Detection range of first sensor EB2 Detection range of second sensor EP1 First ellipse end point EP2 Second ellipse end point F Vehicle K1 First circle K2 Second circle KA Circular section M Center point OBject r Radius R Computing unit S1 First sensor S2 Second sensor SP1 First sensor position SP2 Second sensor position VG Connecting line Z Ellipse section intermediate point

Claims

1. Method for determining the situation of an object by means of a sensor system of a vehicle (F), the vehicle (F) having at least one first sensor (S1) with a first sensor position (SP1) and a second sensor (S2) with a second sensor position (SP2), which is different from the first sensor position (SP1), wherein the method is performed using a computing unit and has the following steps: - calculating at least a subregion of an ellipse (E), the ellipse (E) being formed by points for which the distance from the first sensor position (SP1) via the respective point to the second sensor position (SP2) is constant (S10), and the distance being ascertained from the propagation time of a signal between the sending of the signal by the first sensor and the receiving of the signal reflected from the object by the second sensor; characterized by the further steps of: - determining an elliptical segment (EA) situated both within the detection range (EB1) of the first sensor (S1) and within the detection range (EB2) of the second sensor (S2), the elliptical segment (EA) having a first and a second ellipse end (EP1, EP2) (S11); - determining an elliptical segment intermediate point (Z) located on a perpendicular bisector of the connecting line between the first and second ellipse ends (EP1, EP2) (S12); - determining a circle or a circular segment (KA) that passes through the first and second ellipse ends (EP1, EP2) and the elliptical segment intermediate point (Z) (S13); and - determining the situation of the object on the basis of the circle or the circular segment (KA) (S14).

2. Method according to Claim 1, characterized in that the elliptical segment (EA) extends along the entire region of overlap of the detection range (EB1) of the first sensor (S1) and the detection range (EB2) of the second sensor (S2).

3. Method according to Claim 1 or 2, characterized in that the determination of the circular segment (KA) comprises a calculation of the radius (r) of the circle or the circular segment (KA) and a determination of a centre (M) of this circle or this circular segment (KA).

4. Method according to one of the preceding claims, characterized in that the centre (M) of the circle or circular segment (KA) is determined by determining that point on the perpendicular bisector of the connecting line between the first and second ellipse ends (EP1, EP2) which is at a distance equal to the radius (r) of the circle or the circular segment (KA) from the elliptical segment intermediate point (Z).

5. Method according to one of the preceding claims, characterized in that the first and second sensors (S1, S2) are ultrasonic sensors.

6. Method according to one of the preceding claims, characterized in that the position of the object relative to the vehicle (F) is determined by iteratively repeating the method steps of one of the preceding claims over multiple transmission and reception cycles of the first and second sensors (S1, S2).

7. System for determining the situation of an object comprising a sensor system arranged on a vehicle (F), the sensor system having at least one first sensor (S1) with a first sensor position (SP1) and a second sensor (S2) with a second sensor position (SP2), which is different from the first sensor position (SP1), wherein the system has a computing unit (R) configured to perform the following steps: - calculating at least a subregion of an ellipse (E), the ellipse (E) being formed by points for which the distance from the first sensor position (SP1) via the respective point to the second sensor position (SP2) is constant, and the distance being ascertained from the propagation time of a signal between the sending of the signal by the first sensor and the receiving of the signal reflected from the object by the second sensor; characterized by the further steps of: - determining an elliptical segment (EA) situated both within the detection range (EB1) of the first sensor (S1) and within the detection range (EB2) of the second sensor (S2), the elliptical segment (EA) having a first and a second ellipse end (EP1, EP2); - determining an elliptical segment intermediate point (Z) located on a perpendicular bisector of the connecting line between the first and second ellipse ends (EP1, EP2); - determining a circle or circular segment (KA) that passes through the first and second ellipse ends (EP1, EP2) and the elliptical segment intermediate point (Z); and - determining the situation of the object on the basis of the circle or the circular segment (KA).

8. System according to Claim 7, characterized in that the elliptical segment (EA) extends along the entire region of overlap of the detection range (EB1) of the first sensor (S1) and the detection range (EB2) of the second sensor (S2).

9. System according to Claim 7 or 8, characterized in that the computing unit (R) is configured to determine the circle or the circular segment (KA) by calculating a radius (r) of the circle or the circular segment (KA) and determining a centre (M) of this circle or this circular segment (KA).

10. System according to Claim 9, characterized in that the computing unit (R) is configured to determine the centre (M) of the circle or the circular segment (KA) by determining that point on the perpendicular bisector of the connecting line between the first and second ellipse ends (EP1, EP2) which is at a distance equal to the radius (r) of the circle or the circular segment (KA) from the elliptical segment intermediate point (Z).

11. System according to one of Claims 7 to 10, characterized in that the first and second sensors (S1, S2) are ultrasonic sensors.

12. System according to one of Claims 7 to 11, characterized in that the computing unit (R) is designed to ascertain the position of an object relative to the vehicle (F) by iteratively determining a circle or a circular segment (KA) over multiple transmission and reception cycles of the first and second sensors (S1, S2).