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US-12623721-B2 - Method for projecting a guide line onto a road surface

US12623721B2US 12623721 B2US12623721 B2US 12623721B2US-12623721-B2

Abstract

A method is provided for projecting a guide line onto a road surface. An anticipated trajectory of the motor vehicle is calculated from the speed and steering angle of the motor vehicle. A guide line is projected onto a road surface in front of the motor vehicle. The guide line indicates the anticipated travel path. Whether the motor vehicle is starting a curve is detected based on the steering angle. The guide line contains the shape of a first clothoid in at least a first segment when it is detected that the motor vehicle is starting to travel in a curve.

Inventors

  • Boris Kubitza
  • Jeremias Spiegel

Assignees

  • HELLA GmbH & Co. KGaA

Dates

Publication Date
20260512
Application Date
20231218
Priority Date
20210623

Claims (15)

  1. 1 . A method for projecting a guide line onto a road surface, the method comprising: calculating an anticipated trajectory of a motor vehicle from a speed and a steering angle of the motor vehicle; projecting the guide line onto the road surface in front of the motor vehicle, wherein the guide line indicates the anticipated trajectory; and detecting that the motor vehicle is starting to travel in a curved path when the steering angle exceeds a threshold value; wherein the guide line contains a shape of a first clothoid in at least a first segment upon detecting that the motor vehicle is starting to travel in the curved path.
  2. 2 . The method according to claim 1 , wherein a start of the curved path to be travelled by the motor vehicle is detected when the steering angle exceeds the threshold value after travelling a first distance with a steering angle that is lower than the threshold value.
  3. 3 . The method according to claim 2 , wherein the first distance is at least 10 meters.
  4. 4 . The method according to claim 1 , wherein a start of a curved path to be travelled by the motor vehicle is detected when the steering angle exceeds the threshold value and when the steering angle increases continuously.
  5. 5 . The method according to claim 1 , wherein a start of the curved path to be travelled by the motor vehicle is detected when the steering angle exceeds the threshold value and when the steering angle increases at a steady rate.
  6. 6 . The method according to claim 1 , wherein a start of the curved path to be travelled by the motor vehicle is detected when the steering angle increases continuously over a predefined time period after exceeding the threshold value.
  7. 7 . The method according to claim 1 , wherein a curvature of the first clothoid increases starting from the motor vehicle.
  8. 8 . The method according to claim 1 , wherein the first clothoid is constantly calculated as a function of the steering angle.
  9. 9 . The method according to claim 1 , wherein the guide line has a shape of a second clothoid in at least a second segment, upon detection that the motor vehicle has completed travel along the curved path.
  10. 10 . The method according to claim 9 , wherein a curvature of the second clothoid decreases, starting from the motor vehicle.
  11. 11 . The method according to claim 9 , wherein the second clothoid is constantly calculated as a function of the steering angle.
  12. 12 . The method according to claim 9 , wherein completion of the curved path by the motor vehicle is detected when the steering angle decreases continuously.
  13. 13 . The method according to claim 1 , wherein the guide line has a constant curvature when the steering angle remains constant after starting to travel along the curved path.
  14. 14 . A control unit for a headlamp in a motor vehicle, the control unit comprising: a digital memory; and a processor; wherein instructions are stored in the digital memory with which the processor executes the method according claim 1 .
  15. 15 . A motor vehicle comprising: the control unit according to claim 14 ; and a headlamp.

Description

CROSS REFERENCE This application claims priority to PCT Application No. PCT/EP2022/065188, filed Jun. 3, 2022, which itself claims priority to German Application No. 10 2021 116230.0, filed Jun. 23, 2021, the entireties of both of which are hereby incorporated by reference. FIELD OF THE INVENTION The invention relates to a method for projecting a guide line onto a road surface. BACKGROUND OF THE INVENTION WO 2017/100812 A1 discloses the calculation of an anticipated travel path for a motor vehicle and projection of guide lines onto the road surface in front of the motor vehicle. These are intended to help the driver of the motor vehicle stay in the lane, and decide whether a steering maneuver is necessary. BRIEF SUMMARY OF THE INVENTION In this respect, the fundamental object of the present invention is to increase driving safety. In an example embodiment, an anticipated travel path for the motor vehicle is calculated from the speed and steering angle of the motor vehicle. This anticipated travel path is understood to be a geometric trajectory corresponding to the anticipated movement of the motor vehicle. The anticipated travel path can be calculated, for example, by assuming that the speed and steering angle will remain constant. The anticipated travel path can also be calculated by assuming that the speed and a change in the steering angle will remain constant. It is also possible to calculate the anticipated travel path by assuming that a change in speed and a change in steering angle will remain constant. The steering angle is understood in the framework of this description to be a turning of the wheels of the motor vehicle, preferably the front wheels, away from a straight trajectory. When the wheels are not turned, the vehicle travels along a straight path. When the wheels are turned, the vehicle travels along a curved path corresponding to the steering angle of the wheels. As the steering angle increases, the turning radius of the path decreases. Furthermore, a guide line is projected onto the road surface in front of the motor vehicle. This guide line indicates the anticipated travel path. By way of example, the guide line can correspond to the anticipated travel path. The projection can be obtained with a motor vehicle headlamp, for example. This headlamp can be a matrix, LED, or LCD headlamp. The direction “forward” is understood in the framework of this description to mean the direction in which the motor vehicle is substantially moving. The motor vehicle can only move at a much slower speed in the opposite direction, “reverse,” if at all, because of the transmission used in the motor vehicle. It is detected whether the motor vehicle has started to travel along a curved path based on the steering angle. If it has been detected that the motor vehicle has begun a curve, the guide line follows a first clothoid in at least a first segment. This can be obtained by taking the start of the curved path into account in the calculation of the anticipated travel path. Instead of assuming that the steering angle remains constant in this calculation, it can be assumed that the steering angle changes constantly during a first time interval. Because of the effects of perspective, which result in a strong foreshortening of the guide lines for the driver in the direction of travel, the driver would see a kink where the straight line transitions into an arc segment. This can result in the driver assuming that the transition is more abrupt than it actually is, and thus oversteering. The clothoid in the first segment of the guide line is of particular advantage in increasing driving safety. Prior to starting the curve, the guide line is straight. Once the start of the curve has been detected, the first clothoid is only very slightly curved initially, and this curve increases as it progresses away from the motor vehicle and the motor vehicle moves along the guide line. As a result, the driver no longer sees a kink in the guide line, and is able to gauge the steering angle more accurately. This reduces the risk of the driver oversteering due to a misrepresentation of the curvature with the guide line. According to one embodiment of the invention, the start of a curve by the motor vehicle can be detected if the steering angle exceeds a threshold value after first travelling a distance with a steering angle below the threshold valve. This results in a particularly reliable detection of the start of a curve. The threshold value can be selected such that slight corrections of the steering angle when traveling in a straight line do not exceed the threshold valve. According to one embodiment of the invention, the first distance travelled is at least 10 meters. This is also advantageous in obtaining a particularly reliable detection of the start of a curve. According to one embodiment of the invention, the start of a curve by the motor vehicle can be detected if the steering angle increases continuously. This can be a suppl