Third-order polynomial-based course prediction for driver assistance functions
Methods and systems for performing vehicle driver assistance. One method includes determining, at a controller, whether the vehicle is steering toward a drive-straight state and when the vehicle is steering toward the drive-straight state, calculating, at the controller, a predicted course trajectory using a third order polynomial. The method also includes calculating, at the controller, the predicted course trajectory using a non-third-order function when the vehicle is not steering toward the drive-straight state. In addition, the method includes performing the driver assistance based on the predicted course trajectory.
1. A method of performing driver assistance for a vehicle, the method comprising:
receiving a state signal from at least one dynamic state sensor,
determining, at a controller, whether the vehicle is steering toward a drive-straight state, based on the state signal;
calculating, at the controller, a predicted course trajectory using a third order polynomial in response to a determination that the vehicle is steering toward the drive-straight state;
calculating, at the controller, the predicted course trajectory using a non-third-order function in response to a determination that the vehicle is not steering toward the drive-straight state; and
performing the driver assistance based on the predicted course trajectory.
2. The method of claim 1 , wherein determining whether the vehicle is driving toward the drive-straight state includes determining whether a steering angle of the vehicle is greater than zero and a steering angle velocity of the vehicle is less than zero.
3. The method of claim 1 , wherein determining whether the vehicle is driving toward the drive-straight state includes determining whether a steering angle of the vehicle is less than zero and a steering angle velocity of the vehicle is greater than zero.
4. The method of claim 1 , wherein calculating the predicted course trajectory using a third order polynomial includes calculating a first portion of the predicted course trajectory using the third order polynomial, the first portion extending from the vehicle in a driving direction of the vehicle, and calculating a second portion of the predicted course trajectory using a non-third-order function, the second portion extending from an end of the first portion in the driving direction of the vehicle.
5. The method of claim 4 , wherein calculating the first portion of the predicted course trajectory includes determining a distance along the first portion where the vehicle reaches a zero-curvature point, the zero-curvature point defining the end of the first portion.
6. The method of claim 5 , wherein determining the distance includes calculating the zero-curvature point in a longitudinal direction based on a tangent of a steering angle of the vehicle divided by a distance between a front axle and a rear axle of the vehicle.
7. The method of claim 4 , wherein determining the distance includes calculating the zero-curvature point in a longitudinal direction based on a yaw rate of the vehicle divided by a velocity of the vehicle.
8. The method of claim 4 , wherein calculating the second portion of the predicted course trajectory includes calculating the second portion using a linear model.
9. The method of claim 1 , further comprising, when a velocity of the vehicle is less than approximately 1.0 meters per second, calculating the predicted course trajectory using a non-third-order function.
10. The method of claim 1 , wherein calculating the predicted course trajectory using the third order polynomial includes combining the predicted course trajectory calculated using the third order polynomial and the predicted course trajectory calculated using the non-third-order function.
11. A driver assistance system for a vehicle, the system including:
a vehicle dynamic state sensor; and
a controller configured to:
receive a signal from the vehicle dynamic state sensor,
determine whether the vehicle is steering toward a drive-straight state based on the signal from the vehicle dynamic state sensor,
calculate a predicted course trajectory using a third order polynomial in response to a determination that the vehicle is steering toward the drive-straight state,
calculate the predicted course trajectory using a non-third-order function in response to a determination that the vehicle is not steering toward the drive-straight state, and
perform a driver assistance function based on the predicted course trajectory.
12. The system of claim 11 , wherein the signal indicates at least one selected from the group comprising (i) a steering angle of the vehicle, (ii) a steering angle velocity of the vehicle, (iii) a yaw rate of the vehicle, and (iv) a velocity of the vehicle.
13. The system of claim 11 , wherein the controller determines whether the vehicle is driving toward the drive-straight state based on whether a steering angle of the vehicle is less than zero and a steering angle velocity of the vehicle is greater than zero.
14. The system of claim 11 , wherein the controller is configured to calculate the predicted course trajectory using the third order polynomial by calculating a first portion of the predicted course trajectory using the third order polynomial, the first portion extending from the vehicle in a driving direction of the vehicle, and calculating a second portion of the predicted course trajectory using a non-third-order function, the second portion extending from an end of the first portion in the driving direction of the vehicle.
15. The system of claim 14 , wherein the controller is configured to determine a distance along the first portion where the vehicle reaches a zero-curvature point, the zero-curvature point defining the end of the first portion.
16. The system of claim 15 , wherein the controller is configured to calculate the zero-curvature point in a longitudinal direction based on a tangent of a steering angle of the vehicle divided by a distance between a front axle and a rear axle of the vehicle.
17. The system of claim 15 , wherein the controller is configured to calculate the zero-curvature point in a longitudinal direction based on a yaw rate of the vehicle divided by a velocity of the vehicle.
18. The system of claim 14 , wherein the controller is configured to calculate the second portion of the predicted course trajectory using a linear model.
19. The system of claim 11 , wherein the controller calculates the predicted course trajectory based on combining a predicted course trajectory using the third order polynomial and the predicted course trajectory using the non-third-order function.
20. The system of claim 11 , wherein the controller determines whether the vehicle is driving toward the drive-straight state based on whether a steering angle of the vehicle is greater than zero and a steering angle velocity of the vehicle is less than zero.