System for distance to stop

1. A system, comprising a computer including a processor and a memory, the memory storing instructions executable by the computer to:

receive a distance to stop a vehicle;

plot a trajectory including a plurality of acceleration segments according to the distance, the segments being respective portions of the trajectory prescribing at least one of an acceleration and a jerk over a specified period of time; and

adjust at least one of a vehicle brake and a vehicle propulsion based on the plotted trajectory;

wherein the plotted trajectory includes at least one segment having a prescribed jerk.

2. The system of claim 1 , wherein the instructions further include instructions to determine the trajectory based on a minimized cost function based on an acceleration, a time duration of a first segment of the trajectory, and a total stop duration, the total stop duration being a period of time from a start of the trajectory to an end of the trajectory.

3. The system of claim 2 , wherein the instructions include instructions to determine a deceleration necessary to reach the distance to stop and to recalculate the trajectory with the minimized cost function when the deceleration is below a predetermined threshold.

4. The system of claim 1 , wherein the trajectory includes a positive acceleration segment that prescribes a positive acceleration.

5. The system of claim 4 , wherein the instructions include instructions to start the trajectory with the positive acceleration segment to actuate the vehicle propulsion to move the vehicle from a standstill.

6. The system of claim 1 , wherein the instructions further include instructions to determine at least one of a maximum positive jerk and a maximum negative jerk, and to limit the prescribed jerk of the segments to below the maximum positive jerk and above the maximum negative jerk.

7. The system of claim 1 , wherein the instructions further include instructions to determine a threshold speed, the threshold speed defining when a penultimate segment of the trajectory begins.

8. The system of claim 7 , wherein the threshold speed is determined at least in part based on a period of time assigned to a segment prescribing a negative acceleration.

9. The system of claim 8 , wherein the instructions further include instructions to:

initialize the threshold speed;

determine the trajectory based on the threshold speed, the trajectory including ramp-in, deceleration, ramp-out, and final deceleration segments;

determine a period of time assigned to each segment of the trajectory; and

determine a new trajectory based on a new threshold speed, the new threshold speed being the current threshold speed less a constant speed value, when the sum of the time assigned to the ramp-in and deceleration segments is less than the sum of the time assigned to ramp-out and the final deceleration segments;

wherein the ramp-in segment prescribes a negative jerk, the deceleration segment prescribes a negative acceleration, the ramp-out segment prescribes a positive jerk, and the final deceleration segment prescribes a negative acceleration and is the last segment of the trajectory.

10. The system of claim 1 , wherein the instructions further include instructions to receive an instruction from a virtual vehicle operator to determine the trajectory to stop the vehicle.

11. A method, comprising:

receiving a distance to stop a vehicle;

plotting a trajectory including a plurality of acceleration segments according to the distance, the segments being respective portions of the trajectory prescribing at least one of an acceleration and a jerk over a specified period of time; and

adjusting at least one of a vehicle brake and a vehicle propulsion based on the trajectory;

wherein the trajectory includes a segment having a prescribed jerk.

12. The method of claim 11 , further comprising determining the trajectory based on a minimized cost function based on the acceleration, the time duration of a first segment of the trajectory, and a total stop duration, the total stop duration being a period of time from a start of the trajectory to an end of the trajectory.

13. The method of claim 12 , further comprising determining a deceleration necessary to reach the distance to stop and to recalculate the trajectory with the minimized cost function when the deceleration is below a predetermined threshold.

14. The method of claim 11 , wherein the trajectory includes a positive acceleration segment that prescribes a positive acceleration.

15. The method of claim 14 , further comprising starting the trajectory with the positive acceleration segment to actuate the vehicle propulsion to move the vehicle from a standstill.

16. The method of claim 11 , further comprising determining at least one of a maximum positive jerk and a maximum negative jerk, and to limit the prescribed jerk of the segments to below the maximum positive jerk and above the maximum negative jerk.

17. The method of claim 11 , further comprising determining a threshold speed, the threshold speed defining when the penultimate segment of the trajectory begins.

18. The method of claim 17 , wherein the threshold speed is determined at least in part based on a period of time assigned to a segment defining a negative acceleration.

19. The method of claim 18 , further comprising:

initializing the threshold speed;

determining the trajectory based on the threshold speed, the trajectory including ramp-in, deceleration, ramp-out, and final deceleration segments;

determining a period of time assigned to each segment of the trajectory; and

determining a new trajectory based on a new threshold speed, the new threshold speed being the current threshold speed less a constant speed value, when the sum of the time assigned to the ramp-in and deceleration segments is less than the sum of the time assigned to the ramp-out and the final deceleration segments;

wherein the ramp-in segment prescribes a negative jerk, the deceleration segment prescribes a negative acceleration, the ramp-out segment prescribes a positive jerk, and the final deceleration segment prescribes a negative acceleration and is the last segment of the trajectory.

20. The method of claim 11 , further comprising receiving an instruction from a virtual vehicle operator to determine the trajectory to stop the vehicle.