Method for quantifying vehicle path following performance

1. A method performed by a control unit for controlling a vehicle based on a quantified vehicle path following performance, the method comprising;

obtaining samples of path following performance p i i=1 n-1 , wherein path following performance p i is measured as a track error indicating a discrepancy between a target vehicle state and an actual vehicle state in following a vehicle path,

selecting a subset of the path following performance samples such that the selected samples follow a pre-determined statistical extreme value distribution,

parameterizing the pre-determined statistical extreme value distribution based on the selected samples of path following performance,

quantifying vehicle path following performance based on the parameterized statistical extreme value distribution, and

controlling the vehicle by the control unit based on the quantified vehicle path following performance.

2. The method according to claim 1 , wherein the obtaining comprises obtaining a previously stored set of vehicle path following performance samples.

3. The method according to claim 1 , wherein the obtaining comprises obtaining a set of vehicle path following performance samples during operation of an ego vehicle.

4. The method according to claim 1 , wherein the selecting comprises determining a threshold ζ such that the samples of vehicle path following performance in excess of the threshold ζ, {p i : p i ≮ζ}, follow the pre-determined statistical extreme value distribution.

5. The method according to claim 4 , comprising measuring a time between exceedances metric indicating the time passed between vehicle path following performance samples exceeding the threshold ζ, and monitoring ODD based on the time between exceedances metric.

6. The method according to claim 1 , wherein the pre-determined statistical extreme value distribution is a Generalized Pareto Distribution, GDP.

7. The method according to claim 1 , wherein the pre-determined statistical extreme value distribution is a Generalized Extreme Value distribution, GEV.

8. The method according to claim 1 , wherein a sample of vehicle path following performance comprises any of; lateral vehicle position, longitudinal vehicle position, absolute or squared vehicle position, lateral vehicle velocity, longitudinal vehicle velocity, absolute or squared vehicle velocity, lateral vehicle acceleration, longitudinal vehicle acceleration, absolute or squared vehicle acceleration, curvature, yaw rate, heading, articulation angle.

9. The method according to claim 8 , wherein a sample of vehicle path following performance is determined separately for one or more parts of the vehicle.

10. The method according to claim 1 , wherein a sample of vehicle path following performance is obtained dependent on any of; type of vehicle, type of vehicle combination, vehicle physical dimension parameters, weather condition, road friction, road geometry, and path trajectory geometry.

11. The method according to claim 1 , comprising quantifying the vehicle path following performance as a bounded model by bounding the performance to lie within a range − w ≤b k ≤ w with probability greater than 1−γ, based on the pre-determined statistical extreme value distribution.

12. The method according to claim 1 , comprising determining a confidence value β associated with the pre-determined statistical extreme value distribution.

13. The method according to claim 12 , comprising assessing a sufficiency of gathered vehicle path following performance data for performance quantification based on the confidence value β associated with the pre-determined statistical extreme value distribution.

14. The method according to claim 1 , comprising monitoring an operational design domain, ODD, associated with the vehicle by comparing the parameterized pre-determined statistical extreme value distribution to a set of baseline distribution parameters, wherein operation outside the ODD is indicated by a difference between parameterized pre-determined statistical extreme value distribution parameters and the baseline distribution parameters.

15. A non-transitory computer readable medium carrying a computer program comprising program code for performing the steps of claim 1 when said program product is run on a computer or on processing circuitry of a control unit.

16. A control unit for quantifying vehicle path following performance, the control unit being configured to perform the steps of the method according to claim 1 .

17. A vehicle comprising a control unit according to claim 16 .