System and method for trajectory planning for unexpected pedestrians

• US 9,857,795 B2
• Filed: 03/24/2016
• Issued: 01/02/2018
• Est. Priority Date: 03/24/2016
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Gupta, Rakesh, Cofield, Robert
• Primary Examiner(s): Beaulieu, Yonel
• Assistant Examiner(s): Weeks, Martin A
• Application Number:
  US15/079,917
• Publication Number:
  US 20170277192A1
• Time in Patent Office: 649 Days
• CPC Class Codes: B60K 2360/175 Autonomous driving
• CPC Class Codes: B60K 35/28 characterised by the type of the output information, e.g. video entertainment or vehicle dynamics information; characterised by the purpose of the output information, e.g. for attracting the attention of the driver
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2554/00 Input parameters relating to objects
• CPC Class Codes: B60W 2556/50 of positioning data, e.g. GPS [Global Positioning System] data
• CPC Class Codes: B60W 30/20 Reducing vibrations in the driveline

Abstract

A trajectory planning system for an autonomous vehicle fits a jerk profile including a plurality of phases within a set of acceptable parameters, a jerk value being constant within each phase of the jerk profile. The system parameterizes the jerk profile based on an initial velocity, an initial acceleration, a final velocity, and a final acceleration for the first segment. The system then integrates the jerk profile to determine a first trajectory function, the first trajectory function including a speed for the vehicle at a given time. The system guides the vehicle along the first segment of the path according to the first trajectory function. The system detects an unplanned obstacle along the first segment of the path. The system plans a second trajectory function for a second segment of the path between a current location of the vehicle and a location on the path before the unplanned obstacle.

Claims

1. A method of autonomous guidance of a vehicle comprising:

fitting a first jerk profile including a plurality of phases within a set of acceptable parameters including;

a positive jerk constraint, a negative jerk constraint, a positive acceleration constraint, and a negative acceleration constraint for a first segment of a planned travel path, a jerk value being constant within each phase of the first jerk profile;

parameterizing the first jerk profile based on an initial velocity, an initial acceleration, a final velocity, a final acceleration for the first segment, and a maximum legal speed limit for the first segment;

integrating the first jerk profile to determine a first trajectory function, the first trajectory function including a speed for the vehicle at a given time;

travelling the first segment of the path according to the first trajectory function;

detecting an unplanned obstacle along the first segment of the path; and

planning a second trajectory function for a second segment of the path between a current location of the vehicle and a location on the path before the unplanned obstacle.

2. The method of claim 1, wherein planning the second trajectory function for the second segment comprises:

fitting a second jerk profile including a second plurality of phases within the set of acceptable parameters;

parameterizing the second jerk profile based on a velocity when the object is detected, an acceleration when the object is detected, a final velocity of zero, and a final acceleration of zero; and

integrating the second jerk profile to determine the second trajectory function.

3. The method of claim 2, wherein the second jerk profile includes an increasing deceleration phase, a constant deceleration phase, and a decreasing deceleration phase.

4. The method of claim 3, wherein parameterizing the second jerk profile comprises:

solving the second trajectory function for a stopping distance;

determining that the stopping distance is greater than a length of the second segment; and

iteratively increasing a magnitude of each parameter of the set of acceptable parameters until the stopping distance is less than the length of the second segment.

5. The method of claim 1, wherein parameterizing the first jerk profile comprises:

solving the first trajectory function for a duration of each phase;

determining that the duration for at least one phase is negative; and

increasing a magnitude of each parameter of the set of acceptable parameters until the duration for each phase is positive or each parameter of the set of acceptable parameters reaches a maximum magnitude.

6. The method of claim 1, wherein fitting the first jerk profile including a plurality of phases to constraints for the first segment comprises:

selecting the first jerk profile from a plurality of jerk profiles, each of the plurality of jerk profiles having a different numbers of phases, wherein the selecting includes evaluating each of the jerk profiles in descending order of the number of phases until a jerk profile provides a solution within the constraints having a positive duration for each phase.

7. The method of claim 1, further comprising:

projecting a vehicle current position onto the first segment;

determining a cumulative distance along the first segment between a start point and the projected vehicle current position;

determining a reference time for the vehicle current position in the first trajectory function based on the cumulative distance; and

determining a desired speed for the vehicle by sampling the first trajectory function based on the reference time.

8. The method of claim 1, further comprising:

determining that the unplanned obstacle has cleared the path; and

planning a third trajectory function for a third segment of the path between a current location of the vehicle and an end of the first segment.

9. The method of claim 1, further comprising:

determining an alternative path that avoids the unplanned obstacle;

determining whether the alternate path is feasible; and

planning a trajectory function for the alternate path.

10. A system for autonomous guidance of a vehicle comprising:

a map database providing map data including a path for the vehicle;

a detection system determining a position of an unplanned obstacle on the path;

a processor;

fitting a first jerk profile including a plurality of phases within a set of acceptable parameters including;

a positive jerk constraint, a negative jerk constraint, a positive acceleration constraint, and a negative acceleration constraint for a first segment of a planned travel path, a jerk value being constant within each phase of the first jerk profile, wherein the processor selects the first jerk profile from a plurality of jerk profiles, each of the plurality of jerk profiles having different numbers of phases, wherein the selecting includes evaluating each of the jerk profiles in descending order of the number of phases until a jerk profile provides a solution within the constraints;

parameterizing the first jerk profile based on an initial velocity, an initial acceleration, a final velocity, and a final acceleration for the first segment;

integrating the first jerk profile to determine a first trajectory function, the first trajectory function including a speed for the vehicle at a given time;

guiding the vehicle along the first segment of the path according to the first trajectory function;

detecting an unplanned obstacle along the first segment of the path; and

planning a second trajectory function for a second segment of the path between a current location of the vehicle and a location on the path before the unplanned obstacle.

11. The system of claim 10, wherein the processor planning the second trajectory function for the second segment comprises the processor:

fitting a second jerk profile including a second plurality of phases within the maximum positive jerk constraint, the maximum negative jerk constraint, the maximum positive acceleration constraint, and the maximum negative acceleration constraint;

parameterizing the second jerk profile based on a velocity when the object is detected, an acceleration when the object is detected, a final velocity of zero, and a final acceleration of zero; and

integrating the second jerk profile to determine the second trajectory function.

12. The system of claim 11, wherein the second jerk profile includes an increasing deceleration phase, a constant deceleration phase, and a decreasing deceleration phase.

13. The system of claim 12, wherein the processor:

solves the second trajectory function for a stopping distance;

determines that the stopping distance is greater than a length of the second segment; and

iteratively increases a magnitude of each parameter of the set of acceptable parameters until the stopping distance is less than a length of the second segment.

14. The system of claim 10, wherein the processor:

projects a vehicle current position onto the first segment;

determines a cumulative distance along the first segment between a start point and the projected vehicle current position;

determines a reference time for the vehicle current position in the first trajectory function based on the cumulative distance; and

determines a desired speed for the vehicle by sampling the first trajectory function based on the reference time.

15. The system of claim 10, wherein the processor:

determines that the unplanned obstacle has cleared the path; and

plans a third trajectory function for a third segment of the path between a current location of the vehicle and an end of the first segment.

16. The system of claim 10, wherein the processor:

determines an alternative path that avoids the unplanned obstacle;

determines whether the alternate path is feasible; and

plans a trajectory function for the alternate path.

17. A non-transitory computer-readable medium storing computer executable code for controlling an autonomous vehicle, comprising code to:

fit a first jerk profile including a plurality of phases within a maximum positive jerk constraint, a maximum negative jerk constraint, a maximum positive acceleration constraint, and a maximum negative acceleration constraint for a first segment of a planned travel path, a jerk value being constant within each phase of the first jerk profile;

parameterize the first jerk profile based on an initial velocity, an initial acceleration, a final velocity, and a final acceleration for the first segment;

integrate the first jerk profile to determine a first trajectory function, the first trajectory function including a speed for the vehicle at a given time;

guide the vehicle along the first segment of the path according to the first trajectory function;

detect an unplanned obstacle along the first segment of the path; and

plan a second trajectory function for a second segment of the path between a current location of the vehicle and a location on the path before the unplanned obstacle, wherein the code to plan the second trajectory function comprises code to;

fit a second jerk profile including a second plurality of phases within the maximum positive jerk constraint, the maximum negative jerk constraint, the maximum positive acceleration constraint, and the maximum negative acceleration constraint;

parameterize the second jerk profile based on a velocity when the object is detected, an acceleration when the object is detected, a final velocity of zero, and a final acceleration of zero; and

integrate the second jerk profile to determine the second trajectory function.