Apparatus and method for controlling a vehicle

1. An autonomous vehicle control system configured to guide an autonomous vehicle along a desired path, the autonomous vehicle control system comprising:

a processor; and

a path controller in communication with the processor, the path controller configured to:

receive input signals comprising:

a normal error signal associated with the autonomous vehicle, the normal error signal indicating an off-path deviation of the autonomous vehicle relative to the desired path;

a heading signal associated with the autonomous vehicle, the heading signal indicating a current heading angle of the autonomous vehicle relative to at least one fixed point within a fixed coordinate system; and

a curvature signal associated with the autonomous vehicle, the curvature signal indicating a curvature associated with a current turn radius of the autonomous vehicle;

calculate a curvature rate output signal based on the input signals received at the path controller, the curvature rate output signal configured to guide the autonomous vehicle along the desired path, wherein at least one portion of the desired path comprises a clothoid segment having a continuously changing rate of curvature which varies linearly along the at least one portion of the desired path; and

communicate the curvature rate output signal to a steering control system that is configured to receive the curvature rate output signal and actuate at least one actuator of a steering system associated with the autonomous vehicle to control the direction of movement of the autonomous vehicle based on the curvature rate output signal received from the path controller, wherein the curvature rate output signal represents a continuously changing rate of curvature which varies linearly in order to guide the autonomous vehicle along the at least one portion of the desired path.

2. The autonomous vehicle control system of claim 1 , wherein the steering system is rate-limited and has a finite steering rate.

3. The autonomous vehicle control system of claim 2 , wherein the autonomous vehicle includes a minimum right turn radius and a minimum left turn radius.

4. The autonomous vehicle control system of claim 1 , wherein the path controller is further configured to receive input signals comprising at least one of:

a vehicle position signal;

a vehicle speed signal;

a curvature state signal;

a vehicle state vector signal; and

a desired error signal, wherein the desired error signal indicates a desired off-path deviation of the autonomous vehicle relative to the desired path.

5. The autonomous vehicle control system of claim 1 , wherein the path controller is further configured to linearize normal error dynamics in relation to the desired path by integrating one or more derivatives of the normal error signal received at the path controller.

6. The autonomous vehicle control system of claim 5 , wherein the path controller is further configured to apply at least one gain value to feedback relating to the normal error signal to stabilize the curvature rate output signal, wherein the at least one gain value is selected using a linear quadratic regulator process.

7. A method of controlling an autonomous vehicle comprising:

at a processor associated with a path controller configured to control an autonomous vehicle with a curvature rate output signal in order to guide the autonomous vehicle along a desired path:

receiving a position and heading of the autonomous vehicle relative to at least one fixed point within a fixed coordinate system;

receiving input signals comprising:

a normal error signal associated with the autonomous vehicle, the normal error signal indicating an off-path deviation of the autonomous vehicle relative to the desired path;

a heading signal associated with the autonomous vehicle, the heading signal indicating a current heading angle of the autonomous vehicle relative to the at least one fixed point within the fixed coordinate system; and

a curvature signal associated with the autonomous vehicle, the curvature signal indicating a curvature associated with a current turn radius of the autonomous vehicle;

calculating a curvature rate output signal based on the input signals received at the path controller, the curvature rate output signal configured to guide the autonomous vehicle along the desired path, wherein at least one portion of the desired path comprises a clothoid segment having a continuously changing rate of curvature which varies linearly along the at least one portion of the desired path; and

communicating the curvature rate output signal to a steering control system that is configured to receive the curvature rate output signal and actuate at least one actuator of a steering system associated with the autonomous vehicle; and

controlling the direction of movement of the autonomous vehicle based on the curvature rate output signal, wherein the curvature rate output signal represents a continuously changing rate of curvature which varies linearly in order to guide the autonomous vehicle along the at least one portion of the desired path.

8. The method of claim 7 , wherein the steering system is rate-limited and has a finite steering rate.

9. The method of claim 8 , wherein the autonomous vehicle includes a minimum right turn radius and a minimum left turn radius.

10. The method of claim 7 , wherein receiving input signals at the processor associated with the path controller comprises receiving at least one of:

a vehicle position signal;

a vehicle speed signal;

a curvature state signal;

a vehicle state vector signal; and

a desired error signal, wherein the desired error signal indicates a desired off-path deviation of the autonomous vehicle relative to the desired path.

11. The method of claim 7 , wherein calculating the curvature rate output signal based on the input signals received at the processor associated with the path controller further comprises linearizing normal error dynamics in relation to the desired path by integrating one or more derivatives of the normal error signal received at the path controller.

12. The method of claim 11 , wherein calculating the curvature rate output signal based on the input signals received at the processor associated with the path controller further comprises applying at least one gain value to feedback relating to the normal error signal to stabilize the curvature rate output signal, wherein the at least one gain value is selected using a linear quadratic regulator process.

13. A computer program product for controlling an autonomous vehicle comprising:

a nontransitory computer readable medium; and

computer program code, encoded on the nontransitory computer readable medium, configured to cause at least one processor associated with a path controller to perform the steps of:

receiving a position and heading of the autonomous vehicle relative to at least one fixed point within a fixed coordinate system;

receiving input signals comprising:

a normal error signal associated with the autonomous vehicle, the normal error signal indicating an off-path deviation of the autonomous vehicle relative to a desired path;

a heading signal associated with the autonomous vehicle, the heading signal indicating a current heading angle of the autonomous vehicle relative to the at least one fixed point within the fixed coordinate system; and

a curvature signal associated with the autonomous vehicle, the curvature signal indicating a curvature associated with a current turn radius of the autonomous vehicle;

calculating a curvature rate output signal based on the input signals, the curvature rate output signal configured to guide the autonomous vehicle along the desired path, wherein at least one portion of the desired path comprises a clothoid segment having a continuously changing rate of curvature which varies linearly along the at least one portion of the desired path;

initiating communication of the curvature rate output signal to a steering control system that is configured to receive the curvature rate output signal and actuate at least one actuator of a steering system associated with the autonomous vehicle; and

controlling the direction of movement of the autonomous vehicle based on the curvature rate output signal, wherein the curvature rate output signal represents a continuously changing rate of curvature which varies linearly in order to guide the autonomous vehicle along the at least one portion of the desired path.

14. The computer program product of claim 13 , wherein the steering system is rate-limited and has a finite steering rate.

15. The computer program product of claim 14 , wherein the autonomous vehicle includes a minimum right turn radius and a minimum left turn radius.

16. The computer program product of claim 13 , wherein receiving input signals at the at least one processor associated with the path controller comprises receiving at least one of:

a vehicle position signal;

a vehicle speed signal;

a curvature state signal;

a vehicle state vector signal; and

a desired error signal, wherein the desired error signal indicates a desired off-path deviation of the autonomous vehicle relative to the desired path.

17. The computer program product of claim 13 , wherein calculating the curvature rate output signal based on the input signals received at the at least one processor associated with the path controller further comprises:

linearizing normal error dynamics in relation to the desired path by integrating one or more derivatives of the normal error signal received at the at least one processor associated with the path controller; and

applying at least one gain value to feedback relating to the normal error signal to stabilize the curvature rate output signal, wherein the at least one gain value is selected using a linear quadratic regulator process.