Hands-off signature detection

1. A method comprising:

implementing an autonomous steering system comprising an electronic power steering system comprising a steer-by-wire handwheel actuator;

determining that an autonomous driving mode is active;

analyzing a handwheel torque signal in the electronic power steering system;

applying a low amplitude, high frequency sinusoidal motor command to at least the handwheel actuator;

analyzing attenuation of the low amplitude, high frequency sinusoidal command;

filtering the analyzed handwheel torque signal such that the low amplitude, high frequency sinusoidal command is isolated; and

detecting a signal change in the handwheel torque signal in the range of the low amplitude, high frequency sinusoidal motor command adapted to determine that a user's hands are off the handwheel.

2. The method as in claim 1 , wherein the low amplitude, high frequency sinusoidal motor command ranges from about 30 Hz to about 50 Hz.

3. The method as in claim 1 , wherein detecting a signal change in the torque signal in the range of the low amplitude, high frequency sinusoidal motor command adapted to determine that a user's hands are off the handwheel comprises detecting attenuation of the low amplitude, high frequency sinusoidal motor command.

4. The method as in claim 1 , further comprising generating a hands-off flag indicating hands-off status.

5. The method as in claim 4 , further comprising combining the hands-off flag with at least one existing hands-off detection criteria to supplement hands-off detection.

6. The method as in claim 1 , wherein detecting a signal change in the handwheel torque signal in the range of the low amplitude, high frequency sinusoidal motor command comprises:

determining that a driver estimated torque is below a first predetermined threshold; and

determining that the filtered handwheel torque signature is above a second predetermined threshold for a first duration.

7. A method of hands-off signature detection comprising:

determining that an autonomous driving mode is active within a vehicle;

receiving hands-off detection criteria from a primary hands-off detection system;

applying and monitoring a low amplitude, high frequency sinusoidal command to a handwheel actuator of a steer-by-wire steering system within the vehicle;

monitoring a torque signal via a handwheel torque sensor for change in the torque signal within the range of the applied unique sinusoidal command;

filtering the monitored handwheel torque signal such that the unique sinusoidal command is isolated;

generating a flag based on an observed change in the isolated torque signal; and

combining the flag with the hands-off detection criteria from the primary hands-off detection system to supplement the primary hands-off detection system.

8. The method of hands-off signature detection as in claim 7 wherein the unique sinusoidal command is a low amplitude, high frequency sinusoidal motor command.

9. The method of hands-off signature detection as in claim 8 wherein the low amplitude, high frequency sinusoidal motor command ranges from about 30 Hz to about 50 Hz.

10. The method of hands-off signature detection as in claim 7 wherein monitoring a torque signal via a handwheel torque sensor for change in the torque signal within the range of the applied unique sinusoidal command comprises monitoring attenuation of the unique sinusoidal command attributable to the physical presence of a driver's hand on the steering wheel.

11. The method of hands-off signature detection as in claim 10 , wherein the hands-off detection criteria of the primary hands-off detection system comprises determining driver estimated torque below a third threshold for a second duration.

12. A method of supplementing a system for hands-off signature detection comprising:

determining that an autonomous driving mode is active within a vehicle;

applying and monitoring a low amplitude, high frequency sinusoidal command to a handwheel actuator of a steer-by-wire steering system;

determining that driver estimated torque is below a first predetermined threshold;

performing handwheel torque filtering to isolate the low amplitude, high frequency command;

generating a filtered handwheel torque signature;

determining that the filtered handwheel torque signature is above a second predetermined threshold for a first duration; and

generating a handwheel signature flag; and

communicating the handwheel signature flag to a hands-off detection logic module.

13. A method of supplementing a system for hands-off signature detection as in claim 12 , further comprising combining the handwheel signature flag with at least one hands-off detection criteria of a primary hands-off detection system.

14. A method of supplementing a system for hands-off signature detection as in claim 13 , wherein the at least one hands-off detection criteria of the primary hands-off detection system comprises determining driver estimated torque below a third threshold for a second duration.

15. A method of supplementing a system for hands-off signature detection as in claim 12 , wherein the low amplitude, high frequency sinusoidal motor command ranges from about 30 Hz to about 50 Hz.