Method of controlling a vehicle steering apparatus

1. A method for controlling a steering apparatus of a vehicle with a controller, the method comprising the steps of:

(i) providing a steering signal from the controller indicative of a steering maneuver to be performed;

(ii) calculating a desired parameter of the steering apparatus during the steering maneuver when no external force is applied to a hand wheel of the vehicle;

(ii) measuring the parameter with a sensor during the steering maneuver;

(iv) producing a mode signal by comparing the desired parameter to the measured parameter; and

(v) using a switch to place the vehicle in one of an autonomous driving mode and a manual driving mode based on the mode signal.

2. The method of claim 1 including placing the vehicle in an autonomous driving mode when the mode signal is within a predetermined range.

3. The method of claim 1 including placing the vehicle in a manual driving mode when the mode signal is not within a predetermined range.

4. The method of claim 1 wherein the parameter of the steering apparatus is column torque.

5. The method of claim 4 including placing the vehicle in an autonomous driving mode when the mode signal is within a predetermined range.

6. The method of claim 4 including the steps of determining inertia of the hand wheel of the vehicle, determining a desired rotational acceleration of the hand wheel based on the steering signal, and multiplying the inertia of the hand wheel with the desired rotational acceleration of the hand wheel to determined the desired column torque.

7. The method of claim 6 wherein the steering signal is a desired rotational magnitude of the hand wheel, the step of determining the desired rotational acceleration of the hand wheel of the vehicle includes the steps of:

differentiating the desired hand wheel rotation magnitude relative to time to determine hand wheel rotation rate; and

differentiating the hand wheel rotation rate relative to time.

8. The method of claim 1 including the steps of:

calculating a desired hand wheel position after the steering maneuver is performed based on said steering signal; and

determining the current hand wheel position before the steering maneuver is performed;

rotating the hand wheel toward the desired hand wheel position when the vehicle is in an autonomous driving mode.

9. The method of claim 8 including the step of providing a motor to rotate the hand wheel toward the desired hand wheel position when the vehicle is in the autonomous driving mode.

10. The method of claim 2 wherein the step of measuring the column torque during the steering maneuver is performed by a column torque sensor.

11. The method of claim 1 further including the step of:

continuously repeating the method during operation of the vehicle.

12. The method of claim 1 including switching the vehicle between an autonomous driving mode and a manual mode based on the mode signal.

13. A method for controlling a steering apparatus of a vehicle with a contoller, the method comprising the steps of:

(i) providing a desired hand wheel rotation signal from the controller indicative of a steering maneuver during an autonomous driving mode of the vehicle;

(ii) calculating a desired parameter of the steering apparatus during the steering maneuver when no external force is applied to a hand wheel of the vehicle;

(ii) measuring the parameter with a sensor during the steering maneuver;

(iv) producing a mode signal by comparing the desired parameter to the measured parameter; and

(v) switching the vehicle to a manual driving mode when the mode signal exceeds a predetermined value.