Lane departure haptic warning with compensation for road-caused vibration

1. A lane departure alerting method comprising:

operating a lane detection system to detect that a vehicle is experiencing a lane departure condition;

operating a sensor to detect background vibration experienced by the vehicle;

determining a characteristic making a haptic signal likely to be distinguishable from the background vibration; and

operating a haptic signal generator in response to the lane departure condition to deliver to a driver the haptic signal having the characteristic.

2. The method according to claim 1 wherein the characteristic is at least one of an amplitude of the signal, a waveform of the signal, a frequency of the signal, and a rise/fall time of the signal.

3. The method according to claim 1 wherein the background vibration is caused by travel of the vehicle over a road surface.

4. The method according to claim 1 wherein the sensor is at least one of a steering wheel torque sensor, an accelerometer, and a wheel speed sensor.

5. The method according to claim 1 wherein the haptic signal is applied to a steering wheel of the vehicle.

6. The method according to claim 1 wherein the haptic signal is applied by applying a cyclic torque to a steering gear of the vehicle.

7. The method according to claim 1 wherein the haptic signal generator is an electromechanical vibrator.

8. A method of alerting a vehicle driver to a lane departure condition comprising:

detecting a lane departure condition;

sensing and characterizing a background vibration caused by travel of the vehicle over a road surface;

determining at least one characteristic of a haptic signal giving the haptic signal a high likelihood of being distinguishable from the background vibration by the driver; and

in response to the lane departure condition, delivering to the driver a haptic signal having the at least one characteristic.

9. The method according to claim 8 wherein the at least one characteristic is at least one of an amplitude of the signal, a waveform of the signal, a frequency of the signal, and a rise/fall time of the signal.

10. The method according to claim 8 wherein the background vibration is sensed by at least one of a steering wheel torque sensor, an accelerometer, and a wheel speed sensor.

11. The method according to claim 8 wherein the haptic signal is applied to a steering wheel of the vehicle.

12. The method according to claim 8 wherein the haptic signal is applied by applying a cyclic torque to a steering gear of the vehicle.

13. The method according to claim 8 wherein the haptic signal is generated by an electromechanical vibrator.

14. A haptic alerting system for a vehicle comprising:

a lane detection system determining that the vehicle is departing from a path of travel;

a vibration sensor detecting a background vibration caused by travel over a road surface;

a controller determining a characteristic of a haptic signal required for the haptic signal to be distinguishable by the driver from the background vibration; and

a haptic signal generator activated by the lane detection system to deliver the haptic signal having the characteristic to the driver.

15. The apparatus according to claim 14 wherein the vibration sensor comprises at least one of a steering wheel torque sensor, an accelerometer, and a wheel speed sensor.

16. The apparatus according to claim 14 wherein the characteristic is at least one of an amplitude of the signal, a waveform of the signal, a frequency of the signal, and a rise/fall time of the signal.

17. The apparatus according to claim 14 wherein the haptic signal is applied to a steering wheel of the vehicle.

18. The apparatus according to claim 14 wherein the haptic signal generator comprises an electric motor applying a cyclic torque to a steering gear of the vehicle.

19. The apparatus according to claim 14 wherein the haptic signal generator is an electromechanical vibrator.