Control adaptation of variable gear ratio steering
An adaptive control VGR steering system that varies the steering gear ratio between a vehicle hand-wheel angle and the road wheel angle based on vehicle speed and one or more of hand-wheel angle, driver attentiveness and a driver's driving style and skill.
1. An adaptive control variable gear ratio (VGR) steering system for a vehicle, said system comprising:
a VGR device that changes a gear ratio between a hand-wheel angle of a hand-wheel of the vehicle and a road wheel angle of the vehicle;
a vehicle speed sensor providing a vehicle speed signal of a speed of the vehicle;
a hand-wheel angle sensor providing a hand-wheel angle signal of the hand-wheel angle of the vehicle;
a VGR sub-system that provides a VGR signal to the VGR device for changing the gear ratio, said VGR sub-system using the vehicle speed signal and the hand-wheel angle signal to determine the gear ratio based on a combination of both vehicle speed and a desired yaw-rate gain; and
a style and skill characterization processor that is responsive to vehicle sensor signals from vehicle sensors, said style and skill characterization processor determining a driver's driving style and skill, said style and skill characterization processor providing a driver's driving style and skill signal to the VGR sub-system of the type of driver driving the vehicle, said VGR sub-system using the vehicle speed signal, the hand-wheel angle signal and the driver's driving style and skill signal to determine the gear ratio, where the gear ratio is reduced from a nominal value as the vehicle speed increases for drivers of greater skill.
2. The system according to claim 1 further comprising a driver attentiveness processor that is responsive to vehicle sensor signals from vehicle sensors, said driver attentiveness processor determining an attentiveness of the vehicle driver, said driver attentiveness processor providing a driver attentiveness signal to the VGR sub-system identifying how attentive the driver is, said VGR sub-system determining the gear ratio based on the vehicle speed signal, the hand-wheel angle signal, the driver's driving style and skill signal and the driver attentiveness signal, where the gear ratio is increased from a nominal value as the vehicle speed increases for drivers that are less attentive.
3. The system according to claim 2 wherein the driver attentiveness processor includes a signal processor that receives the hand-wheel angle signal and provides a steering angle signal and a steering angle rate signal, a curvature derivation processor that provides a road curvature signal and a steering activity index processor that receives the steering angle signal, the steering angle rate signal and the road curvature signal, said steering activity index processor calculating a steering activity index that identifies a driver's steering activity, said steering activity index being combined with the driver attentiveness signal, where the gear ratio is increased from the nominal value as the vehicle speed increases for increases in steering activity.
4. The system according to claim 3 wherein the curvature derivation processor receives signals from a digital map and a GPS to determine the road curvature.
5. The system according to claim 2 wherein the driver attentiveness processor determines whether a driver of the vehicle is drowsy to determine the driver attentiveness signal.
6. The system according to claim 2 wherein one of the vehicle sensors is a camera that provides images of the driver.
7. The system according to claim 3 wherein the steering activity index processor uses the following equation to determine the steering activity index:
R
=
c
1
δ
HWA
+
c
2
δ
.
HWA
+
c
3
ρ
c
1
δ
max
+
c
2
δ
.
max
+
c
3
ρ
max
Where R is the steering activity index, {dot over (δ)} HWA is the steering angle rate, 67 HWA is the hand-wheel angle, ρ is the road curvature, δ max and {dot over (δ)} max are pre-defined maximum values for the steering angle and the steering angle rate, respectively, ρ max , is a pre-defined maximum value for the road curvature and c 1 , c 2 and c 3 are predetermined coefficients.
8. The system according to claim 1 wherein the VGR sub-system decreases the gear ratio if the hand-wheel angle increases above a critical threshold value where vehicle tires operate in a non-linear region of lateral force versus tire side slip angle.
9. The system according to claim 8 wherein the critical threshold value decreases as the vehicle speed increases.
10. An adaptive control variable gear ratio (VGR) steering system for a vehicle, said system comprising:
a VGR device that changes a gear ratio between a hand-wheel angle of a hand-wheel of the vehicle and a road wheel angle of the vehicle;
a vehicle speed sensor providing a vehicle speed signal of a speed of the vehicle;
vehicle sensors that provide parameters of the operation of the vehicle;
a style and skill characterization processor that is responsive to vehicle sensor signals from the vehicle sensors, said style and skill characterization processor determining a driver's driving style and skill and providing a driver's driving style and skill signal; and
a VGR sub-system that provides a VGR signal to the VGR device for changing the gear ratio, said VGR sub-system determining the VGR signal based on the speed of the vehicle and the driver's driving style and skill, where the gear ratio is reduced from a nominal value as the vehicle speed increases for drivers of greater skill.
11. An adaptive control variable gear ratio (VGR) steering system for a vehicle, said system comprising:
a VGR device that changes a gear ratio between a hand-wheel angle of a hand-wheel of the vehicle and a road wheel angle of the vehicle;
a vehicle speed sensor providing a vehicle speed signal of a speed of the vehicle;
vehicle sensors that provide vehicle sensor signals identifying parameters of the operation of the vehicle;
a driver attentiveness processor that is responsive to the vehicle sensor signals, said driver attentive processor determining an attentiveness of the vehicle driver, said driver attentiveness processor providing a driver attentiveness signal identifying how attentive the driver is; and
a VGR sub-system that provides a VGR signal to the VGR device for changing the gear ratio, said VGR sub-system determining the gear ratio based on the vehicle speed signal and the driver attentiveness signal, where the gear ratio is increased from a nominal value as the vehicle speed increases for drivers that are less attentive.
12. The system according to claim 11 further comprising a hand-wheel angle sensor providing a hand-wheel angle signal identifying the rotation of the hand-wheel of the vehicle, said VGR sub-system using the hand-wheel angle signal to change the gear ratio based on a combination of vehicle speed, driver attentiveness and a desired yaw-rate gain.
13. The system according to claim 12 wherein the driver attentiveness processor includes a steering activity index processor that calculates a steering activity index that identifies a driver's steering activity, said steering activity index being combined with the driver attentiveness signal, where the gear ratio is increased from a nominal value as the vehicle speed increases for increases in steering activity.
14. The system according to claim 13 wherein the driver attentiveness processor further includes a signal processor that receives the hand-wheel angle signal and provides a steering angle signal and a steering angle rate signal and a curvature derivation processor that provides a road curvature signal, said steering activity index processor being responsive to the steering angle signal, the steering angle rate signal and the road curvature signal to calculate the steering activity index.
15. The system according to claim 14 wherein the steering activity index processor uses the following equation to determine the steering activity index:
R
=
c
1
δ
HWA
+
c
2
δ
.
HWA
+
c
3
ρ
c
1
δ
max
+
c
2
δ
.
max
+
c
3
ρ
max
Where R is the steering activity index, {dot over (δ)} HWA is the steering angle rate, δ HWA is the hand-wheel angle, ρ is the road curvature, δ max and {dot over (δ)} max are pre-defined maximum values for the steering angle and the steering angle rate, respectively, ρ max is a pre-defined maximum value for the road curvature and c 1 , c 2 and c 3 are predetermined coefficients.
16. The system according to claim 11 wherein the VGR sub-system decreases the gear ratio if the hand-wheel angle increases above a critical threshold value where vehicle tires operate in a non-linear region of lateral force versus tire side slip angle.
17. The system according to claim 16 wherein the critical threshold value decreases as the vehicle speed increases.
18. The system according to claim 11 wherein the driver attentiveness processor determines whether the vehicle driver is drowsy to determine the driver attentiveness signal.
19. The system according to claim 11 wherein one of the vehicle sensors is a camera that provides images of the vehicle driver.