Method for Providing a Lanekeeping Assistance Based on Modifying Mechanical Sources of Steering Torques

• US 20100145575A1
• Filed: 12/05/2008
• Published: 06/10/2010
• Est. Priority Date: 12/05/2008
• Status: Active Grant

• Current Assignee: Volkswagen AG
• Original Assignee: Volkswagen Group Of America Incorporated (Volkswagen AG)
• Inventors: Stoschek, Arne, Switkes, Joshua
• Granted Patent: US 9,090,285 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence

Abstract

A method for providing a lanekeeping assistance for a vehicle includes determining road lane characteristics such as a road lane curvature. A vehicle velocity and a vehicle position with respect to a road lane are also determined. A desired steering angle is determined as a function of at least the road lane characteristics. A lanekeeping torque acting on the steering system of the vehicle in order to keep the vehicle on a desired path is determined as a function of at least the desired steering angle. The lanekeeping torque is generated by modifying at least one mechanical steering torque such as a jacking torque, an aligning torque, an inertia torque and a damping torque.

Claims

1. A method for providing a lanekeeping assistance, the method which comprises:

determining road lane characteristics;

determining a vehicle velocity and a vehicle position;

determining a desired steering angle as a function of at least the road lane characteristics;

providing a lanekeeping torque acting on a steering system of a vehicle as a function of at least the desired steering angle; and

generating the lanekeeping torque by modifying at least one mechanical steering torque selected from the group consisting of a jacking torque, an aligning torque, an inertia torque and a damping torque.

2. The method according to claim 1, which comprises determining the road lane characteristics by at least determining a road lane curvature.

3. The method according to claim 1, which comprises determining the desired steering angle as a function of at least the road lane characteristics, the vehicle velocity and the vehicle position with respect to a road lane.

4. The method according to claim 1, wherein the step of determining a vehicle position includes determining a lateral error as a distance between a center of gravity of the vehicle and a desired path of the vehicle and determining a heading angle as an angle between a longitudinal axis of the vehicle and the desired path of the vehicle.

5. The method according to claim 4, which comprises using a road lane centerline as the desired path of the vehicle.

6. The method according to claim 1, which comprises generating the lanekeeping torque such that the steering system of the vehicle guides the vehicle substantially along a desired path.

7. The method according to claim 1, which comprises:

measuring a steering angle of front wheels of the vehicle; and

determining the jacking torque as a substantially linear function of the steering angle.

8. The method according to claim 7, which comprises determining the jacking torque by using the following relation:

τ

_jack=−

K_jack δ

wherein τ

_jack denotes the jacking torque, K_jack is a property of a steering geometry of the steering system and δ

denotes the steering angle of the front wheels of the vehicle;

centering the jacking torque on the desired steering angle in accordance with the following relation;

τ

_jackdes=−

K_jack(δ

−

δ

_des)

wherein τ

_jackdes denotes a desired jacking torque and δ

_des denotes the desired steering angle of the front wheels of the vehicle such that the desired jacking torque is substantially zero if the steering angle substantially matches the desired steering angle and such that an additional jacking torque is generated in accordance with the following relation;

τ

_jackadd=K_jackδ

_des

wherein τ

_jackadd is the additional jacking torque to be added in order to center the jacking torque on the desired steering angle.

9. The method according to claim 1, which comprises:

measuring a steering angle of front wheels of the vehicle;

determining an aligning torque by using the following relation;

${\mathrm{\tau <br><br>}}_{\mathrm{align}}=-K_{\mathrm{align}}<br><br>\left(\frac{\stackrel{.}{e}}{U_x}-\mathrm{\psi <br><br>}+\frac{\mathrm{ar}}{U_x}-\mathrm{\delta <br><br>}\right)$

wherein τ

_align denotes the aligning torque, K_align is a function of steering parameters, ė

denotes a sideways velocity of the vehicle relative to a road lane, U_x denotes a longitudinal speed of the vehicle, ψ

denotes a heading angle as an angular difference between a longitudinal axis of the vehicle and a desired path, a is a distance between a front axle of the vehicle and a center of gravity of the vehicle, r denotes a yaw rate of the vehicle and, and δ

denotes the steering angle.

10. The method according to claim 9, which comprises centering the aligning torque on the desired steering angle, a desired heading angle, and a desired yaw rate in accordance with the following relation:

${\mathrm{\tau <br><br>}}_{{\mathrm{align}}_{\mathrm{des}}}=-K_{\mathrm{align}}<br><br>\left(\frac{\stackrel{.}{e}}{U_x}-\left(\mathrm{\psi <br><br>}-{\mathrm{\psi <br><br>}}_{\mathrm{des}}\right)+\frac{a}{U_x}<br><br>\left(r-r_{\mathrm{des}}\right)-\left(\mathrm{\delta <br><br>}-{\mathrm{\delta <br><br>}}_{\mathrm{des}}\right)\right)$

wherein τ

_aligndes is a desired aligning torque, ψ

_des denotes the desired heading angle, r_des denotes the desired yaw rate of the vehicle, and δ

_des denotes the desired steering angle.

11. The method according to claim 10, which comprises calculating an additional aligning torque by using the following relation:

${\mathrm{\tau <br><br>}}_{{\mathrm{align}}_{\mathrm{add}}}=-K_{\mathrm{align}}<br><br>\left({\mathrm{\psi <br><br>}}_{\mathrm{des}}+\frac{a}{U_x}<br><br>r_{\mathrm{des}}-{\mathrm{\delta <br><br>}}_{\mathrm{des}}\right)$

wherein τ

_alignadd is the additional aligning torque to be added for providing a lanekeeping assistance.

12. The method according to claim 10, which comprises determining the desired yaw rate in accordance with the following relation:

$r_{\mathrm{des}}=\frac{{\mathrm{\delta <br><br>}}_{\mathrm{des}}<br><br>U_x}{L}$

wherein L is a distance between the front axle of the vehicle and a rear axle of the vehicle.

13. The method according to claim 10, which comprises determining the desired heading angle by using the following relation:

${\mathrm{\psi <br><br>}}_{\mathrm{des}}=-\frac{C_f<br><br>\left[{\mathrm{bLC}}_r-{\mathrm{amv}}^2\right]}{L^2<br><br>C_f<br><br>C_r-\left({\mathrm{aC}}_f-{\mathrm{bC}}_r\right)<br><br>{\mathrm{mv}}^2}<br><br>{\mathrm{\delta <br><br>}}_{\mathrm{ff}}$

wherein C_f is a cornering stiffness of front wheels of the vehicle, C_r is a cornering stiffness of rear wheels of the vehicle, L is a distance between the front axle of the vehicle and a rear axle of the vehicle, b is a distance between the center of gravity of the vehicle and a rear axle of the vehicle, m is a total mass of the vehicle, v is a velocity of the vehicle and δ

_ff is a feedforward component of a steering angle correction.

14. The method according to claim 1, which comprises:

measuring a steering angle of front wheels of the vehicle;

determining an inertia and damping torque acting on the steering system of the vehicle by using the following relation;

τ

_effective=−

I_s{umlaut over (δ

)}−

C_s{dot over (δ

)}

wherein τ

_effective is the inertia and damping torque resulting from an inertia of masses of the steering system and resulting from friction in the steering system, I_s and C_s are parameters defining characteristics of an inertia and, respectively, a damping of the steering system and δ

is the steering angle of the front wheels of the vehicle.

15. The method according to claim 14, which comprises determining a desired inertia and damping torque such that an inertia and damping torque acting on a steering wheel of the vehicle is substantially eliminated when the steering wheel turns at a desired rate.

16. The method according to claim 15, which comprises calculating the desired inertia and damping torque by using the following relation:

τ

_IDdes=−

I_s({umlaut over (δ

)}−

{umlaut over (δ

)}_des)−

C_s({dot over (δ

)}−

{dot over (δ

)}_des)

wherein τ

_IDdes is the desired inertia and damping torque and δ

_des is a desired steering angle.

17. The method according to claim 16, which comprises calculating an additional inertia and damping torque by using the following relation:

τ

_IDadd=I_s{umlaut over (δ

)}_des+C_s{dot over (δ

)}_des

wherein τ

_IDadd is the additional inertia and damping torque to be added in order to substantially eliminate an inertia and damping torque acting on the steering wheel of the vehicle when the steering wheel turns at a desired rate.

18. The method according to claim 1, which comprises calculating an additional steering torque τ

_add by adding a number of steering torque components wherein the steering torque components collectively keep the vehicle substantially on a desired path and wherein the steering torque components include at least an additional jacking torque component τ

_jackadd, an additional aligning torque component τ

_alignadd and an additional inertia and damping torque component τ

_IDadd.