METHOD AND SYSTEM FOR DETERMINING A REFERENCE YAW RATE FOR A VEHICLE

• US 20120109458A1
• Filed: 10/28/2010
• Published: 05/03/2012
• Est. Priority Date: 10/28/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Sidlosky, David M.
• Granted Patent: US 8,626,389 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B60G 17/02 Spring characteristics , e.g. mechanical springs and mechanical adjusting meansB60G17/005, B60G17/015 take precedence
• CPC Class Codes: B60G 17/08 Characteristics of fluid dampers adjusting fluid dampers in general F16F9/44 - F16F9/53
• CPC Class Codes: B60G 2400/0523 Yaw rate
• CPC Class Codes: B60T 2210/22 Banked curves
• CPC Class Codes: B60T 2230/02 Side slip angle, attitude angle, floating angle, drift angle
• CPC Class Codes: B60T 2250/03 Vehicle yaw rate
• CPC Class Codes: B60T 2260/09 Complex systems; Conjoint control of two or more vehicle active control systems
• CPC Class Codes: B60T 2270/86 Optimizing braking by using ESP vehicle or tire model
• CPC Class Codes: B60T 8/17551 determining control parameters related to vehicle stability used in the regulation, e.g. by calculations involving measured or detected parameters
• CPC Class Codes: B60W 2510/20 Steering systems
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 40/114 Yaw movement

Abstract

The method and system described herein may be used to determine a reference yaw rate (γ_ref) for a vehicle chassis control system, and may do so across a wide spectrum of vehicle operating conditions. These conditions may include, for example, when the vehicle is being driven: at low and high vehicle speeds, in forward and reverse directions, with front-, rear- and all-wheel steering systems, according to subtle and aggressive driving maneuvers, and on roads with flat or banked surfaces, to cite a few of the potential scenarios. According to an exemplary embodiment, the method and system take into account certain tire dynamics, such as the relaxation length (λ) of the tires, when estimating the reference yaw rate (γ_ref). Once an accurate reference yaw rate (γ_ref) is determined, the vehicle chassis control system may use this estimate to control one or more actuators that can influence the yaw rate of the vehicle. Some non-limiting examples of systems that may include such actuators are chassis systems, brake systems, steering systems, suspension systems, safety systems, stability control systems, traction control systems, torque control systems, or any other system that can affect the vehicle yaw rate. It is also possible for the method and system described herein to determine a reference lateral velocity (V_yref) for the vehicle as well.

Claims

1. A method for determining a reference yaw rate (γ

_ref) for a vehicle, comprising the steps of;

(a) determining a steering angle (δ

);

(b) determining a longitudinal velocity (V_x); and

(c) using the steering angle (δ

), the longitudinal velocity (V_x), and one or more tire dynamic(s) to determine the reference yaw rate (γ

_ref) for the vehicle, wherein the reference yaw rate (γ

_ref) generally corresponds to the ideal yaw rate of the vehicle if the vehicle was driven on a high-coefficient surface.

2. The method of claim 1, where step (a) further comprises determining a steering angle (δ

) by receiving a steering signal from a steering sensor mounted in the vehicle.

3. The method of claim 1, wherein step (a) further comprises determining a front steering angle (δ

_f) and a rear steering angle (δ

_r), and step (c) further comprises using the front steering angle (δ

_f), the rear steering angle (δ

_r), the longitudinal velocity (V_x), and the tire dynamic(s) to determine the reference yaw rate (γ

_ref) for a vehicle that includes steerable rear wheels.

4. The method of claim 1, wherein step (a) further comprises determining an effective steering angle (δ

_eff) with a steering response that has already been linearized, and step (c) further comprises using the effective steering angle (δ

_eff), the longitudinal velocity (V_x), and the tire dynamic(s) to determine the reference yaw rate (γ

_ref).

5. The method of claim 4, wherein step (a) further comprises determining the effective steering angle (δ

_eff) by using a look-up table, a measured steering angle (δ

_meas) is an input of the look-up table, a correction factor (K) is an output of the look-up table, and the effective steering angle (δ

_eff) is determined according to the equation (δ

_eff=Kδ

_meas.

6. The method of claim 1, where step (b) further comprises determining a longitudinal velocity (V_x) by receiving a vehicle speed signal from one or more vehicle speed sensor(s) mounted in the vehicle.

7. The method of claim 1, wherein step (c) further comprises using the steering angle (δ

) and the longitudinal velocity (V_x) to determine a yaw rate linear gain (gγ

_lin) and a yaw rate non-linear gain (gγ

_nonlin), and using the yaw rate linear gain (gγ

_lin) and the yaw rate non-linear gain (gγ

_nonlin) to determine the reference yaw rate (γ

_ref) for a vehicle that is traveling in either forward or reverse directions.

8. The method of claim 7, wherein the yaw rate linear gain (gγ

_lin) is determined according to the equation;

9. The method of claim 1, wherein step (c) further comprises using an effective steering angle (δ

_eff) with a steering response that has already linearized, a yaw rate linear gain (gγ

_lin) and a yaw rate non-linear gain (gγ

_nonlin) to determine an adjusted steering angle (δ

_adj), and using the adjusted steering angle (δ

_adj), the longitudinal velocity (V_x), and the tire dynamic(s) to determine the reference yaw rate (γ

_ref).

10. The method of claim 9, wherein the adjusted steering angle (δ

_adj) is determined according to the equation;

11. The method of claim 1, wherein step (c) further comprises using an adjusted steering angle (δ

_adj), a yaw rate linear gain (gγ

_lin), a yaw rate non-linear gain (gγ

_nonlin), and the longitudinal velocity of the vehicle (V_x) with a dynamic compensator to determine the reference yaw rate (γ

_ref), and the dynamic compensator is based on a linear bicycle model.

12. The method of claim 11, wherein the dynamic compensator uses the adjusted steering angle (δ

_adj) and the longitudinal velocity of the vehicle (V_x) to determine a slip angle (α

).

13. The method of claim 12, wherein the dynamic compensator uses the slip angle (α

), a cornering stiffness (C), the longitudinal velocity of the vehicle (V_x), a time delay (T), and a relaxation length (λ

) to determine a lateral force (F_y).

14. The method of claim 13, wherein the lateral force (F_y) is determined according to the equation:

15. The method of claim 14, wherein the dynamic compensator uses the lateral force (F_y) and the longitudinal velocity of the vehicle (V_x) to determine a yaw rate derivative {dot over (γ

)}.

16. The method of claim 15, wherein the dynamic compensator integrates the yaw rate derivative {dot over (γ

)} to determine the reference yaw rate (γ

_ref).

17. The method of claim 11, wherein the dynamic compensator has a low-speed mode that generates a steady state yaw rate (γ

_ss) for a vehicle that is traveling at very low speeds.

18. The method of claim 1, further comprising the steps of:

determining a gravitational component of a lateral acceleration (a_ygrav) of the vehicle and using the lateral acceleration (a_ygrav) to determine a yaw rate bank compensation (γ

_bank); and

subtracting the yaw rate bank compensation (γ

_bank) from a yaw rate estimate (γ

) to arrive at the reference yaw rate (γ

_ref).

19. The method of claim 1, further comprising the step of:

determining a reference lateral velocity (V_yref), wherein the reference lateral velocity (V_yref) generally corresponds to the ideal lateral velocity of the vehicle if the vehicle was driven on a high-coefficient surface.

20. The method of claim 1, further comprising the steps of:

using the reference yaw rate (γ

_ref) to generate one or more control signal(s);

sending the control signal(s) from a vehicle chassis control system to one or more actuator(s); and

controlling the actuator(s) with the control signal(s) such that the actuator(s) influence the yaw rate of the vehicle.

21. A method for determining a reference yaw rate (γ

_ref) for a vehicle, comprising the steps of;

(a) using a steering angle (δ

) and a longitudinal velocity (V_x) to determine a slip angle (α

);

(b) using the slip angle (α

) and one or more tire dynamic(s) to determine a lateral force (F_y) as a function of time;

(c) using the lateral force (F_y) as a function of time and the longitudinal velocity of the vehicle (V_x) to determine a yaw rate derivative {dot over (γ

)}; and

(d) integrating the yaw rate derivative {dot over (γ

)} to determine the reference yaw rate (γ

_ref), wherein the reference yaw rate (γ

_ref) generally corresponds to the ideal yaw rate of the vehicle if the vehicle was driven on a high-coefficient surface.

22. The method of claim 21, wherein step (b) further comprises using one or more tire dynamic(s) selected from the group consisting of:

a cornering stiffness (C), a time delay (T), or a relaxation length (λ

).

23. A chassis control system for a vehicle, comprising:

a steering sensor providing a steering signal that is representative of a steering angle (δ

);

one or more vehicle speed sensor(s) providing a vehicle speed signal that is representative of a longitudinal velocity (V_x);

a control unit receiving the steering signal from the steering sensor and the vehicle speed signal from the vehicle speed sensor(s), and providing a yaw rate control signal; and

one or more actuator(s) receiving the yaw rate control signal from the control unit, and using the yaw rate control signal to influence the yaw rate of the vehicle, wherein the control unit;

i) uses the steering angle (δ

), the longitudinal velocity (V_x), and one or more tire dynamic(s) to determine a reference yaw rate (γ

_ref) that generally corresponds to the ideal yaw rate of the vehicle if the vehicle was driven on a high-coefficient surface, and ii) uses the reference yaw rate (γ

_ref) to generate the yaw rate control signal.