VEHICLE SYSTEMS CONTROL FOR IMPROVING STABILITY

• US 20080183353A1
• Filed: 01/24/2008
• Published: 07/31/2008
• Est. Priority Date: 01/25/2007
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Kang, Xiaodi, Monsma, William, Post, James W.
• Granted Patent: US 8,229,642 B2
• Time in Patent Office: Days
• US Class Current: 701/42
• CPC Class Codes: B60G 17/0165 to an external condition, e.g. rough road surface, side wind
• CPC Class Codes: B60G 17/0195 characterised by the regulation being combined with other vehicle control systems conjoint control of vehicle sub-units including control of suspension systems B60W10/22
• CPC Class Codes: B60G 17/06 Characteristics of dampers , e.g. mechanical dampersB60G17/015 takes precedence
• CPC Class Codes: B60G 2800/016 Yawing condition
• CPC Class Codes: B60G 2800/212 Transversal; Side-slip during cornering
• CPC Class Codes: B60G 2800/213 by applying forward/backward torque on each wheel individually
• CPC Class Codes: B60G 2800/214 by varying the load distribution
• CPC Class Codes: B60G 2800/215 by applying a braking action on each wheel individually
• CPC Class Codes: B60G 2800/912 Attitude Control; levelling control
• CPC Class Codes: B60G 2800/94 Electronic Stability Program (ESP, i.e. ABS+ASC+EMS)
• CPC Class Codes: B60T 2201/14 Electronic locking-differential
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 2260/06 Active Suspension System
• CPC Class Codes: B60T 2270/302 for all-wheel drive vehicles
• CPC Class Codes: B60T 8/17555 specially adapted for enhancing driver or passenger comfort, e.g. soft intervention or pre-actuation strategies
• CPC Class Codes: B60T 8/1769 specially adapted for vehicles having more than one driven axle, e.g. four-wheel drive vehicles
• CPC Class Codes: B60W 10/18 including control of braking systems
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 10/22 including control of suspension systems
• CPC Class Codes: B60W 2710/22 Suspension systems
• CPC Class Codes: B60W 2720/14 : Yaw
• CPC Class Codes: B60W 2720/30 : Wheel torque
• CPC Class Codes: B60W 2720/403 : between front and rear axle
• CPC Class Codes: B60W 30/02 : Control of vehicle driving stability
• CPC Class Codes: B60W 30/18172 : Preventing, or responsive to skidding of wheels
• CPC Class Codes: B60W 40/064 : Degree of grip
• CPC Class Codes: B60W 40/11 : Pitch movement
• CPC Class Codes: B60W 40/112 : Roll movement
• CPC Class Codes: B60W 40/114 : Yaw movement

Abstract

Improved methods of controlling the stability of a vehicle are provided via the cooperative operation of vehicle stability control systems such as an Active Yaw Control system, Antilock Braking System, and Traction Control System. These methods use recognition of road surface information including the road friction coefficient (mu), wheel slippage, and yaw deviations. The methods then modify the settings of the active damping system and/or the distribution of drive torque, as necessary, to increase/reduce damping in the suspension and shift torque application at the wheels, thus preventing a significant shift of load in the vehicle and/or improving vehicle drivability and comfort. The adjustments of the active damping system or torque distribution temporarily override any characteristics that were pre-selected by the driver.

Claims

1. A cooperative Active Yaw Control (AYC) method for providing vehicle stability comprising the steps of:

providing a vehicle stability assist (VSA) system that determines yaw deviation from a desired pre-determined yaw condition, the system including a vehicle stability assist-Active Yaw Control electronic control unit (VSA-AYC ECU);

providing a system including a Direct Yaw Control drive torque control unit (DYC-ECU) for selectively delivering torque to wheels on the front axle of the vehicle and wheels on the rear axle of the vehicle in different amounts;

shifting torque from wheels on the back axle to wheels on the front axle in order to correct the yaw deviation.

2. The method according to claim 1, further comprising the step of adjusting yaw via braking only if sufficient yaw correction cannot be obtained via the shifting of torque.

3. The method according to claim 1, where torque shifting is accomplished by placing a maximum torque ceiling of the torque applied at each rear wheel.

4. The method according to claim 1, where torque shifting is accomplished by reducing the torque applied to each rear wheel in equivalent amounts.

5. A cooperative Active Damping System (ADS) method for providing enhanced vehicle stability during vehicle braking comprising the steps of:

providing an anti-lock braking system (ABS) on the vehicle;

providing an Active Damping System (ADS) for adjusting the suspension stiffness on the vehicle;

inferring road surface condition via the activation status of the ABS and a vector representation of the longitudinal and lateral acceleration of the vehicle at a particular instant;

when the ABS is activated and the acceleration vector representation is greater than 0.5 g, changing the ADS to a more rigid state than prior to braking system application; and

after a fixed period of time, returning the ADS to a state of rigidity prior to the brake system application.

6. The method of claim 5, wherein the acceleration vector representation is the square root of the sum of the squares of longitudinal vehicle acceleration and lateral vehicle acceleration.

7. The method of claim 5, wherein the fixed period of time is between 1 and 3 seconds.

8. The method of claim 5, wherein the step of changing the ADS to a more rigid state includes increasing suspension stiffness at all four wheels of the vehicle.

9. The method of claim 5, wherein application of the braking system is determined via a Vehicle Stability Assist (VSA) system within the vehicle.

10. A cooperative Active Damping System (ADS) method for providing enhanced stability of a vehicle travelling on a road, comprising the steps of:

providing an Active Damping System (ADS) for adjusting the suspension characteristics on the vehicle;

providing an Antilock Braking System (ABS) on the vehicle;

providing a Traction Control System (TCS) on the vehicle;

providing an Active Yaw Control (AYC) system on the vehicle;

inferring a high coefficient of friction of the road surface when the operational (Activating/Not activating) status of at least one of the ABS, TCS and AYC systems is “

Activating” and

a vector representation of the vehicle'"'"'s longitudinal and lateral acceleration is greater than 0.5 g, and inferring a low coefficient of friction of the road surface when the operational status of at least one of the ABS, TCS and AYC systems is “

Activating”

or the vector representation of acceleration is below 0.3 g; and

upon inferring a high coefficient of road surface friction, adjusting the damping state of the ADS to a high damping setting; and

upon inferring a low coefficient of road surface friction, adjusting the damping state of the ADS to a low damping setting.

11. The method of claim 10, wherein after a fixed period of time of between 1 and 3 seconds, returning the ADS to a damping state prior to inferring the road conditions.

12. The method of claim 10, wherein the changes to the damping state of the ADS override a driver pre-selected damping state of the ADS.

13. A cooperative Active Damping System (ADS) method for providing enhanced vehicle stability comprising the steps of:

providing an Active Damping System (ADS) for adjusting the suspension characteristics on the vehicle;

providing a Traction Control System (TCS) on a vehicle;

using the TCS to determine the slip ratio at each wheel of the vehicle;

if the slip ratio is high at a wheel, stiffening the suspension via the ADS in an area adjacent to that wheel.

14. A cooperative Active Damping System (ADS) method for providing vehicle stability comprising the steps of:

providing a vehicle stability assist (VSA) system that determines yaw deviation from a desired condition, the system including a vehicle stability assist-Active Yaw Control electronic control unit (VSA-AYC ECU);

providing an Active Damping System (ADS) for adjusting the suspension stiffness on the vehicle, at least independently between the front and the rear of the vehicle;

shifting the front to back damping distribution between using the ADS in order to correct the yaw deviation.

15. The method according to claim 14, further comprising the step of reducing yaw deviation via braking if sufficient yaw rate error reduction cannot be obtained via the shifting of suspension stiffness from front to back.

16. A cooperative Traction Control System (TCS) method for providing enhanced vehicle stability comprising the steps of:

providing a Traction Control System (TCS) on a vehicle;

using the TCS to determine the slip ratio at each wheel of the vehicle;

providing a system including a DYC drive torque control distribution ECU for selectively delivering torque to each of the front wheels and rear wheels of the vehicle in different amounts;

shifting the front to back torque distribution between wheels on the front axle and wheels on the rear axle in order to correct the wheel slippage detected by the TCS.

17. The method according to claim 16, further comprising the step of reducing wheel slip via reduction of engine torque if sufficient wheel slip reduction cannot be obtained via the shifting of torque.

18. The method according to claim 17, further comprising the step of reducing wheel slip via braking if sufficient wheel slip reduction cannot be obtained via the shifting of torque.

19. The method according to claim 16, further comprising the step of:

shifting the side to side distribution of torque between wheels on the front axle and wheels on the rear axle in order to correct the detected wheel slip.

20. A method for providing enhanced vehicle stability comprising the steps of:

providing a vehicle with all wheel drive;

providing a Vehicle Stability Assist (VSA) system on the vehicle;

providing a Traction Control system (TCS) on the vehicle;

providing an Active Yaw Control (AYC) system on the vehicle;

inferring a high coefficient of friction of the road surface when the operational (Activating/Not activating) status of at least one of the TCS and AYC systems is “

Activating” and

a vector representation of the vehicle'"'"'s longitudinal and lateral acceleration is greater than 0.5 g and inferring a low coefficient of friction of the road surface when the operational status of each of the TCS and AYC systems is “

Activating”

or the vector representation of acceleration is below 0.3 g; and

upon inferring the coefficient of friction of the road, changing the distribution of torque amongst the vehicle wheels as follows;

if the coefficient of friction is high, implementing a strong side to side and front to rear torque bias; and

if the coefficient of friction is low, implementing a moderate side to side and front to rear torque bias.

21. The method of claim 20, wherein after a fixed period of time between 1 and 3 seconds, returning the distribution of drive torque to a state prior to inferring the road conditions.

22. The method of claim 20, wherein the changes to the distribution of drive torque overrides any driver pre-selected distribution of drive torque.

23. A cooperative Active Yaw Control (AYC) and Traction Control System (TCS) method for providing vehicle stability comprising the steps of:

providing a Traction Control system (TCS) on a vehicle to detect wheel slippage;

providing a vehicle stability assist (VSA) system that determines yaw deviation from a desired condition, the system including a Vehicle Stability Assist-Active Yaw Control electronic control unit (VSA-AYC ECU);

providing a system including a drive torque control ECU for selectively delivering torque to wheels on the front axle of the vehicle and wheels on the rear axle of the vehicle in different amounts;

shifting the front to back torque distribution between wheels on the front axle and wheels on the rear axle in order to correct yaw deviation;

shifting the front to back torque distribution between wheels on the front axle and wheels on the rear axle in order to correct the wheel slippage detected by the TCS;

wherein below a critical vehicle speed of 60 kilometers per hour, the shift of torque requested to correct the wheel slippage detected by the TCS supercedes the shift of torque requested in order to correct the yaw deviation and above the critical vehicle speed the shift of torque requested in order to correct yaw deviation supercedes.