System for driving stability control

• US 5,862,503 A
• Filed: 11/24/1997
• Issued: 01/19/1999
• Est. Priority Date: 11/25/1994
• Status: Expired due to Term

• Current Assignee: ITT Automotive Europe GmbH
• Original Assignee: ITT Automotive Europe GmbH
• Inventors: Geiger, Thomas, Neederkorn, C. Jan, Worsdorfer, Karl-Friedrick, Lammen, Benno, Drumm, Stefan, Eckert, Alfred, Wanke, Peter, Kranz, Thomas, Graber, Johannes
• Primary Examiner(s): ZANELLI, MICHAEL J
• Application Number:
  US08/977,369
• Time in Patent Office: 421 Days
• Field of Search: 701/70, 701/72, 701/83, 701/78, 303/139, 303/140, 303/146, 303/147, 303/148, 303/150, 303/155, 303/167, 303/186, 303/189, 180/197
• US Class Current: 701/78
• CPC Class Codes: B60G 2400/1042 using at least two sensors
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 2230/02 Side slip angle, attitude angle, floating angle, drift angle
• CPC Class Codes: B60T 2270/313 with less than three sensors (yaw rate, steering angle, lateral acceleration)
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 2422/95 Measuring the same parameter at multiple locations of the vehicle
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2520/20 Sideslip angle
• CPC Class Codes: B60W 2720/14 Yaw
• CPC Class Codes: B60W 2720/30 Wheel torque
• CPC Class Codes: B60W 30/02 Control of vehicle driving stability
• CPC Class Codes: B60W 40/064 Degree of grip

Abstract

Apparatus for improving the driving behavior of a vehicle is provided. The vehicle has front and rear axles, each having a plurality of wheels. Each wheel-has a brake. Sensor are provided for measuring the rotational speed of each wheel, the vehicle yaw rate and the vehicle lateral acceleration. An anti-lock braking system provides first preset pressure values for controlling each brake, to prevent the wheels from locking during braking. A traction slip control system provides second preset pressure values for controlling each brake, to prevent the wheels from slipping during acceleration. A brake effort proportioning system provides third preset pressure values for distributing braking pressure between the wheels of the front axle and the wheels of the rear axle. A yawing moment controller provides fourth preset pressure values used to control each brake during cornering, to avoid application to the vehicle of an unbalanced moment which would cause the vehicle to understeer or oversteer. The antilock braking system, traction slip control system, brake effort proportioning means and yawing moment control system all operate independently of one another. A prioritizing mechanism applies criteria to determine a desired brake pressure that is applied to each wheel, based on the outputs of the antilack braking, traction slip control, brake effort proportioning, and yawing moment control systems.

Claims

1. Apparatus for improving the driving behavior of an automotive vehicle tending to oversteering or understeering, the vehicle having a plurality of wheels, each wheel having a brake, said apparatus comprising:

a plurality of sensors for generating signals representing a steering angle, a velocity, a lateral acceleration and a measured yaw rate of the vehicle;

coefficient of friction recognition means, responsive to the velocity, the lateral acceleration, the measured yaw rate and the steering angle, for determining;

(1) a maximum coefficient of friction between the wheels and a surface on which the vehicle travels, and

(2) an instantaneous coefficient of friction that is less than or equal to the maximum coefficient of friction;

vehicle model means responsive to the steering angle, the velocity and the instantaneous coefficient of friction for determining a yaw rate limit and a desired yaw rate that is less than or equal to a yaw rate limit;

comparing means for comparing the measured yaw rate and the desired yaw rate to determine a difference therebetween;

yawing moment control means responsive to the difference for determining a moment that is applied to the vehicle, so that the measured yaw rate is adjusted towards the desired yaw rate; and

means responsive to the yawing moment control means for determining pressure adjustments that are applied to each brake, individually, to generate the moment.

2. Apparatus for controlling an automotive vehicle, the vehicle having a plurality of wheels, each wheel having an individually operable brake, said apparatus comprising:

means for determining a steering angle of the vehicle;

yawing moment control means responsive to the steering angle for determining a yawing moment that is to be applied to the vehicle to prevent one of the group consisting of an undesirable yaw angle, yaw rate and yaw acceleration; and

distribution logic means responsive to the yawing moment control means for determining;

a respectively different weighted coefficient for each individual brake, and

an individual braking pressure to be applied to each respective one of the brakes based on said yawing moment and the respective weighted coefficient of said each respective one brake.

3. Apparatus for controlling an automotive vehicle, the vehicle having a plurality of wheels which contact a surface, each wheel having an individually operable brake, said apparatus comprising:

yawing moment control means for determining a moment that is to be applied to the vehicle to prevent any one of the group consisting of an undesirable yaw angle, yaw rate and yaw acceleration;

slip determining means for determining a longitudinal slip value of each of the wheels, individually;

distribution logic means responsive to the yawing moment control means and the slip determining means for determining an individual braking pressure to be applied to each respective one of the brakes based on said moment, including;

selective actuating means for selectively actuating at least one of the brakes so that the longitudinal slip value of the wheel to which the one brake corresponds is greater than a maximum friction longitudinal slip value at which the coefficient of friction between the wheel and the surface reaches a maximum value, without actuating all of the brakes at longitudinal slip values above the maximum friction longitudinal slip value.

4. In a yaw moment control system for improving the driving behavior of an automotive vehicle tending to oversteering or understeering, the vehicle having a plurality of sensors for measuring a velocity, a steering angle and a yaw rate of the vehicle, and a plurality of wheels including an inside rear wheel, each wheel having a respective brake, a method for controlling the brakes, individually, while turning on a pavement, comprising the steps of:

(a) measuring the velocity, the steering angle and the yaw rate;

(b) determining a desired yaw rate based on the measured velocity and steering angle;

l (c) determining a difference between the desired yaw rate and the measured yaw rate;

(d) calculating a moment that, if applied to the vehicle, would change the yaw rate of the vehicle to the desired yaw rate;

(e) determining whether the vehicle is understeering; and

(f) increasing a braking force of the inside rear brake if the vehicle is understeering, such that the longitudinal slip value of the inside rear wheel is greater than a maximum friction longitudinal slip value at which the coefficient of friction between the wheel and the surface reaches a maximum value, without actuating all of the brakes at longitudinal slip values above the maximum friction longitudinal slip value, thereby to maintain a longitudinal friction force between the inside rear wheel and the pavement while reducing a lateral friction force between the inside rear wheel and the pavement by an amount sufficient to apply the calculated moment to the vehicle.

5. In a yaw moment control system for improving the driving behavior of an automotive vehicle tending to oversteering or understeering, the vehicle having a plurality of sensors for measuring a velocity, a steering angle and a yaw rate of the vehicle, and a plurality of wheels, each wheel having a respective brake, a method for controlling the brakes, individually, while turning on a pavement, comprising the steps of:

(a) measuring the velocity, the steering angle and the yaw rate;

(b) determining a desired yaw rate based on the measured velocity and steering angle;

(c) determining a difference between the desired yaw rate and the measured yaw rate;

(d) calculating a moment that, if applied to the vehicle, would change the yaw rate of the vehicle to the desired yaw rate;

(e) determining whether the vehicle is oversteering; and

(f) increasing a braking force of the outside front brake if the vehicle is oversteering, such that the longitudinal slip value of the outside front wheel is greater than a maximum friction longitudinal slip value at which the coefficient of friction between the wheel and the surface reaches a maximum value, without actuating all of the brakes at longitudinal slip values above the maximum friction longitudinal slip value, thereby to maintain a longitudinal friction force between the outside front wheel and the pavement while reducing a lateral friction force between the outside front wheel and the pavement by an amount sufficient to apply the calculated moment to the vehicle.

6. Yaw moment control apparatus for improving the driving behavior of an automotive vehicle, the vehicle including means for determining a vehicle velocity, a vehicle steering angle, a measured yaw rate, and a vehicle lateral acceleration, said apparatus comprising:

yaw control means for generating a value representing a desired yaw rate adjustment based on the vehicle steering angle, the vehicle velocity and the measured yaw rate;

means for calculating an estimated coefficient of friction based on the vehicle velocity, the lateral acceleration, the measured yaw rate and the steering angle, said estimated coefficient of friction being used by the yaw control means for determining the desired yaw rate adjustment only while the vehicle is traveling through a curve.

7. Yaw moment control apparatus for improving the driving behavior of an automotive vehicle, the vehicle having an engine and front and rear axles, each axle having a plurality of wheels, each wheel having a brake, the vehicle including means for determining a vehicle reference velocity from the rotational velocities of the wheels, said apparatus comprising:

means for receiving signals from a plurality of sensors representing a vehicle steering angle, a lateral acceleration of the vehicle, and a measured yaw rate of the vehicle;

yaw rate change estimating means for generating a yaw rate change value representing a change in vehicle yaw rate based on the vehicle steering angle, the vehicle reference velocity and the measured yaw rate;

means for generating a value representing a velocity of the side slip angle based on the vehicle reference velocity, the lateral acceleration and the measured yaw rate;

yaw control law means for generating a value representing an engine torque adjustment based on the yaw rate change value and the velocity of the side slip angle, said engine torque adjustment value being applied to control the yaw rate of the vehicle; and

means for determining a coefficient of friction based on the vehicle reference velocity, the lateral acceleration, the measured yaw rate and the steering angle, wherein said coefficient of friction is used by the yaw control law means for determining the engine torque adjustment value while the vehicle is traveling through a curve.

8. In a yaw control system of a vehicle having a plurality of wheel brakes, a method for determining pressure adjustments for the brakes, individually, and applying the pressure adjustments to adjust a yawing moment that is applied to the vehicle by the brakes, comprising the steps of:

(1) detecting a condition in which an increase in the brake pressure applied to a first one of the brakes is required to apply the yawing moment to the vehicle while a driver of the vehicle is actuating the brakes to apply a first braking force to the vehicle;

(2) determining a reduction in pressure that is applied to a second one of the brakes; and

(3) reducing pressure in the second brake before initiating the increase in the pressure applied to the first brake.