System for driving stability control

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.

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.

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.

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.

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.

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.