Driving stability control system with selective brake actuation

Apparatus for controlling an automotive vehicle, the vehicle having a plurality of wheels which contact a surface, each wheel having an individually operable brake, the wheels including an inside rear wheel and an outside front wheel, 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 groups consisting of an undesirable yaw angle, yaw rate and yaw acceleration;
• understeering determining means for determining whether the vehicle is understeering;
• slip determining means for determining a longitudinal slip value of each of the wheels, individually;
• and
• distribution logic means responsive to the yawing moment control means, the understeering determining 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:
• 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 moment and the respective weighted coefficient of said one brake, the weighted coefficients of the inside rear brake and the outside front brake being adjusted to actuate the inside rear brake and the outside front brake, so that the longitudinal slip values of the inside rear wheel and the outside front wheel are 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, if the vehicle is understeering, and
• selective actuating means for selectively actuating at least the brakes of the inside rear wheel and outside front wheel based on the weighted coefficients.

Apparatus for controlling an automotive vehicle, the vehicle having a plurality of wheels which contact a surface, each wheel having an individually operable brake, the wheels including an inside front wheel and an outside front wheel, 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;
• oversteering determining means for determining whether the vehicle is oversteering;
• slip determining means for determining a longitudinal slip value of each of the wheels, individually;
• and
• distribution logic means responsive to the yawing moment control means, the oversteering determining 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 actuating the brakes of the inside front wheel and outside front wheel so that the longitudinal slip values of the inside front wheel and outside front wheel are greater than a maximum friction longitudinal slip value at which the coefficient of friction between the wheel and the surface reaches a maximum value, if the vehicle is oversteering, and
• 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 moment and the respective weighted coefficient of said one brake, the weighted coefficients of the inside front brake and the outside front brake being adjusted to actuate the inside front brake and the outside front brake.

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 pressure applied to 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 understeering;
• and
• (f) increasing pressure on 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 pressure applied to 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) determine 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 pressure on 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.

Brake system for a motor vehicle with more than two wheels, comprising:

• braking means for braking at least some of the wheels, wherein the braking means associated with one particular wheel can be actuated independently from the others;
• a control device, which determines the individual braking torques, which the braking means is to apply to the wheels, on the basis of a measured velocity, steering angle and yaw rate of the vehicle input to the control device, and which sends a corresponding plurality of control commands to the braking means;
• a means for determining the actual longitudinal slip of the wheels;
• a means for determining a yawing moment to be generated around the vertical axis of the motor vehicle, and which sends a corresponding value to the control device, which is utilized to prevent one of the group consisting of undesired yaw angles, yaw rates, and yaw accelerations,
• wherein the braking means of at least one wheel can be actuated such that the longitudinal slip of the wheel will be adjusted to a value that is greater than the longitudinal slip at which the maximum frictional connection is reached.