Apparatus and method for stability controlling vehicular attitude using vehicular braking system

A method for stability controlling a vehicular attitude for a vehicle having front left and right and rear left and right road wheels (FL, FR, RL, and RR) and a brake system, the brake system including a master cylinder (14), a plurality of wheel cylinders, each of the wheel cylinders (20) being arranged around a corresponding one of the front left and right road wheels so as to apply a braking force to the corresponding one of the front left and right and rear left and right road wheels according to a braking liquid pressure applied thereto, two separate braking pressure distribution conduits (21, 22) which are so arranged and constructed as to separately distribute a braking liquid pressure into the two of the wheel cylinders arranged around the front left and rear right road wheels and into the other two of the wheel cylinders arranged around the front left and rear right road wheels, respectively, and a control purpose liquid pressure source (13i ) which is so arranged and constructed as to enable an increase in the liquid pressure to be applied to each wheel cylinder independently of the liquid pressure in the master cylinder, the method comprising the steps of:

• a) detecting each road wheel speed of the front left and right road wheels (FL, FR, RL, and RR);
• b) detecting a yaw rate (YAW) of the vehicle;
• c) deriving a lateral acceleration (Y.sub.G) acted upon the vehicle;
• d) deriving a vehicle body speed (Vi) from the respective road wheel speeds;
• e) deriving a slip angle (BETA) of the vehicle body to a vehicular forwarding direction on the basis of the detected yaw rate (YAW), the detected lateral acceleration (Y.sub.G), and the derived vehicle body speed (Vi);
• f) determining whether an oversteer exceeding a predetermined magnitude occurs on the basis of the determined slip angle;
• g) switching a selector (13e, 13f, 13g, and 13h ), the selector being arranged for selectively outputting the liquid pressure from either the master cylinder or the control purpose liquid pressure source through one of the two braking pressure distribution conduits to the wheel cylinders so that the liquid pressure from the control purpose liquid pressure source is supplied to one of the braking pressure distribution conduits through which a front road wheel braking force is given to the wheel cylinder arranged around one of the front left and right road wheels in a direction such as to suppress a yaw moment when determining that the oversteer exceeding the predetermined magnitude occurs.

A method for stability controlling a vehicular attitude for a vehicle having front left and right and rear left and right road wheels (FL, FR, RL, and RR) and a brake system, the brake system including a master cylinder, a plurality of wheel cylinders, each of the wheel cylinders being arranged around a corresponding one of the front left and right road wheels so as to apply a braking force to the corresponding one of the front left and right and rear left and right road wheels according to a braking liquid pressure applied thereto, two separate braking pressure distribution conduits which are so arranged and constructed as to separately distribute a braking liquid pressure into the two of the wheel cylinders arranged around the front left and rear right road wheels and into the other two of the wheel cylinders arranged around the front left and rear right road wheels, respectively, and a control purpose liquid pressure source which is so arranged and constructed as to enable an increase in the liquid pressure to be applied to each wheel cylinder independently of the liquid pressure in the master cylinder, the method comprising the steps of:

• a) detecting each road wheel speed of the front left and right road wheels (FL, FR, RL, and RR);
• b) detecting a yaw rate (YAW) of the vehicle;
• c) deriving a lateral acceleration (Y.sub.G) acted upon the vehicle;
• d) deriving a vehicle body speed (Vi) from the respective road wheel speeds;
• e) deriving a slip angle (BETA) of the vehicle body to a vehicular forwarding direction on the basis of the detected yaw rate (YAW), the detected lateral acceleration (Y.sub.G) ,and the derived vehicle body speed (Vi);
• f) determining whether an understeer exceeding a predetermined magnitude occurs on the basis of the determined slip angle;
• g) switching a selector, the selector being arranged for selectively outputting the liquid pressure from either the master cylinder or the control purpose liquid pressure source through one of the two braking pressure distribution conduits to the wheel cylinders so that the liquid pressure from the control purpose liquid pressure source is supplied to one of the braking pressure distribution conduits through which a front road wheel braking force is given to the wheel cylinder arranged around one of the front left and right road wheels in a direction such as to develop a yaw moment when determining that the understeer exceeding the predetermined magnitude occurs.