Anti-skid control system for automotive vehicles

An anti-skid control system for an automotive vehicle, comprising:

• sensor means for detecting a wheel speed of each road wheel of the vehicle;
• control means for controlling a wheel-brake cylinder pressure of each road wheel;
• compensation means for compensating a different-diameter wheel speed of a different-diameter road wheel with a small-sized tire in case that one of said road wheels is the different-diameter road wheel;
• diameter-difference ratio derivation means for deriving a ratio of diameter-difference between an outside diameter of the different-diameter road wheel and an outside diameter of the other road wheel with a usual tire, on the basis of a maximum wheel speed corresponding to the different-diameter wheel speed and a second highest wheel speed of the wheel speeds detected by said sensor means;
• and
• error rate calculation means for calculating an error rate of the different-diameter wheel speed with respect to the detected wheel speed of the other road wheel, on the basis of said ratio of diameter-difference, except at least during anti-skid control;
• wherein said compensation means compensates the different-diameter wheel speed by said error rate;
• wherein a first calculation means is provided for deriving a compensated vehicle speed from the compensated different-diameter wheel speed, and a second calculation means is provided for deriving a slip ratio of the different-diameter road wheel from the compensated vehicle speed and the compensated different-diameter wheel speed and deriving a slip ratio of the other road wheel from the compensated vehicle speed and the detected wheel speed of the other road wheel,
• wherein said control means controls each wheel-brake cylinder pressure so that the slip ratio is adjusted to a predetermined reference slip ratio.

An anti-skid control system for an automotive vehicle, comprising:

• sensor means for detecting a wheel speed of each road wheel of the vehicle;
• control means for controlling a wheel-brake cylinder pressure of each road wheel to prevent deceleration slip during braking;
• compensation means for compensating a different-diameter wheel speed of a different-diameter road wheel with a small-sized tire in case that one of said road wheels is the different-diameter road wheel;
• diameter-difference ratio derivation means for deriving a ratio of diameter-difference between an outside diameter of the different-diameter road wheel and an outside diameter of the other road wheel with a usual tire, on the basis of a maximum wheel speed corresponding to the different-diameter wheel speed and a second highest wheel speed of the wheel speeds detected by said sensor means;
• and
• error rate calculation means for calculating an error rate of the different-diameter wheel speed with respect to the detected wheel speed of the other road wheel, on the basis of said ratio of diameter-difference, except at least during anti-skid control;
• wherein said compensation means compensates the different-diameter wheel speed by said error rate;
• wherein a first calculation means is provided for deriving a compensated pseudo vehicle speed from the compensated different-diameter wheel speed, and said second calculation means is provided for deriving a slip ratio of the different-diameter road wheel from the compensated pseudo vehicle speed and the compensated different-diameter wheel speed and deriving a slip ratio of the other road wheel from the compensated vehicle speed and the detected wheel speed of the other road wheel,
• wherein said control means controls each wheel-brake cylinder pressure so that the slip ratio is adjusted to a predetermined reference slip ratio,
• wherein said compensation means compensates the different-diameter wheel speed by said error rate under a particular condition in which, in absence of the anti-skid control, said ratio of diameter-difference is greater than a predetermined minimum ratio of diameter-difference corresponding to a threshold of a lower dead zone and less than a predetermined maximum ratio of diameter-difference corresponding to a threshold of an upper dead zone, for a predetermined first period of time.