Braking force angular slip control system

A braking force control system for a vehicle having, a vehicle speed detector for detecting a speed (V) of said vehicle from a R.P.M. of a rear wheel driveshaft and for generating a vehicle speed signal, a steering angle detector provided near a steering wheel on said vehicle for calculating an actual front wheel steering angle (δF(t)) from a steering angle (θ) of said steering wheel and for producing a steering signal, a lateral acceleration sensor mounted on said vehicle for detecting an acceleration amount (ay) in a lateral direction of said vehicle and for producing a lateral acceleration signal, and a yaw rate sensor for detecting an actual yaw rate (γ(t)) of the vehicle when negotiating a corner and for generating a yaw rate signal, comprising:

• an angular velocity calculator responsive to said yaw rate signal, said lateral acceleration signal and said vehicle speed signal for calculating an angular velocity (dβ/dt) of a vehicle body slip by using a predetermined slip equation and for producing an angular velocity signal;
• a vehicle body slip angle calculator responsive to said angular velocity signal and for calculating a body slip angle (β) by integrating thereof and for producing said angular velocity signal so as to easily derive a more exact correction value;
• a yaw rate corrector responsive to said yaw rate signal and said angular velocity signal for calculating a correction amount of said actual yaw rate (γ(t)) and for generating a yaw correction signal;
• a target yaw moment computer responsive to said yaw rate signal, correction signal and said vehicle speed signal for calculating a target yaw moment (Mz(t)) and for generating a target yaw moment signal;
• a brake wheel selector responsive to said yaw rate signal and said target yaw moment signal for choosing a wheel in order to apply a brake force in accordance with a moving condition of said vehicle and for generating a selection signal,
• a target brake force calculator responsive to said yaw moment signal and said selection signal for deriving a target brake force (FB) dependent on said target yaw moment and said moving condition and for generating a target brake force signal;
• and
• a braking force applier responsive to said target braking force signal for determining an optimum braking force to each wheel so as to control said vehicle at a stable condition even when said vehicle is running on a slippery road.

A braking force control method for a vehicle having, a vehicle speed detector for detecting a speed (V) of said vehicle from an R.P.M. of a rear wheel driveshaft, steering angle detector provided near a steering wheel on said vehicle for calculating an actual front wheel steering angle (δ(t)) from an actual steering angle (θ) of said steering wheel, a lateral acceleration sensor mounted on said vehicle for detecting an acceleration amount (ay) in a lateral direction of said vehicle, and a yaw rate sensor for detecting an actual yaw rate (γ(t)) of the vehicle when negotiating a corner, comprising the steps of:

• calculating an angular velocity (dβ/dt) of a vehicle body slip by using a predetermined slip equation;
• deriving a body slip angle (β) by integrating said angular velocity (dβ/dt);
• correcting said actual yaw rate (γ(t)) by subtracting a predetermined correcting coefficient (Gβ2) from said actual yaw rate (γ(t));
• computing a target yaw moment (Mz(t)) by using said previously derived correction amount, said speed (V) and said actual steering angle;
• selecting a wheel in order to apply a brake force in accordance with a moving condition of said vehicle;
• deriving a target brake force (FB) dependent on said target yaw moment (Mz(t)) and said moving condition;
• and
• applying an optimum braking force to each wheel in accordance with said optimum braking force so as to control said vehicle at a stable condition even when said vehicle is running on a slippery road.