Anti-skid brake control system performing skid control with both open and close feedback techniques

An anti-skid brake control system for an automotive brake system comprising:

• a hydraulic brake system including a wheel cylinder for applying braking pressure to a vehicle wheel, and a pressure control valve means associated with said wheel cylinder for adjusting fluid pressure in the wheel cylinder at given first and second rates, said pressure control valve means including a pressure control valve being operative to increase fluid pressure in said wheel cylinder in a first position corresponding to an application mode, to decrease fluid pressure in a second position corresponding to a release mode, and to hold fluid pressure in said wheel cylinder constant in a third position corresponding to a hold mode;
• a wheel speed sensor detecting rotation speed of the wheel and producing a wheel speed indicative signal having a value indicative of the detected wheel speed;
• and
• a controller deriving a control signal for controlling operation of said pressure control valve to operate the latter in one of said first, second and third positions to control the wheel speed at a given optimal relationship to a vehicle speed, said controller controlling the pressure control valve in one cycle of anti-skid control in accordance with a predetermined schedule,
• said controller operative to derive brake control parameters including wheel acceleration and deceleration and a target wheel speed to which wheel speed is to be controlled, and to derive said control signal according to said predetermined schedule in which:
• said pressure control valve is positioned at said third position when derived wheel deceleration becomes greater than a given deceleration threshold in said hold mode of said controller;
• said pressure control valve is positioned at said second position when wheel speed drops lower than said target wheel speed in said release mode of said controller;
• said pressure control valve is positioned at said third position when wheel speed is resumed and is higher than said target wheel speed in said hold mode of the controller;
• and
• said pressure control valve being positioned at said first position when derived wheel acceleration becomes less than a given acceleration threshold in said application mode of the controller, in which fluid pressure in the wheel cylinder is increased at said given first rate until the fluid pressure reaches a predetermined pressure level, said controller controlling said pressure control valve means for adjusting fluid pressure to increase at said given second rate, smaller than said first rate after the fluid pressure reaches said predetermined pressure level, during operation of said pressure control valve in said first position.

An anti-skid brake control system for an automotive brake system comprising:

• a hydraulic brake system including a wheel cylinder for applying braking pressure to a vehicle wheel, and a pressure control valve associated with said wheel cylinder for adjusting fluid pressure in the wheel cylinder, said pressure control valve being operative to increase fluid pressure in said wheel cylinder in a first position corresponding to an application mode, to decrease fluid pressure in said wheel cylinder in a second position corresponding to a release mode, and to hold fluid pressure in said wheel cylinder in a third position corresponding to a hold mode;
• a bypass passage connecting upstream and downstream conduits of said pressure control valve and including an auxiliary valve operative in a closed position to block fluid communication between said upstream and downstream conduits of said pressure control valve through said bypass passage, said auxiliary valve and bypass passage allowing restricted fluid flow at a rate substantially smaller than that allowed to flow through said pressure control valve;
• a wheel speed sensor detecting rotation speed of the wheel and producing a wheel speed indicative signal having a value indicative of the detected wheel speed;
• a controller deriving a wheel acceleration value based on said wheel speed indicative signal and a control signal for controlling operation of said pressure control valve to actuate the latter to one of said first, second and third positions on the basis of said wheel speed indicative signal so as to control the wheel speed at a given optimal relationship to vehicle speed, said controller deriving a wheel acceleration dependant value on the basis of the peak of said wheel acceleration value and controlling the pressure control valve in one cycle of anti-skid control in accordance with a predetermined schedule in which the position of the pressure control valve changes from said first position to said third position after a given period of time variable according to said wheel acceleration dependent value, and operating said auxiliary valve to establish fluid communication through said bypass passage for a given fixed period.

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

• a hydraulic brake system including a wheel cylinder for applying braking pressure to a vehicle wheel, and a pressure control valve means including a pressure control valve associated with said wheel cylinder for adjusting fluid pressure in the wheel cylinder, said pressure control valve being operative to increase fluid pressure in said wheel cylinder in a first position, to decrease the fluid pressure in the wheel cylinder in a second position and to hold the fluid pressure in the wheel cylinder constant in a third position;
• a wheel speed sensor detecting rotation speed of the wheel and producing a wheel speed indicative signal having a value indicative of the detected wheel speed;
• a first means for deriving brake control parameters including wheel acceleration values based on said wheel speed indicative signal;
• a second means for latching the peak value of wheel accleration while wheel speed is increasing;
• and
• a third means for deriving a control signal for actuating said pressure control valve to one of said first, second and third positions based on said brake control parameters, said third means deriving said control signal so as to operate said pressure control valve in said first position, in which the fluid pressure in said wheel cylinder is increased at a first given rate for a first given period of time, and said third means subsequently controlling said pressure control valve means for increasing fluid pressure in said wheel cylinder at a second given rate smaller than said first rate for a second given fixed period after expiration of said first given period, said third means deriving said first given period of time in accordance with the latched peak value of wheel acceleration.

A method for anti-skid controlling an automotive hydraulic brake system including a wheel cylinder and a pressure control valve means including a pressure control valve for controlling fluid pressure in said wheel cylinder, said pressure control valve being operative to increase fluid pressure in said wheel cylinder in a first position, to decrease fluid pressure in the wheel cylinder in a second position and to hold the fluid pressure in the wheel cylinder constant in a third position, the method comprising the steps of:

• detecting wheel speed;
• deriving brake control parameters including wheel acceleration and deceleration based on the detected wheel speed;
• determining the operation mode of said pressure control valve from among said first, second and third positions depending upon the derived brake control parameters;
• detecting the peak value of wheel acceleration;
• deriving a peak-value-dependent period of time based on the detected peak value of wheel acceleration;
• and
• controlling the pressure control valve according to a predetermined schedule for controlling wheel speed at an optimal relationship to a vehicle speed, in which, said pressure control valve is held in said first position for increasing fluid pressure at a first greater rate for said peak-value-dependent period of time and thereafter at a second smaller rate for a given fixed period.