Method and system for deriving wheel acceleration and deceleration in automotive anti-skid brake control systems

Claim 1

An anti-skid brake control system for an automotive hydraulic brake system comprising: a hydraulic brake circuit including a wheel cylinder for applying braking pressure to a vehicle wheel and a pressure control valve disposed within said brake circuit for controlling hydraulic pressure to be applied to said wheel cylinder for adjusting braking pressure, said pressure control valve being operative to increase hydraulic pressure to be applied to the wheel cylinder in a first position thereof, and to decrease the hydraulic pressure in a second position thereof; a wheel speed sensor for outputting sensor signal pulses separated by intervals, said intervals representative of detected wheel rotation speed; a timer for outputting timer signals; a first means for sampling values of the timer signals in response to input of said sensor signal pulses; a second means, operative at a predetermined timing, for deriving wheel speed on the basis of sampled timer signal values; a third means for deriving wheel acceleration or deceleration based on three sampled timer signal values of which the difference between the timed intervals between each pair of timer signal values is greater than a predetermined value; a fourth means for deriving a control signal for controlling said pressure control valve on the basis of wheel speed and wheel acceleration or deceleration derived by said second and third means, so that wheel speed is held at an optimal relationship to vehicle speed; and fifth means for deriving the rate of change of wheel acceleration or deceleration on the basis of the two most recently derived values of wheel acceleration or deceleration from said third means, and deriving extrapolating value of wheel acceleration or deceleration based on said derived rate of change, and, said fifth means feeding said extrapolating value to said fourth means as a replacement of said wheel acceleration or deceleration from said third means during the time interval between successive wheel acceleration or deceleration calculations in said third means.

Claim 12

A method for anti-skid controlling an automotive hydraulic brake system including a hydraulic brake circuit with a wheel cylinder for applying braking pressure to a vehicle wheel, and a pressure control valve operative to increase fluid pressure in said wheel cylinder in a first position thereof, and to decrease the fluid pressure in said wheel cylinder in a second position thereof to hold the fluid pressure in said wheel cylinder constant in a third position; the method comprising the steps of: detecting wheel rotation speed and producing a wheel speed indicative signal; calculating wheel speed based on a value of the wheel speed indicative signal at a given first timing; calculating wheel acceleration or deceleration data based on values of said wheel speed indicative signal at a second timing; deriving an extrapolating value of wheel acceleration on the basis of the calculated wheel acceleration or deceleration at said first timing in synchronism with calculation of said wheel speed; deriving a control signal to control said pressure control valve based on brake control variables including said wheel speed and said wheel acceleration and deceleration, which wheel acceleration or deceleration is replaced by said extrapolating value during the interval between successive wheel acceleration or deceleration calculations.

Claim 13

A method for anti-skid controlling an automotive hydraulic brake system including a hydraulic brake circuit with a wheel cylinder for applying braking pressure to a vehicle wheel, and a pressure control valve operative to increase fluid pressure in said wheel cylinder in a first position thereof, and to decrease the fluid pressure in said wheel cylinder in a second position thereof to hold the fluid pressure in said wheel cylinder constant in a third position; the method comprising the steps of: detecting wheel rotation speed and producing a wheel speed indicative signal; calculating wheel speed based on a value of the wheel speed indicative signal at a given first timing; calculating wheel acceleration or deceleration data based on values of said wheel speed indicative signal at a second timing; deriving an extrapolating value of wheel acceleration on the basis of the calculated wheel acceleration or deceleration at said first timing in synchronism with calculation of said wheel speed; deriving a control signal to control said pressure control valve based on brake control variables including said wheel speed and said wheel acceleration and deceleration, which wheel acceleration or deceleration is replaced by said extrapolating value during the interval between successive wheel acceleration or deceleration calculations.