Abstract: Actual performance is used to determine vehicle braking system maintenance requirements. Measures of wheel slip are determined for each wheel of a vehicle during periods of deceleration. The determined measures of wheel slip are accumulated; and those accumulated for left wheels are compared with those accumulated for right wheels of each axially associated set of wheels, those accumulated for one axially associated set of wheels are compared with those accumulated for each of other axially associated sets of wheels, and those accumulated for tractor wheels are compared with those accumulated for trailer wheels. A predetermined difference between measures of wheel slip indicates the existence of a possible problem with the brake associated with the wheel or at least one of the set of wheels for which the least wheel slip is determined.

Abstract: A method for checking and controlling the quality of output signals from wheel speed sensors installed on wheels of vehicles equipped with an automatic braking system includes determining from sensed wheel speeds the deceleration of a wheel, timing any period of deceleration the level of which is above a predetermined level, defining any wheel speed sensor associated with a wheel having an indicated deceleration above the predetermined level for a time exceeding a predetermined period as being malfunctioning, excluding the output signals from the malfunctioning wheel speed sensor, and replacing the excluded output signals with output signals from a wheel speed sensor installed on an alternate wheel.

Abstract: Method and system for reducing the brake pressure rise rate under low Mu braking surface conditions by utilizing a vehicle reference speed to determine if the wheels are being over-braked. When over-braking occurs, the pressure rise rate is restricted by not allowing an ABS valve to go into an Apply state (approximately 100 psi/sec.), regardless of wheel acceleration levels. A Ramp state is used in place of the Apply state and the pressure rise is therefore limited to approximately 30 psi/sec. to improve wheel control. The Ramp duty cycle is also modified to provide the smallest pressure steps possible with the current valve hardware.

Abstract: Vehicle engine torque, acceleration, deceleration and brake treadle pressure are determined. Vehicle load is calculated from the engine torque and acceleration; and braking system effectiveness is calculated by comparing the determined deceleration with a deceleration predicted for the calculated vehicle load and the determined brake treadle pressure. Values representative of braking system effectiveness are accumulated and evaluated to more accurately determine when braking system service is required than is possible by merely scheduling service according to the amount of elapsed time or the number of miles driven since prior service was performed.