Abstract: A relay valve is operatively disposed between a pressurized air source and a work chamber of a brake booster. The relay valve has a pilot chamber so that the relay valve can feed the work chamber with a pressurized air, the pressure of which corresponding to that of a pressure applied to the pilot chamber. Electromagnetic valves are arranged to selectively connect the pilot chamber with the pressurized air source and the atmosphere. The valves are so controlled by an electronic control unit that the pilot chamber is supplied with pressurized air the pressure of which being determined in accordance with a brake pedal force applied from a brake pedal to an input means of the booster.

Abstract: An anti-skid brake control system derives number of sensor signal pulses to be ignored without sampling the input timing data is cyclically increased in stepwise fashion until the signal-to-signal interval or the duration of each group of sensor signal pulses become larger than a predetermined value. Immediately after determining the number of sensor pulses to be ignored, the sensor signal pulses input subsequently is sampled its input timing value as the first sampled timing data. After sampling the first timing data, system enters sample control mode to ignore the determined number of sensor pulses so as to sample the input timing data with respect to every given number of sensor signal pulses.

Abstract: An electromagnetically operated mechanism produces an unstable first controlled pressure which, under a given condition, is saturated quickly to a degree slightly lower than a target value determined in accordance with an information signal issued from a brake pedal force detecting device. A servo-motor type actuator produces a stable second controlled pressure which, under a given condition, is saturated slowly to the target value. A control mechanism applies only the first controlled pressure to a work chamber of a pneumatic brake booster when the first controlled pressure is higher than the second controlled pressure, and applies only the second controlled pressure to the work chamber after the second controlled pressure becomes higher than the first controlled pressure.

Abstract: An input pressure detecting device is arranged in an input side of a pneumatic brake booster, which comprises an elastic member having a given portion which expands when a pressure is applied to the elastic member, a pressure sensor for issuing, upon receiving a pressure, a signal representative of the intensity of the pressure applied thereto, and an axially movable piston intimately disposed between the given portion of the elastic member and the pressure sensor. Upon application of force to the elastic member due to depression of the brake pedal, the elastic member is compressed causing the given portion to expand and thus applying a corresponding but small pressure to the pressure sensor through the piston.

Abstract: An anti-skid control system records the input timing of the first of every group of sensor pulses of a given size, the given size being so selected that the intervals between recorded inputs are greater than a predetermined value. The anti-skid control system performs this sampling operation as an interrupt routine intermittently interrupting a main job which periodically derives a control signal for increasing, decreasing or holding constant the fluid pressure applied to the wheel cylinder. The occurrences of interruptions are counted and the interrupt count is decremented upon completion of each cycle of the main job. Under normal conditions, the sampling routine is performed in response to every sensor signal pulses. When the counter value becomes larger than a predetermined value, the sampling routine starts to sample only the first pulse of each group of a predetermined number of sensor signals.

Abstract: An anti-skid brake control system controls the operation mode of a pressure control valve in a hydraulic brake circuit for increasing the fluid pressure in its application mode, for decreasing the fluid pressure in its releasing mode and for holding the fluid pressure at a constant value in its holding mode. The control system has a predetermined operation pattern in which the operation modes of the pressure control valve cycle through a predetermined schedule. Measured wheel acceleration and slip rate values dictate which operation modes are to be selected next and when the change from mode to mode should be performed. When the operation mode is to be changed, the next operation mode selected is checked to see if it is consistent with that scheduled. When the selected operation mode is different from the scheduled one, the selected operation mode is modified to perform the operation according to the scheduled operation mode which would otherwise be skipped.

Abstract: An anti-skid brake control system comprises a temporary register for storing successive three input time data from which wheel acceleration and deceleration is calculated whenever the differences of intervals of the sensor signal pulses or duration of the groups of sensor signal pulses is larger than a predetermined calculation threshold. Sampling timing of the sensor signal pulses is determined so that the difference of intervals of sensor signal pulses or the difference of durations of sensor signal pulses is larger than the predetermined calculation threshold. At every derived timing corresponding to the sampling timing, wheel acceleration and deceleration is calculated based on the input timing data values.

Abstract: An anti-skid brake control system includes a fluid pump which facilitates brake release when wheel deceleration, as indicated in a derived wheel acceleration value, exceeds a predetermined level. Since at low vehicle speeds, the sensors used to derive the wheel acceleration value are of unsatisfactory accuracy, the wheel acceleration value itself may be inaccurate. Accordingly, at low vehicle speeds, the fluid pump is effectively disabled by replacing the derived wheel acceleration value with a fixed value greater than the predetermined level.

Abstract: An anti-skid brake control system includes a fluid pump which facilitates brake release when wheel deceleration, as indicated in a derived wheel acceleration value, exceeds a predetermined level. Since at low vehicle speeds, the sensors used to derive the wheel acceleration value are of unsatisfactory accuracy, the wheel acceleration value itself may be inaccurate. Accordingly, at low vehicle speeds, the fluid pump is effectively disabled by replacing the derived wheel acceleration value with a fixed value less than the predetermined level.

Abstract: An anti-skid brake control system performs arithmetic operations for deriving wheel speed on the basis of wheel sensor signal pulses at a first given timing. The first given timing is determined in view of response characteristics of an electromagnetic actuator of a pressure control valve in a hydraulic brake system. The anti-skid control system also performs arithmetic operations for deriving wheel acceleration on the basis of wheel speed sensor signal pulses at a second timing. The second timing is adjusted according to the sensor signal pulse frequency so that the difference between successive pulse intervals or the difference between the durations of successive sensor signal pulse groups exceeds a given value which is the threshold for performing wheel acceleration calculation to obtain a result useful in anti-skid control operation.

Abstract: An anti-skid brake control system for an automotive vehicle has a control module comprising one or more microcomputers. The microcomputer is connected to a wheel speed sensor, which supplies a sensor signal indicative of the wheel speed, and a timer which outputs a timer signal indicative of the elapsed time. The microcomputer has an input time data sampling program for latching the timer signal value and storing the latched timer signal value as input time data for the corresponding sensor signal pulse. The input time data sampling program is executed as an interrupt program independent of a main program which processes the input time data and controls application and release of hydraulic braking pressure to a vehicle wheel in such a manner that wheel speed is adjusted toward an optimum relationship with vehicle speed.

Abstract: An anti-skid control system includes a wheel speed calculation in which newly derived wheel speed is compared with a wheel speed derived at an immediately preceding calculation. When the newly derived instant wheel speed is different from the previously derived old wheel speed beyond a predetermined value which is variable in dependent upon variation of the wheel speed derived at the immediately preceding calculation. A back-up signal is derived and output as a replacement of wheel speed data. The back-up signal may have a value substantially corresponding to a wheel speed data avoiding error component in the instant wheel speed.

Abstract: In an anti-skid brake control system, wheel acceleration or deceleration is calculated at a different timing than the calculation of the wheel speed and a control signal. The intervals between calculations of wheel acceleration and deceleration will often be longer than those of the control signal. Wheel acceleration and deceleration values in the intervals between calculations are extrapolated on the basis of the rate of change derived from the difference between two successively derived wheel acceleration and deceleration values and elapsed time since the last derivation. The extrapolating value is used as a replacement for the most recently derived wheel acceleration in deriving the control signal.

Abstract: An anti-skid control system records the input timing of every n.sup.th sensor signal pulse, where n is so determined that the interval between successively recorded input times is greater than a first predetermined value. A wheel speed calculation is performed whenever three successive input times are recorded. The sample size n is further adjusted until the difference between successive sample-to-sample intervals becomes greater than a second predetermined value. An arithmetic operation for deriving wheel acceleration is performed after the input times for three successive adjusted pulse sampled are recorded.

Abstract: An anti-skid control system, according to the present invention, samples the input timing of the first pulse of each group of a given number of sensor signal pulses, which given number is so adjusted that the difference between the durations of successive pulse groups is great enough to accurately perform the anti-skid control operation based thereupon. Each of the sampling input timing values is provided a label identifying the required processing operations for performing the anti-skid control. The anti-skid control system performs the sampling operation as an interrupt routine intermittently interrupting a main job which derives a control signal for increasing, decreasing or holding constant the fluid pressure applied to the wheel cylinder. The main job contains a plurality of different routines for processing the sampled input data, one of which is to be identified and performed in accordance with the identification in the label.

Abstract: An anti-skid control system samples the input timing of the first pulse of a group of a given number of sensor signal pulses, which given number is so adjusted that the difference between the durations of successive pulse groups is great enough to perform the anti-skid control operation based thereupon. The anti-skid control system performs the sampling operation as an interrupt routine intermittently interrupting a main job which derives a control signal for increasing, decreasing or holding the fluid pressure to be applied to the wheel cylinder. A count of the occurrence of interruption is incremented by one whenever an interrupt occurs and is decremented by one upon completion of each cycle of the main job. The sampling routine is performed in response to the first of each group of the given number of sensor signal pulses.

Abstract: An anti-skid control system takes a procedure for sampling input time data of every given number of sensor signals, which given number is adjusted so as to a difference of period of time measured with respect to mutually adjacent signal-to-signal intervals is great enough to perform the anti-skid control operation based thereupon. The anti-skid control system processes sampling operation as a job to be performed by interrupting main job for deriving control signal for increasing, decreasing or holding the fluid pressure to be applied to the wheel cylinder. The occurrences of interruption are counted up whenever it occurs and counted down upon each cycle of main job is completed. The job for sampling the input time data a performed at each time of inputting of the every given number of sensor signals.

Abstract: An anti-skid brake control system includes a plurality of controllers adapted to control the braking pressure on corresponding vehicle wheels. Each controller receives wheel speed sensor signals from a corresponding wheel speed sensor and derives the rotation speed of the corresponding wheel or wheels. The controller detects failure of the wheel speed sensor to perform a back-up operation in order to continue braking control. The controllers are mutually independent with regard to anti-skid brake control and, on the other hand, are mutually cooperative with regard to the back-up operation when one of the wheel speed sensors fails. The back-up operation includes switching the operation mode of the vehicle brake system from controlled mode to manual mode. Switching of operation mode from the controlled mode to manual mode is performed in each controller at a predetermined timing.

Abstract: An anti-skid brake control system for an automotive vehicle is provided with a fluid pump operative during releasing mode of anti-skid control operation to reduce the fluid pressure in a wheel cylinder. The fluid pump is driven even when the anti-skid control is performed in holding mode for holding the fluid pressure in a wheel cylinder at a constant value. The fluid pump is disabled when the wheel speed is zero and the anti-skid control is performed in other than releasing mode. Thus, wasting of vehicle battery power by unnecessarily driving the fluid pump is avoided.

Abstract: An acceleration sensor acts on the variable-frequency pulses of a speed sensor signal to recognize any variation of the pulse period thereof and to produce an output indicative of the magnitude of the detected variation to within a fixed degree of accuracy. The periods of groups of known, variable number pulse groups are measured with reference to a fixed-frequency clock pulse signal and the measurement periods of successive groups of equal numbers of pulses are compared. If the difference between pulse group periods is zero or less than a predetermined value, the number of pulses in each group is increased in order to increase the total number of clock pulses during the measurement interval. The number of pulses per group is increased until the difference between measured periods exceeds the predetermined value or until the number of pulses per group reaches a predetermined maximum.