GB1353428A - Antiskid system - Google Patents

Abstract

1353428 Determining retardation ALFRED TEVES GmbH 29 June 1972 [2 July 1971] 30406/72 Heading G4H [Also in Division F2] The occurrence of a predetermined retardation of a wheel is determined by counting impulses proportional to wheel rotation in a first count up and count down run, the count up period being determined by the time taken by a second counter to count a predetermined number of oscillator pulses and the pulse flow to said second counter being interrupted during its count down so that, for the desired retardation, the counters reach zero together. The method is used in an antiskid system and the count up and count down are preferably performed by separate counters so that the first counter can be reset and immediately reused. The oscillator frequency is considerably higher than the sensor output pulse frequency. As shown diagrammatically, pulses from the wheel (fsensor) are applied to up counter NZ<SP>+</SP> and down counter NZ- and the oscillator pulses (fosz) are applied to up counter Z<SP>+</SP> and down counter Z-. The first sensor pulse initiates pulses to counter Z<SP>+</SP> and these continue until the count (which may start at zero or some other value GW 1 ) reaches TG 1 . The first sensor pulse after this stops both counters, transfers the values therein to the respective down counters which immediately start counting down and clears the up counters. The up cycle then restarts. If the wheel is being retarded, the down count in NZ- will take longer than the up count in NZ<SP>+</SP> and, if the counts are to reach zero at the same time, for a desired retardation, the pulse flow to counter Z- must be reduced. It is also necessary to compensate for overshooting the count TG 1 in counter Z + while waiting for the sensor pulse to stop the count. This is done by stopping m out of n pulses from the oscillator reaching counter Z- while the count in Z- is above TG 1 and when the count in NZ- is one. The values of m and n are different in these two parts of the count and may take several different values in steps for counts above TG 1 , e.g. at values KG 2 -KG 5 above TG 1 . Blocks V 2 generate a 1 output when the associated counter reaches zero. The outputs are fed directly (for V z Z<SP>-</SP>) and via an inverter REV (for V z NZ<SP>-</SP>) to an AND gate and a 1 output from this gate indicates excessive retardation and actuates the hydraulic control system to release the brakes.