Anti-skid systems

Claim 2

A vehicle anti-skid system comprising a first pulse generator arranged to produce an electrical signal at a frequency directly proportional to the angular velocity of a braked wheel of the vehicle and a flip-flop arranged to change state each time a pulse is received from the first generator, one state of the flip-flop being arranged to initiate a count in a digital counter and the other state of the flip-flop being arranged to terminate the count, a further higher frequency pulse generator being connected between the flip-flop and counter so that the counter records the number of pulses received from the higher frequency pulse generator between successive pulses from the lower frequency pulse generator thus providing a count which is inversely proportional to the angular velocity of the braked wheel, and means responsive to the output of said counter for controlling the braking of said wheel.

Claim 3

A system according to claim 1 in which a digital counter is arranged to count the number of pulses from the first generator in successive time intervals, the number of pulses counted during each time interval being subtracted from the number of pulses counted during the previous time interval in order to obtain a measure of the actual rate of change of velocity of the braked wheel.

Claim 4

A system according to claim 2 in which the count recorded in the digital counter during each time interval is transferred to a down counter at the end of the time interval, and during the next time interval, in which a new count is generated in the digital counter, the count in the down counter is counted down so that at the end of the next time interval the count remaining in the down counter is the difference between the counts recorded by the digital counter in successive time intervals and is therefore proportional to the rate of change of angular velocity of the braked wheel.

Claim 5

A system according to claim 2 in which the count recorded in the digital counter during each time interval is transferred to a first store at the end of the time interval, the count recorded in the counter during the next time interval being subtracted from the previous count now in the first store to give a count proportional to the rate of change of angular velocity of the braked wheel, this count being then transferred to a second store and hence to a comparator in which the count is compared with a count proportional to the maximum permissible rate of change of angular velocity of the braked wheel.

Claim 6

A system according to claim 4 in which at the end of a time interval during which the system detects that the rate of charge of angular velocity of the braked wheel is in excess of the maximum permissible level the count present in the first store is retained and the first store is connected to a further pulse generator which counts down the count in the first store at a rate proportional to the maximum permissible deceleration of the vehicle.

Claim 7

The system according to claim 1 wherein a divider is provided to generate the reciprocal of the count in the counter thereby providing a count directly proportional to the rate of change of the angular velocity of the braked wheel.

Claim 8

A system according to claim 1 wherein a pulse doubler is provided to double the frequency of the pulses from the first generator.

Claim 9

A vehicle anti-skid system comprising: a. first pulse generator means for generating an electrical signal having a frequency directly proportional to the angular velocity of a braked wheel of said vehicle, b. a flip-flop coupled to said first pulse generator, said flip-flop changing states each time a pulse is received from said first pulse generator, c. second pulse generator means having a frequency higher than the frequency of said first pulse generator, d. counter means selectively coupled to said second pulse generator means by the output of said flip-flop, the output of said second pulse generator means being coupled to said counter to initiate a count when said flip-flop is in one state and the output of said second pulse generator being disconnected from said counter to terminate said count when said flip-flop is in its other state, said counter recording the number of pulses received from said second pulse generator between successive pulses from said first pulse generator thereby providing a count which is inversely proportional to the angular velocity of said braked wheel, e. divider means coupled to said counter for generating the reciprocal of the count in said counter thereby producing an output directly proportional to the angular velocity of said braked wheel, f. a first store coupled to said divider, the output of said divider being transferred to said first store at the end of each time interval corresponding to the interval between successive pulses from said first pulse generator, g. a second store coupled to the outputs of said divider and said first store, said second store storing a count proportional to the difference between the outputs of said divider and first store to produce an output proportional to the rate of change of the angular velocity of said braked wheel, and h. comparator means coupled to said second store, said comparator comparing the output of said second store with a count proportional to the maximum permissible rate of change of angular velocity of the braked wheel, the output of said comparator means controlling the braking of said wheel.

Claim 10

A vehicle anti-skid system comprising: a. first pulse generator means for generating an electrical signal having a frequency directly proportional to the angular velocity of a braked wheel of said vehicle, b. a flip-flop coupled to said first pulse generator, said flip-flop changing states each time a pulse is received from said first pulse generator, c. second pulse generator means having a frequency higher than the frequency of said first pulse generator, d. counter means selectively coupled to said second pulse generator means by the output of said flip-flop, the output of said second pulse generator means being coupled to said counter to initiate a count when said flip-flop is in one state and the output of said second pulse generator being disconnected from said counter to terminate said count when said flip-flop is in its other state, said counter recording the number of pulses received from said second pulse generator between successive pulses from said first pulse generator thereby providing a count which is inversely proportional to the angular velocity of said braked wheel, e. divider means coupled to said counter for generating the reciprocal of the count in said counter thereby producing an output directly proportional to the angular velocity of said braked wheel, f. a first store coupled to said divider, the output of said divider being transferred to said first store at the end of each time interval corresponding to the interval between successive pulses from said first pulse generator, g. a second store coupled to the outputs of said divider and said first store, said second store storing a count proportional to the difference between the outputs of said divider and first store to produce an output proportional to the rate of change of the angular velocity of said braked wheel, and h. comparator means coupled to said second store, said comparator comparing the output of said second store with a count proportional to the maximum permissible rate of change of angular velocity of the braked wheel, the output of said comparator means controlling the braking of said wheel.