| 摘要 |
1,238,075. Antiskid control systems. CRANE CO. 25 Oct., 1968, No. 50874/68. Heading F2F. In an anti-skid control system for, e.g. an aircraft, the brake pressure to each wheel is controlled according to the deviation of the instantaneous wheel speed from a reference value representing the speed of the craft. The comparator has a two level output, the second responding to gross error and transient signals is added to the normal " PBM " signal to augment brake relaxation. General arrangement.-As described, a system such as that shown in Fig. 1 is provided for each wheel, and utilizes an A.C. input from a wheeldriven tachometer. The operation of the circuit is mostly self evident from the legends. The analogue convertor provides a stored signal in the reference unit which is compared with the instantaneous value in comparator 30. The touch-down unit modifies the reference signal to provide full relaxation until a " SQUAT OVERRIDE " signal appears as the wheels spin up on landing. COMPENSATION for HYDRAULIC LAG is provided as described below, and a LOCKED WHEEL CROSSOVER links the controls either side. CIRCUIT DETAILS.-Figs. 2a, 2b, show details corresponding to the block diagram of Fig. 1:- Squaring circuit-including Q10. Analogue converter-rectifiers CR14, CR15 and amplifier Q11, Q12. Comparator-Q3, Q4 with series constant current circuit Q14. Reference unit-capacitor C8, charged from the analogue converter through CR2 and discharged by Q15 at a rate modified by the applied braking signals via resistors R50 ... R53 to R37. P.B.M. control circuit-threshold amplifier Q8, Q9 with upper level clamp CR8, charges capacitor C10 which is discharged at a constant current by Q17. The signal on C10 amplified by Q16, Q18 is applied to the Driver. Q6, Q7 to energize the primary control valve and relax the brakes. Transient control circuit-amplifier Q5 sums with P.B.M. signal applied to the driver Q6, Q7. Hydraulic lag is compensated by a signal from the driver emitter Q6 applied to Q19 and fed back to Q5 to augment the initial brake relaxation signal. Brake pressure recovery comprises Q20, Q21, Q22 fed by a signal from Q7 to vary the emitter potential of Q18 by conduction of Q22. Squat circuit charges C9 to cause Q4 to give brake release signal. When wheel signal appears at Q12 on touch-down Q13 conducts to remove the bias. |
