Patent GB-1357146-A (GB)
Title: Automatic brake control circuit
Inventor: BOOHER H
IPC: B60T8/1761
Filed: 1971-09-06
Abstract: 1357146 Automatic control of deceleration  GOODYEAR TIRE & RUBBER CO 6 Sept 1971 [30 Sept 1970] 41506/71 Heading G3R [Also in Division F2] A hydraulic braking system specifically for an aircraft wheel 14 includes a valve 10 responsive to an electrical signal to control the application of pressure to a brake 12 of the wheel 14, the electrical signal being obtained from an integrating amplifier 25 and amplifier 25 being controlled by signals from a skid detector circuit 22, a locked wheel detecting circuit 29 and an automatic brake control circuit 30: the circuit 30 is responsive to vehicle operator initiated brake APPLY and brake REMOVE signals in lines 32, 34 respectively and to a wheel speed dependent voltage from a converter 20 and acts to apply a signal to the amplifier 25 which causes the valve 10 to be operated so as to apply the brake 12 to smoothly achieve a comfortable deceleration rate and to maintain the rate once achieved. As shown, on exciter ring 16 mounted for rotation with the wheel 14 has associated therewith a transducer 18, and pulses generated by the transducer 18 are sent to a convertor 20 which produces a D.C. voltage directly proportional to the wheel speed, which voltage is applied to the skid detector circuit 22, a modulator 26, a locked wheel arming circuit 28, the locked wheel detecting circuit 29, and the automatic brake circuit 30. The automatic circuit 30 shown in Fig. 2 comprises five sections viz. a deceleration detector section 31, a deceleration comparator section 44, an integrator section 42, a gate section 48 and a brake control logic section 46. The section 31 receives the wheel speed proportional voltage from converter 20 and differentiates the signal to give a deceleration proportional signal which is applied to the section 44. The section 44 compares the wheel deceleration with a pre-set reference deceleration and decides whether the wheel deceleration is too high or too low, and if it is too high the output of an amplifier A2 switches to a low state. The output of section 44 is applied to section 42 which integrates the signal so as to provide steadily increasing or decreasing signals at its output that, when applied to the valve 10, will produce a steady change in brake torque to eliminate the deceleration error being sensed by the deceleration comparator section 44. The gate section 48 acts as a series switch at the output of the section 42 and is controlled by the logic section 46 which receives signals from lines 32, 34. With neither an APPLY or REMOVE signal present the switch Q3 of section 48 is held in its off state and amplifier A2 of section 44 is held at its low state by a bias voltage from section 46 and thereby integrator section 42 is held at its zero brake pressure level. When switch 32a is closed and a squat switch 33 is in a landed position, an APPLY signal activates section 46, the signal in line 32 will remove the bias voltage from section 44 and permit it and section 42 to operate normally, and will switch Q3 to a closed state to connect integrator section 42 to the amplifier 25. Thereby pressure increases until wheel deceleration exceeds the reference deceleration. When a REMOVE signal appears in conductor 34 with the APPLY signal present in conductor 32 the bias signal reappears in the section 44. And brake pressure is reduced at a smooth and steady rate. If the APPLY signal is removed the switch Q3 is opened removing the output signal of the section 42 from the amplifier 25 so as to return full braking control to the operator and anti-skid circuits; if the pilot finds it necessary to assume control of the braking effort, he can do so by depressing brake pedal 35 which opens an interlock switch 37 causing section 46 to terminate the APPLY signal. Arming of the switch 32a may energize a solenoid valve which by-passes a pilot-operated power brake metering valve so as to apply hydraulic system pressure to the inlet of the valve 10. The automatic brake control circuits of individual wheels are interconnected through conductor 40.