Patent GB-811514-A (GB)
Title: Control systems for aircraft
Inventor: JOFEH MARCUS LIONEL
IPC: B64C13/24
Filed: 1956-02-24
Abstract: 811,514. Controlling aircraft. SPERRY GYROSCOPE CO. Ltd. Jan. 22, 1957 [Feb. 24, 1956], No. 5817/56. Class 4. In an aircraft manually operated electric servo control system, the system functions in response to a given displacement of the manual controller to produce a rate of turn of the aircraft about one of its axes which is initially high, and subsequently falls with time to a lower value substantially proportional to the displacement of the manual controller. In the embodiment described a control surface 7 is operated by a main controller 1 for normal flying or by a smaller auxiliary controller 15 for fast manoeuvring of the aircraft though the provision of two controllers is stated to be not necessary. Control by each will be described separately. For control during fast manoeuvring relays A1-A4 are set in the energized positions as opposed to the unenergized positions shown in the drawing. Movement of controller 15 develops a signal which is summed algebraically with a signal from a delay network 13 the summed signal being amplified at 18 and added with a signal from rate gyro 10 (to be described). The resultant signal is passed through a variable control device 17 operated in accordance with airspeed and/or Mach number, to counteract the instability in the system that would otherwise occur due to increase in gain in the loop with increase of airspeed, and the signal is amplified at 5 for energization of a servo motor 6 which operates a surface 7, a pick-off 8 supplying a feed back signal to amplifier 5. Displacement of surface 7 causes the aircraft to turn so that rate gyro 10 provides an a.c. output converted to d.c. in a discriminator 11 and this d.c. signal is supplied to a combining circuit 4 both direct and also through relay A1 and delay circuit 13. The circuit 13 may be a resistance-capacitance integrating circuit, the output being of such polarity as to add to the direct rate of turn signal so that when the signal from gyro 10 changes the output from circuit 4 is a signal which increases from one value to another during a time constant corresponding to the time constant of the integrator so that the net input to amplifier 5 is initially high and decreases as the feed back signal constituted by the sum of the rate signal plus a delayed version of the rate gyro signal increases, both the latter signals being of opposite polarity to the signal from controller 15. For normal control with automatic stabilization relays A1-A4 are set as shown in the drawing and controller 1 provides a demand signal which is fed through variable control device 17 to amplifier 5 to energize motor 6. The resulting output signal from gyro 10 through discriminator 11 passes through relay A1 to a polarity reverser 12 before passing through network 13 to combining circuit 4 with the result that the signal from network 13 now tends to decrease the direct output of gyro 10 in the combining circuit 4. To counteract the effect of amplifier 18 the polarity reverser includes an attenuating circuit. Thus, when the rate of turn signal from gyro 10 increases, the total feed-back signal from circuit 4 assumes an initial value which decreases with time and sudden changes in a rate of turn produced by movement of controller 1 will be damped by the change in the signal from the gyro. Under normal control by controller 1 the feed-back loop via pick-off 8 rather than the rate of turn loop tends to dominate the control system, especially at low rate of turn but in manoeuvre mode of control the rate of turn signal from circuit 4 is dominant. The Provisional Specification describes an arrangement in which the signal from circuit 4 is combined in a further combining circuit in opposition with the signal from the auxiliary controller.