Patent GB-827089-A (GB)
Title: Improvements in control systems for dirigible craft
IPC: G05D1/00
Filed: 1956-03-05
Abstract: 827,089. Fluid-pressure servomotor-control systems. MINNEAPOLIS - HONEYWELL REGULATOR CO. March 5, 1956 [March 3, 1955], No. 6931/56. Class 135. [Also in Group XXXV] In apparatus for controlling the attitude of an aircraft comprising an hydraulic differential servomotor system having manually and automatically controlled sections 12 and 14, the latter is provided with an electric circuit 70 to prevent the introduction of automatic control if it would result in an abrupt change in aircraft attitude. Manual control. When pressure fluid is supplied to main 30 it flows via a conduit 31 to the left-hand end of a valve 34 so moving the latter and interrupting communication between opposite sides of a power piston 25 fixed to the aircraft; any subsequent actuation of a control column 23 connected to a valve 21 directs fluid from the conduit 31 to one or other side of the piston 25 to rotate the integral sections 12, 14 about a pivot 15 to " follow-up " the motion of the column 23. Automatic control. (a) Fluid-pressure apparatus.-The section 14 includes a pilot valve 40 positioned by an electric device 41, the valve 40 determining the position of a relay valve 42. Displacement of the valve 40 upsets a balance normally maintained between pressures applied to the ends of a pivoted arm 43, through the valve 42 engaging one end of the arm 43 and a sleeve 44, around the valve 40, abutting the other end of the arm. Should the sleeve 44 be moved by fluid pressure to the left as a result of the valve 40 moving to the right a supply of secondary pressure fluid from a three-way solenoid valve 65 is directed by the valve 40 to the right-hand end of valve 42 so that the opposing force on the lower end of the arm 43 repositions the sleeve and equalizes the pressures at each end of the arm. The valve 42 effects operation of a power piston 50 connected to the attitude control means 18 and to a follower 54 engaging a V-shaped part of a block 53 movable by a spring 55 to normally centre the piston 50 in the event of a failure of the fluid pressure. A fluid-actuated valve 57 normally interconnects the spaces on opposite sides of the piston 50 and controls a conduit 58 leading to the cylinder in which is the block 53. Translation of the piston 50 adjusts a potentiometer 60. (b) Electric control circuit.-A balanced autopilot circuit 71 is connected to an amplifier 72 in circuit with the device 41 whilst signals from the potentiometer 60 are supplied back to the circuit 71 to effect a rebalance thereof; the device 41 exerts a force on the valve 40 in accordance with the magnitude and phase of the unbalanced signal in the circuit 71 which force is opposed by a valve spring 42a. A position-sensing device 76 adjusts the slider 74 of an earthed centre-tapped potentiometer 75 connected to the circuit 71. The latter is also connected to a synchronizing signal generator 80 developing a fixed voltage less than the maximum voltage developed in the potentiometer 75 and consisting of a movable contact 83 actuated by the device 41 and co-operating with one or other of two fixed contacts 81, 82 in circuit with an earthed centre-tapped battery 98 through a relay 86. When the aircraft experiences a small departure from datum the signal voltage from the potentiometer 75 causes operation of the valve 40, which valve after moving a small distance, actuates contact 83 to initiate reverse operation of the device 41 to rebalance the control circuit 71. If the departure from datum is large the arm 100 of contact 83 will engage one or other opposed limit switches 101, 102 to de-energize a lock-out relay coil 103 so opening its contacts 111, 112 and preventing energization of the solenoid valve 65 and hence the supply of fluid to the pilot valve 40 so that the introduction of automatic control is prohibited. The coil 103 is provided with a holding circuit in order that actuation of the limit switches 101, 102 during automatic operation will not effect the energization of the coil 103; during such automatic operation the relay 86 is energized to disconnect the generator 80 from the battery 98.