Patent GB-837123-A (GB)
Title: Control systems for manoeuvrable craft
IPC: B64C13/24
Filed: 1957-06-17
Abstract: 837,123. Automatic steering control systems. SPERRY RAND CORPORATION. June 17, 1957 [June 22, 1956], No. 19020/57. Class 38 (4). [Also in Group XXIX] A control system for manoeuvrable craft including a power motor having a displaceable member connected to displace the craft steering member, control means for the power motor to control its energization and so cause it to displace the steering member by an amount dependent on an " order " signal derived from a controlling instrument or instruments, limiting means initially limiting the displacement of the steering member if the " order " signal exceeds a predetermined amount and motive means energized on the " order " signal exceeding the predetermined amount to adjust the limiting means so as to permit the steering member to be further displaced under the control of the " order signal at a slower rate than that produced when the " order " signal is less than the limiting value. To control, e.g. an aircraft elevator 11, a control valve housing 19 integral with or attached to the cylinder 15 of an hydraulic power motor 12 slidably mounts a valve piston 21 to control the supply and exhaust of pressure liquid to opposite sides of the power motor piston 16 which through its rod 17 is pivotally but fixedly mounted to the aircraft frame 10. An extension of the cylinder 15 which is pivotally connected to an arm 13 to operate the elevator mounts an electrical servomotor 47 comprising a pivoted armature element 50 movable between pole-faces on a stator element 48 and connected by a lever 52 and a rod 39b to the valve piston 21. The servomotor 47 receives signals from an auto pilot 56 which when a control knob 60 is moved to its automatic control position " A to jointly operate switches 60a, 60b, 60c receives " order " signals from a control gyro 62, feedback signals from the elevator by means of a synchro 57 having a rotor and stator connected to the elevator and airframe respectively and stabilization signals sensed by a rate senser 66. In the event of the signals received by the servomotor 47 exceeding a predetermined magnitude the movements of the valve piston 21 are limited by the engagement between a V-slot in a block 37 slidable in guides 40 in the casing 34 of a " safe " control mechanism 33 and a pin 38 carried on a rod 39 connected to the valve piston 21 and slidable in a slot 36a of an arm 36 projecting from the cylinder 15. The casing is pivotally mounted by means of a pin 35 on the arm 36. A synchro 64 detecting relative movement between the arm 36 and the casing 34 passes signals through the switch 60c to a trim amplifier and detector 68 which transmits signals to a trim motor 46. The trim motor 46 through a worm and rack 45 and balance springs 41, 42 moves a link 31 connecting the pilot's control stick 28 and the casing 34 to adjust the position of the casing 34 relative to the cylinder 15 to allow further movement of the pin 38 and hence movement of the valve piston 21 at a slower rate. The effect of the balance springs 41, 42 is to transmit " feel " back to the pilot. Under manual control with power assistance and including stability augmentation, the knob 60 is moved to its " M " position. The switches 60a, 60b then cut the synchro 57 and the control gyro 62 respectively out of circuit whilst the switch 60c cuts the trim motor 46 and couples the synchro 64 to the auto pilot unit 56 to centralize the servomotor 47. On movement of the stick 28, the link 31 rotates the casing 34 about the pivot pin 35 so that the block 37 engages the pin 38 to move the valve piston 21 and hence the cylinder 15 and the elevator. Under this control the trim system is operated manually by the pilot. A knob 84 jointly operating switches 84a, 84b on being moved to " engage " position connects respectively a safe control amplifier and detector unit 82 to transmit signals to an electric motor 70 and a D.C. supply to energize a solenoid 93 when a fluid-pressureoperated switch 100 associated with the pressure liquid supply to the valve 19 and motor 12 is closed. The safe control unit 82 is fed with limit command signals derived either manually at the discretion of the pilot or automatically as a function of a particular flight condition or a combination of conditions which may be either fixed or variable and a feedback signal derived from contact between an arm 37a on the block and an armature of a transducer 80. When these two signals are out of balance the motor 70 is driven in one or other direction which through gearing 71 and a splined shaft 72 rotates a screw-threaded shaft 75 mounted on a spring-loaded collar 76. The collar normally is held against axial movement by a lever 88 pivotally mounted on a fixed abutment 76a for the collar spring and a latch lever 91 held in engagement with a pin 90 on the lever 88 when the solenoid 93 is energized. Thus on rotation of the motor 70 the block 37 can be raised or lowered. The lever 91 which is loaded by a spring 95 in opposition to the solenoid also normally holds a switch 96 in its open position. In the event of either electrical or pressure liquid failure the solenoid 93 will be de-energized, in the latter event, the lack of hydraulic pressure allows the switch 100 to open. The spring 95 will then rotate the lever 91 clockwise to release the pin 90 whence the collar 76 is forced downwards by its spring to force the block 37 into engagement with the pin 38 to lock the valve piston 21. At the same time the switch 96 is closed. On moving the knob 84 to its " disengage " position the switch 84a closes a circuit so that A.C. power supply is connected to rotate the motor 70. Since the block 37 is held against further downward movement, the collar 76 moves upwardly to compress its spring and rotate the lever 88 clockwise. The pin 90 then rides down a cam surface 103 on the lever 91 to move this lever until the switch 96 is again broken and the motor 70 stops with the latch mechanism reset in an operable position. On restoration of electrical and pressure liquid supply and the re-positioning of the switches 84a, 84b in " engaged " position, the solenoid 93 is again energized so that the lever 91 is moved to reengage the pin 90. Downward movement of the collar 76 is then prevented and the synchro 64 through the safe control unit 82 operates to free the pin 38 from the block 37 for normal working. In the event of both electrical and pressure liquid failure the elevator may be moved manually, the engagement of the block 37 and pin 38 causing direct movement of the cylinder 15 and hence the elevator on the casing 34 being moved by the link 31 and the control stick 28. A by-pass valve 104 then transfers liquid from one side of the piston 16 to the other side. The control gyro 62 into which attitude command signals are fed could be substituted by conventional altitude, radio navigation or other flight condition components or the combining of these components with the attitude control gyros.