Patent GB-845920-A (GB)
Title: A gyroscopic reference device for an automatic control system
IPC: G01C21/18
Filed: 1957-05-14
Abstract: 845,920. Automatic control systems for aircraft. BENDIX AVIATION CORPORATION. May 14, 1957 [June 1, 1956], No. 15326/57. Class 38 (4). In a gyroscopic reference including a directional gyro and a vertical gyro for automatically controlling a craft about three axes, the gimbal of one of the gyros is mounted in a further gimbal which is automatically rotated to maintain its plane in a predetermined angular relationship with that of the outer gimbal of the other gyro. Gyroscopic references.-In Fig. 1 the outer gimbal 15 of a vertical gyroscope 11 is pivoted about an athwartship axis in a cradle 13 which is pivoted about a fore and aft axis in an aircraft. The outer gimbal 17 of a directional gyro 12 is pivoted in a further gimbal 18 which is pivoted about a second athwartship axis in cradle 13. Both gyros are provided with systems (not shown) maintaining the spin axes correctly positioned relative to the earth. The plane of gimbal 18 in which the directional gyro is mounted is automatically maintained perpendicular to the plane of the outer gimbal 15 of the vertical gyro by a motor 45 which operates to adjust gimbal 18 in response to changes in the relative position of the gimbals as detected by interconnected inductive pickoffs 31 and 36. Signals derived from an inductive pick-off 102 associated with the directional gyro are applied through inductive devices 111, 110 to control a motor 137 which, in driving the rotor 133 of inductive device 110 to a null position, takes up a position corresponding to aircraft heading. Signals derived from an inductive pick-off 100 associated with a pendulous magnetic compass (not shown) are applied to an inductive device 125 the rotor 122 of which is positioned by motor 137, and signals from rotor 122, representing disagreement between the gyro and the magnetic compass, are applied to a motor 118 which adjusts inductive device 111 to correct errors in the position of motor 137 due to the earth's rotation. Such correction is automatically eliminated by switches 117, 119 when pitch and/or bank is excessive. Signals derived from pick-off 31 are also applied through an inductive device 37 to control a motor 51 which, in driving the rotor 39 of inductive device 37 to a null position, takes up a position corresponding to aircraft pitch angle. Signals derived from an inductive pick-off 71 associated with the vertical gyro correspond to the aircraft bank angle and are applied to a potentiometer 64. Altitude detector.-Signals derived from an E-type pick-off 121<SP>1</SP> associated with a bellows 1191 responsive to static pressure are applied to control a motor 125 which, in driving the pick-off stator to a null position, takes up a position corresponding to the altitude. Mach number detector.-Signals derived from an E-type pick-off 122 associated with a bellows 120 responsive to dynamic pressure are applied to control a motor 126 which, in driving the pick-off stator to a null position, takes up a position corresponding to dynamic pressure. Motors 125, 126 adjust resistors of a Wheatstone bridge circuit 141 the output of which is applied to control a motor 140 which, in re-balancing the bridge circuit, takes up a position corresponding to Mach number. Automatic attitude control.-When manual switch 210 is closed electromagnetic clutches 221R, 221A, 221E, Fig. 2, respectively couple the rudder, ailerons and elevators to motors 3, 31, 311 of servosystems controlled by signals derived from interconnected sine-cosine resolvers 23, 24, 25, 60, 61 and applied through potentiometers 320, 240, 318. Inductive device 7 and generator 6 respectively provide position and rate follow-up signals for the rudder servosystem. Anti-hunt signals are derived from a rate of turn gyro 9 and persistent feedback signals are automatically balanced out in time by signals produced by an inductive device Z driven by a motor X controlled by the feedback signals. Side-slip is eliminated by signals derived from a dynamic vertical detector D. Similar anti-hunting and feedback arrangements are incorporated in the aileron and elevator servosystems. Persistent signals applied to elevator servomotor 3<SP>11</SP> are automatically eliminated by utilizing them to control a motor 3<SP>111</SP> adjusting elevator trim tabs T. Adjustment of the trim tabs is prevented by a switch 186 which is opened by motor 140 when the Mach number exceeds a predetermined value. To maintain a predetermined heading, switch 400 is closed at that heading so that a relay 83 changes over from the position shown and an electromagnetic clutch 90 energized to couple motor 137 to an inductive device 93 signals from which cause a motor 21 to rotate cradle 13 to a bank position corresponding to heading error. Follow-up is provided by an inductive device 89 and the signals from inductive device 93 are varied in accordance with Mach number by motor 140 adjusting a potentiometer 91. Motor 21 adjusts resolvers 23, 24, 25 to control the surfaces in accordance with bank angle. Motor 51 adjusts resolvers 60, 61 and potentiometer 64 to control the surfaces in accordance with pitch angle. Potentiometer 64 is connected to resolver 61 to control the surfaces in accordance with bank error. Control in accordance with heading and pitch error is also introduced by connecting rotors 133 and 39 to resolvers 60 and 25 respectively. The arrangement of resolvers is such that the distribution between the servosystems of control signals corresponding to each error signal is automatically varied to suit the attitude of the craft about its axes. The control signals are varied in accordance with altitude by motor 125 adjusting potentiometers 320, 240, 318. Manual attitude control.-During automatic control fore and aft operation of control column 600 produces signals in inductive device 606 to set the pitch datum and athwartship operation of the control column produces signals in inductive device 602 to set the bank datum. Push button 610, which must be operated before the craft can be put into non-level flight, disconnects the automatic heading control under these conditions. A control column 200 and pedals 202 are provided for direct manual operation of the control surfaces when automatic control is not in operation. When the craft is being steered manually relay 83 is in the position shown and the signal from pick-off 71 is applied to control motor 21 so that cradle 13 is maintained level. Altitude control.-A desired altitude may be maintained by closing a switch 421 at that altitude to couple motor 125 to an inductive device 137<SP>1</SP> producing signals which are applied to resolver 25. Mach number control.-A desired Mach number may be maintained by closing a switch 427 at that speed to couple motor 140 to an inductive device 163 producing signals which are applied to resolver 25. A motor 171, which may be operated in either direction by a manual controller 175, is also coupled to an inductive device 167 producing signals to set the speed datum. Interconnection between switches 421 and 427 prevents simultaneous control of altitude and Mach number. Specifications 662,833 and 663,891 are referred to.