Patent GB-698032-A (GB)
Title: Improvements in or relating to apparatus for controlling a body or craft about at least one axis
IPC: G05D1/08
Filed: 1948-11-12
Abstract: 698,032. Automatic control systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Nov. 12, 1948 [Nov. 14, 1947], No. 29405/48. Class 38 (iv). [Also in Group XX] In an automatic control system a gyro responsive to rate-of-turn of a body or craft about an axis controls servo-mechanism controlling the position of the body or craft about that axis and the gyro is biased in dependence on an operating quantity of the servo-mechanism. In one arrangement of an aircraft automatic pilot, Fig. 8, gyros TG, BG, PG responsive to angular velocity of the aircraft about turn, bank and pitch axes, respectively, control D.C. servomotors RM, AM, EM operating, through reduction gearing, a rudder R, ailerons A and elevators E respectively. Upon course deviation of the craft precession of gyro TG moves a contact relative to opposed fixed contacts TC<SP>1</SP>, TC<SP>2</SP> to energize field winding RGF of a generator RG from a three-terminal D.C. source E<SP>1</SP>, E<SP>2</SP> in such a sense that rudder servomotor RM, supplied by generator RG, runs in the appropriate direction to correct course. Control of the craft about its two other axes is similar. In other arrangements (not shown) each of the opposed fixed gyro contacts is associated with one of two opposed generator fields supplied from a two-terminal D.C. source. In order to produce desired characteristics and attitudes of flight various combinations of the following electromagnetic and mechanical biases may be applied to the precession axes of the gyros. Where relevant to Fig. 8 references are included in brackets. (a) A negative feed-back dependent on servomotor velocity is applied to the turn gyro (TG) by energizing biasing coils (SV<SP>1</SP>, SV<SP>2</SP>) from the output of a bridge circuit associated with the armature of the rudder servomotor (RM). Velocity feed-back is applied to the other two gyros in a similar manner (by coils BV<SP>1</SP>, BV<SP>2</SP>, PV<SP>1</SP>, PV<SP>2</SP>). The coils (SV<SP>1</SP>, SV<SP>2</SP>) biasing the turn gyro are also supplied by the output of a potentiometer (SVP) across the field of the generator supplying the aileron servomotor so that turn tends to be in accordance with bank. The coils (BV<SP>1</SP>, BV<SP>2</SP>) biasing the bank gyro are also supplied by the output of a potentiometer (BVP) across the field of the generator supplying the rudder servomotor so that bank tends to be in accordance with turn. The coils (PV<SP>1</SP>, PV<SP>2</SP>) biasing the pitch gyro are also supplied through a bridge rectifier (41) by the output of a potentiometer (P<SP>5</SP>) across the field of the generator supplying the rudder or aileron servomotor so that up-elevator is applied for either direction of turn or bank. (b) A negative feed-back dependent on rudder position is applied to the turn gyro (TG) by opposed biasing coils (RP<SP>1</SP>, RP<SP>2</SP>) the balance of which is upset when a potentiometer (RP) driven with the rudder moves from a central position. Position feed-back is applied to the other two gyros in a similar manner (by coils AP<SP>1</SP>, AP<SP>2</SP> EP<SP>1</SP>, EP<SP>2</SP>). (c) The turn gyro (TG) is monitored by a direction indicator (labelled) which may be a gyro-stabilized magnetic compass differentially controlling through a double thermionic valve (48) the energization of opposed biasing coils (CU<SP>1</SP>, CU<SP>2</SP>) of the turn gyro. The gyro stabilized magnetic compass may comprise a flux valve compass A.C. output from which is amplified to bias a position-type directional gyro precession of which operates a synchronous transmitter electrically connected to a synchronous receiver (S). The output from the synchronous receiver is applied through an unbalanced bridge circuit including voltage-variable resistors (R<SP>6</SP>), and through a transformer (TR<SP>1</SP>) to the grid circuits of the double valve (48). The unbalanced bridge acts to decrease sensitivity upon large course deviations. Sense discrimination of the output of the transformer (TR<SP>1</SP>) is obtained by comparison with a reference A.C. output of a second transformer (TR<SP>2</SP>). Means (not shown) are provided to lock the rotor of the synchronous receiver (S) when the craft is on a straight course. During manually initiated turns the rotor is unlocked and short-circuited by a relay (STR<SP>1</SP>) which operates when a switch S<SP>5</SP> opens upon a hand wheel (HW) being turned in either direction to initiate the turn. The rotor is then driven by its stator into correspondence with the heading of the craft so as to be always ready to maintain a new straight course. Alternatively the rotor may be driven into correspondence by a separate repeater motor. (d) The bank gyro (BG) is monitored by mounting it to precess about an axis (18) displaced from its centre of gravity so that it is selfbiased mechanically upon deviation from a condition in which the precession axis coincides with the direction of the resultant of the gravitational and athwartship accelerations. (e) The pitch gyro (PG) is monitored by a pendulum (2) differentially controlling through a series of contacts (4) the number of sections of two resistors (PR<SP>3</SP>, PR<SP>4</SP>) in series with coils (PR<SP>1</SP>, PR<SP>2</SP>) biasing the pitch gyro. Instead of a pendulum a chamber communicating with atmosphere through an orifice and developing a pressure dependent on rate of change of altitude may be associated with a diaphragm operating contacts to control differentially the energization of coils biasing the pitch gyro. A further chamber which is automatically sealed by an electromagnet whenever the hand wheel is set for level flight may be associated with a diaphragm mechanically biasing the diaphragm of the rate of change of altitude detector to maintain constant altitude. (f) Turn of the craft in azimuth is effected by rotation of the hand wheel (HW) operating a potentiometer (TP) to energize through a rectifier (42 or 43) one or other of two coils (TP<SP>1</SP> or TP<SP>2</SP>) biasing the turn gyro. Rotation of the hand wheel may also operate another potentiometer (BP) to energize one or other of two coils (BP<SP>1</SP> or BP<SP>2</SP>) biasing the bank gyro in dependence on the turn desired. Rotation of the hand wheel for turn in either direction may operate a potentiometer to increase the energization of a coil biasing the pitch gyro to give the necessary up-elevator instead of obtaining it as at (a) above. (g) Climb or dive of the craft is effected by push-pull operation of the hand wheel (HW) operating a potentiometer (PP) to energize one or other of two coils (PP<SP>1</SP> or PP<SP>2</SP>) biasing the pitch gyro. A further potentiometer operated by push-pull operation of the hand wheel may differentially influence the energiza. tion of two coils biasing the pitch pendulum or the diaphragm of the rate of change of altitude detector. (h) The back gyro may be biased in dependence on rudder velocity and the pitch gyro biased in dependence on aileron position or rudder velocity. Delayed application of rudder and upelevator by increasing the reduction gear ratio between the rudder and the rudder servomotor, increasing the velocity feed-back from the rudder, and reducing or eliminating the position feed-back from the rudder, is referred to. The vibrating action of the gyro controlled contacts may be accentuated by slight unbalance of the gyro rotors. Design of biasing coils and their armatures for producing desired bias characteristics is described in the Specification. Individual control of turn, bank and pitch by separate knobs or by a single control stick with three degrees of freedom is referred to. Specification 698,033 is referred to.