Control systems for moving bodies
The present invention relates to control systems for moving bodies and is particularly though not exclusively concerned with a remote control system for an aerial body such as a missile. 
     In the copending U.S. patent application No. 373881/64, of Sendles, Ser. No. 373,881, filed Jun. 9, 1964, now abandoned in favor of a copending continuation thereof, Ser. No. 660,873, filed Aug. 4, 1967, still pending, there is claimed a missile or other moving body comprising a rotatable portion arranged for rotation relative to another portion of the missile or body, means for rotating said rotatable portion and bringing it to any one of a number of preselected positions in relation to a datum, and means on said rotatable portion for exerting a thrust thereon away from the axis of rotation to produce a steering effect on the missile or body. 
     It is well known that the cost of control equipment used in a missile represents an appreciable portion of the total manufacturing cost of the missile and attempts are constantly being made to reduce the cost and also the bulk and weight of the control equipment. Such economies are particularly desirable in the case of small missiles and although the missile forming the subject of our copending patent application effects useful economies in this direction it is an object of the present invention to provide an improvement in or modification of the missile forming the subject of the copending application, in which the amount of control equipment is still further reduced. 
     According to the present invention, there is provided a missile or other moving body comprising a rotatable portion arranged for rotation relative to another portion of the missile or body, and means for rotating said rotatable portion to bring it to any one of a number of preselected positions in relation to a datum and for exerting a thrust thereon away from the axis of rotation to produce a steering effect on the missile or body. 
    
    
     One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: 
     FIG. 1 is a side elevation of a missile according to the invention, 
     FIG. 2 is a part sectional plan view of a portion of the missile shown in FIG. 1, 
     FIG. 3 is a block schematic diagram of control apparatus housed in the missile, 
     FIG. 4 is a block schematic diagram of part of the apparatus shown in FIG. 3 including details of the contents of one of the units illustrated in FIG. 3, and 
     FIG. 5 is a schematic perspective view of an alternative arrangement of the control surfaces of the missile. 
    
    
     Referring first to FIGS. 1 and 2, a missile 11 comprises a main body portion 12 and a nose portion 13 which is rotatably mounted in bearings 14 on the forward end of the main body portion 12 for rotation about the longitudinal axis of the missile 11 and which houses a free gyroscope 15 which is arranged to generate an electrical signal representative of the roll attitude of the nose portion. The nose portion 13 is provided with a control surface 16 mounted in the nose portion 13 for rotation about a lateral axis passing through the longitudinal axis of the missile 11, the inner end of a shaft 17 supporting the control surface 16 being provided with an eccentrically mounted pin 18 which engages in a peripheral groove 19 in a head 20 of an axially movable push rod 21 coaxial with the rotary axis of the nose portion 13 and extending at one end into the rotatable nose portion 13 and at the other end carrying an armature disc 22 mounted concentrically with respect to the push rod 21 and arranged between and in cooperating relation with a pair of actuator solenoids 23 and 24 mounted in the main body portion 12 and coaxial with the longitudinal axis of the missile 11, the arrangement being such that upon energisation of the solenoid 23 the push-rod 21 is moved forward into the nose portion 13 acting on the eccentrically mounted pin 18 and causing the control surface 16 to be angularly turned in one sense to a first deflected position and upon energisation of the solenoid 24 the push-rod 21 is moved rearward causing the control surface to be angularly turned in the opposite sense to a second deflected position. 
     A fixed surface 25 of the same shape and size as the movable control surface 16 is fixedly mounted on the other side of the nose portion 13 at a predetermined angle of incidence and the arrangement is such that the movable control surface 16 pivots from one of its two deflected positions to the other through an angle which is equally divided by the plane containing the fixed surface 25 and the pivotal axis of the movable control surface 16, the movable control surface 16 moving to a large angle of incidence at one of its deflected positions, hereinafter referred to as the high incidence position, and moving to a low angle of incidence at its other deflected position, hereinafter referred to as the low incidence position. 
     The two solenoids 23 and 24 hereinbefore referred to are energised under the control of apparatus housed in the main body portion 12 of the missile 11. The control apparatus is shown in FIG. 3 and includes a battery 26 for supplying energising current to the solenoids 23 and 24 through a changover switch 27 in a first position of which one of the solenoids 23 and 24 is energised and in a second position of which the other of the solenoids 23 and 24 is energised. A roll-position comparator 28 is provided which compares the signal generated by the gyroscope 15 with a roll-demand signal transmitted from the remote control ground station and fed to the comparator 28 from a signal receiver and decoder 29. The output from the comparator 28 is fed to a roll logic circuit 30 as described in our French Patent Application based on British Patent Application No. 50198/64, the output of which is fed via a roll-amplitude comparator 31 to the changover switch 27, which in response thereto switches to the one or other of its two positions according to whether the signal from the roll logic circuit 30 is positive or negative, and the arrangement is such that the changeover switch 27 is moved to a position which will cause by energisation of the appropriate solenoid and the appropriate setting of the movable control surface 16 at one of its two deflected positions rotation of the nose portion 13 via its shorter path to the required roll attitude, whereupon the output from the roll logic circuit becomes zero and changes sign, causing the changeover switch 27 to switch over with the result that the other solenoid becomes energised. The movable control surface 16 moves to its other position and the nose portion rotates in the opposite sense. The movable control surface 16 then hunts about its undeflected position and the nose portion 13 is held at the required roll attitude. 
     A lateral demand signal is transmitted from the ground station in the form of a mark-space signal and is converted in the decoder 29 to a direct current signal which is applied to the roll-amplitude comparator 31 which in response thereto modifies the amplitude of the output from the logic circuit so that, for example, by an increase in the amplitude of the signal applied to the changeover switch 27, the movable control surface 16 is held for longer times in its deflected positions which results in an increase in the amplitude of the nose roll oscillation and produces a smaller means steering effect on the missile. 
     Referring now to FIG. 4, the roll amplitude comparator 31 takes the form of a Schmidt trigger circuit with blacklash, with the amount of backlash being varied by the output from the decoder 29. The output of the Schmidt trigger circuit feeds the switch 27 which operates the solenoids 23 and 24 in anti-phase. As shown, the roll amplitude comparator 31 comprises an adder unit 32, a zero-level Schmidt trigger circuit 33 and a sign modulator 34. The trigger circuit 33 is arranged to have an output which is positive for positive inputs thereto and negative for negative inputs thereto. The output signal from the trigger circuit 33 is fed to the sign modulator 34 so that the sign of the output signal is given to the roll amplitude demand output of the decoder 29, which is then summed in the adder unit 32 with the output of the roll logic circuit 30 and the summed signal applied as an input to the Schmidt trigger circuit 33. 
     In an alternative embodiment of the invention shown in FIG. 5 the fixed surface is replaced by a second movable control surface 35 which pivots in the same manner and through the same angle as that through which the control surface 16 pivots, but which is operated by a further eccentrically mounted pin 36 so arranged as to cause the second control surface 35 to move with but in opposite sense to the first control surface 16, whereby when the first control surface 16 moves to the high incidence positions the second control surface 35 moves to the low incidence position and when the first control surface 16 moves to the low incidence position the second control surface 35 moves to the high incidence position.