Patent GB-1389587-A (GB)
Title: Weapon firing computer
IPC: F41G3/22
Filed: 1972-08-04
Abstract: 1389587 Gunlaying computers HUGHES AIRCRAFT CO 4 Aug 1972 [12 Aug 1971] 36512/72 Heading G4G Apparatus for determining the range R and direction # (azimuth) of a target from a weapon comprises means for hand-setting rectangular co-ordinate information in a computer which performs a rectangular-to-polar conversion. The various switches shown in the figures may be set as required for various modes of operation. In one mode, the co-ordinate differences between weapon and target, (E T -E W ) and (N T -N W ), being known, are set upon potentiometers 24, 26 which supply analogue voltages to respective stator windings 38, 44 of resolver 40. The rotor of the resolver is turned to produce zero output voltage in rotor winding 46 as indicated by meter 56 and the angle of rotation yields the direction #. At this angular setting, the output of the rotor winding 48 is determined by adjusting potentiometer 52 until the voltages of the rotor and the potentiometer are balanced in summing junction 50, as indicated by the meter 56. This setting yields R. If the co-ordinates of the target are unknown, but those of an observer remote from the weapon are known, the differences (E O -E W ), (N O -N W ) between the co-ordinates of the observer and the weapon may be set upon potentiometers 20, 22 and the corresponding analogue voltages fed to respective summing junctions 36, 42. An analogue of the estimated distance Rot between observer and target set upon potentiometer 28 is fed to the rotor winding of a resolver 30 and the angle of the rotor is set to the estimated bearing # OT  of the target from the observer. The outputs of the stator windings 32, 34 are the rectangular resolutes of R OT  and are added to the corresponding co-ordinate differences (E O -E W ) and (N O -N W ) in the junctions 36, 42, which therefore yield (E T -E W ) amd (N T -N W ). These latter signals are processed as before to yield range R and bearing #. If the observer's co-ordinates are unknown, he may sight the weapon and set the information upon resolver 30 and potentiometer 28. The stator and rotor windings of resolver 40 are switch to ground and ground potential applied via switch S6 to summing junctions 36, 42. The outputs of the summing junctions are applied in turn to the meter 56 as the potentiometers 20, 22 are adjusted to supply voltages which balance those from the resolver 30. These settings represent (E W -B W ) and (N O -N W ). In another method of determining the observers grid position, the target position is set upon potentiometers 24, 26, range and direction R WT , # WT  are set upon resolver 40 and observer's sighting information R OT , # OT  set upon resolver 30. The outputs of the stators of the two resolvers are compared in the summing junctions 36, 42 and the differences, which represent (E O -E W ) and (N O -Q W ), determined by adjustment of potentiometers 20, 22. Errors in direction due to nonstandard conditions may be compensated by applying an adjustable bias from potentiometer 62 to summing junction 60. This bias may be scaled in divider 64 to be proportional to resolver excitation voltage. A range connection to compensate for altitude difference between weapon and target may be applied from potentiometer 66 to summing junction 50. The sign of this correction is determined by a switch 68. The scale factor of the potentiometer 52, which measures R WT , may be adjusted by means of another potentiometer 58 which is set to compensate for observed errors in R WT  upon firing of a test round. The specification describes a control panel in which the co-ordinate potentiometers are associated with mechanical counters for visual display. The drives for the potentiometers and the counters are coupled by a clutch whereby the zero of the potentiometers may be adjusted. Thus, whilst the counters indicate absolute co-ordinate values, the potentiometer settings relate to co-ordinate differences. A modification is described (Fig. 2C, not shown), suitable for application to mortars having a limited choice of elevation angles. In such mortars, range is obtained by adjustment of propellant change. The range is converted to amount of charge required by an extra potentiometer which feeds the summing junction 50. The scale of this potentiometer is adjustable by means of a range of extra resistances selected according to whichever combination of elevation and charge is chosen. This choice also determines selection of a resistance to provide an altitude correction signal. The circuit also comprises a set of resistances which may be selectively coupled to the junction 60 to provide a drift angle correction which is different for different elevation angles.