Patent GB-925820-A (GB)
Title: Improvements in or relating to guidance system for aircraft
IPC: G01S1/30
Filed: 1952-02-01
Abstract: 925,820. Radio navigation. GLENN L. MARTIN CO. Feb. 1, 1952 [Feb. 3, 1951], No. 2744/52. Class 40 (7). In an hyperbolic guidance system which comprises a master station and slave azimuth and range stations, the missile or aircraft flies along a particular azimuth curve which passes over a target until the range curve intersecting the azimuth curve as the target is reacted when a destination signal is generated. Initially, the missile rudder is under coarse control until the required azimuth curve is approached close enough for a change over to fire control to be effected. Drift is compensated by an integrating circuit and gyroscope. If azimuth guidance signals are lost, control is maintained by a gyroscope in the last indicated course. In range, coarse control is maintained until near the target when fire control is substituted. If range signals are lost, an arrival predictor operates the destination signal generator. Receiver circuit (Fig. 2).-The three guidance pulses received from the transmitting stations are received at antenna 8, and separately directed to the azimuth, master and range receivers 10, 11, 12 and fed to the pulse width discriminators 13, 14, 15. The outputs from 13, 14 are fed to the azimuth coarse and fine lane comparators 19, 21 which control the azimuth lane switch 22 which controls the rudder servo-system 25, 26, 27. Drift errors are compensated for by the integrator and gyroscope 28, 29 which feed into the rudder control from the mixer 24. The rudder servoamplifier gain is increased with range to compensate for the divergence between the hyperbolic guidance paths. The destination signal generator 35 causes a missile to dive to the target and in the case of an aircraft, indicates to the pilot the arrival of the aircraft at the destination. If range signals are lost, lost signal switch 32 is energized and 35 is controlled by the arrival predictor and ground speed unit 38, 39. Pulse width discriminator (Fig. 3).-The incoming pulse, received at 40, is passed by the diode clamper 46 if of the predetermined length. If a pulse is shorter than required, the gate generator 45 does not operate, 46 remains conducting and no signal is passed. If the pulse is of the correct length, the gate generator is triggered and the output applied to 46 which now does not conduct. In addition, a further signal, generated by the input pulse at the delay line 48, arrives at and is passed by 46. When the input pulse is too large, the delayed pulse from 48 arrives at 46 when the latter is again conducting due to removal of the gating pulse from 45. Coarse and fine lane comparators (Figs. 4, 5, not shown).-In the coarse comparators, the master and slave pulses are applied to an Eccles- Jordan multi-vibrator, the output of which is a square wave having a length equal to the time separation of the pulses. In the fine comparators, the master and slave pulses are applied to "ringing " oscillators, the phase difference between the outputs being measured. Ground speed unit (Fig. 10).-In the range fine lane region, the range fine lane voltage is applied to differentiating circuit 128, the output of which is proportional to the ground speed and controls the servomotor 135 which adjusts the setting of the output potentiometer 126. The output from 126 is applied as feed-back at 137 so that its setting is proportional to the true ground speed arrival predictor (Fig. 11). With the guidance voltage signals present, at 143 or 144, the voltage is applied through terminal 148 and contact 149 to the grid of cathode follower 150. As the missile approaches the target the range voltages, and the voltage output of 150, decrease. Condenser 151 discharges at a corresponding rate and the voltage at 140 corresponds to remiainng distance to the target. If the guidance signals are lost, the switch 149 connects 150 to the D.C. amplifier 155. The bias of the latter is determined by the ground speed voltage at 157 and the charge on 151. At the balance condition, the condenser voltage falls at a rate directly proportional to the ground speed voltage.