Patent GB-958971-A (GB)
Title: Vehicle guidance system
IPC: G05D1/02
Filed: 1960-09-19
Abstract: 958,971. Radio navigation; phase detectors; transistor circuits. S. A. KNIGHT. Sept. 19, 1960 [Oct. 6, 1959], No. 32115/60. Headings H3A, H3T and H4D. [Also in Division G3] In a vehicle guidance system, transmitter 11, Fig. 1, radiates on a frequency F 1 , transmitter 12 radiates on a frequency F 2  F 1 +f 1 , transmitter 13 radiates on a frequency F 3  = F 2 +f 2 , transmitter 19 radiates a carrier wave of frequency F 4  modulated by frequencies f 1  and f 2  derived in a receiver 21, the vehicle derives one set of frequencies f 1  and f 2  in a receiver 17 from frequencies F 1 , F 2 , F 3 , and a second set thereof by demodulation of the wave of carrier frequency F 4 , a first phase comparator 38 giving outputs +P 1  - P 1  where P 1  corresponds to the difference in phase of the f 1  signals, a similar phase comparator - 39 giving outputs +P 2 , -P 2 , where P 2  corresponds to the difference in phase of the f 2  signals; differentiating circuits 40 ... 43 control a circuit 44 which controls a circuit 45 having inputs from error circuits 47, 48, the error circuit 47 inputs being +P 1 , - P 1  and a signal P 1R  obtained from a record of phase variation when the vehicle is guided manually over the course which is to be followed automatically and the error circuit 48 inputs are similar but corresponding to phase comparison frequency f 2 . Circuits 44, 45 provide for the use of the hyperbolic grid having the higher spatial rate of change of phase in the direction of vehicle travel for longitudinal vehicle guidance, Figs. 2, 3 and 12 (none shown). Phase detection, Fig. 6. D.C. signals P, are afforded by an arrangement comprising symmetrical clipping diodes 54, 55, in conjunction with transistor pairs 50, 51 and 52, 53, followed by differentiating circuits 60, 62 and 61, 63 (with diodes 65, 64 to eliminate negative-going peaks) and a bi-stable circuit 66. Pulse-frequency reduction. Fig. 7. For easier recording of the phase variations over the wanted path a pulse-frequency reducer may be employed; transistors 70, 71 form a monostable circuit with transistor 70 normally conducting. Regular L.F. pulses, e.g. from a relaxation oscillator are applied to transistor 70 via a differentiating network 73, 74 and rectifier 75a to cause transistor 71 to conduct until capacitor 75 discharges by a predetermined amount, the capacitor being rapidly re-charged through diode 76 when transistor 70 conducts. Conduction time of transistor 71 is dependent on the base current of transistor 77; the D.C. output of thephasedetector, Fig. 6, is applied to input 81 and output 80 is connected to input 82. Output 83 may be recorded directly to provide alternating positive and negative pulses of the same relative spacing as those from the collector of transistor 67, Fig. 6, but of much lower repetition rate. The connection at point 85 may be opened, and capacitor 75 short-circuited; the circuit then reverts to a bi-stable trigger. Sensing selector, Figs. 9 and 10. Selector 45, Fig. 4, is illustrated in Fig. 9, the contact wiring therefor being shown in Fig. 10; relay 1 is less sensitive than relay 2, the latter closing when the derivative of the signal from phase detector 38 exceeds that of phase detector 39 thereby selecting the former for front-back guidance. Relay 1 closes when whichever signal is selected for front-back guidance has a positive derivative. Transistor 97 receives an algebraic sum and conducts only when the vehicle is heading north or east; transistor 98 receives an algebraic difference and conducts only as the vehicle moves east or south. Error circuits. Figs. 10, 11. The error circuits comprise opposite-type transistor pairs, Fig. 11, the outputs of which are fed to the relay contacts, Fig. 10.