Patent GB-1317018-A (GB)
Title: Speed head bearing and or time signal generating system for a ship
IPC: G01S13/937
Filed: 1970-07-13
Abstract: 1317018 Ship's radar TOKYO KEIKI SEIZOSHO CO Ltd 13 July 1970 [15 July 1969] 33902/70 Heading H4D A PPI North-up relative motion radar display is provided on a ship A whereby the relative positions B 1r  and BO r  Fig. 1, of a ship B at a previous time t 1  and the present time t 0  are established. The line L B  of the distance vector #d BA , passes through the origin of the display, indicating an impending collision. The Specification describes a system which, fed with the following data:- (1) Velocity and Bearing of ship A: - V A , # A  (2) Bearing of line L B :- # BA . (3) Ranges of ship B at times t 1  and to:- d BA1 , d BA0  (4) The time interval, #t = t 0  - t 1  (5) The ratio of the desired velocity of approach of ship B to that between times t 1  and t 0  :- α = V BAP  produces values of a new bearing and speed for ship A, viz. # AP , VAP, to cause ship B to miss by a predetermined distance C. It can be shown that :- If the vectors are analysed into x and y components (V B A) x , (VBA) v  etc. and these components are represented in the system by corresponding electrical values (EVBA) x , (EVBA) y  etc., then:- The time T from t 0  till ship B is at its nearest, assuming the new course, is given by:- T = Ed BA0 À Cos #<SP>1</SP> BAP  / E VBAP  In the system of Fig. 2, the left hand input units 5, 1, 2, 11, 7, 21, 24 and 27 provide the respective data, l/#t Ed BA1 , Ed BA0 , α, # BA , E C  E VA , # A    Ed AB  = (Ed BA1  - Ed BA0 ) is produced by subtractor 3 and E VBA  = Ed AB /#t is produced by multiplier 4.    Multiplier 10 produces E VBAP  = αE VBA . A sine/cosine resolver 6 having its rotor turned in response to the angle # BA  analyses E VBA  into its components (E VDA ) x , (E VBA ) y . The closest approach distance C P  is given by:- C P  = d BA0 . Sin #<SP>1</SP> BAP . It is desired that C P  = C. Therefore, EC is compared at 20 with the sine output of a resolver 17 fed with Ed BA0  and having its rotor moved by a servomotor 22 receiving the output of the comparator. The servomotor and rotor therefore take up the angle #<SP>1</SP> BAP . This angle is added to # BA  at 13 to give # BAP  which is used to control the rotor of resolver 12 receiving E VBAP  and so giving components (E VBAP ) x  and (E VBAP ) y . The ship speed signal E V.A  is analysed by resolver 25 to give components (EVA) x  and (EVA) y . The obtained component signals are applied to Add/Subtract circuits 30, 31 in combination to give which are fed to respective orthogonal coils of the stator of resolver 32. The rotor also has orthogonal coils, one of which, connected to output terminal 35 is caused by means of servomotor rotor aligner 36 to lie at right angles to the resultant of the fields from the two stator coils, and so give a zero output. The servomotor thus gives angle # AP . The magnitude of the resultant field, picked up by the other rotor coil is proportional to E V.AP  which appears at 39. The component signal Ed BA0 . Cos #<SP>1</SP> BAP  produced by resolver 17 is fed to a potentiometer 41 having a wiper controlled by a servomotor 42 fed with the output of a comparator 40 receiving the output of the potentiometer and E V.BAP . The servomotor thus turns until its input is zero whence R = T. Figs. 3 and 4 (not shown) show switched adaptations whereby the ship A keeps at its original speed, i.e., VAP = VA, or at a predetermined fraction thereof, i.e., VAP = kVA.