Patent GB-1364507-A (GB)
Title: Colision avoidance apparatus
IPC: H03H11/12
Filed: 1971-11-01
Abstract: 1364507 Radar SPERRY RAND CORP 1 Nov 1971 [12 Nov 1970] 50623/71 Heading H4D Collision avoidance apparatus comprises radar means for detecting echoes corresponding to first and second location co-ordinate value, at respective instants of time, of a movable object in the vicinity of said apparatus, means for storing at the first instant of time a representation of the first co-ordinate values, readout control means for reading the storage means at the second instant of time and for modifying the first co-ordinate value by a pre-determined factor, and means for the simultaneous display at the second instant of first and second images representative of the object, in terms of the second co-ordinate value and of the modified first co-ordinate value. As described, a conventional marine azimuth scanning radar system provides video signals on a lead 1, synchronizing signals on leads 17, 17A, and aerial bearing signals on a lead 3. The video signals appear in real time on a PPI display of a CRT 71, but delayed and modified echo signals are superimposed by means of a sum circuit 69. Radial scanning for the CRT 71 is effected by a coil 74, which is supplied by a range sweep generator 77 (with an amplifier 78) under control of the synchronizing signals. Said coil 74 is rotated about the axis of the CRT 71 in synchronism with the radar aerial. The video signals appearing on the lead 1 are also coupled, through a capacitor, to the arm 41 of a write control 33, D.C. bias being provided by a power supply 67. The write control 33 is a threeposition relay in which the arm 41 is connected via a contact 41a or 41c to respective write control electrodes WR of first and second CRT storage tubes Sl, S2 when the relay coil 39 or 39a is energized. When neither coil is energized, the arm 41 is brought to a central disconnected position 41b by springs 42, 42a. The coils 39, 39a, and likewise the coils of other control devices shown in Figs. 1a to 1d, are energized in a requ red sequence by means of a switching apparatus 90, which is driven by a shaft 25c, rotating synchronously with the radar aerial, through 8 : 1 reduction gears (see Fig. 5). A shaft 25a, also rotating in synchronism with the radar aerial, drives the arm 26a of a potentiometer 26, which is fed from a power supply 27. A sawtooth deflection voltage is thereby made available for supply to the azimuth deflection coils 21, 21a of the storage tubes S1, S2, which are operated with B-scope displays, and to a terminal C associated with the CRT 71. The coils 21, 21a are fed through respective adders 29, 29a, having second inputs connected to the output terminals 80a, 80b of a bar control 31. This comprises a relay which connects a bar oscillator 30 (operating, for example, at 500 kHz) to the terminal 80a, or the terminal 80b according to whether its coil 81 is, or is not energized. The range deflection coils 19, 19a of the storage tubes S1, S2 are fed through respective amplifiers 18, 18a by integrators 14, 14a each having one input from a power supply 15, another input from an integrator control 91, and a re-setting input from the synchronizing lead 17 or 17a. The integrator control 91 comprises two relays each of which allows an integrator 14 or 14a to be connected to a respective arm 12, 12a of a potentiometer 11 or 11a. Said arms are ganged and are manually operable. The potentiometers 11, 11a receive outputs from integrators 6, 6a each having one input from a power supply 4 and another from a respective relay comprised in a reset control 10. Operation of a relay connects a power supply 9 to the associated integrator. A read control 35 comprises a two-way two-position relay which in its unoperated state connects a power supply 64 to the read control electrode RE of the storage tube S1 and, through a coupling capacitor, the input of a single shot multivibrator 68 to the target 20 of said tube. When the relay is operated it provides similar connections for the storage tube S2. The output of the multivibrator 68 provides a second input for the sum circuit 69. The erase control electrodes ER of the storage tubes S1, S2 are connected as required to a power supply 54 by an erase control 34, which comprises a threeposition relay with operating coils 47, 48. A target control 53 comprises a two-way twoposition relay which connects either a power supply 15a to the target of the storage tube S1 and a power suply 15b to the target of the storage tube S2, or vice versa. Operation.-This is carried out in successive cycles each corresponding to eight full aerial azimuth scans. The radar video signals are written into the storage tube S1 during a first scan, are held during second and third scans, are read out during each of fourth to seventh scans and are erased during an eighth scan. The same sequence is followed with the storage tube S2, but with a four-scan offset, so that there is no break in the read out (Fig. 6, not shown). In Figs. 1a to 1d the storage tubes S1, S2 are respectively being written into, and read out from. The integrator 14 has input from the power supply 15, and each range scan of the tube S1 is the same. However, the integrator 14a has input both from the power supply 15 and, in a proportion determined by the position of arm 12a of the potentiometer 11a, from the integrator 6a. The voltage from the integrator 6a starts at a value determined by the power supply 4, and rises in saw-tooth fashion until reset. The output from the integrator 14a thus provides range scans of increasing speed with time for the read out from the storage tube S2 (Fig. 7, not shown). The delayed image of a target is of arcuate form owing to the bar oscillator 30, and has an apparent range which is dependent upon the range it had when stored, and the time since storage. By suitably setting the arms 12, 12a of the potentiometers 11, 11a the apparent range can be made to correspond with that which the target would have if it were moving in accordance with the tau collision warning criterion. Inspection of the display of the CRT 71 enables a comparison to be made between present range and bearing with said apparent range and the previous bearing (Fig. 8, not shown). Other embodiments.-A B-scope display may be utilized instead of the PPI display of the CRT 71. Two stationary deflection coils are provided which are fed respectively from the terminals B and C (Fig. 2, not shown). In a third embodiment the storage tubes as well as the display tube have PPI type scanning. Mountings which are rotated in synchronism with the radar aerial about the storage tubes carry main deflection coils fed from the terminal B and auxiliary deflection coils fed from the bar control 31 (Figs. 3, 4, 4a, not shown).