Patent GB-655411-A (GB)
Title: Automatic position plotter
IPC: G01S1/02
Filed: 1947-10-07
Abstract: 655,411. Automatic plotter. BENDIX AVIATION CORPORATION. Oct. 7, 1947, No. 26902. Convention date, Oct. 10, 1946. [Class 40 (i)] [Also in Groups XX and XL (c)] In an automatic position plotter errorvoltages representing the difference between the actual polar co-ordinates of a known position or positions, from a craft (as obtained by R.D.F. for example) and the polar co-ordinates of the same position on a chart with respect to the plotting-cursor, are used to control two servomotors imparting rectangular - co-ordinate movement to the plotting cursor. The error voltage may be derived from Selsyn or potentiometer transmitter units. X and Y movements are imparted to the plotting cursor 22 by motordriven lead-screws 14, 18 which are mounted beneath the chart 10, Fig. 1. The cursor is also attached by wires 34, 34<SP>1</SP> to polar co-ordinate transmitters 24, 26. Selsyn-polar transmitter (Fig. 2).-Each transmitter unit 24, 26 is mounted for "parallel movement" anywhere under the chart (i.e. its base-plate maintains a fixed angle with respect to the chart 10) and comprises an " R " coordinate transmitter 30, a "#" co-ordinate transmitter 28 and a sense-reversing switch 41 to change the phase of the "#" component as the bearing passes through the cardinal points. The wire 34 is stored on a spring-biassed drum 56 and passes round a drum 58 geared to a Selsyn-transmitter 30 so that full stretch of the wire does not make more than one revolution of the Selsyn rotor. The transmitter 30 and drums are carried by a member 32, attached to the rotor spindle 50 of the Selsyn transmitter 28, and also connected by gears 127, 125 to the reversing switch 41. The position of the transmitter unit is marked by a beam of light 51 shining through the chart from a lamp in a housing 42 below the hollow Selsyn shaft, whereby it may be located at the known position. Selsyn follow-up system (Fig. 4).-The actual bearing and range of the known object received by devices 51, 57 causes a corresponding rotation of Selsyn transmitters 64, 71, having their rotors energized from an A.C. supply 70, and their stators connected to the stators of the transmitters 28, 30. The error voltages obtained from the rotors of the transmitters 28, 30 are applied to the sense-reversing switch sectors 47, 49, 53, 55, across pairs of resistors centre-tapped to earth and thence to selector-switches 85, 87, whereby error signals from either part of the unit may be connected to the X and Y amplifiers 112, 114. The X and Y motors driving the cursor are two-phase induction-type having one field coil energized from the amplifier and one from the A.C. supply 70. An identical transmitting system for the other polar co-ordinate unit 26 is also connected to the selector switches 85, 87, whereby the bearing and/or range of two objects may be used to plot a position. Manual control of plotter.-For the greatest accuracy in plotting, the operator will use switches 85, 87 to apply to the X and Y motors the bearing that is more nearly normal to its co-ordinate axis and the range that is more nearly parallel to its axis. Automatic control (Fig. 6).-The selector switches 85, 87 may be replaced by double-poledouble-throw switches 200, 206 connected to opposite segments of a quarter-circle-motordriven distributer 216, the take-off, after amplification, being connected to the X and Y motors through a half-circle distributer 228 driven synchronously with 216. Thereby the signal voltage from two units is applied sequentially in the right sense to the X motor and then sequentially and in the right sense to the Y motor. Thus the signal which gives the greatest degree of accuracy (v. manual control, above), acts in effect as a fine control and the other signal acts as a coarse control to assist approximate positioning of the cursor. Potentiometer system (Fig. 5).-The Selsyn elements of the polar transmitter unit may be replaced by A.C. energized potentiometers 150, 156 connected through transformers 137, 139 to the sense-reversing-switch-contacts and these outputs are selected by the switch 85 for connection to one primary 130 of a differential transformer feeding the Y amplifier 114. The other primary 142 is energized with the actual bearing or range signal from devices 51, 57 connected through a selector switch 98 ganged to the switch 85. The amplifier outputs feed the X and Y motors as before. The apparatus is duplicated for the second polar transmitter. Fully automatic control of the plotting through ganged distributers may be arranged as before, Fig. 7 (not shown). Specification 644,864, [Group XL (c)], is referred to.