Patent GB-886875-A (GB)
Title: Improvements relating to automatic displacement control
Inventor: LEMAY CHRISTOPHER ARCHIBALD GO
IPC: G05B19/4105
Filed: 1957-03-29
Abstract: 886,875. Electric copying machines. ELECTRIC & MUSICAL INDUSTRIES Ltd. March 25, 1958 [March 29, 1957], No. 10451/57. Class 38 (6). In systems for the automatic control of a machine tool of the cutting type-for example an oxy-acetylene cutter-automatic compensation for the varying radius of the cutter is obtained by the introduction of a factor which is dependent upon the speed of movement of the cutter. A flame cutter 1 is controlled in two coordinate directions by servomotors 2, 3 which are controlled in accordance with the signals produced in the stator windings 118, 119 of a resolver 114, velocity feedback in the servo loops being provided by tacho-generators 120, 121 respectively. The servomotors 2, 3 also drive potentiometer devices 6, 7 which produce analogue signals x<SP>1</SP>, y1 representing instantaneous displacements of the cutter 1. Command signals x, y are derived from selectors 9, 12 by means of a reader 16 which extracts from a teleprinter tape coded information of the mannor in which it is desired to govern the operation of the cutter 1. The signals derived by the reader 16 are fed to store arrays X1 . . . X5, Y1 . . . Y5 wherein the signals are converted into alternating voltages representing analogues of the coded values on the tape, the store arrays being sensitized from a programme unit 20 so that the signals are accepted by the store arrays in a desired order. The signals stored in the X, Y arrays are applied to interpolators 21, 22 by way of selector switches 23, 24, which interpolators carry out quadratic interpolation of the x, y signals as a function of a parameter # which parameter is introduced by a servomotor 28 driving shafts 25, 26 to the interpolators 21, 22 and the selectors 9, 12. The command signals x, y are fed to windings 140, 141 of a resolver 139 together with the instantaneous displacement signals x<SP>1</SP>, y<SP>1</SP>; and the signals dx/##, dy/##-derived in the interpolators 21, 22 are fed to windings 101, 104 of a resolver 102 which resolver is driven by a servomotor 111 so as to represent the instantaneous slope of the contour being cut. A second resolver 114 is driven by the servomotor 111, the rotor winding 115 of which is fed with a voltage s-s<SP>1</SP>, that is, a speed control signal s from an A.C. potentiometer 116 minus a signal s<SP>1</SP> representing the instantaneous speed of the cutter, this latter signal s<SP>1</SP> being obtained from a resolver 126 and tacho-generators 120, 121. Rotor winding 117 of resolver 114 is fed from the resolver 139 by way of a transformer 150 with a signal t n  which is a measure of a desired difference between the command displacement and the actual displacement normal to the contour being cut, the transformer 150 introducing a factor which is dependent upon the radius of the cutter. The stator windings 118, 119 of the resolver 114 develop signals which are the command signals x, y modified to account for the instantaneous displacement and speed of the cutter 1 and these modified signals are used to control the servomotors 2, 3 which drive the cutter in its co-ordinate directions. The servomotor 28 which governs the parameter # operates in response to signals t #  obtained from the resolver 139 and ds/## obtained from the resolver 102. Specifications 796,994, 802,472, 830,462, 846,381, 849,091, 863,114 and 882,459 are referred to.