Patent GB-1072692-A (GB)
Title: Signal converter for position data systems
Inventor: DOVE FRANK
IPC: G05D3/14
Filed: 1962-09-01
Abstract: 1,072,692. Signal converters for position data systems. SPERRY GYROSCOPE CO. Ltd. Dec.2, 1963 [Sept. 1, 1962], No.33633/62. Heading G1N. Relates to a signal converter to receive signal from a synchro transmitter and provide a D. C. voltage output which is substantially linearly related to the angular position of the synchro transmitter rotor for more than a full 360‹ rotation thereof, and employs sector actuating switches which set up seven circuit conditions whereby coarse and fine signals are added corresponding to seven 60‹ sectors of possible angular positions of the transmitter rotor. For each position of the rotor in sector 1 position data signals will be transmitted and for corresponding rotor positions in sector 7, 360‹ further on, identical signals will be transmitted. A means which discriminates between whether the rotor is in sector 1 or sector 7 is described later. General Arrangement of Converter. Figs. 1 and 2 (not shown). The output signals from the synchro transmitter 4 are applied to a transformer network T 1 , T 2 , T 3  which in turn supplies sets of main and auxiliary output signals. The main set are representive of the rotor position and constitute fine signals which are supplied to a sector switch unit 3 which adds them to suitable coarse signals from a transformer T 4 . The auxiliary output is supplied to a control unit 11 whereby the control unit causes the operation of switches in the sector switch unit 3 so as to select the appropriate combination of coarse and fine signals whose sum when rectified will give a linear D.C. voltage output through lines 10 at terminals 12 A.B. (Fig. 2). Adding of Coarse and Fine Signals to Give Linear D.C. Voltage Output. (Figs.2, 4). The switches SW1, SW2 etc. are of transistor type and are switched on only during positive half cycles of the A. C. supply and are non conducting during negative half cycles, (described with reference to Fig. 5, not shown) and are operated in correspondence with the angular position of the synchro rotor. Successive operation of switches SW1, SW2 etc. add the output of successive sections of the secondary windings of transformer T 4  to the output at terminals 12 A-B. The portion of this latter output contributed by the outputs from the secondary sections of T 4 , which are switched in series with one secondary winding section of the transformer network T 1 , T 2 , T 3 , corresponds with the 60‹ portion of each sine curve of the latter secondary outputs where the increase is most linear, e.g. in curves 101, 104 (Fig.4) between points P and Q, i.e. from -30‹ to +30‹. In Fig.4 the degrees relate to angular position of the rotor which is plotted against mean signal amplitude of the windings 101 to 106, and the approximate mid points of sectors are 0‹, 60‹, 120‹, 180‹, 240‹, 360‹. The zero reference position is at 0‹ where the output from secondary winding 101 is zero and the secondary is connected by switch SW1 in series with a resistor directly across terminals 12 A-B. The output of 101 increases to a mean amplitude value V at +30‹, point Q when SW2 is closed and SW1 opened. The output of each secondary section of T 4  is taken as being of mean amplitude 2V, so that at point Q as SW2 closes secondary 102 is thereby connected in series with one T 4  secondary section between terminals 111 and 112. Now at point Q the output of 102 is -V so that the total output at terminals 12 A -B is + V as when SW1 was closed. The output of 102 increases and hence the total output increases until at point R the winding 102 output is +V and the total output is 2V + V = 3V, that is a linear increase from +V to +3V. At point R, SW3 closes and SW2 opens, winding 103 being connected in series with two sections of T 4  between terminals 111 and 113 and the total voltage at terminals 12 A-B is therefore 4V - V=3V. The output of 103 increases from -V to +V at point S giving a total output of 4V + V = 5V at this point. Switch SW4 is closed at this point and SW3 opened and the procedure continues the net result being a linear, D. C. voltage output at terminals 12 A-B having a polarity as shown (Fig.2). The transformer T 4  may be connected to a square wave supply from a circuit as Fig. 7 (not shown). Angular Positions in Excess of 360‹. When the rotor is positioned at +330‹ approximately 35‹ of further rotation is provided for. Between 330‹ and 390‹ the fine signal output of secondary 101 is again appropriate. At about 330‹ therefore SW7 closes to connect 101 to the output terminals 12 in series with the whole of the secondary windings, 111 to 117, of transformer T 4 . Arrangements are described including a bi-stable multivibrator circuit Fig. 6 (not shown) which prevent SW1 and SW7 being closed at the same time as the secondary windings of T 4  would be short circuited. The bi-stable multivibrator is triggered to one state which permits the switch SW1 to close during rotor movement +5‹ up to 185‹ while SW7 is inhibited, then the multivibrator is triggered to its second state whereby SW1 cannot close and SW7 is permitted to close in its proper sequence being operative between 185‹ and 365‹. At the 365‹ rotor position the multivibrator triggers so that once again SW7 is inhibited and SW1 will then close and the output from the terminals 12 will suddenly reduce to that corresponding to +5‹ position. If the rotor is turned negatively the sequence of switch operations is reversed. SW1 is inhibited until 175‹, then SW7 is inhibited until -5‹ when SW1 becomes inhibited and SW7 closed. Control of the Switches. (Fig. 3 not shown) This is achieved by combining control windings from various pairs of combinations of secondary windings of transformer network T 1 , T 2 , T 3 , their outputs being applied to terminals (15)(16) which causes two transistors in series to become conductive thereby causing their associated transistor switch to "close" Fig. 5 (not shown). For example consider SW2. A secondary winding (142) is connected in series with secondary (122) the former being in phase with 105 and the latter in phase with 106 so that their combined output will be positive for rotor positions between +270‹ (= -90‹) and +90‹ as shown line e Fig.4. This combined output is applied to terminals (15). Secondary winding (133) is connected in series with (143) and being in phase with 101 and 102 respectively their combined output will be positive for rotor positions between +30 and 210‹ line f Fig.4. This output is applied to terminals (16) for SW2. The result is that SW2 will only be closed over a sector between +30‹ and +90‹, that is where the combinations overlap. None of the other switches closed while the rotor is in this same sector.