Patent GB-1027727-A (GB)
Title: Improvements in or relating to electronic method and apparatus for control of displacements
IPC: G05B19/21
Filed: 1963-12-12
Abstract: 1,027,727. Electric selective signalling ROCHAR ELECTRONIQUE. Dec. 12, 1963 [Dec. 12, 1962], No. 49144/63. Heading G4H. In a system for controlling the position of an object of the kind in which two pulse trains A, B, Fig. 2, are generated representing, by the number of pulses, the displacement of the object and by the phase relationship between the two trains the direction of movement, signals are obtained by gating to represent the four possible conditions or zones of movement: A#, AB, #B, ##, trigger stages being set by each of these conditions and reset by the opposite, a counting or deducting signal being produced only when a trigger stage is set so that oscillations about a transition point do not affect the counter. The input signals are applied to diode gates 50, 51; 53, 54; 56, 57; 59, 60, Fig. 5, and the output from each gate causes a corresponding transistor 66, 69 to conduct. In trigger 76, 77 transistor 76 is set by the AB signal and 77 by the opposite ##. Similarly transistor 80 is set by signal A# and 81 by #B the two triggers are combined in two groups of diode gates 82-85 and 86-89 to produce counting or deducting signals on leads 18, 19 respectively. When a trigger stage, e.g. 76 (AB) is set it provides a signal through resistor 94 to enable a diode gate 82 in a group connected to the " count " output 18 and via resistor 105 to 86 in a second group connected to the " deduct " output. If the next transition is to #, B representing movement in the forward direction trigger stage 81 is set and a pulse via capacitor 96 passes through gate 82 to terminal 18. If it had been a backward transition (to A#) trigger stage 80 would have been set and a pulse passed via capacitor 104 and gate 86 to the deduct output 19. If movement is back into a zone just previously occupied the corresponding trigger stage being already set gives no pulse so that no counting or deducting operation takes place. In Fig. 3 the four conditions are represented as four quadrants and movement of the object by the arrowed line. The first transition from #B to ## causes a counting signal (C), since trigger stage 77 is set by #, B. The next transition from #, # to A# sets trigger stage 80 and produces a counting pulse. Backward movement to ## produces no deducting signal because the corresponding trigger stage is still set. Similarly, forward movement to A# also produces no signal since the stage corresponding to A# is also set. Oscillation about a transition does not, therefore, affect the counter, since both corresponding trigger stages remain set. However movement to the next quadrant AB sets the corresponding stage and produces a count signal. The stage corresponding to the opposite condition #, # is reset. When the direction reverses, e.g. from #B to AB the transition produces no deduct signal because the AB stage is already set but stage A# having been reset by setting of stage #B is set again by the next transition and a deduct signal (D) is produced. The effect is to give the system a lost motion of one transition so that local oscillations are ignored.