Patent GB-1008112-A (GB)
Title: A recording system for a control system
IPC: G05B19/42
Filed: 1962-07-02
Abstract: 1,008,112. Electric correspondence control systems. AMERICAN MACHINE & FOUNDRY CO. July 2, 1962 [July 31,1961], No. 25251/62. Heading G1N. [Also in Division H4] The distance of a member from a reference point is measured electrically by producing a correspondingly, phase-modulated A.C. signal, which is converted to a pulse train of variable mark/ space ratio and recorded on magnetic tape together with a reference pulse train. The record is played back to reproduce the movement of the member. Recording (Fig. 1). Lateral displacement of a manually-controlled member 10 is converted to angular displacement of a shaft 16 by a rack and pinion 12, 14, and is measured by a resolver 18 energized by a sine-wave generator 20, to give a phase-displaced output 30 which is reshaped as square pulses 68 whose mark/space ratio is proportional to the phase displacement, before it is recorded at 71. A reference signal 69 from generator 20 is simultaneously recorded. The circuit includes a frequency divider 50 producing square pulses 53 at half the signal frequency, which are fed to gates 46, 48 in the measuring and reference channels respectively, whereby alternate pulses in both channels are suppressed when the phase difference is between 90 degrees and 270 degrees, but only the measuring channel has alternate pulses suppressed when the phase difference is less than 90 degrees or more than 270 degrees. These pulses 62 and 64 (or 64a) switch on and off respectively a flip-flop circuit 66, thereby producing the appropriate mark/space controlled square pulse train 68 for recording. The mark/space ratio can vary from 1/3 to 3/1. Playback (Fig. 2). The reference signal recorded at 71 is sensed by a pick-up head and used to lock an oscillator 76, reproducing the basic sine wave voltage 101, which is fed to a reference channel resolver 24 and a measuring channel resolver 18 coupled to the member 10 it is desired to position. The sine wave output signals from the resolvers are squared and differentiated to produce pulse train 108 in the reference channel and pulse train 114 in the measuring channel. The information signal recorded at 71 is also picked up and reconstituted as the square pulses 102 having the variable mark/space ratio indicative of the desired position for member 10, and are differentiated and separated at 100 to produce pulse train 106 representing the constant frequency reference signal, and pulse train 104 representing the variable phase measuring signal. Pulse trains 106, 108 control flip-flop 86 to produce square wave signals 110, and pulse trains 104, 114 control flip-flop 84 to produce square wave signals 112. The difference between these square wave signals, obtained at 116, is the difference between the actual position of member 10, and the desired position. This difference signal is therefore integrated and amplified to control member 10 through a servomechanism 122. Electronic means are provided to eliminate jerking control of the member 10 when the mark/space ratio of the reconstituted control signals changes abruptly from 1/3 to 3/1 or vice versa. Specifications 962,750 and 1,008,113 are referred to.