Patent GB-687349-A (GB)
Title: An improved means for recording one or more motions in a machine and for subsequently causing the machine to repeat exactly such recorded motions
IPC: G05B19/42
Filed: 1949-04-04
Abstract: 687,349. Electric control systems. BOWDEN. B. V., and MARSHALL. T. A. H. April 4, 1950 [April 4, 1949], No. 9058/49. Class 40 (i). Apparatus for controlling the movements of a mechanical device comprises means for phase modulating an electric wave in accordance with externally initiated predetermined movements and recording the modulated wave together with a reference wave in a single complex wave track. after which the record is played back to reproduce the complex wave, which is resolved into its constituent waves by band. pass filters, and the phase difference ,between the resultant reference wave and modulated wave controls motor means causing the mechanical device to repeat the initial movements previously executed. In apparatus for controlling the tracking, tilting, and panning motions of a cinematograph camera, a master oscillator O (Fig. 1) produces a frequency of 6000 c.p.s. which is broken down in frequency dividers FD1, FD2, FD3, FD4 to frequencies of 3000 c.p.s., 2000 c.p.s., 1200 c.p.s., and 867 c.p.s. The first or reference frequency is connected directly to a mixer circuit M, and the others are respectively supplied to phase splitters SP1, SP2, SP3, which energize the two or three phase stator windings of magslips MS1, MS2, MS3 whose rotors are mechanically connected to the manual control mechanism H1, H2, H3 of the several camera motions, which may be operated according to a sequence which is to be recorded and repeated. The windings of the displaced rotors respectively produce data signals at the several energization frequencies which are phase modulated in accordance with the magnitudes and senses of the several motions, and are supplied to the mixer whose single complex output comprising the reference signal and the three deflection signals, is recorded in known manner at R upon a film. magnetic wire, or disc. To control the camera motion in accordance with the recorded programme, the record is applied to a playback machine P (Fig. 2) and the respective component frequencies are separated by band pass filters BP1, BP2, BP3, BP4. The reference frequency is doubled in a frequency multiplier FM and divided by 3, 5 and 7 in frequency dividers FD5. FD6 and FD7, to produce reference frequencies energizing the stator windings of magslips MS4, MS5, and MS6 (which may be the same as those used in recording) through phase splitters SP4; SP5 and SP6. The several phase modulated data signals are fed through variable phase shift networks VS1, VS2, VS3 to discriminators D1, D2, D3 together with the outputs of the rotors of the respective magslips, rotated by servo-motors M1, M2, M3 controlled in known manner by the outputs of the discriminators through power amplifiers PA1, PA2, PA3 to drive the corresponding camera mechanisms in such directions as will restore the rotors to positions in which the data signals and the magslip rotor outputs are co-phased. Thus the camera mechanisms are operated in response to the modulations of the corresponding recorded data signals to follow the required programme of movements. The phase shift circuits are adjustable at the beginning of the playback to ensure that the camera starts from the correct position, and a mechanical clutch may. connect each servomotor and magslip: A lower master oscillator frequency may be used and multiplied to give suitable reference and data frequencies, which may be modulated before or after multiplication. The device is applicable to the control of automatic machine tools, and the Provisional Specification states that the data signals may be amplitude, frequency, pulse width, or pulse frequency modulated.