GB1424764A - Speed modulating arrangement - Google Patents

Abstract

1424764 Automatic control of speed COMPAGNIE HONEYWELL BULL 26 March 1973 [29 March 1972] 14380/73 Heading G3R [Also in Division H2] A D.C. motor mechanically connected to a rotating load through a torsion bar is fed with both D.C. and a pulsed current having a repetition rate corresponding to the natural resonant frequency of the load and torsion bar system, the respective amplitudes of the two currents being controlled so that the speed of the load periodically falls to zero. As shown in Fig. 5a, 31 is the load and 33 the motor linked by torsion bar 32. When current supplied to the motor is periodically reversed at the resonant frequency of the system mechanical oscillations will be generated having an amplitude dependent on the maximum current supplied. When the above system is used to drive the type carrier 1 in a printing machine a control system, Fig. 10, is used, in which the output of tachometer 91 is fed into two circuits, one, a peak detector and filter 92 from which is obtained a signal SVM proportional to the velocity modulation and the other a low pass filter 93 giving an output signal SV proportional to the mean velocity. Signal SV is fed into two comparators 94A,94B and is compared in one with the modulation signal SVM and in the other with a mean velocity reference signal SVR. The output signals E 1 , E2 from the comparators are used to control a D.C. current source 95B and a pulse current source 95A respectively. Pulses from a voltage/frequency converter 96 have a frequency proportional to the mean speed of the carrier 1 and are fed through a phase converter 99A to control the frequency of pulse generator 95A. The phase converter is controlled by an error signal from comparator 94C which represents the positional error of the type carrier with respect to the hammers. In a further embodiment Fig. 11 (not shown) the amplitude of the oscillatory movement of the type carrier is detected and compared with a reference signal (SP), which is a constant determined by the spacing of the hammers, the error signal being used to control the pulse current source. A number of methods of arranging the mechanical drive are suggested Figs. 7a-7e (not shown) in some of which two motors are used, one of which may be asynchronous and supplied from an A.C. source.