GB1428126A - Control apparatus - Google Patents

Abstract

1428126 Retro-active position control SPERRY RAND Ltd 8 June 1973 [28 June 1972] 30237/72 Heading G3N In a position controlling servo system an error signal is derived representing the difference between a desired position and an actual position; the error signal is converted into a pulsed control signal and to ensure that unwanted long period fluctuations do not occur in the control signal its integral is compared with that of the error signal and any differences are used to correct the control signal. In Fig. 1 a desired position is fed to input 9 and passes via amplifier 8 to comparator 5. At the comparator the input signal is combined with a triangular wave 13 to give a pulse length modulated control signal which is amplified at 17 and drives a hydraulic or pneumatic valve 1 to operate actuator 2. A movable body 3 is thus driven towards a desired position, its actual position being detected by potentiometer 6 and subtracted from the input signal at 8 to give an error signal on line 12. This error signal and the control signal are fed to integrator 11 where their integrals are substracted to form a correction signal on line 14 which determines the production of the control signal at comparator 5. In the alternative embodiment of Fig. 2 the error signal from subtractor 8 is fed to integrator 11, the output of which controls a flip-flop 18. This latter generates the control signal which passes to amplifier 17 as above and also to the integrator 11. In this case the frequency of the control signal varies with the magnitude of the error signal, while in Fig. 1 the frequency is constant.