SOME ASPECTS OF ANALYSIS AND SYNTHESIS OF MACHINE CONTROL PROBLEMS

Abstract

Automatic control systems engineers have mostly relied on block diagram techniques and signal flow graph methods for analysing the performance of the system. These methods have a distinct advantage over the use of differential equations in that they serve gs visual reminders of cause-and-effect relationships in the phys-ical system. In this work, the physical system has been represented by its structural diagram as proposed by Aiaerman( . The advantage of such a representation is that the elements in any system may be represented as links. Linear systems including that having time lags have been considered and analysed. The effect of a para-meter (gain or time constant) on the system stability is found out using D-partition technique. For unstable systems stabilising devices have been used. The transfer functions of the stabilising devices are realised into physical circuits using conventional network synthesis methods. The transient response is plotted from the D-partition curve. Stability analysis of systems having more than one non-linearity has been carried out using the describing function technique. A practical system-voltage regulation of a synchronous generator- is taken and -V- -vi- studied with (a) neglecting all non-linear effects, (b) considering only th+ non-linearity (saturation type) of the synchronous generator# (c) considering the non-linearities of both the amplidyne and synchronous generator and Cd) considering the non -linearities of amplidyne, main exciter and synchronous generator. The system is found to be unstable for cases (a) and (b) whereas stable for cases Cc) and (d) upto a particular value of frequency. Thus, the stabilising effect of non•linearities has been brought out.