Analysis on Self-Sustained Oscilations Caused by Level Quantization in Digital Control Systems

Abstract

In a D.D.C. system, the amplitude quantization of the input, the internal, and the output signal of the digital processor is done. Usually the relatively gross quantization for the output signal is done, because it is greatly important to take account of the economical significance for the output devices, and because the quantization for the output signal does not affect the performance of the system so much as the others.
In this paper we have discussed the method for obtaining the discrete describing function of the quantizer and analysing the self-sustained oscilations caused by the gross quantization at the output device of the digital processor. In the reference (2) the method has been discussed for analysing the self-sustained oscilations in the system shown in Fig. 1 by representing [sampler+quantizer+hold] in conventional continuous describing function.
But with his method, it is very difficult to analyse the systems with digital compensation. Using the method obtained in our paper, it is easy to analyse the systems with digital compensation, and the systems with more than one syncronized samplers.