Optimum structures of digital controllers in sampled-data systems: a roundoff noise analysis

摘要

The effect of roundoff noise in a digital controller is analysed for a sampled-data system in which the digital controller is implemented in a state-space realisation. A new measure, called averaged roundoff noise gain, is derived. Unlike the traditionally used measure, where the analysis is performed based on an equivalent digital control system, this newly defined averaged roundoff noise gain allows one to take consideration of the inter-sample behaviour. It is shown that this measure is a function of the state-space realisation.