AbstractA new stability analysis technique is developed in this paper for complicated sampled-data systems with both analogue and digital controllers, by frequency-domain equivalence in the continuous-time sense and time-delayed descriptor (or singular) state-space realization remodelling. The technique is independent of the lifting technique and thus employs neither structural nor spectral features of any discrete-time transfer functions of continuous-time plants. The suggested criteria are stated with frequency-domain conditions, involving neither open-loop unstable poles nor contour/locus-orientation-related encirclements counting. The criteria are implementable graphically with locus plotting or numerically tractable without locus plotting. The descriptor remodelling advantages are further exploited in surmounting infinite dimensionality and structural/spectral features unavailability in multi-rate and time-delayed sampled-data systems. Numerical examples are included to illustrate the main results.
Optimum structures of digital controllers in sampled-data systems: a roundoff noise analysis