A control system where the continuous-time plant is controlled with a digital device is a sampled-data system. Under periodic sampling, the sampled-data system is time-varying but also periodic, and thus it may be modeled by a simplified discrete-time system obtained by discretizing the plant. However, this discrete model does not capture the intersample behavior of the real system, which may be critical in a number of applications.
The analysis of sampled-data systems incorporating full time information leads to new challenging control problems with a rich mathematical structure. Many of these problems have been solved only very recently.
Effects of time quantization and noise in level crossing sampling stabilization , Julio H. Braslavsky, Ernesto Kofman and Flavia Felicioni. Proceedigns of the XX Argentine Congress of Automatic Control AADECA 2006. PDF
L_2-induced Norms and Frequency-gains of Sampled-data Sensitivity Operators, J. Braslavsky, R. Middleton and J. Freudenberg. IEEE Transactions on Automatic Control, 43(2), p. 252-8, February 1998. Abstract | Full text (gz-compressed postscript, 121K).
Robustness of Zero-Shifting via Generalized Sampled-Data Hold Functions, Jim Freudenberg, Rick Middleton and Julio Braslavsky. IEEE Transactions on Automatic Control, 42(12):1681-92, December 1997. Abstract | Full text (gz-compressed postscript 130K).
On a Key Sampling Formula Relating the Laplace and Z Transforms, Julio Braslavsky, Gjerrit Meinsma, Rick Middleton and Jim Freudenberg. System and Control Letters 29(4):181-190, 1997. Abstract | Full text (pdf 207K) (gz-compressed postscript 118K).
Frequency Domain Analysis of Sampled-data Control Systems, J. Braslavsky. The University of Newcastle, 1995, ISBN 7259 0905 6. Abstract | Full text as a zip-compressed postscript file (681K) or as a PDF file (1.5M).