Digital regulators redesign with irregular sampling

Abstract:

Although digital control provides the statement of design objectives not achievable with analog controllers, the well understanding and tuning of classical PID controllers or pole placement state feedback often lead to the implementation of digital controllers through the previous design of analog ones. Periodic sampling to discretize either the process or the designed controller, as well as in the digital control implementation, is usually assumed. But many circumstances determine a variable, or even random, sampling period: the computation time, the availability of process variable measurements, the communication delays, and so on. In this paper an analog controller satisfying the control requirements is assumed. Then variations of the sampling period with respect to the nominal one are considered and their effect on the controlled process analyzed. In order to keep the design specifications, some modifications of the classical PID algorithms and state feedback regulators are proposed. The possibility of adaptive controllers redesign is also considered. The problem arised in process control applications when a composition measurement is used and the sampling interval is not totally fixed. The results are illustrated with some examples as well as with the control of a raw materials mill in the cement industry.

Año de publicación:

1991

Keywords:

Fuente:

scopus