DIGITAL CONTROLLER-DESIGN - ALTERNATIVE EMULATION APPROACHES

The emulation approach to digital controller design involves two steps : (1) the design of a continuous controller to satisfy performance and robustness objectives, and (2) the conversion of the continuous contr oller into a digital controller with the objective of obtaining compar able closed-loop system properties. This paper addresses the second st ep of the emulation approach. Previously developed methods are discuss ed, and several new methods are shown to be effective in accounting fo r computational delay and for sample-and-hold delay in closed-loop con trol applications. When the step response of the digitally controlled system is required to be close to that of the corresponding continuous system, the selection of the sampling period T and the emulation perf ormance are related in a fundamental way. This is illustrated in a clo sed-loop example.