Optimal digital redesign of continuous-time systems using fractional-order hold

This paper proposes a novel optimal digital redesign technique using fractional-order hold (f.o.h.) for finding a dynamic digital control law from the available analog counterpart and for simultaneously minimizing a quadratic performance index. A method for converting the dynamic digital control law into a static one, through a tuning parameter, is also presented. The proposed technique can be applied to a system cascaded with a more general class of reference inputs than simple step inputs, and the developed digital controller can be implemented via low cost microcomputers. The superiority of using the fractional-order hold over the zero-order hold and the first-order hold is exploited.