Design and Efficient Implementation of Digital Non-integer Order Controllers for Electromechanical Systems

Digital realization of non-integer-order controllers is important to exploit the benefits provided by these controllers, in terms of flexibility, dynamic performance and robust stability, for applications in mechatronics, industrial and automotive systems. To realize infinite-dimensional fractional-order operators and controllers in the digital domain, a discrete-time approximation is necessary that must be characterized by stable and minimum-phase properties for control purposes. This paper provides a design method useful for a wide class of plants and applies a consolidated approximation technique. Moreover, the practical implementation problems of digital non-integer control algorithms are deeply analyzed by considering the effects of the sampling period, of the conversion between analog and digital domain (and vice versa) and the associated quantization. Results show benefits and limitations of the approach.