Optimal loop shaping compensators for fractional-order model set

The paper deals with parametrization of shaping compensators (filters) ensuring the Bode's ideal control loop shape for an exactly defined class of process models. The class of essentially monotone fractional-order processes is considered. The fractional integrator is used as the optimal open loop reference model. Several aspects of shaping filter implementation on given frequency band are discussed. In contrast to the other known approaches, the exactly computed filter frequency response is approximated by the integer order zero/pole transfer function. The comparison with other methods shows that the direct approximation leads to the significant reduction of the filter order. Arisen filters are applicable especially for processes with large gain or load variations.