Abstract
•A new fractional controller structure is investigated in this paper. The controller is a fractional PID controller cascaded with a fractional order filter.•System to be controlled can be fractional or integer.•The fractional property of the closed loop system is not especially imposed by the controller structure but by the closed loop reference model.•The proposed controller design method uses the IMC paradigm.•The main advantage of the proposed method is that it has no restriction on the class of process models.
Fractional order controller design with a small number of tuning parameters is very attractive. Few attempts have been done recently for some limited cases of models. In this paper, a new approach is developed to design simple fractional-order controllers to handle fractional order processes. The fractional property is not especially imposed by the controller structure but by the closed-loop reference model. The resulting controller is fractional but it has a very interesting structure for its implementation. Indeed, the controller can be decomposed into two transfer functions: a PIυDμ-controller and a simple fractional filter. The new structure is named PIυDμ-FOF-controller. The design method is based on the internal model control (IMC) paradigm.