Robust Fractional Digital Control of a First Order Plus Integrator Process

In this article an approach based on fractional calculus to control a second order linear process with pure integration at the output is presented. The main contribution of this work is the control strategy, which is a variant of the double loop controller where the proportional outer loop controller is replaced by a fractional derivative one, in order to increase the robustness of the controlled system. A digitalization of the non-integer derivative is performed by a continued fraction expansion and Euler conversion method. Simulation results are shown for a reference tracking and disturbance rejection. In addition, it is compared with a conventional state feedback controller in the presence of uncertainty in the process. Thus, a reasonable response rate is accomplished with no overshoot neither system steady -- state error. These features were kept quite unchanged under a relative uncertainty degree of plus-minus 50% in the plant parameters.