Comparing Fractional Order PI Controllers With Variable Gain and Gain-Order for the Networked Control of a Servomotor ?

This paper addresses the use of fractional order control (FOC) in the context of control through networks to minimize or compensate the effect of the time-varying networkinduced delay. In particular, two fractional order strategies are presented based on the adaptation of, on one hand, the gains of a fractional order PI controller, and, on the other hand, both its gains and its order in accordance with the variable delay detected in a networked control system (NCS). The essence of these approaches is to make controller gains and both gains and order delay-dependent by minimizing a defined cost function in order to avoid a decreased control performance. Experimental results, related to the control of the angular velocity of a servomotor through the Internet, show the effectiveness of these fractional order adaptive strategies in comparison with the non-scheduled controller. Likewise, a useful application of variable order PI controllers is presented.