Tuning algorithms for fractional order internal model controllers for time delay processes

This paper presents two tuning algorithms for fractional order IMC controllers for time delay processes. The two tuning algorithms are based on two specific closed loop control configurations: the IMC control structure and the Smith Predictor structure. In the latter, the equivalency between IMC and Smith Predictor control structures is used to tune a fractional order IMC controller as the primary controller of the Smith Predictor structure. Fractional order IMC controllers are designed in both cases in order to enhance the closed loop performance and robustness of classical integer order IMC controllers. The tuning procedures are exemplified for both single-input-single-output as well as multivariable processes, described by first order and second order transfer functions with time delays. Different numerical examples are provided, including a general multivariable time delay process. Integer order IMC controllers are designed in each case, as well as fractional order IMC controllers. The simulation results show that the proposed fractional order IMC controller ensures an increased robustness to modeling uncertainties. Experimental results are also provided, for the design of a multivariable fractional order IMC controller in a Smith Predictor structure for a quadruple-tank system.status: publishe