Robustness Improvement Using the Filtered Smith Predictor Based Fractional Integral-Fractional Derivative Controllers: Application to a Pressure Plant

This article presents a simple frequency domain control technique to tune the parameters of a filtered Smith predictor based fractional integral-fractional derivative (FSP-FIFD) controller. The proposed method provides a practical approach to compensate stable First Order Plus Dead Time (FOPDT) transfer functions based on a filtered Smith predictor (FSP) control structure. In this control structure, an integer order predictor filter is used to improve the noise reduction of the control system. By benefiting from the proposed FSPFIFD controller, not only the phase margin and the gain crossover frequency of the control system are adjustable by tuning the free controller parameters, but also the robustness of the compensated system is enhanced. Finally, the designed FSPFIFD controller is implemented on a laboratory scale pressure plant and the obtained results are compared with those of applying a filtered Smith predictor based PI (FSPPI) controller in a similar structure. The practical results demonstrate the simplicity of application and the effectiveness of the proposed tuning rules.