This article presents a simple method of designing a fractional filter PID controller for second order plus time delay (SOPTD) processes using internal model control (IMC) scheme. There has been limited number of tuning rules for SOPTD processes developed using direct synthesis method and IMC method. The proposed IMC-PID controller using fractional IMC filter results in a controller structure composed of PID controller cascaded with fractional filter. Simulations have been performed on several

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... econd order lag dominant and delay significant processes. Robustness checks are performed for variations in the process parameters and robustness analysis is carried out using sensitivity functions. The proposed controller results in an enhanced control performance for nominal process parameters and with parameter variations. In addition, the effect of measurement noise is also studied for set point tracking and load disturbance variations. A simple IMC-PID controller for SOPTD processes using fractional IMC filter is proposed. Different case studies were analyzed for servo response and regulatory control. It can be concluded from the results that a good closed loop performance is obtained with nominal model and actual model of the process with the proposed controller. The proposed controller resulted in a minimum overshoot in the response in absence of set point weighting. It was also shown that the effort of proposed controller is less for noise corrupted measurements. The robustness for parametric uncertainties is proved with robustness analysis using sensitivity functions. The work is in progress to extend the proposed method for unstable and non-minimum phase systems.