Fractional-Order Tilt Integral Derivative Controller Design Using IMC Scheme for Unstable Time-Delay Processes

The paper proposes a modified IMC-based Smith predictor (SP) control method for unstable time-delay processes. A novel design method to tune the parameters of a fractional-order tilt integral derivative controller has been developed using fractional-order IMC filter and process model parameters. The tuning parameters of the fractional-order filter are calculated from the new robustness index and desired performance constraint. The expected performance constraint satisfies good setpoint tracking and optimal control signal. The significant feature of the presented method is that the fractional IMC-SP structure provides a better outcome without adding much computational complexity. For a given robustness index, the optimal controller, which minimizes the performance constraint, the combination of control effort and integral time squared error, helps calculate the two tuning parameters. The benefit does verify under parameters' uncertainties, external load disturbances and noise. The comparative study with various numerical examples from recently reported methods shows better overall servo and regulatory performances.