Fractional internal-model-control filter-based controller tuning for series cascade unstable plants

The disturbances and plant uncertainties are common in the process industry. In such conditions, the controller must manage robustness from the predefined plant models and be suitable for industrial applications. This paper uses a fractional-order theory in a controller design for a series cascade unstable plant. The methodology is developed using well-known terms for the industry, namely internal-model-control (IMC) and maximum sensitivity. The primary loop is designed with a fractional-order filter-PID controller. The inner loop is built with IMC-PI controller with desired robustness value. In-depth comparisons reveal that the proposed scheme performs better regarding plant uncertainties and load disturbances.