Fractional‐Order Tilt and Smith Predictor Scheme for Non‐Minimum Phase Processes

ABSTRACT In the case of a minimum‐phase system, output reacts to changes in the input as quickly as feasible. In contrast, a non‐minimum phase (NmP) system is dynamic in which the output reacts more slowly to input changes. In the literature, it is seen that such processes are difficult to handle with classical control structures. This paper proposes a fractional order controller with the modified Smith predictor structure. The inner loop is designed with a proportional derivative, making the plant more stable. The outer loop is then developed with a fractional‐order tilt integral derivative type. This new control structure can be designed using the well‐known phase‐margin and maximum sensitivity specifications. A fractional‐order target loop uses simple explicit relations according to the stability margins and plant parameters. Using just two tunable parameters, the inner and outer controllers are designed. In addition, the suggested design is capable of controlling various types of industrial processes dominant in delays, such as stable, integrating, unstable, and non‐minimum phase systems. After a numerical investigation, the method is also practically verified in the two‐tank plant. The performance analysis indicates that the suggested scheme can provide a balanced control between setpoint tracking with robustness, even with large parameter perturbations.