Indirect IFO-TID controller design for process control using shifted relay feedback control

The relay feedback approach is used to identify the real-time process dynamics and controller design based on limit cycle data. An inaccurate estimation of limit cycle parameters leads to erroneous process dynamics identification and hence the controller design. To improve accuracy, this work proposes a shifted relay technique to accurately estimate the limit cycle parameters and then an indirect fractional-order tilted integral derivative (IFO-TID) controller designed based on the estimated limit cycle parameters. The proposed shifted relay method provides flexibility to accurately estimate the limit cycle parameters with a single shifted parameter. A simulation study is carried out to implement the proposed shifted relay technique and then the results are experimentally validated on the four-tank level control system. Its superiority is shown over existing state-of-the-art techniques regarding accuracy under nominal and parametric analyses. Further, the proposed IFO-TID controller performance is compared with some of the existing methods, and it is observed that the proposed methodology is better in robustness and stability.