Robust Fractional-Order Pi Controller With Ziegler-Nichols Rules

Abstract

In process control applications, above 90% of the<br> controllers are of PID type. This paper proposed a robust PI<br> controller with fractional-order integrator. The PI parameters were<br> obtained using classical Ziegler-Nichols rules but enhanced with the<br> application of error filter cascaded to the fractional-order PI. The<br> controller was applied on steam temperature process that was<br> described by FOPDT transfer function. The process can be classified<br> as lag dominating process with very small relative dead-time. The<br> proposed control scheme was compared with other PI controller<br> tuned using Ziegler-Nichols and AMIGO rules. Other PI controller<br> with fractional-order integrator known as F-MIGO was also<br> considered. All the controllers were subjected to set point change and<br> load disturbance tests. The performance was measured using Integral<br> of Squared Error (ISE) and Integral of Control Signal (ICO). The<br> proposed controller produced best performance for all the tests with<br> the least ISE index.