How Fractional-Order Controllers Improve Nonlinear Process Control

Spherical tanks are popular in industries due to their large storage capacity. But managing their liquid levels can be tricky. Traditional PI and PID controllers just don't cut it because these processes are nonlinear. Enter Fractional-Order controllers (FOPI and FOPID), designed using the Approximate Generalized Time Moments (AGTM) optimization technique. This method allows for a more flexible and accurate control process. While the real-time modeling of these tanks is usually simple, following a Single Input Single Output (SISO) model, it often translates into a First Order Plus Dead Time (FOPDT) model.

This means the controllers have to work extra hard to maintain the tank's steady state. Researchers compared controllers based on PI, PID, FOPI, and FOPID, testing their performance with metrics like Integral Squared Error (ISE) and Integral Absolute Error (IAE), as well as factors like rise time and peak time. The results? Fractional-Order controllers, although complex to design, offer better performance and control flexibility. MATLAB and a Data Acquisition (DAQ) device were used to simulate and test these controllers in real-time, showing their exceptional capability.

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