Setpoint weighted PI-FOPD cascade controllers synthesis for unstable time-delayed processes satisfying prespecified...

Area of Science:

• Control Engineering
• Process Control
• Automation Systems

Background:

• Unstable time-delayed (UTD) processes present significant control challenges due to inherent instability and delays.
• Existing controllers often struggle to balance rapid tracking, overshoot reduction, and robustness for UTD systems.
• Model order reduction or delay approximation can introduce inaccuracies in controller design for UTD processes.

Purpose of the Study:

• To introduce a novel setpoint weighted PI-FOPD (SWPI-FOPD) cascade controller with a prefilter for UTD processes.
• To develop a four-stage design strategy for enhancing tracking, minimizing overshoot, and ensuring robustness.
• To provide a systematic procedure for controller gain computation applicable to various UTD process orders.

Main Methods:

• A four-stage design strategy involving optimal and robust FOPD (ORFOPD) and PI (ORPI) controllers.
• Utilizing a gain and phase margin (GPM) tester to determine feasible specification-oriented regions (FSORs).
• Implementing setpoint weighting and a prefilter to manage overshoot and refine reference signals.

Main Results:

• The proposed SWPI-FOPD controller demonstrates rapid tracking response with zero steady-state error.
• Significant reduction in overshoot and integral absolute error (IAE) or integral squared error (ISE) is achieved.
• The controller maintains enhanced robustness against ±10% loop gain perturbations (LGPs).

Conclusions:

• The SWPI-FOPD controller with a prefilter offers a robust and effective solution for controlling UTD processes.
• The systematic design procedure facilitates rapid computation of controller gains.
• Validated through simulations and a practical jacketed CSTR application, showcasing superior performance.