Frequency frame approach on tuning FOPI controller for TOPTD thermal processes

Area of Science:

• Control Engineering
• Process Control
• Thermal Systems

Background:

• Third order plus time delay plants are common in thermal processes like air heaters and boilers.
• Robustness is critical for thermal systems, necessitating advanced controller tuning methods.
• Existing methods for phase curve flattening have limitations.

Purpose of the Study:

• To develop a new method for tuning fractional order proportional-integral controllers.
• To improve the stability, performance, and robustness of thermal process control systems.
• To achieve improved robustness by flattening the phase curve in the Bode plot.

Main Methods:

• A novel 'frequency frame' technique is proposed to tune controllers.
• Gain and phase crossover frequencies are enclosed within a rectangular frame.
• Tuning is achieved by adjusting the frame's edge lengths to modify gain and phase margins, flattening the phase curve.

Main Results:

• The frequency frame method successfully tunes controllers for improved robustness and performance.
• Demonstrations on an electrical air heater and a bagasse fired boiler show enhanced gain and phase properties.
• The method ensures the iso-damping property alongside improved robustness.

Conclusions:

• The proposed frequency frame method offers an effective approach for tuning fractional order controllers in thermal systems.
• This technique significantly enhances system robustness and performance, addressing critical industrial needs.
• The study provides a practical and validated method for improving control of complex thermal processes.