Robust on-line relay automatic tuning of PID control systems

Area of Science:

• Control Engineering
• Automation Systems
• Process Control

Background:

• Proportional-Integral-Derivative (PID) controllers are widely used in industrial automation.
• Astrom's relay autotuning method is a foundational technique for PID controller tuning.
• Existing methods may require process disruption or lack robustness in certain applications.

Purpose of the Study:

• To develop a robust on-line relay automatic tuning method for PID control systems.
• To extend the applicability of Astrom's relay autotuning method.
• To enable non-iterative controller re-tuning for enhanced performance without disrupting closed-loop control.

Main Methods:

• A relay is implemented in an inner loop of a controller-stabilized process.
• Limit cycle oscillations induced by the closed-loop system are utilized for tuning.
• Two tuning methodologies are proposed: a direct method and an indirect method based on an explicit process model.

Main Results:

• The proposed on-line method allows for controller re-tuning without interrupting the closed-loop system.
• Demonstrated enhanced performance compared to the basic relay autotuning method.
• Validation through simulation examples and a real-time experiment.

Conclusions:

• The developed on-line relay autotuning method offers a robust and practical approach for PID control.
• The method provides potential advantages in terms of performance enhancement and operational continuity.
• Successful experimental validation highlights its real-world applicability.