Delay robustness-constrained control of integrating processes with optimal tracking and quantified disturbance...

Area of Science:

• Control Engineering
• Systems Theory
• Process Control

Background:

• Integrating processes are common in industry but sensitive to time delays.
• Existing control methods often struggle with uncertain or variable delays.
• Robustness against delay uncertainty is critical for reliable process operation.

Purpose of the Study:

• To develop a robust two-degree-of-freedom (2-Dof) control scheme for integrating processes with uncertain delays.
• To introduce relative delay margin as a key metric for evaluating delay robustness.
• To derive explicit tuning rules for proportional-derivative (PD) controllers and disturbance observers (DOB).

Main Methods:

• Analytical derivation of PD controller tuning formulae based on relative delay margin.
• Investigation of stability boundaries for parameter analysis.
• Formulation and solution of the optimal tracking problem under delay robustness constraints.
• Quantification of DOB performance balancing delay margin and disturbance rejection.
• Determination of a critical time constant for DOB low-pass filter design.

Main Results:

• Novel explicit tuning formulae for PD controllers were analytically derived.
• Stability boundaries for the 2-Dof control system were identified.
• A trade-off analysis for DOB design was performed, balancing robustness and disturbance rejection.
• Synthetic tuning rules combining analytical design and quantitative adjustment were established.
• Simulations and a water tank experiment validated the proposed scheme's effectiveness.

Conclusions:

• The proposed 2-Dof control scheme effectively enhances robustness against delay uncertainty in integrating processes.
• The developed tuning rules provide a systematic approach for designing reliable control systems.
• The introduced relative delay margin is a valuable metric for assessing and improving delay robustness.