Discrete-time domain two-degree-of-freedom control design for integrating and unstable processes with time delay

Area of Science:

• Control Engineering
• Process Systems Engineering
• Applied Mathematics

Background:

• Integrating and unstable processes with time delays present significant control challenges.
• Existing control methods may struggle with independent optimization of set-point tracking and disturbance rejection.

Purpose of the Study:

• To propose a novel discrete-time two-degree-of-freedom (2DOF) design method for integrating and unstable processes with time delay.
• To analytically design controllers for optimal set-point tracking and load disturbance rejection.
• To enable independent tuning of controllers for enhanced control optimization.

Main Methods:

• Utilizing a recently developed 2DOF control structure.
• Analytically designing a set-point tracking controller based on H2 optimal control specifications.
• Deriving a disturbance rejection controller by proposing a desired closed-loop transfer function.
• Establishing conditions for robust stability and providing tuning guidelines.

Main Results:

• An analytical expression for set-point response is provided for quantitative tuning.
• Sufficient and necessary conditions for robust stability are established for the disturbance rejection controller.
• Independent tuning of controllers is demonstrated to achieve control optimization.

Conclusions:

• The proposed discrete-time 2DOF design method effectively addresses control challenges in integrating and unstable processes with time delays.
• The independent tuning capability allows for optimized performance in both set-point tracking and disturbance rejection.
• The method's effectiveness is validated through illustrative examples from existing literature.