A Hybrid Control Framework for Chemical Processes with Long Time Delay: Theory and Experiments.

Area of Science:

• Control Engineering
• Nonlinear System Dynamics
• Fractional-Order Calculus

Background:

• Traditional control methods struggle with nonlinear systems exhibiting significant time delays.
• Improving transient response and robustness in dead-time processes remains a challenge.
• Integrating internal model concepts with sliding mode control offers potential for enhanced performance.

Purpose of the Study:

• To propose a hybrid control framework combining internal model concepts, sliding mode control (SMC), and fractional-order calculus.
• To develop a modified Smith predictor (SP) tailored for nonlinear systems with substantial delays.
• To enhance the transient responses and robustness of controllers for dead-time processes.

Main Methods:

• A modified Smith predictor (SP) is designed incorporating fractional-order concepts.
• The predictive approach is integrated with a sliding mode control (SMC) controller.
• A dynamical sliding mode controller is formulated by combining predictive and fractional-order elements.

Main Results:

• Numerical simulations demonstrate the proposed controller's performance under step changes, external disturbances, and parametric uncertainty.
• A real-world application on a TCLab Arduino kit shows good performance with minimal chattering.
• The controller exhibited an aggressive response with increased overshoot during disturbance rejection, indicating a need for parameter tuning.

Conclusions:

• The proposed hybrid fractional-order sliding mode controller effectively manages nonlinear systems with delays.
• The controller demonstrates robustness against model mismatches and external disturbances.
• Further optimization of tuning parameters is recommended to refine performance and controller action in specific scenarios.