A unified approach to design controller in cascade control structure for unstable, integrating and stable processes

Area of Science:

• Chemical Engineering
• Control Systems Engineering
• Process Control

Background:

• Cascade control structures (CCS) are widely used for process control.
• Designing controllers for processes with unstable, integrating, and stable dynamics, especially with dead-time, presents significant challenges.
• Existing methods often require approximations or model order reduction, limiting their applicability.

Purpose of the Study:

• To present a unified controller design approach for CCS.
• To achieve enhanced load disturbance rejection for a wide range of process dynamics (unstable, integrating, stable) with dead-time.
• To avoid approximations of dead-time and model order reduction in the design process.

Main Methods:

• A hybrid design approach combining direct synthesis and pole placement methods for inner and outer loop controllers.
• Inner loop controller parameters are determined first.
• Outer loop controller is designed considering the inner loop as part of the primary plant.
• The method is applied directly to higher and lower order processes.

Main Results:

• The proposed unified approach effectively handles unstable, integrating, and stable processes with dead-time.
• The controller design is acquitted from dead-time approximation and model order reduction.
• Simulation results demonstrate the efficacy of the proposed strategy.
• Enhanced regulatory performance is achieved compared to existing literature approaches.

Conclusions:

• The unified controller design for CCS offers a robust solution for diverse process dynamics.
• The method provides superior load disturbance rejection capabilities.
• This approach simplifies controller design by eliminating the need for process approximations.