Design of multiloop PI controllers based on quadratic optimal approach

Area of Science:

• Control Engineering
• Process Control Systems

Background:

• Multiloop PI controllers are essential for complex industrial processes.
• Existing methods for designing multiloop controllers can be complex and computationally intensive.

Purpose of the Study:

• To extend the Linear Quadratic Regulator (LQR) methodology for synthesizing multiloop PI controllers.
• To develop a generalized diagonalization procedure for existing multivariable PI controllers.

Main Methods:

• Obtaining a multivariable P controller and diagonalizing it iteratively.
• Complementing the diagonalized controller with integral action.
• Exploring control weight matrix values to balance output error and control signal.
• Applying the method to a distillation column and a nonlinear CSTR.

Main Results:

• Successful synthesis of multiloop PI controllers with performance comparable to existing techniques.
• Diagonalization of existing multivariable PI controllers to create multiloop versions.
• Demonstrated effectiveness in controlling a distillation column and a nonlinear CSTR.

Conclusions:

• The extended LQR methodology provides an effective approach for designing multiloop PI controllers.
• The developed diagonalization procedure offers a way to adapt existing controllers for multiloop applications.
• The method achieves a favorable balance between control performance and signal usage.