Design of an Optimal Control Strategy for Coupled Tank Systems Using Nonlinear Constraint Optimization With Kharitonov-Hurwitz Stability Analysis

Abstract

The fundamentals of nonlinear constraint optimization are exploited in this paper to design a decentralized PID controller for variable area coupled tank systems. Maintaining the tanks at the desired level is the main objective of the proposed decentralized control algorithm. The benchmark coupled tank systems are modeled to the first order plus dead time (FOPDT) model by designing decoupled subsystems. The control law is designed for decoupled systems to attain the servo response by minimizing loop interactions. Further, the overshoot is reduced by imposing constraints on the maximum closed-loop amplitude ratio of the system. Furthermore, the robustness of the controller is analyzed and stability is verified with the Kharitonov-Hurwitz theorem. A concise comparison is carried out between the proposed control law with existing methods in order to highlight the productive application of the proposed control algorithm. From the results, it envisaged that the proposed controller shows better responses compared to the existing methods. Besides, the efficacious nature of the proposed control scheme is validated by considering a wide range of closed-loop amplitude ratios.

Keywords

• Coupled tank systems
• decouplers
• FOPDT model
• model uncertainty
• PID control
• stability analysis