Design and implementation of the fractional-order controllers for a real-time nonlinear process using the AGTM...

Area of Science:

• Process Control Engineering
• Nonlinear System Dynamics
• Optimization Techniques

Background:

• Spherical tanks are crucial in process industries but present control challenges due to nonlinear behavior and significant dead time.
• Accurate liquid level control in Single Spherical Tank Liquid Level Systems (SSTLLS) is essential for operational efficiency.
• First Order Plus Dead Time (FOPDT) models are commonly used for SSTLLS, requiring effective control strategies.

Purpose of the Study:

• To propose and evaluate the Approximate Generalized Time Moments (AGTM) optimization technique for designing Fractional-Order PI (FOPI) and Fractional-Order PID (FOPID) controllers.
• To compare the performance of AGTM-designed FOPI and FOPID controllers against conventional PI and PID controllers for a nonlinear SSTLLS.
• To validate the effectiveness of the proposed controllers through simulation and real-time implementation.

Main Methods:

• Development of the Approximate Generalized Time Moments (AGTM) optimization technique.
• Design of Fractional-Order PI (FOPI) and Fractional-Order PID (FOPID) controllers using the AGTM method.
• Comparative analysis using Integral Squared Error (ISE), Integral Absolute Error (IAE), rise time, peak time, settling time, overshoot, and steady-state error.
• Implementation in MATLAB and real-time testing using a National Instrument NI-DAQmx 6211 device.

Main Results:

• The designed Fractional-Order controllers based on the AGTM method exhibited superior performance in controlling the nonlinear SSTLLS.
• Quantitative improvements were observed across various performance metrics, including reduced error integrals and enhanced time-domain characteristics.
• The AGTM method provides greater design flexibility for fractional-order controllers.

Conclusions:

• The proposed AGTM optimization technique is effective for designing high-performance FOPI and FOPID controllers for nonlinear SSTLLS.
• Fractional-order controllers offer significant advantages over traditional controllers for systems with nonlinearities and dead time.
• The study validates the practical applicability and superior performance of the proposed control strategy in both simulation and real-time environments.