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Original Article

Optimal Fractional-Order PID Controllers Design for Plasma Current and Horizontal Position Control in IR-T1 Tokamak Based on Particle-Swarm Optimization



Tokamak reactors’ performance is inherently tied to the precise control of plasma shape, position, and current while staying within the operational constraints, specifically managing the control signals and power supply voltages. Furthermore, many tokamak models exhibit strong coupling between control variables, necessitating the use of Multiple-Input Multiple-Output (MIMO) decoupling controllers. The primary control objectives include achieving high tracking and decoupling performance within these operational constraints, along with a focus on robustness. Fractional Order Proportional-Integral-Derivative (FOPID) controllers offer an advantage due to their additional degrees of freedom, which contribute to improved performance, robustness, and flexibility compared to conventional control methods. In light of these advantages, we have designed Optimal FOPID, and also two Integer Order optimal PID (IOPID), controllers for plasma current and horizontal position control in the IR-T1 tokamak, which were optimized using Particle Swarm Optimization to minimize objective functions. Our results have shown that the Integral of Time-weighted Absolute Error (ITAE) criterion exhibits the best tracking and robustness behavior in this context. Examining an actual experimental discharge in this tokamak as a test case, validate that the OFOPID control scheme is effective at maintaining stability when faced with disturbances and fast variations in the plasma parameters.