Simple Robust PID Tuning for Magnetic Levitation Systems Using Model-free Control and ℋ_∞ Control Strategies

This paper proposes two control techniques to provide robust tracking for magnetic levitation systems (MLS): model-free control (MFC) and robust proportional-integral-derivative (PID) control. The proposed MFC does not require a mathematical model. The MFC uses a stabilising local PID controller and a continuous saturation function of a sliding surface. The local stabilising control is achieved through a trial-and-error method, while the other parameters in the sliding surface are tuned to achieve the required tracking and robustness objectives. For robust PID controller, a linear model of MLS is derived. The robustness, tracking, and transient problems are formulated using the ℋ_∞ theory and solved using the genetic algorithm. Experimental verifications are conducted to demonstrate the effectiveness of the proposed controllers.