Hybrid Time-Invariant and Time-Variant Linear Motion Control of a Levitating Platform

This paper investigates motion control strategies for a magnetically levitated (MAGLEV) motion platform actuated by a set of levitated linear flux-switching permanent magnet motors. The vertical levitation is decoupled from the horizontal motion and controlled using an H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</inf> controller, while the focus here is on horizontal thrust control under varying payload conditions and plant uncertainties. PID, H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, and H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</inf> controllers are designed within a two-degree-of-freedom signal-based framework. The controllers are synthesized to yield a similar settling time. First, the H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, and H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</inf> controllers are synthesized using the same weighting functions reflecting desired reference tracking and disturbance rejection. Second, a finite-horizon optimal feedback controller is designed as a time-variant solution for ideal conditions. Finally, all controllers are tested on a high-fidelity engineering verification model with actuator dynamics captured via finite element method based lookup tables. Time- and frequency-domain simulations demonstrate that the H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</inf> controller provides the most robust disturbance rejection, while the finite-horizon controller offers optimal transient performance in the absence of uncertainties. The results highlight trade-offs between performance and robustness, contributing to the development of advanced control strategies for precision MAGLEV systems.