Nonlinear Positioning Technique via Dynamic Current Cut-Off Frequency and Observer-Based Pole-Zero Cancellation Approaches for MAGLEV Applications

Abstract

This article solves the problem caused by high level current feedback gain setting for fast responsiveness of magnetic levitation systems considering the current dynamics and presents advanced nonlinear positioning technology without plant parameter information. The main features of this study are summarized as follows: First, current control demonstrates current ripple reduction and overall performance guarantee through a low feedback gain in the steady state, including a dynamic feedback loop increased by an error variable magnitude in the transient period. Second, the plant parameter information-free velocity observer replaces the observer output error integral action with the disturbance estimation action to improve the closed-loop performance. The simulation results reveal the practical advantages derived from the contributions of this study.INDEX TERMS Magnetic levitation, positioning, variable cut-off frequency, velocity observer, disturbance observer. NOMENCLATURE PLANT VARIABLES M , M LMasses of electromagnet and load. g, K Gravitational acceleration and electromagnetic force coefficient. R c , L cCoil resistance and inductance. M 0 , K 0 , R c,0 , L c,0 Norminal parameter values. wp , wcThe uncertain time varying disturbances.The associate editor coordinating the review of this manuscript and approving it for publication was Philip Pong . p, v p , i c , V Position, velocity, current, voltage of MAGLEV system. p * , i * c Desired position and coil current. p ref , i c,ref Reference position and coil current. ω c , ω p Cut-off frequencies. CONTROLLER VARIABLES e p , e v Estimation errors of position and velocity. d p , dp , d c , dc Lumped disturbance and disturbance estimation. l v,i Design parameters of velocity observer. z ref Control input variable. p p ref − p error.