Robust I&I Adaptive DSC with Disturbance Observer for Maglev System with Output Constraint

This paper proposes a robust immersion and invariance (I&I) adaptive dynamic surface controller (DSC) with disturbance observer (DO) for the tracking control of uncertain output-constrained maglev system subjected to mismatched disturbance. The uncertain maglev system with output constraint is firstly transformed into an equivalent unconstrained one via a constructive nonlinear mapping. Dynamic surface control (DSC) combined with I&I adaption law and extended disturbance observer is designed systematically for the transformed system. The proposed control law overcomes the problem of "explosion of complexity" due to the DSC baseline controller. The robust I&I adaptation law in the control law is developed to recover the unknown parameter of the system, which shapes the dynamics of parameter estimation error and renders the estimation error exponentially converging to a bounded residual set. And the extended disturbance observer is used to handle the time-varying mismatched disturbances in the maglev system. The stability analysis of the overall system shows that all signals of the closed-loop system are bounded and output constraint of the system is not violated as well. The numerical simulation results verify the effectiveness of the proposed controller at last.