Robust levitation control for maglev systems with guaranteed bounded airgap

•There are three major difficulties for the maglev system. The system has a strict magnitude limitation for the airgap, while the system does not satisfy the conventional (global) matching condition. Furthermore, the control input is one-sided (i.e., sign definitive).•A new approach by using a three-step state transformation is proposed to resolve these difficulties.•A robust control is then proposed to guarantee uniform boundedness and uniform ultimate boundedness of the system regardless of the uncertainty.

The robust control design problem for the levitation control of a nonlinear uncertain maglev system is considered. The uncertainty is (possibly) fast time-varying. The system has magnitude limitation on the airgap between the suspended chassis and the guideway in order to prevent undesirable contact. Furthermore, the (global) matching condition is not satisfied. After a three-step state transformation, a robust control scheme for the maglev vehicle is proposed, which is able to guarantee the uniform boundedness and uniform ultimate boundedness of the system, regardless of the uncertainty. The magnitude limitation of the airgap is guaranteed, regardless of the uncertainty.