Robust output-feedback control of a magnetic levitation system

A robust nonlinear output-feedback controller by the k-filter approach is proposed for position-tracking problem of a magnetic levitation system, where only the position measurement is available for control. Instead of the popular adaptive control techniques, a disturbance observer (DOB) is merged into the k-filter based output-feedback controller to compensate the external disturbance and model mismatch, so that a much simpler controller is constructed. Rigorous stability of the nonlinear control system is established. Experimental results are included to show the excellent performance of the designed controller.