On-line variable structure identifier with application to a magnetic levitation system of uncertain loading

A variable structure identification scheme is proposed to achieve fast and stable on- line parameter estimation of a servo system under uncertain loading. Unlike the integral- type of update law, the proposed updated law is of algebraic type, and thus the identifier will not grow indefinitely while suffering unexpected disturbance and/or unmodelled dynamics. To verify the proposed scheme, we performed experiments on its implementation in a magnetic levitation system with uncertain loading. The experimental results has shown that with the incorporated identifier the overall system performance can be improved significantly. Moreover, the preciseness of this identification scheme is also validated through investigating the experimental results.