A general sliding mode output feedback algorithm is developed that takes in
to account parametric uncertainty and external disturbances provided certai
n bounds are known. It has been assumed that the number of states is greate
r than the number of sensors and that there can be a mismatched disturbance
. The details of an eigenvalue perturbation analysis for an uncertain matri
x are presented. A boundary layer has been introduced around each sliding s
urface to eliminate the chattering phenomenon. The results from numerical s
imulations are presented to corroborate the validity of the proposed contro
ller.