Variable structure control based on the characteristic model

Aimed at a class of parameter-unknown control problems, a variable structure control (VSC) method based on the tracking-differentiator (TD) is presented by creating a characteristic model. The model is created by recursive least squares (RLS) method with forgotten factor to estimate the parameters of the model. When the model becomes steady, the output of the model is consistence with the original one. Considering there are always various perturbations in complex conditions, the VSC is applied to control the system with its slide mode´s good quality of insensitive to the perturbations. The numerical simulation results show the validity of the method.