Discrete time sliding mode control for three time scale systems

This paper presents the design of discrete time chatter free sliding mode controller for three time scale system using slow subsystem alone. The obtained state feedback based discrete time sliding mode control (DSMC) is converted into output feedback based using modified fast output sampling (FOS) technique. Modified FOS approach uses previous control input to compute present control input. In modified FOS, control gains for a three time scale system are computed from the lower order subsystems by decomposing the original higher order system into three subsystems. Since three smaller order subsystem problems are to be solved in lieu of one high order problem, numerical ill-conditioning is completely avoided. This method is successfully illustrated by numerical example.