Design of Robust Discretized Sliding Mode Controller: Analysis and Application to Buck Converters

In this article, a new kind of robust digital sliding mode controller is developed to stabilize the output of a class of second-order uncertain systems and is then applied to pulsewidth modulation-based dc-dc buck-type converters with unknown loads and uncertain components. To facilitate the theoretical analysis, a traditional discretized sliding mode controller is first proposed and utilized to such buck-type converters. Theoretical analysis indicates that there is certain steady-state error for the output of the closed-loop systems under such a discretized sliding mode controller. The main reason for the existence of unsatisfactory steady-state error is that the mismatched uncertainties cannot be fully suppressed by the feedback signals from input channels. Motivated by this observation, a new kind of discretized sliding mode controller with disturbances compensation is further proposed and employed to ensure that the steady-state error for the output of the closed-loop uncertain systems can be efficiently eliminated. The robustness of the two discretized sliding mode controllers against component uncertainties and load variations for buck-converters is tested by numerical simulations and experimental studies.