Advanced discrete-time sliding mode control with fast output sampling and its application to buck converter

Abstract

In this paper, a relative degree two (RD2) sliding variable based discrete time sliding mode control (DTSMC) is designed for a linear time invariant system when output sampling is done faster than control input computation. The RD2 framework has been established for better performance and improved robustness of the discrete time sliding mode control system. The paradigm of fast output sampling (FOS) is utilized since it allows control computation using only the sampled output information, which is important from the implementation perspective making the design practical. A formal analysis is presented to establish the range of the controller parameters for this novel combination of DTSMC with RD2 sliding variable in the FOS framework. Also, a quantitative analysis of robustness in terms of ultimate band for the RD2 approach is done and compared with that of the RD1 approach. The theory is validated in a test bench application of a buck converter for tracking voltage references utilizing the FOS paradigm. The FOS paradigm had previously not been tested in any practical system with DTSMC, and this is the first time it is presented for the dc–dc buck converter system.