Nonlinear cascade sliding mode control based on extended state observer method for a DC-DC buck converter: Design and hardware experimentation

Abstract

A nonlinear cascade sliding mode control (NLCSMC) based on extended state observer method is developed for a DC-DC buck converter in the presence of matched disturbances and uncertainties in this paper. First, all the matched and mismatched disturbances in DC-DC buck converter have been defined as a uniformed matched disturbance, including load and input voltage variations. Second, extended state observer is used to estimate the state variables and disturbances of the system that cannot be obtained directly. Third, a novel nonlinear function-based cascade sliding mode control method is proposed to achieve better convergence and disturbance rejection ability. Subsequently, the detailed convergence analysis of the closed-loop system is derived based on Lyapunov tools. Finally, simulation and experimental results are carried out to illustrate the nonlinear cascade sliding mode control based on extended state observer method (nonlinear cascade sliding mode control - extended state observer) has better control performance than linear cascade sliding mode control based on extended state observer method.

A novel composite fixed‐time sliding mode control scheme for second‐order systems with mismatched disturbances: application to Buck converter

“…The proposed DOB guarantees a fixed convergence time irrespective of initial conditions. This property sets it apart from existing DOB‐based SMC schemes documented in the literature, such as those found in [19, 20, 22–24]. As such, the proposed scheme overcomes the limitation of varying convergence times across distinct control entities. …”

“…Step 1: Consider the time interval t ∈ (0, T ob ). Taking the time derivative of the sliding mode variable (19) and from (20), (21) one gives…”

“…However, there is a possibility of significant initial errors due to the large deviation between the desired output and the initial state value, which may lead to large gains and ultimately force the system states to escape to infinity. The works referenced, including [17,[19][20][21][22], do not consider the situation of significant initial errors, thus their Lyapunov proofs are not strict. [1] addresses this situation by providing a rigorous finite-time stability analysis that proves the system variables and states will not escape to infinity during the convergence process of the estimation.…”

“…In another study, [18] introduced an enhanced sliding mode variable with a state‐dependent exponent designed to handle the mismatched disturbance based on [13]. It then proposed an extended state observer‐based SMC method to address the mismatched disturbances present in the Buck converter system in [19]. The same team extended their research to the finite‐time convergence field in [20].…”