Robust super-twisting sliding mode current control for doubly salient electromagnetic machine considering cross-coupling and uncertainties

Purpose This paper aims to proposed a robust super-twisting sliding-mode current control (RST-SMCC) method to address the degradation of current control performance in the doubly salient electromagnetic machine (DSEM) drives caused by cross-coupling and system uncertainties. Design/methodology/approach First, a novel nonlinear smooth function (NSF) is designed to replace the commonly used signum or saturation functions in super-twisting sliding-mode control (ST-SMC). The combination of NSF and ST-SMC effectively suppresses high-frequency chattering, eliminating the need for a low-pass filter (LPF) and thereby completely removing the detrimental effects associated with LPF usage. Second, a decoupling link comprising nominal cross-coupling terms is constructed and incorporated into the d- and q-axis voltages, which enhances the dynamic response and robustness of the current loop. Concurrently, the above measure enables effective suppression of system uncertainties in the current loop without adding any complex algorithms. Furthermore, based on theoretical derivation, a parameter tuning criterion for the proposed RST-SMCC method is designed, facilitating engineering practice. Findings The proposed RST-SMCC method is effective when applied to DSEM drives, demonstrating strong suppression of both cross-coupling and uncertainties in the current loop. The experimental results validate the effectiveness of the proposed method. Originality/value An NSF is designed to replace the signum or saturation functions, which can effectively suppress the chattering. Improving the control structure enables decoupling and suppression of uncertainties. The parameter tuning criteria allow for a significant reduction in tuning difficulty.