Discrete Variable Gain Second-Order Sliding Mode Observer Design for Position-Sensorless Control of Permanent Magnet Synchronous

To address the inherent chattering problem in traditional sliding mode observers, an improved discrete variable-gain second-order sliding mode observer is proposed. This observer automatically adjusts its gains based on the motor's speed and system state, enabling chattering suppression across a wide speed range. To diminish discretization errors during the digital implementation process and enhance estimation accuracy, a discrete-domain back electromotive force model is derived. This model serves as the basis for designing the improved discrete-domain second-order sliding mode observer. The effectiveness of the proposed method is verified through extensive simulations.