An improved fractional-order integral sliding mode controller for permanent magnet synchronous motor with linear/nonlinear switching extended state observer

In order to improve the tracking performance and disturbance rejection of the permanent magnet synchronous motor (PMSM) speed regulation system, an improved fractional-order integral sliding mode controller based on a linear/nonlinear switching extended state observer (IFOISMC + SESO) is designed. First, in order to solve the contradiction between the system response speed and chattering, an IFOISMC speed controller based on a modified variable exponential reaching law (MVERL) is proposed. The MVERL includes the variable gain term and a hyperbolic tangent auxiliary function in the conventional exponential reaching law, establishing deceleration points. Prior to reaching these deceleration points, the convergence speed of the sliding mode variable is accelerated. Upon reaching the deceleration points, the gain of the switching term is reduced, thereby effectively weakening the amplitude of chattering in the controller. Second, to improve the disturbance rejection ability, a linear/nonlinear switching extended state observer (SESO) with dynamic weighting coefficients is proposed to estimate the total disturbance of the PMSM system. Finally, simulation and experimental results indicate that the proposed method possesses the benefits of fast convergence, small chattering, and strong anti-disturbance.