Hybrid Cascaded Differential Compensation Finite-Time Speed Current Single-Loop Control for PMSM Servo System Considering Unmatched Disturbances

The double closed-loop architecture is a universal control structure for speed servo systems. However, in multiloop architecture, the inner-loop limits the response speed of the outer-loop. To this end, a finite-time control strategy suitable for the speed current single-loop control structure is proposed to enhance the dynamic performance of the overall loop. First, compared with the dual-loop architecture, single-loop state estimator needs to be designed with higher order, which will lead to a larger estimation peak. Meanwhile, the estimation pressure of single-loop estimator is higher due to the need to consider both matched and unmatched disturbances. Therefore, a hybrid cascaded finite-time state estimator is proposed to alleviate the estimation pressure and peak phenomenon. In addition, the high-order finite-time state estimator uses only the low-order state estimation error for feedback adjustment when estimating the high-order state, and the output speed of the estimator is limited due to the output value passing through the pure integrator. Consequently, a hybrid cascaded differential compensation finite-time composite controller is further proposed to enhance the performance of the control system. Finally, the effectiveness and superiority of the proposed method were experimentally verified.