State Feedback Speed Control of PMSM using Multithreaded Controller

This paper explores the use of the Multithreaded State Controller (MTSC) method for speed control in permanent magnet synchronous motor (PMSM) drives. The unpopularity of state feedback control (SFC) structures among practitioners is mainly due to the inherent challenge of imposing constraints on internal state variables, as there are no set points for them. The MTSC-based method has facilitated the usage of state feedback control structure for a nonlinear plant model like PMSM by making the imposition of limits on the inner controlled variable ( current) as simple as introduction of a saturation block in cascaded control systems. Using a state-feedback linearization approach, a linear model of the PMSM is derived in the rotating reference frame. Through appropriate selection of states and the linear quadratic (LQR) design method, individual state feedback controllers for controlling d-axis current, q-axis current, and speed are designed. A zero d-axis current control strategy is adopted and all these controllers are executed simultaneously, and an appropriate control signal amongst them is selected in real-time and fed into the plant to achieve the goal of speed control while keeping the current within safe bounds and mitigating the problem of slower dynamics encountered with non-constrained SFC.The simulation study conducted in MAT LAB confirmed the effectiveness of this control approach.