Online Compensation of Mechanical Load Defects with Composite Control in PMSM Drives

Online monitoring of various faults that are associated with the permanent magnet synchronous motor (PMSM) is receiving much attention with the increasing demand in PMSM applications. Mechanical load imbalance is one of the mechanical defects that causes increase in the torque ripple, motor vibration, and can lead to accelerated wear and unstable drive operation, if the fault is undetected. Unlike existing methods that are limited to detection of rotor defects, in this article, a novel composite-control scheme is designed to estimate and compensate for the load torque disturbance (produced due to load imbalance) in the feedforward compensation design. It is shown that the proposed design with the feedback control law provides accurate compensation of load torque disturbance and achieves high-precision speed control (improved tracking performance up to 90% and smaller convergence time of up to 70%). Simulations as well as experimental testing validate the effectiveness and reliability of the proposed scheme.