Robust Speed Regulation for PMSM Servo System With Multiple Sources of Disturbances via an Augmented Disturbance Observer

Permanent magnet synchronous motors are extensively used in high-performance industrial applications. However, plenty of practical factors (e.g., cogging torques, load torques, friction torques, measurement error effects, dead-time effects, and parameter perturbations) in the closed-loop servo system inevitably bring barriers to the high-performance speed regulation, which can be regarded as generalized disturbances. Most of the existing control approaches only focus on one single kind of disturbances. However, the practical servo system is affected by multiple sources of disturbances simultaneously and these disturbances enter into the system through different channels. To this end, this paper systematically analyzes several representative disturbances, particularly including their features and distribution in the practical servo system, and then, specifically puts forward a novel disturbance rejection framework based on a noncascade structure. Under this framework, a comprehensive disturbance observer is proposed to simultaneously and accurately estimate multiple disturbances such that a composite controller can be designed to correspondingly compensate disturbances. Rigorous analysis of stability is established. Comparative experimental results demonstrate that the proposed method achieves a better speed dynamic response and a higher accuracy tracking performance even in the presence of multiple sources of disturbances.