Speed and Position Estimation for PM Synchronous Motor using self-compensated Back-EMF Observers

Precise motion control requires high-accuracy and highbandwidth feedback speed information, often calculated by direct measurement of the rotor position available through the incremental encoder equipping the drive. The resolution of the encoder heavily affects the cost of the drive and the accuracy and bandwidth of the calculated speed. The limitations introduced by a low resolution encoder can be partially reduced by a proper speed calculation (or estimation) algorithm, that therefore plays a key role in modern drive systems. In this paper a comparative analysis of state of-art speed measurement and estimation algorithms suitable for low-resolution incremental encoder equipped drives is presented, aiming at highlighting the specific feature of each one, both from the performance point of view, and from the computational requirements needed for actual implementation. The paper proposes itself as a guide for engineers in the complex choice of the best solution for each application.