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This paper deals with the flux-weakening control of surface-mounted permanent-magnet synchronous motors, taking into account the influence of the resistive voltage drop in the stator windings, whose effect is usually neglected in similar studies. First, the motor equations exploiting the optimal torque-speed limits in the flux-weakening region are evaluated and discussed. Then, the influence of the resistive voltage drop is pointed out, highlighting its effect on the setup of the flux-weakening strategy. Hence, a simplified approach to flux-weakening motor control is presented, useful for the practical implementation in microcontrolled drives. Finally, experimental results are shown, using a position tracking application as a test case. Copyright © 2010 IEEE

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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.