An accurate torque control of permanent magnet brushless motor using low-resolution hall-effect sensors for light electric vehicle applications

In this paper, a microprocessor-based PMSM drive with three hall-effect sensors for detecting rotor position is studied. First, three PMSM control methods, namely 120° six-step with current limit, 180° six-step with current control, synchronous frame vector control, are compared based on some key performance indexes, such as vibration, acoustic noise and efficiency. According to the analysis, a PMSM drive which is combined with 180° six-step current control in lower speed and synchronous frame vector control in middle to high speed range is proposed. Therefore, high torque in low speed and less vibration and acoustic noise in high speed can be obtained. Furthermore, overall system efficiency is improved. Further enhancement of the torque control, a rotor position observer based on average rotor speed and considered loading effect is added to track the interpolated signals from hall-effect sensors. Hence a high resolution rotor position signal is yielded for improving vector control. All the control schemes are implemented by software. Some measured results are provided to show its successful operation and effectiveness on the torque control for PMSM in light electric vehicle applications.