Permanent Magnet Synchronous Machine Torque Estimation Using Low Cost Hall-Effect Sensors

Torque measurement/estimation in permanent magnet synchronous machines (PMSMs) is required in a large variety of applications. Direct torque measurement by means of torque transducers is typically limited to laboratory applications due to cost, reliability, and room concerns. Alternatively, torque can be estimated. Torque estimation methods require accurate knowledge of machine parameters. Injection of a high frequency (HF) signal in the stator via inverter has been shown to be a viable option for online machine parameters identification in PMSMs. However, this introduces concerns on the performance of the machine due to the noise, vibration, and additional losses produced by the HF signal. This article proposes a torque estimation method for PMSMs using low cost Hall-effect sensors. The method is based on the dependency of the leakage flux complex vector due to interaction between permanent magnet flux and stator coil flux and does not interfere with the drive operation of the machine.