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. The most extended torque measurement systems are torque transducers, which are typically limited to laboratory applications due to cost, reliability concerns and room restrictions. 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 because of the HF signals (noise, vibration, additional losses, …). This paper proposes a torque estimation method for PMSMs using low cost Hall-effect sensors. The method is based on the dependency of the leakage flux vector due to interaction between permanent magnet flux and stator coil flux. The proposed method does not interfere with the drive operation of the machine and can also be used to detect maximum torque per ampere (MTPA) trajectory.