Rotor Position Estimation for Aviation Three-Stage Starter/Generators in the Low-Speed Region without High-Frequency Signal Injection

The changeable magnetic saliency of main machine (MM) in aviation three-stage stator/generator (ATSG) makes it difficult to implement the sensorless starting in the low speed region by the machine saliency-based methods. To estimate the rotor position of ATSG (which is also the rotor position of MM), a novel rotor position estimation method based on the harmonic currents in the main exciter (ME) stator windings produced by the rotating rectifier is proposed in this article. The sine and cosine functions on the rotor position without time delay are extracted from the ME stator currents by a constant frequency signal sampling method. Then, the estimated ME rotor position can be obtained by processing the sine and cosine functions through a phase-locked loop. As the ME and MM are mounted on the same shaft, the rotor position of MM can be obtained by the pole ratio between ME and MM. High-frequency (HF) signal injection is not required in the proposed method, so the HF torque ripple and HF loss caused by the injected HF signal can be avoided. The good performance of the proposed method is verified by the experimental results.