Position Estimation Method for Switched Reluctance Motors Based on Magnetic Flux Modulation

There are different position sensors to drive electric machines such as encoders, opto-interrupters, and resolvers to provide information about the position of the rotary part. However, these sensors affect the reliability of the propulsion system and increase the drive system cost considerably. To overcome this problem, this article proposed a novel method for sensing the rotor position of a switched reluctance motor (SRM) used in a hybrid electric vehicle (HEV). In this method, a low-amplitude high-frequency (HF) voltage waveform is injected into the three sets of toroidally wounded HF windings in the back-iron of the machine to modulate the position information in the amplitude of magnetic flux. After filtering the induced voltage in signal windings and processing the output signals, the envelopes of signals are demodulated for further investigation. Voltage Derivative is the method that is proposed in this article. In the Derivative Voltage method, the derivative of the extracted envelope is calculated in each step with regard to the time and the obtained value is compared to the lookup table (LUT) to compute the possible position of the rotor. The proposed method is cheap and maintains the robustness of the machine at the same time. The presented sensing method is studied on the SRM with 24 stator poles and 16 rotor poles. Finite-element analysis (FEA) is used to simulate and validate the efficacy of the proposed sensing technique.