Investigation on Software-based High-speed Envelope Demodulation Strategy for VR Resolvers Considering Circuit Impedance

Variable reluctance (VR) resolvers offer advantages in high-speed applications, but their operational range is limited by the increasing complexity of envelope demodulation at high rotational speeds. This paper proposes a software-based high-speed demodulation strategy, in which the induced voltage is modeled using the excitation coil's equivalent impedance to determine accurate sampling phases. A double-sampling technique is further introduced, fully exploiting all sampling instants within one excitation period that contain accurate position information, thereby increasing the rotor position update rate. Simulation validates the effectiveness of the induced voltage expression considering circuit impedance, and experimental results corroborate the feasibility of the proposed method, which suppresses angle errors at high speeds without modifying the conventional RDC system configuration.