The Leaf-Style Axial Field Variable Reluctance Resolver With an Efficient Decoding System

The leaf-style slotless resolver has been proposed in the form of the stator permanent magnet (PM) variable reluctance resolver. The prototype is specially designed only for high-speed scenarios, as the PM cannot generate a significant motion electro-motive force (EMF) at zero- and very low speed. This article proposes a more practical prototype and its dedicated system, which has two valuable features. First, the resolver size and cost can further reduce to an ignorable level, including only two tiny pieces of iron and a small printed circuit board. The electrical high-frequency excitation is adopted instead of the magnets; then the decoding system can cover the speed range from zero to several kilo r/min. However, the limited space and slotless structure weaken the excitation and EMF signals. The square waveform injection is thus introduced to solve this issue. The hardware circuit and software computation requirements are friendly to be implanted into a cost-sensitive motor driver. The proposed resolver system has been integrated into a servo motor drive system and tested in experiments.