Use of Resolvers in Limited Rotations

Abstract

The electromagnetic structure of the resolvers makes them excellent for difficult applications. Among them, axial flux resolvers show better performance against mechanical faults. However, a complicated resolver-to-digital converter (RDC) overshadows the whole system's reliability. Both of the conventional software and hardware decoding methods suffer from deficiencies, such as difficulty to implement, poor performance against noise, expensive equipment, etc. To overcome these challenges any easy-to-implement software-based RDC is suggested in this paper that is used for rotational forth-and-back motions. In fact, instead of the conventional arc-tangent method to extract the position information from SIN and COS signals, three transfer functions are proposed to estimate the position. Tylors series are used to linearize the transfer functions over the zero position and a transfer function with minimum linearization error over the whole region is selected as opt one. The design process of axial flux resolvers is presented as well. 3-D time-stepping finite element method (FEM) is used to verify the success of the proposed analytical calculations. Finally, prototypes of the different configurations are tested for experimental measurements.