Presentation of a Novel Variable Reluctance Tubular Resolver

Encoders and resolvers are the most common position sensors in controlling electrical machines. However, due to their ability to work under harsh conditions, resolvers are more preferred. In linear position detection, the transversal edge effects and the longitudinal end-effects adversely affect the accuracy of conventional linear resolvers. On the contrary, due to the cylindrical symmetry of tubular machines, they are not subject to the edge effects. With this idea, this article presents a novel linear VR resolver with a tubular structure to achieve higher accuracy than the existing linear resolvers. A magnetic equivalent circuit model is then developed to prove the correct performance of the proposed resolver. It is discussed that the proposed resolver is tolerant of mechanical eccentricities. Different configurations are studied, and finite-element analysis is conducted to analyze the resolver's outputs considering longitudinal end-effects and under mechanical eccentricities. The results show the proposed configuration has a robust performance under eccentricities while its accuracy sharply deteriorates due to the longitudinal end effect. Therefore, an effective method is proposed for compensating the longitudinal end effect. Finally, the compensated resolver is experimentally built and tested to verify the success of the developed sensor.