A Variable Reluctance-Based Planar Dual-Coil Angle Sensor With Enhanced Linearity

Abstract

An easy-to-fabricate, full circle range (0°–360°), planar coil-based variable reluctance (VR) angle transducer with enhanced linearity is presented in this article. The proposed sensor system aims to mitigate the limitations of the existing VR angle sensors, particularly their limited accuracy and nonlinearity, resulting from the inherent sensor output characteristics. By carefully designing the coil geometry to achieve uniform flux distribution and implementing a simple semicircular-shaped rotor, the sensor system offers enhanced performance and linearity. The proposed sensor employs a semicircular-shaped rotor plate (RP) placed between two printed circuit board (PCBs) with four coils each. These coils are strategically designed to ensure a linear variation of inductance with respect to the RP position, resulting in improved linearity in the sensor output. After validating the sensor design through analytical methods and finite-element analysis (FEA), a suitable algorithm was developed for accurately estimating the rotor angle. A sensor prototype was manufactured to evaluate the performance of the sensor system. The prototype showed an excellent linearity with a worst case error of 0.31% and a resolution of 0.11°. The sensor shows negligible sensitivity to axial misalignment of the shaft and the presence of external magnetic objects, highlighting the practical usefulness of the system.